The temperature of a substrate, while the covering is drawing on it’s surface, страница 9

5. Influence of working parameters of technological installation on the dispersion process

Process of cathode dispersion lies in dislodging of neutral particles from the surface of the cathode - target by the accelerated ions. In the previous section process of ionization and acceleration of the charged particles in intercathode space has been considered. In the given section the process of dispersion of the cathode surface will be considered, the influence of working parameters of technological installation on process of dispersion is determined; the dependence of dispersion coefficient on the energy, hade of bombarding particles, working pressure, temperatures of the cathode – target. Various expressions for definition of the dispersion coefficient will be also considered.

5.1 Dependence of the dispersion coefficient on the energy of bombarding particles

There are very many factors which influence on quantity of the atoms which are beaten out by ions from the firm body, that is the dispersion coefficient. We shall consider dependence of the dispersion coefficient on the energy of ionsS(Ei).

Dispersion of the material is observed at the energies of ions more than threshold energy. Threshold energy Еt is understood as the minimal energy. The ion possessing it can beat out atom from the firm body. Threshold energy of dispersion of various materials with the help of ions of various working gases are resulted in table 5.1 [47, 78].

By consideration of dependence of the dispersion coefficient from the energy of ions allocate the following areas: area of threshold energies (Еi <100 eV), area of small energies (Еi=0,1_... 1 keV), area of average energies (Еi =1 … 200 keV), dispersion by splinters of nucleus (Еi> 200keV).

As energy of ions of working gas in magnetron sputtering systems lay in a range 300 … 700 eV we shall stop on consideration of dependence of the dispersion coefficient in the range, which is interesting to us.

Apparently from table 5.1, thresholds of dispersion don’t strongly differ for very different grades of target materials. Nevertheless, the appreciable divergence in speed of increase in the dispersion coefficient S of different materials with increase of energy of primary ions is observed. Function S (Еi) at dispersion by ions of any certain grade can find out appreciable dependence on energy of ions Еi.

Table 5.1 Threshold energy of dispersion of various materials, eV