CN119803736A - A MEMS differential capacitive pressure sensor and a manufacturing method thereof - Google Patents
A MEMS differential capacitive pressure sensor and a manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses a MEMS differential capacitive pressure sensor and a manufacturing method thereof, wherein a pressure sensing structure with a first pressure sensing unit and a second pressure sensing unit is bonded to a substrate with a first groove and a second groove, so that the differential capacitive pressure sensor is manufactured, the manufacturing process is simplified, the production cost is reduced, and the sensitivity of the differential capacitive pressure sensor is increased and the nonlinearity is reduced by arranging mass blocks on a first pressure sensing diaphragm and a second pressure sensing diaphragm of the first pressure sensing unit and the second pressure sensing unit respectively, so that the performance of the sensor is improved.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a MEMS differential capacitive pressure sensor and a manufacturing method thereof.
Background
With the development of Micro-Electro-MECHANICAL SYSTEM, MEMS technology, pressure sensors are an indispensable key device in many industries, and have been widely used in the fields of consumer electronics, automotive electronics, petrochemical industry, biomedical science, national defense and military industry, and the like. Compared with the piezoresistive pressure sensor, the capacitive pressure sensor has the advantages of high sensitivity, low power consumption, good temperature characteristic and the like, and is more suitable for developing high-precision pressure sensors.
In order to further improve the performance of the capacitive pressure sensor, on one hand, the area of a chip is increased, the thickness of a polar plate and the height of a cavity are reduced, but the capacitive pressure sensor is contrary to the miniaturization direction of a device, and is unfavorable for chip integration, and on the other hand, a multi-film structure is formed, but the traditional multi-film structure is overlapped after being etched by layer-by-layer deposition photoetching, so that the process is complex, the limitation of equipment capacity is avoided, and the mass production and the cost reduction of products are unfavorable.
Disclosure of Invention
In the summary, a series of concepts in a simplified form are introduced, which will be further described in detail in the detailed description. The summary of the invention is not intended to define the key features and essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
The invention provides a manufacturing method of an MEMS differential capacitive pressure sensor, which is characterized by comprising the following steps:
Forming a pressure sensing structure:
Providing a first substrate, wherein a first pressure sensing layer is formed on the first substrate;
Sequentially forming a first sacrificial layer, a rigid electrode and a second sacrificial layer on the first pressure sensing layer;
Forming a second pressure sensing layer on the second sacrificial layer, wherein the second pressure sensing layer comprises a second pressure sensing diaphragm, and a first mass block and a second mass block which are positioned on the first surface of the second pressure sensing diaphragm;
removing the first sacrificial layer and the second sacrificial layer to form a first cavity and a second cavity between the first pressure sensing layer and the second pressure sensing 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 sensing layer, wherein the first pressure sensing layer comprises a first pressure sensing diaphragm, and a third mass block and a fourth mass block which are positioned on a second surface of the first pressure sensing diaphragm;
Etching the pressure sensing structure to divide 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.
The first pressure sensing unit comprises a second pressure sensing diaphragm, a first mass block positioned on the first surface of the second pressure sensing diaphragm, a first pressure sensing diaphragm, a third mass block positioned on the second surface of the first pressure sensing diaphragm, a first cavity positioned between the second pressure sensing diaphragm and the first pressure sensing diaphragm, and a rigid electrode penetrating through the first cavity, wherein the second pressure sensing unit comprises a second pressure sensing diaphragm, a second mass block positioned on the first surface of the second pressure sensing diaphragm, a first pressure sensing diaphragm, a fourth mass block positioned on the second surface of the first pressure sensing diaphragm, a second cavity positioned between the second pressure sensing diaphragm and the first pressure sensing diaphragm, and a rigid electrode penetrating through the second cavity.
Illustratively, forming a second pressure sensing diaphragm and first and second masses located on a first surface of the second pressure sensing diaphragm includes:
forming a second pressure-sensitive layer including an upper layer portion and a lower layer portion;
and patterning an upper layer part of the second pressure sensing layer to form a first mass block and a second mass block, wherein a lower layer part of the second pressure sensing layer serves as the second pressure sensing membrane.
