1. 교육목표 1) LED 산업의현장중심적실무능력함양 2) LED 산업신규인력의선실무지식습득 3) LED 제조공정실습을통한신기술개발 GaP & GaN LED 제조공정단기간교육 ( 이론 : 4 시간, 실습 12 시간 ) 제 1 강 Epitaxy (pn junction)

2012 Educational Program for LED Manufacturing Practice LED 제조공정실무 2012. 05. 31-06. 02 김선태 한밭대학교정보전자부품소재연구소

1. 교육목표 1) LED 산업의현장중심적실무능력함양 2) LED 산업신규인력의선실무지식습득 3) LED 제조공정실습을통한신기술개발 GaP & GaN LED 제조공정단기간교육 ( 이론 : 4 시간, 실습 12 시간 ) 제 1 강 Epitaxy (pn junction) 제 2 강 Photolithography & Etching 제 3 강 Metallization 제 4 강 Characterization

2. 교육과정 Day Time Lecture Instructor D1 (TUE) D2 (FRI) 18:00-18:50 Lecture I (Introduction & Epitaxy) Prof. S.T. Kim 19:00-22:00 LED Lab. I (p-n junction) Dr. C.S. Byun 18:00-18:50 Lecture II (PL & Etching) Prof. S.T. Kim 19:00-22:00 LED Lab. II (PL & Etching) Dr. C.S. Byun 09:00-09:50 Lecture III (Metallization) Prof. S.T. Kim D3 (SAT) 10:00-12:50 LED Lab. III (Metallization) Dr. C.S. Byun 14:00-14:50 Lecture IV (Characterization) Prof. S.T. Kim 15:00-18:00 LED Lab. IV (Characterization) Dr. C.S. Byun

3. LED 제조공정 Module Package Epitaxy Chip Process Substrate

4. LED 제조실습 GaP LED GaN LED n-gap substrate p-n juncion by Zn diffusion p-n junction isolation p-gan on Al 2 O 3 substrate p-n juncion by n-zno deposition PhotoLitho for n-layer mesa etch PhotoLitho for electrode pattern Front process End process Al metal contact formation Dicing Chip bonding Wire bonding Characterization

5. Cleanroom Service Room 2 9 3 4 5 6 7 8 17 19 20 21 White Room Yellow Room XPS Lab. 10 16 22 26 27 30 ㅍ 32 18 23 25 28 1 11 12 13 14 15 15 24 25 29 31 1. N 2 Purifier 2. RF Sputter 3. Chiller 4. E-Beam Evaporator 5. Wet Station 6. Screen Printer 7. Wafer Dicing Saw 8. DI Water Generator 9. Solar Cell I-V Meas. 10. Solar Cell IPCE Meas. System 11. Chiller 12. RF Sputter 13. DC Sputter 14. RTP Furnace 15. Oxidation / Diffusion Furnace 16. Clean Bench 17. Wafer Sawing Machine 18. Hall Effect Tester 19. Spin Coater 20. SEM-EDX 21. AFM 22. LCR Meter 23. HP-4155B 24. Probe Station 25. Microscope 26. Ellipsometer 27. Toxic Gas Burner 28. Gas Cabinet 29. Gas Cabinet 30. Contact Mask Aligner 31. Dry Etcher 32. Dual-source XPS

2012 Educational Program for LED Manufacturing Practice (2012. 05. 31-06. 02) LED 제조공정실무 제 1 강제조공정개요 & Epitaxy 김선태 한밭대학교정보전자부품소재연구소

2012 Educational Program for LED Manufacturing Practice (2012. 05. 31-06. 02) LED 제조공정실무 Light Emitting Diode 광방출다이오드 pn 접합다이오드 반도체 반도체물리반도체재료반도체소자반도체공정

0. LED Application

0. LED type SDP-300W (China)

Contents 1. Introduction 2. LED 동작원리 3. Epitaxy (pn junction) 4. GaN epitaxy 5. Practice

I. Introduction 1. Lighting - lead human civilization - 70,000 BC : first oil wick lamp (=torch, Gk) - 3,000 BC : the first candle by Egyptians - 1783 : Argand - the first oil lamp relied on research (1859 : Kerosene) - 1792 : Murdock - the first commercial coal gas lighting - 1826 : Limelight - the first solid-state lighting device - 1876 : Jablochkoff candle - the first electric lighting device - 1879 : Edison Bulb - incandescent filament lamp - 1927 : Fluorescent Lamps - 1959 : Halogen Lamps

