Alumina ceramic coating of vacuum electrostatic chuck, preparation method and application

Abstract

The invention relates to the technical field of coatings, in particular to an aluminum oxide ceramic coating of a vacuum electrostatic chuck and a preparation method and application thereof.The aluminum oxide ceramic coating comprises a conductive bottom layer and a ceramic surface layer, and the conductive bottom layer is prepared from, by weight, 3-8 parts of conductive phase additives, 2-4 parts of polyethylene glycol stearate and 1-3 parts of silicon carbide whiskers; the ceramic surface layer is prepared from the following raw materials in parts by weight: 85 to 92 parts of alpha-aluminum oxide powder, 4 to 10 parts of borosilicate glass powder, 0.5 to 2 parts of magnesium oxide, 1 to 3 parts of zirconium oxide and 3 to 5 parts of polyethylene glycol. The conductive property, the mechanical durability and the environmental adaptability of the prepared coating are matched with one another, the service life of the vacuum electrostatic chuck is prolonged, the equipment maintenance frequency is reduced, and the coating has good conductivity, wear resistance and adhesive strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coating technology, in particular to an alumina ceramic coating of a vacuum electrostatic chuck, a preparation method and application. BACKGROUND

[0002] In the high-end industrial field of semiconductor manufacturing, precision machining, etc., non-contact stable clamping of wafers and substrates is the core prerequisite for ensuring nanoscale process precision. As a key component to replace mechanical clamps, the vacuum electrostatic chuck (ESC) realizes non-destructive adsorption of wafers through electrostatic field coulomb force, and forms a double fixation mechanism combined with the backside vacuum channel, completely eliminating the microscopic stress damage and particle contamination caused by traditional clamping. Especially in advanced processes below 7nm, the wafer thickness is thinned to below 200μm, and the thermal budget control precision needs to reach ±0.1℃, which puts forward extreme requirements for the flatness, thermal conductivity uniformity and plasma corrosion resistance of the chuck. The alumina ceramic coating, with its high hardness, wear resistance and corrosion resistance, has become the preferred material for the insulating layer of the vacuum electrostatic chuck. The Mohs hardness of alumina is 9, and the wear resistance is 266 times that of manganese steel, which can significantly prolong the service life of the chuck.

[0003] In the prior art, high-purity alumina coating faces problems such as static electricity dissipation delay, insufficient adhesion strength and poor wear resistance due to its high insulation characteristics in vacuum electrostatic chuck applications. When the electrostatic field is turned off at the end of processing, the residual charge on the surface of the coating cannot be quickly guided away due to its high resistance characteristics, continuously generating coulomb adsorption force, which causes the wafer to be unable to achieve instantaneous natural detachment. The operator is forced to introduce reverse voltage pulses or mechanical ejector pins and other forced separation means, which not only prolongs the process cycle, but also induces microscopic stress damage on the wafer surface due to mechanical contact or stress concentration, affecting device yield. In addition, the mismatch of the thermal expansion coefficient between the single high-purity alumina material and the metal substrate causes the coating to easily peel off due to insufficient adhesion in thermal cycling; although its hardness is high, its brittleness is significant, and its wear resistance decays quickly under the frequent taking and placing of wafers and plasma erosion, further increasing the frequency of equipment maintenance. In high-intensity production scenarios such as batch production, the cumulative effect of detachment delay and insufficient coating reliability will significantly drag down the overall equipment productivity. SUMMARY

[0004] In order to solve the problems mentioned in the background art, the present application provides an alumina ceramic coating for a vacuum electrostatic chuck, a preparation method and application.

[0005] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0006] An alumina ceramic coating of a vacuum electrostatic chuck, comprising a conductive bottom layer and a ceramic top layer, the conductive bottom layer comprising, by weight fraction, 3-8 parts of a conductive phase additive, 2-4 parts of polyethylene glycol stearate and 1-3 parts of silicon carbide whiskers;

[0007] The ceramic top layer comprises, by weight fraction, 85-92 parts of alpha-alumina powder, 4-10 parts of borosilicate glass powder, 0.5-2 parts of magnesium oxide, 1-3 parts of zirconium oxide and 3-5 parts of polyethylene glycol;

[0008] The conductive phase additive is a composite powder of polymer-coated tin oxide, and the polymer is prepared by polymerization of hydroxypropyl acrylate, isobornyl acrylate and divinylbenzene.

[0009] Further, the preparation steps of the conductive phase additive specifically include:

[0010] a) dispersing tin oxide nanopowder in anhydrous ethanol, adding sodium succinimide sulfonate to form a sol;

[0011] b) mixing hydroxypropyl acrylate, isobornyl acrylate and divinylbenzene to remove oxygen to obtain a monomer mixture;

[0012] c) mixing the sol and the monomer mixture, adding a silane coupling agent, adding an initiator for polymerization, and then performing step-by-step curing to obtain the conductive phase additive.

