Gavin Fisher Cascade Microtech - Keysight€¦ · Cascade Microtech Wafer-Level S ... (different...
Transcript of Gavin Fisher Cascade Microtech - Keysight€¦ · Cascade Microtech Wafer-Level S ... (different...
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Wafer-Level S-Parameter Calibration Techniques
S-Parameter Calibration of Two-Port Setup: How to choose the optimal calibration method?
Gavin Fisher
Cascade Microtech
Wafer-Level S-Parameter Calibration Techniques
Content
Error Modeling of a two-port setup
Calibration methods
– SOLT
Self-calibration routine:
– SOLR
– LRM/LRM+
– LRRM
Conclusion
•Slide 2
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Wafer-Level S-Parameter Calibration Techniques
Error Modeling of a Two Port Setup
Influencing Factors:
– VNA architecture
– Crosstalk between ports
Commonly used models:
– 10(12) Terms
– 7(8) Terms
– 15(16) Terms
•Slide 3
Wafer-Level S-Parameter Calibration Techniques
Reference Channel VNA
N=n+1 receivers
10(12)-term error model
•Slide 4
where :
N - number of receivers
n - number of ports
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Wafer-Level S-Parameter Calibration Techniques
Double Reflectometer VNA
N=2n receivers
7(8)-term or 10-term (converted) model
•Slide 5
where :
N - number of receivers
n - number of ports
Wafer-Level S-Parameter Calibration Techniques
10-Term Model
Reflection terms:
– Directivity, ED
– Source match, ES
– Reflection tracking, ER
•Slide 6
Transmission terms:- Transmission tracking, ET
- Load match, EL
- Crosstalk, EX
Forward direction:
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Wafer-Level S-Parameter Calibration Techniques
SOL Calibration
Reflection measurements:
•Slide 7
( )R
ED
EM
SS
E
DE
MS
AS
+−
−=
11
1111
( ) I
MRSD
I
AR
I
M
I
ADSEEESESSE
11111111=−−+
( ) II
MRSD
II
AR
II
M
II
ADSEEESESSE
11111111=−−+
( ) III
MRSD
III
AR
III
M
III
ADSEEESESSE
11111111=−−+
1:
2:
3:
• Three independent measurement conditions:
• Commonly used standards: - Short, Open, Load (SOL)
Wafer-Level S-Parameter Calibration Techniques
Experiment
Error Correction
•Slide 8
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Wafer-Level S-Parameter Calibration Techniques
Wincal / SOL demonstration
Objective:
– To show how calibration (and Wincal) works
Verification conditions
– Verification series: same standards
Experimental Conditions:
– Regular SOL calibration and measurement of standard
Observation:
– How to use Wincal to apply calibration and show use of Wincal processing raw data directly
•Slide 9
Wafer-Level S-Parameter Calibration Techniques
Wincal / SOL demonstration
In this example we will be using Wincal with
measured data to perform the measurement, but the
data has been measured previously
Screen shots are shown in case existing Wincal
users may want to use the same techniques for off
line processing of raw measurement
•Slide 10
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Wafer-Level S-Parameter Calibration Techniques
Wincal / SOL demonstration
Folder set-up is done in order for Wincal to find the raw data for process under calibration.
Note - MeasFiles folder used to store raw measurements
Files have Vmeas_ as start of file name to denote Wincal will process the raw measurement.
