抄録
It is possible to prepare high-density, moisture-resistive and optically transparent SiNx films by a catalytic chemical vapor deposition (Cat-CVD, often called Hot-Wire CVD) technique at low substrate temperatures such as 353K. The key point is the addition of a large amount of H2 to the SiH4/NH3 system. Gas-phase diagnoses show that, in Cat-CVD processes, the H-atom density in the gas phase is typically more than one order of magnitude higher than that in plasma processes; these H atoms abstract atomic hydrogen on the growing surface and also contribute to the local heating of the substrate surface due to their recombination reactions. In addition, H atoms re-activate the catalyzer surfaces poisoned by SiH4 to increase the decomposition efficiency of NH3. Pressure cooker tests combined with FTIR measurements show that SiNx films thus prepared are highly moisture-resistive even when the substrate temperature is as low as 293K. The water vapor transmission rate of plastic substrates covered with thin SiNx films is less than the detection limits of a MOCON or a cup method. The transmission rate was decreased by more than two orders of magnitude by the SiNx coating. The stress of the SiNx films was typically less than 100 MPa and can be controlled from compressive to tensile by choosing the appropriate deposition conditions. It is concluded that SiNx films prepared by Cat-CVD from SiH4, NH3 and an excess amount of H2 can be used as passivation films for organic materials, including organic light-emitting diodes.
