MEMS pressure sensor, method for manufacturing same, and electronic device

Abstract

A method for manufacturing an MEMS pressure sensor, comprising: sequentially forming a first pressure sensing film layer (211), a first sacrificial layer (212), a first support layer (2131), and a first conductive layer (2132) on a first substrate (210), and sequentially forming a second pressure sensing film layer (221), a second sacrificial layer (222), and a second support layer (2231) on a second substrate (220); etching the first support layer (2131) and the second support layer (2231) respectively to form multiple first relief holes (214) and multiple second relief holes (224); removing a part of the first sacrificial layer to form a first cavity (215), and removing a part of the second sacrificial layer to form a second cavity (225); bonding the first conductive layer (2132) with the second support layer (2231), wherein the first relief holes (214) and the second relief holes (224) are disposed in a staggered manner; and etching the first substrate (210) to form a back cavity (216), and removing the second substrate (220) to expose the second pressure sensing film layer (221). The first conductive layer is bonded with the second support layer, to form the MEMS pressure sensor with two pressure sensing film layers, thereby improving sensitivity and linearity. Also provided are an MEMS pressure sensor and an electronic device.

Description

A MEMS pressure sensor and its preparation method, and electronic device Technical Field

[0001] The present disclosure relates to the field of semiconductor technology, and more particularly to a MEMS pressure sensor, a preparation method thereof, and an electronic device. Background Art

[0002] Micro-Electro-Mechanical System (MEMS) pressure sensors are a cutting-edge research field developed based on MEMS technology. They are suitable for harsh environments such as high shock, high overload, electrical conductivity, corrosion, and radiation, and are widely used in aerospace, electronics, industry, healthcare, and environmental monitoring. Among them, capacitive pressure sensors are a major type of MEMS pressure sensor. Their fundamental principle is to convert pressure changes into capacitance changes.

[0003] According to the capacitance formula, capacitive pressure sensors can be divided into three types: variable pitch type, variable area type, and variable dielectric type. Due to its ease of implementation, variable pitch type capacitive pressure sensors are the most common.

[0004] Summary of the Invention

[0005] In one aspect, the present disclosure provides a method for preparing a MEMS pressure sensor, comprising:

[0006] Providing a first substrate, forming a first pressure-sensitive film layer on a first surface of the first substrate, forming a first sacrificial layer on the first pressure-sensitive film layer, forming a first supporting layer on the first sacrificial layer, and forming a first conductive layer on the first supporting layer; providing a second substrate, forming a second pressure-sensitive film layer on a first surface of the second substrate, forming a second sacrificial layer on the second pressure-sensitive film layer, and forming a second supporting layer on the second sacrificial layer;

[0007] Etching the first supporting layer and the first conductive layer to form a plurality of first release holes penetrating the first supporting layer and the first conductive layer; etching the second supporting layer to form a plurality of second release holes penetrating the second supporting layer;

[0008] A portion of the first sacrificial layer is removed through the plurality of first release holes to form a first cavity between the first supporting layer and the first pressure-sensitive film layer; a portion of the second sacrificial layer is removed through the plurality of second release holes to form a second cavity between the second supporting layer and the second pressure-sensitive film layer;

[0009] bonding the first conductive layer and the second supporting layer so that the first supporting layer, the first conductive layer and the second supporting layer together form a fixed electrode layer, wherein the plurality of first release holes and the plurality of second release holes are arranged alternately;

[0010] The first substrate is etched from the second surface of the first substrate to form a back cavity exposing the first pressure-sensitive film layer; and the second substrate is removed to expose the second pressure-sensitive film layer.

[0011] Illustratively, the preparation method further includes: after forming a second supporting layer on the second sacrificial layer, forming a second conductive layer on the second supporting layer, wherein etching the second supporting layer to form a plurality of second release holes passing through the second supporting layer includes: etching the second supporting layer and the second conductive layer to form a plurality of second release holes passing through the second supporting layer and the second conductive layer; wherein, bonding the first conductive layer to the second supporting layer so that the first supporting layer and the first conductive layer and the second supporting layer together form a fixed electrode layer includes: bonding the first conductive layer to the second conductive layer so that the first supporting layer and the first conductive layer and the second supporting layer together form a fixed electrode layer.

[0012] Exemplarily, the bonding is performed using a vacuum bonding process.

[0013] Exemplarily, the first supporting layer and the second supporting layer include silicon nitride, and the first conductive layer includes polysilicon.

[0014] Another aspect of the present disclosure provides a MEMS pressure sensor, comprising:

[0015] a first substrate, wherein a back cavity penetrating the first substrate is formed in the first substrate;

[0016] a first pressure-sensitive film layer, located on the first surface of the first substrate;

[0017] a first sacrificial layer, located on the first pressure-sensitive film layer and covering a portion of the surface of the first pressure-sensitive film layer;

[0018] a fixed electrode layer comprising a first supporting layer, a second supporting layer, and a first conductive layer located between the first supporting layer and the second supporting layer;

[0019] a second sacrificial layer, located on the fixed electrode layer and covering a portion of the surface of the fixed electrode layer;

[0020] a second pressure-sensitive film layer, located on the second sacrificial layer;

[0021] a first cavity formed between the fixed electrode layer and the first pressure-sensitive film layer;

[0022] a second cavity formed between the fixed electrode layer and the second pressure-sensitive film layer;

[0023] The fixed electrode layer is formed with a plurality of first release holes and a plurality of second release holes facing the first cavity and the second cavity respectively, wherein the plurality of first release holes and the plurality of second release holes do not penetrate the fixed electrode layer and are staggered with each other.

