Double 15-nm-wide metal gates 10 nm apart and 70 nm thick on GaAs

Abstract

A method that can fabricate two narrow but thick metal lines separated by a small gap on a bulk semiconductor substrate is described. By opening a 40-nm-wide trench in a single layer of 70-nm-thick polymethylmethacrylate resist on GaAs using high resolution electron beam lithography, and by double shadow evaporations and a lift-off, two 15-nm-wide metal lines 10 nm apart and 70 nm thick were fabricated on a bulk GaAs substrate. The pitch size of the double metal lines is 25 nm. This is a factor of 2 smaller than the previous smallest pitch size on bulk semiconductors. It is found that the width and spacing of the two lines are uniform over tens of microns. It is also found that metals shadow evaporated on top of the resist can be removed successfully by a lift-off, even though they were connected to the metals in the resist trenches. These results suggest that using this method metal lines with even finer linewidth (<15 nm) can be achieved on a bulk semiconductor substrate.