Characterization of silicon by ion beam techniques

INTRODUCTION C H A R A C T E R I Z A T I O N OF SILICON BY ION BEAM TECHNIQUES P. Siffert Centrede RecherchesNucleaires,Groupede Physiqueet Applicatonsdes Semic0nducteurs(PHASE), 67037 Strasbourg Cedex, France

ABSTRACT: The object

of

this

s e r i e s o f p a p e r s is to r e v i e w the v a r i o u s

p o s s i b i l i t i e s o f f e r e d by i o n beam t e c h n i q u e s f o r of

silicon material

sively

the characterization

and d e v i c e s . T h e f o l l o w i n g t e c h n i q u e s a r e s u c c e s -

considered: - S e c o n d a r y Ion Mass S p e c t r o m e t r y ( S I M S ) -Rutherford

Backscattering

Spectrometry

- L o w E n e r g y Ion S c a t t e r i n g S p e c t r o m e t r y

(RBS) (ISS)

-Charged particle Activation Analysis •- H e a v y Ion X - r a y In o r d e r t o a l l o w characterization

Emi ssi on ( H E H I X E ) comparisons,

h a v e been b r i e f l y

three

o t h e r methods f o r b u l k

considered:

- S p a r k S o u r c e Mass S p e c t r o m e t r y

(SSMS)

- N e u t r on A c t i v a t ion A n a l y s i s -Atomic Emission Spectrometry from Inductively Coupled Plasma.

4

P. Siffert

I N T

R C

D LI C T

I 0

1~

When the planar technology was introduced into solid state electronics a r o u n d 1960, o n e c a n c o n s i d e r t h a t a n e w e r a b e g a n , t h a t o f S I L I C C N . T h i s f i e l d i s in v e r y f a s t e x p a n s i o n ( F i g . 1) a n d h a s g i v e n r i s e to new analytical techniques, among them ion-beam methods. These latter have been introduced ,at least for the higher energy domain, by physicists preparing solid state detectors ,first o f S c h o t t k y t y p e a n d t h e n on t h o s e m a d e b y i o n i m p lantation. Today, s i l i c o n t e c h n o l o g y i s d i r e c t e d in t w o o p p o s i t e d i r e c t i o n s : - micro-devices a s s e m b l e d in v e r y s o p h i s t i c a t e d circuits , highly integrated (V/SI) p r e p a r e d on h i g h p u r i t y s i n g l e c r y s t a l l i n e material, called _"~lectr°nic g r a d e " . S i n c e t h e r e s i d u a l i m p u r i t i e s a r e o f t e n b e l o w 10 E 16 cm , very sensitive methods are needed for analyzing the bulk. For device investigation, on t h e m i c r o n s c a l e , d u e t o m o r e a n d m o r e l a r g e r i n t e g r a t i o n ( F i g . 2), l o c a l a n a l y s i s i s n e e d e d , in g e n e r a l in r a t h e r c l o s e s u r f a c e v i c i n i t y (micron). Here, beam techniques play a dominant role , allowing localized investigati o n s , e v e n i m a g i n g ( F i g . 3). Fig. 1 : Evolution of circuits complexi t y as a f u n c t i o n o f y e a r s ( I ). tGM

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Characterization of silicon by ion beam techniques

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J SELLER J MARKET

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1979

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1981

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1984

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1986

1987

YEAR Fig.

: Evolution future as

of the silicon demand expected by DOE.

in

recent

years

and

in

the

P. Siffert

- m a c r - o - j u n c t i o n s , o p e r a t i n g in the p h o t o v o l t a i c mode and c o n v e r , t i n g d i r e c t l y solar- e n e r g y i n t o e l e c t r i c i t y . For, t h i s put,pose, even i f s i n g l e c r y s t a l l i n e s i l i c o n is a l m o s t e x c l u s i v e l y e m p l o y e d today, in a near` futur'e, p o l y s i l i c o n and even amor,phous f i l m s w i l l be used. F u r t h e r m o r e , to r-educe the c o s t e v e n mot,e, less p u r e s i l i c o n c a l l e d " s o l a r gr,ade m e t a l l u r g i c a l s i l i c o n " , in w h i c h o n l y i m p u r , i t i e s r e d u c i n g the d e v i c e perr`for,mance ( F i g 4) h a v e been e l i m i n a t e d , w i l l pr,obably have to be used. Her,e a g a i n , to i n v e s t i g a t e t he b e h a v i o r o f i m p u r i t i e s w i t h i n as w e l l as at gr,ain boundar,ies, h i g h s p a t i a l r e s o l u tion a n a l y t i c a l methods a r e needed.

