Wafer-level packaged micro-hemispherical gyroscope and processing method thereof

Abstract

The invention belongs to the technical field of micro electro mechanical systems, and discloses a wafer level packaged micro hemispherical gyroscope and a processing method thereof. The wafer-level packaged micro-hemispherical gyroscope provided by the invention comprises a silicon device layer and a cover plate layer, the silicon device layer and the cover plate layer are in eutectic bonding, a groove in the silicon device layer is hemispherical, and a bonding table, the groove and a window in the silicon device layer are all obtained by processing on a first silicon wafer; the groove and the window are used as molds for preparing the harmonic oscillator and the supporting column respectively, the harmonic oscillator and the supporting column are of a structure integrally manufactured by depositing polycrystalline silicon through a low-pressure chemical vapor deposition process, the harmonic oscillator is suspended in the cavity, one end of the supporting column is connected with the bottom surface metal bonding pad, and the other end of the supporting column is connected with the bottom surface metal bonding pad. Silicon oxide serving as a sacrificial layer is deposited between the supporting column and the first silicon wafer, and silicon oxide serving as an oxide layer is deposited between the bottom surface metal bonding pad and the first silicon wafer. The precision, the stability and the batch consistency of the gyroscope are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of micro-electro-mechanical systems, and more particularly relates to a wafer-level packaged micro-hemisphere gyroscope and a processing method thereof. BACKGROUND

[0002] As a core sensor in the field of inertial navigation and attitude control, the performance, cost and mass production capability of the micro-hemisphere gyroscope are highly dependent on the processing technology and packaging technology. The manufacturing process of the traditional micro-hemisphere gyroscope has many technical pain points, which seriously restricts its large-scale application and precision improvement.

[0003] In the preparation of the micro-hemisphere resonator, the traditional process relies on special mold forming or fused quartz blowing technology. The special mold is prone to size deviation due to wear during long-term use, which leads to a decrease in the geometric precision of the resonator. Moreover, the mechanical processing precision of the mold itself limits the miniaturization design, making the prepared micro-hemisphere resonator generally larger in size. The fused quartz blowing process relies on mechanical blowing to shape, which is limited by the material flowability and temperature field uniformity, making it difficult to precisely control the formation of small-sized spherical surfaces. If a smaller size is pursued, defects such as spherical surface collapse and uneven wall thickness may occur, resulting in a significant reduction in yield. Therefore, the film thickness uniformity can only reach the micron level, and the miniaturization preparation is extremely difficult. Not only can it not meet the demand for film thickness uniformity of high-precision micro-hemisphere gyroscopes, but it is also difficult to break through the size limit, which restricts the application of gyroscopes in small-sized devices.

[0004] The assembly of the electrode and the resonator is another key bottleneck. In the traditional process, the electrode and the resonator need to be combined through a micro-assembly step. Due to the limitation of operation precision, it is easy to cause uneven electrode gap, leading to unbalanced electric field distribution, directly reducing the measurement precision and batch consistency of the gyroscope. At the same time, the use of special molds and the step-by-step assembly process further increase the process complexity and error accumulation risk, making it difficult to improve the product yield.

[0005] In the packaging link, the existing technology generally adopts the "device-level vacuum welding" mode, that is, the cutting and separation of individual gyroscopes are completed first, and then the packaging is realized through tube-shell vacuum welding. This method not only requires additional welding equipment and process, resulting in a long production process and high cost, but also is difficult to ensure the consistency of the vacuum degree of batch products, affecting the long-term stability of the gyroscope.

[0006] In addition, the manufacturing of the resonator, electrode and support structure in the traditional process is often carried out in steps, and the cross-process alignment error and material compatibility problem easily cause stress concentration in the structure, leading to performance drift in complex environments such as temperature change and vibration, which is difficult to meet the demand for high reliability and high consistency of sensors in the field of inertial navigation. SUMMARY

[0007] The application provides a wafer-level packaged micro-hemisphere gyroscope and a processing method thereof, and solves the problems of precision, stability and batch consistency of the gyroscope in the prior art.

[0008] The application provides a wafer-level packaged micro-hemisphere gyroscope, which comprises a silicon device layer and a cover plate layer, and the silicon device layer and the cover plate layer are eutectic bonded; the silicon device layer comprises a first silicon wafer, a bonding platform, a groove, a window, a resonator, a support column, a sacrificial layer, an oxide layer and a bottom surface metal pad; wherein the groove is hemispherical, the bonding platform, the groove and the window are obtained by processing on the first silicon wafer, and the groove and the window are used as molds for preparing the resonator and the support column respectively; the resonator and the support column are structures integrally prepared by depositing polycrystalline silicon through a low-pressure chemical vapor deposition process, the resonator is suspended in a cavity formed between the silicon device layer and the cover plate layer, and one end of the support column is connected with the bottom surface metal pad; silicon oxide as the sacrificial layer is deposited between the support column and the first silicon wafer; and silicon oxide as the oxide layer is deposited between the bottom surface metal pad and the first silicon wafer.

