Fabrication of 64 M DRAM with i-line phase-shift lithography

New phase-shift lithography applicable to all device patterns has been developed which combines pattern formation with the shifter alone and edge contrast enhancement with the shifter. Using it one can make 0.3 mu m patterns with i-line photolithography. A 64 M DRAM having memory cells unrestricted by angular considerations was designed for use with this lithography, and experimental 64 M DRAM chips were fabricated. The technique eliminates the need for special pattern design such as assistant patterns. Since it requires only the original design pattern, it is easy to apply to fabrication.<>