A TDDB model of Si3N4-based capacitors in GaAs MMICs

The metal-insulator-metal capacitor (MIMCAP) is a key passive component utilized in GaAs-based MMIC technologies. The dielectric used in MIMCAPs is silicon nitride (Si₃N₄) because of its compatibility with the GaAs processing. This type of capacitor has been ubiquitous in this technology with larger and larger circuits requiring more capacitance per die. There has been a growing realization that the defects present in the nitride affect MMIC product reliability in much the same way as in silicon MOS technologies. In this paper, the reliability of the MIMCAPs is examined by first studying the temperature dependent current conduction in the nitride. Next, the intrinsic breakdown properties of the nitride are determined, and applied to the TDDB theory with suitable modifications. The reliability of MIMCAPs and product die are then predicted. Ramped voltage breakdown measurements on test capacitors as well as long term aging experiments on product die are used to calibrate the TDDB model. Finally, a prediction technique is discussed for product die with arbitrary temperature and voltage histories