A sintering method for high-purity alumina electrostatic chuck ceramics

Abstract

The invention discloses a sintering method for a high-purity alumina electrostatic chuck ceramic, which belongs to the technical field of electrostatic chucks, and comprises the following steps: S1: placing a debinded ceramic green body on a sintering plate, and stacking the green body on a sintering furnace trolley; S2: introducing an inert gas into the sintering furnace to exhaust the oxygen in the sintering furnace, and starting a heating program when the oxygen content drops below 100 ppm, setting the process parameters in the sintering furnace, and setting a first preset time period; S3: setting a second preset temperature range of 900-1000°C, and a second preset time period range of 10-15h; S4: setting a third preset temperature, a temperature range of 1400-1450°C, and a third preset time period range of 15-20h; S5: setting a cooling curve in a fourth preset time period; S6: setting a cooling curve in a fifth preset time period.

Description

Technical Field

[0001] The invention relates to the technical field of electrostatic chucks, and in particular to a sintering method for high-purity alumina electrostatic chuck ceramics. Background Art

[0002] Sintering is a key stage in the preparation of ceramics. Sintering is the process of crystal growth of ceramic particles and the completion of densification by removing the free pores between particles. When preparing high-purity alumina ceramics, due to the addition of fewer additives, it is generally adopted to increase the particle size and activity of the raw material powder to promote sintering. Using alumina fine crystals with small particles, large specific surface area and high surface activity as raw materials can significantly reduce the sintering temperature of alumina ceramics, but the shape and size of the particles are difficult to control. The smaller the particle size, the more serious the particle agglomeration. During sintering, it is inevitable that sintering shrinkage and deformation will occur seriously, causing bending, cracking and delamination of the product. Therefore, some people use special sintering processes, such as hot pressing sintering, hot isostatic pressing sintering, microwave plasma sintering and discharge plasma sintering; or add sintering aids to solve these problems; these methods can be used to increase the sintering driving force of the product and play a role in reducing the sintering temperature. However, the use of special sintering processes has very strict requirements on equipment and technology, and its practicality is relatively low. By introducing sintering aids to form a solid solution mechanism to lower the sintering temperature, while improving the density and strength, it will inevitably reduce the insulation resistance of the material and have an adverse effect on the overall performance of the product.

[0003] The main sintering method of alumina electrostatic chuck is atmosphere pressureless sintering, usually using a two-step sintering process, and sintering to a dense product at a low temperature as much as possible. In order to ensure the activity of metal electrode layers such as W, Ni, and Mo, inert gases such as N2, Ar and reducing gas H2 are mainly introduced into the co-firing of ceramics and internal electrodes to protect them from oxidation. The introduced H2 forms wet hydrogen with water vapor to reduce the oxides on the metal surface, and is also conducive to the discharge of residual carbon from debinding to promote sintering.

[0004] The main defects are: in the atmospheric pressure sintering process, affected by temperature and time, increasing the sintering temperature to promote crystal growth is beneficial to solid-phase diffusion and mass transfer, but too high a temperature promotes secondary crystallization and increases the amount of liquid phase, which not only reduces the strength but also weakens the wear resistance. Sintering time that is too long or too short will lead to the sintered body being not dense or deforming and cracking. In addition, it is also affected by other impurities. A variety of additives and solvents must be introduced into the ceramic powder during the preparation process. Most of the organic substances will be burned and discharged during the debinding process, but it is inevitable that carbon and other substances will remain on the surface of the electrostatic chuck. During the densification process, irregular holes will be formed. These microstructural defects caused by impurities have a significant effect on the densification of alumina wear-resistant ceramics. The flow rate of the introduced atmosphere and the partial pressure of water vapor will have an important impact on the sintered products. When the amount of hydrogen introduced is insufficient, the oxide and carbon residues are not removed cleanly; but when the amount of hydrogen is too large, the activity of the metal atoms reduced by the dielectric layer increases, and the diffusion is accelerated, thereby accelerating the formation of crystal nuclei and crystal growth. The electrode layer grains formed are too large, which affects the performance of the product. In addition, if the water vapor partial pressure is too low, the reaction with the residual carbon will not be complete, and if the water vapor partial pressure is too high, it will cause an oxidation reaction between the metal and the water vapor. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a sintering method for high-purity alumina electrostatic chuck ceramics to solve the problems raised in the background technology.

