A ceramic heating plate, its preparation method and application

Abstract

This invention relates to a ceramic heating plate, its preparation method, and its application. The preparation method of the ceramic heating plate includes the following steps: (1) molding the raw material powder, and the resulting green body undergoes debinding treatment and first machining to obtain a blank to be welded; (2) welding the sleeve tube to the bottom cover plate, and assembling the resulting sleeve body with the blank to be welded obtained in step (1). During the assembly, heating wires and electrode mesh are placed according to the internal structure of the ceramic heating plate. The assembled sleeve body is then welded to the top cover plate to obtain the sleeve structure; (3) the sleeve structure obtained in step (2) is subjected to degassing treatment, hot isostatic pressing sintering, and post-treatment to obtain the ceramic heating plate. This invention uses molding, sleeve welding, and hot isostatic pressing sintering steps to make the ceramic heating plate have the characteristics of high density, high matrix strength, and tight bonding between the welded blank and the heating wire.

Description

Technical Field

[0001] This invention relates to the field of semiconductor equipment technology, specifically to a ceramic heating plate, its preparation method, and its application. Background Technology

[0002] In plasma-enhanced chemical vapor deposition (PECVD), the wafer needs to be heated to ensure the stability of the wafer deposition process and the quality of the coating. The heating plate, as a key component of the PECVD equipment, is mainly used to support the wafer and regulate its temperature. The heating plate contains heating elements that generate heat when energized, thereby raising the temperature of the heating plate.

[0003] Currently, heating plates used in the semiconductor industry are mainly divided into two types: metal heating plates and ceramic heating plates. For example, CN115988689A discloses a method for manufacturing an integrated heating plate. Step one: machining a metal blank into a lower plate using a machine tool; Step two: placing a heating wire on the lower plate and fixing it to the lower plate using inserts cut grooves according to the wire's layout; Step three: casting the upper plate integrally with the lower plate, adding titanium and silicon during the casting process; Step four: processing the cast integrated heating plate using high-temperature forging; Step five: after high-temperature forging, further connecting the upper and lower plates using diffusion welding. However, during the vapor deposition process, a specific gas is introduced into the equipment cavity. Using the aforementioned heating plate may cause a reaction with this gas, thus affecting the wafer surface coating.

[0004] Ceramic heating plates, due to their stable chemical properties and resistance to chemical reactions with gases, as well as superior electrical and thermal conductivity, are increasingly widely used in vapor deposition processes. CN 116403943A discloses a heating plate and its manufacturing method, as well as a semiconductor device. The heating plate includes a temperature regulating layer comprising multiple temperature-regulating regions. The area difference between these regions is less than a target threshold. Each temperature-regulating region is equipped with at least one metal circuit, which regulates the temperature of the region, reducing the temperature difference between different temperature-regulating regions and ensuring uniform temperature across all regions. This manufacturing method uses alumina as the ceramic layer, but the process is relatively complex and has limitations for mass industrial production.

[0005] In addition, the main materials of some ceramic heating plates are aluminum nitride, silicon carbide, etc., which are usually prepared by casting and laminating. However, this method has high requirements for equipment stability, production process parameters, environment, etc., which makes it easy for defects such as cracks to occur inside the ceramic, resulting in a relatively low density. At the same time, the combination with the built-in heating wire is poor, and the heating performance of the prepared heating plate is difficult to meet the requirements. Consequently, the wafer will have abnormal coating due to uneven heating and plate deformation.

[0006] Therefore, in view of the shortcomings of the existing technology, there is an urgent need to provide a method for preparing a ceramic heating plate with high density, high matrix strength, and tight bonding between the welded blank and the heating wire. Summary of the Invention

[0007] The purpose of this invention is to provide a ceramic heating plate and its preparation method and application. By using molding, encapsulation welding and hot isostatic pressing sintering processes, a ceramic heating plate with high density, high matrix bending strength and tight bonding between the ceramic welded blank and the heating wire is obtained.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a ceramic heating plate, the method comprising the following steps:

[0010] (1) The raw material powder is molded, and the resulting green body is subjected to debinding treatment and first machining to obtain the blank to be welded;

[0011] (2) The sheath tube is first welded to the bottom cover plate, and the resulting sheath body is assembled with the blank to be welded obtained in step (1). During the assembly, heating wire and electrode mesh are placed according to the internal structure of the ceramic heating plate. The assembled sheath body is second welded to the top cover plate to obtain the sheath structure.

