JPH0227748A - Electrostatic chucking device and forming method therefor - Google Patents

Abstract

PURPOSE:To reduce the thickness of the whole sheet and to enhance adhesive properties by forming an electrostatic chucking sheet of a laminate made of a first insulating layer, a first adhesive layer, an electrode layer, a second adhesive layer and a second insulating layer. CONSTITUTION:An electrostatic chucking sheet adheres to a metal board 6 through an adhesive layer 43. The sheet is of a laminate sequentially formed of a first insulating layer 31 having a face for placing an article to be attracted, a first adhesive layer 41, an electrode layer 5 for generating polarized charge on the face for placing the article to be attracted of the layer 31, a second adhesive layer 42, and a second insulating layer 32 with 30-40mum. Thermal conductive filler is dispersed in one or more of the layers 43, 41, 42. Thus, the thickness of the whole sheet is reduced to enhance its adhesive properties.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrostatic chuck device having an electrostatic chuck sheet attached thereto capable of holding a conductive material such as a semiconductor wafer in a vacuum, and a method for manufacturing the same.

Conventional technology In recent years, semiconductor manufacturing processes have rapidly become dryer.
In etching equipment, plasma CVD equipment, ion implantation equipment, etching equipment, electron beam lithography, X-ray lithography, etc., samples such as semiconductor wafers can be
Processing is often carried out in a vacuum of Pa or less. Conventionally, mechanical chucks and vacuum chucks have often been used to hold these samples, but mechanical chucks cannot hold the entire sample uniformly on the entire holder, and the sample There is a risk of damage, and there are disadvantages in that the temperature distribution on the sample surface cannot be made uniform. Further, since a vacuum chuck utilizes a pressure difference from atmospheric pressure, it cannot be used in a vacuum chamber. In addition, in ion beam etching equipment, magnetron reactive ion etching equipment, ion implantation equipment, plasma etching equipment, etc., the sample is exposed to high-speed ions, which causes the surface temperature to rise, causing thermal damage to resists, etc. was there. Furthermore, in plasma CVD equipment, the temperature of the sample has a strong influence on the production rate and properties of the produced film, and depending on the surface temperature distribution, there are adverse effects, making it impossible to perform stable processing with high precision. In many cases, it is essential to uniformly align the material.

Therefore, in order to hold the sample and holder thermally uniformly and reliably in a vacuum, an electrostatic chuck system that uses an electrostatic chuck sheet that utilizes electrostatic adsorption force is required!
is very advantageous. Such electrostatic chuck devices, as described for example in British Patent No. 1,443,215, have as their main part a generally flat electrically conductive support member coated with a layer of dielectric material. . This electrostatic chuck has a means for electrically contacting a wafer, which is an object to be attracted, so that a potential difference can be applied between the wafer and the support. This potential difference creates an electrostatic attraction between the dielectric layers, which supports the wafer substantially flat against the conductive layer. The wafer is adsorbed in the vacuum chamber as described above, and the surface farther from the support is irradiated with high-speed ions to be processed.

The third principle of generating electrostatic adsorption force in an electrostatic chuck device
In the figure, 5 is an electrode layer, 3 is an insulating layer,
1 is an adsorbed object (a sample made of a conductive substance), 9 is a DC power supply, and 8 is a switch.

In the above configuration, by grounding the attracting object 1 on the electrode layer 5 via the insulating layer 3 and turning on the switch 8, a voltage is applied between the electrode layer 5 and the attracting object 1 by the power source 9, Between the electrode layer 5 and the adsorbed object 1, the following formula (1) F(N) = 1/2 ・ego cl (V/d) ”
S...(1) (here, ε.=dielectric constant in vacuum,
εa=relative permittivity of the insulating layer 3, ■=voltage of the power supply 9, d: thickness of the insulating layer, S=area of the electrode layer 5).

