MEMS device and manufacturing method therefor

Abstract

A manufacturing method for an MEMS device. The method comprises: forming a first MEMS structure and a second MEMS structure on a first surface of a second substrate (31), wherein a first substrate (21) comprises a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure; sequentially forming a sacrificial layer (22) and a protective layer (23) on a first surface of the first substrate (21); forming a first cavity (211) and a first air extraction hole (213) in the first region, and forming a second cavity (212) in the second region; bonding a second surface of the first substrate (21) to the first surface of the second substrate (31); forming a plurality of second air extraction holes (231) in the protective layer (23); forming a third cavity (221) in the sacrificial layer (22), wherein the second air extraction holes (231) are in communication with the third cavity (221); and extracting air from the first cavity (211) by means of the second air extraction holes (231), the third cavity (221) and the first air extraction hole (213), and filling the second air extraction holes (231) with a metal layer. The manufacturing method for an MEMS device can realize the sealing of air extraction holes without the use of a laser sealing process, thereby solving the problem of the sealing of large-size air extraction holes, and reducing the manufacturing cost. Further provided is an MEMS device.

Description

MEMS device and manufacturing method thereof Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a MEMS device and a manufacturing method thereof. Background Art

[0002] In order to integrate different MEMS devices (such as accelerometers and gyroscopes) with different vacuum degrees in the same wafer, as shown in Figure 1, the first substrate 11 is bonded to the second substrate 12, and the vacuum degrees of some MEMS devices are adjusted during bonding; and, an exhaust hole 121 is etched in the second substrate 12, and air is exhausted through the exhaust hole 121 to increase the vacuum degree of the cavity connected to the exhaust hole 121, that is, the vacuum degree of the remaining MEMS devices is adjusted through the exhaust hole 121, and after the vacuum degree reaches the requirement, a laser sealing process is adopted, and the exhaust holes 121 are sealed one by one using a special machine.

[0003] However, when the thickness of the second substrate 12 is very thick, the etching process capability affects the width of the exhaust holes 121 etched in the second substrate 12, resulting in poor sealing effect or even inability to seal the exhaust holes 121 using the laser sealing process; moreover, the dedicated machine used in the laser sealing process is expensive, and the exhaust holes 121 are sealed one by one during operation, resulting in low sealing efficiency, which in turn leads to high costs.

[0004] Therefore, it is necessary to improve the sealing process of the air extraction holes to avoid the above problems.

[0005] Summary of the Invention

[0006] The object of the present invention is to provide a MEMS device and a manufacturing method thereof, which can achieve the sealing of the exhaust holes without adopting a laser sealing process, while solving the problem of sealing large-sized exhaust holes and reducing costs.

[0007] To achieve the above object, the present invention provides a method for manufacturing a MEMS device, comprising:

[0008] Providing a first substrate and a second substrate, wherein a first surface of the second substrate is formed with a first MEMS structure and a second MEMS structure, and the first substrate includes a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure;

[0009] forming a sacrificial layer and a protective layer in sequence to cover the first surface of the first substrate, wherein the protective layer covers the sacrificial layer;

[0010] Etching the second surface of the first substrate to form a first cavity and a first pumping hole in the first region, and a second cavity in the second region, wherein the first pumping hole exposes the sacrificial layer;

[0011] bonding the second surface of the first substrate to the first surface of the second substrate, wherein the first gas extraction hole is connected to the first cavity after bonding;

[0012] forming a plurality of second exhaust holes in the protective layer; before bonding the second surface of the first substrate to the first surface of the second substrate, releasing a portion of the sacrificial layer through the first exhaust holes to form a third cavity in the sacrificial layer; or, after forming a plurality of second exhaust holes in the protective layer, releasing a portion of the sacrificial layer through the second exhaust holes to form a third cavity in the sacrificial layer; the second exhaust holes are in communication with the third cavity;

[0013] The first cavity is evacuated through the second evacuation hole, the third cavity and the first evacuation hole, and the metal layer is filled in the second evacuation hole.

[0014] Optionally, the positions of the first air extraction hole and the second air extraction hole are staggered.

[0015] Optionally, the width of the second air extraction hole is smaller than the width of the first air extraction hole.

[0016] Optionally, the width of the first air extraction hole is 10 μm to 20 μm, and the width of the second air extraction hole is 1 μm to 5 μm.

[0017] Optionally, a fourth cavity is further formed in the first area; and the step of forming the first cavity, the first air extraction hole, and the fourth cavity in the first area, and forming the second cavity in the second area includes:

[0018] Etching the second surface of the first substrate to form a first cavity and a fourth cavity in the first region, and forming a second cavity in the second region;

[0019] The bottom wall of the fourth cavity is etched to form a first exhaust hole on the bottom wall of the fourth cavity.

[0020] Optionally, before etching the second surface of the first substrate, the method for manufacturing the MEMS device further includes:

[0021] forming a first bonding ring on the second surface of the first substrate;

[0022] Before bonding the second surface of the first substrate to the first surface of the second substrate, the method for manufacturing the MEMS device further includes:

[0023] forming a second bonding ring on the first surface of the second substrate;

[0024] Bonding the second surface of the first substrate to the first surface of the second substrate includes: bonding the second surface of the first substrate to the first surface of the second substrate through the first bonding ring and the second bonding ring.

[0025] Optionally, the first MEMS structure includes a comb-tooth structure of a gyroscope, and the second MEMS structure includes a comb-tooth structure of an accelerometer.

[0026] The present invention also provides a MEMS device, comprising:

[0027] a second substrate, wherein a first surface of the second substrate is formed with a first MEMS structure and a second MEMS structure;

[0028] A first substrate, wherein the second surface of the first substrate is bonded to the first surface of the second substrate; the first substrate includes a first area corresponding to the first MEMS structure and a second area corresponding to the second MEMS structure, the first area is formed with a first cavity and a first pumping hole, and the second area is formed with a second cavity; the first surface of the first substrate is covered with a sacrificial layer and a protective layer, the protective layer covers the sacrificial layer, a third cavity is formed in the sacrificial layer, a plurality of second pumping holes are formed in the protective layer, the first pumping hole is respectively connected to the first cavity and the third cavity, and the third cavity is connected to the second pumping hole; the second pumping hole is filled with a metal layer.

