Stress evolution during and after sputter deposition of Cu thin films onto Si(100) substrates under various sputtering pressures -: art. no. 054908

The stress evolution during and after dc magnetron sputter deposition of Cu thin films with thicknesses of 20 and 300 nm and deposited with a constant rate of 0.1 nm/s onto Si (100) substrates is studied for various sputtering pressures (0.05-6 Pa). The stress was determined by means of in situ wafer curvature measurements using an optical two-beam deflection method. To correlate the stress evolution with the microstructure development, microstructure investigations were performed by scanning electron microscopy, atomic force microscopy, and electron backscatter diffraction. The results show the transition from tensile to compressive stress with decreasing sputtering pressure at different stages of the deposition. The features of the stress evolution during the early stage of deposition can be ascribed to the Volmer-Weber mechanism. For thicker films, three regions of the sputtering pressure can be distinguished concerning their effect on the stress evolution. The transition from compressive to tensile stress was correlated with the evolution from a dense to an open microstructure and with increasing surface roughness by increasing sputtering pressure. The results of the stress and microstructure evolution are interpreted in the context of the mechanisms being discussed in the literature. (C) 2005 American Institute of Physics.