AES, AFM AND TEM STUDIES OF NICR THIN-FILMS FOR CAPACITIVE HUMIDITY SENSORS

A few hundred nanometre thick NiCr layers form the capacitance humidit y sensor electrodes. The electrodes must have the adequate electric re sistance, low mechanical tensions, proper elasticity coefficient in or der to prevent the corruption of the NiCr-dielectric layer joint when the dielectric is saturated by the water vapour. The upper electrode m ust be permeable for the water vapour in order to permit the water vap our to diffuse into the dielectric. The sufficient permeability of the NiCr film is obtained by an evaporation under the deposition incidenc e angle of 75 degrees. The deposition angle is defined as the angle be tween the normal to the substrate surface and the normal to the evapor ating source. The detailed results of NiCr thin film investigation by AES, AFM and TEM are presented. The NiCr thin films are non-homogeneou s and are strongly dependent on deposition conditions. A different vap our pressure of Ni and Cr during the deposition process has a dominant influence on chemical composition of the NiCr thin films. The NiCr th in film evaporated under 0 degrees incidence angle is cracky, while th e layer evaporated under 75 degrees incidence angle has the columnar s tructure. (C) 1998 Elsevier Science S.A.