MEMS Sensors

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 first sealing structure confines the MEMS structure in a vacuum cavity; the substrate 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 sandwich cavity is formed between the second sealing structure and the first sealing structure. According to the embodiments of the present invention, the gas leakage rate can be greatly reduced, and the reliability and life of the MEMS sensor can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a MEMS sensor. Background Art

[0002] Airtight packaging is a common packaging requirement in the MEMS field. MEMS devices such as accelerometers, pressure sensors, angular velocity sensors, etc. have movable parts inside, and it is necessary to provide an airtight cavity for the movable parts to ensure that the movable parts have less damping and static friction inside the cavity. MEMS devices such as uncooled infrared focal plane detectors have microbolometers inside, and it is necessary to reduce the vacuum inside the device to ensure less heat loss from thermal radiation. When the air pressure inside the cavity rises to a vacuum degree that exceeds the set standard, the device sensitivity will drop below the standard value, causing the device to fail. Therefore, airtightness is a key factor in determining the life of the device. Summary of the invention

[0003] The object of the present invention is to provide a MEMS sensor to solve the deficiencies in the related art.

[0004] To achieve the above object, the MEMS sensor provided by the present invention comprises:

[0005] A substrate including a MEMS structure, a first inner welding ring disposed around the MEMS structure, and a first outer welding ring disposed around the first inner welding ring;

[0006] The cover plate includes 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 first sealing structure confines the MEMS structure in a vacuum chamber; the substrate 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.

[0007] 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 the pressure difference between the initial pressure in the vacuum interlayer cavity and the initial pressure in the vacuum cavity is within a predetermined range.

[0008] Optionally, the base plate further includes at least a first intermediate welding ring, which is arranged between the first inner welding ring and the first outer welding ring; the cover plate further includes at least a second intermediate welding ring, which is arranged between the second inner welding ring and the second outer welding ring; the base plate and the cover plate are welded together through the first intermediate welding ring and the second intermediate 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.

[0009] Optionally, a first air gettering layer is provided on a side of the substrate and / or the cover plate located in the vacuum cavity; a second air gettering layer is provided on a side of the substrate and / or the cover plate located in the vacuum interlayer cavity.

[0010] Optionally, the material of the first getter layer and / or the second getter layer includes zirconium or titanium.

[0011] Optionally, the MEMS structure includes a photosensitive area and a non-photosensitive area, and the first gettering layer is located in the non-photosensitive area.

[0012] Optionally, the first inner welding ring and / or the first outer welding ring comprises: a stack of a first adhesion layer, a first barrier layer and a first wetting layer, wherein the first adhesion layer is close to the substrate, the first wetting layer is far away from the substrate, and the first barrier layer is arranged between the first adhesion layer and the first wetting layer; the second inner welding ring and / or the second outer welding ring comprises: a stack of a second adhesion layer, a second barrier layer and a second wetting layer, wherein the second adhesion layer is close to the cover plate, the second wetting layer is far away from the cover plate, and the second barrier layer is arranged between the second adhesion layer and the second wetting layer.

[0013] Optionally, the material of the first adhesion layer and / or the second adhesion layer includes titanium or chromium, the material of the first barrier layer and / or the second barrier layer includes nickel, and the material of the first wetting layer and / or the second wetting layer includes gold.

[0014] 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 the thickness of the first inner welding ring, and the thickness of the first outer connecting end is equal to the thickness 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 includes 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 the thickness of the second inner welding ring, and the thickness of the second outer connecting end is equal to the thickness of the second outer welding ring.

[0015] Optionally, the substrate and / or the cover plate comprises a degassing material layer, and the degassing material layer is arranged in the vacuum interlayer cavity.

[0016] As described in the background technology, when the air pressure inside the cavity rises to a vacuum degree exceeding the set standard, the device will fail. The inventor analyzed the process of increasing air pressure inside the cavity and found that: due to defects in the solder and the interface itself, the vacuum cavity cannot be absolutely sealed. A necessary condition for gas to leak into the cavity is that the partial pressure of the gas outside the cavity is greater than the partial pressure inside the cavity. In the process of gas entering the cavity, the partial pressure of the gas in the cavity will continue to increase until the partial pressure inside and outside the cavity is the same.

