JPH0528773Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrostatic chuck device for holding a wafer in, for example, semiconductor manufacturing equipment.

[Prior art]

Plasma devices that utilize electron cyclotron resonance are used for manufacturing highly integrated semiconductor devices. FIG. 2 is a schematic vertical cross-sectional view of the plasma apparatus configured as an etching apparatus, in which a sample mounting table 3 holding a wafer 4 is placed in a vacuum reaction chamber 9 and a wafer 4 is placed outside the upper wall of the reaction chamber 9. It is installed to face the opening of the installed plasma generation chamber 12. A waveguide 13 is connected to the upper part of the plasma generation chamber 12, and the other end of the waveguide 13 is connected to a magnetron 14.
The microwaves emitted by the magnetron 14 are guided into the plasma generation chamber 12. When a direct current is passed through the excitation coil 11 arranged so as to surround the plasma generation chamber 12 and a necessary raw material gas is supplied into the plasma generation chamber 12, plasma is generated within the plasma generation chamber 12. A diverging magnetic field with a lower magnetic flux density is formed toward the reaction chamber 9 side, and ions and the like of the plasma are projected. As a result, etching and the like are performed on the surface of the wafer 4 on the sample mounting table 3.

In some of these devices, the wafer 4 is placed vertically to prevent dust from adhering to the wafer 4, and plasma is projected from the side. It is necessary not to let it happen.

On the other hand, even when the wafer 4 is placed horizontally, if the temperature of the wafer 4 increases due to plasma projection, there is a risk that the resist will be thermally altered.
This is prevented by closely contacting the sample mounting table 3 and conducting heat to the sample mounting table 3.

In other words, the wafer 4 needs to be held closely to the sample stage 3 not only to be held vertically, but also to be cooled, and a device that uses electrostatic adsorption has been developed as an effective means for this purpose. There is.

FIG. 3 is a block diagram showing the structure of the electrostatic adsorption part of the sample mounting table 3. The electrostatic adsorption part is made by laminating an insulator 1 such as polyimide to cover the surface of a conductor 2 such as an aluminum plate. A sample such as a wafer 4 is placed on the upper surface thereof.
The conductor 2 is connected to a DC power source 6 via a switch 5.
The positive terminal of is connected.

Now, in order to hold the wafer 4 on the sample mounting table 3 having the above-described structure in the plasma apparatus,
First, the sample mounting table 3 is moved into the load lock chamber 10 provided outside one side wall of the reaction chamber 9.
Close the communication port between the

Then, the wafer 4 is placed in the load lock chamber 10.
is placed on the insulator 1 of the sample mounting table 3 and temporarily held using mechanical means (not shown).

Next, after reducing the pressure in the load lock chamber 10 to be equal to the pressure in the reaction chamber 9, that is, to a vacuum state, the communication port with the reaction chamber 9 is opened, and the sample mounting table 3 is placed inside the reaction chamber 9. The wafer 4 and the opening of the plasma generation chamber 12 are moved to a position facing each other, and the communication port is closed.

When the voltage from the DC power source 6 is applied to the conductor 2 by the switch 5 and plasma is simultaneously projected, dielectric polarization occurs in the insulator 1 on the conductor 2, with the upper layer being positive and the lower layer being negative. As a result, the wafer 4 is charged, electrostatically attracted and held on the sample mounting table 3.

[Problem that the invention attempts to solve]

After the sample electrostatically attracted as described above is subjected to the necessary plasma treatment, it is again temporarily held by mechanical means, and then the application of the DC voltage is stopped and released from the electrostatic attraction. It is then moved into the load lock chamber and removed also by mechanical means.

However, even after the application of the DC voltage is stopped, the dielectric polarization charge has a hysteresis characteristic, so the polarization charge remains on the sample.

In order to improve the cooling efficiency of the sample, that is, the degree of close contact with the sample mounting table, a high voltage is applied, and the residual electric charge is also large.

