A MEMS device and a method of manufacturing the same

Abstract

A MEMS device and a method for manufacturing the same, the method comprising: providing a device substrate, the device substrate comprising a MEMS structure region and a bonding region surrounding the MEMS structure region; forming a bonding metal ring structure on the bonding region on a first surface of the device substrate; forming a protective layer to cover at least a bonding surface of the bonding metal ring structure for bonding with a cap substrate; performing at least one cleaning process on the device substrate; at least partially removing the protective layer to expose the bonding surface; and providing a cap substrate, and bonding the cap substrate and the device substrate through the bonding metal ring structure. The method of the present application can form a protective layer on the surface of the bonding metal ring structure, avoiding damage to the bonding metal ring structure during multiple cleaning processes, thereby improving the reliability and yield of the device.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically to a MEMS device and its fabrication method. Background Technology

[0002] MEMS (Micro-Electro-Mechanical Systems) refers to a miniature system that integrates mechanical components, drive components, optical systems, and electronic control systems into a single unit. MEMS devices offer advantages such as small size and low power consumption, leading to a wide range of applications in smartphones, tablets, game consoles, automobiles, drones, and other fields. Commonly used MEMS chips include accelerometers, gyroscopes, pressure sensors, and microphones. Similar to integrated circuits, MEMS devices are also evolving towards higher performance, miniaturization, lower cost, and greater integration.

[0003] In the fabrication process of MEMS devices such as accelerometers and gyroscopes, to achieve complete motion detection, multiple MEMS devices typically need to be integrated onto a single integrated chip. This requires bonding processes to join the cap substrate and the device substrate, which contains the mechanical microstructures required for the MEMS device, into a single unit. Eutectic bonding, such as aluminum-germanium bonding, is a commonly used bonding process. Before eutectic bonding, the device substrate needs to be wet-cleaned to remove etching residues and other impurities. However, during the cleaning process, bonding ring structures (such as aluminum bonding rings) are already formed on the device substrate for bonding. The wet cleaning process often damages these bonding ring structures, affecting the subsequent bonding effect between the device substrate and the cap substrate, thus impacting the reliability of the MEMS device and leading to a decrease in product yield. Summary of the Invention

[0004] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. The summary section of this invention is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0005] To address the existing problems, this invention provides a method for fabricating a MEMS device, comprising:

[0006] A device substrate is provided, the device substrate including a MEMS structure region and a bonding region surrounding the MEMS structure region;

[0007] A bonding metal ring structure is formed in the bonding region on the first surface of the device substrate;

[0008] A protective layer is formed to at least cover the bonding surfaces of the bonded metal ring structure for bonding with the cap substrate;

[0009] The device substrate is cleaned at least once;

[0010] The protective layer is at least partially removed to expose the mating surface;

[0011] A cap substrate is provided, and the cap substrate and the device substrate are bonded together through the bonding metal ring structure.

[0012] Exemplarily, the bonding region on the first surface of the device substrate forms a bonding metal ring structure, comprising:

[0013] An etch stop layer is formed on the first surface of the device substrate;

[0014] The etch stop layer is etched to expose the first surface of the device substrate to form an opening in the bonding region;

[0015] The bonded metal ring structure is formed in the opening, wherein there is a gap between the sidewall of the bonded metal ring structure in the opening and the sidewall of the opening.

[0016] Exemplarily, a protective layer is formed to at least cover the mating surfaces of the bonded metal ring structure for engagement with the cap substrate, including:

[0017] A protective material layer is deposited, which covers the bonded metal ring structure and the etch stop layer and fills the gaps;

[0018] The protective material layer and the etch stop layer are etched to remove the etch stop layer and form the protective layer.

[0019] Exemplarily, the method of this application further includes:

[0020] After the cleaning process but before removing the protective layer, the device substrate is etched from its first surface to form a comb-like structure in the MEMS structure region; or...

[0021] After removing the protective layer and before bonding the cap substrate and the device substrate through the bonding metal ring structure, the device substrate is etched from the first surface of the device substrate to form a comb structure in the MEMS structure region.

