MEMS device and method for manufacturing the same

Abstract

The present invention provides a MEMS device and a manufacturing method thereof. The manufacturing method of the MEMS device includes the steps of providing a first substrate and a second substrate, the first substrate having a first MEMS structure and a second MEMS structure formed on a first surface thereof, the first substrate including a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure; sequentially forming a sacrificial layer and a protective layer on the first surface of the first substrate; forming a first cavity and a first exhaust hole in the first region and a second cavity in the second region; 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 a third cavity in the sacrificial layer communicating with the second exhaust holes; evacuating the first cavity through the second exhaust holes, the third cavity, and the first exhaust holes; and filling the second exhaust hole with a metal layer. The technical solution of the present invention can achieve sealing of the exhaust holes without using a laser sealing process, thereby solving the problem of sealing large-sized exhaust holes and reducing costs.

Description

【Technical Field】 【0001】 The present invention relates to the technical field of semiconductors, and more particularly to MEMS devices and manufacturing methods thereof. 【Background Art】 【0002】 In order to integrate different MEMS devices (e.g., accelerometers and gyroscopes) having different vacuum degrees on the same wafer, as shown in FIG. 1, a first substrate 11 and a second substrate 12 are bonded, and the vacuum degree of some MEMS devices is adjusted during bonding. Further, on the second substrate 12, exhaust holes 121 are formed by etching, and by exhausting through the exhaust holes 121, the vacuum degree of the cavity communicating with the exhaust holes 121 is increased, that is, the vacuum degree of the remaining part of the MEMS device is adjusted through the exhaust holes 121. After reaching the desired vacuum degree, the exhaust holes 121 are sealed one by one using a dedicated machine by a laser sealing process. 【0003】 However, when the thickness of the second substrate 12 is very thick, due to the influence of the etching process ability, the width of the exhaust holes 121 formed by etching on the second substrate 12 becomes large, so the effect of sealing the exhaust holes 121 in the laser sealing process is not preferable, and ultimately it cannot be sealed. In addition to the dedicated machine used in the laser sealing process being expensive, in order to seal the exhaust holes 121 one by one during operation, the sealing efficiency is low, and furthermore, the cost becomes very high. 【0004】 Therefore, in order to avoid the occurrence of the above problems, it is necessary to improve the sealing process of the exhaust holes. 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 An object of the present invention is to provide an MEMS device and a manufacturing method thereof that can achieve the sealing of exhaust holes without adopting a laser sealing process, solve the sealing problem of large-sized exhaust holes, and reduce costs. [Means for solving the problem] 【0006】 To achieve the above objective, the present invention, A step of providing a first substrate and a second substrate, wherein a first MEMS structure and a second MEMS structure are formed on the 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. The steps include sequentially forming a sacrificial layer and a protective layer covering the sacrificial layer so as to cover the first surface of the first substrate, The steps include etching the second surface of the first substrate to form a first exhaust hole in the first region that exposes the first cavity and the sacrificial layer, and forming a second cavity in the second region, The steps include bonding the second surface of the first substrate and the first surface of the second substrate so as to connect the first exhaust hole and the first cavity, The steps include forming a plurality of second exhaust holes in the protective layer and releasing a portion of the sacrificial layer through the first exhaust holes before bonding the second surface of the first substrate to the first surface of the second substrate, or releasing a portion of the sacrificial layer through the second exhaust holes after forming a plurality of second exhaust holes in the protective layer, thereby forming a third cavity in the sacrificial layer that communicates with the second exhaust holes, A method for manufacturing a MEMS device is provided, comprising the steps of: exhausting the first cavity through the second exhaust port, the third cavity, and the first exhaust port, and filling the second exhaust port with a metal layer. 【0007】 The first exhaust port and the second exhaust port are offset from each other, allowing for selection. 【0008】 The width of the second exhaust port is selectable to be smaller than the width of the first exhaust port. 【0009】 The width of the first exhaust port is selectable to be 10 μm to 20 μm, and the width of the second exhaust port is selectable to be 1 μm to 5 μm. 【0010】 The steps of optionally forming a fourth cavity in the first region, forming a first cavity, a first exhaust port and a fourth cavity in the first region and forming a second cavity in the second region are as follows: The steps 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 process includes the step of etching the bottom wall of the fourth cavity to form a first exhaust hole in the bottom wall of the fourth cavity. 【0011】 The manufacturing method of the MEMS device may optionally include the step of etching the second surface of the first substrate, The process further includes the step of forming a first bonding ring on the second surface of the first substrate, Before the step of bonding the second surface of the first substrate to the first surface of the second substrate, the manufacturing method of the MEMS device is as follows: The process further includes the step of forming a second bonding ring on the first surface of the second substrate, The step of bonding the second surface of the first substrate to the first surface of the second substrate includes the step of bonding the second surface of the first substrate to the first surface of the second substrate via the first bonding ring and the second bonding ring. 【0012】 Selectively, the first MEMS structure includes a comb-tooth structure for a gyroscope, and the second MEMS structure includes a comb-tooth structure for an accelerometer. 【0013】 The present invention The device comprises a first substrate and a second substrate, and a first MEMS structure and a second MEMS structure are formed on the first surface of the second substrate. Further, a MEMS device is provided, wherein the second surface of the first substrate is bonded to the first surface of the second substrate, the first substrate includes a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure, the first region has a first cavity and a first exhaust hole formed therein, the second region has a second cavity formed therein, the first surface of the first substrate is covered with a sacrificial layer and a protective layer, the protective layer covers the sacrificial layer, the sacrificial layer has a third cavity formed therein, the protective layer has a plurality of second exhaust holes formed therein, the first exhaust holes communicate with the first cavity and the third cavity respectively, the third cavity communicates with the second exhaust hole, and the second exhaust hole is filled with a metal layer. 