Shielding structure for MEMS device and preparation method thereof

Abstract

The embodiment of the invention relates to a shielding structure for an MEMS device and a preparation method of the shielding structure. The shielding structure comprises a first conductive supporting layer; the device layer is formed on the first conductive supporting layer, and the device layer comprises an MEMS device area and a shielding interconnection area; the device dielectric isolation layer is formed on the device layer; the second conductive support layer is formed on the device dielectric isolation layer; the shielding unit penetrates through the device dielectric isolation layer and is connected with the first conductive supporting layer, the second conductive supporting layer and the shielding interconnection region to form a fixed potential structure; the fixed potential structure surrounds the MEMS device area, and the fixed potential structure and the MEMS device area are electrically insulated through an insulation structure.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of micro-electromechanical systems, and in particular to a shielding structure for a MEMS device and a preparation method thereof. Background Art

[0002] In the prior art, in order to ensure the stable operation of micro-electromechanical system (MEMS) core components, such as MEMS accelerometers, MEMS gyroscopes, MEMS resonators, etc. in complex electromagnetic environments, MEMS devices are usually placed in metal tube shells during post-process packaging to achieve electromagnetic shielding. The disadvantage of this method is that the overall size after packaging is large, which is not convenient for mass production and system integration applications. Summary of the invention

[0003] Based on the above situation of the prior art, the purpose of the embodiments of the present invention is to provide a shielding structure for a MEMS device and a preparation method thereof, which completely encloses the MEMS device in a grounded cavity through a fixed potential structure, thereby achieving electromagnetic shielding without increasing the size of the device.

[0004] To achieve the above object, according to a first aspect of the present invention, there is provided a shielding structure for a MEMS device, comprising:

[0005] a first conductive support layer;

[0006] A device layer, formed on the first conductive support layer, the device layer comprising a MEMS device region and a shielding interconnection region;

[0007] A device dielectric isolation layer, formed on the device layer;

[0008] A second conductive support layer, formed on the device dielectric isolation layer;

[0009] a shielding unit, the shielding unit penetrating the device dielectric isolation layer and connected to the first conductive support layer, the second conductive support layer and the shielding interconnection region to form a fixed potential structure;

[0010] The fixed potential structure surrounds the MEMS device region, and the fixed potential structure is electrically insulated from the MEMS device region by an insulating structure;

[0011] Among them, the materials of the first conductive support layer, the second conductive support layer, the device layer and the shielding unit are conductive materials; the material of the device dielectric isolation layer is insulating material.

[0012] Furthermore, the first conductive support layer is an intermediate support layer, and further comprises:

[0013] A basic dielectric isolation layer, the intermediate support layer being formed on the basic dielectric isolation layer;

[0014] A base support layer, the base medium isolation layer is formed on the base support layer;

[0015] Wherein, the material of the basic dielectric isolation layer is an insulating material, and the material of the basic support layer is a conductive material.

[0016] Furthermore, the first conductive support layer is a basic support layer, and further comprises:

[0017] A basic dielectric isolation layer, formed on the basic support layer;

[0018] An intermediate support layer formed on the base medium isolation layer;

[0019] The device layer is formed on the intermediate support layer;

[0020] The shielding unit penetrates the device dielectric isolation layer and the base dielectric isolation layer, and is connected to the second conductive support layer, the shielding interconnection region, the intermediate support layer and the base support layer to form a fixed potential structure;

[0021] Wherein, the material of the basic dielectric isolation layer is an insulating material, and the material of the intermediate support layer is a conductive material.

[0022] Furthermore, it also includes:

[0023] a dielectric insulating layer, formed on the second conductive supporting layer;

[0024] The dielectric insulating layer is formed with a fixed potential electrode, and the fixed potential electrode is connected to the second conductive supporting layer and is used to provide a fixed potential for the fixed potential structure.

[0025] Furthermore, it also includes:

[0026] An interconnection unit, wherein the interconnection unit penetrates the device dielectric isolation layer and is made of a conductive material;

[0027] The dielectric insulating layer is also formed with a conductive contact structure, and the interconnection unit connects the MEMS device region with the conductive contact structure.

[0028] According to a second aspect of the present invention, there is provided a method for preparing a shielding structure for a MEMS device, comprising the steps of:

[0029] S1. Preparation of MEMS device wafers:

[0030] forming a device support layer;

[0031] forming a device dielectric isolation layer on the device support layer;

[0032] forming a device layer on the device dielectric isolation layer, wherein the device layer includes a MEMS device region and a shielding interconnection region;

[0033] forming a first shielding unit in a shielding interconnection region of the device layer, wherein the first shielding unit penetrates the device dielectric isolation layer;

[0034] S2. Prepare cover wafer:

[0035] Forming a basic support layer;

[0036] S3, bonding the MEMS device wafer and the cover wafer to form a bonded wafer, so that the device support layer, the first shielding unit, the shielding interconnection area and the base support layer are connected;

[0037] S4, thinning the device support layer to form a second conductive support layer, wherein the second conductive support layer, the first shielding unit, the shielding interconnection region and the base support layer form a fixed potential structure;

[0038] Among them, the materials of the basic support layer, the device support layer, the device layer and the first shielding unit are conductive materials; the material of the device dielectric isolation layer is insulating material, the fixed potential structure surrounds the MEMS device area, and the fixed potential structure is electrically insulated from the MEMS device area through an insulating structure.

[0039] Furthermore, the step S2 further includes:

[0040] forming a basic dielectric isolation layer on the basic support layer;

[0041] forming an intermediate supporting layer on the basic dielectric isolation layer, wherein the basic supporting layer and the intermediate supporting layer are insulated from each other;

[0042] In the step S3, the MEMS device wafer and the cover wafer are bonded to form a bonded wafer, so that the device support layer, the first shielding unit, the shielding interconnection area and the intermediate support layer are connected;

[0043] In the step S4, the second conductive support layer, the first shielding unit, the shielding interconnection area and the intermediate support layer form a fixed potential structure;

[0044] Wherein, the material of the basic dielectric isolation layer is an insulating material, and the material of the intermediate support layer is a conductive material.

[0045] Furthermore, the step S2 further includes:

[0046] forming a second shielding unit on the intermediate supporting layer, wherein the second shielding unit penetrates the basic dielectric isolation layer so that the basic supporting layer is connected to the intermediate supporting layer;

[0047] In the step S3, the MEMS device wafer and the cover wafer are bonded to form a bonded wafer, so that the device support layer is connected to the first shielding unit, the shielding interconnection area, the second shielding unit, the base support layer, and the intermediate support layer;

[0048] In the step S4, the second conductive supporting layer, the first shielding unit, the shielding interconnection area, the second shielding unit, the base supporting layer, and the intermediate supporting layer form a fixed potential structure;

[0049] Wherein, the material of the second shielding unit is conductive material.

[0050] Furthermore, the method further comprises the steps of:

[0051] S5, forming a dielectric insulating layer on the second conductive supporting layer, and forming a fixed potential electrode on the dielectric insulating layer;

[0052] Wherein, the fixed potential electrode is connected to the second conductive support layer and is used to provide a fixed potential for the fixed potential structure.

