Surface Preparation and Wet Cleaning for Germanium Surface · SPCC2017 (Surface Preparation and...

SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017

1 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.

Surface Preparation and Wet

Cleaning for Germanium Surface

J. Snow2*, M. Otsuji1, Y. Yoshida1, H. Takahashi1, F.Sebaai3, F. Holsteyns3, M. Sato1 and H. Shirakawa1

1 SCREEN Semiconductor Solutions Co., Ltd.

480-1 Takamiya-cho, Hikone, Shiga, 522-0292 Japan2 SCREEN SPE USA, LLC

820 Kifer Road, Suite B, Sunnyvale, CA 94086 USA3 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



Introduction










Summary


Assumed Logic Device Fabrication


Si Fin

SiGe Fin

SiGe GAA

10nm

7nm

5nm

Candidates

Structure becomes more complex while scaling down

New materials as SiGe, Ge and III-V will be introduced

< 3nm

Ref. imec

Candidates


Key Cleaning Steps on Ge


Material removal PR strip

Unreacted Ni removal

Controlled SiGe/Ge etch Controlled Ge-Fin Trimming

Selective SiGe etch for GAA

Surface preparation Post etch clean

Pre-epi clean

Ge

PR

PR strip

SiGe etch

Ge Ge nanowire


0

1

10

100

1000

110100100010000

Etc

h R

ate

[n

m/m

in]

SC1 conc. (NH4OH/H2O2/H2O=1/1/X)

SiGe/Ge loss in SC1

SiGe 45%

SiGe 55%

Ge 100%

Challenges on Wet Cleaning of SiGe/Ge


[M.Wada et al., Solid State Phenomena 187 (2012) 19]

Ge is easily dissolved in oxidizing solutions, i.e. SC1, DIO3

Ge loss management is mandatory

Diluted Concentrated

0

1

10

100

1000

0.1 1 10 100

Etc

h R

ate

[n

m/m

in]

DIO3 conc. [ppm]

SiGe/Ge loss in DIO3

SiGe 45%

SiGe 55%

Ge 100%



Introduction









– Controlled Ge-Fin Trimming


Summary


PRE on Ge with Conventional Chemistries


0

10

20

30

40

50

60

70

80

90

100

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Ge loss [nm]

PR

E [%

]

UPW

dHCl

dNH4OH

DIO3/HCl DIO3

SC1 (1/1/5000)

Ge

SiGe

Surface lift-off by oxidizing chemistry is the dominant factor for

sufficient particle removal

> 3nm Ge etch for > 90% PRE with conventional chemistries

[H.Takahashi et al., ECS Transactions 2011 41(5), 163-170]

Applicable process:

Post gate etch clean

Particle: 30nm SiO2-Slurry

Measurement: SP2, Haze


0

10

20

30

40

50

60

70

80

90

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0

PR

E [%

]

Ge loss [nm]

AOM (Ammonia/DIO3

Mixture) for Ge Clean

SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.9

AOM

(high NH4OH ratio)

AOM

(low NH4OH ratio)

High PRE with lower Ge loss is obtained by using a clean

with AOM, especially in high pH condition

[H.Takahashi et al., ECS Transactions 2011 41(5), 163-170]

DIO3

SC1

(200/1/20000)

Particle: 30nm SiO2-Slurry

Measurement: SP2, Haze


1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

No clean HCl HF/HCl O3 O3/HCl

Met

al C

on

tam

inat

ion

[at

om

s/cm

2]

Mn

Co

Zn

Ti

Cr

Fe

Ni

HF/HCl performs best: Same trend observed for Si and Ge

surfaces, Native oxide removal by HF + Metal dissolution by HCl

MRE on Ge Surface


Controlled contamination Spin dry Wet treatmentStored in FOUP

8 hours

Ge 500nm

or Bare-Si

TXRF

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

No clean HCl HF/HCl O3 O3/HCl

Met

al C

on

tam

inat

ion

[at

om

s/cm

2]

Mn

Co

Zn

Ti

Cr

Fe

Ni

Under detection limit Under detection limit

MRE on Bare-Si MRE on Ge

Metal solution


1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1 day 3 days 35 days 1 day 3 days 7 days 35 days

No clean HF/HCl

Met

al C

on

tam

inat

ion

[at

om

s/cm

2]

Mn

Co

Zn

Ti

Cr

Fe

Ni

Aging Effect on MRE on Ge Surface


Controlled contamination Spin dry Wet treatmentStored in FOUP

X days

Ge 500nm

No aging effect on MRE with HF/HCl even after 1 month

Under detection limit

TXRFMetal solution


Summary for Surface Preparations on Ge


Recommended cleaning combination

– For particles: AOM (NH4OH/DIO3 mixture)

– For metals: HF/HCl mixture



Introduction










Summary


Challenge & Approach for Galvanic Corrosion


One example: Ge corrosion during wet Ni removal using dHCl

Ge NiGe

e-

GeO dissolves in

aqueous solution

Anode:

Ge + ½ O2 GeO + e-

Cathode:

H+ + e- H2

O2 + 2H2O + 4e- 4OH-

GeNiGe

Ge planar deviceGe-FinFET device

NiGe

Ge

FINSTI

Exposure of Ge & NiGe to the cleaning solution

during Ge integration

[F.Sebaai et al., Solid State Phenomena 219 (2014) 105-108]


10

100

1000

10000

20% 1% 10ppm

Ass

um

ed

DO

in li

qu

id o

n w

afe

r [p

pb

] Ambience-induced

Liquid-induced

Management of Low-O2

Processing


8ppm

450ppb

25ppb

Ambient control allows to achieve low DO condition

(<25ppb) in process liquid on wafer

[Y.Yoshida et al., Solid State Phenomena 219 (2014) 85-88]

Chemistry

Ambient 20% 1% 10ppm

DO in liquid 170ppb 25ppb 25ppb

O2 dissolved

in liquid

O2 conc. in ambient:

X ppm

DO in liquid:

Y ppb


0

0.2

0.4

0.6

0.8

1

1.2

8ppm 450ppb 25ppb

NiG

e lo

ss [

a.u

.]

DO conc. in Liquid on wafer

Selective Ni Removal on Ge-FinFET


DO 8ppm 450ppb 25ppb

SEM

image

VoidVoid No void

NiGe loss with HCl

Void occurrence can be suppressed by the control of the

oxygen concentration in liquid & ambient

[Y.Yoshida et al., Solid State Phenomena 219 (2014) 85-88]

Void occurrence reduced

Void occurrence dependency on DO in HCl



Introduction



SiGe/Ge Surface Preparation





Controlled SiGe/Ge etch


Summary


SiGe Wet Etches Selective to Ge


SiGe etch

Ge Ge nanowire

HK/MG fill

GAA (Gate All Around)

Ge is too sensitive

Conventional chemistries

don’t work on this application

0

1

10

100

1000

110100100010000

Etc

h R

ate

[n

m/m

in]

SC1 conc. (NH4OH/H2O2/H2O=1/1/X)

SiGe 45%

SiGe 55%

Ge 100%

SiGe/Ge loss in SC1

More study is needed on this kind of applications



Introduction



SiGe/Ge Surface Preparations



Material Removals Selective to SiGe/Ge




Summary


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


☺ Unreacted Ni removal

• Low-O2 is promising to full Ni remove without Ge corrosions


SiGe wet etch selective to Ge

• Need more study

Surface Preparation and Wet Cleaning for Germanium Surface · SPCC2017 (Surface Preparation and...

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