[0009] Preferably, the cover plate layer comprises a second silicon wafer, a conductive column, a protective layer, a planar electrode, a metal transition layer and a top surface metal pad; wherein the planar electrode, the conductive column and the top surface metal pad are sequentially connected and form a conductive assembly; the planar electrode corresponds to the lip position of the resonator; the protective layer is located on the surface of the second silicon wafer, and the protective layer is used for electrically isolating the second silicon wafer from the conductive assembly; and the metal transition layer is deposited on the protective layer and corresponds to the position of the bonding platform.

[0010] Preferably, the cover plate layer further comprises a low-temperature activated getter; and the low-temperature activated getter is deposited on the protective layer on the side facing the silicon device layer.

[0011] Preferably, the bonding platform is a bonding platform with a designed depth obtained by deep reactive ion etching, and the designed depth is determined by taking the vibration space of the resonator and the layout area of the planar electrode as the target; the groove is a groove with a preset curvature radius and a preset depth formed by combining low-pressure chemical vapor deposition growth of silicon nitride mask, photolithography and HNA etching; the window is a window formed by combining photolithography and deep reactive ion etching; and the sacrificial layer is preset thickness silicon oxide deposited by low-pressure chemical vapor deposition.

[0012] Preferably, a plurality of planar electrodes are uniformly and symmetrically distributed along the circumference.

[0013] In another aspect, the present application provides a method for processing a wafer-level packaged micro-hemispherical resonator gyroscope, comprising the following steps: Preparation of a silicon device layer, comprising: processing a first silicon wafer to form a bonding pad, a hemispherical recess, and a window, the recess and the window serving as a mold for preparing a resonator and a support column, respectively; depositing silicon oxide as a sacrificial layer; depositing polycrystalline silicon to integrally form the support column and the resonator by a low-pressure chemical vapor deposition process; removing the polycrystalline silicon near the bonding pad to form a lip of the resonator; partially etching the sacrificial layer to release the resonator; Preparation of a cover plate layer; Wafer-level eutectic bonding of the cover plate layer and the silicon device layer; Depositing a top metal pad on the cover plate layer; thinning the silicon device layer to expose the sacrificial layer, and depositing silicon oxide to form an oxide layer; etching the oxide layer to form an opening; and depositing metal to fill the opening and form a bottom metal pad.

[0014] Preferably, the preparation of the cover plate layer comprises: preparing a conductive via corresponding to the position of the lip of the resonator on a second silicon wafer, forming a protective layer on the surface of the second silicon wafer; filling the conductive via with polycrystalline silicon to form a conductive column; preparing a planar electrode on one side of the conductive column; the planar electrode, the conductive column, and the top metal pad are sequentially connected to form a conductive assembly; and depositing a metal transition layer on the protective layer corresponding to the position of the bonding pad.

[0015] Preferably, the preparation of the cover plate layer further comprises: depositing a low-temperature activated getter on the protective layer on the side facing the silicon device layer.

[0016] Preferably, the processing of the first silicon wafer to form a bonding pad comprises: using deep reactive ion etching on the surface of the first silicon wafer to obtain a bonding pad with a designed depth, the designed depth being determined to reserve a vibration space for the resonator and a layout area for the planar electrode at the same time; The processing of the first silicon wafer to form a hemispherical recess comprises: growing silicon nitride as a mask on the surface of the first silicon wafer using a low-pressure chemical vapor deposition process; after defining a recess pattern on the mask through photolithography, removing the mask in the target area through etching; performing isotropic etching using an HNA etching solution to form a hemispherical recess with a preset radius of curvature and a preset depth; and after etching, removing the mask using hot phosphoric acid; The processing of the first silicon wafer to form a window comprises: using a spray coating process to spray and uniformly deposit photoresist in the form of atomized droplets onto the surface of the prepared recess; after photolithographic patterning, etching the first silicon wafer using deep reactive ion etching to form the window; After the groove and the window are obtained, a low-pressure chemical vapor deposition is used to form a preset thickness of silicon oxide on the surface of the first silicon wafer as the sacrificial layer.

[0017] Preferably, the method further comprises, after releasing the resonator, forming a buffer cavity groove on the surface of the first silicon wafer by photolithography; and the buffer cavity groove is bonded and sealed with the cover layer to form a vacuum buffer cavity.

