DE102023132003A1 - Multi-beam microscanner system and method and layer arrangement for its production - Google Patents

Abstract

A multi-beam microscanner system for projecting, in particular for imaging, electromagnetic radiation onto an observation field, in particular into a solid angle emanating from the microscanner system, comprises a substrate stack with a plurality of substrate layers stacked one on top of the other along a stacking direction. A radiation source, in particular a laser radiation source with one or more lasers, for generating the electromagnetic radiation, in particular one or more laser beams, is arranged in or on a first substrate layer of the substrate stack. A second substrate layer of the substrate stack comprises a micro-electro-mechanical system (MEMS) with at least one deflection element arranged in a beam path of the electromagnetic radiation and suspended so as to be capable of rotational oscillation about at least one oscillation axis for deflecting at least one electromagnetic beam emitted by the radiation source in a directionally variable manner. The microscanner system is produced by singulation from a layer arrangement, so that the manufacturing steps for a plurality of microscanner systems that take place prior to singulation can take place at the level of the layer arrangement. An image projection device contains a plurality of multi-beam micro-scanner systems.

Description

The present invention relates to a multi-beam microscanner system for projecting electromagnetic radiation onto an observation field, in particular for imaging. It further relates to a method for producing a plurality of such multi-beam microscanner systems and a layer arrangement that occurs as an intermediate product in the method.

Microscanners, which in technical jargon are also referred to as "MEMS scanners", "MEMS mirrors" or "micromirrors" or in English in particular as "microscanner" or "micro-scanning mirror" or "MEMS mirror", are micro-electromechanical systems (MEMS), more precisely micro-optoelectromechanical systems (MOEMS), from the class of micromirror actuators for the dynamic modulation of electromagnetic radiation, in particular visible light. Depending on the design, the modulating movement of an individual mirror can be translational or rotational about at least one axis. In the first case, a phase-shifting effect is achieved, in the second case a deflection of the incident electromagnetic radiation in a direction dependent on the current orientation of the mirror. In the following, microscanners are considered in which the modulating movement of an individual mirror is, at least partly, rotational.

Microscanners can therefore be used in particular to deflect electromagnetic radiation in order to modulate the deflection direction of an incident electromagnetic beam, in particular a laser beam, by means of a deflection element ("mirror"). This can be used in particular to create a Lissajous projection of the beam into an observation field. This allows, in particular, imaging and sensory tasks to be solved or display functionalities to be implemented. Furthermore, such microscanners can also be used to advantageously irradiate materials, in particular for their processing. Other possible applications include the lighting or illuminating of certain open or closed spaces or spatial areas with electromagnetic radiation, for example in the context of spotlight applications.

Microscanners often consist of a mirror plate (deflection plate) suspended laterally on elastically stretchable springs. A distinction is made between single-axis mirrors, which are preferably mounted so they can rotate around a single axis, and dual-axis and multi-axis mirrors, which allow rotations, particularly rotational oscillations, around a corresponding number of different axes (oscillation axes), especially simultaneously.

A microscanner system for deflecting an electromagnetic beam can thus, in particular, comprise a biaxial microscanner, i.e., a microscanner with two different non-parallel, in particular mutually orthogonal, oscillation axes. However, it is also possible for the microscanner system to comprise a combination of two or more individual microscanners, in particular single-axis microscanners, arranged in series such that the incident beam can be deflected successively by the various individual microscanners of the microscanner system to generate a two-dimensional deflection pattern, such as a raster scan or a Lissajous pattern. In a microscanner system with a combination of two or three single-axis microscanners, their non-parallel oscillation axes can, in particular, be orthogonal to one another in pairs.

In both imaging sensor technology and display functions, a multi-axis microscanner system is used to deflect electromagnetic radiation such as a laser beam or a shaped beam from any other source of electromagnetic radiation at least two-dimensionally, e.g., horizontally and vertically, in order to scan or illuminate an object surface within an observation field. In particular, this can be done by the scanned laser beam sweeping a rectangular area on a projection surface in the observation field. Thus, microscanner systems with at least a two-axis microscanner or with several, in particular two, single- or multi-axis microscanners connected in series in the optical path are used in these applications.

A microscanner system can, in particular, comprise a plurality of single- or multi-axis microscanners, even if these are not connected in series in the above-mentioned sense, but are each individually provided to deflect a dedicated beam. For example, a microscanner system can comprise a plurality of simultaneously operable, in particular multi-axis, microscanners, which can operate independently of one another or in a coordinated manner according to a defined scheme, each deflecting a dedicated beam. Such a microscanner system is referred to herein as a "multi-beam microscanner system."

The wavelength range of the radiation to be deflected can, in principle, be selected from the entire spectrum, from short-wave UV radiation, through the VIS range, NIR range, IR range, FIR range, to long-wave terahertz and radar radiation. The or each radiation source for the electromagnetic radiation can, in particular, itself be an integral component of a microscanner system, particularly a multi-beam system, as is the case in the present solution.

For a range of different microscanner applications, particularly for applications in the field of so-called "wearables", i.e. electronics worn on the body, very compact and cost-effective laser projectors are required. An important design for this purpose features one or more microscanners for beam deflection as well as one or more laser sources. Wearables can particularly include virtual reality (VR) glasses, augmented reality (AR) glasses, mixed reality (MR) glasses and other imaging devices worn on the body. The colors of the light generated by the light sources can, in the optical range of the spectrum, be primary colors of a color model for a color space and, for example, in the case of an RGB color model, be provided by three laser sources, one each for red, yellow and blue light.

In some known designs of microscanner systems, the differently colored laser components of a multicolor laser source (with several correspondingly differently colored individual lasers) are separated by color and hermetically encapsulated in their own TO packages. Since these packages are usually large and expensive, only a limited degree of miniaturization can be achieved.

In the conventional manufacturing of microscanner systems, all components of the microscanner system are individually assembled to form the microscanner system. This applies even to components such as integrated semiconductor circuits, which have previously been mass-processed and manufactured in parallel on semiconductor substrates. They are first separated into chips and then precision-assembled at chip level on a common carrier component of the microscanner system. The components of the microscanner system, which may include one or more MEMS mirrors, heat sinks, submounts, optics, and laser chips, must therefore all be individually mounted, aligned, mounted, contacted, and secured during the manufacturing of the microscanner system.

It is an object of the invention to provide a multi-beam micro-scanner system and a method for its production, so that the multi-beam micro-scanner system can be produced in particular efficiently and can be highly miniaturized.

This problem is solved according to the teaching of the independent claims. Various embodiments and further developments of the solution are the subject of the subclaims.

A first aspect of the solution presented here relates to a multi-beam microscanner system for projecting, in particular for imaging, electromagnetic radiation into an observation field, in particular into a solid angle emanating from the multi-beam microscanner system. The multi-beam microscanner system comprises a monolithic substrate stack with a plurality of substrate layers stacked one on top of the other along a stacking direction. A number N of radiation sources, in particular laser radiation sources, for generating the electromagnetic radiation, for example, several laser beams of the same or different colors, are arranged in or on a first substrate layer of the substrate stack. Here, N > 1 applies, and the N radiation sources are each configured to emit a respective electromagnetic beam as a radiation component of the electromagnetic radiation. A second substrate layer of the substrate stack has, for each radiation source, an associated micro-electro-mechanical system (MEMS) with at least one deflection element arranged in the beam path of the electromagnetic beam of the respective radiation source and suspended so as to be capable of rotational vibration about at least one oscillation axis for deflecting the electromagnetic beam emitted by the respective radiation source in a directionally variable manner.

The term "substrate layer," as used herein, refers to a homogeneous or heterogeneous material layer. In a temperature range intended for use with the multi-beam microscanner system, the material layer is typically a solid. It can, in particular, have a plate-like shape, at least in sections, and, depending on its function, can be made, in particular, from a semiconductor wafer or a material that is at least partially optically transparent in the wavelength range used for projection by the multi-beam microscanner system, such as a glass wafer or an at least partially transparent plastic wafer.

The term “radiation source” as used herein means a source of radiation to be deflected by the microscanner system, in particular scanning, electromagnetic radiation. In particular, it can be a source of laser radiation. The wavelength range of the radiation can in principle be selected from the entire spectrum from short-wave UV radiation, through the VIS range, NIR range, IR range, FIR range, to long-wave terahertz and radar radiation. The term “deflecting element,” as used here, is understood in particular to mean a body that has a reflective surface (mirror surface) that is smooth enough that reflected electromagnetic radiation, e.g., visible light, retains its parallelism according to the law of reflection, thus allowing an image to be created. The roughness of the mirror surface must be less than approximately half the wavelength of the electromagnetic radiation. Roughnesses with a mean roughness Ra ≤ 1000 nm, preferably Ra ≤ 100 nm, and particularly preferably Ra < 5 nm are particularly suitable. The mean roughness indicates the average distance of a measuring point on the surface from the center line. The mean roughness value corresponds to the arithmetic mean of the deviation from the center line and is particularly important in the standard DIN EN ISO 4287:2010 defined. The deflection element can, in particular, be designed as a mirror plate with at least one mirror surface or have such a plate. In particular, the mirror surface itself can consist of a different material, e.g., of a metal, in particular a deposited metal, than the rest of the body of the deflection element.

