SiC and SiC for advanced power applications

Kevin Matocha and Sauvik Chowdhury 17 August 2017 College Park, MD

ARL SiC Workshop - 17 August 2017 Acknowledgments

We acknowledge our sponsors who have supported Monolith Semi’s development of SiC diodes and MOSFETs:

• DE-AR0000442 • W911NF-14-2-0112 and W911-NF-15-2-0088 • DE-SC0011395 • DE-SC0015989 2 Monolith Inc. A fabless supplier of SiC diodes and MOSFETs

SiC epiwafer vendors

150 mm

150mm Monolith Foundry Semiconductor Inc.

• Developed Silicon-compatible SiC MOSFET processes Assembly vendors • Transferred our SiC process into an automotive-quality 150mm CMOS fab – XFab Texas • Confirmed performance and gate oxide reliability • Formed strategic partnership with Littelfuse

3 Monolith: Company Development Timeline

4 Littelfuse - Monolith Partnership Partnership

Monolith Semiconductor Inc. • Industry-leading customer • Deep power semiconductor support and applications expertise

• Global manufacturing and supply chain excellence • High performance and quality SiC MOSFET and • Diverse technology technology portfolio to enrich systems- level engagements • Manufacturing in • Extensive industrial and automotive-qualified 150mm CMOS fab automotive experience

5 New sub-brand: Littelfuse Power

Littelfuse has created a sub-brand to market power semiconductor products, highlighting the increased company focus on power control (IGBTs and SiC devices).

New sub-brand was officially released at PCIM 2017 in Nuremberg, Germany.

This brand includes the Monolith-developed products, now being released and marketed under the Littelfuse Power Semiconductors brand.

Round Rock is selected as the center-of-excellence for Littelfuse Power Semiconductors.

6 Applied Power Electronics Conference – APEC 2017 Defined by Customers. Developed by Monolith. Delivered by Littelfuse.

7 Applied Power Electronics Conference – APEC 2017 Defined by Customers. Developed by Monolith. Delivered by Littelfuse.

APEC 2017 highlights:

• Presented Industrial Tutorial: 4 hr tutorial on SiC diodes, MOSFETs and gate drives

• Released our first 1200V SiC Schottky diodes: 5 and 10 Amps

• Booth entitled “Making SiC Mainstream” highlighting strategic partnership between Littelfuse and Monolith

• Exhibited application support hardware to speed customers to design with SiC diodes and MOSFETs

8 PCIM 2017 - Power Control and Intelligent Motion – Nuremberg Speed. Agility. Flexibility.

9 Power Control and Intelligent Motion – PCIM 2017 Nuremberg Speed. Agility. Flexibility.

11 Go-to-Market Strategy with Littelfuse Brand

Making SiC Mainstream Making SiC Mainstream New Technology Platform Announcement SiC Power Converter Design Toolkits

