JPH118291A - Electrostatic suction device - Google Patents

Abstract

(57) [Summary] An electrostatic chuck having a plurality of electrodes is provided.
A leak current flowing between the electrodes is suppressed, a voltage can be efficiently applied between the electrodes and the object to be adsorbed, and a sufficient attraction force is exhibited. In an electrostatic attraction device having a plurality of electrodes, an electric resistance value between the electrodes is made larger than an electric resistance value between the electrodes and an object to be adsorbed, and a leak current flowing between the electrodes is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck, and more particularly, to an electrostatic chuck used for fixing a wafer during transfer or processing of the wafer in a semiconductor manufacturing apparatus, and suitable for holding the wafer by using an electrostatic force. The present invention relates to a simple electrostatic attraction device and a processing device.

[0002]

2. Description of the Related Art A method of holding an object by using an electrostatic force is used particularly for transferring a wafer in a semiconductor manufacturing apparatus and fixing the wafer during each process. As a holding method for carrying or fixing the wafer, a mechanical holding method using a clamp or the like can be considered, but using an electrostatic force has many advantages in holding the semiconductor wafer. For example, there is no mechanical contact with the processing surface of the wafer, so there is no contamination of the wafer due to abrasion powder, etc. Contact with the
The thermal conductivity is improved, and the temperature control of the wafer becomes easy.

As described above, electrostatic attraction has many advantages as a method for holding a wafer, and is therefore widely applied particularly as a wafer processing electrode in an apparatus such as dry etcher or CVD. Such an electrostatic attraction device is disclosed in, for example, Japanese Patent Application Laid-Open No. 6-120329. In this disclosure, a method is disclosed in which a negative voltage is applied to an electrode arranged at the center, and an electrode for applying a positive voltage is arranged around the electrode, and a wafer is sucked.

[0004]

Problems to be Solved by the Invention
In the electrostatic chucking device disclosed in Japanese Patent Application Publication No. 9-1990, a method is disclosed in which a negative voltage is applied to an electrode arranged in the center, and an electrode for applying a positive voltage is arranged around the electrode, and the wafer is sucked. Have been. In particular, for the purpose of improving the temperature distribution of the wafer during plasma processing, the area of the two electrodes to which a negative voltage is applied is made large. As a method of reducing the residual suction force generated when this electrostatic suction device is used in a plasma, a DC voltage having an absolute value larger than a voltage applied between two electrodes during wafer suction is used. A method of reducing the resistivity of the dielectric film to accelerate the charge elimination by applying a voltage is also disclosed.

[0005] However, in the disclosed examples relating to the electrostatic chuck device having a plurality of electrodes including this disclosed example, no consideration is given to the method of electrically insulating the plurality of electrodes. The leakage current between the electrodes is large, the applied voltage is not efficiently applied between the wafer and the electrodes, and the suction force is insufficient, or the insufficient withstand voltage between the electrodes causes dielectric breakdown and causes a suction error. There's a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable electrostatic attraction device capable of efficiently and sufficiently generating an attraction force.

[0007]

The above object is achieved by making the distance between the plurality of electrodes larger than the thickness of the dielectric film in an electrostatic chuck having a plurality of electrodes.

[0008] It is also achieved by making the volume resistivity of the member electrically insulating the plurality of electrodes larger than the volume resistivity of the dielectric film.

Further, the present invention is attained by providing a member for electrically insulating a plurality of electrodes so as to protrude toward the dielectric film from the surface of the electrodes.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 show a first embodiment of the present invention. FIG. 1 is a perspective view of the electrostatic chuck of the first embodiment of the present invention, and FIG. 2 shows an example in which the electrostatic chuck of the first embodiment of the present invention is applied to a magnetic field microwave plasma processing apparatus. .

