Wide band gap, (GaN, SiC etc.) device evaluation with the Agilent B1505A Accelerate emerging material device development

Wide band gap, (GaN, SiC etc.) device evaluation with the Agilent B1505A Accelerate emerging material device development Stewart Wilson European Sales Manager Semiconductor Parametric Test Systems Autumn 2014. 1 Page Challenges 9/17/2014

Agenda 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 Challenges Page 2

Why Wide Band-Gap (WBG) Semiconductors? Requirements for modern power electronics: Conversion Efficiency Why Wide Band-Gap (WBG) Semiconductors? Reduced losses (switching and conduction) Higher voltage & current Higher frequency Lighter Cooling System High temperature operation Reduced Volume and weight Higher Integration Challenges Page 3

Physical Properties of WBG for Power Devices WBG power devices, with their superior electrical properties, offer great performance improvements. Band gap energy Thermal conductivity Physical Properties of WBG for E (ev) λ (W/cm K) Power g Devices Saturated electron velocity V sat (x10 7 cm/s) 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 Electric breakdown field E c (kv/cm) Wider bandgap energy Higher thermal conductivity Higher saturated electron velocity Higher electric breakdown field Higher temperature operation Higher voltage operation Lower loss (lower Ron) Higher frequency operation Challenges Page 4

SiC/GaN Devices Comparison SiC devices GaN devices SiC/GaN Devices Comparison Source: Yole Development, 2009 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 Source: Yole Development, 2012 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 Challenges Page 5

Agenda 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 Challenges Page 6

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 SiC device GaN device (on Silicon) Power range Several 100 s kw Few kw Max Vb 10 kv Few kv Ron per area <10mΩ/cm 2 1mΩ/cm 2 Challenges Page 7

The Keysight B1505A Overcomes WBG Device Evaluation Challenges 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 Challenges Page 8

Agenda 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 Challenges Page 9

SiC Module Evaluation Equipment Keysight B1505AP-H70: 3kV / 1500A capabilities N1265A Ultra High Current Expander/ Fixture(1500A) Output range Output resistance 500 A 120 mω 1500 A 40 mω -60V 1500 A 500 A -500 A Pulse 60V -1500 A B1505A with HVSMU (3kV) 500 A range 1500 A range Output voltage pulse or current pulse 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 500 μa to 500 A 2 ma to 1500 A Voltage 100 μv to 60V Current accuracy 0.6% 0.8% Challenges Page 10

SiC module evaluation with the Keysight B1505A - SiC Trench MOS module results (1) DUT: APEI/ROHM HT-2100 SiC Trench MOS module Challenges Page 11

High Current Characteristics: Id-Vds measurement ~ SiC Trench MOS module ~ High current (up to 1500 A) Fast Pulsing (down to 10 ms) Oscilloscope View Function (Both Current & Voltage Pulses) Challenges Page 12

On-resistance (Ron) measurement ~ SiC Trench MOS module ~ 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. Challenges Page 13

Breakdown and leakage current measurement ~ SiC Trench MOS module ~ The B1505A can accurately measure breakdown voltage with small leakage current. B1513B HVSMU N1268A UHVU Max Voltage 3kV 10kV Min. Current Resolution 10fA 10pA Measured using B1513B HVSMU Challenges Page 14

Agenda 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 Challenges Page 15

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 Challenges Page 16

What is Current Collapse on GaN HEMT VDD: Low Vg G Id D S Vd VDD Id Vg Vg VDD: High Vd Drain current at higher VDD is smaller than that at lower VDD!? Challenges Page 17

Dynamic On Resistance on GaN HEMT Off On VDD Vd Vg Ron = Vd / Id 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. Challenges Page 18

Why Current Collapse is so Critical? Higher on-resistance after switching from high voltage OFF-state detracts its value on power efficiency. 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. Challenges Page 19

Mechanism of GaN Current Collapse Donghyun Jin, et. al. Mechanisms responsible for dynamic ON-resistance in GaN high-voltage HEMTs, Proc the 2012 24th ISPSD, pp 333-336 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 Challenges Page 20

Keysight B1505A GaN Current Collapse solution using the N1267A HVSMU/HCSMU Fast Switch Apply high-voltage bias at OFF-state HVSMU OFF Switching between HVSMU and HCSMU is synchronized with the switching of device Measure on-current & apply voltage at ON-state HCSMU ON N1267A D Keysight N1267A Gate control MCSMU ON OFF G S Keysight B1505A Challenges Page 21

Operation of N1267A HVSMU/HCSMU Switch OFF-state ON-state HVSMU HCSMU VHV VHC N1267A off G Id(off) D Vd(off) HVSMU VHV HCSMU VHC IHV IHC N1267A on G D Id (on) Vd S S 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). Challenges Page 22

Key Feature Summary of B1505A GaN Current Collapse Solution 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 Challenges Page 23

Static Characteristics Check DUT: High Voltage- GaN-HEMT (EGNB010MK, Sumitomo Electric Device Innovation) Id-Vds measurement Check if device is alive or dead Id(off)-Vds measurement Check the breakdown voltage of device before applying stress bias voltage. Challenges Page 24

GaN Current Collapse measurement using Tracer Test mode Easy to graphically display the current collapse effect with the overlay feature of Tracer Test mode Low VDD Current collapse HVSMU HCSMU HVSMU HCSMU VHV High VDD VDS 0 V HVSMU (Stress voltage setting for OFF-state) 0 V VHV zz HCSMU (Drain voltage setting for ON-state) MCSMU (Gate voltage setting) 0 V VG(off) VG (on) Id-Vds at OFF state Id-Vds at ON state Challenges Page 25

Video of GaN Current Collapse Video Challenges Page 26

Dynamic On-Resistance measurement using Application Test mode EasyEXPERT software is furnished with pre-sets for dynamic on-resistance measurement on a short time scale and a long time scale. HVSMU HCSMU HVSMU VHV HCSMU VDS 0 V HVSMU (Stress voltage setting for OFF-state) 0 V VHV zz HCSMU (Drain voltage setting for ON-state) MCSMU (Gate voltage setting) 0 V VG(off) VG (on) OFF state ON state Challenges Page 27

Video Demo of Dynamic On-Resistance Video Challenges Page 28

Summary 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 Challenges Page 29

Consider Power Device Integration! 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. Challenges Page 30

Power it until breaks What is the maximum DUT capability? 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 N8900 3U - 5 kw, 10 kw, and 15 kw Parallel >100 kw - Up to 1500 V and up to 4000 A Challenges Page 31 31

Continuous Dynamic Source / Load and Measure with DC Power Analyzer, N6700 Modular Power Supply and APS Advanced Power System up 10kW R&D - Validation ATE - Manufacturing 14585A Control and Analysis SW for APS and N6705B No programming required N6700 Modular Power Supply 4ch > 30 modules 20W to 500W N6705B Modular DC Power Analyzer Up to 4ch 600W 150V 50A N79xx APS Advanced Power System 1-10kW -160V 2000A Get the full picture in seconds N69xx N79xx APS Advanced Power System 1-10kW 1-10kW -160V 2000A Optimized for test throughput Challenges Page 32 32

Keysight B1505A Information 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 Challenges Page 33

Questions? Challenges Page 34

Thank you for your kind attention Challenges Page 35