Vacuum plasma technology HiPIMS Technology: advantages and disadvantages Cr - DC Cr - HiPIMS Alessandro Patelli alessandro.patelli@venetonanotech.it
Outline 1. What is HiPIMS Ti target surface 2. What is promised in literature Adhesion promotion Complex shaped substrates Morphology Reactive processes Drawbacks 3. Veneto Nanotech experience Metals TiO2 ZrSiN / NbN TiC 4. Conclusions
Current (ka) HiPIMS: what it is P DC t HiPIMS is a pulsed sputtering process where peak power exceeds of 2 orders of magnitude the mean power HiPIMS is a pulsed sputtering process where a significatve fraction of sputtered atoms is ionised Ar, Ar +, Ti Anders, A. Surface and Coatings Technology 2011. P HiPIMS t 7 6 5 4 3 100 0-100 -200-300 -400 Voltage (V) 2-500 Ar, Ar +, Ar 2+ Ti, Ti +, Ti 2+ 1 0-0,1 0 0,1 0,2 0,3 time (ms) -600-700 -800
Ionised species Cr metal mode CrN reactive mode M. Hala et al., Journal of Applied Physics 107 (2010 )
Ionised species Ulf Helmersson Linköping University, Sweden
Different HiPIMS Cathode voltage Peak current density Peak power density Peak plasma density Ionisation ratio HiPIMS 600-2000 V 0.5-5 A/cm 2 0.5-3 KW/cm 2 10 18 m -3 up to 90% DC 300-700 V < 0.1 A/cm 2 < 50 W/cm 2 10 15 m -3 up to 1% Heuttinger - TruPlasma Highpulse Series 4000 ZPULSER CYPRIUM Melec - SIPP2000IPC- HPPMS Solvix HiPIMS (AE) Cemecon / Chemfilt - Sinex
Adhesion promotion CrN/NbN multilayers When HPPMS is used for substrate etching, the bombarding metal ions are subplanted into the substrate forming a film/substrate interface with thicknesses ranging between 5 and 15 nm A.P. Ehiasarian, J.G. Wen, I. Petrov, J. Appl. Phys. 101 (2007) 054301 Nb HPPMS Biasing -1000V
Complex shaped substrates TiAlN coating deposited on the flank and the rake side of a cutting insert Cu K. Bobzin, et al., J. Mater. Process. Technol. 209 (2008) 165 V. Kouznetsov, et al., Surf. Coat. Technol. 122 (1999) 290.
Microstructure HiPIMS CrN dense polycrystalline J. Alami et al., J. Phys. D: Appl. Phys. 42 (2009) 015304 nanocrystalline featureless
Reactive HiPIMS Al 2 O 3 E. Wallin, U. Helmersson, Thin Solid Films 516 (2008) 6398 It is seen that the dcms process exhibits an unstable transition zone with pronounced hysteresis. On the contrary the HPPMS process (filled circles for both increasing and decreasing O 2 flow) is stable and hysteresis free.
Drawbacks - Deposition rate Ti K. Sarakinos et al., Surface & Coatings Technology 204 (2010) 1661 1684 DC HiPIMS 200 Hz 500 Hz
Drawback - Arcing Carbon content increase More frequent when operated in reactive mode Depends on configuration and energy stored in the generators and cables In industrial applications the presence of arcs should be carefully avoided, and much effort has been dedicated to develop sophisticated arc detection and suppression, integrated in modern HiPIMS power supplies.
Veneto Nanotech Equipment Thin Films 2 axis rotating sampleholder DC+RF biasable Customizable motion Base vacuum 1 10-7 mbar Optical fibre and feedback for reactive sputtering 4 cathodes 4,9 12,5 1/4 2 DC 3KW + 1 HiPIMS 10kW 2 pulsed DC (up to 250kHz) 3KW Dep. rate about 10 µm/h for metals and 2 µm/h for ceramics Chamber volume about 0.7 m 3
Metals DC HiPIMS Cr Cr The high power pulsed magnetron sputtering allows denser coatings Good complex shapes coverage On plastics Increased adhesion Smoother shiny surfaces Pay attention on heating
HiPIMS TiO2 - process Ion fraction depends on peak power The hysteresys is smaller but depends on pulsing frequency
HiPIMS TiO2 coatings properties Tougher films Increased refractive index HiPIMS 200Hz rutile HiPIMS 500Hz anatase / rutile DC amorphous / anatase
HiPIMS ZrSiN - process Zr 0.9 Si 0.1 target Ar 5.3 x 10-3 mbar OES
HiPIMS ZrSiN - Crystal structure GIXRD (2 deg) HiPIMS Amorphous overstoichiometry Zr 3 N 4 5 n m Only ZrN phase is visible Crystal size 8 15 nm Biased samples lower peak intensity HiPIMS N 2 13 sccm : amorphous No heavy changes in texture on flux and bias Overstoichiometry Increasing Si content: (200) shift to higher angles Inhibit (111) plane growth Formation of amorphous Si 3 N 4 phase Si in ZrN in interstitial position D. Pilloud et al. SCT 180-181 (2004) 352
HiPIMS NbN - Crystal structure GIXRD (2 deg) GIXRD DC GIXRD HiPIMS N/Nb = 1,03 22 sccm N/Nb = 0,97 14 sccm N/Nb = 1,00 20 sccm N/Nb = 0,76 12 sccm N/Nb = 1,00 18 sccm N/Nb = 1,00 16 sccm N/Nb = 0,76 10 sccm With HiPIMS overstoichimetric crystal phases not present indc can be achieved Nb 5 N 6
nc a-c/tic - HiPIMS Reactive sputtering: Optical emission spectroscopy characterization (sccm) DC: avarage power: 3,5W/cm 2 HiPIMS: peak power: 600 W/cm 2 same average power between DC and HiPIMS (sccm) Ar 0 sccm C 2 H 2 H emission line * H emission line * With C 2 H 2 No peak at 434.07 nm detected * T. Acsente, et al., Surf Coat. Technol. (2011). Doi:10,1016/j.surfcoat,2011,03,085 Ti + and Ti 0 intensity decreases with increasing C 2 H 2 flow Peak at 434.07 nm detected and seems increase by increasing C 2 H 2 flow
Carbon sites occupancy In HiPIMS higher surface energy and lower H and O content leads to an enhancement of TiC stoichiometric growth Increasing the carbon content microstrain increases
nc a-c/tic - HiPIMS TiC nanocrystals in C amorphous matrix Low temperature deposition (50 C) COF and hardness depends on C content No BIAS
Self lubricant coatings HRTEM C/Ti = 1.1 FFT 2.15 Å nc-tic HiPIMS 2.49 Å TiC (111) 0.249 nm TiC (200) 0.215 nm 5 n m Densely packed TiC grains with size about 10 nm surrounded by small amorphous (C) regions HPPMS High adhesion
Conclusions HiPIMS is a new tool for coatings deposition Mainly costs an deposition rates focus its application in fields where the performances of its coatings is needed Application studies started from mechanical coatings But: Optics Fuel cells Photovoltaic Self-cleaning Nuclear
Acknowledgements Thank you for the attention! Veneto Nanotech researchers M. Colasuonno R. Olivotto for funding
Microstructure A. Anders, Thin Solid Films 518,15 (2010 ), pp. 4087