CVD-based silicon carbide electrostatic chuck and preparation method thereof

Abstract

The invention discloses a CVD (chemical vapor deposition)-based silicon carbide electrostatic chuck and a preparation method thereof, the electrostatic chuck is provided with a ceramic chip structure, the ceramic chip structure is composed of a lower dielectric layer close to a base, an upper dielectric layer far away from the base and an electrode layer located in the middle, and the lower dielectric layer and the upper dielectric layer are made of high-resistance silicon carbide materials. And the electrode layer is made of a low-resistance silicon carbide material and is prepared by CVD (Chemical Vapor Deposition). The electrostatic chuck is more stable in performance, and the uniformity of the thermal conductivity and the thermal expansion coefficient of the ceramic chip can be guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor clamps, in particular to a silicon carbide electrostatic chuck based on CVD and a preparation method thereof. BACKGROUND

[0002] The electrostatic chuck is a clamping tool in semiconductor process, which is based on electrostatic adsorption, and fixes the silicon wafer through the coulomb adsorption force or J-R adsorption force of the electrostatic chuck after applying external high voltage, and is widely used in ion implantation, dry etching, chemical vapor deposition and physical vapor deposition processes. A typical electrostatic chuck generally consists of a metal base, a bonding material layer and a ceramic sheet, and the structure of the ceramic sheet consists of a lower dielectric layer, an upper dielectric layer and an electrode layer therebetween.

[0003] Silicon carbide has excellent physical and chemical properties, such as high thermal conductivity, small thermal expansion coefficient, good wear resistance and high hardness, and is an ideal material for preparing ceramic sheets of electrostatic chuck. There are two main methods for preparing ceramic sheets of electrostatic chuck at present: plasma spraying and high temperature sintering. Because silicon carbide is easy to oxidize and significantly sublimes and decomposes under high temperature and normal pressure conditions, the plasma spraying of pure silicon carbide is difficult to realize in practical application. The high temperature sintering process generally includes flow casting, screen printing, lamination, isostatic pressing, debinding sintering and other processes. The electrode layer is printed on the flow cast sheet and clamped between two flow cast sheets by lamination. In production, problems such as lamination defects and thermal expansion coefficient matching often occur, which leads to delamination between the electrode layer and the dielectric layer, and further causes problems such as poor insulation, resulting in product scrap. In addition, sintering aids and resistance control agents need to be added to silicon carbide during flow casting to promote sintering and meet the resistivity requirements, but this often leads to a decrease in the thermal conductivity of silicon carbide.

[0004] Therefore, it is urgent to design a new electrostatic chuck and its manufacturing process to solve the above problems. SUMMARY

[0005] In order to solve the problems existing in the prior art, the present application provides a high-purity and high-density silicon carbide electrostatic chuck based on CVD and a preparation method thereof.

[0006] In order to achieve the above application purposes, the present application adopts the following technical solutions:

[0007] A silicon carbide electrostatic chuck based on CVD, the electrostatic chuck has a ceramic sheet structure: composed of a lower dielectric layer close to the base, an upper dielectric layer away from the base and an electrode layer in the middle, wherein the lower dielectric layer and the upper dielectric layer are high-resistance silicon carbide materials, and the electrode layer is a low-resistance silicon carbide material, all of which are prepared by CVD.

[0008] In some specific embodiments, the electrostatic chuck further comprises a metal base, a bonding material layer structure, wherein the bonding material layer connects the ceramic sheet and the metal base and protects the ceramic sheet; the metal base is made of metal or its alloy, and the metal base comprises structures of water channels, pin holes, and helium gas holes; preferably, the metal or its alloy is selected from aluminum, aluminum alloy, titanium alloy, and stainless steel.

[0009] The bonding material layer is made of silica gel or other elastic polymers.

[0010] In some specific embodiments, the high-resistance silicon carbide material has a resistivity of 1.0*10 5 ~1.0*10 10 Ω·cm; and the low-resistance silicon carbide material has a resistivity of 1.0*10 -4 ~1.0*10 -1 Ω·cm.