[0029] Optionally, the positions of the first air extraction hole and the second air extraction hole are staggered.

[0030] Optionally, the width of the second air extraction hole is smaller than the width of the first air extraction hole.

[0031] Optionally, the width of the first air extraction hole is 10 μm to 20 μm, and the width of the second air extraction hole is 1 μm to 5 μm.

[0032] Optionally, a fourth cavity communicating with the first air extraction hole is further formed in the first region, and the first air extraction hole is located between the third cavity and the fourth cavity.

[0033] Optionally, the MEMS device further includes:

[0034] a first bonding ring formed on the second surface of the first substrate;

[0035] A second bonding ring is formed on the first surface of the second substrate, and the second surface of the first substrate is bonded to the first surface of the second substrate through the first bonding ring and the second bonding ring.

[0036] Optionally, the first MEMS structure includes a comb-tooth structure of a gyroscope, and the second MEMS structure includes a comb-tooth structure of an accelerometer.

[0037] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0038] 1. The manufacturing method of the MEMS device of the present invention comprises the following steps: forming a sacrificial layer and a protective layer in sequence to cover the first surface of the first substrate; etching the second surface of the first substrate to form a first cavity and a first exhaust hole in the first area, and forming a second cavity in the second area, wherein the first exhaust hole exposes the sacrificial layer; and after bonding the second surface of the first substrate to the first surface of the second substrate, forming a plurality of second exhaust holes in the protective layer; and forming a third cavity in the sacrificial layer to communicate with the second exhaust holes and the first exhaust holes; exhausting the first cavity through the second exhaust holes, the third cavity and the first exhaust holes, and filling the second exhaust holes with a metal layer, so that the exhaust holes can be sealed without adopting a laser sealing process, and the problem of sealing large-sized exhaust holes can be solved, and the cost can be reduced.

[0039] 2. The MEMS device of the present invention comprises: a second substrate, a first surface of the second substrate is formed with a first MEMS structure and a second MEMS structure; a first substrate, the second surface of the first substrate is bonded to the first surface of the second substrate; the first substrate comprises a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure, the first region is formed with a first cavity and a first pumping hole, and the second region is formed with a second cavity; the first surface of the first substrate is covered with a first sacrificial layer and a protective layer, the protective layer covers the first sacrificial layer, a third cavity is formed in the first sacrificial layer, a plurality of second pumping holes are formed in the protective layer, the first pumping hole is respectively connected to the first cavity and the third cavity, and the third cavity is connected to the second pumping hole; the second pumping hole is filled with a metal layer, so that the pumping hole can be sealed without adopting a laser sealing process, and at the same time, the problem of sealing large-sized pumping holes can be solved and the cost can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG1 is a schematic cross-sectional view of a MEMS device;

[0041] FIG2 is a flow chart of a method for manufacturing a MEMS device according to an embodiment of the present invention;

[0042] 3 a to 3 k are schematic cross-sectional views of the MEMS device in the manufacturing method of the device shown in FIG. 2 .

[0043] Among them, the figure marks in Figures 1 to 3k are explained as follows: 11-first substrate; 12-second substrate; 121-exhaust hole; 21-first substrate; 211-first cavity; 212-second cavity; 213-first exhaust hole; 214-fourth cavity; 22-first sacrificial layer; 221-third cavity; 23-protective layer; 231-second exhaust hole; 24-first bonding ring; 25-gas absorption layer; 31-second substrate; 311-semiconductor base; 312-first insulating dielectric layer; 313-conductive structure; 314-second sacrificial layer; 3141-fifth cavity; 315-semiconductor layer; 3151-release hole; 316-second insulating dielectric layer; 32-second bonding ring; 41-metal layer. DETAILED DESCRIPTION

[0044] An embodiment of the present invention provides a method for manufacturing a MEMS device. Referring to FIG. 2 , FIG. 2 is a flow chart of the method for manufacturing a MEMS device according to an embodiment of the present invention. The method for manufacturing a MEMS device includes:

[0045] Step S1, providing a first substrate and a second substrate, wherein a first MEMS structure and a second MEMS structure are formed on a first surface of the second substrate, and the first substrate includes a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure;

[0046] Step S2, sequentially forming a sacrificial layer and a protective layer covering the first surface of the first substrate, wherein the protective layer covers the sacrificial layer;

[0047] Step S3, etching the second surface of the first substrate to form a first cavity and a first pumping hole in the first region, and a second cavity in the second region, wherein the first pumping hole exposes the sacrificial layer;

[0048] Step S4, bonding the second surface of the first substrate to the first surface of the second substrate, wherein the first exhaust hole is connected to the first cavity after bonding;

[0049] Step S5, forming a plurality of second exhaust holes in the protective layer; before bonding the second surface of the first substrate to the first surface of the second substrate, releasing a portion of the sacrificial layer through the first exhaust holes to form a third cavity in the sacrificial layer; or, after forming a plurality of second exhaust holes in the protective layer, releasing a portion of the sacrificial layer through the second exhaust holes to form a third cavity in the sacrificial layer; the second exhaust holes are in communication with the third cavity;

[0050] Step S6: evacuate the first cavity through the second evacuation hole, the third cavity, and the first evacuation hole, and fill the second evacuation hole with a metal layer.

[0051] 3a to 3k , a more detailed description of the method for manufacturing the MEMS device provided in this embodiment is provided. FIG. 3a to 3k are schematic diagrams of the device in the method for manufacturing the MEMS device shown in FIG. 2 , and FIG. 3a to 3k are also schematic diagrams of longitudinal cross-sections of the MEMS device.

[0052] According to step S1, referring to Figures 3a and 3h, a first substrate 21 and a second substrate 31 are provided, a first surface of the second substrate 31 is formed with a first MEMS structure and a second MEMS structure, and the first substrate 21 includes a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure.

