Optimization of Ar-diluted N2 electoron cyclotron resonance plasma for high-quality SiN film growth at low temperature

概要

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The growth characteristics and electrical properties of a thin amorphous SiN film formed by Ar-diluted N2 electron cyclotron resonance (ECR) plasma irradiation at a low temperature of 400℃ have been investigated. It is found that SiN film quality is sensitive to the N2 mixing ratio [N2/(N2+Ar)] and a film having a structure nearest to stoichiometric can be obtained with 60% N2 mixing plasma. An optimized substrate bias contributes to suitable plasma etching effect, which leads to the lowest leakage current density of SiN film with a given equivalent oxide thickness(EOT). Two kinds of impurities, N2 molecules and Ar atoms, are found in the as-grown SiN film. The N2 molecules concentration in SiN film has decisive influence on the film quality. An atomically flat interface between Si and SiN film are shown by high-resolution transmission electron microscope micrograph. The as-grown SiN film shows a leakage current more than orders of magnitude lower than that of thermally grown SiO2 having the same EOT.