Raman image study of defects in ion-implanted and post-annealed silicon

The spatial variation in the crystallinity of recrystallized silicon samples, which are ion-implanted and subsequently flash-lamp annealed, has been studied by Raman imaging. Clusters with a few micron size which contain a high density of defects are created in samples annealed above 700°C. A Raman band of this cluster region is broad and shifts to the lower frequency side of the crystalline silicon band (520.5 cm-1). The peak frequency and width of the broad Raman band characteristic of the clusters change with the position in the clusters. For samples annealed at 700°C, the peak frequency and width of the broad band are nearly constant for different wavelengths of the exciting laser. This result indicates that the spatial variation of the defect density in the cluster is small for samples annealed at low temperatures. For samples annealed at 1000°C, the peak frequency of the broad band shifts to the lower frequency side and the bandwidth increases as the wavelength of the exciting laser becomes longer. This wavelength dependence indicates that the density of defects within the clusters distributes inhomogeneously in depth and decreases in the region close to the free surface.