Electrical Resistance and Stress of Bilayer Co(P)/Cu and Ni(P)/Cu Thin Films

Abstract

The electrical resistance of the metallic bilayer was measured in situ using a resistance furnace. In the isothermal resistance measurements the sheet resistance was measured as a function of time, up to 20 h, at the constant temperature of 400°C. Results show that the sheet resistance of Co(P)/Cu system stays constant for 19 h, while that for the Ni(P)/Cu system continuously changes with time. In the dynamic resistance measurements the sheet resistance was measured as a function of temperature, from 25 to 500°C at the heating rate of 10°C/min. Results show that the dependence of the sheet resistance on temperature for the bilayer Ni(P)/Cu and Co(P)/Cu thin films is at first linear and then deviates from linearity as the temperature increases from room temperature to 500°C. This dependence exhibited irreversibility. The stress of the bimetallic bilayers was measured in situ as a function of temperature in the range from 50 to 500°C using a modified Flexus Z2400S apparatus. Results show that the initial stress at room temperature is compressive. During the first heating cycle the stress state remains compressive and the stress level at the maximum temperature of 450°C is slightly higher than the stress in the as‐deposited film. During the cooling cycle the compressive stress changes into the tensile and continues to accumulate with the decreasing temperature, reaching a maximum value at room temperature.