CONTACT CLEANING FOR BARRIER COATINGS Sheila Hamilton Teknek Ltd 1
OUTLINE • Current market Drivers • What is Contact Cleaning • How does contact cleaning work • Science of adhesion • Surface roughness analysis • Adhesion measurements • Contact Cleaning in a vacuum • Conclusions 2
MARKET DRIVERS • Requirement for increased lifetimes in OLEDs and OPV • Increasing use of Organic functional coatings which are moisture sensitive • Thinner coatings • Thinner films • Static generative materials 3
HOW IT WORKS 4
CLEANING FUNDAMENTALS • Adhesive force between the elastomer roller and the particle must be greater than the force between the particle and the substrate • The adhesive force between the particle and the adhesive must be greater than that between the elastomer roller and the particle 5
MACRO ADHESION RUBBER COPPER STEEL Cu/KAPTON POLYESTER POLYCARBONATE (Gloss) (Matt) 1.17 3.26 0.51 2.55 2.37 SOFT 1.49 3.32 0.81 2.63 1.07 PANEL 0.63 0.81 0.34 1.68 1.4 FILM 0.11 0.11 0.11 0.05 0.12 F3 0.08 0.04 0.07 0.75 0.34 NANO 6
INTERFACIAL FORCES 7
EXAMPLES OF ADHESION FORCES 8
CONTACT AREA Contact area is impacted by • Roller surface roughness • Pressure • Shore hardness • Particle morphology 9
SURFACE ROUGHNESS 10 10
SURFACE ROUGHNESS Scan Size 1 2 3 Sample name Soft 2.169 11.143 38.582 Panel 7.355 13.493 23.467 Nanoclean 3.616 1.400 6.292 Film 7.453 16.861 18.54 F3 31.009 49.085 98.334 11 11
SURFACE OF PANEL ELASTOMER 12 12
SURFACE OF NANOCLEEN ELASTOMER 13 13
ADHESION FORCES Type of Probe Silica Gold-coated silica Polystyrene Sample name Soft 752.08 ± 147.06 951.87 ± 69.48 1027.79 ± 109.82 Panel 848.11 ± 112.98 823.55 ± 160.72 847.12 ± 214.75 Nanoclean 803.08 ± 443.79 285.14 ± 161.34 1073.17 ± 629.94 Film 866.80 ± 144.75 1152.12 ± 125.74 1177.89 ± 81.77 F3 1076.98 ± 420.92 746.64 ± 329.49 813.09 ± 393.31 14 14
SUMMARY • Hydrophobicity of materials is important for adhesion • Adhesion on the macro scale does not relate to the micro scale • Surface roughness on a micro scale causes variations in the adhesion forces 15 15
CLEANING IN A VACUUM • Does the Cleaning system detrimentally affect the performance of the vacuum system ? • Does exposure to high vacuum alter the performance of the cleaning system? 16 16
The use of Teknek equipment in Vacuum Chambers Test Results undertaken as part of the Clean 4 Yield Program Testing carried out by Holst Centre
Introduction In the R2R vacuum tool web cleaning can be very important for removal of particles from the surface of the polymer film reel before deposition. This cleaning could be done with cleaning rollers from Teknek. Cleaning Roller tested; 1.Nanocleen And two kind of adhesive sheets/rollers are tested: 1.Adhesive Blue roller 2.Adhesive ECO roller (Oxy-degradable product) 18
Testing The quality of the elastomer rollers and adhesive sheets are tested before and after vacuum exposure. Tests that are done: • Weight loss before and after vacuum exposure of the rollers and adhesive sheets. • Particle pickup test before and after vacuum exposure of the rollers and adhesive sheet. • Outgassing test of the tacky rollers and adhesive sheets/rollers Residual gas analysis (RGA), short and long time testing. 19
Weight loss rollers before and after vacuum Vacuum test at 1e-7mbar (Scud vacuum system 032), total time in vacuum 66hrs (1 weekend). 4 small rollers are put in vacuum system, weight measurement before and after. Weight measurement: analytical balance (readability 0,0001gr) weight loss [%] difference [gr] weight before weight after type roller vacuum weight average weight loss 0,4%, nr no difference nanoclean 1 16,98 16,91 0,07 0,41% between rollers nanoclean 2 17,16 17,1 0,06 0,35% ultraclean 3 17,44 17,37 0,07 0,40% ultraclean 4 17,55 17,49 0,06 0,34% 0,38% 20
