Electrical Active Defects Research Articles

Rapid thermal annealing of electrically-active defects in virgin and implanted silicon

We have investigated the annealing behaviour of electrically-active defects induced in virgin n-type and residual in As+ implanted p-type silicon after laser irradiation, using the rapid thermal annealing technique (RTA). Spectra from deep level transient spectroscopy (DLTS) show that three majority carrier traps at E (0.32 eV), E (0.45 eV) and E (0.53 eV) were induced in the n-type Si after Nd-Yag laser treatment at 1.6 J cm−2. Annealing in a rapid thermal furnace at 600 °C for times between 5 and 60 s resulted in a linear decrease of the concentration of these defects and for times ≧ 60 s, they are no longer detectable. A similar result was obtained in the case of the multiple energy As+ implanted samples in which two majority carrier traps at H (0.30 eV), H (0.58 eV) and a minority carrier trap E (0.53 eV) completely disappeared after annealing for 45 s at 600 °C, in spite of the very high concentration of the H (0.58 eV) defect (>1015 cm−3 up to a depth of about 1.5 μm). A comparison of the annealing rates of the E (0.32 eV) trap using the RTA and the conventional thermal annealing (CTA) techniques at 600 °C showed that the former is at least 30 times faster than the latter. Sheet resistance measurements show that the level of dopant deactivation, due to post-laser thermal treatment at 500 °C (in order to obtain the same reduction in residual defect concentration), is less in the RTA processed samples than in those annealed using conventional methods. These results lend strong support to the hypothesis of ionization-induced enhancement of defect annealing, and to our knowledge, represent the first report of the observation of the phenomenon using the RTA technique.

Annealing Kinetics during Rapid and Classical Thermal Processing of Laser and Implantation Induced defects in Silicon

AbstractThe annealing behaviour of electrically-active defects in-duced in virgin n-type silicon by-Nd-Yag Laser (1.6 J cm−2,0.53 μm) irradiation has been investigated with Deep Level Transient Spectroscopy (DLTS). The observed defects : E(0.32 eV), E(0.45 eV) and E(0.53 eV) are characteristic of laser treated silicon, and have been reported by a number of workers. Using a rapid thermal furnace at 600°C for durations between 10 and 60s, we have observed a linear decrease in the concentration of these defects, and for times T > 60s, they are seen to disappear. A similar result was obtained in studies carried out on both vir-gin and implanted p-type silicon. This is in sharp contrast to the classical furnace annealing which requires much longer du-rations (20–30 min) at the same temperature (600 °C) in order to obtain the same results. A study of the annealing kinetics for the E(0.32 eV ;σn = 8 × 10−16 cm−2) level between 500 and 650°C in steps of 50°C for the two processes confirms this tendency for all processing temperatures, and shows a difference in ac-tivation energy of practically the same order of magnitude as the ionization energy of the defect (i.e. = 0.31 eV). Induced defects in high temperature > 1000°C in rapid thermal processed (RTA) n-type Si, also annealed out after a further 600°650 °C, 60 s RTA treatment. These results suggest that defect annealing is not a purely thermal mechanism, and lend strong support to the idea of an ionization induced enhancement.

Defects in Amorphous Silicon

ABSTRACTIn this paper we argue that amorphous silicon can be treated as a relaxed continuous random network. The optical and electronic properties are controlled by localized gap states which arise from characteristic features of a disordered tetrahedrally-bonded covalent network. Experimental results are reviewed which indicate that the dominant (perhaps only) electrically-active defect in hydrogenated amorphous silicon is the topologically distinct, silicon dangling bond. Finally, we suggest that the same, disorder-related characteristics might also typify the electronic properties of some macroscopic crystalline silicon defects.