Illustratively, bonding the pressure sensing structure and the second substrate includes:
forming an insulating layer on the second substrate, wherein the insulating layer covers the surface of the second substrate and the bottoms of the first groove and the second groove;
The front surface is directly bonded with the second pressure sensing diaphragm and the insulating layer, the first mass block is suspended in the first groove, and the second mass block is suspended in the second groove.
Illustratively, sequentially forming a first sacrificial layer, a rigid electrode, and a second sacrificial layer on the first pressure-sensitive layer includes:
Sequentially forming a first sacrificial layer and a rigid electrode layer on the first pressure sensing layer;
forming a patterned mask layer over the rigid electrode layer;
Etching the rigid electrode layer by taking the patterned mask layer as a mask to form the rigid electrode and a gap region between the rigid electrodes;
Removing the mask layer;
A second sacrificial layer is formed overlying the rigid electrode and the void region.
Illustratively, before removing the first sacrificial layer and the second sacrificial layer, the method further includes a step of forming a release hole on the second pressure-sensitive film, wherein after bonding the pressure-sensing structure and the second substrate, the first cavity and the first groove are communicated through the release hole to form a first space region, the second cavity and the second groove are communicated through the release hole to form a second space region, and the first space region and the second space region are in a vacuum state or a low-pressure state.
Illustratively, the first substrate includes a silicon-on-insulator substrate including a silicon substrate, a silicon oxide insulating layer, and a single crystal silicon layer disposed in this order from bottom to top, with the single crystal silicon layer as the first pressure-sensitive layer.
The invention also provides a MEMS differential capacitive pressure sensor, comprising:
The pressure sensing structure comprises a first pressure sensing unit and a second pressure sensing unit, wherein the first pressure sensing unit and the second pressure sensing unit are connected through a wiring element, each of the first pressure sensing unit and the second pressure sensing unit comprises a first pressure sensing diaphragm, a rigid electrode and a second pressure sensing diaphragm, the first pressure sensing diaphragm, the rigid electrode and the second pressure sensing diaphragm are positioned on the same plane, the first pressure sensing unit further comprises a first mass block, a third mass block and a first cavity, the first mass block is positioned on a first surface of the second pressure sensing diaphragm, the third mass block is positioned on a second surface of the first pressure sensing diaphragm, the first cavity is positioned between the second pressure sensing diaphragm and the first pressure sensing diaphragm, and the second pressure sensing unit further comprises a second mass block, a fourth mass block and a second cavity, the second mass block is positioned on a second surface of the first pressure sensing diaphragm, and the second cavity is positioned between the second pressure sensing diaphragm and the first pressure sensing diaphragm;
the substrate, be formed with first recess and second recess on the substrate, first pressure sensing unit bond to on the first recess, first cavity with first recess corresponds the setting, second pressure sensing unit bond to on the second recess, the second cavity with the second recess corresponds the setting.
Illustratively, a connection post is further formed between the first pressure-sensing diaphragm and the second pressure-sensing diaphragm, a first end of the connection post is connected to the first surface of the first pressure-sensing diaphragm, a second end of the connection post is connected to the second surface of the second pressure-sensing diaphragm to mechanically couple the first pressure-sensing diaphragm to the second pressure-sensing diaphragm, the connection post passes through the rigid electrode and is not in contact with the rigid electrode, and the rigid electrode is mechanically decoupled from the first pressure-sensing diaphragm and the second pressure-sensing diaphragm.
The first pressure sensing diaphragm of the first pressure sensing unit and the rigid electrode form a first pressure sensing capacitor, the second pressure sensing diaphragm of the first pressure sensing unit and the rigid electrode form a second pressure sensing capacitor, the first pressure sensing diaphragm of the second pressure sensing unit and the rigid electrode form a third pressure sensing capacitor, the second pressure sensing diaphragm of the second pressure sensing unit and the rigid electrode form a fourth pressure sensing capacitor, and the first pressure sensing capacitor, the second pressure sensing capacitor, the third pressure sensing capacitor and the fourth pressure sensing capacitor are connected through a wheatstone bridge.
