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Taiwan Led Forum 2012 Mc Clear Cree (R2 2)
- 1. Silicon Carbide (SiC) LED Chip to Reach
High Performance and Low Cost
mark_mcclear@cree.com
November 1, 2012
- 2. An LED Lamp is a Complex System
LED Chip:
– Determines raw
brightness and efficacy
Phosphor system:
– Determines color point,
color quality and color
point stability SC3
Package:
– Protects the chip and
phosphor
– Helps with light and heat
extraction
– Primary in determining LED
lifetime
Copyright © 2012 Cree, Inc. pg. 3
- 3. Why We Grow GaN on SiC
Simple* 2D ** Cartoon
GaN GaN
SiC Al2O3
GaN on SiC GaN on Sapphire
1: 0.967 1: 1.148
(3.3% mismatch) (14.8% mismatch) • Lattice Mismatch
370W/m°K 23W/m°K
• >15x Thermal
conductivity
* Drawn to scale.
** SiC, GaN, and Al2O3 are actually 3D Hexagonal crystalline structures
Copyright © 2012 Cree, Inc. pg. 4
- 4. Lattice Mismatch Drives Chip Defects
• Minor imperfections
are merely dark
spots
– Fewer defects = brighter
chips
– Brighter chips = lower system
cost
• Major defects
affect production
yield and reliability
in the field
– Yield is strongest driver of
LED cost
Copyright © 2012 Cree, Inc. pg. 5
- 5. Reliability Impact of an Epi Defect
LED Chip LED Chip
Side View Top View
• Normal operation, no defects, current spreads
evenly across the chip surface, uniform light
• Undetected epi defect, point loss of light begins
• Over time, current begins to flow into the
defect, causing it to grow
• Ultimately, the defect causes a cascading failure
of the chip
Copyright © 2012 Cree, Inc. pg. 6
- 6. Testing For Defects – Before They Are a Problem
SiC I
Sapphire
Latent epi defects
can be tested for;
screened out by V
Reverse Voltage test
SiC
Sapphire
Copyright © 2012 Cree, Inc. pg. 7
- 7. US DOE Roadmap
DOE LED Roadmap
US DOE MYPP, April 2012, p.68
Copyright © 2012 Cree, Inc. pg. 8
- 8. How the Roadmap Really Works
LED Chip/Product Architecture
Development History
Chip Gen 3
200
SC3
Lumens Per Watt
150
Chip Gen 2
100
50
Chip Gen 1
2002 2004 2006 2008 2010 2012 2014
Time
Copyright © 2012 Cree, Inc. pg. 9
- 9. XB and EZ LED Chip Architectures
XB Power Chip Architecture EZ Power Chip Architecture
~2002 ~2006
• SiC substrate • SiC substrate
• InGaN epi MQW growth • InGaN epi MQW growth
• Mirror • Mirror
• Contact • Bonding Metal
• Flip • Flip
• Top-side Contact • Add Si substrate
• Bevel saw cut • Remove SiC substrate
• Bottom-side Contact
• Surface roughening
• Top-side Contact
Copyright © 2012 Cree, Inc. pg. 10
- 10. Better Epi, not More Epi
Direct Attach (DA) SiC Chip
2011
SC3
• SiC Substrate
• InGaN epi MQW growth
• Mirror
• Isolation layer
• Contacts and vias
Best combination of
• Flip – Light extraction
• Under-fill – Robust, reliable design
• Bevel cut
– High Yielding, Manufacturable
• Surface cut
– Low cost
Copyright © 2012 Cree, Inc. pg. 11
- 11. DA: Robust, Low Cost Flip Chip Architecture
>25x
Flip Chip X EZ DA units
Chip Thickness 12 125 335 µm
Under-fill area 0.81 0 0.08 mm2
Die Attach/
0.19 1.0 0.92 mm2
Thermal Path
Wire Bonds 0 3 0 --
5x 0.1x
• Direct Attach SiC Chip: SC3
– 25x thicker chip robust, manufacturable (= low cost)
– 1/10th the amount of under-fill less CTE mis-match,
more robust, higher assembly yield (= low cost)
– 5x more die attach area – better thermals, lower RTH,
higher reliably (= lower system cost)
Copyright © 2012 Cree, Inc. pg. 12
- 12. What About GaN on Silicon?
