Feedback capacitor for hemispherical resonant gyroscope and its fabrication method; hemispherical resonant gyroscope

Abstract

This invention discloses a feedback capacitor for a hemispherical resonator gyroscope, comprising a first capacitor electrode layer, a second capacitor electrode layer, a first electrode bonding pad electrically connected to the first capacitor electrode layer, and a second electrode bonding pad electrically connected to the second capacitor electrode layer. The first and second capacitor electrode layers are arranged parallel to each other and have a spacing. The first and second capacitor electrode layers, the first electrode bonding pad, and the second electrode bonding pad are disposed on a resonator electrode substrate. The fabrication method involves depositing a metal layer and coating it with photoresist on the upper surface of a wafer; after exposure, development, and removal of the exposed metal layer, a boss is etched; metal layers are deposited on the bosses, the center of the bosses, and the surface of the conductive bonding pads, and photoresist is coated; after exposure, development, and removal of excess metal layer, patterning is completed; after depositing a metal layer on the lower surface of another wafer, a dicing operation is performed to release the capacitor cover plate from the wafer structure; the capacitor cover plate is then bonded to the boss with conductive adhesive.

Description

Technical Field

[0001] This invention relates to the field of hemispherical resonant gyroscopes (including micro-hemispherical ones), and particularly to a feedback capacitor for a hemispherical resonant gyroscope, its preparation method, and a hemispherical resonant gyroscope including the feedback capacitor. Background Technology

[0002] A hemispherical resonant gyroscope is a rotation sensor that uses the standing wave precession of a hemispherical thin-walled resonator as its principle. It senses inertial rotation despite having no rotating mass. It features high precision, long lifespan, and overload resistance, and is widely used in aerospace and other fields.

[0003] like Figure 1 As shown, in the control circuit of a hemispherical resonator gyroscope, the capacitor voltage (Cv) amplifier is the core component. The gain stability of the Cv amplifier is particularly important, especially in mode-switching and rate-integrating operating modes, determining many indicators of the gyroscope, including its basic accuracy. The Cv amplifier gain mainly depends on the ratio of the feedback capacitor Cf to the capacitance Cs of the hemispherical resonator plates. The performance of the feedback capacitor Cf, especially its stability, directly determines the performance of the gyroscope. Traditionally, precision COG capacitors are used in the detection circuit, but their accuracy and temperature drift performance cannot meet the high-performance requirements of gyroscopes. In particular, their stability is affected by various environmental factors, such as temperature changes, shock disturbances, and stress release.

[0004] in (Sensitive capacitor) and They are directly proportional. That is:

[0005] like Figure 2 As shown, hemispherical resonator gyroscopes all have basically the same structure, namely, a hemispherical resonator is assembled on a base plate with measurement and control electrodes and sealed in a vacuum cavity. The electrode base plate is mostly made of quartz glass with an ultra-low coefficient of expansion, which has superior mechanical properties. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a high-precision feedback capacitor for a hemispherical resonant gyroscope that can optimize the performance of the entire circuit, simplify the structure of the hemispherical resonant gyroscope, and reduce the control difficulty.

[0007] The present invention further provides a method for preparing the above-mentioned feedback capacitor.

[0008] The present invention further provides a hemispherical resonant gyroscope including the above-mentioned feedback capacitor.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A feedback capacitor for a hemispherical resonant gyroscope includes a first capacitor electrode layer, a second capacitor electrode layer, a first electrode bonding pad electrically connected to the first capacitor electrode layer, and a second electrode bonding pad electrically connected to the second capacitor electrode layer. The first capacitor electrode layer and the second capacitor electrode layer are arranged in parallel and have a spacing. The hemispherical resonant gyroscope includes a resonator electrode base plate, and the first capacitor electrode layer, the second capacitor electrode layer, the first electrode bonding pad, and the second electrode bonding pad are disposed on the resonator electrode base plate.

