EXPERIMENTAL AND THEORETICAL-STUDIES OF COATING THICKNESS DISTRIBUTIONS OBTAINED FROM HIGH-RATE ELECTRON-BEAM EVAPORATION SOURCES

The study of the thickness distribution of thin films achieved by an e lectron beam evaporation source is the main purpose of this work. The different parameters which play a rule in the estimation of the coatin g deposition rate for substrates fixed throughout the deposition chamb er are discussed. Three main parameters will be considered: the positi on of the substrate in relation to the evaporation source, the shape o f this source and the space distribution of the evaporated atoms. Whil e the influence of the first two parameters is well known, the effect of the spatial distribution of the vapor beam is considerably less so. Based on previous results showing that, at high evaporation rates, th e distribution of vapour atom velocities does not follow a Maxwell for m, it was possible to justify the experimental thickness distribution obtained on the entire half space over the vapour source. It is also s hown in this paper that the incidence angle of the atoms deposited on the growing film plays an important rule on the film growth mode, lead ing to an important change in its specific gravity. This variation of specific gravity must be taken into account to correctly predict the d eposition rate for any fixed point on the substrate located anywhere i n the vacuum chamber. Finally, it was shown that these analytical mode ls can be applied to the deposition of different materials such as cop per or titanium and even, for a material like chromium that sublimates below the path of the electron beam. For this last case, a Monte Carl o simulation study of the atom emission from the vapour source was nec essary to fit the experimental thickness distribution. (C) 1997 Elsevi er Science S.A.