Aberrations in the exposure tool have been shown to produce line-edge and line-end perturbations on phase-shifting masks that can result in design defects. A pattern matching system has been developed to locate areas in a phase shift mask most sensitive to these lens aberrations. The original prototype of the pattern matcher was developed in the SKILL programming language of Cadence's Design Framework II. Speed and memory limitations prompted the creation of a new C++ binary, which incorporated the core data structures and matching algorithms. Specialized algorithms for partitioning, prefiltering, and compression resulted in a fast and memory efficient matching process. The local layout geometry is automatically output to SPLAT for detailed image analysis with and without aberrations. The pattern matching C++ software supports multi-level compression, layer Booleans, pattern proximity calculations, and many other features. The pattern matching idea has recently been expanded to search for sensitivity to defects, misalignment, reflective notching, laser-assisted thermal processing, and chemical-mechanical polishing. The current software system includes a combined graphical and a text-based interface and can be run on any operating system, independent of Cadence. The web-based version of the pattern matcher allows a user to either input custom layouts and match patterns or select from a list and then perform matching runs from a web browser.
Figure 1: Screenshot of pattern matcher web applet
Figure 2: Large coma and trifoil aberration patterns matched on a small phase-shift mask layout
Figure 3: Coma aberration pattern matched on a complex phase-shift mask