CN112758884A

CN112758884A - MEMS sensor

Info

Publication number: CN112758884A
Application number: CN202110083903.0A
Authority: CN
Inventors: 宋亚伟; 宋学谦; 迟海
Original assignee: Hangzhou Hikmicro Sensing Technology Co Ltd
Current assignee: Hangzhou Hikmicro Sensing Technology Co Ltd
Priority date: 2021-01-21
Filing date: 2021-01-21
Publication date: 2021-05-07

Abstract

The present invention provides a MEMS sensor comprising: a substrate and a cover plate; the substrate comprises a MEMS structure, a first inner welding ring arranged around the MEMS structure, and a first outer welding ring arranged around the first inner welding ring; the cover plate comprises a second inner welding ring and a second outer welding ring arranged around the second inner welding ring; the substrate and the cover plate are welded together through the first inner welding ring and the second inner welding ring to form a first sealing structure, and the MEMS structure is limited in the vacuum cavity through the first sealing structure; the base plate and the cover plate are welded together through the first outer welding ring and the second outer welding ring to form a second sealing structure, and a vacuum interlayer cavity is formed between the second sealing structure and the first sealing structure. According to the embodiment of the invention, the gas leakage rate can be greatly reduced, and the reliability and the service life of the MEMS sensor are improved.

Description

MEMS sensor

Technical Field

The invention relates to the technical field of semiconductor devices, in particular to an MEMS sensor.

Background

Hermetic packaging is a common form of packaging requirement in the MEMS field. MEMS devices, such as acceleration sensors, pressure sensors, angular velocity sensors, etc., have movable components inside, and it is necessary to provide an airtight cavity for the movable components to ensure that the movable components have small damping and static friction inside the cavity. The MEMS device such as an uncooled infrared focal plane detector is internally provided with a microbolometer, and the vacuum degree in the device needs to be reduced so as to ensure smaller heat radiation heat loss. When the air pressure in the cavity is increased to a vacuum degree exceeding a set standard, the sensitivity of the device is reduced to be below a standard value, and the device is failed. Thus, hermetic sealing is a critical factor in determining the lifetime of the device.

Disclosure of Invention

The present invention is directed to a MEMS sensor that solves the problems of the related art.

To achieve the above object, the present invention provides a MEMS sensor including:

a substrate comprising a MEMS structure, a first inner weld ring disposed around the MEMS structure, and a first outer weld ring disposed around the first inner weld ring;

the cover plate comprises a second inner welding ring and a second outer welding ring arranged around the second inner welding ring; the substrate and the cover plate are welded together by the first inner weld ring and the second inner weld ring to form a first seal structure that defines the MEMS structure within a vacuum cavity; the base plate and the cover plate are welded together through the first outer welding ring and the second outer welding ring to form a second sealing structure, and a vacuum interlayer cavity is formed between the second sealing structure and the first sealing structure.

Optionally, the initial pressure in the vacuum interlayer cavity is equal to the initial pressure in the vacuum cavity, or the initial pressure in the vacuum interlayer cavity is greater than the initial pressure in the vacuum cavity, or a pressure difference between the initial pressure in the vacuum interlayer cavity and the initial pressure in the vacuum cavity is within a predetermined range.

Optionally, the substrate further comprises at least a first intermediate weld ring disposed between the first inner weld ring and the first outer weld ring; the cover plate further comprises at least a second intermediate weld ring disposed between the second inner weld ring and the second outer weld ring; the base plate and the cover plate are welded together through the first middle welding ring and the second middle welding ring to form a third sealing structure, a first vacuum interlayer cavity is formed between the third sealing structure and the first sealing structure, and a second vacuum interlayer cavity is formed between the third sealing structure and the second sealing structure.

Optionally, a first gas absorption layer is arranged on one side of the substrate and/or the cover plate, which is located on the vacuum chamber; and a second air suction layer is arranged on one side of the substrate and/or the cover plate, which is positioned on the vacuum interlayer cavity.

