Soft-Error Rate Induced by Thermal and Low Energy Neutrons in 40 nm SRAMs

Abstract

International audienceThe 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

Radiation and COTS at ground level

“…1 bottom). At sea level (New York City), this flux is equal to 7.6 n/cm 2 /h below 1 eV (thermal and epithermal neutrons), 16 n/cm 2 /h for the intermediate part (between 1 eV and 1 MeV) and 20 n/cm 2 /h for the upper part (high energy neutrons above 1 MeV) [18]. This last value is reduced to 13 n/cm 2 /h when integrating the flux above 10 MeV [18].…”

“…At sea level (New York City), this flux is equal to 7.6 n/cm 2 /h below 1 eV (thermal and epithermal neutrons), 16 n/cm 2 /h for the intermediate part (between 1 eV and 1 MeV) and 20 n/cm 2 /h for the upper part (high energy neutrons above 1 MeV) [18]. This last value is reduced to 13 n/cm 2 /h when integrating the flux above 10 MeV [18]. The total neutron flux over the whole energy range (from thermal to high energies) is equal to 43.6 n/cm 2 /h for this location and measurement conditions reported in [17].…”

Thermal Neutron-Induced Single-Event Upsets in Microcontrollers Containing Boron-10

“…Although 11 B-enriched manufacturing products (with a much lower thermal neutron capture cross section) are available for boron doping (such as [6]), the additional cost compared to natural boron may preclude their use in p-type doping for commercial-off-the-shelf (COTS) components not specifically designed for radiation tolerance. Borondoped p-type silicon has been identified as the source of 10 B associated with soft errors in 40-nm SRAMs [7], singleevent burnout (SEB) in power MOSFETs [8], and changes in charge collection efficiency in complementary metal-oxide semiconductor (CMOS) active pixel sensors [7], [9]. Diborane (B 2 H 6 ) and boron trifluoride (BFl 3 ) are gasses used in interconnect processing to aid the nucleation of tungsten plugs in devices at the 90-nm node and below [10], [11].…”

GEANT4 simulations in terms of radiation hardness of commercially available SRAM

“…These systems suffer from neutron [10,11], gamma [12], alpha [13], proton [14], Heavy ions [15] and elementary particle failure [16], due to the generation of single event effects [18,19] and due to a single bit or multi-bit failure [20,21]. This can be generated directly by primary radiation or indirectly by secondary radiation [22].…”