The Effect of Al0.7Ga0.3As Etch Stop Removal on the Preparation of Wafer‐Bonded Compliant Substrates

Abstract

Preparation of GaAs‐based compliant substrates that utilize wafer bonding generally relies on integrated etch stop layers to provide the precise control required to stop selectively on GaAs layers less than 100 Å thick. We demonstrate that removing an etch stop layer with HF or leaves the underlying GaAs layers with rms roughness of 10–20 Å and peak‐to‐peak roughness of 65–150 Å. Following the selective etch, the morphology of the underlying GaAs layer is improved with a wet chemical digital etch comprised of alternate soaks in and , which results in a GaAs surface with rms roughness of ∼2 Å and peak‐to‐peak roughness of ∼20 Å. Lattice‐matched junctions deposited on thin‐bonded GaAs substrates and test substrates that are prepared for growth using the digital etch have electrical characteristics comparable to those deposited on a bulk epi‐ready GaAs substrates. However, similar lattice‐mismatched junctions deposited on the thin‐bonded GaAs substrates and test substrates have dark currents that are more than an order of magnitude higher than those deposited on bulk epi‐ready GaAs substrates. These results suggest that despite the smoothing of the digital etch, the material that remains on the surface of the thin GaAs layer is responsible for the degradation observed in the lattice‐mismatched devices deposited on the thin‐bonded GaAs substrates. © 1999 The Electrochemical Society. All rights reserved. ©2001 American Geophysical Union