[0006] In order to solve the above technical problems, the technical solution of the present invention is:

[0007] A sintering method for high-purity alumina electrostatic chuck ceramics, the method comprising:

[0008] S1: Place the debinded ceramic green body on the setter plate and stack it on the sintering furnace trolley. The stacking gap between the setter plates is 5 to 7 cm to make the gas flow rate between the setter plates in the furnace faster.

[0009] S2: Introduce inert gas into the sintering furnace to exhaust the oxygen in the sintering furnace. When the oxygen content drops below 100ppm, start the temperature increase program, set the process parameters in the sintering furnace, set the first preset time period, and increase to the first preset temperature within the first preset time period. The first preset time period ranges from 5 to 10 hours, and the first preset temperature ranges from 400 to 500°C. In the first preset time period, introduce inert gas and set the gas flow rate to 10 to 15L / min. Adjust the opening of the exhaust valve of the sintering furnace to control the furnace pressure to 10 to 20Pa.

[0010] S3: Set the second preset temperature range to 900-1000°C, the second preset time range to 10-15h, set a heat preservation time when the temperature reaches the highest set temperature, the heat preservation time range is 4-6 hours, during which inert gas and H2 are introduced, wherein the flow rate of the inert gas is set to 5-10L / min, and the flow rate of H2 is set to 5-10L / min. In the second preset time period, the mixed gas of inert gas and H2 is introduced into the water tank, and the heating temperature of the water tank is set to 20-30°C. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 30-40Pa;

[0011] S4: Set the third preset temperature, the temperature range is 1400-1450℃, the third preset time range is 15-20h, set a heat preservation time when the highest set temperature is reached, the heat preservation time range is 4-6 hours, during which inert gas and H2 are introduced, the flow rate of the inert gas is set to 5-10L / min, and the flow rate of H2 is set to 10-15L / min. In the third preset time period, the two mixed gases are introduced into the water tank, and the heating temperature of the water tank is set to 30-40℃. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 80-90Pa;

[0012] S5: a cooling curve is set in the fourth preset time period, the temperature range is from the highest temperature to 700-800°C, the fourth preset time period ranges from 6 to 8 hours, during which inert gas and H2 are introduced, the flow rate of the inert gas is set to 5-10L / min, and the flow rate of H2 is set to 10-15L / min. In the fourth preset time period, the two mixed gases are introduced into the water tank, and the heating temperature of the water tank is set to 30-40°C. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 80-90Pa;

[0013] S6: a cooling curve is set in the fifth preset time period, the fifth preset temperature range is 200-280°C, the fifth preset time period range is 4-6h, during which inert gas and H2 are passed, wherein the flow rate set for the inert gas is 5-10L / min, and the flow rate set for the H2 is 5-10L / min. In the fifth preset time period, a mixed gas of inert gas and H2 is passed into the water tank, and the heating temperature of the water tank is set to 20-30°C. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 30-40Pa. When the program completes the fifth preset time, the sintering furnace is cooled naturally.

[0014] Preferably, the inert gas is N2 or Ar.

[0015] Preferably, in step S6, a preset inert gas is introduced into the sintering furnace when the temperature is naturally lowered, and the gas flow rate is set to 10-15 L / min, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure to 10-20 Pa.

[0016] The above technical solution has the following beneficial effects:

[0017] The present application provides a sintering method for high-purity alumina electrostatic chuck ceramics, which improves the sintering properties of the high-purity alumina electrostatic chuck by improving the sintering process, and solves the problems of high temperature, strict equipment and technical requirements in the existing sintering process, deformation and cracking of products after sintering, or excessive grain growth, which easily lead to low sintering density, low strength and hardness of the products, etc.; the sintering properties of the high-purity alumina electrostatic chuck are improved by regulating the temperature, time, atmosphere flow, humidification box temperature and furnace pressure during the sintering process of the high-purity alumina electrostatic chuck. DETAILED DESCRIPTION

[0018] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0019] A sintering method for high-purity alumina electrostatic chuck ceramics, the method comprising:

[0020] S1: Place the debinded ceramic green body on the setter plate and stack it on the sintering furnace trolley. The stacking gap between the setter plates is 5 to 7 cm, so that the gas flow rate between the setter plates in the furnace is faster and the sintering effect is better.

