MEMS pressure sensor and preparation method thereof, and electronic device

Abstract

The invention provides an MEMS pressure sensor, a preparation method thereof and an electronic device, and the method comprises the steps: providing a first substrate and a second substrate, sequentially forming a first pressure sensing film layer, a first sacrificial layer and a first sub-electrode layer on the first substrate, and sequentially forming a second pressure sensing film layer, a second sacrificial layer and a second supporting layer on the second substrate; respectively etching the first sub-electrode layer and the second supporting layer to form a plurality of first release holes and a plurality of second release holes; removing part of the first sacrificial layer to form a first cavity, and removing part of the second sacrificial layer to form a second cavity; the first sub-electrode layer and the second supporting layer are bonded, and the first release holes and the second release holes are arranged in a staggered mode; and etching the first substrate to form a back cavity, and removing the second substrate to expose the second pressure sensing film layer. According to the scheme, the first sub-electrode layer and the second supporting layer are bonded to form the MEMS pressure sensor with the double pressure sensing film layers, and the sensitivity and the linearity are improved.

Description

Technical Field

[0001] The present invention 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] MEMS pressure sensors are a cutting-edge research field developed on the basis of MEMS technology. They are suitable for harsh environments such as high impact, high overload, conductivity, corrosion, and radiation, and are widely used in fields such as aerospace, electronics, industry, medical and health, and environmental monitoring. Among them, capacitive pressure sensors are a main type of MEMS pressure sensors, and 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-spacing type, variable-area type, and variable-dielectric type. Due to its convenience in implementation, the variable-spacing capacitive pressure sensor is the most common. However, the variable-spacing capacitive pressure sensors in related technologies have poor linearity and low sensitivity, resulting in the need for complex interface circuits for detection, increasing the measurement difficulty and cost. Summary of the Invention

[0004] A series of simplified concepts are introduced in the Summary of the Invention section, which will be further described in detail in the Detailed Description section. The Summary of the Invention section of the present invention does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the protection scope of the claimed technical solution.

[0005] In view of the existing problems, on the one hand, the present invention provides a preparation method of a MEMS pressure sensor, including:

[0006] Providing a first substrate and a second 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 sub-electrode layer on the first sacrificial layer, 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 support layer on the second sacrificial layer, wherein the first sub-electrode layer includes a first support layer and a first conductive layer located on the first support layer;

[0007] Respectively etching the first sub-electrode layer and the second support layer to form a plurality of first release holes penetrating the first sub-electrode layer and a plurality of second release holes penetrating the second support layer;

[0008] Remove part of the first sacrificial layer through the first release hole to form a first cavity between the first sub - electrode layer and the first pressure - sensitive film layer, and remove part of the second sacrificial layer through the second release hole to form a second cavity between the second support layer and the second pressure - sensitive film layer;

[0009] Bond the first sub - electrode layer and the second support layer so that the first sub - electrode layer and the second support layer jointly form a fixed electrode layer, wherein the first release hole and the second release hole are arranged in an interleaved manner;

[0010] 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.

[0011] Exemplarily, it further includes a second conductive layer on the second support layer. The second support layer and the second conductive layer are etched simultaneously, and the bonding step joins the second conductive layer and the first conductive layer.

[0012] Exemplarily, a vacuum bonding process is used for the bonding.

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

[0014] On the other hand, the present invention provides a MEMS pressure sensor, including:

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

[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 part of the surface of the first pressure - sensitive film layer;

[0018] A fixed electrode layer, including a first support layer, a second support layer, and a first conductive layer located between the first support layer and the second support layer;

[0019] A second sacrificial layer, located on the fixed electrode layer and covering part 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] A plurality of first release holes and a plurality of second release holes are formed in the fixed electrode layer, facing the first cavity and the second cavity respectively, wherein neither the first release holes nor the second release holes penetrate through the fixed electrode layer, and they are arranged in an alternating manner.

[0024] Exemplarily, the bottom of the first release hole exposes the second support layer; or

[0025] The fixed electrode layer further includes a second conductive layer located between the first conductive layer and the second support layer, and the bottom of the first release hole exposes the second conductive layer.

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

[0027] On the other hand, the present invention further provides an electronic device, which includes the aforementioned MEMS pressure sensor.

