Non-contact pressure sensor chip leadless packaging structure and preparation method thereof

Abstract

The invention discloses a non-contact pressure sensor chip leadless packaging structure and a preparation method, and belongs to the technical field of MEMS sensors. The packaging body comprises a pressure sensor chip needing to be protected, a silicon carbide sealing plate and a transition plate, the silicon carbide sealing plate and the transition plate play a role in sealing, surface circuit protection and connection, mechanical support is provided by sintering a Kovar alloy contact pin through conductive paste, and suspended connection and electrical connection are ensured. And distances are reserved between the upper part of the packaging main body and the silicon carbide top plate and between the lower part and the silicon carbide bottom plate. The non-contact leadless packaging improves the high temperature resistance of the silicon carbide pressure sensor, facilitates the release of thermal stress in the measurement process, and has the advantages of high material thermal adaptability, high measurement precision, good measurement stability and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of MEMS sensors, and in particular relates to a leadless packaging structure of a non-contact pressure sensor chip and a preparation method thereof. Background Art

[0002] High-temperature pressure sensors are widely used in pressure monitoring in combustion chambers of power equipment such as rocket engines, aircraft engines, heavy-duty gas turbines, and coal-fired gas boilers. It is crucial to conduct pressure tests in high-temperature environments. For example, monitoring the pressure characteristics of high-temperature jets in aircraft engines has a far-reaching impact on the attitude control of engines and spacecraft. As a third-generation wide-bandgap semiconductor material, SiC is widely used in the design and manufacture of high-temperature pressure sensors due to its excellent chemical stability, radiation resistance, and high-temperature resistance. Theoretically, the highest temperature tolerance of SiC material can reach 1600°C, but in fact, most SiC pressure sensors can withstand temperatures no higher than 600°C. In addition to the sensor preparation process, the immaturity of packaging technology is also an important reason why the temperature tolerance of SiC pressure sensors cannot be further improved.

[0003] At present, the high temperature resistant packaging of SiC pressure sensors faces many challenges, including thermal stress between packaging materials and sensor chips, electrical interconnection, etc. In terms of thermal stress, the existing structures usually use the same material as the sensor chip as the packaging substrate to reduce the mismatch of thermal expansion coefficients. However, in a high temperature environment, the same materials will still be out of sync in a short period of time due to heat conduction, resulting in greater thermal stress inside the components. In order to further improve the working stability and service life of the chip, an effective thermal stress isolation method is needed; in terms of electrical interconnection, the most widely used method is bonding through gold wire leads, which is very easy to break in environments with strong corrosion and strong vibration. In order to improve the signal output stability of the sensor chip, a more reliable electrical interconnection method is needed. Summary of the invention

[0004] The present invention provides a leadless packaging structure of a non-contact pressure sensor chip and a preparation method thereof, which reduces the problem of thermal stress concentration of the pressure sensor chip and improves the reliability of high-temperature packaging.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: A contactless pressure sensor chip leadless packaging structure comprises a silicon carbide top plate, a silicon carbide bottom plate and a kovar alloy pin, wherein the silicon carbide top plate and the silicon carbide bottom plate are butt-jointed, a first groove is provided on the silicon carbide top plate, the first groove and the silicon carbide bottom plate form a cavity, a pressure sensor chip is arranged in the cavity, and the pressure sensor chip is inverted; the kovar alloy pin passes through the silicon carbide bottom plate and is connected to the metal ohmic contact circuit of the pressure sensor chip, and a spacing is left between the pressure sensor chip and the silicon carbide bottom plate.

[0006] Furthermore, the pressure sensor chip comprises a sensitive diaphragm, and four pressure sensor piezoresistive strips are arranged along the tangential direction at the edge of the sensitive diaphragm, and the four pressure sensor piezoresistive strips are connected through a metal ohmic contact circuit.

[0007] Furthermore, a silicon carbide sealing plate is fixed on the back of the pressure sensor chip.

[0008] Furthermore, a silicon carbide transition plate is fixed on the front side of the pressure sensor chip, a second groove is formed on the silicon carbide transition plate, and the center of the second groove coincides with the projection of the center of the pressure sensor chip.

[0009] Furthermore, a first through hole is provided on the silicon carbide transition plate, and the first through hole is located directly below the metal ohmic contact circuit in the pressure sensor chip; a first pressure-sensitive channel is provided on the silicon carbide transition plate, and the orthographic projection of the center of the first pressure-sensitive channel coincides with the orthographic projection of the center of the silicon carbide transition plate.

[0010] Furthermore, a gap is left between the silicon carbide sealing plate and the silicon carbide top plate.

[0011] Furthermore, a second through hole is opened on the silicon carbide bottom plate, and the second through hole is located directly below the metal ohmic contact circuit in the pressure sensor chip; at the same time, a second pressure sensing channel is opened on the silicon carbide bottom plate; and a distance is left between the silicon carbide bottom plate and the silicon carbide transition plate.

[0012] Furthermore, the Kovar alloy pin passes through the second through hole.

[0013] The method for preparing the leadless packaging structure of the non-contact pressure sensor chip is characterized by comprising the following steps: Step 1, activating the surfaces of the silicon carbide top plate, the pressure sensor chip and the silicon carbide bottom plate; Step 2, bonding the silicon carbide sealing plate and the pressure sensor chip under pressure at 1.5 MPa to 2.5 MPa for 180s to 270s to obtain a bonding structure; Step 3, filling the second through hole opened on the silicon carbide bottom plate with a conductive paste; Step 4, when the conductive paste is in liquid form, pass the Kovar alloy pin through the conductive paste in the second through hole and contact the metal ohmic contact circuit of the pressure sensor chip, control the pressure sensor chip and the silicon carbide base plate to maintain a distance, and obtain an intermediate structure; Step 5, bonding the silicon carbide top plate and the intermediate structure under pressure at 1.5 MPa to 2.5 MPa for 180s to 270s; Step 6: Sinter the structure obtained in step 5 at 1100° C. to 1300° C. for 2 h to 3 h, and then cool it down to obtain a leadless packaging structure of a non-contact pressure sensor chip.

