Oxide and interface trap densities estimation in ultrathin W/La2O3/Si MOS capacitors

A novel interpretation for conductance spectra obtained by conductance method of La2O3 gated MOS capacitors has been proposed. Two distinct peaks, one with broad spectrum ranging from 10 k to 200 kHz and the other near 1 kHz with a single time constant spectrum, have been observed at depletion condition. The former spectrum can be assigned as the interface traps (Dit) located at the interface between La-silicate and the Si substrate by statistical surface potential fluctuation model. On the other hand, as the latter slow trap signal shows strong influence with the thickness of La-silicate layer, it can be assigned as the trappings (Dslow) at the interface between La2O3 and La-silicate. Finally, the Dit and Dslow trends on annealing temperature are summarized.

A novel interpretation for conductance spectra obtained by conductance method of La2O3 gated MOS capacitors has been proposed. Two distinct peaks (see at the left figure), one with broad spectrum ranging from 10 k to 200 kHz and the other near 1 kHz with a single time constant spectrum, have been observed at depletion condition. The former spectrum can be assigned as the interface traps (Dit) located at the interface between La-silicate and the Si-substrate by statistical surface potential fluctuation model. On the other hand, as the latter slow trap signal shows strong influence with the thickness of La-silicate layer, it can be assigned as the trappings (Dslow) at the interface between La2O3 and La-silicate. Finally, the Dit and Dslow trends on annealing temperature are summarized (see at the right figure). This finding indicates that the density of traps at the interface La2O3 and La-silicate layer cannot be reduced by forming gas annealing.Figure optionsDownload as PowerPoint slideHighlights
► A novel method for estimating trap densities in La2O3 MOS capacitors was proposed.
► Slow traps have been assigned as trapping at the La2O3/La-silicate interface.
► Capture cross-sections of traps can be model by the thickness of La-silicate layer.
► The trapped charges are in good agreement with the shift in the flatband voltage.
► The traps at La2O3/La-silicate interface are not reduced by forming gas annealing.