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

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

[0030] The MEMS pressure sensor, its manufacturing method, and the electronic device according to the embodiments of the present invention bond the first sub-electrode layer and the second support layer so that the first sub-electrode layer and the second support layer jointly form a fixed electrode layer. The first pressure-sensitive film layer and the second pressure-sensitive film layer can respectively form a capacitive structure with the fixed electrode layer, forming a MEMS pressure sensor with a double pressure-sensitive film layer, avoiding problems such as warping and even peeling off due to multi-layer stacking in the related art, improving the sensitivity and linearity of the MEMS pressure sensor, and further improving the device performance and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The following drawings of the present invention are used as a part of the present invention to understand the present invention. The embodiments of the present invention and their descriptions are shown in the drawings to explain the principles of the present invention.

[0032] In the drawings:

[0033] Figure 1 Shows a flowchart of a manufacturing method of a MEMS pressure sensor according to a specific embodiment of the present invention;

[0034] Figures 2A - 2FThe cross-sectional schematic diagram of the device obtained by successively implementing the preparation method of the MEMS pressure sensor according to a specific embodiment of the present invention is shown;

[0035] Figures 3A - 3D The cross-sectional schematic diagram of the device obtained by successively implementing the preparation method of the MEMS pressure sensor according to another specific embodiment of the present invention is shown;

[0036] Figures 4A - 4B The cross-sectional schematic diagram of the MEMS pressure sensor and the PCB board in the electronic device according to a specific embodiment of the present invention is shown;

[0037] Figures 5A - 5B The cross-sectional schematic diagram of the MEMS pressure sensor and the PCB board in the electronic device according to another specific embodiment of the present invention is shown. Specific Embodiments

[0038] Next, the present invention will be described more completely with reference to the accompanying drawings, in which embodiments of the present invention are shown. However, the present invention can be implemented in different forms and should not be construed as limited to the embodiments set forth herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. Like reference numerals denote like elements throughout.

[0039] It should be understood that when an element or layer is referred to as being "on", "adjacent to", "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on", "directly adjacent to", "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Thus, the first element, component, region, layer or part discussed below may be denoted as the second element, component, region, layer or part without departing from the teachings of the present invention.

[0040] Spatial relationship terms such as "under", "below", "beneath", "underneath", "above", "over", 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 orientation shown in the figures, spatial relationship terms are also intended to include different orientations of the device in use and operation. For example, if the device in the drawings is flipped, then an element or feature described as "under other elements" or "beneath them" or "under them" will be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "beneath" can include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatial descriptors used herein are to be interpreted accordingly.

[0041] The purpose of the terms used herein is only to describe specific embodiments and not to limit the present invention. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, specify the presence of the stated features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups. As used herein, the term "and / or" includes any and all combinations of the associated listed items.

[0042] Embodiments of the invention are described herein with reference to cross-sectional views that are schematic illustrations of ideal embodiments (and intermediate structures) of the invention. As such, variations from the illustrated shapes due to, for example, manufacturing techniques and / or tolerances are to be expected. Accordingly, embodiments of the present invention should not be limited to the particular shapes of regions shown herein but include shape deviations resulting from, for example, manufacturing. For example, an implantation region shown as rectangular will typically have rounded or curved features at its edges and / or an implantation concentration gradient, rather than a binary change from the implanted region to the 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 implantation takes place. Thus, the regions shown in the figures are substantially schematic in nature, and their shapes are not intended to show the actual shape of the regions of the device and are not intended to limit the scope of the present invention.

[0043] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will also be understood that terms, such as those defined in commonly used dictionaries, should be understood to have a meaning that is consistent with their meaning in the context of the relevant art and / or this specification, and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0044] To thoroughly understand the present invention, detailed steps and structures will be presented in the following description to illustrate the technical solutions proposed by the present invention. The preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may also have other embodiments.

[0045] In the related art, the sensitivity of the MEMS pressure sensor with a single-layer pressure-sensitive film layer is poor. The MEMS pressure sensor with a single-layer pressure-sensitive film layer can only improve the sensitivity by increasing the area of the pressure-sensitive film layer, which will lead to a poor integration of the device.

[0046] In order to improve the sensitivity of the MEMS pressure sensor without increasing the area of the pressure-sensitive film layer, in the related art, the sensitivity of the MEMS pressure sensor is often improved by forming a multi-layer pressure-sensitive film layer. However, the current process technology for growing multi-layer films layer by layer is still immature, which will induce residual stress. The existence of this residual stress will cause problems such as warping and even film layer peeling during the deposition process of the multi-layer pressure-sensitive film layer structure, resulting in poor linearity of the device and affecting the electrical performance and reliability of the device.

