Packaging method and structure for MEMS devices

Abstract

The application relates to the technical field of micro-electro-mechanical system packaging, in particular to a packaging method of a MEMS (Micro-Electro-Mechanical System) device and a structure thereof. The packaging method of the MEMS device comprises the following steps: a base wafer, a glass cover wafer and a bonding ring wafer are prepared through an etching process; the glass cover wafer and the bonding ring wafer are bonded based on a first bonding mode according to second alignment marks and third alignment marks, so as to form a cover cap wafer; a metal intermediate layer is prepared on the surface of a bonding ring step of the cover cap wafer; the cover cap wafer and the base wafer are bonded through the metal intermediate layer based on a second bonding mode according to the first alignment marks and the second alignment marks, so as to form a packaging wafer with a vacuum sealed chamber; and the packaging wafer is wafer diced along first dicing grooves and second dicing grooves, so as to obtain a MEMS chip unit. According to the technical scheme of the application, the packaging effect of high air tightness, high reliability and low cost can be realized, and the packaging efficiency and packaging yield of the MEMS device can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro-electro-mechanical system packaging, and in particular to a packaging method and structure of a MEMS device. BACKGROUND

[0002] At present, micro-electro-mechanical system (MEMS) device packaging technologies mainly include chip-level packaging and wafer-level packaging. The chip-level packaging technology is relatively mature, but the dicing before packaging can easily damage the movable structure of the MEMS device, and the low packaging efficiency leads to high cost and is not conducive to mass production. The wafer-level packaging technology can realize rapid mass production to reduce production cost, but the traditional wafer-level packaging process is relatively complex, and the packaging technology has problems in packaging yield and efficiency, device service performance and life, etc., which cannot meet the requirements of high airtightness, high reliability and low cost of optical MEMS devices. Therefore, how to provide a stable vacuum sealed cavity and optical path for optical MEMS devices through wafer-level packaging and improve the packaging efficiency and yield has become a problem to be solved. SUMMARY

[0003] The present application aims to at least solve one of the problems in the prior art. To this end, the present application provides a packaging method and structure of a MEMS device, which can achieve high airtightness, high reliability and low cost packaging effect, and improve the packaging efficiency and yield of the MEMS device.

[0004] The first aspect of the present application provides a packaging method of a MEMS device, comprising:

[0005] obtaining a base wafer, wherein the base wafer is provided with a MEMS device, a wafer bonding area, a first alignment mark and a first dicing groove;

[0006] taking a glass wafer as a raw material, pre-treating the glass wafer, based on the MEMS device and the wafer bonding area, making a second dicing groove through an etching process, and making a second alignment mark through an etching process to form a glass cover wafer;

[0007] taking a silicon wafer as a raw material, pre-treating the silicon wafer, based on the wafer bonding area, making a groove and a through hole at a target position through an etching process to form a bonding ring step, and making a third alignment mark through an etching process to form a bonding ring wafer;

[0008] based on a first bonding method, bonding the glass cover wafer and the bonding ring wafer according to the second alignment mark and the third alignment mark to form a cap wafer;

[0009] A metal intermediate layer is made on the surface of the bonding ring step of the cap wafer by a metal thin film deposition process;

[0010] Based on the second bonding mode, the cap wafer and the substrate wafer are bonded through the metal intermediate layer according to the first alignment mark and the second alignment mark, to form a packaged wafer with a vacuum sealed chamber.

[0011] The packaged wafer is diced along the first dicing groove and the second dicing groove respectively to obtain a MEMS chip unit.

[0012] The packaging method of the MEMS device provided by the embodiment of the first aspect of the application has at least the following beneficial effects: a substrate wafer is obtained, the substrate wafer is provided with a MEMS device, a wafer bonding area, a first alignment mark and a first dicing groove; a glass cover wafer is provided, a second alignment mark and a second dicing groove are made on the glass cover wafer; a bonding ring wafer is provided, a groove, a through hole, a bonding ring step and a third alignment mark are made on the bonding ring wafer; a metal intermediate layer is made on the surface of the bonding ring step of the cap wafer by a metal thin film deposition process; the first alignment mark, the second alignment mark and the third alignment mark are used for bonding alignment, the glass cover wafer and the bonding ring wafer are bonded based on a first bonding mode to form a cap wafer, and the metal intermediate layer of the cap wafer and the wafer bonding area of the substrate wafer are bonded based on a second bonding mode to form a packaged wafer with a vacuum sealed chamber; the packaged wafer is diced along the first dicing groove and the second dicing groove respectively to obtain a MEMS chip unit. According to the technical solution of the application, the packaging of the MEMS device is realized by means of secondary bonding, the first alignment mark, the second alignment mark and the third alignment mark are used for bonding alignment, the glass cover wafer, the bonding ring wafer and the substrate wafer are sequentially bonded and connected, so that the glass cover wafer, the bonding ring wafer and the substrate wafer are connected to form a packaged wafer, and a vacuum sealed chamber is formed to provide an optical access. The technical solution can meet the requirements of the air tightness and optical access compatibility of the MEMS device, and can avoid the problems of complex packaging, low efficiency and high cost in the traditional packaging process. Therefore, the application can realize high air tightness, high reliability and low cost packaging effect, and can improve the packaging efficiency and yield of the MEMS device.

[0013] According to some embodiments of the application, the first bonding mode is silicon-glass anodic bonding.