[0018] The one or more technical solutions provided in the present application have at least the following technical effects or advantages: The wafer-level packaged micro-hemisphere gyroscope provided in the present application comprises a silicon device layer and a cover layer, and the silicon device layer and the cover layer are bonded together, wherein the groove in the silicon device layer is hemispherical, the bonding table, the groove and the window in the silicon device layer are obtained by processing on a first silicon wafer, and the groove and the window are used as molds for manufacturing the resonator and the support column, respectively. The resonator and the support column are structures integrally manufactured by a low-pressure chemical vapor deposition process, the resonator is suspended in the cavity, one end of the support column is connected with the bottom metal pad, and the silicon oxide deposited between the support column and the first silicon wafer serves as a sacrificial layer, and the silicon oxide deposited between the bottom metal pad and the first silicon wafer serves as an oxide layer. That is, the present application adopts an in-situ mold etching scheme for the silicon device layer, a high-precision bonding table is first processed on the first silicon wafer by deep reactive ion etching, and then a specific region of the silicon device layer is isotropically etched by using an HNA etching liquid to form a groove with a smooth inner wall and a hemispherical shape. The groove directly serves as a precise mold for manufacturing the resonator, and there is no need to additionally manufacture a special mold. This not only eliminates the processing errors caused by the wear of the traditional mold from the source and improves the precision, but also eliminates the alignment deviation of the split bonding, thereby providing a core guarantee for the improvement of the geometric consistency of the resonator. The present application forms a micro-hemisphere resonator on the surface of the mold through a polycrystalline silicon deposition process, flexibly adjusts the thickness of the resonator film layer by using the controllability of the deposition process, realizes the uniformity of nanoscale, and at the same time meets the design requirements of miniaturization, which is obviously superior to the miniaturization and film thickness control ability of the traditional fused quartz blowing process. The present application releases the resonator structure by etching the sacrificial layer, and integrates the electrodes, the support structure and the packaging by using a wafer-level vacuum packaging process, so that the whole process does not need a micro-assembly step, which can ensure the uniform distribution of the electrode gap and the homogeneous and integrated manufacturing of the support handle and the resonator, thereby avoiding the error accumulation caused by the alignment step in the conventional assembly process. Overall, the present application effectively improves the precision, stability and batch consistency of the gyroscope. In addition, the present application realizes wafer-level vacuum packaging based on a semiconductor process, and does not need subsequent tube shell vacuum welding, thereby simplifying the process and reducing the cost. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A flowchart of a processing method of a wafer-level packaged micro-hemisphere gyroscope provided for Embodiment 1 of the present application; Figure 2 A structure diagram of a first silicon wafer in a processing method of a wafer-level packaged micro-hemisphere gyroscope provided by the embodiment 1 of the present application; Figure 3 A structure diagram of processing the first silicon wafer to form a bonding table in the processing method of the wafer-level packaged micro-hemisphere gyroscope provided by the embodiment 1 of the present application; Figure 4 A structure diagram of processing the first silicon wafer to form a groove in the processing method of the wafer-level packaged micro-hemisphere gyroscope provided by the embodiment 1 of the present application; Figure 5 A structure diagram of processing the first silicon wafer to form a window in the processing method of the wafer-level packaged micro-hemisphere gyroscope provided by the embodiment 1 of the present application; Figure 6 A structure diagram obtained after depositing a sacrifice layer in the processing method of the wafer-level packaged micro-hemisphere gyroscope provided by the embodiment 1 of the present application; Figure 7 A structure diagram obtained after integrally manufacturing a resonator and a support column in the processing method of the wafer-level packaged micro-hemisphere gyroscope provided by the embodiment 1 of the present application; Figure 8 A structure diagram of removing the polysilicon near the bonding table to form a resonator lip in the processing method of the wafer-level packaged micro-hemisphere gyroscope provided by the embodiment 1 of the present application; Figure 9 A structure diagram obtained after releasing the resonator in the processing method of the wafer-level packaged micro-hemisphere gyroscope provided by the embodiment 1 of the present application; Figure 10 A structure diagram of a cover layer in the processing method of the wafer-level packaged micro-hemisphere gyroscope provided by the embodiment 1 of the present application; Figure 11 A structure diagram obtained after bonding the silicon device layer and the cover layer in the processing method of the wafer-level packaged micro-hemisphere gyroscope provided by the embodiment 1 of the present application; Figure 12 A structure diagram obtained after depositing a top metal pad in the processing method of the wafer-level packaged micro-hemisphere gyroscope provided by the embodiment 1 of the present application; Figure 13 A structure diagram obtained after thinning the silicon device layer and depositing an oxide layer in the processing method of the wafer-level packaged micro-hemisphere gyroscope provided by the embodiment 1 of the present application; Figure 14 A structure diagram obtained after etching the oxide layer to form an opening in the processing method of the wafer-level packaged micro-hemisphere gyroscope provided by the embodiment 1 of the present application; Figure 15A structure schematic diagram obtained after a bottom metal pad is made in a processing method of a wafer level packaged micro-hemisphere gyroscope provided by the embodiment 1 of the present application; Figure 16 A planar electrode layout plan view in a wafer level packaged micro-hemisphere gyroscope provided by the embodiment 2 of the present application; Figure 17 A whole structure schematic diagram of a wafer level packaged micro-hemisphere gyroscope provided by the embodiment 3 of the present application. DETAILED DESCRIPTION

[0020] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in combination with the drawings of the specification and specific embodiments.

