Low-temperature plasma deposition of passivating layers with low hydrogen content for optoelectronic devices

We have deposited silicon nitride (SiN) and silicon oxynitride (SiON) thin films at low substrate temperatures (T-s) using 2.45 GHz electron cyclotron resonance plasma enhanced chemical vapour deposition (ECRPECVD) and 13.56 MHz magnetron plasma enhanced chemical vapour deposition (MPECVD) techniques. Either a mixture of SiH4, N2O and Ar or SiH4, N-2 and Ar was taken as precursor gases. In the ECRPECVD the deposition rate varied between 20 to 7 nm/min with the ratio of flow rates of N2O (N-2) to SiH4. The amount of incorporated hydrogen which was determined from nuclear reaction N-15(H-1,alpha,gamma)C-12 analysis (NRA) varied similarly with gas flow rates ratio. By varying this ratio high-quality films with hydrogen content down to 11 at.% could be deposited at T-s = 150 degrees C. In the MPECVD the typical deposition rates were on the order of 350 nm/min at 25 degrees C, substantially higher than has been reported for low-temperature deposition. The hydrogen content was found to be between 3-7 at.%, much lower than is typical for room-temperature PECVD films.