IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Thin Films Monday Sessions
       Session TF+MM-MoM

Paper TF+MM-MoM4
Correlation Between Gas Response of MIS Field-Effect Sensors and the Bond Strength Between the Metal and the Insulator Layer of the Device

Monday, October 29, 2001, 10:40 am, Room 123

Session: Thin Film Sensors
Presenter: A.E. Åbom, Linköping University, Sweden
Authors: A.E. Åbom, Linköping University, Sweden
L. Hultman, Linköping University, Sweden
M. Eriksson, Linköping University, Sweden
Correspondent: Click to Email
Chemical gas sensors based on the field-effect are used in so called electronic noses as a powerful tool for various applications. The response mechanism is, however, not fully understood. In this work we monitor the material properties in order to understand the sensor properties. The sensors used in this work are Metal Insulator Semiconductor field-effect capacitors. The metal, Pt in this case, is grown by dc magnetron sputtering with varying growth parameters, with the Ar pressure ranging between 3 and 60 mTorr. The response to H@sub 2@ can be described by three steps,@footnote 1@ dissociation of H@sub 2@ molecules on the Pt surface, transport of H atoms through the Pt film and adsorption of H (at the metal-oxide interface) as polarized species (either as dipoles or as charged species). The polarized H affects the electric field as a shift in the applied voltage. This voltage shift increases with increasing hydrogen concentration in the ambient and reaches a saturation value depending on the amount of adsorption sites at the interface and on the magnitude of the polarization. We have found that the largest obtained voltage shift varies with the deposition process. The lower the saturation response is, the stronger the film is adhering to the substrate, as measured with e.g. scratch adhesion tests in a Hysitron TriboScope. From in-situ XPS studies it is found that no chemical reactions occur between Pt and SiO@sub 2@. We will discuss how the varying bond strength between the two materials is caused either by mechanical interlocking or electrostatic forces. We will further elaborate on whether the amount of adsorbed H at the interface changes between the different samples due to a varying electron density@footnote 2@ at the interface, or if the separation between the charges in the dipole layer is varying. @FootnoteText@ @footnote 1@ Lundström K.I., Shivaraman, M.S., Svensson, C.M., J. of Appl. Phys. 46(9) 1975 @footnote 2@ Norskov, J.K. Phys. Rev. B 26 (6) 1982.