In‐situ Electrical Measurements on Thick Film Dielectrics

In this paper, it is shown that the so‐called in‐situ electrical measurement technique is a valuable tool for understanding failure mechanisms in thick film dielectrics. The technique makes it possible to measure important electrical characteristics of thick film dielectric systems in the temperature range from room temperature up to 900°C. This information is essential to understand failure mechanisms and to optimise the system with respect to quality and reliability. Mainly two electrical properties have been investigated: (i) the electrical resistance of the dielectric as a function of temperature and (ii) the spontaneous electromotive force occurring at higher temperatures between two metal layers with the dielectric in between. A significant result of the work is the observation of a close correlation between the leakage current measured through the dielectric at elevated temperatures, and the ability of the dielectric to resist shorting and blistering effects during the preparation of circuits. Secondly, from in‐situ voltage measurements, it was confirmed that the mixed metallurgy system Au(bottom)‐dielectric‐Ag(top) acts at 850°C as a spontaneous battery, and the battery voltage (i.e., the spontaneous electromotive force) was measured. Depending on the type of dielectric, a battery voltage up to 200 mV between the two metal layers was observed. As a result of this spontaneous electromotive force, blistering occurs. The battery voltage was shown to be much smaller in unmixed metallurgy systems with Ag(bottom)‐dielectric‐Ag(top) or Au(bottom)‐dielectric‐Au(top). However, if an external voltage of 300 mV is applied to such a system during a temperature profile up to 850°C, blisters can also be induced. This shows unambiguously that blistering is a voltage driven effect.