DE102023203569A1 - Method for calibrating a mold processing device - Google Patents

Abstract

A method for calibrating a shape processing device (10) is provided. The shape processing device is configured to manipulate a shape of a surface (12) of an object to be processed (14) by irradiating a beam (16) of charged particles and, in doing so, to direct the beam in a time sequence to different locations (28) on the surface of the object to be processed on the basis of a time-dependent target control signal (30s). For this purpose, the shape processing device comprises a signal correction module (44) and a steering module (26), wherein the signal correction module is configured to convert the target control signal into an actual control signal (30i) for controlling the steering module by means of a predetermined model (46). The method comprises the steps of: providing a calibration object (48) with a surface (54) which reflects the charged particles and which comprises a plurality of calibration points (56) with a reflectivity which is different from the remaining reflecting surface, irradiating the beam (16) onto the reflecting surface (54) of the calibration object at the calibration points (56) and further points (57) of the surface and detecting a respective intensity of particles of the irradiated beam which are reflected back at the reflecting surface, and correcting the model (46) on the basis of the detected intensities (66-1; 66-2).

Description

Background of the invention

The invention relates to a method for calibrating a shape processing device which is configured to manipulate a shape of a surface of a processing object by irradiating a beam of charged particles.

Out of DE 10 2012 212 199A1 For example, such a device is known. It is configured for surface structuring of micro- or nanostructured components made of glass or ceramic. For this purpose, a particle beam, such as an electron beam, with a diameter in the range of the smallest structures to be created can be directed at selected sub-areas of the surface in order to achieve local compaction and thus a local lowering of the surface in accordance with the desired surface structuring. Furthermore, processing of an optical element of a projection exposure system for microlithography with an electron beam is described. Imaging errors of the projection exposure system caused by the manufacturing process can be compensated by a suitably implemented compaction and an associated change in the shape of the optical surface of an optical element. In addition to the described material compaction, particle beams can also be used for direct material removal from the surface of the irradiated optical element. Furthermore, it is possible to apply material to the surface of the object by suitable irradiation.

Usually, the actual shape of the surface of the optical element is first measured and its deviation from a predetermined target shape is determined. To adapt the surface shape to the target shape, a specification for a control variable of the shape processing device is usually first determined, which is suitable for effecting a desired correction of the surface shape of the optical element. The specification for the control variable can, for example, control a deflection unit for the particle beam in such a way that the particle beam is directed one after the other to irradiation points on the surface of the object being processed, at each of which the particle beam remains for a certain dwell time before being moved as quickly as possible to the next irradiation point.

Unfortunately, the approximation of the surface shape to the target shape that can be achieved with conventional shape processing devices of the type mentioned above is often not sufficiently accurate.

underlying task

It is an object of the invention to provide a method by which the aforementioned problems are solved and, in particular, the surface shape of an object can be adapted to a desired shape with improved accuracy.

Inventive solution

The above-mentioned object can be achieved according to the invention, for example, with a method for calibrating a shape processing device. The shape processing device is configured to manipulate a shape of a surface of a processing object by irradiating a beam of charged particles and to direct the beam in a time sequence to different locations on the surface of the processing object on the basis of a time-dependent target control signal. For this purpose, the shape processing device comprises a signal correction module and a steering module, wherein the signal correction module is configured to convert the target control signal into an actual control signal for controlling the steering module using a predetermined model. The calibration method comprises the steps of: providing a calibration object with a surface that reflects the charged particles and that comprises a plurality of calibration points with a reflectivity that is different from the remaining reflecting surface, irradiating the beam onto the reflecting surface of the calibration object at the calibration points and at other points on the surface, and detecting a respective intensity of particles of the irradiated beam that are reflected back at the reflecting surface, and correcting the model based on the detected intensities.

The given model describes in particular the deflection dynamics of the steering module and is fitted to the recorded intensities according to one embodiment. The beam of charged particles is in particular an electron beam. Alternatively, other charged particles can also be used, such as positrons or protons. A changed reflectivity at the locations of the calibration points is to be understood in particular as meaning that electrons are reflected more strongly or less strongly at the calibration points or possibly not at all. In addition to a classic optical reflection, in which the angle of incidence and the angle of reflection are the same, the term “reflection” also refers to a diffuse reflection, in which at least some of the electrons are scattered back. This means that the surface reflecting the charged particles also includes a surface that backscatters charged particles.

The solution according to the invention is based on the knowledge that the deflection behavior of the shape processing device can depend on the properties of the particle beam, such as the focusing of the particle beam and the beam current, and that the rapid movement of the particle beam between the beam points on the surface of the object being processed can influence the deflection behavior of the shape processing device. For example, the deflection dynamics of a steering module for deflecting the particle beam in the shape processing device can be influenced by inertia effects of magnetic coils used in the steering module and by inertia effects of control electronics of the steering module. Due to high positive and high negative accelerations of the transverse movement of the particle beam when scanning the various beam points, the aforementioned inertia effects can lead to a control signal from the steering module not being implemented precisely.

To solve this problem, according to the invention, the target control signal is converted into an actual control signal using a model and the model is corrected using the described calibration object. The calibration points arranged on the calibration object make it possible to take the above-mentioned inertia effects into account in the model. When using the appropriately corrected model to machine the machining object, the machining errors induced by inertia effects can be at least largely avoided, which means that the surface shape of the machining object can be adapted to the target shape with improved accuracy.

According to a further embodiment, the intensities result in an intensity distribution resolved with respect to the surface of the calibration object, in which the calibration points are each assigned to a calibration pattern, wherein the method further comprises evaluating the intensity distribution, in which a deviation of a shape of at least one of the calibration patterns from a target shape of the calibration pattern is determined, wherein the at least one specific shape deviation is taken into account in the correction. In particular, the shape deviations of all calibration patterns from corresponding target shapes are determined.

