High-purity alumina electrostatic chuck hot isostatic pressing sintering method

Abstract

The invention discloses a high-purity alumina electrostatic chuck hot isostatic pressing sintering method, which belongs to the technical field of electrostatic chucks, and comprises the following steps: S1, placing a green body after glue removal on a setter plate, and stacking the green body on a sintering furnace trolley; s2, putting the green body subjected to rubber removal into an atmosphere furnace for biscuit firing, introducing inert gas into a sintering furnace so as to empty oxygen in the furnace, starting a heating program when the oxygen content is reduced to 100 ppm or below, and setting process parameters in the sintering furnace; s3, the ceramic plate obtained after biscuit firing is placed in a sintering jig; and S4, the ceramic plate obtained after biscuit firing is placed in a hot isostatic pressing furnace, and when the pressure in the furnace is increased to 80 Mpa, a temperature rising program is started. A process scheme is provided for solving the problem of sintering of the nanoscale fine powder high-purity aluminum oxide electrostatic chuck, the problem of cracking deformation generated during fine powder sintering is reduced, the contradiction that higher sintering temperature is needed and grains grow up abnormally and the number is large is solved, the grain size and porosity are reduced, and the density of a sintered product is improved.

Description

Technical Field

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

[0002] In the prior art, sintering is the process by which ceramic particles complete crystal rearrangement and connection, diffusion growth, and discharge of pores between particles to complete densification. Alumina ceramic discs are usually sintered without pressure, with inert gases such as N2, Ar and reducing gas H2 introduced to protect the metal electrode layer such as W, Ni, Mo activity and refine the grains.

[0003] When preparing high-purity alumina ceramic discs, due to the small amount of sintering aids, it is basically solid-phase sintering, and the mass transfer mode is single. In order to improve the diffusion driving force, 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 particle size, large specific surface area and high surface activity as raw materials can significantly reduce the sintering temperature of alumina ceramics. The sintering temperature is reduced by introducing sintering aids to form a solid solution mechanism. In addition, special sintering processes are used, such as hot pressing sintering, hot isostatic pressing sintering, microwave plasma sintering and discharge plasma sintering; these methods can be used to increase the sintering driving force of the product and play a role in reducing the sintering temperature.

[0004] The main defects of the existing technology are: in the traditional sintering process, the temperature and time are regulated. Increasing the sintering temperature to promote crystal growth is beneficial to solid-phase diffusion and mass transfer, but too high a temperature causes abnormal grain growth and secondary crystallization, which will weaken the strength and hardness of the product. Sintering time that is too long or too short will cause the sintered body to be non-dense or deform and crack. In addition, there are problems such as it is difficult to eliminate pores at the grain boundary and the grain size grows too large.

[0005] Fine powder particles have a large specific surface area, close contact between particles, short sintering diffusion path, and can be sintered densely at a lower temperature. However, the shape and size of spherical powders are difficult to control. Secondly, the smaller the particle size, the more serious the particle agglomeration. It is easy to disperse unevenly when preparing porcelain powder slurry, which can easily lead to difficult control of sintering properties, deformation, bending, cracking and delamination during sintering.

[0006] Adding sintering aids can form a solid solution, increase diffusion and mass transfer, and improve density and strength. However, introducing too many additives will inevitably reduce the insulation resistance of the material and have an adverse effect on the overall performance of the product. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a hot isostatic pressing sintering method for a high-purity alumina electrostatic chuck to solve the problems raised in the background technology, improve the sintering properties of the high-purity alumina ceramic disc, and enhance its density and light transmittance.

[0008] In order to solve the above technical problems, the technical solution of the present invention is:

[0009] A high-purity alumina electrostatic chuck hot isostatic pressing sintering method, the isostatic pressing sintering method comprising:

[0010] S1: Place the debinded green billet on the setter plate and stack them 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;

[0011] S2: Place the debinded green body in an atmosphere furnace for biscuit sintering, introduce inert gas into the sintering furnace to exhaust the oxygen in the furnace, start the heating program when the oxygen content drops below 100ppm, and set the process parameters in the sintering furnace;

[0012] S3: Place the bisque-fired ceramic disc in a sintering fixture. The fixture is made of boron nitride or graphite. The surface flatness of the fixture is less than or equal to 0.1 mm. The force on the surface of the ceramic disc is not less than 500N.