[0014] According to some embodiments of the application, the second bonding mode is metal intermediate layer bonding.

[0015] According to some embodiments of the application, the process temperature of the first bonding mode is higher than the process temperature of the second bonding mode.

[0016] According to some embodiments of the present application, the second bonding manner includes gold-silicon eutectic bonding, gold-gold diffusion bonding, and copper-tin solder bonding.

[0017] According to some embodiments of the present application, the base wafer is further provided with a getter, which is activated at a process temperature of the metal interlayer bonding.

[0018] The second aspect of the present application provides a MEMS chip unit, comprising:

[0019] a base wafer provided with a MEMS device, a wafer bonding area, a first alignment mark, and a first dicing groove;

[0020] a glass cover wafer provided with a second dicing groove and a second alignment mark;

[0021] a bonding ring wafer provided with a groove, a through hole, a bonding ring step, and a third alignment mark, wherein the bonding ring step is provided with a metal interlayer;

[0022] The glass cover wafer, the bonding ring wafer, and the base wafer are sequentially bonded and connected to form a packaged wafer with a vacuum sealed chamber.

[0023] The MEMS chip unit provided by the second aspect of the present application has at least the following beneficial effects: a base wafer is obtained, which is provided with a MEMS device, a wafer bonding area, a first alignment mark, and a first dicing groove; a glass cover wafer is provided, on which a second alignment mark and a second dicing groove are made; a bonding ring wafer is provided, on which a groove, a through hole, a bonding ring step, and a third alignment mark are made; a metal interlayer is made on the surface of the bonding ring step of the cover wafer through a metal thin film deposition process; bonding alignment is performed using the first alignment mark, the second alignment mark, and the third alignment mark; the glass cover wafer and the bonding ring wafer are bonded based on a first bonding manner to form a cover wafer, and the metal interlayer of the cover wafer and the wafer bonding area of the base wafer are bonded based on a second bonding manner to form a packaged wafer with a vacuum sealed chamber. According to the technical solution of the present application, the packaging of the MEMS device is realized through a two-step bonding manner, bonding alignment is performed using the first alignment mark, the second alignment mark, and the third alignment mark, and the glass cover wafer, the bonding ring wafer, and the base wafer are sequentially bonded and connected to form a packaged wafer, which surrounds a vacuum sealed chamber to provide an optical access. The technical solution can meet the requirements of the air tightness and optical access compatibility of the MEMS device, and can avoid the problems of complex packaging process, low efficiency, and high cost in the traditional packaging process. Therefore, the present application can realize high air tightness, high reliability, and low cost packaging effect, and can improve the packaging efficiency and yield of the MEMS device.

[0024] According to some embodiments of the present application, the metal intermediate layer comprises a metal bonding layer and a metal keying layer.

[0025] According to some embodiments of the present application, the metal bonding layer is made of one or more of Ti, Gr, Ta, and the metal keying layer is made of one or more of Au, Cu, Sn.

[0026] According to some embodiments of the present application, the substrate wafer is further provided with a getter, which is a Ti metal or a Ti-based alloy thin film material. BRIEF DESCRIPTION OF DRAWINGS

[0027] Additional aspects and advantages of the present application will become apparent and appreciated from the following description including the appended claims taken in conjunction with the accompanying drawings wherein:

[0028] Figure 1 is a flow chart of a packaging method of a MEMS device according to an embodiment of the present application;

[0029] Figure 2 is a structural schematic diagram of a substrate wafer according to an embodiment of the present application;

[0030] Figure 3 is a flow chart of a manufacturing process of a glass cover wafer according to an embodiment of the present application;

[0031] Figure 4 is a flow chart of a manufacturing process of a key ring wafer according to an embodiment of the present application;

[0032] Figure 5 is a flow chart of a manufacturing process of a cap wafer according to an embodiment of the present application;

[0033] Figure 6 is a flow chart of a manufacturing process of a metal intermediate layer according to an embodiment of the present application;

[0034] Figure 7 is a sectional view of a packaging wafer according to an embodiment of the present application;

[0035] Figure 8 is a sectional view of a MEMS chip unit according to an embodiment of the present application;

[0036] Figure 9 is a three-dimensional flow chart of a packaging method of a MEMS device according to an embodiment of the present application. DETAILED DESCRIPTION

[0037] Embodiments of the present application are described below in detail, examples of which are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary only, for the purpose of explaining the present application, and should not be understood as a limitation of the present application.

[0038] In the description of the present application, it should be understood that the orientation description, such as the orientation or position relationship indicated by up, down, front, back, left, right, etc. is based on the orientation or position relationship shown in the drawings, which is only for the purpose of facilitating the description of the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0039] In the description of the present application, the meaning of several is one or more, and the meaning of multiple is more than two, greater than, less than, more than, etc. are understood as not including the number, and above, below, etc. are understood as including the number. If it is described as first, second, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of technical features indicated.

[0040] In the description of the present application, unless otherwise explicitly limited, the words such as setting, installing, connecting, etc. should be broadly understood, and the person skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical solution.

[0041] The present application provides a packaging method and structure of a MEMS device, which can realize high airtightness, high reliability and low cost packaging effect, and improve the packaging efficiency and packaging yield of the MEMS device.

[0042] The embodiments of the present application are further described below in combination with the drawings.

