Microlens direct-write concept for lithography

Abstract

There are significant theoretical advantages to using arrays of high resolution microlenses for photolithography. Aberrations can be smaller, fabrication easier, and high numerical apertures more easily attainable than with conventional stepper lenses. Using an array of microlenses, a large exposure field can be printed with uniform quality. Field flatness problems can be greatly reduced because the flatness of the array is not limited by any fundamental principles, and also the array's shape could even follow the contour of the wafer. By exploiting massive parallelism, high throughput can be achieved. Thus it is possible in principle to eliminate photomasks for short turn-around production runs. Light can be modulated by several schemes in a parallel fashion as we show. Options exist to extend the basic technology into the near x-ray region by using micro mirror objectives of the Schwarzchild type. In order to match the throughput of a wafer stepper, we envision approximately 4000 independent channels operating at about 20 megapixels a second each for a total throughput of 80 billion pixels per second. The illumination source should be a cw laser which would minimize damage to optical elements. A suitable laser might be a 266 nm neodymium YAG laser achieved by frequency quadrupling.