Kss 2010- processes for film stripping

Always Thinking. Better.™

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Copyright © 2010 FSI International All Rights Reserved

FSI Knowledge SERVICES™ Seminar Series 2010

Processes for Film Stripping:Implanted Photoresist and NiPt



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Outline

• HT SPM Chemistry Theory• Film Removal Mechanism

– Ion implanted Photoresist– Post anneal residual NiPt metal

• Optimize the process in reaction chamber• Application Result

– Ion implanted Photoresist

– Post anneal residual NiPt metal

• Summary



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High Temp. boost Chemical (SPM) Reactivity

Half Cell Oxidation Reactions

HSO5- + 2H+ + 2e- HSO4

- + H2O 1.44V

HO• + H+ + e- H2O 2.80V

HSO4• + H+ + e- H2SO4 2.60V

H2O2 + 2H+ + 2e- H2O 1.78V

Mor

e ox

idiz

ing

pow

er

Main application areas are Main application areas are 1.1. FEOL polymer removal after plasma etch-ash / ion implant FEOL polymer removal after plasma etch-ash / ion implant 2.2. MOL metal selective etch for silicide formationMOL metal selective etch for silicide formation

Higher temperature

H2SO4 + H2O2

HSO4• + HO•(36 kcal/mol)

2HO•(51 kcal/mol)

H2O + ½O2

(18 kcal/mol)

H2SO5 + H2O(spontaneous)



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Outline






• Summary



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Implanted Photoresist

Ion implantation process has many variables- Species: B, P, As, Si, Ge, BF2

- Energy: < 1keV to > 1000keV- Dosage: 1x1011 to >1x1016 ions/cm2

- Normal incidence or angled

gate gate

cross-linkedpolymer layer

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

Most challenging where cross-linked resist is bonded to wafer surface especially at wafer edge, near EBR region



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Ion Implantation Causes Cross-Linking and Dehdyrogenation

Figure 4. CP-MAS 13C NMR spectra of pristine resist and crust (As 40keV 1E15cm -2)[Tsvetanova et al., ECS Trans. 25(5), 187(2009)]

CHCH2

O

nCH

CH2

O

m

CHCH2

OH

n

CHCH2

OR

m

CHCH2

O

nCH

CH2

O

nCH

CH2

O

mCH

CH2

O

m

CHCH2

OH

n

CHCH2

OH

n

CHCH2

OR

m

CHCH2

OR

m

CHCH2

OH

nCH

CH2

OR

m

CHCH2

OH

n

CHCH2

OR

m

CHCH2

OH

nCH

CH2

OH

nCH

CH2

OR

mCH

CH2

OR

m

CHCH2

OH

n

CHCH2

OH

n

CHCH2

OR

m

CHCH2

OR

m

Pristine Resist Crust



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High Activation Energy to Remove Crust

Robert Doering and Yoshio Nishi, Handbook of Semiconductor Manufacturing Technology (CRC Press, 2008).

Ashing = Gas Phase

FIGURE 7.57 Relative removal rates of standard i-line photoresist and the implanted carbonized crust layer as afunction of temperature for a oxygen plasma without ion bombardment. Activation energy (Ea) has been calculatedfrom the temperature dependence of the reaction.



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Thermodynamic ConsiderationsSpecies Electro-Chemical

Potential (eV)Reactive with

Bulk ResistReactive with

Cross-Linked Resist

O• (only exist in asher)

----- Y Y

OH• 2.80 Y Y

HSO4• 2.60 Y Y

O3 2.08 Y N

H2O2 1.78 N N

H2SO5 1.44 Y N

O2 1.23 N N

CH2

OH

H2SO5 is more effective than H2O2 because sulfuric acid can both dehydrate and dissolve short chain polymer fragments

Need radicals to attack highly cross-linked resist CH2

O

CH2HO



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Radicals attack cross-links, C-C, C-O, Si-O

CHCH2

O

nCH

CH2

O

m

CHCH2

OH

n

CHCH2

OR

m

CHCH2

O

nCH

CH2

O

nCH

CH2

O

mCH

CH2

O

m

CHCH2

OH

n

CHCH2

OH

n

CHCH2

OR

m

CHCH2

OR

m CHCH2

O

n

Si

silicon wafer

Si Si

OH OH

CHCH2

O

nCH

CH2

O

n

Si

silicon wafer

Si Si

OH OH

HSO4•or

HO•

HSO4•or

HO•

HSO4•or

HO•



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Outline






• Summary



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pH

Vol

tage

Pot

entia

l Corrosion

Passivation

Immunity

Platinum Chemical Reaction Model

Marcel Pourbaix, Atlas of Electrochemical Equilibria, 1974

Aqua regia base :

• Pt + 4NO3- + 8H+ Pt(4+) +NO2+ 4H2O

• Pt(4+)+6Cl- + 2H+ H2PtCl6

Hydrochloric acid base :

• Pt + 2H2O2 + 4H+ Pt(4+) + 4H2O

• Pt(4+) + 6Cl- + 2H H2PtCl6

Sulfuric acid base :

Pt + H2SO4 + H2O2 Pt(OH)2++ + PtO++ + H2SO3



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Low RTP1 NixSi formation behavior

Lih J. Chen, Silicide technology for integrated circuits, IEE 2004

FIGURE 5.3 Sheet resistance versus annealing temperature measured in situ while heating Co/Si and Ni/Si films at 3◦C/s. Note that the lower resistive NiSi phase forms at considerably lower temperature than CoSi2. However, the NiSi film also degrades at lower temperature.



