Interface hardening with deuterium implantation

Incorporation of deuterium to passivate silicon-dangling bonds at the Si-SiO₂ interface through ion implantation before the growth of the gate oxide is the focus of this work. Polycrystalline silicon gate n-channel metal-oxide-semiconductor diodes with 4 nm gate oxide grown on deuterium-implanted p-type silicon (100) substrate were investigated. Deuterium implanted at a light dose of 1 × 10¹⁴/cm² at 25 keV reduced oxide leakage current due to reduction in oxide charge and interface traps. Out-diffusion deuterium during oxidation was observed for lower energy implant. Higher energy implant, on the other hand, causes enhanced substrate damage and prevents deuterium from reaching the Si-SiO₂ interface. Formation of Si-D bonds at the interface as well as in bulk oxide seems to reduce bulk electron traps as noticed in constant current strees measurements. Interface state density N_it as obtained from the conductance measurements suggests that implanted deuterium passivates the silicon dangling bonds, thereby reducing the interface charge. The N_it distribution in silicon bandgap shows that there is significant reduction in N_it for deuterium-implanted samples at an energy position about 0.2 eV above midgap, which corresponds well with P_b0 center 0/-transition level of E_v + 0.85 eV.