On the energy influx to the substrate during sputter deposition of thin aluminium films

Abstract

The integral energy influx during sputtering of thin aluminium films 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/cm2 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 film condensation is determined by the deposition rate and the specific heat of condensation. The rather small contribution of the electrons was measured by SEERS and Langmuir-probes, whereas the influence 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 influx 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-films deposited on large silicon wafers and those films deposited on small iron powder particles can be explained by differences in the thermal balance due to the energy fluxes during the plasma process.