Force Feedback Actuators and MEMS Capacitive Transducers

Abstract

The present invention relates to a force feedback actuator and a MEMS capacitive transducer. A force feedback actuator and a MEMS capacitive transducer are disclosed. The force feedback actuator includes a pair of electrodes and a dielectric member. The pair of electrodes are spaced apart from each other to form a gap. The dielectric member is at least partially disposed in the gap. The dielectric member includes a first portion having a first dielectric constant and a second portion having a second dielectric constant different from the first dielectric constant. The dielectric member and the pair of electrodes are configured to move relative to each other.

Description

Technical Field

[0001] The invention relates to a force feedback actuator and a micro-electromechanical system capacitive transducer. Background Art

[0002] Microphones are deployed in various types of devices, such as personal computers, cellular phones, mobile devices, headsets, earphones, and hearing aid devices. However, as devices become smaller, they require smaller microphones. Smaller microphones experience higher acoustic noise due to airflow and heat loss within the device, and typically have a lower signal-to-noise ratio than larger microphones. Summary of the invention

[0003] One aspect of the present invention relates to a force feedback actuator, comprising: a pair of electrodes spaced apart from each other to form a gap; and a dielectric member at least partially disposed within the gap, the dielectric member comprising a first portion having a first dielectric constant and a second portion having a second dielectric constant, the dielectric member and the pair of electrodes being configured to move relative to each other.

[0004] Another aspect of the present invention relates to a micro-electromechanical system capacitive transducer, which includes: a chamber; a first electrode, which is arranged in the chamber; a second electrode, which is arranged in the chamber and is spaced apart from the first electrode, and the first electrode is electrically isolated from the second electrode; a dielectric member, which is arranged in the chamber, and is at least partially located between the first electrode and the second electrode according to the degree of relative movement between the dielectric member and the first electrode and the second electrode, and the dielectric member includes a first part having a first dielectric constant and a second part having a second dielectric constant. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The foregoing features and other features of the present invention will become more fully apparent from the following description and the appended claims in conjunction with the accompanying drawings. These drawings only depict a number of embodiments according to the present invention and therefore should not be considered as limiting the scope of the present invention. Various embodiments are described in more detail below in conjunction with the accompanying drawings.

[0006] Figure 1 is a side cross-sectional view of an example microphone assembly.

[0007] Figure 2 is a perspective cross-sectional view of an example micro-electromechanical system (MEMS) transducer.

[0008] Figure 3is a diagram showing the capacitance of an idealized dielectric actuator according to the relative positions between a pair of electrodes and a dielectric member.

[0009] Figure 4 It is shown Figure 3 Plot of the electrostatic restoring force of an idealized dielectric actuator as a function of the relative position between a pair of electrodes and a dielectric member.

[0010] Figure 5 is a side cross-sectional view of an example dielectric actuator for a MEMS transducer.

[0011] Figure 6 yes Figure 5 A diagram of the electrostatic restoring force of a dielectric actuator according to the relative position between a pair of electrodes and a dielectric member.

[0012] Fig. 7A is Figure 2 A side cross-sectional view of a dielectric actuator of a MEMS transducer taken at line 7-7.

[0013] Figure 7B is a side cross-sectional view of another example of a dielectric actuator.

[0014] Figure 8 It works on Fig. 7A and Figure 7B Schematic diagram of the electrostatic restoring force on a dielectric actuator.

[0015] Fig. 9 yes Figure 8 A diagram of the electrostatic restoring force of a dielectric actuator depending on the relative position between a pair of electrodes and a dielectric member.

[0016] Fig.10 is a top view of an example MEMS transducer.

[0017] Fig.11 is a top view of another example MEMS transducer.

[0018] Fig.12 is a top view of another example MEMS transducer.

[0019] Fig.13 is a top view of another example MEMS transducer.

[0020] Fig.14 is a flow chart of an example method of manufacturing a dielectric actuator for a MEMS transducer.

[0021] Fig.15 is a side cross-sectional view of electrode material deposited onto an insulating layer.

[0022] Fig.16 yes Fig.15 A side cross-sectional view of the electrode material after an etching operation.

[0023] Fig.17 yes Fig.15 A side cross-sectional view of an electrode material after deposition of a sacrificial material.

[0024] Fig.18 yes Fig.15 A side cross-sectional view of an electrode material after deposition of a first dielectric material.

[0025] Fig.19 yes Fig.15 A side cross-sectional view of an electrode material after deposition of a second dielectric material.

[0026] Fig. 20 yes Fig.15 A side cross-sectional view of the electrode material after removing the sacrificial material from between the electrode material and the first dielectric material.

