1 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd. Surface Preparation and Wet Cleaning for Germanium Surface J. Snow 2*, M. Otsuji 1, Y. Yoshida 1, H. Takahashi 1, F.Sebaai 3, F. Holsteyns 3, M. Sato 1 and H. Shirakawa 1 1 SCREEN Semiconductor Solutions Co., Ltd. 480-1 Takamiya-cho, Hikone, Shiga, 522-0292 Japan 2 SCREEN SPE USA, LLC 820 Kifer Road, Suite B, Sunnyvale, CA 94086 USA 3 IMEC vzw Kapeldreef 75, B-3001 Leuven, Belgium
Outline Introduction Key Cleaning Steps Challenges on Wet Cleaning of SiGe and Ge Ge Surface Preparation PRE (Particle Removal Efficiency) MRE (Metal Removal Efficiency) Material Removal Selective to SiGe/Ge Unreacted Ni Removal Controlled SiGe/Ge Wet Etch SiGe Wet Etch Selective to Ge Summary 2 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
Introduction Key Cleaning Steps Challenges on Wet Cleaning of SiGe and Ge Ge Surface Preparation PRE (Particle Removal Efficiency) MRE (Metal Removal Efficiency) Material Removal Selective to SiGe/Ge Unreacted Ni Removal Controlled SiGe/Ge Wet Etch SiGe Wet Etch Selective to Ge Summary 3 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
4 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd. Assumed Logic Device Fabrication Candidates Si Fin 10nm SiGe Fin < 3nm Candidates 7nm SiGe GAA 5nm Ref. imec Structure becomes more complex while scaling down New materials as SiGe, Ge and III-V will be introduced
5 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd. Surface preparation Post etch clean Pre-epi clean Key Cleaning Steps on Ge Material removal PR strip Unreacted Ni removal Ge PR PR strip Controlled SiGe/Ge etch Controlled Ge-Fin Trimming Selective SiGe etch for GAA SiGe etch Ge Ge nanowire
Etch Rate [nm/min] 6 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd. Etch Rate [nm/min] Challenges on Wet Cleaning of SiGe/Ge 1000 SiGe/Ge loss in DIO 3 1000 SiGe/Ge loss in SC1 Ge 100% 100 100 10 1 0 0.1 1 10 100 DIO 3 conc. [ppm] Ge 100% SiGe 55% SiGe 45% 10 1 0 10000 1000 100 SiGe 55% SiGe 45% 10 SC1 conc. (NH 4 OH/H 2 O 2 /H 2 O=1/1/X) Diluted Concentrated 1 [M.Wada et al., Solid State Phenomena 187 (2012) 19] Ge is easily dissolved in oxidizing solutions, i.e. SC1, DIO 3 Ge loss management is mandatory
Introduction Key Cleaning Steps Challenges on Wet Cleaning of SiGe and Ge Ge Surface Preparation PRE (Particle Removal Efficiency) MRE (Metal Removal Efficiency) Material Removal Selective to SiGe/Ge Unreacted Ni Removal Controlled SiGe/Ge Wet Etch Controlled Ge-Fin Trimming SiGe Wet Etch Selective to Ge Summary 7 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
PRE [%] PRE on Ge with Conventional Chemistries 100 90 80 70 60 50 40 30 20 10 0 DIO 3 /HCl dhcl UPW dnh 4 OH DIO 3 SC1 (1/1/5000) 0.0 1.0 2.0 3.0 4.0 5.0 6.0 Ge loss [nm] [H.Takahashi et al., ECS Transactions 2011 41(5), 163-170] Particle: 30nm SiO 2 -Slurry Measurement: SP2, Haze Ge SiGe Applicable process: Post gate etch clean Surface lift-off by oxidizing chemistry is the dominant factor for sufficient particle removal > 3nm Ge etch for > 90% PRE with conventional chemistries 8 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
9 PRE [%] SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd. AOM (high NH 4 OH ratio) 100 90 80 70 60 50 40 30 20 10 0 AOM (Ammonia/DIO 3 Mixture) for Ge Clean SC1 (200/1/20000) AOM (low NH 4 OH ratio) DIO 3 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Ge loss [nm] Particle: 30nm SiO 2 -Slurry Measurement: SP2, Haze [H.Takahashi et al., ECS Transactions 2011 41(5), 163-170] High PRE with lower Ge loss is obtained by using a clean with AOM, especially in high ph condition
Metal Contamination [atoms/cm2] 10 SE-76-4925-L1 Metal Contamination [atoms/cm2] SCREEN Semiconductor Solutions Co., Ltd. MRE on Ge Surface Ge 500nm or Bare-Si 1.E+14 Metal solution Controlled contamination Spin dry Wet treatment Stored in FOUP MRE on Bare-Si 1.E+14 8 hours MRE on Ge TXRF 1.E+13 1.E+12 1.E+11 Mn Co Zn Ti Cr Fe Ni 1.E+13 1.E+12 1.E+11 Mn Co Zn Ti Cr Fe Ni Under detection limit Under detection limit 1.E+10 No clean HCl HF/HCl O3 O3/HCl 1.E+10 No clean HCl HF/HCl O3 O3/HCl HF/HCl performs best: Same trend observed for Si and Ge surfaces, Native oxide removal by HF + Metal dissolution by HCl