•Slide 11
Wafer-Level S-Parameter Calibration Techniques
Wincal / SOL demonstration
Wincal system set-up
restores default conditions of
instrument, probes, stimulus
etc
•Slide 12
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Wafer-Level S-Parameter Calibration Techniques
Wincal / SOL demonstration
Opening the calibration set-up allows the old
calibration state to be restored, including
measurements if present
•Slide 13
Wafer-Level S-Parameter Calibration Techniques
Wincal / SOL demonstration
With the cal loaded we can hit compute which calculates the error
terms as discussed. Normally we would send these to the instrument
•Slide 14
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Wafer-Level S-Parameter Calibration Techniques
Wincal / SOL demonstration
Hitting the measure button brings up a new blank report
We can store hundreds of individual measurements in a single report
•Slide 15
Wafer-Level S-Parameter Calibration Techniques
Wincal / SOL demonstration
From the report window we can open pre-saved
reports with preset viewing and processing options
•Slide 16
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Wafer-Level S-Parameter Calibration Techniques
Wincal / SOL demonstration
Wincal can either take a measurement from an instrument or use the
currently applied cal to correct a named raw measurement in the
measurement folder
•Slide 17
Wafer-Level S-Parameter Calibration Techniques
Wincal / SOL demonstration
Here we have S-parameter measurements of the SOL standards used
for the calibration and also an additional open standard which is on
wafer and has positive capacitance
•Slide 18
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Wafer-Level S-Parameter Calibration Techniques
Wincal / SOL errors
Objective:
– To show effect of standard misplacement and other errors
Verification conditions
– Verification series: same standards for cal
Experimental Conditions:
– Regular SOL calibration and measurement of standard
Observation:
– How SOL is only as good as the standards you measure
•Slide 19
Wafer-Level S-Parameter Calibration Techniques
Wincal / SOL errors
New calibration loaded
Same standards for cal re-measured (Short / Open iss)
Independent standard re-measured (Air open)
Spot the problem.....
•Slide 20
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Wafer-Level S-Parameter Calibration Techniques
SOL Calibration – Recap..
Reflection measurements:
•Slide 21
( )R
ED
EM
SS
E
DE
MS
AS
+−
−=
11
1111
( ) I
MRSD
I
AR
I
M
I
ADSEEESESSE
11111111=−−+
( ) II
MRSD
II
AR
II
M
II
ADSEEESESSE
11111111=−−+
( ) III
MRSD
III
AR
III
M
III
ADSEEESESSE
11111111=−−+
1:
2:
3:
• Three independent measurement conditions:
• Commonly used standards: - Short, Open, Load (SOL)
Wafer-Level S-Parameter Calibration Techniques
SOLT Calibration
10 unknowns have to be defined
– Step 1. SOL on Port 1 and 2:
•Slide 22
- Step 2. Connect two port together (“Thru”):
,D
E′ ,S
E′ ,R
E′R
E ′′,S
E ′′,D
E ′′and
( )RSDSM
DM
L
EEEES
ESE
′−′′−′
′−′=′
11
11 ( )LSMT
EESE ′′−=′ 121
,L
E ′′F
E ′′- From reverse direction:
prime, double-prime parameters correspond to the forward
and reverse measurement directions respectively.
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Wafer-Level S-Parameter Calibration Techniques
Calibration Standard Requirements
•Slide 23
THRU OPEN SHORT LOAD
Known:
S11, S21, S12, S22
Known:
S11 (S22)
Known:
S11 (S22)
Known:
S11** (S22)
Example:
THRU OPEN SHORT LOAD
Z0=50Ω
α=0, τ=0.5pS
R=inf
C=0.3fF
R=0
L=9pH
R=50
L=10.6pH
Wafer-Level S-Parameter Calibration Techniques
Experiment
SOLT
•Slide 24
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Wafer-Level S-Parameter Calibration Techniques
SOLT Experiment
Objective:
– To prove sensitivity to standard models
Verification conditions:
– Series of CPW different length
Experimental Conditions A:
– Define wrong OSL coefficients (different probe type/pitch)
Observation:
– Accuracy decreases with the frequency, RF “noise” on S21
Experimental Condition B:
– Define extracted data-file models for OSL standards
Observation
– SOLT is as good as you know your standards
•Slide 25
Wafer-Level S-Parameter Calibration Techniques
SOLT Experiment
Wincal settings loaded from file
Calibration settings loaded from file
Calibration populated with measurements and
calculated
Measurements of line standards carried out
•Slide 26
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Wafer-Level S-Parameter Calibration Techniques
SOLT Experiment
•Slide 27
Wafer-Level S-Parameter Calibration Techniques
SOLT Experiment
Looking at coefficients
•Slide 28
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Wafer-Level S-Parameter Calibration Techniques
SOLT Experiment
Open / Load standards look as they should
•Slide 29
Wafer-Level S-Parameter Calibration Techniques
SOLT Experiment
But Lines look terrible
•Slide 30
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Wafer-Level S-Parameter Calibration Techniques
SOLT Experiment
Load inductance now set to correct value
•Slide 31
Wafer-Level S-Parameter Calibration Techniques
SOLT Experiment
Comparison between same line different calibration
•Slide 32
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Wafer-Level S-Parameter Calibration Techniques
Content
Error Modeling of a two-port setup
Calibration methods
– SOLT
Self-calibration routine:
– SOLR
– LRM/LRM+
– LRRM
Conclusion
•Slide 33
Wafer-Level S-Parameter Calibration Techniques
Self Calibration
Requires double reflectometer VNA
Two error matrices [A] and [B] of [T] parameters
7 error terms are in use (normalized to A22)
More information is measured than required
This additional information allows some parameters to be calculated from
within the calibration routine
•Slide 34
=
−
''
4
'
4
''
3
'
3
1
2221
1211
2221
1211
2221
1211
''
2
'
2
''
1
'
1
mm
mm
BB
BB
TT
TT
AA
AA
mm
mm
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Wafer-Level S-Parameter Calibration Techniques
Self Calibration (cont.)
