0.35-MU-M PATTERN FABRICATION USING QUARTZ-ETCH ATTENUATE PHASE-SHIFTING MASK IN AN I-LINE STEPPER WITH A 0.50-NA AND A 0.60-SIGMA

A new method, namely, top critical dimension exposure-defocus tree (TC D E-D Tree), has been developed in this paper and used to analyze simu lation results for quartz-etch attenuated phase-shifting mask (APSM). Simulation studies using Depict-3 (from TMA) on isolated and dense pat terns indicate that numerical aperture (NA) 0.5 has greater depth of f ocus (DOF); NA 0.6 has larger exposure latitude (EL); best degree of c oherence (sigma, sigma) value is between 0.6 approximately 0.7; best i ntensity transmittance (IT) range is 4 approximately 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 mum total DOF for dense line; APSM in our study (zero mask bias, 4% IT, 0 .5 NA, 0.6 sigma) shows a 1.2 mum total DOF (30% improvement). The exp erimental results are highly in agreement with simulation. However, AP SM shows only an insignificant improvement for EL in this study. Stepp er with a NA of 0.5 and a sigma of 0.6 is very suitable for line, spac e and dense line/space pattern transfer using APSM in this study.