Ranjeet Center for Detector & Related Software Technology (CDRST)

1. TCAD Simulation of • Geometry Variation • under HPK campaign Ranjeet Center for Detector & Related Software Technology (CDRST) Department of Physics and Astrophysics, University of Delhi (DU), Delhi, INDIA On behalf of Si Sensor Simulation Group

2. Overview • MSSD • Simulations for different Geometries of MSSD’s • Comparison with Measurements • Simulations for Diodes • Summary and Future Outlook

3. MSSD • Multi-geometry Silicon Strip Detectors (MSSD) • 12 configurations, 32 strips • Differentstrip-width and pitch • Four different pitch values • Three classes of w/p: 0.121 – 0.142 ; 0.221 – 0.242 ; 0.321-0.342 • Differentthicknesses of the sensors (120 / 200 / 290 mm) • N-type and P-type substrates • Interstrip capacitance (Cint) contributes to noise significantly–Measurement vs. Simulation • Effect of isolation on Cint=> SeeMartin’s talk • Effect of Radiation damage on Cint=>SeeRobert’stalk • All device parameters are not known from manufacturer • Tune theseparameters in simulations • Sensitivity of sensorcharacteristics to variousphysical and geometricalparameters 12 Configurations

4. Interstrip Capacitance (Cint) Total Interstrip Capacitance: Cint = CAC + CDC + 2 * CACDC In the range 0.18 < w/p < 0.36, 50 < p < 200 mm & thickness = 300 mm a good approximation isgiven by: C int≈ [ 0.1 + 1.6*(w+20 mm)/p ] pF/cm where wand p are in mm Ref: S. Braibant et. al, NIMA 485 (2002), 343-361

5. Cint : General Trends

6. Effect of QF on Cint (n-type) SYNOPSYS Cint (pF) QF(cm-2) • Cint increases with surface charge density (QF) for values of QF > 1x1011 cm-2 • Cint increases with increase in w/p • For given w/p , Cint is higher for smaller pitch QF(cm-2)

7. Effect of Active Area on Cint (n-type & Y-type) 2-strip structure;Non-irradiated Cintvs. Bias Voltage for N-type for all 12 regions SYNOPSYS Active (total) thickness: 120mm (320 mm) Active (total) thickness: 200 mm (320 mm ) Active (total) thickness: 300 mm (320 mm ) • For n-type : • Cint increases with increase in active area • Cint increases with increase in w/p Cintvs. Bias Voltage for Y-type all 12 regions Active (total) thickness: 120mm (320 mm) Active (total) thickness: 200 mm (320 mm ) Active (total) thickness: 300 mm (320 mm ) • Np= 1e16 cm-3 • dp = 0.5 μm • For Y-type : Smallest Cint at all biases for thickness of 300 mm

8. TCAD Simulation vs. Measurement Active thickness: 300 mm

9. 5-STRIP Simulation 5-strip Structure Simulations SILVACO Simulated Structure (zoomed) • We have considered five strips in which Cint is evaluated by sending AC signal to central electrode and measuring it w.r.t. two adjacent strips (which are shorted).

10. Simulation of Cint for FZ320N • Performed Sensitivity Studies • Substrate Doping Concentration, NB (range: 1.0x1012 cm-3 - 4.0x1012 cm-3 ) • Metal Overhang Width(WMO) • Oxide Thickness (tox) • Junction Depth (XJ) • Coupling Oxide Thickness • Surface charge density , QF (range: 1x1010 cm-2 - 1x1012cm-2 ) SILVACO 2.5x1011 cm-2 2.5x1012 cm-3 1.5x1011 cm-2 3.0x1012 cm-3 1.0x1011 cm-2 3.5x1012 cm-3 • Compared simulated results for various set of (NB , QF) for one structure, keeping other parameters fixed with the experimental results. Once we found the optimized parameter set , we kept the same values of NB and QF for all other designs.

