Design, plasma studies, and ion assisted thin film growth in an unbalanceddual target magnetron sputtering system with a solenoid coil

An original design and solution to the problem of magnetic field interactio ns in a vacuum chamber between two unbalanced magnetron sputtering sources and a solenoid coil serving to increase plasma density in near substrate po sition, is presented. By changing the solenoid coil current strength and di rection, plasma growth conditions in an argon discharge and Ti-magnetron ca thodes were found to vary in a broad region. Langmuir probe analysis shows that an increase in the coil current from 0 to 6 A caused plasma and substr ate floating potentials to change from - 7 to - 30 V and from + 1 to - 10 V , respectively, as well as increasing the ion densities to a biased substra te from 0.2 to 5.2 mA cm(-2) for each of the magnetrons. By using a ferro-p owder magnetic field model, as well as finite element method analysis, we d emonstrate the interference of the three magnetic fields - those of the two magnetrons and the solenoid coil. X-ray diffraction and transmission elect ron microscopy were used to study the microstructure and morphology of Ti-f ilms grown under different ion bombardment conditions. At low Ar-ion-to-Ti- atom arrival rate ratios, J(ion)/J(n) similar to 1.5, at the substrate, var iations of the ion energy, E-ion, from 8 to 70 eV has only a minor effect o n the microstructure and film preferred crystallographic orientation, resul ting in an open/porous structure with defect-rich grains. At a higher J(ion )/J(n) value of similar to 20, films with a well-defined dense structure we re deposited at ion energies of 80 eV, The increase in ion flux also result ed in changes of the Ti film preferred orientation, from an (0 0 0 2) prefe rred orientation to a mixture of (0 0 0 2) and (1 0 (1) over bar 1) orienta tions. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.