鋁/鉬/銅在酸性溶液之蝕刻研究

The Study of Aluminum/Molybdenum/Copper Etching in Acid Solutions

陳漢邦(Han-Bang Chen)

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(2006年)

https://doi.org/10.6342/NTU.2006.10056

摘要

本實驗針對鋁、鉬、銅金屬在酸性蝕刻液中的蝕刻行為進行研究，除了使用單一金屬蝕刻之外，另外還使用雙層金屬結構進行蝕刻，主要可分為三個部分：第一部分為鉬/鋁金屬層蝕刻，第二部分為銅/鉬金屬層蝕刻，第三部分為鉬金屬層蝕刻；皆測量其蝕刻速率的變化、XPS分析表面化學成分、開環電位量測、OM及SEM觀察蝕刻後的圖形。
鉬/鋁金屬層蝕刻的實驗結果發現，降低磷酸的濃度會使的鋁蝕刻速率下降，而鹽酸的加入有助於增加鋁的蝕刻速率，但鹽酸對鋁有pitting corrosion的問題，這會導致蝕刻均勻性變差，因此鹽酸的添加不宜太多，以維持蝕刻後金屬導線的完整。而鉬/鋁雙層金屬蝕刻時普遍都有overhang的情形，但經過over etching之後overhang的情況又會消失，經由開環電位的量測可以解釋這樣的現象。
銅/鉬金屬層蝕刻的實驗結果發現，銅和鉬金屬在蝕刻液中的蝕刻速率相差很大，同時蝕刻難以控制其蝕刻均勻性，不過藉由蝕刻液成份的調整、pH的變化或加入添加劑（BTA）可以拉近兩者的蝕刻速率，以維持蝕刻後的均勻性，但是蝕刻後的taper表現不佳，會對後續薄膜沉積造成影響，實驗發現taper的變化和蝕刻時金屬的電位以及結構中相對的位置有關。
鉬金屬層蝕刻的實驗結果發現，鋁酸蝕刻完後的taper都是垂直的，而雙氧水可以有效地降低taper angle，但是單只有雙氧水的蝕刻速率較慢，若搭配磷酸或是其它的酸性蝕刻液使用，可以有效的增加蝕刻速率及減少鉬金屬的殘留；除了雙氧水之外，高濃度的醋酸搭配磷酸和硝酸使用，也可以有降低taper angle的效果。

關鍵字

鋁 ； 鉬 ； 銅 ； 蝕刻 ； 電化學

並列摘要

The thesis on behavior of aluminum/molybdenum/copper in acidic etching solution was divided into three parts. The study used not only single metal layer but also double metal layers for etching experiments. The first part is etching of Mo/Al metal layers. The second part is etching of Cu/Mo metal layers the third part is etching of Mo metal layer. In the experiments, the etching rate was measured by time measurement of fixed thickness film been etched through. The interface phenomena in the etching process was investigated by open circuit potential measurement. We also analyzed the surface compositions by XPS, and observed the surface morphology by OM and SEM.
The results of Mo/Al etching indicated that adding HCl in etching solution speeded the etching rate when lowering the concentration of H3PO4. The etching uniformity is bad because HCl would pit aluminum surface. There is always overhang on Mo/Al etching, but it disappeared after over etching. This phenomena could be explained by OCP.
From the results of Cu/Mo etching, we could find that the etching rate difference between copper and molybdenum is large. Thus, it is hard to control the etching uniformity. By changing the composition or pH of etchant or adding additives (BTA), we could make the desired etching rate. The taper after etching is not good because of the structure and reaction potential of metals.
After Mo etching in aluminum etchant, the taper angle is almost 90o. Although the etching rate of H2O2 is slow, it could effective lower the taper angle. Concentrated CH3COOH with H3PO4 and HNO3 also could lower the taper angle besides H2O2.

並列關鍵字

Al ； Mo ； Cu ； Etch ； Electrochemical

參考文獻

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