I. Introduction 2. LED history - 1907 : EL observed in SiC (Carborundum) - H.J. Round - 1928 : EL from SiC metal-semiconductor rectifier O.V. Lossev - 1951 : EL from p-n SiC diode - K. Lehovec - 1955 : Visible EL in GaP G.A. Wolff, et al. - 1962 : Visible EL from GaAsP N. Holonyak & S.F. Bevacgua - 1971 : Blue EL from GaN J. Pankove - 1993 : 1 Candela Blue InGaN LED S. Nakamura - 1996 : First commercial white LED - Nichia

I. Introduction 3. Evolution of LED (1) An LED s power conversion (wall-plug) efficiency varies inversely with its optical output power. Wall-plug efficiency can exceed 100%, the unity efficiency, at low applied voltages and high temperatures. Image credit: Santhanam, et al. 2012 American Physical Society

I. Introduction 3. Evolution of LED (2)

I. Introduction 4. LED materials - IV-IV : SiC, SiGe - III-V : GaN, GaAs, GaP - II-VI : ZnO, ZnSe

I. Introduction 5. LED color and materials White InGaN/GaN White (GaN) (x=0.32/y=0.31) White (InGaN) (x=0.32/y=0.31) InGaAlP Green Yellow Verde Green 505 nm Yellow (InGaAlP) 587 nm True Green (InGaN) 525nm Pure Green (InGaAlP) 560nm Green (InGaAlP) 570 nm Orange Orange (InGaAlP) 605 nm Blue (InGaN) Blue (GaN) Blue 470 nm 466 nm Orange Red Org. Red (InGaAlP) 617 nm Red Super Red (InGaAlP) 630 nm Hyper Red (GaAlAs) 645 nm

I. Introduction 6. LED value chain LED 모듈 / 시스템 광학기구, 시스템제어기 RGB, W, UV LED 형광체 패키징 칩공정 LED chip 에피웨이퍼 AlGaAs( 적, IR)/ InGaAlP( 적, 황 )/InGaAlN( 청, 녹, UV) 에피장비 에피성장 기판 GaP, GaAs, GaN, Sapphire, SiC

I. Introduction 7. LED chip processes 에피웨이퍼 pn junction packaging LED chip 전처리진공증착전극형성 Etching 개별화외관검사특성검사 세척 전면증착 PR 코팅 금속에칭 Passivation 외관선별 전기적특성 Etching 후면증착 노광 PR 제거 Dicing 광학적특성 건조 현상 열처리 Expanding

2. LED 동작원리 1. Semiconductor materials 1a 2a 3b 4b 5b 6b 7b 8 1b 2b 3a 4a 5a 6a 7a LED Materials Terminology - elemental semiconductor (Si, Ge) - compound semiconductor (GaAs, GaN, ZnS) - pure semiconductors - impurity semiconductors - n-, p-type semiconductors - direct-, indirect band gap semiconductors Science and Technology - formation (solid, liquid & gas phases) - application (electronics & optoelectronic devices)

2. LED 동작원리 2. Pure semiconductors (Silicone, Si)

2. LED 동작원리 3. n-, p-type semiconductors (a) n-type Arsenic doped Silicone (Si:As) (b) p-type Boron doped Silicone (Si:B)

2. LED 동작원리 4. Compound semiconductors - GaAs Donor impurity : S, Se, Te à As 치환 Acceptor impurity : Zn, Mg à Ga 치환 Amphoteric impurity ; Si à As 치환 : p-type à Ga 치환 : n-type

2. LED 동작원리 5. Direct-, Indirect band gap semiconductors

2. LED 동작원리 6. LED materials

2. LED 동작원리 7. pn junction p n B - h+ M Metallurgical Junction Neutral p-region E Neutral n-region o As+ e- (a) (b) log(n), log(p) W p M W n Space charge region p po n no n i (c) n po r net x = 0 M p no x en d -W p W n x (d) -en a

2. LED 동작원리 8. LED action (1) Electron energy E c E F E v p n + E g ev o ev o Distance into device Electron in CB Hole in VB (a) E c E F E v E g p n + V (b) hu E g (a) 바이어스전압이없는경우 (b) 순방향바이어스 V 가인가된경우. 접합부근그리고 p 쪽에서전자들의확산거리내에서의재결합에의해서광자가방출된다.

2. LED 동작원리 8. LED action (2)

2. LED 동작원리 9. LED characteristics (1) CB 1 2 3 VB (a) E g E c E v E Electrons in CB Holes in VB Carrier concentration per unit energy (b) 2kT 1 /2 kt Relative intensity E g + kt 1 (2.5-3)kT 0 hu 1 hu 2 hu 3 E g hu (c) Relative intensity 1 0 l 2 l 3(d) (a) Recombination in energy band (b) CB 내에서의전자들과 VB 내에서의정공들의에너지분포. 가장높은전자의농도는 E c 보다 1/2 kt 만큼더위에존재한다. (c) (b) 를기반으로광자에너지의함수로서나타낸빛의상대적인세기. (d) (b) 와 (c) 를기반으로하여출력스펙트럼에서파장의함수로나타낸상대적세기. l 1 hu l

2. LED 동작원리 9. LED characteristics (2) (a) 적색 GaAsP LED 로부터의전형적인출력스펙트럼 (b) 전형적인출력광전력대순방향전류. (c) 적색 LED 의전형적인 I-V 특성. Turn-on 전압은약 1.5 V 이다.