[0053] Furthermore, the step S1 further includes:

[0054] forming an interconnection unit in a MEMS device region of the device layer, wherein the interconnection unit penetrates the device dielectric isolation layer;

[0055] The step S5 further includes: forming a conductive contact structure on the dielectric insulating layer;

[0056] Wherein, the interconnection unit connects the MEMS device region with the conductive contact structure.

[0057] Furthermore, the MEMS device region also includes a structural gap of the device; and step S2 further includes:

[0058] forming an air guide groove structure on the base support layer, wherein the air guide groove structure is connected with the structural gap in the bonding wafer;

[0059] After step S4, the method further includes step S4A:

[0060] A third shielding unit is formed on the second conductive support layer of the bonded wafer. During the formation of the third shielding unit, the atmosphere, air pressure and vacuum degree in the structural gap are adjusted, and the third shielding unit fills the air guide groove structure.

[0061] Furthermore, the MEMS device region also includes a structural gap of the device; and step S2 further includes:

[0062] forming an air guide groove structure on the intermediate support layer, wherein the air guide groove structure is connected with the structural gap in the bonding wafer;

[0063] After step S4, the method further includes step S4B:

[0064] A third shielding unit is formed on the second conductive support layer of the bonded wafer. During the formation of the third shielding unit, the atmosphere, air pressure and vacuum degree in the structural gap are adjusted, and the third shielding unit fills the air guide groove structure.

[0065] According to a third aspect of the present invention, there is provided a method for preparing a shielding structure for a MEMS device, comprising the steps of:

[0066] S1. Preparation of MEMS device wafers:

[0067] forming a device support layer;

[0068] forming a device dielectric isolation layer on the device support layer;

[0069] forming a device layer on the device dielectric isolation layer, wherein the device layer includes a MEMS device region and a shielding interconnection region;

[0070] S2. Prepare cover wafer:

[0071] Forming a basic support layer;

[0072] S3, bonding the MEMS device wafer and the cover wafer to form a bonded wafer;

[0073] S4, thinning the device support layer to form a second conductive support layer;

[0074] S5, forming a third shielding unit on the second conductive support layer of the bonded wafer, wherein the third shielding unit penetrates the device dielectric isolation layer; the second conductive support layer is connected to the third shielding unit, the shielding interconnection area and the base support layer to form a fixed potential structure;

[0075] Among them, the materials of the basic support layer, device support layer, device layer and the third shielding unit are conductive materials; the material of the device dielectric isolation layer is insulating material; the fixed potential structure surrounds the MEMS device area, and the fixed potential structure is electrically insulated from the MEMS device area by an insulating structure.

[0076] Furthermore, the step S2 further includes:

[0077] forming a basic dielectric isolation layer on the basic support layer;

[0078] forming an intermediate supporting layer on the basic dielectric isolation layer, wherein the basic supporting layer and the intermediate supporting layer are insulated from each other;

[0079] The shielding interconnection area of ​​the bonded wafer is connected to the intermediate support layer,

[0080] Wherein, the third shielding unit is connected with the second conductive supporting layer, the intermediate supporting layer and the shielding interconnection area to form a fixed potential structure;

[0081] Wherein, the material of the basic dielectric isolation layer is an insulating material, and the material of the intermediate support layer is a conductive material.

[0082] Furthermore, the step S2 further includes forming a second shielding unit on the middle support layer of the cover wafer, wherein the second shielding unit penetrates the basic dielectric isolation layer;

[0083] The second shielding unit is connected to the second conductive supporting layer, the third shielding unit, the base supporting layer and the shielding interconnection area to form a fixed potential structure.

[0084] Furthermore, the method further comprises the steps of:

[0085] S6, forming a dielectric insulating layer on the second conductive supporting layer, and forming a fixed potential electrode on the dielectric insulating layer;

[0086] Wherein, the fixed potential electrode is connected to the second conductive support layer and is used to provide a fixed potential for the fixed potential structure.

[0087] Furthermore, the step S1 further includes:

[0088] forming an interconnection unit in a MEMS device region of the device layer, wherein the interconnection unit penetrates the device dielectric isolation layer;

[0089] The step S6 further includes: forming a conductive contact structure on the dielectric insulating layer;

[0090] Wherein, the interconnection unit connects the MEMS device region with the conductive contact structure.

[0091] Furthermore, the MEMS device region also includes a structural gap of the device; and step S2 further includes:

[0092] forming an air guide groove structure on the base support layer, wherein the air guide groove structure is connected with the structural gap in the bonding wafer;

[0093] The step S5 further comprises:

[0094] A third shielding unit is formed on the second conductive support layer of the bonded wafer. During the formation of the third shielding unit, the atmosphere, air pressure and vacuum degree in the structural gap are adjusted, and the third shielding unit fills the air guide groove structure.

[0095] Furthermore, the MEMS device region also includes a structural gap of the device; and step S2 further includes:

[0096] forming an air guide groove structure on the intermediate support layer, wherein the air guide groove structure is connected with the structural gap in the bonding wafer;

[0097] The step S5 further comprises:

[0098] A third shielding unit is formed on the second conductive support layer of the bonded wafer. During the formation of the third shielding unit, the atmosphere, air pressure and vacuum degree in the structural gap are adjusted, and the third shielding unit fills the air guide groove structure.

[0099] In summary, the embodiment of the present invention provides a shielding structure for a MEMS device and a preparation method thereof, the shielding structure comprising: a first conductive support layer; a device layer, formed on the first conductive support layer, the device layer comprising a MEMS device region and a shielding interconnection region; a device dielectric isolation layer, formed on the device layer; a second conductive support layer, formed on the device dielectric isolation layer; a shielding unit, the shielding unit penetrates the device dielectric isolation layer, and is connected to the first conductive support layer, the second conductive support layer and the shielding interconnection region to form a fixed potential structure. The technical solution provided by the embodiment of the present invention releases or locks the floating potential of the cover wafer and the supporting substrate around the MEMS device through the shielding unit; at the same time, an air guide groove structure connected to the concave cavity structure can also be provided, and when the shielding unit is subsequently manufactured, the vacuum degree of the structural gap accommodating the MEMS device can be adjusted, so that a stable working atmosphere environment can be provided while realizing the electromagnetic shielding of the MEMS device. BRIEF DESCRIPTION OF THE DRAWINGS

[0100] Figure 1 is a schematic structural diagram of a wafer with a MEMS device provided by an embodiment of the present invention;

[0101] Figure 2 is a schematic structural diagram of a cover wafer provided by an embodiment of the present invention;

[0102] Figure 3 is a schematic structural diagram of a cover wafer provided by another embodiment of the present invention;

[0103] Figure 4A It is a schematic diagram of bonding a MEMS device wafer and a cover wafer to form a bonded wafer provided by an embodiment of the present invention;

[0104] Figure 4B It is a schematic diagram of bonding a MEMS device wafer and a cover wafer to form a bonded wafer, and thinning the bonded wafer, provided by an embodiment of the present invention;

[0105] Figure 5 is a schematic diagram of bonding a MEMS device wafer and a cover wafer to form a bonded wafer provided by another embodiment of the present invention;

