1 Device Simulations & Hardware Developments for CBM STS Sudeep Chatterji CBM Group GSI...

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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

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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

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Status last time (Simulations)

Were Simulating Single sided strip detectors Using PISCES and SUPREM

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Status last time (Measurements)

Procured LCR meter

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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.

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10 KHz AC Output

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10 KHz DC Output

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Effect of open calibrationopen probe wires

Before Calibration After Calibration

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C-V characteristic of a 56pF capacitorwith open calibration

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

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I-V characteristic of a 1N4151 p-n diode

Reverse Bias

Forward Bias(current limit 2.5mA)

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Current-Voltage Measurement

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Capacitance-Voltage Measurement

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Coupling Capacitance (CAC)

Typical value ~ 100 pFTo avoid significant signal loss

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Interstrip Capacitance (Cint)

Typical value ~ 1-10 pF Purpose: To determine cross talk, Contributes to ENC Cint = 2 (Cint1 + Cint2) CTot = Cb + Cint

ENC = a + b.CTot e-/pF

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Bias Resistor

Typical Value ~ 1-10 MΩ Provides isolation between the strips Rint is fine if the measured resistance Vs. VBias plateaus The plateau level resistance is the Polysilicon bias resistance

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Interstrip Resistance (Rint)

Typical Value ~ 1-10 GΩ Provides isolation between the strips

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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

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Need of new Measurements (SPICE Model)

The noise of the readout is determined by CTot 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.

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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

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Measurement Table

Resistance of the implantation strip (Rn) can not be measured and Cnb and Cnn+1 measurements do not have a plateau value. These were determined through SPICE simulations.

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TCAD Simulations

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Simulation Grid

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Potential Distribution

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Electric Field Distribution

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Electric Field Distribution

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I-V Characteristics

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Hole Current

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Electron Current

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Hole Current Density

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Electron Current Density

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Electron Current Density

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Electron Current Density

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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