Download No Slide Title

Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
FEE2006 Workshop on Front-End electronics
Perugia, Italia
18-May-2006
E. N. Spencer
SCIPP – UCSC
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
1
The ATLAS Strip Detector Readout
The present ATLAS strip detector readout IC (named ABCD) is
fabricated on the DMILL biCMOS technology.
•
The front-end amplifier, shaper and discriminator is
biCMOS.
•
The back-end pipeline, readout, command decoder, etc. is
all CMOS devices.
The DMILL technology is no longer available and it would likely
not be sufficiently rad-hard for the higher SLHC luminosity, at
least not at the same radii.
A new technology must be chosen.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
2
Deep Sub-micron CMOS a Possibility
One obvious possibility is a complete IC in deep sub-micron CMOS.
•
Radiation hardness of 0.25 mm CMOS has been
demonstrated at levels sufficient for strip use at SLHC
•
Newer 0.13 mm technologies are now being evaluated and
are likely more rad-hard .
A demonstration front-end circuit was designed and fabricated in
0.25 mm CMOS a few years ago and was shown to meet present
ATLAS noise and timing requirements.
A proposal is now being discussed to build a CMOS replacement for
the full ABCD chip to demonstrate feasibility and evaluate
performance.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
3
Past Experience
A biCMOS technology was ideal for the existing ATLAS readout IC
because:
• We have shown for past experiments that the bipolar technology
has advantages over CMOS in power and performance for frontend amplification when the capacitive loads are high and the
shaping times short.
•
•
•
ZEUS-LPS
SSC-SDC
ATLAS-SCT
Tek-Z IC
LBIC IC
ABCD, CAFE-M, CAFE-P ICs
• CMOS is the preferred technology for memory and logic circuits of
the back-end.
• BiCMOS technology afforded both of these optimizations in one IC.
Experience with commercial 0.25 mm CMOS has shown the advantage of
using a volume commercial rather than a niche technology.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
4
Technical Issues
The ATLAS-ID upgrade will put even greater constraints on power.
Can we meet power and shaping time requirements with deep submicron CMOS?
•
Achieving sufficient transconductance of the front-end
transistor typically requires large bias currents.
The crossing time of the SLHC is not yet fixed. If this dictates a faster
shaping time, the transconductance vs. power will become a bigger
issue.
If past experience still applies, a bipolar front-end may be able to
meet noise and timing requirements for less power than a CMOS
solution.
Are there commercial biCMOS technologies that could meet all of our
stringent requirements?
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
5
biCMOS with Enhanced SiGe
The market for wireless communication has now spawned many biCMOS
technologies where the bipolar devices have been enhanced with a
germanium doped base region (SiGe devices).
We have identified at least the following vendors:
•
•
•
•
•
Growing number of fab facilities
IBM (at least
3 generations available)
STm
IHP, (Frankfurt on Oder, Germany)
Motorola
JAZZ
Advanced versions include CMOS with feature sizes of 0.25 mm to 0.13 mm.
The bipolar devices have DC current gains (b) of several 100 and fTs up to
200s of GHz. This implies very small geometries that could afford higher
current densities and more rad-hardness.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
6
Technical Questions
The changes that make SiGe Bipolar technology operate at 100s of
GHz for the wireless industry coincide with the features that
enhance performance for our application.
•
Small feature size increases radiation tolerance.
•
Extremely small base resistance (of order 10-100 W)
affords low noise designs at very low bias currents.
Can these features help save power?
Will the SiGe technologies meet rad-hard requirements?
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
7
The usefulness of a SiGe
bipolar front-end circuit will
depend upon its radiation
hardness for the various
regions (i.e. radii) where
silicon strip detectors might
be used.
18 May 2006
FEE Perugia
Fluence [1014 neq/cm2]
Radiation vs. Radius in Upgraded Tracker
Inner
Pixel
Mid-Radius
Short Strips
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
Outer-Radius
“SCT”
E.N. Spencer
SCIPP-UCSC
8
Tracker Regions Amenable for SiGe
For the inner tracker layers, pixel detectors will be needed, and their
small capacitances allow the use of deep sub-micron CMOS as an
efficient readout technology.
