JPH0422152A - Electrostatic attraction equipment - Google Patents

Abstract

PURPOSE:To increase attractive force by eliminating the period when an AC voltage applied to an electrode becomes zero. CONSTITUTION:A dielectric member 22 composed of polyimide or the like is arranged on a base stand 21. Three electrode layers 23A-23C having the respective fan shapes of 120 deg. angle interval are buried in the dielectric member 22. Terminals 24A-24C are led out from the electrode layer 23A-23C, respectively. Series circuits of power supplies 25UV, W and switches 26UV, W are connected between the terminals 24A and 24B of all retaining parts 2 on a disk 1, respectively. Hence it does not happen that the instantaneous value becomes zero as in the case of single phase AC voltage, and sufficiently intensive electrostatic attractive force can be obtained.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an electrostatic chuck device.

[Conventional technology]

For example, in the vacuum processing equipment of ion implantation equipment and sputtering equipment in semiconductor manufacturing equipment, it is necessary to hold and transport the wafer as the object to be processed in a vacuum, so the suction and holding means is It is only possible to use vacuum adsorption means, which is widely used as an adsorption/holding means in the atmosphere. For this reason, for example, in an ion implantation apparatus, the periphery of the wafer is held by a holding claw, but there is a problem in that particles are generated due to contact between the wafer and the claw. Therefore, an electrostatic adsorption device has been proposed as an adsorption/holding means in vacuum (Japanese Unexamined Patent Publication No. 79545/1983,
(Special Publication No. 1-36707, etc.). In one of these electrostatic adsorption devices, the wafer adsorption surface of the adsorption/holding table is composed of a dielectric material, and a conductive electrode layer is provided below or within this dielectric material over an area approximately equal to the adsorption surface. In this method, a DC voltage is applied between the electrode layer and the wafer. In this method, an electrostatic attraction force (Coulomb force) is generated between the charge on the electrode layer accumulated through the dielectric material by applying a DC voltage and the charge on the wafer, which is different from this charge. It is attracted to and held. In this method, since the electrode is brought into contact with the wafer, there is still the problem of verticle generation. Another method of the electrostatic adsorption device proposed for the light is to provide first and second adsorption parts on the adsorption surface of the holding table, and apply a DC voltage between the electrode layers of these first and second adsorption parts. This is a method of applying voltage. In this method, since the wafer is a conductor, a different type of charge appears on the wafer due to electrostatic induction, and an electrostatic attraction force is generated between this charge and the charge generated by applying voltage to the electrode layer. It is something that causes According to this method, the generation of particles is reduced because the electrode is not brought into contact with the wafer. Note that the publication also describes a method of applying single-phase alternating current between the electrode layer and the wafer or between the electrodes of the first and second suction parts.

[Problem to be solved by the invention]

By the way, in the case of a method in which DC voltage is applied between the wafer and the electrode or between two electrodes, the attractive force (Coulomb force) is strong or dielectric polarization occurs in the dielectric material on the attracting surface, so the voltage application must be stopped. However, there is a disadvantage that some charge remains, which makes it difficult for the object to be attracted to separate from the suction and holding table. Also,
Another drawback is that dust and the like tend to adhere to the object to be absorbed. On the other hand, if an alternating current voltage is applied instead of a direct current voltage, the amount of dust or dirt adhering to the object to be attracted will be reduced, and since dielectric polarization will not occur in the dielectric material, if the voltage application is stopped, the object to be attracted will be can be immediately removed from the suction holding table. However, in the case of the prior art described in the above-mentioned publication, since a single-phase AC voltage is applied, a sufficient attraction force cannot be obtained. That is, the instantaneous voltage applied to the single-phase AC voltage always becomes zero volts at a certain period, and the attractive force also becomes zero at the moment of the instantaneous voltage. In view of the above points, it is an object of the present invention to provide an electrostatic adsorption device that can use an alternating current voltage as the applied voltage and has a large attraction force.

[Means to solve the problem]

In this invention, the surface to be in contact with the object to be attracted is made of a dielectric material, and an electrode is provided below or within the dielectric, and an alternating current voltage is applied to this electrode to attract the object to be attracted. An electrostatic adsorption device that adsorbs by electrostatic attraction force is characterized in that a period in which the AC voltage applied to the electrode becomes zero voltage is eliminated.

[Effect]

In this invention, an AC voltage of three or more phases with a blurred phase is applied between three or more electrodes for electrostatic adsorption, so that the instantaneous value of the applied adsorption voltage does not become zero, and relatively large electrostatic You can get some suction power.