[0106] Figure 6 is a schematic diagram of bonding a MEMS device wafer and a cover wafer to form a bonded wafer provided by another embodiment of the present invention;

[0107] Figure 7 is a schematic diagram of thinning a bonded wafer provided by an embodiment of the present invention;

[0108] Figure 8 is a schematic diagram of forming a second interconnection unit and a dielectric isolation structure on a second conductive support layer provided by an embodiment of the present invention;

[0109] Fig. 9 is a schematic structural diagram of a shielding structure obtained by the preparation method of an embodiment of the present invention;

[0110] Fig.10 is a schematic structural diagram of a shielding structure obtained by a preparation method according to another embodiment of the present invention;

[0111] Fig.11A is a schematic structural diagram of a wafer with a MEMS device provided by another embodiment of the present invention;

[0112] Fig. 11B When preparing a MEMS device wafer according to an embodiment of the present invention, SiO is formed on the upper part of the device layer. 2 Schematic diagram of the layers;

[0113] 12 is a schematic structural diagram of a cover wafer provided by another embodiment of the present invention;

[0114] Fig.13A is a schematic diagram of bonding a MEMS device wafer and a cover wafer to form a bonded wafer provided by another embodiment of the present invention;

[0115] Fig. 13B is a schematic diagram of bonding a MEMS device wafer and a cover wafer to form a bonded wafer provided by another embodiment of the present invention;

[0116] Fig.14A is a schematic diagram of bonding a MEMS device wafer and a cover wafer to form a bonded wafer provided by another embodiment of the present invention;

[0117] Fig. 14B is a schematic diagram of bonding a MEMS device wafer and a cover wafer to form a bonded wafer provided by another embodiment of the present invention;

[0118] Fig.15 is a schematic diagram of bonding a MEMS device wafer and a cover wafer to form a bonded wafer provided by another embodiment of the present invention;

[0119] Fig.16A is a schematic structural diagram of a shielding structure obtained by a preparation method according to another embodiment of the present invention;

[0120] Fig. 16B is a schematic structural diagram of a shielding structure obtained by a preparation method according to another embodiment of the present invention;

[0121] Fig.17A is a schematic structural diagram of a shielding structure obtained by a preparation method according to another embodiment of the present invention;

[0122] Fig. 17B is a schematic structural diagram of a shielding structure obtained by a preparation method according to another embodiment of the present invention;

[0123] Fig. 17C is a schematic structural diagram of a shielding structure obtained by a preparation method according to another embodiment of the present invention;

[0124] Fig.18 It is a schematic structural diagram of a shielding structure obtained by a preparation method according to another embodiment of the present invention. DETAILED DESCRIPTION

[0125] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0126] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in one or more embodiments of the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in one or more embodiments of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0127] The technical solution of the present invention is described in detail below with reference to the accompanying drawings. An embodiment of the present invention provides a method for preparing a shielding structure for a MEMS device, wherein a MEMS device structure is manufactured on the surface of a substrate structure by a MEMS or semiconductor process, and then a cover wafer is bonded to a wafer with a MEMS device, and finally a grounded cavity is formed by setting a shielding unit, and the MEMS device is wrapped in the cavity, etc., to achieve electromagnetic shielding of the MEMS device. The preparation method provided in this embodiment includes the following steps:

[0128] S1, preparing a MEMS device wafer. In step S1, for example, a wafer with a MEMS device is formed from a silicon wafer by using a MEMS or semiconductor process. Figure 1 FIG. 1 shows a schematic diagram of the structure of a wafer with a MEMS device. The MEMS device wafer 10a can be prepared by the following steps:

[0129] S11, forming a device support layer 101a. The device support layer 101a is made of a conductive material, such as silicon, doped polysilicon, metal or other conductive material.

[0130] S12, forming a device dielectric isolation layer 102a on the device support layer 101a. The device dielectric isolation layer 102a is made of an insulating material, such as silicon dioxide, silicon nitride, or other insulating material.

[0131] S13, forming a device layer 103a on the device dielectric isolation layer 102a, wherein the device layer 103a includes a MEMS device region and a shielding interconnection region. Figure 1 As shown, the MEMS device region is, for example, located in the middle region of the device layer 103 a , and the shielding interconnection region is, for example, located in the two side regions of the device layer 103 a .

[0132] S14. A first shielding unit 107a is formed in the shielding interconnection region of the device layer 103a, and the first shielding unit 107a penetrates the device dielectric isolation layer 102a. In the MEMS device region of the device layer 103a, for example, a first interconnection unit 108a, a fixed anchoring structure 104a of the MEMS device, a structural gap 105a of the MEMS device, and a movable structure 106a of the MEMS device can be formed. Among them, the first interconnection unit 108a penetrates the device dielectric isolation layer 102a, and in the MEMS device region of the device layer 103a, the first interconnection unit 108a can be used for electrical connection of the MEMS device. Technicians in the relevant technical field can also choose to adopt other MEMS structures according to different MEMS devices.

[0133] S2, preparing a cover wafer. In step S2, for example, a cover wafer is formed from a silicon wafer by MEMS or semiconductor technology. Figure 2 , a schematic diagram of the structure of the cover wafer is shown in FIG. The cover wafer 20a can be prepared by the following steps:

[0134] S21, forming a basic support layer 201a. The material of the basic support layer 201a is a conductive material, such as silicon, doped polysilicon, metal and other conductive materials. A gas guide groove structure ( Figure 2 (not shown), after forming the bonding wafer 30a, the gas guide groove structure is connected with the structural gap 105a of the MEMS device in the bonding wafer 30a, and is used to adjust the atmosphere, air pressure, vacuum degree and other parameters in the MEMS device during the preparation process. In each embodiment of the present invention, adjusting the air pressure refers to inflating the MEMS device so that it has an air pressure environment greater than the standard atmospheric pressure; adjusting the vacuum degree refers to evacuating the MEMS device so that it has an air pressure environment less than the standard atmospheric pressure.

[0135] According to some optional embodiments, the cover wafer may further include a base dielectric isolation layer and an intermediate support layer, and step S2 may further include:

[0136] S22, forming a basic dielectric isolation layer 202a on the basic support layer 201a. The basic dielectric isolation layer 202a is made of an insulating material, such as silicon dioxide, silicon nitride, or other insulating material.

[0137] S23, forming an intermediate support layer 203a on the base dielectric isolation layer 202a, the material of the intermediate support layer 203a is also a conductive material, and the base support layer 201a and the intermediate support layer 203a are insulated. A cavity structure 204a, a dielectric support column structure 209a and an air guide groove structure can also be formed on the intermediate support layer 203a, and the dielectric support column structure 209a can play an insulating support role.

[0138] According to some optional embodiments, a shielding unit may also be formed on the intermediate supporting layer. Figure 3 A schematic diagram of the structure of a cover wafer of another embodiment is shown in FIG.