Optionally, the material of the first and/or second getter layer comprises zirconium or titanium.

Optionally, the MEMS structure includes a photosensitive region and a non-photosensitive region, and the first gettering layer is located in the non-photosensitive region.

Optionally, the first inner weld ring and/or the first outer weld ring comprises: a stack of a first adhesive layer proximate to the substrate, a first barrier layer distal from the substrate, and a first wetting layer disposed between the first adhesive layer and the first wetting layer; the second inner weld ring and/or the second outer weld ring comprises: a stack of a second adhesive layer proximate to the cover sheet, a second barrier layer distal from the cover sheet, and a second wetting layer disposed between the second adhesive layer and the second wetting layer.

Optionally, the material of the first adhesion layer and/or the second adhesion layer comprises titanium or chromium, the material of the first barrier layer and/or the second barrier layer comprises nickel, and the material of the first wetting layer and/or the second wetting layer comprises gold.

Optionally, a first connecting bridge is arranged between the first inner welding ring and the first outer welding ring, the first connecting bridge includes a first inner connecting end and a first outer connecting end, the first inner connecting end is connected to the first inner welding ring, the first outer connecting end is connected to the first outer welding ring, the thickness of the first inner connecting end is equal to that of the first inner welding ring, and the thickness of the first outer connecting end is equal to that of the first outer welding ring; and/or a second connecting bridge is arranged between the second inner welding ring and the second outer welding ring, the second connecting bridge comprises a second inner connecting end and a second outer connecting end, the second inner connecting end is connected to the second inner welding ring, the second outer connecting end is connected to the second outer welding ring, the thickness of the second inner connecting end is equal to that of the second inner welding ring, and the thickness of the second outer connecting end is equal to that of the second outer welding ring.

Optionally, the substrate and/or the cover plate comprise a layer of gas-releasing material disposed within the vacuum interlayer cavity.

As described in the background, the device will fail when the air pressure inside the cavity rises to a vacuum level that exceeds a set level. The inventor analyzes the process of the air pressure increase in the cavity and finds that: because the solder and the interface have defects, the vacuum cavity cannot be absolutely sealed, and one necessary condition that gas can leak into the cavity is as follows: the partial pressure of the gas outside the cavity is greater than the partial pressure within the cavity. During the process of gas entering the cavity, the partial pressure of the gas in the cavity will continue to increase until the partial pressures inside and outside the cavity are the same.

Based on the above analysis, the present invention provides a MEMS sensor, comprising: a substrate and a cover plate; the substrate comprises a MEMS structure, a first inner welding ring arranged around the MEMS structure, and a first outer welding ring arranged around the first inner welding ring; the cover plate comprises a second inner welding ring and a second outer welding ring arranged around the second inner welding ring; the substrate and the cover plate are welded together through the first inner welding ring and the second inner welding ring to form a first sealing structure, and the MEMS structure is limited in the vacuum cavity through the first sealing structure; the base plate and the cover plate are welded together through the first outer welding ring and the second outer welding ring to form a second sealing structure, and a vacuum interlayer cavity is formed between the second sealing structure and the first sealing structure. The leakage of gas from the ambient environment into the vacuum chamber comprises: firstly, gas in the external environment leaks into a vacuum interlayer cavity; and secondly, leaking gas in the vacuum interlayer cavity into the vacuum cavity.

Compared with the prior art, the invention has the beneficial effects that:

once, both of the above two leaks take time.

And secondly, even if the pressure in the vacuum interlayer cavity is increased due to the leakage in the first step, the initial pressure in the vacuum interlayer cavity is smaller than the pressure in the external environment by several orders of magnitude under the normal welding quality, so that the increasing amplitude is limited.

Research shows that based on the molecular flow model, the smaller the pressure difference between the inside and the outside of the sealing structure is, the smaller the amount of the substance of the gas leaked into the cavity with smaller pressure per unit time is, namely the smaller the gas leakage rate is; because the pressure rise amplitude in the vacuum interlayer cavity is limited, the pressure difference between the vacuum cavity and the vacuum interlayer cavity is still small, and the speed of gas leaking into the vacuum cavity again is very slow, so that the gas leakage rate can be greatly reduced, the reliability of the MEMS sensor is improved, and the service life of the MEMS sensor is prolonged.