[0024] Exemplarily, bottoms of the plurality of first release holes expose the second supporting layer; or

[0025] The fixed electrode layer further includes a second conductive layer located between the first conductive layer and the second supporting layer, and the second conductive layer is exposed at the bottoms of the plurality of first release holes.

[0026] Exemplarily, the first supporting layer and the second supporting layer include silicon nitride, and the first conductive layer includes polysilicon.

[0027] Yet another aspect of the present disclosure provides an electronic device, comprising the aforementioned MEMS pressure sensor.

[0028] Exemplarily, a PCB board is further included, and the second surface of the first substrate of the MEMS pressure sensor is attached to the PCB board.

[0029] Exemplarily, an opening penetrating the PCB is formed in the PCB, and the opening exposes the back cavity of the MEMS pressure sensor.

[0030] The MEMS pressure sensor, preparation method thereof, and electronic device of the disclosed embodiments bond the first conductive layer and the second supporting layer so that the first conductive layer and the second supporting layer together form a fixed electrode layer. The first pressure-sensitive membrane layer and the second pressure-sensitive membrane layer can respectively form a capacitor structure with the fixed electrode layer, thereby forming a MEMS pressure sensor with dual pressure-sensitive membrane layers. This avoids problems such as warping or even falling off caused by stacking multiple membrane layers in related technologies, improves the sensitivity and linearity of the MEMS pressure sensor, and thereby improves the performance and reliability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The following drawings of the present disclosure are incorporated herein as part of the present disclosure for understanding the present disclosure. The drawings show embodiments of the present disclosure and their descriptions are used to explain the principles of the present disclosure.

[0032] FIG1 shows a flow chart of a method for preparing a MEMS pressure sensor provided in an embodiment of the present disclosure.

[0033] 2A-2F are schematic cross-sectional views of a device obtained by sequentially implementing the steps of the method for preparing a MEMS pressure sensor provided by an embodiment of the present disclosure.

[0034] 3A-3D are schematic cross-sectional views of a device obtained by sequentially implementing the steps of a method for preparing a MEMS pressure sensor provided by another embodiment of the present disclosure.

[0035] 4A-4B are schematic cross-sectional views of a MEMS pressure sensor and a PCB board in an electronic device according to an embodiment of the present disclosure.

[0036] 5A-5B are schematic cross-sectional views of a MEMS pressure sensor and a PCB board in an electronic device according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0037] Next, the present disclosure will be described more fully in conjunction with the accompanying drawings, which illustrate embodiments of the present disclosure. However, the present disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the present disclosure to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. Like reference numerals throughout represent like elements.

[0038] 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 may be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may 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 may be 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. Therefore, without departing from the teachings of the present disclosure, the first element, component, region, layer, or part discussed below may be represented as a second element, component, region, layer, or part.

[0039] 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 in addition to the orientations shown in the figures, the spatially relative terms are intended to include different orientations of the device in use and operation. For example, if the device in the drawings is turned over, then the elements or features described as "under" or "beneath" or "beneath" the other elements will be oriented as "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may include other orientations (rotated 90 degrees) and the spatial descriptors used herein are interpreted accordingly.

[0040] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present disclosure. 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 "including", when used in this disclosure, 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.

[0041] Embodiments of the present disclosure are described herein with reference to cross-sectional views which are schematic illustrations of idealized embodiments (and intermediate structures) of the present disclosure. As such, variations from the shapes shown due to, for example, manufacturing techniques and / or tolerances are anticipated. Accordingly, embodiments of the present disclosure should not be limited to the specific shapes of the regions shown herein, but rather include deviations in shapes due to, for example, manufacturing. For example, an implanted region shown as a rectangle typically has rounded or curved features and / or an implant concentration gradient at its edges, rather than a binary change from an implanted region to a non-implanted region. Similarly, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implant passes as the implant is made. Accordingly, the regions shown in the figures are schematic in nature, and their shapes are not intended to illustrate the actual shape of the region of the device and are not intended to limit the scope of the present disclosure.

[0042] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art of the present disclosure. It will also be understood that terms such as those defined in commonly used dictionaries should be understood to have a meaning consistent with their meaning in the context of the relevant art and / or the present disclosure and should not be interpreted as overly formalized unless expressly defined herein.

[0043] In order to fully understand the present disclosure, detailed steps and structures will be provided in the following description to illustrate the technical solutions proposed by the present disclosure. The embodiments of the present disclosure are described in detail below. However, in addition to these detailed descriptions, the present disclosure may also have other implementation methods.

[0044] In the related art, the sensitivity of a MEMS pressure sensor with a single-layer pressure-sensitive membrane is poor, and the sensitivity of a MEMS pressure sensor with a single-layer pressure-sensitive membrane can only be improved by increasing the area of ​​the pressure-sensitive membrane, which will lead to poor integration of the device.

[0045] To improve the sensitivity of MEMS pressure sensors without increasing the area of ​​the pressure-sensitive membrane, related technologies often employ multi-layer pressure-sensitive membranes to enhance their sensitivity. However, the layer-by-layer growth process for these multi-layer membranes is still immature, inducing residual stress. This residual stress can cause the multi-layer pressure-sensitive membrane structure to warp or even detach during deposition, leading to poor device linearity and compromising the device's electrical performance and reliability.

