Minutes of the

"2nd meeting on planning of the work on oxygenated silicon detectors"

17/9 1999

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Contents:
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-Participants
-Transparencies
-Presentations
-- M.Moll
-- J.Carter
-- M.Mannelli
-- T.Ruf
-Discussions and Conclusions

 

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Participants:
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Francois Lemeilleur RD48 - CERN-MIC/SD
Gunnar Lindström RD48 - Hamburg
Steve Watts RD48 - Brunel
Michael Moll RD48 - CERN-MIC/SD
Mike Letheren CERN - MIC
Pierre Jarron CERN - MIC
Thomas Ruf LHCb - CERN
Frederic Teubert LHCb - CERN
Claus Gößling ATLAS - Dortmund
Janet Carter ATLAS - Cambridge
Shaun Roe ATLAS - CERN
Marcello Mannelli CMS - CERN
Liliana Teodorescu CMS - Pisa

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Transparencies:
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Copies of the transparencies have been send to all participants. Please ask me for a copy if you are interested (michael.moll@cern.ch).

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Presentation Michael Moll - RD48
(Update of the results presented by G.Lindstroem on the 1st meeting 5/8/99)
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I presented the latest results of the RD48 (ROSE) collaboration obtained on oxygenated silicon detectors (ROSE test structures) irradiated at the PS in August/September (and some results of older experiments).

a) Material/Test structures used:

* Test structures produced by Sintef (Oslo,Norway), CIS(Erfurt,Gernany), BNL (Brookhaven National Lab, USA), ST-Microelectronics (Catania, Italy) were irradiated.

* Oxygen enrichment (O-diffusion)of these samples was performed at Sintef, CIS, BNL and ST-Microelectronics at various temperatures and diffusion times.

*The silicon was produced by Wacker and Topsil. <111> and <100> in a resistivity range from 1 to 15 Kohmcm was tested. Furthermore diodes processed by BNL on compensated epitaxial silicon produced by ITME has been irradiated.

b) Results(further details/results on transparencies):

* Improved radiation hardness of oxygenated silicon compared to standard silicon was confirmed.

* It was demonstrated that the "oxygen effect" is independent of the diode manufacturer and the company/institute performing the diffusion process.

* A diffusion process of 9 days at 1200C does not show much better results than the minimal tested diffusion time of 16 h at 1150C. Therefore the minimal diffusion time needed to improve the radiation hardness is still an open question. However, this result was obtained only with the CERN scenario measurements (measurements inbetween successive irradiation steps). It has to be confirmed in more detailed annealing measurements which have started right now in Hamburg.

* No difference between <111> and <100> silicon.

* No difference between Wacker and Topsil silicon.

* Unexpected radiation hardness of CIS diodes produced on standard Wacker <111> and Topsil <100> silicon. The reason for this behaviour is up to now unknown and subject to further investigations.

* Compensated (Boron/Phosphorus approx. 1e13cm-3) epitaxial silicon is not radiation harder than standard silicon.

* A comparison between CV at 10 kHz (standard) and 100 kHz has shown that at higher annealing stages (e.g. after more than 1000 min at 80C; where the 10 kHz curve gets obscured by surface state effects close to depletion voltage) the 100 kHz measurement reveals an easier way for a reliable extraction of the depletion voltage.

* Depletion voltage determined from CV measurements is in good agreement with TCT (Transient Charge Technique) measurements (670nm laser front illumination of type inverted diodes)

* Depletion voltage determined from CV measurements (oxygenated and standard silicon) is in good agreement with "CCE-measurements" performed with long wavelength laser 1060nm.

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Presentation Janet Carter - ATLAS SCT
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a) ATLAS SCT - Work on oxygenated detectors

* Tenders are now out for the SCT detectors and include oxygenated detectors as a technical option.

* Option would have to be fully proven by July 2000 to be taken up for series production (i.e. proven on ATLAS prototypes produced by the supplier(s) who have won the tenders in November 1999).

b) current prototyping

* barrel detectors with Sintef (oxygenated and standard) for October/November PS irradiation.

* forward W12 detectors with CIS (oxygenated and standard) for October/November PS irradiation.

