JPH0422153A - Electrostatic attraction equipment - Google Patents

Abstract

PURPOSE:To sufficiently ensure the retaining force of a body to be attracted by using AC voltage as an applied voltage, by a method wherein a dielectic member and electrodes are formed, and a base stand is constituted of elastic material. CONSTITUTION:A dielectic member 22 composed of plastic is arranged on a base stand 21 composed of elastic material. Three electrode layers 23A, 23B, 23C having the respective fan shapes of 120 deg. interval are buried in the dielectic member 22. When distortion like warp exists in a wafer 3 in the above constitution, the base stand 21 and the dielectric member 22 deform in accordance with the shape of the distortion of the wafer. Hence, when distortion like warp is present in the wafer 3, gaps are not generated between the wafer and the dielectric member 22 on the upper surface of a retaining part 2, and the attractive force larger than a specified value can be maintained.

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 sea urchins as the processing object in a vacuum, so it is necessary to use the suction and holding means. In this case, it is not 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 a vacuum (Japanese Patent Application Laid-Open No. 79545/1983,
(Special Publication No. 1-36707, etc.). Conventionally, these electrostatic adsorption devices, as shown in Fig. 6,
For example, on a hard base 10 made of aluminum or ceramic, a dielectric 11 is formed as a wafer adsorption surface,
A conductive electrode layer 12 is provided under this dielectric 11 or within this dielectric 11 over an area approximately equal to the attraction surface, and between this electrode layer 12 and the wafer 13, or two conductive electrode layers are provided, A DC voltage is applied between these electrode layers, and the resulting electrostatic attraction force attracts the wafer to the holding table.

[Problem to be solved by the invention]

Incidentally, the semiconductor wafer 13 is subjected to large temperature changes and pressure changes when it is returned to room temperature after being processed at a high temperature, so as shown in FIG. 5, distortions such as warping may occur. There is. The base of the conventional electrostatic chuck device's wa/'% holding table is
Since it is made of a hard material, if the above distortion occurs, the suction surface and the wafer 13 will be damaged as shown in FIG.
There will be a gap between the two. As a result, the actual electrostatic attraction force becomes small, and there is a fear that sufficient holding force may not be obtained. Therefore, in the conventional electrostatic adsorption device °C, it was necessary to apply a relatively high DC voltage to ensure a strong attraction force. However, 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, but dielectric polarization occurs in the dielectric material on the attraction surface, so the voltage application must be stopped. Even if the charge remains,
For this reason, there is a drawback that the object to be attracted is difficult to separate from the suction holding table. Another drawback is that dust and the like tend to adhere to the object to be attracted. 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, it is impossible to obtain a sufficient attraction force. 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 also use an alternating current voltage as the voltage to be applied, and that can secure a sufficient holding force for an object to be adsorbed. .

[Means to solve the problem]

In the present invention, the object to be contacted with the object to be attracted is a dielectric, and an electrode is provided below or inside the dielectric, and a voltage is applied to this electrode, so that the object to be attracted can be electrostatically In the electrostatic adsorption device that is attracted by attraction, the dielectric and the electrode are formed on the upper surface of a base, and the base is made of an elastic material.

[Effect]

Since the base is made of an elastic material, even if the object to be attracted is distorted, the base deforms according to the distortion during electrostatic suction, so there is no gap between the object to be attracted and the surface to be attracted. Sufficient electrostatic attraction force can be obtained to the object to be attracted without opening.

