Transcript Outline - Bilkent University

Micromachined Antennas for Integration
with Silicon Based Active Devices
Erik Öjefors
Signals and Systems, Dep.of Engineering Sciences
Uppsala University, Sweden
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Outline of talk
• Introduction, applications
• Challenges of on-chip antenna integration
• Design of 24 GHz on-chip antennas
• Crosstalk with on-chip circuits
• Micromachined antenna packaging
• Conclusions and future work
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Introduction
Objective
On-chip antenna integrated with a 24 GHz ISM band
transceiver in SiGe HBT technology for short range
RADAR and communication devices
RFIC
Antenna
Integration
LNA
IF
RF
PA
LO
Crystal
Oscillator
20 MHz
PLL
VCO
12 GHz
1/8
Self-contained SiGe front-end
Aug 2004
RF
DC SHM acting
as a frequency
doubler
3x3 mm large chip
Micromachined Antennas for Integration with Silicon Based Active Devices
Introduction
One application
RADAR for traffic surveillance and anti-collision
warning systems
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Introduction
Advantages of integrated antenna:
• Simplified packaging (no high frequency interconnects)
• Lowered cost due to reduced number of components
• Omnidirectional radiation pattern often needed,
low gain on-chip antenna feasible
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Challenges of on-chip antenna integration
Antenna size can NOT be reduced without consequences!
Minimum Q (quality factor) of small antennas
1
1
1
Q
 
3
ka ka BW
2a
“a” is the radius of a sphere enclosing the antenna. “k” = 2p/l.
High Q leads to small bandwidth and can reduce the efficiency
McClean, " A Re-examination of the Fundamental Limits on the Radiation Q of Electrically
Small Antennas," IEEE Trans AP, May 1996.
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Challenges of on-chip antenna integration
Problem:
Size of antenna is an important parameter due to
the high cost of the processed SiGe wafer
Solution:
Chose antenna types which offer compact
integration with the active circuits
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Proposed integration with active devices
Slot antenna
Active elements integrated
within slot loop
3 mm
Active
devices
Top metallization
3 mm
Active devices
p+ channel stopper
Aug 2004
Si
Micromachined Antennas for Integration with Silicon Based Active Devices
Challenges of on-chip antenna integration
Problem:
Commercial silicon-germanium (SiGe) semiconductor use
low resisistivity (< 20 Wcm) substrates
Solution:
Use of a low loss interface material such as BCB polymer
or micromachining to reduce coupling between antenna
and lossy silicon substrate
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachining
Micromachining – mechanical
shaping of silicon wafers by semiconductor processing techniques
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachining – BCB process flow
Post processing technique compatible with pre-processed
SiGe wafers from commercial semiconductor foundaries
Active circuit
Si
BCB
Si
Gold
Si
Aug 2004
Pre-processed wafer from
foundary
10-20 um BCB layer applied
and cured
Top metallization evaporated and
defined using standard photolithographic techniques
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachining
Surface micromachining of silicon
Slot
BCB,
20 um
10 um
Top metalization
Optional micromachining
Si 11-15 Wcm
Surface micromachining applied to the substrate before
BCB-spin-on
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachining
Bulk micromachining of silicon
Slot
Top metalization
BCB membrane, 10-20 um
Backside
etching
Si
Back side of silicon substrate etched as last step in
processing
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Outline of talk
• Introduction, applications
• Challenges of on-chip antenna integration
• Design of 24 GHz on-chip antennas
• Crosstalk with on-chip circuits
• Micromachined antenna packaging
• Conclusions and future work
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
•
•
•
•
•
•
•
Surface micromachined slot loop antenna
Bulk micromachined slot loop antenna
Inverted F antenna
Wire loop antenna
Meander dipole
Differential patch antenna
Comparison of designed antennas
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Surfaced micromachined slot loop antenna
10, 20 um slot width
2000 um
3000 um
CPW probe pad
BCB, Si
BCB 10-20 um
Si 11-15 Wcm
3000 um
Slot loop length corresponds to one guided wavelength at 22 GHz
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Surfaced micromachined slot loop antenna
Small return loss outside the the operating frequency
indicates that losses are present
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Results – Radiation Pattern
Antenna on 20 um thick BCB interface layer on low resistivity Si
E-plane
enalp-H
0
0
-5
01-
-10
