research paper
Electromagnetic and small-signal modeling
of an encapsulated RF-MEMS switch for
D-band applications
selin tolunay wipf
1
, alexander go
¤ritz
1
, matthias wietstruck
1
, christian wipf
1
,
bernd tillack
1,2
, andreas mai
1
and mehmet kaynak
1,3
In this work, an electromagnetic (EM) model and a small-signal (lumped-element) model of a wafer-level encapsulated (WLE)
radio frequency microelectromechanical systems (RF-MEMS) switch is presented. The EM model of the WLE RF-MEMS
switch is developed to estimate its RF performance. After the fabrication of the switch, the EM model is used to get accurate
S-parameter simulation results. Alternative to the EM model, a small-signal model of the fabricated WLE RF-MEMS switch is
developed. The developed model is integrated into a 0.13 mm SiGe BiCMOS process technology design kit for fast simulations
and to predict the RF performance of the switch from a pure electrical point of view. The 0.13 mm SiGe BiCMOS embedded
WLE RF-MEMS shows beyond state-of-the-art measured RF performances in D-band (110–170 GHz) and provides a high
capacitance C
on
/C
off
ratio of 11.1. The results of the both EM model and small-signal model of the switch are in very good
agreement with the S-parameter measurements in D-band. The measured maximum isolation of the WLE RF-MEMS
switch is 51.6 dB at 142.8 GHz with an insertion loss of 0.65 dB.
Keywords: BiCMOS, mm-wave, wide band, RF-MEMS, SPST, encapsulation, monolithic integration, packaging, modeling
Received 14 October 2016; Revised 13 January 2017; Accepted 17 January 2017; first published online 13 February 2017
I. INTRODUCTION
Monolithic integration of the radio frequency microelectro-
mechanical systems (RF-MEMS) switches has advantages
over the hybrid integration techniques such as bond-wire or
flip-chip due to their less parasitics. The integration of the
RF-MEMS switches into a 0.25 mm SiGe BiCMOS technology
has been demonstrated in [1] and showed valuable results for
this integration technique with respect to reliability, repeat-
ability, and the yield issues [2]. The integration of the
RF-MEMS switch into 0.13 mm SiGe BiCMOS process tech-
nology gives the possibility to use RF-MEMS components
together with very high-performance heterojunction bipolar
transistors (HBTs) [3] and provides circuits with unprece-
dented low attenuation, to be used in antenna switching
matrices and phase shifters [4].
The developments of RF-MEMS switches in literature are
mostly below 40 GHz as a result of the interest in
RF-MEMS devices for the commercial applications. With
the high-performance semiconductor technologies of today,
radar and imaging applications are moving toward the
upper part of the mm-wave spectrum and even beyond. A
promising application of the RF-MEMS switches at
140 GHz is their use in radar front-ends for active imaging
systems (http://project-nanotec.com/). In [5], a transceiver
IC with novel fully integrated differential RF-MEMS SPDT
switch for short-range F-band radar systems is presented.
Lately, an RF-MEMS-based single-pole double-throw
(SPDT) switch is presented in D-band with the lower insertion
loss and the higher isolation values compared with the
field-effect transistor and HBT-based SPDTs [6].
RF-MEMS switches in BiCMOS processes [7] have proven
that they can be solutions for applications, which require low
insertion loss and high isolation even up to 250 GHz [8].
Although the RF-MEMS switches have good RF performances
in all the mm-wave range, packaging is still the challenge on
the way to their commercialization. A good RF-MEMS
package should not only provide the interface to the next
level, but should also be cost and area effective.
