A MEMS device and a manufacturing method thereof

Abstract

A MEMS device and a method for manufacturing the same, the method comprising: providing a top cover layer, the top cover layer including a region for a first MEMS device and a region for a second MEMS device, each formed with a first groove and a second groove; forming a gas release layer in the first groove; performing a first bonding between the top cover layer and the first surface of a first substrate; performing a first patterning process on the first substrate to form a first interdigitated structure of the first MEMS device above the first groove and a second interdigitated structure of the second MEMS device above the second groove; performing a second bonding between the second surface of the first substrate and the second substrate to form a first cavity and a second cavity; the second bonding is further used to heat the gas release layer to generate gas, so that the vacuum level of the first cavity is lower than that of the second cavity. The method for manufacturing a MEMS device according to an embodiment of the present invention can simultaneously form a first MEMS device and a second MEMS device with different vacuum levels.

Description

Technical Field

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

[0002] MEMS (Micro-Electro-Mechanical System) refers to a microsystem that integrates mechanical components, drive components, optical systems, and electronic control systems into a whole. MEMS devices have advantages such as small size and low power consumption, and are widely used in many fields such as smartphones, tablets, game consoles, automobiles, and drones. Commonly used MEMS chips include accelerometers, gyroscopes, pressure sensors, microphones, etc. Similar to integrated circuits, MEMS devices are also developing towards high performance, miniaturization, low cost, and integration.

[0003] To achieve complete motion detection, multiple MEMS devices must be integrated onto a single chip. Different MEMS devices have different requirements for vacuum levels, but current manufacturing processes for integrating multiple MEMS devices struggle to address this issue. Summary of the Invention

[0004] The Summary of the Invention introduces a series of simplified concepts that will be further described in the Detailed Description of the Invention. The Summary of the Invention is not intended to limit the key features and essential features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0005] In order to solve the existing problems, an embodiment of the present invention provides a method for manufacturing a MEMS device, comprising:

[0006] Providing a top cover layer, the top cover layer including a region for a first MEMS device and a region for a second MEMS device, wherein a first groove is formed in the region for the first MEMS device and a second groove is formed in the region for the second MEMS device;

[0007] forming a gas release layer in the first groove;

[0008] Performing a first bonding between the top cover layer and the first surface of the first substrate;

[0009] Performing a first patterning process on the first substrate to form a first interdigitated structure of the first MEMS device above the first groove, and forming a second interdigitated structure of the second MEMS device above the second groove;

[0010] The second surface of the first substrate is bonded to the second substrate for a second time, so that the first groove and the second substrate together form a first cavity for accommodating the first interdigitated structure; and the second groove and the second substrate together form a second cavity for accommodating the second interdigitated structure; the second bonding is also used to heat the gas release layer to generate gas, so that the vacuum degree of the first cavity is lower than the vacuum degree of the second cavity.

[0011] In one embodiment, the gas-releasing layer comprises a polymer material layer.

[0012] In one embodiment, the polymer material layer is made of polyimide.

[0013] In one embodiment, the first bonding temperature is lower than a temperature at which the gas release layer is heated to generate gas, and the second bonding temperature is higher than or equal to a temperature at which the gas release layer is heated to generate gas.

[0014] In one embodiment, before performing the first patterning process on the first substrate, the method further includes:

[0015] A second patterning process is performed on the substrate to form a protrusion on the second surface of the first substrate, wherein a projection position of the protrusion is located outside the first groove and the second groove.

[0016] In one embodiment, before performing the first patterning process on the first substrate, the method further includes:

[0017] A bonding metal layer is formed on the surface of the boss.

[0018] In one embodiment, before forming the gas release layer in the first groove, the method further includes: forming a cap dielectric layer on the cap layer.

[0019] In one embodiment, after performing a second bonding between the second surface of the first substrate and the second substrate, the method further comprises:

[0020] The top cover layer is thinned.

[0021] In one embodiment, the first MEMS device includes an accelerometer and the second MEMS device includes a gyroscope.

[0022] Another aspect of an embodiment of the present invention provides a MEMS device, which is manufactured using the method described above.

[0023] According to the manufacturing method of the MEMS device provided by the present invention, a gas release layer is formed in the first groove of the first MEMS device. The gas release layer is heated to generate gas when the first substrate and the second substrate are bonded, so that the vacuum degree of the first cavity of the first MEMS device is lower than the vacuum degree of the second cavity of the second MEMS device, thereby enabling the first MEMS device and the second MEMS device with different vacuum degrees to be formed simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following drawings of the present invention are incorporated herein as part of the present invention for understanding the present invention. The drawings show embodiments of the present invention and the description thereof is used to explain the principle of the present invention.

