Reduction of phosphorus transient enhanced diffusion due to extended defects in ion implanted silicon

Nuclear Instruments and Methods North-Holland, Amsterdam

in Physics

Research

347

B39 (1989) 347-351

REDUCTION OF PHOSPHORUS TRANSIENT ENHANCED DIFFUSION DUE TO EXTENDED DEFECTS IN ION IMPLANTED SILICON M.

SERVIDORI,

Istituto LAMEL,

F. CEMBALI,

P. ZAUMSEIL

and

E. GABILLI,

and

P. NEGRINI

S. SOLMI

U. WINTER

ftirHalbleiterphysik,

Institut

R. FABBRI,

Consiglio Nazionale delle Ricerche, Via Castagnoli I, 40126 Bologna, Ita&

M. ANDERLE

and

Akademie

der Wissenschaften

der DDR,

Walter-K&sing

Str. 2, 1200 Frankfurt/Oder,

GDR

R. CANTER1

Istituto per la Ricerca Scientifica e Tecnologica, Divisione di Scienza dei Materiali,

38050 Pooo, Italy

Phosphorus was implanted at doses below amorphization threshold in virgin silicon and in silicon containing interstitial and 9CJO”C, 30 min annealing. Triple-crystal X-ray dislocation loops. The loops were formed by high dose Si+ Implantation diffraction and secondary ion mass spectrometry were used for the analysis of implant defects and the determination of P distribution, respectively. Anneal@ were carried out in a furnace in the range between 600 and 900 o C, and by an electron beam at 1000 o C for 10 s. The results obtained show that the presence of loops strongly reduces the phosphorus anomalous diffusion. This phenomenon is a consequence of the absorption by the loops of the interstitial excess coming from dissolution of the clusters produced by the P implant. The influence of the loop position with respect to the P distribution on the extent of P diffusivity is analyzed and discussed.

1. Introduction

2.

Ion implantation generate lous

of dopants

point defects,

diffusion

junctions,

in silicon

phenomena

[l-4].

To

soft post-implantation

such as low temperature thermal

annealings

transient

enhanced

is known

which are responsible

furnace Using

dopant

diffusion

and rapid

processes,

plays

the

a relevant

matrix,

the

face

loops

influences

atoms

is implanted target

undergo

ED, occurs

is located

within

while

to pre-existing

diffusion

(a-c) (ED).

amorphous

a remarkable

layer

in-depth

substrate

in detail

dislocation It will

whenever

anomalous

of interstitial

shift

if the tail of the implanted

by phosphorus

threshold.

reduced

the

loops

the point

diffusivity,

dislocation

loops,

are

of the

the point below

that

ED

due

defects

the dopant

for the

the interstitial

Physics

0 Elsevier Publishing

Science

Publishers

Division)

B.V.

ions were then i) with a dose of

energy,

ii) with

energy.

damage a-c

are included interface,

between

between

beam gun (RTA) evolution

of

samples

having

the

while in the latter

tails are well below the dislocawith

the same doses and energies. All the wafers were then annealed

The

of and

the same peak

set of virgin wafers

planted

doses

all the dopant

case

implanted

range

a dose

The

In the former

was

loops was analyzed

0168-583X/89/$03.50

Phosphorus

of and

so as to have nearly

and damage loops)

After

a layer

20 nm wide

conditions: keV

layer.

min,

dislocation

electron

by

30

tion loop layer. Another

is strongly

responsible

value.

and the original

temperature

defects,

160

the associated

amorphiza-

trapped

and

were chosen

concentration surface

not

amorphous

perfect

and 70 keV

of 1.5 X 1015

50 keV in order to

for

1 x 1014 cme2 energies

cme2,

surface

in two different

set of wafers

at doses

at 9OO’C

2 x 1014 cmm2

and

effect

ions

1 s2 cm resistiv-

One

annealing

interstitial

do

loops.

(North-Holland

a 200 nm thick

furnace

Dopant

[2-51.

on

be shown

inter-

distribution

the gettering

implanted

to

amorphized

annealing

the enhanced

This work analyzes

tion

during

in the crystalline

generated

sufficient

at the amorphous-crystal

included

junction

at a dose

or in a previously

the formation

dislocation

obtain

implanted

If the dopant

“Si+

200 nm deep, was obtained.

of the final depth-distribution

of the dopant. amorphize

with

cmm2, 100 keV and 0.5 X lOI

are necessary,

these

(100) silicon wafers, p-type (boron), ity, were used for the experiments. was implanted

shallow

treatments

(RTA).

role in the determination

fabricate

heatings

to

for anoma-

Experimental

600

(absence

in furnace

and

of

phosphorus

900°C,

at

in the and

by

at 1000 o C for 10 s.

the

lattice

defects

and not having

by X-ray

diffraction,

in the

P im-

the dislocation using a paral-

IV. SEMICONDUCTORS:

Si

348

M. Seruidori et al. / Reduction of P transient enhanced diffusion

lel (n,

n) triple

--n,

rocking

crystal

configuration

curves were simulated

application

of the diffraction

model

ously [8]. The best fits between lated

rocking

parameters ponent

curves

Secondary ployed

were

defining

of lattice

profiles

experimental

ion mass

in the samples

varying

spectrometry before

P’ 70 keV 20 d *g 10

(e ,).

