Method for automatically identifying semiconductor wafers

A method for automatically identifying a semiconductor wafer comprising the steps of:

• providing coded indicia including bars and spaces of a selected length in a predetermined portion of a surface of a semiconductor wafer;
• imparting a relative rotational motion between the semiconductor wafer and a radiant energy sensing means through at least a predetermined arc about an axis perpendicular to the surface of the wafer while imparting a relative linear motion therebetween in a radial direction along the surface of the wafer;
• directing a beam of radiant energy at said predetermined portion of the surface of the wafer along a first predetermined angular direction relative thereto so that the beam of radiant energy is reflected from the space portions of the coded indicia into the radiant energy sensing means along a second angular direction relative to the surface of the wafer;
• sensing, at the radiant energy sensing means, the radiant energy reflected by the space portions of the coded indicia at successively different positions along the length thereof as the relative linear motion is imparted between the wafer and the radiant energy sensing means while the relative rotational motion is imparted therebetween, to generate signals identifying the wafer.