1. Status of technologies
Mauro Citterio
INFN Milano
MPI/Munich 12 February 2009

2. Baseline for SLHC Roadmap for phase II (present Hp) 2yrs ~ 6 yrs LoI
TDR
Shutdown
(new installations)
Activities
Production
~ 2yrs
R&D
Prototypes
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3. Programs for the Atlas upgrades
SiGe tecnology is a viable solution for a new LAr electronics
Mostly for the analog part of the front-end electronics
The importance of investigating such a technology is recognized in the “Expression of Interest”:
R&D Towards the Replacement of the Liquid Argon Calorimeter Front End Electronics for the SLHC (ATU-RD-MN-0001 v.1, 11 February 2008)
e dal programma di ricerca gia’ approvato:
Evaluation of Silicon-Germanium (SiGe) Bipolar Technologies for Use in an Upgraded ATLAS Detector (ATL-P-MN-0007, 18 June 2006)
SiGe is of interest for the inner detector also, an ATLAS common project exists:
There are different requirements for the front-ends of the ATLAS LAr and the ID at sLHC
ID needs real RADHARD chips
ID front end must be an analog/digital ASICs
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4. SLHC expected Fluence Levels
ATLAS Upgrade Radiation Simulation Studies
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5. Dose Levels from the Same Study
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6. Radiation Environment
No specification for radiation levels exist so far
But based upon preliminary simulation studies and to be consistent with what the silicon sensor group is testing to, the present targets are the following levels (which include one safety factor of 2).
Short Strips 6.8x1014 neq/cm2 30 Mrad
Long Strips 3.2x1014 neq/cm Mrad
LAr 9.6x1012 neq/cm2 30 krad
 LAr will benefits from the extensive rad-tests performed to qualify SiGe for ID use
Some preliminary rad-test results exists (mostly on IBM technology ….)
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7. The Common project proposal
The proposal submitted on Jun-2006
The following institutions
are part of the proposal:
USA BNL S.Rescia Columbia Nevis G.Brooijmans LBNL H.Spieler UC Santa Cruz A.A.Grillo U of Pennsylvania M. Newcomer
Italy INFN - Milan M. Citterio
Spain CNM Barcelona M. Ullan
France IN2P3 C. De La Taille
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8. The objective
New generations of bipolar technologies have been commercialized … . These new technologies, which make use of a “strained lattice” silicon-germanium (SiGe) base region to form a heterostructure bipolar transistor (HBT), show promise to meet the demands of the upgraded ATLAS detector and reduce power consumption
Specifically, silicon microstrip detectors planned for the ID and new readout for the LAr detector may be able to substantially reduce the power consumption of their analogue front-end circuits with these new SiGe technologies.
The R&D program will include:
a. Evaluate the radiation hardness of several SiGe technologies and from more than one vendor.
b. Determine which, if any, technologies will meet the radiation requirements for the ATLAS Upgrade.
Design a demonstration circuit for the front-end analogue readout of a silicon microstrip detector and the LAr detector in order to determine the expected noise and timing performance and the expected power consumption of these technologies.
The goal of the program is to determine if some SiGe technologies can be useful for some applications in the upgraded ATLAS detector and to compare such technologies with other potential ones, for example a completely CMOS front-end circuit.
MPI/Munich 12 February 2009

9. Technology selection
At the time the proposal was made, the following potential foundries were identified:
IBM (3 generations available)
IHP
AMS
STm
Motorola
JAZZ
It was initially intended to look at several technologies to sample a cross section what was available.
Early radiation tests of IBM 5HP by UCSC
Radiation tests of IHP (SG25H1, SG25H3, SGb25VD) by Barcelona
A test chip on IHP-SG25H1 by UCSC
Continuing work by IN2P3 with AMS
Given the Frame Contract with IBM, the effort was focused on the available IBM technologies.
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10. Promising results on “old” technologies
Parts from the IBM-5HP, IBM-7HP and the IHP-SG25H1, H3 & VD technologies have been irradiated and the results were previously reported at conferences
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11. On going radiation studies
Based upon the availability of the IBM technologies through CERN and the preference for being compatible with 130 nm CMOS, the collaboration focused lately on the IBM-8HP and the IBM-8WL technologies.
8WL - a less expensive version of the 8HP and possibly more compatible with the 8RF
The electrical characteristics of the 8WL appear to be quite adequate for ATLAS needs.
The IBM-8HP was irradiated with protons at the CERN PS, gammas at the BNL cobalt source and neutrons at the Ljubljana reactor.
Tests on 8WL structures is on going and data are discussed in the SiGe group
8WL parts were irradiated with gammas at BNL and neutrons at Ljubljana and Lowell (US).
MPI/Munich 12 February 2009