[0012] (3) The encapsulation structure obtained in step (2) is subjected to degassing, hot isostatic pressing sintering and post-treatment in sequence to obtain the ceramic heating plate.

[0013] The method for preparing a ceramic heating plate provided by the present invention, through steps of molding, cladding welding and hot isostatic pressing sintering, combined with specific range of molding, cladding welding and hot isostatic pressing sintering process parameters, results in a ceramic heating plate with high density, high flexural strength of the substrate and tight bonding between the welded blank and the heating wire. It can be used in chemical vapor deposition equipment as a carrier to support the wafer and increase the wafer temperature.

[0014] Preferably, the raw material powder in step (1) includes aluminum nitride.

[0015] Preferably, step (1) involves molding a disk to the target size.

[0016] Preferably, the density of the green body in step (1) is >60%, for example, it can be 65%, 70%, 75%, 80% or 85%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Preferably, the temperature of the glue removal process in step (1) is 350-500℃, for example, it can be 350℃, 380℃, 400℃, 450℃ or 500℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] Preferably, the time for the glue removal process in step (1) is 5-8 hours, for example, 5 hours, 5.5 hours, 6 hours, 7 hours or 8 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the glue removal process in step (1) is carried out in a glue removal furnace.

[0020] Preferably, the degumming process in step (1) is carried out in a nitrogen or air atmosphere.

[0021] Preferably, the flatness of the blank to be welded in step (1) is <0.5mm, for example, it can be 0.45mm, 0.4mm, 0.35mm, 0.3mm or 0.2mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, the materials of the sheath, bottom cover, and top cover in step (2) include niobium.

[0023] Preferably, the thickness of the sheath, bottom cover and top cover in step (2) is 2-5mm, for example, it can be 2mm, 2.5mm, 3mm, 4mm or 5mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the sheath, bottom cover, and top cover described in step (2) are chemically cleaned before the first welding.

[0025] The chemical cleaning can remove impurities and oil stains from the surfaces of the sheath, bottom cover, and top cover.

[0026] Preferably, the reagents used for chemical cleaning include degreasing agents or acid solutions.

[0027] Preferably, the acid solution includes nitric acid and / or hydrochloric acid.

[0028] Preferably, in step (2), after the first welding and before assembly, high-purity graphite paper is laid on the inner surface of the main body of the casing.

[0029] The term "high-purity graphite paper" refers to graphite paper with a carbon content of >99.99%.

[0030] Preferably, the thickness of the high-purity graphite paper is 1-3 mm, for example, it can be 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the specific steps of the assembly in step (2) include: preparing 3 blanks to be welded, and sequentially inserting the blanks to be welded, the electrode mesh, the blanks to be welded, the heating wire, and the blanks to be welded into the inside of the main body of the casing.

[0032] Preferably, in step (2), before the second welding, high-purity graphite paper is laid on the surface of the blank to be welded.

[0033] Preferably, the temperature of the degassing treatment in step (3) is 400-550℃, for example, it can be 400℃, 420℃, 450℃, 500℃ or 550℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the degassing treatment time in step (3) is 3-5 hours, for example, it can be 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the vacuum degree of the degassing process in step (3) is <1×10⁻⁶. -3 Pa, for example, could be 0.8 × 10⁻⁶. -3 Pa, 0.6×10 -3 Pa, 0.5×10 -3 Pa, 0.3×10 -3 Pa or 0.1×10 -3 Pa, but not limited to the listed values, applies to other unlisted values ​​within the range as well.

[0036] Preferably, the hot isostatic pressing sintering temperature in step (3) is 1650-1750℃, for example, it can be 1650℃, 1680℃, 1700℃, 1720℃ or 1750℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, the pressure of hot isostatic pressing in step (3) is 160-190 MPa, for example, it can be 160 MPa, 165 MPa, 170 MPa, 180 MPa or 190 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] Preferably, the holding time for hot isostatic pressing sintering in step (3) is 2-5 hours, for example, it can be 2 hours, 2.5 hours, 3 hours, 4 hours or 5 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, after hot isostatic pressing sintering in step (3), the temperature is cooled to ≤100°C in the furnace. For example, it can be 100°C, 95°C, 90°C, 85°C or 80°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the post-processing in step (3) includes the steps of removing the casing, machining, and welding.

