In-situ モニターを用いた窒化物結晶成長の観測In-situ monitoring for LED production 07.07.2011 In-situ モニターを用いた窒化物結晶成長の観測/ 第11回窒化物半導体応用研究会

In-situ モニターを用いた窒化物結晶成長の観測

Dr. Yuto Tomita

Senior engineer

Sales Japan

Outline

07.07.2011 2In-situ モニターを用いた窒化物結晶成長の観測 / 第11回窒化物半導体応用研究会

• Who is LayTec?

• Products / features

• Economical benefit

• Summary

• focus on in-situ & in-line metrology with

optical methods

• market leader in in-situ metrology for

LED and Power device production

• world-wide distribution & service network

Who is LayTec?

LayTec - optical in-situ metrology for thin-films

More than 10 years experience and over 1400

systems in the field!


その場観測光学測定

LED、パワーデバイス生産でトップシェア

日本代理店: 丸文㈱

Sales: total

Strong increase by backlighting business in 2009 and 2010

Still continues in 2011 and 2012 for general lighting!

Sensors sold/year: 1999-2010

0

100

200

300

400

500

600

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

sensors

per

year

Total: over 1400 systems


Outline


• Who is LayTec?

• Products / features


• Summary

Performanceimprovements

• Reliability/lifetime• Brightness• Efficiency

In-situ control – why?

Challenges in LED production

Costreduction

• Yield • Reproducibility• Color uniformity• Wafer size

(up-scaling to 6”)

Key parameters to be controlled• Pocket and wafer temperature • Wafer curvature• Temperature uniformity• Surface morphology• Reproducibility

All by LayTec tools!!07.07.2011 6In-situ モニターを用いた窒化物結晶成長の観測 / 第11回窒化物半導体応用研究会

素子特性の向上

製作コストの削減

特性の安定化、寿命

輝度

効率

生産性、歩留まり

再現性

発光波長の均一性

基板サイズの大型化

基板温度

基板の反り

温度の均一性

表面状態

再現性

LayTec product/feature highlights

LayTec products lineup

Temperature: all models

• EpiTT/EpiCurveTT, Pyro400

• AbsoluT growth temp calibration (+/-1K)

Reflectance: EpiTT and EpiCurveTT series

• Growth rate and morphology

• 405nm for GaN based MQW monitoring

• 633nm for GaAs based materials

Curvature: EpiCurveTT series

• EpiCurve®TT AR – Advanced resolution (aspheric Meas.)

• Alternative blue laser for patterned sapphire


放射温度計(パイロメーター)

温度測定: 全モデルで可

LED光源(多波長)

での反射率測定

反り測定(レーザー)

2軸方向での反り測定、両面研磨やパターン基板にも対応

0.0

0.1

0.2

0.3

600

800

1000

1200

2000 4000 6000 8000 10000 12000

-50

0

50

100

refle

cta

nce

tem

pe

ratu

re / °

C

cu

rva

ture

/ k

m-1

time / s

In-situ measurement in GaN MQW LED

GaN/sapphire MQW LED structure

• reflectance 405nm

• reflectance 950nm

• reactor temperature (熱伝対)

• true temperature (950nm)

• real temperature (400nm)

• wafer curvature

desorp. nucl. GaN buffer MQW cap

(|

)

concave

Flat=0

convex

1. 反射率測定成膜レート

2. 温度測定

3. 反り測定

GaN表面

表面/底面

400nm域はGaNに吸収950nmでは干渉光

横軸: 時間


干渉光成膜レート

熱伝対温度

Pyro400(400nm)

ラインスキャンも可

GaN表面温度

950nm 405nm

Reflectance measurement

Advantage for morphology measurement

950nm 405nm

good morphology

bad morphology: increasing roughness

smooth surface

反射率から表面状態の模索


荒い表面状態光散乱

平坦な表面反射率一定

干渉光安定

干渉光減衰

On-line reproducibility check

Important benefits of LayTec’s EpiNet

loaded reference run

リファレンスデータ

current run

成長ラン

Run #2

Run #1

MQW: InGaN (3nm) / GaN (7nm)

reflectance (405nm)

反射率(950nm)

LayTec tool provides precise real time

run-to-run reproducibility check

再現性を成長中に確認(温度、成長レート、表面状態、反り)


