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Ion energy analysis of a bipolar HiPIMS discharge using a retarding field energy analyser

Sep 19, 2022, 2:40 PM
30m
Auditorium

Auditorium

Nb thin film technology Nb thin film technology

Speaker

Felix Walk ((Remote))

Description

The time evolution of the positive ion energy distribution functions (IEDF's) at the substrate position in an asymmetric bipolar high-power impulse magnetron (HiPIMS) system was determined using a gridded energy analyser. This was done for a range of operating conditions, namely the positive voltage Urev and “on-time” negative pulse duration neg. The magnetron sputtering discharge was equipped with a Nb target. Based on the knowledge of the IEDF's, the bombarding ion flux density $\Gamma_i$ and energy flux density $Q_i$ to a grounded surface were calculated. Time-resolved IEDF measurements showed that ions with energies approaching the equivalent of the positive pulse voltage Urev were generated as the reverse positive voltage phase developed.

On time-average, we observed that increasing the set $U_{rev}$ value (from 0 to 100 V), resulted in a marginal decrease in the ion flux density $\Gamma_i$ to the analyser. However, this is accompanied by a 5-fold increase in the ion energy flux density $Q_i$ compared to the unipolar, $U_{rev}$ = 0 V case. Reducing the negative HiPIMS pulse duration neg (from 130 to 40 µs) at a constant discharge power leads to a modest increase in $\Gamma_i$, but a 4-fold increase in $Q_i$. The results reveal the benefit of the bipolar HiPIMS technique, in which it is possible to control and enhance the power density of ions bombarding a grounded (or fixed bias) substrate, for potentially better tailoring of thin film properties.

Primary authors

Felix Walk ((Remote)) James Bradley (University of Liverpool)

Co-author

Reza Valizadeh (STFC)

Presentation materials