Ring oscillator characteristics of silicon on thin buried oxide (SOTB) were investigated at Vdd down to 0.4V. It was demonstrated that both the propagation delay (τpd) and energy-delay (ED) product of SOTB were smaller than those of bulk devices due to its steeper subthreshold swing. It was found that the τpd variability of SOTB is dominated by global variability because local variability is small due to the intrinsic channel. The origin of τpd variability was analyzed by taking the transistor dc characteristics into account. It was found that the τpd variability of SOTB is caused by the global drive current variability because the effect of resistance (or effective drain current I eff ) is much larger than that of capacitance with Vdd reduction. The τpd variability is mainly caused by the global drive-current variability and thus can be easily reduced by die-to-die substrate bias voltage control.
ASJC Scopus subject areas