[0047] Therefore, in view of the existence of the foregoing technical problems, the present invention proposes a method for preparing a MEMS pressure sensor. As shown in Figure 2, it mainly includes the following steps:

[0048] Step S1: Provide a first substrate and a second substrate. A first pressure-sensitive film layer is formed on the first surface of the first substrate. A first sacrificial layer is formed on the first pressure-sensitive film layer. A first sub-electrode layer is formed on the first sacrificial layer. A second pressure-sensitive film layer is formed on the first surface of the second substrate. A second sacrificial layer is formed on the second pressure-sensitive film layer. A second support layer is formed on the second sacrificial layer. Among them, the first sub-electrode layer includes a first support layer and a first conductive layer located on the first support layer;

[0049] Step S2: Etch the first sub-electrode layer and the second support layer respectively to form a plurality of first release holes penetrating the first sub-electrode layer and a plurality of second release holes penetrating the second support layer;

[0050] Step S3: Remove part of the first sacrificial layer through the first release holes to form a first cavity between the first sub-electrode layer and the first pressure-sensitive film layer, and remove part of the second sacrificial layer through the second release holes to form a second cavity between the second support layer and the second pressure-sensitive film layer;

[0051] Step S4: Bond the first sub-electrode layer and the second support layer so that the first sub-electrode layer and the second support layer jointly form a fixed electrode layer, wherein the first release holes and the second release holes are arranged staggered with each other;

[0052] Step S5, 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.

[0053] The preparation method of the MEMS pressure sensor of the present invention bonds the first sub-electrode layer and the second support layer so that the first sub-electrode layer and the second support layer jointly form a fixed electrode layer. The first pressure-sensitive film layer and the second pressure-sensitive film layer can respectively form a capacitive structure with the fixed electrode layer, forming a MEMS pressure sensor with a double pressure-sensitive film layer, avoiding problems such as warping and even peeling due to multi-layer film stacking in the related art, improving the sensitivity and linearity of the MEMS pressure sensor, and further improving the device performance and reliability.

[0054] Embodiment 1

[0055] Next, refer to Figures 1 to 2F to describe in detail the preparation method of the MEMS pressure sensor of the present invention. Among them, Figure 1 shows a flowchart of the preparation method of the MEMS pressure sensor according to a specific embodiment of the present invention, Figures 2A - 2F shows a cross-sectional schematic diagram of the device obtained by successively implementing the preparation method of the MEMS pressure sensor according to a specific embodiment of the present invention.

[0056] Exemplarily, the preparation method of the MEMS pressure sensor of the present invention includes the following steps:

[0057] First, perform step S1, provide a first substrate and a second substrate. A first pressure-sensitive film layer is formed on the first surface of the first substrate, a first sacrificial layer is formed on the first pressure-sensitive film layer, a first sub-electrode layer is formed on the first sacrificial layer, a second pressure-sensitive film layer is formed on the first surface of the second substrate, a second sacrificial layer is formed on the second pressure-sensitive film layer, and a second support layer is formed on the second sacrificial layer. Among them, the first sub-electrode layer includes a first support layer and a first conductive layer located on the first support layer.

[0058] Specifically, as Figure 2A and Figure 2BAs shown, the first substrate 210 and the second substrate 220 are bulk silicon substrates, which can be at least one of the materials mentioned below: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs, or other III / V compound semiconductors, and also include multi-layer structures composed of these semiconductors, etc., or are silicon-on-insulator (SOI), stacked silicon-on-insulator (SSOI), stacked silicon-germanium-on-insulator (S-SiGeOI), silicon-germanium-on-insulator (SiGeOI), and germanium-on-insulator (GeOI), etc.

[0059] In one example, as Figure 2A shown in Figure 2B shown, 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 be made of materials such as polysilicon, SiGe, etc., and are not limited to a certain one. 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) method, physical vapor deposition (PVD) method, atomic layer deposition (ALD) method, etc., or one of the methods of furnace tube growth and selective epitaxial growth (SEG) can be used to form the first pressure-sensitive film layer 211 and the second pressure-sensitive film layer 221, and the present application does not limit this.

