PRESENT STATE OF FABRICATION OF CHEMICALLY SENSITIVE FIELD-EFFECT TRANSISTORS

Fabrication of reliable chemically sensitive field effect transistors still poses significant technical difficulties. Problems related to in tegrity of the solid state part of the device, integrity of the final sensor package, definition of the sensitive areas in multisensors and casting of the selective membranes have been addressed. Several strate gies, such as employing photosensitive polyimides and electrochemicall y formed encapsulation, were investigated in an attempt to eliminate p rocedures at the individual device level. Performing as many fabricati on steps as possible at the wafer level leads to higher yields and red uces fabrication costs by introducing automated processes. Electrochem ical testing procedures at different fabrication stages of chemically sensitive field effect transistors are also presented.