MEMS pressure sensor, manufacturing method thereof and electronic device

Abstract

The invention provides an MEMS pressure sensor, a manufacturing method thereof and an electronic device, and the method comprises the steps: providing a first substrate, forming at least one first pressure structure on the surface of the first substrate, and enabling the first pressure structure to comprise a first electrode layer and a first sacrificial layer from bottom to top, and a first cavity which penetrates through the first sacrificial layer and exposes the first electrode layer; a second substrate is provided, second pressure structures corresponding to the first pressure structures in number are formed on the surface of the second substrate, and each second pressure structure comprises a second electrode layer, a second sacrificial layer and a third electrode layer from bottom to top; bonding the first sacrificial layer and the third electrode layer, and removing the second substrate to expose the second electrode layer; a plurality of first release holes penetrating through the second electrode layer and a second cavity penetrating through the second sacrificial layer and arranged corresponding to the first cavity are formed, the first release holes are exposed out of the second cavity, the first electrode layer and the third electrode layer form a first variable capacitance structure, and the second electrode layer and the third electrode layer form a second variable capacitance structure. According to the scheme, the first pressure structure and the second pressure structure are bonded to form the differential capacitance type pressure sensor, namely, the first variable capacitance structure and the second variable capacitance structure are formed, pressure is measured through differential output of the first variable capacitance structure and the second variable capacitance structure, the measurement precision is higher, and the measurement precision is higher. And thus, the performance of the MEMS pressure sensor can be improved.

Description

Technical Field

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

[0002] 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. Compared to piezoresistive pressure sensors, capacitive pressure sensors have advantages such as high sensitivity, low power consumption, and good temperature characteristics, and are therefore widely used in various fields.

[0003] Based on the capacitance formula, capacitive pressure sensors can be categorized into three types: variable-pitch, variable-area, and variable-dielectric. Variable-pitch capacitive pressure sensors are the most common due to their ease of implementation. Their principle is that changes in pitch cause changes in capacitance, and an integrated circuit acquires and amplifies the signal. However, the measurement accuracy of variable-pitch capacitive pressure sensors in related technologies is relatively low. Summary of the Invention

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

[0005] In order to solve the existing problems, the present invention provides a method for manufacturing a MEMS pressure sensor, comprising:

[0006] Providing a first substrate, wherein at least one first pressure structure is formed on a surface of the first substrate, the first pressure structure comprising a first electrode layer and a first sacrificial layer from bottom to top, and a first cavity penetrating the first sacrificial layer and exposing the first electrode layer;

[0007] Providing a second substrate, on a surface of which second pressure structures corresponding in number to the first pressure structures are formed, the second pressure structures including, from bottom to top, a second electrode layer, a second sacrificial layer, and a third electrode layer;

[0008] bonding the first sacrificial layer and the third electrode layer, and removing the second substrate to expose the second electrode layer;

[0009] A plurality of first release holes are formed through the second electrode layer and a second cavity is formed through the second sacrificial layer and is arranged corresponding to the first cavity. The first release holes expose the second cavity. The first electrode layer and the third electrode layer constitute a first variable capacitor structure, and the second electrode layer and the third electrode layer constitute a second variable capacitor structure.

[0010] Exemplarily, at least two first pressure structures are formed on the surface of the first substrate, and all the first variable capacitance structures and all the second variable capacitance structures together constitute a Wheatstone bridge.

[0011] Exemplarily, a second release hole is further formed in the first electrode layer, penetrating the first electrode layer and corresponding to the first release hole.

[0012] Exemplarily, the second pressure structure further includes a support layer, which is located between the second substrate and the second electrode layer. The first release hole also penetrates the support layer. After the bonding step, the second substrate is removed and the support layer is exposed.

[0013] Exemplarily, the second pressure structure further includes a bonding layer located on the third electrode layer, and the bonding step bonds the first sacrificial layer and the bonding layer.

[0014] Exemplarily, the bonding is performed using a vacuum bonding process.

[0015] Exemplarily, the first variable capacitance structure and the second variable capacitance structure have the same capacitance when not subjected to pressure.

[0016] Another aspect of the present invention provides a MEMS pressure sensor, comprising:

[0017] a first substrate;

[0018] at least one first pressure structure, located on the surface of the first substrate, comprising a first electrode layer and a first sacrificial layer from bottom to top, and a first cavity penetrating the first sacrificial layer and exposing the first electrode layer;

[0019] a second pressure structure corresponding in number to the first pressure structure, located on the first sacrificial layer, comprising, from bottom to top, a third electrode layer, a second sacrificial layer, a second electrode layer, a second cavity penetrating the second sacrificial layer and corresponding to the first cavity, and a first release hole penetrating the second electrode layer and exposing the second cavity;

[0020] The first electrode layer and the third electrode layer constitute a first variable capacitance structure, and the second electrode layer and the third electrode layer constitute a second variable capacitance structure.

