Position sensing of MEMS motion structures

Abstract

A deflectable micromechanical system includes: a deflectable element; a first anchor electrode and a second anchor electrode; a first spring having a deformable region and coupling the deflectable element to the first anchor electrode; and a second spring having a deformable region and coupling the deflectable electrode to the second anchoring element. At least one of the first spring and the second spring is piezoresistive, and a piezoresistance of the piezoresistive spring changes when the deformable region of the first spring and the deformable region of the second spring are deformed. The first anchor electrode and the second anchor electrode are electrically coupled to a circuit configured to detect a total piezoresistive change of the first spring and the second spring and to determine a deflection of the deflectable element using the piezoresistive change.

Description

Technical Field

[0001] The present invention relates to tilt position sensing of a MEMS (Micro Electro Mechanical System) structure, such as a micromirror, during its operation. Background Art

[0002] MEMS (Micro-Electro-Mechanical Systems) mirrors and mirror arrays have a wide range of applications within fiber optic networks in various modules such as optical switches, optical attenuators, optical tunable filters, etc.

[0003] In addition, MEMS scanning mirrors provide key light scanning functions in modules such as micro projectors, HUDs (head-up displays), and AR / VR. MEMS (micro-electromechanical systems) mirrors are also used in LiDAR (light detection and ranging) for steering laser beams and directing returning laser beams to sensitive detectors.

[0004] To achieve optimal performance, such as optimal resolution and image stability for pico projectors, optimal detection position and resolution for LiDAR, it is very important to have real-time information on the position of the scanning or tilting mirror.

[0005] Traditionally, a bulky and expensive external PSD (position sensing detector) is used to interpret the scanning or tilt mirror position. However, due to cost and footprint limitations, this approach does not provide an effective solution for applications such as LiDAR and AR / VR.

[0006] The present invention uses on-chip sensing elements to provide real-time scanning or tilt mirror position detection with optimal cost, size and performance. Summary of the Invention

[0007] This paper describes various on-chip component designs and their combinations to generate real-time position information of a moving structure in a MEMS device, in this case the position of a scanning or tilting MEMS mirror, with optimal performance, cost, and size. The present invention can also provide real-time motion sensing of tethered moving structures in other related sensor applications.

[0008] One embodiment relates to a deflectable micromechanical system with an integrated piezoresistive deflection sensor, the system comprising: a deflectable element; a first anchoring element and a second anchoring element; a first spring having a deformable region and coupling the deflectable element to the first anchoring element; and a second spring having a deformable region and coupling the deflectable element to the second anchoring element. When the relative position of the deflectable element relative to the anchoring element changes, the deformable region of the first spring and the deformable region of the second spring deform. At least one of the first and second springs is piezoresistive, and when the deformable region of the first and second springs deforms, the piezoresistive spring changes. First and second contacts are located on the first and second anchoring elements, respectively. The first contact is electrically connected to the first anchoring element, and the second contact is electrically connected to the second anchoring element. The first and second contacts are electrically connected to a resistance detection circuit configured to detect a change in the total piezoresistance of the first and second springs and use the change in piezoresistance to determine deflection of the deflectable element. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other features will become more apparent from the following description with reference to the accompanying drawings, which are for illustration purposes only and are not intended to be limiting in any way, in which:

[0010] Figure 1 : Configuration of a MEMS LiDAR system with mirror position feedback control.

[0011] Figures 2a to 2d : Illustration of 1D and 2D MEMS mirrors with hybrid piezoresistive and another additional mirror position sensing.

[0012] Figure 3 : Implementation of a 1D MEMS tilt mirror with piezoresistive sensing and capacitive sensing, with an interleaved comb drive design.

[0013] Figures 4a to 4c : Schematic diagram of the capacitive sensing and piezoresistive sensing mechanisms of a 1D MEMS tilt mirror used in a MEMS mirror design.

[0014] Figure 5 : Implementation of a 1D MEMS tilt mirror with piezoresistive sensing and capacitive sensing with a tilt comb drive design.

[0015] Figures 6a to 6b : Schematic diagram of the capacitive sensing and piezoresistive sensing mechanisms of a 1D MEMS tilt mirror used in a MEMS mirror design.

[0016] Figure 7: Implementation of 1D MEMS tilt mirrors with different flexure / piezoresistor designs.

[0017] Figure 8 : Implementation of 1D MEMS tilt mirror with different capacitive drive and sense comb drive designs.

[0018] Figure 9 : An embodiment of a 2D MEMS tilt mirror with hybrid piezoresistive and capacitive sensing for a first tilt axis and capacitive sensing for a second tilt axis.

[0019] Figure 10 : Exploded view of the structure with different electrical connections for 2D MEMS tilt mirror design.

[0020] Figure 11 : Implementation of a 2D MEMS tilt mirror with hybrid piezoresistive and capacitive sensing for a first tilt axis and an independent capacitive sensing comb drive for a second tilt axis.

[0021] Figure 12 : Implementation of a 2D MEMS tilt mirror with hybrid piezoresistive and capacitive sensing for a first tilt axis and hybrid piezoresistive and capacitive sensing for a second tilt axis.

[0022] Figure 13 : Another embodiment of a 2D MEMS tilt mirror with hybrid piezoresistive and capacitive sensing for a first tilt axis and hybrid piezoresistive and capacitive sensing for a second tilt axis.

[0023] Figure 14 : Configuration for deposition of metal traces on the bulk silicon connecting from the electrodes to the piezoresistor structure.

[0024] Figure 15 : An embodiment of a piezoresistive sensing element having a single electrical connection from a fixed anchor electrode to a moving MEMS structure.

[0025] Figure 16 : An embodiment of a piezoresistive sensing element having multiple electrical connections from a fixed anchor electrode to a moving MEMS structure.

[0026] Figure 17 : Schematic diagram of piezoresistive and capacitive sensing that handles mirror position feedback.

[0027] Figure 18 : An embodiment of mirror position sensing using piezoresistive sensing signals and capacitive sensing signals with complementary sensitivities achieved through hybrid sensing.

[0028] Figure 19: An embodiment of using piezoresistive sensing signals and capacitive sensing signals for mirror drive control and mirror position sensing through hybrid sensing. DETAILED DESCRIPTION

[0029] Figure 1 A symmetrical diagram shows a typical optical LiDAR system with a microelectromechanical system (MEMS) mirror. The system typically consists of a laser source 101, a MEMS mirror scanner 102, a MEMS mirror driver 104, and a photodetector 103. For LiDAR applications, the laser beam deflected by the MEMS mirror propagates to a detection target 106, where it is scattered and reflected. The reflected signal is detected by a photodetector 103. The MEMS mirror 102 also generates a feedback signal 105. This feedback signal is coupled to the MEMS mirror driver 104 for real-time correction of the mirror's pose to achieve optical staring scanning pattern tuning. The feedback signal can also be coupled to 101 to modulate the laser pulse distribution within a scanning cycle. Feedback signal characteristics are highly sought in MEMS LiDAR applications to achieve uniform angular resolution, as generating a linear scanning pattern with a MEMS mirror can be challenging. The feedback signal also needs to be coupled to the receiver to achieve cloud point synchronization, detect target resolution, and prevent pixel shift caused by environmental changes. Similarly, feedback mechanisms are also very beneficial for other applications such as HUDs and micro-projectors. MEMS mirrors with sensor feedback have been described previously. However, the feedback was generated using a single type of mirror position sensing method, which could be capacitive sensing, piezoelectric sensing, piezoresistive sensing, electromagnetic induction sensing, or optical sensing. In this patent, various MEMS mirror position sensing with hybrid sensing methods are proposed. In addition, a piezoresistive resistor design for MEMS mirror position detection is proposed. The specific hybrid sensing combination detailed in this patent is a combination of capacitive sensing and piezoresistive sensing. The piezoresistive-capacitive hybrid (PRCH) sensing method is expected to have high detection accuracy and reliability.

