MEMS differential capacitive pressure sensor and manufacturing method thereof

Abstract

The invention discloses an MEMS differential capacitive pressure sensor and a manufacturing method thereof, the differential capacitive pressure sensor is prepared by bonding a pressure sensing structure with a first pressure sensing unit and a second pressure sensing unit to a substrate with a first groove and a second groove, the manufacturing process is simplified, the production cost is reduced, and the production efficiency is improved. The mass blocks are respectively arranged on the first pressure sensing diaphragm and the second pressure sensing diaphragm of the first pressure sensing unit and the second pressure sensing unit, so that the sensitivity of the differential capacitive pressure sensor is increased, the nonlinearity is reduced, and the performance of the sensor is improved.

Description

Technical Field

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

[0002] With the development of Micro-Electro-Mechanical System (MEMS) technology, pressure sensors have become an indispensable key device in many industries and have been widely used in consumer electronics, automotive electronics, petrochemicals, biomedicine, defense and military industries. Compared with piezoresistive pressure sensors, capacitive pressure sensors have the advantages of high sensitivity, low power consumption, and good temperature characteristics, making them more suitable for the development of high-precision pressure sensors.

[0003] In order to further improve the performance of capacitive pressure sensors, on the one hand, the chip area is increased and the plate thickness and cavity height are reduced, but this runs counter to the miniaturization direction of the device and is not conducive to chip integration; on the other hand, a multi-layer structure is formed, but the traditional multi-layer structure is stacked up by deposition, photolithography and etching layer by layer. The process is complicated and is limited by equipment capabilities, which is not conducive to large-scale production and cost reduction of products. Summary of the invention

[0004] A series of simplified concepts are introduced in the Summary of the Invention, which will be further described in detail in the Detailed Description of the Invention. The Summary of the 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 scope of protection of the claimed technical solution.

[0005] The present invention provides a method for manufacturing a MEMS differential capacitive pressure sensor, which is characterized by comprising:

[0006] Forming the pressure sensing structure:

[0007] Providing a first substrate, on which a first pressure-sensitive layer is formed;

[0008] forming a first sacrificial layer, a rigid electrode and a second sacrificial layer in sequence on the first pressure-sensitive layer;

[0009] forming a second pressure-sensitive layer on the second sacrificial layer, wherein the second pressure-sensitive layer comprises a second pressure-sensitive diaphragm and a first mass block and a second mass block located on a first surface of the second pressure-sensitive diaphragm;

[0010] removing the first sacrificial layer and the second sacrificial layer to form a first cavity and a second cavity between the first pressure-sensitive layer and the second pressure-sensitive layer;

[0011] Providing a second substrate, wherein a first groove and a second groove are formed on the second substrate, the first cavity is arranged corresponding to the first groove, and the second cavity is arranged corresponding to the second groove;

[0012] bonding the pressure sensing structure and the second substrate;

[0013] Removing the first substrate to expose the first pressure-sensitive layer, wherein the first pressure-sensitive layer includes a first pressure-sensitive membrane and a third mass block and a fourth mass block located on a second surface of the first pressure-sensitive membrane;

[0014] etching the pressure sensing structure to separate the pressure sensing structure into a first pressure sensing unit and a second pressure sensing unit;

[0015] The first pressure sensing unit and the second pressure sensing unit are connected through metal wiring.

[0016] Exemplarily, the first pressure sensing unit includes a second pressure-sensitive diaphragm and a first mass block located on a first surface of the second pressure-sensitive diaphragm, a first pressure-sensitive diaphragm and a third mass block located on a second surface of the first pressure-sensitive diaphragm, a first pressure-sensitive diaphragm and a third mass block located on a second surface of the first pressure-sensitive diaphragm, a first cavity located between the second pressure-sensitive diaphragm and the first pressure-sensitive diaphragm, and a rigid electrode running through the first cavity; the second pressure sensing unit includes a second pressure-sensitive diaphragm and a second mass block located on a first surface of the second pressure-sensitive diaphragm, a first pressure-sensitive diaphragm and a fourth mass block located on a second surface of the first pressure-sensitive diaphragm, a second cavity located between the second pressure-sensitive diaphragm and the first pressure-sensitive diaphragm, and a rigid electrode running through the second cavity.

[0017] Exemplarily, forming a second pressure-sensitive diaphragm and a first mass block and a second mass block located on a first surface of the second pressure-sensitive diaphragm includes:

[0018] forming a second pressure-sensitive layer, wherein the second pressure-sensitive layer includes an upper layer portion and a lower layer portion;

[0019] The upper layer of the second pressure-sensitive layer is patterned to form a first mass block and a second mass block, and the lower layer of the second pressure-sensitive layer serves as the second pressure-sensitive membrane.

[0020] Exemplarily, bonding the pressure sensing structure and the second substrate comprises:

[0021] forming an insulating layer on the second substrate, wherein the insulating layer covers a surface of the second substrate and bottoms of the first groove and the second groove;

[0022] The second pressure-sensitive diaphragm is directly bonded to the insulating layer on the front side, the first mass block is suspended in the first groove, and the second mass block is suspended in the second groove.

[0023] Exemplarily, sequentially forming a first sacrificial layer, a rigid electrode, and a second sacrificial layer on the first pressure-sensitive layer includes:

[0024] forming a first sacrificial layer and a rigid electrode layer in sequence on the first pressure-sensitive layer;

[0025] forming a patterned mask layer on the rigid electrode layer;

[0026] Etching the rigid electrode layer using the patterned mask layer as a mask to form the rigid electrodes and gap regions between the rigid electrodes;

[0027] removing the mask layer;

[0028] A second sacrificial layer is formed covering the rigid electrode and the gap region.

