Abstract

Non-stick on pad (NSOP) is a yield limiting factor that can occur due to various reasons such as particle contamination, galvanic corrosion, Fluorine-induced corrosion, process anomalies, etc. The problem of NSOP can be mitigated through a careful process characterization and optimization. In this paper, a bondpad qualification methodology (OSAT) will be discussed. It will be argued that by employing different physical analysis techniques in a failure analysis of wafer fabrication, it is possible to perform comprehensive characterization studies of the Aluminum bondpad so as to develop a robust far backend of line process. A good quality Al bondpad must meet the following four conditions-OSAT: (i) it should be no discoloration (using Optical inspection); (ii) should be defect free (using SEM inspection); (iii) should be with low contamination level (such as fluorine and carbon contamination should be within a control limit) (using Auger analysis) and (iv) should have a protective layer on bondpad surface so as to prevent bondpad corrosion (using TEM).

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