Electrostatic chuck and method of making the same

Abstract

The application discloses an electrostatic chuck and a preparation method thereof. The electrostatic chuck comprises an adsorption layer, the adsorption layer comprises a dielectric layer and an insulating layer, the dielectric layer and the insulating layer are bonded by an adhesive, a plurality of electrode groups are arranged between the dielectric layer and the insulating layer, a buffer layer is arranged at the lower end of the insulating layer, and a reinforcing substrate is arranged at the lower end of the buffer layer. The electrostatic chuck has strong design adaptability, can meet the cell forming process of an LCD high-generation ultra-thin panel, reduces the damage of the electrostatic chuck, prolongs the service life of the electrostatic chuck, and reduces the use cost of the electrostatic chuck.

Description

Technical Field

[0001] This invention relates to the technical field of electrostatic chucks, and more specifically to an electrostatic chuck and its preparation method. Background Technology

[0002] An electrostatic chuck is a new type of clamping device suitable for use in atmospheric or vacuum environments. It is used in the manufacturing process of semiconductor integrated circuits and flat panel displays to clamp wafers and other objects to be processed. It is not limited by atmospheric pressure, can be driven with low energy consumption, and can be precisely controlled by power on and off. When in contact with the object being processed, the adsorption force is uniform and there is no localized force.

[0003] To improve production efficiency and reduce costs, the flat panel display industry is rapidly developing towards higher generation lines, with 10.5-generation and 11-generation lines going into production one after another. The size of TFT and CF glass substrates exceeds 3000mm, and the thickness is as low as 0.3mm. LCD panels are developing towards thinner and more precise designs, thus placing higher demands on the performance of electrostatic chucks.

[0004] A typical example of an electrostatic chuck is the ceramic electrostatic chuck. Ceramic electrostatic chucks generally use materials such as alumina ceramic or aluminum nitride ceramic as the first insulating substrate. After a circuitized electrode layer is created on the first insulating substrate through printing, sputtering, or embedding, a non-circuited second insulating substrate is superimposed on the first insulating substrate with the printed circuitized electrode assembly, and then co-fired. The ceramic substrate and the metal electrode assembly have different coefficients of thermal expansion, which can easily lead to problems such as voids and deformation during medium- and high-temperature co-firing. Existing co-firing equipment for ceramic electrostatic chucks is relatively small, and other large-scale co-firing equipment for non-ceramic electrostatic chucks has excessively large chambers, making precise temperature profile management impossible. Therefore, current production processes and conditions cannot meet the requirements for large-area co-firing of ceramic electrostatic chucks.

[0005] Polyimide electrostatic chucks use a polyimide film as the first insulating layer and copper foil as the electrode assembly, which is sandwiched between the first and second insulating layers. They are laminated using a solid hot-melt adhesive. However, the low surface tension of the polyimide film prevents effective bonding with the adhesive. Furthermore, the adhesive releases gas upon heating, resulting in invisible air bubbles between the first and second insulating layers. In a high vacuum atmosphere, these bubbles expand under pressure, weakening the insulation of the electrode assembly and making it unable to withstand high frequencies and high voltages. While existing polyimide electrostatic chucks can meet the requirements for ODF liquid crystal drop-in in high-generation flat panel display cell assembly processes, they are easily damaged by CF and TFT glass during use, have a short lifespan, and are expensive. Summary of the Invention

[0006] To address the problems in related technologies, this invention proposes an electrostatic chuck and its preparation method, thereby solving the existing problems.

[0007] To achieve the above-mentioned technical objectives, the technical solution of the present invention is as follows:

[0008] An electrostatic chuck includes an adsorption layer comprising a dielectric layer and an insulating layer, the dielectric layer and the insulating layer being bonded together by an adhesive, a plurality of electrode groups being disposed between the dielectric layer and the insulating layer, a buffer layer being disposed at the lower end of the insulating layer, and a reinforcing substrate being disposed at the lower end of the buffer layer.