Dynamic Characterization Platform Toolkit for characterizing the switching behavior of Littelfuse–Monolith SiC MOSFETs and diodes SiC high voltage MOSFETs and diodes are wide-bandgap devices that ensure low conduction and low switching LSIC2SD120 Series Gen 2 SiC Schottky Diodes loss. Maximizing their performance requires more than just plugging them into your application: • Requires characterization board designed for SiC devices with minimal parasitic inductances Near-zero Recovery Time and Low Forward Voltage for Higher System Efficiency • Demands precise measurement of voltage and current waveforms • Calls for careful and optimized gate drive design and layout to minimize noise coupling How would your next power electronics application benefit from higher efficiency, greater robustness, and reduced need for thermal management? With negligible reverse recovery, the new LSIC2SD120 Series of SiC Schottky Diodes reduces switching losses dramatically to boost system efficiency. They also support large surge currents and have a high maximum junction temperature of 175°C. SiC devices can deliver fast switching speeds: Littelfuse offers a new generation of SiC Schottky diodes in voltage classes of 1200 V with current <10ns switching time, ratings from 5 A to 40 A. Choose from two-lead (TO-220), two-lead (TO-252), three-lead (TO-247) (dv/dt) ~100V/ns, (di/ Making SiC Mainstream dt) ~5A/ns or bare die packages. SiC Power Converter Design Toolkits To simplify optimizing the performance of Reverse Recovery Applications our SiC devices in your applications, the 2 Monolith–Littelfuse Dynamic Characterization • Boost diodes in power factor correction Switching losses vs.Si Platform lets you: reduced by 2/3 5 kW Evaluation Converter 1 • -mode power supplies • Characterize switching behavior of SiC SiC SBD • Uninterruptible power supplies devices accurately 0 Discover how our 5 kW evaluation converter kit will help • Solar inverters accelerate your next power converter design • Explore optimized driving via parameter tuning H-Bridge configuration with both high side and low side drivers lets -1 • Industrial motor drives The high switching speed of SiC devices enables very low losses. you perform “Double Pulse” switching test of MOSFET to extract turn- • Accelerate converter design with SiC devices However, careful converter design and layout are required to on and turn-off energies, and switching times; extract MOSFET gate • EV charging and power conversion charge; and extract diode switching energy and charge. Si FRD extract the full benefit of SiC devices. Minimizing inductance in -2 the power loop is crucial. Careful gate drive design and layout are Current (A) Current Its key features include: Features necessary to isolate control circuitry from noise. -3 • 1.7 kV, 100A pulse load capability The Littelfuse–Monolith Dynamic Characterization • Dramatically reduced switching losses • Two separate boards for characterizing Platform is ideal for characterizing the switching compared to Si bipolar diodes Our 5 kW evaluation converter will help accelerate your next design. behavior of our SiC MOSFETs and diodes in -4 SiC devices in surface mount or through- • Extremely fast, temperature-independent By using a modular design strategy and components with similar footprints, we can offer you an extremely hole packages detail. It is available upon request along with an switching behavior versatile and adaptable platform for converter-level testing. application note on how to use it to characterize -5 • Flexible topology – diode or MOSFET in both device performance. To learn how to get your own 50 75 100 125 • Positive temperature coefficient for safe high side and low side dynamic characterization platform and application operation and ease of paralleling Time (nsec) Parameter Minimum Spec. Maximum Spec. • Adjustable gate drive voltage from -5V to 20V note, talk to one of our representatives today. • 175°C maximum operating junction temperature The ultra-short reverse recovery time of the LSIC2SD120 Series Input Voltage 200 V 800 V • Excellent surge capability supports efficient, high-speed switching. Input Voltage 200 V 800 V Switching Frequency 25 kHz 200 kHz Benefits Power 1 kW 5 kW • Suitable for high-frequency power switching; negligible switching losses; reduced stress on Conversion Ratio 25% 75% the opposing switch The evaluation kit is easy to configure to emulate the operating characteristics of your application. • Larger design margin and relaxed thermal Providing application management requirements Configurable operating characteristics: • Enhanced surge capability and extremely • Converter topology low leakage Aids in the design of a wide range of power − Non-synchronous buck electronics applications: design support through − Synchronous buck • Automotive EV / HEV & charging − Non-synchronous boost • Solar & energy storage systems − Synchronous boost • Data & communications power & UPS • Voltage/Current • Industrial drives, HVAC & welding evaluation boards, • Operating frequency • Driving solutions To obtain your own configurable evaluation kit as well as advice on SiC converter design, talk to one of our representatives today. demo converters and Suitable as a platform for: • Introductory converter design APEC & PCIM 2017 – Released • Power density studies • application notes Control theory applications • Guide to proper layout techniques when dealing with SiC devices 1200V SiC Schottky diode portfolio • Evaluating different driving techniques

© 2017 Littelfuse • Dynamic Characterization Platform Revised 0317 13 www.littelfuse.com Dynamic Characterization Demo Board

Super fast switching speed requires: • Optimized layout to minimize inductance • Precise measurement of voltage and current • Optimized gate drive design to minimize noise coupling

Desired features: • Easy swapping of devices for multi-device measurements • Capability of heating device for HT characterization • Accurate V &I measurement for Vgs, Vds, Ids • Realistic layout design with self EMI containment and EMC Design

• Board variations for TO-247-3L, TO-247-4L and TO-263-7L (SMD)

Provides sample high-side/low-side gate drive design for customer evaluation of turn-on and turn-off losses of SiC MOSFETs and diode recovery.

14 5 kW All-SiC Evaluation Converter

Baseline all-SiC 5kW converter, configurable as buck, boost or half-bridge.

Modular gate drive to support custom gate drive development.

Minimum Spec. Maximum Spec. Input Voltage 200 V 800 V Output Voltage 200 V 800 V Switching 25 kHz 200 kHz Frequency Power 1 kW 5 kW Conversion Ratio 25% 75% (Duty Cycle)

Provides customers starting point for 5 kW converter designs with gate drives suitable for switching frequency up to 200 kHz.