Measured matrix:
•Slide 35
1−= BATM
XX,
1
''
4
'
4
''
3
'
3
''
2
'
2
''
1
'
1
−
=
mm
mm
mm
mmM
• Three measurement conditions give [A] and [B]:
Standard Requirements Definitions
T1 Fully known 4
T2 Maximum of two free parameters 2
T3 Maximum of three free parameters 1
H. J. Eul and B. Schiek, "A generalized theory and new calibration procedures for network analyzer self-calibration," Microwave Theory and Techniques, IEEE Transactions on, vol. 39, pp. 724-731, 1991.
Wafer-Level S-Parameter Calibration Techniques
SOLR
Standards used:
– Reflection: Short, Open, Load
– Transmission: Reciprocal
•Slide 36
Standard Requirements Definitions
Short S11, S22 : known 2
Open S11, S22 : known 2
Load S11, S22 : known 2
Reciprocal unknown, S21=S12 1
A. Ferrero and U. Pisani, "Two-port network analyzer calibration using an unknown `thru'," Microwave and Guided Wave Letters, IEEE, vol. 2, pp. 505-507, 1992.
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Wafer-Level S-Parameter Calibration Techniques
Experiment
SOLR
•Slide 37
Wafer-Level S-Parameter Calibration Techniques
SOLR Experiment
Objective:
– To prove sensitivity to standard models
Verification conditions:
– Series of CPW different length
Experimental Conditions A:
– Define wrong OSL coefficients (different probe type/pitch)
Observation:
– Accuracy decrease with the frequency
Experimental Condition B:
– Define extracted data-file models for OSL standards
Observation
– SOLR is as good as you know your OSL standards
•Slide 38
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Wafer-Level S-Parameter Calibration Techniques
SOLR Experiment
SOLR line measurements using initial value for load
inductance
•Slide 39
Wafer-Level S-Parameter Calibration Techniques
SOLR Experiment
Calibration carried out again with correct probe
definitions. Correction applied to original data
•Slide 40
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Wafer-Level S-Parameter Calibration Techniques
Content
Error Modeling of a two-port setup
Calibration methods
– SOLT
Self-calibration routine:
– SOLR
– LRM/LRM+
– LRRM
Conclusion
•Slide 41
Wafer-Level S-Parameter Calibration Techniques
LRM and LRM+
Standards used:
– Transmission: Thru (Line)
– Reflection: Load (Match), Reflect
•Slide 42
Standard Requirements Definitions
Thru/Line Fully known 4
Load/Match S11, S22 : known 2
Reflect unknown, S11=S22 1
H. J. Eul and B. Schiek, "Thru-Match-Reflect: one result of a rigorous theory for de-embedding and network analyzer calibration," in European Microwave Conference, 18th, B. Schiek, Ed., 1988, pp. 909-914.
