As already outlined in the Introduction, the life of optical lithography has been greatly extended by improvement of tools such as high-NA steppers as well as by fine-tuning of DNQ/novolak systems. However, the ever finer linewidths that have to be printed over increasing topography often require additional enhancement of lithographic performance. Advanced resist processing schemes address this need, although usually at the cost of increased process complexity. A number of such schemes are discussed below. Usually their acceptance in a production environment is inversely proportional to the process complexity they are causing. The most widespread scheme is the use of dyed resists on strongly reflecting layers, which does not add any additional or unusual process steps.
Online access to SPIE eBooks is limited to subscribing institutions.