Contamination kinetics of airborne ammonia on chromium-coated … · 2019-04-01 · on...

2-3 April, 2019

Contamination kinetics of airborne ammonia on chromium-coated wafer in cleanroom

conditions

Minh-Phuong TRAN, CEA-Leti, [email protected]é FONTAINE, CEA-Leti, [email protected] GONZÁLEZ-AGUIRRE, Entegris, [email protected] BEITIA, CEA-Leti, [email protected] MOON, Entegris, [email protected] LUNDGREN, Entegris, [email protected]

SPCC 2019 – Portland, USA

CEA–Leti, University Grenoble Aples, 17 rue des Martyrs, 38054 Grenoble, France

Entegris, SAS, Parc Centr’Alp Ouest, 196 rue du Rocher de Lorzier, 38430 Moirans, France

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OUTLINE

1. Introduction

2. Experimental setup

3. NH3 kinetics on Cr-coated wafer

Deposition kinetics vs. [NH3] and %RH

Desorption kinetics vs. %RH

4. Mathematical deposition model - Applications

5. Conclusion

SPCC 2019, Portland USA

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INTRODUCTION

NH3 sources

Wet clean/Wet etch: Salt, NH4OH, NH3/NH4Cl

CVD deposition: TiN – Tetrakis C8H24N4Ti)/NH3

CMP: basic slurries

Material out-gassing, traffic & Industrial pollution

Yield losses

Limit AMCs effect


Airborne molecular contaminations (AMCs)

Footing on DUV resist

Salt (NH4)2SO4, NH4Cl on lens

masks, wafers

T-topping

Salt crystal

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Knowledge of NH3 conta/outgassing

Cross-contamination FOUPs to wafers (NH3)

Test-vehicle

Mathematical deposition model

INTRODUCTION

FOUP contaminated

by wafer outgassing

NH3 contaminant outgassing from

FOUP air up to equilibrium

Contamination transfer

FOUP Air Wafer

Outgassing from wafer

FOUPs sorbed NH3

FOUPs outgassing NH3 FOUPs outgassing

Transfer NH3 to wafers

SPCC 2019, Portland USAP. González-Aguirre et al., Microelectron. Eng., (2019), 205, 53–58

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Liquid Phase Extraction

(LPE process)

Collect NH3 with DI water on

Cr surface

NH3 + H2O NH4+ + OH-

Quantify ion NH4+ by

Ionic Chromatography (IC)

NH4+ ion deposition on Cr

surface

Efficiency of LPE-IC

• Collection by LPE is >95% at first extraction (LPE1)

• LLD for Ammonia: <1.0 x 1011 ion/cm2

Cr wafer (PVD)

confined inert atmosphere (N2)

LPE- DI water

N2

N2


METHODOLOGY

FREE-NH3 SET-UP DEVELOPMENT

Liquid Phase Extraction (LPE process) Quantify NH3 on Cr surface

| 6Confidentiel SPCC 2019, Portland USA

Free-NH3 set-up

Con. set-up

Free-NH3 set-up helps keeping proper surface

from NH3 atmosphere in clean room (<2E11 ion.cm-2)

Free-NH3 set-up

IC analysis of blank surfaces

METHODOLOGY

FREE-NH3 SET-UP DEVELOPMENT

Free-NH3 extract protocol

Water spreading & sampling

in free-NH3 condition


METHODOLOGY – SURFACE PREPARATION

N° Requirements Test-vehicle Si AlCu Cr

1 Blank – Saturation level (orders of magnitude)

2 High affinity to NH3

6 No corrosion caused by NH3

Water rinse (DIW)

Thermal desorption (350°C – 10 min)

Clean wafer contaminated

in NH3 (800ppbv – 2h)

Water rinse Thermal

X 1

00

0

x1

0

Cr-coated wafer - Best candidate as Test-vehicle Establish deposition kinetics

Cr wafer

(200mm)

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EXPERIMENTAL SETUP

c

1st


Thermal Desorption Chamber

Cr wafer (PVD)

Remove efficiently Clean surface

(as deposited) 2.1E11 ion.cm-2

Cleaning surface by Thermal desorption (350°C – 10 min)

Cr wafer (PVD)

confined inert atmosphere (N2)N2

N2

Heating source

350°C, 10 min

Quartz chamber

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EXPERIMENTAL SETUP

NH3 gas

1 ppm

200 mm Chamber

Concentration: 10, 15 and 35-ppbv

(21oC and 1 atm)

Outlet

Dilution air

(Controlled %RH)

