Effects of over-etching time on the characteristics of amorphous IGZO thin-film transistors with back-channel-etch structure

Dry-etch for patterning Mo source/drain electrodes directly on amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with back-channel-etch (BCE) structure was investigated. The over-etching time of reactive ion etching (RIE) had a great influence on the performance of the BCE a-IGZO TFTs. The a-IGZO TFTs with an appropriate over-etching time, such as 20s, was observed with a field effect mobility (μFE) of 6.51 cm²/V·s, a threshold voltage (VTH) of 0.38 V, a subthreshold swing (SS) of 0.39 V/Dec and an I_on/I_off current ratio of 10⁹ even when the channel length L decreased to as small as 5 μm. The BCE a-IGZO TFT also showed a good electrical stability with V_TH shift of 1.09V and -0.77V under positive and negative gate bias stress, respectively.