smart devices - smart probe cards · 2017-03-26 · smart probe cards help to achieve higher...
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Smart sensors - Smart Probe CardsProbing sensor devices requires stimulation with
magnetic fields, infrared radiation or humidity
Dr. Rainer Gaggl, Georg FranzT.I.P.S. Messtechnik GmbH
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Overview
– Wafer level sensor test– Concept of smart probe cards– How to stimulate sensors (IR, humidity, magnetic)– Principal approaches– Choosing a technology– Design examples and performance data– Summary: Considerations for the test engineer
2G.Franz
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Smart sensorsApplication examples
– Automotive: magnetic angle sensor
– Automotive: contactless temperature sensor
– Industrial Automation:humidity sensor
3G.Franz
picture source: austriamicrosystems
picture source: Melexis
picture source:IST-AG.com
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Sensor testWafer level test
– electric and sensor test– standard probing– additional sensor excitation– fast multi-site capability
4G.Franz
D.U.T.
NS
MAGHUM
IR
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Smart probe cardsRequirements
– Standard Testing Platform– Automatic Probe Card Changer– Dockable Interface for sensor excitation– Volume Production– Alignment / Maintenance friendliness
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Smart probe cardsModular design
– Sensor excitation module– Detachable from probe card– One excitation module, multiple probe cards– Module supply through probe card contacts
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Rotating Magnet Probe Card IR Radiation Probe Card
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Smart probe cardsSmart module
– integrated microcontroller– digital interface: set point, status– keeps set point on test interruption: temperature, position, ...– precise closed-loop control
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Example: Rotating Magnet module
Microcontroller
Sensor (Encoder)
Actor (Drive)
Digital InterfaceClosed control loop
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Sensor excitation
Temperature Sensors– thermal radiation– signal ~ absorbed radiation
8G.Franz
D.U.T.
IR
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Infrared radiationPhysics
– surface emission– surface temperature: T– surface emissivity: ε– radiance ~ ε∙T4
Sensor– temperature sensing range: ambient to 100°C– peak radiance: ~ 10µm wavelength
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IR
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IR Radiation SourcesBlack Body
• emissivity 100%• no reflection• larger body size• slower response
Hot Plate• emissivity 90%• reflection 10%• smaller body size• faster response• emissivity uncertainty
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IR
temperature controlled radiator
thermal insulationabsorbed
10% reflected
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IR Probe Card„Hot plate“ design:
– large view angle of sensor– large radiator– close distance– placement inside spider
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IR
radiating area (black surface)
sensitive area chip area
Needle spider with IR radiator installed
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IR Probe CardCharacteristics
– View factor >90% possible– Temperature Range: ambient+10°C to 80°C– Temperature Accuracy: ± 1°C
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IR
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IR Probe CardPerformance
– Temperature Stability: ± 0.1°C – Temperature Uniformity: ± 0.2°C – Stabilizing time: 5 minutes (40°C step)
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IR
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Sensor excitation
Humidity Sensors– capacitance ~ relative humidity (% r.h)– 100% = saturated air– strong temperature dependance
14G.Franz
D.U.T.
HUM
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Humidity Testing
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HUM
Closed System• prober inside chamber• controlled atmosphere• high accuracy• slow
Open System • standard prober• humidity generator• continous flow• mix dry + wet air• fast
wafer
chuck
probe card smart probe card
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Humidity Probe CardCharacteristics
– small mixing chamber– closed-loop humidity control– fast change of humidity possible
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HUM
external unit
Saturated air
Dry air
supply
region of controlled humidity
mixing chamber
controlled heater
humidity sensor
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Humidity Probe CardCharacteristics
– Humidity range: 2 to 98 % r.h.– Temperature range: +5 to +80°C– Flow rate: < 0.5 liter/min
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HUM
external unit
Saturated air
Dry air
supply
chuck
heater
Temperaturecoupled
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Humidity Probe CardPerformance
– Humidity Accuracy: ± 3% r.h. (10-40°C)– Humidity Stability: ± 1% r.h.– Temperature Accuracy: ± 1°C – Stabilizing time: 10 sec. (10% r.h. step)– Stability / Drift: < 1% r.h./year (calibration poss.)
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HUM
Accuracy of integratedsensor for humidity controldepends on temperature
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Sensor excitation
Magnetic Sensors– magnetic flux parallel wafer– signal ~ flux density and direction
19G.Franz
D.U.T.
NS
MAG
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Electromagnet
2 Dipoles• coil and yoke• symmetry arrangement• field lines straight on symmetry
2N-Pole• Superposition of above• Field by vector sum• Direction by coil currents
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NS
MAG
i i
i i
ii
B
B
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Electromagnet
Field homogeneity:• strength and direction non-uniform• can be measured and compensated• additional calibration device needed
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NS
MAG
D.U.T.
D.U.T.
B
B
B
D.U.T.
Flux density [mT]
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Electromagnet
Material Nonlinearities:• Soft magnetic core saturates• Small but visible hysteresis
Reference sensors:• reference sensors (R) fixed to yoke• calibration (C) with precision probe• correction of DUT data
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NS
MAG
i iC R
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Electromagnet
Performance:• DUT size: 3x3mm• field strength: 25mT• angular accuracy: ± 1°• repeatability: ± 1°• rotational speed of field vector max. 10 Hz
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NS
MAG
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Permanent Magnet
Characteristics• DUT size : 10x10mm• field strength: 150 mT
• good field homogeneity• large field for multi-site testing• constant over time
• once-only calibrationfor large multi-site or high angular precision
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NS
MAG
SN
Flux density [T]in wafer plane
D.U.T.
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Permanent Magnet
Performance• positioning time 45°: 200 ms• continouos rotation: 150 rpm• positioning accuracy: ± 0.1°• repeatability: ± 0.1°
• positioning modes: 5 and 45° increments,single rotation,continouos rotation
25G.Franz
NS
MAG
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Comparison
Permanent Magnet
+ precise angular position+ always constant strength+ always constant offset
(multi-site)+ no heat dissipation
- slower stepping
Electromagnet
+ fast change of magnetic angle+ adjustable strength
- coil heating / cooling requirement- reference sensors / correction- speed limit: 10 Hz- low accuracy
26G.Franz
NS
MAG
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SummarySmart probe cards help to achieve higher accuracies by precision controlled sensor excitation. They can also reduce test complexity and effort.
Still wafer probing of sensor devices is a challenge:• In some physical domains it remains difficult to reach the
required accuracy of sensor excitation.• Test engineers must consider effort for calibration of test
equipment in a production environment.• In addition to probe cards calibration tools must be purchased.
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Acknowledgements
• D. Deegan, ex ANALOG DEVICES Limerick• J.P. Whelan, ANALOG DEVICES Limerick• E.D. Sandulescu, INFINEON Bucharest• our staff at T.I.P.S. Messtechnik
THANK YOU FOR YOUR ATTENTION!
28G.Franz