Cree is the only LED supplier to build LEDs on Silicon Carbide. Ever wonder why? Is GaN on Silicon the next big thing? How will LED costs come down?

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