Study of Stress-Induced Leakage Current in Thin Oxides Stressed by Corona Charging in Air: Relationship to Goi Defects

Corona charging in air combined with non-contact oxide charge measurement with a contact potential difference probe provides an unique possibility for fast monitoring of electron tunneling characteristics without preparation of MOS capacitors. It has also been found tha corona charging of thin oxides in the tunneling range is very effective in generating stress-induced leakage current. In this work we demonstrate the sensitivity of the corona stress-induced leakage current magnitude to gate oxide integrity defect density. The experimenta results cover three of the most common gate oxide integrity defects, namely: 1 − the defect induced by heavy metals (Fe.Cu) at a practically important low concentration range of 1×10 10 to 1×10 11 atoms/cm 3 : 2 − the defects originating from interface roughness and 3 − the defects related to crystal originated particles. At low corona stress fluence, these defects play no role in the tunneling characteristics which follow ideal Fowler-Nordheim characteristics for oxides 50Å or thicker and a contribution from a direct tunneling current for thinner oxides. At high corona stress fluences, gate oxide integrity defects control the magnitude of stress-induced leakage current measured at constan oxide field. It is suggested that the gate oxide integrity role is associated with the enhanced rate of the trap generation during stress. It is noted that the present findings employ a novel methodology for gate oxide integrity monitoring based on corona charging and contact potential difference measurement.