21 Photosensitive Polyimide Siloxane GARY C. DAVIS Corporate Research & Development Center, General Electric Company, Schenectady, NY 12301 A photosensitive silicone polyamic acid is described. This material is easily prepared directly from the precursor silicone polyamic acid. Properties and characteristics of this polymer system are discussed including handling, use, and practical photochemistry. Thermal tempering of the photosensitive or crosslinked polymer gives the polyimide siloxane which has been previously shown to be an excellent candidate as an insulating polymer in electronics. The use of such a directly patternable polyimide for dielectric and passivation applications, particularly in micro electronics, should become increasingly important as polyimides become more widely accepted in the industry. The insulating properties of polyimides for microelectronics applications are well known (1). However, patterning of polyimides using photoresist technology can be cumbersome since inorganic protective layers are often required to protect poly imide films during dry etching. Even the use of wet solution development of polyamic acid films still requires the use of a photoresist to form the initial pattern. A photosensitive poly amic acid can simplify processing by acting essentially as its own photoresist. If designed properly, the photosensitive polyamic acid when thermally cured is converted to the parent polyimide with its inherent excellent thermal and electrical properties. Scheme I demonstrates a savings of six steps in device fabrication by the use of a photosensitive polyimide. This paper will report on the preliminary work on the prep aration of a photosensitive polyamic acid which has advantages over previously reported materials (2) in the ease of synthesis and in some properties of final Imide film. 0097-6156/ 84/ 0242-0259S06.00/ 0 © 1984 American Chemical Society
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260
Conventional Dry Etch
Photosensitive
Si Wafer
1.
Apply polyamic acid
2.
Cure to polyimide
1.
•polyimide Si wafer 3.
Protect polyimide •Si0
o
Apply photosensitive . polyimide
///////-
photosensitive "polyimide -Si Wafer
2.
Expose photosensitive polyimide
3.
Develop photosensitive polyimide
4.
Cure to polyimide
Apply photoresist photoresist
5.
Expose Photoresist
6.
Develop Photoresist
7.
Etch S i 0
8.
Strip Photoresist
9.
Etch Polyimide
10.
Remove S i 0
2
Scheme I .
o
Comparison o f P a t t e r n i n g P r o c e s s f o r and P h o t o s e n s i t i v e P o l y i m i d e s .
Conventional
21.
DAVIS
Photosensitive Polyimide
Siloxane
261
Experimental General. I n f r a r e d measurements w e r e p e r f o r m e d u s i n g a N i c o l e t 7199C F T I R on t h i n f i l m s OVLy) c o a t e d on s i l i c o n w a f e r s . T h e s e measurements w e r e u s e d t o f o l l o w t h e UV c u r i n g and t h e r m a l t e m p e r ing of polyamic a c i d f i l m s . B u l k I R s w e r e p e r f o r m e d on a P e r k i n E l m e r 598 I n f r a r e d S p e c t r o p h o t o m e t e r . G l a s s t r a n s i t i o n t e m p e r a t u r e (Tg) m e a s u r e m e n t s w e r e p e r f o r m e d on a P e r k i n E l m e r DSC-2 D i f f e r e n t i a l S c a n n i n g C a l o r i m e t e r . UV e x p o s u r e s w e r e p e r f o r m e d on a PPG M o d e l QC 1202 U l t r a v i o l e t P r o c e s s o r r u n a t 10 t o 20 f t / m i n , t o t a l e x p o s u r e t i m e 15 t o 30 s e c , o r u n d e r 4RS sunlamps l o c a t e d 10 i n c h e s f r o m t h e s a m p l e on a ^ t u r n t a b l e . RS sunlamp i n t e n s i t y was m e a s u r e d t o be 4.3 mW/cm a t 365 nm. Film development was done i n b a t c h f a s h i o n . A l l s o l v e n t s and r e a g e n t s w e r e used as r e c e i v e d . I s o c y a n o t o e t h y l m e t h a c r y l a t e i s an e x p e r i m e n t a l monomer f r o m Dow. N - p h e n y l p h t h a l a m i c a c i d was p r e p a r e d f r o m a p h t h a l i c a n h y d r i d e and a n i l i n e i n m e t h y l e n e c h l o r i d e . f
