Interstitial Carbon Related Defects in Low-Temperature Irradiated Si: FTIR and DLTS Studies

Abstract

The evolution of radiation-induced carbon-related defects in low temperature irradiated oxygen containing silicon has been studied by means of Fourier transform infrared absorption spectroscopy (FTIR) and deep level transient spectroscopy (DLTS). FTIR measurements have shown that annealing of interstitial carbon atom Ci, occurring in the temperature interval 260-300 K, results in a gradual appearance of a number of new absorption bands along with the well known bands related to the CiOi complex. The new bands are positioned at 812, 910.2, 942.6, 967.4 and 1086 cm-1. It has been found that the pair of bands at 910 and 942 cm-1 as well as another set of the bands at 812, 967.4 and 1086 cm-1 display identical behavior upon isochronal annealing, i.e. the bands in both groups appear and disappear simultaneously. The disappearance of the first group occurs at T = 285-300 K while the second group anneals out at T = 310-340 K. These processes are accompanied by an increase in intensity of the bands related to CiOi. It is suggested that intermediate states (precursors) are formed upon the transformation from a single (isolated) Ci atom to a stable CiOi defect. The results obtained in DLTS studies are in agreement with the FTIR data and show unambiguously the formation of CiOi precursors with slightly lower activation energy for the hole emission as compare to that for the main CiOi state.

Annealing Kinetics of the Interstitial Carbon–Dioxygen Complex in Silicon

“…Figure a displays the DLTS spectra for set A sample, and the dominant peak in the as‐irradiated diode is a characteristic signature of the well‐known C i O i complex and appears to consist of two overlapping peaks. It has been reported previously that after irradiation at RT a precursor state, C i O i *, appears and persists up to 50 °C before the transition to the stable C i O i state …”

“…The evolution of C i O i upon post‐irradiation thermal treatments has been studied intensively for decades. In previous deep level transient spectroscopy (DLTS) studies, metastable configurations of C i O i has been reported during isochronal annealing of irradiated Si in the temperature range 280–360 K. It has been suggested that an intermediate state, referred to as C i O i *, appears before the formation of a stable C i O i that persists up to 400 °C. Annealing of C i O i has also been studied by photoluminescence spectroscopy (PL) via monitoring the so‐called C‐line at 789 meV .…”

Carbon-Related Defects in Si:C/Silicon Heterostructures Assessed by Deep-Level Transient Spectroscopy

“…4). Comparing with literature data, 14,15,[25][26][27][28][29][30] it is concluded that the hole trap found in the p-type silicon substrate after RTA most likely corresponds with C i O i -related centers, although the σ p is about one decade higher than the typically reported values. This could be due to the effect of the negative feature observed in Fig.…”

“…In fact, comparing with the data of Ref. 30, one can conclude that the experimental points in Fig. 10 are closer to the Arrhenius plot for the C i O i * precursor center than to the C i O i data.…”

“…The fact that a CZ silicon substrate is used, makes it very likely that C i becomes trapped by O i in the bulk of the wafer. 14,15,[25][26][27][28][29][30] Another potential source of oxygen could be traces of moisture in the RTA annealing ambient, where oxygen diffuses in from the surface. It is also concluded from the DLTS results reported here that during RTA additional carbon atoms are transformed from substitutional into interstitial positions, 31 explaining at least part of the loss of stress after high-temperature annealing.…”