The performance and evaluation of thin film insulating crossovers

Abstract

Various thin film insulating crossovers were studied. All of the crossovers had silicon-monoxide as the dielectric film. The common crossover area was 100 sq. mils (6·45 × 10 −4 cm 2). Although several dielectric thicknesses were investigated, 5000 Å was chosen as the minimum thickness for highly reliable crossovers. Eight crossover combinations were fabricated. These were: Upper Conductor Lower conductor chromium-gold chromium chromium-gold chromium-gold aluminum chromium-gold chromium-gold aluminum aluminum aluminum chromium-gold tantalum-aluminum aluminum tantalum-aluminum aluminum chromium The first 5 crossover combinations were selected for subjection to various environmental stresses. Crossover electrical parameters (capacitance and dissipation factor measured at 1 kHz, d.c. insulation resistance, breakdown voltage, and withstanding voltage) and physical parameters (film adhesion, compatability and degradation), were measured. In addition, the electrical parameters were measured periodically during the environmental stresses. The stresses were: storage at −55°C, 125°C, 200°C for 1000 hr; accelerated ageing at 300°C for 100 hr; temperature cycling from room temperature to 65°C in high humidity; temperature cycling from −65°C to 125°C; and the determination of the breakdown voltage as a function of time. None of the crossovers were overcoated or protected in any way. The breakdown voltage was found to be the most important parameter for evaluation. The distribution of breakdown voltages for a given sample population was found to contain two peaks indicating two failure mechanisms. The experimental procedure for the fabrication and the measuring techniques are described. A merit rating for the crossovers studied is presented. Part of this work was supported by the U.S. Army Electronics Command, Fort Monmouth, New Jersey. Contract No. DA-28-043 AMC-01482(E), 1 July 1965 through 30 September 1966.