Integrated digital force sensors and related methods of manufacture

Information

  • Patent Grant
  • 11255737
  • Patent Number
    11,255,737
  • Date Filed
    Friday, February 9, 2018
    6 years ago
  • Date Issued
    Tuesday, February 22, 2022
    2 years ago
Abstract
In one embodiment, a ruggedized wafer level microelectromechanical (“MEMS”) force sensor includes a base and a cap. The MEMS force sensor includes a flexible membrane and a sensing element. The sensing element is electrically connected to integrated complementary metal-oxide-semiconductor (“CMOS”) circuitry provided on the same substrate as the sensing element. The CMOS circuitry can be configured to amplify, digitize, calibrate, store, and/or communicate force values through electrical terminals to external circuitry.
Description
FIELD OF THE INVENTION

The present disclosure relates to microelectromechanical (“MEMS”) force sensing dies, MEMS switches, and related methods of manufacture. The MEMS force sensing dies and/or MEMS switches can be used for converting force into a digital output code.


BACKGROUND

Current technology MEMS force dies are based on linking the applied force to a sensing diaphragm having strain gauges located on a surface of two or more stacked silicon or glass die. Wire bond pads are positioned around the sensing diaphragm and the resulting structure is packaged, which makes the device relatively large compared to more modern chip-scale packaged sensors and electronics. In addition, current MEMS force dies produce an analog output that must often be routed through an often noisy electrical environment before it is converted to a digital signal.


Current electromechanical switches consist primarily of conductive dome structures that deform to complete an electrical circuit. These switches are limited in their durability as the conductive material, often metal, wears over time. These switches are also incapable of being configured for multiple levels of actuation, which is becoming more desirable as software applications are growing in complexity and require more versatility from the user interfaces designed to control them.


Accordingly, there is a need in the pertinent art for a small, low-cost, digital force sensor.


SUMMARY

A MEMS force sensor including a plurality of sensing elements and digital circuitry positioned on a surface of the force sensor die is described herein. Each sensing element can include a flexure and a sensing element (e.g., piezoresistive strain gauge). In one implementation, four sensing elements can be employed, although additional or fewer sensing elements can also be used. The inclusion of MEMS in a standard complementary metal-oxide-semiconductor (“CMOS”) process allows the sensor to convert its analog output into digital codes and transmit them without loss of signal integrity due to electrical noise.


The MEMS force sensors described herein can be manufactured by bonding a cap wafer to a base wafer (e.g., a force sensor die) that has both the sensing element(s) (e.g., piezoresistive strain gauge(s)) and CMOS power, processing, and communication circuitry. Sensing elements can be formed by etching flexures on the top side of the base wafer. The bond between the base and cap wafers can include a gap produced by protrusions sculptured either on the top of the base wafer and/or on the bottom of the cap wafer. The gap can be designed to limit the displacement of the cap wafer in order to provide force overload protection for the MEMS force sensors. The protrusions and outer wall of the base wafer deflect with applied force, straining the sensing element(s) and producing an analog output signal. The analog output signal can be digitized and stored in on-chip registers of the CMOS circuitry until requested by a host device.


A wafer level MEMS mechanical switch including a base and a cap is also described herein. The mechanical switch employs at least one sensing element. The at least one sensing element is electrically connected to integrated CMOS circuitry on the same substrate. The CMOS circuitry can amplify, digitize, and calibrate force values, which are compared to programmable force thresholds to modulate digital outputs.


A MEMS switch including a plurality of sensing elements positioned on the surface of the switch die is also described herein. In one implementation, four sensing elements can be employed, although additional or fewer sensing elements may also be used. The sensing elements can have their analog outputs digitized and compared against multiple programmed force levels, outputting a digital code to indicate the current state of the switch.


The MEMS switch can be made compact as to only require a small number of input/output (“I/O”) terminals. The outputs of the device can be configured to indicate 2N input force levels, where N is the number of output terminals, which can be programmed by the user. In addition, the device's response can optionally be filtered such that only dynamic forces are measured. The resulting device is a fully-configurable, multi-level, dynamic digital switch.


An example MEMS force sensor is described herein. The MEMS force sensor can include a sensor die configured to receive an applied force. The sensor die has a top surface and a bottom surface opposite thereto. The MEMS force sensor can also include a sensing element and digital circuitry arranged on the bottom surface of the sensor die. The sensing element can be configured to convert a strain on the bottom surface of the sensor die to an analog electrical signal that is proportional to the strain. Additionally, the digital circuitry can be configured to convert the analog electrical signal to a digital electrical output signal.


Additionally, the sensing element can be a piezoresistive, piezoelectric, or capacitive transducer.


Alternatively or additionally, the MEMS force sensor can further include a plurality of electrical terminals arranged on the bottom surface of the sensor die. The digital electrical output signal produced by the digital circuitry can be routed to the electrical terminals. For example, the electrical terminals can be solder bumps or copper pillars.


Alternatively or additionally, the MEMS force sensor can further include a cap attached to the sensor die. The cap can be bonded to the sensor die at a surface defined by an outer wall of the sensor die. In addition, a sealed cavity can be formed between the cap and the sensor die.


Alternatively or additionally, the sensor die can include a flexure formed therein. The flexure can convert the applied force into the strain on the bottom surface of the sensor die. Optionally, the flexure can be formed in the sensor die by etching. The sensing element is arranged on the flexure.


Alternatively or additionally, a gap can be arranged between the sensor die and the cap. The gap can be configured to narrow with application of the applied force such that the flexure is unable to deform beyond its breaking point.


Alternatively or additionally, the digital circuitry can be further configured to provide a digital output code based on a plurality of predetermined force thresholds.


An example method for manufacturing a MEMS force sensor is described herein. The method can include forming at least one sensing element on a surface of a force sensor die, and forming complementary metal-oxide-semiconductor (“CMOS”) circuitry on the surface of the force sensor die. The at least one sensing element can be configured with a characteristic that is compatible with a downstream CMOS process.


Alternatively or additionally, the at least one sensing element can be formed before forming the CMOS circuitry.


Alternatively or additionally, the characteristic can be a thermal anneal profile of the at least one sensing element.


Alternatively or additionally, the method can further include etching an opposite surface of the force sensor die to form an overload gap, etching the opposite surface of the force sensor die to form a trench, and bonding of a cap wafer to the opposite surface of the force sensor die to seal a cavity between the cap wafer and the force sensor die. The cavity can be defined by the trench.


Alternatively or additionally, the method can further include forming of a plurality of electrical terminals on the opposite surface of the force sensor die.


Alternatively or additionally, the force sensor die can be made of p-type or n-type silicon.


Alternatively or additionally, the at least one sensing element can be formed using an implant or deposition process.


Alternatively or additionally, the CMOS circuitry can be configured to amplify and digitize an analog electrical output signal produced by the at least one sensing element.


Alternatively or additionally, the trench can be configured to increase strain on the at least one sensing element when a force is applied to the MEMS force sensor.


Alternatively or additionally, a depth of the overload gap can be configured to provide overload protection for the MEMS force sensor.