[0053] The first substrate 21 may be only a semiconductor base or a wafer including a semiconductor base, etc. Device structures such as transistors may be formed in the first substrate 21 as needed.

[0054] The semiconductor substrate is preferably a double-polished wafer, so that the performance of the structure manufactured in the first substrate 21 is better.

[0055] The first MEMS structure and the second MEMS structure may each include a comb-tooth structure and a proof mass.

[0056] As shown in Figure 3h, the second substrate 31 may include a semiconductor base 311 and a first insulating dielectric layer 312 covering the first surface of the semiconductor base 311, and a conductive structure 313 connected to the semiconductor base 311 is formed in the first insulating dielectric layer 312, and the first insulating dielectric layer 312 exposes the conductive structure 313; device structures may also be formed in the semiconductor base 311 and the first insulating dielectric layer 312, and the device structures may include transistors, etc.

[0057] The second substrate 31 may also include a second sacrificial layer 314 and a semiconductor layer 315 covering the first insulating dielectric layer 312, the semiconductor layer 315 covering the second sacrificial layer 314, and a fifth cavity 3141 formed in the second sacrificial layer 314, the fifth cavity 3141 exposing a portion of the first insulating dielectric layer 312 and a portion of the conductive structure 313; the comb tooth structure and mass block in the first MEMS structure and the comb tooth structure and mass block in the second MEMS structure are formed in the semiconductor layer 315, and release holes 3151 are formed in the comb tooth structure, between the mass blocks and the comb tooth structure, and between the mass blocks, and the release holes 3151 are connected to the fifth cavity 3141, and the fifth cavity 3141 is used to provide a vibration space for the comb tooth structure and the mass block.

[0058] Furthermore, the second substrate 31 may further include a second insulating dielectric layer 316 covering the second surface of the semiconductor base 311 , so as to insulate the second surface of the semiconductor base 311 from other structures.

[0059] Furthermore, as shown in FIG3h , before subsequently bonding the second surface of the first substrate 21 to the first surface of the second substrate 31, the method for manufacturing the MEMS device further includes: forming a second bonding ring 32 on the first surface of the second substrate 31. The second bonding ring 32 may be formed after forming the semiconductor layer 315 and before forming the release hole 3151. The second bonding ring 32 is formed on the semiconductor layer 315.

[0060] The steps of forming the second bonding ring 32 on the first surface of the second substrate 31 may include: first, forming a metal material on the first surface of the second substrate 31 using a sputtering or evaporation process; then, forming a patterned mask layer (not shown) on the metal material; then, etching the metal material using the patterned mask layer as a mask to form the second bonding ring 32; then, removing the patterned mask layer.

[0061] The material of the semiconductor substrate may include Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs, or other III / V compound semiconductors, and may also include a multilayer structure composed of these semiconductors; alternatively, the semiconductor substrate may be silicon-on-insulator (SOI), stacked silicon-on-insulator (SSOI), stacked silicon-germanium-on-insulator (S-SiGeOI), silicon-germanium-on-insulator (SiGeOI), germanium-on-insulator (GeOI), etc. Those skilled in the art may make the selection as needed.

[0062] The material of the semiconductor layer 315 may include Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs or other III / V compound semiconductors, and may also include a multilayer structure composed of these semiconductors.

[0063] The first insulating dielectric layer 312 and the second insulating dielectric layer 316 may be made of at least one insulating material selected from the group consisting of silicon oxide, silicon oxynitride, and silicon nitride. The first insulating dielectric layer 312 may be a stacked structure of at least two layers.

[0064] The conductive structure 313 may be made of polysilicon or metal.

[0065] The material of the second sacrificial layer 314 includes but is not limited to silicon oxide.

[0066] The second bonding ring 32 may be made of metal materials such as germanium, aluminum, copper, nickel, or gold.

[0067] According to step S2 , referring to FIG. 3 a and FIG. 3 b , a first sacrificial layer 22 and a protective layer 23 are sequentially formed to cover the first surface of the first substrate 21 , and the protective layer 23 covers the first sacrificial layer 22 .

[0068] The protection layer 23 is used to protect the first sacrificial layer 22 to prevent the first sacrificial layer 22 from being corroded by a cleaning process or the like in subsequent processes.

[0069] The etching rates of the first sacrificial layer 22 and the protective layer 23 are greatly different. For example, the etching selectivity ratio of the first sacrificial layer 22 to the protective layer 23 is greater than 10, so that when the first sacrificial layer 22 is subsequently etched, the protective layer 23 is avoided from being etched, or only a small amount of etching is performed on the protective layer 23.

[0070] The material of the first sacrificial layer 22 includes but is not limited to silicon oxide.

[0071] The material of the protection layer 23 can be silicon nitride, polycrystalline silicon, or single crystal silicon.

[0072] Furthermore, referring to FIG. 3 c , before subsequently etching the second surface of the first substrate 21 , the method for manufacturing the MEMS device further includes: forming a first bonding ring 24 on the second surface of the first substrate 21 .

[0073] The steps of forming the first bonding ring 24 on the second surface of the first substrate 21 may include: first, forming a metal material on the second surface of the first substrate 21 using a sputtering or evaporation process; then, forming a patterned mask layer (not shown) on the metal material; then, etching the metal material using the patterned mask layer as a mask to form the first bonding ring 24; and then, removing the patterned mask layer. While forming the first bonding ring 24, structures such as a pad may also be formed on the second surface of the first substrate 21.

[0074] The first bonding ring 24 may be made of metal materials such as germanium, aluminum, copper, nickel, or gold.

[0075] The first surface is the front surface, and the second surface is the back surface; or, the first surface is the back surface, and the second surface is the front surface.

[0076] According to step S3 , referring to FIG. 3 d to FIG. 3 f , the second surface of the first substrate 21 is etched to form a first cavity 211 and a first pumping hole 213 in the first region, and a second cavity 212 in the second region. The first pumping hole 213 exposes the first sacrificial layer 22 .

[0077] In one embodiment, a fourth cavity 214 may be formed in the first region.

