non-contact sheet resistance for determining polish ......superior repeatability: 0.3% ncrs vs. 4pp...
TRANSCRIPT
Non-contact Sheet Resistance for Determining Polish RatesDetermining Polish Rates
KLA-TencorWalter Johnson, HaiJing Peng
Outline
• Abstract
• Technology• Technology
• Typical Performance• Repeatability
• Effects of frequency change
• Use Case• ECP Copper monitors• ECP Copper monitors
• Polish Rate on monitors
• ECP Copper on pattern wafers
9/16/20102 confidential
Abstract
Wi h h l f i fWith the move to larger wafers, monitor wafers are getting more expensive. The introduction of non-contact Rs measurements to replace traditional contact Four point Probe measurements saves money throughFour-point Probe measurements saves money through measuring directly on pattern wafers. There are also advantages when determining, polishing rates with a non-contact method in that 4PP generated particles ornon contact method, in that 4PP generated particles or pits are avoided allowing the same wafer to be used for both particle inspection and thickness. Eliminating these particles or pits can also prevent their affect on p p psubsequent polishing steps.
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Non-contact Sheet Resistance (NCRs) capability for thick metal films
Technology : Technology : Conductive layer close to the coil modifies the
coil impedance
Benefits: Better repeatability performance on thick-metal layers with low resistivity (Cu)
Unaffected by surface oxidation Unaffected by surface oxidation
Superior Repeatability: 0.3% NCRs vs. 4PP at 0.5%
Product wafer capability – Rs measurement on complete Copper process (Barrier/seed, pre/post Cu CMP) No mechanical damage to the film or underlying structures
‘Real’ Rs for process monitoring of thick-metal layers
Reduces monitor wafer usage, low COO
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Correlation between 4PP and NCRs
4PP & EC correlation16
NC
y = 0.9954xR2 = 1
12
14
16
8
10
s (O
hm/s
q)4PP & EC correlation
y = 0.9986xR2 = 0.99990.25
0.34
6EC
Rs
Result Spec.Correlation R=0.9999 R>0.99
0.1
0.15
0.2
EC R
s (O
hm/s
q)
0
2
0 2 4 6 8 10 12 14 16
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0
0.05
0 0.05 0.1 0.15 0.2 0.25 0.34PP Rs (Ohm/sq)
4pp Rs (Ohm/sq)
Long Term NCRs Repeatability
10 Day Repeatability KT spec= 5 day <0.5%, Beta agreement 10 day < 0.5%
1.00
e
12.7 K Cu 12K Cu 11.5K Cu
9K Cu 3.5K Cu 1.5KCu
0.10
eet R
esis
tanc
e
0.01AM AM PM AM PM AM PM PM AM PM PM AM PM AM AM PM AM
She
AM AM PM AM PM AM PM PM AM PM PM AM PM AM AM PM AM
9/2 9/3 9/3 9/4 9/4 9/5 9/5 9/6 9/8 9/8 9/9 9/10 9/10 9/11 9/11 9/11 9/12Re pea t
NCRs 12 7 K Cu 12K Cu 11 5K Cu 9K Cu 3 5K Cu 1 5KCu
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NCRs 12.7 K Cu 12K Cu 11.5K Cu 9K Cu 3.5K Cu 1.5KCuRepeatability 0.23% 0.19% 0.18% 0.15% 0.21% 0.35%
10MHz Long Term Repeatability (2)10MHz Long Term Repeatability (2)
Total 11 wafers(200mm), Rs : 0.003~6/, different film thickness/ material
Test conditions: 49 sites/test, 5 tests/day, 6days
1 is calculated based on Rs of each individual site
1 of individual site
(R, )
ThicknessMaterial
R (/ )
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Rs(/ )
2MHz Dynamic RepeatabilityReduced 1 at extremely low Rs2MHz Dynamic RepeatabilityReduced 1 at extremely low Rs
Total 4 wafers(200mm), Rs : 0.003~0.02/, different film thickness/ material
Test conditions: 49 sites/test, 18 repeats, with load/unload
1 is calculated based on average Rs of each test
1 of 49 sites averageg
Reduced 1 by using low frequency
ThicknessMaterial
Rs(/ )
