A MEMS capacitive tactile pressure sensor and its preparation method

Abstract

The present invention proposes a MEMS capacitive tactile pressure sensor, comprising: a substrate; an insulating layer, arranged on the substrate; an electrode, arranged on the insulating layer; a dielectric layer, arranged on the insulating layer and covering the electrode; a tactile sensitive body, arranged on the dielectric layer; wherein the tactile sensitive body constitutes a movable electrode of the MEMS capacitive tactile pressure sensor. The MEMS capacitive tactile pressure sensor proposed in the present invention mainly relies on the area change between the capacitor electrodes to respond to the change of tactile pressure. Compared with the existing MEMS tactile pressure sensor that responds to the change of tactile pressure by changing the electrode spacing, it has the advantages of high linearity and high sensitivity. And the MEMS processing technology can be used for high-precision, high-consistency, low-cost, batch and miniaturized preparation.

Description

Technical Field

[0001] The present invention relates to the field of micro-electromechanical systems (MEMS), and in particular to a MEMS capacitive tactile pressure sensor and a preparation method thereof. Background Art

[0002] Tactile pressure sensor is a kind of sensor used by robots to imitate human tactile function. It is one of the most basic components in the field of bionics and has broad application prospects in the fields of robots, human-computer interaction, etc. Thanks to the miniaturization, high precision and mass production of MEMS technology, MEMS tactile pressure sensor has the advantages of high sensitivity, high reliability, high precision, miniaturization and low cost, and has broad development prospects. Common MEMS tactile pressure sensors include MEMS piezoresistive tactile pressure sensors and capacitive MEMS tactile pressure sensors. The advantage of MEMS piezoresistive tactile pressure sensor is high linearity, but because the piezoresistance coefficient and resistivity are easily affected by temperature, its environmental adaptability is poor. The advantage of common MEMS capacitive tactile pressure sensor is that it is less affected by ambient temperature, but it has disadvantages such as low sensitivity and poor linearity, and the corresponding interface circuit design is difficult. Summary of the invention

[0003] In order to solve some problems existing in the tactile pressure sensor in the art, the present invention proposes a MEMS capacitive tactile pressure sensor and a preparation method thereof, which has the advantages of simple structure and preparation, high sensitivity and good linearity.

[0004] Specifically, the technical solution proposed by the present invention is as follows:

[0005] A MEMS capacitive tactile pressure sensor, the MEMS capacitive tactile pressure sensor comprising:

[0006] substrate;

[0007] an insulating layer, the insulating layer being disposed on the substrate;

[0008] An electrode, wherein the electrode is disposed on the insulating layer;

[0009] a dielectric layer, the dielectric layer being disposed on the insulating layer and covering the electrode;

[0010] a touch sensitive body, the touch sensitive body being disposed on the dielectric layer;

[0011] The tactile sensitive body constitutes a movable electrode of the MEMS capacitive tactile pressure sensor.

[0012] Furthermore, the lower surface of the touch sensitive body in contact with the dielectric layer is arc-shaped.

[0013] Furthermore, the material of the touch sensitive body is an elastic conductive composite material.

[0014] Furthermore, the material of the touch sensitive body is PEDOT:PSS / PDMS.

[0015] Furthermore, the touch sensitive body is arranged opposite to the electrode.

[0016] Furthermore, the touch sensitive body has a height of 1 μm-100 μm.

[0017] Accordingly, the present invention also provides a method for preparing a MEMS capacitive tactile pressure sensor, comprising the following steps:

[0018] Select the substrate,

[0019] forming an insulating layer on the substrate;

[0020] forming an electrode on the insulating layer;

[0021] forming a dielectric layer on the substrate, wherein the dielectric layer covers the electrode;

[0022] forming a sacrificial layer on the dielectric layer;

[0023] etching the sacrificial layer to form a shape of the touch sensitive body;

[0024] forming an elastic conductive composite material on the upper surface of the sacrificial layer;

[0025] The sacrificial layer is removed to release the touch sensitive body.

[0026] Furthermore, the touch sensitive body is in an arc shape.

[0027] Furthermore, the sacrificial layer is an aluminum sacrificial layer.

[0028] Furthermore, the elastic conductive composite material is PEDOT:PSS / PDMS.

[0029] 1. A MEMS capacitive tactile pressure sensor of the present invention mainly relies on the area change between the capacitor electrodes to respond to the change of tactile pressure. Compared with the existing MEMS tactile pressure sensor that responds to the change of tactile pressure by changing the electrode spacing, the sensor of the present invention has the advantage of high linearity.

