Microelectromechanical system device and manufacturing method therefor

Abstract

A microelectromechanical system device. The device comprises a cover sheet (501) provided with a recess (502), and a device piece (503) bonded to the cover sheet (501) and provided with a functional chamber directly facing the recess (502). The cover sheet comprises a substrate (511), a first metal layer (521) and a grounding structure (507), the substrate (511) having a first surface that faces the device piece (503), the recess (502) being formed on the first surface, the first metal layer (521) and the grounding structure (507) being arranged on the part of the first surface except the recess, and the grounding structure (507) being arranged along the periphery of a bonding area where the first metal layer is located. The device piece (503) comprises a substrate (513), a structural layer (523) and a second metal layer (533) which are stacked successively, the structural layer (523) comprising a first portion and a second portion surrounding the first portion, the first portion being located in the functional chamber (504) and forming a structure used for achieving a mechanical function, and the second metal layer (533) being located on the second portion. The cover sheet (501) and the device piece (503) each comprise at least one electrode, and are bonded together by means of the first metal layer (521) and the second metal layer (533), all the electrodes being electrically connected by means of the first metal layer (521) and the second metal layer (533) bonded to each other. Further provided is a manufacturing method for a microelectromechanical system device.

Description

Micro-electromechanical system device and manufacturing method thereof Technical Field

[0001] The embodiments described herein generally relate to the field of semiconductor manufacturing, and more particularly, to micro electro mechanical system (MEMS) devices and methods for manufacturing the same. Background Art

[0002] Electronic devices, such as commercial products (e.g., True Wireless Stereo (TWS), wearables, phones, etc.) and high-end products (e.g., automobiles), often include MEMS devices. For example, MEMS devices such as inertial sensors can be used to form accelerometers, gyroscopes, and other types of sensors. Technical issues

[0003] In recent years, to further increase the density of MEMS devices, technologies have been developed primarily for manufacturing MEMS devices with three-dimensional structures, in which multiple device chips or wafers are integrated across their thickness. When multiple device chips involve at least two or more electrodes (such as a top wafer and a bottom wafer), it is crucial to ensure that all electrodes are grounded to the same potential. Without proper grounding, one of the electrodes will float, causing unwanted charge to accumulate within the electrode. This phenomenon increases the resistance of the electronic device and parasitic capacitance, resulting in slower startup response time and a poor signal-to-noise ratio (SNR).

[0004] Therefore, people hope to provide appropriate grounding structures for MEMS devices. Technical Solutions

[0005] According to one aspect of the present invention, a MEMS device is provided. The MEMS device includes a cover sheet having a groove, and a device sheet bonded to the cover sheet and having a functional cavity facing the groove. The cover sheet includes a substrate and a first metal layer. The substrate has a first surface facing the device sheet, the groove is provided on the first surface, and the first metal layer is provided on the portion of the first surface excluding the groove. The device sheet includes a substrate, a structural layer, and a second metal layer stacked in sequence. The structural layer includes a first portion and a second portion surrounding the first portion. The first portion is located within the functional cavity and has a structure formed therein for achieving a mechanical function. The second metal layer is provided on the second portion. Both the cover sheet and the device sheet include at least one electrode. The cover sheet and the device sheet are bonded together via the first and second metal layers. All electrodes are electrically connected via the bonded first and second metal layers. The cover sheet also includes a grounding structure located on the portion of the first surface excluding the groove and arranged along the periphery of the bonding area where the first metal layer is located.

[0006] In some embodiments, the grounding structure is disposed on both sides or either side of the bonding region.

[0007] In some embodiments, the bonding region is annular, and the grounding structure is disposed along one or both sides of the outer side and the inner side of the bonding region.

[0008] In some embodiments, the grounding structure is a complete annular groove, or one or more short grooves.

[0009] In some embodiments, the first metal layer completely or partially covers the ground structure.