[0011] In another aspect, the method for preparing the aforementioned CVD-based silicon carbide electrostatic chuck comprises the following steps:

[0012] S1, depositing a lower dielectric layer: placing a graphite base with a smooth and clean surface into a CVD deposition furnace, continuously introducing reaction gas and carrier gas, and performing chemical vapor deposition to prepare silicon carbide, thereby obtaining silicon carbide deposited on the graphite base;

[0013] S2, polishing the lower dielectric layer: polishing the silicon carbide of the graphite base prepared in step S1 by machining treatment;

[0014] S3, preparing a mask: adhering a graphite sheet to the surface of the lower dielectric layer with silica sol, and engraving a hollow electrode layer pattern by machining, thereby obtaining a graphite mask and silicon carbide of the graphite base;

[0015] S4, mask high-temperature pretreatment: pretreating the graphite mask and silicon carbide of the graphite base in step S3 to completely remove the organic matter in the silica sol;

[0016] S5, depositing a low-resistance electrode layer: placing the pretreated graphite mask and silicon carbide of the graphite base into a CVD deposition furnace, continuously introducing reaction gas, carrier gas, and doping gas, and performing chemical vapor deposition to prepare doped low-resistance silicon carbide, thereby obtaining a low-resistance silicon carbide electrode layer deposited in the hollow electrode layer pattern and on the lower dielectric layer;

[0017] S6, removing the mask and the graphite base: the silicon carbide with the electrode layer prepared in S5 and the graphite base is cut by machining to remove the graphite base, and the surface of the electrode layer and the outer wall of the lower dielectric layer are polished to remove the low-resistance silicon carbide, then the surface of the graphite mask is sandblasted with quartz sand to remove most of the graphite mask, and the graphite mask residues on the surface of the silicon carbide are removed by high-temperature oxidation;

[0018] S7, depositing the upper dielectric layer: the silicon carbide with the mask and impurities removed in S6 and the electrode layer is placed in a CVD deposition furnace, and the reaction gas and the carrier gas are continuously introduced to perform chemical vapor deposition of silicon carbide to obtain the upper dielectric layer of the electrostatic chuck;

[0019] S8, machining the ceramic sheet: the silicon carbide with the upper dielectric layer deposited in S7 is taken out, which is a ceramic sheet blank with a lower dielectric layer, an electrode layer and an upper dielectric layer, and the blank is machined to polish, thin and polish the surface of the upper dielectric layer, and electrode holes are made by punching to obtain a ceramic sheet suitable for a silicon carbide electrostatic chuck;

[0020] S9: by brazing and bonding, using a bonding material layer to connect the metal base and the ceramic sheet to obtain a silicon carbide electrostatic chuck.

[0021] In some specific embodiments, in step S1, methyltrichlorosilane (MTS) gas is used as the reaction gas to provide silicon and carbon sources, or silane or trichlorosilane is used as the silicon source gas, and propane or ethylene is used as the carbon source gas; hydrogen is used as the carrier gas;

[0022] Preferably, the gas pressure in the CVD deposition furnace is 5-20 kPa, and the temperature is 1400-1500℃;

[0023] More preferably, the flow ratio of the carrier gas to the reaction gas is 10-40:1;

[0024] Further preferably, the thickness of the silicon carbide deposited on the graphite base is 1500-2500 μm.

[0025] In some specific embodiments, the thickness of the graphite sheet used as a mask in step S3 is 0.5-0.8 mm, and the size and shape are consistent with the graphite base;

[0026] Preferably, the thickness of the graphite sheet is the thickness of the low-resistance silicon carbide electrode layer plus a machining allowance of 150-400 μm.

[0027] In some specific embodiments, the pretreatment in step S4 is placed in an argon protective atmosphere, the pretreatment temperature is 1100-1200℃, and the time is 20-60 min;

[0028] Preferably, nitrogen is used as the doping gas in step S5, the pressure in the CVD deposition furnace is 20-60 kPa, and the temperature is 1200-1350℃.

[0029] More preferably, the flow ratio of the carrier gas, the reaction gas and the doping gas in step S5 is 5-20:1:0.005-0.05, and the deposition time is controlled so that the thickness of the silicon carbide is 100-300 μm.

[0030] In some specific embodiments, the high-temperature oxidation in step S6 is performed at a temperature of 600-900℃ in an air atmosphere, and the graphite mask residues on the surface of the silicon carbide are removed by high-temperature oxidation.

[0031] Preferably, after the high-temperature oxidation treatment, a step of cleaning the silicon carbide using a mixed acid solution of concentrated nitric acid with a concentration of 68 wt% and hydrofluoric acid with a concentration of 40 wt% in a volume ratio of 3-6:1:0-5 is further included.

[0032] In some specific embodiments, the specific process of cleaning the silicon carbide using the mixed acid solution is as follows:

[0033] 1) The silicon carbide is cleaned by ultrasonic cleaning for 10-15 min.

[0034] 2) A diluent of the concentrated nitric acid with a concentration of 68% and water in a volume ratio of 1:2-4 is prepared, and the cleaned silicon carbide is soaked in the diluent for 3-5 min.

