Alumina ceramic material with high dielectric properties and method for producing the same

Abstract

The application relates to the field of ceramics, in particular to a high-dielectric-property alumina ceramic material and a preparation method thereof. A special degassing temperature process is formulated for mixed binders, two kinds of raw powders with specific particle sizes are mixed according to a certain ratio to form a particle size bimodal combination, the raw powder density is improved, and two kinds of binders with specific components and dosages are mixed to provide favorable conditions for improving the green body density after degassing, balance the problems of bonding strength and degassing difficulty, according to the thermal decomposition temperatures of the two kinds of binders, segmented heat preservation is adopted to make the binders fully decompose and discharge the green body, so that the prepared alumina ceramic material has excellent dielectric properties.

Description

Technical Field

[0001] This invention relates to the field of ceramics, and more particularly to a high dielectric alumina ceramic material and its preparation method. Background Technology

[0002] With the rapid development of the semiconductor industry, the demand for high-performance alumina materials is constantly increasing. Alumina ceramics used in the semiconductor field can be broadly categorized into two types: one is structural ceramics used in semiconductor equipment, serving as equipment components and emphasizing high purity, high strength, high insulation, and resistance to acid, alkali, and plasma corrosion; the other is insulating and dielectric ceramics used in electrostatic chucks, emphasizing high insulation, high dielectric constant, and low dielectric loss. A high dielectric constant enhances adhesion, low dielectric loss reduces heat generation, and high insulation prevents breakdown under high voltage, making these key factors affecting the performance of electrostatic chucks.

[0003] Alumina ceramics with a purity of 99.7-99.9% typically have a dielectric constant of 8-10 and a dielectric loss tanδ of 1.0*10. -4 -1.0*10 -3 The dielectric strength is 10-15 KV / mm. As the diameter and thickness of silicon wafers continue to increase, the performance requirements for electrostatic chucks are becoming increasingly stringent, making the development of alumina ceramics with higher dielectric properties an urgent matter.

[0004] The challenge in further improving dielectric properties lies in the difficulty of increasing the material density to 3.96 g / cm³ using traditional processes. 3 The theoretical limit is that commonly used organic systems are difficult to fully decompose, resulting in some trace impurities that cannot be discharged before rapid sintering and remain in the material matrix, affecting dielectric loss. Summary of the Invention

[0005] In order to improve the sintering density and reduce the organic matter in alumina ceramic materials, thereby improving the dielectric properties of alumina ceramic materials, this application provides a high dielectric alumina ceramic material and its preparation method.

[0006] In a first aspect, this application provides a method for preparing a high-dielectric-performance alumina ceramic material, comprising the following preparation steps:

[0007] (1) Alumina raw powder, binder, dispersant, defoamer and water ball milling are used to make slurry, and alumina granulated powder is obtained by spray granulation process;

[0008] (2) The alumina granulated powder is cold isostatically pressed to obtain alumina green blank;

[0009] (3) Degrease and remove the glue from the formed alumina green blank to obtain alumina ceramic parts;

[0010] (4) After the glue removal process is completed, the alumina ceramic parts are sintered at high temperature;

[0011] (5) After hot pressing and sintering, alumina ceramic material with high dielectric properties is obtained.

[0012] Furthermore, the alumina raw powder is a composition of alumina with particle sizes D50 of 0.1-1 mm and 1.5-3 mm.

[0013] Furthermore, the adhesive is a PVA and / or acrylic resin adhesive.

[0014] Preferably, the adhesive is a composition of PVA and acrylic resin in a mass ratio of 1-10:1.

[0015] Preferably, the adhesive is a combination of PVA and acrylic resin in a mass ratio of 3:1.

[0016] Furthermore, the mass ratio of the alumina powder, binder, dispersant, defoamer, and water is 45-55: 1.5-3.5: 0.2-0.5: 0.01-0.05: 50-60.

[0017] Furthermore, the particle size D50 of the alumina raw powder is 40-80 μm.

[0018] Furthermore, the pressure for cold isostatic pressing is 200-250 MPa, and the pressure is held for 1-10 minutes.

[0019] Furthermore, the degreasing and gelatin removal process is as follows:

[0020] The initial temperature for degreasing is 0-25℃, the maximum temperature is 500-600℃, and the final temperature is 100-500℃.

