Mechanisms for the Trimethylaluminum Reaction in Aluminum Oxide Atomic Layer Deposition on Sulfur Passivated Germanium

Germanium combined with high-κ dielectrics is investigated for the next generations of CMOS devices. Therefore, we study reaction mechanisms for Al 2 O 3 atomic layer deposition on sulfur passivated Ge using calculations based on density functional theory and total reflection X-ray fluorescence (TXRF). TXRF indicates 6 S/nm 2 and 4 Al/nm 2 after the first TMA/H 2 O reaction cycle, and growth inhibition from the second reaction cycle on. Calculations are performed on molecular clusters representing −GeSH surface sites. The calculations confirm that the TMA reaction does not affect the S content. On fully SH-terminated Ge, TMA favorably reacts with up to three −GeSH sites, resulting in a near tetrahedral Al coordination. Electron deficient structures with a Ge–S site shared between two Al atoms are proposed. The impact of the cluster size on the structures and reaction energetics is systematically investigated.