First results from the Large Dynamic Range Atomic Force Microscope for overlay metrology

TNO is developing a novel Large Dynamic Range Atomic Force Microscope (LDR-AFM), primarily but not exclusively designed for sub-nm accurate overlay metrology. The LDR-AFM combines an AFM with a 6 degrees- of-freedom interferometric positioning stage, thereby enabling measurements of sub-nm features on a wafer over multiple millimeters marker-to-feature distances. The current work provides an overview of recent developments and presents the first results obtained after final integration of the complete system. This includes results on the AFM head development, the validated positioning stage performance, the first AFM images, and long-term stability measurements.