A method for preparing an alumina ceramic sheet for electrostatic chuck by tape casting

Abstract

The application provides a method for preparing an alumina ceramic sheet for an electrostatic chuck by tape casting, wherein the alumina slurry obtained by mixing all raw materials is subjected to tape casting, screen printing, hot pressing, cold isostatic pressing and sintering in sequence, so that the alumina ceramic sheet for the electrostatic chuck with uniform size, good processing performance, high compactness, flat internal dielectric layer and heating layer, stable adsorption performance, uniform heating and excellent bending resistance can be prepared.

Description

Technical Field

[0001] This invention relates to the field of semiconductor component technology, and to a method for preparing electrostatic chucks, specifically to a method for preparing electrostatic chucks by casting alumina ceramic sheets. Background Technology

[0002] Electrostatic chucks play a crucial role in multiple stages of semiconductor manufacturing processes. Modern semiconductor manufacturing processes include wafer cleaning, oxidation, photolithography, etching, and deposition, each of which involves various steps. Among these, ion doping, ion implantation, physical vapor deposition (PVD), and chemical vapor deposition (CVD) all require ensuring the stable fixation of the wafer. Therefore, electrostatic chucks are needed to firmly hold the wafer in place using the attraction force generated by electrostatic charge.

[0003] Electrostatic chucks hold wafers in place using electrostatic adsorption. Their advantages include uniform adsorption across the wafer surface, preventing warping and deformation, and maintaining stable adsorption forces to ensure processing precision. Electrostatic chucks also cause minimal contamination and damage to the wafer, making them suitable for high-vacuum environments. Therefore, electrostatic chucks have become the most widely used wafer clamping tool and are core components of etching equipment, PVD equipment, PECVD equipment, and ion implantation equipment.

[0004] In addition, electrostatic chucks also have a heating function, as temperature control of wafers is crucial in semiconductor processes. Taking dry etching as an example, dry etching requires controlling the wafer at a specific temperature between 100°C and -70°C to maintain certain etching characteristics. Therefore, electrostatic chucks are needed to heat or dissipate heat from the wafer, thereby achieving precise temperature control.

[0005] Currently, electrostatic chucks are mainly made of alumina ceramic sheets or aluminum nitride ceramic sheets as the main material, because ceramic materials have good thermal conductivity, wear resistance, and high hardness, and have an inherent advantage in electrical insulation compared to metal materials.

[0006] Currently, ceramic sheets can be prepared using processes such as slip casting, compression molding, tape casting, and injection molding. Slip casting has a long preparation cycle and low production efficiency; injection molding is suitable for preparing ceramic parts with complex shapes and small dimensions.

[0007] In summary, there is a need to develop a method for preparing alumina ceramic sheets for electrostatic chucks by casting. Summary of the Invention

[0008] In view of the problems existing in the prior art, the present invention provides a method for preparing alumina ceramic sheets for electrostatic chucks by tape casting. The tape casting method involves mixing all raw materials to obtain an alumina slurry, and then sequentially performing tape casting, screen printing, hot pressing, cold isostatic pressing, and sintering. This method can produce alumina ceramic sheets for electrostatic chucks that are uniform in size, have good processing performance, are highly dense, have a flat internal dielectric layer and heating layer, stable adsorption performance, uniform heating, and excellent bending resistance.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] The purpose of this invention is to provide a method for preparing alumina ceramic sheets for electrostatic chucks by tape casting, the tape casting method comprising the following steps:

[0011] (1) Mix alumina powder, organic solvent, dispersant, binder, sintering aid and plasticizer evenly to obtain alumina slurry;

[0012] (2) The alumina slurry is cast and dried to obtain alumina cast blank sheet;

[0013] (3) Prepare several layers of alumina casting blanks, take two of them and form a dielectric layer and a heating layer respectively by screen printing, then stack them according to the target thickness, and hot press them to obtain alumina hot-pressed blanks.

[0014] (4) The alumina hot-pressed blank is subjected to cold isostatic pressing to obtain an alumina blank sheet;

[0015] (5) The alumina blank is sintered to obtain an alumina ceramic sheet for electrostatic chucks.