According to one embodiment, an elliptical deviation of at least one of the calibration patterns from a circular shape is determined when evaluating the intensity distribution. This means that the intensity distribution has an elliptical distortion. In particular, the elliptical deviation is such that the long axis of the ellipse is aligned parallel to the direction of movement of the beam during the transition between two points irradiated one after the other on the surface of the calibration object.

According to a further embodiment, the intensities result in an intensity distribution resolved with respect to the surface of the calibration object, in which the calibration points are assigned to a respective calibration pattern, wherein the method further comprises evaluating the intensity distribution, in which a deviation of a respective position of at least one of the calibration patterns from a target position of the calibration pattern is determined, wherein the at least one specific position deviation is taken into account in the correction. In particular, the position deviations of all calibration patterns from corresponding target positions are determined.

According to one embodiment variant, before the beam is irradiated onto the surface of the calibration object, a respective position of at least one of the calibration points on the surface of the calibration object is measured with an accuracy of less than 10 µm, in particular less than 2 µm, and from this the target position of the calibration pattern used to determine the position deviation is determined. The measurement is carried out in particular with a coordinate measuring machine. In particular, the positions of a majority of the calibration points or all calibration points are measured with the specified accuracy.

According to a further embodiment, the intensity of the particles reflected back from the surface of the calibration object is detected by means of a ring-shaped detector, through the interior of which the beam irradiated onto the surface passes. In particular, the ring-shaped detector is a backscattered electron detector. In particular, the time of measuring the intensity is synchronized with the temporal variation of the irradiation location on the surface, so that the relevant intensity can be assigned to the respective irradiation point.

According to a further embodiment, the beam is irradiated onto the surface of the calibration object along a predetermined trajectory, which includes the calibration points and the other points on the surface of the calibration object.

According to a further embodiment, the beam is irradiated in at least one pass onto the irradiation points comprising the calibration points and the other points on the surface of the calibration object and is moved over the surface between the irradiation points, whereby the irradiation points are irradiated in at least one pass with uniform residence times.

According to a further embodiment, the beam is irradiated in several passes onto the irradiation points comprising the calibration points and the other points on the surface of the calibration object and is moved over the surface between the irradiation points, whereby the irradiation points are irradiated with uniform dwell times in the individual passes and the uniform dwell times are different in the various passes. This means that the uniform dwell times differ from pass to pass. Advantageously, the movement between the irradiation points takes place at a uniform speed. According to one embodiment, the movement takes place over several points on average at a uniform speed.

According to a further embodiment, in a first pass, the irradiation points comprising the calibration points and the other points on the surface of the calibration object are each irradiated with uniform dwell times, and in a second pass, the irradiation points are irradiated with varying dwell times.

According to a further embodiment, a quotient of the recorded intensity of the first pass and the recorded intensity of the second pass is determined at the respective irradiation point and the model is corrected using the intensity quotients. The intensity is understood to mean the intensity of the reflected particles of the irradiated beam.

According to a further embodiment, the calibration object in the area of the reflective surface comprises a metal with an atomic number of at least forty. Examples of metals that can be used here are molybdenum with atomic number 42, tantalum with atomic number 73, tungsten with atomic number 74 and gold with atomic number 79. In particular, the calibration object can be made from one of the metals with an atomic number of at least 40 and can optionally be gold-plated. According to a variant, the calibration object in the area of the reflective surface comprises a metal with an atomic number of at least seventy, such as tantalum, tungsten and/or gold.

According to a further embodiment, the reflective surface at the calibration points differs from the remaining reflective surface due to a changed topography. The changed topography is responsible for the changed reflectivity. The calibration points can be formed by elevations and/or depressions in the reflective surface. According to one embodiment, at least one of the calibration points is formed by a hole in the calibration object, in particular a through hole.

According to a further embodiment, the beam of charged particles is an electron beam.

Furthermore, according to the invention, a method for changing a shape of a surface of a processing object is provided. This method comprises providing a shape processing device which comprises a signal correction module and a steering module, wherein the signal correction module is configured to convert a time-dependent target control signal into an actual control signal for controlling the steering module using a predetermined model. Furthermore, the method comprises calibrating the shape processing device by correcting the model according to the calibration method described above, in particular the calibration method according to one of the embodiments or variants described above. Furthermore, the method according to the invention comprises manipulating the shape of the surface of the processing object using the shape processing device, wherein the actual control signal is generated by the signal correction model from the target control signal using the corrected model, the beam is irradiated onto the surface of the processing object and the beam is deflected by the steering module using the generated actual control signal such that it is directed to different locations on the surface of the processing object.

The features specified with regard to the above-mentioned embodiments, exemplary embodiments or embodiment variants, etc. of the calibration method according to the invention are explained in the description of the figures and the claims. The individual features can be implemented either separately or in combination as embodiments of the invention. Furthermore, they can describe advantageous embodiments that are independently protectable and whose protection may only be claimed during or after the application has been filed.

Short description of the drawings

• 1 ein Ausführungsbeispiel einer Formbearbeitungsvorrichtung zum Manipulieren einer Form einer Oberfläche eines Bearbeitungsobjekts durch Einstrahlung eines Strahls geladener Teilchen,
• 2 ein erstes Ausführungsbeispiel zum Kalibrieren der Formbearbeitungsvorrichtung gemäß 1 unter Verwendung eines Kalibrierobjekts, sowie
• 3 ein weiteres Ausführungsbeispiel zum Kalibrieren der Formbearbeitungsvorrichtung gemäß 1 unter Verwendung eines Kalibrierobjekts.

The above and other advantageous features of the invention are explained in the following detailed description of exemplary embodiments or embodiments according to the invention with reference to the attached schematic drawings. It shows:

• 1 an embodiment of a shape processing device for manipulating a shape of a surface of a processing object by irradiating a beam of charged particles,
• 2 a first embodiment for calibrating the mold processing device according to 1 using a calibration object, as well as
• 3 another embodiment for calibrating the mold processing device according to 1 using a calibration object.

