| AVS 56th International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM2-TuM |
| Session: | Complex and Multifunctional Oxides |
| Presenter: | E. Bersch, University at Albany |
| Authors: | E. Bersch, University at Albany M. Di, University at Albany S. Consiglio, TEL Technology Center, America, LLC R. Clark, TEL Technology Center, America, LLC G. Leusink, TEL Technology Center, America, LLC A.C Diebold, University at Albany |
| Correspondent: | Click to Email |
As the MOSFET SiO2-based gate dielectric layer approaches its fundamental physical limits, the investigation of high-k oxides is ongoing in order to determine which oxides can best continue the scaling of the MOSFET. HfO2, hafnium silicates and nitrided hafnium silicates are leading candidates due to their relatively large band gaps, thermal stability in proximity to Si and relatively high dielectric constants.
The band offsets between the high-k oxide layers and Si in high-k/SiO2/Si films stacks are important parameters in that the gate leakage current depends strongly on them. Recent studies by various groups have also shown that the threshold voltage in MOSFETs with high-k gate oxides can be altered by the presence of an additional oxide layer such as La2O3 or Al2O3.1-3 In the case of a La2O3 interface layer, the flatband voltage shift has been correlated with a shift in the energy level alignment in the high-k gate stack.4
We have used a combination of x-ray photoemission spectroscopy (XPS) and spectroscopic ellipsometry (SE) to measure the valence and conduction band offsets (VBO and CBO, respectively) between high-k layers and Si substrates. We will report VBO and CBO values for HfO2, hafnium silicate and nitrided hafnium silicate films with Si. In addition, we will report measurements of the HfO2-Si band offsets from HfO2/La2O3/SiO2/Si film stacks, noting the effect of the La2O3 layer.
Analysis of XPS spectra of the Si 2p spectra from HfO2/SiO2/Si film stacks will also be reported, which shows that the composition of the SiO2 layer and the energy level alignment between the SiO2 and Si layers were affected by the growth of the HfO2 layer and the annealing of the film stack. These results will be discussed with respect to the band offset measurements for HfO2 film stacks.
Finally, using angle resolved XPS (ARXPS) data we constructed non-destructive compositional depth profiles using a maximum entropy algorithm. A comparison between thickness values extracted from these depth profiles and thicknesses measured with SE will be presented.
References:
1. P. D. Kirsch et al., Appl. Phys. Lett., 92, 092901 (2008).
2. V. Narayanan et al., Symp. VLSI Tech., 178 (2006)
3 K. Iwamoto et al., Appl. Phys. Lett., 92, 132907 (2008)
4. K. Kakushima et al., Appl. Surf. Sci., 254, 6106 (2008).