Gunnar Lindstroem – University of Hamburg 1

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 Hamburgb National Institute for Materials Physics NIMP, Bucharest

Macroscopic Effects in n-MCz Diodes after Neutron Irradiation Depletion Voltage and Reverse Current

WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg 2

Outline:

1. Properties of used diodes

2. Effective doping

3. Reverse current

4. Conclusions

WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg 3

Used material: WODEAN n-MCZ (OKMETIC), P-doped 900 cm, Neff = 4.8E+12 cm-3

Diode processing: CiS Erfurt, thinned to d = 95 mrear contact: P-implanted: Neff = 4.8E+12 cm-3

P-diffused: Neff = 7.7E+12 cm-3

(TD generation during thermal process)

WODEAN workshop, Vilnius University 02/03-June-2007

0 20 40 60 80 100

depth [m]

1015

1016

1017

1018

O-c

onc.

[1/

cm3 ]

8556-01 [O], full process8556-01 [O], full process8556-01 [C], full process8556-01 [C], full process

SIMS O-profiles, 300 m n-MCz

Adam Barcz, ITE WarsawAdam Barcz, ITE Warsaw

[O] = 5e17/cm3, [O] = 5e17/cm3,

[C] < 3e15/cm3 (detection limit)[C] < 3e15/cm3 (detection limit)

O and C concentration:

[O] = 5E+17 cm-3

(outdiffusion below 10 m)

[C] < 3E+15 cm-3

(detection limit)

Diode properties

Gunnar Lindstroem – University of Hamburg 4WODEAN workshop, Vilnius University 02/03-June-2007

Effective doping concentration Dependence on and annealing

-General Reminder-

10-1 100 101 102 103

eq [ 1012 cm-2 ]

1

510

50100

5001000

5000

Ude

p [V

] (

d =

300

m)

10-1

100

101

102

103

| Nef

f | [

1011

cm

-3 ]

600 V

1014cm-2

type inversion

n-type "p-type"

[M.Moll: Data: R. Wunstorf, PhD thesis 1992, Uni Hamburg]

300 m diodes not usable up to 1E+16 n/cm²full depletion voltage exceeds 10 KV!

Cure: use of lower resistivity and thin diodes,hence 100 m and <1kcm

High resistivity FZ silicon:

NC

NC0

gC eq

NYNA

1 10 100 1000 10000annealing time at 60oC [min]

0

2

4

6

8

10

N

eff [

1011

cm-3

]

[M.Moll, PhD thesis 1999, Uni Hamburg]

Annealing function –“Hamburg model“

Short term: beneficial annealingLong term: reverse annealing

time constants depending on temperature!Tann = 80C: 100 to 1000 min (rev.anneal) Tann = RT: 1 to 10 years

Gunnar Lindstroem – University of Hamburg 5WODEAN workshop, Vilnius University 02/03-June-2007

Nmin ≈ NC

NY

Annealing function for n-MCz 100 m diodes

N = Neff,0-Neff(,t) = Na(,tann) + NC0(1-exp(-c)) + gC· + NY(,tann)

Na: beneficial annealingNC: stable damage, NC0(1-exp(-c)): donor removal (NC0 = Neff,0)

gC: acceptor generationNY: reverse annealing (increase of neg. space charge during annealing)

Gunnar Lindstroem – University of Hamburg 6WODEAN workshop, Vilnius University 02/03-June-2007

Annealing time constants

All values measured for Tanneal = 80 °C, no real difference to known results from other Si-diodes (FZ, epi)

Gunnar Lindstroem – University of Hamburg 7WODEAN workshop, Vilnius University 02/03-June-2007

Annealing time constants

All values measured for Tanneal = 80 °C, no real difference to results from MCz with standard process

Annealing behaviour not affected by thermal donors!

Gunnar Lindstroem – University of Hamburg 8WODEAN workshop, Vilnius University 02/03-June-2007

Beneficial annealing amplitude

Saturation fit for Na() misleadingAt =3E+15 n/cm²: tirrad = 25 min, Tirrad = 70-80 °C

hence strong self annealing during annealing!Linear fit for ≤ 1E+15 n/cm² reliable

ga = 1.2E-2 cm-1

Gunnar Lindstroem – University of Hamburg 9WODEAN workshop, Vilnius University 02/03-June-2007

Stable damage component NC

Remember: NC = NC0(1-exp(-c)) + gCC0 = Neff,0 if only P-doping donor removal by formation of E-center (VP)!

Rear side P-implanted: NC0 = 5E+12/cm³ ≈ Neff,0: ok☺Rear side P-diffused: NC0 similar to P-implanted: P-donors removedThermal donor concentration = 2E+12/cm³, stays constant during annealing

donor removal rate c ≈ 1E-14 cm², NC0*c ≈ 5E-2 cm-1: ok ☺acceptor introduction rate = 9E-3cm-1: about 2x larger than for thin FZ, epi!

Gunnar Lindstroem – University of Hamburg 10WODEAN workshop, Vilnius University 02/03-June-2007

Comparison of Neff() at Nmin measured in thin diodes

For tanneal = 8 min at 80 °C

n-MCz

Gunnar Lindstroem – University of Hamburg 11WODEAN workshop, Vilnius University 02/03-June-2007

Side remark (not WODEAN):

Comparison between 50 m n-type and p-type epi diodes after n-irradiation

n-type epi: P-donor removal (small ) + BD donor generation (large )p-type epi: B-acceptor removal (small ) + acceptor generation (large )

Gunnar Lindstroem – University of Hamburg 12WODEAN workshop, Vilnius University 02/03-June-2007

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 : gY0 = 5E-2 cm-1in agreement with other materials

Gunnar Lindstroem – University of Hamburg 13WODEAN workshop, Vilnius University 02/03-June-2007

Reverse current

Annealing function for in comparison to p-epi Linear fit for IFD/Vol as fct. of

Shape of annealing function does not differ significantly from other known results (see RD50 talk E. Fretwurst)

Linear fit for IFD/Vol = · gives = 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)

Gunnar Lindstroem – University of Hamburg 14WODEAN workshop, Vilnius University 02/03-June-2007

Conclusions

• general behaviour of n-MCz diodes as known for other material although [O] = 5E+17 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 = 4.1E-17 Acm-1

Gunnar Lindstroem – University of Hamburg 15WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg 16WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg 17WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg 18WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg 19WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg 20WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg 21WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg 22WODEAN workshop, Vilnius University 02/03-June-2007

0 5 10 15 20 25

depth [m]

1016

51017

51018

51019

51020

51021

D-c

onc.

[1/

cm3 ]

as implantedas implanted1h@400C annealing in Ar with nitide off1h@400C annealing in Ar with nitide off1h@400C annealing in Ar with nitride on1h@400C annealing in Ar with nitride on

D-concentration profile from implantation before and after annealing

Hydrogenation of Silicon – First Attempts

Implantation of 710 keV D, R = 7 m