Browsing by Author "Jau, Yu-Hau"

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Experimental Realization of Thermal Stability Enhancement of Nickel Germanide Alloy by Using TiN Metal Capping
(2017-05-01)
Chou, Chen-Han
;
Tsai, Yi-He
;
Hsu, Chung-Chun
;
Jau, Yu-Hau
;
Lin, Yu-Hsien
In this paper, we demonstrated the enhancement of thermal stability of nickel germanide (NiGe) alloy up to 600 degrees C by using titanium nitride (TiN) metal capping. A high ION/IOFF ratio of 2.9 x 105 was achieved by capping TiN metal on Ni for NiGe alloy formation at 600 degrees C. Detailed analyses were performed for realizing the mechanism for TiN capping on NiGe/Ge, including vertical element diffusion profile observation through depth-profiling X-ray photoelectron spectroscopy (XPS), element diffusion distribution by energy-dispersive X-ray spectroscopy mapping, and direct junction leakage current path detection by conductive atomic force microscopy. The experimental results indicated that TiN capping can reduce the risk of agglomeration and form a graded NiGe/Ge Schottky junction that is beneficial for suppressing the degradation of junction leakage. Subsequently, we compared the electrical performance of TiN/NiGe/n-Ge at various N/Ti ratios of TiNs. Based on the depth-profiling XPS results and electrical performance, TiN with an N/Ti ratio of approximately 1: 1 can resist the Ni and Ge diffusion, which facilitates the suppression of the agglomeration process. However, the TiN capping layers with an N/Ti ratio of less than approximately 1:1 (Ti-rich) were not favorable for resisting Ni and Ge diffusion.
Improving Thermal Stability and Interface State Density of High-kappa Stacks by Incorporating Hf into an Interfacial Layer on p-Germanium
(2016-11)
Tsai, Yi-He
;
Chou, Chen-Han
;
Shih, An-Shih
;
Jau, Yu-Hau
;
Yeh, Wen-Kuan
We propose a new HfGeOx interfacial layer (IL) for the high-kappa gate-stacks on p-type germanium substrate with improved thermal stability as compared with that of conventional GeOx IL. We inserted an additional HfO2 layer after the formation of GeOx in the HfO2/Al2O3/GeOx/Ge gate-stack by using plasma-enhanced atomic layer deposition. Through the use of post-deposition annealing and post-metal annealing, the new system exhibited greater thermal immunity and was stable up to 600 degrees C. We speculate that the improvement originates from the formation of HfGeOx through the combination of HfO2 and GeOx, according to the thermodynamic data. By incorporating Hf into interfacial layer, the fabricated high-kappa gate-stack with an equivalent oxide thickness of 1.2 nm, a low interface states density (D-it) of approximately 3.3 x 10(11) eV(-1) cm(-2), and an impressive gate leakage current of approximately 2.2 x 10(-6) A/cm(2) at VFB-1V.