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Nanoimprint lithography (NIL) is becoming a promising technique for fine-patterning with a lower cost than other lithography techniques. High overlay accuracy is one of the issues in NIL. Using die-by-die alignment with moiré fringe detection, an NIL alignment measurement accuracy below 1 nm and an overlay accuracy below 5 nm have been reported. On the other hand, the requirement for overlay in 2020 is estimated to be 3-4 nm for dynamic random access memory, flash and logic devices. In order to make the overlay accuracy requirement qualify from the semiconductor industry, a lot of technology enhancements, such as the improvement of overlay control accuracy for NIL-tools, image placement accuracy improvement for NIL templates, mix and match technique of NIL, and other lithography tools such as immersion exposure ones, are needed. In this paper, the authors describe the evaluation of the NIL overlay performance using up-to-date NIL tools, and discuss the potentials of NIL overlay in the future. Alignment accuracy, precision, and overlay correction performance of NIL tools, NIL-to-NIL and NIL-to-optical lithography tool distortion matching performance and overlay error structure analysis, are discussed. From these analyses based on NIL overlay data, the authors discuss the possibility of NIL overlay evolution to realize the adaptation to mass production for the 1X-nm device. [ABSTRACT FROM AUTHOR]

Nanoimprint lithography under helium exposure plays an important role in realizing rapid resist spreading. It is expected that the reduction in the surface tension of the resist due to the diffusion of helium would have an impact on the spreading behavior of the resist. By assuming van der Waals potential, the surface tension of the resist under helium exposure is estimated to be reduced by 70%. In our experiment, we obtain an 83% reduction in the surface tension of a resist under helium exposure by evaluating the meniscus shape at the corner of a rectangular imprinted area after UV curing. Furthermore, the C/O composition ratio of the resist after UV curing is found to change due to the exposure. Our study confirms that helium strongly affects the surface tension of the resist. The result also suggests the possibility of the supercritical fluidic behavior of helium in the resist. The resist spreading velocity can be increased by 2.5 times by helium exposure. [ABSTRACT FROM AUTHOR]