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디스플레이 제조기술 특론

디스플레이 제조기술 특론. 강의 8. Si / SiO 2 Etching . Etching of SiO 2 and Si in a CF 4 plasma Adding an oxidizing agent such as O 2 to a CF 4 glow discharge increases the amount of free F. At higher oxygen concentrations, the etch rate drops again. This can be ascribed in part

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디스플레이 제조기술 특론

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  1. 디스플레이 제조기술 특론 강의 8

  2. Si / SiO2Etching • Etching of SiO2 and Si in a CF4 plasma • Adding an oxidizing agent such as O2 • to a CF4 glow discharge increases • the amount of free F. • At higher oxygen concentrations, the etch • rate drops again. This can be ascribed in part • to a lowering in free F because of gas-phase • recombination.

  3. AlEtching • Aluminum is quite stable under normal atmospheric conditions, • resulting from the immediate formation of a very inert native oxide • when it is exposed to air or water. • Aluminum hexachloride is formed readily on exposure of aluminum • with molecular chlorine. • This reaction will only start after the native oxide has been removed. • To remove the native oxide, the Lewis acid BCl3 is added to Cl2.

  4. Pressure Effects

  5. Temperature Effects • Arrhenius expression • where A is a pre-exponential which is weakly dependent on temperature • and EA is the activation energy.

  6. Etching Parameters • TFT에서 Etching 요구사항 • - Taper Profile : 20 ~ 40도 • - Damage 최소화 (High Selectivity) • - Uniformity

  7. Wet Etching Mechanism 1 • Wet Etching 화학적 반응 • - Oxidation • - Dissolution of the oxide • Wet Etchant 구성 • - Oxidation을 위한 Chemical • - Dissolution을 위한 Chemical • - Diluent • - 기타 첨가제

  8. Wet Etching Mechanism 2 • Wet chemical etching usually proceeds by oxidation, followed by the • dissolution of the oxide by a chemical reaction. • Si etchant : HNO3 + HF + H2O or CH3COOH • The overall reaction is • where H2SiF6 is soluble in water. (Oxidation) (Dissociation of the oxide)

  9. Orientation-dependent etching • Some etchants dissolve a given crystal plane of a semiconductor much • faster than other planes; this results in orientation-dependent etching. • A commonly used orientation-dependent etch for silicon consists of a • mixture of KOH in water and isopropyl alcohol. • The ratio of the etch rates for the (100)-, (110)-, and (111)-planes is • 100: 16:1.

  10. Etchant

  11. Wet Etching Parameter • Wet Etching Parameter • - Etchant 조성 • - Etchant 온도 • - Etching 방식 • . Dipping • . Spray • . Dip & Spray • - 기타 : Thin Film 구조, PR의 종류 등

  12. 1. 절연막 Etching (SiO2, SiON, SiNx) 2. ITO Etching 다. ITO는 Residue (잔사)가 남아 100% 이상 Over etching을 함. Wet Etching in TFT Fabrication 1

  13. Wet Etching in TFT Fabrication 2 • Al etching시 일반적으로 Heated etchant (35 ~ 45℃)를 사용. • Etching이 진행되는 동안 수소기체가 발생되어 Al 표면에서 Etching를 • 방해하여 Snow ball이라는 Residue 발생하므로 기포 제거에 주의가 필요.

  14. Wet PR Strip

  15. TFT Fabrication Technology • 7 Mask Technology • 5 Mask Technology • 4 Mask Technology • 3 Mask Technology (under Development)

  16. a-Si (500A) SiOx GATE (3500A) SiNx a-Si SiNx SiNx(E/S) (500A) n+ a-Si n+ a-Si (2000A) (500A) 7 Mask 기술 개요1 Gate Mask : Gate Metal 증착 -> Photo -> Gate Etch -> Gate 형성 GATE MoW GLASS SUBSTRATE GLASS SUBSTRATE Etch Stopper Mask : Gate Insulator (SiO2/SiNx), a-Si, Etch Stopper (SiNx) 증착 -> Photo -> Etch Stopper Etch -> Etch Stopper 형성 Active Mask : n+ 증착 -> Photo -> n+, a-Si, SiNx Etch -> Active 형성 n+ a-Si (500A) a-Si n+ a-Si (500A) ITO Mask : ITO 증착 -> Photo -> ITO Etch -> ITO 형성 a-Si SiOx GATE (3500A) SiNx SiNx(E/S) (500A) SiNx ITO 2000Å (2000A) Contact Mask : Photo -> SiO2 Etch -> Contact 형성 SiO2 GATE

  17. 7 Mask 기술 개요2 n+ a-Si (500A) a-Si Source/Drain Mask : S/D Metal 증착 -> Photo -> S/D Etch -> n+ Etch -> S/D 형성 (500A) a-Si SiOx GATE (3500A) SiNx SiNx SiNx(E/S) (500A) ITO 2000Å n+ a-Si (2000A) Passivation Mask : Passivation (SiNx) 증착 -> Photo -> Passivation Etch -> PVX 형성 n+ a-Si a-Si PASS'N (SiNx 2000A) (500A) SiOx GATE (3500A) SiNx SiNx SiNx(E/S) (500A) ITO 2000Å (2000A)

  18. Passivation : SiNx ITO 5 Mask 기술 개요 Gate : MoW Gate Mask : Gate Metal 증착 -> Photo -> Gate Etch -> Gate 형성 Glass n+ a-Si SiNx Active Mask : Gate Insulator (SiO2/SiNx), a-Si, n+ 증착 -> Photo -> n+, a-Si, SiNx Etch -> Ative 형성 SiO2 Source/Drain : Mo/Al/Mo Source/Drain Mask : S/D Metal 증착 -> Photo -> S/D Etch -> n+ Etch -> S/D 형성 Passivation Mask : Passivation (SiNx) 증착 -> Photo -> Passivation Etch -> PVX 형성 ITO Mask : ITO 증착 -> Photo -> ITO Etch -> ITO 형성

  19. Gate Mask E/S Mask Active Mask ITO Mask Contact Mask S/D Mask PVX Mask 7 Mask & 5 Mask 기술비교 7 Mask 5 Mask • E/S 공정 제거 => TFT 특성 저하 • => n+ Etch 후 H2 Treatment 개발 • S/D 공정과 ITO 공정 순서 변경 => ITO공정에서 Data Open 발생 => ITO Etchant 개발 S/D Metal 개발 Gate Mask Active Mask S/D Mask PVX Mask ITO Mask

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