Z. Li

Brookhaven National Laboratory, Upton, NY 11973-5000, USA

E. Verbitskaya, V. Eremin, A. Ivanov

Ioffe Physico-Technical Institute of Russian Academy of SciencesSt. Petersburg, Russia

J. Härkönen, E.Tuovinen, P. LuukkaHelsinki Institute of Physics, CERN/PH, 1211 Geneva, Switzerland

Initial data on the DRIVE approach: results and analysis

This work has been supported in part by the US Department of Energy, contract No.: DE-AC02-98CH10886, by the grant of the President of Russian Federation # NS-2223.2003.02, by Academy of Finland, and by the EU Intas 03-52-5477 contract; and it is within the framework CERN RD39 and RD50 collaborations

• Introduction• Current/Conventional Approaches

Defect/Impurity/Material Engineering (DIME) Device Structure Engineering (DSE)Device Operational Mode Engineering (DOME)

• New ApproachesDevice Recovery/Improvement Via Elevated

temp annealing (DRIVE)

• Experimental Methods• Results and Discussions• Summary

OUTLINE

• For SLHC, with 1035 cm-2s-1 luminosity, total radiation fluence can be as high as 1016 neq/cm2

• At this highest fluence, detector degrades in many ways:o High leakage current (IL): 4x10-1 A/cm3 at RT!o High full depletion bias (Vfd): 6400 V for 200 m thick STD

FZ detector!o Low charge collection distance due to trapping (CCE(tr)): 20 to 40 m regardless of detector detector thickness and

depletion depth!

• Radiation hard/tolerant Si detectors have to improve with regard to all three problems listed above

• Most conventional approaches may solve only one to two problems

• Need a new, simple/easy approach

Introduction

Name of the approach

R&D group Good for Technology difficulty

Defect/Impurity/Material Engineering

(DIME)

Oxygenation/MCZ Si CERN RD50 Vfd Easy

Diamond/SiC/GaN, etc. CERN RD42, RD50

Vfd Difficult

Device Structure Engineering (DSE)

3d detectors CERN RD50 CCE(tr), Vfd Very difficult

Semi-3d detectors CERN RD50 Vfd Easy

Thin detectors CERN RD50 Vfd Difficult

Device Operational Mode Engineering

(DOME)

Cryogenic Si detectors (LN2 T)

CERN RD39 IL, Vfd Difficult

Cryogenic Si detectors (LHe T)

CERN RD39 IL, Vfd, and

CCE(tr)?

Very difficult

Current/Conventional Approaches

Device Recovery/Improvement Via Elevated temperature annealing (DRIVE)

The DRIVE was first proposed by Z. Li and J. Harkonen on the 5th RD50 Workshop in Florence, Italy, October 14-16, 2004

Preliminary data presented by E. Verbitskaya et al, at the 6th RD50 Workshop, Helsinki, June 2-4, 2005

Thermal annealing of radiation damage has been a conventional way for material/device recovery

It has not been used so far in HE physics detector field for standard FZ and oxygenated FZ Si detectors because :

If the annealing temperature is too high (>450 °C), it will destroy the detector and/or electronics

If the annealing temperature is too low (< 450 °C), the reverse annealing (generation of more negative space charges) will make the detector worse

New Approach

Device Recovery/Improvement Via Elevated temperature annealing (DRIVE) (continues)

However, for high resistivity MCZ Si material/detectors, thermal annealing in the temperature range from 200 °C to 450 °C will generate thermal donor (TD, positive space charge) due to high oxygen concentration [O]

By playing the annealing T and time, and [O] (n-type or p-type MCZ Si), one may adjust the TD creation rate in such a way to cancel the reverse annealing effect, and even better, to compensate the original (as-irradiated) negative space charges, which may bring the full depletion voltage down to a manageable range

Elevated temperature annealing (ETA) will also anneal out/down the detector leakage current, and improve detector CCE by annealing out shallow trapping centers

The DRIVE approach may therefore offer a technology to improve all three areas:

IL, Vfd, CCE (tr)

The degree of difficulty may vary depending on the annealing techniques

New Approach

1.0E+09

1.0E+10

1.0E+11

1.0E+12

1.0E+13

1.0E+14

0 10 20 30 40 50 60 70

Heating time @ 430C

Ne

ff

1 ppma

4,5 ppma

10 ppma

p-type MCZ

n-type MCZ

n-type oxygenated FZ

TD generation in different Si with different [O]

