A porous ceramic core for an electrostatic chuck and a method of making

Abstract

The application discloses a kind of porous ceramic core for electrostatic chuck and its preparation method, it includes ceramic core body, the ceramic core body is cylindrical, the first round hole and multiple oval holes are opened in the upper surface of the ceramic core body, the first round hole is located in the center position of upper surface, the multiple oval holes are located in the periphery of first round hole, the second round hole and multiple third round holes are opened in the lower surface of the ceramic core body, the second round hole is located in the center position of lower surface, the multiple third round holes are located in the periphery of second round hole.By setting first round hole and multiple oval holes on the upper surface of ceramic core body, setting second round hole and third round hole on the lower surface of ceramic core body, and forming each round hole channel in ceramic core body, so that the product not only has excellent filtering performance, but also forms unique adsorption structure, enhances adsorption area, so that it can effectively filter fine particles in the adsorption process.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of electrostatic chucks, and particularly relates to a porous ceramic core for an electrostatic chuck and a preparation method. BACKGROUND

[0002] The ceramic core is resistant to acid and alkali corrosion and has a wide application condition, has certain resistance to most chemical substances, is not easy to be corroded by acid and alkali and the like, has a long service life, has a relatively stable structure and is not easy to deform, and has stable filtration performance. In the electronic industry, especially in high-end fields such as semiconductor manufacturing and liquid crystal display, the production requirements are extremely harsh. Tiny impurity particles can cause defects in electronic products, affecting the performance and reliability of the electronic products. The ceramic filter can meet the strict requirements of the electronic industry due to its high-precision filtration performance and good particle retention capacity. With the continuous progress of electronic technology, higher standards are put forward for the precision, flux and stability of the electronic-grade ceramic filter, which further promotes the innovative development of ceramic filtration technology in the electronic industry, and prompts researchers to continuously explore new ceramic materials and preparation processes to improve the performance of the ceramic filter. The ceramic filter has become a core filtration solution in the fields of water treatment, industrial purification and biological medicine due to its characteristics of adjustable precision, long service life and strong environmental compatibility. In the future, with the integration of biomimetic design, nano modification and intelligent technology, the application boundary of the ceramic filter will continue to expand, and the potential in the fields of new energy and cutting-edge manufacturing is remarkable.

[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 a mold, fills the cavity of the mold with the slurry, and then performs subsequent process steps such as solidification and sintering to obtain a ceramic product with the desired shape and performance. Slip casting can be used for ceramic products with complex shapes, and the prepared ceramic products have high density and good uniformity. However, the mold has strong dependence, and when the shape needs to be changed, the mold needs to be redesigned, which takes a long time and costs a lot. In addition, the ceramic products prepared by slip casting have low pore size precision and large deviation, and it is difficult to accurately control the pore size, so it is not easy to manufacture ceramic components with complex shapes and high precision requirements, such as ceramic components with special-shaped holes or gradient pore structures.

[0004] 3D printing is an additive manufacturing technology that can be used to form ceramic cores with complex internal structures, and can efficiently prepare ceramic products with special-shaped holes or gradient pore structures with high structural precision. At the same time, 3D printing is also a rapid prototyping technology, and its production does not depend on molds. This special manufacturing process is beneficial to quickly verify design ideas, shorten product development cycles and reduce research and development costs. SUMMARY

[0005] In view of the above, the present application aims at the defects of the prior art, and the main purpose is to provide a porous ceramic core for electrostatic chuck and a preparation method, so as to solve the problems that the pore size of the ceramic core is difficult to accurately control and the filtering performance of the ceramic core cannot meet the high standard requirements of the electronic industry.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A porous ceramic core for electrostatic chuck, comprising a ceramic core body, the ceramic core body is in a cylindrical shape, a first circular hole and a plurality of elliptical holes are arranged on the upper surface of the ceramic core body, the first circular hole is located at the center of the upper surface, the plurality of elliptical holes are located around the first circular hole, a second circular hole and a plurality of third circular holes are arranged on the lower surface of the ceramic core body, the second circular hole is located at the center of the lower surface, the plurality of third circular holes are located around the second circular hole, a first circular hole channel and a plurality of second circular hole channels are formed in the ceramic core body, the first circular hole channel is located at the center of the ceramic core body, the first circular hole channel is connected between the first circular hole and the second circular hole, the plurality of second circular hole channels are arranged radially, and the two ends of the plurality of second circular hole channels are respectively connected with the corresponding elliptical hole and the corresponding third circular hole.

[0008] As a preferred solution, the pore size of the first circular hole, the pore size of the second circular hole and the pore size of the third circular hole are the same, and the size is 0.005-0.4mm, the pore size of the elliptical hole is larger than the pore size of each circular hole, and the wall thickness between the adjacent two circular holes is 0.1-0.5mm.

