TW201808782A - MEMS devices and processes - Google Patents

Abstract

A MEMS transducer structure comprises a substrate comprising a cavity. A membrane layer is supported relative to the substrate to provide a flexible membrane. A peripheral edge of the cavity defines at least one perimeter region that is convex with reference to the center of the cavity. The peripheral edge of the cavity may further define at least one perimeter region that is concave with reference to the center of the cavity.

Description

MEMS devices and processes

Embodiments of the present invention relate to microelectromechanical systems (MEMS) devices and processes, and in particular to a MEMS device and process associated with a sensor (eg, a condenser microphone).

Various MEMS devices are becoming more and more popular. MEMS sensors, and in particular MEMS condenser microphones, are increasingly being used in portable electronic devices such as mobile phones and portable computing devices.

A microphone device formed using a MEMS manufacturing process typically includes one or more movable diaphragms and a static backing plate, wherein respective electrodes are deposited on the diaphragm and the backing plate, one of the electrodes for reading/driving and the other electrode for Bias, and wherein the substrate supports at least the diaphragm and typically also supports the backing plate. In the case of MEMS pressure sensors and microphones, readout is typically achieved by measuring the capacitance between the diaphragm electrode and the backplate electrode. In the case of a sensor, the device is driven (i.e., biased) by a potential difference provided across the diaphragm electrode and the backplate electrode.

1a and 1b show schematic and perspective views, respectively, of a known capacitive MEMS microphone device 100. The condenser microphone device 100 includes a diaphragm layer 101 that forms a flexible diaphragm that is free to move in response to a pressure difference generated by sound waves. The first electrode 103 is mechanically coupled to the flexible diaphragm and the two together form a first capacitive plate of the condenser microphone device. The second electrode 102 is mechanically coupled to a substantially rigid structural layer or backing plate 104 that together form a second capacitive plate of the condenser microphone device. The example shown in Figure 1a The second electrode 102 is embedded in the backplane structure 104.

The condenser microphone is formed on a substrate 105 (for example, a germanium wafer) on which an upper oxide layer 106 and a lower oxide layer 107 are formed. Cavities or vias 108 (also referred to hereinafter as substrate cavities) in the substrate and in any of the overlying layers are provided beneath the diaphragm and may be formed, for example, through etch back through the substrate 105. The substrate cavity 108 is connected to a first cavity 109 located directly below the diaphragm. These cavities 108 and 109 can collectively provide an acoustic volume, thus allowing the diaphragm to move in response to acoustic stimuli. The second cavity 110 is interposed between the first electrode 103 and the second electrode 102.

A plurality of holes, hereinafter referred to as vent holes 111, connect the first cavity 109 and the second cavity 110.

A further plurality of holes, hereinafter referred to as sound holes 112, are disposed in the backing plate 104 to allow free movement of air molecules through the backing plate such that the second cavity 110 forms an acoustic relationship with the space on the other side of the backing plate. Part of the volume. The diaphragm 101 is thus supported between two volumes, one volume containing the cavity 109 and the substrate cavity 108 and the other volume containing the cavity 110 and any space above the backing plate. These volumes are sized such that the diaphragm can move in response to sound waves entering through one of the volumes. Generally, the volume through which an incident sound wave reaches the diaphragm is referred to as a "front volume", and another volume that can be substantially sealed is referred to as a "post volume."

In some applications, the backing plate can be disposed in the front volume such that incident sound reaches the diaphragm via the acoustic holes 112 in the backing plate 104. In this case, the size of the substrate cavity 108 can be set to provide at least a substantial portion of the appropriate subsequent volume.

In other applications, the microphone can be configured such that sound can be received through the substrate cavity 108 in use, i.e., the substrate cavity forms part of the channel of the diaphragm and a portion of the front volume. In such applications, the backing plate 104 forms part of the back volume that is typically closed by some other structure, such as a suitable package.

It should also be noted that although FIG. 1 shows that the backing plate 104 is being supported on the side of the diaphragm opposite the substrate 105, it is known that the backing plate 104 is formed to be closest when the diaphragm layer 101 is supported above the substrate. Substrate.

In use, the diaphragm is slightly deformed from its equilibrium position in response to sound waves corresponding to the pressure waves incident on the microphone. The distance between the lower electrode 103 and the upper electrode 102 is correspondingly changed, causing a change in capacitance between the two electrodes, which is then detected by an electronic circuit (not shown). The venting aperture allows the pressure in the first cavity and the second cavity to equalize over a relatively long time scale (in terms of audio), which reduces, for example, the effects of low temperature pressure changes due to temperature changes and the like. , but does not significantly affect the sensitivity of the desired audio.

Those skilled in the art will appreciate that MEMS sensors are typically formed on a wafer prior to singulation. It is increasingly proposed to provide, for example, at least some of the electronic circuitry for sensor readout and/or drive as part of an integrated circuit having sensors. For example, a MEMS microphone can be formed as an integrated circuit having at least some of the amplifier circuits and/or some circuitry for biasing the microphone. The footprint of the area required by the sensor and any circuitry will determine how many devices can be formed on a given wafer and thus affect the cost of the MEMS device. Therefore, it is often desirable to reduce the footprint required to fabricate MEMS devices on a wafer.

In addition to being suitable for use in portable electronic devices, such sensors should also be capable of withstanding the intended handling and use of the portable device, which may include the device being accidentally dropped.

