Study of Organic Thin-film Transistor on Silicon Nitride Gate Dielectrics for Integration in Display Circuits and Arrays

摘要

Research in organic thin-film transistors (OTFTs) has unleashed fascinating opportunities for organic electronics in areas requiring low-temperature processing, large area coverage, mechanical flexibility, and overall low cost. Prospective applications for OTFTs include active matrix organic light-emitting diode (AMOLED) displays, large-area flexible displays, electronic paper (e-paper), radio-frequency identification (RFID) tags, and low-cost and low-end printable electronic devices. The gate dielectric plays an important function in establishing field-effect operation in OTFTs. A variety of gate dielectric materials has been investigated and reported for OTFTs. This paper focuses on the use of silicon nitride (SiN{sub}x), deposited by plasma-enhanced chemical vapour deposition (PECVD). Attractive attributes of SiN{sub}x include low temperature deposition, large-area capability, and good dielectric strength. Various compositions of SiN{sub}x films, ranging from N-rich to Si-rich, are explored to determine an optimal choice for OTFT fabrication. The SiN{sub}x film's composition dictates the dielectric's surface property, which subsequently governs the molecular ordering of the overlying organic semiconductor layer and the quality of the semiconductor-dielectric interface. These physical attributes have a strong bearing on the OTFT characteristics, including threshold voltage (V{sub}T), leakage current (I{sub}(leak)), subthreshold slope (S), on/off current ratio (I{sub}(on)/I{sub}(off)), and field-effect mobility (μ{sub}(FE)). Thus, proper control of the gate dielectric surface property is crucial for attaining higher performance OTFTs.