[0021] Exemplarily, at least two first pressure structures are formed on the surface of the first substrate, and all the first variable capacitance structures and all the second variable capacitance structures together constitute a Wheatstone bridge.

[0022] Yet another aspect of the present invention provides an electronic device, comprising the aforementioned MEMS pressure sensor.

[0023] The MEMS pressure sensor, manufacturing method thereof, and electronic device of the embodiments of the present invention bond the first pressure structure and the second pressure structure to form a differential capacitive pressure sensor, i.e., form a first variable capacitance structure and a second variable capacitance structure, and measure pressure through the differential output of the first variable capacitance structure and the second variable capacitance structure, thereby improving the performance of the MEMS pressure sensor. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0025] In the attached figure:

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

[0027] Figures 2A-2D A schematic cross-sectional view of a device obtained by sequentially implementing a method for manufacturing a MEMS pressure sensor according to a specific embodiment of the present invention is shown;

[0028] Figure 2E A schematic cross-sectional view of a device obtained by implementing a method for manufacturing a MEMS pressure sensor according to another specific embodiment of the present invention is shown;

[0029] Figure 3 The present invention is shown as Figure 2E A schematic diagram of the circuit structure of a Wheatstone bridge according to a specific embodiment is shown. DETAILED DESCRIPTION

[0030] Next, the present invention will be described more fully with reference to the accompanying drawings, which illustrate embodiments of the present invention. However, the present invention can be embodied in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art. In the drawings, the dimensions and relative sizes of layers and regions may be exaggerated for clarity. Like reference numerals throughout represent like elements.

[0031] It should be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it can be directly on, adjacent to, connected to, or coupled to the other element or layer, or there can be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, a first element, component, region, layer, or part discussed below may be represented as a second element, component, region, layer, or part without departing from the teachings of the present invention.

[0032] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," etc., may be used herein for convenience of description to describe the relationship of one element or feature shown in the figures to other elements or features. It should be understood that the spatially relative terms are intended to include different orientations of the device in use and operation in addition to the orientations shown in the figures. For example, if the device in the drawings is flipped, then the elements or features described as "under" or "beneath" or "beneath" the other elements will be oriented as "over" the other elements or features. Thus, the exemplary terms "under" and "under" may include both the upper and lower orientations. The device may be oriented otherwise (rotated 90 degrees or in other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0033] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present invention. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0034] In order to fully understand the present invention, detailed steps and structures will be provided in the following description to illustrate the technical solutions proposed by the present invention. Preferred embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0035] Therefore, in view of the existence of the above technical problems, the present invention proposes a method for manufacturing a MEMS pressure sensor, such as Figure 1 As shown, it mainly includes the following steps:

[0036] Step S1, providing a first substrate, wherein at least one first pressure structure is formed on a surface of the first substrate, the first pressure structure comprising, from bottom to top, a first electrode layer and a first sacrificial layer, and a first cavity penetrating the first sacrificial layer and exposing the first electrode layer;

[0037] Step S2, providing a second substrate, on the surface of which second pressure structures corresponding in number to the first pressure structures are formed, the second pressure structures including, from bottom to top, a second electrode layer, a second sacrificial layer, and a third electrode layer;

[0038] Step S3, bonding the first sacrificial layer and the third electrode layer, and removing the second substrate to expose the second electrode layer;

[0039] In step S4, a plurality of first release holes are formed through the second electrode layer, and a second cavity is formed through the second sacrificial layer and corresponding to the first cavity. The first release holes expose the second cavity. The first electrode layer and the third electrode layer constitute a first variable capacitor structure, and the second electrode layer and the third electrode layer constitute a second variable capacitor structure.

[0040] The manufacturing method of the MEMS pressure sensor of the present invention bonds the first pressure structure and the second pressure structure to form a differential capacitive pressure sensor, that is, forms a first variable capacitance structure and a second variable capacitance structure, and measures pressure through the differential output of the first variable capacitance structure and the second variable capacitance structure, which has higher measurement accuracy and can improve the performance of the MEMS pressure sensor.

[0041] Example 1

[0042] Below, reference Figure 1 、 Figures 2A-2D 、 Figure 2E as well as Figure 3 The manufacturing method of the MEMS pressure sensor of the present invention is described in detail, wherein: Figure 1 FIG2 is a flow chart showing a method for manufacturing a MEMS pressure sensor according to a specific embodiment of the present invention. Figures 2A-2D FIG2 is a cross-sectional view of a device obtained by sequentially implementing a method for manufacturing a MEMS pressure sensor according to a specific embodiment of the present invention; Figure 2E FIG2 is a cross-sectional view of a device obtained by sequentially implementing a method for manufacturing a MEMS pressure sensor according to another specific embodiment of the present invention. Figure 3 The present invention is shown as Figure 2EA schematic diagram of the circuit structure of a Wheatstone bridge according to a specific embodiment is shown.

