Quantitative assessment of the geometrical distortion suffered by the profile of a semiconductor wafer.

摘要

A method for the quantitative assessment of the degree of geometrical deformation undergone by a surface profile of a wafer following the formation of a conformal surface layer employs a simple mechanical profilometer, whose stylus is run over a target morphological detail comprising at least two mutually parallel ridges or reliefs which rise above the plane of the surface of the wafer for a height of between 0.1 and 0.5 mu m, and which enclose between them a depression of a width of between 2 and 4 mu m, in order to determine the elevation of the bottom of the valley between the two ridges relative to the plane of the surface of the wafer from which the ridges rise following the formation of one or more similar surface layers. The vertical measurement of the elevation undergone by the bottom of the valley in itself represents a quantitative index of the vertical and horizontal geometrical deformation undergone by the details of the surface profile of the wafer. In order to determine characteristics of automatic alignability by a particular apparatus employing said target details for automatic alignment, it is possible to establish a maximum value for said distortion index, determined as above, above which the automatic alignment capability is lost.