Fluence and isochronal anneal dependent variations of recombination and DLTS characteristics in neutron and proton
irradiated MCz , FZ and epi-Si structures
J.Vaitkus, T.Čeponis, E.Gaubas, A.Uleckas, J.Višniakov, and J.Raisanen
Vilnius University, Institute of Materials Science and Applied ResearchUniversity of Helsinki
ABSTRACT
A comparative analysis of the recombination, generation and reverse recovery lifetime dependent on stopped protons fluence and isochronal anneal temperature is presented for FZ Si structures. In DLTS, heat treatments indicate transformations of majority and minority carrier traps. These changes are also revealed by variations of the excess carrier decay lifetime. The main transformations can be attributed to hydrogen implantation related defects (VOH etc).Also, a comparative study of the impact of penetrative neutrons and protons on recombination and DLTS characteristics in MCz, FZ and epi-Si structures has been carried out. A nearly linear decrease of the recombination lifetime with fluence of the reactor neutrons from 1012 to 31016 n/cm2 in the MCz grown Si samples corroborates a non-linear introduction rate of dominant recombination centers. An increase of lifetime and a change of carrier decay shape (process) in reactor neutrons irradiated MCZ Si, dependent on fluence, appears under annealing at elevated temperatures (>180 C, for 24 h). Lifetime behavior with heat treatment temperature shows an enhancement of competition between recombination and trapping centers which is the most pronounced for moderate fluences irradiated material.
Outline
Motivation of investigations - comparative analysis of the impact of penetrative and stopped hadrons
Samples: neutron and proton irradiated MCz, FZ and epi-Si structures
Fluence and anneal dependent variations of recombination lifetime and DLTS spectra
Summary
Objectives / investigations
Direct measurements of recombination lifetime fluence dependences:
comparative analysis of carrier decay transients in MCZ, FZ and epi-Si neutron irradiated structures
- Control of possible anneal of defects by comparing neutron and 2 MeV proton irradiated material:
heat treatments 80C +180 + 280 + 380C , 24 h
recombination lifetime variations with energy of protons
recombination characteristics in 2 MeV proton irradiated n-FZ Si
combined investigations of MWR, DLTS and RR in 2MeV proton irradiated structures
cross-sectional scans within structure depth to control defect production profiles
Samples
Irradiation plan March 2007 TRIGA reactor Resp. Gregorarrival HH 15-06-2007, 12:20 in cold box
Material: Wacker FZ <111> 2 kOhmcm 290 µm Process STM W337
W337phi_n [cm-2] FZ
1.00E+13 B11
1.00E+13 E81.00E+14 Q51.00E+14 G131.00E+15 H21.00E+15 H31.00E+16 Q61.00E+16 I13
Irradiation TRIGA reactor November 2006arrival HH: 8. January 2007, by Gregor
Material: ITME p-EPI <111> 150 Ohmcm 50 µm Process: CIS
260868-01 annealingp-EPI 80 °C V_dep [V]
phi_n [cm-2] 50 µm t_max [days] at t_max
3.00E+13 16 31.3 88.11.00E+14 19 31.3 52.83.00E+14 27 31.3 47.91.00E+15 33 31.3 89.03.00E+15 36 31.3 268.01.00E+16 41 2.3 671.0
not irradiated 43* x xnot irradiated 44* x x* breakdown voltage about 60 V, guard ring not working
Irradiation TRIGA reactor March 2004
Material: ITME n-EPI <111> 50 Ohmcm 50 µm Process: CIS
6336-04 annealingn-EPI 80 °C V_dep [V]
phi_n [cm-2] 50 µm t_max [days] at t_max
2.00E+14 06 135.3 59.06.00E+14 08 135.3 3.21.00E+15 11 135.3 18.72.00E+15 17 135.3 90.94.00E+15 24 148.4 240.88.00E+15 28 135.3 450.01.00E+16 32 135.3 478.0
not irradiated 34 x xnot irradiated 35 x x
1
Neutronirradiated FZ
n- epi
p- epi
MCZ wafer pieces
heat treatments 80C +180 + 280 + 380C , 24 h
Samples2
Proton irradiated
FZ n-Si
recombination characteristics in 2 MeV proton irradiated n-FZ Si:-close thickness to epi-, resistivity 25 cm;- close absolute values to neutron irradiated MCZ and FZ Si- combined investigations of MWR, DLTS and RRT on fluence and anneal,- comparison of cross-sectional recombination lifetime profiles
heat treatments 80C +160 + 240 + 280C + 320C , 24 h
1012 1013 1014 1015 101610-1
100
101
102
103
104
Okmetic MCZ<100> 1kOhm·cm 300 m non-processed CISSamples 8556- 14
R (
ns)
Fluence (n/cm2)
Neutron fluence dependent recombination lifetime in MCZ and epi- Si
1013
1014
1015
1016
100
101
102
103
non-irradiated
Fluence (cm-2)
Neutron irradiated FZ diodes n-epi diodes p-epi diodes
(ns
)
Fluence dependent lifetime variations in different particle energy irradiated structures
1012
1013
1014
1015
1016
10-1
100
101
102
103
104
Neutron irradiated material MCZ as-irradiated
Proton irradiated material MCZ RT -50 MeV sFZ RT - 24 GeV/c DOFZ RT - 24 GeV/c V- n- FZ 2 MeV
R (n
s)
Fluence (cm-2
)
100 150 200 250 3000
20
40
60
80
100
120
140
V-cluster (S.Watts)
V2
-/0
V2
=/-
A (V-O)
FZ n-Si diode V
1.9 MeV protons 7x1012 p/cm2
FZ n-Si diode CERN-Oslo
5 MeV electrons 1012 e/cm2
DL
S (
a.u
.)
