MEMS sensor and method for manufacturing the same

Abstract

The present invention provides a MEMS sensor and a manufacturing method thereof, wherein the MEMS sensor comprises: a substrate and a cover plate; the substrate comprises a MEMS structure, a first welding area arranged around the MEMS structure, and a first welding ring located at the first welding area; the cover plate comprises a second welding area, and a second welding ring located at the second welding area; the substrate and the cover plate are welded together by the first welding ring and the second welding ring to form a sealing structure to confine the MEMS structure in a vacuum chamber; at least one of the first welding area and the second welding area has an annular groove or an annular protrusion distributed along the circumferential direction, the first welding area is disposed on the first welding area in a conformal manner, and the second welding area is disposed on the second welding area in a conformal manner. According to the embodiments of the present invention, the gas leakage rate can be 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 and a manufacturing method thereof. 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 and a manufacturing method thereof to solve the deficiencies in the related art.

[0004] To achieve the above object, a first aspect of the present invention provides a MEMS sensor, comprising:

[0005] A substrate, comprising a MEMS structure, a first welding area arranged around the MEMS structure, and a first welding ring located at the first welding area;

[0006] A cover plate, comprising a second welding area, and a second welding ring located at the second welding area; the substrate and the cover plate are welded together through the first welding ring and the second welding ring to form a sealing structure to confine the MEMS structure in a vacuum chamber; at least one of the first welding area and the second welding area has an annular groove or an annular protrusion distributed along the circumferential direction, the first welding area is environmentally friendly located on the first welding area, and the second welding area is environmentally friendly located on the second welding area.

[0007] Optionally, the first welding zone has an annular groove distributed along the circumferential direction, and the second welding zone has an annular protrusion distributed along the circumferential direction, and the annular groove and the annular protrusion make the first welding ring mesh with the second welding ring; or the first welding zone has an annular protrusion distributed along the circumferential direction, and the second welding zone has an annular groove distributed along the circumferential direction, and the annular protrusion and the annular groove make the first welding ring mesh with the second welding ring; or the first welding zone has an annular groove or annular protrusion distributed along the circumferential direction, and the second welding zone is a plane; or the first welding zone is a plane, and the second welding zone has an annular groove or annular protrusion distributed along the circumferential direction.

[0008] Optionally, the annular groove or the annular protrusion includes two or more circles.

[0009] Optionally, the sizes of each circle of the annular grooves or each circle of the annular protrusions are the same or different.

[0010] Optionally, the cross-section of the annular groove or the annular protrusion along the perpendicular direction to the circumferential direction is a triangle, a square, a rectangle, a regular trapezoid or an inverted trapezoid.

[0011] Optionally, the ratio of the depth of the annular groove to the width of the annular groove is greater than 1 / 10; or the ratio of the height of the annular protrusion to the width of the annular protrusion is greater than 1 / 10.

[0012] Optionally, the first welding ring includes, in sequence toward the cover plate: a first adhesion layer, a first barrier layer and a first wetting layer; and / or the second welding ring includes, in sequence toward the substrate: a second adhesion layer, a second barrier layer and a second wetting layer.

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

[0014] Optionally, the first welding area has at least one of a first dielectric layer, a first passivation layer or a first semiconductor layer, the annular groove is located in the first dielectric layer, the first passivation layer or the first semiconductor layer, or the material of the annular protrusion is the first dielectric layer, the first passivation layer or the first semiconductor layer; or the second welding area has at least one of a second dielectric layer, a second passivation layer or a second semiconductor layer, the annular groove is located in the second dielectric layer, the second passivation layer or the second semiconductor layer, or the material of the annular protrusion is the second dielectric layer, the second passivation layer or the second semiconductor layer.

[0015] Optionally, the first welding ring and the second welding ring are welded together by indium-based solder or tin-based solder.

