CN110745774B - A SiC temperature sensor with a cantilever beam structure and its manufacturing method - Google Patents

Abstract

The invention discloses a SiC temperature sensor with a cantilever beam structure and a manufacturing method thereof, wherein the temperature sensor structure comprises: the MEMS device comprises a MEMS cantilever beam with a multilayer structure, a Wheatstone bridge detection circuit and four metal pads. The MEMS cantilever beam with the multilayer structure has a SiC bottom layer, a composite silicon compound middle layer and a top metal layer from bottom to top. The SiC bottom layer comprises three parts: a piezoresistive region, an electrical connection line region, and an undoped region; the composite silicon compound interlayer is formed by stacking a plurality of thin layers of silicon compounds. The Wheatstone bridge detection circuit is formed on the SiC bottom layer through an ion implantation process and consists of a piezoresistive region and an electric connection circuit region, and the electric connection circuit region comprises an electrode and a connection circuit. The SiC temperature sensor can realize accurate measurement of temperature in a high-temperature environment, and not only is insulation protection realized, but also thermal stress damage can be effectively prevented through the composite silicon compound intermediate layer.

Description

A SiC temperature sensor with a cantilever beam structure and its manufacturing method

technical field

The invention belongs to the technical field of wide bandgap semiconductor device preparation, and relates to a method for preparing a temperature sensor, in particular to a SiC temperature sensor with a cantilever beam structure and a method for manufacturing the same.

Background technique

Semiconductor integrated sensors have the characteristics of specific functions, small measurement errors, fast response, small size, low power consumption, and no need for nonlinear calibration. However, most of the existing semiconductor integrated sensors are based on Si-based. Since Si has a narrow band gap (~1.12eV), high temperature resistance, and poor radiation performance, it cannot adapt to high-temperature working environments. Therefore, the highest operating temperature of Si-based sensors on the market is At around 125°C. In addition, Si will react with other substances in harsh environments and is easily oxidized or corroded; the mechanical properties of Si are prone to degradation under high temperature conditions, so Si-based temperature sensors are no longer suitable for complex and harsh working environments.

With people's exploration of harsh environments, especially in the field of high temperature measurement with a temperature higher than 350 °C, there are higher requirements for the high temperature resistance of temperature sensors, and SiC materials have wide band gap, high thermal conductivity, high melting point, Excellent material properties such as excellent mechanical properties, radiation resistance, corrosion resistance, high thermal stability, large piezoelectric coefficient, high saturation electron drift rate and low dielectric constant are ideal materials for making high temperature resistant sensors.

Common semiconductor integrated temperature sensors include platinum resistance type, thermistor type, thermocouple type, PN junction type, etc. With the emergence of MEMS (Micro-Electro-Mechanical System, Micro-Electro-Mechanical System) technology, MEMS temperature sensors such as piezoresistive, piezoelectric, inductive, resonant, and polysilicon micro-bridges have been developed. Because piezoresistive sensors have good sensitivity, small output impedance, and high output linearity, it is very effective to use piezoresistive sensors to measure non-electrical parameters.

Contents of the invention

The purpose of the present invention is to provide a SiC temperature sensor with a cantilever beam structure, so as to ensure that the integrated temperature sensor working in a harsh environment has higher reliability, longer life, better sensitivity and linearity.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A SiC temperature sensor with a cantilever beam structure is characterized in that it includes a bottom-up SiC bottom layer, a composite silicon compound middle layer and a top metal layer, and the Si surface of the SiC bottom layer is implanted and doped by an ion implantation process to form a Stone bridge detection circuit, the undoped area is an insulating protection area, and conductive metal electrically connected to the electrodes of the Wheatstone bridge detection circuit is deposited on the SiC bottom layer to form a metal pad, and the composite silicon compound intermediate layer is used for buffering Thermal stress, the composite silicon compound intermediate layer is formed by stacking multiple thin layers of silicon compound with low thermal expansion coefficient, high dielectric constant, high insulation, and thermal expansion that can generate stress in different directions. By selecting the deposition area of the composite silicon compound intermediate layer to make The metal pad is exposed, the top metal layer and the uppermost layer of the composite silicon compound intermediate layer are deposited on the uppermost layer of the composite silicon compound intermediate layer in the same area, and a cavity is etched in the middle of the C surface of the SiC bottom layer, and at the bottom of the cavity A pattern penetrating the top metal layer is etched to form a MEMS cantilever beam structure.

