In search for the limits of rotating cylindrical magnetron sputtering W. P. Leroy, S. Mahieu, R. De Gryse, D. Depla DRAFT Dept. Solid State Sciences Ghent University Belgium www.draft.ugent.be
Planar Magnetron Sputtering Major disadvantage = non uniform target erosion shorter campaign time more maintenance less target utilization ~45% Harold E. McKelvey 1982 : A rotatable magnetron sputtering apparatus 2
Rotating Cylindrical Magnetron Magnets N Cooling Water Target 3 Plasma Target (cylindrical tube) rotates around a stationary magnet system, introducing each time different segments of the target into the race-track
Benefits Drawbacks Scaling 4 The benefits of rotating cylindrical magnetrons Better target materials utilization (~80% - 90%) => Longer lifetime & Lower costs Better cooling efficiency allowing higher power densities and consequently higher deposition rates No or little variation in sputtering behaviour due to race track deepening Higher stability in reactive sputtering processes Reduced debris formation
Benefits Drawbacks Scaling The drawbacks of rotating cylindrical magnetrons Complexity of the equipment, which translates itself into cost. Almost always working in unbalanced mode Availability of targets sometimes a nightmare, requiring complex metallurgical techniques Not available on a laboratory scale, i.e. hardly any fundamental research 5 Large sizes for industry for increased substrate-sizes, and hence cost reduction
Benefits Drawbacks Scaling Industrial scale of rotating cylindrical magnetrons ~20cm diam. >2.5m long ~12cm diam >1.6m long 6
Benefits Drawbacks Scaling Small-scaled rotating cylindrical magnetron Down-scaling allows (affordable) fundamental research! changeable ISO-K 100 gear box to water cooling 7 20 cm target in vacuum chamber To power supply
Benefits Drawbacks Scaling Advantage for fundamental research on sputtering Rotating target Dynamic system where the sputtered target surface moves in and out of the racetrack Possible to analyze parts of the target surface, which just come out of the race track 8 Possible to analyze the evolution in time of the target surface Different processes come to light, which also occur for planar magnetrons!
9 A first example: influence of the rotation speed discharge voltage (V V) Reactive magnetron sputtering: hysteresis behavior (Al O) 370 350 330 310 290 270 250 0 1 2 3 oxygen flow (sccm) 0.0 RPM 0.2 RPM 0.6 RPM 0.8 RPM 1.0 RPM 2.0 RPM 4 0 RPM 8.0 RPM 21 RPM 60 RPM Hysteresis shifts to lower oxygen flow on increasing the rotation speed D. Depla, J. Haemers, G. Buyle, R. De Gryse, J. Vac. Sci. Technol. Science A 24 (2006) 934
Influence of the rotation speed Differently plotted: the transition points for each rotation speed 10
The first attempt to model To the target Including : chemisorption knock on implantation The vacuum chamber direct ion implantation q o q t q p 11 dp k T q s To the substrate ( ) B = qo qp qt qs dt V + + To the pump q = P.S p
www.draft.ugent.be 12 New experiments needed! Pre-sputtering a stationary target (Aluminium) in metallic mode and afterwards sputter cleaning in pure argon while rotating (and recording V d ) Discharge Voltage (V) 320 300 280 260 0 100 Start sputtering cleaning 200 Time (s) pre-sputtering in metallic mode X.Y. Li, D. Depla, W.P. Leroy, J. Haemers, R. De Gryse, J. Phys. D: Appl. Phys. 41 (2008) 035203 300 400
The peaks in more detail 360 340 peak 1 peak 2 peak 3 peak 4 www.draft.ugent.be 13 discharge voltage (V) 320 300 280 260 240-2 0 2 4 time (s) 6 8 10 round 13 round 11 round 9 round 7 round 5 More rounds
on the target During pre-sputtering: deposition of material onto the target, which forms an oxide layer 14
