Sn-5Ag鍍層在去離子水中對銅遷移之影響

Effect of Sn-5Ag coating on the migration of copper conductors in de-ionized water

本文主要在探討銅導線鍍上Sn-5Ag鍍層後對銅遷移的影響。銅導線鍍上0.67～2 µm厚的Sn-5Ag鍍層，在去離子水中5V偏壓的情況下，可抑制銅導線的電解質遷移，且隨著鍍層厚度的增加，抑制效果愈佳。若經過熱處理（250℃/5分鐘）之後，試片的抗遷移能力亦會大幅提升。藉由在0.01M NaOH水溶液中進行動態陽極極化掃瞄，將有助於了解抑制遷移的機制。在Sn-5Ag鍍層的極化曲線中發現兩個電流峰，其分別對應於SnO及SnO2的生成反應，這兩種氧化物皆提供了保護，防止銅線中銅元素及Sn-5Ag鍍層中銀元素的溶解。因此，在銅導線上鍍上Sn-5Ag鍍層可以有效的抑制遷移。此外，在同樣2 µm的鍍層厚度下，Sn-5Ag鍍層比Sn-10Pb鍍層具有較佳的抗遷移能力。

The effect of Sn-5Ag coating on the electrolytic migration of Cu-conductors has been studied. The Sn-5Ag coating layer with a thickness of 0.67~2 m tends to inhibit the migration of the copper conductor in de-ionized water at a bias of 5 V. The inhibition becomes more efficient with increasing the thickness of the coating. Heat treatment ( 250℃ for 5 minutes) of the coated specimens pronouncedly increases their resistance to electrolytic migration. The investigation of potentiodynamic polarization in 0.01M NaOH is useful in delineation of the migration inhibition mechanism for the Sn-5Ag coated specimens. For Sn-5Ag coated specimen, two passive peaks corresponding to the formation of SnO and SnO2 are observed. Both oxides on the coating provide a protective layer, which prevents copper dissolution from the substrate and silver dissolution from the Sn-5Ag coating. Thus tin oxides resulting from the Sn-5Ag coating effectively inhibit copper migration of the copper conductors. Furthermore, comparing the coatings with the thickness of 2 µm, Sn-5Ag is superior to Sn-10Pb in the inhibition of copper electrolytic migration.