[0030] Figure 2a 、 Figure 2b 、 Figure 2c and Figure 2d An embodiment of a 1-D and 2-D tilting MEMS mirror with a hybrid tilt angle sensing method that combines a specific sensing method with piezoresistive sensing is shown. Figure 2aIn the embodiment of the present invention, for a 1-D tilt MEMS mirror, the design consists of a MEMS mirror 201, actuators / sensors 202a, 202b, flexures / piezoresistors 203a, 203b, and anchors 204a, 204b. The MEMS mirror 201 is used to reflect incident light. The actuators / sensors 202a, 202b are used to move and control the position of the mirror. The actuators can be electrostatic actuators (in-plane comb drive actuators, staggered comb drive actuators, or parallel plate electrostatic actuators), electrothermal actuators, electromagnetic actuators, or piezoelectric actuators, whichever can convert the input drive signal into torsional, lateral, or longitudinal deformation on the MEMS structure. For scanning mirror applications, these actuations cause the mirror to scan. The same actuators also provide sensing of the mirror position. The drive and sensing structures 202a and 202b can be implemented using the same structure or several separate structures. For example, if an electrostatic comb drive actuator is used as the actuator, the same electrostatic comb drive can also be used as a capacitive position sensor. On the other hand, another independent sensing comb drive in addition to the driving comb drive can be used as a sensor. 202a and 202b are also coupled / connected to flexures / hinges 203a and 203b. Since flexures / hinges 203a and 203b will deform when the mirror rotates, the resulting stress and strain of the flexures / hinges can be sensed with the help of piezoresistive sensing elements. These piezoresistive sensing elements can be formed using piezoresistive materials such as doped polysilicon films or doped or implanted silicon. To achieve good sensing results, the piezoresistive elements must be placed in high stress areas of the flexures / hinges, which introduces process difficulties and reliability issues. For example, misalignment of doping and implantation in high stress areas on the flexure / hinge structure will produce poor sensing signals. Due to the high stress of the flexure / hinge structure, delamination of the piezoresistive element / film will also occur.

[0031] In this invention, we use the flexure / hinge structure itself as the piezoresistive sensing element. Figure 2bIn the figure, 211 is a mirror or any other movable structure to be actuated. It is supported by 210 via flexure / hinge 212. 210, 211, and 212 are made of doped single-crystal silicon. Appropriately doped silicon has good piezoresistive properties. 211 can be actuated by external shock and vibration, electrostatic actuators (in-plane comb drive actuators, staggered comb drive actuators, or parallel plate electrostatic actuators), electrothermal actuators, electromagnetic actuators, or piezoelectric actuators. Stress and strain will cause the resistance of the flexure / hinge to change. An electrical interrogation circuit such as a Wheatstone bridge can be used to sense the resistance change and correlate it with the movement and position of 211. This approach will reduce process complexity and improve sensing reliability. For example, there is no need to align doping and implantation regions in high-stress areas on the flexure / hinge structure. It can also avoid selective area doping and implantation processes and delamination of the piezoresistive element / membrane.

[0032] In order to further improve the piezoresistive sensitivity of the flexure / hinge and make full use of the stress distribution of the flexure / hinge, structural optimization was implemented. Some structures such as Figure 15 and Figure 16 shown.

[0033] In addition, Figure 2c In this example, a suitably doped single-crystal silicon flexure / hinge 212 is coated with a conductive film (e.g., a metal film 2110) to mitigate negative effects on 212's piezoresistive sensing. Furthermore, a selective silicon etch 2101 is used to remove silicon to mitigate negative effects on 212's piezoresistive sensing. Furthermore, some regions of the hinge 211 can be doped with certain dopants to alter the conductivity of the flexure / hinge material. Different doping levels enhance the material's piezoelectric sensitivity and mitigate the negative effects of different types of stress on 212's piezoresistive sensing.

[0034] exist Figure 2d In the 2-D tilt MEMS mirror, the design consists of a MEMS mirror 211, first actuators / sensors 212a, 212b, first flexures / piezoresistors 213a, 213b, first fixed anchors 214a, 214b designed for the first axis of rotation, second actuators / sensors 215a, 215b, second flexures / piezoresistors 216a, 216b, and second fixed anchors 217a, 217b designed for the second axis of rotation. The second fixed anchors 217a, 217b are coupled to the first anchors / sensors 212a, 212b, allowing the entire structure for the second axis of rotation to move with the first axis of rotation. The arrangement of the actuators / sensors, flexures, and piezoresistors is the same as for the 1D tilt mirror described above.

[0035] Figure 3An embodiment of a one-dimensional tilting MEMS mirror design featuring PRCH sensing is shown. The structure shown is fabricated from highly doped silicon (n or p). The design is based on a 1D gimbal structure with an electrostatic actuator. MEMS mirror 301 is coupled to two support beams 308a and 308b. Support beams 308a and 308b connect MEMS mirror 301 to flexures / piezoresistors 306 and 307. Flexures / piezoresistors 306 and 307 are used for mirror tilt and serve as piezoresistive sensors for tilt angle. Flexures / piezoresistors 306 and 307 are located on the MEMS mirror's rotation axis 30. Simultaneously, movable comb actuators 309a, 309b, 309c, and 309d are also coupled to 308a and 308b. As shown in the figure, the comb actuators are distributed on both sides of beams 308a and 308b in this embodiment. Flexures / piezoresistors 306 and 307 are connected to fixed anchor electrodes 304 and 305. Flexures / piezoresistors 306 and 307 are the only connections from fixed anchor electrodes 304 and 305 to two support beams 308a and 308b. Wire bond pads are provided on 304 and 305 for external connections. The MEMS mirror 301, two support beams 308a and 308b, flexures / piezoresistors 306 and 307, and movable comb drives 309a, 309b, 309c, and 309d form the moving portion of the MEMS mirror. Due to the high doping level of silicon, all movable portions are electrically connected, and this serves as a common terminal for the MEMS mirror drive. In this embodiment, a set of four fixed comb drives 302a, 302b, 302c, and 302d are designed to correspond to the movable comb drives used for actuation. The fixed comb drives 302a, 302b, 302c, 302d are connected to electrodes 303a, 303b, 303c, 303d via bonding pads on the top to drive the individual comb drives. Each fixed comb drive is electrically isolated from the common terminal and the other fixed comb drives. A pair of movable comb drives and the fixed comb drive form an electrostatic actuator for driving the rotation of the mirror. The staggered vertical comb drive design in use is shown in the enlarged view of the comb drives. The comb teeth of the fixed comb drive 311 and the comb teeth of the movable comb drive 312 are positioned at different heights. Figure 3In the preferred embodiment shown, the teeth of the fixed comb drive 311 are positioned lower than those of the movable comb drive 312. In addition to actuation, the interleaved comb drive, acting as a variable capacitor, also detects when the mirror is rotated. During operation, the common terminal is connected to electrical ground, and a bias voltage is applied to the fixed comb drive. Anchor electrodes 304 or 305 can be connected to ground and then coupled to the common terminal via flexures / piezoresistors 306 or 307, depending on which side is connected. When voltage is applied, electrostatic forces cause the teeth of the fixed comb drive 311 and the movable comb drive 312 to move in a vertical direction parallel to the sidewalls of the comb teeth. This movement is coupled to the two support beams 308a, 308b, the MEMS mirror 301, and the entire movable portion of the mirror tilts along the axis defined by the flexures / piezoresistors 306 and 307. At the same time, as the movable part rotates, the capacitance change of the comb drive can be measured between the anchor electrodes 304, 305 and the electrodes 302a, 302b, 302c, 302d. Figure 3 Flexure / piezoresistor 306 is shown in detail in FIG. Flexure / piezoresistor 306 is coupled to 304 and support beam 308a. When support beam 308a rotates, flexure / piezoresistor 306 deforms to compensate for the torsional deformation caused by support beam 308a. The deformation of flexure / piezoresistor 306 causes a stress change and a change in the resistance of flexure / piezoresistor 306. Simultaneously, at the other end of the mirror, the rotation also causes deformation of flexure / piezoresistor 307, resulting in the same resistance change as flexure / piezoresistor 306. This resistance change is detected by measuring the resistance between anchor electrode 304 and anchor electrode 305. Support beam 308a, MEMS mirror 301, and support beam 308b are made of highly doped silicon and are significantly larger than flexure / piezoresistors 306 and 307. Therefore, the structural resistance of support beam 308a, MEMS mirror 301, and support beam 308b is much lower than that of flexures / piezoresistors 306 and 307. Furthermore, the resistance change is negligible. Therefore, the overall piezoresistance change, primarily contributed by flexures / piezoresistors 306 and 307, is related to the mirror tilt angle.

