Ru CMP Slurry for Ru Bottom Elelctrode Formation Ru CMP Slurry for Ru Bottom Elelctrode Formation...
Transcript of Ru CMP Slurry for Ru Bottom Elelctrode Formation Ru CMP Slurry for Ru Bottom Elelctrode Formation...
Ru CMP Slurry for Ru Bottom Elelctrode Formation
Jin-Goo Park
Division of Materials and Chemical EngineeringHanyang University, Ansan, 426-791, Korea
February 12, 2008
LEVITRONIXCPM Users' Conference 2008 February 12, 2008
Summary
4
Introduction1
Objective2
Results
3
- Ru Bottom Electrode Capacitor
- Static etch rate, Film thickness, Contact angle- Effects of pHs and Abrasive Particle on Ru CMP- Removal Rate and Selectivity of Ru disk- Application of Ru slurry on Patterned Wafer
Outline
5
Characterization Methods
Overview on Ruthenium
Ru (Ruthenium)Ru (Ruthenium)
Electrodes in DRAMs and FRAMs (Kwon et al., J. Electrochem. Soc., 151(2) (2004) C127)
Gate electrode in MOSFETs (Zhong et al., J. Electron. Master., 30 (2001) 1493)
Diffusion barrier and Cu seed layer in interconnect metallization(Brusic et al., 2006 ICPT, October 12-13, 2006, Crowne Plaza Hotel, Foster City, CA)
• Application in ICs (Integrated Circuits)
State at RT hard white metal (platinum group)
Melting point 2607 K
Boling point 4173 K
Work function 4.71 eV
Resistivity 7.1 μΩ·cm
Vertical Image
Excessive recess of Ru surface or loss of oxide current leakage, loss of capacitance
(from Samsung Electronics Co.)
Issues in Ru Bottom Electrode Capacitor
Tilt Image
After Dry etch-back method
Fabrication Process of Bottom Electrode
Interlayer dielectric film
contact
TEOS
Formation of Formation of PatternPattern
Ru layer
DepositionDepositionof Bottom Electrodeof Bottom Electrode
Sacrificial Layer (PR or Oxide)
DepositionDepositionof Sacrificial layerof Sacrificial layer
EtchingEtchingof Sacrificial layerof Sacrificial layer Ru CMPRu CMP RemoveRemove
of Sacrificial layerof Sacrificial layer
(from Samsung Electronics Co.)
Ru Bottom Electrode Capacitor
Ru
Ru
after
before
CMP CMP ProcessProcess
Potential-pH equilibrium diagram for system ruthenium-water, at 251)
1) M. Pourbaix, “Atlas of electochemical equilibria in aqueous solutions”, N. A. C. E. Intl., Houston, TX., 1974.2) S. H. Lee, S. H. Lee, Y. J. Kang, I. K. Kim, J. G. Park, KIEEE, 18 (2005) 803
Ru Pourbaix Diagram
(b) Alkaline SolutionKMnO4 + KOHpH 13.24~13.66
Eh 0.6~0.7 V
(a) Acid Solution 2)
CAN + HNO3pH 0~1
Eh 1.6~1.7 V
(a)
(b)
Highly Acidic Slurry- Harmful to Human Body- Generation of Toxic gas- Oxide Residue
Formation on the Pad
Development of
Less Acidic,
Neutral
or Less Alkaline Slurry
Research Objective
Highly Alkaline Slurry- Selectivity Issue due to
High Etch Rate of Oxide- Erosion Issue
Experimental Materials
Characterization methods
Experimental MaterialsSample Ru wafer and disk
Abrasive Particles Alumina, Fumed Silica particles
Etchant and Oxidiant Chemical A
pH adjustor HCl, NH4OH
CMP Poli-500 (GNP Tech.)
XPSCharacterization FESEM
of Ru wafer surface Static Contact Angle Analyzer (SCA)Variable Angle Spectroscopic Ellipsometry (VASE)
Before CMP After CMP
X 100k X 100k
Ru disk before and after CMP
Potential-pH equilibrium diagram for system ruthenium-water, at 25*
* M. Pourbaix, “Atlas of electochemical equilibria in aqueous solutions”, N. A. C. E. Intl., Houston, TX., 1974.
