A MEMS pressure sensor, a manufacturing method thereof and an electronic device

Abstract

The application provides a MEMS pressure sensor and a preparation method and an electronic device thereof, and the method comprises the following steps: providing a first substrate and a second substrate, the first substrate comprises a first base layer, a first insulating layer and a first sensitive film layer, the first sensitive film layer is provided with a first pressure-sensitive resistor, the second substrate comprises a second base layer, a second insulating layer and a second sensitive film layer, and a cavity is formed in the second sensitive film layer; the second substrate is combined with the first substrate; the second substrate is subjected to a thinning treatment; a second pressure-sensitive resistor is formed in the second sensitive film layer; and the first substrate is etched to form a back cavity and expose the first sensitive film layer. The method integrates sensitive film layers with different ranges into a single chip, reduces the production cost, and promotes the application of a multi-range MEMS pressure sensor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a MEMS pressure sensor, a preparation method thereof and an electronic device. BACKGROUND

[0002] The MEMS pressure sensor is a frontier research field developed on the basis of the MEMS process, which is suitable for harsh environments such as high impact, high overload, conduction, corrosion and radiation, and is widely used in the fields of aerospace, electronics, industry and the like.

[0003] The MEMS pressure sensor is a MEMS device capable of sensing a pressure signal and converting the pressure signal into an electrical signal, such as Figure 1 As shown in the figure, the conventional MEMS pressure sensor includes a substrate layer 100, an insulating layer 101, a sensitive film layer 102, a wire structure 103, a dielectric layer 104, a cavity 105, a pad 106, a conductive contact 107, a piezoresistor 108 and a back cavity 109. However, the MEMS pressure sensor can only realize a single fixed range application, which is limited in many application scenarios requiring multiple ranges. SUMMARY

[0004] A series of simplified concepts are introduced in the summary section, which will be further described in detail in the specific embodiment section. The summary section of the present application does not mean to attempt to limit the key features and necessary technical features of the claimed technical solution, nor to attempt to determine the protection scope of the claimed technical solution.

[0005] In view of the existing problems, the present application provides a preparation method of a MEMS pressure sensor, comprising:

[0006] providing a first substrate and a second substrate, the first substrate comprising a first substrate layer, a first insulating layer and a first sensitive film layer stacked in sequence, a plurality of first piezoresistors being arranged on the first sensitive film layer, the second substrate comprising a second substrate layer, a second insulating layer and a second sensitive film layer stacked in sequence, a cavity being formed in the second sensitive film layer;

[0007] joining one side of the second substrate with the cavity to one side of the first sensitive film layer of the first substrate;

[0008] thinning the second substrate to expose the second sensitive film layer;

[0009] forming a plurality of second piezoresistors on the second sensitive film layer corresponding to the cavity;

[0010] etching the first substrate layer and the first insulating layer to form a back cavity and expose the first sensitive film layer, a plurality of the first pressure sensitive resistors corresponding to the back cavity, wherein the second sensitive film layer corresponding to the cavity has a different thickness from the first sensitive film layer corresponding to the back cavity.

[0011] Exemplarily, before the side of the second substrate formed with the cavity is bonded with the side of the first sensitive film layer of the first substrate, a first dielectric layer is covered on the first sensitive film layer and the first pressure sensitive resistors, and a first conductive structure electrically connected with the first pressure sensitive resistors is formed in the first dielectric layer, wherein the method for forming the first dielectric layer and the first conductive structure comprises:

[0012] covering a first dielectric material layer on the first sensitive film layer;

[0013] forming a first contact hole penetrating through the first dielectric material layer, and filling metal in the first contact hole to form a first conductive contact, wherein the first conductive contact is electrically connected with the first pressure sensitive resistor;

[0014] forming a first pad on the first dielectric material layer, the first pad being electrically connected with the first conductive contact, wherein the first conductive structure comprises the first conductive contact and the first pad electrically connected with the first conductive contact;

[0015] forming a second dielectric material layer to cover the first dielectric material layer and the first pad, and planarizing the second dielectric material layer, wherein the first dielectric layer comprises the first dielectric material layer and the second dielectric material layer.

[0016] Exemplarily, before etching the first substrate layer and the first insulating layer, the method further comprises:

[0017] forming a second dielectric layer to cover the second sensitive film layer and the second pressure sensitive resistor;

[0018] forming a second conductive structure electrically connected with the second pressure sensitive resistor, the second conductive structure penetrating through the second dielectric layer and covering part of the surface of the second dielectric layer;

[0019] forming a via hole on the outside of the cavity, and forming a redistribution layer on the bottom and sidewall of the via hole and part of the surface of the second dielectric layer, the redistribution layer being electrically connected with the first conductive structure, the bottom of the via hole exposing the first pad, and the redistribution layer being in contact with the surface of the first pad to be electrically connected.

[0020] Exemplarily, the thinning process comprises the steps of sequentially removing the second substrate layer and the second insulating layer.

[0021] Exemplarily, a second conductive structure electrically connected with the second piezoresistors is formed, the second conductive structure penetrates through the second dielectric layer and covers part of the surface of the second dielectric layer, and the second conductive structure comprises:

[0022] The second dielectric layer is etched to form a second contact hole, and the second contact hole is filled with metal to form a second conductive contact, and the second conductive contact is electrically connected with the second piezoresistors;

[0023] Second pads are formed on the second dielectric layer, and each of the second pads is electrically connected with a corresponding second piezoresistor through the second conductive contact, and the second conductive structure comprises the second conductive contact and the second pads electrically connected with the second conductive contact.

