Size effects on the optimization of the mechanical resistance and the electrical conductivity of Cu thin films

ROA, SIMÓN; SIRENA, MARTÍN

Materials Today Communications

Elsevier Ltd

Año: 2021 vol. 28

Cu thin films are nowadays attractive components for emergent MEMS based technologies because their high electrical conductivity (σ) and good mechanical properties. In general, σ is negatively affected when the film thickness (t) decreases close to the electron mean free path (le) scale and the mechanical resistance is favored. So, we propose a study of the Cu thin films optimum size conditions to achieve a well-compromise between the mechanical and electrical performance. Films mechanical behavior was studied by Atomic Force Microscopy (AFM) assisted nanoindentation. Results showed considerable increments of the elastic (Ue)-to-total (Ut) strain energy ratios (Ue/Ut) from 0.27 ± 0.02 up to 0.54 ± 0.04 as t was decreased from 2 [µm] to 100 [nm], evidencing a clear films mechanical resistance improvement by reducing t. Our analysis showed that the improvement of the films mechanical resistance easily compensates the negative impact on the electrical conductivity, especially for t>le.