Ge diffusion and bonding state change in metal/high-/Ge gate stacks and its impact on electrical properties

細井 卓治*; 秀島 伊織*; 田中 亮平*; 箕浦 佑也*; 吉越 章隆; 寺岡 有殿; 志村 考功*; 渡部 平司*

Microelectronic Engineering, 109, p.137 - 141, 2013/09

https://doi.org/10.1016/j.mee.2013.03.115

Ge diffusion and chemical bonding states in metal/high-/Ge gate stacks were investigated by synchrotron photoemission spectroscopy to understand their impact on electrical properties. Although Hf germanide was found in HfO/GeO/Ge gate stacks, such germanide could be fully oxidized by using plasma-assisted oxidation. However, Al electrode on HfO/GeO/Ge stacks reduced interfacial GeO layer, resulting in the formation of Al germanide at the Al/HfO interface. No germanide was formed in the stacks with inert Pt electrode, suggesting the Al layer may promote upward diffusion of GeO molecules through the HfO layer. Hf germanide was formed near the HfO/GeO interface probably due to Ge intermixing with the HfO layer in the Pt-gate stacks, in contrast to the enhanced formation of Al germanide in Al-gate stacks. The formation of metal germanide led to severe degradation of insulating properties in metal/high-/Ge stacks.