[0029] Exemplarily, before removing the first sacrificial layer and the second sacrificial layer, the step of forming a release hole on the second pressure-sensitive diaphragm is also included. After bonding the pressure sensing structure and the second substrate, the first cavity and the first groove are connected through the release hole to form a first space region, and the second cavity and the second groove are connected through the release hole to form a second space region. The first space region and the second space region are in a vacuum state or a low-pressure state.

[0030] Exemplarily, the first substrate includes a silicon-on-insulator substrate, which includes a silicon substrate, a silicon oxide insulating layer and a single crystal silicon layer arranged in sequence from bottom to top, and the single crystal silicon layer serves as the first pressure-sensitive layer.

[0031] The present invention also provides a MEMS differential capacitive pressure sensor, comprising:

[0032] A pressure sensing structure, the pressure sensing structure comprising a first pressure sensing unit and a second pressure sensing unit, the first pressure sensing unit and the second pressure sensing unit being connected via a wiring element; wherein the first pressure sensing unit and the second pressure sensing unit both comprise a first pressure-sensitive diaphragm located in the same plane, a rigid electrode located in the same plane, and a second pressure-sensitive diaphragm located in the same plane, the first pressure sensing unit further comprises a first mass block located on a first surface of the second pressure-sensitive diaphragm, a third mass block located on a second surface of the first pressure-sensitive diaphragm, and a first cavity located between the second pressure-sensitive diaphragm and the first pressure-sensitive diaphragm, the second pressure sensing unit further comprises a second mass block located on the first surface of the second pressure-sensitive diaphragm, a fourth mass block located on the second surface of the first pressure-sensitive diaphragm, and a second cavity located between the second pressure-sensitive diaphragm and the first pressure-sensitive diaphragm;

[0033] A substrate having a first groove and a second groove formed thereon, the first pressure sensing unit is bonded to the first groove, the first cavity is arranged corresponding to the first groove, the second pressure sensing unit is bonded to the second groove, and the second cavity is arranged corresponding to the second groove.

[0034] Exemplarily, a connecting column is further formed between the first pressure-sensitive diaphragm and the second pressure-sensitive diaphragm, and a first end of the connecting column is connected to a first surface of the first pressure-sensitive diaphragm, and a second end of the connecting column is connected to a second surface of the second pressure-sensitive diaphragm, so as to mechanically couple the first pressure-sensitive diaphragm and the second pressure-sensitive diaphragm, and the connecting column passes through the rigid electrode and has no contact with the rigid electrode, and the rigid electrode is mechanically decoupled from the first pressure-sensitive diaphragm and the second pressure-sensitive diaphragm.

[0035] Exemplarily, the first pressure-sensitive diaphragm of the first pressure sensing unit and the rigid electrode constitute a first pressure-sensitive capacitor, the second pressure-sensitive diaphragm of the first pressure sensing unit and the rigid electrode constitute a second pressure-sensitive capacitor, the first pressure-sensitive diaphragm of the second pressure sensing unit and the rigid electrode constitute a third pressure-sensitive capacitor, the second pressure-sensitive diaphragm of the second pressure sensing unit and the rigid electrode constitute a fourth pressure-sensitive capacitor, and the first pressure-sensitive capacitor, the second pressure-sensitive capacitor, the third pressure-sensitive capacitor and the fourth pressure-sensitive capacitor are connected via a Wheatstone bridge.

[0036] According to the MEMS differential capacitive pressure sensor and the manufacturing method thereof provided by the present invention, the differential capacitive pressure sensor is prepared by bonding a pressure sensing structure having a first pressure sensing unit and a second pressure sensing unit to a substrate having a first groove and a second groove, thereby simplifying the manufacturing process and reducing the production cost. By respectively arranging mass blocks on the first pressure-sensitive diaphragm and the second pressure-sensitive diaphragm of the first pressure sensing unit and the second pressure sensing unit, the sensitivity of the differential capacitive pressure sensor is increased and the nonlinearity is reduced, thereby improving the performance of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The following drawings of the present invention are used to understand the present invention as part of the present invention. The embodiments of the present invention are shown in the drawings and the description thereof is used to explain the principle of the present invention.

[0038] In the attached figure:

[0039] Figure 1 is a flow chart of a method for manufacturing a MEMS differential capacitive pressure sensor according to an embodiment of the present invention;

[0040] Figures 2A-2JA cross-sectional schematic diagram of a structure obtained by sequentially implementing a method for manufacturing a MEMS differential capacitive pressure sensor according to an embodiment of the present invention;

[0041] Figure 2K According to one embodiment of the present invention Figure 2B A top view of

[0042] Figure 3 A schematic diagram of metal wiring according to an embodiment of the present invention;

[0043] Figure 4 The invention relates to a connection of a first pressure-sensitive capacitor, a second pressure-sensitive capacitor, the third pressure-sensitive capacitor and a fourth pressure-sensitive capacitor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is apparent to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features well known in the art are not described.

[0045] It should be understood that the present invention can be implemented in different forms and should not be construed as being limited to the embodiments presented herein. On the contrary, providing these embodiments will make the disclosure thorough and complete and fully convey the scope of the present invention to those skilled in the art. In the accompanying drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. The same reference numerals throughout represent the same elements.