[0014] Furthermore, in step 2, the silicon carbide sealing plate, the pressure sensor chip and the silicon carbide transition plate are bonded under pressure at 1.5 MPa to 2.5 MPa for 180 seconds to 270 seconds to obtain a bonding structure; the silicon carbide transition plate is provided with a first through hole and a first pressure sensing channel; In the step 3, the conductive paste is filled into the first through hole and the second through hole opened on the silicon carbide bottom plate; In step 4, when the conductive paste is in liquid form, the Kovar alloy pin is passed through the conductive paste in the second through hole and the first through hole and contacts the metal ohmic contact circuit of the pressure sensor chip, and the distance between the silicon carbide transition plate and the silicon carbide base plate is controlled to obtain an intermediate structure.

[0015] Compared with the prior art, the present invention has at least the following beneficial technical effects: The present invention utilizes sintering of Kovar alloy pins to replace the traditional gold wire bonding, thus realizing leadless packaging. The strength of Kovar alloy pins is much higher than that of gold wires, and a layer of high temperature resistant metal coating is electroplated on the surface of Kovar alloy pins, which can not only effectively reduce the problems of gold wire breakage caused by vibration, impact, etc. during high temperature testing, but also improve the environmental adaptability of the packaging structure and the reliability and stability of signal output.

[0016] At the same time, the non-contact Kovar alloy pin mechanical support structure described in the present invention ensures that the structure composed of the silicon carbide sealing plate, the pressure sensor chip, and the silicon carbide transition plate is not in direct contact with the silicon carbide base plate. At this time, the thermal stress on the subsequent packaging shell will not be directly transmitted to the pressure sensor chip through the silicon carbide base plate, thereby reducing the thermal stress concentration on the pressure sensor chip, ensuring the normal operation of the pressure sensor chip in a high temperature environment, and greatly improving the high temperature resistance of the packaging structure.

[0017] Furthermore, a silicon carbide transition plate is arranged under the pressure sensor chip to protect the pressure sensor chip; at the same time, a square groove is arranged on the silicon carbide transition plate, which not only reserves space for the deformation of the sensitive diaphragm, but also reduces the contact area between the silicon carbide transition plate and the pressure sensor chip, effectively solving the problem of thermal stress concentration.

[0018] Furthermore, the pressure sensor chip is sealed and connected to a silicon carbide sealing plate to achieve absolute pressure measurement.

[0019] The pressure sensor chip of the present invention is packaged in a sealed space composed of a silicon carbide top plate and a silicon carbide bottom plate, which isolates the pressure sensor chip from an external harsh environment and improves the reliability of the pressure sensor chip packaging.

[0020] The preparation method of the non-contact full pressure sensor chip leadless packaging structure provided by the present invention provides mechanical support by sintering Kovar alloy pins with conductive slurry, so that a certain distance is maintained between the silicon carbide transition plate and the silicon carbide base plate, thereby realizing leadless packaging of the full pressure sensor chip, reducing thermal stress concentration on the pressure sensor chip, and improving the high temperature resistance of the packaging structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A cross-sectional view of a leadless packaging structure of a non-contact pressure sensor chip of the present invention; Figure 2 It is a front view of the pressure sensor chip of the present invention; Figure 3 It is a front view of the silicon carbide transition plate of the present invention; Figure 4 It is a front view of the silicon carbide base plate of the present invention.

[0022] In the accompanying drawings: 100-silicon carbide top plate; 101-first groove; 200-silicon carbide sealing plate; 300-pressure sensor chip; 301-metal ohmic contact circuit; 302-sensitive diaphragm; 303-pressure sensor piezoresistive strip; 400-silicon carbide transition plate; 401-first through hole; 402-first pressure-sensing channel; 403-second groove; 500-silicon carbide bottom plate; 501-second through hole; 502-second pressure-sensing channel; 600-Kovar alloy pin. DETAILED DESCRIPTION

[0023] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0025] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be another element centered thereon. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be another element centered thereon at the same time. The terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc. used herein 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 invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0027] The present invention provides a leadless packaging structure of a non-contact pressure sensor chip and a preparation method thereof, which reduces the problem of thermal stress concentration of the pressure sensor chip and improves the reliability of high-temperature packaging.

[0028] Reference Figure 1 A non-contact pressure sensor chip leadless packaging structure includes a silicon carbide top plate 100, a silicon carbide sealing plate 200, a pressure sensor chip 300, a silicon carbide transition plate 400, a silicon carbide bottom plate 500, and a Kovar alloy pin 600. The silicon carbide sealing plate 200, the pressure sensor chip 300, and the silicon carbide transition plate 400 are bonded in sequence, and the pressure sensor chip 300 is inverted.

[0029] The silicon carbide top plate 100 is a patterned silicon carbide top plate, the silicon carbide transition plate 400 is a patterned silicon carbide transition plate, and the silicon carbide bottom plate 500 is a patterned silicon carbide bottom plate.

[0030] The center of the silicon carbide top plate 100 coincides with the center of the silicon carbide sealing plate 200 and the sides are parallel to each other; a square first groove 101 is provided on one side of the silicon carbide top plate 100 close to the silicon carbide sealing plate 200. The center of the first groove 101 coincides with the center of the silicon carbide top plate 100 and the sides are parallel to each other, and the side length of the first groove 101 is greater than the side length of the pressure sensor chip 300; the center of the silicon carbide top plate 100 coincides with the center of the silicon carbide sealing plate 200 and the sides are parallel to each other, and a spacing of 20μm~25μm is left between the silicon carbide sealing plate 200 and the silicon carbide top plate 100.