[0036] Figure 4a Shows the use of Figure 3Implementation of PRCH sensing according to the embodiment proposed in [ 1 ]. The exploded view of the structure consists of a movable part 401 including a mirror reflector and actuator, flexures / piezoresistors 411, 421, and a fixed part including fixed comb drives 403a, 403b, 403c, 403d and fixed anchor electrodes 404a and 404b. When a voltage of 0V is applied, the mirror does not move and remains in a neutral position 401. In this position, due to the weight of the movable part, the flexures / piezoresistors 411, 421 are under slight stress. A cross-section of the relative positions of the movable and fixed comb teeth is shown on the side of the figure. The fixed lower comb teeth are represented by reference numerals 41 and 43, and the movable upper comb teeth are represented by reference numerals 40 and 42. The flexure / piezoresistors are represented by reference numeral 44. The capacitance between the fixed lower comb teeth 41, 43 and the movable upper comb teeth 40, 42 remains constant. When the mirror is driven by an external signal, the mirror movable portion tilts to a second position. In this second position, the flexures / piezoresistors 411 and 421 are deformed, and the piezoresistors of the flexures / piezoresistors 411, 421 change when they are under stress. Figure 4a A cross-sectional view of the tilted reflector is shown in the figure on the side of the reflector. Reference numerals 40' and 42' indicate the positions of the movable comb teeth when the reflector is tilted to the second position. Reference numeral 44' indicates a flexure / piezoresistor that deforms when the reflector is tilted. In this case, the comb teeth 42' and 43 are bonded, and an overlapping area is generated between the comb teeth. The capacitance between the comb teeth varies with the overlapping area of ​​the comb drive. Therefore, the tilt angle of the reflector can be derived based on the capacitance value. At the same time, the piezoresistor value also changes as the flexure / piezoresistor 44 deforms to 44'. The stress caused by the deformation will depend on the tilt angle of the movable structure. The piezoresistance change can be measured by electrodes 404a and 404b.

[0037] Figure 4bTwo scenarios for piezoelectrically sensing flexure / hinge detection for deflection are shown. Reference numerals 404a and 404b are anchors. Reference numeral 401 is a movable mirror or proof mass. Reference numerals 411 and 421 are hinges connecting anchors 404a and 404b to movable mirror 401. These structures are made of uniformly and appropriately doped silicon. Silicon itself is a piezoresistive material. When movable mirror 401 tilts, it pulls on hinges / flexures 411 and 421. As an example, in scenario 1, when movable mirror 401 tilts to one side to the second position shown in the figure, hinges 411 and 421 are in tension. Since both hinges are under tensile stress, the piezoresistance will change. Both hinges 411 and 421 will increase or decrease, providing a constructive response. Lateral displacement of movable mirror 401 can be caused by intentionally applying an in-plane force. If the mirror tilts to the other side, hinges 411 and 421 will also be pulled and tensile stress will be generated therein. When the movable mirror 401 tilts to both sides, the piezoresistive response is the same. Sometimes, different information or directional information is required in certain applications. As shown in Case 2, hinge 411 is intentionally tilted in design to produce an asymmetric geometry about the rotation axis, such as Figure 4b As shown in . When the mirror in the second position is displaced in the upward direction (shown by U), the hinge 411 will be under tensile stress. When the mirror in the second position is displaced in the downward direction (shown by D), the hinge 421 will be under compressive stress. Therefore, the response in the two directions can be distinguished. In this case, depending on the design, the hinge 421 may be insensitive to the movable mirror 401 in the first position. With an asymmetric hinge design, Figure 4c The case where two piezoelectric sensors are arranged to form a detection bridge is shown. Reference numerals 404a, 404a', 404b are anchors, and 401 is a movable mirror or mass. Reference numerals 411a, 411b, and 421 are hinges that connect the anchors 404a, 404a', 404b to the movable mirror 401. Hinges 411a and 411b are piezoresistive sensing elements for the movable mirror 401 in the first position. Hinge 411a is asymmetric about the axis of rotation. Hinge 411b is also asymmetric about the axis of rotation. In this case, hinge 421 is a non-position-sensitive hinge, but provides an electrical connection from anchor 404b to the movable mirror 401. When the mirror 401 moves in one direction, as shown in FIG. Figure 4c As shown, hinge 411a is subjected to tensile stress, while hinge 411b is subjected to compressive stress. The different stresses will cause the piezoresistance of hinges 411a and 411b to increase and decrease, respectively. Thus, the two piezoresistive elements can form a Wheatstone bridge to enhance the responsiveness of position sensing. The sensing circuit can use hinge 421 as the output of the bridge.

[0038] Figure 5Another embodiment of a one-dimensional tilting MEMS mirror design with PRCH sensing features is shown. The structure shown in this figure is fabricated from highly doped silicon (n or p). The design is based on a 1D gimbal structure with an electrostatic actuator. The MEMS system mirror 501 is coupled to two support beams 508a and 508b. Support beams 508a and 508b connect the mirror 501 to flexures / piezoresistors 506 and 507. Flexures / piezoresistors 506 and 507 serve as hinges for mirror tilt and also act as piezoresistive sensors for tilt angle. Flexures / piezoresistors 506 and 507 are located on the MEMS mirror's rotation axis 50. Simultaneously, movable comb actuators 509a, 509b, 509c, and 509d are also coupled to support beams 508a and 508b. In the embodiment shown, the comb actuators are located on both sides of support beams 508a and 508b. Flexures / piezoresistors 506 and 507 are connected to fixed anchor electrodes 504 and 505. Flexures / piezoresistors 506 and 507 are the only connections from fixed anchor electrodes 504 and 505 to support beams 508a, 508b and mirror 501. Fixed anchor electrodes 504 and 505 have wire bond pads for external connections. Additional layers 510a and 510b are deposited on top of support beams 508a, 508b and movable comb drives 509a, 509b. The deposited material can be metal, dielectric, polysilicon, etc., and results in a symmetrical weight difference on movable comb drives 509a-509c and 509b-509d. The mirror 501, support beams 508a, 508b, flexures / piezoresistors 506, 507, symmetrical movable comb drives 509a, 509b, 509c, 509d, and additional layers 510a, 510b form the moving portion of the MEMS mirror. All movable components are electrically connected due to the high doping level of silicon, which serves as a common terminal for MEMS mirror actuation. In this embodiment, a set of four fixed comb drives 502a, 502b, 502c, 502d is designed to correspond to the movable comb drives used for actuation. The fixed comb drives 502a, 502b, 502c, 502d are connected to electrodes 503a, 503b, 503c, 503d via top bonding pads to drive the individual comb drives. Each fixed comb drive is electrically isolated from the common terminal and the other fixed comb drives. A pair of movable and fixed comb drives form the electrostatic actuator that drives the mirror's rotation. A magnified view of the comb drive shows the design of a tilted vertical comb drive in use. Reference numeral 511 denotes a fixed comb tooth. Reference numerals 512 and 513 are both movable comb teeth, but 513 has a deposited layer on top. Deposited layer 531b creates a weight difference, causing 513 to sink and 512 to rise, as 513 and 512 are located on opposite sides of the movable portion's rotation axis.Therefore, the comb teeth planes of 512, 513 and the comb teeth plane of 511 are separated by a small angle. The fixed comb teeth 513 will be lower than the movable comb teeth 511, and the movable comb teeth 512 will be higher than the fixed comb teeth 511. In addition to actuation, the tilt comb drive, which acts as a variable capacitor, is also used for sensing when the mirror rotates. During operation, the common terminal is connected to electrical ground, and a bias voltage is applied to the fixed comb drive. The fixed anchor electrode 504 or 505 can be connected to ground and then coupled to the common terminal through the flexure / piezoresistor 506 or 507, depending on which side is connected. When the drive waveform is applied, the electrostatic force will actuate the movable comb teeth 512 and the fixed comb teeth 513 to move the movable comb teeth 212 in a vertical direction parallel to the comb sidewalls. This movement is coupled to support beams 508a, 508b, and reflector 501, and the entire movable portion of the reflector will tilt along the axis defined by flexures / piezoresistors 506 and 507. Simultaneously, as the movable portion rotates, changes in the capacitance of the comb drive can be measured between electrodes 504, 505 and electrodes 502a, 502b, 502c, and 502d. Flexure / piezoresistors 506 are shown in an enlarged view. 506 is coupled to 504 and 508a. As support beam 508a rotates, flexure / piezoresistors 506 deform to compensate for the torsional deformation caused by support beam 508a. The deformation of flexure / piezoresistors 506 causes changes in stress and, consequently, changes in the resistance of flexure / piezoresistors 506. At the same time, at the other end of the reflector, the rotation also causes deformation of flexure / piezoresistors 507, resulting in a change in resistance, similar to that of flexure / piezoresistors 506. This resistance change is detected by measuring the resistance between electrodes 504 and 505. Support beams 508a, reflector 501, and support beams 508b are made of highly doped silicon and are much larger than flexures / piezoresistors 506 and 507. Therefore, the resistance of support beams 508a, reflector 501, and support beams 508b is much smaller than that of flexures / piezoresistors 506 and 507. At the same time, the resistance change is negligible. The total piezoresistance change, primarily contributed by flexures / piezoresistors 506 and 507, is related to the reflector's tilt angle.