[0021] The present application provides a processing method of a wafer level packaged micro-hemisphere gyroscope, referring to Figures 1 to 15 , mainly comprising the following steps: S1, preparing a silicon device layer, comprising: processing a first silicon wafer 201 to form a bonding table 202, a hemispherical groove 203 and a window 204, the groove 203 and the window 204 are respectively used as a mold for preparing a resonator 207 and a support column 206; depositing silicon oxide as a sacrificial layer 205; depositing polycrystalline silicon to integrally make the support column 206 and the resonator 207 by a low pressure chemical vapor deposition process; removing the polycrystalline silicon near the bonding table 202 to form a lip of the resonator 207; partially etching the sacrificial layer 205 to release the resonator 207; S2, preparing a cover plate layer; S3, wafer level eutectic bonding the cover plate layer and the silicon device layer; S4, depositing a top metal pad 213 on the cover plate layer; thinning the silicon device layer to expose the sacrificial layer 205, and depositing silicon oxide to form an oxide layer 214; etching the oxide layer 214 to form an opening 215; depositing metal to fill the opening 215 and form a bottom metal pad 216.

[0022] In S2, the preparation of the cover plate layer comprises: preparing a conductive via hole corresponding to the position of the lip of the resonator 207 on a second silicon wafer 208, forming a protective layer on the surface of the second silicon wafer 208; filling the conductive via hole with polycrystalline silicon to form a conductive column 209; preparing a planar electrode 210 on one side of the conductive column 209; the planar electrode 210, the conductive column 209 and the top metal pad 213 are sequentially connected to form a conductive assembly; depositing a metal transition layer 211 corresponding to the position of the bonding table 202 on the protective layer.

[0023] Further, in S2, the preparation of the cover plate layer can further include: depositing a low-temperature activated getter 212 on the protective layer on the side facing the silicon device layer.

[0024] The application will be further described in Example 1 in combination with detailed steps.

[0025] Example 1 Example 1 provides a wafer-level packaged micro-hemispherical resonator gyroscope processing method, as shown in Figure 1 , including the following steps: Step 101, providing a silicon wafer as a device layer.

[0026] As shown in Figure 2 , a first silicon wafer 201 of a certain thickness is selected as the basic material of the silicon device layer, and all subsequent processes are based on the first silicon wafer 201. The stability and process compatibility need to be ensured.

[0027] Step 102, etching a bonding table on the silicon device layer.

[0028] As shown in Figure 3 , a deep reactive ion etching (DRIE) process is used to etch the bonding table 202 of a certain depth on the upper surface of the first silicon wafer 201: on the one hand, the profile of the bonding table 202 is accurately matched with the bonding area of the cover plate layer, providing a physical alignment reference for the subsequent bonding of the cover plate layer, and avoiding the problem of uneven electrode gap caused by alignment deviation in the traditional precise assembly process; on the other hand, the depth design of the bonding table 202 can reserve the vibration space of the resonator 207 and the layout area of the planar electrode 210 at the same time, avoiding mechanical interference between the cover plate layer and the resonator after packaging, and further simplifying the process without the need for additional process adjustment gap.

[0029] Step 103, etching a hemispherical resonator mold on the silicon device layer.

[0030] As shown in Figure 4As shown, a silicon nitride (Si3N4) layer of a certain thickness is grown on the surface of the first silicon wafer 201 using a low-pressure chemical vapor deposition (LPCVD) process as a mask layer. After defining the groove pattern on the mask layer by photolithography, the mask in a specific area is removed by etching, exposing that specific area of ​​the first silicon wafer 201. Subsequently, isotropic etching is performed using an HNA etching solution (a mixture of nitric acid, hydrofluoric acid, and acetic acid). This process can etch at the same rate in all crystal orientations of silicon, ultimately forming the hemispherical groove 203 with a preset radius of curvature and depth. The inner wall of the groove 203 has both roundness and smoothness. The groove 203 directly serves as the mold for the subsequent fabrication of the resonator 207 of the micro-hemispherical gyroscope. The Si3N4 mask in the HNA etching is used to precisely and selectively protect specific areas on the silicon wafer in an extremely harsh chemical environment, thereby accurately obtaining the designed hemispherical groove 203. After HNA etching, the Si3N4 mask is removed using hot phosphoric acid. Because the LPCVD process offers superior conformal coverage, excellent thickness uniformity, high-quality film properties, and good stress control, it provides a crucial technological foundation for manufacturing high-precision, highly consistent molds for the resonator 207.

[0031] Step 104: Etch the silicon device layer support pillar mold.