[0060] Exemplarily, an insulating layer can also 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 material of the insulating layer can include any one of several dielectric materials. Non-limiting examples include oxides, nitrides, and oxynitrides, especially oxides, nitrides, and oxynitrides of silicon, but do not include oxides, nitrides, and oxynitrides of other elements. The insulating layer can be formed by any one of several methods. Non-limiting examples include ion implantation method, thermal or plasma oxidation or nitridation method, chemical vapor deposition method, and physical vapor deposition method.

[0061] In one example, as Figure 2A shown in Figure 2BAs shown, 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. Exemplarily, the first sacrificial layer 212 and the second sacrificial layer 222 are made of oxide layers, such as materials like silicon oxide and carbon-doped silicon oxide (SiOC), but are not limited to the above examples. In addition, the first sacrificial layer 212 and the second sacrificial layer 222 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) methods. Optionally, the first sacrificial layer 212 and the second sacrificial layer 222 can be patterned, including the following steps: mask layers, such as photoresist layers, are respectively formed on the first sacrificial layer 212 and the second sacrificial layer 222; the first sacrificial layer 212 and the second sacrificial layer 222 are respectively etched using the mask layer as a mask, and then the mask layer is removed. Dry etching, reactive ion etching (RIE), ion beam etching, or plasma etching can be selected in this step.

[0062] In one example, as Figure 2A shown, a first sub-electrode layer 213 is formed on the first sacrificial layer 212. The first sub-electrode layer 213 includes a first support layer 2131 and a first conductive layer 2132 located on the first support layer 2131. Exemplarily, the first support layer 2131 is used to improve the strength and stability of the overall device. Exemplarily, the material of the first support layer 2131 includes silicon nitride. In other embodiments, the material of the first support 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 be selected from metals, or N-type ion-doped polysilicon such as phosphorus, or P-type ion-doped polysilicon such as boron, etc., and is not limited to a certain type.

[0063] In one example, as Figure 2B shown, a second support layer 2231 is formed on the second sacrificial layer 222. Exemplarily, the second support layer 2231 is used to improve the strength and stability of the overall device. Exemplarily, the material of the second support layer 2231 includes silicon nitride. In other embodiments, the material of the second support layer 2231 can also be any other suitable material that can improve the strength and stability of the device.

[0064] In one example, the first support layer 2131 and the second support 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) methods.

[0065] In one example, the first conductive layer 2132 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), atomic layer deposition (ALD), etc. Alternatively, one of the methods of furnace tube growth and selective epitaxial growth (SEG) can be used to form the first conductive layer 2132. The present application does not limit this.

[0066] Next, step S2 is performed to etch the first sub-electrode layer and the second support layer respectively to form a plurality of first release holes penetrating the first sub-electrode layer and a plurality of second release holes penetrating the second support layer. Specifically, as Figure 2C shown in Figure 2D , the first sub-electrode layer 213 and the second support layer 2231 are etched respectively to form a plurality of first release holes 214 penetrating the first sub-electrode layer 213 and a plurality of second release holes 224 penetrating the second support layer 2231. Exemplarily, the plurality of first release holes 214 are arranged at intervals and expose a part of the surface of the first sacrificial layer 212; the plurality of second release holes 224 are arranged at intervals and expose a part of the surface of the second sacrificial layer 222. Optionally, etching the first sub-electrode layer 213 and the second support layer 2231 respectively includes the following steps: forming a mask layer, such as a photoresist layer, on the first sub-electrode layer 213 and the second support layer 2231 respectively; etching the first sub-electrode layer 213 and the second support layer 2231 respectively with the mask layer as a mask to form a plurality of first release holes 214 penetrating the first sub-electrode layer 213 and a plurality of second release holes 224 penetrating the second support layer 2231, and then removing the mask layer. Dry etching, reactive ion etching (RIE), ion beam etching, or plasma etching can be selected in this step. Exemplarily, 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 are less than or equal to 1 um.

[0067] Next, step S3 is performed to remove part of the first sacrificial layer through the first release holes to form a first cavity between the first sub-electrode layer and the first pressure-sensitive film layer, and remove part of the second sacrificial layer through the second release holes to form a second cavity between the second support layer and the second pressure-sensitive film layer. Specifically, as Figure 2C shown in Figure 2DAs shown, part of the first sacrificial layer 212 is removed through the first release hole 214 to form a first cavity 215 between the first sub-electrode layer 213 and the first pressure-sensitive film layer 211, and part of the second sacrificial layer 222 is removed through the second release hole 224 to form a second cavity 225 between the second support layer 2231 and the second pressure-sensitive film layer 221. Exemplarily, a commonly used etching process in the art can be employed 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 Buffer Oxide Etchant can be used to remove part of the first sacrificial layer 212 and part of the second sacrificial layer 222, or 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 ranges 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 ranges of the first sacrificial layer 212 and the second sacrificial layer 222 are 5-10 um, where the release boundary refers to the width of the remaining first sacrificial layer 212 and second sacrificial layer 222.

