On the evolution of the recoverable component of the SiON, HfSiON and HfO2 P-MOSFETs under dynamic NBTI

The evolution of the recoverable (R) component of negative-bias temperature instability (NBTI) is examined, as a function of the number of stress and relaxation cycles, for the SiON, HfSiON, and HfO2 p-MOSFETs. At typical NBTI oxide fields (∼7 MV/cm), a steady and substantial decrease of the R component in the case of the HfO2 p-MOSFET is observed, while the R component of the SiON and HfSiON p-MOSFETs are found to remain constant. A decrease in the R component of the SiON and HfSiON p-MOSFETs is observed only at much higher oxide fields (> 10 MV/cm). Evidence shows that the decrease in the R component is due to a greater tendency for the hole traps in the HfO2 to be transformed into a permanent form (P) under a given oxide field. The result therefore implies that, under typical NBTI oxide fields, the R and P components could share a common defect origin in the case of the HfO2 p-MOSFET. On the other hand, the R and P components are likely to have originated from different defect precursors in the case of the SiON and HfSiON p-MOSFETs. The existence of different oxide fields at which the transformation of the R component into a permanent form occurs for different gate dielectrics implies that the nature of the defect precursors responsible for the R component is intrinsic to the gate dielectric material.