MEMS pressure sensor and pressure detection device

Abstract

The utility model relates to the technical field of sensors, in particular to an MEMS pressure sensor and a pressure detection device. The MEMS pressure sensor comprises a first substrate, a second substrate and a cavity, the first substrate and the second substrate are stacked, and the cavity is sealed between the first substrate and the second substrate. Wherein the second substrate comprises a sensitive film corresponding to the cavity, and an island beam is arranged on one side, facing the first substrate, of the sensitive film; a gap is formed between the first substrate and the island beam, and the gap can allow the island beam to move towards the first substrate when the sensitive film deforms and limit the moving distance of the island beam. According to the scheme, the sensitive film can be prevented from being damaged due to excessive deformation, and the reliability of the sensor can be improved.

Description

Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a MEMS pressure sensor and a pressure detection device. Background Art

[0002] MEMS pressure sensors usually use Si thin films as sensitive membranes for sensing pressure. In existing MEMS pressure sensors, the thinner the sensitive membrane, the higher the sensitivity. However, although thinning the sensitive membrane can increase sensitivity, the mechanical properties of the sensitive membrane will also decrease, which will lead to poor reliability of the sensor. Utility Model Content

[0003] The embodiments of the present application at least provide a MEMS pressure sensor and a pressure detection device, which can prevent the sensitive membrane from being damaged due to excessive deformation, and are beneficial to improving the reliability of the sensor.

[0004] In a first aspect, an embodiment of the present application provides a MEMS pressure sensor, including:

[0005] A first substrate and a second substrate stacked together, and a cavity enclosed between the first substrate and the second substrate;

[0006] Wherein, the second substrate comprises a sensitive film corresponding to the cavity, and an island beam is arranged on a side of the sensitive film facing the first substrate;

[0007] There is a gap between the first substrate and the island beam, and the gap can allow the island beam to move toward the first substrate when the sensitive film is deformed and limit the moving distance of the island beam.

[0008] In the above technical solution, by setting an island beam on the sensitive membrane, the sensitivity of the sensitive membrane can be improved. Specifically, when the chip of the island membrane structure is under pressure, the stress will be highly concentrated in the groove area between the island and the edge, so that the sensitivity is significantly improved, and it can also achieve overvoltage protection and nonlinear internal compensation. In addition, since the interval between the first substrate and the island beam can limit the moving distance of the island beam, the interval between the first substrate and the island beam can also limit the deformation of the sensitive membrane. Specifically, when the external pressure exceeds the detection range of the sensor, the sensitive membrane will deform so that the island beam moves toward the direction close to the first substrate and presses against the first substrate, that is, a limiting effect can be formed between the island beam and the first substrate to limit the maximum deformation of the sensitive membrane. In this way, the deformation and damage of the sensitive membrane when the pressure is too large can be avoided, which is conducive to improving the reliability of the sensor.

[0009] In an optional implementation, a first groove is provided on a side of the first substrate facing the second substrate.

[0010] In an optional embodiment, the second substrate further includes a connecting portion, which is located on a side of the sensitive film facing the first substrate and is used to connect to the first substrate, and a height of the connecting portion is greater than a height of the island beam.

[0011] In an optional implementation, a second groove is provided on a side of the second substrate facing the first substrate, and the island beam is located in the second groove.

[0012] In an optional embodiment, there are multiple island beams, and the multiple island beams are arranged parallel to each other.

[0013] In an optional implementation, a varistor is provided on a side of the sensitive film facing away from the first substrate.

[0014] In an optional implementation, a metal wire is disposed on a side of the second substrate facing away from the first substrate, and the metal wire is connected to the varistor to form a Wheatstone bridge.

[0015] In an optional embodiment, a passivation layer is provided on a side of the second substrate facing away from the first substrate, the passivation layer covers the varistor and the metal wire, and the passivation layer is provided with wiring holes, and the wiring holes are used to connect the metal wire to an external circuit.

[0016] In an optional implementation, an insulating layer is provided on a side of the second substrate facing away from the first substrate, and the varistor is provided on a side of the insulating layer facing away from the second substrate.

[0017] In a second aspect, an embodiment of the present application further provides a pressure detection device, comprising the MEMS pressure sensor described in the second aspect.

