Metalization and Bonds - A Review of Failure Mechanisms

Materials and techniques used for metalization and bonding of silicon devices, particularly integrated circuits, are reviewed, and available data on the reliability of various structures, and on failure mechanisms, are discussed. Metalization systems considered include Al, Mo-Au and Ti-Pt-Au. Bonding methods considered include thermocompression and ultrasonic wire bonding, plus face-down bonding and soldering techniques. Metalization and bond failures are the principal modes of failure in integrated circuits. At high stress levels, inherent failure modes are most significant; these inherent failure modes are not, however, necessarily a factor in reliability at rated stress levels. Manufacturing defects are a major cause of failures at rated stress levels. At present there are no indications of a significant reliability advantage for any bonding or metalization system for general integrated circuit usage. It is predicted that Al will continue to be the most widely used metalization system, with an increasing usage of ultrasonic bonding and face-down bonding techniques.