[0041] As a preferred embodiment of the preparation method described in this invention, the preparation method includes the following steps:

[0042] (1) The raw material powder is molded, and the resulting green body with a density >60% is subjected to debinding treatment at 350-500℃ for 5-8 hours in a nitrogen or air atmosphere in a debinding oven. Then, the first machining is performed to obtain a blank to be welded with a flatness <0.5mm.

[0043] (2) The sheath tube is first welded to the bottom cover plate. High-purity graphite paper with a thickness of 1-3 mm is laid on the inner surface of the obtained sheath body. Three blanks to be welded are prepared. Inside the sheath body, the blanks to be welded, the electrode mesh, the blanks to be welded, the heating wire and the blanks to be welded are sequentially installed. High-purity graphite paper with a thickness of 1-3 mm is laid on the surface of the blanks to be welded. Then the sheath body is second welded to the top cover plate to obtain the sheath structure.

[0044] The thickness of the sheath, bottom cover plate, and top cover plate is 2-5mm; the sheath, bottom cover plate, and top cover plate are chemically cleaned with degreasing agent or acid before the first welding;

[0045] (3) Degas the encapsulation structure obtained in step (2) at 400-550℃ for 3-5 hours, with a vacuum degree <1×10 -3 Pa; then hot isostatic pressing sintering at 1650-1750℃ and 160-190MPa for 2-5 hours, followed by furnace cooling to ≤100℃; after removing the cladding, machining and welding are performed to obtain the ceramic heating plate.

[0046] Secondly, the present invention provides a ceramic heating plate, which is prepared by the method for preparing a ceramic heating plate described in the first aspect.

[0047] The ceramic heating plate provided by the present invention has the characteristics of high density, high bending strength of the matrix, and tight bonding between the welded blank and the heating wire.

[0048] Thirdly, the present invention provides an application of the ceramic heating plate as described in the second aspect, wherein the ceramic heating plate is used in a chemical vapor deposition apparatus.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The method for preparing a ceramic heating plate provided by this invention, through steps of molding, sheath welding, and hot isostatic pressing sintering, combined with specific ranges of molding, sheath welding, and hot isostatic pressing sintering process parameters, enables the prepared ceramic heating plate to achieve a density of 100% and a bending strength of 316 MPa. The welded blank and heating wire are tightly bonded, making it suitable for use in chemical vapor deposition equipment as a carrier to support wafers and increase wafer temperature. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the encapsulation structure provided in Embodiment 1 of the present invention;

[0052] The components are: 1. the main body of the casing; 2. high-purity graphite paper; 3. the blank to be welded; 4. the electrode mesh; and 5. the heating wire. Detailed Implementation

[0053] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0054] Example 1

[0055] This embodiment provides a ceramic heating plate, the preparation method of which includes the following steps:

[0056] (1) The aluminum nitride powder is molded and the resulting green blank with a density of 85% is subjected to debinding treatment at 400°C for 6 hours in a nitrogen atmosphere in a debinding furnace, and then the first machining is performed to obtain a blank to be welded with a flatness of 0.2 mm.

[0057] (2) The niobium sheath tube is first welded to the bottom niobium cover plate. A 2mm thick layer of high-purity graphite paper 2 is laid on the inner surface of the resulting sheath body 1. Three blanks 3 to be welded are prepared. Inside the sheath body 1, the blanks 3 to be welded, the electrode mesh 4, the blanks 3 to be welded, the heating wire 5, and the blanks 3 to be welded are sequentially inserted. A 2mm thick layer of high-purity graphite paper 2 is laid on the surface of the blanks 3 to be welded. Then, the sheath body 1 is second welded to the top niobium cover plate to obtain the sheath structure. A schematic diagram of the obtained sheath structure is shown below. Figure 1 As shown;

[0058] The thickness of the sheath, bottom cover plate, and top cover plate is 3mm; the sheath, bottom cover plate, and top cover plate are chemically cleaned with acetone before the first welding.

[0059] (3) The encapsulation structure obtained in step (2) is subjected to degassing treatment at 450℃ for 4 hours, with a vacuum degree of 0.1×10⁻⁶. -3 Pa; then hot isostatic pressing at 1700℃ and 170MPa for 3h, followed by furnace cooling to 80℃; after removing the cladding, machining and welding are performed to obtain the ceramic heating plate.

[0060] Example 2

[0061] This embodiment provides a ceramic heating plate, the preparation method of which includes the following steps:

[0062] (1) The aluminum nitride powder is molded and the resulting green blank with a density of 75% is subjected to debinding treatment at 350°C for 8 hours in a nitrogen atmosphere in a debinding furnace. Then, the first machining is performed to obtain a blank to be welded with a flatness of 0.3 mm.

