1 Annealing studies of Mimosa19 & radiation hardness studies of Mimosa26 Dennis Doering* 1, Samir Amar-Youcef 1,3,Michael Deveaux 1, Melissa Domachowski 1, Ingo Fröhlich 1, Christian Müntz 1, Sarah Ottersbach 1, Joachim Stroth 1, Franz M. Wagner 2 for the CBM-MVD-Collaboration 1 Goethe University Frankfurt am Main, 2 TU München, Forschungsquelle Heinz Maier-Leibnitz (FRM II), 3 Helmholtz Research School, Frankfurt

2 Outline - MAPS, radiation damage and annealing - Leakage current and annealing - Charge spectrum and annealing - Radiation hardness study of Mimosa26 - Summary

/23 Annealing studies with combined radiation irradiated MAPS 3 Motivation The CBM-experiment (at FAIR) The CBM Micro Vertex Detector based on MAPS Expected radiation dose per CBM running-year: How can a sensor chip tolerate such radiation doses?  Annealing & partially depleted Mimosa26? Dennis Doering CBM Coll Meeting GSI 2010

/23 Operation principle of MAPS Annealing studies with combined radiation irradiated MAPS 4 Reset +3.3V Output SiO 2 N++ N+ P+ P- P+ Diode Epitaxial Layer P-Well Substrate Dennis Doering CBM Coll Meeting GSI 2010

/23 Annealing studies with combined radiation irradiated MAPS 5 Operation principle of MAPS Reset +3.3V Output SiO 2 N++ N+ P+ P- P+ Diode Epitaxial Layer e- Dennis Doering CBM Coll Meeting GSI 2010

/23 Annealing studies with combined radiation irradiated MAPS 6 Operation principle of MAPS Reset +3.3V Output SiO 2 N++ N+ P+ P- P+ Diode Epitaxial Layer e- Dennis Doering CBM Coll Meeting GSI 2010

/23 Annealing studies with combined radiation irradiated MAPS 7 Typesof radiation damage Types of radiation damage To be investigated and improved: Radiation hardness against… … ionizing radiation: Caused by charged particles and photons Energy deposited into the electron cloud Can ionize atoms and destroy molecules Can be studied with X-ray radiation … non-ionizing radiation: Caused by heavy, charged and neutral, particles Energy deposited into the crystal lattice Atoms are displaced Can be studied with fast neutron radiation Farnan I, HM Cho, WJ Weber, "Quantification of Actinide α-Radiation Damage in Minerals and Ceramics." Nature 445(7124): Dennis Doering CBM Coll Meeting GSI 2010

/23 Annealing studies with combined radiation irradiated MAPS 8 Radiation tolerance against radiation Reset +3.3V Output SiO 2 N++ N+ P+ P- P+ SiO 2 Defects generated by non-ionizing radiation. Dennis Doering CBM Coll Meeting GSI 2010

/23 Annealing studies with combined radiation irradiated MAPS 9 Radiation tolerance against radiation Reset +3.3V Output SiO 2 N++ N+ P+ P- P+ SiO 2 Positive Charge Positive charge generated by ionizing radiation. Dennis Doering CBM Coll Meeting GSI 2010

/23 Annealing studies with combined radiation irradiated MAPS 10 Leakage current Reset +3.3V Output SiO 2 N++ N+ P+ P- P+ SiO 2 Positive Charge Leakage current caused by radiation induced defects is collected. Dennis Doering CBM Coll Meeting GSI 2010

/23 Annealing studies with combined radiation irradiated MAPS 11 Annealing Reset +3.3V Output N++ N+ P+ P- P+ SiO 2 Reduced positive Charge Beneficial annealing: Interstitial atoms and vacancies recombine. Reversed annealing: Several defects form stable clusters. Leakage current may increase or decrease due to annealing. Annealing of defects ClusterformationRecombination Dennis Doering CBM Coll Meeting GSI 2010

/23 Annealing studies with combined radiation irradiated MAPS 12 Sensors and irradiation Used chips: Mimosa19 developed by IPHC Strasbourg. Fast reactor neutrons: +(~100kRad γ) → Mostly non-ionizing radiation damage as sensors are not powered. ~10keV X-rays (200kRad): only ionizing radiation damage. Combined radiation: ;1 year room temperature annealing; 200kRad X- rays. Neutron radiation performed by F. Wagner at FRM II Munich. X-ray radiation performed by A. Dierlamm at KIT. Mimosa19 Dennis Doering CBM Coll Meeting GSI 2010

/23 Annealing studies with combined radiation irradiated MAPS 13 Temperature profile T[°C] Time 20°C 80°C Neutron radiation 1 year X-ray radiation Measurements at T=20°C (280h) Heating at T=80°C (73h) Measurements and storage at T=20°C (191h) 2h transport Dennis Doering CBM Coll Meeting GSI 2010

/23 Annealing at room temperature Annealing studies with combined radiation irradiated MAPS 14 Beneficial annealing at T=20°C decreases leakage current by 20%. No reverse annealing observed. -20% Dennis Doering CBM Coll Meeting GSI 2010

/23 Annealing at T=20°C and T=80°C Dennis Doering CBM Coll Meeting GSI 2010 Annealing studies with combined radiation irradiated MAPS 15 Leakage current decreases by ~70% after beneficial annealing at T=20°C and T=80°C. Neutron irradiated sensors exhibits no significant annealing, neither beneficial nor reverse. No reverse annealing observed for up to 70h at T=80°C.

