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1 제 3 장 ( 공정 ) TFT Fab. Process

2 박막트랜지스터기술개발의핵심 1) 제조가격의저감을위한공정단순화 2) 단채널화와전자의이동도향상 3) 포토마스크의수를 4 장이하로하기위한기술개발 4) 신뢰성이높은공정기술 5) 저온에서 poly-si 막 6) 절연막을형성하는기술 7) 불순물제어에의한 CMOS 형성기술 8) 유기 TFT 2

3 LC Materials for Monitor & TV LCs + Δε - Δε LCD Mode Demands to LCs LCD Mode Demands to LCs IPS -High Δε -Low γ 1 -Good reliability (mura-free) VA (MVA, PVA, New-ASV) -Low γ 1 -High Δε for Low Vop & High Light Efficiency FFS -High Δn -Low γ 1 -Good reliability (mura-free) 3

4 Issues for LCD Modes and Development Status LCD Mode Intrinsic Issues IPS V th 1/d, τ off γ 1 d 2 /K 22 Fast Response: d V th Δε γ 1 ; Limitation exists Solutions -CN LCs with High Reliability -New LCs for high Δε and low γ 1 VA τ on Molecular dynamics & γ 1 τ off γ 1 d 2 /K 33 ; Advantage due to bend deformation γ 1 > 100 mpa.s with relatively low Δε FFS V th 1/d, τ off γ 1 d 2 /K 22 Fast Response: d V th Δε γ 1 ; Advantage exists -New LCs for high Δε and low γ 1 (Breakthrough??) -Focus on LCs for low γ 1 with High Reliability 4

5 Wide-Viewing-Angle Technologies used in Production by Korean companies FFS Light Glass LC Molecule OFF ON Electric Field IPS Glass Light Light Metal Off Light On PVA Substrate Light Light 5

6 One Pixel Structure of FFS IPS FFS Glass Glass C s C f C s Glass Glass C s Bus Line C s C LC Cs Bus Line C s C f C LC TFT C pd TFT C pd Gate Bus Line C gd Gate Bus Line C gd Source Bus Line Source Bus Line C total =C gd + C s + C LC (IPS) C total = C gd + C s + C f + C LC (FFS) Cst in Light-Transmitted Area!!! 6

Characteristics of glass substrate for TFT-LCD Corning 7059 & 1737 glass Thermal absorption ratio Corning Corning 1737 Corning Eagle 2000 Corning Annealed Glass (1737) NA 35 (NH Techno glass) Density

7 Characteristics of glass substrate for TFT-LCD Corning 7059 & 1737 glass Thermal absorption ratio Corning Corning 1737 Corning Eagle 2000 Corning Annealed Glass (1737) NA 35 (NH Techno glass) Density 20 o C 2.54g/cm g/cm /cm 3 Thermal expansion / o C ( 0 ~ 300 o C ) 12 ~ 13 ppm ( at 400 o C 2h ) / o C ( 0 ~ 300 o C ) / o C ( at 300 o C ) 2 ~ 3 ppm ( at 600 o C 2h ) roughness ~ Å Relativity of Glass & temperature 7

8 Details of Side(Wedge) type Protection Sheet Vertical Prism Sheet Horizontal Prism Sheet Diffusion Sheet Light Guide Plate (LGP) Reflection Sheet Lamp & Lamp Cover 8

Proccess - Glow discharge in low vapor pressured Mercury by added high electric field - UV ray (253.