First, the configuration and operation of the apparatus will be briefly described with reference to FIG. A quartz tube 20 is installed in the air space 19, and the electrostatic adsorption device 3 is placed in a vacuum processing chamber 21 constituted by the quartz tube 20.
Is used to fix the wafer 12 to the sample stage 22. Although the electrostatic suction device of the present invention is applied to the electrostatic suction device 3,
Details will be described later. Subsequently, the processing gas 2 is placed in the vacuum processing chamber 21.
3 is introduced. The processing gas is turned into plasma by the interaction between the electric field of the microwave and the magnetic field of the coil.
The state becomes 0. The microwave 26 is the microwave generator 2
The light is oscillated by the waveguide 4 and is introduced into the quartz tube 20 through the waveguide 25. A magnetic field is formed in the quartz tube 20 by coils 28, 29 mounted around a microwave resonance box 27. The processing (here, etching processing) is performed by exposing the wafer 12 to the plasma 30. In particular, the etching state is controlled by controlling the incidence of ions by the high frequency power supply 31. Explaining other numbers in the figure, reference numeral 10 denotes a DC power supply for the electrostatic attraction device, and 9 denotes a switch for controlling ON / OFF of the DC power supply.
32 is a coil for protecting the DC power supply from high frequency voltage, 33
Is a blocking capacitor. Numeral 34 denotes exhaust of excess processing gas and reaction products, and is connected to a vacuum pump (not shown here).

Next, the electrostatic attraction device 3 of the present invention will be described in detail with reference to FIG. However, the dimensional ratios of the parts in the figures are different from the actual dimensional ratios for the sake of simplicity, but for the parts that are considered necessary below,
Approximate values are shown in the text.

The basic structure of this device is that two electrodes, ie, a ring electrode 1 and an inner electrode 2
Has a structure in which a dielectric film 5 which is a sintered body of aluminum oxide embedded concentrically is fixed by an adhesive 6. The resistivity of aluminum oxide is about 10 9 Ωcm to 10 13 Ωcm
It has been adjusted to the extent.

The dielectric film 5 has a thickness of 1 mm in total, but is processed so that the thickness of the dielectric film on the two electrodes embedded therein becomes 300 microns. In this embodiment, the material of the electrode is tungsten and the thickness is 50 microns. Normally, it may be about 50 to 100 microns. The surface of the dielectric film 5 has a roughness of 3
It is processed to μm. Then, the surface 1 of this dielectric film
4 is a gas groove 16 for passing a cooling gas introduced from a cooling gas inlet 15 through an external pipe (not shown) to promote cooling of the wafer during processing to the entire back surface of the wafer efficiently. Is engraved at a depth of 100 microns as shown. The gas groove pattern is set so that the temperature distribution of the wafer being processed becomes a desired value.

In the electrostatic chuck of the present embodiment, the ring electrode 1 and the inner electrode 2 are arranged at 5 mm, which is a sufficiently large interval as compared with the thickness of the dielectric film on the electrode. The resistance between the electrodes 2 is set to be sufficiently larger than the resistance between the wafer and the electrodes. The reason is that if the distance between the ring electrode 1 and the inner electrode 2 is too small, when a potential difference is given between the ring electrode 1 and the inner electrode 2, a leak current flows directly between the ring electrode 1 and the outer electrode 2 and the wafer This is because a sufficient voltage is not applied between the electrodes, and the force for attracting the wafer is reduced.

The application of a DC voltage to these two electrodes is as follows:
This is performed via the conducting wire 8 completely sealed by the insulating resin 13. The conductor 8 and each electrode are brazed 7. In this embodiment, the inner electrode 2 is grounded 11, and the ring electrode 1 is connected to the DC power supply 10
, Or grounded 11, and a negative voltage is applied when connected to the DC power supply 10. When a negative voltage is applied to the ring electrode 1 by the switch 9 while a wafer (not shown) is mounted on the surface 14 of the dielectric film 5, a potential difference is generated between the wafer and each electrode. Conversely, if the switch 9 is switched to ground the ring electrode 1, the charge stored between the wafer and each electrode can be eliminated. After the processing, the wafer is processed by up and down movement of four pushers 17 provided concentrically in the electrostatic chuck. Reference numeral 18 denotes an insulating cylinder for insulating the pusher 17 from the electrodes 1, 2 and the aluminum block 4.