[0043] As shown in the drawings, Figure 1 Figure 1 is a flowchart of a packaging method of a MEMS device provided by an embodiment of the present application, and the packaging method of the MEMS device includes but is not limited to steps S110, S120, S130, S140, S150, S160 and S170.

[0044] Step S110: Obtain a substrate wafer, the substrate wafer is provided with a MEMS device, a wafer bonding area, a first alignment mark and a first dicing groove;

[0045] As shown in the drawings, Figure 2 ​As shown, it should be noted that in one embodiment, a prepared base wafer 200 is obtained, and the base wafer 200 is provided with a MEMS device 201, a getter 202, a wafer bonding area 203, a metal pad 204, a driving circuit 205, a first alignment mark 206, and a first scribe groove 207. Among them, in the base wafer 200, the positions of the components such as the MEMS device 201, the metal pad 204, and the driving circuit 205 are fixed, that is, they cannot be changed in the later manufacturing process; and the settings of components such as the getter 202, the wafer bonding area 203, the first alignment mark 206, and the first scribe groove 207 can be changed in the later manufacturing process according to actual conditions, which are not limited here.

[0046] It can be understood that the setting of the positions of the components of the base wafer 200 can provide a position reference for the structure of the subsequently manufactured glass cover wafer 400 and the bonding ring wafer 300. Bonding the obtained base wafer 200 with the subsequently manufactured glass cover wafer 300 and the bonding ring wafer 400 can realize the packaging of the MEMS device, which is conducive to improving the packaging yield of the MEMS device.

[0047] Step S120: Taking a glass wafer as a raw material, pre-treating the glass wafer, and based on the MEMS device and the wafer bonding area, forming a second scribe groove by etching process, and forming a second alignment mark by etching process to form a glass cover wafer;

[0048] As shown in Figure 3 It can be understood that in one embodiment, a glass wafer 301 is taken as a raw material, and the glass wafer 301 is pre-treated. The position of the second scribe groove 302 is determined based on the positions of the MEMS device 201 and the wafer bonding area 203 of the base wafer 200, and the second scribe groove 302 is manufactured by etching process. The position of the second alignment mark 303 is determined according to the bonding alignment requirement, and the second alignment mark 303 is manufactured by etching process, so that the glass cover wafer 300 can be manufactured.

[0049] It should be noted that the glass wafer 301 is a high-precision optical glass material, and using it as a packaging cover plate meets the required optical requirements.

[0050] Step S130: Taking a silicon wafer as a raw material, pre-treating the silicon wafer, and based on the wafer bonding area, forming a groove and a through hole at a target position by etching process and forming a bonding ring step, and forming a third alignment mark by etching process to form a bonding ring wafer;

[0051] As shown in Figure 4As shown, it can be understood that in one embodiment, silicon wafer 401 is used as raw material. The silicon wafer 401 is pre-processed, the wafer thickness is determined based on the MEMS device 201 of the substrate wafer 200, the position and size of the groove 402 and the via 403 are determined based on the wafer bonding region 203, and the groove 402 and the via 403 of the corresponding size are fabricated at the target position by etching process, so that the via 403 provides the packaging cavity of the MEMS device 201, thereby forming the bonding ring step 404 for wafer bonding, and the position of the third alignment mark 405 is determined according to the bonding alignment requirements. The third alignment mark 405 is fabricated by etching process, and the bonding ring wafer 400 can be fabricated.

[0052] Step S140: Based on the first bonding method, the glass cap wafer and the bonding ring wafer are bonded according to the second alignment mark and the third alignment mark to form a cap wafer;

[0053] like Figure 5 As shown, it can be understood that, based on the first bonding method, the glass cap wafer 300 and the bonding ring wafer 400 can be bonded together using the second alignment mark 303 and the third alignment mark 405 to form the cap wafer 500.

[0054] Step S150: Fabricate a metal interlayer on the surface of the bonding ring steps of the cap wafer using a metal thin film deposition process;

[0055] like Figure 6 As shown, it can be understood that a metal intermediate layer 600 is fabricated on the bonding ring step 404 on the cap wafer 500, and the cap wafer 500 and the substrate wafer 200 can be bonded through the metal intermediate layer 600 to obtain the packaged wafer 700.

[0056] Step S160: Based on the second bonding method, the cap wafer and the substrate wafer are bonded through a metal interlayer according to the first alignment mark and the second alignment mark to form a packaged wafer with a vacuum-sealed chamber.

[0057] like Figure 7 As shown, since the glass cap wafer 300 and the bonding ring wafer 400 have completed the bonding operation in step S140 to form the cap wafer 500, at this time, based on the second bonding method, the first alignment mark 206 and the second alignment mark 303 are used for bonding alignment, and the cap wafer 500 and the substrate wafer 200 can be bonded through the metal interlayer 600 to form a packaged wafer 700 with a vacuum-sealed chamber 701.

[0058] Step S170: Divide the packaged wafer along the first dicing groove and the second dicing groove respectively to obtain MEMS chip units.

[0059] As shown in Figure 8 Figure 8 is a sectional view of the MEMS chip unit provided by an embodiment of the present application. The packaging wafer 700 can be cut along the first scribe groove 207 and the second scribe groove 302 respectively by mechanical or laser cutting, and thus independent MEMS chip units can be obtained.