Further, the Wheatstone bridge detection circuit is composed of a piezoresistive area and an electrical connection line area, the electrical connection line area includes electrodes and a connection circuit, and the piezoresistive area and electrodes are interconnected through a connection circuit to form a Wheatstone bridge detection circuit. circuit, the piezoresistive area includes four piezoresistor strips, the four piezoresistor strips are a pair of longitudinal piezoresistor strips and a pair of transverse piezoresistor strips, and the connection circuit is used to connect the four piezoresistor strips The strips are connected end to end, and there are four electrodes distributed on the connection circuit between two adjacent piezoresistor strips. The vertical varistor strips are parallel to the cantilever structure, and the horizontal varistor strips are perpendicular to the cantilever structure. The horizontal and vertical varistor strips are N-type or P-type SiC, and the surface structure of the SiC bottom layer is formed by ion implantation doping process. Processed, preferably, phosphorus ions can be used as the ion implantation material.

The electrical connection line area includes electrodes and connection circuits, and a conductive circuit is formed by heavy doping with ion implantation. The implanted ion type is the same as that in the piezoresistive area, and the same type of N-type or P-type semiconductor is formed. There are four electrodes in total, which are evenly arranged around the temperature sensor. Preferably, a rectangular pattern can be used, and at least one side is longer than 300 μm, so as to realize interconnection with external leads. The undoped region is an undoped SiC bottom layer, which can insulate and protect the Wheatstone bridge detection circuit.

The composite silicon compound intermediate layer is formed by stacking multiple silicon compound thin layers with low thermal expansion coefficient, high dielectric constant, high insulation, and can generate stress in different directions after thermal expansion. At the same time, as an insulating layer, it separates the top metal layer from the Wheatstone bridge detection circuit on the bottom layer of SiC, so as to realize the protection of the circuit.

Preferably, the composite silicon compound intermediate layer formed by stacking multiple silicon compound thin layers can use two layers of silicon compounds, and the silicon compound can use SiO ₂ layer and Si ₃ N ₄ layer, and the thicknesses are 0.3±0.05 μm and 0.2 μm respectively. ±0.02μm. The SiO ₂ layer generates compressive stress after thermal expansion, and the Si ₃ N ₄ layer generates tensile stress after thermal expansion. Therefore, the use of these two materials can relieve the stress concentration phenomenon of the composite silicon compound intermediate layer. The side length of the SiO ₂ layer is equal to the side length of the SiC bottom layer, and the side length of the Si ₃ N ₄ layer is 300±10 μm shorter than the side length of the SiO ₂ layer, and a size margin is reserved for the metal pad to realize the metal pad For the connection with the external circuit structure, the SiO ₂ layer is distributed with four through-hole structures for depositing metal pads. The through-holes are located directly above the electrodes, and the through-holes are slightly larger than the side length of the electrodes by 3-5 μm.

Further, the four varistor strips are prepared by lightly doping or moderately doping a local area of the SiC bottom layer through an ion implantation process, the doping type is N-type or P-type, and the electrodes and connecting circuits are SiC prepared by heavily doping the local area of the bottom layer of SiC with the same type as the varistor strip by ion implantation process.

Further, any adjacent two of the four piezoresistor strips are perpendicular to each other on the extension line, and the four piezoresistor strips are arranged in one direction to form a radial pattern.

Further, there are four metal pads, which are evenly distributed around the temperature sensor. The metal pads include a metal layer at the bottom of the pad and a metal layer at the top of the pad, and the metal layer at the bottom of the pad is placed above the electrode and connected with it To form an ohmic contact, the top metal layer of the pad is placed above the bottom metal layer of the pad and forms electrical contact with it. The top metal layer of the pad connects the metal pad and the external circuit through a lead structure, and the top metal layer of the pad is highly resistant to oxidation.

Further, the metal layer at the bottom of the pad is made of metallic nickel, aluminum or titanium, the metal layer at the top of the pad is made of platinum metal with high oxidation resistance; the metal layer at the bottom of the pad is made of nickel or titanium, the metal layer on the top of the pad is made of platinum metal with high oxidation resistance, and the thickness is 0.05±0.01μm. When the electrode is N-type doped, the metal layer at the bottom of the pad can be made of metal Nickel Ni and other materials, when the electrodes are P-type doped, the metal layer at the bottom of the pad can be made of metal titanium Ti and other materials, with a thickness of 0.25±0.02 μm.