3. Epitaxy (pn junction) 1. pn junction fabrication method (a) diffusion (b) ion implantation (c) epitaxy ( arrangement on ~ ) - Homoepitaxy : Si on Si, GaAs on GaAs, GaN on GaN - Heteroepitaxy : GaAs on Si, GaN on Al 2 O 3, GaAs 1-x P x /GaAs

3. Epitaxy (pn junction) 2. Diffusion Acceptor dopant Zn into n-type GaAs, GaP & GaAs 1-x P x etc. (a) Zn diffused pn junction in GaAs 1-x P x LEDs (b) Zn diffusion ampoule (c) Zn diffusion profile in GaP

3. Epitaxy (pn junction) 3. Epitaxy - 액상성장법 (LPE; Liquid Phase Epitaxy) - 유기금속기상성장법 (MOCVD; Metal Organic Chemical Vapor Deposition) - Hydride 기상성장법 (HVPE; Hydride Vapor Phase Epitaxy) - 분자선성장법 (MBE; Molecular Beam Epitaxy) Main Gas Flow Diffusion Boundary Layer 1 반응기내로 source 주입 transport to surface gas phase reaction surface diffusion desorption of precursor desorption of reaction product 2 source가증착영역으로확산이동 3 precursor가성장표면으로이동 4 precursor가성장표면위에흡착 5 precursor가성장위치로확산 6 박막성장 Adsorption of Precursor Nucleation and Island Growth Step Growth 7 표면반응부산물은표면밖으로탈착

3. Epitaxy (pn junction) 4. Mismatch A. Lattice mismatch 격자정수의불일치에기인하는부정합으로서 homoepitaxy 의경우에도불순물의도핑에의해서도발생

3. Epitaxy (pn junction) 4. Mismatch B. Thermal expansion coefficient mismatch 기판과박막사이의열팽창계수차이에의해발생 (a) at growth temperature (lattice match) (b) at room temperature (lattice mismatch)

3. Epitaxy (pn junction) 4. Mismatch C. Crystallographic mismatch 기판과박막사이의결정구조차이에의해발생

3. Epitaxy (pn junction) 4. Mismatch D. Electron valency mismatch 결합을이루는원자들의전자가가전하중성화조건을만족하지못하는경우에발생 ZnSe/GaAs 의경우 Ga 이표면에배열된경우 Zn 보다는 Se 이먼저부착되는경향이크고, 일단 Ga-Se 결합이형성되면표면이매우안정하게되어 3 차원적인성장이진행됨으로써결함이낮은양질의박막을성장하는것이곤란하다.

3. Epitaxy (pn junction) 5. LPE (1) (a) First LPE of Ge by RCA 1963 년 RCA 에서발명 - 열평형상태에서성장 - 양호한결정성보장 - 매우빠른성장속도 - 급준한계면제어의어려움 - 얇은박막의성장이제한 (b) Phase diagram of the Ga-As system

3. Epitaxy (pn junction) 4. LPE (2) (a) Vertical dipping LPE of GaAs:Si (b) Horizontal slider LPE of Ga 1-x Al x As

3. Epitaxy (pn junction) 5. HVPE GaCl + NH 3 GaN + HCl + H 2 (a) VPE of Ga 1-x Al x As in a vertical reactor (b) VPE of GaN in a horizontal reactor 열평형상태에가까운조건에서성장다양한성장기법이가능비교적양호한결정성보장비교적빠른성장속도얇은박막의성장가능

3. Epitaxy (pn junction) 6. MOCVD (a) Growth of GaAs by MOCVD Step coverage 우수양질의결정성장비교적성장속도가빨라생산성이좋음 현재현장에서널리쓰이는성장방법 (b) GaN Growth system by Nichia Chem.

