A SPATIAL-DISTRIBUTION STUDY OF A BEAM VAPOR EMITTED BY ELECTRON-BEAM-HEATED EVAPORATION SOURCES

This work reports a study of the spatial distribution of atoms evapora ted under vacuum and its influence on the thickness distribution of me tallic films achieved by this technique. Its goal is to justify the (c os theta)(n) law which has been introduced in an empirical way to expl ain the thickness distribution obtained when the evaporation rates are high. Taking into account a collision region just above the vapour so urce, it is possible to determine a new distribution of vapour atom ve locities which is no longer a Maxwell form. The spatial distribution o f the vapour beam was deduced and then it was fitted experimentally. T he comparison between this new distribution function and that deduced from the (cos theta)(n) law leads to a relation able to determine the constant n. This relation shows that the constant n tends to a limitin g value when the evaporation rate increases, whatever the metal evapor ated. These results were verified when the thickness distribution mode ls were compared with these obtained experimentally for three differen t metals (Ti, Cu and Al).