[0025] In the attached figure:

[0026] Figure 1 A schematic flow chart showing a method for manufacturing a MEMS device according to a specific embodiment of the present invention;

[0027] Figures 2A to 2I The cross-sectional view of a semiconductor device obtained by sequentially performing steps in a method for manufacturing a MEMS device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0028] In the following description, numerous specific details are provided to provide a more thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without one or more of these details. In other instances, certain technical features well known in the art are not described to avoid confusion with the present invention.

[0029] It should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the invention to those skilled in the art. In the drawings, the dimensions and relative sizes of layers and regions may be exaggerated for clarity. Like reference numerals throughout represent like elements.

[0030] It should be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it can be directly on, adjacent to, connected to, or coupled to the other element or layer, or there can be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, 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, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, a first element, component, region, layer, or part discussed below may be represented as a second element, component, region, layer, or part without departing from the teachings of the present invention.

[0031] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," etc., may be used herein for convenience of description to describe the relationship of one element or feature shown in the figures to other elements or features. It should be understood that the spatially relative terms are intended to include different orientations of the device in use and operation in addition to the orientations shown in the figures. For example, if the device in the drawings is flipped, then the elements or features described as "under" or "beneath" or "beneath" the other elements will be oriented as "over" the other elements or features. Thus, the exemplary terms "under" and "under" may include both the upper and lower orientations. The device may be oriented otherwise (rotated 90 degrees or in other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0032] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present invention. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0033] Motion sensors often combine a MEMS accelerometer (accelerometer) with a MEMS gyroscope (gyroscope). The accelerometer detects acceleration, while the gyroscope detects angular velocity. To meet the demands for low cost and small size, the accelerometer and gyroscope can be integrated on the same substrate.

[0034] Taking a single-axis gyroscope as an example, its operating principle is as follows: two moving masses move continuously in opposite directions. Applying an angular velocity parallel to the plane of motion generates a Coriolis force perpendicular to the direction of motion, causing the masses to displace in a manner proportional to the applied angular velocity. This displacement causes a change in capacitance between the comb electrodes of the masses and the fixed electrode. Therefore, the angular velocity applied to the gyroscope's input is converted into an electrical parameter that can be detected by a dedicated circuit. An accelerometer operates on a similar principle to a gyroscope, similarly detecting acceleration based on the capacitance change caused by the displacement of the masses.

[0035] Different MEMS devices have different ideal vacuum levels. For example, a key performance metric for a gyroscope is the quality factor, which measures its sensitivity. This factor is primarily influenced by the vacuum level within the cavity. When the gyroscope is not operating, the mass undergoes resonant motion within the cavity. To improve sensitivity, a high vacuum level is required within the cavity. A key performance metric for an accelerometer is the damping factor. The damping factor generally has two modes: structural damping, which is generated by friction between structural layers; and air viscous damping, which is generated by atmospheric pressure and is much stronger than structural damping. The mass of an accelerometer needs to return to its original position after deformation. To prevent adhesion between the interdigitated fingers, a relatively high air viscous damping is required. In other words, to ensure high sensitivity and low power consumption, a gyroscope requires a high vacuum level, while an accelerometer requires a low vacuum level to maintain high performance and reliability. When manufacturing an accelerometer or gyroscope separately, the vacuum level can be controlled by adjusting the gas sealing pressure during the packaging process. However, when integrating an accelerometer and gyroscope, it is difficult to achieve different vacuum levels. One solution is to add a getter to the gyroscope area to increase the vacuum level, but this is not very effective and the cost of the getter is high.

[0036] In order to fully understand the present invention, detailed structures and steps will be provided in the following description to illustrate the technical solutions proposed by the present invention. Preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may also have other implementations.

[0037] Figure 1 A flowchart showing a method for manufacturing a MEMS device according to an embodiment of the present invention is provided; Figures 2A to 2I The cross-sectional view of the semiconductor device obtained by sequentially performing each step of the manufacturing method of the MEMS device according to an embodiment of the present invention is shown. Figure 1 as well as Figures 2A to 2I A method for manufacturing a MEMS device according to an embodiment of the present invention is described in detail.