[0078] The steps of forming a first cavity 211, a first exhaust hole 213 and a fourth cavity 214 in the first region, and forming a second cavity 212 in the second region may include: first, as shown in FIG3d, etching the second surface of the first substrate 21 to form the first cavity 211 and the fourth cavity 214 in the first region, and forming the second cavity 212 in the second region; then, as shown in FIG3f, etching the bottom wall of the fourth cavity 214 and stopping at the first sacrificial layer 22 to form the first exhaust hole 213 on the bottom wall of the fourth cavity 214.

[0079] Among them, because the etching process has requirements for the aspect ratio of the first exhaust hole 213 formed by etching, that is, the etching process cannot be implemented when the aspect ratio of the first exhaust hole 213 is too high, therefore, when the thickness of the first substrate 21 is very thick, it is preferred to first etch the fourth cavity 214 on the second surface of the first substrate 21, and then etch the first exhaust hole 213 on the bottom wall of the fourth cavity 214, that is, to etch through the first substrate 21 in two steps and expose the first sacrificial layer 22. It should be noted that even if the first substrate 21 is etched through in two steps, the width of the first exhaust hole 213 formed is still relatively large.

[0080] Among them, the fourth cavity 214 and the first exhaust hole 213 are both used for exhausting air, and the width of the fourth cavity 214 is greater than the width of the first exhaust hole 213; the first cavity 211 and the second cavity 212 are respectively used to provide vibration space for the first MEMS structure and the second MEMS structure after subsequent bonding, and the width and depth of the fourth cavity 214 are both smaller than the first cavity 211 and the second cavity 212. The formation order of the fourth cavity 214, the first cavity 211 and the second cavity 212 is not limited, and they can be formed simultaneously or at different times.

[0081] Furthermore, as shown in FIG3e , after forming the first cavity 211 and before forming the first gas extraction hole 213, the method for manufacturing the MEMS device may further include forming a gas absorption layer 25 on the bottom wall of the first cavity 211. The gas absorption layer 25 is used to absorb gas to improve the vacuum level of the MEMS device. The gas absorption layer 25 may be made of a metal material.

[0082] According to step S4 , referring to FIG. 3 i , the second surface of the first substrate 21 is bonded to the first surface of the second substrate 31 . After bonding, the fourth cavity 214 and the first exhaust hole 213 are connected to the first cavity 211 .

[0083] Moreover, after bonding, the first cavity 211 is aligned with the first MEMS structure, the second cavity 212 is aligned with the second MEMS structure, and the first cavity 211 and the second cavity 212 are not connected, so that a first MEMS device corresponding to the first cavity 211 and the first MEMS structure and a second MEMS device corresponding to the second cavity 212 and the second MEMS structure are formed on the same substrate.

[0084] Bonding the second surface of the first substrate 21 to the first surface of the second substrate 31 includes: bonding the second surface of the first substrate 21 to the first surface of the second substrate 31 via the first bonding ring 24 and the second bonding ring 32 .

[0085] The first bonding ring 24 and the second bonding ring 32 are both annular structures. The sizes of the first bonding ring 24 and the second bonding ring 32 may be the same or nearly the same. The first bonding ring 24 and the second bonding ring 32 may be eutectic bonded.

[0086] During bonding, the second surface of the first substrate 21 is positioned opposite the first surface of the second substrate 31, and the first bonding ring 24 is aligned with the second bonding ring 32. A certain pressure is applied so that the first bonding ring 24 and the second bonding ring 32 come into contact with each other and, under predetermined conditions, a bonding reaction occurs to form a metal block, thereby further shortening the distance between the first substrate 21 and the second substrate 31. When the first bonding ring 24 and the second bonding ring 32 are made of different materials (for example, the first bonding ring 24 is made of aluminum and the second bonding ring 32 is made of germanium), the metal block is an alloy.

[0087] Moreover, during bonding, the vacuum pressure control process can adopt the vacuum degree required by the second MEMS device corresponding to the second cavity 212, and at this time, the vacuum degree of the second MEMS device corresponding to the second cavity 212 is the same as the vacuum degree of the first MEMS device corresponding to the first cavity 211.

[0088] According to step S5 , referring to FIG. 3 j , the protection layer 23 is etched to form a plurality of second gas extraction holes 231 in the protection layer 23 .

[0089] Furthermore, referring to Figure 3g, before bonding the second surface of the first substrate 21 to the first surface of the second substrate 31, a portion of the first sacrificial layer 22 is released through the fourth cavity 214 and the first exhaust hole 213 to form a third cavity 221 in the first sacrificial layer 22; or, after forming a plurality of second exhaust holes 231 in the protective layer 23, a portion of the first sacrificial layer 22 is released through the second exhaust holes 231 to form a third cavity 221 in the first sacrificial layer 22.

[0090] The second air extraction hole 231 is communicated with the third cavity 221 . The third cavity 221 exposes the protective layer 23 . The width of the third cavity 221 is greater than that of the first air extraction hole 213 .

[0091] In which, a gaseous hydrofluoric acid (Vapor HF, VHF) etching process can be used to release part of the first sacrificial layer 22, that is, gaseous hydrofluoric acid is passed into the fourth cavity 214 and the first gas pumping hole 213 to etch and remove part of the first sacrificial layer 22 through the fourth cavity 214 and the first gas pumping hole 213; or, gaseous hydrofluoric acid is passed into the second gas pumping hole 231 to etch and remove part of the first sacrificial layer 22 through the second gas pumping hole 231.

[0092] Preferably, the positions of the first air extraction holes 213 and the second air extraction holes 231 are staggered. Since metal particles will fall downward through the second air extraction holes 231 when the metal layer 41 is subsequently filled into the second air extraction holes 231, by staggering the positions of the first air extraction holes 213 and the second air extraction holes 231, it is possible to prevent metal particles from falling into the first air extraction holes 213, thereby preventing metal particles from falling into the device through the first air extraction holes 213 and affecting device performance.

[0093] Among them, metal particles will fall and accumulate in the third cavity 221 below the second air extraction hole 231; the first air extraction hole 213 can be aligned with the middle area of ​​the third cavity 221, and the second air extraction hole 231 can be aligned with the edge area of ​​the third cavity 221, so that metal particles fall and accumulate in the edge area of ​​the third cavity 221.