[0016] A second aspect of the present invention provides a method for manufacturing a MEMS sensor, comprising:

[0017] A prefabricated substrate and a prefabricated cover plate are provided respectively, wherein the prefabricated substrate comprises a MEMS structure and a first welding area arranged around the MEMS structure; and the prefabricated cover plate comprises a second welding area;

[0018] forming an annular groove or annular protrusion distributed along the circumferential direction on at least one of the first welding area and the second welding area;

[0019] forming a first welding ring at the first welding area so that the prefabricated substrate forms a substrate, and the first welding ring is disposed on the first welding area in a conformal manner; forming a second welding ring at the second welding area so that the prefabricated cover plate forms a cover plate, and the second welding ring is disposed on the second welding area in a conformal manner;

[0020] The first welding ring and the second welding ring are welded together so that the substrate and the cover plate form a sealing structure, so as to confine the MEMS structure in a vacuum chamber.

[0021] Optionally, the first welding zone has an annular groove distributed along the circumferential direction, and the second welding zone has an annular protrusion distributed along the circumferential direction, and the annular groove and the annular protrusion make the first welding ring mesh with the second welding ring; or the first welding zone has an annular protrusion distributed along the circumferential direction, and the second welding zone has an annular groove distributed along the circumferential direction, and the annular protrusion and the annular groove make the first welding ring mesh with the second welding ring; or the first welding zone has an annular groove or annular protrusion distributed along the circumferential direction, and the second welding zone is a plane; or the first welding zone is a plane, and the second welding zone has an annular groove or annular protrusion distributed along the circumferential direction.

[0022] Optionally, the first welding area has at least one of a first dielectric layer, a first passivation layer or a first semiconductor layer, and the annular groove or the annular protrusion is formed by etching the first dielectric layer, the first passivation layer or the first semiconductor layer; or the second welding area has at least one of a second dielectric layer, a second passivation layer or a second semiconductor layer, and the annular groove or the annular protrusion is formed by etching the second dielectric layer, the second passivation layer or the second semiconductor layer.

[0023] Optionally, the first welding ring is formed by electron beam evaporation or sputtering process, or the second welding ring is formed by electron beam evaporation or sputtering process.

[0024] Optionally, the first welding ring and the second welding ring are welded together by indium-based solder or tin-based solder.

[0025] 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. According to the molecular gas conduction theory, the leakage rate depends on the length of the gas channel.

[0026] 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 welding area arranged around the MEMS structure, and a first welding ring located at the first welding area; the cover plate comprises a second welding area, and a second welding ring located at the second welding area; the substrate and the cover plate are welded together by the first welding ring and the second welding ring to form a sealing structure to confine the MEMS structure in a vacuum chamber; at least one of the first welding area and the second welding area has an annular groove or annular protrusion distributed along the circumferential direction, the first welding area is conformally located on the first welding area, and the second welding area is conformally located on the second welding area.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] On the one hand, under the condition of the same welding ring width, the uneven structure is manufactured by the annular groove and / or the annular protrusion so that the effective length of the gas leakage channel is increased, thereby reducing the gas leakage rate and improving the reliability and life of the MEMS sensor.

[0029] Secondly, the non-planar uneven structure can increase the shear strength of the MEMS sensor, thereby improving the impact resistance reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic cross-sectional structural diagram of a MEMS sensor according to a first embodiment of the present invention;

[0031] Figure 2 is a schematic diagram of a top view of the substrate with the first welding ring removed;

[0032] Figure 3 is a schematic diagram of the structure of the cover plate with the second welding ring removed, viewed from above;

[0033] Figure 4 is a flow chart of a method for manufacturing a MEMS sensor according to a first embodiment of the present invention;

[0034] Figures 5 to 10 yes Figure 4 Schematic diagram of the intermediate structure corresponding to the process in;

[0035] Fig.11 is a schematic cross-sectional structural diagram of a partial structure of a MEMS sensor according to a second embodiment of the present invention;

[0036] Fig.12 is a schematic cross-sectional structural diagram of a partial structure of a MEMS sensor according to a third embodiment of the present invention;

[0037] Fig.13 is a schematic cross-sectional structural diagram of a MEMS sensor according to a fourth embodiment of the present invention;

[0038] Fig.14 FIG. 5 is a schematic cross-sectional structural diagram of a MEMS sensor according to a fifth embodiment of the present invention.

