A MEMS inertial device and its bonding process

Abstract

This invention provides a MEMS inertial device and its bonding process, relating to the field of inertial device technology. The device comprises a silicon substrate, a device layer, and a top cover plate bonded sequentially from bottom to top. A metal wiring layer is bonded between the device layer and the top cover plate. A top cover plate bonding ring is located on the underside of the top cover plate. The metal wiring layer and the top cover plate are bonded through the top cover plate bonding ring, and multiple pads are also bonded to the metal wiring layer. This invention can reduce the manufacturing difficulty of MEMS inertial devices, decrease their size, and lower their cost.

Description

Technical Field

[0001] This invention relates to the field of inertial device technology, and in particular to a MEMS inertial device and its bonding process. Background Technology

[0002] MEMS inertial devices can be widely used in inertial navigation, drones, autonomous driving, intelligent manufacturing, and high-end industrial fields. In existing technologies, the metal traces of MEMS inertial devices are all completed on a silicon substrate. A metal trace layer is grown on the silicon substrate to allow electrical signals from the inertial device layer to be transmitted to the ASIC circuit through this metal trace layer, ultimately enabling MEMS inertial device detection. The current inertial device structure, where metal traces are all completed on a silicon substrate, has a complex manufacturing process, increasing manufacturing difficulty and reducing yield; it also results in high cost, large device area, and significant space requirements, hindering miniaturization. Summary of the Invention

[0003] The purpose of this invention is to provide a MEMS inertial device and its bonding process, aiming to reduce the manufacturing difficulty, size, and cost of MEMS inertial devices. The specific technical solution is as follows:

[0004] A MEMS inertial device includes a silicon substrate, a device layer, and a top cover plate bonded sequentially from bottom to top. A metal trace layer is bonded between the device layer and the top cover plate. The bottom side of the top cover plate has a top cover plate bonding ring. The metal trace layer and the top cover plate are bonded through the top cover plate bonding ring. A plurality of pads are also bonded on the metal trace layer.

[0005] Furthermore, the silicon substrate is bonded to the device layer via a solder ring.

[0006] Furthermore, the metal trace layer includes a metal trace layer body and a plurality of connecting pads electrically connected to the metal trace layer body. Each connecting pad is electrically connected to the solder pad. The upper cover plate and the device layer are bonded to the metal trace layer body through the upper cover plate bonding ring.

[0007] Furthermore, the device layer includes a mass block, a moving comb tooth anchor post, a moving comb tooth, a fixed comb tooth, and a beam structure; the silicon substrate and the moving comb tooth anchor post are bonded through the solder ring; the fixed comb tooth anchor post is etched on the silicon substrate, and the mass block is supported on the middle part of the silicon substrate through the fixed comb tooth anchor post.

[0008] Furthermore, the main body of the metal wiring layer is located on the moving comb tooth anchor and the beam structure.

[0009] Furthermore, the lower side of the upper cover plate also has an upper cover plate fixed comb tooth anchor located in the middle, and the mass block is bonded to the upper cover plate fixed comb tooth anchor.

[0010] Furthermore, the area of ​​the metal trace layer is smaller than the area of ​​the top cover plate.

[0011] Furthermore, the solder ring includes three narrow sides and one wide side; the area of ​​the device layer is smaller than that of the silicon substrate to form a stepped surface on the solder ring, the device layer is square, three edges of the device layer are flush with the solder ring, and the other edge is located inside the solder ring to form the stepped surface on the wide side; a metal trace layer is bonded to the device layer and the stepped surface, the main body of the metal trace layer is located on the device layer, and the plurality of connection pads are located on the stepped surface.

[0012] Furthermore, the area of ​​the device layer is the same as that of the silicon substrate, and all edges of the device layer are flush with the solder ring; the metal trace layer is bonded on the device layer, and the main body of the metal trace layer and the plurality of the connecting pads are all located on the device layer.

[0013] The present invention also provides a bonding process for MEMS inertial devices, used to manufacture the MEMS inertial devices as described above, comprising the following steps:

[0014] S100: Bond the silicon substrate to the device layer; bond the metal trace layer on the device layer; grow pads on the metal trace layer; and etch the device layer.

