矽基異質磊晶工程：從矽鍺異質接合介面的能帶結構分析到甲基化矽基板上的氧化鋅凡得瓦磊晶成長

Si Heteroepitaxial Engineering: From Probing Fine Structure at Commensurate Si/Ge Heterointerface to Incommensurate van der Waals Epitaxial Growth of ZnO on Methylated Si Surface

余家濠(Chia-Hao Yu)

指導教授 ： 溫政彥

國立臺灣大學/工學院/材料科學與工程學研究所/博士(2020年)

https://doi.org/10.6342/NTU202000198

摘要

磊晶(Epitaxy)擴展了材料製程的可能性，但其受限於兩個材料間的晶格不匹配(Lattice mismatch)。本論文從兩個面向的研究以助矽磊晶領域的更進一步發展。磊晶不只能分別整合多種單晶薄膜材料於一單晶基板上，並且能控制晶體的成長方向，於矽的半導體磊晶製程領域，更能進行應變工程(Strain engineering)，將矽薄膜磊晶成長於矽鍺虛擬基體(Virtual substrate)上以獲得應變矽(Strained silicon)，進而提高矽的載子遷移率(Mobility)。隨著近來奈米尺度結構下磊晶成長的研究發展，具有極窄過渡區(Transition region)且無缺陷的矽/鍺異質介面，可透過由下而上(Bottom-up)的氣固固相(Vapor-solid-solid)成長法於高真空的環境下製備。本論文運用掃描穿透式電子顯微鏡的電子能量損失能譜分析(Scanning transmission electron microscopy-electron energy loss spectroscopy, STEM-EELS)以及幾何相位分析法(Geometrical phase analysis, GPA)，以探討矽/鍺異質接面對於材料能帶結構(Band structure)的效應，此研究從微觀角度揭露了大應變下矽/鍺異質接面的電子能帶結構特性。另一方面雖然相稱的(Commensurate)異質磊晶系統可以在一些材料系統上實現，但本質上還是大幅地受限於材料間的晶格不匹配，並且在矽的異質磊晶系統裡，還要考量矽表面極易被氧化而影響磊晶製程的問題。因此在本論文的另一部份，嘗試運用凡得瓦磊晶(van der Waals epitaxy)的機制特性-磊晶材料與基材間不具備化學鍵結，於矽基材上發展凡得瓦磊晶成長。此研究成功地利用嫁接(Grafting)甲基官能基(Functional group)於矽基材表面，建構出不具有懸鍵(Dangling bonds)並且可延緩氧化發生的週期性表面，並在化學浴沉積製程 (Chemical bath deposition)的成長環境下發展出了矽基材上的氧化鋅凡得瓦磊晶成長。此外，更從中發現在氧化鋅的水溶液成長系統中，具有低表面能(Surface energy)的基板表面上會有鋅化合物的自我組裝(Self-assembly)成核特性。透過此一特性以及表面改質(Surface modification)製程，c軸取向氧化鋅奈米結構可直接成長於任意基材表面。

關鍵字

異質磊晶 ； 超高真空化學氣相沉積 ； 矽鍺異質接合奈米線 ； 氣固固相成長 ； 原子層沉積 ； 掃描穿透式電子顯微鏡-電子損失能譜 ； 3D/3D凡德瓦磊晶 ； 化學浴沉積 ； 氧化鋅奈米柱 ； 甲烷化 ； 疏水表面 ； 自我組裝薄膜

並列摘要

Heteroepitaxial growth is largely used in Si industry. Carrier mobility can be enhanced in the strained Si layer by introducing commensurate epitaxial system of Si/SiGe. Epitaxial stress in the heterointerface is determined by the lattice mismatches and the sharpness of the heterointerface. Considering the intrinsic material characteristic, ultimate plate strain is limited, generally < 1%. Recently, preparation of dislocation-free Si/Ge heterojunction is succeeded in nanoscale with the vapor-solid-solid (VSS) growth method. Large degrees of strain engineering, up to 4.2%, are then achievable in this unique structure. Up to now, there is still no experimental analyzation work of the localized strain effect on the band structure of that nanostructure. We therefore use geometrical phase analysis (GPA) to study the degree of strain near the Si/Ge heterointerface and electron energy loss spectroscopy in the scanning transmission electron microscopy (STEM-EELS) mode to further study the localized fine structure at the heterointerface. This research unveils the route to probe the localized fine structure at the Si/Ge heterointerface and potential effect of interface dipole in this system. On the other hand, the available pair selection in the heteroepitaxial material system is still limited by their lattice structures, and Si-based heteroepitaxial growth system is generally vacuum process operated at high temperature. Therefore, we develop a more universal approach for heteroepitaxial growth by grafting the methyl group on Si(111) surface for achieving van der Waals epitaxial growth and deferring the oxidation of the surface. With such a treatment of preparing periodic passivated surface, ZnO nanostructure can be directly epitaxially grown on the methylated Si(111) substrate surface in the chemical bath deposition (CBD) process, with the characteristics of van der Waals epitaxy. Furthermore, self-assembly nucleation behaviors with a preferred orientation at the extended hydrophobic surface are observed on several kinds of hydrophobic substrate surface.

並列關鍵字

Heteroepitaxy ； Ultra-high vacuum chemical vapor deposition ； Si/Ge heterojunction nanowire ； vapor-solid-solid growth ； atomic layer deposition ； Scanning transmission electron microscopy-electron energy loss spectroscopy ； 3D/3D van der Waals epitaxy ； chemical bath deposition ； ZnO nanorod ； Two-step halogenation/methylation ； hydrophobic surface ； self-assembly monolayer

參考文獻

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