15 20 kW Demo

Inductor and size Embedded heat pipe reduction due to 50 kHz switching frequency

Heatsink and fan reduction due to lower loss and higher junction temperature

16 20kW Boost Converter - Power Stage Design

Input Lboost Monolith Vout current 1200V 25 mOhm sensor Cout SiC MOSFETs (MSA12N025A) Monolith Output Boost FET current Two SiC MOSFET and gate sensor Vin used with drive synchronous Monolith rectification Cin Synchronous FET and gate drive Control Card

• Closed loop control with digital controller • Improved power loop design for better device performance. • Fully isolated gate driver and gate driver for noise containment.

17 20 kW Boost Converter - Full Power Test

400

200 Vin (V) 0

60 IL(A) 50

1000 500 Vout (V) 0 30 10 Iout(A) Converter Test Summary 30 50 70 Time (µS) Parameter Input Output • 20 kW delivered by Two discrete Average Voltage (V) 400 817 25 mOhm SiC MOSFETs Average Current (A) 51.3 24.9 Power (kW) 20.52 20.34 • 99% efficiency for heatsink size Current Ripple (%) 27% -- reduction Boost Switch Case Temperature (°C) 63.6 18 Efficiency (%) 99.1 SiC Product Roadmap

19 Outline

• 1200V SiC MOSFETs processed in 150mm CMOS foundry • Static Characteristics (on-resistance, threshold voltage, temperature dependence) • Switching Characteristics • Ruggedness (avalanche, short-circuit) • Reliability (HTRB, threshold voltage stability, power cycling..) • 3300V SiC MOSFETs - Initial characterization • SiC Gate Oxide Reliability

20 1200V, 80mΩ SiC DMOSFET (LSIC1MO12E0080)

Picture of package (LFUS logo?)

Die area = 2.3x4.5 mm2 Output I-V characteristics – 25 °C

• 1200V SiC DMOSFETs fabricated in automotive qualified CMOS foundry • Assembled in TO-247-3L package

21 High Temperature Performance Part: LSIC1MO12E0080

• 40% increase in RDS,ON from room temperature to 150 °C • 650V Silicon SJ MOSFETs show over 2X increase in

RDS,ON ≈ 1.4X

*IPB65R065C7 ≈ 2.3X Infineon 650V, 65mohm CoolMOS C7 datasheet

22 Dynamic Performance Part: LSIC1MO12E0080

Turn-on Turn-off VDD = 800V ID = 20A VGS = -5/20V L = 1.4mH T = 25 °C

RG,ext = 2Ω Drain Current (A) RG,ext = 5Ω RG,ext = 25Ω source voltage (V) - Internal gate

Drain resistance = 1 ohm

Time (s) • Low gate resistance enables very fast switching – limited by ringing due to parasitic inductance

23 • Further reduction in switching energy requires low inductance package Dynamic Performance Part: LSIC1MO12E0080

1000 120 • VDD = 800V Total switching 900 ID = 20A losses < 0.4mJ VGS = -5/20V 100 800 L = 1.4mH (RG,ext = 2ohm) T = 25 °C 700 Energy - on 80 µJ) • Stable switching at 600 Energy - off dV/dt - on peak turn-off dV/dt 500 dV/dt - off 60 > 100 V/ns

400 Peak dV/dt (V/ns)

Switching Energy ( 40 300

200 20 100

0 0 0 5 10 15 20 25 30 External gate resistance (Ω)

24 Avalanche Energy Part: LSIC1MO12E0080

• Positive temperature coefficient of BV • Uniform avalanche in active area of the device enables high avalanche energy

Eav = 0.85J

2 Eav = 12.3 J/cm

25 Short Circuit Performance Part: LSIC1MO12E0080

VGS = 20V

VGS = 18V

VGS = 15V

VGS = 12V

Temp = 25 °C VDD = 600V

• Peak saturation current and short-circuit time is strongly dependent

on gate drive voltage (tsc vs. RDS,ON tradeoff)

• Short circuit time > 6µs for all gate voltages at VDD = 600V

26 Short Circuit SOA Part: LSIC1MO12E0080

• Short circuit time shows strong dependence on VDD, VGS • Short circuit time is comparable to other commercial SiC MOSFETs

27 Gate Threshold Stability: VGS=+25V, 175°C, 5500 hrs Part: LSIC1MO12E0080

Tested 3-lots of 1200V, 80 mΩ SiC MOSFETs for 6 months.

Demonstrated gate threshold stability for 5500+ hours at VGS=25V and 175 °C.