[0010] As a further improvement to the above technical solution: the resonator electrode base plate is provided with a boss, the boss is provided with a capacitor cover plate and the first electrode bonding plate, the first capacitor electrode layer is provided on the lower surface of the capacitor cover plate, the second capacitor electrode layer and the second electrode bonding plate are provided on the upper surface of the resonator electrode base plate, and the second capacitor electrode layer is located below the first capacitor electrode layer.

[0011] As a further improvement to the above technical solution: a groove is provided on the resonator electrode base plate, a capacitor cover plate is provided above the groove, the first capacitor electrode layer is provided on the lower surface of the capacitor cover plate, the first electrode bonding plate is provided on the upper surface of the resonator electrode base plate, and the second capacitor electrode layer and the second electrode bonding plate are provided on the bottom surface of the groove.

[0012] As a further improvement to the above technical solution: the resonator electrode base plate is provided with a groove, the first capacitor electrode layer and the second capacitor electrode layer are arranged opposite to each other on the two sides of the groove, and the first electrode bonding disk and the second electrode bonding disk are provided on the upper surface of the resonator electrode base plate.

[0013] As a further improvement to the above technical solution: the capacitor cover is made of fused silica.

[0014] As a further improvement to the above technical solution: the material of the resonator electrode base plate is fused silica.

[0015] A method for fabricating the feedback capacitor for the aforementioned hemispherical resonant gyroscope includes the following steps: S1. Prepare and clean the wafers used to fabricate the resonator electrode substrate. S2. Deposit a metal layer on the upper surface of the wafer and coat it with photoresist; S3. After exposure, development and removal of the exposed metal layer, the boss is etched out. S4. Remove the metal layer and photoresist, then deposit a metal layer and coat it with photoresist on the boss, the middle of the boss and the surface of the conductive bonding pad. After exposure, development and removal of excess metal layer, patterning is completed and the electrode is released from the wafer structure. S5. Divide into individual resonator electrode base plates; S6. Fabrication of capacitor cover plate: Prepare a wafer for fabricating the capacitor cover plate, the material of which is the same as that of the hemispherical harmonic oscillator; after depositing a metal layer on the lower surface of the wafer, perform a dicing operation to release the capacitor cover plate from the wafer structure; S7. Attach the capacitor cover to the boss with conductive adhesive.

[0016] A method for fabricating the feedback capacitor for the aforementioned hemispherical resonant gyroscope includes the following steps: S1. Prepare and clean the wafers used to fabricate the resonator electrode substrate. S2. Deposit a metal layer on the upper surface of the wafer and coat it with photoresist; S3. After exposure, development and removal of the exposed metal layer, grooves are etched out. S4. Remove the metal layer and photoresist, then deposit a metal layer and coat it with photoresist on the bottom surface of the groove and the upper surface of the wafer. After exposure, development and removal of excess metal layer, patterning is completed, and the electrodes are released from the wafer structure. S5. Fabrication of capacitor cover plate: Prepare a wafer for fabricating the capacitor cover plate, the material of which is the same as that of the hemispherical harmonic oscillator; after depositing a metal layer on the lower surface of the wafer, perform a dicing operation to release the capacitor cover plate from the wafer structure; S6. Attach the capacitor cover to the top of the groove using conductive adhesive.

[0017] A method for fabricating the feedback capacitor for the aforementioned hemispherical resonant gyroscope includes the following steps: S1. Prepare and clean the wafers used to fabricate the resonator electrode substrate. S2. Deposit a metal layer on the upper surface of the wafer and coat it with photoresist; S3. After exposure, development and removal of the exposed metal layer, grooves are etched out. S4. Remove the metal layer and photoresist, then deposit the metal layer and coat the photoresist on the two opposite sides of the groove. After exposure, development and removal of excess metal layer, the patterning is completed and the electrode is released from the wafer structure. S5. The metal layers on the opposite sides of the groove are respectively led into parallel plate feedback capacitors.

