SiGe Heterojunction Bipolar Technology Research Articles

SiGe HBT serial transmitter architecture for high speed variable bit rate intercomputer networking

A monolithic transmitter architecture that addresses difficulties in data retiming at high bit rates has been designed and fabricated. It utilises a quarter-frequency multiplexing scheme, a fully symmetric multiplexer and a feedforward interpolated ring voltage controlled oscillator (VCO), to transmit data in excess of 20 Gbit/s. The symmetric multiplexer has full input and output symmetry designed to have the same delay from any input to the output. Each stage in the VCO controls its delay by linearly interpolating the signals from the previous two stages, yielding a VCO tuning range of 3.7 to 5.5 GHz with a phase noise of −90.2 dBc/Hz at 1 MHz. SiGe heterojunction bipolar technology (HBT) technology with an fT of 50 GHz was used in this design.

Materials and technology issues for SiGe heterojunction bipolar transistors

This paper reviews progress in SiGe heterojunction bipolar technology, with particular emphasis on the influence of materials issues on the technology performance. Low-temperature epitaxy and transient enhanced diffusion are identified as the main materials issues. Three epitaxy approaches are described, namely differential epitaxy, selective epitaxy, and combined selective and non-selective epitaxy. Differential epitaxy has the advantage of a simple growth process, selective epitaxy the advantage that an extrinsic base implant is not needed, and combined expitaxy the advantage that the Si collector and SiGe base can be grown in a single step. Transient enhanced diffusion of the boron in the base is shown to be a constraint on transistor performance, and the incorporation of a carbon concentration of ≈1×10 20 cm −3 in the base is shown to ease this constraint. Preliminary results on SiGe HBTs on wafer bonded SOI substrates are reported. The SOI transistors have characteristics comparable to those of bulk transistors, but the advantage of a gain that is a factor of approximately two higher.

Dopant diffusion control by adding carbon into Si and SiGe: principles and device application

The incorporation of low concentrations of carbon (<10 20 cm −3) into the SiGe region of a heterojunction bipolar transistor (HBT) can significantly suppress boron outdiffusion caused by subsequent processing steps. This effect can be described by coupled diffusion of carbon atoms and Si point defects. We discuss the increase in performance and process margins in SiGe heterojunction bipolar technology by adding carbon. SiGe:C HBTs demonstrate excellent static parameters, exceeding the performance of state-of-the-art SiGe HBTs. Carbon also enhances the high frequency performance, because it allows one to use a high B doping level in a very thin SiGe base layer without outdiffusion from SiGe, even if applying post-epitaxial implants and anneals. Finally, we demonstrate the first modular integration of SiGe:C HBTs into a 0.25 μm, epi-free, dual-gate CMOS platform.

A fully integrated 40-Gb/s clock and data recovery IC with 1:4 DEMUX in SiGe technology

In this paper, a fully integrated 40-Gb/s clock and data recovery (CDR) IC with additional 1:4 demultiplexer (DEMUX) functionality is presented. The IC is implemented in a state-of-the-art production SiGe process. Its phase-locked-loop-based architecture with bang-bang-type phase detector (PD) provides maximum robustness. To the authors' best knowledge, it is the first 40-Gb/s CDR IC fabricated in a SiGe heterojunction bipolar technology (HBT). The measurement results demonstrate an input sensitivity of 42-mV single-ended data input swing at a bit-error rate (BER) of 10/sup -10/. As demonstrated in optical transmission experiments with the IC embedded in a 40-Gb/s link, the CDR/DEMUX shows complete functionality as a single-chip-receiver IC. A BER of 10/sup -10/ requires an optical signal-to-noise ratio of 23.3 dB.

Increasing process margin in SiGe heterojunction bipolar technology by adding carbon

The incorporation of low carbon concentration within the SiGe region of a heterojunction bipolar transistor (HBT) can significantly suppress boron outdiffusion caused by a variety of subsequent processing steps. Thus, it provides greater flexibility in process design and wider latitude in process margin. We demonstrate almost ideal base current characteristics and cutoff, maximum oscillation frequencies of more than 70 GHz, and delays per stage down to 15 ps for ring oscillators with integrated SiGe:C HBT's.

Si-Ge heterojunction bipolar technology for high-speed integrated circuits

This review discusses the fundamentals of SiGe epitaxial base heterojunction bipolar transistor (HBT) technology that have been developed for use in analog and mixed-signal applications in the 1–20 GHz range. The basic principles of operation of the graded base SiGe HBT are reviewed. These principles are then used to explore the design optimization for analog applications. Device results are presented that illustrate some important trade-offs in device design. A discussion of the use of UHV/CVD for the deposition of the epitaxial base profile is followed by an overview of the integrated process. This process, which has been installed on 200 mm wafers in IBM's Advanced Semiconductor Technology Center in Hopewell Junction, N.Y., also includes a full range of support devices. The process has demonstrated SiGe HBT performance, reliability, and yield in a CMOS fabrication with the addition of only one tool for UHV/CVD deposition of the epi-base and, with minimal additional process steps, can be used to fabricate full BiCMOS designs. This paper concludes with a discussion of high-performance circuits fabricated to date, including ECL ring'oscillators, power amplifiers, low-noise amplifiers, voltage-controlled oscillators, and finally a 12-bit DAC that features nearly 3000 SiGe HBT devices demonstrating medium-scale integration.