Transcript Initial stage of Cu electroplating

Potential (VSCE)
Polarization curve for copper Without
deposition
Suppressor
Suppressor
0.0
10mA/cm
2
-0.1
0.04
-0.3
Leveling influence on copper
0
100 200 300 400 500
deposition
fromTime
low(sec)
acid electrolyte
without additives
0.0
10mA/cm
2
0.5 ml/l
-0.1
1.5 ml/l
-0.2
100
200
Time (sec)
Potential (VSCE)
-0.04
The combined action of the all three additives are
provided inhibition of the Cu deposition reaction relative
to additive free electrolyte, although an acceleration of the
Cu deposition relative to the suppressor and
suppressor&leveler additives electrolytes.
0.5 ml/l
-0.08
0
100
200
Time (sec)
300
Detectable Defects:
•
•
•
Single pit
Missing via
Localized protrusion defects (LPDs)
Main electrochemical causes of defects :
•
•
•
•
1 min
Swirl defects
Pits clusters
Embedded defects
Poor wetting of seed layer at the electroplating start
Particles trapped in trenches and vias (sludge)
Sporadic, localized growth due to organic additives
Defects detectible under direct, e.g. visual, optic and SEM
examination
embedded sludge
Blanket
M1
V1
localized area w/ missing Cu
200
400
600
Time (sec)
1 mA/cm
2
2
-0.15
4
-0.20
10 mA/cm
2
800
17 g/l Cu electrolyte with additives
0
200
400
600
V1 seed layer
Time (sec)
1000
Accelerator
0
0.5
1
2.3
Voltage/time curves are presented more polarized values of
voltages at initiation of Cu deposition for M1 and V1 patterned
wafers
in electrolyte with additives than in electrolyte without
( ml/l)
additives. This increase in cathodic potential is provided by
suppression of Cu deposition by additives. After several seconds
the cathodic potential is decreased and depolarization effect
occurred over a longer period of time . This effect is increased
with metal lines density and disappeared with increasing of current
density.
Filling features in additives containing Cu
electrolytes
Large molecules of suppressor
adsorbs preferentially on the
outside of trenches &vias and
inhibits of Cu electrodeposition.
Accelerator accumulated inside
of trench and vias of smaller
features and accelerated the
deposition reaction at the
bottom of trenches and vias.
0.0
Accel
-0.1
-0.2
Supp
-5
Accelerator
Cu2+
2eCu seed
-4
-3
10
10
2
Current (A/cm )
Suppressor
2 min
• Hidden defect: voids
-0.05
2
V1
1 mA/cm
-0.10
2
2
-0.15
4
-0.20
2
10 mA/cm
-0.25
0
200
400
Time (sec)
1mA/cm
2
2mA/cm
2
4mA/cm
2
10mA/cm
600
Polarization curve for copper deposition
+2
from 17 g/l Cu electrolyte with suppessor
D
B
###
###
Conclusions:
• The effects of pattern density (M1 and V1) and
additives on the electrochemical characteristics
of Cu
plating in high- and low-acidic electrolytes
without additives
8 ml/ldetermined
Suppressor
were
1 mV/sec
10
Patterned wafer specimen with M1 and F1 seed layer
after copper electrodeposition from low acid
electrolyte by current density 10mA/cm2 ,deposition
time 1 ,2 minutes.
-0.10
-0.25
Voltage/time curves in galvanostatic mode are shown the small
shift in potential in the first few second of Cu electrodeposition onto
blanket and patterned wafers from additives free electrolyte. These
potential changes likely relate to initial nucleation and surface
morphology changes.