[0035] 3) The mixed acid solution of the concentrated nitric acid with a concentration of 68% and the concentrated hydrofluoric acid with a concentration of 40% is prepared in a volume ratio of 3-6:1, and the mixed acid solution is evenly applied to the surface of the silicon carbide using a piece of absorbent cotton. After the reaction is completed, the silicon carbide is washed with a large amount of distilled water and then air dried, so as to completely remove the residual acid and the silicon oxide impurities on the surface of the silicon carbide.

[0036] In some specific embodiments, the pressure in the CVD deposition furnace in step S7 is 0.5-5 kPa, and the temperature is 1400-1500℃.

[0037] Preferably, the flow ratio of the carrier gas and the reaction gas in step S7 is 10-40:1, and the deposition time is controlled so that the thickness of the silicon carbide is 500-1500 μm, thereby obtaining the upper dielectric layer of the electrostatic chuck.

[0038] In the present application, the electrostatic chuck is formed by growing the lower dielectric layer, the electrode layer and the upper dielectric layer one by one, and the electrode material and the dielectric material are both silicon carbide, so that the interface between the materials can form an atomic-level combination through diffusion, the bonding force is strong, and the thermal expansion coefficients are basically consistent.

[0039] The difficulty of preparing the silicon carbide electrostatic chuck by the CVD method lies in the formation of the electrode layer, including mask selection and demolding. Because the reaction is in a high-temperature environment of 1200-1500 DEG C, the mask should have high-temperature resistance and good chemical stability. In the application, graphite is used as the mask material. Because the electrode layer has a complex shape and the brittleness of graphite itself, the graphite sheet needs to be fixed on the base and then machined to form the mask. Silicon sol is used to fix the graphite sheet, and the method of high-temperature pretreatment is used to remove impurities and avoid affecting the deposition quality of silicon carbide. In the demolding process, the graphite mask is completely removed by the way of quartz sand blasting and high-temperature oxidation, and finally the silicon oxide layer is removed by hydrofluoric acid pickling, the whole process avoids damage to the silicon carbide substrate, and the demolding and impurity removal are relatively easy to realize.

[0040] Compared with the prior art, the application has the following beneficial effects:

[0041] The application uses the CVD method to prepare the silicon carbide electrostatic chuck. Compared with the method of flow forming and then high-temperature sintering, the preparation of the dielectric layer and the electrode layer can be realized without adding sintering aids and other regulating agents, and the heat conduction effect of the dielectric layer is better, which helps to improve the temperature uniformity.

[0042] In the application, the ceramic sheet of the electrostatic chuck is prepared by CVD deposition layer-by-layer growth, the electrode layer and the dielectric layer both use silicon carbide material, the interlayer bonding performance is good, and the problem of easy delamination between the electrode layer and the dielectric layer is solved. In the application, the dielectric layer is integrally deposited and formed, compared with the method of laminating and pressing the flow sheet, the defects are less and the yield is high. At the same time, the whole ceramic sheet is CVD-prepared silicon carbide material, which can ensure the uniformity of the thermal conductivity and the thermal expansion coefficient of the ceramic sheet, and the prepared electrostatic chuck has more stable performance. DETAILED DESCRIPTION

[0043] In order to make the technical problems solved by the application, the technical solutions and beneficial effects more clearly, the application will be further described in detail below with reference to the drawings. It should be understood that the specific implementation described herein is only used to explain the application, and is not used to limit the application.

[0044] In one aspect, the application discloses an electrostatic chuck, and the ceramic sheet structure of the chuck comprises:

[0045] 1) a metal base made of metal or its alloy, which structurally contains water channels, pin holes, helium gas holes and other commonly used structures; wherein the metal base of the application is not particularly limited and can refer to the prior art.

[0046] 2) a bonding material layer made of silica gel or other elastic polymer, such as heat-conductive silica gel, acrylic resin, epoxy resin or a combination thereof, which can effectively alleviate thermal stress generated by the metal base and the ceramic sheet due to different thermal expansion coefficients in the cold and hot cycle, connect the ceramic sheet and the metal base and protect the ceramic sheet. In addition, it can prevent high-voltage leakage and ensure the stability and safety of electrostatic adsorption as an additional insulation layer.

[0047] 3) a ceramic sheet, which comprises a lower dielectric layer close to the metal base, an upper dielectric layer away from the base, and an electrode layer between the upper and lower dielectric layers; wherein the lower dielectric layer and the upper dielectric layer are made of high-resistance silicon carbide material, and the electrode layer is made of low-resistance silicon carbide material, both of which are prepared by CVD.

