The paper draws on the results of modeling the process of dust particles size changing during their transportation from the synthesis area to the substrate. It is considered the process of particle size changing as a result of coagulation which occurs by their movement in the non-homogeneous electric field. It is given the problem statement and the solution method, which enable to calculate the formation of coating defects – large spherical particles of a micron size. The parametrical research of size distribution of agglomerates is conducted and it depends on the depth of the potential well, reagent consumption and carrier gas.