以溶凝膠法製備氧化鉿及氧化鉭之透明薄膜特性研究

Characterization of HfO2 and Ta2O5 transparent thin films prepared by sol-gel method

林宜慶(Yi-Cing Lin)

指導教授 ： 陳至信

中原大學/電機資訊學院/電子工程研究所/碩士(2015年)

https://doi.org/10.6840/cycu201500756

摘要

本論文研究利用溶凝膠法(Sol-Gel)製備的氧化鉿、氧化鉭以及兩者之混合膜，經由不同的混合比例、退火溫度以及薄膜厚度，研究薄膜晶體結構以及光學特性。
溶凝膠法實驗中使用四氯化鉿(HfCl4)及五氯化鉭(TaCl5)為前驅物，經過醇解、水解、縮合及聚合，形成二氧化鉿(HfO_2)、五氧化二鉭(Ta_2 O_5)以及氧化鉿及氧化鉭的混合膜(HfTaO_x)之溶液，並以旋轉塗佈法(Spin Coating)將薄膜旋塗於Si(100)基板上；其中，氧化鉿及氧化鉭之混合薄膜嘗試以不同的HfO_2：Ta_2 O_5比例，分析其X-射線繞射(XRD)圖型來判斷晶格結構品質，並使用橢圓偏光儀量測薄膜厚度及折射率，再以掃描式電子顯微鏡觀察薄膜表面情況以及從斷面觀察薄膜厚度，來驗證橢圓偏光儀所測得之數據，此外還使用同步輻射光源作為激發光，量測薄膜之光致螢光現象，藉以了解此薄膜之特性。
根據量測結果發現，退火溫度越高則氧化鉿、氧化鉭及兩者混合的薄膜多晶結構越顯著；薄膜的厚度由橢偏儀量測以及SEM所得結果，可觀察到膜厚為奈米尺度；薄膜之表面結構在高倍率之SEM下可看出表面有因退火而造成之龜裂及孔隙，而斷面結構看出的薄膜厚度和橢偏儀所量測出之結果相近；氧化鉿的光致螢光結果於250nm至450nm之間，有因薄膜與基板間的反射干涉效應。

關鍵字

溶膠凝膠 ； 氧化鉿 ； 氧化鉭

並列摘要

In this thesis, HfO2, Ta2O5 and the mixed films of both are prepared by the sol-gel method. The thin films crystal structure, optical properties and electrical properties are analyzed by different mixing ratio, annealing temperature and the film thickness. HfCl4 and TaCl5 are precursors in the experiments of sol-gel process. HfO2, Ta2O5 and the mixed solutions of both are formed after alcoholysis, hydrolysis, condensation and polymerization. And then, the films are spin coated on Si (100) substrate by the spin coating method.

We analysis the X- ray diffraction (XRD) pattern to determine the quality of the lattice structure that the sample films are mixed by different hafnium oxide: tantalum oxide ratio. After that, we measure the thickness and refractive index of the films by using ellipsometry, and using the scanning electron microscope (SEM) to observe the surface of the film pattern and the cross-sectional thickness of the films to verify the data that are measured. In order to understand the optical properties of this film, we also use the synchrotron radiation VUV light as the excitation light source to observe the phenomenon of photoluminescence (PL) of the films.

According to the measurement results, the higher annealing temperature we can get the better lattice structure and quality of the hafnium oxide, tantalum oxide and the mixed films of both. We use the ellipsometer to measure the thickness uniformity and refractive index of films. Then comparing the thickness results with SEM cross section images of films. From the surface morphology of film’s SEM results, there are cracks on the surface of films. They are caused by high temperature annealing process. The VUV PL results of HfO2 film show there are PL interference signals of film and substrate between 250nm to 450nm.

並列關鍵字

sol-gel ； HfO2 ； Ta2O5

參考文獻

[9] 洪文進、許登貴、萬明安、郭書瑋、蘇昭瑾，"ITO 透明導電薄膜：從發展與應用到製備與分析"，台北科技大學有機高分子研究所，pp. 2-6，2005

[22] 蔡裕榮，周禮君,“以溶膠凝膠法製備透明導電氧化物薄膜的探討”, Chemistry(The Chinese Chem. SOC., TAIPEI) SEP. Vol. 60, No. 3, pp.307~318(2002).

[43] 莊子毅. "直流濺鍍高品質氮化鋁薄膜之物理與光學特性研究分析." 中原大學電子工程研究所學位論文 (2012): 1-88.

[1] Zhu, J., and Z. G. Liu. "Comparative study of pulsed laser deposited HfO2 and Hf–aluminate films for high-k gate dielectric applications." Applied Physics A 80.8 (2005): 1769-1773.

[2] Armelao, Lidia, et al. "Highly dispersed mixed zirconia and hafnia nanoparticles in a silica matrix: first example of a ZrO2–HfO2–SiO2 ternary oxide system." Advanced Functional Materials 17.10 (2007): 1671-1681.