If a device such as a mobile phone experiences a drop, this can cause not only a mechanical shock due to the impact, but also a high voltage pulse incident on the MEMS sensor. For example, a mobile phone can have a voice 用于 for a MEMS microphone on one side of the device. If the device falls on this side, some of the air can be compressed by the falling device and forced into the squeak. This can cause high voltage pulses incident on the sensor. It has been found that high voltage pulses in conventional MEMS sensors can cause damage to the sensor.

To help prevent any damage that can be caused by such high voltage pulses, it has been proposed that MEMS sensors can be provided with variable vents that provide a variable size between the front and back volumes in use. The flow path. In the case of high pressure, the variable vents provide a relatively large flow path between the volumes to provide a relatively rapid balance between volumes, thereby reducing the extent and/or duration of high pressure events on the diaphragm. However, at lower pressures, the flow path (if present) will be smaller in the expected normal operating range of the sensor.

The variable vent structure thus acts as a type of pressure relief valve to reduce the differential pressure acting on the diaphragm at relatively high differential pressures. However, unlike a venting aperture that may be present in the diaphragm having a fixed area and thus a fixed size flow path, the variable vent has a flow path size that varies in response to the pressure differential. Thus, the extent to which the variable vents permit ventilation depends on the differential pressure acting on the vents, which is significantly dependent on the pressure of at least one of the first volume and the second volume. The variable vents thus provide a variable acoustic impedance.

It will be appreciated that in the diaphragm layer of a MEMS sensor, when the atom of the material is displaced from its equilibrium position due to the action of the force, the material is said to be affected by the stress. Therefore, the force that increases or decreases the interatomic distance between the atoms of the diaphragm layer creates stress in the diaphragm. For example, the diaphragm layer exhibits inherent or intrinsic residual stress when in equilibrium (i.e., when a differential pressure is created across the diaphragm or a negligible differential pressure is created). Further, for example, stress may be generated in the diaphragm layer due to the manner in which the diaphragm is supported in a fixed relationship with respect to the substrate or due to acoustic pressure waves incident on the diaphragm.

The MEMS sensor according to the present invention is intended to respond to acoustic pressure waves that generate transient stress waves on the surface of the diaphragm. Thus, it will be appreciated that the stress exhibited in the diaphragm layer when moving in equilibrium and during use may have a detrimental effect on the performance of the sensor, as described below.

Figure 2 shows a cross-sectional view through a typical sensor structure. Sensor structure contains The diaphragm 101 is movable relative to the rigid backing plate 104 during use. The diaphragm 101 and the backing plate 104 are supported by a substrate 105 that includes a cavity or through hole 108. The electrodes and other features are not shown in Figure 2 for purposes of clarity.

Referring to Figure 3, during movement of the diaphragm 101 during use, and particularly during high input acoustic pressure or extreme conditions such as falling of a mobile device, the diaphragm 101 is likely to contact the substrate 105 that provides support for the diaphragm. For example, the diaphragm 101 may contact the peripheral edge of the substrate 105 that forms a cavity within the substrate, as illustrated by arrow 30.

Embodiments of the present invention generally relate to improving the efficiency and/or performance of sensor structures. Aspects of the invention also relate to mitigating and/or re-stressing the stress within the diaphragm layer, including when the diaphragm is moved or flexed during use.

Aspects of the invention are also directed to relieving and/or diffusing and/or redanging stresses that are created in the membrane when the membrane is displaced during use such that the membrane contacts the substrate supporting the membrane.

According to a first aspect, a MEMS sensor structure is provided that includes a substrate that includes a cavity. The MEMS sensor structure includes a diaphragm layer that is supported relative to the substrate to provide a flexible diaphragm. One of the peripheral edges of the cavity defines at least one perimeter region that is raised relative to a center of the cavity.

The MEMS sensor structure as defined above has the advantage that if the diaphragm contacts one of the peripheral edges of the cavity during use, the diaphragm first contacts the raised portion prior to contacting another portion of the peripheral edge of the cavity .

According to another aspect, a MEMS sensor structure is provided that includes a substrate that includes a cavity. The MEMS sensor structure includes a diaphragm layer supported relative to the substrate to provide a flexible diaphragm, wherein the diaphragm layer includes an active central region and a plurality of support arms, the support arms laterally from the active central region Extending for supporting the diaphragm The central area of action. One of the peripheral edges of the cavity defines at least first and second perimeter regions that are recessed relative to the center of the cavity.

Features of any given aspect can be combined with features of any other aspect, and the various features described herein can be implemented in any combination in any given embodiment.

An associated method of fabricating a MEMS sensor is provided for each of the above aspects.