[0139] S24, forming a second shielding unit 207a on the intermediate support layer 203a, the second shielding unit 207a penetrates the basic dielectric isolation layer 202a, so that the basic support layer 201a is connected to the intermediate support layer 203a. At the same time, a concave cavity structure 204a, a support column isolation structure 205a and a support column structure 206a can also be formed on the intermediate support layer 203a. In addition to forming a conductive connection with the fixed support anchor structure 104a after forming a bonding wafer, the support column structure 206a is electrically insulated from other structures through insulating structures such as the support column isolation structure 205a. A gas guide groove structure can also be formed on the intermediate support layer 203a. The gas guide groove structure is, for example, connected to the concave cavity structure 204a. After forming a bonding wafer 30a, the gas guide groove structure is connected to the structural gap 105a of the MEMS device in the bonding wafer 30a, and is used to adjust the atmosphere, air pressure, vacuum and other parameters in the MEMS device during the preparation process.

[0140] S3 . Bond the MEMS device wafer 10 a and the cover wafer 20 a to form a bonded wafer 30 a . Figure 4A FIG. 4 shows a schematic diagram of bonding a MEMS device wafer and a cover wafer to form a bonded wafer. Figure 4A As shown, a bonded wafer 30a is formed by bonding the MEMS device wafer 10a and the cover wafer 20a. At this time, the first shielding unit 107a is connected to the base support layer 201a, the device support layer 101a and the shielding interconnection area.

[0141] According to some optional embodiments, when a basic dielectric isolation layer and an intermediate support layer are formed in the cover wafer, the bonding of the MEMS device wafer and the cover wafer may be performed in the following steps:

[0142] S3, bonding the MEMS device wafer 10a and the cover wafer 20a to form a bonded wafer 30a, Figure 5 FIG. 4 shows a schematic diagram of bonding a MEMS device wafer and a cover wafer to form a bonded wafer in another embodiment. Figure 5 As shown, the first shielding unit 107a is connected to the device supporting layer 101a, the middle supporting layer 203a and the shielding interconnection region.

[0143] According to some optional embodiments, when a second shielding unit is formed on the middle supporting layer, Figure 6FIG. 2 shows a schematic diagram of bonding a MEMS device wafer and a cover wafer to form a bonded wafer in another embodiment. In this embodiment, the bonding of the MEMS device wafer and the cover wafer may be performed in the following steps:

[0144] S3, bonding the MEMS device wafer 10a and the cover wafer 20a to form a bonded wafer 30a, so that the device support layer 101a, the first shielding unit 107a, the shielding interconnection area, the second shielding unit 207a, the base support layer 201a and the intermediate support layer 203a are connected. Figure 6 It can be seen that the intermediate support layer 203a between the two second shielding units 207a and other intermediate support layers 203a are connected to the same potential, and only the support column structure 206a itself plays a supporting role. It is insulated from the surrounding intermediate support layers and other structures through a physical isolation ring (such as a structural gap), so that the MEMS device itself can obtain a more stable electromagnetic environment.

[0145] In the above embodiments, the materials of the base support layer 201a, the device support layer 101a, the device layer 103a, the intermediate support layer 203a, the first shielding unit 107a and the second shielding unit 207a are conductive materials; the materials of the device dielectric isolation layer 102a and the base dielectric isolation layer 202a are insulating materials. The above fixed potential structure surrounds the MEMS device area, and the fixed potential structure is electrically insulated from the MEMS device area by the insulating structure. The insulating structure may include, for example, the dielectric isolation layer, the cavity structure, and the dielectric support column structure involved in the above embodiments.

[0146] After the bonding step, there is also a step of thinning the bonded wafer. Figure 7 A schematic diagram of thinning a bonded wafer is shown in:

[0147] S4, thinning the device support layer 101a to form a second conductive support layer 301a. Other properties and connection relationships of the second conductive support layer 301a are the same as those of the device support layer 101a.

[0148] After thinning, the second conductive support layer 301a, the first shielding unit 107a, the shielding interconnection region and the base support layer 201a are connected to form a fixed potential structure. In the case where the base dielectric isolation layer 202a and the intermediate support layer 203a are formed in the cover wafer 20a, the second conductive support layer 301a, the first shielding unit 107a, the shielding interconnection region and the intermediate support layer 203a form a fixed potential structure after thinning. In the case where the second shielding unit 207a is formed on the intermediate support layer 203a, the second conductive support layer 301a, the first shielding unit 107a, the shielding interconnection region, the second shielding unit 207a, the base support layer 201a and the intermediate support layer 203a form a fixed potential structure after thinning.

[0149] According to some optional embodiments, when an air guide groove structure is formed on the base support layer 201a, the following steps are also included:

[0150] S4A, forming a third shielding unit on the second conductive support layer 301a of the bonded wafer 30a, and in the process of forming the third shielding unit, adjusting the atmosphere, air pressure and vacuum degree in the structural gap 105a by using the gas guide groove structure, and making the third shielding unit fill the gas guide groove structure.

[0151] According to some optional embodiments, when an air guide groove structure is formed on the middle support layer 203a, the following steps are also included:

[0152] S4B, forming a third shielding unit on the second conductive support layer 301a of the bonded wafer 30a, and in the process of forming the third shielding unit, adjusting the atmosphere, air pressure and vacuum degree in the structural gap 105a by using the air guide groove structure, and making the third shielding unit fill the air guide groove structure.

[0153] According to some optional embodiments, the preparation method further comprises the following steps:

[0154] S5, forming a second interconnect unit 302a and a dielectric isolation structure 303a on the second conductive support layer 301a, Figure 8 Schematic diagram of forming a second interconnection unit and a dielectric isolation structure on a second conductive support layer is shown in FIG.

[0155] According to some optional embodiments, this step may also include:

[0156] A dielectric insulating layer 310a is formed on the upper part of the second conductive support layer 301a, and a fixed potential electrode 308a and a conductive contact structure 304a are formed on the dielectric insulating layer 310a. The fixed potential electrode 308a is connected to the second conductive support layer 301a, and is used to provide a fixed potential for the fixed potential structure. The second interconnect unit 302a can be connected to the first interconnect unit 108a formed in the above-mentioned MEMS device area, and the MEMS device area is connected to the conductive contact structure 304a to form a conductive path of the MEMS device, thereby leading out the electrical signal. The dielectric isolation structure 303a is used to provide dielectric isolation between the second conductive support layer 301a and the conductive path. A metal wire 305a and an electrical signal metal electrode 306a can also be formed in the dielectric insulating layer 310a, which can be electrically connected to the conductive path as needed. Finally, a passivation protection layer 307a located on the top layer can also be formed on the dielectric insulating layer 310a. Fig. 9 FIG. 1 shows a schematic structural diagram of a shielding structure obtained by a preparation method according to an embodiment of the present invention, Fig.10FIG. 2 shows a schematic structural diagram of a shielding structure obtained by a preparation method according to another embodiment of the present invention.

