Porous ceramic core for electrostatic chuck and preparation method

Abstract

The invention discloses a porous ceramic core for an electrostatic chuck and a preparation method thereof, the porous ceramic core comprises a cylindrical ceramic core body, the upper surface of the ceramic core body is provided with a first round hole and a plurality of elliptical holes, the first round hole is located at the center of the upper surface, the plurality of elliptical holes are located at the periphery of the first round hole, and the first round hole is located in the center of the upper surface. A second round hole and a plurality of third round holes are formed in the lower surface of the ceramic core body, the second round hole is located in the center of the lower surface, and the third round holes are located on the periphery of the second round hole. The first round hole and the oval holes are formed in the upper surface of the ceramic core body, the second round hole and the third round hole are formed in the lower surface of the ceramic core body, and the round hole channels are formed in the ceramic core body in a matched mode, so that the product has the excellent filtering performance, a unique adsorption structure is formed, the adsorption area is increased, and the service life of the product is prolonged. And fine particles can be effectively filtered in the adsorption process.

Description

Technical Field

[0001] The present invention relates to the field of electrostatic chuck technology, in particular to a porous ceramic core for an electrostatic chuck and a preparation method thereof. Background Art

[0002] Ceramic cores are resistant to acid and alkali corrosion and have a wide range of applications. They are resistant to most chemicals and are not easily corroded by acids, alkalis, and other chemicals, resulting in a long service life. Their relatively stable structure resists deformation and provides consistent filtration performance. The electronics industry, particularly high-end fields like semiconductor manufacturing and liquid crystal displays, places extremely stringent production requirements. Even tiny impurity particles can cause defects in electronic products, impacting their performance and reliability. Ceramic filters, with their high-precision filtration performance and excellent particle retention, meet the rigorous demands of the electronics industry. Continuous advancements in electronics technology are raising the bar for precision, flux, and stability in electronic-grade ceramic filters. This has further fueled the innovative development of ceramic filtration technology in the electronics industry, prompting researchers to continuously explore new ceramic materials and preparation processes to enhance their performance. Ceramic filters, with their adjustable precision, long life, and strong environmental compatibility, have become a core filtration solution in water treatment, industrial purification, and biomedicine. With the integration of biomimetic design, nano-modification, and intelligent technologies, their application will continue to expand, with significant potential particularly in new energy and cutting-edge manufacturing.

[0003] Slip casting, also known as injection molding, is a common method for preparing ceramic cores. This method controls the fluidity and viscosity of the slurry, injects the slurry into the mold, and fully fills the cavity of the mold with the slurry. Then, through subsequent process steps such as curing and sintering, a ceramic product with the desired shape and performance is finally obtained. Slip casting can be applied to ceramics with more complex shapes, and the prepared ceramics have high density and good uniformity. However, it is highly dependent on the mold. When the shape needs to be changed, the mold redesign cycle is long and the cost is high. In addition, the pore size accuracy of ceramics manufactured by slip casting is not high and the deviation is large. It is difficult to accurately control the pore size, and it is not easy to manufacture ceramic components with particularly complex shapes and high precision requirements, such as those with special-shaped holes or gradient pore structures.

[0004] 3D printing, as an additive manufacturing technology, is well-suited for molding ceramic cores with complex internal structures. It can efficiently produce ceramics with irregularly shaped or gradient pore structures with high structural precision. It is also a rapid prototyping technology that does not rely on molds. This specialized manufacturing process facilitates rapid verification of design ideas, shortens product development cycles, and reduces R&D costs. Summary of the Invention

[0005] In view of this, the present invention addresses the deficiencies in the prior art, and its main purpose is to provide a porous ceramic core for an electrostatic chuck and a preparation method to solve the existing problems that it is difficult to accurately control the pore size of the ceramic core and the filtering performance of the ceramic core is difficult to meet the high standards of the electronics industry.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A porous ceramic core for an electrostatic chuck includes a ceramic core body, which is cylindrical. A first circular hole and multiple elliptical holes are provided on the upper surface of the ceramic core body, wherein the first circular hole is located at the center of the upper surface, and the multiple elliptical holes are located around the first circular hole. A second circular hole and multiple third circular holes are provided on the lower surface of the ceramic core body, wherein the second circular hole is located at the center of the lower surface, and the multiple third circular holes are located around the second circular hole. A first circular channel and multiple second circular channels are formed in the ceramic core body, wherein the first circular channel is located at the center of the ceramic core body, and the first circular channel connects the first circular hole and the second circular hole. The multiple second circular channels are radially arranged, and the two ends of the multiple second circular channels are respectively connected to the corresponding elliptical holes and the corresponding third circular holes.

[0007] As a preferred solution, the apertures of the first circular hole, the second circular hole and the third circular hole are the same, and their sizes are 0.005-0.4mm. The aperture of the elliptical hole is larger than the apertures of each circular hole, and the wall thickness between two adjacent circular holes is 0.1-0.5mm.

[0008] As a preferred solution, the first circular hole and the plurality of elliptical holes are arranged in a petal shape.

[0009] As a preferred solution, the elliptical hole is formed by a circular hole that is inclined 45 degrees outward at a position 2 mm from the upper surface inside the ceramic core body and extends to the upper surface.

