Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
ATLAS Tracker Upgrade UK Workshop Coseners House, 8.07.08 Electrical characteristics of un-irradiated ATLAS07 mini strip sensors A.Chilingarov, Lancaster University Outline 1. Sensors 2. C-V, I-V measurements 3. Punch-through voltages 4. Interstrip resistance 5. Interstrip capacitance 6. Summary 7. Conclusions 2 A.Chilingarov, ATLAS07 mini sensors Available versions (“Zones”) of the ATLAS07 mini-SSDs. Here we report the results for zone 1 (no isolation structure) and for zone 3 (baseline option) sensors. Each zone may additionally have a thin lightly p-doped layer on the surface (“p-spray”). PTP means Punch-Through Protection structure. 3 A.Chilingarov, ATLAS07 mini sensors CV – IV measurements e to LCR meter Backplane Cs . . . . . Rs Rb Bias rail A Both C-V and I-V measurements are made simultaneously. The impedance is measured between the backplane and the bias rail by the LCR meter in Cs-Rs mode (standard frequency is 10kHz). The Cs represents the total capacitance between the strips and the backplane, while the Rs is the average bias resistor divided by the number of strips. 4 A.Chilingarov, ATLAS07 mini sensors IV for ATLAS07 minis at Lancaster Rs-V for ATLAS07 minis at Lancaster 0.04 35 w02-BZ1-P19 w04-BZ1-P7 w27-BZ1-P7 w28-BZ1-P19 w23-BZ3-P21 w04-BZ3-P3 w07-BZ3-P3 25 Rs, kOhm Current, mA 0.03 30 0.02 20 15 w02-BZ1-P19 w04-BZ1-P7 w27-BZ1-P7 w28-BZ1-P19 w23-BZ3-P21 w04-BZ3-P3 w07-BZ3-P3 10 0.01 5 0.00 0 100 200 300 400 500 600 700 800 900 1000 Bias, V 0 0 100 200 300 400 500 600 700 800 Bias, V CV for ATLAS07 minis at Lancaster 1600 Five out of 7 sensors can withstand 1000V bias, two develop a breakdown above 800V. Typical current is below 10 nA (for ~1cm2 area). Depletion voltage values lie between 150 and 180V. Resistance agrees with expectation within a factor of ~1.5 2 1/C , nF -2 1200 800 w02-BZ1-P19 w04-BZ1-P7 w27-BZ1-P7 w28-BZ1-P19 w23-BZ3-P21 w04-BZ3-P3 w07-BZ3-P3 400 0 0 100 200 300 400 500 600 700 800 Bias, V 5 A.Chilingarov, ATLAS07 mini sensors Punch-through resistance measurements A Rb Rstr e Rdyn Negative DC potential, U, varying from 0.5 to 50 V is applied to a strip implant and the resulting current, I, is measured. The slope dU/dI gives the value of effective resistance, Reff, between the strip and the bias rail. Reff represents the bias resistor, Rb, with Rdyn + Rstr in parallel. Here Rdyn is the dynamic resistance of the punch-through gap quickly decreasing with U above the break-through voltage and the Rstr is the strip implant resistance (if the punch-through gap is at the strip end opposite to the contact point). 6 A.Chilingarov, ATLAS07 mini sensors Dynamic resitance for fresh Zone 1 sensors (no p-stops) 10 10 Dynamic resistance for Zone 3 sensors with p-spray: fresh and after 3h at 220V bias w27-bz1-p7 w28-bz1-p19 w02-bz1-p19 w04-bz1-p7 dU/dI, MOhm dU/dI, Mohm 1 with p-spray 1 fresh 0.1 biased for 3h no p-spray w07-bz3-p3 w04-bz3-p3 w07-bz3-p3 w04-bz3-p3 0.01 0 5 10 15 20 25 30 -Ustrip, V 0.1 24 28 32 36 40 44 48 52 -Ustrip, V Dynamic resitance for Zone 3 sensor w23-bz3-p21 (no p-spray) for different time @ 220V bias 10 As expected, zone 1 sensors have a relatively low break-through voltage of ~5 or ~15V. For zone 3 sensors the breakthrough is also observed above 45 V. For all sensors this voltage decreases with time under bias. 1 dU/dI, Mohm fresh biased for 3h 0.1 fresh 1h bias 2h bias 3h bias 0.01 24 28 32 36 -Ustrip, V 40 44 48 52 Note that the strip bias resistors can tolerate up to ~50V voltage drop across them without being burnt. 7 A.Chilingarov, ATLAS07 mini sensors Interstrip resistance measurements A “master” DC potential U0 is applied to a strip implant and the “slave” potential U1 induced at the neighbouring strip implant is measured by a high impedance voltmeter. U1 Io Uo A e Ris V Rb Bias rail The U0 is varied by a few volts around zero and the resulting current I0 is measured. The slope dU0/dI0 gives the value of effective resistance between the strip and the bias rail, R0. The slope dU1/dU0 allows calculation of the effective interstrip resistance, Ris, using an assumption of bias resistor, Rb, being the same at both strips. 