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High Power Measurement Challenges
1
Wide band gap, (GaN, SiC etc.) device
evaluation with the Agilent B1505A Accelerate emerging material device development
Stewart WilsonEuropean Sales Manager
Semiconductor Parametric Test Systems
Autumn 2014.
9/17/2014
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Agenda
High Power
Measurement
Challenges 2
• Why WBG (wide band-gap) semiconductors?
• Evaluation challenges for WBG semiconductors
• WBG Evaluation example with the Agilent B1505A
• SiC module evaluation
• GaN power device evaluation
• Summary
Page
Why Wide Band-Gap (WBG) Semiconductors?
High Power
Measurement
Challenges 3
Conversion Efficiency
• Reduced losses (switching and conduction)
• Higher voltage & current
• Higher frequency
Lighter Cooling System
• High temperature operation
Reduced Volume and weight
• Higher Integration
Why Wide Band-Gap (WBG) Semiconductors?
Requirements for modern power electronics:
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Physical Properties of WBG for Power Devices
High Power
Measurement
Challenges 4
WBG power devices, with their superior electrical properties, offer great
performance improvements.
Band gap energy
Eg (eV)
Thermal conductivity
λ (W/cm K)
Saturated electron
velocity Vsat (x107cm/s)
Electric breakdown
field Ec (kV/cm)
Si 1.12 1.5 1 300
GaN 3.39 1.3 2.2 3300
4H-SiC 3.26 4.9 2 2200
Diamond 5.45 22 2.7 5600
Wider bandgap energy
Higher thermal conductivity
Higher electric breakdown field
Higher saturated electron velocity
Higher temperature operation
Higher voltage operation
Higher frequency operation
Lower loss (lower Ron)
Physical Properties of WBG for Power Devices
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SiC/GaN Devices Comparison
High Power
Measurement
Challenges
Source: Yole Development, 2009Source: Yole Development, 2012
SiC devices GaN devices
4 times better thermal conductivity than GaN
Higher current devices because of lateral
device structure
Easy to develop normally off device
No current collapse phenomena
Difficult to create large diameter wafer
because of micropipe defects.
Expensive wafer cost
Electron mobility twice SiC one
Micropipe-free material
GaN HEMT technology can be transferred
from RF to power applications
GaN devices are less expensive than SiC
Current collapse phenomena
Difficult to develop normally off devices
Lateral devices are limited
SiC/GaN Devices Comparison
5
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Agenda
High Power
Measurement
Challenges 6
• Why WBG (wide band-gap) semiconductors?
• Evaluation challenges for WBG semiconductors
• WBG Evaluation example with the Agilent B1505A
• SiC module evaluation
• GaN power device evaluation
• Summary
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Evaluation Challenges for Wide Band-gap Semiconductors
• Higher current force/measurement (>100A)
• Higher voltage force/measurement (>3000V)
• Accurate low on-resistance (Ron) measurement (sub-mΩ)
• Quantitative GaN current collapse effect evaluation
• Accurate device capacitance (Ciss, Coss etc) measurement
High Power
Measurement
Challenges 7
SiC device GaN device
(on Silicon)
Power range Several 100’s kW Few kW
Max Vb 10 kV Few kV
Ron per area <10mΩ/cm2 1mΩ/cm2
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The Keysight B1505A Overcomes WBG Device Evaluation Challenges
High Power
Measurement
Challenges 8
• Voltage force/measure capability up to 10 kV
• Accurate sub-pA level current measurement at high voltage bias
• Current force/measure capability up to 1500 A
• μΩ resistance measurement capability
• Pulsed measurement capability down to 10 ms
• High voltage/high current fast switch option to characterize GaN current collapse effect
• Capacitance measurement at up to 3000 V of DC bias
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Agenda
High Power
Measurement
Challenges 9
• Why WBG (wide band-gap) semiconductors?
