IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 51, NO. 6, DECEMBER 2004 3781
Proton Radiation Response of Monolithic
Millimeter-Wave Transceiver Building Blocks
Implemented in 200 GHz SiGe Technology
Wei-Min Lance Kuo, Student Member, IEEE, Yuan Lu, Student Member, IEEE, Brian A. Floyd, Member, IEEE,
Becca M. Haugerud, Student Member, IEEE, Akil K. Sutton, Student Member, IEEE,
Ramkumar Krithivasan, Student Member, IEEE, John D. Cressler, Fellow, IEEE, Brian P. Gaucher, Member, IEEE,
Paul W. Marshall, Member, IEEE, Robert A. Reed, Member, IEEE, and Greg Freeman, Senior Member, IEEE
Abstract—This paper presents the first experimental results on
the effects of 63.3 MeV proton irradiation on 60 GHz monolithic
point-to-point broadband space data link transceiver building
blocks implemented in a 200 GHz SiGe heterojunction bipolar
transistor (HBT) technology. A SiGe low-noise amplifier and a
SiGe voltage-controlled oscillator were each irradiated to proton
fluences of ? ?????p/cm?. The device and circuit level
performance degradation associated with these extreme proton
fluences is found to be minimal, suggesting that such SiGe HBT
transceivers should be robust from a proton tolerance perspective
for space applications, without intentional hardening at either the
device or circuit level.
low-noise amplifier (LNA), millimeter-wave, proton irradia-
tion, silicon-germanium (SiGe), transceiver, voltage-controlled
lies in very high bandwidth ( 1 Gb/s) point-to-point commu-
nications data links , . Traditionally, discrete microwave
integrated circuits implemented in III–V technologies (GaAs
modules because they offered significant performance advan-
tages at mm-wave frequencies over Si technologies –.
Unfortunately, such transceiver modules are typically power
hungry, large, heavy and hence costly , . Clearly, for
space applications of such mm-wave data links, achieving low
N IMPORTANT emerging market for millimeter-wave
GHz integratedcircuit (IC) technologies
Manuscript received June1, 2004;revisedSeptember 1, 2004. This workwas
ation Hardened Microelectronics Program, NASA-GSFC under the Electronics
Radiation Characterization Program, IBM, and the Georgia Electronic Design
Center at Georgia Tech.
W.-M. L. Kuo, Y. Lu, B. M. Haugerud, A. K. Sutton, R. Krithivasan,
and J. D. Cressler are with the School of Electrical and Computer Engi-
neering, Georgia Institute of Technology, Atlanta, GA 30308 USA (e-mail:
B. A. Floyd and B. P. Gaucher are with the IBM Research Division, Thomas
J. Watson Research Center, Yorktown Heights, NY 10598 USA.
P. W. Marshall and R. A. Reed are with NASA-GSFC, Greenbelt, MD 20771
G. Freeman is with IBM Microelectronics, Hopewell Junction, NY 12533
Digital Object Identifier 10.1109/TNS.2004.839215
power, small size, light weight, and low cost are essential re-
quirements in addition to maintaining acceptable performance
and high reliability. As will be demonstrated, an alternative
IC technology based on silicon-germanium (SiGe) alloys can
potentially fulfill these requirements , .
SiGe heterojunction bipolar transistor (HBT) technology uti-
lizes bandgap engineering techniques to dramatically improve
transistor-level performance while simultaneously maintaining
strict compatibility with conventional silicon (Si) manufac-
turing . The evolution of SiGe technology is evolving very
rapidly, and has today reached a point where SiGe HBT tech-
nology is of comparable performance with the best-of-breed
eration SiGe HBTs having peak cutoff frequency
200 GHz  and fourth-generation technology having peak
above 300 GHz , the application space for SiGe HBT
technology has further broadened from a variety of analog and
radio frequency (RF) applications to now include monolithi-
cally integrated mm-wave communications systems. SiGe HBT
technology thus combines III–V like device performance with
the high integration, high yield, and hence low cost associated
with Si to facilitate system-on-a-chip solutions. In addition,
SiGe HBTs have also been shown to be robust with respect to
proton irradiation without any additional costly radiation hard-
ening. With these attributes, SiGe HBT technology promises
to provide high performance, high reliability, small size, light
weight, and low cost required for monolithic mm-wave trans-
ceivers for space link applications.
A monolithic mm-wave transceiver capable of operating in
the60GHz ISMband is beingdevelopedusingthird-generation
200 GHz SiGe HBT technology. In addition to short-range
terrestrial wireless broadband applications, such a transceiver
could also find application in inter-satellite communication
links. This paper presents, for the first time, experimental
results on the effects of proton irradiation on critical building
blocks for such a 60 GHz monolithic mm-wave transceiver.
II. PROCESS TECHNOLOGY
The SiGe HBT technology investigated in this paper is the
IBM SiGe 8T technology with 207 GHz peak
peak maximum oscillation frequency
and 285 GHz
. It features
0018-9499/04$20.00 © 2004 IEEE
3782IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 51, NO. 6, DECEMBER 2004
Fig. 1. Schematic cross section of the 200 GHz SiGe HBT.