]Bd[
deru saeM
detalumiS
051
001
05
0
]ged[ elgnA
05-
001-
051-
[dB]
5-
51-
-15
02-
-20
52-
-25
Measured
Simulated
-150
-100
-50
0
Angle [deg]
50
H-plane
100
150
E-plane
Reasonably good agreement between simulated and measured radiation pattern,
(some shadowing in E-plane caused by measurement setup)
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Results – Gain and efficiency
Reference horn
antenna
• Measured gain: -3.4 dBi
Wafer probe station
80 cm
AUT
• Directivity (simulated): 3.2 dBi
• Calculated efficiency: 20 %
Foam material (low
dielectric constant)
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Bulk micromachining – improving efficiency
Slot supported
by BCB
membrane
Si
No trenches
200 m
Trenches can be formed from the back side of the wafer by
chemical wet etching (KOH) or dry etching (DRIE) methods
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Bulk micromachining – improving efficiency
Radiating slots
DRIE
>100 um trench width can be etched
Radiating slots
Anisotropic etching (KOH, TMAH)
Needs wafer thinning (300 um)
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
S(1,1)
trenches..S(1,1)
Bulk micromachining 3D-FEM simulations (HFSS)
freq (20.00GHz to 25.00GHz)
freq (22.00GHz to 30.00GHz)
By etching 200 um wide trenches in the silicon wafer the
simulated input impedance is increased from 60 W to 210 W
at the second resonance, simulated efficiency increased from
20% to >50%
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Bulk Micromachining – Slot Loop Antenna
Micromachined slot loop antenna
sa
wt
Si
Trench (membrane)
Slot
Designed antenna
Silicon space for
active devices
wb
wt
• Trench width wt = 100 um
lg
Results
• Measured gain 0-1 dBi
• Single ended feed (CPW)
Slot
• Impedance 100 Ohm
Top metallization (groundplane)
lg
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Inverted F Antenna
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Inverted F antenna on membrane
Ltr
LF
Ltr
HF
Wtr
Membrane
CPW
feed
Space for
circuits
•
Bent quarterwave radiator formed
by offset fed inverted F
•
Inverted F radiator placed on 2.6
x 0.9 mm BCB membrane
•
Single ended feed
LGP
WGP
Si
Wtr
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Inverted F antenna on membrane
FANT
0
•
Measured input
impedance
50 W at 24 GHz
•
Measured gain 0 dBi
•
Antenna tuning sensitive
to ground plane size
S11 [dB]
-5
-10
-15
Simulated
Measured
-20
15
Aug 2004
20
25
Frequency [GHz]
30
35
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Wire loop antennas
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Wire loop antenna on micromachined silicon
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
24 GHz wire loop antenna on micromachined silicon
•
•
Trench
Slot
•
Si space for
active
devices
LL
W br
W tr
Lc
•
•
•
3 x 3 mm wire loop
360 um wide BCB trenches
covered with BCB membranes
Chip size 3.6 x 3.6 mm
Differential feed
Measured input impedance
75 W at 24 GHz
Measured gain 1-2 dBi
Top metallization (ground-plane)
Wc
Si
Wtr
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Meander dipole antenna
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Meander Dipole on BCB membrane
3.3 mm
0.9 mm
Membrane
Silicon
• Membrane size 3.3 x 0.9 mm
Antenna
Wtr
BCB
• Differential feed
Silicon
• Input impedance at 24 GHz 20W
• Measured antenna gain 0 dBi
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Patch antennas
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Patch
Polarization
3800 um
Differentially fed patch antenna by University of Ulm
BCB
SiGe
Feed point
Ground-plane
Si
• Differential feed – no ground connection
• Suitable for wafer scale packaging
2000 um
Aug 2004
30 um
• Disadvantages – small bandwidth
Micromachined Antennas for Integration with Silicon Based Active Devices
Micromachined 24 GHz antennas
Differentially fed patch antenna transmission line model
Modelled return loss
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Comparison of 24 GHz Antennas
Slot loop
antenna
Wire loop
antenna
Meander
dipole
Inverted F
antenna
Patch
antenna
Trenches,
die size
3.3 x 3.3
mm
Trenches,
die size
3.6 x 3.6
mm
Membrane
size 3.3 x
0.76 mm
Membrane
size 2.6 x
0.9 mm
Thick BCB
area of 3.8
x 1.9 mm
Feed type Single
Differential
and impe- ended
75-100 W
dance
100-200 W
Differential
20-25 W
Single
ended
50 W
Differential
typically
50 W
Gain
0-1 dBi
1-2 dBi
0 dBi
0 dBi
< 7 dBi
Remark
Circuits
within
antenna
footprint
Circuits
within
antenna
footprint
Size at 24
GHz
Aug 2004
Sensitive to Wafer level
size of onintegration
chip
ground
Micromachined Antennas for Integration with Silicon Based Active Devices
Outline
• Introduction, applications
• Challenges of on-chip antenna integration
• Design and results for implemented antennas
• Crosstalk with on-chip circuits
• Micromachined antenna packaging
• Conclusions and future work
