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Electromigration kháng (EM) của Ag là độ tin cậy kết nối mối quan tâm quan trọng nhất mà sẽ xác định phù hợp của nó đối với công nghệ mạch tích hợp. EM là trôi dạt của các ion kim loại như là kết quả của một trong hai vụ va chạm giữa các electron dẫn | Summary 117 Figure 7.4. RBS spectra 3.7 MeV He 2 7 tilt of the diffusion barriers before broken line and after solid line testing at 620 C for 30 minutes in flowing atmosphere N2-5 H2 ambient 8 7.3 Electromigration Resistance Electromigration EM resistance of Ag is the most critical interconnect reliability concern that would determine its suitability for integrated circuit technology. EM is the drift of metal ions as a result of either collision between the conductor electrons and or the metal ions or high electrostatic field force when current is passed through a metal conductor. The direction of mass transport depends on the direction of the net force. When high current densities pass through the metal line voids or hillocks are formed at a point of ion flux divergence Figure 7.5 . Voids and hillocks deform and grow until electrical failure is completed 10 . 118 Silver Metallization Figure 7.5. Schematic to illustrate metal conductor failure due to electromigration 17 Ho and Huntington 11 Patil and Huntington 12 reported that Ag migrates toward the anode for the temperature range 670-877 C. Klotsman et al. 13 and Breitling and Hummel 14 however found that Ag ion transport is toward the cathode and is opposite to the direction of the electron wind. Studies conducted by Hummel et al. showed that the dominating movement path is grain boundaries for temperatures in the range of 225-280 C activation energy of 0.95 eV and surface for the temperature range 160-225 C activation energy of 0.3 eV 15 . In this study the influence of an encapsulation process on the electromigration resistance of Ag has been investigated. The sample configurations used consisted of bare Ag patterns and encapsulated Ag patterns. Compared to bare Ag lines TiN O encapsulated Ag lines exhibited much better electromigration resistance in terms of the time required for the formation of significant number of voids and hillocks. After the encapsulation process the Ag surface is capped by a thin .