[0031] Reference Figure 1 and Figure 2 The pressure sensor chip 300 includes a circular sensitive diaphragm 302 and a back cavity corresponding to the sensitive diaphragm on the back side. Four pressure sensor piezoresistive strips 303 are arranged along the tangential direction at the edge of the sensitive diaphragm. The four pressure sensor piezoresistive strips 303 are arranged at 90 degrees apart. The four pressure sensor piezoresistive strips 303 are connected through a metal ohmic contact circuit 301.

[0032] A silicon carbide sealing plate 200 is disposed above the pressure sensor chip 300. The side length of the silicon carbide sealing plate 200 is equal to the side length of the pressure sensor chip 300, and the centers thereof coincide.

[0033] Reference Figure 1 and Figure 3 A silicon carbide transition plate 400 is arranged below the pressure sensor chip 300. The silicon carbide transition plate 400 is provided with four symmetrically distributed vertical first through holes 401 at the corresponding positions of the metal ohmic contact circuit 301 for subsequent signal transmission; a central through hole is arranged at the center of the silicon carbide transition plate 400 as the first pressure sensing channel 402 of the pressure sensor chip 300. The orthographic projection of the center of the first pressure sensing channel 402 coincides with the orthographic projection of the center of the silicon carbide transition plate 200. A square second groove 403 is provided on the silicon carbide transition plate 400, and the center of the second groove 403 coincides with the center of the pressure sensor chip 300, and the sides are equal in length.

[0034] Reference Figure 1 and Figure 4 A silicon carbide bottom plate 500 is arranged below the silicon carbide top plate 100, the center of the silicon carbide bottom plate 500 coincides with the center of the silicon carbide top plate 100 and the sides are parallel to each other; a second through hole 501 is opened on the silicon carbide bottom plate 500, and the second through hole 501 is located directly below the metal ohmic contact circuit 301 in the pressure sensor chip 300; at the same time, a second pressure-sensing channel 502 is opened on the silicon carbide bottom plate 500, the second pressure-sensing channel 502 is connected to the first pressure-sensing channel 402 and has the same diameter, and the center of the second pressure-sensing channel 502 coincides with the center of the silicon carbide bottom plate 500; a spacing of 25μm~30μm is left between the silicon carbide bottom plate 500 and the silicon carbide transition plate 400.

[0035] The silicon carbide base plate 500 is provided with four symmetrically distributed vertical second through holes 501 at the corresponding positions of the metal ohmic contact circuit 301 for subsequent signal transmission; a central through hole is provided at the central position of the silicon carbide base plate 500 as the second pressure sensing channel 502 of the pressure sensor chip 300.

[0036] The four Kovar alloy pins 600 are of equal length and parallel to each other; the four Kovar alloy pins 600 pass through the four second through holes 501 and are inserted into the four first through holes 401, and the upper ends of the Kovar alloy pins 600 are in full contact with the metal ohmic contact circuit 301, providing mechanical support for the pressure sensor chip 300 and the silicon carbide transition plate 400, and realizing a non-contact mechanical support structure. The centers of the Kovar alloy pins 600, the first through holes 402 and the second through holes 502 coincide with each other.