Furthermore, it should be preferably fabricated using wafer-
level processes to increase the throughput thus decrease the
cost. In wafer bonding approaches of wafer-level packaging
(WLP), the cost of at least one lid wafer is added to the total
production cost [9]. These additional lid wafers can also add
more process steps such as wafer grinding or chemical mech-
anical polishing. The wafer bonding approach not only
increases the cost, but also requires additional area around
the MEMS devices to accommodate the cap. Indeed, WLE
[10–12] has advantages over the WLP with wafer bonding
approach in terms of cost and area. Predictably, WLE
Corresponding author:
S. Tolunay Wipf
Email: tolunay@ihp-microelectronics.com
1
IHP, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
2
Technische Universita
¨t Berlin, HFT4, Einsteinufer 25, 10587, Berlin, Germany
3
Sabanci University, Orta Mahalle, Tuzla 34956, I
˙stanbul, Turkey
1271
International Journal of Microwave and Wireless Technologies, 2017, 9(6), 1271–1278. #Cambridge University Press and the European Microwave Association, 2017
doi:10.1017/S1759078717000137
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approach is also the chosen method for the well-known com-
mercial packaged MEMS devices [13,14].
In the direction of their commercialization, development of
an accurate EM model is essential in order to optimize the RF
performances of the WLE RF-MEMS switches. With a three-
dimensional (3D) finite-element-method (FEM) solver, it is
possible to estimate the RF performances of a WLE
RF-MEMS switch. However, an accurate EM model needs a
careful modeling approach since one of the key elements,
the contact air capacitances in both on and off-states of the
switch are not known before its fabrication. The contact air
capacitances can vary due to process variations. In order to
model the on and off-state of the RF-MEMS switch accurately
the contact capacitances of the fabricated RF-MEMS switch
should be measured. With the known contact area of the
switch and the measured contact air capacitances, the distance
between the RF-signal line and the released membrane can be
calculated by the simple parallel plate capacitance formula.
Afterwards the calculated distance can be given into the EM
model for the accurate EM simulations.
Beside an accurate EM model a pure small-signal model of
the WLE RF-MEMS switch is also necessary especially for the
circuit designers to predict the RF-behavior of the designed
circuits using the switch. A small-signal model of the WLE
RF-MEMS switch increases the simulation speed remarkably
compared with an EM model and gives the possibility to simu-
late the switch with various circuits in a system level. For
mainly these reasons, we have developed a lumped model of
the WLE RF-MEMS switch in Keysight ADS [15] and inte-
grated this model into the design kit of a 0.13 mm SiGe
BiCMOS process technology.
This paper is the extended version of the conference paper in
[16] and contains the technology, fabrication, electromagnetic
(EM) modeling, measurements, and the small-signal modeling
of the thin-film wafer-level encapsulated RF-MEMS switch. To
the best of authors’ knowledge, the demonstrated results
provide the first wafer-level encapsulated (WLE) RF-MEMS
switch, which operates with state-of-the-art RF performances
in D-band in literature. With the developed encapsulation
process, the WLE RF-MEMS switch is packaged in one clean
room during the BEOL fabrication process. The fabricated
WLE RF-MEMS switch provides beyond state-of-the-art
insertion loss of better than 0.67 dB in all D-band.
II. WLE RF-MEMS SWITCH IN
0.13 mM BICMOS TECHNOLOGY
In IHPs 0.25 mm SiGe BiCMOS technology, the RF-MEMS
switch is realized by using Metal1 as the high-voltage (HV)
electrodes, Metal2 (M2) as the RF-signal line and Metal3
(M3) as the suspended movable membrane [1]. In comparison
with the five metallization layers of the IHPs 0.25 mm BEOL,
the 0.13 mm BEOL consists of seven metallization layers with
different metal thicknesses and distances between them. With
IHPs 0.13 mm SiGe BiCMOS technology, the capacitive
RF-MEMS switch is developed between Metal4 (M4) and
TopMetal2 (TM2). In order to minimize the substrate cou-
plings, the RF-signal line is shifted up to Metal5 (M5)
instead of the M2. Moreover, the movable membrane is
thicker in 0.13 mm technology and it significantly changes
the electro-mechanical behavior, the RF performance and
the fabrication process. In summary, the RF-MEMS switch
in 0.13 mm BiCMOS technology is realized with M4 HV elec-
trodes, M5 RF-signal line, TopMetal1 (TM1) movable mem-
brane, and a TM2 plate with releasing holes is placed on top
of the RF-MEMS switches for the wafer-level encapsulation.