1.0E+09

1.0E+10

1.0E+11

1.0E+12

1.0E+13

1.0E+14

0 10 20 30 40 50 60 70

Heating time @ 430C

Ne

ff

10 ppma

One can reach >1014 /cm3 in TD concentration in one hour!Might be enough to cancel – SC generated in irradiation and during reverse

anneal

TD generation at 450 °C in p-type MCZ

Experimental

Detectors: p+-n-n+ pad structures with multiple GRs from n-type MCZ Si with a resistivity of 1 kOhmcm, p+-p-n+ pad structures with multiple GRs, from p-type MCZ Si with a resistivity of 3 kOhmcm

all processed at HIP Irradiation :

P352-18 (p) 9.00E+13 C1-3 (n) 5.90E+13P352-59 (p) 3.60E+14 D2-3 (n) 1.20E+14P352-48 (p) 5.00E+14

protons 20 MeVprotons 24 GeV/c

Annealings

multistep process with a variable time T: 150-450C tann: variable, 10 min up to 120 min/step nitrogen flow fast cooling (~10 min)

Ep protons 24 GeV/c protons 20 MeV # P352-18 P352-59 P352-48 C1-3 D2-3

Fp (cm-2) 91013 3.61014 51014 5.91013 1.21014 annealing

steps 8 12 13 8 10

T (C) 150-450 300-450 450 430-450 430-450

All as-irradiated detectors (p or n-type) have negative space charges before annealingThis means, for n-type detector, the space charge sign inversion (SCSI) occurred

Experimental techniques

Measurements:

After each annealing step (at BNL):

I-V and C-V dependences current pulse response using TCT with a laser pulse generation of non-equilibrium carriers

After final detector annealing (at Ioffe Institute):

Spectra of deep levels (C-DLTS)

Experimental resultsExperimental results

Three stages of the changes of detector characteristics

irrespective to Ep and Fp:

1. Reverse annealing: Irev , Vfd , negative Neff , W TCT signal from the detector p+ side disappears

2. Recovery of reverse current Irev and the signal from p+ side

3. SCSI from negative to positive

Annealing of detectors irradiated by 24 GeV/c protonsAnnealing of detectors irradiated by 24 GeV/c protons

Compensation of acceptor-type radiation induced defects:Thermal Donors areintroduced at 430-450C

Reverse annealing

Recovery of reverse current

24 GeV protons, P352-18, Fp = 91013 cm-2

P352-18, 24 GeV/c protons, Fp = 9e13 cm-2

0.1

1

10

100

1000

1 10 100 1000V (Volt)

I (

A)

before anneal

1: 150 C, 10 min

2: 200 C, 10 min

3: 300 C, 10 min

4: 430 C, 15 min

5: 430 C, 20 min

6: 450 C, 30 min

7: 450 C, 2 h

8: 450 C, 1 h

GRG

2 h

150-300C – Irev is still saturated

Leakage current decreasedby more than one order of magnitude.

24 GeV protons, P352-48, Fp = 51014 cm-2T = 450C

P352-48, 24 GeV/c protons, Fp = 5e14 cm-2

1.0E-02

1.0E-01

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1 10 100 1000V (Volt)

I (u

A)

no anneal

8: 20 min, t_s = 245 min

9: 60 min, t_s = 305 min

10: 30 min, t_s = 335 min

11: 40 min, t_s =375 min

12: 20 min, t_s = 395 min

13: 10 min, t_s = 405 min

Annealing at 450 C

GRG

1 h

• Bulk current decreases after 1st anneal, but the leakage arises at high biases• tann = 305 min: Irev becomes saturated• After final anneal, leakage current decreased by more than 2 orders of magnitude

P352-48, 24 GeV/c protons, Fp = 5e14 cm-2

0.1

1

10

100

1000

1 10 100 1000V (Volt)

I (

A)

no anneal, RTA28 days

1: 60 min

2: 15 min, t_s =75 min

3: 15 min, t_s =90 min

4: 15 min, t_s =105 min

5: 60 min, t_s =165 min

6: 30 min, t_s =195 min

7: 30 min, t_s =225 min

8: 20 min, t_s=245 min

GRG

Annealing at 450 C

Changes of TCT signal: Fp = = 91013 cm-2, P352-18

P352-18, 24 GeV/c protons, Fp = 9e13 cm-2, p+ side

-1.0E-03

0.0E+00

1.0E-03

2.0E-03

3.0E-03

4.0E-03

5.0E-03

6.0E-03

7.0E-03

8.0E-03

9.0E-03

1.0E-02

7.0E-08 7.5E-08 8.0E-08 8.5E-08 9.0E-08 9.5E-08 1.0E-07

t (s)