3. Epitaxy (pn junction) 7. MBE (a) Principle of MBE for growth of Ga 1-x Al x As 비평형상태에서의성장성장속도가느려급준한계면제어및아주얇은박막성장가능초고진공으로불순물이적은양질의결정성장가능 RHEED 장비를이용하여결정성장과정을실시간관찰가능비싼유지비, 느린성장속도로인한생산성의저하

3. Epitaxy (pn junction) 8. Epitaxy methods comparison 성장방법 특징 제한 LPE 기판위에과포화용액에의해성장 기판크기제한및아주얇은층성장제어곤란 HVPE 성장하기위한이송재로 Metal Halide 사용 Al 포함되지않은화합물성장, 두꺼운층만성장 MOCVD Source로유기금속화합물사용 AsH 3 와같은아주독성의 Source를사용 MBE 초고진공상태에서증착 높은증기압을가지는재료의성장은어려움 장점 단점 LPE 매우고품질의재료성장 정확한합금조성을위한거의평형상태에서성장 상대적으로저가격 기판크기제한및아주얇은층성장제어곤란 HVPE 극히고품질의재료성장 Al 포함되지않은화합물만성장, 두꺼운층만성장 MOCVD MBE 비평형상태의시스템으로성장 고품질의재료성장 원자적으로급격한계면가능 주의를요하는비싼성장기술

4. GaN Epitaxy 1. GaN blue LED structure @ GaN heteroepitaxy on Sapphire substrate : large lattice & thermal coefficient mismatch

4. GaN Epitaxy 2. GaN/Al 2 O 3 heteroepitaxy (a) Lattice mismatch with orientation of GaN (b) Planes of Sapphire (c) GaN on c-plane Al 2 O 3 (d) GaN on a-plane Al 2 O 3 (e) GaN on r-plane Al 2 O 3

4. GaN Epitaxy 3. GaN/Al 2 O 3 heteroepitaxy roadblock (1) A. Dislocation Large lattice mismatch overcome with low temperature buffer technology 1986 Akasaki et al. AlN buffer for MOCVD growth of GaN on Al 2 O 3 1991 S. Nakamura et al. GaN buffer for MOCVD growth of GaN on Al 2 O 3

4. GaN Epitaxy 3. GaN/Al 2 O 3 heteroepitaxy roadblock (1) B. Dislocation management (1) ELO (epitaxially lateral overgrowth) mask mask mask mask mask mask mask mask mask substrate substrate substrate T.S. Zheleva, et al. JCG 222, 706 (2001)

4. GaN Epitaxy 3. GaN/Al 2 O 3 heteroepitaxy roadblock (1) B. Dislocation management (2) PE (pendeo epitaxy) seed GaN substrate AlN buffer SiN x mask R.F. Davis, et al. JCG 225, 134 (2001) PE GaN PE GaN K.A. Dunn, et al. MRS Internet J. Nitride Semicond. Res. 5S1, W2.11 (2000).

4. GaN Epitaxy 3. GaN/Al 2 O 3 heteroepitaxy roadblock (2) A. Heat dissipation Thermal conductivity GaN: 1.3 W/Kcm Sapphire: 0.26 W/Kcm Copper: 3.98 W/Kcm 1. Peak broadening 2. EL intensity decreasing 3. Peak energy red-shift S. Figge, et al. JCG 281, 101 (2005)

4. GaN Epitaxy 3. GaN/Al 2 O 3 heteroepitaxy roadblock (2) B. Thermal management (1) LED on free-standing GaN substrate K. Akita, et al. PSS (a)201, 2624 (2004)

4. GaN Epitaxy 3. GaN/Al 2 O 3 heteroepitaxy roadblock (2) B. Thermal management (2) Flip-chip LED using LLO T. Ueda, et al. PSS (c)0, 2219 (2003)

4. GaN Epitaxy 3. GaN/Al 2 O 3 heteroepitaxy roadblock (2) B. Thermal management (3) LED by substrate transfer technique D.S. Wuu, et al. PSS (a)201, 2699 (2004)

4. GaN Epitaxy 3. GaN/Al 2 O 3 heteroepitaxy roadblock (3) C. Efficiency Non-polar GaN growth Transparent Ohmic contact Patterned Sapphire substrate Roughened surface 2011 ICNS, by Samsung High efficient InGaN/GaN blue LED on 8 inch (111) Si substrate

4. GaN Epitaxy 4. GaN/Al 2 O 3 LED

5. Practice 1. n-zno on p-gan/al 2 O 3 LED p-gan on Al 2 O 3 substrate size : 10x10mm p-n juncion by n-zno deposition 1st PhotoLitho for n-layer pattern 2nd PhotoLitho for electrode pattern RF sputter deposition, 1hr mesa wet etching lift-off Al metal by DC sputtering annealing n-mgo p-gan Al 2 O 3 Al Dicing size : 2x2mm Chip bonding Ag paste Wire bonding Characterization I-V, I-L

5. Practice 2. Zn diffused p-n GaP LED n-gap substrate size : 10x10mm p-n juncion by Zn diffusion @ 750 o C for 30 min, Zn 10mg p-n junction isolation mechanical removal 1nd PhotoLitho for electrode pattern Al metal by E-beam evaporation lift-off & annealing p-gap n-gap Al Al Dicing size : 2x2mm Chip bonding Ag paste Wire bonding Characterization I-V, I-L