[0010] According to another aspect of the present invention, a method for manufacturing the aforementioned MEMS device is provided. The method includes forming a cover wafer, forming a device wafer, and bonding the cover wafer and the device wafer together. Forming the cover wafer includes providing a first substrate; forming an oxide layer on a first surface of the first substrate; patterning the oxide layer to form a ground structure and reserve a target bonding area, with the ground structure disposed along the periphery of the target bonding area; forming a first metal layer on the oxide layer corresponding to the target bonding area and the ground structure; and removing portions of the oxide layer and the first substrate to form a recess, such that the first metal layer and the ground structure are disposed on the first surface excluding the recess. Forming the device wafer includes providing a second substrate; and forming a structural layer and a second metal layer on the second substrate, such that the structural layer includes a first portion and a second portion surrounding the first portion, the first portion being located within a functional cavity having a structure for implementing a mechanical function formed therein, and the second metal layer being located on the second portion. Bonding the cover wafer and the device wafer together includes performing a bonding process on the first and second metal layers, such that the cover wafer and the device wafer are bonded together via the first and second metal layers, and all electrodes in the cover wafer and the device wafer are electrically connected via the bonded first and second metal layers.

[0011] In some embodiments, patterning the oxide layer to form a grounding structure and reserving a target bonding area includes: arranging the grounding structure on both sides or on either side of the bonding area.

[0012] In some embodiments, patterning the oxide layer to form a grounding structure and reserving a target bonding area includes: configuring the target bonding area in a ring shape, and configuring the grounding structure along one or both sides of an outer side and an inner side of the target bonding area.

[0013] In some embodiments, patterning the oxide layer to form a grounding structure and reserving a target bonding area includes: providing the grounding structure as a complete annular trench, or as a single or multiple short trenches.

[0014] In some embodiments, when the first metal layer and the second metal layer are bonded, the first metal layer is squeezed out and flows into the ground structure, so that the first metal layer completely or partially covers the ground structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Embodiments of the invention are illustrated by way of example, and not limitation, in the figures of the accompanying drawings in which like references may indicate similar elements.

[0016] FIG. 1A is a schematic diagram illustrating a cross section of a MEMS device according to an embodiment of the present invention.

[0017] FIG. 1B is a schematic diagram illustrating an exemplary relationship between a closed cavity and a bonding ring according to an embodiment of the present invention.

[0018] 2A and 2B are schematic diagrams for explaining an isolated island structure as a ground structure.

[0019] 3A and 3B are schematic diagrams for explaining another isolated island structure as a ground structure.

[0020] 4A , 4B, and 4C are schematic diagrams for explaining a ground structure embedded in a bonding ring.

[0021] FIG4D is a local scanning electron microscope (FA SEM) image of the ground structure.

[0022] FIG. 5A is a schematic diagram illustrating a cross section of another MEMS device according to an embodiment of the present invention.

[0023] FIG. 5B is an enlarged schematic diagram showing the ground structure 507 in FIG. 5A .

[0024] FIG. 6A is a schematic diagram illustrating a cross section of yet another MEMS device according to an embodiment of the present invention.

[0025] FIG. 6B is an enlarged schematic diagram showing the ground structure 607 in FIG. 6A .

[0026] FIG. 7A is a schematic diagram illustrating a cross section of yet another MEMS device according to an embodiment of the present invention.

[0027] FIG. 7B is an enlarged schematic diagram showing the grounding structure 707 in FIG. 7A .

[0028] 8A to 8D illustrate intermediate steps in fabricating a cap piece for a MEMS device according to one embodiment.

[0029] FIG. 9A is a schematic diagram illustrating an exemplary layout of a ground ring.

[0030] FIG. 9B is a schematic diagram illustrating another exemplary layout of a ground ring.

[0031] FIG. 10A is a schematic diagram illustrating a cross section of a bonding area on the left side of a cover sheet according to an embodiment.

[0032] FIG. 10B is a schematic diagram illustrating another cross-section of the bonding area on the left side of the cover sheet according to one embodiment.

[0033] FIG. 10C is a schematic diagram illustrating another cross-section of the bonding area on the left side of the cover sheet according to one embodiment.

[0034] FIG. 11 is a schematic diagram for explaining a cross section of a device wafer according to an embodiment.

[0035] FIG. 12 is a schematic diagram for explaining the structural layers of a MEMS gyroscope.

