Method of forming alignment marks in a semiconductor body.

摘要

A laser beam (20) is used to scribe an alignment mark (26) on the back side (16) of a lightly doped substrate (24) of a silicon wafer (12) containing an heavily doped internal layer (22). The wavelength of the laser beam is chosen such that it passes through the lightly doped substrate without absorption but is absorbed in the heavily doped internal layer to produce therein a defect (29) which has the same position as the scribed alignment mark. Subsequent heating of the wafer causes the defect to migrate upwardly through a lightly doped epitaxial layer (30) to the front side of the wafer and produce therein a visible mirror image of the scribed alignment mark.