Development and characterization of layered, nitrogendoped hafnium oxide and aluminum oxide films for use as wide temperature capacitor dielectrics

Single and multilayer films of nitrogen-doped hafnium oxide and aluminum oxide were fabricated up to 1 mum thick using pulsed DC reactive magnetron sputtering. The relationship between material properties and dielectric performance was investigated for wide temperature capacitor applications. A thorough characterization of the material and dielectric properties of single layer, nitrogen-doped aluminum oxide and nitrogen-doped hafnium oxide films was performed, including morphology, roughness, grain size, composition, dielectric constant, dissipation factor, leakage current, and breakdown strength. The dielectric properties of the films were also characterized across a temperature range of -50 to 200 °C to investigate temperature stability as well as the conduction mechanisms that led to dielectric loss and breakdown in a capacitor at elevated temperatures. Following characterization of the single layer films, multilayer films of two, three, and five layers were constructed and compared to the single layer films to see how the dielectric properties of the films changed with the addition of multiple dielectric interfaces. The dielectric properties of the films were found to improve significantly when additional dielectric/dielectric interfaces were present. Increasing the number of layers was found to considerably reduce leakage current and dissipation factor while increasing the breakdown strength by up to 75%. An investigation of the conduction mechanism of the films indicated that although the same conduction processes were occurring in both the single and multilayer films (Poole-Frenkel conduction and Schottky emission), the manner in which the conduction occurred changed as well as the temperature at which the conduction mechanism began to dominate, ultimately prolonging the breakdown of the dielectric. The results suggest that the layered architecture of the films aids in the dissipation of runaway charges at the dielectric/dielectric interface that lead to decreased loss and increased breakdown strength of the capacitor. The understanding of the fundamental processes that occur in dielectric films and how they affect capacitor performance allows for more advanced capacitors to be manufactured by simply changing the architectures of well-known systems as opposed to developing entirely new materials systems.