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 integrity 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 strategies, such as employing photosensitive polyimides and electrochemically formed encapsulation, were investigated in an attempt to eliminate procedures at the individual device level. Performing as many fabrication steps as possible at the wafer level leads to higher yields and reduces fabrication costs by introducing automated processes. Electrochemical testing procedures at different fabrication stages of chemically sensitive field effect transistors are also presented.