Silicon bragg grating f-p cavity based force feedback type mems accelerometer and manufacturing method

Abstract

The application discloses a force feedback type MEMS accelerometer based on a silicon Bragg grating F-P cavity and a manufacturing method, and belongs to the technical field of microelectromechanical systems. The force feedback type MEMS accelerometer comprises a silicon-based F-P cavity MEMS sensitive structure and a glass electrode substrate. The silicon-based F-P cavity MEMS sensitive structure comprises a flexible beam, a mass block, a common anchor point, a peripheral anchor point, a Bragg grating F-P sensitive cavity, a signal transmission optical fiber and a driving comb tooth. The glass electrode substrate comprises a glass substrate and an electrode. The silicon-based F-P cavity MEMS sensitive structure converts horizontal axis input acceleration into displacement of the mass block, causes the cavity gaps of a pair of oppositely arranged F-P sensitive cavities to oppositely drift, causes opposite transformation of F-P cavity interference light signals, and realizes high-precision differential detection of acceleration. The force feedback type MEMS accelerometer has the advantages of high sensitivity, strong common mode error resistance, large dynamic range and good long-term stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro-electro-mechanical system, in particular to a force feedback MEMS accelerometer based on silicon Bragg grating F-P cavity and a manufacturing method. BACKGROUND

[0002] Optical F-P (Fabry-Pérot) cavity is a typical amplitude splitting multi-beam optical interference cavity, which is generally composed of two parallel plane mirrors with equal refractive index. The incident light is reflected and refracted under the action of one of the mirrors. The refracted light produces the same reflection and refraction when it reaches the other mirror. The light reflected from the first mirror is refracted again, thereby producing a stable phase difference with the first refracted light and having the same propagation direction, so that optical interference phenomenon can be produced. By changing the gap of the F-P cavity, the phase, wavelength and other information of the interference light can be changed, so as to achieve the purpose of measuring weak physical quantities.

[0003] Current optical sensors based on F-P cavity generally construct the core sensitive mechanism through parallel fiber end faces, and the integration and batch degree are greatly limited. Micro-Electro-Mechanical System (MEMS) technology is a new technology that microizes optical detection mechanism and combines with traditional micro-electro-mechanical system. By etching periodic Bragg grating on a silicon substrate, a micromirror structure with a specific transmittance can be realized. By combining two Bragg grating micromirrors, a planar silicon-based F-P cavity structure can be realized. Compared with the F-P cavity MEMS accelerometer constructed by optical fiber, the pure silicon-based technology route has higher integration potential and is easy to be combined with future on-chip optics. The precision of the traditional electrical MEMS accelerometer is limited by many bottlenecks. The MEMS accelerometer with optical interface realized by optical detection mechanism such as F-P cavity is expected to break through the existing precision limit and develop into the next generation of micro accelerometers. SUMMARY

[0004] The present application relates to the technical field of micro-electro-mechanical system, in particular to a force feedback MEMS accelerometer based on silicon Bragg grating F-P cavity and a manufacturing method.

[0005] Technical scheme: the force feedback MEMS accelerometer based on silicon Bragg grating F-P cavity of the present application comprises a silicon-based F-P cavity MEMS sensitive structure and a glass electrode substrate, and the silicon-based F-P cavity MEMS sensitive structure is bonded to the glass electrode substrate through an anchor point.

[0006] The silicon-based F-P cavity MEMS sensing structure comprises a flexible beam, a mass block, a common anchor point, a peripheral anchor point, a Bragg grating F-P sensing cavity, a signal transmission optical fiber and a driving comb, wherein the flexible beam is arranged on both sides of the mass block, the mass block is connected to the common anchor point through the flexible beam, a gap exists between the mass block and the common anchor point, the peripheral anchor point is distributed on the periphery of the mass block and the common anchor point, the signal transmission optical fiber is connected to the Bragg grating F-P sensing cavity and is arranged in the gap between the mass block and the common anchor point, and the driving comb is embedded in the center of the mass block.

[0007] The glass electrode substrate comprises a glass substrate and an electrode arranged on the surface of the glass substrate.