T (K)
0 10 20 30 40 500
20
40
60
80
100
120
140
VVP Si Tomas`Proton energy 2 MeV
fluence 4*1014
p/cm2
(ns
)
x (m)
MW-PCD-depth – scans
in 2 MeV protons irradiated FZ n-Si
0 10 20 30 40 500.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5V FZ n-Si Proton energy 2 MeV
fluence 4*1014 p/cm2
Am
plit
ude (
a.u
.)
x (m)
010
2030
4050
020 40 60 80
100 120 140VVP Si Tomas`Proton energy 2 MeVfluence 4*10
14 p/cm
2
(ns)
x (m
)
0 1 2 3 4 5 610
-3
10-2
10-1
100
UM
WR
(a.u
)
t s)
VVP Si TomoProton energy 2 MeV
fluence 4*1014
p/cm2
x = 40,0 m = 0,065 s = 1,1 s
200µm60µm
n+-Sin-Siρ=0,04 Ωcmρ=25 Ωcm
Apšvitos srautas
0.0 0.1 0.2 0.30
1
2
UM
WR
(a.u
)
t s)
VVP Si TomoProton energy 2 MeV
fluence 4*1014
p/cm2
x= 1 m x= 40 m
0 100 200 30010
0
101
102
103
MCZ 1 k·cm, d= 300 m neutron fluence
1012
cm-2
3·1014
cm-2
1015
cm-2
3·1015
cm-2
MWR amplitude
R(n
s),
MW
R a
mpl
itude
(a.
u.)
X (m)
2 MeV protons
reactor neutrons
Fluence dependent variations of
MW-PCD, DLTS and RRT characteristics
in 2 MeV protons irradiated FZ n-Si
1013
1014
0
400
800
1200
1600
2000
2 MeV protons
RR,
ns
, cm-2
IF=0.5A
IF=1A
IF=2A
IF=4A
IF=6A
IF=8A
IF=10A
1013
1014
1015
100
101
102
2 MeV protons FZ n-Si wafers/diodes
R (
ns)
Fluence (p/cm2)
100 150 200 250 300
0.2
0.4
0.6
0.8
1.0
1.2cluster edge &/or H-?
V2
-/0
V2
=/-
V-O-?
non-irradiated2 MeV protons irradiated
7E12 p/cm2
7E13 p/cm2
7E14 p/cm2
DL
S (
a.u
.)
T (K)
Wafer substrates and diodes
Diodes: power rectifiers/ pin switches
Low injection/excitation level
Low injection level
High injection level
0.18 eV
0.24 eV
0.35 eV / 170K
0.42 eV
Variation of DLT spectra and RRT with anneal and fluence
80 120 160 200 240 2800
200
400
600
800
DL
S (
a.u.
)
T (K)
VVP-Helsinki Si diode
proton irradiated 2MeV, 71012 p/cm2
heated:
80OC: 1h
80OC: 24h
160OC: 24h
200OC: 24h
240OC: 24h
90 120 150 180 210 240 270 3000
100
200
300
400
500 VVP-Helsinki Si diode
proton irradiated 2MeV, 71013 p/cm2
heated:
80OC: 1h
80OC: 24h
160OC: 24h
200OC: 24h
240OC: 24h
DL
S (
mV
)T (K)
80 120 160 200 240 2800
100
200
300 VVP-Helsinki Si diodeproton irradiated 2MeV, 7*1014 p/cm2
heated: 80OC: 1h
80OC: 24h 160OC: 24h
200OC: 24h
DL
S (
a.u
.)
T (K)
Increasingproton fluence
A decrease of amplitude of the DLTS peaks with increaseof the isochronal (24 h) anneal temperature together with transform of the 170 K peak into 140 and 225 K peaks.
This decrease of the amplitude ofthe majority carrier peaks isaccompanied by the enhancement of the minority carrier peaks
as-irradiated
annealed at 2400 C
DLTS
RRT
100 150 200 250 3000
5
10
15
20
25
30
35
40
45
50
DLS
(a.u
.)
