INTRODUCTION

CHARACTERIZATION OF SILICON BY ION BEAM TECHNIQUES

P. Siffert

Centre de Recherches Nucleaires, Groupe de Physique et Applicatons des Semic0nducteurs (PHASE), 67037 Strasbourg Cedex, France

A B S T R A C T :

The o b j e c t o f t h i s s e r i e s o f papers 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 red by i o n beam techn iques f o r t h e c h a r a c t e r i z a t i o n

of s i l i c o n m a t e r i a l and d e v i c e s . The f o l l o w i n g t echn iques a r e succes -

s i v e l y c o n s i d e r e d :

- S e c o n d a r y Ion Mass S p e c t r o m e t r y (S IMS)

- 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 (RBS)

- 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 ( ISS)

- C h a r g e d p a r t i c l e A c t i v a t i o n A n a l y s i s

• -Heavy Ion X - r a y Emi ssi on ( HEHI XE)

In o r d e r t o a l l o w compar i sons , t h r e e o the r methods fo r bulk

c h a r a c t e r i z a t i o n have been b r i e f l y c o n s i d e r e d :

- 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 va t ion A n a l y s i s

- A t o m i c Emiss ion S p e c t r o m e t r y f r o m Induc t i ve l y Coup led P lasma.

4 P. Siffert

I N T R C D LI C T I 0 1~

When the p l a n a r t e c h n o l o g y w a s i n t r o d u c e d i n to s o l i d s t a t e e l e c t r o n i c s a r o u n d 1960, one can c o n s i d e r tha t a n e w e r a began , tha t o f S I L I C C N . T h i s f i e l d is in v e r y f as t e x p a n s i o n ( F i g . 1) and has g i v e n r i s e to n e w a n a - l y t i c a l t e c h n i q u e s , among them i o n - b e a m m e t h o d s . T h e s e l a t t e r have been i n t - r o d u c e d , a t l e a s t f o r the h i g h e r e n e r g y d o m a i n , by p h y s i c i s t s p r e p a r i n g s o l i d s t a t e d e t e c t o r s , f i r s t o f S c h o t t k y t y p e and then on t h o s e m a d e by ion i m p - l a n t a t i o n .

T o d a y , s i l i c o n t e c h n o l o g y is 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 : - m i c r o - d e v i c e s 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 c i r c u i t s , h i g h l y i n t e g r a t e d ( V / S I ) p r e p a r e d on h igh p u r i t y s i n g l e c r y s t a l l i n e m a t e r i a l , c a l l e d _ " ~ l e c t r ° n i c g r a d e " . S i n c e the 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 , v e r y s e n s i t i v e m e t h o d s a r e n e e d e d f o r a n a l y z i n g the b u l k . F o r d e v i c e i n v e s t i g a t i o n , on the m i c r o n s c a l e , due to m o r e and 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 ca l a n a l y s i s is 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 ( m i c r o n ) . H e r e , beam t e c h n i q u e s p l a y a d o m i n a n t r o l e , a l l o w i n g l o c a l i z e d i n v e s t i g a t - i ons , even i m a g i n g ( F i g . 3).

F i g . 1 : E v o l u t i o n o f c i r c u i t s c o m p l e x - i t y as a f u n c t i o n o f y e a r s ( I ).

tGM

I MOS LOGIC - - Z96 ~ • BIPOLAR LOGIC

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F i g u r e 2 : S u r f a c e isnaging o f s i l i c o n c o v e r e d w i t h B , 0 0 0 A a l u m i n i u m s t r i p s as s e e m s by s i m s ( C A M E C A d o c u m e n t )

Characterization of silicon by ion beam techniques 5

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F i g .

J ~__ :$:THE SOLAR PHOTOVOLTAIC ENERGY RESEARCH, DEVELOPMENT AND DEMONSTRATION ACT OF 1978

J (PUBLIC LAW 95-590) SELLER J DATED NOV 4, 1978

MARKET J :Ic~DATA FROM INDUSTRY SURVEY, J AND PUBLISHING MATERIAL

LISTED IN APPENDIX OF MAIN J REPORT I

I I J I I I I 1979 1980 1981 1982 1983 1984 1985 1986

YEAR

: E v o l u t i o n o f t h e s i l i c o n d e m a n d in r e c e n t y e a r s a n d in t h e f u t u r e a s e x p e c t e d b y D O E .

1987

P. Siffert

- macr -o- junc t ions , 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 conver, t ing d i r e c t l y solar- e n e r g y in to e l e c t r i c i t y . For, th is put,pose, even i f s i ng le c r y s t a l l i n e s i l i c o n is a lmost e x c l u s i v e l y employed today, in a near` futur'e, p o l y - s i l i c o n and even amor,phous f i lms w i l l be used. F u r t h e r m o r e , to r-educe the cost even mot,e, less pu re s i l i c o n ca l l ed " 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 wh ich on l y impur, i t ies reduc ing the dev ice perr`for,mance ( F ig 4) have been e l im ina ted , w i l l pr,obably have to be used. Her,e again, to i nves t i ga te the beha- v i o r o f i m p u r i t i e s w i t h i n as we l l as at gr,ain boundar, ies, h igh spa t ia l r e s o l u - t ion a n a l y t i c a l methods a re needed.

