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 field of semiconductor technology, and more particularly to MEMS devices and methods for manufacturing the same. [Background technology]

[0002] In order to integrate different MEMS devices (e.g., accelerometers and gyroscopes) with different vacuum levels on the same wafer, a first substrate 11 and a second substrate 12 are bonded together, and the vacuum level of some of the MEMS devices is adjusted during bonding, as shown in Figure 1. In addition, exhaust holes 121 are formed in the second substrate 12 by etching, and by evacuating air through the exhaust holes 121, the vacuum level of the cavities connected to the exhaust holes 121 is increased. In other words, the vacuum level of the remaining MEMS devices is adjusted through the exhaust holes 121. After the desired vacuum level is reached, the exhaust holes 121 are sealed one by one using a dedicated machine through a laser sealing process.

[0003] However, when the thickness of the second substrate 12 is very thick, the width of the exhaust holes 121 formed by etching in the second substrate 12 becomes large due to the influence of the etching process capacity, so that the effect of sealing the exhaust holes 121 by the laser sealing process is not favorable, and in fact, sealing is impossible. In addition, the dedicated machine used in the laser sealing process is expensive, and since the exhaust holes 121 must be sealed one by one during the process, sealing efficiency is low and costs are very high.

[0004] Therefore, there is a need to improve the exhaust hole sealing process to avoid the above problems. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a MEMS device and a manufacturing method thereof that can realize sealing of exhaust holes without employing a laser sealing process, solve the problem of sealing large exhaust holes, and reduce costs. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides: providing a first substrate and a second substrate, the second substrate having a first surface on which a first MEMS structure and a second MEMS structure are formed, 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 to cover a first surface of the first substrate and a protective layer to cover the sacrificial layer; Etching a second surface of the first substrate to form a first cavity and a first exhaust hole exposing the sacrificial layer in the first region and to form a second cavity in the second region; bonding the second surface of the first substrate to the first surface of the second substrate so as to communicate the first exhaust hole with the first cavity; 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 and the first surface of the second substrate, or releasing a portion of the sacrificial layer through the second exhaust holes after forming the 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; evacuating 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.

[0007] Optionally, the first exhaust hole and the second exhaust hole are offset.

[0008] Optionally, the width of the second exhaust hole is smaller than the width of the first exhaust hole.

[0009] Optionally, the width of the first exhaust hole is between 10 μm and 20 μm, and the width of the second exhaust hole is between 1 μm and 5 μm.

[0010] Optionally, a fourth cavity is further formed in the first region, and the steps of forming the first cavity, the first exhaust hole, and the fourth cavity in the first region and forming the second cavity in the second region include: Etching a second surface of the first substrate to form a first cavity and a fourth cavity in the first region and a second cavity in the second region; and forming a first exhaust hole in the bottom wall of the fourth cavity by etching the bottom wall of the fourth cavity.

[0011] Optionally, before the step of etching the second surface of the first substrate, the method for manufacturing a MEMS device further comprises: 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 and the first surface of the second substrate, the method for manufacturing the MEMS device includes: 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 a 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] Optionally, the first MEMS structure comprises a gyroscope comb structure and the second MEMS structure comprises an accelerometer comb structure.

[0013] The present invention provides a first substrate and a second substrate, a first MEMS structure and a second MEMS structure being formed on a first surface of the second substrate; The present invention further provides a MEMS device, 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, 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 are respectively connected to the first cavity and the third cavity, the third cavity is connected to the second exhaust hole, and the second exhaust hole is filled with a metal layer.

[0014] Optionally, the first exhaust hole and the second exhaust hole are offset.

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

[0016] Optionally, the width of the first exhaust hole is between 10 μm and 20 μm, and the width of the second exhaust hole is between 1 μm and 5 μm.

[0017] Optionally, a fourth cavity communicating with the first exhaust hole is further formed in the first region, and the first exhaust hole is located between the third cavity and the fourth cavity.

