Effective passivation of defects in Ge-rich SiGe-on-insulator substrates by Al₂O₃ deposition and subsequent post-annealing

A method of Al₂O₃ deposition and subsequent post-deposition annealing (Al₂O₃-PDA) was proposed to passivate electrically active defects in Ge-rich SiGe-on-insulator (SGOI) substrates, which were fabricated using Ge condensation by dry oxidation. The effect of Al₂O₃-PDA on defect passivation was clarified by surface analysis and electrical evaluation. It was found that Al ₂O₃-PDA could not only suppress the surface reaction during Al-PDA in our previous work [Yang H, Wang D, Nakashima H, Hirayama K, Kojima S, Ikeura S. Defect control by Al-deposition and the subsequent post-annealing for SiGe-on-insulator substrates with different Ge fractions. Thin Solid Films 2010; 518: 2342-5.], but could also effectively passivate p-type defects generated during Ge condensation. The concentration in the range of 10¹⁶-10¹⁸cm^-3 for defect-induced acceptors and holes in Ge-rich SGOI drastically decreased after Al₂O ₃-PDA. As a result of defect passivation, the electrical characteristics of both back-gate p-channel and n-channel metal-oxide- semiconductor field-effect transistors fabricated on Ge-rich SGOI were greatly improved after Al₂O₃-PDA.