A pressure sensitive element and a method for producing the same

Abstract

The application discloses a pressure-sensitive element and a preparation method thereof, and relates to the technical field of semiconductors. The pressure-sensitive element comprises a device layer, a buried oxygen layer and a substrate layer which are sequentially stacked, part of the device layer and the buried oxygen layer are hollowed out to form a sensitive structure, and the substrate layer is hollowed out at positions corresponding to the sensitive structure to form notches. The sensitive structure comprises a support part, a support beam, a driving part, a shielding electrode and an induction electrode. The two sides of the shielding electrode are provided with the induction electrode, and a first induction structure is arranged between the induction electrode and the shielding electrode. The two sides of the shielding electrode are provided with the driving part, the driving part comprises a first driving electrode and a second driving electrode, the second driving electrode is connected with the shielding electrode, and a second induction structure is arranged between the second driving electrode and the first driving electrode. The application uses the buried oxygen layer as a strain control layer, the buried oxygen layer has a thick structure, a high growth temperature and strong strain control capability, and has a large vertical vibration amplitude, so that the electric field induction capability can be greatly improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a pressure-sensitive element and its fabrication method. Background Technology

[0002] Existing electrostatically driven voltage-sensitive elements are mainly horizontally driven, which are limited by the micrometer-level distance between the sensing electrode and the shielding electrode, resulting in limited vibration amplitude and weak detection signal.

[0003] Vertical vibration mode is not limited by the distance between the sensing structure and the shielding structure. Compared with horizontal vibration, the amplitude can be increased by orders of magnitude, thereby improving the sensitivity of the sensor. Conventional piezoelectric driving methods based on the inverse piezoelectric effect, such as PZT thin films, can achieve electric field sensing and measurement through vertical vibration or torsion. Although there are many types and complex PZT piezoelectric thin film preparation processes, the repeatability, stability and consistency of the piezoelectric coefficient of the prepared films still need to be improved, resulting in low reliability. Moreover, the processing technology is more complex and costly than that of traditional voltage-sensitive elements. Summary of the Invention

[0004] This application aims to solve one of the aforementioned technical problems in the prior art. To this end, embodiments of this application provide a pressure-sensitive element.

[0005] This application also provides a method for preparing a pressure-sensitive element.

[0006] According to an embodiment of the first aspect of this application, a pressure-sensitive element is provided, comprising a device layer, a buried oxide layer and a substrate layer stacked sequentially, wherein a portion of the device layer and the buried oxide layer are hollowed out to form a sensitive structure, and the substrate layer is hollowed out at a position corresponding to the sensitive structure to form a slot; The sensitive structure includes a support part, a support beam, a drive part, a shielding electrode, and a sensing electrode. The shielding electrode is connected to the support part located at the edge of the slot through the support beam, so that the shielding electrode is mounted above the slot. The sensing electrode is provided on both sides of the shielding electrode. The sensing electrode is not connected to the shielding electrode. A first sensing structure is provided between the sensing electrode and the shielding electrode. The shielding electrode is provided with a driving part on both sides. The driving part includes a first driving electrode and a second driving electrode. The first driving electrode is not connected to the shielding electrode, and the second driving electrode is connected to the shielding electrode. A second sensing structure is provided between the second driving electrode and the first driving electrode. The shielding electrode deforms away from the substrate layer under the internal stress of the buried oxide layer, so that the shielding electrode and the sensing electrode are on different planes, and the second driving electrode is on different planes from the first driving electrode.

