Experimental Realization of Thermal Stability Enhancement of Nickel Germanide Alloy by Using TiN Metal Capping

Chen Han Chou, Yi He Tsai, Chung Chun Hsu, Yu Hau Jau, Yu Hsien Lin, Wen Kuan Yeh, Chao Hsin Chien

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6 Scopus citations


In this paper, we demonstrated the enhancement of thermal stability of nickel germanide (NiGe) alloy up to 600 °C by using titanium nitride (TiN) metal capping. A high IONIOFF ratio of 2.9× 105 was achieved by capping TiN metal on Ni for NiGe alloy formation at 600 °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.

Original languageEnglish
Article number7885604
Pages (from-to)2314-2320
Number of pages7
JournalIEEE Transactions on Electron Devices
Issue number5
StatePublished - 1 May 2017


  • Agglomeration
  • germanium
  • nickel germanide (NiGe)
  • Schottky junction
  • thermal stability
  • TiN capping


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