Investigation of temperature gradients with regard to thermomigration in aluminium metallizations

For high temperature automotive applications a 0.35 μm aluminium CMOS is one of the common technology processes. In this process Ti/Al/Ti/TiN stacks are used as metallization. These aluminium stacks form TiAl₃ layers during the following annealing step. The thermal-electrical and thermo-mechanical properties of this metallization is different from titanium or aluminium. Hence the forming TiAl₃ layer influences the thermalelectrical, thermo-mechanical behaviour and reduces the current capability. The influence of the deposition temperatures on the thermal-electrical behaviour is investigated. Three different deposition temperatures of 150 °C, 250 °C and 470 °C were considered. Also the behaviour of anisotropic etching was investigated with regard to the reduced current capability.