CN204569410U - To the insensitive MEMS chip of encapsulation stress - Google Patents

Abstract

The utility model discloses a MEMS chip insensitive to package stress, which comprises a base plate, a lower electrode layer, a MEMS movable structure layer and a cover plate, at least one lower cavity is provided on the base plate, and at least one upper cavity is provided on the cover plate. Cavity, lower electrode layer, low-temperature glass and cover plate form at least one sealed cavity, MEMS movable structure and lower electrode are surrounded in the sealed cavity, pressure welding blocks are made on the pressure welding seat outside the sealed cavity, the lower electrode layer and MEMS activities The structural layers are parallel to each other and electrically insulated from each other by an intermediate oxide layer. In the MEMS chip provided by the utility model, the electrical signals of the MEMS active structure and the lower electrode are all transmitted to the lower conductive area through the soft conductive strip of the lower electrode layer, and then the sealed cavity is drawn out from the lower conductive area, and the MEMS active structure and the lower electrode are connected to the bottom plate. The contact area is very small, so only a small part of the stress caused by the package is transmitted to the MEMS structure, which has little effect on the performance of the MEMS chip.

Description

MEMS chips insensitive to package stress

technical field

The utility model relates to a MEMS chip, in particular to a MEMS chip which is not sensitive to packaging stress.

Background technique

MEMS (Micro-Electro-Mechanical Systems) is the abbreviation of micro-electro-mechanical systems. MEMS chip manufacturing technology uses micro-fabrication technology, especially semiconductor wafer manufacturing technology, to manufacture various micro-mechanical structures, combined with application-specific control integrated circuits (ASICs), Composition of intelligent micro-sensors, micro-actuators, micro-optical devices and other MEMS components. MEMS components have the advantages of small size, low cost, high reliability, strong resistance to harsh environments, low power consumption, high intelligence, easy calibration, and easy integration. They are widely used in consumer electronics products, such as mobile phones and tablets. Computers, toys, digital cameras, game consoles, air mice, remote controls, GPS, etc.; in the defense industry, such as smart bombs, missiles, aerospace, navigation, diving, unmanned aircraft, etc., and industrial products, such as automobiles, communications , robotics, intelligent transportation, industrial automation, environmental monitoring, platform stability control, modern agriculture, security monitoring, etc. MEMS components are the cornerstone of Internet of Things technology and the core components of industrial modernization.

The performance of MEMS devices depends largely on the processing technology and packaging technology of MEMS chips, especially the temperature characteristics of MEMS devices. In the existing MEMS chip, the contact area between the MEMS active structure and the bottom plate is usually large, and the electrodes in the vertical direction are directly fabricated on the bottom plate as the lower electrode. When the subsequent MEMS chip is packaged, the bottom plate of the chip must be in contact with the packaging material, such as the MEMS chip bottom plate It is installed on the package tube base through the adhesive, so that when the ambient temperature changes, the stress generated by the packaging material is different due to the difference in thermal expansion coefficient between the adhesive and the material of the package shell and the material of the MEMS chip (usually Si). It will be conducted to the bottom plate of the MEMS chip, and then conducted from the bottom plate of the MEMS to the MEMS structure and the lower electrode, causing a small deformation of the MEMS structure, thereby generating false signals and affecting the performance of the MEMS device. There are several ways to reduce the impact of packaging on MEMS performance. One is to use a material with a thermal expansion coefficient similar to that of Si material as the package shell; The contact area of the package case. However, the disadvantages of these methods are: one, the material with the same thermal expansion coefficient as the Si material cannot be used to make the shell; two, the soft die-mounting adhesive will cause some MEMS devices to fail to work, because the shell needs to be provided for the active MEMS structure. Reaction force, and the soft glue cannot withstand too high temperature, and is incompatible with some packaging processes, such as metal melting; third, the contact area between the MEMS chip and the package shell is too small, which will affect the ability of the MEMS device to resist mechanical shock. Therefore, the above methods cannot solve the problem fundamentally. To solve the problem fundamentally, the MEMS structure must be designed to be insensitive to the stress caused by the packaging material. One of the most effective methods is that the MEMS active structure has only one contact with the MEMS chip bottom plate. point, and there is only one contact point between the sensing or driving electrodes in the vertical direction of the MEMS and the bottom plate of the MEMS chip, and the two contact points are close enough. In this way, only a small part of the deformation of the bottom plate of the MEMS chip caused by the thermal expansion of the packaging material is transmitted to the MEMS structure, and the performance of the MEMS chip is very little affected by the packaging material.

Utility model content

The technical problem to be solved by the utility model is to provide a MEMS chip insensitive to package stress, which has small size, good performance and low cost.