[0043] Exemplarily, the method for manufacturing the MEMS pressure sensor of the present invention includes the following steps:

[0044] First, step S1 is performed to provide a first substrate, on the surface of which at least one first pressure structure is formed. The first pressure structure includes a first electrode layer and a first sacrificial layer from bottom to top, and a first cavity penetrating the first sacrificial layer and exposing the first electrode layer.

[0045] In one example, if Figure 2A As shown, the first substrate 210 is a bulk silicon base, which can be at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs or other III / V compound semiconductors, including a multilayer structure composed of these semiconductors, or 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.

[0046] In one example, if Figure 2A As shown, at least one first pressure structure is formed on the surface of the first substrate 210, and the first pressure structure includes a first electrode layer 211 and a first sacrificial layer 212 from bottom to top, and a first cavity 213 that penetrates the first sacrificial layer 212 and exposes the first electrode layer 211. For example, Figure 2A What is shown is that one first pressure structure is formed on the surface of the first substrate 210 . In other embodiments, two, three or more first pressure structures may be formed on the surface of the first substrate 210 , which will not be described in detail here.

[0047] In one example, the first electrode layer 211 can be made of materials such as doped polysilicon, SiGe, or amorphous silicon after implantation and annealing, and is not limited to any one of these materials. The first electrode layer 211 can be formed by chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or the like, or can be formed by furnace growth or selective epitaxial growth (SEG), and this application does not impose any restrictions on this.

[0048] In one example, the first sacrificial layer 212 is an oxide layer, such as silicon oxide and carbon-doped silicon oxide (SiOC), but is not limited to the above examples. Furthermore, the first sacrificial layer 212 can be formed by various deposition methods commonly used in the art, such as plasma-enhanced chemical vapor deposition (PECVD), low-pressure chemical vapor deposition (LPCVD), physical vapor deposition, or atomic layer deposition (ALD).

[0049] In one example, the first cavity 213 is obtained by etching away a portion of the first sacrificial layer 212. For example, an etching process commonly used in the art can be used to remove a portion of the first sacrificial layer 212. For example, a dry etching process or a wet etching process can be used to remove a portion of the first sacrificial layer 212. More specifically, a buffered oxide etchant can be used to remove a portion of the first sacrificial layer 212. Alternatively, gaseous hydrogen fluoride (VHF) can be used to remove a portion of the first sacrificial layer 212. For example, the release boundary range of the first sacrificial layer 212 can be reasonably set according to actual needs, where the release boundary refers to the width of the remaining first sacrificial layer 212.

[0050] In one example, an insulating layer may be formed between the first substrate 210 and the first electrode layer 211. The insulating layer may be made of any of several dielectric materials, non-limiting examples of which include oxides, nitrides, and oxynitrides, particularly silicon oxides, nitrides, and oxynitrides, but not oxides, nitrides, and 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, plasma-enhanced chemical vapor deposition, low-pressure chemical vapor deposition, and physical vapor deposition.

[0051] Next, step S2 is performed to provide a second substrate, on the surface of which second pressure structures corresponding in number to the first pressure structures are formed, and the second pressure structures include a second electrode layer, a second sacrificial layer and a third electrode layer from bottom to top.

[0052] In one example, if Figure 2BAs shown, the second substrate 220 is a bulk silicon base, which can be at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs or other III / V compound semiconductors, including a multilayer structure composed of these semiconductors, or 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.

[0053] In one example, if Figure 2B As shown, a second pressure structure corresponding to the number of the first pressure structure is formed on the surface of the second substrate 220, and the second pressure structure includes a second electrode layer 221, a second sacrificial layer 222 and a third electrode layer 223 from bottom to top. Figure 2B What is shown is that a second pressure structure is formed on the surface of the second substrate 220. In other embodiments, two, three or more second pressure structures can also be formed on the surface of the second substrate 220. No further details are given here, but the number of second pressure structures must correspond to the number of first pressure structures.

[0054] In one example, the second electrode layer 221 and the third electrode layer 223 can be made of materials such as doped polysilicon, SiGe, or amorphous silicon after implantation and annealing, and are not limited to any one material. The second electrode layer 221 and the third electrode layer 223 can be formed by chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or the like, or can be formed by furnace growth or selective epitaxial growth (SEG), and this application does not impose any restrictions on this.

[0055] In one example, the second sacrificial layer 222 is an oxide layer, such as silicon oxide and carbon-doped silicon oxide (SiOC), but is not limited to the above examples. Furthermore, the second sacrificial layer 222 can be formed by various deposition methods commonly used in the art, such as plasma-enhanced chemical vapor deposition (PECVD), low-pressure chemical vapor deposition (LPCVD), physical vapor deposition, or atomic layer deposition (ALD).

[0056] In one example, an insulating layer may be formed between the second substrate 220 and the second electrode layer 221. The insulating layer may be made of any of several dielectric materials, non-limiting examples of which include oxides, nitrides, and oxynitrides, particularly silicon oxides, nitrides, and oxynitrides, but not oxides, nitrides, and 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, plasma-enhanced chemical vapor deposition, low-pressure chemical vapor deposition, and physical vapor deposition.