[0060] It can be understood that, according to the technical scheme of the present application, the packaging of the MEMS device is realized by secondary bonding, the bonding alignment is performed by using the first alignment mark 206, the second alignment mark 303 and the third alignment mark 405, the cap wafer 500 is formed by bonding the glass cover wafer 300 and the bonding ring wafer 400 based on the first bonding mode, and the packaging wafer 700 is formed by bonding and connecting the cap wafer 500 and the base wafer 200 based on the second bonding mode through the metal intermediate layer 600, and the vacuum sealed chamber 701 is surrounded to provide the optical access. The technical scheme can meet the compatibility of the air tightness and the optical access of the MEMS device, and can avoid the problems of complex packaging, low efficiency and high cost in the traditional packaging process. Therefore, the present application can realize the packaging effect of high air tightness, high reliability and low cost, and can improve the packaging efficiency and the packaging yield of the MEMS device.

[0061] It should be noted that the pre-treatment operation includes cleaning, gluing, photoetching, developing and other process operations. The pre-treatment operation facilitates the etching operation on the wafer structure, and thus the packaging wafer 700 meeting the requirements can be obtained.

[0062] It should be noted that, in an embodiment, the first alignment mark 206, the second alignment mark 303 and the third alignment mark 405 are cross-shaped alignment marks.

[0063] It should be noted that, in an embodiment, the etching process is a reactive ion etching process.

[0064] According to some embodiments of the present application, the first bonding mode is silicon-glass anodic bonding.

[0065] According to some embodiments of the present application, the second bonding mode is metal intermediate layer bonding.

[0066] According to some embodiments of the present application, the process temperature of the first bonding mode is higher than the process temperature of the second bonding mode.

[0067] ​Understandably, in one embodiment, the first bonding method is silicon-glass anodic bonding, and the second bonding method is metal interlayer bonding. Encapsulating MEMS devices through this two-stage bonding method ensures high packaging yield and efficiency. Furthermore, the process temperature for silicon-glass anodic bonding between the glass cap wafer 300 and the bonding ring wafer 200 is higher than the process temperature for metal interlayer bonding between the cap wafer 500 and the substrate wafer 200. This ensures that the second metal interlayer bonding operation will not negatively impact the cap wafer 500, thereby guaranteeing high hermeticity, high reliability, and low-cost packaging, and improving the packaging yield of MEMS devices.

[0068] According to some embodiments of the present invention, the second bonding method includes gold-silicon eutectic bonding, gold-gold diffusion bonding, and copper-tin solder bonding.

[0069] It is understandable that the second bonding method, namely the bonding of the cap wafer 500 and the substrate wafer 200 through the metal interlayer 600, can include three methods: gold-silicon eutectic bonding, gold-gold diffusion bonding, and copper-tin eutectic bonding. It should be noted that the bonding temperature of the metal interlayer is different for different bonding methods.

[0070] According to some embodiments of the present invention, the substrate wafer is further provided with a getter, which is activated at the process temperature of the metal interlayer bonding.

[0071] like Figure 9 As shown, it can be understood that operations such as cleaning, spin coating, photolithography, development, and etching on the wafer yield a glass cap wafer 300, a bonding ring wafer 400, and a substrate wafer 200. Bonding the glass cap wafer 300 and the bonding ring wafer 400 together via silicon-glass anodic bonding yields a cap wafer 500. Further bonding the cap wafer 500 and the substrate wafer 200 together via metal interlayer bonding yields a packaged wafer 700, thus realizing the packaging of the MEMS device. Simultaneously, the substrate wafer 200 is also provided with a getter 202, which is activated at the process temperature of the metal interlayer bonding to absorb residual gases. After obtaining the packaged wafer 700, dicing the packaged wafer 700 along the first dicing groove 207 and the second dicing groove 302 yields independent MEMS chip units. The technical solution of this invention enables the packaging of MEMS devices through secondary bonding, ensuring high hermeticity, high reliability, and low cost packaging effects, as well as improving the packaging yield of MEMS devices.

[0072] It should be noted that the packaging method for MEMS devices can also be applied to other devices such as infrared devices, such as angular velocity accelerators, energy harvesters, or infrared sensors, without specific limitations here.

[0073] As shown in Figures 2 to 9 the second aspect of the present application provides a MEMS chip unit, comprising:

[0074] a base wafer 200, provided with a MEMS device 201, a wafer bonding area 203, a first alignment mark 206 and a first scribe groove 207;

[0075] a glass cover wafer 300, provided with a second scribe groove 302 and a second alignment mark 303;

[0076] a bonding ring wafer 400, provided with a groove 402, a through hole 403, a bonding ring step 404 and a third alignment mark 405, wherein the bonding ring step 404 is provided with a metal intermediate layer 600;

[0077] The glass cover wafer 300, the bonding ring wafer 400 and the base wafer 200 are sequentially bonded and connected to form a packaging wafer 700 with a vacuum sealed chamber 701.

