臨界尺寸之高解析度光學量測

Abstract

臨界尺寸是在量測中所必須分辨的最小尺寸。在各種量測領域中，由於技術的發展與產品的更新，臨界尺寸也愈來愈微小。在半導體元件的製程中，臨界尺寸量測技術的發展有助於提高製作的良率。對於半導體元件的量測，主要有線寬量測，疊對量測，膜厚量測，材料分析，及粗糙度分析等，臨界尺寸量測是本論文研究的方向。 對於線寬的量測是採用跨焦取像量測法。在此研究中，結合了邊界元素法及物理光學追跡法來模擬有限光柵經顯微系統在光偵測器上的成像情況。當連續移動有限光柵對顯微物鏡的物距時，可以得到數幅含有光柵資訊的影像，藉由理論及量測的分析比對，可以得知有限光柵的幾何結構，此方法對於線寬的量測具有奈米等級的橫向解析度。 對於半導體元件的疊對量測，我們提出一干涉式散射儀架構來量測疊對光柵上層與下層之間的位移，藉由疊對光柵的量測可以得知在半導體製程中層與層之間的位移。在此研究中，首先建立所需要的演算法，在此使用修正過的嚴格耦合波演算架構，以符合所建立的量測系統，接著設計及製作一疊對光柵，並使用所架設的量測系統對此結構作一量測及分析量測的結構以得到層與層之間的位移。

Critical dimension (CD) is the smallest size which must be resolved in specific measurement. The CD becomes smaller and smaller due to developments of technology and innovations of products. In the fabrication of integrated circuit, reliable CD measurement is the key procedure to improve the yields. The CD measurements include line-width, overlay, thickness, material, and roughness, etc. In this thesis we focus on the high resolution optical metrology for CD measurement. For the measurement of line-width, we use the through-focus focus-metric method to measure the line-width. In this research, we combine the boundary element method and physical optical propagation to simulate the images of a finite grating. The images with different object distance are obtained when moving the finite grating along the optical axis. These images contain the information of the geometric structure of grating. By measuring and analyzing the finite grating, we can obtain the geometric structure of grating. The results show that the through-focus focus-metric method is sensitive for recognizing the line-width and nano-scale resolution could be achieved. For the overlay measurement, we proposed a new method, interfero- scatterometry, to measure the overlaid grating. By measuring the overlaid grating, the overlay between different layers in the integrated circuit can be obtained. First, we modify the rigorous coupled wave algorithm for our measurement system, and then design and fabricate an overlaid grating. After measuring and analyzing the grating by the interfero-scatterometer, we obtain the overlay between different layers.