9 Lamp 1. Principle & Structure of CCFL(Cold cathode Fluorescence Lamp) 1. Normal glow discharge 2. Rare gas & mercury (a few mg) 3. Proccess - Glow discharge in low vapor pressured Mercury by added high electric field - UV ray (253.7nm) emitted these ultraviolet rays excite the phosphor. - Excited phosphor atoms return to low energy level, the visible light is emitted. (Its wave length is decided by the phosphor material.) 9

10 Lamp 2. Characteristic color x, y coordinates - White region - x=0.298±0.01, y=0.295±0.01 (in case of 14 Lamp) - Color control mixing R G B Phosphor materials 3. Lamp & Lamp Cover - Lamp cover absorbed >60% of light - Only ~30% light entered LGP - Need New design and new materials for Wedge for Direct 10

11 Light Guide Plate (LGP) 1. Flat LGP / Shaped LGP by Mold injection 2. Polymer materials = PMMA 3. General Characteristics of PMMA as a Light Guiding Color General Usage LGP Application Remarks Transparent Half-Trans Transparent Depend on process & Materials Specific Weight Reflect Index 1.49 ~ Optical Energy Gap Optical Transmittance 3.8 ~ 4.4 ev 3.8 ev - 88 ~ 93 (0.1, 350~850nm) 93 Below the 380nm, Absorption region Olefin resin Yellowish of LGP 11

12 3. Lens Film - Structure (Vertical, Horizontal) - Function : To enhance bright & Light exit angle Θ=~70 o Θ Diffusion film LGP - Brightness Enhanced Film (BEF), DBEF, MBEF, etc - 3M, Exclusive Patent 12

13 Further Research for Flat Lamp 1. E 리 (External Fluorescence Lamp) EE 리 (external electrode free lamp) - AFL (arrayed fluorescence lamp) - Possible to form Array & Mosaic with 1 inverter - Sustain voltage is higher than that of CCFL (1000~1400) (~800 or lower) Gnd Hot Inverter 13

Electrode structure - Parallel electrode with

14 Further Research for Flat Lamp 2. Osram Flat Lamp 15 Flat Lamp Inverter 1. Specification - 15, 7000cd/m2, 48Watt 2. Results cd/m2, Uniformity of ~70% 3. Electrode structure - Parallel electrode with dendritic tip 4. Drawbacks - Heat/Weight/Inverter size Electrode structure spacer 14

15 박막트랜지스터특성에영향을주는요소 15

16 박막트랜지스터의전기적특성 전이 (Transfer) 특성 출력 (output) 특성 16

대표적 TFT 의구조 1) Coplanar type 2) Stagger type Source Gate Drain Gate Gate Insulator a-si:h Source Gate Insulator a-si:h Drain Glass substrate Glass substrate 3) Inverted

17 대표적 TFT 의구조 1) Coplanar type 2) Stagger type Source Gate Drain Gate Gate Insulator a-si:h Source Gate Insulator a-si:h Drain Glass substrate Glass substrate 3) Inverted Stagger type Source Drain a-si:h Gate Insulator Gate Glass substrate 4) Inverted Stagger - ISI type Source Etch stopper a-si:h Gate Insulator Gate Glass substrate Drain 17

18 TFT 배선재료 18

19 TFT 구조도 (1) (SID SHORT COURSE, 2001) 19

20 TFT 구조도 (1) (SID SHORT COURSE, 2001) 20

21 대표적 TFT 구조들의공정및특징 21

22 LTPS TFT-LCD 와 AMOLED 의비교 (1) 22

23 LTPS TFT-LCD 와 AMOLED 의비교 (2) 23

24 LTPS TFT-LCD 와 AMOLED 의비교 (2) ( 경희대학교보고서, 저온폴리실리콘 TFT Array 및공정기술, 2002) 24

25 I-V Characteristics of a-si TFT(1) (SID SHORT COURSE, 2001) 25

26 I-V Characteristics of a-si TFT(2) (SID SHORT COURSE, 2001) 26

27 결정화방법비교 27

28 AMOLED 의화소구조 ( 경희대학교보고서, 저온폴리실리콘 TFT Array 및공정기술, 2002) 28

29 세계 OLED 시장분석 29

30 세계 OLED 시장전망 30

31 OLED 기술개발전망 31

32 저주파수 HPD-CVD 장비 32

33 목표및평가방법 ( 경희대학교보고서, 저온폴리실리콘 TFT Array 및공정기술, 2002) 33

34 박막의특성평가방법 34

35 비정질박막트랜지스터 2.2 비정질박막트랜지스터의제조기술 가. Sputter 기술나. CVD 기술다. Photolithography 기술라. Dry etching 기술마. Wet etching 기술바. 세정기술아. 차기 line 동향 35