[0022] Exemplarily, the device substrate includes a substrate layer, a sacrificial layer on the substrate layer, and a structural layer on the sacrificial layer, the structural layer being used to form the comb structure. After forming the comb structure, the method of this application further includes:

[0023] The sacrificial layer is removed at the same time as the protective layer.

[0024] For example, the at least one cleaning process includes a first cleaning process, wherein the cleaning agent used in the first cleaning process includes hydroxylamine and its derivatives; and / or

[0025] The at least one cleaning process includes a second cleaning process, wherein the cleaning agent used in the second cleaning process includes a hydroxydopamine organic solvent.

[0026] For example, the material of the bonded metal ring structure includes at least one of the following: aluminum, germanium, copper, tin, nickel, and gold.

[0027] Exemplarily, a cavity is formed on the side of the cap substrate facing the device substrate, and an bonding layer is formed on the outer side of the cavity of the cap substrate for bonding with the device substrate. Bonding the cap substrate and the device substrate using the bonding metal ring structure includes:

[0028] The bonding layer of the cap substrate and the bonding metal ring structure of the device substrate are bonded together, and the cavity corresponds to the MEMS structure region.

[0029] For example, the comb structure includes the mechanical microstructure required for at least one MEMS device, such as a MEMS gyroscope or a MEMS accelerometer.

[0030] In another aspect, the present invention provides a MEMS device, which is manufactured using the method described above.

[0031] The MEMS device and its fabrication method according to the present invention can form a protective layer on the surface of the bonding metal ring structure, which at least avoids damage to the bonding surface of the bonding metal ring structure during the cleaning process. Furthermore, removing the protective layer after cleaning will not affect the subsequent bonding of the device substrate and the cap substrate, thereby improving the bonding effect and thus improving the reliability and yield of the device. Attached Figure Description

[0032] The following drawings, which are incorporated herein by reference as part of this invention, are provided for understanding the invention. The drawings illustrate embodiments of the invention and their descriptions, serving to explain the principles of the invention.

[0033] In the attached image:

[0034] Figures 1A to 1C A cross-sectional schematic diagram of a device obtained by sequentially implementing a method for fabricating a MEMS device in the related art is shown.

[0035] Figures 2A to 2FA cross-sectional schematic diagram of the device obtained by sequentially implementing the fabrication method of the MEMS device in one embodiment is shown.

[0036] Figure 3 A flowchart illustrating a method for fabricating a MEMS device in one embodiment is shown. Detailed Implementation

[0037] The invention will now be described more fully with reference to the accompanying drawings, which illustrate embodiments of the invention. However, the invention can be embodied in various forms and should not be construed as limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. The same reference numerals denote the same elements throughout.

[0038] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this invention, the first element, component, area, layer, or portion discussed below may be referred to as the second element, component, area, layer, or portion.

[0039] Spatial relation terms such as “below,” “under,” “below,” “under,” “above,” “above,” etc., are used herein for convenience of description to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, then the element or feature described as “below” or “under” the other element or feature will be oriented “above” the other element or feature. Therefore, the exemplary terms “below” and “under” can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or otherwise) and the spatial descriptive terms used herein will be interpreted accordingly.

[0040] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprise” and / or “comprising,” when used in this specification, identify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0041] Embodiments of the invention are described herein with reference to cross-sectional views that serve as schematic diagrams of ideal embodiments (and intermediate structures). Thus, variations in the shape shown can be anticipated due to, for example, manufacturing techniques and / or tolerances. Therefore, embodiments of the invention should not be limited to the specific shapes of the regions shown herein, but include shape deviations due to, for example, manufacturing processes. For example, implantation regions shown as rectangular typically have rounded or curved features at their edges and / or implantation concentration gradients, rather than a binary change from implantation regions to non-implantation regions. Similarly, the buried regions formed by implantation can result in some implantation in the region between the buried region and the surface traversed during implantation. Therefore, the regions shown in the figures are substantially schematic, and their shapes are not intended to show the actual shapes of the regions of the device and are not intended to limit the scope of the invention.

[0042] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms as defined in commonly used dictionaries shall be construed as having the meaning consistent with their meaning in the relevant field and / or the context of this specification, and shall not be interpreted in an ideal or overly formal sense, unless expressly defined herein.