Problem to be Solved by the Invention However, when processing is performed using a beam of high-velocity ions, thermal energy is generated within the wafer, but if the generated thermal energy is not easily dissipated, local This will cause expansion and deformation. Although electrostatic chucks such as those described in the above-mentioned British patent clamp the wafer very firmly, there is usually a dielectric layer between the wafer and the support. Generally speaking, the thermal conductivity of the dielectric material constituting the dielectric layer is not particularly high, and the dielectric layer required to generate the electrostatic attraction force does not allow effective heat flow toward the support than the wafer. However, it becomes a hindrance. In conventional electrostatic chuck devices, a means for cooling an object to be attracted is generally to forcibly cool a support such as a metal base by water cooling or the like. However, this method cannot provide sufficient cooling.

Therefore, with the conventional electrostatic chuck device, the surface temperature cannot be kept low and stable, and it has not been possible to sufficiently perform stable processing with high precision required as a state-of-the-art technology.

The present invention has been made in view of this serious problem.

Therefore, an object of the present invention is to improve the thermal contact property between an electrostatic chuck sheet and an object to be adsorbed, as well as the thermal value 4 property (heat dissipation property) of the electrostatic chuck sheet itself, and to improve the thermal property of the electrostatic chuck sheet itself. It is an object of the present invention to provide an electrostatic chuck device that controls the temperature rise of an adsorbed object to be as low as possible, improves the adsorption force, and enables stable processing with higher precision.

Means and Effects for Solving the Problems The present inventors have determined that in order to keep the temperature rise of non-adsorbed objects exposed to high-speed ions as low as possible, Focusing on the need to solve two problems: 1) lowering the contact thermal resistance between the object to be attracted and the electrostatic chuck sheet and improving thermal conductivity, and as a result of diligent efforts, the present invention was completed. I ended up doing it.

One of the electrostatic chuck devices of the present invention is formed by adhering an electrostatic chuck sheet to a metal base via an adhesive layer, and the electrostatic chuck sheet has a surface on which an object to be attracted is placed. A first insulating layer, a first adhesive layer, an electrode layer for generating polarized charges on the surface of the first insulating layer on which an object to be attracted is placed, a second adhesive layer, and a second insulating layer. The film thickness will be 30~40
It is characterized by being a laminate with zero tension.

FIGS. 1 and 2 are schematic diagrams of the electrostatic chuck device of the present invention, respectively. In FIG. a second insulating layer;
41 is a first adhesive layer, 42 is a second adhesive layer, 43 is an adhesive layer for bonding the electrostatic chuck sheet to a metal base (hereinafter referred to as the third adhesive layer), 5 is an electrode layer, 6 is gold I
a substrate, 7 is a gap, and 10 is the inside of a vacuum chamber.

In FIG. 2, an adhesion improving layer is provided on the first insulating layer. Since the back surface of the object to be attracted has unevenness (depending on the type of wafer, unevenness of around 1- to 7-position is observed), when electrostatically adsorbed, in the normal case, the first insulating layer A gap 7 as shown in FIG. 1 is created between the adsorbent and the back surface of the adsorbed object, and in a vacuum, since there is no air in this gap, it effectively becomes a heat insulating part and has a significantly increased thermal resistance. Therefore, it is preferable to provide an adhesion-improving layer to prevent the formation of such voids.The adhesion-improving layer should be as thin as possible within the thickness range of 3 to 100 mm depending on the condition of the back surface of the object to be adsorbed. It is formed by coating or bonding and curing. In detail, the elastic modulus is 1 to 10,00
It is effective to use rubber-based or silicone-based materials within the range of 0 hg/-. This adhesion improving layer has
A highly thermally conductive filler may be blended.

First and second insulation! f131.32 is made of a material with excellent reliability such as heat resistance and voltage resistance. As is clear from the above equation (1), the electrostatic adsorption force is caused by the insulating layers 31, 32.
The thickness has a big influence. Therefore, by making the thickness as thin as possible within a range that can sufficiently withstand the voltage V applied between the electrodes, we have developed a highly heat resistant material with excellent withstand voltage characteristics, which makes it possible to improve the electrostatic adsorption force. It is necessary to use plastic film. From this point of view, in the present invention, it is preferable to use a thin polyimide film having a thickness of 5 to 75 cm or a plastic film having heat resistance of 150° C. or more.

