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

4 Status last time (Measurements)  Procured LCR meter

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 10 KHz AC Output

7 10 KHz DC Output

8 Effect of open calibration open probe wires Before CalibrationAfter Calibration

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

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

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

12 Current-Voltage Measurement

13 Capacitance-Voltage Measurement

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

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

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 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 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 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 TCAD Simulations

23 Simulation Grid

24 Potential Distribution

25 Electric Field Distribution

26 Electric Field Distribution

27 I-V Characteristics

28 Hole Current

29 Electron Current

30 Hole Current Density

31 Electron Current Density

32 Electron Current Density

33 Electron Current Density

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