Figure 1 shows the schematic cross-section of the WLE
RF-MEMS switch in IHPs 0.13 mm SiGe BiCMOS technology.
Integration of the RF-MEMS switch starts with the standard
BEOL flow of the passives. Before the releasing process,
TM2 of the RF and DC pads and the TM2 grid of the
RF-MEMS switches are reached with the passivation
opening. With the defined etching area, the RF-MEMS
switches are released by hydrofluoric acid vapor phase
etching (HFVPE) through the TM2 grid down to M4 HV elec-
trodes (Fig. 2). The last steps of the process flow include the
4mm-thick high deposition rate (HDR) oxide deposition on
the TM2 grid to close the open holes and have the
RF-MEMS switches encapsulated. Finally, the HDR oxide
covered pads are reopened by reactive ion etch (RIE) to
provide electrical connections for the measurements (Fig. 3).
For the success of the wafer-level encapsulation, different
design modifications are done and process parameters are opti-
mized. In detail, the TM2 grid’s hole size was one of the most
important design parameter for both the HFVPE and the wafer-
level encapsulation. For the investigation of the hole size impact,
the quadratic hole sizes are varied with the side length of 1.25,
1.5, 1.75, and 2.0 mm. Together with the TM2 thickness of d¼
3mm it results in aspect ratios (AR ¼d/a) from 2.4 down to
1.5. Besides during the varied hole sizes, the distances
between the holes are taken identical with the holes sizes.
Beside the hole size, the plasma-enhanced chemical vapor
deposition process for the HDR oxide deposition is optimized
Fig. 2. The scanning electron microscopy (SEM) image of the released
RF-MEMS switch before the wafer-level encapsulation (including the focus
ion beam (FIB) cross-section).
Fig. 1. The schematic cross-section of the 0.13 mm BiCMOS process
technology, including the embedded WLE RF-MEMS switch.
1272 selin tolunay wipf et al.
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to achieve the required low step coverage. By minimizing the
process temperature of the HDR oxide deposition it is also
intended to reduce its influence on the active elements of
the front-end-of-line and on the mechanical behavior of the
RF-MEMS switch. Consequently, a maximum temperature
of 2008C for HDR oxide deposition has been developed to
achieve closing of the TM2 grid holes.
As a result of the variable TM2 grid hole size investigation,
successfully encapsulated RF-MEMS switches are achieved
with an AR of 2.4 and 2.0 (Figs 4(a) and 4(b)). With an AR
of 1.7, a carbon containing material inside the closing holes
is determined by energy-dispersive X-ray spectroscopy
(EDX), which is coming from the spin-coating of the photo-
resist mask before the RIE opening of the pads (Fig. 4(c)).
The photoresist enters from the TM2 grid holes in case of a
not fully closed TM2 grid holes. Clearly with an AR of 1.5, a
fully closed encapsulation also could not be achieved
(Fig. 4(d)). Indeed, with AR of 2.4 and 2.0 it was possible to
close the TM2 grid holes while pretending the unwanted
HDR oxide deposition through the holes into the cavity.
III. EM MODELING
During the development of the RF-MEMS switch in the
0.13 mm SiGe BiCMOS technology, an accurate EM model
is built up in ANSYS HFSS 3D FEM solver (Fig. 5(a)). For
the accurate EM model in the 3D FEM solver, the distances
between TM1 membrane and M5 RF-signal line for both off
(d
off
) and on-states (d
on
) of the switch are needed to be
inserted into the simulator.
