Improvement in Device Performance of a-InGaZnO Transistors by Introduction of Ca-Doped Cu Source/Drain Electrode

This letter reports the effects of Ca doping into Cu films, which was used as a source/drain (S/D) electrode for high performance amorphous In-Ga-Zn-O (IGZO) thin-film transistors (TFTs) with a low resistive-capacitive delay time. The IGZO TFTs with Ca-doped Cu S/D exhibited three times higher saturation mobility (16 cm²/Vs) and substantially lower subthreshold gate swing of 0.39 V/decade than the control devices with pure Cu S/D. The SIMS profile and cross-sectional transmission electron microscopy showed that Ca effectively prevented the Cu atoms from diffusing into channel IGZO region presumably as a result of Ca-O bond formation, which is responsible for their superior device performances.