[0016] The alumina slurry obtained by mixing all raw materials is first cast and dried to obtain alumina cast blank sheets. This method has the advantages of simple and efficient process, short production cycle, and easy mass production. Then, two of the several layers of alumina cast blank sheets are screen printed to form a dielectric layer and a heating layer, respectively. They are then stacked according to the target thickness and subjected to hot pressing and cold isostatic pressing in sequence. This can further improve the density and bonding strength of the alumina blank sheets, effectively ensuring the density requirements. After sintering, alumina ceramic sheets for electrostatic chucks with uniform size, good processing performance, high density, flat internal dielectric and heating layers, stable adsorption performance, uniform heating, and excellent bending resistance can be prepared.

[0017] As a preferred technical solution of the present invention, the organic solvent in step (1) includes at least one of ethanol, butanone, toluene, isopropanol, cyclohexane or acetone.

[0018] Preferably, the dispersant in step (1) includes at least one of herring oil, polyethylene glycol oleate, or sucrose.

[0019] Preferably, the sintering aid in step (1) includes at least one of yttrium oxide, magnesium oxide, zirconium oxide, or silicon dioxide.

[0020] Preferably, the plasticizer in step (1) includes at least one of polyethylene glycol, butyl benzyl phthalate, or dibutyl phthalate.

[0021] Preferably, the adhesive in step (1) comprises polyvinyl butyral and / or polyvinyl alcohol.

[0022] Preferably, in the alumina slurry of step (1), by mass percentage, alumina comprises 20-40 wt%, for example 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%, etc.; organic solvent comprises 32-40 wt%, for example 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, or 40 wt%, etc.; and dispersant comprises 0.3-0.7 wt%, for example 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, or 0.7 wt%, etc. Sintering aids 0.05-0.07 wt%, such as 0.05 wt%, 0.055 wt%, 0.06 wt%, 0.065 wt%, or 0.07 wt%, etc.; plasticizers 3-8 wt%, such as 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, or 8 wt%, etc.; binders 10-25 wt%, such as 10 wt%, 13 wt%, 15 wt%, 17 wt%, 20 wt%, 22 wt%, or 25 wt%, etc., but not limited to the listed values. Other unlisted values ​​within the above range also apply.

[0023] Preferably, step (1) further includes coloring additives, wherein alumina powder, organic solvent, coloring additives, dispersant, binder, sintering aid and plasticizer are mixed evenly to obtain alumina slurry.

[0024] As a preferred technical solution of the present invention, the mixing in step (1) is carried out using a mill with a mixing tank.

[0025] Preferably, the mixing speed is 300-400 r / min, such as 300 r / min, 310 r / min, 330 r / min, 350 r / min, 360 r / min, 380 r / min or 400 r / min, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0026] Preferably, the mixing time is 18-24h, such as 18h, 19h, 20h, 21h, 22h, 23h or 24h, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0027] As a preferred technical solution of the present invention, before the casting process described in step (2), the alumina slurry is further degassed.

[0028] Preferably, the degassing is performed in a degassing machine.

[0029] Preferably, the degassing temperature is 25-65℃, such as 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃ or 65℃, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0030] Preferably, the degassing time is 2-3 hours, such as 2 hours, 2.1 hours, 2.3 hours, 2.5 hours, 2.6 hours, 2.8 hours, or 3 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0031] Preferably, the viscosity of the slurry is adjusted to 8000-12000 mPa·s through the degassing process, such as 8000 mPa·s, 8500 mPa·s, 9000 mPa·s, 9500 mPa·s, 10000 mPa·s, 10500 mPa·s, 11000 mPa·s, 11500 mPa·s, or 12000 mPa·s, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0032] As a preferred technical solution of the present invention, the casting process in step (2) is carried out using a casting machine.

[0033] Preferably, the height of the scraper for casting in step (2) is 0.8-1.6 mm, such as 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm or 1.6 mm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0034] Preferably, the casting speed in step (2) is 0.1-0.25 m / min, such as 0.1 m / min, 0.12 m / min, 0.15 m / min, 0.17 m / min, 0.2 m / min, 0.22 m / min or 0.25 m / min, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0035] Preferably, the thickness of the alumina casting blank in step (2) is 0.6-1.2 mm, such as 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm or 1.2 mm, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0036] As a preferred technical solution of the present invention, before the hot pressing in step (3), the method further includes: cutting several layers of alumina cast blanks into target size and shape pieces by a slicing machine, taking two pieces to form a dielectric layer and a heating layer by screen printing, and then stacking them according to the target thickness, so that the cast ceramic pieces with the printed dielectric layer and the cast ceramic pieces with the printed heating layer are placed in the required positions respectively.