[0021] The heating rate from the initial temperature to 300℃ is 0.05-1℃ / min, and the temperature is held at 300℃ for 60-1000 minutes;

[0022] The heating rate from 300℃ to the highest temperature is 0.05-1℃ / minute, and the highest temperature is held for 400-1500 minutes;

[0023] The cooling rate from the highest temperature of -300℃ is 1-5℃ / minute; the cooling rate from 300℃ to the final temperature is 1-5℃ / minute.

[0024] Furthermore, the degreasing and gelatin removal process is as follows:

[0025] The heating rate from the initial temperature to 120℃ is 0.5-2℃ / minute, and the temperature is held at 120℃ for 10-100 minutes;

[0026] The heating rate for 120-270℃ is 0.05-1℃ / minute, and the holding time at 270℃ is 150-200 minutes;

[0027] The heating rate for 270-300℃ is 0.05-1℃ / minute, and the holding time at 300℃ is 150-200 minutes;

[0028] The heating rate at 300-350℃ is 0.05-1℃ / minute, and the holding time at 350℃ is 200-400 minutes;

[0029] The heating rate at 350-450℃ is 0.05-1℃ / minute, and the holding time at 450℃ is 200-400 minutes;

[0030] The heating rate from 450℃ to the highest temperature is 0.05-1℃ / minute, and the highest temperature is held for 300-500 minutes;

[0031] The cooling rate from the highest temperature of -300℃ is 1-5℃ / minute; the cooling rate from 300℃ to the final temperature is 1-5℃ / minute.

[0032] Furthermore, the highest temperature for high-temperature sintering is 1630-1650℃, and under the protective atmosphere of nitrogen or argon, pressure is applied at 1000-1200℃, with a maximum pressure of 30-45 MPa.

[0033] Secondly, this application provides a high dielectric alumina ceramic material obtained by the preparation method described in this application.

[0034] Beneficial effects: 1. This application has developed a special debinding temperature process for mixed binders. Two raw powders with specific particle sizes are mixed in a certain ratio to form a bimodal particle size combination, which improves the density of the raw powder. The mixing of the two binders with specific components and dosages provides favorable conditions for improving the density of the green body after debinding, balancing the issues of bonding strength and debinding difficulty. According to the thermal decomposition temperature of the two binders, segmented heat preservation is adopted to fully decompose and debind them from the green body, so that the prepared alumina ceramic material has excellent dielectric properties.

[0035] 2. Further, the cold isostatic pressing pressure was increased from the commonly used 100-150 MPa to 200-250 MPa, which reduced the amount of binder used and provided favorable conditions for increasing the density of the preform after debinding. This further improved the excellent dielectric properties of the prepared alumina ceramic material.

[0036] 3. Using the scheme described in this application, after powder granulation, cold isostatic pressing, debinding, and hot pressing sintering, a sintered density of 3.9-4 g / cm³ is obtained. 3 The dielectric constant is 10⁻¹¹, and the dielectric loss tanδ < 1*10 -3High dielectric alumina ceramic material with a dielectric strength of 15-20 KV / mm. Detailed Implementation

[0037] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments.

[0038] Example 1: A method for preparing a high dielectric alumina ceramic material, comprising the following preparation steps:

[0039] Traditional single-particle-size powder granulation method:

[0040] (1) Alumina raw powder (purity of 99.9%, particle size D50 of 1.7 mm), binder, dispersant, defoamer and pure water in a mass ratio of 46.88:2.8:0.3:0.02:50, were ball-milled to make a slurry. The granulated powder was obtained by spray granulation process and the particle size D50 of the granulated powder was 60 μm.

[0041] The binder is a mixture of PVA and acrylic resin in a mass ratio of 3:1; the dispersant is Nikko Chemical SC-0505K dispersant; and the defoamer is Nikko Chemical CC-130B defoamer.

[0042] (2) Fill the alumina granulated powder into the mold and perform cold isostatic pressing; the pressure of cold isostatic pressing is 230 MPa and the pressure is held for 2 minutes.

[0043] (3) Place the formed alumina green blank into a debinding furnace for degreasing and debinding;

[0044] The initial temperature for glue removal is 25℃, the maximum temperature is 600℃, and the final temperature is 150℃.