11. Simulation Parameters – Same for all 12 configurations 1.Substrate Doping Conc. (NB) = 3.0x1012 cm-3 2. Surface Charge Density  (QF) = 1.0x1011 cm-2 3. Temp = 21 deg C corresponding to 294 K 4) n+ implant of 30 micron from the back side 5) Junction depth of 1.5 micron 6) Strip length for normalization = 3.0490 cm 7) Total device depth is 320 micron. 8.) Frequency = 1MHz SILVACO Only Width and Pitch are changed in 12 configurations (according to MSSD design) keeping all other parameters same.

12. FZ320N (regions #5 to #8) SILVACO MSSD Structure No-5 MSSD Structure No-5 MSSD Structure No-6 Meas.#1 Meas.#2 Excellent agreement with One and within 10% of other two Meas.#3 Excellent agreement with One and within 10% of other two SIMULATION Cint (pF) Cint (pF) Reverse Bias (V) Reverse Bias (V) MSSD Structure No-8 MSSD Structure No-7 Excellent agreement Excellent agreement One of the Expt. result Cint (pF) Cint (pF) Reverse Bias (V) 12 Reverse Bias (V)

13. FZ320N (regions #5 to #8) Red Color – Simulation Others - Measurements SYNOPSYS MSSD Structure No-5 MSSD Structure No-6 Cint (pF) Cint (pF) Reverse Bias (V) Reverse Bias (V) MSSD Structure No-8 MSSD Structure No-7 Cint (pF) Cint (pF) Reverse Bias (V) Reverse Bias (V)

14. Cross - Validation SYNOPSYS MSSD Structure No-3 SILVACO Simulation results consistent between SILVACO and SYNOPSYS

15. Results – Cint for FZ320N All regions SILVACO • Cintvs. Bias Voltage • Only Width and Pitch are changed in 12 configurations (according to MSSD design) keeping all other parameters same • Mostly excellent agreement for all 12 configurations Meas.#1 Meas.#2 Meas.#3 SIMULATION

16. FZ200N (regions#5 to #8) SYNOPSYS Red Color – Simulation Others - Measurements MSSD Structure No-6 MSSD Structure No-5 Cint (pF) Cint (pF) Reverse Bias (V) Reverse Bias (V) MSSD Structure No-7 MSSD Structure No-8 Cint (pF) Cint (pF) Reverse Bias (V) Reverse Bias (V)

17. FZ120N (regions #5 to #8) Red Color – Simulation Others - Measurements SYNOPSYS MSSD Structure No-6 MSSD Structure No-5 Cint (pF) Cint (pF) Reverse Bias (V) Reverse Bias (V) MSSD Structure No-8 MSSD Structure No-7 Cint (pF) Cint (pF) Reverse Bias (V) Reverse Bias (V)

18. Cint of Non-Irradiated MSSD SYNOPSYS • Cint simulated matches well with the parameterization within 20% • Slight variation in Cint for approx. same w/p • Three classes of w/p: 0.121 – 0.142 ; Cint: 1.1 – 1.9 • w/p: 0.221 – 0.242 ; Cint: 1.4 – 2.4 • w/p: 0.321 - 0.342 ; Cint: 1.8 – 3.0 • Increase in width for given pitch increases Cint SILVACO

19. Diode Simulations For Large and Small Diodes (non-irradiated)

20. Simulation structure For Small Diode Diode center Periphery Guard SILVACO Zoomed view 12.5µm 32.5µm 50µm 22.5µm Total implant area 2mm x 2mm 17µm 1mm Total implant area 2mm x 2mm 28µm 660µm Schematics Diode center Guard Periphery Implant

21. IV & CV comparison at 293K SILVACO (pF-2) Red color: Experimental result Blue:Sim. with guard grounded Green : Sim. with guard floating Simu. With Guard grounded Simu. With Guard floating Three Exp results Full depletion voltage ~ 200V Parameterization of Nb = 3x1012cm-3 From MSSD simulations – seems good • Measurements were reproduced by simulation • No temperature effect on Capacitance in simulations as well as in measurement

