Bonding Pad Test Structure for Detecting CMP Galvanic Corrosion

The patent applies preliminary action by designing a test structure with a test pad and connection trace before the actual bonding process. This test structure allows detection of galvanic corrosion and bonding failures in advance, enabling preventive measures to be taken before the corrosion affects the actual electrical connections. The test pad is specifically designed with a larger area than the bonding pad to enhance sensitivity to galvanic corrosion effects.

The patent uses an intermediary approach by introducing a test pad as a mediator between the CMP process and the actual bonding pad. The test pad serves as a sacrificial element that undergoes the same CMP process and is exposed to the same galvanic corrosion risks, but its primary function is to provide detectable signals about the corrosion status without compromising the critical electrical connections.

The patent applies segmentation by separating the detection function from the manufacturing process. Instead of relying on a single in-line defect tool, the patent divides the detection capability into a dedicated test structure (test pad and connection trace) that can be probed separately. This segmentation allows the use of simple, fast probing methods that maintain manufacturing efficiency while achieving the precise detection capability needed for galvanic corrosion.

The patent replaces complex mechanical inspection systems with a simpler electrical probing method. Instead of using sophisticated in-line defect tools with complex optical or mechanical scanning systems, the patent substitutes an electrical probe that measures resistance or continuity between the test pad and bonding pad. This substitution maintains high productivity while achieving precise detection of galvanic corrosion through electrical property changes.