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Description
Ken Shono1 Yoshiyuki Kotani1 Tsutomu Hosoda1 Kenji Imanishi1 Yoshimori Asai1 Ronald Barr2 Kurt Smith2 Yifeng Wu2 Likun Shen2 Saurabh Chowdhury2 Lee McCarthy2 Jim McKay2 John Gritters2 Peter Smith2 Sung Yea2 Primit Parikh2

1, Transphorm Japan, Yokohama, , Japan
2, Transphorm, Goleta, California, United States

1.Introduction
Automotive quality GaN power switch rated 650V was realized. GaN on Si D-mode HEMT is in production with 6 inch SiCMOS manufacturing fab[ref.1,2]. Cascode configuration with low voltage SiMOSFET realized E-mode. Qualification test with AEC-Q101 automotive standard[ref.3] was successfully finished. Acceleration model for high voltage switching was established from accelerated life test. Cosmic ray induced single event burn out(SEB) test was also conducted[ref.4]. Failure rate for SEB was 1.5 FIT with zero failure at 600V that is two orders smaller than the FIT for SiMOSFET.

2.Device structure
AlGaN/GaN epitaxial layers were grown on Si wafer by metal organic chemical vapor deposition(MOCVD). Insulating gate with Al gate electrode was employed to achieve low gate leakage current. Ohmic contact was Al alloy with barrier metal layer. Metallization layer was Al with CVD Silicon dioxide and Silicon nitride layer. 30V Si MOSFET was used for cascode. Package type of industries standard TO247, TO220 and PQFN8x8 are in production.

3.High voltage reliability
Current collapse was a challenge for high voltage GaN HEMT. On resistance increase of our GaN HEMT is within 20% at 700V stress. High voltage switching test and high voltage reverse bias test at >1000V were conducted to derive the acceleration model. Acceleration model for the gate insulator TDDB was derived from the step stress test. Extrapolated life time for high voltage stress was >20 years for 0.1% failure.

4.Package reliability
Highly stressed temperature cycle test revealed the failure mode was delamination between the lead frame and the AlN insulator bottom of the die. Acceleration model was (delta-T)^n with n=-9. Stress simulation agreed with the experimental results. Extrapolated life time was >1E6 cycle for delta-T=100.

5.Single event burnout
Cosmic ray induced single event burnout(SEB) is fatal for high reliability applications. Nuclear reaction between cosmic rays and semiconductor atoms generate ionized particles. Ionized particle generates electron and hole pairs. In SiMOSFET, parasitic bipolar transistor turns on by the electron and hole current.
Accelerated neutron irradiation test was conducted at RCNP of Osaka university. Failure rate was <1.5 FIT at 600V and <3 FIT at 800V. Failure rate for commercially available 600V super junction SiMOSFET was 290 FIT at 600V. GaN HEMT is robust to SEB because of no parasitic bipolar transistor.

6.Conclusion
Cascode GaN HEMT is ready for automotive quality, small form factor and high efficiency applications.

References
[1] P. Parikh, et. al. “Commercialization of 600V GaN HEMTs,” 2014 SSDM, Tsukuba, Sep., 2014.
[2] T. Kikkawa, et. al. 600 V JEDEC-Qualified Highly Reliable GaN HEMTs on Si Substrates,” IEEE IEDM, San Francisco, Dec. 2014.
[3] AEC-Q101, Automotive Electronics Council.
[4] C. D. Davidson, et. al., 26th Ann. Int. Telecommunications Energy Conference, 2004, p.503.

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