成長於氧化鎂基板上之氮氧化鈦與碳氧化鈦磊晶薄膜結構與特性研究

Abstract

氮氧化鈦(TiNxOy) 與碳氧化鈦(TiCxOy)由於其獨特的特性，在科技領域中已成為非常受人矚目的材料。氮氧化鈦與碳氧化鈦由於具有相對新穎的組成，因此仍需要許多的研究與分析工作，以了解其相關特性。儘管目前已有許多相關的研究，但因欠缺單晶材料，而無法獲得基本性質。因此，在本研究中，將於MgO基板上沉積高品質之TiNxOy與TiCxOy 磊晶薄膜，並探討TiNxOy在氫電漿蝕刻下的蝕刻狀況與穩定性。同時針對TiNxOy與TiCxOy 磊晶薄膜的機械性質，進行深入的研究。 本論文研究的TiC0.47O0.69與TiNxOy磊晶薄膜是使用脈衝雷射沉積法(pulsed laser deposition)於MgO基板上成長，薄膜具有不同化學的組成 (0.63 < x < 1.11, 0.1 < y < 0.55)。X光光電子能譜(X-ray photoelectron spectroscopy, XPS)及X光繞射(X-ray diffraction, XRD)的分析結果顯示，以異質磊晶方式沉積於MgO基板上的TiNxOy與TiCxOy 薄膜，其結晶性佳，並且均處於完全壓縮應變(fully compressive strain)的狀態之下。所沉積的TiNxOy與TiC0.47O0.69 磊晶薄膜也都具有良好的導電特性。經由穿透式電子顯微鏡(Transmission electron microscopy, TEM)的分析得知，TiNxOy與TiC0.47O0.69 薄膜內所含有的差排密度低，而原子力顯微鏡(Atomic force microscopy, AFM)的分析則顯現兩者的薄膜表面均相當平整。當氧的含量增加，會減少TiNxOy薄膜的導電性及晶格常數，殘留應力也因此隨之而減小。 另一方面，對TiNxOy磊晶薄膜進行氫電漿處理。掃描式電子顯微鏡(Scanning electron microscopy, SEM)、AFM以及XPS 的分析結果顯示，TiNxOy的蝕刻與化學穩定性與氫氣壓力大小有著強烈的關係。當氫氣壓力低於40 Torr時，TiNxOy仍然相當穩定並保有其良好的結晶性。隨著壓力的增加，將可能導致倒角錐狀之蝕刻凹坑的形成。 關於TiNxOy與TiC0.47O0.69薄膜的機械性質，則使用奈米壓痕技術(nanoindentation)來加以量測。以TiNxOy薄膜而言，其薄膜硬度(H)與楊氏係數(E)分別約為17~26 GPa 以及 355~430 GPa，不論是薄膜硬度或是楊氏係數，均隨著氧含量的增加而減小，隨著氮含量的增加而變高。而硬度與楊氏係數降低的同時，也發現其殘留壓應力亦會變小。另外在 TiCxOy 薄膜方面， TiC0.47O0.69經過量測所得到的數值為 H ~ 21 ± 1.7 GPa以及 E ~ 390 ± 6.4GPa。

Titanium oxynitride (TiNxOy) and titanium oxycarbide (TiCxOy) have become very attractive materials in the field of science and technology due to their unique properties. Because titanium oxynitride and titanium oxycarbide are of relatively new compositions, therefore, they still need more works and characterizations to explore their properties. Although there have been relatively large amounts of studies on titanium oxynitrides and titanium oxycarbides, some basic properties of the films have not been established due to the lack of single crystals. Therefore, in the thesis, we report the epitaxial growth of TiNxOy and TiCxOy films on MgO substrates. We also study the stability and etching of TiNxOy in hydrogen plasma. Mechanical properties of epitaxial TiNxOy and TiCxOy films are especially investigated. The epitaxial TiC0.47O0.69 and TiNxOy films with different chemical composition (0.63 < x < 1.11, 0.1 < y < 0.55) were deposited on MgO substrates by pulsed laser deposition method. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analyses showed that the TiNxOy and TiC0.47O0.69 films are heteroepitaxially grown on MgO with good crystallinity and they are under compressive strain. Both deposited epitaxial TiNxOy and TiCxOy are very electrically conducting. Transmission electron microscopy analyses showed that TiNxOy and TiCxOy films contain a low density of dislocations. Atomic force microscopy (AFM) revealed very smooth surfaces of TiNxOy and TiC0.47O0.69 films. The increase in oxygen content reduces electrical conductivity and the lattice parameters of TiNxOy films, and residual stress decreases as a consequence. Epitaxial TiNxOy films were treated under hydrogen plasma generated from microwave. Scanning electron microscopy (SEM), AFM, and XPS results showed that the stability and etching of TiNxOy strongly depend on hydrogen gas pressure. TiNxOy was very chemically stable and remained with good crystallinity under hydrogen pressure below 40 Torr. With increase of pressure, it may lead to the formation of etch pits in inverse pyramid shape. The mechanical properties of TiNxOy and TiC0.47O0.69 films were characterized using nanoindentation. For TiNxOy films, hardness H and Young’s modulus E are about 17 - 26 GPa and 355 - 430 GPa, respectively; both H and E decrease with increasing oxygen content and increase with increasing nitrogen content; a reduction of H and E with decreasing residual compressive stress are also observed. Titanium oxycarbide film with composition of TiC0.47O0.69 shows the value of H ~ 21 ± 1.7 GPa and E ~ 390 ± 6.4GPa.