MEMS device and manufacturing method thereof

Abstract

The invention discloses an MEMS device and a manufacturing method thereof, and the method comprises the steps: forming a first MEMS structure: providing a first substrate, forming a first sensing layer on the first substrate, and sequentially forming a first cavity and a second sensing layer on the first sensing layer; forming a second MEMS structure: providing a second substrate, forming a third sensing layer on the second substrate, and sequentially forming a second cavity and a fourth sensing layer on the third sensing layer; bonding the second sensing layer and the fourth sensing layer to form a common sensing layer; the part, corresponding to the first cavity, of the first substrate is removed, and the first sensing layer forms a movable sensing layer. According to the MEMS device and the manufacturing method thereof provided by the invention, the stacked double-layer capacitor structure is prepared by adopting a heterogeneous bonding mode, the process is simple, the implementation is high, the prepared device structure does not need to be plugged, the problem that the sensing layer is uneven due to hole plugging is avoided, and the reliability of the device is improved. The reliability problems of air leakage and the like of the hole blocking structure caused by repeated pressure measurement motion of the upper-layer pressure sensing film of the sealing cavity are also avoided, and the service life and the yield of the device are improved.

Description

Technical Field

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

[0002] Micro-Electro-Mechanical Systems (MEMS) technology is a rapidly developing high-tech field in recent years. It utilizes advanced semiconductor manufacturing processes to achieve mass production of devices such as sensors and actuators. Compared to their traditional counterparts, MEMS devices offer significant advantages in terms of size, power consumption, weight, and price. In the market, major applications of MEMS devices include pressure sensors, accelerometers, and silicon microphones.

[0003] Current capacitive pressure sensors primarily employ silicon surface micromachining technology, utilizing thin-film deposition, photolithography, and etching processes to fabricate the sensor structure. The fabrication process is mostly concentrated on the surface region of the wafer's front side. A number of release holes are etched into the central region of the upper electrode using an etching process. Then, a sacrificial layer is etched through the release holes to create movable cavities for the upper electrode. These release holes are then sealed using a plugging structure, forming a closed absolute pressure chamber for pressure measurement. However, the plugging process creates uneven protrusions on the flat surface of the sensitive membrane structure, introducing uncontrollable stress factors. This stress affects the critical sensitive membrane structure, increasing measurement errors. Furthermore, the sealed chamber may experience leaks and other failures during long-term use due to reliability issues, severely impacting device lifespan and 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] This invention provides a method for manufacturing a MEMS device, comprising:

[0006] Forming the first MEMS structure:

[0007] A first substrate is provided, and a first sensing layer is formed on the first substrate;

[0008] A first cavity and a second sensing layer are sequentially formed on the first sensing layer;

[0009] Forming a second MEMS structure:

[0010] A second substrate is provided, and a third sensing layer is formed on the second substrate;

[0011] A second cavity and a fourth sensing layer are sequentially formed on the third sensing layer;

[0012] The second sensing layer and the fourth sensing layer are bonded together to form a common sensing layer;

[0013] Remove the portion of the first substrate corresponding to the first cavity to form a movable sensing layer from the first sensing layer.

[0014] For example, the movable sensing layer and the common sensing layer constitute a movable capacitor, and the common sensing layer and the third sensing layer constitute a reference capacitor.

[0015] For example, forming a first cavity on the first sensing layer includes:

[0016] A first sacrificial layer and a second sensing layer are sequentially formed on the first sensing layer;

[0017] Multiple first through holes are formed on the second sensing layer;

[0018] The first cavity is formed by removing a portion of the first sacrificial layer through multiple first through-holes.

[0019] For example, a plurality of second through holes are formed on the fourth sensing layer, and a plurality of first through holes are correspondingly disposed with a plurality of second through holes. After the second sensing layer and the fourth sensing layer are bonded, the plurality of first through holes and the plurality of second through holes are connected, and the first cavity and the second cavity form a common cavity.

[0020] Exemplarily, the method further includes a step of thinning the second substrate to a thickness of 40 μm to 50 μm.

[0021] For example, the thickness range of the first sensing layer, the second sensing layer, the third sensing layer and the fourth sensing layer includes 1um to 5um, and the first sensing layer, the second sensing layer, the third sensing layer and the fourth sensing layer are made of doped polycrystalline silicon.