1.8

N -type

N

m

~

m

0

~

i

1.0

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Ik

Fig.

4 : Effect of v a r i o u s

i m p u r i t i e s on e f f i c i e n c y o f s i n g l e c r y s t a l l i n e

N and P - t y p e s i l i c o n s o l a r c e l l s

(SALLES

(2)).

7.

Characterization of silicon by ion beam techniques M o r e g e n e r a l l y , in o u r o p i n i o n , the key w o r d s in s i l i c o n technology w i l l be e l e c t r o n s , photons and ions ,not o n l y in the m a n u f a c t u r i n g p r o c e s s of t h e d e v i c e s , i n c l u d i n g masks, but a l s o for the c h a r a c t e r i z a t i o n of both the s t a r t i n g m a t e r i a l and the v a r i o u s l a y e r s p r e p a r e d on it: dopant d i f f u s i o n , ion implantation p r o f i l e s and l a t e r a l d i s t r i b u t i o n s , s i l i c i d e s . . . Table I summ a r i z e s the m a j o r a n a l y t i c a l t e c h n i q u e s w h i c h have been developped .

p a r l i c l e Induced ) < - r a y m i l lion (PIXE) h l s h * n ~ - g y heaVy I ~ 1 ~ndo. Ced X - r a y em~lll[ort (;-IF.J~IXE surface ¢~el! I ~ by ~ l l y sis o f n e u t r a t aim I ~ impa¢l radlat I ~• | S C A N IIF;I) charged particle activatl~ analy•l. n u c l e a r rea©l i ~ •

s~ondary ion mail lpectroicopy ( s IM.5) I ~ m[¢ ~ p r o b e mass ~ a l y l i ! (IMM,A ) Rutherford bicklcatterlng ipec. .y ( R B S ) chlr9~ pertlClel actlvatl~ ar~l yl[ s (c PAA) n ~ t e a P p e a c t l o~1 ion l e a tt e r l n 9 s p K t r o s c o p y

I.S~ eleclr~ ~rgy m e l r y ( EF--L ) • lectr~

photon actl vat I ~ enal y l l • (PAA) l a s e r p r o b e mess s p l c c r o m e t r y (LPMS)

m] ¢ r o • ~ p y

eleCtrOfl SPeCt r O•COpy

UV pnoloel~lron tUPS)

eleCtron microProbe snalysil (EMP) jca~lng tp~lmi ii[~ ele¢ Ir~ m~croscow (STEM)

(EM)

X ~ e y Induced p h o t o - e l ~ t r ~ spectroscopy IXPS) e l e c t r o ~ spmclroscoPy f o r A~S)

TABLE

los• spectrol

X-ray fl~r~c~* I p * c t ru~ l a s e r induced optical e m l s • i o •p*ctroscopy i um Inesc41~ce phlon a b s o r p t i o n

lpectro•cop~

I: V a r i o u s t e c h n i q u e s used for c h a r a c t e r i z a t i o n ions e l e c t r o n s and photons.

using

H e r e , we r e s t r i c t o u r s e l f to r e v i e w the m a j o r ion beam methods for silicon characterization•They have given r i s e to s e v e r a l i n t e r n a t i o n a l m e e t i n g s ( 3 - ? ) s i n c e the e a r l i e r c o n f e r e n c e in Y o r k t o w n H e i g h t s in 19?3. S e v e r a l books and r e v i e w p a p e r s (8 - 31) have c o n s i d e r e d v a r i o u s a s p e c t s of the p r o b l e m . H o w e v e r , to o u r knowledge, none of them have put s p e c i a l e m p h a s i s on s o l a r s i l i c o n . T h e methods we a r e c o n s i d e r i n g are: 1. S e c o n d a r y Ion M a s s S p e c t r o m e t r y , by R. S T U C K and P . S I F F E R T 2. R u t h e r f o r d B a c k s c a t t e r i n g S p e c t r o m e t r y by J . J . G R O B and P • S I F F E R T 3. L o w E n e r g y Ion S c a t t e r i n g S p e c t r o m e t r y by ,J• ,.I. G R O B and P . S I F F E R T 4. A c t i v a t i o n ,z~J'lalysis by U s i n g C h a r g e d P a r t i c l e A c c e l e r a t o r s ~by U . L . DE BRUN 5. H e a v y Ion Induced X - r a y E m i s s i o n by Ch. H E I T Z In o r d e r to a l l o w c o m p a r i s o n s w i t h o t h e r t e c h n i q u e s , t h r e e of them a r e briefly described: 6. S p a r k S o u r c e M a s s S p e c t r o m e t r y by L . L A S N E , J. G A Z E T - T A L V A N D E and J . Y . B A R R A U D ?. N e u t r o n A c t i v a t i o n A n a l y s i s by G. R E V E L 8. A t o m i c E m i s s i o n S p e c t r o m e t r y from I n d u c t i v e l y C o u p l e d P l a s m a by D. M O R V A ~ I , J• A~vtOUROUX, P . C L A R A Z . In all t h e s e methods, detection limits and s e n s i t i v i t y play an important role. These terms are defined as follows:

8

P. Siffert

- d e t e c t i o n l i m i t : c o r r e s p o n d s to the minimum c o n c e n t r a t i o n of an i m p u r i t y w h i c h d e l i v e r s in the a n a l y t i c a l s e t - u p a s i g n a l w i t h 95 ~/o c o n f i d e n c e . T h e s i g n a l N must e x c e e d the b a c k g r o u n d N B by t h r e e t i m e s the s q u a r e r o o t of the b a c k g r o u n d (32). - s e n s i t i v i t y : is the s l o p e of the c a l i b r a t i o n cuPve [° e. the change of s i g n a l o u t p u t w i t h i n c r e m e n t of the i m p u r i t y c o n c e n t r a t i o n .

i

I--- AC -.4

NMIN*f

SENSITIVITY = TAN a = A-"~"

3v~ B

LD L o

,~

MATERIAL CONCENTRATION

= DETECTION LIMIT

NMIN = MINIMUM DETECTABLE IMPURITY COUNT Ne

Fig.

5

:

= BACKGROUND COUNT

D e f i n i t i o n o f s e n s i t i v i t y and d e t e c t i o n (A. G. LIEBERIViA~I N B S (32)).

limit

R E F E R E N C E S I. 2. 3. 4. 5. 6. 7.

G . E . M O O R E P r o g r e s s in D i g i t a l I n t e g r a t e d E l e c t r o n i c s IEEE Inter. E l e c t r o n . D e v i c e s M e e t i n g (1975) D. S A L L E S ,unpublished work. J . W . M A Y E R , J. F. Z I E G L E R (ed$) Ion Beam S u r f a c e L a y e r A n a l y s i s P r o c . Y o r k t o w n H e i g h t s C o n f . T h i n S o l i d F i l m s 19 (1974) O. M E Y E R , G. L I N K E R , F. K A E P P L E R (eds) Ion Beam S u r f a c e L a y e r Analysis. P r o c . K a r l s r u h e C o n f . Ed. P l e n u m P r e s s (1976) A. W O L I C K I , J . W . B U T L E R , P . A . T R E ~ D C (eds) Ion Barn A n a l y s i s P r o c . W a s h i n g t o n C o n f . N u c l . I n s t r . Meth. 149 (1978) H . H . A N D E R S E N , d. B ~ T T I G E R , H. KNLID S E N Ion Beam ~ r l a l y s i s P r o c . A a r h u s C o n f . N u c l . I n s t r . Meth 168 (1980) J.~.BIRD, G.J.CLARK ion Beam A n a l y s i s Nucl. Instr. M e t h . 181 (1981).

Proc. Sydney Conf.

FUNDAMENTAL e. Atomic Collision and P e n e t r a t i o n S t u d i e s . C o n f . P r o c . C h a l k R i v e r ( 1 9 6 7 ) U n i v e r s i t y o f T o r o n t o P r e s s (1967) 9. D . W . P A L M E R , M. W. T H O M P S O N , P . D . T O W N S E N D A t o m i c C o l l i s i o n P h e n o m e n a in S o l i d s C o n f . P r o c . U n i v e r s i t y of S u s s e x (1969) N o r t h H o l l a n d ed A m s t e r d a m (1970)

Characterization of silicon by ion beam techniques 10. 11. 12.

D . V . M O R G A N (ed) C h a n n e l l i n g J. W i l e y N e w Y o r k (1973) S. D A T Z , B. R. A P P L E T O N , C. D. M O A K (~ds) P r o c . C o n f . G a t l i n b u r g ( 1 9 7 3 ) P l e n u m P r e s s (1975). F . W. S A R I S , W. F . V A N D E R WEG ( e d s ) C o n f . P r o c . A m s t e r d a m (1975) N u c l . I n s t r . M e t h . 132 ( 1 9 7 6 ) .

