Monolith Semiconductor Inc. ARL SiC MOSFET Workshop 14 August 2015 Kevin Matocha, President 408 Fannin Ave Round Rock, TX 78664 Bringing SiC to our World.
Acknowledgments Office of Science SBIR Prog. Office We acknowledge our sponsors who have supported Monolith Semi s development of SiC diodes and MOSFETs: DE-AR0000442 W911NF-14-2-0112 DE-SC0011395 IIP-1332039 ECCS-0335765 Monolith Semiconductor: Bringing SiC to our World. 2
SiC epiwafer vendors Monolith Semi: A fabless manufacturer of SiC diodes and MOSFETs 150 mm 150mm Silicon Foundry Monolith Semiconductor Inc. Assembly vendors MOSFET with best performance and reliability Low cost manufacturing in high-volume CMOS fab Low capital, Fast time to market Monolith Semiconductor Inc. 3
December 2012 Monolith Semiconductor incorporated December 2013 Inked agreement with domestic high-volume 150mm silicon foundry 2014 Demonstrated first SiC DMOSFETs on 150mm wafers in USA 2013 2014 2015 May 2013 Demonstrated SiC DMOSFETs 1700V, 5.5 mω-cm 2 5 Amp Stable at 225 C 2014 Demonstrated 1200V SiC Schottky diodes on 150mm wafers 150 mm 2015 Engineering samples to select customers 75 mm Monolith Semiconductor Trajectory 4
2014: Monolith Semi relocated to Round Rock (Austin), TX Ithaca, NY Round Rock, TX Monolith Semiconductor: Bringing SiC to our World 5
Monolith Semi s SiC Power MOSFET Technology Steady state performance On-resistance, blocking voltage Transient behavior Switching losses under high-speed switching, fast dv/dt > 50V/ns Gate oxide stability and reliability Exploring the temperature boundaries Remaining items to resolve Monolith Semi s SiC MOSFET Technology 6
90 80 Vgs=0V to 20V, 5V steps 2.5 Measured with V GS =0 V 70 2 Drain Current (A) 60 50 40 30 20 R DS,on =45 mω R sp,on =3.1 mω-cm 2 Drain Current (ma) 1.5 1 0.5 10 0 0 2 4 6 8 10 12 0 0 200 400 600 800 1000 1200 1400 1600 1800 Drain Voltage (V) Drain Voltage (V) Packaged device results On-resistance: 45 mω (V GS =20V) 50 mω (V GS =15V) Specific on-resistance: 3.1 mω-cm 2 Blocking Voltage: 1700V Monolith Semi s 1200V, 45 mω (3.1 mω-cm 2 ) DMOSFETs on 150mm SiC wafers. 7
Specific on-resistance vs. Temperature Monolith Semi s SiC MOSFETs have superior on-resistance at all temperatures. 16 14 Supplier 2 Specific on-resistance: R sp,on (mω-cm 2 ) 12 10 8 6 4 2 0 Supplier 1 Gen1 Gen2 0 25 50 75 100 125 150 175 200 Temperature ( C) Monolith Semi s SiC MOSFETs are suitable for 175 C operation. 8
Switching losses of Monolith Semi s 1200V, 45 mω SiC MOSFETs Device: Monolith Semi 1200V, 45 mω SiC DMOSFETs in TO-247 Test conditions V DS =700 V I D =20 A and 30 A Characterized switching energy with varying gate resistance from R G =1 to 10 Ω. 700V V GS I D V DS 20A R G =5.1 Ω 30A I L Monolith Semi s SiC MOSFETs have switching loss 10x lower than Si IGBTs. 9
Switching loss characterization of Monolith Semi s 45 mω SiC MOSFETs Turn-off at 30A, 700V occurs in less than 20 ns Turn-on and turn-off times are dominated by packaging parasitic inductances @ R G 2 Ω. Current (A) 35 30 25 20 15 10 I D 10 Ω 5.1 Ω 2 Ω 1 Ω R g(ext) (Ω) E on (mj) I D =19.5A E off (mj) I D =19.5A E off (mj) I D =28.5A 10 0.61 0.23 0.39 5.1 0.50 0.16 0.27 2 0.42 0.11 0.2 1 0.40 0.11 0.17 Voltage (V) 5 0 20ns -5 2.96 2.97 2.98 2.99 3 3.01 3.02 3.03 3.04 800 700 600 500 400 300 200 Time (µs) 10 Ω 5.1 Ω 2 Ω 1 Ω -100 2.96 2.97 2.98 2.99 3 3.01 3.02 3.03 3.04 Time (µs) Monolith Semi s SiC MOSFETs have switching loss 10x lower than Si IGBTs. 100 0 20ns 10
