Transient Radiation Effects in SOI Memories

This paper presents the first measurements of transient radiation effects on SOI discrete devices and an LSI memory. A commercially processed LSI SOI memory, a 4K × 1 SRAM on SIMOX, was tested for SEU, and transient ionizing radiation effects as a function of bias conditions and dose rate. The SEU error rate was found to be between 1.5 and 2.5 × 10-8 errors/bit-day for the 10% worst-case orbit model. The output voltage logic upset level was greater than 1.6 × 1010 rad(Si)/sec for Vcc supply voltage variations of -10% and +20% with Vsub at -10 V. For the discrete devices and memory, the measured transient photocurrents were larger than the calculated volumetric photocurrent generated in the active device region. This increased transient response is postulated to be due to the gain of the parasitic phototransistor of the dielectrically isolated MOS device.