Alternatively or additionally, the electrical terminals can be solder bumps or copper pillars.


An example MEMS switch is also described herein. The MEMS switch can include a sensor die configured to receive an applied force. The sensor die has a top surface and a bottom surface opposite thereto. The MEMS switch can also include a sensing element and digital circuitry arranged on the bottom surface of the sensor die. The sensing element can be configured to convert a strain on the bottom surface of the sensor die to an analog electrical signal that is proportional to the strain. Additionally, the digital circuitry can be configured to convert the analog electrical signal to a digital signal, and provide a digital output code based on a plurality of predetermined force thresholds.


Alternatively or additionally, the digital circuitry can be further configured to compare the digital signal to the predetermined force thresholds. Optionally, the predetermined force thresholds are relative to a baseline. Alternatively or additionally, the digital circuitry can be further configured to update the baseline at a predetermined frequency. For example, the baseline can be updated by comparing the digital signal to an auto-calibration threshold.


Other systems, methods, features and/or advantages will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be protected by the accompanying claims.





BRIEF DESCRIPTION OF THE FIGURES

The components in the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding parts throughout the several views. These and other features of will become more apparent in the detailed description in which reference is made to the appended drawings.



FIG. 1 is an isometric view of the top of an example MEMS force sensor according to implementations described herein.



FIG. 2 is a top view of the MEMS force sensor of FIG. 1.



FIG. 3 is a cross-sectional view of the MEMS force sensor of FIG. 1.



FIG. 4 is an isometric view of the bottom of the MEMS force sensor of FIG. 1.



FIG. 5 is a cross-sectional view of an example base wafer of an integrated p-type MEMS-CMOS force sensor using a piezoresistive sensing element (not to scale) according to implementations described herein.



FIG. 6 is a cross-sectional view of an example base wafer of an integrated n-type MEMS-CMOS force sensor using a piezoresistive sensing element (not to scale) according to implementations described herein.



FIG. 7 is a cross-sectional view of an example base wafer of an integrated p-type MEMS-CMOS force sensor using a polysilicon sensing element (not to scale) according to implementations described herein.



FIG. 8 is a cross-sectional view of an example base wafer of an integrated p-type MEMS-CMOS force sensor using a piezoelectric sensing element (not to scale) according to implementations described herein.



FIG. 9 is an isometric view of the top of an example MEMS switch according to implementations described herein.



FIG. 10 is an isometric view of the bottom of the MEMS switch of FIG. 9.



FIG. 11 is an example truth table describing the outputs of a two-bit digital output.



FIG. 12 depicts a flow chart describing an example baselining process.





DETAILED DESCRIPTION

The present disclosure can be understood more readily by reference to the following detailed description, examples, drawings, and their previous and following description. However, before the present devices, systems, and/or methods are disclosed and described, it is to be understood that this disclosure is not limited to the specific devices, systems, and/or methods disclosed unless otherwise specified, and, as such, can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.


The following description is provided as an enabling teaching. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made, while still obtaining beneficial results. It will also be apparent that some of the desired benefits can be obtained by selecting some of the features without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations may be possible and can even be desirable in certain circumstances, and are contemplated by this disclosure. Thus, the following description is provided as illustrative of the principles and not in limitation thereof.


As used throughout, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a MEMS force sensor” can include two or more such MEMS force sensors unless the context indicates otherwise.


The term “comprising” and variations thereof as used herein is used synonymously with the term “including” and variations thereof and are open, non-limiting terms.


Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.


As used herein, the terms “optional” or “optionally” mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.


A MEMS force sensor 10 for measuring a force applied to at least a portion thereof is described herein. In one aspect, as depicted in FIGS. 1-4, the force sensor 10 includes a base 11 (also sometimes referred to as a “sensor die” or “force sensor die”) and a cap 12. The base 11 and the cap 12 can be bonded at one or more points along the surface formed by an outer wall 13 of the base 11. In other words, the base 11 and the cap 12 can be bonded at a peripheral region of the MEMS force sensor 10. It should be understood that the peripheral region of the MEMS force sensor 10 is spaced apart from the center thereof, i.e., the peripheral region is arranged near the outer edge of the MEMS force sensor 10. Example MEMS force sensors where a cap and sensor die are bonded in peripheral region of the MEMS force sensor are described in U.S. Pat. No. 9,487,388, issued Nov. 8, 2016 and entitled “Ruggedized MEMS Force Die;” U.S. Pat. No. 9,493,342, issued Nov. 15, 2016 and entitled “Wafer Level MEMS Force Dies;” U.S. Patent Application Publication No. 2016/0332866 to Brosh et al., filed Jan. 13, 2015 and entitled “Miniaturized and ruggedized wafer level mems force sensors;” and U.S. Patent Application Publication No. 2016/0363490 to Campbell et al., filed Jun. 10, 2016 and entitled “Ruggedized wafer level mems force sensor with a tolerance trench,” the disclosures of which are incorporated by reference in their entireties. The bonded area(s) can therefore be arranged in proximity to the outer edge of the MEMS force sensor 10 as opposed to in proximity to the central region thereof. This allows the bonded area(s) to take up a large percentage of the surface area between the cap 12 and the base 11, which results in a MEMS force sensor with improved strength and robustness.


The cap 12 can optionally be made of glass (e.g., borosilicate glass) or silicon. The base 11 can optionally be made of silicon. Optionally, the base 11 (and its components such as, for example, the boss, the outer wall, the flexure(s), etc.) is a single continuous piece of material, i.e., the base 11 is monolithic. It should be understood that this disclosure contemplates that the cap 12 and/or the base 11 can be made from materials other than those provided as examples. This disclosure contemplates that the cap 12 and the base 11 can be bonded using techniques known in the art including, but not limited to, silicon fusion bonding, anodic bonding, glass frit, thermo-compression, and eutectic bonding.


The internal surfaces between the base 11 and the cap 12 form a sealed cavity 14. The sealed cavity 14 can be formed by etching a trench (e.g., as described below with regard to FIGS. 5-8) from the base 11 and then sealing a volume between the bonded base 11 and cap 12. For example, the volume is sealed between the base 11 and the cap 12 when adhered together, which results in formation of the sealed cavity 14. The trench can be etched by removing material from the base 11 (e.g., the deep etching process described herein). Additionally, the trench defines the outer wall 13 and at least one flexure 16. In FIGS. 1-3, the trench is continuous and has a substantially square shape. It should be understood that the trench can have other shapes, sizes, and/or patterns than the trench shown in FIGS. 1-3, which is only provided as an example. Optionally, the trench can form a plurality of outer walls and/or a plurality of flexures. Example MEMS force sensors having a cavity (e.g., trench) that defines a flexible sensing element (e.g., flexure) are described in U.S. Pat. No. 9,487,388, issued Nov. 8, 2016 and entitled “Ruggedized MEMS Force Die;” U.S. Pat. No. 9,493,342, issued Nov. 15, 2016 and entitled “Wafer Level MEMS Force Dies;” U.S. Patent Application Publication No. 2016/0332866 to Brosh et al., filed Jan. 13, 2015 and entitled “Miniaturized and ruggedized wafer level mems force sensors;” and U.S. Patent Application Publication No. 2016/0363490 to Campbell et al., filed Jun. 10, 2016 and entitled “Ruggedized wafer level mems force sensor with a tolerance trench,” the disclosures of which are incorporated by reference in their entireties. The sealed cavity 14 can be sealed between the cap 12 and the base 11 when the cap 12 and the base 11 are bonded together. In other words, the MEMS force sensor 10 has a sealed cavity 14 that defines a volume entirely enclosed by the cap 12 and the base 11. The sealed cavity 14 is sealed from the external environment.


