Enhanced Proton and Neutron Induced Degradation and Its Impact on Hardness Assurance Testing

Abstract

It is shown that protons and neutrons can induce enhanced degradation in power MOSFETs, including both trench and planar geometry devices. Specifically, large shifts in current-voltage characteristics can be observed at extremely low proton total dose levels (as low as ~ 2 rad(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> )). These shifts can induce significant increases in device ldquooffrdquo state leakage current. Neutron irradiations show similar degradation at equivalent fluence levels, even though neutrons do not deposit dose due to direct ionization. These data suggest that the mechanism responsible for the enhanced degradation is a microdose effect associated with secondary particles produced through nuclear interactions between protons and neutrons and the materials in integrated circuits. The secondary particles deposit enough charge in the gate oxide to induce a parasitic drain to source leakage path in the transistor. Although the results are demonstrated here for only trench and planar geometry power MOSFETs, microdose effects can impact the radiation response of other integrated circuit types. Hardness assurances issues implications are discussed.