1. Otilia Militaru Université catholique de Louvain, Belgium
9th International Conference on Large Scale Applications
and Radiation Hardness of Semiconductor Detectors, Florence, Italy
RD50 Collaboration –
recent results on developing very high
radiation resistant silicon detectors
Otilia Militaru
Université catholique de Louvain, Belgium
on behalf of RD50

2. Otilia Militaru, on behalf of RD50, RD09 Conference, Italy
SUMMARY
RD50
Radiation environment and requirements for silicon sensors at Super LHC ;
-Presentation of RD50 Collaboration, members;
Some examples of the activities from several research directions
within RD50 Collaboration (this presentation explain only some recent results
and does not cover all domains) ;
Complete description one can find on the next RD 50 Status Report ;
-Possible solutions for Super LHC silicon sensors ;
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

3. SLHC will need more radiation tolerant tracking detector
The challenge : Signal degradation for LHC
Silicon Sensors
RD50
(Mara Bruzzi, 4th Trento Workshop on Advanced Detectors, 17 February 2009)
Pixel sensors: max. cumulated fluence for LHC and SLHC
SLHC will need more radiation tolerant tracking detector
challenges: Granularity, Powering, Cooling, Connectivity, Triggering, Low mass, Low cost !
Strip sensors: max. cumulated fluence for LHC and SLHC
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

4. High radiation environment and requirements for Si sensors at SLHC
RD50
Values from simulations for the CMS detector
done by M. Huhtinen
The aim of RD50 is to find new detector materials, type, geometries and technologies for SLHC
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

5. Detailed member list: http://cern.ch/rd50
Development of Radiation Hard Semiconductor Devices for High Luminosity Colliders
RD50
250 Members from 48 Institutes
41 European and Asian institutes Belarus (Minsk), Belgium (Louvain), Czech Republic (Prague (3x)), Finland (Helsinki), Germany (Dortmund, Erfurt, Freiburg, Hamburg, Karlsruhe, Munich), Italy (Bari, Bologna, Florence, Padova, Perugia, Pisa, Torino, Trento), Lithuania (Vilnius), Netherlands (NIKHEF), Norway (Oslo (2x)), Poland (Warsaw(2x)), Romania (Bucharest (2x)), Russia (Moscow, St.Petersburg), Slovenia (Ljubljana), Spain (Barcelona, Valencia), Switzerland (CERN, PSI), Ukraine (Kiev), United Kingdom (Glasgow, Lancaster, Liverpool)
8 North-American institutes Canada (Montreal), USA (BNL, Fermilab, New Mexico, Purdue, Rochester, Santa Cruz, Syracuse)
1 Middle East institute Israel (Tel Aviv)
Detailed member list:
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

6. Scientific Organization of RD50 Development of Radiation Hard Semiconductor Devices for High Luminosity Colliders
RD50
Spokespersons
Mara Bruzzi, Michael Moll
INFN Florence, CERN ECP
Defect / Material Characterization Bengt Svensson (Oslo University)
Defect Engineering Eckhart Fretwurst (Hamburg University)
Pad Detector Characterization G. Kramberger (Ljubljana)
New Structures R. Bates (Glasgow University)
Full Detector Systems Gianluigi Casse (Liverpool University)
Characterization of microscopic
properties of standard-, defect engineered and new materials pre- and post-irradiation WODEAN project
(G. Lindstroem)
Development and testing of defect engineered silicon:
- Epitaxial Silicon
- High res. CZ, MCZ
- Other impurities H, N, Ge, …
- Thermal donors
- Pre-irradiation
Test structure characterization IV, CV, CCE
NIEL
Device modeling
Operational conditions
Common irrad.
Standardisation of macroscopic measurements (A.Chilingarov)
3D detectors
Thin detectors
Cost effective solutions
3D (M. Boscardin)
Semi 3D (Z.Li)
LHC-like tests
Links to HEP
Links to R&D of electronics
Comparison: pad-mini-full detectors
Comparison of detectors different producers (Eremin)
pixel group (D.
Bortoletto,T. Rohe)
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

7. Radiation Damage in Silicon Sensors
RD50
Defect /Material Engineering of Si
Bulk damage due to NIEL (non-ionizing energy loss)
Change of effective doping conc. (change in full depletion bias voltage) ;
Increase of the leakage current (contributes to the noise) ;
Decrease of charge collection (affects the detector performance) ;
Surface damage due to IEL
(ionizing energy loss)
-Generates accumulation layer between the strips, due to positive charge enhancement in the silicon oxide (affects interstrip capacitance -noise factor, breakdown behavior)
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