[0021] S2: Introduce inert gas into the sintering furnace to exhaust the oxygen in the sintering furnace. When the oxygen content drops below 100ppm, start the temperature increase program, set the process parameters in the sintering furnace, set the first preset time period, and increase to the first preset temperature within the first preset time period. The first preset time period ranges from 5 to 10 hours, and the first preset temperature ranges from 400 to 500°C. In the first preset time period, introduce inert gas and set the gas flow rate to 10 to 15L / min. Adjust the opening of the exhaust valve of the sintering furnace to control the furnace pressure to 10 to 20Pa.

[0022] In some other embodiments, the flow rate of the inert gas introduced in the first preset time period is 10 L / min or 15 L / min, or 12 L / min, and the furnace pressure is controlled to be 10 Pa or 20 Pa by adjusting the opening of the exhaust valve of the sintering furnace. The furnace pressure of the sintering furnace can also be set to 15 Pa.

[0023] S3: Set the second preset temperature range to 900-1000°C, the second preset time range to 10-15h, set a heat preservation time when the temperature reaches the highest set temperature, the heat preservation time range is 4-6 hours, during which inert gas and H2 are introduced, wherein the flow rate of the inert gas is set to 5-10L / min, and the flow rate of H2 is set to 5-10L / min. In the second preset time period, the mixed gas of inert gas and H2 is introduced into the water tank, and the heating temperature of the water tank is set to 20-30°C. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 30-40Pa;

[0024] In some other embodiments, when the inert gas and H2 are introduced in the second preset time period, the flow rate of the inert gas is set to 5L / min or 10L / min, and the flow rate of the H2 is set to 5L / min or 10L / min. In the second preset time period, the mixed gas of the inert gas and H2 is introduced into the water tank, and the heating temperature of the water tank is set to 20°C or 30°C. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 30Pa or 40Pa.

[0025] S4: Set the third preset temperature, the temperature range is 1400-1450℃, the third preset time range is 15-20h, set a heat preservation time when the highest set temperature is reached, the heat preservation time range is 4-6 hours, during which inert gas and H2 are introduced, the flow rate of the inert gas is set to 5-10L / min, and the flow rate of H2 is set to 10-15L / min. In the third preset time period, the two mixed gases are introduced into the water tank, and the heating temperature of the water tank is set to 30-40℃. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 80-90Pa;

[0026] In some embodiments, during the third preset time period, inert gas and H2 are introduced, wherein the flow rate of the inert gas is set to 5L / min or 10L / min, and the flow rate of H2 is set to 10L / min or 15L / min. During the third preset time period, the two mixed gases are introduced into the water tank, and the heating temperature of the water tank is set to 30°C or 40°C. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 80Pa or 90Pa.

[0027] S5: a cooling curve is set in the fourth preset time period, the temperature range is from the highest temperature to 700-800°C, the fourth preset time period ranges from 6 to 8 hours, during which inert gas and H2 are introduced, the flow rate of the inert gas is set to 5-10L / min, and the flow rate of H2 is set to 10-15L / min. In the fourth preset time period, the two mixed gases are introduced into the water tank, and the heating temperature of the water tank is set to 30-40°C. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 80-90Pa;

[0028] In some embodiments, during the fourth preset time period, inert gas and H2 are introduced, the flow rate of the inert gas is set to 5L / min or 10L / min, and the flow rate of H2 is set to 10L / min or 15L / min. During the fourth preset time period, the two mixed gases are introduced into the water tank, and the heating temperature of the water tank is set to 30°C or 40°C. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 80Pa or 90Pa.

