The Cu/PtSi metallurgy is studied for reaction and thermal stability using several barrier layers, Cr, Ti, W, and amorphous C. Using preformed PtSi and Cr, Ti, and W barrier layers, Cu is found to react with PtSi around 350 °C. The results are compared with those using similar barriers for the Al/PtSi structure, where an improvement in thermal stability by 50-150 °C is observed. The low thermal stability of the Cu/PtSi structures is attributed to the high affinity of Cu to Si, with the Cu silicide formation starting around 200 °C for a Cu/Si structure. Using an amorphous carbon barrier for the Cu/PtSi structure, a small amount of Cu silicide is observed at 400 °C, but not at 600 °C. Migration of Cu into the structure, however, makes uncertain the effectiveness of the carbon barrier. The results are compared with those of Al/C/PtSi, Al/C/Pd/Si, and C/Cu/SiO2 to understand the mechanism involved.