[0013] S4: Place the bisque-fired ceramic plate in a hot isostatic pressing furnace, evacuate the hot isostatic pressing furnace and introduce inert gas to exhaust the remaining oxygen in the furnace. When the furnace is pressurized to 80Mpa, start the heating program. The first preset temperature range is 800-1000℃, the first preset time period range is 6-8h, the second preset temperature range is 1250-1350℃, the second preset time period range is 4-6h. When the temperature is raised to the highest set temperature, a holding time is set. The holding time range is 2-4 hours. During this period, due to the increase in temperature, the gas in the container expands, and the container pressure increases with the temperature. The maximum pressure is 200MPa. Set a cooling curve. The third preset temperature is 500-600℃, the time is 4-6h, and then the temperature is naturally reduced.

[0014] Preferably, in step S2, the process parameters in the sintering furnace are set, the temperature is raised to a first preset temperature within a first preset time period, the first preset time period range is 5 to 10 hours, the first preset temperature range is 400 to 500°C, the second temperature range is 1000 to 1200°C, the second preset time period range is 10 to 15 hours, a holding time is established, the holding time range is 1 to 2 hours, a cooling process is preset, the temperature range is 200 to 300°C, the time period range is 10 to 12 hours, one of the gases N2 and Ar is introduced within the set temperature, and the gas flow rate is set to 10 to 15 L / min, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 30 to 60 Pa.

[0015] Preferably, in step S2, the inert gas introduced into the sintering furnace is N2 or Ar, and in step S4, the inert gas introduced into the hot isostatic pressing furnace after evacuation is N2 or Ar.

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

[0017] The present application provides a process solution for solving the electrostatic chuck sintering of nano-level fine powder high-purity alumina, reduces the cracking and deformation problems caused by fine powder sintering, solves the contradiction between the need for higher sintering temperature and the abnormal growth and large number of grains, reduces the grain size and porosity, and improves the density of the sintered product;

[0018] The obtained product has a smooth surface, no internal stratification or cracking, a uniform and translucent gray appearance, and a bulk density of 3.9 g / cm 3 , hardness is 1700HV1. DETAILED DESCRIPTION

[0019] 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.

[0020] Example 1

[0021] A high-purity aluminum oxide electrostatic chuck hot isostatic pressing sintering method, the isostatic pressing sintering method comprising the following steps:

[0022] S1: Place the debinded green billet on the setter plate and stack it on the sintering furnace trolley; the setter plates are stacked with a gap of 5 cm or 7 cm to make the gas flow rate between the setter plates in the furnace faster, which is convenient for subsequent sintering;

[0023] S2: Place the debinded green body in an atmosphere furnace for biscuit firing, introduce inert gas into the sintering furnace, the inert gas is N2 or Ar, to exhaust the oxygen in the furnace, start the heating program when the oxygen content drops below 100ppm, set the process parameters in the sintering furnace, rise to the first preset temperature within the first preset time period, the first preset time period ranges from 5 to 10h, the first preset temperature ranges from 400 to 500℃, set the second temperature range is 1000 to 1200℃, the second preset time period ranges from 10 to 15h, set a heat preservation time, the heat preservation time ranges from 1 to 2 hours, preset a cooling process, the temperature range is 200 to 300℃, the time range is 10 to 12h, introduce one of the gases N2 and Ar within the set temperature, 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 at 30 to 60Pa;

[0024] S3: Place the bisque-fired ceramic disc in a sintering fixture. The fixture is made of boron nitride or graphite. The surface flatness of the fixture is less than or equal to 0.1 mm. The force on the surface of the ceramic disc is not less than 500N.

