Pulsed DC magnetron sputter deposition is widely used for

							TIME AND ENERGY-RESOLVED MASS SPECTROMETRY ON PULSED-
MAGNETRON PLASMA

JW Bradley, H Bäcker, S Karkari and PJ Kelly*

Dept. of Physics, UMIST, Sackville St. Manchester, M60 1QD, UK
*Institute for Materials Research, University of Salford, M5 4WT, UK


Pulsed plasmas are now of great interest within the academic and industrial
communities. One area in which the pulse technique (frequency range 20-350 kHz)
has been of great benefit is in reactive magnetron sputtering. However, these devices
have not been explored in detail.

In this study we measure the time and energy resolved mass spectra of the ionic
species in a pulsed magnetron discharge (frequencies 20-100 kHz). We have
developed a new technique that allows us the measure with a time resolution of 2 µs
the evolution of the energy and flux of ions (e.g. Ar+, and Ti+) at a material substrate.
The mass spectrometer (Hiden EQP 300) has a specially made end-cap containing two
fine meshes fixed to the front barrel. Through the synchronized application of bias
potentials to the meshes the ions can be electro-statically gated to obtain time resolved
spectra.

The results show that in the initial pulse phase, when the power supply turns from
‘on’ to ‘off’, a large positive voltage overshoot (V1 ∼ +180 V) in the discharge
waveform leads to the generation of a significant number of both Ar+ and ionised
sputtered species at high plasma potentials (> 150 V, lasting for about 1 µs). In the
positive reverse phase, (cathode potential typically V2 ∼ +50 V) ions are detected with
energies of about 20-50 eV, as the plasma potential is lifted up throughout the
discharge. In the ‘on’ phase, (cathode voltage V3 ∼ -400V) ions are detected with
energy distributions similar to those in the DC magnetron. The significance of these
results is discussed.