In the electrostatic chuck having the above structure, the resistance value between the electrodes is larger than that between the electrodes and the object, so that the leak current flowing between the electrodes is small, and the voltage is sufficiently applied between the electrodes and the wafer. Therefore, the attraction force can be sufficiently exhibited.

In this embodiment, the two electrodes are arranged on concentric circles, but it is not always necessary to have such a structure. In this embodiment, the number of the electrodes is two, but the number is not necessarily two and may be three or more. Furthermore, in the present embodiment, the interval between the two electrodes is set to 5 mm, but it is not always necessary to stick to this, and the resistance between the electrodes is set to be larger than the resistance of the dielectric film between the electrode and the wafer. It is evident that the voltage applied between the electrodes can be efficiently applied between the wafer and the electrodes if there is an interval larger than the thickness of the dielectric film on the electrodes.

FIG. 3 shows an electrostatic chuck according to a second embodiment of the present invention. FIG. 4 is an enlarged view of a power supply portion to a ring electrode described later. In this embodiment, an aluminum electrode 36 whose surface is coated with a dielectric film 38 made of alumina oxide by thermal spraying is fixed on an insulating table 35 made of an insulating material with bolts (not shown). ing. The resistivity of the dielectric film is adjusted from about 10 9 Ωcm to about 10 13 Ωcm. A ring-shaped groove 43 is cut around the entire circumference of the electrode 36, and an insulating ring 37 made of pure alumina is embedded in the groove by thermal spraying. The insulating ring 37, the electrode 36, and the insulating base 35 are provided with one through hole 44, and an insulating cylinder 45 is embedded in the through hole 44. The conducting wire 8 is inserted into the insulating cylinder 45, and is electrically connected to a tungsten ring electrode 39 provided over the entire circumference of the insulating ring 37 at intervals of 2 mm with the electrode 36 by thermal spraying. I have. The ring electrode 39 has a thickness of 50 microns, and the surface is flush with the surface of the electrode 36. That is, before spraying on the insulating ring 37, the ring is polished to a depth of about 50 microns on the entire ring before spraying. Thereafter, a dielectric film 38 is formed on the electrode 36 by thermal spraying, and a gas groove 1 having a depth of 100 μm is formed on the surface similarly to the first embodiment.
6 are provided. In the electro-adsorption device of this embodiment, the thickness of the dielectric film is 300 μm and the surface roughness is 3 μm.

In this embodiment, the application of voltage to each electrode can be performed on the ring electrode 39 by switching the switch 9 on the above-described conductor 8.
, A negative voltage can be applied. The electrode 11 is supplied with a ground 11 potential via a conducting wire 42 in an insulating tube 40.

In the electro-adsorption device configured as described above, the ring electrode 39 and the electrode 36 are insulated by an insulating ring having much higher resistance than the dielectric film.
No leakage current flows between the ring electrode 6 and the ring electrode 39, and the applied voltage is applied between the wafer and the electrode 36 and the ring electrode 39, so that a sufficient attraction force can be generated. Further, in this embodiment, since the resistivity of the insulating ring 37 is very large, the distance between the electrode 36 and the ring electrode 39 can be made smaller than in the first embodiment of the present invention. It is clear from the description of the first embodiment that the design should be such that the electric resistance value is larger than the resistance of the dielectric film on the electrode.

FIG. 5 shows a third embodiment of the present invention. FIG. 6 is an enlarged view of a power supply portion of the ring electrode according to the third embodiment. This embodiment is different from the second embodiment in that an insulating ring 41 for insulating the ring electrode 39 from the electrode 36 is formed to protrude from the surfaces of the electrode 36 and the ring electrode 39.

In the electrostatic attraction device configured as described above, since the electrical insulation between the electrode and the ring electrode is further ensured, it is possible to provide an electrostatic attraction device capable of sufficiently exerting the attraction force.

FIG. 7 is an enlarged view of a power supply portion of a ring electrode according to a fourth embodiment of the present invention. In this embodiment, the ring-type dielectric film 48 on the ring electrode 39 is formed by the insulating ring 46.
And the dielectric film 47 on the electrode 36 are completely separated.

