Analysis of Buried Nitride Layers Produced by Ion Implantation

Optical devices like waveguides and electrooptical switches became significant for transmission of information in the last years. By implantation of nitrogen and oxygen in silicon, SiO sub x N sub y -layers with a gradient in their refractive index can be produced. These implanted buried layers can then be used as a planar waveguide. To form well defined buried layers with these characteristics, the tool of ion-implantation was chosen. After the implantation, the samples were annealed for one to six hours at a temperature of 1300 deg C. To investigate the composition of the layers, ion beam analysis methods like Rutherford Backscattering (RBS) and Nuclear Reaction Analysis (NRA) were used. The distribution of exp 15 N was determined by NRA with the exp 15 (p, alpha ) exp 12 C-reaction at 1 MeV. The Q-value of this reaction is 4.964 MeV, so that the signal of the a-particles from the nitrogen can be separated from the bulk proton spectrum. In combination with the exp 16 O( alpha , alpha ) exp 16 O-resonance energies lower than 3.045 MeV (in the region of a nearly constant scattering cross section) the depth distributions of nitrogen implanted samples were determined with regard to the implantation and annealing conditions for several samples. It was found that the nitrogen implanted in SiO sub 2 disappears during implantation and annealing with respect to implantation and annealing temperatures. For implantation in < 110 > oriented silicon in random direction, the nitrogen distribution does not change very much with implantation and annealing considerations.