Adhesion studies of Cu‐Cr alloys on Al2O3

Adhesion of Cu‐Cr alloys to c‐axis sapphire wafers has been studied. A large increase in peel strength was observed when the Cr content exceeded 15 at. % for the as‐deposited alloy films. The high measured peel strength can be attributed to Cr that segregates to the sapphire‐alloy interface due to its high free energy in the metastable alloy structure. Heat treatment was found to greatly enhance the adhesion of low Cr containing (15 at. %) Cu‐Cr alloys to c‐axis sapphire. Cr was found to segregate to the sapphire‐alloy interface or separate as spherical precipitates in the Cu matrix upon appropriate thermal treatment. Increase in peel strength between sapphire and the low Cr alloy interface was observed at annealing temperatures as low as 200 °C.