In order to solve the above-mentioned technical problems, a technical solution adopted by the utility model is: provide a kind of MEMS chip that is not sensitive to the packaging stress, including the bottom plate with at least one lower cavity, the lower electrode layer, the MEMS active structure layer, at least one The cover plate of the upper cavity, the lower electrode in the lower electrode layer and the MEMS active structure in the MEMS active structure layer are sealed in order from bottom to top by the bottom plate, the second oxide layer, the lower conductive region and the lower sealing region, low temperature glass, cover In a sealed cavity surrounded by the board, the cover plate is combined with the lower conductive area and the lower sealing area of the lower electrode layer through the low-temperature glass, the bottom plate and the lower electrode layer are combined through a silicon-silicon dioxide bonding process, and the lower electrode layer is connected to the MEMS. The structural layers are parallel to each other, and the lower electrode layer includes at least two lower welding seats, at least two lower conductive regions, a lower sealing region, a lower electrode, a lower bonding region, a sealing region isolation ditch, a lower electrode isolation ditch, at least two conductive The lower bonding area includes a conductive bonding column and a lower electrode anchor area, the conductive bonding column includes a second conductive plug, the lower pressing seat includes a first conductive plug, the lower electrode includes a bump plug, and the lower electrode has a The bump is fixed on the bottom plate bonding column of the bottom plate through the anchor area of the lower electrode; the MEMS active structure layer includes a MEMS active structure, at least two upper pressure welding seats, a sealing stopper, a first sealing groove, a second sealing groove, and a partition The groove, the anchor area, and the sealing stopper are respectively located above the lower sealing area and the lower conductive area. The MEMS active structure is fixed on the bottom plate bonding column through the anchor area, the middle oxide layer, and the conductive bonding column, and the conductive bonding column passes through the first A conductive plug is electrically connected; each upper welding seat is provided with a metal welding block.

In a preferred embodiment of the present invention, the MEMS movable structure and the lower electrode are fixed on the same bottom plate bonding column, the contact point area between the two and the bottom plate is very small, and they are very close in the horizontal direction, which is caused by the attractive force of the package. Only a very small part of the deformation of the base plate is transmitted to the MEMS structure.

In a preferred embodiment of the present invention, the lower conductive area includes a first lower conductive area and a second lower conductive area divided by the sealing area isolation groove, and the lower electrode layer further includes a first conductive strip and a second conductive strip, The first conductive strip is connected to the first lower conductive area, and the second conductive strip is connected to the second lower conductive area. The first conductive strip and the second conductive strip are spring-shaped to transmit electrical signals and greatly reduce the stress caused by packaging. conduction to the bottom electrode or MEMS active structure.

In a preferred embodiment of the present invention, the upper pressure welding seat includes the first upper pressure welding seat and the second upper pressure welding seat, so the metal pressure welding block on it includes the first metal pressure welding block, the second metal pressure welding block solder bumps.

In a preferred embodiment of the present invention, the electrical signal conduction path of the lower electrode is the first conductive strip, the first lower conductive area, the first lower welding seat, the first conductive plug, the first upper welding seat, the second A metal pressure welding block; the electrical signal conduction path of the MEMS active structure is the anchor area, the second conductive plug, the conductive bonding column, the second conductive strip, the second lower conductive area, the second lower pressure welding seat, and the first conductive plug , the second upper pressure welding seat, and the second metal pressure welding block.

The beneficial effects of the utility model are: the MEMS chip provided by the utility model is not sensitive to the package stress, the lower electrode and the MEMS movable structure are sealed in a sealed cavity, and the contact area between the lower electrode and the MEMS movable structure and the bottom plate is very large. Small, in the subsequent packaging, the MEMS chip bottom plate is mounted on the package base through the die-mounting glue, and only a very small part of the stress caused by the difference in thermal expansion coefficient between the packaging material and the MEMS chip bottom plate Si material is conducted to the lower electrode and In terms of the MEMS active structure, in this way, the signal of the MEMS chip is very little affected by the ambient temperature, which improves the performance of the MEMS chip, reduces the requirements for subsequent packaging, and reduces the packaging cost.

Description of drawings

Fig. 1 is a schematic cross-sectional structure diagram of a preferred embodiment of a MEMS chip insensitive to packaging stress of the present invention.

Fig. 2 is a schematic diagram of the cross-sectional structure of the MEMS chip without the cover plate and the low-temperature glass.

FIG. 3 is a top view of the MEMS active structure layer in FIG. 2 .

FIG. 4 is a top view of the lower electrode layer in FIG. 2 .

