GB1287930A - - Google Patents

Abstract

1287930 Thermistors PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 31 Dec 1969 [31 Dec 1968] 63487/69 Heading H1K A thermistor comprises a layer consisting of one or more transition metal oxides formed by cathode sputtering having two spaced electrodes on one face, and an auxiliary electrode layer on the opposite face extending over an area which overlaps the two other electrodes, external connections being made to the two electrodes on the one face. As shown, Fig. 2, a Ge substrate 30 is provided with an insulating layer 31 of silica or alumina on which is deposited a Ni-Cr layer covered with a thicker Ni layer to form an auxiliary electrode layer 32, a layer 33 of thermistor material is deposited by sputtering through a mask, a layer of Ni-Cr is deposited over the surface, photomasked and etched to form two electrodes, 34, 33, to which external connections (not shown) are applied. The structure forms two thermistors connected in series by the auxiliary electrode 32, the current path through the thermistor material being perpendicular to its major surfaces. The upper electrodes 34, 35 extend on to the insulating layer 31 to provide contact pads, Fig. I (not shown). If the substrate is a conductive material which forms an ohmic contact with the thermistor material it may be utilized as the auxiliary electrode. A plurality of thermistors may be formed in a single layer of thermistor material, Figs. 3 and 4 (not shown), by depositing Ni-Cr and Ni layers on a glass substrate (70), photomasking and etching to form a plurality of auxiliary electrodes (71 to 74), depositing a layer (75) of thermistor material over the substrate, vapour depositing Ni-Cr and Ni layers, and photomasking and etching to form two electrodes (76, 77, 78, 79, 80, 81; 82, 83) overlying each of the auxiliary electrodes (71, 72, 73, 74, respectively). The metals Mn; Fe, Co and Ni are mentioned as transition metals whose oxides may be used for the thermistor material which may be deposited by sputtering using a mixed oxide target or by reactive sputtering of the metals in an oxidizing atmosphere.