ION I M P L A N T A T I O N 13. 14. 15. 16. 17. 18. 19. 20. 21 22.

J. W AYER, L.E RIKSON,J. A. DAVIS Ion I m p l a n t a t i o n in S e m i c o n d u c t o r s . A c a d e m i c P r e s s ( 1 9?0) F.H. EISEN, L.T. CHADDERTON,J.A. DAVIS I o n I m p l a n t a t i o n in S e m i conductors. P roc. Conf. Thousand Oaks. G o r d o n and B r e a c h ed. New York (1971). I. R U G E , J. G R A U L ( e d s ) Ion I m p l a n t a t i o n in S e m i c o n d u c t o r s . P r o c . Conf. Garmisch Partenkirchen S p r i n g e r V e r l a g ed (1971). B . L . C R O W D E R ( e d ) Ion I m p l a n t a t i o n in S e m i c o n d u c t o r s and O t h e r M a t e r i a l s Pr'oc. C o n f . Y o r k t o w n H e i g h t s P l e n u m P r e s s (1973) G. D E A N N A L E Y , J. H. F R E E M A N p R. S . N E L S O N , J. S T E P H E N Ion I m p l a n t a t i o n N o r t h H o l l a n d A m s t e r d a m (1973). S. N A M B A ( e d ) I o n I m p l a n t at ion in S e m i c o n d u c t o r s P r o c . C o n f . Osaka . Plenum tess (1975). P.D. TOWNSEND,J.C. KELLY, N.E.W. H A R T L E Y (eds) Ion I m p l a n t a t i o n S p u t t e r i n g and t h e i r A p p l i c a t i o n s A c a d e m i c P r e s s N e w Y o r k (1976) G. K A R T E R , W . A . vRANT Ion Implantation of Semiconductors Wiley, New York (1977;. F. C H E R N O W , J . A . B O R D E I - < S , D . K . B R I C E (eds) Ion I m p l a n t a t i o n in S e m i c o n d u c t o r s and O t h e r M a t e r i a l s P r o c . B o u l d e r C o n f . P l e n u m P r e s s (1977). J . K . H I R O V E N (ed) I o n I m p l a n t a t i o n T r e a t i s e on M a t e r i a l S c i e n c e and T e c h n o l o g y V o l . 18 A c a d e m i c P r e s s (1980).

MATERIAL 23. 24. 25. 26. 27. 28. 29. 30. 31.

I NVESTIGATION

P . F . K A N E , G . B . L A R R A B E E (eds) C h a r a c t e r i z a t i o n o f S o l i d S u r f aces P l e n u m P r e s s (1974). J . F . Z I E G L E R ( e d ) N e w Uses of Ion A c c e l e r a t o r s P l e n u m P r e s s (75) G. C A R T E R , J . S. C O L L I G O N , W . A . G R A N T A p p l i c a t i o n o f Ion Beams to M a t e r i a l s I nst i t u t e o f P h y s i c s C o n f . S e r i e s 28 (1976) L o n d o n . A.W. CZANDERNA(ed) M e t h o d s of S u r f a c e A n a l y s i s . E l s e v i e r A m s t e r d a m (19 75). J . W . A Y E R , E. RI M I N I I on Beam H a n d b o o k f o r M a t e r i a l A n a l y s i s A c a d e m i c P r e s s N e w o r k (1977). A . C A C H A R D, J. P. T H O M A S ~ M a t e r i a l C h a r a c t e r i z a t i o n u s i n g Ion Beams P l e n u m P r e s s (1977). W . K . C H U , J . W . A Y E R , M. A. NICOLP__T B a c k s c a t t e r i n g S p e c t r o m e t r y A c a d e m i c P r e s s N e w Y o r k (1978) L . F I E R M A N S , J. V E N N I K , W. D E K E Y S E R El e c t r o n and Ion S p e c t r o m e t r y of S o l i d s . P l e n u m r e s s (1978) G.B. LARRABEE~ VLSI Electronics~Microstructure Science Vol. 2 p. 3? ed. N . E I N S P R U C H . A c a d e m i c P r e s s (1981). 888888888888

32.

A.G. LIEBERMAN

N B S S p e c i a l P u b l i c a t i o n 4 0 0 - 2 3 p. 3(1976)