[0032] like Figure 5 As shown, a spray coating process is used to spray photoresist in the form of atomized droplets and uniformly deposit it on the surface of the prepared hemispherical groove 203. After photolithography patterning, DRIE is used to etch the window 204 of the silicon device layer onto the first silicon wafer 201. The window 204 is used as a mold for fabricating the support pillar 206.

[0033] Step 105: Deposit the sacrificial layer.

[0034] like Figure 6 As shown, after forming the groove 203 and the window 204, that is, after etching the mold of the resonator 207 and the mold of the support pillar 206, a uniformly thick layer of silicon oxide is deposited on the surface of the first silicon wafer 201 as the sacrificial layer 205. The thickness of the sacrificial layer 205 needs to be precisely controlled according to the preset gap between the resonator 207 and the mold of the resonator 207. On the one hand, this reserves an etching channel for the subsequent suspension and release of the resonator 207, and on the other hand, it provides physical support for the subsequent fabrication of the resonator 207.

[0035] Step 106: Deposit polycrystalline silicon to integrally fabricate support pillars and resonators.

[0036] As shown in Figure 7 , the LPCVD process is used for polysilicon deposition, and the support column 206 and the resonator 207 are simultaneously and integrally manufactured. This process can prepare high-quality, low-stress, and high-uniformity polysilicon thin film, which has excellent conformal coverage capability, can make polysilicon grow uniformly along the vertical sidewall of the window 204, the bottom, and the complex arc-shaped inner wall of the micro-hemisphere mold (i.e., the groove 203), makes the support column 206 closely adhere to the window 204 and the crystalline quality stable, and the sacrificial layer 205 exists between the support column 206 and the first silicon wafer 201, which can avoid the short circuit between the support column 206 and the first silicon wafer 201. In addition, this method can ensure that the resonator 207 with the same thickness is deposited in each area of the mold curved surface, effectively avoiding the structural connection error and thickness deviation that may be caused by step-by-step manufacturing. In this processing mode, the resonator 207 and the support column 206 form a homogeneous and closely connected overall structure, which not only guarantees the vibration stability of the resonator 207 in the suspended state after release, but also the uniform polysilicon film layer and structural consistency are the core guarantee for the subsequent gyroscope performance consistency and high-precision measurement.

[0037] Step 107, remove excess polysilicon.

[0038] As shown in Figure 8 , the photoresist is sprayed and uniformly deposited on the surface of the structure that has been prepared in the form of atomized droplets by using the spray coating process. After photolithography patterning, the polysilicon in the exposed area is removed by DRIE.

[0039] Step 108, release the resonator structure.

[0040] As shown in Figure 9 , the hydrofluoric acid solution (HF) is introduced, and by controlling the etching time and the concentration of the etching solution, the sacrificial layer 205 is selectively etched, the resonator 207 structure is released, and the resonator 207 is suspended in the cavity. The sacrificial layer 205 between the support column 206 and the first silicon wafer 201 is retained.

[0041] Step 109, manufacture the cover layer.

[0042] As shown in Figure 10As shown, the fabrication of the cover plate layer begins with the second silicon wafer 208, which is dimensionally matched to the first silicon wafer 201. Based on the predetermined position of the lip of the resonator 207 on the silicon device layer, photolithographic alignment is performed in the corresponding area of ​​the second silicon wafer 208. Conductive vias are fabricated at the corresponding positions on the second silicon wafer 208 using through-silicon via (TSV) technology. A protective layer is formed on the surface of the second silicon wafer 208 using a thermo-oxidative process, and the material of the protective layer is silicon oxide. Polycrystalline silicon is filled into the conductive vias using LPCVD to form the conductive pillars 209. Metal is deposited on the side of the cover plate layer facing the resonator 207 (i.e., the side of the conductive pillars 209), and the pattern is defined by photolithographic etching to form the planar electrode 210 that precisely corresponds to the position of the lip of the resonator 207. The planar electrode 210 achieves ohmic contact with the conductive post 209, and its size and spacing are strictly matched with the lip of the resonator 207, ensuring uniform capacitive coupling with the lip of the resonator 207 after subsequent bonding, providing a stable operating area for the gyroscope's driving and detection. Simultaneously, metal is deposited at the location corresponding to the bonding stage 202 as the metal transition layer 211 for bonding, providing a foundation for the success rate and reliability of subsequent bonding steps. The low-temperature activated getter 212 is deposited by LPCVD in a specific area on the side of the capping layer facing the resonator 207.

[0043] Step 110: Bonding the device wafer to the cover wafer.

[0044] like Figure 11 As shown, the cover plate layer prepared above is aligned and eutectic bonded to the silicon device layer. This ensures precise alignment of the planar electrode 210 of the cover plate layer with the lip of the resonator 207 on the silicon device layer, guaranteeing the consistency and uniformity of the capacitor gap from the source. Simultaneously, a vacuum cavity is formed between the silicon device layer and the cover plate layer. That is, the cover plate layer and the silicon device layer are eutectic bonded at the wafer level to seal the cavity and create a stable vacuum environment.