The term "monolithic", as used here, with reference to a body (in particular a substrate stack), means that the body is formed in one piece, such that the various substrates or layers of the stack are firmly connected to one another, so that the substrate stack forms a single unit. Any components formed in the substrate stack, in particular the radiation source and MEMS, are formed integrally with the substrate stack or as part thereof, in particular such that the substrate stack completely defines these components. In particular, the MEMS assigned to the radiation sources can also be combined as an integrated monolithic MEMS, in which an assigned deflection element is formed for each radiation source.

The terms "comprises," "includes," "has," "includes," "has," "has," "having," or any other variation thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a method or apparatus that includes or has a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or that are inherent in such a method or apparatus.

Furthermore, unless explicitly stated to the contrary, "or" refers to an inclusive "or" and not an exclusive "or." For example, a condition A or B is satisfied by one of the following conditions: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and both A and B are true (or present).

As used herein, the terms "a" or "an" are defined to mean "one or more." The terms "another" and "another," and any other variations thereof, are defined to mean "at least one other."

The term “plurality”, as used herein, shall mean “two or more”.

The terms "first," "second," "third," and similar terms in the description and claims are used to distinguish between similar or otherwise similarly named elements and not necessarily to describe a sequential, spatial, or chronological order. It is understood that the terms so used are interchangeable under appropriate circumstances, and the embodiments of the solution described herein may function in orders other than those described or illustrated herein.

The term "configured" or "set up" to perform a specific function (and respective variations thereof), as used here where appropriate, is to be understood as meaning that a relevant device or component thereof is already in a configuration or setting in which it can perform the function or is at least adjustable - i.e. configurable - so that it can perform the function after being set accordingly. The configuration can be carried out, for example, by appropriately setting parameters of a process sequence or of switches or the like for activating or deactivating functionalities or settings. In particular, the device can have a plurality of predetermined configurations or operating modes, so that configuration can be carried out by selecting one of these configurations or operating modes.

A multi-beam microscanner system according to the first aspect can be used advantageously in They can be manufactured within the framework of parallel processing, in which a layer arrangement is constructed from substrates corresponding to the substrate layers of the multi-beam microscanner system, such that a plurality of multi-beam microscanner systems are formed simultaneously and adjacently by the construction of the layer arrangement and can be obtained from this by subsequent singulation. The multi-beam microscanner systems can thus be manufactured, in particular, within the framework of parallel processing "at wafer level" (wafer-level processing), with all or at least a subset of the respective individual components of the multi-beam microscanner systems being formed in the layer structure of the layer arrangement. This also eliminates the need for individual packaging of components prior to integration of the components into the multi-beam microscanner system, which saves space and thus achieves a particularly compact design and manufacturing efficiency (particularly integration density). This also makes it possible to dispense with individual packaging of individual components of the multi-beam microscanner system, such as laser sources.

In the following, the term "layer arrangement" is used for a layer stack of substrates in which a plurality of multi-beam microscanner systems are formed. A layer arrangement can be produced, in particular, by stacking substrates, each of which is made of wafers, in particular (at least predominantly) from a semiconductor material such as silicon. However, the term "layer arrangement" also encompasses arrangements that result from dividing, in particular cutting, such a layer stack and, after dividing, comprise two or more of the microscanner systems. For example, rectangular pieces, each comprising a plurality of microscanner systems, can be cut from a wafer stack with a circular cross-section (perpendicular to the stacking direction). Such rectangular pieces are each particularly suitable as "tiles" for tiling image projection devices by arranging a plurality of such tiles in a grid. In this way, even large-area image projection devices can be created efficiently.

The term "substrate stack" is used herein to distinguish it from the term "layer arrangement" specifically for the layer structure within a single microscanner system. Within the framework of the aforementioned parallel processing "at the wafer level," the layer arrangement can thus first be manufactured before a plurality of microscanner systems are obtained from it by singulation, e.g., using a sawing process. Their respective layer structures form their respective substrate stacks, which in turn were obtained from stacked substrates of the layer arrangement as a section of the layer arrangement obtained during singulation.

Since the multi-beam microscanner system can generate a plurality of electromagnetic beams, in particular simultaneously, and deflect each of them individually or in a coordinated manner, microprojectors with particularly high radiation output and highly variable radiation patterns can be realized.

Various exemplary embodiments of the multi-beam microscanner system are described below, each of which, unless expressly excluded or technically impossible, can be combined with each other as well as with the other aspects of the present solution described below.

In some embodiments, at least one, in particular each, of the radiation sources or the multi-beam microscanner system as a whole is configured to emit the electromagnetic radiation generated by it at least predominantly as a focused beam with a beam direction deviating by an angle of no more than 10° from the stacking direction of the substrate stack. The beam direction can coincide, for example, at least substantially, with the stacking direction, in particular deviate from it by no more than 1°. This allows for particularly compact designs, since the entire beam path within the respective microscanner systems runs through the stack structure. Thus, the stack structure can also be used for targeted beam guidance and beam shaping based on its design, in particular by possibly integrating optical elements. Furthermore, particularly in the case where the multi-beam microscanner system as a whole is configured to emit the electromagnetic radiation generated by it at least predominantly as a focused beam, particularly high radiation intensities and, in the case of differently colored radiation from two or more of the radiation sources, also a focused beam with a correspondingly mixed color can be generated.

In some embodiments, at least one of the radiation sources is configured to emit its respective electromagnetic beam in a wavelength range that differs at least proportionally from a wavelength range of the beam of at least one radiation source, in particular does not overlap therewith. This allows the realization of a multi-beam microscanner system that Depending on the control of the radiation sources, different colors can be displayed time-dependently and/or as a mixed color.

In particular, the microscanner system can have at least two monochromatic radiation sources whose emission wavelengths are selected differently so that together they span an at least two-dimensional color space extending across different colors. The individual colors of the color space can then be specifically selected, for example, by appropriately controlling the individual radiation sources and/or MEMS of the microscanner system. Such a multi-beam microscanner system thus forms a microprojector that can display different colors in its projection area, in particular with temporal and/or spatial variability. The multi-beam microscanner system can thus be designed, for example, as an RGB module for at least partially displaying a color space based on the RGB color model.

In some embodiments, the radiation sources are configured such that the beam directions of their respective bundled beams run parallel and adjacent to one another in such a way that the bundled beams of the radiation sources are perceivable in the observation field as adjacent, differently colored subpixels of a pixel formed by the subpixels as a whole. Thus, analogous to an LCD or LED display, multicolor-capable pixels can be generated during projection, in which the pixel color perceivable by a viewer is achieved through the interaction of neighboring subpixels of different wavelengths or colors. The individual monochrome subpixels, in particular the radiation sources and any associated optics, can thus be optimized with regard to the respective wavelength, while the entire pixel is multicolor-capable due to the different wavelengths of its subpixels. It is nevertheless also conceivable for the subpixels to share elements or to be identical to one another and designed for a broadband rather than just monochrome wavelength range, which can also facilitate production.

For example, this could apply to anti-reflection coatings ("AR coatings") or so-called highly reflective coatings ("HR coatings"), where a subpixel-specific design would be rather challenging in terms of manufacturing technology. A subpixel-specific design, optimized for a monochrome wavelength, could, however, be particularly useful for diffractive (grating-like) structures for beam shaping, since these can generally be produced side by side without difficulty—even in parallel processing—and only need to be adapted to the respective subpixel wavelength with regard to the "grating constants."

In some embodiments, all radiation sources are configured to emit their respective electromagnetic beam, in particular (with respect to the integral of the radiation intensity I(λ) over the wavelength λ) predominantly or even exclusively, in a wavelength range that is the same for all radiation sources and has a width of a maximum of 100 nm, in particular a maximum of 50 nm, or monochromely at a wavelength that is the same for all radiation sources. In this way, projectors fed by all radiation sources and thus with high radiation output can be realized for the specific, narrow wavelength range. In particular, in the case of the aforementioned bundled beam, a high radiation intensity can be achieved. The wavelength range can in particular lie in a spectral range of a single primary color, i.e. in a spectral range that is located in the spectrum and is limited in such a way that all individual colors in this spectral range belong to the same primary color, such as blue, green, yellow, or red. For example, all radiation sources can combine their respective radiation in a single common. emit in a narrowly defined wavelength range (e.g. green: e.g. 515 nm ... 525 nm, blue: e.g. 415 nm ... 435 nm, or red: e.g. 625 nm ... 700 nm).

In some embodiments, the substrate stack has at least one further substrate layer, in or on which, for each radiation source, an associated, in particular diffractive or refractive, beam-shaping optic is formed for beam shaping, which is configured to shape, in particular to collimate, the at least one electromagnetic beam of the respective radiation source before and/or after its deflection by the deflection element associated with the respective radiation source. The provision of one or more beam-shaping layers in the substrate stack makes it possible to implement any requirements regarding the beam profile of the electromagnetic radiation to be projected into the observation field by the microscanner system by the substrate stack itself, in particular by components belonging to it and thus to the microscanner system itself, so that external optics for this purpose can be dispensed with. This can also be used to reduce the overall space requirement and thus to miniaturize the projection solution as a whole. In addition, beam shaping can be carried out in close spatial proximity, i.e. at a short distance, from the respective radiation source, which is particularly useful for improving the optical properties of the microscanner system itself or of the components integrated into the radiation projected into the observation field can be used.

