ANNEALING AND STRIPPING STUDIES ON 57Fe IN SILICON

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ANNEALING AND STRIPPING STUDIES ON 57Fe IN SILICON

S. Damgaard, J. Petersen, G. Weyer

To cite this version:

S. Damgaard, J. Petersen, G. Weyer. ANNEALING AND STRIPPING STUDIES ON 57Fe IN SILI- CON. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-427-C1-428. �10.1051/jphyscol:19801166�.

�jpa-00219653�

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JOURNAL DE PHYSIQUE

Cotl~que Cl,@tppl4ment

au

n

^O

1, Tome

41,

janvier 1980, page C1-427

ANNEALING AND STRIPPING SllJD1f.S QN $'$e IN SILICOlJ

S. Damgaard, J.W. Peeersen and G . V+y,ez

Institrc6e

of Physics, University of Aarhus, DK-8000 Aarhus C, Denmark.

1. Introduction

An implantatipn of high doses of 5 7 ~ e _,.,..,

I I I I I

(10'

5 - ~ q 1

6atoms/~m2) into silicon results in MBss- bauer spectra which c o n s i ~ t of two broadeqed lines of nearly equal inteqsity (1

1.

Experimental eviden- ce has been obtained that the main part of these ppectra is due to a quadrupole split doublet [ Z ] ,

From isochroqal annealiftg studies on implanted samples ( 3 1 , it is established that the Massbauer

spectrum changes drastically upon an annealing a-

-

hove 600 OC. The quadrupole splitting changes frqn E 2 0.8 mm/sec to E

=

0.45 mm/sec.

Q Q

The distributioo 06 iron in a roomrtemperafure implanted sample is well known [ 4 ] . However, no eyt

6D2 perimental information on the distribution of iron

after an annealing has so far been given.

-

¹ ^'-⁵ ⁰ ^+.S ^{+ I}

It is demonstrated here that the iron depth VELOCITY rmmlsecl

profile after a high temperature annealing ($0o0~) Figure : Mbssbauer spectra of 57Fe in (a) changes drastically and a depth dependence of the

directly aPtey the implantcltion, (b) 87ter anneal- Mbssbauer spectra is found.

ing at 600'~ and 9 0 0 ' ~

f ~ r

20 min, and

(el

after 2. Experimental results and discussion

The 5 7 ~ e was implanted in Si single crystals (F2.n-type,S@m) using an isotope separator (8OkeV at r.t. to a dose of 1-10' 5atoms/cm2). Fqr such im- plantation conditionsr 3 Gaussian diskribufi~n q4 iron in silicon with an average depth of ~ ~ ~ 6 6 0 4 and a half width of Rp= 220 A is ~btained 141.

Conversion electron Mbssbauer spepbra were measured in backscatterinq geometry usiqg a 10 mCi

"CO (Rh) source. The implanted sample was incar- porated in a parallel plate avalanche aounter 151.

stripp$ng of".100 A 5rom

t;hc

annealed sample, Figure la displays the Mbssbauer spectrum measured directly after the implantation. The data have bean qqalysed assuming a quadrupole spLit doublet, The splikting is determined to E n

Q

=

0:9 qd'sep, the isomer shift to 6 r! 0.2 mm($e~

(relative to a-Fe)

,

and the linewidth to

r =

0.5 d s e c ? It is clear, however, from the &-

~ ~ P U S miefit that more lines have to be include4 for a gatisfactory explanation of the spectqqm,

In fig.lb, the Mbssbauer spectrum aftel; the sample has been annealed consecutively for 20 min

29

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19801166

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CI-428 JOURNAL DE PHYSIQUE

a t 6 0 0 ' ~ and 9 0 0 ' ~ i s shown. I f analysed i n terms of a quadrupole s p l i t d o u b l e t t h e s p l i t t i n g and t h e l i n e w i d t h d e c r e a s e t o Ep = 0.45 mm/sec and

r

= 0.35 mm/sec. The t o t a l a r e a of t h e spectrum i n - c r e a s e s w h i c h i n d i c a t e s t h a t t h e Debye-Waller f a c t - o r h a s i n c r e a s e d . Again, obviously, more than two l i n e s a r e n e c e s s a r y f o r a r e a s o m b l e f i t t o t h e d a t a .