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38 TFT Panel Process 38

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42 Metal for TFT-LCD Process TFT-LCD에서 Metal의역할 Gate & S / D Bus Line Pixel Electrode Capacitor Electrode PAD Align Key Black Matrix Mask Static Charge Protect Required - Resistance : Signal Delay - Etching : Taper, CD Uniformity, Etch Rate - Thermal Characteristic : Heat Expansion, Hillock - 내화학성 : 타 Etchant, 세정, Developer, Stripper - 전기화학반응 : 두 Metal의접촉이 Galvanic Cell형성 - 신뢰성 : PAD재료로쓰일경우 Corrosion - Contact 저항 : Metal간의 Contact, S/D Contact - Other : LC 세정액 42

43 Metal deposition Metal deposition PVD CVD Sputtering Evaporation PECVD Inert gas E-gun or crucible source Reactive gas (reactive gas plasma) Advantage Advantage High purity deposition Multi-sputtering with good controls High deposition rate In-situ surface cleaning No trapped gases Disadvantage No radiation damage Impurity in the sputter gas Disadvantage Radiation or ion damage Poor control on deposition rate Target material dependence Not suitable for compound DC, RF(AC) Sputtering Poor Step coverage Required - Step coverage ( CVD >> Sputtering >> Evaporation ) - No damage during deposition (Evaporation >> CVD >> Sputtering) - No stress, Good adhesion - Smooth films - Crystalline films Advantage Excellent step coverage High throughput Selective deposition possible High deposition rate Disadvantage Limited to available precursors Not suitable for compound Particle generation Rougher surfaces Gas entrapment Toxic hazardous gas Decomposition procducts 43

44 가. Sputter 기술 -Sputtering 은기체의 Plasma 에서생성된고 energy 의양이온이전기적으로음극인 Target 물질은쳐내는물리적인현상이며이에의해 Target 물질이기판위에증착된다. -Sputter 공정에서즉착하는물질중특히 Issue 가되는것은 Gate 와 S/D 물질이다. 금속 비저항 ( Ωcm) 녹는점 ( ) 결정구조 Ag 2.0 (1.6) 961 FCC Cu 2.3 (1.7) 1083 FCC Al 3.1 (2.7) 660 FCC Mo 11.5 (5.4) 2610 FCC Cr 21.0 (12.9) 1875 BCC Ni 50 (7.8) 1453 BCC ITO 180~200 - Cubic Bixbyite 44

45 DC diode discharge 에서의여러가지현상 45

46 Required Resistivity ( ì Øcm) 디스플레이공학 Panel 의대각선길이에따른 Gate, S/D 물질의요구되는비저항 Diagonal Size (inch) Gate VGA(GV) Gate XGA(GX) Gate HDTV(GH) Data VGA(DV) Data XGA(DX) Data HDTV(DH) Al-Nd Mo Cr á-ta MoTa 46

47 Resistivity ( ì Øcm) Stress (dyne/ ² ) 디스플레이공학 Al-Nd 합금의성질 E E E E E É 100 É 150 É Depo Â µ -1.0E E Temperature ( É ) Al-Nd alloy 의증착온도에따른비저항및 PECVD Anneal 후의비저항 Al-Nd 와 pure Al Stress 의 Thermal Hysteresis 47

48 Resistivity (μω cm ) Stress (E+10 dyne/ cm2 ) 디스플레이공학 Cr 의성질 (2.2mTorr) Pressure (Pa) Pressure (Pa) 증착압력과온도에따른 Cr 의 Resistivity ( 좌 ) 및 Stress ( 우 ) 48

