(1) Dipartimento di Ingegneria - Università di Perugia, Italy (2) IOM CNR Perugia, Italy

1. CNR-IOM and University of Perugia 4DInSiDe: Innovative Silicon Detectors for particletracking in 4Dimensions activity D. Passeri1 and F. Moscatelli2 (1) Dipartimento di Ingegneria - Università di Perugia, Italy(2) IOM CNR Perugia, Italy

2. CNR-IOM and University of Perugia • Staff F. Moscatelli CNR-IOM PG A. Morozzi AR, INFN & Uni PG D. Passeri PA, Uni PG • Others 3 MS Thesis students (tirocinio)

3. Outline • CNR-IOM and University of Perugia are involved in WP1, WP2 and WP3.

4. WP1: Sensor design and fabrication • Sensor design – Technology CAD. • Synopsys Sentaurus TCAD to define the details of the design. • This activity will be carried out jointly by INFN and UniPg. • Milestones • Optimization of the gain layer design and its terminations using trenches. • Completion of the design for the first  production. • Definition of a double-sided process with a thin entrance window. • Completion of the design for the final production. • Deliverables: • Q2: First sensorprototype. • Q4: Specifications for low material budget, fill factor and thin entrance window. • Q5: Finalsensordemonstrator.

5. WP2: Modelling of Radiation tolerance, test-structure testing • Evolution of the Perugia Model by including the mechanisms of acceptor removal and interface charge trapping that are strongly affecting the behavior of LGAD sensors above fluences of 1E15 neutron/cm2. • Milestones: • Understanding of dopant deactivation effects within the radiation damage model – electrical analysis of the intentional introduction of impurities [e.g. Carbon]. • Model validations via comparison with available test measurements. • Identification of the most radiation-hard structures. • Deliverables: • Q1: Test structure design. • Q4,Q6: Report on irradiated and non-irradiated structures (first production and demonstrator). • Q4,Q6 : TCAD model of LGAD under hadron and neutronirradiation.

6. WP3: Sensor testing and validation • Another key aspect of the testing phase is the validation of radiation damage model when applied to the LGAD sensor design. For this reason, in close collaboration with CNR-IOM PG, specific test structure will be design and irradiated to fluences well above our goal of 5E15 (1-MeV neutron)/cm2. • Milestones: • Test of sensors in the laboratory (CV, IV, laser, sources, temperature scans). • Identification of the best design and construction techniques. • Deliverables: • Q4,Q6: Report on sensors properties (first production and demonstrator). • Q4,Q6: Full characterization for each sensor variation (report on the space and time resolution, dead area, efficiency for low energy x-ray detection, and radiation resistance).

7. Perugia Measurement setup Semi-automatic PA 200 Karl SussPerugia

8. Instruments 2 SMU Keithley 237 1 SMU Keithley 236 2 SMU HP 4210 1 CV MeterKeithley 595 1 HF CV MeterKeithley 590 1 LCR Meter 4284A 1 Switching Matrix 707 (6 card 8x12, 1 of them HV 1000 V)

9. Hall Effect System Magneticfield 1 T Measurements of resistivity, mobility and carrier concentration using the Van der Pauwmethod. Sample holder to be made.

10. New instruments: probe station MPI TS2000 SE New probe station semi-automatic. The tender iscompleted(expected in September 2019). Triaxialthermalchuck -60°C ÷ +200°C V up to 1 kV. Microchamber. Probe card adapter. 4 probes.

12. TCAD Simulations • Modern TCAD tools(1) offer a wide variety of approaches,characterized by different combinations among physical accuracy and comprehensiveness, application versatility and computational demand -> mixed-mode approaches can be efficiently followed. • A number of different physical damage mechanisms actually may interact in a non-trivial way. Deep understanding of physical device behavior therefore has the utmost importance, and device analysis tools may help to this purpose. • Bulk and surface radiation damage have been taken into account by means of the introduction of deep level radiation induced traps whose parameters are physically meaningful and whose experimental characterization is feasible. • Within a hierarchical approach, increasingly complex models have been considered, aiming at balancing complexity and comprehensiveness. (1) Sentaurus Device

13. TCAD Simulations • 20 floating node licenses (Advanced TCAD suite) • 4 PC – 1 Workstation

14. Once upon a time... (1996) • Numerical analysis and physical modelling of semiconductor devices. • Modelling of the interaction between ionizing particle / silicon substrate compatible with Box Integration Method simulation scheme. • Grad can be distributed in time and space according to the numerical spatial and time discretization algorithms.