Detailed description of embodiments according to the invention

In the embodiments or embodiments or variants described below, functionally or structurally similar elements are provided with the same or similar reference numerals as far as possible. Therefore, in order to understand the features of the individual elements of a specific embodiment, reference should be made to the description of other embodiments or the general description of the invention.

To facilitate the description, a Cartesian xyz coordinate system is shown in the drawing, from which the respective positional relationship of the components shown in the figures results. In 1 the y-direction runs perpendicular to the drawing plane, the x-direction to the right and the z-direction upwards.

In 1 an embodiment of a shape processing device 10 for manipulating a shape of a surface 12 of a processing object 14 by irradiating a beam of charged particles in the form of a particle beam 16 is shown schematically. Specifically, the shape processing device 10 is used to change the shape of the surface 12 of the processing object 14, which can be in the form of an optical element, by means of electron irradiation. As an example, a mirror for the EUV wavelength range, i.e. for electromagnetic radiation with a wavelength of less than 100 nm, in particular a wavelength of approximately 13.5 nm or approximately 6.8 nm, is shown as an optical element. This can be an optical element for an illumination system or projection optics of a projection exposure system for EUV microlithography or DUV microlithography with a wavelength of approximately 365 nm, approximately 248 nm or approximately 193 nm. The optical element that can be changed by means of the shape processing device 10 can be a deflection mirror, facets of a facet mirror of an illumination optics or a mirror of a projection optics of a projection exposure system.

However, the shape processing device 10 is also suitable for high-precision surface shape production or surface shape modification of other optical elements, such as mirrors for other wavelength ranges, lenses or optical elements with diffractive structures, or also for objects that do not form an optical element.

The shape processing device 10 contains an irradiation head 18 in the form of a particle irradiation device for generating a particle beam 16 directed and bundled at selectable locations on the surface 12. The particle beam can be designed for material removal or for material application to the surface 12.

In the 1 In the embodiment of the irradiation head 18 illustrated, the particle beam 16 is formed by electrons, which means that the irradiation head 18 is an electron irradiation device. In other embodiments, positrons or ions can also be used, for example in systems for IBF surface processing. When ions are used, these are typically neutralized after acceleration in the electric field before hitting the surface. The particle beam 16 is in particular energetically designed in such a way that, depending on the energy dose, a more or less pronounced local removal or a more or less pronounced local compaction of the material of the object 14 being processed on the surface 12 is brought about. The energy dose is to be understood as the energy per area which is introduced into the object 14 being processed by the particle beam 16. The energy dose is therefore dependent in particular on the length of time the electron beam remains at the selected location and on its intensity.

Both material removal and local compaction cause a local lowering of the surface 12 on the object 14 being processed, such as an optical element. Compaction occurs particularly in amorphous materials through a redistribution of electron bonds. Local compaction takes place in all spatial directions, ie not only does a local surface lowering take place in the area of a surface element in the negative z-direction, but also a compaction parallel to the surface 12. This creates forces acting parallel to the surface 12. Forces, whereby stresses are induced in the processing object 14. These stresses can cause a deformation of a surface section that is significantly larger than the surface element affected by the local compaction. The surface section can comprise part of the surface 12 or the entire surface 12.

To generate the particle beam 16 in the form of an electron beam, the irradiation head 16 designed as a particle irradiation device contains 1 an electron source 20 and an acceleration unit 22. For example, a hot cathode, a crystal cathode or a field emission cathode can be used as the electron source 20. The acceleration unit 22 accelerates and focuses the electrons emitted by the electron source 20. For this purpose, the acceleration unit 22 can have an anode with a high positive electrostatic potential compared to the electron source 20 and a small exit opening for the accelerated electrons. To focus and adjust the intensity of the particle beam 16, the acceleration unit 22 also contains a control electrode, for example a Wehnelt cylinder. The intensity or the beam current indicates the number of electrons that pass through an area imaginary perpendicular to the electron beam per unit of time.

To focus the particle beam 16 coming from the acceleration unit 22, the irradiation head 18 further comprises a focusing unit 24 with suitably designed electrical or magnetic components.

With a steering module 26 in the form of a deflection unit of the irradiation head 18, the particle beam 16 can be deflected in both the x and y directions. For this purpose, the steering module 26 also contains suitably designed electrical or magnetic components. The steering module 26 can contain two separate deflection units, one for deflecting the particle beam 16 in the x direction and one for deflecting the particle beam 16 in the y direction. Depending on the setting of the steering module 26, the particle beam 16 strikes the surface 12 of the optical element 14 at a specific location (x _i , y _i ). Such a location (x _i , y _i ) is shown in 1 designated by the reference numeral 28.

In this way, a large number of different locations 28 on the surface 12 can be irradiated one after the other, thus achieving a spatially resolved distribution of effect in the form of an energy dose distribution over the surface 12. The spatially resolved energy dose distribution here is to be understood as a distribution of the introduced energy per area as a function of the spatial coordinates (x, y) of the surface 12 of the optical element 14. The irradiation can, for example, be carried out in a grid-like manner or continuously over the entire surface. An irregular or regular arrangement of different locations to be irradiated, for example in rows, circles, ellipses or the like, is also possible.

To avoid absorption of the electrons of the particle beam 16 by air, the irradiation head 18 further comprises a vacuum chamber in which the electron source 20, the acceleration unit 22, the focusing unit 24, the steering module 26 and the object 14 to be processed or at least the surface 12 of the object 14 are arranged.

