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 imperative 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 studies the effect of these parameters on RLT variation. Through experiments and modeling, it has been found that flatter wafers with lower nanotopography, and thinner RLT lead to better uniformity. However, for studying RLT variation, accurate metrology is critical. Currently, all metrology is done using destructive cross-section SEM, which is only useful for studying a few reference cases locally. To this end, nondestructive optics based methods, including the Through-focus Scanning Optical Microscopy (TSOM) method have also been explored in this paper. Simulations reveal potential to measure mean RLT, RLT variation and changes in feature dimension to an accuracy of 1nm. Experimental validation and calibration are in the process of being conducted. Subsequent development of this technique can lead to a viable in-line metrology solution for RLT underneath features.
Proceedings Title: Metrology Inspection and Process Control
Conference Dates: February 19-23, 2012
Conference Location: San Jose, CA
Conference Title: SPIE Advanced Lithography
Pub Type: Conferences
residual layer thickness, RLT metrology , Jet-and-Flash Imprint Lithography, TSOM, nanometrology