Particle pickup test before and after vacuum Tungsten particles are put in oven tray (60degree) and after getting out of oven the rollers are rolled into the metal powder (6 times) After tungsten particle pickup the roller is rolled over a 6"adhesive sheet. The weight of the sheet is measured before and after on a balance with readability 0.1gr Width roller: 25mm. Rollers are stored in high vacuum system, adhesive sheets in a low and high vacuum system. adhesive sheet particle pickup roller vacuum difference [gr] weight before weight after condition condition weight Roller nanocleen 4,3 4,6 0,3 ambient ambient 4,3 4,5 0,2 1 weekend in vac (0.1 mbar) No difference in 4,3 4,5 0,2 particle pickup for 18 hrs in high vac (1e-6 mbar) rollers and/or 4,3 4,5 0,2 1 weekend in vac (1e-6mbar) ambient adhesive sheets in 4,2 4,5 0,3 1 weekend in vac (1e-6mbar) ambient vacuum or ambient conditions !! ultracleen 4,3 4,5 0,2 ambient ambient 4,3 4,5 0,2 1 weekend in vac (0.1 mbar) 4,3 4,5 0,2 18hrs in high vac (1e-6mbar) 4,4 4,6 0,2 1 weekend in vac (1e-6mbar) ambient 4,3 4,5 0,2 1 weekend in vac (1e-6mbar) ambient Repeatability test (after cleaning roller repeat particle pickup measurement). ultraclean 4,3 4,5 0,2 ambient ambient 4,3 4,5 0.2 nanoclean 4,3 4,6 0,3 ambient ambient 4,3 4,5 0,2 21
Outgassing test rollers (RGA analysis) nanocleen roller no PDMS A common surface contaminant is silicone oil or polydimethylsiloxane, which has been found to result in a group of ion fragments serving as fingerprints (for example, positive secondary ions at m/z 28, 73, 147, 207, 221 and 281, which are assigned to Si + , SiC 3 H 9 + , Si 2 C 5 H 15 O + ,Si 3 C 5 H 15 O 3 + ,Si 3 C 7 H 21 O 2 + and Si 4 C 7 H 21 O 4 + , respectively). 22 - CONFIDENTIAL -
24 hrs. Outgassing test Teknek adhesive rolls (ECO and Blue) – RGA analysis Remark: • No PDMS (peak 73) signal visible for both adhesive rolls !! • Both adhesive rolls contain quite a lot of water, specially the blue adhesive roll. After 24hrs the ECO contains no more water. Teknek blue after 6hrs pumping contains much water. . 23
Conclusions • Weight loss before and after high vacuum storage of the nanocleen Teknek roller is about 0.4%. • The nanocleen rollers and adhesive rollers (Teknek Blue and ECO) show no peaks in the RGA analysis, so there is no outgassing from this roller in vacuum. Measured weight loss is probably due to moisture/water outgassing. • The particle pickup rate for the rollers and adhesive foil is not influenced by storing under high vacuum (1e-6mbar during a weekend) !! • The nanocleen rollers in combination with the adhesive blue or ECO rollers are the best option for our R2R tool. Specially because there is no outgassing in vacuum and particle pickup rate is not influenced by vacuum. An additional advantage of the nanocleen roller is that this elastomer is static dissipative . 24
AREAS OF APPLICATION • After stripping of protective film to remove possibility of static induced recontamination • Immediately prior to sputtering to remove any particles deposited from the walls of the chamber • Before rewind to stop particles imprinting on the layer below or fracturing the film • Cleaning the protective film at rewind prior to application to stop damage to the coating 25 25
Special Machine 26
The Vacuum Chamber In the R2R vacuum tool cleaning is very important for removal of particles from the machine. This cleaning can be done with: • Industrial vacuum cleaner with HEPA filter Very suited for removal of large SiN flakes around the microwave tubes and other locations • Tissues with IPA Very suited for cleaning drums • Tacky roller (Teknek) Very suited for cleaning walls/shields of all the chambers < 28 28
Cleaning results Shieldings PC1 Backside foil LL1- PC1 1 PC1 walls LL1 bottom Shieldings PC1 Bottom PC1 Bottom PC1 1 Backside foil dirty because of removal slit < 29 29
Summary With the Teknek contamination audit kit the Rollcoat machine is cleaned on several locations. And it can be a very useful extension for cleaning the tool. Lots of small dirt (mostly SiN dust) can be removed from walls/bottoms/doors/shieldings etc. The best cleaning is done with a rough vacuum clean and after this a fine clean with the Teknek roll. < 30 30
Conclusions • Contact Cleaning can be used to clean films in a high vacuum environment • No detriment has been found to the operation of the vacuum chamber not to the cleaning efficiency of the elastomer roller and adhesive • Teknek has developed a small footprint machine specifically for this application 31
Acknowledgements • University of Sheffield Polymer Centre • The Holst Centre, Eindhoven • Clean4Yield European Programme 32
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