[0018] Optionally, the MEMS device comprises: a first bonding ring formed on the second surface of the first substrate; The substrate further includes a second bonding ring formed on the first surface of the second substrate, and 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] Optionally, the first MEMS structure comprises a gyroscope comb structure and the second MEMS structure comprises an accelerometer comb structure. [Effects of the Invention]

[0020] Compared with the prior art, the technical means of the present invention have 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 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 and a second cavity in the second region, and exposing the sacrificial layer to the first exhaust hole, 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 communicating with the second exhaust holes and the first exhaust holes, and evacuating the first cavity through the second exhaust holes, the third cavity, and the first exhaust hole, and filling the second exhaust hole with a metal layer can be performed. This makes it possible to seal the exhaust hole without using a laser sealing process, solve the problem of sealing a large-sized exhaust hole, and reduce costs. 2. The MEMS device of the present invention includes a first substrate and a second substrate, a first surface of the second substrate having a first MEMS structure and a second MEMS structure formed thereon, and a second surface of the first substrate 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, and 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, and 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, and the first exhaust holes communicate with the first cavity and the third cavity, respectively, and the third cavity communicates with the second exhaust hole. The second exhaust holes are filled with a metal layer, so that the exhaust holes can be sealed without using a laser sealing process, and the sealing problem of large-sized exhaust holes can be solved and costs can be reduced. [Brief explanation of the drawings]

[0021] [Figure 1]FIG. 1 is a cross-sectional view of a MEMS device. [Figure 2] 1 is a flowchart of a method for manufacturing a MEMS device according to an embodiment of the present invention. [Figure 3a] 3A to 3C are cross-sectional views of the MEMS device shown in FIG. 2 in a manufacturing method thereof. [Figure 3b] 3A to 3C are cross-sectional views of the MEMS device shown in FIG. 2 in a manufacturing method thereof. [Figure 3c] 3A to 3C are cross-sectional views of the MEMS device shown in FIG. 2 in a manufacturing method thereof. [Figure 3d] 3A to 3C are cross-sectional views of the MEMS device shown in FIG. 2 in a manufacturing method thereof. [Figure 3e] 3A to 3C are cross-sectional views of the MEMS device shown in FIG. 2 in a manufacturing method thereof. [Figure 3f] 3A to 3C are cross-sectional views of the MEMS device shown in FIG. 2 in a manufacturing method thereof. [Figure 3g] 3A to 3C are cross-sectional views of the MEMS device shown in FIG. 2 in a manufacturing method thereof. [Figure 3h] 3A to 3C are cross-sectional views of the MEMS device shown in FIG. 2 in a manufacturing method thereof. [Figure 3i] 3A to 3C are cross-sectional views of the MEMS device shown in FIG. 2 in a manufacturing method thereof. [Figure 3j] 3A to 3C are cross-sectional views of the MEMS device shown in FIG. 2 in a manufacturing method thereof. [Figure 3k] 3A to 3C are cross-sectional views of the MEMS device shown in FIG. 2 in a manufacturing method thereof. DETAILED DESCRIPTION OF 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 a method for manufacturing a MEMS device according to one embodiment of the present invention, the method for manufacturing the MEMS device includes: Step S1 of 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, the first substrate including a first region corresponding to the first MEMS structure and a second region corresponding to the second MEMS structure; Step S2 of sequentially forming a sacrificial layer to cover the first surface of the first substrate and a protective layer to cover the sacrificial layer; Step S3: etching the second surface of the first substrate to form a first cavity and a first exhaust hole exposing the sacrificial layer in the first region, and to form a second cavity in the second region; a step S4 of bonding the second surface of the first substrate to the first surface of the second substrate so as to communicate the first exhaust hole with the first cavity; Step S5: 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 and 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 the second exhaust holes in the protective layer, thereby forming a third cavity in the sacrificial layer that communicates with the second exhaust holes; and step S6 of evacuating the first cavity through the second exhaust hole, the third cavity, and the first exhaust hole, and filling a metal layer into the second exhaust hole.

[0023] Next, referring to Figures 3a to 3k, the manufacturing method of the MEMS device provided in this embodiment will be introduced in more detail. Figures 3a to 3k are schematic diagrams of the device in the manufacturing method of the MEMS device shown in Figure 2, and Figures 3a to 3k are also schematic vertical cross-sectional views of the MEMS device.

[0024] In step S1, referring to Figures 3a and 3h, a first substrate 21 and a second substrate 31 are provided, and a first MEMS structure and a second MEMS structure are formed on a 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 simply be a semiconductor substrate, or 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.

[0026] Here, in order to improve the performance of the structure fabricated on the first substrate 21, the semiconductor substrate is preferably a double-side polished substrate.

[0027] The first MEMS structure and the second MEMS structure may both include a comb-tooth structure and a mass portion.