FIG. 5 is a diagram of the conduction path of electrical signals in the lower electrode, the MEMS active structure, and the lower electrode and the MEMS active structure.

The marks of the components in the drawings are as follows: 2', base plate, 4', cover plate, 10, lower electrode layer, 14, middle oxide layer, 14a, vertical electrode spacing, 16b, first conductive plug, 16c, second conductive Plug, 17b, bump plug, 17c, bump, 19a, sealing area isolation ditch, 19b, lower electrode isolation ditch, 20a, lower pressure welding seat, 20a', top view of the first lower pressure welding seat, 20a'', the first 20b, lower conductive area, 20b', first lower conductive area top view, 20b'', second lower conductive area top view, 20c, conductive bonding post, 20d, lower sealing area, 20e, lower Electrode, 20f, lower electrode anchor area, 21, lower cavity, 22, second oxide layer, 23, base plate sealing area, 24, base plate bonding post, 25, lower bonding area, 30, MEMS active structure layer, 30a , Upper pressure welding seat, 30a', top view of the first upper pressure welding seat, 30a'', top view of the second upper pressure welding seat, 30b, sealing stopper, 30b', top view of sealing stopper, 30c, anchor area, 30e, MEMS active structure, 31a, first sealing groove, 31b, separation groove, 31c, second sealing groove, 32, photoresist pattern, 33, metal pad, 33a', top view of the first metal pad, 33b' , the top view of the second metal pressure welding block, 35a, the first conductive strip, 35b, the second conductive strip, 38, the second sealing area, 38', the top view of the second sealing area, 40, the pressure welding cavity, 41, the upper cavity, 50, low-temperature glass, 51, sealed cavity, 53, pressure-welded window.

Detailed ways

The preferred embodiments of the utility model will be described in detail below in conjunction with the accompanying drawings, so that the advantages and characteristics of the utility model can be more easily understood by those skilled in the art, so that the protection scope of the utility model can be defined more clearly .

Please refer to Fig. 1, the utility model embodiment comprises:

A MEMS chip that is not sensitive to packaging stress, including a bottom plate 2' with two lower cavities 21, a lower electrode layer 10, a MEMS active structure layer 30, a cover plate 4' with an upper cavity 41, and a lower electrode layer 10 The lower electrode 20e in the MEMS active structure layer 30 and the MENS active structure 30e in the MEMS active structure layer 30 are sealed in order from the bottom to the top by the bottom plate 2', the second oxide layer 22 (thickness is generally 1-2 microns), the lower conductive region 20b, the lower In a sealed cavity 51 surrounded by the sealing area 20d, the low-temperature glass 50, and the cover plate 4', the cover plate 4' is combined with the lower conductive area 20b and the lower sealing area 20d of the lower electrode layer 10 through the low-temperature glass 50, and the bottom plate 2' and The lower electrode layer 10 is bonded by a silicon-silicon dioxide bonding process. The atmosphere and pressure in the sealed cavity 51 can vary according to the functions of the MEMS chip. For example, an accelerometer needs an inert gas at a certain pressure, and a gyroscope needs a vacuum. The base plate 2' provides mechanical support and mechanical protection for the MEMS structure, and is made of Si material; the cover plate 4' provides mechanical protection for the MEMS structure, and it can be a Si material or a non-Si material, such as glass. As a transparent window for optical MEMS devices.

