Linear Plasma Sources for Surface Modification and Deposition for Large Area Coating Dr Tony Williams Gencoa Ltd, UK Victor Bellido-Gonzalez, Dr Dermot Monaghan, Dr Joseph Brindley, Robert Brown SVC 2016, Indianapolis, IL, USA L-8 (Wed 11 th May 2016 @ 9:40am)
Current source technology summary Five DC, AC & Hipims source examples for large areas The case for pre-treatment / deposition with self - regulating smart operation Conclusions 2
Linear Plasma Sources for Surface Modification and Deposition for Large Area Coating Dr Tony Williams Gencoa Ltd 3
Plasma Pre-treatment & Deposition Products for Large Areas A wide variety of different source technologies exist depending upon need Focus of this presentation Plasma Treatment Product Categories: DC linear ion sources DC magnetron based plasma treaters AC type dual electrode plasma sources AC type plasma CVD sources Hipps + positive beam ion etching DC or pulsed DC inverse sputter box DC or AC hollow cathode Microwave & RF linear source technology Application / typical current uses Low speed web & glass Low to High speed / power web Low to High speed / power web PECVD deposition web or glass Etching of metallic substrates Etching of metallic substrates Low to High speed / power web PECVD mainly solar cells hard to scale / high cost
DC Linear ion sources Plasma Treatment Sources
Linear ion sources are typically used to pre-treat before sputter coating scalable robust devices based upon DC power Linear ion sources are a powerful means to improve coating adhesion and device performance - liberates moisture and burn-off hydrocarbons. The linear ions sources work at sputtering pressures and with low substrate speeds of <5m/min. Automatic gas feedback control via the DC power supply makes operation much more simple self-regulated beams that adapts to chamber conditions.
Main advantage is easy scaling and simple operation
Easy to scale - Internal mounting im4700 worlds longest linear ion source 4.7m long beam length
Elcometer abrasion test (ISO 11998) Ion pre-treatment is a powerful means to improve coating adhesion and device performance Abrasion resistance of coatings Rubbing in wet conditions Load: 100 gr. No. Cycles: 500 Comparative results of coating with and without ion beam pre-treatment Results of single pass plasma pre-treat Sample without ion-beam pretreatment Sample treated by ion beam NREL
Comparison of tempered glass with and without the use of a single pass plasma pre-treat with linear ion source Parallel on-axis in-lens secondary electron detection Sample not treated by ion beam Sample with ion-beam pre-treatment Samples without ion beam pretreatment show a hazy reflection. Due to small bubbles (5 mm) in the coating. After the tempering process no visible defects were detected on the coating. SEM analysis confirm the good state of the coating.
Example of practical uses for linear ion sources for surface preparation - VISTA telescope - Parana 11 Flame Nebula (VISTA image) Credit: ESO Parana Chile VISTA Telescope
Example of practical uses for linear ion sources for surface preparation - VISTA telescope - Parana VISTA Telescope mirror coater Ion Source IM1500 At VISTA with geometrical mask 12
Large mirror ion etching linear ion sources ideal as easy to scale and accurate beam control preventing mirror damage Large mirror coaters 2-4.5m optics 13 Ion source Sputter source
Results Atomic Force Microscope Surface Roughness Untreated example ( from masked area of T-1K-R03X) Zerodur λ/20 Highly Polished (un-etched)
Results AFM 3D Mapping 1h Treatment T-1K-R01 T-1.5K-R02 T-2K-R03 The overall surface roughness doesn t change substantially with the ion bombardment, however composite nanotopography is enhanced
Pros and cons of DC inverted magnetron plasma sources Plus points Highly scalable and controllable plasma beam DC power hence lower cost levels Weakness Low power levels slow speeds only Less plasma excitation High voltage beam 500-1500 volt mean beam energies Self-neutralized by electron tunnel effect no charge build-up on insulating substrates Easy to implement and use if gas has auto feedback control Carbon anode and cathode prevents contamination Process Flexibilty can be used for PECVD and PEALD Can damage sensitive structures does not lead to increased roughness Low rate etching of the substrates 1 Angstrom per pass for oxides, 40 Angstroms for polymers Separate gas control leads to variable beam properties Source can etch rapidly if of a metallic nature and high power Very low rates, so only useful for R&D or seed layers
DC magnetron based plasmas for surface pre-treatment Plasma Treatment Sources
A wide variety of internal and external DC magnetron based plasma treating designs based upon process & system requirements
Pros and cons of DC based magnetron plasma sources Plus points Highly scalable and controllable plasma & can run at high substrate speeds and powers DC or pulsed power hence relatively lower cost levels than RF and microwave Self-neutralized plasma no charge buildup on insulators Can run in poisoned mode or gettering mode Pulsed DC required for moisture rich atmospheres Single electrode Weakness Less plasma excitation voltages typically less than 500V Need to manage the power load to substrate type and atmosphere needs feedback control Need to prevent arcing on the target by pulsing power modes Not suitable for very reactive environments, eg PECVD
