CONTINUOUS WRITING METHOD FOR HIGH-SPEED ELECTRON-BEAM DIRECT WRITINGSYSTEM HL-800D

Hitachi has developed a new e-beam direct writing system named HL-800D [Y. Sakitani, H. Yoda, Y. Shibata, T. Yamazaki, and K. Ohbitu, J. Vac . Sci. Technol. B 10, 2759 (1992)]. This system has been developed for mass production of ultra-large scale integrated circuits such as a 25 6M-DRAM manufactured with high accuracy and high throughput. To achiev e a productive level of throughput, this system employs a continuous w riting method with variable stage speed. In the method, an e-beam trac es a moving wafer stage accurately using deflections during continuous writing, and the wafer stage moves with the most suitable speed depen ding on the writing pattern density. The continuous writing method mak es considerable improvement in throughput compared with a conventional ''step and repeat'' stage moving method. Stitching accuracy is confir med by test writing.