V (

Vo

lt)

37

47

56

66

76

86

96

106

116

146

167

196

216

247

297

346

before anneal

V (Volt): P352-18, 24 GeV/c protons, Fp = 9e13 cm-2, n+ side

-1.0E-03

0.0E+00

1.0E-03

2.0E-03

3.0E-03

4.0E-03

5.0E-03

6.0E-03

3.5E-08 4.0E-08 4.5E-08 5.0E-08 5.5E-08 6.0E-08 6.5E-08 7.0E-08 7.5E-08

t (s)

V (

Vo

lt)

27

47

56

76

86

96

106

116

146

176

196

196

246

345

395

before anneal

V (Volt):

SC (-)p+/p/n+ structureHigh field on the n+ side

SCSI: SCSI: tann(450 C) = 210 min

P352-18, 24 GeV/c protons, Fp = 9e13 cm-2, p+ side

-0.005

0

0.005

0.01

0.015

0.02

0.025

0.03

1.50E-08 2.00E-08 2.50E-08 3.00E-08 3.50E-08 4.00E-08

t (s)

V (

Vo

lt)

20

40

60

80

100

120

140

160

180

200

220

240

260

300

400

500

600

after 8th anneal450 C, 60 min

t_s(450) = 210 min

V (Volt):

P352-18, 24 GeV/c protons, Fp = 9e13 cm-2, n+ side

-0.002

0

0.002

0.004

0.006

0.008

0.01

0.012

2.00E-08 2.50E-08 3.00E-08 3.50E-08 4.00E-08 4.50E-08 5.00E-08

t (s)

V (

Vo

lt)

250

300

350

400

450

500

550

600

650

700

750

800

850

900

950

1000

V (Volt):

after 8th anneal450 C, 60 min

t_s(450) = 210 min

SC (+)

p+/n/n+ structureHigh field on the p+ side

Neff evolutionNeff derived from TCT measurements

Reverseannealing

Neff recoveryup to SCSI

Neff evolution

P352-18, 24 GeV/c, 9e13 cm-2

-4.0E+13

-3.0E+13

-2.0E+13

-1.0E+13

0.0E+00

0 100 200 300 400 500

T (C)

Ne

ff (

cm

-3)

t_ann =15 min

t_ann = 10 min

Range of reverse annealing

Neff vs. tann, 24 GeV/c protons

-7.0E+13

-6.0E+13

-5.0E+13

-4.0E+13

-3.0E+13

-2.0E+13

-1.0E+13

0.0E+00

1.0E+13

2.0E+13

0 50 100 150 200 250 300 350 400 450

t (min)

Nef

f (c

m-3

)

P352-18, 9e13 cm-2 P352-59, 3.6e14 cm-2 P352-48, 5e14 cm-2

Tann = 450 C

Range of TD introduction

Finally

Fp (cm-2) Vfd (Volt) Neff (cm-3)

9.00E+13 250 3.6E+123.60E+14 460 6.7E+125.00E+14 500 7.3E+12

All positive space charge

Since these are all initially p-type wafers withless than 1011/cm3 donors, the positive spacecharge has to be thermal donor

+SC

-SC

-SC

Annealing of detectors irradiated by 20 MeV protonsAnnealing of detectors irradiated by 20 MeV protons

Compensation of acceptor-type radiation induced defects:Thermal Donors areintroduced at 430-450C

n-type detectors before irradiation,initially (+SC)

All positive space chargeafter annealing (+SC)

After irradiation, space charge signinverted to negative (“p”) (-SC)

Recovery of reverse current

C1-3, 20 MeV protons, Fp = 5.9e13 cm-2

0.01

0.1

1

10

100

1000

1 10 100 1000V (Volt)

I (

A)

1: 430 C,20 min+RTA2: 450 C,60 min

3: 450 C,15 min

4: 450 C,15 min

5: 450 C,15 min

6: 450 C,60 min

7: 450 C,30 min

8: 450 C,15 min

GRG

1 h

D2-3, 20 MeV protons, Fp = 1.2e14 cm-2

0.01

0.1

1

10

100

1000

1 10 100 1000V (Volt)