[0046] Therefore, in view of the existence of the aforementioned technical problems, the present disclosure proposes a method for preparing a MEMS pressure sensor, as shown in FIG1 , which mainly includes the following steps S1 - S5 .

[0047] Step S1: providing a first substrate, forming a first pressure-sensitive film layer on a first surface of the first substrate, forming a first sacrificial layer on the first pressure-sensitive film layer, forming a first supporting layer on the first sacrificial layer, and forming a first conductive layer on the first supporting layer; providing a second substrate, forming a second pressure-sensitive film layer on a first surface of the second substrate, forming a second sacrificial layer on the second pressure-sensitive film layer, and forming a second supporting layer on the second sacrificial layer;

[0048] Step S2, etching the first supporting layer and the first conductive layer to form a plurality of first release holes penetrating the first supporting layer and the first conductive layer; etching the second supporting layer to form a plurality of second release holes penetrating the second supporting layer;

[0049] Step S3, removing a portion of the first sacrificial layer through the plurality of first release holes to form a first cavity between the first supporting layer and the first pressure-sensitive film layer; removing a portion of the second sacrificial layer through the plurality of second release holes to form a second cavity between the second supporting layer and the second pressure-sensitive film layer;

[0050] Step S4, bonding the first conductive layer and the second supporting layer so that the first supporting layer, the first conductive layer, and the second supporting layer together form a fixed electrode layer, wherein the plurality of first release holes and the plurality of second release holes are arranged alternately;

[0051] Step S5 , etching the first substrate from the second surface of the first substrate to form a back cavity exposing the first pressure-sensitive film layer, and removing the second substrate to expose the second pressure-sensitive film layer.

[0052] The preparation method of the MEMS pressure sensor disclosed in the present invention bonds the first conductive layer and the second supporting layer so that the first conductive layer and the second supporting layer together form a fixed electrode layer. The first pressure-sensitive membrane layer and the second pressure-sensitive membrane layer can respectively form a capacitor structure with the fixed electrode layer, thereby forming a MEMS pressure sensor with dual pressure-sensitive membrane layers. This avoids the problems of warping or even falling off caused by the stacking of multiple membrane layers in related technologies, improves the sensitivity and linearity of the MEMS pressure sensor, and thus improves the device performance and reliability.

[0053] Example 1

[0054] Below, the preparation method of the MEMS pressure sensor disclosed in the present invention is described in detail with reference to Figures 1 to 2F, wherein Figure 1 shows a flow chart of the preparation method of the MEMS pressure sensor provided in an embodiment of the present invention, and Figures 2A-2F show cross-sectional schematic diagrams of a device obtained by sequentially implementing the steps of the preparation method of the MEMS pressure sensor provided in an embodiment of the present invention.

[0055] Illustratively, the method for preparing the MEMS pressure sensor disclosed herein includes the following steps S1-S5.

[0056] First, step S1 is performed to provide a first substrate and a second substrate, wherein a first pressure-sensitive film layer is formed on a first surface of the first substrate, a first sacrificial layer is formed on the first pressure-sensitive film layer, a first conductive layer is formed on the first sacrificial layer, a second pressure-sensitive film layer is formed on a first surface of the second substrate, a second sacrificial layer is formed on the second pressure-sensitive film layer, and a second supporting layer is formed on the second sacrificial layer, wherein the first conductive layer includes a first supporting layer and a first conductive layer located on the first supporting layer.

[0057] Specifically, as shown in Figures 2A and 2B, the first substrate 210 and the second substrate 220 are bulk silicon substrates, which may include at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs, or other III / V compound semiconductors. In some embodiments, the first substrate 210 and the second substrate 220 may also include a multilayer structure composed of at least one of Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs, or other III / V compound semiconductors. In some embodiments, the first substrate 210 and the second substrate 220 may also 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).

[0058] In one example, as shown in Figures 2A and 2B, a first pressure-sensitive film layer 211 is formed on the first surface of the first substrate 210, and a second pressure-sensitive film layer 221 is formed on the first surface of the second substrate 220. Exemplarily, the first pressure-sensitive film layer 211 and the second pressure-sensitive film layer 221 can respectively include materials such as polysilicon or SiGe, and are not limited to any one of them. Among them, the first pressure-sensitive film layer 211 and the second pressure-sensitive film layer 221 can be formed by chemical vapor deposition (CVD), physical vapor deposition (PVD) or atomic layer deposition (ALD). Alternatively, the first pressure-sensitive film layer 211 and the second pressure-sensitive film layer 221 can be formed by one of furnace tube growth and selective epitaxial growth (SEG), which is not limited in the present disclosure.

[0059] For example, an insulating layer may be formed between the first substrate 210 and the first pressure-sensitive film layer 211, and between the second substrate 220 and the second pressure-sensitive film layer 221. The insulating layer may be made of any of several dielectric materials, non-limiting examples of which include oxides, nitrides, or oxynitrides, particularly silicon oxides, nitrides, or oxynitrides, but not oxides, nitrides, or oxynitrides of other elements. The insulating layer may be formed using any of several methods, non-limiting examples of which include ion implantation, thermal or plasma oxidation or nitridation, chemical vapor deposition, or physical vapor deposition.

