The Influence of Defects on Compatibility and Yield of the HfO2-PolySilicon Gate Stack for CMOS Integration

Hafnium-based dielectrics are under wide consideration for high-K gate dielectric applications. Since the gate electrode typically used in CMOS integration consists of polysilicon with n- or p-type dopants, compatibility of the HfO2layer with the polySi deposition and dopant activation steps is critical. Capacitors were fabricated with HfO2films deposited by ALD and MOCVD, and using polysilicon gate electrodes deposited by CVD processes. These devices showed leakage failures with yields that were observed to depend on the area, dielectric thickness and annealing conditions during the process. Investigation of the root cause of these leakage failures suggested that the leakage failures may be caused by a defect-related mechanism. The implication of this is that the leakage occurs at localized ‘defect’ sites rather than broadly through the HfO2layer. Emission microscopy analysis and physical characterization of the HfO2film were used to corroborate the proposed model. Defect density was observed to be strongly dependent on the processing of the dielectric film. In order to make Hf-based dielectric stacks compatible with polysilicon for conventional CMOS transistor integration with acceptable yield, further postdeposition treatment may be necessary to eliminate or cure the defects.