[0063] (2) The niobium sheath tube is first welded to the bottom niobium cover plate. A 1mm thick high-purity graphite paper 2 is laid on the inner surface of the resulting sheath body 1. Three blanks 3 to be welded are prepared. Inside the sheath body 1, the blanks 3 to be welded, the electrode mesh 4, the blanks 3 to be welded, the heating wire 5 and the blanks 3 to be welded are sequentially installed. A 1mm thick high-purity graphite paper 2 is laid on the surface of the blanks 3 to be welded. Then the sheath body 1 is second welded to the top niobium cover plate to obtain the sheath structure.

[0064] The thickness of the sheath, bottom cover plate, and top cover plate is 2mm; the sheath, bottom cover plate, and top cover plate are chemically cleaned with methanol before the first welding.

[0065] (3) The encapsulation structure obtained in step (2) is subjected to degassing treatment at 400℃ for 5 hours, with a vacuum degree of 0.5×10⁻⁶. -3 Pa; then hot isostatic pressing at 1650℃ and 160MPa for 5h, followed by furnace cooling to 90℃; after removing the cladding, machining and welding are performed to obtain the ceramic heating plate.

[0066] Example 3

[0067] This embodiment provides a ceramic heating plate, the preparation method of which includes the following steps:

[0068] (1) The aluminum nitride powder is molded and the resulting green blank with a density of 65% is subjected to debinding treatment at 500°C for 5 hours in the air atmosphere of the debinding oven, and then the first machining is performed to obtain a blank to be welded with a flatness of 0.45mm.

[0069] (2) The niobium sheath tube is first welded to the bottom niobium cover plate. A 3mm thick high-purity graphite paper 2 is laid on the inner surface of the resulting sheath body 1. Three blanks 3 to be welded are prepared. Inside the sheath body 1, the blanks 3 to be welded, the electrode mesh 4, the blanks 3 to be welded, the heating wire 5 and the blanks 3 to be welded are sequentially installed. A 3mm thick high-purity graphite paper 2 is laid on the surface of the blanks 3 to be welded. Then the sheath body 1 is second welded to the top niobium cover plate to obtain the sheath structure.

[0070] The thickness of the sheath, bottom cover plate, and top cover plate is 5mm; the sheath, bottom cover plate, and top cover plate are chemically cleaned with a 20% hydrochloric acid solution before the first welding.

[0071] (3) The encapsulation structure obtained in step (2) is degassed at 550℃ for 3 hours, with a vacuum degree of 0.8×10⁻⁶. -3 Pa; then hot isostatic pressing at 1750℃ and 190MPa for 2h, followed by furnace cooling to 100℃; after removing the cladding, machining and welding are performed to obtain the ceramic heating plate.

[0072] Example 4

[0073] This embodiment provides a ceramic heating plate. The difference between the preparation method of the ceramic heating plate and that of Embodiment 1 is that, except for adjusting the density of the green body in step (1) to 70%, the rest is the same as that of Embodiment 1.

[0074] Example 5

[0075] This embodiment provides a ceramic heating plate. The difference between the preparation method of the ceramic heating plate and that of Embodiment 1 is that, except for adjusting the flatness of the blank to be welded in step (1) to 0.6 mm, the rest is the same as that of Embodiment 1.

[0076] Example 6

[0077] This embodiment provides a ceramic heating plate. The difference between the preparation method of the ceramic heating plate and that of Embodiment 1 is that, except for adjusting the temperature of the degassing treatment in step (3) to 350°C, the rest is the same as that of Embodiment 1.

[0078] Example 7

[0079] This embodiment provides a ceramic heating plate. The difference between the preparation method of the ceramic heating plate and that of Embodiment 1 is that, except for adjusting the temperature of the degassing treatment in step (3) to 600°C, the rest is the same as that of Embodiment 1.

[0080] Example 8

[0081] This embodiment provides a ceramic heating plate. The difference between the preparation method of the ceramic heating plate and that of Embodiment 1 is that, except that the temperature of hot isostatic pressing sintering in step (3) is adjusted to 1600℃, the rest is the same as that of Embodiment 1.

[0082] Example 9

[0083] This embodiment provides a ceramic heating plate. The difference between the preparation method of the ceramic heating plate and that of Embodiment 1 is that, except that the temperature of hot isostatic pressing sintering in step (3) is adjusted to 1800℃, the rest is the same as that of Embodiment 1.

