RF Characterization of Schottky Diodes in 65-nm CMOS

Schottky diodes in 65-nm CMOS have been designed, measured up to 67 GHz, and modeled in the reverse-bias voltage range. An array of 8 × 8 minimum-sized parallel diode junctions is compared with a single-junction diode and to linear arrays of 3, 12, and 64 elements of the same total area. An iterative analysis method and a more detailed equivalent circuit than that used in previous work are developed to extract the junction capacitance, the stray capacitance, and the series resistances separately. Based on the equivalent circuit model, the extrapolation of the diode RF behavior to frequencies beyond the measurement range is discussed. The relevance of the cutoff frequency of the Schottky junction itself for evaluation of the suitability of the diodes in millimeter-wave and terahertz applications is explained.