Gate-first process compatible, high-quality in situ SiNx for surface passivation and gate dielectrics in AlGaN/GaN MISHEMTs

摘要

In the research of passivation/gate dielectrics for AlGaN/GaN based high electron mobility transistors (HEMTs), in situ SiNx has specific advantages over ex situ SiNx in terms of lower defects level and higher dielectric quality. In this paper, an in situ grown SiNx layer as thick as 47nm was deposited on AlGaN/GaN heterostructure by metalorganic chemical vapor deposition, with capabilities of functioning simutanously as passivation and gate dielectrics verified. Systematical investigations have been performed on the in situ SiNx in aspects of bulk dielectric quality, interface property and dielectric reliability. Correspondingly, high leakage suppression ability with leakage current <10(-)(8) A cm(-2) at 125 degrees C, near-ideal dielectric breakdown strength of similar to 13.2 MV cm(-1), high interface quality with state density of similar to 3.0 x 10(12 )eV(-1) cm(-2) have been revealed. In the dielectric reliability analysis, a maximum forward bias as high as 19.5 V (similar to 3.66 MV cm(-1)) for a ten-year lifetime at the failure level of 0.01% was obtained. Subsequent experiments also revealed the gate-first process compatibility of this high-quality in situ SiNx, providing additional process convenience and design flexibility for AlGaN/GaN HEMTs.