Karl-Heinz Muller

Physical and technological limits in optimal and X-ray lithography

Abstract If we assume that optical steppers for deep UV lithography can be developed down to wavelengths of 248 nm, but not further, then the focus depth requirement of device manufacturing will restrict the minimum linewidth to 0.5 μm for standard single layer resists and perhaps to 0.35 μm for advanced complex resists systems. While optical lithography is resolution limited, an analysis of the overlay budget reveals that X-Ray synchrotron lithography is confined by overlay requirements. When a compensation mechanism for linear mask and wafer distortion can be realized, then minimum linewidths of 0.3 to 0.35 μm with chip sizes up to 30 mm would be feasible with X-Rays. A comparison of the lithography performance with future DRAM demands indicates that optical lithography would meet the requirements down to 16M or 64M, and X-Ray lithography down to 256M.