Comparison of substrate curvature and resonant frequency thin film stress mapping techniques

A crosscutting issue for Next Generation Lithographies is the ability to monitor and control the uniformity of thin film stresses. Because the global stress fields of thin film layers can introduce distortions in lithographic masks, it is essential that the characteristics of these stress fields be understood and controlled, in order to achieve the high resolution and positioning accuracy required. This paper provides a comparison between resonant frequency and substrate curvature stress mapping techniques. Experiments have been performed using the UW-CMC Rack RFT device and the commercially available Tencor FLX 5510. Measurements across two IBM diagnostic masks identify the magnitude and uniformity of as-deposited SiON film stress. An analysis of the accuracy and limitations of the experimental methods is discussed.