SiGe/Si 介面應變場之X光表面三光繞射研究

Interfacial strain in multi-layer materials play a very important role in affecting the device performance, such as the yield of semiconductor electronic devices and the output power of solar-energy batteries. Here we report on the studies of interfacial strain in the SiGe/Si sample system using the so-called Bragg-surface three-beam diffraction. A CCD(Charge Coupled Device) is employed to monitor the image of the surface diffracted beam as a function of the Bragg angle θ and azimuth angle ϕ of rotation around the interface normal. The latter also reflects the effective depth of surface X-ray propagation according to the dynamical theory of diffraction. Consequently, the interfacial strain versus effective depth can be mapped out. It is found that the interfacial strain field is mainly affected by the growth direction of thin layers and the crystal lattice type of the substrate. The closer to the interface the larger the strain.

關鍵字

SiGe/Si

並列摘要

現今的多層材料中，當兩種不同晶體的晶格常數相當接近時，其介面將會因為兩種晶體的連結造成此處的晶格常數有所變化，而晶格常數的變化，在許多材料應用中，常會發生問題，例如在太陽能電池的光轉率不好等等，因此若能有效掌握此變化量，將可對此問題提供重要資訊。在本碩士論文中，主要探討應變場(strain field)在SiGe/Si的介面對於晶格的變化。在實驗部分，我們利用電荷耦合元件(Charge Coupled Device)去拍攝各種不同角度的繞射圖形，在數據分析部分，我假設在每組ϕ-scan中強度最強的地方為參考原點，利用此點及繞射幾何去計算其晶格常數的變化，並將計算出的晶格常數，分別對θ、ϕ、X光穿透深度作圖。由這些圖形進一步分析應變場的分佈情況，最後得到三個重要的結論，其一，長晶的方向將影響應變場的大小，其二，晶體的特性將影響應變場的分布情形，其三，接近介面的地方，由於應變場較大，因此，晶格常數成震盪變化。