[0013] Further, the average particle size of the alpha-alumina powder is 1-50 microns, the average particle size of the borosilicate glass powder is 0.5-10 microns, and the aspect ratio of the silicon carbide whiskers is 20-50.

[0014] Further, the average particle size of the tin oxide nanopowder in step a) is 10-100 nm, and the mass ratio of the tin oxide nanopowder, sodium succinimide sulfonate and anhydrous ethanol is (8-9.5):1:(160-170).

[0015] Further, in step b), the mass ratio of isobornyl acrylate, hydroxypropyl acrylate and divinylbenzene is (17-20):(5-7):(1.5-3).

[0016] Further, in step c), the silane coupling agent is selected from at least one of KH-570, KH-560 or KH-550, and the addition amount is 3-5% of the mass of the tin oxide nanopowder.

[0017] Further, in step c), the initiator is selected from at least one of azobisisobutyronitrile, benzoyl peroxide or azobisisoheptyl nitrile, and the addition amount is 1-3% of the total mass of hydroxypropyl acrylate and isobornyl acrylate.

[0018] Further, the temperature of the polymerization reaction in step c) is 65-75 DEG C, and the time of the polymerization reaction is 4-8h.

[0019] Further, the step c) is specifically: the first stage temperature is 75-80 DEG C, the time is 30-40min, the second stage temperature is 80-85 DEG C, the time is 50-60min, and the third stage temperature is 95-100 DEG C, and the time is 100-120min.

[0020] According to another aspect of the present application, a preparation method of the alumina ceramic coating of the above-mentioned vacuum electrostatic chuck is provided, comprising the following steps:

[0021] S1, the conductive bottom layer raw materials are mixed, ball milled with deionized water as a medium, the solid content is adjusted to 45-55wt%, and the conductive bottom layer slurry is obtained;

[0022] S2, the ceramic surface layer raw materials are mixed and ball milled, the solid content is adjusted to 65-75wt%, and the ceramic surface layer slurry is obtained;

[0023] S3, the conductive bottom layer slurry is air sprayed on the surface of the pretreated vacuum electrostatic chuck substrate, solidified, and the ceramic surface layer slurry is plasma sprayed.

[0024] Further, the amount of deionized water added in step S1 is 100-150% of the total mass of the powder.

[0025] Further, the temperature of the solidification in step S3 is 110-120 DEG C, and the time of the solidification is 1-2h.

[0026] Further, the process parameters of the plasma spraying in step S3 are: power 35-45kW, main gas Ar flow rate 45-55SLPM, auxiliary gas H2 flow rate 8-12SLPM, spraying distance 90-110mm, and powder feeding rate 25-35g / min.

[0027] According to still another aspect of the present application, the alumina ceramic coating is applied in a semiconductor wafer processing equipment.

[0028] The present application has the following beneficial effects:

[0029] 1、In the technical scheme of the present application, the conductive bottom layer and the insulating ceramic surface layer are designed to form a charge directional guide channel. The polymer in the conductive bottom layer forms a continuous conductive network by coating tin oxide, and the residual charge on the wafer interface is quickly guided into the metal substrate of the chuck through the network after power off, thereby eliminating the charge retention defect of the traditional pure alumina coating, avoiding reverse voltage or mechanical pin forced separation operation, and reducing the micro stress damage of the wafer.

[0030] 2. In the technical solution of the present invention, the ceramic surface layer is mainly composed of high-hardness α-alumina powder, supplemented by components such as borosilicate glass powder, which can form a hard and wear-resistant surface.

[0031] At the same time, the silicon carbide whiskers added to the conductive bottom layer play a role in toughening and resisting stress, extending the service life of the vacuum electrostatic chuck in frequent use and potential wear environments.

[0032] 3. The alumina ceramic coating prepared by the present invention helps to reduce the release of volatile substances in a vacuum environment and reduce the risk of contamination to the wafer processing environment.

[0033] At the same time, the optimized surface condition of the surface layer can reduce scratches during wafer contact. DETAILED DESCRIPTION

[0034] The technical solutions of the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, but not all of the embodiments.

[0035] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0036] The invention provides an alumina ceramic coating for a vacuum electrostatic chuck, comprising a conductive bottom layer and a ceramic surface layer.