[0039] Figure 6a Shows the use of Figure 5The PRCH sensing process of the embodiment and tilted comb drive design proposed in

[15] is shown. The exploded view of the structure consists of a movable part 601 including a mirror reflector and actuator, flexures / piezoresistors 611 and 621, and a fixed part including fixed comb drives 603a, 603b, 603c, 603d and fixed anchoring structures 604a and 604b. Additional deposited layers 631 and 641 are deposited on top of a single side of the movable comb. When a voltage of 0V is applied, the mirror does not move and remains in the neutral position 601. 611 and 621 are under slight stress due to the weight of the movable part. A cross-section of the relative positions of the movable and fixed comb teeth is shown in the side view in the figure. Reference numerals 61 and 63 are fixed comb teeth, and reference numerals 60 and 62 are movable comb teeth. Reference numeral 64 is the flexure / piezoresistor. Due to the additional deposited layer 65 on one side of the comb, the comb teeth are tilted to a very small angle in the neutral position. The movable comb and the fixed comb are fully bonded in the neutral position, and the capacitance between the combs is maximum in this position. When the mirror is driven by an external signal, the movable part of the mirror tilts to the second position, as shown in FIG. Figure 6a As shown in the middle part of the figure. Flexures / piezoresistors 611 and 621 deform, and the piezoresistors of flexures / piezoresistors 611 and 621 change when they are under stress. A cross-sectional view of the tilted mirror is shown sideways in the figure. Reference numerals 60' and 62' are movable comb teeth when the mirror is tilted. Reference numeral 64' is the flexure / piezoresistors that deform when the mirror is tilted. As the tilt angle increases, comb teeth 62' and 63 gradually separate. The capacitance between the comb teeth varies with the overlapping area of ​​the comb drive in the vertical direction. Therefore, the capacitance value can be correlated with the tilt angle of the mirror. At the same time, the piezoresistors also change when the mirror tilts and flexure / piezoresistors 64 deform to 64'. The stress caused by the deformation will depend on the tilt angle of the movable structure. The piezoresistance change can be measured by the bonding pads on 604a and 604b.

[0040] Figure 6b Shown is the case of a piezoelectric sensing flexure / hinge for rotation detection. Figure 6b(1) shows a side view of the hinge structure. In this case, 604a is the end of the hinge / flexure connected to the anchor. 601 is the end of the hinge / flexure connected to the movable part when there is no rotation. 611 is the hinge / flexure when there is no rotation, and it is stress neutral. The hinge structure is made of appropriately doped silicon (with piezoresistive properties). Reference numeral 50 is the axis of rotation, and in this case the axis is located in the middle of hinge 604a. When the movable object rotates, hinge 604a will remain the same as when it was anchored. Mirror 601 will rotate to the second position in the figure. When mirror 601 rotates, only the position changes, but the construction of mirror 601 should not change because it is located on a solid movable object (bulk material). At the same time, hinge 611 will deform as it rotates. It can be calculated that the stress distribution on the hinge will be divided into compression type and tension type. 612a represents the part of the hinge with compression stress. 612b represents the part of the hinge with tension stress. However, since compressive and tensile stresses in most cases result in opposite responses of piezoresistance change, the piezoresistive response weakens as the effects of the different stresses cancel out. There are different methods to increase the piezoelectric sensitivity to deflection. Figure 6b In (2), the hinge is removed. In this case, the hinge is reduced by half compared to the case in (1). The new hinge is only half the height, but the other structures remain unchanged. In this case, the rotation axis 50 is located at the bottom of 604a. When the movable object rotates, the reflector 601 will rotate to the second position, and the compressive stress will be the main factor affecting the piezoresistance of the hinge. Therefore, the piezoelectric response sensitivity is higher than in the case in (1) because the cancellation effect caused by different stress types is much smaller. Figure 6b (3) shows another way to reduce the negative effects of cancellation caused by different stresses. In this case, the majority of the hinge is a low-doped p-type silicon region 611b. However, there is a higher doping layer on top of the hinge (i.e., 611a). When the hinge rotates, the stress distribution on the hinge will be divided into a compressive region 612b and a tensile region 612c, similar to the situation in (1). In this case, the higher doping region 612a falls entirely within the compressive stress region 612b. When an external circuit is established to detect the change in piezoresistance of the hinge / flexure, the current will be mainly concentrated in the higher doping region 612a due to the higher conductivity. The effect of compressive stress on piezoelectric sensing will be more significant than that of tensile stress. As a result, the cancellation effect caused by different types of stress is minimized.

[0041] Figure 7Four more embodiments of a 1-D tilting MEMS mirror with different flexures / piezoresistors for PRCH sensing are shown. In the first embodiment, the flexures / piezoresistors are straight beams 706 and 707. Flexures / piezoresistors 706 and 707 define the MEMS mirror's rotational axis 70. Flexure / piezoresistors 706 are coupled to a movable portion 701 and a fixed anchor structure 704. Flexure / piezoresistors 707 are coupled to a movable portion 701 and a fixed anchor electrode 705. Flexures / piezoresistors 706 and 707 are the only connections from the fixed anchor electrodes 704 and 705 to the movable portion 701. The movable portion 701 is the electrical common for all flexures / piezoresistors. Pads are present on the fixed anchor electrodes 704 and 705 for external electrical connections. The piezoresistance is measured from the fixed anchor electrodes 704 to 705. Reference numerals 702a, 702b, 702c, and 702d are vertical comb drive actuators, which may be of a staggered comb drive design or a tilted comb drive design, such as Figure 3 and Figure 5 The other structures in the embodiment are as described in the embodiment shown. Figure 3 and Figure 5 The driving and PRCH sensing mechanisms of this embodiment are the same as those of Figure 3 and Figure 5 The implementation method is the same as in .

[0042] In a second embodiment, the flexure / piezoresistors at each end include a pair of structures 716a, 716b on one end and a pair of structures 717a, 717b on the other end. The pair of structures 716a-716b and the pair of structures 717a-717b define the axis of rotation 71. The pair of structures 716a, 716b and the pair of structures 717a, 717b are located on opposite sides of the axis of rotation 71. Structure 716a is coupled to the movable portion 711 and the fixed anchor electrode 714a. Structure 716b is coupled to the movable portion 711 and the fixed anchor electrode 714b. Structure 717a is coupled to the movable portion 711 and the fixed anchor electrode 715a. A pair of structures 717b is coupled to the movable portion 711 and the fixed anchor electrode 715b. The pair of structures 716a and 716b is the only connection from the fixed anchor electrodes 714a and 714b to the movable portion 711. A pair of structures 717a and 717b are the only connections from the fixed anchor electrodes 715a and 715b to the movable portion 711. The movable portion 711 is the electrical common for all flexures / piezoresistors. Bond pads for external electrical connections are present on the fixed anchor electrodes 714a, 714b, 715a, 715b. Reference numerals 712a, 712b, 712c, 712d are vertical comb drive actuators, which can be either a staggered comb drive design or a tilted comb drive design, as shown in FIG. Figure 3 and Figure 5 Other structures and Figure 3 and Figure 5 The capacitance sensing mechanism of the embodiment is the same as Figure 3 and Figure 5 The embodiment of FIG. 1 is the same as that of FIG. 1 . At the same time, the piezoresistance is measured from any combination of a pair of structures 716a, 716b and a pair of structures 717a, 717b through fixed anchor electrodes 714a, 714b, 715a, 715b because all four flexures / piezoresistors undergo deformation when 711 rotates. Single or multiple flexures / piezoresistors can be used for tilt angle sensing. For example, in one case, the resistance of a pair of structures 716a-716b is measured by fixed anchors 714a and 714b for mirror tilt angle sensing. In another case, the resistance of a pair of structures 716a-716b and a pair of structures 717a-717b are measured by fixed anchor electrodes 714a, 714b and fixed anchor electrodes 715a, 715b, respectively, for mirror tilt angle sensing.

