鋁在磷酸溶液中之電化學行為及其蝕刻之研究

The study of electrochemical characteristics and etching behaviors in phosphoric acid solutions

呂文雄(Wen-Hsiung Lu)

指導教授 ： 顏溪成

國立臺灣大學/工學院/化學工程學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.00149

摘要

本實驗針對鋁在磷酸溶液中的電化學特性和蝕刻行為做研究：其主要的系統為磷酸系統，之後再加入硝酸，醋酸等觀察其電化學特性之變化其實刻速率之改變，並利用交流阻抗的技術觀察其表面化學特性之改變；線性直流極化技術觀察其蝕刻速率之改變；XPS分析其表面之組成。
實驗結果發現在磷酸系統中，其蝕刻表面時之氧化層行為分為三區，分別為低濃度區( < 3M )的氧化層快速消耗；中濃度區( 3 M ~ 7 M )的平衡氧化層厚度；以及高濃度區( > 7 M )的再次快速消耗氧化層，這是因為鋁表面之氧化鋁分為兩層，其內部的緻密層和外部的多孔層對於蝕刻行為的抵抗力不同所致，實驗中我們也發現，加入硝酸可以大幅提高在高濃度區的蝕刻速率，這是因為硝酸能將表面之鋁氧化成氧化鋁，而氧化鋁和磷酸根反應之快速，因此可以大幅提高蝕刻速率。而蝕刻鋁所產生之氫氣是因為氧化鋁蝕刻之後露出少許的鋁，而氫離子對鋁的蝕刻則會產生大量氫氣，這也是為什麼在濃磷酸中，氫氣產生的又急又快，在低濃度磷酸中，氣泡只能少量的生成。
最後我們也探討醋酸對於整個蝕刻行為的幫助，並了解到醋酸為有機酸對於降低介面阻力(潤濕)有很大的幫助。

關鍵字

鋁 ； 蝕刻 ； 磷酸 ； 電化學

並列摘要

In this study, we focused on the aluminum electrochemical characteristics and etching behaviors in the phosphoric acid solution, nitric acid and the phosphoric-nitric acid solution, respectively. In the experiments, we measured the etching rates by electrochemical polarization and the interface phenomena by Electrochemical Impedance Spectra (EIS) technique. We also analyzed the surfaces which were etched by different etchants with XPS.
The results showed that the etching behaviors in the phosphoric acid solutions were discussed with three concentration regions: in the low concentration region (< 3M), the surface alumina thickness decreased rapidly; in the middle concentration region (3M~7M), the thickness reached a steady state thickness and kept a constant value; in the high concentration region (>7M), the alumina thickness decreased again and became a very thin alumina film on the surface. Because the alumina on the surface had two different structures, the inner part is dense alumina and the outer part is porous alumina. They showed various etching behaviors in the three concentration regions. We also found out that nitric acid could oxidize the aluminum surface. That is why the etching rate increased rapidly in the high concentration region. In the high phosphoric acid concentration region, the alumina layer became very thin and H+ can etch aluminum to generate the hydrogen bubbles. This is why the bubbles generation in the low phosphoric acid concentration is slow and in the high phosphoric acid concentration region, it is fast.
Finally, we found out the acetic acid is an organic acid which decreased surface resistance and reduced the surface roughness.

並列關鍵字

Al ； Etch ； Phosphoric Acid ； Electrochemical

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