JP2002151582A - Two-pole electrostatic chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-pole electrostatic chuck capable of improving largely its dielectric strength. SOLUTION: The two-pole electrostatic chuck is fabricated by using a metal plate equally halved by an insulator in equal areas as its seatings and at the same time as its two electrodes and then, by forming insulation films by thermal spraying on the surfaces of the electrodes. That is, such a metal plate as an aluminum plate is so halved as to make equal to each other the areas of the halved right and left metal plates, and the insulator is bonded or joined by a bonding agent or a brazing to the clearance between the divided portions. Alternatively, after so halving a metal plate in a concentrically circular way as to make equal to each other the areas of the halved metal plates, an insulator is so fitted into the clearance between the divided portions as to subject it to a shrinkage fitting. Hereupon, the thickness of the insulator is 0.2-2 mm. The roughness of the surface of the electrode is made not smaller than 5 μm in Rmax, and the material of the electrode can be allowably a metal-ceramics composite material obtained by mixing compositely the powder of a ceramics with a metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrostatic chuck, and more particularly, to a bipolar electrostatic chuck.

[0002]

2. Description of the Related Art Electrostatic chucks have recently been widely used as components for semiconductor manufacturing equipment and the like. The reason is that, compared with mechanical chucking and vacuum chucks, advantages such as less dust generation and use even in vacuum have been recognized.

[0003] This electrostatic chuck is classified into a monopolar type and a bipolar type. Of these, an insulating film is formed on the surface of a metal pedestal by thermal spraying, an electrode is formed on the upper surface by thermal spraying, and an insulating film is further formed on the upper surface by thermal spraying. There is a bipolar electrostatic chuck that forms a film. However, this bipolar electrostatic chuck has a problem in that many pores remain in the sprayed insulating film, so that the insulating film causes dielectric breakdown. For this reason, sealing treatment has been performed from the surface of the upper insulating film to the inside with a resin such as epoxy to improve the insulation resistance.

[0004]

However, in this bipolar electrostatic chuck, the insulating film-electrode-insulating film and the sprayed portion are three layers thick, so that the sealing material such as epoxy reaches the lower insulating film. Therefore, there has been a problem that the dielectric breakdown cannot be suppressed and the insulation resistance cannot be greatly improved.

In order to solve this problem, first, a sealing treatment is applied to an insulating film formed below, a sealing treatment is also applied to the formed electrode, and a sealing treatment is further applied to the upper insulating film formed last. Although it is conceivable to perform a sealing treatment for each layer that is to be treated, since the surface of the sprayed film subjected to the sealing treatment becomes extremely smooth in this method, the sprayed film applied to the upper portion is applied to the lower sprayed film. There is a problem that it is difficult to adhere.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of a bipolar electrostatic chuck for forming an insulating film by thermal spraying, and has as its object to provide a bipolar electrostatic chuck capable of greatly improving insulation resistance. It is to provide a chuck.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have divided a metal plate into two parts of the same area with an insulator, and made the divided metal plate into a pedestal. With two electrodes, the insulating film needs to be formed only on the pedestal, that is, only one layer on the upper surface of the electrode. Therefore, the present inventors completed the present invention by finding that a bipolar electrostatic chuck capable of greatly improving the insulation resistance was obtained. I came to.

That is, the present invention provides (1) an insulating material having the same area
A bipolar electrostatic chuck (Claim 1), characterized in that the divided metal plate is used as a pedestal and two electrodes are formed at the same time, and an insulating film is formed on the electrode surface by thermal spraying.
(2) The method of dividing the metal plate into two parts by an insulator is a method of first dividing the metal plate into two equal parts on the left and right sides, and bonding or joining the insulator to the gap between the divided parts with an adhesive or a brazing material. The bipolar electrostatic chuck according to claim 1, wherein (3) the metal plate is made of an insulating material.
The dividing method is to first divide the metal plate into two parts concentrically and to have the same area, and to make the inner divided metal plate a metal plate having a smaller thermal expansion coefficient than the outer metal plate. 2. The bipolar electrostatic capacitor according to claim 1, wherein an insulator having a larger coefficient of thermal expansion than the inner metal plate and a smaller coefficient of thermal expansion than the outer metal plate is inserted into the gap and shrink-fitted. A chuck (claim 3);
(4) The bipolar electrostatic chuck (Claim 4) according to any one of claims 1 to 3, wherein the thickness of the insulator of the divided portion is 0.2 to 2 mm, and (5) the electrode. 5. The bipolar electrostatic chuck according to claim 1, wherein the surface roughness of the bipolar chuck is 5 μm or more in Rmax (Claim 5). (6) The electrode is a composite of ceramic powder and metal. The gist is a bipolar electrostatic chuck according to any one of claims 1 to 5, wherein the chuck is made of a metal-ceramic composite material.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. First, a metal plate having a predetermined size, shape and thickness, for example, a metal plate made of aluminum or an aluminum alloy is prepared. The metal plate is divided into two equal areas on the left and right. An insulator such as alumina is fitted into the gap between the two divided parts, and the two parts are electrically insulated to the left and right by bonding or brazing by heating or the like with an adhesive or brazing material.

