Method of processing a semiconductor

Abstract

An improvement of the prior art method of processing large scale integrated (LSI) semiconductors is disclosed, wherein an etching procedure, which was previously performed as the final processing step, is now done at an earlier stage to preclude damage to the surface of the wafer on which the active devices are formed. In the prior art method of fabricating an active device on a semiconductor wafer, an undesirable layer of field oxide manifests itself on the reverse side when the field oxide is grown on the obverse or principal side of the wafer. The prior processing philosophy was to allow the oxide layer to remain on the wafer until after the processing was completed and, as a final step, the undesired oxide coating was removed. This was done by carefully placing the wafer in a pool of etchant so that only the reverse side is etched. Since the wafer is only about 12 mils thick, the operator had to exercise extreme caution in placing the wafer in the etchant to prevent the etchant from creeping up the thickness dimension of the wafer and thus etching the obverse side. Our novel method contemplates modifying the processing steps of the prior art by removing the undesired field oxide before the circuits or active devices have been completely formed, when the wafer may be completely immersed in the etchant without damaging or etching areas on the active portion of the wafer.