[0027] In the following detailed description, various embodiments are described with reference to the accompanying drawings. The skilled person will appreciate that the drawings are schematic and simplified for clarity, and therefore the drawings only show details essential to understanding the present invention, while other details are omitted. Throughout the text, the same reference numerals refer to the same elements or components. Therefore, it will not be necessary to describe the same elements or components in detail with respect to each of the drawings. DETAILED DESCRIPTION

[0028] Performance losses in microphones, particularly in microelectromechanical systems (MEMS) microphones, are due to viscous losses from airflow resistance within the device. Viscous losses limit the signal-to-noise ratio (SNR) of the microphone. To improve the SNR, the microphone can be packaged and placed under reduced pressure (e.g., near vacuum). Once packaged, the sensing diaphragm of the microphone is subjected to loads associated with atmospheric pressure fluctuations. In some embodiments, a force feedback actuator can be used to compensate for these sensed atmospheric pressure fluctuations. The force feedback actuator includes a dielectric comb structure or dielectric grid that engages an array of conductive pins. The dielectric grid has two functions. The first function is to operate as an actuator to provide force feedback to the pressure diaphragm in order to offset the reaction force generated by the atmospheric pressure. When a voltage is applied to adjacent pins, a force is generated on the dielectric grid to pull the dielectric grid parallel to the pins, further engaging the dielectric grid with the pins, thereby increasing the capacitance between the pins. The second function of the dielectric grid is to act as a sensor. The low frequency portion of the sensed signal provides a means of adjusting the force feedback voltage to compensate for changes in atmospheric pressure, while the high frequency portion of the sensed signal represents the desired acoustic signal. Examples of force feedback actuator designs are provided in U.S. Patent No. 62 / 769,468, filed November 19, 2018, U.S. Patent Application No. 62 / 773,989, filed November 30, 2018, and PCT / US2019 / 023260, filed March 20, 2019, the entire contents of which are incorporated herein by reference in their entirety.

[0029] The dielectric grid is disposed in a gap formed between adjacent pins and is configured to move relative to the pins in response to acoustic activity and changes in atmospheric pressure. It has been found that changes in the material properties of the dielectric grid along the direction of movement between the dielectric grid and the pins can affect the performance of the force feedback actuator. In particular, these changes in material properties can cause instabilities due to gradients in electrostatic forces as the grid moves relative to the pins.

[0030] The present invention provides an improved dielectric grid for a force feedback actuator. The structure of the dielectric grid is designed to improve the sensitivity of the force feedback actuator and increase the overall operating range by controlling the size and position of the gaps formed in the various dielectric members of the dielectric grid during the manufacturing process. It has been found that the size and position of these gaps directly affect the gradient of the electrostatic force encountered during operation (e.g., the change of the electrostatic force with the relative position of the dielectric grid with respect to the pin).

[0031] like Figure 1As shown, one implementation relates to a microphone assembly 10. The microphone assembly 10 includes a housing 12, a MEMS transducer 100, and an integrated circuit (IC) 14. The housing 12 includes a substrate 16 and a cover 18 coupled to an upper surface 20 of the substrate 16. The substrate 18 is fastened to the substrate 16 along the perimeter of the cover 18. The cover 18 and the substrate 16 together form an interior 22 (e.g., a hollow cavity, etc.). The cover 18 may include an atmospheric balance vent 26 (e.g., an opening, a hole, etc.), which provides fluid communication between the environment surrounding the housing 12 and the interior 22. The atmospheric balance vent 26 prevents damage to the housing 12 and / or other components of the microphone assembly 10, which may otherwise occur due to extreme temperature and / or pressure fluctuations in the environment surrounding the microphone assembly 10. The MEMS transducer 100 and the IC 14 are positioned within the interior 22 and connected to the upper surface 20.

[0032] Substrate 16 includes an acoustic port 28 aligned with MEMS transducer 100 so that MEMS transducer 100 is exposed to pressure changes through acoustic port 28. In various illustrative embodiments, the relative position between MEMS transducer 100 and acoustic port 28 may be different. For example, acoustic port 28 may be formed on cover 18 instead of substrate 16, and MEMS transducer 100 may be adjacent to acoustic port 28. In these cases, MEMS transducer 100 may be aligned with acoustic port 28. Figure 1 The situation shown in FIG. 1 is the opposite. The MEMS transducer 100 generates an electrical signal based on a pressure change transmitted to the MEMS transducer 100 through the acoustic port 28. The pressure change can be a change in the ambient atmospheric pressure (e.g., the pressure of the environment surrounding the microphone assembly 10) and / or a pressure change caused by an acoustic stimulus such as sound. The IC 14 is coupled to the MEMS transducer 100 and is configured to interpret the electrical signal generated by the MEMS transducer 100. Figure 1 As shown, IC 14 is hardwired to MEMS transducer 100 using leads and traces 30 to form an electrical connection between MEMS transducer 100 and IC 14. IC 14 is also electrically connected to substrate 16 and pads 32 to communicate with a device to which microphone assembly 10 is connected (e.g., a personal computer, a cellular phone, a mobile device, a headset, an earphone device, a hearing aid device, etc.). In some embodiments, IC 14 includes acoustic signal and atmospheric signal processing circuitry and / or software to interpret the electrical signals from MEMS transducer 100.

