Apparatus for thin-film stress measurement with integrated four-point bending equipment: Performance and results on Cu films

New insight into the mechanical behavior of thin metallic films on substrat es can be obtained by a novel experimental technique. It comprises stress m easurements by the wafer curvature technique in combination with a four-poi nt bending of beam-shaped samples. A dedicated apparatus was constructed wh ich allows such experiments in high vacuum between room temperature and 500 degreesC to be carried out. It has a stress measurement sensitivity better than 0.1 MPa and a long-term stability better than +/-0.2 MPa over 24 h in the case of a 1 mum thick film. Strains up to 0.8% could be imposed by a f our-point bending on films grown on 380 mum thick Si substrates before crac king of the substrates. Both the thermal cycling and the four-point bending technique were used to investigate the plastic behavior of 1 mum thick Cu films on oxidized Si substrates. (C) 2000 American Institute of Physics. [S 0034-6748(01000201-5].