Defect generation in silicon
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T H E g e n e r a t i o n of d e f e c t s in s i l i c o n w a f e r s during d e v i c e p r o c e s s i n g h a s been w e l l d o c u m e n t e d . 1 D e f e c t s , p a r t i c u l a r l y in conjunction with i m p u r i t y p r e c i p i t a t i o n , can a l t e r the w a f e r c o n d u c t i v i t y , the c a r r i e r m o b i l i t y , and the m i n o r i t y c a r r i e r l i f e t i m e . As s u c h , d e f e c t s can be the c a u s e of i n c r e a s e d l e a k a g e c u r r e n t s in i n d i v i d u a l d e v i c e s and can lead to l o w e r p r o c e s s i n g y i e l d s in f a b r i c a t i o n of i n t e g r a t e d c i r c u i t s . We r e p o r t h e r e s o m e o b s e r v a t i o n s made on d e f e c t g e n e r a t i o n in e s s e n t i a l l y d e f e c t - f r e e s i l i c o n w a f e r s . Some t e c h n i q u e s s u i t a b l e f or e l i m i n a t i n g t h e s e p r o c e s s g e n e r a t e d d e f e c t s w i l l be d i s c u s s e d . The e f f e c t s of the p r o c e s s g e n e r a t e d d e f e c t s on m i n o r i t y c a r r i e r l i f e t i m e and on the p e r f e c t i o n of diode a r r a y s will be p r e s e n t e d . EXPERIMENTAL TECHNIQUES The w a f e r s used in t h e s e s t u d i e s w e r e (111), N - t y p e , 25 to 100 o h m - c m s i l i c o n , 0.005 in. thick and 0.875 in. d i a m . The f r o n t side of the w a f e r s , which would have been the side used f o r d e v i c e f a b r i c a t i o n , w a s " q u s o " * *"Quso" is the trade name for an alkalinesuspensionof microfineprecipitated silica. p o l i s h e d . The back s i d e s of the w a f e r s r e c e i v e d s e v e r a l t r e a t m e n t s to be d e s c r i b e d below. S e v e r a l b a t c h e s of w a f e r s f r o m v a r i o u s v e n d o r s w e r e t e s t e d . S e v e r a l w af e r s f r o m e a c h batch w e r e S i r t l 2 e t c h e d f o r 15 m i n p r i o r to p r o c e s s i n g , and on all of the w a f e r s r e p o r t e d h e r e e x c e p t one, the e t c h pit d e n s i t y w a s l e s s than 102 p e r sq c m . On that one batch, the etch pit d e n s i t y w as 102 p e r sq cm o v e r m o s t of the w a f e r , but a few cloudy r e g i o n s with etch pit d e n s i t i e s up to 104 p e r sq cm were observed. S e v e r a l w a f e r s f r o m e a c h batch of w a f e r s w e r e o x i dized in e i t h e r dry 02 o r s t e a m and the SiO2 was s t r i p p e d f r o m the w a f e r s . T h e s e w a f e r s w e r e then S i r t l e t c h e d and both the p a t t e r n s of e t c h pits and the etch pit d e n s i t i e s w e r e c o r r e l a t e d with the p r o c e s s i n g of the backs and e d g e s of the w a f e r s . The p a t t e r n s of D. J. DUMIN is Member of the Technical Staff, RCA Laboratories, Princeton, N.J.W.N. HENRY is Processing Engineer, RCA Electronic Components Division, Lancaster, Pa. This manuscript is based on a paper presented at the annual conference sponsored by the Electronic Materials Committee of the Institute of Metals Division of the Me
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