In the 1 In the embodiment shown, the irradiation head 18 is provided with a target control signal 30s which specifies the irradiation of the surface 12 of the processing object along a processing trajectory 32b. The processing trajectory 32b is shown in the upper right section of 1 shown as an example. In this illustration, a circular area designated Ω' represents a processing area 34 on the surface 12 of the object 14 to be processed, i.e. a processing area accessible to the particle beam 16. The design of the processing area 34 as a circular area is to be understood as an example. Other shapes of the processing area, such as oval, square, rectangular or other types of shapes are conceivable. The inner area of the processing area Ω' contains a usable area 36, which is designated Ω. In the case in which the object 14 to be processed is an optical element for a lithography projection exposure system, the usable area Ω is a surface section on the optical element which, when installed in the projection exposure system, is arranged in a usable beam path. In other words, the usable area Ω is the surface section actually used in the later operation of the optical element or contains this. The usable area Ω is also in the 1 shown top view is circular.

The in 1 The embodiment of the processing trajectory 32b shown comprises a plurality of trajectory sections 38 in the form of parallel lines or parallel sections of the processing trajectory. The trajectory sections 38 indicate the path of the particle beam 16 on the surface 12 during operation of the shape processing device 10, with adjacent processing trajectories 32b being traveled in the same direction by the particle beam 16. Between the processing trajectories 32b, the particle beam "jumps back" in each case. On the processing Points are drawn at equal distances along the beam trajectories 32b. These represent respective beam entry points 40 for the particle beam 16. 1 To simplify the drawing, only some are designated with the reference numeral 40. At each of the irradiation points 40, the particle beam 16 stops during the processing of the surface 12 and remains at the respective location for a predetermined dwell time τ (reference numeral 62).

The dwell time τ typically varies from irradiation point 40 to irradiation point 40 or at least between sections with a group of irradiation points 40 irradiated with the same dwell time τ. Between the irradiation points, the particle beam 16 moves at the highest possible speed. The intensity of the particle beam 16, ie the irradiation rate of the charged particles, remains constant over the entire processing trajectory 32b according to one embodiment, ie the dose of charged particles emitted at the individual locations of the processing trajectory 32b depends solely on the duration of the particle beam's stay at the relevant locations. The distance between the trajectory sections 38 is in 1 drawn relatively large for illustrative purposes.

According to an embodiment not shown, the distance between adjacent trajectory sections 38 (in the y-direction according to 1 ) the distance between the beam points 40 (in x-direction according to 1 ) on the trajectory sections 38. According to one embodiment, the distance between the irradiation points 40 and/or the trajectory sections 38 is in the order of magnitude of the beam cross-section of the particle beam 16, ie if the area irradiated by the particle beam 16 at an irradiation point 40 is defined as pixels, the pixels are directly adjacent to one another according to this embodiment.

The shape processing device 10 further contains a control device 42 for controlling the irradiation head 18. The control device 42 is designed to provide the above-mentioned target control signal 30s for the steering module 26. The control device 42 determines this from a predetermined target change for the shape of the surface 12 of the object being processed 14. The target control signal 30s specifies a control recipe for the steering module 26, with which the particle beam 16 is moved along the above-described processing trajectory 32b with defined dwell times at defined irradiation points 40 over the surface 12 with the aim of generating an effect distribution in the form of the energy dose distribution on the surface 12. This effect distribution has a suitable characteristic for generating the predetermined target change in the shape of the surface 12. The target change is usually determined by measuring the actual surface shape and comparing the measured shape with a target shape, i.e. the target change is the change in the surface shape that is required to give the surface the target shape.

mittels eines mit dem Bezugszeichen 46 bezeich- neten Modells ${\left[\begin{array}{cc}{G}_{xx}\left(s\right)\left(x,y\right)& 0\\ 0& G_{yy}\left(s\right)\left(x,y\right)\end{array}\right]}^{-1}$

in das mit dem Bezugszeichen 30i bezeichnete Ist-Steuerungssignal ${\left[\begin{array}{c}{I}_x\left(t\right)\\ I_y\left(\text{t}\right)\end{array}\right]}_{ist}$

um. Die Umsetzung mittels des Modell 46 geschieht wie folgt: $${\left[\begin{array}{c}{I}_x\left(t\right)\\ I_y\left(\text{t}\right)\end{array}\right]}_{ist}={\left[\begin{array}{cc}{G}_{xx}\left(s\right)\left(x,y\right)& 0\\ 0& G_{yy}\left(s\right)\left(x,y\right)\end{array}\right]}^{-1}{\left[\begin{array}{c}{I}_x\left(t\right)\\ I_y\left(\text{t}\right)\end{array}\right]}_{soll}$$

The target control signal 30s generated by the control device 42 is converted by a signal correction module 44 into an actual control signal 30i, which is then used to control the steering module 26. Both the target control signal 30s and the actual control signal 30i comprise a time-varying current control specification I _x (t) for controlling the deviation of the particle beam 16 in the x direction and a time-varying current control specification I _y (t) for controlling the deviation of the particle beam 16 in the y direction. The signal correction module 44 sets the target control signal designated by the reference symbol 30s ${\left[\begin{array}{c}{I}_x\left(t\right)\\ I_y\left(\text{t}\right)\end{array}\right]}_{sOll}$

by means of a model designated by the reference numeral 46 ${\left[\begin{array}{cc}{G}_{xx}\left(s\right)\left(x,y\right)& 0\\ 0& G_{yy}\left(s\right)\left(x,y\right)\end{array}\right]}^{-1}$

into the actual control signal designated by reference numeral 30i ${\left[\begin{array}{c}{I}_x\left(t\right)\\ I_y\left(\text{t}\right)\end{array}\right]}_{ist}$

The implementation using Model 46 is as follows: $${\left[\begin{array}{c}{I}_x\left(t\right)\\ I_y\left(\text{t}\right)\end{array}\right]}_{ist}={\left[\begin{array}{cc}{G}_{xx}\left(s\right)\left(x,y\right)& 0\\ 0& G_{yy}\left(s\right)\left(x,y\right)\end{array}\right]}^{-1}{\left[\begin{array}{c}{I}_x\left(t\right)\\ I_y\left(\text{t}\right)\end{array}\right]}_{sOll}$$

The model 46 describes the deflection dynamics of the steering module 26, i.e. it provides the target control signal 30s with a lead which compensates for dynamic effects of the control signal. These dynamic effects can be due to inertia effects of magnetic coils used in the steering module 26 as well as inertia effects of the control electronics of the steering module.