[0010] A method for preparing a porous ceramic core for an electrostatic chuck. The ceramic core body uses 3D printing technology to customize the pore structure. The printed pores and the pores formed by the pore-forming agent are combined to achieve a collaborative filtration effect. The pore sizes of the printed pores and the pore-forming agent are designed to differ to form a pore size gradient. The ceramic core body comprises the following raw materials in parts by weight: 50-70 parts of ceramic aggregate, 0.5-4 parts of sintering aid, 1-8 parts of binder, 5-25 parts of pore-forming agent, 0.5-4 parts of dispersant, and 0.1-3 parts of toughening agent. The preparation process includes the following steps: S1: First, pre-mix the required amount of binder, dispersant, toughening agent, and sintering aid in proportion to each other into an internal mixer, heat from room temperature to 160-170°C, and mix for 0.5-1.5 hours; S2: Add the required amount of ceramic aggregate to the premix in step S1, and finally add the pore-forming agent, and continue mixing for 3-4 hours to ensure uniform dispersion; after mixing, cool the mixture to room temperature, and then crush the solidified mixture through a crusher to break it into 1-5mm granular feed as a spare raw material for printing; S3: Use engineering software to build a 3D printing digital model, slice the model, load the processed file into a 3D printer, and use the printing raw materials prepared in step S2 to print to form a ceramic core blank of the desired shape; S4: Burn the ceramic core blank printed in step S3 with alumina powder. In an air atmosphere, heat the temperature from room temperature to 600-750°C at a rate of 0.2-1°C / min, and maintain the constant temperature for 0.5-2h. In a protective atmosphere, continue to heat the temperature to 1400-1500°C at a rate of 1.5-5°C / min, and maintain the constant temperature for 0.5-2h. Then, heat the temperature to 1600-1700°C at a rate of 1-2°C / min, and maintain the constant temperature for 2-10h. S5: After the insulation is completed, the temperature is first lowered to 900-1000°C at a rate of 1-3°C / min, then lowered to 300-400°C at a rate of 0.5-1°C / min, and finally cooled to room temperature with the furnace at a rate of 1-3°C / min, and the finished porous ceramic core for the electrostatic chuck is taken out.

[0011] As a preferred solution, the ceramic aggregate is at least one of kaolin, diatomaceous earth, alumina, silicon carbide, quartz sand, cordierite, and mullite, and the aggregate particle size is 6-30 μm.

[0012] As a preferred solution, the sintering aid is at least one of boron oxide, magnesium oxide, calcium oxide, titanium oxide, and zirconium oxide, and the particle size of the sintering aid is 0.1-2 μm.

[0013] As a preferred solution, the binder is at least one of polyethylene, polypropylene, and polycarbonate.

[0014] As a preferred embodiment, the pore-forming agent is at least one of graphite, starch, wood powder, flour, and polystyrene microspheres. Pore-forming agents of different particle sizes and types are selected according to the needs of pore formation: when starch is used as the pore-forming agent, the particle size is reduced to 5-10 μm through enzymatic hydrolysis or acid hydrolysis modification; when polystyrene microspheres are used as the pore-forming agent, the particle size is 100-300 μm.

[0015] As a preferred solution, the dispersant is at least one of beeswax, oleic acid, and stearic acid; and the toughening agent is at least one of silicon carbide whiskers, alumina fibers, and graphite fibers.

[0016] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, it can be seen from the above technical solution that: By setting a first circular hole and a plurality of elliptical holes on the upper surface of the ceramic core body, setting a second circular hole and a third circular hole on the lower surface of the ceramic core body, and forming various circular channels in the ceramic core body, this product not only has excellent filtering performance, but also forms a unique adsorption structure, which enhances the adsorption area and enables it to effectively filter fine particles during the adsorption process. The present invention also makes the pressure on the adsorption surface uniform through the design of radially arranged channels, which is beneficial to protecting the ceramic core. At the same time, the micropores are evenly arranged in a petal shape, so that the mechanical properties of the ceramic core body in all directions remain consistent, the mechanical strength stability is improved, and its service life is extended. In addition, the present invention adopts a 3D printing molding method, which can accurately control the size of the micropores, ensure the uniformity of the size of each micropore, and at the same time, combined with the pore-forming agent to form pores, the synergistic effect has a good filtering effect. In addition, the present invention further improves the filtering performance of the ceramic core by designing the relative pore size of the printed holes and the pore-forming agent to form a pore gradient.

[0017] In order to more clearly illustrate the structural features and effects of the present invention, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a three-dimensional schematic diagram of a preferred embodiment of the present invention; Figure 2 is a top view of a preferred embodiment of the present invention; Figure 3 It is a cross-sectional view of a preferred embodiment of the present invention.

[0019] Description of the accompanying drawings: 10. Ceramic core body; 11. First circular hole; 12. Elliptical hole; 13. Second circular hole; 14. Third circular hole; 15. First circular channel; 16. Second circular channel. DETAILED DESCRIPTION

[0020] Please refer to Figures 1 to 3 As shown, it shows the specific structure of a porous ceramic core for an electrostatic chuck according to a preferred embodiment of the present invention, including a ceramic core body 10.