[0024] Exemplarily, a first conductive line structure electrically connected with the first piezoresistors is further formed in the first sensitive film layer, and the first conductive line structure electrically connects a plurality of the first piezoresistors to form a Wheatstone bridge component.

[0025] Exemplarily, a second conductive line structure electrically connected with the second piezoresistors is further formed in the second sensitive film layer, and the second conductive line structure electrically connects a plurality of the second piezoresistors to form a Wheatstone bridge component.

[0026] Another aspect of the present application provides a MEMS pressure sensor, comprising:

[0027] A first substrate comprises a first base layer, a first insulating layer and a first sensitive film layer, and a plurality of first piezoresistors are arranged in the first sensitive film layer;

[0028] A second sensitive film layer, a cavity is formed in the second sensitive film layer, one side of the second sensitive film layer in which the cavity is formed is connected with one side of the first sensitive film layer of the first substrate, and a plurality of second piezoresistors are formed in a part of the second sensitive film layer corresponding to the cavity;

[0029] A back cavity is formed in the first substrate, and penetrates through the first base layer and the first insulating layer and exposes the first sensitive film layer, wherein the second sensitive film layer corresponding to the cavity has a different thickness from the first sensitive film layer corresponding to the back cavity.

[0030] Exemplarily, the MEMS pressure sensor further comprises:

[0031] A first dielectric layer covers the first sensitive film layer and the first piezoresistors, and the

[0032] The first dielectric layer comprises a first dielectric material layer and a second dielectric material layer which are stacked in sequence.

[0033] a second dielectric layer covering the second sensitive film layer and the second piezoresistor;

[0034] a first conductive structure, the first conductive structure comprising a first conductive contact and a first pad, the first conductive contact being located in the first dielectric material layer, the first pad being located in the second dielectric material layer, and the first pad electrically connecting the first conductive contact;

[0035] a second conductive structure, the second conductive structure comprising a second conductive contact and a second pad, the second conductive contact being located in the second dielectric layer, the second pad being located on the second dielectric layer, and the second pad electrically connecting the second conductive contact;

[0036] a first wire structure located in the first sensitive film layer, the first wire structure electrically connecting a plurality of the first piezoresistors to form a Wheatstone bridge component, wherein the first conductive contact electrically connects the first wire structure;

[0037] a second wire structure located in the second sensitive film layer, the second wire structure electrically connecting a plurality of the second piezoresistors to form a Wheatstone bridge component, the second conductive contact electrically connecting the second wire structure;

[0038] a via hole located outside the cavity, the via hole exposing the first pad at the bottom thereof;

[0039] a re-wiring layer covering the bottom and sidewall of the via hole, and part of the surface of the second dielectric layer, and electrically connecting the first piezoresistor.

[0040] In still another aspect, the present application provides an electronic device comprising the MEMS pressure sensor as described above.

[0041] The MEMS pressure sensor and the manufacturing method thereof according to the embodiments of the present application integrate pressure sensors of different ranges into a single chip, realize multi-range measurement, reduce production cost, and promote the application of multi-range MEMS pressure sensors. BRIEF DESCRIPTION OF DRAWINGS

[0042] The following drawings for the present application are hereby incorporated as part of the present application for the purpose of understanding the present application. The drawings in the present application and the description thereof serve to explain the principles of the present application.

[0043] In the drawings:

[0044] Figure 1 A cross-sectional schematic view of a device obtained by implementing a prior art manufacturing method of a MEMS pressure sensor is shown;

[0045] Figure 2 A flow chart of a method of fabricating a MEMS pressure sensor according to an embodiment of the present application is shown;

[0046] Figures 3A-3L Cross-sectional views of a device obtained by sequentially performing the method of fabricating a MEMS pressure sensor according to an embodiment of the present application are shown. DETAILED DESCRIPTION

[0047] The present application will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the application are shown. This application may, however, be embodied in many different 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 application to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions are exaggerated for clarity. Like reference numerals may

[0048] It will be understood that when an element or layer is referred to as being "on" or "adjacent" or "connected" or "coupled" to another element or layer, it can be directly on, adjacent, connected or coupled to the other element or layer or one or more intervening elements or layers can be present. In contrast, when an element is referred to as being "directly on," "directly adjacent," "directly connected" 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. can 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 application.

[0049] Spatially relative terms, such as "beneath", "below", "lower", "under", "above", "upper" and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) 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 or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" or "over" the other elements or features. Thus, the exemplary term "below" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0050] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. 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 one or more of the associated listed items.

[0051] Embodiments of the application are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the application. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, embodiments of the application should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and / or a gradient of implant concentration at its edges rather than a binary change between implanted and non-implanted regions. Similarly, a buried region formed by implantation can result in some implantation in a region between the buried region and a surface through which the implantation occurs. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region of a device and are not intended to limit the scope of the application.

