Noise modeling and SiGe profile design tradeoffs for RF applications

This paper investigates SiGe profile design tradeoffs for low-noise RF appl ications at a given technology generation (i.e., fixed minimum feature size and thermal cycle). An intuitive model relating structural parameters and biases to noise parameters is used to identify the noise limiting factors i n a given technology. The noise performance can be improved by pushing more Ge into the base and creating a larger Ge gradient in the base. To maintai n the SiGe film stability, the retrograding of the Ge into the collector ha s to be reduced, leading to a stronger f(T) - I-C roll-off at high injectio n. Two low-noise profiles were designed and fabricated explicitly for impro ving minimum noise figure (NFmin) without sacrificing gain, linearity, freq uency response, or the stability of the SiGe strained layer. A 0.2 dB NFmin was achieved at 2.0 GHz with an associated gain (G(assoc)) of 13 dB.