Uniform Residual Layer Creation in Ultraviolet Nanoimprint Using Spin Coat Films for Sub-100-nm Patterns with Various Pattern Densities

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In the case of spin coat films, the variation in residual layer thickness (RLT) caused by the variation in pattern density is a problem encountered in UV nanoimprint lithography (NIL). To solve this problem, we proposed the use of capacity-equalized molds in which pattern depths are modified to equalize pattern capacity per unit area at any location. Although the effectiveness of these molds was validated using molds with various pattern sizes of the order of hundreds of micrometers, the dimensions in those cases were large and the aspect ratios were far too small in comparison with the values that would be required in the device patterns to be fabricated by nanoimprinting. In this study, we evaluate the applicability of using a capacity-equalized mold with nanometer-scale patterns. A capacity-equalized mold with two-step-depth structures and sub-100-nm wide patterns was successfully fabricated as designed while maintaining the groove width. By using a capacity-equalized mold, the standard deviation of RLT of UV-nanoimprinted patterns can be reduced to less than one-third of that obtained using a conventional mold. The UV-nanoimprinted patterns using a capacity-equalized mold were uniformly transferred onto a Si substrate.
2013-06-25