Ceramic electrostatic chuck, preparation method thereof and plasma equipment

Abstract

The invention discloses a ceramic electrostatic chuck, a preparation method thereof and plasma equipment, and the preparation method of the ceramic electrostatic chuck comprises the following steps: carrying out ball milling on ceramic powder, an organic solvent and a dispersing agent, and uniformly mixing to obtain ceramic mixed slurry; uniformly stirring and mixing the ceramic mixed slurry, a photosensitive resin monomer and a photoinitiator at a high speed to obtain photosensitive ceramic slurry; 3D printing equipment is provided, computer-aided software in the 3D printing equipment is used for designing a three-dimensional model of a ceramic body internally provided with an air inlet hole, an air outlet hole and a runner, and a formed ceramic body is obtained through printing according to the three-dimensional model; placing the formed ceramic blank in a high-temperature sintering furnace for sintering to obtain a ceramic pad with an air inlet hole, an air outlet hole and a runner inside; and the ceramic pad and the aluminum alloy base are assembled, and the ceramic electrostatic chuck is obtained. A gas uniformizing structure is arranged in the ceramic pad, and the problems of gas leakage and metal pollution caused by the fact that the gas uniformizing structure is arranged on the aluminum alloy base are solved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a ceramic electrostatic chuck, a preparation method thereof and plasma equipment. Background Art

[0002] In the field of semiconductor manufacturing and precision machining, the gas uniformity structure of a ceramic electrostatic chuck usually refers to a gas distribution system designed inside the chuck, which aims to ensure that the gas (such as helium) is evenly distributed on the entire surface of the chuck. This structure is very important for maintaining uniform adsorption and temperature control on the surface of the chuck. For example, the helium gas uniformity structure usually includes three parts: a helium inlet hole, a helium flow channel, and a helium outlet hole. The helium gas uniformity structure introduces helium through the helium inlet hole, and the pressure of helium at each position in the helium flow channel is uniform. Then, the helium gas flows out from multiple helium outlet holes on the upper surface of the ceramic electrostatic chuck at the same time. The purpose is to ensure that the helium pressure of different helium outlet holes is uniform.

[0003] Ceramic electrostatic chucks usually consist of an aluminum alloy base and a ceramic pad on the surface of the aluminum alloy base. Figure 1 As shown, currently, the helium uniform gas structure prepared by the prior art is usually located in the aluminum alloy base 2, as shown in FIG. Figure 2 A and Figure 2 As shown in B, two layers of aluminum alloy bases (aluminum alloy base A and aluminum alloy base B) with holes are welded into a complete aluminum alloy base, so that the helium uniform gas structure is located in the complete aluminum alloy base. However, during welding, the joints between aluminum alloy base A and aluminum alloy base B are often not airtight enough, resulting in helium leakage; in addition, the solder added to the aluminum alloy welding surface usually contains metal particles. Due to the complex structure of the joints, these metal particles are difficult to be cleaned and removed, resulting in the risk of the entire ceramic electrostatic chuck being contaminated by metal particles. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the helium uniform gas structure of the ceramic electrostatic chuck prepared by the existing preparation method that is prone to leakage and metal contamination.

[0005] In order to achieve the above object, the present invention provides a method for preparing a ceramic electrostatic chuck, which comprises at least the following steps:

[0006] Step S1, preparation of photosensitive ceramic slurry: mixing ceramic powder, organic solvent and dispersant by ball milling to obtain ceramic mixed slurry; mixing the ceramic mixed slurry, photosensitive resin monomer and photoinitiator by high-speed stirring to obtain photosensitive ceramic slurry;

[0007] Step S2, 3D printed ceramic body: providing a 3D printing device, using computer-aided software in the 3D printing device to design a three-dimensional model of a ceramic body with air inlets, air outlets, and flow channels, adding the photosensitive ceramic slurry into a material tank of the 3D printing device, and printing to obtain a formed ceramic body after light curing according to the three-dimensional model;

[0008] Step S3, sintering: placing the formed ceramic body in a high-temperature sintering furnace for sintering to obtain a ceramic pad having air inlets, air outlets and flow channels inside;

[0009] Step S4, preparation of a ceramic electrostatic chuck: assembling the ceramic pad and the aluminum alloy base to obtain a ceramic electrostatic chuck.