[0038] First refer to Figure 1 The method for manufacturing a MEMS device according to an embodiment of the present invention is described as follows. Figure 1 As shown, the method 100 for manufacturing a MEMS device includes the following steps:

[0039] In step S101, a top cover layer is provided, wherein the top cover layer includes a region for a first MEMS device and a region for a second MEMS device, wherein a first groove is formed in the region for the first MEMS device, and a second groove is formed in the region for the second MEMS device;

[0040] In step S102, a gas release layer is formed in the first groove;

[0041] In step S103, the top cover layer is first bonded to the first surface of the first substrate;

[0042] At step S104, a first patterning process is performed on the first substrate to form a first interdigitated structure of the first MEMS device above the first groove, and a second interdigitated structure of the second MEMS device above the second groove;

[0043] In step S105, the second surface of the first substrate is bonded to the second substrate for a second time, so that the first groove and the second substrate together form a first cavity for accommodating the first interdigitated structure; and the second groove and the second substrate together form a second cavity for accommodating the second interdigitated structure; the second bonding is also used to heat the gas release layer to generate gas, so that the vacuum degree of the first cavity is lower than the vacuum degree of the second cavity.

[0044] According to the method 100 for manufacturing a MEMS device provided in an embodiment of the present invention, a gas release layer is formed in a first groove of a first MEMS device. The gas release layer is heated to generate gas when bonding the first substrate and the second substrate, so that the vacuum degree of the first cavity of the first MEMS device is lower than the vacuum degree of the second cavity of the second MEMS device, thereby enabling the simultaneous formation of a first MEMS device and a second MEMS device with different vacuum degrees.

[0045] The following combination Figures 2A to 2I The implementation process of the method for manufacturing a MEMS device according to an embodiment of the present invention is exemplarily described.

[0046] First, refer to Figure 2A, providing a top cover layer 201. The material of the top cover layer 201 includes polysilicon, single crystal silicon, silicon on insulator or other suitable semiconductor materials. The top cover layer 201 includes an area for the first MEMS device and an area for the second MEMS device, and the area for the first MEMS device and the area for the second MEMS device are used to form the first MEMS device and the second MEMS device, respectively. In some embodiments, the first MEMS device is an accelerometer and the second MEMS device is a gyroscope, and the vacuum degree required for the accelerometer and the gyroscope is different. In other embodiments, the first MEMS device and the second MEMS device can also be other MEMS devices with different vacuum degree requirements.

[0047] A first groove 202 is formed on the first surface of the top cover layer 201 in an area corresponding to the first MEMS device, and a second groove 203 is formed in an area corresponding to the second MEMS device. The first groove 202 and the second groove 203 will subsequently constitute cavities of the first MEMS device and the second MEMS device, respectively. The surface opposite the first surface of the top cover layer 201, i.e., the surface where the first groove 202 and the second groove 203 are formed, is defined as the second surface.

[0048] Reference Figure 2A and Figure 2B When forming the first groove 202 and the second groove 203, the top cover layer 201 may be patterned first to form the first groove 202, and then patterned to form the second groove 203; alternatively, the top cover layer 201 may be patterned first to form the second groove 203, and then patterned to form the first groove 202. In some embodiments, the first groove 202 and the second groove 203 may also be formed simultaneously in a single patterning process.

[0049] In some embodiments, see Figure 2C After forming the first groove 202 and the second groove 203, a capping dielectric layer 204 may be formed to cover the capping layer 201. For example, the material of the capping dielectric layer 204 may include tetraethyl orthosilicate (TEOS). Other oxides may also be used as the material of the capping dielectric layer 204. The capping dielectric layer 204 is used to isolate and bond the capping layer 204 to the first substrate 206.

[0050] Afterwards, refer to Figure 2D , forming a gas release layer 205 in the first groove 202. For example, a gas release material layer with a predetermined thickness covering the first surface of the top cover layer 201 may be formed first, and then the gas release material layer may be etched to form the gas release layer 205 in the first groove 202.

[0051] The gas release layer 205 can generate gas when heated, thereby achieving different vacuum levels in the cavities of the first and second MEMS devices. In some embodiments, the temperature during bonding of the top cover layer 201 to the first substrate 206 is lower than the temperature at which the gas release layer 205 generates gas when heated, while the temperature during bonding of the first substrate to the second substrate is higher than or equal to the temperature at which the gas release layer 205 generates gas when heated. This ensures that the gas release layer 205 does not generate gas when bonding the top cover layer 201 to the first substrate 206, but does generate gas when bonding the first substrate 206 to the second substrate 208, ensuring that the gas generated by heat is sealed within the cavity.

[0052] In some embodiments, the gas-releasing layer 205 may be a polymer material layer that decomposes upon heating to generate gas. The polymer material layer may be any material that can decompose upon heating to generate gas, and whose decomposition temperature satisfies the requirements. In some embodiments, the polymer material layer includes polyimide (PI), which has a low cost and a suitable decomposition temperature. In other embodiments, the polymer material layer may also include polyimide (PBO), dry film, or the like.