[0017] Based on the above analysis, the present invention provides a MEMS sensor, including: a substrate and a cover plate; the substrate includes 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 includes 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 first sealing structure confines the MEMS structure in a vacuum cavity; the substrate 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 gas leakage from the external environment into the vacuum cavity includes: a first step, the gas leakage from the external environment into the vacuum interlayer cavity; a second step, the gas in the vacuum interlayer cavity leaks into the vacuum cavity.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] First, both of the above two steps of leakage take time.

[0020] Secondly, even if the first leakage causes the pressure in the vacuum interlayer cavity to rise, since the initial pressure in the vacuum interlayer cavity is relatively small, under normal welding quality, this pressure is several orders of magnitude smaller than the pressure of the external environment, and thus the increase is limited.

[0021] Third, the study shows that based on the molecular flow model, the smaller the pressure difference between the inside and outside of the sealing structure, the smaller the amount of gas that leaks into the cavity with a lower pressure per unit time, that is, the smaller the gas leakage rate; since the pressure rise 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 at which the gas leaks into the vacuum cavity again is extremely slow, which can greatly reduce the gas leakage rate and improve the reliability and life of the MEMS sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic cross-sectional structural diagram of a MEMS sensor according to a first embodiment of the present invention;

[0023] Figure 2 is a schematic cross-sectional structural diagram of a MEMS sensor according to a second embodiment of the present invention;

[0024] Figure 3 is a schematic cross-sectional structural diagram of a partial structure of a MEMS sensor according to a third embodiment of the present invention;

[0025] Figure 4 is a schematic cross-sectional structural diagram of a MEMS sensor according to a fourth embodiment of the present invention;

[0026] Figure 5 is a schematic top view of the structure of a substrate in a MEMS sensor according to a fifth embodiment of the present invention;

[0027] Figure 6 4 is a schematic diagram of a top view of a cover plate in a MEMS sensor according to a fifth embodiment of the present invention.

[0028] To facilitate understanding of the present invention, all reference numerals appearing in the present invention are listed below:

[0029] MEMS sensor 1, 2, 3, 4 substrate 11

[0030] MEMS structure 110 first inner welding ring 111

[0031] First outer welding ring 112 Cover plate 12

[0032] Second inner welding ring 121 Second outer welding ring 122

[0033] First sealing structure 13 vacuum chamber 13a

[0034] Second sealing structure 14 vacuum sandwich cavity 14a

[0035] First air getter layer 20 Second air getter layer 21

[0036] First adhesive layer 11a First barrier layer 11b

[0037] First wetting layer 11c Second adhesive layer 12a

[0038] Second barrier layer 12b Second wetting layer 12c

[0039] The first middle welding ring 113 The second middle welding ring 123

[0040] The third sealing structure 15 The first vacuum sandwich cavity 15a

[0041] Second vacuum sandwich chamber 15b First connecting bridge 16

[0042] First internal connection terminal 16a First external connection terminal 16b

[0043] Second connecting bridge 17 Second inner connecting end 17a

[0044] The second external connection terminal 17b DETAILED DESCRIPTION

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0046] Figure 1 FIG. 4 is a schematic cross-sectional structural diagram of a MEMS sensor according to a first embodiment of the present invention.

[0047] Reference Figure 1 As shown, the MEMS sensor 1 of the first embodiment includes:

[0048] The substrate 11 includes a MEMS structure 110, a first inner welding ring 111 disposed around the MEMS structure 110, and a first outer welding ring 112 disposed around the first inner welding ring 111;

[0049] The cover plate 12 includes a second inner welding ring 121 and a second outer welding ring 122 arranged around the second inner welding ring 121; the substrate 11 and the cover plate 12 are welded together through 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 confines the MEMS structure 110 in a vacuum cavity 13a; the substrate 11 and the cover plate 12 are welded together through the first outer welding ring 112 and the second outer welding ring 122 to form a second sealing structure 14, and a vacuum interlayer cavity 14a is formed between the second sealing structure 14 and the first sealing structure 13.

[0050] The substrate 11 may include a first semiconductor substrate, and the MEMS structure 110 is arranged on the first semiconductor substrate. The MEMS structure 110 may be determined according to the type of the 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 no covering on the upper surface. This embodiment does not limit the MEMS structure 110, and it only needs to be set in a vacuum environment.