[0028] Here, as shown in FIG. 3h, the second substrate 31 may include a semiconductor substrate 311 and a first insulating dielectric layer 312 covering a first surface of the semiconductor substrate 311, and a conductive structure 313 connected to the semiconductor substrate 311 is formed in the first insulating dielectric layer 312, and the conductive structure 313 is exposed from the first insulating dielectric layer 312, and a device structure may further be formed in the semiconductor substrate 311 and the first insulating dielectric layer 312, and the device structure may include a transistor, etc.

[0029] The second substrate 31 may further 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, a fifth cavity 3141 formed in the second sacrificial layer 314, a portion of the first insulating dielectric layer 312 and a portion of the conductive structure 313 exposed to the fifth cavity 3141, the semiconductor layer 315 forming the comb tooth structure and mass portion of the first MEMS structure and the comb tooth structure and mass portion of the second MEMS structure, release holes 3151 formed in the comb tooth structure, between the mass portions and the comb tooth structure, and between the mass portions, the release holes 3151 communicating with the fifth cavity 3141, the fifth cavity 3141 providing a vibration space for the comb tooth structure and mass portion.

[0030] The second substrate 31 may further include a second insulating dielectric layer 316 covering the second surface of the semiconductor substrate 311 to insulate the second surface of the semiconductor substrate 311 from other structures.

[0031] 3h, before the subsequent step of bonding the second surface of the first substrate 21 to the first surface of the second substrate 31, the method for manufacturing a 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 is formed and before the release hole 3151 is formed.

[0032] The step 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 by 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, 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 may 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 can select the material 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 may include a multilayer structure made of these semiconductors.

[0035] The material 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 metal.

[0037] The material of the second sacrificial layer 314 includes, but is not limited to, silicon oxide.

[0038] The material of the second bonding ring 32 may include a metal material such as germanium, aluminum, copper, nickel, or gold.

[0039] In step S2, referring to FIGS. 3a and 3b, 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.

[0040] Here, the protective layer 23 is intended to protect the first sacrificial layer 22 so that the first sacrificial layer 22 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 are significantly different. For example, by setting the etching selectivity of the first sacrificial layer 22 to the protective layer 23 to be greater than 10, when the first sacrificial layer 22 is subsequently etched, the protective layer 23 is not etched or is slightly etched.

[0042] The material of the first sacrificial layer 22 includes, but is not limited to, silicon oxide.

[0043] The material of the protective layer 23 may be silicon nitride, polycrystalline silicon, single crystal silicon, or the like.

[0044] Also, referring to FIG. 3c, before the subsequent step of etching the second surface of the first substrate 21, the method for manufacturing the MEMS device further includes the step of forming a 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 a sputtering or evaporation process, subsequently forming a patterned mask layer (not shown) on the metal material, subsequently etching the metal material using the patterned mask layer as a mask to form the first bonding ring 24, and subsequently removing the patterned mask layer. Here, a structure such as a pad may be formed on the second surface of the first substrate 21 simultaneously with forming the first bonding ring 24.

[0046] The material of the first bonding ring 24 may include a metal material 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 step 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 FIG. 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 FIG. 3f, etching the bottom wall of the fourth cavity 214 down to the first sacrificial layer 22 to form a 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 hole 213 formed by etching, i.e., if the aspect ratio of the first exhaust hole 213 is too high, the first exhaust hole 213 cannot be etched by the etching process. Therefore, when the first substrate 21 is very thick, it is preferable 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, 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 hole 213 is still large.

[0052] Here, the fourth cavity 214 and the first exhaust hole 213 are both for exhausting air, and the width of the fourth cavity 214 is larger than the width of the first exhaust hole 213. The first cavity 211 and the second cavity 212 are respectively for providing a vibration space for 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 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, and they may be formed simultaneously or at different times.

[0053] 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 absorbing layer 25 on a bottom wall of the first cavity 211 to absorb gas and increase the degree of vacuum of the MEMS device. The material of the gas absorbing layer 25 may be a metal material.

[0054] In step S4, referring to FIG. 3i, the second surface of the first substrate 21 is bonded to the first surface of the second substrate 31, and after bonding, the fourth cavity 214 and the first exhaust hole 213 are connected to the first cavity 211.

