0.32 /spl mu/m pitch on-gird random line pattern formation by dense dummy pattern and double exposure in KrF wavelength

0.32 /spl mu/m pitch on-grid random line pattern formation by double exposure is proposed based on optical image calculations. For first exposure, mask patterns consist with designed patterns and dummy patterns, which are laid out at all on-grid positions with the pitch of 0.32 /spl mu/m, and attenuated phase shift mask and annular illumination are applied. The imaging performance is significantly enhanced because all patterns in the mask are categorized "dense" with the same pitch. The mask pattern for the second exposure is simply generated from the designed pattern with resizing by appropriate amount. The pattern size in this mask becomes much larger than that in the first exposure mask. Consequently, large exposure latitude can be obtained by conventional exposure method. As a result, the 0.32 /spl mu/m pitch on-grid random line patterns are formed with DOF larger than 0.6 /spl mu/m in KrF wavelength.