[0018] In the above technical solution, by setting an island beam on the sensitive membrane, the sensitivity of the sensitive membrane can be improved. Specifically, when the chip of the island membrane structure is under pressure, the stress will be highly concentrated in the groove area between the island and the edge, so that the sensitivity is significantly improved, and it can also achieve overvoltage protection and nonlinear internal compensation. In addition, since the interval between the first substrate and the island beam can limit the moving distance of the island beam, the interval between the first substrate and the island beam can also limit the deformation of the sensitive membrane. Specifically, when the external pressure exceeds the detection range of the sensor, the sensitive membrane will deform so that the island beam moves toward the direction close to the first substrate and presses against the first substrate, that is, a limiting effect can be formed between the island beam and the first substrate to limit the maximum deformation of the sensitive membrane. In this way, the deformation and damage of the sensitive membrane when the pressure is too large can be avoided, which is conducive to improving the reliability of the sensor.

[0019] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. The drawings herein are incorporated into the specification and constitute a part of the specification. These drawings illustrate embodiments consistent with the present application and are used together with the specification to illustrate the technical solutions of the present application. It should be understood that the following drawings only illustrate certain embodiments of the present application and should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can also be obtained based on these drawings without creative work.

[0021] Figures 1 to 10 The present invention shows a preparation process of a MEMS pressure sensor provided in an embodiment of the present application;

[0022] Figure numerals: 1, first substrate; 11, first groove; 2, second substrate; 21, bottom silicon layer; 211, sensitive film; 212, island beam; 213, connecting part; 214, second groove; 22, top silicon layer; 221, varistor; 23, buried oxide layer; 3, cavity; 4, oxide film; 41, connecting hole; 54, metal wire; 6, passivation layer; 61, wiring hole. DETAILED DESCRIPTION

[0023] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0024] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limitations on the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0025] The term "first" or "second" in the specification and claims of this application may include one or more of the features explicitly or implicitly. In the description of this application, unless otherwise specified, "plurality" means two or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally means that the objects connected before and after are in an "or" relationship.

[0026] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0027] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0028] The embodiment of the present application provides a MEMS pressure sensor, which can prevent the sensitive membrane from being deformed and damaged when the pressure is too high, and is conducive to improving the reliability of the sensor.

[0029] refer to Fig.10 The MEMS pressure sensor provided in the embodiment of the present application includes a first substrate and a second substrate stacked together, and a cavity enclosed between the first substrate and the second substrate. The second substrate includes a sensitive film corresponding to the cavity, and an island beam is provided on the side of the sensitive film facing the first substrate. There is a gap between the first substrate and the island beam, and the gap allows the island beam to move toward the direction close to the first substrate when the sensitive film is deformed and limits the moving distance of the island beam.

[0030] In the above technical solution, by setting an island beam on the sensitive membrane, the sensitivity of the sensitive membrane can be improved. Specifically, when the sensitive membrane is compressed, the stress will be highly concentrated in the groove area between the island beam and the edge, so that the sensitivity is significantly improved, and it can also achieve overvoltage protection and nonlinear internal compensation.

[0031] In addition, since the spacing between the first substrate and the island beam can limit the moving distance of the island beam, the spacing between the first substrate and the island beam can also limit the deformation of the sensitive film. Specifically, when the external pressure exceeds the detection range of the sensor, the sensitive film will deform so that the island beam moves toward the first substrate and presses against the first substrate, that is, a limiting effect can be formed between the island beam and the first substrate to limit the maximum deformation of the sensitive film. In this way, the sensitive film can be prevented from being deformed and damaged when the pressure is too large, which is conducive to improving the reliability of the sensor.

[0032] Optionally, the first substrate may include single crystal silicon or polycrystalline silicon. Figure 1 As shown, in this embodiment, the first substrate is shown to be single crystal silicon.

[0033] Optionally, the second substrate may include a single crystal silicon or SOI substrate. Figure 3 As shown, in this embodiment, the second substrate is a SOI substrate. In a specific configuration, the side of the second substrate facing the first substrate may be the bottom silicon layer of the SOI substrate, and the side of the second substrate facing away from the first substrate may be the top silicon layer of the SOI substrate.

