EFFECT OF MOLECULAR-WEIGHT ON POLY(METHYL METHACRYLATE) RESOLUTION

Electron-beam lithography's resolution limit is greater than the beam diameter due to resist limitations as well as electron interaction wit h solids. We examine the effect of molecular weight on the resolution of poly(methyl methacrylate) (PMMA). The experimental procedure uses t hin Si3N4 in order to reduce the backscattered electron contribution t o the exposure, and the resist contrast standard deviation sigma was d etermined. Molecular weights of 950x10(3), 120x10(3), and 15x10(3) amu were used. It is found that relatively equivalent exposure and resolu tion are found in each case, and that the entanglement threshold is ei ther lower than thought, or is not a factor in the resolution of PMMA. Lines as small as 7 nm are found in the highest molecular weight. (C) 1996 American Institute of Physics.