利用溶膠旋轉塗佈法備製鈦酸鈷高介電層

Abstract

在這篇論文裡，我們利用溶膠旋轉塗佈法備製具有高介電係數的鈦酸鈷CoTiO3介電層，並且對600~900oC不同溫度退火後的樣品做詳細的研究。穿透式電子顯微鏡(TEM)的影像顯示著，CoTiO3 與矽基板之間經過四百度的氧化後會產生2.2 奈米的間隙層(interfacial layer)。根據X光繞射(XRD)圖形分析可知，這塗佈上去的CoTiO3介電層的結晶溫度大約介於六百到七百度之間。我們也利用掃描式探針顯微鏡(SPM)描繪出經過不同溫度退火的CoTiO3介電層的表面形貌，而高於六百度退火的樣品，其表面粗操度會有急遽上升的現象發生。化學分析電子能譜儀(ESCA)的結果顯示，較高溫度的退火會導致較厚的間隙層與較純的化學鍵結。而更進一步的ESCA分析確定了這塗佈上去並且經過六百度退火的介電層的原子濃度比例，[Co]:[Ti]:[O]約為1:1:3。經過六百度退火的CoTiO3的電子傳導性質，在氮化鉭(TaN)/ CoTiO3/矽基板這樣的結構中由蕭基發射機制主導。而經過六百度退火的CoTiO3捕捉電子的特性會受到溫度、施加電壓與加電壓時間的影響。介電質CoTiO3的高介電常數(k~40.2)是藉由高解析度TEM影像與電容電壓(C-V)曲線求得。另外，我們利用高解析度X光電子能譜儀(HR-XPS)偵測出二氧化矽與CoTiO3 間的價帶能量差(ΔEv) ，其值大約為4.0電子伏特；二氧化矽與CoTiO3的能隙(Eg)分別為9.0與2.2電子伏特。因此，在這篇論文中，CoTiO3與二氧化矽的直接校準，CoTiO3與Si的間接校準也就被成功地決定了!

In this thesis we form the high-κ dielectric CoTiO3 by sol-gel spin coating method followed by different annealing temperature 600~900oC. The image of transmission electron microscopy (TEM) reveals that 2.2 nm interfacial layer is between Si-sub and CoTiO3 annealed at 400oC. According to X-ray diffraction (XRD) analysis, crystallization temperature of the spin-on dielectric is between 600 and 700oC. Scanning probe microscope (SPM) describes surface morphology of the spin-on dielectrics with different annealing temperature and the surface roughness abruptly increases as annealing temperature higher than 600 oC. Electron spectroscopy for chemical analysis (ESCA) shows that higher temperature annealing results in thicker interfacial layer and pure chemical bonding. Furthermore ESCA also confirms that the spin-on dielectric with 600oC annealing has atomic concentration ratio [Co]:[Ti]:[O]~1:1:3. The spin-on film CoTiO3 with 600oC annealing has Schottky emission conduction mechanism for the TaN/ CoTiO3/ Si-sub structure. And the trapping characteristics of spin-on film CoTiO3 with 600oC annealing is affected by temperature, applied stress voltage and stress time. High electrical permittivity (k~40.2) of CoTiO3 dielectric is extracted via the high resolution transmission electron microscopy (HR-TEM) image and C-V curves. In addition, the valence energy band offset between thermally grown SiO2 and spin-on CoTiO3 is about 4.0eV, which is detected by high resolution X-ray photoelectron spectroscopy (HR-XPS). The band energy gaps of thermally grown SiO2 and spin-on CoTiO3 are 9.0 and 2.2 eV, respectively. The energy band alignment of spin-on CoTiO3 directly with SiO2 and indirectly with Si is successfully determined in this thesis.