微電子純銅表面氧化層整合分析之研究

Electrochemical and optical analyses of the surface oxide layer on copper in microelectronics

銅為優異良導體，廣泛應用於各種微電子導電層與線路，但由於銅易氧化，往往造成電阻增加甚至元件失效。以IC模組導線架為例，銅表面氧化層之形成與環氧模壓樹脂間常發生之脫層問題息息相關，包括氧化銅種類與厚度、比例等等均為影響要因。為提昇氧化層厚度與相種類之效率並維持精準度，本研究結合光譜分析（傅利葉轉換紅外線光譜儀（Fourier transform infrared spectroscopy））與電化學還原方法（Coulometric reduction method）提出整合方案。本研究選擇冷軋純銅片與電鍍銅，模擬die attachment、wire bonding以及高溫劣化等特定溫度進行恆溫處理，獲得不同氧化程度之銅表面予以分析。實驗結果顯示，FTIR光譜可迅速判別氧化層表面相種類，此外，根據還原電位及其變化，可推估縱深方向之氧化銅相種類與厚度。

Due to its excellent electrical conductance, copper is usually used as interconnect and metallization materials. However, surface copper oxide layer readily forms during fabrication or assembly processes. Electrical resistance will thus increases and even causes device failure problems. For instance, formation of copper oxides plays an important role in the delamination between epoxy molding compounds (EMC) and lead frames. The type and thickness of surface oxide layer, as well as the ratio of CuO/Cu2O are all affecting factors. How to efficiently and precisely identify the oxide phases and measure the oxide thickness is very crucial. In this study, the analysis of oxidized layer of electroplated copper and cold rolled copper by means of electrochemical and optical methods are developed. Isothermal heating simulating fabrication processes, such as molding and curing, is carried out to obtain different oxidation conditions. Coulometric reduction method and FTIR (Fourier transform infrared spectroscopy) are adopted to analyze the surface oxide layer. According to the absorption peaks of FTIR curves, the oxidized surface can be easily identified. In combination with the reduction potential and reduction time obtained from the coulometric reduction test, the variation of oxide phases along the through-thickness direction can also be revealed.