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Lower Anneal Temperature Address Nickel Diffusion but Creates New Problem in Strip Process (HCl attack)



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Outline






• Summary



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ViPR+™ (Steam-Injected SPM) Maximizes Exothermic Energy Release and Boosts Chemical Reactivity

mix with steam

0 20 40 60 80 100

0

186

enthalpyof mixtureincluding

vapor(J/g)

weight percentage H2SO4 in water

0°C

21°C38°C

66°C93°C 121°C

149°C

288°C

260°C

232°C

204°C

177°C

104°C

110°C

121°C

149°C

177°C

204°C

232°C

372

Heat of Vaporization = The Steam Advantage

0 20 40 60 80 100

0

186

enthalpyof mixtureincluding

vapor(J/g)

weight percentage H2SO4 in water

0°C

21°C38°C

66°C93°C 121°C

149°C

288°C

260°C

232°C

204°C

177°C

104°C

110°C

121°C

149°C

177°C

204°C

232°C

372

Heat of Vaporization = The Steam Advantage

1001009090808070706060weight % H2SO4

GAS

LIQUID

149°C

177°C

204°C

232°C260°C

150°C96%

enth

alpy

mix with water/H2O2

Typical Wet Bench On Wafer <150ºC

FSI ViPR™ Technology On Wafer >150ºC + high reactivity

STEAM

Typical Single Wafer On Wafer >150ºC

Steam Injection enabled by Closed Chamber & Energetic Nozzle Array



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Linear Spray Nozzle Array Enhances Film Removal(1) Multiple spray dispense for mixing with steamSpray bar chemical delivery provides better mixing with steam, higher local flow rate, thinner boundary layer and larger area processing

(2) Entire wafer surface processed at same timeSpray bar dispense provides greater and more uniform coverage than single point nozzle. Spray bar dispense provides greater and more uniform wafer temperature than point nozzle.

Single Point Nozzle Linear Nozzle Array steam



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Energized Chemical Aerosol to Boost Reactivity

Reactivity enhancement1. POU mixing to retain transient phase

chemical radical

2. N2 or Steam energized chemical aerosol to • Better wet ability• Higher collision probability /

Better mass transfer• Provide additional mechanical

force to peel off film

3. Use linear spray bar to maximize the amount of chemical mass in surface reaction.

SPM distributed evenly across wafer

N2 flow keeps fumes out

Exhaust keeps chamber pressure slightly negative, prevents escape of fumes



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Outline






• Summary



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Implanted Photoresist Removal By Hot SPM

dissolution ofthinner sidewallcrust by radicalreaction+ dissolution of underlying PR bydirect solvation

crust lift-off + dissolutionof crust layerby radical reaction

dissolutionof attachedcrust layerby radical reaction

ion implantationcreates cross-linked“crust” on surfaceand sidewall of PR

Physical force

Chemical force



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FSI ORION® ViPR™ Resist Strip Capability

All Wet Resist Strip

Implant Type Pre Gateand PAC

ViPR

LDDand PLAD

ViPR+

S/D

ViPR+

Implant Level Up to 1E14 up to 1E1510 keV

up to 5E1510 keV

Dispense time (sec)

15 40 100

SPM usage (liter/wafer)

0.38 1.0 2.5

Oxide loss(Å) < 0.1 ~0.2 ~0.3

Nitride loss(Å) <0.5 <1.0 ~1.5

8-chamber Thruput (wph)

200 150 115

(includes 30 second, room temperature, SC1 step)



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Low Material Loss – Oxide and Nitride

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49

measurement point (concentric circles, 1=ctr, 49=edge)

ma

teri

al

los

s (

Å)

■ 80s, 4:1SPM + 30s RT SC1 - furnace silicon nitride

80s, 4:1SPM + 30s RT SC1 - furnace silicon oxide

▲ 40s, 10:1ViPR+ + 30s RT SC1 - furnace silicon nitride

∆ 40s, 10:1ViPR+ + 30s RT SC1 - furnace silicon oxide

(ERF 10297, ERF 10347, lab 2010_04_23)



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Outline






• Summary



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NiPt selective Etch for NiPtSi formation

PtPtPt

Si Si

Si substrateNixSiNixSi

NixSi NixSi

Si Si

Si substrate

Pt : atomic weight 195 Ni : atomic weight 58.7TiN : capping

RTP

SelectiveWet Etch

PtPtPt

HTSPM

HTSPM

Or cluster

PtPtPt

O

++

OHH

OHH

OH H

OH H

++++

Pt(OH)2++ PtO++

Pt

O

H

O

H

+ + Pt

O

+ +



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ViPR™ Process Enables Wide Range of Anneal Conditions w/o Silicide Degradation

POR (HCl)

ViPR

Silicide Attack

Presented by Stephane Zoll (ST) at KSS 2008 Seminar in Grenoble



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NiPt Selective Process Latitude

0

50

100

150

200

250

300

350

5% 5% 5% 5% 5% 5% 10% 10% 10% 10%

Pt (%)

NiP

t fil

m th

ickn

ess

ViPR 60s

ViPR 90s



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Outline






• Summary



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Summary

• Thermal entropy will boost the chemical reactivity for film removal and application proven

• High temperature SPM will extend the same chemical for advanced CMOS manufacturing process

• Proper modulation of both chemical / mechanical force will optimize the process

Kss 2010- processes for film stripping

Technology

fsi international

semiconductor international

ion bombardment

niptalways thinking

ion implantation causes6cross

e h2o

ash ion implant

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