APPARATUS FOR THE LASER-OPTICAL MEASUREMENT OF STRESS IN THIN-FILMS -RESULTS ON CUNI

Dedicated to the investigation of the temperature dependence of mechan ical stress in thin films (up to 700 degrees C in vacuum), a sensitive apparatus has been built up to measure the substrate curvature of a b eam-shaped sample by deflection of a splitted laser beam from both end s. The measuring sensivity is about 0.1 MPa for a typical film thickne ss of 1000 nm. The long-term value over 24 h is about +/-0.5 MPa due t o ambient-temperature drifts. The determination of absolute stress mag nitudes is possible by comparative measurements between the measuring bending beam and a reference one before and after film deposition or f ilm removal. Investigations on sputtered Cu0.57Ni0.42Mn0.01 films have shown that (1) the stress relaxes above 300 degrees C and remains nea rly constant between 430 and 550 degrees C during the first heating, ( 2) a hysteresis behavior occurs during the repeated cycles, and (3) th e stress at room temperature increases a little with the cycle number. (C) 1998 American Institute of Physics. [S0034-6748(98)03010-X].