[0043] To fully understand this invention, detailed steps and structures will be set forth in the following description to illustrate the technical solution proposed by this invention. Preferred embodiments of the invention are described in detail below; however, in addition to these detailed descriptions, the invention may have other embodiments.

[0044] In related technologies, during the fabrication of MEMS devices such as inertial sensors, methods such as aluminum-germanium bonding are often used to bond the device substrate and the cap substrate. For example, ... Figures 1A to 1CAs shown, firstly, an etch stop layer 101 is formed on the first surface of the device substrate; the etch stop layer 101 is etched to expose the first surface of the device substrate to form an opening; the bonding metal ring structure 102 is formed in the opening, wherein there is a gap between the sidewall of the bonding metal ring structure 102 in the opening and the sidewall of the opening; then, the etch stop layer is removed; then, the device substrate is etched from the first surface of the device substrate to form a comb structure 103; after that, cleaning is performed, for example, multiple wet cleanings, such as a first cleaning process. The cleaning agent used in the first cleaning process includes hydroxylamine and its derivatives, and also includes solvents, water, chelating agents, etc. Since the bonding metal ring structure 102 is exposed during the first cleaning process, the cleaning agent of the first cleaning process directly contacts the bonding metal ring structure 102, causing damage to the surface of the bonding metal ring structure 102 (e.g., black spots and pits), affecting the subsequent bonding effect. Alternatively, a second cleaning process is also performed, in which the cleaning agent includes hydroxydopamine-based organic solvents. Because the bonded metal ring structure 102 is exposed during the second cleaning process, the cleaning agent in the second cleaning treatment directly contacts the bonded metal ring structure 102, which can cause damage to the surface of the bonded metal ring structure 102 (e.g., corrosion damage, making the surface of the bonded metal ring structure 102 rough and thus yellowing), thereby affecting the subsequent bonding effect. Therefore, since the bonded metal ring structure 102, for example, made of aluminum, undergoes multiple wet cleaning processes after deposition, the cleaning agent in these wet cleaning processes causes varying degrees of damage to the bonded metal ring structure 102, affecting the bonding effect and reducing reliability.

[0045] Therefore, in view of the aforementioned technical problems, this invention proposes a method for fabricating MEMS devices, such as... Figure 3 As shown, it mainly includes the following steps:

[0046] Step S1, providing a device substrate, the device substrate including a MEMS structure region and a bonding region surrounding the MEMS structure region;

[0047] Step S2: A bonding metal ring structure is formed in the bonding region on the first surface of the device substrate;

[0048] Step S3: Form a protective layer to at least cover the bonding surface of the bonded metal ring structure for bonding with the cap substrate;

[0049] Step S4: Perform at least one cleaning process on the device substrate;

[0050] Step S5: Remove at least partially the protective layer to expose the mating surface;

[0051] Step S6: Provide a cap substrate and bond the cap substrate and the device substrate together through the bonding metal ring structure.

[0052] The MEMS device and its fabrication method according to the present invention can form a protective layer on the surface of the bonding metal ring structure, which at least avoids damage to the bonding surface of the bonding metal ring structure during the cleaning process. Furthermore, removing the protective layer after cleaning will not affect the subsequent bonding of the device substrate and the cap substrate, thereby improving the bonding effect and thus improving the reliability and yield of the device.

[0053] Example 1

[0054] Below, we will refer to the appendix. Figures 2A to 2F The manufacturing method of the MEMS device of the present invention will be described in detail. By way of example, the manufacturing method of the MEMS device of the present invention includes the following steps:

[0055] First, step S1 is performed to provide a substrate and a device substrate, the device substrate including a MEMS structure region and a bonding region surrounding the MEMS structure region.

