Comparison of Standard and Low-Dose Separation-by-Implanted-Oxygen Substrates for 0.15 µm SOI MOSFET Applications

The influence of buried oxide thickness on short-channel effects in silicon-on-insulator metal-oxide-semiconductor field-effect transistors (SOI MOSFET's) is investigated. It is shown by analytical modeling and numerical simulation that, although a thin buried oxide helps to reduce the charge-sharing component of source and drain electric fields through the oxide layer, substrate depletion underneath the thin buried oxide counteracts the oxide thinning. Although this effect is desired below the source and drain regions to maintain the SOI inherent low junction capacitances, it is detrimental to short-channel-effect suppression. The calculated results are experimentally confirmed on 0.1 µm SOI MOSFET's fabricated on both standard and low-dose separation-by-implanted-oxygen (SIMOX) substrates. A new structure for 0.15 µm SOI MOSFET applications on a thin buried oxide substrate is proposed in which substrate depletion below the channel-forming region can be suppressed locally using self-aligned deep ion implantation.