Excimer Laser Stepper For Submicron Lithography

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Abstract
To investigate the way to half micron photolithography, experiments have been performed with a high numerical aperture lens, with multilayer and contrast enhancement layer resist processes, and with an excimer laser deep UV exposure system. The 0.6 N.A. lens is for the g-line and has a 5 mm by 5 mm field size. Single layer resist exposures show good profiles at 0.6 μm line/space with no effect of highly oblique illumination, and a depth of focus of 1.25 μm. Multilayer resists using spin-on-glass and contrast enhancement layers improve the resolution to 0.375 μm with the large N.A. lens. This lens, which proves the practicality of achieving better resolution through larger N.A. and improved resist, has been made available as a first generation small field half micron stepper. As a more advanced experiment, a KrF excimer laser stepper with an achromatic quartz/fluorite lens of N.A. = 0.37 shows no effect of speckle and has produced 0.35 μm L/S in PMMA which proves the usefulness of achieving higher resolution through shorter wavelength. The resolution with MP2400 photoresist is only 0.4 μm because of the high deep UV absorption, and points out the need for more work on practical deep UV resists. In addition, much more work remains on alignment, lasers, and illuminators to make possible a production excimer stepper.© (1987) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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