Abstract: Electron cyclotron resonance plasma enhanced chemical vapor deposition was used to produce amorphous hydrogenated silicon nitride（a-SiN_x:H） under different gas flow ratios of SiH₄（80% Ar diluted） and NH₃.Optical emission spectroscopy was used to investigate the plasma behavior,while Fourier Transform Infrared（FTIR） was used to measure the bond configuration of a-SiN_x:H films.It is found that the variation of Si radical concentration in the plasma causes the decrease of the film growth rate with the increase of NH₃ flow rate.The blue shift for Si-N and Si-H stretching mode with the increasing NH₃ flow rate can be attributed to that more N atoms with a higher electro-negativity are bonded into the a-SiN_x:H film.The amount of bonded hydrogen into the a-SiN_x:H films is calculated to be of a rather low level,about 15% or so.The growth mechanism of a-SiN_x:H films is also discussed.