0.35 μm pattern fabrication using quartz-etch attenuate phase-shifting mask in an I-line stepper with a 0.50 NA and a 0.60 sigma

Abstract

A new method, namely, top critical dimension exposure-defocus tree (TCD E-D Tree), has been developed in this paper and used to analyze simulation results for quartz-etch attenuated phase-shifting mask (APSM). Simulation studies using Depict-3 (from TMA) on isolated and dense patterns indicate that numerical aperture (NA) 0.5 has greater depth of focus (DOF); NA 0.6 has larger exposure latitude (EL); best degree of coherence (σ, sigma) value is between 0.6∼0.7; best intensity transmittance (IT) range is 4∼6 %; the effect of mask bias on DOF and EL is rather small. The effect of sigma on space patterns including contact holes shows an inverse trend compared with lines. While conventional binary intensity mask (BIM) shows a 0.9 μm total DOF for dense line; APSM in our study (zero mask bias, 4% IT, 0.5 NA, 0.6 sigma) shows a 1.2 μm total DOF (30% improvement). The experimental results are highly in agreement with simulation. However, APSM shows only an insignificant improvement for EL in this study. Stepper with a NA of 0.5 and a sigma of 0.6 is very suitable for line, space and dense line/space pattern transfer using APSM in this study.