鈷合金薄膜之無電鍍製程探討

本研究以無電鍍法沉積鈷鐵金屬薄膜於銅片表面，目的在探討不同製程條件對鍍膜成分之影響，提供膜的製備以及鍍膜成分預估之依據。實驗方法是以pH＝10、11、12與45oC、65oC以及85oC作為鍍浴條件，並以兩種不同Fe/Co比之試劑進行討論。實驗結果指出，鍍膜中鐵含量會受到製程條件的變動而明顯改變，當鍍浴pH升高時，鍍膜中鐵含量會有明顯下降之趨勢；當鍍浴溫度由45oC調整至85oC時，也會有相同之結果。另外，實驗以次磷酸鈉作為還原劑使用，不可避免地在鍍膜中會有磷的沉積，從實驗結果可以發現，鍍膜中磷含量受到鍍浴溫度變動的影響，並無一致性之結果；但隨著pH值的改變，由pH＝10提高至pH＝12時，則會有減少的趨勢發生。因此於本研究可以得知，鍍膜中鐵、磷含量容易受到鍍浴條件(pH值以及溫度)所影響，其中又以改變pH值而有更明顯的變動。

關鍵字

無電鍍；鈷鐵；覆晶構裝

並列摘要

This thesis is to study the electroless plating process of Co-Fe alloy thin films on copper. Co can act as a diffusion barrier material of Cu in flip chip packaging. However, its reaction rate with solders are too fast. According to the previous research, adding Fe can suppress the IMC thickness at the soldering joints. Co-Fe alloy thin films are thus potential diffusion barrier layer materials in flip chip packaging. Electroless plating process is a widely-used process in electronic industry. This thesis is to investigate the electroless plating process of the Co-Fe alloy thin films. The effects of the pH values, temperatures, and Fe/Co ratios in the plating bath upon the plating alloy thin films are investigated. Experimental results indicate that the Fe contents in the plating alloy thin films decrease when the pH values increase from 10 to 12. At a fixed pH value, the Fe contents in the plating alloy thin films also decrease with the increasing temperatures from 45 to 85oC. Since the sodium hypophosphite is used as the reducing agent, the plating alloy thin films inevitably contain certain phosphorus. The phosphorus in the plating alloy thin films decrease from pH=10 to pH=12, and show no regular trend with temperatures. In process conditions used in this study, the P contents in the plating Co-Fe alloy thin films are lower than 7wt%. Based on the experimental results, the effect of the pH values upon the Fe and P contents in the plating alloy thin films is larger than the temperatures.