Jean Roggen

Electrical characterisation and reliability studies of thick film gas sensor structures

The three major problems of gas sensing devices are the sensitivity to gases, the selectivity towards different gases and the electrical stability of the device. This paper describes the study of the electrical stability of a thick film SnO/sub 2/ gas sensor which has been investigated with an in-situ conductance measurement technique, in order to understand the disturbing problems of the resistance drift of the sensor material during the operation of the gas sensor. For this purpose a new test structure has been realised in screen printing technology, such that each layer in the gas sensor can be characterised and the influence of the top layer on underlying layers can be investigated. By using in-situ conductance measurements the relevant electrical properties are measured continuously during a predefined temperature profile. The in-situ technique offers both a high measurement accuracy, as well as the availability of many data points when compared to conventional off-line testing methods. As a result, a complete electrical characterisation of the gas sensor could be done very accurately.

Electromigration: Investigation of heterogeneous systems

Abstract Electromigration is a phenomenon where atoms are driven from their lattice positions due to an electric current. In general two types of electromigration systems can be distinguished: the heterogeneous system, in which electromigration failure occurs at the interface of two distinct parts on the interconnection while in the second, homogeneous case the failure occurs within the interconnection itself. The first type of electromigration is reported in this study and off-chip gold ball bonds on aluminium metallization are used as an example. In-situ electrical measurements of the resistance change as a function of time with different temperature and current stresses are performed. A good understanding of the kinetics of the resistance change could be obtained which helps in the characterisation of the processes active during the degradation of the interconnections.