GaN GaN GaN
SiC Al2O3 Si
GaN on SiC GaN on Sapphire GaN on Silicon
1: 0.967 1: 1.148 1: ??
Most analysis assumes GaN on Si will achieve:
– Same yield as SiC/Sapphire
– Same performance as SiC/Sapphire
– Same reliability as SiC/Sapphire Are
– Wafer bowing and other technical
challenges are cheaply/easily solved
these good
– 8” Si fabs are fully depreciated and can assumptions?
deal with Compound Semi complexities
– LED fabs are somehow not depreciated at all
– Giant LED companies are asleep, have not
fully analyzed this technology also
Copyright © 2012 Cree, Inc. pg. 13
- 13. But Silicon Substrates are Really Cheap!
• True. $200-300 cheaper
(currently; 6”, 150mm)
• But…
– There are >17,000 1*1mm chips
on a 150mm wafer
– 5% better yield on SiC – or even
sapphire – could completely offset
this difference in substrate cost
• And, GaN on Si may also
– …require additional materials and
process steps to fabricate
– …have poorer chip reliability
– …have lower lumen output, LPW
performance due to higher defect
rates… (dimmer chips = higher
system cost)
Copyright © 2012 Cree, Inc. pg. 14
- 14. Higher Performance LEDs Saving Money –
At The System Level
• SiC LEDs can be driven
harder, run hotter
• You are paying for the
lumens anyway, SiC allows
you to use them (= low cost)
http://ledsmagazine.com/features/9/2/3
Copyright © 2012 Cree, Inc. pg. 15
- 15. Higher Performance LEDs Means Fewer LEDs
Reducing LED count is a much stronger lever on
reducing system cost than cutting LED ASP...
Copyright © 2012 Cree, Inc. pg. 16
- 16. Hypothetical Example of the Cost Impact of Increasing
LED Performance, Fully Utilizing LED Capacity
• 4000 lm LED Area
Light
• Includes optics, LED
cost, reduction of LED
count, driver, housing
• Driving harder reduces
system level cost
LED Optic
Driver Housing
Copyright © 2012 Cree, Inc. pg. 17
- 17. Real Example of the Cost Impact of Increasing LED
Performance, Fully Utilizing LED Capacity
2007 2011
• 42 LEDs • 8 LEDs
• 650 lm • 575 lm
• 12W • 10.5W
>$100 Commercial $<25 Retail
Wholesale
Copyright © 2012 Cree, Inc. pg. 18
- 18. Get all the Lumens You are Paying For
Drive hard, run hot, save money
• > 1100 lumens (hot)
• < 20 Watts
• > 55 lumens/Watt
• ≥ 80 CRI
• > .90 Power Factor
• Energy Star light
distribution
Omni-directional, same cost as
LP/MP snow cone!!!
http://www.cree.com/ref
Copyright © 2012 Cree, Inc. pg. 19
- 19. SiC: Reliably Driving Harder, Saving Money
TM-21
Lumen
Maintenance
Projection
Copyright © 2012 Cree, Inc. pg. 20
- 20. Same Performance, 60% Lower LED Cost
• Identical downlights:
Same flux, CCT, CRI, light
distribution
• Both exceed Energy Star
LPW and lifetime
requirements
√
√
√
√
√
http://www.cree.com/products/pdf/XLamp_XPG_Operating_Capacity.pdf
Copyright © 2012 Cree, Inc. pg. 21
- 21. Next 2x Lumen/$ Product Platform Coming Soon
350 2011
Platforms
300 SC3
2013 NextGen 2012 SC³
250 Platforms Platforms XM-L
200 200 LPW XT-E
Lumens
in 2012
150
XB-D XP-G
100
50 XP-E
0
Cost (log)
Copyright © 2012 Cree, Inc. pg. 22
- 22. SiC Highest Performance, Low Cost
SC3
XLamp Discrete
• Low LED cost XB-D
– Lowest defects, highest yields
XT-E
– Shipping billions. TODAY.
• Highest reliability XP-G2
– Fewer defects NEW
– Robust screen for field defects
– 2-15x better thermal conductivity
XLamp HVW
than silicon, sapphire
– Higher reliable operating temperatures XM-L HVW
• Lowest overall system cost XT-E HVW
– Higher drive currents, higher lumens XLamp Arrays
– Fewer LEDs per system MT-G2
Copyright © 2012 Cree, Inc. pg. 23