Silicon nitride thin films prepared by the electron cyclotron resonance plasma chemical vapor deposition method

Abstract

Silicon nitride thin films prepared by the electron cyclotron resonance plasma chemical vapor deposition method at low substrate temperature (<60 °C) exhibited excellent physical and electrical properties. The refractive indices of the films were 1.9∼2.0 at a wavelength of 633 nm. The etch rate in a buffered HF solution was extremely low (0.5 nm/min). The resistivity and breakdown voltage were >1017 Ω⋅cm and >10 MV/cm, respectively. These properties of silicon nitride thin films are close to those of stoichiometric silicon nitride (Si3N4) prepared by the thermal chemical vapor deposition method at high temperature (>600 °C). The interface trap state density between the silicon nitride film and silicon substrate was 4×1011 cm2/eV in the silicon band gap. An optical emission spectroscopy during the deposition indicated that the intensities of nitrogen molecular ions were much stronger than those of nitrogen molecules, and the silane was sufficiently decomposed into silicon and hydrogen atoms. It is considered that the excellent properties of the silicon nitride thin films are related to the existence of a large amount of nitrogen molecule ions.