[0009] As a preferred solution, the first circular hole and the plurality of elliptical holes are arranged in a petal shape.

[0010] As a preferred solution, the elliptical hole is formed by tilting the circular hole outward by 45 degrees at a distance of 2mm from the upper surface inside the ceramic core body and extending to the upper surface.

[0011] A preparation method of a porous ceramic core for electrostatic chuck, the ceramic core body adopts 3D printing technology to customize the pore structure, combines printing pore with pore-forming agent pore to achieve the effect of synergistic filtration, and designs the size difference of the printing pore and the pore-forming agent pore to form a pore size gradient; the ceramic core body comprises the following weight parts of raw materials: ceramic aggregate 50-70 parts, sintering aid 0.5-4 parts, binder 1-8 parts, pore-forming agent 5-25 parts, dispersing agent 0.5-4 parts, and toughening agent 0.1-3 parts; during preparation, the following steps are included:

[0012] S1: first premixing treatment, the required mass parts of binder, dispersing agent, toughening agent and sintering aid are put into a banbury mixer, heated from room temperature to 160-170℃, and mixed for 0.5-1.5h;

[0013] S2: Add the required mass fraction of ceramic aggregate to the premix of step S1, and finally add the pore-forming agent, continue to mix for 3-4 h to ensure uniform dispersion; after mixing is completed, cool the mixture to room temperature, then crush the solidified mixture through a crusher to form a granular feedstock of 1-5 mm in size for printing standby;

[0014] S3: Use engineering software to construct a 3D printing digital model, slice the model, load the processed file into the 3D printer, and use the printing standby material prepared in step S2 to print, forming a ceramic core blank of the required shape;

[0015] S4: Buried burn the ceramic core blank printed in step S3 with alumina powder, in an air atmosphere, from room temperature to 600-750℃ at a heating rate of 0.2-1℃ / min, maintain constant temperature for 0.5-2h; continue to increase the temperature to 1400-1500℃ at a heating rate of 1.5-5℃ / min in a protective atmosphere, maintain constant temperature for 0.5-2h, and then increase the temperature to 1600-1700℃ at a heating rate of 1-2℃ / min, maintain constant temperature for 2-10h;

[0016] S5: After holding, first decrease the temperature to 900-1000℃ at a rate of 1-3℃ / min, then decrease the temperature to 300-400℃ at a rate of 0.5-1℃ / min, and finally cool to room temperature at a rate of 1-3℃ / min, take out the electrostatic chuck and obtain the porous ceramic core product.

[0017] As a preferred solution, the ceramic aggregate is at least one of kaolin, diatomite, alumina, silicon carbide, quartz sand, cordierite, and mullite, and the aggregate particle size is 6-30μm.

[0018] 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 sintering aid particle size is 0.1-2μm.

[0019] As a preferred solution, the binder is at least one of polyethylene, polypropylene, and polycarbonate.

[0020] As a preferred solution, the pore-forming agent is at least one of graphite, starch, wood powder, flour, and polystyrene microspheres; according to the pore-forming needs, different particle sizes and types of pore-forming agents are selected: when starch is selected as the pore-forming agent, the particle size is reduced to 5-10μm through enzymatic hydrolysis or acid hydrolysis modification treatment; when polystyrene microspheres are selected as the pore-forming agent, the particle size is 100-300μm.

[0021] 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.

[0022] Compared with the prior art, the present application has obvious advantages and beneficial effects, and specifically, the above technical solution can know that:

[0023] By setting the first circular hole and the plurality of elliptical holes on the upper surface of the ceramic core body, setting the second circular hole and the third circular hole on the lower surface of the ceramic core body, and cooperating with the formation of the respective circular hole channels in the ceramic core body, the product not only has excellent filtering performance, but also forms a unique adsorption structure, enhances the adsorption area, and can effectively filter fine particles in the adsorption process. In addition, the radial arrangement of the hole channels makes the adsorption surface pressure conductive uniform, which is beneficial to the protection of the ceramic core, and the petal-shaped uniform distribution of the micropores makes the mechanical properties of the ceramic core body in each direction consistent, improves the mechanical strength stability, and prolongs the service life. In addition, the 3D printing forming method is adopted, the size of the micropores can be accurately controlled, the uniformity of the micropore size is ensured, and the pore-forming agent is combined to form pores, which has a good filtering effect. In addition, the relative pore size of the printing hole and the pore-forming agent is designed to form a pore size gradient, which further improves the filtering performance of the ceramic core.

[0024] To make the structural features and effects of the present application clearer, the present application will be described in detail below in combination with the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0025] Fig. 1 is a perspective view of a preferred embodiment of the present application;

[0026] Fig. 2 is a top view of a preferred embodiment of the present application;

[0027] Fig. 3 is a sectional view of a preferred embodiment of the present application.

