Photomask array placement on slices in LSI processing

Abstract A method is presented for determining the location of the photomask array placement on slices that realizes the maximum number of available bars per slice in integrated circuit manufacturing. This method takes into account the slice diameter and the flat length variation encountered in material. The variation in the radius of the usable area of the slice caused by processing (photolithography or metallization) is also explicitly taken into account. A simple method for locating the photomask array correctly on the slice is described. Results of calculations for 2- and 3-in. slices are presented. The optimized gain in bars per slice for 3-in. slices vs 2-in. slices is a factor of 2·3–2·7. There are preferred bar sizes if one wishes to reduce the potential variation in bars per slice caused by random array placement.