[0021] The ceramic core body 10 is cylindrical, and a first circular hole 11 and a plurality of elliptical holes 12 are provided on the upper surface of the ceramic core body 10. The first circular hole 11 is located at the center of the upper surface, and the plurality of elliptical holes 12 are located around the first circular hole 11. A second circular hole 13 and a plurality of third circular holes 14 are provided on the lower surface of the ceramic core body 10. The second circular hole 13 is located at the center of the lower surface, and the plurality of third circular holes 14 are located around the second circular hole 13. A first circular channel 15 and a plurality of second circular channels 16 are formed in the ceramic core body 10. The first circular channel 15 is located at the center of the ceramic core body 10, and the first circular channel 15 connects the first circular hole 11 and the second circular hole 13. The plurality of second circular channels 16 are radially arranged, and the two ends of the plurality of second circular channels 16 are respectively connected to the corresponding elliptical holes 12 and the corresponding third circular holes 14, which can ensure that the filtered liquid flows more evenly.

[0022] In this embodiment, the diameters of the first circular hole 11, the second circular hole 13, and the third circular hole 14 are identical, ranging from 0.005 to 0.4 mm. The diameter of the elliptical hole 12 is slightly larger than the diameters of the other circular holes, and the wall thickness between adjacent circular holes is 0.1 to 0.5 mm. Furthermore, the first circular hole 11 and the plurality of elliptical holes 12 are arranged in a petal-like pattern. The elliptical holes 12 are formed by extending 45 degrees outward from the top surface of the ceramic core body 10, 2 mm from the top surface.

[0023] The present invention also discloses a method for preparing a porous ceramic core for an electrostatic chuck. The ceramic core body 10 uses 3D printing technology to customize the pore structure, combining printed pores with pore-forming agents to achieve a collaborative filtration effect. The pore sizes of the printed pores and pore-forming agents are designed to differ to form a pore size gradient. The ceramic core body 10 includes the following raw materials by weight: 50-70 parts of ceramic aggregate, 0.5-4 parts of sintering aid, 1-8 parts of binder, 5-25 parts of pore-forming agent, 0.5-4 parts of dispersant, and 0.1-3 parts of toughening agent. The preparation process includes the following steps: S1: First, pre-mix the required amount of binder, dispersant, toughening agent and sintering aid in proportion and put them into an internal mixer, heat from room temperature to 160-170°C, and mix for 0.5-1.5h.

[0024] S2: Add the required amount of ceramic aggregate to the premix in step S1, and finally add the pore-forming agent, and continue mixing for 3-4 hours to ensure uniform dispersion; after mixing, cool the mixture to room temperature, and then crush the solidified mixture through a crusher into 1-5mm granular feed as a spare raw material for printing.

[0025] S3: Use engineering software to build a 3D printing digital model, slice the model, load the processed file into the 3D printer, and use the printing raw materials prepared in step S2 to print to form a ceramic core blank of the required shape.

[0026] S4: Use alumina powder to bury the ceramic core blank printed in step S3. In an air atmosphere, heat the temperature from room temperature to 600-750℃ at a rate of 0.2-1℃ / min, and maintain the constant temperature for 0.5-2h. Slowly increase the temperature to avoid the violent decomposition of organic matter and cracking. In a protective atmosphere, continue to heat the temperature at a rate of 1.5-5℃ / min to 1400-1500℃, maintain the constant temperature for 0.5-2h, and then heat the temperature at a rate of 1-2℃ / min to 1600-1700℃ and maintain the constant temperature. 2-10h, a staged sintering process is adopted, which quickly densifies at 1400-1500℃ to initially form a porous structure skeleton, and performs limited densification at 1600-1700℃ to obtain porous ceramics with high porosity and certain strength; at the same time, the heating rate is faster in the first stage, i.e. heating to 1400-1500℃, and slower in the second stage, i.e. heating to 1600-1700℃, which can effectively reduce thermal stress, compensate for shrinkage, and avoid pore closure caused by local deformation.

[0027] S5: After the insulation is completed, the temperature is first cooled to 900-1000℃ at a rate of 1-3℃ / min, then to 300-400℃ at a rate of 0.5-1℃ / min, and finally cooled to room temperature with the furnace at a rate of 1-3℃ / min, and the finished porous ceramic core for electrostatic chuck is taken out. The cooling process adopts a three-stage cooling method. In the first stage, the temperature is quickly cooled from 1600-1700℃ to 900-1000℃ at a rate of 1-3℃ / min to inhibit grain growth. In the second stage, the temperature is slowly cooled to 300-400℃ at a rate of 0.5-1℃ / min to avoid excessive cooling, which increases thermal stress and phase change stress and causes cracks in the ceramic. In the third stage, the thermal stress is reduced and the cooling can be slightly accelerated, cooling to room temperature at a rate of 1-3℃ / min.

