Laser micro-scale thermal wave characterization of heat transport processes in modern semiconductor structures and devices

Heat transferring through the interfaces of diode structures assembled by various techniques in high voltage stacks and from multijunction solar cells to the ceramic baseplate are investigated by laser thermal wave methods. A theoretical model of thermal wave propagation in such structures is developed. It takes into account specific features of semiconductor structure surface processing, metallization and joining technology regimes. It is shown that the laser thermal wave methods can be successfully applied to the qualitative and quantitative characterization of thermal contacts between semiconductor elements in pulse power high voltage switches in real dynamic regimes of their pulse operation. It is also demonstrated that these methods make it possible to evaluate the homogeneity of thermal properties along the interfaces of soldered metal layers in the case of solar cells and diode stacks and to characterize their degradation due to thermocycling. An example of subsurface details imaging in various silicon structures and circuits by the laser scanning thermal wave method is presented as well.