Starting at a radius of about 20 cm, at fluence levels of 1015 n/cm2, short
strips can be used, with a detector length of about 3 cm and capacitances
on the order of 5 pF.
At a radius of about 60 cm, the expected fluence is a few times 1014 n/cm2,
and longer strips of about 10 cm and capacitance of 15 pF can be used.
It is in these two outer regions with sensors with larger capacitive loads
where bipolar SiGe might be used in the front-end readout ASICs with
welcome power savings while still maintaining fast shaping times.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
9
Evaluation of SiGe Radiation Hardness
The Team
D.E. Dorfan, A. A. Grillo, A. Jones, G.F. Martinez-McKinney,
M. Mendoza, P. Mekhedjian, J. Metcalfe, H. F.-W. Sadrozinski,
G. Saffier-Ewing, A. Seiden, E. N. Spencer, M. Wilder
SCIPP-UCSC
Collaborators:
A. Sutton, J.D. Cressler, A.P. Gnana Prakash
Georgia Tech, Atlanta, GA 30332-0250, USA
F. Campabadal, S. Díez, C. Fleta, M. Lozano,
G. Pellegrini, J. M. Rafí, M. Ullán
CNM (CSIC), Barcelona
S. Rescia et al.
BNL
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
10
Potential CMOS Front-End
J. Kaplon et al., 2004 IEEE Rome Oct 2004, use 0.25 mm CMOS
For CMOS: Input transistor: 300 mA, other transistors 330 mA (each 20 – 90 mA)
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
11
High-Rate Front-End Initial Targets for ATLAS-S
• Input signal polarity: Both, either positive from p-strips or negative from n-strips,
polarity switch needed
• Gain at comparator input, >100 mV/fC.
• Noise:
<= 1500 e- for unirradiated module.
<=1800 e- for irradiated module.
• Peaking time: 20 ns, for 25 ns crossing for this study. Upgrade could use 25 ns
crossing as at present, but could be 20, 15, or 10 ns, with correspondingly lower
analog shaping time.
•Total time walk for signal at comparator output: < 16 ns, 1.05 fC to 10 fC, for 1 fC
threshold
•Minimum PSRR, 10 kHz-100 kHz: 20 dB, 10 MHz-60 MHz10: -14 dB (Should be
improved if feasible).
•Power: minimum net power dissipation, as other specifications permit, < 400 mW for
analog section including differential comparator output @ 15 pF detector load. < 160
mW @ 6 pF load.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
12
Evaluating SiGe with Design: IHP Submission
Depending upon the performance (especially radiation hardness) of the bipolar
process, power savings could be realized in both the front transistor and in the
other parts of the analog circuit.
To evaluate these design questions, UCSC recently submitted for fabrication the
High Rate Front –End IC, HRFE, using the IHP SG25H1 SiGe BiCMOS process
through the Europractice mini@sic program.
IHP SG25H1:
• 200 GHz ft npn’s , minimum .21 x .84 mm
• npn b is ~150
• npn re is 50 W for minimum npn
• 0.25 mm CMOS
• Available on mini@sic Europractice
• Full Cadence kit supported by IHP
• Back annotation of layout is supported
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
13
HRFE: BiCMOS Front-End
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
14
HRFE Digital LVDS Buffer
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
15
Transient Differential Shaper Response 2 fC to 32 fC
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
16
Noise versus Detector Capacitance @ 40 mA bias for Q1
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
17
Noise versus Detector Capacitance @ 150 mA bias for Q1
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
18
Timewalk: 10 fC as Zero time, 50 attoF drive needed
above 1 fC for 16 ns timewalk
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
19
Comparator Latching with small Threshold Control
Steps through Voltage Threshold
Apply 400 mA threshold steps:
Comparator LVDS output either full
width or fully off.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
20
First SiGe High-rate Radiation Testing
Radiation testing has been performed on some SiGe devices by our
Georgia Tech collaborators up to a fluence of 1x1014 p/cm2 and they
have demonstrated acceptable performance. (See for example:
http://isde.vanderbilt.edu/Content/muri/2005MURI/Cressler_MURI.ppt)
In order to extend this data to higher fluences, we obtained some
arrays of test structures from our collaborator at Georgia Tech.
These were from a b-enhanced 5HP (called 5AM) process from IBM.