As already mentioned above, the particle beam 16 is moved at the highest possible speed when scanning the processing trajectory 32b between two beam points 40, but remains static at the location of the beam points 40. The particle beam 16 is thus exposed to high positive and negative accelerations. Due to the inertia effects mentioned above, this can lead to the beam movement intended by the target control signal 30s not being implemented precisely. This inaccuracy is compensated by means of the lead generated by the model 46. In other words, the actual control signal 30i generated by means of the model 46 is corrected in such a way that the dynamic error effects are taken into account, ie the beam movement actually intended by the target control signal 30s is brought about when the steering module 26 is controlled by means of the generated actual control signal 30i.

The model 46 in the illustrated embodiment represents a diagonal matrix whose element a ₁₁ is defined by the transfer function G _xx (s)(x,y) and whose element a ₂₂ is defined by the transfer function G _yy (s)(x,y), where s is a Laplacian variable.

2 illustrates a first embodiment of a method for calibrating the mold processing device 10. For this purpose, the mold processing device 10 comprising the irradiation head 18, the control device 42 and the signal correction module 44 is assigned a calibration object 48, a ring-shaped detector 50 and an evaluation device 52. The calibration object 48 has a surface 54 which reflects the charged particles of the particle beam 16 and which has a plurality of calibration points 56 with a reflectivity which is different from the remaining reflecting surface 54. The calibration object 48 is arranged in the calibration arrangement according to 2 instead of the processing object 14 according to 1 in the particle beam 16. In the lower left section of 2 the calibration object 48 is shown in plan view. The calibration points, of which only some are provided with the reference number 56 for the sake of clarity, form a two-dimensional grid.

According to one embodiment, the calibration object 48 is a square or round metal plate with through holes 58, which form the calibration points 56 with the changed reflectivity on the surface 54. In this case, the reflectivity at the location of the through holes 58 is essentially or even completely eliminated. According to one embodiment, the metal plate forming the calibration object 48 comprises a metal with an atomic number of at least forty, for example the calibration object 48 comprises molybdenum, tantalum, tungsten and/or gold. The surface of such a metal plate is considered to be reflective with respect to the electrons of the particle beam 16 in the sense of this text. Thus, the term "reflection" is understood to mean not only a classic optical reflection, in which the angle of incidence and the angle of reflection are the same, but also a diffuse reflection, in which at least some of the electrons are scattered back.

The ring-shaped detector 50 is arranged in the space between the irradiation head 18 and the calibration object 48, preferably just below the irradiation head 18. In particular, the ring-shaped detector 50 is a backscattered electron detector. The detector 50 is arranged in such a way that the particle beam 16 can be irradiated through the interior of the ring-shaped detector 50, i.e. through the recess 60 in the interior of the ring, onto the surface 54 of the calibration object 48. The particle beam 16 is thrown back, in particular reflected, by the reflective surface 54, whereby the degree of reflection at the location of the calibration points 56 is greatly reduced or no reflection takes place there. The reflected particle beam 16r then hits the ring-shaped detector 50, which records the temporal intensity profile of the electrons of the particle beam 16 thrown back by the reflective surface 54 by recording the charge Q(t) received over time.

bezeichnet und gibt eine Kalibriertrajektorie 32k des Teilchenstrahls 16 an, welche beispielsweise, wie die Bearbeitungstrajektorie 32b gemäß 1, mäanderförmig über die Oberfläche 54 verläuft. Dabei ist die Bahn der Kalibriertrajektorie 32k so konfiguriert, dass der Teilchenstrahl 16 alle Kalibrierpunkte 56 abfährt und zwar so, dass der Teilchenstrahl 16 an jedem der Kalibrierpunkte 56 sowie jeweils mehreren dazwischen liegenden Punkten 57 stoppt und an jedem der Punkte 56 und 57 die gleiche Verweilzeit τ₁ (Bezugszeichen 62-1) verbleibt, bevor der Teilchenstrahl 16 zum nächsten Punkt weiterbewegt wird. Mit anderen Worten gibt das Steuerungssignal 30s-k1 vor, den Teilchenstrahl 16 auf die Oberfläche 54 an den Kalibrierpunkten 56 sowie weiteren Einstrahlpunkten 57 der Oberfläche 54 mit einer einheitlichen ersten Verweilzeit τ₁ einzustrahlen. Sowohl die Kalibrierpunkte 56 als auch die weiteren Einstrahlpunkte 57 werden in diesem Text als Einstrahlpunkte 40 bezeichnet.In the calibration mode, the control device 42 sends a calibration target control signal 30s-k1 for a first pass of the particle beam 16 over the surface 54 of the calibration object 48. This control signal 30s-k1 is in 2 with ${\left[\begin{array}{c}{I}_x\left(t\right)\\ I_y\left(\text{t}\right)\end{array}\right]}_{{\mathrm{<figure-callout\; id="1"\; label="\tau "\; filenames="DE102023203569A1\_0008.png,DE102023203569A1\_0009.png"\; state="\{\{state\}\}">\tau </figure-callout>}}_1}$

and indicates a calibration trajectory 32k of the particle beam 16, which, for example, like the processing trajectory 32b according to 1 , runs in a meandering shape over the surface 54. The path of the calibration trajectory 32k is configured such that the particle beam 16 travels past all the calibration points 56, namely such that the particle beam 16 stops at each of the calibration points 56 and at several points 57 in between, and the same dwell time τ ₁ (reference number 62-1) remains at each of the points 56 and 57 before the particle beam 16 is moved on to the next point. In other words, the control signal 30s-k1 specifies that the particle beam 16 is to be irradiated onto the surface 54 at the calibration points 56 and other irradiation points 57 of the surface 54 with a uniform first dwell time τ _1. Both the calibration points 56 and the other irradiation points 57 are referred to in this text as irradiation points 40.