As the polyimide film, for example, Kapton (Ka
lltQn (manufactured by DuPont), Avical (manufactured by Kanebuchi Chemical Industries, Ltd.), Ubilex (manufactured by Ube Industries, Ltd.), Nimitsu (manufactured by Nitto Electric Industries, Ltd.), Suberiofilm (manufactured by Mitsubishi Plastics, Inc.), etc. In addition, examples of plastic films that are heat resistant to 150°C or higher include fluororesins (fluoroethylene-propylene copolymer, etc.), polyether sulfone, polyether ether ketone, stretched polyethylene terephthalate,
Stretched polystyrene, polycarbonate, oriented nylon,
Examples include hardened polyvinyl chloride, stretched polypropylene, cellulose triacetate, and silicone rubber.

In addition, alumina, zirconium fluoride,
It is effective to use a filler with high thermal conductivity such as boron nitride with a particle size of 5a+ or less dispersed in a solid content ratio of 20 to 70%, but contrary to the effect of thermal conductivity, the withstand voltage characteristics Therefore, sufficient consideration must be given to this point when using the product.

For the first and second contact layers, an adhesive with excellent adhesive strength and heat resistance for both the insulating layer and the F4 pole layer is required, and a thermosetting or two-component curing adhesive is used. For example, adhesives such as polyester, polyurethane, polyimide, epoxy, and modified polyamide are effective.
These adhesives can be used alone or in mixtures.

In the present invention, these first and second adhesive layers include:
It is more effective to use a filler such as alumina, zirconium nitride, boron nitride, silica, etc., which has a particle size of 5a or less and is dispersed in a solid content ratio of 5 to 80%, which can improve thermal conductivity.

The thickness of the adhesive coating film is suitably 3 to 30 .mu.m to maintain adhesive strength, and the thickness is preferably 5 to 10 .mu.m from the viewpoint of processability. Since voltage resistance is ensured by the first and second insulating layers, the thickness of the first and second adhesive layers can be made any thinner as long as the adhesive strength is not insufficient.

As the electrode layer, copper foil with a film thickness of 50 chains or less is usually used, but other metal foils such as NL, Cr, Fe, A1, etc. may also be used, and in some cases, metal foils processed by metal vapor deposition may be used, or conductive foils may be used. It can also be used even if it has been coated with a synthetic paint. , Ip
For L foils, those with a thickness of around 201 mm have the best workability.

Furthermore, in order to prevent discharge from occurring, the electrode layer is preferably sealed by the first and second adhesive layers so that its edges are not exposed to the outside.

The electrostatic chuck sheet having the above-mentioned layer structure is adhered to the metal substrate by the third adhesive layer, and the same adhesives as those for the above-mentioned first and second adhesive layers can be used. . In addition, it is preferable to add a filler to this adhesive layer for the purpose of increasing thermal conductivity.The thickness of the adhesive layer formed between the electrostatic chuck sheet and the metal base is 3 to 30 mm. Preferably within the range of captivity.

In the present invention, the electrostatic chuck sheet to be adhered onto the metal substrate must have a total film thickness of 30 to 400 m, preferably 80 to 150 m. When the thickness becomes thinner than 30 mm, problems arise in terms of workability, and when it becomes thicker than 400 mm, the temperature rises rapidly and the wafer surface temperature becomes high.

