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NQS modelling with HiCuM: What works, what doesn't
A. Bhattacharyya, C. Maneux, S. Frégonèse, T. Zimmer
IMS - University Bordeaux 1, France
2/12
Outline
Introduction
NQS basics
High frequency Y parameters
NQS model implementation inside HICUM
Vertical NQS implementation
Modeling results
NQS modeling with HICUML2
Scaling of NQS parameters
Conclusion
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Introduction: NQS basics
NQS basics:
As the operating frequency approaches the cutoff frequency, the transistor can
no longer follows external excitations instantaneously. (Non Quasi Static effect)
Transient variation of electron concentration inside the base
Switch-off Switch-on
From Suzuki IEEE TED 1992
4/12
Phase of admittance parameters show NQS effect.
HICUM- Productization and Support Update, Oct 2007.
Introduction: high frequency Y parameters
Phase(y.11) Phase(y.21)
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xf
Qdeix=V(Xf)
Qdei
1Ω
alqf*Tf
Phase shift network with excess charge.
HBT HICUML2V24
1
deideix
D
sT
.D fT alqf T
NQS model implementation : vertical NQS
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Itzf
xf1
alit*Tf
V(xf2) V(xf1)
xf2
1Ω
alit*Tf/3
xf1TD/3
TD1Ω
xf2
Itzf
Phase shift network with transfer current (HICUML2).
' 21 ( )
tzf
txf
D D
II
sT sT
' 21 ( )
tzf
txf
D D
II
sT sT
Weil-McNamee formulation
Gyrator equivalent formulation (L. Lemaitre)
( * * ( 1)) ( 2)tzf f
dI alit T V xf V xf
dt
( 1) ( * / 3* ( 2)) ( 2)f
dV xf alit T V xf V xf
dt
( 2)xfI V xf
NQS model implementation: vertical NQS
( 2)xfI V xf
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DEV_L3W0_27E1B1C1
freq [LOG]
p
ha
se
(h.m
.21
) p
ha
se
(h.s
.21
) [
E+
0]
1E+8 1E+9 1E+10 1E+11 1E+12-150
-100
-50
0
DEV_L3W0_27E1B1C1
freq [LOG]
ph
ase
(h.m
.21
) p
ha
se
(h.s
.21
) [
E+
0]
1E+8 1E+9 1E+10 1E+11 1E+12-150
-100
-50
0
Modeling results: NQS modeling with HICUM L2
h21: phase (current gain) VBE=0.76V -> 0.92V, VCE=1.2V
NQS flag = 0
alit=0,alqf=0
NQS flag = 1
alit=0.8,alqf=0.2
NQS effect in h21 phase and modeled using HICUM L2V24 model in a
transistor of LE = 3µm and WE = 0.27µm.
VBE VBE
Compact modeling of transistor having B3T technology and BiCMOS9MW layout. (fT peak =240GHz)
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DEV_L3W0_27E1B1C1
freq [LOG]
p
ha
se
(h.m
.21
) p
ha
se
(h.s
.21
) [
E+
0]
1E+8 1E+9 1E+10 1E+11 1E+12-150
-100
-50
0
Parameter optimization in different devices
Modeling results: NQS modeling with HICUM L2
VBE=0.76V -> 0.92V, VCE=1.2V
NQS effect in h21 phase and modeled using HICUM L2.24 model for transistors having emitter
Lengths (LE) = 3µm, 5µm, 10µm and emitter width (WE) = 0.27µm.
VBE
DEV_L5W0_27E1B1C1
freq [LOG]
p
ha
se
(h.m
.21
) p
ha
se
(h.s
.21
) [
E+
0]
1E+8 1E+9 1E+10 1E+11 1E+12-150
-100
-50
0
VBE
DEV_L10W0_27E1B1C1
freq [LOG]
p
ha
se
(h.m
.21
) p
ha
se
(h.s
.21
) [
E+
0]
1E+8 1E+9 1E+10 1E+11 1E+12-150
-100
-50
0
VBE
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Large transistors show abnormality in h21 phase at high injection level
h21 phase for different WE (0.54, 0.84, 1.08µm) with same LE (10µm) at VBE=0.76V ->
0.92V, VCE= 0.8V, 1.2V
DEV_L10W0_54E1B1C1
freq [LOG]
p
ha
se
(h.m
.21
) p
ha
se
(h.s
.21
) [E
+0
]
1E+8 1E+9 1E+10 1E+11 1E+12-2.5
-2.0
-1.5
-1.0
-0.5
0.0
VBE=0.92V
DEV_L10W0_84E1B1C1
freq [LOG]
p
ha
se
(h.m
.21
) p
ha
se
(h.s
.21
) [E
+0
]
1E+8 1E+9 1E+10 1E+11 1E+12-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
VBE=0.92V
DEV_L10W1_08E1B1C1
freq [LOG]
p
ha
se
(h.m
.21
) p
ha
se
(h.s
.21
) [E
+0
]
1E+8 1E+9 1E+10 1E+11 1E+12-3.5
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
VBE=0.88V, 0.92V
Modeling results: NQS modeling with HICUM L2
VBE
VBE
VBE
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NQS parameters are optimized for low injection level and plotted against emitter length (LE) and real emitter area (considering the spacer width of 55 nm).
Modeling results: : Scaling of NQS parameters
0
0,2
0,4
0,6
0,8
1
1,2
0 5 10 15
alit,
alq
f
LE(µm)
alit_0.76alqf_0.76alit_0.80alqf_0.80
0.5
alit= 1.0
alqf= 0.5
0
0,2
0,4
0,6
0,8
1
1,2
0 2 4 6 8 10
alit,
alq
f
AE0(µm2)
alqf_0.76alit_0.76alit_0.80alqf_0.80
0.5
alqf decreases at higher emitter area
Constant over length
NQS parameters at VBE=0.76V and 0.80V and VCE=1.2V
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Conclusion
NQS basic is presented is presented while showing the HICUMimplementation.
HBT Modeling results with HICUM L2V24 model are presented.
HICUM provides good results but at high frequency and long devices thereis scope for modification (essderc paper 2011, submitted).
Transistors with higher emitter widths show abnormality in h21 phase at highinjection.
Scaling of two NQS parameters show that constant value of NQS parameters(alit=1, alqf=0.5) provide a good modeling accuracy.
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Acknowledgment
This work is part of the:
• DOTFIVE project supported by the European Commission through the Seventh
Framework Programme for Research and Technological Development.
Acknowledgements also to the MEDEA+ “SIAM” project.
We want to thank ST microelectronics and XMOD Technologies for helpfuldiscussions.
