Chemistry and band offsets of HfO2 thin films for gate insulators

Abstract

Interfacial chemistry and band offsets of HfO2 films grown on Si(100) substrates are investigated using high-resolution angle-resolved photoelectron spectroscopy and are correlated with interfacial structures revealed by transmission electron microscope. Hf 4f and O 1s spectra show similar chemical shifts indicating the existence of a double layer structure consisting of a HfO2, upper layer and a SiO2-rich Hf1−xSixO2 lower layer. Two types of valence band offsets are clearly determined by a double subtraction method to be 3.0 and 3.8 eV that can be attributed to ΔEv1 for the upper layer HfO2/Si and ΔEv2 for the lower layer Hf1−xSixO2/Si, respectively.

First principles investigation of defect energy levels at semiconductor-oxide interfaces: Oxygen vacancies and hydrogen interstitials in the Si–SiO2–HfO2 stack

“…49,50 For the interface between silicon and monoclinic HfO 2 , we obtained a valence band offset of 2.9 eV, very close to the measured value of 3.0 eV. 51,52 This level of agreement provides confidence for the quantitative determination of defect levels with respect to the silicon band edges.…”

Chemical states and electronic structure of a HfO2∕Ge(001) interface

“…Since we determined VB offsets precisely, we can estimate conduction band offsets if an accurate band 7 gap energy of HfO 2 becomes available. In the literature, band gaps in the range of 5.2 -6.0 eV have been reported for HfO 2 depending on the film deposition technique, post deposition thermal treatment and measurement method [11,14,15]. With the well known Ge band gap of 0.66 eV, we have estimated conduction band offsets between Ge and HfO 2 as 1.8~2.6 eV.…”

Energy-band alignment of HfO2∕SiO2∕SiC gate dielectric stack

“…Similar behavior has also been reported in HfO 2 / IL/ Si system. 9,10 The smaller band offset of 1.5 eV corresponds to the HfO 2 / SiC band offset while the larger band offset of 2.2 eV is due to the interfacial SiO 2 / SiC band offset. It should be mentioned here that the interfacial SiO 2 / SiC band offset of 2.2 eV in HfO 2 / SiO 2 / SiC structure is smaller than the bulk SiO 2 / SiC band offset of 2.7 eV.…”

“…The band gap of HfO 2 is found to be 5.3 eV from the O 1s loss spectroscopy which is consistent with the reported results. 10,14 Based on the results presented in this letter, the diagrams for the energy-band alignment for HfO 2 / SiC and HfO 2 / SiO 2 / SiC systems are drawn schematically in Fig. 5.…”