Focus Probe Technique for Edge Detection and Linewidth Measurement of Microstructures with Nanometer Resolution

微結構邊緣偵測及線寬量測至奈米解析度的聚焦探頭技術

范光照(Kuang-Chao Fan) ； 林器躉(Chi-Duen Lin) ； 李瑞君(Ruijun Li) ； 陳亮嘉(Liang-Chia Chen) ； Yuri Chugui

《中國機械工程學刊》 38卷3期 (2017/06) Pp. 253-260

摘要

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 paper presents 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. 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. 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.

關鍵字

Focus probe ； Microstructure ； Edge detection ； Linewidth

並列摘要

傳統的顯微技術對於微奈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，本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。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階高時，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1 奈米的解析度。實驗得知微結構的邊緣偵測與線寬量測都可達到±35 nm (±2σ)以下的不確定度。本文所提出的技術在理論及裝置上都很簡單，可克服光學顯微技術法受到繞射極限的問題，也有可能達到線上量測的目的。