[0157] The method for preparing a shielding structure for a MEMS device provided in this embodiment of the present invention realizes the preparation of a shielding structure for a MEMS device. The shielding structure uses a shielding unit (such as a first shielding unit 107a, a second shielding unit 207a, and a third shielding unit) to connect one or more of the base support layer, the device support layer, and the intermediate support layer to the shielding interconnection area of ​​the device layer to form a fixed potential structure, and finally connects to a fixed potential or grounding, and accommodates the core structure of the MEMS device in the shielding structure. The core structure of the MEMS device and the shielding structure are physically isolated or dielectrically isolated by an insulating structure, and the electromagnetic shielding of the core structure of the MEMS device is achieved without additionally increasing the size of the device. In addition, by setting an air guide groove structure connected to the concave cavity structure, the vacuum degree of the structural gap accommodating the MEMS device can be adjusted when the shielding unit is subsequently manufactured, so that a stable working atmosphere environment can be provided while realizing the electromagnetic shielding of the MEMS device. The MEMS device involved in the embodiment of the present invention includes but is not limited to sensitive device structures such as resonators, accelerometers, gyroscopes, and pressure sensors. By placing the MEMS device in the shielding structure, the environmental adaptability of the device can be greatly improved.

[0158] An embodiment of the present invention further provides a method for preparing a shielding structure for a MEMS device. The preparation method of this embodiment comprises the following steps:

[0159] S1. Prepare MEMS device wafer. Fig.11A A schematic structural diagram of a wafer with a MEMS device in another embodiment is shown in FIG.

[0160] S11, forming a device support layer 101b. The device support layer 101b is made of a conductive material, such as silicon, doped polysilicon, metal or other conductive material.

[0161] S12, forming a device dielectric isolation layer 102b on the device support layer 101b. The device dielectric isolation layer 102b is made of an insulating material, such as silicon dioxide, silicon nitride, or other insulating material.

[0162] S13. Form a device layer 103b on the device dielectric isolation layer 102b. The device layer 103b includes a MEMS device region and a shielding interconnection region.

[0163] According to some optional embodiments, step S1 may further include:

[0164] S14, forming a first interconnect unit 108b, a fixed anchor structure 104b of the MEMS device, a structural gap 105b of the MEMS device, and a movable structure 106b of the MEMS device in the MEMS device region of the device layer 103b. The first interconnect unit 108b passes through the device dielectric isolation layer 102b. In the MEMS device region of the device layer 103b, the first interconnect unit 108a can be used for electrical connection of the MEMS device.

[0165] According to some optional embodiments, the step S1 of preparing the MEMS device wafer may further include forming SiO on the upper portion of the device layer 103b. 2 Layer 109b, to form Si-SiO with cover wafer 20b 2 Bonding or SiO 2 -SiO 2 Bonding, Fig. 11B Figure 2 shows that when preparing a MEMS device wafer, SiO is formed on the upper part of the device layer. 2 Schematic diagram of the layers.

[0166] S2. Prepare a cover wafer. The cover wafer 20b can be prepared by the following steps:

[0167] S21. Form a basic support layer 201b. The material of the basic support layer 201b is a conductive material, for example, it can be a conductive material such as silicon, doped polysilicon and metal. According to some optional embodiments, a cavity structure 204b and a dielectric support column structure 209b can also be formed on the basic support layer 201b. The dielectric support column structure 209b can play an insulating support role. An air guide groove structure 208b can also be formed on the basic support layer 201b. The air guide groove structure 208b is, for example, connected to the cavity structure 204b. After forming the bonding wafer 30b, the air guide groove structure 208b is connected to the structural gap 105b of the MEMS device in the bonding wafer 30b, and is used to adjust the atmosphere, air pressure, vacuum degree and other parameters in the MEMS device during the preparation process. Fig. 12A Schematic diagram of the structure of the cover wafer of this embodiment is shown in FIG.

[0168] According to some optional embodiments, the preparation of the cover wafer may further include the following steps:

[0169] S22, forming a basic dielectric isolation layer 202b on the basic support layer 201b, wherein the basic dielectric isolation layer 202b is made of an insulating material, such as silicon dioxide, silicon nitride or other insulating material.

[0170] S23, forming an intermediate support layer 203b on the base dielectric isolation layer 202b, the material of the intermediate support layer 203b is also a conductive material, the base support layer 201b and the intermediate support layer 203b are insulated. A cavity structure 204b, a support column isolation structure 205b, a support column structure 206b and an air guide groove structure 208b can also be formed on the intermediate support layer 203b. Fig. 12B and Fig. 12C Schematic diagrams of the structures of the cover wafer of this embodiment are shown in FIG.

[0171] According to some optional embodiments, a shielding unit may also be formed on the intermediate supporting layer:

[0172] S24, forming a second shielding unit 207b on the intermediate support layer 203b, the second shielding unit 207b penetrates the basic dielectric isolation layer 202b. A gas guide groove structure 208b may also be formed on the intermediate support layer 203b, the gas guide groove structure 208b is, for example, connected to the concave cavity structure 204b, and the gas guide groove structure 208b is connected to the structural gap 105b of the MEMS device in the bonding wafer 30b after forming the bonding wafer 30b, and is used to adjust the atmosphere, air pressure, vacuum degree and other parameters in the MEMS device during the preparation process. Fig.12D Schematic diagram of the structure of the cover wafer of this embodiment is shown in FIG.

[0173] S3, bonding the MEMS device wafer 10b and the cover wafer 20b to form a bonded wafer 30b. When forming an intermediate support layer 203b on the base dielectric isolation layer 202b, the intermediate support layer 203b is connected to the shielding interconnection area of ​​the bonded wafer 30b.

[0174] Fig.13A FIG. 1 shows a schematic diagram of bonding a MEMS device wafer and a cover wafer to form a bonded wafer when the cover wafer is only formed with a base support layer and a gas guide groove structure is formed on the base support layer. Fig.13A As shown, an air guide groove structure 208b is formed on the base support layer 201b. Fig. 13B The upper part of the device layer is shown in Fig. 2 When the MEMS device wafer and the cover wafer are bonded together, a schematic diagram of a bonded wafer is formed. Fig.14A , when the cover wafer further includes a base dielectric isolation layer and an air guide groove structure is formed on the intermediate support layer, in which the MEMS device wafer and the cover wafer are bonded to form a schematic diagram of a bonded wafer. Fig. 14B Figure 2 shows that when preparing a MEMS device wafer, SiO is formed on the upper part of the device layer. 2When the second shielding unit and the air guide groove structure are formed on the intermediate support layer, the MEMS device wafer and the cover wafer are bonded to form a schematic diagram of a bonded wafer. Fig.15 , a schematic diagram of bonding a MEMS device wafer and a cover wafer to form a bonded wafer is shown in FIG.

[0175] According to some optional embodiments, the preparation method further comprises the steps of:

[0176] S4. Thinning the device support layer 101b to form a second conductive support layer 301b.

[0177] S5. Form a second interconnect unit 302b, a dielectric isolation structure 303b and a third shielding unit 309b on the second conductive support layer 301b of the bonding wafer 30b. The third shielding unit 309b penetrates the device dielectric isolation layer 102b. The third shielding unit 309b is connected to the base support layer 201b, the second conductive support layer 301b and the shielding interconnection area to form a fixed potential structure. When only the base support layer is formed in the cover wafer, Fig.16A The schematic diagram of the structure of the shielding structure obtained by the preparation method of this embodiment is shown in FIG. Fig. 16B The figure shows that SiO is formed on the upper part of the device layer of the MEMS device wafer. 2 In the case of the layer, a schematic structural diagram of the shielding structure is obtained.

