JP2576294B2 - Wafer suction / release method for electrostatic chuck - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for attracting and detaching a wafer from an electrostatic chuck which applies a voltage to an electrode in an insulator to attract the wafer onto the insulator.

In the manufacture of semiconductor devices, the above-mentioned electrostatic chuck is sometimes used for transporting a wafer from the viewpoint of dust prevention. In that case, it is desired that the wafer conveyed by suction is quickly released when the wafer is released.

[0003]

2. Description of the Related Art As shown in a sectional view of a main part of FIG. 2, an electrostatic chuck has a two-electrode electrode 2a,
The electrodes 3a and 2b have appropriate values (for example, 1.5 KV) of voltages 3a and 2b with opposite polarities and equal absolute values.
3b is applied to adsorb and hold the wafer 4 on the surface of the insulator 1. At this time, an electrostatic force caused by electric charges induced in the insulator 1 and the wafer 4 is used as the attraction force. Then, when the wafer 4 is detached, the charge is lost.

FIG. 3 is a characteristic diagram of an applied voltage according to a conventional example when the electrostatic chuck is used. In the figure, the positive side 5a and the negative side 5b indicate voltage history curves of the applied voltages 3a and 3b, respectively, A indicates at the time of adsorption, B indicates at the time of holding, and C indicates at the time of detachment.

At the time of suction A, the values of the applied voltages 3a and 3b are set so that the wafer 4 can be sucked, and at the time of holding B, the values of the applied voltages 3a and 3b set at the time of suction A are maintained. At the time of separation C, the values of the applied voltages 3a and 3b are set to zero.

However, in reality, there is a problem that even when the values of the applied voltages 3a and 3b are set to zero, it takes a long time to detach the wafer 4 and it is difficult to detach the wafer 4 in a short time. Further, if the values (absolute values) of the applied voltages 3a and 3b at the time of suction A are set low to facilitate the separation, poor suction occurs when the wafer 4 is slightly away from the insulator 1.

[0007] In view of this, a method is adopted in which the values of the applied voltages 3a and 3b at the time of adsorption A are set to a sufficient value, and at the time of desorption C, the applied voltages 3a and 3b are switched to the opposite polarities and applied. There is also.

[0008]

The problem that the above-mentioned separation becomes difficult is that a large electric charge induced in the insulator 1 and the wafer 4 by the applied voltages 3a and 3b during the adsorption A and the retention B is:
For a while (about several minutes) even if the applied voltage 3a, 3b is set to zero
This is caused to make it difficult for the wafer 4 to be detached while remaining.

On the other hand, the method in which the applied voltages 3a and 3b are switched to the opposite polarities at the time of separation C and applied positively neutralizes the above-mentioned charges, which seems to be good at first glance. Of course, the time is not constant, so there are many troubles withdrawal.

Accordingly, the present invention relates to a method for adsorbing / releasing a wafer of an electrostatic chuck as described above, and more particularly, to a method for reliably adsorbing a wafer at the time of adsorption, and easily detaching the wafer at the time of detachment. For the purpose of providing.

[0011]

FIG. 1 is a characteristic diagram of an applied voltage according to an embodiment. In FIG. 1, a positive side 6a and a negative side 6b are voltage histories of the applied voltages 3a and 3b shown in FIG. Curves A, B, and C show the time of adsorption, the time of holding, and the time of desorption, as in FIG.

In order to achieve the above object, the method of the present invention will be described with reference to FIGS.
In the electrostatic chuck which applies the voltages 3a and 3b to the wafer 4 and suctions the wafer 4 on the insulator 1, the applied voltages 3a and 3b are held at A when the wafer 4 is suctioned as shown by voltage history curves 6a and 6b. The time B is made different from the time C at the time of detachment, and the applied voltages 3a and 3b at the time of holding B are made lower than those at the time of suction A, so that the wafer 4
It is characterized in that it is separated.

It is desirable that the applied voltages 3a and 3b at the time of holding B be set to a low value within a range where the holding of the wafer 4 can be continued.

[0014]

In order to surely adsorb the wafer 4, the wafer 4 can be adsorbed even if the wafer 4 is slightly away from the insulator 1, that is, the electrostatic force due to the electric charge induced on the insulator 1 and the wafer 4 is reduced. It is necessary to increase the applied voltages 3a and 3b at the time of adsorption A so as to be sufficient for the adsorption of. For this reason, in the conventional example, there has been a problem that detachment is difficult.