According to the MEMS differential capacitive pressure sensor and the manufacturing method thereof, the differential capacitive pressure sensor is manufactured by bonding the pressure sensing structure with the first pressure sensing unit and the second pressure sensing unit to the substrate with the first groove and the second groove, so that the manufacturing process is simplified, the production cost is reduced, and the sensitivity of the differential capacitive pressure sensor is increased and the nonlinearity is reduced by arranging the mass blocks on the first pressure sensing diaphragm and the second pressure sensing diaphragm of the first pressure sensing unit and the second pressure sensing unit respectively, so that the performance of the sensor is improved.
Drawings
The following drawings are included to provide an understanding of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and their description to explain the principles of the invention.
In the accompanying drawings:
FIG. 1 is a flow chart of a method of manufacturing a MEMS differential capacitive pressure sensor in accordance with one embodiment of the invention;
FIGS. 2A-2J are schematic cross-sectional views of a structure obtained by sequentially implementing a method of fabricating a MEMS differential capacitive pressure sensor according to one embodiment of the present invention;
FIG. 2K is a top view of FIG. 2B according to one embodiment of the invention;
FIG. 3 is a schematic diagram of a metal wiring according to one embodiment of the present invention;
Fig. 4 is a connection of a first voltage sensing capacitor, a second voltage sensing capacitor, the third voltage sensing capacitor and a fourth voltage sensing capacitor according to one embodiment of the invention.
Detailed Description
In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the invention may be practiced without one or more of these details. In other instances, well-known features have not been described in detail in order to avoid obscuring the invention.
It should be understood that the present invention may be embodied in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size of layers and regions, as well as the relative sizes, may be exaggerated for clarity. Like numbers refer to like elements throughout.
It will be understood that when an element or layer is referred to as being "on," "adjacent," "connected to," or "coupled to" another element or layer, it can be directly on, adjacent, connected, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.
Spatially relative terms, such as "under," "below," "beneath," "under," "above," "over," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements or features described as "under" or "beneath" other elements would then be oriented "on" the other elements or features. Thus, the exemplary terms "below" and "under" may include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatially relative descriptors used herein interpreted accordingly.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.
In order to provide a thorough understanding of the present invention, detailed steps and detailed structures will be presented in the following description in order to explain the technical solution presented by the present invention. Preferred embodiments of the present invention are described in detail below, however, the present invention may have other embodiments in addition to these detailed descriptions.
The invention provides a manufacturing method of a MEMS differential capacitive pressure sensor, as shown in FIG. 1, comprising the following steps:
Step S110, a pressure sensing structure is formed, namely a first substrate is provided, a first pressure sensing layer is formed on the first substrate, a first sacrificial layer, a rigid electrode and a second sacrificial layer are sequentially formed on the first pressure sensing layer, a second pressure sensing layer is formed on the second sacrificial layer, the second pressure sensing layer comprises a second pressure sensing membrane, a first mass block and a second mass block which are positioned on the first surface of the second pressure sensing membrane, and the first sacrificial layer and the second sacrificial layer are removed to form a first cavity and a second cavity between the first pressure sensing layer and the second pressure sensing layer;
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;
step S130, bonding the pressure sensing structure and the second substrate;
Step 140, removing the first substrate to expose the first pressure sensing layer, wherein the first pressure sensing layer comprises a first pressure sensing diaphragm, and a third mass block and a fourth mass block which are positioned on a second surface of the first pressure sensing diaphragm;
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;
Step S160, connecting the first pressure sensing unit and the second pressure sensing unit through metal wiring.
Next, a method for manufacturing the MEMS differential capacitive pressure sensor according to the present invention will be described in detail with reference to fig. 2A to 2J, wherein fig. 2A to 2J are schematic cross-sectional views of structures obtained by sequentially implementing the method for manufacturing the MEMS differential capacitive pressure sensor according to an embodiment of the present invention.
First, step S110 is performed to form the pressure sensing structure 210.
Illustratively, as shown in fig. 2A, a first substrate 211 is provided, the first substrate 211 having a first pressure sensitive layer 212 formed thereon.
