phys. stat. sol. (c) 3, No. 3, 448–451 (2006) / DOI 10.1002/pssc.200564170

© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

SiGe HBT BiCMOS technology for millimeter-wave applications

Alvin Joseph*1

, Mattias Dahlstrom1, Qizhi Liu

1, Bradley Orner

1, Xuefeng Liu

1,

David Sheridan1, Robert Rassel

1, Jim Dunn

1, and David Ahlgren

2

1 IBM Semiconductor Research and Development Center, Essex Junction, VT 05452, USA 2 Hopewell Junction, NY 12590, USA

Received 15 September 2005, revised 23 September 2005, accepted 18 October 2005

Published online 22 February 2006

PACS 84.40.Lj, 85.30.Pq, 84.40.Dc

We present the advances in Silicon Germanium Heterojunction Bipolar Transistor (SiGe HBT) and

BiCMOS technology capabilities to address the emerging millimetre-wave (mmWave) applications. SiGe

HBTs with fMAX performance reaching 350 GHz that are integrated with advanced CMOS and high-

frequency passives is envisioned to allow better integration capability for mmWave applications. This ca-

pability of SiGe HBT BiCMOS technology is discussed relative to an InP HBT technology.

© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The SiGe HBT BiCMOS technology which was commercialized in 1997 with a 50 / 80 GHz (fT / fMAX)

NPN bipolar transistor in the 0.5 µm lithography node, has been a great market success. This success can

be attributed to the ability of these technologies to provide a very competitive integrated radio solution

on a single chip. Armed with the capability of integrating a very high-performance SiGe HBT, high

performance CMOS, and high quality passive devices in a relatively low-cost SiGe BiCMOS technology

opens up the market potential for future millimeter-wave applications, such as, 60 GHz WLAN and 77

GHz automotive radar. Automotive radar applications require a high dynamic range bipolar device with

high linearity and low 1/f noise, attributes easily satisfied by the SiGe HBTs. Increasing the bandwidth

through the techniques of real time correction and synthesis of analog signals using high-performance

CMOS devices provide a compelling argument for a SiGe BiCMOS technology. Compound semicon-

ductor technologies, such as, GaAs pHEMTs dominate the millimeter-wave applications today by pro-

viding the critical performance requirements, albeit at a higher cost. Emerging technology solutions like

GaN HEMTs, GaAs MHEMT, and InP HBTs are expected to provide improved performances for such

applications at higher frequency regimes, however, does not address higher level of integration or cost.

While these esoteric technologies can rival SiGe HBTs for performance, the more conventional silicon-

based SiGe BiCMOS technology offers a unique potential for millimeter-wave transceiver integration on

a chip and thereby reduced cost for mass market penetration [1].

The heart of a SiGe BiCMOS technology is the SiGe HBT that has seen a steady improvement in

performance since its introduction with a 50 GHz fT NPN. The pace of advancement in the SiGe HBT

performance has been remarkable with a recent report of 300 / 350 GHz performances [2]. As the per-

formance of SiGe HBTs are pushed towards 500 GHz, it will be increasingly important to understand the

device performance bottlenecks and the associated tradeoffs in device optimization. In this study, we

chose to compare two high-performance SiGe HBTs built on 0.13µm BiCMOS node with a research-

level high-performance InP HBT. SiGe BiCMOS technologies chosen are: (a) 8HP - 0.13 µm / 210 GHz

production technology [3], (b) 8XP - 0.13 µm / 300 GHz development technology. Both these technolo-

* Corresponding author: e-mail: josepha@us.ibm.com

phys. stat. sol. (c) 3, No. 3 (2006) 449

www.pss-c.com © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

gies share similar process integration techniques to achieve the BiCMOS capability, however, 8XP in-

corporates advanced HBT vertical profile for improved performance capability. The InP HBT is a type-I

DHBT with InGaAs/InAlAs superlattice base-collector grade layers which demonstrates 491 / 415 GHz

performance [4].

Fig. 1 Gummel characteristics for high-performance SiGe HBTs in comparison to an InP HBT.

