HiPIMS Deposition of Metal and Oxide Coatings

Transcription

1 HiPIMS Deposition of Metal and Oxide Coatings 1 GT West, 1 PJ Kelly, 1 P Barker, 2 JW Bradley and 2 A Mishra 1. Surface Engineering Group, Manchester Metropolitan University, UK 2. Electrical Engineering and Electronics, University of Liverpool, UK HiPIMS Workshop - Colorado School of Mines, 2010

2 Presentation Overview Introduction to our Equipment Deposition Rate, Substrate Temperature and Plasma Potential Reactive HiPIMS and Process Control Oxide Coating Properties Discussion and Conclusions

3 HiPIMS Power Delivery System 0 50 Hz, 0.5 kw, Ti Target, Ar G as, 100 us P uls e Time V oltage, v

4 HiPIMS target waveforms Voltage, V Power (kw) and Current (A) Time, us Voltage (V) Current (A) Power (kw) -10

5 Substrate Floating Potential Waveform - HiPIMS

6 Gencoa HiPIMS Magnetron and Drum Rotatable Substrate Holder HiPIMS Magnetron

7 Thermal Energy Flux to Substrate 1. Thermal flux probe:- (a) Material Copper (b) Probe diameter 24 mm (c) Thermal capacity 3.1 J/K 2. Deposition rate monitor:- (a) Model Maxtek TM400 (b) Crystal Silver (c) Frequency 6 MHz

8 Experimental Procedure: Previous studies Thermocouple Copper disc Central axis of chamber Ceramic block Langmuir probe Stainless steel plate Ceramic tube Substrate mount Insulator To electrical Feed through Charged particles contribute >70% to thermal flux at substrate in pulsed DC mode M Čada, JW Bradley, GCB Clarke and PJ Kelly Study of the particle power density at an isolated substrate in a pulsed DC magnetron discharge, submitted to J. Appl. Phys.

9 Temporal evolution of thermal energy Substrate power flux, P = dt/dt. Cp/A

10 Operational parameters 1. Operating pressure Pa 2. Average power 680 W 3. Target material Titanium (150mm circular planar) 4. Sputtering gas Argon 5. Location of probes 100mm above the race-track and parallel to discharge centreline 6. Mode of operation 1. DC, 100 KHz and 350 KHz with 50% duty factor 2. HiPIMS 75 Hz, 100 Hz and 150 Hz 7. Four magnetic field strengths 260, 320, 380, 440 G

11 Deposition rate in DC and Pulsed DC Magnetic Field Strength (G) 260

12 Deposition rate in HiPIMS Magnetic Field Strength (G)

13 Comparison of Thermal flux in DC, pulsed DC and HiPIMS discharges Magnetic Field Strength (G)

14 Thermal flux/deposition rate Magnetic Field Strength (G)

15 Summary of Thermal Flux/Dep. Rate Study 1. Thermal flux and deposition rate measurements were carried out in DC, pulsed DC and in HiPIMS mode in four different magnetic field configurations. 2. Deposition rate in HiPIMS increased with decreasing magnetic field, however it decreased in DC and pulsed DC mode. 3. Deposition rate increased with frequency in HiPIMS mode, however it decreased with increasing frequency in pulsed DC mode. 4. It was observed that the thermal flux in HiPIMS mode is considerably lower compared to DC and pulsed DC discharge. 5. Thermal flux/deposition rate decreased with magnetic field strength in HiPIMS mode, however it increased in DC and pulsed modes of operations.

16 Substrate Temperature Substrate Temperature, C HiPIMS DC Time-Averaged Power, kw

17 XRD spectrum of Titanium grown via DC magnetron sputtering counts (002) Theta

18 XRD spectrum of Titanium grown via HiPIMS at 1kHz counts (002) Theta

19 XRD spectrum of Titanium grown via HiPIMS at 250 Hz counts (010) (002) Theta

20 Plasma Potential of HiPIMS Discharges

21 Reactive Sputtering and Process Control in HiPIMS

22 A New Route to High-Performance Functional Films on Polymeric Web

23 Project Aims To deposit high quality TCO coatings on PET/PEN web using HIPIMS in a lab-scale system at MMU, then a pilot-scale reel-toreel system at Oxford. Perform diagnostic study of HIPIMS discharge

24 HiPIMS Characteristics Ave Voltage (50 Hz, 200 µs)

25 Hysteresis Behaviour: ZnO:Al HiPIMS Characteristics Peak Voltage HiPIMS Characteristics Time Average Voltage

26 ZnO:Al Hysteresis in HiPIMS Peak Voltage, V(-ve) O2 increases O2 decreases Oxygen Flow, (arb units)

27 Hysteresis dependency on deposition rate and pumping speed may explain why it is not always observed in HiPIMS

28 Process Control: OEM Megatech - Reactaflo closed-loop feedback system Monitors metal emission lines Fibre optic probe, monochromator, fastresponse piezo valve Poor signal with HiPIMS discharge

29 Process Control: V T Monitor change in voltage as target poisons Target age/condition varies voltage over time Unstable discharge in HiPIMS means operating voltage changes from run to run (10 s of V) Unable to give suitable control without hysteresis analysis before every coating run

30 Process Control: P Partial Feedback from Baratron gauge Control via fast-response m.f.c. Low deposition rate for HiPIMS Low oxygen flow could not be controlled Technically feasible, method in use elsewhere

31 Process Control: OEM Revisited Gencoa Speedflo - HiPIMS Better signal for HiPIMS than standard systems Monitors ion emission lines via filters Worked well with Ti ions Problems with Zn ion emission f.m.s. reduces to minimum, then increases! Monitor oxygen instead

32 Titania Coatings TiO 2 coatings deposited onto glass DC, pulsed-dc and HiPIMS discharges at different frequencies (same pulse-width) Equal time-averaged powers OEM process control

33 Raman Spectra for TiO 2 films DC Pulsed-DC Counts HiPIMS Rutile Anatase Raman Shift/cm shift / cm-1-1

34 Raman Spectra for TiO 2 films 48 Hz 200 Hz Counts 248 Hz Rutile Raman shift / cm-1 Raman Shift/cm -1

35 Conclusions HiPIMS deposition rate increases with reduced magnetic field strength Energy delivery per unit deposition can be increased via HiPIMS Substrate temperatures remain low Potential Well present in plasma extending beyond target

36 Conclusions Reactive HiPIMS Hysteresis is seen for reactive deposition in HiPIMS dependent on equipment Partial pressure control possible, but also dependent on coating system OEM demonstrated to effectively control deposition process Film properties modified in both metallic and reactive HiPIMS deposition modes