[0048] CVD is an important material preparation technology. By carefully designing the reaction path, the target product is solid and other by-products are gaseous, which chemically ensures the purity of the product. By accurately controlling the temperature and gas flow of the reaction, an ideal surface reaction environment is created, so that the reactant molecules can form a dense coating structure through continuous growth and surface migration.

[0049] In the present application, the entire ceramic sheet is made of CVD-prepared silicon carbide material, the bonding performance between the dielectric layer and the electrode layer is good, and the uniformity of the thermal conductivity and the thermal expansion coefficient of the ceramic sheet can be ensured. Therefore, the ceramic sheet of the electrostatic chuck provided by the present application has a high-quality dielectric layer, which has superiorities in heat dissipation and functional stability.

[0050] Another aspect of the present application discloses a preparation method of the above-mentioned CVD-based silicon carbide electrostatic chuck, and the specific steps are as follows:

[0051] S1: depositing a lower dielectric layer. Put a graphite substrate with a smooth and clean surface into the deposition furnace of the CVD equipment, continuously pass in the reaction gas and the carrier gas, control the furnace pressure to be 5-20 kPa, and perform chemical vapor deposition at 1400-1500℃ to prepare silicon carbide. The flow ratio of the carrier gas to the reaction gas is 10-40:1, the deposition time is controlled to make the thickness of the silicon carbide 1500-2500μm, and the silicon carbide deposited on the graphite substrate is obtained.

[0052] In this step S1, MTS gas is used as the reaction gas, which can provide silicon source and carbon source at the same time. Silane or trichlorosilane can also be used as the silicon source gas, and propane or ethylene can be used as the carbon source gas. Hydrogen is used as the carrier gas.

[0053] S2: polishing the lower dielectric layer. Stop the reaction, take out the silicon carbide with the graphite substrate prepared in step S1, and perform machining treatment. After polishing, the lower dielectric layer of the electrostatic chuck is obtained.

[0054] S3: Preparation of mask. A graphite sheet with a thickness of 0.5-0.8 mm is adhered to the surface of the lower dielectric layer with silica sol, and the hollow electrode layer pattern is engraved by machining to obtain a graphite mask. In particular, the graphite sheet is machined to expose the lower dielectric layer of silicon carbide.

[0055] In this step S3, the thickness of the graphite sheet used as the mask is 0.5-0.8 mm, and the size is consistent with the graphite matrix. The thickness of the graphite sheet is the thickness of the low-resistance silicon carbide electrode layer plus a machining allowance, which is usually 150-400 μm.

[0056] S4: Mask high-temperature pretreatment. The silicon carbide with the graphite mask and graphite matrix in step S3 is placed in an argon protective atmosphere at a temperature of 1100-1200 °C for 20-60 min for pretreatment, so that the organic matter in the silica sol is completely removed.

[0057] S5: Deposition of low-resistance electrode layer. The pretreated silicon carbide with the graphite mask and graphite matrix is placed in the deposition furnace of the CVD equipment, and the reaction gas, carrier gas and doping gas are continuously introduced, and the gas pressure in the furnace is controlled at 20-60 kPa, and the chemical vapor deposition is carried out at 1200-1350 °C to prepare doped low-resistance silicon carbide. The flow ratio of carrier gas to reaction gas and doping gas is 5-20:1:0.005-0.05, and the deposition time is controlled so that the thickness of the silicon carbide is 100-300 μm, to obtain a low-resistance silicon carbide electrode layer deposited in the hollow electrode layer pattern and on the lower dielectric layer.

[0058] In this step, the reaction gas and carrier gas are the same as in step S1, nitrogen is used as the doping gas, and the microstructure of the deposited silicon carbide is controlled by process parameters to finally obtain low-resistance silicon carbide.

[0059] S6: Removal of mask and graphite matrix. Stop the reaction and take out the silicon carbide with the electrode layer and graphite matrix prepared in step S5. First, the graphite matrix is cut off by machining, and the low-resistance silicon carbide on the surface of the electrode layer and the outer wall of the lower dielectric layer is polished, then the surface of the graphite mask is sandblasted with quartz sand to remove most of the graphite mask. After that, the temperature is raised to 600-900 °C, and the graphite mask residues on the surface of the silicon carbide are removed by high-temperature oxidation in an air atmosphere. Finally, a mixed acid solution of nitric acid and hydrofluoric acid is prepared by mixing concentrated nitric acid with a concentration of 68%, concentrated hydrofluoric acid with a concentration of 40% and deionized water in a volume ratio of 3-6:1:0-5, for example, using a piece of absorbent cotton to dip the mixed acid solution and evenly apply it on the surface of the silicon carbide. After the reaction is complete, rinse thoroughly with distilled water to completely remove residual acid and reaction impurities.