[0025] S4: placing the bisque fired ceramic plate in a hot isostatic pressing furnace, and introducing an inert gas into the hot isostatic pressing furnace after evacuating the vacuum, wherein the inert gas is N2 or Ar, to exhaust the remaining oxygen in the furnace, and starting the heating program when the furnace is pressurized to 80Mpa, wherein the first preset temperature range is 800-1000°C, and the first preset time period range is 6-8h, and the temperature is raised to the first preset temperature range within the first preset time period, and the second preset temperature range is 1250-1350°C, and the second preset time period range is 4-6h, and a heat preservation time is set when the temperature is raised to the highest set temperature, and the heat preservation time range is 2-4 hours, during which the gas in the container expands due to the temperature rise, and the container pressure increases with the temperature, and the maximum pressure is 200MPa, and a cooling curve is set, wherein the third preset temperature is 500-600°C, and the time is 4-6h, and then the temperature is naturally cooled to room temperature;

[0026] The present application improves the sintering properties of high-purity alumina ceramic discs by regulating the sintering process during the sintering process, thereby improving the density and light transmittance;

[0027] During the biscuit firing process, under the condition of continuous introduction of N2 or Ar, the residual carbon inside the high-purity alumina ceramic disk is slowly discharged from the surface, the organic matter of the ceramic disk is removed at the first preset temperature and the second preset temperature, the grains are coarsened and homogenized, and the particles are connected to each other with a certain strength, but they have not been sintered yet, and the number of grain growth is very small, so they will not bend or crack due to sintering shrinkage;

[0028] Under the hot isostatic pressing sintering process, within the first preset temperature range, as the temperature rises, the pressure on the high-purity alumina ceramic disc in all directions increases, which increases the density of the green body and makes the crystal particles grow evenly. In this way, when sintered into porcelain at a higher temperature, the resulting grains will be finer and more uniform, thereby achieving the purpose of improving the structure and performance. The second preset temperature and time are a longer heating and holding period, which uses grain boundary diffusion to expel 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 the Densification takes precedence over grain boundary movement, thereby achieving the purpose of densification of the green body while effectively inhibiting abnormal grain growth. During the sintering process, the pressure of the graphite fixture and the slowing down of the cooling rate reduce the bending of the green body during sintering, and at the same time make the sintering shrinkage of the product as consistent as possible in all directions to reduce the sintering deformation of the product. During biscuit sintering and hot isostatic pressing sintering, the inert gas will protect the electrode layer metal from being oxidized at high temperatures and maintain the activity of the electrode. After the neck begins to grow, the closed pores are discharged from the grain boundary as much as possible under the action of high pressure, and most of the pores at the grain boundary disappear, obtaining the density and light transmittance of the high-purity alumina ceramic disk;

[0029] The present application provides a process solution for solving the electrostatic chuck sintering of nano-level fine powder high-purity alumina, reduces the cracking and deformation problems caused by fine powder sintering, solves the contradiction between the need for higher sintering temperature and the abnormal growth and large number of grains, reduces the grain size and porosity, and improves the density of the sintered product;

[0030] The obtained product has a smooth surface, no internal stratification or cracking, a uniform and translucent gray appearance, and a bulk density of 3.9 g / cm 3 About, hardness is about 1700HV1.

[0031] Example 2

[0032] A high-purity aluminum oxide electrostatic chuck hot isostatic pressing sintering method, the isostatic pressing sintering method comprising the following steps:

[0033] S1: Place the debinded green billet on the setter plate and stack them 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;

[0034] S2: Place the debinded green body in an atmosphere furnace for bisque firing, introduce an inert gas into the sintering furnace, the inert gas is N2 or Ar, to exhaust the oxygen in the furnace, start the heating program when the oxygen content drops below 100ppm, set the process parameters in the sintering furnace, and heat to the first preset temperature within the first preset time period, the first preset time period ranges from 5 to 10h, the first preset temperature ranges from 450 to 500℃, the second temperature ranges from 1100 to 1200℃, the second preset time period ranges from 10 to 15h, and the second preset temperature ranges from 1100 to 1200℃. The temperature is raised to the second preset temperature within a time period. After reaching the second preset temperature, a heat preservation time is set, the heat preservation time range is 1 hour or 2 hours, a cooling process is preset, the temperature range is 200-300°C, and the cooling time range is 10-12 hours. One of the gases N2 and Ar is introduced within the set temperature, and the flow rate of the introduced gas N2 or Ar 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 at 30Pa or 60Pa, or 45Pa;

[0035] S3: Place the bisque-fired ceramic disc in a sintering fixture. The fixture is made of boron nitride or graphite. The surface flatness of the fixture is less than or equal to 0.1 mm. The force on the surface of the ceramic disc is not less than 500N.