[0055] Furthermore, after bonding, the first cavity 211 is abutted against the first MEMS structure, the second cavity 212 is abutted against the second MEMS structure, and the first cavity 211 and the second cavity 212 are not connected, so that the first cavity 211 and a first MEMS device corresponding to the first MEMS structure, and the second cavity 212 and a second MEMS device corresponding to 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 a 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] The first bonding ring 24 and the second bonding ring 32 are both annular structures, and the first bonding ring 24 and the second bonding ring 32 may have the same or approximately the same dimensions, 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 is placed opposite the first surface of the second substrate 31, the first bonding ring 24 is butted against the second bonding ring 32, and a predetermined pressure is applied. Once the first bonding ring 24 and the second bonding ring 32 come into contact, a bonding reaction occurs under set conditions to form a metal block, and the distance between the first substrate 21 and the second substrate 31 becomes closer. Here, if the first bonding ring 24 and the second bonding ring 32 are made of different materials (for example, if 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.

[0059] Furthermore, during bonding, the vacuum pressure control process may adopt the vacuum level required for the second MEMS device corresponding to the second cavity 212, and at this time, 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 FIG. 3j, the protective layer 23 is etched to form a plurality of second exhaust holes 231 in the protective layer 23.

[0061] 3g, before bonding the second surface of the first substrate 21 and the first surface of the second substrate 31, a third cavity 221 is formed in the first sacrificial layer 22 by releasing a portion of the first sacrificial layer 22 through the fourth cavity 214 and the first exhaust hole 213. Alternatively, after forming the plurality of second exhaust holes 231 in the protective layer 23, a third cavity 221 is formed in the first sacrificial layer 22 by releasing a portion of the first sacrificial layer 22 through the second exhaust hole 231.

[0062] The second exhaust hole 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 hole 213 .

[0063] Here, a portion of the first sacrificial layer 22 can be released by a vapor hydrofluoric acid (VHF) etching process, i.e., vapor hydrofluoric acid is introduced into the fourth cavity 214 and the first exhaust hole 213, and etching is performed through the fourth cavity 214 and the first exhaust hole 213 to remove a portion of the first sacrificial layer 22. Alternatively, vapor hydrofluoric acid is introduced into the second exhaust hole 231, and etching is performed through the second exhaust hole 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 misaligned. When the metal layer 41 is later filled into the second exhaust hole 231, metal particles will fall through the second exhaust hole 231. By misaligning the first exhaust hole 213 and the second exhaust hole 231, the metal particles can be prevented from falling and entering the first exhaust hole 213, and therefore the metal particles can be prevented from falling through the first exhaust hole 213, entering the inside of the device, and affecting device performance.

[0065] Here, the metal particles fall and accumulate in the third cavity 221 below the second exhaust hole 231. By abutting the first exhaust hole 213 against the middle region of the third cavity 221 and abutting the second exhaust hole 231 against the edge region of the third cavity 221, the metal particles can fall and accumulate in the edge region of the third cavity 221.

[0066] Preferably, the width of the second exhaust hole 231 is smaller than the width of the first exhaust hole 213, so that the metal layer 41 can be quickly and sufficiently filled into the second exhaust hole 231 later, i.e., the hole can be quickly sealed.

[0067] More preferably, the width of the first exhaust hole 213 is 10 μm to 20 μm, and the width of the second exhaust hole 231 is 1 μm to 5 μm.

[0068] The etching process requires a certain aspect ratio for the first exhaust holes 213 formed by etching. That is, if the aspect ratio of the first exhaust holes 213 is too high, the etching process cannot be performed. Furthermore, if the first substrate 21 is very thick, the width of the first exhaust holes 213 formed by etching the first substrate 21 will also be large. In this case, directly using a laser sealing process to seal the first exhaust holes 213 will result in poor results and ultimately no sealing. Furthermore, the dedicated machinery used in the laser sealing process is expensive, and the first exhaust holes 213 must be sealed one by one during the process, resulting in low sealing efficiency and high costs. Therefore, in the method for manufacturing a MEMS device provided by the present invention, the second exhaust holes 231 communicating with the first exhaust holes 213 are formed in the protective layer 23, and then a metal layer 41 is filled in the second exhaust holes 231 to achieve sealing, thereby sealing the exhaust holes without using a laser sealing process. Furthermore, compared to sealing using a laser sealing process, the method for manufacturing a MEMS device provided by the present invention solves the problem that the laser sealing process results in poor sealing results or even no sealing at all for large-width first exhaust holes 213, and enables sealing of the second exhaust holes 231 of any width, resulting in better sealing results. Furthermore, sealing can be achieved using a general deposition machine without using expensive dedicated machines, and the entire second exhaust hole 231 can be sealed at the same time, 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 hole 231, the third cavity 221 and the first exhaust hole 213, thereby bringing the first MEMS device corresponding to the first cavity 211 to the required vacuum level, and a metal layer 41 is filled into the second exhaust hole 231 to seal the second exhaust hole 231, and by sealing the second exhaust hole 231, the third cavity 221, the first exhaust hole 213, the fourth cavity 214 and the first cavity 211 are sealed.