【0014】 The first exhaust port and the second exhaust port are offset from each other, allowing for selection. 【0015】 The width of the second exhaust port is selectable to be smaller than the width of the first exhaust port. 【0016】 The width of the first exhaust port is selectable to be 10 μm to 20 μm, and the width of the second exhaust port is selectable to be 1 μm to 5 μm. 【0017】 Selectively, a fourth cavity communicating with the first exhaust port is further formed in the first region, and the first exhaust port is located between the third cavity and the fourth cavity. 【0018】 Selectable, the MEMS device is A first bonding ring formed on the second surface of the first substrate, The device further comprises a second bonding ring formed on the first surface of the second substrate, wherein the second surface of the first substrate and the first surface of the second substrate are bonded via the first bonding ring and the second bonding ring. 【0019】 Selectively, the first MEMS structure includes a comb-tooth structure for a gyroscope, and the second MEMS structure includes a comb-tooth structure for an accelerometer. [Effects of the Invention] 【0020】 Compared with the prior art, the technical means of the present invention has the following beneficial effects. 1. According to the manufacturing method of the MEMS device of the present invention, the steps of sequentially forming a sacrificial layer and a protective layer so as to cover the first surface of the first substrate, and etching the second surface of the first substrate to form a first cavity and a first exhaust hole in the first region, forming a second cavity in the second region, and exposing the sacrificial layer to the first exhaust hole; after bonding the second surface of the first substrate and 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 that communicates with the second exhaust hole and the first exhaust hole; evacuating the first cavity through the second exhaust hole, the third cavity and the first exhaust hole, and filling the metal layer into the second exhaust hole can achieve the sealing of the exhaust hole without adopting a laser sealing process, solve the sealing problem of large-sized exhaust holes, and reduce the cost. 2. According to the MEMS device of the present invention, it includes a first substrate and a second substrate. On the first surface of the second substrate, a first MEMS structure and a second MEMS structure are formed. The second surface of the first substrate is bonded to the first surface of the second substrate. The first substrate includes a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure. A first cavity and a first exhaust hole are formed in the first region, a second cavity is formed in the second region, 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 exhaust holes are formed in the protective layer, the first exhaust holes communicate with the first cavity and the third cavity respectively, the third cavity communicates with the second exhaust hole, and the second exhaust hole is filled with a metal layer. Therefore, the sealing of the exhaust hole can be realized without adopting a laser sealing process, solve the sealing problem of large-sized exhaust holes, and reduce the cost. 【Brief Description of the Drawings】 【0021】 [Figure 1]It is a schematic cross-sectional view of a MEMS device. [Figure 2] It is a flowchart of a method for manufacturing a MEMS device according to an embodiment of the present invention. [Figure 3a] It is a schematic cross-sectional view of a device in the method for manufacturing the MEMS device shown in FIG. 2. [Figure 3b] It is a schematic cross-sectional view of a device in the method for manufacturing the MEMS device shown in FIG. 2. [Figure 3c] It is a schematic cross-sectional view of a device in the method for manufacturing the MEMS device shown in FIG. 2. [Figure 3d] It is a schematic cross-sectional view of a device in the method for manufacturing the MEMS device shown in FIG. 2. [Figure 3e] It is a schematic cross-sectional view of a device in the method for manufacturing the MEMS device shown in FIG. 2. [Figure 3f] It is a schematic cross-sectional view of a device in the method for manufacturing the MEMS device shown in FIG. 2. [Figure 3g] It is a schematic cross-sectional view of a device in the method for manufacturing the MEMS device shown in FIG. 2. [Figure 3h] It is a schematic cross-sectional view of a device in the method for manufacturing the MEMS device shown in FIG. 2. [Figure 3i] It is a schematic cross-sectional view of a device in the method for manufacturing the MEMS device shown in FIG. 2. [Figure 3j] It is a schematic cross-sectional view of a device in the method for manufacturing the MEMS device shown in FIG. 2. [Figure 3k] It is a schematic cross-sectional view of a device in the method for manufacturing the MEMS device shown in FIG. 2. 【Mode for Carrying Out the Invention】 【0022】 One embodiment of the present invention provides a method for manufacturing a MEMS device. Referring to FIG. 2 which is a flowchart of the method for manufacturing a MEMS device according to an embodiment of the present invention, the method for manufacturing the MEMS device is as follows. Step S1 provides a first substrate and a second substrate, wherein a first MEMS structure and a second MEMS structure are formed on the 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. Step S2 involves sequentially forming a sacrificial layer and a protective layer covering the sacrificial layer so as to cover the first surface of the first substrate, Step S3 involves etching the second surface of the first substrate to form a first exhaust hole in the first region that exposes the first cavity and the sacrificial layer, and forming a second cavity in the second region. Step S4 involves bonding the second surface of the first substrate and the first surface of the second substrate so as to connect the first exhaust hole and the first cavity, Step S5 involves forming a plurality of second exhaust holes in the protective layer and releasing a portion of the sacrificial layer through the first exhaust holes before bonding the second surface of the first substrate to the first surface of the second substrate, or releasing a portion of the sacrificial layer through the second exhaust holes after forming a plurality of second exhaust holes in the protective layer, thereby forming a third cavity in the sacrificial layer that communicates with the second exhaust holes. The process includes step S6, which involves exhausting the first cavity through the second exhaust port, the third cavity, and the first exhaust port, and filling the second exhaust port with a metal layer. 【0023】 Next, the manufacturing method for the MEMS device provided in this embodiment will be introduced in more detail with reference to Figures 3a to 3k. Figures 3a to 3k are schematic diagrams of the device in the manufacturing method for the MEMS device shown in Figure 2, and Figures 3a to 3k are also schematic diagrams of the longitudinal cross-section of the MEMS device. 