The already mentioned with reference to 1 The signal correction module 44 described converts the target control signal 30s-k1 by means of the model 46 into a corresponding actual control signal 30i-k1 for controlling the steering module 26. The temporal charge curve Q(t) detected by the detector 50 in the first run of the calibration by controlling by means of the control signal 30s-k1 is converted by a signal conversion unit 64 of the evaluation device 52 into a temporal intensity curve I(t) _{τ 1} implemented. By comparing it with the calibration trajectory 32k specified by the control signal 30s-k1 on the surface 54 of the calibration object 48, the intensity curve I(t) _{τ 1} than in 2 The measured intensity distribution I ₁ ^m (x,y) designated by the reference numeral 66-1 can be represented on the surface 54.

bezeichnet ist. Das Kalibrier-Soll-Steuerungssignal 30s-k2 unterscheidet sich von dem Kalibrier-Soll-Steuerungssignal 30s-k1 darin, dass sich die zugrunde liegende einheitliche Verweilzeit τ₂ von der einheitlichen Verweilzeit τ₁ des Kalibrier-Soll-Steuerungssignals 30s-k1 unterscheidet. Als Endergebnis des zweiten Durchlaufs ermittelt die Signalumsetzeinheit 64 einen Intensitätsverlauf I(t)_τ2 sowie daraus eine mit dem Bezugszeichen 66-2 bezeichnete Intensitätsverteilung I₂ ^m(x,y) auf der Oberfläche 54.For a second run of the calibration mode, the control device 42 provides a calibration target control signal 30s-k2, which is ${\left[\begin{array}{c}{I}_x\left(t\right)\\ I_y\left(\text{t}\right)\end{array}\right]}_{{\mathrm{<figure-callout\; id="2"\; label="\tau "\; filenames="DE102023203569A1\_0007.png"\; state="\{\{state\}\}">\tau </figure-callout>}}_2}$

The calibration target control signal 30s-k2 differs from the calibration target control signal 30s-k1 in that the underlying uniform dwell time τ ₂ differs from the uniform dwell time τ ₁ of the calibration target control signal 30s-k1. As the end result of the second run, the signal conversion unit 64 determines an intensity curve I(t) _{τ 2} and therefrom an intensity distribution I ₂ ^m (x,y) designated with the reference numeral 66-2 on the surface 54.

In 2 a corresponding partial area of the intensity distributions 66-1 and 66-2 is shown, which corresponds to the area of two calibration points 56 on the surface 54. The calibration points 56 are each represented in the intensity distributions 66-1 and 66-2 by calibration patterns 68. Due to the dynamic effects of the control signal described above, the calibration patterns 68 deviate elliptically in their shape from a desired shape in the form of a circle 70, wherein the long semi-axis a of the ellipse is aligned parallel to the direction of movement of the particle beam 16. The deviation of the length of the semi-axis a from the radius of the underlying circular shape 70 depends on the dwell time 62; as a rule, the semi-axis a is larger the shorter the dwell time 62 is. Furthermore, the position P of the calibration pattern 68, also designated by the reference numeral 69, depends on the dwell time 62. The determination of the length a of the semi-axis or the determination of the deviation of the length a from the radius of the circular shape 70 thus represents a determination of the shape deviation 71 of the calibration pattern 68 from the circular shape 70.

The evaluation device 52 therefore determines by evaluating the intensity distribution 66-1 the length of the semi-axes a _i ^m (τ ₁ ) as well as the positions P _i ^m (τ ₁ ), in particular the length of the semi-axes a ₁ ^m (τ ₁ ) and a ₂ ^m (τ ₁ ) as well as the positions P ₁ ^m (τ ₁ ) and P ₂ ^m (τ ₁ ) of the two exemplary in 2 shown calibration pattern 68 for the dwell time τ ₁ . Analogously, the evaluation device 52 determines the length of the semi-axes a _i ^m (τ ₂ ) and the positions P _i ^m (τ ₂ ), in particular the length of the semi-axes a ₁ ^m (τ ₂ ) and a ₂ ^m (τ ₂ ) and the positions P ₁ ^m (τ ₂ ) and P ₂ ^m (τ ₂ ) of the two exemplary in 2 shown calibration pattern 68 for the residence time τ ₂ .

In the embodiment shown, the evaluation device 52 further comprises a simulation unit 72, which is configured to simulate the intensity distributions resulting from the two runs on the reflective surface 54 using the model 46 and the calibration target control signals 30s-k1 and 30s-k2. These are shown in 2 denoted by I ₁ ^ref (x,y) and I ₂ ^ref (x,y) respectively and correspond to the measured intensity distributions I ₁ ^m (x,y) and I ₂ ^m (x,y). The evaluation device 52 determines from the simulated intensity distributions I ₁ ^ref (x,y) and I ₂ ^ref (x,y) the length of the semi-axes a _i ^ref (τ ₁ ) and a _i ^ref (τ ₂ ) and if applicable the positions P _i ^ref (τ ₁ ) and P _i ^ref (τ ₂ ), in particular the length of the semi-axes a ₁ ^ref ₍ τ ₁ ), a ₂ ^ref (τ ₁ ), a ₁ ^ref (τ ₂ ) and a ₂ ^ref (τ ₂ ) and if applicable the positions P ₁ ^ref (τ ₁ ), P ₂ ^ref (τ ₁ ), P ₁ ^ref (τ ₂ ) and P ₂ ^ref (τ ₂ ) of the two exemplary in 2 shown simulated calibration pattern 68 for the residence times τ ₁ and τ ₂ .

According to one embodiment variant, the positions of the calibration points 56 on the surface 54 of the calibration object 48 are measured with a high degree of accuracy using a suitable position measuring device, such as a coordinate measuring machine 74. According to one embodiment, the accuracy is less than 10 µm, in particular less than 2 µm. The target positions P _i ^ref of the calibration patterns 68 in the intensity distributions 66-1 and 66-2, designated by the reference symbol 76, result from the measured positions.

