The Effects of Crystallization on Mechanical Mechanism and Residual Stress of Sputtered Ag Thin Films

Abstract

Silver film is widely used in optoelectronic and semiconductor industries, but its stress problem has not been verified. Sputtered Ag films of different thicknesses were used to investigate the effect of the crystallization on their solidification residual stress and electrical properties. From XRD data (2θ > 90°), an increase the thickness of the Ag film from 30 to 400 nm, not only raised the index of crystallization, but also obtained a lower resistivity. However, the peak (331) had a dissolution tendency due to the residual stress. The grain size of Ag films with greater thickness had grown because of the longer sputtering duration. Due to variations in the crystallized texture, the 30 and 110 nm films showed no sign of elasticity under nano-indentation testing. Under low-energy XRD (30 kV-20 µA), the 30 nm film not only had more residual stress, but also formed a new plane of diffraction at 104.2° of 2θ and the actual compressive stress value was 14.94 MPa. After an electrical current induced crystallization (EIC) test, the resistivity and residual stress of Ag film were improved.