30‧‧‧ arrow

55‧‧‧The edge of the support arm

61‧‧‧perimeter/protruding

63‧‧‧Zhoujie District

63a‧‧‧First recessed part/first perimeter area

63b‧‧‧Second recessed/second perimeter

65‧‧‧ Edge of the support arm / S-shaped curve

65a‧‧‧First edge/S-shaped curve

65b‧‧‧Second edge/S-shaped curve

100‧‧‧Capacitive MEMS microphone device

101‧‧‧ diaphragm layer

102‧‧‧second electrode

103‧‧‧First electrode/diaphragm electrode

104‧‧‧Structural or backplane/backplane structure

105‧‧‧Substrate

106‧‧‧ upper oxide layer

107‧‧‧lower oxide layer

108‧‧‧cavity or through hole/substrate cavity

109‧‧‧First cavity

110‧‧‧Second cavity

111‧‧‧ venting holes

112‧‧‧ Sound hole

300‧‧‧ sensor

301‧‧‧First diaphragm zone/action diaphragm zone/action center zone

302‧‧‧Second/Non-active diaphragm area

303‧‧‧Support arm

304‧‧‧channel or gap

305, 306‧‧‧ installation table

308‧‧‧ dotted line

318‧‧‧ peripheral edge of the cavity / thicker dashed line

For a better understanding of the present invention, and in order to demonstrate the embodiments of the present invention, reference will now be made to the accompanying drawings in which FIG. 1a and FIG. 1b illustrate a cross-sectional view and perspective view of a known MEMS microphone structure; FIG. A cross-sectional view through the MEMS sensor structure is illustrated; FIG. 3 illustrates the deflection of the diaphragm in the MEMS sensor structure of FIG. 2; FIG. 4 illustrates a plan view of the MEMS sensor structure; FIG. 5 illustrates a plan view of the MEMS sensor structure; Section of the MEMS sensor structure; Figure 6b illustrates a section of a MEMS sensor device in accordance with another embodiment; Figure 6c illustrates a section of a MEMS sensor device in accordance with another embodiment; Figure 6d illustrates a MEMS in accordance with another embodiment Section of the sensor device; Figure 7 is an example of a MEMS sensor device in accordance with an embodiment; and Figure 8 illustrates a section of a MEMS sensor device in accordance with an embodiment.

In sensors such as those described above with respect to Figures 1a, 1b, 2, and 3, the diaphragm layer may be formed of a material such as tantalum nitride and may be deposited to have inherent residual stresses in the diaphragm during equalization. The diaphragm is thus formed so as to be substantially supported around its entire circumference. The diaphragm can thus be considered to be affected by the tension, which is equivalent to the drum skin stretched over the frame. Thus, to provide uniform behavior and uniform stress distribution, the membrane is typically formed into a generally circular configuration.

For example, to form the sensor structure illustrated in FIG. 1a, one or more pedestal layers can be formed on the substrate 105, and then the sacrificial material layer can be deposited and patterned to form a substantially circular shape. The sacrificial material is used to define the space in which the cavity 109 will be formed. One or more layers may then be deposited on the sacrificial material to form the membrane 101. The venting opening 111 can be formed in the diaphragm layer along with any venting structure such as described with reference to Figure 2a or Figure 2b. A further layer of sacrificial material can then be deposited on top of the separator and patterned to define the cavity 110. A backing layer can then be deposited. To form the substrate cavity 108, etch back can be performed. To ensure that the sacrificial material, rather than the block etchback, which would be less accurate, defines the cavity 109, it is ensured that the opening of the substrate cavity is smaller than the cavity 109 and is located within the area of the cavity 109. The sacrificial material can then be removed to exit the cavities 109 and 110 and release the septum. The diaphragm layer thus extends into the side wall structure which also supports the backing plate. All sides of the flexible membrane itself are supported and constrained and are substantially circular in shape.

Although this type of process produces good device properties, the use of a circular diaphragm tends to result in some inefficient use of the germanium wafer.

For a variety of reasons, it is most common and/or cost effective to treat the 矽 region in a generally rectangular block area. Thus, the area designated on the germanium wafer for the MEMS sensor is typically substantially square or rectangular in shape. This area needs to be large enough to cover a generally circular sensor structure. This is often inefficient for wafer use, since the corner regions of this designated sensor area are not effectively used. This limit can be made on the number of sensor structures and circuits on a given wafer. Of course, it will be possible to fit more sensors on the wafer by reducing the size of the sensor, but this will have any effect on the resulting sensitivity and is therefore undesirable.

In the embodiments described herein, the sensor is based on a design that utilizes substantially rectangular or square regions more efficiently. For a given sensor sensitivity, this design is equivalent The circular design requires a smaller area.

Figure 4 illustrates an example of a sensor 300 whereby different shapes are used instead of a circular diaphragm. Figure 4 illustrates the sensor diaphragm 101 and thus the section through the sensor, but the backing plate can have substantially the same shape. The membrane is not substantially circular in shape and instead has a polygonal shape in this example. In general, the membrane has a shape that will substantially fill a square region defined by the perimeter of the membrane. In other words, if one considers that it will completely contain the smallest possible square area of the membrane 101, the membrane will cover a larger proportion of this area, for example the membrane may cover at least 90% of this square area. It will be appreciated that for a circular diaphragm of diameter D, the smallest square area will have the side of D. The area of the circle (π.D ² /4) will thus cover approximately 78% of the area (D ² ) of this square.

The entire area illustrated in Figure 4 is provided with a layer of membrane material. However, in the example illustrated in FIG. 4, the membrane material layer is divided into a first membrane region 301 (which will be referred to herein as an active membrane region or simply as an active membrane), and a plurality of second regions 302 ( It will be referred to as a non-active membrane zone or an inactive membrane). The inactive diaphragm region 302 is illustrated in FIG. 4 by a shaded region, wherein the unshaded region corresponds to the active diaphragm 301.

Thus, the active diaphragm includes a central region supported by a plurality of arms 303 (eg, where the diaphragm electrode 103 will be positioned). In some embodiments, the arms can be evenly distributed substantially around the perimeter of the diaphragm. The substantially uniform distribution of the arms can help to avoid undesirable stress concentrations. In the example illustrated in Figure 4, there are four arms 303, and thus there are four separate non-active diaphragm zones 302, although it will be appreciated that in other embodiments there may be more or fewer arms, but preferably. There will be at least three arms in the ground.