SiC MOSFET Gate oxide reliability The gate oxide is considered the Achilles heel of Silicon Carbide MOSFETs, particularly for high temperature operation We have spent must of 2014/2015 to: - Improve the wearout reliability of SiC gate oxides - Reduce the extrinsic failure rates - Improve threshold voltage stability - Evaluate devices at temperatures up to 275 C Monolith Semi s SiC MOSFET Technology 11
Monolith Semi: SiC MOSFET Gate Oxide Reliability @ 300 C testing @ NIST 47.5V 45V 41V 43V 38V SiC gate oxide reliability characterization by NIST. Probability 0.6 0.2 Gate oxide reliability 0.045 NIST logo 0.014 0.003 T=300 C 1e+1 1e+2 1e+3 1e+4 1e+5 1e+6 Failure time (seconds) At T=300 C and V G =20V, extrapolated 1% failure life is > 10 10 sec (100 yrs). We continue to validate the reliability of Monolith gate oxides. Constant voltage TDDB stress testing of 50 nm SiC gate oxide. No early failures, even at 300 C. Failure time (seconds) 1e+10 1e+9 1e+8 1e+7 1e+6 1e+5 1e+4 1e+3 1e+2 1e+1 1% 50% T=300 C 25 30 35 40 45 50 Voltage Monolith Semi s SiC gate oxides project sufficient life at high temperatures. 12
Monolith Semi SiC MOSFETs: ARL Testing NBTI at 175 C Dr. Ron Green and Dan Habersat @ Army Research Lab tested Monolith Semi s 1200V, 45 mω MOSFETs packaged in TO-247 Tested at V GS =-15V @ 175 C for extended stress times and characterized the threshold voltage shift. V T (V) 3.0 2.5 2.0 1.5 1.0 0.5 NBTS -15V 175 C Dev G4 2014 Measured at 28 C Measured at 175 C Less than < 175mV shift after 200 hrs at 175 C. 0.0 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7 Cumulative Stress Time (s) Monolith Semi s threshold voltage shifts less than 175mV after 200 hrs @ 175 C. 13
Monolith Semi power MOSFET NBTI/PBTI: Testing the limits, 175 C and beyond Bare die mounted to a copper plate with Silver paint, die are in room air. Used ARL Test method for NBTI/PBTI hysteresis measured at temperature Set temperature, stabilize. Bias V GS =-15V, 60 sec Sweep -15V to +20V, V DS =0.1V Bias V GS =+20V, 60 sec Sweep +20V to -15V, V DS =0.1V Bias V GS =-15V, 1000 sec Sweep -15V to +20V, V DS =0.1V Bias V GS =+20V, 1000 sec Sweep +20V to -15V, V DS =0.1V Threshold voltage is defined at constant current of 1mA. Monolith Semiconductor: Bringing SiC to our World 14 Monolith Semiconductor Proprietary
Monolith Semi SiC MOSFETs: High temperature transfer characteristics Drain&Current&@Vds=0.1V&(Amps)& Transfer&Characteris@cs&25 C&to&275 C& 1.E+00& 1.E$01& 1.E$02& 1.E$03& 1.E$04& 25C& 1.E$05& 150C& 1.E$06& 175C& 1.E$07& 225C& 1.E$08& 250C& 1.E$09& 275C& 1.E$10& $1& 0& 1& 2& Gate&Voltage&(V)& 3& 4& 5& Comparison of transfer characteristics measured after V GS =-15V, 60sec. Monolith Semiconductor: Bringing SiC to our World 15 Monolith Semiconductor Proprietary
Gate BTS: Short-term Bias Temperature Stress up to 275 C, 60 and 1000 seconds Drain&Current&@Vds=0.1V&(Amps)& Drain&Current&@Vds=0.1V&(Amps)& CY1452@05&@&175 C&@&60&and&1000sec& 1.E+00' 1.E$01' 1.E$02' 1.E$03' 1.E$04' 1.E$05' $15V'to'20V,'60s' 1.E$06' +20V'to'$15V,'60s' 1.E$07' $15V'to'20V,'1000s' 1.E$08' +20V'to'$15V,'1000s' 1.E$09' $1' 0' 1' 2' Gate&Voltage&(V)& 3' 4' 5' CY1452@05&@&275 C&@&60&and&1000sec& 1.E+00' 1.E$01' 1.E$02' 1.E$03' 1.E$04' 1.E$05' $15V'to'20V,'60s' 1.E$06' +20V'to'$15V,'60s' 1.E$07' $15V'to'20V,'1000s' 1.E$08' +20V'to'$15V,'1000s' 1.E$09' $1' 0' 1' 2' Gate&Voltage&(V)& 3' 4' 5' Mounted die to copper plate using Silver paint. Test method: Set temperature, stabilize Bias V GS =-15V, 60 sec Sweep -15V to +20V, V DS =0.1V Bias V GS =+20V, 60 sec Sweep +20V to -15V, V DS =0.1V Bias V GS =-15V, 1000 sec Sweep -15V to +20V, V DS =0.1V Bias V GS =+20V, 1000 sec Sweep +20V to -15V, V DS =0.1V Monolith Semiconductor: Bringing SiC to our World 16 Monolith Semiconductor Proprietary