Drawings

FIG. 1 is a schematic cross-sectional structural view of a MEMS sensor in accordance with a first embodiment of the present invention;

FIG. 2 is a schematic cross-sectional structural view of a MEMS sensor in accordance with a second embodiment of the present invention;

FIG. 3 is a schematic cross-sectional structure view showing a partial structure of a MEMS sensor according to a third embodiment of the present invention;

FIG. 4 is a schematic cross-sectional structural view of a MEMS sensor in accordance with a fourth embodiment of the present invention;

FIG. 5 is a schematic top view of a substrate in a MEMS sensor according to a fifth embodiment of the invention;

fig. 6 is a schematic top view of a cover plate in a MEMS sensor according to a fifth embodiment of the present invention.

To facilitate an understanding of the invention, all reference numerals appearing in the invention are listed below:

MEMS sensor 1, 2, 3, 4 substrate 11

MEMS structure 110 first inner solder ring 111

First outer weld ring 112 cover plate 12

Second inner weld ring 121 and second outer weld ring 122

First sealing structure 13 vacuum chamber 13a

Second seal structure 14 vacuum interlayer cavity 14a

First getter layer 20 and second getter layer 21

First adhesion layer 11a first barrier layer 11b

First wetting layer 11c second adhesive layer 12a

Second barrier layer 12b second wetting layer 12c

First intermediate weld ring 113 and second intermediate weld ring 123

Third seal structure 15 first vacuum interlayer cavity 15a

The second vacuum interlayer cavity 15b and the first connecting bridge 16

First inner connection end 16a and first outer connection end 16b

Second connection bridge 17 second inner connection end 17a

Second outer connection end 17b

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Fig. 1 is a schematic cross-sectional structure diagram of a MEMS sensor according to a first embodiment of the present invention.

Referring to fig. 1, a MEMS sensor 1 according to the first embodiment includes:

a substrate 11 including a MEMS structure 110, a first inner solder ring 111 disposed around the MEMS structure 110, and a first outer solder ring 112 disposed around the first inner solder ring 111;

a cover plate 12 including a second inner weld ring 121, and a second outer weld ring 122 disposed around the second inner weld ring 121; the substrate 11 and the cover plate 12 are welded together by the first inner welding ring 111 and the second inner welding ring 121 to form a first sealing structure 13, and the first sealing structure 13 defines the MEMS structure 110 in the vacuum cavity 13 a; the base plate 11 and the cover plate 12 are welded together by the first outer welding ring 112 and the second outer welding ring 122 to form the second sealing structure 14, and a vacuum interlayer cavity 14a is formed between the second sealing structure 14 and the first sealing structure 13.

The substrate 11 may include a first semiconductor substrate on which the MEMS structure 110 is disposed. The MEMS structure 110 may depend on the type of MEMS sensor 1. For example, when the MEMS sensor 1 is an acceleration sensor, a pressure sensor, or an angular velocity sensor, the MEMS structure 110 may include a fixed electrode and a movable electrode. The movable electrode may be a cantilever beam supported at one end, or a cantilever beam supported at both ends. For another example, when the MEMS sensor 1 is an uncooled infrared focal plane detector, the MEMS structure 110 includes a photosensitive structure with an uncovered upper surface. The MEMS structure 110 is not limited in this embodiment, and only needs to be disposed in a vacuum environment.

The material of the first inner and outer solder rings 111 and 112 is metal, such as copper or aluminum. The first inner bonding ring 111 and the first outer bonding ring 112 may be located on the same layer as the metal layer in the MEMS structure 110, i.e., they are fabricated in the same process step, or they may be fabricated additionally.