[0052] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and / or the

[0053] For a thorough understanding of the application, reference should be made to the following detailed description, in conjunction with the accompanying drawings, in which:

[0054] Therefore, in view of the foregoing technical problems, the present application provides a preparation method of a MEMS pressure sensor, as shown in the accompanying drawings, which mainly comprises the following steps: Figure 2 The preparation method of the MEMS pressure sensor comprises the following steps:

[0055] Step S1: Provide a first substrate and a second substrate. The first substrate includes a first base layer, a first insulating layer and a first sensitive film layer stacked sequentially. A plurality of first varistors are disposed on the first sensitive film layer. The second substrate includes a second base layer, a second insulating layer and a second sensitive film layer stacked sequentially. A cavity is formed in the second sensitive film layer.

[0056] Step S2: Join the side of the second substrate where the cavity is formed with the side of the first substrate where the first dielectric layer is formed;

[0057] Step S3: Thin the second substrate to expose the second sensitive film layer;

[0058] Step S4: A plurality of second varistors are formed on the portion of the second sensitive film layer corresponding to the cavity;

[0059] Step S5: Etch the first substrate layer and the first insulating layer to form a back cavity and expose the first sensitive film layer. A plurality of first varistors correspond to the back cavity. The second sensitive film layer corresponding to the cavity has a different thickness than the first sensitive film layer corresponding to the back cavity.

[0060] The method for fabricating a MEMS pressure sensor of the present invention integrates sensitive film layers with different ranges onto a single chip, thereby achieving multi-range measurement, reducing production costs, and promoting the application of multi-range MEMS pressure sensors.

[0061] Example 1

[0062] Below, for reference Figures 2-3H The method for fabricating the MEMS pressure sensor of the present invention is described in detail, wherein, Figure 2 A flowchart illustrating a method for fabricating a MEMS pressure sensor according to a specific embodiment of the present invention is shown. Figures 3A-3H The diagram shows a cross-sectional view of the device obtained by sequentially implementing a method for fabricating a MEMS pressure sensor according to a specific embodiment of the present invention.

[0063] Exemplarily, the method for fabricating the MEMS pressure sensor of the present invention includes the following steps:

[0064] First, step S1 is performed, providing a first substrate and a second substrate. The first substrate includes a first base layer, a first insulating layer and a first sensitive film layer stacked sequentially. A plurality of first piezoresistors are disposed in the first sensitive film layer. The second substrate includes a second base layer, a second insulating layer and a second sensitive film layer stacked sequentially. A cavity is formed in the second sensitive film layer. Preferably, the cavity is a vacuum cavity. The MEMS pressure sensor is an absolute pressure sensor.

[0065] Specifically, as shown in Figure 3A A first substrate is provided, which includes a first base layer 300, a first insulating layer 301 and a first sensitive film layer 302.

[0066] The first substrate can be a silicon-on-insulator (SOI) substrate, which can be prepared in any suitable manner, such as an oxygen implantation isolation technique or a bonding technique, in some embodiments. The first substrate can also be any other suitable substrate.

[0067] The first insulating layer 301 can include any of a number of dielectric materials, non-limiting examples of which include oxides, nitrides and oxynitrides, particularly oxides, nitrides and oxynitrides of silicon, but not oxides, nitrides and oxynitrides of other elements. The first insulating layer 301 can be formed in any of a number of ways, non-limiting examples of which include ion implantation methods, thermal or plasma oxidation or nitridation methods, chemical vapor deposition methods and physical vapor deposition methods. The thickness of the first insulating layer 301 is typically 0.1 to 2 microns, but can be adjusted accordingly by those skilled in the art as needed in this embodiment.

[0068] The first sensitive film layer 302 is formed on the first insulating layer 301, which can optionally be a single-crystal silicon layer. The thickness of the sensitive film layer affects the range of the MEMS pressure sensor, and in general, the thinner the sensitive film layer, the smaller the range of pressure measurement; the thicker the sensitive film layer, the greater the range of pressure measurement. In this embodiment, those skilled in the art will understand that the thickness of the first sensitive film layer 302 should be selected as appropriate according to actual needs.

[0069] In one example, as shown in Figure 3A A plurality of first wire structures 303 and a plurality of first piezoresistors 304 are formed in the first sensitive film layer 302 by ion implantation, or the first wire structures can be formed in any other suitable manner, such as by depositing a metal to form the first wire structures 303.

[0070] In one embodiment, four first piezoresistors 304 can be formed in the first sensitive film layer 302. The four first piezoresistors 304 can be distributed respectively at the center of the four ends of the first sensitive film layer 302, with adjacent two first piezoresistors 304 perpendicular to each other and opposite two first piezoresistors 304 parallel to each other. Alternatively, other suitable arrangements can also be used.

[0071] In one example, as shown in Figure 3AAs shown, multiple first conductor structures 303 electrically connect multiple first varistors 304 to form a Wheatstone bridge component. When the first sensitive film layer 302 deforms due to pressure changes, the resistance values ​​of the multiple first varistors 304 located in the first sensitive film layer 302 also change. The differential output of the Wheatstone bridge becomes a non-zero value, that is, the output voltage value is proportional to the pressure, thereby realizing pressure measurement. Those skilled in the art should recognize that since the processes for forming the sensitive film layer, varistors, and conductor structures are very mature, their detailed processes will not be described here. Refer to conventional designs and process parameters in the art.