[0084] Example 10

[0085] This embodiment provides a ceramic heating plate. The difference between the preparation method of the ceramic heating plate and that of Embodiment 1 is that, except that the pressure of hot isostatic pressing in step (3) is adjusted to 150 MPa, the rest is the same as that of Embodiment 1.

[0086] Example 11

[0087] This embodiment provides a ceramic heating plate. The difference between the preparation method of the ceramic heating plate and that of Embodiment 1 is that, except that the pressure of hot isostatic pressing in step (3) is adjusted to 200 MPa, the rest is the same as that of Embodiment 1.

[0088] Comparative Example 1

[0089] This comparative example provides a ceramic heating plate. The difference between the preparation method of the ceramic heating plate and that of Example 1 is that, except that the hot isostatic pressing sintering described in step (3) is replaced with pressureless sintering, the rest is the same as that of Example 1.

[0090] Comparative Example 2

[0091] This comparative example provides a ceramic heating plate. The difference between the preparation method of the ceramic heating plate and that of Example 1 is that, except that the hot isostatic pressing sintering in step (3) is replaced by hot pressing sintering at 1700℃, the rest is the same as that of Example 1.

[0092] The density of the ceramic heating plates prepared in Examples 1-11 and Comparative Examples 1 and 2 was tested by the water displacement method, the flexural strength of the matrix was tested by a universal testing machine, and the degree of bonding between the welded blank and the heating wire was detected by scanning electron microscopy. The results are expressed as "tightly bonded", "relatively tightly bonded", and "not tightly bonded". The results are shown in Table 1.

[0093] Table 1

[0094] Density (%) Bending strength (MPa) Degree of bonding between the weld blank and the heating wire Example 1 100 316 Closely integrated Example 2 99 263 Closely integrated Example 3 99 295 Closely integrated Example 4 95 237 Closely integrated Example 5 97 225 loosely bonded Example 6 96 259 loosely bonded Example 7 97 266 Closely integrated Example 8 93 193 loosely bonded Example 9 97 273 loosely bonded Example 10 92 195 loosely bonded Example 11 99 271 The bond is tight (but the deformation is severe). Comparative Example 1 97 210 Closely integrated Comparative Example 2 98 229 Closely integrated

[0095] As can be seen from Table 1, the ceramic heating plate prepared by the preparation method provided by the present invention has the characteristics of high density, high matrix strength, and tight bonding between the welded blank and the heating wire.

[0096] A comparison of Examples 1 and 4 shows that if the density of the green body after molding is too low, it will affect the density and strength of the finished product. A comparison of Examples 1 and 5 shows that if the flatness of the blank to be welded is too high after the first machining, it will not be conducive to the tight bonding between the welded blank and the heating wire. A comparison of Examples 1 and Examples 6 and 7 shows that if the degassing temperature is too low or too high, it will reduce the bending strength of the finished product and also lead to a decrease in the bonding degree between the welded blank and the heating wire. A comparison of Examples 1 and Examples 8-11 shows that the temperature and pressure of hot isostatic pressing have a significant impact on the density, strength, and bonding degree between the welded blank and the heating wire of the ceramic heating plate. Exceeding the limit range will degrade the overall performance.

[0097] As can be seen from the comparison between Example 1 and Comparative Examples 1 and 2, the use of pressureless sintering or hot pressing sintering will significantly reduce the bending strength of the ceramic heating plate.

[0098] In summary, the method for preparing a ceramic heating plate provided by the present invention, through steps of molding, cladding welding, and hot isostatic pressing sintering, combined with specific ranges of molding, cladding welding, and hot isostatic pressing sintering process parameters, enables the prepared ceramic heating plate to achieve a density of 100%, a bending strength of 316 MPa, and a tight bond between the welded blank and the heating wire. It can be used in chemical vapor deposition equipment as a carrier to support wafers and increase wafer temperature.

[0099] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a ceramic heating plate, characterized in that, The preparation method includes the following steps: (1) The raw material powder is molded, and the resulting green blank is subjected to debinding treatment and first machining to obtain a blank to be welded; the density of the green blank is >60%; the flatness of the blank to be welded is <0.5mm; (2) The sheath tube is first welded to the bottom cover plate, and the resulting sheath body is assembled with the blank to be welded obtained in step (1). During the assembly, the heating wire and electrode mesh are placed according to the internal structure of the ceramic heating plate. The assembled sheath body is second welded to the top cover plate to obtain the sheath structure. (3) The encapsulation structure obtained in step (2) is subjected to degassing treatment, hot isostatic pressing sintering and post-treatment in sequence to obtain the ceramic heating plate; the temperature of the degassing treatment is 400-550℃; the temperature of the hot isostatic pressing sintering is 1650-1750℃; the pressure of the hot isostatic pressing sintering is 160-190MPa.