[0051] The first inner welding ring 111 and the first outer welding ring 112 are made of metal, such as copper or aluminum. The first inner welding ring 111 and the first outer welding ring 112 can be located in the same layer as the metal layer in the MEMS structure 110, in other words, they can be made in the same process or separately.

[0052] The cover plate 12 may include a second semiconductor substrate. The second inner welding ring 121 and the second outer welding ring 122 are made of metal, such as copper or aluminum.

[0053] The cross-sectional dimensions of the first inner welding ring 111 and the second inner welding ring 121 are preferably consistent, and the cross-sectional dimensions of the first outer welding ring 112 and the second outer welding ring 122 are preferably consistent, so that the welding can be fully aligned and the welding effect is improved.

[0054] 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 can be achieved by using indium-based solder or tin-based solder. Indium-based solder and tin-based solder are alloys with indium and tin as main components, doped with other metals such as gold, silver, and copper. Indium-based solder is, for example, In 97 Ag3 or In 95 Ag5.

[0055] 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 the factory, the pressure in the vacuum interlayer cavity 14a is equal to the pressure in the vacuum cavity 13a, that is, the initial pressure in the vacuum interlayer cavity 14a is equal to the initial pressure in the vacuum cavity 13a.

[0056] The thickness of the first inner welding ring 111 and the first outer welding ring 112 may be equal or different, and the thickness of the second inner welding ring 121 and the second outer welding ring 122 may be equal or different. The sum of the thickness of the first inner welding ring 111 and the second inner welding ring 121 is equal to the sum of the thickness of the first outer welding ring 112 and the second outer welding ring 122.

[0057] In other embodiments, the welding of the first inner welding ring 111 and the second inner welding ring 121 can be performed in a first vacuum environment, and the welding of the first outer welding ring 112 and the second outer welding ring 122 can be performed in a second vacuum environment, and the pressure of the second vacuum environment is less than or much less than the pressure of the external environment, and greater than or slightly greater than the pressure of the first vacuum environment. The pressure of the external environment is generally one atmosphere. Thus, the initial pressure in the vacuum interlayer cavity 14a is greater than or slightly greater than the initial pressure in the vacuum cavity 13a, but less than or much less than the pressure of the external environment.

[0058] In other embodiments, the pressure difference between the initial pressure in the vacuum interlayer cavity and the initial pressure in the vacuum cavity can also be controlled within a predetermined range. No matter which one is larger, as long as the difference between the two is within the predetermined range and much smaller than the external environment pressure, during specific preparation, the pressure difference between the two can be controlled within a predetermined range by controlling the amount of getter in the vacuum interlayer cavity and the amount of getter in the vacuum cavity. Here, the predetermined range can be within E-3Torr or other values ​​that can achieve normal operation of the device in the vacuum cavity.

[0059] The gas in the external environment leaks into the vacuum chamber 13a, including: a first step, the gas in the external environment leaks into the vacuum interlayer chamber 14a; a second step, the gas in the vacuum interlayer chamber 14a leaks into the vacuum chamber 13a.

[0060] Compared with the vacuum cavity 13a being separated from the external environment only by the first sealing structure 13, the leakage of gas from the external environment into the vacuum cavity 13a only includes one step, which can prolong the time for the MEMS sensor 1 to fail.

[0061] Secondly, even if the first leakage causes the pressure in the vacuum interlayer cavity 14a to rise, the increase is limited because the initial pressure in the vacuum interlayer cavity 14a is relatively small.

[0062] Third, the study shows that based on the molecular flow model, the smaller the pressure difference between the inside and outside of the sealing structure, the smaller the amount of gas that leaks into the cavity with a lower pressure per unit time, that is, the smaller the gas leakage rate. Since the pressure rise 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 at which the gas leaks into the vacuum cavity 13a again is extremely slow, which can greatly reduce the gas leakage rate and improve the reliability and life of the MEMS sensor 1.

[0063] In some embodiments, the ratio of the distance L between the first inner welding ring 111 and the first outer welding ring 112 to the width W of the first inner welding ring 111 (or the first outer welding ring 112) is preferably in the range of 0.1 to 0.3 (including the endpoint values) to reduce the width of the vacuum interlayer cavity 14a and improve the surface utilization of the substrate 11.