[0018] A hemispherical resonant gyroscope includes a vacuum-sealed cover, a hemispherical resonator, a resonator electrode base plate, and a vacuum-sealed base plate. The vacuum-sealed cover and the vacuum-sealed base plate are connected to form a vacuum cavity. The resonator electrode base plate is disposed in the vacuum cavity, and the hemispherical resonator is disposed on the resonator electrode base plate. The resonator electrode base plate is provided with the aforementioned feedback capacitor for the hemispherical resonant gyroscope.

[0019] Compared with the prior art, the advantages of the present invention are as follows: This invention discloses a feedback capacitor for a hemispherical resonant gyroscope. The feedback capacitor Cf is directly designed onto the resonator electrode base plate, allowing it to be sealed within the vacuum cavity of the hemispherical gyroscope. Due to the superior mechanical properties of the resonator electrode base plate and its operation in a vacuum environment, a high-precision feedback capacitor can be obtained. Simultaneously, the feedback capacitor Cf and the measurement and control resonator electrode base plate capacitor Cs proportionally change with the environment. Because Cs and Cf are close together, long-term proportional stability is ensured, optimizing the overall circuit performance. Furthermore, since the CV amplifier accurately reflects the precession of the micro-hemispherical shape, compensation for the resonator electrode base plate capacitor can be eliminated. Using the feedback capacitor of this invention, the full-angle gyroscope can be directly converted from analog to digital (ADC) after CV amplification without time-division multiplexing, facilitating subsequent all-digital processing and significantly reducing control complexity.

[0020] The method for preparing the feedback capacitor for a hemispherical resonator gyroscope disclosed in this invention can simultaneously prepare the resonator electrode base plate and the feedback capacitor thereon, which can reduce the number of steps and reduce the preparation cost. Furthermore, since Cs and Cf are prepared using the same process and are close to each other, it is beneficial to ensure long-term stability of the ratio.

[0021] The hemispherical resonator gyroscope disclosed in this invention includes the aforementioned feedback capacitor and therefore also has the aforementioned advantages.

[0022] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the control circuit of the hemispherical resonant gyroscope involved in this invention. Figure 2 This is a schematic diagram of the decomposed state of the hemispherical resonant gyroscope involved in this invention.

[0024] Figure 3 This is a schematic flowchart of the first embodiment of the preparation method of the present invention.

[0025] Figure 4 This is a schematic diagram of the etched boss structure in the first embodiment of the preparation method of the present invention.

[0026] Figure 5This is a schematic diagram of the structure of the deposited metal layer in the first embodiment of the preparation method of the present invention.

[0027] Figure 6 This is a schematic diagram of the structure of the capacitor cover plate in the first embodiment of the preparation method of the present invention.

[0028] Figure 7 This is a schematic flowchart of the second embodiment of the preparation method of the present invention.

[0029] Figure 8 This is a schematic diagram of the etched groove structure in the second embodiment of the preparation method of the present invention.

[0030] Figure 9 This is a schematic diagram of the structure of the deposited metal layer in the second embodiment of the preparation method of the present invention.

[0031] Figure 10 This is a cross-sectional view of the deposited metal layer in the second embodiment of the preparation method of the present invention.

[0032] Figure 11 This is a schematic diagram of the structure of the capacitor cover plate in the second embodiment of the preparation method of the present invention.

[0033] Figure 12 This is a schematic flowchart of the third embodiment of the preparation method of the present invention.