[0072] In one example, such as Figure 3B As shown, a first dielectric material layer 305 is formed on the first sensitive film layer 302. The first dielectric material layer 305 is etched to form a first contact hole, which penetrates the first dielectric material layer 305 and exposes a portion of the first conductive wire structure 303. The first dielectric material layer 305 may include any of several dielectric materials, and non-limiting examples include oxides, nitrides, and oxides of oxynitrides, especially oxides, nitrides, and oxides of silicon. In this embodiment, the first dielectric material layer 305 may be silicon dioxide.

[0073] In one example, such as Figure 3C As shown, metal is filled into the first contact hole to form a first conductive contact 306, and a first pad 307 is formed on the first dielectric material layer 305. The first pad 307 is electrically connected to the corresponding first varistor 304 through the first conductive contact 306 and the first wire structure 303, and the first pad 307 serves as the input and output port of the pressure sensor chip, connecting to the external circuit. The first conductive contact 306 and the first pad 307 together form the first conductive structure. Optionally, the material of the first pad 307 can be one or more metals such as aluminum, copper, gold, titanium, sodium, and platinum.

[0074] In some embodiments, the first conductor structure 303 may include a first lead-out portion and a second lead-out portion, wherein the first lead-out portion and the second lead-out portion are respectively located on both sides of the Wheatstone bridge component formed by the first varistor, for connecting the input terminal and the output terminal of the Wheatstone bridge component respectively, and the number of the first conductive structure may be two, which are respectively electrically connected to the first lead-out portion and the second lead-out portion.

[0075] In one example, the method of this application further includes: Figure 3DAs shown, a second dielectric material layer 308 is deposited, covering the first dielectric material layer 305 and the first pad 307. The second dielectric material layer 308 can be made of the same material as the first dielectric material layer 305 or a different material. In this embodiment, the second dielectric material layer 308 is made of silicon dioxide. The second dielectric material layer 308 is then planarized to obtain a flat surface, in preparation for subsequent processes. The first dielectric material layer 305 and the second dielectric material layer 308 together form a first dielectric layer.

[0076] In one example, as shown in FIG. 3B, a second substrate is provided, which includes a second base layer 309, a second insulating layer 310, and a second sensitive film layer 311. Figure 3E

[0077] In some embodiments, the second substrate can be a silicon-on-insulator (SOI) substrate. In some embodiments, the second substrate can be prepared in any suitable manner, such as an oxygen implantation isolation technique or a bonding technique. The second substrate can also be any other suitable substrate.

[0078] The second insulating layer 310 can include any of a number of dielectric materials, non-limiting examples of which include oxides, nitrides, and oxynitrides, particularly oxides, nitrides, and oxynitrides of silicon, but not oxides, nitrides, and oxynitrides of other elements. The second insulating layer 310 can be formed in any of a number of ways, non-limiting examples of which include ion implantation methods, thermal or plasma oxidation or nitridation methods, chemical vapor deposition methods, and physical vapor deposition methods. The thickness of the second insulating layer 310 is typically in the range of 0.1 to 2 micrometers, but can be adjusted accordingly by those skilled in the art as needed.

[0079] The second sensitive film layer 311 is formed on the second insulating layer 310. Optionally, the second sensitive film layer 311 is a single-crystal silicon layer. The second sensitive film layer 311 can have a different thickness or the same thickness as the first sensitive film layer 302. The thickness of the sensitive film layer affects the range of the MEMS pressure sensor. Generally, the thinner the sensitive film layer, the smaller the range of pressure measurement; the thicker the sensitive film layer, the larger the range of pressure measurement. In this embodiment, those skilled in the art will understand that the thickness of the second sensitive film layer 311 should be selected as appropriate according to actual needs.

[0080] In one example, as shown in FIG. 3B, a second substrate is provided, which includes a second base layer 309, a second insulating layer 310, and a second sensitive film layer 311. Figure 3E

[0081] ​​Subsequently, step S2 is performed to bond the side of the second substrate with the cavity to the side of the first sensitive film layer of the first substrate.

[0082] In one example, such as Figure 3F As shown, a bonding process is used to bond the side of the second substrate with the cavity to the side of the first sensitive film layer of the first substrate to form a single unit. In this embodiment, a first dielectric layer is also formed between the side of the second substrate with the cavity and the side of the first sensitive film layer of the first substrate, for indirect bonding. Alternatively, in some embodiments, the side of the second substrate with the cavity is directly bonded to the side of the first sensitive film layer of the first substrate. More specifically, a bonding process is used to bond the second sensitive film layer 311 to the second dielectric material layer 308 to form a single unit. Optionally, a bonding layer can be formed on the side of the second substrate with the cavity before the bonding process. The bonding layer can be made of silicon oxide, nitride, or oxynitride. After bonding, the second sensitive film layer 311 is located above the second dielectric material layer 308. Optionally, the bonding process can use one of the following bonding processes: low-temperature electrostatic bonding, anodic bonding, etc.

[0083] Subsequently, step S3 is performed to thin the second substrate to expose the second sensitive film layer.

[0084] Specifically, such as Figure 3G As shown, the second substrate is thinned to sequentially remove the second base layer and the second insulating layer, thereby exposing the second sensitive film layer 311. The thinning process can be performed using methods including, but not limited to, chemical mechanical polishing or etching processes.

[0085] Subsequently, step S4 is performed to form a plurality of second varistors on the portion of the second sensitive film layer corresponding to the cavity.