[0060] In this step, quartz sand is used as the blasting medium. The hardness of quartz sand is between that of graphite and silicon carbide. During blasting, it can effectively remove the graphite mask while causing minimal damage to the silicon carbide electrode layer.

[0061] Further, the specific process of using hydrofluoric acid to pickle silicon carbide in this step can be as follows: First, clean the silicon carbide with ultrasound for 10-15 minutes; then, prepare a diluted solution of 68% nitric acid and water at a volume ratio of 1:2-4, and immerse the cleaned silicon carbide in the diluted solution for 3-5 minutes; finally, prepare a mixed acid solution of 68% nitric acid, 40% hydrofluoric acid, and deionized water at a volume ratio of 3-6:1:0-5, apply the mixed acid solution evenly to the surface of the silicon carbide with degreased cotton, and after the reaction is complete, rinse with plenty of distilled water, and then air dry naturally to thoroughly remove residual acid and impurities such as silicon oxide on the surface of the silicon carbide.

[0062] S7: Deposition of the dielectric layer. The silicon carbide with the electrode layer, cleaned of the mask and impurities from step S6, is placed in the deposition furnace of the CVD equipment. Reactive gas and carrier gas are continuously introduced, and the furnace pressure is controlled at 0.5-5 kPa. Chemical vapor deposition is performed at 1400-1500℃ to prepare the silicon carbide. The flow ratio of carrier gas to reactive gas is 10-40:1. The deposition time is controlled to achieve a silicon carbide thickness of 500-1500 μm, resulting in the dielectric layer on the electrostatic chuck.

[0063] In this step, preferably, the reaction gas and carrier gas are the same as in step S1.

[0064] S8: Machining the ceramic sheet. Take out the silicon carbide with the deposited upper dielectric layer from step S7; this is a ceramic sheet blank with a lower dielectric layer, an electrode layer, and an upper dielectric layer. Machin the blank by grinding, thinning, and polishing the surface of the upper dielectric layer, and drill electrode holes to obtain a ceramic sheet suitable for a silicon carbide electrostatic chuck.

[0065] S9: A silicon carbide electrostatic chuck is obtained by connecting the metal base and the ceramic plate through brazing and bonding, using a bonding material layer.

[0066] The present invention will be further explained and illustrated below through more specific embodiments, but these do not constitute any limitation.

[0067] Example 1

[0068] Silicon carbide electrostatic chucks were prepared by CVD, following these steps:

[0069] S1: Deposition of the dielectric layer. A smooth and clean graphite substrate is placed in the deposition furnace of a CVD system. MTS gas and hydrogen are continuously introduced, and the furnace pressure is controlled at 15 kPa. Silicon carbide is prepared by chemical vapor deposition at 1420℃. The flow ratio of hydrogen to MTS gas is 25:1, and the deposition time is controlled to achieve a silicon carbide thickness of 2000 μm, resulting in silicon carbide deposited on the graphite substrate.

[0070] S2: Polish the lower dielectric layer smooth. Stop the reaction, remove the silicon carbide with graphite substrate prepared in step S1, and perform machining. After polishing smooth, the lower dielectric layer of the electrostatic chuck is obtained.

[0071] S3: Mask preparation. A graphite sheet with a thickness of 0.8 mm and a shape and size consistent with the graphite substrate is adhered to the surface of the lower dielectric layer using silica sol. The electrode layer pattern is then engraved by machining until the silicon carbide lower dielectric layer is exposed, thus obtaining the graphite mask.

[0072] S4: High-temperature pretreatment of the mask. The silicon carbide with graphite mask and graphite substrate from step S3 is pretreated in an argon protective atmosphere at 1200℃ for 45 minutes to remove organic matter from the silica sol.

[0073] S5: Deposition of a low-resistivity electrode layer. Pretreated silicon carbide with a graphite mask and graphite substrate is placed in the deposition furnace of a CVD system. MTS gas, hydrogen, and nitrogen are continuously introduced, and the furnace pressure is controlled at 45 kPa. Chemical vapor deposition is performed at 1250°C to prepare doped low-resistivity silicon carbide. The flow rate ratio of hydrogen, MTS gas, and nitrogen is 10:1:0.02. The deposition time is controlled to achieve a silicon carbide thickness of 250 μm, resulting in a low-resistivity silicon carbide electrode layer deposited within a perforated electrode pattern and above the underlying dielectric layer.