[0022] For example, before removing the portion of the first substrate corresponding to the first cavity, the method further includes: etching the first substrate to form a four-corner support structure at the bottom of the first substrate, the four-corner support structure being used to fix the MEMS device to the packaging substrate.

[0023] For example, the method further includes the step of forming a metal wiring layer on the second substrate, the metal wiring layer being connected to the third sensing layer, the common sensing layer and the movable sensing layer, respectively.

[0024] The present invention also provides a MEMS device manufactured according to any one of the above methods, comprising: a first substrate, wherein a first sensing layer, a first cavity, a common sensing layer, a second cavity, a third sensing layer, and a second substrate are sequentially formed on the first substrate; wherein the first substrate includes an opening corresponding to the first cavity, so that the first sensing layer forms a movable sensing layer.

[0025] For example, the MEMS device includes a pressure sensor, and the sensing layer includes a pressure sensing membrane.

[0026] According to the MEMS device and its manufacturing method provided by the present invention, a stacked double-layer capacitor structure is prepared by heterogeneous bonding. The process is simple and highly feasible. The prepared device structure does not require plugging, which avoids the problem of uneven sensing layer caused by plugging. It also avoids reliability problems such as air leakage caused by repeated pressure measurement of the pressure-sensing diaphragm on the upper layer of the sealed cavity. This improves the service life and yield of the device. Attached Figure Description

[0027] 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.

[0028] In the attached image:

[0029] Figure 1 A flowchart illustrating a method for manufacturing a MEMS device according to an embodiment of the present invention;

[0030] Figures 2A-2F A cross-sectional schematic diagram of the structure obtained by sequentially implementing the manufacturing method of the MEMS device according to an embodiment of the present invention;

[0031] Figure 3 This is a top view schematic diagram of a MEMS device according to an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of the structure of an electronic device including the MEMS device of the present invention. Detailed Implementation

[0033] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0034] It should be understood that the invention can be embodied in various forms and should not be construed as being 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.

[0035] 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.

[0036] 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.

[0037] 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 “comprising” and / or “including,” 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.

[0038] To fully understand this invention, detailed steps and structures will be presented 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.

[0039] This invention provides a method for manufacturing a MEMS device, such as... Figure 1 As shown, it includes:

[0040] Step S110: Forming a first MEMS structure: providing a first substrate, forming a first sensing layer on the first substrate, and sequentially forming a first cavity and a second sensing layer on the first sensing layer;

[0041] Step S120: Forming a second MEMS structure: providing a second substrate, forming a third sensing layer on the second substrate, and sequentially forming a second cavity and a fourth sensing layer on the third sensing layer;

[0042] Step S130: Bond the second sensing layer and the fourth sensing layer to form a common sensing layer;

[0043] Step S140: Remove the portion of the first substrate corresponding to the first cavity to form a movable sensing layer from the first sensing layer.

[0044] Below, for reference Figures 2A to 2F The method for manufacturing the MEMS device of the present invention is described in detail, wherein, Figures 2A to 2F This is a cross-sectional schematic diagram of the structure obtained by sequentially implementing the manufacturing method of the MEMS device according to an embodiment of the present invention.

[0045] First, execute step S110, such as Figure 2A-2B As shown, a first MEMS structure 100 is formed by providing a first substrate 101, forming a first sensing layer 103 on the first substrate 101, and sequentially forming a first cavity 107 and a second sensing layer 105 on the first sensing layer 103.

[0046] For example, forming a first cavity 107 on the first sensing layer 103 includes: sequentially forming a first sacrificial layer 104 and a second sensing layer 105 on the first sensing layer 103; forming a plurality of first through holes 106 on the second sensing layer 105; and removing a portion of the first sacrificial layer 104 through the plurality of first through holes 106 to form the first cavity 107.

[0047] In one embodiment, such as Figure 2A As shown, a first substrate 101 is provided. The first substrate 101 can be any suitable semiconductor substrate, such as a silicon substrate. It can also be at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP or other III / V compound semiconductors, including multilayer structures composed of these semiconductor materials, or silicon on insulator (SOI), silicon on insulator stacked on insulator (SSOI), silicon on insulator stacked on insulator (S-SiGeOI), silicon on insulator (SiGeOI) and germanium on insulator (GeOI), or it can also be a double-side polished wafer (DSP), or a ceramic substrate such as alumina, quartz or glass substrate, etc.