The cover plate 12 may include a second semiconductor substrate. The material of the second inner weld ring 121 and the second outer weld ring 122 is metal, such as copper or aluminum.

The cross-sectional dimensions of the first inner weld ring 111 and the second inner weld ring 121 are preferably identical, and the cross-sectional dimensions of the first outer weld ring 112 and the second outer weld ring 122 are preferably identical, so that the welds can be perfectly aligned, improving the welding effect.

The first inner bonding ring 111 and the second inner bonding ring 121, and the first outer bonding ring 112 and the second outer bonding ring 122 may be bonded by using an indium-based solder or a tin-based solder. The indium-based solder and the tin-based solder are alloys in which indium and tin are main components and other metals such as gold, silver, and copper are doped. The indium-based solder is, for example, In₉₇Ag₃Or In₉₅Ag₅。

In this embodiment, the welding of the first inner welding ring 111 and the second inner welding ring 121, and the welding of the first outer welding ring 112 and the second outer welding ring 122 are performed in the same vacuum environment, so that when the MEMS sensor 1 leaves a factory, the pressure inside the vacuum interlayer cavity 14a is equal to the pressure inside the vacuum cavity 13a, that is, the initial pressure inside the vacuum interlayer cavity 14a is equal to the initial pressure inside the vacuum cavity 13 a.

The thicknesses of the first inner weld ring 111 and the first outer weld ring 112 may be equal or different, and the thicknesses of the second inner weld ring 121 and the second outer weld ring 122 may be equal or different. The sum of the thicknesses of the first and second inner weld rings 111 and 121 is equal to the sum of the thicknesses of the first and second outer weld rings 112 and 122.

In other embodiments, the welding of the first inner welding ring 111 and the second inner welding ring 121 may be performed in a first vacuum environment, and the welding of the first outer welding ring 112 and the second outer welding ring 122 may be performed in a second vacuum environment, where the pressure of the second vacuum environment is less than or much less than the external environment pressure, and is greater than or slightly greater than the pressure of the first vacuum environment. The ambient pressure is typically one atmosphere. Thus, the initial pressure in the vacuum interlayer cavity 14a is made to be greater than or slightly greater than the initial pressure in the vacuum cavity 13a, but less than or much less than the external ambient pressure.

In other embodiments, the pressure difference between the initial pressure in the vacuum interlayer cavity and the initial pressure in the vacuum cavity may be controlled within a predetermined range, no matter which of the initial pressure in the vacuum interlayer cavity and the initial pressure in the vacuum cavity is large, as long as the difference between the initial pressure in the vacuum interlayer cavity and the initial pressure in the vacuum cavity is within the predetermined range and is much smaller than the external environment pressure, during specific preparation, the pressure difference between the vacuum interlayer cavity and the getter may be controlled within the predetermined range by controlling the amount of the getter in the vacuum interlayer cavity and the amount of the getter in the vacuum cavity, where the predetermined range may be within E-3Torr or other values that can realize normal operation of devices in the vacuum cavity.

The leakage of gas from the external environment into the vacuum chamber 13a includes: firstly, gas in the external environment leaks into the vacuum interlayer cavity 14 a; in the second step, the gas in the vacuum interlayer chamber 14a leaks into the vacuum chamber 13 a.

Once, both of the above two leaks take time. Compared with the vacuum cavity 13a which is separated from the external environment only by the first sealing structure 13, the gas leakage from the external environment into the vacuum cavity 13a only comprises a one-step scheme, and the time for the MEMS sensor 1 to fail can be prolonged.

Secondly, even if the first step leakage causes the pressure in the vacuum interlayer cavity 14a to rise, the rise amplitude is limited because the initial pressure in the vacuum interlayer cavity 14a is small.

Research shows that based on the molecular flow model, the smaller the pressure difference between the inside and the outside of the sealing structure is, the smaller the amount of the gas substance leaked into the cavity with the smaller pressure per unit time is, that is, the smaller the gas leakage rate is. Because the pressure rise amplitude in the vacuum interlayer cavity 14a is limited, the pressure difference between the vacuum cavity 13a and the vacuum interlayer cavity 14a is still small, and the speed of gas leaking into the vacuum cavity 13a again is extremely slow, so that the gas leakage rate can be greatly reduced, and the reliability and the service life of the MEMS sensor 1 are improved.