【Example】

An embodiment in which the electrostatic adsorption device according to the present invention is applied to a high current type ion implantation device will be described below with reference to the drawings. As shown in FIG. 4, a high-current type ion implanter has a plurality of ion implanters installed on a disk 1 placed in a vacuum chamber along its circumferential direction in order to alleviate heat generation caused by ion implantation. A semiconductor wafer holding part 2 is provided, the semiconductor wafer 3 is held in the holding part 2, and the disk 1 is rotated, for example, in the direction shown by the arrow 4, with the center position as the rotation axis, and the disk 1 is, for example, A configuration is adopted in which ions are implanted into a plurality of semiconductor wafers 3 at once by making a reciprocating linear movement in the direction shown by the arrow 5. Each holding part 2 has an electrostatic adsorption mechanism, and as shown in the cross-sectional view of FIG. It will be done. In this dielectric body 22, for example, a first
As shown in the figure, in this example, three fan-shaped electrode layers 23A, 23B, and 23C each have an interval of 120°.
It has a sandwich-like structure. In this example, the thickness of the dielectric 22, including the electrode layer, is
For example, it is said to be about 25 ku. Terminals 24A, 24B, and 24C are led out from each electrode layer 23A, 23B, and 23C. Then, the terminal 24 of the entire holding part 2 on the disk 1
A and 24B are connected between a series circuit of a power supply 25U and a switch 260 that generate an AC voltage El shown in FIG. 3A, and between terminals 24B and 24C are connected an AC voltage EV (AC voltage A series circuit of a 25V power supply and a 26V switch is connected between terminals 24C and 24A, which generates an AC voltage EW (20° phase difference between EU and EU) as shown in Figure 3C. A series circuit of a power supply 25W and a switch 26W, which generates a power of 25W and 26W, is connected. As the power source 25U, 25V, and 25W, a commercial three-phase AC power source can be used. In this case, the switches 26U, 26V, and 26W are made to interlock with each other, and are turned on when the wafer 3 is placed on the holding section 2. Switch 26U, 26V, 26
When W is turned on, each electrode layer 23A, 23B, 23C
The alternating current voltages EUEV and EW are applied between them. Then, charges appear on the wafer 3, which is a conductor, through the dielectric 22 due to electrostatic induction, and are attracted to the holding portion 2 by Coulomb force. In this case, the voltage applied to the electrode layers 23A, 23B, and 23C is a three-phase AC voltage, as shown in FIG. 3, so it does not become an instantaneous value or zero unlike a single-phase AC voltage. , a sufficiently strong electrostatic attraction force can be obtained. Note that the base 21 of the holding portion 2 may be made of aluminum or ceramic. However, as in the example above,
When the base 21 is made of an elastic material such as silicone rubber, when the wafer 3 is warped, the dielectric 22 has the same structure as an extremely thin flexible substrate, so the shape of the warp of the wafer will be corrected. The base 21 deforms accordingly. Therefore, even if the wafer 3 is deformed such as warping, no gap will be created between the wafer 3 and the holding part 2, and a suction force greater than a predetermined value can be maintained. Note that the number of electrodes and the number of phase-shifted AC voltages may of course be three or more. Further, in the above embodiment, an example was explained in which the electrostatic adsorption voltage application area for the wafer was divided into three areas, but even if a multiphase AC voltage is applied at the - electrode, the applied adsorption voltage is zero with respect to the wafer. The period can be set to zero. Furthermore, a DC bias may be provided. In this case, it is better to use a low DC bias voltage. Further, the above example is a case where the electrostatic adsorption device according to the present invention is applied to an ion implantation device, but as stated at the beginning, the present invention is also applicable to sputtering devices, other vacuum processing devices, and vacuum transfer devices. Needless to say, it can also be applied to Moreover, it is applicable not only to the vacuum but also to the holding and transport of the adsorbed object in the atmosphere. Furthermore, the object to be adsorbed is not limited to semiconductor wafers.
Any conductive material can be used.

【Effect of the invention】

As explained above, according to the present invention, since an alternating current voltage is applied between the electrodes, the amount of dust attached to the object to be attracted is reduced. Furthermore, when the applied voltage is cut off, no charge remains on the dielectric material, so the object to be attracted can easily be removed. Further, in this invention, since a polyphase AC voltage of three or more phases is applied between a plurality of electrodes, a predetermined electrostatic attraction force can be ensured.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an embodiment of the electrostatic adsorption device according to the present invention, FIG. 2 is a cross-sectional view taken along line A-A, and FIG. 3 is a diagram showing an example of a plurality of alternating current voltages having different phases. FIG. 4 is a diagram for explaining essential parts of an ion implantation apparatus to which the present invention is applied. 2. Wafer holding part 3 - semiconductor wafer 21, base 22; dielectrics 23A, 23B, 23C; electrode layers 2.4A, 24B, 24C; terminals 25U, 25V, 25W, 3-phase AC power source EU, EV, E
W, 3-phase AC voltage agent Patent attorney Tadashi Sato Bifu Bamboo IPv side view Figure 1 A-A% side view Figure 2

Claims (1)

[Claims] The surface to be in contact with the object to be attracted is made of a dielectric material, and an electrode is provided below or within the dielectric material,
An electrostatic adsorption device that applies an alternating current voltage to the electrode and adsorbs the object by electrostatic attraction, characterized in that a period in which the alternating current voltage applied to the electrode becomes zero voltage is eliminated. Electrostatic adsorption device.