Electron spin and cyclotron resonance of laser annealed silicon

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Submitted on 1 Jan 1980

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Electron spin and cyclotron resonance of laser annealed

silicon

A. Goltzené, J.C. Muller, C. Schwab, P. Siffert

To cite this version:

21

Electron

_spin

and

_cyclotron

resonance

of

laser

annealed

silicon

(*)

A. Goltzené

_(**),

J. C. Muller

_(***),

C. Schwab

_(**),

P. Siffert

_(***)

(**) Laboratoire de Spectroscopie et d’Optique du _{Corps Solide,}

Associé au C.N.R.S. n° 232, Université Louis-Pasteur, 5, rue de l’Université, 67000 Strasbourg, France (***) Centre de Recherches Nucléaires, Groupe de Physique et _Applications des Semiconducteurs (PHASE),

67037 Strasbourg Cedex, France

Résumé. 2014 Les _mesures de RPE et de résonance

cyclotron ont montré que le recuit laser de Si est corrélé à

l’appa-rition de _signaux attribués au défaut _[V + _Oi]- dans le matériau non _dopé, et à une forte diminution du _signal

RPE du donneur dans Si

_implanté

P. Abstract. -

EPR and _cyclotron resonance _{investigations} have been

_performed

on laser annealed Si _{wafers, leading}

to the identification of the

_[V

+ _{Oi]- complex} in

_virgin

Si and to a donor

_{signal quenching}

in

_P-implanted

Si.

Revue Phys. Appl. 15 (1980) 21-23 JANVIER 1980, PAGE 21 1

Classification

Physics Abstracts

73.20Hb - 76.30 - 79.20Ds

Introduction. - Laser

annealing techniques

have been

_investigated

_recently

for

_improving

various

semiconducting

devices such as

integrated

circuits

and solar cells.

Initial studies have shown that the

_restoring

mecha-nism of the

_damaged

surface

_layers

or of

_amorphous

deposits

on _top of the

single

crystalline

silicon

sub-strate will

_depend

on the

_lasing

mode. CW illumina-tion is believed to initiate a solid

_phase

_epitaxial

process, whereas the

pulsed

mode induces a

_liquid

epitaxial

regrowth

as soon as _{the power}

_density

exceeds some

_threshold,

_lying

close to 1

J/cm2

[1].

To our

_knowledge,

no direct determination of the

residual defects which remain in these restored

_layers

have been

_{tempted, although}

some

_deep

levels have

already

been identified

_by

sensitive electrical

trans-port measurement such as DLTS

_[2]

or TSC

_[3].

Therefore the aim of this work was to

_investigate

these defects

_by

electron

_paramagnetic

resonance

(EPR),

which is a _very

specific technique.

In some

instances,

it will also allow to record

_cyclotron

reso-nance

_(CR)

data

_{simultaneously.}

Expérimental.

- EPR and CR have been

performed

on

_{high purity}

and on

_phosphorus

implanted silicon.

The

_high

_purity

silicon was float zone material

of _n-type, with a

_high

_resistivity

of

104

Q cm. The

concentrations of the residual

_impurities

were as

fo llows : 0 1’-1 1016

cm - 3, B and

P N

1012

cm - 3 ;

wafer orientation was

_[110].

(*) Conférence _présentée au _Congrès de la Société Française de

Physique (Toulouse, 25-30 _{juin 1979).}

The

_implanted

material was of low

resistivity

(160 S2 cm)

and of initial

_p-type

_(B

_doped).

Doses of

5 x

1016

to

10" cm - 2 p31

ions were

_implanted

at 10-15 keV on each side of

_[111]

_]

oriented wafers.

The

_{expected penetration}

_depth

at these

_energies

is about 50 nm.

The anneals were

_performed

in air with a

Q-switch-ed

_ruby

laser

_(03BB

= 694.3

nm)

with _a

pulse

duration of 25 ns at half _{power. The power}

_density

was

2.7 J

cm-2

for the

_virgin

silicon to be well above the

melting

temperature

and _up to 10 successive shots

have been

_employed.

For the

_implanted

silicon,

the laser _energy was set

_just

_up to the threshold _energy

(~

1.1 J

_{cm- 2).}

After this

_operation,

_samples

of

3 x 4 x 1 mm3 were cut out from the 6 mm diameter spots in order to insure a

_{good homogeneity.}

EPR and CR measurements were done at 4.2 K

and 9.3 GHz on stacks made of 2 or 3

_samples

to

enhance the lowest

_signals.

Results. - The

virgin

silicon

_samples

are EPR

signal

free. After the laser

anneal,

an

_isotropic

line

appears with a Landé factor ₉₁ = 2.005 5

± 0.000 5.

After

_etching

off the surface

_layer,

or after a thermal

anneal at 500°C for 30

min,

this

_{signal disappears}

again.

Maximum

_signal

_intensity

_corresponds

to

some

1013

_spins.

A

_light

irradiation is needed to observe a CR

signal (Fig.

2).