[0043] In a third embodiment, the flexure / piezoresistors at each end include three parallel structures: 726a, 726b, and 728 at one end and 727a, 727b, and 729 at the other end. A zoomed-in view shows more detail. Reference numerals 728 and 729 denote the main flexures / piezoresistors that support the rotation of the MEMS mirror and define the rotation axis 72. Reference numerals 726a and 726b denote supporting flexures / piezoresistors located adjacent to the main flexure / piezoresistors 728. Reference numerals 727a and 727b denote supporting piezoelectric structures located adjacent to the main flexure / piezoresistors 729. Support flexure / piezoresistors 726a are coupled to the movable portion 721 and the fixed anchor electrode 724a. Support flexure / piezoresistors 726b are coupled to the movable portion 721 and the fixed anchor electrode 724b. Support flexure / piezoresistors 727a are coupled to movable portion 721 and fixed anchor electrode 725a. Support flexure / piezoresistors 727b are coupled to movable portion 721 and fixed anchor electrode 725b. Main flexure / piezoresistors 728 are coupled to movable portion 721 and fixed anchor electrode 724c. Main flexure / piezoresistors 729 are coupled to movable portion 721 and fixed anchor electrode 725c of support flexure / piezoresistors. Support flexure / piezoresistors 726a, 726b and main flexure / piezoresistors 728 are the only connections from fixed anchor electrodes 724a, 724b, 724c to movable portion 721. The support flexures / piezoresistors 727a, 727b and the main flexure / piezoresistors 729 are the only connections from the fixed anchor electrodes 725a, 725b, 725c to the movable portion 721. The movable portion 721 is common to all flexures / piezoresistors. There are bonding pads on the fixed anchor electrodes 724a, 724b, 724c, 725a, 725b, 725c for external electrical connections. Reference numerals 722a, 722b, 722c, 722d are vertical comb drive actuators, which can be either a staggered comb drive design or a tilted comb drive design, as shown in FIG. Figure 3 and Figure 5 Other structures and Figure 3 and Figure 5 The capacitance sensing mechanism of this embodiment is the same as Figure 3 and Figure 5. Simultaneously, piezoresistance is measured from any combination of supporting flexures / piezoresistors 726a, 726b, 727a, 727b and main flexures / piezoresistors 728, 729 via fixed anchor electrodes 724a, 724b, 725a, 725b, 724c, 725c, since all six flexures / piezoresistors undergo deformation as the movable portion 721 rotates. A single flexure / piezoresistors pair or multiple flexure / piezoresistors pairs can be used for tilt angle sensing. For example, in one embodiment, the resistance of supporting flexures / piezoresistors 726a-726b can be measured via fixed anchor electrodes 724a and 724b for mirror tilt angle sensing. In another embodiment, the resistance of the support flexures / piezoresistors 726a-726b and the support flexures / piezoresistors 725a-725b can be measured by fixed anchors 724a-724b and fixed anchors 725a-725b for mirror tilt angle sensing, respectively. In another embodiment, the resistance of the flexures / piezoresistors 726a-728 and the flexures / piezoresistors 726b-728 can be measured by fixed anchors 724a-724c and 724b-724c for mirror tilt angle sensing, respectively.

[0044] In the fourth embodiment, the flexure / piezoresistors on each end include a pair of structures 736, 7311 on one end and a pair of structures 737, 7312 on the other end. All structures 736, 7311, 737, 7312 are on a straight line defining the rotation axis 73 of the MEMS mirror. Structures 736, 7311, 737, 7312 coincide with the rotation axis 71. Structure 736 is coupled to the movable portion 731 and the fixed anchor electrode 734. Structure 737 is coupled to the movable portion 711 and the fixed anchor electrode 735. Structure 7311 is coupled to the movable portion 731 and the fixed anchor electrode 738. Structure 7312 is coupled to the movable portion 731 and the fixed anchor electrode 739. Structures 736, 737, 7311, 7312 are the only connections from the fixed anchor electrodes 734, 735, 738, 739 to the movable portion 731. The movable portion 731 is the electrical common for all flexures / piezoresistors. There are pads for external electrical connections at 734, 735, 738, and 739. Reference numerals 732a, 732b, 732c, and 732d are vertical comb drive actuators, which can be either staggered comb drive designs or tilted comb drive designs, such as Figure 3 and Figure 5 Other structures and Figure 3 and Figure 5 The capacitance sensing mechanism of the embodiment is the same as Figure 3 and Figure 5The embodiment is the same as in . At the same time, the piezoresistance is measured from any combination of structures 736, 737, 7311, 7312 by fixed anchors 734, 735, 738, 739 because all four flexures / piezoresistors undergo deformation when the movable part 731 rotates. A single flexure / piezoresistors or multiple flexures / piezoresistors can be used for tilt angle sensing. For example, in one case, the resistance of structure pair 7311-7312 can be measured by anchors 738 and 739 for mirror tilt angle sensing. In another case, the resistance of pairs 7311-736 and pairs 7312-737 can be measured by anchors 738, 734 and 739, 735, respectively, for mirror tilt angle sensing.

[0045] Figure 8 Two further embodiments of a 1-D tilting MEMS mirror with different drive and sense comb drive designs for PRCH sensing are shown. In the first embodiment, in addition to the fixed drive comb drive, four further independent comb drives for sensing are arranged in the design. Reference numeral 801 is the movable part comprising the MEMS mirror and the movable frame, and can rotate along axis 80. The movable part 801 is the electrical common of the device, and it is coupled to electrodes 804 and 805 via flexures / piezoresistors 806 and 807. Reference numerals 802a, 802b, 802c, 802d are the drive comb drives designed for mirror actuation, with the fixed comb drives coupled to bonding pad structures 803a, 803b, 803c, 803d for external drive signal connection, and the movable comb drives coupled to the MEMS mirror movable part 801 as a common terminal. Reference numerals 808a, 808b, 808c, and 808d are extended comb drives for mirror tilt angle sensing, wherein the fixed comb drives are connected to electrodes 809a, 809b, 809c, and 809d for external sensing signal connection, and the movable comb drives are arranged next to the movable comb drives of the driving comb drives. The comb drives for driving and sensing can be of an interleaved comb drive design or a tilted comb drive design, such as Figure 3 and Figure 5 The flexures / piezoresistors 806 and 807 may include single or multiple flexure structures, such as Figure 7 The electrodes 804 and 805 may include Figure 7 The single or multiple structures described in the embodiments. Figure 3 and Figure 5As for sensing, the mechanism of capacitance sensing is the same as that of the embodiment in FIG4 and FIG6, except that the capacitance sensing signal is measured between electrodes 809a, 809b, 809c, 809d and electrodes 804, 805. The mechanism of piezoresistance sensing is the same as that of the embodiment in FIG4, FIG6 and FIG6. Figure 7 The implementation method is the same as in .

[0046] In a second embodiment, two additional independent sensing comb drives are arranged alongside the MEMS mirror in the design. Reference numeral 811 is the movable portion comprising the MEMS mirror and a movable frame, and is rotatable along axis 81. Movable portion 811 is the electrical common of the device, and is coupled to electrodes 814 and 815 via flexures / piezoresistors 816 and 817. Reference numerals 812a, 812b, 812c, 812d are the drive comb drives designed for mirror actuation, with fixed comb drives coupled to bond pad structures 813a, 813b, 813c, 813d for external drive signal connections, and movable comb drives coupled to the MEMS mirror movable portion 811 as a common terminal. Reference numerals 818a and 818b are additional comb drives for mirror tilt angle sensing, wherein the fixed comb drive is connected to electrodes 819a and 819b for external sensing signal connection, and the movable comb drive is connected to the movable part 811 located next to the MEMS mirror. The comb drive for driving and sensing can be a staggered comb drive design or a tilted comb drive design, such as Figure 3 and Figure 5 The flexures / piezoresistors 816 and 817 may include single or multiple flexure structures, such as Figure 7 The electrodes 814 and 815 may include Figure 7 The single or multiple structures described in the embodiments. Figure 3 and Figure 5 As for sensing, the mechanism of capacitance sensing is the same as that of the embodiment in FIG4 and FIG6 except that the capacitance sensing signal is measured between 819a, 819b and electrodes 814, 815. The mechanism of piezoresistance sensing is the same as that of the embodiment in FIG4, FIG6 and FIG6. Figure 7 The implementation method is the same as in .