The mean value of the distance between the TM1 mem-
brane and M5 RF-signal line in off-state is 900 nm in IHPs
0.13 mm SiGe BiCMOS technology. However, the off and
on-state contact air capacitances of the fabricated RF-MEMS
switch can vary over the wafer due to process variations
such as different surface roughness, metal and oxide thick-
nesses or stress behaviors of the TM1 membrane. In order
to estimate the possible RF performance differences due to
the process variations, parametric EM simulations with differ-
ent d
off
and d
on
are performed (Fig. 5(b) and 5(c)). For the
insertion loss in the parametric EM simulation the membrane
position is swept from 100 nm above the specified TM1 layer
until 100 nm below with a step size of 50 nm. Figure 6 shows
the change of the insertion loss curves with different d
off
values. Varying d
off
by 200 nm leaded to 0.16 dB change of
insertion loss at 170 GHz. Furthermore, the parametric EM
simulations are extended with different d
on
values for the iso-
lation curves. The distance d
on
is stepwise (10 nm) decreased
starting from 100 down to 40 nm and the simulation results
are shown in Fig. 6. Decreasing d
on
by 60 nm caused a reson-
ance frequency shift from the upper end of the D-band to the
lower end. Briefly, the varying d
off
due to process variations
did not affect the insertion loss tremendously but the reson-
ance frequency shifted significantly with the varying d
on
(Fig. 6). For this reason we extract the contact air capacitances
from the C–Vmeasurements of the RF-MEMS switch to have
an accurate 3D FEM result of the D-band RF-MEMS switch
especially for the on-state. Based on the extracted contact air
capacitances (C
off
and C
on
) and the known contact area of
Fig. 3. The SEM image of the WLE RF-MEMS switch (including the FIB
cross-section).
Fig. 4. The focused ion beam SEM images of the wafer-level encapsulation on
the aspect ratios (a) AR ¼2.4, (b) AR ¼2.0, (c) AR ¼1.7 (including the EDX
analysis), and (d) AR ¼1.5.
Fig. 5. EM simulation model in ANSYS HFSS for D-band BiCMOS embedded
WLE RF-MEMS switch (a) with the schematic diagram for the parametric EM
simulations for different, (b) d
off
, and (c) d
on
values.
em and small-signal modeling of an encapsulated rf-mems switch for d-band applications 1273
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the switch, d
off
and d
on
can be calculated using the simple par-
allel plate capacitor equation and inserted into the EM model.
IV. MEASUREMENTS
A) C–VMeasurements
The thin-film WLE RF-MEMS switch is initially characterized
by C–Vmeasurements. For the C–Vmeasurements, the high-
frequency impedance analyzer Agilent E4991 for the range
from 1 MHz to 3 GHz is used and the capacitance values
are taken from 3 GHz. An Open/Short/Load calibration on
an impedance standard substrate (ISS) from Cascade
Microtech is applied before measurement of the WLE
RF-MEMS switch to remove measurement setup parasitics.
The capacitance values are measured for the actuation vol-
tages between 280 to +80 V with 5 V steps. Figure 7 shows
the measured C–Vgraph of the WLE RF-MEMS switch and
the extracted contact air capacitance versus actuation
voltage graph. Extraction of the contact air capacitances is
done with the help of an additional test structure that consists
of a RF-signal line without membrane and encapsulation grid.
With the test structure, the coupling capacitance (52 fF) from
the signal line to the silicon substrate is measured and the
contact air capacitances are extracted by its subtraction. The
contact air capacitances are extracted as 13.4 fF C
off
and
149 fF C
on
with a C
on
/C
off
ratio of 11.1. Moreover, it is
observed that the pull-in occurs after 50 V and the on-state
capacitance is stable after 65 V of actuation.
B) Scattering parameter measurements
The two port S-parameters of the WLE RF-MEMS switch are
measured on wafer from 110 to 170 GHz. For the measure-
ment, a setup from Rhode & Schwarz, consisting of a four-
port ZVA24 as VNA/system controller and two ZVA170
Millimeter-Wave Converters, are used. The Cascade 75 mm
pitch infinity(R) GSG waveguide probes are connected via a
WR6 waveguide s-bend with the millimeter-wave modules.
For calibration, the ISS 138–356 is placed together with an
RF absorber on an auxiliary ceramic chuck and a full
two-port LRRM calibration is performed. To actuate the
membrane of the RF-MEMS switch a 100 V Agilent Source
Measurement Module E5281B is used.