[0039] To facilitate understanding of the present invention, all reference numerals appearing in the present invention are listed below:

[0040] MEMS sensor 1, 2, 3, 4, 5 substrate 11

[0041] MEMS structure 110 first welding area 111

[0042] First welding ring 112 Cover plate 12

[0043] Second welding area 121 Second welding ring 122

[0044] Sealing structure 13 Vacuum chamber 13a

[0045] Annular groove 14 Annular protrusion 15

[0046] First passivation layer 113 Second dielectric layer 123

[0047] First adhesive layer 112a First barrier layer 112b

[0048] First wetting layer 112c Second adhesion layer 122a

[0049] Second barrier layer 122b Second wetting layer 122c

[0050] Prefabricated base plate 11' Prefabricated cover plate 12'

[0051] Solder layer 16 DETAILED DESCRIPTION

[0052] 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.

[0053] Figure 1 FIG. 4 is a schematic cross-sectional structural diagram of a MEMS sensor according to a first embodiment of the present invention. Figure 2 is a schematic diagram of a top view of the substrate with the first welding ring removed; Figure 3 It is a schematic diagram of the structure of the cover plate with the second welding ring removed, viewed from above.

[0054] Reference Figures 1 to 3 As shown, the MEMS sensor 1 of the first embodiment includes:

[0055] The substrate 11 includes a MEMS structure 110, a first welding area 111 disposed around the MEMS structure 110, and a first welding ring 112 located at the first welding area 111;

[0056] The cover plate 12 includes a second welding area 121 and a second welding ring 122 located in the second welding area 121; the substrate 11 and the cover plate 12 are welded together by the first welding ring 112 and the second welding ring 122 to form a sealing structure 13, so as to confine the MEMS structure 110 in the vacuum cavity 13a; the first welding area 111 has an annular groove 14 distributed along the circumference, and the second welding area 121 has an annular protrusion 15 distributed along the circumference, the first welding ring 112 is conformally located on the first welding area 111, and the second welding ring 122 is conformally located on the second welding area 121.

[0057] 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.

[0058] In this embodiment, refer to Figure 1 and Figure 2 As shown, the first welding area 111 has a first passivation layer 113. The annular groove 14 is located in the first passivation layer 113. The material of the first passivation layer 113 may be silicon nitride. In other embodiments, the first welding area 111 may have a first dielectric layer, and the annular groove 14 is located in the first dielectric layer. The material of the first dielectric layer may be silicon dioxide. Or, the first welding area 111 may have a first semiconductor layer, and the annular groove 14 is located in the first semiconductor layer. The material of the first semiconductor layer may be doped polysilicon or a single crystal silicon substrate. Or, the annular groove 14 is located in a stacked structure of at least two layers among the first dielectric layer, the first passivation layer and the first semiconductor layer. This embodiment does not limit the material type of the first welding area 111.

[0059] The cover plate 12 may include a second semiconductor substrate.

[0060] In this embodiment, refer to Figure 1 and Figure 3As shown, the second welding area 121 has a second dielectric layer 123. The material of the annular protrusion 15 is the second dielectric layer 123. The material of the second dielectric layer 123 can be silicon dioxide. In other embodiments, the second welding area 121 can have a second passivation layer, and the material of the annular protrusion 15 is the second passivation layer. The material of the second passivation layer can be silicon nitride. Or, the second welding area 121 can have a second semiconductor layer, and the material of the annular protrusion 15 is the second semiconductor layer. The material of the second semiconductor layer can be doped polycrystalline silicon or a single crystal silicon substrate. Or, the material of the annular protrusion 15 is in a stacked structure of at least two layers of the second dielectric layer, the second passivation layer and the second semiconductor layer. This embodiment does not limit the material type of the second welding area 121.

[0061] The first welding ring 112 and the second welding ring 122 are made of metal, such as copper or aluminum. The first welding ring 112 is conformally located on the first welding area 111, which means that the first welding ring 112 is thin, and the cross-section of the annular recessed area enclosed by the surface of the first welding ring 112 away from the first welding area 111 along the vertical circumferential direction is consistent with the cross-section of the annular groove 14 along the vertical circumferential direction.

