This paper discusses the effect of ionizing radiation on two types of deformable MEMS mirrors. Little effect was observed in the technology that was based on electrostatic deflection, consistent with the structural design that does not contain insulators between the two sections. Significant changes in the operating characteristics were observed for the second type of mirror, which uses piezoelectric material for actuation. The mirrors required higher total dose levels before they were affected compared to MEMS accelerometers, which can be explained by the larger interelement spacing used in the mirror arrays.

Different silicon avalanche photodiode structures are compared for the effects of 51-MeV protons on dark current, photocurrent, and noise. Large differences in depletion region volumes contributed to differences in sensitivity to bulk dark current increases. At high fluences, ionization damage appeared to be the dominant mechanism for dark current increases in some devices. Increases in 1/f-type noise and supplemental gamma ray testing indicate that these high dark current increases are due to surface damage effects. A discussion of structural parameters that may heighten radiation sensitivity is presented, including doping levels and p-n junction termination techniques.

Breakdown of thin gate oxides from heavy ions is investigated using capacitor test structures. Soft breakdown was observed for 45 Å oxides, but not for 75 Å oxides. Lower critical fields were observed when experiments were done with high fluences during each successive step. This implies that oxide defects play an important role in breakdown from heavy ions and that breakdown occurs more readily when an ion strike occurs close to a defect site. Critical fields for 75 Å oxides are low enough to allow gate rupture to occur at normal supply voltages for ions with high LET.

A two-step modeling approach is developed for single-event transients in linear circuits that uses the PISCES device simulation program to calculate transient currents in key internal transistor structures. Those currents are then applied at the circuit level using the SPICE circuit analysis program. The results explain the dependence of transients on input differential voltage, as well as the dependence of transient signals on output loading conditions. Error rate predictions based on laboratory testing and modeling are in close agreement with the observed number of "trips" in comparators within power control modules that have operated in a deep space environment for nearly three years.

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