[0030] 2. In addition, for existing MEMS tactile pressure sensors that respond to changes in tactile pressure by changing the spacing between electrodes, in order to prevent tactile pressure from causing contact between capacitor electrodes and the resulting sensor overload problem, the capacitor electrodes are often kept at a larger spacing, which causes the existing sensors to have small initial capacitance and low sensitivity. However, the MEMS capacitive tactile pressure sensor of the present invention mainly relies on the change in the area between capacitor electrodes to respond to changes in tactile pressure, and the spacing between capacitor electrodes can be kept at a smaller value, which helps to improve the initial capacitance and sensitivity of the sensor.

[0031] 3. The MEMS capacitive tactile pressure sensor of the present invention can be manufactured in a high-precision, high-consistency, low-cost, batch-based and miniaturized manner using MEMS processing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic cross-sectional structure diagram of a MEMS tactile pressure sensor according to one embodiment of the present invention;

[0033] Figure 2 This is a method for preparing a MEMS tactile pressure sensor according to one embodiment of the present invention; wherein: 1 is a tactile sensitive body, 2 is a dielectric layer, 3 is an electrode, 4 is an insulating layer, and 5 is a substrate. DETAILED DESCRIPTION

[0034] To make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. However, it will be appreciated by those skilled in the art that in the embodiments of the present invention, many technical details are proposed in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present application can be implemented. The division of the following embodiments is for the convenience of description, and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined and referenced with each other without contradiction.

[0035] Example 1

[0036] See also Figure 1 The present invention proposes a MEMS capacitive tactile pressure sensor, which includes: a substrate 5; an insulating layer 4, which is arranged on the substrate 5; an electrode 3, which is arranged on the insulating layer 4; a dielectric layer 2, which is arranged on the insulating layer 4 and covers the electrode 3; a tactile sensitive body 1, which is arranged on the dielectric layer 2; wherein the tactile sensitive body 1 constitutes a movable electrode of the MEMS capacitive tactile pressure sensor.

[0037] Furthermore, the substrate 5 is a rigid substrate or a flexible substrate, including any one or more of silicon wafer, glass, stainless steel, polyimide, polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), and has a thickness of 20 μm-5000 μm.

[0038] Furthermore, the insulating layer 4 is disposed on the upper surface of the substrate 5 , and the material of the insulating layer 4 is, for example, at least one of silicon dioxide or silicon nitride, with a thickness of 100 nm-1000 nm; the insulating layer 4 is used to achieve electrical isolation between the electrode 3 and the substrate 5 .

[0039] Furthermore, the electrode 3 is arranged on the upper surface of the insulating layer 4, and the material of the electrode 3 is metal, preferably at least one of Al, Ti, Au, Cu, and Pt, and the thickness is 50nm-500nm; the electrode 3 serves as a fixed electrode of the MEMS capacitive tactile pressure sensor.

[0040] Furthermore, the dielectric layer 2 is arranged on the upper surface of the insulating layer 4 and covers the electrode 3. The material of the dielectric layer 2 is at least one of silicon dioxide or silicon nitride, and the thickness is 50nm-500nm; the dielectric layer 2 serves as the dielectric layer of the MEMS capacitive tactile pressure sensor.

[0041] Furthermore, the lower surface of the tactile sensitive body 1 (i.e., the side in contact with the dielectric layer 2) is arc-shaped with a height of 1 μm-100 μm; the width of the tactile sensitive body 1 is determined by the range and resolution required by the sensor, the larger the width, the larger the range of the sensor, but on the other hand, the larger the width, the lower the resolution of the sensor; the tactile sensitive body 1 is arranged on the upper surface of the dielectric layer 2 and faces the electrode 3 below; the material of the tactile sensitive body 1 is an elastic conductive composite material, preferably PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)) / PDMS; the tactile sensitive body 1 constitutes a movable electrode of a MEMS capacitive tactile pressure sensor.

[0042] The working principle of a MEMS capacitive tactile pressure sensor proposed by the present invention is as follows: the tactile sensitive body 1, the dielectric layer 2 and the electrode 3 constitute the sensitive capacitor of the MEMS capacitive tactile pressure sensor. Under the action of tactile pressure, the tactile sensitive body 1 is deformed, resulting in an increase in the contact area between the tactile sensitive body 1 and the dielectric layer 2, and causing the effective relative area between the movable electrode and the fixed electrode of the sensitive capacitor to increase, thereby causing the capacitance value to change. The greater the tactile pressure, the greater the deformation of the tactile sensitive body 1, the greater the contact area with the dielectric layer 2, the greater the effective area of ​​the two electrodes, and the corresponding capacitance value, thereby realizing the conversion of tactile pressure to electrical signals. It can be seen from the above that the MEMS capacitive tactile pressure sensor of the present invention mainly responds to changes in tactile pressure through changes in the relative area between the capacitor electrodes. Because the capacitance value is proportional to the relative area between the electrodes, the sensor of the present invention has high linearity.

