andy blue edgeless & slim edge detectors andrew blue, on behalf of the rd50 collaboration

Andy Blue

Edgeless & Slim Edge DetectorsAndrew Blue, on behalf of the RD50 Collaboration

Andy BlueAndy Blue VERTEX 2014

Slim Edge & “Edgeless” sensors

• Standard silicon detectors have a relatively large insensitive region around their active area. – This dead region is due to presence of multiple guard rings and the clearance for the dicing street of the

sensors

– It can extend to more than a few mm’s, depending on the detector application

• To remove inactive regions around each sensor reduced edge or “edgeless” sensors are required.

• Such sensor designs in conjunction with through-silicon vias (TSV) would also result in a reduction in radiation length, making edgeless sensors a promising option for the particle physics community.

– Without the need for shingling/ overlapping of sensors

• Such sensors utilize one of a number of methods to reduce the number of guard rings and their pitch so to increase the active area of tiled detectors, and a (non-exhaustive) list of techniques proposed for such a reduction in dead area follows


Slim Edge

• Slim edges reduce the dead area by reducing the number of guard rings used in tandem with the reduction of the distance from the outer guard ring to the cut edge.

• Further reductions can be made in a double sided (n-on-n) process by placing the guard rings on the back surface such that they overlap the edge pixels/strips on the front side

Example of slim edge devices proposed for the IBL, where edge pixels on the sensor surface overlap the guard rings structures on the back.


Active Edge

Active Edge devices turn the physical cut edge of the sensor into a junction

Allows the depletion of the silicon all the way to the physical edge.

The sensors sidewalls are cut using dry etch techniques to eliminate the microscopic damage associated with the sawing.

The sidewalls of the cut edges are then doped to compensate for the high level of defects at the sidewall, and passivated with a thermal oxide layer

Active edge pixel senor under test, showing less than 50m from the edge pixel to the sensor edge


Scribe Cleave & Passivate

• Diamond Stylus• Laser• XeF2 Etch• DRIE Etch• Saw cut

• Tweezers (manual)• Loomis Industries LSD-100• Dynatex, GTS-150

• Native Oxide + Radiation or

N-type•Native SiO2 + UV light or High T•PEVCD SiO2

•PEVCD Si3N4

•ALD “nanostack” of SiO2 & Al203

P-type•ALD of AL2O3

• All treatment is post processing & low temperatures

• Etch scribing can be done during fabrication


RD-50 work

• Many studies investigating slim edge & edgeless technology being carried out via RD50– Some already covered in this conference

• ‘3D detectors in ATLAS’: Sebastian Grinstein

• ‘RD50 Overview’: Marcos Fernandez Garcia

– Today I will talk about• Active edge devices with varying thicknesses and levels of irradiations

• Irradiations to study the passivation layers used for slim edge devices

• Micro focused X-rays for CCE measurements of SCP and Active edge devices


Active Edge – FE-I4 Assemblies

• Much progress is being made in to the study of Active Edge devices– Latest studies include

• Test Beam results with thin pixel sensors at High Eta• Characterization of Active edge pixels after irradiations• Comparison of CCE for pixels sensors of different Active thicknesses

• 125m Edge implemented in FE-I3 and FE-I4 sensors

• 50m implemented in only FE-I3 devices


CCE of Active Edge pixels after irradiations

• 100 m thick sensor with 125 m slim edge bump-bonded to an FE-I3 (1500 e- threshold)

• 87% CCE at 300V for both inner and edge pixels after irradiations of

• 1x1015neq/cm2 (KIT)• 5x1015neq/cm2 (Ljubljana)

• p-type MCZ 100 m thick sensors with 125 m slim edge (FEi4 & 1100e-

threshold )• Compatible charge collection properties between edge and inner pixels


CCE for different thicknesses of Active Edge pixels

• The 100-150 m thick sensors show higher charge collection up to a fluence of 4-5x1015neq/cm2

• At higher fluence the effect of charge trapping teens to equalize the charge collection efficiency for all thicknesses

• 100m thick Slim Edge Irradiated devices taking ~500V


– How does the processing involved to produce slim edge/edgeless devices affect detector efficiencies of DUT edges before and after irradiation?

– Emerging pattern• No issues with Radiation Hardness for N-type devices• However for P-type devices

– High currents at low ionisation doses <1x1014ncm-2

– No significant excess on the edge for high ionizing dose >1x1014ncm-2

– No issues for neutron-irrad. samples

– Has led to a series of investigations (Laser, source testbeams, irradiations)

– Today will talk about• Irradiations to study the passivation layers used for slim edge devices• Micro focused X-ray for CCE measurements of SCP & active edge

devices

SCP devices - Observations


P-type SCP Devices After Irradiation

• To investigate, 12 SCP p-type strip devices (CIS) were irradiated at LANL in 2011– Results were inconclusive

• High fluence devices (3/3 at 1x1016neq & 3/3 at 1x1015neq) show expected post-rad leakage current

• Low fluence devices (1/3 at 1x1013neq & 1/3 at 1x1014neq) showed early breakdown!