[0036] FIG. 13 is another local scanning electron microscope (FA SEM) image of the ground structure.

[0037] FIG. 14 is a flow chart of a method of manufacturing a MEMS device according to an embodiment. Modes for Carrying Out the Invention

[0038] This specification discloses one or more embodiments that incorporate features of the present invention. The disclosed embodiments are merely exemplary of the present invention. The scope of the present invention is not limited to the disclosed embodiments. The present invention is defined by the following claims.

[0039] The described embodiments and references in the specification to "one embodiment," "an embodiment," "an example embodiment," etc., indicate that the described embodiments may include a particular feature, structure, or characteristic, but not every embodiment will necessarily include that particular feature, structure, or characteristic. Furthermore, these phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described as being associated with one embodiment, it should be understood that it is within the knowledge of those skilled in the art to associate that feature, structure, or characteristic with other embodiments, whether or not explicitly described.

[0040] The terms used in the embodiments of the present invention are only used to describe specific embodiments and are not intended to limit the present invention. The singular forms "a", "an", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly dictates otherwise.

[0041] It should be understood that the term "and / or" used herein simply describes the relationship between associated objects, indicating three possible relationships. For example, the expression "A and / or B" can include three situations: A alone, A and B simultaneously, and B alone. Furthermore, the character " / " generally indicates that the associated objects are in an "or" relationship.

[0042] It should be noted that the directional terms "up," "down," "left," and "right," etc., described in the embodiments of the present invention are described from the perspectives shown in the accompanying drawings and should not be construed as limiting the embodiments of the present invention. Furthermore, in this context, it should be understood that when a component is referred to as being connected "above / up" or "below / lower" to another component, the component may be connected not only directly to the "above / up" or "below / lower" of the other component, but also indirectly to the "above / up" or "below / lower" of the other component via an intermediate component.

[0043] MEMS devices are high-tech devices measuring a few millimeters or smaller, with internal structures typically at the micrometer or nanometer scale. MEMS devices can include multiple components (such as movable elements) to implement mechanical functions. MEMS devices can also include MEMS acoustic sensors, MEMS pressure sensors, and MEMS inertial sensors. MEMS inertial sensors typically include MEMS accelerometers and MEMS gyroscopes.

[0044] FIG1A is a schematic diagram illustrating a cross-section of a MEMS device according to an embodiment of the present invention. The MEMS device includes a cover wafer 101 and a device wafer 103. Cover wafer 101 and device wafer 103 may be bonded together using a suitable bonding technique, such as fusion bonding or eutectic bonding.

[0045] The cover wafer 101 may include a base 111. According to one embodiment, the base 111 of the cover wafer 101 may be formed of silicon. Alternatively, the base 111 of the cover wafer 101 may be formed of other semiconductor materials, including silicon germanium (SiGe), silicon carbide, and the like.

[0046] The substrate 111 has a first surface facing the device wafer 103. The cover wafer 101 has a groove 102 on the first surface and includes a first metal layer 121 disposed on a portion of the first surface excluding the groove 102.

[0047] The device wafer 103 may include a substrate 113. According to one embodiment, the substrate 113 of the device wafer 103 may have a material similar to that of the substrate 111 of the cover wafer 101. However, the substrates of the cover wafer 101 and the device wafer 103 do not necessarily have to be made of the same material.

[0048] Device wafer 103 may further include a structure layer 123 and a second metal layer 133 stacked in sequence. Device wafer 103 is provided with a functional cavity 104 that faces recess 102. Structure layer 123 includes a first portion and a second portion surrounding the first portion. The first portion is located within functional cavity 104, which contains a structure for implementing a mechanical function. Second metal layer 133 is located on the second portion.

[0049] Since the MEMS device needs to operate in a sealed environment, the cover wafer 101 and the device wafer 103 are bonded together through the first metal layer 121 and the second metal layer 133, thereby sealing the corresponding active elements (or structures that implement mechanical functions) of the MEMS device in a closed cavity 105. The cavity 105 includes a groove 102 and a functional cavity 104 defined by the cover wafer 101 and the device wafer 103.

