Wafer transfer apparatus and device and method for cleaning robot arm in wafer transfer apparatus

A wafer transfer apparatus includes a robot arm and a robot arm cleaning device that injects purge gas into a vacuum nozzle of the robot arm under a normal stand-by state wherein the robot arm does not suction a wafer, to clean the vacuum nozzle. The robot arm cleaning device comprises a solenoid valve adapted to supply and intercept air, a first air valve adapted to selectively maintain and release a vacuum state in response to the air supplied from the solenoid valve, and a second air valve adapted to selectively supply and intercept a purge gas in response to the air supplied from the solenoid valve. The robot arm holds a wafer by a vacuum state of the vacuum nozzle when the first air valve is opened, and the vacuum nozzle is cleaned by the purge gas supplied when the second air valve is opened.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 from Korean Patent Application No. 2002-0036616, filed on Jun. 28, 2002, the contents of which are hereby incorporated by reference in their entirety as if fully set forth herein.

BACKGROUND AND SUMMARY

1. Technical Field

The present invention relates to a wafer transfer apparatus, and more particularly, to a robot arm cleaning device for cleaning a robot arm in a wafer transfer apparatus under a normal stand-by state when the robot arm does not adsorb or suction a wafer.

In general, the tendency toward gradually increasing density and smaller sized semiconductor devices, and the tendency toward multi-layer wire structures in a semiconductor device, worsen the step coverage of the device. In order to improve the step coverage, several kinds of planarizing methods, such as an SOG (Spin on Glass), an Etch Back and a Reflow, etc., are being developed so as to be applied to a planarizing process of a wafer.

Such wafer planarizing processes include a mechanical polishing method and a chemical polishing method. In the mechanical polishing method, a characteristic of a polished layer is changed due to the mechanical polishing process, which can cause a defect on a semiconductor chip. In the chemical polishing method, although the changed-process layer is not formed thereon, a precisely flattened shape cannot be obtained very well. Therefore, a planarizing process is required to execute a polishing work by combining this mechanical polishing method with the chemical polishing method. Such a process is known as a chemical mechanical polishing (CMP) process.

For the CMP process, a wafer is installed on a polishing head by a vacuum or surface tension. During the process, the wafer is held between a polishing pad provided on a polishing table, and the polishing head applying a constant pressure to the wafer. The polishing pad rotates while simultaneously the polishing head rotates and oscillates.

The wafer surface and the polishing pad are in contact with each other by the weight of the polishing head and an applied pressurizing force. Slurry, used as a process fluid, moves into a small gap between the contacting faces of the polishing pad and the wafer. Polishing particles from the slurry and surface projections of the pad perform a mechanical removing operation. Meanwhile, a chemical component in the slurry also performs a chemical removing operation.

A CMP system includes a wafer storing unit having a cassette for accommodating wafers to be polished, a rinsing unit for rinsing and drying the polished wafers, and a wafer transfer apparatus for transferring the wafers between these process units.

The wafer transfer apparatus of such a CMP system is provided with a valve unit for controlling a vacuum On/Off operation, such a valve unit being illustrated in FIG.1.

Referring toFIG. 1, the valve unit includes a solenoid valve60for supplying or cutting off air by an electric control, and an air valve62for maintaining or releasing a vacuum state by air supplied from the solenoid valve60.

Under a normal stand-by state, when a robot arm64of the wafer transfer apparatus does not adsorb or suction the wafer, the solenoid valve60is closed and air is not supplied to the N/C (Normal Close) air valve62. Therefore, a vacuum nozzle66of the robot arm64is not maintained in a vacuum state. When, at this time, the vacuum nozzle66is not maintained in a vacuum state, air flows in through the vacuum nozzle66to thus maintain an atmospheric pressure state.

However, when the wafer transfer apparatus transfers a wafer, the solenoid valve60is opened and air is supplied to the N/C (Normal Close) air valve62. When air is supplied to the air valve62, the air valve62is opened, and thereby the vacuum nozzle66of the robot arm64maintains a vacuum state to thus suction or adsorb the wafer.

Thus, the robot arm64in the wafer transfer apparatus adsorbs or suctions the wafer by using the vacuum nozzle66in a vacuum state. However, when not adsorbing the wafer, the vacuum nozzle66adopts an atmospheric state, not the vacuum state. Therefore, a problem occurs that an alien substance or fumes, etc. is deposited on or in the vacuum nozzle66and clogs up the vacuum nozzle66.