It is

_{performed using}

an unfiltered 55 W _quartz iodine

_lamp,

_illuminating

the

_sample

within the

_{cavity through}

an

_{optical port.}

After the

laser anneal

_only

_slight

variations are observed : the hole CR linewidth

decreases,

whereas the electron

22

Fig. 1. - EPR of 104 03A9

cm _{n-type Si,} after laser _annealing.

Fig. 2. _{- Cyclotron} resonance _(CR) of 104 Q cm _{n-type Si,} for

Ho slightly off a ₍₁₁₀₎ direction. _Intensity and linewidth are

measur-ed for the electron CR (el e2) and the _heavy hole CR _(h2).

Fig. 3. - EPR of

P-implanted Si, before _(a) and after _(b) laser

annealing.

CR linewidth

increases,

but both their intensities decrease.

For the

_implanted

_Si,

an

_isotropic

EPR _{line appears}

at g2 = 2.000 ± 0.002

(Fig.

3).

Before

annealing,

the

_spin

number

_corresponds

to some

1014 cm - 3.

After the laser

_shots,

the

_intensity

of this line decreases

approximately

by

one order of

_magnitude.

Preliminary

measurements of CR in these

_samples

have shown a more

_complex

_behaviour,

_needing

further

_{investigations.}

Discussion. - To the defect

signed by

g

in virgin

silicon

_samples,

we _{may compare} some

_already

known

_signal.

_However, we add the

_possibility

of

getting

averaged g’s

either

_by

_poor local

_{crystallinity}

of

_by

motional effects. We are thus left with the

following possibilities :

- the

vacancy-interstitial complex

[ V

+

_{0;] -}

with gBl = 2.005 0

(B1

center

_{[4]) ;}

- the unidentified defect

occurring

as well in

crystalline

[5]

or

_{amorphous [6] silicon,}

with the

iso-tropic

Landé _{factor 2.005 g} 2.007.

However the latter center has never been observed in _purest silicon

_by

_{EPR ;}

_{consequently,}

we are left

with the

_B,

1 center.

Furthermore,

this attribution is

in accordance with the observation of a level at

Ec -

0.18 eV

_by

DLTS and also ascribed to the same

[ V

+

_0;]-

center

_[2].

-The

_intensity

of the CR resonance

_signal

is

propor-tional to the carrier

lifetimes,

therefore to the inverse of the concentration of recombination centers. Thus

it is deduced that the latter increase after the

_regrowth

of the

_layer.

The CR linewidth is

_proportional

to the inverse of the mean collision time of carriers and therefore

to the

_scattering

centers concentration. The fact that the electron CR linewidth increases indicates that the

negatively charged

centers

_{concentration,}

as for

example

the

_{[ V}

+

_{0;] -}

_complexes,

increase after

the laser shots.

These results

_clearly

indicate the need of

operat-ing

in vacuum for

_using

these

_{techniques during}

semi-conductor

_processing.

The _g2 center in the P

_implanted

silicon has a Landé

factor close to that of the conduction

band,

gcB = 1.998 75 and is

obviously

due to the P shallow donors

_[7].

_Indeed,

_supposing

that the

1014 31p

ions

are redistributed in the 200 nm molten

_layer,

their

concentration is

_always

more than

1018

_{cm - 3,}

still

high

enough

to induce motional

_{narrowing effects}

which _{suppress the}

P4+

_{hyperfine splitting.}

After

the

anneal,

most of these donors become EPR

inactive,

possibly

by heterogeneous

segregation.

Conclusion. -

Investigation

of laser annealed silicon

_samples

_by

EPR and CR

_yields

new information

about residual defects both in

_regrowth

of

_virgin

sili-con and of

_{damaged implanted layers.}

Agreement

is found between EPR

results,

leading

to the identification of the

_{[ V}

+

_{0;]- complex,}

in

virgin

silicon and CR data.

In

_{phosphorus-implanted}

_silicon,

the laser

23

References

[1] GIBBONS, J. F., Proc. _of the laser _effects ion implanted.

Semi-conductors, Catania 1978 _(Editor E. _Rimini) p. 103.

[2] BENTON, J. L., KIMERLING, L. C., MILLER, G. L., ROBINSON, D. A. H. and CELLER, G. K., Proc. Catania 1978, p. 543.

JOHNSON, N. M., GOLD, R. B., LIETOLA, A. and GIBBONS, J. _F., Proc. of laser solid interaction and laser processing symposium 28.11-1.12. A.I.P. Conf. Proc. (Edited by

Ferris S. D., Leamy J. H. and Poate J. M., Boston, U.S.A.)

1978, p. 550.

[3] MULLER, J. C., SCHARAGER, C., TOULEMONDE, M. and SIFFERT,

P., Rev. _{Phys. Appl.} 14 _(1979).

[4] CORBETT, J. W., Electron Radiation _Damage in Semiconductors and Metals, Solid State Phys. Suppl. 7 _(Academic Press,

N.Y.) 1966, p. 60.

[5] LEPINE, D., Phys. Rev. B 6 ₍₁₉₇₂₎ 436.

[6] SOLOMON, I., BIEGELSEN, D. and _KNIGHTS, J. C., Solid State Commun. 22 ₍₁₉₇₇₎ 505.