Phase Shift Mask Monitor Scanner Focus

With the development of IC industry towards to high integrated density, both the critical dimension and resolution of photolithography are becoming smaller and smaller, and it results in the decrease of the depth of focus (DOF). So the scanner focus's monitor need to be more precise and stable.A novel scanner focus monitor method and system with phase shift mask were introduced and experimented. The experimental results show that overlay measurement with phase shift mask can much precisely and stably monitor the focus of scanner instead of the conventional CD measurement due to the reduction of disturbance factors. This method also can be used to monitor the chuck flatness, lens tilt, lens heating and lens distortion. Besides that the method is very useful for engineer to solve the wafer edge defocus and by shot yield loss issue.