[0062] In other words, when the cross section of the annular groove 14 along the vertical circumference is a triangle, the cross section of the annular recessed area enclosed by the surface of the first welding ring 112 away from the first welding area 111 along the vertical circumference is a triangle. When the cross section of the annular groove 14 along the vertical circumference is a square, the cross section of the annular recessed area enclosed by the surface of the first welding ring 112 away from the first welding area 111 along the vertical circumference is a square. When the cross section of the annular groove 14 along the vertical circumference is a rectangle, the cross section of the annular recessed area enclosed by the surface of the first welding ring 112 away from the first welding area 111 along the vertical circumference is a rectangle (refer to Figure 1 When the cross section of the annular groove 14 along the vertical circumference is a regular trapezoid, the cross section of the annular recessed area enclosed by the surface of the first welding ring 112 away from the first welding area 111 along the vertical circumference is a regular trapezoid. When the cross section of the annular groove 14 along the vertical circumference is an inverted trapezoid, the cross section of the annular recessed area enclosed by the surface of the first welding ring 112 away from the first welding area 111 along the vertical circumference is an inverted trapezoid.

[0063] The second welding ring 122 is conformally located on the second welding area 121, which means that the second welding ring 122 is thin, and the cross-section of the annular protrusion area formed on the surface of the second welding ring 122 away from the second welding area 121 along the vertical circumferential direction is consistent with the cross-section shape of the annular protrusion 15 along the vertical circumferential direction.

[0064] In other words, when the cross section of the annular protrusion 15 along the vertical circumference is a triangle, the cross section of the annular protrusion area formed on the surface of the second welding ring 122 away from the second welding area 121 along the vertical circumference is a triangle. When the cross section of the annular protrusion 15 along the vertical circumference is a square, the cross section of the annular protrusion area formed on the surface of the second welding ring 122 away from the second welding area 121 along the vertical circumference is a square. When the cross section of the annular protrusion 15 along the vertical circumference is a rectangle, the cross section of the annular protrusion area formed on the surface of the second welding ring 122 away from the second welding area 121 along the vertical circumference is a rectangle (refer to Figure 1 When the cross section of the annular protrusion 15 along the vertical circumference is a regular trapezoid, the cross section of the annular protrusion area formed by the surface of the second welding ring 122 away from the second welding area 121 along the vertical circumference is a regular trapezoid. When the cross section of the annular protrusion 15 along the vertical circumference is an inverted trapezoid, the cross section of the annular protrusion area formed by the surface of the second welding ring 122 away from the second welding area 121 along the vertical circumference is an inverted trapezoid.

[0065] Reference Figure 1 As shown, the annular groove 14 and the annular protrusion 15 can make the first welding ring 112 and the second welding ring 122 mesh. The shape and size of the solder layer (not shown) match the meshing surface of the first welding ring 112 and the second welding ring 122. After the first welding ring 112 and the second welding ring 122 are welded by solder, on the one hand, under the condition of the same welding ring width, compared with the solution that the welding surfaces of the first welding ring 112 and the second welding ring 122 are both flat, this solution can manufacture an uneven structure, and the advantage is that: it can increase the effective length of the leakage channel for external gas to enter the vacuum chamber 13a, thereby reducing the gas leakage rate and improving the reliability and life of the MEMS sensor 1. Especially for infrared detectors, the temperature change of the MEMS structure 110 after receiving the target infrared radiation is very weak. In order to minimize the heat loss of the bridge surface caused by air convection, the vacuum degree in the vacuum chamber 13a is required to be below E-3Torr. The uneven structure of the first welding ring 112 and the second welding ring 122 reduces the packaging leakage rate of the vacuum chamber 13a, prolongs the vacuum maintenance time in the chamber, and directly ensures the reliability of the infrared detector.

[0066] Secondly, the welding surface between the first welding ring 112 and the second welding ring 122 is a non-planar uneven structure, which can improve the shear strength of the MEMS sensor 1, thereby improving the impact resistance reliability.

[0067] Third, for the MEMS structure 110 with high requirements for shock resistance, the annular groove 14 and the annular protrusion 15 enable the first welding ring 112 and the second welding ring 122 with relatively thin thickness to mesh, which can further improve the shear strength of the MEMS sensor 1, thereby improving the shock resistance reliability.

[0068] To further increase the length of the gas leakage channel, refer to Figure 1 As shown, the ratio between the depth D of the annular groove 14 and the width W1 of the annular groove 14 is greater than 1 / 10; the ratio between the height H of the annular protrusion 15 and the width W2 of the annular protrusion 15 is greater than 1 / 10.

