Low-frequency noise assessment of border traps in Al2O3 capped DRAM peripheral MOSFETs

Abstract

Low-frequency noise has been used to study the impact of an Al2O3 work-function-engineering cap layer on the gate oxide quality of SiO2/HfO2 DRAM peripheral n- and pMOSFETs. It is shown that from the 1/f-like spectra a border trap density profile can be extracted, which depends on whether the cap is deposited below or above the HfO2 layer. In general, the presence of Al in the high-κ material leads to a higher trap density, with a maximum concentration close to or at the SiO2/HfO2 interface, where a dipole layer is expected to form. When removing the cap layer from the SiO2 interfacial layer, excess generation-recombination-like noise is introduced for the n-channel devices, indicating the presence of dry-etching damage at the SiO2/HfO2 interface.