[0068] Next, step S4 is executed to bond the first sub-electrode layer and the second support layer so that the first sub-electrode layer and the second support layer jointly form a fixed electrode layer, wherein the first release hole and the second release hole are arranged in an interleaved manner. Specifically, as Figure 2E shown, the first sub-electrode layer 213 and the second support layer 2231 are bonded so that the first sub-electrode layer 213 and the second support layer 2231 jointly form a fixed electrode layer 230. More specifically, the first conductive layer 2132 and the second support layer 2231 are bonded, wherein the first release hole 214 and the second release hole 224 are arranged in an interleaved manner. Exemplarily, the first release hole 214 and the second release hole 224 are arranged in an interleaved manner 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 jointly form a first capacitance structure, and the second pressure-sensitive film layer 221 and the fixed electrode layer 230 jointly form a second capacitance structure. Moreover, the first capacitance structure and the second capacitance structure are independent of each other and do not affect each other. And a MEMS pressure sensor with a double pressure-sensitive film layer is obtained by bonding. Compared with the multi-mode layer stacking method in the related art, problems such as warping or even peeling off of the film layer can be effectively avoided. The first pressure-sensitive film layer 211 and the second pressure-sensitive film layer 221 are more uniformly stressed, and the linearity of the device is better. Exemplarily, before bonding the first sub-electrode layer 213 and the second support layer 2231, it further includes: planarizing the surfaces of the first sub-electrode layer 213 and the second support layer 2231 to make their surfaces meet the bonding requirements.

[0069] In one example, a vacuum bonding process is adopted to bond the first sub-electrode layer 213 and the second support layer 2231. Specifically, in an ultra-high vacuum environment, when the surfaces of the planarized first sub-electrode layer 213 and the second support layer 2231 are in close enough contact, the distance between the surface atoms of the two can be further reduced through the molecular force (van der Waals force or hydrogen bond) between adjacent interfaces, so that covalent bonds are directly formed at the interface, enabling the first sub-electrode layer 213 and the second support layer 2231 to be joined. Exemplarily, by adopting an ultra-high vacuum bonding process to bond the first sub-electrode layer 213 and the second support layer 2231, the vacuum degree of the device can be guaranteed, and compared with the silicon-silicon high-temperature bonding process, the operation is simple and the thermal budget can be reduced.

[0070] Finally, step S5 is executed 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 the second substrate is removed to expose the second pressure-sensitive film layer. Specifically, as Figure 2F shown, 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 use, including but not limited to, chemical mechanical polishing or etching processes, etc.

[0071] Exemplarily, when an insulating layer is further formed between the first substrate 210 and the first pressure-sensitive film layer 211, forming the back cavity 216 includes: 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 a part of the insulating layer to form the back cavity 216. Exemplarily, when an insulating layer is further 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, a commonly used etching process in the art such as dry etching can be selected to etch the first substrate 210. Specifically, the bosch etching process can be adopted to etch the first substrate 210. Exemplarily, a wet etching process can be selected to remove the insulating layer. Specifically, a buffer oxide etchant can be adopted to remove the insulating layer, or gaseous hydrogen fluoride (VHF) can be adopted to remove the insulating layer. Exemplarily, 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 can be removed simultaneously.

[0072] It is worth mentioning that, with reference to Figures 2A to 2F the preparation method of the MEMS pressure sensor described in Figure 3A , the first sub-electrode layer 213 is bonded to the second support layer 2231. More specifically, the first conductive layer 2132 is bonded to the second support layer 2231. In another embodiment, as Figures 3A to 3D shown, it further includes a second conductive layer 2232 located on the second support layer 2231. Hereinafter, with reference to Figures 3A - 3D , a detailed description will be given to the preparation method of the MEMS pressure sensor according to another specific embodiment of the present invention, in which

