Development of high on/off current ratio in p-type copper oxide thin-film transistors with a back-end-of-line compatible process

The objective of this study is to develop an efficient process to synthesize wafer scale p-type cuprous oxide (Cu2O) with the back-end-of-line (BEOL) compatible process (<400 °C). Metallic copper is deposited on SiO2/Si substrates followed by rapid thermal oxidation to oxidize it into large-area, uniform Cu2O. Bottom-gate Cu2O thin-film transistors (TFTs) were fabricated as gate dielectric on 100 nm thermal oxide. The results of the ID-VG curve demonstrate that we have successfully fabricated BEOL-compatible p-type Cu2O TFTs. The drain-off current can be achieved to 0.1 pA, with the highest on/off ratio reaching up to 6 orders. Significantly, the TFT with an on/off ratio of 106 is sufficient to meet the requirements for digital circuit applications, including logic circuits, and the BEOL-compatible process (<400 °C) can fulfill the demands of monolithic 3D integrated circuits, expanding the scope of functional integration applications. Additionally, positive bias stress reliability testing indicated a high-quality passivation layer. These findings suggest that material improvements have significantly enhanced the performance of Cu2O TFTs.