The base 11 has a top surface 18a and a bottom surface 18b. The top and bottom surfaces 18a, 18b are arranged opposite to each other. The trench that defines the outer wall 13 and flexure 16 is etched from the top surface 18a of the base 11. A contact surface 15 is arranged along a surface of the cap 12 (e.g., along the top surface thereof) for receiving an applied force “F.” The force “F” is transmitted from the cap 12 through the outer wall 13 to at least one flexure 16. The MEMS force sensor 10 can include an air gap 17 (also sometimes referred to as a “gap” or “overload gap”) between a portion of the base 11 and cap 12. The air gap 17 can be within the sealed cavity 14. For example, the air gap 17 can be formed by removing material from the base 11 (e.g., the shallow etching process described herein). Alternatively, the air gap 17 can be formed by etching a portion of the cap 12. Alternatively, the air gap 17 can be formed by etching a portion of the base 11 and a portion of the cap 12. The size (e.g., thickness or depth) of the air gap 17 can be determined by the maximum deflection of the at least one flexure 16, such that the air gap 17 between the base 11 and the cap 12 will close and mechanically stop further deflection before the at least one flexure 16 is broken. The air gap 17 provides an overload stop by limiting the amount by which the at least one flexure 16 can deflect such that the flexure does not mechanically fail due to the application of excessive force. Example MEMS force sensors designed to provide overload protection are described in U.S. Pat. No. 9,487,388, issued Nov. 8, 2016 and entitled “Ruggedized MEMS Force Die;” U.S. Pat. No. 9,493,342, issued Nov. 15, 2016 and entitled “Wafer Level MEMS Force Dies;” U.S. Patent Application Publication No. 2016/0332866 to Brosh et al., filed Jan. 13, 2015 and entitled “Miniaturized and ruggedized wafer level mems force sensors;” and U.S. Patent Application Publication No. 2016/0363490 to Campbell et al., filed Jun. 10, 2016 and entitled “Ruggedized wafer level mems force sensor with a tolerance trench,” the disclosures of which are incorporated by reference in their entireties.


Referring now to FIGS. 3 and 4, the side and bottom views of the MEMS force sensor 10 are shown, respectively. The MEMS force sensor 10 includes at least one sensing element 22 disposed on the bottom surface 18b of the base 11. Optionally, a plurality of sensing elements 22 can be disposed on the bottom surface 18b of the base 11. This disclosure contemplates that the sensing element(s) 22 can be diffused, deposited, or implanted on the bottom surface 18b of the base 11. The sensing element 22 can change an electrical characteristic (e.g., resistance, capacitance, charge, etc.) in response to deflection of the at least one flexure 16. The change in electrical characteristic can be measured as the analog electrical signal as described herein. In one implementation, the sensing element 22 can optionally be a piezoresistive transducer. For example, as strain is induced in the at least one flexure 16 proportional to the force “F” applied to the contact surface 15, a localized strain is produced on the piezoresistive transducer such that the piezoresistive transducer experiences compression or tension, depending on its specific orientation. As the piezoresistive transducer compresses and tenses, its resistivity changes in opposite fashion. Accordingly, a Wheatstone bridge circuit including a plurality (e.g., four) piezoresistive transducers (e.g., two of each orientation relative to strain) becomes unbalanced and produces a differential voltage (also sometimes referred to herein as an “analog electrical signal”) across the positive signal terminal and the negative signal terminal. This differential voltage is directly proportional to the applied force “F” on the cap 12 of the MEMS force sensor 10. As described below, this differential voltage can be received at and processed by digital circuitry (e.g., CMOS circuitry 23), which is also disposed on the base 11. For example, the digital circuitry can be configured to, among other functions, convert the analog electrical signal to a digital electrical output signal. Although piezoresistive transducers are provided as an example sensing element, this disclosure contemplates that the at least one sensing element 22 can be any sensor element configured to change at least one electrical characteristic (e.g., resistance, charge, capacitance, etc.) based on an amount or magnitude of an applied force and can output a signal proportional to the amount or magnitude of the applied force. Other types of sensing elements include, but not limited to, piezoelectric or capacitive sensors.


It is further contemplated that the analog electrical signals produced by the at least one sensing element 22 in a Wheatstone bridge configuration can optionally be processed by digital circuitry that resides on the same surface as the at least one sensing element 22. In one implementation, the digital circuitry is CMOS circuitry 23. The CMOS circuitry 23 can therefore be disposed on the bottom surface 18b of the base 11 as shown in FIG. 4. In other words, both the sensing element 22 and the CMOS circuitry 23 can be provided on the same monolithic substrate (e.g., the base 11, which can optionally be made of silicon). This is as opposed to routing the analog electrical signals produced by the at least one sensing element 22 to digital circuitry external to the MEMS force sensor 10 itself. It should be understood that routing the analog electrical signal to circuitry external to the MEMS force sensor 10 may result in loss of signal integrity due to electrical noise. The CMOS circuitry 23 can optionally include one or more of a differential amplifier or buffer, an analog-to-digital converter, a clock generator, non-volatile memory, and a communication bus. Additionally, the CMOS circuitry 23 can optionally include programmable memory to store trimming values that can be set during a factory calibration. The trimming values can be used to ensure that the MEMS force sensor 10 provides an accurate absolute force output within a specified margin of error. Furthermore, the programmable memory can optionally store a device identifier (“ID”) for traceability. CMOS circuitry is known in the art and is therefore not described in further detail below. This disclosure contemplates that the CMOS circuitry 23 can include circuits other than those provided as examples. For example, this disclosure contemplates that CMOS circuitry 23 can optionally include components to improve accuracy, such as an internal voltage regulator or a temperature sensor. As described herein, the differential analog output of the Wheatstone bridge can be amplified, digitized, and stored in a communication buffer until it is requested by a host device. The MEMS force sensor 10 can also include at least one electrical terminal 19 as shown in FIGS. 3 and 4. The electrical terminals 19 can be power and/or communication interfaces used to connect (e.g., electrically, communicatively) to a host device. The electrical terminals 19 can be solder bumps or metal (e.g., copper) pillars to allow for wafer-level packaging and flip-chip assembly. Although solder bumps and copper pillars are provided as examples, this disclosure contemplates that the electrical terminals 19 can be any component capable of electrically connecting the MEMS force sensor 10 to a host device. Additionally, it should be understood that the number and/or arrangement of electrical terminals 19 is provided only as examples in FIGS. 3 and 4.