[0028] The ceramic aggregate is at least one of kaolin, diatomaceous earth, alumina, silicon carbide, quartz sand, cordierite, and mullite, with a particle size of 6-30 μm. The sintering aid is at least one of boron oxide, magnesium oxide, calcium oxide, titanium oxide, and zirconium oxide, with a particle size of 0.1-2 μm. The binder is at least one of polyethylene, polypropylene, and polycarbonate. The pore-forming agent is at least one of graphite, starch, wood flour, flour, and polystyrene microspheres. Pore-forming agents of varying particle sizes and types are selected based on pore-forming requirements. When starch is used as a pore-forming agent, the particle size is reduced to 5-10 μm through enzymatic hydrolysis or acid hydrolysis. When polystyrene microspheres are used as pore-forming agents, the particle size is 100-300 μm. The dispersant is at least one of beeswax, oleic acid, and stearic acid. The toughening agent is at least one of silicon carbide whiskers, alumina fibers, and graphite fibers.

[0029] Furthermore, the nozzle used in the aforementioned 3D printer features a double-layer structure with an inner and outer shell. The inner shell is made of zirconia ceramic, which has an extremely low thermal expansion coefficient and high-temperature resistance, making it less susceptible to thermal deformation and reduced printing accuracy. The outer shell is made of copper-nickel alloy, which combines high thermal conductivity with good thermal stability, reducing deformation caused by heat accumulation and adapting to high-temperature operations. The nozzle temperature is controlled between 120-160°C to minimize aperture deviation caused by thermal expansion. Furthermore, the aperture size of the 3D printer nozzle is strictly controlled and dynamically adjusted based on the print structure and actual printing accuracy requirements. Generally, a nozzle aperture of 2-20μm is used for printing pores of 5-30μm, and a nozzle aperture of 100-300μm is used for printing pores of 150-200μm. Furthermore, the 3D printing platform is equipped with a cooling circulation system to maintain the printing platform at a suitable temperature, which facilitates the finalization of the printed product. Compared to traditional air cooling, circulating water cooling ensures more uniform and sufficient cooling of the printed product, reducing internal micropore clogging caused by thermal stress. Other 3D printing technologies include 3DP injection molding, FDM fused deposition modeling, SLA stereolithography, SLS selective laser sintering, and DLP digital light processing. To further improve printing accuracy, SLA stereolithography and DLP digital light processing can be used as molding methods, requiring the addition of photosensitive resin to the feedstock.

[0030] After the finished porous ceramic core for electrostatic chuck is prepared, the final porous ceramic core for electrostatic chuck is tested by bubble pressure method. The size and distribution of the through-pore diameter of the prepared ceramic core are obtained based on the relationship between pressure and pore diameter, and its filtration performance is evaluated, verifying the feasibility of the present invention in improving the filtration effect.

[0031] Structurally, the present invention adopts an aperture gradient design. The aperture of the elliptical hole 12 on the upper surface is slightly larger than the aperture of the first circular hole 11. The large-aperture elliptical hole 12 intercepts coarse particles, and the fluid entering the first through-hole 11 presents a three-dimensional flow inside the ceramic core body 10, which can be fully filtered and effectively filter fine particles. The connecting channel of the second circular channel 16 is designed to be inclined on the side of the elliptical hole 12, which further intercepts coarse particles on the one hand and increases the adsorption area on the other hand. The radial arrangement of each channel and the uniform arrangement of the micropores in the shape of petals make the mechanical properties of the ceramic core body 10 similar in all directions. At the same time, the pressure distribution in each channel is uniform, which improves the overall mechanical strength of the ceramic core and makes the structure more stable.

[0032] In terms of technology, in order to precisely control the size of the micropores, the present invention makes improvements in both printing holes and pore-forming agents. The nozzle aperture directly affects the minimum extrusion line width, and is a key parameter that affects printing accuracy and structural details, and has a huge impact on the accuracy of the printing aperture. The thermal stability of the nozzle affects the accuracy of its own aperture. During the printing process, the nozzle will inevitably expand and deform due to heat. To improve the accuracy of its own aperture, the nozzle should be made of a material with a very small thermal expansion coefficient. In addition to the selection of nozzle materials, heat accumulation can also be reduced through cyclic cooling to reduce the adverse effects of thermal expansion and deformation on aperture accuracy. In terms of pore-forming agents, pore-forming powders of different particle sizes are selected to form micropores of different apertures, and the pore-forming powders are screened to ensure that the pore size distribution of the formed micropores is uniform. In addition, the uniformity of the pore-forming powder during the mixing process must be ensured, and the uneven particle size distribution of the pore-forming powder caused by agglomeration must be reduced by adding a suitable dispersant and using a suitable mixing method.

[0033] The present invention enhances filtration performance by regulating the relative sizes of printed pores and pore-forming agent pores to create a pore size gradient. Two control methods are available: one is to design the printed pores to a large pore size of 100-300 μm and the pore-forming agent pores to a small pore size of 5-20 μm, which is relatively easy to implement; the other is to design the printed pores to a small pore size of 5-20 μm and the pore-forming agent pores to a large pore size of 100-300 μm, which places higher demands on the printer. The finished product was tested using the bubble pressure method.

