Recent developments on Monolithic Active Pixel Sensors (MAPS) for charged particle tracking. Outline The MAPS sensor (reminder) MIMOSA-22, a fast MAPS-sensor

Recent developments on Monolithic Active Pixel Sensors (MAPS) for charged particle tracking.

Outline• The MAPS sensor (reminder)• MIMOSA-22, a fast MAPS-sensor• The SUZE-1 FEE chip• Random Telegraph Signal and radiation damage• Summary and Conclusion

Michael Deveaux on behalf of IPHC Strasbourg, IKF Frankfurt/M

(Irradiations: F.M. Wagner, MEDAPP, FRM II reactor Munich)

M. Deveaux, 12th CBM Collaboration Meeting, 13 - 18 Oct. 2008 JINR Dubna, Russia 2

The operation principle of MAPS

Reset+3.3V+3.3V

Output

SiO2 SiO2 SiO2

N++ N++N+ P+

P-

P+


How to build fast MAPS for the MVD: IPHC Strasbourg

Sensor array

Discriminators On - chip zero suppression

Bonding pads + output Amplis.

Pixel column

Readout busExpected time resolution: ~10 µs (~100 kFrame/s)

MIMOSA-16 and 22 SUZE-1


Last years status: MIMOSA-16

32 col. of 128 pixels (25 μm pitch, integrated CDS )1 Discriminator/column

Tests at CERN-SPS ( 180 GeV pi−) in Summer 2007

Threshold: 6 mV Detection efficiency: 99.88 ± 0.05 (stat) % Fake rate: <10−5 Spatial resolution: 4.6 μm

Proof of principle for MAPS with on-pixel CDS and on-chip discriminator (small size only).


MIMOSA-22, a fast and big chip

MIMOSA – 22:

• Test the MIMOSA-16 concept with higher surface32 cols x 128 pixels => 128 cols x 576 pixels

• 17 different (improved) pixels designs:New high gain / low noise pixelsRadiation hard pixels

Build smaller pixels18.4 μm instead of 25 µm

Read-out time 100 μs ( 104 frames/s )• JTAG slow control• Programmable test DACs for disciminator tests• 40 MHz digital data output

Tested with Fe-55 source and CERN 100 GeV/c pion beam


Test results of the new preaplifyers

Noise: • 10 < N < 14 e− ENC + 5 e− ENC Fix pattern noise (individual pixel offset)• Rad hard: 1e− ENC more than standard versionCCE : • 3x3 pixels : 70 – 80 % • 5x5 pixels : 80 – 90 %

Standard SB-Pixel design (Mimosa-16):• Successfully used since MIMOSA-4• No dead time• Noise: ~15e- with on-pixel CDS, else ~ 9e-

New inMIMOSA-22


Beam test results of MIMOSA-22

Discriminator Threshold Discriminator Threshold

All pixels of interest show:Detection efficiency: >99.8% Fake hit rate: O(10-4 – 10-5)Spatial resolution: ~3.5 µm (~ Pitch / 5)

Detection efficiency Fake hit rate


How to build fast MAPS for the MVD

Sensor array

Discriminators On - chip zero suppression

Bonding pads + output Amplis.

Pixel column

Readout bus

SUZE-1

SUZE – 1 data sparsification circuit

• Chip with integrated Ø and output memories (no pixels)• Algorithm:

Step1: find up to 6 series of 4 neighbour pixels / raw in block of 64 cols.Step2: Read-out all blocks, keep up to 9 series of 4 pixels.

• Output memory: 4 x (512x16 bits) taken from AMS I.P. lib.

• Surface: 3.9 × 3.6 mm²

• Test result: Works fine up to 115% clock frequencyCan handle up to 100 hits/frame at 104 frame/s


Next Step: MIMOSA-26

MIMOSA-22 Sensor

SUZE-1 Ø -suppression

circuit

MIMOSA-26

MIMOSA-26

Pixels + Ø-suppression• Expanded surface:

1152 cols x 576 pixels21.2 x 10.6 mm²18.6 µm pixel pitch

• Expanded data sparsification circuit 18 blocks of 64 columns Max. 9 clusters per row

• Data rate: 80 Mbits/s• Submission November 2008


Radiation hardness studies

together with


Random Telegraph Signal

Sig

nal [

AD

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Time

Random Telegraph Signal: • Modulation of an output signal between two “quantum levels”. • Random period length.• RTS in MAPS sensors first described by Hopkinson (2000)*

Output signal of two MAPS pixels

RTS may generate fake-hits if amplitude exceeds discriminator threshold.Problem for MAPS being used in HEP – experiments?

D. Doering, Bachelor Thesis

D. D

oeri

ng, B

ache

lor

The

sis

* G.R

. Hopkinson: “R

adiation Effects in a C

MO

S A

ctive P

ixel Sensor”, IE

EE

-NS

S V

ol. 47, No. 6, P

. 2480


Fake hit rate of MAPS with Random Telegraph Signal

Affected SB-pixels remain sensitiv.The fake hit rate of MAPS shrinks with cooling.Identified RTS pixels contribute ~60 – 80 % of all fake hits.

MIMOSA-18 (SB-pixel, irradiated at MEDAPP, FRM II, Munich)

Preliminary

D. D

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ache

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The

sis


Distribution of RTS-pixelsD

. Doe

ring

, Bac

helo

r T

hesi

s

Pixel X

Pixel Y Normal Pixel

RTS Pixel

Up to ~10% of all pixels are affected.Masking of pixels is not possible but pixels stay sensitivOperate pixels, tolerate fake hits ( ~ 104 / frame for full MVD)Note: Fast MAPS might show less RTS than MIMOSA-18


Sensors with improved charge collection efficiency

MIMOSA-Pixelwith 10 x 10 µm²

Standard collection diode( ~ 3 x 4 µm²)


Sensors with improved charge collection efficiency

How to escapehere?

Bigger collection diodes may improve CCEImproved CCE => improved radiation hardnessTested with MIMOSA-19 (by IPHC)

Diode 1 Diode 2


Results

A. Büdenbender, Bachelor Thesis

Charge collection efficiency is indeed substantially increased

But the bigger collection diodes generate more noise

T= -20 °C


S/N of the sensors

A. B

üden

bend

er, B

ache

lor

The

sis

Both MIMOSA-18 and MIMOSA-19 seem fairly radiation hardBig diodes have no advantages because of high noise

Insufficient S/N


Summary

At IPHC, a first sizable chip with column parallel readout was producedand tested in the CERN – SPS pion beam:Features: • reduced noise 15 e- => 10 – 14 e- , det. eff. > 99.8 %• pitch 18.4 μm, resolution = 3.5 µmAn FEE chip with cluster finding circuits (SUZE-1) was successfully tested.

MIMOSA-26 integrating the full discrimination chain will be submittedin November.

Radiation hardness tests were undertaken at IKF:

A radiation hardness of 1013 neq/cm² has been shown for two pixel concepts

The effect of Random Telegraph Signal was identified as dominating sourceof background hits in MAPS

Studies on RTS suggest, that RTS can be tolerated if chips are cooled

Documents

Recent developments on Monolithic Active Pixel Sensors (MAPS) for charged particle tracking. Outline The MAPS sensor (reminder) MIMOSA-22, a fast MAPS-sensor