[0034] Optionally, the sensitive film and the island beam can be formed by thinning a part of the bottom silicon layer of the SOI substrate. Specifically, the bottom silicon layer of the SOI substrate (the side of the second substrate facing the first substrate) is thinned locally to form a second groove and an island beam located in the second groove, such as Figure 5 It should be understood that the second groove makes the second substrate partially thinned, and the thinned area can be used as a sensitive film of the second substrate.

[0035] Optionally, the number of island beams can be multiple. Figure 5 As shown, in this embodiment, the number of island beams is two, and the two island beams are arranged parallel to each other. It should be understood that the number of island beams can be more or less, and this embodiment of the application does not make specific limitations on this.

[0036] Optionally, in order to provide a gap between the island beam and the first substrate, a groove may be provided on the first substrate. For example, a first groove is provided on a side of the first substrate facing the second substrate, such as Figure 2 That is, the first groove allows a gap between the island beam and the first substrate, and the depth of the first groove is the gap between the island beam and the first substrate. It should be understood that the first groove can also form a cavity together with the second groove.

[0037] Optionally, in order to provide a gap between the island beam and the first substrate, a connecting portion with a height higher than the island beam may be provided on the second substrate. For example, the second substrate further includes a connecting portion, which is located on the side of the sensitive film facing the first substrate and is used to connect with the first substrate, and the height of the connecting portion is greater than the height of the island beam. That is, when the second substrate is connected to the first substrate, the second substrate is specifically connected to the first substrate through the connecting portion, and the height difference between the connecting portion and the island beam is the gap between the island beam and the first substrate. It should be understood that the connecting portion may be the peripheral portion of the second groove, and the height difference between the connecting portion and the island beam may be achieved by grinding.

[0038] It should be noted that the direction of the above height is consistent with the direction in which the island beam moves toward the first substrate.

[0039] refer to Fig.10 Optionally, in order to detect pressure, a varistor can be set on the sensitive film. In the specific setting, the varistor can be set on the side of the sensitive film away from the first substrate, and when the second substrate adopts an SOI substrate, the varistor can be formed by doping and etching the top silicon layer of the SOI substrate. In addition, the varistor can be set in the thinned area of ​​the sensitive film, that is, the varistor can be set in a staggered manner with the island beam.

[0040] In practical applications, there may be more than one varistor, for example, there may be four varistors, two of which are located on both sides of one island beam, and the other two varistors are located on both sides of another island beam.

[0041] Furthermore, the varistors may form a Wheatstone bridge. For example, a metal line may be provided on the side of the second substrate facing away from the first substrate, and four varistors are interconnected by the metal line to form a Wheatstone bridge, such as Fig. 9 and Fig.10 shown.

[0042] refer to Fig.10 Optionally, a passivation layer may be provided on the side of the second substrate facing away from the first substrate, and the passivation layer covers the varistor and the metal wire. In this way, leakage can be prevented and the anti-leakage effect of the sensor can be improved. In a specific setting, the passivation layer may be provided with a wiring hole, and the wiring hole is used to connect the metal wire to an external circuit.

[0043] refer to Fig.10 Optionally, an insulating layer may be provided on the side of the second substrate facing away from the first substrate, and the varistor is provided on the side of the insulating layer facing away from the second substrate. In this way, leakage can be prevented and the anti-leakage effect of the sensor can be improved. It should be understood that when the second substrate adopts an SOI substrate, the insulating layer may be a buried oxide layer of the SOI substrate.

[0044] The embodiment of the present application provides a method for preparing a MEMS pressure sensor, which is used to prepare the above-mentioned MEMS pressure sensor.

[0045] refer to Figures 1 to 10 The method for preparing a MEMS pressure sensor provided in an embodiment of the present application comprises:

[0046] Step S100, providing a first substrate and a second substrate, wherein the first substrate has a first surface and a second surface opposite to each other, and the second substrate has a third surface and a fourth surface opposite to each other;

[0047] Step S200, etching a first groove on a first surface of a first substrate;

[0048] Step S300, etching a second groove on the third surface of the second substrate to form a sensitive film and an island beam disposed on a side of the sensitive film;

[0049] Step S400: Bond the third surface of the second substrate and the first surface of the second substrate to form a cavity enclosed between the first substrate and the second substrate, wherein the island beam is located in the cavity, and there is a gap between the island beam and the first substrate, and the gap allows the island beam to move toward the direction close to the first substrate when the sensitive film is deformed and limits the moving distance of the island beam.

