Dual-layer thermal nanoimprint lithography without dry etching

We report a novel dual-layer thermal nanoimprint with non-compatible polymer layers—poly(methyl methacrylate) (PMMA) on poly(3-hexylthiophene) (P3HT). Depending on mold depth, pattern size and polymer layer thickness, the dual-layer thermal nanoimprint can yield two different patterning results—single-layer patterning and double-layer patterning. The single-layer patterning is successfully performed with a delicate PMMA volume control and a very thin P3HT layer. Double-layer patterning is achieved when a thick and smooth P3HT layer is formed under a thin PMMA layer. Based on the mixing temperature as well as the glass transition temperatures of both polymers, the optimal nanoimprint temperature range is determined for dual-layer thermal nanoimprint. Because the pattern definition is completed without a dry etching step, this patterning technique can be applied to organic functional materials whose electrical properties can be critically degraded when exposed to oxygen dry etching in conventional thermal nanoimprint. The dual-layer thermal nanoimprint is expected to find important applications in the fabrication of high-performance organic electronic devices. (paper)