CAMBRIDGE 10 & 11th APRIL 2018

Ammonia cross contamination: FOUP to wafer evaluation and its volatile acids comparison

Paola González-Aguirre, Entegris, paola.gonzalez@entegris.comHervé Fontaine, CEA-Leti, herve.fontaine@cea.frSung In Moon, Entegris, sungin.moon@entegris.comMinh Phuong Tran, CEA-Leti, minh-phuong.tran@cea.frJorgen Lundgren, Entegris, jorgen.lundgren@entegris.comCarlos Beitia, CEA-Leti, carlos.beitia@cea.fr

Surface Preparation and Cleaning Conference

| SPCC2018

OUTLINE

◦ Introduction

◦ Issues/objectives

◦ Experimental protocol

◦ Results

• Contaminant sorption by the FOUPs

• Contaminant outgassing from the FOUPs

• Contaminant transfer to wafers

◦ Conclusions

Manufacturing/Development Research

45 nm 32/28 nm 22/20 nm 16/14 nm 10 nm

2

| SPCC20183

FOUP/WAFER MOLECULAR CONTAMINATION

Demonstration of a cross-contamination chain between FOUP & wafers

FOUP contamination Transfer FOUP to wafers

FOUP equilibration

Sorption of AMCs from CR air, released from stored wafers, equipment connection…

Sensitive subsequent outgassing, transfer to wafers (promoting defectivity)

FOUPs must protect the wafer environment from AMCsCross-molecular contamination: AMCs FOUP Wafer

Wafer DEFECTIVITY

[AMC]

Time % RH

| SPCC20184

INTRODUCTION: AMC

oAirborne molecular contamination (AMC) may be responsible for severe yield losses

oAmong AMCs, HX are well known as root cause of defectiveness

Many sources of ammonia in fabs:• Staff members • Surface functionalization from priming agents• Cleaners• Polishing slurries materials

Corrosion of a Cu

1 µm

TiFx crystalgrowth on

TiN

Al lines corrosion

o Fabs feedback concerning ammoniao Photolithography (T-topping)o Crystal growth un photomasko Time dependent Hazeo Post CMP

| SPCC20185

GOALS

◦Compare critical NH3 molecular contamination behavior in two Entegris FOUP models, in terms of:

◦Contaminant, sorption and subsequent release

◦Contaminant cross-contamination on stored wafers

A300 EBM/CNT SPECTRA PC

Polycarbonate EBM/C-nanotubes

| SPCC20186

IC = Ion Chromatography, LPE = Liquid Phase ExtractionTest carried by twice

EXPERIMENTAL PROTOCOL

0) FOUP CONDITIONINGClean room equilibration

(21°C 40% RH) 7days

1) INTENTIONAL CONTAMINATION

10µL- droplet 24h

2) PURGE(N2 gun) 5 min

3) OUTGASSING MONITORING IMPINGER-IC

(once per day) 8 days

HF 2.0% 11.2ppmHCl 3.7% 11.6ppm

NH3 2,9% 14.7ppm & 0.29% 1.47ppm

3) STORAGE of Cu-WAFERS, LPE-IC

| SPCC20187

SORPTION/OUTGASSING BY PC FOUPs

Contamination phase

Outgassingphase

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 50 100 150 200 250 300 350 400

[co

nta

min

ant]

pp

bv

T(h)

0

50

100

150

200

250

300

350

400

24 44 64 84 104 124 144 164

NH3 : 22,86 A3 HCl : 22,45 A3 HF : 15,77A3

Steric effectAffinity to polymer NH3 < HCl < HF

OutgassingNH3 > HCl > HF

HCl

HF

NH3

HCl

HF

NH3

• Immediate Strong outgassing after purge, followed of a concentration equilibrium

• Solubility is the outgassing driving force

NH3 < HCl < HF

| SPCC20188

SORPTION/OUTGASSING BY EBMCNT FOUPs

Contamination phase

Outgassing phase

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 20 40 60 80 100 120 140 160 180

[co

nta

min

ant]

pp

bv

T(h)

F- EBMCNT Cl- EBMCNT NH4+ EBMCNT

-20

30

80

130

180

230

280

24 44 64 84 104 124 144 164

Affinity to polymer

NH3 < HCl < HF

OutgassingNH3 > HCl > HF

HCl

HF

NH3

HF

HCl

NH3 • Strong outgassing for HCl andNH3 after purge, followed of aconcentration equilibrium

• No detectable outgassing in HFcase LLD (low limit detection)for F- 0.62ppbv

• In the NH3 case, in respect toPC material the maximumoutgassing is detected somehours later after purge