(i.e. the b was ~250 rather than ~100.)
The parts were tested at UCSC and with the help of RD50
collaborators (Michael Moll & Maurice Glaser) they were irradiated
in Fall 2004 at the CERN PS and then re-tested at UCSC.
For expediency, all terminals were grounded during the irradiation
This gives slightly amplified rad effects compared to normal biasing.
Annealing was performed after initial post-rad testing.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
21
Irradiated Samples
ATLAS Upgrade
Outer Radius
Pre-rad
4.15 x 1013
1.15 x 1014
3.50 x 1014
Mid Radius
Inner Radius
1.34 x 1015
18 May 2006
FEE Perugia
3.58 x 1015
1.05 x 1016
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
22
Radiation Damage Mechanism
Forward Gummel Plot for 0.5x2.5 mm2
Ic,Ib vs. Vbe Pre-rad and After 1x1015 p/cm2 & Anneal Steps
Radiation damage
increases base
current causing the
gain of the device to
degrade.
Collector current
remains the same
Base current
increases after
irradiation
Gain=Ic/Ib (collector
current/base current)
Vbe [V]
Ionization Damage (in the spacer oxide layers)
• The charged nature of the particle creates oxide trapped charges and
interface states in the emitter-base spacer increasing the base current.
Displacement Damage (in the oxide and bulk)
• The incident mass of the particle knocks out atoms in the lattice
structure shortening hole lifetime, which is inversely proportional to
the base current.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
23
Annealing Effects
Annealing of 0.5x2.5 mm2: Current Gain, b, vs. Ic
Pre-rad and After 1x1015 p/cm2 & Anneal Steps
Current Gain, b
Before Irradiation
After Irradiation
After Irradiation
& Full Annealing
Ic [A]
We studied the effects of annealing. The performance improves appreciably. In the case
above, the gain is now over 50 at 10mA entering into the region where an efficient chip
design may be implemented with this technology. The annealing effects are expected to be
sensitive to the biasing conditions. We plan to study this in the future.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
24
Initial Results
Current Gain, b, vs. Ic for 0.5x10 mm2
Pre-rad and for All Fluences Including Full Annealing
Before Irradiation
Gain, bb
Current Gain,
Current
Lowest Fluence
Increasing Fluence
Highest Fluence
Ic [A]
After irradiation, the gain decreases as the fluence level increases. Performance is still
very good at a fluence level of 1x1015 p/cm2. A typical Ic for transistor operation might be
around 10 mA where a b of around 50 is required for a chip design. At 3x1015, operation
is still acceptable for certain applications.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
25
Universality of Results
D(1/b)
Post-rad & Anneal to Pre-rad @ Jc=10mA
Proton Fluence [p/cm2]
Ratio of Current Gain, b
Post-rad & Anneal to Pre-rad @ Jc=10 mA
Proton Fluence [p/cm2]
Universal behavior independent of transistor geometry when compared at the same
current density Jc. For a given current density D(1/b) scales linearly with the log of
the fluence. This precise relation allows the gain after irradiation to be predicted for
other length SiGe HBTs. Note there is little dependence on the initial gain value.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
26
5HP Log-Log Plot of Ib Radiation Induced Leakage versus Ic
Ib(post-irrad) - Ib(pre-irrad) [A]
Change in Base Leakage Current for a 0.5x10 mm2
Transistor for Several Fluences
1.E-05
1.E-06
Fluence p/cm2
1.E-07
3.00E+13
1.00E+14
3.00E+14
1.E-08
1.E-09
1.00E+15
3.00E+15
1.00E+16
1.E-10
1.E-11
1.E-12
Vce=0.75 V
1.E-13
1.E-13
1.E-11
1.E-09
1.E-07
1.E-05
1.E-03
Ic [A]
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
27
Feasibility for ATLAS ID Upgrade
Qualifications for a good transistor:
A gain of 50 is a good figure of merit for a transistor to use in a front-end
circuit design.
Low currents translate into increased power savings.