[0078] It can be understood that the MEMS chip unit includes the base wafer 200, the glass cover wafer 300 and the bonding ring wafer 400, the metal intermediate layer 600 and the like, and the glass cover wafer 300, the bonding ring wafer 400 and the base wafer 200 are sequentially bonded and connected to form the packaging wafer 700 with the vacuum sealed chamber 701. That is, according to the technical solution of the present application, the packaging of the MEMS device is realized by means of secondary bonding, the first alignment mark 206, the second alignment mark 303 and the third alignment mark 405 are used for bonding alignment, the glass cover wafer 300 and the bonding ring wafer 400 are bonded to form the cover cap wafer 500 based on the first bonding mode, and the cover cap wafer 500 and the base wafer 200 are bonded and connected based on the second bonding mode through the metal intermediate layer 600, so as to form the packaging wafer 700 with the vacuum sealed chamber 701. The vacuum sealed chamber 701 can provide an optical path, which can avoid the problems of complex packaging, low efficiency and high cost in the traditional packaging process while meeting the compatibility of the air tightness and the optical path of the MEMS device. Therefore, the present application can realize the packaging effect of high air tightness, high reliability and low cost, and can improve the packaging efficiency and yield of the MEMS device.

[0079] According to some embodiments of the present application, the metal intermediate layer 800 includes a metal bonding layer 601 and a metal bonding layer 602.

[0080] According to some embodiments of the present application, the metal bonding layer 601 is made of one or more of Ti, Gr and Ta, and the metal bonding layer 602 is made of one or more of Au, Cu and Sn.

[0081] It can be understood that the material of the metal intermediate layer 800 can be selected according to actual conditions, wherein the metal bonding layer 601 can be made of Ti, Cr or Ta, and the metal bonding layer 602 can be made of Au, Cu or Sn in one or a combination of multiple, which is not specifically limited herein.

[0082] According to some embodiments of the present application, the substrate wafer 200 is further provided with a getter 202 which is a Ti metal or a Ti-based alloy thin film material.

[0083] It should be noted that, based on the metal intermediate layer bonding method, the cap wafer 500 and the substrate wafer 200 can be bonded to form a packaged wafer 700 through the metal intermediate layer 600. Specifically, the metal intermediate layer bonding includes gold-silicon eutectic bonding, gold-gold diffusion bonding and copper-tin solder bonding. It should be noted that the bonding temperatures corresponding to different metal intermediate layer bonding methods are different. Specifically, the packaging method of the MEMS device of the present application is described in detail below in combination with three embodiments.

[0084] Specifically, in the first embodiment, the packaging process of the packaging method of the MEMS device is as follows:

[0085] Firstly, a substrate wafer 200 is obtained, which is provided with a MEMS device 201, a getter 202, a wafer bonding area 203, a metal pad 204, a driving circuit 205, a first alignment mark 206 and a first dicing groove 207 structure. In this embodiment, the wafer bonding area 203 of the substrate wafer 200 is an unprocessed silicon material.

[0086] Secondly, a glass cover wafer 300 is made, and the glass wafer 301 is pattern-transferred through steps of cleaning, uniform coating, photoetching, developing and etching; the second dicing groove 302 and the second alignment mark 303 are made by using photoresist as a mask through an etching process, thereby completing the preparation of the glass cover wafer 300.

[0087] Thirdly, a bonding ring wafer 400 is made. Firstly, the positions of the groove 402, the through hole 403, the bonding ring step 404 and the third alignment mark 405 of the bonding ring wafer 400 are determined, and the mask pattern is transferred to the surface of the silicon wafer 401 through steps of cleaning, uniform coating, photoetching and developing, and the groove structure 402 of the bonding ring wafer 400 is made through an etching process; further, the through hole structure 403 and the structure of the bonding ring step 404 of the bonding ring wafer 400 are made through an etching process by repeating steps of cleaning, uniform coating, photoetching and developing; the position of the third alignment mark 405 in the bonding ring wafer 400 is determined according to the wafer bonding alignment requirement, and the third alignment mark 405 of the bonding ring wafer 400 is made through an etching process, thereby completing the preparation of the bonding ring wafer 400.

[0088] Fourthly, the cap wafer 500 is manufactured. First, the alignment between the glass cover wafer 300 and the bonding ring wafer 400 is completed by using the second alignment mark 303 and the third alignment mark 405, and then silicon-glass anodic bonding is performed. Specifically, the specific operation of silicon-glass anodic bonding is as follows: first, vacuum is extracted, the gas in the bonding cavity is extracted to a certain degree and maintained until the end of bonding; second, the temperature in the cavity is gradually increased to the rated temperature in three stages, and the temperature is 400°C; third, the glass cover wafer 300 and the bonding ring wafer 400 are pressurized to a certain pressure by two electrodes, and the pressure is maintained until the end of bonding; fourth, high voltage is applied to the glass cover wafer 300 and the bonding ring wafer 400 by two electrodes, and the voltage is maintained for a certain time. Under this process condition, the silicon-glass anodic bonding process can be completed, and the cap wafer 500 is obtained.

[0089] Fifthly, the metal intermediate layer 800 is manufactured. The metal intermediate layer 800 including the metal adhesive layer 601 and the metal bonding layer 602 is manufactured on the surface of the bonding ring step 404 by using a magnetron sputtering process or the like. By adjusting the sputtering power and the sputtering gas flow, the cap wafer 500 is maintained at a certain temperature range, and the target material is gradually deposited on the surface of the bonding ring step 404 to form a continuous film. The metal intermediate layer 800 obtained by the above process includes the metal adhesive layer 601 and the metal bonding layer 602, wherein the metal adhesive layer 601 is a 50 nm thick Cr metal layer, and the metal bonding layer 602 is a 500 nm thick Au metal layer.