[0028] BRIEF DESCRIPTION OF DRAWINGS:

[0029] 10, ceramic core body; 11, first circular hole; 12, elliptical hole; 13, second circular hole; 14, third circular hole; 15, first circular hole channel; 16, second circular hole channel. DETAILED DESCRIPTION

[0030] Please refer to Figs. 1 to 3 , which shows the specific structure of a porous ceramic core for an electrostatic chuck, including a ceramic core body 10.

[0031] The ceramic core body 10 is cylindrical, the upper surface of the ceramic core body 10 is provided with a first circular hole 11 and a plurality of elliptical holes 12, the first circular hole 11 is located at the center position of the upper surface, the plurality of elliptical holes 12 are located around the first circular hole 11, the lower surface of the ceramic core body 10 is provided with a second circular hole 13 and a plurality of third circular holes 14, the second circular hole 13 is located at the center position of the lower surface, and the plurality of third circular holes 14 are located around the second circular hole 13, the ceramic core body 10 is formed with a first circular hole channel 15 and a plurality of second circular hole channels 16, the first circular hole channel 15 is located at the center position of the ceramic core body 10, the first circular hole channel 15 is communicated between the first circular hole 11 and the second circular hole 13, the plurality of second circular hole channels 16 are radially arranged, and the two ends of the plurality of second circular hole channels 16 are communicated with the corresponding elliptical holes 12 and the corresponding third circular holes 14 respectively, so that the flow of the filtrate is more uniform.

[0032] In the embodiment, the diameters of the first circular hole 11, the second circular hole 13 and the third circular hole 14 are the same, and the size is 0.005-0.4mm, the diameter of the elliptical hole 12 is slightly larger than that of each circular hole, and the wall thickness between adjacent two circular holes is 0.1-0.5mm. In addition, the first circular hole 11 and the plurality of elliptical holes 12 are arranged in petal shape. The elliptical hole 12 is formed by tilting the circular hole by 45 degrees outward at a distance of 2mm from the upper surface inside the ceramic core body 10 and extending to the upper surface.

[0033] The application also discloses a preparation method of the porous ceramic core for the electrostatic chuck, the ceramic core body 10 adopts the 3D printing technology to customize the pore structure, combines the printing pore with the pore forming agent to achieve the synergistic filtering effect, and designs the size difference of the printing pore and the pore forming agent to form the pore diameter gradient; the ceramic core body 10 includes the following raw materials in weight parts: ceramic aggregate 50-70 parts, sintering aid 0.5-4 parts, binder 1-8 parts, pore forming agent 5-25 parts, dispersing agent 0.5-4 parts and toughening agent 0.1-3 parts. In the preparation, the following steps are included:

[0034] S1: firstly, pre-mixing treatment, the required mass parts of the binder, the dispersing agent, the toughening agent and the sintering aid are put into a banbury mixer, heated from room temperature to 160-170 DEG C, and mixed for 0.5-1.5h.

[0035] S2: then, the required mass parts of the ceramic aggregate are added to the pre-mixed material in the step S1, finally, the pore forming agent is added, and the mixing is continued for 3-4h to ensure uniform dispersion; after the mixing is completed, the mixture is cooled to room temperature, then the solidified mixture is crushed by a crusher, and the crushed particles of 1-5mm are used as the printing standby raw material.

[0036] S3: Adopting engineering software to build 3D printing digital model, slicing the model, loading the file into 3D printer after processing, printing using the printing standby material prepared in S2 step, forming the ceramic core blank with the required shape.

[0037] S4: Buried firing the ceramic core blank printed in S3 step with alumina powder, in air atmosphere, from room temperature to 600-750℃ at 0.2-1℃ / min heating rate, keeping constant temperature for 0.5-2h, slow heating can avoid cracking caused by the violent decomposition of organic matter; in protective atmosphere, continue to 1400-1500℃ at 1.5-5℃ / min heating rate, keep constant temperature for 0.5-2h, then to 1600-1700℃ at 1-2℃ / min heating rate, keep constant temperature for 2-10h, adopting the segmented sintering process, rapid densification at 1400-1500℃ to form the porous structure skeleton, limited densification at 1600-1700℃ to obtain the porous ceramic 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 shrinkage and avoid pore closure caused by local deformation.

[0038] S5: After keeping constant temperature, first decrease to 900-1000℃ at 1-3℃ / min, then to 300-400℃ at 0.5-1℃ / min, finally cool to room temperature with the furnace at 1-3℃ / min, take out the electrostatic chuck to get the finished porous ceramic core. The cooling process adopts three-stage cooling method, the first stage is to decrease from 1600-1700℃ to 900-1000℃ at 1-3℃ / min to inhibit grain growth, the second stage is to decrease to 300-400℃ at 0.5-1℃ / min to avoid cracks caused by thermal stress and phase transformation stress, the third stage is to cool to room temperature at 1-3℃ / min with reduced thermal stress.