[0056] like Figure 2A As shown, the device substrate 200 includes a base layer 210, a sacrificial layer 220, and a structural layer 230. The base layer 210 may include a substrate and a device structure formed on the substrate. The substrate may be a bulk silicon substrate, specifically at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs, or other III / V compound semiconductors, including multilayer structures composed of these semiconductors, or the substrate may be silicon-on-insulator (SOI), silicon-on-insulator stacked (SSOI), silicon-on-insulator stacked germanium (S-SiGeOI), silicon-on-insulator germanium (SiGeOI), or germanium-on-insulator (GeOI), etc. The device structure includes transistors, which form part of a control circuit. Exemplarily, the transistors include CMOS devices, specifically including NMOS devices and PMOS devices, as well as other semiconductor devices. Exemplarily, a dielectric layer covers the device structure, and a metal interconnect structure is formed in the dielectric layer. Optionally, the interconnect structure includes interconnect devices such as conductive vias, and is not limited to any one of them.

[0057] The sacrificial layer 220 can also be formed using materials such as silicon oxide, silicon nitride, or other suitable materials. The structural layer 230 can be used for subsequent fabrication of the comb tooth structure, and can specifically be at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs, or other III / V compound semiconductors, including multilayer structures composed of these semiconductors. The thickness of the structural layer 230 can be determined according to the dimensions of the intended comb tooth structure.

[0058] The device substrate includes a MEMS structure region and a bonding region surrounding the MEMS structure region. The MEMS structure region is used to form a subsequent comb structure, while the bonding region is used to form a bonding metal ring structure in the region, wherein the bonding region surrounds the MEMS structure region.

[0059] Next, in step S2, a bonding metal ring structure is formed in the bonding region on the first surface of the device substrate.

[0060] In one example, such as Figure 2A As shown, forming a bonding metal ring structure 250 in a bonding region on a first surface of the device substrate 200 includes the following steps: First, forming an etch stop layer 240 on the first surface of the device substrate 200; etching the etch stop layer 240 to expose the first surface of the device substrate 200 to form an opening in the bonding region; forming the bonding metal ring structure 250 in the opening, wherein there is a gap between the sidewall of the bonding metal ring structure 250 in the opening and the sidewall of the opening, wherein the method of forming the bonding metal ring structure 250 in the opening may include: forming a metal material layer to cover the etch stop layer 240 and fill the opening in the etch stop layer 240; forming a mask layer, such as a photoresist layer, on the metal material layer; etching the metal material layer with the mask layer as a mask, stopping at the etch stop layer 240, to form the bonding metal ring structure 250, wherein the top surface of the bonding metal ring structure 250 is higher than the top surface of the etch stop layer 240; and then removing the mask layer. In addition to serving as a stop layer during the etching process to form the bonded metal ring structure 250, preventing damage to the device substrate 200, the etch stop layer 240 also prevents metal atoms from migrating into the device substrate 200 due to the large-area coverage of metal material layers such as aluminum on the first surface of the device substrate 200. Furthermore, since some cleaning steps are performed after aluminum etching, the presence of the etch stop layer 240 can prevent damage to the device substrate 200 during cleaning.

[0061] More specifically, in some embodiments, the etch stop layer 240 may not be formed, and the method for forming the bonded metal ring structure 250 may include: depositing a metal material layer on a first surface of the device substrate 200; then forming a mask layer, such as a photoresist layer, on the metal material layer; etching the metal material layer using the mask layer as a mask to form the bonded metal ring structure 250; and then removing the mask layer. The etch stop layer 240 may serve as a stop layer during the etching process to form the bonded metal ring structure 240. Optionally, the material of the etch stop layer 240 may include silicon oxide, silicon nitride, silicon oxynitride, or other suitable materials.

[0062] In some embodiments, the material of the bonding metal ring structure 240 includes at least one of the following: aluminum, germanium, copper, tin, nickel, gold, or other metal materials suitable for bonding. In some embodiments, a metal material layer may be deposited on the first surface of the device substrate 200 using a sputtering or evaporation process. Subsequently, the metal material layer may be etched using etching processes such as dry etching, reactive ion etching (RIE), ion beam etching, or plasma etching.

[0063] In some embodiments, the method of this application further includes: forming electrode trenches exposing a first surface of the device substrate 200 in the etch stop layer, and forming electrodes in the electrode trenches that are higher than the top surface of the etch stop layer. The material of the electrodes may include at least one of tungsten, aluminum, titanium, copper, gold, nickel, chromium, tantalum, cobalt, molybdenum, polycrystalline silicon, and doped monocrystalline silicon.