[0045] The heating rate from the initial temperature to 120℃ is 0.7℃ / min, and the temperature is held at 120℃ for 60 minutes.

[0046] The heating rate is 0.2℃ / minute for temperatures ranging from 120 to 270℃, and the temperature is held at 270℃ for 180 minutes.

[0047] The heating rate is 0.2℃ / minute for temperatures ranging from 270 to 300℃, and the temperature is held at 300℃ for 180 minutes.

[0048] The heating rate is 0.1℃ / minute for temperatures between 300-350℃, and the temperature is held at 350℃ for 300 minutes.

[0049] The heating rate is 0.1℃ / minute for temperatures between 350-450℃, and the temperature is held at 450℃ for 300 minutes.

[0050] The heating rate from 450℃ to the highest temperature is 0.1℃ / minute, and the highest temperature is held for 420 minutes;

[0051] The cooling rate from the highest temperature of -300℃ is 2℃ / minute; the cooling rate from 300℃ to the final temperature is 2℃ / minute.

[0052] (4) After the glue removal process is completed, the alumina ceramic parts are taken out from the glue removal furnace and put into the hot pressing sintering furnace for high-temperature sintering. The maximum temperature is 1645℃. During the sintering process, circulating nitrogen or argon is introduced as a protective atmosphere and pressurized at 1100℃. The maximum pressure is 45Mpa.

[0053] High-temperature sintering process: 25℃ to 1000℃, heating rate 3℃ / min; 1000℃ to 1645℃, heating rate 3℃ / min, pressure increased from 0 to 45 MPa; 1645℃ and pressure held for 2 hours; 1645℃ to 1000℃, cooling rate 3℃ / min, pressure released from 45 MPa to 0 MPa; then natural cooling.

[0054] (5) After hot pressing and sintering, the alumina ceramic parts are removed to obtain alumina ceramic material with high dielectric properties.

[0055] Example 2, a method for preparing a high dielectric alumina ceramic material, differs from Example 1 in that the particle size D50 of the alumina raw powder is 0.88 mm.

[0056] Example 3, a method for preparing alumina ceramic material with high dielectric properties, differs from Example 1 in that:

[0057] 1) The mass ratio of alumina powder, binder, dispersant, defoamer, and pure water is 45.68:4:0.3:0.02:50;

[0058] 2) The alumina raw powder is a composition of two different particle sizes, D50, of 0.88 mm and 1.7 mm respectively, with a weight ratio of 7:3.

[0059] 3) The adhesive is PVA.

[0060] 4) Degreasing and glue removal process: The glue removal starts at 25℃, reaches a maximum of 600℃, and ends at 150℃.

[0061] The heating rate from the initial temperature to 300℃ is 1℃ / minute, and the temperature is held at 300℃ for 60 minutes.

[0062] The heating rate from 300℃ to the highest temperature is 1℃ / minute, and the highest temperature is held for 420 minutes;

[0063] The cooling rate from the highest temperature of -300℃ is 2℃ / minute; the cooling rate from 300℃ to the final temperature is 2℃ / minute.

[0064] Example 4, a method for preparing a high dielectric alumina ceramic material, differs from Example 1 in that:

[0065] 1) The mass ratio of alumina powder, binder, dispersant, defoamer, and pure water is 47.68:2:0.3:0.02:50;

[0066] 2) The alumina raw powder is a composition of two different particle sizes, D50, of 0.88 mm and 1.7 mm respectively, with a weight ratio of 7:3.

[0067] 3) The adhesive is acrylic resin; because acrylic resin has a high viscosity, the amount used can be appropriately reduced, and the weight ratio is 2.0% of the total amount.

[0068] 4) Degreasing and glue removal process: The glue removal starts at 25℃, reaches a maximum of 600℃, and ends at 150℃.

[0069] The heating rate from the initial temperature to 400℃ is 1℃ / minute, and the temperature is held at 400℃ for 60 minutes.

[0070] The heating rate from 400℃ to the highest temperature is 1℃ / minute, and the highest temperature is held for 420 minutes;

[0071] The cooling rate from the highest temperature of -400℃ is 2℃ / minute; the cooling rate from 400℃ to the final temperature is 2℃ / minute.

