STRUCTURAL ANISOTROPY IN OBLIQUE-INCIDENCE THIN METAL-FILMS

A three-dimensional ballistic deposition model for thin film growth has been developed, incorporating the mechanisms of shadowing and relaxation which are essential to microstructure formation. In addition to generating columnar structure similar to that found in films deposited at low temperature, the simulation produces columns which become elliptic cylinders as the angle of incident vapor flux is increased. The model clearly confirms that this structural anisotropy which develops in the film plane is due to self-shadowing in the growing film. The anisotropy, originally revealed in magnetic and electrical properties of obliquely deposited alloys, appears as the elongation of column structure in a direction perpendicular to the plane of incidence. In agreement with titanium films sputtered using a planar magnetron at 65 mPa argon pressure, simulations show a maximum ratio of column major axis to minor axis of about 2 at a deposition angle of 60-degrees. The effect is seen to decrease in both simulations and real films at higher angles of incidence.