[0010] Optionally, in step S1, the ball milling further includes adding a dopant, and mixing evenly to obtain a ceramic mixed slurry.

[0011] Optionally, the dopant includes at least one or more of titanium dioxide, silicon dioxide, and magnesium oxide.

[0012] Optionally, in step S1, the photoinitiator comprises any one or more of 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, 2-dimethylamino-2-benzyl-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and methyl benzoylformate.

[0013] Optionally, in step S1, the ceramic powder includes any one of aluminum oxide, aluminum nitride, and silicon carbide.

[0014] Optionally, in step S2, the three-dimensional model of the ceramic body having an air inlet, an air outlet and a flow channel inside specifically refers to a three-dimensional model of the ceramic body having a flow channel inside, an air outlet on the upper surface of the ceramic body, and an air inlet on the lower surface of the ceramic body, and the air inlet, air outlet and flow channel are connected.

[0015] Optionally, in step S3, the temperature in the high temperature sintering furnace is 1000°C to 1650°C.

[0016] The present invention also provides a ceramic electrostatic chuck, which is prepared by the above preparation method.

[0017] Optionally, the ceramic electrostatic suction cup comprises an aluminum alloy base and a ceramic pad located on the surface of the aluminum alloy base, the ceramic pad has a flow channel inside, the upper surface of the ceramic pad has an air outlet, and the lower surface of the ceramic pad has an air inlet, and the flow channel, the air outlet, and the air inlet are connected; the aluminum alloy base contains an air inlet hole that runs through the aluminum alloy base, and the air inlet hole of the aluminum alloy base is connected to the air inlet hole of the ceramic pad.

[0018] The present invention also provides a plasma device, which at least comprises the ceramic electrostatic chuck described above.

[0019] Compared with the prior art, the beneficial effects of the present invention include at least:

[0020] (1) The preparation method of the present invention comprises preparing a photosensitive ceramic slurry, using computer-aided software in a 3D printing device to design a three-dimensional model of a ceramic body having an air inlet, an air outlet, and a flow channel inside, and according to the three-dimensional model, after photocuring, printing the photosensitive ceramic slurry to obtain a formed ceramic body, sintering the ceramic body to obtain a ceramic pad having an air inlet, an air outlet, and a flow channel inside, and assembling the ceramic pad with an aluminum alloy base to obtain a ceramic electrostatic chuck. This preparation method can realize the transfer of the traditional gas-uniform structure located inside the aluminum alloy base to the inside of the ceramic pad, thereby avoiding the problems of helium leakage and metal contamination caused by the gas-uniform structure being located inside the aluminum alloy.

[0021] (2) 3D printing technology can form structures with complex shapes inside the ceramic pad, and sintering technology can further improve the density, strength, and corrosion resistance of the ceramic pad. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The schematic cross-sectional view of a ceramic electrostatic chuck with a helium uniform gas structure located inside an aluminum alloy base prepared by prior art.

[0023] Figure 2 This is a schematic diagram of the layered processing and welding of the aluminum alloy base in the prior art:

[0024] A is a schematic diagram of the aluminum alloy base before welding; B is a schematic diagram of the aluminum alloy base after welding.

[0025] Figure 3 Schematic diagram of the tape casting process for manufacturing ceramic electrostatic chucks in the prior art.

[0026] Figure 4 The present invention is a flow chart of a method for manufacturing a ceramic electrostatic chuck.

[0027] Figure 5 It is a schematic cross-sectional view of a ceramic pad with a helium uniform gas structure located inside prepared by the present invention.

[0028] Figure 6 This is a schematic diagram of the upper surface structure of a ceramic electrostatic chuck with a helium uniform gas structure prepared in the present invention located inside a ceramic pad.

