Backside interferometric methods for localization of ESD-induced leakage current and metal shorts

Transient interferometric mapping (TIM) setup for ns-time ESD testing is adapted for post-stress failure analysis. Probing from the chip backside using the thermo-optical effect is used for localization of heating place related to failure. Two variants of 2D holographic interferometers, a Michelson and a “Wollaston” one, are used for a rough identification of a failure site. An adapted scanning heterodyne interferometer is used for accurate position determination with a 2 μm space resolution. The methods are applied to identify ESD damage and metal shorts. Sensitivity and space resolution are analyzed, supported by a 3D-thermal simulation of repetitive heating signal. A power sensitivity of 50 μW for a single point heat source is demonstrated.