Metal-insulator-metal capacitors were used for determining the DC and frequency-dependent characteristics of ultra-thin Al2O3 (Th-ox = 22 nm). For this purpose, a state-of-the-art insulating layer was formed using atomic deposition, which enables enhanced performance of devices and application within the back-end of line stage of a CMOS process. As part of the analysis, DC and low frequency CV measurements are used to determine the electric field to breakdown, the dominant conduction mechanisms, and the dielectric constant, whereas small-signal modelling allows for characterizing the frequency-dependent behaviour of the Al2O3 layer using LCR measurements from 100 Hz to 1 MHz. This avoids using dedicated RF test structures as for measuring S-parameters. Moreover, since it is demonstrated here that the parasitic effect of the series impedance associated with the metal electrodes is significant within this frequency range, an RLGC equivalent circuit is used to determine the intrinsic properties of the layer. In this way, the effective loss tangent and dielectric constant were straightforwardly extracted from AC data.