[0036] S4: Place the bisque-fired ceramic plate in a hot isostatic pressing furnace, and introduce inert gas into the hot isostatic pressing furnace after evacuating the vacuum. The inert gas is N2 or Ar to exhaust the remaining oxygen in the furnace. When the hot isostatic pressing furnace is pressurized to 80Mpa, the heating program is started. The first preset temperature range is 800-1000℃, and the first preset time period range is 6-8h. The first preset temperature range is reached within the first preset time period. The second preset temperature range is 1250-1350℃, and the second preset time period range is 4-6h. When the temperature is raised to the highest set temperature, a holding time is set. The holding time range is 2 hours or 4 hours. During this period, due to the increase in temperature, the gas in the container expands, and the container pressure increases with the temperature. The maximum pressure is 200MPa. A cooling curve is set. The third preset temperature is 500-600℃, and the time is 4h or 6h. Then the temperature is naturally cooled to room temperature.

[0037] 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 high-purity alumina electrostatic chuck hot isostatic pressing sintering method, characterized in that: The isostatic sintering method comprises: S1: Place the debinded green billet on the setter plate and stack them 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: Place the debinded green body in an atmosphere furnace for biscuit sintering, introduce inert gas into the sintering furnace to exhaust the oxygen in the furnace, start the heating program when the oxygen content drops below 100ppm, and set the process parameters in the sintering furnace; S3: Place the bisque-fired ceramic disc in a sintering fixture. The fixture is made of boron nitride or graphite. The surface flatness of the fixture is less than or equal to 0.1 mm. The force on the surface of the ceramic disc is not less than 500N. S4: Place the bisque-fired ceramic plate in a hot isostatic pressing furnace, evacuate the hot isostatic pressing furnace and introduce inert gas to exhaust the remaining oxygen in the furnace. When the furnace is pressurized to 80Mpa, start the heating program. The first preset temperature range is 800-1000℃, the first preset time period range is 6-8h, the second preset temperature range is 1250-1350℃, the second preset time period range is 4-6h. When the temperature is raised to the highest set temperature, a holding time is set. The holding time range is 2-4 hours. During this period, due to the increase in temperature, the gas in the container expands, and the container pressure increases with the temperature. The maximum pressure is 200MPa. Set a cooling curve. The third preset temperature is 500-600℃, the time is 4-6h, and then the temperature is naturally reduced.

2. A high-purity alumina electrostatic chuck hot isostatic pressing sintering method according to claim 1, characterized in that: In the step S2, the process parameters in the sintering furnace are set, the temperature is raised to a first preset temperature within a first preset time period, the first preset time period ranges from 5 to 10 hours, the first preset temperature ranges from 400 to 500°C, the second temperature range is set to 1000 to 1200°C, the second preset time period ranges from 10 to 15 hours, a holding time is established, the holding time ranges from 1 to 2 hours, a cooling process is preset, the temperature range is 200 to 300°C, the time period range is 10 to 12 hours, one of the gases N2 and Ar is introduced within the set temperature, and the gas flow rate is set to 10 to 15 L / min, and the opening of the exhaust valve of the sintering furnace is adjusted to control the furnace pressure at 30 to 60 Pa.

3. A high-purity alumina electrostatic chuck hot isostatic pressing sintering method according to claim 1, characterized in that: In the step S2, the inert gas introduced into the sintering furnace is N2 or Ar, and in the step S4, the inert gas introduced into the hot isostatic pressing furnace after evacuation is N2 or Ar.