To the best of authors’ knowledge, the 0.13 mm BiCMOS
embedded thin-film WLE RF-MEMS switch is the first
RF-MEMS switch in literature, which operates with state-of-
the-art RF performances in D-band. The comparison of
the measured and simulated S-parameter results of the
WLE RF-MEMS switch is given in Fig. 8. The switch
shows maximum isolation of 51.6 dB at 142.8 GHz with
the insertion loss of 0.65 dB. For the insertion loss
curves, the signal reflection due to mismatch is considered
by IL ¼10 ×log (|S
21
|
2
/(1–|S
11
|
2
)). Based on the measured
C
on
and C
off
capacitances (Fig. 7) and the considered
1200 mm
2
contact area, d
off
is calculated as 800 nm and
d
on
as 70 nm. The calculated d
off
and d
on
values are then
inserted into the EM model for the comparison with the
S-parameter measurements. The 3D FEM simulation results
are in very good agreement with the measured S-parameters
in the 110–170 GHz frequency band.
V. LUMPED-ELEMENT MODELING
Although the 3D FEM solvers provide accurate EM simulation
results with the calculated d
off
and d
on
values from the
Fig. 6. The simulated S-parameters of the WLE RF-MEMS switch with
varying TM1 membrane and M5 RF-signal line distances due to process
variation.
Fig. 7. The measured C–Vgraph of the WLE RF-MEMS switch (red) and the
extracted contact air capacitance versus voltage graph (black).
Fig. 8. The comparison of the measured and simulated S-parameters for
up-state S
21
(black), insertion loss (blue), and isolation (red) of the WLE
RF-MEMS switch.
1274 selin tolunay wipf et al.
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extracted contact air capacitances (C
off
and C
on
), lumped-
element models give faster simulation results. Furthermore,
a lumped model of a RF-MEMS switch [17] increases the
usage of the device since with the help of the lumped-model,
RF-MEMS switches can be simulated in various circuits on
system level. In this study, the lumped-element model of the
WLE RF-MEMS switch based on RLC components is devel-
oped and simulated in Keysight ADS. The main capacitances
for the lumped-element model of the WLE RF-MEMS switch
are shown on the process cross-section in Fig. 9.
Similar to the EM model, the extracted contact parameters
of the switch is necessary for the lumped-element model of the
RF-MEMS switch especially in on-state. Figure 10 shows the
lumped-element model of the WLE RF-MEMS switch. The
extracted contact air capacitances (C_cont), C
off
of 13.4 fF
and C
on
of 149 fF are used to model the contact region.
Furthermore in the on-state model, the contact resistance of
5kVis also considered.
For the S-parameter simulation with the lumped-element
model, port1 and port2 are terminated with 50 ohm. The
M5 RF-signal line is modeled using RLC components
between the two ports and the arms of the membrane are
modeled as inductors (L_arm1, L_arm2) with series resistors
(R_arm1, R_arm2). C_elect1 and C_elect2 are the parasitic
capacitances between the TM1 membrane and the M4 high-
voltage electrodes. The values of the RLC elements of the
lumped model for both states of the switch are given in
Table 1 below. Due to the down bending of the TM1 mem-
brane in on-state, C_elec1 and C_elec2 values are modeled
slightly larger compared to the off-state values. Table 2
shows the varied C_elec1, C_elec2 and C_cont values with
respect to the states of the WLE RF-MEMS switch.
Both the 3D FEM model and the lumped-element model
consider the effect of the wafer-level encapsulation on the
RF-MEMS switch. For the wafer-level encapsulation to
include in the lumped-element model, TM2 plate is
modeled with series inductances (L_encap1, L_encap2,
L_encap3, L_encap4, L_encap5) and resistances (R_encap1,
R_encap2, R_encap3, R_encap4, R_encap5). Additionally for
its effect on the RF-MEMS switch, the coupling capacitances
(C_encapSL1, C_encapSL2, C_encapSL3, C_encapSL4)
between the TM2 plate and the M5 RF-signal line is also
inserted into the lumped-model. As a final point, the substrate
effects are considered in the model and inserted as parallel
capacitance (C_subst) and resistance (R_subst) between
ground and the RF-signal lines.
