Total Dose Radiation-Bias Effects in Laser-Recrystallized SOI MOSFET's

Laser-recrystallized polysilicon over an insulating layer, such as silicon dioxide, provides a new approach for the fabrication of active devices which are dielectrically isolated from the substrate. This paper deals with initial radiation studies for gamma radiation doses from 1 krad to 1 Mrad(Si) on n- and p-channel MOSFET's fabricated in such laser-recrystallized silicon. The n-channel devices were used to investigate the effect of interfacial charge trapping at both the gate oxide/ and underlying oxide/ recrystallized silicon interface. Data on radiation-induced leakage currents and threshold shifts are presented as a function of radiation dose for worst-case irradiation-bias conditions and for various substrate biases during irradiation. Additionally, the effect of a deep boron implant is presented. Although a hardened process was not used to fabricate the MOSFET's, the results show promise for a radiation-hardened alternative to SOS when logic design allows negative substrate biasing and for a radiation-hardened stacked non-planar three-dimensional circuitry.