49 Resistivity ( ì Ø ) Resistivity ( ì Ø ) 디스플레이공학 Heater Setting Â µ ( É ) O2 À (sccm) Heater 의 Setting 온도에따른 ITO Film 의비저항변화 O2 유량에따른비저항변화 49

50 O2 유량과 ITO Film 의표면변화 O2 유량의증가에따른 ITO Film 의표면 SEM 변화 ( 60,000) (O2 : 0.4sccm) (O2 : 1.2sccm) (O2 : 2.0sccm) 50

51 Rs (Ω/ ㅁ ) Rs (Ω/ ㅁ ) 디스플레이공학 O2 유량및 Anneal 전후에따른 IZO, ITO 의 Rs 특성 증착한 ITO, IZO 의 Anneal 전후 Rs ( 두께 1200A ) ITO (as depo Rs) IZO (as depo Rs) ITO (anneal Rs) IZO (anneal Rs) 0 0.6sccm 1.4sccm 2.2sccm 3.0sccm O₂유량 증착한 ITO, IZO 의 Anneal 전후 Rs ( 두께 1200A ) 10 ITO (as depo Rs) ITO (anneal Rs) 5 IZO (as depo Rs) IZO (anneal Rs) 0 0.6sccm 1.4sccm 2.2sccm 3.0sccm O₂유량 51

52 Low resistive metals for the bus lines of TFT-LCD Item Ag Cu Al AlNd Resistivity ( cm) ~ 4.5 Hillock X O X O Anti-Corrosion X X Adhesion to Glass or a-si X X O O Dry Etching X O Reflectance O X O O n+a-si Contact O O X X ITO Contact O O X X Target Coast O recycle O O X (O Good, Not So Good, X Bad) 52

53 High-Aperture-Ratio TFT-LCD Using a Low Dielectric Material n + Drain/Source Pixel Electrode (ITO) Organic insulator a- Si:H Gate SiNx Data line 53

54 TFT on Color Filter Structure A) Color Filter patterning Top Glass Substrate Ni Silicide Passivation Common Electrode ITO (Pixel electrode) B) BCB TFT fabrication C) BM Patterning 54

55 나. CVD 기술 -CVD 는화학기상증착으로반응기체가반응기내에서반응기에공급되는에너지원 ( 열에너지, 광에너지, rf power, DC) 에의해활성화되어화학적으로반응하여원하는기판위에안정된막을형성하는기술이다. (1)APCVD(Atmospheric Pressure Chemical Vapor Deposition) - 상압에서열에너지에의해분해된반응가스들이기판표면에서결합하면서박막을형성, 빠른 gas flow 요구. (2)LPCVD(Low Pressure Chemical Vapor Deposition) - 진공펌프를이용한저압상태에서열에너지에의해화학반응이이루어지며질량의전달속도가빠르기때문에온도컨트롤이중요. (3)PECVD(Plasma Enhanced Chemical Vapor Deposition) - glow 방전에의하여높은에너지를얻은전자가중성상태의가스분자와충돌하여활성화되고, 이들이화학반응을일으켜박막을형성. 55

56 P-5000 PECVD Chamber 개략도 56

(1)Electron-Impact Dissociation reaction dissociation 반응에의해중성입자가매우 reactive 한 radical 로전환된다. reactive radical 은원자상태이거나또는불완전한화학결합을하고있는원자들의집합체로전기적으로는중성이다.

57 (1)Electron-Impact Dissociation reaction dissociation 반응에의해중성입자가매우 reactive 한 radical 로전환된다. reactive radical 은원자상태이거나또는불완전한화학결합을하고있는원자들의집합체로전기적으로는중성이다. 대부분의 Plasma surface reaction 화학반응은 radical 들에의하여이루어진다. e + O 2 O + O + e (2) Electron-Impact Ionization reaction Electron 이중성원자와충돌하여외각전자를방출로인하여이온화되는반응으로간혹 dissociation 과동시에발생하기도한다. e + O 2 O e ( Ionization ) e + O 2 O + + O + 2e ( Ionization + Dissociation ) e + SF 6 SF 6- SF 5- + F ( Electron Attachment ) (3) Electron-Impact Excitation reaction Electron 과 radical 의충돌에의하여 radical 이불안정한여기상태로천이하는반응으로 vibration 또는 rotational excitation 도발생한다. e + F F* + e ( Excitation ) PECVD 반응원리 57