(SIMS)

t

the

of the com-

to the surface

beam to measure

the

previ-

and calcu-

by

distribution

normal

with a caesium

through

described

obtained

the depth

strain

[6,7]. All the

by computer

was em-

the phosphorus

and after annealing.

0 3. Results

and discussion

3. I. Damage

The double previous

A furnace

at 900°

as perfect

buried

layer situation

implanted.

SC wafer can

deforms

indicated

be seen

within

the surface

by a dashed

that

remember

in silicon

like defects

[l].

a loop

layer

shown relief

annealing

implanted line

in fig.

la.

recovery

islands

ascribed

the annealing dissolution the dotted clusters,

the

in releasing

temperature

profile

and this strain recovery

of

only defects

(light

and that a marked

along with that due to the

line) represent

able to influence

the situations phosphorus

in

diffu-

samples seen

lb

shows

the damage

after annealing

that all the damage

both in the sample

evolution

in the

same

at 800 o C for 30 min. It can be due to P implant

containing

the

the dislocation

wafer

without

increase

loops is observed. modify cI

is removed loops and

the

Since

the associated

distribution

interstitials action increase

the heating

Table

cluster

concentrations The

the results

The peak values

The

following

process

the SC wafer;

This

of the clusters

due

factor

anneal-

relative

to

in the loops

from

K = 1.14 X 1O-24

remarks

modifies

(
collapsed

was obtained can

the original

ii) the interstitial

implant

in the 200 nm thick completely

their

sink

size [l].

along with the areas under by the loops (Is) and the

dissolve with

This

after different

of e I

of the interstitials

last quantity

the proportionality [l].

loops of

dissolution.

until the dissolution

and

in the

line) can only be

dislocation

in the loop

the loop layer are reported, the lI distributions given (C,).

loops,

is completed.

1 summarizes

ing processes.

200 nm (heavy

by the underlying from

a

by the

at 800 o C does not

of the pre-existing

to an increase

occurs

to P implant

Correspondingly,

strain produced

strain (light line), the change

below

coming

leads

loops.

in the lattice

the configuration

hence

RTA

sivity are left in the two wafers. Fig.

in

remarkable

that this

point defects

is too low to initiate

the

of the interstitial clusters [ 11, we can say that profile alone, relative to the interstitial l I loops

Fig. 1. Strain (z I ) profiles due to: (a) dislocation loops in an SC wafer (light line), damage of 70 keV P+ implant before (dashed line) and after (dotted line) 600 o C, 30 min annealing in a wafer without loops; (b) dislocation loops in an SC wafer annealed at 800°C for 30 min (light line) and dislocation loops in an SC wafer implanted with 70 keV P+ after the same heating (heavy line).

due to absorption

damage

[l]. Since it was ascertained

and the same profile

dislocation

to

strain

A strong

at this low temperature

is ineffective

point-

at 600 ’ C for 30

as a dotted recently

is

with P and not containing residual

occurs

the

one has to

and interstitial

to the

amorphous

which

islands

rise

was

It

400

200 Depth (nm)

due to P is

dose and energy,

gives

reduction

to the

due to P, as in the case of

A furnace

min of the sample

according

profiles,

at similar

in the form of amorphous

made at

layer. Although

for both

that the damage

Si+ implantation

implant

distribution

amorphous

is the same

asso-

line in the same figure.

the damage

the recrystallized

sign of E I

profile

dose in a virgin or an layer

0

loops.

of SC is shown in fig.

line. A phosphorus

0

to as the start-

The strain

70 keV energy and 1 X 1014 cm-* profile

epiof a

in which phosphorus

with the loop distribution

10

to the

regrows

dislocation

referred

*g

[l].

to the formation

(SC) for the samples

la by a continuous

substrate

which

perfect

,-’

surface

tail of inter-

crystalline

and

interstitial

will be subsequently

in the

thick

exponential

will be hereafter

ing condition

nm

silicon,

silicon,

of

ions described

200

C for 30 min leads

of the amorphous

taxially

ciated

a

in the underlying

heating

recovery

of silicon

produces

layer and a nearly

defects

This

implant

section

amorphous stitial

20

analysis

be made:

I,

through

cm3/atom i) only

the

loop configuration

in

clusters

surface

due to the P

layer of SC wafer

at 750 o C for 60 min. Concurrently

dissolution,

the interstitial

concentration

in

349

M. Seruidori et al. / Reduction of P transient enhanced diffusion

Table 1 Maximum of strain distribution (EF ), integral strain (I,) and concentration of interstitials collapsed in the dislocation loops (C,) determined after different implant and annealing Processes. Starting condition (SC) is the result of the process leading to the formation of a buried layer of dislocation loops in otherwise perfect silicon. Process

lo3 frnax I

10’ I,(cm)

loo-‘” C,(cm-‘)

Starting condition (SC) SC+8OO’C, 30 min se+ loooOc, 10 s

1.7OkO.05 1.72 + 0.05 1.15kO.03

6.3 ZtE 0.2 6.3 * 0.2 5.5 * 0.2

5.5 + 0.4 5.5 f 0.4 4.8 it 0.3

SC+P* 70 keV+750”C, 15 min SC+P+70keV+750°C,60min SC+Pe 70keV+750°C,240min SC+P+70keV+800°C,30min SC+P* 70keV+1000°C,10s

2.43 k 0.07 2.37 k 0.07 2.39 2 0.07 2.28 i 0.07 1.51~0.05

.%0+0.3 8.1+0.3 8.lkO.3 7.6 * 0.3 6.7iO.3

7.0 * 0.5 7.1*0.5 7.1 rf 0.5 6.1* 0.5 5.9kO.4

SC+P+160keV+8~°C,30~n

3.10*0.09

9.7 * 0.4

8.5 ~fr0.6

the loops increases, until higher annealing temperatures promote the beginning of loop recovery. All the results reported till now refer to the damage analysis in an SC wafer and in an SC wafer implanted with 1 x lOI cm-’ >70 kev P ions. Qualitatively similar considerations can be made if an SC wafer is implanted with phosphorus at 2 x 1014 cms2 dose and 160 keV energy. The strain distribution of the damage produced by the P implant is wider and higher than in the

0

0 30

3.2. Analysis of phosphorus distributions

20 10 I/

n

previous case (fig. 2a, dashed line), and reaches a depth greater than loop position. The recovery by a 600 o C, 30 mm annealing of the amorphous islands gives the strain profile relative to interstitial clusters, shown in the figure as a dotted line. The dotted profile in the sample without dislocation loops and the same profile with the light one in the wafer containing the extended defects represent the defect distributions which are able to affect phosphorus diffusivity during subsequent heatings at higher temperatures. Fig. 2b shows the situation after SOO”C, 30 min annealing. Unlike fig. 1, a residual fraction of clusters survives in the sample without loops, whereas a still more marked increase in e I below 200 nm occurs if the clusters dissolve in presence of them. Even in this case one deduces that strong absorption of interstitials by the adjacent loops and gettering effect were operating, as no clusters are detected in the wafer with loops. The enhancement of interaction between pre-existing loops and interstitials released from cluster dissolution, as observed for 160 keV P implant, can be interpreted as the consequence of a higher cluster density given by P ions and a partial overlapping between cluster and loop distributions. This condition favours a stronger gettering action. A numerical summary is reported in table 1.

-

” 0

‘, 200 Depth

I

I

b)

400 (nm)

Fig. 2. The profiles are read in the same way as in fig. 1, but refer to P+ implanted at 160 keV. In (b) the residual damage of P+ implant

in the wafer

without line).

loops

is shown

(dotted

The effect of the dislocation loops on P diffusivity is evidenced by SIMS measurements. The evolution of P distribution after annealing at 800 o C for 10 min is shown by the profiles reported in fig. 3 for specimens implanted at 70 and 160 keV. The results show the reduction of ED in presence of dislocation loops. As to the samples implanted at 70 keV without pre-existing dislocations (light line), a marked broadening of the profile is observed (fig. 3a); this is due to a strong ED assisted by the interstitial excess generated by cluster dissolution. In the presence of IV. S~M~~ONDUCTO~S:

Si

M. Servidori et al. / Reduction of P transient enhanced diffusion

350

I 800

1Oy

-

I I I ‘C, 10min

I

I

I

pearance presence

:

----as

implanted loops : -without loops

of the 70 keV P damage (fig. lb) and the of a residual fraction of the 160 keV P damage

(fig. 2b, dotted

-with

heating

line),

A reduced observed

effect

after

difference

I

sistent

with

extended

-

b) :

extent

by TCD

after

the same

the loops

at 1000°C

on for

depths

P diffusivity

is

10 s. In fact

the

in the samples

loops was only 25 nm and about

70 and 160 keV

a) -

I I

of

RTA

in the junction

and without

I I

observed

process.