In the electrostatic chuck device of the present invention, one or more of the first adhesive layer, the second four contact layers, and the third adhesive layer include:
It is preferable that a thermally conductive filler is dispersed therein, and a thermally conductive filler can also be dispersed in the adhesion improving layer. Ideally, these thermally conductive fillers have a particle size of 2 or less, and if the coating film has a thickness of 201 or more, particles with a particle size of up to 10 m can be used. Examples of materials that can be used for the adhesion improving layer include ZrBz, TiB2, B
N, VB2, Ti N, W2 BS, LaBa, M
o5iz, Al2O5, BeO, crystal poron nitride (C-BN) SiO□, diamond, etc.
This is effective in terms of plasma resistance.

Fillers that can be used in the first adhesive layer, second adhesive layer, and third adhesive layer include Cu, A1.
Examples include fine metal powders such as Ag, Cr, Ni, Sn, and others.

In the present invention, for the purpose of improving thermal conductivity, a certain pattern of cooling gas passages is provided on the surface of the electrostatic chuck sheet, and low-pressure inert gas such as N, He, Ne, etc. It is preferable because it is filled with or passes through.

Next, a method for manufacturing the electrostatic chuck device of the present invention will be explained. First, a curable adhesive is applied to a plastic film having 111 thermal properties, a metal foil is bonded thereto, and then a curing treatment is performed. Next, on the bonded metal foil surface,
The resist films are laminated together and subjected to pattern exposure, development, etching, washing, and drying to form a predetermined shape @f!
form a layer.

A heat-resistant plastic film coated with a curable adhesive is bonded to the etched metal foil surface, and a laminate sheet is created by performing a curing process. The created laminated sheet is punched out according to the shape of the metal base to create an electrostatic chuck sheet.Next, a curable adhesive is applied onto the metal base to form the electrostatic chuck sheet created above. An electrostatic chuck device can be created by bonding them together and curing them.

Examples Next, the present invention will be explained by examples and ratio examples. Note that all parts are based on weight.

Example 1! 25a+ thick polyimide film (Ubilex 2
5S (manufactured by Ube Industries, Ltd.) to a thickness of 10 tIM, a first adhesive layer adhesive having the following composition was applied to
It was dried at 0°C.

Polyamide resin (Platabonta M-995, manufactured by Nippon Rilsan Co., Ltd.) 445.2 parts High-purity epoxy resin (Epicote YL979, manufactured by Yuka Shell Co., Ltd.) 222.6 parts Novolac phenol resin (Tamanol 752, manufactured by Arayo Kagaku Co., Ltd.) (Crosslinked) agent) 111.3 parts Dicyandiamide (manufactured by Wako Pure Chemical Industries, Ltd.) (Crosslinking accelerator) 0.57 parts After drying, electrolytic copper foil (1/202, manufactured by Nippon Mining Co., Ltd.) was laminated to 40 to 16 (1"C) The step curing process was performed for 24 hours until the negative photosensitive film (02^■EC-
T538 (manufactured by Hoechst Japan) was attached to the copper foil side. An electrode of a predetermined shape was formed by a procedure of exposure, development, etching, washing, and drying.

On the other hand, another polyimide film (Ubilex 25S
) was coated with a second adhesive layer adhesive having the same composition as above, bonded to the patterned electrode surface formed above, and cured in the same manner. The total thickness of the obtained laminated sheet was 100 μm. This laminated sheet is molded to match the dimensions of the metal base, bonded to the At base using the same adhesive as above, and cured in the same manner as above to create an electrostatic chuck device. did.

Comparative Example 1 The same procedure was carried out except that a 50-thick polyimide film (Upilex 50S) was used instead of the polyimide film (Ubilex 25S) used in Example 1, and the thickness of the adhesive layer was 20 m. An electrostatic chuck device was created. In this case, the total thickness of the laminated sheet was 180 mm.

Using the electrostatic chuck devices of Example 1 and Comparative Example 1, wafers were subjected to plasma etching treatment in a vacuum of I Pa, and the surface temperatures of the wafers were compared.

In this case, the At substrate was forcedly cooled to 5°C by water flow,
The sheet surface of the electrostatic chuck device was heated to 20°C.