AC type dual electrode plasma treaters (2kV) for surface pre-treatment Magnetically enhanced AC type higher voltage plasma Magnetic packs angle adjustment for plasma web interaction adjust
COMPACT AC powered magentically enhanced dual electrode operates with a medium frequency generator Very small sources possible less than 60mm space required. Water cooled dual electrodes Pre-distributed gas injection
Pros and Cons of AC based magnetically enhanced plasma sources Plus Points Switching high voltage AC plasma of high intensity Self-neutralized switching plasma potential no charge build-up on substrate or target more robust in dirty environments Double electrode switching from positive to negative so stable anode and cathode Highly scalable and controllable plasma & can run at high substrate speeds and powers Can run in poisoned mode or gettering mode Weakness Could damage the substrate adjust the magnetic angles to prevent damage Higher cost compared to single electrode DC Higher cost compared to single electrode DC Need to manage the power load to substrate type and atmosphere needs feedback control
AC type dual electrode plasma treaters (2kV) for surface pretreatment for PACVD
Dual Electrode AC-MF better for chemical etching processes high plasma excitement In dual AC-MF plasma discharges on each electrode the voltage alternates between cathode and anode potential providing an stable impedance for the plasma discharge
Pros and Cons of AC based magnetically enhanced Chemical plasma sources Plus Points Two separate electrodes easy to integrate and adapt to different process chambers by re-positioning Highly scalable and controllable plasma & can run at high substrate speeds and powers gas pumping capacity dependant Precursor delivery external to the sources and injected directly into the high intensity plasma zone reduces electrode contamination & extends life Integrated Speedflo PEM control for automatic process control and gas delivery option of in-vacuum or remote OPTIX plasma monitoring Weakness Fixed voltage once setup The main challenge is the precursor gas delivery into the plasma space and separate from the plasma source Need to guard against sand like deposit in source needs gas separation and easy to clean Rates are mainly dependant upon vacuum pumping capacity
Hipps New High Impulse Positive pulses for rapid ion etching of Hip v metallic substrates at earth potential
Unique and patent pending use of a Hipps power mode with positive pulsing for high rate etching of substrates Hip v cleaning box to collect sputtered material to prevent system and substrate contamination Power Supply: Hipps 6kW (500 Amp maximum, +1.4kV) multiple power supplies for higher powers. Highly ionized argon and other background gases accelerated towards the metallic plates at upto 1.4 kv with 400A peak pulses substrate at earth potential hence the substrate is effectively -1.4 kv relative to the plasma source. The sources should be angled at upto 45 deg for maximum sputter efficiency and to allow better collection of sputtered material. Rapid removal of surface oxides and contamination high speed substrates Stand alone source easy system integration (customer to supply cleaning box)
Voltage (kv) 3.5 3 2.5 2 1.5 1 Unique and patent pending use of a Hipps power mode with positive pulsing for high rate etching of substrates positive pulse drives magnetically guided ions at a high acceleration voltage towards an earthed substrate for rapid etching Hip v 0.5 0-20 0 20 40 60 80 100 120 140 160 180-0.5 Time (μs)
Internal Ion Beams for cleaning tube internal diameters not easy to achieve by conventional means + DC discharge (no ion etching of internal wall) Copper inner wall Hip v Internal Ion Bombarder +kv
Hip v Positive etching plasma source - compact design scalable design multiple 6 kw PSU s in parallel Compact design 166mm x 180mm and to any length (longer sources may require more power supplies connected in parallel) new source development on-going Based upon high voltage / current positive pulse plasma cleaning / etching subject to a Gencoa patent application An alternative to inverted magnetron sputter etching for strip steel and metallic substrates Hip v Von Ardenne
Hip v plasma sources New alternative to inverted magnetron sputter boxes Positive pulse source Inverted sputter box Unique technology with highest plasma activation available Hipps based High voltage and currents best to sputter native surface oxides quickly More compact - No need for magnetics behind the substrate as in the case of sputter boxes Angled beam for maximum sputter efficiency 45 deg ion bombardment angle results in max sputter yield Easier cleaning and system maintenance all debris is directed away from the source DC based DC slower, pulsing need to prevent arcing Require components both side of the substrate Normal magnetron type plasma Debris collects in the source and the substrate
Conclusions Choice of the correct plasma pre-treatment device depends upon process requirement Large scale optics and slow moving substrates Best solution Linear ion sources High speed substrate pre-treatment Reactive chemical etching / PACVD Metallic strip / substrate cleaning DC magnetron or AC dual electrode AC dual electrode / AC hollow cathode Hipps positive pulse or inverted sputter box
Gencoa is actively combining technologies and developing ways to enhance thin film devices Thank you for your attention Thank You Please visit us at Booth 506 Gencoa