Stress-Polarity-Independent Negative Threshold Voltage Shift in HfO_2/TiN P-Channel Metal Oxide Semiconductor Field-Effect Transistor

摘要

The stress-polarity-independent threshold voltage shift characteristics of HfO_2 p-channel metal oxide semiconductor field-effect transistor (pMOSFET) with a TiN/p+ polycrystalline silicon electrode have been investigated. Positively charged defect states are shown to be generated under both positive and negative voltage stresses in HfO_2 pMOSFET. Further enhancement of positive threshold voltage shift under the positive voltage stress is observed when HfO_2 thickness is increased. In the analyses by charge pumping measurement, significant generation and relaxation of the interface state during the positive voltage stress and relaxation cycle were observed near the HfO_2/SiO_2 interface. This suggests that the generation of positively charged defect states under a positive voltage stress is related to traps in the HfO_2 layer rather than in the interfacial SiO_2 layer.