Current Voltage Characteristics through Grains and Grain Boundaries of High-k Dielectric Thin Films Measured by Tunneling Atomic Force Microscopy

Abstract

Leakage current distributions of high‐k dielectric thin films (8 nm HfSixOy and 5 nm ZrO2) were measured by tunneling atomic force microscopy (TUNA). In contrast to the thick HfSixOy film, where grains and grain boundaries can be seen by TUNA topography maps, ZrO2 films show no topography roughness. But large leakage current fluctuations can be seen for both dielectrics by TUNA current images. Higher leakage currents were found to flow through the grain boundaries of both analyzed high‐k dielectric films. Furthermore, local current voltage (I‐V) characteristics could successfully be measured precisely localized at grains and at grain boundaries, respectively, of the ZrO2 film. The obtained local I‐V curves showed significant differences between grains and grain boundaries, respectively. In the case of the ZrO2 film, the leakage current through the grain boundaries was up to 8 times larger than that through the grains at a substrate voltage of −3.5 V.