The first substrate 211 may be any suitable semiconductor base, such as a silicon base, which may also be at least one of Si, ge, siGe, siC, siGeC, inAs, gaAs, inP or other III/V compound semiconductors, multi-layer structures comprising these semiconductor materials, etc., or silicon-on-insulator (SOI), silicon-on-insulator (SSOI), silicon-germanium-on-insulator (S-SiGeOI), silicon-germanium-on-insulator (SiGeOI), and germanium-on-insulator (GeOI), or may also be a double-sided polished silicon wafer (Double Side Polished Wafers, DSP), or a sapphire substrate, ceramic substrate, quartz or glass substrate, etc., such as Al 2O3.
The material of the first pressure sensitive layer 212 includes, but is not limited to, single crystal silicon. The conventional semiconductor process method of forming the first pressure sensitive layer 212 may be selected as needed, for example, one of Low Pressure Chemical Vapor Deposition (LPCVD) formed by a Chemical Vapor Deposition (CVD) method, a Physical Vapor Deposition (PVD) method, an Atomic Layer Deposition (ALD) method, or the like, laser Ablation Deposition (LAD), and Selective Epitaxial Growth (SEG), or one of Low Temperature Chemical Vapor Deposition (LTCVD), rapid Thermal Chemical Vapor Deposition (RTCVD), and Plasma Enhanced Chemical Vapor Deposition (PECVD).
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 voltage sensing layer 212. The P-type ion doping concentration of the SOI substrate is 2 multiplied by 10 19cm-3, the thickness of the substrate silicon is about 400 mu m, the thickness of the oxide layer is about 0.5 mu m, and the thickness of the monocrystalline silicon layer is about 3 mu m. The surface of the SOI substrate may also be thermally oxidized to form an insulating layer, which is silicon dioxide, having a thickness of about 0.5 μm.
Illustratively, as shown in fig. 2B and 2C, a first sacrificial layer 213, a rigid electrode 214, and a second sacrificial layer 215 are sequentially formed on the first pressure sensitive layer 212.
Illustratively, sequentially forming the first sacrificial layer 213, the rigid electrode 214, and the second sacrificial layer 215 on the first pressure-sensitive layer 212 includes sequentially forming the first sacrificial layer 213 and the 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 with the patterned mask layer as a mask to form the rigid electrode 214 and a void region between the rigid electrodes, removing the mask layer, and forming the second sacrificial layer 215 covering the rigid electrode and the void region.
In one embodiment, as shown in fig. 2B, first, the first sacrificial layer 213 is formed on the first pressure sensitive layer 212, where the material of the first sacrificial layer 213 includes, but is not limited to, silicon dioxide, and the thickness of the first sacrificial layer 213 is about 2 μm, and the forming method of the first sacrificial layer 213 may use LPCVD or any of the existing technologies known to those skilled in the art, and will not be repeated here.
In one embodiment, as shown in fig. 2B, a rigid electrode layer is then formed on the first sacrificial layer 213, where the material of the rigid electrode layer includes, but is not limited to, polysilicon, and the method for forming the rigid electrode layer may be any prior art known to those skilled in the art, and will not be described herein. 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 a void region between the rigid electrodes 214. The method of etching the rigid electrode layer may be any prior art technique known to those skilled in the art, and preferably dry etching, including but not limited to Reactive Ion Etching (RIE), ion beam etching, plasma etching, laser ablation, or any combination of these methods. The masking layer is then removed, forming the structure shown in fig. 2B and 2K.
In one embodiment, the upper and lower surfaces of the rigid electrode 214 may further include an electrode dielectric layer, including but not limited to a silicon nitride layer, and the electrode dielectric layer may be formed by any method known to those skilled in the art, and will not be described herein.
In one embodiment, as shown in fig. 2C, the second sacrificial layer 215 is formed on the rigid electrode 214, where the material of the second sacrificial layer 215 includes, but is not limited to, silicon dioxide, and the thickness of the second sacrificial layer 215 is about 3 μm, and any technique known to those skilled in the art may be used for forming the second sacrificial layer 215, which is not described herein.
