Surface-Imaging Lithography,

Surface-imaging lithography is a technique which was first described by Taylor et al. 1 nearly ten years ago. In this approach, a pattern is defined at the surface or near-surface regions of a resist rather than throughout the entire resist thickness. Surface-imaging can eliminate problems such as reflectivity variations due to different substrates or topography in optical lithography and backscattering in electron-beam lithography 2. The use of surface-imaging has also proven beneficial for deep-UV optical lithography, where the high absorbance of most resists necessitates such an approach. Resist absorption is also problematic for projection printing with soft x-ray radiation the 1e attenuation length ranges from 300 nm for 13.5-nm x-rays to less than 100 nm with 39-nm x-rays 3.