Gregory ClarkeTechnological Plasmas Research Group Time resolved diagnostics for pulsed magnetron plasmas

Gregory ClarkeTechnological Plasmas Research Group Magnetrons Magnetron Variable magnetic field Substrates Glass, polymers, metals etc Target Metallic and semi-conducting Pulsed DC Power supply Frequencies 0 – 350 kHz Chamber Gases Mixtures of Ar, O 2, N 2 etc N S S N N S

Gregory ClarkeTechnological Plasmas Research Group Analysis techniques Probes: –Electrical: Langmuir, double, triple, emissive –Energy: Thermal –Magnetic field: B-dot Optical emission spectroscopy Film characteristics: Structure, topography, composition Optical imaging Energy resolved mass spectroscopy

Gregory ClarkeTechnological Plasmas Research Group Optical imaging ICCD camera fitted with a zoom lens Observe different species by the use of filters Short exposure times (50 ns) Sweep exposure window through pulse cycle Record temporal and spatial evolution Purpose: To observe the effect of the driving voltage waveform on the spatial and temporal distribution of emission from plasma Magnetron Substrate ICCD Camera P C Window Target Filters Power supply Oscilloscope Delay generator Chamber

Gregory ClarkeTechnological Plasmas Research Group Filters Several optical filters were employed. Optical emission spectroscopy performed to identify the spectral lines within the bandwidth of each filter. Filter with a central wavelength of 750 nm, chosen so as to observe two transitions in argon neutrals.

Gregory ClarkeTechnological Plasmas Research Group Sample image Cathode Substrate The red box represents the temporal location when the data recorded

Gregory ClarkeTechnological Plasmas Research Group Movie: Raw data

Gregory ClarkeTechnological Plasmas Research Group Optical imaging: Abel inversion Technique: Data collected along ‘line of sight’ can be used to produce radial profiles where, E(r) = emissivity of the plasma I (y) = line integrated intensity R = radius of the plasma y = displacement of the intensity profile r = radial distance from the axis of symmetry Central axis Standard two dimensional images can be processed to produce radial profiles that are perpendicular to the line of sight Plasma cathode r y R

Gregory ClarkeTechnological Plasmas Research Group Movie: Abel inverted data

Gregory ClarkeTechnological Plasmas Research Group Detached region  m Normalised emissivity (arb units) Axial distance z (mm) Emissivity ‘Cold’ electron density Electron density plots courtesy of Dr. Alena Vetushka

Gregory ClarkeTechnological Plasmas Research Group Energy resolved mass spectroscopy Energy resolved mass analyser modified to enable time resolved measurements Argon ion energy distribution functions recorded throughout the duration of the pulse cycle Exposure time of 1  s Sweep exposure window through pulse cycle Purpose: To observe the effect of the driving voltage waveform on the ion energy distribution functions (IEDF’s) of argon ions arriving at the substrate mass spectrometer substratemagnetron target chamber central axis of chamber

Gregory ClarkeTechnological Plasmas Research Group Movie: IEDF 1 Data recorded using: 1  s steps between successive data sets

Gregory ClarkeTechnological Plasmas Research Group Movie: IEDF 2 Data recorded using: 100 ns steps between successive data sets

Gregory ClarkeTechnological Plasmas Research Group Method of production ? Time dependent variation in plasma potential assessed via emissive probe

Gregory ClarkeTechnological Plasmas Research Group Conclusions Imaging –Yield information on the structure of the discharge –The presence of different electron energy groups Time and energy resolved mass spectroscopy –Record the temporal variation in the energy of ions arriving at the substrate –Results suggest methods of production Results are in agreement with those suggested by other techniques

Gregory ClarkeTechnological Plasmas Research Group Acknowledgements o EPSRC o Dr Alena Vetushka (probe measurements) o Dr Paul Bryant (Abel inversion) o Prof Nick Braithwaite o Mr Alan Roby