[0090] Step 6: Fabricate the packaging wafer 700. The substrate wafer 200 and the cap wafer 500 are interconnected under vacuum through metal interlayer bonding, and the getter 202 is activated at the bonding temperature. On a lithography machine, the substrate wafer 200 and the cap wafer 500 are aligned using the first alignment mark 206, the second alignment mark 303, and the third alignment mark 405, so that the metal interlayer 800 on the bonding ring step 404 structure is in close contact with the wafer bonding region 403 of the substrate wafer 200. Specifically, the metal interlayer bonding process is as follows: First, a vacuum is drawn, removing gas from the bonding cavity to a certain level and maintaining this level until bonding is complete. Second, the temperature is gradually increased in three stages to the rated temperature of 380°C and maintained for a certain period. Third, pressure is applied to the substrate wafer 200 and the cap wafer 500 to a certain pressure and maintained until bonding is complete. Fourth, the getter 202 is activated when the bonding process temperature reaches a certain level, absorbing residual active gases in the sealed MEMS cavity after packaging. Fifth, annealing is performed. After the temperature reaches the rated level and is maintained for a certain period, heating is stopped, allowing the wafer to cool naturally, thus completing the bonding process. Under these process conditions, the Au-Si eutectic bonding process yields a vacuum-packaged optical MEMS wafer 700. The glass cap wafer 300, the bonding ring wafer 400, and the substrate wafer 200 are connected to form a vacuum-sealed cavity 701 for the MEMS device and provide an optical path.

[0091] The seventh step is wafer dicing. The cap wafer 500 and the substrate wafer 200 in the wafer-level packaging are diced separately, that is, the packaging wafer 700 is diced to obtain independent MEMS chip units, thereby realizing the packaging of MEMS devices.

[0092] Specifically, in the second embodiment, the packaging process of the MEMS device packaging method includes the following steps:

[0093] The first step is to fabricate a substrate wafer 200 and set up a structure including a MEMS device 201, a getter 202, a wafer bonding region 203, a metal pad 204, a driving circuit 205, a first alignment mark 206, and a first dicing groove 207. In this embodiment, the wafer bonding region 203 of the substrate wafer 200 is a metal interlayer 800, which includes a metal bonding layer 601 and a metal bonding layer 602. The metal bonding layer 601 is a 50nm thick Cr metal layer, and the metal bonding layer is a 500nm thick Au metal layer.

[0094] Second step, making glass cover wafer 300, glass wafer 301 through cleaning, uniform glue, photoetch, development, etching steps for pattern transfer; using photoresist as a mask, through etching process to make second scribing groove 302, second alignment mark 303 structure, so as to complete the preparation of glass cover wafer 300.

[0095] Third step, making bonding ring wafer 400, first determine the position of the groove 402, through hole 403, bonding ring step 404, third alignment mark 405 of the bonding ring wafer 400; using cleaning, uniform glue, photoetch, development to transfer mask pattern to the surface of silicon wafer 401, through etching process to make groove 402 structure of bonding ring wafer 400, repeat cleaning, uniform glue, photoetch, development steps, through etching process to make through hole 403 structure and bonding ring step 404 structure of bonding ring wafer 400; according to the wafer bonding alignment requirements, determine the position of the third alignment mark 405 in the bonding ring wafer 400, through etching process to make the third alignment mark 405 of the bonding ring wafer 400, to complete the preparation of bonding ring wafer 400.

[0096] Fourth step, making cap wafer 500, first use the second alignment mark 303 and the third alignment mark 405 to complete the alignment of the glass cover wafer 300 and the bonding ring wafer 400, and then perform silicon-glass anodic bonding. Specifically, the specific operation of silicon-glass anodic bonding: first step, vacuumizing, the gas in the bonding cavity is extracted to a certain degree and maintained until the end of bonding; second step, heating, the temperature in the cavity gradually rises to the rated temperature in three stages, the temperature is 400℃; third step, pressurizing, the glass cover wafer 300 and the bonding ring wafer 400 are pressurized to a certain pressure by two electrodes, and maintained until the end of bonding; fourth step, power on, the glass cover wafer 300 and the bonding ring wafer 400 are loaded with high voltage by two electrodes, and maintained for a certain time. Under this process condition, the silicon-glass anodic bonding part process can be completed, so as to obtain the cap wafer 500.

[0097] Fifth step, making metal intermediate layer 800, using magnetron sputtering process to make metal intermediate layer 800 including metal adhesive layer 601 and metal bonding layer 602 on the surface of bonding ring step 404, by adjusting the sputtering power and sputtering gas flow, maintaining the cap wafer 500 in a certain temperature range, the target material gradually deposits on the surface of the bonding ring step 404 to form a continuous film. The metal intermediate layer 800 obtained by the above process includes metal adhesive layer 601 and metal bonding layer 602, wherein the metal adhesive layer 601 is a 50nm thick Cr metal layer, and the metal bonding layer 602 is a 500nm thick Au metal layer.