In some embodiments, the ratio of the spacing L between the first inner solder ring 111 and the first outer solder ring 112 to the width W of the first inner solder ring 111 (or the first outer solder ring 112) is preferably in the range of: 0.1-0.3 (inclusive) to reduce the width of the vacuum interlayer cavity 14a and improve the surface utilization of the substrate 11.

Fig. 2 is a schematic cross-sectional structure diagram of a MEMS sensor according to a second embodiment of the present invention. Referring to fig. 2, the MEMS sensor 2 of the second embodiment is substantially the same as the MEMS sensor 1 of the first embodiment, and differs therefrom only in that: the substrate 11 and the cover plate 12 are provided with a first getter layer 20 on one side of the vacuum chamber 13a, and the substrate 11 and the cover plate 12 are provided with a second getter layer 21 on one side of the vacuum interlayer chamber 14 a.

The first getter layer 20 and the second getter layer 21 are used for absorbing gas, and accordingly, the degree of vacuum in the vacuum chamber 13a and the degree of vacuum in the vacuum interlayer chamber 14a are reduced.

In this embodiment, the first and second getter layers 20 and 21 are activated before the welding of the first and second inner weld rings 111 and 121 and the first and second outer weld rings 112 and 122. Activation may be achieved by heating the first getter layer 20 and the second getter layer 21.

The material of the first getter layer 20 and/or the second getter layer 21 may comprise zirconium or titanium.

In other embodiments, the first getter layer 20 may be disposed only on one side of the substrate 11 located in the vacuum chamber 13a, or only on one side of the cover plate 12 located in the vacuum chamber 13 a. The second getter layer 21 may be disposed only on one side of the substrate 11 positioned in the vacuum interlayer cavity 14a, or only on one side of the cover plate 12 positioned in the vacuum interlayer cavity 14 a.

For a MEMS sensor in which only the first gas absorption layer 20 is provided, the first gas absorption layer 20 may be activated after the welding of the first and second inner weld rings 111 and 121, and the first and second outer weld rings 112 and 122. Since the first inner bonding ring 111 and the second inner bonding ring 121, and the first outer bonding ring 112 and the second outer bonding ring 122 are bonded in the same vacuum environment, the pressure of the vacuum chamber 13a is equal to that of the vacuum interlayer chamber 14a after bonding. At this time, the first gas-absorption layer 20 is activated, the first gas-absorption layer 20 absorbs the gas in the vacuum cavity 13a, and the initial pressure of the vacuum cavity 13a can be reduced, so that the initial pressure of the vacuum interlayer cavity 14a is slightly greater than the initial pressure of the vacuum cavity 13 a. The ambient pressure during the above welding, i.e. the initial pressure of the vacuum interlayer cavity 14a, is much lower than the external ambient pressure. Activation may be accomplished by heating first getter layer 20.

In some embodiments, when the MEMS structure 110 includes a photosensitive structure, the photosensitive structure corresponds to a photosensitive region, and the remaining region is a non-photosensitive region, and the first gas-absorbing layer 20 is preferably located in the non-photosensitive region if it reduces the light transmittance.

In some embodiments, substrate 11 and/or cover plate 12 further comprise a layer of gas-releasing material. For example, the circuit structure of the MEMS sensor 2 uses a photoresist as a mask layer in a patterning process, and the photoresist may have residues in a removal process and remain in the circuit structure; this residual photoresist can release gases in certain usage environments of the MEMS sensor 2, such as at high temperatures, and is thus a layer of outgassing material. The layer of gas-releasing material is preferably disposed within the vacuum interlayer cavity 14a as opposed to being disposed within the vacuum cavity 13 a.

