Investigation of Multiple-bit Upsets in Anisotropic SRAM Device

Key words: 
• single event effect /
• static random access memory /
• anisotropic layout /
• multiple-bit upset

Abstract: Heavy ion experimental results reveal that the ratio of multiple-bit upset (MBU) in static random access memory (SRAM) increases for ions with higher linear energy transfer (LET) value or at larger angle of incidence, even exceeds the ratio of single-bit upset. The diffusion distance of charges in single ion track can be several micrometers. The MBU patterns of device under test are influenced by both the anisotropic distribution of sensitive volumes and the track direction. Horizontal configuration turns out to be the predominant double-bit upset pattern due to the vertical isolation (bit-line contacts) of adjacent sensitive volumes. L-shaped and squareshaped configurations are the main triple-bit upset and quadruple-bit upset patterns, respectively. Finally,implications for MBU hardness strategies and evaluation methods are discussed.