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!