[0037] Preferably, the conductive bottom layer comprises the following raw materials in parts by weight: 3-8 parts of conductive phase additive, 2-4 parts of polyethylene glycol stearate and 1-3 parts of silicon carbide whiskers;

[0038] Specifically, the conductive phase additive may be 3 parts, 4 parts, 5 parts, 6 parts, 7 parts and 8 parts, polyethylene glycol stearate may be 2 parts, 3 parts and 4 parts, and silicon carbide whiskers may be 1 part, 2 parts, 2.5 parts and 3 parts.

[0039] Preferably, the ceramic surface layer comprises the following raw materials in parts by weight: 85-92 parts of α-alumina powder, 4-10 parts of borosilicate glass powder, 0.5-2 parts of magnesium oxide, 1-3 parts of zirconium oxide and 3-5 parts of polyethylene glycol;

[0040] Specifically, it can be 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, 91 parts and 92 parts of α-alumina powder, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts and 10 parts of borosilicate glass powder, 0.5 parts, 1 part, 1.5 parts and 2 parts of magnesium oxide, 1 part, 1.5 parts, 2 parts, 2.5 parts and 3 parts of zirconium oxide, and 3 parts, 4 parts and 5 parts of polyethylene glycol.

[0041] In the alumina ceramic coating provided by the present application, the preparation step of the conductive phase additive specifically comprises:

[0042] a) dispersing tin oxide nano powder in anhydrous ethanol, adding sodium succinimide, and forming a sol;

[0043] b) mixing hydroxypropyl acrylate, isobornyl acrylate and divinylbenzene to deoxidize, to obtain a monomer mixture;

[0044] c) mixing the sol and the monomer mixture, adding a silane coupling agent, adding an initiator to perform a polymerization reaction, and performing ladder curing to obtain the conductive phase additive.

[0045] In the alumina ceramic coating provided by the present application, the average particle size of the α-alumina powder is preferably 1-50 μm, and specifically can be 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm and 50 μm.

[0046] In the alumina ceramic coating provided by the present application, the average particle size of the borosilicate glass powder is preferably 0.5-10 μm, and specifically can be 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm and 10 μm.

[0047] In the alumina ceramic coating provided by the present application, the aspect ratio of the silicon carbide whisker is preferably 20-50, and specifically can be 20, 30, 40 and 50.

[0048] In the alumina ceramic coating provided by the present application, the average particle size of the tin oxide nano powder in step a) is preferably 10-100 nm, and specifically can be 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm and 100 nm.

[0049] In the alumina ceramic coating provided by the present application, the mass ratio of the tin oxide nano powder, sodium succinimide and anhydrous ethanol in step a) is preferably (8-9.5):1:(160-170), and specifically can be (8:1:160), (9:1:160), (9.5:1:160), (8:1:165), (8:1:170), (8.5:1:160), (8.5:1:170), (9:1:170) and (9.5:1:170).

[0050] In the alumina ceramic coating provided by the present application, the mass ratio of isobornyl acrylate, hydroxypropyl acrylate and divinylbenzene in step b) is preferably (17-20):(5-7):(1.5-3), and can be (17:5:1.5), (18:5:1.5), (19:5:1.5), (20:5:1.5), (17:6:2), (17:7:3), (18:6:1.5), (18:6:2), (19:6:2), (20:6:2), (17:5:2.5), (17:5:3), (18.5:6:2) and (20:7:3).

[0051] In the alumina ceramic coating provided by the present application, the silane coupling agent is selected from KH-570, KH-560 or KH-550, and the addition amount is preferably 3-5% of the mass of the tin oxide nano powder, and can be 3%, 3.5%, 4%, 4.2%, 4.5%, 4.8%, 4.9% and 5%.

[0052] In the alumina ceramic coating provided by the present application, the initiator is selected from azobisisobutyronitrile, benzoyl peroxide or azobisisoheptyl nitrile, and the addition amount is preferably 1-3% of the total mass of hydroxypropyl acrylate and isobornyl acrylate, and can be 1%, 1.2%, 1.5%, 1.8%, 2%, 2.5%, 2.6%, 2.9% and 3%.

[0053] In the alumina ceramic coating provided by the present application, the temperature of the polymerization reaction in step c) is preferably 65-75℃, and can be 65℃, 66℃, 67℃, 68℃, 69℃, 70℃, 71℃, 72℃, 73℃, 74℃ and 75℃.

[0054] In the alumina ceramic coating provided by the present application, the time of the polymerization reaction in step c) is preferably 4-8h, and can be 4h, 5h, 6h, 7h and 8h.