8 A.Chilingarov, ATLAS07 mini sensors Fresh w07-bz3-p3, 13.5.08: Uslave vs. Umaster for different Ubias 328 326 324 322 320 Uslave, mV 318 316 314 312 310 308 Ub=10V 306 Ub=20V 304 -4 -2 0 2 4 Umaster, V Typical dependence of the induced voltage (Uslave) vs. the voltage applied to the neighbouring strip (Umaster). Normally the slope dU1/dU0 is ~1mV/V which means Ris ~ 106 Rbias i.e. ~1000 GOhm. The spread of the points around the linear fit determines the Ris error. 9 A.Chilingarov, ATLAS07 mini sensors Interstrip R for Zone 3 sensor w23-bz3-p21 (no p-spray): bias ramps up and down after 3 hours at 200 V 1600 1400 Ris, GOhm 1200 1000 800 600 400 200 fresh 3h bias 0 1 10 Ubia s , V 100 1000 Interstrip R for Zone 3 sensors w ith p-spray: bias ram ps up and dow n after a tim e @ 200 V 2000 1800 For zone 3 sensors the interstrip resistance Ris does not depend on bias in the range 10-200V and doesn’t change after sensor remaining at 200V bias during 3 hours. 1600 Ris, GOhm 1400 Typical Ris value is ~1000 GOhm. 1200 1000 800 600 400 w07-bz3-p3 fresh w07-bz3-p3 3h bias 200 w04-bz3-p3 fresh w04-bz3-p3 10' bias 0 1 10 Ubia s , V 100 10 1000 A.Chilingarov, ATLAS07 mini sensors Interstrip R for Zone 1 sensors w ith p-spray: bias ram ps up and dow n after 3 hours at 200 V 1400 1200 Ris, GOhm 1000 800 600 400 w02-bz1-p19 fresh 200 w02-bz1-p19 3h bias w04-bz1-p7 fresh w04-bz1-p7 3h bias 0 1 10 100 Ubia s , V 1000 For zone 1 sensors without pspray the Ris behaviour is more complicated. Nevertheless above 100V bias the Ris remains above 100 GOhm even after 3 hours at 200V bias. Interstrip R for Zone 1 sensors w ithout p-spray: bias ram ps up and dow n after ~3 hours at 200 V 1.E+03 1.E+02 fresh senso rs, ramp up 1.E+01 after 3h bias, ramp do wn Ris, GOhm 1.E+00 For fresh zone 1 sensors with pspray the Ris also doesn’t depend on bias in the range 10-200V but after 3 hour biasing by 200V it decreases and becomes slightly bias dependent with Ris value of ~500 GOhm above 100V bias. 1.E-01 1.E-02 1.E-03 w28-bz1-p19 fresh w28-bz1-p19 3h bias 1.E-04 w27-bz1-p7 fresh w27-bz1-p7 3.5h bias 11 1.E-05 1 10 Ubia s , V 100 1000 A.Chilingarov, ATLAS07 mini sensors Interstrip capacitance measurements The capacitance is measured between an aluminium outer strip and two its nearest neighbours connected together. The LCR meter operates in Cp-D mode. Standard measurement frequency is 100 kHz. to LCR meter The strips are grounded through ~1 MW resistors to keep their DC potential fixed. 12 A.Chilingarov, ATLAS07 mini sensors Interstrip capacitance Cis vs. Ubias Interstrip capacitance versus bias (sensors w01-17 have p-spray) 0.8 Zone 1(no p-stop) 0.7 Below 300V the Cis has a complicated behaviour with bias but above 300V it almost flattens and gradually converges to a value of ~0.6 pF for all sensor types. p-spray 0.6 no spray Cis, pF 0.5 Zone 3 (with p-stop) 0.4 0.3 w28-bz1-p19 w27-bz1-p7 w02-bz1-p19 w04-bz1-p7 w23-bz3-p21 w04-bz3-p3 w07-bz3-p3 KEK data 0.2 0.1 Our results are in a reasonable agreement with KEK measurements. 0 0 100 200 300 Ubias, V 400 500 600 13 A.Chilingarov, ATLAS07 mini sensors Interstrip capacitance Cis vs. time at Ubias = 600V Interstrip C vs. time at 600V (sensors w01-17 have p-spray) 0.64 0.63 Zone 1 (no p-stop) At 600V bias the Cis further converges with time to a common value of ~0.61 pF for all sensor types. 0.62 Cis, pF 0.61 0.6 0.59 Zone 3 (with p-stop) 0.58 w28-bz1-p19 w27-bz1-p7 w02-bz1-p19 w04-bz1-p7 w23-bz3-p21 w04-bz3-p3 w07-bz3-p3 0.57 0.56 The measurements were made at ~22oC temperature and 3545% relative humidity. 