Influence of plasma-etch damage on the interface states in SOI structures investigated by capacitance-voltage measurements and simulations

Au/SiO₂/n-Si metal-oxide-silicon-on-insulator (MOSOI) capacitors were fabricated to study the damage caused by reactive ion etching (RIE) on (1 1 0) oriented silicon-on-insulator (SOI) substrates. The MOSOI capacitors with an etch-damaged SOI layer were characterized by capacitance-voltage (C-V) measurements and compared to the sacrificial oxidation treated samples and the reference samples without etching treatment. The measurements revealed that C-V curves significantly change and a negative voltage shift occurs for plasma-damaged capacitors. The simulated band diagram profiles and potential distribution of the corresponding structures indicate that the C-V shift is mainly due to the removal of a parasitic depletion capacitance (C_p) in the substrate, when the interface charges (Q_f) are present at the gate oxide/SOI interface. For etch-damaged MOSOI samples, the surface roughness and the interface charges (Q_f) have been found to increase by ∼1.94 × 10¹² cm^-2 with respect to the reference devices, whereas the increase was reduced for sacrificial-oxidation treated samples, which implies a recovery from the plasma-induced etch damage on SOI structures.