[0015] S200: Etching is performed on the underside of the upper cover plate wafer to form the upper cover plate bonding ring;

[0016] S300. The upper cover plate and the device layer are bonded to the metal trace layer through the upper cover plate bonding ring to form a MEMS inertial device.

[0017] The present invention provides a MEMS inertial device and its bonding process, which has the following beneficial effects:

[0018] This invention comprises a silicon substrate, a device layer, and a top cover plate bonded sequentially from bottom to top. A metal trace layer is bonded on the device layer, and a top cover plate bonding ring is located on the underside of the top cover plate. The top cover plate and the device layer are bonded to the metal trace layer via the top cover plate bonding ring. This allows the metal traces to run on the device layer instead of the substrate, avoiding the complex process flow caused by running on the substrate. Furthermore, the signal is led out from the connection pad on the outside of the top cover plate, eliminating the need for through-silicon via (TSV) technology on the top cover plate, thus reducing the manufacturing difficulty of MEMS inertial devices. In addition, the metal traces are bonded to the bonding ring, and the metal traces can serve as both an adhesion layer for the bonding ring and a signal connection, thereby reducing the size and cost of MEMS inertial devices. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the MEMS inertial device provided by the present invention;

[0020] Figure 2 This is a schematic diagram of the silicon substrate structure of the present invention;

[0021] Figure 3 This is a schematic diagram of the silicon substrate bonding device layer of the present invention;

[0022] Figure 4 This is a schematic diagram of the structure of the device layer bonding metal trace layer after etching.

[0023] Figure 5 This is a schematic diagram of the structure of the device layer after etching.

[0024] Figure 6 This is a top view of the device layer after etching.

[0025] Figure 7 This is a schematic diagram of the structure of the upper cover plate according to an embodiment of the present invention;

[0026] Figure 8 This is a schematic diagram of the structure of the upper cover plate according to another embodiment of the present invention;

[0027] Figure 9 This is a schematic diagram of the first step of the TSV process for the MEMS inertial device of the present invention.

[0028] Figure 10 This is a schematic diagram of the second step of the TSV process for the MEMS inertial device of the present invention.

[0029] Figure 11 This is a schematic diagram of the third step of the TSV process for the MEMS inertial device of this invention.

[0030] Reference numerals: 10, MEMS inertial device; 100, silicon substrate; 110, solder ring; 111, narrow edge; 112, wide edge; 113, stepped surface; 120, fixed comb tooth anchor; 200, device layer; 210, mass block; 220, moving comb tooth anchor; 230, moving comb tooth; 240, fixed comb tooth; 250, beam structure; 300, metal trace layer; 310, metal trace layer body; 320, connecting pad; 330, solder pad; 400, top cover plate; 410, top cover plate bonding ring; 420, top cover plate fixed comb tooth anchor. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clearly illustrate the purpose of the embodiments of the present invention.

[0032] Example 1: This example provides a MEMS inertial device 10, see reference. Figure 1 As shown, it includes a silicon substrate 100, a device layer 200, and a cover plate 400 bonded sequentially from bottom to top.

[0033] See Figure 2 As shown, a solder ring 110 and a fixed comb anchor 120 are etched on the silicon substrate 100. In a preferred embodiment, the silicon substrate 100 is square, and the solder ring 110 is a square frame aligned with the edge of the silicon substrate 100. The fixed comb anchor 120 is cylindrical.

[0034] See Figure 3-6 As shown, the silicon substrate 100 and the device layer 200 are bonded together by a solder ring 110.

[0035] A metal trace layer 300 is bonded between the device layer 200 and the top cover plate 400. After etching, the metal trace layer 300 forms a metal trace layer body 310 and multiple connecting pads 320 electrically connected to the metal trace layer body 310. Each connecting pad 320 is electrically connected to a solder pad 330.

