Non-Destructive Inspection Method for Detecting Open Failures in Flip Chip Structures

A new nondestructive evaluation method of adhesion condition between a Si chip and small metallic bumps in a flip chip bonding structure is proposed. The local deformation of a surface of a Si chip mounted on a substrate increases drastically between two bumps with decrease of the thickness of the chip thinner than 200 μm. The magnitude of the local deformation exceeds 100 nm easily. Once the lack or delamination of the metallic bumps occurs at the interface, the local deformation at a surface of a Si chip around the bump changes remarkably. The change of the magnitude of the local deformation reaches about 50 nm to 600 nm depending on the thickness of the chip. Such a small change of deformation can be measured using a scanning blue laser microscope. Therefore, the adhesion condition of the area-arrayed bumps can be examined by measuring the local deformation of a surface of an LSI chip mounted on a substrate.