Assessment of the adhesion quality of fusion-welded silicon wafers with nonlinear ultrasound

Diffusion bonded silicon wafers are employed in the semiconductor industry. Their bonding quality must be monitored by a nondestructive testing technique. We present an ultrasonic technique allowing us to monitor the quality of the diffusion bond by measuring the anharmonic content of a transmitted ultrasonic wave. The anharmonicity is caused by weak bonds and manifests itself at high dynamic strains exerted by the ultrasonic wave. The source of nonlinearity is located in the rim of delaminations in the interface.