The preparation and application of tantalum thin film passive components

Abstract

The paper commences with a comparison of thin film and diffused passive components, then describes the methods of fabricating resistors and capacitors by using sputtered tantalum and also inductors using nichrome/gold. The reasons for choosing tantalum as the resistor material and sputtering as the deposition method are discussed.The work described in the paper has concentrated on making resistor and capacitor dimensions as small as possible without seriously affecting their properties. Resistors less than 0.001 in wide and capacitors with 1 pF per 0.001 in square of electrode area can be made, so that small, and thus economical, circuits can be realized.The performance of thin film resistors, capacitors and inductors is given and one section is devoted to the behaviour of resistors when dissipating high powers (over 1 kW/in2) at elevated temperatures.Methods of bringing together active devices and the thin film components are considered, emphasizing that since the active and passive devices can be made small, then the method of combining the two should take advantage of these small dimensions. The two methods discussed are the ‘flip-chip’ techniques for adding active devices to a substrate with thin film components and the use of an active substrate, in which the thin film components are fabricated on oxidized silicon which contains the active devices. The use of ‘flip-chip’ techniques for mounting integrated circuits on thin film interconnection patterns is also discussed.Examples are given which demonstrate how thin film resistors, capacitors and inductors with active or passive substrates can be used in electronic circuits.