Enhanced Mask to Wafer Alignment for 'A' Level Exposure On Perkin-Elmer Microalign Tools
Original Publication Date: 1985-Jun-01
Included in the Prior Art Database: 2005-Feb-19
An "A" level exposure is the exposure of a mask pattern onto a blank wafer which has no patterns on its surface. There has to be a center alignment between the mask and the blank wafer. To meet this requirement, a set-up wafer which has marks on its surface is loaded into the wafer stage. The mask position is adjusted to align with the marks on the wafer surface as finely as possible. After alignment is completed with the set-up wafer, blank wafers are subsequently loaded into the aligned position. No readjustment of the wafer position is required.