[0009] Furthermore, the dielectric layer and the insulating layer are polyimide films; the buffer layer is a structural layer with strong kinetic energy buffering and deformation recovery capabilities; and the reinforcing substrate is a structural layer with strong hardness and insulating properties.

[0010] Furthermore, the electrode assembly includes several electrode layers, with adjacent electrode layers bonded together by the adhesive, and the upper and lower surfaces of the electrode layers are two symmetrical corrugated surfaces.

[0011] Furthermore, the corrugated peaks and troughs of the two adjacent corrugated surfaces of two adjacent electrode layers are opposite each other.

[0012] A method for preparing an electrostatic chuck includes the following steps: S1, modifying the surface of the contact surface between the dielectric layer, the electrode assembly and the insulating layer by using a potassium permanganate solution of a certain proportion;

[0013] S2. A raw material adhesive solution containing one or more components of ethylene and vinyl acetate is obtained by a high temperature and high pressure method. An appropriate amount of organic or inorganic adhesive aids and modifying solvents that can provide adhesion and insulation strength are added to the raw material adhesive solution to obtain the adhesive.

[0014] S3. The dielectric layer (2) and the electrode assembly (3) are pre-composite by coating or spraying. Then, the dielectric layer (2) and the electrode assembly (3) are bonded in a vacuum hot pressing chamber by vacuum hot pressing. Then, the insulating layer (4) is bonded to the adhesive (5). Finally, the bonded body composed of the dielectric layer (2) and the electrode assembly (3) and the bonded body composed of the insulating layer (4) and the adhesive (5) are bonded together.

[0015] S4. The buffer layer and the reinforcing substrate are sequentially attached to the lower end of the insulating layer.

[0016] Furthermore, the vacuum atmosphere pressure range of the vacuum thermocompression chamber is -0.08 MPa to -0.8 MPa, the internal temperature is 200℃ to 280℃, and the pressing pressure ranges from 3 tons to 8 tons.

[0017] Furthermore, the thickness of the electrode layer is less than or equal to 0.02 mm, and the spacing between two adjacent electrode layers is less than or equal to 0.02 mm.

[0018] The beneficial effects of the present invention are: the electrostatic chuck of the present invention has strong design adaptability and can meet the cell assembly process of high-generation ultra-thin LCD panels; it reduces damage to the electrostatic chuck and improves its service life; and it reduces the cost of using the electrostatic chuck. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a cross-sectional view of an electrostatic chuck according to the present invention;

[0021] Figure 2 This is a cross-sectional view of the electrode assembly described in this invention;

[0022] Figure 3 This is a cross-sectional view of two adjacent electrode layers as described in this invention.

[0023] In the picture:

[0024] 1. Ultra-thin glass substrate; 2. Dielectric layer; 3. Electrode assembly; 3-1. Electrode layer; 3-1-1. Corrugated surface peaks; 3-1-2. Corrugated surface troughs; 4. Insulating layer; 5. Adhesive; 6. Buffer layer; 7. Reinforcing substrate. Detailed Implementation

[0025] 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0026] like Figure 1-3 As shown, an electrostatic chuck according to an embodiment of the present invention includes an adsorption layer, the adsorption layer including a dielectric layer 2 and an insulating layer 4, the dielectric layer 2 and the insulating layer 4 being bonded together by an adhesive 5, a plurality of electrode groups 3 being provided between the dielectric layer 2 and the insulating layer 4, a buffer layer 6 being provided at the lower end of the insulating layer 4, and a reinforcing substrate 7 being provided at the lower end of the buffer layer 6.

[0027] In one embodiment of the present invention, the buffer layer 6 may be made of polyurethane material and foamed to have strong kinetic energy buffering and absorption and deformation recovery capabilities. The substrate 7 may be made of aluminum alloy material and precision machined and surface oxidized to have strong hardness and certain insulation properties.

