第五章 結論
本論文實驗主要探討矽鍺薄膜異質接合結構的材料性質與機械性質並 進行高溫氧化處理加以分析。首先在矽基板上生長 200 nm 厚度的矽鍺薄 膜，接著是使用ESCA、SIMS、XRD、AFM 進行第一階段材料之分析，歸 納的結論如下:
1. 在元素鍵結方面，從 ESCA 量測氧化層可觀察出矽鍺薄膜異質接合結 構由於高溫氧化處理下，氧元素除了會與矽元素鍵結在表面形成二氧 化矽(SiO
2
)之外，也發現二氧化鍺(GeO2
)之鍵結形成。2. 在元素分布方面，由 SIMS 分析可得知，鍺元素會與矽元素同時進行 氧化作用。但由於矽之氧化能力相對於鍺來的高，因此氧化鍺最終會 被矽還原成鍺原子而堆積(pile-up)在介面層形成高鍺濃度之矽鍺表 面。
3. 在晶格組成結構方面，從 XRD 可觀察出，高溫氧化處理後的矽鍺薄 膜異質接合結構中鍺的波鋒有明顯的向右偏移，且鍺含量下降之趨 勢，此為鍺濃度擴散至矽基材之現象。此外，並從曲線震盪特性中發 現高溫導致應變鬆弛(strain relaxation)之現象發生。
4. 在表面變化方面，由 AFM 之 3D 表面形貌可觀察出高溫氧化處理後 的矽鍺薄膜異質接合結構的表面粗糙度有明顯上升之現象，而且有方 格圖形(cross-hatch patterns)等缺陷的產生。另外在 1000 ℃時也有島
狀物產生。從 AFM 可歸納出，高溫氧化處理後的矽鍺薄膜異質接合 結構與高溫氧化處理前的試片相較之下有粗糙度增加、產生島狀物以 及差排的現象。
第二階段利用奈米壓痕探討高溫氧化處理後做機械性質之分析。利用 奈米壓痕的力道控制模式分析負載-卸載曲線特性，並搭配 AFM 觀察負載-卸載後壓痕型態的變化，最後再以奈米壓痕之連續勁度模式分析硬度以及 楊氏模數做分析，可得知以下結論：
1. 在奈米壓痕之力量控制模式下，負載過程中產生曲線不連續之“pop in”之現象，此為矽鍺薄膜有差排產生及塑性變形之現象。
2. 在奈米壓痕之力量控制模式實驗後，再以 AFM 觀察未經高溫氧化處 理之薄膜表面，出現堆積隆起(pile-up)的現象。但與高溫氧化處理後 之試片做比較時，高溫氧化處理後試片之堆積隆起(pile-up)的程度變 小(抵抗塑性變形的程度增加)，壓痕的彈性回復量增加(抵抗彈性變形 機制方面增加)。
3. 在奈米壓痕之連續勁度模式下，以 200 nm 之壓痕深度觀察壓痕深度 範圍於0 至 50 nm 時，因為矽鍺表面有鍺隆起(pile-up)之緣故，高溫 氧化處理後的所量測出來的硬度值及楊式模數較小。反之，壓痕深度 在100 到 200 nm 之間時，在高溫氧化處理下藉由應變鬆弛所導致錯 位差排(misfit dislocation)的形成會造成硬度及楊式模數較大。因此，
必須特別注意矽鍺薄膜之表面經高溫氧化處理而產生結構性強度之 下降，尤其在後續製程例如化學機械研磨、封裝等皆可能對薄膜表面 產生破壞性的影響，進而使整體元件產生失效的可能性。
第六章 後續研究工作
在後續研究工作方面可以於矽鍺異質接面結構做進一步的製程參數以 及後續處理的改變。相關研究工作如下：
1. 改變矽鍺薄膜中鍺摻雜濃度，探討相對應之結構強度。此外在高溫氧 化處理方面，將嘗試不同之溫度處理及時間，使不同鍺摻雜濃度之矽 鍺薄膜於相對應合適之氧化參數下使其形成一穩定之鍺元素漸變 層，且於高應變鬆弛下保持低缺陷的結構特性。此外，矽鍺薄膜表面 在經後續化學機械研磨時必須在研磨參數上做最佳化之處理，以在達 成表面平坦化的同時，亦能維持穩定之結構強度、高應變鬆弛以及高 鍺濃度堆積之理想虛擬基材。
2. 針對高溫氧化處理前後之矽鍺薄膜以有限元素法模擬壓痕試驗，模擬 淺層壓痕以排除基材效應，量測薄膜在應變鬆弛前後其相對應硬度及 楊式模數之變化關聯。
3. 在材料特性研究方面，利用穿透式電子顯微鏡(TEM)分析儀器直接觀 察矽鍺異質接面結構於高溫氧化處理過後貫穿性差排以及錯位差排 分布變化情形，探討不同鍺摻雜濃度下之薄膜在高溫氧化處理後應變 鬆弛之機制與相對應缺陷產生情形。
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