<title>Mask image formation by electron beam deposition from vapor phase</title>

Abstract

Dry resistless process was studied of mask image formation by electron beam deposition from hydrocarbon precursor undecane (C₁₁H₂₄) on substrates of SiO₂ (layer 80 nm) on silicon and cupper (layer 430 nm) on silicon. A mask in form of grating of 5-150 nm height strips was created in a cell introduced into the scanning electron microscope CamScan. Strips thickness &delta; was considerably more than the beam size and depended on substrate material: for SiO₂ &delta;=0.6 &mu;m, for Cu&delta;=2 &mu;m. Strong dependence of growth rate <i>V</i> (at Cu) on the line scan time &tau; was found out. At beam current 1.0 nA varying &tau; from 20 ms to 13 s led to 7.4 times decreasing <i>V</i>. This effect most likely is caused by significant diffusion delays at &tau;=13 s in precursor transport into reaction zone during the pixel time. The ion beam etching of substrates through the deposited mask was carried out. SiO₂ substrate was etched by SF₆ ions, Cu substrate was etched by Ar ions. In both cases etching rate of mask material were close to etching rate of substrate. In mask deposited on SiO₂ thin (about 1 nm) intermediate surface layer was found having significantly more (8-10 times) etching resistance than the basic mask material.