1 radiation damage effects in monolithic active pixel sensors implemented in an 0.18µm cmos process...

1

Radiation damage effects in Monolithic Active Pixel Sensors Implemented in an 0.18µm CMOS process

Dennis Doering, Goethe-University Frankfurt am Main

on behalf of the CBM-MVD-Collaboration

Outline- MAPS sensors- Mechanism of ionizing radiation damage- Going to a smaller 0.18µm feature size- Status of radiation hardness- Conclusion

ADvanced

MOnolithic

Sensors for

/17Dennis Doering: MAPS in 0.18µm CMOS process DPG Dresden March 2013 2/14

Applications of MAPS

Picture STAR

Picture CBM

International Linear ColliderCBM-Experiment (FAIR, GSI)

STAR-Experiment

MAPS are developed for applications as vertex detector since 1999 at IPHC (Strasbourg).

Possible ITS-Upgrade ALICE

/17/14

Operation principle of MAPS

Dennis Doering: MAPS in 0.18µm CMOS process DPG Dresden March 2013 3

+3.3VOutput

SiO2

N+ P+

P-P+

Diode

Epitaxial Layer

P-Well

Source Follower

/17/14

Noise measurement


1) Measured noise [mV] at the output 2) Charge-to-voltage conversion by the readout chain gain3) Calculate ENC [e]

+3.3V

Readout chain Gain

Measured noise [mV]

ENC [e]

Output

/17/14Dennis Doering: MAPS in 0.18µm CMOS process DPG Dresden March 2013 5

Classes of radiation damage

To be investigated and improved: Radiation hardness against…

… ionizing radiation:• Energy deposited into the electron cloud• Can ionize atoms and destroy molecules• Caused by charged particles and photons

… non-ionizing radiation:• Energy deposited into the crystal lattice• Atoms are displaced• Caused by heavy (fast leptons, hadrons),

charged and neutral particlesFarnan I, HM Cho, WJ Weber, 2007. "Quantification of Actinide α-Radiation Damage in Minerals and Ceramics." Nature 445(7124):190-193.

DPG Mainz 2012 HK 12.8

~10 14 neq with high-resistivity sensor

Discussed in this talk

/17/14

Ionizing radiation damage effects


1) Ionizing radiation damage generates electrons at Si/SiO2 interface2) Leakage current and ENC [e] increases3) Gain is constant4) Measured noise [mV] increases

+3.3V

Gain

Measured noise [mV]

ENC [e]

Output

0,0 0,2 0,4 0,6 0,8 1,00,00

0,05

0,10

0,15

0,20

0,25

0,30

Ga

in [

mV

/e]

Ionizing radiation dose [Mrad]

Gain [mV/e] Measured noise [mV] ENC [e]

M.Deveaux PHD-Thesis 2007 Su1-Mi15 +10°C 0.7ms

lines to guide the eye

0

1

2

3

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5

Me

asu

red

no

ise

[m

V]

0

5

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20

25

30

35

40

45

EN

C [

e]

/17/14

Going to smaller feature size


1) Measured noise [mV] decreases!

Mind the different scale!

0 10,00

0,05

0,10

0,15

0,20

0,25

0,30

Gain

[m

V/e

]



M.Deveaux PHD-Thesis 2007 Su1-Mi15 +10°C 0.7ms 0

1

2

3

4

5

Measu

red n

ois

e [m

V]

0

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EN

C [e]

0.35µm CMOS process „new“ 0.18µm CMOS process

0 3 100,00

0,05

0,10

0,15

0,20

0,25

0,30

Gain

[m

V/e

]



Dennis Doering

0

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Measu

red n

ois

e [m

V]

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EN

C [e]

/17/14



1) Measured noise [mV] decreases! 2) Reason: Gain drops after 10Mrad


0 10,00

0,05

0,10

0,15

0,20

0,25

0,30

Gain

[m

V/e

]




1

2

3

4

5

Measu

red n

ois

e [m

V]

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EN

C [e]


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0,05

0,10

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Gain

[m

V/e

]



Dennis Doering

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red n

ois

e [m

V]

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C [e]

/17/14



1) Measured noise [mV] decreases! 2) Reason: Gain drops after 10Mrad3) ENC [e] does not increase up to 3Mrad, after 10Mrad increase to ~30e


0 10,00

0,05

0,10

0,15

0,20

0,25

0,30

Gain

[m

V/e

]




1

2

3

4

5

Measu

red n

ois

e [m

V]

0

5

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15

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25

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45

EN

C [e]


0 3 100,00

0,05

0,10

0,15

0,20

0,25

0,30

Gain

[m

V/e

]



Dennis Doering

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red n

ois

e [m

V]

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C [e]

/17/14

Comparison of 0.18 and 0.35µm process


- 0.18µm has a much more larger intrinsic ionizing radiation tolerance than 0.35µm- Still drawbacks in noise.