8. Available Irradiation Sources in RD50
RD50 approaches to develop radiation harder tracking detectors
RD50
To understand the factors that generate radiation damage and their effects :
Simulation of defect properties and kinetics;
irradiations with different particles at different energies;
understand the long-term annealing effects and the microscopic defects that generates these effects ;
different process technologies;
different silicon manufacturers ;
different thicknesses 300, 200, 150, 100, 50 µm ;
silicon rich in Oxygen: DOFZ, CZ, MCZ, Epitaxial sensors ; Oxygen dimer & hydrogen enriched Silicon;
influence of processing technology ;
other type of sensors like : thin detectors (Silicon-On-Insulator SOI technology), p-type material (n+ in p), 3D and semi 3D detectors , strixels detectors; cost effective detectors !!!
Available Irradiation Sources in RD50
24 GeV/c protons, PS-CERN
10-50 MeV protons, Jyvaskyla +Helsinki
Fast neutrons, Louvain
26 MeV protons, Karlsruhe
TRIGA reactor neutrons, Ljubljana
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

9. RD50 approaches to develop radiation harder tracking detectors
(Mara Bruzzi, 4th Trento Workshop on Advanced Detectors, 17 February 2009)
Material
Thickness [mm]
Symbol 
(cm)
[Oi]
(cm-3)
Standard FZ (n- and p-type)
50,100,150,300 FZ
1–3010 3
< 51016
Diffusion oxygenated FZ (n- and p-type)
300
DOFZ
1–710 3
~ 1–21017
Magnetic Czochralski Si, Okmetic, Finland (n- and p-type)
100, 300
MCz
~ 110 3
~ 51017
Czochralski Si, Sumitomo, Japan
(n-type) Cz
~ 8-91017
Epitaxial layers on Cz-substrates, ITME, Poland (n- and p-type)
25, 50, 75, 100,150
EPI
50 – 100
< 11017
Diffusion oxyg. Epitaxial layers on CZ 75
EPI–DO
~ 71017
Standard for
particle detectors
Used for pixel
detectors
“New” material
DOFZ silicon - Enriched with oxygen on wafer level, inhomogeneous distribution of oxygen
CZ/MCZ silicon - high Oi (oxygen) and O2i (oxygen dimer) concentration (homogeneous) - formation of shallow Thermal Donors possible
Epi silicon - high Oi , O2i content due to out-diffusion from the CZ substrate (inhomogeneous) - thin layers: high doping possible (low starting resistivity)
Epi-Do silicon - as EPI, however additional Oi diffused reaching homogeneous Oi content
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

10. Impact of defects on Detector properties
RD50
Cluster related hole traps as
source for long term annealing
I. Pintilie, E. Fretwurst, G. Lindström APL 92, 2008
WODEAN project (initiated in 2006, 10 RD50 institutes, guided by G.Lindstroem, Hamburg)
Defect Analysis on irradiated samples performed with the various tools available inside the RD50 network (DLTS, TSC, TCT, etc.);
Identify defects (energy levels in the band gap) responsible for Trapping, Leakage Current, change of Neff and longterm/reverse annealing ;
TSC spectra on neutron irradiated samples EPI-DO and MCz, for different annealing time at 80oC.
Cluster related hole traps H(116K), H(140K) and H(152K) (not present after γ-irradiation) are observed in neutron irradiated n-type Si diodes during 80oC annealing.
Concentrations (delimited by the peak surface) are increasing with annealing time therefore cluster related hole traps contribute to long term/ reverse annealing ; direct correlation with C-V measurements at room T.
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

11. Impact of defects on Detector properties
RD50
I. Pintilie, E. Fretwurst, G. Lindström APL 92, 2008
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

12. Mixed irradiations: protons and neutrons
RD50
It is not straightforward that damage produced by two different irradiation particles adds together ;
The annealing behavior of MCz-n shows that:
- Positive space charge is introduced by charged hadrons;
-Negative space charge is introduced by neutrons -> Compensation of the effects (space charge) in mixed irradiation field and consequent reduction of Vfd ;
Also the evolution of defects after irradiation might be different owing to different ratio of point defects and clusters defects;
| Neff| ~|gc,p Φ eq,p + gc,n Φeq,n|
For FZ
Similar introduction rate of stable defects gc,p and gc,n result in almost linear increase of the Neff with eq. fluence
RD50 Status report
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

