Ultrathin Al/sub 2/O/sub 3/ and HfO/sub 2/ gate dielectrics on surface-nitrided Ge |
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Authors: | James Jer-Hueih Chen Bojarezuk NA Jr Huiling Shang Copel M Hannon JB Karasinski J Preisler E Banerjee SK Guha S |
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Affiliation: | Microelectron. Res. Center, Univ. of Texas, Austin, TX, USA; |
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Abstract: | We have studied ultrathin Al/sub 2/O/sub 3/ and HfO/sub 2/ gate dielectrics on Ge grown by ultrahigh vacuum-reactive atomic-beam deposition and ultraviolet ozone oxidation. Al/sub 2/O/sub 3/-Ge gate stack had a t/sub eq//spl sim/23 /spl Aring/, and three orders of magnitude lower leakage current compared to SiO/sub 2/. HfO/sub 2/-Ge allowed even greater scaling, achieving t/sub eq//spl sim/11 /spl Aring/ and six orders of magnitude lower leakage current compared to SiO/sub 2/. We have carried out a detailed study of cleaning conditions for the Ge wafer, dielectric deposition condition, and anneal conditions and their effect on the electrical properties of metal-gated dielectric-Ge capacitors. We show that surface nitridation is important in reducing hysteresis, interfacial layer formation and leakage current. However, surface nitridation also introduces positive trapped charges and/or dipoles at the interface, resulting in significant flatband voltage shifts, which are mitigated by post-deposition anneals. |
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