EFFECTS OF ION IRRADIATION ON THE RESIDUAL-STRESSES IN CR THIN-FILMS

Cr films sputtered onto {100} Si substrates at room temperature were f ound to be under residual tension, as revealed by wafer curvature meas urements. A 150 nm thick Cr film was bombarded with 300 keV Ar ions af ter deposition. The intrinsic residual tensile stress increased slight ly and then decreased with further increase in the ion dose. For ion d oses >1 x 10<SUP>15</SUP> ions/cm<SUP>2</SUP>, the stress in the film became compressive and increased with increasing dose. Transmission el ectron microscopy revealed that the grain boundaries in as-deposited C r have columnar porosity. A Cr film, ion irradiated to a dose of 5 x 1 0<SUP>15</SUP> ions/cm2, showed no grain boundary porosity. The change s in the residual stress during ion irradiation are explained by consi dering Ar incorporation in the film and the manner the manner in which irradiation may change the interatomic distances and forces. (C) 1998 <SUP></SUP> American Institute of Physics.