[0057] Next, step S3 is performed to bond the first sacrificial layer and the third electrode layer, and remove the second substrate to expose the second electrode layer.

[0058] In one example, if Figure 3 As shown, the first sacrificial layer 212 and the third electrode layer 223 are bonded, and the second substrate 220 is removed to expose the second electrode layer 221. Exemplarily, a vacuum bonding process is used to bond the first sacrificial layer 212 and the third electrode layer 223. Exemplarily, a conventional thinning and etching process can be used to remove the second substrate 220. Exemplarily, when an insulating layer is formed between the second substrate 220 and the second electrode layer 221, the insulating layer is removed simultaneously with the removal of the second substrate 220.

[0059] Finally, step S4 is performed to form a plurality of first release holes penetrating the second electrode layer and a second cavity penetrating the second sacrificial layer and arranged corresponding to the first cavity, wherein the first release holes expose the second cavity, the first electrode layer and the third electrode layer constitute a first variable capacitor structure, and the second electrode layer and the third electrode layer constitute a second variable capacitor structure.

[0060] In one example, if Figure 2D As shown, a plurality of first release holes 226 are formed through the second electrode layer 221, and a second cavity 227 is formed through the second sacrificial layer 222 and corresponding to the first cavity 213. The first release holes 226 expose the second cavity 227. The first electrode layer 211 and the third electrode layer 223 constitute a first variable capacitor structure, and the second electrode layer 221 and the third electrode layer 223 constitute a second variable capacitor structure. For example, when subjected to pressure, the change in capacitance of the first variable capacitor structure and the second variable capacitor structure is equal, facilitating subsequent calculation and processing. For example, the change in capacitance value referred to herein refers to the absolute value of the change in capacitance value.

[0061] In one example, the capacitance values ​​of the first variable capacitance structure and the second variable capacitance structure are equal when not under pressure, so as to facilitate subsequent calculation and processing.

[0062] In one example, if Figure 2B 、 Figure 2C and Figure 2D As shown, the second pressure structure further includes a support layer 224, which is located between the second substrate 220 and the second electrode layer 221. The first release hole 226 also penetrates the support layer 224. After the bonding step, the second substrate 220 is removed and the support layer 224 is exposed. Exemplarily, the support layer 224 can further improve the strength and stability of the device. Exemplarily, the material of the support layer 224 includes but is not limited to SiCN, SiN, SiC, SiON, etc. Exemplarily, the support layer 224 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).

[0063] In one example, if Figure 2B As shown, when forming the second pressure structure, the second electrode layer 221 and the support layer 224 in the area where the first release holes 226 are to be formed can be removed first and filled with the second sacrificial layer 222. In this way, in the step of forming the first release holes 226, only the second sacrificial layer 222 filled with the second electrode layer 221 and the support layer 224 needs to be removed. Alternatively, the second electrode layer 221 and the support layer 224 in the area where the first release holes 226 are to be formed can be removed by etching in the step of forming the first release holes 226 to form a plurality of first release holes 226. For example, the first release holes 226 can be formed by an etching process commonly used in the art, for example, a dry etching process or a wet etching process. More specifically, a buffered oxide etchant can be used, or gaseous hydrogen fluoride (VHF) can be used.

[0064] In one example, if Figure 2D As shown, the second cavity 227 is obtained by removing a portion of the second sacrificial layer 222 through the first release hole 226. By way of example, an etching process commonly used in the art can be used to remove a portion of the second sacrificial layer 222. For example, a wet etching process can be used to remove a portion of the second sacrificial layer 222. More specifically, a buffered oxide etchant (Buffer Oxide Etchant) can be used to remove a portion of the second sacrificial layer 222. Alternatively, gaseous hydrogen fluoride (VHF) can be used to remove a portion of the second sacrificial layer 222. By way of example, the release boundary range of the second sacrificial layer 222 can be reasonably set according to actual needs, wherein the release boundary refers to the width of the remaining second sacrificial layer 222.

[0065] In one example, if Figure 2BAs shown, the second pressure structure further includes a bonding layer 225 located on the third electrode layer 223. Figure 2C As shown, in the bonding step, the first sacrificial layer 212 is bonded to the bonding layer 225. Exemplarily, the material of the bonding layer 225 includes SiO2, SiCN, SiN, SiC, and SiON. Exemplarily, bonding the first sacrificial layer 212 through the bonding layer 225 results in a better bonding effect.

[0066] In one example, if Figure 2A and Figure 2D As shown, the first electrode layer 211 further includes a second release hole 214 that penetrates the first electrode layer 211 and corresponds to the first release hole 226. For example, a common etching process in the art can be used to etch the first electrode layer 211 to form the second release hole 214. For example, by forming the second release hole 214 that penetrates the first electrode layer 211 and corresponds to the first release hole 226, the morphologies of the first and second variable capacitor structures are kept consistent, thereby making it easier to equalize the capacitance values ​​of the first and second variable capacitor structures when not under pressure, facilitating subsequent calculations and processing.

