A method for manufacturing a vacuum chuck with high surface flatness for wafer processing

Abstract

The application discloses a preparation method of a vacuum chuck with high surface flatness for wafer processing. The method uses chloride ion-free hydratable magnesium oxide and tea polyphenol as raw materials, and prepares a porous ceramic sheet with high surface flatness through pressure filtration forming and high-temperature sintering. The porous ceramic sheet prepared has a pore diameter of 80-300 nm, a porosity of 42%-67%, and a flatness of less than 20 nm on the surface without polishing. The porous ceramic sheet can be loaded into a metal holder to form the vacuum chuck with high surface flatness.

Description

Technical Field

[0001] This invention belongs to the field of chip processing technology, and specifically relates to a method for preparing a vacuum chuck. Background Technology

[0002] In the semiconductor industry, vacuum chucks are essential tools for holding and positioning wafers for processing or inspection. Vacuum chucks are used in various stages of semiconductor manufacturing, including dicing, cleaning, coating, exposure, inspection, and testing. The main principle of a vacuum chuck is to create a vacuum within the clamping area to attract and fix the workpiece, ensuring stable and precise positioning, thereby guaranteeing the accuracy and reliability of the processing.

[0003] The core component of a traditional vacuum chuck is made of alumina ceramic (99.5% purity) to prevent heavy metal contamination. Because the clamp top is made of porous alumina ceramic with pores ranging from 2 to 20 micrometers, dust can easily enter these channels due to the relatively large pore size, reducing clamping flatness (A new vacuum pin chuck for ArFlaser lithography, Microelectronic Engineering 61–62 (2002) 113–121).

[0004] With advancements in semiconductor technology, the surface roughness of jigs for processing wafers within a 30mm square area must be less than 30 nanometers. Simultaneously, porous vacuum chucks must possess relatively low resistivity to prevent static electricity generation. Existing vacuum chucks, whose core component is porous ceramic, suffer from poor surface smoothness, uneven pore size, and large pore diameters due to the use of ceramic precursor powder sintering as raw material. This allows dust to easily enter the channels, affecting surface flatness. Furthermore, the high resistivity makes them prone to static electricity generation, failing to meet practical application requirements. Summary of the Invention

[0005] This invention aims to provide a vacuum chuck with high surface flatness for wafer processing, thereby solving the problems mentioned in the background art. The technical solution of this invention includes the following steps: First, take 100 grams of water and add 0.05-0.5 grams of tea polyphenols to dissolve them, maintaining a temperature of 0-10°C. Second, add 100-200 grams of chloride-free, hydrated magnesium oxide (at a temperature below 10°C) to the above solution, stirring until a slurry is formed. Third, under a temperature of 15-30°C, press the above ceramic slurry into sheets within 30 minutes under a pressure of 10-1000 MPa in a mold. Fourth, hydrate the pressed ceramic sheets in water for 1-10 days. Fifth, dry the hydrated ceramic sheets and heat-treat them at a high temperature of 1200-1600°C to obtain porous ceramic sheets with high surface flatness. The prepared porous ceramic sheet has a pore size of 80–300 nm, a porosity of 42%–67%, and an unpolished surface flatness of less than 20 nm. Finally, the porous ceramic sheet is placed in a metal holder to form a vacuum chuck with high surface flatness.

[0006] The purpose of adding tea polyphenols in the first step is to act as a retarder to slow down the hydration rate of hydrateable magnesium oxide. Maintaining a low temperature is to control the hydration rate and prevent the slurry from solidifying before tableting. The third step, the filter press molding process, is not a conventional porous ceramic preparation process because filter presses are typically used for sludge dewatering in the environmental protection field. In the field of porous ceramic preparation technology, existing fine ceramic raw materials usually lack viscosity and therefore cannot be molded by filter press. However, hydrateable magnesium oxide, due to the gel formed by the reaction of its particle surface with water, possesses gelling properties, and the reaction is not yet complete, thus it can be molded by filter press. After filter press molding, the volume of the powder is restricted, and the hydrateable magnesium oxide continues to react with water. The newly generated gel fills the pores of the original hydrateable magnesium oxide, resulting in a homogenized structure. The original pores are eliminated, and it becomes a uniform magnesium hydroxide gel. Finally, high-temperature heat treatment transforms the uniform magnesium hydroxide gel into a high-surface-smoothness magnesium oxide porous ceramic.

[0007] Beneficial effects: The present invention discloses a method for preparing a vacuum chuck for wafer processing with high surface flatness. It uses hydrateable magnesium oxide powder as raw material, achieves a uniform structure through confined gelation, and obtains a porous ceramic material with high surface flatness through heat treatment. The material has a uniformly distributed pore size at the submicron and nanometer scales and controllable porosity. No organic pore-forming agents are used, and the preparation method is green and environmentally friendly. The vacuum chuck assembled using the prepared porous ceramic has high surface flatness and small pores, making it difficult for dust to enter. Attached Figure Description

[0008] Figure 1 The image shows a SEM image of the porous ceramic surface prepared in Example 1.