Figure 11 shows the comparison between the measured
S-parameters of the fabricated WLE RF-MEMS switch with
simulation results of the EM model and the lumped-element
model. Both EM model and lumped-element model simula-
tion results are in very good agreement with the measured
S-parameter results in the D-band.
Finally, the presented lumped-element model of the WLE
RF-MEMS switch is integrated into the IHPs SG13G2 and
Fig. 9. The process cross-section of the WLE RF-MEMS switch, including the
main capacitances of the lumped-element model.
Fig. 10. The lumped-element model of the WLE RF-MEMS switch.
Table 1. Small-signal component values of the WLE RF-MEMS switch.
L_encap1,L_encap2,
L_encap3,L_encap4,
L_encap5
R_encap1,R_encap2,
R_encap3,R_encap4,
R_encap5
C_encapSL1,
C_encapSL4
C_encapSL2,
C_encapSL3
L_arm1,
L_arm2
R_arm1,
R_arm2
C_pad1,
C_pad2
L_SL1,L_SL6
70 pH 0.5 V2 fF 3 fF 15 pH 0.5 V11 fF 42 pH
L_SL2,L_SL5 L_SL3,L_SL4 R_SL1,R_SL2,R_SL3,R_SL4,
R_SL5,R_SL6
C_SL1,C_SL5 C_SL2,C_SL4 C_SL3 C_subst R_subst
3 pH 1 pH 0.5 V3 fF 1.65 fF 10 fF 170 fF 400 V
em and small-signal modeling of an encapsulated rf-mems switch for d-band applications 1275
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SG13S process design kits in Keysight ADS. Figure 12 shows
the parameterized RF-MEMS cell in the ADS schematic envir-
onment including the selectable state parameter between off
(up) and on (down)-states. With the integration of the WLE
RF-MEMS switch into the design kit, the presented WLE
RF-MEMS switch can be combined in system-level simula-
tions with the IC components.
Table 2. Small-signal component values of the WLE RF-MEMS switch,
varied due to states.
States C_elec1,C_elec2 C_cont R_cont
Off-state 10 fF 13.4 fF (1)
On-state 12 fF 149 fF 5 kV
Fig. 11. The comparison of the measured, EM modeled and small-signal modeled S-parameters for (a) up-state S
21
, (b) up-state S
11
, (c) up-state insertion loss, and
(d) down-state isolation of the WLE RF-MEMS switch.
Fig. 12. Design kit integrated WLE RF-MEMS switch in Keysight ADS.
1276 selin tolunay wipf et al.
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VI. CONCLUSION
This paper has presented the EM modeling and lumped-
element modeling of a thin-film WLE RF-MEMS switch
embedded in IHPs 0.13 mm SiGe BiCMOS process technology
for D-band applications. Both developed models show a very
good agreement with the measured S-parameter results. With
the developed WLE RF-MEMS switch, maximum isolation of
51.6 dB at 142.8 GHz is achieved with a 0.65 dB insertion loss.
ACKNOWLEDGEMENTS
The authors thank to the team of the IHP pilot line for excel-
lent support. This work was supported by the European
Commission under the Contract no. 288531-NANOTEC
(www.project-nanotec.com).
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Selin Tolunay Wipf was born in May
1987. She received her B.S. degree from
the Electronics Engineering program of
Sabanci University, Istanbul, Turkey, in
2010 and her M.S. degree from the
Electrical and Electronics Engineering
Department of Bogazici University
(BUEE), Istanbul, Turkey, in 2012. She
joined the MEMS group of IHP Micro-
electronics in 2012 and has been working on the RF optimiza-
tions of the MEMS devices for the mm-wave applications.
Since 2015, she is a member of the Heterointegration group
of IHP with a focus on the RF design, optimization, and char-
acterization of the RF-MEMS switches above 100 GHz appli-
cations. Mrs. Selin Tolunay Wipf was involved in the FP7
projects UTMOST in Bogazici University, FLEXWIN, and
NANOTEC in IHP microelectronics.
