Atomic layer deposition of Al₂O₃ on H-passivated Si: Al(CH₃)₂OH surface reactions with H/Si(100)-2×1

Infrared absorption studies of Al(CH₃)₃ interacting with H-terminated Si reveal that O incorporation from gas-phase impurities may be a crucial factor in interface formation in atomic layer deposition. Hybrid density-functional calculations have therefore been carried out on silicon cluster models to investigate the possible pathways for reaction between the important atomic layer deposition side-reaction product Al(CH₃)₂OH (DMAOH) and the H/Si(100)-2×1 surface. Comparisons with the analogous surface reactions for Al(CH₃)₃ and H₂O are made. In general, the DMAOH surface reaction pathways are characterized by an activation of reactions involving the OH groups and suppression of CH₃ group reactions, compared to Al(CH₃)₃ and H₂O. A unique reaction pathway for DMAOH and the H/Si(100)-2×1 surface is identified resulting in the deposition of -O-Al(CH₃)₂ on the surface, which is significant since it represents an atomic-layer interface between Si and Al₂O₃. This reaction has an energy barrier of 1.3 eV and is the most thermodynamically favored pathway with an exothermicity of 0.9 eV.