Simulation fidelity issues when using gamma-ray simulators for TREE testing CMOS SRAM

Factors that influence the fidelity of gamma-ray TREE testing are investigated. Specifically, package-induced dose enhancement in 256K CMOS static-random-access-memories (SRAMs) and dose enhancement from finite-range electrons produced (by gamma-ray interactions) in materials external to the SRAM packages are studied. Two gamma-ray simulators with significantly different spectra are used in the studies. The spectral differences produced less change in SRAM upset levels than did surrounding materials of equal mass density but differing atomic number. The implication for gamma-ray simulation testing is that individual devices within electronic systems may respond quite differently in gamma-ray TREE testing because of the structural materials within the system than when tests are performed on these individual devices without the system present.<
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