[0039] The ceramic aggregate is at least one of kaolin, diatomite, alumina, silicon carbide, quartz sand, cordierite and mullite, and the aggregate particle size is 6-30 microns. The sintering aid is at least one of boron oxide, magnesium oxide, calcium oxide, titanium oxide and zirconium oxide, and the sintering aid particle size is 0.1-2 microns. The binder is at least one of polyethylene, polypropylene and polycarbonate. The pore-forming agent is at least one of graphite, starch, wood powder, flour and polystyrene microspheres; according to the pore-forming requirement, different particle sizes and types of pore-forming agents are selected: when starch is selected as the pore-forming agent, the particle size is reduced to 5-10 microns through enzymatic hydrolysis or acid hydrolysis modification treatment; when polystyrene microspheres are selected as the pore-forming agent, the particle size is 100-300 microns. 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.

[0040] In addition, the nozzle used in the 3D printing has a double-layer structure of an embedded body and a sleeve body, the embedded body is made of zirconia ceramic, has a very low thermal expansion coefficient and high temperature resistance, and is not easy to deform due to heat to reduce the printing precision; the sleeve body is made of copper-nickel alloy, has high thermal conductivity and good thermal stability, can reduce deformation caused by heat accumulation, and is suitable for high-temperature operation. The nozzle temperature is controlled at 120-160 DEG C, so as to reduce the pore size deviation caused by thermal expansion. In addition, the pore size of the nozzle of the 3D printer is strictly controlled, and is dynamically controlled according to the printing structure and actual printing precision requirement. Generally, when the pore size to be printed is 5-30 microns, the nozzle pore size can be 2-20 microns, and when the pore size to be printed is 150-200 microns, the nozzle pore size can be 100-300 microns. In addition, the 3D printing platform is provided with a cooling circulation system, so that the printing platform can maintain a proper temperature, which is beneficial to the shaping of the printed product. Compared with traditional air cooling, the circulation water cooling can make the printed product be cooled more uniformly and sufficiently, and reduce internal micro-pore blockage caused by thermal stress. In addition, the 3D printing technology that can be used includes 3DP jet molding, FDM fused deposition modeling, SLA light curing molding, SLS selective laser sintering molding and DLP digital light processing molding. In order to further improve the printing precision, SLA light curing molding and DLP digital light processing molding can be selected as the molding method, and therefore, photosensitive resin needs to be added to the supply.

[0041] After the porous ceramic core product for an electrostatic chuck is prepared, the final porous ceramic core product for an electrostatic chuck is tested by a bubble pressure method, the size and distribution of the through holes of the prepared ceramic core are obtained according to the relationship between the pressure and the pore size, the filtration performance is evaluated, and the feasibility of improving the filtration effect is verified.

[0042] In structure, the application adopts the aperture gradient design, the aperture of the oval hole 12 on the upper surface is slightly larger than the aperture of the first circular hole 11, the large-aperture oval hole 12 intercepts coarse particles, the fluid entering the first through hole 11 presents three-dimensional flow inside the ceramic core body 10, can obtain sufficient filtration, and effectively filters fine particles. The connecting hole of the second circular hole 16 is designed to be inclined on one side of the oval hole 12, which further intercepts coarse particles and increases the adsorption area. The radial arrangement of each hole and the uniform distribution of the petal-shaped micropores make the mechanical properties of the ceramic core body 10 in each direction similar, and the pressure distribution in each hole is uniform, thereby improving the mechanical strength of the ceramic core as a whole and making the structure more stable.

[0043] In the process, in order to accurately control the pore size of the micropore, the application improves from the aspects of printing hole and pore forming agent. The nozzle aperture directly affects the minimum extrusion line width, which is a key parameter affecting printing precision and structural details, and has a great influence on the printing aperture precision; the thermal stability of the nozzle affects the precision of its own aperture, and the nozzle inevitably expands and deforms due to heat during printing. In order to improve the precision of its own aperture, the nozzle should be made of a material with a very small thermal expansion coefficient; in addition to selecting the nozzle material, the adverse effects of thermal expansion deformation on the precision of the aperture can also be reduced by circulating cooling to reduce heat accumulation. In terms of pore forming by pore-forming agent, different particle sizes of pore-forming powder are selected to form micropores with different apertures, and the pore-forming powder is sieved to ensure that the formed micropores have uniform aperture distribution. In addition, it is necessary to ensure the uniformity of the pore-forming powder during the mixing process, to reduce the uneven particle size distribution of the pore-forming powder caused by the addition of appropriate dispersants and the use of suitable mixing methods.

[0044] In the method, the application forms an aperture gradient by regulating the relative size of the printing hole and the pore formed by the pore-forming agent, thereby enhancing the filtering performance. There are two regulation methods, one is to design the printing hole as a large aperture of 100-300 μm and the pore-forming agent as a small aperture of 5-20 μm, which is relatively easy to achieve; the other is to design the printing hole as a small aperture of 5-20 μm and the pore-forming agent as a large aperture of 100-300 μm, which requires a higher printer. The finished product is tested by the bubble pressure method.

