AlSixOy as a high-transmittance embedded material of ternary attenuated phase-shifting mask and correlation between chemical composition and optical properties of AlSixOy in 193 nm lithography

Abstract

AlSixOy (Al : Si : O = 1 : 0.36 : 0.88) thin film has the potential for use as a new and high-transmittance (T% similar to 35%) embedded layer of an attenuated phase-shifting mask (AttPSM) in 193 nm lithography. Increasing the compositions of Al2O3, SiO2 and other oxides increases n and decreases k in AlSixOy. Compared to a conventional AttPSM (T% < 10%), the high-T% AttPSM assisted by opaque Cr scattering bars can achieve a greater depth of focus, 0.45 <mu>m for a 0.10 mum isolated line. Under the conditions of BCl3/Cl-2 = 30/7 seem, chamber pressure 3 mTorr; source power 1400 W and RF bias power 30 W, the etching selectivity of AlSixOy over positive resist EP-1EG is 7.7 : 1. Under those of BCl3/Cl-2/O-2 = 35/7/3.2 seem, the selectivity of AlSixOy over substrate fused silica is 5.8 : 1. A 0.25-mum-line/space (1 : 1) etched pattern was successfully fabricated using AlSixOy as an embedded layer.