Speakers
Description
As semiconductor packaging advances toward high density integration and heterogeneous integration, internal packaging defects such as voids, cracks, and interconnect failures become increasingly concealed. Conventional active infrared thermography (AIT) is constrained by thermal diffusion in packaging materials, which makes accurate localization and depth resolved interpretation of internal defects difficult. This paper proposes a multi harmonic infrared thermal tomography (MH-ITT) method based on electrothermal feedback induced nonlinearity. The proposed method requires no external thermal excitation. By applying a DC bias superimposed with a single tone AC excitation, the temperature dependent resistance of semiconductor devices triggers electrothermal coupling nonlinearity and naturally generates higher order harmonic thermal responses inside the device. Theoretical analysis and simulations indicate that different harmonics correspond to different effective thermal wave frequencies and thermal diffusion lengths. Therefore, they provide depth distributed tomographic slices. Experiments on a failed microcontroller unit (MCU) demonstrate that the proposed method enables three dimensional characterization of an internal hotspot in a packaged device. The proposed method provides an efficient and physically interpretable approach for three dimensional nondestructive inspection and fault reproduction of internal defects in packaged semiconductor devices.
