Stress and resistivity control in sputtered molybdenum films and comparison with sputtered gold
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two groups above, b e i n g 1) r e a d i l y o x i d i z a b l e , 2) fcc in c r y s t a l s t r u c t u r e , and 3) low m e l t i n g . E X P E R I M E N T A L PROCEDURES Sputtering System The s p u t t e r i n g s y s t e m used 3 is a F r e o n - b a f f l e d (-40~ diffusion-pumped system employing a titanium s u b l i m a t i o n pump with liquid n i t r o g e n t r a p p i n g and p r o v i d i n g a d d i t i o n a l i m p u r i t y g e t t e r i n g by m e a n s of m o l y b d e n u m p r e s p u t t e r e d s u r f a c e s s u r r o u n d i n g the d i s c h a r g e r e g i o n , F i g . 1. T h e s e p r o v i s i o n s make possible an i n i t i a l p r e s s u r e of (1 to 3) x 10 -8 t o r r before i n t r o d u c t i o n of the u l t r a p u r e argon s p u t t e r i n g gas (Matheson i o n i z a t i o n g r a d e , 99.999 pct m i n i m u m purity). The a r g o n p r e s s u r e is c o n t r o l l e d by m e a n s of a G r a n v i l l e - P h i l l i p s A u t o m a t i c P r e s s u r e C o n t r o l l e r and m o t o r i z e d v a l v e through the m o n i t o r i n g of a P i r a n i gage. F i l m t h i c k n e s s c o n t r o l and r e p r o d u c i b i l i t y a r e achieved a u t o m a t i c a l l y by the use of a film t h i c k n e s s c a l i b r a t i o n to d e t e r m i n e and p r e s e t the c o r r e s p o n d i n g
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Fig. 1--Schematic drawing of carousel sputtering chamber (not to scale). Substrates, indicated by small rectangles, are shown only on the top and bottom faces of the octagonal substrateholder. VOLUME 2, MARCH 1971-699
total i n t e g r a t e d cathode c u r r e n t . The d i s c h a r g e can then be i n i t i a t e d and, after the p r e s e t total charge h a s been a c c u m u l a t e d , the d i s c h a r g e is a u t o m a t i c a l l y t u r n e d off. The e s s e n t i a l f e a t u r e s of the s p u t t e r i n g c h a m b e r a r e shown in Fig. 1. The s y s t e m c o n t a i n s two 15.2 cm diam cathodes, one p o s i t i o n e d above and the other below an e i g h t - s i d e d r o t a t a b l e s u b s t r a t e h o l d e r . The c a t h o d e - t o anode s e p a r a t i o n is 43 m m . T h i s design p e r m i t s , in a single p u m p - d o w n , p r e s p u t t e r i n g a g a i n s t a blank anode face and u n i f o r m s p u t t e r i n g of up to four 1 in. diam s u b s t r a t e s s i m u l t a n e o u s l y u n d e r seven d i f f e r e n t s e t s of s p u t t e r i n g c o n d i t i o n s , u s i n g e i t h e r one of two cathode m a t e r i a l s . The c a r o u s e l s u b s t r a t e h o l d e r is heated by m e a n s of an i n t e r n a l t u n g s t e n f i l a m e n t . A t h e r m o c o u p l e attached to the outside wall, Fig. 2, is used to c o n t r o l a u t o m a t i c a l l y the s u b s t r a t e holder t e m p e r a t u r
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