[0064] Subsequently, step S3 is performed to form a protective layer to at least cover the bonding surfaces of the bonded metal ring structure for bonding with the cap substrate.

[0065] Specifically, the method for forming a protective layer may include the following steps: First, such as Figure 2A As shown, a protective material layer 260a is deposited, which covers the bonding metal ring structure 250 and the etch stop layer 240 and fills the gaps, and also covers the exposed first surface of the device substrate 200; then, as Figure 2B As shown, a protective material layer and an etch stop layer are etched to remove the etch stop layer and form the protective layer 260. The protective layer 260 at least covers the bonding surface of the bonding metal ring structure 250 for bonding with the cap substrate (i.e., the surface of the bonding metal ring structure 250 facing away from the device substrate 200), or the protective layer 260 may cover the entire surface of the bonding metal ring structure 250, or the protective layer 260 may cover the entire surface of the bonding metal ring structure 250 and a portion of the first surface of the device substrate 200. The protective layer 260 can protect and isolate the bonding metal ring structure 250 to prevent it from being damaged during subsequent cleaning processes.

[0066] In some other embodiments, the etch stop layer may not be formed, or the etch stop layer may be formed first, and then the etch stop layer may be removed after the bonding metal ring structure 250 is formed.

[0067] The material of the protective layer 260 may include tetraethyl or ...

[0068] Subsequently, step S4 is performed to clean the device substrate at least once.

[0069] The cleaning process can be used to remove residues generated during the etching process. The at least one cleaning process includes a first cleaning process. The cleaning agent used in the first cleaning process includes hydroxylamine and its derivatives. The cleaning agent in the first cleaning process also includes solvents, water, chelating agents, etc. Since the bonded metal ring structure 250 is covered with a protective layer 260 during the first cleaning process, the cleaning agent of the first cleaning process can be prevented from directly contacting the bonded metal ring structure 250, thereby avoiding damage to the surface of the bonded metal ring structure 250 (such as black spots and pits), and thus improving the effect of subsequent bonding.

[0070] In some embodiments, at least one cleaning process includes a second cleaning process. The cleaning agent used in the second cleaning process includes a hydroxydopamine-based organic solvent. The second cleaning can remove etching residues, such as polymer residues remaining at the edges of the pattern due to dry etching. Since the bonded metal ring structure 250 is covered with a protective layer 260 during the second cleaning process, the cleaning agent of the second cleaning process can be prevented from directly contacting the bonded metal ring structure 250, thereby avoiding damage to the surface of the bonded metal ring structure 250 (e.g., corrosion damage, which makes the surface of the bonded metal ring structure 250 rough and yellow), thus improving the effect of subsequent bonding.

[0071] In some embodiments, such as Figure 2DAs shown, the method of this application further includes: etching the device substrate 200 from the first surface of the device substrate 200 to form a comb structure 270 in the MEMS structure region. Specifically, a patterned mask layer, such as a patterned photoresist layer, can be formed on the first surface of the device substrate 200. The patterned mask layer defines the pattern of the comb structure. The structure layer 230 of the device substrate 200 is etched using a process such as dry etching or wet etching with the patterned mask layer as a mask, stopping at the sacrificial layer 220 to form the comb structure 270. After etching is completed, the patterned mask layer can be removed, for example by ashing the photoresist layer.

[0072] It is worth mentioning that the aforementioned cleaning process can be performed after the comb tooth structure 270 is formed, or one of the first cleaning process and the second cleaning process can be performed before the comb tooth structure 270 is formed, and the other of the first cleaning process and the second cleaning process can be performed after the comb tooth structure 270 is formed, or the cleaning process can be performed before the comb tooth structure 270 is formed.

[0073] The comb structure includes the mechanical microstructure required for at least one MEMS device, such as a MEMS gyroscope or a MEMS accelerometer. For example, it may include comb structures for both gyroscopes and accelerometers. The number and size of these comb structures can be configured according to the manufacturing requirements of the accelerometer and gyroscope. Multiple comb structures can be located in different regions of the device substrate.