[0055] In the alumina ceramic coating provided by the present application, the stepwise curing in step c) is specifically: the first stage temperature is preferably 75-80℃, and can be 75℃, 76℃, 77℃, 78℃, 79℃ and 80℃, and the time is preferably 30-40min, and can be 30min, 35min and 40min; the second stage temperature is preferably 80-85℃, and can be 80℃, 81℃, 82℃, 83℃, 84℃ and 85℃, and the time is preferably 50-60min, and can be 50min, 55min and 60min; the third stage temperature is preferably 95-100℃, and can be 95℃, 96℃, 97℃, 98℃, 99℃ and 100℃, and the time is preferably 100-120min, and can be 100min, 110min and 120min.

[0056] Further, the application provides a preparation method of the alumina ceramic coating, specifically comprising the following steps:

[0057] S1, mixing the conductive bottom layer raw materials, ball milling with deionized water as medium, adjusting the solid content to 45-55wt%, to obtain a conductive bottom layer slurry;

[0058] S2, mixing and ball milling the ceramic top layer raw materials, adjusting the solid content to 65-75wt%, to obtain a ceramic top layer slurry;

[0059] S3, air spraying the conductive bottom layer slurry on the surface of the pretreated vacuum electrostatic chuck substrate, solidifying, and then plasma spraying the ceramic top layer slurry.

[0060] In the preparation method provided by the application, the amount of deionized water added in step S1 is preferably 100-150% of the total mass of the powder, and can be specifically 100%, 105%, 110%, 120%, 125%, 130%, 140%, and 150%.

[0061] In the preparation method provided by the application, the temperature of solidification in step S3 is preferably 110-120℃, and can be specifically 110℃, 111℃, 112℃, 113℃, 114℃, 115℃, 116℃, 117℃, 118℃, 119℃, and 120℃.

[0062] In the preparation method provided by the application, the time of solidification in step S3 is preferably 1-2h, and can be specifically 1h, 1.5h, and 2h.

[0063] In the preparation method provided by the application, the process parameters of plasma spraying in step S3 are preferably as follows: power 35-45kW, which can be specifically 35kW, 36kW, 37kW, 38kW, 39kW, 40kW, 42kW, and 45kW; main gas Ar flow rate 45-55SLPM, which can be specifically 45SLPM, 46SLPM, 47SLPM, 48SLPM, 50SLPM, 52SLPM, 54SLPM, and 55SLPM; auxiliary gas H2 flow rate 8-12SLPM, which can be specifically 8SLPM, 9SLPM, 10SLPM, 11SLPM, and 12SLPM; spraying distance 90-110mm, which can be specifically 90mm, 95mm, 100mm, 105mm, and 110mm; powder feeding rate 25-35g / min, which can be specifically 25g / min, 28g / min, 30g / min, 32g / min, and 35g / min.

[0064] For a clearer understanding, the following examples and comparative examples are described in detail.

[0065] Example 1 A method for preparing an alumina ceramic coating of a vacuum electrostatic chuck, comprising the following steps:

[0066] a) 8 g of tin oxide nano-powder with an average particle size of 10 nm is dispersed in 160 g of anhydrous ethanol, 1 g of sodium succinimide is added to form a sol.

[0067] b) 17 g of isobornyl acrylate, 5 g of hydroxypropyl acrylate and 1.5 g of divinylbenzene are mixed and deoxygenated to obtain a monomer mixture.

[0068] c) The sol and the monomer mixture are mixed, 0.24 g of silane coupling agent KH-570 is added, 0.22 g of azobisisobutyronitrile is added and polymerized at 65°C for 4 h, and then step curing is performed, the first stage temperature is 75°C, the time is 30 min, the second stage temperature is 80°C, the time is 50 min, the third stage temperature is 95°C, and the time is 100 min, to obtain a conductive phase additive.

[0069] S1, 3 parts of the conductive phase additive prepared above, 2 parts of polyethylene glycol stearate, and 1 part of silicon carbide whisker with an aspect ratio of 20 are mixed, deionized water accounting for 100% of the total mass of the powder is used as a medium for ball milling for 4 h, the solid content is adjusted to 45 wt%, and a conductive bottom layer slurry is obtained.

[0070] S2, 85 parts of α-alumina powder with an average particle size of 1 μm, 4 parts of borosilicate glass powder with an average particle size of 0.5 μm, 0.5 parts of magnesium oxide, 1 part of zirconium oxide, and 3 parts of polyethylene glycol are mixed and ball milled for 4 h, the solid content is adjusted to 65 wt%, and a ceramic top layer slurry is obtained.

[0071] S3, the conductive bottom layer slurry is air sprayed on the surface of the pretreated vacuum electrostatic chuck substrate at a pressure of 0.3 MPa, and cured at 110°C for 1 h, and then the ceramic top layer slurry is plasma sprayed, the plasma spraying parameters are: power 35 kW, main gas Ar flow rate 45 SLPM, auxiliary gas H2 flow rate 8 SLPM, spraying distance 90 mm, and powder feeding rate 25 g / min.

