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Macroscopic Effects in n-MCz Diodes after Neutron
Irradiation Depletion Voltage and Reverse Current
G. Lindstroem a, E. Fretwurst a, F. Hönniger a,
A. Junkes a, K. Koch a and I. Pintilie a,b a
Institute for Exp. Physics, University of
Hamburg b National Institute for Materials
Physics NIMP, Bucharest
WODEAN workshop, Vilnius University
02/03-June-2007
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• Outline
• Properties of used diodes
• Effective doping
• Reverse current
• Conclusions

WODEAN workshop, Vilnius University
02/03-June-2007
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Diode properties
Used material WODEAN n-MCZ (OKMETIC), P-doped
900 Wcm, Neff 4.8E12 cm-3 Diode processing
CiS Erfurt, thinned to d 95 mm rear contact
P-implanted Neff 4.8E12 cm-3 P-diffused
Neff 7.7E12 cm-3 (TD generation during
thermal process)
O and C concentrationO 5E17
cm-3(outdiffusion below 10 mm) C lt 3E15
cm-3(detection limit)
WODEAN workshop, Vilnius University
02/03-June-2007
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Effective doping concentration Dependence on F
and annealing-General Reminder-
High resistivity FZ silicon
Annealing function Hamburg model
300 mm diodes not usable up to 1E16 n/cm²full
depletion voltage exceeds 10 KV! Cure use of
lower resistivity and thin diodes,hence 100 mm
and lt1kWcm
Short term beneficial annealingLong term
reverse annealingtime constants depending on
temperature!Tann 80C 100 to 1000 min
(rev.anneal) Tann RT 1 to 10 years
WODEAN workshop, Vilnius University
02/03-June-2007
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Annealing function for n-MCz 100 mm diodes
DN Neff,0-Neff(F,t) Na(F,tann)
NC0(1-exp(-cF)) gCF NY(F,tann)
Na beneficial annealingNC stable damage,
NC0(1-exp(-cF)) donor removal (NC0 Neff,0)
gCF acceptor generationNY reverse
annealing (increase of neg. space charge during
annealing)
NY
DNmin NC
WODEAN workshop, Vilnius University
02/03-June-2007
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Annealing time constants
All values measured for Tanneal 80 C, no real
difference to known results from other Si-diodes
(FZ, epi)
WODEAN workshop, Vilnius University
02/03-June-2007
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Annealing time constants
All values measured for Tanneal 80 C, no real
difference to results from MCz with standard
processAnnealing behaviour not affected by
thermal donors!
WODEAN workshop, Vilnius University
02/03-June-2007
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Beneficial annealing amplitude
Saturation fit for Na(F) misleadingAt F3E15
n/cm² tirrad 25 min, Tirrad 70-80 Chence
strong self annealing during annealing!Linear
fit for F 1E15 n/cm² reliablega 1.2E-2 cm-1
WODEAN workshop, Vilnius University
02/03-June-2007
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Stable damage component NC
Remember NC NC0(1-exp(-cF)) gCFNC0 Neff,0
if only P-doping donor removal by formation of
E-center (VP)!
Rear side P-implanted NC0 5E12/cm³ Neff,0
ok?Rear side P-diffused NC0 similar to
P-implanted P-donors removedThermal donor
concentration 2E12/cm³, stays constant during
annealingdonor removal rate c 1E-14 cm², NC0c
5E-2 cm-1 ok ?acceptor introduction rate
9E-3cm-1 about 2x larger than for thin FZ, epi!
WODEAN workshop, Vilnius University
02/03-June-2007
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Comparison of Neff(F) at DNmin measured in thin
diodes
For tanneal 8 min at 80 C
n-MCz
WODEAN workshop, Vilnius University
02/03-June-2007
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Side remark (not WODEAN)
Comparison between 50 mm n-type and p-type epi
diodes after n-irradiation
n-type epi P-donor removal (small F) BD donor
generation (large F)p-type epi B-acceptor
removal (small F) acceptor generation (large F)
WODEAN workshop, Vilnius University
02/03-June-2007
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Reverse annealing amplitude NY
Assumed annealing function 1st and 2nd order for
best fitNY sum of both amplitudes
reliable!Saturation fit with acceptor
introduction rate for small F gY0 5E-2 cm-1in
agreement with other materials
WODEAN workshop, Vilnius University
02/03-June-2007
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Reverse current
Annealing function for a in comparison to p-epi
Linear fit for IFD/Vol as fct. of F
Shape of annealing function does not differ
significantly from other known results (see RD50
talk E. Fretwurst)
Linear fit for IFD/Vol aF gives a
4.1E-17Acm-1which is the generally accepted value
Results are in general agreement with known
datasome deviations of annealing function (as
for all thin diodes) from the old fit (M. Moll)
WODEAN workshop, Vilnius University
02/03-June-2007
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Conclusions

• general behaviour of n-MCz diodes as known for
  other material although O 5E17 cm-2 is large
• thermal donors generated in n-MCz before
  irradiation are not affected by radiation damage
• Complete donor removal observed with rate
  constant c 1E-14 cm²
• Acceptor introduction rate gC 9E-3 cm-1 about
  2 x larger than for other known materials
• Reverse current in accordance with other data
  a 4.1E-17 Acm-1

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02/03-June-2007
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Hydrogenation of Silicon First
Attempts Implantation of 710 keV D, R 7 mm
WODEAN workshop, Vilnius University
02/03-June-2007