Process margin in ArF lithography using an alternating phase-shifting mask

Abstract

We have developed ArF excimer laser lithography using an alternating phase-shifting mask (PSM) for 0.10 micrometer device fabrication. The process margin and the requirement of phase accuracy were discussed for fabricating 0.10 micrometer patterns. We clarified the factor which have an influence on the resist process margin. It was found that the phase error has a great influence on the depth-of-focus (DOF), and the mask structures and the mask bias affect on the exposure latitude. The exposure latitude for the dual-trench type PSM reached over 1.3 times as large as it for the single-trench type. 0.10 micrometer patterns have been achieved with the DOF of 0.8 micrometer and the exposure latitude of 14% by optimizing the phase shift on the dual-trench type mask. Furthermore, the exposure latitude has been improved up to 16.5% by adding the mask bias of - 0.04 micrometer on the opaque area. By a feasibility study with the 10X dual-trench type masks, it was suggested that the phase accuracy of plus or minus 2 degrees was required for 0.10 micrometer pattern fabrication.