Kss 2010- processes for film stripping

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Processes for Film Stripping:
Implanted Photoresist and NiPt

Always Thinking. Better.™

FSI Knowledge SERVICES™ Seminar Series 2010
Copyright © 2010 FSI International All Rights Reserved

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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

• Summary


3
High Temp. boost Chemical (SPM) Reactivity
Main application areas are
1. FEOL polymer removal after plasma etch-ash / ion implant
2. MOL metal selective etch for silicide formation
(spontaneous)
H2SO4 + H2O2 H2SO5 + H2O
(18 kcal/mol) (51 kcal/mol) (36 kcal/mol)
2HO• HSO4• + HO•
H2O + ½O2
Higher temperature

Half Cell Oxidation Reactions

More oxidizing power
HSO5- + 2H+ + 2e- HSO4- + H2O 1.44V

H2O2 + 2H+ + 2e- H2O 1.78V
HSO4• + H+ + e- H2SO4 2.60V
HO• + H+ + e- H2O 2.80V

4
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
cross-linked
polymer layer

gate gate

Most challenging where cross-linked resist is bonded
to wafer surface
 especially at wafer edge, near EBR region
photo source: P. Gillespie et al, Semiconductor International, October, 1999


Ion Implantation Causes 6

Cross-Linking and Dehdyrogenation
Pristine Resist Crust
CH2 CH2 CH2 CH2
CH CH CH CH
n m n m

OH OR
OH OH OR OR
O O

CH CH CH CH
CH2 CH2 CH2 CH2
n m n m

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)]

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High Activation Energy to Remove Crust

Ashing = Gas Phase

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

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


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Thermodynamic Considerations
Species Electro-Chemical Reactive with Reactive with
Potential (eV) Bulk Resist Cross-Linked Resist
CH2
HO CH2
Need radicals to attack
CH2 O
highly cross-linked resist
OH

O• (only exist in ----- Y Y
asher)
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

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

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Radicals attack cross-links, C-C, C-O, Si-O
CH2 CH2
CH CH
HSO4• n m
or
HO•
OH OR
HSO4• O O
or
HO•
CH CH CH2
CH2 CH2
n m CH
n

HSO4•
O OH OH
or
HO• Si Si Si

silicon wafer


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Outline



• Summary


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Platinum Chemical Reaction Model

 Aqua regia base :
• Pt + 4NO3- + 8H+  Pt(4+) +NO2+ 4H2O
Passivation
• Pt(4+)+6Cl- + 2H+  H2PtCl6
Corrosion
Voltage Potential

 Hydrochloric acid base :
• Pt + 2H2O2 + 4H+  Pt(4+) + 4H2O
Immunity • Pt(4+) + 6Cl- + 2H  H2PtCl6

 Sulfuric acid base :
Pt + H2SO4 + H2O2  Pt(OH)2++ + PtO++ + H2SO3

pH

Marcel Pourbaix, Atlas of Electrochemical Equilibria, 1974

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Low RTP1 NixSi formation behavior

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

Lower Anneal Temperature Address Nickel Diffusion but 13

Creates New Problem in Strip Process (HCl attack)


14
Outline



• Summary


121°C
121°C

149°C
149°C
177°C
177°C
204°C
204°C
232°C
232°C
ViPR+™ (Steam-Injected SPM) Maximizes Exothermic 15

7 ° 4 ° 2° 0 ° 8
17 20 23 26 28
C C C C
Energy Release and Boosts Chemical Reactivity
Steam Injection enabled by Closed Chamber & Energetic Nozzle Array
STEAM
mix with steam 260°C
232°C
204°C
FSI ViPR™ Technology
On Wafer >150ºC + high reactivity
177°C
enthalpy

149°C
GAS

Typical Single Wafer
150°C On Wafer >150ºC
mix with water/H2O2
96%
LIQUID

60 70 80 90 100
weight % H2SO4 Typical Wet Bench
On Wafer <150ºC
149°C Copyright © 2010 FSI International All Rights Reserved

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Linear Spray Nozzle Array Enhances Film Removal
(1) Multiple spray dispense for mixing with steam
Spray 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 time
Spray 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
SPM distributed evenly across wafer
Reactivity enhancement
N2 flow keeps fumes out 1. 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
Exhaust keeps chamber pressure slightly reaction.
negative, prevents escape of fumes


18
Outline



• Summary


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Implanted Photoresist Removal By Hot SPM

ion implantation dissolution of crust lift-off dissolution
creates cross-linked thinner sidewall + dissolution of attached
“crust” on surface crust by radical of crust layer crust layer
and sidewall of PR reaction by radical reaction by radical reaction
+
dissolution of
underlying PR by
direct solvation

Physical force
Chemical force


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FSI ORION ViPR™ Resist Strip Capability
®

All Wet Resist Strip
Implant Type Pre Gate LDD S/D
and PAC and PLAD
ViPR ViPR+ ViPR+
Implant Level Up to 1E14 up to 1E15 up to 5E15
10 keV 10 keV

Dispense time 15 40 100
(sec)
SPM usage 0.38 1.0 2.5
(liter/wafer)
Oxide loss(Å) < 0.1 ~0.2 ~0.3

Nitride loss(Å) <0.5 <1.0 ~1.5

8-chamber 200 150 115
Thruput (wph)
(includes 30 second, room temperature, SC1 step)

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Low Material Loss – Oxide and Nitride

1.2
■ 80s, 4:1SPM + 30s RT SC1 - furnace silicon nitride
1.0
material loss (Å)

0.8

0.6 ▲ 40s, 10:1ViPR+ + 30s RT SC1 - furnace silicon nitride

0.4
 80s, 4:1SPM + 30s RT SC1 - furnace silicon oxide
0.2
∆ 40s, 10:1ViPR+ + 30s RT SC1 - furnace silicon oxide
0.0
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)

(ERF 10297, ERF 10347, lab 2010_04_23)


22
Outline



• Summary


23
NiPt selective Etch for NiPtSi formation

Si Si Pt Pt Pt

Si substrate HT
SPM
Pt : atomic weight 195
Ni : atomic weight 58.7
TiN : capping
Pt Pt Pt

Selective
HT
RTP Wet Etch SPM

O
H H

O

O
+ Pt + + Pt +
NixSi NixSi

Si Si Pt(OH)2++ PtO++
NixSi NixSi
Or cluster
Si substrate
H H H H

O O O

+ Pt + Pt + Pt +
+ + O O
H H H H


ViPR™ Process Enables Wide Range of Anneal 24

Conditions w/o Silicide Degradation

Silicide
POR (HCl) Attack

ViPR

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

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NiPt Selective Process Latitude

350 ViPR 90s

300
NiPt film thickness

250

200 ViPR 60s

150

100

50

0
5% 5% 5% 5% 5% 5% 10% 10% 10% 10%

Pt (%)

26
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


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