[0094] Preferably, the width of the second air extraction hole 231 is smaller than the width of the first air extraction hole 213 , so that the metal layer 41 can quickly fill the second air extraction hole 231 , that is, quickly seal the hole.

[0095] More preferably, the width of the first air extraction hole 213 is 10 μm to 20 μm, and the width of the second air extraction hole 231 is 1 μm to 5 μm.

[0096] Since the etching process has requirements on the aspect ratio of the first exhaust hole 213 formed by etching, that is, when the aspect ratio of the first exhaust hole 213 is too high, the etching process cannot be implemented. Therefore, when the thickness of the first substrate 21 is very thick, the width of the first exhaust hole 213 formed by etching the first substrate 21 is also large. At this time, if the laser sealing process is directly used to seal the first exhaust hole 213, the effect of sealing the first exhaust hole 213 is not good or even cannot be sealed; in addition, the dedicated machine used for the laser sealing process is expensive, and the first exhaust holes 213 are sealed one by one during operation, resulting in low sealing efficiency, which in turn leads to high costs. Therefore, the manufacturing method of the MEMS device provided by the present invention forms the second air pumping hole 231 connected to the first air pumping hole 213 in the protective layer 23, and subsequently uses a filling metal layer 41 to seal the second air pumping hole 231, so that the air pumping hole can be sealed without using a laser sealing process; and, compared with the use of a laser sealing process for sealing, the manufacturing method of the MEMS device provided by the present invention can solve the problem that the laser sealing process has a poor sealing effect on the first air pumping hole 213 with a large width or even cannot seal the hole. The manufacturing method of the MEMS device can seal the second air pumping hole 231 of any width, and the sealing effect is better; and, the sealing can be achieved by using a conventional deposition machine, without the need for an expensive special machine, and all the second air pumping holes 231 can be sealed at the same time, so that the sealing efficiency is significantly improved, thereby reducing the cost.

[0097] According to step S6, referring to Figure 3k, the first cavity 211 is evacuated through the second air pumping hole 231, the third cavity 221 and the first air pumping hole 213, so that the first MEMS device corresponding to the first cavity 211 reaches the required vacuum degree; and the metal layer 41 is filled in the second air pumping hole 231 to achieve the sealing of the second air pumping hole 231, which can achieve the sealing of the second air pumping hole 231, and then achieve the sealing of the third cavity 221, the first air pumping hole 213, the fourth cavity 214 and the first cavity 211.

[0098] The metal layer 41 can be deposited in the second evacuation holes 231 using a process requiring a certain degree of vacuum, such as a physical vapor deposition process or an evaporation process. Before performing the physical vapor deposition or evaporation process, the chamber needs to be evacuated. During this process, since the first cavity 211 is connected to the outside world through the second evacuation holes 231, the third cavity 221, and the first evacuation holes 213, gas within the first cavity 211 can be extracted during the evacuation process, ensuring that the vacuum level of the first cavity 211 meets the requirements of the first MEMS device. Since the second cavity 212 is not connected to the outside world, the evacuation step does not affect the vacuum level of the second cavity 212, and the vacuum level of the second cavity 212 remains at the vacuum level during the bonding process. This allows the first and second MEMS devices formed on the same substrate to have different vacuum levels. The subsequent process of depositing the metal layer 41 is also performed in the same vacuum chamber, ensuring that the first cavity 211 maintains the required vacuum level after the metal layer 41 is deposited.

[0099] In addition, the process temperature range used when depositing the metal layer 41 in the second exhaust hole 231 using the physical vapor deposition process is 400℃~500℃, and the process temperature used when depositing the metal layer 41 in the second exhaust hole 231 using the evaporation process is room temperature. Compared with the high temperature of 700℃~800℃ used when depositing the insulating material in the second exhaust hole 231 using the chemical vapor deposition process, the process temperature used when depositing the metal layer 41 using the physical vapor deposition process and the evaporation process is lower, so that the metal block formed by the bonding reaction between the first bonding ring 24 and the second bonding ring 32 can be prevented from being melted by high temperature during the sealing process, thereby avoiding bonding abnormalities.

[0100] The first MEMS device may be a gyroscope, the second MEMS device may be an accelerometer, the first MEMS structure may include the comb teeth structure and mass block of the gyroscope, and the second MEMS structure may include the comb teeth structure and mass block of the accelerometer; or, the first MEMS device may be an accelerometer, the second MEMS device may be a gyroscope, the first MEMS structure may include the comb teeth structure and mass block of the accelerometer, and the second MEMS structure may include the comb teeth structure and mass block of the gyroscope.

[0101] From the above content, it can be seen that the manufacturing method of the MEMS device of the present invention is to sequentially form a first sacrificial layer and a protective layer covering the first surface of the first substrate; etch the second surface of the first substrate to form a first cavity and a first pumping hole in the first area, and form a second cavity in the second area, and the first pumping hole exposes the first sacrificial layer; and after bonding the second surface of the first substrate to the first surface of the second substrate, form a plurality of second pumping holes in the protective layer; and form a third cavity connected to the second pumping holes and the first pumping holes in the first sacrificial layer; pump the first cavity through the second pumping holes, the third cavity and the first pumping holes, and fill the metal layer in the second pumping holes, so that the pumping holes can be sealed without using a laser sealing process, and the problem of sealing large-sized pumping holes can be solved, and the cost can be reduced.

[0102] An embodiment of the present invention provides a MEMS device, comprising: a second substrate, a first surface of which is formed with a first MEMS structure and a second MEMS structure; a first substrate, a second surface of which is bonded to the first surface of the second substrate; the first substrate comprises a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure, the first region is formed with a first cavity and a first pumping hole, and the second region is formed with a second cavity; the first surface of the first substrate is covered with a sacrificial layer and a protective layer, the protective layer covers the sacrificial layer, a third cavity is formed in the sacrificial layer, a plurality of second pumping holes are formed in the protective layer, the first pumping hole is respectively connected to the first cavity and the third cavity, and the third cavity is connected to the second pumping hole; the second pumping hole is filled with a metal layer.