[0045] Example one:

[0046] Aluminum oxide powder is selected as the ceramic aggregate, magnesium oxide is selected as the sintering aid, paraffin is selected as the binder, polypropylene is selected as the plasticizer, a mixture of graphite, starch and wood powder is selected as the pore-forming agent, stearic acid is selected as the dispersant, and polyethylene is selected as the toughening agent. The following describes the steps included in the preparation method of the ceramic core in detail.

[0047] First premixing treatment, open the mixer to preheat to 160℃, polypropylene particles 5 parts, stearic acid 0.5 parts, polyethylene 0.4 parts and magnesium oxide powder 1 parts are put into it, mixing. After continuous stirring for 30 minutes, put in paraffin wax 3 parts, continue to stir for 15 minutes until the paraffin is completely dissolved. Then, every 5 minutes, 11 parts of alumina powder is added to the mixer, a total of 55 parts of alumina powder. After continuous stirring for 30 minutes, 8 parts of pore forming agent is added, then forward stirring for 1.5 hours, and then reverse stirring for 1.5 hours. Then, the mixture is discharged and cooled, and the solidified mixture is crushed by a crusher to form 1-5mm granular feedstock for printing.

[0048] After slicing the 3D printing digital model, load it into the machine, and put the standby small particle raw material into the 3D printer. Through precise layer-by-layer stacking, the material of each layer is accurately fused together to form a ceramic core blank with an elliptical structure by printing an inclined circular hole at a distance of 2mm from the upper surface of the sample. After the ceramic core blank cools to room temperature, it is removed.

[0049] The printed ceramic core blank is buried and burned with alumina powder. In an air atmosphere, the temperature is raised from room temperature to 600℃ at a rate of 1℃ / min, and kept constant for 2h to completely volatilize and decompose the organic matter such as pore forming agent, and initially form a pore skeleton. In a protective atmosphere, continue to raise the temperature to 1400℃ at a rate of 4℃ / min, keep constant for 1h, then raise the temperature to 1600℃ at a rate of 2℃ / min, keep constant for 2h, and sinter in stages to reduce thermal stress and avoid causing pore closure. Finally, the ceramic core product is taken out after cooling to room temperature in the furnace.

[0050] The prepared ceramic core not only has controllable and adjustable micropores, but also has excellent filtering performance, which can meet the needs of the electronic industry.

[0051] Example two

[0052] The ceramic core body comprises the following raw materials by weight: ceramic aggregate 55 parts, sintering aid 1.5 parts, binder 2 parts, pore forming agent 10 parts, dispersant 1 part, and toughening agent 1 part; 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.

[0053] When preparing, the following steps are included:

[0054] S1: First premixing treatment, the required mass parts of binder, dispersant, toughening agent, sintering aid are put into the mixer, heated from room temperature to 160℃, and mixed for 0.5h.

[0055] S2: Add the required mass parts of ceramic aggregate to the premix of step S1, and finally add the pore-forming agent. Continue to mix for 3 h to ensure uniform dispersion. After mixing is complete, cool the mixture to room temperature. Then, crush the solidified mixture in a crusher to form granular feedstock of 1-5 mm in size for use as a printing standby material.

[0056] S3: Use engineering software to construct a 3D printing digital model. Slice the model, and then load the processed file into a 3D printer. Use the printing standby material prepared in step S2 to print, thereby forming a ceramic core blank of the required shape.

[0057] S4: Burial firing of the ceramic core blank printed in step S3 is performed using an alumina powder. In an air atmosphere, the temperature is increased from room temperature to 650°C at a rate of 0.2°C / min, and then held constant for 0.5 h. In a protective atmosphere, the temperature is further increased to 1450°C at a rate of 1.5°C / min, and then held constant for 0.5 h. The temperature is then increased to 1620°C at a rate of 1°C / min, and then held constant for 3 h.

[0058] S5: After holding at temperature is complete, the temperature is first decreased to 900°C at a rate of 1°C / min, and then decreased to 300°C at a rate of 0.5°C / min. Finally, the temperature is decreased to room temperature at a rate of 1°C / min. The electrostatic chuck is removed, and the porous ceramic core product is obtained.

[0059] Example Three

[0060] The ceramic core body comprises the following raw materials by weight: ceramic aggregate 60 parts, sintering aid 2 parts, binder 4 parts, pore-forming agent 15 parts, dispersing agent 1.5 parts, and toughening agent 1.3 parts. The ceramic aggregate is diatomite. The sintering aid is calcium oxide. The binder is polyethylene. The pore-forming agent is a mixture of graphite, starch, and wood powder. The dispersing agent is oleic acid. The toughening agent is alumina fiber.

