An Analysis of the Significance of the ¹⁴N(n, p) ¹⁴C Reaction for Single-Event Upsets Induced by Thermal Neutrons in SRAMs

The thermal neutron threat to the reliability of electronic devices caused by B-10 capture is a recognized issue that prompted changes in the manufacturing process of electronic devices with the aim of limiting as much as possible the presence of this isotope nearby device sensitive volumes (SVs). N-14 can also capture thermal neutrons and release low-energy protons (LEPs; through the N-14(n, p)C-14 reaction) that have high enough linear energy transfer (LET) to cause single-event upsets (SEUs). Typically, nitrogen is used in thin barrier layers made of TaN or TiN or even as insulator in the form of Si3N4. Numerical simulations on SVs calibrated on proton and ion experimental data and with an accurate description of the metallization layer on top of the sensitive region show that the presence of nitrogen in these thin barrier layers can be enough to justify the experimentally observed thermal neutron SEU cross section for a static random access memory (SRAM) sensitive to LEPs. Nevertheless, the expected SEU cross section from thermal neutrons is usually a few orders of magnitude lower than that of high-energy particles, therefore, not representing an important threat in atmospheric applications. At the same time, for high-energy accelerators, the contribution to the total soft error rate (SER) could become substantial, though easy to handle by margins.