Practical Considerations and Solutions for Temperature ... · BCTM '07. IEEE , 2007, pp. 26-29....

Practical Considerations and Solutions for Temperature-Dependent S-Parameter Measurement for Accurate Parameter Extraction of Advanced RF DevicesAdvanced RF Devices

Gavin Fisher, Application Engineer

Andrej Rumiantsev, Product Marketing Manager

Agenda

� Why on-wafer thermal?

� Investigation background

� RF characterisation systems

� Mechanical effects of temperature transition – probe

and chuck growthand chuck growth

� Measured electrical effect of thermal transition

� Suggested practical calibration approach with real life

data

� Effect of load resistance variation

� How to use WinCal XE to calibrate, de-embed and

measurement data

� Conclusion

Why On-Wafer Over-Temperature Test?

� Devices are increasingly temperature dependent

� RF device characterization and modeling need

S-parameters at several temperature and bias points

� Multiple temps between -40 and 125°C common

� ITRS predicts further extension of the temperature range

"Radio frequency and analog/mixed-signal technologies for wireless communications," International Technology Roadmap for Semiconductors, ITRS, p.

36, 2011.

Example of FoM: fT(T) and fMAX(T)

P. Chevalier, N. Zerounian, B. Barbalat, et al., "On the use of cryogenic measurements to investigate the potential of Si/SiGe:C HBTs for terahertz

operation," in Bipolar/BiCMOS Circuits and Technology Meeting, 2007. BCTM '07. IEEE, 2007, pp. 26-29.

Motivation: Three Contradictions

� Temperature variation typically requires re-calibration at

every temperature

� Calibration standards are temperature dependent

– Calibration kit (ISS) must be treated appropriately*

� Continuously increasing demand for higher

New challenges hard to deal with

� Continuously increasing demand for higher

characterization frequencies (e.g. mmW range) and

measurement accuracy

A. Rumiantsev and R. Doerner, “Verification of wafer-level calibration accuracy at high temperatures ” in ARFTG Microwave Measurements

Conference-Spring, 71st, 2008, pp. 103-106.

"High-frequency, over-temperature measurements and modeling," in Application Note Beaverton, OR, USA: Cascade Microtech, Inc.

Agenda



� RF thermal test issues





data



measurement data

� Conclusion

Intention of Investigation

� Re-visit application note of with modern equipment

and wider measurement range

Calibration / Measurement Issues and Solutions

Problem Solution

RF Standards temperature dependency

Maintain ambient or measure load resistance*)

Probes misplacement w.r.tstandards on transition

Re-adjuststandards on transition

Probe characteristics vary during the calibration process

Calibration duration to be kept as short as possible.

When is the system stable Use of WinCal stability measurements – automated reports possible

*) A. Rumiantsev, G. Fisher, R. Doerner. “Sensitivity Analysis of Wafer-Level over Temperature RF Calibration”, to be presented ARFTG-80th

Agenda








data



measurement data

� Conclusion

Typical on Wafer Test System - Open

Typical on Wafer Test System - Closed

� PNA-X vector network

analyzer from Agilent

� Probe positioners

� Probe station with -60°C

to 300°C thermal systemto 300°C thermal system

� Calibration software

� SMU

� eVue digital vision system

� In a temperature

controlled lab

Engineering on Wafer Test System....

Typical on Wafer Test System

� 110 GHz Infinity probes

� 104-783 W Band ISS

� 1 mm 24 cm Cables

� Anti-moding absorber

13

� Torque wrench

Typical on Wafer Test System

� Dry, frost-free environment

� Auxiliary chucks

� Roll-out chuck

� Stable repeatable platen

� TopHat™

14

Agenda



� RF thermal test issues





data



measurement data

� Conclusion

Mechanical Effects of Growth

� Probes grow / retract with temperature chuck in Z

and for E/W orientation in X

� Some movement in Y but comparatively minimal

� For significant thermal changes evaluate theta also


� Initial contact set to 19370 at ambient

� Initial separation 474 um


� Position of probes not varied on positioner

� Chuck temperature -40°C


� Probe contact remade by adjusting chuck position only

� Probes marks are now 550 um apart 76 um delta

� Chuck needs to be raised 37 um higher

Temperature / Electrical Evaluation Work

� Probe equipped with

K thermocouples

and data logger

� Sensors attached to

probe body,

connector and mountconnector and mount

System Stability

� Instrumentation itself must be stable

� Use math / memory at selected IF bandwidth

� Temperature control essential

� For Agilent PNA-X “Error-corrected range 23°C ±3°C

with less than 1°C deviation from calibration”with less than 1°C deviation from calibration”

� Thermal system transitioning can effect room

temperature

System Stability

� System stability can also be measured by conducting a

cal and using a the WinCal monitoring function or by

sequentially conducting open re-measurements

� Example below takes a monitoring measurement every

5 minutes

System Stability Controlled 27°C

� System was stable for 1 hour at 27 degrees

Agenda








data



measurement data

� Conclusion

Measured Electrical Effect of Thermal Transition

� Following calibration another method used WinCal

sequencing can be used to take repetitive

measurements in normal measurement window

� Of primary interest is to be able to see end of change

to determine if the system is stable

Measured Electrical Effect of Thermal Transition -40°C to -20°C


� WinCal is also capable of showing differences from a

particular trace – Similar to monitoring measurements

Measured Electrical Effect of Thermal Transition -40°C to -20°C


5

6

7

8

%

Difference in S11 at 95 GHz with TimeDuring -40°C to -20°C Transition, %

0

1

2

3

4

5

0 10 20 30 40 50 60

%

Time (Minutes)