Status: Origin identified, being fixed with opimized transistor layout

Transistor layout in 0.18µm not yet optimized for noise

0 1 2 3 4 5 6 7 8 9 100369

1215182124273033

EN

C [e]


0.35µm 0.18µm

/17/14

Signal to noise ratio


Signal to noise ratio well above the critical value of 15.Þ Expect tolerance to 3Mrad, plausibly also to 10Mrad.(Both to be confirmed in a beam time)

0 1 2 3 4 5 6 7 8 9 100

5

10

15

20

25

30

35

40

45

50

Sig

na

l to

no

ise

ra

tio


Critical limit

Sr-90-

/17/14

Beam test result by IPHC Strasbourg


15 3095

96

97

98

99

100

De

tect

ion

eff

icie

ncy

[%

]

Temperature [°C]

Non-irradiated

1Mrad & 1013neq

/cm²

Pixel pitch: 20x40µm²Integration time: 32µs

Pion beam@SPS

MIMOSA-32 L4_1

CMOS 0.18µm process

CBMSIS100

0.18µmMIMOSA-32

Rad. hard. non-io. >1013 neq >1013 neq

Rad. hard. io > 1 Mrad > 1Mrad

Radiation hardness requirements of CBM@SIS100 achieved by MIMOSA-32.

/17/14

Summary


MAPS implemented in a smaller (0.18µm) feature size CMOS process.

- Noise of 0.18µm is still higher than known from 0.35µm. - Possible Origin identified, optimization is ongoing.

- Sufficient radiation tolerance for CBM@SIS100 was demonstrated in a beam test.

- Noise of only ~30e and S/N>30 (MPV) observed after 10Mrad. - Sufficient for excellent detection efficiencies for MIPS (to be confirmed in beam test).

- Next steps:

Add on-chip data sparsification circuits without losing radiation tolerance.

/17/14

Conclusion


High-resistivity

Smaller feature size

Radiation damage: Ionizing

Radiation damage: Non-ionizing

/17/14

Progress in sensor development


CBMSIS100

MAPS*(2003)

Single point res. ~ 5 µm 1.5 µm

Material budget < 0.3% X0 ~ 0.1% X0

Rad. hard. non-io. >1013 neq 1012 neq

Rad. hard. io > 1 Mrad 200 krad

Time resolution < 30 µs ~ 1 ms

*Optimized for one parameter

/17/14

Non-ionizing radiation: High-resistivity


0 5 10 15 20 25 30 35 401011

1012

1013

1014

1015

MIMOSA-18AHR* (2011)

MIMOSA-9

MIMOSA-9

MIMOSA-15 (2006)MIMOSA-18 (2008)

Sensor based on low-resistivity EPI layer

Ra

dia

tion

to

lera

nce

[n

eq/c

m²]

Pixel pitch [µm]*operated at -34°C

Preliminary

Sensor based on high-resistivity EPI layer

Shown:DPG Mainz 2012 HK 12.8Paper in preparation for publication

High resistivity epitaxial layer increases radiation hardness by one order of magnitude

/17/14

Ionizing radiation: 0.18µm process


15 3095

96

97

98

99

100

De

tect

ion

eff

icie

ncy

[%

]

Temperature [°C]

Non-irradiated

1Mrad & 1013neq

/cm²

Pixel pitch: 20x40µm²Integration time: 32µs

Pion beam@SPS

MIMOSA-32 L4_1

CMOS 0.18µm process

CBMSIS100

0.18µmMIMOSA-32

Rad. hard. non-io. >1013 neq >1013 neq

Rad. hard. io > 1 Mrad > 1Mrad

/17/14

Progress in sensor development


CBMSIS100

MAPS*(2003)