Thus, there is one or more channels or gaps 304 between the active diaphragm 301 and the material of the inactive membrane region 302. Conveniently, a continuous layer of separator material can be deposited during fabrication, and then channel 304 can be etched through the membrane material to form active and inactive regions. The channels may be shaped such that the side edges of the arms exhibit a smooth or continuous profile rather than being formed by one or more straight lines. This case is illustrated in FIG. 5 described later.

Each arm 303 of the active diaphragm region 301 can include at least one mounting station 305 for the diaphragm layer relative to the substrate and possibly also to the backing plate support active region 301. A mounting station 306 for supporting the inactive diaphragm region may also be present in the inactive diaphragm region.

Mounting stations 305 and 306 can take a variety of forms. For example, the mounting station can include sidewalls of the sensor structure and the diaphragm layer can extend into the sidewalls. However, in some examples, the mounting station can be a region of the diaphragm material that contacts the substrate or the support structure that is raised from the substrate. The mounting station may also include an area for the support structure of the backing plate to contact the diaphragm. The diaphragm at the mounting station is thus effectively held in place and prevented from any substantial movement relative to the substrate and/or backing plate.

The material of the diaphragm layer can thus be deposited within the intrinsic stress as previously described. The plurality of arms of the active zone 301 are generally diffused away from the center of the active diaphragm and can therefore be used to effectively maintain the diaphragm in tension. As mentioned, the arms can be evenly spaced around the active diaphragm. Additionally, the mounting points of the active diaphragm 301 (e.g., mounting station 305) may be substantially equidistant from the center of the active diaphragm - even having a substantially square diaphragm layer. It is possible that this is because the membrane material at the "side" of the square configuration has been separated into non-active membrane regions that are not directly connected to the active membrane region. This configuration therefore means that the stress distribution in the central portion of the active diaphragm is substantially uniform when it is at equilibrium and the active diaphragm is deflected by the incident pressure stimulus, wherein most of the stress modulation occurs instead in the arms. . The active diaphragm will thus behave in a manner similar to a circular diaphragm whose perimeter is constrained. All sides are constrained to be the condition of a square diaphragm or a polygonal diaphragm as illustrated in Figure 4.

This design is advantageous because it provides an active diaphragm region having a response similar to a circular diaphragm having a radius equal to the distance between the center of the diaphragm and the mounting table 305 of the arm. However, to make this corresponding circular diaphragm, the sensor would require a larger rectangular area of the substrate. Therefore, by using a design such as that illustrated in Figure 4, compared to a circular diaphragm having similar performance, The area required for the sensor on the wafer can be reduced.

However, when this type of MEMS sensor is subjected to stress conditions such as high acoustic signals, including, for example, when a portable device containing a MEMS sensor is dropped, the diaphragm may occur to the extent that the active diaphragm region contacts the substrate supporting the diaphragm. deflection. Referring to Figure 4, it will be appreciated that since each arm 303 of the active diaphragm region 301 is deflected toward the support substrate, after extreme conditions, each arm 303 will contact the edge of the substrate when forming a cavity or through hole, the cavity The edge is illustrated by dashed line 308.

This point is further illustrated in Figure 5, which shows that the initial point of contact between the active diaphragm region and the edge 318 of the cavity is at the edge 55 of the support arm 303 that acts on the diaphragm region. This can cause the diaphragm to become damaged when the support arm 303 acting on the diaphragm region contacts the edge 318 in the cavity of the support substrate.

This is especially the case when the diaphragm is considered to be affected by the intrinsic stress, whereby the support arm 303 maintains the intrinsic stress in the diaphragm.

Figure 6a shows an example of a MEMS sensor structure in accordance with an embodiment. In Figure 6a, only a plan view of a section of a MEMS sensor is shown for purposes of clarity. Figure 6a shows a plan view of a diaphragm layer of, for example, a sensor structure similar to the sensor structure of Figure 4, having a central region 301 and a plurality of support arms 303 (one of the support arms shown in this section), and Inactive diaphragm zone 302. The peripheral edge 318 of the underlying cavity within the substrate supporting the diaphragm is shown in dashed lines. It will be appreciated that since Figure 6a shows a cross-sectional view through the diaphragm layer, the MEMS sensor structure can include other features such as a rigid backing plate (not shown).

Thus, in accordance with an embodiment, a MEMS sensor structure includes a substrate that includes a cavity. The membrane layer is supported relative to the substrate to provide a flexible membrane. The peripheral edge 318 of the cavity defines at least one perimeter region 61 that is raised relative to the center of the cavity.

It should be noted that the reference to the center of the cavity herein means that the traverse cavity is parallel to the The center of the plane of the distorted diaphragm.

It should also be noted that the reference to the term bulge herein is intended to encompass not only the perimeter region that provides the curved path of the convex shape (ie, the contour or surface of a smooth or continuous curve that resembles a circle or a spherical outer shape), but also A perimeter region comprising at least one of the first and second linear segments that meet at one or more points to define a raised region is contemplated. The term bump is also intended to encompass a perimeter region having a plurality of bitwise linear segments that together form a raised region or form a convex curved path. Thus, in the embodiment of Figure 6a and other embodiments described herein, the raised portion may comprise a curved path, or a series of two or more than two bitwise linear portions.

The raised portion 61 of the perimeter region in the peripheral edge of the cavity has the advantage that if the flexible membrane is deflected significantly toward the underlying substrate and cavity during use, for example, in response to a high acoustic input signal or device drop, The central region of the support arm 303 (crossing the width of the support arm 303) will contact the raised portion 61 in the peripheral edge of the cavity in the substrate before the edge 65 of the support arm 303 contacts the peripheral edge. In this manner, since the central region of the support arm 303 is first contacted, this inherently stronger central region absorbs energy, thereby reducing the likelihood of the membrane tearing or damaging at its edges.