[0060] In one example, as shown in Figures 2A and 2B, a first sacrificial layer 212 is formed on the first pressure-sensitive film layer 211, and a second sacrificial layer 222 is formed on the second pressure-sensitive film layer 221. By way of example, the first sacrificial layer 212 and the second sacrificial layer 222 include oxide layers, such as silicon oxide and carbon-doped silicon oxide (SiOC), but are not limited to the above examples. Furthermore, the first sacrificial layer 212 and the second sacrificial layer 222 can be formed using various deposition methods commonly used in the art, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD).

[0061] In one example, as shown in FIG2A , a sub-electrode layer 213 is formed on the first sacrificial layer 212, and the sub-electrode layer 213 includes a first supporting layer 2131 and a first conductive layer 2132 located on the first supporting layer 2131. Exemplarily, the first supporting layer 2131 is used to improve the strength and stability of the entire device. Exemplarily, the material of the first supporting layer 2131 includes silicon nitride. In other embodiments, the material of the first supporting layer 2131 can also be any other suitable material that can improve the strength and stability of the device. Exemplarily, the material of the first conductive layer 2132 can include metal or polysilicon doped with N-type ions such as phosphorus or polysilicon doped with P-type ions such as boron, etc., and is not limited to any one type.

[0062] In one example, as shown in FIG2B , a second supporting layer 2231 is formed on the second sacrificial layer 222. Exemplarily, the second supporting layer 2231 is used to improve the strength and stability of the entire device. Exemplarily, the material of the second supporting layer 2231 includes silicon nitride. In other embodiments, the material of the second supporting layer 2231 can also be any other suitable material that can improve the strength and stability of the device.

[0063] In one example, the first supporting layer 2131 and the second supporting layer 2231 can be formed by a deposition method commonly used in the art, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD).

[0064] In one example, the first conductive layer 2132 can be formed by a deposition method commonly used in the art, for example, it can be formed by chemical vapor deposition (CVD), physical vapor deposition (PVD) or atomic layer deposition (ALD), or the first conductive layer 2132 can be formed by furnace tube growth or selective epitaxial growth (SEG), which is not limited in this disclosure.

[0065] Next, step S2 is performed to etch the sub-electrode layer and the second supporting layer separately to form a plurality of first release holes penetrating the sub-electrode layer and a plurality of second release holes penetrating the second supporting layer. Specifically, as shown in Figures 2C and 2D, the sub-electrode layer 213 and the second supporting layer 2231 are etched separately to form a plurality of first release holes 214 penetrating the sub-electrode layer 213 and a plurality of second release holes 224 penetrating the second supporting layer 2231. Exemplarily, the plurality of first release holes 214 are spaced apart and expose a portion of the surface of the first sacrificial layer 212; the plurality of second release holes 224 are spaced apart and expose a portion of the surface of the second sacrificial layer 222. In some embodiments, etching the sub-electrode layer 213 and the second supporting layer 2231 separately includes the following steps: forming a mask layer, such as a photoresist layer, on the sub-electrode layer 213 and the second supporting layer 2231; etching the sub-electrode layer 213 and the second supporting layer 2231 separately using the mask layer as a mask to form a plurality of first release holes 214 penetrating the sub-electrode layer 213 and a plurality of second release holes 224 penetrating the second supporting layer 2231; and then removing the mask layer. Dry etching, such as reactive ion etching (RIE), ion beam etching, or plasma etching, can be used in this step. For example, the sizes of the first release holes 214 and the second release holes 224 can be reasonably set according to actual needs, for example, the sizes of the first release holes 214 and the second release holes 224 can be less than or equal to 1 μm.

[0066] Next, step S3 is performed to remove a portion of the first sacrificial layer through the first release hole to form a first cavity between the sub-electrode layer and the first pressure-sensitive film layer, and to remove a portion of the second sacrificial layer through the second release hole to form a second cavity between the second supporting layer and the second pressure-sensitive film layer. Specifically, as shown in Figures 2C and 2D, a portion of the first sacrificial layer 212 is removed through the first release hole 214 to form a first cavity 215 between the sub-electrode layer 213 and the first pressure-sensitive film layer 211, and a portion of the second sacrificial layer 222 is removed through the second release hole 224 to form a second cavity 225 between the second supporting layer 2231 and the second pressure-sensitive film layer 221. Exemplarily, an etching process commonly used in the art can be used to remove part of the first sacrificial layer 212 and part of the second sacrificial layer 222. For example, a wet etching process can be used to remove part of the first sacrificial layer 212 and part of the second sacrificial layer 222. More specifically, a buffered oxide etchant (Buffer Oxide Etchant) can be used to remove part of the first sacrificial layer 212 and part of the second sacrificial layer 222. Alternatively, gaseous hydrogen fluoride (VHF) can be used to remove part of the first sacrificial layer 212 and part of the second sacrificial layer 222. Exemplarily, the release boundary range of the first sacrificial layer 212 and the second sacrificial layer 222 can be reasonably set according to actual needs. For example, the release boundary range of the first sacrificial layer 212 and the second sacrificial layer 222 is 5-10um, wherein the release boundary refers to the distance between the side wall of the first cavity 215 and the side wall of the first release hole 214 closest to the side wall of the first cavity 215, or the distance between the side wall of the second cavity 225 and the side wall of the second release hole 224 closest to the side wall of the second cavity 225.