MAPS* (2012)

Single point res. ~ 5 µm 1.5 µm 1 µm

Material budget < 0.3% X0 ~ 0.1% X0 ~ 0.05% X0

Rad. hard. non-io. >1013 neq 1012 neq >3·1014 neq

Rad. hard. io > 1 Mrad 200 krad > 1 Mrad

Time resolution < 30 µs ~ 1 ms ~ 25 µs

*Optimized for one parameter

High-resistivity

0.18µm process

0.18µm process

See: HK 9.5 Mo 12:15: Dennis Doering: MAPS in 0.18µm process

This Session


High-resistivity

0.18µm process

/17/14

CMOS Monolithic Active Pixel Sensors


CBMSIS100

MAPS(2003)

0.35µm(2010)


Mat. budget [X0] < 0.3% ~ 0.1% ~ 0.05%

Rad. hard. non-io. [neq/cm²] >1013 1012 >1013

Rad. hard. io. [krad] > 1 000 200 > 500

Time resolution < 30 µs ~ 1 ms 110 µs

/17/14

CMOS Monolithic Active Pixel Sensors


CBMSIS100

MAPS(2003)

0.35µm(2010)

0.18µm(2012)


Mat. budget [X0] < 0.3% ~ 0.1% ~ 0.05%

Rad. hard. non-io. [neq/cm²] >1013 1012 >1013

Rad. hard. io. [krad] > 1 000 200 > 500 Smaller oxid layers

Time resolution < 30 µs ~ 1 ms 110 µs More complex logic possible

/17/14

Ionizing rad. Damage: Signal to Noise ratio


P1 P2 P3 P4 P5 P6 P7 P8 P9 P100

10

20

30

40

+20°C -20°C

Sig

na

l to

No

ise

Matrix

10MradSr-90

Dennis Doering

Preliminary

Critical limit

Signal to Noise ratios seem sufficient even after 10Mrad

/17/14

Open issues: Noise tails


Mi32TER

0 10 20 30 40 50 60 70 80 90 1001

10

100

En

trie

s

Noise [e]

0.35 µm 0.18µm

Dennis Doering

/17/14

Open issues: Noise tails


Mi32TER

0 10 20 30 40 50 60 70 80 90 1001

10

100

En

trie

s

Noise [e]

0.35 µm 0.18µm Std source follower 0.18µm Tiny gate source follower

Dennis Doering

Probable origin: 1/f-noise

/17/14

Deep Pwell: PMOS-transistors possible


0 20 40 60 80 100 120 140 160 180 2000

200

400

600

800

1000

1200

1400

1600

1800 Undefined state Low state High state

Mi32terP7 "seed"

Yie

ldCharge collected [ADC]

Dennis Doering

No change in charge spectrum observed, Þ It is allowed to operate a PMOS transistors without drawbacks in charge collection

P7: deep pwell everywhere

Mi32TER

Deep P-Well

DiodePMOS-Transistor(simplified)

d

/17/14

0 25 50 75 100 125 150 175 200 225 2500

200

400

600

800

1000

1200

1400

1600

NO deep Pwell Deep Pwell: d=6µm Deep Pwell: d=10µm

Mi32ter+20°C "seed"no clamp

Yie

ld

Charge collected [ADC]

Dennis Doering

Deep PWell hampers charge collection, reduces depleted zone of diode.Recovered for d=10µm:

Size of the diode hole?


Mi32TER

Deep P-Well


d

/17/14

Ionizing rad. damage: Response to MIPs


0 50 100 150 200250 300 350400 450 500550 600

20

40

60

80

100

120

140

160

180

200 +20°C unirradiated +20°C 3Mrad -20°C 3Mrad

Mi32 P6

Yie

ld


Dennis Doering

As expected: No influence on the response

Zeigen?

/17/14

Noise and fake hit rate


P4 P2 P6 P51,801,851,901,952,002,052,102,152,202,252,302,352,402,452,50

-70°C -20°C +20°C

No

ise

[A

DC

]

Decreasing transistor size

Dennis Doering

P4 P2 P6 P51E-5

1E-4

1E-3 -70°C -20°C 20°C

Fa

ke h

it ra

teDecreasing transistor size

Dennis Doering

Threshold: 5 x noise

Noise increases with decreasing transistor size.Fake hit rates increases despite of noise adapted thresholds => Non GaussianNo clear temperature trend=>1/f noise?