Less than 300mV shift after 5500 hours at 175 C. HTGB, ° VGS = 25V, T = 175 °C No successive shift observed after first readpoint.

Monolith’s gate threshold stability is robust, at 175°C for 5x the duration of the standard qualification requirements.

28 Gate Threshold Stability: VGS=-10V, 175°C, 2500 hrs Part: LSIC1MO12E0080

Tested 3-lots of 1200V, 80 mΩ SiC MOSFETs for 3 months.

Demonstrated gate threshold stability for 2500+ hours at VGS=-10V and 175 °C.

Negligible shift after 2500 hours at 175 °C. HTGB, VGS = -10V, T = 175 °C

29 High Temperature Reverse Bias (VDS=960V, T=175 °C) Part: LSIC1MO12E0080

Tested 3-lots of 1200V, 80 mΩ SiC MOSFETs for 1000 hours (77 devices per lot)

No shifts in BV, leakage current or other electrical parameters 30 Power Cycling (ΔTJ=100°C) Part: LSIC1MO12E0080

Power cycling on 3 lots (77 devices per lot) from 25 °C to 100 °C

(ton = toff = 5 minutes, biased in first quadrant)

No shifts in electrical parameters

31 Temperature Cycling (-55 °C to 150 °C) Part: LSIC1MO12E0080

Temperature cycling on 3 lots (77 devices per lot) from -55 °C to 150 °C

No shifts in electrical parameters

32 Summary – 1200V SiC MOSFETs Part: LSIC1MO12E0080

• Demonstrated robust and reliable 1200V SiC DMOSFETs processed in 150mm CMOS fab • Excellent static and dynamic performance • Avalanche and SC performance is similar to commercially available SiC MOSFETs • Completed 3-lot reliability testing at 175 °C

• Extended VTH stability tested up to 5500 hours (VGS = 25V) and 2500 hrs (VGS = -10V) • No parametric shifts under HTRB, IOL, TC

33 3.3kV SiC MOSFETs

25 Rsp Drift Rsp JFET 20 Rsp Ch

) Rsp Sub

cm2 15 Total -

(mohm 10 sp R 5

0 2 2.5 3 3.5 4 4.5 5 JFET Width (µm) Biggest resistance contribution: Drift JFET

Can significantly reduce RSP with Die size = 3.15 x 3.15 mm2 additional JFET 34 Experimental Results

3.3kV SiC MOSFET (with JFET doping)

VTH = 3.75V RDS,ON = 240mΩ 2 Ron,sp = 13.3 mΩ-cm

Blocking voltage is > 3.6kV (instrument limit)

35 Effect of JFET Doping

No JFET doping 2 • Typical Ron,sp < 13 mΩ.cm with JFET doping

• Reduced variability in on- resistance – JFET resistance Increasing JFET doping is not dependent on epi doping variation

• Impact on reverse bias oxide electric field – HTRB reliability

36 JFET Width Future Work

• Demonstrated prototype 3300V SiC DMOSFETs • BV > 3.6kV 2 • Ron,sp < 13 mohm.cm with JFET doping

• Future work • Dynamic characterization • Reliability (Effect of JFET design on HTRB)

37 Gate Oxide Reliability – Prior Work

• Excellent intrinsic gate oxide • TDDB at Eox from 7.8MV/cm to 9.7MV/cm (150C to 300C) reliability (projected lifetime > 100yrs at 300C, VGS=20V) • No extrinsic failures on over 600 MOS (device area ~ • What is the effect of full device 0.01 mm2) processing, area scaling? * Z. Chbili et al, ICSCRM 2015 38 TDDB – 1200V, 80mΩ SiC MOSFETs Part: LSIC1MO12E0080

175 °C

TDDB on 80mohm SiC MOSFETs (active area ~ 6.9 mm2)

225 °C

39 SiC Gate Oxide Reliability Part: LSIC1MO12E0080

• Excellent agreement between TDDB data from test structures and fully processed 80mΩ DMOSFETs

• Gate oxide reliability of SiC MOSFETs can be as good as that of silicon MOS devices

40 Summary

• 1200V, 80mΩ SiC MOSFETs processed in 150mm CMOS foundry • State of the art performance and ruggedness

• Extended HTGB testing shows no VTH instability • Scaled voltage up to 3300V SiC DMOSFETs 2 with BV > 3.6kV and Ron,sp < 13 mohm.cm • Excellent gate oxide reliability from TDDB data on 1200V, 80mΩ SiC MOSFETs

41