[0007] The aforementioned pressure-sensitive element has at least the following beneficial effects: The pressure-sensitive element of this application is based on the SOI process to fabricate the sensitive structure of the electric field sensor. It adopts the method of retaining the SOI oxide layer at the bottom of the sensor structure region as the strain material. Due to the presence of silicon oxide, the shielding electrode undergoes stress warping in the vertical direction. Since the second driving electrode is on the shielding electrode, it will also undergo warping deformation along with the shielding electrode, so that the second driving electrode and the first driving electrode are not on the same plane. Vertical vibration driven by electrostatic force can be realized. When a voltage is applied to the first driving electrode, the voltage acts on the second sensing structure to drive the second driving electrode to move in the vertical direction. Since the shielding electrode is connected to the second driving electrode, it drives the shielding electrode to move in the vertical direction. When an external electric field exists, the vertical movement of the movable shielding electrode generates a periodic electric field shielding on the adjacent sensing electrode structure through the first sensing structure, causing periodic changes in the surface charge of the sensing electrode and thus generating an induced current. By detecting the current generated by the sensing electrode, electric field measurement is realized. Compared with existing technologies, this application utilizes a buried oxide layer as a strain control layer. The buried oxide layer has a thick structure, a high growth temperature, strong strain control capability, and a large vertical vibration amplitude, which can significantly improve the electric field sensing capability and thus improve the sensitivity of the piezoresistive element. Furthermore, the strain control vertical drive method of this application does not require the preparation of piezoelectric materials, resulting in low preparation cost and simple process.

[0008] According to the pressure-sensitive element of the first aspect embodiment of this application, the first sensing structure includes a first sensing tooth and a second sensing tooth. A plurality of the first sensing teeth are arranged in an array on the side of the sensing electrode facing the shielding electrode, and a plurality of the second sensing teeth are arranged in an array on the side of the shielding electrode corresponding to the sensing electrode. The first sensing teeth and the second sensing teeth are staggered so that there is a second sensing tooth between two adjacent first sensing teeth.

[0009] According to the pressure-sensitive element of the first aspect embodiment of this application, the distance between the first sensing tooth and the second sensing tooth is less than 50 μm, the tooth width of the first sensing tooth and the second sensing tooth is in the range of 5 μm-100 μm, and the tooth length of the first sensing tooth and the second sensing tooth is in the range of 5 μm-50 μm.

[0010] According to the pressure-sensitive element of the first aspect embodiment of this application, the second sensing structure includes a third sensing tooth and a fourth sensing tooth. A plurality of the third sensing teeth are arranged in an array on the side of the first driving electrode facing the shielding electrode, and a plurality of the fourth sensing teeth are arranged in an array on the side of the second driving electrode corresponding to the first driving electrode. The third sensing teeth and the fourth sensing teeth are staggered so that there is a fourth sensing tooth between two adjacent third sensing teeth.

[0011] According to the pressure-sensitive element of the first aspect embodiment of this application, the distance between the third sensing tooth and the fourth sensing tooth is less than 10 μm, the tooth width of the third sensing tooth and the fourth sensing tooth is in the range of 2 μm-10 μm, and the tooth length of the first sensing tooth and the second sensing tooth is in the range of 5 μm-50 μm.

[0012] According to the pressure-sensitive element of the first aspect of this application, the thickness of the device layer is less than or equal to 100 μm.

[0013] According to the pressure-sensitive element of the first aspect of this application, the thickness of the buried oxide layer is less than or equal to 5 μm.

[0014] According to the pressure-sensitive element of the first aspect of this application, the thickness of the substrate layer is less than or equal to 1 mm.

[0015] According to the pressure-sensitive element of the first aspect of this application, a metal electrode layer is disposed on the surface of the device layer of the support portion, the sensing electrode and the first driving electrode. The metal electrode layer on the support portion is used for grounding, the metal electrode layer on the first driving electrode is used for electrical connection with an AC voltage source, and the metal electrode layer on the sensing electrode is used for electrical connection with an external detection unit. The thickness of the metal electrode layer is less than or equal to 1 μm.

