Electrode paste for electrostatic chuck and preparation method and application thereof

Abstract

The application relates to an electrode slurry for an electrostatic chuck and a preparation method and application thereof, and belongs to the technical field of electrostatic chuck. According to weight parts, the electrode slurry for the electrostatic chuck comprises 50-95 parts of metal composite powder and 5-50 parts of an organic carrier; the metal composite powder is a shell-core structure, and from inside to outside, the shell-core structure comprises a conductive metal powder, an alumina bonding layer and an aerogel coating layer. The alumina bonding layer is formed by thermal decomposition and conversion of an alumina precursor; and the aerogel coating layer is a porous coating layer composed of alumina aerogel powder. The application solves the long-existing contradiction between sedimentation and glue discharge in the manufacturing of the electrode of the electrostatic chuck, and provides a brand-new solution for the manufacturing of the electrostatic chuck with high performance and high reliability.

Description

Technical Field

[0001] This invention relates to the field of electrostatic chuck technology, and in particular to an electrode paste for electrostatic chucks, its preparation method, and its application. Background Technology

[0002] Electrostatic chucks are key components used to hold wafers in semiconductor etching, chemical vapor deposition, and other equipment. Their core structure is typically formed by bonding multiple layers of alumina ceramic ribbons through a co-firing process, with metal electrodes embedded between the layers. Currently, these electrodes are mostly printed using pastes formulated with high-density metal powders such as palladium (Pd), tungsten (W), or their alloys.

[0003] However, this process has the following inherent technical challenges:

[0004] (1) Sedimentation problem: Due to the extremely high specific gravity of metal powders such as palladium and tungsten, sedimentation is very likely to occur during the preparation, storage and printing of slurry, resulting in uneven slurry composition. Ultimately, this leads to uneven electrode thickness and inconsistent resistance distribution after sintering, which seriously affects the adsorption uniformity and reliability of the electrostatic chuck.

[0005] (2) Risk of debonding and cracking: To solve the sedimentation problem, it is often necessary to add organic thixotropic agents (such as cellulose derivatives, polyamide wax, etc.) to the slurry. However, these high molecular weight organics are difficult to completely and smoothly decompose and expel during the subsequent high-temperature co-firing process. The gas generated by its pyrolysis is prone to form high pressure in the dense ceramic layer, which leads to defects such as cracks and holes in the ceramic strip or at the interface, reducing the product yield and mechanical strength.

[0006] Therefore, there is an urgent need to develop a new solution that can fundamentally and synergistically address slurry stability, adhesive discharge smoothness, and electrode functionality. Summary of the Invention

[0007] To address the problems of uneven sedimentation caused by the use of high-density metal powder in existing electrostatic chuck electrode pastes, and the difficulties in high-temperature debinding and cracking caused by the addition of thixotropic agents to improve sedimentation, this invention provides an electrode paste for electrostatic chucks, its preparation method, and its application.

[0008] This invention is achieved through the following technical solution:

[0009] The first objective of this invention is to provide an electrode paste for an electrostatic chuck, wherein, by weight, the electrode paste comprises 50 to 95 parts of metal composite powder and 5 to 50 parts of organic carrier;

[0010] The metal composite powder has a core-shell structure, consisting of conductive metal powder, an alumina bonding layer, and an aerogel coating layer from the inside out.

[0011] The alumina bonding layer is formed by the thermal decomposition and transformation of the alumina precursor; the alumina bonding layer is tightly bonded to the metal composite powder to form an amorphous / crystalline alumina thin layer.

[0012] The aerogel coating layer is a porous coating layer composed of alumina aerogel powder; the aerogel coating layer is attached to the surface of the alumina adhesive layer.

[0013] In one embodiment of the present invention, the conductive metal powder is a single metal powder or a metal alloy; the metal is palladium and / or tungsten.

[0014] In one embodiment of the present invention, the volume median diameter D50 of the conductive metal powder is 100 nm to 10 μm.

