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Generation of vacancy-related defects during focused swift-ion beam implantation of silicon. I.Capan 1 , M.Jakšić 1 , Ž. Pastuović 1, 2 , Rainer Siegele 2 , David Cohen 2 1 Ruđer Bošković Institute, Zagreb, Croatia - PowerPoint PPT Presentation
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Generation of vacancy-related defects during focused swift-ion beam implantation of silicon
I.Capan1, M.Jakšić1, Ž. Pastuović1,2, Rainer Siegele2, David Cohen2
1Ruđer Bošković Institute, Zagreb, Croatia2 Centre for Accelerator Science, IER, ANSTO, 1 New Illawarra Rd, Lucas heights NSW 2234, Australia
Split, 8-10 October 2012 Silicon Detector Workshop 2
Introduction
Influence of high energies/high fluences of particles on silicon-based detectors;
Can heavier ions offer cost effective simulation of radiation damage produced in semiconductor detectors by p, n, e?
Ion beams dense regions of vacancies and interstitials in bulk semiconductor clustering;
Electrically active cluster-related damage in silicon: Structure? Capture kinetics?
Split, 8-10 October 2012 Silicon Detector Workshop 3
40 60 80 100 120 140 160 180 200 220 240 260 280 300
0.0
0.1
0.2
0.3
0.4
0.5
Si ion implantation Neutron irradiation (/ 3.5) 4 MeV electrons (/ 4)
C, p
F
Temperature, K
Introduction
RD’s in n-type CZ Si
V2(=/-)
V2(-/0)
VO
?
VOVO
VVVV
Split, 8-10 October 2012 Silicon Detector Workshop 4
Introduction Divacancy & ion mass effect
Split, 8-10 October 2012 Silicon Detector Workshop 5
Introduction
Models for interpretation of the DLTS observed mass effect:
(i) the lattice distortation and strain due to accumulated damage produced by heavy ions in the highly localized collision cascades can prevent, to a large extent, the electronic bond switching. The effect increases with ion mass because a density of elastic energy deposition, i.e. primary defect generation rate increases and causes larger distrortation and strain in the crystal lattice. Since the electronic bond switching is a thermally activated process, V2(=/-) peak is more influenced by the lattice strain than V2(-/0) peak (V2(=/-) defect has a low activation temperature of 115K ), PRB 55 (1997);
Split, 8-10 October 2012 Silicon Detector Workshop 6
Introduction Models for interpretation of the DLTS observed mass
effect:
(ii) suppression of the DLTS signal from shallow states is due to a local depletion of the carrier concentration in the dense defect cascade region which leads to incomplete occupation of the shallow states such as VO and V2(=/-) in heavy ion implanted n-Si, PRB 65 (2002);
(iii) additional electrically active defects, e.g., vacancy-clusters (Vx, x>2) that artificially enhance the V2(-/0) signal, J. Appl. Phys. 93 (2003);
Split, 8-10 October 2012 Silicon Detector Workshop 7
Experiment The materials used in our experiment were phosphorus-
doped Czohralski-grown (CZ) silicon wafers with initial resistivities of (1–2) cm.
The Au/n-Si Schottky diodes were formed by thermal evaporation of gold on etched Si surface
The samples (D=1mm) were uniformly irradiated at RT with scanning focused 8.3 MeV Si3+ ion micro-beam (I=5 fA @ F=4x1012 ions/cm-2s-1) up to dose of 1010 cm-2.
Deep traps were characterized with depth resolving deep level transient spectroscopy (DLTS).
Split, 8-10 October 2012 Silicon Detector Workshop 8
Results CV
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.51E13
1E14
free
car
rier
con
cent
ratio
n (c
m-3
)
depth (mm)
Depth profile
Averaged energy loss profiles of 8.3 MeV Si ions implanted in 100nm Au/n-Si Schottky diode (TRIM) w threshold for dense vacancy regime (PRB79)
0 1x104 2x104 3x104 4x104 5x1040.01
0.1
1
10
100
1000
8.3 MeV Si
en
erg
y lo
ss (
eV
//io
n)
depth ()
NON-ionization (NIEL) ionization (LET)
Threshold for 1.2 v/A/ion = 25.2 eV/A/ion (Td=21eV)25.2
DLTS scan
Split, 8-10 October 2012 Silicon Detector Workshop 9
Results DLTS
100 150 200 250
-0.06
-0.04
-0.02
0.00
DL
TS
sig
nal (
pF)
Temperature (K)
8.3 Si MeV
52 54 56 58 60 62
-9
-8
-7
-6
-5
ln(e
/T2 )
1/kT
V2(-/0)
Ec-0.40 eV
Activation energy VO VV VP
0.170.23
0.420.45XX
Low-doped material!
??
Is it a point-likeIs it a point-like defect?defect?
Split, 8-10 October 2012 Silicon Detector Workshop 10
Results DLTS Capture kinetics
-5 -4 -3 -2 -10.06
0.08
0.10
0.12
0.14
0.16
DL
TS
am
plit
ude
(pF
)
log (tp)
Tmax = 188 K
8.3 MeV Si+
1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.01
0.000
0.002
0.004
0.006
)exp(1
t
CC
Point-like defect kinetics!Point-like defect kinetics!
PRB 79 075206
Split, 8-10 October 2012 Silicon Detector Workshop 11
Results Defect depth profiling with DLTS
VV X1 X2
0.420.53
Two new deep defect states from interstitial-rich region emerge!
??
Two DLTS spectra (@ Two DLTS spectra (@ -1 – -0.2 V -1 – -0.2 V & @& @ -5 – -3 V-5 – -3 V) combined!) combined!
Vacancy- rich region
Interstitial-rich region
0.78
Split, 8-10 October 2012 Silicon Detector Workshop 12
Results Laplace DLTSLDLTS measured at 225K, i.e. the activation energy of VV (-/0) ~0.4 eV for: a)Vacancy-rich region (-2, -1 V)b)Interstitial-rich region (-5, -2.8 V)
Si : SiT=225K(Ec-0.4 eV)
LDLTS spectra from as implanted and annealed (180C 40min) sample measured at 225K for: a)Vacancy-rich region (-2, -1 V)b)Interstitial-rich region (-5, -2.8 V)
Split, 8-10 October 2012 Silicon Detector Workshop 13
Conclusions
VO and V2(=/-) completely suppressed 0.40 eV vacancy-related defect 0.40 eV cluster-related defect And the model is ...
Split, 8-10 October 2012 Silicon Detector Workshop 14
TODO
Scanning capaictance microscopy (SCM)