[0016] According to an embodiment of the second aspect of this application, a method for preparing the pressure-sensitive element described in the first aspect embodiment is provided, comprising the following steps: Photoresist is coated on the surface of the device layer and photolithography is performed to transfer the pattern of the metal electrode layer to the surface of the device layer. The metal electrode layer is deposited at the first predetermined surface position of the device layer by evaporation or magnetron sputtering to form the metal electrode layer. Remove the photoresist from the surface of the device layer and remove the metal electrode layer that is not located on the first preset surface; Photoresist is coated again on the surface of the device layer and photolithography is performed to transfer the pattern of the sensitive structure to the second preset surface of the device layer. The sensitive structure is etched using a deep silicon etching device, wherein the etching stops when the buried oxide layer surface is reached. After the sensitive structure is etched, the buried oxide layer is etched using dry etching or wet etching until the substrate is exposed on the surface. An organic protective material is coated onto the surfaces of the device layer and the sensitive structure; Photoresist is coated on the side of the substrate layer facing away from the device layer and photolithographic exposure is performed to transfer the pattern of the groove to the side of the substrate layer facing away from the device layer. The groove is etched out using a deep silicon etching equipment. The etching process stops after reaching the buried oxide layer. Remove the organic protective material from the surface of the device layer and the sensitive structure.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description. Attached Figure Description

[0018] The present application will be further described below with reference to the accompanying drawings and embodiments; Figure 1 This is a schematic diagram of the structure of the pressure-sensitive element in an embodiment of this application. Figure 1 ; Figure 2 This is a schematic diagram of the structure of the pressure-sensitive element in the embodiments of this application. Figure 2 ; Figure 3 This is a schematic diagram of the second sensing structure in an embodiment of this application; Figure 4 This is a schematic diagram of the structure of the first sensing structure in an embodiment of this application; Figure 5 This is a schematic diagram of the fabrication process of the pressure-sensitive element in the embodiments of this application.

[0019] Reference numerals: Substrate 110, Groove 111, Buried oxide layer 120, Metal electrode layer 130, Device layer 140, Support 210, First driving electrode 220, First extension arm 221, Third sensing tooth 222, Sensing electrode 230, First sensing tooth 231, Shielding electrode 240, Second extension arm 241, Fourth sensing tooth 2411, Second sensing tooth 242, Support beam 250. Detailed Implementation

[0020] This section will describe in detail the specific embodiments of this application. Preferred embodiments of this application are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of this application, but they should not be construed as limiting the scope of protection of this application.

[0021] In the description of this application, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0022] In the description of this application, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0023] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0024] Reference Figure 1 and Figure 2 The pressure-sensitive element provided in this application embodiment includes a device layer 140, a buried oxide layer 120 and a substrate layer 110 stacked sequentially. Parts of the device layer 140 and the buried oxide layer 120 are hollowed out to form a sensitive structure. The substrate layer 110 is hollowed out at the position corresponding to the sensitive structure to form a slot 111, so that the sensitive structure is in a suspended state, thereby enabling a part of the sensitive structure to move vertically under the action of external force.

[0025] The sensitive structure includes a support part 210, a support beam 250, a drive part, a shielding electrode 240, and a sensing electrode 230. The shielding electrode 240 is connected to the support part 210 located at the edge of the slot 111 through the support beam 250, so that the shielding electrode 240 is mounted above the slot 111 and is in a suspended state.

[0026] In the embodiments shown in this application, the shielding electrode 240 is rectangular, and the four corners of the shielding electrode 240 are respectively connected to the four support portions 210 on the substrate layer 110 through the support beam 250.

[0027] In this embodiment, sensing electrodes 230 are provided on both sides of the shielding electrode 240. The sensing electrodes 230 are disposed on the substrate layer 110. The sensing electrodes 230 are not connected to the shielding electrode 240. A first sensing structure is provided between the sensing electrodes 230 and the shielding electrode 240.

[0028] The shielding electrode 240 has a driving unit on both sides. The driving unit includes a first driving electrode 220 and a second driving electrode. The first driving electrode 220 is not connected to the shielding electrode 240, and the second driving electrode is connected to the shielding electrode 240. A second sensing structure is provided between the second driving electrode and the first driving electrode 220.