Illustratively, prior to forming the second pressure sensitive layer, a step of forming a plurality of connection studs 217 between the first pressure sensitive layer 212 and the second pressure sensitive layer is also included. The first end of the connection post 217 is connected to the first pressure sensitive layer 212, and the second end of the connection post 217 is connected to the second pressure sensitive layer to mechanically couple the first pressure sensitive layer 212 with the second pressure sensitive layer. And the connection post 217 passes through the void region between the rigid electrodes 214 without contacting the rigid electrodes 214 to mechanically decouple the rigid electrodes 214 from the first and second pressure sensitive layers 212 and 214.
In one embodiment, as shown in fig. 2C, 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, which pass through the void areas between the rigid electrodes 214 and expose the first pressure sensitive layer 212. Next, the through holes are filled with a material such as silicon nitride, and the excess silicon nitride is removed by a Chemical Mechanical Polishing (CMP) process to form a plurality of connection pillars 217, wherein the connection pillars 217 have a height of about 6 μm, a length of 50 μm to 200 μm, and a width of about 5 μm.
Illustratively, as shown in fig. 2D, a second pressure sensing layer 216 is formed on the second sacrificial layer 215, the second pressure sensing layer 216 including a second pressure sensing diaphragm 2161 and a first mass 2162 and a second mass 2163 on a first surface of the second pressure sensing diaphragm 2161.
Illustratively, forming the first mass 2162 and the second mass 2163 of the second pressure-sensing diaphragm 2161 face of the second pressure-sensing diaphragm 2161 includes forming a second pressure-sensing layer 216, the second pressure-sensing layer 216 including an upper portion and a lower portion, and patterning the upper portion of the second pressure-sensing layer 216 to form the first mass 2162 and the second mass 2163, the lower portion of the second pressure-sensing layer serving as the second pressure-sensing diaphragm 2161.
In one embodiment, the material of the second pressure-sensitive layer 216 includes, but is not limited to, polysilicon, and any technique known to those skilled in the art may be used for forming the second pressure-sensitive layer 216, and will not be described herein. Next, a patterned mask layer (not shown) is formed on the second pressure-sensitive layer 216, and an upper portion of the second pressure-sensitive layer 216 is etched using a photolithography process to form a first mass 2162 and a second mass 2163, and a lower portion of the second pressure-sensitive layer 216, which is not etched, is used as the second pressure-sensitive film 2161, the height of the bosses of the first mass 2162 and the second mass 2163 is about 1 μm, and the thickness of the second pressure-sensitive film 2161 is about 2 μm. It should be noted that the above-described forming method of the second pressure sensing diaphragm 2161 and the first mass 2162 and the second mass 2163 is merely exemplary, and other methods may be used to form the second pressure sensing diaphragm 2161 and form the first mass 2162 and the second mass 2163 on the first surface of the second pressure sensing diaphragm 2161. Wherein the first surface of the second pressure sensing diaphragm 2161 is a surface remote from the rigid electrode 214. By providing mass blocks on the surfaces of the first pressure sensing diaphragm and the second pressure sensing diaphragm, the linearity of the pressure sensor can be improved.
Illustratively, as shown in fig. 2E, 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 sensitive layer 212 and the second pressure sensitive layer 216.
Illustratively, 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.
In one embodiment, as shown in fig. 2E, the second pressure sensing diaphragm 2161 is etched to form a plurality of release holes 2164 on the second pressure sensing diaphragm 2161. Next, any prior art etching known to those skilled in the art is used to remove the first sacrificial layer 213 and the second sacrificial layer 215, preferably wet etching, where the solution of wet etching is selective, and for the case that silicon dioxide is selected for the first sacrificial layer 213 and the second sacrificial layer 215, monocrystalline silicon or polycrystalline silicon is selected for the first pressure sensitive layer 212 and the second pressure sensitive layer 216, polycrystalline silicon is selected for the rigid electrode 214, and silicon nitride is selected for the connection post 217, the solution of wet etching may be a BOE solution, where the BOE solution is made of HF, NH4F and deionized water. With the void regions between the plurality of release holes 2164 and the rigid electrode 214, wet etching removes portions of the first and second sacrificial layers 213 and 215 to form first and second cavities 2181 and 2182 between the first and second pressure sensing layers 212 and 216, respectively, and the remaining portions of the first and second sacrificial layers 213 and 215 serve as supporting portions of the first and second cavities 2181 and 2182, respectively. Wherein the first cavity 2181 and the second cavity 2182 are used to form a first pressure sensing unit and a second pressure sensing unit, respectively, in a subsequent step, the first mass 2162 corresponds to the position of the first cavity 2181, and the second mass 2163 corresponds to the position of the second cavity 2182, as shown in fig. 2E.
