In-situ spectroscopic ellipsometry and structural study of HfO2 thin films deposited by radio frequency magnetron sputtering

Abstract

We have investigated the reduction of unwanted interfacial SiO 2 layer at HfO 2 /Si interface brought about by the deposition of thin Hf metal buffer layer on Si substrate prior to the deposition of HfO 2 thin films for possible direct contact between HfO 2 thin film and Si substrate, necessary for the future generation devices based on high-j HfO 2 gate dielectrics. Reactive rf magnetron sputtering system along with the attached in-situ spectroscopic ellipsometry (SE) was used to predeposit Hf metal buffer layer as well as to grow HfO 2 thin films and also to undertake the in-situ characterization of the high-j HfO 2 thin films deposited on n-type h100i crystalline silicon substrate. The formation of the unwanted interfacial SiO 2 layer and its reduction due to the predeposited Hf metal buffer layer as well as the depth profiling and also structure of HfO 2 thin films were investigated by in-situ SE, Fourier Transform Infrared spectroscopy, and Grazing Incidence X-ray Diffraction. The study demonstrates that the predeposited Hf metal buffer layer has played a crucial role in eliminating the formation of unwanted interfacial layer and that the deposited high-j HfO 2 thin films are crystalline although they were deposited at room temperature. V C 2014 AIP Publishing LLC.

Investigation of HfO2 Thin Films on Si by X-ray Photoelectron Spectroscopy, Rutherford Backscattering, Grazing Incidence X-ray Diffraction and Variable Angle Spectroscopic Ellipsometry

“…The start of the photoelectron loss-energy spectrum, after setting the energy of the O 1s peak maximum to zero loss energy, was defined by linearly extrapolating the segment of maximum negative slope (dash-lines in the Figure 4) to the background level in each of the spectra [29][30][31]. The bandgap values of S1, S2, and S3 are as follows: 5.65 eV, 5.57 eV and 5.10 eV, which are in agreement with our results by variable angle spectroscopic ellipsometry (VASE) in Section 3.4, and previously reported bandgap values for HfO2 in different references [3,[32][33][34][35][36][37]. The high-resolution XPS fitting results of the O 1s peaks of S1, S2, and S3 are shown in (a-c), respectively, with experiment data (short dash lines), fitting result (red solid lines), and background (chartreuse solid lines).…”

Importance of CdS buffer layer thickness on Cu2ZnSnS4-based solar cell efficiency

“…Psi (Ψ) and Delta (Δ) are the ellipsometric parameters which measure the phase and amplitude changes of incident light, respectively. In order to define the thickness of the grown film, an appropriate optical model was constructed, and measured and modeled ellipsometric data were fitted [26]. As an optical model for the CdS films, the generalized oscillator (gen-osc) function, which is suitable for semiconductor film, was used.…”

Comparision of in situ spectroscopic ellipsometer and ex situ x-ray photoelectron spectroscopy depth profiling analysis of HfO2/Hf/Si multilayer structure

“…The HfO 2 film was prepared by RF magnetron sputtering technique employing a high purity Hf target with 2 a inch diameter, a 0.25 inch thickness, and a 99.9% purity. The schematic representation of our magnetron sputtering system coupled with an in situ SE system was given in a previous study [14].…”

“…As a result, an appropriate optical model was constructed for our (Ψ, Δ) ellipsometric data for the fitting. Our film stack was composed of three layers on Si substrate, i.e., Air/HfO 2 /SiO 2 /c-Si (from top to bottom in the respective order) [14]. As an optical model, the Cauchy dispersion relation which is a polynomial function, was used.…”