No abstract

Line width roughness (LWR) reduction is a critical issue for low k1 ArF immersion lithography. Various approaches such as materials, exposure technology and the track process have been performed for LWR reduction during lithography process. It was reported that the post-development bake process had good performance for LWR reduction (1) . However, the post-development bake process induced large CD change owing to the degradation of large isolated resist pattern (2) . Therefore post-development process with small iso-dense bias is required in low k1 ArF immersion lithography. The resist smoothing process is one of the candidates for LWR reduction with small iso-dense bias. This method whereby the resist pattern surface is partially melted in organic-solvent atmosphere was shown to have a significant LWR reduction effect on resist patterns (3) . This paper reports on the application of the resist smoothing process to the ArF immersion resist pattern after development. It was found that the resist smoothing process was effective to reduce LWR for ArF immersion resist. As a result of LWR trace from after development to after the hard mask etching process, the effect of LWR reduction with the resist smoothing process continued after the hard mask etching process. Furthermore CD change of large isolated patterns with the smoothing process was smaller than in the case of postdevelopment bake process. We confirmed that the resist smoothing process is an effective method for decreasing LWR in ArF immersion lithography.