[0103] The MEMS device of this embodiment is described in more detail below with reference to FIG. 3 k . FIG. 3 k is a schematic longitudinal cross-sectional view of the MEMS device.

[0104] A first MEMS structure and a second MEMS structure are formed on the first surface of the second substrate 31 .

[0105] The first MEMS structure and the second MEMS structure may each include a comb-tooth structure and a proof mass.

[0106] The second substrate 31 may include a semiconductor base 311 and a first insulating dielectric layer 312 covering the first surface of the semiconductor base 311, wherein the first insulating dielectric layer 312 has a conductive structure 313 connected to the semiconductor base 311 formed therein, and the first insulating dielectric layer 312 exposes the conductive structure 313; a device structure may also be formed in the semiconductor base 311 and the first insulating dielectric layer 312, and the device structure may include a transistor, etc.

[0107] The second substrate 31 may also include a second sacrificial layer 314 and a semiconductor layer 315 covering the first insulating dielectric layer 312, the semiconductor layer 315 covering the second sacrificial layer 314, and a fifth cavity 3141 formed in the second sacrificial layer 314, the fifth cavity 3141 exposing a portion of the first insulating dielectric layer 312 and a portion of the conductive structure 313; the comb tooth structure and mass block in the first MEMS structure and the comb tooth structure and mass block in the second MEMS structure are formed in the semiconductor layer 315, and release holes 3151 are formed in the comb tooth structure, between the mass blocks and the comb tooth structure, and between the mass blocks, and the release holes 3151 are connected to the fifth cavity 3141, and the fifth cavity 3141 is used to provide a vibration space for the comb tooth structure and the mass block.

[0108] Furthermore, the second substrate 31 may further include a second insulating dielectric layer 316 covering the second surface of the semiconductor base 311 , so as to insulate the second surface of the semiconductor base 311 from other structures.

[0109] The second surface of the first substrate 21 is bonded to the first surface of the second substrate 31 ; the first substrate 21 includes a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure.

[0110] The first substrate 21 may be only a semiconductor base or a wafer including a semiconductor base, etc. Device structures such as transistors may be formed in the first substrate 21 as needed.

[0111] The semiconductor substrate is preferably a double-polished wafer, so that the performance of the structure manufactured in the first substrate 21 is better.

[0112] The material of the semiconductor substrate may include Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs, or other III / V compound semiconductors, and may also include a multilayer structure composed of these semiconductors; alternatively, the semiconductor substrate may be silicon-on-insulator (SOI), stacked silicon-on-insulator (SSOI), stacked silicon-germanium-on-insulator (S-SiGeOI), silicon-germanium-on-insulator (SiGeOI), germanium-on-insulator (GeOI), etc. Those skilled in the art may make the selection as needed.

[0113] The material of the semiconductor layer 315 may include Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs or other III / V compound semiconductors, and may also include a multilayer structure composed of these semiconductors.

[0114] The first insulating dielectric layer 312 and the second insulating dielectric layer 316 may be made of at least one insulating material selected from the group consisting of silicon oxide, silicon oxynitride, and silicon nitride. The first insulating dielectric layer 312 may be a stacked structure of at least two layers.

[0115] The conductive structure 313 may be made of polysilicon or metal.

[0116] The material of the second sacrificial layer 314 includes but is not limited to silicon oxide.

[0117] A first cavity 211 and a first air extraction hole 213 are formed in the first region, and a second cavity 212 is formed in the second region.

[0118] The first cavity 211 is aligned with the first MEMS structure, and the second cavity 212 is aligned with the second MEMS structure. The first cavity 211 and the second cavity 212 are used to provide vibration space for the first MEMS structure and the second MEMS structure, respectively. The first cavity 211 and the second cavity 212 are not connected, so that a first MEMS device corresponding to the first cavity 211 and the first MEMS structure and a second MEMS device corresponding to the second cavity 212 and the second MEMS structure are formed on the same substrate.

[0119] The first surface of the first substrate 21 is covered with a first sacrificial layer 22 and a protective layer 23, the protective layer 23 covers the first sacrificial layer 22, a third cavity 221 is formed in the first sacrificial layer 22, and a plurality of second air pumping holes (i.e., the second air pumping holes 231 in Figure 3j) are formed in the protective layer 23, the first air pumping holes 213 are respectively connected to the first cavity 211 and the third cavity 221, the third cavity 221 is connected to the second air pumping holes 231, and the width of the third cavity 221 is greater than the width of the first air pumping holes 213; the second air pumping holes 231 are filled with a metal layer 41.

[0120] The first surface is the front surface, and the second surface is the back surface; or, the first surface is the back surface, and the second surface is the front surface.

[0121] The protection layer 23 is used to protect the first sacrificial layer 22 to prevent the first sacrificial layer 22 from being corroded by a cleaning process or the like.

[0122] The etching rates of the first sacrificial layer 22 and the protective layer 23 are greatly different. For example, the etching selectivity ratio of the first sacrificial layer 22 to the protective layer 23 is greater than 10, so that when the first sacrificial layer 22 is etched to form the third cavity 221, the protective layer 23 is avoided from being etched, or only a small amount of etching is performed on the protective layer 23.

[0123] The material of the first sacrificial layer 22 includes but is not limited to silicon oxide.

[0124] The material of the protection layer 23 can be silicon nitride, polycrystalline silicon, or single crystal silicon.

[0125] The first region may further form a fourth cavity 214 communicating with the first air extraction hole 213 . The first air extraction hole 213 is located between the third cavity 221 and the fourth cavity 214 . The fourth cavity 214 communicates with the first cavity 211 .

[0126] The width of the fourth cavity 214 is greater than the width of the first air extraction hole 213 ; the width and depth of the fourth cavity 214 are both smaller than those of the first cavity 211 and the second cavity 212 .

[0127] The MEMS device may further include a gas absorption layer 25 formed on the bottom wall of the first cavity 211. The gas absorption layer 25 is used to absorb gas to improve the vacuum level of the MEMS device. The gas absorption layer 25 may be made of metal.

