Defect characterization in Unibond/sup R/ wafers by photoluminescence spectroscopy and transmission electron microscopy

Summary form only given. A Unibond/sup R/ wafer fabricated by a combination of bonding and layer splitting (Smart-Cut/sup R/) is regarded as one of the most promising silicon-on-insulator (SOI) wafers for next generation devices. The defect characterization of the wafer is, however, lagging because of the difficulty in measuring thin layers. In this paper, we report on the characterization of microdefects in Unibond/sup R/ wafers by photoluminescence (PL) spectroscopy and mapping together with transmission electron microscopy (TEM). When an SOI wafer is excited by visible light, the light penetrates deep into the base wafer, and hence the PL is mainly from the base wafer. In contrast, UV light is predominantly absorbed in the superficial Si layer and the excited carriers are confined within this layer because of the presence of a buried oxide layer which acts as a diffusion barrier. As a result, a characteristic "condensate luminescence" is emitted from the superficial layer (Tajima et al. 1997). Therefore, the visible and UV excitations enable us to perform the selective detection of PL from the base wafer and the superficial Si layer, respectively. We show the presence of oxygen precipitates not only in the base wafers but in the superficial Si layers on the basis of the deep-level emission in the PL spectra, the oxygen striation pattern in the PL mapping, and the precipitate image in the TEM observations.