[0070] Here, the metal layer 41 can be deposited on the second exhaust hole 231 using a process requiring a high vacuum level, such as a physical vapor deposition process or an evaporation process. Before performing the physical vapor deposition or evaporation process, the cavity must be evacuated. During this step, the first cavity 211 is connected to the outside through the second exhaust hole 231, the third cavity 221, and the first exhaust hole 213. Therefore, gases within the first cavity 211 can be extracted during the evacuation process, and the first cavity 211 can be maintained at the vacuum level required for the first MEMS device. Because the second cavity 212 is not connected to the outside, the evacuation step does not affect the vacuum level of the second cavity 212, which remains at the vacuum level required for the bonding process. Therefore, the first and second MEMS devices formed on the same substrate can have different vacuum levels. Thereafter, the process of depositing the metal layer 41 is also performed in the same vacuum cavity, so that after the metal layer 41 is deposited, the first cavity 211 still maintains the required vacuum level.

[0071] Furthermore, the process temperature range used when depositing the metal layer 41 on the second exhaust holes 231 by a physical vapor deposition process is 400°C to 500°C, and the process temperature used when depositing the metal layer 41 on the second exhaust holes 231 by an evaporation process is room temperature. Compared to the high process temperature of 700°C to 800°C used when depositing an insulating material on the second exhaust holes 231 by a chemical vapor deposition process, the process temperature used when depositing the metal layer 41 by the physical vapor deposition process and the evaporation process is 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 comprise a gyroscope comb structure and mass, and the second MEMS structure may comprise an accelerometer comb structure and mass, or the first MEMS device may be an accelerometer, the second MEMS device may be a gyroscope, the first MEMS structure may comprise an accelerometer comb structure and mass, and the second MEMS structure may comprise a gyroscope comb structure and mass.

[0073] As can be seen from the above, the method for manufacturing a MEMS device of the present invention includes the steps of sequentially forming a first sacrificial layer and a protective layer 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 and 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 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 first sacrificial layer that communicates with the second exhaust holes and the first exhaust holes, and evacuating the first cavity through the second exhaust holes, the third cavity, and the first exhaust hole, and filling the second exhaust hole with a metal layer. This makes it possible to seal the exhaust hole without using a laser sealing process, solve the problem of sealing large-sized exhaust holes, and reduce costs.

[0074] One embodiment of the present invention provides a MEMS device comprising a first substrate and a second substrate, a first surface of the second substrate having a first MEMS structure and a second MEMS structure formed thereon, the second surface of the first substrate being bonded to the first surface of the second substrate, the first substrate including 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 formed in the first region, a second cavity formed in the second region, the first surface of the first substrate being covered with a sacrificial layer and a protective layer, the protective layer covering the sacrificial layer, a third cavity formed in the sacrificial layer, a plurality of second exhaust holes formed in the protective layer, the first exhaust holes communicating with the first cavity and the third cavity, respectively, the third cavity communicating with the second exhaust hole, and the second exhaust hole being filled with a metal layer.

[0075] Next, the MEMS device of this embodiment will be introduced in more detail with reference to FIG. 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 a first surface of the second substrate 31 .

[0077] The first MEMS structure and the second MEMS structure may both 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 a first surface of the semiconductor substrate 311, the first insulating dielectric layer 312 having a conductive structure 313 connected to the semiconductor substrate 311 formed therein, the conductive structure 313 being exposed from the first insulating dielectric layer 312, and the semiconductor substrate 311 and the first insulating dielectric layer 312 may further have a device structure formed therein, the device structure may include a transistor or the like.

