2001 december review detector research & development for particle physics at liverpool improving...

2001 December Review

Detector Research & Development for Particle Physics at Liverpool

Improving Radiation Hardness

Monolithic Active Pixels

Detectors for Very Large Area Arrays

Future Directions


Segmented Semiconductor Devices For Charged Particle Detection

Semiconductor detectorsare based on segmented diodes which collect charges produced by ionising radiation

The position resolution comes primarily from thegranularity which exploits standard microchip processing technology



Radiation damage to silicon detectorsincreases reverse currents, creates interface trapped charge, introduces traps reducing charge collection efficiencieschanges the effective doping concentrations

Studies of the latter effect have shown significant improvements under charged hadron irradiation when high concentrations of interstitial oxygen are introduced

However, unlike in the case of n-side read-out detectors, the charge collection efficiencies for p-side read-out detectors do not plateau with voltage until well above the depletion voltage

This is usually assigned to the effect of trapping


Detectors Studied at Liverpool

The following were carried out with miniature ATLAS p-side strip detectors using a fast current amplifier

Also extensively studied are diodes and full-size devices (p-side and n-side strips), the latter using LHC speed 128 channel analogue read-out.


Evaluation of Trapping Effects

Capacitance – Voltage Derived Depletion Voltage

0

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

0.0014

0.0016

0 50 100 150 200 250 300 350

Bias [V]

1/C

2 [p

F-2

]

1.90.11014p/cm2

Oxygenated MiniatureMicro-strip Detector

VFD = 100 7 V from fitting C(V)


Evaluation of Trapping Effects

Corresponding Charge Collection Efficiency vs Voltage

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 200 400 600 800

Bias [V]

No

rma

lis

ed

co

lle

cte

d c

ha

rge

Q (10 ns)

Q (25 ns)

Q (40 ns)

Q (80 ns)

100 V


Old ATLAS Irradiated n-in-n Results

21014p/cm2


Trapping and Ballistic Deficit

The trapping probability is expected to depend on the carrier velocity and hence the field.

At the LHC, electronics response times are close to charge collection times. Therefore signal loss due to incomplete charge integration must also be considered.

(Also velocity / field dependent.)

Non-irradiated p-strip Detector


Influence of Ballistic Deficit

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 200 400 600 800

Bias [V]

No

rmal

ise

d c

olle

cte

d c

har

ge

Q (10 ns)

Q (25 ns)

Q (40 ns)

Q (80 ns)

Miniature detectors irradiated to 1.91014p/cm2

Non-Oxygenated Oxygenated

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 100 200 300 400 500 600 700 800

Bias [V]

No

rmal

ise

d c

olle

cte

d c

har

ge

Q (10 ns)

Q (25 ns)

Q (40 ns)

Q (80 ns)





0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600 800

Bias [V]

Nor

mal

ised

col

lect

ed c

harg

e

Q (10 ns)

Q (25 ns)

Q (40 ns)

Q (80 ns)

0

0.2

0.4

0.6

0.8

1

1.2

0 200 400 600 800

Bias [V]

Nor

mal

ised

col

lect

ed c

harg

e

Q (10 ns)

Q (25 ns)

Q (40 ns)

Q (80 ns)





0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600 800 1000

Bias [V]

No

rma

lise

d c

oll

ect

ed

ch

arg

e

Q (10 ns)

Q (25 ns)

Q (40 ns)

Q (80 ns)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600 800

Bias [V]

No

rmal

ise

d c

olle

cte

d c

har

ge

Q (10 ns)

Q (25 ns)

Q (40 ns)

Q (80 ns)


Non-Oxygenated Detectors: Relative Ballistic Deficit

Oxygenated

0

0.2

0.4

0.6

0.8

1

1.2

0 100 200 300 400 500 600

Bias [V]

QV/Q

V(8

0 n

s)

Q (10 ns)

Q (25 ns)

Q (40 ns)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600 800

Bias [V]

QV/Q

V(8

0 n

s)

Q (10 ns)

Q (25 ns)

Q (40 ns)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600 800

Bias [V]

QV/Q

V(8

0 n

s)

Q (10 ns)

Q (25 ns)

Q (40 ns)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600 800 1000

Bias [V]

QV/Q

V(8

0 n

s)Q (10 ns)

Q (25 ns)

Q (40 ns)

5.11014 p/cm22.91014 p/cm2

1.91014 p/cm2Non-irradiated


Oxygenated Detectors: Relative Ballistic Deficit

5.11014 p/cm2

2.91014 p/cm21.91014 p/cm2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600 800

Bias [V]

QV/Q

V(8

0 n

s)

Q (10 ns)

Q (25 ns)

Q (40 ns)

0

0.2

0.4

0.6

0.8

1

1.2

0 200 400 600 800

Bias [V]

QV/Q

V(8

0 n

s)

Q (10 ns)

Q (25 ns)

Q (40 ns)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600 800

Bias [V]

QV/Q

V(8

0 n

s)

Q (10 ns)

Q (25 ns)

Q (40 ns)


Fits to the Charge Collection Efficiency

The above results suggest that, particularly at high doses, the ballistic deficit is not a major factorfor LHC speed operation

In the following fits, sufficient integration time has anyway been allowed such that the only charge loss is due to trapping

Free parameters: attenuation length ,depletion voltage VFD total generated charge Q0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 200 400 600 800 1000

Bias [V]

Q/Q

0

Oxygenated

Non-oxygenated

1.91014 p/cm2



2.91014 p/cm2

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 200 400 600 800 1000

Bias [V]