58 단일막의주요특성 Gate SiNx Film 조건 GH GL DEPO RATE (A /min) Uniformity (STD, Edge 15mm) 63 Refractive Index Stress (dyne/cm2) 1.0E E+10 WER (A /min,500:1hf) 60 N-H Bond (E22/cm3) Si-H Bond (E22/cm3) N-H/Si-H RATIO TOTAL H (E22/cm3) Dielectric Constant

59 a-si Film 조건 DEPO RATE (A / MIN) 960 Uniformity (STD, Edge 15mm) 31 Refractive Index 4.02 Stress (dyne/cm2) -3.50E+9 Si-H/Si-H2 Ratio 2.6 H Concentration (Area) 5.7 Resistivity(Ωcm)

60 n+ a-si Film 조건 AL AH AL AH DEPO RATE (A / MIN) Uniformity (STD, Edge 15mm) Refractive Index Stress (dyne/cm2) -3.9E+9-4.7E+9-2.0E+9-4.0E+9 Si-H/Si-H2 Ratio H Concentration (Area) Conductivity(DARK, ATM상태 ) 8.30E E E E-9 60

61 Passivation SiNx Film조건 DEPO RATE (A / MIN) 2070 Uniformity (STD, Edge 15mm) 51 Refractive Index Stress (dyne/cm2) -5.0e+9 WER(A /MIN, 500:1HF) 140 N-H Bond (E22/cm3) 2.16 Si-H Bond (E22/cm3) 0.52 N-H/Si-H Ratio 4.15 Total H (E22/cm3) 2.69 Dielectric Constant

62 다. Photolithography 기술 - 사진공정은마스크상에설계된패턴을공정제어규격하에웨이퍼상에구현하는기술 62

63 양성감광제와음성감광제비교 63

64 화학변화에의한선택적현상과정 64

65 PR 코팅방법 중앙에서떨어뜨리는방식 Slit & Spin 방식 65

66 Stepper 의원리및기본구성 66

67 Aligner 의기본구성 67

68 Scanning Projection Exposure Schematic View 68

라. Dry etching 기술 - 전기방전이생기면반응 Gas 들의일부가 Ionize 되어 Electron 과 Ion 이공존하는상태로일정공간에, 일정시간동안존재하는데이를 PLASMA 라하며이를이용한 Etch 를 Plasma Etch 또는 Dry Etch 라고부른다.

69 라. Dry etching 기술 - 전기방전이생기면반응 Gas 들의일부가 Ionize 되어 Electron 과 Ion 이공존하는상태로일정공간에, 일정시간동안존재하는데이를 PLASMA 라하며이를이용한 Etch 를 Plasma Etch 또는 Dry Etch 라고부른다. (1) 장점 -비등방식각이가능하여정확한패턴의형성이가능하다. -고순도의산을사용하지않으므로비용이저렴하다. -자동화가가능하므로수율과생산고가높다. (2) 단점 -많은공정변수를갖는다. -복잡한물리, 화학반응을수반하므로공정의이해가어렵다. -플라즈마내의이온의충격이나래디칼에의한손상및오염의문제가있다. -건식식각에어려운물질이많다.(Cu, Pt) 69

70 PE(Plasma Etch) MODE 70

71 RIE(Reactive Ion Etch) MODE 71

72 TCP(Transformer Coupled Plasma)MODE ( 특징 ) 1.GLASS에 DAMAGE가많음. 2.SINx/SI/Ta/MO/ITO/AL/Cr 등의 ETCH 3.LOW PRESSURE(100mTorr 이하 ) 4.HIGH DENSITY가가능하여 THROUGHT PUT에유리. : 주MODEL - LAM LAM ETCHER특징 > COOLING방법 : He COOLING > CLAMPING방법 : ESC (Electrostatic Chucking ) 72

