Synthesis of silicon oxynitride layers by dual ion-implantation and their annealing behaviour

Abstract

Single crystal n-type silicon samples were implanted at room temperature sequentially by molecular oxygen ( 16O 2 +) and nitrogen ( 14N 2 +) in different proportions to high fluence levels ranging from 5 × 10 16 to 1 × 10 18 ions cm −2 to synthesize silicon oxynitride layers of various compositions. Rapid thermal annealing (RTA) of some samples was carried out at different temperatures in nitrogen ambient. Fourier transform infrared (FTIR) measurements were performed on as-implanted and on annealed samples. The FTIR studies show that the structure of ion-beam synthesized oxynitride layers are strongly dependent on total ion-fluence as well as on the ratio of implanted oxygen and nitrogen. The Si x O y N z structures formed at lower fluence levels are homogeneous, at intermediate fluence levels are composed of separate phases of oxide, nitride and some complexes of O, N and Si and at higher fluence levels seem to have again homogeneous silicon oxynitride complex structures (Si x O y N z ) due to sputter limited profile of implanted ions. RTA studies show pronounced structural changes of the ion-beam synthesized layers on heat treatment at different temperatures. The spectra of annealed samples showed shift of the peak towards higher wave number. The ESR signal of silicon samples implanted to different fluence levels exhibited an isotropic g-value of 2.0045 corresponding to D-center with line width 8 G. The spin density was found to decrease with increase in ion-fluence.