Tunable dielectric properties of a parylene dielectric layer through surface-modulation by click chemistry

A dielectric serves as a separator between the semiconductor and the electrode in thin-film transistors (TFTs), playing a crucial role in attracting carriers through polarization by an electric field. In this study, copper-catalyzed azide/alkyne click reactions were adopted to modulate the dielectric and electrical properties of a polymer gate dielectric poly[(ethynyl-p-xylylene)-co-(p-xylylene)] (ethynyl parylene). A custom-synthesized ethynyl parylene dielectric layer is fabricated using chemical vapor polymerization, which yields smooth conformal films. Four types of azide materials - benzyl azide, aminopropyl azide, trimethylsilyl azide, and biotin-PEG3-azide - are utilized as dielectric constant modulators via click reactions. With only approximately 1% surface modulation, the dielectric constant of ethynyl parylene is nearly double that of pristine ethynyl parylene, whereas the leakage current density remains unchanged. Finally, IGZO TFTs are successfully fabricated using surface-modulated ethynyl parylene as the gate dielectric. Therefore, the click reaction of a polymer gate dielectric is an effective method to tune its properties while maintaining the interface properties of the front channel.