www.draft.ugent.be 15 Comparison of the two pre-sputter modes discharge voltage (V) 340 320 300 280 260 240 0 100 200 300 time (s) poisoned mode metallic mode 400 500 In poisoned mode : faster sputter cleaning than in metallic mode Reason : the deposited layer is much thinner because the deposition rate is much lower
Back to the modelling (with redeposition) 16 D. Depla, X.Y. Li, S. Mahieu, K. Van Aeken, W.P. Leroy, J. Haemers, R. De Gryse, A. Bogaerts, J. Appl. Phys. 107 (2010) 113307
How to obtain a good deposition profile? 17 Download the latest version: www.draft.ugent.be K. Van Aeken, S. Mahieu, D. Depla, J. Phys. D.:Appl. Phys. 41 (2008) 205307
A MC code called SImulation of Metal TRAnsport through the gas phase: is a neutral test particle Monte Carlo code designed to simulate the metal flux during magnetron sputter deposition SRIM Geometry Source type energy distr. at target 18 deposition profile, energy & angle arriving particles K. Van Aeken, S. Mahieu, D. Depla, J. Phys. D.:Appl. Phys. 41 (2008) 205307
: making depositions obsolete 19 download it free at www.draft.ugent.be K. Van Aeken, S. Mahieu, D. Depla, J. Phys. D.:Appl. Phys. 41 (2008) 205307
Noble gas retention? Sputtering Ti in Xe/N 2 while examining with in-situ RBS Done at Rossendorf W. Möller T i 20 Steady-state concentration of Xe of 3.4% (Ti) and 9.8% (TiN) found in the race track!! Angular resolved measurements -> no desorption of the Xe! (short time-scale) S. Mahieu, W.P. Leroy, D. Depla, S. Schreiber, W. Möller, APL 93 (2008) 061501
Noble gas retention! Steady-state concentration stable in function of time after sputtering 12 11 Xe % 10 9 8 21 7 0 1 10 100 1000 10000 time (sec) Energy Resolved Mass Spectrometry: Xe-atoms get sputtered from the target! S. Mahieu, W.P. Leroy, D. Depla, S. Schreiber, W. Möller, APL 93 (2008) 061501
effects: detrimental for layers Superconducting films YBCO N S S N S N S N N S S N 22 N S S S N N => negative atomic oxygen? Position 1: transition Position 2 : T c <69 K Position 3 : no Tc
effects: energy distribution of the species Y sputtered in Ar/O 2 Cps (a.u.) 10 5 10 4 10 3 10 2 10 1 0 50 Al sputtered in Ar/O 2 Cps (a.u.) 100 150 E (ev) 10 6 O - 10 5 10 4 10 3 10 2 23 10 1 0 50 100 150 E (ev) O - O 2 - YO 2-200 200 YO - 250 250 AlO - AlO 2-300 300 O 2 - Not only O -, but also O 2-, MO -, MO 2 -
effects: direction of the species Comparison between a planar and a rotatable magnetron -80-70 70 80 24 Masspec Masspec Masspec Masspec -30 30-20 -10 0 20 10-60 -50 Masspec -40-30 -20-10 Measuring the angular distribution of O - ions Masspec 0 Masspec 30 20 10 S. Mahieu, W.P. Leroy, K. Van Aeken, D. Depla J. Appl. Phys. 106 (2009) 093302 40 50 60
effects: angular distribution -80-70 -60-50 -40 Al in Ar/O 2 80 70 60 50 40 25-30 30-20 -10 0 10 20 'O exp' 'O SiMTRA' 'O/Al SiMTRA (a.u.)' 'magnetron' -30-20 -10 0 10 20 30 'O exp' 'O SiMTRA' 'O/Al SiMTRA (a.u.)' 'magnetron' huge difference in behaviour planar rotatable: low amount O - / Al for angles >15 low amount O - / Al for angles >30 AND angles <15 S. Mahieu, W.P. Leroy, K. Van Aeken, D. Depla J. Appl. Phys. 106 (2009) 093302
26 Pushing the limits: on a rotating cylindrical magnetron 6x10 3 Intensity HiPIMS (a.u.) 4 2 0 280 DC HiPIMS 300 Al-target Al (1+) Al (1+) Al (1+) 320 340 360 wavelength (nm) 380 (a) Al (0) Al (0) is possible on rotating cylindrical magnetrons, with increased metal ionization 400 Intensity HiPIMS (a.u.) 2x10 3 1 20x10 3 15x10 3 10x10 3 5x10 3 0x10 3 In ntensity DC (a.u.) DC HiPIMS Ti (1+) 365 370 Wavelength (nm) W. P. Leroy, S. Mahieu, D. Depla, A. P. Ehiasarian, JVST A 28 (2010) 108 360 Ti-target Ti (0) Ti (0) Ti (1+) (b) 375 2x10 3 1x10 3 Intensity DC (a.u.)
