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Silicon provides a good exemplar for a consideration of the critical parameters that affect the uncertainty for neutron dosimetry metrics, e.g., total kerma, ionizing kerma, displacement damage energy. In addition to the energy-dependent cross section uncertainty found in the ENDF-6 formatted nuclear data files, one must also address uncertainty due to: a) models used, e.g., modeling of the recoil ion energy from the capture gamma reaction; b) the damage partition function that is used to divide the deposited energy into ionization and displacement components, e.g., the Robinson partition function; c) recoil ion stopping power; d) treatment of the displacement threshold region for some damage metrics, e.g., the Kinchin-Pease dpa [1]; e) treatment of the angle-dependence of the lattice atom displacement when examining the creation of Frenkel pairs. Work with silicon [2] clearly established the critical importance of considering cross-reaction correlations. Analysis [3] has also addressed the effect of correlations between nuclear data evaluations for different isotopes in the naturally occurring elements. When we go from Si to other modern semiconductor materials, like GaAs, GaN, and SiGe, we also need to address the uncertainty due to: a) the treatment of the polyatomic lattice atoms within the damage partition function [4]; b) use of damage metrics that show an additional dependence upon the energy of the recoil atom [5], e.g., the arcdpa efficiency [6] which exhibits an energy-dependent uncertainty that has uncertainty contributions from the model-based functional form uncertainty as well as from the model- or experiment-based data calibration; c) the correlation between the calculated damage metric and the useful experimental metrics, e.g., use of dpa or the number of Frenkel pairs created as a metric for the minority carrier recombination lifetime [7]. In some cases the use of modified damage metrics, e.g., 1-MeV(Si)-Eqv. Fluence, can reduce the overall uncertainty by looking at damage ratios and removing some of systematic uncertainty terms.
This paper starts with a summary of the status of our uncertainty quantification in silicon semiconductors and then extends the discussion to ongoing work with GaAs and GaN semiconductors. We then address emerging issues that are associated with SiGe and small feature-sizes (<5 nm) semiconductors found in FinFET and gate-all-around (GAA) devices.
[1] M. Robinson, O. Oen, “On the Use of Thresholds in Damage Energy Calculations,” Journal of Nuclear Materials, Vol. 110, pp. 147-149, 1982.
[2] P. Griffin, “Uncertainty Characterization of Silicon Damage Metrics,” IEEE Trans. On Nuclear Science, Vol. 66, No. 1, pp. 327-336, Jan. 2019. http://dx.doi.org/10.1109/TNS.2018.2876058
[3] J.-Ch. Sublet, et al., “Neutron-induced damage simulations: Beyond defect production cross-section, displacement per atom and iron-based metrics,” Eur. Phys. J. Plus, Vol. 134, 350 (2019). https://doi.org/10.1140/epjp/i2019-12758-y
[4] C. Coulter, D.M. Parkin, “Damage Energy Functions in Polyatomic materials, Journal of Nuclear Materials, Vol.88, pp. 249-260, 1980.
[5] P. Griffin, et al., “Neutron Damage Equivalence in GaAs”, IEEE Trans. On Nuclear Science, Vol. 38, No. 6, pp. 1216-1224, December 1991.
[6] K. Nordlund, et al., “Improving atomic displacement and replacement calculations with physically realistic damage models,” Nature Communications,9, 1084 (2018). https://doi.org/10.1038/s41467-018-03415-5
[7] G. C. Messenger, M. A. Ash, The Effects of Radiation on Electronic Systems, Van Nostrand Reinhold Company, 1986.
*This work was supported in part by the U.S. Department of Energy under contract DE-NA0003525. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.
The views expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government.