In the electrostatic attraction device configured as described above, since the electrical insulation between the electrode and the ring electrode is further ensured, it is possible to provide an electrostatic attraction device capable of sufficiently exerting an attraction force.

[0027]

As described above, according to the present invention, in an electrostatic chuck having a plurality of electrodes, the electric resistance between each electrode is larger than the electric resistance between the electrode and the object to be adsorbed. It is possible to provide an electrostatic attraction device in which a leak current flowing therebetween is small, a voltage is sufficiently applied between the electrode and the wafer, and an attraction force can be reliably exhibited.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an electrostatic chuck according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional view showing an example of a processing apparatus on which the electrostatic suction device of the present invention is mounted.

FIG. 3 is a perspective view showing an electrostatic chuck according to a second embodiment of the present invention.

FIG. 4 is an enlarged view of a power supply portion of the electrostatic chuck according to the second embodiment of the present invention.

FIG. 5 is a perspective view showing an electrostatic chuck according to a third embodiment of the present invention.

FIG. 6 is an enlarged view of a power supply portion of an electrostatic chuck according to a third embodiment of the present invention.

FIG. 7 is an enlarged view of a power supply portion of an electrostatic chuck according to a fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ring electrode, 2 ... Inner electrode, 3 ... Electrostatic adsorption device, 4 ...
Aluminum block, 5: Dielectric film, 6: Adhesive, 7: Brazing, 8: Lead wire, 9: Switch, 10: DC power supply, 11
... ground, 12 ... wafer, 13 ... resin, 14 ... dielectric film surface, 15 ... cooling gas inlet, 16 ... gas groove, 17 ... pusher, 18 ... insulating cylinder, 19 ... atmosphere, 20 ... quartz tube,
21: vacuum processing chamber, 22: sample stage, 23: processing gas, 2
4: microwave generator, 25: waveguide, 26: microwave, 27: microwave resonance box, 28: coil, 29 ...
Coil, 30 plasma, 31 high frequency power supply, 32 coil, 33 blocking capacitor, 34 exhaust, 3
5: insulating table, 36: electrode, 37: insulating ring, 38: dielectric film, 39: ring electrode, 40: insulating cylinder, 41: insulating ring, 42: conducting wire, 43: groove, 44: through hole, 45:
Insulating cylinder, 46 ... insulating ring, 47 ... dielectric film, 48 ... ring type dielectric film.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Saburo Kanai 794, Higashi-Toyoi, Kazamatsu, Kamamatsu, Yamaguchi Prefecture Inside the Kasado Plant of Hitachi, Ltd. Inside the Kasado Plant of Hitachi, Ltd.

Claims (5)

[Claims] 1. An electrostatic attraction device for electrostatically adsorbing and holding an object to be adsorbed, comprising at least a plurality of electrodes for giving a potential difference between said object to be adsorbed and a dielectric film; An electrostatic adsorption device, wherein an electric resistance value is larger than an electric resistance value of a dielectric film between the object and the electrode. 2. An electrostatic attraction device for electrostatically adsorbing and holding an object to be attracted, comprising at least a plurality of electrodes for providing a potential difference between the object to be attracted and the dielectric film, and An electrostatic attraction device, wherein a distance is larger than a thickness of the dielectric film. 3. An electrostatic attraction device for electrostatically adsorbing and holding an object to be attracted, comprising at least a plurality of electrodes for providing a potential difference between the at least one object to be absorbed and the dielectric film, wherein the plurality of electrodes are electrically connected. An electrostatic attraction device characterized in that a volume resistivity of a member to be electrically insulated is larger than a volume resistivity of the dielectric film. 4. The electrostatic attraction device according to claim 3, wherein
A member for electrically insulating a plurality of electrodes protrudes from a surface on which the electrodes are arranged. 5. The electrostatic attraction device according to claim 3, wherein
A member for electrically insulating a plurality of electrodes is exposed on a surface of a dielectric film.