[0008] Further, the Bragg grating F-P sensing cavity comprises a first Bragg grating F-P sensing cavity and a second Bragg grating F-P sensing cavity, and the signal transmission optical fiber comprises a first signal transmission optical fiber and a second signal transmission optical fiber; the first Bragg grating F-P sensing cavity and the second Bragg grating F-P sensing cavity have the same structure and each comprise a detection grating and a fixed grating, the detection grating is fixed on the mass block, the fixed grating is fixed on the peripheral anchor point, the gap between the mass block and the peripheral anchor point constitutes the cavity of the F-P cavity, and the signal transmission optical fiber is connected to the fixed grating.

[0009] When the mass block generates displacement, the cavities of the first Bragg grating F-P sensing cavity and the second Bragg grating F-P sensing cavity are reversely offset, and then the output light generates opposite phase offsets, so that the acceleration of the accelerometer is calculated through optical differential detection.

[0010] Further, the detection grating and the fixed grating are composed of silicon thin walls with equal gaps, the thickness is equal to the thickness of the mass block, and the central wavelength is adjusted by the thickness of the thin wall and the thickness between the thin walls.

[0011] Further, the flexible beam comprises a first flexible beam, a second flexible beam, a third flexible beam and a fourth flexible beam, the first flexible beam and the second flexible beam are arranged on one side of the mass block, and the third flexible beam and the fourth flexible beam are arranged on the other side of the mass block.

[0012] Further, the driving comb is composed of two parts of the movable comb and the fixed comb which are staggered and have equal intervals, wherein the movable comb is connected to the mass block, and the fixed comb is bonded on the glass substrate of the bottom layer.

[0013] The movable comb and the fixed comb respectively receive a driving voltage and a ground signal to generate an electrostatic driving force.

[0014] Further, the force feedback type MEMS accelerometer further comprises a first blocker and a second blocker which are arranged on both sides of the mass block and are distributed in the gap between the mass block and the peripheral anchor point.

[0015] Further, the electrode comprises a common bonding electrode, a common leading electrode, a driving bonding electrode and a driving leading electrode, the common bonding electrode is located directly below the common anchor point, the common bonding electrode is connected with the common leading electrode through a lead wire, the common bonding electrode is used for forming a ground signal connection, and the common leading electrode is used for connecting an external ground signal.

[0016] The driving bonding electrode is located directly below the driving comb tooth, and the driving bonding electrode is connected with the driving leading electrode through a lead wire.

[0017] The manufacturing method of the force feedback type MEMS accelerometer based on the silicon Bragg grating F-P cavity in another aspect of the present application comprises the following steps:

[0018] S1, cleaning and preparing a glass substrate;

[0019] S2, etching the glass substrate through a hydrofluoric acid solution or gas to form an electrode shallow groove;

[0020] S3, sequentially depositing metal chromium and gold through an electron beam evaporation or a magnetron sputtering process to form a signal electrode;

[0021] S4, cleaning and preparing a low-resistance silicon substrate, and forming an anchor point structure through deep silicon etching;

[0022] S5, bonding the low-resistance silicon substrate with the glass substrate to form an electrical connection between the upper silicon sensitive structure and the lower electrode;

[0023] S6, releasing a mass block structure through deep silicon etching, and simultaneously forming a flexible beam structure, a Bragg grating F-P cavity structure and a groove of a signal transmission optical fiber;

[0024] S7, aligning and mounting the signal transmission optical fiber in the shallow groove of the peripheral anchor point to form a complete MEMS accelerometer device.

[0025] Advantages: compared with the prior art, the present application has the following advantages:

[0026] 1. The present application uses deep silicon etching to manufacture a Bragg grating F-P cavity on a silicon substrate, and combines the horizontal axis MEMS sensitive structure to realize the core sensitive structure of the F-P cavity MEMS accelerometer on the silicon substrate, which has the advantages of high integration and high detection precision;

[0027] 2. The present application realizes the force feedback mechanism of the F-P cavity MEMS accelerometer by arranging electrostatic driving combs in the mass block, which can effectively overcome the problem of narrow linear interval in the optical interference effect, expand the detection range of the accelerometer, and enhance the detection stability;

