Suppression of Electrical Breakdown in Silicon Nitride Films Deposited by Catalytic Chemical Vapor Deposition at Temperatures Below 200 °C

Abstract

Silicon nitride (SiN(x)) films for a gate dielectric layer of thin film transistors were deposited by catalytic chemical vapor deposition at a low temperature (< or = 200 degrees C). A mixture of SiH4, NH3 and H2 was used as a source gas. Metal-insulator-semiconductor (MIS) capacitor structures were fabricated for current-voltage (I-V) and capacitance-voltage (C-V) measurements. The breakdown voltage characteristics of the SiN(x) films were improved by the increase of NH3/SiH4 and H2/SiH4 mixing ratios and substrate temperatures. H2 treatment was attempted to improve the breakdown voltage further. A breakdown voltage as high as 6.6 MV/cm was obtained after H2 annealing at 180 degrees C. The defect states inside the SiN(x) films were analyzed by photoluminescence spectra. Silicon dangling bonds (2.5 eV) and nitrogen dangling bonds (3.1 eV) were observed. These defect states inside the SiN(x) films disappeared after H2 annealing. Flat band voltage shifts were observed in C-V curves, and their magnitudes decreased as the defect states inside the SiN(x) films decreased.