Highly controllable dual-gate microcrystalline silicon thin film transistor processed at low temperature (T < 180 °C)

The addition of a top-gate to a bottom gate microcrystalline silicon thin film transistor (TFT) that is processed at a maximum temperature of 180 °C, is shown to lead to a very efficient control of the threshold voltage VTH. A real time control of CMOS pairing is then possible. The value of the coupling coefficient that is the ratio of the variation of VTH on the variation of the voltage of the top-gate control is 0.7. This efficient control is mainly due to the use of very thin, 50 nm thick, active layer and to its electrical quality that leads to a full depletion.

► We fabricated dual-gate microcrystalline silicon TFTs at very low temperature (T < 180 °C).
► We demonstrated a very efficient control of the threshold voltage VTH.
► The coupling coefficient can be compared to the usual values of fully depleted SOI FETs.
► The high efficiency is mainly due to the use of very thin film and to its electrical quality.