Raman spectroscopy to investigate gallium nitride light emitting diodes after assembling onto copper substrates

Mechanical stress is developed in the materials during and after manufacturing of devices. In microelectronics components, like integrated circuits, the stress in the interconnections is a very crucial phenomenon. Consequences are defects, which are more serious with the constantly increasing complexity and miniaturization of the devices. To develop strategies to minimize the stress phenomena, it is essential to analyze the stress morphology. Micro-Raman spectroscopy is an effective technique to measure local patterns with spatial resolution of less than micrometers. Focus of this study is the monitoring of stress induced on blue gallium nitride LEDs after soldering onto copper substrate. Stress values above 1 GPa are observed, which indicate compressive stress, especially in the central area of the LED. The results are discussed in terms of thermal expansion coefficients and soldering process, with the aim to enhance the reliability of the interconnections, optimize the bonding processes and provide crucial data for the improvement of packaging design.