Reduction of pattern noise in scanning lithographic system illuminators

摘要

An illumination system for a scanning lithography system used in the manufacture of semiconductor devices having a multiplex array or multi-image array resulting in pattern noise that is reduced by a spatially frequency modulated multiplex array or frequency modulating the pulse rate of a pulsed laser source. A pulsed laser source is used to illuminate a reticle containing a pattern thereon to be reproduced onto a semiconductor. An illumination system using a multiplex array or multi-image array to obtain macro uniformity of an illumination slot or field introduces micro non-uniformity that results in undesirable pattern noise or fixed pattern noise resulting in undesirable imaging properties. The undesirable effects of the pattern noise are eliminated or substantially reduced by spatially modulating the multiplex array in a scanning direction so that the periodic pattern has a linear magnification dependent on position. In another embodiment the pulse rate of the pulsed laser source is frequency modulated. The present invention improves linewidth control, linewidth variation, and edge roughness. <IMAGE>