[0028] 3、The application adopts a pair of reverse symmetrical Bragg grating F-P cavities as optical sensitive mechanism, the cavity gap changes reversely with input acceleration, so that optical differential detection can be realized, and detection error caused by common mode interference can be inhibited;

[0029] 4、The application adopts silicon-glass bonding process to realize the complete structure of F-P cavity optical MEMS accelerometer, uses bottom electrode to realize transmission of driving signal and force feedback control, and can realize miniaturization packaging and integration of the core sensitive structure of the accelerometer. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Fig. 1 is a structural schematic diagram of the accelerometer in the application;

[0031] Figure 2 Fig. 2 is a front view of the accelerometer in the application;

[0032] Figure 3 Fig. 3 is a top view of the upper structure of the accelerometer in the application;

[0033] Figure 4 Fig. 4 is a top view of the lower structure of the accelerometer in the application;

[0034] Figure 5 Fig. 5 is a manufacturing process flow chart of the application.

[0035] In the figure, 1 is a silicon-based F-P cavity MEMS sensitive structure; 2 is a peripheral anchor point; 3 is a mass block; 4 is a first common anchor point; 5-1 is a first flexible beam; 5-2 is a second flexible beam; 6 is a first stopper; 7 is a driving comb; 7-1 is a movable comb; 7-2 is a fixed comb; 8 is a first signal transmission optical fiber; 9-1 is a first detection incident light; 9-2 is a first detection output light; 10 is a first Bragg grating F-P sensitive cavity; 11 is a second common anchor point; 12-1 is a third flexible beam; 12-2 is a fourth flexible beam; 13 is a second stopper; 14 is a second Bragg grating F-P sensitive cavity; 15 is a second signal transmission optical fiber; 16-1 is a second detection incident light; 16-2 is a second detection output light; 17 is a glass substrate; 18-1 is a first common lead-out electrode; 18-2 is a second common lead-out electrode; 19-1 is a third common lead-out electrode; 19-2 is a fourth common lead-out electrode; 20-1 is a first driving lead-out electrode; 20-2 is a fifth driving lead-out electrode; 20-3 is a third driving lead-out electrode; 21-1 is a second driving lead-out electrode; 21-2 is a sixth driving lead-out electrode; 21-3 is a fourth driving lead-out electrode; 22-1 is a first common bonding electrode; 22-2 is a second common bonding electrode; 23-1 is a third common bonding electrode; 23-2 is a fourth common bonding electrode; 24-1 is a first driving bonding electrode; 24-2 is a second driving bonding electrode; 25-1 is a third driving bonding electrode; 25-2 is a fourth driving bonding electrode; 26 is a fifth driving bonding electrode; 27-1 is a first common lead wire; 27-2 is a second common lead wire; 28-1 is a third common lead wire; 28-2 is a fourth common lead wire; 29-1 is a first driving lead wire; 29-2 is a fifth driving lead wire; 29-3 is a third driving lead wire; 30 is a first driving interconnection lead wire; 31-1 is a second driving lead wire; 31-2 is a sixth driving lead wire; 31-3 is a fourth driving lead wire; 32 is a second driving interconnection lead wire; and 33 is a glass electrode substrate. DETAILED DESCRIPTION

[0036] The embodiments of the present application will be further described in conjunction with the drawings and examples. It can be understood that the specific embodiments described herein are merely illustrative of the present application and are not a limitation of the present application. In addition, it should be noted that, for the convenience of description, only the parts related to the embodiments of the present application are shown in the drawings, rather than all the structures.

[0037] In the following description, specific details are set forth such as target system architecture, techniques, etc. in order to provide a thorough understanding of the present application. However, persons skilled in the art will understand that the present application can be practiced without such specific details. In other instances, well-known structures, devices, circuits, and methods have not been described in detail in order to avoid obscuring the present application.

[0038] It should be understood that the term "comprising" as used in the specification and in the claims indicates the presence of the recited features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0039] It should also be understood that the term "and / or" as used in the specification and in the claims indicates any combination of one or more of the associated listed items and all possible combinations thereof.