The process of forming the at least one sensing element 22 and the CMOS circuitry 23 on the same surface (e.g., the bottom surface 18b) of the base 11 can be generalized as a three-stage process. The first stage is the creation of the at least one sensing element 22 by way of either diffusion, deposition, or implant patterned with a lithographic exposure process. The second stage is the creation of the CMOS circuitry 23 through standard CMOS process procedures. And the third stage is the creation of base 11 elements, which includes the outer wall 13, sealed cavity 14, at least one flexure 16, and air gap 17. It is contemplated that these stages can be performed in any order that the manufacturing processes allow.


The first stage includes the steps to form the at least one sensing element (e.g., sensing element 22 shown in FIG. 4). Referring now to FIGS. 5 through 8, common CMOS processes begin with a p-type silicon wafer 101. This disclosure contemplates that a p-type silicon wafer can be used to manufacture the MEMS force sensor described above with regard to FIGS. 1-4. It should be understood, however, that similar CMOS processes can be adapted to other starting materials, such as an n-type silicon wafer. Additionally, this disclosure contemplates that semiconductor wafers other than silicon can be used. The sensing element (e.g., at least one sensing element 22 shown in FIG. 4) can be implemented as either an n-type diffusion, deposition, or implant 102 as shown in FIG. 5, or a p-type diffusion, deposition, or implant 202 fully contained in an n-type well 204 as shown in FIG. 6. In the former aspect (i.e., n-type diffusion, deposition, or implant of FIG. 5), the terminals of the sensing element include highly-doped n-type implants 103 that connect to the n-type diffusion, deposition, or implant 102. In the latter aspect (i.e., p-type diffusion, deposition, or implant of FIG. 6), the terminals of the sensing element include highly-doped p-type implants 203 that connect to the p-type diffusion, deposition, or implant 202, while the n-type well 204 receives a voltage bias through a highly-doped n-type implant 105.


In an alternative aspect, the sensing element can be implemented as either an n-type or p-type poly-silicon implant 302 as shown in FIG. 7, which is available in the common CMOS process as gate or capacitor layers through n-type or p-type implant. As shown in FIG. 7, the terminals of the sensing element include low resistance silicided poly-silicon 303 that connect to the implant 302. In yet another alternative aspect, the sensing element can be implemented with piezoelectric layer 402 in combination with top electrode 401 and bottom electrode 403 as shown in FIG. 8. Additionally, as shown in FIGS. 5-8, the electrical connections between the sensing element and digital circuitry (e.g., CMOS circuitry 23 as shown in FIG. 4) can be implemented with conductive inter-connection layers 112 and vias 113. The inter-connection layers 112 and vias 113 can optionally be made of metal, for example.


The second stage includes the lithographic, implant, anneal, deposition, and etching processes to form the digital circuitry (e.g., CMOS circuitry 23 as shown in FIG. 4). These processes are widely utilized in industry and described in the pertinent art. As such, these processes are not described in detail herein. The second stage can include creation of an NMOS device 110 including n-type source and drain implants 108. The second stage can also include creation of a PMOS device 111 including p-type source and drain implants 109. The p-type source and drain implants 109 are provided in an n-type well, which receives a voltage bias through a highly-doped n-type implant 105. Additionally, each of the NMOS device 110 and PMOS device 111 can include a metal-oxide gate stack 107. It should be understood that the second stage can include creation of a plurality of NMOS and PMOS devices. The NMOS and PMOS devices can form various components of the digital circuitry (e.g., CMOS circuitry 23 shown in FIG. 4). The digital circuity can optionally include other components, which are not depicted in FIGS. 5-8, including, but not limited to, bipolar transistors; metal-insulator-metal (“MIM”) and metal-oxide-semiconductor (“MOS”) capacitors; diffused, implanted, and polysilicon resistors; and/or diodes.


As described above, the sensing element and digital circuitry (e.g., sensing element 22 and CMOS circuitry 23 shown in FIG. 4) can be disposed on the same monolithic substrate (e.g., the base 11 shown in FIG. 4). This disclosure therefore contemplates that each of the processing steps (i.e., first stage processing steps) utilized in the creation of the sensing element (e.g., at least one sensing element 22 shown in FIG. 4) is compatible with the downstream processing steps (i.e., second stage processing steps) utilized in the creation of the digital circuitry (e.g., CMOS circuitry 23 shown in FIG. 4) in implementations where the sensing element(s) are created before the digital circuitry. For example, the n-type diffusion, deposition, or implant 102 (e.g., as shown in FIG. 5) or the p-type diffusion, deposition, or implant 202 (e.g., as shown in FIG. 6) can be designed such that it will arrive at its target depth after the anneal processes utilized in the creation of the digital circuitry (e.g., CMOS circuitry 23 shown in FIG. 4). Similar design considerations can be made for each of the features described above and related to the sensing element. Alternative processes can include formation of the terminals for the sensing element (e.g., implants 103 shown in FIG. 5 or implants 105, 203 shown in FIG. 6) that are performed at any point during or after formation of the digital circuitry (e.g., CMOS circuitry 23 shown in FIG. 4), which would impose different requirements on the anneal steps.


The third stage includes the MEMS micro-machining steps that are performed on the p-type silicon wafer 101. It should be understood that the p-type silicon wafer 101 of FIGS. 5-8 can correspond to the base 11 of the MEMS force sensor 10 shown in FIGS. 1-4. This disclosure contemplates that the third stage steps can be performed before or after performance of the first and second stages, depending on the capabilities of the manufacturing processes. As described above with regard to FIGS. 1-4, the base 11 can be etched to form the air gap 17, the outer wall 13, and the at least one flexure 16. A shallow etch can form the air gap 17. A deep etch can form the outer wall 13 and the at least one flexure 16. The deep etch is shown by reference number 106 in FIGS. 5-8. As shown in FIGS. 5-8, the sensing element is formed on a surface of the at least one flexure. Thereafter, the base (e.g., base 11 shown in FIGS. 1-4) is bonded to the cap (e.g., cap 12 shown in FIGS. 1-4) as described above. As a result, a sealed cavity (e.g., sealed cavity 14 shown in FIGS. 1-3) is formed. Electrical terminals (e.g., electrical terminals 19 as shown in FIGS. 3-4) can be added after all wafer processing is complete.


