Mask and wafer inspection and cleaning for Proximity X-ray Lithography

Over the past five years that the IBM Advanced Lithography Facility (ALF) has been operational, we have learned much about the practical aspects of proximity X-ray lithography: synchrotron reliability; mask manufacturing; process development; and mask and wafer handling, inspection, and cleaning. Because proximity X-ray printing requires small mask-to-wafer gaps (on the order of <30 mu m), the primary concern is protecting the mask from large foreign material (FM). Particle heights greater than the gap represent a mask scratch or breakage risk that must be managed. ALF, the IBM Advanced Mask Facility (AMF), and the Proximity X-ray Lithography Association have developed techniques for inspection and cleaning of masks and wafers to address both large and small FM concerns. This paper will review the practical implementation of inspection and cleaning techniques as presently used in ALF and AMF.