Abrading – Machine – Combined
Reexamination Certificate
2000-01-04
2002-08-13
Hail, III, Joseph J. (Department: 3723)
Abrading
Machine
Combined
C451S288000, C451S287000, C451S057000
Reexamination Certificate
active
06431964
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a planarization apparatus and method, and more particularly to a planarization apparatus and method for planarizing the reverse of a semiconductor wafer on which no chip is formed in a semiconductor wafer manufacturing process.
2. Description of Related Art
A planarization apparatus for grinding the reverse (one side) of a semiconductor wafer has chucks for holding the wafer by suction, a rough grinding wheel, a fine grinding wheel, a reverse cleaning unit, and the like. One chuck holds the obverse (the other side) of the wafer, and then the rough grinding wheel is pressed against the reverse of the wafer. The reverse of the wafer is roughly ground by rotating the chuck and the grinding wheel. The roughly-ground wafer is detached from the chuck and is held by another chuck for the fine grinding so that the wafer can be finely ground by the fine grinding wheel. The finely-ground wafer is transferred to the reverse cleaning unit so that the reverse of the wafer can be cleaned. That completes the grinding of the reverse of one wafer by the planarization apparatus.
The wafer whose reverse has already been ground is transferred from the planarization apparatus to an etching apparatus, which etches the wafer to remove a machining deteriorated layer formed at the reverse of the wafer.
If the wafer is ground into an extremely thin wafer close to a standardized article, the wafer is damaged (cracked or chipped) because of the machining deteriorated layer when the wafer is transferred from the planarization apparatus to the etching apparatus.
To address this problem, the conventional planarization apparatus grinds the wafer to such a thickness as not to damage the wafer during the transfer. With respect to the thickness of the wafer, the planarization apparatus roughly grinds the wafer with the thickness of 725 &mgr;m sliced from an ingot to the thickness of 250 &mgr;m, and finely grinds the wafer to the thickness of 200 &mgr;m. The wafer is machined to the standardized thickness of 50 &mgr;m at the etching step.
The conventional planarization apparatus, however, cannot grind the wafer close to the standardized thickness in order to prevent the wafer from being damaged during the transfer. For this reason, a machining allowance (150 &mgr;m in the above example) is large at the etching step. Thus, it takes a long time to etch the wafer, and the throughput cannot be improved.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide a planarization apparatus and method which improve the throughput without damaging a workpiece.
The above object can be achieved by providing a planarization apparatus which comprises a holding means for holding a workpiece and a grinding means which has a grinding wheel for grinding the workpiece and grinds one side of the workpiece by the grinding wheel, the planarization apparatus comprising: a polishing means for polishing the one side of the workpiece, the polishing means comprising a rotating means for rotating a polishing head and a positioning mechanism for setting an interval between the polishing head and the workpiece.
The above object can be achieved by providing a planarization apparatus comprising: a holding means for holding a workpiece; a rough grinding means for roughly grinding the workpiece held by the holding means; a fine grinding means for finely grinding the workpiece roughly ground by the rough grinding means in the state wherein the holding means is holding the workpiece; a polishing means for polishing the workpiece finely ground by the fine grinding means in the state wherein the holding means is holding the workpiece; and a moving means for moving the holding means to a rough grinding position for the rough grinding means, a fine grinding position for the fine grinding means, and a polishing position for the polishing means.
The above object can be achieved by providing a planarization method using a planarization apparatus comprising: holding means for holding a workpiece; grinding means for grinding the workpiece held by the holding means; polishing means for polishing the workpiece ground by the grinding means; moving means for moving the holding means to a grinding position for the grinding means to grind the workpiece and to a polishing position for the polishing means to polish the workpiece; and wherein the polishing means polishes the workpiece by an amount more than an amount required for removing a machining deteriorated layer formed by the grinding, calculated by doubling a standard deviation, and less than a larger value between an amount required for correcting an unevenness of a thickness during the grinding and removing the machining deteriorated layer, calculated by sextupling a standard deviation, and 20 &mgr;m.
The above object can be achieved by providing a planarization method using a planarization apparatus comprising: holding means for holding a workpiece; rough grinding means for roughly grinding the workpiece held by the holding means; fine grinding means for finely grinding the workpiece roughly ground by the rough grinding means; polishing means for polishing the workpiece finely ground by the grinding means; moving means for moving the holding means to a rough grinding position for the rough grinding means, a fine grinding position for the fine grinding means and to a polishing position for the polishing means; wherein the fine grinding means finely grinds the workpiece by an amount more than an amount required for removing a machining deteriorated layer formed by the rough grinding, calculated by doubling a standard deviation, and less than a larger value between an amount required for correcting an unevenness of a thickness during the rough grinding and removing the machining deteriorated layer, calculated by sextupling a standard deviation, and 150 &mgr;m; and wherein the polishing means polishes the workpiece by an amount more than an amount required for removing a machining deteriorated layer formed by the fine grinding, calculated by doubling a standard deviation, and less than a larger value between an amount required for correcting an unevenness of a thickness during the fine grinding and removing the machining deteriorated layer and calculated by sextupling a standard deviation, and 20 &mgr;m.
According to the present invention, the planarization apparatus having the grinding means is provided with the polishing means, and this enables the grinding and polishing of the wafer in one apparatus. In the polishing method using the polishing means, the positioning mechanism positions the polishing head with respect to the workpiece, and the polishing head is pressed against the workpiece and is rotated by the rotating means. Consequently, the workpiece is polished. Since there is no necessity of transferring the workpiece from the planarization apparatus to the etching apparatus, the grinding means can grind the workpiece close to the standardized thickness. This reduces the time required for polishing the workpiece, and improves the throughput. The polishing removes the machining deteriorated layer formed by the grinding, and eliminates the necessity of etching in a post-treatment. This simplifies the entire structure of the workpiece manufacturing line, and reduces the size of the workpiece manufacturing line.
The workpiece may be polished in a constant pressure processing or in a constant cutting depth processing.
According to the present invention, the grinding means grinds the workpiece held by the holding means, and then, the polishing means polishes the workpiece after the moving means moves the holding means to the polishing position. More specifically, the workpiece held by the holding means is ground and polished, and it enables the accurate machining without damaging the workpiece. On the other hand, an apparatus, which transfers the workpiece from a holding means for grinding means to a holding means for a polishing means has such a problem that the w
Ishikawa Toshihiko
Katagiri Yasushi
Nixon & Peabody LLP
Safran David S.
Tokyo Seimitsu Co. Ltd.
Wilson Lee
LandOfFree
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