[0073] specifically, first, as Figure 3A shown, a second substrate 220 is 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 support layer 2231 is formed on the second sacrificial layer 222, and a second conductive layer 2232 is formed on the second support layer 2231. Then, as Figure 3B shown, in the process step of forming the first release holes 224, the second conductive layer 2232 is etched while etching the second support layer 2231, that is, the second conductive layer 2232 and the second support layer 2231 are etched to form a plurality of second release holes 224 penetrating through the second conductive layer 2232 and the second support layer 2231. Next, as Figure 3C shown, in the bonding process step, the first 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 first sub-electrode layer 213, the second conductive layer 2232 and the second support layer 2231 jointly form a fixed electrode layer 230. Finally, as Figure 3D shown, 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 difference between this embodiment and the above-described embodiment is only that a second conductive layer 2232 is further formed on the second support layer 2231, and the remaining processes are the same. Specifically, reference can be made to the above, and details will not be repeated here.

[0074] In one example, the material of the second conductive layer 2232 can be selected from metal, N-type ion-doped polysilicon such as phosphorus, P-type ion-doped polysilicon such as boron, etc., and is not limited to a certain type. Exemplarily, the first conductive layer 2132 and the second conductive layer 2232 are made of the same material. In the bonding step of bonding the second conductive layer 2232 and the first conductive layer 2132, since the bonding surface is the first conductive layer 2132 and the second conductive layer 2232, and their materials are the same, the bonding effect can be better.

[0075] 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), atomic layer deposition (ALD), etc. Or, the second conductive layer 2232 can be formed by one of furnace tube growth and selective epitaxial growth (SEG). The present application does not limit this.

[0076] It is worth mentioning that the above steps are only examples. On the premise of no conflict, the order of the above steps can also be adjusted.

[0077] So far, the key steps of the preparation method of the MEMS pressure sensor of the present invention have been described. For the complete preparation of the MEMS pressure sensor, other steps may also be included, which will not be elaborated here one by one.

[0078] In summary, in the preparation method of the MEMS pressure sensor of the present invention, by bonding the first sub-electrode layer and the second support layer to jointly form a fixed electrode layer, the first pressure-sensitive film layer and the second pressure-sensitive film layer can respectively form a capacitive structure with the fixed electrode layer, forming a MEMS pressure sensor with a double pressure-sensitive film layer. Compared with the MEMS pressure sensor with a single pressure-sensitive film layer in the related art, it can improve the sensitivity of the MEMS pressure sensor without increasing the area of the pressure-sensitive film layer, and avoid problems such as warping and even peeling caused by multi-layer stacking in the related art, improving the linearity and sensitivity of the MEMS pressure sensor, and further improving the device performance and reliability.

[0079] Embodiment 2

[0080] The present invention also provides a MEMS pressure sensor, which is prepared by the method in the first embodiment above. As Figure 2F as Figure 3D shown, the MEMS pressure sensor of the present invention includes:

[0081] A first substrate 210, in which a back cavity 216 penetrating the first substrate 210 is formed;

[0082] The first pressure-sensitive film layer 211 is located on the first surface of the first substrate 210;

[0083] The first sacrificial layer 212 is located on the first pressure-sensitive film layer 211 and covers a partial surface of the first pressure-sensitive film layer 211;

[0084] The fixed electrode layer 230 includes a first support layer 2131, a second support layer 2231, and a first conductive layer 2132 located between the first support layer 2131 and the second support layer 2231;

[0085] The second sacrificial layer 222 is located on the fixed electrode layer 230 and covers a partial surface of the fixed electrode layer 230;

[0086] The second pressure-sensitive film layer 221 is located on the second sacrificial layer 222;

[0087] The first cavity 215 is formed between the fixed electrode layer 230 and the first pressure-sensitive film layer 211;

[0088] The second cavity 225 is formed between the fixed electrode layer 230 and the second pressure-sensitive film layer 221;

[0089] 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 are formed in the fixed electrode layer 230. Among them, both the first release holes 214 and the second release holes 224 penetrate through the fixed electrode layer 230 and are arranged in an alternating manner.

[0090] In one example, the first release holes 214 and the second release holes 224 are arranged in an alternating manner 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 jointly form a first capacitive structure, and the second pressure-sensitive film layer 221 and the fixed electrode layer 230 jointly form a second capacitive structure, and the first capacitive structure and the second capacitive structure are independent of each other and do not affect each other.