As a result of the test, when 10 wafers were processed, Example 1
In the case of , the wafer surface temperature remained at 75°C, but in the case of Comparative Example 1, it rose to 80 to 90°C.

Example 2 An electrostatic chuck sheet with a thickness of 100 mm was prepared in the same manner as in Example 1, and a rubber adhesive having the following composition, which is elastic at room temperature and has low tackiness, was applied to the top surface to a thickness of 6 mm. After drying at 120℃ for 15 minutes, 150℃
Cure treatment was performed for 3 hours to form an adhesion improving layer for improving adhesion to the adsorbed object. The total thickness of the obtained electrostatic chuck sheet was 109a''C''.

100 parts of acrylonitrile-butadiene rubber (Tubol 1001, manufactured by Nippon Seon Co., Ltd.) 5 parts of sodium dimethyldithiocarbamate (Accel SOD, manufactured by Kawaguchi Chemical Industries, Ltd.) (vulcanizing agent) 5 parts The obtained electrostatic chuck sheet was prepared in Example 1. Similarly, At
An electrostatic chuck device was created by bonding it to a substrate, and a similar test was conducted. As a result, the wafer surface temperature was 50 to 6
It was confirmed that the temperature could be kept to a low temperature of 0°C.

Example 3 Instead of the adhesion-improving layer in Example 2, a paint with the following composition in which a highly thermally conductive filler was mixed and dispersed in adhesive liquid silicone rubber was applied to a thickness of 6 mm, and dried at 150°C. After that, it was cured at 150° C. for 3 hours, and an electrostatic chuck sheet was produced in the same manner.

Liquid silicone rubber (5E3221, manufactured by Toshiba Silicone Co., Ltd.) 100 parts Zirconium fluoride (F type, manufactured by Nihon Shinkinzoku Co., Ltd., particle size 2-3s) 50 parts Toluene
120 copies of the obtained electrostatic chuck sheet were bonded to an A1 substrate in the same manner as in Example 1 to create an electrostatic chuck device and tested in the same manner. As a result, an effect of lowering the wafer surface temperature by 2 to 3° C. compared to the case of Example 2 was observed. Furthermore, since zirconium hydride was added, it was possible to prevent the adhesion of the liquid silicone rubber from being too good, and it was possible to obtain an appropriate adhesion.

Example 4 In the layer structure in Example 2, paints with the following composition in which a thermally conductive filler was added and dispersed were used as the adhesive layers above and below the electrodes, that is, the first and second adhesive layers, each having a thickness of 61 mm. The sheets were coated, dried at 170°C, bonded together, and step-cured at 40 to 160°C for 24 hours to produce an electrostatic chuck sheet in the same manner as in Example 1.

Polyamide resin (1 Latabonda M-995, manufactured by Nippon Rilsan Co., Ltd.) 445.2 parts High purity epoxy VI4 (Epicote YL979, manufactured by Yuka Shell Co., Ltd.) 222.6 parts Novoladzuku phenol resin (Tamanol 752, manufactured by Arayo Kagakusha Co., Ltd.) (Crosslinking agent> 111.3 parts Dicyandiamide (manufactured by Aiko Pure Chemical Industries, Ltd.) (Crosslinking accelerator> 0.57 parts Zirconium hydride (E type, manufactured by Nippon Shinkinzoku Co., Ltd., particle size 2-3) 780 parts Toluene 400 parts IPA
400 copies of the obtained electrostatic chuck sheet were bonded to an AI substrate in the same manner as in Example 1 to create an electrostatic chuck device and tested in the same manner. As a result, actually! The effect of lowering the wafer surface temperature by 4 to 5°C was observed compared to the case of Example 1 and 2.

Effects of the Invention According to the present invention, the entire thickness of the electrostatic chuck sheet can be made as thin as possible to the extent that the properties in use are not impaired, and the close contact between the object to be attracted and the surface of the electrostatic chuck sheet can be reduced. I can store up my sexuality.