[0079] The second substrate 31 may further 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, a fifth cavity 3141 formed in the second sacrificial layer 314, a portion of the first insulating dielectric layer 312 and a portion of the conductive structure 313 exposed to the fifth cavity 3141, the semiconductor layer 315 forming the comb tooth structure and mass portion of the first MEMS structure and the comb tooth structure and mass portion of the second MEMS structure, release holes 3151 formed in the comb tooth structure, between the mass portions and the comb tooth structure, and between the mass portions, the release holes 3151 communicating with the fifth cavity 3141, the fifth cavity 3141 providing a vibration space for the comb tooth structure and mass portion.

[0080] The second substrate 31 may further include a second insulating dielectric layer 316 covering the second surface of the semiconductor substrate 311 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 simply be a semiconductor substrate, or may be a wafer or the like including a semiconductor substrate, and a device structure such as a transistor may be formed on the first substrate 21 as needed.

[0083] Here, in order to improve the performance of the structure fabricated on the first substrate 21, the semiconductor substrate is preferably a double-side 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 may 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 can select the material 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 may include a multilayer structure made of these semiconductors.

[0086] The material 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 metal.

[0088] The material of the second sacrificial layer 314 includes, but is not limited to, silicon oxide.

[0089] A first cavity 211 and a first exhaust hole 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, and the first cavity 211 and the second cavity 212 are intended to provide vibration space for the first MEMS structure and the second MEMS structure, respectively. Since the first cavity 211 and the second cavity 212 are not connected, the first cavity 211 and the first MEMS device corresponding to the first MEMS structure, and the second cavity 212 and the second MEMS device corresponding to the second MEMS structure are formed on the same substrate.

[0091] A first sacrificial layer 22 and a 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 are respectively connected to the first cavity 211 and the third cavity 221, the third cavity 221 is connected to the second exhaust hole 231, the width of the third cavity 221 is larger 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 the first sacrificial layer 22 is not corroded by a cleaning process or the like.

[0094] The etching rates of the first sacrificial layer 22 and the protective layer 23 are significantly different. For example, by setting the etching selectivity of the first sacrificial layer 22 to the protective layer 23 to be greater than 10, when the first sacrificial layer 22 is etched to form the third cavity 221, the protective layer 23 is not etched or is slightly etched.

[0095] The material of the first sacrificial layer 22 includes, but is not limited to, silicon oxide.

[0096] The material of the protective layer 23 may be silicon nitride, polycrystalline silicon, single crystal silicon, or the like.

[0097] The first region may further have a fourth cavity 214 communicating with the first exhaust hole 213, the first exhaust hole 213 being 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 hole 213 , and both the width and depth of the fourth cavity 214 are smaller than the first cavity 211 and the second cavity 212 .

[0099] The MEMS device may further include a gas absorbing layer 25 formed on the bottom wall of the first cavity 211 to absorb gas and increase the degree of vacuum in the MEMS device. The gas absorbing layer 25 may be made of a metal material.

[0100] Preferably, the first exhaust hole 213 and the second exhaust hole 231 are misaligned. When filling the second exhaust hole 231 with the metal layer 41, metal particles fall through the second exhaust hole 231. Therefore, by misaligning the positions of the first exhaust hole 213 and the second exhaust hole 231, it is possible to prevent the metal particles from falling and entering the first exhaust hole 213, and therefore it is possible to prevent the metal particles from falling through the first exhaust hole 213, entering the inside of the device, and affecting device performance.

[0101] Here, the metal particles fall and accumulate in the third cavity 221 below the second exhaust hole 231. By abutting the first exhaust hole 213 against the middle region of the third cavity 221 and abutting the second exhaust hole 231 against the edge region of the third cavity 221, the metal particles can fall and accumulate in the edge region of the third cavity 221.

[0102] Preferably, the width of the second exhaust hole 231 is smaller than the width of the first exhaust hole 213, so that the metal layer 41 can quickly and sufficiently fill the second exhaust hole 231, i.e., quickly achieve hole sealing.

[0103] More preferably, the width of the first exhaust hole 213 is 10 μm to 20 μm, and the width of the second exhaust hole 231 is 1 μm to 5 μm.

