SMART
Study of radiation damage induced by 26MeV
protons and reactor neutrons on heavily irradiated MCz,
FZ and Epi silicon detectors
N. Manna
Dipartimento Interateneo di Fisica & INFN di Bari
on behalf of the SMART Collaboration*
(*)
INFN sections of Bari, Firenze, Perugia, Pisa;
External collaborators INFN Padova, Trieste & ITC-IRST Trento
™
Layout and materials of SMART detectors
™
™
Post-irradiation measurements
Analysis: MCz n Inversion or Double Junction?
CCE MCz p
Epitaxial
MOS – Interstirp Capacitance
™
Conclusions
8th RD50 - Workshop on Radiation hard semiconductor devices for very high luminosity colliders
PRAGUE, 25-28 June, 2006
Wafer Layout
Test2: GCD, Van der Paw
SMART
Test1: Diode+Mos 9 RD50 common wafer procurement
(produced by Okmetic - Vantaa,
Finland)
Square
MGdiodes
9 Wafer Layout designed by the SMART
Collaboration
S1 S2 S3 S4 S5
S6 S7 S8 S9 S10
9 Masks and process by ITC-IRST
9
Microstrip
detectors
50 mm pitch
64 strips
100 mmpitch
32 strips
Inter-strip Capacitance test
Round MG-diodes
10 different strip geometries
μ-strip #
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
pitch (μm) p+ width (μm) Metal width (μm)
50
15
23
50
20
28
50
25
33
50
15
19
50
15
27
100
15
23
100
25
33
100
35
43
100
25
37
100
25
41
PRODUCTION
MCz Samples
RUN I
p-on-n
22 wafers
SMART
Fz Samples
<100> ρ>500 Ω*cm thick=300μm
<111> ρ>6KΩ*cm th.=300μm
9 Standard: LTO, sintering @ 420C
9 Standard Process
9 no LTO (pass. layer), sint. @ 380C
9 no LTO,
sintering @ 350C
Epi Samples
ρ≈500Ω*cm th.=150μm
9 no LTO, sintering @ 380C + TDK
<100> ρ>1.8 KΩ*cm thick=300μm
RUN II
n-on-p
24 wafers
MCz Samples
9 No over-glass passivation
<100> ρ>5KΩ*cm th.=200 mm
9 Low dose p-spray (3.0E12 cm-2)
9 Low dose p-spray (3.0E12 cm-2)
9 High dose p-spray (5.0E12 cm-2)
9 High dose p-spray (5.0E12 cm-2)
Irradiation
April 2006
SMART
Set up for the irradiation @ JSI(Ljubljana)
Irradiation with reactor neutrons in Ljubljana
12 fluences: 5.0x1013 8.5x1015 1-MeV n/cm2
27 mini-sensors, 11 test structure (capts),100 diodes
60 % n-type, 40 % p-type
Thanks to V.Cindro and G.Kramberger
June 2006
Irradiation with 26 MeV protons at the
Cyclotron of the Forschungszentrum Karlsruhe
10 fluences: 1.2x1014 - 6x1015 1-MeV n/cm2
20 mini-sensors, 8 test structure(capts), 100 diodes
60 % n-type, 40 % p-type
Thanks to A. Furgeri
Set up for the irradiation @ FZK(Karlsruhe)
Post Irradiation Characterization SMART
™ On Diodes:
IV and CV measurements (@ 0 °C or 20 °C)
- immediately after irradiation before annealing
- repeated after annealing steps (@ 20, 60 or 80 °C)
- Charge Collection Efficiency
in order to:
(1) follow the radiation damage evolution on bulk current
and effective doping concentration;
(2) determine the effective irradiation fluences
(3) estimate the inversion and double junction fluence
(4) test Vdep with charge collection to validate CV measurements
and Determine Charge Collection Efficiency at full depletion
™
On Mos devices:
CV (@ 0 0C)
- immediately after irradiation before annealing
- repeated after annealing steps(@ 80 0C)
in order to study:
variation of the oxide charge as a function of the irradiation fluence
in order to understand the behavior of the interstrip capacitans
Depletion voltage after irr.
(Fz n Type inversion)
PROTON IRRADIATION
Typical behaviour for
standard FZ_n
SMART
We are following annealing
at room temperature
T=200C
Depletion voltage after irr.