[0072] Example 2 A method for preparing an alumina ceramic coating of a vacuum electrostatic chuck, comprising the following steps:

[0073] a) 9 g of tin oxide nano-powder with an average particle size of 50 nm is dispersed in 160 g of anhydrous ethanol, 1 g of sodium succinimide is added to form a sol.

[0074] b) 18 g of isobornyl acrylate, 6 g of hydroxypropyl acrylate and 2 g of divinylbenzene are mixed and deoxygenated to obtain a monomer mixture.

[0075] c) mixing the sol and the monomer mixture, adding 0.405 g of silane coupling agent KH-560, adding 0.48 g of azobisisobutyronitrile, and carrying out polymerization reaction at 71 °C for 6 h, and carrying out step curing, with the first stage temperature being 77 °C, the first stage time being 35 min, the second stage temperature being 83 °C, the second stage time being 55 min, and the third stage temperature being 98 °C, the third stage time being 110 min, to obtain the conductive phase additive.

[0076] S1, mixing 6 parts of the conductive phase additive prepared above, 3 parts of polyethylene glycol stearate, and 2 parts of silicon carbide whiskers with a length-diameter ratio of 40, adding deionized water as a medium at 125% of the total mass of the powder, and ball milling for 6 h, to obtain a conductive bottom layer slurry with a solid content of 50 wt%.

[0077] S2, mixing 89 parts of α-alumina powder with an average particle size of 30 μm, 6 parts of borosilicate glass powder with an average particle size of 5 μm, 1 part of magnesium oxide, 2 parts of zirconium oxide, and 4 parts of polyethylene glycol, and ball milling for 6 h, to obtain a ceramic top layer slurry with a solid content of 70 wt%.

[0078] S3, air spraying the conductive bottom layer slurry on the surface of a pretreated vacuum electrostatic chuck substrate at a pressure of 0.6 MPa, and curing at 120 °C for 2 h, and then plasma spraying the ceramic top layer slurry, with the plasma spraying parameters being: power 45 kW, main gas Ar flow rate 55 SLPM, auxiliary gas H2 flow rate 12 SLPM, spraying distance 110 mm, and powder feeding rate 35 g / min.

[0079] Example 3 A method for preparing an alumina ceramic coating of a vacuum electrostatic chuck, comprising the following steps:

[0080] a) dispersing 9.5 g of tin oxide nano-powder with an average particle size of 100 nm in 170 g of anhydrous ethanol, and adding 1 g of sodium succinimide to form a sol.

[0081] b) mixing 20 g of isobornyl acrylate, 7 g of hydroxypropyl acrylate, and 3 g of divinylbenzene to remove oxygen, to obtain a monomer mixture.

[0082] c) mixing the sol and the monomer mixture, adding 0.475 g of silane coupling agent KH-550, adding 0.81 g of azobisisobutyronitrile, and carrying out polymerization reaction at 75 °C for 8 h, and carrying out step curing, with the first stage temperature being 80 °C, the first stage time being 40 min, the second stage temperature being 85 °C, the second stage time being 60 min, and the third stage temperature being 100 °C, the third stage time being 120 min, to obtain the conductive phase additive.

[0083] S1, 8 parts of the prepared conductive phase additive, 4 parts of polyethylene glycol stearate, 3 parts of silicon carbide whiskers with a length-diameter ratio of 50 were mixed, and 150% of the total mass of the powder of deionized water was used as a medium for ball milling for 8h, the solid content was adjusted to 55wt%, and a conductive bottom layer slurry was obtained.

[0084] S2, 92 parts of α-alumina powder with an average particle size of 50μm, 10 parts of borosilicate glass powder with an average particle size of 10μm, 2 parts of magnesium oxide, 3 parts of zirconium oxide and 5 parts of polyethylene glycol were mixed and ball milled for 8h, the solid content was adjusted to 75wt%, and a ceramic surface layer slurry was obtained.

[0085] S3, the conductive bottom layer slurry was air sprayed on the surface of the pretreated vacuum electrostatic chuck substrate, the pressure was 0.6MPa, and the slurry was cured at 120℃ for 2h, then the ceramic surface layer slurry was plasma sprayed, the parameters of the plasma spraying were: power 45kW, main gas Ar flow rate 55SLPM, auxiliary gas H2 flow rate 12SLPM, spraying distance 110mm, and powder feeding rate 35g / min.

[0086] Comparative Example 1

[0087] The difference between this comparative example and Example 1 is that no conductive phase additive is added, and the remaining steps are the same as those of Example 1.

