Low-frequency noise behavior of polysilicon emitter bipolar junction transistors: a review

Abstract

For many analog integrated circuit applications, the polysilicon emitter bipolar junction transistor (PE-BJT) is still the preferred choice because of its higher operational frequency and lower noise performance characteristics compared to MOS transistors of similar active areas and at similar biasing currents. In this paper, we begin by motivating the reader with reasons why bipolar transistors are still of great interest for analog integrated circuits. This motivation includes a comparison between BJT and the MOSFET using a simple small-signal equivalent circuit to derive important parameters that can be used to compare these two technologies. An extensive review of the popular theories used to explain low frequency noise results is presented. However, in almost all instances, these theories have not been fully tested. The effects of different processing technologies and conditions on the noise performance of PE-BJTs is reviewed and a summary of some of the key technological steps and device parameters and their effects on noise is discussed. The effects of temperature and emitter geometries scaling is reviewed. It is shown that dispersion of the low frequency noise in ultra-small geometries is a serious issue since the rate of increase of the noise dispersion is faster than the noise itself as the emitter geometry is scaled to smaller values. Finally, some ideas for future research on PE-BJTs, some of which are also applicable to SiGe heteorjunction bipolar transistors and MOSFETs, are presented after the conclusions.Key words: 1/f noise in bipolar transistors, low frequency noise, noise in scaled devices, impact of technology on noise performance, noise comparison, temperature effects, figure-of-merit, polysilicon emitter bipolar junction transistors

1/f noise in SiGe HBTs fabricated on CMOS-compatible thin-film SOI

“…Figure 7 shows the base current noise power spectral density S IB of fully-depleted SiGe HBTs-on-SOI (interpolated at 10 Hz) versus emitter area A E , for increasing base current bias I B . The data shows a reciprocal emitter area dependence, which is typical of most SiGe HBTs, as reported in [11,12,13]. The temperature dependence of the 1/f noise in SiGe HBTs-on-SOI has also been investigated across the temperature range of 27°C and 200°C, as shown in Figure 8.…”

Dispersion study of DC and Low Frequency Noise in SiGe:C Heterojunction Bipolar Transistors used for mm-Wave to Terahertz applications

“…These current and areal dependencies lead us to deduct that the main 1/f noise sources are homogenously distributed in the emitter-base (EB) junction [7,8].…”

<formula formulatype="inline"><tex Notation="TeX">$1/f$</tex></formula> Noise Model for NPN Bipolar Junction Transistors Based on Radiation Effect

“…When the exponent is close to unity, the Hooge mobility fluctuations are believed to be responsible for the low frequency noise, while is indicative of carrier number fluctuations. Several noise models of bipolar junction transistors were introduced in detail in [20].…”