Chemical Physics of Digital Etching

We have investigated the Chemisorption of halogens on semiconductor surfaces in order to develop a better understanding of passivation and etching of these surfaces. We have shown that halogen chemisorption occurs onto both Si111 and GaAs100 via both dissociative chemisorption and abstraction. In abstractive chemisorption of a diatomic molecular halogen, one halogen atoms sticks to the surface while the other is ejected back into the gas phase. The abstraction process can be chemically selectivity for one of the two atoms in an interhalogen such as ICl. Furthermore, both abstraction and dissociation can be chemically selective for the Ga atoms on the GaAs100 surface. The chemisorption of halogens can passivate the surface both chemically and electronically. Passivation occurs when a stable homogeneous monolayer of surface monohalide is formed. For GaAs100, passivation can unpin the Fermi level this is a critical step in developing a CMOS technology of GaAs. We are now studying the deposition of insulators on GaAs for use in high speed low power wireless communication and satellite technology with support from DoD.