Further, the composite silicon compound intermediate layer includes a SiO ₂ layer and a Si ₃ N ₄ layer with opposite stress after thermal expansion, the SiO ₂ layer is deposited on the SiC bottom layer around the metal pad, and the Si ₃ N ₄ layer is deposited on the _SiO2 layer.

Further, the top metal layer is made of a metal material with high coefficient of thermal expansion, high elasticity and good ductility. Preferably, the top metal layer may be metallic copper Cu with a thickness of 0.5-5 μm.

A method for preparing a SiC temperature sensor with a cantilever beam structure, characterized in that it comprises the following steps:

Step 1. Perform SiC deep cavity etching on the middle part of the C surface of the SiC bottom layer by a femtosecond laser to form a SiC film with a cavity, which is convenient for post-production of MEMS cantilever beams;

Step 2. Fabricate a mask 1 for preparing varistor strips on the Si surface of the SiC bottom layer, lightly or moderately dope the SiC bottom layer in the pattern area of the mask 1 by using an ion implantation process, and remove the mask 1 , forming four varistor strips;

Step 3: Fabricate mask 2 for preparing electrodes and connecting circuits on the Si surface of the SiC bottom layer, use ion implantation to heavily dope the SiC bottom layer in the pattern area of mask 2, remove mask 2, and form electrodes and Connect the circuit to complete the preparation of the Wheatstone bridge detection circuit on the SiC bottom layer;

Step 4. Make a mask three for preparing metal pads on the Si surface of the SiC bottom layer, and then deposit conductive metal on the pattern area of the mask three and the mask three by evaporation coating or sputtering coating, and remove the mask After three, metal pads are formed, and the metal pads are located directly above the corresponding electrodes;

Step 5, making mask 4 on the metal pad in step 4, depositing _SiO2 film in the pattern area of mask 4 and mask 4, after removing mask 4, forming the _SiO2 layer deposited on the SiC bottom layer;

Step 6. Prepare mask 5 on the SiO ₂ layer, deposit Si ₃ N ₄ film on the pattern area of mask 5 and mask 5, and remove the mask 5 to form a Si ₃ N ₄ layer deposited on the SiO ₂ layer , by controlling the shape of the mask five, the area of the Si ₃ N ₄ layer is smaller than that of the SiO ₂ layer, so that the metal pad is exposed outside.

Step 7, prepare mask 6 on the SiO ₂ layer, deposit a conductive metal film on the pattern area of mask 6 and mask 6, and remove the mask 6 to form a top metal layer with the same size as the Si ₃ N ₄ layer;

Step 8, patterning the cavity bottom area of the SiC bottom layer by femtosecond laser to form a cantilever beam structure on the SiC bottom layer;

Step 9: Prepare a mask 7 on the upper surface of the top metal layer with a shape corresponding to the pattern etched on the SiC bottom layer in step 8, and use wet etching to sequentially pattern the top metal layer, the composite silicon compound intermediate layer, and penetrate the pattern of the SiC bottom layer Form a cantilever beam structure, and then remove mask 7 to make a SiC temperature sensor blank;

Step 10: Perform high-temperature annealing on the SiC temperature sensor blank to form an ohmic contact between the metal layer at the bottom of the pad and the electrode, and complete the manufacture of the SiC temperature sensor with a cantilever beam structure.

Further, before step 1 deep cavity etching, according to the range of the prepared SiC temperature sensor, the C surface of the SiC bottom layer needs to be thinned.

Further, in the step 8, the patterned etching is carried out in the inner area surrounded by the Wheatstone bridge detection circuit, and the etched pattern is in the shape of a king.