In some embodiments, the substrate stack comprises at least one third substrate layer with, for each radiation source, a first beam-shaping optic formed therein for beam shaping, wherein the first beam-shaping optics are each configured to shape the electromagnetic beam of the respective associated radiation source before it is deflected by the deflection element associated with the respective radiation source.

In some embodiments, the substrate stack, in addition to or instead of the at least one third substrate layer, has at least one fourth substrate layer, each radiation source having a second beam-shaping optics formed therein for beam shaping, wherein the second beam-shaping optics are each configured to shape the at least one electromagnetic beam of the respective associated radiation source after its deflection by the deflection element associated with the respective radiation source.

In both cases, and especially in the case of the combination of at least a third substrate layer with at least a fourth substrate layer, beam shaping can, in particular, comprise collimating the respective beam. This allows the imaging properties, in particular the achievable image sharpness, of the microscanner system to be optimized.

In some embodiments, at least one of the beam-shaping optics assigned to a respective radiation source comprises an axicon, a parabolic mirror, and/or a planar deflecting mirror for at least partially shaping the electromagnetic beam emitted by the assigned radiation source. In the case of an axicon, this can in particular be designed as a reflective axicon. In all of the aforementioned cases, the beam-shaping optics can be arranged such that it directs the beam emitted by the assigned radiation source onto the deflection element by means of reflection at the beam-shaping optics, in particular onto a mirror surface of the deflection element, which is arranged on a side of the deflection element facing away from the radiation source (when the deflection element is in a non-deflected rest position). The deflection element can in particular have a central opening through which the beam emitted by the assigned radiation source can at least partially reach the beam-shaping optics, where it can be reshaped and directed onto the mirror surface of the deflection element. Beam shaping can, in particular, comprise generating an annular beam cross-section. The use of one or a combination of several of the aforementioned types of beam-shaping optics can thus be used, on the one hand, to generate a desired beam shape and/or, on the other hand, to achieve a particularly compact design, since the beam does not have to be guided laterally around the deflection element. However, it is also possible, instead, to provide a beam feedthrough in the substrate in which the deflection element is formed, at a location other than that of the deflection element, through which the beam from the associated radiation source can at least partially reach the radiation optics without first passing through or impinging on the deflection element.

One or more of the beam-shaping optics can also be designed as collimators. The collimators can, in particular, be configured such that they collimate only along a single spatial dimension running perpendicular to the beam direction, i.e., for example, they transform a circular beam cross-section into a linear, in particular rectilinear, beam cross-section. This can be used, in particular, to achieve a corresponding collimation for each oscillation axis of the deflection element. In another variant, the collimators can be configured such that they transform a divergent elliptical beam into a collinear beam with a circular beam cross-section.

In some embodiments, the substrate stack has at least a fifth substrate layer, in or on which at least one driver circuit for electrically controlling one or more, in particular all, of the radiation sources and/or at least one driver circuit for controlling one or more, in particular all, drives of the rotational oscillation movements of one or more of the deflection elements about their respective at least one oscillation axis is formed. The or each fifth substrate layer can in particular be a semiconductor substrate in or on which the driver circuit(s) is/are formed as an integrated circuit. The fifth substrate layer can in particular be interconnected to the first substrate layer and connected thereto, directly or indirectly via a wiring level as a further substrate layer, so that the spatial distance between a respective radiation source and the respective driver circuit for its control and thus electrical resistance and/or electromagnetic interference (from outside or through induction or similar) can be kept very low. At least one driver circuit can be used in particular as a driver circuit for several, in particular all, radiation sources or drives, for example as an integrated circuit, or as separate circuit for each radiation source or drive, in particular by means of separate integrated circuits.

In some embodiments, the first substrate layer is arranged between the fifth substrate layer and the second substrate layer, viewed along the stacking direction. Thus, in particular, the emission direction for the electromagnetic radiation can be defined as pointing away from both the first and the fifth substrate layer, so that the fifth substrate layer, which is usually opaque (particularly in the case of a semiconductor material), does not interfere with the beam path.

Specifically, in some variants of these embodiments, (i) the fifth substrate layer for each deflection element has the associated driver circuit for controlling a drive for the oscillating movement of the respective deflection element; (ii) the second substrate layer for each deflection element has at least one actuator for driving the oscillating movement of the respective deflection element; and (iii) the first substrate layer for each actuator has an electrical line running through it for the direct or indirect electrical connection of the actuator to the driver circuit for controlling the drive. The line can in particular be designed as a so-called "via", for example, in the case of one or more silicon layers in the substrate stack, as a through-silicon via (TSV) or, in the case of one or more glass layers in the layer stack, as a through-glass via (TGV). These variants also promote a compact design, particularly in the lateral direction (i.e., in the layer plane), since the line runs through the first substrate layer.

In some embodiments, the substrate stack has at least a sixth substrate layer, by means of which a first cavity formed in the substrate stack is hermetically sealed. Specifically, the deflection element or at least one of the deflection elements can be arranged in the hermetically sealed cavity and suspended so as to be capable of rotational vibration about the at least one vibration axis. Thus, on the one hand, the deflection element is well protected against unwanted external influences, such as chemical or mechanical influences or interfering radiation, and on the other hand, this design also promotes a particularly compact design of the microscanner system. The cavity can, in particular, be evacuated and thus serve as a vacuum encapsulation in order to reduce or minimize air frictional resistance that would otherwise occur during the vibrational movement, depending on the quality of the vacuum, or in particular even to at least substantially avoid it entirely.

In some embodiments, at least one of the radiation sources, in particular each radiation source, is arranged at least partially within a second cavity formed in the first substrate layer for each radiation source individually or for several, in particular all, of the radiation sources jointly. This allows the same or similar advantages to be achieved with respect to the radiation source as with the first cavity with respect to the deflection element.

Specifically, in some of these embodiments, a surface section of a side wall of at least one second cavity has at least one electrically conductive, in particular metallic, layer for establishing a respective electrical connection for at least one radiation source arranged at least partially in this respective second cavity. This also allows for a particularly space-efficient electrical connection of the radiation source.

The term "electrical conductivity" (and variations thereof), as used herein, refers to a physical quantity that indicates the ability of a substance to conduct electrical current. "Electrically conductive" or "electrically conducting" is understood here to mean an electrical conductivity of at least 10 ⁶ S/m (at 25 °C).

In some embodiments, at least one first cavity and/or second cavity is evacuated or contains a gas at a pressure below normal pressure, which consists at least predominantly of a protective gas. The at least one first and/or second cavity can thus in particular be evacuated, i.e. contain a gas with a gas pressure of 10 Pa (10 ^-4 bar) or less (every real vacuum is not completely free of matter). In the case of the first cavity, this is particularly advantageous with regard to oscillation of the deflection element that is as free of gas friction and thus with low losses. In the case of the second cavity, however, other advantages are more important, such as corrosion protection and protection against contamination of the radiation source. In particular, it is also possible for one of the two cavities to be evacuated (e.g. the first cavity), while the other cavity (e.g. the second cavity) is filled with a protective gas (in particular below normal pressure).

In some embodiments, the multi-beam microscanner system further comprises: (i) a seventh layer arranged in the respective beam paths of at least two of the radiation sources and designed as a diffusing screen or a ground glass screen such that when irradiated with the beams of these at least two radiation sources, a schematic image is created; and (ii) projection optics for projecting the intermediate image into the observation field. The seventh layer can in particular be arranged along the course of the beam paths after the respective deflection element, so that the intermediate image is generated at the seventh layer by the impingement of the rays previously deflected at the associated deflection element. The projection optics, which can in particular have a projection lens, is then arranged such that it projects the intermediate image created at the seventh layer in transmission or reflection into the observation field (i) directly or (ii) indirectly through one or more further layers of the substrate stack.

In some embodiments, at least one, in particular each, of the radiation sources comprises one or more of the following radiation emitters for at least partially generating their respective electromagnetic beam: edge-emitting laser, surface-emitting laser (Vertical Cavity Surface Emitting Laser, VCSEL), superluminescent diode (SLED), mini-LED, microLED. These radiation emitters can be applied or incorporated onto the first substrate layer, e.g., a silicon substrate or another mechanically suitable carrier substrate, in particular by a suitable transfer process.

In some embodiments, at least one deflection element has rotational symmetry with respect to an axis of symmetry running parallel to the stacking direction, and the radiation source associated with the respective deflection element is configured such that the electromagnetic beam generated during operation runs along the axis of symmetry of the associated deflection element and through an opening therein. Such a configuration can also be used to realize particularly compact designs, since beam deflection around the deflection element can be omitted. Furthermore, highly symmetrical designs can also be realized overall.

In some embodiments, one or more of the substrate layers, such as the first substrate layer and/or the second substrate layer, each have at least one alignment mark, by means of which at least two of the substrate layers of the microscanner system are aligned with one another in a dimension running transversely to the stacking direction. This allows the precision of the relative alignment of the various substrate layers to be increased, particularly with regard to achieving high-precision alignments in which optical disturbances (e.g., aberrations) caused by misalignments are reduced to at least negligible levels.