[0086] Specifically, such as Figure 3H As shown, multiple second wire structures 313 and multiple second varistors 314 are formed in the second sensitive film layer 311 by ion implantation.

[0087] In this embodiment, four second varistors 314 can be formed in the second sensitive film layer 311. Optionally, the four second varistors 314 are respectively distributed at the center of the four ends of the second sensitive film layer 311, with two adjacent second varistors 314 perpendicular to each other and two opposing second varistors 314 parallel to each other. Alternatively, other suitable arrangements may also be used.

[0088] In one example, such as Figure 3HAs shown, multiple second conductor structures 313 electrically connect multiple second piezoresistors 314 to form a Wheatstone bridge component. When the second sensitive membrane layer 311 deforms due to pressure changes, the resistance of the multiple second piezoresistors 314 located in the second sensitive membrane layer 311 also changes, and the differential output of the Wheatstone bridge becomes a non-zero value, that is, the output voltage value is proportional to the pressure, so as to realize pressure measurement.

[0089] In some embodiments, after forming a plurality of second varistors, the method further includes the following steps: forming a second dielectric layer covering the second sensitive film layer and the second varistor; forming a second conductive structure electrically connected to the second varistor, the second conductive structure penetrating the second dielectric layer and covering a portion of the surface of the second dielectric layer; forming a via on the outside of the cavity, and forming a redistribution layer on the bottom and sidewalls of the via and a portion of the surface of the second dielectric layer, the redistribution layer being electrically connected to the first conductive structure.

[0090] Specifically, such as Figure 3I As shown, a second dielectric layer 315 is formed on the second sensitive film layer 311. The second dielectric layer 315 may include any of several dielectric materials, including oxides, nitrides, and oxide oxynitrides, particularly oxides, nitrides, and oxide oxynitrides of silicon. In this embodiment, the second dielectric layer 315 may be silicon dioxide. Similarly, the second dielectric layer 315 may be formed using any of a variety of methods. Non-limiting examples include chemical vapor deposition and physical vapor deposition methods.

[0091] In one example, such as Figure 3I As shown, the second dielectric layer 315 is etched to form a second contact hole. The second contact hole penetrates the second dielectric layer 315 and exposes a portion of the second conductive structure 313, such as the first lead-out portion and the second lead-out portion of the second conductive structure 313. The first lead-out portion and the second lead-out portion can lead out the input terminal and the output terminal of the Wheatstone bridge component in the second sensitive film layer 311, respectively.

[0092] In one example, such as Figure 3JAs shown, the metal is filled in the second contact hole to form a second conductive contact 316, and a second pad 317 is formed on the second dielectric layer 315, the second pad 317 is electrically connected through the second conductive contact 316 and the second conductive wire structure 313, thereby through the second conductive wire structure 313 and the corresponding second piezoresistor 314. The second conductive contact 316 and the second pad 317 together constitute a second conductive structure, the second conductive structure penetrates through the second dielectric layer 315 and covers part of the surface of the second dielectric layer 315. The number of the second conductive structure can be multiple, for example, can be two, to lead out the input and output ends of the Wheatstone bridge components in the second sensitive film layer 311 respectively, and the second pad 317 can be used as the port of the input and output of the corresponding pressure sensor of the second sensitive film layer to connect with the external circuit.

[0093] In one example, as shown in FIG. 4, the second dielectric layer 315, the second sensitive film layer 311 and part of the first dielectric layer are etched to form a through hole 318, the through hole 318 penetrates through the second dielectric layer 315, the second sensitive film layer 311 and exposes part of the surface of the first pad 307. In this embodiment, the etching process can be selected as a deep reactive ion etching process. Figure 3K

[0094] Subsequently, a re-wiring layer 319 is formed on the side wall and bottom of the through hole 318 and part of the surface of the second dielectric layer 315, wherein the re-wiring layer 319 is in contact with the upper surface of the first pad 307 to electrically connect the first conductive structure.

[0095] Optionally, the method for forming the re-wiring layer 319 comprises:

[0096] Depositing a seed layer on the bottom and side wall of the through hole 318;

[0097] Forming the re-wiring layer 319 on the seed layer by electroplating.

[0098] Optionally, the seed layer can be grown by electroplating or electroless plating. In some embodiments, the seed layer can be formed by physical vapor deposition or suitable technology. It should be noted that the seed layer is a metal layer, which can include one or more metal layers. For example, the seed layer can include a first metal layer and a second metal layer located on the first metal layer, the first metal layer can be a titanium layer, and the second metal layer can be a copper layer. In some embodiments, the seed layer can also be selected from other suitable metals. In this embodiment, the re-wiring layer 319 can be multi-layered, and the multi-layered re-wiring layer 319 can be repeatedly formed by electroplating process.

[0099] The two re-wiring layers 319 located on both sides of the cavity can be used as the port of the input and output of the corresponding pressure sensor of the first sensitive film layer to connect with the external circuit respectively.

[0100] ​Finally, step S5 is performed to etch the first substrate layer and the first insulating layer to form a back cavity and expose the first sensitive film layer. A plurality of first varistors correspond to the back cavity, wherein the second sensitive film layer corresponding to the cavity has a different thickness than the first sensitive film layer corresponding to the back cavity.