Fig. 3 is a schematic cross-sectional structure of a partial structure of a MEMS sensor according to a third embodiment of the present invention. Referring to fig. 3, the MEMS sensor 3 of the third embodiment is substantially the same as the MEMS sensors 1 and 2 of the first and second embodiments, and differs therefrom only in that: the first inner weld ring 111 and the first outer weld ring 112 sequentially include, toward the cover plate 12: a first adhesive layer 11a, a first barrier layer 11b, and a first wetting layer 11 c; the second inner weld ring 121 and the second outer weld ring 122 sequentially include, toward the substrate 11: a second adhesive layer 12a, a second barrier layer 12b, and a second wetting layer 12 c.

In this embodiment, the first adhesive layer 11a is made of a metal having good adhesion to the first semiconductor substrate and matching thermal expansion coefficient, and the metal includes, for example, titanium or chromium. The first barrier layer 11b is selected to be a metal, such as nickel, that adheres well to both the first wetting layer 11c and the first adhesion layer 11a, has a coefficient of thermal expansion between the two layers, and has intermediate solderability. The first wetting layer 11c is also an oxidation preventing layer, and a metal having stable performance, good wettability, difficult oxidation, and good brazing performance is selected, and the metal includes, for example, gold. The second adhesive layer 12a is made of a metal having good adhesion to the second semiconductor substrate and a coefficient of thermal expansion matched thereto, and the metal includes, for example, titanium or chromium. The second barrier layer 12b is selected to be a metal, such as nickel, that adheres well to both the second wetting layer 12c and the second adhesion layer 12a, has a coefficient of thermal expansion between the two layers, and has intermediate solderability. The second wetting layer 12c is also an oxidation preventing layer, and a metal having stable properties, good wettability, difficult oxidation, and good brazing properties is selected, and the metal includes, for example, gold.

In other embodiments, only the first inner welding ring 111 may sequentially include, toward the cover plate 12: a first adhesive layer 11a, a first barrier layer 11b, and a first wetting layer 11 c; or only the first outer weld ring 112 comprises in sequence, towards the cover plate 12: a first adhesive layer 11a, a first barrier layer 11b, and a first wetting layer 11 c; or only the second inner solder ring 121 comprises in sequence towards the substrate 11: a second adhesive layer 12a, a second barrier layer 12b, and a second wetting layer 12 c; or only the second outer solder ring 122 comprises in sequence towards the substrate 11: a second adhesive layer 12a, a second barrier layer 12b, and a second wetting layer 12 c.

Fig. 4 is a schematic cross-sectional structure diagram of a MEMS sensor according to a fourth embodiment of the present invention. Referring to fig. 4, the MEMS sensor 4 of the fourth embodiment is substantially the same as the MEMS sensors 1, 2, and 3 of the first, second, and third embodiments, and differs therefrom only in that: the substrate 11 further includes a first intermediate weld ring 113, the first intermediate weld ring 113 being disposed between the first inner weld ring 111 and the first outer weld ring 112; the cover plate 12 further comprises a second intermediate weld ring 123, the second intermediate weld ring 123 being disposed between the second inner weld ring 121 and the second outer weld ring 122; the base plate 11 and the cover plate 12 are welded together by the first intermediate welding ring 113 and the second intermediate welding ring 123 to form a third sealing structure 15, a first vacuum interlayer cavity 15a is formed between the third sealing structure 15 and the first sealing structure 13, and a second vacuum interlayer cavity 15b is formed between the third sealing structure 15 and the second sealing structure 14.

The initial pressure in the first vacuum interlayer chamber 15a and the initial pressure in the second vacuum interlayer chamber 15b are preferably equal to the initial pressure in the vacuum chamber 13 a.

In this embodiment, the gas leakage from the external environment into the vacuum chamber 13a includes: firstly, gas in the external environment leaks into the second vacuum interlayer cavity 15 b; secondly, gas in the second vacuum interlayer cavity 15b leaks into the first vacuum interlayer cavity 15 a; in the third step, the gas in the first vacuum interlayer chamber 15a leaks into the vacuum chamber 13 a. Compared with the MEMS sensor 1 of the first embodiment, the MEMS sensor 4 of the present embodiment can further reduce the gas leakage rate, improve the reliability, and prolong the lifetime.

