Analysis of Thermomechanical Stresses in Silicon During Heating of Aluminum Interconnects on its Surface by a Pulse Current

Abstract

The work is focused on the analysis of thermomechanical stresses in silicon during pulse current heating of interconnections which were exposed to single current pulses with a duration of up to 250 µs and a current density amplitude of up to 2 × 10¹¹ A/m². When modeling thermal “loads”, film conductors on silicon with a thickness of up to 3 µm and a width of 10–75 µm were considered. Based on the experimental oscillograms taken from sections of the test structures during the passage of a current pulse and the calculation performed, the maximum temperatures on the silicon surface near the thermal shock source were determined. It has been experimentally revealed that the passage of current pulses with an amplitude of 2 × 10¹¹ A/m² and a duration of up to 250 µs leads to thermal destruction of interconnects and contributes to the formation of plastic deformation regions in the near-surface layer of silicon. It was revealed that with a decrease in the track width, the nature of the melting of the film conductor does not change. It was also established that a significantly higher specific energy is required to melt narrower tracks. The analysis of the maximum temperature gradients identified the places of the most probable cracking. The formation of cracks in the near-surface layer of a semiconductor at a depth of 2.5 µm after the passage of a single current pulse was experimentally detected. An assessment was made of the magnitude of mechanical stresses arising in the structure during thermal shock.