The lower electrode layer 10 and the MEMS active structure layer 30 are made from the same SOI wafer, the lower electrode layer 10 is located below the MEMS active structure layer 30, the two are parallel to each other, and are electrically insulated from each other by the intermediate oxide layer 14, and the intermediate oxide layer The thickness of 14 is determined according to the vertical electrode spacing 14a between the lower electrode layer 10 and the MEMS active structure layer 30 required by the MEMS chip, and is usually 1-3 microns. There is a conductive plug between the MEMS active structure layer 30 and the lower electrode layer 10 for conducting electrical signals, and a bump 17c to prevent suction. The thickness of the lower electrode layer 10 is generally 5 to 60 microns, and the lower electrode layer 10 includes a lower bonding seat 20a, a lower conductive region 20b, a lower sealing region 20d, a lower electrode 20e, and a lower bonding region 25, and simultaneously forms a sealing region isolation ditch 19a, lower electrode isolation groove 19b, the lower bonding area 25 is used for bonding with the bottom plate 2', which includes conductive bonding pillars 20c, lower electrode anchor area 20f, and the position of the lower bonding area 25 is aligned with the bottom plate of the bottom plate 2' The bonding column 24, the lower electrode anchor area 20f is used to support the entire structure of the lower electrode 20e, and the conductive bonding column 20c includes a second conductive plug 16c, which is used to support the MEMS active structure 30e and transmit its signal to the lower conductive area 20b ; The lower conductive area 20b is actually connected to the pattern of the conductive bonding column 20c (not shown in the figure); the lower pressure welding seat 20a includes the first conductive plug 16b, the lower pressure welding seat 20a, the lower conductive area 20b 1. The position of the lower sealing area 20d is aligned with the base sealing area 23 of the base plate 2', the position of the lower electrode 20e is aligned with the lower cavity 21, the lower electrode 20e includes a bump plug 17b, and there is a bump 17c on the lower electrode 20e. The electrode anchor region 20f is fixed on the base plate bonding post 24 of the base plate 2 ′. The thickness of the MEMS active structure layer 30 is generally 10-100 microns, and the MEMS active structure layer 30 includes a MEMS active structure 30e, an upper pressure welding seat 30a, a sealing block 30b, a first sealing groove 31a, a second sealing groove 31c, and a separation groove 31b, the anchor area 30c, and the sealing block 30b are respectively located above the lower sealing area 20d and the lower conductive area 20b, and the MEMS movable structure 30e is fixed on the bottom plate bonding column 24 through the anchor area 30c, the middle oxide layer 14, and the conductive bonding column 20c The upper part is electrically connected with the conductive bonding post 20c through the first conductive plug 16b; the upper bonding seat 30a is provided with a metal bonding block 33 for leading out electrical signals during subsequent packaging.

Please refer to FIG. 2 , FIG. 3 is a top view of the MEMS active structure layer 30 in FIG. 2 ; FIG. 4 is a top view of the bottom electrode layer 10 in FIG. 2 . In FIG. 3 , it includes two parts of sealing block 30b and MEMS active structure 30e. In FIG. 4 it includes two parts of lower electrode 20e and lower electrode anchor region 20f, and each lower electrode 20e includes two bump plugs 17b. In Fig. 2, the MEMS movable structure 30e and the lower electrode 20e are fixed on the same base plate bonding post 24, the contact point area between the two and the base plate 2' is very small, and they are very close in the horizontal direction, the base plate caused by the package attraction Only a very small part of the 2' deformation is conducted to the MEMS structure, so it has little effect on the performance of the MEMS chip.

The electrical signal of the MEMS active structure 30e is transmitted to the lower conductive region 20b of the lower electrode layer 10 through the conductive plug, then transmitted to the outside of the sealed cavity 51 through the lower conductive region 20b, and then transmitted to the upper pressure welding seat of the MEMS active structure layer 30 through the conductive plug 30a, finally transmitted to the metal pad 33; the electrical signal of the lower electrode 20e is transmitted to the outside of the sealed cavity 51 through the lower conductive region 20b, transmitted to the upper pressure soldering seat 30a of the MEMS active structure layer 30 through the conductive plug, and finally transmitted to the metal Pressure welding block 33. The conduction paths of electrical signals in the lower electrode 20e, the MEMS active structure 30e, and the lower electrode 20e and the MEMS active structure 30e will be described below in detail with reference to FIG. 5 . The lower conductive region 20b includes a first lower conductive region 20b' and a second lower conductive region 20b'' divided by the sealing area isolation trench 19a, and the lower electrode layer 20 also includes a first conductive strip 35a, a second conductive strip 35b, and a second conductive strip 35a. A conductive strip 35a is connected to the first lower conductive region 20b', and a second conductive strip 35b is connected to the second lower conductive region 20b''. The first conductive strip 35a and the second conductive strip 35b are part of the lower electrode layer 10, formed at the same time as the lower electrode 20e, and their pattern is thin and curved, in the shape of a spring, for transmitting electrical signals, while greatly reducing the impact caused by packaging. The stress is conducted to the lower electrode 20e or the MEMS active structure 30e. The upper pressure welding seat 30a includes a first upper pressure welding seat 30a' and a second upper pressure welding seat 30a'', so the metal pressure welding block 33 thereon includes a first metal pressure welding block 33a', a second metal pressure welding block 33b'. The electrical signal of the MEMS movable structure 30e passes through the anchor region 30c, the second conductive plug 16c, the conductive bonding column 20c, the second conductive strip 35b, the second lower conductive region 20b'', and the second lower soldering seat 20a'', The first conductive plug 16b and the second upper bonding seat 30a'' are conducted to the second metal bonding block 33b'; the electrical signal of the lower electrode 20e passes through the first conductive strip 35a, the first lower conductive region 20b', the first The lower pressure welding seat 20a', the first conductive plug 16b, and the first upper pressure welding seat 30a' are conducted to the first metal pressure welding block 33a'.

