SiGe HBT for application in BiCMOS technology: II. Design, technology and performance

Abstract

SiGe technology has acquired great importance in recent years. Recent advances made in the SiGe HBT technology for analogue applications are discussed in this two-part review paper. Strain, stability, reliability, mobility of charge carriers, bandgap narrowing and effective density of states of SiGe layers have been discussed in part I. This paper (part II) is devoted to the HBTs: their design and performance. The two designs of the HBTs developed by IBM and by Daimler-Benz are discussed. Their relative merits and constraints imposed by the stability criterion on each design are described. The technology used for implementing the two designs is also described. The dc and ac characteristics and Ge profiles needed to optimize different figures of merit are discussed in detail. The parasitic barriers created by outdiffusion of B and also on operating the HBT at high current densities are explained. High injection barriers can be suppressed by a special design of the Ge profiles. Introduction of C in the base suppresses outdiffusion of B. HBTs with SiGeC base layers are discussed. Issues involved in simultaneous optimization of f T , f max and BV CEO are addressed. Values of f T , f max and BV CEO of high-performance HBTs are compiled and given in a table. The noise characteristics of the SiGe HBTs are far superior to those of III-V devices. Noise in SiGe HBTs is discussed in detail. Finally, a summary of selected circuits that have been fabricated using SiGe HBTs is given.

Electrodeposition of Ge, Si and SixGe1−x from an air- and water-stable ionic liquid

“…9,10 A lot of work has also been done on the use of ''SiGe'' HBTs for bipolar complementary metal oxide semiconductor (BiCMOS) applica-tions. 11,12 The high operating frequency of ''SiGe'' BiCMOS (up to 120 GHz) makes it an attractive material for the dualuse application spaces such as wireless communications and advanced radar systems. 13 However, the application of ''SiGe'' is not only limited to HBTs; investigations on the use of this material in variety of devices such as solar cells, 14 modulation-doped field-effect transistors (MODFET), 15,16 resonant tunneling diodes (RTD), [17][18][19] infrared detectors 20 and light-emitting diodes 21 have been considered.…”

Characterization of silicon–germanium heterojunction bipolar transistors degradation in silicon–germanium BiCMOS technologies

“…As the B profile is getting broader, the width of the p-type base region also increases and Ge-free base regions with larger band-gaps form. In the emitterbase junction, the absence of Ge atoms reduces the emitter-injection efficiency and lowers the current gain [6]. A parasitic energy barrier occurring in the Ge-free collectorbase (CB) junction suppresses the electron transport toward the collector region, which reduces the early voltage and degrades the AC characteristics [6].…”

“…In the emitterbase junction, the absence of Ge atoms reduces the emitter-injection efficiency and lowers the current gain [6]. A parasitic energy barrier occurring in the Ge-free collectorbase (CB) junction suppresses the electron transport toward the collector region, which reduces the early voltage and degrades the AC characteristics [6]. In addition, the BV CEO of the HDC HBT was smaller than that of the control HBT, which should be attributed to the decrease in the collector-base breakdown voltages (BV CBO ) as shown in Fig.…”

Controllable Growth and Unexpected Effects of Ge Nanocrystals

“…22 A variety of methods such as thermal evaporation, magnetron sputtering, and chemical vapor deposition are available to prepare Au/Ge thin films or nanoparticles. Since the properties of thin films strongly depend on their microstructure, composition, atomic structure, local chemistry of interfaces, and crystal defects, which all result from the fabrication process, the influence of morphology and nanostructure on material properties is especially remarkable.…”