Characterization of the energy flux toward the substrate during magnetron sputter deposition of ZnO thin films

Abstract

The characterization of energy influxes from plasma to substrate during sputter deposition of ZnO films is presented and discussed. Measurements were carried out in a triple rf magnetron sputter deposition system using calorimetric probes in various Ar/N 2 and Ar/H 2 mixtures at typical substrate positions. By variation of the probe bias the different contributions originating from the kinetic energy of charge carriers, the recombination of charge carriers (electrons and ions) at the surface as well as the contributions from the impact of neutral sputtered particles and subsequent film growth were determined. Radial scans in the substrate plane were recorded to obtain information about inhomogeneities in the total energy influx.The results show that the crystallinity reaches its optimum at that Ar/N 2 ratio where the influence of the bombarding ions reaches its lowest value, indicating the destructive character of ion impact. Radial measurements indicate the influence of the magnetic field on the homogeneity of the energy influx caused by the superposition of the three (balanced) magnetic configurations. The superposition leads to an 'unbalanced character' resulting in a lowering of the electron trapping. The admixture of H 2 leads to a drastic increase in the energy influx due to molecule formation at the (substrate/probe) surface.

On the Impact of Electron Temperature in Magnetron Sputtering Benchmarked with Energy Flux Measurements

“…In addition, it is also reported that different contributions have different impact, depending on if the energy transfer is connected to momentum transfer by kinetic impact of ions and fast neutrals or if it is caused by surface processes like recombination, molecule formation and film growth. Especially ion bombardment is known to be crucial for optimizing the film properties [31,32]. Since the energy balance depends on the process gas, because plasma parameters and sputter yields vary, we have also taken a closer look at the different contributions caused by electrons, ions, electron-ion recombination, impact of sputtered neutrals, and film growth, as previously described in section 2.3.…”

MgH 2 thin films deposited by one-step reactive plasma sputtering

“…However, a further increase of the H 2 partial pressure up to 0.28 Pa does not lead to an increase of the MgH 2 content (66%). The reduced % MgH 2 with higher H 2 partial pressure may be due to an increase in the energy deposition through H recombination on the surface [16,17]. A comprehensive description and quantitative assessment of the changes in particle fluxes and carried energy depending on the plasma parameters has been carried out.…”

Calorimetric Probes for Energy Flux Measurements in Process Plasmas

“…Of course the maximum energy of the ions is also determined by the sheath potential, but the mean energy is well below that value. It has recently been shown, that the mean kinetic energy is in the range of 0.3 − 0.5 · Φ sh [74,75]. • When they are formed in the bulk plasma they are attracted to the most dense region where the plasma potential has its most positive value.…”