[0029] S6: a cooling curve is set in the fifth preset time period, the fifth preset temperature range is 200-280°C, the fifth preset time period range is 4-6h, during which inert gas and H2 are passed, wherein the flow rate set for the inert gas is 5-10L / min, and the flow rate set for the H2 is 5-10L / min. In the fifth preset time period, the mixed gas of inert gas and H2 is passed into the water tank, and the heating temperature of the water tank is set to 20-30°C. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 30-40Pa. When the program completes the fifth preset time, the sintering furnace is naturally cooled, and the preset gas inert gas is passed, and the gas flow rate is set to 10-15L / min, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 10-20Pa.

[0030] In some embodiments, during the fifth preset time period, inert gas and H2 are passed, wherein the flow rate set for the inert gas is 5L / min or 10L / min, and the flow rate set for the H2 is 5L / min or 10L / min. During the fifth preset time period, the mixed gas of inert gas and H2 is passed into the water tank, and the heating temperature of the water tank is set to 20°C or 30°C. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 30Pa or 40Pa. When the program completes the fifth preset time, the sintering furnace is naturally cooled, and the preset gas inert gas is passed, and the gas flow rate is set to 10L / min or 15L / min, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure to 10Pa or 20Pa.

[0031] In the first preset temperature range of 400-500°C, under the continuous inert gas N2 or Ar, the residual carbon inside the electrostatic chuck is slowly discharged from the surface. After this stage, the organic matter content inside the electrostatic chuck is the least, and the gap between the powder particles is the largest. At the second preset temperature and the third preset temperature, wet hydrogen is introduced into the electrostatic chuck to build a channel. At the same time, at the third preset temperature, the debinding time is extended to make the debinding rate smoother to avoid the generation of cracks and holes inside the electrostatic chuck.

[0032] A two-step sintering process is adopted. In the second preset temperature range and the third preset temperature range, the heating time is firstly gradually extended to increase the density of the ceramic body to more than 70%, so that the pores in the entire body are in an unstable connected state. The purpose is to allow the grains in the ceramic body to complete "coarsening" and "homogenization" at a lower temperature first, so that when sintered into porcelain at a higher temperature, the obtained grains will be finer and more uniform, thereby achieving the purpose of improving the structure and improving the performance. Secondly, two longer holding times are set to use grain boundary diffusion to discharge the gas and reduce the generation of pores at the grain boundaries. At the same time, the network structure of the entire particle remains unchanged. From the sintering theory, the difference between grain boundary diffusion energy and grain boundary migration energy is used to make densification take precedence over grain boundary movement, thereby achieving the purpose of completing the densification of the body while effectively suppressing the abnormal growth of grains;

[0033] Starting from the second preset temperature curve, the gas in the furnace is introduced with wet hydrogen, which can take away the organic carbon residue on the surface and inside of the electrostatic chuck in the early stage of sintering, reduce cracking and delamination during the sintering of the green body, and make the sintering shrinkage of the product as consistent as possible in all directions to reduce the sintering deformation of the product. Starting from the middle stage of sintering, the amount of hydrogen introduced and the temperature of water vapor are increased to protect the electrode layer metal from being oxidized at high temperature, reduce the metal oxide layer on the surface, maintain the electrode activity and enhance the bonding between the electrode layer and the dielectric layer. After the neck begins to grow, more oxygen ions can overflow from the crystal surface to combine with hydrogen ions, which can reduce the grain size and make the grain more uniform when the grain grows. In the late stage of sintering, the generation of pores can be reduced to improve the density.

[0034] In the early stage of sintering, the furnace pressure is maintained at a slightly positive pressure, firstly to prevent air from entering the furnace to oxidize the product, and secondly to discharge the residual carbon of the product out of the furnace as soon as possible after combustion. In the middle and late stages of sintering, the furnace pressure is gradually increased to accelerate the flow of wet hydrogen in the furnace, which is conducive to promoting sintering.