Next, as another method for dividing the metal plate into two parts, first, the metal plate is divided into two concentric circles having the same area. The inner metal plate divided into two is a metal plate having a smaller thermal expansion coefficient than the outer metal plate. Then, an insulator having a larger coefficient of thermal expansion than the inner metal plate and a smaller coefficient of thermal expansion than the outer metal plate is fitted into the gap between the inner metal plate and the outer metal plate, and the concentric circle is formed by shrink fitting the insulator. It is divided into two parts electrically insulated.

[0011] The thickness of the insulator fitted into the divided portions is preferably 0.2 to 2 mm, and the thickness of the insulator is 0.1 mm.
If it is thinner than 2 mm, it is difficult to make it electrically insulated. On the other hand, if it is thicker than 2 mm, it becomes difficult for the sprayed film to adhere, and the portion where the attraction force is not generated becomes too large. This is the same area 2
This means that two electrodes serving as the divided pedestals have been manufactured.

The surface of the electrode thus obtained is ground with a diamond grindstone or the like so that the surface roughness is 5 μm or more in Rmax. The surface roughness of the electrode is preferably as rough as possible within a range that does not adversely affect the insulating film formed on the upper surface, and more preferably 10 μm or more in Rmax. When the surface roughness Rmax is smoother than 5 μm, the sprayed film formed on the upper surface is hard to adhere.

An insulating film made of, for example, alumina or the like is formed on the surface of the electrode by plasma spraying or the like. The thickness of the insulating film may be about 0.3 to 0.6 mm. Thus, a bipolar electrostatic chuck is manufactured. Since only one insulating film is thus formed, even if a sealing process is performed on this surface, the sealing material sufficiently spreads over the pores of the insulating film. A bipolar electrostatic chuck having greatly improved insulation resistance is obtained.

If the pedestal, ie, the electrode is made of a metal-ceramic composite material in which ceramic is combined with metal instead of metal, the electrode is of course an electrode because it has the same electrical conductivity as metal. In addition, since the coefficient of thermal expansion can be controlled by controlling the content of the ceramic powder, it can be adjusted to the coefficient of thermal expansion of the insulating film, and has higher rigidity and heat resistance than metal. The improvement results in a bipolar electrostatic chuck that is even better than an electrostatic chuck made of metal.

[0015]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples of the present invention and Comparative Examples.

Example 1 (1) Production of Bipolar Electrostatic Chuck After cutting an aluminum plate of φ200 × 2 mm into a semicircle so as to have the same area, a 1 mm thick aluminum plate was cut between the cut surfaces of the aluminum plate. An alumina plate was fitted, and the aluminum plate and the alumina plate were joined by brazing with an Ag-Cu-Ti composition braze to produce an electrode divided into two parts on the left and right.

The surface of the obtained two electrodes is defined as a surface roughness Rm.
Grinding was performed by surface grinding so that ax became 7 μm. An alumina film was plasma-sprayed to a thickness of 500 μm on the ground surface. After sealing this alumina film with a SiO ₂ -based sealing material, the surface of the alumina film is made to have a thickness of 300 mm.
Polishing was performed to a thickness of μm to produce a bipolar electrostatic chuck.

(2) Evaluation After applying voltages of different polarities to the obtained electrostatic chuck to attract the silicon wafer, the applied voltage was increased to 3 kV to determine whether the alumina film was broken or not. Was examined by law. Table 1 shows the results.

(Examples 2 and 3) An electrostatic chuck was prepared and evaluated in the same manner as in Example 1 except that the thickness of the alumina plate and the surface roughness of the electrode were set forth in Table 1. Table 1 also shows the results.

