Comparison of photocurrent enhancement and upset enhancement in CMOS devices in a medium-energy X-ray environment

Radiation-induced upset levels in SA3001 static random access memories (SRAMs) and SA3246 clock integrated circuits (ICs) have been measured in a medium-energy flash X-ray environment (average photon energy approximately 100 keV), where dose-enhancing effects are very important. By comparing device responses using a non-dose-enhancing ceramic package lid and a dose-enhancing Kovar/gold lid, dose-enhancement factors for photocurrent and upset were generated. The observed upset enhancement factors of 3.0+or-0.5 (SRAM) and 2.2+or-0.2 (clock IC) are in excellent agreement with measurements of photocurrent enhancement factors (2.5+or-0.5) in diodes processed with the same diffusions as the complementary metal-oxide-semiconductor (CMOS) ICs irradiated in a steady-state X-ray environment. These results indicate that upset is dominated by the radiation-induced transient supply current in these ICs, and that steady-state diode photocurrent measurements are a good predictor of both photocurrent and upset enhancement for ICs made with this technology.<
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