三光布拉格表面繞射之以次皮米解析Si0.7Ge0.3/Si介面應變縱向深度剖面分析研究

Depth profiles with sub-picometer resolution of the interfacial strains of Si0.7Ge0.3/Si using three-beam Bragg-surface diffraction

鄭燕宗(Zheng, Yan Zong)

指導教授 ： 張石麟

國立清華大學/理學院/物理學系/博士(2016年)

摘要

在奈米級(nano scale)半導體元件中，如何增加這些元件的效能(performance)是許多企業及研究者致力的目標之一。現今的半導體元件中，大部分是由薄膜系統所構成，在奈米尺寸下，其應變(strain)將直接影響元件間的載子遷移率(carrier mobility)，這個現象又可應用在所謂的應變工程(strain-engineering) [1-5]，即是利用晶體所受之應變來改善元件的效能。因此，應力對於元件的效能而言，將是扮演關鍵的角色之一。然而，目前存在的量測方法中，如穿透式電子顯微鏡(Transmission Electron Microscope, TEM)、同調性X光繞射成像(Coherent X-ray diffraction Image, CDI)和掠角繞射(Grazing incident X-ray diffraction, GIXD)分別受到破壞性量測、造價昂貴而無法廣泛被業界應用和穿透深度不足之缺點而有所限制。而在應變工程中，為了量測微小之應力，利用三光布拉格表面繞射的方法來發展”次皮米解析度之縱向剖析介面應力”，其布拉格表面繞射幾何，是由一個利用大角度入射(wide-angle incidence)以激發出對稱式布拉格繞射光(symmetric Bragg diffraction)，和一個沿著樣品表面傳遞之表面繞射光所組成。這項研究是利用布拉格表面繞射之幾何，並且選擇(004)/(202)、(004)/ (0-22)、(004)/ (4-22)三組面來進行。此外，為了實現以次皮米解析度剖析介面應力之實驗 ，我們選擇被半導體裝置廣泛應用的異質結構Si0.7Ge0.3/Si，以發展此項技術。最終，利用空間強度分佈之數據圖，並以多層邊界之X光動力繞射理論模擬空間強度數據，解析Si0.7Ge0.3/Si之異質接面的應力分佈。此外，此繞射方法未來或可將目前各量測應力技術之解析度，從奈米尺寸提升至次皮米尺寸。

關鍵字

X光繞射 ； 布拉格定律 ； 表面繞射 ； 薄膜 ； 應力 ； 異質結構 ； 矽鍺

並列摘要

For nano-semiconductor devices, how to enhance the device performance is one of the main goals of the semiconductor industries. As many devices are composed of thin-film systems in nano-scale, the carrier mobility would be directly governed by the strain of the thin film systems. The phenomenon could be applied to the strain-engineering [1-4] processes, which use the strain to improve the device performance and yet broaden their application [6]. Consequently, the strain is one of the important factors to the performeance of the device. However, the conventional methods of the strain measurement, transmission electron microscopy, TEM [7, 8], coherent X-ray diffraction image, CDI [9-13] and grazing incident X-ray diffraction, GIXD, are limited by destructive probing nature, the price of the instrument and the penetration depth, respectively. To dimension such a minor strain in strain-engineering processes, the depth profile with the sub-pico resolution of the interfacial strains are proposed by using three-beam Bragg-surface diffraction (BSD) [14, 15]. BSD is consisted of a symmetric Bragg diffraction at a wide-angle incidence and a surface diffraction, propagating along the interface of the sample. The three BSD, (004)/(202), (004)/ (0-22), (004)/ (4-22) were measured in this study. Moreover, we applied the hetero structure, Si0.7Ge0.3/Si, which are frequently used as semiconductor devices, to develop the technology of mapping the strain vs. depth with a sub-picometer resolution. Due to the structural proximity of the Si0.7Ge0.3 film and Si substrate, the surface diffraction of Si0.7Ge0.3 thin-film and Si substrate are simultaneously excited during the diffractive processes. Kiessig-like fringes are shown up in the vertical spatial intensity distributions (tth-scan). For mapping the stain in depth perpendicular to the hetero-junction, the spatial intensity were simulated by multi-layer dynamical theory [16-19] of X-ray diffraction for crystalline materials. Furthermore, the diffraction method reported in this dissertation may push the resolution of the current strain measurements from a dozen of nanometers to sub-pico meters regime in the future.

並列關鍵字

X-ray diffraction ； Bragg ； surface diffraction ； thin-film ； strain ； hetero structure ； SiGe

參考文獻

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