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Defect Analysis in Bonded and H + Split Silicon-on-Insulator Wafers by Photoluminescence Spectroscopy and Transmission Electron Microscopy

Defects in silicon-on-insulator wafers fabricated by bonding and H+ splitting technique (Unibond wafers [Unibond is a registered trademark of SOITEC.]) were characterized by photoluminescence (PL) spectroscopy together with transmission electron microscopy (TEM). PL from the superficial Si layer and that from the supporting substrate were separately analyzed using UV and visible light as an excitation source, respectively. The deep-level PL band appeared around 0.8 eV both in the superficial layer and the substrate with a spectral shape similar to that often observed in oxygen precipitated Si crystals. Correspondingly, TEM observation revealed precipitates and related defects. These results allow us to conclude that the defects in Unibond wafers originate in oxygen precipitation during the two-step annealing in the wafer fabrication process.