[0035] The present invention provides a process scheme for solving the problem of electrostatic chuck sintering of nano-level fine powder high-purity alumina, reduces cracking and deformation generated during fine powder sintering, solves the contradiction between the need for a higher sintering temperature and the large number of abnormally grown grains, reduces the grain size and porosity, and improves the density of the sintered product. The obtained ceramic product has a smooth surface, no internal stratification and cracking, a uniform and translucent white appearance, a volume density of about 3.8g / cm3, and a hardness of 1800HV1;

[0036] Wherein, the above-mentioned inert gas is N2 or Ar;

[0037] The present application provides a sintering method for high-purity alumina electrostatic chuck ceramics, which improves the sintering properties of the high-purity alumina electrostatic chuck by improving the sintering process, and solves the problems of high temperature, strict equipment and technical requirements in the existing sintering process, deformation and cracking of products after sintering, or excessive grain growth, which easily lead to low sintering density, low strength and hardness of the products, etc.; the sintering properties of the high-purity alumina electrostatic chuck are improved by regulating the temperature, time, atmosphere flow, humidification box temperature and furnace pressure during the sintering process of the high-purity alumina electrostatic chuck.

[0038] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A sintering method for high-purity alumina electrostatic chuck ceramics, characterized in that: The method comprises: S1: Place the debinded ceramic green body on the setter plate and stack it on the sintering furnace trolley. The stacking gap between the setter plates is 5 to 7 cm to make the gas flow rate between the setter plates in the furnace faster. S2: Introduce inert gas into the sintering furnace to exhaust the oxygen in the sintering furnace. When the oxygen content drops below 100ppm, start the temperature increase program, set the process parameters in the sintering furnace, set the first preset time period, and increase to the first preset temperature within the first preset time period. The first preset time period ranges from 5 to 10 hours, and the first preset temperature ranges from 400 to 500°C. In the first preset time period, introduce inert gas and set the gas flow rate to 10 to 15L / min. Adjust the opening of the exhaust valve of the sintering furnace to control the furnace pressure to 10 to 20Pa. S3: Set the second preset temperature range to 900-1000°C, the second preset time range to 10-15h, set a heat preservation time when the temperature reaches the highest set temperature, the heat preservation time range is 4-6 hours, during which inert gas and H2 are introduced, wherein the flow rate of the inert gas is set to 5-10L / min, and the flow rate of H2 is set to 5-10L / min. In the second preset time period, the mixed gas of inert gas and H2 is introduced into the water tank, and the heating temperature of the water tank is set to 20-30°C. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 30-40Pa; S4: Set the third preset temperature, the temperature range is 1400-1450℃, the third preset time range is 15-20h, set a heat preservation time when the highest set temperature is reached, the heat preservation time range is 4-6 hours, during which inert gas and H2 are introduced, the flow rate of the inert gas is set to 5-10L / min, and the flow rate of H2 is set to 10-15L / min. In the third preset time period, the two mixed gases are introduced into the water tank, and the heating temperature of the water tank is set to 30-40℃. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 80-90Pa; S5: a cooling curve is set in the fourth preset time period, the temperature range is from the highest temperature to 700-800°C, the fourth preset time period ranges from 6 to 8 hours, during which inert gas and H2 are introduced, the flow rate of the inert gas is set to 5-10L / min, and the flow rate of H2 is set to 10-15L / min. In the fourth preset time period, the two mixed gases are introduced into the water tank, and the heating temperature of the water tank is set to 30-40°C. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 80-90Pa; S6: a cooling curve is set in the fifth preset time period, the fifth preset temperature range is 200-280°C, the fifth preset time period range is 4-6h, during which inert gas and H2 are passed, wherein the flow rate set for the inert gas is 5-10L / min, and the flow rate set for the H2 is 5-10L / min. In the fifth preset time period, a mixed gas of inert gas and H2 is passed into the water tank, and the heating temperature of the water tank is set to 20-30°C. At the same time, a heating belt is added to the pipeline from the water tank outlet to the furnace for pipeline heating, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 30-40Pa. When the program completes the fifth preset time, the sintering furnace is cooled naturally.

2. The sintering method of a high-purity alumina electrostatic chuck ceramic according to claim 1, characterized in that: The inert gas is N2 or Ar.

3. The sintering method of a high-purity alumina electrostatic chuck ceramic according to claim 1, characterized in that: In the step S6, a preset inert gas is introduced into the sintering furnace when the temperature is naturally reduced, and the gas flow rate is set to 10-15 L / min, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure to 10-20 Pa.