Steam-Injected SPM Process for All-Wet Stripping of ... · 5.5 min Steam-Injected SPM. ... • Trade-off between POU heat of mixing temperature gain and dilution effect • Patent-pending

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Copyright © 2009 FSI International All Rights Reserved

SRC/SEMATECH ERC for EBSM Teleseminar - July 9, 2009

Steam-Injected SPM Process for All-Wet Stripping of Implanted Photoresist

Jeffery W. Butterbaugh

FSI International, 3455 Lyman Blvd., Chaska, MN 55318 [email protected]

Always Thinking. Better.™Copyright © 2009 FSI International All Rights Reserved

2/18


Outline

• Motivation• Implanted PR – All-Wet Stripping Challenge• SPM (Sulfuric acid – hydrogen Peroxide Mixture)

– Making it More Reactive• Results• Summary


3/18


Low Material Loss – An “All-Wet” Driver

Lower material loss requirements during cleaning driven byultra-shallow junction (USJ) source-drain extension (SDE) or lightly-doped drain (LDD)

low materia

l loss

ultra-shallow jct


4/18


Stripping Implanted Photoresist

Ion implantation process – affects stripping- Species: B, P, As, Si, Ge, BF2- Energy: < 1keV to > 1000keV- Dosage: 1x1011 to >1x1016 ions/cm2

- Normal incidence or angled

gate gate

dehydrogenated,amorphous

carbon layer

photo source: P. Gillespie et al, Semiconductor International, October, 1999

Most challenging where carbonized PR fused to wafer surface

especially at wafer edge, near EBR region


5/18


High Activation Energy to Remove Crust

Robert Doering and Yoshio Nishi, Handbook of Semiconductor Manufacturing Technology (CRC Press, 2007).


6/18


SPM – Making it More Reactive

H2 SO5 + H2 O

Higher temperature

Half Cell Oxidation Reactions

HSO5- + 2H+ + 2e- HSO4

- + H2 O 1.44V

HO• + H+ + e- H2 O 2.80V

HSO4 • + H+ + e- H2 SO4 2.60V

H2 O2 + 2H+ + 2e- H2 O 1.78V

Mor

e ox

idiz

ing

pow

er

HSO4 • + HO•2HO•

H2 O added with 31% H2 O2will force this equilibrium backto the leftH2 SO4 + H2 O2


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SPM Mixing is Exothermic

0

20

40

60

80

100

120

140

0 30 60 90 120 150H2O2 Added (cc)

Fina

l Tem

pera

ture

(Deg

. C)

4:3 98°2:1 91°

1:1 86°4:1 68°

10:1 38° rise

4:5 82°

Resulting temperature when 20°

C 31% H2 O2 is mixed with 100 cc of 20°

C 96% H2 SO4 .

4:3 ratio gives highest temperature rise, but higher concentration is desired(H2 O2 includes 69% water, which dilutes and lowers reactivity)

highest POU mixing temperature (66%H2 SO4 ; 10%H2 O2 ; 24% H2 O)

higher concentration(90%H2 SO4; 2%H2 O2 ; 8% H2 O)


8/18


How to Achieve High Temperature Without Dilution?

• Pre-heating SPM above 150°C causes rapid degradation of H2 O2 before contacting the wafer

• POU 4:3 SPM mixing gives temperature boost, but causes dilution

• Preheating H2 SO4 above 150°C requires specialized fluid handling

First, lets review a useful tool for illustrating the advantage of steam injection . . . .

SOLUTION = STEAM INJECTION (ViPR+)


9/18


Sulfuric Acid Enthalpy-Concentration Diagram

0 20 40 60 80 100

0

186

enthalpyof mixtureincluding

vapor(J/g)

weight percentage H2 SO4 in water

0°C

21°C38°C

66°C93°C 121°C

149°C

288°

C26

0°C

232°

C20

4°C

177°

C

104°C

110°C

121°C

149°C

177°C204°C232°C

372

gas

liquid

• Mixing sulfuric acid and water produces interesting energetics

• Enthalpy-Concentration diagram allows easy analysis of mixing temperature effects

• gas-liquid equilibrium

• isotherms

• minor differences between 100% H2 O (B.P.=100°C) and 69%H2 O/31%H2 O2 (B.P.=107°C)


10/18


Mixing Room Temperature 96% Sulfuric Acid with Water

0 20 40 60 80 100

0

186enthalpy

of mixtureincluding

vapor(J/g)


