THE INFLUENCE OF ION ENERGY, ION FLUX, AND ETCH TEMPERATURE ON THE ELECTRICAL AND MATERIAL QUALITY OF GAAS ETCHED WITH AN ELECTRON-CYCLOTRON-RESONANCE SOURCE

The residual damage incurred to GaAs via etching with a Cl-2/Ar plasma generated by an electron cyclotron resonance (ECR) source was investi gated as a function of variations in ion energy, ion flux, and etching temperature. The residual damage and electrical properties of GaAs we re strongly influenced by changes in these etching parameters. Lattice damage was incurred in all processing situations in the form of small dislocation loops. GaAs etched at high ion energies with 200 W rf pow er, exhibited a defect density five times higher than GaAs etched at l ower ion energies with 20 W rf power. This enhanced residual damage at the higher rf powers was paralleled by a degradation in the unanneale d contact resistance. Higher etch rates, which accompany the higher rf power levels, caused the width of the disordered region to contract a s the rf power was elevated. Therefore, the residual etch damage is in fluenced by both the generation and removal of defects. Increasing the microwave power or ion flux resulted in elevating the residual defect density, surface roughness, and unannealed contact resistance. GaAs e tched at high temperatures, similar to 350 degrees C, resulted in a lo wer contact resistance than GaAs etched at 25 degrees C. The high temp erature etching augmented the defect diffusion which in turn lowered t he near surface defect density. This decrease in residual damage was d eemed responsible for improving the electrical performance at 350 degr ees C. The electrical measurements were found to be more sensitive to the density of defects than the vertical extent of disorder beneath th e etched surface. Results of this investigation demonstrate that in or der to minimize material damage and improve electrical performance, et ching with an ECR source should be performed at low rf and microwave p owers with a high substrate temperature. (C) 1995 American Institute o f Physics.