[0088] Comparative Example 2

[0089] The difference between this comparative example and Example 2 is that no hydroxypropyl acrylate is added, and the remaining steps are the same as those of Example 2.

[0090] Comparative Example 3

[0091] The difference between this comparative example and Example 3 is that no isobornyl acrylate is added, and the remaining steps are the same as those of Example 3.

[0092] The aluminum alloy (6061-T6) substrate was ultrasonically cleaned with acetone for 10min to remove oil stains, sandblasted with alumina sand (particle size 50μm) at a pressure of 0.2MPa to make the surface roughness Ra=0.8μm and enhance the adhesion of the coating, and dried in an oven at 80℃ for 30min to prepare a pretreated substrate with a size of 50mm×50mm×5mm. The coating was prepared according to the steps of Examples 1-3 and Comparative Examples 1-3.

[0093] (I) Conductivity test: reference ASTM D257 "Standard Test Methods for DC Resistance or Conductance of Insulating Materials".

[0094] The surface resistance (unit: Ω / square) of each sample was measured at three positions (center, left edge and right edge) using a four-probe resistometer, a voltage of 10V was applied, and the reading was recorded after stabilization, repeated three times, and the average resistance of each sample was calculated.

[0095] The results are shown in Table 1:

[0096] Table 1. Coating surface resistance test results

[0097] Sample Average surface resistance (Ω / square) Example 1 1.85 x 10 3 ]] Example 2 3.92 x 10 3 ]] Example 3 9.67 x 10 3 ]] Comparative Example 1 4.16 x 10 12 ]] Comparative Example 2 2.81 x 10 5 ]] Comparative Example 3 8.24 x 10 5 ]]>

[0098] (II) Abrasion resistance test: Refer to ASTM D4060 "Standard Test Method for Abrasion Resistance of Organic Coatings Using Taber Abrader".

[0099] Using a CS-10 grinding wheel, a load of 500 g, and a rotation speed of 60 rpm, each sample was subjected to 1000 cycles of wear. The weight loss before and after wear was measured (unit: mg), and the weight loss rate was calculated. .

[0100] The results are shown in Table 2:

[0101] Table 2. Coating wear resistance test results

[0102] Sample Average weight loss (mg) Weight loss rate (%) Example 1 8.35 1.64 Example 2 9.72 1.92 Example 3 12.08 2.42 Comparative Example 1 18.97 3.78 Comparative Example 2 32.15 6.45 Comparative Example 3 44.83 8.98

[0103] (III) Adhesion strength test: Refer to ASTM D4541 "Standard Test Method for Pull-off Strength of Coatings Using a Portable Adhesion Tester".

[0104] Use an aluminum alloy pulling rod with a diameter of 20mm and fix it to the coating surface with epoxy resin adhesive. Apply tension in the vertical direction at a speed of 1mm / min until the coating peels off. Record the maximum pull-off force (unit: MPa) and calculate the average pull-off strength (unit: MPa). , where σ is the pull-off strength (unit: MPa), F is the maximum pull-off force (unit: N), and A is the cross-sectional area of ​​the pull-off column (unit: mm²).

[0105] The results are shown in Table 3:

[0106] Table 3. Coating adhesion strength test results

[0107] Sample Average peel strength (MPa) Example 1 25.37 Example 2 22.64 Example 3 18.92 Comparative Example 1 8.15 Comparative Example 2 5.48 Comparative Example 3 12.16

[0108] As shown in Table 1, the conductive phase additives were added to Examples 1-3, and the average surface resistance was at a relatively low level, which was 1.85×10 3 Ω / square, 3.92×10 3 Ω / square, 9.67×10 3Ω / square. This is because the conductive phase additive contains tin oxide nano powder, which has a certain conductivity. During the preparation process, it is uniformly dispersed in the coating system through a series of reactions such as monomer mixing and polymerization, forming a conductive network, so that electrons can be relatively easily conducted in the coating, thereby giving the coating good conductivity, significantly improving the charge dissipation ability of the coating, and helping to reduce wafer desorption delay.

[0109] Comparative Example 1 does not add a conductive phase additive, and the average surface resistance is as high as 4.16 x 10 12 Ω / square, almost insulating. This is because the addition of conductive phase additives is lacking, and the coating lacks channels to conduct electrons, which cannot form an effective conductive network, resulting in a large coating resistance and poor conductivity. The average surface resistance of Comparative Example 2, which does not add hydroxypropyl acrylate, and Comparative Example 3, which does not add isobornyl acrylate, is higher than that of the examples, respectively 2.81 x 10 5 Ω / square, 8.24 x 10 5 Ω / square. Acrylic acid hydroxypropyl ester and acrylic acid isobornyl ester may play a role in adjusting the structure and properties of the polymer during polymerization, affecting the formation and dispersion of the conductive phase additive. The lack of one of the monomers may cause changes in the structure of the polymer, resulting in uneven dispersion of the tin oxide nano powder and damage to the formation of the conductive network, thereby causing the coating to conduct electricity.