T (K)
VVP-Helsinki Si diode
proton irradiated 2MeV, 71012
p/cm2
heated at 320oC
170Hz 120Hz 70Hz
E (meV) cmP1 186 8.67E-13 P2 203 2.9E-14 P3 250 2.75E-15 P4 495 3 E-12
Anneals: 80C +160 + 240 + 280C + 320C , 24 h
Majority carrier traps
Variation of the DLT spectra for majority and minority carrier traps
90 120 150 180 210 240 270 3000
100
200
300
400
500VVP-Helsinki Si diode
proton irradiated 2MeV, 71013 p/cm2
heated:
80OC: 1h
80OC: 24h
160OC: 24h
200OC: 24h
240OC: 24h
DL
S (
mV
)
T (K)50 100 150 200 250 300 350
-80
-40
0
40
80
as- irradiated 2MeV 7E13 U
R=-0.2 V, U
1=0.2
f= 40 Hz f= 70 Hz f=100 Hz f=170 Hz
DL
T (
a.u.
)
T (K)
80 120 160 200 240 2800
100
200
300 VVP-Helsinki Si diode
proton irradiated 2MeV, 7*1014 p/cm2
heated:
80OC: 1h
80OC: 24h
160OC: 24h
200OC: 24h
DL
S (
a.u
.)
T (K)
Shift of the DLTS peaks with decrease of absolute amplitude
Decrease of the peak amplitude ascribed to majority carrier traps is accompanied by increase of the minority carrier peaks
UR=-10V, majority carrier traps UR=-0.2 V, majority+minority carrier traps
as-irradiated annealed at 240 C 24h
UR=-10V, majority carrier traps
50 100 150 200 250 300 350-500
-400
-300
-200
-100
0
100
T (K)
DLT
(a.
u.)
anneled at 240 C for 24 h 2MeV 7E13 U
R=-0.2 V, U
1=0.2
f= 70 Hz f=100 Hz f=120 Hz f=170 Hz f=220 Hz
UR=-0.2 V, majority+minority carrier traps
50 100 150 200 250 300 350
-400
-300
-200
-100
0
100
T (K)
DLT
(a.
u.)
2MeV 7E13 U
R=-0.2 V, U
1=0.2 V
f=170 Hz as-irradiated annealed at +240 C 24h
P1=0.494 eV, =7.4E-14 cm2
P2=0.552 eV, =5.3E-14 cm2
2MeV 7E13 p/cm2, annealed 240o C 24 h
Minority carrier traps
P1
P2
Lifetime in neutron irradiated MCZ Si under heat treatments
1012 1013 1014 1015 101610-4
10-3
10-2
10-1
100
101
Okmetic MCZ<100> 1kcm as-irradiated
Heat treated at Tann= 800 C
for tanneal = 5 min 30 min 24 h Waker W337 FZ diodes- un-annealed
n-epi diodes 800 C-long anneal
p-epi diodes 800 C-long anneal
Rec
ombi
natio
n lif
etim
e (
s)
Neutron fluence (n/cm2)
1012
1013
1014
1015
1016
10-4
10-3
10-2
10-1
100
101
Eff
ectiv
e lif
etim
e (
s)
Neutron fluence cm-2
MCZ Si 1k*cm
d=300m1
80 oC
180 280 380
2
180 oC
280 380
0 20 40 60 80 100 120
10-2
10-1
100
101
102
UM
WR (
a.u.
)
t (s)
Okmetic MCZ Si 1kOhm*cm300m
1E12 n/cm2
80 oC 24h
180 oC 24h
280 oC 24h
380 oC 24h
0 20 40 6010
-3
10-2
10-1
100
101
UM
WR (
a.u.
)
t (s)
Okmetic MCZ Si 1kOhm*cm300m
1E14 n/cm2
80 oC 24h
180 oC 24h
280 oC 24h
380 oC 24h
Anneals:80C +180 + 280 + 380C, 24 h
Recombination Recombination+ trapping effect
1012 1013 1014 1015 1016
100
101
102
103
104
R*K
tr=
eff (
ns)
fluence (n/cm2)
linear increase of density of the trapping centers variation of density of the trapping centers
with fluence described by Gaussian distribution with max
at 1E14 n/cm2
SUMMARY 1
Lifetime decreases from few s to about of 200 ps with enhancement of neutron irradiation fluence ranging from 1012 to 31016 n/cm2 in the as-irradiated material.
Lifetime values are nearly the same for neutron irradiated wafer and diode samples. These values are close to that in >20 MeV proton irradiated various Si diodes. However, absolute values of recombination lifetime are significantly shorter in the 2 MeV protons irradiated FZ Si when using the same scale of fluences.
A nearly linear decrease of the recombination lifetime with fluence of the reactor neutrons from 1012 to 31016 n/cm2 in the MCz grown Si samples corroborates a non-linear introduction rate of dominant recombination centers.
SUMMARY 2
For 2 MeV protons (stopped within the base range of a PIN diode) irradiated Si, production of recombination defects in ~2 MeV protons irradiated FZ Si is efficient, and lifetime depth profiles correlate with stopping range of particles. In DLTS, heat treatments indicate transformations of majority and minority carrier traps. These changes are also revealed by variations of the excess carrier decay lifetime. The main transformations can be attributed to hydrogen implantation related defects (VOH etc).
An increase of lifetime and a change of carrier decay shape (process) in reactor neutrons irradiated MCZ Si, dependent on fluence, appears under annealing at elevated temperatures (>180 C, for 24 h). Lifetime behavior with heat treatment temperature shows an enhancement of competition between recombination and trapping centers.
Thank You for attention!