[0104] Since the first cavity 211 communicates with the second exhaust hole 231, the third cavity 221, and the first exhaust hole 213, the first cavity 211 can be evacuated via the second exhaust hole 231, the third cavity 221, and the first exhaust hole 213, thereby achieving a required vacuum level in the first MEMS device corresponding to the first cavity 211. Furthermore, by filling the second exhaust hole 231 with the metal layer 41, the second exhaust hole 231 can be sealed (hermetically sealed), and further the third cavity 221, the first exhaust hole 213, the fourth cavity 214, and the first cavity 211, which communicate with the second exhaust hole 231, can be sealed.

[0105] The MEMS device is a first bonding ring 24 formed on the second surface of the first substrate 21; The substrate further includes a second bonding ring 32 formed on the first surface of the second substrate 31, and 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 a metal material such as germanium, aluminum, copper, nickel, or gold.

[0107] The first bonding ring 24 and the second bonding ring 32 are both annular structures, and the first bonding ring 24 and the second bonding ring 32 may have the same or approximately the same dimensions, 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 is placed opposite the first surface of the second substrate 31, the first bonding ring 24 is butted against the second bonding ring 32, and a predetermined pressure is applied. Once the first bonding ring 24 and the second bonding ring 32 come into contact, a bonding reaction occurs under set conditions to form a metal block, and the distance between the first substrate 21 and the second substrate 31 becomes closer. Here, if the first bonding ring 24 and the second bonding ring 32 are made of different materials (for example, if 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.

[0109] In addition, when bonding, the vacuum level required for the second MEMS device corresponding to the second cavity 212 may be adopted, and at this time, 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] Because the first cavity 211 is connected to the outside through the second exhaust hole 231, the third cavity 221, and the first exhaust hole 213, gas can be extracted from the first cavity 211, and the first cavity 211 can be maintained at the required vacuum level for the first MEMS device. Because the second cavity 212 is not connected to the outside, evacuating the first cavity 211 does not affect the vacuum level of the second cavity 212, and the second cavity 212 still maintains the same vacuum level as during the bonding process. Therefore, the first and second MEMS devices formed on the same substrate can have different vacuum levels. Furthermore, because the process of filling the metal layer 41 is also performed in the same vacuum cavity, the first cavity 211 still maintains the required vacuum level after filling the metal layer 41.

[0111] The first MEMS device may be a gyroscope, the second MEMS device may be an accelerometer, the first MEMS structure may comprise a gyroscope comb structure and mass, and the second MEMS structure may comprise an accelerometer comb structure and mass, or the first MEMS device may be an accelerometer, the second MEMS device may be a gyroscope, the first MEMS structure may comprise an accelerometer comb structure and mass, and the second MEMS structure may comprise a gyroscope comb structure and mass.

[0112] 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, the etching process cannot be performed. Furthermore, if the first substrate 21 is very thick, the width of the first exhaust holes 213 formed by etching the first substrate 21 will also be large. In this case, directly using a laser sealing process to seal the first exhaust holes 213 will result in poor results and ultimately no sealing. Furthermore, the dedicated machinery used in the laser sealing process is expensive, and the first exhaust holes 213 must be sealed one by one during the process, resulting in low sealing efficiency and high costs. Therefore, in the MEMS device provided by the present invention, the second exhaust holes 231 communicating with the first exhaust holes 213 are formed in the protective layer 23, and sealing is achieved by filling the second exhaust holes 231 with the metal layer 41, thereby sealing the exhaust holes without using a laser sealing process. Furthermore, compared to sealing using a laser sealing process, the MEMS device provided by the present invention solves the problem that the laser sealing process results in poor sealing results for large-width first exhaust holes 213, and even results in no sealing at all. Instead, sealing of the second exhaust holes 231 of any width in the MEMS device can be achieved, resulting in better sealing results. Furthermore, sealing can be achieved using a general deposition machine without using expensive dedicated machines, and the entire second exhaust hole 231 can be sealed at the same time, significantly improving sealing efficiency and reducing costs.

[0113] As can be seen from the above, the MEMS device of the present invention comprises a first substrate and a second substrate, a first surface of the second substrate having a first MEMS structure and a second MEMS structure formed thereon, and a second surface of the first substrate being bonded to the first surface of the second substrate, the first substrate including 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 formed in the first region, and a second cavity formed in the second region, the first surface of the first substrate being covered with a first sacrificial layer and a protective layer, the protective layer covering the first sacrificial layer, a third cavity formed in the first sacrificial layer, and a plurality of second exhaust holes formed in the protective layer, the first exhaust holes communicating with the first cavity and the third cavity respectively, and the third cavity communicating with the second exhaust hole, and the second exhaust hole being filled with a metal layer, thereby sealing the exhaust holes without using a laser sealing process, solving the problem of sealing large-sized exhaust holes, and reducing costs.