[0034] Example 1: Alumina powder is selected as the ceramic aggregate, magnesium oxide as the sintering aid, paraffin wax as the binder, polypropylene as the plasticizer, a mixture of graphite, starch, and wood flour as the pore-forming agent, stearic acid as the dispersant, and polyethylene as the toughening agent. The following details the steps involved in the preparation of the ceramic core: First, pre-mix the mixture, turn on the internal mixer and preheat it to 160°C, add 5 parts of polypropylene particles, 0.5 parts of stearic acid, 0.4 parts of polyethylene and 1 part of magnesium oxide powder, and mix them. After continuous stirring for 30 minutes, add 3 parts of paraffin wax and continue stirring for 15 minutes until the paraffin wax is completely dissolved. Then, add 11 parts of alumina powder to the internal mixer every 5 minutes, for a total of 55 parts of alumina powder. After continuous stirring for 30 minutes, add 8 parts of pore-forming agent, then stir in the forward direction for 1.5 hours, and then stir in the reverse direction for 1.5 hours. Subsequently, the mixture is discharged and cooled, and the solidified mixture is crushed by a crusher into 1-5mm granular feed as a spare raw material for printing.

[0035] After the 3D printed digital model is sliced, it is loaded onto the machine and loaded with the spare small particles of raw material for 3D printing. Through precise layer stacking, each layer of material is precisely fused together. An inclined circular hole is printed 2 mm from the top surface of the sample to form a ceramic core blank with an elliptical structure. The ceramic core blank is removed after cooling to room temperature.

[0036] The printed ceramic core blank is buried and fired with alumina powder. In an air atmosphere, the temperature is raised from room temperature to 600°C at a rate of 1°C / min and held constant for 2 hours to completely volatilize and decompose organic matter such as the pore-forming agent, thereby initially forming a porous framework. Under a protective atmosphere, the temperature is then raised to 1400°C at a rate of 4°C / min and held constant for 1 hour. Then, the temperature is raised to 1600°C at a rate of 2°C / min and held constant for 2 hours. Sintering is performed in stages to reduce thermal stress and prevent pore closure. Finally, the core is cooled to room temperature in the furnace and the finished ceramic core is removed.

[0037] The ceramic core manufactured not only has controllable and adjustable micropores, but also has excellent filtering performance, which can meet the needs of the electronics industry.

[0038] Example 2 The ceramic core body includes the following raw materials in parts by weight: 55 parts of ceramic aggregate, 1.5 parts of sintering aid, 2 parts of binder, 10 parts of pore-forming agent, 1 part of dispersant, and 1 part of toughening agent; the ceramic aggregate is alumina; the sintering aid is magnesium oxide; the binder is polypropylene; the pore-forming agent is a mixture of graphite, starch, and wood powder; the dispersant is stearic acid; and the toughening agent is alumina fiber.

[0039] The preparation comprises the following steps: S1: First, pre-mix the required amount of binder, dispersant, toughening agent and sintering aid in proportion and put them into an internal mixer, heat from room temperature to 160°C, and mix for 0.5h.

[0040] S2: Add the required amount of ceramic aggregate to the premix in step S1, and finally add the pore-forming agent, and continue mixing for 3 hours to ensure uniform dispersion; after mixing, cool the mixture to room temperature, and then crush the solidified mixture through a crusher into 1-5mm granular feed as a spare raw material for printing.

[0041] S3: Use engineering software to build a 3D printing digital model, slice the model, load the processed file into a 3D printer, and use the printing raw materials prepared in step S2 to print to form a ceramic core blank of the desired shape; S4: Use alumina powder to bury the ceramic core blank printed in step S3, and increase the temperature from room temperature to 650℃ at a rate of 0.2℃ / min in an air atmosphere, and maintain a constant temperature for 0.5h; under a protective atmosphere, continue to increase the temperature to 1450℃ at a rate of 1.5℃ / min, maintain a constant temperature for 0.5h, and then increase the temperature to 1620℃ at a rate of 1℃ / min, and maintain a constant temperature for 3h.

[0042] S5: After the heat preservation is completed, the temperature is first lowered to 900°C at a rate of 1°C / min, then to 300°C at a rate of 0.5°C / min, and finally cooled to room temperature with the furnace at a rate of 1°C / min, and the finished porous ceramic core for the electrostatic chuck is taken out.

[0043] Example 3 The ceramic core body includes the following raw materials in parts by weight: 60 parts of ceramic aggregate, 2 parts of sintering aid, 4 parts of binder, 15 parts of pore-forming agent, 1.5 parts of dispersant, and 1.3 parts of toughening agent; the ceramic aggregate is diatomaceous earth; the sintering aid is calcium oxide; the binder is polyethylene; the pore-forming agent is a mixture of graphite, starch, and wood flour; the dispersant is oleic acid; and the toughening agent is alumina fiber.

[0044] The preparation comprises the following steps: S1: First, pre-mix the required amount of binder, dispersant, toughening agent and sintering aid in proportion and put them into an internal mixer, heat from room temperature to 163°C, and mix for 1 hour.

[0045] S2: Add the required amount of ceramic aggregate to the premix in step S1, and finally add the pore-forming agent, and continue mixing for 3.5 hours to ensure uniform dispersion. After mixing, cool the mixture to room temperature, and then crush the solidified mixture through a crusher into 1-5mm granular feed as a spare raw material for printing.