[0050] The MEMS pressure sensor prepared according to the above method can improve the sensitivity of the sensitive membrane by setting an island beam on the sensitive membrane. Specifically, when the chip of the island membrane structure is under pressure, the stress will be highly concentrated in the groove area between the island and the edge, so that the sensitivity is significantly improved, and it can also realize overvoltage protection and nonlinear internal compensation.

[0051] In addition, since the spacing between the first substrate and the island beam can limit the moving distance of the island beam, the spacing between the first substrate and the island beam can also limit the deformation of the sensitive film. Specifically, when the external pressure exceeds the detection range of the sensor, the sensitive film will deform so that the island beam moves toward the first substrate and presses against the first substrate, that is, a limiting effect can be formed between the island beam and the first substrate to limit the maximum deformation of the sensitive film. In this way, the sensitive film can be prevented from being deformed and damaged when the pressure is too large, which is conducive to improving the reliability of the sensor.

[0052] In step S100, the first substrate may include single crystal silicon or polycrystalline silicon. Figure 1 As shown, in this embodiment, the first substrate is shown to be single crystal silicon.

[0053] In step S100, the second substrate may include a single crystal silicon or an SOI substrate. Figure 3As shown, in this embodiment, the second substrate is shown to be an SOI substrate. In a specific configuration, the third surface of the second substrate can be the bottom silicon layer of the SOI substrate, and the fourth surface of the second substrate can be the top silicon layer of the SOI substrate.

[0054] In step S200, the first surface of the first substrate is etched by dry etching or wet etching.

[0055] In step S300, the third surface of the second substrate is etched by dry etching, so that the size and boundary of the sensitive film can be accurately controlled, which is beneficial to improving the performance and yield of the chip.

[0056] In step S300, a second groove is etched on the third surface of the second substrate, which is actually etching a part of the third surface of the second substrate (the bottom silicon layer of the SOI substrate).

[0057] It should be understood that the second groove causes the second substrate to be partially thinned, and the thinned area can serve as a sensitive film of the second substrate.

[0058] It should also be understood that the number of island beams can be multiple. For example, the number of island beams is two, and the two island beams are arranged parallel to each other. Figure 5 shown.

[0059] In step S300, before etching the second groove on the third surface of the second substrate, the method further includes: performing a thinning process on the third surface of the second substrate, such as Figure 4 In this way, the second substrate can be thinned to a desired thickness so that the height of the island beam meets the design requirements.

[0060] In some embodiments, in order to detect pressure, the method may further include: forming a piezoresistor on the fourth surface of the second substrate.

[0061] In a specific implementation, when the second substrate is an SOI substrate, the varistor can be formed by doping and etching the top silicon layer of the SOI substrate. In addition, the varistor can be set in the thinned area of ​​the sensitive film, that is, the varistor can be staggered with the island beam.

[0062] In practical applications, there may be more than one varistor, for example, there may be four varistors, two of which are located on both sides of one island beam, and the other two varistors are located on both sides of another island beam.

[0063] Further, after forming the varistor on the fourth surface of the second substrate, the method may further include: forming a metal wire on the fourth surface of the second substrate, the metal wire and the varistor are connected to form a Wheatstone bridge, such as Fig. 9 and Fig.10shown.

[0064] In some embodiments, before forming the metal wire on the fourth surface of the second substrate, the method may further include: forming an oxide film on the fourth surface of the second substrate, the oxide film covering the varistor, the metal wire being disposed on the oxide film and connected to the varistor through a connection hole on the oxide film, such as Figure 8 shown.

[0065] In some embodiments, after forming the metal line on the fourth surface of the second substrate, the method may further include: forming a passivation layer on the fourth surface of the second substrate, the passivation layer covering the varistor and the metal line, such as Fig.10 As shown. In this way, leakage can be prevented and the anti-leakage effect of the sensor can be improved. In the specific setting, the passivation layer can be provided with a wiring hole, and the wiring hole is used to connect the metal wire to the external circuit.

