基於像散式光學之膜厚量測方法之開發

Abstract

光學輪廓儀為一種非接觸式量測儀器，可以用來量測樣品的表面輪廓、反射率以及粗糙度等資訊，目前已經被廣泛應用於電子電機、半導體製程、生醫工程以及微機電元件等各種領域。相較於接觸式表面輪廓儀，光學輪廓儀有著量測速度快、不會傷害到樣品表面、不需要探針耗材等優點。然而目前許多致力於光學輪廓儀之研究，主要用於量測待測樣品之表面資訊，沒有辦法得到樣品之內部資訊。為了得到薄膜樣品之上下表面資訊，本論文利用商用DVD讀取頭以及自製之共振掃描器設計一像散式光學輪廓儀，透過此像散式光學輪廓儀對半透明薄膜樣品進行掃描量測，除了有著相較於過去像散式光學輪廓儀更快的Z軸掃描速度，同時也可以透過像散式原理得到薄膜上下表面之聚焦誤差訊號(Focus error signal)，進而透過分析計算求得薄膜厚度。論文最後透過商用雷射共焦顯微鏡校正，本論文建構之像散式光學輪廓儀系統可以有效量測約10 μm至40 μm之薄膜厚度。

Optical profilometer is a non-contact measuring instrument for measuring the sample surface profile, reflectivity and roughness information, which has been widely used in electronics, semiconductor manufacturing processes, biomedical engineering, and MEMS. Comparing with the contact profilometer, the optical profilometer has the advantages of fast scanning, sample protection, and no need for stylus. Currently, most studies on optical profilometer mainly focus on the surface information of the samples, and the sub-surface information of the sample is not available. To overcome this limitation, an astigmatic optical profilometer equipped a commercial DVD pick up head and a homemade resonant scanner was developed. Comparing with the previous astigmatic optical profilometer, the proposed system can achieve a faster Z-axis scanning speed and obtain the focus error signal on upper and lower surfaces of the semi-transparent thin film through astigmatic principle. Moreover, an analysis method was proposed to calculate the thin film thickness. The experimental result was verified by a commercial laser confocal microscope. The astigmatic optical profilometer constructed in this thesis can effectively measure the thin film with a thickness from 10 μm to 40 μm.