[0029] The shielding electrode 240 deforms in a direction away from the substrate layer 110 under the internal stress of the buried oxide layer 120, so that the shielding electrode 240 and the sensing electrode 230 are in different planes, and the second driving electrode and the first driving electrode 220 are in different planes.

[0030] The pressure-sensitive element of this application is based on the SOI process to fabricate the sensitive structure of the electric field sensor. It adopts the method of retaining the SOI oxide layer at the bottom of the sensor structure region as the strain material. Due to the presence of silicon oxide, the shielding electrode 240 undergoes stress warping in the vertical direction. Since the second driving electrode is on the shielding electrode 240, it will also undergo warping deformation along with the shielding electrode 240, so that the second driving electrode and the first driving electrode 220 are not on the same plane. Vertical vibration driven by electrostatic force can be realized. When a voltage is applied to the first driving electrode 220, the voltage acts on the second sensing structure and can drive the second driving electrode to move in the vertical direction. Since the shielding electrode 240 is connected to the second driving electrode, it drives the shielding electrode 240 to move in the vertical direction.

[0031] When an external electric field exists, the movable shielding electrode 240 generates a periodic electric field shielding on the adjacent sensing electrode 230 structure through the first sensing structure during its vertical movement. This causes periodic changes in the surface charge of the sensing electrode 230, thereby generating an induced current. By detecting the current generated by the sensing electrode 230, the electric field measurement is achieved.

[0032] Compared with the prior art, this application uses the buried oxide layer 120 as the strain control layer. The buried oxide layer 120 has a thick structure, high growth temperature, strong strain control capability, and large vertical vibration amplitude, which can significantly improve the electric field sensing capability and thus improve the sensitivity of the piezoresistive element. Moreover, the strain control vertical driving method of this application does not require the preparation of piezoelectric materials, has low preparation cost, and simple process.

[0033] Among them, such as Figure 1 , Figure 2 and Figure 3As shown, the second sensing structure includes a third sensing tooth 222 and a fourth sensing tooth 2411. A plurality of third sensing teeth 222 are arranged in an array on the side of the first driving electrode 220 facing the shielding electrode 240, and a plurality of fourth sensing teeth 2411 are arranged in an array on the side of the second driving electrode corresponding to the first driving electrode 220. The third sensing teeth 222 and the fourth sensing teeth 2411 are staggered so that there is a fourth sensing tooth 2411 between two adjacent third sensing teeth 222.

[0034] It should be noted that the third sensing tooth 222 does not have an oxygen layer 120 on one side of the slot, while the fourth sensing tooth 2411 has an oxygen layer 120 on one side of the slot.

[0035] Due to the presence of the buried oxygen layer 120, the second driving electrode undergoes a greater deformation than the first driving electrode 220 along with the shielding electrode 240, causing the third sensing tooth 222 and the fourth sensing tooth 2411 to be on different planes (when the pressure-sensitive element of this application is placed horizontally, that is, the horizontal heights are different, the horizontal height of the fourth sensing tooth 2411 is higher than that of the third sensing tooth 222), which can realize vertical vibration driven by electrostatic force. When a voltage is applied to the first driving electrode 220, the voltage acts on the third sensing tooth 222, which can drive the fourth sensing tooth 2411 to move in the vertical direction. Since the shielding electrode 240 is connected to the second driving electrode, it can also drive the shielding electrode 240 to move in the vertical direction.

[0036] like Figure 1 and Figure 2 As shown, the driving unit also includes a driving electrode body and a first extension arm 221. The first extension arm 221 extends along the width direction of the shielding electrode 240, and third sensing teeth 222 are arranged in an array along the length direction of the first extension arm 221. The arrangement direction of the third sensing teeth 222 is parallel to the length direction of the shielding electrode 240. Correspondingly, the second driving electrode includes a second extension arm 241, which extends along the width direction of the shielding electrode 240. Fourth sensing teeth 2411 are arranged in an array along the length direction of the second extension arm 241, and the arrangement direction of the fourth sensing teeth 2411 is parallel to the length direction of the shielding electrode 240. Since the width of the second extension arm 241 is smaller than that of the first extension arm 221, the structural rigidity of the second extension arm 241 is lower than that of the first extension arm 221. Even though it is also subjected to the internal stress of the buried oxide layer 120, the warping deformation of the second extension arm 241 is greater than that of the first extension arm 221. Even if the shielding electrode 240 does not produce excessive warping deformation, the warping deformation of the second extension arm 241 itself can make the fourth sensing tooth 2411 and the third sensing tooth 222 change to be in different planes, thereby satisfying the basic structural basis of electrostatic force drive.