The SiC temperature sensor of the cantilever beam structure of the present invention has the following working principle: because the thermal expansion coefficients of the SiC bottom layer, the composite silicon compound intermediate layer, and the top metal layer are different and have a large difference, when the temperature of the MEMS cantilever beam changes due to changes in the external environment temperature , Thermal stress will be generated between the layers in the MEMS cantilever beam. Under the action of thermal stress, the MEMS cantilever deforms, bending up or down, and the varistor strips in the SiC bottom layer also bend up or down. As the temperature of the external environment increases or decreases, the bending degree of the MEMS cantilever beam will increase or decrease accordingly, and the bending degree of the piezoresistor strip will also increase or decrease accordingly. Due to the existence of the piezoresistive effect of the SiC semiconductor material, the resistivity of the varistor strip will change, and the change of the resistivity is positively correlated with the bending degree of the MEMS cantilever beam. The degree of deformation during work is different, and the change of resistivity is also different, which breaks the balance of the Wheatstone bridge. Therefore, the Wheatstone bridge detection circuit can successfully convert the resistance change in the circuit into the change of current or voltage value and output it to the outside. . According to this principle, the sensor can be used to convert the environmental temperature signal into an electrical signal, and after data processing, a one-to-one functional relationship between the temperature value and the electrical signal value can be formed, thereby realizing temperature measurement.

Beneficial effect

1. Compared with the existing Si-based integrated sensor, the technical solution of the present invention uses SiC as the sensor base material, which has higher reliability when working in harsh environments, especially high temperature and strong corrosive environments , longer life, more stable sensitivity, better linearity and shorter response time.

2. Compared with the existing Si-based piezoresistive temperature sensor, the technical solution of the present invention uses an ion implantation process to form an electrical connection circuit in the SiC bottom layer, avoiding the traditional Si-based piezoresistive sensor using wires to connect four piezoresistors The way that the strips form a Wheatstone bridge not only reduces the probability of sensor failure due to lead connection failure, but also reduces the signal loss in the Wheatstone bridge and improves the sensitivity of the sensor.

3. Compared with the existing Si-based piezoresistive temperature sensor, the technical solution of the present invention innovatively adds a composite silicon compound intermediate layer, which has the effect of resisting thermal shock, realizes the protection of the SiC bottom layer, and serves as a An insulating layer separates the top metal layer from the Wheatstone bridge detection circuit on the SiC bottom layer to protect the circuit.

Description of drawings

FIG. 1 is a schematic diagram of a three-dimensional structure of a SiC temperature sensor with a cantilever beam structure provided by an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a SiC temperature sensor with a cantilever beam structure provided by an embodiment of the present invention.

FIG. 3 is a schematic diagram of a post-mask structure for making a mask pattern in Step 3 of the embodiment of the present invention.

4 is a schematic diagram of the structure after forming a piezoresistive region and removing a mask in Step 3 of the embodiment of the present invention.

FIG. 5 is a schematic diagram of the structure after the second mask for making the mask pattern in step 4 of the embodiment of the present invention.

FIG. 6 is a schematic diagram of the structure after mask 2 is removed in step 4 of the embodiment of the present invention for forming an electrical connection circuit region.

FIG. 7 is a schematic diagram of the structure of the mask after making the mask pattern in step 5 of the embodiment of the present invention.

FIG. 8 is a schematic structural diagram after depositing a metal pad and removing a mask 3 in step 6 of the embodiment of the present invention.

FIG. 9 is a schematic diagram of the post-mask structure for making a mask pattern in Step 7 of the embodiment of the present invention.

10 is a schematic diagram of the structure after depositing a SiO ₂ layer and removing the mask 4 in Step 8 of the embodiment of the present invention.

FIG. 11 is a schematic diagram of the post-mask structure for making a mask pattern in Step 9 of the embodiment of the present invention.

Fig. 12 is a schematic diagram of the structure after depositing the Si ₃ N ₄ layer and removing the mask five times in Step 10 of the embodiment of the present invention.

FIG. 13 is a schematic diagram of the post-mask structure of mask pattern making in Step 11 of the embodiment of the present invention.

14 is a schematic diagram of the structure after depositing the top metal layer and removing the mask six in step 12 of the embodiment of the present invention.

FIG. 15 is a schematic diagram of the post-mask structure for making a mask pattern in Step 14 of the embodiment of the present invention.

Fig. 16 is a partial sectional view of a SiC temperature sensor with a cantilever beam structure according to the present invention.

