Mechanisms Limiting EOT Scaling and Gate Leakage Currents of High- $k$/Metal Gate Stacks Directly on SiGe
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This letter addresses mechanisms responsible for a high gate leakage current Jg) and a thick interfacial layer in the surface channel SiGe pFET enabling transistor fabrication with sub-1-nm equivalent-oxide-thickness (EOT) high-k/metal gate stack. The primary mechanism limiting EOT scaling is Ge-enhanced Si oxidation resulting in a thick (1.4-nm) SiOx interface layer. A secondary mechanism, i.e., Ge diffusion (>3%) into high-k, results in high Jg. In the framework of this understanding, we optimized a high-k nitridation process to form as an efficient diffusion barrier, which reduces both O and Ge diffusion resulting in the total gate stack EOT ∼0.9 nm with Jg comparable to that of bulk Si substrate samples. The proposed plasma nitridation process enables fabrication of the sub-1-nm EOT gate-first gate stack with HfSiON dielectric directly on SiGe without Si cap. © 2009 IEEE.
author list (cited authors)
Huang, J., Kirsch, P. D., Oh, J., Lee, H., Majhi, P., Harris, H. R., ... Jammy, R.