Channel Nanoscaling of InGaZnO TFTs and Circuits via Focused Ion Beam

Thin-film transistors (TFTs) on flexible substrates are crucial components for the development of wearable sensors and smart electronic systems. Various strategies have been explored to enable these devices to achieve high-frequency performance and meet the requirements of data communication systems. Among the strategies investigated, scaling the length of the TFT channel stands out as one of the most promising strategies in terms of compatibility and feasibility. However, the fabrication process of thin-film semiconductors on non-rigid substrates poses challenges to the scaling of the TFT channel length. In this study, a focused ion beam (FIB) based on Au and Ge ion sources is employed to pattern a nanometric channel for flexible InGaZnO TFTs. The FIB technique enables scaling the TFT channel length down to 78 and 73 nm using Au and Ge ion beams, respectively. However, induced ion implantation in the substrate leads to significant changes in the electrical TFT performance. The DC and AC performance of the TFTs with Au-milled channels demonstrate a notable improvement compared to the TFTs with Ge-milled channels, resulting in a field-effect mobility of 3 cm 2 V –1 s –1 and a transit frequency of 80.8 MHz. These values are six and ten times higher, respectively, than those of the Ge-milled TFTs. Furthermore, logic NOT gates consisting of two FIB-milled TFTs in a diode load configuration are reported, suggesting the compatibility of this approach for implementing scaled circuits on flexible substrates.