[0045] Step 111: Fabricate the cover plate metal electrode.

[0046] like Figure 12 As shown, a top metal pad 213 is deposited at a corresponding position on the upper surface of the cover plate layer using LPCVD. The top metal pad 213 is connected to the conductive post 209, providing a reliable electrical connection for the gyroscope signal output. In other words, metal pads are deposited at corresponding positions on the cover plate layer, completing the overall packaging and signal output structure.

[0047] Step 112, thinning the device layer wafer and depositing the oxide layer.

[0048] As shown in Figure 13 , the wafer is turned upside down to expose the sacrificial layer 205 by Chemical Mechanical Polishing (CMP) to thin the first silicon wafer 201. Then a certain thickness of silicon oxide is deposited on the surface by LPCVD to form the oxide layer 214, which serves as support and electrical insulation.

[0049] Step 113, etching the oxide layer to form the window.

[0050] As shown in Figure 14 , the oxide layer 214 is patterned by photolithography, and the window 215 is formed by DRIE etching in the corresponding area.

[0051] Step 114, making the bottom metal pad.

[0052] As shown in Figure 15 , the metal is deposited in the window 215 area by LPCVD technology to fill the window 215 and form the bottom metal pad 216, which provides reliable electrical connection for the gyroscope signal lead-out, i.e. realizes the electrical signal lead-out of the resonator.

[0053] Corresponding to the above-mentioned processing method of the wafer-level packaged micro-hemisphere gyroscope provided by the present application, the present application also provides a wafer-level packaged micro-hemisphere gyroscope, which is described below with Example 2.

[0054] Example 2: Example 2 provides a wafer-level packaged micro-hemisphere gyroscope, as shown in Figure 15 , mainly comprising a silicon device layer and a cover layer, and the silicon device layer and the cover layer are bonded by eutectic bonding.

[0055] Among them, the silicon device layer includes a first silicon wafer 201, a bonding platform 202, a groove 203, a window 204, a resonator 207, a support column 206, a sacrificial layer 205, an oxide layer 214 and a bottom metal pad 216.

[0056] The groove 203 is hemispherical, the bonding platform 202, the groove 203 and the window 204 are obtained by processing on the first silicon wafer 201, the groove 203 and the window 204 are used as molds for manufacturing the resonator 207 and the support column 206 respectively; the resonator 207 and the support column 206 are structures integrally manufactured by depositing polycrystalline silicon through a low-pressure chemical vapor deposition process, the resonator 207 is suspended in a cavity formed between the silicon device layer and the cover plate layer, one end of the support column 206 is connected with the bottom metal pad 216; silicon oxide as the sacrificial layer 205 is deposited between the support column 206 and the first silicon wafer 201; silicon oxide as the oxide layer 214 is deposited between the bottom metal pad 216 and the first silicon wafer 201.

[0057] The cover plate layer includes a second silicon wafer 208, a conductive column 209, a protective layer, a planar electrode 210, a metal transition layer 211 and a top metal pad 213.

[0058] The planar electrode 210, the conductive column 209 and the top metal pad 213 are sequentially connected to form a conductive assembly; the planar electrode 210 corresponds to the lip position of the resonator 207; the protective layer is located on the surface of the second silicon wafer 208, and the protective layer is used for electrically isolating the second silicon wafer 208 from the conductive assembly; the metal transition layer 211 is deposited on the protective layer, and the metal transition layer 211 corresponds to the position of the bonding platform 202.

[0059] In addition, the cover plate layer can further include a low-temperature activated getter 212; the low-temperature activated getter 212 is deposited on the protective layer on the side facing the silicon device layer.

[0060] The silicon device layer in the application forms the mold for the deposition of the resonator 207 by patterning and etching the groove 203 into a specific shape. The resonator 207 is formed by depositing a certain thickness of polysilicon in the mold, which avoids the processing errors caused by mold wear in the traditional process, and improves the processing precision. At the same time, this process has strong flexibility. By adjusting the deposition parameters, the wall thickness and spherical curvature radius of the resonator 207 can be flexibly adjusted to adapt to the needs of different ranges of gyroscopes (such as low angular velocity high precision or high angular velocity wide range). The support column 206 and the resonator 207 are made of the same material, which is made by depositing polysilicon. The two are closely connected to achieve the suspension of the resonator 207 in the cavity. In addition, a bias voltage can be applied to the resonator 207 through the support column 206. The conductive column 209 in the application is connected to the external pad to create an electrical path between the planar electrode 210 and the external circuit. The metal transition layer 211 can increase the reliability of the bonding. The protective layer provides physical protection for the second silicon wafer 208, and also serves as an electrical isolation between the second silicon wafer 208 and the external pad. The silicon device layer and the cover layer are connected by eutectic bonding to form a cavity. The silicon device layer is made with a certain height of the bonding table 202, which is precisely controllable in size to ensure that the electrode gap between the resonator 207 and the planar electrode 210 is uniformly distributed after bonding, thereby greatly improving the precision and stability of the micro-hemisphere gyroscope. The low-temperature activated getter 212 is used to ensure a good vacuum degree in the cavity, that is, the low-temperature activated getter 212 can achieve a higher vacuum degree in the micro-hemisphere gyroscope cavity after activation, and the low-temperature activated getter 212 can reduce air damping and improve the quality factor, without subsequent tube shell vacuum welding, simplifying the process steps and reducing development costs. The micro-hemisphere gyroscope wafer provided by the application is integrally formed without assembly steps, which improves the consistency of the micro-hemisphere gyroscope.

[0061] For example, as shown in Figure 16 The 8 planar electrodes are arranged on the cover layer in a one-to-one correspondence with the above-mentioned positions, with 4 of them as drive electrodes and the other 4 as detection electrodes.

[0062] The above design is the most widely used angle scheme, and different numbers of lips and distribution angles can be selected according to different control methods. That is, a plurality of planar electrodes are uniformly and symmetrically distributed along the circumference, and the number can be adjusted by the control scheme, and the drive electrodes and the detection electrodes are alternately and symmetrically distributed along the circumference.

[0063] The wafer-level packaged micro-hemisphere gyroscope provided in embodiment 2 can be obtained by using the processing method of the wafer-level packaged micro-hemisphere gyroscope described in embodiment 1, and thus can also be understood by referring to the description of embodiment 1, which will not be repeated here.

[0064] Embodiment 3: Embodiment 3 differs from embodiment 2 in that embodiment 3 adds a vacuum buffer cavity to delay gas permeation and prolong the vacuum maintenance time of the main vacuum cavity, further improving the service life of the gyroscope. That is, a buffer cavity groove is also formed on the surface of the first silicon wafer by lithography, and the buffer cavity groove is bonded and sealed with the cover layer to form a vacuum buffer cavity.

[0065] Specifically, embodiment 3 adds a plurality of vacuum buffer cavities (as shown in FIG. 17) outside the main vacuum cavity formed by bonding the silicon device layer and the cover layer, and the vacuum buffer cavities are formed by bonding and sealing the buffer cavity groove on the surface of the silicon device layer with the cover layer, forming a multi-stage gas barrier path of “external environment → buffer cavity → main vacuum cavity”. The micro-hemisphere resonator of the micro-hemisphere gyroscope is very sensitive to air damping in high-speed vibration, and the wafer-level packaged micro-hemisphere gyroscope with a vacuum buffer cavity can effectively delay the gas permeation speed, ensure the vacuum degree of the main vacuum cavity of the micro-hemisphere gyroscope, and significantly improve the service life of the micro-hemisphere gyroscope.

[0066] In terms of processing method, after the silicon device layer preparation process of steps 101 to 108 in embodiment 1 is completed, the buffer cavity groove position is defined on the surface of the first silicon wafer by lithography, and the buffer cavity groove with a preset depth is etched by DRIE. The buffer cavity groove is as shown in A, B, C, D, E, F in FIG. 17 (it should be noted that these are only position illustrations, and the position and number can be flexibly adjusted according to the design parameters such as vacuum barrier requirement and device size). That is, the silicon device layer preparation further includes: after releasing the resonator, forming a buffer cavity groove on the surface of the first silicon wafer by lithography. Then follow the subsequent processes such as cover layer preparation, eutectic bonding, and metal pad fabrication in embodiment 1, and the buffer cavity groove of the silicon device layer is sealed with the cover layer to form a vacuum buffer cavity after bonding. Figure 17

[0067] Embodiment 3 does not change the original core process and basic structure, but only adds a vacuum buffer cavity structure, which significantly improves the vacuum stability of the main vacuum cavity without increasing the process complexity, and adapts to long-life use scenarios.

[0068] ​Finally, it should be noted that the above detailed description is merely illustrative of the technical solutions of the present application and is not limiting, and although the present application has been described in detail with reference to the examples, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present application, and all should be covered in the scope of the claims of the present application.

Claims

1. A wafer level packaged microhemispherical resonator gyroscope, characterized by, Comprise: A silicon device layer and a cover layer, the silicon device layer and the cover layer are eutectic bonded; The silicon device layer comprises a first silicon wafer, a bonding platform, a recess, a window, a resonator, a support column, a sacrificial layer, an oxide layer and a bottom surface metal pad; wherein the recess is hemispherical, the bonding platform, the recess and the window are obtained by machining on the first silicon wafer, the recess and the window are respectively used as a mold for preparing the resonator and the support column; the resonator and the support column are structures integrally made by depositing polycrystalline silicon through a low pressure chemical vapor deposition process, the resonator is suspended in a cavity formed between the silicon device layer and the cover layer, one end of the support column is connected with the bottom surface metal pad; silicon oxide is deposited between the support column and the first silicon wafer as the sacrificial layer; silicon oxide is deposited between the bottom surface metal pad and the first silicon wafer as the oxide layer.