[0050] For ease of explanation, the region where the first metal layer 121 and the second metal layer 133 are located is referred to as the bonding region 106. The bonding region 106 can take any desired form. For example, the bonding region 106 can be a bonding ring surrounding the enclosed cavity 105. FIG1B is a schematic diagram illustrating an exemplary relationship between the enclosed cavity 105 and the bonding ring 106 according to one embodiment of the present invention. However, the bonding region is not limited to the examples provided herein.

[0051] The cover plate 101 and the device plate 103 each include at least one electrode. It is very important to ensure that all electrodes of the MEMS device are grounded at the same potential because without proper grounding, one of the electrodes will be electrically floating and cause unwanted charge to accumulate within the electrode.

[0052] To provide proper grounding, MEMS devices include a ground structure for electrically connecting all electrodes. In some cases, an isolated island structure is formed as the ground structure.

[0053] In the design shown in Figures 2A and 2B, the structure of the MEMS device is similar to that of the MEMS device shown in Figures 1A and 1B, except that a grounding structure 207 is formed within the enclosed cavity 205. Referring to Figures 2A and 2B, the MEMS device includes a cover plate 201 and a device plate 203. Cover plate 201 includes a substrate 211, a first metal layer 221, a first grounding electrode 231, and is provided with a groove 202. Device plate 203 includes a substrate 213, a structural layer 223, a second metal layer 233, and a second grounding electrode 243, and is provided with a functional cavity 204. First grounding electrode 231 and second grounding electrode 243 constitute grounding structure 207. Thus, a grounding structure is formed. However, this design occupies unnecessary useful functional space within the enclosed cavity, reducing the area of ​​the active device structure.

[0054] In another design shown in Figures 3A and 3B, the structure of the MEMS device is similar to that of the MEMS device shown in Figures 1A and 1B, except that a grounding structure 307 is formed outside the closed cavity 305. Referring to Figures 3A and 3B, the MEMS device includes a cover plate 301 and a device plate 303. Cover plate 301 includes a substrate 311, a first metal layer 321, and a first grounding electrode 331, and is provided with a groove 302. Device plate 303 includes a substrate 313, a structural layer 323, a second metal layer 333, and a second grounding electrode 343, and is provided with a functional cavity 304. First grounding electrode 331 and second grounding electrode 343 constitute grounding structure 307. In this way, a grounding structure is provided. However, this design increases the overall size of the chip.

[0055] In other cases, the grounding structure is embedded in the bonding ring. In the design shown in Figures 4A, 4B, and 4C, the structure of the MEMS device is similar to that of the MEMS device shown in Figures 1A and 1B, except that the grounding structure 407 is embedded in the bonding ring 406. Referring to Figures 4A, 4B, and 4C, the MEMS device includes a cover plate 401 and a device plate 403. Cover plate 401 includes a substrate 411, a first metal layer 421, and a grounding ring 431, and is provided with a groove 402. Device plate 403 includes a substrate 413, a structural layer 423, and a second metal layer 433, and is provided with a functional cavity 404. The first metal layer 421, the grounding ring 431, and the second metal layer 433 constitute the grounding structure 407. In this way, the grounding structure is formed. Figure 4D is a partial scanning electron microscope (FA SEM) image of the grounding structure. It can be seen that the step height of the bonding interface creates an unnecessary gap 408 on the bonding ring. This will weaken the bond and may cause the seal to degrade over time.

[0056] In some embodiments, a MEMS device includes a cover and a device wafer. The cover wafer includes a base, a ground structure, and a first metal layer. The first metal layer is formed by depositing a first metal material and patterning it to form a bond ring structure in a target bonding area. The first metal material completely or partially covers the ground structure. The ground structure is formed along the periphery of the bond ring structure. The device wafer includes a substrate and a second metal layer. The second metal layer is bonded to the first metal layer to achieve a sealed environment while providing proper grounding.