[0037] The above-mentioned method for preparing a leadless packaging structure of a non-contact pressure sensor chip comprises the following steps: Step 1: Preparation of silicon carbide top plate 100: Step 1.1, take a piece of silicon carbide wafer, clean and dry it; Step 1.2, etching a first groove 101 on the front side of the silicon carbide wafer completed in step 1.1; Step 1.3, thermally oxidizing the silicon carbide wafer processed in step 1.2 to form an insulating layer on the surface of the silicon carbide wafer to obtain a silicon carbide top plate 100; Step 2: Preparation of silicon carbide sealing plate: Step 2.1, take a piece of silicon carbide sheet and thin it; Step 2.2, thermally oxidizing the silicon carbide wafer processed in step 2.1 to form an insulating layer on the surface of the silicon carbide wafer to obtain a silicon carbide sealing plate 200; Step 3: Preparation of pressure sensor chip: Step 3.1, take an N-type silicon carbide sheet to make a silicon carbide substrate; Step 3.2, epitaxially growing an insulating layer on the front side of the silicon carbide substrate, and epitaxially growing a layer of N-type silicon carbide on the insulating layer; Step 3.3, etching four pressure sensor piezoresistive strips 303 on the N-type silicon carbide; Step 3.4, thermally oxidizing the silicon carbide substrate to deposit a silicon dioxide insulating layer; Step 3.5, sputtering a metal layer on the silicon dioxide insulating layer, patterning the metal layer, and then annealing it at a high temperature of 800° C. to 900° C. for 2 min to 8 min to form a metal ohmic contact circuit 301; Step 3.6, ICP etching a back cavity on the back side of the silicon carbide substrate to form a pressure-sensitive diaphragm 302, thereby obtaining a pressure sensor chip 300; Step 4: Preparation of silicon carbide transition plate 400: Step 4.1, take a piece of silicon carbide sheet and thin it; Step 4.2, etching a second groove 403 on the front side of the silicon carbide wafer completed in step 4.1; Step 4.3, four first through holes 401 and one first pressure-sensing channel 402 are processed by laser on the silicon carbide wafer completed in step 4.2, and the first pressure-sensing channel 402 passes through the bottom surface of the second groove 403; Step 4.4, thermally oxidizing the silicon carbide wafer, depositing an insulating layer on the surface of the silicon carbide wafer, and obtaining a silicon carbide transition plate 400; Step 5: Preparation of silicon carbide base plate 500: Step 5.1, take a piece of N-type silicon carbide wafer and thin it; Step 5.2, laser processing four second through holes 501 and one second pressure-sensing channel 502 on the silicon carbide sheet completed in step 5.1, wherein the second pressure-sensing channel 502 passes through the silicon carbide sheet; Step 5.3, thermally oxidizing the silicon carbide wafer and depositing an insulating layer to obtain a silicon carbide base plate 500; Step 6: Preparation of Kovar alloy pins: Step 6.1, take four 4J29 Kovar alloy pins, polish and clean the surface to remove grease; Step 6.2, placing the Kovar alloy pin in an electroplating bath, electroplating a layer of gold on the surface, and obtaining the Kovar alloy pin 600; Step 7: Packaging structure preparation: Step 7.1, the processed silicon carbide top plate 100, silicon carbide sealing plate 200, pressure sensor chip 300, silicon carbide transition plate 400, silicon carbide bottom plate 500 are cleaned with acetone, alcohol, SPM, hydrofluoric acid solution and deionized water in sequence, and blown dry; Step 7.2, placing the silicon carbide top plate 100, silicon carbide sealing plate 200, pressure sensor chip 300, silicon carbide transition plate 400, and silicon carbide bottom plate 500 processed in step 7.1 in a plasma treatment machine, and activating the surface with oxygen ions; Step 7.3, transferring the silicon carbide sealing plate 200, the pressure sensor chip 300, and the silicon carbide transition plate 400 processed in step 7.2 to a bonding machine, and arranging them neatly in the order of silicon carbide sealing plate 200, pressure sensor chip 300, and silicon carbide transition plate 400 from top to bottom, and bonding them under pressure of 1.5 MPa to 2.5 MPa for 180s to 270s at room temperature to obtain structure A; Step 7.4, fill the first through hole 401 and the second through hole 501 with conductive paste by screen printing, wherein the thickness of the conductive paste filled in the first through hole 401 is equal to the thickness of the silicon carbide transition plate 400, and the thickness of the conductive paste filled in the second through hole 501 is equal to the thickness of the silicon carbide base plate 500; Step 7.5, when the conductive paste is in liquid form, insert the Kovar alloy pin into the conductive paste of the first through hole 401 and the second through hole 501, control the distance between the silicon carbide transition plate 400 and the silicon carbide base plate 500 in structure A to be 25 μm-30 μm, and preform the conductive paste at room temperature of 22°C-25°C to obtain structure B; Step 7.6, transfer the silicon carbide top plate 100 and structure B processed in step 7.2 to a bonding machine, and place them neatly in the order of silicon carbide top plate 100 and structure B from top to bottom, and bond them under pressure of 1.5MPa~2.5MPa for 180s~270s at room temperature to achieve alignment and bonding connection between the silicon carbide top plate 100 and the silicon carbide bottom plate 500 in structure B; Step 7.7: Place the structure obtained in step 7.6 into a high temperature furnace, sinter at 1100°C to 1300°C for 2h to 3h, and then naturally cool to room temperature to obtain a non-contact pressure sensor chip leadless packaging structure.

[0038] The following are specific embodiments. It should be noted that these embodiments are preferred examples of the present invention and are used for those skilled in the art to understand the present invention, but the present invention is not limited to these embodiments.