[0074] S6: Removal of the mask and graphite substrate. Stop the reaction and remove the silicon carbide with electrode layer and graphite substrate prepared in step S5. First, machine the graphite substrate and polish away redundant low-resistivity silicon carbide on the surface of the electrode layer and the outer wall of the lower dielectric layer. Then, sandblast the surface of the graphite mask with quartz sand to remove most of the graphite mask. Afterward, raise the temperature to 850°C and remove any remaining graphite mask residue from the silicon carbide surface through high-temperature oxidation in air. Finally, prepare a mixed acid solution of nitric acid and hydrofluoric acid by mixing 68% concentrated nitric acid, 40% hydrofluoric acid, and deionized water in a volume ratio of 5:1:3. Apply the mixed acid solution evenly to the silicon carbide surface using degreased cotton. After the reaction is complete, rinse thoroughly with plenty of distilled water to remove any residual acid and reaction impurities.

[0075] S7: Deposition of the dielectric layer. The silicon carbide with the electrode layer, cleaned of the mask and impurities from step S6, is placed in the deposition furnace of the CVD equipment. Reactive gas and carrier gas are continuously introduced, and the furnace pressure is controlled at 3 kPa. Chemical vapor deposition is performed at 1420℃ to prepare the silicon carbide. The hydrogen to MTS gas flow ratio is 25:1, and the deposition time is controlled to achieve a silicon carbide thickness of 1200 μm, resulting in the dielectric layer on the electrostatic chuck.

[0076] S8: Machining the ceramic sheet. Take out the silicon carbide with the deposited upper dielectric layer from step S7; this is a ceramic sheet blank with a lower dielectric layer, an electrode layer, and an upper dielectric layer. Machin the blank by grinding, thinning, and polishing the surface of the upper dielectric layer, and drill electrode holes to obtain a ceramic sheet suitable for a silicon carbide electrostatic chuck.

[0077] S9: A silicon carbide electrostatic chuck is obtained by connecting the metal base and the ceramic plate through brazing and bonding, using a bonding material layer.

[0078] Example 2

[0079] Similar to Example 1, except that the furnace pressure in step S5 is changed from 45 kPa to 25 kPa.

[0080] Example 3

[0081] Similar to Example 1, except that the furnace pressure in step S5 is changed from 45 kPa to 60 kPa.

[0082] Example 4

[0083] Similar to Example 1, except that the flow ratio of hydrogen, MTS gas and nitrogen in step S5 is changed from 10:1:0.02 to 15:1:0.02.

[0084] Example 5

[0085] Similar to Example 1, except that the flow ratio of hydrogen, MTS gas and nitrogen in step S5 is changed from 10:1:0.02 to 10:1:0.005.

[0086] Comparative Example 1

[0087] The electrostatic chuck is prepared using the existing method of equal casting and high-temperature sintering, following the steps below:

[0088] S1: 75 parts by weight of silicon carbide, 10 parts by weight of boron nitride, 15 parts by weight of aluminum nitride, 0.6 parts by weight of yttrium fluoride, 95 parts by weight of anhydrous ethanol, 0.8 parts by weight of triethyl phosphate, 1.6 parts by weight of acrylic resin and 1.6 parts by weight of dibutyl phthalate are mixed and ball-milled to obtain silicon carbide slurry, which is then cast into cast sheets.

[0089] S2: The cast sheet from step S1 is processed into a green body through slicing, laser drilling, screen printing, and isostatic pressing. The conductive paste used for screen printing is a conductive ceramic paste, which is prepared by mixing and grinding 16 parts by weight of titanium carbide, 24 parts by weight of silicon carbide powder, 24 parts by weight of butyl carbitol, 0.5 parts by weight of fumed silica, 4 parts by weight of methylcellulose, 2 parts by weight of acrylic resin, and 3 parts by weight of ceramic formula powder. The ceramic formula powder is a 1:1 mixture of yttrium oxide and silicon oxide. Warm isostatic pressing is used at 75℃, 32MPa, and a holding time of 8 minutes.

[0090] S3: After the green body from step S2 is machined into a circle, it undergoes debinding, plasma discharge sintering, and finally pressureless annealing to produce a ceramic green body. Both the debinding and sintering processes occur in an argon protective atmosphere. Hot pressing sintering is used at a temperature of 2050℃ and a pressure of 50MPa.

