利用光學繞射術與原子力顯微術檢測奈米幾何特性

Abstract

本論文係利用光學繞射術與原子力顯微術檢測奈米幾何特性。在半導體產業中，必須在微米與奈米的製程中準確的量測奈米結構。本論文利用光學繞射術與原子力顯微術改進方法測量奈米幾何特性的研究，包括光柵間距檢查、奈米粒徑檢測及液體折射率的檢測技術。 本研究的液體折射率是利用光學繞射原理，結合浸潤的方式量測出液體的折射率，這種方式不需要用到特殊的容器，光路與設計也都很簡單，初步的結果得知，本實驗折射率在1.3左右的範圍時準確度約為 0.003。此外，本論文也探討利用動態光散射技術量測聚苯乙烯的奈米粒徑技術與不確定度分析，本文選用均一分散良好的聚苯乙烯標準球，並考慮動態光散射法的各項誤差源，使動態光散射法可以追溯到國際SI單位制，並使用電重力氣膠平衡法與動態光散射法做比較，以驗證本方法的正確性。最後，本研究發展利用原子力顯微鏡量測小於50 nm線寬的尺寸，本文分析了許多造成量測的誤差因素，並將此方法的量測不確定度控制在低於5 nm，95 % 的信賴水準內。

This dissertation mainly focused on nano-scale geometric inspections by using optical diffractometry and atomic force microscopy. The demand on accurate measurements of the nano-structure is more important for the microprocesses and nanotechnology in the semiconductor industry. In this study, an improved method for measuring the nano-scale geometric inspections by using optical diffractometry and atomic force microscopy is presented, and consists of grating pitch inspection, nanopaticle inspection, and refractive index inspection. In this dissertation, liquid of refractive index demonstrates the feasibility of using a laser refractometer based on immersion diffractometry for measuring the refractive index of liquids. Unlike other methods, the proposed method does not involve a special cell. Moreover, alignment and measuring processes are simple. Preliminary results indicate that the accuracy of the proposed method is about 0.003 for a refractive index of around 1.3. In addition, uncertainties in measuring polystyrene nanospheres by using dynamic light scattering (DLS) have been evaluated for nano-particle sizing. In order to establish the traceability to SI units of the DLS method, related parameters have been considered. Mono-dispersed polystyrene latex spheres (PLS) are selected as reference materials. Measurement results of nanospheres by using DLS are compared with that by using electrogravitational aerosol balance (EAB) method. Uncertainties for both DLS and EAB methods were determined. In addition, the decay rate is found to dominate measurement uncertainty in each nanosphere size. Finally, we developed a method using an AFM instrument for critical dimension (CD) measurements of sub 50 nm linewidth. Measurements were carried out for various three-dimensional nanoscale structures and used to estimate the effect of the uncertainty factors on the CD values. Experimental results show that the developed method of linewidth measurement can be controlled with an uncertainty smaller than 5 nm and with a confidence level of 95%.