[0028] In one embodiment of the present invention, the dielectric layer 2 and the insulating layer 4 are mainly untreated polyimide films. A potassium permanganate solution of a certain proportion is used to modify the surface of the contact surfaces between the dielectric layer 2, the electrode assembly 3, and the insulating layer 4, thereby enhancing the adhesion properties of these contact surfaces.

[0029] In one embodiment of the present invention, a raw material adhesive solution containing one or more components of ethylene and vinyl acetate is obtained by a high-temperature and high-pressure method. An appropriate amount of organic or inorganic adhesive aids and modifying solvents that provide adhesion and insulation strength are mixed into the raw material adhesive solution to obtain adhesive 5. The dielectric layer 2 and electrode assembly 3 are pre-composite using a coating or spraying method. The dielectric layer 2 and electrode assembly 3 are then bonded together in a vacuum hot-pressing chamber using a vacuum hot-pressing method. The electrode assembly 3 is fabricated using etching or other methods to achieve the desired shape. Figure 2 The pattern structure shown has a thickness of less than or equal to 0.02 mm and a spacing of less than or equal to 0.02 mm. This pattern structure is called a bipolar structure or a Coulomb force electrostatic chuck. Then, the above bonding process is repeated on the insulating layer 4 and the adhesive 5, and then pre-bonded with the composite of dielectric layer 2 and electrode assembly 3 obtained in the above manner.

[0030] In one embodiment of this invention, a specified thickness is achieved through repeated processes such as adhesive bonding, vacuum lamination, and vacuum hot pressing. If the materials, adhesives, pressing sequence, thickness, and other conditions do not meet the aforementioned set values, problems such as decreased adsorption force, deformation, and deterioration of surface flatness will occur after disconnection from the power source. Furthermore, the vacuum atmosphere pressure is preferably set within the range of -0.08 to -0.8 MPa, the cavity temperature within the range of 200 to 280°C, and the pressing pressure within the range of 3 to 8 tons. If the vacuum atmosphere pressure, temperature, and pressing pressure are lower than the aforementioned set values, problems such as bubbles, delamination under vacuum, and deterioration of surface flatness will occur.

[0031] In one embodiment of the present invention, such as Figure 2-3The structure of the electrode assembly is shown. The electrode assembly 3 includes several electrode layers 3-1. Two adjacent electrode layers 3-1 are bonded together by an adhesive 5. The upper and lower surfaces of the electrode layers 3-1 are two symmetrical corrugated surfaces. The corrugated peaks 3-1-1 and corrugated troughs 3-1-2 of the two adjacent corrugated surfaces of two adjacent electrode layers 3-1 are opposite each other. The adhesive 5 is a hybrid thermosetting adhesive that can enhance the structural strength of the adsorption layer and meet the stability requirements under ultra-high vacuum, high frequency and high pressure conditions.

[0032] In one embodiment of this invention, the thickness of the adsorption layer obtained by the above method after processing is 0.1 mm to 0.3 mm. Such flexible materials cannot maintain a horizontal state without a supporting plane. Furthermore, the ultra-thin glass substrate 1 may be contaminated with foreign objects or experience changes in bonding pressure during the previous cutting process. Therefore, simply using the adsorption layer cannot achieve the adsorption and bonding functions of the ultra-thin glass substrate 1. This application selects a buffer layer 6 to enhance the buffering capacity of the adsorption layer. The buffer layer 6 is in the form of double-sided adhesive and is then bonded to the reinforcing substrate 7 to obtain a complete electrostatic chuck. This electrostatic chuck can, to a certain extent, overcome the problem of damage to the electrostatic chuck caused by localized stress due to foreign objects during the manufacturing process of the ultra-thin glass substrate 1, further reducing usage costs and increasing service life.