[0101] Specifically, such as Figure 3L As shown, the first base layer 300 and the first insulating layer 301 are etched to form a back cavity 320, exposing a first sensitive film layer 302. To enable multi-range measurement, the second sensitive film layer 311 corresponding to the cavity 312 has a different thickness than the first sensitive film layer 302 corresponding to the back cavity 320. The thickness of the sensitive film layer affects the measurement range of the MEMS pressure sensor; generally, the thinner the sensitive film layer, the smaller the pressure measurement range; the thicker the sensitive film layer, the larger the pressure measurement range. In this embodiment, the thickness of the first sensitive film layer 302 corresponding to the back cavity 320 can be greater than the thickness of the second sensitive film layer 311 corresponding to the cavity 312, or the thickness of the second sensitive film layer 311 corresponding to the cavity 312 can be greater than the thickness of the first sensitive film layer 302 corresponding to the back cavity 320. The thickness of the first sensitive film layer 302 corresponding to the back cavity 320 can be adjusted by etching the first sensitive film layer 302 when forming the back cavity, or by thinning the first sensitive film layer 302 before forming the first varistor. Similarly, the thickness of the second sensitive film layer 311 corresponding to the cavity 312 can be adjusted by etching the second sensitive film layer 311 when forming the cavity, or by thinning the second sensitive film layer 311 before forming the second varistor.

[0102] By the above preparation method, a pressure sensor is formed on one side of the back cavity, and another pressure sensor is formed on the side away from the back cavity, and the two pressure sensors have different ranges. That is, on one side of the back cavity, the back cavity 320, the first sensitive film layer 302, the first piezoresistor 304, the first conductive structure, the rewiring layer 319, etc. constitute a first pressure sensor, and on the side away from the back cavity, the cavity 312, the second sensitive film layer 311, the second piezoresistor 314, the second conductive structure, etc. constitute a second pressure sensor. The first pressure sensor is used for back pressure sensing, that is, measuring the pressure from the side of the back cavity, below the first sensitive film layer 302; and the second pressure sensor is used for front pressure sensing, that is, measuring the pressure away from the side of the back cavity, above the second sensitive film layer 311. In this embodiment, the first pressure sensor and the second pressure sensor can only measure the pressure of the fluid, that is, when the fluid pressure acts on the MEMS pressure sensor chip, the first sensitive film layer 302 and / or the second sensitive film layer 311 are deformed, so that the first piezoresistor 304 and / or the second piezoresistor 314 change in resistance value due to the piezoresistive effect, and the pressure signal is converted into an electrical signal through the Wheatstone bridge, realizing multi-range measurement.

[0103] The key steps of the preparation method of the MEMS pressure sensor of the present application have been described so far. The complete preparation of the MEMS pressure sensor can also include other steps, which will not be described here. It is worth mentioning that the above step sequence can be adjusted without conflict.

[0104] In summary, the preparation method of the MEMS pressure sensor of the present application integrates sensitive film layers of different ranges into a single chip, realizes multi-range measurement, reduces production cost, and promotes the application of multi-range MEMS pressure sensors.

[0105] Embodiment Two

[0106] The present application also provides a MEMS pressure sensor prepared by the method of the above embodiment one, as shown in the figure, the MEMS pressure sensor of the present application comprises: Figure 3L The first substrate comprises a first base layer 300, a first insulating layer 301 and a first sensitive film layer 302, and a plurality of first piezoresistors 304 are arranged in the first sensitive film layer 302.

[0107] The first substrate comprises a first base layer 300, a first insulating layer 301 and a first sensitive film layer 302, and a plurality of first piezoresistors 304 are arranged in the first sensitive film layer 302.

[0108] a second sensitive film layer 311, in which a cavity 312 is formed, one side of the second sensitive film layer 311 in which the cavity 312 is formed is bonded to one side of the first sensitive film layer 302 of the first substrate, and a plurality of second pressure sensitive resistors 314 are formed in a region of the second sensitive film layer 311 corresponding to the cavity 312;

[0109] a back cavity 320 formed in the first substrate and penetrating through the first substrate layer 300 and the first insulating layer 301 and exposing the first sensitive film layer 302, wherein the second sensitive film layer 311 corresponding to the cavity 312 has a different thickness of the first sensitive film layer 302 corresponding to the back cavity 320, corresponding to different pressure sensing ranges respectively.

[0110] In one example, as shown in Figure 3L The first insulating layer 301 can include any of a number of dielectric materials, non-limiting examples of which include oxides, nitrides, and oxynitrides, particularly oxides, nitrides, and oxynitrides of silicon, but not oxides, nitrides, and oxynitrides of other elements. The first insulating layer 301 can be formed using any of a number of methods, non-limiting examples of which include ion implantation methods, thermal or plasma oxidation or nitridation methods, chemical vapor deposition methods, and physical vapor deposition methods. The thickness of the first insulating layer 301 is typically 0.1 micrometers to 2 micrometers, but can be adjusted accordingly by those skilled in the art according to actual needs in this embodiment.

[0111] In this embodiment, the first sensitive film layer 302 and the second sensitive film layer 311 can be single-crystal silicon layers.