[0040] In addition, in the description of the application and in the claims, the terms "first", "second", and the like are used only to distinguish descriptions, and cannot be understood as indicating or implying relative importance.

[0041] In the present application, the reference "one embodiment" or "some embodiments" and the like means that the target features, structures or characteristics described in connection with the embodiment are included in one or more embodiments of the present application. Therefore, the statements "in one embodiment", "in some embodiments", "in other some embodiments", "in further some embodiments" and the like appearing in different places in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized.

[0042] Embodiment one

[0043] The force feedback type MEMS accelerometer based on the silicon Bragg grating F-P cavity described in the present embodiment has a structural schematic diagram as shown in Figure 1 The electrostatic feedback type MEMS accelerometer includes a silicon-based F-P cavity MEMS sensitive structure 1 and a glass electrode substrate 33, and the silicon-based F-P cavity MEMS sensitive structure 1 is bonded to the glass electrode substrate 33 through an anchor point;

[0044] The silicon-based F-P cavity MEMS sensitive structure 1 includes a flexible beam, a mass block 3, a common anchor point, a peripheral anchor point 2, a Bragg grating F-P sensitive cavity, a signal transmission optical fiber and a driving comb tooth 7, wherein the mass block 3 is located at the center position of the silicon-based F-P cavity MEMS sensitive structure 1, realizing the conversion of acceleration quantity to displacement quantity, the flexible beam is arranged on both sides of the mass block 3, and the mass block 3 is connected to the common anchor point through the flexible beam;

[0045] The peripheral anchor point 2 is annular, and the peripheral anchor point 2 is distributed on the periphery of the mass block 3 and the common anchor point, for protecting the core structure and providing fixed support;

[0046] The mass block 3 and the common anchor point have a gap therebetween, the signal transmission optical fiber and the Bragg grating F-P sensitive cavity are connected and arranged in the gap between the mass block 3 and the common anchor point, and the driving comb tooth 7 is embedded in the center position of the mass block 3.

[0047] The glass electrode substrate 33 includes a glass substrate 17 and an electrode arranged on the surface of the glass substrate 17.

[0048] In combination Figure 1 As shown, the electrostatic feedback MEMS accelerometer is a double-layer structure, the upper layer is a silicon-based F-P cavity MEMS sensitive structure 1, and the lower layer is a glass electrode substrate 33, and the silicon-based F-P cavity MEMS sensitive structure 1 of the upper layer is bonded to the glass electrode substrate 33 through an anchor point.

[0049] The silicon-based F-P cavity MEMS sensitive structure 1 includes a flexible beam, a mass block 3, a common anchor point, a peripheral anchor point 2, a Bragg grating F-P sensitive cavity, a signal transmission optical fiber, and a driving comb tooth 7.

[0050] The flexible beam includes a first flexible beam 5-1, a second flexible beam 5-2, a third flexible beam 12-1, and a fourth flexible beam 12-2, the first flexible beam 5-1 and the second flexible beam 5-2 are arranged on one side of the mass block 3, and the third flexible beam 12-1 and the fourth flexible beam 12-2 are arranged on the other side of the mass block 3.

[0051] The common anchor point includes a first common anchor point 4 and a second common anchor point 11, the first common anchor point 4 is arranged on one side of the mass block 3, and the second common anchor point 11 is arranged on the other side of the mass block 3. The mass block 3 is connected to the first common anchor point 4 through the first flexible beam 5-1 and the second flexible beam 5-2, and the mass block 3 is connected to the second common anchor point 11 through the third flexible beam 12-1 and the fourth flexible beam 12-2. A space right-angle coordinate system is established, taking the transverse cross section of the electrostatic feedback MEMS accelerometer as the XOY coordinate plane and taking the longitudinal cross section of the accelerometer as the YOZ coordinate plane, as shown in the figure. Figure 2 As shown, when a Y-direction horizontal acceleration signal a is input, the mass block 3 generates a Y-direction horizontal displacement under the support of the flexible beam;