[0039] Example 1 A method for preparing a leadless packaging structure of a non-contact pressure sensor chip comprises the following steps: Step 1: Take a piece of N-type silicon carbide wafer A with a thickness of 350 μm and a size of 4 mm×4 mm, clean it with acetone, ethanol and deionized water respectively to remove organic and tiny solid particle pollutants on its surface, and dehydrate and dry it; Step 2. Processing a square first groove 101 on the front side of the silicon carbide wafer A by using ICP shallow etching, where the side length of the groove may be 350 μm and the depth may be 300 μm; Step 3: Take a piece of N-type silicon carbide wafer B with a thickness of 350 μm and a size of 3 mm×3 mm, thin it to 50 μm, wash it with acetone, ethanol and deionized water respectively, and dehydrate and dry it; Step 4: In an air atmosphere, the silicon carbide wafer A and the silicon carbide wafer B are subjected to thermal oxidation etching. The thermal oxidation condition may be calcining at 600° C. for 2 hours, and a layer of SiO2 is grown on the surface thereof. The thickness of the SiO2 layer may be 100 nm, and a silicon carbide top plate 100 and a silicon carbide sealing plate 200 are obtained respectively. Step 5: Take a piece of N-type silicon carbide wafer C with a thickness of 350 μm and a size of 3 mm×3 mm, thin it to 150 μm, wash it with acetone, ethanol and deionized water respectively, and dehydrate and dry it; Step 6. Perform two homogeneous epitaxial layer growths on the Si surface of the N-type silicon carbide wafer C completed in step 5. The specific process is that aluminum is used as the doping ion for the first time to form a P-type epitaxial layer in a silane, propane, and trimethylaluminum atmosphere; nitrogen is used as the doping ion for the second time to grow an N-type epitaxial layer on the P-type epitaxial layer in a silane, propane, and nitrogen atmosphere. The thickness of both types of epitaxial layers can be 2μm; Step 7. Four piezoresistive strips 303 of the pressure sensor tangentially located at the edge of the sensitive diaphragm are shallowly etched in the N-type epitaxial layer by RIE. The size of the piezoresistive strips 303 may be: 200 μm in length, 10 μm in width, and 3 μm in thickness; Step 8: The back of the silicon carbide wafer C completed in step 7 is deeply etched by ICP, and the etching depth can be 100 μm to form a pressure sensitive membrane 302 with a thickness of 50 μm. The silicon carbide wafer C after thermal oxidation etching is calcined at 600° C. for 2 hours in an air atmosphere to grow a layer of SiO2 on its surface, and the thickness of the SiO2 layer can be 100 nm. Step 9. Apply glue and pattern the front side of the silicon carbide wafer C completed in step 8, wet-etch the SiO2 layer by HF to form an ohmic contact window, and then remove the glue and clean it; Step 10. Sputter a metal layer on the front side of the silicon carbide wafer C, and use wet etching to pattern the metal layer, leaving only the metal layer at the ohmic contact window, and anneal at 800° C. for 8 min to form a metal ohmic contact circuit 301, thereby obtaining a pressure sensor chip 300; Step 11. Take a piece of N-type silicon carbide sheet E with a thickness of 350μm and a size of 3mm×3mm, and thin it to 50μm. Use ICP shallow etching to process a square second groove 403 on the front side, the side length of the second groove 403 can be 1.7mm, and the depth can be 20μm; use femtosecond laser processing technology to process the first through hole 401 at the corresponding position of the ohmic contact window, and the diameter of the first through hole 401 can be 300μm; use femtosecond laser processing technology to process the first pressure-sensing channel 402 at the center position, and the diameter of the first pressure-sensing channel 402 can be 100μm; in an air atmosphere, thermally oxidize and etch the silicon carbide sheet E after the thermal oxidation condition, which can be calcined at 600℃ for 2h, and a layer of SiO2 is grown on its surface, and the thickness of the SiO2 layer can be 100nm, to obtain a silicon carbide transition plate 400; Step 12, take a piece of N-type silicon carbide sheet E with a thickness of 350μm and a size of 4mm×4mm, and thin it to 150μm. Use femtosecond laser processing technology to process the first through hole 501 at the corresponding position of the ohmic contact window, and the diameter of the through hole can be 300μm; use femtosecond laser processing technology to process the second pressure-sensitive channel 502 at the center position, and the diameter of the second pressure-sensitive channel 502 is equal to the diameter of the first pressure-sensitive channel, which can be 100μm; in an air atmosphere, thermally oxidize and etch the processed silicon carbide sheet E, and the thermal oxidation conditions can be calcined at 600℃ for 2h, and a layer of SiO2 is grown on its surface, and the thickness of the SiO2 layer can be 100nm, to obtain a silicon carbide base plate 500; Step 13. Clean the silicon carbide top plate 100, the silicon carbide sealing plate 200, the pressure sensor chip 300, the silicon carbide transition plate 400 and the silicon carbide bottom plate 500 with acetone, alcohol, SPM, hydrofluoric acid solution and deionized water in sequence, and blow dry; Step 14: Place the silicon carbide top plate 100, silicon carbide sealing plate 200, pressure sensor chip 300, silicon carbide transition plate 400 and silicon carbide bottom plate 500 processed in step 12 in a plasma treatment machine, and activate the surface with oxygen ions; Step 15. Transfer the silicon carbide sealing plate 200, the pressure sensor chip 300 and the silicon carbide transition plate 400 processed in step 13 to a bonding machine, and bond them under pressure of 1.5 MPa for 270 seconds at room temperature to obtain structure A; Step 16. Fill the first through hole 401 and the second through hole 501 with conductive silver paste by screen printing. The thickness of the conductive silver paste is equal to the thickness of the silicon carbide transition plate 400 and the silicon carbide base plate 500, which are 50 μm and 150 μm respectively. Step 17. When the conductive silver paste is in liquid form, the electroplated Kovar alloy pin is inserted into the first through hole 401 and the second through hole 501. The length of the Kovar alloy pin can be 3 mm. The distance between the silicon carbide transition plate 400 and the silicon carbide base plate 500 in the control structure A can be 25 μm. The conductive silver paste is preformed at room temperature of 22° C.-25° C. to obtain structure B. Step 18. Transfer the silicon carbide top plate 100 and structure B to a bonding machine, pressurize and bond them at 1.5 MPa for 270 seconds at room temperature, and align and bond the silicon carbide top plate 100 with the silicon carbide bottom plate 500 in structure B; Step 19. Place the structure processed in step 18 into a high-temperature furnace, sinter at 1100° C. for 3 hours, and then cool to room temperature naturally to obtain a non-contact pressure sensor chip leadless packaging structure.