12. Gummel-Poon Plots Show Typical Damage
Gamma, neutron and proton irradiations show increased base leakage current.
The increased base current lowers the DC gain, which is the one of the most important consequences of radiation damage.
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13. Figures of Merit
The DC current gain after radiation varies considerably with bias current.
Based upon circuit design studies like ones already presented, we have established a nominal bias current density of 16 A/m2, i.e. a current density at which most circuits will be biased and at which we want a minimum gain to be held.
Small size transistors can operate at lower bias while larger ones like those used for the first stage amplifier will need more bias.
We also established a “figure of merit” of 50 for the desired minimum gain. The circuits can operate with less but this is our target for these studies.
While several electrical characteristics were measured pre and post irradiation (e.g. forward Gummel-Poon, reverse Gummel-Poon, Early voltage, etc.), we will focus on the change in DC current gain (beta) for this presentation.
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15. The data in the following slides are from Alex Grillo presentation at CERN on June, 3rd, 2008.
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16. 8HP Neutron Irradiation
The vertical line marks the nominal bias current density.
The gain doesn’t scale with Jc as well as we have seen with other old bipolar technologies. The variations are not chip-to-chip as each figure contains data from only one chip array of transistors.
Parts up to target fluence hold up well.
MPI/Munich 12 February 2009

17. Effects of Thermal Neutrons
Some parts with irradiated with a cadmium shield to filter out thermal neutrons.
The parts don’t seem to show a large sensitivity to the thermal neutrons. The difference with and without the shield is not larger than the inherent variations.
MPI/Munich 12 February 2009

18. 8HP Gamma Irradiation
The parts behave very well up to 50 Mrad. Also, the gains scale with Jc much better than for the neutron data.
At 100 Mrad, the performance becomes very weak, but we are not sure if this is real.
(See next slide.)
In any case 100 Mrad is well beyond our target.
MPI/Munich 12 February 2009

19. 8HP Gamma Biased vs. Unbiased
The 50 Mrad biased parts are slightly less damaged than the parts grounded during irradiation as we would expect.
However, the 100 Mrad grounded parts behave much better than the biased ones leading us to believe something strange happened during the 100 Mrad biased irradiation.
MPI/Munich 12 February 2009

20. 8HP Proton Irradiation
The bottom two plots look very marginal. The 3x1015 data probably does not meet our target but it exceeds our target fluence.
This proton irradiation, however, had many problems. The PS broke down several times requiring the parts to be stored and then re- installed in the beam line.
MPI/Munich 12 February 2009

21. 8HP Proton Biased vs. Unbiased
Again comparing biased to unbiased, the 3x1015 biased parts show a little less damage as expected.
However, the 6.8x1014 biased parts a little worse than the unbiased ones adding to our concern that something odd happened during these long, multiple start proton irradiations at the PS.
The 8HP proton irradiation would have to be redone before making any conclusions.
MPI/Munich 12 February 2009

22. 8WL Neutron Irradiation @ Ljubljana
Here are three plots of three different 8WL transistor types: HP, MB, HB. The different letters are different transistors of different size on each chip.
We have irradiated parts to three other fluences but they have not been measured yet. This data point is closest to our target fluence.
MPI/Munich 12 February 2009

23. 8WL Neutron Irradiation @ Lowell
Here are measurements of some parts irradiated with neutrons at the Lowell facility (US).
There parts show more damage at 6x1014 than those irradiated at Ljubljana.
We have not used this facility before and these measurements became available just last Friday. (Different backgrounds?)
More work is needed to understand the differences between the two sets of neutron data.
MPI/Munich 12 February 2009

24. 8WL Gamma Irradiation - First Look
8WL parts were (are being) irradiated with gammas at BNL to doses of 1, 10, 25 and 50 Mrad.
Here is a first look at some of the data.
MPI/Munich 12 February 2009

25. Preliminary conclusions
A lot of data have been collected; some are still coming in; not all are analyzed.
Both the 8HP and the 8WL appear to meet the radiation tolerance requirements for LAr and probably the long-strip silicon tracker.
For the short-strip silicon tracker, it is not so clear.
The remainder of the data must be analyzed and possibly more irradiations performed to answer some of the questions.
MPI/Munich 12 February 2009

26. Possible Applications
The collaborators on this SiGe evaluation come from the ATLAS silicon strip tracker community and the LAr community.
The font-end amplifer-shaper-comparator for the silicon tracker
The front-end amplifier-shaper for LAr
The front-end board ADC for LAr (?)
An IC submission “submitted” in Nov with the 8WL technology.
The submission includes a silicon tracker front-end circuit, a LAr front-end circuit and an array of test structures.
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27. From Mitch presentation (Nov. 2008)
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29. Transmission line terminating preamplifier (Hybrid circuit adopted by ATLAS LAr)
Input stage with bipolar transistors  it can be easily extended to SiGe.
The “local feedback” gives low noise (Rnoise = 10 W) and badwidth with low power (50 mW) and good linearity
Three “different” (Zin e Imax) hybrids:imply changing the values of three components but IDENTICAL CIRCUIT
With CD = 330 pF, and 16 nsec 50 W line
<tpeak>= 47.2 ns, rms = 0.3 ns
ENI= 49.3 nA, rms = 0.53 nA
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30. From Mitch presentation (Nov. 2008)
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31. Technology comparison geared to RF
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38. From Philippe presentation (Nov. 2008)
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42. Technology comparison geared to RF
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44. SiGe is more expensive than CMOS, BUT less expensive than GaAs: this is the real advantage in RF industry.
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45. In our field ….. The price is not our only concern
Moreover all the components models are well suited for RF application, less importance is given to low frequency behavior.
We need noise info
We need “ad hoc” library
The information about SiGe at cryogenics temperatures are old
Besides it is not clear that devices “optimized” for speed ad room temperature can operate effectively at LAr temperature
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46. SiGe Cressler Book
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