A MEMS switch device is also described herein. Referring now to FIGS. 9-10, an example MEMS switch device 50 is shown. The MEMS switch device 50 can include a base 51 having a top surface 58a and a bottom surface 58b. The MEMS switch device 50 can also include a cap 52 bonded to the base 51, which forms a sealed cavity 54 therebetween. As shown in FIG. 10, at least one sensing element 62 and digital circuitry 63 (e.g., CMOS circuitry) are arranged on the bottom surface 58b of the base 51. Electrical terminals 59 are also arranged on the bottom surface 58b of the base 51. The electrical terminals 59 can be used to electrically and/or communicatively connect the MEMS switch device to a host device. The electrical terminals 59 can facilitate wafer-level packaging and flip-chip assembly. Additionally, a contact surface 55 on which force is applied is shown in FIG. 9. When force is applied, it is transferred from the cap 52 to the base 51, where strain is induced in the bottom surface 58b thereof. An electrical characteristic of the sensing element 62 changes in response to the localized strain. This change is captured by an analog electrical signal produced by the sensing element 62. The analog electrical signal is transferred to the digital circuitry 63 for further processing. It should be understood that the MEMS switch device 50 is similar to the MEMS force sensor described above with regard to FIGS. 1-8. Accordingly, various features of the MEMS switch device 50 are not described in further detail below.


As described above, the MEMS switch device 50 can optionally include a plurality of sensing elements 62 configured as a Wheatstone bridge. The analog electrical signals produced by the sensing elements 62 in a Wheatstone bridge configuration can optionally be processed by complementary metal-oxide-semiconductor (CMOS) circuitry (e.g., digital circuitry 63) that resides on the bottom surface 58b of the base 51. In other words, both the sensing elements 62 and the CMOS circuitry can be arranged on the same surface of the base. As described above, the CMOS circuitry can include a differential amplifier or buffer, an analog-to-digital converter, a clock generator, non-volatile memory, and/or one or more digital outputs. The one or more digital outputs can be configured to change state when one or more force thresholds are reached. In this way, the MEMS switch device 50 can be used as a single-level or multi-level binary switch. For instance, in one aspect with two digital outputs, three force levels (e.g., predetermined force thresholds) can be programmed above the nominal zero-force, enabling a three-level switch. FIG. 11 is a truth table describing the outputs (D1, D2) of a two-bit digital output (e.g., a digital output code). In FIG. 11, the three force thresholds are f1, f2, and f3. This disclosure contemplates that the number of outputs and the number/value of force thresholds can vary according to the design of the MEMS switch device 50. The digital outputs can be configured to indicate 2N input force levels, where N is the number of output terminals. The digital outputs/input force levels can be programmed by the user.


Additionally, the CMOS circuitry can optionally include programmable memory to store trimming values that can be set during a factory calibration. The trimming values can be used to ensure that the MEMS switch device 50 provides accurate force level detection within a specified margin of error. Furthermore, the programmable memory can optionally store a device ID for traceability. This disclosure contemplates that the CMOS circuitry can include circuits other than those provided as examples. For example, this disclosure contemplates CMOS circuitry optionally including components to improve accuracy, such as an internal voltage regulator or a temperature sensor.


In one aspect, it may be desirable to maintain consistent force level transitions independent of any offset or static force applied to the MEMS switch device 50. In this aspect, the MEMS switch device 50 can be configured to compare a dynamic force to the programmed force thresholds, filtering any low frequency response caused by various conditions including mechanical preload and temperature variation. This can be achieved by performing a low-frequency baseline operation that compares the current force input to an auto-calibration threshold. FIG. 12 is a flow chart illustrating example operations for the baselining process. At 1202, the MEMS switch device enters an active state, for example, in response to an applied force. At 1204, the baseline is set. At 1206, if the current force input is less than the auto-calibration threshold, the current force input is set as the new baseline until the next operation. In other words, operations return to 1204. On the other hand, at 1206, if the current force input is greater than the auto-calibration threshold, the baseline remains unchanged as shown at 1208. The auto-calibration threshold and frequency of the operation can be programmable in a manner similar to the switching force thresholds, for example, to an auto-calibration threshold of 0.5N and a baselining frequency of 10 Hz. It should be understood that the values for the auto-calibration threshold and baselining frequency are provided only as examples and can have other values.


Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims
  • 1. A microelectromechanical (“MEMS”) switch, comprising: a sensor die configured to receive an applied force, wherein the sensor die comprises a top surface and a bottom surface opposite thereto,a sensing element arranged on the bottom surface of the sensor die, wherein the sensing element is configured to convert a strain to an analog electrical signal that is proportional to the strain, anddigital circuitry arranged on the bottom surface of the sensor die, wherein the sensing element and the digital circuitry are arranged on the same surface of the sensor die, and wherein the digital circuitry is configured to:convert the analog electrical signal to a digital signal, andprovide a digital output code based on a plurality of predetermined force thresholds.
  • 2. The MEMS switch of claim 1, wherein the digital circuitry is further configured to compare the digital signal to the predetermined force thresholds.
  • 3. The MEMS switch of claim 1, wherein the predetermined force thresholds are relative to a baseline.
  • 4. The MEMS switch of claim 3, wherein the digital circuitry is further configured to update the baseline at a predetermined frequency.
  • 5. The MEMS switch of claim 4, wherein the baseline is updated by comparing the digital signal to an auto-calibration threshold.
  • 6. The MEMS switch of claim 1, wherein the sensing element is formed by diffusion or implantation.
  • 7. The MEMS switch of claim 1, wherein the sensing element is formed by a polysilicon process from an integrated circuit process.
  • 8. The MEMS switch of claim 1, further comprising a plurality of electrical terminals arranged on the bottom surface of the sensor die, wherein the digital output code provided by the digital circuitry is routed to the electrical terminals.
  • 9. The MEMS switch of claim 8, wherein the electrical terminals comprise solder bumps or copper pillars.
  • 10. The MEMS switch of claim 1, further comprising a cap attached to the sensor die at a surface defined by an outer wall of the sensor die, wherein a sealed cavity is formed between the cap and the sensor die.
  • 11. The MEMS switch of claim 10, wherein the sensor die comprises a flexure formed therein, and wherein the flexure converts the applied force into the strain on the bottom surface of the sensor die.
  • 12. The MEMS switch of claim 11, wherein the flexure is formed in the sensor die by etching.
  • 13. The MEMS switch of claim 10, wherein a gap is arranged between the sensor die and the cap, and wherein the gap is configured to narrow with application of the applied force such that the flexure is unable to deform beyond its breaking point.
  • 14. The MEMS switch of claim 1, wherein the sensing element comprises a piezoresistive, piezoelectric, or capacitive transducer.
CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 USC 371 national phase application of PCT/US2018/017564 filed on Feb. 9, 2018, which claims the benefit of U.S. provisional patent application No. 62/456,699, filed on Feb. 9, 2017, and entitled “INTEGRATED DIGITAL FORCE SENSOR,” and U.S. provisional patent application No. 62/469,094, filed on Mar. 9, 2017, and entitled “SOLID STATE MECHANICAL SWITCH,” the disclosures of which are expressly incorporated herein by reference in their entireties.

