以超高真空化學氣相沉積系統成長鍺磊晶層於磷化銦鎵/砷化鎵基板之研究

Abstract

為了解決矽半導體元件在線寬持續縮小的趨勢下所遇到的問題，以鍺磊晶薄膜作為通道材料因應其高電動遷移率(1900 cm2/V-s)的特性被視為一種可行的解決方案。本篇論文首度利用超高真空化學氣相沉積系統(UHVCVD)成長鍺磊晶層於磷化銦鎵/砷化鎵基板，並對於此結構的特性與成長機制做進一步的探討。 透過表面化學電子能譜儀(XPS)分辨出表面元素覆蓋率不同之磷化銦鎵上成長鍺磊晶層的誘導期(incubation time)有所不同，這是由於鍺原子與銦原子及鎵原子之鍵結能差異所致。根據熱毛細力理論(thermodynamic theory of capillarity)的計算，鍺磊晶層成長於磷化銦鎵/砷化鎵基板的模式為3D成長(Volmer-Weber growth mode)；利用掃描式電子顯微鏡(SEM)和穿透式電子顯微鏡(TEM)的成像能夠進一步驗證此成長機制。透過高解析度穿透式電子顯微鏡(HR-TEM)可以證明此論文中成長的鍺磊晶層擁有非常好的結晶品質以及極低的缺陷密度；而光微區分析(EDS)的結果也顯示鍺和磷化銦鎵之間的接面處只有極少的相互擴散(interdiffusion)產生。在螢光光譜(PL)的分析中可發現鍺磊晶層直接能隙(0.8 eV)的放射光譜，由此亦可間接證明成長出來的鍺金屬有非常好的品質。 從本論文結果可得知鍺和磷化銦鎵及砷化鎵的異質接面結構可應用於p型金氧半場效電晶體(MOSFET)，甚至可與n型三五族快速電子遷移率電晶體互相整合以利於之後CMOS元件的發展。

Epitaxial Ge film for channel material is regarded as the solution to the problems of the limitations of silicon-based device performance as continuing reducing the feature size because of its high hole mobility (1900 cm2/V-s). Ge epitaxial film was firstly grown on In0.5Ga0.5P/GaAs (100) with 6°-offcut toward [110] substrates by ultra-high vacuum chemical vapor deposition (UHVCVD). The structure was designed for the fabrication of p-channel MOSFET, and thus the p-channel MOSFET can be useful for beyond-the-CMOS-roadmap logic applications. The incubation time was found to be associated with the surface composition ratio of InGaP characterized by X-ray photoelectron spectroscopy (XPS). The growth mode of epitaxial Ge grown on In0.5Ga0.5P/GaAs (100) is the Volmer-Weber growth, calculated by the thermodynamic theory of capillarity and the pattern was further characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Good single crystal quality and low defect density of Ge films were observed according to high-resolution TEM images. Minimal interdiffusion and sharp interface between Ge and InGaP was demonstrated by energy-dispersive X-ray spectroscopy (EDS) line scan profile of TEM. Direct band gap emission at 0.8 eV of Ge epitaxial film was detected by photoluminescence (PL) spectrum.