EVIDENCE OF HETEROEPITAXIAL GROWTH OF COPPER ON BETA-TANTALUM

Crystallographic orientations between thin-sputtered Cu film and beta- Ta adhesion layer have been studied using high resolution electron mic roscopy and electron diffraction. Tetragonal beta-Ta deposited on SiO2 has a strong texture with its closest packed plane (002) parallel to the film surface. On (002) beta-Ta, the growth of(lll) Cu is preferred . Even though more than 100 beta-Ta grains are found under a single Cu grain, the Ta grains under a Cu grain have long range in-plane textur e with [330] direction aligned parallel to the [220] direction of Cu. This orientational coincidence is explained by the heteroepitaxial rel ationship between the hexagonal close-packed atomic array in Cu (111) plane and the pseudohexagonal configuration of beta-Ta atoms in (002) plane with a misfit strain of 7.6%. (C) 1997 American Institute of Phy sics.