[0067] In one example, the voltage across the first variable capacitor structure and the voltage across the second variable capacitor are respectively collected and differentially output to the integrated circuit for processing. In this case, the third electrode layer 223 serves as a pressure-sensitive film layer. Assuming that the capacitance value of the first variable capacitor structure when not under pressure is C1 and the capacitance value of the second variable capacitor structure when not under pressure is C2, when under pressure, assuming that the change in the capacitance value of the first variable capacitor structure is ΔC1 and the change in the capacitance value of the second variable capacitor structure is ΔC2, then the capacitance value of the first variable capacitor structure is C1+ΔC1 and the capacitance value of the second variable capacitor structure is C2-ΔC2. At this time, the voltage value across the first variable capacitor structure and the voltage value across the second variable capacitor change accordingly. By collecting the change in the differential output of the voltage values ​​across the two, the capacitance value changes ΔC1 and ΔC2 can be measured, and the corresponding pressure value can be obtained. Since the differential output is obtained, the measurement accuracy is higher and the interference of common-mode noise can be effectively offset. For example, when two or more first and second pressure structures are formed, all first pressure structures should be connected in parallel, and all second pressure structures should be connected in parallel. In this case, the sum of the voltages across all first variable capacitor structures and the sum of the voltages across all second variable capacitors are used for differential output. For example, when the capacitance values ​​of the first and second variable capacitor structures change by the same amount when subjected to pressure, assuming the capacitance value change is ΔC, the capacitance value of the first variable capacitor structure is C1+ΔC, and the capacitance value of the second variable capacitor structure is C2-ΔC, which is more convenient and efficient to calculate.

[0068] In one example, at least two first pressure structures are formed on the surface of the first substrate, and all the first variable capacitance structures and all the second variable capacitance structures together constitute a Wheatstone bridge. Figure 2E As shown, taking the formation of two first pressure structures on the surface of the first substrate 210 as an example, after bonding and related processing, the two first pressure structures and the two second pressure structures respectively form two first variable capacitance structures and two second variable capacitance structures, and the two first variable capacitance structures and the two second variable capacitance structures together constitute a Wheatstone bridge. For example, Figure 2E As shown, the first electrode layers 211 of two adjacent first pressure structures are isolated from each other, the second electrode layers 221 of two adjacent second pressure structures are isolated from each other, and the third electrode layers 223 of two adjacent second pressure structures are connected to each other.

[0069] In one example, if Figure 3As shown, a first variable capacitance structure Cs and a second variable capacitance structure Cr are respectively provided on the two bridge arms of the Wheatstone bridge. The first variable capacitance structure Cs on one bridge arm is connected to the positive electrode of the power supply, and the second variable capacitance structure Cr on the other bridge arm is connected to the positive electrode of the power supply. Assuming that the capacitance value of the first variable capacitance structure Cs when not under pressure is C1, and the capacitance value of the second variable capacitance structure Cr when not under pressure is C2, when pressure is applied, the capacitance values ​​of the first variable capacitance structure Cs and the second variable capacitance structure Cr both change. Assuming that the capacitance value change of the first variable capacitance structure Cs when under pressure is ΔC1, and the capacitance value change of the second variable capacitance structure Cr when under pressure is ΔC2, then the capacitance value of the first variable capacitance structure Cs is C1+ΔC1, and the capacitance value of the second variable capacitance structure Cr is C2-ΔC2. This causes the output voltage between V+ and V- to change. By measuring the output voltage, the capacitance value changes ΔC1 and ΔC2 can be obtained, and the corresponding pressure value can be obtained, thus completing the pressure measurement. For example, the pressure is measured by a Wheatstone bridge, which has a higher measurement accuracy than that by a variable capacitance structure and a second variable capacitance structure. Figure 3 The Wheatstone bridge structure shown is only an example. In other embodiments, there may be two first variable capacitance structures Cs on one bridge arm and two second variable capacitance structures Cr on the other bridge arm. This application does not limit this. For example, the initial capacitance values ​​of the first variable capacitance structure Cs and the second variable capacitance structure Cr can be set to equal capacitance values. At this time, the Wheatstone bridge is in a balanced state. When subjected to pressure, the Wheatstone bridge becomes unbalanced, and the change in the output voltage is easier to measure. For example, the change in the capacitance value of the first variable capacitance structure Cs and the second variable capacitance structure Cr when subjected to pressure can be set to be equal. At this time, the change in the output voltage is easier to measure. For example, as Figure 2EIt is shown that two first pressure structures and two second pressure structures are formed. In other embodiments, three or more first pressure structures and two second pressure structures can also be formed. In this case, several first variable capacitance structures and several second variable capacitance structures are arranged on one bridge arm of the Wheatstone bridge, and the remaining first variable capacitance structures and second variable capacitance structures are arranged on the other bridge arm. Exemplarily, the first variable capacitance structures on each bridge arm are connected in parallel, and the second variable capacitance structures on each bridge arm are connected in parallel. Among them, four or any positive even multiples of the first pressure structures and the second pressure structures can be formed. In this case, half of the first variable capacitance structure and half of the second variable capacitance structure are respectively provided on the two bridge arms of the Wheatstone bridge, the first variable capacitance structure on each bridge arm is connected in parallel, and the second variable capacitance structure on each bridge arm is connected in parallel. At this time, due to the symmetrical arrangement of the capacitances on the two bridge arms of the Wheatstone bridge, the measurement method is simpler and more efficient.

