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A. Dorokhov, IPHC, Strasbourg, France
Description of pixel designs in Mimosa22
Andrei Dorokhov Institut Pluridisciplinaire Hubert Curien (IPHC)
Strasbourg, France
03/04/2008
e-mail address: [email protected]
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A. Dorokhov, IPHC, Strasbourg, France
Pixel designs
Standard and Radiation tolerant nwell diode designs Different schematic concepts:
1. Reset diode and standard amplifier (like in Mimosa8)2. Reset diode and amplifier with improved load 3. Continuously biased (self-biased) from feedback and
amplifier with improved load (like in Mimisa15 test structures and Mimosa16)
4. Reset diode from feedback, time variant feedback, amplifier with improved load (similar to Mimosa1819 test structures)
5. Reset diode from feedback, time variant feedback, standard amplifier
CDS with clamping capacitance
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A. Dorokhov, IPHC, Strasbourg, France
Nwell diode designs
Size from 3.4 um x 3.4 um - to 4.5 um x 4.5 um Standard with thick oxide around Nwell Radiation tolerant with thin gate oxide around Nwell
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A. Dorokhov, IPHC, Strasbourg, France
Amplifier schematics (1): standard common source + reset
in
out
bias
signal current
M2
M3
IdM1
reset
Nwell / Pepi
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A. Dorokhov, IPHC, Strasbourg, France
Amplifier schematics (2): improved common source + reset
in
out
bias
signal current
M2
M3
IdM1
reset
Nwell / Pepi
M4
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A. Dorokhov, IPHC, Strasbourg, France
Amplifier schematics (3): improved common source + continuously biased from feedback
(self-biased)
out
signal current
Nwell / Pepi
Pdiff / Nwell in
out
M2
M3
Id
M4M5
Low-pass filter
feedback
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A. Dorokhov, IPHC, Strasbourg, France
Amplifier schematics (4): improved common source + reset from feedback (time-variant
feedback)
signal current
Nwell / Pepi
in
out
M2
M3
Id
M4M5
Time-variant feedback
reset
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A. Dorokhov, IPHC, Strasbourg, France
Amplifier schematics (5): standard common source + reset from feedback (time-variant
feedback)
signal current
Nwell / Pepi
in
out
M2
M3
Id
M4
Time-variant feedback
reset
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A. Dorokhov, IPHC, Strasbourg, France
Summary of pixel concepts
(1,2) reset (and amplifier bias) from constant voltage - may be difficult to find working point due to CMOS
process variation - diode leakage current dispersion after irradiation may
significantly degrade performance (3) self-biased from feedback
+ performances should be more stable to process variation
+ diode leakage is compensated by forwardly biased diode
- “pedestal memory effect” from previous hit, even removed after CDS, changing the performance of amplifier
(4,5) reset from feedback + more stable performances for process variation - diode leakage current dispersion after irradiation will
significantly degrade performance
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A. Dorokhov, IPHC, Strasbourg, France
Simulation results
Name ( design concept)
Conversion, [uV/e]
Noise, [uV]
Noise, [e]
Amplifier current, [uA]
S1 (4) 99 728 7 5S2 (4) 89 590 7 5S3 (4) 82 561 7 7S4 (4) 80 570 7 7S5 (4) 83 558 7 7S6 (3) 54 830 15 7S7 (3) 54 828 15 7S8 (3) 51 811 16 7S9 (3) 57 852 15 7S10 (2) 70 544 8 7S11 (4) 72 518 7 9S12 (2) 70 543 8 7S13 (1) 64 440 7 7S14 (5) 68 449 7 4S15 (1) 64 439 7 7S16 (1) 36 318 9 7S17 (1) 34 313 9 7
Simulation with Spectre, parasitic capacitances for diodes, metal lines and transistors are extracted by Frédéric Morel
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A. Dorokhov, IPHC, Strasbourg, France
Measurement results
1. Short results summary of measurements and analysis from Mathieu Goffe:1. S6, S7, S8, S9, S10, S12, S13, S15, S16, S17 are
working fine at standard conditions at 100MHz clock2. For working pixels the charge collection in seed ~30%,
cluster 3x3: 60-80%, in cluster 5x5 : 80-90%, noise from 10e to 13e
3. The other pixels have to be investigated further – one need to vary the frequency, readout pattern, analogue voltages – at least to understand the reason why they don’t show good performances seen in simulations (this is foreseen for the end of April)
2. However, there are at least few working amplifier concepts:1,2,3.
3. Two designs S6 and S10 have different concepts: reset and self-biased from feedback, they are featured with radiation tolerant version of nwell diode -> one can have close look at their performances
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A. Dorokhov, IPHC, Strasbourg, France
Measurement results for S6 and S10
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A. Dorokhov, IPHC, Strasbourg, France
Measurement results for S6 and S10
S6, pedestal dispersion + noise
S10, pedestal dispersion + noise
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A. Dorokhov, IPHC, Strasbourg, France
Measurement results for S6 and S10
S6, pedestal mean dispersion
S10, pedestal meandispersion
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A. Dorokhov, IPHC, Strasbourg, France
Measurement results for S6 and S10
S6, pedestal sigma dispersion
S10, pedestal sigma dispersion
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A. Dorokhov, IPHC, Strasbourg, France
Influence of pixel hit frequency
1. Designs with reset are not sensitive to “memory” effect – charge is always restored to a fixed value
2. Continuously biased diode will store some fraction of charge from previously incident particle, even if the signal completely reconstructed after CDS, there is “internal memory” in the nwell diode -> charge is accumulated and circuit can go to non-linear state
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A. Dorokhov, IPHC, Strasbourg, France
Influence of pixel hit frequency: simulation
1. Single pixel hit frequency 2Hz for 30um x 30um pitch2. Noise – Gaus : SIGMA=15 e3. Signal - Landau distribution: MPV=200e, SIGMA=50e 4. Initial nwell diode voltage 0.7 V5. Amplifier gain -10, offset 1.1 V6. Frame readout (integration time) time 160 us (==1000
pixels in column, 100MHz clock)
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A. Dorokhov, IPHC, Strasbourg, France
Influence of pixel hit frequency
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A. Dorokhov, IPHC, Strasbourg, France
Influence of pixel hit frequency
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A. Dorokhov, IPHC, Strasbourg, France
Influence of pixel hit frequency
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A. Dorokhov, IPHC, Strasbourg, France
Influence of pixel hit frequency
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A. Dorokhov, IPHC, Strasbourg, France
Influence of pixel hit frequency
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A. Dorokhov, IPHC, Strasbourg, France
Influence of pixel hit frequency
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A. Dorokhov, IPHC, Strasbourg, France
Influence of pixel hit frequency
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A. Dorokhov, IPHC, Strasbourg, France
Influence of pixel hit frequency
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A. Dorokhov, IPHC, Strasbourg, France
Influence of pixel hit frequency
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A. Dorokhov, IPHC, Strasbourg, France
Conclusions
1. There two pixel candidates for PHASE1: designs S6 and S10
2. Radiation hardness and hit frequency issues has to be carefully studied for these candidates – one of those may be not suitable for real experiment…