AVS 45th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM-ThM

Paper EM-ThM2
Development of Surface Morphology During H@sub 2@ Plasma Processing of GaAs(001)

Thursday, November 5, 1998, 8:40 am, Room 316

Session: Compound Semiconductor Surface Chemistry
Presenter: S.W. Robey, National Institute of Standards and Technology
Correspondent: Click to Email
There is interest in hydrogen plasma etching as a route to low temperature, dry processing for oxide removal from semiconductors. The surface morphology that develops is a determining factor in the success of subsequent device fabrication, making it important to understand surface processes that can influence morphology development during plasma exposure. In situ Auger spectroscopy and RHEED were used in conjunction with ex situ AFM to investigate the development of surface morphology on H@sub 2@ plasma etched GaAs(001) surfaces. Etching of the GaAs, subsequent to the oxide removal, at temperatures above 600 K led to Ga-rich surfaces with a tendency for [11n]-type facet formation. Initial attack on the GaAs surface typically occurred in a localized manner leading to the formation of etch pits. Aligned rows of etch pits are often observed due to preferential etching at mis-cut steps. The preferential attack significantly influences subsequent morphology development. Height-difference correlation functions suggest scaling at small lengths with a roughness exponent in the range of 0.7 - 0.8. A crossover occurs for separations of ~ 30 nm to 60 nm, depending on substrate temperature. The crossover length appears to correlate with typical etch pit dimensions. For larger separations, the slope is much smaller, with some evidence of additional structure in the 100 nm to 200 nm range. Correlations between diffraction and AFM data, connections to continuum models for surface etching including processes such as diffusion, redeposition, etc., and comparison to other experimental work will be discussed.