[0037] Among them, such as Figure 1 , Figure 2 and Figure 4 As shown, the first sensing structure includes a first sensing tooth 231 and a second sensing tooth 242. A plurality of first sensing teeth 231 are arranged in an array on the side of the sensing electrode 230 facing the shielding electrode 240, and a plurality of second sensing teeth 242 are arranged in an array on the side of the shielding electrode 240 corresponding to the sensing electrode 230. The first sensing teeth 231 and the second sensing teeth 242 are arranged alternately so that there is a second sensing tooth 242 between two adjacent first sensing teeth 231.

[0038] Among them, the first sensing tooth 231 has no buried oxygen layer 120 on one side of the groove, while the second sensing tooth 242 has a buried oxygen layer 120 on one side of the groove.

[0039] In this configuration, the array direction of the first sensing teeth 231 is parallel to the length direction of the shielding electrode 240, and the setting direction of the first sensing teeth 231 is parallel to the width direction of the shielding electrode 240. The array direction of the second sensing teeth is parallel to the length direction of the shielding electrode 240, and the setting direction of the second sensing teeth 242 is parallel to the width direction of the shielding electrode 240. The staggered arrangement of the first sensing teeth 231 and the second sensing teeth 242, as well as the fact that the first sensing teeth 231 and the second sensing teeth 242 are not on the same plane due to warping deformation, means that when an external electric field is present, the vertical movement of the movable shielding electrode 240 causes the first sensing teeth 231 to periodically shield the second sensing teeth 242 of the adjacent sensing electrode 230, causing periodic changes in the surface charge of the sensing electrode 230 and generating an induced current. By detecting the current generated by the sensing electrode 230, electric field measurement is achieved.

[0040] In this embodiment of the application, the distance between the first sensing tooth 231 and the second sensing tooth 242 is less than 50 μm, the tooth width of the first sensing tooth 231 and the second sensing tooth 242 is in the range of 5 μm-100 μm, and the tooth length of the first sensing tooth 231 and the second sensing tooth 242 is in the range of 5 μm-50 μm. If the sensing tooth is too short, it will reduce the sensing area; if it is too long, it will cause stress warping of the tooth itself, making it difficult to control the warping state of the overall sensing structure.

[0041] In some specific embodiments, the distance between the first sensing tooth 231 and the second sensing tooth 242 is 10 μm, the tooth length of the first sensing tooth 231 and the second sensing tooth 242 is 10 μm, and the tooth width of the first sensing tooth 231 and the second sensing tooth 242 is 10 μm.

[0042] In some other embodiments, the distance between the third sensing tooth 222 and the fourth sensing tooth 2411 is less than 10 μm, the tooth width of the third sensing tooth 222 and the fourth sensing tooth 2411 is in the range of 2 μm to 10 μm, and the tooth length of the first sensing tooth 231 and the second sensing tooth 242 is in the range of 5 μm to 50 μm.

[0043] In some specific embodiments, the distance between the third sensing tooth 222 and the fourth sensing tooth 2411 is 3 μm, the tooth length of the third sensing tooth 222 and the fourth sensing tooth 2411 is 10 μm, and the tooth width of the third sensing tooth 222 and the fourth sensing tooth 2411 is 5 μm.

[0044] In some embodiments shown in this application, the thickness of device layer 140 is less than or equal to 100 μm. In specific embodiments, the thickness of device layer 140 is 10 μm or 20 μm.

