Nanoscale electrical characterization of thin oxides with conducting atomic force microscopy

Abstract

Atomic force microscopy using with a conductive tip and a highly sensitive preamplifier is used for Fowler-Nordheim (FN) current measurements in the sub-pA range on various thin MOS gate and EEPROM tunneling oxides. Simultaneously with the oxide topography, local oxide thinning and electrically weak spots are detected quantitatively on a nanometer scale length in two dimensions. From the FN-fits to the microscopic I-V measurements, the effective area involved in the tunneling process (50-250 nm/sup 2/) and the local oxide thickness can be determined. The microscopic behaviour agrees excellently with macroscopic I-V curves so that the method can be correlated with standard reliability tests. Since the measurements are performed on the bare oxide surface, the method is suitable for in-line monitoring.