Q/Q

0

Oxygenated

Non-oxygenated

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 200 400 600 800 1000Bias [V]

Q/Q

0 Oxygenated

Non-oxygenated

5.11014 p/cm2



Detector label

Fluence[p cm-2]

Oxygenenrichme

nt

VFD [V](From C-V)

VFD [V](From CCE)

[m]

NI Non irr. No 49 2 50 2

SO1 1.90.1 · 1014 Yes 100 7 90 2 1338 15

SN1 1.90.1 · 1014 No 150 8 137 2 1407

220

SO2 2.90.2 · 1014 Yes 121 7 130 2 1224

138

SN2 2.90.2 · 1014 No 218 15 214 4 1313

122

SO3 5.1 0.4 · 1014 Yes 181 15 196 3 731 84

SN3 5.10.4 · 1014 No 320 20 348 7 781 55



The fitted values of VFD agree with each other and with other oxygenated data (taking account of the relative neutron to proton damage factor)

The fitted values of Q0:18.10.3, 18.20.3, 17.70.3, 18.10.6, 18.20.4 and 18.30.4 are all consistent and agree with the pre-irradiation value 17.90.3



The dependence of Q/Q0 and therefore on leads to a value of eff = 5.60.610-16cm2/ns (1/ = eff )Assuming this value allows extrapolation of CCE to high

0

0.2

0.4

0.6

0.8

1

1.2

0 1E+14 2E+14 3E+14 4E+14 5E+14 6E+14

Fluence [p cm-2]

Q/Q

0

(Charge collected at VFD)/Q0 - Ox. detectors

(Maximum collected charge)/Q0 - Ox. detectors

(Charge collected at VFD)/Q0 - Non-ox. detectors

(Maximum collected charge)/Q0 - Non-ox. detectors



Because for p-strip read-out, the trapping significantly affects the CCE(V), the improvements in VFD due to oxygenation do not give correspondingly large effects in terms of CCE The trapping dependence on the field leads to CCE(VFD) being higher for non-oxygenated than oxygenated detectors by ~5%

Read-out from the high-field n-side gives less dependence on trapping leading to the CCE(V) V behaviour below VFD

This would imply that for high doses, n-side readout should benefit more from oxygenation of the substrate


Consequences for LHC-b

The LHC-b vertex detector is proposed to use oxygenated n-strip detectors for which the first prototypes have just been delivered to Liverpool and have very recently been irradiated in the CERN PS


Proposed LHC-b Detectors

LHC-b uses back-to-back thinned disks for r and plus double-metal routing


Consequences for ATLAS

LHC-b and the pixel systems of ATLAS and CMS need to maximise their survival; n-side readout oxygenated detectors look to offer the best possibilities

Super-LHC with factor of 10 increased luminosity would also need such technology


The Use of p-type Silicon

Detectors produced with n-side read-out do suffer from the disadvantage of requiring potentially expensive double-sided processing

Use of p-type substrates does provide a viable alternative where cost is of paramount importance

Comparison of p-type and n-type detectors after 31014 p/cm2


Monolithic Active Pixel Sensors

CCDs have been used at SLAC to achieve excellent spatial resolution for b, c and tagging.

The future Linear Collider would be an excellent environment to use this technology.

However, MAPS may prove to be a more radiation tolerant, faster, cheaper alternative with greater built-in functionality.

SLD 300 million pixel array



MAPS use standard very fine lithography (deep sub-micron) processing such that each pixel (20m20m) contains its own diode contact to the substrate, amplifier, read-out switches and possibly simple signal processing.

The very low input capacitance means that, even at room temperature, the input noise is only a few electrons, so the typically 10m epitaxial layer is still thick enough for signals of up to thirty times the noise to be produced.

The use of standard processing allows integration of all read-out features onto the same silicon die (‘camera on a chip’)



Liverpool has helped initiate the ‘PRIMA’ proposal to the Technology Fund (with CLRC,Royal Marsden, LMB Cambridge, Marconi, Surrey and Glasgow) for £3M which was one of the 26 out of 230 proposal to go to full application.

Liverpool is part of the international collaboration looking to explore use of such technology at TESLA.



Liverpool, with Cambridge and QMW initiated the use of 150mm wafers within ATLAS with Micron processing 2 detectors on a single wafer to Liverpool mask designs

For NASA’s Gamma-ray Large Area Space Telescope, we designed masks for 10cm10cm strip detectors which have been processed and delivered to the collaboration



Silicon detectors have dropped a factor of ten in price in the last decade. However, substrate costs are now a significant fraction of the total for high purity material.

Conjugate polymers are being actively developed as semiconductor materials suitable for large area flat display screens.

If devices can be produced which are sensitive to ionising radiation then very large area (several thousand square metre) solid-state high spatial resolution detectors may be achievable.

MAPS technology could also eventually prove cost effective for very large areas.


Future Directions

Semiconductor detectors will continue to improve in radiation hardness with charge collection efficiency finally limiting performance (1015 n/cm2).

Fine lithography allows very radiation hard circuits to be designed which, if integrated onto appropriate substrate structures, could give low mass pixel detectors of 100MRad, many 1015 n/cm2 radiation hardness.

Very large areas could be affordably instrumented with very high spatial resolution detectors in the future using the Moores Law extrapolation of conventional circuitry costs plus MAPS technology or new, much cheaper, substrate materials such as conjugate polymer diodes.

2001 december review detector research & development for particle physics at liverpool improving...

Documents

review detectors

review trapping

review oxygenated detectors

review fits

high slide

nonirradiated slide

review consequences

substrate slide