【0024】 In step S1, with reference to Figures 3a and 3h, a first substrate 21 and a second substrate 31 are provided, wherein a first MEMS structure and a second MEMS structure are formed on the first surface of the second substrate 31, 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. 【0025】 The first substrate 21 may be simply a semiconductor substrate, or it may be a wafer or the like equipped with a semiconductor substrate, and a device structure such as a transistor may be formed on the first substrate 21 as needed. 【0026】 In order to further optimize the performance of the structure fabricated on the first substrate 21, the semiconductor substrate is preferably a double-sided polished substrate. 【0027】 Both the first MEMS structure and the second MEMS structure may include a comb-tooth structure and a mass portion. 【0028】 Here, as shown in Figure 3h, the second substrate 31 may comprise a semiconductor substrate 311 and a first insulating dielectric layer 312 covering the first surface of the semiconductor substrate 311, and a conductive structure 313 connected to the semiconductor substrate 311 is formed on the first insulating dielectric layer 312, the conductive structure 313 being exposed from the first insulating dielectric layer 312, and a device structure may be further formed on the semiconductor substrate 311 and the first insulating dielectric layer 312, the device structure may comprise a transistor or the like. 【0029】 The second substrate 31 may further comprise a second sacrificial layer 314 covering the first insulating dielectric layer 312 and a semiconductor layer 315, wherein the semiconductor layer 315 covers the second sacrificial layer 314, a fifth cavity 3141 is formed in the second sacrificial layer 314, a part of the first insulating dielectric layer 312 and a part of the conductive structure 313 are exposed to the fifth cavity 3141, and the semiconductor layer 315 has a comb-tooth structure and mass portion in the first MEMS structure and a comb-tooth structure and mass portion in the second MEMS structure, release holes 3151 are formed in the comb-tooth structure, between the mass portion and the comb-tooth structure and between the mass portion, the release holes 3151 are in communication with the fifth cavity 3141, and the fifth cavity 3141 is for providing a vibration space between the comb-tooth structure and the mass portion. 【0030】 Furthermore, the second substrate 31 may further include a second insulating dielectric layer 316 that covers the second surface of the semiconductor substrate 311, in order to insulate the second surface of the semiconductor substrate 311 from other structures. 【0031】 Furthermore, as shown in Figure 3h, prior to the step of bonding the second surface of the first substrate 21 and the first surface of the second substrate 31, the method for manufacturing the MEMS device further includes the step of forming a second bonding ring 32 on the first surface of the second substrate 31. Here, the second bonding ring 32 may be formed on the semiconductor layer 315 after the semiconductor layer 315 has been formed and before the release hole 3151 has been formed. 【0032】 The step of forming the second bonding ring 32 on the first surface of the second substrate 31 may include the steps of first forming a metal material on the first surface of the second substrate 31 by 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, and then removing the patterned mask layer. 【0033】 The material of the semiconductor substrate may include Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs, or other III / V compound semiconductors, or it may include a multilayer structure composed of these semiconductors. Alternatively, the semiconductor substrate may be silicon on an insulator (SOI), multilayer silicon on an insulator (SSOI), multilayer silicon germanium on an insulator (S-SiGeOI), silicon germanium on an insulator (SiGeOI), and germanium on an insulator (GeOI), etc. A person skilled in the art can select as needed. 【0034】 The material of the semiconductor layer 315 may include Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs, or other III / V compound semiconductors, or it may include a multilayer structure composed of these semiconductors. 【0035】 The materials of the first insulating dielectric layer 312 and the second insulating dielectric layer 316 may be at least one of insulating materials such as silicon oxide, silicon oxynitride, and silicon nitride, and the first insulating dielectric layer 312 may have a structure in which at least two layers are stacked. 【0036】 The material of the conductive structure 313 may be polycrystalline silicon or a metal. 【0037】 The material of the second sacrificial layer 314 contains, but is not limited to, silicon oxide. 【0038】 The material of the second bonding ring 32 may include metallic materials such as germanium, aluminum, copper, nickel, or gold. 【0039】 In step S2, with reference to Figures 3a and 3b, a first sacrificial layer 22 and a protective layer 23 are formed in sequence to cover the first surface of the first substrate 21, with the protective layer 23 covering the first sacrificial layer 22. 【0040】 Here, the protective layer 23 is intended to protect the first sacrificial layer 22 so that it is not corroded by a cleaning process or the like in a subsequent process. 【0041】 The etching rates of the first sacrificial layer 22 and the protective layer 23 differ significantly. For example, by setting the etching selectivity ratio of the first sacrificial layer 22 and the protective layer 23 to greater than 10, when the first sacrificial layer 22 is etched later, the protective layer 23 is either not etched at all or is only slightly etched. 【0042】 The material of the first sacrificial layer 22 contains, but is not limited to, silicon oxide. 【0043】 The material of the protective layer 23 may be silicon nitride, polycrystalline silicon, or monocrystalline silicon, etc. 【0044】 Referring to Figure 3c, prior to the step of etching the second surface of the first substrate 21, the method for manufacturing the MEMS device further includes the step of forming the first bonding ring 24 on the second surface of the first substrate 21. 【0045】 The step of forming the first bonding ring 24 on the second surface of the first substrate 21 may include the steps of first forming a metal material on the second surface of the first substrate 21 by 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. Here, at the same time as forming the first bonding ring 24, a structure such as a pad may be formed on the second surface of the first substrate 21. 【0046】 The material of the first bonding ring 24 may include metallic materials such as germanium, aluminum, copper, nickel, or gold. 【0047】 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. 【0048】 In step S3, referring to Figures 3d to 3f, the second surface of the first substrate 21 is etched to form a first cavity 211 and a first exhaust hole 213 in the first region, a second cavity 212 in the second region, and the first sacrificial layer 22 is exposed to the first exhaust hole 213. 