像散式光學輪廓儀之量化高度量測方法之設計與開發

Abstract

光學表面輪廓儀為一表面量測儀器，已被廣泛應用於量測各式精密工件、微機電元件、薄膜、 醫學器材等不同之領域。相較於接觸式表面輪廓儀，光學表面輪廓儀不需直接接觸待測樣品， 具有速度快、不易傷害樣品且不需探針等耗材之優點。像散式光學輪廓儀使用DVD讀取頭作為核心量測元件，其聚焦誤差訊號(Focus Error Signal)可量測奈米級表面結構形貌，具有速度快、高解析度、結構緊緻等優點。然而，聚焦誤差訊號深受表面反射率之影響。因此，除了需要針對樣品反射率進行校正外，若表面上具有不同反射率之材料，將無法得到量化之三維高度影像。為實現定量高度量測，本論文提出Z軸回饋控制模式以及Z軸掃描模式，並自行開發像散式光學輪廓儀系統以及高度計算分析程式。實驗以CS-20NG以及R2L2S1N兩種樣品進行測試。實驗結果顯示所開發之系統可成功定量量測CS-20NG表面上之20 nm微小結構。掃描R2L2S1N1之結果顯示Z軸掃描模式可量測具不同反射率材料之表面，實現定量之結構高度量測。此外，Z軸掃描模式亦可同時對表面反射率之特性進行成像。

The optical profilometer is a powerful instrument for measuring the surface morphology, which has been widely utilized in many different applications such as precise mechanical components, MEMS, membranes, and medical devices. Comparing with the contact profilometer, the optical profilometer doesn't need a stylus to contact with the sample. Therefore, it has advantages such as high speed, sample protection and no cost for the stylus. The astigmatic optical profilometer uses a DVD pick-up head as a core measurement component, and the focus error signal can be used to measure the surface structure at nanoscale. The astigmatic optical profilometer has advantages of high speed, high resolution, and compact size. However, the focus error signal is affected by the surface reflectivity significantly. Therefore, a calibration procedure is required for each sample with reflectivities. Moreover, the quantitative measurement can not be obtained on a sample consisting of complex materials. To solve this problem, two operation modes called the Z-axis feedback control mode and the Z-axis scanning mode were proposed in this thesis. An astigmatic optical profilometer system and a height calculation program were developed. Two stardard samples (CS-20NG and R2L2S1N1) were measured in the experiments. The experimental results show that the 20 nm height structures on CS-20NG can be measured quantitatively. The results on R2L2S1N1 show that the Z-axis scanning mode can achieve quantitative height measurement on the surface consisting of two materials with different reflectivities. Furthermore, the surface reflectivity can also be imaged in the Z-axis scanning mode.