PCT Information
Filing Document Filing Date Country Kind
PCT/US2018/017564 2/9/2018 WO 00
Publishing Document Publishing Date Country Kind
WO2018/148503 8/16/2018 WO A
US Referenced Citations (378)
Number Name Date Kind
4594639 Kuisma Jun 1986 A
4658651 Le Apr 1987 A
4814856 Kurtz et al. Mar 1989 A
4849730 Izumi et al. Jul 1989 A
4914624 Dunthorn Apr 1990 A
4918262 Flowers et al. Apr 1990 A
4933660 Wynne Jun 1990 A
4983786 Stevens Jan 1991 A
5095401 Zavracky et al. Mar 1992 A
5159159 Asher Oct 1992 A
5166612 Murdock Nov 1992 A
5237879 Speeter Aug 1993 A
5320705 Fujii et al. Jun 1994 A
5333505 Takahashi et al. Aug 1994 A
5343220 Veasy et al. Aug 1994 A
5349746 Gruenwald et al. Sep 1994 A
5351550 Maurer Oct 1994 A
5483994 Maurer Jan 1996 A
5510812 O'Mara et al. Apr 1996 A
5541372 Baller et al. Jul 1996 A
5543591 Gillespie et al. Aug 1996 A
5565657 Merz Oct 1996 A
5600074 Marek et al. Feb 1997 A
5673066 Toda et al. Sep 1997 A
5773728 Tsukada et al. Jun 1998 A
5889236 Gillespie et al. Mar 1999 A
5921896 Boland Jul 1999 A
5969591 Fung Oct 1999 A
6012336 Eaton et al. Jan 2000 A
6028271 Gillespie et al. Feb 2000 A
6159166 Chesney et al. Dec 2000 A
6243075 Fishkin et al. Jun 2001 B1
6348663 Schoos et al. Feb 2002 B1
6351205 Armstrong Feb 2002 B1
6360598 Calame et al. Mar 2002 B1
6437682 Vance Aug 2002 B1
6555235 Aufderheide et al. Apr 2003 B1
6556189 Takahata et al. Apr 2003 B1
6569108 Sarvazyan et al. May 2003 B2
6610936 Gillespie et al. Aug 2003 B2
6620115 Sarvazyan et al. Sep 2003 B2
6629343 Chesney et al. Oct 2003 B1
6668230 Mansky et al. Dec 2003 B2
6720712 Scott et al. Apr 2004 B2
6788297 Itoh et al. Sep 2004 B2
6801191 Mukai et al. Oct 2004 B2
6809280 Divigalpitiya et al. Oct 2004 B2
6812621 Scott Nov 2004 B2
6822640 Derocher Nov 2004 B2
6868731 Gatesman Mar 2005 B1
6879318 Chan et al. Apr 2005 B1
6888537 Benson et al. May 2005 B2
6915702 Omura et al. Jul 2005 B2
6931938 Knirck et al. Aug 2005 B2
6995752 Lu Feb 2006 B2
7138984 Miles Nov 2006 B1
7173607 Matsumoto et al. Feb 2007 B2
7190350 Roberts Mar 2007 B2
7215329 Yoshikawa et al. May 2007 B2
7218313 Marcus et al. May 2007 B2
7224257 Morikawa May 2007 B2
7245293 Hoshino et al. Jul 2007 B2
7273979 Christensen Sep 2007 B2
7280097 Chen et al. Oct 2007 B2
7318349 Vaganov et al. Jan 2008 B2
7324094 Moilanen et al. Jan 2008 B2
7324095 Sharma Jan 2008 B2
7336260 Martin et al. Feb 2008 B2
7337085 Soss Feb 2008 B2
7345680 David Mar 2008 B2
7367232 Vaganov May 2008 B2
7406661 Väänänen et al. Jul 2008 B2
7425749 Hartzell et al. Sep 2008 B2
7426873 Kholwadwala et al. Sep 2008 B1
7449758 Axelrod et al. Nov 2008 B2
7460109 Satai et al. Dec 2008 B2
7476952 Vaganov et al. Jan 2009 B2
7508040 Nikkei et al. Mar 2009 B2
7554167 Vaganov Jun 2009 B2
7607111 Vaananen et al. Oct 2009 B2
7620521 Breed et al. Nov 2009 B2
7629969 Kent Dec 2009 B2
7649522 Chen et al. Jan 2010 B2
7663612 Bladt Feb 2010 B2
7685538 Fleck et al. Mar 2010 B2
7698084 Soss Apr 2010 B2
7701445 Inokawa et al. Apr 2010 B2
7746327 Miyakoshi Jun 2010 B2
7791151 Vaganov et al. Sep 2010 B2
7819998 David Oct 2010 B2
7825911 Sano et al. Nov 2010 B2
7829960 Takizawa Nov 2010 B2
7903090 Soss et al. Mar 2011 B2
7921725 Silverbrook et al. Apr 2011 B2
7952566 Poupyrev et al. May 2011 B2
7973772 Gettemy et al. Jul 2011 B2
7973778 Chen Jul 2011 B2
8004052 Vaganov Aug 2011 B2
8004501 Harrison Aug 2011 B2
8013843 Pryor Sep 2011 B2
8026906 Mölne et al. Sep 2011 B2
8044929 Baldo et al. Oct 2011 B2
8068100 Pryor Nov 2011 B2
8072437 Miller et al. Dec 2011 B2
8072440 Pryor Dec 2011 B2
8096188 Wilner Jan 2012 B2
8113065 Ohsato et al. Feb 2012 B2
8120586 Hsu et al. Feb 2012 B2
8120588 Klinghult Feb 2012 B2
8130207 Nurmi et al. Mar 2012 B2
8134535 Choi et al. Mar 2012 B2
8139038 Chueh et al. Mar 2012 B2
8144133 Wang et al. Mar 2012 B2
8149211 Hayakawa et al. Apr 2012 B2
8154528 Chen et al. Apr 2012 B2
8159473 Cheng et al. Apr 2012 B2
8164573 DaCosta et al. Apr 2012 B2
8183077 Vaganov et al. May 2012 B2
8184093 Tsuiki May 2012 B2
8188985 Hillis et al. May 2012 B2
8199116 Jeon et al. Jun 2012 B2
8212790 Rimas-Ribikauskas et al. Jul 2012 B2
8237537 Kurtz et al. Aug 2012 B2
8243035 Abe et al. Aug 2012 B2
8250921 Nasiri et al. Aug 2012 B2
8253699 Son Aug 2012 B2
8260337 Periyalwar et al. Sep 2012 B2
8269731 Molne Sep 2012 B2
8289288 Whytock et al. Oct 2012 B2
8289290 Klinghult Oct 2012 B2
8297127 Wade et al. Oct 2012 B2
8319739 Chu et al. Nov 2012 B2
8325143 Destura et al. Dec 2012 B2
8350345 Vaganov Jan 2013 B2
8363020 Li et al. Jan 2013 B2
8363022 The et al. Jan 2013 B2
8378798 Bells et al. Feb 2013 B2
8378991 Jeon et al. Feb 2013 B2
8384677 Mak-Fan et al. Feb 2013 B2
8387464 McNeil et al. Mar 2013 B2
8405631 Chu et al. Mar 2013 B2
8405632 Chu et al. Mar 2013 B2
8421609 Kim et al. Apr 2013 B2
8427441 Paleczny et al. Apr 2013 B2
8436806 Almalki et al. May 2013 B2
8436827 Zhai et al. May 2013 B1
