Low-Frequency Noise Characterization of BEOL Metal–Insulator–Metal Capacitors

Abstract

Dielectrics are fundamental building blocks in both analog and digital electronic devices, serving various purposes, including insulating metal lines and interconnect levels in the back-end-of-line (BEOL). In this article, we investigate the leakage and low-frequency noise (LFN) properties of three different types of dielectrics, from the low-k organo-silicate glass (OSG3.0) and silica (SiO2) to the high-k alumina (Al2O3). Test structures are large area (up to $200\times 200~\mu $ m2) metal-insulator–metal (MIM) capacitors, with TiN or TaNTa electrodes, that mimic well the BEOL architecture. In particular, to the best of our knowledge, no LFN study has been reported for OSGs, which are the most used class of dielectrics in the BEOL. From a physical side, current-voltage (I–V) characterization reveals that in all three dielectrics, the conduction is bulk dominated and assisted by traps, rather than limited by electrode injection. LFN measurements (LFNMs) show a typical 1/f current power spectral density (PSD) ( ${S}_{I}$ ) for all three dielectrics with a strongly bias-dependent gate noise parameter $(\text {GNP})\propto {S}_{I}/{I}^{{2}}$ (I being the dc current), suggesting a highly nonuniform energy trap distribution, especially for Al2O3 devices. SiO2-based capacitors demonstrated the lowest leakage at equivalent fields and superior noise performance at comparable leakage currents. Al2O3 devices exhibited the highest leakage, while OSG3.0 samples showed the poorest noise characteristics, marked by pronounced electrical instability and nonstationary random telegraph signal (RTS) events.