[0046] It should be understood that when an element or layer is referred to as being "on, adjacent to, connected to or coupled to other elements or layers, it may be directly on, adjacent to, connected to or coupled to other elements or layers, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on, directly adjacent to, directly connected to or directly coupled to other elements or layers, there may be no intervening elements or layers. It should be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below may be represented as a second element, component, region, layer or part.

[0047] Spatially relative terms such as "under," "below," "below," "under," "above," "above," etc., may be used herein for ease of description to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that in addition to the orientations shown in the figures, the spatially relative terms are intended to include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, then the elements or features described as "under other elements" or "under" or "under" will be oriented as "on" the other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may be oriented otherwise (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0048] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0049] In order to fully understand the present invention, detailed steps and detailed structures will be presented in the following description to illustrate the technical solution proposed by the present invention. The 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.

[0050] The present invention provides a method for manufacturing a MEMS differential capacitive pressure sensor, such as Figure 1 As shown, including:

[0051] Step S110: forming a pressure sensing structure: providing a first substrate, on which a first pressure-sensitive layer is formed; forming a first sacrificial layer, a rigid electrode, and a second sacrificial layer in sequence on the first pressure-sensitive layer; forming a second pressure-sensitive layer on the second sacrificial layer, wherein the second pressure-sensitive layer includes a second pressure-sensitive diaphragm and a first mass block and a second mass block located on a first surface of the second pressure-sensitive diaphragm; removing the first sacrificial layer and the second sacrificial layer to form a first cavity and a second cavity between the first pressure-sensitive layer and the second pressure-sensitive layer;

[0052] Step S120: providing a second substrate, wherein a first groove and a second groove are formed on the second substrate, the first cavity is arranged corresponding to the first groove, and the second cavity is arranged corresponding to the second groove;

[0053] Step S130: bonding the pressure sensing structure and the second substrate;

[0054] Step S140: removing the first substrate to expose the first pressure-sensitive layer, where the first pressure-sensitive layer includes a first pressure-sensitive membrane and a third mass block and a fourth mass block located on a second surface of the first pressure-sensitive membrane;

[0055] Step S150: etching the pressure sensing structure to divide the pressure sensing structure into a first pressure sensing unit and a second pressure sensing unit;

[0056] Step S160: connecting the first pressure sensing unit and the second pressure sensing unit through metal wiring.

[0057] Below, reference FIG. 2A to FIG. 2J The manufacturing method of the MEMS differential capacitive pressure sensor of the present invention is described in detail, wherein: FIG. 2A to FIG. 2J The cross-sectional schematic diagram is a structure obtained by sequentially implementing the method for manufacturing a MEMS differential capacitive pressure sensor according to an embodiment of the present invention.

[0058] First, step S110 is performed to form a pressure sensing structure 210 .

[0059] For example, Figure 2A As shown, a first substrate 211 is provided, and a first pressure-sensitive layer 212 is formed on the first substrate 211 .

[0060] The first substrate 211 can be any suitable semiconductor substrate, such as a silicon substrate, and can also be at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP or other III / V compound semiconductors, including multilayer structures composed of these semiconductor materials, or silicon on insulator (SOI), stacked silicon on insulator (SSOI), stacked silicon germanium on insulator (S-SiGeOI), silicon germanium on insulator (SiGeOI) and germanium on insulator (GeOI), or can also be double-sided polished silicon wafers (Double Side Polished Wafers, DSP), or can be sapphire substrates such as Al2O3, ceramic substrates, quartz or glass substrates, etc.

[0061] The material of the first pressure-sensing layer 212 includes but is not limited to single crystal silicon. The conventional semiconductor process method for forming the first pressure-sensing layer 212 can be selected as needed, such as one of low pressure chemical vapor deposition (LPCVD), laser ablation deposition (LAD) and selective epitaxial growth (SEG) formed by chemical vapor deposition (CVD), physical vapor deposition (PVD) or atomic layer deposition (ALD), or one of low temperature chemical vapor deposition (LTCVD), rapid thermal chemical vapor deposition (RTCVD) and plasma enhanced chemical vapor deposition (PECVD).

[0062] In one embodiment, the first substrate 211 is an SOI substrate, which includes a substrate silicon, an oxide layer and a single crystal silicon layer, and the single crystal silicon layer is used as the first pressure-sensitive layer 212. The P-type ion doping concentration of the SOI substrate is 2×10 19 cm -3 The thickness of the substrate silicon is about 400 μm, the thickness of the oxide layer is about 0.5 μm, and the thickness of the single crystal silicon layer is about 3 μm. The surface of the SOI substrate can also be thermally oxidized to form an insulating layer, which is silicon dioxide and has a thickness of about 0.5 μm.

[0063] For example, Figure 2B and 2C As shown, a first sacrificial layer 213 , a rigid electrode 214 and a second sacrificial layer 215 are sequentially formed on the first pressure-sensing layer 212 .

[0064] Exemplarily, sequentially forming a first sacrificial layer 213, a rigid electrode 214, and a second sacrificial layer 215 on the first pressure-sensitive layer 212 includes: sequentially forming a first sacrificial layer 213 and a rigid electrode layer on the first pressure-sensitive layer 212; forming a patterned mask layer on the rigid electrode layer; etching the rigid electrode layer using the patterned mask layer as a mask to form the rigid electrode 214 and a gap region between the rigid electrodes; removing the mask layer; and forming a second sacrificial layer 215 covering the rigid electrode and the gap region.

