Interfacial oxide formation from intrinsic oxygen in W-HfO_(2) gated silicon field-effect transistors

摘要

We report the effects of ultrahigh vacuum and nitrogen annealing on self-aligned W-gated HfO_(2) n-field-effect transistors. While rapid thermal annealing in a nitrogen ambient significantly improved the channel mobility, there is a corresponding increase in the gate dielectric thickness of up to 20 A. Here we show that this increase is due to the formation of interfacial oxides between the HfO_(2) and the silicon, caused by the diffusion of oxygen from the W gates. The results point to the importance of oxygen solubility in metals, which may be significant in many candidate gate electrodes.