本研究成功地利用聚苯乙烯(Polystyene, PS)奈米球微影術在矽鍺基材上製備出大面積、規則排列的PS奈米球陣列作為模板(Template)，並以此模板先後鍍製適當厚度比例之非晶矽中間層(a-Si)與鎳金屬(Ni)薄膜，形成Ni/a-Si雙層結構之奈米點陣列。隨後再將Ni/a-Si奈米點進行退火熱處理，探討其結構在退火過程中的相變化，以及奈米點與矽鍺基材的界面反應。 在研究中發現，Ni/a-Si奈米點在經過350 ℃退火後即可形成低電阻相之NiSi，並在退火溫度持續增加到800 ℃仍可以維持穩定的低電阻相NiSi。由穿透式電子顯微鏡(TEM)可發現Ni/a-Si雙層結構奈米點在退火過程中，其形貌可維持原本三角形奈米點，不受高溫退火影響下而造成形貌改變。其奈米點在經過高溫800 ℃退火下，與矽鍺基材界面仍十分平整並無觀察到任何的鍺偏析現象，顯示增加恰當比例的中間矽層對於熱穩定性的改善上有顯著的效應。 Ni/a-Si奈米點試片在經過900 ℃退火後則發現在奈米點周圍開始出現大量奈米線生成。經TEM及EDS之分析，顯示其為非晶質之二氧化矽奈米線。推測其生成機制應為固-液-固(Solid-Liquid-Solid, SLS)之成長機制。 In this study, we demonstrated that large-area, 2-D well-ordered arrays of Ni/amorphous-Si bilayer nandods were successfully fabricated on (001)Si0.7Ge0.3 substrate by nanosphere lithography. The phase transformated and structureal evolution of the Ni silicide nanocontacts after different heat treatments were investigated. Based on the TEM and SAED analyses, it is found that low-resistivity NiSi nanodots were successfully grown on Si0.7Ge0.3 substrate at an annealing temperature as low as 350 ℃, and the crystal structure of the grown NiSi was polycrystalline. NiSi nanodots exhibit excellent thermal stability after annealing at 800 ℃. The TEM images revealed that the shape of nanodots was not significantly changed and no Ge segregation were found after annealing. With an interposing a-Si film as the sacrificial layer, the thermal stability of NiSi nanodot was significantly improved. Many fine nanowires of 15-40 nm in diameter were observed from the regions of nanodots after annealing at 900 ℃. Selected-area electron diffraction and TEM/EDS analysis indicated that the nanowires were composed of Si and O and their structure was amorphous SiOx(a-SiOx) nanowires could be explained by the solid-liquid-solid (SLS) mechanism.