[0072] Example 5, a method for preparing a high dielectric alumina ceramic material, differs from Example 1 in that: the alumina raw powder is a composition of two different particle sizes, with D50 of 0.88 mm and 1.7 mm respectively, in a weight ratio of 7:3.

[0073] Performance testing

[0074] Alumina ceramic parts obtained from Examples 1, 2, 3, 4, and 5 were selected for comparative experiments.

[0075] Test methods: The dielectric constant, dielectric loss and insulation strength of alumina ceramics were tested and compared using a density meter, impedance analyzer and insulation strength tester.

[0076] Experimental results: The data from the experiment conducted using the above method are shown in Table 1.

[0077] Table 1. Performance Test List of Examples and Comparative Examples

[0078]

[0079] The results in the table above show that the dielectric constant, dielectric loss, and dielectric strength of the alumina ceramic parts used in this invention are all improved compared to traditional processes, which enhances the dielectric properties of alumina materials and is beneficial for developing higher-performance electrostatic chucks.

[0080] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing alumina ceramic material with high dielectric properties, characterized in that, The preparation steps include the following: (1) Alumina raw powder, binder, dispersant, defoamer and water ball milling are used to make slurry, and alumina granulated powder is obtained by spray granulation process; (2) The alumina granulated powder is cold isostatically pressed to obtain alumina green blank; (3) Degrease and remove the glue from the formed alumina green blank to obtain alumina ceramic parts; (4) After the glue removal process is completed, the alumina ceramic parts are sintered at high temperature; (5) After hot pressing and sintering, alumina ceramic material with high dielectric properties is obtained; The alumina raw powder is a composition of alumina with particle sizes D50 of 0.1-1 mm and 1.5-3 mm; The adhesive is a PVA and / or acrylic resin adhesive; The mass ratio of the alumina powder, binder, dispersant, defoamer, and water is 45-55: 1.5-3.5: 0.2-0.5: 0.01-0.05: 50-60; The pressure for cold isostatic pressing is 200-250 MPa, and the pressure is held for 1-10 minutes. The degreasing and gelatin removal process is as follows: The initial temperature for degreasing is 0-25℃, the maximum temperature is 500-600℃, and the final temperature is 100-500℃. The heating rate from the initial temperature to 300℃ is 0.05-1℃ / min, and the temperature is held at 300℃ for 60-1000 minutes; The heating rate from 300℃ to the highest temperature is 0.05-1℃ / minute, and the highest temperature is held for 400-1500 minutes; The cooling rate from the highest temperature of -300℃ is 1-5℃ / minute; the cooling rate from 300℃ to the final temperature is 1-5℃ / minute. The degreasing and gelatin removal process is as follows: The heating rate from the initial temperature to 120℃ is 0.5-2℃ / minute, and the temperature is held at 120℃ for 10-100 minutes; The heating rate for 120-270℃ is 0.05-1℃ / minute, and the holding time at 270℃ is 150-200 minutes; The heating rate for 270-300℃ is 0.05-1℃ / minute, and the holding time at 300℃ is 150-200 minutes; The heating rate at 300-350℃ is 0.05-1℃ / minute, and the holding time at 350℃ is 200-400 minutes; The heating rate at 350-450℃ is 0.05-1℃ / minute, and the holding time at 450℃ is 200-400 minutes; The heating rate from 450℃ to the highest temperature is 0.05-1℃ / minute, and the highest temperature is held for 300-500 minutes; The cooling rate from the highest temperature of -300℃ is 1-5℃ / minute; the cooling rate from 300℃ to the final temperature is 1-5℃ / minute.

2. The method for preparing a high dielectric alumina ceramic material according to claim 1, characterized in that, The particle size D50 of the alumina powder is 40-80 μm.

3. The method for preparing a high-dielectric-performance alumina ceramic material according to claim 1, characterized in that, The highest temperature for high-temperature sintering is 1630-1650℃. Under the protective atmosphere of nitrogen or argon, pressure is applied at 1000-1200℃, with a maximum pressure of 30-45 MPa.

4. A high dielectric alumina ceramic material obtained by the preparation method according to any one of claims 1-3.

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