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SiC “Super” Junction Transistors Operating at 500 o C. Siddarth Sundaresan 1 , Ranbir Singh 1 , R. Wayne Johnson 2 1 GeneSiC Semiconductor Inc. 2 Auburn University. A significant portion of this research was performed under a Phase I SBIR grant from U.S. NASA (Award #NNX11CE28P).

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SiC “Super” Junction Transistors Operating at 500 oC

Siddarth Sundaresan1, Ranbir Singh1,

R. Wayne Johnson2

1GeneSiC Semiconductor Inc.

2Auburn University

A significantportion of this research was performed under a Phase I SBIR grant from U.S. NASA (Award #NNX11CE28P)

presentation outline
Presentation Outline
  • SiC “Super” Junction Transistor (SJT) Device Structure
  • On-state characteristics up to 500 °C
  • Blocking voltage characteristics up to 500 °C
  • High temperature switching characteristics
    • Comparison with state-of-the-art Si IGBTs
  • Short-circuited safe-operation area (SCSOA)
  • Avalanche ruggedness
  • Overload current and voltage turn-off
overview of sic super junction transistors sjts
Overview of SiC “Super” Junction Transistors (SJTs)
  • SJTs are high current gain SiC NPN BJTs developed by GeneSiC in 1200 V – 10 kV ratings.
  • Unlike Si BJTs, SiC SJTs are majority carrier devices
    • Fast switching speeds
    • Square RBSOA
    • Positive temperature co-efficient of VF
  • Free from SiC MOS reliability issues, which are especially severe at high operating temperatures.
  • High current gain (β>70) results in low Gate current drive requirements.

Source

Gate

N+ Source

P Base

N- Drift

N+ Substrate

Drain

off eutectic au sn die attach method
Off-eutectic Au-Sn die attach method
  • Ni-Au metallization on the SiC die
  • Sandwich Eutectic 80-20 AuSn pre-forms with TM = 280 °C between SiC die and Au plated substrate
  • Shift TM to 450 °C by decreasing Sn to 10 wt%.
    • Bonding conditions: 450 C/60 min in a vacuum furnace, bonding force = 500 grams

Au-20wt%Sn

Au-10wt%Sn

sjt output characteristics up to 500 c
SJT Output Characteristics up to 500 °C
  • Up to 300 °C, output characteristics indicate purely unipolar operation
  • Above 300 °C, distinct quasi-saturation regions are observed implying minority carrier injection into n- layer
    • Increased voltage drop across n- layer and higher carrier lifetime at higher temperatures
variation of current gain with temperature
Variation of Current Gain with temperature
  • Current gain (β) shows a negative temperature co-efficient up to 300 °C due to increasing ionization of Al acceptors in p-Base layer.
  • At > 300 °C, positive temperature co-efficient of β is due to increasing carrier lifetime in p-Base layer.
sjt blocking characteristics up to 500 c
SJT Blocking Characteristics up to 500 °C
  • SJT blocking up to 500 °C demonstrated
  • The sharp increase in leakage current above 350 °C correlates well with the increase of intrinsic carrier concentration in 4H-SiC
    • First ever demonstration of blocking voltage characteristics of a high-voltage SiC transistor at 500 °C
high temperature switching characterization setup
High-temperature switching characterization setup
  • Inductively clamped chopper circuit and standard double-pulse gate drive scheme used for SJT switching measurements.
  • A 100 nF dynamic capacitor is used to speed up switching transients by providing high dynamic Gate currents.
high temperature sjt switching transients
High-Temperature SJT Switching transients
  • VDS = 800 V, ID = 7 A
  • Ultra-fast < 15 ns Drain current rise and fall times measured at 250 °C
  • Temperature independent switching characteristics obtained due to unipolar SJT operation, even at 250 °C
eon and eoff comparison with state of the art si igbts
Eon and Eoff comparison with state-of-the-art Si IGBTs
  • Temperature independent Eon and Eoff for the all SiC, SJT+JBS free-wheeling diode pair up to 250 °C.
  • SiC SJT enables higher temperature operation and lowest overall switching energy losses, compared to all-Si or hybrid Si-SiC power modules.
switching performance comparison with state of the art si igbt technologies
Switching performance comparison with state-of-the-art Si IGBT technologies
  • The SiC SJT + Schottky Diode combination offers a 64% reduction in total power losses as compared to state-of-the-art Si IGBT/Rectifier co-packs.
  • Test frequency = 100 kHz, D=0.7
rbsoa investigations overload current voltage turn off
RBSOA Investigations – Overload Current, Voltage turn-off

Over-current (22A) turn-off

Over-voltage(1250 V) turn-off

Successfully turned-off 7 A toa Drain Voltageof 1250 V in 115 ns

  • Successfully turned-off 22 A (740 A/cm2) toa Drain Voltageof 800 V in 110 ns
avalanche robustness
Avalanche Robustness
  • 1200 V SJT driven to avalanche by unclamped inductive switching (without free-wheeling diode).
  • Single-pulse avalanche energy of 20.4 mJ and tAV=5 µs obtained for turning-off 7 A at 1500 V.
  • Slight improvement in breakdown voltage observed after the 934 hour UIS testing with EAV=2.3 mJ pulses at a 30% duty cycle and 14.3 kHz switching frequency.
o peration under hard short circuited fault conditions
Operation under (hard) short-circuited fault conditions
  • 1200 V/3 mm2 SJT directly turned-on to a short-circuited load at VDS=800 V with IG = 200 mA
  • A short-circuit withstand time (tSC) = 22 µs and ISC = 10-12 A were recorded
  • Device destruction occurred at 24 µs
  • Low ISC at VDS = 800 V due to lack of short-channel effects in output characteristics.
summary of results
Summary of Results
  • 500 °C operation of 1200 V-rated SiC SJTs demonstrated
    • First-ever demonstration of blocking-mode operation of a power transistor at 500 °C.
    • Output characteristics indicate unipolar operation at temperatures < 300 °C; distinct quasi-saturation regions form at 400-500 °C.
    • Temperature co-efficient of SJT current gain changes from negative to positive at > 300 °C.
  • Temperature independent, low switching losses obtained up to 250 °C.
  • 1200 V/5 A-rated SJT turned-off ID = 22 A (740 A/cm2) at 800 V; and 7 A at VDS = 1200 V, indicating square RBSOA.
  • SJT demonstrated good avalanche robustness
    • EAS = 20.4 mJ
    • No deterioration in device performance after a 934 hour repetitive avalanche stress.
  • Obtained reasonbly high tsc = 22 µs under short-circuit load conditions at VDS = 800 V
    • enabled by a low ISC =12 A at 800 V.
250 c capable 650 v and 1200 v sic schottky rectifiers
250 °C capable 650 V and 1200 V SiC Schottky rectifiers
  • GeneSiC’s 650 V/1,5,20 A and 1200 V/1,5,20 A SiC Schottky rectifiers with TJ = 250 °C capability are now available as bare die!
    • Please contact Micross components or GeneSiC Semiconductor for product information and pricing.

650 V/20 A SiC SBD

1200 V/20 A SiC SBD

IR = 55 µA at 1200 V

IR = 32 µA at 650 V