1. TCAD Simulations of Silicon Detectors operating at High Fluences D
TCAD Simulations of Silicon Detectors operating at High Fluences D. Passeri(1,2), F. Moscatelli(2,3), A. Morozzi(1,2), G.M. Bilei(2)
(1) Dipartimento di Ingegneria - Università di Perugia, Italy (2) Istituto Nazionale Fisica Nucleare - Sezione di Perugia, Italy
(3) Istituto per la Microelettronica e i Microsistemi - CNR Bologna, Italy

2. Outline Introduction & background.
TCAD simulations and radiation damage models.
Simulation results and comparison with experimental data.
Alternative material/detector layout analysis.
Conclusions.

3. Background... (1996)
Numerical analysis and physical modelling of semiconductor devices.
Modelling of the interaction between ionizing particle / silicon substrate compatible with BIM simulation scheme.
Grad can be distributed in time and space according to the numerical spatial and time discretization algorithms (HFIELDS UniBO)…

4. Radiation Damage Modeling
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:

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

6. “University of Perugia” model (2)
More than 20 specific journal papers on 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.

7. LHC CMS Si Tracker Design
Choice of the Si-Strip detector substrate resistivity.
Strip geometry optimization (w/p, metal overhang).
Metal overhang effect on the electron layer at the Si/SiO2 interface

8. LHC CMS Si Tracker Design (2)
Metal overhang effects on the electric field / potential distribution.
[1] D. Passeri et al., Optimization of Overhanging-Metal Microstrip Detectors: Test and Simulation, IEEE Trans. on Nuclear Science, Vol. 48, No. 3, June 2001

9. New “University of Perugia” model9

10. Detector Optimization
DC simulation - steady-state parameter evaluation: interstrip isolation (RINT) as function of dose.
TV simulation – “active” detector behavior: charge collection as a function of radiation damage (fluence).
Isolated
Not isolated

11. Interstrip Resistance
Comparison between measured and simulated interstrip resistance.
[1] Measurements from F. Moscatelli, D. Passeri, A. Morozzi, R. Mendicino, G.-F. Dalla Betta and G. M. Bilei, Combined Bulk and Surface Radiation Damage Effects at Very High Fluences in Silicon Detectors: Measurements and TCAD Simulations, IEEE Trans. On Nuclear Science, Vol. 63, No. 5, October 2016

12. Charge collection at T=248 K, @VBIAS
CCE of sample n+/p strip at T=248 K and different VBIAS. …?
[1] Measurements from Affolder et al., Collected charge of planar silicon detectors after pion and proton irradiations up to 2.2x1016 neq cm2 " NIM A, Vol. 623 (2010), pp

13. Alternative Materials: SiC
Measurements vs. Simulations of charge collection (distance) of Silicon Carbide (SiC) p+/n diodes.

14. Alternative Material: Diamond
Charge Collection Efficiency as a response to a MIP irradiation is selected as figure of merit for the model validation.
Simulations vs. Measurements for different diamond qualities, vendors, dimensions.
Sample from
Sample from
[1] A. Morozzi, Development and application of state-of-the-art device/circuit level TCAD simulation tools for the optimization of innovative Silicon-on-Diamond (SoD) semiconductor devices, PhD Thesis, University of Perugia, 2016.

15. Conclusions (1)
Silicon radiation damage modelling scheme, suitable for commercial TCAD tools (e.g. Synopsys Sentaurus).
Predictive capabilities extended to HL-LHC radiation damage levels (e.g. fluences > 2.0×1016 cm-2 1 MeV neutrons).
New materials / detector layout options investigation.
Further validation with experimental data comparisons.
Application to the optimization of HL-LHC pixel detectors (3D detectors, 2D planar detectors, …)  AIDA2020 WP7.2.

16. Conclusions (2)
Radiation damage model has been developed for 1 MeV neutron equivalent fluences up to 21016 cm-2 and it can be used for different particles considering the Non Ionizing Energy Loss (NIEL) hypothesis and the hardness factor k.
Model can be used for the design and optimization of future particle detectors (pixel, strips, ecc.) considering different geometries and thicknesses
Model could be extended up to fluences of the order of 1 MeV n/cm2 taking into account radiation damage effects at these very high fluences