聚焦探頭應用於微階高的邊緣偵測與線寬量測之研究

Abstract

本論文提出一種利用藍光DVD讀取頭做為聚焦探頭並配合一奈米定位平台的新方法，可從全反射光強變化的理論偵測到邊緣位置。此法有別於傳統的顯微技術對於微米尺度的微結構因受到表面特性及繞射極限的影響很難偵測到其邊緣。探頭之聚焦方式為像散法，利用聚焦曲線之線性區域作量測。當此探頭聚焦到微結構的基層面上時，全反射光強為最大，而當聚焦探頭掃描經過微結構的邊緣時，全反射光強將逐漸減弱。理論分析得知當聚焦光的中心線到達邊緣時的全反射光強為最小，此位置可由奈米定位平台量測到一奈米的解析度。並且可從聚焦曲線之線性區域特性量測階高值。實驗得知微結構的邊緣偵測及線寬量測都可達到±35 nm (±2σ)以下的不確定度。 本文所提出之聚焦探頭量測技術在理論及裝置上都很簡單，可克服傳統光學顯微技術法受到繞射極限的問題，未來也有可能應用在線上量測之目的。

The edge detection of micro/nano-scaled microstructures is difficult to achieve by conventional microscopes due to the sensitivity to the property of measured surface and the effect of diffraction limit. This thesispresents a new technique by using a blue-ray DVD pick-up head as the focus sensor in association with a nanopositioning stage. The measurement method of edge detection is based on the principle of total reflection energy. This new method, the total reflection energy will be maximal when the substrate surface is on the focus point of the probe. It will be gradually reduced when the focused beam scans across the edge. From the theoretical analysis, the edge position is found right on the centerline of the focused beam and this position can be directly detected by the nanopositioning stage to the resolution of 1 nm. Using linear curve characteristic, the value of step-height can be calculated. Experimental results show that the uncertainty of measured edge position, and linewidth are all within ±35 nm (±2σ). The proposed technique is simple in principle and easy to setup. This technique can overcome the conventional diffraction limit of optical microscope and is possible for in-situ measurement.