Intragranular strain and mosaicity in Cu thin films during fast thermomechanical fatigue
Abstract Modern high-power semiconductor devices in automotive applications are subjected to overload pulses with heating rates up to 106 K ∙ s−1, causing temperature spikes of up to 300 °C. Cu thin films in these devices function not only as electrical conductors but also as primary heat sinks, fac...
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| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Nature Portfolio
2025-07-01
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| Series: | npj Materials Degradation |
| Online Access: | https://doi.org/10.1038/s41529-025-00629-z |
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| Summary: | Abstract Modern high-power semiconductor devices in automotive applications are subjected to overload pulses with heating rates up to 106 K ∙ s−1, causing temperature spikes of up to 300 °C. Cu thin films in these devices function not only as electrical conductors but also as primary heat sinks, facilitating rapid thermal dissipation. This study investigated thermomechanical fatigue in Cu thin films under application-relevant conditions within a 100–400 °C temperature range. High-frequency (20 kHz) X-ray diffraction measurements revealed compressive stresses of up to −293 MPa, surpassing the yield strength of bulk Cu. Dark-field X-ray microscopy tracked selected grains in situ over 1000 applied cycles, with either 200 µs or 20 ms pulse lengths. The observed grains exhibited a pronounced tendency to develop low-angle grain boundaries, which interacted with high-angle boundaries and led to constrictions in the grain shape. Structural inhomogeneities exhibited localized alternating tensile and compressive 2nd-order strains, connecting them to strain localization and deterioration of electric properties. |
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| ISSN: | 2397-2106 |