[0040] Example 2 A method for preparing a leadless packaging structure of a non-contact pressure sensor chip comprises the following steps: Step 1: Take a piece of N-type silicon carbide wafer A with a thickness of 350 μm and a size of 4 mm×4 mm, clean it with acetone, ethanol and deionized water respectively to remove organic and tiny solid particle pollutants on its surface, and dehydrate and dry it; Step 2. Processing a square first groove 101 on the front side of the silicon carbide wafer A by ICP shallow etching, wherein the side length of the groove may be 350 μm and the depth may be 300 μm; Step 3: Take a piece of N-type silicon carbide wafer B with a thickness of 350 μm and a size of 3 mm×3 mm, thin it to 50 μm, wash it with acetone, ethanol and deionized water respectively, and dehydrate and dry it; Step 4: In an air atmosphere, the silicon carbide wafer A and the silicon carbide wafer B are subjected to thermal oxidation etching. The thermal oxidation condition may be calcining at 600° C. for 2 hours, and a layer of SiO2 is grown on the surface thereof. The thickness of the SiO2 layer may be 100 nm, and a silicon carbide top plate 100 and a silicon carbide sealing plate 200 are obtained respectively. Step 5: Take a piece of N-type silicon carbide wafer C with a thickness of 350 μm and a size of 3 mm×3 mm, thin it to 150 μm, wash it with acetone, ethanol and deionized water respectively, and dehydrate and dry it; Step 6. Perform two homogeneous epitaxial layer growths on the Si surface of the N-type silicon carbide wafer C completed in step 5. The specific process is that aluminum is used as the doping ion for the first time to form a P-type epitaxial layer in a silane, propane, and trimethylaluminum atmosphere; nitrogen is used as the doping ion for the second time to grow an N-type epitaxial layer on the P-type epitaxial layer in a silane, propane, and nitrogen atmosphere. The thickness of both types of epitaxial layers can be 2μm; Step 7. Four piezoresistive strips 303 of the pressure sensor tangentially located at the edge of the sensitive diaphragm are shallowly etched in the N-type epitaxial layer by RIE. The size of the piezoresistive strips 303 may be: 200 μm in length, 10 μm in width, and 3 μm in thickness; Step 8: The back of the silicon carbide wafer C completed in step 7 is deeply etched by ICP, and the etching depth can be 100 μm to form a pressure sensitive membrane 302 with a thickness of 50 μm. The silicon carbide wafer C after thermal oxidation etching is calcined at 600° C. for 2 hours in an air atmosphere to grow a layer of SiO2 on its surface, and the thickness of the SiO2 layer can be 100 nm. Step 9. Apply glue and pattern the front side of the silicon carbide wafer C completed in step 8, wet-etch the SiO2 layer by HF to form an ohmic contact window, and then remove the glue and clean it; Step 10. Sputter a metal layer on the front side of the silicon carbide wafer C, and use wet etching to pattern the metal layer, leaving only the metal layer at the ohmic contact window, and anneal at 850° C. for 5 min to form a metal ohmic contact circuit 301, thereby obtaining a pressure sensor chip 300; Step 11. Take a piece of N-type silicon carbide sheet E with a thickness of 350μm and a size of 3mm×3mm, and thin it to 50μm. Use ICP shallow etching to process a square second groove 403 on the front side, the side length of the second groove 403 can be 1.7mm, and the depth can be 20μm; use femtosecond laser processing technology to process the first through hole 401 at the corresponding position of the ohmic contact window, and the diameter of the first through hole 401 can be 300μm; use femtosecond laser processing technology to process the first pressure-sensing channel 402 at the center position, and the diameter of the first pressure-sensing channel 402 can be 100μm; in an air atmosphere, thermally oxidize and etch the silicon carbide sheet E after the thermal oxidation condition, which can be calcined at 600℃ for 2h, and a layer of SiO2 is grown on its surface, and the thickness of the SiO2 layer can be 100nm, to obtain a silicon carbide transition plate 400; Step 12, take a piece of N-type silicon carbide sheet E with a thickness of 350μm and a size of 4mm×4mm, and thin it to 150μm. Use femtosecond laser processing technology to process the first through hole 501 at the corresponding position of the ohmic contact window, and the diameter of the through hole can be 300μm; use femtosecond laser processing technology to process the second pressure-sensitive channel 502 at the center position, and the diameter of the second pressure-sensitive channel 502 is equal to the diameter of the first pressure-sensitive channel, which can be 100μm; in an air atmosphere, thermally oxidize and etch the processed silicon carbide sheet E, and the thermal oxidation conditions can be calcined at 600℃ for 2h, and a layer of SiO2 is grown on its surface, and the thickness of the SiO2 layer can be 100nm, to obtain a silicon carbide base plate 500; Step 13. Clean the silicon carbide top plate 100, the silicon carbide sealing plate 200, the pressure sensor chip 300, the silicon carbide transition plate 400 and the silicon carbide bottom plate 500 with acetone, alcohol, SPM, hydrofluoric acid solution and deionized water in sequence, and blow dry; Step 14: Place the silicon carbide top plate 100, silicon carbide sealing plate 200, pressure sensor chip 300, silicon carbide transition plate 400 and silicon carbide bottom plate 500 processed in step 12 in a plasma treatment machine, and activate the surface with oxygen ions; Step 15. Transfer the silicon carbide sealing plate 200, the pressure sensor chip 300 and the silicon carbide transition plate 400 processed in step 13 to a bonding machine, and bond them under pressure of 2.0 MPa for 225 seconds at room temperature to obtain structure A; Step 16. Fill the first through hole 401 and the second through hole 501 with conductive silver paste by screen printing. The thickness of the conductive silver paste is equal to the thickness of the silicon carbide transition plate 400 and the silicon carbide base plate 500, which are 50 μm and 150 μm respectively. Step 17. When the conductive silver paste is in liquid form, the electroplated Kovar alloy pin is inserted into the first through hole 401 and the second through hole 501. The length of the Kovar alloy pin can be 3 mm. The distance between the silicon carbide transition plate 400 and the silicon carbide base plate 500 in the control structure A can be 27.5 μm. The conductive silver paste is preformed at room temperature of 22° C.-25° C. to obtain structure B. Step 18. Transfer the silicon carbide top plate 100 and structure B to a bonding machine, pressurize and bond them at 2.0 MPa for 225 seconds at room temperature, and align and bond the silicon carbide top plate 100 with the silicon carbide bottom plate 500 in structure B; Step 19. Place the structure processed in step 18 into a high-temperature furnace, sinter at 1200° C. for 2.5 hours, and then cool to room temperature naturally to obtain a non-contact pressure sensor chip leadless packaging structure.

