Spatial analysis of failure sites in large area MIM capacitors using wavelets

Abstract

The spatial distribution of failure sites in large area (104–105μm2) metal-insulator-metal (MIM) capacitors with high-K dielectric (HfO2) is investigated using angular wavelets. The failure sites are the consequence of constant or ramped electrical stress applied on the capacitors. Because of the important local thermal effects that take place during stress, the failure sites become visible as a point pattern on the top metal electrode. In case of less damaged devices, the results obtained with the wavelet variance method are consistent with an isotropic distribution of breakdown spots as expected for a Poisson point process (complete spatial randomness). On the contrary, for severely damaged devices, the method shows signs of preferred directions of degradation related to the voltage probe location. In this case, the anisotropy is confirmed by alternative spatial statistics methods such as the angular point-to-event distribution and the pair correlation function.