Abrading – Machine – Rotary tool
Reexamination Certificate
1999-06-18
2001-06-05
Hail, III, Joseph J. (Department: 3723)
Abrading
Machine
Rotary tool
C451S041000, C451S286000, C451S287000, C451S289000, C414S749200, C414S936000
Reexamination Certificate
active
06241592
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polishing apparatus for polishing a workpiece such as a semiconductor wafer to a flat mirror finish, and more particularly to a polishing apparatus having a pusher for transferring a workpiece between a top ring of a polishing apparatus and a robot associated with the polishing apparatus.
2. Description of the Related Art
Recent 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 &mgr;m wide, it requires that surfaces on which pattern images are to be focused 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 surfaces of semiconductor wafers is to polish them with a polishing apparatus.
Conventionally, a polishing apparatus has a turntable and a top ring which rotate at respective individual speeds. A polishing cloth is attached to the upper surface of the turntable. A semiconductor wafer to be polished is placed on the polishing cloth and clamped between the top ring and the turntable. An abrasive liquid containing abrasive grains is supplied onto the polishing cloth and retained on the polishing cloth. During operation, the top ring exerts a certain pressure on the turntable, and the surface of the semiconductor wafer held against the polishing cloth is therefore polished by a combination of chemical polishing and mechanical polishing to a flat mirror finish while the top ring and the turntable are rotated.
It has been customary to install a robot to transfer a semiconductor wafer therefrom to the top ring before it is polished, and to transfer the semiconductor wafer from the top ring thereto after it is polished. That is, the semiconductor wafer is transferred directly between the top ring and the hand of the robot which is associated with the polishing apparatus.
However, to transfer a semiconductor wafer directly between the top ring and the hand of the robot causes a conveyance error because the top ring and the robot usually have irregularities in conveying accuracy.
In order to improve the conveying accuracy of the top ring and the robot, it is preferable to install a pusher at a transfer position for the semiconductor wafer. In this case, the pusher has such a function as to place thereon a semiconductor wafer, to be polished, which has been conveyed by the hand of the robot, and then to lift and transfer the semiconductor wafer onto the top ring which has been moved over the pusher. Further, the pusher has another function as to receive the semiconductor wafer which has been polished from the top ring, and then to transfer the semiconductor wafer onto the hand of the robot. Therefore, the pusher can smoothly transfer the semiconductor wafer between the top ring and the hand of the robot without a conveyance error.
The pusher, however, has to be positionally adjusted highly accurately with respect to both the top ring and the hand of the robot. Troublesome and time-consuming operations are required to set an accurate transfer position where the pusher is to be positioned.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a polishing apparatus having a pusher which can improve transfer accuracy of a workpiece such as a semiconductor wafer.
According to one aspect of the present invention, there is provided a polishing apparatus for polishing a surface of a workpiece comprising: a turntable having a polishing surface; a top ring for supporting the workpiece to be polished and pressing the workpiece against the polishing surface; and a pusher for transferring the workpiece between the top ring and the pusher itself; the pusher comprising: a workpiece support for supporting the workpiece; an actuating unit for moving the workpiece support in a vertical direction; a sliding mechanism movable within a horizontal plane; and a first positioning mechanism for positioning the workpiece support and the top ring with respect to each other in association with the sliding mechanism when the workpiece is transferred between the workpiece support and the top ring.
The positioning mechanism may comprise at least one engaging member for engaging a predetermined portion of the top ring when the workpiece support is moved toward the top ring by the actuating unit. The engaging member may comprise a guide post which engages an outer circumferential surface of the top ring.
The workpiece support may have a workpiece holder having a plurality of guide pins for guiding the workpiece which is removed from the top ring toward a location provided on the workpiece holder. The sliding mechanism may be provided between the workpiece support and the actuating unit, and comprises a pair of sliding mechanisms disposed perpendicularly to each other and each having a rail and a slider movable along the rail.
According to another aspect of the present invention, there is provided a polishing apparatus for polishing a surface of a workpiece comprising: a turntable having a polishing surface; a top ring for supporting the workpiece to be polished and pressing the workpiece against said polishing surface; and a pusher for transferring the workpiece between said top ring and said pusher; said pusher comprising: a workpiece support for supporting the workpiece; an actuating unit for moving said workpiece support in a vertical direction; and a first positioning mechanism for positioning said workpiece support and said top ring with respect to each other when the workpiece is transferred between the workpiece support and the top ring.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate a preferred embodiment of the present invention by way of example.
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Kojima Shunichiro
Togawa Tetsuji
Ebara Corporation
Hail III Joseph J.
Nguyen George
Wenderoth , Lind & Ponack, L.L.P.
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