MECHANICAL-STRESS IN COEVAPORATED BETA-FESI2-FILMS ON SILICON SUBSTRATES(UPSILON THIN)

Amorphous thin films of FeSi2+v (v less than or equal to +/- 0.12) of 310 nm were prepared by simultaneous electron beam evaporation of Si a nd Fe onto Si-wafers. Mechanical stresses caused by the evaporation pr ocess and subsequent annealing up to about 700 degrees C were analyzed by laser-optical substrate curvature measurements. Large tensile film stress is generated due to structural relaxation of the amorphous fil m material during deposition and annealing up to 400 degrees C. Surpri singly, the crystallization to beta-FeSi2 at about 400 degrees C does only induce a very small stress component for v less than or equal to 0, but a distinct tensile stress for v > 0. The material densification during the phase transition is mainly translated into film thickness reduction. As no stress relaxation reduces the high tensile stress of 1300-1600 MPa cracking and delamination was observed. (C) 1998 Elsevie r Science B.V. All rights reserved.