Growth of nano crystalline near α phase tantalum thin films at room temperature using cylindrical magnetron cathode

Abstract

The much desired α (bcc) Tantalum (Ta) thin films are grown at room temperature using a newly designed cylindrical magnetron cathode (with rotating magnets geometry) with pulsing power. The new design has facilitated oblique incidence of adatoms. The electron temperature of the plasma has been enhanced due to the pulsing frequency (100 kHz). These two factors: oblique incidence of adatoms and enhanced electron temperature are presumed to be responsible for the formation of α phase Ta thin films at room temperature. The volume fractions of α and β phases have been evaluated from the X-ray data. The effect of pulsing (0–100 kHz) on the structural, electrical and mechanical properties of Ta thin films has also been studied. With the pulsing frequency, the lattice spacing in the Ta thin films increases (due to the incorporated argon) resulting in an increase in the compressive stress. Up to 75 kHz of the pulsing frequency, the Ta films formed are in the β phase (tetragonal) with ~ 13 nm grain size. At 100 kHz pulsing, the change in the surface morphology also indicates the phase change in the film.