旋轉平台之原子力顯微鏡於多側壁樣本以達成全方位高精度掃描

Omnidirectional precision scanning of AFM on a sample with multiple sidewalls using rotating stage

黃冠瑋(Kuan-Wei Huang)

指導教授 ： 傅立成

共同指導教授 ： 蔡坤諭(Kuen-Yu Tsai)

國立臺灣大學/電機資訊學院/電機工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202102412

摘要

原子力顯微鏡是一種極為高精度的掃描儀器，能夠透過原子探針重建奈米等級的樣本三維表面輪廓。此儀器能廣泛應用於不同領域，如奈米材料科技、半導體製程、微機電結構檢測、生物醫學等。其中，半導體製程技術日益精進，逐漸縮小化的半導體元件針對其側壁的檢測顯得更加重要。以微機電檢測為例，經過製成加工後得到的樣本，需要檢查於樣本側壁上的線寬粗糙度(LWR)以及線緣粗糙度(LER)。國際半導體發展路線圖(ITRS)，更是有規定相關的關鍵尺寸(CD)，以確保樣本製造符合設計規定。
然而近年來，傳統原子力顯微鏡掃描逐漸顯現出它的缺點，尤其是針對常見的四方形或圓形之島型結構樣本，已逐漸無法完成高精準度的多側壁樣本掃描。此外，對於高解析度重建的深度或島型結構樣本都將受制於傳統原子力顯微鏡的幾何探針形狀。最終，以現有的掃描方式而言，將無法有效解決側壁掃描時產生的失真與低解析度問題。
本論文提出針對樣本側壁的檢測方法，並引進旋轉的概念，將旋轉平台安裝於傳統原子力顯微鏡系統中。我們首先設計旋轉平台與壓電平台之合作式系統，使樣本能安裝於旋轉平台上，達成全方向性旋轉以解決傳統原子力顯微鏡探針幾何所造成的掃描失真問題。接著，設計合作式系統之校正流程以求出平台旋轉中心，藉此完成壓電平台與旋轉平台系統之探針定位，最後透過所提出之圖像重建方法，重建全方向性高精度側壁3D樣本輪廓。

關鍵字

壓電平台與旋轉馬達之合作式系統 ； 圓心校正 ； 圖像重建

並列摘要

Atomic Force Microscope(AFM) is a powerful and high-precision scanning instrument that can reconstruct 3D topography of specimens in nano-scale resolution. AFM is comprehensively applied to different research fields, such as nanomaterial technology, semiconductor industry, Micro-Electro-Mechanical System (MEMS) inspection, biomedicine, etc. In the case of semiconductors, since semiconductor technology advances by leaps and bounds, the inspection of the sidewall of the shrinking semiconductor components is much more critical. Take MEMS detection as an example; we need to inspect the line width roughness (LWR) and the line edge roughness (LER) of the sample after processing. International Technology Roadmap for Semiconductors (ITRS) also stipulates the related critical dimension (CD) of every size node to ensure that the manufactory accords to the requirement.
Nonetheless, conventional AFM structure has aged, gradually showing its inability to precisely scan multi-directional samples, particularly for island feature specimens, where square and circle contours are a common theme. In addition, the acquisition of high-resolution scan for deeper or island features is hindered by the geometric of traditional probes. Lastly, existing scanning schemes cannot effectively cope with problems such as distortions and low-resolution at the sample sidewalls.
This paper proposes a new method for sidewall inspection and brings in a concept of rotation. For achieving our objective, we mount a rotating stage in our homemade AFM system. We build a cooperative system including piezo stage and rotating stage to make our sample mounted on it and achieve omnidirectional scanning, which addresses the scanning distorted problems caused by the geometric of probe tip. We further design a rotating center calibration process of the cooperative system to find the rotating center of the stage to complete our tip positioning. Finally, we use the proposed precision reconstruction method to reconstruct an omnidirectional and high-precision 3D topography of sample.

並列關鍵字

A cooperative system with piezo stage and rotating stage ； rotating center calibration process ； the precision reconstruction method

參考文獻

[1] G. Binning, C. F. Quate, and C. Gerber, “Atomic force microscope,” Physical Review Letters, vol. 56, pp.930–933, 1986.

[2] R. Kneedler, S. Borodyansky, D. Klyachko, L. A. Vasilyev, A. H. Buxbaum, and T. B. Morrison, “3D metrology solution for the 65-nm node,” Proc. of SPIE, 2004, pp. 905–911, vol. 5567.

[3] G. A. Dahlen et al., “TEM validation of CD AFM image reconstruction,” Proc. of SPIE, 2007, pp. 1–12, vol. 6518.

[4] H.-C. Liu, Jason R. Osborne, Gregory A. Dahlen, Johann Greschner, Thomas Bayer, Samuel Kalt, and Georg Fritz, “Recent CD AFM probe developments for sub-45 nm technology nodes,” Proc. of Metrology, Inspection, and Process Control for Microlithography XXII, 2008, pp 1-7, vol. 6922.

[5] G. Dai, W. Häßler-Grohne, D. Hüser, H. Wolff, H. Danzebrink, L. Koenders, and H. Bosse, “Development of a 3D-AFM for true 3D measurements of nanostructures,” Meas. Sci. Technol, vol. 22, no. 9, 2011.