[0061] Preparation includes the following steps:

[0062] S1: First, pre-mixing treatment is performed. The required mass parts of binder, dispersing agent, toughening agent, and sintering aid are added to a mixer, and heated from room temperature to 163°C. Mixing is performed for 1 h.

[0063] S2: Add the required mass parts of ceramic aggregate to the premix of step S1, and finally add the pore-forming agent. Continue to mix for 3.5 h to ensure uniform dispersion. After mixing is complete, cool the mixture to room temperature. Then, crush the solidified mixture in a crusher to form granular feedstock of 1-5 mm in size for use as a printing standby material.

[0064] S3: Adopting engineering software to build 3D printing digital model, processing the model by slicing, loading the processed file into 3D printer, printing using the printing standby raw material prepared in S2 step, forming the ceramic core blank with the required shape.

[0065] S4: Buried burning the ceramic core blank printed in S3 step with alumina powder, in air atmosphere, from room temperature to 680℃ at a heating rate of 0.5℃ / min, keeping constant temperature for 1h; in protective atmosphere, continuing to 1490℃ at a heating rate of 3℃ / min, keeping constant temperature for 1h, then to 1650℃ at a heating rate of 1℃ / min, keeping constant temperature for 4h.

[0066] S5: After keeping warm, first to 950℃ at a cooling rate of 2℃ / min, then to 400℃ at a cooling rate of 1℃ / min, finally cooling to room temperature with the furnace at a cooling rate of 2℃ / min, taking out the electrostatic chuck to get the porous ceramic core product.

[0067] Example Four

[0068] The ceramic core body comprises the following raw materials by weight: ceramic aggregate 60 parts, sintering aid 2 parts, binder 5 parts, pore-forming agent 18 parts, dispersing agent 2 parts, toughening agent 1 part; 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 dispersing agent is stearic acid; the toughening agent is alumina fiber.

[0069] When preparing, the following steps are included:

[0070] S1: First premixing treatment, putting the required mass parts of binder, dispersing agent, toughening agent and sintering aid into the internal mixer in proportion, heating from room temperature to 160℃, mixing for 0.5h.

[0071] S2: Then adding the required mass parts of ceramic aggregate to the premixing material in S1 step, finally adding the pore-forming agent, continuing to mix for 3h to ensure uniform dispersion; after mixing, cool the mixture to room temperature, then crush the solidified mixture through a crusher to form 1-5mm granular feedstock as printing standby raw material.

[0072] S3: Adopting engineering software to build 3D printing digital model, processing the model by slicing, loading the processed file into 3D printer, printing using the printing standby raw material prepared in S2 step, forming the ceramic core blank with the required shape.

[0073] S4: The ceramic core blank printed in S3 step is buried with alumina powder, and is heated from room temperature to 650°C at a heating rate of 0.2°C / min in an air atmosphere, and is kept at a constant temperature for 0.5 h; under a protective atmosphere, it is continuously heated to 1450°C at a heating rate of 1.5°C / min, and is kept at a constant temperature for 0.5 h, and is heated to 1620°C at a heating rate of 1°C / min, and is kept at a constant temperature for 3 h.

[0074] S5: After keeping at a constant temperature, it is first cooled to 900°C at a cooling rate of 1°C / min, and is then cooled to 300°C at a cooling rate of 0.5°C / min, and is finally cooled to room temperature with the furnace at a cooling rate of 1°C / min, and the electrostatic chuck is taken out to obtain the porous ceramic core product.

[0075] Example Five

[0076] The ceramic core body comprises the following raw materials by weight: ceramic aggregate 66 parts, sintering aid 2 parts, binder 5 parts, pore-forming agent 16 parts, dispersing agent 3 parts, and toughening agent 1.5 parts; 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 powder; the dispersing agent is stearic acid; and the toughening agent is alumina fiber.

[0077] In the preparation, the following steps are included:

[0078] S1: First, pre-mixing treatment, the required mass parts of binder, dispersing agent, toughening agent, and sintering aid are put into a banbury mixer, heated from room temperature to 170°C, and mixed for 1.5 h.

[0079] S2: Then, the required mass parts of ceramic aggregate are added to the pre-mixed material in S1 step, and finally the pore-forming agent is added, and the mixing is continued for 3 h to ensure uniform dispersion; after the mixing is completed, the mixture is cooled to room temperature, and then the solidified mixture is crushed by a crusher to form a granular feed of 1-5 mm for printing standby raw material.

[0080] S3: A 3D printing digital model is constructed using engineering software, the model is processed by slicing, the processed file is loaded into a 3D printer, and the printing standby raw material prepared in S2 step is used for printing to form a ceramic core blank of the required shape.

