JPH0636583Y2 - Electrostatic chuck - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrostatic chuck used for holding a sample in a semiconductor manufacturing apparatus, for example.

[Prior art]

As an electrostatic chuck using electrostatic attraction, a metal plate electrode that is a conductor is embedded inside a disk-shaped ceramic (Al ₂ O ₃ ) that is an insulator (hereinafter referred to as an embedded type),
It is known that a polyimide film, which is an insulator, is attached to the surface of a metal disk electrode, which is a conductor, with an adhesive (hereinafter referred to as a coating type). The two electrostatic chucks will be described below.

FIG. 3 is a schematic vertical cross-sectional view of the buried type. A disk-shaped insulator 32 includes a metal plate electrode 31 integrally molded in the vicinity of its surface (upper surface) during ceramic firing, and the electrode 31 is On the back side of the central part, the threaded part 33
The other end of the terminal 33 having a is inserted into the insulator 32 and connected by brazing, and the end of the terminal 33 having the screw portion 33a is connected to a power source (not shown) that applies a voltage to induce an electrostatic force. To be done.

An insulating cylinder 34 having a flange portion 34a at its lower end is fitted around the periphery of the terminal 33 immediately below the back surface of the insulator 32 to the substantially central portion of the screw portion 33a. Flange portion 34a of the insulating tube 34
A water cooling jacket 35 having a through hole 35a therein is fitted on the outer periphery of the upper part and the periphery of the lower half of the insulator 32 to allow water to flow therethrough for cooling. The insulating cylinder 34 and the water cooling jacket 35 are tightly held by the insulator 32 by screwing a nut 36 onto the threaded portion 33a of the terminal 33 and tightening the nut 36.

On the other hand, FIG. 4 is a schematic vertical sectional view of the above-mentioned coating type, in which a film thickness of about 50 μm is formed as an insulating film on the surface (upper surface) of the metal disc electrode 41.
Polyimide film 40 of m is attached with an adhesive, and electrode 41
A film-like insulating film 42 is coated on the surface of the lower half of the film. The electrode 41 has a columnar shape on the back surface side of the central portion thereof and has an insulating film 42 at the other end of the terminal 43 having a threaded portion 43a at one end.
The end portion of the terminal 43 having the threaded portion 43a is connected to a power source (not shown) that applies a voltage to induce an electrostatic force. Other devices are the same as those of the buried type, so the same reference numerals as in FIG.

[Problems to be solved by the invention]

In the conventional buried type as described above, because of the structure in which the metal electrode 31 of a different material is placed inside the ceramic insulator 32, firing cracking occurs due to the difference in expansion coefficient between the ceramic and the metal during firing of the ceramic, It is difficult to secure the flatness and surface roughness of the surface of ceramics (hereinafter referred to as the adsorption surface) that causes a decrease in yield and electrostatically adsorbs. Also, in order to increase the adsorption force, the adsorption surface is ground after the ceramics are fired. However, it is difficult to set the thickness from the adsorption surface to the electrode to a desired value. In addition, there is a problem that ceramic cracks occur during heating of the terminal 33 and the electrode 31 during brazing, resulting in poor contact between the terminal and the electrode due to imperfect brazing.

On the other hand, in the coating type, the number of manufacturing steps is reduced as compared with the embedded type due to the structure in which the polyimide film 40 is attached to the metal disk electrode 41 with an adhesive, but the film surface is flattened when the polyimide film is bonded. However, a gap is formed between the adsorbate that is electrostatically adsorbed on the polyimide film and the polyimide film (hereinafter, also referred to as an adsorbing surface like the embedded type), and the adsorbing power is low. Moreover, since the upper limit of the heat resistant temperature of polyimide is around 200 ° C., electrostatic adsorption under high temperature conditions is difficult, and the life of the polyimide film is short.

The present invention has been made in view of such circumstances, and its purpose is to reduce the number of manufacturing steps, improve the suction force and the insulating property, and improve the heat resistance and durability of the suction surface. An object is to provide an electrostatic chuck in which the contact between the electrode and the electrode is strong.

[Means for solving problems]

In the electrostatic chuck according to the present invention, a conductor is coated with an insulating film, and a DC voltage is applied between an object to be attracted and the conductor,
In an electrostatic chuck for adsorbing an object to be adsorbed on the insulating film, a film formed by ceramic spraying, which covers the entire surface of the conductor surface except the connection portion with a terminal to which a DC voltage is applied. It is characterized by comprising an insulating film having a thickness of 100 to 500 μm.