/23 Spectrum before and after X-ray radiation Dennis Doering CBM Coll Meeting GSI 2010 Annealing studies with combined radiation irradiated MAPS 16 X-ray irradiation shifted the spectrum to lower values. Calibration peak Cd-109-source

/23 Spectrum after annealing Dennis Doering CBM Coll Meeting GSI 2010 Annealing studies with combined radiation irradiated MAPS 17 Annealing recovers the shift of the spectrum. Calibration peak Cd-109-source

/23 Calibration peak and annealing Dennis Doering CBM Coll Meeting GSI 2010 Annealing studies with combined radiation irradiated MAPS 18 The position of the calibration peak is recovered. Not completely recovered after combined radiation.  combined radiation damage effect? Cd-109-source

/23 Mimosa26 Dennis Doering CBM Coll Meeting GSI 2010 Radiation hardness studies of Mimosa26 19 Analog output digital output pixel array: 1152 columns*576 rows pitch 18.4 µm More details: Talk C.Schrader Two versions: Standard and partially depleted

/23 Partially depleted Mimosa V Output SiO 2 N++ N+ SiO 2 P++ GND +3.3V E Dennis Doering CBM Coll Meeting GSI 2010 Radiation hardness studies of Mimosa26 20

/23 First analysis results Dennis Doering CBM Coll Meeting GSI 2010 Radiation hardness studies of Mimosa26 21 Mimosa26 SpectrumMimosa26 Noise First tests successfully performed at T= -20°C and. Preliminary

/23 Comparison standard and depleted sensor Dennis Doering CBM Coll Meeting GSI 2010 Radiation hardness studies of Mimosa26 22 Fe-55 4 pixel cluster T=-20°C Peak of the standard sensor is shifted to lower energy. Peak of the depleted sensor is not shifted. The depleted sensor seems to be more radiation hard than the standard sensor, to be confirmed in beam tests (June 2010). Shift after irradiation No shift

/23 Annealing studies with combined radiation irradiated MAPS 23 Summary Annealing -Systematic annealing studies on MAPS have been performed. -Annealing has been studied comparing individual (X-ray, neutron) with combined irradiation. -Beneficial annealing effects are observed for X-ray and combined irradiation. -Significant annealing effects for only neutron irradiation are not observed. -Reverse annealing effects have not been observed. -Annealing recovers the charge spectrum shift after X-ray radiation completely. Mimosa26 -Mimosa26 radiation hardness studies are started. -Depleted Mimosa26 seems to be more radiation hard than standard sensors. Conclusion -Annealing seems to be a promising strategy to recover the radiation induced performance losses in the MAPS-based vertex detectors like the MVD of CBM. Thank you for your attention Dennis Doering CBM Coll Meeting GSI 2010

24 Backup

/23 Noise and Collection peak Dennis Doering CBM Coll Meeting GSI 2010 Annealing studies with combined radiation irradiated MAPS 25 Only depleted sensors

/23 Calibration peak Dennis Doering CBM Coll Meeting GSI 2010 Annealing studies with combined radiation irradiated MAPS 26 Depleted Standard Vetotrigger: Only diode hits

/23 Time UKUK I Reset Reset transistor is opened refilling the capacity. C +3.3V K Reset transistor Operation principle of the preamplifier Dennis Doering CBM Coll Meeting GSI 2010 Annealing studies with combined radiation irradiated MAPS 27

/23 Time UKUK I Leakage U F0 U F1 C +3.3V K Reset transistor CDS= U F0 - U F1 2. Leakage current lowers slightly the voltage. The voltage is measured twice and compared (CDS). Operation principle of the preamplifier Dennis Doering CBM Coll Meeting GSI 2010 Annealing studies with combined radiation irradiated MAPS 28

/23 Time UKUK I Reset CDS= U F0 - U F1 2 U F0 U F1 3. Reset transistor is opened again refilling the capacity. C +3.3V K Reset transistor Operation principle of the preamplifier Dennis Doering CBM Coll Meeting GSI 2010 Annealing studies with combined radiation irradiated MAPS 29

/23 Time UKUK K I Reset I Leakage particle I Signal U F0 U F1 U F0 U F1 4. A particle generates signal charge, which lowers the voltage and increases the CDS. C +3.3V K Reset transistor CDS= U F0 - U F1 Operation principle of the preamplifier Dennis Doering CBM Coll Meeting GSI 2010 Annealing studies with combined radiation irradiated MAPS 30

/23 Time UKUK U F0 U F1 U F0 U F1 U F0 U F1 5. During the next frame no particle, only leakage current is measured. I Reset I Leakage C +3.3V K Reset transistor CDS=U F0 - U F1 Operation principle of the preamplifier Dennis Doering CBM Coll Meeting GSI 2010 Annealing studies with combined radiation irradiated MAPS 31

/23 Time K Threshold Hit identified! Measurement of leakage current Variation: Noise 6. A threshold is applied to identify a hit which might be generated by a particle. CDS= U F0 - U F1 Operation principle of the preamplifier Dennis Doering CBM Coll Meeting GSI 2010 Annealing studies with combined radiation irradiated MAPS 32

/23 Defect annealing Dennis Doering CBM Coll Meeting GSI 2010 Annealing studies with combined radiation irradiated MAPS 33 Defect migrationComplex formation Complex dissociation EmEm EfEf EdEd E m, E f and E d depends on temperature. => Each defect has a activation temperature. So heating the sensor may transform the defects. Heating more activates more defects. In addition question of probability.