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Wafer-Level S-Parameter Calibration Techniques
LRM vs. LRM+
Differ in requirements for Load standard:
– LRM for coaxial applications
– LRM+ for on-wafer calibration
•Slide 43
Method Load R X
LRM Known R1=R2=50Ω 0
LRM+ Known R1, R2
Arbitrary
X1, X2
Arbitrary
R. F. Scholz, F. Korndorfer, B. Senapati, and A. Rumiantsev, "Advanced technique for broadband on-wafer RF device characterization," in ARFTG Microwave Measurements Conference-Spring, 63rd, 2004, pp. 83-90.
Wafer-Level S-Parameter Calibration Techniques
Experiment
LRM/LRM+
•Slide 44
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Wafer-Level S-Parameter Calibration Techniques
LRM/LRM+ Experiment 1
Objective:
– To prove sensitivity to the Load
Verification conditions:
– Open, Short, Load, CPW’s
Experimental Conditions A:
– Asymmetrical Load
Observation:
– Offset in reflection coefficient for high-reflective elements
•Slide 45
Wafer-Level S-Parameter Calibration Techniques
LRM/LRM+ Experiment 1
Calibration applied for LRM+ and measurements computed
LRM is calculated and the same raw data is computer with LRM
For both calibrations Reflect was short so open makes good validation structure
Loads were assymetric – RH was 49 ohms which LRM+ is set up for
•Slide 46
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Wafer-Level S-Parameter Calibration Techniques
LRM/LRM+ Experiment 1
LRM shows divergence in Port1 and Port 2 Open (not
used in cal) due to load inductance assymetry
•Slide 47
Wafer-Level S-Parameter Calibration Techniques
LRM/LRM+ Experiment 2
Objective:
– To prove sensitivity to the Load
Verification conditions:
– Open, Short, Load, CPW’s
Experimental Conditions A:
– Load as a resistor (50 Ohm)
Observation:
– Impact of Zref
•Slide 48
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Wafer-Level S-Parameter Calibration Techniques
LRRM
Standards used:
– Transmission: Thru (Line)
– Reflection: Reflect(Open), Reflect(Short), Load(Match)
•Slide 49
Standard Requirements Definitions
Thru/Line Fully known 4
Reflect (Open) unknown, S11=S22 1
Reflect(Short) unknown, S11=S22 1
Load(Match) S11 (or S22) known 1
A. Davidson, K. Jones, and E. Strid, "LRM and LRRM calibrations with automatic determination of load inductance," in ARFTG Microwave Measurements Conference-Fall, 36th, 1990, pp. 57-63.
Wafer-Level S-Parameter Calibration Techniques
LRRM(cont.)
Requirements to the Load standard
•Slide 50
Load Impedance R L
Inductance approximation
Z = R+jωL
Known Arbitrary,
unknown
• Unknown L can be found by the automated load inductance extraction algorithm
L. Hayden, "An enhanced Line-Reflect-Reflect-Match calibration," in ARFTG Microwave Measurements Conference-Spring, 67th, 2006, pp. 143-149.
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Wafer-Level S-Parameter Calibration Techniques
Experiment
LRRM
•Slide 51
Wafer-Level S-Parameter Calibration Techniques
LRRM Experiment 1
Objective:
– To show LRRM relative immunity to probe misplacement
Verification conditions:
– CPW’s
Experimental Conditions A:
Observation:
– Line measurements comparatively immune to probe misplacement
•Slide 52
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Wafer-Level S-Parameter Calibration Techniques
Probes in normal position
•Slide 53
Wafer-Level S-Parameter Calibration Techniques
Probes misplaced
•Slide 54
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Wafer-Level S-Parameter Calibration Techniques
LRRM Experiment 1
SOLT based calibrations show much more noise in
line measurement•Slide 55
Wafer-Level S-Parameter Calibration Techniques
Choosing Calibration Strategy
Understanding of strengths and limitations is essential!
Re-measuring of calibration standards ≠ verification!
•Slide 56
Method Application
SOLT • Well defined conditions
• Frequencies < 40GHz
SOLR • Rectangular configurations
• Double-side probing
LRM • Not recommended for wafer-level applications
LRM+ • Broadband on-wafer calibration
LRRM • Broadband ISS calibration