Radiation effect in SRAM and DRAM memory devices and their mitigations

The dedicated space Memory devices (specially RAM) are suffering with Single Event Effect because of cosmic rays. The Single Event Effect when an energized particle impacts a semiconductor, it generates electrons and holes and deposits a small electrical charge to the silicon. The cosmic rays contain Protons, Neutrons, Alpha particles and heavy ions. The energy of particles is in the range of 10 MeV to 105 MeV per nucleon. The Alpha particles (14%) and Heavy ions (<1%) do direct ionization within a device. The protons (protons and neutrons around 85%) may cause Single Event Effects via direct ionization in a very sensitive device, but more likely the protons will cause indirect electron-hole pair formation via a nuclear reaction in a sensitive device area. The neutrons of any energy perform only nuclear fission and by these nuclear fission the secondary particles like alpha particle and high energetic ions come into existence and secondary particle generates holes and electrons. This problem of Single Event Effect is not only happening in Space, it also happens in natural environment at earth because of thermal neutrons. Thermal neutrons are the high energetic neutrons of cosmic rays which lose their energy by environmental material scattering and reach equilibrium energy of around 25 MeV. This low energy thermal neutrons do nuclear fission with Boron isotope (10B). Boron is often present in semiconductor devices as a result of doping or in a glass passivation layer. Natural boron is composed of 19.9% 10B and 80.1% 11B. The reaction 10B (n,a) 7Li produces an alpha particle and the residual 7Li which both have enough energy to produce Single Event Effect. n + 10B 103/4 3/4 a (1.78 MeV) + 7Li (0.84MeV) + g (0.48MeV). Generally Single Event Effect generate Soft and hard Errors in Memory devices, When the permanent damage occur in the circuit so it would be hard error and when the flipping occur (i.e. transient or non transient error) so it would be Soft error. These errors are depending on the nucleons, energy of particle, linear energy transfer and the position of this charge collection. So in this paper we will discuss the phenomena of radiation Effect (Single Event Effect) in Static Memory and Dynamic Memory, with individual particle effects and How to mitigation technique of these effects. (author)