[0070] In one example, when the area of ​​the MEMS pressure sensor remains unchanged, as the number of first pressure structures and second pressure structures increases, the area of ​​the single third electrode layer 223 used as the pressure-sensing membrane layer is smaller, thereby making the measurement linearity higher.

[0071] It is worth mentioning that the above steps are only examples, and the order of the above steps can be adjusted without conflict.

[0072] This completes the description of the key steps of the method for manufacturing the MEMS pressure sensor of the present invention. The manufacture of a complete MEMS pressure sensor may also include other steps, such as forming pads that lead out the first variable capacitor structure and the second variable capacitor structure, etc., which will not be described in detail here.

[0073] In summary, the MEMS pressure sensor manufacturing method of the present invention bonds the first and second pressure structures to form a differential capacitive pressure sensor, namely, forming a first variable capacitance structure and a second variable capacitance structure. Pressure is measured using the differential output of the first and second variable capacitance structures, resulting in higher measurement accuracy and thus improving the performance of the MEMS pressure sensor. Furthermore, the first and second variable capacitance structures can form a Wheatstone bridge, further enhancing measurement accuracy.

[0074] Example 2

[0075] The present invention also provides a MEMS pressure sensor, as shown below Figure 2D 、 Figure 2E and Figure 3 A MEMS pressure sensor according to a specific embodiment of the present invention is described. The MEMS pressure sensor is manufactured by the method of the first embodiment. Figure 2D As shown, the MEMS pressure sensor of the present invention includes:

[0076] a first substrate 210;

[0077] At least one first pressure structure, located on the surface of the first substrate 210, including a first electrode layer 211 and a first sacrificial layer 212 from bottom to top, and a first cavity 213 penetrating the first sacrificial layer 212 and exposing the first electrode layer 211;

[0078] The second pressure structure, which has the same number as the first pressure structure, is located on the first sacrificial layer 212 and includes, from bottom to top, a third electrode layer 223, a second sacrificial layer 222, and a second electrode layer 221, as well as a second cavity 227 penetrating the second sacrificial layer 222 and corresponding to the first cavity 213, and a first release hole 226 penetrating the second electrode layer 221 and exposing the second cavity 227.

[0079] The first electrode layer 211 and the third electrode layer 223 constitute a first variable capacitor structure, and the second electrode layer 221 and the third electrode layer 223 constitute a second variable capacitor structure.

[0080] For example, Figure 2A The figure shows that a first pressure structure and a second pressure structure are formed. In other embodiments, two, three or more first pressure structures and second pressure structures may be formed, which will not be described in detail here.

[0081] In one example, the capacitance values ​​of the first variable capacitance structure and the second variable capacitance structure are equal when not under pressure, to facilitate subsequent calculations and processing. In one example, the changes in the capacitance values ​​of the first variable capacitance structure and the second variable capacitance structure are equal when under pressure, to facilitate subsequent calculations and processing. Exemplarily, the change in capacitance value referred to herein refers to the absolute value of the change in capacitance value.

[0082] In one example, if Figure 2D As shown, the first substrate 210 is a bulk silicon base, which can be at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs or other III / V compound semiconductors, including a multilayer structure composed of these semiconductors, or 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.

[0083] In an example, the first electrode layer 211 , the second electrode layer 221 and the third electrode layer 223 may be made of materials such as doped polysilicon, SiGe or amorphous silicon after implantation and annealing, and are not limited to any one material.

[0084] In one example, the first sacrificial layer 212 and the second sacrificial layer 222 are made of oxide layers, such as silicon oxide and carbon-doped silicon oxide (SiOC), but are not limited to the above examples.

[0085] In one example, if Figure 2D As shown, the second pressure structure further includes a support layer 224, and the first release hole 226 also penetrates the support layer 224. For example, the support layer 224 can further improve the strength and stability of the device. For example, the material of the support layer 224 includes but is not limited to SiCN, SiN, SiC, SiON, etc.

[0086] In one example, if Figure 2D As shown, the second pressure structure further includes a bonding layer 225. Exemplarily, the material of the bonding layer 225 includes SiO2, SiCN, SiN, SiC, and SiON.

[0087] In one example, if Figure 2D As shown, a second release hole 214 is formed in the first electrode layer 211 and penetrates the first electrode layer 211 and is arranged corresponding to the first release hole 226 .

