Stress Measurement in Al‐Si‐Cu Interconnection Layers

Stress has been measured in Al‐Si‐Cu layers with different Si and Cu concentrations. Temperature variation of the intrinsic stress is measured at temperatures ranging from 25 to 450°C. In Al‐1%Si‐0.5%Cu layers, which have been extensively used in interconnection, stress changes from tensile to compression with increasing temperature. In the cooling process from 450°C, stress changes to tensile and increases linearly with decreasing temperature. It decreases, however, rapidly below 200°C and reaches 327 MPa at room temperature. Room temperature stress of 218 MPa in as‐deposited layer increases to 327 MPa after annealing at 450°C. The room temperature stress after annealing decreases from 327 to 231 MPa with decreasing Cu concentration from 0.5% to zero. This result clearly shows that lower intrinsic stress is attained in low Cu concentration layers at room temperature. Glancing angle x‐ray diffraction image plate measurement shows that (111) Al plane is tilted to random direction by angles ranging from 0 to 16°.