Latest IV and CVtests on
microstrip siliconsensors for theCMS Tracker
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Elena Graverini
Latest IV and CV tests on microstrip siliconsensors for the CMS Tracker Upgrade
Elena Graverini
August 30, 2012
Latest IV and CVtests on
microstrip siliconsensors for theCMS Tracker
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Elena Graverini
The test MSSDs
Region 1 2 3 4 5 6 7 8 9 10 11 12Strip width (µm) 16 34 10 8.5 28 58 18 15.5 40 82 26 22.5Strip pitch (µm) 120 240 80 70 120 240 80 70 120 240 80 70
Al (µm) 29 47 23 21.5 41 71 31 28.5 53 95 39 35.5Al/W 1.81 1.38 2.30 2.53 1.46 1.22 1.72 1.84 1.33 1.16 1.50 1.56W/P 0.13 0.14 0.13 0.12 0.23 0.24 0.23 0.22 0.33 0.34 0.33 0.32
Latest IV and CVtests on
microstrip siliconsensors for theCMS Tracker
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Elena Graverini
Tested MSSDs
Not irradiatedSensor IV CV Cint
FZ200P 02 MSSD 1 August 20 August 13FZ200Y 04 MSSD 1 August 20 August 10FZ200N 10 MSSD 2 August 17 August 13FZ320N 05 MSSD 2 August 21 August 22 August 15FZ320N 07 MSSD 2 August 21 August 14FZ320P 03 MSSD 2 August 20 August 21 August 14
IrradiatedSensor Irradiation IV CV
M200N 04 MSSD 1 8.2 1014 p; 5 1014 n August 27 August 27FZ200N 04 MSSD 2 1.0 1015 p; 5 1014 n August 28 August 28FZ320N 05 MSSD 1 8.6 1014 p; 5 1014 n August 29 August 29FZ320Y 05 MSSD 1 9.5 1014 p; 5 1014 n August 30 August 30
All tests performed at -20◦CDatabase CV data from 2011 for FZ200P 02 MSSD 1,FZ200Y 04 MSSD 1, FZ200N 10 MSSD 2 and FZ320N 07 MSSD 2FZ320P 02 MSSD 2 (irradiated) was broken during shipment from CERN
Latest IV and CVtests on
microstrip siliconsensors for theCMS Tracker
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Elena Graverini
Leakage current
If the bias voltage is raised over VFD , thermally generated pairsbegin to be pulled out of the depleted region, giving a reversecurrent Ileak proportionalto the dopant concentration (' chargecarriers concentration) ni .The charge carriers densities at the termalequilibrium are given by:
n ∝ e− EC −E fkT (electrons)
p ∝ e− Ef −E VkT (holes)
where EC is the energy of the condution band, EV that of the valence bandand Ef is the Fermienergy.Mass Action Law
n · p ≡ n2i ∝ e− ∆EkT with ∆E ≡ EC − EV =⇒ n i ∝ e− ∆E
2kT
A decrease of 7◦C in temperature results approximately in a factor12 of
leakage current reduction.
Latest IV and CVtests on
microstrip siliconsensors for theCMS Tracker
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Elena Graverini
IV measurements at -20◦C
IV measurements at -20◦C and comparison with database data(+20◦C)Ileak should fallby a factor 25 to 26
Observed factor:I+20◦I−20◦
' 30Preliminary! Background/pedestalcurrent is not constant andhas not been subtracted from the data samples.
Latest IV and CVtests on
microstrip siliconsensors for theCMS Tracker
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Elena Graverini
Light insulation
Added light insulation to theautomatic probe station.
Latest IV and CVtests on
microstrip siliconsensors for theCMS Tracker
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Elena Graverini
CV measurements at -20◦C
As a check, a CV measurement was performed twice, at -20◦C and+20◦C:
Latest IV and CVtests on
microstrip siliconsensors for theCMS Tracker
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Elena Graverini
Irradiated sensors
M200N 04 MSSD 1Irradiation:8.2 1014p/cm2 plus 5 1014n/cm2
It was stored at -20◦C =⇒ need to warm it up in a dry box beforetransporting it to the probe station, to avoid moisture biassing themeasurementsAfter irradiation the leakage current is much greater than before.Fixed two missing ground connections in the test circuit
Latest IV and CVtests on
microstrip siliconsensors for theCMS Tracker
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Elena Graverini
Irradiated sensors
FZ200N 04 MSSD 2 (IV)Irradiation:1015p/cm2 plus 5 1014n/cm2
It seems that there was a problem with the IV test performed in July 2012at CERN: all the regions show the same current, very lowIt also seems that the sensor was irradiated before the measurementsperformed at CERN in April 2012 (flat lines:September 2011, same regions)
Latest IV and CVtests on
microstrip siliconsensors for theCMS Tracker
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Elena Graverini
Irradiated sensors
FZ200N 04 MSSD 2 (CV)It looks like something bad happened with the CV test performed in July 2012 atCERN: there’s no agreement between that data set and any other, while ourlatest tests are similar to those of April2012
Latest IV and CVtests on
microstrip siliconsensors for theCMS Tracker
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Elena Graverini
Irradiated sensors
FZ320N 05 MSSD 1 (IV)Irradiation:8.6 1014p/cm2 plus 5 1014n/cm2
Probably irradiated before April2012What happened between 2012 and 2011?
Latest IV and CVtests on
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Elena Graverini
Irradiated sensors
FZ320N 05 MSSD 1 (CV)After irradiation the Vfd goes from ∼250V to ∼650V