Next, step S120 is performed, as shown in fig. 2F, a second substrate 220 is provided, where a first groove 221 and a second groove 222 are formed on the second substrate 220, the first cavity 2181 is disposed corresponding to the first groove 221, and the second cavity 2182 is disposed corresponding to the second groove 222.
The second substrate 220 may be any suitable semiconductor base, such as a silicon base, which may also be at least one of Si, ge, siGe, siC, siGeC, inAs, gaAs, inP or other III/V compound semiconductors, multi-layer structures comprising these semiconductor materials, etc., or a silicon-on-insulator (SOI), silicon-on-insulator (SSOI), silicon-germanium-on-insulator (S-SiGeOI), silicon-germanium-on-insulator (SiGeOI), and germanium-on-insulator (GeOI), or may also be a double-sided polished silicon wafer (Double Side Polished Wafers, DSP), a sapphire substrate, a ceramic substrate, a quartz or glass substrate, etc., which may also be Al 2O3, etc.
In one embodiment, as shown in fig. 2F, the second substrate 220 employs a silicon base, and the first groove 221 and the second groove 222 are formed on the second substrate 220 through a photolithography process. The arrangement of the first and second grooves 221 and 222 is such that the second cavity 2182 corresponds to the second groove 222 while the first cavity 2181 corresponds to the first groove 221 in the subsequent step.
In one embodiment, as shown in fig. 2F, the method further includes a step of forming an insulating layer 223 on the second substrate 220, the insulating layer 223 covering the surface of the second substrate 220 and the bottoms of the first recess 221 and the second recess 222. The insulating layer 223 may be formed by vapor deposition or thermal oxidation of the second substrate 220, which is not limited in the present application.
Next, step S130 is performed, as shown in fig. 2G, to bond the pressure sensing structure 210 and the second substrate 220.
Illustratively, bonding the pressure sensing structure 210 and the second substrate 220 includes bonding the second pressure sensing diaphragm 2161 directly to the insulating layer 223 on the front surface, the first mass 2162 being suspended within the first recess 221, the second mass 2163 being suspended within the second recess 222.
In one embodiment, as shown in fig. 2G, the second pressure sensing diaphragm 2161 side of the pressure sensing structure 210 is directly bonded to the front surface of the recess side of the second substrate 220, the first cavity 2181 corresponds to the first recess 221, the second cavity 2182 corresponds to the second recess 222, the first mass 2162 is suspended in the first recess 221 after bonding, the second mass 2163 is suspended in the second recess 222, and the height of the second pressure sensing diaphragm relative to the bottoms of the first recess and the second recess is about 10 μm. After bonding, the first cavity 2181 and the first groove 221 are communicated through the release hole to form a first space region, the second cavity 2182 and the second groove 222 are communicated 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, and the low-pressure state refers to a low-pressure state close to vacuum, for example, the air pressure in the first space region and the second space region is less than 0.1MPa.
Next, step S140 is performed, as shown in fig. 2H, the first substrate 211 is removed to expose the first pressure-sensitive layer 212, and the first pressure-sensitive layer 212 includes a first pressure-sensitive membrane 2121, and a third mass 2122 and a fourth mass 2123 located on a second surface of the first pressure-sensitive membrane.