Example 4 A metal-ceramic composite material having a thermal expansion coefficient of 6.2 × 10 ⁻⁶ / ° C. and a diameter of 140 × 10 mm (SiC powder 70% by volume, aluminum alloy 30% by volume), and having an outer diameter of 141.5 mm and an inner diameter of 139.5 having a thermal expansion coefficient of 8.0 × 10 ⁻⁶ / ° C.
Amm and 10 mm thick alumina is fitted in an environment of 100 ° C., and the outer diameter of the outer diameter is further 200 mm and the inner diameter is 141 mm having a thermal expansion coefficient of 10.5 × 10 ⁻⁶ / ° C.
10 mm thick metal-ceramic composite material (Si
C powder 55% by volume and aluminum alloy 45% by volume) were similarly fitted in an environment of 100 ° C., cooled, and shrink-fitted to produce electrodes concentrically divided into two. The surface of the electrode was ground so that the surface Rmax became 10 μm as in the example, and an alumina film was plasma-sprayed to a thickness of 500 μm on the ground surface as in the example 1. After sealing the alumina film with an epoxy-based sealing material, the surface of the alumina film was 300 μm thick as in Example 1.
Then, a polishing process was performed to obtain a bipolar electrostatic chuck, which was evaluated in the same manner as in Example 1. Table 1 shows the results.
Shown in

(Comparative Example) For comparison, in Comparative Example 1, a conventional bipolar electrostatic chuck was manufactured and evaluated. The manufacturing method is as follows. An alumina film having a thickness of 300 μm is formed on the upper surface of an aluminum plate of φ200 × 2 mm by plasma spraying, a mask is formed on the upper surface, and a tungsten film as an electrode is formed on the upper surface by plasma spraying. After forming an alumina film having a thickness of 500 μm on the upper surface by plasma spraying and then performing a sealing treatment from the upper portion with an epoxy sealing material, polishing processing so that the thickness of the upper alumina film becomes 300 μm. Thus, an electrostatic chuck was produced, and evaluated in the same manner as in the examples. Table 1 also shows the results.

[0022]

[Table 1]

As is clear from Table 1, all of the examples are 3
Even when a voltage as high as kV was applied, the dielectric breakdown of the alumina film did not occur. When the alumina film was observed by SEM,
The sealing material was widespread in all the examples in the alumina film, and it is considered that this did not result in dielectric breakdown. This indicates that the present invention can greatly improve the insulation resistance of the electrostatic chuck.

On the other hand, in Comparative Example 1, the dielectric breakdown of the alumina film occurred at a voltage of 1.2 kV. When the alumina film was observed by SEM in the same manner as in the example, it was considered that the sealing material did not spread over the alumina film on the upper part of the aluminum plate, which caused the insulation resistance to be much lower than in the example.

[0025]

As described above, with the bipolar electrostatic chuck according to the present invention, even if it is a bipolar electrostatic chuck in which an insulating film is formed by thermal spraying, an electrostatic chuck capable of greatly improving the insulation resistance can be obtained. Can be used as a chuck. As a result, an electrostatic chuck that does not cause dielectric breakdown of the insulating film can be obtained, and its use in fields such as semiconductor and flat panel display manufacturing apparatuses can be greatly expected in the future.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomoyuki Ogura 2-4-2 Daisaku, Sakura City, Chiba Pref. Central Research Institute of Pacific Cement Co., Ltd. (72) Inventor Tatsuya Shiogai 2-4 Daisaku, Sakura City, Chiba Pref. 2 Pacific Cement Co., Ltd. Central Research Laboratory F-term (reference) 5F004 BB22 5F031 HA02 HA03 HA10 HA18 5F045 EM05

Claims (6)

[Claims] 1. A bipolar electrostatic chuck characterized in that a metal plate divided into two parts of the same area by an insulator is used as a pedestal and two electrodes are formed at the same time, and an insulating film is formed on the surface of the electrodes by thermal spraying. . 2. A method of dividing a metal plate into two parts by using an insulator. First, the metal plate is divided into two equal parts on the left and right sides, and an insulator is bonded or joined to a gap between the divided parts with an adhesive or a brazing material. The bipolar electrostatic chuck according to claim 1, wherein: 3. A method of dividing a metal plate into two parts by using an insulator. First, the metal plate is concentrically divided into two parts having the same area, and the inner metal plate divided into two parts has a higher thermal expansion coefficient than the outer metal plate. A metal plate with a smaller thermal expansion coefficient than the inner metal plate and a smaller thermal expansion coefficient than the outer metal plate in the gap between the divided parts, and shrink-fit it. The bipolar electrostatic chuck according to claim 1, wherein: 4. The thickness of the insulator at the divided portion is 0.2 to 0.2.
4. The bipolar electrostatic chuck according to claim 1, wherein the diameter is 2 mm. 5. The electrode has a surface roughness of 5 μm in Rmax.
5. The bipolar electrostatic chuck according to claim 1, wherein the distance is at least m. 6. The bipolar electrostatic chuck according to claim 1, wherein the electrode is made of a metal-ceramic composite material in which metal is mixed with ceramic powder.