|AVS 57th International Symposium & Exhibition|
|Thin Film||Wednesday Sessions|
|Session:||High K Dielectrics for Si Electronics|
|Presenter:||E.J. Bersch, University at Albany|
|Authors:||E.J. Bersch, University at Albany
M. Di, University at Albany
S.A. Consiglio, Tokyo Electron America Inc.
R.D. Clark, Tokyo Electron America Inc.
G.J. Leusink, Tokyo Electron America Inc.
A.C. Diebold, University at Albany
|Correspondent:||Click to Email|
There has been much attention paid recently to the lowering of the threshold voltage (Vt) that is accomplished by including an additional ultrathin (~5-10 Å) oxide layer in the high-k/metal gate metal oxide semiconductor field effect transistor (MOSFET) gate stack. We have investigated the TiN/HfO2/La2O3/SiO2/p-Si stack, where the La2O3 layer is the so-called Vt-shift layer. For several variations of this stack, where both the thickness and the position of the La2O3 layer were systematically varied, we measured two quantities directly related to the Vt, the flatband voltage (Vfb) and the Si band bending. The Vfb was measured using capacitance-voltage (C-V) measurements on stacks with 500 Å TiN layers, and the Si band bending was measured on sister wafers with 30 Å TiN layers. For a set of samples where the thickness of the La2O3 between the HfO2 and SiO2 layers was varied, we observed that the Vfb and Si band bending both become more negative as the thickness of the La2O3 was increased. For a set of samples where position of the La2O3 within the HfO2 layer was varied, we observed that the Vfb and Si band bending became less negative as the amount of HfO2 between the La2O3 and the SiO2 was increased. These observations support the proposition that there is a dipole at the La2O3/SiO2 interface which affects the Si band bending, as has been reported in the literature.1,2 We have also observed that there is a difference in the Vfb and Si band bending in TiN/HfO2/La2O3/SiO2/p-Si stacks with thermally grown and chemically grown SiO2 layers. Results of this study as well as one where the thickness of thermally grown SiO2 layers was varied will be presented, and it implications on the theory of the interface dipole with be discussed.
1. K. Kita, et al., Appl. Phys. Lett, 94, 132902 (2009).
2. P.D. Kirsch, et al., Appl. Phys. Lett., 92, 092901 (2008).