Radiation Dose Effects in Trigate SOI MOS Transistors

Abstract

N-channel trigate SOI MOSFETs have been irradiated with <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60 </sup> Co gamma rays at doses up to 6 Mrad(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). The threshold voltage shift at 6 Mrad is less than 10 mV in transistors with a gate length of 0.3 mum. At 6 Mrad(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), the current drive reduction in the same devices is 10% if V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> =0 V during irradiation and 20% if V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> =1 V during the irradiation. The generation of positive charges in the BOX increases the electron concentration at the bottom interface of the silicon fins. Inversion electrons at the bottom interface have a higher mobility than the electrons at the (110)-oriented fin sidewalls. As a result, an increase of transconductance with dose is observed at moderate doses [<1 Mrad(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> )]. At higher doses, the usual mobility degradation caused by interface trap generation is observed