Effects of O2 Plasma Treatments on the Photolithographic Patterning of PEDOT:PSS

Abstract

Poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is known for its potential to replace indium–tin oxide in various devices. Herein, when fabricating finger-type PEDOT:PSS electrodes using conventional photolithography, the cross-sectional profiles of the patterns are U-shaped instead of rectangular. The films initially suffer from non-uniformity and fragility as well as defects owing to undesirable patterns. Adding a small amount of hydrolyzed silane crosslinker to PEDOT:PSS suspensions increases the mechanical durability of PEDOT:PSS patterns while lifting off the photoresist. To further improve their microfabrication, we observe the effects of two additional oxygen (O2) plasma treatments on conventional photolithography processes for patterning PEDOT:PSS, expecting to observe how O2 plasma increases the uniformity of the patterns and changes the thickness and U-shaped cross-sectional profiles of the patterns. Appropriately exposing the patterned photoresist to O2 plasma before spin-coating PEDOT:PSS improves the wettability of its surface, including its sidewalls, and a similar treatment before lifting off the photoresist helps partially remove the spin-coated PEDOT:PSS that impedes the lift-off process. These two additional processes enable fabricating more uniform, defect-free PEDOT:PSS patterns. Both increasing the wettability of the photoresist patters before spin-coating PEDOT:PSS and reducing its conformal coverage are key to improving the photolithographic microfabrication of PEDOT:PSS.

Water-Soluble Biomass Resist Materials Based on Polyglucuronic Acid for Eco-Friendly Photolithography

“…The watersoluble biomass resist material, when spin coated on PMMA wafers for 65 s, demonstrated a film thickness uniformity comparable to that of the prior natural polysaccharide(pullulan)based resist materials, promising prospects for biomaterial applications. Wettability is also expected to be improved by removing traces of contamination on the PMMA wafer using plasma treatment or other methods [36]. We plan to improve the uniformity of film thickness.…”