1-MEMS cantilever beam, 2-Wheatstone bridge detection circuit, 21-piezoresistive area, 211-longitudinal varistor strip, 212-transverse varistor strip, 22-electrical connection line area, 221-electrode, 222- Connection circuit, 3-metal pad, 31-pad bottom metal layer, 32-pad top metal layer, 4-SiC bottom layer, 41-undoped region, 5-compound silicon compound middle layer, 51-SiO ₂ layer , 52-Si ₃ N ₄ layers, 6-top metal layer, 71-mask 1, 72-mask 2, 73-mask 3, 74-mask 4, 75-mask 5, 76-mask 6 , 77-mask VII.

detailed description

The specific implementation of a cantilever beam structure SiC temperature sensor and its manufacturing method involved in the present invention will be further explained below in conjunction with the accompanying drawings.

The present invention provides a SiC temperature sensor with a cantilever beam structure, the temperature sensor includes a MEMS cantilever beam 1, a Wheatstone bridge detection circuit 2 and a metal pad 3, and the MEMS cantilever beam 1 with a multi-layer structure is from bottom to top There are three layers on the top, which are SiC bottom layer 4, composite silicon compound middle layer 5 and top metal layer 6; the SiC bottom layer 4 includes three parts: piezoresistive region 21, electrical connection circuit region 22 and undoped region 41; The piezoresistive regions 21 are four piezoresistor strips in the Wheatstone bridge detection circuit 2, which include a pair of vertical piezoresistor strips 211 and a pair of transverse piezoresistor strips 212, and the electrical connection circuit area 22 is In the Wheatstone bridge detection circuit 2, the electrical circuit for realizing the interconnection of piezoresistor strips, the undoped region 41 is an undoped SiC bottom layer 4, which plays the role of insulation and protection for the Wheatstone bridge detection circuit 2 The composite silicon compound intermediate layer 5 is a composite intermediate layer formed by stacking multiple silicon compound thin layers. In this embodiment, SiO ₂ and Si ₃ N ₄ are used in this embodiment. The silicon compound composite layer stacked from bottom to top has a thickness of 0.3 ±0.05μm and 0.2±0.02μm. SiO ₂ layer 51 generates compressive stress after thermal expansion, and Si ₃ N ₄ layer 52 generates tensile stress after thermal expansion, so the use of these two materials can alleviate the stress concentration phenomenon caused by temperature changes in the composite silicon compound intermediate layer 5 during use; The side length of the SiO ₂ layer 51 is equal to the side length of the SiC bottom layer 4, and the side length of the Si ₃ N ₄ layer 52 is smaller than the side length of the SiO ₂ layer 51 by 300±10 μm, leaving a size margin for the metal pad 3, In order to realize the connection between the metal pad 3 and the external circuit structure, the SiO ₂ layer 51 is distributed with four through hole structures for depositing the metal pad 3, the through holes are located directly above the electrode 221, and the through holes are slightly larger than the side length of the electrode 221 by 3 ~5 μm. The top metal layer 6 is a metal layer with high thermal expansion coefficient, high elasticity, high ductility and other properties. In this embodiment, metal copper Cu is used, of course, metal silver Ag, gold Au, aluminum Al, etc. can also be used. .

The Wheatstone bridge detection circuit 2 is composed of a piezoresistive area 21 and an electrical connection circuit area 22, the electrical connection line area 22 includes an electrode 221 and a connection circuit 222, and the piezoresistive area 21 and the electrode 221 are interconnected through the connection circuit 222 Form the Wheatstone bridge detection circuit 2, in the present embodiment, any adjacent two of the four piezoresistor strips are perpendicular to each other on the extension line, and the four piezoresistor strips are arranged in one direction to form a radial pattern; this implementation In the example, the Wheatstone bridge detection circuit 2 is formed by implanting phosphorous ions by ion implantation process, the piezoresistive region 21 is formed by light doping or medium doping, and the electrical connection circuit 222 is formed by heavy doping.

The metal pad 3 includes a metal layer 31 at the bottom of the pad and a metal layer 32 at the top of the pad. The metal layer 31 at the bottom of the pad is placed above the electrode 221 and forms an ohmic contact with it, and the metal layer 32 at the top of the pad is placed at the bottom of the pad. Above the metal layer 31 and form electrical contact with it, and the metal layer 32 on the top of the pad has a high degree of oxidation resistance, and the metal pad 3 is connected to the external circuit through a lead structure to realize the electrical signal output of the temperature sensor; in this embodiment, the pad The bottom metal layer 31 is nickel Ni, and the top metal layer 32 of the pad is platinum Pt.