1.8

N m ~ m 0 ~ i

N - t ype

1 . 0

I k

P - t y p e

F ig . 4 : E f fec t 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 ency of s ing le c r y s t a l l i n e

N and P - t ype s i l i c o n so l a r ce l l s ( S A L L E S (2)).

Characterization of silicon by ion beam techniques 7.

M o r e genera l l y , in our opinion, the key words in s i l i con technology wi l l be e lec t rons , photons and ions ,not only in the manufactur ing p rocess of t h e dev ices , i n c l u d i n g masks, but a lso for the c h a r a c t e r i z a t i o n of both the s ta r t ing mater ia l and the v a r i o u s l aye rs p r e p a r e d on it: dopant d i f fusion, ion implantat ion p r o f i l e s and la tera l d is t r ibu t ions , s i l i c i d e s . . . T a b l e I sum- m a r i z e s the major ana ly t ica l techniques which have been developped .

s~onda ry i on mai l l pec t ro i - copy ( s IM.5) I ~ m[¢ ~probe mass ~a l y l i ! (IMM, A ) Ruther fo rd b ick lca t te r lng i pec .

.y (RBS) ch l r9~ pe r t lC le l ac t l va t l~ a r~ l y l [ s ( c PAA) n~ teaP peac t l o~1

ion l ea tt e r ln9 spK t roscopy I.S~

photon act l vat I ~ enal y l l • (PAA) l ase r p robe mess sp lcc romet ry ( LPMS)

e lec l r~ ~ rgy los • spec t ro l me l ry ( EF--L )

• l e c t r~ m] ¢ ro •~py (EM)

X~ey Induced pho to -e l~ t r~ spec t roscopy IXPS) e lec t ro~ spmclroscoPy fo r

A~S) eleCtrOfl SPeCt r O•COpy

UV pno loe l~ l ron lpec t ro •cop~ tUPS)

pa r l i c l e Induced )< - ray m i l - l i on (P IXE) h lsh *n~ -gy heaVy I~1 ~ndo. Ced X - ray em~lll[ort (;-IF.J~IXE sur face ¢~e l ! I ~ by ~ l l y sis o f neu t ra t a im I ~ impa¢l rad la t I ~ • |SCAN IIF;I) charged par t i c l e ac t i va t l~ ana ly • l . nuc lea r rea©l i ~ •

e leCt ron mic roProbe sna lys i l (EMP) j ca~ lng tp~ lmi i i [ ~ e le¢ I r ~ m~c roscow (STEM)

X- ray f l ~ r~c~ * I p * c t ru~ l ase r induced opt ica l emls • io • p * c t r oscopy i um Inesc41~ce

phlon absorp t ion

T A B L E I: V a r i o u s techniques used for c h a r a c t e r i z a t i o n using ions e lec t rons and photons.

Here , we r e s t r i c t o u r s e l f to r e v i e w the major ion beam methods for s i l i con c h a r a c t e r i z a t i o n • T h e y have given r i s e to severa l in te rna t iona l meet ings (3 -? ) s ince the e a r l i e r conference in York town Heights in 19?3. S e v e r a l books and r e v i e w papers (8 - 31) have cons idered v a r i o u s aspects of the problem. H o w e v e r , to our knowledge, none of them have put specia l empha- s is on so lar s i l i con .

The methods we a re cons ide r ing are: 1. Secondary Ion Mass 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. Low 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. Ac t iva t ion ,z~J'lalysis by Us ing Charged P a r t i c l e A c c e l e r a t o r s ~by U . L .

DE B R U N 5. Heavy Ion Induced X - r a y Emiss ion by Ch. H E I T Z

In o r d e r to a l low compar isons wi th o ther techniques, th ree of them a re b r i e f l y descr ibed:

6. S p a r k S o u r c e Mass 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

?. Neu t ron Ac t iva t ion A n a l y s i s by G. R E V E L 8. Atomic Emiss ion S p e c t r o m e t r y from Induct ive ly Coupled Plasma by D.

MORVA~I , J• A~vtOUROUX, P. C L A R A Z .

In all these methods, detect ion l imits and s e n s i t i v i t y play an important ro le . T h e s e terms are def ined as fol lows:

8 P. Siffert

- de tec t ion l im 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 se t -up a s igna l w i t h 95 ~/o conf idence. The s igna l N must exceed the background N B by t h ree t imes the square root of the backg round (32). - s e n s i t i v i t y : is the s lope of the c a l i b r a t i o n cuPve [° e. the change of s igna l output w i t h i nc remen 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 NMIN *f

3v~ B

I--- AC -.4

SENSITIVITY = TAN a = A-"~"

MATERIAL CONCENTRATION ,~ LD

L o = DETECTION LIMIT

NMIN = MINIMUM DETECTABLE IMPURITY COUNT

N e = BACKGROUND COUNT

F i g . 5 : D e f i n i t i o n of s e n s i t i v i t y and de tec t ion l im i t (A. G. LIEBERIViA~I N B S (32)).