[0088] In one example, the voltage across the first variable capacitor structure and the voltage across the second variable capacitor are respectively collected and differentially output to the integrated circuit for processing. In this case, the third electrode layer 223 serves as a pressure-sensitive film layer. Assuming that the capacitance value of the first variable capacitor structure when not under pressure is C1 and the capacitance value of the second variable capacitor structure when not under pressure is C2, when under pressure, assuming that the change in the capacitance value of the first variable capacitor structure is ΔC1 and the change in the capacitance value of the second variable capacitor structure is ΔC2, then the capacitance value of the first variable capacitor structure is C1+ΔC1 and the capacitance value of the second variable capacitor structure is C2-ΔC2. At this time, the voltage value across the first variable capacitor structure and the voltage value across the second variable capacitor change accordingly. By collecting the change in the differential output of the voltage values ​​across the two, the capacitance value changes ΔC1 and ΔC2 can be measured, and the corresponding pressure value can be obtained. Since the differential output is obtained, the measurement accuracy is higher and the interference of common-mode noise can be effectively offset. For example, when two or more first and second pressure structures are formed, all first pressure structures should be connected in parallel, and all second pressure structures should be connected in parallel. In this case, the sum of the voltages across all first variable capacitor structures and the sum of the voltages across all second variable capacitors are used for differential output. For example, when the capacitance values ​​of the first and second variable capacitor structures change by the same amount when subjected to pressure, assuming the capacitance value change is ΔC, the capacitance value of the first variable capacitor structure is C1+ΔC, and the capacitance value of the second variable capacitor structure is C2-ΔC, which is more convenient and efficient to calculate.

[0089] In one example, if Figure 2E As shown, at least two first pressure structures are formed on the surface of the first substrate, and all the first variable capacitance structures and all the second variable capacitance structures together constitute a Wheatstone bridge. Figure 2E As shown, taking the formation of two first pressure structures on the surface of the first substrate 210 as an example, after bonding and related processing, the two first pressure structures and the two second pressure structures respectively form two first variable capacitance structures and two second variable capacitance structures, and the two first variable capacitance structures and the two second variable capacitance structures together constitute a Wheatstone bridge. For example, Figure 2E As shown, the first electrode layers 211 of two adjacent first pressure structures are isolated from each other, the second electrode layers 221 of two adjacent second pressure structures are isolated from each other, and the third electrode layers 223 of two adjacent second pressure structures are connected to each other.

[0090] In one example, if Figure 3As shown, a first variable capacitance structure Cs and a second variable capacitance structure Cr are respectively provided on the two bridge arms of the Wheatstone bridge, wherein the first variable capacitance structure Cs on one bridge arm is connected to the positive electrode of the power supply, and the second variable capacitance structure Cr on the other bridge arm is connected to the positive electrode of the power supply. Assuming that the capacitance value of the first variable capacitance structure Cs when not subjected to pressure is C1, and the capacitance value of the second variable capacitance structure Cr when not subjected to pressure is C2, when subjected to pressure, the capacitance values ​​of the first variable capacitance structure Cs and the second variable capacitance structure Cr both change. Assuming that the change in the capacitance value of the first variable capacitance structure Cs is ΔC1, and the change in the capacitance value of the second variable capacitance structure Cr is ΔC2, then the capacitance value of the first variable capacitance structure Cs is C1+ΔC1, and the capacitance value of the second variable capacitance structure Cr is C2-ΔC2, so that the voltage value of the output voltage between V+ and V- changes. By measuring the output voltage, the change in capacitance value ΔC can be obtained, and then the corresponding pressure value can be obtained, that is, the pressure measurement is completed. For example, the pressure is measured by a Wheatstone bridge, which has a higher measurement accuracy than that by a variable capacitance structure and a second variable capacitance structure. Figure 3 The Wheatstone bridge structure shown is only an example. In other embodiments, there may be two first variable capacitance structures Cs on one bridge arm and two second variable capacitance structures Cr on the other bridge arm. This application does not limit this. For example, the initial capacitance values ​​of the first variable capacitance structure Cs and the second variable capacitance structure Cr can be set to equal capacitance values. At this time, the Wheatstone bridge is in a balanced state. When subjected to pressure, the Wheatstone bridge becomes unbalanced, and the change in the output voltage is easier to measure. For example, the change in the capacitance value of the first variable capacitance structure Cs and the second variable capacitance structure Cr when subjected to pressure can be set to be equal. At this time, the change in the output voltage is easier to measure. For example, as Figure 2E It is shown that two first pressure structures and two second pressure structures are formed. In other embodiments, three or more first pressure structures and two second pressure structures can also be formed. In this case, several first variable capacitance structures and several second variable capacitance structures are arranged on one bridge arm of the Wheatstone bridge, and the remaining first variable capacitance structures and second variable capacitance structures are arranged on the other bridge arm. Exemplarily, the first variable capacitance structures on each bridge arm are connected in parallel, and the second variable capacitance structures on each bridge arm are connected in parallel. Among them, four or any positive even multiples of the first pressure structures and the second pressure structures can be formed. In this case, half of the first variable capacitance structure and half of the second variable capacitance structure are respectively provided on the two bridge arms of the Wheatstone bridge, the first variable capacitance structure on each bridge arm is connected in parallel, and the second variable capacitance structure on each bridge arm is connected in parallel. At this time, due to the symmetrical arrangement of the capacitances on the two bridge arms of the Wheatstone bridge, the measurement method is simpler and more efficient.