量子井戸内の単膜(<10nm)も可視化

温度

Curvature measurement

Effect of curvature on PL uniformityInGaN MQW growth: comparison of two wafers

(|

)

concave

flat

convex

wafer 1

wafer 2 narrow PLflat wafer

wafer 2

wafer 1

data courtesy of F. Brunner, FBH Berlin

broad PLbowed wafer

~ 50km-1

反り基板波長不均一

フラット基板波長均一

PLマッピング


MQW

反りを制御して歩留まり向上(EpiCurveTT Two)


Curvature engineering for GaN/Si device

0 20 40 60 80

-100

-50

0

50

100

150

cooling

GaN

GaN:Si,Ge [Si] ~ 8x10

18 cm

-3

[Ge] ~ 1.7x1019

cm-3

Curv

atu

re (

km

-1)

Time (min)

seed and GaN buffer

LT

-AlN

GaN/Si has lattice mismatch

Curvature engineering

necessary

GaN/Si格子定数の違いから反りが発生

反りの制御が必要

• GaN doping with (n-type)

• Si: crack at RT

• Ge: crack free and flat

Geドープは室温にてフラットな基板

新しい材料の研究開発に貢献

GaN:Si GaN:Ge

07.07.2011 12In-situ モニターを用いた窒化物結晶成長の観測 / 第11回窒化物半導体応用研究会 Data courtesy of

University Magdeburg


Asphericity measurement – EpiCurveTT AR

Sub-curvature

aspherical

Main-curvature

spherical

spherical curvature

asphericity

Reflectance(405nm)

Temperature: MOCVD

Temperature: LayTec

• semipolar GaN on m-plane

sapphire

• growth of semipolar GaN

creates strong asphericity

different in-plane strain

2軸方向での反りのモニターリングも可能

詳細な反りの制御が可能 (EpiCurveTT AR)


Outline


• Who is LayTec?

• Products

• Features


• Summary

Economical aspects EpiTT

• 2” wafer config

• GaN on sapphire

• 6h process time

• 2% yield improvement only

achievable by 405nm MQW

monitoring

• Full production

In-situ monitoring for LED production


EpiTT: 温度(950nm)と成長レートの制御LEDの生産現場(2“)にて約6ヶ月で設備投資の減価償却が可能

原価償却シミュレーション

Economical aspects EpiCurveTT

• 2” vs 4” wafer config

• GaN on sapphire

• 6h process time

• 10% yield improvement due

to curvature measurement

• Full production

In-situ monitoring for LED production


EpiCurveTT: 温度(950nm)、成長レート、反りの制御4“の生産現場にて約2ヶ月で設備投資の減価償却が可能

原価償却シミュレーション

Outline


• Who is LayTec?

• Products

• Features


• Summary

• Key parameters to be controlled

• Temperature: ternary composition and doping rate

• Thickness and growth rate

• Curvature: Temperature uniformity during critical layer and flat wafer at

room temperature

温度、膜厚、反りの制御によりLEDやパワーデバイスの生産性向上

• using in-situ reflectometry, uniformity of growth rate can be optimized

quickly saving time and money

成長パラメーター制御により短期間での原価償却が可能

• curvature is crucial

• even for accurate and uniform susceptor surface temperature

wafer bowing occurs up to Twafer ~ ±10 K

• effect worsens for larger wafers

• with EpiCurve® series used for bow-control Twafer <~ ±1 K

• real surface temeprature of GaN/sapphire substrate is necessary

基板の大型化に伴いGaNの表面温度(Pyro400)や多軸上の反り(EpiCurveTT AR)が必要

In-situ monitoring solution

Summary


Some gemsneed a little

extra help to

sparkle

www.laytec.de


extra help to

sparkle

www.laytec.de


extra help to

sparkle

www.laytec.de

LayTec AG 冨田勇人 ([email protected])

LayTec日本販売代理店: 丸文㈱

ご清聴ありがとうございました。

In-situ monitoring

System set-up

MOCVD

EpiCurveTT Two

optical head

control and analysis

computer

emissivity corrected

pyrometry (TT)

• wafer temperature

• wafer selective ± 1K

• 450 - 1300°C

T / °C

double wavelength

reflectance (R)• wafer selective

• growth rate

• = 950nm and 633nm or 488nm or 405nm

R

wafer bowing /

curvature

• wafer selective curvature

• temperature uniformity

• cracking of layers and ternary composition

1/r [km-1]


放射温度計(補正済み)

多波長反射率

反り測定

2. Reflectance measurement

Advantage of a double wavelength sensor

•Growth rate analysis: fitting from oscillation in reflectance data

•Detailed information: thick GaN by 950nm and MQW by 405nm

Sapphire

2μm GaN:Si(5x1018)