In order to avoid this problem, the charge just before the separation C should be as small as possible so that the remaining time of the charge at the separation C is short. By the way, since the attraction force (electrostatic force) acting on the wafer 4 is inversely proportional to the distance between the electric charges, when the wafer 4 is adsorbed and comes into contact with the insulator 1, the attraction force is applied to the holding of the wafer 4. On the other hand, the size becomes unnecessarily large.

Therefore, if it is considered that the holding is continued after the wafer 4 is adsorbed, the applied voltage 3a,
3b can be made lower than that of A during adsorption. The present invention focuses on this point. That is, if the applied voltages 3a and 3b at the time of holding B are lowered, the above-mentioned electric charges which are largely induced at the time of adsorption A become smaller before the release time C according to the decrease of the applied voltages 3a and 3b. , The wafer 4 can be easily separated.

[0017]

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

In the embodiment, the applied voltages 3a and 3b are applied to the voltage history curves 6a and 6b shown in FIG.
As shown in the above, the difference is made between A at the time of suction of the wafer 4, A at the time of holding, and C at the time of detachment, and the applied voltages 3a and 3b at the time of holding B are set at
And the applied voltages 3a and 3b are set to zero at the time of separation C. Compared to the prior art, only the applied voltages 3a and 3b at the time of holding B are qualitatively different.

The values of the applied voltages 3a and 3b at the time of adsorption A are +1.5 KV and -1.5 KV, respectively.
It is adsorbed even at a distance of about 0.5 to 1 mm. The values of the applied voltages 3a and 3b at the time of holding B are +0.5 KV and -0.5 KV, respectively, and the wafer 4 is securely held even when the electrostatic chuck is moved for transportation or the like.

The values of the applied voltages 3a and 3b at the time of separation C are zero as described above, and the wafer 4 has separated within 30 seconds. By the way, the value of the applied voltage 3a and 3b at the time of holding B is + 1.5K respectively.
V, -1.5 KV (with A at the time of adsorption), that is, according to the method of the conventional example shown in FIG. 3, it took one minute or more to detach the wafer 4.

Further, the applied voltages 3a and 3b at the time of separation C are switched to the opposite polarity to the polarity at the time of holding B, and the respective values are set to -0.5KV and + 0.5K.
When V was set, the time required for detachment of the wafer 4 was further reduced. In that case, no trouble occurred due to the application time. This is considered to be due to a synergistic effect between the fact that the above-described induced charge is small before the separation time C and the value of the applied voltages 3a and 3b is low.

Therefore, when the electrostatic chuck is used for transporting a wafer, the time required for detaching the wafer can be reduced to half or less, and the transport time can be reduced.

Although the above-mentioned electrostatic chuck is also used in a semiconductor manufacturing apparatus for supporting a wafer, it is easily understood that the present invention is effective in detaching the wafer even in such a case.

[0024]

As described above, according to the present invention, the present invention relates to a wafer chucking / detaching method for an electrostatic chuck which applies a voltage to an electrode in an insulator and chucks the wafer on the insulator. It can be surely adsorbed, and of course, when detached, the wafer can be easily detached which has been difficult to detach in a short time in the past, for example, an electrostatic chuck was used for transporting the wafer. In this case, there is an effect that the transport time can be reduced by shortening the time required for detaching the wafer.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram of an applied voltage according to an embodiment.

FIG. 2 is a sectional view of a main part for describing an electrostatic chuck.

FIG. 3 is a characteristic diagram of an applied voltage according to a conventional example.

[Explanation of symbols]

 1 Insulator 2a, 2b Electrode 3a, 3b Applied voltage 4 Wafer 5a, 5b, 6a, 6b Voltage history curve

Claims (2)

(57) [Claims] A voltage (3a, 3a) is applied to electrodes (2a, 2b) in an insulator (1).
3b), the applied voltage (3a, 3b) is applied when the wafer (4) is attracted (A) and when the wafer (4) is held (B) in the electrostatic chuck that attracts the wafer (4) onto the insulator (1) by applying ) And the time of detachment (C), and the applied voltage at the time of holding (B) is lower than that at the time of adsorption (A) to detach the wafer (4). Wafer adsorption / release method for electro chuck. 2. The applied voltage (3a, 3b) at the time of holding (B) is:
2. The method according to claim 1, wherein the value is set to a low value within a range where the holding of the wafer (4) can be continued.