[0074] The comb structure can also be called a mass block. When the MEMS device moves, the capacitance between the comb structures and between the comb and the second substrate changes, thereby converting motion parameters into electrical parameters.

[0075] It is worth mentioning that, for simplicity, the accompanying drawings of this application only show a portion of the complete MEMS device.

[0076] Then, step S5 is performed to remove at least partially the protective layer to expose the mating surface.

[0077] To avoid the protective layer negatively affecting subsequent bonding, the protective layer is at least partially removed to expose the bonding surface; more specifically, as shown in... Figure 2E As shown, the entire protective layer can be removed to expose the entire bonded metal ring structure 250. The protective layer can be removed using dry etching, wet etching, or vapor phase etching processes, such as using gaseous hydrogen fluoride (VHF) to etch and remove the protective layer. In some embodiments, the sacrificial layer 220 can also be removed simultaneously with the protective layer. For example, the sacrificial layer beneath the structural layer 230 can be etched and removed by introducing gaseous hydrogen fluoride (VHF) into the gaps between the comb-like structures.

[0078] It is worth mentioning that the comb structure 270 can also be performed after step S5, and the protective layer and sacrificial layer can be removed separately.

[0079] Subsequently, step S6 is performed, providing a cap substrate, and bonding the cap substrate and the device substrate through the bonding metal ring structure.

[0080] Specifically, such as Figure 2F As shown, a cavity is formed on the side of the cap substrate facing the device substrate. A bonding layer 310 is formed on the outer side of the cap substrate 300 for bonding with the device substrate 200. The cap substrate 300 and the device substrate 200 are bonded through the bonding metal ring structure 250, including: bonding the bonding layer 310 of the cap substrate 300 to the bonding metal ring structure 250 of the device substrate 200. The cavity corresponds to the MEMS structure region, that is, the cavity structure corresponds to the comb structure. The comb structure in different regions can correspond to different cavities, that is, the cap substrate can form multiple cavities.

[0081] The cap substrate 300 is a bulk silicon substrate, which can be at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs, or other III / V compound semiconductors, including multilayer structures composed of these semiconductors, or silicon-on-insulator (SOI), silicon-on-insulator stacked (SSOI), silicon-on-insulator stacked (S-SiGeOI), silicon-on-insulator (SiGeOI), or germanium-on-insulator (GeOI). The cap substrate 300 includes a first region and a second region, the first region corresponding to the formation of a first MEMS device, and the second region corresponding to the formation of a second MEMS device. The first MEMS device can be a gyroscope, and the second MEMS device can be an accelerometer.

[0082] The bonding layer 310 is made of metals such as germanium, aluminum, copper, nickel, and gold. In some embodiments, a metal material layer can be deposited on the side of the cap substrate 300 used for bonding with the device substrate 200 using sputtering or evaporation processes. Dry etching, reactive ion etching (RIE), ion beam etching, plasma etching, and other etching processes can be used in this step. In some embodiments, if one of the bonding metal ring structure 250 and the bonding layer 310 is made of aluminum and the other of germanium, then the bonding process uses aluminum-germanium eutectic bonding.

[0083] It is worth mentioning that the above steps are only examples, and the order of the steps can be adjusted without conflict.

[0084] This concludes the description of the key steps in the manufacturing method of the MEMS device of the present invention. Other steps may also be included in the complete fabrication of the MEMS device, which will not be elaborated here.

[0085] The MEMS device and its fabrication method according to the present invention can form a protective layer on the surface of the bonding metal ring structure, which at least avoids damage to the bonding surface of the bonding metal ring structure during the cleaning process. Furthermore, removing the protective layer after cleaning will not affect the subsequent bonding of the device substrate and the cap substrate, thereby improving the bonding effect and thus improving the reliability and yield of the device.

[0086] Example 2

[0087] This invention also provides a MEMS device, which can be fabricated by the method described in Embodiment 1 above. Specifically, the MEMS device includes a device substrate and a cap substrate bonded together. A bonding metal ring structure is formed on the surface of the device substrate facing the cap substrate, and a bonding layer is formed on the surface of the cap substrate facing the device substrate. The device substrate and the cap substrate are bonded together by the bonding metal ring structure and the bonding layer. A comb-like structure is formed on the device substrate. Since the device of this invention is fabricated using the aforementioned method, it has the same advantages as the aforementioned method.

