STUDY OF H- BEAMS FOR ION-PROJECTION LITHOGRAPHY

The desired properties of ion sources used in ion-projection lithograp hy are high brightness and low energy spread. Due to a very stringent demand in many other applications, the state of the art of negative hy drogen ion (H-) beams has advanced significantly in recent years. H- i on beams with the transverse ion temperature of about 0.3 eV have been obtained from surface plasma sources in pulsed mode operation [V. G. Dudnikov and G. E. Derevyankin, AIP Conf. Proc. 287, 239 (1994)]; a de sign for a cw source to achieve a comparable, or even lower energy spr ead and high brightness has been reported [S. K. Guharay, M. Reiser, a nd V. G. Dudnikov, Rev. Sci. Instrum. 65, 1745 (1994)]. The energy spr ead of H+ ion beams now in use is in the range of about 6-10 eV. This renders the H- ion beams an attractive alternative to the H+ ion beams for ion-projection lithography. No data of H- ion exposure of resists are available, and we have carried out experiments illuminating PMMA resists with various doses of H- ions and H+ ions at 24 keV. Within ex perimental accuracy the exposure characteristics (e.g., sensitivity an d contrast) are identical for both H- and H+ ions. (C) 1995 American V acuum Society.