on a rotating cylindrical magnetron: angular distributions Measuring the angular distribution of the deposition rate 0 0.002 20 40 DC 5µs 15µs 20µs 27 0.001 0 60 0.001 0.002 Dep Rate / Pav Huge decrease of deposition rate Angular distribution of adparticles looks similar W. P. Leroy, S. Konstantinidis S. Mahieu, R. Snyders, D. Depla, in preparation 80 Preliminary Results
on a rotating cylindrical magnetron: angular distributions Measuring the angular distribution of the total Energy Flux 0.3 0 20 0.25 0.2 40 DC 5µs 15µs 15µs 28 0.15 0.1 0.05 0 60 0.05 0.1 0.15 0.2 0.25 0.3 Total energy Flux (a.u.) Only limited drop in total energy flux Change in the angular distribution W. P. Leroy, S. Konstantinidis S. Mahieu, R. Snyders, D. Depla, in preparation 80 Preliminary Results
Small-scaled rotating cylindrical magnetron enables (affordable) fundamental research 340 discharge voltage (V) 320 300 280 260 240 0 100 200 300 time (s) poisoned mode metallic mode 400 500 plays an important role in the reactive behaviour of magnetrons (both rotatable as planar) www.draft.ugent.be 29 can be used to simulate any deposition profile in any possible set-up
30 Xe % 12 11 10 9 8 7 0 1 10 100 1000 10000 time (sec) -80-70 -60 0 0.3 0.25 0.2 0.15 0.1 0.05 0-50 -40-30 -20-10 0 10 20 30 40 'O exp' 'O SiMTRA' 'O/Al SiMTRA (a.u.)' 'magnetron' 20 40 DC 5µs 15µs 15µs 60 80 0.05 0.1 0.15 0.2 0.25 0.3 Total energy Flux (a.u.) 50 60 70 80 Noble gas atoms are retained within the target Angular distribution of (detrimental) negative species is very different for planar and rotatable is possible on a rotatable and angular resolved measurements can give more fundamental insights in
Acknowledgements Financial Support: A.P. Ehiasarian (SHU) S. Konstantinidis & R. Snyders (UMH) DRAFT colleagues: 31 www.draft.ugent.be
JOIN US at RSD2010 in Ghent!!! RSD 2010 International Conference on Reactive Sputter Deposition 9 & 10 December 2010 Ghent, Belgium 32 * Ion - Solid Interactions Invited Speaker: prof. dr. W. Möller Keynote Speaker: prof. dr. S. Lucas * Stress in polycrystalline films Invited Speaker: prof. dr. E. Chason Keynote Speaker: prof. dr. G. Abadias * Smart Coatings Invited Speaker: prof. dr. Matthias Wuttig Keynote Speaker: prof. dr. A. Billard * Pulsed Plasmas Invited Speaker: prof. dr. U. Helmersson Keynote Speaker: dr. Stephanos www.rsd2010.be