Beam-lead Schottky-barrier diodes for low-noise integrated microwave mixers

Abstract

This paper describes the fabrication and performance of beam lead <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</tex> on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n^{+}</tex> silicon-molybdenum, barrier dual Schottky diodes. The fabrication is by a process sequence which allows the use of a single molybdenum gold-metal deposition step for both the Schottky barrier and beam-lead interconnection system. Typical <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I-V</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/C^{2}-V</tex> plots indicate uniformity of barrier heigh and n factor. Values of n less than 1.1 were measured with the barrier height at 0.61 eV. Measurements of change in barrier height with temperature up to 500°C show less than ± 10 mV variation. Dc characteristics of these devices give forward current matching of ± 10 mV at 1 mA. The R <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</inf> is 10 ohms and the C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</inf> is less than 0.3 pF, giving an RC product less than 3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> seconds. Using these devices in a chrome-gold on alumina microstrip integrated mixer, overall single sideband noise figures of 6.5-7.0 dB were measured, with a 1.5 dB IF noise figure, at 9.4 GHz. Measured noise figure was essentially constant over a range of 1-10 mW of local oscillator power, and the diodes will with stand over 500 mW CW RF power. These values compare favorably with discrete packaged devices. Fabrication in series pairs, matched quads or other configurations can be accomplished with good uniformity.