As a result, it becomes difficult to remove the sample due to the residual electrostatic adsorption force, and there is a risk that the sample may be damaged.

The present invention was developed in view of the above circumstances, and its purpose is to provide an electrostatic adsorption device that can easily and reliably remove the residual charge after electrostatic adsorption has stopped, thereby making it possible to easily remove the sample. do.

[Means for solving problems]

An electrostatic chucking device according to the present invention is an electrostatic chucking device made by laminating a conductor and an insulator, and applying a DC voltage to the conductor to attract an object onto the insulator. The apparatus is characterized by comprising an AC power source that generates an AC voltage with a variable output to be applied to the conductor, and means for switching between the AC voltage generated by the AC power source and the DC voltage.

[Effect]

The device of the present invention switches the DC voltage applied to the conductor to an AC voltage with variable output, and attenuates this voltage to zero. Then, the electrostatic attraction force of the object to be attracted is eliminated.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, this invention will be specifically explained based on drawing which shows the Example.

FIG. 1 is a block diagram showing the structure of an electrostatic adsorption device according to the present invention (hereinafter referred to as the device of the present invention).

The electrostatic chuck portion on which the sample such as the wafer 4 is placed is the same as that shown in FIG. That is, an insulator 1 such as polyamide is laminated to cover the surface of a conductor 2 such as an aluminum plate, and a wafer 4 is placed on top of the insulator 1 .

The conductor 2 is connected to a common terminal of a changeover switch 7, and the common terminal is connected to either the positive terminal of the DC power supply 6, the empty terminal, or the AC power supply 8, and the negative terminal of the DC power supply 6 and the AC power supply 8 are connected to each other. The power supply is collectively grounded.

The AC power supply 8 includes an AC voltage regulator and is configured to be able to change the AC voltage.

Next, the operation of the present invention configured as described above will be explained.

First, the electrostatic adsorption mechanism for the wafer 4 is
The condition is the same as the one shown in the figure. That is, in the reaction chamber,
When the changeover switch 7 is connected to the DC power supply 6 side, a DC voltage is applied, and plasma is projected at the same time, dielectric polarization occurs in the insulator 1, the wafer 4 is charged, and the insulator 1
is electrostatically attracted to the top.

Then, when releasing the electrostatic adsorption after plasma treatment, the changeover switch 7 is connected to the AC power source 8 side to apply an AC voltage, and at the same time, while projecting plasma again to release the electrostatic adsorption, the AC voltage is attenuated to zero. .

Then, the polarized charges remaining on the insulator 1 and the wafer 4 due to the DC voltage are erased by the AC voltage which is gradually attenuated to zero. Then, since the AC voltage becomes zero, no new dielectric polarization occurs in the insulator 1.

As a result, electrostatic adsorption force is completely eliminated. In addition, the structure of the electrostatic attraction part in the present device is not limited to this embodiment, and a bipolar type structure having a pair of electrodes in an insulator may also be used.

〔effect〕

In the present device, the sample can be easily removed because residual charges due to dielectric polarization can be quickly erased. As a result, conventionally, the voltage was limited and the degree of adhesion was reduced so that the sample could be removed without damaging it, but this is no longer necessary, and it is now possible to apply a high voltage, increasing the degree of adhesion of the sample.
The present invention has excellent effects such as improved cooling efficiency.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the structure of an electrostatic chuck device according to the present invention, FIG. 2 is a schematic vertical sectional view showing the structure of a plasma device, and FIG. 3 is a block diagram showing the structure of a conventional product. 1... Insulator, 2... Conductor, 4... Wafer,
6...DC power supply, 8...AC power supply.

Claims (1)

[Claims for Utility Model Registration] An electrostatic adsorption device comprising a laminated conductor and an insulator, applying a DC voltage to the conductor to adsorb an object onto the insulator, An electrostatic adsorption device comprising: an AC power source that generates an AC voltage with a variable output that is applied to the conductor; and means for switching between the AC voltage generated by the AC power source and the DC voltage.