[Action]

According to the present invention, the insulating film is formed by ceramic spraying, and since it covers the entire surface of the conductor except the connecting portion between the conductor and the terminal, it is seamless and can be used in plasma or DC voltage. In addition, the leakage current is extremely small even when a high-frequency voltage is applied, and it is also possible to integrally attach it to the outer peripheral surface of the connection part between the conductor and the terminal by thermal spraying, which strengthens the connection part itself. Moreover, since there is no need for masking, the number of steps can be greatly reduced.

The reason why the thickness of the insulating film is 100 to 500 μm is as follows. That is, if it exceeds 500 μm, the adsorption force may be insufficient. If it is less than 100 μm, it may be insufficient in terms of insulation, heat resistance and durability.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to the drawings showing an embodiment thereof. FIG. 1 shows an electrostatic chuck (hereinafter,
FIG. 2 is a schematic vertical cross-sectional view of a device of the present invention), in which the metal disc electrode 1 is connected to the other end of a terminal 3 having a screw portion 3a at one end and having a columnar shape on the back surface side of the central portion thereof. The surface is covered with a ceramic sprayed film 2 as an insulating film, except for the connection between the electrode 1 and the terminal 3. The end of the terminal 3 having the threaded portion 3a is connected to a power source (not shown) that applies a voltage to induce an electrostatic force. An insulating cylinder 4 having a flange 4a at its lower end is fitted around the periphery of the terminal 3 immediately below the back surface of the electrode 1 covered with the ceramic spray-coated film 2 to the substantial center of the screw 3a. Insulation cylinder 4
The water-cooling jacket 5 having a through-hole 5a inside for cooling water by passing water around the upper portion of the flange 4a of the electrode 4 and around the lower half of the electrode 1 covered with the ceramic sprayed film 2 is external. It is fitted. Insulation cylinder 4 and water cooling jacket 5
Is tightly held on the electrode 1 covered with the ceramic sprayed film 2 by screwing the nut 6 onto the threaded portion 3a of the terminal 3 and tightening the nut 6. The surface (upper surface) of the ceramic sprayed film 2 is subjected to a grinding treatment so as to have a film thickness of 100 μm to 500 μm.
By controlling the film thickness in this way, it is possible to secure the flatness and surface roughness of the ceramic sprayed film 2 and increase the electrostatic attraction force.

FIG. 2 is a graph showing the relationship between the electric field strength and the induced electrostatic force when the electrostatic adsorption treatment is performed using the device of the present invention. The electric field strength (kV / μm) is plotted on the horizontal axis on a logarithmic scale. Similarly, the electrostatic force is plotted on the logarithmic scale on the vertical axis, and the relationship between the electric field strength and the electrostatic force is shown when the relative permittivity ε _s of the sample to be adsorbed on the adsorption surface is 2, 4 or 6, Shows.

〔effect〕

As described above, in the electrostatic chuck according to the present invention, the insulating film is formed by ceramic spraying and over the entire surface of the conductor except the connecting portion between the conductor and the terminal, and since the insulating film is seamless, there is no leakage current. Is extremely small, and in some cases the outer peripheral surface of the connection between the conductor and the terminal is also sprayed, so the connection is reinforced, and there is no need to perform masking when forming the insulating film. Can be reduced. While the film thickness of 100 to 500 μm ensures a high adsorption force, the desired performance can be obtained in terms of insulation, heat resistance and durability. Therefore, in combination with the small leak current, an electrostatic chuck suitable for use in plasma or for application of a voltage in which a high frequency voltage is superimposed on a DC voltage can be realized.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing the structure of an electrostatic chuck according to the present invention, and FIG.
FIG. 3 is a graph showing the relationship between the electric field strength and the electrostatic force induced during the electrostatic adsorption process, FIG. 3 is a schematic vertical sectional view showing the structure of a conventional embedded electrostatic chuck, and FIG. 4 is the same conventional coated type. It is a schematic longitudinal cross-sectional view which shows the structure of an electrostatic chuck. 1 ... Electrode, 2 ... Ceramic sprayed film, 3 ... Terminal

Claims (1)

[Scope of utility model registration request] 1. An electrostatic chuck in which a conductor is coated with an insulating film, a DC voltage is applied between the object to be attracted and the conductor, and the object is attracted to the insulating film. An electrostatic chuck comprising an insulating film having a film thickness of 100 to 500 μm formed by ceramic spraying, which covers the entire surface of the conductor surface excluding a connection portion with a terminal for applying a DC voltage. .