[0033] The MEMS transducer 100 is configured to sense acoustic activity and changes in atmospheric pressure. The MEMS transducer 100 includes a pressure diaphragm 102 and a force feedback actuator 200 (eg, a dielectric actuator, a comb actuator, etc.) coupled to the pressure diaphragm 102. Figure 1As shown, the pressure diaphragm 102 is in fluid communication with the acoustic port 28 and is configured to transmit pressure fluctuations to the force feedback actuator 200. Specifically, the pressure diaphragm 102 is configured to transmit pressure fluctuations through a rigid support member 34 (eg, a protrusion) extending between the pressure diaphragm 102 and the force feedback actuator 200.

[0034] like Figure 1 As shown, at least a portion of the force feedback actuator 200 is sealed relative to the environment surrounding the microphone assembly 10 (e.g., the acoustic port 28 and the interior 22). Specifically, at least a portion of the force feedback actuator 200 is disposed in a closed chamber 106 formed between the first transducer substrate 104 and the pressure diaphragm 102. The closed chamber 106 is sealed at a low pressure close to a vacuum. In some embodiments, the closed chamber 106 has a pressure less than or substantially equal to 30Pa. In some embodiments, the closed chamber 106 has a pressure less than or substantially equal to 10Pa. Figure 1 As shown, the lower surface of the pressure diaphragm 102 is in fluid communication with the environment surrounding the microphone (eg, the acoustic port 28 ) outside of the closed chamber 106 .

[0035] Figure 2 Shows Figure 1 2 is a perspective view of a force feedback actuator 200. The force feedback actuator 200 includes a support structure 202, a cantilever diaphragm 206, and a plurality of fixed fingers 208. The support structure 202 is coupled to the cantilever diaphragm 206 and the fixed fingers 208, and is configured to support the cantilever diaphragm at a position relative to the fixed fingers 208. Figure 1 As shown, the support structure 202 is "sandwiched" or otherwise disposed between the first transducer substrate 104 and the pressure diaphragm 102. Figure 2 As shown, support structure 202 includes a base 210 (e.g., a silicon wafer) and an insulating layer 212 deposited on an upper surface of base 210. Base 210 defines a central opening 214 extending from the upper surface through the lower surface of base 210. Suitable materials for insulating layer 212 include silicon dioxide, silicon nitride, and silicon oxynitride.

[0036] The cantilever diaphragm 206 is coupled to the upper surface of the insulating layer 212 and extends above the central opening 214, so that the cantilever diaphragm 206 substantially covers the central opening 214. A first end of the cantilever diaphragm 206 is coupled to the insulating layer 212, and a second end (e.g., an unsupported end) is disposed above the central opening 214 near the inner periphery of the base 210. The structure of the cantilever diaphragm 206 is designed to respond to a pressure diaphragm 102 (e.g., from a rigid support member 34 (e.g., extending between the pressure diaphragm 102 and the cantilever diaphragm 206) Figure 1)) in a direction parallel to the central axis of the base 210 (e.g., as Figure 2 As shown in the figure, the Figure 2 As shown, the cantilever diaphragm 206 includes a plurality of movable fingers 216 disposed at the second end. The movable fingers 216 form a plurality of rectangular fins arranged in a substantially parallel orientation relative to each other. In other embodiments, the shape of the movable fingers 216 may be different.

[0037] like Figure 2 As shown, the fixed fingers 208 are coupled to the upper surface of the insulating layer 212 at the end of the base 210 opposite to the first end of the cantilever diaphragm 206. The fixed fingers 208 are arranged in a substantially parallel orientation relative to each other across the upper edge of the central opening 214. The fixed fingers 208 are spaced apart from each other to form a plurality of channels or gaps 218, which are configured to accommodate the movable fingers 216 of the cantilever diaphragm 206 therein. In other words, the movable fingers 216 are interposed between the fixed fingers 208, so that each of the fixed fingers 208 is surrounded by the movable fingers 216 on at least two sides.

[0038] The movable finger 216 is configured to respond to an incident signal incident on the MEMS transducer 100 (eg, reference Figure 1 The pressure on the pressure diaphragm 102 fluctuates and moves relative to the fixed finger 208 to generate an electrical signal. Figure 2 In the illustrated implementation, the fixed fingers 208 are pins or conductors arranged in two staggered groups that are electrically isolated from each other. The conductors can be made of polysilicon material or another suitable conductor. The first group of conductors are electrically connected to each other by a first metal interconnect 219 (e.g., polysilicon material or another suitable conductor), which extends across the upper surface of the first group of conductors to form a first electrode 220. The second group of conductors are electrically connected to each other by a second metal interconnect 222, which extends across the upper surface of the second group of conductors to form a second electrode 224.

