Non-Lithographic Patterning

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Modern electronic devices commonly require thin conductive patterns that are to be used for electrodes, metallization or interconnect lines. These patterns are typically fabricated by the photolithographic technique combined with vapor deposition. Although lithography can provide high-resolution patterns, it also requires high-cost facilities and a number of process steps including photoresist deposition, developing, and etching. The increasing demand for low-cost, low-temperature, and large-area fabrication has led to a fervent search for alternatives. Our laboratory has developed laser-direct thin film patterning and printing techniques. This approach involves the light-matter interaction where a laser pulse impinging on the film-substrate interface generates a thermo-elastic force into the film and that a moderate cohesion of the nanostructured film enables the localized desorption of material upon irradiation by a spatially-modulated laser beam, giving a good fidelity of pattern transfer. Sharp-edged patterns with feature sizes scaled down to 2 micrometer could be fabricated over several square centimeters by a single pulse with a pulse energy as low as 850 mJ. This method uses the same type of optical modulation as in conventional lithography, but does not require any photoresist or vacuum processes. Not only being compatible with low-temperature and large-area fabrication, it also significantly reduces the total process steps required for conventional lithographic patterning. We are currently doing research to realize sub-micrometer scale patterning.