The manufacturing method of the SiC temperature sensor of a kind of cantilever beam structure of the present embodiment, it comprises the following steps:

Step 1. According to the requirements of the measurement range, the C-surface of the SiC bottom layer 4 is thinned by grinding and polishing processes, and the SiC bottom layer 4 is thinned to the thickness of the required measurement range.

Step 2. On the basis of step 1, perform SiC deep cavity etching on the C-surface of the SiC bottom layer 4 by a femtosecond laser to form a SiC film with a cavity, which is convenient for post-production of the MEMS cantilever beam 1 .

Step 3. On the basis of step 2, make a mask 71 for preparing piezoresistive strips on the Si surface of the SiC bottom layer 4, for controlling the shape and size of the piezoresistive region 21 during ion implantation, mask 1 The shape of 71 is shown in Figure 3. Lightly or moderately doped the SiC bottom layer 4 in the pattern area of the mask one 71 to form the piezoresistive region 21, and then removed the mask one 71 to form four piezoresistor strips, as shown in FIG. 4 .

Step 4. On the basis of step 3, make a mask 2 72 for preparing the electrical connection circuit region 22 on the Si surface of the SiC bottom layer 4, and control the shape and size of the electrical connection circuit region 22 during ion implantation. The shape of membrane two 72 is shown in FIG. 5 . The SiC bottom layer 4 in the pattern area of the second mask 72 is heavily doped to form the electrical connection circuit area 22 . Then the second mask 72 is removed to form the electrical connection circuit region 22, as shown in FIG. 6 .

Step 5. On the basis of step 4, make a mask 3 73 on the Si surface of the SiC bottom layer 4 for controlling the shape and size of the metal pad 3. The shape of the mask 3 73 is shown in FIG. 7 .

Step 6. On the basis of step 5, deposit the conductive metal used to make the metal pad 3 in the pattern area of the mask 3 73 by evaporation coating or sputter coating process. Preferably, the metal layer 31 material at the bottom of the pad can be Metal nickel Ni is used with a thickness of 0.25±0.02 μm, and the material of the metal layer 32 on the top of the pad can be metal platinum Pt with a thickness of 0.05±0.01 μm. Then the mask three 73 is removed, and the metal pad 3 electrically connected to the electrode 221 is formed on the SiC bottom layer 4, as shown in FIG. 8 .

Step 7. On the basis of step 6, make a mask 4 74 on the upper surface of the metal pad 3 for depositing the SiO ₂ layer 51 and controlling its shape and size. The shape of the mask 4 74 is shown in FIG. 9 .

Step 8. On the basis of step 7, a SiO _{2 film is deposited on the mask 474 and the pattern area of the mask 4 74 by a chemical vapor deposition (CVD) process. Preferably, the thickness of the SiO 2 film} is 0.3±0.03 μm. Then remove the mask 474 to form a SiO ₂ layer 51 deposited on the SiC bottom layer 4, as shown in FIG. 10 .

Step 9. On the basis of step 8, make a mask 5 75 on the upper surface of the SiO ₂ layer 51 for depositing the Si ₃ N ₄ layer 52 and controlling its shape and size. The shape of the mask 5 75 is shown in FIG. 11 .

Step 10. On the basis of step 9, deposit a Si ₃ N ₄ film on the pattern area of the mask five 75 and the mask five 75 by a chemical vapor deposition (CVD) process, preferably, the thickness of the Si ₃ N ₄ film is 0.2± 0.02 μm. Then remove the mask five 75 to form the Si ₃ N ₄ layer 52 deposited on the SiO ₂ layer 51 , as shown in FIG. 12 .

Step 11. On the basis of step 10, make a mask 6 76 on the upper surface of the SiO ₂ layer 51 for depositing the top metal layer 6 and controlling its shape and size. The shape of the mask 6 76 is as shown in FIG. 13 .

Step 12. On the basis of step 11, deposit a metal film on the pattern area of the mask six 76 and the mask six 76 by evaporation coating or sputter coating process, preferably, the material of the metal film can be metal copper Cu, thickness 0.3 to 5 μm. Then the mask 6 76 is removed to form the top metal layer 6 deposited on the Si ₃ N ₄ layer 52 , as shown in FIG. 14 .

