Evolution of Si0.982C0.018 pseudomorphic layer after excimer laser annealing

Abstract

We have studied the effect of excimer laser annealing on a high-quality Si0.982C0.018 pseudomorphic layer, using Fourier transform infrared (FTIR) spectroscopy, Raman spectrometry, and x-ray diffraction. The substitutional carbon concentration is found to decrease as a function of fluence for 50 laser pulses performed at room temperature and vacuum. The strain profile evolution is obtained with x-ray diffraction and dynamical diffraction simulations. After melting, most of the strain is released, and a new FTIR and Raman peak appears around 830 cm−1. This feature is attributed to the formation of SiC microprecipitates and V-O asymmetrical centers. A mechanism for the substitutional carbon removal is proposed. It involves SiC precipitation and reaction between V-O and substitutional carbon to form volatile CO. In the case of pulsed laser induced epitaxy, we predict that the highest substitutional carbon content should be obtained with one laser pulse in an oxygen-free ambiant. From these results, it is inferred that pulsed-laser-induced epitaxy is suitable for the localized patterning of ultrashallow buried Si1−yCy junctions.