High quality silicon nitride deposited by Ar/N2/H2/SiH4 high-density and low energy plasma at low temperature

Abstract

The high-quality PECVD silicon nitride has been deposited by high-density and low-ion-energy plasma at 400°C and the effect of the process parameters, such as silane and nitrogen flow rate, pressure, on its structure and electrical properties has been investigated. The experimental results show that silane flow rate is the most sensitive parameter for determining deposition rate and N/Si atomic ratio of silicon nitride in the range of process parameters employed. The change of nitrogen flow rate leaded to slightly change in deposition rate, however, it effects significantly on the refractive index or densification of silicon nitride. With the addition of hydrogen gas in plasma, the hysteresis of C–V characteristics of MIS structure decreases from 0.4 to 0.1V. The moderate increment of ion energy makes further reduction in the hysteresis of C–V characteristics of MIS from 0.1V to below 0.05V. The interface trap density of 6.2×1010 (ev−1cm-2), deduced from the high frequency and quasistatic C–V characteristics of the MIS structure, is about the same as that of LPECVD silicon nitride deposited at the range of 750–850°C. The stoichiometric silicon nitride of excellence electric and structural properties is obtained by Ar/N2/H2/SiH4 high-density and low ion energy plasma.