• Evaluation challenges for WBG semiconductors
• WBG Evaluation example with the Agilent B1505A
• SiC module evaluation
• GaN power device evaluation
• Summary
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SiC Module Evaluation Equipment
• Keysight B1505AP-H70: 3kV / 1500A capabilities
High Power
Measurement
Challenges 10
60V-60V
-1500 A
-500 A
500 A
1500 A
Pulse
500 A range 1500 A range
Output voltage pulse or current pulse
Measurement current or voltage
Maximum current ±500 A ±1500 A
Maximum voltage ±60 V
Output peak power 7.5 kW 22.5 kW
Pulse Period 10 μs~1 ms
Current Measurement 500 μA to 500 A 2 mA to 1500 A
Voltage Measurement 100 μV to 60V
Current accuracy ≦ 0.6% ≦ 0.8%
Output range Output resistance
500 A 120 mΩ
1500 A 40 mΩ
N1265A Ultra
High Current
Expander/
Fixture(1500A)
B1505A with
HVSMU (3kV)
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SiC module evaluation with the Keysight B1505A - SiC Trench MOS module Measurement results (1)
High Power
Measurement
Challenges 11
DUT: APEI/ROHM HT-2100 SiC Trench MOS module
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High Current Characteristics:Id-Vds measurement ~ SiC Trench MOS module ~
High Power
Measurement
Challenges 12
High current
(up to 1500 A)
Fast Pulsing
(down to 10 ms)
Oscilloscope View Function
(Both Current & Voltage Pulses)
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On-resistance (Ron) measurement ~ SiC Trench MOS module ~
High Power
Measurement
Challenges 13
Using a precision high current source, on resistance can be measured precisely
with sub-milliohm resolution.
Note: Kelvin (4-wire) resistance measurement techniques need to be employed.
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Breakdown and leakage current measurement ~ SiC Trench MOS module ~
High Power
Measurement
Challenges 14
The B1505A can accurately measure breakdown voltage with small leakage current.
Measured using B1513B HVSMU
Max
Voltage
Min. Current
Resolution
B1513B
HVSMU
3kV 10fA
N1268A
UHVU
10kV 10pA
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Agenda
High Power
Measurement
Challenges 15
• Why WBG (wide band-gap) semiconductors?
• Evaluation challenges for WBG semiconductors
• WBG Evaluation example with the Agilent B1505A
• SiC module evaluation
• GaN power device evaluation
• Summary
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Key Issues of Today’s GaN Power Devices
• GaN lateral device
• Current collapse phenomenon
• Drain current reduction after the application of high voltage
stress.
• Normally-on operation
• Negative threshold voltage. Normally-off operation is required
for system safety.
• GaN vertical device
• Lack of good quality large area substrate at reasonable price
High Power
Measurement
Challenges 16
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What is “Current Collapse” on GaN HEMT
High Power
Measurement
Challenges 17
D
G
S
VDD
Vg
Vd
Id
Vd
Id
VDD: Low
VDD: High
Vg
Vg
– Drain current at higher VDD is smaller than that at lower VDD!?
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“Dynamic On Resistance” on GaN HEMT
High Power
Measurement
Challenges 18
Vd
Vg
VDD
Ron = Vd / Id
Off On
VDD
time
• On resistance changes dynamically after changing from OFF-state to ON-state.
• On resistance is depending on VDD and duration of OFF-state.
• Caused by the same mechanism with the current collapse phenomena observed at IV measurement.
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Why Current Collapse Measurement is so Critical?
High Power
Measurement
Challenges 19
• Finding physical mechanism of current collapse is necessary to maximize value of GaN
FET.
• To know on-resistance value at actual timing is necessary for optimum circuit design.
Higher on-resistance after switching from high voltage OFF-state detracts its
value on power efficiency.
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Mechanism of GaN Current Collapse
High Power
Measurement
Challenges 20
• Traps exist traps with various time constants
• Fast response and slow response have to be measured
• Various techniques to reduce current collapse are under development
Donghyun Jin, et. al. “Mechanisms responsible for dynamic ON-resistance
in GaN high-voltage HEMTs”, Proc the 2012 24th ISPSD, pp 333-336
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Keysight B1505A GaN Current Collapse solution using the N1267A HVSMU/HCSMU Fast Switch
High Power
Measurement
Challenges 21
D
Apply high-voltage bias at OFF-state
Measure on-current &
apply voltage at ON-state
Gate control
N1267A
HVSMU
MCSMUS
G
HCSMU
OFF
ON
OFF
ON
Switching between HVSMU
and HCSMU is synchronized
with the switching of device
Keysight B1505A
Keysight N1267A
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Operation of N1267A HVSMU/HCSMU Switch
High Power
Measurement
Challenges 22
HVSMU
HCSMUD
S
offVd(off)
Id(off)
G
OFF-state
N1267A
VHV
VHC
D
S
on
Vd
VHV
Id (on)IHC
IHV
G
ON-state
HVSMU
HCSMUVHC
N1267A
• The diode switch is reverse biased (off). So the
HCSMU is disconnected from the device.
• Drain bias is applied by HVSMU.
• Once the device is turned on, Id(on) starts to flow.
• The output voltage of HVSMU is lowered because
Id(on) exceeds its current compliance.
• The diode switch is forward biased (on).