[0048] Next, as Figure 2A As shown, a first insulating layer 102, a first sensing layer 103, a first sacrificial layer 104, and a second sensing layer 105 are sequentially formed on the first substrate 101. The material of the first insulating layer 102 includes, but is not limited to, an oxide layer, and the method for forming the first insulating layer 102 can employ any existing technology well known to those skilled in the art, such as thermal oxidation, vapor deposition, etc. The materials of the first sensing layer 103 and the second sensing layer 105 include, but are not limited to, doped polysilicon, and the thickness of the first sensing layer 103 and the second sensing layer 105 ranges from 1µm to 5µm. The material of the first sacrificial layer 104 includes, but is not limited to, an oxide layer, and the thickness of the first sacrificial layer 104 can be set as needed. By controlling the thickness of the first sacrificial layer 104, the spacing between the first sensing layer 103 and the second sensing layer 105 is controlled, thereby controlling the capacitance value between the first sensing layer 103 and the second sensing layer 105. The formation process of the first sensing layer 103, the first sacrificial layer 104 and the second sensing layer 105 can employ any existing technology well known to those skilled in the art, such as low-pressure chemical vapor deposition (LPCVD), laser ablation deposition (LAD) and selective epitaxial growth (SEG) formed by chemical vapor deposition (CVD), physical vapor deposition (PVD) or atomic layer deposition (ALD), or low-temperature chemical vapor deposition (LTCVD), thermally rapid chemical vapor deposition (RTCVD) and plasma-enhanced chemical vapor deposition (PECVD).

[0049] Next, as Figure 2B As shown, a plurality of first vias 106 are formed on the second sensing layer 105. Specifically, a patterned mask layer (not shown) is formed on the second sensing layer 105 by photolithography, and then the second sensing layer 105 is etched to form a plurality of first vias 106. The method of etching the second sensing layer 105 can employ any existing technology well known to those skilled in the art, preferably dry etching, which includes, but is not limited to, reactive ion etching (RIE), ion beam etching, plasma etching, laser ablation, or any combination of these methods.

[0050] Next, the first sacrificial layer 104 is etched through multiple first vias 106 to form a first cavity 107 and a first support portion 104' surrounding the first cavity. The method of etching the first sacrificial layer 104 can employ any existing technology well known to those skilled in the art, preferably wet etching. The wet etching solution is selective. In the case where the first sacrificial layer 104 is silicon oxide and the first sensing layer 103 and the second sensing layer 105 are doped polysilicon, the wet etching solution can be a BOE solution, which is prepared from HF, NH4F and deionized water.

[0051] Next, step S120 is performed to form a second MEMS structure 200: a second substrate 201 is provided, and a third sensing layer 203 is formed on the second substrate 201; a second cavity 207 and a fourth sensing layer 205 are sequentially formed on the third sensing layer 203.

[0052] For example, forming a second cavity 207 on the third sensing layer 203 includes: sequentially forming a second sacrificial layer 204 and a fourth sensing layer 205 on the third sensing layer 203; forming a plurality of second through holes 206 on the fourth sensing layer 205; and removing a portion of the second sacrificial layer 204 through the plurality of second through holes 206 to form the second cavity 207.

[0053] The method for forming the second MEMS structure 200 can refer to the method for forming the first MEMS structure 100 described above, and will not be repeated here.

[0054] Next, proceed with step S130, as follows: Figure 2C As shown, the second sensing layer 105 and the fourth sensing layer 205 are bonded to form a common sensing layer.

[0055] In one embodiment, before bonding the second sensing layer 105 and the fourth sensing layer 205, a chemical mechanical polishing step is included to bring the surfaces of the second sensing layer 105 and the fourth sensing layer 205 to the required bonding condition. Then, the second sensing layer 105 and the fourth sensing layer 205 are bonded to each other, thereby achieving the bonding of the first MEMS structure 100 and the second MEMS structure 200.

[0056] In one embodiment, a plurality of first through holes 106 formed on the second sensing layer 105 are correspondingly disposed with a plurality of second through holes 206 formed on the fourth sensing layer 205. After the second sensing layer 105 and the fourth sensing layer 205 are bonded, the plurality of first through holes 106 and the plurality of second through holes 206 are interconnected, and the first cavity 107 and the second cavity 207 form a common cavity. Since the second sensing layer 105 and the fourth sensing layer 205 are bonded using a vacuum bonding process, the common cavity formed by the first cavity 107 and the second cavity 207 maintains a vacuum state or a low-pressure state close to a vacuum, for example, the air pressure inside the cavity is less than 10 Pa.

