the 4pp: obsolete or timeless - american vacuum society...1997 tencor merges with kla kla management...
TRANSCRIPT
-
The 4PP: Obsolete or Timeless
Walt Johnson
KLA-Tencor
-
7/18/20092
Short History of the 4PP
1978 Tencor introduces the M-gage
• Replaced my +/- 10% Veeco 4PP with an M-Gage (4PP obsolete?)
1983 Prometrix Introduces dual configuration +/-1%
• Bought an OmniMap
1985 Prometrix reviews future
• Management decides 4PP has 2 yrs life
1994 Prometrix merges with Tencor
Tencor management drops M-Gage, decides 4PP has 2 more yrs
1997 Tencor merges with KLA
KLA management decides the 4PP has 2 more years
-
7/18/20093
The Status of the 4PP
So where do we stand today?
-
7/18/20094
Markets addressed by the 4PP
Metals
Metal sheet resistance
Metal thickness assuming a given resistivity
Metal resistivity assuming a given thickness
Ion Implant
Dose monitoring (post anneal assuming a given anneal level)
Ion activation (post anneal assuming a given dose level)
-
7/18/20095
NCRs (eddy current) Replaces 4PP for metals(at least for thick metals on high resistance substrates)
Pre and Post Polish Diameter Scans With RS300 4PP and RS300 NCRs
10,000
11,000
12,000
13,000
14,000
15,000
16,000
17,000
18,000
1 9 17 25 33 41 49
Position across wafer (L-R)
Co
pp
er
Fil T
hic
kn
ess (
Å)
Rs200 4PP 1585B PRE Rs200 E.C. 1585B PRE
Rs200 4PP 1585B PST Rs200 E.C. 1585B PST
Pre-Polish
Post-Polish
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7/18/20096
Copper Removal Correlation
Overall correlation between
4PP and NCRs (on multiple
wafer sets)
y = 0.9874x
R2 = 0.9987
-2000
0
2000
4000
6000
8000
10000
12000
14000
0 5000 10000 15000
4PP Removal Rate(A)
NC
Rs
Re
mo
va
l R
ate
(A)
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7/18/20097
New Eddy Current Probe Development (Patent pending)
The direction of eddy current by current probe is parallel to film surface and less sensitive to via sidewall coverage
The direction of eddy current by new probe is perpendicular to film surface which should have better sensitivity
Standard
EC probeNew EC
probe
TSV
Eddy
current
Metal film
Metal film
Eddy
current
Coil Coil
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7/18/20098
Eddy Current Signal on Unfilled & Filled Via
Filled and unfilled via shall show difference in eddy current signal
TSV
Eddy
current
Metal film
Unfilled TSV Filled TSV
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7/18/20099
3.83E-02
3.85E-02
3.87E-02
3.89E-02
3.91E-02
3.93E-02
3.95E-02
3.97E-02
-150 -100 -50 0 50 100 150
Y (mm)
Rs
(o
hm
/sq
)
Slot1
Slot2
Y-direction Diameter Scan (in arrow direction)
Peak area correlates to via coverage
Repeated via peaks super-imposed on the global Rs non-uniform distribution
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7/18/200910
Rs Peak Area Calculation Algorithm
Rs peak area correlates to via coverage
0.0388
0.0389
0.0390
0.0391
0.0392
0.0393
0.0394
0.0395
-50 -40 -30 -20 -10 0 10 20 30 40 50
Radius (mm)
Rs (
oh
m/s
q)
Rs
Baseline
0.00000
0.00002
0.00004
0.00006
0.00008
0.00010
0.00012
0.00014
0.00016
0.00018
0.00020
-50 -40 -30 -20 -10 0 10 20 30 40 50
Radius (mm)
Delt
a R
s (
oh
m/s
q)
Original
Rs
Eliminate
Baseline
Curve
Calculate
Peak Area
Area
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7/18/200911
Hi Density Rs Measurement in Die (Slot 4)
0.0
15
0.0
16
0.0
17
0.0
18
0.0
19
0.0
2
0.0
21
0.0
22
0.0
23
0.0
24
-10
01
02
03
04
05
06
0Y
(m
m)
Rs (ohms/sq)
Depending on
if Rs variations
are of interest,
recipe set up
will need to be
used to either
measure
those areas or
avoid them.
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7/18/200912
Improved USJ Measurements with Hx probes
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7/18/200913
Activation Development & Control
Conventional Four-Point Probe results on 0.5 keV Boron USJ
0
500
1000
1500
2000
2500
0˚C 1300˚C 1350˚C
Laser anneal Temperature
Sh
eet
resis
tan
ce (
Oh
m/s
q.)
