Stone working – Sawing – Rotary
Patent
1998-04-21
1999-12-28
Rose, Robert A.
Stone working
Sawing
Rotary
134 26, 134 34, B28D 102
Patent
active
060067365
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a method and apparatus for washing a sliced silicon ingot, and more particularly to a method for washing a silicon ingot which has already been sliced to form a plurality of silicon wafers.
As is well known in the prior art, a silicon wafer is formed by cutting or slicing a certain thickness such as, for example 880 .mu.m from a silicon ingot having a generally cylindrical shape. In this instance, the silicon ingot is supported by a holder of a cutting machine. Slicing the ingot generates a substantial amount of particulate matter which adheres to the ingot. After the silicon ingot has been sliced, it is immersed in a bath containing a relatively costly detergent. The detergent includes a surfactant and a special oil to remove the particulate matter. The detergent is preferably used to as long as possible because of its substantial cost.
However, the detergent rapidly becomes filled with the particulate matter which results in a loss of chemical activity of the detergent. It will then no longer effectively remove the particulate matter from the ingot and must be replaced with fresh detergent.
In light of the above, it is a principal object of the present invention to provide an improved method and apparatus for washing a sliced silicon ingot for substantially slowing the rate of loss of chemical activity of the detergent.
Another object of the invention is to provide an improved method and apparatus for washing a worked silicon ingot for reducing the consumption of detergent.
Generally, a method for preparing semiconductor wafers from monocrystalline ingots comprises the steps of mounting the ingot on a holder. The ingot is sliced through at closely spaced longitudinal intervals thereby forming slits, each pair of slits defining a semiconductor wafer in the ingot. The sliced ingot is washed with water to remove particulate matter from the ingot which was generated during the step of slicing through the ingot and adhered to the ingot and which accumulates in the slits. Washing the ingot with detergent chemically removes particulate matter remaining following the step of washing the ingot with water. The step of washing the ingot with detergent occurs after said step of washing the ingot with water. The wafers are then separated from the holder for further individual processing of the wafers.
In another aspect of the invention, a apparatus for pre-washing a sliced silicon ingot generally comprises a support for holding the ingot. Nozzles are adapted to deliver jets of water against the ingot for flushing particulate matter from the ingot. A carrying device mounts the nozzles for movement longitudinally back and forth over substantially the full length of the ingot.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and features of the invention will become more readily apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:
FIG. 1 is a schematic, fragmentary perspective view showing a sliced silicon ingot attached to a holder by a carbon block;
FIG. 2 is a schematic front elevation showing a pre-washing machine to be used for carrying out the method of the present invention;
FIG. 3 is a right side elevation of the pre-washing machine of FIG. 2;
FIG. 4 is an enlarged fragmentary elevation of the pre-washing machine of FIG. 2 showing a holder arm supporting the ingot at the right end of sliced silicon ingot;
FIG. 5 is an enlarged fragmentary elevation of the pre-washing machine of FIG. 2 showing the holder arm supporting the ingot at the left end of the ingot in a raised position;
FIG. 6 is a fragmentary right side elevation of the pre-washing machine of FIG. 3 illustrating the mounting of a support arm of the pre-washing machine;
FIG. 7 is an elevation showing a plurality of nozzles mounted on the support arm for spraying the ingot; and
FIG. 8 is a fragmentary right side elevation of the support arm of FIG. 7.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
As shown in FIG. 1, a plurality of sil
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Kato Koichi
Kawamura Ryoichi
Kosako Masahiro
Suzuki Yoshihiro
Takami Keiichi
MEMC Electronic Materials , Inc.
Rose Robert A.
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