[0046] S3: Use engineering software to build a 3D printing digital model, slice the model, load the processed file into the 3D printer, and use the printing raw materials prepared in step S2 to print to form a ceramic core blank of the required shape.

[0047] S4: Use alumina powder to bury the ceramic core blank printed in step S3, and increase the temperature from room temperature to 680℃ at a rate of 0.5℃ / min in an air atmosphere, and keep the constant temperature for 1h; under a protective atmosphere, continue to increase the temperature to 1490℃ at a rate of 3℃ / min, keep the constant temperature for 1h, and then increase the temperature to 1650℃ at a rate of 1℃ / min, and keep the constant temperature for 4h.

[0048] S5: After the insulation is completed, the temperature is first lowered to 950°C at a rate of 2°C / min, then to 400°C at a rate of 1°C / min, and finally cooled to room temperature with the furnace at a rate of 2°C / min, and the finished porous ceramic core for the electrostatic chuck is taken out.

[0049] Example 4 The ceramic core body includes the following raw materials in parts by weight: 60 parts of ceramic aggregate, 2 parts of sintering aid, 5 parts of binder, 18 parts of pore-forming agent, 2 parts of dispersant, and 1 part of toughening agent; the ceramic aggregate is alumina; the sintering aid is magnesium oxide; the binder is polypropylene; the pore-forming agent is a mixture of graphite, starch, and wood powder; the dispersant is stearic acid; and the toughening agent is alumina fiber.

[0050] The preparation comprises the following steps: S1: First, pre-mix the required amount of binder, dispersant, toughening agent and sintering aid in proportion and put them into an internal mixer, heat from room temperature to 160°C, and mix for 0.5h.

[0051] S2: Add the required amount of ceramic aggregate to the premix in step S1, and finally add the pore-forming agent, and continue mixing for 3 hours to ensure uniform dispersion; after mixing, cool the mixture to room temperature, and then crush the solidified mixture through a crusher into 1-5mm granular feed as a spare raw material for printing.

[0052] S3: Use engineering software to build a 3D printing digital model, slice the model, load the processed file into the 3D printer, and use the printing raw materials prepared in step S2 to print to form a ceramic core blank of the required shape.

[0053] S4: Use alumina powder to bury the ceramic core blank printed in step S3, and increase the temperature from room temperature to 650℃ at a rate of 0.2℃ / min in an air atmosphere, and maintain a constant temperature for 0.5h; under a protective atmosphere, continue to increase the temperature to 1450℃ at a rate of 1.5℃ / min, maintain a constant temperature for 0.5h, and then increase the temperature to 1620℃ at a rate of 1℃ / min, and maintain a constant temperature for 3h.

[0054] S5: After the heat preservation is completed, the temperature is first lowered to 900°C at a rate of 1°C / min, then to 300°C at a rate of 0.5°C / min, and finally cooled to room temperature with the furnace at a rate of 1°C / min, and the finished porous ceramic core for the electrostatic chuck is taken out.

[0055] Example 5 The ceramic core body includes the following raw materials in parts by weight: 66 parts of ceramic aggregate, 2 parts of sintering aid, 5 parts of binder, 16 parts of pore-forming agent, 3 parts of dispersant, and 1.5 parts of toughening agent; the ceramic aggregate is alumina; the sintering aid is magnesium oxide; the binder is polypropylene; the pore-forming agent is a mixture of starch and wood flour; the dispersant is stearic acid; and the toughening agent is alumina fiber.

[0056] The preparation comprises the following steps: S1: First, pre-mix the binder, dispersant, toughening agent, and sintering aid in the required proportions by weight into an internal mixer, heat from room temperature to 170°C, and mix for 1.5 hours.

[0057] S2: Add the required amount of ceramic aggregate to the premix in step S1, and finally add the pore-forming agent, and continue mixing for 3 hours to ensure uniform dispersion; after mixing, cool the mixture to room temperature, and then crush the solidified mixture through a crusher into 1-5mm granular feed as a spare raw material for printing.

[0058] S3: Use engineering software to build a 3D printing digital model, slice the model, load the processed file into the 3D printer, and use the printing raw materials prepared in step S2 to print to form a ceramic core blank of the required shape.

[0059] S4: Use alumina powder to bury the ceramic core blank printed in step S3, and increase the temperature from room temperature to 650℃ at a heating rate of 1℃ / min in an air atmosphere, and keep the constant temperature for 1h; under a protective atmosphere, continue to increase the temperature to 1450℃ at a heating rate of 3℃ / min, keep the constant temperature for 1h, and then increase the temperature to 1680℃ at a heating rate of 1℃ / min, and keep the constant temperature for 4h.

[0060] S5: After the insulation is completed, the temperature is first lowered to 950°C at a rate of 2°C / min, then to 400°C at a rate of 0.5°C / min, and finally cooled to room temperature with the furnace at a rate of 3°C / min, and the finished porous ceramic core for the electrostatic chuck is taken out.

[0061] Example 6 The ceramic core body includes the following raw materials in parts by weight: 65 parts of ceramic aggregate, 3.5 parts of sintering aid, 7 parts of binder, 21 parts of pore-forming agent, 3.8 parts of dispersant, and 2.5 parts of toughening agent; the ceramic aggregate is diatomaceous earth; the sintering aid is calcium oxide; the binder is polyethylene; the pore-forming agent is a mixture of graphite, starch, and wood flour; the dispersant is oleic acid; and the toughening agent is alumina fiber.