[0091] S4: The ceramic blank from step S3 is precision machined to obtain a ceramic sheet that can be used for electrostatic chucks. Then, a silicon carbide electrostatic chuck is obtained through brazing, bonding, and surface treatment.

[0092] The thermal conductivity of the dielectric layer of the electrostatic chuck was tested according to GB / T 39862-2021 standard; the volume resistivity of the electrode layer was tested using a four-probe resistivity tester; and the coefficient of thermal expansion of the electrode layer was tested according to GB / T 16535-2008 standard.

[0093] Table 1. Volume resistivity of electrode layers under different processes in Examples 1-5

[0094] Example 1 Example 2 Example 3 Example 4 Example 5 Volume resistivity (Ω-cm) 0.008 0.041 0.004 0.003 0.073

[0095] Table 2. Performance Comparison of Electrostatic Chucks Prepared by Two Methods

[0096] Thermal conductivity of dielectric layer (W / (m-K)) The thermal expansion coefficient (10 -6 / K) of the dielectric layer and the electrode layer Example 1 214 4.5、4.6 Comparative Example 1 142 4.0、4.4

[0097] As shown in Table 1, when depositing a low-resistivity electrode layer, a higher furnace gas pressure results in a higher deposition rate and a lower final volume resistivity of the electrode layer. Increasing the proportion of hydrogen or nitrogen doping in the gas feedstock is beneficial for reducing the volume resistivity of the electrode layer.

[0098] As shown in Table 2, the electrostatic chuck prepared by CVD in this invention has a higher thermal conductivity than that prepared by conventional tape casting and high-temperature sintering. This is because the dielectric layer prepared by CVD has higher purity, reducing phonon scattering and resulting in higher thermal conductivity. Furthermore, since the thermal expansion coefficients of the dielectric layer and the electrode layer in this invention are essentially the same, the prepared electrostatic chuck exhibits good bonding performance, is less prone to delamination, and has a high yield.

[0099] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A CVD-based silicon carbide electrostatic chuck, characterized by, The electrostatic chuck has a ceramic sheet structure: composed of a lower dielectric layer close to the base, an upper dielectric layer away from the base, and an electrode layer in the middle, wherein the lower dielectric layer and the upper dielectric layer are high-resistance silicon carbide materials, and the electrode layer is a low-resistance silicon carbide material, both of which are prepared by CVD.

2. The silicon carbide electrostatic chuck of claim 1, wherein, It also includes a metal base and a bonding material layer structure, wherein the bonding material layer connects the ceramic sheet and the metal base and protects the ceramic sheet; the metal base is made of metal or its alloy, and the metal base includes the structure of water channel, pin hole and helium hole; preferably, the metal or its alloy is selected from aluminum, aluminum alloy, titanium alloy and stainless steel; The bonding material layer is made of silica gel or other elastic polymers.

3. The production method according to claim 1 or 2, characterized by, The high resistivity silicon carbide material has a resistivity of 1.0 x 10 5 ~1.0 x 10 10 Ω-cm; and the low resistivity silicon carbide material has a resistivity of 1.0 x 10 -4 ~1.0 x 10 -1 Ω-cm.

4. The method of producing a CVD-based silicon carbide electrostatic chuck according to any one of claims 1 to 3, characterized by, The method comprises the following steps: S1, depositing a lower dielectric layer: placing a graphite substrate with a smooth and clean surface into a CVD deposition furnace, continuously introducing reaction gas and carrier gas, and preparing silicon carbide by chemical vapor deposition to obtain silicon carbide deposited on the graphite substrate; S2, polishing the lower dielectric layer: machining the silicon carbide prepared in step S1 to polish the lower dielectric layer; S3, preparing a mask: adhering a graphite sheet to the surface of the lower dielectric layer with silica sol, and engraving a hollow electrode layer pattern by machining to obtain a graphite mask and silicon carbide with a graphite substrate; S4, mask high-temperature pretreatment: pretreating the graphite mask and silicon carbide with a graphite substrate in step S3 to completely remove the organic matter in the silica sol; S5, depositing a low-resistance electrode layer: placing the pretreated graphite mask and silicon carbide with a graphite substrate into a CVD deposition furnace, continuously introducing reaction gas, carrier gas and doping gas, and preparing doped low-resistance silicon carbide by chemical vapor deposition to obtain a low-resistance silicon carbide electrode layer deposited in the hollow electrode layer pattern and on the lower dielectric layer; S6, removing the mask and the graphite substrate: machining the graphite substrate and polishing the surface of the electrode layer and the outer wall of the lower dielectric layer to remove the redundant low-resistance silicon carbide, then sandblasting the surface of the graphite mask with quartz sand to remove most of the graphite mask, and then removing the graphite mask residues on the surface of the silicon carbide by high-temperature oxidation; S7, depositing an upper dielectric layer: placing the graphite mask and the impurities removed in step S6 and the silicon carbide with the electrode layer into a CVD deposition furnace, continuously introducing reaction gas and carrier gas, and depositing silicon carbide by chemical vapor deposition to obtain an upper dielectric layer of the electrostatic chuck; S8, machining the ceramic sheet: taking out the silicon carbide with the deposited upper dielectric layer in step S7, which is a ceramic sheet blank with a lower dielectric layer, an electrode layer and an upper dielectric layer, machining the blank, polishing and thinning the surface of the upper dielectric layer, and making electrode holes by punching to obtain a ceramic sheet suitable for a silicon carbide electrostatic chuck; S9: by brazing and bonding, using the bonding material layer to connect the metal base and the ceramic sheet to obtain a silicon carbide electrostatic chuck.

