A projection lens distortion error map is created using standard overlay targets and a special numerical algorithm. A reticle including a 2-dimensional array of standard overlay targets is exposed several times onto a photoresist coated silicon wafer using a photolithographic stepper. After exposure,...http://www.google.de/patents/US20020071112?utm_source=gb-gplus-sharePatent US20020071112 - Method and apparatus for self-referenced projection lens distortion mapping