[0065] In one embodiment, Figure 2B As shown, first, a first sacrificial layer 213 is formed on the first pressure-sensitive layer 212. The material of the first sacrificial layer 213 includes but is not limited to silicon dioxide. The thickness of the first sacrificial layer 213 is about 2 μm. The first sacrificial layer 213 can be formed by LPCVD or any existing technology well known to those skilled in the art, which will not be repeated here.

[0066] In one embodiment, Figure 2BAs shown, a rigid electrode layer is then formed on the first sacrificial layer 213. The material of the rigid electrode layer includes but is not limited to polysilicon. The method for forming the rigid electrode layer can adopt any existing technology well known to those skilled in the art, which will not be described in detail here. Next, a patterned mask layer (not shown) is formed on the rigid electrode layer, and the rigid electrode layer is etched using the patterned mask layer as a mask to form the rigid electrode 214 and the gap area between the rigid electrodes 214. Among them, the method for etching the rigid electrode layer can adopt any existing technology well known to those skilled in the art, preferably dry etching, and dry etching includes but is not limited to reactive ion etching (RIE), ion beam etching, plasma etching, laser ablation or any combination of these methods. The mask layer is then removed to form a Figure 2B and 2K The structure shown.

[0067] In one embodiment, the upper and lower surfaces of the rigid electrode 214 may further include an electrode dielectric layer, which includes but is not limited to a silicon nitride layer. The electrode dielectric layer may be formed by any prior art known to those skilled in the art, which will not be described in detail herein.

[0068] In one embodiment, Figure 2C As shown, a second sacrificial layer 215 is formed on the rigid electrode 214. The material of the second sacrificial layer 215 includes but is not limited to silicon dioxide. The thickness of the second sacrificial layer 215 is about 3 μm. The method for forming the second sacrificial layer 215 can adopt any existing technology well known to those skilled in the art, which will not be repeated here.

[0069] Exemplarily, before forming the second pressure-sensitive layer, the step of forming a plurality of connecting posts 217 between the first pressure-sensitive layer 212 and the second pressure-sensitive layer is also included. The first end of the connecting post 217 is connected to the first pressure-sensitive layer 212, and the second end of the connecting post 217 is connected to the second pressure-sensitive layer, so as to mechanically couple the first pressure-sensitive layer 212 with the second pressure-sensitive layer. In addition, the connecting post 217 passes through the gap area between the rigid electrodes 214 and has no contact with the rigid electrodes 214, so as to mechanically decouple the rigid electrodes 214 from the first pressure-sensitive layer 212 and the second pressure-sensitive layer.

[0070] In one embodiment, Figure 2C As shown, the second sacrificial layer 215 and the first sacrificial layer 213 are etched to form a plurality of through holes penetrating the second sacrificial layer 215 and the first sacrificial layer 213, and these through holes pass through the gap area between the rigid electrodes 214 and expose the first pressure-sensing layer 212. Next, these through holes are filled with silicon nitride or other materials, and the excess silicon nitride is removed by a chemical mechanical polishing (CMP) process to form a plurality of connecting pillars 217, and the connecting pillars 217 have a height of about 6 μm, a length of 50 μm to 200 μm, and a width of about 5 μm.

[0071] For example, Figure 2D As shown, a second pressure-sensitive layer 216 is formed on the second sacrificial layer 215 , and the second pressure-sensitive layer 216 includes a second pressure-sensitive diaphragm 2161 and a first mass block 2162 and a second mass block 2163 located on a first surface of the second pressure-sensitive diaphragm 2161 .

[0072] Exemplarily, forming the first mass block 2162 and the second mass block 2163 on the surface of the second pressure-sensitive diaphragm 2161 includes: forming a second pressure-sensitive layer 216, the second pressure-sensitive layer 216 including an upper portion and a lower portion; patterning the upper portion of the second pressure-sensitive layer 216 to form the first mass block 2162 and the second mass block 2163, and the lower portion of the second pressure-sensitive layer serves as the second pressure-sensitive diaphragm 2161.

[0073] In one embodiment, the material of the second pressure-sensitive layer 216 includes but is not limited to polysilicon. The method for forming the second pressure-sensitive layer 216 can adopt any existing technology known to those skilled in the art, which will not be described in detail here. Next, a patterned mask layer (not shown) is formed on the second pressure-sensitive layer 216, and the upper layer of the second pressure-sensitive layer 216 is etched by a photolithography process to form a first mass block 2162 and a second mass block 2163. The lower layer of the second pressure-sensitive layer 216 that has not been etched serves as the second pressure-sensitive diaphragm 2161. The boss heights of the first mass block 2162 and the second mass block 2163 are about 1 μm, and the thickness of the second pressure-sensitive diaphragm 2161 is about 2 μm. It should be noted that the above-mentioned method for forming the second pressure-sensitive diaphragm 2161 and the first mass block 2162 and the second mass block 2163 is only exemplary, and other methods can be used to form the second pressure-sensitive diaphragm 2161 and form the first mass block 2162 and the second mass block 2163 located on the first surface of the second pressure-sensitive diaphragm 2161. The first surface of the second pressure-sensitive diaphragm 2161 is a surface away from the rigid electrode 214. By arranging mass blocks on the surfaces of the first pressure-sensitive diaphragm and the second pressure-sensitive diaphragm, the linearity of the pressure sensor can be improved.

[0074] For example, Figure 2E As shown, the first sacrificial layer 213 and the second sacrificial layer 215 are removed to form a first cavity 2181 and a second cavity 2182 between the first pressure-sensing layer 212 and the second pressure-sensing layer 216 .

