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Formation of polycrystalline silicon germanium/HfO2 gate stack structure using inductively coupled plasma etching

2003; American Institute of Physics; Volume: 21; Issue: 4 Linguagem: Inglês

10.1116/1.1586283

1520-8559

Jinghao Chen, K. M. Tan, Nan Wu, Won Jong Yoo, Daniel S.-P. Chan,

Nanowire Synthesis and Applications

A gate stack structure consisting of a polycrystalline silicon germanium (poly-SiGe) conductor and a HfO2 dielectric on a silicon substrate was formed by inductively coupled plasma etching using HBr/Cl2/O2. Etch rates of poly-SiGe with 46% Ge were 1.7–2.0 times higher than those of polycrystalline silicon, depending on processing conditions. In the small feature sized devices of 100 nm gates, the notching at the sidewall of poly-SiGe was pronounced up to the depth of 50 nm. The amount of notching increased with increasing inductive power and pressure, and decreasing rf bias power. A HfO2 etch rate of 950 Å/min was obtained at the condition of 550 W inductive power, 360 W rf bias power, and 10 mTorr pressure. Etch rates of HfO2 increased with increasing inductive power and rf bias power. Etching selectivity of poly-SiGe with respect to HfO2 increased significantly with the addition of 3.8% O2 to HBr, and it was possible to control the selectivity in the range of 15–70 by changing the rf bias power. The change in etching selectivity was considered mainly due to the change in HfO2 film property, originating from the incorporation of O into the remaining nonvolatile Hf and the reformation of HfOx during etching.