FORMATION OF BURIED OXYNITRIDE LAYERS IN SILICA GLASS BY ION-IMPLANTATION

Buried oxynitride layers were formed in silica glass by N+ only or both N+- and Si+-ion implantation. These samples were characterized by secondary-ion mass spectroscopy, Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, and scanning electron microscope. The depth profile of implanted N without Si implantation is a trapezoidal shape at a high-dose condition (more than about 3 × 10 16 ions/cm2). In the N+ implantation only, a part of implanted N reacts with Si, and forms a SiON layer which is thermally unstable. In both Si+ (100 keV, 1 × 1017 ions/cm2) and N+ (50 keV, 11× 1017 cm2) implantation, the depth profile of N is a Gaussian distribution, and the thermal stability of a SiON layer is dramatically improved. However, bubbles were generated near the projected range of Si and N at a high-dose condition (the total dose was 4 × 1017 ion/cm2 and the dose ratio Si/N=3/4). The generation of bubbles was suppressed by two-step N+ implantation (40 and 60 keV).