[0075] Exemplarily, before removing the first sacrificial layer 213 and the second sacrificial layer 215 , a step of forming a release hole 2164 on the second pressure-sensitive diaphragm 2161 is further included.

[0076] In one embodiment, Figure 2E As shown, the second pressure-sensitive diaphragm 2161 is etched to form a plurality of release holes 2164 on the second pressure-sensitive diaphragm 2161. Next, the first sacrificial layer 213 and the second sacrificial layer 215 are etched away by any prior art known to those skilled in the art, preferably by wet etching, and the wet etching solution is selective. In the present invention, the first sacrificial layer 213 and the second sacrificial layer 215 are made of silicon dioxide, the first pressure-sensitive layer 212 and the second pressure-sensitive layer 216 are made of single crystal silicon or polycrystalline silicon, the rigid electrode 214 is made of polycrystalline silicon, and the connecting column 217 is made of silicon nitride. The wet etching solution can be a BOE solution, which is prepared from HF, NH4F and deionized water. By utilizing the gap region between the plurality of release holes 2164 and the rigid electrode 214, a portion of the first sacrificial layer 213 and the second sacrificial layer 215 are removed by wet etching to form a first cavity 2181 and a second cavity 2182 located between the first pressure-sensing layer 212 and the second pressure-sensing layer 216, respectively. The remaining portions of the first sacrificial layer 213 and the second sacrificial layer 215 serve as support portions for the first cavity 2181 and the second cavity 2182, respectively. The first cavity 2181 and the second cavity 2182 are respectively used to form a first pressure sensing unit and a second pressure sensing unit in subsequent steps, respectively. The first mass block 2162 corresponds to the position of the first cavity 2181, and the second mass block 2163 corresponds to the position of the second cavity 2182, as shown in FIG. Figure 2E shown.

[0077] Next, step S120 is performed, such as Figure 2F As shown, a second substrate 220 is provided, on which a first groove 221 and a second groove 222 are formed, the first cavity 2181 is arranged corresponding to the first groove 221 , and the second cavity 2182 is arranged corresponding to the second groove 222 .

[0078] The second substrate 220 can be any suitable semiconductor substrate, such as a silicon substrate, and can also be at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP or other III / V compound semiconductors, including multilayer structures composed of these semiconductor materials, or silicon on insulator (SOI), stacked silicon on insulator (SSOI), stacked silicon germanium on insulator (S-SiGeOI), silicon germanium on insulator (SiGeOI) and germanium on insulator (GeOI), or can also be double-sided polished silicon wafers (Double Side Polished Wafers, DSP), or can be sapphire substrates such as Al2O3, ceramic substrates, quartz or glass substrates, etc.

[0079] In one embodiment, Figure 2FAs shown, the second substrate 220 is a silicon substrate, and a first groove 221 and a second groove 222 are formed on the second substrate 220 by a photolithography process. The arrangement of the first groove 221 and the second groove 222 is set according to the first cavity 2181 and the second cavity 2182, so that in the subsequent steps, the first cavity 2181 corresponds to the first groove 221, and the second cavity 2182 corresponds to the second groove 222.

[0080] In one embodiment, Figure 2F As shown, the method further includes forming an insulating layer 223 on the second substrate 220, wherein the insulating layer 223 covers the surface of the second substrate 220 and the bottoms of the first groove 221 and the second groove 222. The insulating layer 223 can be formed by vapor deposition or by thermal oxidation of the second substrate 220, which is not limited in the present application.

[0081] Next, step S130 is performed, such as Figure 2G As shown, the pressure sensing structure 210 and the second substrate 220 are bonded.

[0082] Exemplarily, bonding the pressure sensing structure 210 and the second substrate 220 includes: directly bonding the second pressure-sensitive diaphragm 2161 to the insulating layer 223 on the front side, the first mass block 2162 is suspended in the first groove 221, and the second mass block 2163 is suspended in the second groove 222.

[0083] In one embodiment, Figure 2G As shown, one side of the second pressure-sensitive membrane 2161 of the pressure sensing structure 210 is directly bonded to the front side of the groove of the second substrate 220, the first cavity 2181 corresponds to the first groove 221, and the second cavity 2182 corresponds to the second groove 222. After bonding, the first mass block 2162 is suspended in the first groove 221, and the second mass block 2163 is suspended in the second groove 222. The height of the second pressure-sensitive membrane relative to the bottom of the first groove and the second groove is about 10μm. After bonding, the first cavity 2181 and the first groove 221 are connected through the release hole to form a first space area, and the second cavity 2182 and the second groove 222 are connected through the release hole to form a second space area. The first space area and the second space area are in a vacuum state or a low pressure state. The low pressure state refers to a low pressure state close to vacuum, for example, the air pressure in the first space area and the second space area is less than 0.1MPa.

[0084] Next, step S140 is performed, such as Figure 2HAs shown, the first substrate 211 is removed to expose the first pressure-sensitive layer 212 , which includes a first pressure-sensitive membrane 2121 and a third mass block 2122 and a fourth mass block 2123 located on the second surface of the first pressure-sensitive membrane.

[0085] In one embodiment, Figure 2H As shown, since the first substrate 211 uses an SOI substrate, and the single crystal silicon layer in the SOI substrate is used as the first pressure-sensitive layer 212, the first substrate 211 is removed to remove only the substrate silicon and the oxide layer of the SOI substrate, so as to expose the single crystal silicon layer as the first pressure-sensitive layer 212, and then the upper layer of the first pressure-sensitive layer 212 is etched by a photolithography process to form the second mass block 2122 and the fourth mass block 2123, and the lower layer of the first pressure-sensitive layer 212 that is not etched is used as the first pressure-sensitive diaphragm 2121. It should be noted that the above-mentioned method for forming the first pressure-sensitive diaphragm 2121 and the second mass block 2122 and the fourth mass block 2123 is only exemplary, and other methods can be used to form the first pressure-sensitive diaphragm 2121, and to form the second mass block 2122 and the fourth mass block 2123 located on the second surface of the first pressure-sensitive diaphragm 2121. Among them, the second surface of the first pressure-sensitive diaphragm 2121 is a surface away from the rigid electrode 214.

[0086] Next, step S150 is performed, such as Fig.2I As shown, the pressure sensing structure 210 is etched to separate the pressure sensing structure into a first pressure sensing unit 2101 and a second pressure sensing unit 2102 .

[0087] In one embodiment, Fig.2I As shown, the first pressure-sensing diaphragm 2121, the first sacrificial layer, the rigid electrode 214, the second sacrificial layer, the second pressure-sensing diaphragm 2161 and the insulating layer 223 between the first cavity 2181 and the second cavity 2182 are etched away until the second substrate 220 is exposed, so that the first pressure sensing unit 2101 and the second pressure sensing unit 2102 are completely separated.

[0088] For example, Fig.2IAs shown, the separated first pressure sensing unit 2101 includes a second pressure-sensitive diaphragm 2161 and a first mass block 2162 located on the first surface of the second pressure-sensitive diaphragm, a first pressure-sensitive diaphragm 2121 and a third mass block 2122 located on the second surface of the first pressure-sensitive diaphragm, a first cavity 2181 located between the second pressure-sensitive diaphragm and the first pressure-sensitive diaphragm, and a rigid electrode 214 running through the first cavity. The first pressure-sensitive diaphragm, the rigid electrode, and the second pressure-sensitive diaphragm of the first pressure sensing unit 2101 are all rectangular diaphragms, with an effective length of about 400 μm, an effective width of about 100 μm, and a thickness of about 2 μm. The height of the boss of the first mass block and the third mass block is about 1 μm, the spacing between the first pressure-sensitive diaphragm and the rigid electrode is about 2 μm, and the spacing between the second pressure-sensitive diaphragm and the rigid electrode is about 2 μm. The separated second pressure sensing unit 2102 includes a second pressure-sensitive diaphragm 2161 and a second mass block 2163 located on the first surface of the second pressure-sensitive diaphragm, a first pressure-sensitive diaphragm 2121 and a fourth mass block 2123 located on the second surface of the first pressure-sensitive diaphragm, a second cavity 2182 located between the second pressure-sensitive diaphragm and the first pressure-sensitive diaphragm, and a rigid electrode 214 that runs through the second cavity. The first pressure-sensitive diaphragm, the rigid electrode, and the second pressure-sensitive diaphragm of the second pressure sensing unit 2102 are all rectangular diaphragms, with an effective length of about 400 μm, an effective width of about 100 μm, and a thickness of about 2 μm. The height of the boss of the second mass block and the fourth mass block is about 1 μm, the spacing between the first pressure-sensitive diaphragm and the rigid electrode is about 2 μm, and the spacing between the second pressure-sensitive diaphragm and the rigid electrode is about 2 μm.

[0089] Next, execute step S160, such as Figure 2J As shown, the first pressure sensing unit 2101 and the second pressure sensing unit 2102 are connected via metal wiring.

[0090] In one embodiment, the first pressure-sensitive membrane of the first pressure sensing unit 2101 is connected to the second pressure-sensitive membrane of the second pressure sensing unit 2102 through metal wiring, and the first pressure-sensitive membrane of the second pressure sensing unit 2102 is connected to the second pressure-sensitive membrane of the first pressure sensing unit 2101. In addition, the rigid electrode of the first pressure sensing unit 2101 and the rigid electrode of the second pressure sensing unit 2102 are respectively led out through metal wiring, such as Figure 3 shown.

[0091] The key steps of the method for manufacturing the MEMS differential capacitive pressure sensor of the present invention have been introduced so far. A plurality of other process steps may be required for the complete device preparation, which will not be described one by one here.

[0092] It is worth mentioning that the order of the above steps is only an example. Under the premise of no conflict, the order of the above steps can also be swapped or performed alternately.

[0093] The present invention also provides a MEMS differential capacitive pressure sensor, such as Figure 2J As shown, including:

[0094] A pressure sensing structure 210, the pressure sensing structure comprising a first pressure sensing unit 2101 and a second pressure sensing unit 2102, the first pressure sensing unit 2101 and the second pressure sensing unit 2102 being connected via a wiring element; wherein the first pressure sensing unit 2101 and the second pressure sensing unit 2102 both comprise a first pressure-sensitive membrane 2121 located on the same plane, a rigid electrode 214 located on the same plane, and a second pressure-sensitive membrane 2161 located on the same plane, the first pressure sensing unit 2101 further comprises a first mass block 2162 located on the first surface of the second pressure-sensitive membrane, a third mass block 2122 located on the second surface of the first pressure-sensitive membrane, and a first cavity 2181 located between the second pressure-sensitive membrane and the first pressure-sensitive membrane, and the second pressure sensing unit 2102 further comprises a second mass block 2163 located on the first surface of the second pressure-sensitive membrane, a fourth mass block 2123 located on the second surface of the first pressure-sensitive membrane, and a second cavity 2182 located between the second pressure-sensitive membrane and the first pressure-sensitive membrane;

[0095] A substrate 220 is provided with a first groove 221 and a second groove 222, the first pressure sensing unit 2101 is bonded to the first groove 221, the first cavity 2181 is arranged corresponding to the first groove 221, the second pressure sensing unit 2102 is bonded to the second groove 222, and the second cavity 2182 is arranged corresponding to the second groove 222.

