Wet Etch - bandi.chungbuk.ac.kr

1 Wet Etch1. Wet etching 2. SiO2etching3. Si3N4etching4. Aluminum etching5. Si etching6. Wafer Cleaning1. Wet etching * * Selectivity * * Isotropic etching * Pattern size * Wet etching wafer (sliced wafer ) thermal oxidation : pre-furnace cleaning (organic metallic ) film strip Wet etching mechanism 3 :Transport -- Reaction --- By-product removal Etch rate Anisotropy / Selectivity Endpoint A etch B (100) (110) etch .- (a) (100) V , U.

2 - (b) etch .2. SiO2etching 1. HF * SiO2+ 6HF--- SiF6+ 2H2O + H2 * 49% HF : H2O = 1 : 10 ; 200-400A/min at 22~30oC 2. Buffered HF 49% HF : NH4F = 1 : 6 ; 800-1000A/min at 22~30oC 3. CVD oxide thermal oxide 25% BOE NH4F : etching rate , HF pH , F . SiO2etch : SiO2 etch : , porosity, microstructure, . , CVD oxide etch rate > thermal oxide etch rate oxide etch rate > oxide etch rate 3. Si3N4etching 1. Etchant; 85% H3PO4( ) 2. ; 20A/min at 180oC 3. Endpoint , Overetch 4. ; quartz 5.

3 H2O ; 4. Si etching 1. HF + HNO3+ CH3 COOH 2. 500-1000A 3. PR 4. Doped poly; undercut (HNO3) + (CH3 COOH) + (HF) Si etching (HNO3) + (CH3 COOH) + (HF)' HNO3 Si SiO2 . HF SiO2 . CH3 COOH HNO3 . (CH3 COOH H2O .) silicon etching orientation etching . (111) (110) (100) bond , etching . 'KOH + IPA' etching etching KOH etching . : KOH in water + IPA(isopropyl alcohol) 19 wt% KOH in DI water at 80 C . (100) : (110) : (111) = 100 : 16 1 etching .

4 5. Aluminum etching 1. Etchant: H3PO4: HNO3: CH3 COOH : H2O = 16 : 1 : 1: 2 2. HNO3 Al2O3 H3PO4 Al2O3 3. etching rate; 1000 -3000 A/min at 35-45oC 4. Endpoint 5. 10 overetch , etch undercut solutionTemp.(oC) Si-HF + HNO3+ CH3 COOH-KOH-N2H4 ( + CH3 CHOOHCH3)roomSiO2-HF-HF + NH4 FroomAlH3PO4+ HNO3+ CH3 COOH + H2O50 Si3N4H3PO4( )150 6. Wafer cleaning : NH4OH, HCl : HNO3-HCl (1:3 ), RCA , HF-HNO3 : H2O2, H2SO4 : TCE(Trichroloethylane), NaOH RCA (Standard cleaning )(1) SC-1 ; -DI-H2O: NH4OH :H2O2(1:1:5) 70~75C 5 - DI water 1min. - Chemical oxide : 49%HF-H2O 15sec - DI water (2) SC-2 : atomic & inic -DI-H2O: HCl :DI-H2O2(6:1:1) 70~75C 5~10 - DI water (DI 10~18 M -cm ) (3) rinse in DI water, N2blow - : wafer.

5 - RCA : SC-1 SC-2 exhaust hood (NH3vapor HCl vapor NH4Cl smoke water ) SC-1 H2O2 , NH4OH silicon . 75 C , H2O2 . Solution H2O2 . 1. Al wet etch ( ) Al2O3 ( ) Al2O3 2. SiO2wet etch ( ) etch 1. HNO3, H3PO42. HF