【0049】 In one embodiment, a fourth cavity 214 may be formed in the first region. 【0050】 The steps of forming a first cavity 211, a first exhaust hole 213, and a fourth cavity 214 in the first region and a second cavity 212 in the second region may include, first, as shown in Figure 3d, 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 the second cavity 212 in the second region; and then, as shown in Figure 3f, etching the bottom wall of the fourth cavity 214 up to the first sacrificial layer 22 to form the first exhaust hole 213 in the bottom wall of the fourth cavity 214. 【0051】 Here, the etching process has requirements regarding the aspect ratio of the first exhaust holes 213 formed by etching. That is, if the aspect ratio of the first exhaust holes 213 is too high, etching cannot be achieved by the etching process. Therefore, when the thickness of the first substrate 21 is very thick, it is preferable to first form the fourth cavity 214 on the second surface of the first substrate 21 by etching, and then form the first exhaust holes 213 on the bottom wall of the fourth cavity 214 by etching. That is, the first substrate 21 is etched through in two steps to 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 formed first exhaust holes 213 is still large. 【0052】 Here, both the fourth cavity 214 and the first exhaust port 213 are for exhaust, and the width of the fourth cavity 214 is greater than the width of the first exhaust port 213. The first cavity 211 and the second cavity 212 are for providing vibration space to the first MEMS structure and the second MEMS structure after bonding, and the width and depth of the fourth cavity 214 are both smaller than those of the first cavity 211 and the second cavity 212. The order in which the fourth cavity 214, the first cavity 211 and the second cavity 212 are formed is not limited; they may be formed simultaneously or at different times. 【0053】 Furthermore, as shown in Figure 3e, after the step of forming the first cavity 211 and before the step of forming the first exhaust hole 213, the method for manufacturing the MEMS device may further include the step of forming a gas absorption layer 25 on the bottom wall of the first cavity 211 for absorbing gas and increasing the vacuum level of the MEMS device. The material of the gas absorption layer 25 may be a metallic material. 【0054】 In step S4, referring to Figure 3i, the second surface of the first substrate 21 and the first surface of the second substrate 31 are bonded, and after bonding, the fourth cavity 214 and the first exhaust hole 213 and the first cavity 211 become in communication. 【0055】 Furthermore, after bonding, the first cavity 211 is abutted against the first MEMS structure, and the second cavity 212 is abutted against the second MEMS structure, and the first cavity 211 and the second cavity 212 are not in communication with each other, so that the first MEMS device corresponding to the first cavity 211 and the first MEMS structure, and the second MEMS device corresponding to the second cavity 212 and the second MEMS structure are formed on the same substrate. 【0056】 The step of bonding the second surface of the first substrate 21 to the first surface of the second substrate 31 includes the step of 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. 【0057】 Both the first bonding ring 24 and the second bonding ring 32 have annular structures, and the dimensions of the first bonding ring 24 and the second bonding ring 32 may be the same or approximately the same, and the first bonding ring 24 and the second bonding ring 32 may be eutectic bonded. 【0058】 During bonding, the second surface of the first substrate 21 and the first surface of the second substrate 31 are placed facing each other, the first bonding ring 24 and the second bonding ring 32 are brought into contact, and a predetermined pressure is applied. This causes the first bonding ring 24 and the second bonding ring 32 to come into contact, and a bonding reaction occurs under set conditions to form a metal block, bringing the distance between the first substrate 21 and the second substrate 31 closer. Here, if the materials of the first bonding ring 24 and the second bonding ring 32 are different (for example, if the material of the first bonding ring 24 is aluminum and the material of the second bonding ring 32 is germanium), the metal block is an alloy. 【0059】 Furthermore, during bonding, the vacuum pressure control process may employ the vacuum level required for the second MEMS device corresponding to the second cavity 212, in which case the vacuum level of the second MEMS device corresponding to the second cavity 212 is the same as the vacuum level of the first MEMS device corresponding to the first cavity 211. 【0060】 In step S5, referring to Figure 3j, the protective layer 23 is etched to form a plurality of second exhaust holes 231 in the protective layer 23. 【0061】 Referring to Figure 3g, before bonding the second surface of the first substrate 21 and 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. Alternatively, after forming a plurality of the 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. 【0062】 The second exhaust port 231 communicates with the third cavity 221, the protective layer 23 is exposed to the third cavity 221, and the width of the third cavity 221 is greater than the width of the first exhaust port 213. 【0063】 Here, a portion of the first sacrificial layer 22 can be released by a vapor-phase hydrofluoric acid (VHF, VHF) etching process, that is, by introducing vapor-phase hydrofluoric acid into the fourth cavity 214 and the first exhaust port 213 and etching through the fourth cavity 214 and the first exhaust port 213 to remove a portion of the first sacrificial layer 22. Alternatively, by introducing vapor-phase hydrofluoric acid into the second exhaust port 231 and etching through the second exhaust port 231 to remove a portion of the first sacrificial layer 22. 【0064】 Preferably, the first exhaust hole 213 and the second exhaust hole 231 are offset from each other. When the metal layer 41 is later filled into the second exhaust hole 231, metal particles will fall through the second exhaust hole 231. Therefore, the offset between the first exhaust hole 213 and the second exhaust hole 231 prevents metal particles from falling into the first exhaust hole 213, thus preventing metal particles from falling through the first exhaust hole 213, entering the inside of the device, and affecting the device performance. 【0065】 Here, the metal particles fall and accumulate in the third cavity 221 below the second exhaust port 231. By aligning the first exhaust port 213 with the intermediate region of the third cavity 221 and the second exhaust port 231 with the edge region of the third cavity 221, it becomes possible for the metal particles to fall and accumulate in the edge region of the third cavity 221. 【0066】 Preferably, the width of the second exhaust port 231 is smaller than the width of the first exhaust port 213, so that the metal layer 41 can be quickly and sufficiently filled into the second exhaust port 231 later, i.e., the hole can be quickly sealed. 【0067】 More preferably, the width of the first exhaust port 213 is 10 μm to 20 μm, and the width of the second exhaust port 231 is 1 μm to 5 μm. 