[0053] Next, see Figure 2E , bonding the first surface of the top cover layer 201 to the first substrate 206. Exemplarily, the bonding process between the top cover layer 201 and the first substrate 206 is fusion bonding, the temperature of which is lower than the temperature at which the gas release layer 205 decomposes under heat. Exemplarily, the material of the first substrate 206 may include polycrystalline silicon, single crystal silicon, silicon on insulator, or other suitable semiconductor materials. After bonding the first surface of the top cover layer 201 to the first substrate 206, the first substrate 206 may be thinned to have an appropriate thickness.

[0054] After the top cover layer 201 is bonded to the first substrate 206, the first substrate 206 covers the first groove 202 and the second groove 203, forming a sealed cavity. However, since the first substrate 206 needs to be patterned later to reopen the sealed cavity, the bonding temperature of the top cover layer 201 and the first substrate 206 is lower than the thermal decomposition temperature of the gas release layer 205 to prevent the gas release layer 205 from decomposing at this time and thus escaping the generated gas when the sealed cavity is reopened.

[0055] Next, see Figure 2FA second patterning process is performed on the first substrate 206 to form bosses. The projected positions of the bosses are located outside the first and second grooves 202, 203, leaving space for the formation of the interdigital structure above the first and second grooves 202, 203. The patterning process here is referred to as the second patterning process to distinguish it from the first patterning process described below, and is not intended to limit the specific process. The bosses provide mechanical support and electrical conductivity for the interdigital structure.

[0056] In some embodiments, after the bosses are formed, a metal bonding layer 207 is formed on top of the bosses for metal bonding with the metal interconnect structure of the first substrate 206. In some embodiments, the material of the metal bonding layer 207 includes metal materials such as germanium, aluminum, copper, nickel, and gold. In some embodiments, a metal layer can be deposited on the patterned surface of the first substrate 206 using a sputtering or evaporation process, and then the metal layer is patterned to form the metal bonding layer 207 on the surface of the bosses.

[0057] See also Figure 2G After forming the bosses and the metal bonding layer 207, the first substrate 206 is subjected to a first patterning process to form an interdigital structure. While the interdigital structure is being formed, the first cavity and the second cavity are opened and communicate with the outside world again.

[0058] The interdigitated structure can also be called a mass block. When the MEMS device moves, the capacitance between the interdigitated structures and between the interdigitated and the second substrate changes, thereby converting the motion parameters into electrical parameters. Specifically, the first patterning process includes patterning the first substrate 206 in the area of ​​the first MEMS device to form a plurality of first interdigitated structures, and patterning the first substrate 206 in the area of ​​the second MEMS device to form a plurality of second interdigitated structures. For example, the first interdigitated structure is the interdigitated structure of an accelerometer, and the second interdigitated structure is the interdigitated structure of a gyroscope. The number, size, etc. of the two can be set according to the process requirements of the accelerometer and the gyroscope.

[0059] Next, see Figure 2H , a second bonding is performed between the first substrate 206 and the second substrate 208. The second bonding is also used to heat the gas release layer 205 to generate gas, thereby lowering the vacuum level of the first cavity to a lower level than that of the second cavity. Exemplarily, the temperature of the second bonding is higher than the temperature of the first bonding.

[0060] The second substrate 208 includes a semiconductor substrate, a device structure, and an interconnect structure. The semiconductor substrate may be made of, but is not limited to, at least one of the following materials: silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbon (SiC), silicon germanium carbon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP), or other III / V compound semiconductors, or may be silicon-on-insulator (SOI), stacked silicon-on-insulator (SSOI), stacked silicon germanium-on-insulator (S-SiGeOI), silicon germanium-on-insulator (SiGeOI), or germanium-on-insulator (GeOI). The device structure includes a transistor, which forms part of a control circuit for providing control signals to the first MEMS device and the second MEMS device. Exemplarily, the transistor includes a CMOS device, specifically an NMOS device and a PMOS device, as well as other semiconductor devices.

[0061] For example, a dielectric layer covers the device structure, and a metal interconnection structure is formed in the dielectric layer. The top of the metal interconnection structure is electrically connected to the MEMS device through the metal bonding layer 207 and the bumps of the first substrate 206.

[0062] The second bonding may include metal bonding the metal bonding layer 207 to the metal interconnect structure in the second substrate 208. The metal bonding temperature is higher than the temperature at which the gas release layer 205 generates gas when heated, so that the gas release layer 205 generates gas when heated. After the second bonding, the top cover layer 201, the first substrate 206, and the second substrate 208 together form a sealed first cavity and a second cavity. The gas generated by the gas release layer 205 when heated is sealed within the first cavity, making the vacuum level of the first cavity lower than the vacuum level of the second cavity.

