Katsuyoshi Washio

A 3-10 GHz bandwidth low-noise and low-power amplifier for full-band UWB communications in 0.25- /spl mu/m SiGe BiCMOS technology

We have developed a SiGe HBT low-noise amplifier (LNA) for ultra-wideband (UWB) systems. We reduced the noise figure (NF) over the frequency range from 3.1 to 10.6 GHz (the FCC-specified UWB range) by using a novel LNA structure with an inductor-terminated, common-base input stage in front of a resistive-feedback amplifier. The circuit topology simultaneously enables increased gain for the input stage and wideband noise matching. On-chip measurement using microwave probes has shown that the LNA - fabricated using commercially available 0.25- /spl mu/m SOI SiGe BiCMOS technology - provides a wide 3-dB bandwidth of 14.5 GHz, an S21 of 22 dB, and a low noise figure ranging from 2.7 dB to 3.9 dB, along with low power consumption of 13.2 mW. Deviation of the S21 group delay is kept within 25 ps to ensure faithful signal amplification. The LNA occupies a chip area of 0.49 mm/sup 2/.

A wide-dynamic-range, high-transimpedance Si bipolar preamplifier IC for 10-Gb/s optical fiber links

A wide-dynamic-range, high-transimpedance preamplifier IC for 10-Gb/s optical fiber links was developed using a 0.3-/spl mu/m Si bipolar process. The preamplifier with a limiting amplifier enables a wide dynamic range from 16 /spl mu/App to 2.5 mApp and a high transimpedance of 1 k/spl Omega/ (2 k/spl Omega/ in the differential output mode). Moreover, careful circuit design achieves a transimpedance fluctuation of 0.5 dBR and an average equivalent input noise current density of 12 pA//spl radic/Hz. This preamplifier IC has the highest transimpedance of any Si bipolar preamplifier for 10-Gb/s operation. Thus, the preamplifier is suitable for 10-Gb/s short-haul optical fiber links and can be used to provide a low-cost system.

SiGe-on-insulator substrate fabricated by melt solidification for a strained-silicon complementary metal–oxide–semiconductor

We have developed a novel technique for fabricating completely strain-relaxed SiGe-on-insulator substrates. It features melt solidification to solve the problems of high defect density and a rough surface concerning SiGe substrates for a strained-silicon complementary metal–oxide–semiconductor. The technique involves three main steps: (1) growth of a SiGe layer on a silicon-on-insulator (SOI) substrate, (2) SiO2 capping to prevent germanium evaporation during annealing, and (3) melting and solidifying the SiGe layer accompanied with germanium diffusion into the SOI layer. The defect density of the fabricated substrate is less than 1000 cm−2 and its surface roughness is 0.39 nm (rms).

Ultra-low-power and high-speed SiGe base bipolar transistors for wireless telecommunication systems

Ultra-low-power and high-speed SiGe base bipolar transistors that can be used in RF sections of multi-GHz telecommunication systems have been developed. The SiGe base and a poly-Si/SiGe base-contact were formed by selective growth in a self-aligned manner. The transistors have a very small base-collector capacitance (below 1 fF for an emitter area of 0.2/spl times/0.7 /spl mu/m) and exhibit a high maximum oscillation frequency (30-70 GHz) at low current (5-100 /spl mu/A). The power-delay product of an ECL ring oscillator is only 5.1 fJ/gate for a 250-mV voltage swing. The maximum toggle frequency of a one-eighth static divider is 4.7 GHz at a switching current of 68 /spl mu/A/FF.