[0045] In some specific embodiments, the thickness of the buried oxide layer 120 is less than or equal to 5 μm.

[0046] In some embodiments shown in this application, the thickness of the substrate layer 110 is less than or equal to 1 mm; in specific embodiments, the thickness of the substrate layer 110 is 300 μm or 200 μm.

[0047] In this embodiment, a metal electrode layer 130 is disposed on the surface of the device layer 140 of the support portion 210, the sensing electrode 230, and the first driving electrode 220. The metal electrode layer 130 on the support portion 210 is used for grounding, the metal electrode layer 130 on the first driving electrode 220 is used for electrical connection to an AC voltage source, and the metal electrode layer 130 on the sensing electrode 230 is used for electrical connection to an external detection unit. The thickness of the metal electrode layer 130 is less than or equal to 1 μm. In some specific embodiments, the thickness of the metal electrode layer 130 is 300 nm, 200 nm, or 500 nm.

[0048] The pressure-sensitive element of this application applies an AC voltage with the same natural vibration frequency in the vertical direction as the shielding electrode 240 to the third sensing tooth 222 of the first driving electrode 220, so that an electrostatic driving force in the vertical direction is generated between the third sensing tooth 222 and the fourth sensing tooth 2411 of the second driving electrode. This drives the shielding electrode 240 to vibrate up and down, causing the second sensing tooth 242 to periodically shield the sensing electrode 230, thereby causing a change in the induced charge on the surface of the sensing electrode 230. The magnitude of the external electric field intensity, i.e., the value of the corresponding external voltage, is obtained by calculating the amount of charge change.

[0049] like Figure 5 As shown in the embodiments of this application, a method for preparing the above-mentioned pressure-sensitive element is also provided, which specifically includes the following steps: Photoresist is coated on the surface of device layer 140 and photolithographic exposure is performed to transfer the pattern of metal electrode layer 130 to the surface of device layer 140. Metal electrode layer 130 is deposited at a first preset surface position of device layer 140 by evaporation or magnetron sputtering. The photoresist on the surface of device layer 140 and the metal electrode layer 130 not located on the first preset surface are removed.

[0050] First, photoresist is coated and photolithographically exposed on the surface of the device layer 140 on the SOI substrate, and the electrode pattern is transferred to the SOI wafer surface. Then, a metal electrode layer 130 is deposited on the surface using evaporation or magnetron sputtering. The material of the metal electrode layer 130 includes, but is not limited to, one or more combinations of Au, Pt, and Al. The photoresist and the metal electrodes deposited on the photoresist surface are removed by immersion and stripping with acetone or similar solvents.

[0051] Photoresist is coated again on the surface of device layer 140 and photolithographic exposure is performed to transfer the pattern of the sensitive structure to the second preset surface of device layer 140. The sensitive structure is etched using a deep silicon etching apparatus, wherein the etching stops when it reaches the surface of buried oxide layer 120. Specifically, photoresist is coated on the surface of device layer 140 and photolithographic exposure is performed to transfer the sensitive structure to the wafer surface where device layer 140 is located; then, a deep silicon etching apparatus is used to etch the third sensing tooth 222, the fourth sensing tooth 2411, the shielding electrode 240, the sensing electrode 230, and the support beam 250, etc., which are used to generate electrostatic driving force; the etching stops when it reaches buried oxide layer 120, at which point the silicon oxide in the etched area is exposed on the surface.

[0052] After the sensitive structure is etched, the buried oxide layer 120 is etched using either dry or wet etching until the substrate layer 110 is exposed. During the etching process, a photoresist coating is used to continue etching the exposed silicon oxide buried oxide layer 120 until the substrate layer 110 is exposed. The silicon oxide etching method can be dry etching, using etching gases such as, but not limited to, HF, SO2, and CF4. Wet etching can also be used, with etchants including, but not limited to, buffered hydrofluoric acid (BOE) solution.

