were made i n t h e r e c r y s t a l l i z e d m a t e r i a l . A s u r f a c e m o b i l i t y of 650 c m z /~. s e c . was o b s e r v e d i n t h e t r a n s i s t o r s , and a 1 n s e c . d e l a y p e r s t a g e was measured i n t h e r i n g o s c i l l a t o r s [L = 5 pm). 1 . I n t r o d u c t i o n . -S i l i c o n -O n -I n s u l a t o r (SO11 t e c h n o l o g i e s a r e a n a t t r a c t i v e a l t e r n a t i v e f o r VLSI c i r c u i t m a n u f a c t u r i n g , owing t o

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... such a d v a n t a g e s a s reduced p a r a s i t i c c a p a c i t a n c e s , l a t c h -u p immunity and i n s e n s i t i v i t y t o a l p h a p a r t i c l e s . F u r t h e r m o r e , t h e c o s t p e r w a f e r i s p r o m i s i n g l y low when such t e c h n i q u e s based on t h e r e c r y s t a l l i z a t i o n o f a p o l y s i l i c o n f i l m d e p o s i t e d on a low-cost s u b s t r a t e ( g l a s s o r o x i d i z e d m e t a l l u r g i c a l s i l i c o n w a f e r ) a r e u s e d . Many d i f f e r e n t e n e r g y beams have been i n v e s t i g a t e d f o r t h e m e l t i n g and r e c r y s t a l l i z a t i o n of s i l i c o n f i l m s d e p o s i t e d on a n i n s u l a t o r , among them cw l a s e r s [ I ) , lamps (21, o r s t r i p h e a t e r s [ 3 ) . A l l t h e s e t e c h n i q u e s o p e r a t e i n t h e same way: t h e s i l i c o n f i l m , which may b e e n c a p s u l a t e d o r n o t , i s m e l t e d d u r i n g t h e s c a n n i n g , t h e n quenched i n such a way t h a t l a r g e c r y s t a l l i t e s a r e o b t a i n e d . T y p i c a l g r a i n s i z e s of 5 pm X 1 0 um a r e o b t a i n e d w i t h cw l a s e r s y s t e m s , w h i l e much l a r g e r g r a i n s (1000 pm X s e v e r a l mml a r e o b t a i n e d u s i n g lamps o r s t r i p h e a t e r s . However, i n a l l t h e s e t e c h n i q u e s , t h e l o c a t i o n of t h e remaining d e f e c t s ( g r a i n b o u n d a r i e s o r s u b g r a i n b o u n d a r i e s ) i s always random. The consequence of t h i s random l o c a t i o n o f d e f e c t s i s t h a t a g r a i n boundary may be l o c a t e d i n a t r a n s i s t o r somewhere i n t h e SO1 c h i p r e s u l t i n g i n a m a l f u n c t i o n o f t h a t t r a n s i s t o r , and o f t h e c i r c u i t , which i s o f c o u r s e u n a c c e p t a b l e . 2 . C o n t r o l o f t h e g r a i n boundary l o c a t i o n . -C o n t r o l o f t h e t e m p e r a t u r e g r a d i e r i t s i n t h e quenching s i l i c o n f i l m i m m e d i a t e l y f o l l o w i n g beam i r r a d i a t i o n i s a key t o a c h i e v i n g l a r g e s i n g l ec r y s t a l s . T h i s c a n b e managed e i t h e r by c o n t r o l l i n g t h e h e a t f l o w from t h e s i l i c o n f i l m t o w a r d s t h e s u b s t r a t e (41 o r by s p a t i a l l y m o d u l a t i n g t h e e n e r g y d e p o s i t e d i n t h e f i l m (51. I n t h i s e x p e r i m e n t , we h a v e u s e d t h e s o -c a l l e d Article published online by EDP Sciences and available at http://dx.