[0041] Example 3 A method for preparing a leadless packaging structure of a non-contact pressure sensor chip comprises the following steps: Step 1: Take a piece of N-type silicon carbide wafer A with a thickness of 350 μm and a size of 4 mm×4 mm, clean it with acetone, ethanol and deionized water respectively to remove organic and tiny solid particle pollutants on its surface, and dehydrate and dry it; Step 2. Processing a square first groove 101 on the front side of the silicon carbide wafer A by ICP shallow etching, wherein the side length of the groove may be 350 μm and the depth may be 300 μm; Step 3: Take a piece of N-type silicon carbide wafer B with a thickness of 350 μm and a size of 3 mm×3 mm, thin it to 50 μm, wash it with acetone, ethanol and deionized water respectively, and dehydrate and dry it; Step 4: In an air atmosphere, the silicon carbide wafer A and the silicon carbide wafer B are subjected to thermal oxidation etching. The thermal oxidation condition may be calcining at 600° C. for 2 hours, and a layer of SiO2 is grown on the surface thereof. The thickness of the SiO2 layer may be 100 nm, and a silicon carbide top plate 100 and a silicon carbide sealing plate 200 are obtained respectively. Step 5: Take a piece of N-type silicon carbide wafer C with a thickness of 350 μm and a size of 3 mm×3 mm, thin it to 150 μm, wash it with acetone, ethanol and deionized water respectively, and dehydrate and dry it; Step 6. Perform two homogeneous epitaxial layer growths on the Si surface of the N-type silicon carbide wafer C completed in step 5. The specific process is that aluminum is used as the doping ion for the first time to form a P-type epitaxial layer in a silane, propane, and trimethylaluminum atmosphere; nitrogen is used as the doping ion for the second time to grow an N-type epitaxial layer on the P-type epitaxial layer in a silane, propane, and nitrogen atmosphere. The thickness of both types of epitaxial layers can be 2μm; Step 7. Four piezoresistive strips 303 of the pressure sensor tangentially located at the edge of the sensitive diaphragm are shallowly etched in the N-type epitaxial layer by RIE. The size of the piezoresistive strips 303 may be: 200 μm in length, 10 μm in width, and 3 μm in thickness; Step 8: The back of the silicon carbide wafer C completed in step 7 is deeply etched by ICP, and the etching depth can be 100 μm to form a pressure sensitive membrane 302 with a thickness of 50 μm. The silicon carbide wafer C after thermal oxidation etching is calcined at 600° C. for 2 hours in an air atmosphere to grow a layer of SiO2 on its surface, and the thickness of the SiO2 layer can be 100 nm. Step 9. Apply glue and pattern the front side of the silicon carbide wafer C completed in step 8, wet-etch the SiO2 layer by HF to form an ohmic contact window, and then remove the glue and clean it; Step 10. Sputter a metal layer on the front side of the silicon carbide wafer C, and use wet etching to pattern the metal layer, leaving only the metal layer at the ohmic contact window, and anneal at 900° C. for 2 min to form a metal ohmic contact circuit 301, thereby obtaining a pressure sensor chip 300; Step 11. Take a piece of N-type silicon carbide sheet E with a thickness of 350μm and a size of 3mm×3mm, and thin it to 50μm. Use ICP shallow etching to process a square second groove 403 on the front side, the side length of the second groove 403 can be 1.7mm, and the depth can be 20μm; use femtosecond laser processing technology to process the first through hole 401 at the corresponding position of the ohmic contact window, and the diameter of the first through hole 401 can be 300μm; use femtosecond laser processing technology to process the first pressure-sensing channel 402 at the center position, and the diameter of the first pressure-sensing channel 402 can be 100μm; in an air atmosphere, thermally oxidize and etch the silicon carbide sheet E after the thermal oxidation condition, which can be calcined at 600℃ for 2h, and a layer of SiO2 is grown on its surface, and the thickness of the SiO2 layer can be 100nm, to obtain a silicon carbide transition plate 400; Step 12, take a piece of N-type silicon carbide sheet E with a thickness of 350μm and a size of 4mm×4mm, and thin it to 150μm. Use femtosecond laser processing technology to process the first through hole 501 at the corresponding position of the ohmic contact window, and the diameter of the through hole can be 300μm; use femtosecond laser processing technology to process the second pressure-sensitive channel 502 at the center position, and the diameter of the second pressure-sensitive channel 502 is equal to the diameter of the first pressure-sensitive channel, which can be 100μm; in an air atmosphere, thermally oxidize and etch the processed silicon carbide sheet E, and the thermal oxidation conditions can be calcined at 600℃ for 2h, and a layer of SiO2 is grown on its surface, and the thickness of the SiO2 layer can be 100nm, to obtain a silicon carbide base plate 500; Step 13. Clean the silicon carbide top plate 100, the silicon carbide sealing plate 200, the pressure sensor chip 300, the silicon carbide transition plate 400 and the silicon carbide bottom plate 500 with acetone, alcohol, SPM, hydrofluoric acid solution and deionized water in sequence, and blow dry; Step 14: Place the silicon carbide top plate 100, silicon carbide sealing plate 200, pressure sensor chip 300, silicon carbide transition plate 400 and silicon carbide bottom plate 500 processed in step 12 in a plasma treatment machine, and activate the surface with oxygen ions; Step 15. Transfer the silicon carbide sealing plate 200, the pressure sensor chip 300 and the silicon carbide transition plate 400 processed in step 13 to a bonding machine, and bond them under pressure of 2.5 MPa for 180 seconds at room temperature to obtain structure A; Step 16. Fill the first through hole 401 and the second through hole 501 with conductive silver paste by screen printing. The thickness of the conductive silver paste is equal to the thickness of the silicon carbide transition plate 400 and the silicon carbide base plate 500, which are 50 μm and 150 μm respectively. Step 17. When the conductive silver paste is in liquid form, the electroplated Kovar alloy pin is inserted into the first through hole 401 and the second through hole 501. The length of the Kovar alloy pin can be 3 mm. The distance between the silicon carbide transition plate 400 and the silicon carbide base plate 500 in the control structure A can be 30 μm. The conductive silver paste is preformed at room temperature of 22° C.-25° C. to obtain structure B. Step 18. Transfer the silicon carbide top plate 100 and structure B to a bonding machine, pressurize and bond them at 2.5 MPa for 180 seconds at room temperature, and align and bond the silicon carbide top plate 100 with the silicon carbide bottom plate 500 in structure B; Step 19. Place the structure processed in step 18 into a high-temperature furnace, sinter at 1300° C. for 2 hours, and then cool to room temperature naturally to obtain a non-contact pressure sensor chip leadless packaging structure.

[0042] The term "consisting of" describing a combination shall include the identified elements, ingredients, parts or steps and other elements, ingredients, parts or steps that do not substantially affect the basic novel characteristics of the combination. The use of the terms "comprising" or "including" to describe a combination of elements, ingredients, parts or steps herein also contemplates embodiments that consist essentially of these elements, ingredients, parts or steps. By using the term "may", it is intended to illustrate that any of the attributes described that "may" be included are optional.