NH3 generator

Constant CNH3

cCr coated-wafer – 100 nm PVD

2nd

o Cr-coated wafers: Physical Vapor Deposition (PVD) - 100nm Cr

o Diluted NH3 gas by clean air, controlled humidity


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Saturation at 1.9E14 (ion.cm-2)

Cmax and Kads independent on CNH3-gas

𝐶 = 𝐶𝑚𝑎𝑥 − (𝐶𝑚𝑎𝑥 − 𝐶𝑜)exp[−𝑘𝑎𝑑𝑠𝐶𝑔𝑡]

RESULTS – NH3 DEPOSITION ON Cr WAFER

NH3 Deposition Kinetics on Cr at 40%RH, varying NH3 concentration


𝐶 = 𝐶𝑚𝑎𝑥 − 𝐶𝑜 𝑘𝑎𝑑𝑠𝐶𝑔𝑡 − 𝐶𝑜

Type Langmuir deposition

Kads determined from slope (short time)

0 2 4 6 8 10 12 14 16 18 20

0

5E13

1E14

1,5E14

2E14

2,5E14

Exp. 10 ppbv

Exp. 15 ppbv

Exp. 35 ppbv

Calcul. 10 ppbv

Calcul. 15 ppbv

Calcul. 35 ppbv

NH

3 a

mo

un

t (N

H4

+ /c

m2)

Time (h)

Kads=0.04 ± 30% ppbv-1.h-1

Saturation: Cmax=1.9E14 (ion.cm-2)

40%RH

Co=2.1E11 (ion.cm-2)Kads=0.04 ± 30% ppbv-1.h-1

time

NH3 gas concen. (ppbv)

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0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

0

5E13

1E14

1,5E14

2E14

2,5E14

40RH Exp.

20RH Exp.

<1RH Exp.

40RH Calcul.

20RH Calcul.

<1RH Calcul.

NH

3 a

mou

nt

(NH

4+/c

m2)

Time (h) Saturation level, Cmax depending on %RH

Increase %RH increasing Cmax & decrease Kads

H2Ovapor favors NH3 deposition

Agreement with HF deposition on Cu-coated

surface [Ref]

𝐶 = 𝐶𝑚𝑎𝑥 − (𝐶𝑚𝑎𝑥 − 𝐶𝑜)exp[−𝑘𝑎𝑑𝑠𝐶𝑔𝑡]

Deposition Kinetics on Cr at 15-ppbv, varying %RH (Humidity)


Type Langmuir deposition

Kads determined from slope (short time)

Co=2.09E11 (ion.cm-2)

40%RH: Cmax=1.95E14 (ion.cm-2)

15-ppbv

20%RH: Cmax=1.78E14 (ion.cm-2)

<1%RH: Cmax=1.21E14 (ion.cm-2) 𝐶 = 𝐶𝑚𝑎𝑥 − 𝐶𝑜 𝑘𝑎𝑑𝑠𝐶𝑔𝑡 − 𝐶𝑜

F. Herrán, H. Fontaine et al., Solid State Phenomena, 2016, vol. 255, pp. 323–328

Kads


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Langmuir modified model

– Deposition

Cmax (ion.cm-2) = 1.65E12(RH) + 1.32E14

MATHEMATICAL MODEL

Experimental results

𝑪 = 𝑪𝒎𝒂𝒙 − (𝑪𝒎𝒂𝒙 − 𝑪𝒐)𝒆𝒙𝒑[−𝑲𝒂𝒅𝒔𝑪𝒈𝒕]

𝑪𝒎𝒂𝒙 independent on Cg at %RH = 40

𝑪𝒎𝒂𝒙 linearly dependent on %RH at Cg= 15 (ppbv)


Cmax (ion.cm-2)

Cg (NH3)

1.9E14 (ion.cm-2)

Cmax (ion.cm-2)

%RH

A = 1.65E12

B = 1.32E14

Csurface = f (RH, Cg, t)

[NH3]surf = f( RH, CNH3, time)

(1)


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Kads (ppbv-1.h-1) = -7.06E-4(RH) + 7.28E-2

Experimental results


𝑲𝒂𝒅𝒔 independent on Cg at %RH = 40

𝑲𝒂𝒅𝒔 linearly dependent on %RH at Cg= 15 (ppbv)


𝑲𝒂𝒅𝒔 (ppbv-1.h-1)

Cg (NH3)

0.04

%RH

A’ = -7.06E-4

B’ = 7.28E-2


[NH3]surf = f( RH, CNH3, time)

(2)

𝑲𝒂𝒅𝒔 (ppbv-1.h-1)