[0096] In one embodiment, the first plane where the first pressure-sensitive membrane 2121 is located, the second plane where the rigid electrode 214 is located, and the third plane where the second pressure-sensitive membrane 2161 is located are parallel or nearly parallel (for example, the angle is less than 5°).

[0097] In one embodiment, the first cavity 2181 is connected to the first groove 221 to form a first space region, and the second cavity 2182 is connected to the second groove 222 to form a second space region. The first space region and the second space region are in a vacuum state or a low-pressure state, and the low-pressure state refers to a low-pressure state close to vacuum (for example, the air pressure is less than 0.1 MPa).

[0098] Exemplarily, a connecting column 217 is further formed between the first pressure-sensitive diaphragm 2121 and the second pressure-sensitive diaphragm 2161, wherein a first end of the connecting column 217 is connected to a first surface of the first pressure-sensitive diaphragm 2121, and a second end of the connecting column 217 is connected to a second surface of the second pressure-sensitive diaphragm 2161, so as to mechanically couple the first pressure-sensitive diaphragm 2121 and the second pressure-sensitive diaphragm 2161, so that the deformation of the first pressure-sensitive diaphragm 2121 and the second pressure-sensitive diaphragm 2161 are consistent. The connecting column 217 passes through the rigid electrode 214 and has no contact with the rigid electrode, and the rigid electrode 214 is mechanically decoupled from the first pressure-sensitive diaphragm 2121 and the second pressure-sensitive diaphragm 2161, so that the deformation of the first pressure-sensitive diaphragm 2121 and the second pressure-sensitive diaphragm 2161 is independent of the rigid electrode 214.

[0099] Exemplarily, the first pressure-sensitive diaphragm 2121 of the first pressure sensing unit 2101 and the rigid electrode 214 constitute a first pressure-sensitive capacitor, the second pressure-sensitive diaphragm 2161 of the first pressure sensing unit 2101 and the rigid electrode 214 constitute a second pressure-sensitive capacitor, the first pressure-sensitive diaphragm 2121 of the second pressure sensing unit 2102 and the rigid electrode 214 constitute a third pressure-sensitive capacitor, the second pressure-sensitive diaphragm 2161 of the second pressure sensing unit 2102 and the rigid electrode 214 constitute a fourth pressure-sensitive capacitor, and the first pressure-sensitive capacitor, the second pressure-sensitive capacitor, the third pressure-sensitive capacitor and the fourth pressure-sensitive capacitor are connected via a Wheatstone bridge, such as Figure 4 shown.

[0100] According to the MEMS differential capacitive pressure sensor and the manufacturing method thereof provided by the present invention, the differential capacitive pressure sensor is prepared by bonding a pressure sensing structure having a first pressure sensing unit and a second pressure sensing unit to a substrate having a first groove and a second groove, thereby simplifying the manufacturing process and reducing the production cost. By respectively arranging mass blocks on the first pressure-sensitive diaphragm and the second pressure-sensitive diaphragm of the first pressure sensing unit and the second pressure sensing unit, the sensitivity of the differential capacitive pressure sensor is increased and the nonlinearity is reduced, thereby improving the performance of the sensor.

[0101] The present invention has been described by the above embodiments, but it should be understood that the above embodiments are only for the purpose of example and description, and are not intended to limit the present invention to the scope of the described embodiments. In addition, it can be understood by those skilled in the art that the present invention is not limited to the above embodiments, and more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications all fall within the scope of the protection claimed by the present invention. The protection scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for manufacturing a MEMS differential capacitive pressure sensor, characterized in that: include: Forming the pressure sensing structure: Providing a first substrate, on which a first pressure-sensitive layer is formed; forming a first sacrificial layer, a rigid electrode and a second sacrificial layer in sequence on the first pressure-sensitive layer; forming a second pressure-sensitive layer on the second sacrificial layer, wherein the second pressure-sensitive layer comprises a second pressure-sensitive diaphragm and a first mass block and a second mass block located on a first surface of the second pressure-sensitive diaphragm; removing the first sacrificial layer and the second sacrificial layer to form a first cavity and a second cavity between the first pressure-sensitive layer and the second pressure-sensitive layer; Providing a second substrate, wherein a first groove and a second groove are formed on the second substrate, the first cavity is arranged corresponding to the first groove, and the second cavity is arranged corresponding to the second groove; bonding the pressure sensing structure and the second substrate; Removing the first substrate to expose the first pressure-sensitive layer, wherein the first pressure-sensitive layer includes a first pressure-sensitive membrane and a third mass block and a fourth mass block located on a second surface of the first pressure-sensitive membrane; etching the pressure sensing structure to separate the pressure sensing structure into a first pressure sensing unit and a second pressure sensing unit; The first pressure sensing unit and the second pressure sensing unit are connected through metal wiring.