[0052] The Bragg grating FP sensitive cavity includes a first Bragg grating FP sensitive cavity 10 and a second Bragg grating FP sensitive cavity 14, and the signal transmission fiber includes a first signal transmission fiber 8 and a second signal transmission fiber 15. The first Bragg grating FP sensitive cavity 10 and the second Bragg grating FP sensitive cavity 14 have the same structure, both including a detection grating and a fixed grating. The detection grating is fixed on the mass block 3, and the fixed grating is fixed on the peripheral anchor point 2. The gap between the mass block 3 and the peripheral anchor point 2 constitutes the cavity of the FP cavity, and the signal transmission fiber is connected to the fixed grating. Specifically, the fixed grating of the first Bragg grating FP sensitive cavity 10 is located at the port of the first signal transmission fiber 8, and the fixed grating of the second Bragg grating FP sensitive cavity 14 is located at the port of the second signal transmission fiber 15.

[0053] like Figure 3 As shown in the top view of the upper structure of the accelerometer, the first Bragg grating FP sensitive cavity 10 is located at the lower right of the upper structure, and the second Bragg grating FP sensitive cavity 14 is located at the upper left of the upper structure. When the mass block 3 is displaced, the first detection incident light 9-1 is transmitted to the first Bragg grating FP sensitive cavity 10 via the first signal transmission fiber 8, and the second detection incident light 16-1 is transmitted to the second Bragg grating FP sensitive cavity 14 via the second signal transmission fiber 15. The reflected first detection output light 9-2 and second detection output light 16-2 produce opposite phase shifts due to the cavity offset, and thus the output light produces opposite phase shifts. The acceleration of the accelerometer is calculated through optical differential detection. The first detection output light 9-2 is transmitted out via the first signal transmission fiber 8, and the second detection output light 16-2 is transmitted out via the second signal transmission fiber 15 for signal processing.

[0054] In the Bragg grating FP sensing cavity, the detection grating and the fixed grating are composed of silicon thin walls with equal spacing, the thickness of which is equal to that of the mass block 3. The center wavelength that passes through is controlled by the thickness of the thin walls and the thickness between the thin walls.

[0055] The drive comb 7 is positioned at the center of the mass block 3 to balance the inertial force brought about by the input acceleration, keeping the mass block 3 in its initial position, thereby realizing the force feedback working mode.

[0056] Furthermore, the driving comb 7 consists of two parts: staggered, equally spaced movable comb teeth 7-1 and fixed comb teeth 7-2, wherein the movable comb teeth 7-1 are connected to the mass block 3, and the fixed comb teeth 7-2 are bonded to the bottom glass substrate 17.

[0057] The movable comb tooth 7-1 and the fixed comb tooth 7-2 receive the driving voltage and the ground signal respectively, generating electrostatic driving force.

[0058] The electrostatic feedback MEMS accelerometer further comprises a first stopper 6 and a second stopper 13, the first stopper 6 is arranged on one side of the mass 3, the second stopper 13 is arranged on the other side of the mass 3, and is distributed in the gap between the mass 3 and the peripheral anchor 2. As shown in the figure, the first stopper 6 is arranged at the lower left in the top view of the upper structure of the accelerometer, the second stopper 13 is arranged at the upper right, and is fixed inside the peripheral anchor, for preventing the mass 3 from causing a large impact on the flexible beam by inertia force under the action of excessive instantaneous acceleration, thereby damaging the structure of the device. Figure 3

[0059] Further, the electrodes comprise a common bonding electrode, a common lead-out electrode, a drive bonding electrode and a drive lead-out electrode, the common bonding electrode is located directly below the common anchor, the common bonding electrode is connected to the common lead-out electrode through a lead wire, and the common bonding electrode is used to form a ground signal connection, and the common lead-out electrode is used to connect an external ground signal.

[0060] The drive bonding electrode is located directly below the drive comb tooth, and the drive bonding electrode is connected to the drive lead-out electrode through a lead wire.

