Compositional and structural studies of amorphous silicon-nitrogen alloys deposited at room temperature using a sputtering-type electron cyclotron resonance microwave plasma

High-quality amorphous silicon-nitrogen alloys (a-SiNx) have been deposited at room temperature by a sputtering-type electron cyclotron resonance (ECR ) plasma. A detailed analysis of the properties of a-SiNx films in terms of their composition, microstructure and dielectric characteristics was perfo rmed using Xray photoelectron spectroscopy, infrared (IR) spectroscopy and ramp current-voltage measurement techniques. Their characteristics were cor related with the N-2 gas flow rate (NGFR) in the ECR plasma formation. The dependence of solid-state [N]/[Si] ratios in the films on the NGFR indicate d that the film composition changed from non-stoichiometry to stoichiometry as the NGFR increased from 0.5 to 1 sccm. The dependence of the IR spectra on the NGFR indicated that silicon nitride network was well ordered for an NGFR of 1 sccm, in which the dielectric breakdown-field was over 4 MVcm(-1 ). However, when the NGFR was over 1 seem, significant N=N triple bonds (ga seous N-2 molecule) were formed and were trapped inside the films. These N- 2 molecules formed many voids and defects; and enhanced disorder in the net work. This is well correlated by chemical etch and IR results. The dependen ce of dielectric properties of a-SiNx films on the NGFR demonstrated that t hese voids and defects lead to a decrease in average dielectric breakdown f ield and an obvious increase in the distribution of the low breakdown field .