【0068】 The etching process has requirements regarding the aspect ratio of the first exhaust holes 213 formed by etching. Specifically, if the aspect ratio of the first exhaust holes 213 is too high, etching cannot be achieved by the etching process. Therefore, when the thickness of the first substrate 21 is very thick, the width of the first exhaust holes 213 formed by etching the first substrate 21 also becomes large. In this case, directly employing a laser sealing process to seal the first exhaust holes 213 results in undesirable effects and ultimately makes sealing impossible. Furthermore, in addition to the high cost of the specialized machinery used in the laser sealing process, the sealing efficiency is low because each of the first exhaust holes 213 is sealed one by one during the process, resulting in very high costs. Accordingly, in the manufacturing method of the MEMS device provided in the present invention, a second exhaust hole 231 communicating with the first exhaust hole 213 is formed in the protective layer 23, and sealing is achieved by later filling the second exhaust hole 231 with a metal layer 41, thereby enabling sealing of the exhaust holes without employing a laser sealing process. Furthermore, compared to sealing using a laser sealing process, the manufacturing method for MEMS devices provided in this invention solves the problem that the sealing effect of the large-width first exhaust port 213 is undesirable, or even impossible, with the laser sealing process. It enables sealing of the second exhaust port 231 of any width, resulting in a more desirable sealing effect. In addition, sealing can be achieved using general deposition machinery without employing expensive specialized machinery, and the entire second exhaust port 231 can be sealed simultaneously, significantly improving sealing efficiency and reducing costs. 【0069】 In step S6, referring to Figure 3k, the first cavity 211 is evacuated through the second exhaust port 231, the third cavity 221, and the first exhaust port 213 to bring the first MEMS device corresponding to the first cavity 211 to the required vacuum level, and the second exhaust port 231 is sealed by filling the second exhaust port 231 with the metal layer 41, thereby achieving sealing of the third cavity 221, the first exhaust port 213, the fourth cavity 214, and the first cavity 211. 【0070】 Here, the metal layer 41 can be deposited in the second exhaust port 231 by employing a process that requires a certain level of vacuum, such as a physical vapor deposition process or an evaporation process. Before performing the physical vapor deposition or evaporation process, the cavity needs to be evacuated. In this step, since the first cavity 211 communicates with the outside through the second exhaust port 231, the third cavity 221, and the first exhaust port 213, the gas in the first cavity 211 can be extracted during the evacuating process, and the vacuum level of the first cavity 211 can be set to the vacuum level required for the first MEMS device. Since the second cavity 212 does not communicate with the outside, the evacuating step does not affect the vacuum level of the second cavity 212, and the vacuum level of the second cavity 212 still maintains the vacuum level at the time of the bonding process. Therefore, the first MEMS device and the second MEMS device formed on the same substrate can have different vacuum levels. Subsequently, the process of depositing the metal layer 41 is also carried out in the same vacuum cavity, so that the first cavity 211 still maintains the required vacuum level after the deposit of the metal layer 41. 【0071】 Furthermore, the process temperature range used when depositing the metal layer 41 on the second exhaust port 231 by the physical vapor deposition process is 400°C to 500°C, while the process temperature used when depositing the metal layer 41 on the second exhaust port 231 by the evaporation process is room temperature. Compared to the high temperature of 700°C to 800°C used as the process temperature when depositing the insulating material on the second exhaust port 231 by the chemical vapor deposition process, the process temperatures used when depositing the metal layer 41 by the physical vapor deposition process and the evaporation process are lower. This prevents the metal block formed by the bonding reaction between the first bonding ring 24 and the second bonding ring 32 from melting at high temperatures during the sealing process, and further prevents bonding abnormalities. 【0072】 The first MEMS device may be a gyroscope, the second MEMS device may be an accelerometer, the first MEMS structure may include a comb-tooth structure and a mass part of a gyroscope, and the second MEMS structure may include a comb-tooth structure and a mass part of an accelerometer. Alternatively, the first MEMS device may be an accelerometer, the second MEMS device may be a gyroscope, the first MEMS structure may include a comb-tooth structure and a mass part of an accelerometer, and the second MEMS structure may include a comb-tooth structure and a mass part of a gyroscope. 【0073】 As can be seen from the above, the method for manufacturing a MEMS device of the present invention involves the steps of sequentially forming a first sacrificial layer and a protective layer so as 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 region, forming a second cavity in the second region, and exposing the first sacrificial layer to the first exhaust hole; bonding the second surface of the first substrate and the first surface of the second substrate, forming a plurality of second exhaust holes in the protective layer, forming a third cavity communicating with the second exhaust hole and the first exhaust hole in the first sacrificial layer; and exhausting the first cavity through the second exhaust hole, the third cavity and the first exhaust hole, and filling the second exhaust hole with a metal layer. This method makes it possible to seal the exhaust hole without employing a laser sealing process, solve the problem of sealing large exhaust holes, and reduce costs. 【0074】 One embodiment of the present invention provides a MEMS device comprising a first substrate and a second substrate, wherein a first MEMS structure and a second MEMS structure are formed on the first surface of the second substrate, the second surface of the first substrate is bonded to the first surface of the second substrate, the first substrate includes a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure, a first cavity and a first exhaust hole are formed in the first region, a second cavity is formed in the second region, 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 holes communicate with the first cavity and the third cavity, the third cavity communicates with the second exhaust hole, and the second exhaust hole is filled with a metal layer. 【0075】 Next, the MEMS device of this embodiment will be introduced in more detail with reference to Figure 3k, which is a schematic longitudinal cross-sectional view of the MEMS device. 【0076】 A first MEMS structure and a second MEMS structure are formed on the first surface of the second substrate 31. 【0077】 Both the first MEMS structure and the second MEMS structure may include a comb-tooth structure and a mass portion. 