Leakage currents do not scale with fluencelow fluence (< 1x1014): reduced edge performancehigh fluence (>1x1014): resistive edge

8A

0.8A

0.1A

Pre-Irrad

Post-Irrad


• Possible issues with the Si-Alumina interface– One theory is that a thin layer of AlxSiOy forming between Si and Al2O3

– Forms as part of the ALD process– This oxide layer gains more of its (positive) interface charges with first few Mrad,

counteracting the necessary negative oxide from alumina

• To check this hypothesis MOS capacitors were fabricated at the CNM microfabrication facility with Al2O3 as the dielectric. The capacitors allow assessment of the effective charge density via C-V curves

• We irradiated the devices to figure out how the charge density changes with dose

• The capacitors were irradiated at LANL with 800 MeV protons in January 2014. The fluence was up to 6.8x1014 p/cm2 (34 Mrad)

(equivalence: 1015 p/cm2 = 0.71x1015 neq/cm2 = 50 Mrad)

• Irradiations with gammas took place at BNL in December 2013, up to 30 Mrad

Irradiated P-type SCP devices


Test Devices

5 Squared shaped MOS

• 4 Wafers: 100 mm-diameter (100) Cz Si P-type• 400nm SiO2 field isolation & patterning

• 500 nm Al (99.5%)/Cu (0.5%) & patterning• Wafer backside metallization• ½ wafer post metallization anneal (PMA)

• 20 min @350oC in N2/H2

• Atomic Layer DepositionAl2O3

CleaningALS (ToC, precursors)Post-deposition anneal

Al2O3 Process 1Wafer 1: 40nm CNMWafer 2: 20nm CNM

Al2O3 Process 2Wafer 3: 20nm NRLWafer 4: 40nm NRL


Capacitance-Voltage Wafer Mapping

-2 -1.5 -1 -0.5 0 0.5 1 1.5 21

2

3

4

5

6

7

x 10-10 6852-2-PMA 20 nm ALD Al2O3 CNM 25 MOS capacitors 0.002304 cm2

Voltage [V]

Cap

acit

ance

[F

]

inv->acc acc->inv

-20-15-10-50

10-10

10-5

100

6852-2-PMA 20 nm ALD Al2O3 CNM TZDB 25 MOS capacitors 6.4e-005 cm2

Gate voltage [V]|Lea

kage

cur

rent

den

sity

| [A

/cm

2]

1st sweep2nd sweep

25 chips½ wafer

A2 = 2.3·10-3 cm2

Good yield

Good uniformity


nonirrad 100 krad 300 krad 1 Mrad 3 Mrad 10 Mrad 30Mrad-4

-3

-2

-1

0

1

x 1012

gamma irradiation dose

Eff

ecti

ve t

rap

ped

ch

arg

es [

cm-2

]

Al2O3 40 nm CNM PMAAl2O3 20 nm CNM PMAAl2O3 20 nm NRL PMAAl2O3 40 nm NRL PMAAl2O3 40 nm NRL NoPMA

-5 -4 -3 -2 -1 0 1 2 3 4 51

1.5

2

2.5

3

3.5

4x 10

-10

Al2O3 40 nm CNM PMA

Voltage [V]

Cap

acit

ance

mea

sure

d [

F]

Non-irrad. inv->accNon-irrad. acc->inv100 krad inv->acc100 krad acc->inv300 krad inv->acc300 krad acc->inv1 Mrad inv->acc1 Mrad acc->inv3 Mrad inv->acc3 Mrad acc->inv10 Mrad inv->acc10 Mrad acc->inv30Mrad inv->acc30Mrad acc->inv

gamma irradiation

Rad-hard

gamma-radiation-hardnessin process 2 Al2O3 with PMA

positive charge trappingin process 1 Al2O3

C-V Results from Gamma Irradiations

Positive Charge0.1, 0.3, 1, 3, 10 & 30 Mrad


nonirrad 70 krad 347 krad 0.96 Mrad 3.965 Mrad 7.35 Mrad 34.2 Mrad-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

x 1012

proton irradiation doseEff

ecti

ve t

rap

ped

ch

arg

es [

cm-2

]

Al2O3 40 nm CNM PMAAl2O3 20 nm CNM PMAAl2O3 20 nm NRL PMAAl2O3 40 nm NRL PMAAl2O3 40 nm NRL NoPMA

Rad-hard

-4 -3 -2 -1 0 1 2 3 4 5

1

1.5

2

2.5

3

3.5

4x 10

-10

Al2O3 40 nm CNM PMA

Voltage [V]

Cap

acit

ance

mea

sure

d [

F]

Non-irrad. inv->accNon-irrad. acc->inv70 krad inv->acc70 krad acc->inv347 krad inv->acc347 krad acc->inv0.96 Mrad inv->acc0.96 Mrad acc->inv3.965 Mrad inv->acc3.965 Mrad acc->inv7.35 Mrad inv->acc7.35 Mrad acc->inv34.2 Mrad inv->acc34.2 Mrad acc->inv

proton irradiation dose


positive charge trappingin process 1 Al2O3

C-V Results from Proton Irradiations

Positive Charge

0.07, 0.35, 0.96,3.97, 7.35 & 34.2 Mrad


MOS capacitors designed to assess the radiation hardness of Al2O3 layer used in Scribing Cleaving Passivation (SCP) process for p-type bulk Si devices have been successfully fabricated. The capacitors allow us to measure the effective dielectric charge density, critical for the SCP performance

Al2O3 was deposited with 2 different processes at 2 facilities

Additionally, we intentionally varied the deposition thickness (20 nm and 40 nm) and post-metallization annealing step

The devices were irradiated at LANL with protons and at BNL with gammas with TID up to 34 Mrad

The initial assessment of post-rad performance indicates an interesting dichotomy between the 2 deposition processes:

In one case the radiation-induced changes in effective charge density are negligible

In another case it scales nearly linearly with dose

We may need to vary the processing with a future fabrication to figure out which of the processing differences influenced the different radiation performance

Summary of Al203 Irradiations


Further CCE studies of SCP devices

Many studies in various technologies (n-type & p-type) have taken place

Would like to use technique for studying

• Edge Pixels/Strips

• Inter-strip/pixel charge collection profile (<5m beam spot)

– Use Focussed X-rays

Sensor Type Origin Edge-Active area Distance

(mm)

Signal Readout Beam Ref

P-type strips PPS (CIS) ~200 Binary (PTSM) 90Sr V. Fadeyev et al‘Pixel 2012, NIM A 731 (260-262) 2013

N-type Strips GLAST (HPK) ~200 Analog (ALiBaVa) 90Sr R. Mori et alJINST 7 P05002 2012

P-type 3D pixels IBL (CNM) 50 FEi3 & FEi4 CERN Testbeam

S Grinstein et al‘RESMDD12, NIM A 730 (28-32) 2013

G. Pellegrini et alPixel 2012, NIM A 731 (198-200) 2013

P-type Strips PPS (CIS) Analog (ALiBaVa) 90Sr A. Macchiolo

P-type Strips n-irradiated

PPS (CIS) 110-220 Single-channel Laser-TCT

I Mandić et al., NIMA 751 (2014) 41-47.

P-type Strips n-irradiated

PPS (CIS) 150 Analog (ALiBaVa) 90Sr A. Macchiolo


Micro focused X-rays for CCE measurements

• Used the Diamond Light Source base in Oxford, UK

– Beam station B16– Comprises of a water-cooled fixed-exit double

crystal monochromator that is capable of providing monochromatic beams over a 2-20 Kev photon energy range.

– An unfocused monochromatic beam is provided to the experimental hutch.

– A compound refractive lens (CRL) was used to produce a 15 Kev micro-focused X-ray beam.

– The size of the micro-focussed beam was determined by measuring transmissions scans with a 200 m gold wire.

– The derivative of these scans gave a beam shape which had a FWHM of 2.5m


SCP devices

Device Irradiated Bulk Thickness (m) Strip Pitch (m) Edge strip to edge (m)

1 - N 200 80 28

2 4.8x1014 ncm-2 P 100 80 170

• SCP strip sensors

• N-type & P-type

• 80m Strip pitch

• Wire bonded to ALiBaVa readout system

• Irradiated samples cooled to -15oC With peltier + chiller


Micro-focussed X-Ray beam: CCE of SCP

Scan of the edge of the strip detector with full guard ring structures a) shows the mean signal size with an ADC cut of 10, (b) has an ADC cut of 40.

Scan of the cleaved edge of the strip detector. (a) Shows the mean signal size with an ADC cut of 10, (b) has an ADC cut of 40.

(a)

(a)

(b)

(b)


Irradiated SCP devices

• Preliminary results from latest testbeam. After 4.8x1014 ncm-2, charge is collected on edge strips

• 12KeV beam, 2.5m FWHM• 10m Step size,. T= -8oC• Analysis to follow (CCE v bias)

300V 500V

Edge Strip: 305m to SCP edge


Active Edge devices

Device Implant Bulk Thickness (mm) Pixel to Edge (mm) Calculated Full depletion voltage (V)

NN-200-50 N N 200 50 28

NP-100-100 N P 100 100 10

NP-100-50 N P 100 50 10

• VTT/Advacam Active Edge sensors

• Sensors flip-chip bonded to Timepix2

• 55m x 55m pixels

• Measurements taken in pixel counting mode


Over Edge Scans - Active Edge/Timepix


Side & Corner Scans – Active Edge/Timepix


Future Work & Conclusions

• A lot of work continues in RD50 investigating slim edge & Edgeless devices– Shown today

• Studies of Active Edge Devices– Effect of sensor thickness, geometries, radiation hardness etc.

• Investigations into the effect of interface irradiations– AlxSiOy layers effecting p-type SCP devices

• Use of micro focus X ray beam for charge collection measurements– Technique developed to study inter-strip/pixel behaviour

– Future work (includes)• 2nd Production of Active Edge devices at Advacam

– 50, 100 & 150 m thicknesses– Pixels & diodes with different edges to investigate post-irradiation breakdown

properties

• More irradiations and tests planned for SCP devices


Backup Slides


0.1, 0.3, 1, 3, 10, 30 Mrad

6 proton fluences

20 nm & 40 nm Al2O3 from processes 1 & 2 with PMA+ 40 nm Al2O3 from process 2 without PMA

6 gamma doses

1.39x1012, 6.94x1012, 1.92x1013,7.93x1013, 1.47x1014, 6.84x1014 p/cm2

0.070, 0.347, 0.960,3.965, 7.350, 34.200 Mrad

5 Selected Wafers


process 1 Al2O3

-40-35-30-25-20-15-10-5010

-10

10-5

100

Al2O3 40 nm CNM PMA

Gate voltage [V]|Le

ak

ag

e c

urr

en

t d

en

sit

y|

[A/c

m2

]

nonirrad70 krad347 krad0.96 Mrad3.965 Mrad7.35 Mrad34.2 Mrad

proton irradiationdose

-40-35-30-25-20-15-10-5010

-10

10-5

100

Al2O3 40 nm NRL PMA

Gate voltage [V]|Le

ak

ag

e c

urr

en

t d

en

sit

y|

[A/c

m2

]



-20-15-10-5010

-10

10-5

100

Al2O3 20 nm NRL PMA

Gate voltage [V]|Le

ak

ag

e c

urr

en

t d

en

sit

y|

[A/c

m2

]



-20-15-10-5010

-10

10-5

100

Al2O3 20 nm CNM PMA

Gate voltage [V]|Le

ak

ag

e c

urr

en

t d

en

sit

y|

[A/c

m2

]



Fowler-Nordheim conduction regime

(≈2.8 eV)

proton-radiation-hardnessin process 2 Al2O3 with PMA

I-V Results from Proton Irradiations


-40-35-30-25-20-15-10-5010

-10

10-5

100

Al2O3 40 nm CNM PMA

Gate voltage [V]|Le

ak

ag

e c

urr

en

t d

en

sit

y|

[A/c

m2

]

nonirrad100 krad300 krad1 Mrad3 Mrad10 Mrad30Mrad

gammairradiation

-20-15-10-5010

-10

10-5

100

Al2O3 20 nm CNM PMA

Gate voltage [V]|Leak

ag

e c

urr

en

t d

en

sit

y| [A

/cm

2]

nonirrad100 krad300 krad1 Mrad3 Mrad10 Mrad30 Mrad

gammairradiation

-20-15-10-5010

-10

10-5

100

Al2O3 20 nm NRL PMA

Gate voltage [V]|Le

ak

ag

e c

urr

en

t d

en

sit

y|

[A/c

m2

]


gammairradiation

-40-35-30-25-20-15-10-5010

-10

10-5

100

Al2O3 40 nm NRL PMA

Gate voltage [V]|Lea

kag

e c

urr

en

t d

en

sit

y|

[A/c

m2]


gammairradiation


Fowler-Nordheim conduction regime

(≈2.8 eV)

process 1 Al2O3

I-V Results from Gamma Irradiations


Capacitance-Voltage Wafer Mapping

-4

-3

-2

-1

0

1

2

0 10 20 30 40

Ln(-L

n(1-

F))

|Breakdown voltage| [V]

40 nm Al2O3 ALDCNM PMA40 nm Al2O3 ALDCNM NoPMA20 nm Al2O3 ALDCNM PMA20 nm Al2O3 ALDCNM NoPMA20 nm Al2O3 ALD NRLPMA20 nm Al2O3 ALD NRLNoPMA40 nm Al2O3 ALD NRLPMA40 nm Al2O3 ALD NRLNoPMA

90%

25%

50%

andy blue edgeless & slim edge detectors andrew blue, on behalf of the rd50 collaboration

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