[0064] Figure 2 Schematic diagram of the cross-sectional structure of a MEMS sensor according to the second embodiment of the present invention. Figure 2 As shown, the MEMS sensor 2 of the second embodiment is substantially the same as the MEMS sensor 1 of the first embodiment, with the only difference being that a first air absorption layer 20 is provided on one side of the substrate 11 and the cover plate 12 located in the vacuum cavity 13a, and a second air absorption layer 21 is provided on one side of the substrate 11 and the cover plate 12 located in the vacuum interlayer cavity 14a.

[0065] The first getter layer 20 and the second getter layer 21 are used to absorb gas, and correspondingly reduce the vacuum degree in the vacuum cavity 13 a and the vacuum degree in the vacuum interlayer cavity 14 a .

[0066] In this embodiment, the first getter layer 20 and the second getter layer 21 are activated before welding the first inner welding ring 111 and the second inner welding ring 121, and the first outer welding ring 112 and the second outer welding ring 122. The activation can be achieved by heating the first getter layer 20 and the second getter layer 21.

[0067] The material of the first getter layer 20 and / or the second getter layer 21 may include zirconium or titanium.

[0068] In other embodiments, the first air gettering layer 20 may be disposed only on one side of the substrate 11 located in the vacuum cavity 13a, or only on one side of the cover plate 12 located in the vacuum cavity 13a. The second air gettering layer 21 may be disposed only on one side of the substrate 11 located in the vacuum interlayer cavity 14a, or only on one side of the cover plate 12 located in the vacuum interlayer cavity 14a.

[0069] For a MEMS sensor that only has the first air absorption layer 20, the first air absorption layer 20 can be activated after the first inner welding ring 111 and the second inner welding ring 121, and the first outer welding ring 112 and the second outer welding ring 122 are welded. Since the first inner welding ring 111 and the second inner welding ring 121, and the first outer welding ring 112 and the second outer welding ring 122 are welded in the same vacuum environment, the pressure of the vacuum cavity 13a and the vacuum interlayer cavity 14a are equal after welding. At this time, the first air absorption layer 20 is activated, and the first air absorption layer 20 absorbs the gas in the vacuum cavity 13a, which can reduce the initial pressure of the vacuum cavity 13a, so that the initial pressure of the vacuum interlayer cavity 14a is slightly greater than the initial pressure of the vacuum cavity 13a. The environmental pressure during the above welding, that is, the initial pressure of the vacuum interlayer cavity 14a is much smaller than the external environmental pressure. Activation can be achieved by heating the first air absorption layer 20.

[0070] 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. If the first gettering layer 20 reduces light transmittance, it is preferably located in the non-photosensitive region.

[0071] In some embodiments, the substrate 11 and / or the cover plate 12 further include a degassing material layer. For example, in the circuit structure of the MEMS sensor 2, the circuit structure uses a photoresist as a mask layer in the patterning process, and the photoresist may remain in the circuit structure during the removal process; the residual photoresist will release gas in certain use environments of the MEMS sensor 2, such as high temperature, and thus, the residual photoresist is a degassing material layer. Compared with being arranged in the vacuum cavity 13a, the degassing material layer is preferably arranged in the vacuum interlayer cavity 14a.

[0072] Figure 3 FIG. 1 is a schematic cross-sectional view of a partial structure of a MEMS sensor according to a third embodiment of the present invention. Figure 3 As shown, 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, with the only difference being that: the first inner welding ring 111 and the first outer welding ring 112 include, in sequence toward the cover plate 12: a first adhesion layer 11a, a first barrier layer 11b and a first wetting layer 11c; the second inner welding ring 121 and the second outer welding ring 122 include, in sequence toward the substrate 11: a second adhesion layer 12a, a second barrier layer 12b and a second wetting layer 12c.

[0073] In this embodiment, the first adhesion layer 11a is selected from a metal having good adhesion to the first semiconductor substrate and matching thermal expansion coefficient, such as titanium or chromium. The first barrier layer 11b is selected from a metal having good adhesion to the first wetting layer 11c and the first adhesion layer 11a, a thermal expansion coefficient between the two layers, and a medium welding performance, such as nickel. The first wetting layer 11c is also an anti-oxidation layer, and a metal having stable performance, good wettability, difficulty in oxidation, and good brazing performance is selected, such as gold. The second adhesion layer 12a is selected from a metal having good adhesion to the second semiconductor substrate and matching thermal expansion coefficient, such as titanium or chromium. The second barrier layer 12b is selected from a metal having good adhesion to the second wetting layer 12c and the second adhesion layer 12a, a thermal expansion coefficient between the two layers, and a medium welding performance, such as nickel. The second wetting layer 12c is also an anti-oxidation layer, and a metal having stable performance, good wettability, difficulty in oxidation, and good brazing performance is selected, such as gold.