DEBMCNT < DPC

| SPCC2018

0

1000

2000

3000

4000

5000

6000

7000

8000

0 50 100 150 200

[NH

3]

pp

bv

T(h)

NH4+ EBMCNT

NH4+ PC

0

1000

2000

3000

4000

5000

6000

7000

8000

0 50 100 150 200

[HC

l] p

pb

v

T(h)

Cl- EBMCNT

Cl- PC

0

1000

2000

3000

4000

5000

6000

7000

8000

0 50 100 150 200

HF-

] p

pb

v

T(h)

F- EBMCNT

F- PC

9

Outgassing PC > EBMCNTContaminant affinity to polymer PC > EBMCNT

Outgassing zoom

Contamination/outgassing

COMPARATIVE SORPTION/OUTGASSING FOUPs ABILITY

0

50

100

150

200

250

300

350

24 74 124 174

[HF]

pp

bv

0

50

100

150

200

250

300

350

24 74 124 174

[HC

l] p

pb

v

0

50

100

150

200

250

300

350

24 74 124 174

[NH

3]p

pb

v

HClHF NH3

| SPCC201810

[1] F. Herran, H. Fontaine, P. Gonzalez-Aguirre, C. Beitia, J. Ohlsen, J. Lundgren. A mathematical model forecasting HF adsorption onto Cu-coated wafers as a function of airborne concentration and moisture, Solid State Phenomena (2016), 255-323[2] M-P Tran, P Gonzalez-Aguirre, C Beitia, J Lundgren, S-I Moon, H Fontaine. Deposition of volatile chlorohydric acid on copper wafer depending on humidity and HCl airborne concentration, SPCC2018[3 ] H. Fontaine; G. Demenet; V. Enyedi; S. Cetre. Study of the airborne SO2 and NH3 contamination on Cr, MoSi and quartz surfaces of photomasks, Photomasks Technology 2010, Vol 7823, pp28

VEHICLE TEST FOR CONTAMINATION TRANSFER EVALUATION

Need of a proper vehicle test for ammonia cross contamination• Affinity to contaminant• Knowledge of a kinetic model

ACIDS (HF, HCl)

◦ Cu wafers

◦ AlCu wafers

BASES (NH3)

◦ Cu wafers

◦ AlCu wafers

◦ Si wafers

◦ Cr wafers

Co = 1.5E11 (ion/cm2)Cmax = 1.9E14 (ion/cm2)RH = 40%

Langmuir deposition model – Cr-NH3

𝑪 = 𝑪𝒎𝒂𝒙 − (𝑪𝒎𝒂𝒙−𝑪𝒐)𝒆−𝒌𝒂𝒅𝒔𝑪𝒈𝒕 [3]

• Cu wafers not suitable: NH4+

analysis not available• Surface AlCu is not very

sensitive to NH3.

• Si surfaces no sensitive to NH3

contamination

[F-] = [F-max]*(1 – exp(-k’t)) [1]

K=f(RH%, [HF]), F-max=f(RH%)

[Cl-] = (k*[CHCl])*[t] + [Cl0-] [2]

K= kinetic constant

| SPCC2018

0

20

40

60

80

100

120

140

24 74 124 174

[HX

] p

pb

v

Time (h)

11

CONTAMINATION TRANSFER FOUP TO WAFER

0.0E+00

3.0E+14

6.0E+14

9.0E+14

1.2E+15

0 5 10 15 20 25

X-

con

c. [

ion

s cm

-2]

Time [h]

International Roadmap for Devices and Systems (IRDS 2013) ●HF 1E14 ● HCl 1E13

PC

EBMCNT

HFHCl

HF vs HCl kinetic deposition on Cu wafer& equivalent average HX concentration

• HX transfer to Cu-coated wafers: HF > HCl• Large FOUP outgassing rates depend on HX reservoir and diffusion kinetics, and then FOUPs exhibits a strong

HCl outgassing but low transfer to copper wafers

SHCl < SHF

DEBMCNT < DPC

70 ppbv HF

0.5 ppbv HF

1.5 ppbv HCl

6.3 ppbv HClHCl PC

HCl EBMCNT

HF EBMCNT

HF PC

Outgassing phase in a empty FOUP

(static condition)

| SPCC201812

AMMONIA SORPTION/OUTGASSING OF FOUPs

NH3 kinetic deposition on Cr waferppb air Time to 90%

saturation

2 26.7h

10 5.4h

24 2.3h

73 42 min

270 12 min

0

1000

2000

3000

4000

5000

6000

7000

8000

0 20 40 60 80 100 120 140 160

con

tam

inan

t co

nc

(pp

bv)

Time (h)

NH4+ EBMCNT NH4+ PC low NH4+ EBMCNT low NH4+ PC

0

50

100

150

200

250

300

350

400

24 44 64 84 104 124 144

Time (h)

0

10

20

30

40

50

60

70

80

90

24 30 36 42 48

EBMCNT

EBMCNT

Immediately after purge!

