Realization of sub-80-nm small-space patterning in ArF photolithography

In optical lithography, small space patterning is the most difficult task. The direct small-space patterning is not good enough with resolution enhancement technique (RET) in sub-80 nm level. Two sequential processes normally achieve the small space. Once the pattern is forming a larger pattern normally, and then makes them shrink to fit to the designed size by additional process. Usually resist thermal flow process has been used to obtain small space as additional process, which has several process issues such as flow amount control of isolated and dense small contacts, uniformity degradation and bowing profile. In order to solve these issues, we introduced the resolution enhancement lithography assisted by chemical shrink (RELACS) and shrink assist film for enhancement resolution (SAFIER) process in ArF lithography. In this paper, the RELACS and SAFIER process are compared with the resist thermal flow process for sub-80 nm space using ArF exposure tool. With the application of this process, we confirmed the improvement of in-wafer uniformity and the successful implementation of sub-80nm small space patterning regardless of pitch size and pattern arrangement.