Dielectric permittivity of Si/sub 3/N/sub 4/ and SiO/sub 2/ 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 /spl epsi//sub r/'/spl ap/7 to /spl epsi//sub r/'/spl ap/22 for silicon nitride at the low frequency side of the spectrum. Similar results are obtained for silicon oxide. The increase of /spl epsi//sub 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.