Roll-to-roll Technology for Transparent High Barrier Films

Transcription

1 Roll-to-roll Technology for Transparent High Barrier Films Presented at the AIMCAL Fall Technical Conference, October 19-22, 2008, Myrtle Beach, SC, USA Nicolas Schiller, John Fahlteich, Matthias Fahland, Waldemar Schönberger Fraunhofer FEP, Germany page 1 FEP Fraunhofer Institut Elektronenstrahl- unda Plasmat echnik

2 Outline Motivation and Approach Magnetron PECVD process Layer properties Summary and Conclusion page 2

3 Outline Motivation and Approach Magnetron PECVD process Layer properties Summary and Conclusion page 3

4 "Be flexible:" Flexible displays, signage, lightning, and solar cells offer unique application and cost saving potentials. Source: Konarka Source: PolymerVision page 4

5 Flexible substrates Potential benefits for designers and users thin, low weight new design concepts Ultra low cost applications Potential benefits for producers Roll-to-roll production scheme However, Encapsulation is needed to protect the device from water vapor and oxygen page 5

6 water vapor permeation barrier Electronic device oxygen today: Ultra-High-Barrier olny with glass not flexible flexible solar cell flexible OLED future: thin film encapsulation for ultra-high-barrier low cost flexible page 6

7 Direct Encapsulation vs. Barrier Foil Direct Encapsulation Barrier Foil All encapsulation processes must be compatible Substrate exposed to (plasma) process All in vacuum roll-to-roll encapsulation possible Free choice for processes (combine vacuum and non-vacuum processes) OLED and barrier development independent Additional process: lamination page 7

8 Requirements and coating technologies for transparent barriers Combination Processes Organic Electronic Devices Sputtering Evaporation Polymers (intrinsic) Solar Modules Food Packaging Water Vapour Transmission [g / m² day] page

9 Challenge of thin film encapsulation defect in barrier layer barrier layer Substrate (polymer film, OLED, solar cell ) Models suggest that barrier performance is controlled by defects in the barrier layer. (The layer itself is supposed to be impermeable.) All concepts to improve barrier performance are focused to hinder the growth of defects. page 9

10 Concept: dense single layer Virtually defect free or low defect single barrier layer [2] sputtered Al 2 O 3 barrier layer Substrate GA - Super Sapphire Atomic Layer Deposition thin layer by layer deposition [1] Ion-beam assisted sputter deposition [2] [1] P. F. Carcia et al.: APPLIED PHYSICS LETTERS 89, (2006) page 10 [2] R. Dunkel: High Performance low cost single layer barrier coatings on plastic, General Atomics Produktpräsentation

11 Concepts: graded single layer Graded (organic/inorganic/organic) layer [1] Substrate (polymer film, OLED, solar cell ) inorganic organic Variation of film composition by changing process gas Batch-process not applicable for roll-to-roll encapsulation [1] A. G. Erlat et al.: Ultra-High Barrier Coatings for Flexible Organic Electronics, SVC 48th Technical Conference Proceedings, p. 116 (2005) page 11

12 Multi-layer barrier defect in barrier layer barrier layer interlayer barrier layer Substrate (polymer film, OLED, solar cell ) defect decoupling: tortuous path for moisture and oxygen diffusion increased lag time of diffusion decoupling of mechanical stress page 12

13 Example: multi-layer barrier with ORMOCER s barrier layer ("PVD-layer") ORMOCER barrier layer ("PVD-layer") Substrate (polymer film, OLED, solar cell ) page 13

14 Outline Motivation and Approach Magnetron PECVD process Layer properties Summary page 14

15 All-in-vacuum approach: interlayer by Magnetron PECVD barrier layer ("PVD-layer") interlayer: PECVD-layer barrier layer ("PVD-layer") Substrate (polymer film, OLED, solar cell ) "PVD-layer": Layer deposited by Physical Vapor Deposition (e.g.sputtering) page 15

16 Why PECVD / PVD multilayer structure? Main Goal: Development of an all-in-vacuum encapsulation technology for flexible electronic devices Cost reduction with roll-to-roll encapsulation Magnetron-based PECVD and PVD run in one machine at the same time suitable for production of barrier films as well as direct encapsulation page 16