In some embodiments, one or more of the substrate layers, such as the first substrate layer and/or the second substrate layer, each have at least one alignment accuracy feature, based on which the accuracy of the relative alignment of at least two of the substrate layers of the microscanner system with respect to at least one spatial dimension (in particular orthogonally and/or along the stacking direction) can be determined. Using the at least one alignment accuracy feature, the quality of the microscanner system or precursors thereof can be evaluated, in particular before the layer arrangement is separated into individual microscanner systems. This can also be used, in particular, to select out stacks or (after separation) microscanner systems that do not meet a predetermined quality criterion as evidenced by this evaluation. This increases manufacturing efficiency because the selected substrate stacks or microscanner systems do not need to be further processed. It also ensures that products with misalignments are not delivered to the market undetected. As a quality criterion (e.g., permissible tolerance range), a tolerance of a maximum of 5 µm, preferably a maximum of 1 µm, or even better, a maximum of only 0.3 µm, has proven to be a proven quality criterion, particularly for lateral precision (i.e., across, especially orthogonal, to the stacking direction). In the dimension along the stacking direction, tests have shown a spacing accuracy for the spacing of consecutive substrate layers in the substrate stack (or the corresponding substrates of the layer arrangement before separation) of a maximum of 100 µm, preferably a maximum of 10 µm, and particularly preferably a maximum of 1 µm.

In some embodiments, the microscanner system further comprises one or more cooling elements, each extending into or through at least two of the substrate layers and made of a material that has increased thermal conductivity compared to its respective immediate surroundings in the substrate stack. The cooling elements can, in particular, comprise metallic material fillings, depending on the type of substrate layers used, in so-called through-silicon vias (TSV) or through-glass vias (TGV) as heat sinks. This allows heat, in particular heat generated by the radiation source during its operation, to be effectively dissipated in the microscanner system along the heat transport paths defined by the cooling elements, without the need for cooling elements external to the stack.

A second aspect of the present solution relates to a layer arrangement with a plurality of stacked layers along a stacking direction. laminated substrates which are fastened to one another at the respective interfaces of adjacent substrates by means of a respective bond, such as a wafer bond, an anode bond, or a eutectic bond, depending on the material of the substrates. In the layer arrangement, a plurality of, in particular mutually similar, multi-beam microscanner systems according to the first aspect are formed adjacent to one another in such a way that the multi-beam microscanner systems can each be obtained from the layer arrangement by singulation, in particular sawing or laser cutting. Each of the multi-beam microscanner systems contains a respective section of the layer arrangement, so that the stacked regions of the substrates of the layer arrangement contained in the respective section each form one of the substrate layers of the microscanner system formed in the respective section.

The term "substrate," as used herein, refers to a homogeneous or heterogeneous material layer, as with the previously introduced term "substrate layer." In a temperature range intended for use with the microscanner system, the material layer is typically present as a solid. In particular, it may have a plate-like shape, at least in sections. "Substrate" as a term is used herein to designate a material layer that is simultaneously a proportional component of a plurality of the microscanner systems (in particular, all microscanner systems) in the layer arrangement. In contrast, the term "substrate layer" is used to designate a material layer that, after being separated from the layer arrangement, is only part of one of the microscanner systems. The separation can be carried out, in particular, using known separation methods for separating chips from semiconductor substrates, such as sawing or laser cutting. In particular, the separation can be carried out by separating the layer arrangement along cutting lines that run transversely, in particular orthogonally, to the stacking direction.

The term "substrate" can refer in particular to a wafer, such as a wafer made of semiconductor material or a material that is at least partially transparent in a wavelength range used by the microscanner system for projection, such as a glass material or plastic. The shape of a main surface of the substrate, in particular the wafer, can in particular be circular (cf. 2 ) or rectangular, although other shapes are not excluded. In particular, the layer arrangement can contain both semiconductor substrates and glass substrates (the same applies to the substrate stack of the multi-beam microscanner systems with regard to its substrate layers). Furthermore, it is possible that, in addition to or instead of one or more glass substrates, a plastic substrate that is at least partially transparent in the relevant wavelength range is included in the layer arrangement. Such plastic substrates can in particular be designed as plastic optical wafers, i.e., contain one or more imaging optics. Such plastic substrates are generally more cost-effective to manufacture than glass substrates. They can advantageously be arranged in the layer arrangement, particularly where no hermeticity requirements are met for the layer arrangement during the manufacturing process and no subsequent high-temperature steps are necessary. In this case, one or more plastic substrates with additional optical functions, such as a "relay optic" or "beam widening optic," can be connected downstream of the MEMS in the respective beam path in a cost-effective manner. Such downstream optics can be particularly useful when a specific augmented reality waveguide (e.g., a spectacle lens in the case of a glasses application) requires a certain magnification of the beam cross-section in order to suppress parasitic artifacts that would otherwise occur.

A third aspect of the present solution relates to an image projection device for projecting an image into a projection field, wherein the image projection device comprises a plurality of multi-beam microscanner systems according to the first aspect of the present solution, each configured to display one pixel of the image to be projected. The projection field thus results from the superposition of the individual observation fields of the individual microscanner systems, wherein these observation fields can be overlapping or separate from one another. A mixture of these two alternatives is also conceivable, in particular to achieve an image display in which both color-variable and monochrome image areas occur. In some embodiments, the image projection device comprises one or more layer arrangements according to the second aspect, wherein each of the layer arrangements contains a respective number of at least two of the microscanner systems of the image projection device. In this way, even large image projection devices, in particular with a wide variety of projection field contours, can be manufactured particularly efficiently. This can be achieved in particular by assembling the image projection device in a tiled manner (see above) by arranging several layer arrangements (and possibly further individual micro-scanner systems) in a grid-like manner, each of which serves as “tiles”.

A fourth aspect of the present solution relates to a method for producing a plurality of microscanner systems according to the first aspect, the method comprising: (i) stacking a plurality of substrates along a stacking direction to produce a layer arrangement according to the second aspect, wherein adjacent substrates in the layer arrangement are fastened to one another at their interface therebetween, in particular by means of a respective bond; and (iii) separating at least two of the microscanner systems from the layer arrangement to obtain individual microscanner systems. In particular, to achieve particularly high manufacturing efficiency, 100 or more, in particular even 1,000, 10,000 or more microscanner systems can be separated from the layer arrangement, for which purpose the layer arrangement then contains at least this number of microscanner systems.

The layer arrangement according to the second aspect can thus be regarded in particular as an intermediate product in the parallelized production of a plurality of microscanner systems according to the first aspect.

The term "stacking" of substrates refers to any form of creating a layered arrangement of successive material layers along the stacking direction, with each material layer being referred to as a "substrate." This can therefore particularly involve stacking solid substrates, such as wafers. Depending on the material, layer deposition, for example, by liquid deposition followed by drying or curing, sputtering, or gas deposition processes (such as chemical vapor deposition, CVD), or mixed forms, are also conceivable.

In some embodiments of the method, stacking the substrates on top of one another involves forming at least two partial layer arrangements by stacking two or more substrates on top of one another in each partial layer arrangement. Adjacent substrates in each partial layer arrangement are fastened to one another at their intermediate interface, in particular by means of a respective bond (in particular by wafer bonding). The partial layer arrangements and optionally further substrates are then stacked on top of one another and fastened to one another at the interfaces, in particular again by means of a respective bond, in order to form the layer arrangement as a whole. In this case, it is particularly possible to align the substrates and/or partial stacks to be connected to one another very precisely in order to achieve an optimal fit. Fitting accuracies in the sub-micrometer range are particularly advantageous and achievable here. Furthermore, it is also possible to form housings for the microscanner systems on a stack basis, i.e., before singulation. This can be done in particular, similar to pure semiconductor wafers, in the sense of so-called wafer-level packaging (WLP).

One or more of the optionally present further substrates can be arranged in particular between the partial layer arrangements, so that the stacking of the partial layer arrangements can take place not only directly, but instead also indirectly, namely including one or more further substrates lying between the partial layer arrangements.

The formation of partial layer arrangements can be used particularly advantageously to implement process parallelization, in which two or more partial layer arrangements are produced simultaneously, thus enabling an increase in throughput. For example, different stacking stations can be used simultaneously in a production line to produce the various partial layer arrangements before these and, if necessary, the other substrates are assembled to form the overall layer arrangement. This also makes it easy to implement manufacturing differences, such as different individual processes or process controls for the individual partial layer arrangements, without having to consider other partial layer arrangements or their production, for example with regard to usable processes or temperature or pressure ranges.

In some embodiments, an alignment mark is generated in or on at least one selected substrate, and at least one other substrate is aligned with respect to its position relative to the selected substrate(s) using the respective alignment mark during formation of the layer arrangement. In particular, all substrates can be aligned relative to one or more of the other substrates using such alignment marks. This allows for highly precise alignment of the substrates with one another and thus, in particular, high optical quality of the microscanner systems.

In some embodiments, before singulation: in or on a first substrate of the layer arrangement, for each of the multi-beam microscanner systems formed in the layer arrangement, the radiation sources assigned to it, each having one or more radiation emitters, are formed in situ or assembled individually or combined as a prefabricated component, in particular simultaneously (and thus highly efficiently) for all microscanner systems of the layered arrangement. During the production of the layered arrangement, the first substrate thus equipped with the radiation sources of the multi-beam microscanner systems is then aligned as a whole relative to a second substrate, in particular using the alignment markings of the individual substrates involved in the alignment.