The MEMS chip provided by the utility model is small in size, good in performance and low in cost. The electrical signals of the MEMS movable structure 30e and the lower electrode 20e are all transmitted to the lower electrode layer 10 through the soft first conductive strip 35a and the second conductive strip 35b. The conductive region 20b leads to the sealed cavity 51 from the lower conductive region 20b, and the contact area between the MEMS active structure 30e and the lower electrode 20e and the bottom plate 2' is very small, so only a small part of the stress caused by the packaging is conducted to the MEMS structure. The performance impact of MEMS chips is minimal.

The above is only an embodiment of the utility model, and does not limit the patent scope of the utility model. Any equivalent structure or equivalent process conversion made by using the utility model specification and accompanying drawings, or directly or indirectly used in other Related technical fields are all included in the patent protection scope of the present utility model in the same way.

Claims (10)

1. A MEMS chip insensitive to packaging stress, comprising a base plate with at least one lower cavity, a lower electrode layer, a MEMS active structure layer, a cover plate with at least one upper cavity, lower electrodes and MEMS in the lower electrode layer The MEMS active structure in the active structure layer is sealed in a sealed cavity surrounded by the bottom plate, the second oxide layer, the lower conductive area and the lower sealing area, the low-temperature glass, and the cover plate from bottom to top. The combination of the lower conductive area and the lower sealing area of the lower electrode layer is characterized in that the bottom plate and the lower electrode layer are combined through a silicon-silicon dioxide bonding process, the lower electrode layer and the MEMS active structure layer are parallel to each other, and the lower electrode layer includes at least two A lower welding seat, at least two lower conductive areas, a lower sealing area, a lower electrode, a lower bonding area, an isolation ditch in the sealing area, an isolation ditch for the lower electrodes, at least two conductive strips, the lower bonding area includes conductive bonding columns , The anchor area of the lower electrode, the second conductive plug is included in the conductive bonding column, the first conductive plug is included in the lower pressure welding seat, the lower electrode includes a bump plug, and there is a bump on the lower electrode, which is fixed on the bottom plate through the anchor area of the lower electrode on the bottom plate bonding column; the MEMS active structure layer includes MEMS active structure, at least two upper pressure welding seats, sealing stopper, first sealing groove, second sealing groove, separation groove, anchor area, and the sealing stopper is respectively located on the lower Above the sealing area and the lower conductive area, the MEMS active structure is fixed on the bottom plate bonding column through the anchor area, the intermediate oxide layer, and the conductive bonding column, and is electrically connected to the conductive bonding column through the first conductive plug; each upper pressure welding Metal pressure welding blocks are arranged on the seat. 2. The MEMS chip insensitive to packaging stress according to claim 1, characterized in that the MEMS movable structure and the lower electrode are fixed on the same bottom plate bonding post. 3 . The MEMS chip insensitive to packaging stress according to claim 1 , wherein the lower conductive region comprises a first lower conductive region and a second lower conductive region divided by isolation grooves in the sealing region. 4 . 4. The MEMS chip insensitive to packaging stress according to claim 1, wherein the lower electrode layer also includes a first conductive strip and a second conductive strip, the first conductive strip is connected to the first lower conductive region, and the second conductive strip is connected to the first conductive strip. The two conductive strips are connected with the second lower conductive region. 5 . The MEMS chip insensitive to packaging stress according to claim 4 , wherein the first conductive strip and the second conductive strip are spring-shaped. 6 . The MEMS chip insensitive to packaging stress according to claim 1 , wherein the upper pressure welding seat comprises a first upper pressure welding seat and a second upper pressure welding seat. 7 . The MEMS chip insensitive to packaging stress according to claim 6 , wherein the metal pad includes a first metal pad and a second metal pad. 8 . The MEMS chip insensitive to package stress according to claim 1 , characterized in that the press-down soldering seat comprises a first pressing-down soldering seat and a second pressing-down soldering seat. 9 . 9. The MEMS chip insensitive to packaging stress according to any one of claims 1 to 8, wherein the electrical signal conduction path of the lower electrode is the first conductive strip, the first lower conductive region, the first lower pressure The welding seat, the first conductive plug, the first upper pressing welding seat, and the first metal pressing welding block. 10. The MEMS chip insensitive to packaging stress according to any one of claims 1 to 8, wherein the electrical signal conduction path of the MEMS active structure is an anchor region, a second conductive plug, a conductive bonding column, a first Two conductive strips, a second lower conductive area, a second lower welding seat, a first conductive plug, a second upper welding seat, and a second metal welding block.