ELECTRON-BEAM BLOCK EXPOSURE SYSTEM FOR A 256-M DYNAMIC RANDOM-ACCESSMEMORY

A block exposure system is developed to expose a 256 M DRAM pattern. F our mask deflectors deflect beams to select one of 48 blocks of stenci l patterns in a 5 mm region in diameter on a mask. Each mask pattern i s extracted as a unit of repetitions from the dynamic random access me mory (DRAM) pattern, which is demagnified to 1/100 on a wafer. In a 25 6 M DRAM contact hole layer, only two blocks are used to expose memory cell regions. Forty-six blocks are for sense amplifier and decoder re gions. The total hot number of the layer is decreased to 21.5 X 10(6) with the block exposure system, which is about 1/8 of that with a conv entional shaped beam system. One chip is exposed in 11.5 s. Throughput is 10 wafers (6 in.)/h for the contact hole layer.