[0069] In addition, the first welding ring 112 and the second welding ring 122 are preferably welded together by indium-based solder. In some embodiments, tin-based solder welding can also be used. In certain use environments of the MEMS sensor 1, such as high temperatures, the organic flux in the solder paste solder will volatilize and release gas, causing the pressure in the vacuum cavity 13a to increase. Compared with solder paste solder, indium-based solder or tin-based solder does not have organic flux, and therefore will not release gas at high temperatures, and will not affect the vacuum degree in the vacuum cavity 13a. Indium-based solder and tin-based solder are alloys with indium and tin as the main components, respectively, and doped with other metals such as gold, silver, and copper. Indium-based solder, for example, is In 97 Ag3 or In 95 Ag5.

[0070] The first embodiment of the present invention also provides Figures 1 to 3 A method for manufacturing a MEMS sensor. Figure 4 It is a flowchart of the production method. Figures 5 to 10 yes Figure 4 Schematic diagram of the intermediate structure corresponding to the process in .

[0071] First, refer to Figure 4 Step S1 in Figure 5 and Figure 6 As shown, a prefabricated substrate 11 ′ and a prefabricated cover plate 12 ′ are provided respectively. The prefabricated substrate 11 ′ includes a MEMS structure 110 and a first welding area 111 disposed around the MEMS structure 110 ; the prefabricated cover plate 12 ′ includes a second welding area 121 .

[0072] The prefabricated 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.

[0073] In this embodiment, refer to Figure 5As shown, the first welding area 111 has a first passivation layer 113. The material of the first passivation layer 113 may be silicon nitride. In other embodiments, the first welding area 111 may have a first dielectric layer or a first semiconductor layer. The material of the first dielectric layer may be silicon dioxide. The material of the first semiconductor layer may be doped polysilicon or a single crystal silicon substrate. Or the first welding area 111 has a stacked structure including at least two layers of the first dielectric layer, the first passivation layer and the first semiconductor layer. This embodiment does not limit the material type of the first welding area 111.

[0074] The prefabricated cover plate 12 ′ may include a second semiconductor substrate.

[0075] In this embodiment, refer to Figure 6 As shown, the second welding area 121 has a second dielectric layer 123. The material of the second dielectric layer 123 can be silicon dioxide. In other embodiments, the second welding area 121 can have a second passivation layer or a second semiconductor layer. The material of the second passivation layer can be silicon nitride. The material of the second semiconductor layer can be doped polysilicon or a single crystal silicon substrate. Or, the second welding area 121 has a stacked structure including at least two layers of the second dielectric layer, the second passivation layer and the second semiconductor layer. This embodiment does not limit the material type of the second welding area 121.

[0076] Next, refer to Figure 4 Step S2 in Figure 7 and Figure 8 As shown, an annular groove 14 distributed along the circumferential direction is formed in the first welding area 111 ; and an annular protrusion 15 distributed along the circumferential direction is formed in the second welding area 121 .

[0077] The annular groove 14 and the annular protrusion 15 can be realized by dry etching. Specifically, step S2 may include:

[0078] Step S21, forming photoresist layers on the prefabricated substrate 11' and the prefabricated cover plate 12' respectively; then exposing the photoresist layers using corresponding masks; and developing to form respective patterned photoresist layers.

[0079] In step S22 , the first passivation layer 113 is dry-etched using the corresponding patterned photoresist layer as a mask to form an annular groove 14 in the first passivation layer 113 ; the second dielectric layer 123 is dry-etched using the corresponding patterned photoresist layer as a mask to form an annular protrusion 15 in the second dielectric layer 123 .

[0080] Step S23, removing the remaining photoresist layer by ashing.

[0081] Next, refer to Figure 4 Step S3 in Fig. 9 and Fig.10As shown, a first welding ring 112 is formed in the first welding area 111 to form the prefabricated substrate 11' into the substrate 11, and the first welding ring 112 is conformally located on the first welding area 111; a second welding ring 122 is formed in the second welding area 121 to form the prefabricated cover plate 12' into the cover plate 12, and the second welding ring 122 is conformally located on the second welding area 121.

