Dielectric permittivity of Si3N4 and SiO2 increased by electrode profile and material

The dielectric permittivity of thin films of silicon nitride and silicon oxide deposited on a silicon wafer can considerably be increased by the geometrical form and the material of the counter (gate) electrode. A conventional disc-like electrode either consisting of Pd or Au results in the well known permittivity data for both dielectrics. However, the use of a Pd electrode with a Gaussian-like profile yields an increase of the permittivity from ε_r´≈7 to ε _r´≈22 for silicon nitride at the low frequency side of the spectrum. Similar results are obtained for silicon oxide. The increase of ε_r´ is assumed to be due to an enhanced absorption of hydrogen (protons) from the atmosphere by the thin and scattered edges of the Gaussian-like Pd electrode. The protons diffuse into the dielectric film and contribute directly or indirectly to the permittivity