Polyimide Siloxane (SiPI). I n t o a 500 c c 3 n e c k r o u n d bottomed f l a s k e q u i p p e d w i t h a m e c h a n i c a l s t i r r e r and n i t r o g e n b y p a s s i s p l a c e d 54.00 gms (0.17 m o l e s ) o f 3 , 3 , 4 , 4 ' - b e n z o p h e n o n e t e t r a c a r b o x y l i e d i a n h y d r i d e d i s s o l v e d i n 250 c c o f s i e v e d r i e d N - m e t h y l p y r r o l i d o n e ( B & J ) . To t h e s t i r r e d s o l u t i o n i s added 23.22 gms (0.12 m o l e s ) o f m e t h y l e n e d i a n i l i n e f o l l o w e d by 12.6 gms (0.05 moles) o f bis-l,3-gamma a m i n o p r o p y l t e t r a m e t h y l d i s i l o x a n e . The v i s c o u s s o l u t i o n i s a l l o w e d t o s t i r a t room t e m p e r a t u r e f o r 24 hours. 1
Isocyanatoethyl Methacrylate Modified Polyimide Siloxane (PSiPI). I n t o a 100 c c 1 n e c k r o u n d b o t t o m e d f l a s k p r o t e c t e d f r o m l i g h t and e q u i p p e d w i t h a m a g n e t i c s t i r r i n g b a r and a n i t r o g e n b y p a s s , i s p l a c e d 35 gms o f 28% s o l i d s i n N - m e t h y l p y r r o l i d i o n e (NMP) p o l y i m i d e s i l o x a n e ( S i P I ) and 5.5 gms o f i s o c y a n o t o e t h y l methacrylate. The r e a c t i o n m i x t u r e i s s t i r r e d a t room t e m p e r a t u r e f o r 24 h r s . The e v o l u t i o n o f CO- b e g i n s i m m e d i a t e l y , y e t some i s o c y a n a t e r e m a i n s f o r a b o u t 24 n r s . I n some r e a c t i o n s t o l u e n e i s added t o r e d u c e t h e i n i t i a l v i s c o s i t y o f t h e s o l u t i o n . Toluene i s a l s o found t o improve s p i n c o a t i n g c a p a b i l i t i e s of t h e polymer solution. P r i o r t o c o a t i n g , a s e n s i t i z e r package i s added. A t y p i c a l p a c k a g e c o n s i s t s o f 4% M i c h l e r ' s K e t o n e and 4% N - m e t h y l diethanolamine. The f i n a l s o l u t i o n i s s t o r e d c o l d ( ^ ° C ) ; h o w e v e r , i t i s warmed t o room t e m p e r a t u r e p r i o r t o u s e . P S i P I F i l m Préparation. A c l e a n e d ( a c i d washed o r o x y g e n p l a s m a descummed) s i l i c o n w a f e r i s s p i n c o a t e d w i t h P S i P I and d r i e d a t 100°C f o r 1 h o u r . The w a f e r i s t h e n masked and e x p o s e d . Typical t i m e s a r e 30 s e c on t h e PPG U l t r a v i o l e t P r o c e s s o r and 5 m i n u n d e r RS Sunlamps. The u n e x p o s e d a r e a i s t h e n d e v e l o p e d t y p i c a l l y u s i n g 0.5N NaOH. The p a t t e r n e d f i l m i s t h e n t h e r m a l l y tempered a t 200°C f o r 1 h r f o l l o w e d by 300°C f o r 1 h r t o c o n v e r t i t t o t h e i m i d e .
POLYMERS IN ELECTRONICS
262 R e s u l t s and
Discussion
The p h o t o s e n s i t i v e p o l y a m i c a c i d d i s c u s s e d h e r e i s made d i r e c t l y f r o m t h e p r e c u r s o r p o l y a m i c a c i d . Of t h e few o t h e r p h o t o s e n s i t i v e polyamic a c i d s reported i n the l i t e r a t u r e ( 2 ) , the workers i n i t i a l l y p h o t o - f u n c t i o n a l i z e t h e monomers. T h i s l a t t e r a p p r o a c h r e q u i r e s more s t e p s and r e q u i r e s more c a r e a s t h e p h o t o s e n s i t i v e m o i e t y i s i s o l a t e d and c a r r i e d t h r o u g h t h e e n t i r e s y n t h e s i s process. A c o m p a r i s o n o f t h e two p r o c e s s e s i s shown i n Scheme I I . Our p o l y m e r r e q u i r e s a r e a c t i o n b e t w e e n a c a r b o x y l i c a c i d o r a m i d e and a m o l e c u l e c o n t a i n i n g a p h o t o l a b i l e g r o u p . Candidates considered f o r that molecule included g l y c i d y l methacrylate 1, a c r y l o y l c h l o r i d e 2, and i s o c y a n o t o e t h y l m e t h a c r y l a t e (IEM) 3.
