Control of Threshold Voltage of O-FET by Modifying of Side Chain Groups on Polymer Gate Dielectrics

• Published in: Journal of Photopolymer Science and Technology Vol. 23; no. 3; pp. 327 - 332
• Main Authors: Nakako, Hideo, Kumashiro, Yasushi, Yamamoto, Kazunori
• Format: Journal Article
• Language: English
• Published: Hiratsuka The Society of Photopolymer Science and Technology(SPST) 01.01.2010; Japan Science and Technology Agency
• Subjects: Bisphenols; Curing; Electric potential; epoxy resin; Epoxy resins; Esterification; Esters; gate insulator; Gates; hysteresis; organic field effect transistor; Semiconductors; Threshold voltage
• ISSN: 0914-9244; 1349-6336; 1349-6336
• DOI: 10.2494/photopolymer.23.327

The printing process requires the gate insulating material to have the solution processability of solution before curing, and the chemical resistance, high resistivity, high breakdown voltage, and organic field effect transistor (O-FET) properties after curing. The epoxy resin using the esterified bisphenol F as hardener satisfied these conditions except high threshold voltage (Vth) of O-FET. In this paper, the Vth was found to be brought not from the inside of the gate insulator but from the interface between the gate insulator and the semiconductor. Eight types of epoxy resins consisting of bisphenol F esterified were prepared with different pendant groups on the ester groups. By the SFG spectrum, the pendant groups on the ester groups existed on the surface. The Vth and δVth (hysteresis of O-FET) correlated with the γp/γtotal, which is the index of the polarity effect on the surface free energy. This meant that the pendant groups on the ester groups existed on the surface and affected Vth and δVth. The epoxy resin with bisphenol F esterified with dimethyl pendant groups showed the O-FET properties with small Vth and δVth (-1.1 V and 0.2 V, respectively) keeping the superior characteristics of epoxy resin such as solubility, chemical resistance, high breakdown voltage (7.6 MV/cm), and high resistivity (2.7 x 1014 Ωcm).