【0078】 The second substrate 31 may comprise a semiconductor substrate 311 and a first insulating dielectric layer 312 covering the first surface of the semiconductor substrate 311. A conductive structure 313 connected to the semiconductor substrate 311 is formed on the first insulating dielectric layer 312, and the conductive structure 313 is exposed from the first insulating dielectric layer 312. A device structure may be further formed on the semiconductor substrate 311 and the first insulating dielectric layer 312, and the device structure may include a transistor or the like. 【0079】 The second substrate 31 may further comprise a second sacrificial layer 314 covering the first insulating dielectric layer 312 and a semiconductor layer 315, wherein the semiconductor layer 315 covers the second sacrificial layer 314, a fifth cavity 3141 is formed in the second sacrificial layer 314, a part of the first insulating dielectric layer 312 and a part of the conductive structure 313 are exposed to the fifth cavity 3141, and the semiconductor layer 315 has a comb-tooth structure and mass portion in the first MEMS structure and a comb-tooth structure and mass portion in the second MEMS structure, release holes 3151 are formed in the comb-tooth structure, between the mass portion and the comb-tooth structure and between the mass portion, the release holes 3151 are in communication with the fifth cavity 3141, and the fifth cavity 3141 is for providing a vibration space between the comb-tooth structure and the mass portion. 【0080】 Furthermore, the second substrate 31 may further include a second insulating dielectric layer 316 that covers the second surface of the semiconductor substrate 311, in order to insulate the second surface of the semiconductor substrate 311 from other structures. 【0081】 The first substrate 21 has a second surface bonded to the first surface of the second substrate 31, and includes a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure. 【0082】 The first substrate 21 may be simply a semiconductor substrate, or it may be a wafer or the like that includes a semiconductor substrate, and a device structure such as a transistor may be formed on the first substrate 21 as needed. 【0083】 In order to further optimize the performance of the structure fabricated on the first substrate 21, the semiconductor substrate is preferably a double-sided polished substrate. 【0084】 The material of the semiconductor substrate may include Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs, or other III / V compound semiconductors, or it may include a multilayer structure composed of these semiconductors. Alternatively, the semiconductor substrate may be silicon on an insulator (SOI), multilayer silicon on an insulator (SSOI), multilayer silicon germanium on an insulator (S-SiGeOI), silicon germanium on an insulator (SiGeOI), and germanium on an insulator (GeOI), etc. A person skilled in the art can select as needed. 【0085】 The material of the semiconductor layer 315 may include Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs, or other III / V compound semiconductors, or it may include a multilayer structure composed of these semiconductors. 【0086】 The materials of the first insulating dielectric layer 312 and the second insulating dielectric layer 316 may be at least one of insulating materials such as silicon oxide, silicon oxynitride, and silicon nitride, and the first insulating dielectric layer 312 may have a structure in which at least two layers are stacked. 【0087】 The material of the conductive structure 313 may be polycrystalline silicon or a metal. 【0088】 The material of the second sacrificial layer 314 contains, but is not limited to, silicon oxide. 【0089】 A first cavity 211 and a first exhaust port 213 are formed in the first region, and a second cavity 212 is formed in the second region. 【0090】 The first cavity 211 is abutted against the first MEMS structure, and the second cavity 212 is abutted against the second MEMS structure. The first cavity 211 and the second cavity 212 are each for providing vibration space to the first MEMS structure and the second MEMS structure, and the first cavity 211 and the second cavity 212 are not in communication with each other. As a result, the first MEMS device corresponding to the first cavity 211 and the first MEMS structure, and the second MEMS device corresponding to the second cavity 212 and the second MEMS structure are formed on the same substrate. 【0091】 The first sacrificial layer 22 and the protective layer 23 cover the first surface of the first substrate 21, the protective layer 23 covers the first sacrificial layer 22, a third cavity 221 is formed in the first sacrificial layer 22, a plurality of second exhaust holes (i.e., second exhaust holes 231 in Figure 3j) are formed in the protective layer 23, the first exhaust holes 213 communicate with the first cavity 211 and the third cavity 221 respectively, the third cavity 221 communicates with the second exhaust hole 231, the width of the third cavity 221 is greater than the width of the first exhaust hole 213, and the second exhaust hole 231 is filled with a metal layer 41. 【0092】 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. 【0093】 The protective layer 23 is intended to protect the first sacrificial layer 22 so that it is not corroded by the cleaning process or the like. 【0094】 The etching rates of the first sacrificial layer 22 and the protective layer 23 differ significantly. For example, by setting the etching selectivity ratio of the first sacrificial layer 22 and the protective layer 23 to greater than 10, when the first sacrificial layer 22 is etched to form the third cavity 221, the protective layer 23 is either not etched at all or is slightly etched. 【0095】 The material of the first sacrificial layer 22 contains, but is not limited to, silicon oxide. 【0096】 The material of the protective layer 23 may be silicon nitride, polycrystalline silicon, or monocrystalline silicon, etc. 【0097】 A fourth cavity 214 communicating with the first exhaust port 213 may be further formed in the first region, with the first exhaust port 213 located between the third cavity 221 and the fourth cavity 214, and the fourth cavity 214 communicating with the first cavity 211. 【0098】 Here, the width of the fourth cavity 214 is greater than the width of the first exhaust port 213, and both the width and depth of the fourth cavity 214 are smaller than those of the first cavity 211 and the second cavity 212. 【0099】 The MEMS device may further include a gas absorption layer 25 formed on the bottom wall of the first cavity 211 for absorbing gas and increasing the vacuum level of the MEMS device. The material of the gas absorption layer 25 may be a metallic material. 【0100】 Preferably, the first exhaust hole 213 and the second exhaust hole 231 are offset from each other. When the metal layer 41 is filled into the second exhaust hole 231, metal particles fall through the second exhaust hole 231. Therefore, the offset between the first exhaust hole 213 and the second exhaust hole 231 prevents metal particles from falling into the first exhaust hole 213, thus preventing metal particles from falling through the first exhaust hole 213, entering the inside of the device, and affecting the device performance. 