三光布拉格表面繞射方法研究矽鍺/矽薄膜之界面應變結構

Investigating Interface Strains for thin-film SiGe on Si Substrate Using three-beam Bragg Surface Diffraction

梁軒(Liang, Hsuan)

指導教授 ： 張石麟

國立清華大學/理學院/物理學系/碩士(2013年)

https://doi.org/10.6843/NTHU.2013.00563

摘要

本論文主要以布拉格表面繞射方法研究薄膜－基板系統的界面應變結構。本研究發展出一套新的方法，用以研究相似的異質結構之界面/表面訊息。其主要概念為使用相近材料製作基底－薄膜系統，如矽與摻雜鍺之矽鍺薄膜，計算應變結構下薄膜與基板的所有繞射條件，選擇條件相近或相同的繞射光，使得入射光能同時激發薄膜與基板之表面繞射光，用以研究表面與界面訊息。繞射產生時，入射光大部分能量以薄膜的表面繞射方式損耗，導致光的穿透深度較淺，此時基板的訊號為確切的表面訊息。
以矽為基底、摻雜鍺之矽鍺為薄膜，控制鍺的濃度亦能控制其晶格常數以及繞射條件。以入射光強度、晶體結構、繞條件等資訊可計算其穿透深度，並可針對不同厚度的薄膜進行基板的表面測量。
本實驗微幅改變X光入射角θ、樣品方位角φ、薄膜厚度t，收取被同時激發的繞射光之空間中強度分布，藉以觀察入射光穿透深度的變化，而實驗數據中晶體外的繞射光之空間強度分布，以及晶體內垂直電場強度變化，都可以動力繞射理論計算模擬之。
本實驗我們以掠角繞射方法驗證了薄膜因應變而形成之長方體結構，並以特定實驗方法證明界面對表面繞射光之影響，提出一套解釋。

關鍵字

繞射 ； 表面繞射光 ； 布拉格 ； 界面 ； 應力 ； 應變結構

並列摘要

On this research, we investigated interface Strains for thin-film SiGe on Si substrate by using surface diffraction.
A new method is developed and employed to detect the interface information of heteroepitaxial structure.
The main concept is to choose the similar or identical diffraction condition of the thin-film system which is manufactured by similar materials and do some research about the interface/surface of the thin-film system.
By calculating the diffraction condition about the crystal of the thin-film system, both of the Si substrate and SiGe thin-film can be excited at the same time.
When the diffraction occurs, most energy of the incident beam is consumed by surface diffraction of the thin-film. Due to the penetration depth is shallow; the received signal is exact the surface information of the substrate. The diffraction condition can be controlled by tuning the concentration of Germanium doped in the thin-film. When increasing the concentration, the lattice constant increased, and vise versa.
Through analysis the intensity of incident beam、lattice constant, and diffraction condition of the sample, we can estimate the penetration depth and compare it with experimental result, by carefully tuning the x-ray penetration depth, the structural information coming from the substrate under various thickness thin-film then can easily be reached.
By slightly changing θ、φ of the sample with various thickness, we can get the information of the penetration depth、the spatial intensity distribution outside the crystal, and the intensity change of vertical electric field inside the crystal. The results are also comparable with the theory.
The tetragonal structure of SiGe thin-film due to strain was confirmed by Grazing Incident Diffraction. In addition, we also developed a method to show the interface’s effect to Bragg-surface diffraction, and give an theoretical explanation.

並列關鍵字

diffraction ； surface diffraction ； bragg ； interface ； strain ； strain structure

參考文獻

[1] S.-L. Chang, X-ray multiple-wave diffraction: theory and Applications, Springer,Berlin (2004).

[2] John C. Bean, Science 11 October 1985, Volume 230, Number 4722

[4] E. Kasper [ Properties of Strained and Relaxed Silicon Germanium (INSPEC,

Beach, California, 1986)

[3] Universite’ P. et M. Curie, Paris ,Dynamical theory of X-ray Diffraction,ch.8.first public (2001)