Proximity effect correction for an electron beam direct writing system EX-7

A new proximity effect correction software system has been developed, which is characterized by the usage of an approximate correction dose formula. The arrayed shot method was developed and a hierarchical data format was used to compact the amount of EB data. An inversion method has also been developed and a hierarchical pattern layout structure was used to accelerate the correction calculation speed. The proximity effect correction system has been installed into a high voltage electron beam direct writing system EX-7 and has been applied to some LSI patterns. The calculation time for correction was about 0.7 h for a 4 MDRAM and about 1 h for a 20 k gate array by using a 14 MIPS computer. The amount of EB data was about 40 Mbytes for the DRAM and about 50 Mbytes for the gate array.