Fig. 2 Current gain as a function for JC for high-performance SiGe HBTs compared to InP HBT.

Firstly in Fig. 1, we look at the Gummel curves for these 3 devices, indicating that the SiGe HBTs be-

have ideally over a wide range of bias (VBE). The higher Ge ramp utilized in the 8XP base increases its

collector current density (JC) and therefore the current gain (see Fig. 2). In sharp contrast, the InP HBT

has non-ideal collector and base currents leading to a much lower current gain and increased VBE re-

quirement for sustaining similar JC as the SiGe HBT. The forced-IB output curves measured for these

devices, in Fig. 3, shows few interesting differences, namely, the heterojunction in InP HBT introduce

VCE-offset of approximately 0.2 V that are not present in SiGe HBTs. On the other hand, InP HBTs show

higher breakdown voltage compared to the SiGe HBT because of its wider collector bandgap. High-JC

operation cause self-heating as observed in the output curves, however, we expect that the higher thermal

conductivity of silicon substrate relative to the InP substrate allows for better thermal management and

the ability to reliably operate at the peak-fT bias conditions.

1.E-09

1.E-08

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lle

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m2)

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InP HBT

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Collector Current Density (mA/µm2)

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rre

nt

Ga

in

8HP

8XP

InP HBT

450 A. Joseph et al.: SiGe HBT BiCMOS technology for millimeter-wave applications

© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.pss-c.com

Fig. 3 Output curves for multiple high-performance SiGe HBTs compared to InP HBT.

Fig. 4 Small-signal (fT and fMAX) performance of high-performance SiGe HBTs relative to InP HBT.

Fig. 5 Noise figure performance of 200 / 280 GHz (fT / fMAX) high-performance SiGe HBT in 8HP.

In Fig. 4, relative to the 8HP device the tighter vertical profile design utilized in the 8XP HBT improves

the fT to 300 GHz. Since the CCB increases with the fT improvement one attains by the collector optimiza-

tion, the base resistance (Rbb) has to be commensurately reduced to improve fMAX simultaneously. In

8XP, with the optimization of the extrinsic base profile we were able to achieve an fMAX of 330 GHz and

0

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0.12 x 36 µm2

phys. stat. sol. (c) 3, No. 3 (2006) 451

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can be further improved to 400 GHz. Clearly, the lithographical advantage in SiGe BiCMOS technology

allows low-power operation compared to InP HBTs. While the InP HBT attains 491 GHz fT due to the

reduced collector-base transit time (τCB), the SiGe HBT achieves 300 GHz at ~2x lower IC. Also, the

reduction in Rbb leads to improved NFmin at millimeter-wave frequencies for the SiGe HBTs (see Fig. 5).

Such device trends are expected to continue into the future with 500+ GHz SiGe HBTs.

Fig. 6 RF performance of PIN diodes built in 8HP.

Compound semiconductor technologies possess favorable technology features such as, semi-insulating

substrate, through-via holes etc., which are important for millimeter-wave applications. For a fully inte-

grated transceiver solution at millimeter-wave frequencies, the SiGe BiCMOS technology needs to ad-

dress transmission lines for tuners, THz Schottky barrier diode for mixers, low insertion loss PIN diode

T/R switches, higher resistivity substrate for lower loss, and through wafer via-hole features [5]. As an

example, Fig. 6, shows the RF performance of a native vertical PIN diode built in 8HP that has been

improved to 13db isolation at 60 GHz by simple process modifications. Further advances in these capa-

bilities along with the HBT performance improvement will be the key to success of SiGe BiCMOS tech-

nologies at millimeter-wave applications

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HBT technology with fMAX / fT =350 / 300 GHz and gate delay below 3.3 ps, Tech. Dig. IEEE Internat. Electron

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2061–2069 (2005).

[5] P. Russer, IEEE Trans. Microw. Theory Tech. 46(5), Part 2,590–603 (1998).

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B)

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PIN Diode

8HP

8HP w/ thicker i-region