[0110] As can be seen from Table 2, the average weight loss and weight loss rate of Examples 1-3 are relatively low, such as the average weight loss of Example 1 is 8.35 mg, and the weight loss rate is 1.64%. The ceramic face layer slurry contains α-alumina powder, borosilicate glass powder and other components, which form a hard and dense structure in the coating. α-alumina has high hardness and wear resistance, and borosilicate glass powder can react with alumina and other components at high temperatures to enhance the bonding force and density of the coating, thereby improving the wear resistance of the coating. At the same time, the silicon carbide whiskers in the conductive bottom layer slurry also play a certain reinforcing role. Silicon carbide whiskers have high strength and high modulus, and can withstand the stress during wear and tear, reducing the wear of the coating. This shows that the coating of the present application has excellent wear resistance, which helps to extend the service life of the vacuum electrostatic chuck and reduce the maintenance requirements due to wear and tear.

[0111] Comparative Example 1 did not add the conductive phase additive, and the average weight loss was 18.97 mg, and the weight loss rate was 3.78%, which was significantly higher than that of the examples. It may be that the conductive phase additive not only gives the coating conductivity, but also improves the microstructure of the coating to some extent, making the coating more dense and uniform. Without the conductive phase additive, the structure of the coating may have defects, leading to more easily peeling and wear during wear, and the wear resistance decreases. Comparative Example 2 did not add hydroxypropyl acrylate, and Comparative Example 3 did not add isobornyl acrylate, and the average weight loss and weight loss rate increased significantly, such as the average weight loss of Comparative Example 2 was 32.15 mg, and the weight loss rate was 6.45%. The absence of hydroxypropyl acrylate and isobornyl acrylate affects the structure and properties of the polymer, and then affects the dispersion of the conductive phase additive and the overall structure of the coating. The uneven structure makes the coating more easily damaged during wear, and the wear resistance decreases significantly.

[0112] As can be seen from Table 3, the average peel strength of Examples 1-3 is higher, such as the average peel strength of Example 1 is 25.37 MPa. The rough surface of the pretreated substrate enhances the mechanical interlocking force between the coating and the substrate, and various components in the conductive primer slurry and the ceramic topcoat slurry form good chemical bonding and physical bonding during the curing process. The components such as polyethylene glycol stearate in the conductive primer slurry can improve the wettability of the slurry and the substrate, and promote the close combination of the coating and the substrate; the components such as polyethylene glycol in the ceramic topcoat slurry also help to improve the cohesion of the coating and the adhesion to the bottom layer. It shows that the present application realizes high adhesion strength through the cooperation of materials and process, which helps to improve the reliability of the coating under thermal cycling and mechanical stress, and reduces the equipment maintenance frequency.

[0113] Comparative Example 1 did not add the conductive phase additive, and the average peel strength was only 8.15 MPa. The conductive phase additive may play a certain promoting role in the combination process of the coating and the substrate, which can fill the small pores on the surface of the substrate, increase the contact area of the coating and the substrate, and improve the mechanical interlocking force. Without the conductive phase additive, the combination of the coating and the substrate is not tight enough, resulting in a decrease in adhesion strength. The adhesion strength of Comparative Examples 2-3 decreases: Comparative Example 2 does not add hydroxypropyl acrylate, and Comparative Example 3 does not add isobornyl acrylate, and the average peel strength decreases compared with the examples, and the average peel strength of Comparative Example 2 is 5.48 MPa. The absence of hydroxypropyl acrylate and isobornyl acrylate affects the structure and properties of the polymer, and then affects the overall performance of the coating. The uneven polymer structure may cause stress concentration points in the coating, which is more easily damaged during the peel test, resulting in a decrease in adhesion strength.

[0114] In summary, examples 1-3 by introducing tin oxide nano-powder-based conductive phase additives, build a uniform conductive network, significantly reduce the surface resistance. At the same time, the ceramic face layer of examples 1-3 with α-alumina and borosilicate glass powder as the core, combined with the reinforcing effect of silicon carbide whisker in the conductive bottom layer, form a hard-tough synergistic structure, the wear loss rate is as low as 1.64-2.42%. In addition, by the substrate sandblasting pretreatment to enhance the mechanical interlocking, combined with the wettability improvement of polyethylene glycol stearate in the conductive bottom layer and the chemical bonding of polyethylene glycol in the ceramic face layer, realize high adhesive strength.

