Experimental Test Results Of Pattern Placement Metrology On Photomasks With Laser Illumination Source Designed To Address Double Patterning Lithography Challenges

摘要

Double Patterning Lithography techniques place significantly greater demand on the requirements for pattern placement accuracy on photomasks. The influence of the pellicle on plate bending is also a factor especially when the pellicle distortions are not repeatable from substrate to substrate. The combination of increased demand for greater accuracy and the influence of pellicle distortions are key factors in the need for high resolution through-pellicle in-die measurements on actual device features. The above requirements triggered development of a new generation registration metrology tool based on in-depth experience with the LMS IPRO4. This paper reports on the initial experimental results of DUV laser illumination on features of various sizes using unique measurement algorithms developed specifically for pattern placement measurements.