[0047] Figure 9An embodiment of a two-dimensional tilt MEMS mirror with PRCH sensing implemented on one axis of rotation and capacitive sensing implemented on the other axis is shown. The structure shown in the figure is made of highly doped silicon (n or p). The design is based on a 2D gimbal structure with electrostatic actuators. The mirror 901 has two axes of rotation, which are a first axis of rotation 90 and a second axis of rotation 91. For the first axis 90, the drive and sense structure and the operating mechanism are the same as for the 1D tilt MEMS mirror with PRCH sensing. Reference numerals 906 and 907 are flexures / piezoresistors for piezoresistive angle sensing of the mirror rotation and axis 90, the flexure / piezoresistors design and piezoresistive sensing mechanism can be used with a variety of other MEMS mirrors. Figure 3 、 Figure 5 、 Figure 7 The same as any embodiment shown in FIG. 904, 905 are fixed anchor electrodes for piezoresistors 906 and 907. The fixed anchor electrode design can be Figure 3 、 Figure 5 、 Figure 7 Reference numerals 902a, 902b, 902c, 902d are drive and sense comb drives for shaft 90, which may be staggered comb drive designs or tilted comb drive designs, independent or integrated sense comb drive designs, such as Figure 3 、 Figure 5 and Figure 8Depicted in the illustrated embodiment. Reference numeral 910 is a frame that provides mechanical support for all movable parts rotating around axis 90. The universal joint rotates along a second axis of rotation 91 and is applied to the frame 910. Reference numerals 916 and 917 are flexures that support rotation around 91. One end of the flexures 916 and 917 is coupled to the frame 910, and the other end is coupled to support beams 914a and 914b, which are further coupled to the MEMS mirror 901. A tilt comb drive is designed for driving and sensing the rotating axis 91. Reference numerals 918a, 918b, 918c, 918d are movable comb drives for axis 91 coupled to support beams 914a and 914b. Additional layers 920a and 920b are deposited on top of the combs 918a and 918c. Reference numerals 919a, 919b, 919c, and 919d denote fixed combs driven to rotate about axis 91. Combs 919a and 919c are coupled to inner frame 911, while combs 919b and 919d are coupled to inner frame 912, for different tilt orientations. Frames 911 and 912 are designed to provide mechanical support and electrical connections for fixed combs 919a, 919b, 919c, and 919d. Frame 911 is coupled to flexure 909a, which in turn couples to fixed anchor electrode 908a. Frame 912 is coupled to flexure 909b, which in turn couples to fixed anchor electrode 908b. 909a and 909b are located on axis 90, and bonding pads are present on electrodes 908a and 908b. Frames 911 and 912 are electrically isolated but mechanically coupled to frame 910 using bonding structure 913. Bonding structure 913 is designed to mechanically bond but electrically isolate different components. As shown in the figure, several bonding structures identical to bonding structure 913 exist between frames 911 and 910, and between frames 912 and 910. Reflector 901, support beams 914a, 914b, and combs 918a, 918b, 918c, and 918d form a movable component that rotates about axis of rotation 91. The entire axis of movable portion 91 is coupled to frame 910 via flexures 916 and 917. Because flexures 916 and 917 only support the reflector's rotation about 91 and otherwise restrict rotation, the entire structure coupled to frame 910 moves with it as it rotates about 90. Regarding the rotation around 91, the mirror 901, the support beams 914a, 914b, the flexures 916, 917 and the combs 918a, 918b, 918c, 918d form a movable part that rotates around 91, while they can also rotate around 90 together with the frame 910. At the same time, they are electrically coupled to a common terminal through the flexures 916 and 917.When a drive signal is applied to electrodes 908a, 908b, the signal is transmitted to fixed comb drives 919a, 919b, 919c, 919d via flexures 909a, 909b and inner frames 911, 912, all made of conductive, doped silicon. Movable comb drives 918a, 918b, 918c, 918d are connected to a common ground terminal. The drive and capacitive sensing mechanism is based on the rotating shaft 91 of the tilting comb drive. Figure 5 The mirror rotations about axes 90 and 91 are decoupled and do not interfere with each other during the 2-axis rotation.

[0048] Figure 10 Shown Figure 9 An exploded view of an embodiment of a 2D MEMS mirror is shown in FIG, wherein the structures are separated by electrical connections. In this example, the Figure 5 The embodiment shown in FIG. 100 shows a tilt comb drive for both axes. The entire structure 1008 is a common end of the device connected to ground during operation. These components include movable combs, mirrors, and frames for the drives of the different axes. Reference numerals 1002 and 1003 are fixed combs for the comb drive of axis 1001. Fixed comb drives 1002 and 1003 are separate for different tilt directions (clockwise and counterclockwise). During operation, drive and sense signals are connected to fixed comb drives 1002 and 1003. Both fixed comb drives 1002 and 1003 are mechanically bonded to frame 1008. Reference numerals 1004, 1005, 1006, and 1007 are fixed combs for the comb drive of axis 1000. Fixed comb drives 1004 and 1007 are a pair of comb drives for clockwise or counterclockwise drive. Fixed comb drives 1005, 1006 are a pair of comb drives for the other direction of rotation. During operation, drive signals and sense signals are connected to fixed comb drives 1004, 1005, 1006, 1007.

[0049] Figure 11 Another embodiment of a two-dimensional tilting MEMS mirror with PRCH sensing implemented on one rotation axis and capacitive sensing implemented on another axis is shown. The structure shown in the figure is made of highly doped silicon (n or p). As shown in the figure, 1100 and 1101 are the first and second rotation axes of the MEMS mirror. Figure 9The main difference compared to the illustrated embodiment is that the secondary independent comb drive is designed as a capacitive sensor for the mirror tilt angle about the second rotational axis. In addition to the actuator comb drive for the second rotational axis, an additional sensing comb drive is provided. 1123a, 1123b, 1123c, and 1123d are movable combs for the sensing comb drive, coupled to support beams 1114a and 1114b. 1124a, 1124b, 1124c, and 1124d are fixed combs for the sensing comb drive for axis 1101, coupled to inner frames 1125 and 1126. 1125 and 1126 are designed to provide mechanical support and electrical connections to the fixed sensing combs 1124a, 1124b, 1124c, and 1124d. 1125 is coupled to flexure 1122a, which in turn is coupled to fixed anchor electrode 1121a. 1126 is coupled to flexure 1122b and then to fixed anchor electrode 1121b. 1122a and 1122b are located on axis 1100 and there are bonding pads on electrodes 1121a and 1121b. 1125 and 1126 are both electrically isolated but mechanically coupled to intermediate inner frames 1111 and 1112 via bonding structure 1113. 1113 is a bonding structure designed to mechanically bond but electrically isolate different components. Capacitive sensing signals are detected from electrodes 1121a, 1121b. The structure and drive, sensing mechanism are similar to the above in addition to an independent internal sensing comb drive designed for second axis mirror angle sensing. Figure 9 The same as shown in the embodiment shown.

[0050] Figure 12 An embodiment of a two-dimensional tilting MEMS mirror with PRCH sensing implemented on two axes of rotation is shown. The structure shown in the figure is made of highly doped silicon (n or p). The design is based on a 2D gimbal structure with electrostatic actuators. The mirror 120 has two axes of rotation, a first axis of rotation 1200 and a second axis of rotation 1201. For the first axis 1200, the drive and sensing structure and the operating mechanism are the same as for the 1D tiled MEMS mirror with PRCH sensing. Reference numerals 1206 and 1207 are flexures / piezoresistors for mirror rotation and piezoresistive angle sensing of axis 1200. The flexure / piezoresistors design and piezoresistive sensing mechanism can be used with Figure 3 、 Figure 5 、 Figure 7 The same as any embodiment shown in FIG. 1204, 1205 are fixed anchor electrodes of piezoresistors 1206 and 1207. The fixed anchor electrode design can be Figure 3 、 Figure 5 、 Figure 7Reference numerals 1202a, 1202b, 1202c, 1202d are drive and sense comb drives for axis 1200, which may be staggered comb drive designs or tilted comb drive designs, independent or integrated sense comb drive designs, such as Figure 3 、 Figure 5 and Figure 8Depicted in the illustrated embodiment. Reference numeral 1210 is a frame that provides mechanical support for all movable parts rotating about axis 1200. The universal joint rotates along a second rotation axis 1201 applied to the frame 1210. Reference numerals 1216 and 1217 (in an enlarged view) are flexures / piezoresistors that support rotation about 1201 and piezoresistive angle sensing. One end of the piezoresistors 1216 and 1217 is coupled to the frame 1210, and the other end is coupled to support beams 1214a and 1214b for the rotation axis 1201. The support beams 1214a and 1214b are further coupled to the MEMS mirror 1201. A tilt comb drive is designed for driving and capacitive sensing of the rotation axis 1201. Reference numerals 1218a, 1218b, 1218c, and 1218d are the movable comb drives of shaft 1201, which are coupled to support beams 1214a and 1214b. Additional layers 1220a and 1220b are deposited on top of combs 1218a and 1218c. Reference numerals 1219a, 1219b, 1219c, and 1219d are the fixed comb drives of shaft 1201. For different tilt orientations, fixed comb drives 1219a and 1219c are coupled to inner frame 1211, while fixed comb drives 1219b and 1219d are coupled to inner frame 1212. Frames 1211 and 1212 are designed to provide mechanical support and electrical connections for fixed comb drives 1219a, 1219b, 1219c, and 1219d. Frame 1211 is coupled to flexure 1209a, which in turn is coupled to fixed anchor electrode 1208a. Frame 1212 is coupled to flexure 1209b, which in turn is coupled to fixed anchor electrode 1208b. Frames 1209a and 1209b are located on shaft 1200, and bonding pads are present on electrodes 1208a and 1208b. Frames 1211 and 1212 are electrically isolated but mechanically coupled to frame 1210 via bonding structure 1213. Bonding structure 1213 is designed to mechanically combine but electrically isolate different components. As shown in the figure, several bonding structures similar to those in 1213 are arranged between frames 1211 and 1210, and between frames 1212 and 1210. Reflector 1201, support beams 1214a and 1214b, and comb drives 1218a, 1218b, 1218c, and 1218d form a movable portion that rotates about rotation axis 1201. The entire movable portion is coupled to frame 1210 via flexures 1216 and 1217. Because flexures 1216 and 1217 only support the reflector for rotation about axis 1201 and restrict other rotations, the entire structure coupled to frame 1210 rotates with frame 1210 about axis 1201. Simultaneously, the movable portion can also rotate along with frame 1210 about axis 1200. Furthermore, the movable portion is electrically coupled to a common terminal via flexures 1216 and 1217.When a drive signal is applied to electrodes 1208a, 1208b, the signal is transmitted through flexures 1209a, 1209b and inner frames 1211, 1212 (as they are all made of conductively doped silicon) to fixed comb drives 1219a, 1219b, 1219c, 1219d. The movable comb drives 1218a, 1218b, 1218c, 1218d are connected to a common ground terminal. The drive and capacitive sensing mechanism based on the rotating axis 1201 of the tilted comb drives is similar to the conventional drive and capacitance sensing mechanism. Figure 5 The same as described in the embodiment of FIG. To implement piezoresistive angle sensing of the rotating shaft 1201, a pair of additional electrodes 1223 and 1224 for piezoresistive sensing are arranged on the shaft 1200. Electrodes 1223 and 1224 are connected to the frame 1210 via flexures 1225 (in the enlarged view) and 1226. Therefore, electrodes 1223 and 1224 are connected to a common terminal. Reference numeral 1227 (in the enlarged view) is a metal bonding pad deposited on electrode 1223. Metal traces 1221 are deposited on the flexure 1225 and the frame 1210 to connect the metal bonding pad 1227 and the flexure / piezoresistor 1217. Reference numeral 1228 (in the enlarged view) is a metal bonding pad deposited on electrode 1224. Metal traces 1222 are deposited on flexure 1226 and frame 1210 to connect metal bond pads 1227 to flexure / piezoresistors 1216. Metal traces are non-piezoresistive, and if the silicon structure is covered by metal traces, the piezoresistive change caused by structural deformation of the silicon is minimized. The piezoresistive change about rotation axis 1201 can be measured from bond pads 1227 and 1228. The mirror rotations about axes 1200 and 1201 are decoupled and do not interfere with each other during the two-axis rotation.

[0051] Figure 13 An embodiment of a two-dimensional tilting MEMS mirror for PRCH sensing on two rotation axes is shown. In addition to the design of the piezoresistors for angle sensing of the axis 1301, the structural design and operating mechanism are similar to Figure 12 The embodiment shown is the same. A pair of parallel flexures / piezoresistors are designed for sensing purposes. The structure of the vertical axis piezoresistive angle sensing is detailed in the enlarged view. Only one side of the flexure / piezoresistors for the second axis is used for angle detection. Reference numerals 1321 and 1322 are metal traces that connect the electrodes to the second axis sensing piezoresistive elements. Reference numerals 1301a and 1301b are flexures / piezoresistors. The entire flexure / piezoresistors are electrically isolated from the outer frame (common end), but are mechanically connected to the frame through bonding structures 1314a, 1314b, 1314c. Metal traces can be deposited on the bonding structures. At the same time, in order to avoid electrical bridging of the piezoresistors and the common end, the metal traces should be isolated from the common end.

[0052] Figure 14 The structure of the metal traces and metal bond pads for piezoresistive sensing on the second axis of rotation is shown. 1401 is the electrode for piezoresistive angle sensing of the second axis of rotation. As shown in the figure, the metal traces and bonds deposited on the hinges, electrodes and connecting structures have two basic configurations. In one configuration, 1402 is a deposited metal layer. 1403 is bulk silicon. In this case, the metal layer shunts the connection of the silicon. When deformation occurs, the metal layer reduces the piezoresistive change of the silicon. In the other configuration, 1404 is a metal layer, 1405 is an insulating layer, and 1406 is bulk silicon. The bond pads and traces are completely insulated from the bulk silicon. If this schematic is used, the effects of electrical coupling from the silicon or resistance changes due to accidental deformation can be eliminated. For Figure 12 and Figure 13 In the embodiment in, both configurations can be used for piezoresistive angle sensing about a second axis of rotation.

[0053] Figure 15 Different embodiments of a piezoresistor design with a single electrode connected to the movable portion of the MEMS mirror are shown. Reference numeral 1501 is a fixed anchor electrode, and reference numeral 1502 is the movable portion of the MEMS mirror. The flexure / piezoresistor can be a single-beam design or a multi-beam design. Reference numerals 1503, 1504, 1505, and 1506 are embodiments for a single-beam design. Reference numerals 1507, 1508, 1509, and 1510 are embodiments for a dual-beam design. The resistance from the fixed anchor electrode 1501 to the movable portion of the MEMS mirror 1502 is determined by the beam profile (such as beam width, beam length, and material conductivity). The sensitivity of the piezoresistors as a function of rotation angle can be determined by different design shapes.

[0054] Figure 16Various embodiments of piezoresistors with multiple electrodes connected to a movable mirror portion are shown. Reference numerals 1601a, 1601b, and 1601c denote fixed anchor electrodes, and 1602 denotes the movable MEMS mirror portion. In one embodiment, 1603a and 1603b denote separate flexures / piezoresistors connecting the different electrodes 1601a and 1601b to the movable MEMS mirror portion 1602. As the mirror rotates, flexures 1603a and 1603b deform simultaneously. Thus, two piezoresistors are arranged in parallel for piezoresistive sensing. 1604a, 1604b, 1605a, and 1605b illustrate examples of flexures with identical parallel piezoresistors. Asymmetric designs, shown as 1606a and 1606b, can also be used as flexures / piezoresistors. In this embodiment, the piezoresistors can produce different responses for different tilt directions. Reference numerals 1607a, 1607b, 1607c are for a triple flexure / piezoresistor design. All three flexures / piezoresistors are independent and provide greater flexibility for piezoelectric sensing.

[0055] Figure 17An embodiment of a MEMS mirror application using PRCH sensing is shown. This embodiment includes a MEMS mirror 1700, a piezoresistive mirror position sensing signal 1701, a capacitive mirror position sensing signal 1703, a front-end piezoresistive signal processor 1702, a front-end capacitive signal processor 1704, and a back-end processor 1705. 1700 is a MEMS mirror that can generate a PRCH sensing signal indicating the mirror's position during motion. 1701 is the piezoresistive sensing signal generated by 1700, which is then processed by a front-end resistive signal processor 1702. Front-end resistive signal processor 1702 is a front-end circuit that can convert raw signal 1701 into a digital format or other format interpretable by back-end processor 1705. In one embodiment, front-end resistive signal processor 1702 is a standalone circuit connected to the MEMS mirror package. In another embodiment, front-end resistive signal processor 1702 is an integrated circuit disposed within the same carrier material as 1700. In another embodiment, front-end resistive signal processor 1702 is directly integrated with mirror 1700 using compatible manufacturing processes. On the other hand, mirror 1700 can also generate a capacitive mirror position sensing signal 1703. Capacitive mirror position sensing signal 1703 is then processed by a front-end capacitive signal processor 1704, which can convert the raw signal 1703 into a digital format or other format that can be interpreted by a back-end processor 1705. In one embodiment, front-end capacitive signal processor 1704 is a standalone circuit connected to the MEMS mirror package. In another embodiment, front-end capacitive signal processor 1704 is an integrated circuit disposed within the same carrier material as 1700. In another embodiment, front-end capacitive signal processor 1704 is directly integrated with 1700 using a compatible manufacturing process. Back-end processor 1705 is a back-end processor that converts voltage into mirror position data and transmits angle-related information to other components of the system. In one embodiment, back-end processor 1705 is an integrated circuit that combines the signals from the PRCH sensors, calibrates the voltage-to-position relationship, and converts the voltage into mirror position. Back-end processor 1705 also generates signals used to adaptively tune the drive waveform of the MEMS mirror to maintain stable scanning performance. The backend processor 1705 also generates synchronization signals for the MEMS mirror position.

[0056] Figure 18Figure 1 is a diagram illustrating one embodiment of post-processing of PRCH sensing signals for a MEMS mirror. A piezoresistive sensing signal 1801 and a capacitive sensing signal 1802 are measured from the MEMS mirror. These signals are sampled simultaneously by circuits 1803 and 1804. Circuits 1803 and 1804 may be amplifier and analog-to-digital converter circuits. The outputs of circuits 1803 and 1804 are processed by a digital signal processing unit 1806, primarily for signal correlation. A drive signal 1805 is also used for correlation processing. Within digital signal processing unit 1806, four primary tasks occur: frequency detection; phase detection; amplitude correction; and detection signal compensation. For frequency and phase detection, the two outputs from piezoresistive and capacitive sensing can be used independently or differentially to obtain frequency and amplitude information. For amplitude correction, capacitive and piezoresistive sensing have different correction relationships between the signal and the absolute mirror tilt angle. These correction relationships are preloaded into the system through an additional calibration process. The signals from piezoresistive and capacitive sensing can also be used in a complementary manner. Typically, piezoresistive sensing is more sensitive to large mirror tilt angles, while capacitive sensing is more sensitive to small tilt angles. Therefore, these two different detection methods can be combined to achieve high sensitivity across the entire mirror scanning range. After signal processing, feedback information is sent to the detector output 1807 for mirror position and the light source modulator 1808 for synchronization of light pulses and mirror position.