[0015] In one embodiment of the present invention, the alumina precursor is one or more of aluminum acetylacetonate, aluminum isopropoxide, and aluminum tris(2,2,6,6-tetramethyl-3,5-heptadecanoate).

[0016] In one embodiment of the present invention, the particle size of the alumina aerogel powder is 0.1 μm to 50 μm;

[0017] And / or, the specific surface area of ​​the alumina aerogel powder is >300 m². 2 / g.

[0018] In one embodiment of the present invention, the method for preparing the metal composite powder includes the following steps:

[0019] S1. Dissolve the alumina precursor in an anhydrous organic solvent to obtain a precursor solution; under stirring and ultrasonic dispersion, add conductive metal powder so that its surface is fully wetted and coated by the precursor solution.

[0020] S2. The slurry obtained in step S1 is dried at 40℃~80℃ to form an alumina adhesion layer;

[0021] S3. Add the alumina aerogel powder to the system obtained in step S2 and mix, so that the alumina aerogel powder adheres to the surface of the alumina adhesion layer to form an aerogel coating layer.

[0022] S4. The material obtained in step S3 is subjected to heat treatment, solidification and shearing to obtain metal composite powder for electrostatic chucks.

[0023] In one embodiment of the present invention, in step S1, the alumina precursor is at least one of aluminum acetylacetonate, aluminum isopropoxide, and aluminum tris(2,2,6,6-tetramethyl-3,5-heptadecanoate); the anhydrous organic solvent is at least one of xylene, toluene, acetone, or tetrahydrofuran.

[0024] In one embodiment of the present invention, in step S1, the concentration of the precursor solution is 10wt%~25wt%.

[0025] In one embodiment of the present invention, in step S4, the temperature of the heat treatment is 300℃~500℃; and the dispersion rate of the shearing is 3000r / min~10000r / min.

[0026] In step S4, the dispersion speed of 3000 r / min to 10000 r / min and the heat treatment achieve two key transformations: First, the surface-coated precursor is completely decomposed and transformed into a strong alumina binder layer; second, during the formation process, this alumina binder layer forms a strong chemical bond and physical anchor with the attached alumina aerogel particles, ultimately forming a stable "metal core-binder layer-aerogel shell" composite structure. Furthermore, in step S4, utilizing the low specific gravity of the aerogel powder, excess uncoated aerogel powder is removed by compressed air.

[0027] In one embodiment of the present invention, the organic carrier includes one or more of an intermediate, an organic solvent, and a dispersant.

[0028] In one embodiment of the present invention, the organic solvent comprises terpineol; the dispersant comprises oleic acid.

[0029] In one embodiment of the present invention, the Brinell viscosity of the electrode slurry is 200 Pa·s to 250 Pa·s; and the fineness of the electrode slurry is less than 25 μm.

[0030] The second objective of this invention is to provide a method for preparing the electrode slurry, wherein metal composite powder and organic carrier are mixed in a planetary mixer and dispersed using a three-roll mill to obtain the electrode slurry for electrostatic chucks.

[0031] Specifically, ethyl cellulose is mixed with diethylene glycol-butyl ether acetate and heated to obtain an intermediate.

[0032] Metal composite powder is stirred, mixed and dispersed with an organic carrier to obtain an electrode slurry for electrostatic chucks; the organic carrier includes one or more of an intermediate, an organic solvent and a dispersant.

[0033] A third objective of this invention is to provide the application of the electrode paste in the preparation of electrostatic chucks.

[0034] This invention utilizes different forms of alumina (precursor and aerogel) to fully leverage the high specific surface area of ​​aerogel and the adhesive properties of the precursor to prepare metal composite powders. First, conductive metal powder is pre-coated with a precursor solution. Then, the incompletely cured precursor layer acts as an 'adhesive' to capture aerogel particles. Finally, a single heat treatment simultaneously cures the alumina bonding layer and locks in the aerogel shell, yielding the metal composite powder. This method overcomes the technical bottleneck of achieving uniform and robust composites between aerogel and high-density conductive metal powders due to their vastly different physical properties, achieving the goals of anti-settling and uniformity with minimal introduction of organic matter.

