Improvements in model-based assist feature placement algorithms

Demanding process window constraints have increased the need for effective assist feature placement algorithms that are robust and flexible. These algorithms must also allow for quick ramp up when changing nodes or illumination conditions. Placement based on the optical components of real process models has the potential to satisfy all of these requirements. We present enhancements to model-based assist feature algorithms. These enhancements include exploration of image-processing techniques that can be exploited for contact-via AF placement, model-based mask rule check (MRC) conflict resolution, the application of models to line-space patterns, and a novel placement technique for contact-via layers using a specially-built single modeling kernel.