Evaluation of various alternating phase shifting mask processes for KrF lithography

摘要

It is reported that Alternating Phase Shifting Mask (Alt. PSM) enhances the resolution and depth of focus and reduces the mask error enhancement factor efficiently. In spite of above-mentioned advantages, Alt. PSM is rarely used for some problems. One of the problems is the image imbalance between the transmittance of the shift and the nonshift area on Alt. PSM. To minimize the image imbalance, various manufacturing processes are introduced for both single and dual trench structures. In this paper, the image balance was simulated with AIMS and the Solid-CM~(TM) program. The pattern profile, CD, depth and a phase uniformity of Alt. PSM were investigated experimentally. We carried out 3 types of processes (Figure 1) (a) single trench (wet etch process), (b) single trench (dry etch process with undercuts), (c) dual trench (dry etch process with undercuts). The type (a) showed 12 nm of CD uniformity, 1.56° of phase shift uniformity and 63 A of the shift depth. And its transmittance of the shift region was 99.85 %. For the type (b), its CD uniformity, phase shift uniformity, depth uniformity and the transmittance of the shift region were 15 nm, 11.56?, 208 A and 99.76 %, respectively. And the experiments of the type (c) are now under way.