[0067] Next, step S4 is performed to bond the sub-electrode layer to the second supporting layer so that the sub-electrode layer and the second supporting layer together form a fixed electrode layer, wherein the first release holes and the second release holes are arranged alternately. Specifically, as shown in Figure 2E, the sub-electrode layer 213 is bonded to the second supporting layer 2231 so that the sub-electrode layer 213 and the second supporting layer 2231 together form a fixed electrode layer 230. More specifically, the first conductive layer 2132 is bonded to the second supporting layer 2231, wherein the first release holes 214 and the second release holes 224 are arranged alternately. Exemplarily, the first release holes 214 and the second release holes 224 are staggered to isolate the first cavity 215 from the second cavity 225, so that the first pressure-sensitive film layer 211 and the fixed electrode layer 230 together constitute a first capacitor structure, and the second pressure-sensitive film layer 221 and the fixed electrode layer 230 together constitute a second capacitor structure, and the first capacitor structure and the second capacitor structure are independent of each other and do not affect each other. A MEMS pressure sensor with dual pressure-sensitive film layers is obtained by bonding. Compared with the multi-film layer stacking method in the related art, it can effectively avoid problems such as film warping or even falling off. The first pressure-sensitive film layer 211 and the second pressure-sensitive film layer 221 are subjected to more uniform force, and the linearity of the device is better. Exemplarily, before bonding the sub-electrode layer 213 to the second supporting layer 2231, the surface of the sub-electrode layer 213 and the second supporting layer 2231 is flattened to meet the bonding requirements.

[0068] In one example, a vacuum bonding process is used to bond the sub-electrode layer 213 to the second support layer 2231. Specifically, in an ultra-high vacuum environment, when the surfaces of the flattened sub-electrode layer 213 and the second support layer 2231 reach sufficiently close contact, the molecular forces (van der Waals forces or hydrogen bonds) between adjacent interfaces can further shorten the distance between the surface atoms of the two, thereby directly forming a covalent bond at the interface, so that the sub-electrode layer 213 and the second support layer 2231 are bonded. Exemplarily, by using an ultra-high vacuum bonding process to bond the sub-electrode layer 213 to the second support layer 2231, the vacuum degree of the device can be ensured, and compared to the silicon-silicon high-temperature bonding process, the operation is simple and the thermal budget can be reduced.

[0069] Finally, step S5 is performed to etch the first substrate from the second surface of the first substrate to form a back cavity exposing the first pressure-sensitive film layer, and remove the second substrate to expose the second pressure-sensitive film layer. Specifically, as shown in Figure 2F, the first substrate 210 is etched from the second surface of the first substrate 210 to form a back cavity 216 exposing the first pressure-sensitive film layer 211, and the second substrate 220 is removed to expose the second pressure-sensitive film layer 221. Exemplarily, the second surface of the first substrate 210 is opposite to the first surface. Exemplarily, the second substrate 220 can be thinned to remove the second substrate 220. Specifically, the thinning method can include but is not limited to chemical mechanical polishing or etching processes.

[0070] Exemplarily, when an insulating layer is formed between the first substrate 210 and the first pressure-sensitive film layer 211, the back cavity 216 can be formed in the following manner: etching the first substrate 210 from the second surface of the first substrate 210 and stopping at the insulating layer to form a cavity; then, removing part of the insulating layer to form the back cavity 216. Exemplarily, when an insulating layer is formed between the second substrate 220 and the second pressure-sensitive film layer 221, after removing the second substrate 220, the insulating layer also needs to be removed to expose the second pressure-sensitive film layer 221. Exemplarily, an etching process commonly used in the art, such as dry etching, can be used to etch the first substrate 210. For example, a Bosch etching process can be used to etch the first substrate 210. Exemplarily, a wet etching process can be used to remove the insulating layer. Specifically, a buffered oxide etchant (Buffer Oxide Etchant) can be used to remove the insulating layer, or gaseous hydrogen fluoride (VHF) can be used to remove the insulating layer. For example, after removing the second substrate 220 and etching the first substrate 210 , the insulating layers between the first substrate 210 and the first pressure-sensitive film layer 211 and between the second substrate 220 and the second pressure-sensitive film layer 221 may be removed simultaneously.

[0071] It is worth noting that the method for fabricating the MEMS pressure sensor described with reference to Figures 2A to 2F involves bonding the sub-electrode layer 213 to the second support layer 2231, and more specifically, bonding the first conductive layer 2132 to the second support layer 2231. In another embodiment, as shown in Figure 3A , a second conductive layer 2232 located on the second support layer 2231 is further included. The method for fabricating the MEMS pressure sensor provided by another embodiment of the present disclosure is described in detail below with reference to Figures 3A to 3D , wherein Figures 3A-3D illustrate cross-sectional schematic diagrams of a device obtained by sequentially implementing the steps of the method for fabricating the MEMS pressure sensor provided by another embodiment of the present disclosure.