HCl-free selective epitaxial Si-Ge growth by LPCVD for high-frequency HBTs

Low-temperature HCl-free selective silicon germanium epitaxial growth using low-pressure chemical vapor deposition was developed. By utilizing the incubation period of the poly-SiGe growth on SiO/sub 2/, sufficient selectivity was obtained without the use of HCl gas. The advantages of this HCl-free process are sufficient growth rate at low temperature (660/spl deg/C) and capability of high-concentration boron doping without surface roughening. The thickness uniformity of the selectively grown layers throughout a wafer was good and the local loading effect did not appear. These results show the process can be used for fabricating heterojunction bipolar transistors (HBTs). The HBTs fabricated using the process have excellent yields and high-frequency characteristics, that is, 80-GHz cutoff frequency and 160-GHz maximum oscillation frequency. These characteristics and good uniformity of cutoff frequency throughout a wafer show that developed selective growth process can be applied to production of SiGe HBTs.

Self-aligned complementary bipolar technology for low-power dissipation and ultra-high-speed LSIs

Fully symmetrical complementary bipolar transistors for low power-dissipation and ultra-high-speed LSIs have been integrated in the same chip using a 0.3-/spl mu/m SPOTEC process. Reducing the surface concentration of the boron by oxidation at the surface of the boron diffusion layer suppressed the upward diffusion of boron from the subcollector of the pnp transistor during epitaxial growth. This enabled thin epitaxial layer growth for both npn and pnp transistors simultaneously. Cutoff frequencies of 30 and 32 GHz were obtained in npn and pnp transistors, respectively. Simulated results showed that the power dissipation is reduced to 1/5 in a complementary active pull-down circuit compared with an ECL circuit. >

100-GHz f/sub T/ Si homojunction bipolar technology

Rapid vapor-phase doping (RVD) provides very shallow and abrupt boron profiles. A cutoff-frequency of 100 GHz was achieved with a Si BJT having a base formed by RVD. Self-aligned metal/IDP (SMI) technology can reduce base resistance and collector capacitance. Combining RVD with SMI technology, a maximum oscillation frequency of 74 GHz and a 13.6-ps delay time in an ECL ring oscillator were achieved. The results showed homojunction transistors are valid for future high-speed and high-frequency applications.

Design aspects of 32.7-GHz bandwidth AGC amplifier IC with wide dynamic-range implemented in SiGe HBT

The design methodology for optimizing the peaking control of the variable gain amplifier stage and a self-aligned selective-epitaxial SiGe HBT allow the implementation of an AGC amplifier IC with both a wide bandwidth of 32.7 GHz and a wide input dynamic-range of 19 dB, respectively. A low noise-figure of 18 dB and a clear eye diagram at 25 Gb/s were achieved.

12-ps ECL using low-base-resistance Si bipolar transistor by self-aligned metal/IDP technology

A self-aligned metal/IDP (SMI) technology is proposed to reduce the external base resistance and to enable fabrication of high-speed bipolar transistors. This SMI technology produces a self-aligned base electrode of stacked layers of metal and in situ-doped poly-Si (LDP) with a small thermal budget by selective tungsten CVD. It provides the low base resistance and a shallow link base for the small-collector capacitance and the high-cutoff frequency. The base resistance is reduced to a half that in a transistor having a conventional poly-Si base electrode. A maximum oscillation frequency of 81 GHz and a 12.2-ps gate delay time in an ECL ring oscillator at a voltage swing of 250 mV were achieved by using the SMI technology even with an ion-implanted base.

A variable inductor using mutual-current control and application to a SiGe 4.5-GHz VCO for wide tuning range

A novel variable inductor using mutual current control was developed and applied to a 4.5-GHz SiGe voltage controlled oscillator (VCO). It consists of a primary inductor, a secondary inductor, and a variable capacitor, and its inductance can be tuned by adjusting the capacitance of the capacitor. It was designed for application to a proposed 4.5-GHz VCO in 0.25-/spl mu/m SiGe BiCMOS technology. It exhibited a large inductance variation of 22% and a high quality factor of 24 at 4.5 GHz in electro-magnetic simulation. The VCO has a 1.2-GHz tuning range, 32% wider than that of a conventional VCO, and a low phase noise of -121.8 dBc/Hz (at a 1-MHz offset frequency).