• The drain bias source is shifted to the HCSMU,
• The drain current Id(on) is the sum of current from
HCSMU(IHC) and HVSMU(IHV).
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Key Feature Summary of B1505A GaN Current Collapse Measurement Solution
High Power
Measurement
Challenges 23
• Dynamic on-resistance measurement from a short time scale to a longer
time scale
• Minimum 20µs fast switch from OFF-state to ON-state
• High speed sampling with minimum 2μs sampling rate
• Long term variation measurement with log sampling
mode
• Wider voltage/current range and precise measurement
• Max 3000V OFF-state voltage stress
• Max 20A ON-state drain current
• Capture small variation with max 6 digit resolution
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Static Characteristics Check
High Power
Measurement
Challenges 24
Id(off)-Vds measurement
DUT: High Voltage-High Power GaN-HEMT
(EGNB010MK, Sumitomo Electric Device Innovation)
Check the breakdown voltage of device
before applying stress bias voltage.
Check if device is
alive or dead
Id-Vds measurement
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Low VDD
High VDD
Current
collapse
GaN Current Collapse measurement using Tracer Test mode
High Power
Measurement
Challenges 25
zz
Easy to graphically display the current collapse effect with the overlay feature of
Tracer Test mode
MCSMU(Gate voltage setting)
HCSMU
(Drain voltage setting
for ON-state)
HVSMU(Stress voltage setting
for OFF-state)
Id-Vds at OFF state
VG(off)
0 V
0 V
VHV
VG (on)
VDS0 V
VHV
HVSMU
HCSMUHVSMU HCSMU
Id-Vds at ON state
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Video of GaN Current Collapse Measurement
High Power
Measurement
Challenges 26
Video
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Dynamic On-Resistance measurementusing Application Test mode
High Power
Measurement
Challenges 27
zz
MCSMU(Gate voltage setting)
HCSMU(Drain voltage setting
for ON-state)
HVSMU(Stress voltage setting
for OFF-state)
VG(off)
0 V
0 V
VHV
VG (on)
VDS0 V
VHV
HVSMU
HCSMUHVSMU HCSMU
OFF state ON state
EasyEXPERT software is furnished with pre-sets for dynamic on-resistance
measurement on a short time scale and a long time scale.
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Video Demo of Dynamic On-Resistance Measurement
High Power
Measurement
Challenges 28Video
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Summary
High Power
Measurement
Challenges 29
• Wide voltage/current range up to 1500A/10kV
• μΩ resistance measurement capability
• Pulsed measurement capability down to 10 us
• Accurate sub-pA level current measurement at high voltage bias
• GaN current collapse measurement
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Consider Power Device Integration!
High Power
Measurement
Challenges 30
After characterization, devices are integrated in the final DUT
power application.
• How does your final DUT work at full power and dissipation?
• How does it manage the thermal stress?
Power devices need to be tested with realistic operating
conditions for electrical performances and thermal stress.
The test demand high power source and power analysis tools.
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Power it until breaksWhat is the maximum DUT capability?
High Power
Measurement
Challenges 31
A common testing requirement : stress power devices until they
break.
This is done by:
Applying continuous high current
Cycle on and off to thermal cycle connections and integration
How Keysight can help :
N8900 Programmable Basic Auto-ranging Power Supplies
3U
- 5 kW, 10 kW, and 15 kW
Parallel >100 kW
- Up to 1500 V and up to
4000 AN8900
31
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Continuous Dynamic Source / Load and Measurewith DC Power Analyzer, N6700 Modular Power Supply and APS Advanced Power System up 10kW
High Power
Measurement
Challenges 32
R&D - Validation – ATE - Manufacturing
N79xx APS
Advanced Power System1-10kW -160V 2000A
N6705B Modular
DC Power AnalyzerUp to 4ch 600W 150V 50A
14585A
Control and Analysis SW
for APS and N6705BNo programming required
N6700 Modular Power Supply 4ch
> 30 modules 20W to 500W
N69xx N79xx
APS Advanced Power System 1- 10kW1-10kW -160V 2000A
Optimized for test throughputGet the full picture in seconds
32
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Keysight B1505A Information
High Power
Measurement
Challenges 33
Keysight B1505A literature available for download from
www.keysight.com/find/b1505a
B1505A Data Sheet
Handbook
Application Notes
Also, you can see more application videos at the Agilent
B1505A Youtube channel:
http://www.youtube.com/user/agilentParaPwrAnalyz
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Questions?
High Power
Measurement
Challenges 34
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Thank you for your kind attention
High Power
Measurement
Challenges 35
