Tantalum-film technology

In tantalum film circuitry, capacitors, resistors, and rudimentary interconnections are all produced in a single pattern of tantalum. Important processes are discussed in detail including 1) sputtering, by which tantalum films are produced, 2) pattern generation, and 3) anodization, by which capacitor dielectrics are formed and by which resistors are protected and adjusted to value. Predominantly the discussion is based on developments and practices of Bell Telephone Laboratories. Capacitors withstand stresses of several million volts/cm, have low leakages, a temperature coefficient of +200 to +250 ppm/°C, and a dissipation factor at 1 kc of 1 per cent maximum. Resistors of outstanding quality can be made from tantalum nitride produced by reactive sputtering. These resistors have high electrical stability and low temperature coefficients and can be fabricated to initial tolerances as low as 0.01 per cent. Because of the versatility of tantalum technology, a wide variety of circuit types can be fabricated. Tantalum technology is particularly valuable in the fabrication of thin-film integrated circuits with severe precision requirements as in the precise tuning of thin-film notch filters, and for distributed parameter networks.