0.55 0 40 80 Time, min 120 160 200 14 A.Chilingarov, ATLAS07 mini sensors Interstrip C for different sensors 0.615 0.614 0.613 The strip length, L, is 8000 mm for zone 3 sensors and 8060 mm for zone 1 sensors. Assuming the whole measured capacitance being scalable with L the capacitance per unit length was calculated. 0.612 Cis, pF 0.611 L=8060 mm 0.61 L=8000 mm 0.609 0.608 0.607 0.606 0.605 0 0.5 1 1.5 2 2.5 3 3.5 4 Zone+0.5*(p-spray) No systematic difference due to the sensor type or the p-spray presence was observed. The average Cis value is 0.758+-.003 pF/cm where the error is the points r.m.s. spread. Interstrip C per unit length for different sensors 0.762 0.761 0.760 Cis/L, pF/cm 0.759 0.758 <C> = 0.758 +- .003 pF/cm 0.757 0.756 0.755 0.754 0.753 0 0.5 1 1.5 2 2.5 3 3.5 4 15 Zone+0.5*(p-spray) A.Chilingarov, ATLAS07 mini sensors Comparison with the SCT sensors Interstrip capacitance per unit length versus pitch 0.85 SCT wedges/Lancs Atlas07 minis SCT MPI/NIKHEF 0.01 pF abs.uncertainty Linear (SCT wedges/Lancs) 0.80 NIKHEF Cis, pF/cm 0.75 0.70 y = -0.007x + 1.2664 2 R = 0.996 0.65 w12 w32 w31 w21 w22 0.60 60 65 70 75 80 85 90 Average pitch, um The observed Cis/L agrees well with the data measured for the SCT sensors. An absolute LCR meter uncertainty of 0.01 pF is also shown in the error. Thus the Cis in ATLAS07 minis can be regarded as simply geometrical one. 16 A.Chilingarov, ATLAS07 mini sensors Frequency dependence of the Cis Normalised Cis vs frequency for two measurements with w32-312 Frequency dependence of the interstrip capacitance 1.02 0.85 w23-bz3-p21/400V w23-bz3-p21/600V w07-bz3-p3/600V w04-bz3-p3/600V w02-bz1-p19/600V w04-bz1-p7/600V w28-bz1-p19/600V w27-bz1-p7/600V 0.80 0.98 0.96 Cis/Cis(100kHz) Cis, pF 0.75 1.00 0.70 0.65 0.94 0.92 0.90 0.88 0.60 19.06.08 25.06.08 0.86 0.84 0.55 0 100 200 300 400 500 600 Frequency, kHz 700 800 900 1000 10 100 1000 Frequency, kHz For the frequencies above 100kHz the Cis for the mini SSDs is by ~10% higher. However for the SCT sensors there is <1% difference between the Cis values in the range from 100kHz to 1MHz. Measurements with longer strips are necessary to distinguish between the changes with frequency due to the whole strip (scalable with L) and to the strip edges (independent of L). 17 A.Chilingarov, ATLAS07 mini sensors Summary of the results presented in this talk Sensor name p-spray Breakdown onset, V I, mA at 1000V I, mA at brkd.onset Vdep,V Rbias, MOhm Interstrip R, GOhm Zone 1 - PTP*, no p-stops p-through onset, V Interstrip C, pF (in fresh sensors) w02-BZ1-P19 Yes >1000 0.0084 174 1.22 442 15 0.608 w04-BZ1-P7 Yes >1000 0.0317 174 1.32 535 15 0.613 w27-BZ1-P7 No >1000 0.0068 153 1.30 604 5.5 0.614 w28-BZ1-P19 No >1000 0.0061 159 1.25 280 4.5 0.610 >1000 0.0071 167 1.21 890 47.5 0.607 Zone 3 - no PTP, p-stops w23-BZ3-P21 No w04-BZ3-P3 Yes 810 20.1 0.0078 183 1.23 853 48.5 0.606 w07-BZ3-P3 Yes 830 18.4 0.0078 182 1.19 1008 48.5 0.608 * PTP – Punch-Through Protection structure Note: the interstrip resistance values are given at 200V bias and after 3 hours where appropriate. 18 A.Chilingarov, ATLAS07 mini sensors Conclusions 1. 2. 3. 4. 5. Typically ATLAS mini SSDs show a stable behaviour up to at least 800 V. More than a half of them can be operated up to 1000V bias. The depletion voltage values are below 200V. The punch-through protection structure implemented in zone 1 sensors operates according to expectations with a break-through voltage below 15 V. For all sensor types the interstrip resistance exceeds 100 GOhm for bias voltage above 100V. The interstrip capacitance values for all sensor types are very similar and agree with those for ATLAS SCT sensors scaled by the length. The bias resistors have the value in the range 1.2 - 1.3 MOhm. They are able to withstand up to ~50V voltage drop across them without thermal destruction. 19 A.Chilingarov, ATLAS07 mini sensors