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DEPTH RESOLUTION IN ION SPUTTERING - AN ASPECT OF QUANTITATIVEMICROANALYSIS
J. Giber, D. Marton, J. László
To cite this version:
J. Giber, D. Marton, J. László. DEPTH RESOLUTION IN ION SPUTTERING - AN ASPECT OF
QUANTITATIVEMICROANALYSIS. Journal de Physique Colloques, 1984, 45 (C2), pp.C2-115-C2-
118. �10.1051/jphyscol:1984226�. �jpa-00223939�
30URNAL DE PHYSIQUE
Colloque C2, supplément au n°2, Tome 45, février 1984 page C2-115
DEPTH RESOLUTION IN ION SPUTTERING - AN ASPECT OF QUANTITATIVE MICROANALYSIS
J. Giber, D. Marton and J. Laszlo
Physical Institute of the Technical University,Budapest, 1111 Budafoki ut 8., Hungary
Résumé - La résolution en profondeur des profils de pulvérisa- tion a été déterminée en utilisant des multicouches Ni-Cr. Nous avons aussi développé une méthode pour l'évaluation quantitati- ve des résultats. La résolution en profondeur mesurée à l'aide des couches métalliques polycristallines, est fortement influ- encée par la diffusion intermétallique entre couches.
Abstract - The depth resolution of sputter depth profiling has been analysed using Ni-Cr multilayer structures. A new method has been developed to quantify the results. The depth resolu- tion measured using polycrystalline metallic layers is strongly influenced by mutual diffusion of the layers.
The depth resolution of sputter depth profiling is a crucial factor from the point of view of quantitative analysis performed with SIMS, AES, ESCA etc. The finite depth resolution of the measurement leads to primcipal profile distortion which may be mathematically described by a resolution function g (3-z) which is convolved with the measured profile c(J) [1]:
(1) where k is the sensitivity factor.
The determination of the real profile requires therefore
determination of the g function that can be obtained experimentally from the sputter profiling of step function concentration profiles, which being distorted during the measurement may be characterized by the cr standard deviations of the measured nearly error function type profiles. The depth resolution is defined as z=2tf [2], The sample profiles should be strictly rectangular for this measurement, because deviations from that (which are usually due to diffusion processes in practical cases) lead to additional interface broadening. The indep- endent interface broadenings due to different phenomena can be summarized quadratically [3]:
(2) The determination of depth resolution is required usually
according to a depth scale, because it is necessary partly when using eq. (1) and when one studies the sputtering process [4]. The use of
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984226
JOURNAL DE PHYSIQUE
F i g . 1
Az
2 v s z d e t e r m i n e d b y AES method u s i n g P H I S A M 545 equipment, 5 kev ~ r + i o n s p u t t e r i n gF i g . 2
A z 2 v s z d e t e r m i n e d b y SIMS method u s i n g B q l z e r s equipment, 3 keV Ar i o n s p u t t e r i n g w i t h o u t ( " A r m ) and w i t h oxygen j e t ( " 0 2 " )
s i n g l e l a y e r systems f o r t h i s purpose i s d i f f i c u l t , because one needs t h e n a s e r i e s o f i d e n t i c a l i n t e r f a c e s . A more advantageous method t h a t has been suggested b y Hofmann e t a 1 . [ 5 ] uses m u l t i l a y e r s t r u c t u r e s w i t h u n i f o r m l a e r t h i c k n e s s e s . The e v a l u a t i o n o f t h e w a v e - l i k e d e p t h p r o f i l e s o x t a i n e d i n such measurements i s a l s o d i f f i c u l t , b u t can be c a r r i e d o u t under c e r t a i n assumptions:
1
-
t h e d i s t o r t e d p r o f i l e i s w e l l approximated b y s u p e r p o s i t i o n o f e r r o r f u n c t i o n s c e n t e r e d a t t h e i n t e r f a c e s ,2
-
t h e n e a r e s t n e i g h b o u r a p p r o x i m a t i o n i s v a l i d , i.e. A z<
d, 3-
t h e s e n s i t i v i t y f a c t o r s a r e independent o f t h e c o n c e n t r a t i o n w i t h i n t h e l i m i t s o f t h e m i n i m a l and maximal o c c u r i n g c o n c e n t r a t i o n s .While assumption 1 h o l d s f o r t h e most cases e x c e p t if t h e i n f o r m - a t i o n d e p t h o r cascade m i x i n g a r e t h e main f a c t o r s d e t e r m i n i n g t h e i n t e r f a c e b l u r r i n g , and assumption 2 h o l d s u n l e s s v e r y t h i n l a y e r s o r v e r y deep l y i n g i n t e r f a c e s a r e analysed, t h e v a l i d i t y o f assumption 3 i s q u e s t i o n a b l e , b e f o r e a l l i n S I M S d e p t h p r o f i l i n g -
Unequal s e n s i t i v i t y f a c t o r s f o r d i f f e r e n t c o n c e n t r a t i o n s can
change t h e d e p t h r e s o l u t i o n f o r i o n y i e l d s as compared w i t h t h e d e p t h r e s o l u t i o n o f c o n c e n t r a t i o n s . I n t h i s sense t h e d e p t h r e s o l u t i o n s d e t e r m i n e d from S I M S i o n y i e l d s a r e i n f l u e n c e d b y s e n s i t i v i t y f a c t o r changes w i t h c o n c e n t r a t i o n and can be d i f f e r e n t f o r d i f f e r e n t t y p e s o f ions.
On t h e b a s i s o f t h e assumptions l i s t e d above t h e d e p t h r e s o l u t i o n can be c a l c u l a t e d a c c o r d i n g t o t h e e x p r e s s i o n
The r e s u l t s o f e v a l u a t e d measurements c a r r i e d o u t on d i f f e r e n t N i - C r samples a r e shown i n F i g s . 1, 2 and 3. These samples were
o b t a i n e d b y vacuum e v a p o r a t i o n on unheated s u b s t r a t e s . The d e t a i l s of t h e experiment a r e d e s c r i b e d elsewhere [6]. The e x p e r i m e n t a l r e s u l t s can be f i t t e d t o an eq.:
where A z i s t h e "measured" d e p t h r e s o l u t i o n and A z c and a a r e S a m p l e 342
d
=
10,6nmFig. 3
A z v s z d e t e r m i n e d b y 2 AES method u s i n g PH SAM
545 equipment, 3 keV ~ r +
i o n s p u t t e r i n g , The A z = 1.2 z and 2 Az2 = 0.6 z l i n e s c o r r e s p o n d t o s t r a i g h t l i n e s i n F i g . 3 r e f . [ 4 ] .
C2-118 JOURNAL DE PHYSIQUE
d e t e r m i n e d b y t h e c h e m i c a l c o m p o s i t i o n o f t h e samples and f o r Ni-Cr m u l t i l a y e r sandwiches a n a l y s e d h e r e A z c = 6-8 nm and a=0,2.. .0,5 nm.
The i n t e r f a c e b l u r r i n g due t o s p u t t e r i n g and measurement f a c t o r s a r e t h e n
a z S = J A z '
-
AZ: =6
(5)i n accordance w i t h what i s p r e d i c t e d b y t h e t h e o r i e s o f s t a t i s t i c a l s p u t t e r i n g and cascade m i x i n g [ 7 , 8 1 on one hand, and b y s u r f a c e ronghening [ 9 ] on t h e o t h e r .
References:
HO P.S., LEWIS J.E., S u r f . S c i . 55, (1976) 335.
HOFMANN S., S u r f . I n t e r f . Anal.
2,
(1980) 148.WERNER H.W., HORNSTRA J., WARMOLTZ N., S u r f . I n t e r f . Anal. i n press SEAH M. P., HUNT C . P., S u r f . I n t e r f . Anal. 5, (1983) 33.
HOFMANN S., ZALAR A., T h i n S o l i d F i l m s 60,-(1979) 201.
GIBER J., MARTON D.,
L A S Z L ~
J., HANUSOVSZKY A., STINGEDER P., Vacuum 33, (1983) 117.HOFER W.O.
,
LITTMARK U., Phys. L e t t . 71A, (1979) 457.HOFMANN S., Appl. Ph s., 13, (1977) 2 m
SEAH M. P., LEA C . , T x i n s a i d F i l m s
