Germanium Surface Conditioning and Passivation

Germanium (Ge) is a candidate to replace silicon (Si) as channel material for the gate electrode. Due to the aqueous solubility and the thermal instability of germanium dioxide (GeO2), cleaning solutions used for Si are ineffective and must be adapted to this material. Hydrogen passivation of the Ge surface, as compared to Si, is more difficult to achieve and the H-terminated Ge surface is unstable. Various methods are being used to stabilize the Ge surface; such as, oxidation of the Ge to stoichiometric GeO2, oxynitridation, and even nitridation of the Ge substrate. Oxide-free Ge-surfaces can also be achieved by using hydrochloric acid (HCl) or other treatments. Sulfur-containing passivation is shown to prevent interaction of the Ge channel with the hafnium oxide (HfO2) gate. Metal and particle removal can be achieved using highly diluted cleaning solutions. This chapter discusses the various methods to passivate the surface and the surface analysis results. Controlled Vocabulary Terms germanium compounds; hafnium compounds; nitridation; passivation; silicon