[0034] The labels in the diagram represent: 1. Vacuum-sealed cover; 2. Hemispherical resonator; 3. Resonator electrode base plate; 31. Boss; 32. Groove; 4. Vacuum-sealed base plate; 5. Capacitor cover plate; 61. First capacitor electrode layer; 62. Second capacitor electrode layer; 63. First electrode bonding reel; 64. Second electrode bonding reel. Detailed Implementation In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0036] In this invention, unless otherwise explicitly specified and limited, the terms "assembly," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Example 1 In the detection circuit, feedback and matching capacitors requiring high stability are typically around 10pF. The specific capacitance depends on the hemispherical resonator and the specific circuit. For a parallel-plate capacitor, only the geometric dimensions need to be adjusted according to the product characteristics. In this example, using 10pF as an example, the reference structural dimensions for the design and fabrication method, and the required structural dimensions of the parallel-plate capacitor, can be obtained from the following formula:

[0039] Where C is the capacitance value. Let be the vacuum permittivity, A be the area of ​​the electrode, a be the length of the electrode, c be the width of the electrode, and d be the distance between the electrodes.

[0040] That is, when the area across the capacitor is 1 square millimeter and the gap is 1 μm, the capacitance reaches approximately 10 pF. The number and location of the feedback capacitors can also be manufactured according to specific requirements. In this embodiment, there are four capacitors, which are located around the resonator electrode base plate 3.

[0041] 1) Prepare a wafer typically used for fabricating the resonator electrode substrate 3 (preferably, the wafer is made of fused silica, which has superior mechanical properties), and clean it thoroughly, as follows: Figure 3 As shown in section (a); 2) Preferably, a chromium layer is sputtered onto the upper surface of the wafer and then photoresist is spin-coated, specifically as follows: Figure 3 As shown in section (b), the material of the metal layer, the deposition method, and the photoresist coating method can also be adjusted in other embodiments; 3) After exposure, development, and removal of the exposed chromium layer, a 1µm high boss 31 is etched, specifically as follows: Figure 3 As shown in sections (c) and (d), the shape of the boss 31 is as follows: Figure 4 As shown, it can also be other shapes to support the capacitor cover 5; 4) After removing the photoresist and chromium layer, deposit a metal layer on the boss 31, the central area of ​​each group of bosses 31, and the surface of the conductive bonding pad. Then, perform photolithography and development according to steps 2) and 3) to remove excess metal, complete the patterning, and release the electrodes from the wafer structure. At this time, the boss 31 is electrically connected to the first electrode bonding pad 63, and the second capacitor electrode layer 62 is electrically connected to the second electrode bonding pad 64, as detailed below. Figure 3 Parts (e) and (f) in the text and Figure 5 As shown; 5) Divided into individual electrode base plates; 6) Fabricating capacitor cover 5: Prepare a wafer of appropriate size and thickness (the wafer material must be the same as the material of the hemispherical harmonic oscillator 2; in this embodiment, it is fused silica). Figure 3 As shown in section (g); after depositing metal layers such as chromium and gold on the lower surface of the wafer; a dicing operation is performed to release the capacitor cover 5 from the wafer structure, as shown. Figure 3 As shown in part (h); 7) Attach the capacitor cover 5 to the boss 31 using conductive adhesive, as shown in the following steps. Figure 3 Part (i) and Figure 6 As shown, at this time, the metal layer on the lower surface of the capacitor cover plate 5 and the boss 31 are electrically connected and electrically connected to the first electrode bonding plate 63. In this way, the first electrode bonding plate 63 can be connected to the external circuit through bonding. Since the second capacitor electrode layer 62 and the second electrode bonding plate 63 are electrically connected, they can also be connected to the external circuit through bonding, thereby forming a complete and highly stable plate capacitor.

