Bubble evolution mechanism and defect repair during the fabrication of high-quality germanium on insulator substrate

Abstract

We investigate the effect of the annealing temperature and annealing time on the bubble evolution on the hydrogen ion (H+)-implanted germanium (Ge) substrate. It is found that the H2 aggregates gradually with the increase of the annealing time, and the aggregation rate of the H2 increases with the increase of the annealing temperature. Low-temperature Ge/Si wafer bonding (a-Ge interlayer) and Smart-Cut™ technique are applied to fabricate high-quality Ge-on-insulator (GOI). It is proved that thick Ge film is more difficult to be exfoliated from the Ge substrate. As long as the pressure in the bubbles is high enough, although the bubbles do not burst on the Ge surface, the lateral diffusion of H2 may occur to trigger the exfoliation of the Ge film. The contact of the wafers leads to the lateral merging of the small bubbles, resulting in the increase of the bubble size at the edge of the big void. It is believed that high bonding strength between Ge and SiO2 is essential to resist the high pressure in the bubble for the successful exfoliation of the Ge film. The point defects in the Ge film can be totally eliminated either by high-temperature annealing or by nanosecond pulse laser annealing, resulting in the improvement of the Ge film quality.