Patent ID: 7253428

Claim:
A method for identifying a type of semiconductor device being fabricated on a substrate by evaluating an identification mark comprising at least one recess in the substrate surface through at least one layer formed over the mark, comprising: scanning electromagnetic radiation of at least one wavelength across at least a portion of the substrate including the at least one recess, the at least one wavelength at least partially penetrating at least one layer of a material opaque to visible wavelengths of electromagnetic radiation to an identifying mark embedded within materials that are opaque to visible wavelengths of electromagnetic radiation; measuring an intensity of radiation of the at least one wavelength reflected by different locations of the at least a portion of the substrate; detecting locations at which the intensity changes from substantially a baseline intensity; and correlating each location at which the intensity changes from substantially the baseline intensity to at least one characteristic which distinguishes characters of the identification mark from other features on or in the substrate to reveal the identification mark and to identify the type of semiconductor device being fabricated on the substrate.