[0042] Example 2 1) Prepare a wafer typically used for fabricating the resonator electrode substrate 3 (preferably, the wafer is made of fused silica, which has superior mechanical properties), and clean it thoroughly, as follows: Figure 7 As shown in section (a); 2) Preferably, a chromium layer is sputtered onto the upper surface of the wafer and then photoresist is spin-coated, specifically as follows: Figure 7 As shown in section (b), the material of the metal layer, the deposition method, and the photoresist coating method can also be adjusted in other embodiments; 3) After exposure, development, and removal of the exposed chromium layer, a 1µm deep groove 32 is etched, specifically as follows: Figure 7 As shown in parts (c) and (d), the shape of the groove 32 is as follows: Figure 8 As shown, it can also be other shapes. The area above the groove 32 is used to place the capacitor cover plate 5. 4) After removing the photoresist and chromium layer, deposit a metal layer on the ground plane of groove 32 and the upper surface of the wafer. Then, perform photolithography and development according to steps 2) and 3) to remove excess metal, complete the patterning, and release the electrodes from the wafer structure. Specifically, as follows... Figure 7Parts (e) and (f) in the text and Figure 9 , Figure 10 As shown; 5) Fabricating capacitor cover 5: Prepare a wafer of appropriate size and thickness (the wafer material must be the same as the material of the hemispherical harmonic oscillator 2; in this embodiment, it is fused silica). Figure 7 As shown in section (g); after depositing metal layers such as chromium and gold on the lower surface of the wafer; a dicing operation is performed to release the capacitor cover 5 from the wafer structure, as shown. Figure 7 As shown in part (h); 6) Attach the capacitor cover 5 to the groove 32 using conductive adhesive, as shown in the following steps: Figure 7 Part (i) and Figure 11 As shown, at this time, the metal layer on the lower surface of the capacitor cover plate 5 and the first electrode bonding plate 63 are electrically connected, so the first electrode bonding plate 63 can be connected to the external circuit through bonding. Since the second capacitor electrode layer 62 and the second electrode bonding plate 63 are electrically connected, they can also be connected to the external circuit through bonding, thus forming a complete and highly stable plate capacitor.

[0043] Example 3 like Figure 12 As shown, when the hemispherical resonator 2 and the resonator electrode base plate 3 are made of the same material, such as fused silica, a groove 32 can be opened on the resonator electrode base plate 3, and conductive metal surfaces can be deposited on the opposite sides of the groove 32 and wires can be led out to form a parallel plate capacitor to meet the requirements.

[0044] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A feedback capacitor for a hemispherical resonant gyroscope, characterized in that: The feedback capacitor includes a first capacitor electrode layer (61), a second capacitor electrode layer (62), a first electrode bonding pad (63) electrically connected to the first capacitor electrode layer (61), and a second electrode bonding pad (64) electrically connected to the second capacitor electrode layer (62). The first capacitor electrode layer (61) and the second capacitor electrode layer (62) are arranged in parallel and have a gap. The hemispherical resonant gyroscope includes a resonator electrode base plate (3). The first capacitor electrode layer (61), the second capacitor electrode layer (62), the first electrode bonding pad (63), and the second electrode bonding pad (64) are disposed on the resonator electrode base plate (3).

2. The feedback capacitor for a hemispherical resonant gyroscope according to claim 1, characterized in that: The resonator electrode base plate (3) is provided with a boss (31), and the boss (31) is provided with a capacitor cover plate (5) and a first electrode bonding plate (63). The first capacitor electrode layer (61) is located on the lower surface of the capacitor cover plate (5), and the second capacitor electrode layer (62) and the second electrode bonding plate (64) are located on the upper surface of the resonator electrode base plate (3), and the second capacitor electrode layer (62) is located below the first capacitor electrode layer (61).

3. The feedback capacitor for a hemispherical resonant gyroscope according to claim 1, characterized in that: The resonator electrode base plate (3) is provided with a groove (32), and a capacitor cover plate (5) is provided above the groove (32). The first capacitor electrode layer (61) is provided on the lower surface of the capacitor cover plate (5), the first electrode bonding plate (63) is provided on the upper surface of the resonator electrode base plate (3), and the second capacitor electrode layer (62) and the second electrode bonding plate (64) are provided on the bottom surface of the groove (32).

4. The feedback capacitor for a hemispherical resonant gyroscope according to claim 1, characterized in that: The resonator electrode base plate (3) is provided with a groove (32), the first capacitor electrode layer (61) and the second capacitor electrode layer (62) are arranged opposite to each other on the two sides of the groove (32), and the first electrode bonding disk (63) and the second electrode bonding disk (64) are provided on the upper surface of the resonator electrode base plate (3).

