Reliability issues of SiC power MOSFETs toward high junction temperature operation

There still remain a number of reliability problems to be resolved with regard to long-term high junction temperature operation of SiC power devices because at present they simply follow Si-based technology. In this paper, various reliability issues for power DMOS devices on 4H-SiC operated at a junction temperature of more than 200 °C are extensively discussed in terms of five manifest problems and potential treats: (1) interlayer dielectric erosion, (2) Al spearing, (3) Ni2Si contact disappearance, (4) electrode delamination, and (5) gate time-dependent dielectric breakdown. Preventive measures for these issues are proposed, including the use of a Ta/TaN barrier metal, a SiCH barrier dielectric, decarbonised Ni2Si and an ONO gate dielectric, and their effectiveness is experimentally verified. A viable device structure and fabrication process that successfully incorporate these measures are then presented. Finally, a storage life of more than 5380 hours at 300 °C is demonstrated for 1 × 1 mm2 4H-SiC power DMOS devices incorporating selected countermeasures. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)