Science &Technology
Flexible glass substratesfor continuous manufacturing
Corning - S. Garner , G. Merz , J. Tosch,J. Matusick, X. Li , D. Marshall
CAMM - C. Chase, J. Steiner, D. Yepez,J. Switzer, P. Moschak
February 9, 2011
2© Corning Incorporated 2011Science & Technology
Outline
• Flexible glass for electronic devices
• Flexible glass mechanical reliability– Strength– Coatings– Stress
• Roll-to-roll photolithography
• Summary
3© Corning Incorporated 2011Science & Technology
Flexible Glass Enables High-Quality ElectronicsSubstrate choice critical for device fabrication & performance• Substrate integrates designs, materials, & processes
– Essential for overall optimization– Glass enables improved resolution, registration, performance & lifetime
Flexible Glass•Thermal stability•Dimensional stability•Hermeticity•Optical transmission•Surface roughness
Device DesignsE-paper, touch sensor, PV, OLED
MaterialsConductor, semiconductor, dielectric
Continuous Processes•Patterning (gravure, ink jet, photolithography)•Etching (wet, plasma)•Coating (lamination, slot die, vacuum)
Capabilities
Requirements
Flexible glasssubstrate
Flexible glassbarrier
4© Corning Incorporated 2011Science & Technology
Glass Surface & Bulk Properties Optimize DevicesFlexible glass device capability demonstrated in <170µm LCD
• Twisted nematic LCD• qVGA (320 x RGB x 240)• 4”diagonal (80mm x 60mm)• Pixel size 83µm x 250µm• Aperture 52%
• a-Si:H active matrix backplane• TFT channel L=10µm, W=50µm
• Polymeric substrates not compatible– 300°C backplane fabrication– 210°C frontplane fabrication
• 75µm flexible glass thickness– LC cell <170µm
S. Hoehla, et al., “Full Color AM-LCDs on Flexible Glass Substrates”, IDW 2010, p.1689-1692.
5© Corning Incorporated 2011Science & Technology
0
20
40
60
80
100
200 400 600 800Wavelength (nm)
Tran
smis
sion
(%)
Glass Enables Performance & Process OptimizationFlexible glass offers dimensional stability for R2R fabrication
Surface Roughness
Glass PEN Polyimide
0
1
2
3
4
A B A B A B
Ra
(nm
) Ra
0
50
100
150
200
Rpv
(nm
)
Rpv
Optical TransmissionGlass
PEN
Polyimide
Dimensional Stability
0
10
20
30
40
50
0 0.5 1 1.5 2Strain (%)
Stre
ss (M
Pa)
Glass25°C
PEN25°C
Polyimide25°C
& 150°C
150°C
150°C
6© Corning Incorporated 2011Science & Technology
Mechanical Reliability of Flexible GlassSubstrate solutions optimized for continuous processing
• Mechanical reliability of glass understood– Failure due to distributions of defects & applied stresses– Bend strength independent of thickness
• Mechanical reliability requires controlling defects & applied stress– High strength glass forming including surfaces & edges– Protecting substrate from damage– Managing stresses during conveyance, handling & application
0
100
200
300
400
500
0 5 10 15 20 25 30Bend Radius (cm)
Ben
d St
ress
(MPa
)
500µm100µm
50µm
1.000.100.01
90
50
2010
5
21
Bend Radius (cm)
Failu
rePr
obab
ility
(%)
0.11Bend Radius (cm)
10
100µm200µm
~10mm
7© Corning Incorporated 2011Science & Technology
Glass After Forming is Inherently StrongManaging defect size & distribution enables reliability• Pristine glass surfaces are extremely strong
– Bend strengths >6GPa measured in substrate compositions– Subsequent handling & environment can reduce strength ~100x
• Glass strength depends on glass history– Quality of surfaces & edges critical
1000500200100502010
99
90
50
20
10
5
2
1
Bend Stress (MPa)
Failu
rePr
o bab
ilit y
( %)
Surface damage
Crack systems
Edge quality affects bend strength
Surface quality affects bend strength
8© Corning Incorporated 2011Science & Technology
Protective Coatings Preserve Glass StrengthCoating selection specific to application
• Crack systems form when flaw size & stress reach threshold
• Coatings minimize contact damage induced during:– Handling, packaging, shipping– Device manufacturing– In-service use
• Coating optimized for specific device & fabrication processes– Material & thickness selected for anticipated conditions– Full-width and partial-width coatings enable different device designs– Mechanical properties dominated by glass
Coated Substrate Cross-Section
70µm glass 10µm coatings
9© Corning Incorporated 2011Science & Technology
Convey Flexible Glass with Roller SystemsRequires managing bend stress during device fabrication
• Flexible glass is flexible –Do not handle as rigid substrate– Stiffness of 50µm glass 120µm PEN– Control stresses through roller handling system– Approach compatible with sheet-fed or roll-to-roll systems
Conveyance in CAMM ECD Tool Al Sputtering in CAMM General Vac System
Un-wind
Re-wind Glass webDeposition
drum
Glass web
10© Corning Incorporated 2011Science & Technology
Flexible Glass is Compatible with R2R ProcessingDemonstrated continuous ITO patterning
CoolingDrum
ITO Deposition Slot Die Coating
Supply Roll Take-Up Roll
Exposure
Supply Roll Take-Up Roll
Development & Etch
11© Corning Incorporated 2011Science & Technology
• Spooled glass with partial width coating• 10µm ITO lines with 30 Ω resistivity
Roll-to-Roll Patterning of 10µm ITO LinesDeposition, slot coat, repeated exposure, develop & etch
Patterned Photoresist
Reflection
Transmission
50µm
50µm
Patterned ITO
Reflection
Transmission
50µm
50µm
12© Corning Incorporated 2011Science & Technology
Summary
• Flexible glass offers advantages for device designs, materials & processes– Includes dimensional & thermal stability and hermeticity– Enables high performance active devices
• Glass mechanical reliability understood– Form high initial strength & minimize defects– Manage stresses with appropriate conveyance– Optimized solutions are application specific
• Flexible glass is compatible with continuous processing– Demonstrated patterning of 10µm ITO lines– Process optimizations possible to take advantage of glass capabilities
13© Corning Incorporated 2011Science & Technology
Acknowledgements
• Corning– Scott Glaesemann– Don Clark– Jill VanDewoestine– Michael Sorensen
• CAMM– Mark Poliks