Gate BTS: Short-term Bias Temperature Stress up to 275 C Threshold Voltage after stress Hysteresis ΔV T : between -15/+20V Threshold)Voltage)(V) 1.6 1.4 1.2 1.0 0.8 +20V -15V Delta_VT,*VT2,VT1*(Volts) 0.350 0.300 0.250 0.200 0.150 1000 sec 60 sec 0.6 0.100 0.4 Solid: 60 sec stress 0.050 0.2 Dashed: 1000 sec stress 0.000 0.0 100 150 200 250 300 100 150 200 250 300 Temperature* ( C) Temperature) ( C) Observe <300mV hysteresis even up to 275 C. NBTI/PBTI data suggests we can extend SiC MOSFETs to beyond 175 C. Monolith Semiconductor: Bringing SiC to our World 17 Monolith Semiconductor Proprietary
SiC MOSFET NBTI/PBTI: Short-term Bias Temperature Stress up to 275 C Performed NBTI/PBTI on bare die for short times up to 275 C. Before Stress Observe <300mV hysteresis even up to 275 C. NBTI/PBTI data suggests we can extend Monolith SiC MOSFET beyond 175 C. After 275ºC Stress How do we assemble devices to take advantage of Monolith Semi s high-temperature capability? Monolith Semiconductor: Bringing SiC to our World 18 Monolith Semiconductor Proprietary
Monolith Semi Qualification Testing: HTGB +20/-10V, 750 hrs @ 175 C Threshold)Voltage)Shift,)ΔVT)(Volts) High8Temperature)Gate)Bias:)810V,)T=175 C 0.1 0.05 Dashed: commercial SiC MOSFETs 0!0.05!0.1 Solid lines:!0.15 0 200 400 600 800 Time)(hours) Monolith Threshold)Voltage)Shift,)ΔVT)(Volts) 0.3 0.25 0.2 0.15 0.1 0.05 0 High8Temperature)Gate)Bias:)+20V,)T=175 C Dashed: commercial SiC MOSFETs Solid lines: 0 200 400 600 800 Time)(hours) Monolith For Monolith Semi devices, V T shift saturates in < 48 hours. Monolith Semi SiC MOSFET HTGB results after 750 hrs @ 175 C: HTGB @ -10V, 175 C: < -100mV shift after 750 hrs. HTGB @ +20V, 175 C: < +250mV shift after 750 hrs. Monolith Semi SiC MOSFETs have state-of-art threshold voltage stability @ 175 C. 19 Monolith Semiconductor Proprietary
Monolith Semi s SiC Power MOSFET Technology Developed SiC MOSFET production on high-volume 150mm silicon line Steady state performance Demonstrated 1200V SiC MOSFETs, 3.1 mohm-cm 2 Superior performance up to 175 C Transient behavior Demonstrated switching with 10% of the losses of IGBTs Gate oxide stability and reliability Demonstrated short-term stability even up to 250 C Developed high-quality SiC gate oxidation process Characterized silicon-like intrinsic gate oxide reliability Verified gate oxide reliability up to 300 C Demonstrated state-of-art threshold stability at 175 C+, 750 hours Monolith Semi s SiC MOSFETs demonstrate world-leading performance. 20
Remaining items to resolve Qualification tests to ensure field reliability SiC specific Gate oxide reliability predictions and operating life: Are we really as reliable as silicon devices? How do we validate this? What are the error bars? How can we prevent and screen extrinsic defects? Assembly: What assembly techniques are required to achieve > 200 C Main objective: Develop silicon-like levels of confidence in SiC products. Monolith Semiconductor: Bringing SiC to our World 21
Monolith Semiconductor Inc. Monolith Semi has developed world-class SiC MOSFETs in a scalable, high-quality manufacturing environment. Our company focus is to deliver qualified SiC MOSFETs to our customers. Bringing SiC to our World.