Comparative physical and electrical metrology of ultrathin oxidesin the 6 to 1.5 nm regime |
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Authors: | Ahmed K. Ibok E. Bains G. Chi D. Ogle B. Wortman J.J. Hauser J.R. |
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Affiliation: | Conexant Syst. Inc., Newport Beach, CA; |
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Abstract: | In this work, five methods for measuring the thickness of ultra-thin gate oxide layers in MOS structures were compared experimentally on n+ poly-SiO2-p-Si structures. Three methods are based on electrical capacitance-voltage (C-V) and current-voltage (I-V) data and the other two methods are HRTEM and optical measurement. MOS capacitors with oxide thickness in the range 17-55 Å have been used in this study. We found that thickness extracted using QM C-V and HRTEM agree within 1.0 Å over the whole thickness range when a dielectric constant of 3.9 was used. Comparison between thickness extracted using quantum interference (QI) I-V technique and optical measurement were also within 1.0 Å for thickness 31-47 Å. However, optical oxide thickness was consistently lower than the TEM thickness by about 2 Å over the thickness range under consideration. Both optical measurement and QM C-V modeling yield the same thickness as the nominal oxide thickness increases (>50 Å) |
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