Low temperature thermal ALD of a SiN_x interfacial diffusion barrier and interface passivation layer on Si_xGe_{1- x}(001)...

Atomic layer deposition of a silicon rich SiN_x layer on Si_0.7Ge_0.3(001), Si_0.5Ge_0.5(001), and Si_0.5Ge_0.5(110) surfaces has been achieved by sequential pulsing of Si₂Cl₆ and N₂H₄ precursors at a substrate temperature of 285 °C. XPS spectra show a higher binding energy shoulder peak on Si 2p indicative of SiO_xN_yCl_z bonding while Ge 2p and Ge 3d peaks show only a small amount of higher binding energy components consistent with only interfacial bonds, indicating the growth of SiO_xN_y on the SiGe surface with negligible subsurface reactions. Scanning tunneling spectroscopy measurements confirm that the SiN_x interfacial layer forms an electrically passive surface on p-type Si_0.70Ge_0.30(001), Si_0.50Ge_0.50(110), and Si_0.50Ge_0.50(001) substrates as the surface Fermi level is unpinned and the electronic structure is free of states in the band gap. DFT calculations show that a Si rich a-SiO_0.4N_0,4 interlayer can produce lower interfacial defect density than stoichiometric a-SiO_0.8N_0.8, substoichiometric a-Si₃N₂, or stoichiometric a-Si₃N₄ interlayers by minimizing strain and bond breaking in the SiGe by the interlayer. Metal-oxide-semiconductor capacitors devices were fabricated on p-type Si_0.7Ge_0.3(001) and Si_0.5Ge_0.5(001) substrates with and without the insertion of an ALD SiO_xN_y interfacial layer, and the SiO_xN_y layer resulted in a decrease in interface state density near midgap with a comparable C_max value.