0.25-μm lithography development using positive mode top surface imaging photoresist

Abstract

As design rules for ULSI chip sets continue to require sub-O.3j.un resolution for high density patterns the drive toward shorter wavelength (248nm), and higher numerical aperture (<O.5NA) steppers will continue. Process development on these advanced lithography systems is made difficult for a variety of reasons. The first of these is cost, the most modem steppers available today can cost <$5 million per system making it necessary to keep manufacturing cost in check by extending life times to more than one generation chip set. Secondly, working at 248nm and high numerical aperture tends to reduce process latitudes making manufacturing processes inherently more difficult to control. Last but not least, photoresist and antireflective coatings needed for even the simplest processes historically have had major environmental sensitivity problems or material compatibility problems associated with them. These issues have been addressed by such developments as phase shift masks, off axis illumination techniques, and major advances in resist technology. So far these types of cures have proven to be both costly and extremely complicated to implement in a manufacturing environment.