* barrel detectors with Micron (oxygenated and standard) irradiated in August - now CCE being measured

* forward detectors with Micron 6" - probably irradiation in October/November ?

c) future plans

* depending on the companies that have won the relevant tenders

* All changes in the manufacturing process (as especially the oxygenation) have to be fully proven by the standard ATLAS qualification program before being accepted for serial production.

* Hamamatsu is considering also the production of O-enriched

Si-detectors. Prototypes are expected early spring 2000.

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Presentation Marcello Mannelli - CMS
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* oxygenated CMS detectors have been produced by ST-Microelectronics Catania

a) <100> 2kohmcm and 5kohmcm (72h 1150C)

b) <111> 2kohmcm and 5kohmcm (24h 1150C)

will most probably not be ready for irradiation in October/November beam time.

* for the same material the depletion voltage determined from CV measurements on pad and strip detectors can differ significantly

depending on the ratio between the strip width and the pitch (details on the transparencies)

* after a fluence of 3x10e14 protons cm-2 (24 GeV) an incomplete "donor removal" was observed (i.e. the use of low resistivity material is advantageous).

* CMS have drafted a paper on the reported results, which will be available after CMS approval by end September.

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Comments by Thomas Ruf - LHCb
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* LHCb detectors will face up to 1e14cm-2 per year. It is foreseen to replace them after 3 years of operation.

* Main priority: Find manufacturer that can produce very thin detectors (150mum); oxygenated silicon could be useful but is not put as an option for the tendering (primary goal are thin detectors).

* Time scale: TDR in 2001; Tender in Summer 2001

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Discussion about furture work and Conclusions
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* Janet Carter/Marcello Mannelli:

The oxygenated silicon has to be tested with "full size" prototype detectors. For a final decision which material will be used tests with

protons, pions and neutrons are needed.

* Further experiments foreseen by RD48 (Lindstroem/Watts/Lemeilleur):

- Oxygen diffusion experiments with less than 16h (1150C) diffusion times in order to determine the minimal diffusion time needed to get the "oxygen effect" (in order to save costs for the oxygen enrichement process).

- Simulations of the primary damage in silicon. Is it possible to

predict the particle dependence of the "oxygen effect" by splitting the NIEL into defects related to point defects (low energie transfer to Primary Knock on Atom) and to disordered regions (high energy transfer to PKA)?

* Common agreement:

Test structures and microstrip detectors from the same wafer should be irradiated together with RD48 diodes in order to confirm the results so far mostly obtained on test structures. (J.Carter: Since the amount of available ministrip detectors is limited only a certain part (e.g. one group) of the ROSE collaboration should be involved in this experiment).

* Further irradiation experiments should be coordinated with respect to the devices to be irradiated and the time schedules for neutron/pion/proton irradiations by Michael Moll (RD48)

Craig Buttar (ATLAS)

Andreas Furtjes (CMS)

Frederic Teubert (LHCb)

* A proposition on mutual participation in the various experiments was discussed with some sharing in the following irradiation jobs: RD48 will primarily use the PS proton shuttle for simultaneous irradiation of miniature microstrip detectors and pad diodes (warm exposure with succeeding C/V, I/V and CCE measurements) while ATLAS resp. CMS will do a similar study with their full sized detectors in the cold box using the standard readout techniques available there. It is clear that the RD48 comparitive irradiations can be performed at PS (protons), TRIGA-Ljubljana (neutrons) and PSI-Villigen (pions), whereas the large detector irradiation under bias and at -7degr could only be done at the PS and possibly at Ljubljana. The beam accessibility and geometrical irradiation environments have to be checked with Ljubljana and PSI. For a possible PSI beamtime (early 2000) the PSI responsibles have to be contacted immediately.

* A further meeting should be scheduled after such experiments have been coordinated (after the next PS irradiation run in November).

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Michael Moll Tel: +41 22 76 74280
Division EP-MIC-SD Fax: +41 22 76 79075
CERN Email:
michael.moll@cern.ch
CH-1211 Geneve 23 WWW:
http://sesam.desy.de/~moll
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