1. CNM double-sided 3D strip detectors before and after neutron irradiation Celeste Fleta, Richard Bates, Chris Parkes, David Pennicard, Lars Eklund (University of Glasgow) Giulio Pellegrini (IMB-CNM, Barcelona) 15 April 2008

2. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Outline  Double sided 3D detectors  Structure  Simulations  Fabrication at CNM  Technology  Fabricated devices  Tested devices: 3D pad and strip detectors  I-V and C-V before and after irradiation  Charge collection setup  Charge collection in non-irradiated strip detectors  Conclusions and future plans In this talk I will present the I-V and C-V characteristics of double sided 3D n-type detectors before and after reactor neutron irradiation to 5×10 15 1MeV n/cm 2. I will also show the charge collection from a a Sr90 MIP source of a strip detector before irradiation.

3. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Double sided 3D detectors Alternative 3D structure proposed by IMB-CNM –Electrodes etched from opposite sides of the wafer –Columns do not pass through full substrate thickness Also being investigated by FBK-irst

4. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Double sided 3D detectors Short charge collection times because both carrier types mainly drift horizontally High drift velocity as the electric field can be increased even after full depletion. Disadvantages: low field region below columns Undepleted No damage10 16 n eq /cm 2 100V bias 250 µm columns both devices DS3D has slightly higher collection at low damage (greater device thickness) But at high fluence CCE matches standard 3D of same column length Performance comparable to standard 3D

5. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Double sided 3D fabrication at CNM First run is p-in-n: –250 μm p+ columns in 300 μm n-type substrate n-Si (p+) 27.5  m Electrode fabrication: 1.ICP etching of the holes: Bosch process, ALCATEL 601-E 2.Holes partially filled with 3 µm LPCVD poly 3.Doping with P or B 4.Holes passivated with 2 µm TEOS SiO 2 (all fabrication done in-house)

6. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Wafers Two 4” wafers produced, one used for the electrical tests, the other for bumpbonding - 6 Medipix2 - 6 ATLAS pixels - 1 Pilatus - 4 short strips - 1 long strip - 6 pad diodes - Test structures

7. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Wafers Two 4” wafers produced, one used for the electrical tests, the other for bumpbonding - 6 Medipix2 - 6 ATLAS pixels - 1 Pilatus - 4 short strips - 1 long strip - 6 pad diodes - Test structures

8. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Devices tested: 3D pad and strip detectors Pad detector: 90×90 p-holes, pitch 55 µm, ~5×5 mm 2 Strip detector: 50 strips, 50 holes/strip, pitch 80 µm, ~4×4 mm 2, DC coupled 3D guard ring Collecting electrodes (p)

9. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Pre-irradiation results in pad detectors Guard ring and central diode at 0V, backside biased, T = 21˚C Lateral depletion at 2.4 V (pitch 55 µm), full depletion at ~8.5 V Current per hole 0.1–10 pA Two detectors tested to 40 V, one to 200 V, without signs of breakdown

10. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Pre-irradiation results in strip detectors Measured with 3 strips and guard ring at 0V, backside biased Strip currents ~100 pA (T = 21˚C) in all 4 detectors (2 pA/hole) Can reliably bias detectors to 50 V (20 times lateral depletion voltage) Capacitance to backplane 10 pF/strip Guard ring currents vary: highest 20 μA, lowest 0.03 μA at 10V

11. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta C-V and I-V after irradiation of strip detectors Irradiation and dosimetry: TRIGA Mark II research reactor, Jozef Stefan Institute, Ljubljana 5×10 15 n eq /cm 2 Detectors not annealed, kept at -13ºC Non-irradiated: C stable after 10 V Irradiated:Substrate not fully depleted at 40V C measured between strip and backplane, 21ºC:

12. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta C-V and I-V after irradiation of strip detectors (2) Same setup as non-irradiated characterisation, 21˚C Currents too high to bias to full depletion Simulation: V(lat. depletion) = ~50V  I(50V) ~ 20 µA/strip at 20˚C This gives a reasonable value of the current damage constant, α ~ 6×10 -17 A/cm Need to re-test at low temperature 5×10 15 n eq /cm 2

13. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta MIP test setup with LHCb Velo electronics Stand-alone setup Sr90 source and scintillator / PMT trigger Beetle strip readout chip (128 channels) –Positive or negative polarity –Analogue sampling of strip signal every 25ns Logic only accepts triggers arriving at a specific time relative to the sampling clock –Ensures sampling at peak of pulse –Allows measurement of front-end pulse shape TELL1 readout board reads out up to 4 modules –ADC conversion of data –Controls Beetle settings, test pulses etc. LHCb software decodes and processes data –Pedestal subtraction, linear common-mode subtraction, clustering (See L. Eklund’s talk at the 11 th RD50 Workshop, http://rd50.web.cern.ch/rd50/)

14. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Modules Pre-production hybrids from LHCb Inner Tracker Beetle chips Pitch Adaptors (produced in Glasgow) Sensors Alumina baseboards (96% Al 2 O 3, Coors Tek)

15. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta 3D detector module CNM 3D strip detectors are DC coupled, but the leakage current per strip of non- irradiated detectors (100 pA) is low enough to allow direct connection to the Beetle front end For irradiated detectors AC coupling is needed  RC filter

16. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta MIP test results on non-irradiated CNM 3D sensors (20V) Fitted with Landau convoluted with Gaussian More low-amplitude hits seen than expected from Landau –Possibly due to particles passing through columns? Most probable value 24.6 ADC counts Typical noise 1.75 ADC counts Signal/noise = 15 Hit spectrum from CNM 3D

17. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Clusters: planar vs 3D Planar 38% single strip clusters

18. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Clusters: planar vs 3D 3D 84% single strip clusters Planar 38% single strip clusters

19. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Future plans: 3D Medipix 3 Medipix3D (+ 1 planar) have been bump bonded at VTT Will be tested with the USB Interface for Medipix (CTU, Prague) Tests with X-ray dental source in Glasgow; beam test in Diamond Light Synchrotron planned for June Medipix3D. Image: VTT Finlan d

20. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Future plans: new run Started in February. Estimated end June P- and N- type substrates (8 + 8 wafers)  Collection in N- and P- electrodes respectively  Usable ATLAS pixel detectors in the p-type wafers FULL 3D structure in 3P + 3N wafers  300 µm substrate  12 µm holes (instead of 10µm) Same wafer layout as first run

21. 3rd Workshop on Advanced Silicon Radiation DetectorsC. Fleta Summary Double sided 3D pad and strip detectors fabricated by CNM have been characterized at the University of Glasgow Unirradiated pad detectors show lateral depletion at 2.4 V, full depletion at 8.5 V 3D strip detectors before irradiation: –100 pA/strip (2 pA/hole) –Signal/noise = 15 –Very low charge sharing compared to planar detectors 3D strips after irrad ( 5×10 15 n eq /cm 2 ): –Difficult to test due to high leakage currents, need to re-test with cooling –I > 20 µA/strip –Not fully depleted at 40 V –CCE tests still to do Next: Medipix2 pixels Looking forward to the new run!