2. The manufacturing method according to claim 1, characterized in that The first pressure sensing unit includes a second pressure-sensitive diaphragm and a first mass block located on a first surface of the second pressure-sensitive diaphragm, a first pressure-sensitive diaphragm and a third mass block located on a second surface of the first pressure-sensitive diaphragm, a first pressure-sensitive diaphragm and a third mass block located on a second surface of the first pressure-sensitive diaphragm, a first cavity located between the second pressure-sensitive diaphragm and the first pressure-sensitive diaphragm, and a rigid electrode running through the first cavity; the second pressure sensing unit includes a second pressure-sensitive diaphragm and a second mass block located on a first surface of the second pressure-sensitive diaphragm, a first pressure-sensitive diaphragm and a fourth mass block located on a second surface of the first pressure-sensitive diaphragm, a second cavity located between the second pressure-sensitive diaphragm and the first pressure-sensitive diaphragm, and a rigid electrode running through the second cavity.

3. The manufacturing method according to claim 1, characterized in that: Forming a second pressure-sensitive diaphragm and a first mass block and a second mass block located on a first surface of the second pressure-sensitive diaphragm includes: forming a second pressure-sensitive layer, wherein the second pressure-sensitive layer includes an upper layer portion and a lower layer portion; The upper layer of the second pressure-sensitive layer is patterned to form a first mass block and a second mass block, and the lower layer of the second pressure-sensitive layer serves as the second pressure-sensitive membrane.

4. The manufacturing method according to claim 1, characterized in that: Bonding the pressure sensing structure and the second substrate includes: forming an insulating layer on the second substrate, wherein the insulating layer covers a surface of the second substrate and bottoms of the first groove and the second groove; The second pressure-sensitive diaphragm is directly bonded to the insulating layer on the front side, the first mass block is suspended in the first groove, and the second mass block is suspended in the second groove.

5. The manufacturing method according to claim 1, characterized in that: Sequentially forming a first sacrificial layer, a rigid electrode, and a second sacrificial layer on the first pressure-sensitive layer comprises: forming a first sacrificial layer and a rigid electrode layer in sequence on the first pressure-sensitive layer; forming a patterned mask layer on the rigid electrode layer; Etching the rigid electrode layer using the patterned mask layer as a mask to form the rigid electrodes and gap regions between the rigid electrodes; removing the mask layer; A second sacrificial layer is formed covering the rigid electrode and the gap region.

6. The manufacturing method according to claim 1, characterized in that: Before removing the first sacrificial layer and the second sacrificial layer, the step of forming a release hole on the second pressure-sensitive diaphragm is also included. After bonding the pressure sensing structure and the second substrate, the first cavity and the first groove are connected through the release hole to form a first space area, and the second cavity and the second groove are connected through the release hole to form a second space area. The first space area and the second space area are in a vacuum state or a low-pressure state.

7. The manufacturing method according to claim 1, characterized in that: The first substrate includes a silicon-on-insulator substrate, which includes a silicon substrate, a silicon oxide insulating layer and a single-crystal silicon layer arranged in sequence from bottom to top, and the single-crystal silicon layer is used as the first pressure-sensitive layer.

8. A MEMS differential capacitive pressure sensor, characterized in that: include: A pressure sensing structure, the pressure sensing structure comprising a first pressure sensing unit and a second pressure sensing unit, the first pressure sensing unit and the second pressure sensing unit being connected via a wiring element; wherein the first pressure sensing unit and the second pressure sensing unit both comprise a first pressure-sensitive diaphragm located in the same plane, a rigid electrode located in the same plane, and a second pressure-sensitive diaphragm located in the same plane, the first pressure sensing unit further comprises a first mass block located on a first surface of the second pressure-sensitive diaphragm, a third mass block located on a second surface of the first pressure-sensitive diaphragm, and a first cavity located between the second pressure-sensitive diaphragm and the first pressure-sensitive diaphragm, the second pressure sensing unit further comprises a second mass block located on the first surface of the second pressure-sensitive diaphragm, a fourth mass block located on the second surface of the first pressure-sensitive diaphragm, and a second cavity located between the second pressure-sensitive diaphragm and the first pressure-sensitive diaphragm; A substrate having a first groove and a second groove formed thereon, the first pressure sensing unit is bonded to the first groove, the first cavity is arranged corresponding to the first groove, the second pressure sensing unit is bonded to the second groove, and the second cavity is arranged corresponding to the second groove.

9. The MEMS differential capacitive pressure sensor according to claim 8, characterized in that: A connecting column is further formed between the first pressure-sensitive diaphragm and the second pressure-sensitive diaphragm, wherein a first end of the connecting column is connected to a first surface of the first pressure-sensitive diaphragm, and a second end of the connecting column is connected to a second surface of the second pressure-sensitive diaphragm, so as to mechanically couple the first pressure-sensitive diaphragm and the second pressure-sensitive diaphragm, and the connecting column passes through the rigid electrode and has no contact with the rigid electrode, and the rigid electrode is mechanically decoupled from the first pressure-sensitive diaphragm and the second pressure-sensitive diaphragm.

10. The MEMS differential capacitive pressure sensor according to claim 8, characterized in that: The first pressure-sensitive diaphragm of the first pressure sensing unit and the rigid electrode constitute a first pressure-sensitive capacitor, the second pressure-sensitive diaphragm of the first pressure sensing unit and the rigid electrode constitute a second pressure-sensitive capacitor, the first pressure-sensitive diaphragm of the second pressure sensing unit and the rigid electrode constitute a third pressure-sensitive capacitor, the second pressure-sensitive diaphragm of the second pressure sensing unit and the rigid electrode constitute a fourth pressure-sensitive capacitor, and the first pressure-sensitive capacitor, the second pressure-sensitive capacitor, the third pressure-sensitive capacitor and the fourth pressure-sensitive capacitor are connected via a Wheatstone bridge.

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