Vacancy-Type Defects in MOSFETs with High-k Gate Dielectrics Probed by Monoenergetic Positron Beams

摘要

Vacancy-type defects in MOSFET structures fabricated with high-k (HfSiON) gate dielectrics were studied by monogenetic positron beams. An expansion of open volumes in HfSiON fabricated on Si substrates using atomic layer deposition technique was observed with increasing nitrogen concentration. This fact was discussed in terms of a role of nitrogen in Hf-related oxide using results obtained by first-principles calculation and XPS. MOSFETs fabricated by F{sup}+-channel implantation technique were also characterized. The major defect species which causes the V{sub}(th) shift of MOSFETs was identified as vacancy-fluorine complexes (such as V{sub}3F{sub}2) locate in channel regions of Si substrates. The preset work suggests that positron annihilation can be used to detect microscopic defects in MOSFETs, and it is a useful tool for determining process parameters for MOSFET fabrications with high-k gate dielectrics.