Wide-field deep-UV wafer stepper for 0.35-μm production

Abstract

Device manufacturers and lithographic equipment makers are presently preparing for circuit production at design rules of 0.35 micrometers . It is evident that optical steppers will be the production tools, but the choice between i-line and deep UV (DUV) steppers (248 nm) is still a matter of debate. This paper reports the progress made in the development of DUV steppers for production purposes. As a successor to the earlier DUV machine, discussed at the SPIE conference in 1990, which uses a TTL alignment system and automatic excimer laser wavelength control, a new DUV stepper has recently been developed with a new lens at 248 nm wavelength, a 29.7 mm diameter field and a numerical aperture (NA) of 0.5. The stepper body is similar to that of the wide field, i-line systems which have been in production since 1991. The key design parameters and results are reported, including imaging performance down to 0.25 micrometers in both negative and positive resists and a high overlay accuracy based on the TTL alignment system. The capability of matching with i-line systems also is reported.