For this purpose, the adjustment may, in particular, comprise (i) activating the respective radiation sources of at least two microscanner systems that are not directly adjacent in the layer arrangement and are preferably far apart from each other, and (ii) aligning the first substrate with at least one other of the substrates (or vice versa) based on a radiation pattern generated overall by the activated radiation sources. The further the activated radiation sources are from each other, the higher the achievable adjustment accuracy is generally.

In some embodiments, the method further comprises: (i) measuring a thickness of the produced layer arrangement prior to singulation; (ii) comparing the measured thickness with a tolerance criterion defined for this purpose; (iii) if the measured thickness exceeds a value classified as tolerable by the tolerance criterion, selecting the layer arrangement and omitting singulation; and (iv) otherwise performing singulation. This also allows the quality of the microscanner system or precursors thereof to be evaluated and used to increase the efficiency of the manufacturing process and for quality assurance.

The features and benefits explained with regard to the first aspect of the solution also apply to the other aspects of the solution.

Further advantages, features and possible applications of the present solution will become apparent from the following detailed description in conjunction with the figures.

• 1A und 1B schematisch gemäß zweier beispielhafter Ausführungsformen je eine Querschnittansicht durch einen einzelnen MEMS-Projektor innerhalb eines Mikroscannersystems sowie ein daraus zusammengesetztes mehrstrahliges Mikroscannersystem;
• 2 schematisch eine beispielhafte Ausführungsform einer Schichtanordnung mit einer Mehrzahl von jeweils mehrstrahligen Mikroscannersystemen, z. B. nach 1A oder 1B;
• 3 ein Flussdiagramm zur Veranschaulichung einer beispielhaften Ausführungsform eines Verfahrens zur Herstellung einer Mehrzahl von Mikroscannersystemen, z. B. nach 1A oder 1B ;
• 4 eine schematische Darstellung einer Bildprojektionsvorrichtung mit einer Projektionseinheit auf Basis einer Mehrzahl mehrstrahliger Mikroscannersysteme;
• 5 eine Aufsicht auf eine erste Ausführungsform der Projektionseinheit aus 4, bei der je Mikroscannersystem verschiedenfarbige MEMS-Projektoren vorgesehen sind; und
• 6 eine Aufsicht auf eine zweite Ausführungsform der Projektionseinheit aus 4, bei der jedes Mikroscannersystem für sich nur gleichfarbige MEMS-Projektoren aufweist.

It shows:

• 1A and 1B schematically, according to two exemplary embodiments, a cross-sectional view through a single MEMS projector within a microscanner system and a multi-beam microscanner system composed thereof;
• 2 schematically an exemplary embodiment of a layer arrangement with a plurality of multi-beam microscanner systems, e.g. according to 1A or 1B ;
• 3 a flowchart illustrating an exemplary embodiment of a method for producing a plurality of microscanner systems, e.g. according to 1A or 1B ;
• 4 a schematic representation of an image projection device with a projection unit based on a plurality of multi-beam micro-scanner systems;
• 5 a plan view of a first embodiment of the projection unit from 4 , in which different colored MEMS projectors are provided for each microscanner system; and
• 6 a plan view of a second embodiment of the projection unit from 4 , in which each microscanner system has only MEMS projectors of the same color.

In the figures, like reference numerals designate like, similar, or corresponding elements. Elements shown in the figures are not necessarily drawn to scale. Rather, the various elements shown in the figures are depicted in such a way that their function and general purpose will be understood by those skilled in the art. Connections and couplings between functional units and elements shown in the figures may also be implemented as indirect connections or couplings, unless expressly stated otherwise.

The 1A and 1B show, according to an exemplary embodiment, in their lower part a microscanner system 100 having - for example three - individual MEMS projectors, and in the upper part of the figure a single one of these MEMS projectors 100a as a cross-sectional view according to a section along a section line AA through a section assigned to the MEMS projector 100a of a 2 shown layer arrangement 200.

The MEMS projector 100a (partially) comprises a substrate stack comprising a plurality of substrate layers 102 to 118 stacked one upon another along a stacking direction 101, each of which has an at least approximately or partially plate-like shape. Adjacent substrate layers are mechanically connected to one another, which, depending on the material of the respective substrate layers to be connected, can be achieved in particular by means of a known wafer bonding method, such as direct bonding, anodic bonding, eutectic bonding, chemical bonding, glass frit bonding or adhesive bonding.

The base substrate of the substrate stack is a plate-shaped semiconductor substrate layer 102, in particular a semiconductor chip with a circuit integrated therein (in particular one for each MEMS projector). In the present example, the semiconductor substrate layer 102 contains, on the one hand, a first driver circuit 102a for a drive device with at least one actuator (e.g., a piezo actuator) for driving an oscillatory movement of a deflection element 112a of the MEMS projector 100a, and a second driver circuit 102b, which is configured as a driver circuit for a laser device 120 of the MEMS projector 100a, serving as a radiation source.

The laser device 120 may include a laser ( 1A) or multiple lasers ( 1B) , in particular laser diodes, as radiation emitters 120a. In the case of multiple radiation emitters, these can differ or match, in particular with regard to the wavelengths of the laser radiation 130 they can emit. For example, three lasers can be provided that represent the primary colors of a color model of a color space, such as the primary colors red (R), green (G), and blue (B) of the RGB color model, so that by superimposing their laser radiation, a wide variety of colors from the color space can be represented by the laser device 120 itself and thus by a single MEMS projector. The lasers can, in particular, be integrated into a common component that represents the laser device 120. In particular, such a laser device 120 can also be designed such that it effects beam combination (e.g., superimposition of the individual R, G, B beams at one point). For this purpose, the laser device 120 can, in particular, have optical conductors 120b. The radiation emitters 120a and the optical conductors 120b (waveguides) can, in particular, also be integrated together (and possibly with additional components such as filters, e.g., tunable filters) in a photonic integrated circuit (PIC). The following types of radiation emitters are particularly suitable: edge-emitting lasers, surface-emitting lasers, superluminescent diodes, mini-LEDs, and micro-LEDs. The radiation emitters 120a of the laser device 120 can be selected to be the same or different in terms of their type. It is also conceivable that the aforementioned beam combining does not already occur in the laser device 120, but only in a subsequent region of the beam paths of the individual beams from the various radiation sources. The substrate stack can accordingly be designed such that the beam paths of the various radiation sources initially run separately before they are combined in the region of one or more layers following the laser device 120, for which purpose, in particular, a correspondingly configured optically active substrate layer can be provided.

In the substrate stack, substrate layer 102 is followed by another substrate layer 104, with a connection layer with electrical contacts 124a to 124c located between the two layers for electrically connecting terminals of driver circuits 102a and 102b to electrical lines 126 and 122, respectively, for connection to the drive device for deflection element 112a and to laser device 120, respectively. Laser device 120 is at least partially housed in a cavity 104a of substrate layer 104. Substrate layer 104 thus corresponds to the aforementioned "first" substrate layer.

The connection layer can be continuous, for example as a continuous wiring layer, or present in places, in particular in the form of only the electrical contacts 124a to 124c, which can be formed in particular by soldered connections or via eutectic bond connections. In particular, one or more of these connections can be specifically designed to act both as a mechanical connection (possibly with hermetic sealing) and as an electrical connection. In addition to the electrical contacts 124a to 124c, an electrically insulating material, in particular an underfill (so-called "underfill"; not shown), can also be present in order to strengthen the mechanical connection between the substrate layers 102 and 104, for example within the framework of a material-to-material connection (adhesive connection). In particular, the underfilling can also be designed to at least partially compensate for differences in thermal expansion coefficients between the two substrate layers 102 and 104 in order to increase the temperature resistance of the substrate stack and thus the reliability of the microscanner system 100.

In addition, one or more cooling elements 136 can be arranged for cooling in one or more substrate layers of the substrate stack, in particular in the substrate layer 104. They can in particular be designed as channels filled with a highly thermally conductive material, in particular a metal, e.g. of the TSV or TGV type, so that they can act as a heat sink with respect to their environment. Their course can in particular be aligned parallel to the stacking direction 101. In addition, they can be thermally connected to another, stronger heat sink, such as a heat sink (not shown), in order to to be able to better dissipate the heat they absorb.

In the further construction of the substrate stack, the substrate layer 104 is followed by a further substrate layer 106, which is formed from a material that is at least partially transparent in the wavelength range of the laser source 120 (in the case of multiple lasers, in their total used wavelength range), in particular from glass or a transparent plastic. The substrate layer 106 is configured to collimate electromagnetic radiation emitted by the laser source 120 by means of beam-shaping optics (e.g., by means of fast-axis collimation, FAC) or to focus it, in each case in particular in a radiation plane spanned by the stacking direction and a direction orthogonal thereto, in which a (first) oscillation axis of the deflection element 112a extends. In a microscanner system having two oscillation axes for the deflection element, the first oscillation axis can, in particular, be selected such that its associated natural and/or resonant frequency is greater than that of the other oscillation axis. The substrate layer 106 can, in particular, also be configured to form the above-mentioned optically effective substrate layer for beam combining.