[0081] S4: The ceramic core blank printed in S3 step is buried with alumina powder, and is heated from room temperature to 650°C at a heating rate of 1°C / min in an air atmosphere, and is kept at a constant temperature for 1 h; under a protective atmosphere, it is continuously heated to 1450°C at a heating rate of 3°C / min, and is kept at a constant temperature for 1 h, and is heated to 1680°C at a heating rate of 1°C / min, and is kept at a constant temperature for 4 h.

[0082] S5: After the completion of the heat preservation, first reduce to 950℃ at the rate of 2℃ / min, then reduce to 400℃ at the rate of 0.5℃ / min, finally cool to room temperature with the furnace at the rate of 3℃ / min, take out the electrostatic chuck with the porous ceramic core finished product.

[0083] Example six

[0084] The ceramic core body comprises the following raw materials by weight: ceramic aggregate 65 parts, sintering aid 3.5 parts, binder 7 parts, pore-forming agent 21 parts, dispersing agent 3.8 parts, toughening agent 2.5 parts; the ceramic aggregate is diatomite; the sintering aid is calcium oxide; the binder is polyethylene; the pore-forming agent is a mixture of graphite, starch and wood powder; the dispersing agent is oleic acid; the toughening agent is alumina fiber.

[0085] In preparation, the following steps are included:

[0086] S1: First, pre-mixing treatment, proportionally put the required mass parts of binder, dispersing agent, toughening agent, sintering aid into the internal mixer, heat from room temperature to 163℃, mix for 1h.

[0087] S2: Then add the required mass parts of ceramic aggregate to the pre-mixed material in step S1, and finally add the pore-forming agent, continue to mix for 3.5h to ensure uniform dispersion; after the mixing is completed, cool the mixture to room temperature, then crush the solidified mixture through a crusher to form 1-5mm granular feedstock for printing standby.

[0088] 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 standby material prepared in step S2 to print, forming a ceramic core blank of the required shape.

[0089] S4: Buried burn the ceramic core blank printed in step S3 with alumina powder, in air atmosphere, from room temperature to 680℃ at the rate of 0.5℃ / min, keep constant temperature for 1h; continue to increase the temperature to 1490℃ at the rate of 3℃ / min under protective atmosphere, keep constant temperature for 1h, then increase the temperature to 1650℃ at the rate of 1℃ / min, keep constant temperature for 4h;

[0090] S5: After the completion of the heat preservation, first reduce to 950℃ at the rate of 2℃ / min, then reduce to 400℃ at the rate of 1℃ / min, finally cool to room temperature with the furnace at the rate of 2℃ / min, take out the electrostatic chuck with the porous ceramic core finished product.

[0091] Comparative example one

[0092] The difference between the present comparative example and the above-mentioned example 1 is that the porous ceramic core of the present comparative example adopts a slip casting forming process (the circular channel structure described in the present application cannot be formed under the slip casting process). The rest of the present comparative example is the same as example 1, which will not be repeated here.

[0093] Comparative Example Two

[0094] The difference between the present comparative example and the above-mentioned example 1 is that the porous ceramic core of the present comparative example does not adopt a segmented sintering process but is directly raised to 1600-1700℃. The rest of the present comparative example is the same as example 1, which will not be repeated here.

[0095] Comparative Example Three

[0096] The difference between the present comparative example and the above-mentioned example 1 is that the porous ceramic core of the present comparative example cancels the pore size gradient design. The rest of the present comparative example is the same as example 1, which will not be repeated here.

[0097] Table 1 is the test data of examples one to six

[0098]

[0099] Table 2 is the test data of comparative examples one to three

[0100]

[0101] From examples one to five, it can be known that by optimizing the raw materials and the ratio, the raw materials and the ratio described in example one can obtain higher porosity, larger circular holes and through hole diameters, larger pore size gradient, and thus the obtained porous ceramic has the best filtering effect. The porous ceramic obtained in example one also has good compressive strength, which is conducive to obtaining a longer service life.

[0102] From comparative example one and example one, it can be known that although slip casting forming can obtain a relatively strong compressive strength, it cannot form the circular channel structure described in the present application, and the porosity is significantly lower than that of 3D printing forming, so the filtering performance is relatively poor.

[0103] From comparative example two and example one, it can be known that the porous ceramic obtained without using the segmented sintering process has a lower porosity. This is because compared with the segmented sintering process, the thermal stress is larger during the sintering process, causing the through hole to shrink and deform or even close, and the smaller through hole diameter D50 also well proves this point.

[0104] From comparative example three and example one, it can be known that without the pore size gradient design, although the porosity obtained is comparable to that of example one, on the one hand, the through hole diameter is too large, without the assistance of micro-pores for filtration, the filtering performance is poor, and on the other hand, without the gradient density structure in example one, the overall compressive strength is insufficient due to the lack of high-density structure as a support body, and the service life is significantly reduced.