[0033] In practical use, the adsorption layer is provided with several through gas channels. The lower end of the gas channel is connected to a gas flow control unit in a vacuum chamber and is connected to a positive pressure gas source. The adsorption layer is also provided with several lifting device through holes. The adsorption layer is installed on the lifting device. The lifting device is connected to the lower drive power device, control unit, gas flow control unit, negative pressure gas source and other components. The ultra-thin glass substrate 1 is loaded to the set position. The lifting device extends out of the plane of the dielectric layer 2. The head of the lifting device is provided with a vacuum element. When it contacts the ultra-thin glass substrate 1, it starts negative pressure adsorption. The lifting device descends to make the ultra-thin glass substrate 1 contact the dielectric layer 2. The ultra-thin glass substrate 1 is adsorbed onto the dielectric layer 2 by the electrostatic force generated by the electrostatic chuck power supply applying a DC high voltage of opposite polarity at both ends of the adjacent electrode layers 3-1. The vacuum processing device completes the processing of the ultrathin glass substrate 1. The vacuum element at the head of the lifting device will contact the ultrathin glass substrate 1 and start negative pressure adsorption. At the same time, the opposite polarity DC high voltage is applied to both ends of the adjacent electrode layer 3-1 to release it. Under the action of the lifting device, the ultrathin glass substrate 1 completes the separation from the dielectric layer 2.

[0034] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an electrostatic chuck, characterized in that, The device includes an adsorption layer, which comprises a dielectric layer (2) and an insulating layer (4). The dielectric layer (2) and the insulating layer (4) are bonded together by an adhesive (5). Several electrode groups (3) are provided between the dielectric layer (2) and the insulating layer (4). A buffer layer (6) is provided at the lower end of the insulating layer (4). A reinforcing substrate (7) is provided at the lower end of the buffer layer (6). The electrode group (3) comprises several electrode layers (3-1). Two adjacent electrode layers (3-1) are bonded together by the adhesive (5). The upper and lower surfaces of the electrode layers (3-1) are two symmetrical corrugated surfaces. The corrugated peaks (3-1-1) and corrugated troughs (3-1-2) of two adjacent corrugated surfaces of two adjacent electrode layers (3-1) are opposite each other. The device includes the following steps: S1. The contact surfaces of the dielectric layer (2), the electrode group (3) and the insulating layer (4) are modified by using a potassium permanganate solution of a certain ratio; S2. A raw material adhesive solution containing one or more components of ethylene and vinyl acetate is obtained by high temperature and high pressure method. An appropriate amount of organic or inorganic adhesive aids and modified solvents that can provide adhesion and insulation strength are added to the raw material adhesive solution to obtain the adhesive (5). S3. The dielectric layer (2) and the electrode assembly (3) are pre-composite by coating or spraying. Then, the dielectric layer (2) and the electrode assembly (3) are bonded in a vacuum hot pressing chamber by vacuum hot pressing. Then, the insulating layer (4) is bonded to the adhesive (5). Finally, the bonded body composed of the dielectric layer (2) and the electrode assembly (3) and the bonded body composed of the insulating layer (4) and the adhesive (5) are bonded together. S4. The buffer layer (6) and the reinforcing substrate (7) are sequentially attached to the lower end of the insulating layer (4).

2. The method for preparing an electrostatic chuck according to claim 1, characterized in that, The dielectric layer (2) and the insulating layer (4) are polyimide films; the buffer layer (6) is a structural layer with strong kinetic energy buffer absorption and deformation recovery capabilities; the reinforcing substrate (7) is a structural layer with strong hardness and insulation properties.

3. The method for preparing an electrostatic chuck according to claim 1, characterized in that, The vacuum atmosphere pressure range of the vacuum thermocompression chamber is -0.08 MPa to -0.8 MPa, the temperature inside the chamber is 200℃ to 280℃, and the pressing pressure ranges from 3 tons to 8 tons.

4. The method for preparing an electrostatic chuck according to claim 1, characterized in that, The thickness of the electrode layer (3-1) is less than or equal to 0.02 mm, and the distance between two adjacent electrode layers (3-1) is less than or equal to 0.02 mm.

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