【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 holder 2 is provided, the semiconductor wafer 3 is held in the holder 2, and the disk 1 is rotated, for example, in the direction shown by the arrow 4, with its center position as the rotation axis, and the disk is A configuration is adopted in which C ions are implanted into a plurality of semiconductor wafers \3 by reciprocating linear movement in the direction shown by arrow 5. Each holding part 2 has an electrostatic adsorption mechanism, and is made of a bone material, for example, as shown in the cross-sectional view of FIG. A dielectric material 22 made of plastic, such as polyimide, is provided on a base 2 made of silicone rubber. As shown in FIG. 1, three fan-shaped electrode layers 23A, 23B, and 23C are embedded in this dielectric 22, each having a piece spacing of 120° in this example, forming a sandwich-like structure. I am doing 6-. In this example, the dielectric 22
The thickness is, for example, about 25 mm including the electrode layer,
The structure is similar to that of a so-called flexible board. Terminals 24A, 24B, and 24C are led out from each electrode layer 23A, 23B, and 23C. Then, the terminal 24 of the entire holding section 2 on the disk l
A and 24B are connected between a series circuit of a power supply 25U and a switch 26U that generate an AC voltage EU 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 the terminals 24C and 24A, which generates an AC voltage EW (120° phase difference from the AC voltage EU) as shown in FIG. A series circuit consisting of a power source 25W and a switch 26W, which generates a power of 25W or 26W, is connected. As the power source 25U, 25V, and 25W, a commercial three-phase AC power source can be used. In the case of Kono, switch f 26 U, 26 V,
26 W Ha, they are made to work together, and the sea urchin /
When the head 3 is placed on the holding part 2, it is turned on. When the switch 26U 26V, 26W is turned on, the AC voltage EU is applied between each electrode layer 23A, 23B, 23C. EV and EW are applied. Then, an electric charge appears on the conductive body /X3 due to electrostatic induction via the dielectric body 22, and is attracted to the holding portion 2 by Coulomb force. In this case, since the base 21 is made of an elastic material such as silicone rubber, if the wafer 3 is warped or otherwise distorted, the dielectric 22 has the same structure as an extremely thin flexible substrate. The base 21 and the dielectric 22 are deformed as shown in FIG. 5 in accordance with the shape of the distortion of the tool. Therefore, even if the wafer 3 is deformed such as warping, no gap will be created between it and the dielectric 22 on the upper surface of the holding part 2, and it is possible to maintain a suction force stronger than a predetermined value. can. Incidentally, when the present inventor conducted an experiment on electrostatic adsorption of a distorted tool, the adsorption force when the base was made of ceramic was 2°65 g/c+n 2
If the base is made of silicone rubber with an elastic modulus of 50 kg/cIT12, the suction force will be 13°33g/cIT11.
2, and it was confirmed that when the base is made of silicone rubber, it is possible to obtain about five times as much suction force as when the base is made of ceramic. Furthermore, in this example, the voltage applied to the electrode layers 23A, 23B, and 23C is a three-phase AC voltage, as shown in FIG. 3, so a single-phase AC voltage is applied between the two electrodes. Unlike the case, the instantaneous value does not become zero, and a sufficiently strong electrostatic attraction force can be obtained. The above example is an example of applying an AC voltage between multiple electrodes to perform electrostatic adsorption, or a case of applying a DC voltage or an AC voltage between an electrode and a wafer, or a case of applying an AC voltage between two electrodes. Of course, the present invention can also be applied to the case where a DC voltage is applied to. In addition, the above examples are cases in which the electrostatic adsorption device according to the present invention is applied to an ion implantation device, or as mentioned at the beginning, the present invention is applicable to sputtering devices, other vacuum processing devices, and vacuum transfer devices. Needless to say, it can also be applied to Further, the material of the base is not limited to silicone rubber, and various elastic materials can be used. Further, the present invention is applicable not only to holding and transporting an adsorbed object in the atmosphere, but also in the atmosphere. Furthermore, the object to be attracted is not limited to the semiconductor wafer/1, but any conductive object can be used.

【Effect of the invention】

As explained above, according to the present invention, the base of the electrostatic adsorption device is made of an elastic material, so even if the object to be adsorbed is warped or otherwise distorted, it will be able to accommodate the distortion during electrostatic adsorption. Since the base will not be deformed and a gap will not be created between the base and the object to be attracted, sufficient adsorption force can be obtained. Therefore, according to the electrostatic adsorption device according to the present invention, it is possible to use an alternating current voltage as the applied voltage, which reduces the amount of dust attached to the object to be adsorbed, and when the applied voltage is cut off, the dielectric Since there is no charge remaining in the adsorbent, the adsorbed object can be easily removed.

[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 the main parts of an ion implantation apparatus to which the present invention is applied, FIG. 5 is a diagram for explaining the present invention in detail, and FIG. FIG. 2 is a diagram for explaining an example of a device. 2. Wafer holding part 3: semiconductor wafer 21; base 22; dielectrics 23A, 23B, 23C, electrode layers 24A, 24B, 24C, terminals 25U, 25V, 25W; 3I AC power source EU, EV,
EW, 3-phase AC voltage

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,
In an electrostatic attraction device in which a voltage is applied to the electrode and the object to be attracted is attracted by electrostatic attraction, the dielectric material and the electrode are formed on the upper surface of a base, and the base is elastic. An electrostatic adsorption device characterized by being made of a material.