Abstract
由於氮化鈦(TiN)具有絕佳的阻礙擴散性質以及良好的導電性並且有 高熱穩定性，所以成為目前使用最頻繁的阻障材料，尤其是在積體電路上 的應用。但隨著積體電路尺寸的縮小(0.35μm以下)及外貌比值(aspect ratio)的提高，傳統的物理氣相沈積(PVD)法階梯覆蓋性不佳(step coverage)，若欲獲得較佳的階梯覆蓋性，則TiN薄膜就必須藉由化學氣相 沈積(CVD)法來生長。近來利用CVD法生長TiN薄膜已經被廣泛的研究，而 這些被提出來的方法以TiCl4+NH3 及MOCVD法居多，但前者需使用具危險 性的TiCl4而後者有原料價格昂貴的缺點，所以吾人乃嘗試利用一固態錯 化合物【TiCl4(NH3)2]來做為生長TiN薄膜的前驅物(precursor)，以期克 服上述的缺點。在薄膜生長實驗條件方面，生長溫度在450∼650℃，操作 壓力0.3∼1.0 Torr，然後透過一些分析方法瞭解到吾人所生長的薄膜呈 現N原子不足的情形，而形成如Ti2N及Ti3N2-x晶體結構出現；在薄膜性質 方面，電阻係數隨著生長溫度的增加而下降，但因薄膜組成不 佳使得電 阻係數值皆偏大；而在薄膜生長速率方面，薄膜厚度隨生長溫度提高而增 大；在薄膜組成方面，透過AES的分析我們得到Ti/N=1.2∼1.3的組成，對 於薄膜表面型態的分析，我們透過SEM與AFM的觀察可發現到TiN薄膜之晶 粒隨著生長溫度的提高而有聚集的現象，使得晶粒尺寸有增大的趨勢。除 了實驗部份外，吾人亦透過熱力學的分析，來針對本實驗系統作理論性的 探討，我們以參與反應的物種當作區分系統的準則，因此可區分為Ti-N- H-Cl-Si與Ti-N-H-Cl-Si-O兩個系統，然後探討操作變數對整個反應系統 的影響，期望透過理論的分析與實驗結果的比較，而能提出整個反應機制 。 Thin titanium nitride(TiN) films are used as a diffusion barrier in VLSI contacts, because of their excellent thermal stability, low resistivity andgood barrier properties.However, with the continuous shrinkage of VLSI'sdimension(to less than 0.35μm) and enhanced aspect ratio, if one wants to obtain a higherstep coverage,the traditional PVD(physical vapor deposition) method was unableto achieve the claim.Therefore the CVD(chemical vapor deposition) techniquehas to be utilized to deposit thin films.Recently, CVD method to deposit TiN filmshas been extensively studied,usingeither TiCl4+NH3 or organometallic(OM) precursors. Yet the TiCl4 is a dangerous liquid and the OM precursors in MOCVD are veryexpensive.In this work,we'll tryto use a single solid complex[i.e.TiCl4(NH3)2]as the precursor to deposit TiNfilms for overcoming the above drawbacks.In ourexperiments, the deposition temperature was 450 to 650℃ and operatingpressure0.3 to 1.0 Torr. The films were characterized by typical techniquessuch as XRD,AES, XPS.We found that the films were N-deficient crystalline phases,e.g. Ti2Nand Ti3N2-x. In other films properties,the film resistivity decreased withincreasing deposition temperature,but the deviation was large due to thenonuniformity in film composition. The growth rate of the TiN films increasedwith increasing deposition temperature.The Ti/N ratio of the films characterizedby AES was about 1.2-1.3. Film morphology as revealed by AFM and SEM indicatedthat grains of the TiN films coalescenced together and size was subsequentlyincreased with increasing deposition temperature.In addition to experiments,we also carried out thermodynamic analysis onthese reaction systems, whichinclude the Ti-N-H-Cl-Si.Ti-N-H-Cl-Si and Ti-N-H- Cl-Si-O depending upon whetheroxygen is considered in the analysis.The effects of various operating parameters on the formation of TiN were analyzed.These results were then compared with datafrom our experimental studies to give us insight on the reaction mechanismleading to the formationof TiN films.