Iowa S t a t e U n i v e r s i t v Ames, Iowa A b s t r a c t R e a c t i v e I o n E t c h i n g ( R I E ) which combines some advantages o f b o t h plasma e t c h i n g and s p u t t e r e t c hi n g has been used i n p r o c e s s i n g ZnO/Si and A l N / S i s t r u c t u r e f o r a c o u s t i c wave d e v i c e s . In t h i s s t u d y , t h e e t c h i n g gases used a r e CF4, HC1 and HI w i t h v a r y i n g amounts o f 02 and A r . The s u b s t r a t e s o f i n t e r e s t , which a r e p l a c e d on t h e cathode e l e ct r o d e o f a p a r a l l e l p l a t e r f r e a c t i o n chamber, a r e ZnO, A l N , A l , S i and SiO2. E t c h i n g was t y p i c a l l y c a r r i e d o u t a t 50 m i l l i t o r r s p r e s s u r e and 75 w a t t s r f power. When u s i n g CF4 and 4% 02 gas, S i e t c h r a t e was measured as h i g h as 2500 Ao/min. t h e ZnO and A1N e t c h r a t e s were v e r y l o w i n r e a ct i v e i o n e t c h i n g o r were found u n a t t a c k e d i n CF4 plasma e t c h i n g . By u s i n g t h i s h i g h e t c h s e l e ct i v i t y , edqe-only s u p p o r t e d ZnO and A1N p l a t e s were c o n s t r u c t e d f r o m ZnO/Si o r A l N / S i composite s t r u c t u r e . When HI gas was used, t h e e t c h r a t e o f ZnO was determined t o be 2000 Ao/min. The e t c h s e l e c t i v e r a t i o s found here were 4 0 : l o v e r S i 0 2 and mo e t h a n 1OO:l o v e r S i and A l . The l o w A1 mask e r o s i o n and h i g h s t o p p i n g r a t i o f o r ZnO o v e r S i on Al/ZnO/Si s t r u c t u r e i s o f p r a c t i c a l importance o r b o t h BAW and SAW d e v i c e s . However, I n t r o d u c t i o n Due t o new demand o f microwave d e v i c e s i n a s m a l l dimension and h i g h e r p a c k i n g d e n s i t i e s f o r i n t e q r a t e d c i r c u i t f a b r i c a t i o n , a s e l e c t i v e and a n i s o t r o p i c e t c h p r o c e s s i n g t e c h n i q u e t u r n s o u t t o be tremendously i m p o r t a n t . In t h i s work, r ea c t i v e i o n e t c h i n q which removes m a t e r i a l s by a c o m b i n a t i o n o f chemical r e a c t i o n and i o n bombardment was s t u d i e d i n p r o c e s s i n g Al/ZnO/Si and A l / A l N / S i s t r u c t u r e s f o r a c o u s t i c wave d e v i c e s . S p u t t e r e t c h i n g , d e s c r i b e d elsewhere,l i s t h e process o f u s i n g A r i o n beams i m p i n g i n g on a s u rf a c e t o s p u t t e r o f f m a t e r i a l b y momentum t r a n s f e r . The e t c h i s u s u a l l y h i g h l y a n i s o t r o p i c b u t n o t s e l e c t i v e f o r one m a t e r i a l o v e r a n o t h e r . Plasma e t c h i n g . 2~3 i n w h i c h t h e r e a c t a n t s p e c i e s c o l l i d e and r e a c t w i t h t h e s u r f a c e t o be etched, produces v o l a t i l e compounds w h i c h a r e t h e n pumped o u t by t h e vacuum system. T h i s r e s u l t s i n s e l e c t i v e e t c h i n g w i t h an a n i s o t r o p i c e t c h p r o f i l e . r e a c t i v e i o n e t c h i n q 4 ...

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