[0037] Preferably, the hot pressing in step (3) is performed using a hot press.

[0038] Preferably, the hot pressing temperature in step (3) is 90-160℃, such as 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃ or 160℃, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0039] Preferably, the pressure of hot pressing in step (3) is 20-30 MPa, such as 20 MPa, 21 MPa, 23 MPa, 25 MPa, 26 MPa, 28 MPa or 30 MPa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0040] Preferably, the holding time of hot pressing in step (3) is 10-15 min, such as 10 min, 11 min, 12 min, 13 min, 14 min or 15 min, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0041] As a preferred technical solution of the present invention, step (4) includes: placing the alumina hot-pressed blank into an aluminum foil bag and drawing a vacuum, controlling the vacuum degree to ≤0.1Pa, and then placing the vacuum-packed alumina hot-pressed blank into a cold isostatic pressing device.

[0042] Preferably, the pressure of the cold isostatic pressing in step (4) is 200-250 MPa, such as 200 MPa, 210 MPa, 220 MPa, 230 MPa, 240 MPa or 250 MPa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0043] Preferably, the holding time of cold isostatic pressing in step (4) is 5-10 min, such as 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0044] As a preferred technical solution of the present invention, the alumina blank is degreased before sintering in step (5).

[0045] Preferably, the degreasing is carried out in a degreasing furnace.

[0046] Preferably, the degreasing temperature is 600-800℃, such as 600℃, 630℃, 650℃, 670℃, 700℃, 720℃, 750℃, 780℃ or 800℃, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0047] Preferably, the defatting heat preservation time is 3-5 hours, such as 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0048] As a preferred technical solution of the present invention, the sintering in step (5) is carried out in a vacuum sintering furnace.

[0049] Preferably, the sintering in step (5) is carried out in a mixed gas atmosphere of nitrogen and hydrogen.

[0050] Preferably, the sintering temperature in step (5) is 1750-1850℃, such as 1750℃, 1760℃, 1770℃, 1780℃, 1790℃, 1800℃, 1810℃, 1820℃, 1830℃, 1840℃ or 1850℃, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0051] Preferably, the holding time for sintering in step (5) is 2-5 hours, such as 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0052] As a preferred technical solution of the present invention, the casting method includes the following steps:

[0053] (1) Alumina powder, organic solvent, coloring additive, dispersant, binder, sintering aid and plasticizer are put into a mixing tank and placed on a grinding mill. The speed is adjusted to 300-400 r / min and the time is 18-24 h. After mixing evenly, alumina slurry is obtained. In the alumina slurry, according to the mass percentage, alumina is 20-40 wt%, organic solvent is 32-40 wt%, dispersant is 0.3-0.7 wt%, sintering aid is 0.05-0.07 wt%, plasticizer is 3-8 wt%, and binder is 10-25 wt%.

[0054] (2) Pour the alumina slurry into a degassing machine and degas it at 25-65℃ for 2-3 hours. Adjust the viscosity of the slurry to 8000-12000 mPa·s. Pour the degassed slurry into a casting machine for casting. Adjust the scraper height to 0.8-1.6 mm and the casting speed to 0.1-0.25 m / min. After drying, obtain an alumina casting blank sheet with a thickness of 0.6-1.2 mm.

[0055] (3) Prepare several layers of alumina cast blanks, cut them into target size and shape pieces by a slicing machine, take two pieces to form a dielectric layer and a heating layer by screen printing, and stack them according to the target thickness so that the cast ceramic pieces with the printed dielectric layer and the cast ceramic pieces with the printed heating layer are placed in the required positions. Put the stacked whole into a hot press for hot pressing, adjust the temperature to 90-160℃, adjust the pressure to 20-30MPa, and adjust the holding time to 10-15min to obtain alumina hot-pressed blanks;

[0056] (4) The alumina hot-pressed blank is placed in an aluminum foil bag and vacuumed. The vacuum degree is controlled to be ≤0.1Pa. The vacuum-packed alumina hot-pressed blank is then placed in a cold isostatic pressing equipment for cold isostatic pressing. The pressure is adjusted to 200-250MPa and the holding time is adjusted to 5-10min to obtain an alumina blank sheet.

[0057] (5) The alumina blank is placed in a degreasing furnace and degreased at 600-800℃ for 3-5 hours. Then it is placed in a vacuum sintering furnace and sintered at 1750-1850℃ for 2-5 hours in a mixed atmosphere of nitrogen and hydrogen to obtain an alumina ceramic sheet for electrostatic chucks.

