VIABILITY OF CONVENTIONAL KRF IMAGING FOR 150 NM LITHOGRAPHY

Viability of conventional KrF imaging featuring a numerical aperture o f 0.6 for 150 nm lithography is investigated by applying a novel proce ss to reduce resist thickness down to around 100 nm. Both simulation d ata of aerial image contrast and resist development are applied to und erstand a degradation model of clear process window predicted by the a erial image contrast calculations. Comparing simulation results of the process windows' dependencies on the resist thickness, which are deri ved from combinations of aerial image contrast and resist development calculations, experimental results respecting the process windows' dep endencies on the resist thickness are then discussed to elucidate how the aerial image contrast could be degraded. It is found that the mini mum requirements of the process windows of 150 nm equal lines and spac es for the early stage of 1 Gbit dynamic random access memory developm ent could narrowly be guaranteed in the case of the thickness range of less than 300 nm, and also that a great advance in the process window would be obtained when using an unconventional imaging system with 2/ 3 annular aperture. Further improvement of the degraded resist profile s is demonstrated in order to obtain a more stable pattern fabrication process. (C) 1997 American Vacuum Society.