Anodic s t r i p p i n g of a s u r f a c e l a y e r (%I00 A ) y i e l d s t h e Mijssbauer spectrum i n f i g . 1 ~ . A f i t with a s i n g l e l i n e d e t e r m i n e s t h e isomer s h i f t t o

6 = -0.1 mn/sec ( r e l a t i v e t o a - F e ) and

r=

0.3 mm/sec.

From t h e i n t e n s i t y of t h e l i n e it can be concluded t h a t o n l y -10% o f t h e i r o n i s l e f t a f t e r t h e s u r f a - c e l a y e r h a s been removed and correspondingly 90%

i s found i n t h e s u r f a c e l a y e r . Thus spectrum l b is dominantly due t o t h e i r o n i n t h e s u r f a c e l a y e r . In f a c t , t h e spectrum shown i n f i g . l b d i s p l a y s a f i t with two independent l i n e s 6,= -0.13 ( 3 ) mm/sec, 6 =

= 0 - 0 3 ( 3 ) mm/sec ( r e l a t i v e t o a-Fe)

,

and

r,=

= 0 . 3 6 ( 3 ) mm/sec,

T2

= 0.27(3) mm/sec. The l i n e a t 6 = -0.13(3) mm/sec i s much b r o a d e r than t h e o t h e r and t h e m i s f i t i n d i c a t e s t h e p r e s e n c e of a n o t h e r l i n e a t about 6

-

-0.1 mm/sec ( r e l a t i v e t o a-Fe) a l s o .in t h i s spectrum.

The compound FeSiP shows a quadrupole d o u b l e t with about t h e same s p l i t t i n g and isomer s h i f t [ 6 ] a s spectrum l b , t h u s presumably t h i s s t r u c t u r e is formed i n t h e s u r f a c e l a y e r a f t e r a high-temper- a t u r e annealing.

The s i n g l e l i n e o f spectrum l c i s o n l y s l i g h t - l y broader t h a n t h e n a t u r a l l i n e w i d t h . T h e r e f o r e it i s tempting t o assume t h a t t h i s spectrum i s due t o i r o n atoms on h i g h l y symmetric l a t t i c e s i t e s i n t h e s i l i c o n m a t r i x . It should b e noted, however, t h a t t h e c o n c e n t r a t i o n of i r o n f o r t h i s f r a c t i o n i s a t l e a s t 3 o r d e r s o f magnitude above t h e max- imum s o l i d s o l u b i l i t y [7

1.

3. Conclusion

Room-temperature implanted samples of i r o n

i n

s i l i c o n c o n s i s t of two d i f f e r e n t f r a c t i o n s of i r o n a f t e r an a n n e a l i n g a t 6 0 0 ' ~ and 9 0 0 ' ~ . I n a s u r f a c e l a y e r (1,100 fi),which shows a d o u b l e t speCtrum,presumably n r e c i r i t a t e s . of FeSiP a r e formed. A t l a r g - e r d e p t h s a small f r a c t i o n o f t h e i r o n atoms shows a s i n g l e t spectrum. T h i s i s a t t r i b u t e d t o i r o n oc- cupying well-defined s i t e s i n t h e s i l i c o n l a t t i c 8 . T h i s work h a s been supported by t h e Danish N a t u r a l S c i e n c e Research Council.

References

[ I ] Sawicka, B.D., Sawicki, J . , and Stanek, J . , J.

Physique C o 1 l o q . z (1976) C6-879

[ 2 ] Sawicka, B.D. and Sawicka, J . A . , Phys.Lett.

64A (1977) 311

-

1.31 Sawicki, J.Sawicka, B., Stanek, J . , and Kowalski, J., Phys.Stat.Sol.(b)

77

(1976) K1 [ 4 ] Lindhard, J . , S c h a r f f , M . , and S c h i @ t t , H.E.,

Kgl.Danske Videnskab.Selskab,Wat.-Fys.Medd.2 (1963) no.14

[5! Weyer, G . , MBssbauer E f f e c t Method., ( e d s .Gru- vermann, I.J. and S e i d e l , C.W.),

10

(1976) 301 [ 6 ] Vojtechovsky. K . , and Zemcik, T . , C2ech.J.

P h y s . 5 2 (1974) 171

[7! rileber, E. and R i o t t e , H.G., Appl.Phys.Lett.3-3.

(1978) 433