A bump structure having a barrier layer and a method of making the bump structure are provided. In some embodiments, the bump structure includes a conductive pad, a conductive bump, and a barrier layer. The conductive contact pad comprises a contact pad material. The conductive bump overlies the conductive pad and includes a lower bump layer and an upper bump layer covering the lower bump layer. The barrier layer is configured to block the movement of the contact pad material from the conductive pad to the upper bump layer along sidewalls of the lower bump layer. In some embodiments, the barrier layer is a spacer that lines the sidewalls of the lower bump layer. In other embodiments, the barrier layer is between the barrier layer and the conductive contact pad and spaces the sidewalls of the lower bump layer from the conductive contact pad.
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