[0098] Sixth, the packaging wafer 700 is made, the substrate wafer 200 and the cap wafer 500 are interconnected by metal intermediate layer bonding under vacuum, and the getter 202 is activated at the bonding temperature. The alignment of the substrate wafer 200 and the cap wafer 500 is completed on the photolithography machine by using the first alignment mark 206, the second alignment mark 303 and the third alignment mark 405, so that the metal intermediate layer 800 on the bonding ring step 404 structure is in close contact with the wafer bonding area 403 of the substrate wafer 200. Specifically, the specific operation of metal intermediate layer bonding: first step, vacuumizing, the gas in the bonding cavity is extracted to a certain degree and maintained until the end of bonding; second step, heating, the temperature in the cavity is gradually increased to the rated temperature 350℃ in three stages, and maintained for a certain time; third step, pressurizing, the substrate wafer 200 and the cap wafer 500 are pressurized to a certain pressure and maintained until the end of bonding; third step, activating the getter 202, the getter 202 is activated when the bonding process temperature rises to a certain temperature, and absorbs the residual active gas in the sealed cavity of the packaged MEMS; fourth step, annealing, after the temperature rises to a certain extent and is maintained for a certain time, the heating is stopped and the wafer is naturally cooled, and the bonding is completed. Under this process condition, the process of Au-Au diffusion bonding part is completed, and the vacuum packaged optical MEMS packaging wafer 700 can be obtained. Among them, the glass cover wafer 300, the bonding ring wafer 400 and the substrate wafer 200 are connected to form a vacuum sealed cavity 701 of the MEMS device together, and provide an optical access.

[0099] Seventh, wafer dicing processing, the cap wafer 500 and the substrate wafer 200 in the wafer level packaging are cut respectively, that is, the packaging wafer 700 is cut, and independent MEMS chip units can be obtained, so as to realize the packaging of the MEMS device.

[0100] Specifically, in the third embodiment, the packaging process of the MEMS device packaging method comprises the following steps:

[0101] First, the substrate wafer 200 is made, and the structures of the MEMS device 201, the getter 202, the wafer bonding area 203, the metal pad 204, the driving circuit 205, the first alignment mark 206 and the first dicing groove 207 are set. In this embodiment, the wafer bonding area 203 of the substrate wafer 200 is a metal intermediate layer 800, and the metal intermediate layer 800 comprises a metal adhesive layer 601 and a metal bonding layer 602, wherein the metal adhesive layer 601 is a 50nm thick Ti metal layer, and the metal bonding layer 602 is a 1.5μm thick Sn metal layer.

[0102] Second step, making glass cover wafer 300, glass wafer 301 through cleaning, uniform glue, photoetch, development, etching steps for pattern transfer; using photoresist as a mask, through etching process to make second scribing groove 302, second alignment mark 303 structure, so as to complete the preparation of glass cover wafer 300.

[0103] Third step, making bonding ring wafer 400, first determine the position of the groove 402, through hole 403, bonding ring step 404, third alignment mark 405 of the bonding ring wafer 400; using cleaning, uniform glue, photoetch, development to transfer mask pattern to the surface of silicon wafer 401, through etching process to make groove 402 structure of bonding ring wafer 400, repeat cleaning, uniform glue, photoetch, development steps, through etching process to make through hole 403 structure and bonding ring step 404 structure of bonding ring wafer 400; according to the wafer bonding alignment requirements, determine the position of the third alignment mark 405 in the bonding ring wafer 400, through etching process to make the third alignment mark 405 of the bonding ring wafer 400, to complete the preparation of bonding ring wafer 400.

[0104] Fourth step, making cap wafer 500, first use the second alignment mark 303 and the third alignment mark 405 to complete the alignment of the glass cover wafer 300 and the bonding ring wafer 400, and then perform silicon-glass anodic bonding. Specifically, the specific operation of silicon-glass anodic bonding: first step, vacuumizing, the gas in the bonding cavity is extracted to a certain degree and maintained until the end of bonding; second step, heating, the temperature in the cavity gradually rises to the rated temperature in three stages, the temperature is 400℃; third step, pressurizing, the glass cover wafer 300 and the bonding ring wafer 400 are pressurized to a certain pressure by two electrodes, and maintained until the end of bonding; fourth step, power on, the glass cover wafer 300 and the bonding ring wafer 400 are loaded with high voltage by two electrodes, and maintained for a certain time. Under this process condition, the silicon-glass anodic bonding part process can be completed, so as to obtain the cap wafer 500.

[0105] Fifth step, making metal intermediate layer 800, using magnetron sputtering process to make metal intermediate layer 800 including metal adhesive layer 601 and metal bonding layer 602 on the surface of bonding ring step 404, by adjusting the sputtering power and sputtering gas flow, maintaining the cap wafer 500 in a certain temperature range, the target material gradually deposits on the surface of the bonding ring step 404 to form a continuous film. The metal intermediate layer 800 obtained by the above process includes metal adhesive layer 601 and metal bonding layer 602, wherein the metal adhesive layer 601 is a 50nm thick Ti metal layer, and the metal bonding layer 602 is a 2μm thick Cu metal layer.