[0091] Exemplarily, the materials of the first support layer 2131 and the second support layer 2231 include silicon nitride. In other embodiments, the material of the second support layer 2231 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 be selected from metals, N-type ion-doped polysilicon such as phosphorus, or P-type ion-doped polysilicon such as boron, etc., and is not limited to a certain one.

[0092] In one example, as Figure 2F shown, the bottom of the first release hole 214 exposes the second support layer 2231; or, as Figure 3DAs shown, the fixed electrode layer 230 further includes a second conductive layer 2232 located between the first conductive layer 2132 and the second support layer 2231, and the bottom of the first release hole 214 exposes the second conductive layer 2232. Exemplarily, the material of the second conductive layer 2232 can be selected from metals, N-type ion-doped polysilicon such as phosphorus, or P-type ion-doped polysilicon such as boron, etc., and is not limited to a certain type.

[0093] In one example, the first support layer 2131 and the second support layer 2231 can be formed by various deposition methods commonly used in the art, such as by chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD), etc.

[0094] 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, such as by chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD), etc. Alternatively, one of the methods of furnace tube growth and selective epitaxial growth (SEG) can be used to form the first conductive layer 2132, and the present application does not limit this.

[0095] So far, the introduction of the structure of the MEMS pressure sensor of the present invention has been completed. For a complete device, there may be other component structures, which will not be elaborated one by one here.

[0096] Due to the MEMS pressure sensor of the present invention, the first pressure-sensitive film layer and the second pressure-sensitive film layer can respectively form a capacitive structure with the fixed electrode layer, forming a MEMS pressure sensor with a double pressure-sensitive film layer. Compared with the MEMS pressure sensor with a single pressure-sensitive film layer in the related art, it can improve the sensitivity of the MEMS pressure sensor without increasing the area of the pressure-sensitive film layer, and avoid problems such as warping and even peeling off due to multi-layer stacking in the related art, improving the linearity and sensitivity of the MEMS pressure sensor, and further improving the device performance and reliability.

[0097] Embodiment III

[0098] The present invention also provides an electronic device, which includes the MEMS pressure sensor described in Embodiment II or the MEMS pressure sensor prepared by the method described in Embodiment I.

[0099] In one example, as Figure 4A And Figure 4BAs shown, the electronic device of the present application 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. Exemplarily, 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 received by the first pressure-sensing film layer 211 is a fixed value, set as P1. At this time, P1 can be used as the reference pressure. Then, the distance between the first pressure-sensing film layer 211 and the fixed electrode layer 230 is fixed. Therefore, the capacitance value of the first capacitance structure formed by the first pressure-sensing film layer 211 and the fixed electrode layer 230 is also a fixed value, set as C1. At this time, the capacitance value C1 can be used as the reference capacitance value. At this time, the second pressure-sensing film layer 221 deforms under the action of the external pressure. It is assumed that the external pressure received by the second pressure-sensing film layer 221 is P2, which causes the distance between the second pressure-sensing film layer 221 and the fixed electrode layer 230 to change, and further causes the capacitance value output by the second capacitance structure formed by the second pressure-sensing film layer 221 and the fixed electrode layer 230 to change, set as C2. Then, C2 can be compared with C1, that is, the overall output capacitance of the device at this time is |C1 - C2|. Then, the difference is converted into the corresponding pressure and corresponding operations are performed with the reference pressure P1 to obtain the magnitude of the external pressure. Exemplarily, the second surface of the first substrate 210 can be attached to the PCB board 240 through Surface Mounted Technology (SMT). Exemplarily, Figure 4A The difference from Figure 4B the MEMS pressure sensor shown is that Figure 4B a second conductive layer 2232 is further formed between the first conductive layer 2132 and the second support layer 2231 in the MEMS pressure sensor shown.

[0100] In one example, as Figure 5A the difference from Figure 5B shown, an opening 250 penetrating the PCB board 240 is formed in the PCB board 240, and the opening 250 exposes the back cavity 216 of the MEMS pressure sensor. In this embodiment, the first pressure-sensing film layer 211 and the second pressure-sensing film layer 221 are simultaneously in contact with the external pressure. It is assumed that the external pressure received by the first pressure-sensing film layer 211 is P1 and the external pressure received by the second pressure-sensing film layer 221 is P2. At this time, P1 is equal to P2. It is also assumed that the capacitance output by the first capacitance structure formed by the first pressure-sensing film layer 211 and the fixed electrode layer 230 is C1, and the capacitance output by the second capacitance structure formed by the second pressure-sensing film layer 221 and the fixed electrode layer 230 is 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 received by the device can be calculated. Exemplarily, Figure 5A The difference from Figure 5B the MEMS pressure sensor shown is that Figure 5BThe shown MEMS pressure sensor further forms a second conductive layer 2232 between the first conductive layer 2132 and the second support layer 2231.