[0128] Preferably, the positions of the first air extraction holes 213 and the second air extraction holes 231 are staggered. Since metal particles will fall downward through the second air extraction holes 231 when the metal layer 41 is filled into the second air extraction holes 231, by staggering the positions of the first air extraction holes 213 and the second air extraction holes 231, it is possible to prevent metal particles from falling into the first air extraction holes 213, thereby preventing metal particles from falling into the device through the first air extraction holes 213 and affecting device performance.

[0129] Among them, metal particles will fall and accumulate in the third cavity 221 below the second air extraction hole 231; the first air extraction hole 213 can be aligned with the middle area of ​​the third cavity 221, and the second air extraction hole 231 can be aligned with the edge area of ​​the third cavity 221, so that metal particles fall and accumulate in the edge area of ​​the third cavity 221.

[0130] Preferably, the width of the second air extraction hole 231 is smaller than the width of the first air extraction hole 213 , so that the metal layer 41 can quickly fill the second air extraction hole 231 , that is, quickly seal the hole.

[0131] More preferably, the width of the first air extraction hole 213 is 10 μm to 20 μm, and the width of the second air extraction hole 231 is 1 μm to 5 μm.

[0132] Since the first cavity 211 is connected with the second air pumping hole 231, the third cavity 221 and the first air pumping hole 213, the first cavity 211 can be evacuated through the second air pumping hole 231, the third cavity 221 and the first air pumping hole 213, so that the first MEMS device corresponding to the first cavity 211 can reach the required vacuum degree; and, by filling the metal layer 41 in the second air pumping hole 231, the second air pumping hole 231 can be sealed (sealed), so that the third cavity 221 connected with the second air pumping hole 231, the first air pumping hole 213, the fourth cavity 214 and the first cavity 211 can be sealed.

[0133] The MEMS device further includes:

[0134] A first bonding ring 24 is formed on the second surface of the first substrate 21;

[0135] The second bonding ring 32 is formed on the first surface of the second substrate 31 . The second surface of the first substrate 21 and the first surface of the second substrate 31 are bonded via the first bonding ring 24 and the second bonding ring 32 .

[0136] The second bonding ring 32 may be made of metal materials such as germanium, aluminum, copper, nickel, or gold.

[0137] The first bonding ring 24 and the second bonding ring 32 are both annular structures. The sizes of the first bonding ring 24 and the second bonding ring 32 may be the same or nearly the same. The first bonding ring 24 and the second bonding ring 32 may be eutectic bonded.

[0138] During bonding, the second surface of the first substrate 21 is positioned opposite the first surface of the second substrate 31, and the first bonding ring 24 is aligned with the second bonding ring 32. A certain pressure is applied so that the first bonding ring 24 and the second bonding ring 32 come into contact with each other and, under predetermined conditions, a bonding reaction occurs to form a metal block, thereby further shortening the distance between the first substrate 21 and the second substrate 31. When the first bonding ring 24 and the second bonding ring 32 are made of different materials (for example, the first bonding ring 24 is made of aluminum and the second bonding ring 32 is made of germanium), the metal block is an alloy.

[0139] Furthermore, during bonding, the vacuum degree required by the second MEMS device corresponding to the second cavity 212 may be adopted, and at this time, the vacuum degree of the second MEMS device corresponding to the second cavity 212 is the same as the vacuum degree of the first MEMS device corresponding to the first cavity 211 .

[0140] Because the first cavity 211 is connected to the outside world through the second exhaust hole 231, the third cavity 221, and the first exhaust hole 213, the gas within the first cavity 211 can be extracted, thereby ensuring that the vacuum level of the first cavity 211 meets the requirements of the first MEMS device. However, the second cavity 212 is not connected to the outside world, so that when the first cavity 211 is evacuated, the vacuum level of the second cavity 212 is not affected, and the vacuum level of the second cavity 212 remains at the vacuum level during the bonding process. As a result, the first MEMS device and the second MEMS device formed on the same substrate can have different vacuum levels. In addition, the process of filling the metal layer 41 is also carried out in the same vacuum chamber, so that after filling the metal layer 41, the first cavity 211 still maintains its required vacuum level.

[0141] The first MEMS device may be a gyroscope, the second MEMS device may be an accelerometer, the first MEMS structure may include the comb teeth structure and mass block of the gyroscope, and the second MEMS structure may include the comb teeth structure and mass block of the accelerometer; or, the first MEMS device may be an accelerometer, the second MEMS device may be a gyroscope, the first MEMS structure may include the comb teeth structure and mass block of the accelerometer, and the second MEMS structure may include the comb teeth structure and mass block of the gyroscope.

[0142] Since the etching process has requirements on the aspect ratio of the first exhaust hole 213 formed by etching, that is, the etching process cannot be implemented when the aspect ratio of the first exhaust hole 213 is too high, therefore, when the thickness of the first substrate 21 is very thick, the width of the first exhaust hole 213 formed by etching the first substrate 21 is also large. At this time, if the laser sealing process is directly used to seal the first exhaust hole 213, the effect of sealing the first exhaust hole 213 is not good or even cannot be sealed; in addition, the dedicated machine used for the laser sealing process is expensive, and the first exhaust holes 213 are sealed one by one during operation, resulting in low sealing efficiency, which in turn leads to high costs. Therefore, in the MEMS device provided by the present invention, since the second air pumping hole 231 connected to the first air pumping hole 213 is formed in the protective layer 23, and the second air pumping hole 231 is filled with the metal layer 41 to achieve sealing, the air pumping hole can be sealed without adopting a laser sealing process; and, compared with the laser sealing process for sealing, the MEMS device provided by the present invention can solve the problem that the laser sealing process has a poor sealing effect on the first air pumping hole 213 with a large width or even cannot be sealed. The second air pumping holes 231 of any width in the MEMS device can be sealed, and the sealing effect is better; and, the sealing can be achieved by using a conventional deposition machine, without the need for an expensive special machine, and all the second air pumping holes 231 can be sealed at the same time, so that the sealing efficiency is significantly improved, thereby reducing the cost.