[0057] In one embodiment, the method further includes a step of thinning the second substrate 201. Specifically, chemical mechanical polishing (CMP) is used to thin the second substrate 201 to a thickness of 40µm to 50µm. By maintaining a relatively large thickness of the second substrate 201, deformation of the third sensing layer 203 is avoided, ensuring the undeformed state of the second cavity 207. The third sensing layer 203 and the common sensing layer together form a fixed capacitor that does not change with pressure, serving as a reference capacitor.

[0058] Next, proceed with step S140, as follows: Figure 2D-2E As shown, the portion of the first substrate 101 corresponding to the first cavity 107 is removed so that the first sensing layer 103 forms a movable sensing layer.

[0059] Exemplarily, before removing the portion of the first substrate 101 corresponding to the first cavity 107, the method further includes: etching the first substrate 101 to form a four-corner support structure 108 at the bottom of the first substrate 101. The four-corner support structure 108 includes four support pillars disposed at the four corners of the bottom of the first substrate 101, the four support pillars being independent of each other, such as... Figure 3 As shown, the four-corner support structure 108 is used to fix the MEMS device to the packaging substrate.

[0060] In one embodiment, such as Figure 2DAs shown, a quadrangular support structure 108 is formed at the bottom of the first substrate 101. Specifically, a patterned mask layer (not shown) is formed on the first substrate 101 using a photolithography process, and then the first substrate 101 is etched to form the quadrangular support structure 108. The etching method for the first substrate 101 can employ any existing technology well known to those skilled in the art, preferably dry etching, which includes, but is not limited to, reactive ion etching (RIE), ion beam etching, plasma etching, laser ablation, or any combination of these methods.

[0061] In one embodiment, such as Figure 2E As shown, the portion of the first substrate 101 corresponding to the first cavity 107 is etched to form an opening 109. The etching method for the first substrate 101 can employ any existing technology well-known to those skilled in the art, preferably deep reactive ion etching (DRIE). Specifically, gaseous silicon hexafluoride (SF6 / C4F8) is selected as the process gas, and an RF power supply is applied to create high ionization of the silicon hexafluoride reaction inlet gas. During the etching step, the operating pressure is controlled at 20 mTorr-8 Torr, the frequency power at 600 W, and the DC bias voltage can be continuously controlled within -500V-1000V to ensure the requirements of anisotropic etching. The deep reactive ion etching system can be any commonly used equipment and is not limited to a specific model.

[0062] The aforementioned deep reactive ion etching (DRIE) stops at the first insulating layer 102 or the first sensing layer 103, so that the first sensing layer 103 forms a movable sensing layer. The movable sensing layer and the common sensing layer constitute a movable capacitor. Taking a MEMS device as a pressure sensor as an example, the above sensing layers are all pressure sensing films. When the MRMS pressure sensor is running, the movable sensing layer deforms, and the movable capacitor formed by the movable sensing layer and the common sensing layer is used to measure pressure. The reference capacitor formed by the third sensing layer 203 and the common sensing layer serves as a reference, thereby improving the measurement accuracy of the MEMS device.

[0063] Next, as Figure 2F As shown, the method also includes the step of forming a metal wiring layer 208 on the second substrate 201, wherein the metal wiring layer 208 is connected to the third sensing layer, the common sensing layer and the movable sensing layer respectively.

[0064] In one embodiment, the metal wiring layer 208 is typically made of aluminum or gold. The metal wiring layer 208 includes metal traces and PAD structures, which are respectively connected to the third sensing layer, the common sensing layer and the movable sensing layer, and output test signals.

[0065] This concludes the introduction of the key steps in the manufacturing method of the MEMS device of the present invention. Further processes may be required for complete device fabrication, which will not be elaborated here.

[0066] It is worth mentioning that the order of the above steps is only for example. Without conflict, the order of the above steps can be changed or performed alternately.

[0067] The present invention also provides a MEMS device manufactured by the above method, such as... Figure 2F and 3 As shown, it includes:

[0068] A first substrate 101 is provided on which a first sensing layer 103, a first cavity 107, a common sensing layer, a second cavity 207, a third sensing layer 203, and a second substrate 201 are sequentially formed; wherein, the first substrate 101 includes an opening 109 corresponding to the first cavity 107, so that the first sensing layer 103 forms a movable sensing layer.

