Abstract: With NH3 , SiH4 and N2 as reaction gas, silicon-rich nitride thin films were produced by plasma enhanced chemical vapor deposition method . In the case of optimizing other depositional parameters, the effects of NH3 flow rate were studied on the structures and on optical properties of silicon-rich SiNx thin films.The bonding situation and band gap structures of the film samples were analyzed by Fourier transform infrared absorption , ultraviolet-visible absorption spectrum and XRD .Its research result shows that with the increase of NH3 flow rate, the Si-N bond and N-H bond in the films are strengthened , but the Si-H bond is descended and moves to high wave-number.Meanwhile, the film transformation occurs from amorphous SiN x phase to small crystal Si3N4 phase .Besides , with the increase of NH3 flow rate, the optical band gap of the film is widened gradually and the order degree of the microscopic structures is decreased .In addition, the analysis of XRD pattern shows that the size of the average crystal grain in the films increases gradually with the increase of NH3 flow rate.Based on the above analysis , the conclusion comes that an appropriate increase of NH3 flow rate will contribute to the transformations of films from amorphous SiNx phase to small crystal Si3N4 phase.

Key words: With NH3 , SiH4 and N2 as reaction gas, silicon-rich nitride thin films were produced by plasma enhanced chemical vapor deposition method . In the case of optimizing other depositional parameters, the effects of NH3 flow rate were studied on the structures and on optical properties of silicon-rich SiNx thin films.The bonding situation and band gap structures of the film samples were analyzed by Fourier transform infrared absorption , ultraviolet-visible absorption spectrum and XRD .Its research result shows that with the increase of NH3 flow rate, the Si-N bond and N-H bond in the films are strengthened , but the Si-H bond is descended and moves to high wave-number.Meanwhile, the film transformation occurs from amorphous SiN x phase to small crystal Si3N4 phase .Besides , with the increase of NH3 flow rate, the optical band gap of the film is widened gradually and the order degree of the microscopic structures is decreased .In addition, the analysis of XRD pattern shows that the size of the average crystal grain in the films increases gradually with the increase of NH3 flow rate.Based on the above analysis , the conclusion comes that an appropriate increase of NH3 flow rate will contribute to the transformations of films from amorphous SiNx phase to small crystal Si3N4 phase.