ADVANCED PROCESS TECHNOLOGY IN JAPAN .1. LITHOGRAPHIC TECHNOLOGY FOR FUTURE ULSIS

Lithographic technology for future ULSI is one of the largest concerns of the semiconductor industry. The minimum feature size for 64 Mbit DRAMs will be around 0.3 to 0.4-mu-m. This is almost the same as the wavelength of the exposure source used in conventional steppers. Excimer laser sources and phase shifting mask technology are now being intensively investigated for the purpose of delineating such fine patterns by means of optical lithography. Attempts will be made to extend optical lithography beyond the 64 Mbit DRAM generation by further reducing wavelength and/or introducing novel exposure and processing ideas. Other approaches, such as electron beam lithography and x-ray lithography, are also under development. Recent Japanese activities in the area of lithographic technologies for future ULSI fabrication are reviewed in this paper.