Direct and indirect determination of hydrogen-boron complexes in float-zone silicon wafers

Abstract

Hydrogen-boron (HB) pairs and hydrogen dimers (H2) can be measured in silicon wafers directly using cryogenic Fourier Transform-Infrared (FT-IR) spectroscopy, or indirectly through a resistivity change upon annealing. The change in the HB and the H2 concentrations during annealing of hydrogenated float zone silicon wafers shows good agreement with both approaches, both with respect to absolute values as well as the temporal evolution. Thus, the model where H2 dissociates and provides a source of H+ that can passivate B− and form HB pairs is supported. FT-IR measurements show that there is a small concentration of HB pairs in the wafers prior to annealing, presumably depending on the firing process used. In addition, the total hydrogen concentration visible using FT-IR is not constant, indicating the presence of a hydrogen state that is hidden from detection optically, while still contributing to the passivation of acceptors.