(MCz n Type inversion?)
SMART
The annealing behaviour is typical of type inverted (p-type) material after Φ4 , but ……
T=200C
PROTON IRRADIATION
SMART
Double Junction (DJ) effect
For very high fluences (of the order of 1014 neq/cm2) a depletion region can be
observed on both sides of the device for STFZ p+/n diodes. In STFZ DJ arises
after inversion. The opposite in MCz! This may explain Vdep(Φ,t) profiles.
•Double junction effect has been
observed on MCz already at
Φ = 3×1014 n/cm2
Strip readout
side: no over
depletion
•At the fluence Φ=1.3×1015 n/cm2
the dominant junction is still on the
p+ side
p+
n+
3.0E+04
V = 282 V
E (V/cm)
2.5E+04
2.0E+04
1.5E+04
1.0E+04
5.0E+03
0.0E+00
0
0.01
0.02
x (cm)
0.03
Electric field extracted
from fit - TCT data
No SCSI on MCz up to
Fake “SCSI” on MCz at Φ ~2×1014 neq/cm2
Φ ~1.3×1015 neq/cm2
1.
Minimum on Vdep vs fluence
TCT measurements
2.
Slope of annealing curves
Double junction model
PROTON IRRADIATION
SMART
N1 = b1 (φi − φ )
N 2 = b2 (φ − φ0 )
bi = introduction rate of defect in the
junctions
Фi =inversion fluence
Ф0 =double junction
formation fluence
3 N1 N 2
Vdep ∝ ( N1 + N 2 ) −
( N1 + N 2 )
Annealing @60 0C
(MCz n Type)
Φ (1014n*cm-2)
SMART
Φ (1014n*cm-2)
NEUTRON IRRADIATION
T=600C
Annealing @ 800C
NEUTRON IRRADIATION
PROTON IRRADIATION
Up to 60 min at
80 C for
neutron irr. Fz
and MCz show
the same
behavior.
extrapolated
The difference in the annealing
for protons started at longer
ann. Times, where MCz improved.
SMART
Charge Collection Efficiency SMART
Si detectors MCz p-type
PROTON IRRADIATION
700
600
Depletion Voltage (V)
Φ = 6.8 1013 cm-2
500
400
300
0
50
100
150
200
Annealing time (min)
CCE 100%
At full
depletion
250
VCCE ~ VCV
1.0
1.0
CCE
CV
0.8
=270±20V
VCV
=270±20V
0.8
0.6
0.6
0.4
0.4
0.2
0.2
300μm Cz p-type diode
14
-2
φ=0.68x10 cm annealed for 252' at 80°C
0.0
Carlo Tosi, Mara Bruzzi
II Workshop Trento 2006
VCCE
-2
0
SMG16 f=0.68E15
SMG12 f=5.4E14
SMG10 f=4E14
SMG7 f=2.7E14
SMG5 f=2E14
SMG4 f=1.4E14
SMG26 f=1E14
300
SMG2 f=0.68E14
SMG1 f=0.4E14
CCE
100
0
100
200
300
Voltage, V
400
500
0.0
Normalized C
200
Charge Collection Efficiency SMART
of Si detectors MCz p-type
PROTON IRRADIATION
700
600
Depletion Voltage (V)
Φ = 2.7 1014 cm-2
500
400
300
1,1
1,1
200
50
100
150
200
Annealing time (min)
250
1,0
0,9
0,9
0,8
0,8
VCCE = 540 V
VCV = 500V
but
CCE ~ 86%
CCE ~ 96%
500V
700V
=540±20V
VCCE
0,7
CCE, %
0
CCE
CV
1,0
0,6
0,6
0,5
0,5
0,4
0,4
0,3
0,3
300μm Cz p-type diode
14
-2
φ=4x10 cm annealed for 240' at 80°C
0,2
0,1
Carlo Tosi, Mara Bruzzi
II Workshop Trento 2006
0,7
0,2
0,1
0
100
200
300
400
500
Voltage, V
600
700
800
900
1000
-2
0
SMG16 f=0.68E15
SMG12 f=5.4E14
SMG10 f=4E14
SMG7 f=2.7E14
SMG5 f=2E14
SMG4 f=1.4E14
SMG26 f=1E14
300
SMG2 f=0.68E14
SMG1 f=0.4E14
Normalized C
100
CCE of single pad MCz Si n-on-p
SMART
PROTON IRRADIATION
0,8
=350±20V
=340±20V
-2
VCCE
VCV
0,6
0,6
0,4
0,4
0,2
0,2
300μm Cz p-type diode
14
-2
φ=2x10 cm annealed for 60' at 80°C
200
300
400
500
1,1
600
CCE
CV
1,0
Voltage, V
0,9
-2
100
0,0
0,8
Normalized C
0
Φ = 6.8 1014 cm-2
CCE 75 % @ Vfd = 350V
CCE 90% @ 700V
0,7
CCE
CCE, %
0,8
0,0
Φ = 1.36 1014 cm-2
CCE 100%
at full depletion VCCE ~ VCV = 340V
1,0
CCE
CV
Normalized C
1,0
V = 800V
T = - 30°C
VCV=335±20V
VCCE=365±20V at 80%
0,6
0,5
0,4
300μm Cz p-type diode
14
φ=6.8x10 not annelaed
0,3
0,2
100
200
300
400
500
Voltage V
600
700
800
• Strong increase of
the depletion voltage
vs fluence
• Vdepl at the
minimum is around 10
V: inversion or double
junction effect?
