A Comparative Study of E-Beam Deposited Gate Dielectrics on Channel Width-Dependent Performance and Reliability of <i>a</i>-IGZO Thin-Film Transistors

• Main Authors: Gwomei Wu, Anup K. Sahoo, Dave W. Chen, J. W. Chang
• Format: Article
• Language: English
• Published: MDPI AG 2018-12-01
• Series: Materials
• Subjects: <i>a</i>-IGZO; thin-film transistor; e-beam; gate dielectric; reliability
• Online Access: https://www.mdpi.com/1996-1944/11/12/2502

A comparative study on the effects of e-beam deposited gate dielectrics for amorphous indium gallium zinc oxide (<i>a</i>-IGZO) thin-film transistors (TFTs) has been carried out using SiO₂, Si₃N₄, and Ta₂O₅ dielectric materials. The channel width dependent device electrical performances were investigated using three different sizes of 500 &#956;m, 1000 &#956;m, and 1500 &#956;m. The reliability characteristics were revealed by the threshold voltage variation and drain current variation under positive bias stress. The e-beam deposited high-k dielectric Ta₂O₅ exhibited the highest stability at the stress voltage of 3 V for 1000 s due to its high capacitance density at 34.1 nF/cm². The threshold voltage variation along the channel width decreased from SiO₂, then Si₃N₄, to Ta₂O₅, because of the increased insulating property and density of capacitance. The SiO₂-based <i>a</i>-IGZO TFT achieved a high field effect mobility of 27.9 cm²/V&#183;s and on&#8315;off current ratio &gt; 10⁷ at the lower channel width of 500 &#956;m. The gate leakage current also decreased with increasing the channel width/length ratio. In addition, the SiO₂ gate dielectric-based <i>a</i>-IGZO TFT could be a faster device, whereas the Ta₂O₅ gate dielectric would be a good candidate for a higher reliability component with adequate surface treatment.