[0057] Figure 5A is a schematic cross-sectional view illustrating another MEMS device according to an embodiment of the present invention. Figure 5B is an enlarged schematic view showing the grounding structure 507 of Figure 5A. In the design shown in Figures 5A and 5B, the MEMS device structure is similar to that of the MEMS device shown in Figures 1A and 1B, except that the grounding structure 507 is located on both sides of the bonding ring. Referring to Figures 5A and 5B, the MEMS device includes a cover plate 501 and a device plate 503. Cover plate 501 includes a base plate 511, a first metal layer 521, a grounding ring, and is provided with a groove 502. Device plate 503 includes a base plate 513, a structural layer 523, and a second metal layer 533, and is provided with a functional cavity 504. The first metal layer 521, the grounding ring, and the second metal layer 533 constitute the grounding structure 507. The first metal layer 521 and the second metal layer 533 are located in the bonding area 506 and face each other. The grounding rings are located along the outer and inner sides of the bonding area 506, respectively.

[0058] Figure 6A is a schematic cross-sectional view illustrating another MEMS device according to an embodiment of the present invention. Figure 6B is an enlarged schematic view showing the grounding structure 607 of Figure 6A. In the design shown in Figures 6A and 6B, the structure of the MEMS device is similar to that of the MEMS device shown in Figures 1A and 1B, except that the grounding structure 607 is located outside the bonding ring. Referring to Figures 6A and 6B, the MEMS device includes a cover plate 601 and a device plate 603. Cover plate 601 includes a base 611, a first metal layer 621, and a grounding ring, and is provided with a groove 602. Device plate 603 includes a base 613, a structural layer 623, and a second metal layer 633, and is provided with a functional cavity 604. The first metal layer 621, the grounding ring, and the second metal layer 633 constitute the grounding structure 607. The first metal layer 621 and the second metal layer 633 are located in the bonding area 606 and face each other. The grounding ring is provided along the outside of the bonding area 606.

[0059] FIG7A is a schematic cross-sectional view illustrating another MEMS device according to an embodiment of the present invention. FIG7B is an enlarged schematic view showing the grounding structure 707 of FIG7A . In the design shown in FIG7A and FIG7B , the structure of the MEMS device is similar to that of the MEMS device shown in FIG1A and FIG1B , except that the grounding structure 707 is located inside the bonding ring. Referring to FIG7A and FIG7B , the MEMS device includes a cover plate 701 and a device plate 703. Cover plate 701 includes a base 711, a first metal layer 721, and a grounding ring, and is provided with a groove 702. Device plate 703 includes a base 713, a structural layer 723, and a second metal layer 733, and is provided with a functional cavity 704. The first metal layer 721, the grounding ring, and the second metal layer 733 constitute the grounding structure 707. The first metal layer 721 and the second metal layer 733 are located in the bonding area 706 and face each other. The grounding ring is disposed along the inside of the bonding area 706.

[0060] In the MEMS devices shown in FIG. 5A , FIG. 5B , FIG. 6A , FIG. 6B , FIG. 7A and FIG. 7B , during the bonding process, the cover wafer and the device wafer are bonded together through the first metal layer and the second metal layer, and the grounding of the MEMS device is completed at the same time.

[0061] Figures 8A through 8D illustrate intermediate steps in fabricating a cover for a MEMS device according to an embodiment of the present invention. Figure 8A is a schematic cross-sectional view of a substrate on which a cover is formed, according to an embodiment. Substrate 811 can be formed of silicon, silicon germanium, silicon carbide, or similar materials. Alternatively, substrate 811 can be a silicon-on-insulator (SOI) substrate. An SOI substrate can include a semiconductor material layer (e.g., silicon, germanium, etc.) formed on an insulator layer (e.g., buried oxide), which is formed within a silicon substrate. Other substrates that can be used include multilayer substrates, gradient substrates, and hybrid orientation substrates.

[0062] Figure 8B is a schematic cross-sectional view of a cover sheet after an oxide deposition process is performed on one side of the substrate in Figure 8A according to one embodiment. As shown in Figure 8B, an oxide layer is formed on the surface of substrate 811. The oxide deposition can be formed using a deposition process such as CVD.

