EPILEDS
LED－Epitaxy
Lecturer: Chingju Pan
Epileds Technologies, Inc.
Outline
EPILEDS
Introduction
Semiconductor material parameters
Basic concept of CVD
MOCVD tool introduction
Devices for epitaxial quality control
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Evolution of Light & Human
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Now
Before
LED
Edison
 Light is indispensable to people!!!
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LED market in Government policy
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LED Industries Introduction
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磊晶
Source : 工研院IEK ，2014年3月)
晶粒
封裝
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HB-LED Market Forecast
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Source : LEDinside，2014年6月
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HB-LED Market Place
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 The
market forecast for high-brightness(HB) - LED
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Lighting、Backlight Market
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Source : LEDinside，2014年6月
Source : NPD DisplaySearch ，2014年3月
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Application Area of LED Lighting
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Source : Osram; Nord light: Philips: ITRI
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White LED
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Source : ITRI,產業經濟與趨勢研究中心
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RGB LED
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 植物照明新趨勢
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UV LED
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 紫外線光療、文件與鈔票防偽偵測、美甲
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Outline
EPILEDS
Introduction
Semiconductor material parameters
Basic concept of CVD
MOCVD tool introduction
Devices for epitaxial quality control
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LED產業價值鏈
EPILEDS
( 越峰、鑫晶鑽)
單晶成長
藍寶石基板後段加工製程(兆遠、兆晶、晶美)
藍寶石基板加工
LED晶粒
LED磊晶片
光鋐科技
晶電、廣鎵、璨圓、新世紀、泰谷…
LED封裝
億光、東貝、光寶、
佰鴻、宏齊…
LED燈具
PHILIPS、GE、
OSRAM…
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Periodic table of elements
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 III-V
& II-V periodic table classification
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III-V & II-V binary materials
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Direct Bandgap
Indirect Bandgap
III-V compound semiconductors
Total atomicity of IIIA:VA = 1:1
The relationship between the bandgap and
the lattice constant for III-V、II-VI materials
e.g. AlxGa1-xAs, (AlxGa1-x)yIn1-yP,
InxGa1-xN, AlxGa1-xN
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Semiconductor material parameters
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(Direct bandgap)
(Indirect bandgap)
III-nitride based semiconductor material & substrate parameters
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GaN-based Material
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Major Advantage
Major Disadvantage
 Direct Wide bandgap
 High defect density
 Direct bandgap of InGaN and AlGaN
 Lower concentration of p-type GaN:Mg
series materials
 Full visible color emission
 Lower p-type activation efficiency by
thermal treatment
 High Saturated electron drift velocity  Without suitable substrates
 High breakdown electric field
 Wafer dimension cost
 Highly chemical stability
 low dielectric constant
 Unique emission spectra
 Dry etching process dominated the
device fabrication
 Oxidation/junction passivation
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Emission wavelength vs. materials
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y
色
度
座
標
值
x色度座標值
Properties of commercialized LED CIE Chromaticity diagram for LED
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InxGa1-xN-based LEDs
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350
400
450
500
550
600nm
435-445nm
445-455nm
455-465nm
465-475nm
475-485nm
485-495nm
495-515nm
515-535nm
The distribution of the InxGa1-xN LED wavelength
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Emission mechanism of LED
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Band Diagram
Ec
Conduction Band
Light emitting
Ec
acceptor
donor
+V
P-type
MQW
N-type
Ev
Ev
Valence Band
-V
-V
+V +V
Advantages：
 High quantum efficiencies
 Control of the emission wavelength in LED by
modulating the well thickness of MQWs
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Outline
EPILEDS
Introduction
Semiconductor material parameters
Basic concept of CVD
MOCVD tool introduction
Devices for epitaxial quality control
ChingjuPan
Compare of epitaxial methods
EPILEDS
Growth method
time
features
limit
LPE
(Liquid phase
epitaxy)
1963
Growth form
supersaturated
solution onto
substrate
Limited substrate areas
and poor control over the
growth of very thin layers
VPE
(Vapor phase
epitaxy
1958
Use metal halide as
transport agents to
grow
No Al contained
compound, thick layer
MBE
(Molecular Beam
Epitaxy)
1958
1967
Deposit epilayer at
ultrahigh vacuum
Hard to grow materials
with high vapor pressure
MOCVD
(Metal-Organic
Chemical Vapor
Deposition)
1968
Use metalorganic
compounds as the
sources
Some of the sources like
AsH3 are very toxic.