[0053] An organic protective material is coated on the surface of the device layer 140 and the sensitive structure. This organic protective material can be a positive photoresist, a negative photoresist, or other materials with good ductility that are easy to thin film, in order to protect the sensitive structure from the influence of subsequent processing steps, such as damage caused by external forces.

[0054] Photoresist is coated and patterned on the side of the substrate layer 110 facing away from the device layer 140. The pattern of the groove 111 is transferred to the side of the substrate layer 110 facing away from the device layer 140. The groove 111 is etched out using a deep silicon etching device. The etching process stops after reaching the buried oxide layer 120. Remove the organic protective material from the surface of device layer 140 and sensitive structures.

[0055] Compared with existing methods for fabricating pressure-sensitive elements, the pressure-sensitive element of this application has the following advantages: 1. The sensitive structure of the electric field sensor is fabricated based on SOI process. The method of retaining the buried oxide layer 120 at the bottom of the sensor structure region as the strain material is adopted. Due to the presence of silicon oxide, the driving part and the shielding electrode 240 are subjected to stress warping in the vertical direction. Due to the stiffness difference between the third sensing tooth 222 and the fourth sensing tooth 2411, the warping amplitude of the fourth sensing tooth 2411 is greater than that of the third sensing tooth 222, so that the fourth sensing tooth 2411 and the third sensing tooth 222 are in different planes. 2. Applying voltage to the third sensing tooth 222 of the first driving electrode 220 can drive the fourth sensing tooth 2411 of the second driving electrode to move in the vertical direction. The shielding electrode 240 is connected to the fourth sensing tooth 2411 of the second driving electrode, thereby driving the shielding electrode 240 to move in the vertical direction. 3. When an external electric field is present, the vertical movement of the movable shielding electrode 240 generates a periodic electric field shielding on the adjacent sensing electrode 230, causing a periodic change in the surface charge of the sensing electrode 230 and generating an induced current. By detecting the current generated by the sensing electrode 230, the electric field measurement is realized. 4. The strain material is derived from the buried oxide layer 120 in the middle of the SOI wafer, which does not require additional process growth. After the substrate layer 110 at the bottom of the sensitive structure region is removed by the etching process, the device layer 140 and the buried oxide layer 120 at the bottom of the device layer 140 are retained in the sensitive structure region, which is simple process. 5. After the sensitive structure of the device layer 140 is etched, the exposed bottom buried oxide layer 120 is further etched by dry etching process to achieve separation between the movable shielding electrode 240 and the first driving electrode 220 and the sensing electrode 230. 6. To obtain better performance, the patterning and etching of the silicon oxide layer in the sensitive structure area can be achieved by photoresist stereolithography and ultraviolet exposure lithography, so that the strain-controlled oxide layer is only retained on the surface of the fourth sensing tooth 2411 of the second driving electrode. 7. Using SOI buried oxide layer 120 as a strain control layer, the oxide layer structure is thick, the growth temperature is high, the strain control capability is strong, the vertical vibration amplitude is large, the electric field induction capability is improved, and the sensor sensitivity is improved.

[0056] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application.

Claims

1. A pressure-sensitive element, characterized in that: It includes a device layer, a buried oxide layer and a substrate layer stacked in sequence. Parts of the device layer and the buried oxide layer are cut out to form a sensitive structure. The substrate layer is cut out at the position corresponding to the sensitive structure to form a slot. The sensitive structure includes a support part, a support beam, a drive part, a shielding electrode, and a sensing electrode. The shielding electrode is connected to the support part located at the edge of the slot through the support beam, so that the shielding electrode is mounted above the slot. The sensing electrode is provided on both sides of the shielding electrode. The sensing electrode is not connected to the shielding electrode. A first sensing structure is provided between the sensing electrode and the shielding electrode. The shielding electrode is provided with a driving part on both sides. The driving part includes a first driving electrode and a second driving electrode. The first driving electrode is not connected to the shielding electrode, and the second driving electrode is connected to the shielding electrode. A second sensing structure is provided between the second driving electrode and the first driving electrode. The shielding electrode deforms away from the substrate layer under the internal stress of the buried oxide layer, so that the shielding electrode and the sensing electrode are on different planes, and the second driving electrode is on different planes from the first driving electrode.