[0035] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0036] (1) Anti-settling properties: The spatial steric hindrance and network support formed by the aerogel coating layer enable each high-density conductive metal powder to be uniformly and stably suspended in the slurry, which significantly improves the uniformity and consistency of electrode printing.

[0037] (2) Low organic content and excellent debinding performance: By using composite powder, the electrode slurry of the electrostatic chuck does not need to add complex and high molecular weight organic substances such as thixotropic agents and surfactants, which greatly reduces the organic matter that needs to be pyrolyzed and discharged during the sintering process of the electrode slurry, significantly reducing the risk of defects such as cracks and bubbles during co-firing, and improving product yield and mechanical integrity.

[0038] (3) High purity and good compatibility: The final electrode composition consists only of metal and alumina, which has excellent chemical compatibility with the alumina ceramic material of the electrostatic chuck body. There is no interfacial reaction or impurity phase generation, which is conducive to improving the interfacial bonding strength and long-term service reliability.

[0039] (4) This invention cleverly solves the long-standing contradiction between sedimentation and glue removal in the manufacturing of electrostatic chuck electrodes through material design and preparation process, providing a brand-new material solution for the manufacturing of high-performance and high-reliability electrostatic chucks. Detailed Implementation

[0040] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0041] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0042] This invention provides an electrode slurry for electrostatic chucks, its preparation method, and its application, aiming to solve the problems of slurry sedimentation and high-temperature adhesive removal through a unique structural design.

[0043] The core feature of the composite powder is its three-layer composite structure, consisting of conductive metal powder, an alumina binder layer, and an aerogel coating layer from the inside out.

[0044] Core: Conductive metal powder, such as palladium, tungsten or their alloy powder, provides electrical functionality.

[0045] Alumina binder layer: an amorphous / crystalline alumina thin layer formed by the thermal decomposition and transformation of the alumina precursor (aluminum acetylacetonate) and tightly bonded to the metal core.

[0046] Aerogel coating layer: A loose, porous coating layer composed of discrete alumina aerogel powder particles attached to the intermediate adhesive layer, with a thickness of 0.1 μm to 2 μm.

[0047] Furthermore, the method for preparing the metal composite powder for electrostatic chucks according to the present invention includes the following steps:

[0048] S1. Dissolve the alumina precursor (preferably aluminum acetylacetonate) in an anhydrous organic solvent (the anhydrous organic solvent is at least one of xylene, toluene, acetone, or tetrahydrofuran) to prepare a precursor solution with a concentration of 10wt%~25wt%. Under stirring and ultrasonic dispersion, add conductive metal powder to ensure its surface is fully wetted and coated by the precursor solution.

[0049] S2. The slurry is gently dried at 40℃~80℃ to remove most of the solvent, allowing the precursor to initially solidify on the surface of the metal powder, forming a viscous "wet gel" coating layer, i.e., the alumina adhesion layer. This step aims to obtain pre-coated metal powder that still retains a certain degree of surface activity and adhesion.

[0050] S3. Before the pre-coated metal powder is completely dry and hardened, add dried alumina aerogel powder (particle size 0.1μm~50μm, specific surface area >300 m² / g) to the system and mix under low shear force. Utilize the residual viscosity of the pre-coating layer to effectively adhere the alumina aerogel powder particles to the surface of the metal powder.

[0051] S4. The material obtained in step S3 is subjected to heat treatment, solidification and shearing, and then sieved to obtain metal composite powder for electrostatic chucks.

[0052] During mass production, the uniformly mixed material from step S3 can be dispersed at high speed in a high-shear mixing reactor at 3000~10000 rpm, and then heat-treated at 300℃~500℃. Finally, the dispersed powder is sieved through a 200-mesh sieve to obtain the metal composite powder for electrostatic chucks.