15. Radiation damage modelling • Numerical modelling of radiation damage effects in semiconductor devices. • Deep-level recombination centres / traps radiation induced. • Explicit contribution of the trapped charges to the charge density (modified Poisson equation): • Continuity equation for both free and trapped carriers:

16. “University of Perugia” model • Hierarchical approach based on increasing number of deep-level recombination centres / trap states. • Comprehensive modelling of device behaviour: • - depletion voltage, leakage current (a), “double peak” shaped electric field, charge collection efficiency, … • Meaningful and physics based parametrization. • Three levels with donor removal and increased introduction rate (to cope with direct inter-defect charge exchange – numerically overwhelmed effect). • -type and -type substrates. • OK for fluences up to 1015 cm-2 1 MeV neutrons.

17. “University of Perugia” model (2) More than 20 specific journal paperson TCAD radiation damage modelling … [1] D. Passeri, P. Ciampolini, G.M. Bilei, and F. Moscatelli, Comprehensive Modeling of Bulk-Damage Effects in Silicon Radiation Detectors, IEEE Trans. on Nuclear Science, vol. 48, no. 5, October 2001. [2] M. Petasecca, F. Moscatelli, D. Passeri, and G. U. Pignatel, Numerical Simulation of Radiation Damage Effects in p- Type and n-Type FZ Silicon Detectors, IEEE Trans. on Nuclear Science, vol. 53, no. 5, October 2006.

18. New “University of Perugia” model • Extend the predictive capabilities to HL-LHC radiation damage levels (e.g. fluences > 2.0×1016 cm-2 1 MeV neutrons). • Keep low the number of traps (e.g. fitting parameters). • New effects (e.g. charge multiplication <- avalanche effects). • Physically grounded approach. • No over-specific modelling (one model fits all…). • Predictive capabilities @, @T, @Vbias, …

19. Radiation damage effects

20. Radiation damage modeling approach MODEL PARAMETERS EXTRACTION TEST STRUCTUREMEASUREMENTS CHARGE COLLECTION MODEL VALIDATION • Modelling the effects of the radiation damage. • Predictive insight of the behaviour of detectors, aiming at their performance optimization. DETECTOR OPTIMIZATION

21. Radiation damage effects (2) • Ionization -> SURFACE damage • - build-up of trapped charge in the oxide; • - increase in the number of bulk oxide traps. • - increase in the number of interface traps; • - QOX, NIT • Atomic Displacement -> BULK damage • - silicon lattice defect generations; • - point and cluster defects; • - increase of deep-level trap states; • - NT T. R. Oldham, F. B. McLean, Total Ionizing Dose Effects in MOS Oxides and Devices, IEEE Trans. on Nuclear Science, vol. 50, no. 3, June 2003

22. Traps characteristics • Traps provide allowed energy states within the band-gap, affecting the device behavior to many respects, e.g. by altering the effective doping, by enhancing recombination, by increasing leakage… • Several models, e.g. Shockley–Read–Hall recombination, depend on traps implicitly • Traps can be specified in terms of: • Type (Acceptor, Donor) • Energy Distribution (Level, Gaussian, Uniform, …) • Capture cross-sections (electron, holes) • Concentration / Spatial distributions

23. Work plan: simulations • Bulkradiation damage modelling: • - extension of the three-level UniPG modelling (capture cross section, charge multiplication, avalanche effects). • Interfaceradiation damage modelling: • - oxide fixed charge and interface trap state @fluence; • - systematic study of acceptor/donor states at different energies. • Understanding of dopant deactivation effects within the radiation damage model – electrical analysis of the intentional introduction of impurities [e.g. Carbon]. • Technology (process) dependent effect -> deep level parameterization, oxide charge density, interface trap energy and density, cross sections (e/h), trap type (acceptor or donor). • Comparison with literature data/dedicated measurements in terms of static parameters (R, C) and charge collection properties. • Identification of the most radiation-hard structures.