Ru Pourbaix Diagram
(b) Alkaline SolutionKMnO4 + KOHpH 13.24~13.66
Eh 0.6~0.7 V
(a) Acid SolutionCAN + HNO3
pH 0~1Eh 1.6~1.7 V
(a)
(b)
(c)
(c) Chemical ApH : 4.5~5
Eh : 0.8 ~ 1 V
Static Etch Rate
The static etch rate and passivation film thickness increased with increase
of chemical A concentration.
The contact angle decreased
due to the formation of Ru oxide.
0.00 0.02 0.04 0.06 0.08 0.100
5
10
15
20
25
30
Chemical A
Chemical A Concentration (M)
Stat
ic E
tch
Rat
e (n
m/m
in)
Contact Angle
0.00 0.02 0.04 0.06 0.08 0.100
10
20
30
40
50
60
70
80
Chemical A
Chemical A Concentration (M)
Con
tact
Ang
le (
O)
0.00 0.02 0.04 0.06 0.08 0.100
5
10
15
20
25
30
Chemical A
Chemical A Concentration (M)
Film
Thi
ckne
ss o
n R
u (n
m)
Passivation film thickness
Static etch rate, Passivation film thickness and Wettability of Ru
XPS Surface Analysis on Ru
In treated Ru in Chemical A,Ru concentration decreasedand O concentration increased.
These results mean that the Ru oxide was formed on Ru surface in Chemical A.
0 1 2 30
102030405060708090
100
Chemical A 0.1 M
Sputtering Time (min)
Ato
mic
Con
cent
ratio
n (%
)
O 1s
Ru 3d
0 1 2 30
102030405060708090
100
Ato
mic
Con
cent
ratio
n (%
)
Sputtering Time (min)
bare Ru
O 1s
Ru 3d
Ru 3d O 1s
As received Ru wafer 97.5 % 2.5 %
Treated Ru wafer(Chemical A 0.1 M)
90 % 10 %
Bare Ru treated Ru
- Chemical A 0.1 M(pH adjustor : HCl, NH4OH)
pH 4 ~ 10Eh 0.7 ~ 1.2 V
- pH 4 ~ 7
Formation of RuO4, H2RuO5
or RuO2·2H2O
- pH 7 ~ 10
Formation of RuO4-
or RuO2 · 2H2O
Eh of Ru as a function of pHsin Chemical A 0.1 M
pH adjustor : HCl, NH4OH
pH
Eh (V
vs.
SH
E)
Chemical A 0.1 M
- Perruthenate (RuO4-) solutions are unstable and decompose into RuO2 · 2H2O and O2
1, 2)
4RuO4- + 6H2O + 4H+
4(RuO2 · 2H2O) (insoluble) + 3O2
- The RuO4 is very soluble in water with the formation of “hyperruthenic acid”, H2RuO5.1, 2)
4RuO4- + 4H+ RuO2.2H2O + 3RuO4
H2O + RuO4 (soluble) H2RuO5
pH 4 ~ 7
pH 7 ~ 10
Representative Reactions
1) M. Pourbaix, “Atlas of electochemical equilibria in aqueous solutions”, N. A. C. E. Intl., Houston, TX., 1974.2) L. Davidson, Y Quinn and D. E Steele, Platinum Metals Rev., 1998, 42, (3), 90-98
Electrochemical Analysis
1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.010.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8Chemical A 0.1 M, pH adjustor : HCl, NH4OH
i (A/cm2)
E
(V v
s. S
HE)
pH 8
pH 10 pH 9
pH 6 pH 4
Increase of Corrosion Current
Decrease of Corrosion Current
- pH 4 ~ 7
The corrosion current increased
up to pH 6 due to the dissolution
of soluble RuO4.
- pH 7 ~ 10
The corrosion current decreased
with increase of pH
due to the formation of
insoluble RuO2 · 2H2O.