[0053] Example 1

[0054] This embodiment provides a method for preparing electrode paste for electrostatic chucks, as detailed below:

[0055] (1) Preparation of metal composite powder for electrostatic chucks, the specific steps are as follows:

[0056] S1. Precursor coating: Add 50g of aluminum acetylacetonate to 450g of xylene and stir magnetically (500rpm) for 30min to prepare a precursor solution with a concentration of 10wt%; then add 100g of palladium powder with a particle size of 1μm to the solution, stir magnetically (500rpm) for 5min, and then sonicate at 300W for 30min to ensure that the surface of the palladium powder is fully wetted by the precursor solution and coated.

[0057] S2. Preliminary drying: Place the slurry obtained in step S1 in a forced-air drying oven and gently dry it at 60°C for 30 minutes to remove most of the solvent, so that the precursor is initially solidified on the surface of the metal powder to form an alumina adhesion layer; the purpose of this step is to obtain a pre-coated metal powder with both surface activity and adhesion ability.

[0058] S3. Aerogel Composite: When the pre-coated metal powder obtained in step S2 has not been completely dried and hardened, 10g of dry alumina aerogel powder (particle size 200nm) is added to the system. The system is placed in a mixer and mixed at a speed of 100 rpm under low shear force conditions. With the help of the adhesiveness of the pre-coated layer, the alumina aerogel powder particles are effectively adhered to the surface of the alumina adhesion layer.

[0059] S4. Simultaneous heat treatment and curing: Place the uniformly mixed material from step S3 into a muffle furnace, first heat it to 120°C at a heating rate of 2°C / min, and hold it at that temperature for 1 hour; then heat it to 400°C at a heating rate of 5°C / min, and hold it at that temperature for 2 hours to complete the simultaneous heat treatment and curing.

[0060] S5. Take out the powder processed in step S4, cool it to 80°C and put it into a mixer. Shear it at a speed of 5000 rpm to disperse the agglomerated powder evenly. Finally, sieve the dispersed powder through a 200-mesh sieve to obtain metal composite powder for electrostatic chucks.

[0061] (2) Preparing intermediates: Ethyl cellulose (model STD10, manufacturer: Dow Chemical, place of origin: USA) and diethylene glycol-butyl ether acetate (BCA) are weighed at a mass ratio of 1:9. BCA is heated to 60°C in a water bath while stirring. At the same time, the weighed ethyl cellulose is slowly added to BCA and stirred until the ethyl cellulose is completely and uniformly dissolved in BCA. After cooling to room temperature, the intermediate is obtained and set aside.

[0062] (3) Weigh 79.5g of the metal composite powder prepared in step (1), 16g of the intermediate obtained in step (2), 4g of terpineol and 0.5g of oleic acid, and put them into the wide-mouth bottle of the planetary mixer. First, stir with a scraper until initially uniform, and then use the planetary mixer to mix at 800 rpm for 3 minutes to obtain the sample slurry. Disperse the sample slurry 5 times with a three-roll mill and test to confirm that its dispersion fineness is less than 25μm and its Brookfield viscosity is between 50Pa·s and 250Pa·s, thus obtaining the electrode slurry for electrostatic chucks.

[0063] Example 2

[0064] This embodiment provides a method for preparing electrode paste for electrostatic chucks, similar to Embodiment 1, except that:

[0065] In step (3), the amount of metal composite powder added is 80g, and no oleic acid is added; the remaining steps are consistent with those in Example 1.

[0066] Example 3

[0067] This embodiment provides a method for preparing electrode paste for electrostatic chucks, similar to Embodiment 1, except that:

[0068] In step (3), the amount of metal composite powder added is 85g, the amount of intermediate added is 10g, the amount of terpineol added is 5g, and oleic acid is not added; the remaining steps are consistent with those in Example 1.

[0069] Example 4

[0070] This embodiment provides a method for preparing electrode paste for electrostatic chucks, similar to Embodiment 1, except that:

[0071] In step (3), the amount of metal composite powder added is 90g, the amount of intermediate added is 4g, the amount of terpineol added is 6g, and oleic acid is not added; the remaining steps are consistent with those in Example 1.