Difference in S11 at 95 GHz

Measured Electrical Effect of Thermal Transition -40°C to 25°C

Temperature Variation S11 with Chuck / Probe -40°C to 25°C

AR2

AR2 It will be nice if you could make a better graph out of here: font size 24pt, better readable... Andrej Rumiantsev, 10/24/2012

Transition +27°C to +75°C S11 Variation

Transition +27°C to +75°C S11 Variation

AR3

Variation in Phase +25°C to +75°C S11, Degrees

Phase Change +27°C to +75°C Transition

AR4

Variation in ISS Temperature

AR5

Variation in ISS Temperature

AR6

Temperature Variation of Probe Body / Mount

27 °C

Calibrations

-40 °C

-20 °C

0 °C

jn1

jn1 Andrej Rumiantsev 24-Oct-12It will be nice if you could make a better graph out of here: font size 24pt, better readable... jnakaya, 10/31/2012

Thermal transient – 40°C Calibration

� Calibration duration approximately 2 min,

32 frequency points, 100 Hz IF bandwidth

Agenda








data



measurement data

� Conclusion

Over-Temperature Calibration Approach

Device Measurement Procedure

� Reduced set of -40,-20,0,27,75,125°C measurements

� Instrument set up for speed

– 100 Hz IF (20 or lower preferred)

– 32 points segmented– 32 points segmented

� Biasing done manually for single device 0.85 Vb and 1

Vc for all temp points (peak fmax). Automation possible

with sequencing

� LRRM calibration was used


� Devices measure cold and biased

� Open and Short de-embedding

structures measured for all

temperatures

� Measurements done in raw and � Measurements done in raw and

corrected

� Raw measurements allow post

calibration manipulation with

different calibration sets

Probe Adjustment

� Load - Probe geometry

adjusted for each temp point

� ISS pre-aligned before

adjustment

� Best results

– Probes at temperature– Probes at temperature

– Move to ISS and adjust

– Move back to wafer until

stable once again

– Full-auto cal at ISS

– Time delay can be

frustrating...


� Make sure LRRM is set to calculate Load inductance at

110 GHz

WinCal Speed Improvements

� Repeatability and Validation tests turned off

� Validation can be carried out over wafer using “post-correct reflect” – no measurement required

� Monitoring was left off but this could be done as soon as probes over wafer or correct Raw cal open

Multi-Temperature Calibration Validation

� All calibrations were valid

� Use view data items and drag renamed % to new report

Dealing with Probe Movement

� Probe movement during the cal can effect thru delay

If open validation fails thru delay can be adjusted

Failed Monitoring after DUT Measurements (125°C)

� Likely calibration was just too slow

� Calibration period less that 1:30 a must

Good Monitoring before and after DUT Measurement (75°C)

� If only measuring 1 device monitor after DUT measurement

Technique to Reduce Drift Effects

� Calibrate at higher than required temperature to suit

expected temperature drop

� Re-monitor at desired temperature set point

� Simulated here - chuck temp was at 113°C for 125°C

calibration

Actual device Masons Gain Measurements –Correct Calibration

Actual Device Masons Gain Measurements –Ambient Calibration Applied to Raw Data

Actual Device data – Effect of Different Calibration Applied to the Same Data

Using WinCal to View Differences in Measurements with the Same Calibration

Using WinCal to Compute

Using Wincal to Compute Differences in Measurements from the Same Calibrations

Calibration Error Bound Variation

Agenda








data



measurement data

� Conclusion

Effect of Load Resistance Variation

� 27 calibrations loaded

� Error terms compared by varying load resistance by 1%

� At 125°C load measured 50.75 Ώ using 4156

Variation in Error Bounds with RL Variation for 1% and 2% Load Variation

A Different Approach – Load at DUT Temp

� Assumes that worst variation is load resistance

� Currently the subject of ARFTG paper development

“Sensitivity Analysis of Wafer-Level over Temperature RF

Calibration" to be submitted to 80th ARFTG

� Load resistance measured using parametric instrument� Load resistance measured using parametric instrument

A Different Approach – Load at DUT Temp

� Temperature still changes – Absorber raised ISS from

chuck

� Further experiments to evaluate this approach required

Agenda








data



measurement data

� Conclusion

Use of WinCal for PPR and Parameter Extract

� Measurements of DUT various, Open pads and Short

pads to be in same Report

� WinCal can perform PPR on the fly for all DUT

measurements if required

Use of WinCal for PPR and Parameter Extract

� Preferred is to use Math ScratchPad to product

individual data items – useful for swapping with other

reports

Agenda








data



measurement data

� Conclusion

Conclusion

� Accuracy of on-wafer over-temperature RF

measurements up to 110 GHz can be improved

� High-speed calibration with monitoring after

stabilisation is the recommended method

� Different calibration required per temperature� Different calibration required per temperature

� Reduce instrument IF bandwidth to highest tolerable,

use low number of points

� WinCal repeatability / verification is not needed

during calibration process over ISS

� WinCal greatly aids the calibration process

Any Questions?

Thank you for attending.

For questions, please contact:

Gavin Fisher, Application EngineerGavin Fisher, Application Engineer

[email protected]

+44-121-2860170

Practical Considerations and Solutions for Temperature ... · BCTM '07. IEEE , 2007, pp. 26-29....

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