In the semiconductor industry, a device that can measure the surface profile of thin film like photoresist with high accuracy and high speed is needed. Since the surface of photoresist is very smooth and deformable, a device is required that will measure vertically with nanometer resolution and not damage the film during the measurement. We developed an apparatus using a multi-ball cantilever and white light interferometer to measure the surface profile of thin film. However, this system, as assessed with a scanning method, suffers from the presence of a moving stage and systematic sensor errors. Therefore, this paper describes an approach using a multi-ball cantilever as coupled distance sensors together with an autocollimator as an additional angle measuring device, which has the potential for self-calibration of a multi-ball cantilever. Using this method, we constructed an experimental apparatus and made measurements on resist film. The results demonstrated the feasibility of the constructed multi-ball cantilever system with the autocollimator for measuring thin film with high accuracy. © 2008 Elsevier Inc. All rights reserved.
Liu, S., Watanabe, K., Chen, X., Takahashi, S., & Takamasu, K. (2009). Profile measurement of a wide-area resist surface using a multi-ball cantilever system. Precision Engineering, 33(1), 50–55. https://doi.org/10.1016/j.precisioneng.2008.03.004