Alexander Go
¨ritz was born in 1981. He
studied Electrical Engineering (micro-
electronics – semiconductor technology)
at the Technische Universita
¨t Dresden.
He received the Dipl.-Ing. degree in
2011. In 2012, he joined IHP Technol-
ogy Department and started working
on the development of MEMS for
mm-wave applications and their thin-
film wafer-level encapsulation. In parallel, he applies and im-
proves the HF vapor phase-etching process to release the
established MEMS devices. Since 2014 he has been involved
in the creation and application of general Back-End-Of-Line
(BEOL) process flows to realize BEOL wafer for cost-efficient
test platforms for passive devices. Meanwhile he also partici-
pates in the development of microfluidic channel, bolometer,
and graphene-based devices. Mr. Alexander Go
¨ritz worked on
the FP7 projects, FLEXWIN, and NANOTEC.
Matthias Wietstruck was born in 1984.
He graduated with a diploma in micro-
systems technology from the University
of Applied Sciences in Berlin in 2009. He
joined the IHP Technology Department
in 2010 and has been working in the area
of MEMS for mm-wave applications.
Since 2013 he has been started the re-
search activities in the area of through-
silicon via technology and heterogeneous 3D integration at
IHP. His current research focuses on the design and integra-
tion of TSVs into the BiCMOS technology as well as tempor-
ary and permanent wafer bonding for heterogeneous 3D
integration. Since 2015, he is heading the Heterointegration
group at IHP.
em and small-signal modeling of an encapsulated rf-mems switch for d-band applications 1277
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Christian Wipf joined the Technology
Department of IHP in 2005 and received
his M.Sc. in Electrical Engineering
from the University of Technology,
Cottbus, Germany, in 2008. He is work-
ing in the field of characterization of
electronic devices and circuits up to
and above 100 GHz within the Technol-
ogy Department. Furthermore, he is de-
signing high voltage control circuitries for MEMS matrix
applications.
Bernd Tillack received the Ph.D. degree
in 1980. In 1981, he joined the IHP
Frankfurt (Oder), Germany, as a staff
member of the process technology.
Since 2014 he has been heading the
IHP as scientific director. His research
interests include SiGe BiCMOS technol-
ogy development following the “More
than Moore” strategy for embedded
system applications. Since 2008 he has a professorship for Si-
based high-frequency technologies at the Berlin Institute of
Technology (TU Berlin).
Andreas Mai received his diploma in
physics from the Technical University
of Brandenburg (Cottbus) together
with “Advanced Micro Devices”
(AMD) in 2006. Subsequent he joined
the IHP Technology Department. He
worked in the Process Integration
group on the development of a 130 nm
SiGe-BiCMOS technology with for
mm-wave applications and focus on the integration of
RF-LDMOS transistors. He received his Ph.D. in 2010 and
became the project leader for the technical coordination,
yield enhancement and technology stabilization of IHPs
MPW-technologies. In 2013, he got the position as group
leader of the “Process Integration”. Since 2015 he has been
the acting technology department head with the main respon-
sibilities for operation of IHPs 200 mm-SiGe-BiCMOS pilot
line and technology service activities of IHP. Dr. Mai is the
IEEE member and chairs the processing committee of the
ECS SiGe, Ge & Related Compounds Symposium.
Mehmet Kaynak received his B.S.
degree from Electronics and Communi-
cation Engineering Department of Is-
tanbul Technical University (ITU) in
2004, took the M.S. degree from Micro-
electronic program of Sabanci Univer-
sity, Istanbul, Turkey in 2006 and
received the Ph.D. degree from Tech-
nical University of Berlin, Berlin, Ger-
many in 2014. He joined the technology group of IHP
Microelectronics, Frankfurt (Oder), Germany in 2008. From
2008 to 2015, he has led the MEMS development at IHP.
Since 2015, he has been the department head of technology
group at IHP. Dr. Kaynak is being affiliated as Adjunct Profes-
sor at Sabanci University, Turkey. Dr. Kaynak has published
over 100 peer-reviewed journal and conference publications
as an author or co-author. He has granted seven patents.
1278 selin tolunay wipf et al.
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