[0061] As shown in the figure, from the top view of the lower structure of the accelerometer, it can be seen that the glass electrode substrate 33 is a rectangular structure as a whole, and its area is slightly larger than that of the upper structure, and the upper structure is bonded to the center position of the glass substrate 17. Figure 4 The common bonding electrode comprises a first common bonding electrode 22-1, a second common bonding electrode 22-2, a third common bonding electrode 23-1 and a fourth common bonding electrode 23-2, the first common bonding electrode 22-1 and the second common bonding electrode 22-2 are located at one end of the glass substrate 17, and the third common bonding electrode 23-1 and the fourth common bonding electrode 23-2 are located at the other end of the glass substrate 17. The right half of the first common bonding electrode 22-1 and the left half of the second common bonding electrode 22-2 are located directly below the first common anchor 4, and are used to form a ground signal connection. The right half of the third common bonding electrode 23-1 and the left half of the fourth common bonding electrode 23-2 are located directly below the second common anchor 11, and are used to form a ground signal connection.

[0062] The common lead-out electrode comprises a first common lead-out electrode 18-1, a second common lead-out electrode 18-2, a third common lead-out electrode 19-1 and a fourth common lead-out electrode 19-2, the first common lead-out electrode 18-1 and the second common lead-out electrode 18-2 are located at one end of the glass substrate 17, and the third common lead-out electrode 19-1 and the fourth common lead-out electrode 19-2 are located at the other end of the glass substrate 17 and are located on the lower side of the upper structure of the accelerometer, and are used to connect an external ground signal.

[0063]

[0064] ​​The lead lines include common lead lines, drive lead lines and drive interconnection lead lines. The common lead lines include a first common lead line 27-1, a second common lead line 27-2, a third common lead line 28-1 and a fourth common lead line 28-2. The first common lead line 27-1 is used to connect the first common bonding electrode 22-1 and the first common lead-out electrode 18-1. The second common lead line 27-2 is used to connect the second common bonding electrode 22-2 and the second common lead-out electrode 18-2. The third common lead line 28-1 is used to connect the third common bonding electrode 23-1 and the third common lead-out electrode 19-1. The fourth common lead line 28-2 is used to connect the fourth common bonding electrode 23-2 and the fourth common lead-out electrode 19-2.

[0065] The drive bonding electrodes include a first drive bonding electrode 24-1, a second drive bonding electrode 24-2, a third drive bonding electrode 25-1, a fourth drive bonding electrode 25-2 and a fifth drive bonding electrode 26. The right half of the first drive bonding electrode 24-1, the right half of the second drive bonding electrode 24-2, the left half of the third drive bonding electrode 25-1 and the left half of the fourth drive bonding electrode 25-2 are located below the fixed comb tooth 7-2. The fifth drive bonding electrode 26 is located at the center of the glass substrate 17 and is located directly below the fixed comb tooth 7-2, which is used to form a drive signal connection.

[0066] The drive lead-out electrodes include a first drive lead-out electrode 20-1, a second drive lead-out electrode 21-1, a third drive lead-out electrode 20-3, a fourth drive lead-out electrode 21-3, a fifth drive lead-out electrode 20-2 and a sixth drive lead-out electrode 21-2. The drive lead-out electrodes are outside the periphery of the upper structure of the accelerometer and are used to connect external drive signals.

[0067] The drive lead lines include a first drive lead line 29-1, a second drive lead line 31-1, a third drive lead line 29-3, a fourth drive lead line 31-3, a fifth drive lead line 29-2 and a sixth drive lead line 31-2. The first drive lead line 29-1 is used to connect the first drive bonding electrode 24-1 and the first drive lead-out electrode 20-1. The second drive lead line 31-1 is used to connect the third drive bonding electrode 25-1 and the second drive lead-out electrode 21-1. The third drive lead line 29-3 is used to connect the second drive bonding electrode 24-2 and the third drive lead-out electrode 20-3. The fourth drive lead line 31-3 is used to connect the fourth drive bonding electrode 25-2 and the fourth drive lead-out electrode 21-3. The fifth drive lead line 29-2 is used to connect the fifth drive bonding electrode 26 and the fifth drive lead-out electrode 20-2. The sixth drive lead line 31-2 is used to connect the fifth drive bonding electrode 26 and the sixth drive lead-out electrode 21-2.

[0068] The drive interconnect leads include a first drive interconnect lead 30 and a second drive interconnect lead 32. The first drive interconnect lead 30 is used to connect the first drive lead 20-1, the third drive lead 20-3 and the fifth drive lead 20-2. The second drive interconnect lead 32 is used to connect the second drive lead 21-1, the fourth drive lead 21-3 and the sixth drive lead 21-2.