[0066] In some embodiments, before forming the varistor on the fourth surface of the second substrate, the method may further include: forming an insulating layer on the fourth surface of the second substrate, and the varistor is arranged on the side of the insulating layer away from the second substrate. In this way, leakage can be prevented and the leakage prevention effect of the sensor is improved. It should be understood that when the second substrate adopts an SOI substrate, the insulating layer can be a buried oxide layer of the SOI substrate.

[0067] An embodiment of the present application also provides a pressure detection device, including the MEMS pressure sensor of the second aspect.

[0068] The pressure detection device of the embodiment of the present application, wherein the MEMS pressure sensor can improve the sensitivity of the sensitive membrane by setting an island beam on the sensitive membrane. Specifically, when the chip of the island membrane structure is under pressure, the stress will be highly concentrated in the groove area between the island and the edge, thereby significantly improving the sensitivity, and it can also realize overpressure protection and nonlinear internal compensation.

[0069] In addition, since the spacing between the first substrate and the island beam can limit the moving distance of the island beam, the spacing between the first substrate and the island beam can also limit the deformation of the sensitive film. Specifically, when the external pressure exceeds the detection range of the sensor, the sensitive film will deform so that the island beam moves toward the first substrate and presses against the first substrate, that is, a limiting effect can be formed between the island beam and the first substrate to limit the maximum deformation of the sensitive film. In this way, the sensitive film can be prevented from being deformed and damaged when the pressure is too large, which is conducive to improving the reliability of the sensor.

[0070] In some embodiments, the pressure detection device further comprises a processor, and the processor is electrically connected to the MEMS pressure sensor. In practical applications, the processor can process the electrical signal to obtain the pressure exerted on the sensitive membrane.

[0071] In some embodiments, the pressure detection device further comprises a communication module, which is electrically connected to the MEMS pressure sensor. In practical applications, the communication module can send an electrical signal to a terminal so that the terminal processes the electrical signal and obtains the pressure on the sensitive membrane.

[0072] One or more embodiments of this specification are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of this specification should be included in the scope of protection of this application.

[0073] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A MEMS pressure sensor, characterized in that: include: A first substrate and a second substrate stacked together, and a cavity enclosed between the first substrate and the second substrate; Wherein, the second substrate comprises a sensitive film corresponding to the cavity, and an island beam is arranged on a side of the sensitive film facing the first substrate; There is a gap between the first substrate and the island beam, and the gap can allow the island beam to move toward the first substrate when the sensitive film is deformed and limit the moving distance of the island beam.

2. The MEMS pressure sensor according to claim 1, characterized in that: A first groove is provided on a side of the first substrate facing the second substrate.

3. The MEMS pressure sensor according to claim 1, characterized in that: The second substrate further includes a connecting portion, which is located on a side of the sensitive film facing the first substrate and is used to connect with the first substrate, and a height of the connecting portion is greater than a height of the island beam.

4. The MEMS pressure sensor according to claim 1, characterized in that: A second groove is provided on a side of the second substrate facing the first substrate, and the island beam is located in the second groove.

5. The MEMS pressure sensor according to claim 4, characterized in that: There are multiple island beams, and the multiple island beams are arranged parallel to each other.

6. The MEMS pressure sensor according to claim 1, characterized in that: A varistor is arranged on the side of the sensitive film facing away from the first substrate.

7. The MEMS pressure sensor according to claim 6, characterized in that: A metal wire is disposed on a side of the second substrate facing away from the first substrate, and the metal wire is connected to the varistor to form a Wheatstone bridge.

8. The MEMS pressure sensor according to claim 7, characterized in that: A passivation layer is provided on a side of the second substrate facing away from the first substrate, the passivation layer covers the varistor and the metal wire, and the passivation layer is provided with a wiring hole, and the wiring hole is used to connect the metal wire to an external circuit.

9. The MEMS pressure sensor according to claim 6, characterized in that: An insulating layer is provided on a side of the second substrate facing away from the first substrate, and the varistor is provided on a side of the insulating layer facing away from the second substrate.

10. A pressure detection device, characterized in that: A MEMS pressure sensor comprising any one of claims 1-9.

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