After a further substrate layer 108, which serves as a spacer and has a central opening through which the beam path of the radiation 130 collimated by the substrate layer 106 passes, a further substrate layer 110 follows in the stack structure. Similar to the substrate layer 106, it is formed from a material that is at least partially transparent in the wavelength range of the laser source 120, in particular from glass or a transparent plastic. It serves to (further) collimate the radiation 130 by means of beam-shaping optics (e.g., by means of slow-axis collimation, SAC) or to focus it, in each case in a further radiation plane spanned by the stack direction and a direction orthogonal thereto, in which a second oscillation axis of the deflection element 112a runs, which oscillation axis is orthogonal to the first oscillation axis. By combining the two substrate layers 106 and 110, the radiation can be collimated across its entire cross-section, so that after passing through the substrate layer 110, it can be described as a parallel beam. The substrate layers 106 and 110 thus each correspond to an aforementioned "third" substrate layer. Optionally, however, a stacked structure is also possible in which the substrate layers 108 and 110 are omitted.

This is followed in the stack structure by a further substrate layer 112, in which a cavity 112b is formed centrally, in which the deflection element 112a is located. 1A and 1B simultaneously shown in three different positions, with the middle position, represented by black bars, corresponding to a rest position of the deflection element 112a. The deflection element 112a has a ring shape, in particular that of a circular ring, so that it has a central opening 112d through which the radiation 130 coming from the substrate layer 110 can pass, as in 1A and 1B illustrated in each case. The substrate layer 112 thus corresponds to the aforementioned "second" substrate layer. The deflection element 112a can, in particular, have a rotational symmetry, such as a circular symmetry or an n-fold rotational symmetry, with respect to a symmetry axis 112c running parallel to the stacking direction 101.

In order to be able to generate a projection, in particular a multi-dimensional one, the deflection element 112a is attached to a frame-shaped section of the substrate layer 112 surrounding it via a suspension with one or more springs in such a way that it can simultaneously perform a rotational oscillation around each of the oscillation axes. The suspension can in particular be configured such that each of the rotational oscillations is harmonic in an angular range up to a maximum deflection angle when it occurs as a free oscillation, i.e., that the restoring force of the springs with respect to the respective oscillation axis obeys Hooke's law, at least to a good approximation. It is also conceivable that the suspension is configured such that the deflection element 112a and its suspension form a Duffing oscillator.

To drive the oscillations, a drive device (not shown) is provided on the deflection element 112a. It can, in particular, comprise one or more piezo actuators, which are mounted, for example, on one or more of the springs in order to deform them by applying force when appropriately controlled by the driver circuit 102a. This deformation can cause the deflection element 112a to deflect from its rest position in order to initiate and/or continuously continue a one- or multi-dimensional oscillation of the deflection element 112a. In the aforementioned case where the substrate layers 108 and 110 are omitted, the substrate layer 112 can directly follow the substrate layer 106 in the stack structure. The substrate layer 112, together with the drive device, forms a MEMS, which in turn forms a component of the MEMS projector as a whole.

The drive device is connected to the driver circuit 102a via connecting lines guided through the underlying part of the substrate stack. of which in 1A and 1B In each case, only one connecting line 126 is shown by way of example. Electrically conductive, in particular metallic, connecting bond connections 128 are provided at the interfaces between adjacent substrate layers of the part of the substrate stack through which the connecting lines extend in order to achieve good electrical conductivity along the or each line 126 as a whole.

For the connection bonds 128, metal-eutectic bonds, such as gold-tin bonds, or direct metal bonding processes, such as gold-gold bonds, are particularly suitable. For the vertical electrical line sections of the line(s) 126 in the substrate stack, electrically conductive vias are introduced into the respective substrate layers, for example, a so-called through-glass via (TGV) in the case of a glass substrate layer or a so-called through-silicon via (TSV) in the case of a silicon substrate layer. In addition to electrical conduction, the electrical lines 126, including the respective associated connection bonds 128, can also be used for thermal dissipation, which is particularly important for the substrate layer 104 with the typically heat-generating laser device 120.

The substrate layer 112 is followed by a further substrate layer 114, which, together with substrate layers 110 and 112, hermetically seals the cavity 112b with the deflection element 112a on all sides. Accordingly, the cavity 112b can be evacuated or at least filled with a gas under negative pressure, so that gas friction losses during the oscillation of the deflection element 112a can be (almost) completely avoided or at least significantly reduced. One or more, in particular all, further cavities that may be present in the substrate stack can also be hermetically sealed and evacuated or under negative pressure. This can apply in particular to a cavity between the two collimator substrate layers 106 and 110 and/or to the cavity 104a in the substrate layer 104 in which the laser device 120 is located.

In the stacked structure, the substrate layer 114 is followed by another beam-shaping substrate layer 116, in which a transmitting axicon 116a is formed with a central reflection surface 116b applied thereon, acting as an additional reflective axicon. However, it is also conceivable that the substrate layers 114 and 116 coincide, i.e., form a single substrate layer structured to form the axicon.

In both cases, as in 1A and 1B shown in each case, there is a further substrate layer 118, which acts as a cover layer and simultaneously as a transmitting axicon or as a converging lens. The axicon 116a with the reflection surface 116b is arranged such that the radiation 130 coming from the layer 114 during operation of the microscanner system 100 passes through the axicon 116a onto the reflection surface 116b, from where it is reflected onto the side of the deflection element 112a facing away from the laser device 120, on which side a mirror surface of the deflection element 112a is located. The radiation is reflected again at this mirror surface of the deflection element 112a in order to be projected through the substrate layer 114, the axicon 116a, a cavity between the substrate layers 116 and 118, and finally through the substrate layer 118 as a beam bundled by the latter into the observation field.

The substrate layers 114, 116, and 118 are therefore each formed, at least in the region of the beam path of the radiation 130, from a material that is at least partially transparent in the wavelength range of the laser source 120 (with the exception of the reflection surfaces 116a and 116b). The material can be glass or a transparent plastic, and the materials of the various substrate layers 114 to 118 mentioned above can also be different from one another. The substrate layers 116 and 118 each correspond to an aforementioned "fourth" substrate layer.

Instead of the axicon, other beam shaping optics are also conceivable, such as a parabolic mirror or a planar deflection mirror.

The substrate layer 114 can also be designed in particular as a ground glass or diffusing glass, so that when irradiated with the rays deflected by the deflection element, an intermediate image is formed thereon, which is then projected into the observation field by the substrate layers 116 and 118, which act as projection optics.

The stack structure of the MEMS projector 100a may further comprise rewirings (not shown) for electrical connections, wherein the rewirings may be formed in particular as rewiring levels at or near the interfaces between adjacent substrate layers, in particular in or on the substrate layers 102, 104 and/or 112.

In particular, several, in particular even all, substrate layers of the MEMS projector 100a can have a rotational symmetry with respect to the symmetry axis 112c, for example, circular symmetry or, in the case of a square floor plan, fourfold rotational symmetry.

The further reference numerals 201 to 203 and 200 will only be referred to below with reference to the 2 and 3 be addressed.

2 schematically illustrates an exemplary embodiment of a layer arrangement 200, in particular a wafer stack, with a plurality of multi-beam microscanner systems, e.g., microscanner systems 100 according to 1A or 1B The microscanner systems are arranged laterally next to one another, similar to semiconductor chips on a semiconductor wafer. The stacked substrates of the layer arrangement 200 form, in each case proportionally, the substrate layers of each of the microscanner systems 100 formed in the layer arrangement and thus also of their MEMS projectors 100a. 1A and 1b Cross sections of the respective microscanner system 100, each shown proportionally for only one MEMS projector, can be obtained, for example, from the dashed line AA.

3 shows a flowchart illustrating an exemplary embodiment 300 of a method for manufacturing a plurality of microscanner systems, e.g., microscanner systems 100 according to 1A or 1B .

In the method 300, a layer arrangement 200 is first produced in processes 305 to 320 according to 2 In each of the processes 305 to 315, only a part of the layer arrangement 200 is produced as a respective partial layer arrangement 201, 202 or 203 thereof as a precursor. These partial layer arrangements 201, 202 or 203, like the layer arrangement 200, are each produced proportionally for a single MEMS projector 100a in 1A or 1B illustrated. Each of the processes 305 to 320 can, for example, be carried out in a dedicated production station or production line. In particular, the processes 315 and one or both of the processes 305 and 310 can be carried out in a temporally overlapping manner, i.e., at least partially simultaneously. However, it is also conceivable to carry out the processes sequentially, in particular by means of a single production line. The order of the processes 310 and 315 can be freely selected.

Specifically, in process 305, the partial layer arrangement 201 is created by connecting substrates corresponding to the substrate layers 106 to 110. This can be done, in particular, in an evacuated or negatively pressurized chamber, so that later, in each of the resulting microscanner systems 100, a respective cavity hermetically enclosed by substrate layers 106 to 110 for each MEMS projector 100a is evacuated or under negative pressure. If the substrates are not already supplied ready-made, the process 305 can also include the production of these substrates. The partial layer arrangement 201 forms a collimator or focusing optics for the radiation 130 for each MEMS projector 100a to be formed in the layer arrangement 200, as previously described with reference to 1A and 1B was explained in detail.

In process 310, the partial layer arrangement 201 is supplemented with the substrates corresponding to the substrate layers 112 with the deflection element 112a and the substrate layer 114 to form the partial layer arrangement 202. If or to the extent that these substrates are not already supplied ready-made, the process 310 may also include the production of these substrates.

In process 315, the partial layer arrangement 203 is produced, wherein, in particular, the layer 104, which has already been structured as a precursor, is populated with the radiation source 120. In addition, substrates corresponding to the substrate layers 102 and 104, including the connection layer 124, are connected to one another. If or to the extent that these substrates are not already supplied as precursors, the process 315 can also include the production of these substrates (as precursors). The radiation source is contacted via the connection layer 124.