[0072] Specifically, as shown in FIG3A , a second substrate 220 is first provided. A second pressure-sensitive film layer 221 is formed on the second substrate 220. A second sacrificial layer 222 is formed on the second pressure-sensitive film layer. A second supporting layer 2231 is formed on the second sacrificial layer 222. A second conductive layer 2232 is formed on the second supporting layer 2231. Next, as shown in FIG3B , in the process step of forming the second release holes 224, the second conductive layer 2232 is etched simultaneously with the second supporting layer 2231. That is, the second conductive layer 2232 and the second supporting layer 2231 are etched to form a plurality of second release holes 224 that penetrate the second conductive layer 2232 and the second supporting layer 2231. Next, as shown in FIG3C , in the bonding process step, the sub-electrode layer 213 is bonded to the second conductive layer 2232. More specifically, the second conductive layer 2232 is bonded to the first conductive layer 2132. At this time, the sub-electrode layer 213, the second conductive layer 2232, and the second supporting layer 2231 together form the fixed electrode layer 230. Finally, as shown in FIG3D , the first substrate 210 is etched from the second surface of the first substrate 210 to form a back cavity 216 exposing the first pressure-sensitive film layer 211, and the second substrate 220 is removed to expose the second pressure-sensitive film layer 221. For example, the difference between this embodiment and the embodiment described above is only that the second conductive layer 2232 is also formed on the second supporting layer 2231. The rest of the process is the same. For details, please refer to the above and will not be repeated here.

[0073] In one example, the material of the second conductive layer 2232 can include metal, polysilicon doped with N-type ions such as phosphorus, or polysilicon doped with P-type ions such as boron, and is not limited to any one material. For example, the first conductive layer 2132 and the second conductive layer 2232 are made of the same material. Thus, during the bonding step of joining the second conductive layer 2232 to the first conductive layer 2132, since the bonding surfaces are the first conductive layer 2132 and the second conductive layer 2232, and both are made of the same material, a better bonding effect can be achieved.

[0074] In one example, the second conductive layer 2232 can be formed by various deposition methods commonly used in the art, for example, it can be formed by chemical vapor deposition (CVD), physical vapor deposition (PVD) or atomic layer deposition (ALD), or the second conductive layer 2232 can be formed by furnace tube growth and selective epitaxial growth (SEG), which is not limited in this disclosure.

[0075] It is worth mentioning that the above steps are only examples, and the order of the above steps can be adjusted without conflict.

[0076] The description of the key steps of the method for preparing the MEMS pressure sensor disclosed herein has been completed. The preparation of a complete MEMS pressure sensor may also include other steps, which will not be detailed here.

[0077] In summary, the preparation method of the MEMS pressure sensor disclosed in the present invention bonds the sub-electrode layer and the second supporting layer to form a fixed electrode layer. The first pressure-sensitive film layer and the second pressure-sensitive film layer can respectively form a capacitor structure with the fixed electrode layer, thereby forming a MEMS pressure sensor with dual pressure-sensitive film layers. Compared with the MEMS pressure sensor with a single pressure-sensitive film layer in the related art, the sensitivity of the MEMS pressure sensor can be improved without increasing the area of ​​the pressure-sensitive film layer, and the problems such as warping or even falling off caused by the stacking of multiple film layers in the related art are avoided, thereby improving the linearity and sensitivity of the MEMS pressure sensor, thereby improving the device performance and reliability.

[0078] Example 2

[0079] The present disclosure further provides a MEMS pressure sensor, which is prepared by the method of the aforementioned embodiment 1. As shown in FIG2F and FIG3D , the MEMS pressure sensor of the present disclosure includes:

[0080] A first substrate 210, wherein a back cavity 216 is formed in the first substrate 210 and penetrates the first substrate 210;

[0081] The first pressure-sensitive film layer 211 is located on the first surface of the first substrate 210;

[0082] a first sacrificial layer 212 , located on the first pressure-sensitive film layer 211 and covering a portion of the surface of the first pressure-sensitive film layer 211 ;

[0083] The fixed electrode layer 230 includes a first supporting layer 2131 , a second supporting layer 2231 , and a first conductive layer 2132 located between the first supporting layer 2131 and the second supporting layer 2231 ;

[0084] The second sacrificial layer 222 is located on the fixed electrode layer 230 and covers a portion of the surface of the fixed electrode layer 230;

[0085] The second pressure-sensitive film layer 221 is located on the second sacrificial layer 222;

[0086] The first cavity 215 is formed between the fixed electrode layer 230 and the first pressure-sensitive film layer 211;

[0087] The second cavity 225 is formed between the fixed electrode layer 230 and the second pressure-sensitive film layer 221;

[0088] The fixed electrode layer 230 is formed with a plurality of first release holes 214 and a plurality of second release holes 224 facing the first cavity 215 and the second cavity 225 respectively. The first release holes 214 and the second release holes 224 do not penetrate the fixed electrode layer 230 and are staggered with each other.

[0089] In one example, the first release hole 214 and the second release hole 224 are staggered to isolate the first cavity 215 and the second cavity 225 from each other, so that the first pressure-sensitive film layer 211 and the fixed electrode layer 230 together constitute a first capacitor structure, and the second pressure-sensitive film layer 221 and the fixed electrode layer 230 together constitute a second capacitor structure, and the first capacitor structure and the second capacitor structure are independent of each other and do not affect each other.

[0090] Illustratively, the material of the first supporting layer 2131 and the second supporting layer 2231 includes silicon nitride. In other embodiments, the material of the second supporting layer 2231 can also be any other suitable material that can improve the strength and stability of the device. Illustratively, the material of the first conductive layer 2132 can include metal, polysilicon doped with N-type ions such as phosphorus, or polysilicon doped with P-type ions such as boron, etc., and is not limited to any one material.

