A high dose and high accuracy variable shaped electron beam exposure system for quartermicron device fabrication

An electron beam exposure system, EX‐7, has been developed for advanced device technology development of quartermicron VLSI ICs such as a 64M bit dynamic RAM. The EX‐7 utilizes the variable shaped beam, continuously moving stage and vector scanning concept.1,2 For the quartermicron PMMA (polymethyl‐methacrylate) resist pattern formation, the system can write patterns with a 50 kV acceleration voltage and a 50 μC/cm2 dosage. Double electrostatic octopole deflectors have been developed to assure beam positioning accuracy. Deflection distortion can be reduced to 0.01 μm by an automatic calibration method. The beam edge resolution is 0.125 μm at 1 μm‐square beam size and 200 A/cm2 current density. A newly developed hierarchical pattern definition method has greatly improved data compaction capability and reduced the conversion time from CAD LSI data to EX‐7 data. The data conversion is accomplished by a large scale computer within 15 min for 108 flash/chip VLSI IC pattern data. The throughput of the EX‐7 is 5...