[0101] The electronic device can be any electronic product or device such as a mobile phone, a tablet computer, a notebook computer, a netbook, a game console, a television, a VCD, a DVD, a navigator, a camera, a video camera, a voice recorder, an MP3, an MP4, a PSP, etc., or can be an intermediate product having the above MEMS pressure sensor, for example: a mobile phone motherboard having the integrated circuit. The electronic device according to the embodiment of the present invention has better performance due to the use of the above MEMS pressure sensor.

[0102] Although multiple embodiments are described herein, it should be understood that those skilled in the art can conceive of various other modifications and embodiments, and they will all fall within the spirit and scope of the concept disclosed by the present invention. More particularly, various modifications and changes can be made in the arrangement and / or components of the combination of the subject matter within the scope of the present invention disclosure, the drawings, and the appended claims. In addition to the modifications and changes in the components and / or arrangements, the use of alternative means will also be an obvious choice for those skilled in the art.

Claims

1. A method for fabricating a MEMS pressure sensor, characterized in that, the method comprises: providing a first substrate and a second 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 sub-electrode layer on the first sacrificial layer, 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 support layer on the second sacrificial layer, wherein the first sub-electrode layer comprises a first support layer and a first conductive layer located on the first support layer; etching the first sub-electrode layer and the second support layer respectively to form a plurality of first release holes penetrating through the first sub-electrode layer and a plurality of second release holes penetrating through the second support layer; removing part of the first sacrificial layer through the first release holes to form a first cavity between the first sub-electrode layer and the first pressure-sensitive film layer, and removing part of the second sacrificial layer through the second release holes to form a second cavity between the second support layer and the second pressure-sensitive film layer; bonding the first sub-electrode layer and the second support layer so that the first sub-electrode layer and the second support layer jointly form a fixed electrode layer, wherein the first release holes and the second release holes are arranged staggeredly with each other; etching the first substrate from a 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.

2. The fabrication method according to claim 1, characterized in that, further comprising a second conductive layer located on the second support layer, etching the second conductive layer while etching the second support layer, and the bonding step bonds the second conductive layer and the first conductive layer.

3. The fabrication method according to claim 1 or 2, characterized in that, a vacuum bonding process is adopted for the bonding.

4. The fabrication method according to claim 1 or 2, characterized in that, the first support layer and the second support layer comprise silicon nitride, and the first conductive layer comprises polysilicon.

5. A MEMS pressure sensor, characterized in that, comprises: a first substrate, a back cavity penetrating through the first substrate is formed in the first substrate; a first pressure-sensitive film layer, located on a first surface of the first substrate; a first sacrificial layer, located on the first pressure-sensitive film layer and covering a partial surface of the first pressure-sensitive film layer; a fixed electrode layer, comprising a first support layer, a second support layer and a first conductive layer located between the first support layer and the second support layer; a second sacrificial layer, located on the fixed electrode layer and covering a partial surface of the fixed electrode layer; a second pressure-sensitive film layer, located on the second sacrificial layer; a first cavity, formed between the fixed electrode layer and the first pressure-sensitive film layer; a second cavity, 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 are formed in the fixed electrode layer, facing the first cavity and the second cavity respectively, wherein neither the first release holes nor the second release holes penetrate the fixed electrode layer, and they are arranged in an interleaved manner.

6. The MEMS pressure sensor according to claim 5, wherein, the bottom of the first release hole exposes the second support layer; or the fixed electrode layer further includes a second conductive layer located between the first conductive layer and the second support layer, and the bottom of the first release hole exposes the second conductive layer.

7. The MEMS pressure sensor according to claim 5, wherein, the first support layer and the second support layer include silicon nitride, and the first conductive layer includes polysilicon.

8. An electronic device, wherein, the electronic device includes the MEMS pressure sensor according to any one of claims 5-7.

9. The electronic device according to claim 8, wherein, it further 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, wherein, an opening penetrating the PCB board is formed in the PCB board, and the opening exposes the back cavity of the MEMS pressure sensor.

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