[0114] The above description is merely a description of preferred embodiments of the present invention and does not limit the scope of the present invention in any way. Any changes and modifications made by those skilled in the art based on the above disclosure are included in the scope of protection of the claims. [Explanation of symbols]

[0115] 11 First board 12 Second board 121 Exhaust vent 21 First board 211 First Cavity 212 Second cavity 213 First Exhaust Vent 214 4th cavity 22 First Sacrificial Layer 221 Third Cavity 23 Protective layer 231 Second exhaust port 24 First Bonding Ring 25 Gas absorption layer 31 Second board 311 Semiconductor substrate 312 First insulating dielectric layer 313 Conductive Structure 314 Second Sacrificial Layer 3141 5th cavity 315 Semiconductor layer 3151 Release hole 316 Second insulating dielectric layer 32 Second bonding ring 41 Metal layer

Claims

1. providing a first substrate and a second substrate, wherein a first surface of the second substrate has a first MEMS structure and a second MEMS structure formed thereon, 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 covering a first surface of the first substrate and a protective layer covering the sacrificial layer; Etching a second surface of the first substrate to form a first cavity and a first exhaust hole exposing the sacrificial layer in the first region and to form a second cavity in the second region; bonding the second surface of the first substrate to the first surface of the second substrate so as to communicate the first exhaust hole with the first cavity; 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 and the first surface of the second substrate, or releasing a portion of the sacrificial layer through the second exhaust holes after forming the 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; evacuating 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.

2. The method for manufacturing a MEMS device according to claim 1 , wherein the first exhaust hole and the second exhaust hole are offset from each other.

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

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

5. A fourth cavity communicating with the first exhaust hole is further formed in the first region, and the steps of forming the first cavity, the first exhaust hole, and the fourth cavity in the first region and forming the second cavity in the second region include: Etching a second surface of the first substrate to form a first cavity and a fourth cavity in the first region and a second cavity in the second region; The method for manufacturing a MEMS device according to claim 1 , further comprising the step of: etching a bottom wall of the fourth cavity to form a first exhaust hole in the bottom wall of the fourth cavity.

6. prior to the step of etching the second surface of the first substrate, 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; forming a second bonding ring on the first surface of the second substrate; 2. The method for manufacturing a MEMS device according to claim 1, wherein the step of bonding the second surface of the first substrate to the first surface of the second substrate includes a 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.

7. 10. The method of claim 1, wherein the first MEMS structure comprises a gyroscope comb structure and the second MEMS structure comprises an accelerometer comb structure.

8. a first substrate and a second substrate, a first MEMS structure and a second MEMS structure being formed on a first surface of the second substrate; a second surface of the first substrate bonded to a first surface of the second substrate, the first substrate including 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 formed in the first region, a second cavity formed in the second region, the first surface of the first substrate covered with a sacrificial layer and a protective layer, the protective layer covering the sacrificial layer, a third cavity formed in the sacrificial layer, a plurality of second exhaust holes formed in the protective layer, the first exhaust holes communicating with the first cavity and the third cavity, respectively, the third cavity communicating with the second exhaust holes, and the second exhaust holes being filled with a metal layer.

9. The MEMS device according to claim 8 , wherein the first exhaust hole and the second exhaust hole are offset from each other.

10. The MEMS device according to claim 8 , wherein the width of the second exhaust hole is smaller than the width of the first exhaust hole.

11. 11. The MEMS device according to claim 10, wherein the width of the first exhaust hole is 10 μm to 20 μm, and the width of the second exhaust hole is 1 μm to 5 μm.

12. 9. The MEMS device of claim 8, wherein a fourth cavity communicating with the first exhaust hole is further formed in the first region, and the first exhaust hole is located between the third cavity and the fourth cavity.

13. a first bonding ring formed on the second surface of the first substrate; 9. The MEMS device of 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.

14. 9. The MEMS device of claim 8, wherein the first MEMS structure comprises a gyroscope comb structure and the second MEMS structure comprises an accelerometer comb structure.

15. The MEMS device according to claim 8, further comprising a gas absorbing layer formed on a bottom wall of the first cavity for absorbing gas to increase the degree of vacuum in the MEMS device.

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