[0105] The design of the present application focuses on: by setting the first round hole and multiple oval holes on the upper surface of the ceramic core body, setting the second round hole and the third round hole on the lower surface of the ceramic core body, and cooperating with the formation of each round hole in the ceramic core body, so that the product not only has excellent filtering performance, but also forms a unique adsorption structure, enhances the adsorption area, so that it can effectively filter fine particles in the adsorption process. And the design of the present application makes the adsorption surface pressure conductive uniform, which is beneficial to protect the ceramic core, and the micropores are uniformly arranged in petal shape, so that the mechanical properties of the ceramic core body in each direction remain consistent, improve the mechanical strength stability, and prolong the service life. In addition, the present application adopts the forming method of 3D printing, which can accurately control the size of the micropore, ensure the uniformity of each micropore size, and combine with pore forming agent to form pore, which has good filtering effect. In addition, the present application also designs the relative pore size of the printing hole and the pore forming agent, forms a pore size gradient, and further improves the filtering performance of the ceramic core.

[0106] The above is only a preferred embodiment of the present application, not any limitation on the technical scope of the present application, so any slight modification, equivalent change and modification of the above embodiment according to the technical essence of the present application still belongs to the scope of the technical scheme of the present application.

Claims

1. A method for preparing a porous ceramic core for an electrostatic chuck, characterized in that: The porous ceramic core for the electrostatic chuck includes a ceramic core body, which is cylindrical. The upper surface of the ceramic core body has 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 has 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. The ceramic core body has a first circular channel and multiple second circular channels. The first circular channel is located at the center of the ceramic core body and connects the first circular hole and the second circular hole. The multiple second circular channels are arranged radially, and their two ends are connected to the corresponding elliptical hole and the corresponding third circular hole, respectively. The ceramic core body utilizes 3D printing technology to customize its pore structure, combining pore formation through printing and pore-forming agents to achieve a synergistic filtration effect. The design incorporates a difference in pore size between the printed and pore-forming processes to create a pore size gradient. The ceramic core body comprises the following raw materials by weight: 50-70 parts ceramic aggregate, 0.5-4 parts sintering aid, 1-8 parts binder, 5-25 parts pore-forming agent, 0.5-4 parts dispersant, and 0.1-3 parts toughening agent. During preparation... Includes the following steps: S1: First, premix the ingredients. Add the required mass of binder, dispersant, toughening agent, and sintering aid to a mixer according to the specified proportions. Heat the mixture from room temperature to 160-170℃ and mix for 0.5-1.5 hours. S2: Add the required mass of ceramic aggregate to the premix from step S1, and finally add the pore-forming agent. Continue mixing for 3-4 hours to ensure uniform dispersion. After mixing, cool the mixture to room temperature, and then crush the solidified mixture into 1-5mm granules for feeding as raw material for printing. 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 and form a ceramic core blank of the required shape. S4: Embed the ceramic core blank printed in step S3 with alumina powder, raise the temperature from room temperature to 600-750℃ in air atmosphere at a rate of 0.2-1℃ / min, and hold the temperature for 0.5-2h; under a protective atmosphere, continue to raise the temperature to 1400-1500℃ at a rate of 1.5-5℃ / min, hold the temperature for 0.5-2h, and then raise the temperature to 1600-1700℃ at a rate of 1-2℃ / min, and hold the temperature for 2-10h. S5: After the heat preservation is completed, first reduce the temperature to 900-1000℃ at a cooling rate of 1-3℃ / min, then reduce it to 300-400℃ at a cooling rate of 0.5-1℃ / min, and finally cool it to room temperature with the furnace at a cooling rate of 1-3℃ / min. Then take out the finished product of the porous ceramic core for the electrostatic chuck.

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

3. The method for preparing a porous ceramic core for an electrostatic chuck according to claim 1, characterized in that: The first circular hole and multiple elliptical holes are arranged in a petal-like pattern.

4. The method for preparing a porous ceramic core for an electrostatic chuck according to claim 1, characterized in that: The elliptical hole is formed by the circular hole being inclined outward at 45 degrees from the upper surface at a distance of 2 mm inside the ceramic core body and extending to the upper surface.

5. The method for preparing a porous ceramic core for an electrostatic chuck according to claim 1, characterized in that: 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.

6. The method for preparing a porous ceramic core for an electrostatic chuck according to claim 1, characterized in that: 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.

7. The method for preparing a porous ceramic core for an electrostatic chuck according to claim 1, characterized in that: The adhesive is at least one of polyethylene, polypropylene, and polycarbonate.

8. The method for preparing a porous ceramic core for an electrostatic chuck according to claim 1, characterized in that: The pore-forming agent is at least one of graphite, starch, wood flour, wheat flour, and polystyrene microspheres; depending on the pore-forming requirements, different particle sizes and types of pore-forming agents are selected: 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.

9. The method for preparing a porous ceramic core for an electrostatic chuck according to claim 1, characterized in that: 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.

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