[0082] The first welding ring 112 and the second welding ring 122 are made of metal, such as copper or aluminum. The first welding ring 112 can be formed by electron beam evaporation or sputtering. The second welding ring 122 can also be formed by electron beam evaporation or sputtering.

[0083] The electron beam evaporation or sputtering process can form a metal layer on the entire surface, and the metal layer in the area outside the first welding area 111 and the second welding area 121 can be removed by a dry etching process or a wet etching process.

[0084] The thickness of the metal layer is relatively thin. For the substrate 11, the thickness of the metal layer satisfies: the cross section of the annular concave area enclosed by the surface of the metal layer away from the first welding area 111 along the vertical circumferential direction is consistent with the cross section of the annular groove 14 along the vertical circumferential direction. For the cover plate 12, the thickness of the metal layer satisfies: the cross section of the annular convex area enclosed by the surface of the metal layer away from the second welding area 121 along the vertical circumferential direction is consistent with the cross section of the annular protrusion 15 along the vertical circumferential direction.

[0085] Before forming the metal layer by electron beam evaporation or sputtering, the prefabricated substrate 11' and the prefabricated cover plate 12' can be immersed in an organic solvent and ultrasonically vibrated to clean the residue. The organic solvent can be at least one of acetone, ethanol, ether, and isopropanol.

[0086] Afterwards, refer to Figure 4 Step S4 in Figure 1 As shown, the first welding ring 112 and the second welding ring 122 are welded together, so that the substrate 11 and the cover plate 12 form a sealing structure 13 to confine the MEMS structure 110 in the vacuum chamber 13 a.

[0087] This step is preferably welded in a vacuum environment, and specifically, a vacuum bonding machine can be used for welding. In the vacuum bonding machine, the solder reaches the melting point and begins to melt, and the solder quickly spreads on the wetting layer of the first welding ring 112 and the second welding ring 122 to fill the uneven structure. After cooling, the solder solidifies and forms a chain-like tooth structure extending in the radial direction with the first welding ring 112 and the second welding ring 122.

[0088] The first welding ring 112 and the second welding ring 122 are preferably welded together by indium-based solder. In some embodiments, tin-based solder can also be used for welding. Compared with solder paste solder, indium-based solder and tin-based solder do not have organic flux, so they will not release gas at high temperature and will not affect the vacuum degree in the vacuum chamber 13a.

[0089] Fig.11 FIG. 1 is a schematic cross-sectional view of a partial structure of a MEMS sensor according to a second embodiment of the present invention. Fig.11 As shown, the MEMS sensor 2 and the manufacturing method thereof of the second embodiment are substantially the same as the MEMS sensor 1 and the manufacturing method thereof of the first embodiment, with the only difference being that the annular groove 14 and the annular protrusion 15 include two circles.

[0090] The number of the annular grooves 14 and the annular protrusions 15 is the same. In this embodiment, the dimensions of the annular grooves 14 are the same, including the width and depth; the dimensions of the annular protrusions 15 are also the same, including the width and height. In other embodiments, the dimensions of the annular grooves 14 can be different, such as the width and / or depth; the dimensions of the annular protrusions 15 can be different, such as the width and / or height.

[0091] In other embodiments, the annular groove 14 and the annular protrusion 15 may include more than two circles.

[0092] The more the number of the annular grooves 14 and the annular protrusions 15 is, the longer the effective length of the gas leakage channel can be.

[0093] Fig.12 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. Fig.12 As shown, the MEMS sensor 3 and the manufacturing method thereof of the third embodiment are substantially the same as the MEMS sensors 1 and 2 and the manufacturing methods thereof of the first and second embodiments, with the only difference being that: the first welding ring 112 includes, in sequence toward the cover plate 12: a first adhesion layer 112a, a first barrier layer 112b and a first wetting layer 112c; the second welding ring 122 includes, in sequence toward the substrate 11: a second adhesion layer 122a, a second barrier layer 122b and a second wetting layer 122c.