[0029] Figure 7 This is a schematic cross-sectional view of a ceramic electrostatic chuck with a helium uniform gas structure prepared in the present invention located inside a ceramic pad.

[0030] Figure identification: 1-ceramic pad, 2-aluminum alloy base. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0032] As described in the background technology, based on the above-mentioned defect that the helium gas uniformity structure of the ceramic electrostatic chuck is located in the aluminum alloy base, it is expected to transfer the helium gas uniformity structure from the aluminum alloy base to the ceramic pad of the ceramic electrostatic chuck. This can not only avoid the helium leakage problem caused by poor welding quality, but also use an acidic cleaning agent to clean the inside of the helium gas uniformity structure during the subsequent cleaning process without corroding the ceramic pad, thereby effectively solving the problem of metal particle pollution.

[0033] At present, the main process technology for manufacturing ceramic pads (ceramic green bodies) is tape casting, but it is difficult to prepare a helium uniform gas structure with a hollow structure in the ceramic green body through this method. Tape casting is a relatively mature molding method that can obtain high-quality, ultra-thin ceramic sheets. Figure 3 As shown, the method first mixes ceramic powder with solvent, dispersant, binder and plasticizer in appropriate proportions to form a casting slurry with a certain viscosity. The casting slurry flows into the material tank and is scraped and applied to a special base belt with a certain thickness by a scraper. After drying and curing in a drying chamber, the film of the green belt is peeled off from the top, and then the green belt is punched, laminated and processed according to the size and shape of the finished product to prepare a ceramic body to be sintered. It can be seen that this method cannot prepare a ceramic body with a specific hollow structure inside.

[0034] like Figure 4 As shown, the present invention provides a method for preparing a ceramic electrostatic chuck, which at least comprises the following steps:

[0035] Step S1, preparation of photosensitive ceramic slurry: ball-milling ceramic powder, organic solvent and dispersant to obtain ceramic mixed slurry; stirring the ceramic mixed slurry, photosensitive resin monomer and photoinitiator at high speed to obtain photosensitive ceramic slurry.

[0036] In some embodiments, the ceramic powder comprises any one of aluminum oxide, aluminum nitride, and silicon carbide. The purity of the ceramic powder is 95% to 100%, the mass fraction is 25% to 50%, and the particle size is 0.05 μm to 50 μm. If the particle size of the ceramic powder is too large, the density will not be high during the sintering process. If the particle size is too small, more other substances need to be added to help shape the ceramic mixed slurry, which will easily lead to a decrease in solid content and affect the performance of the ceramic after sintering.

[0037] In order to improve the sintering performance of the ceramic body in the later stage and adjust the resistivity of the ceramic body, a dopant with a mass fraction of 0% to 5% is added during ball milling, and the ceramic powder, organic solvent, dispersant and dopant are evenly mixed by ball milling to obtain a ceramic mixed slurry. In some embodiments, the dopant includes at least one or more of titanium dioxide, silicon dioxide and magnesium oxide.

[0038] The organic solvent comprises any one or more of anhydrous ethanol, IPA, acetone, and toluene, and the mass fraction of the organic solvent is 45% to 75%.

[0039] The dispersant comprises ethanolamine or ammonium polyacrylate, and the mass fraction of the dispersant is 0.2% to 3%.

[0040] In step S1, a photosensitive resin monomer is also added. The photosensitive resin monomer will polymerize into a polymer structure after being exposed to light, so that the ceramic slurry will no longer flow. The photosensitive resin monomer is an acrylic resin photosensitive resin monomer, such as 1,6-hexanediol diacrylate (HDDA), and the mass fraction of the photosensitive resin monomer is 30% to 70%.

[0041] The photoinitiator comprises any one or more of 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester (TPO-L), 2-dimethylamino-2-benzyl-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and methyl benzoylformate (MBF).

[0042] Step S2, 3D printed ceramic body: provide a 3D printing device, use the computer-aided software in the 3D printing device to design a three-dimensional model of a ceramic body with air inlets, air outlets, and flow channels inside, add the photosensitive ceramic slurry into the material tank of the 3D printing device, and print and obtain a formed ceramic body according to the three-dimensional model after light curing.

