HIGH-SPEED ELECTRON-BEAM CELL PROJECTION EXPOSURE SYSTEM

An electron beam cell projection system has been developed that can ef fectively expose the fine, demagnified resultant pattern of repeated a nd non-repeated patterns such as the 256 Mb DRAM on a semiconductor wa fer. Particular attention was given to the beam shaping and deflecting optics, which has two stage deflectors for the cell projection beam s election as well as the beam sizing, and three stage deflectors for ob jective deflection. The cell mask with a rectangular aperture and mult iple figure apertures is fabricated by modified Si wafer processes. A new exposure control data for the cell projection is proposed. This da ta is fitted for the combination of pattern data for the cell mask pro jection and pattern data for the variable rectangular shape beam withi n the divided units of the objective deflection. On this exposure syst em, selective exposure of the desired pattern becomes possible on the semiconductor wafer while a mounting stage of the wafer is being moved , even if the pattern exposure of the repeated and non-repeated patter ns is to be carried out. The total overhead time for selecting a subse t of multiple figures and a rectangular aperture of the cell mask is l ess than 5 seconds/wafer. The estimated throughput of this system is a pproximately 20 wafers/hour.