精密光學鍍膜的監控技術

Thickness Monitoring for Precise Optical Interference Coatings

李正中(Cheng-Chung Lee)

《科儀新知》 185期 (2011/12) Pp. 4-11

https://doi.org/10.29662/IT.201112.0001

摘要

精密光學薄膜的製鍍需要精確的膜層厚度監控才能完成。本文陳述了五種膜厚監控方法：計時監控法、石英震盪監控法、傳統光學監控法、光學導納軌跡監控法，以及反射係數相位擷取監控法，並分析各種方法的優點與缺點。計時監控法與石英震盪監控法簡單便宜，但無法知道鍍上去薄膜的折射率，因此精密光學薄膜一般會以光學鍍膜的監控來完成。導納軌跡監控法具有視覺識別效果，容易做膜厚誤差補償，而且不需另加硬體， 在傳統的光學監控機台加上軟體即可完成，因此容易實現。反射係數相位擷取監控法是非常精確的監控方法，但必須要有一組干涉儀及陣列偏振相位 CCD 相機，因此機台的總價位比傳統光學鍍膜機要高一些，但比加裝橢圓偏振儀要簡單、精確， 所佔空間小，對振動不敏感且便宜。

並列摘要

High quality thin film optical filters need high precision film thickness monitoring during the deposition. There are several methods can do the thickness monitoring, named as time-counting monitoring, quartz-oscillation monitoring, traditional optical monitoring, optical admittance loci monitoring and phase-extraction monitoring. Each method has its advantage and disadvantage. Since no information about refractive index of the depositing thin film can be provided by time-counting monitoring or quartz-oscillation monitoring, optical monitoring is preferred if an optical filter needs film thickness controlled very precisely during the deposition, although time-counting monitoring and quartz-oscillation monitoring are cheaper and simpler. Optical admittance loci monitoring has an advantage of visual control so that it has a better error correction mechanism. Besides it can be applied on a traditional optical coating machine by the implantation of software without any additional hardware. Phase-extraction monitoring is the most precise monitoring method, it needs the installation of an interferometer and a camera with polarization array, however, it is vibration insensitive, compact and cheaper than using ellipsometer and having much better performance than an ellipsometric system.