In other embodiments, two or more intermediate sealing structures may be disposed between the first sealing structure 13 and the second sealing structure 14 to further reduce the leakage rate of the gas.

Fig. 5 is a schematic top view of a substrate in a MEMS sensor according to a fifth embodiment of the invention. Fig. 6 is a schematic top view of a cover plate in a MEMS sensor according to a fifth embodiment of the present invention. Referring to fig. 5 and 6, the MEMS sensor of the fifth embodiment is substantially the same as the MEMS sensors 1, 2, 3, and 4 of the first, second, third, and fourth embodiments, and differs only in that: a first connecting bridge 16 is arranged between the first inner welding ring 111 and the first outer welding ring 112, the first connecting bridge 16 comprises a first inner connecting end 16a and a first outer connecting end 16b, the first inner connecting end 16a is connected to the first inner welding ring 111, the first outer connecting end 16b is connected to the first outer welding ring 112, the thickness of the first inner connecting end 16a is equal to that of the first inner welding ring 111, and the thickness of the first outer connecting end 16b is equal to that of the first outer welding ring 112; a second connecting bridge 17 is arranged between the second inner welding ring 121 and the second outer welding ring 122, the second connecting bridge 17 includes a second inner connecting end 17a and a second outer connecting end 17b, the second inner connecting end 17a is connected to the second inner welding ring 121, the second outer connecting end 17b is connected to the second outer welding ring 122, the thickness of the second inner connecting end 17a is equal to that of the second inner welding ring 121, and the thickness of the second outer connecting end 17b is equal to that of the second outer welding ring 122.

The first connecting bridge 16 is used for balancing the solder on the first inner solder ring 111 and the first outer solder ring 112. In other words, in the case of excessive solder on the first inner solder ring 111, the solder can flow to the first outer solder ring 112 through the first connecting bridge 16; conversely, in the case of an excess of solder on the first outer solder ring 112, the solder can flow to the first inner solder ring 111 through the first connecting bridge 16.

In this embodiment, the thicknesses of the first inner solder ring 111 and the first outer solder ring 112 are equal, so that the first connecting bridge 16 between the first inner connecting end 16a and the first outer connecting end 16b can be a horizontal transition, a zigzag transition, a wavy transition, a zigzag transition, a step-shaped transition, a convex cambered transition, or a concave cambered transition.

In other embodiments, the thicknesses of the first inner and outer solder rings 111, 112 may be different, and thus, the first connecting bridge 16 between the first inner connecting end 16a and the first outer connecting end 16b may be a slope-shaped planar transition, a zigzag-shaped transition, a wavy-shaped transition, a zigzag-shaped transition, a step-shaped transition, a convex cambered transition, a concave cambered transition, or the like.

The material of the first connection bridge 16 may be the same as that of the first inner weld ring 111 (or the first outer weld ring 112). The first connecting bridges 16 are preferably provided in plurality, and the plurality of first connecting bridges 16 are uniformly distributed in the circumferential direction of the first inner weld ring 111 (or the first outer weld ring 112).

The second connecting bridge 17 is used to balance the solder on the second inner solder ring 121 and the second outer solder ring 122. In other words, in the case of excessive solder on the second inner solder ring 121, the solder can flow to the second outer solder ring 122 through the second connecting bridge 17; conversely, in the case of an excess of solder on the second outer solder ring 122, the solder can flow to the second inner solder ring 121 via the first connecting bridge 16.

In this embodiment, the thicknesses of the second inner welding ring 121 and the second outer welding ring 122 are equal, so that the second connecting bridge 17 between the second inner connecting end 17a and the second outer connecting end 17b can be a horizontal transition, a zigzag transition, a wavy transition, a zigzag transition, a step-shaped transition, a convex cambered transition, or a concave cambered transition.