[0058] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0059] The casting molding preparation method of the present invention involves mixing all raw materials to obtain an alumina slurry, and then sequentially performing casting molding, screen printing, hot pressing, cold isostatic pressing, and sintering to prepare an alumina ceramic sheet for electrostatic chucks that is uniform in size, has good processing performance, high density, a flat internal dielectric layer and heating layer, stable adsorption performance, uniform heating, and excellent bending resistance. Detailed Implementation

[0060] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0061] Example 1

[0062] This embodiment provides a method for preparing alumina ceramic sheets for electrostatic chucks by tape casting, the method comprising the following steps:

[0063] (1) Alumina powder, a mixture of ethanol and butanone in a volume ratio of 1:1, black additives, herring oil, a mixture of yttrium oxide and magnesium oxide in a mass ratio of 3:2, polyethylene glycol, and polyvinyl butyral were placed in a mixing tank and placed on a grinding mill. The speed was adjusted to 350 r / min and the time was 20 h. After mixing evenly, an alumina slurry was obtained. The alumina slurry contained, by mass percentage, 35 wt% alumina, 34.44 wt% organic solvent, 0.5 wt% dispersant, 0.06 wt% sintering aid, 5 wt% plasticizer, and 25 wt% binder.

[0064] (2) The alumina slurry is poured into a degassing machine and degassed at 50°C for 2.5 hours. The viscosity of the slurry is adjusted to 10000 mPa·s. The degassed slurry is poured into a casting machine for casting. The doctor blade height is adjusted to 1.2 mm and the casting speed is adjusted to 0.2 m / min. After drying, an alumina casting blank with a thickness of 1.0 mm is obtained.

[0065] (3) Prepare several layers of alumina cast blanks, cut them into target size and shape pieces by a slicing machine, take two pieces to form a dielectric layer and a heating layer by screen printing, and stack them according to the target thickness so that the cast ceramic pieces with the printed dielectric layer and the cast ceramic pieces with the printed heating layer are placed in the required positions. Put the stacked whole into a hot press for hot pressing, adjust the temperature to 120℃, adjust the pressure to 25MPa, and adjust the holding time to 15min to obtain alumina hot press blank;

[0066] (4) The alumina hot-pressed blank is placed in an aluminum foil bag and vacuumed to control the vacuum degree ≤0.1Pa. Then the vacuum-packed alumina hot-pressed blank is placed in a cold isostatic pressing equipment for cold isostatic pressing. The pressure is adjusted to 230MPa and the holding time is adjusted to 8min to obtain an alumina blank sheet.

[0067] (5) The alumina blank is placed in a degreasing furnace and degreased at 700°C for 4 hours. Then it is placed in a vacuum sintering furnace and sintered at 1800°C for 3 hours in a mixed atmosphere of nitrogen and hydrogen to obtain a black alumina ceramic sheet for electrostatic chucks.

[0068] Example 2

[0069] This embodiment provides a method for preparing alumina ceramic sheets for electrostatic chucks by tape casting, the method comprising the following steps:

[0070] (1) Alumina powder, a mixture of ethanol and butanone in a volume ratio of 1:1, black additives, herring oil, a mixture of yttrium oxide and magnesium oxide in a mass ratio of 3:2, polyethylene glycol, and polyvinyl butyral were placed in a mixing tank and placed on a grinding mill. The speed was adjusted to 350 r / min and the time was 20 h. After mixing evenly, an alumina slurry was obtained. The alumina slurry contained, by mass percentage, 35 wt% alumina, 34.44 wt% organic solvent, 0.5 wt% dispersant, 0.06 wt% sintering aid, 5 wt% plasticizer, and 25 wt% binder.

[0071] (2) The alumina slurry is poured into a degassing machine and degassed at 25°C for 2 hours. The viscosity of the slurry is adjusted to 8000 mPa·s. The degassed slurry is poured into a casting machine for casting. The scraper height is adjusted to 0.8 mm and the casting speed is adjusted to 0.1 m / min. After drying, an alumina casting blank with a thickness of 0.6 mm is obtained.

