ENHANCED FORMATION OF Si NANOCRYSTALS IN SiO2 BY LIGHT-FILTERING RAPID THERMAL ANNEALING

Abstract

In this work, silicon-rich oxide (SRO) films with designed thickness of ~100 nm were deposited by a bipolar pulse and radio frequency magnetron co-sputtering. For comparison, the samples were then treated in a nitrogen atmosphere by conventional rapid thermal annealing (CRTA) or light-filtering rapid thermal annealing (LRTA) at 900–1100°C for 2 min. Raman spectra, grazing incident X-ray diffraction (XRD), transmission electron microscopy (TEM), Hall measurements, and current density–voltage measurements were carried out to analyze the microstructural and electrical properties of samples. Compared with the control sample using CRTA method, the crystalline volume fraction and number density of Si nanocrystals ( Si NCs ) in silicon oxide prepared by LRTA were greatly increased. The quantum effects of the short wave-length light (less than 800 nm) of these tungsten halogen lamps during the rapid thermal annealing process have negative effects on the formation of Si NCs in SiO 2 films. Si NCs with crystal volume fraction of 73%, average size of 2.53 nm, and number density of ~1.1 × 1012 cm-2 embedded in the amorphous SiO 2 matrix can be formed by LRTA at 1100°C. Enhancement of more than one order of magnitude in conductivity and higher current density were obtained from the LRTA annealed sample compared to the CRTA annealed sample. The improvements in conductivity and current density were attributed to the high density Si NCs . Our results show that the LRTA method is a suitable annealing tool for the formation of Si NC in thin SiO x films.