Residual layer thickness control and metrology in jet and flash imprint lithography

Jet-and-Flash Imprint Lithography (J-FIL) has demonstrated capability of high-resolution patterning at low costs. For accurate pattern transfer using J-FIL, it is necessary to have control of the residual layer thickness (RLT) of cured resist underneath features. Variation in RLT leads to critical dimension variation, thereby degrading device performance. Substrate nanotopography and feature density variation are two unavoidable sources of variation in RLT uniformity. The first part of this paper demonstrates the effect of these parameters on RLT variation. Through experiments and modeling, it has been observed that flatter wafers with lower nanotopography and thinner RLT lead to better RLT uniformity. However, for studying RLT variation, accurate metrology is critical. Currently, all metrology is done using destructive cross-section scanning electron microscopy (SEM), which may not be sufficient for process control. To this end, nondestructive optics-based methods, including the Through-focus Scanning Optical Microscopy (TSOM) method have been explored in this paper. Simulations reveal the potential to measure mean RLT, RLT variation, and uncertainty in feature dimension to an accuracy of 1 nm. Experimental validation and calibration are works in progress. Subsequent development of this technique can lead to a viable in-line metrology solution for RLT underneath features.