Influences of ion energy on morphology and preferred orientation of chromium thin films prepared by ion beam and vapor deposition

The influences of ion irradiation on morphologies and preferred orientations of Cr thin films prepared by ion-beam and vapor deposition were studied. Cr films were prepared onto Si (100) wafers by evaporation of Cr and simultaneous irradiation with Ar ions. The energies of Ar ions were changed in the range of 0.5-20.0 keV, and transport ratios of irradiated Ar ions to vaporized Cr atoms, Ar/Cr, to the substrates were kept at 0.033. Vaporized Cr atoms were deposited onto substrates at an angle of 45 degrees and Ar ions were irradiated normal to the substrates. Si substrates were kept at low temperature during deposition. The experimental results show that the morphologies and the preferred orientations were varied due to the change of ion irradiating energy though other conditions were constant. Every Cr film takes a clear columnar structure. The column widths of Cr films are augmented with increase of ion energy. The columnar growth direction turns toward the deposition direction with increase of ion energy up to 5.0 keV. With further increase of ion energy the direction changes to perpendicular to the substrate, parallel to the direction of the ion irradiation. The preferred orientation to the substrate normal changes from random to (100) orientation through (110) and (100) orientation with increasing of ion energy. The reasons were understood as the mixed effects of nuclear and electronic energy transfers due to the collisions between Cr atoms and irradiated Ar ions. (C) 1998 American Vacuum Society. [S0734-2101(98)10304-4].