Low-temperature formation of silicon nitride film by direct nitridation employing high-density and low-energy ion bombardment

High-integrity silicon nitride films can be obtained at a temperature of 400°C using a newly developed high-density (> 10¹² cm^-3) plasma characterized by low ion bombardment energies of below 7 cV. It was found for the first time that stoichiometric silicon nitride can be formed at a temperature of 400°C by precise control of nitrogen partial pressure to generate N₂⁺ in plasma. The growth rate and the electrical properties of this silicon nitride are similar to those of thermally grown nitride. Moreover, hysteresis of the C-V curve attributed to charge traps in the silicon nitride film disappeared with the addition of hydrogen to Ar/N₂ plasma, and the leakage current of the nitride film was decreased dramatically by irradiating in Ar/N₂/H₂ plasma after Ar/N₂ plasma nitridation. These technologies are very promising for fabricating feature metal substrate silicon-on-insulator (SOI) devices and silicon nitride gate metal-insulator-semiconductor field effect transistors (MISFETs).