Ultrathin semiconductor layer masks for high vacuum focused Ga ion beam lithography

The application of thin semiconductor layers as etch masks for high vacuum lithography is described. Heteroepitaxial layers of In0.53Ga0.47As or InP, as thin as 30 Å, were grown by molecular beam epitaxy and patterned using a focused beam of Ga ions. The Ga ion beam exposure is very rapid, since only a small amount of the mask material needs to be removed, and readily produces features with submicron sizes. The patterned thin layer can then be used as a mask for deep, material selective etching. The feasibility of selective dry etching of InP based compounds is discussed. This combination of molecular beam epitaxy and efficient precision patterning techniques is expected to result in a new flexibility in design and fabrication of semiconductor devices.