矽鍺異質接面結構退火效應與奈米機械特性之研究

Abstract

本論文主要研究將矽鍺薄膜沈積於矽基板上，以合成矽鍺/矽異質接面結構，在學界上稱為虛擬基板(virtual substrate)。利用這種 Si1-xGex/Si 異質接面結構可製作並取代一般常見的矽半導體元件，主要應用於半導體元件異質雙極電晶體(heterojunction bipolar transistors, HBT) 、場效電晶體(modulation doped field-effect transistor, MODFET)，甚至近年來 SiGe TFT (Thin Film Transistor)薄膜電晶體。 本實驗對矽鍺/矽異質接面結構做奈米機械性質探測與材料分析。首先，利用超高真空化學氣相沈積矽鍺薄膜於矽基板上，形成矽鍺/矽異質接面結構。其次將多組試片分別以不同溫度參數進行退火溫度處理並做初步材料分析，實驗係以原子力顯微鏡分析表面形貌。最後以奈米量測中兩種量測模式為主軸進行研究。 由原子力顯微鏡分析結果顯示，隨著退火溫度的上升，試片表面島狀 化結構愈明顯，其表面粗糙度也隨之增加；另外，由Ｘ光散射分析儀(XRD)之實驗結果顯示，隨著退火溫度的上升，材料的特性波鋒產生偏移現象，顯示鍺成分經由退火而漸漸產生擴散現象。 經由奈米壓痕量測到的數值分析結果顯示隨著退火溫度的上升，結構中的差排密度有增加的趨勢。另外，實驗發現在四次負載-卸負載模式作用力 30mN 下，經 500 度退火 30 分鐘後結構表面開始出現破裂情形(Crack)。本論文研究結果可提供未來矽鍺/矽虛擬基板在退火製程技術及機械可靠度上之應用參考。

Since new high-quality devices are essential for future highly intelligent information and optoelectronics systems, there are urgent requirements for research and development on the high performance optoelectronic devices which can enable ultrahigh speed operation and excellent electronic transfer characteristics. Silicon germanium (SiGe) raises great interest due to its useful features in many optoelectronic applications, including thin-film transistors (TFTs), modulation-doped field effect transistors (MODFETs), metal-oxide-semiconductor field effect transistors (MOSFETs), hetero-junction bipolar transistors (HBTs), optical modulators, and other applications. This study examines the structural and nano-mechanical properties of Silicon Germanium (Si0.8Ge0.2) hetero-structures (that is, virtual substrate) deposited by ultrahigh vacuum chemical vapor deposition (UHVCVD) with different thermal annealing at 400~600oC for 30 minutes. Through the Berkovich nanoindentation test followed by force mode and continuous stiffness measurement, two topics are included. One is to discuss the annealing effect on Si0.8Ge0.2 hetero-structures. Various measurement technologies, including high-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), X-Ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and auger electron spectroscopy (AES) analysis, were used to characterize the materials properties of the Si0.8Ge0.2 hetero-structures. The other is to discuss the mechanical properties of SiGe hetero-structures on different maximum penetrations. On the continuous stiffness measurement it has been found that the modulus (M) and hardness (H) of SiGe hetero-structures increases from 13.8±0.7GPa to 14.2±0.6GPa with increasing annealing temperature. It is suggested that the dislocations nucleation is produced by lattice mismatch and thermal annealing. On the force mode, it has been found that the hetero-structure was destroyed by 4-cycles loading-unloading and 30mN loads.