13. Mixed irradiations: protons and neutrons
RD50
For Cz
The different sign of introduction rate of stable defects gc,p and gc,n leads to reduction of Neff with eq. fluence for n-type, (as expected for neutrons only, but not for pions that show a strong type inversion). For p-type show an increase, but slightly at high fluence -> strong polarization of the detector (meaning the balance between positive and negative space charge regions turns in favour of positive space charge )
RD50 Status report
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

14. Mixed irradiations: protons and neutrons
RD50
RD50 Status Report 2008
The evolution of Vfd of mixed (neutrons and protons) irradiated detectors during long term annealing confirm the results.
MCz n-type, Vfd decreases and increase afterwards -> shows the behaviour typical for detector with predominantly positive space charge ;
MCz p-type, Vfd increases but with a lower rate.
The long term annealing of MCz is delayed
Before irradiation
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

15. Mixed irradiations: protons and neutrons
RD50
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

16. Charge multiplication for p-type
RD50
I.Mandic et al. NIM A 603 (2009) ;
for p-type material strip detectors irradiated with neutrons up to 1 x1016 n/cm2
300 µm
140 µm
measurements (taken at -20oC) were limited by instability caused by the leakage current
increase ;
calculated and measured leakage current coincide, but not for higher fluences ;
The high bias voltages are still below the Vfd (calculated from the introduction rate
of stable acceptors) so the detectors were partially depleted, only ;
Simulations were done, calculating the charge generation by a MIP in similar structure
considering the effective trapping time teff for e- and holes, 1/teff (e and h) = βe,h x Φ
and the results underestimate the exp. values;
Possible conclusion: the electric field is so high at highly irradiated detectors
and very high bias voltage that appears an effect of multiplication of charge carriers
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

17. Charge multiplication for EPI-material
RD50
CCE as a function of bias voltage for n-type and p-type EPI diodes after proton irradiations (Cz-substrate) J.Lange at al. 14th RD50 workshop Freiburg 2009
Almost saturation for low fluences at high voltages
n-type: Stronger increase for high fluences (avalanche effects) p-type: approximately linear increase for Feq≥2.7x1015 cm-2
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

18. 300 µm n-in-p Micron sensors
G. Casse, 14th RD50, Freiburg 5-7 June 2009.
24GeV/c protons irradiated COLD, all but the 3.1E15 cm-2 series
RED: irradiated with 24GeV/c protons
Other: 26MeV protons
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy 18

19. 140 and 300 mm n-in-p Micron sensors after 1x1016 neq 26MeV p
G. Casse, 14th RD50, Freiburg 5-7 June 2009.
Evidence for multiplication? Or other effect, like field dependent de-trapping? Even after heavy irradiation it is possible to recover the entire ionised charge.
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy 19

20. Otilia Militaru, on behalf of RD50, RD09 Conference, Italy
3-D detectors design
RD50
Gain: Decoupling of detector thickness and distance for charge collection: column electrodes are etched into the sensor and doped ;
Shorter distance between electrodes: lower depletion voltage, lower trapping
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

21. Otilia Militaru, on behalf of RD50, RD09 Conference, Italy
3-D detectors design
RD50
[ U. Parzefall et al.,”Silicon microstrip detectors in 3D technology for the sLHC”, doi: /j.nima ]
FBK-IRST (Trento) and CNM (Barcelona):
First step was production of 3D-STC (single type column) detectors
The columns only from one side and one doping type, not completely penetrating, charge collection is slower and less (than planar detectors) due to the low electric field.
3D-DDTC (double-sided, double type column) but still not fully penetrating ;
Column overlap determines the performance.
3D-STC and 3D-DDTC
0.9 x 1015 neq/cm2
Test beam results .. See Friday talk of Michael Koehler !
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy

22. Conclusions-recommendations for SLHC
RD50
Outer Layers (R>20cm, F<1015neq/cm2)
– p-type silicon microstrip detectors show good results
collected charge >10000e- (300μm) at 500V after F=1015 neq/cm2 ;
no reverse annealing in CCE ;
MCz could be considered;
MCz has improved performance in mixed fields due to compensation of n and p damage ;
Innermost Layers (R<20cm, F~1016 neq/cm2)
active thickness reduced due to trapping ;
thin planar silicon still an option ;
3D detectors good option, but technology has to be improved;
01/10/2009
Otilia Militaru, on behalf of RD50, RD09 Conference, Italy