8451245 Heubel et al. May 2013 B2
8456440 Abe et al. Jun 2013 B2
8466889 Tong et al. Jun 2013 B2
8477115 Rekimoto Jul 2013 B2
8482372 Kurtz et al. Jul 2013 B2
8493189 Suzuki Jul 2013 B2
8497757 Kurtz et al. Jul 2013 B2
8516906 Umetsu et al. Aug 2013 B2
8931347 Donzier et al. Jan 2015 B2
8973446 Fukuzawa Mar 2015 B2
8984951 Landmann et al. Mar 2015 B2
9032818 Campbell May 2015 B2
9097600 Khandani Aug 2015 B2
9487388 Brosh Nov 2016 B2
9493342 Brosh Nov 2016 B2
9709509 Yang Jul 2017 B1
9772245 Besling et al. Sep 2017 B2
10962427 Youssefi et al. Mar 2021 B2
20010009112 Delaye Jul 2001 A1
20030067448 Park Apr 2003 A1
20030128181 Poole Jul 2003 A1
20030189552 Chuang et al. Oct 2003 A1
20040012572 Sowden et al. Jan 2004 A1
20040140966 Marggraff et al. Jul 2004 A1
20050083310 Safai et al. Apr 2005 A1
20050190152 Vaganov Sep 2005 A1
20060028441 Armstrong Feb 2006 A1
20060244733 Geaghan Nov 2006 A1
20060272413 Vaganov et al. Dec 2006 A1
20060284856 Soss Dec 2006 A1
20070035525 Yeh et al. Feb 2007 A1
20070046649 Reiner Mar 2007 A1
20070070046 Sheynblat et al. Mar 2007 A1
20070070053 Lapstun et al. Mar 2007 A1
20070097095 Kim et al. May 2007 A1
20070103449 Laitinen et al. May 2007 A1
20070103452 Wakai et al. May 2007 A1
20070115265 Rainisto May 2007 A1
20070132717 Wang et al. Jun 2007 A1
20070137901 Chen Jun 2007 A1
20070139391 Bischoff Jun 2007 A1
20070152959 Peters Jul 2007 A1
20070156723 Vaananen Jul 2007 A1
20070182864 Stoneham et al. Aug 2007 A1
20070229478 Rosenberg et al. Oct 2007 A1
20070235231 Loomis et al. Oct 2007 A1
20070245836 Vaganov Oct 2007 A1
20070262965 Hirai et al. Nov 2007 A1
20070277616 Nikkel et al. Dec 2007 A1
20070298883 Feldman et al. Dec 2007 A1
20080001923 Hall et al. Jan 2008 A1
20080007532 Chen Jan 2008 A1
20080010616 Algreatly Jan 2008 A1
20080024454 Everest Jan 2008 A1
20080030482 Elwell et al. Feb 2008 A1
20080036743 Westerman et al. Feb 2008 A1
20080083962 Vaganov Apr 2008 A1
20080088600 Prest et al. Apr 2008 A1
20080088602 Hotelling Apr 2008 A1
20080094367 Van De Ven et al. Apr 2008 A1
20080105057 Wade May 2008 A1
20080105470 Van De Ven et al. May 2008 A1
20080106523 Conrad May 2008 A1
20080174852 Hirai et al. Jul 2008 A1
20080180402 Yoo et al. Jul 2008 A1
20080180405 Han et al. Jul 2008 A1
20080180406 Han et al. Jul 2008 A1
20080202249 Yokura et al. Aug 2008 A1
20080204427 Heesemans et al. Aug 2008 A1
20080211766 Westerman et al. Sep 2008 A1
20080238446 DeNatale et al. Oct 2008 A1
20080238884 Harish Oct 2008 A1
20080259046 Carsanaro Oct 2008 A1
20080284742 Prest et al. Nov 2008 A1
20080303799 Schwesig et al. Dec 2008 A1
20090027352 Abele Jan 2009 A1
20090027353 Im et al. Jan 2009 A1
20090046110 Sadler et al. Feb 2009 A1
20090102805 Meijer et al. Apr 2009 A1
20090140985 Liu Jun 2009 A1
20090184921 Scott et al. Jul 2009 A1
20090184936 Algreatly Jul 2009 A1
20090213066 Hardacker et al. Aug 2009 A1
20090237275 Vagnov Sep 2009 A1
20090237374 Li et al. Sep 2009 A1
20090242282 Kim et al. Oct 2009 A1
20090243817 Son Oct 2009 A1
20090243998 Wang Oct 2009 A1
20090256807 Nurmi Oct 2009 A1
20090256817 Perlin et al. Oct 2009 A1
20090282930 Cheng et al. Nov 2009 A1
20090303400 Hou et al. Dec 2009 A1
20090309852 Lin et al. Dec 2009 A1
20090314551 Nakajima Dec 2009 A1
20100013785 Murai et al. Jan 2010 A1
20100020030 Kim et al. Jan 2010 A1
20100020039 Ricks et al. Jan 2010 A1
20100039396 Ho et al. Feb 2010 A1
20100053087 Dai et al. Mar 2010 A1
20100053116 Daverman et al. Mar 2010 A1
20100066686 Joguet et al. Mar 2010 A1
20100066697 Jacomet et al. Mar 2010 A1
20100079391 Joung Apr 2010 A1
20100079395 Kim et al. Apr 2010 A1
20100079398 Shen et al. Apr 2010 A1
20100097347 Lin Apr 2010 A1
20100102403 Celik-Butler et al. Apr 2010 A1
20100117978 Shirado May 2010 A1
20100123671 Lee May 2010 A1
20100123686 Klinghult et al. May 2010 A1
20100127140 Smith May 2010 A1
20100128002 Stacy et al. May 2010 A1
20100153891 Vaananen et al. Jun 2010 A1
20100164959 Brown et al. Jul 2010 A1
20100220065 Ma Sep 2010 A1
20100271325 Conte et al. Oct 2010 A1
20100289807 Yu et al. Nov 2010 A1
20100295807 Xie et al. Nov 2010 A1
20100308844 Day et al. Dec 2010 A1
20100309714 Meade Dec 2010 A1
20100315373 Steinhauser et al. Dec 2010 A1
20100321310 Kim et al. Dec 2010 A1
20100321319 Hefti Dec 2010 A1
20100323467 Vaganov et al. Dec 2010 A1
20100328229 Weber et al. Dec 2010 A1
20100328230 Faubert et al. Dec 2010 A1
20110001723 Fan Jan 2011 A1
20110006980 Taniguchi et al. Jan 2011 A1
20110007008 Algreatly Jan 2011 A1
20110012848 Li et al. Jan 2011 A1
20110018820 Huitema et al. Jan 2011 A1
20110032211 Christoffersen Feb 2011 A1
20110039602 McNamara et al. Feb 2011 A1
20110050628 Homma et al. Mar 2011 A1
20110050630 Ikeda Mar 2011 A1
20110057899 Sleeman et al. Mar 2011 A1
20110063248 Yoon Mar 2011 A1
20110113881 Suzuki May 2011 A1
20110128250 Murphy et al. Jun 2011 A1
20110141052 Bernstein et al. Jun 2011 A1
