Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
1999-01-07
2001-06-12
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C438S689000, C438S691000, C438S748000, C438S753000, C216S092000
Reexamination Certificate
active
06245678
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor wafer, in particular, to a method for mirror-finishing the beveled surfaces located at the peripheral rims of semiconductor wafers.
2. Description of the Related Art
Conventionally, beveling of the peripheral rims of semiconductor wafers has been performed for the purpose of avoiding chipping or breakage during the process of polishing or flattening such as lapping. Recently, high flatness of the beveled peripheral portions is required so as to enhance the yield during device processing. Therefore, it is necessary to finish them by mirror-polishing. The mirror-polishing of the peripheral portions of the semiconductor wafers has been performed by using a polishing unit as follows: A beveling device, in which a grinding wheel is installed, shapes the beveled portions of semiconductor wafers. Then, a polishing unit, whose surface is provided with a polishing pad affixed thereon, is guided to urge against the beveled portions of the semiconductor wafer to be polished. Afterward, mirror-polishing is performed by supplying slurry.
However, to accurately polishing the beveled portions with the aid of the polishing unit, it is essential to analyze the slanted angle of the beveled portion and control the polishing unit based on the analyzed data.
Furthermore, to polish the beveled portion into the shape of a taper, three surfaces have to be polished. Those are thr front-side tapered surface, the outer peripheral surface, and the rear-side tapered surface. The three surfaces have to be polished by separate polishing units and the wafer has to be turned over, therefore processing time is long.
In addition, the boundary portions among the front-side tapered surface, the outer peripheral surface, and the rear-side tapered surface are quite difficult to be mirror-polished. Therefore, there exists a possibility that the boundary portions will remain not mirror-polished.
SUMMARY OF THE INVENTION
In view of the above-described problems, the object of this invention is to provide a method for manufacturing semiconductor wafers, which is capable of precisely performing mirror-finishing without being influenced by the shape of the beveled portions of semiconductor wafers, and can perform mirror-finishing more efficiently compared with conventional methods.
The above object is achieved by employing spin-etching process when the beveled portions formed on the outer peripheries of semiconductor wafers are to be mirror-finished. The mirror-surface treatment of the beveled portions may be performed while carrying out mirror-finishing of the semiconductor wafer surfaces. Namely, the beveled portions formed on the outer peripheries of semiconductor wafers are mirror-finished through spin-etching process at the same time the semiconductor wafer surfaces are spin-etched. Naturally, in case that a beveled portion is mirror-finished solely, an etching-protection film is formed to cover the whole semiconductor wafer except the beveled portion, and the etching-protection film is removed after spin-etching. This can achieve mirror-finishing of the beveled portion solely. Furthermore, if etchant turns around and follows exceeding the beveled portion to reach the rear surface of the semiconductor wafer, part of the rear surface will be mirror-finished. This will bring about irregular color or improper glossiness on the rear surface. To avoid this drawback, gas is guided to radially flow from the rear surface toward the edge of the semiconductor wafer. Therefore, excess etchant can be blown off from the rear surface of the semiconductor wafer.
According to the present invention, the following advantages can be achieved.
(1) Compared with conventional mirror-treatment, which is performed by polishing, of the beveled portions formed on the outer peripheries of semiconductor wafers; the processing time according to this invention is shorter. Furthermore, mirror-finishing of the surfaces and the outer peripheries of semiconductor wafers can be performed simultaneously. Therefore, processing in this invention is very efficient.
(2) Because the spin-etching is employed, the outcome will not be influenced by the shape of the beveled portions formed in the preceding process. Therefore, a mirror-finishing can be performed uniformly. In addition, finishing of the beveled portion boundary which is not surely attained in the conventional mechanical polishing can be definitely performed.
(3) Non-contact processing is used; therefore work-strain layer incurred by mechanical working will not happen.
REFERENCES:
patent: 5800725 (1998-09-01), Kato et al.
patent: 6043156 (2000-03-01), Kai et al.
Ishii Akihiro
Yamamoto Hiroaki
Komatsu Electronic Metals Co. Ltd.
Niebling John F.
Oliff & Berridg,e PLC
Zarneke David A.
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