17 Reactive Magnetron Sputtering page 17

18 Magnetron PECVD CH 3 Si O Si pressure range: ca. 0, Pa High potential for large area/wide web processing coating rate > 400 nm m/min page 18

19 Combination of Sputtering with Magnetron based PECVD multilayer stack for barriers page 19

20 Outline Motivation and Approach Magnetron PECVD process Layer properties Summary and Conclusion page 20

21 Layer composition (HMDSO) reference (sputtered SiO 2 ) Concentration [at. %] C O Si Ti Process parameters: 2.3 W/cm², HMDSO+O 2 = 80 sccm measured using XPS low amount of target material (Ti) incorporated into the layers composition adjustable from silicon oxide like to polymer like layers HMDSO/(HMDSO + O2) [%] page 21

22 Mechanical Properties 10 9 sputtered SiN x substrate: PET 75 µm hardness [GPa] sputtered SiO 2 SiC x O y - PECVD hardness measured for HMDSO:O2 = 1:10 using Nano-indentation lower hardness compared to sputtered layers low internal stress HMDSO/(HMDSO + O 2 ) [%] page 22

23 Permeation Barrier Properties of SiO x C y 5,0 WVTR [g/(m²d)] 4,5 4,0 3,5 3,0 2,5 2,0 1,5 1,0 0,5 0, film thickness [nm] ratio HMDSO:O 2 7:73 20:60 40:40 substrate: 125 µm PET polymer like layers reflect barrier properties of substrate SiOx-like layers: WVTR > 0.2 g/(m 2 d) increase of barrier performance at high thickness page 23

24 Single layer optical coating (SiO x C y on PET) 100 TEOS-based process 80 Low internal stress Transmission [%] nm 240 nm uncoated PET Wavelength [nm] page 24

25 Magnetron PECVD in optical multilayer stacks SiO x C y + reactively sputtered TiO Transmission [%] appr. 640 nm TiO 2 SiO x C y Wavelength [nm] PET substrate page 25

26 Pilot sputter roll coater coflex 600 flexible substrates (polymer webs, thin metal foils) 600 mm deposition width web speed 0, m/min 6 coating stations (dual magnetrons) Pulsed Magnetron Sputtering Magnetron PECVD page 26

27 Pilot roll coater novoflex 600 flexible substrates (polymer webs, thin metal foils) 600 mm deposition width web speed 0, m/min double side coating 5 coating stations combination of evaporation, sputtering and PECVD page 27

28 Scaling up to pilot-scale reactive sputtering Magnetron- PECVD page 28

29 Deposition Rates HMDSN 10 kw deposition rate increases with monomer flow higher rates at higher power: 400 nm*m/min possible at 20 kw (7 W/cm²) with HMDSO and HMDSN page 29

30 Long term process stability plasma impedance increases within first 30 min dynamic deposition rate stabilizes within 15 min rate drift within 6 hours ±5% page 30

31 Multilayer barriers - Sputtering + Magnetron-PECVD ZnSnOx 75 nm PEN WVTR = 0,045 g/(m²d) SiO x - PECVD - 60 nm (7:73) ZnSnOx 75 nm PEN WVTR = 0,045 g/(m²d) ZnSnOx 75 nm SiO x - PECVD - 60 nm (7:73) ZnSnOx 75 nm PEN WVTR = 0,007 g/(m²d) page 31

32 Outline Motivation and Approach Magnetron PECVD process Layer properties Summary page 32

33 Summary A novel concept for the all-in-vacuum, roll-to-roll deposition of multilayer barrier stacks has been developed. The basis of the concept is the in-line combination of magnetron sputtering and a magnetron PECVD-process. The magnetron PECVD process offers several benefits low working pressure of 0.5 Pa up to few Pa, thus allowing the in-line combination with sputtering process wide range of properties for SiOxCy layers high potential for large area processing by using dual magnetrons as power source high coating rates (> 400 nm m/min) Our basic concept allows an all-in-vacuum roll-to-roll deposition of multilayer barrier stacks. The process has been installed in a pilot-scale multi-chamber pilot roll-to-roll coater. page 33 FEP Fraunhofer Institut Elektronenstrahl- unda Plasmat echnik