A novel methodology of critical dimension statistical process control

SPC (statistical process control) is a necessary tool for IC fabrication processing, especially when device dimensions are shrinking to 0.3 μm and beyond. Most fabs have real time SPC systems to help process engineers to control process quality. In addition to real time SPC systems, some other process control methodologies and indices may be necessary for enhancement of process control monitoring. We have applied a statistical program to analyze CD (critical dimension) variation and drift that mainly comes from machine and process induced variation. In order to respond in timely fashion to CD drift or shift caused by a machine, we generate a daily report using the concepts of “hypotheses testing” and “maximum shift” for the process engineer. In order to minimize process induced variation, we found that lens heating compensation, dynamic focusing and top antireflective coating (TARC) application are effective