22. For Large Diode SILVACO Guard Periphery Periphery Diode center Diode center 22.5µm 12.5µm Guard mm Total implant area mm x mm Total implant area 4.893 mm x 4.893mm 17µm 2.4465mm Total implant area 4893mm x 4893mm 90µm 660µm Zoomed view Zoomed view Periphery Implant Guard Schematics

23. CV comparison for large diode SILVACO (pF-2) Slightly lower Capacitance for simulations • Same parameters are used in Large Diode simulations (Nb, Tau0, QF etc) • Full depletion ~ 200V for measurements and simulations

24. Summary & Outlook • Converged to same set of simulation parameters • Cross-calibrated SILVACO & SYNOPSYS • Simulations are performed for all MSSD configurations for different thicknesses • Interstrip Capacitance simulations match well with measurements for MSSD as well as for diodes • Simulations also match within 20% with parameterization • Difficult to manage experimental data : spread of values is very large ( both in low & high voltage). We agree with a "preferred" subset of measurement. • Maintaining TWikihttps://twiki.cern.ch/twiki/bin/viewauth/CMS/SiSensorSimulation Outlook • Cint is measured experimentally up to 400 V : we cannot check breakdown performance at High voltage. • Simulations on breakdown voltage and CCE for MSSD ongoing

25. Backup

26. Results – Cintvs Bias for FZ320N Simulation at DESY (SYNOPSYS) Red Color – Simulation, Others - Measurements QF = 1x1011cm-2 Region-8 Region-6 Region -5 Region -2 Region -3 Region -4 Region -1 Region-7 Region -12 Region -10 Region -11 Region -9

27. Results – Cintvs Bias for FZ200N Simulation at DESY (SYNOPSYS) Red Color – Simulation, Others - Measurements QF = 1x1011cm-2 Region-8 Region -5 Region-6 Region-7 Region -2 Region -3 Region -4 Region -1 Region -12 Region -10 Region -11 Region -9

28. Results – Cintvs Bias for FZ120N Simulation at DESY (SYNOPSYS) Red Color – Simulation, Others - Measurements QF = 1x1011cm-2 Region-8 Region -5 Region -1 Region -2 Region-6 Region-7 Region -3 Region -4 Region -12 Region -10 Region -11 Region -9

29. Participating Groups • DESY • Thomas Eichhorn • Tool: Synopsys • Helsinki Institute of Physics • TimoPeltola • Tool: Synopsys • Karlsruhe Institute of Technology • Alexander Dierlamm, Robert Eber, Andreas Nürnberg, Martin Strelzyk • Tool: Silvaco, Synopsys • University of Pisa • University of Delhi • AshutoshBhardwaj, KirtiRanjan, Ranjeet, R K Shivpuri • Tool: Silvaco Sensor Upgrade Meeting 1.11.2012

30. CompArison with Claudio’s paper • Comparison with Review article: • “Device Simulations of Isolation Techniques for Silicon Microstrip Detectors Made on p-Type Substrates” by Claudio Piemonte, IEEE TRANS. NUCL. SCI., VOL. 53, NO. 3, JUNE 2006. • General Trends were same (although we don’t have exact simulation parameters as used by Claudio). Validation with some other papers are also carried out. Silvaco TCAD Sim. Paper Silvaco TCAD Sim. Paper 30

31. large variations in Leakage currents for different Large diodes ! 293K Apparently, there seems to be large variation in Tau0s for different samples!

32. IV Measurements at 253K • Large fluctuation as well as variation in currents at 253K between different Diodes • Measurements are not reproducible due to large fluctuation for same diode

33. IV comparison at 253K • Large fluctuation in currents even for the same diodes • TauN0=TauP0 = 1.6x10-2 sec. was used to match the current