[0062] The preparation comprises the following steps: S1: First, pre-mix the required amount of binder, dispersant, toughening agent and sintering aid in proportion and put them into an internal mixer, heat from room temperature to 163°C, and mix for 1 hour.

[0063] S2: Add the required amount of ceramic aggregate to the premix in step S1, and finally add the pore-forming agent, and continue mixing for 3.5 hours to ensure uniform dispersion. After mixing, cool the mixture to room temperature, and then crush the solidified mixture through a crusher into 1-5mm granular feed as a spare raw material for printing.

[0064] S3: Use engineering software to build a 3D printing digital model, slice the model, load the processed file into the 3D printer, and use the printing raw materials prepared in step S2 to print to form a ceramic core blank of the required shape.

[0065] S4: The ceramic core blank printed in step S3 is buried and fired with alumina powder. The temperature is raised from room temperature to 680°C at a rate of 0.5°C / min in an air atmosphere and maintained at a constant temperature for 1 hour. In a protective atmosphere, the temperature is further raised at a rate of 3°C / min to 1490°C and maintained at a constant temperature for 1 hour. The temperature is then raised to 1650°C at a rate of 1°C / min and maintained at a constant temperature for 4 hours. S5: After the insulation is completed, the temperature is first lowered to 950°C at a rate of 2°C / min, then to 400°C at a rate of 1°C / min, and finally cooled to room temperature with the furnace at a rate of 2°C / min, and the finished porous ceramic core for the electrostatic chuck is taken out.

[0066] Comparative Example 1 The difference between this comparative example and the above-mentioned Example 1 is that the porous ceramic core of this comparative example adopts the slip injection molding process (the slip injection process cannot form the circular channel structure of the present invention). The rest of the contents of this comparative example are the same as those of Example 1 and will not be repeated here.

[0067] Comparative Example 2 The difference between this comparative example and the above-mentioned Example 1 is that the porous ceramic core of this comparative example does not adopt a staged sintering process but is directly sintered to 1600-1700° C. The rest of the contents of this comparative example are the same as those of Example 1 and will not be repeated here.

[0068] Comparative Example 3 The difference between this comparative example and the above-mentioned embodiment 1 is that the porous ceramic core of this comparative example does not have the pore size gradient design. The rest of the contents of this comparative example are the same as those of embodiment 1 and will not be repeated here.

[0069] Table 1 is the test data of Examples 1 to 6

[0070] Table 2 is the test data of comparative examples 1 to 3

[0071] As can be seen from Examples 1 to 5, by optimizing the raw materials and their proportions, the raw materials and proportions described in Example 1 can achieve higher porosity, larger pore and through-hole diameters, and a larger pore size gradient, thereby achieving the best filtration effect in the porous ceramic. The porous ceramic obtained in Example 1 also has good compressive strength, which is conducive to a longer service life.

[0072] It can be seen from Comparative Example 1 and Example 1 that although grouting molding can obtain strong compressive strength, it cannot obtain the circular channel structure described in the present invention. Its porosity is significantly lower than that of 3D printing molding, and thus the filtration performance is relatively poor.

[0073] From Comparative Example 2 and Example 1, it can be seen that the porous ceramic obtained without the staged sintering process has a lower porosity. This is because compared with the staged sintering process, the greater thermal stress during the sintering process causes the through-holes to shrink, deform, or even close. The smaller through-hole diameter D50 also well demonstrates this point.

[0074] It can be seen from Comparative Example 3 and Example 1 that although the porosity equivalent to that of Example 1 can be obtained without adopting the pore gradient design, on the one hand, the through-hole diameters are too large, there is no micropore-assisted filtration, and the filtration performance is poor. On the other hand, there is no gradient density structure in Example 1, and there is a lack of a high-density structure as a support body. The overall compression strength is insufficient, and the service life is significantly reduced.

[0075] The design focus of the present invention is: by setting a first circular hole and a plurality of elliptical holes on the upper surface of the ceramic core body, setting a second circular hole and a third circular hole on the lower surface of the ceramic core body, and forming various circular channels in the ceramic core body, the product not only has excellent filtering performance, but also forms a unique adsorption structure, which enhances the adsorption area and enables it to effectively filter fine particles during the adsorption process. And the present invention makes the pressure on the adsorption surface uniform through the design of radially arranged channels, which is beneficial to protecting the ceramic core. At the same time, the micropores are evenly arranged in a petal shape, so that the mechanical properties of the ceramic core body in all directions remain consistent, the mechanical strength stability is improved, and its service life is extended. In addition, the present invention adopts a 3D printing molding method, which can accurately control the size of the micropores, ensure the uniformity of the size of each micropore, and at the same time, combine with the pore-forming agent to form pores, and the synergistic effect has a good filtering effect. In addition, the present invention further improves the filtering performance of the ceramic core by designing the relative pore size of the printed holes and the pore-forming agent to form a pore gradient.