5. The feedback capacitor for a hemispherical resonant gyroscope according to claim 2 or 3, characterized in that: The capacitor cover (5) is made of fused silica.

6. The feedback capacitor for a hemispherical resonant gyroscope according to any one of claims 1 to 4, characterized in that: The material of the resonator electrode base plate (3) is fused silica.

7. A method for preparing a feedback capacitor for a hemispherical resonant gyroscope as described in claim 2, characterized in that: Includes the following steps: S1. Prepare and clean the wafer used to fabricate the resonator electrode substrate (3); S2. Deposit a metal layer on the upper surface of the wafer and coat it with photoresist; S3. After exposure, development and removal of the exposed metal layer, the boss is etched (31). S4. Remove the metal layer and photoresist, then deposit the metal layer and coat the photoresist on the boss (31), the middle of the boss (31) and the surface of the conductive bonding pad. After exposure, development and removal of excess metal layer, patterning is completed and the electrode is released from the wafer structure. S5, Divide into individual resonator electrode base plates (3); S6. Preparation of capacitor cover plate (5): Prepare a wafer for making capacitor cover plate (5) with the same material as the hemispherical harmonic oscillator (2); after depositing a metal layer on the lower surface of the wafer, perform a dicing operation to release the capacitor cover plate (5) from the wafer structure. S7. Attach the capacitor cover (5) to the boss (31) with conductive adhesive.

8. A method for preparing a feedback capacitor for a hemispherical resonant gyroscope as described in claim 3, characterized in that: Includes the following steps: S1. Prepare and clean the wafer used to fabricate the resonator electrode substrate (3); S2. Deposit a metal layer on the upper surface of the wafer and coat it with photoresist; S3. After exposure, development and removal of the exposed metal layer, grooves are etched (32). S4. Remove the metal layer and photoresist, then deposit the metal layer and coat the photoresist on the bottom surface of the groove (32) and the upper surface of the wafer. After exposure, development and removal of excess metal layer, patterning is completed and the electrodes are released from the wafer structure. S5. Preparation of capacitor cover plate (5): Prepare a wafer for making capacitor cover plate (5) with the same material as the hemispherical harmonic oscillator (2); after depositing a metal layer on the lower surface of the wafer, perform a dicing operation to release the capacitor cover plate (5) from the wafer structure. S6. Attach the capacitor cover (5) to the top of the groove (32) with conductive adhesive.

9. A method for preparing a feedback capacitor for a hemispherical resonant gyroscope as described in claim 4, characterized in that: Includes the following steps: S1. Prepare and clean the wafer used to fabricate the resonator electrode substrate (3); S2. Deposit a metal layer on the upper surface of the wafer and coat it with photoresist; S3. After exposure, development and removal of the exposed metal layer, grooves are etched (32). S4. Remove the metal layer and photoresist, then deposit the metal layer and coat the photoresist on the opposite sides of the groove (32). After exposure, development and removal of excess metal layer, patterning is completed and the electrode is released from the wafer structure. S5, the metal layers on the opposite sides of the groove (32) are respectively wired to form a parallel plate feedback capacitor.

10. A hemispherical resonant gyroscope, comprising a vacuum-sealed cover (1), a hemispherical resonator (2), a resonator electrode base plate (3), and a vacuum-sealed base plate (4), wherein the vacuum-sealed cover (1) and the vacuum-sealed base plate (4) are connected to form a vacuum cavity, the resonator electrode base plate (3) is disposed within the vacuum cavity, and the hemispherical resonator (2) is disposed on the resonator electrode base plate (3), characterized in that: The resonator electrode base plate (3) is provided with a feedback capacitor for a hemispherical resonator gyroscope as described in any one of claims 1 to 6.

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