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Chemical Vapor Deposition (CVD)
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 利用含有所需成分的氣相反應物經化學反應‚在基板上形成非揮發性的固態膜
 反應氣體被導入反應腔中‚於以加熱的基板表面上‚經分解及反應而形成薄膜
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MOCVD reaction steps
EPILEDS
Carrier gas (e.g. H2, N2)
Organometallics
(e.g. Ga(CH3)3, NH3)
Gas Stream
Gas-phase reactions
chemisorption
Surface diffusion
Desorption
Surface
reactions
Growth
Wafer
Susceptor
在基板上成長非晶形半導體薄膜的一種方式
Optimum Growth Conditions:
Temperature
V/III ratio
Total flow rate
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MOCVD System for Epitaxy Growth
EPILEDS
MOCVD成長薄膜時，主要將載流氣體(Carrier gas)通過有機金屬反應源
容器時(Reactor Chamber)，將反應源的飽和蒸氣帶至反應腔中與其它反
應氣體混合，然後在被加熱的基板上發生化學反應促成薄膜的成長。
Main components of MOCVD
 Reactor: temperature, pressure, flow rate, V/III ratio, uniform…
 Precursor: MO source (e.g. TMGa, TEGa, TMIn, TMAl, Cp2Mg)
Hydride source (e.g. NH3, SiH4 )
 Gas handling & mixing system: MFCs, PCs, Gas purifier…
 Scrubber
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Outline
EPILEDS
Introduction
Semiconductor material parameters
Basic concept of CVD
MOCVD tool introduction
Devices for epitaxial quality control
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MOCVD
EPILEDS
Reactor cabinet
Heater power supply unit
Electrical cabinet
Gas mixing cabinet Glove box cabinet
Process determines the properties and nature of the LED
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MOCVD 1-Aixtron Reactor
Planetary reactor schematic
2‫)״‬
8 x (3 x
= 24 x 2‫״‬
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Susceptor
Ceiling
Nozzle
Satellite disk
RF coil
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MOCVD 2-Veeco Reactor
EPILEDS
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MOCVD 3 - Thomas Swan
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D:Showerhead
B:Heater
I:Reactor
M:Exhaust
Reactor 主要是所有氣體混合及發生反應的地方
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Showerhead
EPILEDS
showerhead
Susceptor
Group III
Group V
cooling
藉由showerhead將氣體帶入反應腔內
Reactor
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Susceptor-1
EPILEDS
37x2”
55x2”=14x4”
24x2”
31x2”
可承載各種數量、種類、厚度晶片的承載盤
69x2”=19x4”
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69x2” Manual Loader
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Susceptor-2
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可承載各種數量、種類、厚度晶片的承載盤
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Heater
Radio Frequency (RF) coils
Tungsten-rhenium coils
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Rhenium alloy coils
Susceptor吸收從加熱器提供的能量而達到薄膜成長所需溫度
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MOCVD component－Precursor
EPILEDS
TMIn
TMGa
CP2Mg
TMAl TEGa
有機金屬或氫化物反應源經由管路或調節器流入Reactor內
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MOCVD component－Gas
handling & mixing systemEPILEDS
Run and vent lines
Run/Vent Switch是決定管路中的氣體是流入反應腔(Run)
亦或是直接排至廢氣管路(Vent)
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Vacuum system
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Exhaust piping system
PT/ filter
DOR Pump
Vacuum Pump
Anti-chamber
pump
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MOCVD component－Scrubber
EPILEDS
廢氣系統是負責吸附及處理所有通過系統的有毒氣體
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Outline
EPILEDS
Introduction
Semiconductor material parameters
Basic concept of CVD
MOCVD tool introduction
Devices for epitaxial quality control
ChingjuPan
Screen layout
EPILEDS
 Temperature、flow rate、pressure…etc
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Epi-TT system
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double-wavelength reflectometer and
emissivity corrected pyrometer
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Graph windows of Epi-TT
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 Growth temperature
 reflectance
 refractive index
 growth rate
 layer thickness
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ARGUS system
EPILEDS
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GaN LED Structure
EPILEDS
Contact layer
P-GaN
source for GaN-based material growth
 TMGa
 NH3
MQW
 TMAl
 TMIn
Strain release layer
 SiH4
 Cp2Mg
N-GaN (GaN: Si)
H2 and N2 gas as the carrier gas
u-GaN
Nucleation Layer
Sapphire
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Characterization devices
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 Photoluminescence : Wp, SDV, Intensity, Thickness…etc.
 Reflectivity : R
 XRD : MQW thickness, FWHM
 Lehighton : sheet resistance
 Optical microscopy : particle, defect
 Electroluminescence : Wd, Vf, IV , HW
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Photoluminescence (PL)
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Wp, SDV, Intensity, Thickness
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Reflectivity (R)
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UV-visible
surface status rough
incident light would be scattered
less reflective light signal
surface status
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X-ray Diffraction (XRD)
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Active layer
InGaN signal
MQW thickness, FWHM
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Lehighton
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sheet resistance
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EPILEDS
Thank you for your attention
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