In process 320, to form the entire layer arrangement 200, the previously produced partial stacks 202 and 203 are assembled and supplemented by substrates corresponding to the substrate layers 116 and 118. Depending on the type of substrates to be connected, the various wafer bonding methods already discussed above can be used to connect the adjacent substrates and subsequently also the partial layer arrangements 201, 202, and 203, as well as the layer arrangement 200 as a whole. Alignment markings 132 can be provided on one or more of the substrates for the relative alignment of the substrate layers to be connected of the respective partial stacks 201 to 203 to one another, and subsequently of the partial layer arrangements 202 and 203 to one another, before or during the respective connection. In addition, to increase the accuracy of the alignment and/or for later evaluation of the layer arrangement produced or the microscanner systems 100 separated therefrom, one or more alignment accuracy features 134, for example in scale form, can be provided on relevant substrates or substrate layers, e.g. as illustrated on Sub strat layer 104, are formed or have been formed previously.

Instead or additionally, the alignment may comprise activating at least two microscanner systems that are not directly adjacent in the layer arrangement, wherein the substrate corresponding to the first substrate layer ("first") and thus the radiation sources 120 are aligned with respect to at least one, in particular all, of the other substrates based on a radiation pattern generated overall by the activated radiation sources. This is an advantageous method for achieving particularly high alignment precision, particularly in connection with the mutual alignment of partial stacks 201 to 203.

Once the layer arrangement is complete, it can be tested as a whole in a test process 325. For this purpose, its thickness, particularly its maximum thickness, is measured and compared with a previously defined tolerance criterion, such as a permissible tolerance range for the thickness. If the tolerance criterion is not met (330 - no), the layer arrangement as a whole is rejected as defective (350).

Otherwise (330 - yes), the method continues with a test process 335, in which the microscanner systems 100 formed in the layer arrangement are individually, but preferably simultaneously, tested at the layer arrangement level (i.e., in the case of wafers, at the wafer level). If defects are detected in certain microscanner systems 100, these can be marked as faulty and/or classified as defective in associated data structures.

Then, in a singulation process 340, the completed layer arrangement 200 is singulated into the individual, already tested, microscanner systems 100 contained therein. This can be done, in particular, using a sawing process. Such sawing processes, e.g., using diamond-coated saws, can in particular correspond to those known from semiconductor technology for singulating semiconductor wafers into individual chips.

Microscanner systems previously marked or classified as defective can then be individually selected, in particular rejected, in a subsequent selection process 345.

In 4 is schematically shown according to various embodiments (cf. 5 and 6 ) illustrates an image projection device 400 with a projection unit 405 based on a plurality of multi-beam microscanner systems 100. In addition to the projection unit 405, the image projection device 400 additionally has a signal processing unit 415 in a common housing 410, in which images to be projected by the projection unit into a projection field 420, e.g., still images or moving images (e.g., videos or animations), can be processed based on their associated image data, for example for rendering or further image processing processes, such as filtering, color adjustments, resolution adjustments, etc. In addition, the image projection device 400 can also have further (in 4 not shown) components, such as a communication interface for receiving image data representing the images to be projected or a power supply unit, such as a battery, for supplying the image projection device 400 with power.

5 illustrates a first embodiment 500 of the projection unit 405 from 4 , in which 100 different colored MEMS projectors are provided per microscanner system. In the projection unit 405, several multi-beam microscanner systems 100 are provided, e.g. according to 1A , arranged in a grid pattern. In this example, each of the microscanner systems 100 has three different MEMS projectors 100a. In particular, they can be selected such that together they span an RGB color space, so that each microscanner system 100 has a MEMS projector 100a-R for "red" color, a MEMS projector 100a-G for "yellow" color, and a MEMS projector 100a-B for "blue" color, which together can project a color-variable pixel (image point), the color of which can be variably determined depending on the control of the individual MEMS projectors by superimposing their respective emitted beams, in particular also time-dependently. By means of the control, the respective intensity of the radiation emitted by the MEMS projectors can be adjusted. Due to their monolithic construction, the microscanner systems 100 each form a "tile," from which the grid-like arrangement is composed as a "tiling." Each tile can thus be understood as the source of a color-variable "pixel," and each MEMS projector 100a therein as the source of a subpixel of a subpixel color corresponding to the emission color of the MEMS projector 100a. Instead of the 5 In addition to the 3 × 3 tiling shown, other tilings can also be used, so that matrix-shaped n × m tilings with n, m ∈ ℕ are possible here. Furthermore, non-matrix-shaped arrangements are also conceivable. Each MEMS projector 100a can be configured to emit only monochrome radiation. Instead, it is also possible for it to emit radiation at least predominantly from a single color (e.g., in this case, red, Yellow, or blue) limited wavelength range.

6 illustrates a second embodiment 600 of the projection unit from 4 , in which each microscanner system 100 has only MEMS projectors 100a of the same color, but which otherwise corresponds to the first embodiment 500 of 5 Each tile therefore only provides one “color”.

In both embodiments 500 and 600, the individual microscanner systems 100 can be present as separate components that have been combined to form the arrangement in the sense of an assembly. However, it is also possible for all or at least a subset of two or more of the microscanner systems 100 to still be monolithically integrated within a layer arrangement 200, i.e., they have not been separated from it.

LIST OF REFERENCE SYMBOLS

100

Micro scanner system

100a

MEMS projector

100a-R

MEMS projector for emitting red radiation

100a-G

MEMS projector for emitting yellow radiation

100a-B

MEMS projector for emitting blue radiation

101

Stacking direction

102

Substrate layer with driver circuits

102a

Driver circuit for driving the deflection element

102b

Driver circuit for laser device

104

“first” substrate layer with laser device

104a

Cavity for holding the laser device

106

Substrate layer with collimator for first oscillation axis

108

Substrate layer as spacer layer

110

Substrate layer with collimator for a second oscillation axis

112

“second” substrate layer with deflection element

112a

deflection element

112b

Cavity for accommodating the deflection element

112c

axis of symmetry

112d

Opening in the deflection element

114

Substrate layer as a lid for the cavity with deflection element

116

Substrate layer with first and second axicon

118

Substrate layer with third axicon or convex lens

120

Radiation source, in particular laser device

120a

Radiation emitters, especially laser diodes

120b

optical conductors

122

electrical cable for connecting the laser device

124a-c

electrical contacts

126

electrical cable for connecting a drive device for the deflection element

128

electrically conductive connection bonds

130

electromagnetic radiation, especially (laser) radiation

130-i

electromagnetic beam of the i-th radiation source

132

Adjustment markings

134

Adjustment accuracy feature

136

Cooling element

200

Layer arrangement, in particular wafer stacks

201-203

Partial layer arrangements

300

Manufacturing process for microscanner systems with a layer arrangement as an intermediate product

305-350

Processes under Procedure 300

400

Image projection device

405

Projection unit

405a, b

various embodiments of the projection unit 405

410

Housing

415

Signal processing unit

420

Projection field, superposition of the observation fields of the individual microscanner systems of the image projection device

500

first embodiment of the projection unit 405

600

second embodiment of the projection unit 405

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• DIN EN ISO 4287:2010 [0016]

Claims (33)