73 Dry etching 에서사용되는물질과 etching gas Material Gas plasma 종류 Si CF4, CF4 + O2, CCl2F2 POLY Si CF4, CF4 + O2, CF4N2 Amorphous Si CF4, CF4 + O2, SiO2 CF4, CF4 + O2, HF SiN CF4, CF4 + O2, HF Mo CF4, CF4 + O2 W CF4, CF4 + O2 Au Pt Ti Al Cr C2Cl2F4 CF4 + O2, C2Cl2F4 + O2 CF4 CCl4, CCl4 + Ar, BCl3, Cl2 Cl2, CCl4, CCl4 + Ar, O2 73

74 TFT 공정흐름개략도 (DRY & WET ETCH 비교 ) DRY ETCH 특징 WET ETCH 특징 1. 설비가격이고가이다. 1. 설비가격이상대적으로저가이다. 2. 설비유지비용이싸다. ( 사용 Gas가일반적으로저가임 ) 2. 설비유지비용이비싸다. (Chemical 등자재비가격이비쌈 ) 3. Clean Process ( 폐기물이적다 ) 3. 폐기물이다량발생한다. 4. 양산성이불리하다 4. 양산성이유리하다 5. 설비 Control이용이하다 5. 설비 Control이복잡하다 6. 미세 Pattern가공이유리하다 6. 미세 Pattern가공이불리하다 7. 많은 Process Parameter 8. Wet Etch보다복잡하다. 9. Etching Damage유. 74

75 N A L IC SY HP WOL WOL H IG H H IG H WOL 디스플레이공학 구분 PE RIE SPUTTER ETCH ETCH MECHANISM + R PRODUCT R Ion PRODUCT + Ion PRODUCT PRESSURE > 0.1Torr < 0.1Torr < 0.1Torr WAFER LOCATION GROUNDED ELECTRODE POWERED ELECTRODE POWERED ELECTRODE ETCH SPECIES FREE RADICAL RADICAL 반응성이온 불활성이온 REACTION CHEMICAL CHEMICAL PHYSICAL PHYSICAL A MSAL P L A IO T CAER HCT E RET T UPS IO T CAER HCT E IE R HCT E N IC ME HC Y IT IV H IG H T CEL ES H IG H IC P ORT O IS WOL IC P ORT O IS NA RE WOL WOP H IG H ER USSERP Etch Mode 별 Etch 특성및경향비교 75

76 여러가지 dry etching 개념 Pitch PR Etched film Bar Space Lateral Etch 개념의도해 CD Bar 의개념도해 PR PR High over etch 필요함 Pattern Bias 개념의도해 Overetch 개념의도해 76

77 Active Etch 과정 Etching PR N+ a-si a-si G-SiNx Glass Active Etch Profile 77

78 n+ Channel ETCH 과정 Etching S/D Cr N+ a-si a-si G-SiNx Gate Metal Channel 부사진 정상 Channel 이물 78

79 Etching Etching PR Passivation Cr Contact Hole & Data Pad Etch PR Passivation G-SiNx Gate Matel Gate Pad Etch Contact Hole Gate Pad 79

80 Etching 공정의기본개념 80

81 Taper Etching Mechanism 81

82 Photoresist Lifting 에의한 Taper Etching Mechanism Al/Mo 적층구조에서 Taper Etching Mechanism 82

DISPLAY CLASS Electronic Information Displays CRT Flat Panel Display Projection Emissive Display Non Emissive Display Cathode Ray Tube Light Valve FED

2002. 4. 4. DISPLAY CLASS Electronic Information Displays CRT Flat Panel Display Projection Emissive Display Non Emissive Display Cathode Ray Tube Light Valve FED VFD PDP OLED ELD LED LCD ECD DMD DC Type