Study of radiation damage in silicon detectors for high ... - F9

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46 3. Irradiation Facility3.5 Measurement Setup, Methods and AnalysisIn the scope of this work, full depletion voltage (FDV) and bulk reverse current weremeasured on samples under study. The measurement setup as used in the laboratory isdescribed while the one used at the reactor was described in section 3.3.2. Since bothsetups are only slightly dierent, the same measurement method and analysis were used.3.5.1 Laboratory SetupHP 4284ALCR meterKEITHLEY 237HV meas. unitR=4.7kΩC=100nFcca. 3mBPPADGRFigure 3.10: Measurement setup as used in the laboratory. BP, TOP and GR are connectionsto sample back plane, pad and guard ring, respectively.The main components of the measurement setup were a LCR meter, a precise ampermeterand a high voltage source (up to cca. 1000 V). All units were computer controlled.In the laboratory, a HP4284A LCR measure unit and a KEITHLEY 237 high voltagesource-measure unit were used. A Yokogawa UT15 temperature controller connected toa Pt100 sensor placed close to the sample was used to measure the sample temperature.All units were controlled and read out by a personal computer, where some on-line dataanalysis was also performed.To measure the capacitance at dierent depletion depths, i.e. at dierent voltages,an external DC voltage has to be applied to the sample. In the laboratory, a KEITHLEY237 high voltage source-measure unit was used as an external power source. It can provideDC voltage up to 1100 V with a current limit of 1 mA. To shield the LCR meter from highDC biasing voltages, decoupling capacitors were used as shown in gure 3.10. To reduce
3. Irradiation Facility 47the inuence of changes in the small impedance of the voltage source on the measurements,decoupling resistors have been used (gure 3.10).Most of the measurements were performed in a thermostat chamber at 5 C. Whenstored, samples were kept at stable temperature in one of the temperature stabilisedchambers. For biasing during storage Wentzel high voltage power supplies were used.Annealing and reverse annealing have been accelerated by heating in an oven stabilisedto 60 C, stable to about 2 C. Temperature history during heating was measured by aPt100 sensor, placed close to the sample and connected to a Yokogawa controller. Thetemperature was read from the controller by computer and stored to a le. Measuredtemperature history was used to correct the equivalent heating time for temperaturevariations (eq. 4.5).3.5.2 C/V MeasurementsFull depletion voltage was determined from the kink in C/V plot (see section 2.1.6). Itwas used to determine the average eective dopant concentration according to equations2.10 and 2.13.Capacitance versus voltage curves were measured by Hewlet-Packard LCR meter.Capacitance is determined from the complex impedance. It is calculated from the measuredamplitude and phase shift of the current signal in response to an AC measuringvoltage with user selected frequency. The AC voltage amplitude can be set from 5 mV to2V.High measurement voltages give theadvantage of better signal to noise ratio. Theyare however a signicant disturbance at bias voltages of few volts. Thus at the reactorthe amplitude of the measurement voltage was kept at 1 V due to harsh measurementconditions (long partially unshielded cables). At the laboratory, it was usually kept atlower values, typically 10 mV.Both HP4284A and HP4263B 23 LCR meters provide means to transform measuredcomplex impedance to dierent physical parameters according to a selected model. Sincea partially depleted diode can be roughly described by an equivalent circuit as presentedin gure 3.11, an adequate RC model should be selected. HP LCR-meters oer a serialand a parallel RC model, neither of them corresponding to the equivalent circuit. Thusan approximate inuence of each component inthemodel from g. 3.11 was estimated.Let us consider the most common case in these studies, a partially depleted diodeof 1 cm 2 area and 300 m thickness, irradiated to about 10 14 n/cm 2 . Measurementtemperature of 5 C and measuring frequency of 10 kHz are assumed.23A HP4263B LCR measure unit was used at the reactor, see section 3.3.2.
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UNIVERSITY OF LJUBLJANAFACULTY OF M
Page 5: Najprej gre moja zahvala delovnima
Page 8 and 9: PovzetekSevalne poskodbe v siliciju
Page 10 and 11: 3.5 Measurement Setup, Methods and
Page 13 and 14: 1IntroductionSilicon detectors play
Page 15 and 16: 1. Introduction 7Figure 1.2: Schema
Page 17 and 18: 1. Introduction 9R(cm)Z(cm)Figure 1
Page 19 and 20: 2Operation and Radiation Damage of
Page 21 and 22: 2. Operation and Radiation Damage o
Page 43 and 44: 3Irradiation Facility3.1 The Reacto
Page 45 and 46: 3. Irradiation Facility 373.3 Irrad
Page 47 and 48: 3. Irradiation Facility 39Fission p
Page 49 and 50: 3. Irradiation Facility 413.4 Irrad
Page 51 and 52: 3. Irradiation Facility 43Figure 3.
Page 53: 3. Irradiation Facility 45Figure 3.
Page 57 and 58: 3. Irradiation Facility 49width of
Page 59 and 60: 3. Irradiation Facility 51The full
Page 61 and 62: 3. Irradiation Facility 53percent.
Page 63 and 64: 4Time Development of DefectsIn this
Page 65 and 66: 4. Time Development ofDefects 57* F
Page 67 and 68: 4. Time Development ofDefects 59val
Page 69 and 70: 4. Time Development ofDefects 61for
Page 71 and 72: 4. Time Development ofDefects 63Fig
Page 87 and 88: 4. Time Development ofDefects 79An
Page 89 and 90: 5Dose Rate Dependence5.1 Motivation
Page 91 and 92: 5. Dose Rate Dependence 83Figure 5.
Page 93 and 94: 5. Dose Rate Dependence 85Figure 5.
Page 95 and 96: 5. Dose Rate Dependence 87could be
Page 97 and 98: 6Inuence of Bias VoltageIt was a ge
Page 99 and 100: 6. Inuence of Bias Voltage 91energy
Page 101 and 102: 6. Inuence of Bias Voltage 93Figure
Page 103 and 104: 6. Inuence of Bias Voltage 95Figure
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6. Inuence of Bias Voltage 97Figure
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6. Inuence of Bias Voltage 99that t
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6. Inuence of Bias Voltage 101(abou
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6. Inuence of Bias Voltage 103Figur
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7Comparison with Other GroupsWhile
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7. Comparison with Other Groups 107
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8ConclusionsA systematic study of r
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8. Conclusions 111Implications for
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9Povzetek doktorskega dela9.1 UvodS
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9. Povzetek doktorskega dela 115Ski
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9. Povzetek doktorskega dela 117sre
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9. Povzetek doktorskega dela 1199.2
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9. Povzetek doktorskega dela 121Sli
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9. Povzetek doktorskega dela 123Ce
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9. Povzetek doktorskega dela 127Cep
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9. Povzetek doktorskega dela 129Mer
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9. Povzetek doktorskega dela 131Sam
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9. Povzetek doktorskega dela 1379.6
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10Appendix: List of Symbols and Abb
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10. Appendix: List of Symbols and A
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References[1] J. Straver et al., Nu
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[27] A.M. Ougang et al.: Dierential
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[57] M. Huhtinen et al, HU-SEFT-R-1
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