Polishing apparatus and method

Abstract

A turntable with an abrasive cloth mounted thereon and a top ring positioned above the turntable are independently rotatably provided. The top ring holds a workpiece to be polished and presses the workpiece against the abrasive cloth. The turntable and the top ring are rotated to polish the surface of the workpiece to a flat mirror finish on the abrasive cloth. A rotatable brush pressed against the abrasive cloth is rotated about an axis substantially perpendicularly to the plane of the abrasive cloth, and oscillated substantially radially between radially inner and outer positions over the abrasive cloth. A cleaning solution is sprayed from a nozzle onto the abrasive cloth. The turntable has a bank along an outer circumferential edge thereof for preventing a protective solution, which is supplied to the abrasive cloth to keep the abrasive cloth wet and prevent it, from flowing off the turntable when the turntable is stationary.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to a polishing apparatus in general and more particularly to a polishing apparatus for polishing a workpiece such as a semiconductor wafer to a flat mirror finish with an abrasive cloth.2. Description of the Related ArtRecent rapid progress in semiconductor device integration demands smaller and smaller wiring patterns or interconnections and also narrower spaces between interconnections which connect active areas. One of the processes available for forming such interconnection is photolithography. Though the photolithographic process can form interconnections that are at most 0.5 .mu.m wide, it requires that surfaces on which pattern images are to be focused on by a stepper be as flat as possible because the depth of focus of the optical system is relatively small.It is therefore necessary to make the surfaces of semiconductor wafers flat for photolithography. One customary way of flattening the surfa...

AI Technical Summary

Benefits of technology

It is therefore an object of the present invention to provide a polishing apparatus which as a dressing device capable of uniformly cleaning the entire surface of an abrasive cloth and effectively removing abrasive grains from the abrasive cloth thereby to reliably prepare the abrasive cloth in readiness for reuse.

Another object of the present invention is to provide a polishing apparatus which can prevent an abrasive cloth mounted on an upper surface of a turntable from drying.

According to another aspect of the present invention, there is provided a polishing apparatus for polishing a surface of a workpiece, comprising: a turntable with an abrasive cloth mounted on an upper surface thereof; a top ring positioned above the turntable for supporting the workpiece to be polished and pressing the workpiece against the abrasive cloth; and a bank provided on the turntable along an outer circumferential edge thereof for preventing a protective solution, which is supplied to said abrasive cloth to keep the abrasive cloth from drying when the turntable is held at rest, from flowing off the turntable, the bank having a slanted surface inclined downwardly in a radially inward direction of the turntable for allowing the protective solution to be scattered away from the turntable over the slanted surface under centrifugal forces when the turntable is rotated.

When the turntable is held at rest with no polishing process being carried out, a protective solution such as pure water is put over the abrasive cloth to keep the abrasive cloth from drying. The supplied protective solution is prevented from flowing off the turntable by the bank along the outer circumferential edge of the turntable. Therefore, the abrasive cloth is reliably prevented from drying while it is not in use. When the turntable is rotated to polish a workpiece, the protective solution is scattered away from the turntable over the bank under centrifugal forces. Therefore, the protective solution is not left on the surface of the abrasive cloth and does not obstruct the polishing process. The slanted surface of the bank allows the protective solution to be smoothly discharged off the turntable upon rotation of the turntable.

According to still another aspect of the present invention, there is provided a polishing apparatus for polishing a surface of a workpiece, comprising: a turntable with an abrasive cloth mounted on an upper surface thereof; a top ring positioned above the turntable for supporting the workpiece to be polished and pressing the workpiece against the abrasive cloth; a rotatable brush facing the abrasive cloth; first actuating means for rotating the rotatable brush about an axis substantially perpendicular to the plane of the abrasive cloth; second actuating means for reciprocally moving the rotatable brush substantially radially between radially inner and outer positions over the abrasive cloth; and a nozzle for supplying a cleaning solution onto the abrasive cloth; and a bank provided on the turntable along an outer circumferential edge thereof for preventing a protective solution, which is supplied to the abrasive cloth to keep the abrasive cloth from drying when the turntable is held at rest, from flowing off the turntable, the bank having a slanted surface inclined downwardly in a radially inward direction of the turntable for allowing the protective solution to be scattered away from the turntable over the slanted surface under centrifugal forces when the turntable is rotated.

Problems solved by technology

As the polishing process progresses, the abrasive cloth is clogged with abrasive grains contained in the abrasive material.

The conventional dressing device is however disadvantageous in that it fails to clean the entire surface of the abrasive cloth 34 uniformly and cannot fully remove the abrasive grains which have embedded in the abrasive cloth This is because, as shown in FIG. 9(a), the abrasive cloth 34 is swept only in one direction depending on the rotational direction of the turntable 33, and hence the abrasive grains are removed from the abrasive cloth 34 only in one direction.

The dressing device shown in FIGS. 8(a) and 8(b) has a similar problem inn that it fails to achieve uniform cleaning of the entire surface of the abrasive cloth 34 and full removal of the abrasive grains which have stuck to the abrasive cloth 34.

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