2. The pressure-sensitive element according to claim 1, characterized in that: The first sensing structure includes a first sensing tooth and a second sensing tooth. A plurality of the first sensing teeth are arranged in an array on the side of the sensing electrode facing the shielding electrode, and a plurality of the second sensing teeth are arranged in an array on the side of the shielding electrode corresponding to the sensing electrode. The first sensing teeth and the second sensing teeth are arranged alternately so that there is a second sensing tooth between two adjacent first sensing teeth.

3. The pressure-sensitive element according to claim 2, characterized in that: The distance between the first sensing tooth and the second sensing tooth is less than 50 μm, the tooth width of the first sensing tooth and the second sensing tooth is in the range of 5 μm-100 μm, and the tooth length of the first sensing tooth and the second sensing tooth is in the range of 5 μm-50 μm.

4. The pressure-sensitive element according to claim 2, characterized in that: The second sensing structure includes a third sensing tooth and a fourth sensing tooth. A plurality of the third sensing teeth are arranged in an array on the side of the first driving electrode facing the shielding electrode, and a plurality of the fourth sensing teeth are arranged in an array on the side of the second driving electrode corresponding to the first driving electrode. The third sensing teeth and the fourth sensing teeth are arranged alternately so that there is a fourth sensing tooth between two adjacent third sensing teeth.

5. The pressure-sensitive element according to claim 4, characterized in that: The distance between the third sensing tooth and the fourth sensing tooth is less than 10 μm, the tooth width of the third sensing tooth and the fourth sensing tooth is in the range of 2 μm-10 μm, and the tooth length of the first sensing tooth and the second sensing tooth is in the range of 5 μm-50 μm.

6. The pressure-sensitive element according to claim 1, characterized in that: The thickness of the device layer is less than or equal to 100 μm.

7. The pressure-sensitive element according to claim 1, characterized in that: The thickness of the buried oxide layer is less than or equal to 5 μm.

8. The pressure-sensitive element according to claim 1, characterized in that: The thickness of the substrate layer is less than or equal to 1 mm.

9. The pressure-sensitive element according to any one of claims 1 to 8, characterized in that: Metal electrode layers are provided on the surfaces of the device layers of the support portion, the sensing electrode, and the first driving electrode. The metal electrode layer on the support portion is used for grounding, the metal electrode layer on the first driving electrode is used for electrical connection with an AC voltage source, and the metal electrode layer on the sensing electrode is used for electrical connection with an external detection unit. The thickness of the metal electrode layer is less than or equal to 1 μm.

10. A method for preparing the pressure-sensitive element according to claim 9, characterized in that, Includes the following steps: Photoresist is coated on the surface of the device layer and photolithography is performed to transfer the pattern of the metal electrode layer to the surface of the device layer. The metal electrode layer is deposited at the first predetermined surface position of the device layer by evaporation or magnetron sputtering to form the metal electrode layer. Remove the photoresist from the surface of the device layer and remove the metal electrode layer that is not located on the first preset surface; Photoresist is coated again on the surface of the device layer and photolithography is performed to transfer the pattern of the sensitive structure to the second preset surface of the device layer. The sensitive structure is etched using a deep silicon etching device, wherein the etching stops when the buried oxide layer surface is reached. After the sensitive structure is etched, the buried oxide layer is etched using dry etching or wet etching until the substrate is exposed on the surface. An organic protective material is coated onto the surfaces of the device layer and the sensitive structure; Photoresist is coated on the side of the substrate layer facing away from the device layer and photolithographic exposure is performed to transfer the pattern of the groove to the side of the substrate layer facing away from the device layer. The groove is etched out using a deep silicon etching equipment. The etching process stops after reaching the buried oxide layer. Remove the organic protective material from the surface of the device layer and the sensitive structure.

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