[0178] According to certain optional embodiments, when a basic dielectric isolation layer and an intermediate support layer are formed in the cover wafer, the third shielding unit 309b can be connected to the second conductive support layer 301b, the intermediate support layer 203b and the shielding interconnection area to form a fixed potential structure. Fig.17A A schematic structural diagram of the shielding structure obtained by the preparation method of this embodiment is shown in FIG.

[0179] According to some optional embodiments, when an air guide groove structure is formed on the intermediate support layer, a third shielding unit 309b is formed on the second conductive support layer 301b of the bonded wafer 30b. In the process of forming the third shielding unit 309b, the atmosphere, air pressure, vacuum and other parameters in the structural gap 105b of the MEMS device are adjusted through the air guide groove structure 208b. After each parameter is adjusted to a desired state, the state is maintained, and the third shielding unit 309b continues to extend toward the intermediate support layer 203b, so that the third shielding unit 309b finally fills the air guide groove structure 208b, thereby locking the atmosphere, air pressure and vacuum environment in the structural gap 105b of the MEMS device. The finally prepared shielding structure does not have the air guide groove structure 208b. Fig. 17B A schematic structural diagram of the shielding structure obtained by the preparation method of this embodiment is shown in FIG. Fig. 17C Figure 2 shows that when preparing a MEMS device wafer, SiO is formed on the upper part of the device layer. 2 In the case of the layer, a schematic structural diagram of the shielding structure is obtained.

[0180] According to certain optional embodiments, when a second shielding unit 207b is formed on the intermediate supporting layer 203b, the third shielding unit 309b can be connected to the second shielding unit 207b and connected to the second conductive supporting layer 301b, the intermediate supporting layer 203b, the base supporting layer 201b and the shielding interconnection area to form a fixed potential structure.

[0181] Fig.18 A schematic structural diagram of the shielding structure obtained by the preparation method of this embodiment is shown in FIG.

[0182] In the above embodiments, the base support layer 201b, the device support layer 101b, the second conductive support layer 301b, the intermediate support layer 203b, the device layer 103b and the third shielding unit 309c are made of conductive materials; the device dielectric isolation layer 102b and the base dielectric isolation layer 202b are made of insulating materials. The fixed potential structure surrounds the MEMS device area, and the fixed potential structure is electrically insulated from the MEMS device area by the insulating structure.

[0183] According to certain optional embodiments, in the above step S5, a third shielding unit 309b is formed on the second conductive support layer 301b of the bonded wafer 30b, and the third shielding unit 309b can also penetrate the device dielectric isolation layer 102b and the basic dielectric isolation layer 202b at the same time, so that the third shielding unit 309b is connected to the second conductive support layer 301b, the basic support layer 201b and the shielding interconnection area to form a fixed potential structure.

[0184] According to some optional embodiments, the preparation method further comprises the steps of:

[0185] S6. Form a dielectric insulating layer 310b on the second conductive support layer 301b, and form a fixed potential electrode 308b and a conductive contact structure 304b on the dielectric insulating layer 310b. The fixed potential electrode 308b is connected to the second conductive support layer 301b, and is used to provide a fixed potential for the fixed potential structure. The second interconnect unit 302b can be connected to the first interconnect unit 108b formed in the above-mentioned MEMS device area, and connect the MEMS device area with the conductive contact structure 304b to form a conductive path of the MEMS device. The dielectric isolation structure 303b is used to provide dielectric isolation between the second conductive support layer 301b and the conductive path. Metal wires 305b and electrical signal metal electrodes 306b can also be formed in the dielectric insulating layer 310b, which can be electrically connected to the conductive path as needed. Finally, a metal and passivation protection layer 307b located on the top layer can be formed on the dielectric insulating layer 310b. In the above embodiments, the shielding structure obtained is as follows Fig.16A , Fig. 16B , Fig.17A , Fig. 17B , Fig. 17C as well as Fig.18 shown.

[0186] The method for preparing a shielding structure for a MEMS device provided in this embodiment of the present invention forms a shielding unit on the device support layer of the bonded wafer after forming a bonded wafer, and can also fill an air guide groove structure for adjusting parameters such as atmosphere, air pressure and vacuum degree in the gap of the MEMS device structure, which can be selected according to the needs and process level of the MEMS device.

[0187] On the basis of the above embodiments, different wafers with MEMS devices are bonded to different cover wafers to form different bonded wafers. When performing the bonding step, the bonding processes used in different embodiments are slightly different, which can be Si-Si direct bonding, Si-SiO 2 Bonding, SiO 2 -SiO 2 Bonding, and then set different shielding units according to the needs of different devices and process conditions to meet the needs of MEMS devices for microcavities with different vacuum degrees and shielding.

[0188] The method for preparing the shielding structure for MEMS devices provided in the above embodiment of the present invention can meet the requirements of MEMS devices for different vacuum degrees and shielding. The floating potential of the cover wafer and the supporting substrate around the MEMS device is released or locked by the shielding unit; at the same time, an air guide groove structure connected to the concave cavity structure can also be provided. When the shielding unit is subsequently manufactured, the vacuum degree of the structural gap accommodating the MEMS device can be adjusted, so that a stable working atmosphere environment can be provided while realizing the electromagnetic shielding of the MEMS device.

[0189] The embodiment of the present invention further provides a shielding structure for a MEMS device, the shielding structure is as follows Figure 4B As shown, including:

[0190] First conductive support layer In this embodiment, the first conductive support layer is, for example, a base support layer 201a.

[0191] The device layer 103a is formed on the base support layer 201a, and the device layer 103a includes a MEMS device region and a shielding interconnection region.

[0192] The device dielectric isolation layer 102a is formed on the device layer 103a.

[0193] The second conductive support layer 301a is formed on the device dielectric isolation layer 102a. The shielding unit, for example, is a first shielding unit 107a formed in the shielding interconnection area of ​​the device layer 103a. The shielding unit penetrates the device dielectric isolation layer 102a, and is connected to the base support layer 201a, the device support layer 101a and the shielding interconnection area to form a fixed potential structure. The shielding unit can also be, for example, a third shielding unit 309b formed on the second conductive support layer 301b of the bonding wafer 30b. The third shielding unit 309b penetrates the device dielectric isolation layer 102b and extends to the shielding interconnection area of ​​the device layer 103b, and is connected to the base support layer 201b, the second conductive support layer 301b and the shielding interconnection area to form a fixed potential structure. The schematic diagram of the shielding structure of this embodiment is shown in FIG. Fig.16A As shown. The fixed potential structure surrounds the MEMS device area, and the fixed potential structure is electrically insulated from the MEMS device area by an insulating structure. Among them, the material of the basic support layer 201a, 201b, the device support layer 101a, 101b, the device layer 103a, 103b and the shielding unit is a conductive material; the material of the device dielectric isolation layer 102a, 102b is an insulating material. According to some optional embodiments, the shielding structure also includes:

[0194] The basic dielectric isolation layer 202a is formed on the basic supporting layer 201a.

[0195] The middle support layer 203a is formed on the base dielectric isolation layer 202a.

[0196] The device layer 103a is formed on the intermediate support layer 203a.

