Role of Bulk HfO2 and Interfacial SiO2 Layer in Breakdown Characteristics of TiN/HfO2/SiO2/Si Gate Stacks

Defect generation in the interfacial SiO2 layer seems to be the leading breakdown mechanism in metal/high-k/interfacial layer/Si gate stack. In this work we reaffirm the claim by studying systematically the breakdown mechanisms of HfO2 and SiO2 separately, deposited under same growth conditions. Individual breakdown characteristics of HfO2 without any interfacial layer using MIM capacitors and in situ steam grown (ISSG) SiO2 MOS capacitors with of identical thicknesses were compared (I-t, Stress-induced leakage current) to that of the high-κ/IL/metal gate stack. It was observed that charge trapping and stress-induced trap formation in the interfacial layer continues to be the soft spot for grate stack breakdown.