A novel surface patterning using FIB and in-situ etching

We introduce here a novel approach for in-situ maskless processing of GaAs substrates. It provides the function of both positive and negative lithography by the use of Ga+ focused ion beam (FIB) for direct lateral patterning of the surface and the in-situ etching with AsBr3 for a layer-by-layer precise control of the patterned structures. A latent image is formed in the native oxide as well as in its underlying substrate surface by the irradiation of the Ga+. Depending on the quantity of Ga+ dose, the irradiated area becomes either resistant to the subsequent AsBr3 etching (negative pattern) by the formation of the stable oxide of Ga2O3 or preferentially to be etched (positive pattern) by the amorphization of the substrate. This maskless and organic resist-free processing is considered to be a highly attractive method because it can provide the functions of direct patterning of an etch-stop oxide layer on the substrate or an etch-enhanced region in the substrate with a nano-scale controllability in conjunction with an atomically precise controllability in etching to obtain various kinds of three dimensional structures.