[0043] Multiple elements, ingredients, parts or steps can be provided by a single integrated element, ingredient, part or step. Alternatively, a single integrated element, ingredient, part or step can be divided into separate multiple elements, ingredients, parts or steps. The disclosure "one" or "an" used to describe an element, ingredient, part or step is not intended to exclude other elements, ingredients, parts or steps.

[0044] It should be understood that the above description is for illustration and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teachings should not be determined with reference to the above description, but rather with reference to the foregoing claims and the full scope of equivalents to which such claims are entitled. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended to be a waiver of such subject matter, nor should it be considered that the applicant has not considered such subject matter to be part of the disclosed inventive subject matter.

Claims

1. A non-contact pressure sensor chip leadless packaging structure, characterized in that: The invention comprises a silicon carbide top plate (100), a silicon carbide bottom plate (500) and a kovar alloy pin (600), wherein the silicon carbide top plate (100) and the silicon carbide bottom plate (500) are butt-jointed, a first groove (101) is provided on the silicon carbide top plate (100), the first groove (101) and the silicon carbide bottom plate (500) form a cavity, a pressure sensor chip (300) is arranged in the cavity, and the pressure sensor chip (300) is inverted; the kovar alloy pin (600) passes through the silicon carbide bottom plate (500) and is connected to a metal ohmic contact circuit (301) of the pressure sensor chip (300), and a spacing is left between the pressure sensor chip (300) and the silicon carbide bottom plate (500).

2. The non-contact pressure sensor chip leadless packaging structure according to claim 1, characterized in that: The pressure sensor chip (300) comprises a sensitive diaphragm (302), four pressure sensor piezoresistive strips (303) are arranged along the tangential direction at the edge of the sensitive diaphragm (302), and the four pressure sensor piezoresistive strips (303) are connected via a metal ohmic contact circuit (301).

3. The non-contact pressure sensor chip leadless packaging structure according to claim 1, characterized in that: A silicon carbide sealing plate (200) is fixed on the back side of the pressure sensor chip (300).

4. The non-contact pressure sensor chip leadless packaging structure according to claim 1, characterized in that: A silicon carbide transition plate (400) is fixed on the front side of the pressure sensor chip (300), a second groove (403) is provided on the silicon carbide transition plate (400), and the center of the second groove (403) coincides with the center projection of the pressure sensor chip (300).

5. A non-contact pressure sensor chip leadless packaging structure according to claim 1 or 4, characterized in that: The silicon carbide transition plate (400) is provided with a first through hole (401), and the first through hole (401) is located directly below the metal ohmic contact circuit (301) in the pressure sensor chip (300); the silicon carbide transition plate (400) is provided with a first pressure sensing channel (402), and the orthographic projection of the center of the first pressure sensing channel (402) coincides with the orthographic projection of the center of the silicon carbide transition plate (200).

6. The non-contact pressure sensor chip leadless packaging structure according to claim 1, characterized in that: A gap is left between the silicon carbide sealing plate (200) and the silicon carbide top plate (100).

7. The non-contact pressure sensor chip leadless packaging structure according to claim 1, characterized in that: The silicon carbide base plate (500) is provided with a second through hole (501), the second through hole (501) being located directly below the metal ohmic contact circuit (301) in the pressure sensor chip (300); at the same time, the silicon carbide base plate (500) is provided with a second pressure sensing channel (502); and a spacing is left between the silicon carbide base plate (500) and the silicon carbide transition plate (400).

8. The non-contact pressure sensor chip leadless packaging structure according to claim 7, characterized in that: The Kovar alloy pin (600) passes through the second through hole (502).

9. The method for preparing a leadless package structure of a non-contact pressure sensor chip according to claim 1, characterized in that: The following steps are involved: Step 1: activating the surfaces of the silicon carbide top plate (100), the pressure sensor chip (300) and the silicon carbide bottom plate (500); Step 2, bonding the silicon carbide sealing plate (200) and the pressure sensor chip (300) under pressure at 1.5 MPa to 2.5 MPa for 180 seconds to 270 seconds to obtain a bonding structure; Step 3, filling the second through hole (501) opened on the silicon carbide base plate (500) with a conductive paste; Step 4: When the conductive paste is in liquid form, the Kovar alloy pin (600) is passed through the conductive paste in the second through hole (501) and contacts the metal ohmic contact circuit (301) of the pressure sensor chip (300), and the pressure sensor chip (300) and the silicon carbide base plate (500) are controlled to maintain a distance to obtain an intermediate structure; Step 5, bonding the silicon carbide top plate (100) and the intermediate structure under pressure at 1.5 MPa to 2.5 MPa for 180 seconds to 270 seconds; Step 6: Sinter the structure obtained in step 5 at 1100° C. to 1300° C. for 2 h to 3 h, and then cool it down to obtain a leadless packaging structure of a non-contact pressure sensor chip.

10. The method for preparing a leadless package structure of a non-contact pressure sensor chip according to claim 9, characterized in that: In the step 2, the silicon carbide sealing plate (200), the pressure sensor chip (300) and the silicon carbide transition plate (400) are bonded under pressure at 1.5 MPa to 2.5 MPa for 180 seconds to 270 seconds to obtain a bonding structure; the silicon carbide transition plate (400) is provided with a first through hole (401) and a first pressure sensing channel (402); In the step 3, the conductive paste is filled into the first through hole (401) and the second through hole (501) opened on the silicon carbide base plate (500); In step 4, when the conductive paste is in liquid form, the Kovar alloy pin is passed through the conductive paste in the second through hole (501) and the first through hole (401) and contacts the metal ohmic contact circuit (301) of the pressure sensor chip (300), and the distance between the silicon carbide transition plate (400) and the silicon carbide base plate (500) is controlled to be maintained, thereby obtaining an intermediate structure.

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