Monolayer Halftone Phase-Shifting Mask for KrF Excimer Laser Lithography

Abstract

A new monolayer halftone phase-shifting mask has been developed. The phase-shifting film consists of the compounds SiO2 and Cr2O3. The transmittance of the film is controlled by changing the mixing ratio of the two materials. Our mask can be easily fabricated because the structure of the mask is very simple and the film is considerably thicker than the Cr layer of the original double-layer halftone phase-shifting mask. Experimental results using a KrF excimer laser stepper confirm the effect of increasing the depth of focus of hole patterns.