[0112] Further, as shown in Figure 3L In some embodiments, the MEMS pressure sensor of the present application further comprises:

[0113] a first dielectric layer covering the first sensitive film layer 302 and the first pressure sensitive resistor 304, the first dielectric layer including a first dielectric material layer 305 and a second dielectric material layer 308 stacked in sequence; one side of the first substrate in which the cavity is formed is indirectly bonded to one side of the first sensitive film layer of the first substrate through the first dielectric layer;

[0114] a second dielectric layer 315 covering the second sensitive film layer 311 and the second pressure sensitive resistor 314;

[0115] a first conductive structure including a first conductive contact 306 and a first pad 307, the first conductive contact 306 being located in the first dielectric material layer 305, the first pad 307 being located in the second dielectric material layer 308, and the first pad 307 being electrically connected to the first conductive contact 306;

[0116] The second conductive structure includes a second conductive contact 316 and a second pad 317. The second conductive contact 316 is located in the second dielectric layer 315, the second pad is located on the second dielectric layer 315, and the second pad 317 is electrically connected to the second conductive contact 316.

[0117] The first conductor structure 303 is located in the first sensitive film layer 302. The first conductor structure 303 electrically connects a plurality of first varistors 304 to form a Wheatstone bridge component, wherein the first conductive contact is electrically connected to the first conductor structure.

[0118] The second wire structure 313 is located in the second sensitive film layer 311. The second wire structure 313 electrically connects a plurality of second varistors 314 to form a Wheatstone bridge component. The second conductive contact 316 is electrically connected to the second wire structure 313.

[0119] A through-hole 318 is located outside the cavity 312, and the bottom of the through-hole exposes the first pad.

[0120] A redistribution layer 319 covers the bottom and sidewalls of the via 318, as well as a portion of the surface of the second dielectric layer 315, and is electrically connected to the first varistor 304.

[0121] In one example, such as Figure 3L As shown, the first dielectric layer includes a first dielectric material layer 305 and a second dielectric material layer 308. The first dielectric material layer 305, the second dielectric material layer 308, and the second dielectric layer 315 can include any of several dielectric materials, with non-limiting examples including oxides, nitrides, and oxides of oxynitrides, particularly oxides, nitrides, and oxides of silicon. In this embodiment, the first and second dielectric layers can be selected as silicon dioxide.

[0122] like Figure 3L As shown, in this embodiment, the thickness of the first sensitive membrane layer 302 corresponding to the back cavity 320 may be greater than the thickness of the second sensitive membrane layer 311 corresponding to the cavity 312, or the thickness of the second sensitive membrane layer 311 corresponding to the cavity 312 may be greater than the thickness of the first sensitive membrane layer 302 corresponding to the back cavity 320, so as to integrate pressure sensors with different ranges onto a single chip.

[0123] That is, on the side of the back cavity, the back cavity 320, the first sensitive film layer 302, the first piezoresistor 304, the first conductive structure, the rewiring layer 319 and the like constitute the first pressure sensor, while on the side away from the back cavity, the cavity 312, the second sensitive film layer 311, the second piezoresistor 314, the second conductive structure and the like constitute the second pressure sensor, the first pressure sensor and the second pressure sensor have different ranges, for example, the range of the first pressure sensor is smaller than the range of the second pressure sensor, or the range of the second pressure sensor is smaller than the range of the first pressure sensor.

[0124] The structure of the MEMS pressure sensor of the present application is introduced so far, and other component structures can also be included for the complete device, which will not be described here.

[0125] The MEMS pressure sensor of the present application is formed with sensitive film layers of different ranges, realizing the integration of pressure sensors of different ranges on one chip, meeting the measurement requirements of multi-range pressure, reducing the production cost, and promoting the application of multi-range MEMS pressure sensors.

[0126] Embodiment Three

[0127] Another embodiment of the present application also provides an electronic device comprising the MEMS pressure sensor of embodiment two.

[0128] The electronic device of the present embodiment can be a mobile phone, a tablet computer, a notebook computer, a netbook, a game console, a television, a VCD, a DVD, a navigator, a camera, a video camera, a recording pen, an MP3, an MP4, a PSP, or any other electronic product or device, and can also be any intermediate product comprising the MEMS pressure sensor. The electronic device of the present embodiment has better performance due to the use of the above-mentioned MEMS pressure sensor.

[0129] Although a plurality of embodiments are described herein, it should be understood that various other modifications and embodiments can be conceived by those skilled in the art, which will fall within the spirit and scope of the disclosed concept. More particularly, various modifications and changes can be made in the arrangement and / or component parts of the subject matter within the scope of the present disclosure, the accompanying drawings, and the appended claims. In addition to the modifications and changes of the component parts and / or arrangement, the use of alternative ways is also an obvious choice for those skilled in the art.

Claims

1. A method of fabricating a MEMS pressure sensor, characterized by, The method comprises: providing a first substrate and a second substrate, the first substrate comprising a first base layer, a first insulating layer and a first sensitive film layer stacked in sequence, a plurality of first piezoresistors being arranged on the first sensitive film layer, the second substrate comprising a second base layer, a second insulating layer and a second sensitive film layer stacked in sequence, a cavity being formed in the second sensitive film layer; joining one side of the second substrate with the cavity to one side of the first sensitive film layer of the first substrate; performing a thinning process on the second substrate to expose the second sensitive film layer; forming a plurality of second piezoresistors on a portion of the second sensitive film layer corresponding to the cavity; etching the first base layer and the first insulating layer to form a back cavity and expose the first sensitive film layer, a plurality of the first piezoresistors corresponding to the back cavity, wherein the second sensitive film layer corresponding to the cavity has a different thickness from the first sensitive film layer corresponding to the back cavity.

