DEFECT ANALYSIS IN BONDED AND H-ON-INSULATOR WAFERS BY PHOTOLUMINESCENCE SPECTROSCOPY AND TRANSMISSION ELECTRON-MICROSCOPY( SPLIT SILICON)

Defects in silicon-on-insulator wafers fabricated by bonding and H+ sp litting technique (Unibond wafers [Unibond is a registered trademark o f SOITEC.]) were characterized by photoluminescence (PI,) spectroscopy together with transmission electron microscopy (TEM). PL from the sup erficial Si layer and that from the supporting substrate were separate ly analyzed using UV and visible light as an excitation source, respec tively. The deep-level PL band appeared around 0.8 eV both in the supe rficial layer and the substrate with a spectral shape similar to that often observed in oxygen precipitated Si crystals. Correspondingly, TE M 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 fabric ation process.