[0043] The 3D printing device at least includes a printing area, an energy generator, computer-aided software, slicing software, and a material tank. First, a three-dimensional model of a ceramic body with air inlets, air outlets, and flow channels is designed using computer-aided software modeling, and the slicing software is used to partition the three-dimensional model into layer-by-layer cross-sections; according to the cross-sectional information in the three-dimensional model, the photosensitive ceramic slurry in the material tank is added to the printing area, and the energy generator emits an energy beam to scan and irradiate the photosensitive ceramic slurry added layer by layer in the printing area. The photosensitive ceramic slurry is cured under the irradiation of the energy beam, and the photosensitive ceramic slurry is printed in layers multiple times and formed by light to obtain a formed ceramic body.

[0044] It can be understood that in order to obtain a ceramic pad with a hollow structure inside, the three-dimensional model of the ceramic body specifically refers to a three-dimensional model in which the ceramic body has a helium flow channel inside, a helium outlet hole on the upper surface of the ceramic body, and a helium inlet hole on the lower surface of the ceramic body, and the helium inlet hole, the helium flow channel, and the helium outlet hole are connected. Therefore, after printing using the three-dimensional model, the interior of the prepared ceramic pad can have a helium uniform gas structure, such as Figure 5 shown.

[0045] For a ceramic electrostatic chuck, a metal electrode or a heater is usually contained inside it, so when 3D printing is performed in step S2, the ceramic body can be formed into two parts. The lower part of the ceramic body is first printed and formed using the above 3D printing method, and then the metal electrode or heater is prepared on the surface of the lower part of the ceramic body by screen printing, electroplating, physical vapor deposition, etc., and then the upper part of the ceramic body is printed on the surface of the metal electrode or heater using the above 3D printing method.

[0046] Step S3, sintering: placing the formed ceramic body in a high-temperature sintering furnace for sintering to obtain a ceramic pad having air inlets, air outlets and flow channels inside.

[0047] Before sintering, the formed ceramic body is placed in a low-temperature furnace to remove the photocurable resin in the ceramic body.

[0048] When sintering the formed ceramic body, the sintering temperature has a decisive influence on the physical properties and microstructure of the ceramic material:

[0049] (1) Densification and strength enhancement: Sintering temperature plays a vital role in the densification of ceramics. At higher temperatures, the powder particles in the ceramic material will more effectively migrate and move grain boundaries, resulting in the elimination of pores and shrinkage of the material, thereby obtaining a dense ceramic body with increased strength.

[0050] (2) Effect on porosity: Sintering temperature also directly affects the porosity of ceramic materials. Higher temperatures and longer holding times will reduce the size of pores, thereby reducing the overall porosity of the material, which in turn affects the strength and durability of the material.

[0051] In some embodiments, the temperature in the high temperature sintering furnace is 1000°C to 1650°C.

[0052] Step S4, preparation of a ceramic electrostatic chuck: assembling the ceramic pad and the aluminum alloy base to obtain a ceramic electrostatic chuck.

[0053] It can be understood that in order to allow helium to pass into the helium flow channel from the helium inlet hole, an inlet hole is provided through the bottom of the aluminum alloy base, and the inlet hole is connected to the helium inlet hole of the ceramic pad. Helium can enter the helium inlet hole of the ceramic pad from the inlet hole at the bottom of the aluminum alloy base, and then enter the helium flow channel of the ceramic pad.

[0054] After the ceramic pad with the helium uniform gas structure inside is prepared, the ceramic pad is assembled with the aluminum alloy base by adhesive bonding, or by high-temperature brazing, to obtain Figure 6 , 7 The helium uniformity structure shown is a ceramic electrostatic chuck located inside the ceramic pad 1 .

[0055] The ceramic electrostatic chuck prepared by the preparation method of the present invention can be used in plasma equipment, and the plasma equipment can be a capacitively coupled plasma etching equipment or an inductively coupled plasma etching equipment.