Mi32TER

ELT Std Small Tiny

SF Transistor sizeELT Std Small Tiny

SF Transistor size

/17/14

Vary the transistor size


Mi32TER

0 50 100 150 200 250 3001E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

P5 Tiny P6 Small P2 Std. P4 ELT

Fak

e hi

t rat

e

Applied threshold [e]

Dennis Doering

-20°C


Deep P-Well


d

0 25 50 75 100 125 150 175 200 225 2500

200

400

600

800

1000

1200

1400

1600

P2 Reference P6 Small transistor P7 as P6, but Deep pwell small hole P8 as P6, but deep pwell large hole

Mi32ter+20°C "seed"no clamp

Yie

ld


No DPWelld= 6µmd=10µm

For d=6µm, the depletion depth and the CCE is slighly reducedMostly recovered for d=10µm


0 10 20 30 40 50 60 70 80 90 1001

10

100

Entrie

s

Noise [e]

Mi18AHR A2 Mi32ter P2 Std. Mi32ter P5 Tiny SF

Dennis Doering

0 20 40 60 80 100 120 140 160 180 2000

200

400

600

800

1000

1200

1400

1600

1800 -20°C No clamping -20°C Low clamping -20°C High clamping

Mi32terP7 "seed"

Yie

ld


Dennis Doering

/17/14

Fake hit rate (transistor size)


0 50 100 150 200 250 3001E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

P5 Tiny P6 Small P2 Std. P4 ELT

Fake

hit

rate

Applied threshold [e]

Dennis Doering

-20°C

Small transistor => dramatically higher fake hit rate

/17/14

A possible explanation


0 1 2 3 4 5 6 7 80

10

20

30

40 P2 Std.

P5 Tiny

Ent

ries

Noise [ADC]

-70°C

Dennis Doering

NP

ixel p

er b

in

hottest pixel ~50e

hottest pixel > 80e

Small gate => wide noise distribution => many hot pixels


Width Length Noise [ADU](20°C, +/-10%)

Gain [e/ADU](20°C)

Noise [ENC](20°C, +/-10%)

ELT 1.85 12.1 22.4

1.5 µm 0.2 µm 1.87 11.1 20.8

0.9 µm 0.2 µm 2.15 10.5 22.5

0.5 µm 0.2 µm 2.41 10.1 24.3

Small gate => 10% more gain

Small gate =>25% more noise

Small gate => 20% more noise

Noise standard:PedestalFinal

In TOWER 0.18µm: Small gate => Few more gainSmall gate => Substantially more noise

/17Dennis Doering: MAPS in 0.18µm CMOS process DPG Dresden March 2013 35/14

Applications of MAPS

Picture STAR

Picture CBM

International Linear ColliderCBM-Experiment (FAIR, GSI)

STAR-Experiment

MAPS are developed for applications as vertex detector since 1999 at IPHC (Strasbourg).

/17/14

Operation principle


SiO2

N+ P+

P-

P+

Sensing diode

Epitaxial Layer

P-Well

Substrate

N+

50 µm

~50 µm thin sensors low material budget ⇒High granularity good spatial resolution ⇒

10-40 µm => a few µm resolution

/17/14

Operation principle


SiO2

N+ P+

P-

P+

Epitaxial Layer

P-Well

Substrate

e-

N+

e-

Particle

Sensing diode

/17/14

Non-ionizing radiation effects:Signal response


SiO2

N+ P+

P-

P+

Epitaxial Layer

P-Well

Substrate

N+

e-

Sensing diode

Defects

/17/14

Signal response


0 200 400 600 800 1000 1200 1400 1600 1800 20000

500

1000

1500

2000

2500

3000

3500

4000

4500

En

trie

s [1

bin

=4

AD

C]

Charge collected [e]

Unirradiated

Irradiated ( 3·1014neq

/cm2 )

MIMOSA-18 AHR 10µm Ru-106-T= -34°C

MPV: (591 ± 4) e(491 ± 20) e

/17/14

Non-ionizing radiation effects: Leakage current/Noise


SiO2

N+ P+

P-

P+

Epitaxial Layer

P-Well

Substrate

N+

--

Sensing diode

Defects

/17/14

5

10

15

20

25

30

35

40

45

50

55

60

No

ise

[e]

