Cu₂O p-type Thin-Film Transistors with Enhanced Switching Characteristics for CMOS Logic Circuit by Controlling Deposition Condition and Annealing in the N₂ Atmosphere

Abstract

Cuprous oxide (Cu2O) p-type thin-film transistors (TFTs) can be practically applied for complementary metal oxide semiconductor (CMOS) logic circuits, but the electrical performances are still insufficient due to high off-current and low field-effect mobility. Here, we have demonstrated Cu2O TFTs with improved field-effect mobility and low off-current through reduction of cupric oxide (CuO) impurities and dissociative Cu defects with the combination of deposition and annealing conditions. Copper oxide was deposited by radio frequency sputtering in mixed gases of argon and oxygen. After that, the deposited copper oxide was annealed at 800 °C in the tube furnace under a N2 atmosphere instead of a high vacuum condition. The fabricated Cu2O thin film had a high crystalline quality, the ratio of dissociative Cu defects decreased from 11.3 to 3.1%, and the electrical performances of the TFT including the fabricated Cu2O thin film exhibited the field-effect mobility of 1.11 ± 0.05 cm2/V·s, the on/off current ratio of 4.68 ± 0.8 × 104, and the subthreshold swing value of 3.91 ± 0.21 V dec–1. The fabricated Cu2O TFT showed a Vth shift of 3.31 V in the transfer curve under negative bias stress. Nitrogen plays a role in promoting Cu2O phase formation while it prevents CuO phase formation during the annealing process. In addition, oxygen added during sputtering increases the ratio of CuO in the copper oxide thin film and works effectively to reduce dissociative Cu defects in the annealing process. To determine the feasibility of the CMOS logic circuit, we also demonstrated the inverter with n-type indium–gallium–zinc oxide (IGZO) TFT and p-type Cu2O TFT, which showed a voltage gain of 14 at V DD = 20 V.

Oxide Semiconductor Heterojunction Transistor with Negative Differential Transconductance for Multivalued Logic Circuits

“…The substrate was ultrasonically cleaned in acetone and IPA for 15 min each, and finally, UV/ozone cleaning was performed for 15 min. As in a previously reported study, 51 a 300 Å thick Cu 2 O thin film was fabricated by depositing CuO X using RF sputtering and postannealing in a tube furnace at 800 °C for 1 min under nitrogen flow conditions. After the Cu 2 O thin film was patterned through photolithography and wet etching, an IGZO thin film was deposited using RF sputtering and annealed in the atmosphere at 250 °C for 1.5 min with RTA.…”

“…OSs are versatile candidates for semiconductor materials as next-generation electronic devices because of their intrinsic advantages such as high mobility, scalability, low cost, low leakage current, and application of conventional semiconductor manufacturing processes in industries. − For these reasons, OSs have been utilized in a variety of applications, including thin-film TRs (TFTs), photocatalysts, solar cells, and flexible devices . Indium gallium zinc oxide (IGZO), a representative n-type OS, is employed for switching TFTs which enable low power consumption such as flat-panel displays (FPDs). , Although n-type OS TFTs can be fabricated with conventional CMOS processes, the poor electrical properties of p-type OSs have made it difficult to fabricate heterojunction TRs with NDT properties. − However, the performance of a p-type copper­(I) oxide (Cu 2 O) TFT has recently been improved through many studies, with reports of its utilization in logic circuits based on CMOS technology composed of IGZO and Cu 2 O TFTs. − It has been difficult to apply a p-type OS to various application fields beyond CMOS circuits, but as its performance improves, its use in various fields is increasing.…”

Negative Capacitance for Stabilizing the Logic State in a Tunnel Field-Effect Transistor

“…These thin films can be utilized in the fabrication of back-end-of-line-compatible complementary metal oxide semiconductor (CMOS) circuits . Among these, atomic-layer-deposited Cu-based CMOS devices are promising for high performance in terms of high mobility, low off-current, etc. − Thus, these are attractive for real-world applications, i.e., photonic, spectroscopic, photoelectronic, and energy-harvesting purposes. − …”

Compositional Engineering of Cu-Doped SnO Film for Complementary Metal Oxide Semiconductor Technology

“…For example, amorphous IGZO has been implemented for commercialization in flexible displays; 7 complementary logics based on p-type Cu 2 O and n-type counterparts IGZO, ZTO, etc., have been demonstrated. 8,9 Nevertheless, incompatibility between multiple metal oxide semiconductor processes can lead to complex layouts and high costs that are not suitable for commercial applications.…”

“…Because of their advantages, low power dissipation, wide noise margin (NM), and large-volume manufacturing, complementary metal oxide semiconductor (CMOS) logics have facilitated the growth of the integrated circuit industry. − However, traditional silicon-based CMOS circuits face fundamental challenges of rigidity and brittleness, which hinders their application in emerging flexible electronics, including wearable devices, artificial skins, flexible displays, etc. − In contrast, metal oxide semiconductors show the greatest potential for commercial applications in flexible electronics due to their high carrier mobility and low-temperature deposition processes on plastic substrates. For example, amorphous IGZO has been implemented for commercialization in flexible displays; complementary logics based on p-type Cu 2 O and n-type counterparts IGZO, ZTO, etc., have been demonstrated. , Nevertheless, incompatibility between multiple metal oxide semiconductor processes can lead to complex layouts and high costs that are not suitable for commercial applications.…”