Scaling of SOI/PMOS transistors

This paper reports results from a study including the weak inversion behaviour of P-channel MOS transistors fabricated in polycrystalline silicon. The devices have a wide range of channel dopings, with channel lengths and widths down to 1.25 microns. The use of very thin polysilicon enables the gate to modulate the channel conductivity of devices in fine-grain polysilicon with gate voltage excursions of under five volts. The devices have a slow turn-on and exhibit an extended weak-inversion region. Weak-inversion currents increase with applied drain voltages up to about 5 volts, with long channel devices also showing this phenomenon. Short-channel effects are seen as the channel length approaches 2 microns and are mitigated by using a higher channel doping. Device currents drop sharply below a channel width of 2 microns, although the narrow-width effect is not as pronounced as the short-channel effects.