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Rs(/ )
Measurement Range
NCRs is complementary to 4PP measurement, towards extremely low sheet resistance
1
1.2
4PP
Material Ratio
Cu 1.00
10µm 1µm .1µm 10nm 1nm 1A .1ACu= 1.7µ.cm .01A
0 6
0.8
1
(%)
NC 10MHzNC 2MHz
Al 1.64
Mo 3.02
W 3.22
Pt 6 09
0.4
0.6
1Sig
ma Under developmentPt 6.09
Ta 7.60
Ti 24.8
TiSi2 9.30
0
0.2
0.001 0.01 0.1 1 10 100 1000 10000 100000
TiN 12.8
TaN 130
Ag 0.94
Ni 4 20
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Rs (Ohms/sq)Ni 4.20
Co 3.85
NCRs Edge Exclusion
Edge Exclusion (EE) Calculation:
EE = (Measured Gap - Physical Gap) / 2
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NC Probe used in EE test: SN37817, w/ shield
Cross Wafer Uniformity Pre & Post Polish
Pre and Post Polish Diameter Scans With RS300 4PP and RS300 NCRs
16,000
17,000
18,000
14,000
15,000
,
Fil T
hick
ness
(Å)
Rs200 4PP 1585B PRE Rs200 E.C. 1585B PRE
Rs200 4PP 1585B PST Rs200 E.C. 1585B PST
11 000
12,000
13,000
Cop
per
10,000
11,000
1 9 17 25 33 41 49
Position across wafer (L-R)
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Good correlation between 4PP and NCRs from the same tool
Copper Removal on 10 Wafers (EC vs 4PP)
Sequential Diameter Scans Across 10 Wafers (plotted on one chart)
Tool Comparison of Pre-Post Polish Measurement
12 000
14,000Wafer 1 Wafer 4Wafer 3 Wafer 5 Wafer 6 Wafer 7 Wafer 8 Wafer 9 Wafer Wafer 2
8,000
10,000
12,000
Rem
oval
(Å
Rs200 4PP Rs200 E.C.
2,000
4,000
6,000
Cu
R
01 51 101 151 201 251 301 351 401 451
Position across slots 1-12
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Removal Rate Correlation
Removal Rate correlation
y = 0.9805x + 8.7746R2 = 1.000010,000
12,000
14,000
Removal is in total thicknessWith units in
4 000
6,000
8,000
,
RS2
00 E
C
With units in Angstroms (Å)
0
2,000
4,000
0 2,000 4,000 6,000 8,000 10,000 12,000 14,000
RS200 4PP
P f t C l t l ti b t 4PP d NCR
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Perfect Cu removal rate correlation between 4PP and NCRs
18 Month Operation (without re-cal)
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NCRs Throughput
Throughput Tests
80
50
60
70
t
20
30
40
Thro
ughp
ut
0
10
20
0 10 20 30 40 50 60 70 80 90
Sites Spec Measured
5 40 59
Number of sites in pattern
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49 15 17
81 6 7
Particle TestsBaseline
Slot # 1 2 3 4 5 6 7 8 9 10 Original Defects 373 251 232 329 204 284 234 283 286 289Defects Added 54 42 53 70 66 70 89 57 24 149 AvgTested Wafers 54 53 66 89 24 57.2Control Wafers 42 70 70 57 149 59.75
Slot 10 (a control) was the top wafer and was removed from
the calculations
Average of -2 PWP indicate
the calculations
there is no particles added
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Pattern ECP Cu Demo Information
Demo purpose: Demonstrate the ability to measure sheet resistance of ECP pattern waferDemonstrate the ability to measure sheet resistance of ECP pattern wafer
with non-contact Eddy Current method on RS 300 platform, including: EC Rs correlation with Cu thickness
Dynamic repeatability without pattern recognition to show positioningDynamic repeatability without pattern recognition to show positioning accuracy and impact to measurement result
Wafers: ECP pattern wafer with ~ 1 µm electroplated Cu ECP pattern wafer with ~ 1 µm electroplated Cu
Diameter: 300 mm
Edge: ~2 mm edge clearance
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Pattern Structure
Step x: 18.36 mm
Step y: 14 17 mm Step y: 14.17 mm
Upper Left Corner: (-6 mm, 0 mm)
-6 0-6,0
14 17mm
18 36mm
14.17mm
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18.36mm
