Analysis of radiation-hardening techniques for 6T SRAMs with structured layouts

Abstract

We analyze two complementary radiation-hardening techniques for 6T SRAM memories compatible with structured layouts. One approach relies on the individual selection of the threshold voltage of each of the four transistors forming the cross-coupled inverters of the SRAM cell. The other one is based on the modification of the widths of all pmos or all nmos transistors of the cell. The first technique does not affect the cell layout. The second one increases the minimum width of all pmos by a factor cp and the minimum width of all nmos by a factor cn. This prevents the formation of diffusion bends, allowing structured layouts. Both techniques provide an improvement in SEU robustness.