defect kinetics in epi /cz silicon after co 60 - irradiation
DESCRIPTION
Defect kinetics in Epi /Cz silicon after Co 60 - irradiation. I. Pintilie *, G. Lindstroem**, E. Fretwurst** , F. Hoeniger and B . G. S vensson ** * * National Institute of Materials Physics, Bucharest, Romania ** Institute of Experimental Physics - University of Hamburg, Hamburg, Germany - PowerPoint PPT PresentationTRANSCRIPT
Defect kinetics in Epi/Cz silicon after Co60- irradiation
I. Pintilie*, G. Lindstroem**, E. Fretwurst**, F. Hoeniger and B.G. Svensson***
* National Institute of Materials Physics, Bucharest, Romania
** Institute of Experimental Physics-University of Hamburg, Hamburg, Germany
*** Oslo University, Dept.of Physics, Oslo, Norway
Motivation- The divacancy annealing mechanisms proposed for STFZ after low irradiation doses cannot explain the results obtained in Epi/Cz diodes after high doses of irradiation
EPI-Silicon wafers: <111>, n/P, 50 Ωcm, 50 μm on 300 μm Cz-substrate, CiS process
Sample STFZ DOFZ EPI/Cz
SIMS [O]<5*1016 1.2*1017 (1.5- 30)*1016
Carbon concentration for all materials
at detection limit [C] 5.71015 cm-3
Irradiation source: Brookhaven National Laboratory for 60Co--photons
0 5 10 15 20 25 30 35 40 45 50
1E16
1E17
Oxy
gen
Con
cent
ratio
n (c
m-3)
Epilayer thickness (m)
SIMS
Annealing experiments
80 120 160 200 240 280T [K]
-0.01
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
DL
TS
Sign
al [
pF]
as irradiatedas irradiated
VV(-/0)+X(-/0)VV(-/0)+X(-/0)
120 min 250oC120 min 250oC
E(140)E(140)
360 min 250oC360 min 250oC E(110)+X(=/-)+VV(=/-)14 h 250oC14 h 250oC39 h 250oC39 h 250oC215 h at 250oC215 h at 250oC
E(175)E(175) E(245)E(245)
Annealing DOFZ at 250oC
X defect – two acceptor states - Identified as V2O 1) Proposed formation mechanism1): V2 +Oi V2O(with DV2 = 3x10-3 exp (-1.3eV) instead of the former DV2 = 0.1 exp (-1.3eV) )
1) Monakov et al, Phys Rev B, Volume 65, 233207 (2002)
80 120 160 200 240 280T [K]
-0.01
0.01
0.03
0.05
0.07
0.09
DL
TS
Sign
al [
pF]
as irradiatedas irradiatedVV(-/0)VV(-/0)
2 h 250oC2 h 250oCVV(=/-)VV(=/-)
E(140)E(140)
6 h 250oC6 h 250oC14 h 250oC14 h 250oC30 h 250oC30 h 250oC65 h 250oC65 h 250oC113 h at 250oC113 h at 250oC212 h at 250oC212 h at 250oC
E(110)E(110)E(175)E(175)
Annealing STFZ
• low irradiation doses (4 Mrad) – the X defect is formed in oxygen enriched material via the annealing of divacancy for T> 2500C
80 100 120 140 160 180 200
0
5
10
15
20
25
V2
=/-
X=/-
X-/0
V2
-/0
TS
C s
ignal (
pA
)
Temperature (K)
30min@200C 40min@300C 60min@300C 160 min@300C 240min@300C 440min@300C 1220min@300C
• high irradiation doses (>100 Mrad) – X center formed in concentration higher than of V2 for T> 2500C
80 100 120 140 160 180 200
0
5
10
15
20
V2
=/-
X=/-
X-/0
V2
-/0
TS
C s
igna
l (pA
)
Temperature (K)
30min@200C 60min@300C 80 min@300C 160min@300C 440 min@300C 560min@300C 1220min@300C
Dose = 315 Mrad±10% Dose = 520 Mrad ±10%
Epi/Cz material – T = 300 0C
[X]~3x[V2] [X]~5x[V2]
X defect – Identified as V2O2 2) via: V2 +O2 V2O2 and VO+VO
(with DV2 = 0.1 exp (-1.3eV) and DVO(T)=6Exp(-1.8eV/KT) cm2/s)
2) I.Pintilie et al- 6th and 7th RD50 workshops
Which defect reactions at T>250 C can produce more V2O ?