SUMMARY OF THE SiGe HBT PARAMETERS
copper interconnects with a thick top layer aluminum metal-
lization and a full suite of passive elements. This advance in the
SiGe state-of-the-art to 200 GHz transistor performance was
only achieved by radically altering the structure of previous
SiGe HBT design points. The present technology employs a
novel, reduced thermal cycle, “raised extrinsic base” structure,
and utilizes conventional deep and shallow trench isolation, an
in situ doped polysilicon emitter, and an unconditionally stable,
25% peak Ge, C-doped, graded ultra-high vacuum/chemical
vapor deposition (UHV/CVD) epitaxial SiGe base. The de-
vice structure has been scaled laterally to 0.12
stripe width in order to minimize base resistance and thus
improve the frequency response and noise characteristics. Such
a raised extrinsic base structure facilitates the elimination of
any out-diffusion of the extrinsic base, thereby significantly
lowering the collector-base junction capacitance. This SiGe
HBT technology has not been intentionally radiation-hardened
in any way. A schematic cross section of the SiGe HBT is
shown in Fig. 1. Typical transistor parameters are summarized
in Table I.
The goal of this work was to carefully assess the impact
of radiation exposure on actual 60 GHz monolithic mm-wave
transceiver building blocks implemented in 200 GHz SiGe
HBT technology, and use an additional transistor-level ra-
diation experiment to better understand the observed circuit
response. A 60 GHz mm-wave transceiver block diagram is
shown in Fig. 2. Two key components are chosen for this study:
one is the low-noise amplifier (LNA), which is used to amplify
the received signals while adding minimal noise; the other is
the voltage-controlled oscillator (VCO), which is used to gen-
erate local oscillator (LO) signals for up-and down-conversion
60-GHz mm-wave space communications transceiver block diagram
Fig. 3. Measured forward mode Gummel characteristics.
characterized before and after being irradiated, along with SiGe
HBT dc and ac test structures needed for correlating changes in
circuit performances back to device parameters.
Since extremely few samples of the LNA and the VCO were
available, only one sample of each circuit was irradiated, along
withtwo samplesofdc teststructures and twosamples ofactest
structures, with each sample containing multiple devices. The
samples were irradiated with 63.3 MeV protons at the Crocker
Nuclear Laboratory at the University of California at Davis.
The dosimetry measurements used a five-foil secondary emis-
located several meters upstream of the target establish a beam
spatial uniformity of 15% over a 2.0 cm radius circular area.
Beam currents from about 20 nA to 100 nA allow testing with
proton fluxes from
dosimetry system has been previously described , , and
is accurate to about 10%. At proton fluences of
p/cm , the measured equivalent gamma dose was
approximately 135 and 6,759 krad(Si), respectively. The SiGe
HBT dc test structures, ac test structures, and circuits were irra-
diated with all terminals floating. Previous studies have shown
proton/cm s. The
KUO et al.: PROTON RADIATION RESPONSE OF MONOLITHIC MILLIMETER-WAVE TRANSCEIVER BUILDING BLOCKS 3783
Fig. 4. Measured inverse mode Gummel characteristics.
Fig. 5. Deembedded ?-parameters at peak ? .
Fig. 6.Measured ?
and Mason’s ? versus frequency at peak ? .
that this has minimal effect on the transistor-level radiation re-
sponse . All samples were irradiated to a proton fluence of
Fig. 7. Extracted base resistance ?? ? versus collector current.
Fig. 8. Extrapolated ?
versus collector current density.
Fig. 9. Schematic of the SiGe LNA.
p/cm , while the ac test structures were re-irradiated
with another proton fluence of
net fluence of
p/cm . Since proton irradiation causes
both ionization damage and displacement damage, the two
cannot be easily separated without further neutron and gamma
p/cm resulting in a
3784 IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 51, NO. 6, DECEMBER 2004
Fig. 10. Die micrograph of the SiGe LNA.
Fig. 11. Measured pre-and post-radiation gain of the SiGe LNA.
Fig. 12.Measured pre-and post-radiation noise figure of the SiGe LNA.
IV. TRANSISTOR-LEVEL RESPONSE
Measurements of the SiGe HBT dc and ac test structures
were made to quantify the transistor-level radiation response.
Only the results of the device with standard emitter area of
devices with other emitter areas. Proton tolerance of a pre-pro-
duction third-generation SiGe HBT technology has previously
been reported in . The SiGe HBTs used in this investigation
represent an improved version of the one examined in , this
SUMMARY OF THE SiGe TRANSCEIVER BUILDING BLOCK PARAMETERS
Fig. 13.Schematic of the SiGe VCO.
Fig. 14.Die micrograph of the SiGe VCO.
time with an optimized ideal base current, reduced base resis-
tance, and improved noise performance. The measured forward
and inverse mode Gummel characteristics, shown in Figs. 3 and
4, reveals a remarkably minor degradation of the base current at
a few Mrad(Si). The results obtained were in close agreement
with the ones reported in  and, for brevity, are not discussed
in detail here.