[0039] The movable fingers 216 form a dielectric grid of the force feedback actuator 200. Each movable finger 216 is made of a dielectric material such as silicon nitride. In operation, when the cantilever diaphragm 206 moves under sound pressure, the movable fingers 216 (e.g., dielectric members) move up and down within the gap 218 between adjacent conductors. A bias voltage is applied between the first electrode 220 and the second electrode 224, and an electrical signal is extracted based on the voltage change measured due to the position of the movable fingers 216. The applied bias voltage generates an electrostatic field between the first electrode 220 and the second electrode 224, which provides a restoring electrostatic force that counteracts the relative movement between the dielectric member and the electrodes (e.g., counteracts the mechanical force applied to the cantilever diaphragm 206 by the pressure diaphragm 102). Among other benefits, separating the first electrode 220 from the second electrode 224 by the dielectric material significantly reduces the lateral force that causes the electrodes to collapse toward each other. The reduction in lateral force between the electrodes reduces the limitations associated with the geometry of the fingers that can be used for the force feedback actuator 200 (e.g., width / thickness of the fingers, length that the fingers extend above the central opening 214, etc.), which in turn can allow the geometry to be optimized to produce a higher output signal compared to other configurations.

[0040] Reference Figure 2 The design of the force feedback actuator 200 described should not be considered limiting. Many variations are possible without departing from the inventive concepts disclosed herein. For example, in some embodiments, the materials used for the fixed finger 208 and the movable finger 216 can be opposite, so that the electrode moves relative to the fixed dielectric material (for example, so that the movable finger 216 is made of a conductive material and the fixed finger 208 is made of an insulating material). In some embodiments, the cantilever diaphragm 206 and the movable finger 216 can be integrally formed as a single unitary structure. In other embodiments, the movable finger 216 can be made of a different material deposited on or otherwise coupled to the second end of the cantilever diaphragm 206. In an implementation where the movable finger 216 is used as an electrode, the metal interconnects 219, 222 can be arranged along the upper surface of the movable finger 216. In various illustrative embodiments, the precise location of the metal interconnects 219, 222 relative to the fixed finger 208 or the movable finger 216 can also be different.

[0041] Figure 3 to Figure 4 The performance of a force feedback actuator 300 is conceptually shown, which has the same Figure 2 The force feedback actuator 200 described above is similarly constructed. In particular, Figure 3 to Figure 4 The performance of an ideal force feedback actuator 300 is shown, where the material properties of the dielectric member 316 (eg, the movable finger) are uniform throughout the dielectric member 316 . Figure 33 shows the capacitance change of the force feedback actuator according to the relative position between the dielectric member 316 and the pair of electrodes 320, and Figure 4 The electrostatic restoring force (ie, pulling force) between the dielectric member 316 and the electrode 320 is shown in a similar position range. Figure 2 The cross-sectional view of the interdigitated comb structure formed by the movable and fixed fingers at the position indicated by line 7-7 in FIG. 7 shows the actual position of the dielectric member 316 relative to the electrode 320. It is noted that these figures show that the capacitance varies approximately linearly ( ) within the useful operating range of the force feedback actuator (e.g., in the range between about 0.5 μm and 4.5 μm). Figure 3 ), resulting in an almost constant electrostatic force ( Figure 4 ).

[0042] The performance characteristics of the force feedback actuator will be Figure 3 to Figure 4 In particular, imperfections such as voids in the dielectric member, non-uniform material properties, and electric fringe fields to the surrounding environment will affect the electrostatic force gradient and the corresponding sensitivity that can be achieved by the force feedback actuator. Among other possibilities, voids and other imperfections in the dielectric member are caused by the natural accumulation of materials (e.g., material deposition) during manufacturing. Figure 5 An example of how material properties may vary across the cross-section of dielectric member 400 (as a result of internal voids 402) is shown. Figure 6 As shown, the voids 402 in the dielectric member 400 cause the dielectric constant to vary along the height of the dielectric member 400 (e.g., vertically between the upper and lower surfaces of the dielectric member 400), which affects the electrostatic restoring force as the dielectric member 400 moves relative to the electrode 404. Figure 6 In , this variation is shown as an electrostatic force gradient between approximately 0.5 μm and 2.75 μm. Figure 6 The electrostatic force gradient shown in FIG. 4 will vary depending on the shape of void 402 and the depth to which void 402 extends into dielectric member 400 .