2. The wafer-level packaged microhemispherical resonator gyroscope of claim 1, wherein, The cover layer comprises a second silicon wafer, a conductive column, a protective layer, a planar electrode, a metal transition layer and a top surface metal pad; wherein the planar electrode, the conductive column and the top surface metal pad are sequentially connected to form a conductive assembly; the planar electrode corresponds to the lip position of the resonator; the protective layer is located on the surface of the second silicon wafer, and the protective layer is used to electrically isolate the second silicon wafer and the conductive assembly; the metal transition layer is deposited on the protective layer, and the metal transition layer corresponds to the position of the bonding platform.

3. The wafer-level packaged microhemispherical resonator gyroscope of claim 2, wherein, The cover layer further comprises a low-temperature activated getter; the low-temperature activated getter is deposited on the protective layer on the side facing the silicon device layer.

4. The wafer-level packaged microhemispherical resonator gyroscope of claim 2, wherein, The bonding platform is a bonding platform with a designed depth obtained by deep reactive ion etching, and the designed depth is determined to reserve the vibration space of the resonator and the layout area of the planar electrode at the same time; the recess is a recess with a preset curvature radius and a preset depth formed by combining low pressure chemical vapor deposition growth of silicon nitride mask, photolithography and HNA etching; the window is a window formed by combining photolithography and deep reactive ion etching; a low pressure chemical vapor deposition is used to deposit a preset thickness of silicon oxide as the sacrificial layer.

5. The wafer-level packaged microhemispherical resonator gyroscope of claim 2, wherein, A plurality of planar electrodes are uniformly and symmetrically distributed along the circumference.

6. A method of processing a wafer level packaged microhemispherical resonator gyroscope, characterized by, Comprise the following steps: Preparation of a silicon device layer, comprising: machining a first silicon wafer to form a bonding platform, a hemispherical recess and a window, the recess and the window are respectively used as a mold for preparing a resonator and a support column; depositing silicon oxide as a sacrificial layer; integrally making a support column and a resonator by depositing polycrystalline silicon through a low pressure chemical vapor deposition process; removing the polycrystalline silicon near the bonding platform to form the lip of the resonator; partially etching the sacrificial layer to release the resonator; Preparation of a cover layer; Wafer-level eutectic bonding of the cover layer and the silicon device layer; Depositing a top surface metal pad on the cover layer; thinning the silicon device layer to expose the sacrificial layer and depositing silicon oxide to form an oxide layer; etching the oxide layer to form an opening; depositing metal to fill the opening and form a bottom surface metal pad.

7. The method of processing a wafer-level packaged microhemispherical resonator gyroscope according to claim 6, wherein, The preparation of the cover plate layer comprises: preparing a conductive via hole corresponding to the lip position of the resonator on a second silicon wafer, forming a protective layer on the surface of the second silicon wafer; filling the conductive via hole with polysilicon to form a conductive column; preparing a planar electrode on one side of the conductive column; the planar electrode, the conductive column and the top surface metal pad are sequentially connected to form a conductive assembly; and depositing a metal transition layer corresponding to the bonding platform position on the protective layer.

8. The method of claim 7, wherein the method further comprises: The preparation of the cover plate layer further comprises: depositing a low-temperature activated getter on the protective layer on the side facing the silicon device layer.

9. The method of claim 7, wherein the method further comprises: Processing the first silicon wafer to form a bonding platform comprises: using deep reactive ion etching on the surface of the first silicon wafer to obtain a bonding platform with a designed depth, and the designed depth is determined to reserve the vibration space of the resonator and the layout area of the planar electrode at the same time as the target; Processing the first silicon wafer to form a hemispherical groove comprises: growing silicon nitride as a mask on the surface of the first silicon wafer using low-pressure chemical vapor deposition process; after defining the groove pattern on the mask through photolithography, removing the mask in the target area by etching; using HNA etching liquid isotropic etching process for etching to form a hemispherical groove with a preset radius of curvature and a preset depth; after etching, removing the mask using hot phosphoric acid; Processing the first silicon wafer to form a window comprises: using a spray coating process to spray and uniformly deposit photoresist in the form of atomized droplets onto the surface of the prepared groove, and after photolithographic patterning, using deep reactive ion etching to etch the first silicon wafer to form the window; After obtaining the groove and the window, a predetermined thickness of silicon oxide is deposited on the surface of the first silicon wafer as the sacrificial layer using low-pressure chemical vapor deposition.

10. The method of claim 7, wherein the method further comprises: The preparation of the silicon device layer further comprises: after releasing the resonator, forming a buffer cavity groove on the surface of the first silicon wafer through photolithography; and bonding and sealing the buffer cavity groove with the cover plate layer to form a vacuum buffer cavity.

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