In order to achieve high packaging density and high performance of LSI assembly, 3D stacking approach of electronic and opto-electronic devices has been considered where chip to chip interconnections are realized via micro through-holes formed by rapid excimer laser drilling. Since local damages due to temperature increase and thermal stress might cause device degradation, it is crucial for the process optimization to evaluate the quantity of thermal and stress fields around holes. In this study, we conducted transient thermo-mechanical finite element analysis for laser drilling of GaAs and Si chips considering temperature dependence of materials properties. Relationship among laser fluence, pulse width, repetition times, and the temperature increase and thermal stress are thoroughly investigated using 2-dimensional axisymmetric models.
Laser drilling is one of the promising methods for manufacturing fine-patterned and noble devices in electronic packaging. In order to realize 3D packaging by via hole drilling on Si chip devices by short pulse laser without damage, we developed the basic method predicting heat damage based on thermal conduction by finite element analysis. Quantitative prediction of heat affected zone (HAZ) where temperature exceeds the threshold value was employed in variety of process parameters such as power density, pulse width and beam profiles of laser. Numerical result showed that melting zone (MZ) size by a single shot of excimer laser was nearly same as irradiated area size in case of 7 μm of irradiated diameter, 10.2 J/cm2 of fluencies and 50 ns to 1 μs of pulse width, and that HAZ size was independent of pulse width consequently. It was found that spatial beam profile did not affect MZ size although HAZ size was slightly changed. Thermal degradation was predicted to be enhanced in case that the beam was irradiated near the edge of chip.