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Crosstalk with active circuits
Slot mode E-field
Parallel-plate
mode
BCB
Si 11-15 Wcm
p+ layer, active
device area
Parallel plate modes can be excited between the
antenna groundplane and conductive active device area
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Crosstalk with active circuits
Slot mode E-field
BCB substrate
contact
BCB
Si 11-15 Wcm
p+ layer, active
circuit ground
Parallel plate modes short circuited by BCB via to
substrate, crosstalk improvement of 30 dB possible in
some cases
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Outline of talk
• Introduction, applications
• Challenges of on-chip antenna integration
• Design and results for implemented antennas
• Crosstalk with on-chip circuits
• Micromachined antenna packaging
• Conclusions and future work
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Packaging of Micromachined Antennas
Glob top
Si
Active devices
LTCC carrier
• LTCC (Low Termperature Co-fired Ceramic) used as a carrier for
flip-chip or wire-bonded device
• Glob-top encapsulation obviates the need for a packaging lid
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Packaging of Micromachined Antennas
Glob-top
Type
Loss
tangent
Dielectric
constant
Amicon S 7503
Silicone
3.1
Semicosil 900LT
Silicone
Lord CircuitSaf TM
ME-455
Lord CircuitSaf TM
ME-430
Namics XV68410209
Epoxy cavity
fill
Epoxy glob
top
Side fill
0.0005 / 1
kHz
0.005 / 50
Hz
0.006 / 1
MHz
0.006 / 1
MHz
0.008 / 1
MHz
Aug 2004
3.0
3.37
3.7
3.5
Micromachined Antennas for Integration with Silicon Based Active Devices
Packaging - Evaluated Glob-tops
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Packaging – glob top characterization
Measured resonator insertion loss – single tape (100 um dielectric)
-20
S21 [dB]
-30
-40
-50
Air
Amicon silicone
Semicosil silicone
Namics side-fill
ME430 epoxy
ME455 epoxy
-60
-70
-80
22
Aug 2004
22.5
23
23.5
24
f [GHz]
24.5
25
25.5
Micromachined Antennas for Integration with Silicon Based Active Devices
26
Packaging – glob top characterization
Glob-top
Single
layer fr
[GHz]
Double
layer fr
[GHz]
Single
layer Q0
Double
layer Q0
No glob-top / Air
24.67
24.85
95
75
Amicon S 7503
23.14
23.44
75
50
Semicosil 900LT
23.41
23.98
67
65
Lord CircuitSaf
ME-455
Lord CircuitSaf
ME-430
Namics XV68410209
22.84
23.26
95
72
22.66
22.87
95
67
22.78
22.96
87
71
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Packaging - Summary
• A low cost packaging method for 24 GHz MMIC’s is
proposed
• Ferro A6-S ceramic LTCC evaluated at 24 GHz
• Glob-top, cavity fill and side fill polymers characterized epoxy based materials better than silicone ones
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Packaging – future and ongoing work
Membrane / glob-top compatibility
Preliminary results promising – no membrane breakage
for > 10 mm2 membranes covered with BCB glob tops
Glob-top covered antennas – electrical performance
Glop-top covered loop and dipole antennas mounted on
standard FR4 printed circuit boards – characterization
pending
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Outline
• Introduction, applications
• Challenges of on-chip antenna integration
• Design and results for implemented antennas
• Crosstalk with on-chip circuits
• Micromachined antenna packaging
• Conclusions and future work
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Conclusions
• Integration of an on-chip antenna with a 24 GHz
circuits in SiGe technology has been proposed
• 24 GHz on-chip antennas, suitable for integration,
have been manufactured and evaluated
• Micromachining of the silicon substrate yields antennas
with reasonable efficiency
• Simple glob-top packaging for micromachined
antennas has been evaluated
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Future and ongoing work
• Characterization and modeling of the manufactured
antennas
• Improve antenna measurement techniques
• Integrate the antenna with SiGe receiver/transmitter
• Demonstrate packaging of micromachined antennas
• Integrate opto-electronic devices with antennas
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices
Future and ongoing work
Ring slot antenna integrated with 24 GHz receiver*
being manufactured
Micromachined trenches
to be inserted in silicon
Slot in metal 3
Receiver
3 mm
Substrate contacts
Transistor test structures
3 mm
Aug 2004
*Receiver is designed by
University of Ulm
Micromachined Antennas for Integration with Silicon Based Active Devices
Acknowledgements
• The entire ARTEMIS consortium:
Staff at University of Ulm, CNRS/LAAS Toulouse,
Atmel GmbH, Sensys Traffic, VTT Electronics
• Klas Hjort and Mikael Lindeberg at Ångström Laboratory
This work was financially supported by the European
Commision through the IST-program
Aug 2004
Micromachined Antennas for Integration with Silicon Based Active Devices