Deep defect levels in different silicon materials...
Transcript of Deep defect levels in different silicon materials...
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