In the embodiment of Figure 6a, the raised portion 61 of the peripheral edge 318 of the cavity rests under the central region of the support arm 303 of the diaphragm.

Reference is made to Figure 6b in accordance with another embodiment. As with Figure 6a, the raised portion 61 of the peripheral edge of the cavity rests under the central region of the support arm 303 of the diaphragm. As mentioned above, after the diaphragm has undergone considerable deflection during use, this means that a relatively strong portion of the diaphragm first contacts the cavity edge 318.

Additionally, the peripheral edge 318 of the cavity in Figure 6b further defines at least one perimeter region 63 that is recessed relative to the center of the cavity.

It should be noted that in a manner similar to the term bump as described above, in this document Reference to the term recess is intended to encompass not only the perimeter region that provides the curved path of the concave shape (ie, a contour or surface that is curved inwardly like a circle or sphere), but also encompasses one or more points. Meeting to provide a perimeter region of at least the first and second linear segments of the recessed region. The term recess is also intended to encompass a perimeter region having a plurality of bitwise linear segments that together form a recessed region. Thus, in the embodiment of Figure 6b and other embodiments described herein, the recessed portion may comprise a curved path, or a series of two or more than two bitwise linear portions.

In an example such as the one shown in Figure 6b, the diaphragm includes an active central zone and a plurality of support arms 303 (one of which is shown for clarity) extending laterally from the active central zone Used to support the central area of the diaphragm.

The apex of the raised portion 61 may lie above and below the center of the support arm 303 substantially in the lateral direction.

The recessed perimeter region includes recessed portions 63a and 63b of the peripheral edge of the cavity underlying the edge of the support arm 303 (the edges 65a, 65b are the active portions of the diaphragm 303 and the non-acting portion 302 of the diaphragm layer) The gap between them, as explained earlier with reference to Figure 4).

This has the advantage that the relatively weaker portion of the diaphragm (i.e., the edges 65a, 65b of the support arm 303) is less likely to contact the cavity edge 318, or in the event of contact, the stronger raised portion 61 will first diffuse from Most of the force or energy of the impact.

Thus, in accordance with some embodiments, the raised portion is positioned about the periphery of the cavity such that after the flexible membrane is deflected toward the cavity during use, the flexible membrane contacts prior to contacting another portion of the peripheral edge of the cavity a raised portion of the peripheral edge of the cavity.

For example, in the case of a diaphragm of this type having an active diaphragm region supported by a plurality of support arms, the raised portion is positioned around the periphery of the cavity such that after the flexible diaphragm is deflected toward the cavity during use The central portion of the support arm of the flexible diaphragm contacts the raised portion on the peripheral edge of the cavity just prior to contacting the edge region of the support arm.

According to an embodiment of the invention, the concave portion (e.g., the concave portion 63a, 63b) is positioned around the periphery of the cavity such that after the flexible membrane is deflected toward the cavity during use, the flexible membrane is in contact Another portion of the peripheral edge of the cavity then contacts the recessed portion.

By way of example, in the case of a diaphragm of this type having an active diaphragm region supported by a plurality of support arms, generally the recessed portion is positioned around the periphery of the cavity such that the flexible membrane is oriented during use. After the cavity is deflected, the edge of the support arm of the flexible diaphragm contacts the recessed portion on the peripheral edge of the cavity just after contacting the central region of the support arm.

The embodiment of Figure 6b shows a MEMS structure in which the first recessed portion 63a and the second recessed portion 63b are positioned or configured around the perimeter of the cavity such that after the flexible membrane is deflected toward the cavity during use, The first edge 65a and the second edge 65b of the support arm 303 of the flexible diaphragm contact the recessed portions 63a, 63b on the peripheral edge of the cavity just after contacting the central portion of the support arm 303.

Referring to Figure 6c, according to another aspect, the cavity can be considered to have a nominal shape having, for example, a substantially circular, rectangular, pentagonal or octagonal shape. Figure 6c shows a section taken from an example in which the nominal shape of the cavity is similar to the shape of Figure 5, which is illustrated by the thicker dashed line 318 on the side and the thinner dashed line in the corner section. In other words, the nominal shape of the cavity is a rectangular shaped cavity having curved corners. According to some embodiments, the perimeter of the cavity may thus be defined to include a nominal shape, and wherein the raised portion 61 extends inwardly toward the center of the cavity compared to the nominal shape of the cavity. In a similar manner, according to some embodiments, the perimeter of the cavity includes a nominal shape, and wherein the recessed portions 63a, 63b extend outwardly away from the center of the cavity, as compared to the nominal shape of the cavity.

The recessed portions 63a, 63b can have a radius of curvature that is less than the radius of curvature of at least one other portion of the peripheral edge, such as a concave portion that forms part of the nominal shape of the cavity.

According to another aspect as illustrated in Figure 6d, the edge portion of the support arm 303 A path segment can be included that includes one or more bend points, such as a sigmoid curve 65. One or more bend points or S-curves 65a, 65b on the diaphragm overlie respective recessed portions 63a, 63b on the peripheral edge of the cavity. Further details of this aspect and its advantages can be found in more detail in the application P3087, which is also filed by the same applicant in the present application.

In the same application, a MEMS sensor is defined that includes a flexible membrane that is supported at a support edge relative to a substrate. The flexible diaphragm includes a first unrestricted edge, wherein the first unrestricted edge depicts a path from a first end at or near the first end of the support edge. a first path segment is defined between a first path point and a second path point on the first unconstrained edge, and wherein the first path segment depicts a linear path between the first path point and the second path point The distance path varies, and the first path segment includes at least two bend points at which the flexible diaphragm tends to bend in response to a given deflection of the flexible diaphragm.