[0115] In the description of the specification, the description referring to the terms "preparation example", "example", "each example" and the like means that the specific features, structures, materials or characteristics described in connection with the example or preparation example are included in at least one example or preparation example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same example or preparation example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more examples or preparation examples in a suitable manner.

[0116] The above only describes the preferred embodiments of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can make equivalent replacements or changes to the technical solutions and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. An alumina ceramic coating for a vacuum electrostatic chuck, characterized in that: The method comprises a conductive bottom layer and a ceramic surface layer, wherein the conductive bottom layer comprises the following raw materials by weight: 3-8 parts of a conductive phase additive, 2-4 parts of polyethylene glycol stearate and 1-3 parts of silicon carbide whiskers; The ceramic surface layer comprises the following raw materials in parts by weight: 85-92 parts of α-alumina powder, 4-10 parts of borosilicate glass powder, 0.5-2 parts of magnesium oxide, 1-3 parts of zirconium oxide and 3-5 parts of polyethylene glycol; The conductive phase additive is a composite powder of polymer-coated tin oxide, and the polymer is prepared by polymerization reaction of hydroxypropyl acrylate, isobornyl acrylate and divinylbenzene.

2. The alumina ceramic coating according to claim 1, characterized in that The preparation steps of the conductive phase additive specifically include: a) dispersing tin oxide nanopowder in anhydrous ethanol and adding sodium octyl succinate sulfonate to form a sol; b) mixing hydroxypropyl acrylate, isobornyl acrylate, and divinylbenzene and deoxygenating them to obtain a monomer mixture; c) mixing the sol and the monomer mixture, adding a silane coupling agent, adding an initiator to carry out a polymerization reaction, and performing step-by-step curing to obtain a conductive phase additive.

3. The alumina ceramic coating according to claim 1, characterized in that The average particle size of α-alumina powder is 1-50 μm; The average particle size of borosilicate glass powder is 0.5-10 μm; The aspect ratio of silicon carbide whiskers is 20-50.

4. The alumina ceramic coating according to claim 2, characterized in that The average particle size of the tin oxide nanopowder in step a) is 10-100 nm; In step a), the mass ratio of tin oxide nanopowder, sodium octyl succinate sulfonate and anhydrous ethanol is (8-9.5):1:(160-170).

5. The alumina ceramic coating according to claim 2, characterized in that: In step b), the mass ratio of isobornyl acrylate, hydroxypropyl acrylate and divinylbenzene is (17-20): (5-7): (1.5-3); In step c), the silane coupling agent is selected from at least one of KH-570, KH-560 and KH-550, and the amount added is 3-5% of the mass of the tin oxide nanopowder; In step c), the initiator is selected from at least one of azobisisobutyronitrile, benzoyl peroxide and azobisisoheptylonitrile, and the added amount is 1-3% of the total mass of hydroxypropyl acrylate and isobornyl acrylate.

6. The alumina ceramic coating according to claim 2, characterized in that: In step c), the polymerization reaction temperature is 65-75° C., and the polymerization reaction time is 4-8 hours; Step c) of the mid-step curing is as follows: the first stage temperature is 75-80°C, the time is 30-40 minutes, the second stage temperature is 80-85°C, the time is 50-60 minutes, and the third stage temperature is 95-100°C, the time is 100-120 minutes.

7. A method for preparing an alumina ceramic coating according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Mix the conductive base material raw materials, ball-mill with deionized water as the medium, and adjust the solid content to 45-55 wt % to obtain a conductive base material slurry; S2. Mixing and ball-milling the ceramic surface layer raw materials to adjust the solid content to 65-75 wt % to obtain a ceramic surface layer slurry; S3. Air-spray the conductive bottom layer slurry onto the pre-treated surface of the vacuum electrostatic chuck substrate, solidify it, and then plasma-spray the ceramic surface layer slurry.

8. The preparation method according to claim 7, characterized in that In step S1, the amount of deionized water added is 100-150% of the total mass of the powder; The curing temperature in step S3 is 110-120° C., and the curing time is 1-2 hours.

9. The preparation method according to claim 7, characterized in that The process parameters of plasma spraying in step S3 are: power 35-45 kW, main gas Ar flow rate 45-55 SLPM, auxiliary gas H2 flow rate 8-12 SLPM, spraying distance 90-110 mm, and powder feeding rate 25-35 g / min.

10. Use of the alumina ceramic coating according to any one of claims 1 to 6 in semiconductor wafer processing equipment.