PRINTABILITY OF X-RAY MASK DEFECTS AT VARIOUS PRINTING CONDITIONS AND CRITICAL DIMENSIONS

Because of the large cost associated with inspection and repair of sub-half-micrometer 1:1 x-ray masks, it is worthwhile to determine precisely the defect requirements. The printed resist image of x-ray mask defects is simulated with the simulator XMAS (x-ray lithography modelling and simulation) for different mask defect sizes. The printed defect size increases with increasing mask defect size. If it reaches 1/10 of the smallest printed linewidth, the corresponding mask defect size is regarded as critical. Mask defects equal to or larger than the critical size must be repaired. The critical sizes of different types of x-ray mask defects are evaluated giving the desired defect requirements. The simulations are confirmed by a comparison between a physical and a simulated print of a designed mask defect. The investigation is confined to the use of a synchrotron as the x-ray source.