A multi-beam microscanner system (100) for projecting electromagnetic radiation (130) into an observation field, wherein: the microscanner system (100) comprises a monolithic substrate stack with a plurality of substrate layers (102,..., 118) stacked one on top of the other along a stacking direction (101); a number N of radiation sources (120) for generating the electromagnetic radiation (130) is arranged in or on a first substrate layer (104) of the substrate stack, where N > 1 and the N radiation sources are each configured to emit a respective electromagnetic beam (130-i) as a radiation component of the electromagnetic radiation (130); a second substrate layer (112) of the substrate stack has, for each radiation source (120), an associated MEMS with at least one deflection element (112a) arranged in the beam path of the electromagnetic beam (130-i) of the respective radiation source and suspended so as to be capable of rotational vibration about at least one vibration axis, for deflecting an electromagnetic beam emitted by the respective radiation source (120) in a directionally variable manner. Multi-beam microscanner system (100) according to Claim 1 , wherein at least one of the radiation sources (120) or the multi-beam microscanner system (100) as a whole is configured to emit the electromagnetic radiation generated by it at least predominantly as a bundled beam with a beam direction deviating by an angle of maximum 10° from the stacking direction (101) of the substrate stack. Multi-beam microscanner system (100) according to Claim 1 or 2 , wherein at least one of the radiation sources (120) is configured to emit its respective electromagnetic beam (130-i) in a wavelength range which differs at least proportionally from a wavelength range of the beam (130-i) of at least one radiation source (120). Multi-beam microscanner system according to Claims 2 and 3 , wherein the radiation sources (120) are designed such that the beam directions of their respective bundled beams run parallel and adjacent to one another such that the bundled beams of the radiation sources (120) are perceptible in the observation field as mutually adjacent, differently colored subpixels of a pixel formed by the subpixels as a whole. Multi-beam microscanner system according to Claim 3 or 4 , wherein the microscanner system has at least two monochromatic radiation sources (120) whose emission wavelengths are selected differently so that together they span an at least two-dimensional color space. Multi-beam microscanner system (100) according to Claim 1 or 2 , wherein all radiation sources (120) are configured to emit their electromagnetic beam (130-i) in a wavelength range that is the same for all radiation sources and has a width of a maximum of 100 nm, in particular a maximum of 50 nm, or monochromely at a wavelength that is the same for all radiation sources (120). Multi-beam microscanner system (100) according to one of the preceding claims, wherein the substrate stack has at least one further substrate layer (106; 110; 116; 118), in or on which, for each radiation source, an associated beam-shaping optic is formed for beam shaping, which is configured to shape the electromagnetic beam (130-i) of the respective radiation source (120) before and/or after its deflection by the deflection element (112a) associated with the respective radiation source. Multi-beam microscanner system (100) according to Claim 7 , wherein the substrate stack has, as each such further substrate layer, at least one third substrate layer (106; 110), each with a radiation source (120) formed therein and a first beam-shaping optical unit for beam shaping, wherein the first beam-shaping optical units are each configured to shape the electromagnetic beam (130-i) of the respective associated radiation source (120) before it is deflected by the deflection element (112a) associated with the respective radiation source (120). Multi-beam microscanner system (100) according to Claim 7 or 8 , wherein the substrate stack has, as each such further substrate layer, at least one fourth substrate layer (116; 118), each with a radiation source (120) and a second beam-shaping optic (116a, 118) formed therein for beam shaping, wherein the second beam-shaping optics (116a, 118) are each configured to shape the at least one electromagnetic beam (130) of the respective associated radiation source after its deflection by the deflection element (112a) associated with the respective radiation source (120). Multi-beam microscanner system (100) according to one of the Claims 7 until 9 , wherein at least one of the beam-forming optics assigned to a respective radiation source (120) comprises an axicon, a parabolic mirror, and/or a planar a deflecting mirror for at least partially shaping the electromagnetic beam emitted by the associated radiation source (120). Multi-beam microscanner system (100) according to one of the preceding claims, wherein the substrate stack has at least one fifth substrate layer (102), in or on which at least one driver circuit (102b) for electrically controlling one or more of the radiation sources (120) and/or at least one driver circuit (102a) for controlling one or more drives of the rotary oscillatory movements of one or more of the deflection elements (112a) about their respective at least one oscillation axis is formed. Multi-beam microscanner system (100) according to Claim 11 , wherein, viewed along the stacking direction (101), the first substrate layer (104) is arranged lying between the fifth substrate layer (102) and the second substrate layer (112). Multi-beam microscanner system (100) according to Claim 12 , wherein: the fifth substrate layer (102) for each deflection element has the associated driver circuit (102a) for controlling a drive of the oscillating movement of the respective deflection element (112a); the second substrate layer (112) for each deflection element has at least one actuator for driving the oscillating movement of the respective deflection element (112a); and the first substrate layer (104) for each actuator has an electrical line running through it for the direct or indirect electrical connection of the actuator to the driver circuit (102a) for controlling the drive. Multi-beam microscanner system (100) according to one of the preceding claims, wherein the substrate stack has at least one sixth substrate layer (114), by means of which a first cavity (112b) associated with each deflection element is formed and hermetically sealed in the substrate stack. Multi-beam microscanner system (100) according to Claim 14 wherein each of these deflection elements is arranged in the respective first cavity (112b) assigned to it and is suspended so as to be capable of rotational vibration about the at least one vibration axis. Multi-beam microscanner system (100) according to one of the preceding claims, wherein at least one of the radiation sources (120) is arranged at least partially within a second cavity (104a) formed in the first substrate layer (104) individually for each radiation source or jointly for a plurality of the radiation sources. Multi-beam microscanner system (100) according to Claim 16 , wherein a surface section of a side wall of at least one second cavity (104a) has at least one electrically conductive layer for producing a respective electrical connection of at least one radiation source (120) arranged at least partially in this respective second cavity. Multi-beam microscanner system (100) according to one of the Claims 14 until 17 , wherein at least one first cavity (112b) or second cavity (104a) is evacuated or contains a gas at a gas pressure below normal pressure, which gas consists at least predominantly of a protective gas. A multi-beam microscanner system (100) according to any one of the preceding claims, further comprising: a seventh layer arranged in the respective beam paths of at least two of the radiation sources and configured as a diffusing screen or a ground glass such that, upon irradiation with the beams of these at least two radiation sources, an intermediate image is formed on the seventh layer; and projection optics for projecting the intermediate image into the observation field. Multi-beam microscanner system (100) according to one of the preceding claims, wherein at least one of the radiation sources (120) has one or more of the following radiation emitters (120a) for at least partially generating its respective electromagnetic beam (130-i): edge-emitting laser, surface-emitting laser, superluminescent diode, mini-LED, micro-LED. Multi-beam microscanner system (100) according to one of the preceding claims, wherein at least one deflection element (112a) has a rotational symmetry with respect to an axis of symmetry (112c) running parallel to the stacking direction (101), and the radiation source (120) associated with the respective deflection element is designed such that the electromagnetic beam (130) generated by it during operation runs along the axis of symmetry (112c) of the associated deflection element (112a) and through an opening (112d) therein. Multi-beam microscanner system (100) according to one of the preceding claims, wherein one or more of the substrate layers each have at least one alignment mark (132) by means of which at least two of the substrate layers of the microscanner system (100) are aligned with one another in a dimension running transversely to the stacking direction (101). Multi-beam microscanner system (100) according to one of the preceding claims, wherein one or more of the substrate layers (102,...,118) each have at least one alignment accuracy feature (134) by means of which the accuracy of the relative alignment of at least two of the substrate layers (102,...,118) of the microscanner system (100) with respect to at least one spatial dimension can be determined. Multi-beam microscanner system (100) according to one of the preceding claims, further comprising one or more cooling elements (136) which each extend into or through at least two of the substrate layers and are formed from a material which has an increased thermal conductivity compared to its respective immediate surroundings in the substrate stack. A layer arrangement (200) comprising a plurality of substrates stacked one upon another along a stacking direction (101), which are secured to one another at the respective interfaces of adjacent substrates by means of a respective bond connection; wherein, in the layer arrangement (200), a plurality of multi-beam microscanner systems (100) according to one of the preceding claims are formed adjacent to one another in such a way that the multi-beam microscanner systems can each be obtained from the layer arrangement (200) by separation; and wherein each of the multi-beam microscanner systems (100) contains a respective section of the layer arrangement (200), such that the stacked regions of the substrates of the layer arrangement (200) contained in the respective section each form one of the substrate layers of the microscanner system (100) formed in the respective section. Image projection device (400) for projecting an image into a projection field (420), wherein the image projection device (400) comprises a plurality of multi-beam microscanner systems (100) configured to display one pixel of the image to be projected, according to one of the Claims 1 until 24 has. Image projection device (400) according to Claim 26 , comprising one or more layer arrangements (200) according to Claim 25 wherein each of the layer arrangements (200) contains a respective number of at least two of the microscanner systems (100) of the image projection device (400). Method (300) for producing a plurality of multi-beam microscanner systems (100) according to one of the Claims 1 until 24 , wherein the method (300) comprises: stacking (305, ...,320) a plurality of substrates along a stacking direction (101) to form a layer arrangement (200) according to Claim 25 to produce, wherein adjacent substrates in the layer arrangement (200) are fastened to one another at their intermediate interface; and singulating (330) the substrate stack to obtain at least two singulated multi-beam microscanner systems from the layer arrangement. Procedure (300) according to Claim 28 , wherein the stacking (305, ..., 320) comprises: forming at least two partial layer arrangements (201, ..., 203) by stacking two or more of the substrates per partial layer arrangement (201, ..., 203) on top of each other, wherein adjacent substrates in each partial layer arrangement (200) are fastened to one another at their interface therebetween by means of a respective bond connection; and stacking and fastening the partial layer arrangements (201, ..., 203) and optionally further substrates to one another in order to form the layer arrangement (200) as a whole. Procedure (300) according to Claim 28 or 29 , wherein an alignment mark (132) is produced in or on at least one selected substrate and at least one other substrate is adjusted with respect to its relative position to the selected substrate(s) by means of the respective alignment mark (132) during formation of the layer arrangement. Method (300) according to one of the Claims 28 until 30 , wherein before the singulation (340): in or on a first substrate of the layer arrangement (200), for each of the multi-beam micro-scanner systems (100) formed in the layer arrangement (200), the radiation sources (120) respectively assigned to it, which each have one or more radiation emitters (120a), are formed in situ or mounted individually or combined as a prefabricated component; and during the production of the substrate stack, the first substrate thus equipped with the radiation sources (120) of the multi-beam micro-scanner systems (100) is adjusted as a whole relative to a second substrate. Procedure (300) according to Claim 31 , wherein the adjustment comprises: activating the respective radiation sources (120) of at least two multi-beam microscanner systems that are not immediately adjacent in the layer arrangement (200); and aligning the first substrate with at least one other of the substrates based on a radiation pattern generated overall by the activated radiation sources (120). Method (300) according to one of the Claims 28 until 32 , further comprising: measuring (325) a thickness of the produced layer arrangement (200) before singulation; comparing (330) the measured thickness with a tolerance criterion defined in this regard; if the measured thickness has a value beyond a value classified as tolerable by the tolerance criterion, selecting (350) the layer arrangement (200) and omitting singulation (340); and otherwise carrying out singulation (340).

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