20110141053 Bulea et al. Jun 2011 A1
20110187674 Baker et al. Aug 2011 A1
20110209555 Ahles et al. Sep 2011 A1
20110227836 Li et al. Sep 2011 A1
20110242014 Tsai et al. Oct 2011 A1
20110267181 Kildal Nov 2011 A1
20110267294 Kildal Nov 2011 A1
20110273396 Chung Nov 2011 A1
20110291951 Tong Dec 2011 A1
20110298705 Vaganov Dec 2011 A1
20110308324 Gamage et al. Dec 2011 A1
20120032907 Koizumi et al. Feb 2012 A1
20120032915 Wittorf Feb 2012 A1
20120038579 Sasaki Feb 2012 A1
20120044169 Enami Feb 2012 A1
20120044172 Ohki et al. Feb 2012 A1
20120050159 Yu et al. Mar 2012 A1
20120050208 Dietz Mar 2012 A1
20120056837 Park et al. Mar 2012 A1
20120060605 Wu et al. Mar 2012 A1
20120061823 Wu et al. Mar 2012 A1
20120062603 Mizunuma et al. Mar 2012 A1
20120068946 Tang et al. Mar 2012 A1
20120068969 Bogana et al. Mar 2012 A1
20120081327 Heubel et al. Apr 2012 A1
20120086659 Perlin et al. Apr 2012 A1
20120092250 Hadas et al. Apr 2012 A1
20120092279 Martin Apr 2012 A1
20120092294 Ganapathi et al. Apr 2012 A1
20120092299 Harada et al. Apr 2012 A1
20120092324 Buchan et al. Apr 2012 A1
20120105358 Momeyer et al. May 2012 A1
20120105367 Son et al. May 2012 A1
20120113061 Ikeda May 2012 A1
20120127088 Pance et al. May 2012 A1
20120127107 Miyashita et al. May 2012 A1
20120139864 Sleeman et al. Jun 2012 A1
20120144921 Bradley et al. Jun 2012 A1
20120146945 Miyazawa et al. Jun 2012 A1
20120146946 Wang et al. Jun 2012 A1
20120147052 Homma et al. Jun 2012 A1
20120154315 Aono Jun 2012 A1
20120154316 Kono Jun 2012 A1
20120154317 Aono Jun 2012 A1
20120154318 Aono Jun 2012 A1
20120154328 Kono Jun 2012 A1
20120154329 Shinozaki Jun 2012 A1
20120154330 Shimizu Jun 2012 A1
20120162122 Geaghan Jun 2012 A1
20120169609 Britton Jul 2012 A1
20120169617 Mënpää Jul 2012 A1
20120169635 Liu Jul 2012 A1
20120169636 Liu Jul 2012 A1
20120188181 Ha et al. Jul 2012 A1
20120194460 Kuwabara et al. Aug 2012 A1
20120194466 Posamentier Aug 2012 A1
20120200526 Lackey Aug 2012 A1
20120204653 August et al. Aug 2012 A1
20120205165 Strittmatter et al. Aug 2012 A1
20120218212 Yu et al. Aug 2012 A1
20120234112 Umetsu et al. Sep 2012 A1
20120256237 Lakamraju et al. Oct 2012 A1
20120286379 Inoue Nov 2012 A1
20120319987 Woo Dec 2012 A1
20120327025 Huska et al. Dec 2012 A1
20130008263 Kabasawa et al. Jan 2013 A1
20130038541 Bakker Feb 2013 A1
20130093685 Kalu et al. Apr 2013 A1
20130096849 Campbell et al. Apr 2013 A1
20130140944 Chen et al. Jun 2013 A1
20130187201 Elian Jul 2013 A1
20130239700 Benfield et al. Sep 2013 A1
20130255393 Fukuzawa et al. Oct 2013 A1
20130341741 Brosh Dec 2013 A1
20130341742 Brosh Dec 2013 A1
20140007705 Campbell et al. Jan 2014 A1
20140028575 Parivar et al. Jan 2014 A1
20140055407 Lee et al. Feb 2014 A1
20140090488 Taylor et al. Apr 2014 A1
20140283604 Najafi Sep 2014 A1
20140367811 Nakagawa et al. Dec 2014 A1
20150110295 Jenkner Apr 2015 A1
20150241465 Konishi Aug 2015 A1
20160069927 Hamamura Mar 2016 A1
20160245667 Najafi et al. Aug 2016 A1
20160332866 Brosh et al. Nov 2016 A1
20160363490 Campbell et al. Dec 2016 A1
20170103246 Pi et al. Apr 2017 A1
20170234744 Tung et al. Aug 2017 A1
20190383675 Tsai et al. Dec 2019 A1
20200149983 Tsai May 2020 A1
20200234023 Tsai et al. Jul 2020 A1
Foreign Referenced Citations (23)
Number Date Country
101341459 Jan 2009 CN
101458134 Jun 2009 CN
101801837 Aug 2010 CN
201653605 Nov 2010 CN
101929898 Dec 2010 CN
102062662 May 2011 CN
102998037 Mar 2013 CN
103308239 Sep 2013 CN
102853950 Mar 2015 CN
104535229 Apr 2015 CN
104581605 Apr 2015 CN
104919293 Sep 2015 CN
105934661 Sep 2016 CN
102010012441 Sep 2011 DE
2004-156937 Jun 2004 JP
2010147268 Jul 2010 JP
9310430 May 1993 WO
2004113859 Dec 2004 WO
2007139695 Dec 2007 WO
2011065250 Jun 2011 WO
2013067548 May 2013 WO
2015106246 Jul 2015 WO
2019023552 Jan 2019 WO
Non-Patent Literature Citations (6)
Entry
PCT/US2018/017564, International Search Report and Written Opinion dated Jun. 15, 2018, 11 pages.
Mei, T., et al., “Design and Fabrication of an Integrated Three-Dimensional Tactile Sensor for Space Robotic Applications,” Micro Electro Mechanical Systems, MEMS '99, Twelfth IEEE International Conference, Orlando Florida, Jan. 21, 1999, pp. 112-117.
Nesterov, V., et al., “Modelling and investigation of the silicon twin design 3D micro probe,” Journal of Micromechanics and Microengineering, vol. 15, 2005, pp. 514-520.
Extended European Supplementary Search Report issued in EP 18751209.0, dated Oct. 22, 2020 (7 pages).
Office Action issued for Chinese Application No. 201880023913.1, dated Dec. 25, 2020 (with English-language translation).
Office Action issued for Chinese Application No. 201880023913.1, dated Sep. 10, 2021 (with English-language translation).
Related Publications (1)
Number Date Country
20190383676 A1 Dec 2019 US
Provisional Applications (2)
Number Date Country
62456699 Feb 2017 US
62469094 Mar 2017 US