New suspended gate FET technology for physical deposition of chemically sensitive layers

Abstract The chemically sensitive layer that is located underneath the suspended gate metal of the field-effect transistor has until now been deposited exclusively by electrochemical means. A new method for the physical deposition of the sensitive layer within the suspended gate structure has been developed. By introducing the single-layer lift-off process to the fabrication sequence of the device, it is now possible to deposit selective materials before the suspended gate is made. Therefore general thin-film techniques can be used. This offers the advantage that materials of great interest, such as non-soluble metal oxides, can be deposited. Also all chips on a wafer can be processed at the same time.