Deep defect levels in different silicon materials before and after proton irradiation

Jörg Stahl, E. Fretwurst, G. Lindström und I. Pintilie*

University of Hamburg

*National Institute of Materials Physics, Bucharest, Romania

Topics• Motivation• Material properties• Experimental procedures• Measurements• Conclusion

Motivation

0 2 .1014 4 .1 014 6 .1 014 8 .10 14 1015

Φ p [cm 2]

0

300

600

900

Vde

p [V

] for

d=3

00 µ

m

2 .1 012

4 .1 012

6 .1 012

8 .1 012

10 13

Nef

f [cm

-3]

Cz-TD k il ledCz-TD k il ledCz-TD generatedCz-TD generatedCE- standard FZCE- standard FZCF- D O F Z 12 h /1150o CCF- D O F Z 12 h /1150o CCG -D O F Z 48 h/1150 oCCG -D O F Z 48 h/1150 oCCH -D O F Z 72 h/1150 oCCH -D O F Z 72 h/1150 oC

C E R N scenario experiment - 2 0 G eV /c pro tons

N SC E N ARI ON - 02 | 4.7.200 2

The oxygen concentration in CZ-Material is extremely high due to the manufactoring

Investigations (RD48) had shown that extra oxygen improves the radiation hardness

Material properties

Material:

5 mm

5 mmSi

Al • Wacker <111> n-type FZ-materialresistivity ρ= 3-4 kΩcm STFZ

• CZ-material ρ= 1 kΩcmTD killed and TD generated

• Detectors processed by CiS• Thickness: 280 µm

Irradiation:

• proton beam at CERN (20 GeV – 24 GeV p+)• Irradiation at room temperature• Fluence: 4*1010-1*1012

Experimental procedures

Experimental procedures

• Macroscopic properties- CV/IV – measurements

• Defect characterization by C-DLTFS- applicable for low irradiated samples only- determination of trap parameter:activation energy, capture cross section, trap concentration

- identification of electron and hole traps

• High Resolution DLTFS- Separation of defects with similar properties

High Resolution DLTFS Simulation

Tempscan

T [K]

DL

TS

Sign

al [p

F]

5*10108*1010NT [1/cm3]

1*10142*1014σn [cm2]

0.4350.420Ea [eV]

L2L1

Spectra

The number of coefficients regulates the width of the distribution,The more coefficients, the closer the distribution approaches the delta-function

DLT

S Si

gnal

[pF]

32 coefficients

TW [s]D

LTS

Sign

al [p

F]

60 coefficients

TW [s]

Results

10.2*1010

2.01*1014

0.420

Calc.

5.82*1010

1.03*1014

0.435

Calc.

5*10108*1010NT [1/cm3]

1*10142*1014σn [cm2]

0.4350.420Ea [eV]

L2L1

Simulation with 3 Levels

7.5*1010

0.84*1014

0.437

Calc.

5*1010

1*1014

0.440

L2

11.8*1010

1.06*1014

0.404

Calc.

12.7*1010

1.27*1014

0.421

Calc.

8*10106*1010NT [1/cm3]

1*10141*1014σn [cm2]

0.4200.400Ea [eV]

L2L1

DL

TS

Sign

al [p

F]

Tempscan

T [K]

Results

TW [s]

DLT

S Si

gnal

[pF]

It is also possible to simulate four levels, but for measurements,it is not reasonable to work with more than three levels!

Levels with similar properties

After 60Co-gamma irradiation VV(=/-) is expected tohave the same introduction rate as VV(-/0)!

Tw [s]

DLT

S si

gnal

[pF]

High Resolution DLTFS

With the refolding method the levels are fitinto the spectra

Results

Level 1:Materialdefect

Level 2:VV(=/-)

Material defects

The only trap visible are the thermal donors!

UR = -20 VUP = -0.1 VtP = 100 ms

Defects after p+ irradiation

UR = 20 VUP = 0.1 VtP = 100 ms

0

2

4

6

8

Co

nc *

10

10

1 2 3 4Ci

Concentration Ci

before irradiation

after irradiation

after 863 min at 80°C

after 4 min at 80°C

Is there also Ci in CZ?

Annealing Ci in STFZ

Concentration of TD after p+ irradiation

before irradiation

after irradiation

after 863 min at 80°C

0.117863 minTD gen

0.131863 minTD kill

TD gen

TD gen

TD gen

TD kill

TD kill

TD kill

0.1164 min

0.120irr.

0.103unirr.

0.1344 min

0.136irr.

0.120unirr.

EAStatus

Activation energies

0

5E+11

1E+12

2E+12

2E+12

Conc

1 2 3 4 5 6 7 8 9TD kill Td gen

Concentration TD

after 4 min at 80°C

Different thermal donors

From the shift of the peak, it can be seen, that the thermal donorsare different in the TD killed and TD generated material!

Isothermal measurement CZ

0.001 0.010 0.100 1.000 10.000

Tw [s]

DL

TS

sig

nal

[pF

]

CZ0831CZ1315

0.4

0.0

0.2

Separation of Levels

TD kill after irrad

TD gen 4 min at 80°C TD kill 4 min at 80°C

No fit possible!

TD gen after irrad

Introduction rates after p+ irradiation

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

IR

1 3 5 7 9 11 13 15 17 19 21 23L170 VV(-/0)+?

Introduction rates before and after annealing

4

863Standard

TD kill

TD gen

4

863

4

863

Is it possible to separate VV+?

No!

This peakcontains atleast four levels!

Clusters?

Defects after irradiation

The Ci-defect is visible in STFZ material, but not in CZ-material

UR = -20 VUP = 3 VtP = 100 ms

Introduction rates after p+ irradiation

4

863Standard

TD kill

TD gen

4

863

4

8630

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

IR (1

/cm

)

1 3 5 7 9 11 13 15 17 19 21 23Ci CiOi

Introduction rates before and after annealing

Conclusions

With high resolution DLTFS levels withsimilar parameters can be separated

More than one TD contibutes to theTD-peak in the DLTS-spektrum

The TDs in the TD killed and the TD gen.material are different in Ea and σ.

The L170-defect disappears after long annealingin the STFZ-, but not in the CZ-material

Defects after irradiation

UR = 20 VUP LasertP = 100 ms