300
Without Accelerator
+2
0.02
0
1.0 ml/l
-0.06
-2
2
10mA/cm
2.3 ml/l
-3
10
10
2
Current (A/cm )
+2
2
Accelerator
1 min
Blanket
V1
M1
The effect of current density on Cu
17 g/l Cu electrolyte
additives
deposition characteristics
inwith
electrolyte
1
M1 seed layer
with additives
M1
Leveler (ml/l)
0
0.5
1
1.5
1.0 ml/l
0
2 mA/cm
0.00
Without Leveler
10
Electrolyte 2 & 10 mA/cm2
-0.2
-0.05
Suppressor:
2 ml
4 ml
6 ml
8 ml
-0.2
-2
SEM micrographs filled trenches and
squares (face view )
-0.1
-0.4
Electrolyte 1 without additives
B
B
B
B
B
from 17 g/l Cu electrolyte with suppessor
Potential (V SCE)
10
10
2
Current (A/cm )
1 mV/s
-0.3
The effect of pattern density on Cu
Influence of suppersordeposition
on copper
characteristics
deposition from low acid electrolyte.
+2
B
D
F
H
-2
0.0
Potential (V SCE)
Electrolyte 2 &Blanket
-3
10
10
2
Current (A/cm )
0.1
Potential (VSCE)
10
-0.3
-4
-0.3
-3
Blanket
V1
M1
10
Potential (VSCE)
The effect of additives
-0.2
-4
-0.2
-4
Supp
-5
V1
-0.1
10
Leveler
Supp+Lev
0.0
M1 and V1 wafers were presented by different
pattern density and aspect ration.
8 ml/l Suppressor
-0.1
1 mV/s
-0.4
Surface Examination: SEM, HRSEM, EDS
without
additives
Supp+Lev+Acc
M1
Electrolyte 1
Techniques & Methods:
Electrochemical Tests:
Potentiostatic measurements;
Galvanostatic measurements.
1 mV/sec
Potential (VSCE)
g/L
g/L
ppm
ml/L
ml/L
ml/L
0.1
The study of electrochemical characteristics of copper
deposition was performed in 3-electrode electrochemical
cell equipped with Pt counter electrode and saturated
calomel reference electrode:
Blanket wafer
0.0
Electrolyte 2
Copper
40 g/L
Sulfuric acid
10 g/L
Chloride
50 ppm
Accelerator
2.3 ml/L
Suppressor
8 ml/L
Leveler
1.5 ml/L
Current-Voltage characteristic of Cu
deposition from additives free electrolytes
Potential (VSCE)
Electrolyte 1
Copper
17
Sulfuric acid
180
Chloride
50
Accelerator
2.3
Suppressor
8
Leveler
1.5
Three types of Cu seeded wafers supplied by
Tower/Motorolla were used as substrate:
• Blanket wafer
• Trench pattern (M1 step)
• Via pattern (V1 step)
Potential (V SCE)
The effect of additives on currentvoltage profile of Cu in high acidic
electrolyte.
Two types of acid copper electrolytes were examined:
1- low copper content & high acidity (pH 0.7)
2- high copper content & low acidity (pH 1.9)
Potential (V S.C.E.)
Introduction.
The successful implementation of copper electroplating
in the metallization of chip interconnect structures
derives from the use the electrolyte additives to affect
the local deposition rate. The additives compounds
added in copper plating solution to improve deposit
properties are consumed on wafer surface and
suppress the kinetics of Cu deposition.
Since interior location of trenches and vias are less
accessible to any additives, less suppression of the
reaction kinetics occurs there, causing higher
deposition rates and supperfilling of trenches and
vias .
Objectives of initial stage of copper electroplating
study were:
•Evaluation of copper electroplating features in
commercial electrolytes used within electroplating
process
•Estimation of the effect of wafer density patterning
(M1 and V1) on the electrochemical characteristics of
copper electrodeposition.
•Determination of the effect of additives additions
(accelerator, suppressor and leveler) on electroplating
parameters
-2
10
• Current-voltage working windows for Cu-plating
were defined. The current range of up to 10
mA/cm2 was established to be safe. The copper
surface potential in this range remains above 0.28 V (SCE) , i.e. voids formation due to
hydrogen evolution is avoided
• It is possible to accurately control features’ filling
in the current range established