TRAJECTORY DISPLACEMENT EFFECT IN PARTICLE PROJECTION LITHOGRAPHY SYSTEMS - MODIFICATIONS TO THE EXTENDED 2-PARTICLE THEORY AND MONTE-CARLOSIMULATION TECHNIQUE

The extended two-particle model for statistical interactions in partic le beams, developed by Jansen [Coulomb Interactions in Particle Beams (Academic, Boston, 1990)], has been refined to improve the accuracy of the predictions of the trajectory displacement effect in particle bea m projection systems. The original theory was developed for probe form ing systems, such as electron and ion scanning microscopes and Gaussia n or shaped beam lithography systems. Fit functions are used within th e theory to express part of the numerical output into explicit analyti cal prescriptions. These functions were found to become inaccurate for the relatively wide beams typically used in the more recently develop ed projection type lithography systems. New fit functions are presente d which extend the applicability of the theory to the wide beams and d oublet configurations used in projection systems. The Monte Carlo prog ram MONTEC, used to verify the results of the analytical theory, has b een modified as well to account for the first order space charge magni fication effect. This effect could be ignored for the relatively small spots of Gaussian and shaped beam systems, but would yield a signific ant overestimation of the trajectory displacement effect-assumed to be identical to the remaining blur after refocusing-for the wide images used in projection type of systems. The refined analytical theory and the modified MONTEC program have been used to evaluate the impact of s tatistical interactions on the performance of the SCALPEL electron pro jection system and a hypothetical ion projection lithography system, r epresenting a simplified model of the IMS ALG-1000 (He+) system. The a nalytical predictions are in good agreement with the Monte Carlo resul ts. An estimate of the total system resolution, determined by the comb ined effect of statistical interactions and geometrical aberrations, i ndicates that maximum attainable beam current for a 0.18 mu m design r ule is about 25 mu A for the SCALPEL and 0.2-0.3 mu A for the ion proj ection system, leading to an similar to 10X higher throughput for the former taking the difference in resist sensitivities for electrons and ions into account. (C) 1998 American Institute of Physics. [S0021-897 9(98)06620-1]