[0106] In the sixth step, the packaging wafer 700 is manufactured. The substrate wafer 200 and the cap wafer 500 are interconnected by metal intermediate layer bonding under vacuum, and the getter 202 is activated at the bonding temperature. The alignment of the substrate wafer 200 and the cap wafer 500 is completed on the photolithography machine by using the first alignment mark 206, the second alignment mark 303 and the third alignment mark 405, so that the metal intermediate layer 800 on the bonding ring step 404 structure is in close contact with the wafer bonding area 403 of the substrate wafer 200. Specifically, the specific operation of the metal intermediate layer bonding is as follows: in the first step, vacuum is performed, the gas in the bonding cavity is extracted to a certain degree and maintained until the end of the bonding; in the second step, the temperature is raised, the temperature in the cavity is gradually raised to the rated temperature 300℃ in three stages, and maintained for a certain period of time; in the third step, the pressure is increased, the substrate wafer 200 and the cap wafer 500 are pressurized to a certain pressure, and maintained until the end of the bonding; in the third step, the getter 202 is activated, the getter 202 is activated when the bonding process temperature rises to a certain temperature, and the residual active gas in the sealed cavity of the packaged MEMS is absorbed. In the fourth step, annealing is performed. After the temperature is raised to a certain extent and maintained for a certain period of time, the heating is stopped and the wafer is naturally cooled, and the bonding is completed. Under the process conditions, the process of the Cu-Sn solder bonding part is completed, and the vacuum packaged optical MEMS packaging wafer 700 can be obtained. The glass cover wafer 300, the bonding ring wafer 400 and the substrate wafer 200 are connected to form a vacuum sealed cavity 701 of the MEMS device together, and an optical path is provided.

[0107] In the seventh step, the wafer dicing process is performed. The cap wafer 500 and the substrate wafer 200 in the wafer level packaging are cut respectively, that is, the packaging wafer 700 is cut, and the independent MEMS chip unit can be obtained, so that the packaging of the MEMS device is realized.

[0108] It can be understood that the glass cover wafer 300 is formed by etching the glass wafer 301, the bonding ring wafer 400 is formed by etching the silicon wafer 401, the cap wafer 500 is obtained by bonding the bonding ring wafer 400 and the glass cover wafer 300 through the silicon-glass anodic bonding method, the metal intermediate layer 600 is made on the surface of the bonding ring step 404, the packaging wafer 700 is obtained by bonding the cap wafer 500 and the substrate wafer 200 through the metal intermediate layer bonding method, and the independent MEMS chip unit is obtained by cutting the packaging wafer 700 along the first dicing groove 207 and the second dicing groove 302. Since the packaging wafer 700 can provide the packaging cavity and the optical path of the MEMS device, the packaging effect of high airtightness, high reliability and low cost can be realized, and the packaging efficiency and the packaging yield of the MEMS device can be improved through the technical scheme of the application.

[0109] In the description of the specification, reference to "one embodiment", "some embodiments", "an exemplary embodiment", "an example", "a specific example", or "some examples" means that a particular feature, structure, material, or characteristic being described is included in at least one embodiment or example of the application. The appearances of the phrases "in one embodiment", "in some embodiments", "in an exemplary embodiment", "an example", "a specific example", or "some examples" in various places in the specification are not necessarily referring to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0110] The above is the specific description of the preferred embodiment of the present application, but the present application is not limited to the above-mentioned embodiments, and those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application, and these equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims

1. A packaging method for a MEMS device, characterized in that, include: Obtain a substrate wafer, wherein the substrate wafer is provided with MEMS devices, a wafer bonding area, a first alignment mark and a first dicing groove; Using glass wafers as raw materials, the glass wafers are pre-processed, and based on the MEMS device and the wafer bonding area, a second dicing groove is made by etching, and a second alignment mark is made by etching, to form a glass-capped wafer. Using silicon wafers as raw materials, the silicon wafers are pre-processed, and based on the wafer bonding area, grooves and vias are made at the target positions through etching processes to form bonding ring steps, and a third alignment mark is made through etching processes to form a bonding ring wafer. Based on the first bonding method, the glass cap wafer and the bonding ring wafer are bonded according to the second alignment mark and the third alignment mark to form a cap wafer; A metal interlayer is fabricated on the surface of the bonding ring step of the cap wafer using a metal thin film deposition process; After the cap wafer is formed based on the first bonding method, the cap wafer and the substrate wafer are bonded through the metal interlayer based on the second bonding method according to the first alignment mark and the second alignment mark to form a packaged wafer with a vacuum-sealed chamber. The process temperature of the first bonding method is higher than that of the second bonding method. The packaged wafer is diced along the first dicing groove and the second dicing groove respectively to obtain MEMS chip units.

2. The packaging method according to claim 1, characterized in that, The first bonding method is silicon-glass anodic bonding.

3. The packaging method according to claim 2, characterized in that, The second bonding method is metal interlayer bonding.

4. The packaging method according to claim 3, characterized in that, The second bonding method includes gold-silicon eutectic bonding, gold-gold diffusion bonding, and copper-tin solder bonding.

5. The packaging method according to claim 3, characterized in that, The substrate wafer is also provided with a getter, which is activated at the process temperature of the metal interlayer bonding.

6. A MEMS chip unit, characterized in that, The MEMS chip unit is obtained by the packaging method according to any one of claims 1 to 5.

7. The MEMS chip unit according to claim 6, characterized in that, The metal interlayer includes a metal bonding layer and a metal bonding layer.

8. The MEMS chip unit according to claim 7, characterized in that, The metal bonding layer is made of one or more of Ti, Gr, and Ta, and the metal bonding layer is made of one or more of Au, Cu, and Sn.

9. The MEMS chip unit according to claim 6, characterized in that, The substrate wafer is also provided with a getter, which is Ti metal or Ti-based alloy thin film material.

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