The interactions of thermal and low energy (<1 MeV) neutrons with natural boron-doped silicon has been investigated using Geant4 numerical simulations. The consequences of these interactions on the soft-error rate of 40 nm SRAM at ground level have been carefully analyzed and quantified from thermal neutron accelerated tests at LLB facility, real-time altitude measurements on the ASTEP platform and numerical simulation using a new version of the TIARA Monte-Carlo code (TIARA-G4) capable of taking into account a more accurate description of the SRAM geometry and the true isotopic composition of circuit materials from silicon to back-end-of-line levels.