線上彩色共焦精密顯微形貌掃描量測系統之發展

Development of an In-situ Chromatic Confocal Measuring System for Precision Microscopic Surface Profi lometry

在本文中，運用線型顯微彩色共焦量測原理，其利用寬帶光源結合自行研發的彩色色散物鏡，建立線掃描（line scan）寬帶波長共焦數學模型，以產生波長準確映射到量測深度之轉換關係。同時，本研究重點在於整合發展一套彩色共焦探頭與三軸精密掃描系統，對量測系統的21項體積誤差進行量測與校正，並進行最佳化之精密機構設計與調校，使掃描系統之體積誤差能維持在一個精準的等級。經由實際量測的驗證，經過精密校正機構之量測與校正，系統在驗證標準階高塊的重覆度，其在一個可量測範圍（field of view，275×275 µm2）內，其量測標準差可維持在次微米等級的量測水準。同時，所研製設備具有對工業微元件三維形貌進行實測之能力，由各類微結構三維形貌實例之量測結果分析中，可驗證其量測結果的精確度可以達到次微米等級。 This article presents the development of an in-situ chromatic confocal line-scan measuring system using wavelength-resolved chromatic confocal principle and the analysis and optimization of volumetric errors of the developed measuring platform to achieve one-shot and high-accuracy microscopic surface profilometry in an integrated three-axis scanning instrument. Optical confocal measurement for microscopic surface profilometry has become extremely important due to its high longitudinal measurability range and excellent vertical resolution. A chromatic confocal probe employing broadband light as well as a chromatic dispersion objective is integrated with a 3 axis scanning platform to establish in-situ 3-D profile measurement in one-shot manner. The developed confocal system is designed and analyzed to characterize the system volumetric errors, such as positioning errors, angular deviation, moving straightness and squareness between the three axes. It is implemented by measuring and analyzing of 21 volumetric errors in 3-axis system for system optical alignment and installation, thus the volumetric errors can be minimized by optimal machine alignment and integration. Our experimental tests on standard targets have verified that the developed system can perform the measurement precision with one standard deviation to be controlled within 0.1 m m. Some industrial parts, such as semiconductor wafers, have been also verified with its effectiveness in sub-micro scale measurement and reconstruction of 3-D microscopic surface profiles.