[0197] According to some optional embodiments, the first conductive support layer is, for example, an intermediate support layer 203a, and the shielding structure further includes:

[0198] The intermediate support layer 203a is formed on the basic dielectric isolation layer 202a.

[0199] The basic support layer 201a, the basic dielectric isolation layer 202a is formed on the basic support layer 201a. The shielding unit penetrates the device dielectric isolation layer 102a, and is connected to the device support layer 101a, the intermediate support layer 203a and the shielding interconnection area of ​​the device layer 103a to form a fixed potential structure. The schematic diagram of the shielding structure involved in this embodiment is shown in FIG. Fig. 9 The material of the basic dielectric isolation layer 202a is an insulating material, and the material of the intermediate support layer 203 is a conductive material.

[0200] According to some optional embodiments, the shielding unit is, for example, a first shielding unit 107a formed in the shielding interconnection area of ​​the device layer and a second shielding unit 207a formed in the intermediate support layer 203a. The shielding unit penetrates the device dielectric isolation layer 102a and the base dielectric isolation layer 202a, and is connected to the device support layer 101a, the intermediate support layer 203a, the base support layer 201a and the above-mentioned shielding interconnection area to form a fixed potential structure. The schematic diagram of the shielding structure involved in this embodiment is shown in FIG. Fig.10 The shielding unit may also be, for example, a third shielding unit 309b formed on the second conductive support layer 301b of the bonding wafer 30b. The third shielding unit 309b penetrates the device dielectric isolation layer 102b and is connected to the device support layer 101b (or the thinned device support layer 301b), the intermediate support layer 203b and the above-mentioned shielding interconnection area to form a fixed potential structure. The schematic diagram of the shielding structure involved in this embodiment is shown in Fig.17A The shielding unit may also be, for example, a third shielding unit 309b formed on the second conductive support layer 301b of the bonding wafer 30b and a second shielding unit 207a formed on the intermediate support layer 203a. The shielding unit penetrates the device dielectric isolation layer 102b and the base dielectric isolation layer 202a, and is connected to the second conductive support layer 301b, the intermediate support layer 203b, the base support layer 201b and the above-mentioned shielding interconnection area to form a fixed potential structure. The schematic diagram of the shielding structure involved in this embodiment is shown in Fig.18 shown.

[0201] According to some optional embodiments, the shielding structure further includes:

[0202] The dielectric insulating layer 310a is formed on the second conductive supporting layer 301a.

[0203] The dielectric insulating layer 310a is formed with a fixed potential electrode 308a, which is connected to the second conductive support layer 301a and is used to provide a fixed potential for the above-mentioned fixed potential structure.

[0204] The interconnection unit runs through the device dielectric isolation layer 102a and is made of a conductive material.

[0205] The conductive contact structure 304a is formed in the dielectric insulating layer, and the interconnection unit is used to connect the MEMS device region with the conductive contact structure. The interconnection unit is, for example, a first interconnection unit 108a formed in the MEMS device region of the device layer 103a and a second interconnection unit 302a formed on the device support layer 101a (or the thinned device support layer 301a). The first interconnection unit 108a and the second interconnection unit 302a are connected, and the MEMS device region is connected to the conductive contact structure 304a, forming a conductive path of the MEMS device, thereby leading out the electrical signal.

[0206] In summary, the embodiments of the present invention relate to a shielding structure for MEMS devices and a preparation method thereof, which can meet the requirements of MEMS devices for different vacuum degrees and shielding. The floating potential of the cover wafer and the supporting substrate around the MEMS device is released or locked by the shielding unit; at the same time, an air guide groove structure connected to the concave cavity structure can also be provided. When the shielding unit is subsequently manufactured, the vacuum degree of the structural gap accommodating the MEMS device can be adjusted, so that a stable working atmosphere environment can be provided while realizing the electromagnetic shielding of the MEMS device.

[0207] It should be understood that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present invention (including claims) is limited to these examples; under the idea of ​​the present invention, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other changes in different aspects of one or more embodiments of the present invention as described above, which are not provided in detail for the sake of simplicity. The above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the scope of protection of the present invention. In addition, the claims attached to the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the attached claims, or the equivalent forms of such scope and boundaries.

Claims

1. A shielding structure for a MEMS device, characterized in that: include: a first conductive support layer; A device layer, formed on the first conductive support layer, the device layer comprising a MEMS device region and a shielding interconnection region; A device dielectric isolation layer, formed on the device layer; A second conductive support layer, formed on the device dielectric isolation layer; a shielding unit, the shielding unit penetrating the device dielectric isolation layer and connected to the first conductive support layer, the second conductive support layer and the shielding interconnection region to form a fixed potential structure; The fixed potential structure surrounds the MEMS device region, and the fixed potential structure is electrically insulated from the MEMS device region by an insulating structure; Among them, the materials of the first conductive support layer, the second conductive support layer, the device layer and the shielding unit are conductive materials; the material of the device dielectric isolation layer is insulating material.

2. The shielding structure according to claim 1, characterized in that: The first conductive support layer is an intermediate support layer, and further comprises: A basic dielectric isolation layer, the intermediate support layer being formed on the basic dielectric isolation layer; A base support layer, the base medium isolation layer is formed on the base support layer; Wherein, the material of the basic dielectric isolation layer is an insulating material, and the material of the basic support layer is a conductive material.

3. The shielding structure according to claim 1, characterized in that: The first conductive support layer is a basic support layer, and further comprises: A basic dielectric isolation layer, formed on the basic support layer; An intermediate support layer formed on the base medium isolation layer; The device layer is formed on the intermediate support layer; The shielding unit penetrates the device dielectric isolation layer and the base dielectric isolation layer, and is connected to the second conductive support layer, the shielding interconnection region, the intermediate support layer and the base support layer to form a fixed potential structure; Wherein, the material of the basic dielectric isolation layer is an insulating material, and the material of the intermediate support layer is a conductive material.

4. The shielding structure according to any one of claims 1 to 3, characterized in that: Also includes: a dielectric insulating layer, formed on the second conductive supporting layer; The dielectric insulating layer is formed with a fixed potential electrode, and the fixed potential electrode is connected to the second conductive supporting layer and is used to provide a fixed potential for the fixed potential structure.

5. The shielding structure according to claim 4, characterized in that: Also includes: An interconnection unit, wherein the interconnection unit penetrates the device dielectric isolation layer and is made of a conductive material; The dielectric insulating layer is also formed with a conductive contact structure, and the interconnection unit connects the MEMS device region with the conductive contact structure.

6. A method for preparing a shielding structure for a MEMS device, characterized in that: Includes steps: S1. Preparation of MEMS device wafers: forming a device support layer; forming a device dielectric isolation layer on the device support layer; forming a device layer on the device dielectric isolation layer, wherein the device layer includes a MEMS device region and a shielding interconnection region; forming a first shielding unit in a shielding interconnection region of the device layer, wherein the first shielding unit penetrates the device dielectric isolation layer; S2. Prepare cover wafer: Forming a basic support layer; S3, bonding the MEMS device wafer and the cover wafer to form a bonded wafer, so that the device support layer, the first shielding unit, the shielding interconnection area and the base support layer are connected; S4, thinning the device support layer to form a second conductive support layer, wherein the second conductive support layer, the first shielding unit, the shielding interconnection region and the base support layer form a fixed potential structure; Wherein, the materials of the base support layer, the device support layer, the device layer and the first shielding unit are conductive materials; The device dielectric isolation layer is made of insulating material. The fixed potential structure surrounds the MEMS device region. The fixed potential structure is electrically insulated from the MEMS device region by an insulating structure.