3 4 5 6 7 8 9 10 110
10
20
30
40
50
60
70
80
Ru w afer
Chem ical A 0.1 MpH adjustor : HCl, NH 4OH
pH
Con
tact
Ang
le (
O)
3 4 5 6 7 8 9 10 110
2
4
6
8
10
pH
Ru wafer
Chem ical A 0 .1 MpH adjustor : H Cl, NH 4O H
Film
Thi
ckne
ss o
n R
u (n
m)
In Acid Region- High static etch rate was measureddue to the dissolution of soluble RuO4.- A relatively high passivation film and low contact angle were measured.
Static etch rate, Passivation film thickness and Wettability of Ru
3 4 5 6 7 8 9 10 110
10
20
30
40
50
60
R u w afer
NaIO 4 0.1 M , pH adjustor : H Cl, N H 4O H
pH
Stat
ic E
tch
Rat
e (n
m/m
in)
pH Adjustor : HCl, NH4OHStatic Etch Rate
Passivation film thickness Contact Angle
- Ru Concentration: pH 6 < pH 9
- O Concentration : pH 6 > pH 9
At pH 6, dissolution and oxidation of Ru were higher than those at pH 9
0.0 0.5 1.0 1.5 2.00
102030405060708090
100
Chemical A 0.1 M at pH 6
Sputtering Time (min)
Ato
mic
Con
cent
ratio
n (%
) O1s,ls1
Ru3d
0.0 0.5 1.0 1.5 2.00
102030405060708090
100
Chemical A 0.1 M at pH 6
O1s
Ru3d
Sputtering Time (min)
Ato
mic
Con
cent
ratio
n (%
)
XPS Analysis of Ru as a function of pHs
pH 6 pH 9
pH Ru 3d O 1s
6 89 at% 11 at%
9 97 at% 3 at%
2 4 6 8 10 12-40
-30
-20
-10
0
10
20
30
40γ-Al2O3 500 ppm
No addition Chemical A
0.5 wt%
Ionic Strength : KCl 10-3 MpH Control : HCl and NaOH
Zeta
Pot
entia
l (m
V)
pH of Solution2 4 6 8 10 12
0
500
1000
1500
2000
2500
3000
3500
γ-Al2O3 500 ppm No addition Chemical A
0.5 wt%
Ionic Strength : KCl 10-3 MpH Control : HCl and NaOH
Mea
n Pa
rtic
le S
ize
(nm
)pH of Solution
Zeta Potential Mean Particle Size
In addition of Chemical A- The Decrease of Zeta Potential (The Adsorption of Anion from Chemical A)
: IEP (pH 9 pH 4)- The Migration of the Maximum Point of Particle Size : pH 9.3 pH 4
Alumina with and without Chemical A
2 4 6 8 10 12-50
-40
-30
-20
-10
0
10
20
30
40
50
Ionic Strength : KCl 10-3MpH Control : HCl and NaOH
fumed silica 500 ppm No addition Chemical A
0.5 wt%
Zeta
Pot
entia
l (m
V)
pH of Slurry2 4 6 8 10 12
0
500
1000
1500
2000
2500
3000
3500
fumed silica 500 ppm No addition Chemical A
0.5 wt%
Ionic Strength : KCl 10-3MpH Control : HCl and NaOH
Mea
n Pa
rtic
le S
ize
(nm
)
pH of Slurry
Fumed Silica with and without Chemical A
Zeta Potential Mean Particle Size
In addition of Chemical A
- Little Adsorption of Anion from Chemical A on Silica
: Little Change of Zeta Potential and Particle Size
Removal Rate as a function of pHs
The trend of removal rate of Ru was very similar to that of static etch rate.
The removal rate of Ru was the highest at pH 6 due to high etch rate.
Alumina slurry showed a higher Ru removal rate than silica slurry
due to higher hardness of alumina.
