As semiconductor device geometry shrinks down to the 100 nm order for the m
ost critical layers, requirements for overlay accuracy have become increasi
ngly strict in the semiconductor manufacturing process; One contribution to
overlay error (particularly alignment error) originates from the process a
nd tool interaction. Therefore, it is necessary to improve the alignment ac
curacy of both the process and the tool. Alignment errors can be separated
into tool-induced shift (TIS): wafer-induced shift (WIS), and TIS-WIS inter
action. In this study, optimization of the alignment mark will be proposed
in order to reduce not only TIS, but also WIS for the XRA-1000, which is th
e volume production stepper of proximity X-ray lithography (PXL).