Depletion Voltage (V)
Epitaxial 150µm
SMART
600
500
400
300
200
Lubiana neutrons (Padova)
Lubiana neutrons (Firenze)
26 MeV protons
100
0
0
10
20
30
40
50
14
-2
Fluence (x10 cm 1 MeV n)
Neutrons Irradiation - Annealing
700
600
500
400
14
Neutrons: “inverted-like”
behaviour
-2
Φ=8.5x10 cm
14
-2
Φ=16x10 cm
300
14
-2
Φ= 42.5 x10 cm
200
100
0
0
20
40
60
80
100
120
140
o
Annealing Time at 80 C (min)
Depletion Voltage (V)
Depletion Voltage (V)
Epitaxial Annealing
Proton Irradiation - Annealing
140
120
Φ=6.05 x 10
100
14
cm
-2
Protons: “not inverted-like”
behaviour
80
60
40
0
10
20
30
40
o
Annealing Time at 80 C (min)
SMART
MOS
Capacitance (F)
vfb
Cint
-10
1.36x10
-10
1.32x10
-10
1.28x10
-10
1.24x10
Φ = Pre-irr
-10
1.20x10
-2
14
Φ = 1.2 x10
14
-10
Φ =3.6 x10
1.16x10
14
Φ =6.1 x10
-10
1.12x10
14
Φ =18 x10
-50
-25
0
25
50
75
100
125
cm
-2
cm
-2
cm
-2
cm
150
-V gate (V)
Measured before annealing @ 0oC
See Piemonte’s talk 7th RD50 - Workshop
SMART
Annealing studies at 80 °C on the MOS structure
SMART
Fz p-type with high p-spray
f= 1K Hz
1.26E-10
1.25E-10
1.24E-10
The Vfb decreases
with annealing time
until saturation
1.23E-10
1.22E-10
1.21E-10
1.20E-10
1.19E-10
W084 T1 14 1KHz 6E14
W084 T1 14 2 min
W084 T1 14 4 min
W084 T1 14 12 min
W084 T1 14 20 min
1.18E-10
1.17E-10
1.16E-10
-200
-100
0
100
200
300
- Vgate (V)
Conclusions
SMART
1. From TCT measurements the MCz n-type diodes irradiated with protons are not type
inverted up to fluence 1*1015 ncm-2 and DJ observed above 3*1014ncm-2
2. Experimental measurements are in better agreement with a Double Junction model than
standard one.
3. Work in progress to improve this model in agreement with the experimental
measurements and investigate the annealing behavior through this model.
4. No difference with the irradiation (proton-neutron) in terms of DJ model.
5. CV and CCE profiles and full depletion voltage values in good agremeent up to Φ = 1.36
1014 cm-2.
6. CCE 96% and 90% at the highest fluences tested (2.7 - 6.8*1014cm-2 ) and at different
annealing steps ( 0 and 252min at 80°C).
7. Epitaxial-150μm n-type diodes behaves like “inverted” @ 8*1014cm-2
8. The Vfb increases continuously with fluence
9. Interstrip Capacitance variation observed on Microstrip sensors up to 6*1014cm-2.