[0088] It is worth mentioning that a complete device may also include other components, which will not be elaborated here.

[0089] Although several embodiments have been described herein, it should be understood that many other modifications and embodiments will be conceived by those skilled in the art, all of which will fall within the spirit and scope of the disclosed concept. More particularly, various modifications and changes can be made in terms of the arrangement and / or components of the subject matter within the scope of the disclosure, drawings, and appended claims. In addition to modifications and changes in components and / or arrangement, the use of alternative methods will also be obvious to those skilled in the art.

Claims

1. A method for fabricating a MEMS device, characterized in that, The method includes: A device substrate is provided, the device substrate including a MEMS structure region and a bonding region surrounding the MEMS structure region; A bonding metal ring structure is formed in the bonding region on the first surface of the device substrate; A protective layer is formed to at least cover the bonding surface of the bonded metal ring structure for bonding with the cap substrate, wherein the material of the protective layer is ethyl silicate, oxide, or nitride; The device substrate is cleaned at least once; The protective layer is at least partially removed to expose the mating surface; A cap substrate is provided, and the cap substrate and the device substrate are bonded together through the bonding metal ring structure.

2. The preparation method according to claim 1, characterized in that, The bonding region on the first surface of the device substrate forms a bonding metal ring structure, including: An etch stop layer is formed on the first surface of the device substrate; The etch stop layer is etched to expose the first surface of the device substrate to form an opening in the bonding region; The bonded metal ring structure is formed in the opening, wherein there is a gap between the sidewall of the bonded metal ring structure in the opening and the sidewall of the opening.

3. The preparation method according to claim 2, characterized in that, A protective layer is formed to at least cover the bonding surfaces of the bonded metal ring structure for bonding with the cap substrate, including: A protective material layer is deposited, which covers the bonded metal ring structure and the etch stop layer and fills the gaps; The protective material layer and the etch stop layer are etched to remove the etch stop layer and form the protective layer.

4. The preparation method according to claim 1, characterized in that, The method in this application also includes: After the cleaning process but before removing the protective layer, the device substrate is etched from its first surface to form a comb-like structure in the MEMS structure region; or... After removing the protective layer and before bonding the cap substrate and the device substrate through the bonding metal ring structure, the device substrate is etched from the first surface of the device substrate to form a comb structure in the MEMS structure region.

5. The preparation method according to claim 4, characterized in that, The device substrate includes a substrate layer, a sacrificial layer on the substrate layer, and a structural layer on the sacrificial layer. The structural layer is used to form the comb tooth structure. After forming the comb tooth structure, the method of this application further includes: The sacrificial layer is removed at the same time as the protective layer.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The at least one cleaning process includes a first cleaning process, wherein the cleaning agent used in the first cleaning process includes hydroxylamine and its derivatives; and / or The at least one cleaning process includes a second cleaning process, wherein the cleaning agent used in the second cleaning process includes a hydroxydopamine organic solvent.

7. The preparation method according to any one of claims 1 to 5, characterized in that, The materials of the bonded metal ring structure include at least one of the following: aluminum, germanium, copper, tin, nickel, and gold.

8. The preparation method according to any one of claims 1 to 5, characterized in that, A cavity is formed on the side of the cap substrate facing the device substrate. An bonding layer is formed on the outer side of the cap substrate, on the side used for bonding with the device substrate. The cap substrate and the device substrate are bonded together using the bonding metal ring structure, including: The bonding layer of the cap substrate and the bonding metal ring structure of the device substrate are bonded together, and the cavity corresponds to the MEMS structure region.

9. The preparation method according to any one of claims 4 to 5, characterized in that, The comb structure includes the mechanical microstructure required for at least one MEMS device, such as a MEMS gyroscope or a MEMS accelerometer.

10. A MEMS device, characterized in that, The MEMS device is prepared using the method described in any one of claims 1-9.

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