EL-4 COLUMN AND CONTROL

This article describes the electron optical column and some of its electronic controls for the new generation of electron-beam lithography system at IBM, designated EL-4. This new column utilizes variable shaped-beam technology and incorporates dual shaping optics for both triangular and rectangular shapes and triple deflection. The EL-4 system was designed for high-throughput 1/4 mum lithography with an edge resolution of 50 nm (extendable to 1/10 mum groundrules) over a 10 mm x 10 mm field. The beam deflection optics uses a dual variable axis immersion lens system to achieve two stages of magnetic deflection and one stage of electric deflection. By design, all three stages of deflection are telecentric to eliminate overlay errors resulting from target plane height variations. A pixel throughput increase from our existing state-of-the-art system, the EL-3, of over an order of magnitude was required for this new system to write the next generation circuit patterns within reasonable times. A unique mechanical design approach for the column, utilizing a double-walled construction, combines the required mechanical rigidity and vacuum environment with exceptional electromagnetic interference shielding.