Prevention of diffusion of aluminum elements by ceramic coating with organometallic polymers

This study examines the performance of ceramic barrier coatings derived from organosilicon polymers as diffusion barriers in suppressing aluminum atom diffusion into copper substrates and identifies the temperature range over which this diffusion inhibition remains effective. The coatings were prepared from two different precursors: polycarbosilane, which upon pyrolysis at 800 °C yielded an amorphous silicon carbide layer, and polysilsesquioxane, which produced an amorphous silicon oxycarbide layer. Coating thickness was controlled by processing parameters such as spin–coating speed and polymer concentration, enabling systematic evaluation of thickness–dependent properties. Experimental results revealed that aluminum penetration and diffusion occurred through the amorphous silicon oxycarbide layer after heat treatment at 650 °C for 1 h. In contrast, the amorphous silicon carbide layer effectively prevented aluminum diffusion under the same conditions and only allowed penetration after heating at 675 °C for 1 h. Furthermore, increasing the coating thickness significantly improved thermal stability, with no aluminum penetration observed even after heating at 750 °C for 1 h. X–ray diffraction analysis of samples exhibiting diffusion confirmed the formation of AlCu and Al2Cu intermetallic phases at the interface. These findings demonstrate that amorphous silicon carbide provides superior diffusion resistance compared to amorphous silicon oxycarbide and highlight the critical role of coating thickness in enhancing thermal durability. The results suggest that organosilicon–derived ceramic layers are promising candidates for improving the reliability of aluminum–copper clad systems in high–temperature applications.