Photomask fabrication utilizing a Philips/Cambridge vector scan e-beam system

摘要

In this Era of shrinking design constraints, two (2) of the many concerns facing E-Beam mask makers are: (1) data snapping on design grids smaller than E-Beams can fabricate and (2) dense designs with submicron features forcing smaller beam steps which radically effect write time and throughput. The Philips/Cambridge Vector Scan E-Beam provides novel approaches to meet Western Digitals 0.05 $mu gird resolution, yet still maintain reasonable throughput. Using CATS Transcription, designs are fractured into two (2) or three (3) distinct patterns called a Bulk/Sleeve or Bulk/Double sleeve technique. The Bulk pattern comprised the majority of the pattern and is written at a large beam size. The Sleeve is a border pattern around all geometries written at a much smaller beam size. This combination allows throughput because of the large beam sized Bulk pattern yet gives high resolution, and edge acuity with the small beam sized sleeve pattern. By combining a Bulk and Sleeve pattern exposure matrix with a smaller bias reduction a sleeve of 1.2 $mu is currently utilized in production. Additionally sleeve size reduction reduces the complexity of the C Format trapezia and virtually eliminates data snapping. An interesting by-product of this Bulk/Sleeve technique allows multiple exposures for the different patterns to help alleviate proximity exposure effects in extremely dense designs.