MEASUREMENT OF THE ANGULAR-DISTRIBUTION OF SPUTTERED NEUTRALS IN A PLANAR MAGNETRON GEOMETRY

In the low temperature regime (T<0.3T(m)), the microstructure of sputt ered films is determined predominantly by the mechanisms of self-shado wing. Shadowing effects are directly related to the angular distributi on of incoming sputtered particles. The angular distributions of coppe r and lead particles sputtered by Ar+ ions in a planar magnetron geome try were measured using a differentially pumped pinhole camera. The pr essure in the pinhole camera was lower by a factor of 10 compared to t he ambient working gas. Thus it was possible to monitor the angular di stribution of the incoming sputter particles for working gas pressures up to 4 Pa. Transparent films of the impinging particles were deposit ed on semicircular transparent substrates. Their relative thicknesses were measured by optical densitometry, giving a direct representation of the angular distribution at aa arbitrarily chosen point of the sput ter chamber. A comparison of the measured angular distributions with d istributions calculated for the particular geometry of the experimenta l setup under neglection of gas phase scattering shows that for low ga s pressures, the angular distribution is determined mainly by the shap e of the target erosion zone, which implies a significant deviation fr om isotropy. Increasing the gas pressure leads to a broadening of the angular distributions towards isotropy of particle incidence. Nonethel ess, the geometry of the erosion zone still has a measurable influence on the shape of the distribution.