2. The method of claim 1, wherein, Before the joining of one side of the second substrate with the cavity to one side of the first sensitive film layer of the first substrate, a first dielectric layer is covered on the first sensitive film layer and the first piezoresistors, a first conductive structure electrically connected to the first piezoresistors being formed in the first dielectric layer, wherein the method for forming the first dielectric layer and the first conductive structure comprises: covering a first dielectric material layer on the first sensitive film layer; forming a first contact hole penetrating through the first dielectric material layer and filling metal in the first contact hole to form a first conductive contact, wherein the first conductive contact is electrically connected to the first piezoresistor; forming a first pad on the first dielectric material layer, the first pad being electrically connected to the first conductive contact, wherein the first conductive structure comprises the first conductive contact and the first pad electrically connected to the first conductive contact; forming a second dielectric material layer to cover the first dielectric material layer and the first pad and planarizing the second dielectric material layer, wherein the first dielectric layer comprises the first dielectric material layer and the second dielectric material layer.

3. The method of claim 2, wherein, After forming a plurality of the second piezoresistors and before etching the first base layer and the first insulating layer, the method further comprises: forming a second dielectric layer to cover the second sensitive film layer and the second piezoresistor; forming a second conductive structure electrically connected to the second piezoresistor, the second conductive structure penetrating through the second dielectric layer and covering part of the surface of the second dielectric layer; forming a via hole on the outside of the cavity and forming a redistribution layer on the bottom and sidewall of the via hole and part of the surface of the second dielectric layer, the redistribution layer being electrically connected to the first conductive structure, the bottom of the via hole exposing the first pad, and the redistribution layer being in contact with the surface of the first pad to be electrically connected.

4. The method of claim 1, wherein, The thinning process comprises the steps of sequentially removing the second base layer and the second insulating layer.

5. The method of claim 3, wherein, forming a second conductive structure electrically connected with the second piezoresistors, the second conductive structure penetrating through the second dielectric layer and covering part of the surface of the second dielectric layer, comprising: etching the second dielectric layer to form a second contact hole, and filling the second contact hole with metal to form a second conductive contact electrically connected with the second piezoresistors; forming second pads on the second dielectric layer, each of the second pads being electrically connected with a corresponding second piezoresistor through the second conductive contact, wherein the second conductive structure comprises the second conductive contact and the second pads electrically connected with the second conductive contact.

6. The method of claim 1, wherein, The first sensitive film layer also has a first wire structure electrically connected with the first piezoresistors, and the first wire structure electrically connects a plurality of the first piezoresistors to form a Wheatstone bridge component.

7. The method of claim 1, wherein, The second sensitive film layer also has a second wire structure electrically connected with the second piezoresistors, and the second wire structure electrically connects a plurality of the second piezoresistors to form a Wheatstone bridge component.

8. A MEMS pressure sensor, characterized by, The MEMS pressure sensor comprises: a first substrate comprising a first base layer, a first insulating layer, and a first sensitive film layer, and a plurality of first piezoresistors disposed on the first sensitive film layer; a second sensitive film layer having a cavity formed therein, one side of the second sensitive film layer being joined to one side of the first sensitive film layer of the first substrate, and a plurality of second piezoresistors being formed in a portion of the second sensitive film layer corresponding to the cavity; a back cavity formed in the first substrate and penetrating through the first base layer and the first insulating layer to expose the first sensitive film layer, wherein the second sensitive film layer corresponding to the cavity has a different thickness from the first sensitive film layer corresponding to the back cavity, corresponding to different pressure sensing ranges, respectively.

9. The MEMS pressure sensor of claim 8, wherein, The MEMS pressure sensor further comprises: a first dielectric layer covering the first sensitive film layer and the first piezoresistors, the first dielectric layer comprising a first dielectric material layer and a second dielectric material layer stacked in sequence; a second dielectric layer covering the second sensitive film layer and the second piezoresistors; a first conductive structure comprising a first conductive contact and a first pad, the first conductive contact being located in the first dielectric material layer, and the first pad being located in the second dielectric material layer and electrically connected with the first conductive contact; a second conductive structure comprising a second conductive contact and a second pad, the second conductive contact being located in the second dielectric layer, and the second pad being located on the second dielectric layer and electrically connected with the second conductive contact; a first wire structure located in the first sensitive film layer, the first wire structure electrically connecting a plurality of the first piezoresistors to form a Wheatstone bridge component, wherein the first conductive contact is electrically connected with the first wire structure; A second conductive wire structure is located in the second sensitive film layer, and the second conductive wire structure electrically connects a plurality of the second piezoresistors to form a Wheatstone bridge component. The second conductive contact electrically connects the second conductive wire structure. A through hole is located outside the cavity, and the through hole exposes the first pad at the bottom. A rewiring layer covers the bottom and sidewall of the through hole, and part of the surface of the second dielectric layer, and electrically connects the first piezoresistor.

10. An electronic device, comprising: The electronic device comprises the MEMS pressure sensor of any one of claims 8-9.

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