Thermally controlled alignment for wafer-scale lithography

A primary limitation in nanoimprint lithography is lack of alignment consistency between multiple fields. Simultaneous imprinting of several fields is highly desirable for enhanced throughput, yet placement errors in template fabrication and other factors limit field-to-field accuracy. Here, we describe a method to improve overlay simultaneously across many fields via continuous, in situ control of localized temperature distributions. In this method, interferometric moire alignment signals from an array of microscopes are analyzed to form a map of distortion and control the distribution of heat in real time. Thermal cross-talk between fields is minimized using a microchannel wafer chuck. We demonstrate simultaneous operation of feedback loops that stabilize alignment over a 100-mm span to 0.5 nm (3 sigma). (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE)