15 September 1995 Influence of the TiNx/TiSy/poly-Si gate preparation process on MOS-structure properties and reliability
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Abstract
The behavior of the MOS-structure composed of TiNx/TiSiy upper layer, 3500 angstrom thick LPCVD poly-Si layer, 200-300 angstrom thick thermal oxide grown on p-Si substrate were studied at various conditions of the fabrication process. The TiNx/TiSiy layer was formed by rapid thermal annealing (RTA) of the 200 angstrom thick titanium film previously sputter deposited on the poly-Si in nitrogen contained ambient. Samples with different compositions were obtained by varying the nitrogen content between 0% and 25% in Ar + N2 mixture. Cross-section transmission electron microscopy (TEM) investigation show the silicide/poly-Si interface roughness appears to be smaller when nitrogen content increases in the Ar + N2 working gas. TEM studies of the surface morphology reveal adding of nitrogen to the working gas yield a decrease in grain size of the film up to two-tree times if it reaches an upper limit. Measurements of sheet resistance of the titanium silicide/nitride layer displays these observations. In order to check how the process of formation of the upper layer influences the MOS-structure performances electrophysical measurements were taken. They show a decrease of instability of the work function ((Phi) ms) values as well as negligible rize of interface state density when sintering of the silicide layer is carried out in nitrogen contained ambient. Fowler-Nordheim electron injection experiments demonstrate some increase of defects density in oxide at heat treatment at higher temperatures.
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Victor M. Ivkin, Valentin V. Baranov, "Influence of the TiNx/TiSy/poly-Si gate preparation process on MOS-structure properties and reliability", Proc. SPIE 2636, Microelectronic Device and Multilevel Interconnection Technology, (15 September 1995); doi: 10.1117/12.221129; https://doi.org/10.1117/12.221129
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