Investigating FinFET Sidewall Passivation Using Epitaxial (100)Ge and (110)Ge Metal–Oxide–Semiconductor Devices on AlAs/GaAs.

Device-quality crystallographically oriented epitaxial (100)Ge and (110)Ge were grown on GaAs substrates using a large bandgap AlAs buffer. Electrical characteristics of p-type metal-oxide-semiconductor (pMOS) capacitors, fabricated from the aforementioned material stacks, are presented for the first time. High-resolution cross-sectional transmission electron microscopy analysis demonstrated atomically abrupt heterointerfaces between Al2O3/Ge as well as Ge/AlAs for both (100) and (110) orientations. Various process conditions were implemented during MOS capacitor fabrication to study their impact on the Al2O3/Ge interface. The fabricated pMOS devices demonstrated excellent electrical characteristics with efficient modulation of the Fermi level from midgap to the conduction band edge, corresponding to a minimum Dit value of 1.2 × 1011 cm-2·ev-1 on (100)Ge, indicative of a high-quality oxide/Ge heterointerface, and an effective electrical passivation of the Ge surface. Postdeposition annealing under O2 was found to be less effective at reducing oxide trap density (NOT) as compared to forming gas or O2 postmetallization anneals (PMA), indicating that metal-induced bandgap states at the gate metal/dielectricinterface have a notable impact on Ge pMOS NOT. On the other hand, a tradeoff must be made between NOT and the equivalent oxide thickness when performing PMA under O2 or forming gas ambient. [ABSTRACT FROM PUBLISHER]