[0063] Figure 8B further illustrates the patterning of the oxide layer to form a grounding ring 831 therein. The patterning process can be accomplished by depositing a common masking material (e.g., photoresist, not shown) on the oxide layer. The masking material is then patterned, and the oxide layer is etched according to the pattern to form the grounding ring 831 and to preserve the target bonding area 806. As shown in Figure 8B, the grounding ring 831 is positioned along the outer and inner sides of the bonding area 806. Furthermore, the oxide layer labeled 809 on the center surface of the substrate 811 is a sacrificial oxide layer for the cover sheet. During the release process of the cover sheet, this portion 809 helps shorten the release time of the cover sheet.

[0064] Figure 8C is a schematic cross-sectional view of the cover wafer after a metal layer is formed on the oxide layer and in the ground ring according to one embodiment. Metal layer 821 is deposited on the oxide layer of target bonding area 806 and ground ring 831. The metal layer can be formed of materials such as aluminum, copper, and gold.

[0065] Figure 8D is a schematic cross-sectional view of a cover sheet after forming a groove according to one embodiment. Oxide layer 809 and a portion of substrate 811 are removed to form groove 802. This portion of oxide layer 809 serves as a sacrificial oxide layer. The sacrificial oxide layer can be treated using a high-frequency vapor etching process. Therefore, this portion of oxide layer 809 is removed. As shown in Figure 8D, other areas, such as the area where metal layer 821 is located, may be protected.

[0066] It should be noted that the grounding ring shown in FIG8B can be a loop along the outer periphery and / or inner periphery of the target bonding area. FIG9A is a schematic diagram for illustrating an exemplary layout of the grounding ring. As shown in FIG9A , two complete grounding structure rings 931 are arranged along the outer side and inner side of the target bonding area 906, and a portion of the oxide layer 909 is arranged on the central surface of the substrate. FIG9B is a schematic diagram for illustrating another exemplary layout of the grounding ring. As shown in FIG9B , two rings 931 with single or multiple short grooves are arranged along the outer side and inner side of the target bonding area 906, and a portion of the oxide layer 909 is arranged on the central surface of the substrate. Each groove can be of any shape and size and is not limited here.

[0067] As described above, a grounding structure can be formed by patterning an oxide on silicon. FIG10A is a cross-sectional schematic diagram illustrating a bonding area located on the left side of a cover sheet according to one embodiment. As shown in FIG10A , grounding structures 1031 are disposed on both sides of a target bonding area 1006. FIG10B is another cross-sectional schematic diagram illustrating a bonding area located on the left side of a cover sheet according to one embodiment. As shown in FIG10B , grounding structures 1031 are disposed outside of the target bonding area 1006. FIG10C is another cross-sectional schematic diagram illustrating a bonding area located on the left side of a cover sheet according to one embodiment. As shown in FIG10C , grounding structures 1031 are disposed inside of the target bonding area 1006.

[0068] FIG11 is a schematic cross-sectional view illustrating a device wafer according to an embodiment. A base substrate 1113 is provided in the figure. According to an embodiment, the base substrate 1113 may be made of a material similar to that of the base substrate 811. However, the base substrate 1113 and the base substrate 811 do not necessarily need to be made of the same material.

[0069] A structural layer 1123 and a second metal layer 1133 are sequentially formed on substrate 1113. A functional cavity 1104 is also formed. Structural layer 1123 includes a first portion and a second portion surrounding the first portion. The first portion is located within functional cavity 1104, and a structure for achieving mechanical functionality is formed within the cavity. Second metal layer 1133 is located on the second portion.

[0070] After manufacturing the cover wafer and the device wafer, such as the cover wafer shown in FIG8D and the device wafer shown in FIG11 , the cover wafer and the device wafer are bonded together through the first metal layer and the second metal layer to form a MEMS device, such as the MEMS device shown in FIG5A .

[0071] It should be understood that the structural layers described in the above embodiments can be any structure that implements the mechanical functions of a MEMS device. Figure 12 is a schematic diagram illustrating the structural layers of a MEMS gyroscope. As shown in Figure 12, the MEMS gyroscope includes a drive structure 1 and a detection structure 2. Drive structure 1 is used to generate a drive signal, and detection structure 2 is used to detect the angular velocity of the carrier based on the generated drive signal. Detection structure 2 includes a comb-like structure 3. The structural layers can be formed using any existing manufacturing process. The structural layers are not limited here and can adopt any structure as needed.

