The Interstitial Carbon–Dioxygen Center in Irradiated Silicon

We investigated, experimentally as well as theoretically, defect structures in electron irradiated Czochralski-grown silicon (Cz-Si) containing carbon. Infrared spectroscopy (IR) studies observed a band at 1020 cm−1 arisen in the spectra around 300 °C. Its growth occurs concomitantly with the decay out of the well-known vacancy-oxygen (VO) defect, with a Local Vibrational Mode (LVM) at 830 cm−1 and carbon interstitial-oxygen interstitial (CiOi) defect with a LVM at 862 cm−1, in silicon (Si). The main purpose of this work is to establish the origin of the 1020 cm−1 band. One potential candidate is the carbon interstitial-dioxygen (CiO2i) defect since it is expected to form upon annealing out of the CiOi pair. To this end, systematic density functional theory (DFT) calculations were used to predict the lowest energy structure of the (CiO2i) defect in Si. Thereafter, we employed the dipole–dipole interaction method to calculate the vibrational frequencies of the structure. We found that CiO2i defect has an LVM at ~1006 cm−1, a value very close to our experimental one. The analysis and study of the results lead us to tentatively correlate the 1020 cm−1 band with the CiO2i defect.

Low Resistance Ohmic Contact Formation on 4H-SiC C-Face with NbNi Silicidation Using Nanosecond Laser Annealing

Non-equilibrium laser silicidations for low-resistance ohmic contact to 4H-SiC C-face with carbon-interstitial type metal, Nb was demonstrated. In a conventional nickel silicide (NiSi) electrode on SiC, a carbon agglomeration at the silicide/SiC interface occurs, and constant resistance between NiSi and SiC substrate becomes larger. For suppressing the carbon agglomeration, in this research, nanoseconds non-equilibrium laser annealing was introduced, and also carbon-interstitial type metal Nb to form metal carbides was introduced. Ni/Nb/SiC multilayer contact and NbNi mixed contact were formed on C-face side of 4H-SiC wafers. Electrical contact properties were investigated after 45 nanoseconds pulse laser annealing in N2 ambient. As the result, at the NbNi mixed contact, specific contact resistance of 2.4×10-4 Ωcm2 was realized.