[0069] The upper silicon-based FP cavity MEMS sensing structure converts the horizontal Y-axis input acceleration into the displacement of the mass block. This displacement causes the cavity gap of a pair of oppositely arranged FP sensing cavities to drift in opposite directions, thereby triggering the inverse phase transformation of the FP cavity interference optical signal, ultimately achieving high-precision differential detection of acceleration. A set of driving comb teeth is arranged inside the mass block to realize force feedback control.

[0070] The upper silicon-based FP cavity MEMS sensing structure first converts the horizontal Y-axis input acceleration 'a' into the displacement of the mass block. According to Newton's second law, the inertial force F of the mass and the resulting static displacement... They are respectively:

[0071] ,

[0072] ,

[0073] Where m is the mass of the mass block and k is the elastic coefficient of the cantilever beam.

[0074] The static displacement This results in a cavity for a pair of opposing Bragg grating FP sensitive cavities. A reverse drift occurs, which is represented as: This leads to an inverse phase transformation of the intensity of the interferometric light in the FP cavity, and the intensity of the reflected light... This can be approximated as:

[0075] ,

[0076] ,

[0077] Where L represents the initial cavity length, R is the input light intensity, and R is the reflectivity of the Bragg mirror. Let λ be the phase difference, λ be the wavelength of light, and n be the refractive index of the cavity medium.

[0078] Differential detection of the out-of-phase reflected light ultimately converts acceleration into light intensity. Furthermore, a set of driving comb teeth is arranged inside the mass block to perform electrostatic force feedback control based on the real-time differential results, maintaining the mass block's position at its initial equilibrium position, thereby achieving the conversion of acceleration into the final feedback force.

[0079] Example 2

[0080] like Figure 5 As shown in the figure, the manufacturing method of the force feedback MEMS accelerometer based on a silicon Bragg grating FP cavity in this embodiment includes the following steps:

[0081] Step 1: Clean and prepare the glass substrate, such as... Figure 5 Figure (a) in the middle;

[0082] Step 2: The glass substrate is etched using a hydrofluoric acid solution or gas to form shallow electrode trenches, such as... Figure 5 Figure (b) in the middle;

[0083] Step 3: Sequentially deposit metallic chromium and gold using electron beam evaporation or magnetron sputtering to form signal electrodes, such as... Figure 5 Figure (c) in the middle;

[0084] Step 4: Clean and prepare the low-resistivity silicon substrate, and form anchor point structures through deep silicon etching, such as... Figure 5 Figure (d) in the middle;

[0085] Step 5: Bond the low-resistivity silicon substrate to the glass substrate to form an electrical connection between the upper silicon sensing structure and the lower electrode, such as... Figure 5 Figure (e) in the middle;

[0086] Step 6 involves releasing the mass block structure through deep silicon etching, while simultaneously forming the flexible beam structure, the Bragg grating FP cavity structure, and the groove for the signal transmission fiber, such as... Figure 5 Figure (f) in the middle;

[0087] Step 7: Align the signal transmission fiber with the shallow groove installed at the outer anchor point to form a complete MEMS accelerometer, such as... ​ Figure (g) in the diagram.