[0074] In other embodiments, only the first inner welding ring 111 may include, in sequence, the following: a first adhesion layer 11a, a first barrier layer 11b, and a first wetting layer 11c, toward the cover plate 12; or only the first outer welding ring 112 may include, in sequence, the following: a first adhesion layer 11a, a first barrier layer 11b, and a first wetting layer 11c, toward the cover plate 12; or only the second inner welding ring 121 may include, in sequence, the following: a second adhesion layer 12a, a second barrier layer 12b, and a second wetting layer 12c, toward the substrate 11; or only the second outer welding ring 122 may include, in sequence, the following: a second adhesion layer 12a, a second barrier layer 12b, and a second wetting layer 12c, toward the substrate 11.

[0075] Figure 4 FIG. 4 is a schematic cross-sectional view of a MEMS sensor according to a fourth embodiment of the present invention. Figure 4 As shown, 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 the only difference is that: the substrate 11 further includes a first intermediate welding ring 113, which is arranged between the first inner welding ring 111 and the first outer welding ring 112; the cover plate 12 further includes a second intermediate welding ring 123, which is arranged between the second inner welding ring 121 and the second outer welding ring 122; the substrate 11 and the cover plate 12 are welded together through 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.

[0076] The initial pressure in the first vacuum interlayer cavity 15a and the initial pressure in the second vacuum interlayer cavity 15b are preferably equal to the initial pressure in the vacuum cavity 13a.

[0077] In this embodiment, the gas in the external environment leaks into the vacuum cavity 13a, including: the first step, the gas in the external environment leaks into the second vacuum interlayer cavity 15b; the second step, the gas in the second vacuum interlayer cavity 15b leaks into the first vacuum interlayer cavity 15a; the third step, the gas in the first vacuum interlayer cavity 15a leaks into the vacuum cavity 13a. Compared with the MEMS sensor 1 of the first embodiment, the MEMS sensor 4 of this embodiment can further reduce the gas leakage rate, improve reliability and lifespan.

[0078] In other embodiments, two or more intermediate sealing structures may be provided between the first sealing structure 13 and the second sealing structure 14 to further reduce the gas leakage rate.

[0079] Figure 5 FIG. 5 is a schematic top view of the structure of a substrate in a MEMS sensor according to a fifth embodiment of the present invention. Figure 6 FIG. 5 is a schematic diagram of a top view of a cover plate in a MEMS sensor according to a fifth embodiment of the present invention. Figure 5 and Figure 6 As shown, 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 the only difference is that a first connecting bridge 16 is provided between the first inner welding ring 111 and the first outer welding ring 112, the first connecting bridge 16 includes 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 the thickness of the first inner welding ring 111, and the first outer connecting end 16b is connected to the first outer welding ring 112. The thickness of an outer connecting end 16b is equal to the thickness 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, and 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, and 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 the thickness of the second inner welding ring 121, and the thickness of the second outer connecting end 17b is equal to the thickness of the second outer welding ring 122.

[0080] The first connecting bridge 16 is used to balance the solder on the first inner welding ring 111 and the first outer welding ring 112. In other words, if there is too much solder on the first inner welding ring 111, it can flow to the first outer welding ring 112 through the first connecting bridge 16; conversely, if there is too much solder on the first outer welding ring 112, it can flow to the first inner welding ring 111 through the first connecting bridge 16.

[0081] In this embodiment, the thickness of the first inner welding ring 111 is equal to that of the first outer welding ring 112. Therefore, 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 serrated transition, a wavy transition, a broken line transition, a step transition, a convex arc transition, or a concave arc transition, etc.

[0082] In other embodiments, the thickness of the first inner welding ring 111 and the first outer welding ring 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 sloped plane transition, a serrated transition, a wavy transition, a broken line transition, a step transition, a convex arc transition, or a concave arc transition, etc.