Removal Rate
3 4 5 6 7 8 9 10 110
20
40
60
80
100
120
140
160
180
Fumed Silica
Alumina
Chemical A 0.1 M + Abrasive Particle 2 wt% pH adjustor : HCl, NH4OH
pH
Rem
oval
Rat
e (n
m/m
in)
fumed Silica Slurry
0
10
20
30
40
50
60
0
20
40
60
80
100
120
140
160
180Chemical A 0.1 M + fumed Silica 2 wt% pH adjustor : HCl, NH4OH
Rem
oval
Rat
e (n
m/m
in)
Ru TEOS
Selectivity
109864
pH
Selectivity
Selectivity
Alumina Slurry- At pH 8 ~ 9 : High Selectivity (Ru : TEOS = 22 : 1)
Fumed Silica Slurry- At pH 6 ~ 8 : High Selectivity (Ru : TEOS = 22 : 1)
0
10
20
30
40
50
60
0
20
40
60
80
100
120
140
160
180Chemical A 0.1 M + Alumina 2 wt% pH adjustor : HCl, NH4OH
Rem
oval
Rat
e (n
m/m
in)
Ru TEOS
Selectivity
109864
pH
Selectivity
Alumina Slurry fumed Silica Slurry
※ Low pH (4 ~ 7)
Removal Mechanism of Ru
- The Formation of Soluble RuO4
- High Chemical Removal by the dissolution of Soluble RuO4
- Mechanical Removal of RuO4 by Abrasive Particle and Pad
Chemical Removal >> Mechanical Removal
Ru
Pad
Ru oxide (soluble RuO4)
Abrasive Particle
Dissolved Ru Oxide
※ High pH (7 ~ 10)
Removal Mechanism of Ru
- The Formation of thin Insoluble RuO2·2H2O- Low Chemical Removal due to the Insoluble RuO2·2H2O- Mechanical Removal of RuO4 by Abrasive Particle and Pad
Chemical Removal << Mechanical Removal
Ru
Pad
Ru oxide (insoluble H2RuO5)
Abrasive Particle
Dissolved Ru Oxide
Reference Ru Patterned wafer
38 nm
RuTEOSReference Ru Patterned Wafer
- Thickness of deposited Ru layer wasabout 38 nm.
- The each capacitor was connectedby deposited Ru layer.
X 30K
X 100K, Tiling : 60°
Slurry : Chemical A 0.1 M + Alumina 2 wt% (pH 4) CMP time : 1 min
Ru
TEOS
X 30K X 100K
X 100K, Tiling : 60°
In the case of slurry at pH 4- Each capacitor was isolated after CMP.
- Ru over etching was generated due to
high etch rate of Ru.
Ruover etching
Slurry : Chemical A 0.1 M + Alumina 2 wt% (pH 6)CMP time : 1 min
RuTEOS
Ruover etching
In the case of slurry at pH 6- Each capacitor was isolated after CMP.
- Ru over etching was become seriously.
X 30K X 100K
X 100K, Tiling : 60°
Slurry : Chemical A 0.1 M + Alumina 2 wt% (pH 9)CMP time : 1 min
RuTEOS
In the case of slurry at pH 9- Ru over etching was prevented
due to low etch rate of Ru.- The plarnarity and isolation of each
capacitor were acquired successfully after CMP.
X 30K X 100K
X 100K, Tiling : 60°
We successfully developed Ru CMP slurry at alkaline pH.
Optimized Slurry- Chemical A 0.1 M, Alumina 2 wt%, pH 9- Removal Rate
Ru : 70 nm/min, SiO2 : 3.2 nm/min- Selectivity
Ru : SiO2 ( 22 : 1 )
The Mechanism of Ru CMP can be explained.- In slurry at pH 4 ~ 7,
Chemical effect is dominant on Ru CMPdue to the dissolution of soluble RuO4.
- In slurry at pH 8 ~ 10,Mechanical effect is dominant on Ru CMP
due to the formation of insoluble RuO2·2H2O.
Summary
Acknowledgments
Lab of Excellence in the Ministry of Education and Human
Resources Development (MOE), the Ministry of Commerce,
Industry and Energy (MOCIE) , and the Ministry of Labor
(MOLAB)
Post BK21 program
Hynix Semiconductor