透過微結構調整以改善電鍍銅之腐蝕特性

Improvement of the Etching Characteristics of Electroplated Cu Films through Microstructure Modification

林平洲(P.C. Lin) ； 李承宇(C.Y. Lee) ； 楊政憲(C.H. Yang) ； 林鈺銘(Y.M. Lin) ； 何政恩(C.E. Ho)

《鑛冶：中國鑛冶工程學會會刊》 65卷2期 (2021/06) Pp. 45-54

https://doi.org/10.30069/MM.202106_65(2).05

摘要

近年來，為了增強銅導線與印刷電路板（printed circuit boards, PCBs）介電材料之結合強度，以有機棕化處理（organic brown oxidation treatment）粗化電鍍銅表面已被廣泛使用在PCB的增層技術上。然而，在經過有機棕化製程後，導線表面偶爾會出現一些直徑約幾微米，高度約2 μm的異常銅凸塊。異常銅凸塊（Cu protrusions）的產生將大幅地降低銅導線與介電材的結合強度（特別是細銅線路），甚至可能會在後續增層時產生氣泡。本研究之總目標即在探討異常銅凸塊的生成機制，並從中找到解決方式。透過一系列的場發射掃描式電子顯微鏡（FE-SEM）輔以電子背向散射繞射（EBSD）技術、共軛焦雷射掃描顯微鏡（CLSM）、及聚焦離子束顯微鏡（FIB）等分析，我們發現異常銅凸塊主要係由具特定晶粒取向（〈001〉｜｜ND及〈101〉｜｜ND）之大晶粒所構成。研究進一步發現，造成電鍍銅出現大晶粒的原因和電鍍藥液配方及電鍍後的熱處理製程有很大關聯。最終，我們提出了調整銅微結構的方法，以改善異常銅凸塊的生成數量。此一研究對於細銅線路的可靠度將有很大幫助。

關鍵字

電鍍銅 ； 有機棕化處理 ； 異常銅凸塊 ； 腐蝕 ； 擇優取向

並列摘要

The surface topography of electroplated copper (Cu) plays a dominant role in the bondability between Cu and dielectric materials of printed circuit boards (PCBs). Organic brown oxidation treatment is one of the common methods for roughening the Cu surface topography to enhance its adhesive strength with the PCB substrates. Our previous study (Surf. Coat. Technol., 2020, vol. 386, 125471) showed that some unusual Cu protrusions (diameter: a few micrometers; height: approximately 2 μm) may be created over the Cu surface after the organic brown oxidation process, which might significantly degrade the bonding strength between fine Cu lines and PCB dielectric materials and even yields undesired bubbles under Cu during PCB lamination process. We investigated the surface topography of electroplated Cu after organic brown oxidation by using a field-emission scanning electron microscope (FE-SEM) in combination with an electron backscatter diffraction (EBSD) analysis system, a confocal laser scanning microscope (CLSM), and a focused ion beam (FIB). The investigations showed that the unusual Cu protrusions were primarily consisted of large Cu grains with specific crystallographic orientations of＜001＞||ND and＜101＞||ND. The formation mechanism of the undesired Cu protrusions and its mitigation strategy were established in this study that will be beneficial to improve fine Cu line characteristics.

並列關鍵字

Electroplated Cu ； Organic brown oxidation treatment ； Unusual Cu protrusions ； Corrosion ； Preferred orientation