| Summary: | 碩士 === 國立交通大學 === 材料科學與工程系 === 91 === This work utilized the electroless plating technology, accompanying with the photolithography and etching processes, to prepare Ni/Cu double-layered metal bumps on AlN substrate. In addition, by depositing solder by electro-plating on Ni/Cu to simulate the interfacial reaction of Ni/Cu metal bump and solder, we evaluated the feasibility of electroless plating technology to under bump metallization (UBM) for flip chip bonding. From X-ray diffraction analysis, the Ni-P film was consisted of amorphous and microcrystalline structure and the Cu film was polycrystalline. After annealing at 250 ℃ for 1 hour, both of the structures of Ni-P and Cu layers had no change. By forming Ni metal lines on AlN substrate within photolithography process, we were able to achieve the structure of 2μm thick Ni/Cu double layer metal lines and 5-μm-height metal bumps by using the electroless plating technique. From the scanning electron microscopy (SEM) observation, we found that the thickness of intermetallic compounds (IMCs) increased with the time of thermal treatment at 250 ℃. When the time exceeded 2 hours, the thickness of IMCs had no distinct raise. Both the IMCs and Ni film had the same thickness (4μm). From element linear scanning, we identified that the Ni-P film was a good diffusion barrier layer since Sn could not diffuse through the Ni-P layer. The IMCs were consisted of Ni3Sn4, Ni3Sn4 and Cu6Sn5, as revealed by XRD and EDS analyses. After thermal treatment for 12 hours, the IMCs gradually were replaced by Ni-Sn-Cu solid solution due to dissolution of Ni and Cu.
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