Accurate Reactive Ion Etching of Si, Ge and P Doped Ge in an SF₆-O₂ Radio-Frequency Plasma

Abstract

The effect of reactive ion etching (RIE) of Silicon (Si), Germanium (Ge) and highly phosphorous doped Germanium (Ge:P) in an SF 6 -O 2 plasma has been studied. We find that the etch characteristics of etch rate and sidewall profile are greatly affected by the O 2 content. Etching rates of Ge and Ge:P depend on the O 2 content with a significant reduction up to 20% of O 2 . We also find that an anisotropic sidewall etching mechanism exists and is dependent on the percentage of O 2 (%O 2 ) in the plasma. Sidewall angles range from a minimum of 66° to a maximum of 166°, where a critical concentration for etching angle exists where the etching angle can alternate from below 90° to above 90°. In combination, both features allow for precision plasma etching of Si, Ge and P:Ge.

Nanostructured Germanium with >99% Absorption at 300–1600 nm Wavelengths

“…On the other hand, nanostructure formation is suppressed also when the O 2 flow is overly high with respect to SF 6 , since the etch rate of germanium is heavily reduced. [ 32 ] Hence, the optimization of the gas composition is critical. In this work, a SF 6 :O 2 gas flow ratio of 25:33 sccm was found to be optimal for producing uniform nanostructures throughout the wafer.…”