Effects of applied mechanical uniaxial and biaxial tensile strain on the flatband voltage of (001), (110), and (111) metal-oxide-silicon capacitors
Journal
IEEE Transactions on Electron Devices
Journal Volume
56
Journal Issue
8
Pages
1736-1745
Date Issued
2009
Author(s)
Abstract
The flatband-voltage shift of metal–oxide–silicon capacitors is investigated under the application of low-level stress (up to 220 MPa of biaxial stress and 380 MPa of uniaxial stress) to different substrate orientations. We propose that the flatband-voltage shift be modeled as the net effect of silicon-band-edge shifts and modulation of the separation between the band edge and the Fermi level under low levels of applied mechanical strain. For the (001) n-type substrate, a negative flatband-voltage shift is observed due mainly to the downward shift of the conduction-band edge, while a positive flatband-voltage shift is observed for the (001) p-type substrate due to the upward shift of the valence-band edge. For the uniaxial tensile strain on n-substrate capacitors for (110) and (111) substrates, the modulation of band-edge and Fermi-level separation by the conduction-band density of states exceeds the downward shift of the conduction band, which induces a positive flatband shift that is distinct from that observed in the (001) n-substrate. The shift of the band edges is determined by the proposed model and compared with theoretical calculations.
Type
journal article