Radiation hardening of oxynitrides formed by low energy nitrogen implantation into silicon prior to oxidation

摘要

Silicon oxynitride (SiO_xN_y) insulators have been obtained by low-energy nitrogen ion implantation into Si substrates prior to conventional or rapid thermal oxidation. Theses films have been used as gate insulators in enhancement mMOSFETs and MOS capacitors. MOS capacitors were used to obtain capacitance-voltage(C-V) and current-voltage(I-V) measurements. A relative dielectric constant of 3.9 was adopted to extract the film thickness from C-V curves, resulting in values between 6nm and 12nm. Oxynitride breakdown electric fields of 21 MV/cm to 35 MV/cm were obtained form IV- measurements. nMOSFETs were bombarded with H~+ ion beams (energy of 170kev and doses of 0, 10~(12, 10~(13) and 10~(14) protons/cm~2) to investigate radiation hardening. MnMOSFET electrical characteristics, such as threshold voltages(V_T), transconductances(Gm) and sub-threshold slope(S), were extracted before and after proton radiation. For high dose bombardment, Gm is reduced, V_T and S are increased. These device performance degradation was significant only for doses > 10~(12) protons/cm~2.