5. The preparation method according to claim 4, characterized in that, In step S1, methyltrichlorosilane (MTS) gas is used as the reaction gas to provide the silicon source and carbon source, or silane or trichlorosilane is used as the silicon source gas, and propane or ethylene is used as the carbon source gas; hydrogen is used as the carrier gas; Preferably, the gas pressure in the CVD deposition furnace is 5-20 kPa, and the temperature is 1400-1500℃; More preferably, the flow ratio of the carrier gas to the reaction gas is 10-40:1; Further preferably, the thickness of the silicon carbide deposited on the graphite substrate is 1500-2500 μm.

6. The preparation method according to claim 4, characterized in that, In step S3, the thickness of the graphite sheet used as the mask is 0.5-0.8 mm, and the size is consistent with that of the graphite substrate; Preferably, the thickness of the graphite sheet is the thickness of the low-resistance silicon carbide electrode layer plus a machining allowance of 150-400 μm.

7. The preparation method according to claim 4, characterized in that, In step S4, the pretreatment is performed in an argon protective atmosphere, the pretreatment temperature is 1100-1200℃, and the time is 20-60 min; Preferably, in step S5, nitrogen is used as the doping gas, the gas pressure in the CVD deposition furnace is 20-60 kPa, and the temperature is 1200-1350℃; More preferably, in step S5, the flow ratio of the carrier gas, the reaction gas, and the doping gas is 5-20:1:0.005-0.05, and the deposition time is controlled so that the thickness of the silicon carbide is 100-300 μm.

8. The preparation method according to claim 4, characterized in that, In step S6, the high-temperature oxidation is performed at a temperature of 600-900℃ in an air atmosphere, and the graphite mask residues on the surface of the silicon carbide are removed by high-temperature oxidation; Preferably, after the high-temperature oxidation treatment, a step of preparing a mixed acid solution of nitric acid and hydrofluoric acid by mixing concentrated nitric acid with a concentration of 68 wt%, concentrated hydrofluoric acid with a concentration of 40 wt%, and deionized water in a volume ratio of 3-6:1:0-5, using absorbent cotton to dip the mixed acid solution and uniformly apply it to the surface of the silicon carbide, and after the reaction is complete, rinsing with distilled water to completely remove the residual acid solution and reaction impurities.

9. The production method according to claim 8, characterized by, The specific process of using hydrofluoric acid to clean the silicon carbide is as follows: 1) ultrasonic cleaning the silicon carbide for 10-15 min; 2) preparing a diluent of concentrated nitric acid with a concentration of 68% and water in a volume ratio of 1:2-4, and immersing the cleaned silicon carbide in the diluent for 3-5 min; 3) preparing a mixed acid solution of nitric acid and hydrofluoric acid by mixing concentrated nitric acid with a concentration of 68% and concentrated hydrofluoric acid with a concentration of 40% in a volume ratio of 3-6:1, using absorbent cotton to dip the mixed acid solution and uniformly apply it to the surface of the silicon carbide, and after the reaction is complete, rinsing with a large amount of distilled water, and then naturally air-drying to completely remove the residual acid solution and silicon oxide impurities on the surface of the silicon carbide.

10. The method of claim 4, wherein, In step S7, the gas pressure in the CVD deposition furnace is 0.5-5 kPa, and the temperature is 1400-1500℃; Preferably, in step S7, the flow ratio of the carrier gas to the reaction gas is 10-40:1, and the deposition time is controlled so that the thickness of the silicon carbide is 500-1500 μm, thereby obtaining the upper dielectric layer of the electrostatic chuck.