[0072] (3) Prepare several layers of alumina cast blanks, cut them into target size and shape pieces by a slicing machine, take two pieces to form dielectric layer and heating layer by screen printing, and stack them according to the target thickness so that the cast ceramic pieces with dielectric layer and the cast ceramic pieces with heating layer are placed in the required positions. Put the stacked whole into a hot press for hot pressing, adjust the temperature to 90℃, adjust the pressure to 20MPa, and adjust the holding time to 10min to obtain alumina hot press blank;

[0073] (4) The alumina hot-pressed blank is placed in an aluminum foil bag and vacuumed. The vacuum degree is controlled to be ≤0.1Pa. The vacuum-packed alumina hot-pressed blank is then placed in a cold isostatic pressing equipment for cold isostatic pressing. The pressure is adjusted to 200MPa and the holding time is adjusted to 5min to obtain an alumina blank sheet.

[0074] (5) The alumina blank is placed in a degreasing furnace and degreased at 600°C for 3 hours. Then it is placed in a vacuum sintering furnace and sintered at 1750°C for 2 hours in a mixed atmosphere of nitrogen and hydrogen to obtain a black alumina ceramic sheet for electrostatic chucks.

[0075] Example 3

[0076] This embodiment provides a method for preparing alumina ceramic sheets for electrostatic chucks by tape casting, the method comprising the following steps:

[0077] (1) Alumina powder, a mixture of ethanol and butanone in a volume ratio of 1:1, black additives, herring oil, a mixture of yttrium oxide and magnesium oxide in a mass ratio of 3:2, polyethylene glycol, and polyvinyl butyral were placed in a mixing tank and placed on a grinding mill. The speed was adjusted to 350 r / min and the time was 20 h. After mixing evenly, an alumina slurry was obtained. The alumina slurry contained, by mass percentage, 35 wt% alumina, 34.44 wt% organic solvent, 0.5 wt% dispersant, 0.06 wt% sintering aid, 5 wt% plasticizer, and 25 wt% binder.

[0078] (2) The alumina slurry is poured into a degassing machine and degassed at 65°C for 3 hours. The viscosity of the slurry is adjusted to 12000 mPa·s. The degassed slurry is poured into a casting machine for casting. The doctor blade height is adjusted to 1.6 mm and the casting speed is adjusted to 0.25 m / min. After drying, an alumina casting blank with a thickness of 1.2 mm is obtained.

[0079] (3) Prepare several layers of alumina cast blanks, cut them into target size and shape pieces by a slicing machine, take two pieces to form a dielectric layer and a heating layer by screen printing, and stack them according to the target thickness so that the cast ceramic pieces with the printed dielectric layer and the cast ceramic pieces with the printed heating layer are placed in the required positions. Put the stacked whole into a hot press for hot pressing, adjust the temperature to 160℃, adjust the pressure to 30MPa, and adjust the holding time to 15min to obtain alumina hot press blank;

[0080] (4) The alumina hot-pressed blank is placed in an aluminum foil bag and vacuumed to control the vacuum degree ≤0.1Pa. Then the vacuum-packed alumina hot-pressed blank is placed in a cold isostatic pressing equipment for cold isostatic pressing. The pressure is adjusted to 250MPa and the holding time is adjusted to 10min to obtain an alumina blank sheet.

[0081] (5) The alumina blank is placed in a degreasing furnace and degreased at 800°C for 5 hours. Then it is placed in a vacuum sintering furnace and sintered at 1850°C for 5 hours in a mixed atmosphere of nitrogen and hydrogen to obtain a black alumina ceramic sheet for electrostatic chucks.

[0082] Example 4

[0083] This embodiment provides a method for preparing alumina ceramic sheets for electrostatic chucks by casting. The only difference from Embodiment 1 is that the sintering temperature in step (5) is 1700℃.

[0084] Example 5

[0085] This embodiment provides a method for preparing alumina ceramic sheets for electrostatic chucks by tape casting. The only difference from Embodiment 1 is that the sintering temperature in step (5) is 1900℃.

[0086] Comparative Example 1

[0087] This comparative example provides a method for preparing alumina ceramic sheets for electrostatic chucks by casting. Compared with Example 1, the only difference is that the cold isostatic pressing in step (4) is completely omitted. That is, the alumina hot-pressed blank obtained in step (3) is directly placed into a degreasing furnace for degreasing, and then placed into a vacuum sintering furnace for sintering.