[0072] It can be seen that according to an embodiment of the present invention, forming a grounding structure along the periphery of the bonding ring structure can maximize the use of the effective device area and cavity area. This helps to optimize the feasibility of reducing the chip size. This is particularly beneficial for providing two or more electrodes with grounding capabilities during bonding, because it ensures that the entire device is connected to the same potential, minimizing the space wasted by forming a repeated grounding structure for each electrode. In addition, providing a grounding structure along the outside / inside of the bonding area allows excess metal material squeezed out during the bonding process to flow into the grounding groove instead of flowing into the device active area or adjacent active chips. In addition, after the grounding structure is formed outside the effective bonding area, no step height difference will appear in the bonding area, thereby retaining the optimal bonding area. This avoids the generation of gaps at the bonding interface. Therefore, as shown in Figure 13, it can be ensured that the bonding quality and bonding strength are not affected. FIG13 is another partial scanning electron microscope (FA SEM) image of a ground structure, which may be the ground structure shown in region 506 in FIG5B , region 606 in FIG6B , region 706 in FIG7B , or region 1006 in FIG10A , FIG10B , and FIG10C . It can be seen that when the ground structure is arranged along the periphery of the bond ring, no observable voids are observed at the bond interface of the bond ring in the FA SEM image.

[0073] A method of manufacturing the MEMS device shown in Figure 5A will be described below. Figure 14 is a flow chart of a method of manufacturing a MEMS device according to an embodiment.

[0074] As shown in FIG14 , a method for manufacturing a MEMS device is provided, which is used to manufacture the MEMS device in the aforementioned embodiments.

[0075] At block 1402, a cover sheet is formed.

[0076] At block 1404 , a device die is formed.

[0077] At block 1406 , the cover wafer and the device wafer are bonded together.

[0078] In some embodiments, a cover sheet is formed as follows: A substrate is provided. An oxide layer is formed on the substrate surface and patterned to form a ground ring and a reserved target bonding area. A metal layer is formed on the oxide layer over the target bonding area and the ground ring. Portions of the oxide layer and substrate are removed to form a recess. It will be appreciated that the cover sheet manufacturing process is similar to that shown in Figures 8A to 8D and will not be further described here.

[0079] In some embodiments, a device wafer is formed as follows: A substrate is provided. A structural layer and a second metal layer are sequentially formed on the substrate. A functional cavity is formed. The structural layer includes a first portion and a second portion surrounding the first portion. The first portion is located within the functional cavity, and a structure for implementing a mechanical function is formed in the functional cavity. The second metal layer is located on the second portion.

[0080] In some embodiments, the cover wafer and the device wafer are bonded together via a first metal layer and a second metal layer, thereby sealing the corresponding movable element (or structure for realizing mechanical functions) of the MEMS device in a closed cavity. The closed cavity includes a groove and a functional cavity defined by the cover wafer and the device wafer. The closed cavity provides a sealed environment for the operation of the MEMS device.

[0081] It should be understood that the MEMS device performs the above operations in a vacuum environment, thereby drying the moisture and / or organic gas in the functional cavity, so that the operating performance of the MEMS device remains stable, the operating reliability of the MEMS device is improved, and the service life of the MEMS device is extended.

[0082] This specification discloses one or more embodiments that incorporate features of the present invention. The disclosed embodiments are merely illustrative of the present invention. The scope of the present invention is not limited to the disclosed embodiments. The present invention is defined by the appended claims.

[0083] The terms used herein when describing the various embodiments are intended only to describe specific embodiments and are not intended to be limiting. As used in the description of the various embodiments and in the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. In addition, it should be understood that the term "and / or" as used herein refers to and includes any and all possible combinations of one or more of the associated listed items. It should be further understood that the terms "includes," "including," "comprises," and / or "comprising" as used in this specification specify the presence of stated features, integers, steps, actions, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, actions, elements, components, and / or combinations thereof.