[0057] Figure 19 is another diagram illustrating an embodiment of post-processing of a PRCH sensing signal for a MEMS mirror. Reference numeral 1901 denotes a capacitive sensing signal generated by the MEMS mirror. The capacitive sensing signal is used for both MEMS mirror control and sensing. For control, a phase detector 1902 extracts the phase of the capacitive sensing signal. A feedback control unit 1903 then uses this phase information to generate a MEMS mirror drive signal, which in turn controls the mirror scanning. This feedback control loop is phase-locked to achieve consistent mirror scanning control. Simultaneously, the capacitive sensing signal is used to extract mirror scanning frequency, phase, and amplitude information 1907. Meanwhile, the piezoresistive sensing signal 1902 is sampled by a real-time sampling circuit 1905. This real-time sampling circuit 1905 may comprise an amplifier and an analog-to-digital converter circuit. The output from the real-time sampling circuit 1905 is then processed by a digital signal processing unit 1906 to convert the voltage into an angle using preloaded calibration data. This conversion can be calibrated by 1907 to increase the robustness of the sensing loop. The feedback information will then be transmitted to the detector output 1908 for the mirror position and to the light source modulator 1909 for synchronization of the light pulses and the mirror position, or to any other relevant interface depending on the application.

Claims

1. A deflectable micromechanical system with an integrated piezoresistive deflection sensor, the system comprising: a deflectable element; a first anchoring element and a second anchoring element; a first spring having a deformable region and coupling the deflectable element to the first anchoring element; a second spring having a deformable region and coupling the deflectable element to the second anchoring element; The deformable region of the first spring and the deformable region on the second spring deform when the relative position of the deflectable element with respect to the anchoring element changes; as well as At least one of the first spring and the second spring is piezoresistive, and when the deformable region of the first spring and the deformable region of the second spring are deformed, the piezoresistive of the piezoresistive spring changes; and wherein the first contact and the second contact are located on the first anchoring element and the second anchoring element respectively; the first contact is electrically connected to the first anchoring element, and the second contact is electrically connected to the second anchoring element; The first contact and the second contact are electrically coupled to a resistance detection circuit configured to detect a change in a total piezoresistance of the first spring and the second spring and to use the change in piezoresistance to determine a deflection of the deflectable element.

2. The system according to claim 1, wherein: The first and second anchoring elements, the deflectable element, the first spring, and the second spring are made of the same material.

3. The system according to claim 1, wherein: The material is doped silicon.

4. The system according to claim 1, wherein: The first contact and the second contact are made of metal.

5. The system according to claim 1, wherein The first and second springs are partially covered with a metal layer that has good electrical contact with the underlying material.

6. The system according to claim 5, wherein: The metal deposition changes the overall resistance of the piezoresistive spring.

7. The system according to claim 5, wherein: The metal deposition covers the areas of the spring that have a low piezoresistive response.

8. The system according to claim 1, wherein: The system is an indirect detection system for measuring force, pressure, acoustic signals, speed, acceleration, rotation rate.

9. The system according to claim 1, wherein: The deflectable element is a micro-platform capable of carrying an object.

10. The system of claim 1 , further comprising at least one or more sets of anchoring elements, contacts, and springs to support the deflectable element, each additional spring connecting an additional anchoring element to the deflectable element, the additional spring being capable of being piezoresistive or non-piezoresistive, the additional contacts being located on the anchoring elements.

11. The system according to claim 10, wherein: Two or more piezoresistive springs can form a bridge sensor for deflection detection.

12. The system according to claim 10, wherein: The piezoresistive springs are made of the same material.

13. The system of claim 1, wherein: The system forms a single-axis universal joint structure and rotates along a first rotation axis. The springs are arranged along the first axis, and the geometric shape of at least one spring is non-centrally symmetric about the first rotation axis.

14. The system according to claim 13, wherein: The deflectable element is superimposed on the reflector or mechanically connected to the reflector.

15. The system according to claim 13, wherein: The deflectable element is mechanically connected to an electrostatic actuator or a thermoelectric actuator or an electromagnetic actuator or a piezoelectric actuator.

16. The system of claim 13, wherein: The non-centrosymmetric configuration is due to the design layout sketch or the manufacturing process.

17. The system of claim 13, wherein: When the mirror is tilted clockwise or counterclockwise from a neutral position, the non-centrosymmetric piezoresistive spring produces opposite responses.

18. The system of claim 13, wherein: The system is positioned on a second deflectable platform that rotates along a second axis of rotation that is non-parallel to the first axis to form a two-dimensional gimbal.

19. The system according to claim 18, wherein The system is a 2D tilting micromirror.

20. The system of claim 18, wherein: The first axis is not a fixed axis, but moves with rotation about the second axis.

21. The system of claim 13, further comprising at least one or more sets of anchoring elements, contacts, and springs to support the deflectable element, each additional spring connecting an additional anchoring element to the deflectable element, the additional spring being capable of being piezoresistive or non-piezoresistive, and additional contacts being located on the anchoring elements.

22. The system of claim 21, wherein: Two or more piezoresistive springs can form a bridge sensor for deflection detection.

23. The system of claim 21, wherein: The piezoresistive spring is uniformly doped silicon.

24. The system of claim 1, wherein: The piezoresistive spring is formed with two regions having different doping concentration levels, ie, a first doping level region and a second doping level region, the first doping level region having a higher doping concentration than the second doping level region.

25. The system of claim 24, wherein: The first doping level region is located within the deformable region of the piezoresistive spring.

26. The system of claim 24, wherein: The system forms a single-axis gimbal structure and rotates along a first axis.

27. The system of claim 24, wherein: The deflectable element is superimposed on the reflector or mechanically connected to the reflector.

28. The system of claim 24, wherein: The deflectable element is mechanically connected to an electrostatic actuator or a thermoelectric actuator or an electromagnetic actuator or a piezoelectric actuator.

29. The system of claim 24, wherein: The first doping level region is located on a surface of the piezoresistive spring structure.

30. The system of claim 24, wherein: During deformation, the first doping level region overlaps a high stress region on the piezoresistive spring.

31. The system of claim 24, wherein: The system is positioned on a second deflectable platform that rotates along a second axis of rotation that is non-parallel to the first axis to form a two-dimensional gimbal.

32. The system of claim 31, wherein: The system is a 2D tilting micromirror.

33. The system of claim 31, wherein: The first axis moves as it rotates about the second axis.

34. The system of claim 24, further comprising at least one or more sets of anchoring elements, contacts, and springs to support the deflectable element, each additional spring connecting an additional anchoring element to the deflectable element, the additional spring being capable of being piezoresistive or non-piezoresistive, and additional contacts being located on the anchoring elements.

35. The system of claim 24, wherein: Two or more piezoresistive springs can form a bridge sensor for deflection detection.

36. A sensing system for detecting a deflected position of a deflectable micromechanical system, the system comprising: A deflectable system, the deflectable system comprising: a deflectable element; a transducer for converting deflection of the deflectable element into a capacitive signal; and a transducer for converting deflection of the deflectable element into a piezoresistive signal; and A resistance detection circuit is configured to: converting the capacitance sensing signal into a first electrical signal; converting the piezoresistive signal into a second electrical signal; and The first electrical signal and the second electrical signal are processed to calculate a position of the deflectable element.

37. The system of claim 36, wherein: The system has the functionality to sense temperature and compensate for the effects of temperature changes.

38. The system of claim 36, wherein: The circuit is partially or fully integrated into an integrated circuit chip.

39. The system of claim 36, wherein: The deflectable element has more than one dimension of motion, and there are multiple capacitive transducers, piezoresistive transducers, and detection circuits to sense deflection in each dimension.

40. The system of claim 36, wherein: The deflectable system is a micro-platform capable of carrying optical components, optical detectors, and optical light sources.

41. The system of claim 36, wherein: The deflectable micromechanical system is a micromechanical mirror system.

42. The system of claim 41, wherein: The micromechanical mirror is a tilted mirror or a mirror or a tilted mirror array.

43. The system of claim 41, wherein: The micromechanical mirror is a translation mirror or a translation mirror array.

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