Combining surface microtopography and subsurface defect imaging for broad-spectrum metalization defect quantification

Describes and reviews examples of metalization characterizations that result when submicron-resolution surface topography (imaged by laser deflection) and subsurface defect imaging (detected by laser-based thermal wave modulated reflectance) are performed simultaneously. By contrasting the set of imaged signals (6 in all, recorded in typically 4 min for typical (100 μm)² area), immediate identification of subsurface versus surface defects is obtained. The dominant defect type is then revealed and the degree of spatial correlation of one defect type with another is learned. Because all the data are obtained nondestructively, the device wafer may then be subjected to stress and reimaged to determine the growth rates or interactions of the defect types