Asymmetric Driving Current Modification of CMOS LTPS-TFTs With HfO₂ Gate Dielectric

In this paper, the asymmetric driving current Idrv modification of CMOS low-temperature poly-Si thin-film transistors (LTPS-TFTs) with HfO2gate dielectric is demonstrated by the interfacial layer (IL) engineering of HfO2/poly-Si interface. P-channel LTPS-TFT has much higher Idrv ~ 0.789 mA than the n-channel LTPS-TFT ~ 0.274 mA under the same overdrive gate voltage. This asymmetric Idrvis due to the characteristics of field effect mobility μFEthat p-channel LTPS-TFT has much higher hole μFE~ 80.16 cm2/Vs than the electron μFE~ 38.26 cm2/V s of n-channel LTPS-TFT. The modification of HfO2/poly-Si interface by O2plasma can enhance the electron μFE ~ 34% and reduce the hole μFE~ 22.4%, resulting in balanced Idrvof CMOS LTPS-TFTs that n-channel device shows Idrv~ 0.553 mA and p-channel device shows Idrv~ 0.590 mA. In addition, the phonon scattering would also be improved by the IL growth and recovered to initial condition after IL removal. Consequently, the IL engineering of CMOS LTPS-TFTs with HfO2gate dielectric would be a good candidate for the application of system-on-panel or 3-D integrated circuits.