850 Spike
950 Spike
1000 Spike
1020 Spike
1040 Spike
1050 Spike
Laser anneal improving activation
and lowering Rs.
(Junction depth not changed due to laser.)
4PP provides sensitivity for process
development & monitoring to detect small
temperature fluctuations
No
activation
increase
Increased
activation
& junction
depth
Customer “A” data
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7/18/200914
Discovering Annealer Problems on a 0.5 keV B+ implant
High variations toward upper left edge of wafer 14 points in area show measurement error or data outside sigma filter
Center ring possibly due to thermocouple from annealer
Three higher Rs regions around center possibly due to pedestal in annealer
Excellent matching between probe heads, and results repeatability
Probe head 2 Probe head 3Probe head 1
Customer “C” data
Yield-limiting detail analysis of Anneal process equipment
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7/18/200915
Long-Term Repeatability
BF2 1.5E14, 8
KEV
25 repeats
BF2 1E14, 5
KEV
25 repeats
As 1E14, 5 KEV
25 repeats
As 1E14, 3
KEV
25 repeats
Mean 1451 2508 1252 1613
% Stdev 0.16% 0.21% 0.14% 0.12%
Repeatability on BF2 and Arsenic
USJ implant maps is excellent
Customer “C” data
Repeatability of Contour Map Results:
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7/18/200916
Alternate Implant Monitoring Techniques
IonScan
Metrix e-beam
TW
SemiLab / FSM / Quantox (KLA-Tencor)
Microwave ?
-
7/18/200917
TP to Rs Comparison
Another example of laser anneal optimization with TP including comparison with Rs
-
7/18/200918
Junction Leakage Limits 4PP Usage
Hx Four-point Probe Data
0
1000
2000
3000
4000
5000
6000
14 15 16 17 18 19 20 21 22 23 24 25
Slot #
Sh
eet
Resis
tan
ce (
Oh
m/s
q.)
1175C
1225C
1275C
1325C
1E15 B, 100 eV 1E15 BF2, 500 eV
No PAI No PAI
Ge PAI
Xe PAI
Ge PAI
Xe PAI
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7/18/200919
SPV, JPV or LPV
Correlation of RsL & QTX Lifetime
0.70
0.90
1.10
1.30
1.50
1.70
1.90
2.10
2.30
55.00 56.00 57.00 58.00 59.00 60.00 61.00 62.00 63.00 64.00
Lifetime (uS)
Rs
L L
ea
ka
ge
Quantox SPV Decay
0
0.1
0.2
0.3
0.4
0.5
0.6
1.00E-04 1.00E-03 1.00E-02
Time (s)
Vs(V
)
Wafer 3
Wafer 2
Wafer 1
-
7/18/200920
4PP Method
The 4PP leakage through substrate can be modeled by following
equivalent circuit
When Ileakage
-
7/18/200921
4PP Method (for leakage)
Measured Rs is a function of applied current for a fixed diode leakage density
-
7/18/200922
Increased Leakage below 1275˚ Anneal
Slot 20
0.995
0.996
0.997
0.998
0.999
1
1.001
1.002
1.003
1.004
1.005
0 50 100 150 200 250
MicroAmps
Re
lati
ve
Sh
ee
r R
es
ista
nc
e
1175°C
1225°C
1275°C
1325°C
-
7/18/200923
Current Ramp Comparison to SPV
Correlation of RsL & QTX Lifetime
0.70
0.90
1.10
1.30
1.50
1.70
1.90
2.10
2.30
55.00 56.00 57.00 58.00 59.00 60.00 61.00 62.00 63.00 64.00
Lifetime (uS)
Rs
L L
ea
ka
ge
Correlation of Rs slope & Lifetime
-1.E-03
-8.E-04
-6.E-04
-4.E-04
-2.E-04
0.E+00
55.00 56.00 57.00 58.00 59.00 60.00 61.00 62.00 63.00 64.00
Lifetime (uS)
Slo
pe o
f R
s (
1u
A-5
00u
A)
Quantox SPV Decay
0
0.1
0.2
0.3
0.4
0.5
0.6
1.00E-04 1.00E-03 1.00E-02
Time (s)
Vs(V
)
Wafer 3
Wafer 2
Wafer 1
-
7/18/200924
Present Status of the 4PP
New (and older) technologies eddy current, TW, SPV etc. adding information on traditional 4PP
applications
BUT!!!
4PP
Still not ready to give up