0°C

21°C38°C

66°C93°C 121°C

149°C

288°

C26

0°C

232°

C20

4°C

177°

C

104°C

110°C

121°C

149°C

177°C204°C232°C

372

0

40

80

120

160

0 20 40 60 80 100


adiabatic mixing temperature(°C)

maximum temperature at about 130°C and 4:3 mixing ratio(66%H2 SO4 ; 10%H2 O2 ; 24%H2 O)

Connecting two points produces an adiabatic mixing curve


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Mixing 95°C 96% Sulfuric Acid with Water

0 20 40 60 80 100

0

186enthalpy

of mixtureincluding

vapor(J/g)


0°C

21°C38°C

66°C93°C 121°C

149°C

288°

C26

0°C

232°

C20

4°C

177°

C

104°C

110°C

121°C

149°C

177°C204°C232°C

372

0

4080

120160

200

0 20 40 60 80 100



boiling point at about 190°C and 2.5:1 mixing ratio(77%H2 SO4 ; 6%H2 O2 ;17%H2 O)

Starting with 95°C H2 SO4 causes intersection with gas-liquid curve


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Mixing 150°C 96% Sulfuric Acid with Water

0 20 40 60 80 100

0

186enthalpy

of mixtureincluding

vapor(J/g)


0°C

21°C38°C

66°C93°C 121°C

149°C

288°

C26

0°C

232°

C20

4°C

177°

C

104°C

110°C

121°C

149°C

177°C204°C232°C

372

04080

120160200240

0 20 40 60 80 100



boiling point at about 210°C and a 4:1 mixing ratio(83%H2 SO4 ; 4%H2 O2 ;13%H2 O)

Starting with 150°C H2 SO4 allows 4:1 mixing ratio before boiling


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Mixing 150°C 96% Sulfuric Acid with Water and Steam

0 20 40 60 80 100

0

186enthalpy

of mixtureincluding

vapor(J/g)


0°C

21°C38°C

66°C93°C 121°C

149°C

288°

C26

0°C

232°

C20

4°C

177°

C

104°C

110°C

121°C

149°C

177°C204°C232°C

372

Heat of Vaporization = The Steam Advantage

heating water from 21°C to 100°C =331 J/g

converting water from liquid to gas at 100°C =2270 J/g


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Mixing 150°C 96% Sulfuric Acid with Water and Steam

0 20 40 60 80 100

0

186enthalpy

of mixtureincluding

vapor(J/g)


0°C

21°C38°C

66°C93°C 121°C

149°C

288°

C26

0°C

232°

C20

4°C

177°

C

104°C

110°C

121°C

149°C

177°C204°C232°C

372

140

180

220

260

80 100



boiling point at about 232°C and an equivalent 5.5:1 mixing ratio(86%H2 SO4 ; 3%H2 O2 ;11%H2 O)

add 31% H2 O2 to reach 10:1mixing ratio then add steam

Using steam provides temperature boost with minimal dilution


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Results on Implanted Photoresist

Time to clear blanket 2.5x1014 ions/cm2, 40keV As implanted photoresist dropped from 50 min SPM to 5.5 min SPM

20 min Standard POU SPMResist Still Present

5.5 min Steam-Injected SPMResist Stripped

⇒

2.5x1014 ions/cm2, 40 keV As Implant

batch spray system


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All-Wet PR Strip with Low Material Loss

Dose(ion/cm2)

Energy & species

SPM time (min)

oxideloss(Å)

5x1014 40keV As 4 <0.2

1x1015 2keV As 4 <0.2

3x1016 7keV BF3 (PLAD) 4 <0.2

FSI ZETA® System (Batch Spray) with ViPR™ Technology for Steam-Injected SPM Stripping Implanted Photoresist

LDD implantITRS indicates

<0.3 Å


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Very Fast Single-Wafer Photoresist Stripping

0

25

50

75

100

standard POU SPM

steam-injectedPOU SPM

time

to s

trip

(s) 5E14 / 40keV

1E15 / 2keV

SP

M c

hem

ical

cos

t ($/

waf

er)

0

$0.42

$0.84

$1.25

$1.67

[standard SPM = POU mixing with 150°C sulfuric acid]

80% Reduction in Time and Cost for Single Wafer Stripping of Arsenic-implanted Photoresist


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Summary

• Sulfuric acid – hydrogen peroxide mixture continues to be a common approach to all-wet implanted PR strip

• Trade-off between POU heat of mixing temperature gain and dilution effect

• Patent-pending Steam-Injected SPM process provides increased temperature at the wafer surface with minimal dilution

• Steam-Injected SPM process meets ITRS material loss requirements for LDD implants

Documents

Steam-Injected SPM Process for All-Wet Stripping of ... · 5.5 min Steam-Injected SPM. ... • Trade-off between POU heat of mixing temperature gain and dilution effect • Patent-pending