The transistor scattering-parameters ( -parameters) were
measured from 1 to 45 GHz at each bias point and subsequently
deembedded using an “open-short” method. The current gain
, Mason’s unilateral gain
were then calculated from the deembedded
, and base resistance
KUO et al.: PROTON RADIATION RESPONSE OF MONOLITHIC MILLIMETER-WAVE TRANSCEIVER BUILDING BLOCKS 3785
Fig. 15. Measured power spectrum of the pre-irradiated SiGe VCO.
Theand were extrapolated from
20 dB/decade slope line to 0 dB. Typical pre-and
post-radiation deembedded S-parameters biased at peak
shown in Fig. 5, the associated
Fig. 6, and the extracted
is shown in Fig. 7. The extrapolated
and upto p/cm protonfluencesareshownin
post-radiation results. The most apparent proton-induced de-
vice degradation lies in the increase of
caused by displacement effects in the neutral base region and
the deactivation of boron dopants. Clearly, these third-genera-
tion SiGe HBTs are remarkably hard to proton irradiation at the
transistor level without any intentional hardening.
and Mason’s are shown in
in Fig. 7, presumably
V. LOW-NOISE AMPLIFIER
The LNA is a crucial building block in the SiGe monolithic
mm-wave transceiver since it is the first gain stage in the re-
ceiver path used to amplify the weak incoming signals from the
antenna. The noise figure (NF) of the LNA adds directly to that
of the overall transceiver . Thus, gain and NF are two key
metrics, along with the input impedance match
output impedance match
The 60 GHz SiGe LNA, whose schematic is shown in Fig. 9,
is adjustable by changing the second-stage bias current. The
LNA die micrograph is shown in Fig. 10, and the LNA occu-
pies an area of
mm . The pre-and post-radiation
LNA gain and NF are shown in Figs. 11 and 12, respectively.
The ripple in NF (Fig. 12) is attributed to the measurement
setup rather than to the LNA itself. The LNA gain decreased
by 0.5 dB, NF increased by 0.4 dB,
increased by 1.5 dB. Detailed results are summarized
in Table II.
The proton-induced changes in the SiGe LNA performance
are minor, proving that it is robust from a proton irradiation
perspective for space applications. The increase in
attributed to the effects of proton irradiation on the microstrips
The degradation in gain may be attributed to the slight decrease
(Fig. 5) of the SiGe HBTs after irradiation. The increase
in NF may be attributed to the increase in
HBTs, which adds directly to the NF of the LNA . More
detailed characterizations of the proton-induced changes on the
LNA at mm-wave frequencies.
(Fig. 7) of the SiGe
VI. VOLTAGE-CONTROLLED OSCILLATOR
The VCO is another key building block in the SiGe mono-
lithic mm-wave transceiver. It is used to generate the local os-
cillator (LO) signals for the up-and down-conversion mixers
purity of the VCO output is also key and is characterized by the
phase noise. Phase noise can cause reciprocal mixing in the re-
of which are detrimental to proper transceiver functionality.
3786IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 51, NO. 6, DECEMBER 2004
Fig. 16. Measured power spectrum of the post-irradiated SiGe VCO.
The SiGe VCO, whose schematic is shown in Fig. 13, em-
ploys a differential Colpitts architecture with microstrips and
base-collector junction varactors . The VCO die micrograph
is shown in Fig. 14, and the die occupies an area of
mm . The pre-and post-radiation VCO power spectra are
shown in Figs. 15 and 16, respectively. The VCO operating fre-
at 1 MHz offset. Detailed results are summarized in Table II.
The proton-induced changes in the SiGe VCO performance
are minor, proving that it is robust from a proton irradiation per-
spectivefor space applications. The shiftin operating frequency
may be attributed to the effects of proton irradiation on the mi-
of the VCO, as well as on the SiGe HBTs. The degradation
in phase noise may be attributed to an increase in SiGe HBT
noise  that is up-converted into
phase noise. Similar observations were made in , but in that
case on a 5 GHz VCO using first-generation SiGe HBT tech-
nology. More detailed characterizations of the proton-induced
changes on the microstrips, base-collector junction varactors,
effects on the VCO at mm-wave frequencies.
The effects of 63.3 MeV proton irradiation on 60 GHz
monolithic mm-wave transceiver building blocks implemented
in third-generation SiGe HBT technology have been investi-
gated for the first time. A 60 GHz SiGe HBT LNA and VCO
were irradiated to proton fluences of
degradation associated with these extreme proton fluences is
found to be minor, suggesting that mm-wave SiGe transceiver
building blocks should be robust to proton irradiation for space
applications. However, for complete radiation hardness qualifi-
cation, proton irradiation studies need to be complemented with
thorough SEU sensitivity investigations. Since first generation
SiGe HBT technology was prone to SEU sensitivity , the
200 GHz SiGe HBT technology might also be SEU sensitive
and, hence, not be completely radiation hard.
p/cm . The
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