US Patent 7820366 Method of writing identifying information on wafer

A method of writing identifying information comprises: the step of forming a metal film on a wafer; the step of forming a resist layer on the metal film; the step of exposing the resist layer by projecting a pattern for an alignment mark on the resist layer; the first development step of developing the resist layer; the step of exposing the resist layer by projecting a pattern for the identifying information onto the resist layer using the pattern formed in the resist layer in the first development step as a reference of a location; the second development step of developing the resist layer; the step of selectively etching the metal film using the resist layer as an etching mask; and removing the resist layer.