[0043] Fig. 7A Shown by Figure 2 A cross-sectional view of a movable finger (eg, dielectric member) and a fixed finger (eg, electrode) of a force feedback actuator 200. Specifically, Fig. 7AA cross section through a pair of electrodes (e.g., a first electrode 220 and a second electrode 224) and a dielectric member 216 is shown. The height 217 of the dielectric member 216 between the upper surface and the lower surface of the dielectric member 216 is in a range between about 3 μm and 10 μm. The overall width 221 of the dielectric member 216 in the lateral direction between the pair of electrodes is in a range between about 1 μm and 300 μm. In other embodiments, the overall dimensions of the dielectric member 216 may be different. Fig. 7A As shown, a pair of electrodes are spaced apart from each other to form a gap 218. A dielectric member 216 is disposed at a central position within the gap 218 between the pair of electrodes. The width of the dielectric member 216 is less than the width of the gap 218, such that the dielectric member 216 is spaced apart from both the first electrode 220 and the second electrode 224. In some implementations, the width 226 of the gap 218 between the dielectric member 216 and at least one of the first electrode 220 and the second electrode 224 is in a range between about 100 nm and 300 nm. In other embodiments, the spacing between the dielectric member 216 and the electrodes 220, 224 may be different.

[0044] The dielectric member 216 includes a dielectric gradient in at least two directions through the dielectric member 216. As referred to herein, a dielectric gradient refers to a change in a material property and / or dielectric constant along the dielectric member 216 in a given direction. The dielectric gradient can be generated by using a secondary material and / or by forming air pockets in the dielectric member 216 via an etching process. In particular, the dielectric member 216 includes a plurality of dielectric materials (e.g., portions) stacked or otherwise arranged along a lateral direction between a pair of electrodes. In other words, the dielectric member 216 includes a controlled dielectric gradient having the following characteristics: a discrete change in the relative dielectric constant (e.g., a discrete change associated with a change in a material property between a first dielectric material and a second dielectric material) is perpendicular to a relative movement direction between the dielectric member 216 and the pair of electrodes (e.g., as Fig. 7A The dielectric member 216 also includes a controlled dielectric gradient along the direction of relative movement between the dielectric member 216 and a pair of electrodes due to a change in material properties near the lower end of the dielectric member 216.

[0045] like Fig. 7A As shown, the dielectric member 216 includes a first portion, shown as a first dielectric material 228, and a second portion, shown as a second dielectric material 230, the second dielectric material 230 being at least partially disposed within the first dielectric material 228. Figure 7B As shown, the dielectric gradient in the dielectric member 250 is formed by air pockets 252 etched into the first dielectric material 254 (eg, in place of Fig. 7AIn some implementations, the second dielectric material 230 may be provided with air pockets in the second dielectric material 230, etc. Fig. 7A The air pockets 252 are etched into the first dielectric material 254 in substantially the same shape as the second dielectric material 228 shown, or another suitable shape, to reduce the electrostatic force gradient within the operating range of the force feedback transducer 200. Figure 7B In an embodiment, the air cavity 252 is etched into the first dielectric material 254 with a certain taper, so that the width of the air cavity 252 is larger near the upper end of the dielectric member 250 than the lower end.

[0046] like Fig. 7A As shown, the second dielectric material 230 is centrally disposed within the first dielectric material 228 such that the second dielectric material 230 is surrounded on at least three sides by the first dielectric material 228. The second dielectric material 230 extends downwardly into the first dielectric material 228 along a majority of the height of the dielectric member 216. Fig. 7A As shown, the thickness 232 of the first dielectric material 228 is substantially uniform along the perimeter of the second dielectric material 230. In some implementations, the thickness 232 of the first dielectric material 228 is in a range between approximately 100 nm and 300 nm, and / or is substantially the same as the width 226 of the gap 218 between the first dielectric material 228 and each of the first electrode 220 and the second electrode 224. It is noted that the shape of the second dielectric material 230 is substantially uniform throughout the depth of the dielectric member 216, resulting in discrete changes in the dielectric constant perpendicular to the relative movement direction between the dielectric member 216 and the pair of electrodes. Fig. 7A In the illustrated embodiment, the second dielectric material 230 has a rectangular shape when viewed in cross-section. In other embodiments, the shape of the second dielectric material 230 may be different. For example, Figure 8 The lower corners of the rectangle shown in the figure can be rounded. The inner sidewall of the first dielectric material 228 (where the second dielectric material 230 engages with the first dielectric material 228) can be tapered at a certain angle (e.g., 5°, etc.) or another angle based on manufacturing constraints and / or the desired performance of the force feedback actuator 200. For example, the second dielectric material 230 can replace Figure 7B The air pockets 252 shown in FIG. 2 (eg, the second dielectric material 230 may be deposited or otherwise formed into the Figure 7B 252, such that the width of the second dielectric material 230 is greater near the upper end of the dielectric member than the lower end). In other words, the second dielectric material 230 can at least partially form a V-shape where the second dielectric material 230 engages the first dielectric material 228 (e.g., at the interface between the first dielectric material 228 and the second dielectric material 230). The tapering results in a continuous change in the dielectric constant along the height of the second dielectric material 228.

