NEGATIVE PMMA AS A HIGH-RESOLUTION RESIST - THE LIMITS AND POSSIBILITIES

Poly(methylmethacrylate) (PMMA) which is commonly used as a positive r esist can also be used in a negative manner with exposure at higher do se levels. In this paper we investigate the full potential of this res ist for high-resolution pattern definition. We show that although the point spread exposure distribution is similar to that for positive PMM A, features of the order of 10 nm are easily achieved. These resist st ructures can be transferred into the underlying materials using plasma etch techniques to a similar degree of resolution. The density of res ist features is also greater than for positive PMMA with features of s imilar to 15 nm in width being possible on a 30 nm pitch. The instabil ity of the resist structures at extreme linewidths has been identified as a potential problem in utilizing the process.