[0063] In some embodiments, after the first substrate 206 and the second substrate 208 are bonded, the back side of the top cover layer 201 may be thinned to have a desired thickness.

[0064] like Figure 2I As shown, in some embodiments, after the back side of the first substrate 206 is thinned, the top cover layer 201 and the first substrate 206 may be sliced ​​(diced) to separate different MEMS devices.

[0065] At this point, the process steps of the manufacturing method of the MEMS device according to an embodiment of the present invention have been completed. It can be understood that the manufacturing method of the MEMS device according to the embodiment of the present invention not only includes the above steps, but may also include other necessary steps before, during or after the above steps, which are all included in the scope of the manufacturing method according to the embodiment of the present invention.

[0066] According to the manufacturing method of the MEMS device provided by the present invention, a gas release layer is formed in the first groove of the first MEMS device. The gas release layer is heated to generate gas when the first substrate and the second substrate are bonded, so that the vacuum degree of the first cavity of the first MEMS device is lower than the vacuum degree of the second cavity of the second MEMS device, thereby enabling the first MEMS device and the second MEMS device with different vacuum degrees to be formed simultaneously.

[0067] like Figure 2I As shown, an embodiment of the present invention further provides a MEMS device, which is manufactured by the manufacturing method 100 of the MEMS device as described above. Specifically, the MEMS device includes a first MEMS device and a second MEMS device integrated on a second substrate, the first MEMS device having a first cavity, the second MEMS device having a second cavity, and a gas release layer formed in the first cavity, so that the vacuum degree of the first cavity is less than the vacuum degree of the second cavity. In one embodiment, the first MEMS device is an accelerometer and the second MEMS device is a gyroscope. Since the MEMS device of the embodiment of the present invention is manufactured using the above method, the first MEMS device and the second MEMS device integrated on the same substrate have different vacuum degrees.

[0068] The present invention has been described through the above-described embodiments. However, it should be understood that the above-described embodiments are for illustrative and illustrative purposes only and are not intended to limit the present invention to the described embodiments. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the above-described embodiments and that various variations and modifications may be made based on the teachings of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing a MEMS device, characterized in that: The method comprises: Providing a top cover layer, the top cover layer including a region for a first MEMS device and a region for a second MEMS device, wherein a first groove is formed in the region for the first MEMS device and a second groove is formed in the region for the second MEMS device; forming a gas release layer in the first groove; Performing a first bonding between the top cover layer and the first surface of the first substrate; Performing a first patterning process on the first substrate to form a first interdigitated structure of the first MEMS device above the first groove, and forming a second interdigitated structure of the second MEMS device above the second groove; The second surface of the first substrate is bonded to the second substrate for a second time, so that the first groove and the second substrate together form a first cavity for accommodating the first interdigitated structure; and the second groove and the second substrate together form a second cavity for accommodating the second interdigitated structure; the second bonding is also used to heat the gas release layer to generate gas, so that the vacuum degree of the first cavity is lower than the vacuum degree of the second cavity.

2. The manufacturing method according to claim 1, wherein The gas release layer includes a polymer material layer.

3. The manufacturing method according to claim 2, wherein: The material of the polymer material layer includes polyimide.

4. The manufacturing method according to claim 1, wherein: The first bonding temperature is lower than a temperature at which the gas release layer is heated to generate gas, and the second bonding temperature is higher than or equal to a temperature at which the gas release layer is heated to generate gas.

5. The manufacturing method according to claim 1, wherein: Before performing the first patterning process on the first substrate, the method further includes: A second patterning process is performed on the substrate to form a protrusion on the second surface of the first substrate, wherein a projection position of the protrusion is located outside the first groove and the second groove.

6. The manufacturing method according to claim 5, wherein: Before performing the first patterning process on the first substrate, the method further includes: A bonding metal layer is formed on the surface of the boss.

7. The manufacturing method according to claim 1, wherein: Before forming the gas release layer in the first groove, the method further includes: forming a cap dielectric layer on the cap layer.

8. The manufacturing method according to claim 1, wherein: After performing a second bonding between the second surface of the first substrate and the second substrate, the method further includes: The top cover layer is thinned.

9. The manufacturing method according to any one of claims 1 to 8, characterized in that The first MEMS device includes an accelerometer, and the second MEMS device includes a gyroscope.

10. A MEMS device, characterized in that: The MEMS device is manufactured by the method according to any one of claims 1 to 9.

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