[0047] The material properties of the first dielectric material 228 and the second dielectric material 230 are selected to minimize the variation in the dielectric constant across the dielectric member 216. Fig. 7A In an embodiment, the first dielectric material 228 is made of a silicon nitride material and the second dielectric material 230 is made of a polysilicon material. The combination of materials and the relative thicknesses of the various material layers can be adjusted to obtain the desired material properties of the dielectric member 216 (e.g., an average dielectric constant across the dielectric member 216, etc.). Among other benefits, the polysilicon material can be deposited at a lower pressure than silicon nitride, which reduces the risk of internal voids forming during manufacturing. The outer silicon nitride ensures that the dielectric member 216 has sufficient mechanical strength under load.

[0048] Figures 8 to 9 The improvement in electrostatic force gradient that can be achieved by using a dielectric member 216 having a controlled dielectric gradient (e.g., multiple sections, each section having a different dielectric constant) is shown. Figure 6 Large changes (e.g., gradients) in the electrostatic forces observed in Fig. 7A and Figure 8 The dielectric member 216 shown in FIG. 2 exhibits a nearly constant (eg, flat) electrostatic restoring force as a function of position over a large operating range (eg, between approximately 0.5 μm and 4.5 μm).

[0049] It should be understood that the design of the dielectric member 216 can be used in various alternative force feedback actuator configurations. For example, Fig.10 Shows something like Figure 2 Similarly, the movable fingers and the fixed fingers form an interdigitated comb structure, which is arranged on a single side of the cantilever diaphragm 506 (for example, Fig.10 The opposite end of the cantilever diaphragm 506 is fastened to the transducer substrate 510 by the diaphragm anchor 834, and the opposite end may include a silicon oxide layer deposited above or below the cantilever diaphragm 506. Fig.11 A force feedback actuator 600 is shown that includes an interdigitated comb structure on both sides of a movable diaphragm 606. The diaphragm 606 is coupled to a transducer substrate 610 (e.g., a base) at both an upper side of the transducer substrate 610 and a lower side opposite the upper side. The diaphragm 606 includes a plurality of interdigitated comb structures on either side of the diaphragm 606 (e.g., a base). Fig.11 The movable fingers 616 on the left and right sides (as shown) extend outwardly away from the diaphragm 606 in a direction parallel to the diaphragm (eg, parallel to the upper surface of the transducer substrate 610).

[0050] Fig.12Another example force feedback actuator 700 is shown. The force feedback actuator 700 includes a diaphragm 706 that is Fig.11 The diaphragm 606 is constructed in a similar manner. However, Fig.11 The difference is, Fig.12 The movable finger 716 shown in the actuator 700 extends downward from the diaphragm 706 in a substantially perpendicular orientation relative to the diaphragm 706 (e.g., parallel to the axis of the central opening defined by the transducer substrate 710). The fixed finger 708 is disposed below the diaphragm 706 and is coupled to the transducer substrate 710 at both ends so that the fixed finger 708 extends across the central opening. The movable finger 716 extends into the gap formed between adjacent fixed fingers 708. In this way, the fixed finger 708 and the movable finger 216 can be at least partially disposed within the central opening. In operation, the movable finger 216 moves into and out of the central opening in a direction parallel to the axis of the central opening (e.g., Fig.12 in and out of pages).

[0051] Fig.13 Yet another implementation of a force feedback actuator 800 is shown. The force feedback actuator 800 includes a plurality of pillars 816 extending parallel to the axis of the central opening. The pillars 816 are supported within the central opening by metal interconnects 819, 822, either end of which is connected to the transducer substrate. The diaphragm 806 is a waffle structure including a plurality of openings 815. Each opening 815 is configured to accommodate a corresponding one of the pillars 816 therein. The outer end of the diaphragm 806 is disposed in a groove formed in the upper surface of the transducer substrate 810. The force feedback actuator 800 additionally includes a diaphragm anchor 834, which is configured to support the end of the diaphragm 806 and prevent the diaphragm 806 from separating from the transducer substrate 810 during normal operation. Figures 10 to 13 The number and geometry of the fixed and movable fingers shown in FIG. 1 may vary in various exemplary embodiments.

[0052] Fig.14 A flow chart of a method 900 for manufacturing a force feedback actuator for a MEMS transducer according to an illustrative embodiment is shown. The method 900 may be used Figure 1 to Figure 2 The force feedback actuator 200 is used to achieve this. Figure 1 to Figure 2 To describe method 900. Additionally, Figures 15 to 20 The various steps of method 900 are conceptually illustrated in FIG. 900 , which is a cross-sectional view through the movable finger and the fixed finger of the force feedback actuator (see FIG. Figure 2 Line 7-7) shows the various steps.

