Strain selectivity of SiGe wet chemical etchants

TL;DR

This study examines how strain affects the etching rates of SiGe with two wet etchants, finding no strain selectivity but a dependence on Ge content for one etchant, and confirming isotropic etching behavior.

Contribution

It demonstrates that strain does not influence etching rates in SiGe with these solutions, highlighting the primary role of Ge content and isotropic etching characteristics.

Findings

No appreciable strain selectivity in etching rates

Etching rates depend mainly on Ge content for NH4OH:H2O2

Both etchants exhibit isotropic etching without facet preference

Abstract

We investigate the effect of strain on the etching rate of two SiGe wet etchants, namely NH4OH:H2O2 and H2O2. For both etchants, we found that there is no appreciable strain selectivity, i.e. the etching rates do not depend on the actual strain state in the SiGe films. Instead, for the NH4OH:H2O2 solution, the rates are primarily determined by the Ge content. Finally, we show that both etchants are isotropic with no preferential etching of particular facets.