Claims

1. A force feedback MEMS accelerometer based on a silicon Bragg grating F-P cavity, characterized in that, The silicon-based F-P cavity MEMS sensing structure is bonded to the glass electrode substrate through an anchor point. The silicon-based F-P cavity MEMS sensing structure comprises a flexible beam, a mass block, a common anchor point, a peripheral anchor point, a Bragg grating F-P sensing cavity, a signal transmission optical fiber and a driving comb, wherein the flexible beam is arranged on both sides of the mass block, the mass block is connected to the common anchor point through the flexible beam, a gap exists between the mass block and the common anchor point, the peripheral anchor points are distributed on the periphery of the mass block and the common anchor point, the signal transmission optical fiber is connected to the Bragg grating F-P sensing cavity and is arranged in the gap between the mass block and the common anchor point, and the driving comb is embedded in the center of the mass block. The glass electrode substrate comprises a glass substrate and an electrode, and the electrode is arranged on the surface of the glass substrate. The Bragg grating F-P sensing cavity comprises a first Bragg grating F-P sensing cavity and a second Bragg grating F-P sensing cavity, and the signal transmission optical fiber comprises a first signal transmission optical fiber and a second signal transmission optical fiber; the first Bragg grating F-P sensing cavity and the second Bragg grating F-P sensing cavity have the same structure and each comprise a detection grating and a fixed grating, the detection grating is fixed on the mass block, the fixed grating is fixed on the peripheral anchor point, the gap between the mass block and the peripheral anchor point constitutes a cavity of the F-P cavity, and the signal transmission optical fiber is connected to the fixed grating. When the mass block generates displacement, the cavities of the first Bragg grating F-P sensing cavity and the second Bragg grating F-P sensing cavity are reversely offset, and then the output light generates opposite phase shifts, so that the acceleration of the accelerometer is calculated through optical differential detection.

2. The force feedback MEMS accelerometer based on a silicon Bragg grating F-P cavity according to claim 1, characterized in that, The detection grating and the fixed grating are composed of silicon thin walls with equal gaps, and the thickness is equal to the thickness of the mass block, and the center wavelength passing through is adjusted by the thickness of the thin wall and the thickness between the thin walls.

3. The force-feedback MEMS accelerometer based on a silicon Bragg grating F-P cavity according to claim 1, characterized in that, The flexible beam comprises a first flexible beam, a second flexible beam, a third flexible beam and a fourth flexible beam, the first flexible beam and the second flexible beam are arranged on one side of the mass block, and the third flexible beam and the fourth flexible beam are arranged on the other side of the mass block.

4. The force-feedback MEMS accelerometer based on a silicon Bragg grating F-P cavity according to claim 1, characterized in that, The driving comb is composed of two parts of the movable comb and the fixed comb which are staggered and have equal intervals, wherein the movable comb is connected to the mass block, and the fixed comb is bonded on the glass substrate of the bottom layer; The movable comb and the fixed comb respectively receive a driving voltage and a ground signal to generate an electrostatic driving force.

5. The force-feedback MEMS accelerometer based on a silicon Bragg grating F-P cavity according to claim 1, characterized in that, The first blocker and the second blocker are arranged on both sides of the mass block and are distributed in the gap between the mass block and the peripheral anchor point.

6. The force-feedback MEMS accelerometer based on a silicon Bragg grating F-P cavity according to any one of claims 1 to 5, characterized in that, The electrode comprises a common bonding electrode, a common lead-out electrode, a driving bonding electrode and a driving lead-out electrode, the common bonding electrode is located directly below the common anchor point, the common bonding electrode is connected to the common lead-out electrode through a lead line, and the common bonding electrode is used for forming a ground signal connection; the common lead-out electrode is used for connecting an external ground signal; The driving bonding electrode is located directly below the driving comb, and the driving bonding electrode is connected to the driving lead-out electrode through a lead line.

7. A manufacturing method of a force feedback MEMS accelerometer based on a silicon Bragg grating F-P cavity, characterized in that, A method for preparing the silicon-based Bragg grating F-P cavity force feedback MEMS accelerometer of claim 1 comprises the following steps: S1, cleaning and preparing a glass substrate; S2, etching the glass substrate by a hydrofluoric acid solution or gas to form an electrode shallow groove; S3, depositing metal chromium and gold in sequence by electron beam evaporation or magnetron sputtering process to form a signal electrode; S4, cleaning and preparing a low-resistance silicon substrate, and forming an anchor point structure by deep silicon etching; S5, bonding the low-resistance silicon substrate with a glass substrate to form an electrical connection between the upper silicon sensing structure and the lower electrode; S6, releasing a mass structure by deep silicon etching, and simultaneously forming a flexible beam structure, a Bragg grating F-P cavity structure, and a groove of a signal transmission optical fiber; S7, aligning and installing the signal transmission optical fiber in the shallow groove of the peripheral anchor point to form a complete MEMS accelerometer device.

Images