SR X-RAY-LITHOGRAPHY TECHNOLOGIES FOR 1 GBIT-SCALE DRAM FABRICATION PROCESS

A synchrotron radiation (SR) X-ray lithography system including a comp act storage ring, a beamline, a stepper, masks and resist process has systematically been developed. This racetrack-type SR ring is construc ted of two superconducting bending magnets and operated in a persisten t current mode with a very low helium consumption of 2 l/hr. A full en ergy injection of 600 MeV was performed, and an electron beam current of 380 mA has been stored with no beam instability. The beamline and t he X-ray proximity stepper were designed and installed for application to the less than 0.2 mu m-rule ULSI fabrication. The technologies of stress-free X-ray masks and the chemical amplification resist process were also developed. An applicability test for our SR lithography tech nologies in fabricating 1 Gbit-scale DRAM cell arrays has been carried out, and the total overlay error of less than 80 nm was obtained arou nd the memory-cell test chip.