EVALUATION OF CRITICAL DESIGN PARAMETERS OF AN ION PROJECTOR FOR 1-GBIT DRAM PRODUCTION

The Advanced Lithography Group (ALG) a consortium of industry and university institutes in the US and Europe has the aim to produce an Ion projection lithography tool ALG-1000 for 0.18 mum geometry and below. The base of the machine is a new ion optical column developed by IMS, Vienna for exposing 20 mm x 20 mm fields at 3x reduction. The errors of the first two lenses (diverging lens and field lens) are fully compensated in 3rd order by an asymmetric Einzellens projecting an ion image of the stencil mask onto the wafer substrate with better than 2 mrad telecentricity. Remaining are errors of 5th order resulting in minimum calculated distortions of less than 30 nm. Space charge effects have been investigated with high transparency masks in two different ion projects. An indication for a space charge effect was observed in the case of the Alpha 5x system with a crossover energy of 7.5 keV if the beam current was raised above 10 nA. The experiments with the IPLM-02 system with a crossover at approximately 50 keV, more representative for the conditions in the ALG-1000 with a crossover energy of 200 keV, allowed the resolution of 0.18 mum lines and spaces even at high currents of up to 2 muA.