Study of structure and surface modification of silicon-on-insulator (SOI) devices synthesized by dual ion implantation

Abstract

Silicon oxynitride (Si xO yN z) buried layers were synthesized by high fluence (≥ 1 × 10 17 ions-cm − 2 ) ion implantation of O + and N + sequentially into single crystal silicon at 150 keV to produce silicon-on-insulator (SOI) structures. The structures of the SOI devices were analyzed by FTIR and XRD measurements and the surface modification by using atomic force microscopy (AFM). The FTIR measurements on the implanted samples (≤ 1 × 10 18 ion-cm − 2 ) show a single absorption band in the wavenumber range 1300–750 cm − 1 attributed to the formation of silicon oxynitride bonds in silicon. The integrated absorption band intensity is found to increase with increase in the fluence. The samples with nitrogen–oxygen sequence of implantation showed nitrogen-rich oxynitride formation whereas samples with oxygen–nitrogen sequence resulted in oxygen-rich oxynitride. The formation of separate phases of Si–O and Si–N bonds was observed at high fluence level (≅ 2 × 10 18 ions-cm − 2 ). The XRD studies show the formation of mixed phases of Si 2N 2O and SiO 2 in the sample. The structures of the ion beam synthesized silicon oxynitride layers are found to be strongly dependent on the sequence of implantation. The surface roughness is observed to be very small at lower fluences and it increases as we go to high fluence levels due to heavy damage caused by implantation. The conical hill like structures on the silicon surface is seen due to heavy surface swelling and sputtering phenomena.