[0094] In this embodiment, the first adhesion layer 112a is selected from a metal that has good adhesion to the first passivation layer 113 and a matching thermal expansion coefficient, such as titanium or chromium. The first barrier layer 112b is selected from a metal that has good adhesion to the first wetting layer 112c and the first adhesion layer 112a, a thermal expansion coefficient between the two layers, and a medium welding performance, such as nickel. The first wetting layer 112c is also an anti-oxidation layer, and a metal with stable performance, good wettability, difficulty in oxidation, and good brazing performance is selected, such as gold. The second adhesion layer 122a is selected from a metal that has good adhesion to the second dielectric layer 123 and a matching thermal expansion coefficient, such as titanium or chromium. The second barrier layer 122b is selected from a metal that has good adhesion to the second wetting layer 122c and the second adhesion layer 122a, a thermal expansion coefficient between the two layers, and a medium welding performance, such as nickel. The second wetting layer 122c is also an anti-oxidation layer, and a metal with stable performance, good wettability, difficulty in oxidation, and good brazing performance is selected. For example, the metal is gold.

[0095] In other embodiments, only the first welding ring 112 may include, in sequence, the following: a first adhesion layer 112a, a first barrier layer 112b, and a first wetting layer 121c toward the cover plate 12; or only the second welding ring 122 may include, in sequence, the following: a second adhesion layer 122a, a second barrier layer 122b, and a second wetting layer 122c toward the substrate 11.

[0096] Fig.13 FIG. 4 is a schematic cross-sectional view of a MEMS sensor according to a fourth embodiment of the present invention. Fig.13 As shown, the MEMS sensor 4 and the manufacturing method thereof of the fourth embodiment are substantially the same as the MEMS sensors 1, 2, 3 and the manufacturing methods thereof of the first, second and third embodiments, with the only difference being that the first welding area 111 has an annular protrusion 15 distributed along the circumferential direction, and the second welding area 121 has an annular groove 14 distributed along the circumferential direction.

[0097] Reference Fig.13 As shown, the annular protrusion 15 and the annular groove 14 can enable the first welding ring 112 to mesh with the second welding ring 122 .

[0098] Fig.14 FIG. 5 is a schematic cross-sectional view of a MEMS sensor according to a fifth embodiment of the present invention. Fig.14 As shown, the MEMS sensor 5 and its manufacturing method of the fifth embodiment are substantially the same as the MEMS sensors 1, 2, 3, 4 and their manufacturing methods of the first, second, third and fourth embodiments, with the only difference being that the first welding area 111 has an annular groove 14 distributed along the circumferential direction, and the second welding area 121 is a plane.

[0099] The first welding ring 112 is conformally located on the first welding area 111, so that the surface of the first welding ring 112 away from the first welding area 111 encloses an annular recessed area, and the cross-section of the annular recessed area along the vertical circumferential direction is consistent with the cross-section of the annular groove 14 along the vertical circumferential direction. The second welding ring 122 is conformally located on the second welding area 121, so that the surface of the second welding ring 122 away from the second welding area 121 is a plane.

[0100] Reference Fig.14 As shown, the solder layer 16 includes a first surface and a second surface opposite to each other. The shape and size of the first surface match the shape and size of the first welding ring 112 , and the shape and size of the second surface match the shape and size of the second welding ring 122 .

[0101] In other embodiments, the first welding area 111 may have annular protrusions 15 distributed along the circumferential direction, and the second welding area 121 may be a plane; or the first welding area 111 may be a plane, and the second welding area 121 may have annular grooves 14 distributed along the circumferential direction; or the first welding area 111 may be a plane, and the second welding area 121 may have annular protrusions 15 distributed along the circumferential direction.

[0102] 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, comprising a MEMS structure, a first welding area arranged around the MEMS structure, and a first welding ring located at the first welding area; A cover plate, comprising a second welding area, and a second welding ring located at the second welding area; the substrate and the cover plate are welded together through the first welding ring and the second welding ring to form a sealing structure, so as to confine the MEMS structure in a vacuum chamber; at least one of the first welding area and the second welding area has an annular groove or an annular protrusion distributed along the circumferential direction, the first welding ring is located on the first welding area in a conformal manner, and the second welding ring is located on the second welding area in a conformal manner; Wherein, the first welding area has an annular groove distributed along the circumferential direction, and the second welding area has an annular protrusion distributed along the circumferential direction, and the annular groove and the annular protrusion make the first welding ring mesh with the second welding ring; or the first welding area has an annular protrusion distributed along the circumferential direction, and the second welding area has an annular groove distributed along the circumferential direction, and the annular protrusion and the annular groove make the first welding ring mesh with the second welding ring, and the protrusion height of the annular protrusion matches the depth of the annular groove; The ratio of the depth of the annular groove to the width of the annular groove is greater than 1 / 10, and the ratio of the height of the annular protrusion to the width of the annular protrusion is greater than 1 / 10.