The MEMS sensor can include a second unrestricted edge depicting a path from a first end at or near the second end of the support edge, wherein the second path segment of the second unrestricted edge is defined by the second unrestricted Between the first path point and the second path point on the edge, and wherein the second path segment depicts a path having a changed distance from the linear path between the first path point and the second path point, the second path segment One or more bend points are included at which the flexible membrane tends to bend in response to a given deflection of the flexible membrane.

In accordance with another embodiment, a MEMS sensor can include a flexible diaphragm supported at a support edge relative to a substrate, the diaphragm including respective extensions extending at or near the first end and the second end of the support edge An unrestricted edge and a second unrestricted edge, wherein the first unrestricted edge and the second unrestricted edge each depict a path, the path segment defining a first path point and a second on each of the unrestricted edges Between path points, each path segment contains at least two bending points at which the flexible diaphragm tends to respond to the flexible diaphragm It bends for a given deflection.

7 shows a complete view of a MEMS sensor structure in accordance with the embodiment of FIG. 6d, wherein the sensor includes a substrate including a cavity, the edges of which are illustrated by dashed lines 318. The diaphragm layer is supported relative to the substrate to provide a flexible membrane. In this example, the diaphragm includes an active central zone 301 and a plurality of support arms 303 that extend laterally from the active central zone for supporting the active central zone of the diaphragm.

The peripheral edge 318 of the cavity defines at least one perimeter region 61 that is raised relative to the center of the cavity.

The peripheral edge 318 of the cavity defines a first recessed portion 63a and a second recessed portion 63b corresponding to each of the support arms 303, whereby the first recessed portion 63a and the second recessed portion 63b surround the periphery of the cavity The positioning is such that the concave portions lie under the corresponding first edge 65a and second edge 65b of the support arm 303.

The first recessed portion 63a and the second recessed portion 63b are positioned around the periphery of the cavity such that after the flexible diaphragm is deflected toward the cavity during use, the first edge 65a of the support arm 303 of the flexible diaphragm and The second edge 65b contacts the recessed portions 63a, 63b on the peripheral edge of the cavity just after contacting the central portion of the support arm 303.

Moreover, the embodiment of Figure 7 includes a support arm 303: the edge portions 65a, 65b of the support arm (303) include one or more bend points, such as an S-shaped curve. One or more bend points or sigmoidal curves (65a, 65b) on the diaphragm overlie the recessed portions (63a, 63b) on the peripheral edge of the cavity.

Figure 8 depicts an embodiment similar to Figure 7, but excluding the raised portion 61 of Figure 7. Thus defining a MEMS sensor structure comprising: a substrate comprising a cavity, the diaphragm layer being supported relative to the substrate to provide a flexible diaphragm, wherein the diaphragm layer comprises an active central region and a plurality of support arms 303, the supports The arm extends laterally from the center of action for use The central portion of the diaphragm is supported, and wherein the peripheral edge of the cavity defines at least a first perimeter region 63a and a second perimeter region 63b that are recessed relative to a center of the cavity.

The first perimeter zone 63a and the second perimeter zone 63b extend away from the center of the cavity. The first perimeter zone 63a and the second perimeter zone 63b have a smaller radius of curvature than other recessed portions of the peripheral edge of the cavity. The perimeter regions 63a, 63b lie under the edges 65a, 65b on the support arm 303.

This embodiment also has the advantage of reducing the likelihood that the edge of the support arm will contact the edge of the substrate.

As can be seen from the above, the embodiments described herein help to reduce stress and damage to the diaphragm layer in MEMS sensor structures.

In the embodiments described herein, according to some examples, the cavity includes a through hole through the substrate.

In the embodiments described herein, according to some examples, the cavity forms part of a larger cavity within the substrate.

In the embodiments described herein, according to some examples, a cavity is formed in a surface of the substrate corresponding to the side on which the diaphragm is supported.

The cavity can be formed, for example, using a sacrificial layer (eg, when the cavity is similar to the type of cavity 109 shown in Figure Ia).

In other examples, the cavity is formed using an etch process (eg, etch back through the substrate).

The cavity can form a portion that passes through a larger through hole of the substrate. In some embodiments, the perimeter of the cavity is the same shape as the perimeter of the via. In other embodiments, the perimeter of the cavity is different from the perimeter of the via.

In some examples, the perimeter of the cavity includes at least one raised and recessed portion, and wherein the perimeter of the through opening has a circular or rectangular or pentagonal or octagonal shape.

In embodiments including a plurality of support arms, a plurality of raised and/or recessed portions as described above may be provided. In embodiments having a plurality of support arms, the support arms are evenly spaced about the central region of action of the diaphragm.

In some examples, the membrane is generally square or rectangular in shape, and wherein the central region of the membrane is affected by intrinsic stress.

In the embodiments described herein, the cross-section of the perimeter of the cavity is in a plane parallel to the surface of the substrate.

A MEMS sensor in accordance with embodiments described herein may include a capacitive sensor, such as a microphone.

MEMS sensors in accordance with embodiments described herein may further include readout circuitry such as low noise amplifiers, voltage references and charge pumps for providing higher voltage bias, analog to digital conversion or output digital interfaces, or more complex analogies And/or digital processing or circuitry, or other components. Thus, an integrated circuit comprising a MEMS sensor as described in any of the embodiments herein can be provided.