Fluence: 3.50E14 p/cm 2 (2.17x10 14 neq/cm2)
Fluence: 1.34E15 p/cm 2 (8.32x10 14 neq/cm2)
Transistor Size mm2
0.5x1
0.5x2.5
0.5x10
0.5x20
4x5
Transistor Size mm2
0.5x1
0.5x2.5
0.5x10
0.5x20
4x5
b=50
cirrad
2.E-06
4.E-06
3.E-05
5.E-05
9.E-06
Ic anneal
5.E-08
8.E-07
2.E-06
5.E-07
At 3.5x1014 in the outer region (60 cm),
where long (10 cm) silicon strip detectors
with capacitances around 15pF will be used,
the collector current Ic is low enough for
substantial power savings over CMOS!
18 May 2006
FEE Perugia
b=50
cirrad
3.E-05
7.E-05
4.E-04
1.E-04
Ic anneal
1.E-07
4.E-06
9.E-06
6.E-05
1.E-05
At 1.34x1015 closer to the mid radius (20 cm),
where short (3 cm) silicon strip detectors with
capacitance around 5pF will be used, the
collector current Ic is still good for a front
transistor, which requires a larger current while
minimizing noise. We expect better results from
3rd generation IBM SiGe HBTs.
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
28
IHP - Another SiGe Vendor
CNM has obtained a first set of test structures from IHP and is
proceeding with that evaluation.
• 2 Test chip wafer pieces with ~20 chips
• 2 Technologies:
- SGC25C (bipolar module equivalent to SG25H1)
- SG25H3 (Alternative technology)
• Edge effects:
- Test chips came from edge of wafer
- Will be solved in future samples
Irradiations with gammas to 10 Mrad and 50 Mrad have been
performed. Neutrons and protons to be done.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
29
Preliminary Results for IHP from CNM
IHP SGC25C SiGe technology
• Bipolar transistors equivalent to SG25H1 technology (fT = 200 GHz)
• No Annealing !
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
30
Second IHP Technology
IHP SG25H3 SiGe technology
• fT = 120 GHz, Higher breakdown voltages
• Annealing after 50 Mrads: 48 hours, very good recovery
• Very low gains before irradiation (edge wafer transistors)
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
31
Continuing Studies of IBM Technologies
We are continuing the studies of three IBM technologies (5HP, 7HP
and 8HP) using neutrons, gammas and protons.
8HP comes with
0.13 mm CMOS
5AM & 5HP comes with
0.25 mm & 0.50 mm CMOS
Neutron irradiation is in progress at Ljubljana. Gammas are being done at
BNL now(May 2006) with protons to follow this spring.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
32
Preliminary! 8HP Beta change with 10 MRad Gamma Irradiation
(Biased During Irradiation)
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
33
Conclusions on SiGe Evaluation So Far
First tests of one SiGe biCMOS process indicate that the bipolar
devices may be sufficiently rad-hard for the upgraded ATLAS
tracker, certainly in the outer-radius region and even perhaps in the
mid-radius region.
A design on the IHP SG25 H1 process indicates that such a SiGe
front-end circuit will achieve significant power savings.
More work is needed to both confirm the radiation hardness and
arrive at more accurate estimates of power savings.
In particular, with so many potential commercial vendors available,
it is important to understand if the post-radiation performance is
generic to the SiGe technology or if it is specific to some versions.
Other ATLAS Upgrade collaborators are optimizing the minimum
analog power achievable with CMOS.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
34
Work Ahead
Along with our collaborators, we plan two parallel paths of work.
We will complete the irradiation studies of several SiGe processes. In
particular, we plan to test at least the IBM 5HP, IBM 7HP, IBM 8HP, IHP
SGC25C (eq. to SG25H1), IHP SG25H3 and IHP SGB25VD.
•
CNM will focus on the IHP technologies.
•
UCSC on IBM.
To obtain a better handle on the true power savings, we have submitted an
IHP 8 channel amplifier/comparator April 2006. This work is in parallel with
IHP radiation characterization. UCSC will continue this direct evaluation by
design with testing.
The BNL LAr Calorimeter group is also engaged in SiGe qualification and is
gamma irradiating the IBM SiGe.
Once the SiGe evaluation is mature, a choice can be made between SiGe
bipolar or CMOS for the front-end to be married with the CMOS backend.
18 May 2006
FEE Perugia
Silicon Germanium BICMOS: Irradiation
Resistance and Low Power Analog Applications
E.N. Spencer
SCIPP-UCSC
35