Influence of phosphorus doping on hydrogen content and optical losses in PECVD silicon oxynitride

摘要

PECVD Phosphorus-doped silicon oxynitride layers (n=1.5) were deposited from N2O, 2%SiH4/N2, NH3 and 5%PH3/Ar gaseous mixtures. Chemical bonds were determined by Fourier transform infrared spectroscopy. N–H bond concentration of the layers decreased from 3.29×10-21 to 0.45×10-21 cm−3, as the 5%PH3/Ar flow rate increased from 0 to 60 sccm. A simultaneous decrease of O–H related bonds was also observed within the same phosphine flow range. The optical loss of slab-type waveguides at λ=1505 nm was found to decrease from 14.1 to 6.2 dB/cm as the 5%PH3/Ar flow rate increased from 0 to 30 sccm, respectively. Moreover, the optical loss values around λ=1400 and 1550 nm were found to decrease from 4.7 to below 0.2 dB/cm and from 1.8 to 1.0 dB/cm respectively. These preliminary results are very promising for applications in low-loss integrated optical devices.