[0091] In one example, as shown in FIG2F , the second supporting layer 2231 is exposed at the bottom of the first release hole 214. Alternatively, as shown in FIG3D , the fixed electrode layer 230 further includes a second conductive layer 2232 located between the first conductive layer 2132 and the second supporting layer 2231, and the second conductive layer 2232 is exposed at the bottom of the first release hole 214. For example, the material of the second conductive layer 2232 may include, but is not limited to, a metal, polysilicon doped with N-type ions such as phosphorus, or polysilicon doped with P-type ions such as boron.

[0092] In one example, the first supporting layer 2131 and the second supporting layer 2231 can be formed by various deposition methods commonly used in the art, for example, they can be formed by chemical vapor deposition (CVD), physical vapor deposition (PVD) or atomic layer deposition (ALD).

[0093] In one example, the first conductive layer 2132 and the second conductive layer 2232 can be formed by various deposition methods commonly used in the art, for example, they can be formed by chemical vapor deposition (CVD), physical vapor deposition (PVD) or atomic layer deposition (ALD), or the first conductive layer 2132 can be formed by furnace tube growth and selective epitaxial growth (SEG), and the present disclosure does not limit this.

[0094] This concludes the introduction to the structure of the MEMS pressure sensor disclosed herein. A complete device may also include other components, which will not be detailed here.

[0095] Due to the MEMS pressure sensor disclosed in the present invention, the first pressure-sensitive membrane layer and the second pressure-sensitive membrane layer can respectively form a capacitor structure with the fixed electrode layer, forming a MEMS pressure sensor with dual pressure-sensitive membrane layers. Compared with the MEMS pressure sensor with a single pressure-sensitive membrane layer in the related art, the sensitivity of the MEMS pressure sensor can be improved without increasing the area of ​​the pressure-sensitive membrane layer, and the problems such as warping or even falling off caused by the stacking of multiple membrane layers in the related art are avoided, thereby improving the linearity and sensitivity of the MEMS pressure sensor, thereby improving the device performance and reliability.

[0096] Example 3

[0097] The present disclosure further provides an electronic device, which includes the MEMS pressure sensor described in the second embodiment or the MEMS pressure sensor prepared by the method described in the first embodiment.

[0098] In one example, as shown in FIG4A and FIG4B , the electronic device of the present disclosure further includes a PCB board 240, and the second surface of the first substrate 210 of the MEMS pressure sensor is attached to the PCB board 240. For example, a closed cavity is formed between the back cavity 216 of the first substrate 210 and the PCB board 240. At this time, the pressure on the first pressure-sensitive film layer 211 is a fixed value, which is set to P1. At this time, P1 can be used as a reference pressure. At this time, the distance between the first pressure-sensitive film layer 211 and the fixed electrode layer 230 is fixed, so the capacitance value of the first capacitor structure formed by the first pressure-sensitive film layer 211 and the fixed electrode layer 230 is also a fixed value, which is set to C1. At this time, the capacitance value C1 can be used as a reference capacitance value. At this time, the second pressure-sensitive film layer 221 is in the external environment. Under the action of pressure, deformation occurs, and the external pressure on the second pressure-sensitive film layer 221 is set to P2, so that the distance between the second pressure-sensitive film layer 221 and the fixed electrode layer 230 changes, and the capacitance value output by the second capacitor structure composed of the second pressure-sensitive film layer 221 and the fixed electrode layer 230 changes, and is set to C2. Then C2 can be compared with C1, that is, the overall output capacitance of the device at this time is |C1-C2|, and the difference is converted into the corresponding pressure and the corresponding operation is performed with the reference pressure P1 to obtain the magnitude of the external pressure. For example, the second surface of the first substrate 210 can be attached to the PCB board 240 by surface mount technology (SMT). For example, the difference between the MEMS pressure sensors shown in Figure 4A and Figure 4B is that the MEMS pressure sensor shown in Figure 4B also has a second conductive layer 2232 formed between the first conductive layer 2132 and the second support layer 2231.

[0099] In one example, as shown in Figures 5A and 5B, an opening 250 is formed in the PCB board 240 and penetrates the PCB board 240. The opening 250 exposes the back cavity 216 of the MEMS pressure sensor. In this embodiment, the first pressure-sensitive film layer 211 and the second pressure-sensitive film layer 221 are simultaneously exposed to external pressure. The external pressure applied to the first pressure-sensitive film layer 211 is set to P1, and the external pressure applied to the second pressure-sensitive film layer 221 is set to P2. In this case, P1 is equal to P2. The capacitance output by the first capacitor structure formed by the first pressure-sensitive film layer 211 and the fixed electrode layer 230 is set to C1, and the capacitance output by the second capacitor structure formed by the second pressure-sensitive film layer 221 and the fixed electrode layer 230 is set to C2. The overall output capacitance of the device is C1 + C2. By measuring the overall output capacitance of the device, the magnitude of the external pressure applied to the device can be converted. Exemplarily, the difference between the MEMS pressure sensors shown in FIG. 5A and FIG. 5B is that the MEMS pressure sensor shown in FIG. 5B further includes a second conductive layer 2232 formed between the first conductive layer 2132 and the second support layer 2231 .

