1. the Sixth International "Hiroshima" Symposium Giulio Pellegrini Technology of p-type microstrip detectors with radiation hard p-spray, p-stop and moderate p-spray insulations G.Pellegrini 1, C.Fleta 2, F.Campabadal 1, M. Lozano 1, J.M. Rafí 1, M.Ullán 1 1 Centro Nacional de Microelectrónica, Barcelona Spain 2 University of Glasgow, Glasgow, UK

2. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 2 Outline P-type detectors Detector isolation technologies Simulation and measurements Conclusions

3. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 3 P-type detectors Technology: N type strips on p-type substrate N side read-out takes advantage of the presence of the high electric field on the read-out side after irradiation. Needs insulation between strips in order to compensate the electron layer formed below the oxide: P-stop P-spray Moderate p-spray More complex technology 6 or 7 photolithographic layers The most radiation hard technology

4. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 4 P-stop isolation First n-on-p detectors fabricated with p-stop isolation. Different implants were used to find the optimum value. Pitch 120  m, p-stop width 7  m, strip width 20  m

5. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 5 Radiation hardness Baby microstrip detectors fabricated at CNM in collaboration with Liverpool University Efficiency of Charge Collection in 280 um thick p-type SSD After 7.5 *10 15 p/cm 2, charge collected is > 6,500 e - (1)First results on charge collection efficiency of heavily irradiated microstrip sensors fabricated on oxygenated p-type silicon. NIM-A, num 518, Feb. 2004, pp. 340-342. G. Casse, P.P. Allport, S. Martí, M. Lozano, P. R. Turner. (2)Comparison of radiation hardness of P-in-N, N-in-N and N-in-P silicon pad detectors IEEE Trans. on Nucl. Sci., V. 52, Issue 5, Part 2, Oct. 2005 Page(s):1468 – 1473, M. Lozano, G. Pellegrini, C. Fleta, C. Loderer, J. M. Rafí, M. Ullán, F. Campabadal, C. Martínez, M. Key, G. Casse, P. Allport N-on-p strip detectors with p-stop isolation (1) Pad detectors (2)

6. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 6 Annealing p-type G. Casse, “Overview of n-side read-out microstrip devices”, RD50/FDS meeting 2005. Annealing (@80 o C) behaviors of the collected charge after proton irradiation to 3.5. 10 15 cm -2. At high voltage the collected charge appears to be stable. It is known that the full depletion voltage as determined by CV measurements appears to follow the expected evolution. N-on-p strip detectors with p-stop isolation Pad detectors “Annealing Studies of Magnetic Czochralski Silicon Radiation Detectors”, G.Pellegrini et al., Nucl. Instr. and Meth. Volume 552, Issues 1-2, 21 October 2005.

7. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 7 Electronic Noise G. Casse, “Overview of n-side read-out microstrip devices”, RD50/FDS meeting 2005. Baby microstrip detectors fabricated by Hamamatsu micro-discharge noise Micro-discharges can represent the earliest mechanism of failure for micro-strip detectors when operated at high voltage.

8. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 8 P-spray isolation To avoid the problem of microdischarges p-spray isolation was used to fabricate microstrip and pad detectors. P-spray has to: Insulate strips Keep VBD > VFD Variables: Oxide thickness Implant dose Implant energy Thermal budget fixed Optimization through: Simulation (ISE-TCAD) Engineering runs (3) Conflicting conditions

9. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 9 Simulation of p-spray p-spray V BD (V) Diodes Energy (keV) Dose (cm -2 ) SimulatedMeasured 4510 12 900 V700 V 15010 12 750 V650 V 455×10 12 210 V250 V Electric field at the breakdown point

10. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 10 P-spray: calibration runs Characteristics of n-in-p pad detectors with p-spray isolation p-sprayCurrent at V FD +20 V Energy (keV) Dose (cm -2 ) StripsRing 4510 12 50 ± 30 nA2 ± 1 mA 15010 12 90 ± 40 nA150 ± 40 µA 455×10 12 1.4 ± 1.1 µA300 ± 30 nA

11. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 11 Effect of oxide charge Strip detector Irradiation: 50 Mrad, Co60 gamma source MOS Capacitor CV measurements Oxide charge Before: 1  10 11 cm -2 After:3  10 12 cm -2 Fast build-up of damage in the oxide layer Reach a saturation value for the oxide charge of about 2-3  10 12 cm -2 at about 100-200 krad (few LHC weeks) The oxide charge will be saturated well before the bulk damage will start to affect the operation of the detectors This oxide charge increases inversion layer, canceling the p-spray insulation It is very important to ensure that insulation is maintained after first irradiation, not only in fresh or bulk damaged detectors. “Technology development of p-type microstrip detectors with radiation hard p-spray isolation”, G. Pellegrini et al., Nucl. Instr. and Meth A 2006 In Press, Corrected Proof, Available online 28 July 2006

12. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 12 Neutron irradiation read a 3cm p-type detector using the ATLAS SCTDAC readout. SCTDAC is optimised for n-type sensor. SCT readout: binary ABCD3T chip P-type irradiated with neutrons (10 15 n/cm 2 ) Please look at C. Lacasta poster in this conference Signal induced by 1060 nm pulsed laser illumination, n-in-p detector after 7.5 10 15 p cm -2. (G.Casse,RD50 Status Report 2004)

13. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 13 Final process Rd50 mask Guard rings CCE and noise measurements on strip detector undergoing by RD50 collaboration

14. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 14 P-spray vs p-stop P-spray Is a critical technology Low repeatability of the p-spray process. Detectors performance are very sensitive to the p-spray isolation dose implanted. Isolation dependent on charge oxide before and after irradiation The surface damage usually leads to higher leakage currents before irradiation P-stop Requires a minimum strip pitch depending on the design rules of the manufacturer ‘Leaky channels’ can severely reduce the yield, hence the necessity of a minimum width of the p-stop implant High electrical field in P-stop corner This high electric files may cause micro-discharge noise

15. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 15 Moderated p-spray We can take the best from the two options: Moderated P-spray An old (1997) patent from MPI presented the basics Technology has to be optimized We have developed through simulation a technology for p-type detectors with moderated p-spray insulation Boron implant parameters are selected from our previous experience with microstrip with p-stops With less p-spray implanted charge, we obtain: Higher breakdown voltages Good insulation before and after irradiation Eliminate the high field corner in the p-stop causing microdischarges No necessity of redundancy in the p-stop implants.

16. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 16 Simulation of moderated p- spray Simulated device RD50 mask set (pitch 80 μm, strip width 32 μm) Single p-stop between the strips: width 10 μm Substrate: P-type,, 30 kΩ·cm Oxide charge density: 10 11 cm -2 (non-irradiated device) P-implant parameters: Fixed energy, dose: 50 keV, 10 13 cm -2 Fixed oxide implant thickness for the p-stop area We have fabricated devices with these p-stop implant parameters and they show a satisfactory electrical behavior The objective of the simulations is to determine the optimum profile in the p- spray area

17. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 17 Technology First: oxidation, photolithography p-stop regions, wet oxide etching, oxidation, photoresist striping At this point there are two different oxide thicknesses thin oxide in the p-stop area and a thicker oxide on the rest of the silicon surface (“p-spray area”) P-implant (Energy 50 keV, dose 10 13 cm -2 ) Finish with the usual fabrication process

18. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 18 Simulated Devices profilesI-V curves

19. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 19 Doping profile comparison P-stop only Moderated p-spray N strip P-stop P-spray

20. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 20 Electric field comparison P-stop only Moderated p-spray microdischarches? N strip P-stop P-spray

21. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 21 Experimental Results

22. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 22 Experimental Results Test structure to measure interstrip resistance

23. the Sixth International "Hiroshima" Symposium Giulio Pellegrini 23 Conclusions P-type detectors seems the best detector option for the future sLHC experiments as they gather beneficial properties: electron collection junction always at the strip side partial depletion operation possible very high radiation hardness stable annealing We have developed three technologies for p-type detectors with the different isolation techniques: p-spray, p-stops and moderated p-spray Detectors have been fabricated, irradiated with protons, neutrons, and gammas, and they work properly