[0036] After etching the portion of the device layer 200 located inside the metal trace layer body 310, a mass block 210, a moving comb anchor 220, moving comb teeth 230, fixed comb teeth 240, and a beam structure 250 are formed. The moving comb anchor 220 is bonded to the solder ring 110. The mass block 210 is supported on the silicon substrate 100 by the fixed comb anchor 120. The fixed comb teeth 240 are distributed around the mass block 210, and the moving comb teeth 230 are distributed around the beam structure 250. The moving comb anchor 220 is connected to the moving comb teeth 230 through the beam structure 250, so that the moving comb teeth 230 are suspended above the silicon substrate 100, and the beam structure 250 is suspended between the moving comb anchor 220 and the moving comb teeth 230, and surrounds the mass block 210 within the moving comb anchor 220. The metal trace layer body 310 is located on the moving comb anchor 220 and the beam structure 250. In this embodiment, the device layer is connected to the device structure in a suspended state by a beam anchored by a solder ring, which effectively reduces device stress and improves performance. Furthermore, arranging metal traces on the beam of the device layer helps reduce contact resistance and parasitic parameters such as capacitance and resistance.

[0037] In a preferred embodiment, the mass block 210 is square.

[0038] In one embodiment, the moving comb teeth 230 correspond one-to-one with the fixed comb teeth 240.

[0039] In a preferred embodiment, the beam structure 250 includes a square frame and four straight beams connecting the square frame to the corresponding sides of the movable comb tooth anchor 220. Optionally, the beam structure 250 can be a straight beam structure as shown in the figure, or it can be a U-shaped beam or an L-shaped beam.

[0040] See Figure 7 As shown, the upper cover plate 400 has an upper cover plate bonding ring 410 on its lower side.

[0041] See Figure 1 As shown, the upper cover plate 400 is bonded to the device layer 200 and the silicon substrate 100 to form a MEMS inertial device. The upper cover plate 400 and the device layer 200 are bonded to the metal trace layer body 310 through the upper cover plate bonding ring 410, and multiple pads 330 are exposed outside the upper cover plate 400.

[0042] In the preferred embodiment, see Figure 8 As shown, the lower side of the upper cover plate 400 also has an upper cover plate fixed comb tooth anchor 420 located in the middle, and the mass block 210 is bonded to the upper cover plate fixed comb tooth anchor 420.

[0043] In a preferred embodiment, the area of ​​the metal wiring layer 300 is smaller than the area of ​​the top cover plate 400.

[0044] In one embodiment, such as Figure 2-6As shown, the solder ring 110 includes three narrow sides 111 and one wide side 112; the area of ​​the device layer 200 is smaller than that of the silicon substrate 100 to form a stepped surface 113 on the solder ring 110; the device layer 200 is square; three edges of the device layer 200 are flush with the solder ring 110, and the other edge is located inside the solder ring 110 to form a stepped surface 113 on the wide side 112; a metal trace layer 300 is bonded to the device layer 200 and the stepped surface 113; the main body 310 of the metal trace layer is located on the device layer 200; and multiple connecting pads 320 are located on the stepped surface 113.

[0045] In a preferred embodiment, the three edges of the movable comb tooth anchor 220 are aligned with the solder ring 110, forming a square shape; the upper cover bonding ring 410 has the same shape and size as the movable comb tooth anchor 220, forming a square shape.

[0046] In another embodiment, the area of ​​device layer 200 is the same as that of silicon substrate 100, and all edges of device layer 200 are flush with solder ring 110; a metal trace layer 300 is bonded on device layer 200, and the metal trace layer body 310 and a plurality of connecting pads 320 are all located on device layer 200.

[0047] In a preferred embodiment, all edges of the moving comb anchor 220 are flush with the solder ring 110.

[0048] Example 2: This example provides a bonding process for a MEMS inertial device, used to manufacture the MEMS inertial device 10 as described above, including the following steps:

[0049] S100, see reference Figure 9 As shown, a solder ring 110 and a fixed comb tooth anchor 120 are etched on a silicon substrate 100. A SiO2 layer is grown on the solder ring 110 and the fixed comb tooth anchor 120. The silicon substrate 100 and the device layer 200 are bonded through the solder ring 110. A metal trace layer 300 is bonded on the device layer 200. Pads (PADs) 330 are grown on the metal trace layer 300. The metal trace layer 300 is etched to form a metal trace layer body 310 and multiple connecting pads 320 electrically connected to the metal trace layer body 310. The device layer 200 is etched to form a mass block 210, a moving comb tooth anchor 220, a moving comb tooth 230, a fixed comb tooth 240, and a beam structure 250.