7. The preparation method according to claim 6, characterized in that: The step S2 further comprises: forming a basic dielectric isolation layer on the basic support layer; forming an intermediate supporting layer on the basic dielectric isolation layer, wherein the basic supporting layer and the intermediate supporting layer are insulated from each other; In the step S3, the MEMS device wafer and the cover wafer are bonded to form a bonded wafer, so that the device support layer, the first shielding unit, the shielding interconnection area and the intermediate support layer are connected; In the step S4, the second conductive support layer, the first shielding unit, the shielding interconnection area and the intermediate support layer form a fixed potential structure; Wherein, the material of the basic dielectric isolation layer is an insulating material, and the material of the intermediate support layer is a conductive material.

8. The preparation method according to claim 7, characterized in that: The step S2 further comprises: forming a second shielding unit on the intermediate supporting layer, wherein the second shielding unit penetrates the basic dielectric isolation layer so that the basic supporting layer is connected to the intermediate supporting layer; In the step S3, the MEMS device wafer and the cover wafer are bonded to form a bonded wafer, so that the device support layer is connected to the first shielding unit, the shielding interconnection area, the second shielding unit, the base support layer, and the intermediate support layer; In the step S4, the second conductive supporting layer, the first shielding unit, the shielding interconnection area, the second shielding unit, the base supporting layer, and the intermediate supporting layer form a fixed potential structure; Wherein, the material of the second shielding unit is conductive material.

9. The preparation method according to any one of claims 6 to 8, characterized in that: Also includes the steps: S5, forming a dielectric insulating layer on the second conductive supporting layer, and forming a fixed potential electrode on the dielectric insulating layer; Wherein, the fixed potential electrode is connected to the second conductive support layer and is used to provide a fixed potential for the fixed potential structure.

10. The preparation method according to claim 9, characterized in that: The step S1 further comprises: forming an interconnection unit in a MEMS device region of the device layer, wherein the interconnection unit penetrates the device dielectric isolation layer; The step S5 further includes: forming a conductive contact structure on the dielectric insulating layer; Wherein, the interconnection unit connects the MEMS device region with the conductive contact structure.

11. The preparation method according to claim 6, characterized in that: The MEMS device area also includes a structural gap of the device; and step S2 further includes: forming an air guide groove structure on the base support layer, wherein the air guide groove structure is connected with the structural gap in the bonding wafer; After step S4, the method further includes step S4A: A third shielding unit is formed on the second conductive support layer of the bonded wafer. During the formation of the third shielding unit, the atmosphere, air pressure and vacuum degree in the structural gap are adjusted, and the third shielding unit fills the air guide groove structure.

12. The preparation method according to claim 7 or 8, characterized in that: The MEMS device area also includes a structural gap of the device; and step S2 further includes: forming an air guide groove structure on the intermediate support layer, wherein the air guide groove structure is connected with the structural gap in the bonding wafer; After step S4, the method further includes step S4B: A third shielding unit is formed on the second conductive support layer of the bonded wafer. During the formation of the third shielding unit, the atmosphere, air pressure and vacuum degree in the structural gap are adjusted, and the third shielding unit fills the air guide groove structure.

13. A method for preparing a shielding structure for a MEMS device, characterized in that: Includes steps: S1. Preparation of MEMS device wafers: forming a device support layer; forming a device dielectric isolation layer on the device support layer; forming a device layer on the device dielectric isolation layer, wherein the device layer includes a MEMS device region and a shielding interconnection region; S2. Prepare cover wafer: Forming a basic support layer; S3, bonding the MEMS device wafer and the cover wafer to form a bonded wafer; S4, thinning the device support layer to form a second conductive support layer; S5, forming a third shielding unit on the second conductive support layer of the bonded wafer, wherein the third shielding unit penetrates the device dielectric isolation layer; the second conductive support layer is connected to the third shielding unit, the shielding interconnection area and the base support layer to form a fixed potential structure; Wherein, the materials of the base support layer, the device support layer, the device layer and the third shielding unit are conductive materials; The material of the device dielectric isolation layer is an insulating material; the fixed potential structure surrounds the MEMS device area, and the fixed potential structure is electrically insulated from the MEMS device area by an insulating structure.

14. The preparation method according to claim 13, characterized in that: The step S2 further comprises: forming a basic dielectric isolation layer on the basic support layer; forming an intermediate supporting layer on the basic dielectric isolation layer, wherein the basic supporting layer and the intermediate supporting layer are insulated from each other; The shielding interconnection area of ​​the bonded wafer is connected to the intermediate support layer, Wherein, the third shielding unit is connected with the second conductive supporting layer, the intermediate supporting layer and the shielding interconnection area to form a fixed potential structure; Wherein, the material of the basic dielectric isolation layer is an insulating material, and the material of the intermediate support layer is a conductive material.

15. The preparation method according to claim 14, characterized in that: The step S2 further includes forming a second shielding unit on the middle supporting layer of the cover wafer, wherein the second shielding unit penetrates the basic dielectric isolation layer; The second shielding unit is connected to the second conductive supporting layer, the third shielding unit, the base supporting layer and the shielding interconnection area to form a fixed potential structure.

16. The preparation method according to any one of claims 13 to 15, characterized in that: Also includes the steps: S6, forming a dielectric insulating layer on the second conductive supporting layer, and forming a fixed potential electrode on the dielectric insulating layer; Wherein, the fixed potential electrode is connected to the second conductive support layer and is used to provide a fixed potential for the fixed potential structure.

17. The preparation method according to claim 16, characterized in that: The step S1 further comprises: forming an interconnection unit in a MEMS device region of the device layer, wherein the interconnection unit penetrates the device dielectric isolation layer; The step S6 further includes: forming a conductive contact structure on the dielectric insulating layer; Wherein, the interconnection unit connects the MEMS device region with the conductive contact structure.

18. The preparation method according to claim 13, characterized in that: The MEMS device area also includes a structural gap of the device; and step S2 further includes: forming an air guide groove structure on the base support layer, wherein the air guide groove structure is connected with the structural gap in the bonding wafer; The step S5 further comprises: A third shielding unit is formed on the second conductive support layer of the bonded wafer. During the formation of the third shielding unit, the atmosphere, air pressure and vacuum degree in the structural gap are adjusted, and the third shielding unit fills the air guide groove structure.

19. The preparation method according to claim 14 or 15, characterized in that: The MEMS device area also includes a structural gap of the device; and step S2 further includes: forming an air guide groove structure on the intermediate support layer, wherein the air guide groove structure is connected with the structural gap in the bonding wafer; The step S5 further comprises: A third shielding unit is formed on the second conductive support layer of the bonded wafer. During the formation of the third shielding unit, the atmosphere, air pressure and vacuum degree in the structural gap are adjusted, and the third shielding unit fills the air guide groove structure.

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