Characteristics of Silicon Nitride Films Deposited by Cat-CVD at a Low Temperature (100 ℃)

Abstract

Silicon nitride (SiNx) films for use as gate dielectric layers in thin-film transistors (TFTs) were deposited by catalytic chemical vapor deposition (Cat-CVD) at a low substrate temperature (100 ºC). Filament geometry, spacing between the filament and the substrate, and process pressure were optimized to deposit reliable dielectric films at 100 ºC. Silane (SiH4), ammonia (NH3) and hydrogen (H2) were used as source gases, and the flow ratios of NH3 / SiH4 and H2 / SiH4 were varied from 10 to 60 and from 20 to 200, respectively. An in-situ chemical annealing was performed by using H2 during the deposition process. As a result, SiNx films having a composition close to stoichiometry, having an electrical resistivity of 1012 ohm∙cm and a breakdown field strength of 7 MV/cm, were obtained. These films are believed to be applicable to TFTs on plastic substrates.