P implants,

the fact

defects

that

respectively.

both

and transient

of which

decreases

This

dopant ED

with

with

0 for the is con-

segregation

on

are phenomena

the

temperature

increase

]5,91.

4. Conclusions i)

The interstitial dissolve stitials

0

0.2

lead

ii)

loops

between

(heavy

which the dislocations tion

results

greater

and hence

concentration action

P atoms.

This

diffusivity,

at 200

played

to lower

dopant

tail and the junction

depth

similar

implanted dopant

loops.

The absorption

distribution

stitials

on the extended

of 70 keV energy, side.

even

loops.

reason

interstitials

further

20 min

the

in the the same

obtained

for

interloop

iii) The presence prevent,

of a dislocation

via

trapping atoms,

of

by the dislocation of the clusters

loop

silicon

below

planted

P distribution

is shallower

barrier

fects through dopants

that

implanted

the loop

depth,

of P diffusivity. than in the absence diffusion

related

excess

is the

hanced

diffusion.

factor

[3,5].

exceeds excess

rise to an appreciable

less evident are closely

layers

P distribution

enhancement iv) The enhanced

de-

the lack of ED for

of the interstitial

giving

are a

of point

in pre-amorphized

a fraction

in the bulk,

loops

for the passage

them and explains

P dif-

if the im-

than their depth.

the dislocation

In the case where the original diffuses

the loops,

to and

anomalous

in the region

demonstrates

faster.

is able

interstitials

any detectable

fusivity This

layer

This

ED

and the cluster

phenomena, responsible

is however

of the loops. i.e. for

dissolution

the interstitial transient

en-

the

escape

the ED

shift

and silicon

inter-

atoms

in the sample

process.

at 800” C leads

is

without

fraction

of the clusters

the trapping

of

in the An adto no

at 70 keV and to a

for P implanted matches

from

of phosphorus

a non-negligible

of P implanted result

References

on the dislocation

is larger than in the case

than

of annealing

junction This

were

by dissolution

redistribution

shown).

are nearly

the loops collect

of this, is that

released

still evident (not

loops also on

distribution

is peaked

defects

if lower

tail of P implant ditional

P the

with the reduced

of the P atoms

because

In spite

noticeable, The

results

released

in the dislocation

at 160 keV (fig. 3b). In this case the

initial

either

The for

annealing.

Qualitatively samples

by

the P flow beyond

the

the

of the interstitials

very effective

defect

evidence

by the dislocation

therefore,

as those before

the point

of phosphorus.

together

at

at depths

of interstitials

nm gives

phenomenon,

only in

the P distribu-

contrast,

reduces

the diffusivity

contributes

layer;

profile

By

strongly

peak

gettering

loop

flattened.

defects

ED

and 200 nm, depth

200 nm the absorption

the extended excess

we observe

are: in this region

in fact

than

line),

the surface

to an increase

The absorption

phosphorus

the region

by P implantation

and

loops makes the disappearance

Fig. 3. SIMS profiles of P implanted at 70 keV (a) and 160 keV (b) after 800 o C, 10 rain annealing.

dislocation

generated

annealing

size.

0.6

04 Depth (pm)

clusters

during

quite

at 160 keV

well the disap-

[l] M. Servidori, Z. Sourek and S. Solmi, J. Appl. Phys. 62 (1987) 1723. [2] S. Sohni, R. Angelucci, F. Cembali, M. Servidori and M. Anderle, Appl. Phys. Lett. 51 (1987) 331. [3] T.O. Sedgwick, A.E. Michel, V.R. Deline, S.A. Cohen and J.B. Lasky, J. Appl. Phys. 63 (1988) 1452. [4] M. Servidori, R. Angelucci, F. Cembali, P. Negrini, S. Solmi, P. Zaumseil and U. Winter, J. Appl. Phys. 61 (1987) 1834. [5] S. Solmi and M. Servidori, in: Ion Implantation in Semiconductors, eds. D. Stievenard and J.C. Bourgoin (Trans. Techn. Publications Ltd., 1986) p. 65.

351

M. Servidori et al. / Reduction of P transient enhanced diJJmion [6] P. Zaumseil, Phys. Status SoIidi (a)91 (1985) K31. [7] P. Zaumseil, U. Winter, F. Cembali, M. Servidori Sourek, Phys. Status Solidi (a)100 (1987) 95.

and Z.

[S] F. Cembali, M. Servidori and A. Zani, Solid-State 28 (1985) 933. [9] M.M. Mandurah, K.C. Saraswat, C.R. Helms Kamins, J. Appl. Phys. 51 (1981) 5755.

Electron. and

IV. SEMICONDUCTORS:

T.I.

Si