Taiwan Led Forum 2012 Mc Clear Cree (R2 2)

[email protected]

November 1, 2012

Silicon Carbide (SiC) LED Chip to Reach High Performance and Low

Cost

Copyright © 2012 Cree, Inc. pg. 3

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

Package:– Protects the chip and

phosphor– Helps with light and heat

extraction– Primary in determining

LED lifetime

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pg. 4Copyright © 2012 Cree, Inc.

GaN on SiC

1: 0.967 (3.3% mismatch)

GaN on Sapphire

1: 1.148 (14.8% mismatch)

Why We Grow GaN on SiC

GaN

SiC

GaN

Al2O3

• Lattice Mismatch

• >15x Thermal conductivity

370W/m°K 23W/m°K

Simple* 2D ** Cartoon

* Drawn to scale. ** SiC, GaN, and Al2O3 are actually 3D Hexagonal crystalline structures


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


Reliability Impact of an Epi Defect

LED ChipSide View

LED ChipTop 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


Testing For Defects – Before They Are a Problem

I

V

Latent epi defects can be tested for; screened out by Reverse Voltage

test

SiC

Sapphire

Sapphire

SiC


US DOE Roadmap

US DOE MYPP, April 2012, p.68

DOE LED Roadmap


Chip Gen 2

Chip Gen 3

Chip Gen 1

LED Chip/Product Architecture Development History

How the Roadmap Really Works

Time

Lu

men

s P

er

Watt

2004 2006 2010

200

100

150

50

2012 201420082002

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XB and EZ LED Chip Architectures

• SiC substrate• InGaN epi MQW growth• Mirror• Contact• Flip• Top-side Contact• Bevel saw cut

XB Power Chip Architecture

• SiC substrate• InGaN epi MQW growth• Mirror• Bonding Metal• Flip• Add Si substrate• Remove SiC substrate• Bottom-side Contact• Surface roughening• Top-side Contact

EZ Power Chip Architecture

~2002 ~2006


Better Epi, not More Epi

• SiC Substrate• InGaN epi MQW growth• Mirror• Isolation layer• Contacts and vias• Flip• Under-fill• Bevel cut• Surface cut

Best combination of– Light extraction– Robust, reliable design– High Yielding,

Manufacturable– Low cost

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2011

Direct Attach (DA) SiC Chip


DA: Robust, Low Cost Flip Chip Architecture

Flip Chip X EZ DA units

Chip Thickness 12 125 335 µm

Under-fill area 0.81 0 0.08 mm2

Die Attach/Thermal Path

0.19 1.0 0.92 mm2

Wire Bonds 0 3 0 --

• Direct Attach SiC Chip:– 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)

>25x

0.1x5x

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GaN on SiC

1: 0.967

GaN on Sapphire

1: 1.148

What About GaN on Silicon?

GaN

SiC

GaN

Al2O3

GaN on Silicon

GaN

Si

1: ??

Most analysis assumes GaN on Si will achieve:– Same yield as SiC/Sapphire– Same performance as SiC/Sapphire– Same reliability as SiC/Sapphire– Wafer bowing and other technical

challenges are cheaply/easily solved– 8” Si fabs are fully depreciated and can

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

Are these good

assumptions?


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)


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

http://ledsmagazine.com/features/9/2/3


Higher Performance LEDs Means Fewer LEDs

Reducing LED count is a much stronger lever on reducing system cost than cutting LED ASP...


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

Driver

Optic

Housing


Real Example of the Cost Impact of Increasing LED Performance, Fully Utilizing LED Capacity

2007• 42 LEDs• 650 lm• 12W

>$100 Commercial Wholesale

2011• 8 LEDs• 575 lm• 10.5W

$<25 Retail


Get all the Lumens You are Paying For

• > 1100 lumens (hot)• < 20 Watts• > 55 lumens/Watt• ≥ 80 CRI• > .90 Power Factor• Energy Star light

distribution

http://www.cree.com/ref

Drive hard, run hot, save money

Omni-directional, same cost as LP/MP snow cone!!!

http://www.cree.com/ref


SiC: Reliably Driving Harder, Saving Money

TM-21Lumen

MaintenanceProjection


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

http://www.cree.com/products/pdf/XLamp_XPG_Operating_Capacity.pdf


Next 2x Lumen/$ Product Platform Coming Soon

0

50

100

150

200

250

300

350

Cost (log)

Lu

men

s

2011Platforms

2012 SC³ Platforms

1mm2 DA chip

0.7mm2 DA chip

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2013 NextGen Platforms

2mm2 EZ chip

1mm2 EZ chip

4mm2 EZ chip

XB-D

XT-E

XP-E

XP-G

XM-L

200 LPW in 2012


SiC Highest Performance, Low Cost

XT-E

XP-G2

XB-D

XLamp Discrete

XLamp HVW

XM-L HVW

XT-E HVW

MT-G2

XLamp Arrays

NEW

• Low LED cost– Lowest defects, highest yields– Shipping billions. TODAY.

• Highest reliability– Fewer defects– Robust screen for field defects– 2-15x better thermal conductivity

than silicon, sapphire– Higher reliable operating

temperatures

• Lowest overall system cost– Higher drive currents, higher

lumens– Fewer LEDs per system

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Taiwan Led Forum 2012 Mc Clear Cree (R2 2)

Documents

chip surface

epi defect led chipled

led asp

led lifetimecopyright

led capacity2007

led lamp

substrate cost

thicker chip robust