A correction unit 78 of the evaluation device 52 now processes according to the 2 illustrated embodiment, the values of the semi-axes a _i ^m (τ ₁ ) and a _i ^m (τ ₂ ), the simulated semi-axes a _i ^ref (τ ₁ ) and a _i ^ref (τ ₂ ), the positions P _i ^m (τ ₁ ) and P _i ^m (τ ₂ ) measured by means of the detector 50, the target positions P _i ^ref determined by means of the coordinate measuring machine 74 and, if applicable, the target positions P _i ^ref (τ ₁ ) and P _i ^ref (τ ₂ ) determined by simulation and determines therefrom corrected transfer functions G _xx ^corr and G _yy ^corr for the model 46. In other words, the model 46 used by the signal correction module 44 in the processing mode of the shape processing device 10 is corrected by determining the corrected transfer functions G _xx ^corr and G _yy ^corr .

According to the 2 In the embodiment illustrated, the _correction unit 78 processes the data _mentioned by calculating the values of the semi-axes of the individual calibration points 56 are subtracted from one another (a _i ^m (τ ₁ ) - a _i ^m (τ ₂ )). The same is done for the simulated values of the semi-axes (a _i ^ref (τ ₁ ) - a _i ^ref (τ ₂ )). Furthermore, the positions P _i ^m (τ ₁ ) measured for the first dwell time τ ₁ by means of the detector 50 are subtracted from the target positions P _i ^ref determined by means of the coordinate measuring machine 74 (P _i ^m (τ ₁ ) - P _i ^ref ). The same is done with regard to the positions P _i ^m (τ ₂ ) measured for the second dwell time τ ₂ (P _i ^m (τ ₂ ) - P _i ^ref ). Before the difference is formed, the target positions P _i ^ref (τ ₁ ) and P _i ^ref (τ ₂ ) determined by simulation for the various dwell times τ ₁ and τ ₂ can optionally be compared with the target positions P _i ^ref determined by means of the coordinate measuring machine 74. Alternatively, the position values P _i ^ref (τ ₁ ) and P _i ^ref (τ ₂ ) can also be used instead of the position values P _i ^ref to form the difference between the position values.

After the difference formation described above, the correction unit 78 calculates the differences of the semi-axis values (a _i ^m (τ ₁ ) - a _i ^m (τ ₂ ) and a _i ^ref (τ ₁ ) - a _i ^ref (τ ₂ )) as well as the differences of the positions (P _i ^m (τ ₁ ) - P _i ^ref and P _i ^m (τ ₂ ) - P _i ^ref ).

By recalculating these calculation results, the corrected transfer functions G _xx ^corr and G _yy ^corr for the corrected model 46k are determined.

According to a further embodiment, the correction of the model 46 is carried out only on the basis of the deviation of the semi-axis a from the radius of the circular shape 70 determined for a dwell time τ or for several dwell times. The deviation determined for a dwell time already contains sufficient information for at least an approximate determination of the correction. Optionally, in this embodiment, further parameters mentioned above can be used to improve the accuracy of the correction determination.

According to a further embodiment, the correction of the model 46 is carried out only on the basis of the deviation of the respective position of the calibration patterns 68 from their target positions 76, determined for only one dwell time τ or for several dwell times. This deviation already contains sufficient information to at least approximately determine the correction. Optionally, in this embodiment, further parameters mentioned above can be used to improve the accuracy of the correction determination.

3 illustrates another embodiment of a method for calibrating the mold processing device 10. This differs from the embodiment according to 2 that instead of two calibration target control signals 30s-k1 and 30s-k2, each with a uniform dwell time τ ₁ or τ _2, a first target control signal 30s-k1 with a uniform dwell time τ ₁ for controlling the irradiation head in the first run and a further target control signal 30s-k3 with a varying dwell time τ _var (see reference numeral 62-3) for controlling the irradiation head 18 in the second run are specified.

In the lower right section of 3 the local intensity profile 67-1 in the x-coordinate direction of an exemplary intensity distribution, which was generated by means of the calibration target control signal 30s-k1 with the uniform dwell time τ ₁ , is shown. This intensity profile 67-1 corresponds, for example, to a line of an embodiment of the in 2 The calibration patterns 68 are visible as minima in the intensity curve 67-1. The intensity curve 67-1 shows the calibration patterns 68. 3 The local intensity curve 67-3 shown above the intensity curve 67-1 shows an example of the corresponding section of the intensity distribution generated by means of the calibration target control signal 30s-k3 with the varying residence time τ _var .

When evaluating the determined intensity distributions, the correction unit 78 forms intensity quotients at the individual locations of the intensity distributions by dividing the relevant intensity from the intensity distribution generated in the second run with the calibration target control signal 30s-k3 by the relevant intensity from the intensity distribution generated in the first run with the calibration target control signal 30s-k1. The result of this quotient formation is shown by way of example by the curve 67-q, which is created by forming the quotients of the intensity curves 67-1 and 67-3. Analogous to the evaluation according to 2 results in the evaluation according to 3 , which is based on the intensity quotients, corrected transfer functions G _xx ^corr and G _yy ^corr for the corrected model 46k.