R E F E R E N C E S

I . G . E . MOORE P r o g r e s s in D i g i t a l I n teg ra ted E l e c t r o n i c s IEEE In te r . E l e c t r o n . D e v i c e s Meet ing (1975)

2. D. S A L L E S , u n p u b l i s h e d wo rk . 3. 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 He igh ts Conf . T h i n S o l i d F i l m s 19 (1974) 4. 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

A n a l y s i s . P r o c . K a r l s r u h e Conf . Ed. P lenum P r e s s (1976) 5. 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 . Wash ing ton Conf . Nuc l . I ns t r . Meth. 149 (1978) 6. 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 Conf . N u c l . I n s t r . Meth 168 (1980)

7. J . ~ . B I R D , G . J . C L A R K ion Beam A n a l y s i s P r o c . Sydney Conf . N u c l . I n s t r . Meth. 181 (1981).

F U N D A M E N T A L e. A tom ic C o l l i s i o n and P e n e t r a t i o n Stud i e s . Conf . P r o c . Cha lk R i v e r

(1967) 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 tom ic C o l l i s i o n

Phenomena in S o l i d s Conf . P r o c . U n i v e r s i t y of Sussex (1969) N o r t h Ho l l and ed Ams te rdam (1970)

10. 11.

12.

Characterization of silicon by ion beam techniques

D . V . MORGAN (ed) C h a n n e l l i n g J. W i l e y New Y o r k (1973) S. D A T Z , B. R. A P P L E T O N , C. D. MOAK (~ds) P r o c . Conf . G a t l i n b u r g (1973) 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 . Amste rdam (1975) N u c l . I ns t r . Meth. 132 ( 1976) .

ION I M P L A N T A T I O N

13. J. W A Y E R , L . E R I K S O N , J . A . D A V I S Ion Imp lan ta t ion in S e m i c o n d u c - t o r s . Academic P r e s s ( 1 9?0)

14. F . H . E I S E N , L . T . C H A D D E R T O N , J . A . D A V I S Ion Imp lan ta t ion in S e m i c o n d u c t o r s . P roc . Conf . Thousand O a k s . Gordon and B reach ed. New Y o r k (1971) .

15. I. RUGE, J. G R A U L (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 . P r o c . Conf . Ga rm isch P a r t e n k i r c h e n S p r i n g e r V e r l a g ed (1971).

16. B . L . CROWDER(ed) 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. Conf . Y o r k t o w n H e i g h t s P lenum P r e s s (1973)

17. G. D E A N N A L E Y , J. H. FREEMANp R. S. N E L S O N , J. S T E P H E N Ion Imp lan ta t i on N o r t h H o l l a n d Ams te rdam (1973).

18. S. N A M B A (ed) I o n Imp lan t at ion in S e m i c o n d u c t o r s P r o c . Conf . Osaka . P lenum tess (1975) .

19. P . D . T O W N S E N D , J . C . K E L L Y , N . E . W . H A R T L E Y (eds) Ion Imp lan ta t ion 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 Academic P r e s s New Y o r k (1976)

20. G. K A R T E R , W . A . v R A N T Ion I m p l a n t a t i o n of S e m i c o n d u c t o r s W i l ey , New Y o r k (1977; .

21 F. CHERNOW, J . A . BORDEI -<S ,D .K . B R I C E (eds) Ion Imp lan ta t ion in S e m i c o n d u c t o r s and O the r M a t e r i a l s P r o c . B o u l d e r Conf . P lenum P r e s s (1977).

22. J . K . H I R O V E N (ed) Ion 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 Vo l . 18 Academic P r e s s (1980).

M A T E R I A L I N V E S T I G A T I O N

23. 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 of S o l i d S u r f - aces P lenum P r e s s (1974).

24. J . F . Z I E G L E R (ed) New Uses of Ion A c c e l e r a t o r s P lenum P r e s s (75) 25. 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 of 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 Conf . S e r i e s 28 (1976) London . 26. A . W . C Z A N D E R N A ( e d ) Methods of S u r f a c e A n a l y s i s . E l s e v i e r

Ams te rdam (19 75). 27. J . W . A Y E R , E. RI MINI I on Beam Handbook fo r M a t e r i a l A n a l y s i s

Academic P r e s s New o r k (1977). 28. A. C A C H A R D, J. P. THOMAS~ M a t e r i a l C h a r a c t e r i z a t i o n us ing Ion

Beams P lenum P r e s s (1977). 29. W . K . CHU, 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

Academic P r e s s New Y o r k (1978) 30. 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 ec t ron 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 ress (1978) 31. G . B . L A R R A B E E ~ V L S I E l e c t r o n i c s ~ M i c r o s t r u c t u r e Sc i ence Vo l . 2

p. 3? ed. N. E I N S P R U C H . Academic P r e s s (1981).

888888888888

32. A . G . L I E B E R M A N N B S Spec ia l P u b l i c a t i o n 400-23 p. 3(1976)