2-DIMENSIONAL AND 3-DIMENSIONAL INTERDIGITAL CAPACITORS AS BASIC ELEMENTS FOR CHEMICAL SENSORS

Interdigital capacitors (IDCs) as the basic components of miniaturized sensors used in the field of chemical analysis offer a means of optimally matching the component to the properties of the chemically sensitive material. There is also a certain flexibility as regards the choice of the substrate, which constitutes a decisive factor with respect to further signal processing. Thus, for example, IDCs can be produced on ceramics, glass or an Si/SiO2 system. With a corresponding coating they can be used for tests in both liquids and gases. Simulation methods used to obtain the sensitivity as a function of the structural width and structural height of two- or three-dimensional IDC structures are presented. In the case of gas sensors with a thin sensitive layer, whose mechanism is based on the interaction between the surface of the layer and the gas molecules, two-dimensional structures are very useful. In the case of porous gas-sensitive coatings, three-dimensional IDC structures make it possible to utilize bulk effects, which gives rise to a much higher sensitivity.