24. Work plan: measurements • Measurements on dedicated test structures e.g. gated diodes, MOS capacitors and MOSFETs on p-spray/different substrates. • Different technologies (e.g. FBK, HPK, …). • High-Frequency and Quasi-Stationary C , MOSFET VTH and I-V characteristics, … • Irradiation campaign with x-ray and protons/neutrons at very high fluences(> 5x1015neq/cm2). • Measurements after irradiation -> trap parameter extraction, TCAD model validation. • Predictive application of the model -> sensor design and optimization.

25. Starting point / current activities recap

26. New “University of Perugia” model • From C-V measurements of MOS capacitors: • DIT assessed by using the C-V High-Low method. • HF measurements at 100 kHz with a small signal amplitude of 25 mV. • QS characteristics measured with delay times of 0.5 s using a voltage step of 100 mV. • NEFF obtained from VFB measurements. MODEL PARAMETERS EXTRAPOLATION TEST STRUCTUREMEASUREMENTS MODEL VALIDATION DETECTOR OPTIMIZATION • DIT interface trap density • NIT integrated interface trap density • NOX oxide charge density • NEFF effective oxide charge density • From I-Vmeasurements of MOSFETS: • After X-rays irradiation  • ΔVth is separated into a contribution due to NIT and NOX from IDS-VGS of MOSFET (method proposed in McWorther Applied Physics Letters 48, 133 (1986)) +

27. IFX p-type: summary of measurements • Evaluate differences among three processes in terms of NEFF and NIT ( process variability) • Higher differences at lower doses.

28. HPK p-type: summary of measurements • Evaluate different technology options on radiation hardness. • Similar values of NEFF and NIT for HPK devices with different pstop/pspray isolation.

29. New “University of Perugia” model Conduction Band EC MODEL EC - 0.56 eV Acceptor Band • Interface trap state energy modelling PARAMETERS EXTRAPOLATION EV+ 0.6 eV Donor Band EV Valence Band TEST STRUCTUREMEASUREMENTS MODEL VALIDATION DETECTOR OPTIMIZATION

30. New “University of Perugia” model Interface trap state energy modeling evolution: A (literature data)  B  C  D (in-house measurements). A C B D

31. IFX MOS capacitors • Measurement campaign • Doses range 0.05–100Mrad(SiO2) • Carried out in Padova (IT) 2S process PS-S process ACC CLF DEPL CHF INV

32. IFX gated diodes • p-type substrate. • IFX 2S process • I-V simulations. vs measurements at different doses.

33. HPK test structures • Same modeling scheme to simulate C-V of MOS and Rinterstrip. • Good agreement between simulations and measurements using the same model used to simulate MOS capacitors. MOS capacitors with pstop Rinterstrip –pstop implant

34. Study of the combined effect of TCAD bulk and surface radiation damage models on the Charge Collection (CC) performance of silicon strips as a function of the particle hit position. Combined Surface and Bulk TCAD model Acceptor EC-0.42eV AcceptorEC-0.46eV Donor EV+0.36eV DonorEC-0.23eV Acceptor EC-0.42eV AcceptorEC-0.46eV

35. Study of the combined effect of TCAD bulk and surface radiation damage models on the Charge Collection (CC) performance of silicon strips as a function of the particle hit position. Combined Surface and Bulk TCAD model

36. The new “University of Perugia” Model Bulk damage modelling scheme • CC for n-type silicon strips. A. Affolder et al, NIMA Vol. 623 (2010), pp. 177-179. Surface damage modelling scheme