[0072] Comparative Example 1

[0073] This comparative example provides a method for preparing electrode paste for electrostatic chucks, similar to Example 1, except that:

[0074] In step (3), the metal composite powder was replaced with 79g of palladium powder (particle size 1μm); 0.5g of THIXATROLMAX (purchased from Haimings) was added; the remaining steps were the same as in Example 1.

[0075] Comparative Example 2

[0076] This comparative example provides a method for preparing electrode paste for electrostatic chucks, similar to Example 1, except that:

[0077] In step (2), the metal composite powder is replaced with 79g of palladium powder; 0.5g of alumina aerogel powder (particle size 200nm) is added; the remaining steps are consistent with those in Example 1.

[0078] Comparative Example 3

[0079] This comparative example provides a method for preparing electrode paste for electrostatic chucks, similar to Example 1, except that:

[0080] In step (2), the metal composite powder is replaced with 79g of palladium powder; 0.5g of nano alumina (particle size 200nm) is added; the remaining steps are consistent with those in Example 1.

[0081] Comparative Example 4

[0082] This comparative example provides a method for preparing electrode paste for electrostatic chucks, similar to Example 1, except that:

[0083] In step (2), the metal composite powder is replaced with 79.5g of water glass composite powder; the remaining steps are consistent with those in Example 1.

[0084] The preparation method of the water glass composite powder is similar to that of the metal composite powder used for electrostatic chuck in Example 1, except that the precursor in step S1 is replaced with water glass.

[0085] Performance testing

[0086] The electrode pastes obtained from the above embodiments and comparative examples were used for printing and laminating the ceramic layer of an electrostatic chuck, and then their conductivity and sheet resistance were tested.

[0087] 1) Visually inspect whether the electrode slurry has separated into layers (organic on top, powder on the bottom) after standing for 24 hours.

[0088] 2) Preparation of conductivity samples:

[0089] Electrode paste was screen-printed onto alumina raw material tape (purchased from Nippon Electric Glass) using a screen printing plate (parallel array with grid lines 5cm in length and 250μm in width, spaced 2mm apart). The printed alumina raw material tape was then dried in a 60℃ oven for 15 minutes and then sintered in a muffle furnace at 1300℃ for 2 hours to obtain conductivity test samples for measuring resistivity.

[0090] 2) Sheet resistivity test:

[0091] Thickness test: Five grid lines at different locations on the sample were selected. Using a Will Semiconductor SP1103W-sek profilometer, three test points were taken at different locations on each grid line to measure the grid line thickness and calculate the average value in μm.

[0092] Resistance measurement: The resistance of the above 5 grid lines is measured using an ohmmeter, and the average value is calculated in mohms.

[0093] Sheet resistivity calculation: It is calculated according to the formula sheet resistivity (mohm / □) ​​= (resistance × thickness) / (200 × standard thickness 5μm).

[0094] 3) Preparation of laminated samples:

[0095] Electrode paste was screen-printed onto alumina raw material tape using a screen printing plate (parameters: 480-11-M14E4-2x2cm, no mesh knots). The printed alumina raw material tape was then dried in a 60℃ oven for 15 minutes. Two blank alumina raw material tapes were stacked on top of the alumina raw material tape with the printed electrodes. After alignment and lamination, the samples were first sintered in a muffle furnace at 1300℃ for 2 hours, and then subjected to hot isostatic pressing at 1400℃ and 150MPa for 2 hours to obtain the laminated test sample.

[0096] Sintering morphology: Directly visually observe whether there are cracks or discoloration on the surface of the stacked test sample, and visually observe whether there are cracks under backlight (the electrostatic chuck is translucent after sintering).

