Effects of ambient conditions in thermal treatment for Ge(001) surfaces on Ge-MIS interface properties

Effects of thermal treatment under various ambient conditions for Ge(0 0 1) substrates on MIS interface properties have been investigated. Ge-MIS capacitors with Al gates have been fabricated by depositing SiO2 layers on thermally treated Ge surfaces. We characterized the interface structures by transmission electron microscopy, x-ray photoelectron spectroscopy and C-V, G-F (conductance-frequency) measurements. It is found that the ambient conditions significantly change the MIS interface structures and, thus, the interface trap density. As a result, the thermal treatment under O-2 ambient condition is very effective at decreasing the interface trap density and the slow trap density as well. This decrease in the interface traps is attributable to the reduction in dangling bonds by forming stoichiometric GeO2 at the MIS interfaces.