[0056] In summary, the present invention provides a method for preparing a ceramic electrostatic chuck, comprising the following steps: mixing ceramic powder, an organic solvent, and a dispersant by ball milling to obtain a ceramic mixed slurry, mixing the ceramic mixed slurry, a photosensitive resin monomer, and a photoinitiator to obtain a photosensitive ceramic slurry; using computer-aided software in a 3D printing device to design a three-dimensional model of a ceramic blank having an air inlet, an air outlet, and a flow channel inside, adding the photosensitive ceramic slurry into a material trough, and printing a formed ceramic blank according to the three-dimensional model, sintering the ceramic blank to obtain a ceramic pad having a helium uniform gas structure inside, and assembling the ceramic pad with an aluminum alloy base to obtain a ceramic electrostatic chuck. The preparation method of the present invention realizes the transfer of the traditional helium uniform gas structure on the aluminum alloy base to the ceramic pad, avoiding the problems of helium leakage and metal contamination.

[0057] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A method for preparing a ceramic electrostatic chuck, characterized in that: At least the following steps are included: Step S1, preparation of photosensitive ceramic slurry: mixing ceramic powder, organic solvent and dispersant by ball milling to obtain ceramic mixed slurry; mixing the ceramic mixed slurry, photosensitive resin monomer and photoinitiator by high-speed stirring to obtain photosensitive ceramic slurry; Step S2, 3D printed ceramic body: providing a 3D printing device, using computer-aided software in the 3D printing device to design a three-dimensional model of a ceramic body with air inlets, air outlets, and flow channels, adding the photosensitive ceramic slurry into a material tank of the 3D printing device, and printing to obtain a formed ceramic body after light curing according to the three-dimensional model; Step S3, sintering: placing the formed ceramic body in a high-temperature sintering furnace for sintering to obtain a ceramic pad having air inlets, air outlets and flow channels inside; Step S4, preparation of a ceramic electrostatic chuck: assembling the ceramic pad and the aluminum alloy base to obtain a ceramic electrostatic chuck.

2. The preparation method according to claim 1, characterized in that In step S1, the ball milling process also includes adding a dopant, and mixing evenly to obtain a ceramic mixed slurry.

3. The preparation method according to claim 2, characterized in that: The dopant includes at least one or more of titanium dioxide, silicon dioxide and magnesium oxide.

4. The preparation method according to claim 1, characterized in that: In step S1, the photoinitiator comprises any one or more of 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, 2-dimethylamino-2-benzyl-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and methyl benzoylformate.

5. The preparation method according to claim 1, characterized in that: In step S1, the ceramic powder includes any one of aluminum oxide, aluminum nitride, and silicon carbide.

6. The preparation method according to claim 1, characterized in that: In step S2, the three-dimensional model of the ceramic body with air inlet holes, air outlet holes and flow channels inside specifically refers to a three-dimensional model of the ceramic body with flow channels inside, air outlet holes on the upper surface of the ceramic body and air inlet holes on the lower surface of the ceramic body, and the air inlet holes, air outlet holes and flow channels are connected.

7. The preparation method according to claim 1, characterized in that: In step S3, the temperature in the high temperature sintering furnace is 1000°C to 1650°C.

8. A ceramic electrostatic chuck, characterized in that: The ceramic electrostatic chuck is prepared by the preparation method described in any one of claims 1 to 7.

9. The ceramic electrostatic chuck according to claim 8, characterized in that The ceramic electrostatic suction cup comprises an aluminum alloy base and a ceramic pad located on the surface of the aluminum alloy base, the ceramic pad has a flow channel inside, the upper surface of the ceramic pad has an air outlet, and the lower surface of the ceramic pad has an air inlet, and the flow channel, the air outlet, and the air inlet are connected; the aluminum alloy base contains an air inlet through-hole that runs through the aluminum alloy base, and the air inlet through-hole of the aluminum alloy base is connected to the air inlet hole of the ceramic pad.

10. A plasma device, characterized in that: The plasma device comprises at least the ceramic electrostatic chuck according to claim 8 or 9.

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