[0053] At 902, a polysilicon layer (e.g., fixed fingers 208) is provided. The polysilicon layer can be deposited or otherwise formed on an insulating layer of silicon nitride (e.g., transducer substrate or base 210). At 904, the polysilicon layer is etched to form a plurality of trenches (e.g., gaps 218) into the polysilicon layer. The trenches extend through the thickness of the polysilicon layer to form a plurality of fingers that are electrically isolated from each other by the insulating layer. Fig.16 In the illustrated implementation, the width 226 of each trench is approximately 1.4 μm, and the depth 227 of each trench is approximately 5 μm. In other implementations, the trench dimensions may be different.

[0054] At 906, a sacrificial layer (e.g., oxide layer 213) is deposited along the inner walls of each trench and along the outer surfaces of the polysilicon layer and the insulating layer. The thickness 229 of the sacrificial layer is about 200 nm, although the thickness 229 can vary depending on the design parameters of the force feedback actuator. At 908, a first dielectric material (e.g., silicon nitride, first dielectric material 228) is deposited on top of the sacrificial layer (see Fig.18 ). Likewise, the thickness 232 of the first dielectric material may vary according to design parameters. Fig.18 In the illustrated implementation, the thickness 232 of the first dielectric material is approximately 200 nm. The first sacrificial material defines voids or air pockets.

[0055] At 910, a second dielectric material (e.g., polysilicon, second dielectric material 230) is deposited into the void formed by the first dielectric material. Block 910 may include completely filling the void with the second dielectric material. Block 910 may additionally include etching away residual layers of the first dielectric material and the second dielectric material from the upper surface of the first polysilicon layer (e.g., electrodes 220, 224) (e.g., planarizing). At 912, the sacrificial oxide layer is etched away to release the first dielectric material and the second dielectric material (e.g., dielectric member 216) from the fixed fingers of the polysilicon. In other implementations, method 900 may include additional, fewer, and / or different operations.

[0056] The subject matter described in this article sometimes illustrates different components contained in or connected to different other components. It will be understood that the architecture depicted in this way is merely exemplary, and in fact, many other architectures that obtain the same function can be implemented. In a conceptual sense, any arrangement of components for achieving the same function is effectively "associated" to achieve the desired function. Thus, any two components combined in this article to obtain a specific function can be regarded as "associated" with each other to achieve the desired function, regardless of the architecture or intermediate components. Similarly, any two components associated in this way can also be regarded as "connected at work" or "connected at work" to achieve the desired function, and any two components that can be associated in this way can also be regarded as being able to "connect at work" to each other to achieve the desired function. Specific examples of connection at work include, but are not limited to, physically compatible and / or physically interacting components and / or wirelessly interactive and / or wirelessly interactive components and / or logically interactive and / or logically interactive components.

[0057] Regarding the use of plural and / or singular terms herein, those skilled in the art can translate from plural to singular and / or from singular to plural when appropriate, depending on the context and / or application. For clarity, various singular / plural permutations may be explicitly set forth herein.

[0058] Those skilled in the art will understand that, in general, the terms used herein, and especially in the appended claims (e.g., the bodies of the appended claims), are generally intended to be “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “comprising” should be interpreted as “including but not limited to,” etc.).

[0059] Although the drawings and description can illustrate a specific order of method steps, unless otherwise specified above, the order of these steps may be different from the steps depicted and described. In addition, unless otherwise specified above, two or more steps may be performed simultaneously or partially simultaneously. Such variations may, for example, depend on the selected software and hardware systems and the designer's choice. All of these variations are within the scope of the present invention. Similarly, software implementations of the described methods may be accomplished using standard programming techniques with rule-based logic and other logic to accomplish various connection steps, processing steps, comparison steps, and decision steps.

[0060] Those skilled in the art will further understand that if a specific number of a recited claim is intended to be stated, such intent will be explicitly stated in the claim, and in the absence of such a statement, no such intent exists. For example, to aid understanding, the following appended claims may contain the use of the introductory phrases "at least one" and "one or more" to introduce claim statements. However, the use of these phrases should not be interpreted as implying that the reference to a claim by the indefinite article "a" or "an" will limit any particular claim containing such a recited claim statement to an invention containing only one such statement, even if the same claim includes the introductory phrases "one or more" or "at least one", and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should generally be interpreted as meaning "at least one" or "one or more"); the same is true for the use of definite articles used to refer to claim statements. In addition, even if a specific number of recited claim statements is explicitly stated, those skilled in the art will recognize that such a statement should generally be interpreted as meaning at least the stated number (e.g., a detailed statement of "two statements" without other modifiers generally means at least two statements, or two or more statements).

[0061] Furthermore, in those cases where a convention similar to “at least one of A, B, and C, etc.” is used, generally speaking, such construction is intended in the sense that one skilled in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include, but is not limited to, systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). In those cases where a convention similar to “at least one of A, B, or C, etc.” is used, generally speaking, such construction is intended in the sense that one skilled in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include, but is not limited to, systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). One skilled in the art would further understand that any disjunctive words and / or phrases that actually present two or more alternative terms, whether in the specification, claims, or drawings, should be understood to contemplate the possibility of including one, either, or both of these terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

[0062] Additionally, use of the terms "about," "approximately," "approximately," "substantially," etc. means plus or minus ten percent unless otherwise indicated.