[0043] Example 2

[0044] See also Figure 2 The present invention also provides a method for preparing a MEMS tactile pressure sensor, comprising the following steps:

[0045] S1: Select substrate,

[0046] S2: forming an insulating layer on the substrate;

[0047] S3: forming an electrode on the insulating layer;

[0048] S4: forming a dielectric layer on the substrate, wherein the dielectric layer covers the electrode;

[0049] S5: forming a sacrificial layer on the dielectric layer;

[0050] S6: etching the sacrificial layer to form a shape of the touch sensitive body;

[0051] S7: forming an elastic conductive composite material on the upper surface of the sacrificial layer;

[0052] S8: removing the sacrificial layer to release the touch sensitive body.

[0053] Specifically:

[0054] A substrate is selected, for example, a 300 μm thick N-type (100) single crystal silicon wafer is selected as the substrate 5, and a plasma chemical vapor deposition (PECVD) method is used to form about 200 nm of silicon dioxide as the insulating layer 4 on the upper surface of the substrate 5; of course, the material of the insulating layer 4 can also include other suitable materials in the art, such as silicon nitride.

[0055] An electrode having a thickness of about 200 nm is prepared on the upper surface of the insulating layer 4 by electron beam evaporation and lift-off technology, and the electrode is made of, for example, Pt.

[0056] For example, a plasma chemical vapor deposition (PECVD) technique is used to form about 50 nm of silicon nitride as the dielectric layer 2 on the upper surface of the insulating layer 4;

[0057] A sacrificial layer of about 1 μm thick is formed on the upper surface of the dielectric layer 2 by thermal evaporation, for example, the sacrificial layer is made of Al, and the desired shape of the touch sensitive body 1 is formed in the Al sacrificial layer by photolithography and isotropic wet etching with H3PO4 solution, for example, an arc shape.

[0058] Forming an elastic conductive composite material on the upper surface of the Al sacrificial layer by spin coating and heating and drying, the elastic conductive composite material is, for example, PEDOT:PSS / PDMS;

[0059] The Al sacrificial layer and the elastic conductive composite material attached to the Al sacrificial layer are selectively removed using H3PO4 solution to form the tactile sensitive body 1 and finally complete the preparation of the device.

[0060] Compared with the prior art, the present invention has the following advantages:

[0061] 1. A MEMS capacitive tactile pressure sensor proposed in the present invention mainly relies on the area change between the capacitor electrodes to respond to the change of tactile pressure. Compared with the existing MEMS tactile pressure sensor that responds to the change of tactile pressure by changing the electrode spacing, the sensor of the present invention has the advantage of high linearity.

[0062] 2. In addition, for existing MEMS tactile pressure sensors that respond to changes in tactile pressure by changing the spacing between electrodes, in order to prevent tactile pressure from causing contact between capacitor electrodes and the resulting sensor overload problem, the capacitor electrodes are often kept at a larger spacing, which causes the existing sensors to have small initial capacitance and low sensitivity. However, the MEMS capacitive tactile pressure sensor of the present invention mainly relies on the change in the area between capacitor electrodes to respond to changes in tactile pressure, and the spacing between capacitor electrodes can be kept at a smaller value, which helps to improve the initial capacitance and sensitivity of the sensor.

[0063] 3. The MEMS capacitive tactile pressure sensor proposed in the present invention can be manufactured with high precision, high consistency, low cost, batch production and miniaturization by using MEMS processing technology.

[0064] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the contents disclosed by the present invention should be included in the protection scope recorded in the claims.

Claims

1. A method for preparing a MEMS capacitive tactile pressure sensor, characterized in that: The following steps are involved: Select the substrate, forming an insulating layer on the substrate; forming an electrode on the insulating layer; forming a dielectric layer on the substrate, wherein the dielectric layer covers the electrode; forming a sacrificial layer on the dielectric layer, wherein the sacrificial layer is formed by thermally evaporating aluminum; Etching the sacrificial layer to form a shape of a touch sensitive body, wherein the shape of the touch sensitive body is an arc, and the width of the touch sensitive body is determined by the range and resolution required by the sensor; forming an elastic conductive composite material on the upper surface of the sacrificial layer; The sacrificial layer is removed to release the touch sensitive body; the touch sensitive body is arranged opposite to the electrode; wherein, The tactile sensitive body constitutes the movable electrode of the MEMS capacitive tactile pressure sensor; under the action of tactile pressure, the tactile sensitive body is deformed, resulting in an increase in the contact area between the tactile sensitive body and the dielectric layer, and causing the effective relative area between the movable electrode and the fixed electrode of the sensitive capacitor to increase, causing the capacitance value to change.

2. The method for preparing a MEMS capacitive tactile pressure sensor according to claim 1, characterized in that: The elastic conductive composite material is PEDOT:PSS / PDMS.

3. The method for preparing the MEMS capacitive tactile pressure sensor according to claim 1, characterized in that: The touch sensitive body has a height of 1 μm to 100 μm.

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