11 Metal Contamination [atoms/cm2] SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd. Aging Effect on MRE on Ge Surface Ge 500nm Metal solution TXRF Controlled contamination Spin dry Stored in FOUP Wet treatment X days 1.E+14 1.E+13 1.E+12 1.E+11 1.E+10 Under detection limit 1 day 3 days 35 days 1 day 3 days 7 days 35 days Mn Co Zn Ti Cr Fe Ni No clean HF/HCl No aging effect on MRE with HF/HCl even after 1 month
Summary for Surface Preparations on Ge Recommended cleaning combination For particles: AOM (NH 4 OH/DIO 3 mixture) For metals: HF/HCl mixture 12 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
Introduction Key Cleaning Steps Challenges on Wet Cleaning of SiGe and Ge Ge Surface Preparation PRE (Particle Removal Efficiency) MRE (Metal Removal Efficiency) Material Removal Selective to SiGe/Ge Unreacted Ni Removal Controlled SiGe/Ge Wet Etch SiGe Wet Etch Selective to Ge Summary 13 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
14 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd. Challenge & Approach for Galvanic Corrosion One example: Ge corrosion during wet Ni removal using dhcl GeO dissolves in aqueous solution Ge NiGe Anode: Ge + ½ O 2 GeO + e - e - Cathode: H + + e - H 2 O 2 + 2H 2 O + 4e - 4OH - NiGe Ge NiGe STI Ge FIN Ge planar device Ge-FinFET device [F.Sebaai et al., Solid State Phenomena 219 (2014) 105-108] Exposure of Ge & NiGe to the cleaning solution during Ge integration
15 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd. Assumed DO in liquid on wafer [ppb] Management of Low-O 2 Processing O 2 conc. in ambient: X ppm 10000 8ppm Ambience-induced Liquid-induced DO in liquid: Y ppb 1000 450ppb 100 25ppb Chemistry O 2 dissolved in liquid 10 20% 1% 10ppm Ambient 20% 1% 10ppm DO in liquid 170ppb 25ppb 25ppb [Y.Yoshida et al., Solid State Phenomena 219 (2014) 85-88] Ambient control allows to achieve low DO condition (<25ppb) in process liquid on wafer
NiGe loss [a.u.] Selective Ni Removal on Ge-FinFET 1.2 1 0.8 0.6 0.4 NiGe loss with HCl DO 8ppm 450ppb 25ppb SEM image Void occurrence dependency on DO in HCl Void Void No void 0.2 0 8ppm 450ppb 25ppb DO conc. in Liquid on wafer Void occurrence reduced [Y.Yoshida et al., Solid State Phenomena 219 (2014) 85-88] Void occurrence can be suppressed by the control of the oxygen concentration in liquid & ambient 16 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
Introduction Key Cleaning Steps Challenges on Wet Cleaning of SiGe and Ge SiGe/Ge Surface Preparation PRE (Particle Removal Efficiency) MRE (Metal Removal Efficiency) Material Removal Selective to SiGe/Ge Unreacted Ni Removal Controlled SiGe/Ge etch SiGe Wet Etch Selective to Ge Summary 17 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
Etch Rate [nm/min] 18 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd. SiGe Wet Etches Selective to Ge SiGe etch HK/MG fill Ge Ge nanowire 1000 100 10 1 SiGe/Ge loss in SC1 Ge 100% SiGe 55% SiGe 45% GAA (Gate All Around) Ge is too sensitive Conventional chemistries don t work on this application 0 10000 1000 100 10 1 SC1 conc. (NH4OH/H2O2/H2O=1/1/X) More study is needed on this kind of applications
Introduction Key Cleaning Steps Challenges on Wet Cleaning of SiGe and Ge SiGe/Ge Surface Preparations PRE (Particle Removal Efficiency) MRE (Metal Removal Efficiency) Material Removals Selective to SiGe/Ge Unreacted Ni Removal Controlled SiGe/Ge Wet Etch SiGe Wet Etch Selective to Ge Summary 19 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
Summary SiGe/Ge Surface Preparation Particle removal on Ge surface AOM is recommended for particle removal steps 0.4 nm etch of Ge to achieve ~100% PRE Metal removal for overall cleaning applications: Sufficient removal confirmed by HF/HCl mixture cleaning Material Removal Selective to SiGe/Ge Unreacted Ni removal Low-O 2 is promising to full Ni remove without Ge corrosions Controlled SiGe/Ge Wet Etch SiGe wet etch selective to Ge Need more study 20 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.