• V2 +O → V2O
• V+VO → V2O
Should exists a source of V
• Most probable VO can be the V source – it dissociates during annealing at T >250 C
• VO → V + O
Defect reactions
Vacancy-Oxygen related defect reactions
Diffusion reactions• V + O → VO• V+VO → V2O• V+V → V2
• V2 +O → V2O• V2 +O2 → V2O2 • V+O2 → VO2 • VO+O→ VO2
• V +VO2 → V2O2 • VO+VO → V2O2 Dissociation reactions• VO → V + O • V2O → V +VO• V2O2 → VO+VO• V2 → V +V
Defect reactions with other impurities*
Diffusion reactions• VO+H→ VOH• V2 +H → V2H• V +H → VH• CiOi+H→ COH• V+CiOi → CsOi• Ci+V → Cs• Ci+Oi → CiOi• V+ CiCs→ CsCsDissociation reactions• VOH → VO + H • V2H → V +VH• VH → V+H• CiCs → Ci+Cs
*Do not affect the V-O defect reactions as long as [H]<1015 cm-3
Parameters used for simulations
• [Oi] = profile from SIMS • [VO] = 1.1x1012 x Dose (Mrad) x cm-3
• r = 5x10-10m
Diffusion parameters(updated to nowdays literature)
• DVO(T)=6Exp(-1.8eV/KT) cm2/s; • DVV(T)= 3x10-3exp(-1.3eV/KT) cm2/s; • DOd(T)=3x10-4exp(-1.3eV/KT) cm2/s; • Doi(T)=0.17exp(-2.54eV/KT) cm2/s• DV(T)= 4.5x10-4exp(-0.3eV/KT) cm2/s; • DCi(T)= 4.4x10-1exp(-0.87eV/KT)
cm2/s;
Dissociation• K
VO = 1 x 1013exp(-2.1eV/KT) s-1;
• KV2O2 = 1.5 x 1013exp(-2.1eV/KT) s-1
• KV2O = 2 x 1013exp(-2.1eV/KT) s-1
0 5 10 15 20 25 30 35 40 45 50
1E16
1E17
Oxy
gen
Con
cent
ratio
n (c
m-3)
Epilayer thickness (m)
SIMS
Oi profile - from SIMS measurements
0 5000 10000 15000 20000 25000
0.0
2.0x1012
4.0x1012
6.0x1012
8.0x1012
1.0x1013
1.2x1013
1.4x1013
1.6x1013
520 Mrad - Tannealing
=3000C
Def
ect
conc
entr
atio
n (c
m-3)
Annealing time (min)
V2O
2- numerical
distance from the surface (m)
Oi<5x1016 cm-3 5 10 15 20 25 30
Oi:(5x1016-1017) cm-3 35 40
Oi>1017 cm-3 45 50
Xexp
0 5000 10000 15000 20000 25000-1x1012
0
1x1012
2x1012
3x1012
4x1012
5x1012
6x1012
7x1012
8x1012
9x1012
1x1013
520 Mrad - Tannealing
=3000C
Def
ect c
once
ntra
tion
(cm
-3)
Annealing time (min)
V2O- numerical
distance from the surface (m)
Oi<5x1016 cm-3 5 10 15 20 25 30
Oi:(5x1016-1017) cm-3 35 40
Oi>1017 cm-3 45 50
Xexp
520 Mrad - T=3000C
V2O2 V2O
0 5 10 15 20 25 30 35 40 45 50
1E16
1E17
Oxygen C
oncentr
ation (
cm
-3)
Epilayer thickness (m)
SIMS
-100 0 100 200 300 400 500 600 700 800 900 1000
0.0
5.0x1011
1.0x1012
1.5x1012
2.0x1012
2.5x1012
520 Mrad - Tannealing
=3000C
Def
ect c
once
ntra
tion
(cm
-3)
Annealing time (min)
V2 exp V2 average
0 5000 10000 15000 20000
0.0
2.0x1012
4.0x1012
6.0x1012
8.0x1012
1.0x1013
520 Mrad - Tannealing
=3000C
Def
ect c
once
ntra
tion
(cm
-3)
Annealing time (min)
V2O2 average Xexp V2O average
520 Mrad - T=3000C
0 200 400 600 800 1000
0.0
5.0x1011
1.0x1012
1.5x1012
2.0x1012
2.5x1012
3.0x1012
570 Mrad - Tannealing
=3200C
Def
ect c
once
ntra
tion
(cm
-3)
Annealing time (min)
V2 average V2 exp
570 Mrad - T=3200C
-1000 0 1000 2000 3000 4000 5000 6000 7000
0
2x1012
4x1012
6x1012
8x1012
1x1013
1x1013
570 Mrad - Tannealing
=3200C
Def
ect c
once
ntra
tion
(cm
-3)
Annealing time (min)
V2O2 average X exp V2O average
• Simulations based on a more complex system of defect reactions show that both V2O and V2O2 defects should form at elevated temperature.
• With VO as single initial source for vacancies and for the irradiation dose range investigated here: V2O2 can be produced in a similar concentration with X center V2O can be produced in a concentration higher than V2 but in a much smaller concentration than of the X center
• Further studies are under discussion regarding the existence of additional single V migrating from Cz substrate.
Conclusions