Therefore, it is an object of the present invention to provide a wafer transfer apparatus having a robot arm cleaning device, and an associated method of cleaning the robot arm, in which a vacuum nozzle of the robot arm is prevented from being clogged up by alien substances or fumes etc. when in a normal stand-by state wherein a wafer is not being suctioned or adsorbed by the robot arm.

Another object of the present invention is to provide a wafer transfer apparatus having a robot arm cleaning device, and an associated method of cleaning the robot arm, in which a vacuum nozzle is prevented from being clogged up by injecting air into the vacuum nozzle of the robot arm when in a normal stand-by state wherein a wafer is not adsorbed or suctioned by the robot arm.

In one aspect of the invention, in a wafer transfer apparatus of a semiconductor fabricating apparatus, a robot arm cleaning device comprises a solenoid valve for supplying or intercepting air by an electrical control, a first air valve for performing a control to maintain or release a vacuum state by air supplied from the solenoid valve, a second air valve for supplying or cutting off N2gas by air supplied from the solenoid valve, and a robot arm, in which a wafer is adsorbed or suctioned by a vacuum state of a vacuum nozzle when the first air valve is opened, and in which the vacuum nozzle thereof is cleaned by the N2gas supplied thereto when the second air valve is opened.

To achieve one or more of these objects, a method of cleaning a robot arm of a wafer transfer apparatus of a CMP system includes releasing a vacuum state of the robot arm under a normal stand-by state when the robot arm does not adsorb or suction the wafer, and purging the vacuum nozzle of the robot arm with N2gas so as to eliminate any alien substance or fumes.

DETAILED DESCRIPTION

In the inventive description, details of widely known functions or constructions will be omitted so as not to obscure unnecessarily the gist of the present invention.

FIG. 2is a schematic view of one embodiment of a robot arm cleaning device of a wafer transfer apparatus.

With reference toFIG. 2, the robot arm cleaning device includes a solenoid valve70for supplying or intercepting air in response to an electrical control; a first air valve72for maintaining or releasing a vacuum state in response to air supplied from the solenoid valve70; a second air valve74for supplying or cutting off a purge or cleaning gas (beneficially N2) in response to the air supplied from the solenoid valve70; and a robot arm76having a vacuum nozzle78, which adsorbs or suctions a wafer by the vacuum state of the vacuum nozzle78when the first air valve72is opened, and which is cleaned by the purge or cleaning gas supplied when the second air valve74is opened.

An operation of this embodiment will be described in detail referring toFIG. 2, as follows.

In a normal stand-by state wherein the wafer transfer apparatus does not transfer a wafer, a robot arm76does not adsorb or suction a wafer. In that case, the solenoid valve70is “Off” and air is not supplied to the first and second air valves72,74. Since the first air valve72is a normal-closed (N/C) air valve, the vacuum nozzle78of the robot arm76does not maintain a vacuum state.

At this time, when the vacuum state is not maintained in the vacuum nozzle78, since air is not supplied to the normal opened (N/O) second air valve74, the valve74is open so that it supplies a purge or cleaning gas to the robot arm76, and injects the purge or cleaning gas into the vacuum nozzle78. The purge or cleaning gas injected into the vacuum nozzle78thereby removes any alien substance or fumes deposited within the vacuum nozzle78, to prevent the vacuum nozzle78from being clogged up by air that may tend to try to flow in through the vacuum nozzle78so as to preserve an atmospheric pressure state and release the vacuum state. Beneficially, the purge or cleaning gas is N2.

However, when the wherein the wafer transfer apparatus transfers a wafer, the wafer the robot arm64adsorbs or suctions a wafer. In that case, the solenoid valve70is “On” and supplies air to the first and second air valves72,74. When air is supplied to the first air valve72, the first air valve72is opened, and when the first air valve72is opened, the vacuum nozzle78of the robot arm76maintains a vacuum state to adsorb or suction the wafer. In order that the robot arm76adsorbs or suctions the wafer, the solenoid valve70should be “On.” When the solenoid valve70becomes “On,” air is supplied to the first air valve72to open the first air valve72. When the first air valve72is opened, the vacuum state in the vacuum nozzle78of the robot arm76is maintained to adsorb or suction the wafer. At this time, when air is supplied to the second air valve74, it is closed and the purge or cleaning gas (beneficially, N2) is not injected into the vacuum nozzle78.

As aforementioned, in accordance with the present invention, there is an advantage of preventing a vacuum nozzle from being clogged up by using a purge or cleaning gas provided through the vacuum nozzle of a robot arm under a stand-by state when the wafer transfer apparatus does not transfer a wafer.