利用廣波域光譜實現光學薄膜之即時導納軌跡監控

在科技蓬勃發展的現在，光學薄膜品質的要求與日俱增，尤其對某些特殊用途之光學元件，不僅要求滿足高精度之光學性質，並且製程花費昂貴，為使成品符合預期設計，更精確且強大之監控方法是許多人研究的課題。其中，光學監控同時包含了薄膜厚度和折射率的資訊，觀測的是薄膜成長中即時的光學表現，因此被視為鍍製光學薄膜中最佳的監控方式。傳統光學監控，均假設材料折射率為定值做設計，並觀測穿透率或反射率隨薄膜成長之變化，以此作為停鍍點及誤差補償之依據，但事實上在整個鍍膜過程中，材料之折射率並非定值，若依循設計膜厚做停鍍點，將會使實際成品與設計不符。此外，目前雖有橢偏術和廣波域光譜監控可提供較完整之監控資訊，但因所需考慮的波長數目多，判斷停鍍點不易明確。本研究提出一種新式光學監控系統，基於舊有光學監控之基礎，結合廣波域與單波長監控之優點，且同時彌補各自不足之處，使停鍍點判斷更為精確，可獲得更廣波域的監控資訊，並將實際製程中時變之折射率、膜厚也納入監控考量，擺脫舊有系統，只能將折射率做為定值假設之困境。本系統不僅架設簡易且便宜穩定，極具發展潛力，可預期在不久將來，即可成為實際應用於市場上之主流新式光學監控系統。

關鍵字

導納軌跡；光學監控；薄膜

並列摘要

Monitoring is a key factor that influences the performance of output optical coatings. Among conventional methods, monitoring by time counting needs not only stable deposition rate but also constant refractive index of materials.. In those conventional methods, the most popular one is the variable monochromatic wavelength monitor. Not only does it have more flexibility than single wavelength monitor but also clearer rule of termination point selection than that in broadband wavelength monitor. In broadband monitor, there are many wavelengths need to be considered and it is hard to make sure when is the correct termination time, since the transmittance spectrum would not change the same as expected one during deposition resulting from the refraction index change or thickness error of the previously deposited films. Although the broadband wavelength monitor or ellipsometry monitor can provide more real time inspections of the optical performance of deposited films, they have no clearer mechanism on judging the most important thing in monitor that is determining the termination point with correct error compensation. By analyzing optical admittance loci in one central wavelength, the whole design spectrum shape and position can be kept in the spectrum of output filters. In this article, we propose a novel method to gather the broadband spectrum information and convert the information to single wavelength optical admittance loci. It combines the advantages of broadband and single wavelength monitor to let operator terminate the deposition in one absolute point with good error compensations.

並列關鍵字

admittance loci ； optical monitoring ； thin film

參考文獻

[1] H. K. Pulker, Coatings on Glass, Elsevier, Amsterdam, Chap. 7, pp. 297-299 (1984).

[2] A. Wajid, “On the accuracy of the quartz-crystal microbalance (QCM) in thin-film depositions”, Sensors and Actuators A, 63, pp. 41-46 (1997)

[3] H. A. Macleod, “Turning value monitoring of narrow-band all-dielectirc thin-film optical filters”, Optica Acta, 19, pp. 1-28. (1972)

[4] H. A. Macleod, “Error compensation mechanisms in some thin-film monitor systems”, Opt. Acta, 17, pp. 907-930. (1977)

[5] S. Larouche, A. Amassian, B. Baloukas, and L. Martinu, “Turning-point monitoring is not simply optical thickness compensation”, Optical Interference Coatings Ninth Topical Meeting, TuE8.( 2004)

國際替代計量

利用廣波域光譜實現光學薄膜之即時導納軌跡監控

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