MATHEMATICAL MODEL



– Deposition


𝑪 = 1.65E12RH+1.32E14− (1.65E12RH+1.32E14 − 𝑪𝒐)𝒆𝒙𝒑[−(−7.06E−4)RH +7.28E−2)𝑪𝒈𝒕]



[NH3]surf = f ( RH, CNH3, time)

(1)

Co = 2.1E11 ion.cm-2

Model validation: <1% – 40%RH (Humidity) & 1 – 35-ppbv (NH3 airborne concentration)

Initial Clean surface: Co = 2.1E11 ion.cm-2

MATHEMATICAL MODEL



– Deposition

Cmax (ion.cm-2) = 1.65E12(RH) + 1.32E14

Kads (ppbv-1.h-1) = -7.06E-4(RH) + 7.28E-2 (2)

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RESULT

NH3 DESORPTION FROM AMMONIA SATURATED CR WAFEREL


NH3-saturated surface of Cr waferFree-NH3 flow (<1% or 40%RH)

Free-NH3 flow

Set-up: Desorption Chamber (Polymer)

Varying RH (<1% and 40%)

1180 mL/min

Desorption kinetics slower vs. Deposition

Not fully desorption (plateau 1.1E13 ion.cm-2)

• 40%RH: 160h desorption

• <1%RH: 260h desorption

• Plateau ~6% of saturated amount

60% removal NH3 in 20h (40%RH)

Model application at 160h @40%RH

~ 5-pptv NH3 concentration (cannot control)

At 40%RH: higher efficient in removing NH3

from saturated-Cr wafers

Agreement with desorption HF on Cu [Ref]0 50 100 150 200 250 300 350 400 450 500

0,0E+00

5,0E+13

1,0E+14

1,5E+14

2,0E+14

2,5E+14

40 RH Desorption

<1 RH Desorption

NH

3 a

mo

un

t (N

H4+/c

m2)

Time (h)

40%RH

<1%RH

Blank level 1.1E13 (ion.cm-2)

NH3 saturation

1.95E14 (ion.cm-2) at 40%RH

F. Herrán, H. Fontaine et al., Solid State Phenomena, 2016, vol. 255, pp. 323–328

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APPLICATION OF MATHEMATICAL MODEL


Example 1: Cr-coated surface serves as Test-vehicle

FOUPs (PC, PEI, EBM, EBMCNT)

Calculation of average-NH3 airborne concentration (Cg) in FOUPs

Example 2: Calculation of time for appearance of haze or salt crystals on Photomask (Cr)

at specification of Cg (ppbv) of NH3 and %RH in lithography zones or in equipment

Calculate time from mathematical model

P. González-Aguirre et al., Microelectron. Eng., (2019), 205, 53–58

FOUPs outgassing

Transfer NH3 to wafer

[NH3]surf = f ( RH, CNH3, time)

Agreement experimental data

FOUPs

transfer NH3

to Cr wafers

Calculation

Conta.

Purge (5 min)

Outgassing

21.5 ppbv

11 ppbv8.5 ppbv

22.5 ppbv

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Development of free-NH3 set-up for LPE-IC protocol avoid cross conta. from clean room air

Establishment of NH3 deposition kinetics knowledge of NH3 contamination model

Cmax (saturation level) and Kads (adsorption coefficient)

Dependent on humidity (%RH)

Independent on (Cg)

Langmuir modified deposition model

Desorption

Humid condition favors desorption (vs. Dry)

Desorption kinetic: Slower than Deposition

No full desorption presence of few pptv of NH3 in desorption chamber

Apply model to calculate average-Cg and time in mini-enviroment

Dry condition is highly recommended in sensible zones to AMCs

CONCLUSIONS

C=[NH3]surf

t

40%RH

Cmax=1.95E14 ion.cm-2𝑪 = 𝑪𝒎𝒂𝒙 − (𝑪𝒎𝒂𝒙 − 𝑪𝒐)𝒆𝒙𝒑[−𝑲𝒂𝒅𝒔𝑪𝒈𝒕]

[NH3]surf = f (RH, Cg-NH3 , t)Kads = A’(RH) + B’

Cmax = A(RH) + B

Co = 2.1E11 ion.cm-2

Langmuir deposition model

Cg = 0 – 35 (ppbv)

%RH = 0 - 40


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Univ. Grenoble Alpes, CEA, LETI

Sylviane CÊTRENicolas CHEVALIERCarmelo CASTAGNAGarcia ROLANDPierre LEYGNAC


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Contamination kinetics of airborne ammonia on chromium-coated … · 2019-04-01 · on...

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