【0101】 Here, the metal particles fall and accumulate in the third cavity 221 below the second exhaust port 231. By aligning the first exhaust port 213 with the intermediate region of the third cavity 221 and the second exhaust port 231 with the edge region of the third cavity 221, it becomes possible for the metal particles to fall and accumulate in the edge region of the third cavity 221. 【0102】 Preferably, the width of the second exhaust port 231 is smaller than the width of the first exhaust port 213, so that the metal layer 41 can be quickly and sufficiently filled into the second exhaust port 231, i.e., the hole can be quickly sealed. 【0103】 More preferably, the width of the first exhaust port 213 is 10 μm to 20 μm, and the width of the second exhaust port 231 is 1 μm to 5 μm. 【0104】 Since the first cavity 211 communicates with the second exhaust port 231, the third cavity 221, and the first exhaust port 213, the first cavity 211 can be evacuated through the second exhaust port 231, the third cavity 221, and the first exhaust port 213, thereby enabling the first MEMS device corresponding to the first cavity 211 to reach the required vacuum level. Furthermore, by filling the second exhaust port 231 with the metal layer 41, the second exhaust port 231 is sealed, and the third cavity 221, the first exhaust port 213, the fourth cavity 214, and the first cavity 211, which communicate with the second exhaust port 231, can also be sealed. 【0105】 The MEMS device is A first bonding ring 24 formed on the second surface of the first substrate 21, The device further comprises a second bonding ring 32 formed on the first surface of the second substrate 31, wherein 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. 【0106】 The material of the second bonding ring 32 may include metallic materials such as germanium, aluminum, copper, nickel, or gold. 【0107】 Both the first bonding ring 24 and the second bonding ring 32 have annular structures, and the dimensions of the first bonding ring 24 and the second bonding ring 32 may be the same or approximately the same, and the first bonding ring 24 and the second bonding ring 32 may be eutectic bonded. 【0108】 During bonding, the second surface of the first substrate 21 and the first surface of the second substrate 31 are placed facing each other, the first bonding ring 24 and the second bonding ring 32 are brought into contact, and a predetermined pressure is applied. This causes the first bonding ring 24 and the second bonding ring 32 to come into contact, and a bonding reaction occurs under set conditions to form a metal block, bringing the distance between the first substrate 21 and the second substrate 31 closer. Here, if the materials of the first bonding ring 24 and the second bonding ring 32 are different (for example, if the material of the first bonding ring 24 is aluminum and the material of the second bonding ring 32 is germanium), the metal block is an alloy. 【0109】 Furthermore, when bonding, the vacuum level required for the second MEMS device corresponding to the second cavity 212 may be adopted, in which case the vacuum level of the second MEMS device corresponding to the second cavity 212 is the same as the vacuum level of the first MEMS device corresponding to the first cavity 211. 【0110】 Since the first cavity 211 communicates with the outside through the second exhaust port 231, the third cavity 221, and the first exhaust port 213, gas in the first cavity 211 can be extracted, and the vacuum level of the first cavity 211 can be set to the vacuum level required for the first MEMS device. Since the second cavity 212 does not communicate with the outside, the vacuum level of the second cavity 212 is not affected when the first cavity 211 is evacuated, and the vacuum level of the second cavity 212 still maintains the vacuum level at the time of the bonding process. Therefore, the first MEMS device and the second MEMS device formed on the same substrate can have different vacuum levels. Furthermore, since the process of filling the metal layer 41 is also carried out in the same vacuum cavity, the first cavity 211 still maintains the required vacuum level after the metal layer 41 has been filled. 【0111】 The first MEMS device may be a gyroscope, the second MEMS device may be an accelerometer, the first MEMS structure may include a comb-tooth structure and a mass part of a gyroscope, and the second MEMS structure may include a comb-tooth structure and a mass part of an accelerometer. Alternatively, the first MEMS device may be an accelerometer, the second MEMS device may be a gyroscope, the first MEMS structure may include a comb-tooth structure and a mass part of an accelerometer, and the second MEMS structure may include a comb-tooth structure and a mass part of a gyroscope. 【0112】 The etching process has requirements regarding the aspect ratio of the first exhaust holes 213 formed by etching. Specifically, if the aspect ratio of the first exhaust holes 213 is too high, etching cannot be achieved by the etching process. Therefore, when the thickness of the first substrate 21 is very thick, the width of the first exhaust holes 213 formed by etching the first substrate 21 also becomes large. In this case, directly employing a laser sealing process to seal the first exhaust holes 213 results in undesirable effects and ultimately makes sealing impossible. Furthermore, in addition to the high cost of the specialized machinery used in the laser sealing process, the sealing efficiency is low because each of the first exhaust holes 213 is sealed one by one during the process, resulting in very high costs. Accordingly, in the MEMS device provided by the present invention, a second exhaust hole 231 communicating with the first exhaust hole 213 is formed in the protective layer 23, and sealing is achieved by filling the second exhaust hole 231 with the metal layer 41. Thus, sealing of the exhaust holes can be achieved without employing a laser sealing process. Furthermore, compared to sealing using a laser sealing process, the MEMS device provided by the present invention solves the problem of undesirable, and even impossible, sealing of the large width of the first exhaust port 213 by the laser sealing process. It enables sealing of the second exhaust port 231 of any width in the MEMS device, resulting in a more desirable sealing effect. In addition, sealing can be achieved using general deposition machinery without employing expensive specialized machinery, and the entire second exhaust port 231 can be sealed simultaneously, significantly improving sealing efficiency and reducing costs. 【0113】 As can be seen from the above description, the MEMS device of the present invention comprises a first substrate and a second substrate, a first MEMS structure and a second MEMS structure are formed on the first surface of the second substrate, the second surface of the first substrate is bonded to the first surface of the second substrate, the first substrate includes a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure, a first cavity and a first exhaust hole are formed in the first region, a second cavity is formed in the second region, 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 exhaust holes are formed in the protective layer, the first exhaust holes communicate with the first cavity and the third cavity respectively, the third cavity communicates with the second exhaust hole, and the second exhaust hole is filled with a metal layer. Therefore, sealing of the exhaust holes can be achieved without employing a laser sealing process, the problem of sealing large-sized exhaust holes can be solved, and costs can be reduced. 