[0084] For ease of explanation, the above description has been described with reference to specific embodiments. However, the above illustrative discussions are not intended to be exhaustive or to limit the scope of the claims to the precise forms disclosed. Many modifications and variations are possible in light of the above teachings. These embodiments were chosen to best explain the underlying principles of the claims and their practical application, thereby enabling others skilled in the art to best utilize these embodiments and make various modifications as appropriate to the particular application contemplated.

Claims

1. A microelectromechanical system (MEMS) device, characterized in that, Comprising: A cover sheet provided with a groove; And A device sheet bonded to the cover sheet and provided with a functional cavity facing the groove; wherein, The cover sheet includes a substrate and a first metal layer. The substrate has a first surface facing the device sheet. The groove is provided on the first surface. The first metal layer is provided on the portion of the first surface except the groove; The device sheet includes a substrate, a structure layer, and a second metal layer stacked in sequence. The structure layer includes a first portion and a second portion surrounding the first portion. The first portion is located in the functional cavity and a structure for realizing a mechanical function is formed in the functional cavity. The second metal layer is located on the second portion; Both the cover sheet and the device sheet include at least one electrode. The cover sheet and the device sheet are bonded together through the first metal layer and the second metal layer. All the electrodes are electrically connected through the mutually bonded first metal layer and second metal layer; The cover plate further includes a grounding structure located on the portion of the first surface except the groove and disposed along the periphery of the bonding region where the first metal layer is located.

2. The MEMS device according to claim 1, characterized in that, The grounding structure is disposed on both sides or any one side of the bonding region.

3. The MEMS device according to claim 1, characterized in that, The bonding region is annular. The grounding structure is disposed along one or both of the outer side and the inner side of the bonding region.

4. The MEMS device according to claim 3, characterized in that, The grounding structure is a complete annular groove or one or more short grooves.

5. The MEMS device according to claim 1, characterized in that, The first metal layer completely or partially covers the grounding structure.

6. A method for manufacturing a microelectromechanical system (MEMS) device, characterized in that, The method includes: Forming a cover sheet; Forming a device sheet; and Bonding the cover sheet and the device sheet together; Wherein, forming the cover sheet includes: Providing a first substrate; Forming an oxide layer on the first surface of the first substrate; Patterning the oxide layer to form a grounding structure and reserve a target bonding region. The grounding structure is disposed along the periphery of the target bonding region; Forming a first metal layer on the oxide layer corresponding to the target bonding region and the grounding structure; and Removing part of the oxide layer and the first substrate to form a groove, so that the first metal layer and the grounding structure are disposed on the portion of the first surface except the groove; Wherein, forming the device sheet includes: Providing a second substrate; and Forming a structure layer and a second metal layer on the second substrate, so that the structure layer includes a first portion and a second portion surrounding the first portion. The first portion is located in the functional cavity and a structure for realizing a mechanical function is formed in the functional cavity, and the second metal layer is located on the second portion; Wherein, bonding the cover sheet and the device sheet together includes: Performing a bonding process on the first metal layer and the second metal layer, so that the cover sheet and the device sheet are bonded together through the first metal layer and the second metal layer. All the electrodes in the cover sheet and the device sheet are electrically connected through the mutually bonded first metal layer and second metal layer.

7. The method according to claim 6, characterized in that, Patterning the oxide layer to form the grounding structure and reserve the target bonding region includes: disposing the grounding structure on both sides or any one side of the target bonding region.

8. The method according to claim 6, characterized in that, Patterning the oxide layer to form the grounding structure and reserve the target bonding region includes: setting the target bonding region as an annular shape, and disposing the grounding structure on one or both of the outer side and the inner side of the target bonding region.

9. The method according to claim 8, characterized in that, Patterning the oxide layer to form the grounding structure and reserve the target bonding region includes: setting the grounding structure as a complete annular groove, or setting it as a single or multiple short grooves.

10. The method according to claim 6, characterized in that When bonding the first metal layer and the second metal layer, the first metal layer is extruded and flows into the grounding structure, so that the first metal layer completely or partially covers the grounding structure.

Images