[0143] From the above content, it can be seen that the MEMS device of the present invention includes: a second substrate, a first surface of the second substrate is formed with a first MEMS structure and a second MEMS structure; a first substrate, the second surface of the first substrate is bonded to the first surface of the second substrate; the first substrate includes a first area corresponding to the first MEMS structure and a second area corresponding to the second MEMS structure, the first area is formed with a first cavity and a first pumping hole, and the second area is formed with a second cavity; the first surface of the first substrate is covered with a first sacrificial layer and a protective layer, the protective layer covers the first sacrificial layer, a third cavity is formed in the first sacrificial layer, a plurality of second pumping holes are formed in the protective layer, the first pumping hole is respectively connected to the first cavity and the third cavity, and the third cavity is connected to the second pumping hole; the second pumping hole is filled with a metal layer, so that the sealing of the pumping hole can be achieved without adopting a laser sealing process, and at the same time it can solve the problem of sealing large-sized pumping holes and reduce costs.

[0144] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention. Any changes and modifications made by ordinary technicians in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method for manufacturing a MEMS device, characterized in that: include: Providing a first substrate and a second substrate, wherein a first surface of the second substrate is formed with a first MEMS structure and a second MEMS structure, and the first substrate includes a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure; forming a sacrificial layer and a protective layer in sequence to cover the first surface of the first substrate, wherein the protective layer covers the sacrificial layer; Etching the second surface of the first substrate to form a first cavity and a first pumping hole in the first region, and a second cavity in the second region, wherein the first pumping hole exposes the sacrificial layer; Bonding the second surface of the first substrate to the first surface of the second substrate, wherein the first gas extraction hole is connected to the first cavity after bonding; forming a plurality of second air extraction holes in the protective layer; Before bonding the second surface of the first substrate to the first surface of the second substrate, releasing part of the sacrificial layer through the first exhaust hole to form a third cavity in the sacrificial layer; or after forming a plurality of the second exhaust holes in the protective layer, releasing part of the sacrificial layer through the second exhaust hole to form a third cavity in the sacrificial layer; The second air extraction hole is communicated with the third cavity; The first cavity is evacuated through the second evacuation hole, the third cavity and the first evacuation hole, and a metal layer is filled in the second evacuation hole.

2. The method for manufacturing a MEMS device according to claim 1, wherein: The positions of the first air extraction hole and the second air extraction hole are staggered.

3. The method for manufacturing a MEMS device according to claim 1, wherein: The width of the second air pumping hole is smaller than the width of the first air pumping hole.

4. The method for manufacturing a MEMS device according to claim 3, wherein: The width of the first air extraction hole is 10 μm to 20 μm, and the width of the second air extraction hole is 1 μm to 5 μm.

5. The method for manufacturing a MEMS device according to claim 1, wherein: The first region further comprises a fourth cavity connected to the first air extraction hole; the steps of forming the first cavity, the first air extraction hole and the fourth cavity in the first region, and forming the second cavity in the second region include: Etching the second surface of the first substrate to form a first cavity and a fourth cavity in the first region, and forming a second cavity in the second region; The bottom wall of the fourth cavity is etched to form a first exhaust hole on the bottom wall of the fourth cavity.

6. The method for manufacturing a MEMS device according to claim 1, wherein: Before etching the second surface of the first substrate, the method for manufacturing the MEMS device further includes: forming a first bonding ring on the second surface of the first substrate; Before bonding the second surface of the first substrate to the first surface of the second substrate, the method for manufacturing the MEMS device further includes: forming a second bonding ring on the first surface of the second substrate; Bonding the second surface of the first substrate to the first surface of the second substrate includes: bonding the second surface of the first substrate to the first surface of the second substrate through the first bonding ring and the second bonding ring.

7. The method for manufacturing a MEMS device according to claim 1, wherein: The first MEMS structure includes a comb-teeth structure of a gyroscope, and the second MEMS structure includes a comb-teeth structure of an accelerometer.

8. A MEMS device, characterized in that: include: A first substrate and a second substrate, wherein a first surface of the second substrate is formed with a first MEMS structure and a second MEMS structure; The second surface of the first substrate is bonded to the first surface of the second substrate; the first substrate includes a first area corresponding to the first MEMS structure and a second area corresponding to the second MEMS structure, the first area is formed with a first cavity and a first exhaust hole, and the second area is formed with a second cavity; the first surface of the first substrate is covered with a sacrificial layer and a protective layer, the protective layer covers the sacrificial layer, a third cavity is formed in the sacrificial layer, a plurality of second exhaust holes are formed in the protective layer, the first exhaust hole is respectively connected to the first cavity and the third cavity, and the third cavity is connected to the second exhaust hole; the second exhaust hole is filled with a metal layer.

9. The MEMS device according to claim 8, characterized in that: The positions of the first air extraction hole and the second air extraction hole are staggered.

10. The MEMS device according to claim 8, characterized in that: The width of the second air pumping hole is smaller than the width of the first air pumping hole.

11. The MEMS device according to claim 10, characterized in that: The width of the first air extraction hole is 10 μm to 20 μm, and the width of the second air extraction hole is 1 μm to 5 μm.

12. The MEMS device according to claim 8, characterized in that The first region further forms a fourth cavity connected to the first air extraction hole, and the first air extraction hole is located between the third cavity and the fourth cavity.

13. The MEMS device according to claim 8, characterized in that The MEMS device further comprises: A first bonding ring formed on the second surface of the first substrate; A second bonding ring is formed on the first surface of the second substrate, and the second surface of the first substrate is bonded to the first surface of the second substrate through the first bonding ring and the second bonding ring.

14. The MEMS device according to claim 8, characterized in that: The first MEMS structure includes a comb-teeth structure of a gyroscope, and the second MEMS structure includes a comb-teeth structure of an accelerometer.

15. The MEMS device according to claim 8, characterized in that It also includes a gas absorption layer formed on the bottom wall of the first cavity, and the gas absorption layer is used to absorb gas to improve the vacuum degree of the MEMS device.

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