Sub-120 nm patterning in KrF lithography

Recently a 130 nm design rule device has been attempted with OAI (Off Axis Illumination) and PSM (Phase Shift Mask) in KrF, and is thought to be the nodal point of KrF and ArF lithography. However, the ArF process has not yet matured, so an extension of KrF is considered for sub-120 nm patterning. The process margins, especially exposure latitude, are investigated on the basis of the amount of 1st order light into the entrance pupil. At first, 120 nm patterns were tried for the annular condition on the basis of that result. A modified dipole was suggested for sub 120 nm patterning. For design of the dipole, asymmetry in X and Y directions was taken into consideration. The availability of a modified dipole is evaluated for 110 nm dense lines and 130nm or less device patterns.