【0114】 The above description is merely an explanation of preferred embodiments of the present invention and does not limit the scope of the invention in any way, and any modifications or alterations made by those skilled in the art based on the above disclosure are included within the scope of protection of the claims. [Explanation of symbols] 【0115】 11. First circuit board 12 Second board 121 Exhaust port 21 First board 211 First Cavity 212 Second Cavity 213 First exhaust port 214 Fourth Cavity 22. First layer of casualties 221 Third Cavity 23 Protective layer 231 Second exhaust port 24. First bonding ring 25 Gas absorption layer 31 Second board 311 Semiconductor substrates 312 First insulating dielectric layer 313 Conductive Structure 314 Second layer of victims 3141 Fifth Cavity 315 Semiconductor layer 3151 Release hole 316 Second insulating dielectric layer 32. Second bonding ring 41 Metal layer

Claims

[Claim 1] A step of providing a first substrate and a second substrate, wherein a first MEMS structure and a second MEMS structure are formed on the 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. The steps include sequentially forming a sacrificial layer and a protective layer covering the sacrificial layer so as to cover the first surface of the first substrate, The steps include etching the second surface of the first substrate to form a first exhaust hole in the first region that exposes the first cavity and the sacrificial layer, and forming a second cavity in the second region, The steps include bonding the second surface of the first substrate and the first surface of the second substrate so as to connect the first exhaust hole and the first cavity, The steps include forming a plurality of second exhaust holes in the protective layer and releasing a portion of the sacrificial layer through the first exhaust holes before bonding the second surface of the first substrate to the first surface of the second substrate, or releasing a portion of the sacrificial layer through the second exhaust holes after forming a plurality of second exhaust holes in the protective layer, thereby forming a third cavity in the sacrificial layer that communicates with the second exhaust holes, A method for manufacturing a MEMS device, comprising the steps of: exhausting the first cavity through the second exhaust port, the third cavity, and the first exhaust port, and filling the second exhaust port with a metal layer. [Claim 2] A method for manufacturing a MEMS device according to claim 1, characterized in that the first exhaust port and the second exhaust port are offset from each other. [Claim 3] A method for manufacturing a MEMS device according to claim 1, characterized in that the width of the second exhaust port is smaller than the width of the first exhaust port. [Claim 4] A method for manufacturing a MEMS device according to claim 3, characterized in that the width of the first exhaust port is 10 μm to 20 μm, and the width of the second exhaust port is 1 μm to 5 μm. [Claim 5] A fourth cavity communicating with the first exhaust port is further formed in the first region, and the steps of forming the first cavity, the first exhaust port and the fourth cavity in the first region and forming the second cavity in the second region are as follows: The steps 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; A method for manufacturing a MEMS device according to claim 1, characterized by comprising the step of etching the bottom wall of the fourth cavity to form a first exhaust hole in the bottom wall of the fourth cavity. [Claim 6] Before the step of etching the second surface of the first substrate, The process further includes the step of forming a first bonding ring on the second surface of the first substrate, Before the step of bonding the second surface of the first substrate to the first surface of the second substrate, The process further includes the step of forming a second bonding ring on the first surface of the second substrate, The method for manufacturing a MEMS device according to claim 1, characterized in that the step of bonding the second surface of the first substrate to the first surface of the second substrate includes the step of bonding the second surface of the first substrate to the first surface of the second substrate via the first bonding ring and the second bonding ring. [Claim 7] A method for manufacturing a MEMS device according to claim 1, characterized in that the first MEMS structure comprises a comb-tooth structure for a gyroscope, and the second MEMS structure comprises a comb-tooth structure for an accelerometer. [Claim 8] The device comprises a first substrate and a second substrate, wherein a first MEMS structure and a second MEMS structure are formed on the first surface of the second substrate. A MEMS device characterized in that the second surface of the first substrate is bonded to the first surface of the second substrate, the first substrate includes a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure, a first cavity and a first exhaust hole are formed in the first region, a second cavity is formed in the second region, 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 holes communicate with the first cavity and the third cavity respectively, the third cavity communicates with the second exhaust hole, and the second exhaust hole is filled with a metal layer. [Claim 9] The MEMS device according to claim 8, characterized in that the first exhaust port and the second exhaust port are offset from each other. [Claim 10] The MEMS device according to claim 8, characterized in that the width of the second exhaust port is smaller than the width of the first exhaust port. [Claim 11] The MEMS device according to claim 10, characterized in that the width of the first exhaust port is 10 μm to 20 μm, and the width of the second exhaust port is 1 μm to 5 μm. [Claim 12] The MEMS device according to claim 8, characterized in that a fourth cavity communicating with the first exhaust port is further formed in the first region, and the first exhaust port is located between the third cavity and the fourth cavity. [Claim 13] A first bonding ring formed on the second surface of the first substrate, The MEMS device according to claim 8, further comprising a second bonding ring formed on the first surface of the second substrate, wherein the second surface of the first substrate and the first surface of the second substrate are bonded via the first bonding ring and the second bonding ring. [Claim 14] The MEMS device according to claim 8, characterized in that the first MEMS structure comprises a comb-tooth structure for a gyroscope, and the second MEMS structure comprises a comb-tooth structure for an accelerometer. [Claim 15] The MEMS device according to claim 8, further comprising a gas absorption layer formed on the bottom wall of the first cavity for absorbing gas and increasing the vacuum level of the MEMS device.