Incorporation, Diffusion Et Segregation D'impuretes Dans Le Silicium Polycristallin

bond o f i m p u r i t i e s a t t h e s u r f a c e o f p o l y c r y s t a l l i n e s i 1 i c o n samples g rown on a c a r b o n r i b b o n . B e s i d e s m a i n i m p u r i t i e s ( c a r b o n and o x y g e n ) , a l w a y s p r e s e n t a t c o n c e n t r a t i o n s a r o u n d t h e i r l i m i t o f s o l u b i l i t y i n s i l i c o n , m e t a l i m p u r i t i e s have been f o u n d : t h e i r n a t u r e v a r i e s f r o m a sample t o a n o t h e r . T h e i r s p a t i a l d i s t r i b u t i o n i s n o t random: some a r e s t r i c t l y c o n f i n e d a t t h e s u r f a c e ( s o d i u m ) , whereas o t h e r s a r e i n t h e s u p e r f i c i a l o x i d i z e d l a y e r ( c a l c i u m , magnesium) o r l o c a l i z e d a t t h e o x i d e bu1 k s i 1 i c o n i n t e r f a c e ( i r o n ) . M e t a l i m p u r i t i e s a r e coming f r o m t h e c a r b o n r i b b o n a n d a r e i n c o r p o r a t e d t o s i l i c o n d u r i n g t h e g r o w t h p r o c e s s . I t i s n o t y e t p o s s i b l e t o g i v e a mode1 o f d i f f u s i o n p r o c e s s e s o f i m p u r i t i e s s i n c e t h e y a r e t o o numerous and i n t e r a c t one w i t h t h e o t h e r . However o x y g e n seems t o p l a y a l e a d i n g r ô l e i n t h e s p a t i a l d i s t r i b u t i o n o f m e t a l i m p u r i t i e s .