[0076] The above description is merely a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A porous ceramic core for an electrostatic chuck, characterized in that: It includes a ceramic core body, which is cylindrical. The upper surface of the ceramic core body is provided with a first circular hole and multiple elliptical holes. The first circular hole is located at the center of the upper surface, and the multiple elliptical holes are located around the first circular hole. The lower surface of the ceramic core body is provided with a second circular hole and multiple third circular holes. The second circular hole is located at the center of the lower surface, and the multiple third circular holes are located around the second circular hole. A first circular channel and multiple second circular channels are formed in the ceramic core body. The first circular channel is located at the center of the ceramic core body. The first circular channel connects the first circular hole and the second circular hole. The multiple second circular channels are radially arranged, and the two ends of the multiple second circular channels are respectively connected to the corresponding elliptical holes and the corresponding third circular holes.

2. The porous ceramic core for an electrostatic chuck according to claim 1, characterized in that: The apertures of the first circular hole, the second circular hole and the third circular hole are the same, and are 0.005-0.4 mm. The aperture of the elliptical hole is larger than the apertures of the circular holes, and the wall thickness between two adjacent circular holes is 0.1-0.5 mm.

3. The porous ceramic core for an electrostatic chuck according to claim 1, wherein: The first circular hole and the plurality of elliptical holes are arranged in a petal shape.

4. The porous ceramic core for an electrostatic chuck according to claim 1, wherein: The elliptical hole is formed by a circular hole which is inclined 45 degrees outward at a position 2 mm away from the upper surface inside the ceramic core body and extends to the upper surface.

5. A method for preparing a porous ceramic core for an electrostatic chuck according to any one of claims 1 to 4, characterized in that: The ceramic core body adopts 3D printing technology to customize the pore structure, combines the printing pores and the pore forming agent to achieve the effect of collaborative filtration, and designs the pore size difference between the printing pores and the pore forming agent to form a pore size gradient; the ceramic core body includes the following raw materials by weight: 50-70 parts of ceramic aggregate, 0.5-4 parts of sintering aid, 1-8 parts of binder, 5-25 parts of pore forming agent, 0.5-4 parts of dispersant, and 0.1-3 parts of toughening agent; during preparation, The following steps are involved: S1: First, pre-mix the required amount of binder, dispersant, toughening agent, and sintering aid in proportion to each other into an internal mixer, heat from room temperature to 160-170°C, and mix for 0.5-1.5 hours; S2: Add the required amount of ceramic aggregate to the premix in step S1, and finally add the pore-forming agent, and continue mixing for 3-4 hours to ensure uniform dispersion; after mixing, cool the mixture to room temperature, and then crush the solidified mixture through a crusher to break it into 1-5mm granular feed as a spare raw material for printing; S3: Use engineering software to build a 3D printing digital model, slice the model, load the processed file into a 3D printer, and use the printing raw materials prepared in step S2 to print to form a ceramic core blank of the desired shape; S4: Burn the ceramic core blank printed in step S3 with alumina powder. In an air atmosphere, heat the temperature from room temperature to 600-750°C at a rate of 0.2-1°C / min, and maintain the constant temperature for 0.5-2h. In a protective atmosphere, continue to heat the temperature to 1400-1500°C at a rate of 1.5-5°C / min, and maintain the constant temperature for 0.5-2h. Then, heat the temperature to 1600-1700°C at a rate of 1-2°C / min, and maintain the constant temperature for 2-10h. S5: After the insulation is completed, the temperature is first lowered to 900-1000°C at a rate of 1-3°C / min, then lowered to 300-400°C at a rate of 0.5-1°C / min, and finally cooled to room temperature with the furnace at a rate of 1-3°C / min, and the finished porous ceramic core for the electrostatic chuck is taken out.

6. The method for preparing a porous ceramic core for an electrostatic chuck according to claim 5, wherein: The ceramic aggregate is at least one of kaolin, diatomaceous earth, alumina, silicon carbide, quartz sand, cordierite, and mullite, and the aggregate particle size is 6-30 μm.

7. The method for preparing a porous ceramic core for an electrostatic chuck according to claim 5, wherein: The sintering aid is at least one of boron oxide, magnesium oxide, calcium oxide, titanium oxide and zirconium oxide, and the particle size of the sintering aid is 0.1-2 μm.

8. The method for preparing a porous ceramic core for an electrostatic chuck according to claim 5, wherein: The binder is at least one of polyethylene, polypropylene and polycarbonate.

9. The method for preparing a porous ceramic core for an electrostatic chuck according to claim 5, wherein: The pore-forming agent is at least one of graphite, starch, wood powder, flour, and polystyrene microspheres. Pore-forming agents of different particle sizes and types are selected according to the needs of pore formation: when starch is used as the pore-forming agent, the particle size is reduced to 5-10 μm through enzymatic hydrolysis or acid hydrolysis modification treatment; when polystyrene microspheres are used as the pore-forming agent, the particle size is 100-300 μm.

10. The method for preparing a porous ceramic core for an electrostatic chuck according to claim 5, wherein: The dispersant is at least one of beeswax, oleic acid, and stearic acid; and the toughening agent is at least one of silicon carbide whiskers, alumina fibers, and graphite fibers.

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