Stress and oxidation in CuNi thin films

The stress evolution of a 400 nm thick Cu0.57Ni0.42Mn0.01 or resistive film on oxidized silicon substrate was investigated during a thermal cycle to 5 50 degrees C using a laser-optical substrate-curvature technique. Cycle-sto p-prepared samples were used to clarify the correlation between stress deve lopment and oxidation, especially by concentration-depth profiling using Au ger electron spectroscopy. In the stress curve, the striking feature associ ated with oxidation is a tensile stress component of about 500 MPa between 300 and 380 degrees C. This stress component is semiquantitatively explaine d by grain-boundary diffusion of Ni to the surface and the induced contract ion of the CuNi(Mn) layer due to the material lost. With progressive oxidat ion, a CuO/NiO double layer forms, growing without an essential contributio n of diffusion within CuNi(Mn) and, therefore, without oxidation-induced st ress development. (C) 1999 Elsevier Science S.A. All rights reserved.