2. The preparation method according to claim 1, characterized in that, The raw material powder in step (1) includes aluminum nitride.

3. The preparation method according to claim 1, characterized in that, The temperature for the glue removal process in step (1) is 350-500℃.

4. The preparation method according to claim 1, characterized in that, The time for the glue removal process in step (1) is 5-8 hours.

5. The preparation method according to claim 1, characterized in that, The debinding process in step (1) is carried out in a nitrogen or air atmosphere.

6. The preparation method according to claim 1, characterized in that, The materials of the sheath, bottom cover, and top cover in step (2) include niobium.

7. The preparation method according to claim 1, characterized in that, The thickness of the sheath, bottom cover plate and top cover plate in step (2) is 2-5mm.

8. The preparation method according to claim 1, characterized in that, In step (2), the sheath, bottom cover plate and top cover plate are chemically cleaned before the first welding.

9. The preparation method according to claim 8, characterized in that, The reagents used in the chemical cleaning include degreasing agents or acids.

10. The preparation method according to claim 1, characterized in that, Step (2) After the first welding and before assembly, high-purity graphite paper is laid on the inner surface of the main body of the casing.

11. The preparation method according to claim 10, characterized in that, The thickness of the high-purity graphite paper is 1-3 mm.

12. The preparation method according to claim 1, characterized in that, The specific steps of the assembly in step (2) include: preparing 3 blanks to be welded, and sequentially inserting the blanks to be welded, the electrode mesh, the blanks to be welded, the heating wire, and the blanks to be welded into the inside of the main body of the casing.

13. The preparation method according to claim 1, characterized in that, Step (2) Before the second welding, high-purity graphite paper is laid on the surface of the blank to be welded.

14. The preparation method according to claim 1, characterized in that, The degassing process in step (3) takes 3-5 hours.

15. The preparation method according to claim 1, characterized in that, The vacuum degree of the degassing process in step (3) is <1×10 -3 Pa.

16. The preparation method according to claim 1, characterized in that, The holding time for hot isostatic pressing sintering in step (3) is 2-5 hours.

17. The preparation method according to claim 1, characterized in that, After hot isostatic pressing sintering in step (3), the temperature is cooled to ≤100℃ in the furnace.

18. The preparation method according to claim 1, characterized in that, The post-processing described in step (3) includes the steps of removing the casing, machining, and welding.

19. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) The raw material powder is molded, and the resulting green body with a density > 60% is subjected to debinding treatment at 350-500℃ for 5-8 hours in a nitrogen or air atmosphere, and then subjected to the first machining to obtain a blank to be welded with a flatness < 0.5mm. (2) The sheath tube is first welded to the bottom cover plate. High-purity graphite paper with a thickness of 1-3 mm is laid on the inner surface of the obtained sheath body. Three blanks to be welded are prepared. The blanks to be welded, the electrode mesh, the blanks to be welded, the heating wire and the blanks to be welded are sequentially installed inside the sheath body. High-purity graphite paper with a thickness of 1-3 mm is laid on the surface of the blanks to be welded. Then the sheath body is second welded to the top cover plate to obtain the sheath structure. The thickness of the sheath, bottom cover plate, and top cover plate is 2-5mm; the sheath, bottom cover plate, and top cover plate are chemically cleaned with degreasing agent or acid before the first welding; (3) Degas the encapsulation structure obtained in step (2) at 400-550℃ for 3-5 hours, with a vacuum degree <1×10 -3 Pa; then hot isostatic pressing sintering at 1650-1750℃ and 160-190MPa for 2-5 hours, followed by furnace cooling to ≤100℃; after removing the cladding, machining and welding are performed to obtain the ceramic heating plate.

20. A ceramic heating plate, characterized in that, The ceramic heating plate is prepared by the method for preparing a ceramic heating plate according to any one of claims 1-19.

21. An application of the ceramic heating plate as described in claim 20, characterized in that, The ceramic heating plate is used in a chemical vapor deposition (CVD) apparatus.

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