[0091] In one example, when the area of ​​the MEMS pressure sensor remains unchanged, as the number of first pressure structures and second pressure structures increases, the area of ​​the single third electrode layer 223 used as the pressure-sensing membrane layer is smaller, thereby making the measurement linearity higher.

[0092] This concludes the introduction to the structure of the MEMS pressure sensor of the present invention. A complete device may also include other component structures, such as pads for leading out the first variable capacitance structure and the second variable capacitance structure, which will not be detailed here.

[0093] Because the MEMS pressure sensor of the present invention comprises a first variable capacitance structure and a second variable capacitance structure, and can measure pressure through the differential output of the first and second variable capacitance structures, it offers higher measurement accuracy, thereby improving the performance of the MEMS pressure sensor. Furthermore, the first and second variable capacitance structures can form a Wheatstone bridge, further enhancing measurement accuracy.

[0094] Example 3

[0095] The present invention further provides an electronic device, which includes the MEMS pressure sensor described in the second embodiment or the MEMS pressure sensor manufactured by the method described in the first embodiment.

[0096] 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 embodiment of the present invention, due to its use of the aforementioned MEMS pressure sensor, has improved performance.

[0097] Although a number of embodiments have been 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 disclosed herein. More particularly, various modifications and changes may be made to the arrangements and / or component parts of the subject matter within the scope of the present disclosure, the accompanying drawings, and the appended claims. In addition to modifications and changes to the component parts and / or arrangements, the use of alternatives will also be readily apparent to those skilled in the art.

Claims

1. A method for manufacturing a MEMS pressure sensor, characterized in that: The method comprises: Providing a first substrate, wherein at least one first pressure structure is formed on a surface of the first substrate, the first pressure structure comprising a first electrode layer and a first sacrificial layer from bottom to top, and a first cavity penetrating the first sacrificial layer and exposing the first electrode layer; Providing a second substrate, on a surface of which second pressure structures corresponding in number to the first pressure structures are formed, the second pressure structures including, from bottom to top, a second electrode layer, a second sacrificial layer, and a third electrode layer; bonding the first sacrificial layer and the third electrode layer, and removing the second substrate to expose the second electrode layer; A plurality of first release holes are formed through the second electrode layer and a second cavity is formed through the second sacrificial layer and is arranged corresponding to the first cavity. The first release holes expose the second cavity. The first electrode layer and the third electrode layer constitute a first variable capacitor structure, and the second electrode layer and the third electrode layer constitute a second variable capacitor structure.

2. The manufacturing method according to claim 1, characterized in that At least two first pressure structures are formed on the surface of the first substrate, and all the first variable capacitance structures and all the second variable capacitance structures together constitute a Wheatstone bridge.

3. The manufacturing method according to claim 1, characterized in that A second release hole is further formed in the first electrode layer, penetrating the first electrode layer and corresponding to the first release hole.

4. The manufacturing method according to claim 1, characterized in that The second pressure structure further includes a support layer, which is located between the second substrate and the second electrode layer. The first release hole also penetrates the support layer. After the bonding step, the second substrate is removed and the support layer is exposed.

5. The manufacturing method according to claim 1, characterized in that The second pressure structure further includes a bonding layer located on the third electrode layer, and the bonding step bonds the first sacrificial layer and the bonding layer.

6. The manufacturing method according to claim 1, characterized in that The bonding is performed using a vacuum bonding process.

7. The manufacturing method according to claim 1, characterized in that The first variable capacitance structure and the second variable capacitance structure have the same capacitance when not under pressure.

8. A MEMS pressure sensor, characterized in that: include: a first substrate; at least one first pressure structure, located on the surface of the first substrate, comprising a first electrode layer and a first sacrificial layer from bottom to top, and a first cavity penetrating the first sacrificial layer and exposing the first electrode layer; a second pressure structure corresponding in number to the first pressure structure, located on the first sacrificial layer, comprising, from bottom to top, a third electrode layer, a second sacrificial layer, a second electrode layer, a second cavity penetrating the second sacrificial layer and corresponding to the first cavity, and a first release hole penetrating the second electrode layer and exposing the second cavity; The first electrode layer and the third electrode layer constitute a first variable capacitance structure, and the second electrode layer and the third electrode layer constitute a second variable capacitance structure.

9. The MEMS pressure sensor according to claim 8, wherein: At least two first pressure structures are formed on the surface of the first substrate, and all the first variable capacitance structures and all the second variable capacitance structures together constitute a Wheatstone bridge.

10. An electronic device, characterized in that: The electronic device comprises the MEMS pressure sensor according to any one of claims 8 to 9.

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