100nm (Al)GaN:Mg 950nm

950nm

405nm

MQWs 405nm

p-GaN 950nm

n-GaN 950nm


400nm域はGaNに吸収

GaN表面

GaN 表面/底面

GaN 表面/底面

反射率の振幅から成長レートを算出波長を使い分ける事によってそれぞれの層での測定が可能

干渉光成長レート

New: get all three at same time

• 405nm is optimized for

• thin layers (MQWs)

• morphology monitoring


• growth rate measurements


• emissivity correction

1. Reflectance measurement


Data courtesy of Ferdinand-Braun-Institute, Berlin

405nm

633nm

950nm

従来: 2波長までの選択3波長の同時測定が可能(2011年末)

2波長からのアップグレード可

2. Temperature measurement

Pyrometry at 950nm and 400 nm

Pyro400: 400nmEpiTT/EpiCurve TT: 950nm

GaN/Si GaN/Sapphire GaN/Sapphire

Si

λ<950nmGraphite GaN

λ<400nm

Measured: wafer temperature

= changed by wafer bow

Line scan measurement OK

Measured: pocket temperature

= unchanged by wafer bow

Line scan measurement NG

Measured: GaN temperature

= changed by wafer bow

Line scan measurement OK


ラインスキャン可GaN/Siデバイス

ラインスキャン可 LED大型基板

測定温度: グラファイト LED小型基板

(放射温度計)

1014

1016

1018

1020

1022

1024

1082

1084

1086

1088

1090

1044

1046

1048

1050

1052

1054

1036

1038

1040

1042

1044

1046

position

position

position

position

desorp GaN beginGaN end SL

5000 10000 15000 20000

600

800

1000

1200

tem

pe

ratu

re / °

C

2. Temperature measurement

Pyro400 in GaN/AlGaN MQW laser

wafer temperature linescans of 2“ wafer

(GaN最表面温度ラインスキャンデータ)

desorption

(= pocket)

note: all diagrams have same 10K T-scale

GaN buffer GaN buffer superlattice MQWstabilizing

714

716

718

720

722

724

1050

1052

1054

1056

1058

1060

position

position

MQWcap

Pyro400 (GaNの温度測定)

• Pyrometer at 400nm

• Temp of GaN on

transparent substrate


熱伝対温度

Pyro400(400nm)

EpiTT(950nm)

基板の反りによらず圧力やガスの種類により変化

• Fractional reflection of incident light at

layer surface and layer/substrate

interface interference effect

• Max. intensity Ireflected: 2nd = mλ

• Min. intensity Ireflected: 2nd = (m + ½) λ

• During growth dynamic interference

pattern growth rate r = d/t

Technical background

Growth rate / thickness

determination

Growth rate determination:

Max. reflectance: r * t = mλ/2n or min. reflectance: r * t = (m + ½) λ /2n

Reflectometry – powerful tool for growth rate monitoring


• Devices heterostructures

• GaN-based layers:

• 950nm highly transparent:

Growth data of thick buffer layers,

no data from quantum wells

• 405nm highly absorbing:

Growth data of quantum wells


Why double wavelength

reflectance measurement?

For accurate growth monitoring a double wavelength reflectance

sensor is required!

2nd wavelength has to be suitable for the specific material!

susceptor

GaN

Reflected

1. 950nm

2. 405nm

Incident:

1. 950nm

2. 405nm

InGaN QW



Advantage of a double wavelength sensor

• Detailed information: thick GaN by 950nm and MQW by 405nm

Suitable wavelength combination is mandatory for successful

device production!

Sapphire

2μm GaN:Si(5x1018)

100nm (Al)GaN:Mg 950nm

950nm

405nm

MQWs 405nm

p-GaN 950nm

n-GaN 950nm


• relation between emitted radiation of a

body at a certain wavelength

temperature Planck’s law

• Main part of the spectra – infrared

• Choose one wavelength detect the

emitted radiation get the

temperature - pyrometry


Temperature monitoring

Pyrometry is the powerful tool for growth temperature

monitoring

Any drawback?

