Suppressing Undesired Channel Length‐Dependent Electrical Characteristics of Fully Integrated InGaZnO Thin‐Film Transistors via Defect Control Layer

Abstract

InZnO have been used to replace conventional Si-based TFTs because of their superior electrical properties, transparency, and large-area applicability. [1][2][3][4] With above promising competitivities, oxide semiconductor technologies have been commercialized in active matrix flat-panel displays. [5,6] Recently, such semiconductors have found many applications beyond display backplanes, for example, as versatile sensors (e.g., detecting distance, pressure, and light), artificial neuromorphic computing, memory devices, and in healthcare systems. [7][8][9][10][11][12][13] Interestingly, Tan et al. exhibited imitating biological synaptic behaviors and implementing image detection by using IGZO based sensory device as an artificial photonic synapse with electric potential modulation. [7] Despite the mass production in display industry, a gap remains between emerging oxide TFTs and conventional Si-based TFTs in terms of field effect mobility (µ FE ), stability, and process immunity; such issues still limit widespread commercialization of oxide TFTs. [14,15] To expand oxide TFT technology for broader applications in displays, a short-channel capability is in high demand; this property can boost the driving current, increase integration density, reduce the dead area, and enhance productivity. Besides, it is necessary to enable low leakage current in the scaled device. Hua et al. demonstrated steep switching behavior accompanied with negligible leakage using 2D transition metal dichalcogenides of molybdenum disulfide (MoS 2 ), and Shukla et al. reported comparable device characteristics using hybrid phase transition of vanadium dioxide (VO 2 ). [16,17] Similarly, IGZO TFTs represents negligible leakage current (<1 pA), favorable for low power consumption. [3,14] To retain the advantages of a low leakage current in the short channel, the threshold voltage (V th ) must be carefully controlled, so operation in the enhancement mode is preferred. [18,19] However, the well-known short-channel effects ("hot carrier", drain-induced barrier lowering [DIBL], and reduced channel resistance) render the electrical characteristics inconsistent when the channel length (L CH ) is shortened. [20][21][22] Typically, the L CH value of oxide TFTs reported to date is about a few Demand for increased scalability of oxide thin-film transistors (TFTs) continues to rise, along with the need for ever-higher integration densities and driving currents. However, the undesirable channel length (L CH )-dependency renders short channels difficult. To overcome such behavior in back-channel etched devices, back-channel interface engineering using commercially favorable silicon oxide (SiO x ) and the effects thereof on the electrical characteristics of fully integrated TFTs are investigated. Process-dependent investigation reveals that a sequential formation of double-layered SiO x with a defect control layer (DCL) effectively alleviates back-channel damage. The proposed method imparts advanced functionality to conventional materials of SiO x . The DCL p...