On the energy in¯ux to the substrate during sputter deposition of thin aluminium ®lms H. Kersten a, * , G.M.W. Kroesen b , R. Hippler a a University of Greifswald, Department of Physics, 17487 Greifswald, Germany b Eindhoven University of Technology, Department of Physics, 5600MB Eindhoven, The Netherlands. Abstract The integral energy in¯ux during sputtering of thin aluminium ®lms onto silicon wafers as well as onto small micro-disperse iron powder particles has been determined to be in the order of 0.02±0.2 J/cm 2 s depending on the discharge power (10±100 W) and the target-to-substrate distance (15±4 cm). The thermal power at the substrate consists mainly of the kinetic energy of charge carriers and sputtered particles, and the released condensation heat. The contribution due to ®lm condensation is determined by the deposition rate and the speci®c heat of condensation. The rather small contribution of the electrons was measured by SEERS and Langmuir-probes, whereas the in¯uence of the ions as well as of the sputtered particles on the energy balance was studied by energy-resolved mass spectrometry. The measured integral energy in¯ux which has been determined from the increase of the substrate temperature at the sputtering process is in good accordance with the sum of the various contributions calculated by simple model assumptions. The observed differences in the microstructure between Al- ®lms deposited on large silicon wafers and those ®lms deposited on small iron powder particles can be explained by differences in the thermal balance due to the energy ¯uxes during the plasma process. q 1998 Elsevier Science S.A. All rights reserved. Keywords: Energy in¯ux; Thermal power; Magnetron sputtering; Powder processing 1. Introduction Thin ®lm coatings play an important role for improving the properties of a great variety of materials. Among the several commercially available systems magnetron sputter- ing sources are often employed. A characteristic feature of thin ®lm deposition by magnetron sputtering in comparison to thermal evaporation is the higher kinetic energy of the particles arriving at the substrate. The integral energy in¯ux (J in ) during sputtering in¯uences the thermal conditions at the substrate surface and, hence, in addition to momentum transfer it effects the microstructure and morphology as well as adhesion and residual stress of the deposited ®lms [1,2]. In the present study the effect of the energy in¯ux on the microstructure of thin aluminium ®lms deposited on ¯at silicon wafers as well as on small micro-disperse iron powder particles has been investigated. Film deposition on con®ned powders by magnetron sputtering is a rather new technology. There exists various perspectives for plasma- modi®ed powder particles, e.g. for chemical catalysis (large speci®c surfaces) and for the enhancement of optical, mechanical, and thermal properties of small particles (pigments, toners). Under our experimental conditions, the measured integral energy in¯ux (thermal power), which has been determined from the rise of the substrate temperature (T S ) during the sputtering process, consists mainly of the kinetic energy of charge carriers and sputtered particles, and the released condensation heat. The contribution of ions (J ion ) and elec- trons (J e ) can be distinguished by variation of the substrate potential. For suf®ciently negative substrate potentials (V sub ! V pl , V pl : plasma potential) the ions of the inert gas (Ar 1 ) and the ionized sputter material (Al 1 ) are accel- erated in the potential drop in front of the substrate. On the other hand, for V sub ,0 the contribution of the electrons, which depends also from the kind of the electron energy distribution function (EEDF), becomes more important. The effect of sputtered particles (J n ) on the energy balance is estimated by the product of their ¯ux density and their mean kinetic energy which has been determined from the energy distribution of the sputtered species. Finally, the contribution J c due to the condensation of aluminium particles has been determined by measuring the deposition rate and knowledge of the speci®c heat of condensation. Thin Solid Films 332 (1998) 282±289 0040-6090/98/$ - see front matter q 1998 Elsevier Science S.A. All rights reserved. PII S0040-6090(98)01067-0 * Corresponding author Tel.:100 49 3834 864782; fax:100 49 3834864701; e-mail: kersten@physik.uni-greifswald.de.