THE EFFECT OF HYDROGEN AND TEMPERATURE ON THE OPTICAL GAPS OF SILICON-NITRIDE AND COMPARATIVE STOICHIOMETRY STUDIES ON SIN THIN-FILMS

The optical properties of a variety of silicon nitride films prepared by different techniques are investigated with conventional and synchro tron radiation spectroscopic ellipsometry. The existence of hydrogen i n near-stoichiometric SiN films is found to cause a red-shift of the f undamental and mean optical gaps, thought to be due to the existence o f Si-H bonds. Temperature-dependent measurements up to 700 K reveal a recession of the fundamental gap and an increase of the mean optical g ap with temperature. Analysis of the experimental spectra with the mic roscopic tetrahedron model indicates the superiority of the chemical v apour deposition growth technique in terms of film quality and homogen eity. Finally, a new method is used for the determination of the [N]/[ Si] concentration ratio from tetrahedron model analysis and the result s compare well to those from Rutherford backscattering spectroscopy an d nuclear reaction analysis.