A New Method of Formation of the Masking Image (Relief) Directly during the Electron-Beam Exposure of the Resist

摘要

A new method of dry electron-beam etching of some positive resists directly during exposure is proposed. It is shown that exposure of the PMMA resist (the layer 80-85 nm thick on the Si wafer) by electrons with energy of 15-20 keV in vacuum at temperatures of 115-170℃ (above the glass-transition temperature of the PMMA) leads to the effective etching of the resist at relatively low exposure doses by a factor of 10-100 smaller than the exposure doses of this resist in the conventional "wet" lithography. It is assumed that the direct etching proceeds by the mechanism of the radical-chain depolymerization of the PMMA resist to a monomer. The high efficiency of the suggested method for the formation of spatial 3D structures in the PMMA resist is shown.