[0100] The electronic device can be any electronic product or device, such as a mobile phone, tablet computer, laptop computer, netbook, game console, television, VCD, DVD, navigation system, camera, camcorder, voice recorder, MP3, MP4, PSP, or any other electronic product or device. It can also be an intermediate product incorporating the aforementioned MEMS pressure sensor, such as a mobile phone motherboard incorporating the integrated circuit. The electronic device of the disclosed embodiment has improved performance due to its use of the aforementioned MEMS pressure sensor.

[0101] Although a number of embodiments are described herein, it should be understood that a variety of other modifications and embodiments may be devised by those skilled in the art, all of which fall within the spirit and scope of the concepts of the present disclosure. More particularly, within the scope of the present disclosure, the accompanying drawings, and the appended claims, various modifications and changes may be made in the arrangement and / or component parts of the subject matter in combination. In addition to modifications and changes in component parts and / or arrangements, feature substitutions that are obvious to those skilled in the art also fall within the scope of the present disclosure, the accompanying drawings, and the appended claims.

Claims

1. A method for preparing a MEMS pressure sensor, characterized in that: The method comprises: Providing a first substrate, forming a first pressure-sensitive film layer on a first surface of the first substrate, forming a first sacrificial layer on the first pressure-sensitive film layer, forming a first supporting layer on the first sacrificial layer, and forming a first conductive layer on the first supporting layer; Providing a second substrate, forming a second pressure-sensitive film layer on a first surface of the second substrate, forming a second sacrificial layer on the second pressure-sensitive film layer, and forming a second supporting layer on the second sacrificial layer; Etching the first supporting layer and the first conductive layer to form a plurality of first release holes penetrating the first supporting layer and the first conductive layer; Etching the second supporting layer to form a plurality of second release holes penetrating the second supporting layer; removing a portion of the first sacrificial layer through the plurality of first release holes to form a first cavity between the first supporting layer and the first pressure-sensitive film layer; removing a portion of the second sacrificial layer through the plurality of second release holes to form a second cavity between the second supporting layer and the second pressure-sensitive film layer; Bonding the first conductive layer to the second supporting layer so that the first supporting layer, the first conductive layer and the second supporting layer together form a fixed electrode layer, wherein the plurality of first release holes and the plurality of second release holes are arranged alternately with each other; Etching the first substrate from the second surface of the first substrate to form a back cavity exposing the first pressure-sensitive film layer; The second substrate is removed to expose the second pressure-sensitive film layer.

2. The preparation method according to claim 1, characterized in that: The preparation method further comprises: after forming a second supporting layer on the second sacrificial layer, forming a second conductive layer on the second supporting layer, Wherein, etching the second supporting layer to form a plurality of second release holes penetrating the second supporting layer comprises: etching the second supporting layer and the second conductive layer to form a plurality of second release holes penetrating the second supporting layer and the second conductive layer; The step of bonding the first conductive layer to the second supporting layer so that the first supporting layer, the first conductive layer and the second supporting layer together form a fixed electrode layer comprises: The first conductive layer is bonded to the second conductive layer so that the first supporting layer and the first conductive layer and the second supporting layer and the second conductive layer together form a fixed electrode layer.

3. The preparation method according to claim 1 or 2, characterized in that: The bonding is performed using a vacuum bonding process.

4. The preparation method according to claim 1 or 2, characterized in that: The first supporting layer and the second supporting layer include silicon nitride, and the first conductive layer includes polysilicon.

5. A MEMS pressure sensor, characterized in that: include: a first substrate, wherein a back cavity penetrating the first substrate is formed in the first substrate; A first pressure-sensitive film layer, located on the first surface of the first substrate; a first sacrificial layer, located on the first pressure-sensitive film layer and covering a portion of the surface of the first pressure-sensitive film layer; A fixed electrode layer, comprising a first supporting layer, a second supporting layer and a first conductive layer located between the first supporting layer and the second supporting layer; a second sacrificial layer, located on the fixed electrode layer and covering a portion of the surface of the fixed electrode layer; A second pressure-sensitive film layer, located on the second sacrificial layer; A first cavity is formed between the fixed electrode layer and the first pressure-sensitive film layer; A second cavity is formed between the fixed electrode layer and the second pressure-sensitive film layer; A plurality of first release holes and a plurality of second release holes facing the first cavity and the second cavity are formed in the fixed electrode layer, wherein the plurality of first release holes and the plurality of second release holes do not penetrate the fixed electrode layer and are arranged alternately with each other.

6. The MEMS pressure sensor according to claim 5, characterized in that: The bottoms of the plurality of first release holes expose the second supporting layer; or The fixed electrode layer further includes a second conductive layer located between the first conductive layer and the second supporting layer, and the second conductive layer is exposed at the bottoms of the plurality of first release holes.

7. The MEMS pressure sensor according to claim 5, characterized in that: The first supporting layer and the second supporting layer include silicon nitride, and the first conductive layer includes polysilicon.

8. An electronic device, characterized in that: The electronic device comprises the MEMS pressure sensor according to any one of claims 5-7.

9. The electronic device according to claim 8, characterized in that: It also includes a PCB board, and the second surface of the first substrate of the MEMS pressure sensor is attached to the PCB board.

10. The electronic device according to claim 9, characterized in that: An opening penetrating the PCB board is formed in the PCB board, and the opening exposes the back cavity of the MEMS pressure sensor.

Images