[0009] Figure 2 This is a SEM image of the interior of the porous ceramic prepared in Example 1. Detailed Implementation

[0010] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0011] Example 1:

[0012] The first step involves dissolving 0.08 g of tea polyphenols in 100 g of water. The second step involves adding 200 g of chloride-free, hydrated magnesium oxide to the solution and stirring until a slurry is formed. The third step involves pressing the ceramic slurry into sheets under a pressure of 50 MPa. The fourth step involves hydrating the pressed ceramic sheets in water for 7 days. The fifth step involves drying the hydrated ceramic sheets and then heat-treating them at 1400℃ to obtain porous ceramic sheets with high surface flatness. The prepared porous ceramic sheets have a pore size of 278 nm, a porosity of 59%, and an unpolished surface flatness of less than 20 nm. Finally, the porous ceramic sheets are placed in a metal holder to create a vacuum chuck with high surface flatness.

[0013] Example 2:

[0014] The first step involves dissolving 0.05 g of tea polyphenols in 100 g of water. The second step involves adding 100 g of chloride-free, hydrated magnesium oxide to the solution and stirring until a slurry is formed. The third step involves pressing the ceramic slurry into sheets under a pressure of 10 MPa. The fourth step involves hydrating the pressed ceramic sheets in water for 10 days. The fifth step involves drying the hydrated ceramic sheets and then heat-treating them at 1200℃ to obtain porous ceramic sheets with high surface flatness. The prepared porous ceramic sheets have a pore size of 256 nm, a porosity of 67%, and an unpolished surface flatness of less than 20 nm. Finally, the porous ceramic sheets are placed in a metal holder to create a vacuum chuck with high surface flatness.

[0015] Example 3:

[0016] The first step involves dissolving 0.1 g of tea polyphenols in 100 g of water. The second step involves adding 120 g of chloride-free, hydrated magnesium oxide to the solution and stirring until a slurry is formed. The third step involves pressing the ceramic slurry into sheets under a pressure of 20 MPa. The fourth step involves hydrating the pressed ceramic sheets in water for 8 days. The fifth step involves drying the hydrated ceramic sheets and then heat-treating them at 1300℃ to obtain porous ceramic sheets with high surface flatness. The prepared porous ceramic sheets have a pore size of 300 nm, a porosity of 62%, and an unpolished surface flatness of less than 20 nm. Finally, the porous ceramic sheets are placed in a metal holder to create a vacuum chuck with high surface flatness.

[0017] Example 4:

[0018] The first step involves dissolving 0.5 grams of tea polyphenols in 100 grams of water. The second step involves adding 200 grams of chloride-free, hydrated magnesium oxide to the solution and stirring until a slurry is formed. The third step involves pressing the ceramic slurry into sheets under a pressure of 1000 MPa. The fourth step involves hydrating the pressed ceramic sheets in water for one day. The fifth step involves drying the hydrated ceramic sheets and then heat-treating them at 1600℃ to obtain porous ceramic sheets with high surface flatness. The prepared porous ceramic sheets have a pore size of 80 nanometers, a porosity of 42%, and an unpolished surface flatness of less than 20 nanometers. Finally, the porous ceramic sheets are placed in a metal holder to create a vacuum chuck with high surface flatness.

[0019] Example 5:

[0020] The first step involves dissolving 0.4 grams of tea polyphenols in 100 grams of water. The second step involves adding 150 grams of chloride-free, hydrated magnesium oxide to the solution and stirring until a slurry is formed. The third step involves pressing the ceramic slurry under 500 MPa pressure to form sheets. The fourth step involves hydrating the pressed ceramic sheets in water for 3 days. The fifth step involves drying the hydrated ceramic sheets and then heat-treating them at 1400℃ to obtain porous ceramic sheets with high surface flatness. The prepared porous ceramic sheets have a pore size of 145 nm, a porosity of 52%, and an unpolished surface flatness of less than 20 nm. Finally, the porous ceramic sheets are placed in a metal holder to create a vacuum chuck with high surface flatness.

Claims

1. A method for fabricating a vacuum chuck with high surface flatness for wafer processing, characterized in that: The process includes the following steps: First, take 100 grams of water, add tea polyphenols to dissolve, and maintain a low temperature of 0-10℃; Second, add 100-200 grams of chloride-free, hydrateable magnesium oxide (below 10℃) to the above solution and stir evenly to form a slurry; Third, press the above ceramic slurry into a sheet in a mold within 30 minutes at a temperature of 15℃-30℃; Fourth, place the pressed ceramic sheet in water to allow the hydration reaction to continue; Fifth, dry the hydrated ceramic sheet and heat-treat it at a high temperature of 1200℃-1600℃ to obtain a porous ceramic sheet with high surface flatness; The pore size of the prepared porous ceramic sheet is 80-300 nanometers, the porosity is 42%-67%, and the surface flatness without polishing is less than 20 nanometers; Finally, the porous ceramic sheet is placed in a metal holder to form a vacuum suction cup with high surface flatness.

2. The method for preparing a high surface flatness vacuum chuck for wafer processing according to claim 1, characterized in that: The amount of tea polyphenols added is 0.05 to 0.5 grams.

3. The method for preparing a high surface flatness vacuum chuck for wafer processing according to claim 1, characterized in that: The pressure for pressing the filter sheets in the mold is 10MPa to 1000MPa.

4. The method for preparing a high surface flatness vacuum chuck for wafer processing according to claim 1, characterized in that: The water is left to stand for 1 to 10 days.

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