[0069] In one embodiment, the first substrate 101 can be any suitable semiconductor substrate, such as a silicon substrate. A four-corner support structure 108 is formed on the bottom of the first substrate 101 for fixing the MEMS device to the packaging substrate. The first substrate 101 also includes an opening 109 corresponding to the first cavity 107, exposing the first insulating layer 102 or the first sensing layer 103, so that the first sensing layer 103 forms a movable sensing layer, and the movable sensing layer and the common sensing layer constitute a movable capacitor.

[0070] In one embodiment, a first insulating layer 102, a first sensing layer 103, a first cavity 107, a common sensing layer, a second cavity 207, a third sensing layer 203, a second insulating layer 202, and a second substrate 201 are sequentially formed on a first substrate 101. The materials of the first insulating layer 102 and the second insulating layer 202 include, but are not limited to, oxide layers, and the thicknesses of the first insulating layer 102 and the second insulating layer 202 are typically smaller than the thicknesses of the first sensing layer 103 and the third sensing layer 203. The materials of the first sensing layer 103, the common sensing layer, and the third sensing layer 203 include, but are not limited to, doped polysilicon, and the thicknesses of the first sensing layer 103 and the third sensing layer 203 range from 1µm to 5µm, while the thickness of the common sensing layer is greater than the thicknesses of the first sensing layer 103 and the third sensing layer 203. The first cavity 107 and the second cavity 207 are surrounded by a first support portion 104' supporting the first cavity and a second support portion 204' supporting the second cavity, respectively. The materials of the first support portion 104' and the second support portion 204' include, but are not limited to, silicon oxide. The thickness of the first support portion 104' and the second support portion 204' can be set as needed. By controlling the thickness of the first support portion 104' and the second support portion 204', the distance between the first cavity 107 and the second cavity 207 can be controlled, thereby controlling the capacitance value between the first sensing layer 103 and the common sensing layer, as well as the capacitance value between the second sensing layer 203 and the common sensing layer.

[0071] In one embodiment, a plurality of first through holes 106 formed on the second sensing layer 105 are correspondingly disposed with a plurality of second through holes 206 formed on the fourth sensing layer 205. After the second sensing layer 105 and the fourth sensing layer 205 are bonded to form a common sensing layer, the plurality of first through holes 106 and the plurality of second through holes 206 are interconnected, and the first cavity 107 and the second cavity 207 form a common cavity. The common cavity formed by the first cavity 107 and the second cavity 207 maintains a vacuum state or a low-pressure state close to a vacuum, for example, the air pressure inside the cavity is less than 10 Pa.

[0072] In one embodiment, the thickness of the second substrate 201 ranges from 40µm to 50µm. Because the second substrate 201 maintains a relatively large thickness, deformation of the third sensing layer 203 is avoided, ensuring the second cavity 207 remains undeformed. The third sensing layer 203 and the common sensing layer together constitute a reference capacitor. By simultaneously incorporating a movable capacitor and a reference capacitor in a MEMS device, the sensitivity and anti-interference capability of the MEMS device can be improved.

[0073] In one embodiment, a metal wiring layer 208 is also formed on the second substrate 201. The metal wiring layer 208 includes metal traces and PAD structures, which are respectively connected to the third sensing layer, the common sensing layer and the movable sensing layer to output test signals.

[0074] The present invention also provides an electronic device, such as Figure 4 As shown, it includes a packaging substrate 400, on which the MEMS device described above is fixed as is.

[0075] In one embodiment, the MEMS device is fixed to the packaging substrate 400 by the four-corner support structure 108, achieving packaging with the movable sensing layer facing downwards, such as... Figure 4 As shown, this avoids the surface contamination problem that is easily caused by packaging with the movable sensing layer film facing upwards, thus improving the reliability of MEMS devices and extending their service life.

