The effects of molecular weight on the exposure characteristics of poly(methylmethacrylate) developed at low temperatures

Poly(methylmethacrylate) (PMMA) with various molecular weights exposed using 50keV electron beam have been investigated at subzero developer temperatures. Contrast curves for Methyl Isobutyl Ketone (MIBK):Isopropyl Alcohol (IPA)=1:3 and MIBK:IPA=1:7 developers were determined. The contrast curves for different molecular weight PMMA resists converge into a single curve at lower temperatures. At low temperatures, the line edge roughness and resolution improved. However, minimum line pitch shows no significant improvement while dose latitudes for a particular line pitch increased. It is shown that at low temperatures, linewidth resolution and periodicity are invariant for the different PMMA molecular weights (50K to 2.2M) used in this work.