Hydrogen implantation-induced defects in bulk Si studied by Raman spectrometry

Ion implantation is a subject of interest because it is widely used in the semiconductor industry, to modify the carrier density in a transistor channel region and to enable splitting in the wafer bonding process. In the case of SOI wafers produced by SmartCut™, the implantation of light ions creates only a small amount of damage in the materials. Thus, H-implanted Si remains crystalline and only small changes are observed in physical properties as compared to non-implanted silicon crystal. However, as energy is applied to the system, by heating for example, H-implanted Si undergoes extreme stress eventually breaking the crystal. We have investigated the changes in the Si crystal during this process using Raman spectroscopy. Examining the slight shift and enlargement of the phonon peak and applying the spatial correlation model characterized defects. We could extract a phonon correlation length L, the shorter the L value, the larger the amount of defects. Variations due to H concentration (implantation depth profile relative to the surface) were investigated by using different excitation wavelengths (probe depths of 20–500 nm). Samples were also thinned by etching so that the defect density could be measured with fixed excitation energy (fixed probe depth). Finally, we draw the variation of L. All results were compared to the vacancy profiles simulated with the binary collision code IMSIL. Good agreement was obtained between the defect profiles estimated by both methods.