[0063] The foregoing description of exemplary embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or limited to the precise form disclosed, and modifications and variations may be made in light of the above teachings or may be acquired from practice of the disclosed embodiments. The scope of the invention is intended to be defined by the appended claims and their equivalents.

Claims

1. A force feedback actuator, comprising: a pair of electrodes spaced apart from each other to form a gap; as well as A dielectric member is at least partially disposed within the gap, the dielectric member including a first portion having a first dielectric constant and a second portion having a second dielectric constant, the dielectric member and the pair of electrodes being configured to move relative to each other.

2. The force feedback actuator according to claim 1, wherein: The second portion is at least partially disposed within the first portion.

3. The force feedback actuator according to claim 1, wherein: The dielectric constant of the dielectric member changes in a direction perpendicular to a direction of relative movement between the dielectric member and the pair of electrodes, or changes along a direction of relative movement between the dielectric member and the pair of electrodes.

4. The force feedback actuator according to claim 1, wherein: The pair of electrodes is one of a plurality of pairs of electrodes arranged in a comb shape, and wherein the dielectric member is one of a plurality of dielectric members interposed between the pair of electrodes of the plurality of pairs of electrodes.

5. The force feedback actuator according to claim 1, wherein: The first portion is made of silicon nitride material, and wherein the second portion is made of polysilicon material.

6. The force feedback actuator according to claim 1, wherein: When viewed in a cross section through the pair of electrodes and the dielectric member, the second portion is surrounded by the first portion on at least three sides.

7. The force feedback actuator according to claim 1, wherein: The height of the dielectric member is in the range of 3 μm to 10 μm.

8. The force feedback actuator according to claim 1, wherein: The width of the dielectric member is in the range of 1 μm to 3 μm.

9. The force feedback actuator according to claim 1, wherein: The thickness of the first portion is in the range of 100 nm to 300 nm.

10. The force feedback actuator according to claim 1, wherein: A width of a gap between the first portion and one of the pair of electrodes is in a range between 100 nm and 300 nm.

11. The force feedback actuator according to claim 1, wherein: The force feedback actuator forms part of a micro-electro-mechanical system transducer.

12. A micro-electromechanical system capacitive transducer, the micro-electromechanical system capacitive transducer comprising: Chamber; a first electrode disposed in the chamber; a second electrode disposed in the chamber and spaced apart from the first electrode, the first electrode being electrically isolated from the second electrode; a dielectric member disposed in the chamber, the dielectric member being at least partially located between the first electrode and the second electrode according to a degree of relative movement between the dielectric member and the first electrode and the second electrode, The dielectric member includes a first portion having a first dielectric constant and a second portion having a second dielectric constant.

13. The micro-electromechanical system capacitive transducer according to claim 12, wherein: When an electric field is applied between the first electrode and the second electrode, the dielectric member including the first portion having the first dielectric constant and the second portion having the second dielectric constant provides a relatively constant restoring electrostatic force over a larger range of relative movement between the dielectric member and the first electrode and the second electrode than a dielectric member without portions having different dielectric constants.

14. The MEMS capacitive transducer according to claim 12, wherein: An electric field applied between the first electrode and the second electrode provides a restoring electrostatic force that counteracts relative movement between the dielectric member and the first electrode and the second electrode caused by a mechanical force.

15. The MEMS capacitive transducer according to claim 12, wherein: The dielectric member includes a dielectric constant having the following characteristics: a discrete change in the dielectric constant between the first portion and the second portion is perpendicular to or along a direction of relative movement between the dielectric member and the first electrode and the second electrode.

16. The MEMS capacitive transducer according to claim 12, wherein: The first portion of the dielectric member is silicon nitride, and the second portion of the dielectric member is polysilicon.

17. The MEMS capacitive transducer according to claim 12, wherein: The dielectric member has different dielectric constants perpendicular to a direction of relative movement between the dielectric member and the first electrode and the second electrode, or along a direction of relative movement between the dielectric member and the first electrode and the second electrode.

18. The MEMS capacitive transducer according to claim 12, wherein: The chamber is at least partially evacuated, and the dielectric member or the first and second electrodes are coupled to a member outside the chamber, wherein a mechanical force applied to the member outside the chamber causes the relative movement between the dielectric member and the first and second electrodes.

19. The micro-electromechanical system capacitive transducer according to claim 18, wherein: The member disposed outside the chamber is a diaphragm.

20. The MEMS capacitive transducer according to claim 12, wherein: The dielectric gradient is provided by air pockets in the dielectric member.

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