In one embodiment, as shown in fig. 2H, since the first substrate 211 is an SOI substrate, and the single crystal silicon layer in the SOI substrate is used as the first pressure sensitive layer 212, removing the first substrate 211 removes only the substrate silicon and the oxide layer of the SOI substrate to expose the single crystal silicon layer as the first pressure sensitive layer 212, and then etches an upper portion of the first pressure sensitive layer 212 by using a photolithography process to form the second mass 2122 and the fourth mass 2123, and a lower portion of the first pressure sensitive layer 212 that is not etched is used as the first pressure sensitive membrane 2121. It should be noted that the above-described forming method of the first pressure-sensitive diaphragm 2121 and the second and fourth masses 2122 and 2123 is merely exemplary, and other methods may be used to form the first pressure-sensitive diaphragm 2121 and form the second and fourth masses 2122 and 2123 on the second surface of the first pressure-sensitive diaphragm 2121. Wherein the second surface of first pressure sensing diaphragm 2121 is the surface remote from rigid electrode 214.
Next, step S150 is performed, as shown in fig. 2I, to etch the pressure sensing structure 210 to divide the pressure sensing structure into a first pressure sensing unit 2101 and a second pressure sensing unit 2102.
In one embodiment, as shown in fig. 2I, 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 to completely separate the first pressure sensing unit 2101 and the second pressure sensing unit 2102.
Illustratively, as shown in fig. 2I, the separated first pressure sensing cell 2101 includes a second pressure sensing diaphragm 2161 and a first mass 2162 located on a first surface of the second pressure sensing diaphragm, a first pressure sensing diaphragm 2121 and a third mass 2122 located on a second surface of the first pressure sensing diaphragm, a first cavity 2181 located between the second pressure sensing diaphragm and the first pressure sensing diaphragm, and a rigid electrode 214 extending through the first cavity. The first pressure sensing diaphragm, the rigid electrode, and the second pressure sensing diaphragm of the first pressure sensing unit 2101 are rectangular diaphragms, the effective length is about 400 μm, the effective width is about 100 μm, the thicknesses are about 2 μm, the heights of the bosses of the first mass block and the third mass block are about 1 μm, the distance between the first pressure sensing diaphragm and the rigid electrode is about 2 μm, and the distance between the second pressure sensing diaphragm and the rigid electrode is about 2 μm. The separated second pressure sensing cell 2102 includes a second pressure sensing diaphragm 2161 and a second mass 2163 located on a first surface of the second pressure sensing diaphragm, a first pressure sensing diaphragm 2121 and a fourth mass 2123 located on a second surface of the first pressure sensing diaphragm, a second cavity 2182 located between the second pressure sensing diaphragm and the first pressure sensing diaphragm, and a rigid electrode 214 extending through the second cavity. The first pressure sensing diaphragm, the rigid electrode and the second pressure sensing diaphragm of the second pressure sensing unit 2102 are rectangular diaphragms, the effective length is about 400 μm, the effective width is about 100 μm, the thicknesses are about 2 μm, the heights of the bosses of the second mass block and the fourth mass block are about 1 μm, the distance between the first pressure sensing diaphragm and the rigid electrode is about 2 μm, and the distance between the second pressure sensing diaphragm and the rigid electrode is about 2 μm.
Next, step S160 is performed, as shown in fig. 2J, connecting the first pressure sensing unit 2101 and the second pressure sensing unit 2102 by metal wiring.
In one embodiment, the first pressure sensing diaphragm of the first pressure sensing unit 2101 is connected to the second pressure sensing diaphragm of the second pressure sensing unit 2102 by a metal wiring, and the first pressure sensing diaphragm of the second pressure sensing unit 2102 is connected to the second pressure sensing diaphragm of the first pressure sensing unit 2101. Further, the rigid electrode of the first pressure sensing unit 2101 and the rigid electrode of the second pressure sensing unit 2102 are also led out respectively by metal wirings, as shown in fig. 3.
The key steps of the method for manufacturing the MEMS differential capacitive pressure sensor of the present invention are described so far, and a plurality of other processes may be required for the preparation of the complete device, which will not be described in detail herein.
It should be noted that the order of the steps is merely an example, and the order of the steps may be exchanged or alternatively performed without conflict.
