Daniel Hiller1

1, Research School of Engineering, Australian National University, Canberra, Australian Capital Territory, Australia

The first part of the talk will deal with (sub-)monolayers of ALD metal oxides, mainly Al2O3, deposited onto tunnel-SiO2. Wet-chemically grown and dry-thermally oxidized tunnel-SiO2 have a different surface termination, which leads to a different initial deposition during the first ALD-cycles. Despite the deposition of just sub-monolayers the Si-surface passivation can reach very good levels, even before a forming gas annealing, while maintaining a low contact resistivity due to tunneling through the ultra-thin layer stack. The surface passivation is explained via the formation of induced acceptor states in SiO2, which capture electrons from the dangling bonds at the Si/SiO2 interface so that these defects are electronically deactivated, while a negative fixed charge in the dielectric layer enables field effect passivation [1,2,3].

In the second part, the kinetics of the thermal activation as well as the annihilation of the grown-in defects in float-zone (FZ) Si wafers are studied. In the critical temperature window between approx. 400-800°C the bulk-lifetime of FZ-Si is decreased by more than 2 orders of magnitude and this degradation takes place on very short timescales. In addition to conventional furnace annealing, rapid thermal annealing (RTA) and millisecond flash lamp annealing (FLA) were studied. It will be demonstrated that also the recovery of the bulk lifetime can be achieved by thermal treatments that are much shorter and at lower temperatures than previously reported. Finally, the role of impurities detected by SIMS and their possible defect configurations (modelled by density functional theory) are discussed.

[1] D. König & D. Hiller et al., Sci. Rep. 7, 46703 (2017)
[2] D. Hiller et al., ACS Appl. Mater. Interfaces 10, 30495 (2018)
[3] D. Hiller et al., J. Appl. Phys. 125, 015301 (2019)