The Residual Stress Of Metal Copper Film And Electrical Characteristics

In this paper, Cu thin film samples were deposited on silicon (Si) substrate and Polyvinylidene Fluoride (PVDF) substrate by RF and DC magnetron sputtering with different deposition conditions. Their structural, mechanical, electrical properties and surface morphology were measured by X-ray diffraction (XRD), electronic film stress distribution of the tester, Hall Effect measurement, atomic force microscopy (AFM) and scanning electron microscope (SEM), respectively. The effects of several parameters on the properties of Cu films were studied. In addition, the author analyzed the relationships between microstructures and other electrical properties of the metal Cu thin film materials and tried to explain the flexible PVDF substrate surface morphology of porous Cu film to the influence of the electrical properties. Several important results were obtained:Firstly, the influence of different sputtering process parameters on the nature of metal Cu films was discussed.(1) With the increase of sputtering time, the linear growth of the Cu film thickness was observed and the Cu films were deposited on Si substrate exhibit very good crystalline characteristics. Grain size of the sample increased, the surface roughness decreases and resistivity decreased significantly with increasing deposition, the resistivity reaching a minimum of2.29μΩ.cm in this research. Residual stress of Cu thin films were shown for the tensile stress, and decreases gradually with the increase of sputtering time, with the increase of the residual stress, the resistivity of Cu films also increased.(2) With increasing sputtering pressure, the Cu films are still showing good crystalline characteristics, but the grain size gradually decreases. The resistivity of Cu film gradually also increased with increasing sputtering pressure, the electrical properties of the samples has not improved. In this research, with the increase of sputtering pressure, the residual stress of Cu film from the compressive stress to the tensile stress change, the compressive stress is reduced, tensile stress is increased, and resistivity of Cu film was increases with the residual stress changes.(3) With increasing sputtering power, Cu thin films are still showing good crystalline characteristics and the grain size gradually increased. The resistivity reaching a minimum of2.66μΩ.cm when sputtering power is140W in this research. Residual stress of Cu films were shown for the tensile stress which gradually increased with increasing sputtering power, the resistivity is gradually reduced with increasing residual tensile stress.Secondly, the Cu films were deposited on soft PVDF substrates, the crystalline properties compared to the Cu thin films were deposited on the Si substrate were worse, the Cu (200) oriented XRD peak was observed. With increasing sputtering pressure, the intensity of diffraction peaks and the crystal grain size first increased and then decreased. The surface morphology of the Cu film is porous. The resistivity of the porous Cu is much larger than that fabricated on Si substrate. Furthermore, the resistivity increases simultaneously with the increasing of Cu film surface aperture, but the resistivity of Cu film still decreases with the increasing grain size. The range of resistivity from20μΩ.cm to240μΩ.cm and the electrical properties is the best at sputtering pressure0.5Pa.Thirdly, from the experiment, comprehensive analysis on the electrical properties of the porous Cu film combined with theoretical models. The result shows that the resistivity of Cu film deposited on the PVDF substrates mostly depended on the surface morphology. With the morphology fluctuations change increasing, the resistivity of the Cu films also increased. And analysis of the interaction between microstructure and electrical properties of the metal Cu films from the two aspects of the theoretical models and actual experimental results in this research.