Temperature [°C]

Unirradiated

1014neq

/cm2

3·1014neq

/cm2

-3

Noise


Rad

iatio

nda

mag

e

/17/14

5

10

15

20

25

30

35

40

45

50

55

60

-34-27-15

No

ise

[e]

Temperature [°C]

Unirradiated

1014neq

/cm2

3·1014neq

/cm2

-3

Noise


Rad

iatio

nda

mag

e

Cooling

2 times higher noise with respect to unirradiated

/17/14

Non-ionizing radiation effects


SiO2

N+ P+

P-

P+

Epitaxial Layer

P-Well

Substrate

N+

e-

--

Sensing diode

Defects

/17/14



SiO2

N+ P+

P-

P+

Epitaxial Layer

P-Well

Substrate

N+

e-

--

Radiationdamage

Sensing diode

Defects

/17/14

Signal to Noise ratio


0 5 10 15 20 25 300

10

20

30

40

50

60

70

80

20µm (operated at room temp.) 10µm (operated at -20°C)

Sig

na

l to

No

ise

Radiation dose [1013neq

/cm2]

S/N limit (MIPS)

Technical feasible limits reached:- Pixel pitch- Operating temperature

Region of interest

?

/17/14

High-resistivity


Larger depleted volumes guided charge collection ⇒ ⇒ Improved charge collection efficiency (CCE)

SiO2

N+ P+

P-

P+

Epitaxial Layer

P-Well

Substrate

depleted volume

Low-resistivity High-resistivity

High-resistivity: Decrease of doping concentration in epitaxial layer.

Sensing diode

/17/14

Signal response


0 200 400 600 800 1000 1200 1400 1600 1800 20000

500

1000

1500

2000

2500

3000

3500

4000

4500

En

trie

s [1

bin

=4

AD

C]


Low resistivity unirradiated

MIMOSA-18 AHR 10µm Ru-106-T= -34°C MPV: (293 ± 5) e

/17/14

Signal response


More charge collected in a high resistivity epitaxial layer.

0 200 400 600 800 1000 1200 1400 1600 1800 20000

500

1000

1500

2000

2500

3000

3500

4000

4500

En

trie

s [1

bin

=4

AD

C]


Low resistivity unirradiated High resistivity unirradiated


(591 ± 4) e

/17/14

Signal response


Radiation damage effect after 3·1014neq/cm²: Some signal get lost due to recombinations. However, the high resistivity sensor is even irradiated better than the low resistivity sensor unirradiated.

0 200 400 600 800 1000 1200 1400 1600 1800 20000

500

1000

1500

2000

2500

3000

3500

4000

4500

En

trie

s [1

bin

=4

AD

C]


Low resistivity unirradiated High resistivity unirradiated

High resistivity 3·1014neq

/cm2


(591 ± 4) e(491 ± 20) e

/17/14

Improvements using high resistivity


0 5 10 15 20 25 300

10

20

30

40

50

60

70

80

Low-resistivity 20µm (operated at room temp.) Low-resistivity 10µm (operated at -20°C) High-resistivity 10µm (operated at -34°C)

Sig

nal to

Nois

e (R

u-1

06

)

Radiation dose [1013neq

/cm2]

Error bars: Signal fit uncertainty * 10% noise uncertainty

*Beam test is pending

S/N limit (MIPS)

*

Parameters:- Pixel pitch- Operating temperature- Resistivity of epitaxial layer

/17/14

How to improve the non-ionizing radiation hardness of MAPS:- Operate the sensor at low temperature ( -30°C)- Small pixel pitch ( 10µm)- High-resistivity epitaxial layer (used here 400 Ωcm)

Conclusion


/17/14

How to improve the non-ionizing radiation hardness of MAPS:- Operate the sensor at low temperature ( -30°C)- Small pixel pitch ( 10µm)- High-resistivity epitaxial layer (used here 400 Ωcm)

⇒ Radiation hardness beyond 3·1014neq/cm²

Conclusion


1 radiation damage effects in monolithic active pixel sensors implemented in an 0.18µm cmos process...

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