| 摘要: | 當元件尺度持續縮小至奈米尺度階段時，深入了解未來先進奈米元件中金屬薄膜與半導體基材間之界面反應是相當重要的一項課題。因此在本研究中將針對大面積二維規則之鎳、鈷金屬奈米點陣列的製備及其金屬薄膜經不同退火處理後與矽晶基材間之界面反應進行探究分析。 為了在矽晶基材上製備大面積周期性之鎳、鈷金屬奈米點，在本研究中利用聚苯乙烯奈米球微影術(Polystyrene nanosphere lithography, PS NSL) 先在矽晶基材上製備大面積、自行組裝 (Self-Assembly) 排列規則的PS 球陣列結構充當模板 (Template)，再於此模板上鍍製鎳、鈷金屬薄膜，經球體舉離步驟後即可於矽晶基材上形成尺寸均勻且具二維週期排列的金屬奈米點陣列。 由掃描式電子顯微鏡(SEM)、穿透式電子顯微鏡(TEM)及選區繞射(SAED)分析後可發現磊晶的二矽化鎳(NiSi2)與二矽化鈷(CoSi2)奈米點陣分別於350 ℃、 550 ℃即生成。而從電子繞射圖形分析鑑定得知其與 (001) Si 基材之磊晶方位關係為[001]NiSi2 (or CoSi2)// [001]Si，(200)NiSi2 (or CoSi2)// (400)Si。此結果顯示接近奈米尺度之鎳、鈷金屬點陣可促進磊晶結構矽化物的成長。另外，磊晶金屬矽化物點陣的尺寸隨退火溫度的升高而逐漸減小。進一步經高分辨電子顯微鏡(HRTEM) 分析觀察可發現，此磊晶金屬矽化物奈米點的形狀為一倒金字塔角錐狀。其金字塔角錐狀之塔底面平行於(001)Si，而塔底之四邊刻面平行<110>Si。另外，磊晶相之金屬矽化物奈米點與矽晶相交於{111}晶面。此外，在鎳金屬點陣列研究方面，當退火溫度升至900 ℃時，可發現在鎳矽化物奈米粒子上有許多非晶質氧化矽 (SiOx) 奈米線開始生成，其直徑約在15-20 nm 之間。在Ni-Si系統中，此非晶質SiOx 奈米線的生成可歸因於固-液-固 (solid-liquid-solid, SLS) 之成長機制。 另ㄧ方面，在本研究中，經由調變PS 球膠體溶液之滴製步驟與舉離條件，可成功地於(001)矽晶基材上製備六角週期排列的奈米環陣列。經由一系列的實驗觀察與分析結果，得知可能的奈米環陣列生成機制與乾燥過程中之縱向毛細力造成球體形變之作用力有關，並且其奈米環結構的直徑可藉由控制界面活性劑的濃 度而調變。 As the device dimensions scale down to nanometer region, in-depth understanding the reaction mechanisms between the nanoscale metal thin film and semiconductor substrate will play an important role in defining the use of these nanoscale building blocks in advanced nanodevices. Therefore, in this study,particular emphases are focused on the fabrication of large-area, 2D-ordered nickel and cobalt metal dot arrays and the interfacial reactions of nickel and cobalt metal dots on Si substrates after different heat treatments. To fabricate large periodic arrays of Ni and Co metal nanodots on silicon substrate, an effective and economical technique –polystyrene nanosphere lithography (PS NSL) was utilized. After 20-nm-thick metal thin films deposition and subsequent lift-off of the PS spheres template, an ordered hexagonal array of triangular metal dots was formed on the surface of Si substrate. From the SEM, TEM, and SAED analysis, epitaxial NiSi2 and CoSi2 nanodot arrays were found to form at a temperature as low as 350 ℃ and 550 ℃, respectively. The orientation relationships of epitaxial metal disilicide nanodots with respect to (001)Si substrates were identified to be [001] NiSi2 (or CoSi2) // [001] Si and (200) NiSi2 (or CoSi2) // (400) Si. The results indicated that the growth of epitaxial NiSi2 and CoSi2 is more favorable for the metal dot array samples. In addition, the sizes of the silicide nanodots were found to decrease with annealing temperature. The epitaxial metal disilicide nanodots were identified to be inverse pyramids in shape. The bases of the pyramidal metal disilicide nanodots are parallel to the (001)Si wafer surface and the faceted edges of the bases of the pyramids are along the <1 1 0> Si directions. The epitaxial metal disilicide nanodot/Si interfaces were found to be faceted with {1 1 1}interface planes. Furthermore, for the nickel nanodot samples annealed at 900 ℃,amorphous SiOx nanowires were found to grow on individual nickel silicide nanoparticles. The diameters of these nanowires are in the range of 15–20 nm, and the growths of a-SiOx were controlled by the solid-liquid-solid (SLS) mechanism. On the other hand, by tuning the drop-coating processes and lift-off conditions,hexagonal periodic nanoring arrays were successfully fabricated on (001)Si substrates. In addition, the diameters of nanorings can be controlled by adjusting the concentration of surfactant. Based on the results of a series of observation and analysis, the possible formation mechanism of nanoring arrays might be related to the normal capillary force deforms PS spheres during the drying of a suspension droplet. |