0.2 0.4 0.6 0.8 1.0 1.2 1.4

800°C

700°C

600°C

500°C

inca

nd

esce

nce

in

ten

sity

photon energy / eV

950nm

Planck spectra




• Fractional reflection of incident light at layer surface and

layer/substrate interface interference effect

Proper correction of pyrometry signal necessary!

e

Interferred e2500 3000 3500 4000 4500

0.2

0.3

0.4

2500 3000 3500 4000 4500650

675

700

725

overgrowth

material A

growth

material B

substrate

material A

refle

cta

nce

time / s

tem

pe

ratu

re / °

C

pyrometry at 950nm

substrate

material A

growth

material B

overgrowth

material A




• Reflectance measurement necessary for emissivity correction

Effective solution – combination of growth rate and temperature

monitoring in one sensor EpiTT by LayTec

emissivity corrected temperature

reflectance at 950nm

pyrometry at 950nm

2500 3000 3500 4000 4500

0.2

0.3

0.4

2500 3000 3500 4000 4500650

675

700

725

overgrowth

material B

growth

material B

substrate

material A

reflecta

nce

time / s

tem

pera

ture

/ °C

interfered R

e

interfered eR


EpiCurve® TT measurement principle

plane substrate

susceptor



plane substrate

susceptor

emission light

emission

measurement at 950nm

Method 1: intensity measurement of emission light



plane substrate

susceptor

reflectance

measurement

incident light reflected light

Method 2: normal incidence reflectometry



Method 3: distance variation of parallel laser beams

2D CCD

camera

xo

plane substrate

susceptor

parallel laser beam

curvature

measurement



XD(z)

substrate / wafer

(bent due to strain)

susceptor

parallel laser beam

zT

Method 3: distance variation of parallel laser beams


EpiCurve®TT AR

Now: three spots for simultaneous measurement in two directions

X

susceptor

zT

Y

x

y

New

EpiCurve AR!


EpiCurve – limitations with red laser

EpiCurve®TT Blue

single side polished sapphire double side polished sapphire patterned sapphire substrate (pss)

interference

single spots double spots diffuse spots


Performance of EpiCurve TT AR blue

EpiCurve®TT Blue

single side polished sapphire double side polished sapphire patterned sapphire substrate (pss)

single spots

GaN layer GaN layer GaN layer

single spots single spots

(after coalescence)blue laser light is absorbed in GaN


Measurement on double side polished wafers

EpiCurve®TT Blue

• using blue laser (405nm)

• same form factor as EpiCurve TT

Two and EpiCurve AR

• available for AIXTRON planetary

MOCVD systems (G3, G4, G5)


Measurement on double side polished wafers

EpiCurve®TT Blue

• GaN on sapphire and SiC: transparent for red laser

reflexion also at polished backside

• GaN on sapphire and SiC at growth temperature opaque for blue laser

no reflexion at polished backside

improved

signal-to-noise

ratio

• AlN/GaN/AlGaN

on double-side

polished 4H-SiC


2000 4000 6000 8000 10000 12000 14000

0.0

0.1

0.2

0.3

0.0

0.1

0.2

0.3

0.0

0.1

0.2

0.3

0.0

0.1

0.2

0.3

time / s

Ref

lect

ion

at 6

33nm

Growth on patterned sapphire substrates

EpiCurve®TT Blue

Plain sapphire

Patterns have strong influence on reflectance signature


0 2000 4000 6000 8000 10000 12000

0

50

100

150

200

Sapphire

PS1

PS2

PS3

Cur

vatu

re /

km-1

time / s

Growth on patterned sapphire substrates

EpiCurve®TT Blue

• Curvature can be measured on substrates and coalesced layers

• Patterned substrates can significantly reduce strain in GaN layers.

all measured with blue laser


AbsoluT: Temperature calibration tool

patent pending

AbsoluT: calibration light source

• provides reference temperature

• hot susceptor surface is mimicked by this handheld reference light source

• performs transmission measurement through viewport

• 950nm light source

• uniform emitting area

• equals a temperature of 925°C

(black body calibrated)

• put below showerhead or ceiling


Effect of AbsoluT during production

• MQW temp before and

after calibration for an

EpiTwinTT on Crius

• Improved (R2R)³ variation

• Ring to ring

• Run to run

• Reactor to reactor

• Accurate SPC

• No consumable

AbsoluT: Temperature calibration tool

Reliable base for statistical growth temperature control


3. Curvature measurement


|narrow PLflat wafer

wafer 2


bin size 0.57 nm

45% in center bin

75% in +/- 1 nm

フラット基板波長均一

横軸: LEDの数縦軸: 波長


3. Curvature measurement


(|

)

concave

flat

convex

wafer 1 (


bin size 0.57 nm

only 20%

in center bin(s)

broad PLbowed wafer

反り基板波長不均一

横軸: LEDの数縦軸: 波長


Documents

In-situ モニターを用いた窒化物結晶成長の観測In-situ monitoring for LED production 07.07.2011 In-situ モニターを用いた窒化物結晶成長の観測/ 第11回窒化物半導体応用研究会