[0097] Porosity: The sintered laminated test sample was cut along a direction perpendicular to the inner electrode, and the cross-section was polished. Electron microscopy was used to photograph the cross-section electrode. After grayscale two-dimensional processing of the photographs using ImageJ, the porosity was calculated by the area ratio of pores (black areas) to electrodes (white areas), i.e., black area / (total black + white area)%.

[0098] The test results are shown in Table 1 below:

[0099] Table 1

[0100]

[0101] As can be seen from Table 1, no stratification phenomenon was observed in any of the examples, indicating that the composite powder can effectively resist sedimentation and has better uniformity than the comparative examples with other methods such as adding thixotropic agents and nanopowder alone.

[0102] The sheet resistivity of the embodiments is better than that of the comparative examples, indicating that the composite powder method reduces the addition of organic matter and other substances, achieving a better sintering effect, and thus has a better degree of densification and a lower sheet resistivity.

[0103] The example showed no sintering defects, indicating that due to the use of composite powder, the electrode slurry does not require the removal of large amounts of organic matter during sintering, and all its components are alumina, exhibiting excellent compatibility with the substrate (e.g., thermal expansion and contraction). Therefore, the cracking problems caused by thermal mismatch or the discoloration problems caused by impurities, as seen in the comparative example, will not occur.

[0104] Because the embodiments use composite powder, the electrode slurry does not need to release a large amount of organic matter during the sintering process, thus resulting in better sintering density and lower porosity.

[0105] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An electrode paste for an electrostatic chuck, characterized in that, By weight, the electrode slurry comprises 50 to 95 parts of metal composite powder and 5 to 50 parts of organic carrier; The metal composite powder has a core-shell structure, consisting of conductive metal powder, an alumina bonding layer, and an aerogel coating layer from the inside out. The alumina adhesive layer is formed by the thermal decomposition and transformation of the alumina precursor; The aerogel coating layer is a porous coating layer composed of alumina aerogel powder.

2. The electrode paste according to claim 1, characterized in that, The conductive metal powder is a single metal powder or a metal alloy; the metal is palladium and / or tungsten.

3. The electrode paste according to claim 1, characterized in that, The median volume diameter (D50) of the conductive metal powder is 100 nm to 10 μm.

4. The electrode paste according to claim 1, characterized in that, The alumina precursor is one or more of aluminum acetylacetonate, aluminum isopropoxide, and aluminum tris(2,2,6,6-tetramethyl-3,5-heptadecanoate).

5. The electrode paste according to claim 1, characterized in that, The particle size of the alumina aerogel powder is 0.1 μm to 50 μm; And / or, the specific surface area of ​​the alumina aerogel powder is >300 m². 2 / g.

6. The electrode paste according to claim 1, characterized in that, The preparation method of the metal composite powder includes the following steps: S1. Dissolve the alumina precursor in an anhydrous organic solvent to obtain a precursor solution; under stirring and ultrasonic dispersion, add conductive metal powder so that its surface is fully wetted and coated by the precursor solution. S2. The slurry obtained in step S1 is dried at 40℃~80℃ to form an alumina adhesion layer; S3. Add the alumina aerogel powder to the system obtained in step S2 and mix, so that the alumina aerogel powder adheres to the surface of the alumina adhesion layer to form an aerogel coating layer. S4. The material obtained in step S3 is subjected to heat treatment, solidification and shearing to obtain metal composite powder for electrostatic chucks.

7. The electrode paste according to claim 6, characterized in that, In step S4, the temperature of the heat treatment is 300℃~500℃; And / or, the shearing dispersion rate is 3000 r / min to 10000 r / min.

8. The electrode paste according to claim 1, characterized in that, The organic carrier includes one or more of an intermediate, an organic solvent, and a dispersant.

9. The method for preparing the electrode paste according to any one of claims 1-8, characterized in that, The metal composite powder and organic carrier are mixed in a planetary mixer and dispersed using a three-roll mill to obtain the electrode slurry for the electrostatic chuck.

10. The use of the electrode paste according to any one of claims 1-8 in the preparation of an electrostatic chuck.

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