[0088] The electrostatic chucks prepared by the above embodiments and comparative examples were subjected to the following tests using alumina ceramic sheets. The specific test results are summarized in Table 1. Among them, a density meter was used to test the density, an ultrasonic scanner was used to detect the internal defect rate, the uniform suction force was tested after energizing to test the adsorption performance, the temperature difference of the thermal field uniformity was tested after energizing to test the heating uniformity, and a resistivity meter was used to test the volume resistivity.

[0089] Table 1

[0090]

[0091] In summary, the molding preparation method of the present invention, by sequentially performing spray granulation, molding, cold isostatic pressing and machining, screen printing, lamination and sintering on an alumina slurry obtained by mixing all raw materials, can produce alumina ceramic sheets for electrostatic chucks that are uniform in size, have good processing performance, high density, smooth internal dielectric and heating layers, stable adsorption performance, uniform heating and excellent bending resistance; wherein, the density is >99.8%, the internal defect rate is <0.5%, and the uniform suction force is >1000g / cm. 2 Thermal uniformity: temperature difference < 3℃; volume resistivity > 1×10⁻⁶ 13 Ω·cm.

[0092] This invention illustrates the detailed process equipment and process flow through the above embodiments. However, this invention is not limited to the detailed process equipment and process flow described above, meaning that this invention does not necessarily depend on the detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, addition of auxiliary components, and selection of specific methods, all fall within the protection scope and disclosure scope of this invention.

Claims

1. A method for preparing alumina ceramic sheets for electrostatic chucks by tape casting, characterized in that, The casting process includes the following steps: (1) Mix alumina powder, organic solvent, dispersant, binder, sintering aid and plasticizer evenly to obtain alumina slurry; (2) The alumina slurry is cast and dried to obtain alumina cast blank sheet; (3) The several layers of alumina cast blanks are cut into target size and shape pieces by a slicing machine. Two pieces are taken and screen-printed to form a dielectric layer and a heating layer, respectively. They are then stacked according to the target thickness so that the cast ceramic pieces with the dielectric layer and the cast ceramic pieces with the heating layer are placed in the required positions. After hot pressing at 90-160℃, alumina hot-pressed blanks are obtained. (4) The alumina hot-pressed blank is subjected to cold isostatic pressing to obtain an alumina blank sheet; (5) The alumina blank sheet is sintered to obtain an alumina ceramic sheet for electrostatic chucks; The sintering temperature in step (5) is 1750-1850℃.

2. The preparation method according to claim 1, characterized in that, The organic solvent in step (1) includes at least one of ethanol, butanone, toluene, isopropanol, cyclohexane or acetone.

3. The preparation method according to claim 1, characterized in that, The dispersant in step (1) includes at least one of herring oil, polyethylene glycol oleate, or sucrose.

4. The preparation method according to claim 1, characterized in that, The sintering aid in step (1) includes at least one of yttrium oxide, magnesium oxide, zirconium oxide, or silicon dioxide.

5. The preparation method according to claim 1, characterized in that, The plasticizer in step (1) includes at least one of polyethylene glycol, butyl benzyl phthalate, or dibutyl phthalate.

6. The preparation method according to claim 1, characterized in that, The adhesive in step (1) comprises polyvinyl butyral and / or polyvinyl alcohol.

7. The preparation method according to claim 1, characterized in that, In the alumina slurry of step (1), by mass percentage, there are 20-40 wt% alumina, 32-40 wt% organic solvent, 0.3-0.7 wt% dispersant, 0.05-0.07 wt% sintering aid, 3-8 wt% plasticizer, and 10-25 wt% binder.

8. The preparation method according to claim 1, characterized in that, Step (1) also includes coloring additives, which are mixed evenly with alumina powder, organic solvent, coloring additives, dispersant, binder, sintering aid and plasticizer to obtain alumina slurry.

9. The preparation method according to claim 1, characterized in that, The mixing in step (1) is carried out using a mill with a mixing tank.

10. The preparation method according to claim 9, characterized in that, The mixing speed is 300-400 r / min.

11. The preparation method according to claim 9, characterized in that, The mixing time is 18-24 hours.

12. The preparation method according to claim 1, characterized in that, Before the casting process described in step (2), the process further includes degassing the alumina slurry.

13. The preparation method according to claim 12, characterized in that, The degassing is performed in a degassing machine.

14. The preparation method according to claim 12, characterized in that, The degassing temperature is 25-65℃.

15. The preparation method according to claim 12, characterized in that, The degassing time is 2-3 hours.

16. The preparation method according to claim 12, characterized in that, The viscosity of the slurry is adjusted to 8000-12000 mPa‧s through the degassing process.