PC

PC

• Strong outgassing afterpurge, followed of aconcentration equilibrium

• Given the poor NH3 polymeraffinity (comparing with HF,HCl)Solubility: NH3 < HCl < HF

• Contaminant concentrationlocated mainly in thesurface

DNH3: DPC > DEBMCNT

Initial contamination concentration 14.7 ppmv vs 1.47ppmv

Cmax = 1.9E14 (NH4+/cm2

| SPCC201813

CONTAMINATION TRANSFER FOUP TO WAFER

Csat Cr

NH3 deposition on Cr wafer after 40min Cr wafer exposure & [NH3] required to rich this transfer

• Consequence of the NH3 Immediate PC strong outgassing respect to the belated NH3 outgassingin EBMCNT the low transfer to Cr wafers (as in HCl case) is due to a low NH3 solubility

• This transfer is in agreement to the assumption DEBMCNT < DPC

0

10

20

30

40

50

60

70

80

90

24 30 36 42 48

[NH

3]

pp

bv

Time (h)After purge 24h after purge

8.3E+13

3.9E+134.8E+13

8.6E+13

0.0E+00

2.0E+13

4.0E+13

6.0E+13

8.0E+13

1.0E+14

1.2E+14

PC EBMCNT BLANK

Blank Blank

1.7E14 (NH4+/cm2)

5.2E13 (NH4+/cm2)

1.5E14 (NH4+/cm2)

9.6E13 (NH4+/cm2)

11ppbv

21.5ppbv 22.5ppbv

8.5ppbv

| SPCC201814

K. Hatakeyama et al. Chemical recycling of polycarbonate in dilute aqueous ammonia solution under hydrothermal conditions, J. Mater. Cyces Waste Manag. 16 (2014) 124–130

PC & NH3 REACTION

PC and EBMCNT compatibility with NH3 solution (TGA characterization)

PC degradation by NH3

| SPCC2018

SUMMARY

→ Contaminant FOUP affinity : NH3 < HCl < HF, FOUP contamination f (S,D) & PC > EBMCNT

→ Contaminant outgassing after purge: NH3 > HCl > HF , mainly f (solubility) & & PC > EBMCNT

→Contaminant acid transfer to wafer: HCl < HF, mainly f(diffusivity) & PC > EBMCNT

→Assuming same vehicle test the expected contaminant transfer to wafers will follow:

NH3 < HCl < HF & PC > EBMCNT

→ PC use is not suitable in NH3 environments due it’s reactivity

15

Among the tested FOUPs, EBM/CNT is the most efficient to limit NH3, HF & HCl contamination transfer to wafers → reduced wafer

defectiveness is expected

Entegris®, the Entegris Rings Design™, Pure Advantage™ and Clarilite® are trademarks of Entegris, Inc. ©2017 Entegris, Inc. All rights reserved.

16

| SPCC201817

RESULTS ANALYSIS

- [Cont]air increases and penetrates the polymer membrane

- [Cont]surf is defined by Solubility- Penetrant’s flow governed by diffusivity- FOUP’s contamination f (D, S)

- [Cont]air increases until [Cont]surf reach the equilibrium solubility

- Outgoing diffusion continues: [Cont]surf is progressively reduced [Cont]air is pulled down

- [Cont]air is mainly solubility-dependent

- Any contaminant molecule released will be retained by the wafer

- [Cont]air 0 (cont affinity to wafer) then [Cont]surf 0 as well

- Dair >> Dpolymer Cont transfer to Cu mainly governed by Dpolymer

M Cualfield, C.W Extrand, S.I Moon, Estimating Hydrochloric acid and Ammonium Hydroxide Loss, Controlled Environments Magazine, 2011T.Q Nguyen PhD Thesis (2012)P. Gonzalez-Aguirre, H. Fontaine, R. Pastorello, C. Beitia, J. Ohlsen, J. Lundgren HF transport coefficients in polymers used for microelectronic applications. Defect and Diffusion Forum (2016), 68-76

* Public soon

• NH3 D in PFA are greater than HCl• HCl D in PC is greater than HF • HCl S in PC is lower than HF

From literature:

We postulate:

• S in PC & EBMCNT follows NH3 < HCl < HF• D & S are lower in EBMCNT than PC*