[0083] The material of the first connection bridge 16 can be the same as that of the first inner welding ring 111 (or the first outer welding ring 112). There are preferably multiple first connection bridges 16, and the multiple first connection bridges 16 are evenly distributed in the circumferential direction of the first inner welding ring 111 (or the first outer welding ring 112).

[0084] The second connecting bridge 17 is used to balance the solder on the second inner welding ring 121 and the second outer welding ring 122. In other words, if there is too much solder on the second inner welding ring 121, it can flow to the second outer welding ring 122 through the second connecting bridge 17; conversely, if there is too much solder on the second outer welding ring 122, it can flow to the second inner welding ring 121 through the first connecting bridge 16.

[0085] In this embodiment, the thickness of the second inner welding ring 121 is equal to that of the second outer welding ring 122. Therefore, 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 serrated transition, a wavy transition, a broken line transition, a step transition, a convex arc transition, or a concave arc transition, etc.

[0086] In other embodiments, the thickness 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 sloped plane transition, a serrated transition, a wavy transition, a broken line transition, a step transition, a convex arc transition, or a concave arc transition, etc.

[0087] The material of the second connection bridge 17 can be the same as that of the second inner welding ring 121 (or the second outer welding ring 122). There are preferably multiple second connection bridges 17, which are evenly distributed in the circumferential direction of the second inner welding ring 121 (or the second outer welding ring 122).

[0088] In other embodiments, the first connecting bridge 16 and the second connecting bridge 17 in the MEMS sensor can be used selectively.

[0089] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A MEMS sensor, characterized in that: include: A substrate including a MEMS structure, a first inner welding ring disposed around the MEMS structure, and a first outer welding ring disposed 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 first sealing structure confines the MEMS structure in a vacuum chamber; the substrate 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 sandwich cavity is formed between the second sealing structure and the first sealing structure; the cover plate is in the shape of a straight plate; The MEMS sensor is an uncooled infrared focal plane detector; A first connecting bridge is provided between the first inner welding ring and the first outer welding ring; and / or a second connecting bridge is provided between the second inner welding ring and the second outer welding ring.

2. The MEMS sensor according to claim 1, characterized in that: 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 the pressure difference between the initial pressure in the vacuum interlayer cavity and the initial pressure in the vacuum cavity is within a predetermined range.

3. The MEMS sensor according to claim 1, characterized in that: The base plate further includes at least a first intermediate welding ring, which is arranged between the first inner welding ring and the first outer welding ring; the cover plate further includes at least a second intermediate welding ring, which is arranged between the second inner welding ring and the second outer welding ring; the base plate and the cover plate are welded together through the first intermediate welding ring and the second intermediate 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, characterized in that: A first air-absorbing layer is arranged on a side of the substrate and / or the cover plate located in the vacuum cavity; a second air-absorbing layer is arranged on a side of the substrate and / or the cover plate located in the vacuum interlayer cavity.

5. The MEMS sensor according to claim 4, characterized in that: The material of the first getter layer and / or the second getter layer includes zirconium or titanium.

6. The MEMS sensor according to claim 5, characterized in that: The MEMS structure includes a photosensitive area and a non-photosensitive area, and the first gettering layer is located in the non-photosensitive area.

7. The MEMS sensor according to claim 1, characterized in that: The first inner welding ring and / or the first outer welding ring include, in sequence toward the cover plate: a first adhesion layer, a first barrier layer and a first wetting layer; the second inner welding ring and / or the second outer welding ring include, in sequence toward the substrate: a second adhesion layer, a second barrier layer and a second wetting layer.

8. The MEMS sensor according to claim 7, characterized in that: The material of the first adhesion layer and / or the second adhesion layer includes titanium or chromium, the material of the first barrier layer and / or the second barrier layer includes nickel, and the material of the first wetting layer and / or the second wetting layer includes gold.

9. The MEMS sensor according to claim 1, characterized in that: When a first connecting bridge is provided 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 the thickness of the first inner welding ring, and the thickness of the first outer connecting end is equal to the thickness of the first outer welding ring; when a second connecting bridge is provided between the second inner welding ring and the second outer welding ring, the second connecting bridge includes 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 the thickness of the second inner welding ring, and the thickness of the second outer connecting end is equal to the thickness of the second outer welding ring.

10. The MEMS sensor according to claim 1, characterized in that: The substrate and / or the cover plate comprises a degassing material layer, and the degassing material layer is arranged in the vacuum interlayer cavity.

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