Conformal atomic layer etching for Ge based on sacrificial oxide with higher Gibbs free energy of formation

Abstract

Layer-by-layer conformal atomic layer etching (cALE) for Ge is demonstrated by alternating processes consisting of the self-limiting deposition of a sacrificial oxide and the self-stop etching of the sacrificial oxide and interfacial layer (IL). The critical point of cALE is the formation of the GeOx IL between Ge and the sacrificial oxide. Accordingly, a sacrificial oxide with higher Gibbs free energy of formation was selected and investigated in the cALE process for the formation of more GeOx to increase the Ge etching rate. The cALE process presents a linear dependence of the etching depth on the cALE cycles, along with an accurate etching rate (several Å per cALE cycle) and a low surface roughness of Ge. In addition, the transmission electron microscopy images of three-dimensional fin structures of Ge demonstrate the damage-free Ge surface as well as the conformal etching of cALE. The result shows that the cALE technique can achieve precise etching of Ge accompanied with the self-limiting, self-stop, damage-free, layer-by-layer, and conformal characteristics, which is highly favorable to Ge-based nanoelectronic devices in advanced semiconductor technology nodes.