2. The MEMS sensor according to claim 1, characterized in that: The annular groove or the annular protrusion includes two or more circles.

3. The MEMS sensor according to claim 2, characterized in that: The sizes of the annular grooves in each circle or the annular protrusions in each circle are the same or different.

4. The MEMS sensor according to claim 1, characterized in that: The cross section of the annular groove or the annular protrusion along the perpendicular direction to the circumferential direction is a triangle, a square, a rectangle, a regular trapezoid or an inverted trapezoid.

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

6. The MEMS sensor according to claim 1, characterized in that: The first welding area has at least one of a first dielectric layer, a first passivation layer or a first semiconductor layer, the annular groove is located in the first dielectric layer, the first passivation layer or the first semiconductor layer, or the material of the annular protrusion is the first dielectric layer, the first passivation layer or the first semiconductor layer; Or the second welding area has at least one of a second dielectric layer, a second passivation layer or a second semiconductor layer, the annular groove is located in the second dielectric layer, the second passivation layer or the second semiconductor layer, or the material of the annular protrusion is the second dielectric layer, the second passivation layer or the second semiconductor layer.

7. The MEMS sensor according to claim 1, characterized in that: The first welding ring and the second welding ring are welded together by using indium-based solder or tin-based solder.

8. A method for manufacturing a MEMS sensor, characterized in that: include: Providing a prefabricated substrate and a prefabricated cover plate respectively, wherein the prefabricated substrate comprises a MEMS structure and a first welding area arranged around the MEMS structure; The prefabricated cover plate includes a second welding area; forming an annular groove or annular protrusion distributed along the circumferential direction on at least one of the first welding area and the second welding area; A first welding ring is formed in the first welding area so that the prefabricated substrate forms a substrate, and the first welding ring is located on the first welding area in an environmentally friendly manner; a second welding ring is formed in the second welding area so that the prefabricated cover plate forms a cover plate, and the second welding ring is located on the second welding area in an environmentally friendly manner; wherein, the first welding area has an annular groove distributed along the circumference, and the second welding area has an annular protrusion distributed along the circumference, and the annular groove and the annular protrusion make the first welding ring mesh with the second welding ring; or the first welding area has an annular protrusion distributed along the circumference, and the second welding area has an annular groove distributed along the circumference, and the annular protrusion and the annular groove make the first welding ring mesh with the second welding ring; and the protrusion height of the annular protrusion matches the depth of the annular groove; the ratio between the depth of the annular groove and the width of the annular groove is greater than 1 / 10, and the ratio between the height of the annular protrusion and the width of the annular protrusion is greater than 1 / 10; The first welding ring and the second welding ring are welded together so that the substrate and the cover plate form a sealing structure, so as to confine the MEMS structure in a vacuum chamber.

9. The method for manufacturing a MEMS sensor according to claim 8, characterized in that: The first welding area has at least one of a first dielectric layer, a first passivation layer or a first semiconductor layer, and the annular groove or the annular protrusion is formed by etching the first dielectric layer, the first passivation layer or the first semiconductor layer; Or the second welding area has at least one of a second dielectric layer, a second passivation layer or a second semiconductor layer, and the annular groove or the annular protrusion is formed by etching the second dielectric layer, the second passivation layer or the second semiconductor layer.

10. The method for manufacturing a MEMS sensor according to claim 8, characterized in that: The first welding ring is formed by electron beam evaporation or sputtering process, or the second welding ring is formed by electron beam evaporation or sputtering process.

11. The method for manufacturing a MEMS sensor according to claim 8, characterized in that: The first welding ring and the second welding ring are welded together by using indium-based solder or tin-based solder.

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