One or more MEMS sensors in accordance with embodiments described herein may be positioned within a package. This package can contain one or more sounds. A MEMS sensor in accordance with embodiments described herein may be positioned within a package along with a separate integrated circuit including a readout circuit, which may include analog and/or digital circuits such as low noise amplifiers, for providing Voltage reference for higher voltage bias and charge pump, analog to digital conversion or output digital interface or more complex analog or digital signal processing.

According to another aspect, an electronic device is provided that includes a MEMS sensor in accordance with any of the embodiments described herein. For example, the electronic device may include at least one of: a portable device; a battery-powered device; an audio device; a computing device; a communication device; a personal media player; a mobile phone; a game device; Device.

According to another aspect, an integrated circuit is provided that includes a MEMS sensor as described in any of the embodiments herein.

According to another aspect, a method of fabricating a MEMS sensor is provided, wherein the MEMS sensor comprises a MEMS sensor as described in any of the embodiments herein.

Moreover, in the embodiments described herein, it will be appreciated that the sensor can include other components such as an electrode or backplate structure in which the flexible membrane layer is supported relative to the backplate structure. The backing structure can include a plurality of holes through the backing plate structure.

Although various embodiments describe MEMS condenser microphones, the invention is also applicable to any form of MEMS sensor other than a microphone, such as a pressure sensor or an ultrasonic transmitter/receiver.

Embodiments of the invention may be effectively implemented within the scope of different material systems, however, the embodiments described herein are particularly advantageous for MEMS sensors having a diaphragm layer comprising tantalum nitride.

The MEMS sensor can be formed on the sensor die and, in some cases, can be integral with at least some of the electronic components used to operate the sensor.

In the embodiments described above, it should be noted that references to sensor elements may include various forms of sensor elements. For example, the sensor element can comprise a single diaphragm in combination with a backing plate. In another example, the sensor element includes a plurality of individual sensors, such as a plurality of diaphragm/backplate combinations. The individual sensors of the sensor elements can be configured similarly or in different ways such that the sensors respond to the acoustic signals in different ways, for example, the elements can have different sensitivities. The sensor elements can also include different individual sensors positioned to receive acoustic signals from different channels.

It should be noted that in the embodiments described herein, the sensor element may comprise, for example, a microphone device comprising one or more membranes, wherein the electricity for reading/driving The electrode is deposited on the membrane and/or the substrate or the backing plate. In the case of a MEMS pressure sensor and a microphone, the electrical output signal can be obtained by measuring a signal related to the capacitance between the electrodes. However, it should be noted that these embodiments are also intended to encompass that the output signal is derived by monitoring a piezoresistive or piezoelectric element or actually monitoring the source. The embodiments are also intended to cover the case where the sensor element is a capacitive output sensor in which the diaphragm is moved by an electrostatic force generated by a change in a potential difference applied across the electrode, including an example of an output sensor, wherein the piezoelectric element It is fabricated using MEMS technology and is stimulated to cause movement of the flexible member.

It should be noted that the embodiments described above may be used in a range of devices including, but not limited to, analog microphones, digital microphones, pressure sensors, or ultrasonic sensors. The invention can also be used in several applications including, but not limited to, consumer applications, medical applications, industrial applications, and automotive applications. For example, typical consumer applications include portable audio players, wearable devices, laptops, mobile phones, PDAs, and personal computers. Embodiments can also be used in voice activated or voice controlled devices. Typical medical applications include hearing aids. Typical industrial applications include active noise cancellation. Typical automotive applications include hands-free setup, acoustic collision sensors, and active noise cancellation.

It should be noted that the above-mentioned embodiments are illustrative and not limiting, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. The word "comprising" does not exclude the presence of the elements or the steps of the elements or steps recited in the claims. Features. Any reference signs in the scope of the patent application should not be construed as limiting the scope.

Claims (45)

