INFLUENCE OF CHARGE-EXCHANGE ON ION-NEUTRAL ARRIVAL RATES IN AN ION-ASSISTED DEPOSITION SYSTEM

During ion-assisted deposition of TiN using Kaufman sources the pressure in the substrate chamber can rise to about 10(-2) Pa. This leads to charge-exchange collisions and as a result, a component of fast neutral atoms in the energetic beam. This paper considers the transport of 100-500 eV Ar+ or N2+ ions through a gas mixture of argon and nitrogen of known composition. Charge exchange cross sections for N2+ --> N2, Ar+ --> Ar, Ar+ --> N2, and N2+ --> Ar reactions have been used to calculate the neutral component of the beam. The results show that the neutral component is only weakly dependent on the primary ion energies and ion species. The magnitude of this component for a constant total pressure of 3 x 10(-2) Pa varies between 10% and 60% as the partial pressures of nitrogen (and argon) vary between 1 and 3 x 10(-2) Pa.