I (

A)

1: 430 C, 20 min+RTA 6 mns2: 450 C, 60 min

3: 450 C, 15 min

4: 450 C, 15 min

5: 450 C, 15 min

6: 450 C, 30 min

7: 450 C, 20 min

8: 450 C, 1 h

9: 450 C, 30 min

10: 450 C, 20 mint_s = 265 min

GRG

Leakage is observed in I-V curves

Annealing time at 450 C for SCSI vs. Fp

0

50

100

150

200

250

300

350

400

450

0.0E+00 1.0E+14 2.0E+14 3.0E+14 4.0E+14 5.0E+14 6.0E+14

Fp (cm-2)

t_a

nn

(m

in)

24 GeV/c protons

20 MeV protons

T = 450 C

Annealing time at 450C required for SCSI

Defect spectra after SCSIDefect spectra after SCSI

-6.5

-4.5

-2.5

-0.5

1.5

50 100 150 200 250 300

Temperature (K)

DLT

S s

ign

al (

pF

)

C1_3

P352-18

P352-48

P204-I-A3-7

Ci-OiRD2

with injection

C-DLTS spectra

Reference spectra:P204-I-A3-7:24 GeV/cFp = 1.51011 cm-2

-0.1

0.4

0.9

1.4

50 100 150 200 250 300Temperature (K)

DLT

S s

ign

al (

pF

)

C1_3

P352-18

P352-48

P204-I-A3-7

V-O VV-

VV--

Continuous defect spectra Increase of tann

is favorable(for P352-48 tann is maximal)

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

50 100 150 200 250 300

Temperature ([K)

DLT

S s

ign

al (

pF

)

experim. fit E1 E2 E3

E5 E4 E6 E7 E8

E1

E3E4

E6

E2

E5

E7

E8Electron traps

P352-1824 GeV/c, 91013 cm-

2

Hole traps

-6.5

-5.5

-4.5

-3.5

-2.5

-1.5

-0.5 50 100 150 200 250 300

Temperature (K)

DLT

S s

ign

al (

pF

)

experim. fit H1 H2 H4 H3 H5

H4

H1H3

H2H5

Defect parameters

Electron traps

DL H1 H2 H3 H4 H5

E (eV) Ev + 0.203 Ev + 0.28 Ev + 0.3 Ev + 0.37 Ev + 0.545 (cm2) 1.0E-16 1.0E-15 3.0E-16 4.0E-16 1.0E-15N (cm-3) 1.5E+12 1.6E+12 7.0E+11 5.4E+12 1.3E+12

Hole traps

DL E1 E2 E3 E4 E5 E6 E7 E8

E (eV) Ec – 0.18 Ec – 0.196 Ec – 0.26 Ec – 0.25 Ec – 0.37 Ec – 0.41 Ec – 0.515 Ec – 0.6 (cm2) 3.0E-15 7.0E-16 2.0E-15 3.0E-17 3.0E-15 1.0E-15 5.0E-15 2.0E-15N (cm-3) 1.0E+12 4.5E+11 2.0E+11 2.8E+11 6.9E+11 7.2E+11 4.5E+11 2.6E+11

P352-1824 GeV/c, 91013 cm-2

Defects detected after annealing are presumably products of RDs decay Concentrations of defects after annealing are <10% of as-irradiated RD concentrations Minimal concentrations correspond to the maximal annealing time (P352-48)

Ways of ETAWays of ETA

May be different:

1) localized laser anneal; 2) localized anneal using a lamp; 3) annealing using pre-built-in external heating resistors; 4) annealing using leakage current of the detector itself;5) RT annealing using ultrasonic power

4) and 5) may be the easiest and most practical method

Multiple annealing steps at smaller doses maybe favorable

Fine tuning of the annealing time is required for precise manipulation of thermal donor introduction and resulting Neff

– further studies are needed

o The conventional approaches may not solved all the radiation induced problems

o The new approach, DRIVE, could offer a perfect solution to radiation induced problems, especially at high fluences for SLHC

o Recovery of the positive space charge and detector reverse current is realized by ETA at 450C

o By changing annealing temp, time, one may get a perfect receipt for different fluences

o P-type MCZ Si may be the best material due to its higher [O] than that of n-type MCZ o Different annealing techniques may be used for DRIVE depending on the experiment conditions

o Further studies on detector CCE, on FZ Si, and effect of radiation/annealing cycles are underway

ConclusionsConclusions