The above description of exemplary embodiments, embodiments or variants is to be understood as exemplary. The disclosure made thereby enables the person skilled in the art to understand the present invention and the associated advantages, and on the other hand also includes obvious changes and modifications to the structures and methods described in the understanding of the person skilled in the art. Therefore, all such changes and modifications, insofar as they fall within the scope of the invention as defined in the appended claims, as well as equivalents, are intended to be covered by the protection of the claims.

list of reference symbols

10

mold processing device

12

surface

14

processing object

16

particle beam

16r

reflected particle beam

18

irradiation head

20

electron source

22

acceleration unit

24

focusing unit

26

steering module

28

place on the surface

30s

target control signal

30s-k1

first calibration target control signal

30s-k2

additional calibration target control signal

30s-k3

additional calibration target control signal

30i

actual control signal

32b

processing trajectory

32k

calibration trajectory

34

processing area

36

usable space

38

trajectory section

40

point of incidence

42

control device

44

signal correction module

46

Model

48

calibration object

50

ring-shaped detector

52

evaluation device

54

reflective surface

56

calibration points

57

points between the calibration points

58

through hole

60

recess

62

dwell time

64

signal conversion unit

66-1

intensity distribution

66-2

intensity distribution

67-1

local intensity profile

67-3

local intensity profile

67-q

course of the intensity quotient

68

calibration sample

69

position of the calibration pattern

70

circular shape

71

form deviation

72

simulation unit

74

coordinate measuring machine

76

target positions

78

correction unit

QUOTES INCLUDED IN THE DESCRIPTION

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

Cited patent literature

• DE 102012212199 A1 [0002]

Claims (15)

Method for calibrating a shape processing device (10) which is configured to manipulate a shape of a surface (12) of a processing object (14) by irradiating a beam (16) of charged particles and, in doing so, to direct the beam in a time-dependent sequence to different locations (28) on the surface of the processing object on the basis of a time-dependent target control signal (30s), wherein the shape processing device comprises a signal correction module (44) and a steering module (26), wherein the signal correction module is configured to convert the target control signal into an actual control signal (30i) for controlling the steering module by means of a predetermined model (46), and wherein the method comprises the steps: - providing a calibration object (48) with a surface (54) reflecting the charged particles, which surface comprises a plurality of calibration points (56) with a reflectivity that is different from the remaining reflecting surface, - irradiating the beam (16) onto the reflective surface (54) of the calibration object at the calibration points (56) and further points (57) of the surface and detecting a respective intensity of particles of the irradiated beam reflected at the reflective surface, and - correcting the model (46) based on the detected intensities (66-1; 66-2). procedure according to claim 1 , in which the intensities result in an intensity distribution (66-1; 66-2) resolved with respect to the surface of the calibration object, in which the calibration points (56) are each assigned to a calibration pattern (68), wherein the method further comprises evaluating the intensity distribution, in which a deviation (71) of a shape of at least one of the calibration patterns from a desired shape (70) of the calibration pattern is determined, wherein the at least one specific shape deviation is taken into account in the correction. procedure according to claim 2 , in which an elliptical deviation of at least one of the calibration patterns (68) from a circular shape (70) is determined when evaluating the intensity distribution. Method according to one of the preceding claims, in which the intensities result in an intensity distribution (66-1; 66-2) resolved with respect to the surface (54) of the calibration object (48), in which the calibration points (56) are assigned to a respective calibration pattern (68), wherein the method further comprises evaluating the intensity distribution, in which a deviation of a respective position (69) of at least one of the calibration patterns from a target position (76) of the calibration pattern is determined, wherein the at least one specific position deviation is taken into account in the correction. procedure according to claim 4 , in which, before the beam (16) is irradiated onto the surface (54) of the calibration object, a respective position of at least one of the calibration points (56) on the surface of the calibration object is measured with an accuracy of less than 10 µm and the target position (76) of the calibration pattern (68) used to determine the position deviation is determined therefrom. Method according to one of the preceding claims, in which the intensity of the particles reflected at the surface (54) of the calibration object (48) is detected by means of an annular detector (50), through the interior (60) of which the beam (16) irradiated onto the surface passes. Method according to one of the preceding claims, in which the beam is irradiated onto the surface of the calibration object along a predetermined trajectory (32k) which comprises the calibration points (56) and the further points (57) of the surface of the calibration object. Method according to one of the preceding claims, in which the beam is irradiated in at least one pass onto the irradiation points comprising the calibration points (56) and the further points (57) of the surface of the calibration object and is moved over the surface between the irradiation points, the irradiation points in the at least one pass being irradiated with uniform dwell times (62). Method according to one of the preceding claims, in which the beam (16) is irradiated in a plurality of passes onto the irradiation points comprising the calibration points (56) and the further points (57) of the surface (54) of the calibration object and is moved over the surface between the irradiation points, wherein the irradiation points are irradiated in the individual passes with uniform dwell times (62-1, 62-2) and the uniform dwell times are different in the various passes. Method according to one of the preceding claims, in which in a first pass the irradiation points comprising the calibration points (56) and the further points (57) of the surface of the calibration object are each measured with uniform residence times (62-1) and in a second pass the irradiation points are irradiated with varying residence times (62-3). procedure according to claim 10 , in which a quotient of the recorded intensity of the first pass and the recorded intensity of the second pass is determined at the respective incident point and the model is corrected using the intensity quotients (67-q). Method according to one of the preceding claims, wherein the calibration object (48) in the region of the reflective surface (54) comprises a metal having an atomic number of at least forty. Method according to one of the preceding claims, in which the reflective surface (54) at the calibration points (56) differs from the remaining reflective surface by a changed topography. A method according to any preceding claim, wherein the beam of charged particles is an electron beam (16). Method for changing a shape of a surface (12) of a processing object (14) with the steps: - providing a shape processing device (10) which comprises a signal correction module (44) and a steering module (26), wherein the signal correction module is configured to convert a time-dependent target control signal (30s) into an actual control signal (30i) for controlling the steering module by means of a predetermined model (46), - calibrating the shape processing device by correcting the model (46) according to the method according to one of the preceding claims, and - manipulating the shape of the surface (12) of the processing object by means of the shape processing device (10), wherein the actual control signal is generated by the signal correction model from the target control signal based on the corrected model (46k), the beam (16) is irradiated onto the surface of the processing object and the beam is guided by the steering module based on the generated actual control signal is deflected such that it is directed to different locations (56, 57) on the surface of the object being processed.

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