The present invention also provides a MEMS differential capacitive pressure sensor, as shown in fig. 2J, comprising:
A pressure sensing structure 210 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 2012 being connected by a wiring element, wherein the first pressure sensing unit 2101 and the second pressure sensing unit 2102 each comprise a first pressure sensing diaphragm 2121 on a same plane, a rigid electrode 214 on a same plane and a second pressure sensing diaphragm 2161 on a same plane, the first pressure sensing unit 2101 further comprising a first mass 2162 on a first surface of the second pressure sensing diaphragm, a third mass 2122 on a second surface of the first pressure sensing diaphragm and a first cavity 2181 between the second pressure sensing diaphragm and the first pressure sensing diaphragm, the second pressure sensing unit 2102 further comprising a second mass 2163 on a first surface of the second pressure sensing diaphragm, a fourth mass 2123 on a second surface of the first pressure sensing diaphragm and a second cavity 2182 between the second pressure sensing diaphragm;
A substrate 220, a first groove 221 and a second groove 222 are formed on the substrate 220, the first pressure sensing unit 2101 is bonded to the first groove 221, the first cavity 2181 is disposed 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 disposed corresponding to the second groove 222.
In one embodiment, the first plane in which the first pressure sensing diaphragm 2121 resides, the second plane in which the rigid electrode 214 resides, and the third plane in which the second pressure sensing diaphragm 2161 resides are parallel or nearly parallel (e.g., less than 5 °).
In one embodiment, the first cavity 2181 communicates with the first recess 221 to form a first space region, and the second cavity 2182 communicates with the second recess 222 to form a second space region, where 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 (for example, the air pressure is less than 0.1 MPa) near vacuum.
Illustratively, a connecting post 217 is further formed between the first pressure sensing diaphragm 2121 and the second pressure sensing diaphragm 2161, a first end of the connecting post 217 is connected to the first surface of the first pressure sensing diaphragm 2121, and a second end of the connecting post 217 is connected to the second surface of the second pressure sensing diaphragm 2161, so as to mechanically couple the first pressure sensing diaphragm 2121 and the second pressure sensing diaphragm 2161, so that the deformations of the first pressure sensing diaphragm 2121 and the second pressure sensing diaphragm 2161 are consistent. The connection post 217 passes through and is not in contact with the rigid electrode 214, and the rigid electrode 214 is mechanically decoupled from the first pressure sensing diaphragm 2121 and the second pressure sensing diaphragm 2161, so that deformation of the first pressure sensing diaphragm 2121 and the second pressure sensing diaphragm 2161 is independent of the rigid electrode 214.
Illustratively, the first pressure sensing diaphragm 2121 of the first pressure sensing unit 2101 and the rigid electrode 214 form a first pressure sensing capacitor, the second pressure sensing diaphragm 2161 of the first pressure sensing unit 2101 and the rigid electrode 214 form a second pressure sensing capacitor, the first pressure sensing diaphragm 2121 of the second pressure sensing unit 2102 and the rigid electrode 214 form a third pressure sensing capacitor, and the second pressure sensing diaphragm 2161 of the second pressure sensing unit 2102 and the rigid electrode 214 form a fourth pressure sensing capacitor, and the first pressure sensing capacitor, the second pressure sensing capacitor, the third pressure sensing capacitor and the fourth pressure sensing capacitor are connected by a wheatstone bridge, as shown in fig. 4.
According to the MEMS differential capacitive pressure sensor and the manufacturing method thereof, the differential capacitive pressure sensor is manufactured by bonding the pressure sensing structure with the first pressure sensing unit and the second pressure sensing unit to the substrate with the first groove and the second groove, so that the manufacturing process is simplified, the production cost is reduced, and the sensitivity of the differential capacitive pressure sensor is increased and the nonlinearity is reduced by arranging the mass blocks on the first pressure sensing diaphragm and the second pressure sensing diaphragm of the first pressure sensing unit and the second pressure sensing unit respectively, so that the performance of the sensor is improved.
The present invention has been illustrated by the above-described embodiments, but it should be understood that the above-described embodiments are for purposes of illustration and description only and are not intended to limit the invention to the embodiments described. In addition, it will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that many variations and modifications are possible in light of the teachings of the invention, which variations and modifications are within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (10)
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