Small-Area Map
Map scan (2mm square) in a circular area of 80 mm diameter near the center
Scribe line
near the center Periodical RS pattern aligned with
dies and scribe line features Step X: 18 36 mm Step X: 18.36 mm
Step Y: 14.16 mm
View Notch
Scribe lineDie
View Notch
Die
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Diameter Scan Across Whole Wafer
3 Line scans with step size 400 µm, 1 for x direction and 2 for y direction X scan at Y = 0 (diameter scan across COW)
Y scan at X = 0 (diameter scan across COW)
Y scan at X = -6 mm (scribe line)
0 021
0.022
0.023
Ohm
/sq)
X Scan at Y=0
Y Scan at X=0
Y Scan at X=-6mm
0.019
0.02
0.021Rs
(O
0.017
0.0182.5mm film
edge exclusion2.5mm film
edge exclusion
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-150 -100 -50 0 50 100 150
X or Y (mm)
Diameter Scan Converted to Thickness
A typical copper resistivity of 1.85 µΩ-cm was used for this conversion. Lines scans at two X values are used for comparison.
1
1.05
0.95
1
ess(
um)
0.9Thic
kne
Y Scan at X=0
0.8
0.85Y Scan at X=-6mm
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-150 -100 -50 0 50 100 150X or Y (mm)
Overall Map
Dense map with 1209 sites (square array, up to R = 145.5 mm) Some internal feature of the dies visible
Overall non-uniformity of Rs
150
100
150
0
50
-150 -100 -50 0 50 100 150
(ohm
s/sq
)
-100
-50 Rs
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-150
Map at Scribe Line Crossing
Rs mapped at 262 scribe line crossing sites up to R = 145.9 mm No feature of die visible
Overall non-uniformity of Rs
X(mm) = -6.0 + column × 18.36
Y(mm) = +0 0 + row x 14 16
100
150Y(mm) = +0.0 + row x 14.16
0
50
-150 -100 -50 0 50 100 150 q)
-100
-50
Rs
(ohm
s/sq
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-150
Short Term Repeatability Map on Die Center
Dynamic repeatability shows current system is well below the standard Rs system spec of 0.5% 254 dies, 20 load/unload repeats
0.025 0.5%Rs Avg
Average Rs and 1 sigma based on each die
Each line representsEach point
0 021
0.023
q) 0 3%
0.4%
%)
Rs Avg
Stdev(%)
Each line represents a row of diesrepresents the
mean of 20 repeats
0.019
0.021
Rs(
Ohm
/sq
0.2%
0.3%
1 Si
gma(
%
0.015
0.017
-150 -100 -50 0 50 100 1500.0%
0.1%Each point represents 1 of 20 repeats
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150 100 50 0 50 100 150
Y(mm)
RS 300 (RS200 w/NCRs) is Complementary to 4PP
BENEFIT NCRs 4PP
Improved thick metal Rs measurement
No probing damage to films; inert to surface oxidation; better
repeatability
Performance subject to native surface oxide and probe metal
contamination
Blanket film on-product-wafer Rs measurement capability
Metal Rs capability on Cu ECP process. Measurement of
barrier/seed/Cu films on product wafer
Probing damage to patterned structures underneath metal films
wafer
No metal cross contamination Non-contact Residue metal on probe causes cross contamination
Lower CoO No consumables Probes are a consumable item
9/16/201025 confidentialSingle platform advantage Cover entire sheet resisitivity application space; on-tool calibration for
Eddy current; customers do not need to justify a stand-alone tool
Summary
Non-contact Rs (NCRs) or thickness shown for thick metal filmsfilms
NCRs can eliminate issues resulting from 4PP marks on monitors which could effect polishing, particle tests or p g preclaim
Huge cost savings
Product or pattern wafers can be used instead of monitor wafers in many cases (using die intersection values)
Potential valuable on-product information relating to over die or pattern values
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