1. 1 Device Simulations & Hardware Developments for CBM STS Sudeep Chatterji CBM Group GSI Helmholtz Centre for Heavy Ion Research CBM Collaboration Meeting, Split, Croatia 6 October, 2009

2. 2 Outline  Status last time  Measurements  I-V and C-V setup  labview programs  Results on some devices  Simulations  SYNOPSIS TCAD packages  Some results  SPICE simulation (What’s the need)  Next Sensor prototype from CIS  Future Plans

3. 3 Status last time (Simulations)  Were Simulating Single sided strip detectors  Using PISCES and SUPREM

4. 4 Status last time (Measurements)  Procured LCR meter

5. 5 HV Isolation Box for LCR meter RC High Pass Filter  Purpose:  The leakage current can only flow through PA, no other path is allowed.  The AC signal sourced by LCR meter goes in DUT and then is sunk by LCR.  The operation of LCR and PA are decoupled.  Realisation:  The HV side of DUT is coupled via a blocking capacitor to H connector.  A large R prevents the AC signal sourced by H to be sank by power supply.  L conn. needs to be decoupled so that leakage current does not reach LCR.

6. 6 10 KHz AC Output

7. 7 10 KHz DC Output

8. 8 Effect of open calibration open probe wires Before CalibrationAfter Calibration

9. 9 C-V characteristic of a 56pF capacitor with open calibration

10. 10 I-V characteristic of a 91kOhm resistor (reverse bias voltage)

11. 11 I-V characteristic of a 1N4151 p-n diode Reverse Bias Forward Bias (current limit 2.5mA)

12. 12 Current-Voltage Measurement

13. 13 Capacitance-Voltage Measurement

14. 14 Coupling Capacitance (C AC )  Typical value ~ 100 pF  To avoid significant signal loss

15. 15 Interstrip Capacitance (C int )  Typical value ~ 1-10 pF  Purpose: To determine cross talk, Contributes to ENC  C int = 2 (C int1 + C int2 )  C Tot = C b + C int  ENC = a + b.C Tot e-/pF

16. 16 Bias Resistor  Typical Value ~ 1-10 MΩ  Provides isolation between the strips  R int is fine if the measured resistance Vs. V Bias plateaus  The plateau level resistance is the Polysilicon bias resistance

17. 17 Interstrip Resistance (R int )  Typical Value ~ 1-10 GΩ  Provides isolation between the strips

18. 18 Flat Band Voltage  Used to extract the surface oxide charge (Quality of Oxide)  Important parameter for surface radiation damage  Need to probe MOS device for this measurement

19. 19 Need of new Measurements (SPICE Model)  The noise of the readout is determined by C Tot seen by the preamplifier  Not only the Capacitance (C) but also the resistance (R) values affect signal processing and various sources of noise.  It is not possible to measure all the R and C especially after irradiation  Radiation damage also induces variation in the macroscopic parameters, such as resistance and capacitance values.

20. 20 Need of new Measurements (SPICE Model)  R and C that could not be measured are treated as free parameters in SPICE model and are extracted through the fitting procedure.  Some parameters could be measured but could not reach a plateau value with frequency

21. 21 Measurement Table  Resistance of the implantation strip (R n ) can not be measured and C nb and C nn+1 measurements do not have a plateau value. These were determined through SPICE simulations.

22. 22 TCAD Simulations

23. 23 Simulation Grid

24. 24 Potential Distribution

25. 25 Electric Field Distribution

26. 26 Electric Field Distribution

27. 27 I-V Characteristics

28. 28 Hole Current

29. 29 Electron Current

30. 30 Hole Current Density

31. 31 Electron Current Density

32. 32 Electron Current Density

33. 33 Electron Current Density

34. 34 Summary/Future Plans  TCAD simulation running successfully (on batch farm)  Plan to start SPICE simulation (P-SPICE installed)  Decide with CIS the simulation parameters  Radiation Damage in DSSDs (help needed from Physicists)  In hardware, plan to carry out full sensor characterization  Design Probe card and Multiplexer (or explore market)  Irradiation of Sensors/Annealing studies  Accepted in 2009 IEEE NSS:  Development of Radiation hard Silicon Sensors for the CBM Silicon Tracking System using simulation approach - Oral  The Silicon Tracker of the CBM Experiment at FAIR: Detector Developments and First in-beam Characterization - Poster