Optical surface thickness measuring technique - uses separation of point source and secondary image to determine thickness of semiconductor at primary image point

摘要

The surface (E) to be studied is situated at right angles to the optical axis of an objective lens (1). A point light source (S0) situated on the axis forms an illuminated area which is a function of the distance (h) between a reference plane passing through a point (S1) and the surface (E). The surface is at least partially reflecting and returns through the objective a fraction of the radiation forming an image (S3) of the point (S2) on the test surface. The distance between the source and final image (S0-S3) is a function of the magnification of the objective (1) and the thickness (h) of the relief of the surface, measured relative to the reference plane (SO-S3=2RG squared).