Step 13. On the basis of step 12, the C-surface of the SiC bottom layer 4 thin film is etched by a femtosecond laser to carve out a Wang pattern area, so that the SiC bottom layer 4 forms a cantilever beam structure.

Step 14. On the basis of step 13, make a mask 777 on the upper surface of the top metal layer 6 that is the same as the SiC bottom layer 4 king pattern, for patterning the cantilever beam structure and controlling its shape and size, mask 7 The shape of 77 is as shown in Figure 15; the top metal layer 6, the composite silicon compound intermediate layer 5 are patterned and the king pattern of the SiC bottom layer 4 is penetrated in sequence by wet etching to form a cantilever beam structure, and then the mask 777 is removed, The SiC temperature sensor blank is made, and the shape is shown in Figure 1.

Step 15. On the basis of step 14, high-temperature annealing is performed on the SiC temperature sensor blank to form an ohmic contact between the metal layer 31 at the bottom of the pad and the electrode 221 . So far, the SiC temperature sensor with a cantilever beam structure is manufactured.

It should be pointed out that in the embodiment of the present invention, the pattern etched in order to form the cantilever beam structure is not limited to the shape of a king, and can be any other shape, as long as the cantilever is formed in the area of the Wheatstone bridge detection circuit 2 on the SiC bottom layer 4. Yes, the king shape provided in the embodiment of the present invention is only an optimal embodiment for matching the shape of the Wheatstone bridge detection circuit 2 in the embodiment, and does not represent a limitation on the shape of the cantilever figure.

It should also be pointed out that when the present invention prepares the Wheatstone bridge detection circuit 2, it is formed by doping the SiC bottom layer 4 by an ion implantation process. The implantation of phosphorus ions provided in this embodiment is actually not limited to phosphorus ions. Just an example.

The above embodiments are merely illustrations for the technical solution of the present invention. A cantilever beam structure SiC temperature sensor and its manufacturing method involved in the present invention are not limited to the content described in the above embodiments, but are subject to the scope defined in the claims. Any modifications, supplements or equivalent replacements made by those skilled in the art of the present invention on the basis of the embodiments are within the protection scope of the claims of the present invention. In addition, the contents not described in detail in the text are all prior art.

Claims (10)

1. The utility model provides a SiC temperature sensor of cantilever beam structure which characterized in that: including SiC bottom, compound silicon compound intermediate level and top metal layer from bottom to top, form Wheatstone bridge detection circuitry through the doping of ion implantation technology on the Si face of SiC bottom, undoped region is the insulation protection region, deposit the conducting metal with Wheatstone bridge detection circuitry's electrode electricity intercommunication on the SiC bottom, form the metal pad, compound silicon compound intermediate level is used for buffering thermal stress, and compound silicon compound intermediate level can produce the not equidirectional stress by a plurality of low thermal expansion coefficient, high dielectric constant, high insulating nature, thermal expansion after the silicon compound thin layer pile up and form, makes the metal pad expose through the deposition area of selecting compound silicon compound intermediate level, top metal layer and compound silicon compound intermediate level the same area deposition of superiors on compound silicon compound intermediate level, the C face middle part etching of SiC bottom has the cavity, and the sculpture has the figure that runs through the top metal layer bottom the cavity, forms MEMS cantilever beam structure.

2. The SiC temperature sensor of claim 1, wherein: the Wheatstone bridge detection circuit comprises four piezoresistor strips, electrodes and a connecting circuit for connecting the four piezoresistor strips and the electrodes, wherein the four piezoresistor strips are a pair of longitudinal piezoresistor strips and a pair of transverse piezoresistor strips, the connecting circuit is used for connecting the four piezoresistor strips end to end, and the four electrodes are distributed on the connecting circuit between the two adjacent piezoresistor strips.

3. The SiC temperature sensor of claim 2, wherein: the four piezoresistor strips are prepared by carrying out light doping or middle doping on a local area of the SiC bottom layer through an ion implantation process, the doping type is N type or P type, and the electrodes and the connecting circuit are prepared by carrying out heavy doping with the same type as the piezoresistor strips on the local area of the SiC bottom layer through the ion implantation process.

4. The SiC temperature sensor of claim 2, wherein: any two adjacent piezoresistor strips are mutually vertical on the extension line, and the four piezoresistor strips are arranged in a unidirectional mode to form a radial shape.