[0050] S200, see reference Figure 10 As shown, an upper cover plate bonding ring 410 and an upper cover plate fixed comb tooth anchor post 420 are formed by etching on the underside of the upper cover plate (CAP) 400 wafer, and a SiO2 layer is grown on the upper cover plate bonding ring 410 and the upper cover plate fixed comb tooth anchor post 420.

[0051] S300, see reference Figure 11As shown, the upper cover plate 400 and the device layer 200 are bonded to the metal wiring layer 300 through the upper cover plate bonding ring 410 to form the MEMS inertial device 10.

[0052] It should be noted that steps S100 and S200 are not in any particular order.

[0053] Those skilled in the art should understand that the present invention can be implemented in many other specific forms without departing from the spirit and scope of the invention. Any changes or modifications made by those skilled in the art based on the embodiments of the present invention and the above disclosure shall fall within the protection scope of the claims.

Claims

1. A MEMS inertial device comprising a silicon substrate, a device layer and an upper cap bonded in that order from bottom to top, characterized in that, A metal trace layer is bonded between the device layer and the upper cover plate, the lower side of the upper cover plate has an upper cover plate bonding ring, the metal trace layer is bonded to the upper cover plate through the upper cover plate bonding ring, and a plurality of pads are further bonded on the metal trace layer; the metal trace layer comprises a metal trace layer main body and a plurality of connection pads electrically connected to the metal trace layer main body, the metal trace layer main body and the plurality of connection pads are both located on the device layer, each connection pad is electrically connected to the pad respectively, and the upper cover plate is bonded to the device layer through the upper cover plate bonding ring and the metal trace layer main body.

2. The MEMS inertial device of claim 1, wherein, The silicon substrate is bonded to the device layer through the solder ring.

3. The MEMS inertial device of claim 2, wherein, The device layer comprises a mass block, a moving comb anchor column, a moving comb, a fixed comb, and a beam structure; the silicon substrate is bonded to the moving comb anchor column through the solder ring; a fixed comb anchor column is etched on the silicon substrate, and the mass block is carried on the middle part of the silicon substrate through the fixed comb anchor column.

4. The MEMS inertial device of claim 3, wherein, The metal trace layer main body is located on the moving comb anchor column and the beam structure.

5. The MEMS inertial device of claim 3, wherein, The lower side of the upper cover plate further has an upper cover plate fixed comb anchor column located in the middle part, and the mass block is bonded to the upper cover plate fixed comb anchor column.

6. The MEMS inertial device of claim 1, wherein, The area of the metal trace layer is smaller than the area of the upper cover plate.

7. The MEMS inertial device of claim 2, wherein, The solder ring comprises three narrow sides and one wide side; the area of the device layer is smaller than that of the silicon substrate to form a stepped surface on the solder ring, the device layer is square, three edges of the device layer are flush with the solder ring, and the other edge is located inside the solder ring to form the stepped surface on the wide side; the metal trace layer is bonded on the device layer and the stepped surface, the metal trace layer main body is located on the device layer, and the plurality of connection pads are located on the stepped surface.

8. The MEMS inertial device of claim 2, wherein, The area of the device layer is the same as that of the silicon substrate, and all edges of the device layer are flush with the solder ring; the metal trace layer is bonded on the device layer, and the metal trace layer main body and the plurality of connection pads are both located on the device layer. 9.A bonding process of a MEMS inertial device, used for manufacturing the MEMS inertial device according to any one of claims 1-8, comprising the following steps: S100, bonding the silicon substrate to the device layer; bonding the metal trace layer on the device layer, growing pads on the metal trace layer, and etching the device layer; S200, etching the lower side of the upper cover plate wafer to form the upper cover plate bonding ring; S300, bonding the upper cover plate to the device layer through the upper cover plate bonding ring and the metal trace layer to form the MEMS inertial device.

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