Therefore, according to the present invention, the temperature rise of the object can be reduced by 6
The temperature can be controlled at a low temperature of 0 to 80°C or less, and the surface temperature increases when the adsorbed object is exposed to high-speed ions through ion beam etching, magnetron reactive ion etching, plasma etching, ion implantation, etc. It is possible to prevent thermal damage to the resist and the like.

Furthermore, when a highly thermally conductive filler is dispersed and mixed, the overall thermal conductivity of the electrostatic chuck device is greatly improved, and as a result, the surface temperature of the adsorbed object exposed to high-speed ions can be lowered by 60°C. It is possible to maintain an unprecedentedly low temperature below ℃. Therefore, microfabrication of the adsorbed object can be performed stably with high precision and high unidirectionality. Furthermore, since the thickness of the insulating layer on which the object to be attracted is placed is reduced to near the limit of breakdown voltage, the electrostatic attraction force can be increased accordingly. Therefore, the electrostatic chuck device of the present invention can also be applied to general applications where the object to be attracted does not cause thermal problems.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of an example of the electrostatic chuck device of the present invention, FIG. 2 is a schematic sectional view of another example of the electrostatic chuck device of the present invention, and FIG. 3 is a schematic sectional view of an example of the electrostatic chuck device of the present invention. FIG. 2 is an explanatory diagram illustrating the principle of generation of electrostatic force. DESCRIPTION OF SYMBOLS 1... Adsorption object, 2... Adhesion improvement layer, 3... Insulating layer, 31... First insulating layer, 32... Second insulating layer, 41... First adhesive layer, 42... second adhesive layer, 43... third adhesive layer, 5... electrode layer, 6...
Metal base, 7... void, 8... switch, 9...
DC power supply, 10... Inside the vacuum chamber. Patent Applicant Tomoekawa Paper Mills Co., Ltd. Representative Patent Attorney Tsuyoshi Fuchibe Figure 1 1 Side 10 Figure 2

Claims (5)

[Claims] (1) An electrostatic chuck sheet is bonded onto a metal base via an adhesive layer, and the electrostatic chuck sheet includes a first insulating layer having a surface on which an object to be attracted is placed, a first A film with a thickness of 30 mm formed by sequentially laminating an adhesive layer, an electrode layer for generating polarized charges on the surface of the first insulating layer on which the object to be attracted is placed, a second adhesive layer, and a second insulating layer. An electrostatic chuck device characterized in that it is a laminate of ~400 μm. (2) A thermally conductive filler is dispersed in one or more of the adhesive layer, the first adhesive layer, and the second adhesive layer for bonding the electrostatic chuck sheet to the metal base. The electrostatic chuck device according to claim 1. (3) An electrostatic chuck sheet is bonded onto a metal base via an adhesive layer, and the electrostatic chuck sheet has an adhesion improving layer for placing an object to be attracted, and a first insulating layer. , 1st
A laminate with a film thickness of 30 to 400 μm consisting of an adhesive layer, an electrode layer for generating polarized charges on the surface of the first insulating layer on which an object to be attracted is placed, a second adhesive layer, and a second insulating layer. An electrostatic chuck device characterized by being a body. (4) A thermally conductive filler is dispersed in one or more of the adhesive layer, the first adhesive layer, and the second adhesive layer for bonding the electrostatic chuck sheet to the metal base. The electrostatic chuck device according to claim 3, characterized in that: (5) A step of applying a curable adhesive to a heat-resistant plastic film, bonding it with metal foil, and then performing a curing process, bonding a resist film to the metal foil surface, and performing pattern exposure. A process of developing and performing an etching process, a process of bonding a heat-resistant plastic film coated with a curable adhesive to the etched metal foil surface and performing a curing process, and a process of attaching the formed laminate sheet to the metal foil. It consists of a process of forming an electrostatic chuck sheet by punching according to the shape of the base, and a process of applying a curable adhesive to the metal base, bonding the electrostatic chuck sheet, and curing it. A method for creating an electrostatic chuck device characterized by: