G.Pellegrini 1 , C.Fleta 2 , F.Campabadal 1 , M. Lozano 1 , J.M. Rafí 1 , M.Ullán 1

the Sixth International "Hiroshima" SymposiumGiulio Pellegrini

Technology of p-type microstrip detectors with Technology of p-type microstrip detectors with radiation hard p-spray, p-stop and moderate p-spray radiation hard p-spray, p-stop and moderate p-spray

insulationsinsulations

G.Pellegrini1, C.Fleta2, F.Campabadal1,

M. Lozano1, J.M. Rafí1, M.Ullán1

1Centro Nacional de Microelectrónica, Barcelona Spain2University of Glasgow, Glasgow, UK

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OutlineOutline

• P-type detectors

• Detector isolation technologies

• Simulation and measurements

• Conclusions

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P-type detectorsP-type detectors

• Technology: N type strips on p-type substrate

• N side read-out takes advantage of the presence of the high electric field on the read-out side after irradiation.

• Needs insulation between strips in order to compensate the electron layer formed below the oxide:

• P-stop• P-spray • Moderate p-spray

• More complex technology• 6 or 7 photolithographic layers• The most radiation hard technology

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P-stop isolationP-stop isolation

First n-on-p detectors fabricated with p-stop isolation. Different implants were used to find the optimum value.

N+/P/P+

1,E+09

1,E+10

1,E+11

1,E+12

1,E+13

1,E+14

1,E+15

1,E+16

1,E+17

1,E+18

1,E+19

1,E+20

1,E+21

0 1000 2000 3000 4000 5000 6000

d (nm)

Co

nce

ntr

atio

n (

cm-3

)

Strip

back inplant

P-stop 1E13 cm-2

P-stop 1E14 cm-2

Pitch 120m, p-stop width 7m, strip width 20m

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Radiation hardnessRadiation hardness

Baby microstrip detectors fabricated at CNM in collaboration with Liverpool University

Efficiency of Charge Collection in 280 um thick p-type SSDAfter 7.5 *1015 p/cm2, charge collected is > 6,500 e-

(1) First results on charge collection efficiency of heavily irradiated microstrip sensors fabricated on oxygenated p-type silicon. NIM-A, num 518, Feb. 2004, pp. 340-342. G. Casse, P.P. Allport, S. Martí, M. Lozano, P. R. Turner.

(2) Comparison of radiation hardness of P-in-N, N-in-N and N-in-P silicon pad detectors IEEE Trans. on Nucl. Sci., V. 52, Issue 5, Part 2, Oct. 2005 Page(s):1468 – 1473, M. Lozano, G. Pellegrini, C. Fleta, C. Loderer, J. M. Rafí, M. Ullán, F. Campabadal, C. Martínez, M. Key, G. Casse, P. Allport

N-on-p strip detectors with p-stop isolation (1)

Pad detectors (2)

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Annealing p-typeAnnealing p-type

G. Casse, “Overview of n-side read-out microstrip devices”, RD50/FDS meeting 2005.

Annealing (@80 oC) behaviors of the collected charge after proton irradiation to 3.5. 1015 cm-2. At high voltage the collected charge appears to be stable. It is known that the full depletion voltage as determined by CV measurements appears to follow the expected evolution.

N-on-p strip detectors with p-stop isolation

Pad detectors

“Annealing Studies of Magnetic Czochralski Silicon Radiation Detectors”, G.Pellegrini et al., Nucl. Instr. and Meth. Volume 552, Issues 1-2, 21 October 2005.

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Electronic NoiseElectronic Noise

G. Casse, “Overview of n-side read-out microstrip devices”, RD50/FDS meeting 2005.

Baby microstrip detectors fabricated by Hamamatsu

micro-discharge noise

Micro-discharges can represent the earliest mechanism of failure for micro-strip detectors when operated at high voltage.

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P-spray isolationP-spray isolation

P+

P

N+

P-spray (p+)

MetalPolysilicon

Oxide

+++++

Oxide charge

Electron inversion layer

-----------

To avoid the problem of microdischarges p-spray isolation was used to fabricate microstrip and pad detectors.

P-spray has to:

• Insulate strips

• Keep VBD > VFD

Variables:

• Oxide thickness

• Implant dose

• Implant energy

• Thermal budget fixed

Optimization through:

• Simulation (ISE-TCAD)

• Engineering runs (3)

Conflictingconditions

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Simulation of p-spraySimulation of p-spray

p-spray VBD (V) Diodes

Energy(keV)

Dose(cm-2)

Simulated Measured

45 1012 900 V 700 V

150 1012 750 V 650 V

45 5×1012 210 V 250 V

Electric field at the breakdown point

Without p-spray

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P-spray: calibration runsP-spray: calibration runs

Characteristics of n-in-p pad detectors with p-spray isolation

p-spray Current at VFD+20 V

Energy(keV)

Dose(cm-2)

Strips Ring

45 1012 50 ± 30 nA 2 ± 1 mA

150 1012 90 ± 40 nA 150 ± 40 µA

45 5×1012 1.4 ± 1.1 µA 300 ± 30 nA

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Effect of oxideEffect of oxide chargecharge

Strip detector

Irradiation:50 Mrad, Co60 gamma source

MOS Capacitor CV measurements

Oxide charge

• Before: 11011 cm-2

• After: 31012 cm-2

• Fast build-up of damage in the oxide layer

• Reach a saturation value for the oxide charge of about 2-31012 cm-2 at about 100-200 krad (few LHC weeks)

• The oxide charge will be saturated well before the bulk damage will start to affect the operation of the detectors

• This oxide charge increases inversion layer, canceling the p-spray insulation

• It is very important to ensure that insulation is maintained after first irradiation, not only in fresh or bulk damaged detectors.

“Technology development of p-type microstrip detectors with radiation hard p-spray isolation”, G. Pellegrini et al., Nucl. Instr. and Meth A 2006 In Press, Corrected Proof, Available online 28 July 2006

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Neutron irradiationNeutron irradiation

100150

200250

300350

400450

500550

600650

700750

800850

900950

10001050

11001150

0

100

200

300

400

500

600

[Laser - Irrad] Charge .vs. Vbias

Vbias (V)Q

(p

Vs)

10 20 30 40 50 60 70 100 150 200

-0.1

0.0999999999999999

0.3

0.5

0.7

0.9

1.1

1.3

1.5

1.7

1.9

[Source - No Irrad.] - Charge .vs. Vbias

Vbias (V)

Q (

nVs)

n-type

p-type

n-type

p-type•read a 3cm p-type detector using the ATLAS SCTDAC readout.•SCTDAC is optimised for n-type sensor.•SCT readout: binary ABCD3T chip

P-type irradiated with neutrons (1015 n/cm2)

Please look at C. Lacasta poster in this conference

Signal induced by 1060 nm pulsed laser illumination, n-in-p detector after 7.5 1015 p cm-2.(G.Casse,RD50 Status Report 2004)

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Final processFinal process

Rd50 mask

3297-NP-DOFZ300um, SILHRP(9/05) OXG

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

0 50 100 150 200 250 300 350 400

Vrev (V)

I@2

0º

(A)

Wafer 5Wafer 5Wafer 6Wafer 7Wafer 8Wafer 9

Guard rings

CCE and noise measurements on strip detector undergoing by RD50 collaboration

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P-spray vs p-stopP-spray vs p-stop

• P-spray

• Is a critical technology

• Low repeatability of the p-spray process.

• Detectors performance are very sensitive to the p-spray isolation dose implanted.

• Isolation dependent on charge oxide before and after irradiation

• The surface damage usually leads to higher leakage currents before irradiation

• P-stop

• Requires a minimum strip pitch depending on the design rules of the manufacturer

• ‘Leaky channels’ can severely reduce the yield, hence the necessity of a minimum width of the p-stop implant

• High electrical field in P-stop corner

• This high electric files may cause micro-discharge noise

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Moderated p-sprayModerated p-spray

We can take the best from the two options: Moderated P-spray

An old (1997) patent from MPI presented the basics

Technology has to be optimized

We have developed through simulation a technology for p-type detectors with moderated p-spray insulation

Boron implant parameters are selected from our previous experience with microstrip with p-stops

With less p-spray implanted charge, we obtain:

• Higher breakdown voltages

• Good insulation before and after irradiation

• Eliminate the high field corner in the p-stop causing microdischarges

• No necessity of redundancy in the p-stop implants.

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Simulation of moderated p-Simulation of moderated p-sprayspray

Simulated device• RD50 mask set (pitch 80 μm, strip width 32 μm)• Single p-stop between the strips: width 10 μm• Substrate: P-type, <100>, 30 kΩ·cm• Oxide charge density: 1011 cm-2 (non-irradiated device)

P-implant parameters: • Fixed energy, dose: 50 keV, 1013 cm-2

• Fixed oxide implant thickness for the p-stop area• We have fabricated devices with these p-stop implant parameters and they

show a satisfactory electrical behavior

The objective of the simulations is to determine the optimum profile in the p-

spray area

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TechnologyTechnology

• First: oxidation, photolithography p-stop regions, wet oxide etching, oxidation, photoresist striping

• At this point there are two different oxide thicknesses

• thin oxide in the p-stop area and a thicker oxide on the rest of the silicon surface (“p-spray area”)

• P-implant (Energy 50 keV, dose 1013 cm-2)

• Finish with the usual fabrication process

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Simulated DevicesSimulated Devices

profiles I-V curves

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Doping profile comparisonDoping profile comparison

X

Y

20 30 40

-2

0

2

4

6

AcceptorConcentration2.2E+19

2.9E+09

4.0E-01

5.4E-11

7.4E-21

1.0E-30

diode_np_mdr.grd - n1_des_moderatedpspray400min_10um_Qox1e11_h1X

Y

20 30 40

-5

0

5

10

AcceptorConcentration2.2E+19

2.9E+09

4.0E-01

5.4E-11

7.4E-21

1.0E-30

diode_np_mdr.grd - n1_des_solopstop_10um_Qox1e11_h1000V.dat

P-stop only

Moderatedp-spray

N strip P-stop

P-spray

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Electric field comparisonElectric field comparison

X

Y

20 30 40

-2

0

2

4

6

ElectricField3.2E+05

2.5E+05

1.9E+05

1.3E+05

6.3E+04

0.0E+00

diode_np_mdr.grd - n1_des_moderatedpspray340min_10um_Qox1e11_h1

X

Y

20 30 40

-5

0

5

10

ElectricField3.2E+05

2.6E+05

1.9E+05

1.3E+05

6.4E+04

0.0E+00

diode_np_mdr.grd - n1_des_solopstop_10um_Qox1e11_h1000V.dat

P-stop only

Moderatedp-spray

microdischarches?N strip P-stop

P-spray

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Experimental ResultsExperimental Results

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Experimental ResultsExperimental Results

moderate 228moderate 260moderate 290 p-spray p-stop100

101

102

103

104

105

106

107

108

Re

sis

tan

ce

(o

hm

)

Test structure to measure interstrip resistance

moderate 228moderate 260moderate 290 p-spray p-stop

0

1x105

2x105

3x105

4x105

5x105

6x105

7x105

Re

sist

ance

(oh

m)

Gamma irradiationtotal dose 50 Mrad

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ConclusionsConclusions

P-type detectors seems the best detector option for the future sLHC experiments as they gather beneficial properties:• electron collection• junction always at the strip side• partial depletion operation possible• very high radiation hardness• stable annealing

We have developed three technologies for p-type detectors with the different isolation techniques: p-spray, p-stops and moderated p-spray

Detectors have been fabricated, irradiated with protons, neutrons, and gammas, and they work properly

G.Pellegrini 1 , C.Fleta 2 , F.Campabadal 1 , M. Lozano 1 , J.M. Rafí 1 , M.Ullán 1

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Transcript of G.Pellegrini 1 , C.Fleta 2 , F.Campabadal 1 , M. Lozano 1 , J.M. Rafí 1 , M.Ullán 1