Wafer scale nanoimprint lithography: distortion improvement and stabilization

NanoImprint Lithography (NIL) is not a novel technology anymore(1) but huge progress has been achieved for its industrial introduction since its first reporting. One of the main evolutions concerns the use soft stamp media(2),which is now a standard technology. EVG introduced this technology with a full wafer imprint solution (the size of the stamp corresponds to the size of the wafer to print)(3) and results obtained since five years are at the state of the art. Repeatability, uniformity, sub-50nm resolution and high aspect ratio patterns are addressed at the same time(4-6). Nevertheless, some challenges still remain, as e.g overlay(7) and in particular the distortion phenomenona(8), which contribute to the remaining overlay next to global translation and rotation. This study is focused on distortion effect which appears during NIL process using flexible backplanes and its minimization by using different materials. A polymer backplane is compared with a glass backplane which are used as carrier to the soft stamp material. A dedicated methodology to precisely measure this distortion is implemented to remove global alignment signature. Distortion signature is firstly evaluated with a standard soft stamp material and process of reference already established. Distortion fingerprint mapping is obtained for each wafer. Thanks to this mapping, a monitoring distortion plot is extracted, in order to follow the evolution of the distortion depending on wafers (wafer-to-wafer) and lots (lot-tolot). This study highlights that the use of a glass backplane developed by EVG clearly allows to improve the distortion in terms of magnitude but also of stability.