[0076] In one embodiment, the four-corner support structures 108 of the MEMS device are fixed to the packaging substrate 400 using a four-corner dispensing method. Traditional packaging methods typically involve coating the entire bottom or perimeter of the MEMS device with adhesive, bonding it to the packaging substrate 400. Due to the large contact area between the MEMS device and the packaging substrate 400, and the difference in their coefficients of thermal expansion, the MEMS device experiences significant volume deformation due to temperature changes during use. This deformation stress is transmitted to the interior of the MEMS device, leading to errors. This application addresses this by performing a two-step etching process on the first substrate 101 to form a structure with support pillars only at the four corners on the bottom. Figure 3 As shown, during encapsulation, bonding is performed in the four corner areas, ensuring uniform deformation and avoiding stress introduction, resulting in good temperature stability. The raised, hollowed-out structure between the four corner support structures 108 can form a pressure transmission channel, transmitting pressure to the surface of the movable sensing film at the bottom center of the MEMS device.

[0077] According to the MEMS device and its manufacturing method provided by the present invention, a stacked double-layer capacitor structure is prepared by heterogeneous bonding. The process is simple and highly feasible. The prepared device structure does not require plugging, which avoids the problem of uneven sensing layer caused by plugging. It also avoids reliability problems such as air leakage caused by repeated pressure measurement of the pressure-sensing diaphragm on the upper layer of the sealed cavity. This improves the service life and yield of the device.

[0078] The present invention has been described through the above embodiments. However, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the invention to the scope of the described embodiments. Furthermore, those skilled in the art will understand that the present invention is not limited to the above embodiments, and many more variations and modifications can be made based on the teachings of the present invention, all of which fall within the scope of protection claimed by 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, include: Forming the first MEMS structure: A first substrate is provided, and a first sensing layer is formed on the first substrate; A first cavity and a second sensing layer are sequentially formed on the first sensing layer; Forming a second MEMS structure: A second substrate is provided, and a third sensing layer is formed on the second substrate; A second cavity and a fourth sensing layer are sequentially formed on the third sensing layer; The second sensing layer and the fourth sensing layer are bonded together to form a common sensing layer; Remove the portion of the first substrate corresponding to the first cavity to form a movable sensing layer from the first sensing layer.

2. The method for manufacturing a MEMS device as described in claim 1, characterized in that, The movable sensing layer and the common sensing layer constitute a movable capacitor, and the common sensing layer and the third sensing layer constitute a reference capacitor.

3. The method for manufacturing a MEMS device as described in claim 1, characterized in that, Forming the first cavity on the first sensing layer includes: A first sacrificial layer and a second sensing layer are sequentially formed on the first sensing layer; Multiple first through holes are formed on the second sensing layer; The first cavity is formed by removing a portion of the first sacrificial layer through multiple first through-holes.

4. The method for manufacturing a MEMS device as described in claim 3, characterized in that, The fourth sensing layer has a plurality of second through holes, and the plurality of first through holes are correspondingly arranged with the plurality of second through holes. After the second sensing layer and the fourth sensing layer are bonded, the plurality of first through holes and the plurality of second through holes are connected, and the first cavity and the second cavity form a common cavity.

5. The method for manufacturing a MEMS device as described in claim 2, characterized in that, It also includes a step of thinning the second substrate to make the thickness of the second substrate 40um to 50um.

6. The method for manufacturing a MEMS device as described in claim 2, characterized in that, The thickness range of the first sensing layer, the second sensing layer, the third sensing layer and the fourth sensing layer includes 1um to 5um, and the first sensing layer, the second sensing layer, the third sensing layer and the fourth sensing layer are made of doped polycrystalline silicon.

7. The method for manufacturing a MEMS device as described in claim 1, characterized in that, Before removing the portion of the first substrate corresponding to the first cavity, the method further includes: The first substrate is etched to form a four-corner support structure at the bottom of the first substrate, the four-corner support structure being used to fix the MEMS device to the packaging substrate.

8. The method for manufacturing a MEMS device as described in claim 5, characterized in that, It also includes the step of forming a metal wiring layer on the second substrate, the metal wiring layer being connected to the third sensing layer, the common sensing layer and the movable sensing layer respectively.

9. A MEMS device manufactured by the method according to any one of claims 1 to 8, characterized in that, include: A first substrate, wherein a first sensing layer, a first cavity, a common sensing layer, a second cavity, a third sensing layer, and a second substrate are sequentially formed on the first substrate; wherein the first substrate includes an opening corresponding to the first cavity, so that the first sensing layer forms a movable sensing layer.

10. The MEMS device as described in claim 9, characterized in that, The MEMS device includes a pressure sensor, and the sensing layer includes a pressure sensing membrane.

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