Leakage current and dielectric breakdown behavior in annealed SiO2 aerogel films

Leakage current and dielectric breakdown behavior in annealed SiO2 aerogel films for intermetal dielectric applications was investigated in a metal-insulator-semiconductor structure. SiO2 aerogel films with porosities of 70% exhibited Poole-Frenkel conduction both before and after annealing. After annealing at 450 and 700 degrees C, the leakage current density improved over the current range of the applied field. This behavior was characterized by different chemical evolutions in each annealing step, beginning with the removal of residual organics up to 450 degrees C and then with the removal of residual surface hydroxyl, along with subsequent microstructural changes, up to 700 degrees C. Except in the few initial failure modes, intrinsic dielectric breakdown was not observed up to 1 MV/cm for as-deposited or 450 degrees C annealed films. However, in the case of the 700 degrees C annealed film, the dielectric breakdown strength was degraded. It was inferred that this early breakdown in 700 degrees C annealed film was caused by a randomly enhanced electric field at the irregular asperity of the rough interface. This was confirmed by investigation of the interface roughness between the electrode and the film. (C) 1998 American Institute of Physics.