Edge modification of semiconductor wafers before epitaxial deposition - by grinding edges with profiled tool to form rounded edge with tapering planes merging with surfaces, an epi-crown being deposited

摘要

The semiconductor wafer is processed, before epitaxial depsn, by removing the sharp corners and forming a profile on the edge in a single operation. The profile is a tapering plane (50) from the top surface to the edge and from the bottom surface (54) to the edge. The length of the taper from the top surface (52) is less than that from the bottom surface (56). The angle between the tapering plane and the surface into which it leads is pref 15-30 degrees. Also claimed is the use of curved planes for the taper. The wafer is then submitted to epitaxial deposition on the top surface of the wafer (88,89), resulting in a deposition also on the edge (90) and tapered part of the underside (92). The profile is formed by grinding of the wafer's edge by a profiled grinding tool in which the shape of the tapering planes has been formed, including a curved surface (58) for the part of the edge between the tapers. In the tool the outer edge (82) at the top of the tool is set back compared with that of the lower part of the groove. USE/ADVANTAGE - The process requires a single step to complete the rounding of the edge and formation of both tapering planes. The use of two different lengths allows elimination of the epi-crown during subsequent deposition. This improves the yield of devices made on those wafers. The process is used for the prepn of semiconductor wafers for epitaxial depsn.