17. The preparation method according to claim 1, characterized in that, The casting process described in step (2) is carried out using a casting machine.

18. The preparation method according to claim 1, characterized in that, The height of the scraper used in step (2) of the casting process is 0.8-1.6 mm.

19. The preparation method according to claim 1, characterized in that, The casting speed in step (2) is 0.1-0.25 m / min.

20. The preparation method according to claim 1, characterized in that, The thickness of the alumina casting blank in step (2) is 0.6-1.2 mm.

21. The preparation method according to claim 1, characterized in that, The hot pressing in step (3) is performed using a hot press machine.

22. The preparation method according to claim 1, characterized in that, The pressure of hot pressing in step (3) is 20-30 MPa.

23. The preparation method according to claim 1, characterized in that, The holding time for hot pressing in step (3) is 10-15 minutes.

24. The preparation method according to claim 1, characterized in that, Step (4) includes: placing the alumina hot-pressed blank into an aluminum foil bag and vacuuming it to control the vacuum degree to ≤0.1Pa, and then placing the vacuum-packed alumina hot-pressed blank into a cold isostatic pressing device.

25. The preparation method according to claim 1, characterized in that, The pressure of the cold isostatic pressing in step (4) is 200-250 MPa.

26. The preparation method according to claim 1, characterized in that, The holding time for cold isostatic pressing in step (4) is 5-10 minutes.

27. The preparation method according to claim 1, characterized in that, Before sintering in step (5), the alumina blank sheet is degreased.

28. The preparation method according to claim 27, characterized in that, The degreasing is carried out in a degreasing furnace.

29. The preparation method according to claim 27, characterized in that, The degreasing temperature is 600-800℃.

30. The preparation method according to claim 27, characterized in that, The defatting process is maintained at a temperature of 3-5 hours.

31. The preparation method according to claim 1, characterized in that, The sintering in step (5) is carried out in a vacuum sintering furnace.

32. The preparation method according to claim 1, characterized in that, The sintering in step (5) is carried out in a mixed gas atmosphere of nitrogen and hydrogen.

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

34. The preparation method according to claim 1, characterized in that, The casting process includes the following steps: (1) Alumina powder, organic solvent, coloring additive, dispersant, binder, sintering aid and plasticizer are put into a mixing tank and placed on a grinding mill. The speed is adjusted to 300-400 r / min and the time is 18-24 h. After mixing evenly, alumina slurry is obtained. In the alumina slurry, by mass percentage, alumina 20-40 wt%, organic solvent 32-40 wt%, dispersant 0.3-0.7 wt%, sintering aid 0.05-0.07 wt%, plasticizer 3-8 wt%, binder 10-25 wt%; (2) Pour the alumina slurry into a degassing machine and degas it at 25-65℃ for 2-3 hours. Adjust the viscosity of the slurry to 8000-12000 mPa‧s. Pour the degassed slurry into a casting machine for casting. Adjust the scraper height to 0.8-1.6 mm and the casting speed to 0.1-0.25 m / min. After drying, obtain an alumina casting blank sheet with a thickness of 0.6-1.2 mm. (3) Prepare several layers of alumina cast blanks, cut them into target size and shape pieces by a slicing machine, take two pieces to form dielectric layer and heating layer by screen printing, and stack them according to the target thickness so that the cast ceramic pieces with dielectric layer and the cast ceramic pieces with heating layer are placed in the required positions. Put the stacked whole into a hot press for hot pressing, adjust the temperature to 90-160℃, adjust the pressure to 20-30MPa, and adjust the holding time to 10-15min to obtain alumina hot press blank; (4) The alumina hot-pressed blank is placed in an aluminum foil bag and vacuumed. The vacuum degree is controlled to be ≤0.1Pa. The vacuum-packed alumina hot-pressed blank is then placed in a cold isostatic pressing equipment for cold isostatic pressing. The pressure is adjusted to 200-250MPa and the holding time is adjusted to 5-10min to obtain an alumina blank sheet. (5) The alumina blank is placed in a degreasing furnace and degreased at 600-800℃ for 3-5 hours. Then it is placed in a vacuum sintering furnace and sintered at 1750-1850℃ for 2-5 hours in a mixed atmosphere of nitrogen and hydrogen to obtain alumina ceramic sheet for electrostatic chuck.

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