In other embodiments, the thicknesses of the second inner welding ring 121 and the second outer welding ring 122 may be different, and thus, the second connecting bridge 17 between the second inner connecting end 17a and the second outer connecting end 17b may be a slope-shaped plane transition, a zigzag transition, a wavy transition, a broken line-shaped transition, a step-shaped transition, a convex cambered transition, or a concave cambered transition.

The material of the second connection bridge 17 may be the same as that of the second inner weld ring 121 (or the second outer weld ring 122). The second connecting bridges 17 are preferably plural, and the plural second connecting bridges 17 are uniformly distributed in the circumferential direction of the second inner weld ring 121 (or the second outer weld ring 122).

In other embodiments, the first connecting bridge 16 and the second connecting bridge 17 in the MEMS sensor can be used alternatively.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A MEMS sensor, comprising:

2. The MEMS sensor of claim 1, wherein the initial pressure within the vacuum interlayer cavity is equal to the initial pressure within the vacuum cavity, or the initial pressure within the vacuum interlayer cavity is greater than the initial pressure within the vacuum cavity, or a pressure difference between the initial pressure within the vacuum interlayer cavity and the initial pressure within the vacuum cavity is within a predetermined range.

3. The MEMS sensor of claim 1, wherein the substrate further comprises at least a first intermediate weld ring disposed between the first inner weld ring and the first outer weld ring; the cover plate further comprises at least a second intermediate weld ring disposed between the second inner weld ring and the second outer weld ring; the base plate and the cover plate are welded together through the first middle welding ring and the second middle welding ring to form a third sealing structure, a first vacuum interlayer cavity is formed between the third sealing structure and the first sealing structure, and a second vacuum interlayer cavity is formed between the third sealing structure and the second sealing structure.

4. The MEMS sensor according to claim 1, wherein the substrate and/or the cover plate is provided with a first getter layer at one side of the vacuum chamber; and a second air suction layer is arranged on one side of the substrate and/or the cover plate, which is positioned on the vacuum interlayer cavity.

5. The MEMS sensor of claim 4, wherein the material of the first and/or second gettering layers comprises zirconium or titanium.

6. The MEMS sensor of claim 5, wherein the MEMS structure comprises a photosensitive region and a non-photosensitive region, the first gettering layer being located at the non-photosensitive region.

7. The MEMS sensor according to claim 1, wherein the first inner weld ring and/or the first outer weld ring comprises, in order towards the cover plate: a first adhesive layer, a first barrier layer and a first wetting layer; the second inner weld ring and/or the second outer weld ring sequentially comprise in the direction of the substrate: a second adhesion layer, a second barrier layer, and a second wetting layer.

8. The MEMS sensor of claim 1, wherein the material of the first and/or second adhesion layers comprises titanium or chromium, the material of the first and/or second barrier layers comprises nickel, and the material of the first and/or second wetting layers comprises gold.

9. The MEMS sensor of claim 1, wherein a first connection bridge is disposed between the first inner bonding ring and the first outer bonding ring, the first connection bridge comprising a first inner connection end and a first outer connection end, the first inner connection end being connected to the first inner bonding ring, the first outer connection end being connected to the first outer bonding ring, the first inner connection end having a thickness equal to a thickness of the first inner bonding ring, the first outer connection end having a thickness equal to a thickness of the first outer bonding ring; and/or a second connecting bridge is arranged between the second inner welding ring and the second outer welding ring, the second connecting bridge comprises a second inner connecting end and a second outer connecting end, the second inner connecting end is connected to the second inner welding ring, the second outer connecting end is connected to the second outer welding ring, the thickness of the second inner connecting end is equal to that of the second inner welding ring, and the thickness of the second outer connecting end is equal to that of the second outer welding ring.

10. The MEMS sensor of claim 1, wherein the substrate and/or the cover plate comprises a layer of outgassing material disposed within the vacuum interlayer cavity.