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

Abstract

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.

Non-Residual Layer Transfer of High Viscous Ultraviolet Photocurable Resin Using Liquid Transfer Technique

“…A problem with UV-NIL is that an extra resin layer called the residual layer (RL) [3][4][5][6] is generated between the curable resin pattern and the substrate. This RL must be removed before the dry etching process, so a thin or nonexistent RL is desirable in the UV-NIL process.…”

Bubble-free high-speed UV nanoimprint lithography using condensable gas with very low global warming potential

“…We have demonstrated that the rapid bubble-free filling of mold pattern cavities with dimensions ranging from several tens of nanometers (45 nm half-pitch) to several hundreds of micrometers can be accomplished by using PFP as the environmental gas in UV-NIL and PAK-01 resin (Toyo Gosei). [17][18][19][20] A PFP atmosphere is not only a potential means of achieving quick and bubble-free cavity filling, but also has benefits such as decreasing the viscosity of the UV-curable resin, 18) decreasing the amount of resin that sticks to the mold during demolding, 19) and lowering demolding forces to approximately one-third of that performed in air. 20) However, the global warming potential (GWP) of PFP of 1030 may prevent its industrial use because of environmental concerns.…”

The Photopolymer Science and Technology Award

“…However, due to pattern density, the residual layer thickness is not always uniform. To solve this problem, the authors proposed the volute uniform mold of the pattern cavity and demonstrated its performance in UV nanoimprint lithography [9]. 3) Smooth demolding To prevent adhesion between the UV curable polymer and the mold, the mold surface is coated with an anti-sticking layer.…”