5. The SiC temperature sensor of claim 2, wherein: the metal bonding pad comprises a bonding pad bottom metal layer and a bonding pad top metal layer, the bonding pad bottom metal layer is arranged above the electrode and forms ohmic contact with the electrode, the bonding pad top metal layer is arranged above the bonding pad bottom metal layer and forms electric contact with the bonding pad bottom metal layer, and the bonding pad top metal layer is connected with the metal bonding pad and an external circuit through a lead structure.

6. The SiC temperature sensor of claim 5, wherein: the metal layer at the bottom of the bonding pad is made of metal nickel, metal aluminum or titanium, and the metal layer at the top of the bonding pad is made of metal platinum with high oxidation resistance.

7. The SiC temperature sensor of claim 1, wherein: the composite silicon compound interlayer comprises SiO with opposite stress after thermal expansion ₂ Layer and Si ₃ N ₄ Layer of said SiO ₂ A layer deposited on the SiC bottom layer around the metal pad, the Si ₃ N ₄ Layer deposition on SiO ₂ On the layer.

8. The SiC temperature sensor of claim 1, wherein: the top metal layer is made of a metal material with high thermal expansion coefficient, high elasticity and good ductility.

9. A preparation method of a cantilever beam structured SiC temperature sensor is characterized by comprising the following steps:

step 1, performing SiC deep cavity etching on the middle part of the C surface of a SiC bottom layer through femtosecond laser to form a SiC film with a cavity, so that an MEMS cantilever beam can be conveniently manufactured in the later stage;

step 2, manufacturing a first mask for preparing the piezoresistor strips on the Si surface of the SiC bottom layer, carrying out light doping or middle doping on the SiC bottom layer of a first mask pattern region by adopting an ion implantation process, and removing the first mask to form four piezoresistor strips;

step 3, manufacturing a second mask for preparing an electrode and a connecting circuit on the Si surface of the SiC bottom layer, heavily doping the SiC bottom layer of the second mask pattern region by adopting an ion implantation process, removing the second mask, forming the electrode and the connecting circuit, and completing the preparation of the Wheatstone bridge detection circuit on the SiC bottom layer;

step 4, manufacturing a third mask for preparing a metal bonding pad on the Si surface of the SiC bottom layer, depositing conductive metal in the pattern area of the third mask and the third mask through an evaporation coating or sputtering coating process, removing the third mask, and forming the metal bonding pad, wherein the metal bonding pad is positioned right above the corresponding electrode;

step 5, manufacturing a mask IV on the metal bonding pad in the step 4, and depositing SiO in the pattern areas of the mask IV and the mask IV ₂ Removing the mask to form SiO deposited on the SiC bottom layer ₂ A layer;

step 6, in SiO ₂ Preparing a mask five on the layer, and depositing Si in the pattern areas of the mask five and the mask five ₃ N ₄ Removing the mask five to form a film deposited on SiO ₂ Si on the layer ₃ N ₄ Layer, by controlling the shape of mask five, so that Si ₃ N ₄ Layer area less than SiO ₂ A layer so that the metal pad is exposed to the outside;

step 7, in SiO ₂ Preparing a mask six on the layer, depositing a metal film in the pattern area of the mask six and the mask six, and removing the mask six to form an area and Si ₃ N ₄ A top metal layer of the same size;

step 8, performing graphical etching on the cavity bottom area of the SiC bottom layer through femtosecond laser to form a cantilever beam structure on the SiC bottom layer;

step 9, preparing a mask seven with a shape corresponding to the graph etched on the SiC bottom layer in the step 8 on the upper surface of the top metal layer, sequentially penetrating the top metal layer, the graph of the composite silicon compound middle layer and the graph of the SiC bottom layer by adopting wet etching to form a cantilever beam structure, and then removing the mask seven to prepare a SiC temperature sensor blank;

and step 10, carrying out high-temperature annealing on the SiC temperature sensor blank to form ohmic contact between the metal layer at the bottom of the bonding pad and the electrode, and finishing the manufacturing of the SiC temperature sensor with the cantilever beam structure.

10. The method for producing the SiC temperature sensor according to claim 9, characterized in that: before the deep cavity etching in the step 1, thinning the C surface of the SiC bottom layer according to the measuring range of the prepared SiC temperature sensor.

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