A MEMS sensor structure comprising: a substrate comprising a cavity; a diaphragm layer supported relative to the substrate to provide a flexible diaphragm; wherein a peripheral edge of the cavity defines a cavity relative to the cavity At least one perimeter region of the center of the protrusion. The MEMS sensor of claim 1, wherein the peripheral edge of the cavity further defines at least one perimeter region that is recessed relative to the center of the cavity. The MEMS sensor of claim 1 or 2, wherein the diaphragm comprises an active central zone and a plurality of support arms (303) extending laterally from the active central zone for Supporting the central region of the diaphragm. The MEMS sensor of claim 3, wherein a raised portion of the peripheral edge of the cavity is underneath a central region of one of the support arms (303) of the diaphragm. The MEMS sensor of claim 4, wherein the apex of a convex portion substantially undulates in a lateral direction at a center of a support arm (303). The MEMS sensor of any one of claims 3 to 5, wherein a concave portion of the peripheral edge of the cavity is under the edge of one of the support arms (303). A MEMS sensor according to any of the preceding claims, wherein a raised portion is positioned around the periphery of the cavity such that the flexible membrane is deflectable after being deflected toward the cavity during use The diaphragm contacts the raised portion of the peripheral edge of the cavity just prior to contacting another portion of the peripheral edge of the cavity. The MEMS sensor of claim 7, wherein when attached to the third item of the patent application, a convex portion is positioned around the periphery of the cavity such that the flexible diaphragm is oriented during use. After the cavity is deflected, the support arm of the flexible diaphragm A central portion contacts the raised portion of the peripheral edge of the cavity just prior to contacting an edge region of the support arm. The MEMS sensor of claim 2, wherein the recessed portion is positioned around the periphery of the cavity such that the flexible diaphragm is deflected toward the cavity during use, the flexible diaphragm The recessed portion is contacted just after contacting another portion of the peripheral edge of the cavity. The MEMS sensor of claim 9, wherein the recessed portion is positioned around the periphery of the cavity, so that the flexible diaphragm is oriented during use. After the cavity is deflected, an edge of one of the support arms of the flexible diaphragm contacts the recessed portion of the peripheral edge of the cavity after contacting a central region of the support arm. A MEMS sensor according to claim 10, comprising first and second recessed portions (63a, 63b) positioned around the periphery of the cavity such that the flexible diaphragm faces the during use After the cavity is deflected, the first and second edges (65a, 65b) of one of the support arms (303) of the flexible diaphragm contact the periphery of the cavity after contacting a central region of the support arm (303) The concave portions (63a, 63b) on the edges. A MEMS sensor according to any of the preceding claims, wherein the periphery of the cavity comprises a nominal shape, and wherein a convex portion faces the cavity compared to the nominal shape of the cavity The center extends inward. A MEMS sensor according to any of the preceding claims, wherein the periphery of the cavity comprises a nominal shape, and wherein a recessed portion is remote from the cavity compared to the nominal shape of the cavity The center extends outward. The MEMS sensor of any one of claims 2 to 13, wherein the concave portion in the periphery of the cavity comprises another one of the periphery smaller than the cavity A radius of curvature of the radius of curvature of the concave portion. The MEMS sensor of any one of claims 3 to 14, wherein one of the edge portions of one of the support arms (303) includes one or more bending points or an S-shaped curve. The MEMS sensor of claim 15, wherein the one or more bending points or sigmoidal curves (65a, 65b) on the diaphragm overlie a concave portion of a peripheral edge of the cavity (63a, 63b). A MEMS sensor according to any of the preceding claims, wherein a raised portion and/or a recessed portion comprises a curved path, or a series of two or more than two bitwise linear portions. A MEMS sensor according to any of the preceding claims, wherein the cavity comprises a through hole through one of the substrates. The MEMS sensor of any one of clauses 1 to 17, wherein the cavity forms a portion of a larger cavity within the substrate. A MEMS sensor according to any one of the preceding claims, wherein the cavity is formed in a surface of the substrate corresponding to a side on which the diaphragm is supported. A MEMS sensor according to any of the preceding claims, wherein the cavity is formed using a sacrificial layer. A MEMS sensor according to any of the preceding claims, wherein the cavity is formed using an etching process. A MEMS sensor according to any of the preceding claims, wherein the cavity forms a portion that passes through a larger through hole of the substrate. The MEMS sensor of claim 23, wherein the periphery of the cavity is the same shape as the periphery of the through hole. The MEMS sensor of claim 23, wherein the periphery of the cavity The periphery of the through hole has a different shape. The MEMS sensor of claim 25, wherein the periphery of the cavity comprises at least one protrusion and a recessed portion, and wherein the periphery of the through hole has a circular or rectangular or pentagon or eight Edge shape. The MEMS sensor of any of claims 3 to 26, comprising a plurality of support arms and corresponding protrusions and/or recesses. The MEMS sensor of any of claims 3 to 27, wherein the support arms are evenly spaced around the active central region of the diaphragm. A MEMS sensor according to any of the preceding claims, wherein the membrane is substantially square or rectangular in shape. The MEMS sensor according to any one of claims 3 to 29, wherein the active central region of the diaphragm is affected by intrinsic stress. A MEMS sensor structure comprising: a substrate comprising a cavity; a diaphragm layer supported relative to the substrate to provide a flexible diaphragm, wherein the diaphragm layer comprises an active central region and a plurality of support arms (303) the support arms extend laterally from the active central region for supporting the active central region of the diaphragm; wherein a peripheral edge of the cavity defines at least a recess that is recessed relative to a center of the cavity First and second perimeter areas. The MEMS sensor of claim 31, wherein the at least first and second perimeter regions extend away from the center of the cavity. The MEMS sensor of claim 32, wherein the at least first and second perimeter regions (63a, 63b) have one compared to at least one other recessed portion of the peripheral edge of the cavity. Smaller radius of curvature. The MEMS sensor of claim 32, wherein the at least first and second perimeter regions are located in a region corresponding to one of the first and second edges of one of the support arms of the diaphragm The center of the cavity extends. A MEMS sensor according to any of the preceding claims, wherein the periphery of the cavity is in a plane parallel to the surface of the substrate. A MEMS sensor according to any of the preceding claims, wherein the sensor comprises a capacitive sensor. A MEMS sensor according to any of the preceding claims, wherein the sensor comprises a microphone. The MEMS sensor of claim 36 or 37, further comprising a readout circuit. The MEMS sensor of claim 38, wherein the readout circuitry can include analog and/or digital circuitry and/or other components. A MEMS sensor according to any of the preceding claims, wherein the sensor is positioned within a package having a sound. An electronic device comprising the MEMS sensor of any of the preceding claims. The electronic device of claim 41, wherein the device is at least one of: a portable device; a battery powered device; an audio device; a computing device; a communication device; a media player; a mobile phone; a gaming device; and a voice controlled device. An integrated circuit comprising a MEMS sensor and a readout circuit as claimed in any of the preceding claims. A method of fabricating a MEMS sensor, wherein the MEMS sensor comprises as an application The MEMS sensor of any one of clauses 1 to 40. A MEMS sensor substantially as hereinbefore described with reference to the accompanying drawings.