1
2
3
Model system s t u d i e s w i t h t h e s e m a t e r i a l s u s i n g N-phenylp h t h a l a m i c a c i d 4, i n d i c a t e d t h a t 3 was t h e most p r o m i s i n g c a n d i date. As i n t y p i c a l r e a c t i o n s o f e p o x i d e s w i t h c a r b o x y l i c a c i d s (3), r e a c t i o n of 4 w i t h 1 r e q u i r e d temperatures i n excess of 100°C. E x t e n d e d t i m e a t 100°C, h o w e v e r , c a u s e s u n d e s i r e d i m i d ization. R e a c t i o n o f 4 w i t h 2 was shown t o be f e a s i b l e , b u t was n o t f u r t h e r p u r s u e d . The a n h y d r i d e l i n k a g e f o r m e d w o u l d l i k e l y
be t o o h y d r o l y t i c a l l y u n s t a b l e and p r o n e t o p r e i m i d i z a t i o n d u r i n g film drying. R e a c t i o n o f 4 w i t h 3^ was f o u n d t o be s l o w a t room t e m p e r a t u r e but l i k e r e p o r t e d r e a c t i o n s between c a r b o x y l i c a c i d s and i s o c y a n a t e s c o u l d be a c c e l e r a t e d by a m i n e s and t i n compounds (4). S i m i l a r r a t e i n c r e a s e s were found i n t h e c a t a l y z e d r e a c t i o n o f IEM w i t h t h e a c i d a m i d e p o l y m e r . The u s e o f a c a t a l y s t i s n o t n e c e s s a r y t o p r e p a r e P S I P I ; however, t h e n o n - c a t a l y z e d r e a c t i o n r e q u i r e s 24 h o u r s compared t o l e s s t h a n 1 h o u r f o r a c a t a l y z e d reaction. I n t h e model system s t u d y , even a f t e r an e q u i v a l e n t o f 3 has r e a c t e d w i t h 4, ^-H and C nmr a s w e l l a s F T I R a n a l y s i s o f t h e p r o d u c t i n d i c a t e s t h a t some c a r b o x y l i c a c i d r e m a i n s . I t i s c o n c e i v a b l e t h a t some o f t h e 3^ i s o c y a n a t e r e a c t s w i t h t h e a m i d e g r o u p o f 4 ( 5 ) . However, e v e n i f t h i s r e a c t i o n o c c u r s , t h e 1 3
21.
DAVIS
Photosensitive
Polyimide
Siloxane
263
Monomer Approach
Scheme I I .
A Comparison o f Processes f o r P r e p a r i n g sensitive Polyimides.
Photo-
264
POLYMERS IN ELECTRONICS
o r i g i n a l g o a l o f a c i d a m i d e f u n c t i o n a l i z a t i o n has b e e n accom p l i s h e d t o g i v e a p h o t o s e n s i t i v e m a t e r i a l w h i c h would u l t i m a t e l y y i e l d an i m i d e on t h e r m a l t r e a t m e n t . The r e a c t i o n p r o d u c t o f 3 w i t h 4 was n o t f u r t h e r c h a r a c t e r i z e d . The r e s t o f t h i s p a p e r d e a l s e x c l u s i v e l y w i t h t h e IEM m o d i f i e d S i P I . The amount o f IEM r e q u i r e d t o g i v e a p o l y m e r w h i c h c o u l d be s u c c e s s f u l l y p h o t o c r o s s l i n k e d i s i m p o r t a n t ( T a b l e I ) . As e x p e c t e d , t h e more p o l y m e r g r o u p s f u n c t i o n a l i z e d , t h e more p h o t o r e a c t i v e t h e p o l y m e r , y e t i t i s i m p o r t a n t n o t t o add t o o much IEM a s t h i s l e a d s t o g e l l f o r m a t i o n p r i o r t o UV e x p o s u r e . A 1:1 r a t i o o f IEM t o p o l y m e r i c c a r b o x y l i c a c i d g r o u p was f o u n d t o be o p t i m a l .
Table I .
D e t e r m i n a t i o n o f Optimum R a t i o o f IEM t o C a r b o x y l i c A c i d f o r S i P I Polymer M o d i f i c a t i o n Equivalent Solution After E x p o s u r e and IEM/COOH R e a c t i o n (24 h r s ) Development R e s u l t s 0 No g e l l No P a t t e r n , F i l m D i s s o l v e d °·2 No g e l l P a t t e r n , F i l m Thinned °· No g e l l P a t t e r n , Some T h i n n i n g !·° No g e l l Pattern, Minimal Thinning · No g e l l Pattern, Minimal Thinning 1.5 Gell a
b
5
1
2
R e a c t i o n r u n a t room t e m p e r a t u r e u s i n g 4 0 % Ί . 8 μ f i l m s ( d r i e d 60°C/20 min) P r o c e s s o r ) and 1 m i n d e v e l o p e r
SiPI solution in
NMP
p r i o r t o 30 s e c e x p o s u r e (PPG (0.5N NaOH)
UV
S h e l f - l i f e of p h o t o s e n s i t i v e polyamic a c i d s i s important. We have found t h a t t h e P S i P I polymer s o l u t i o n s ( c o n t a i n i n g s e n s i t i z e r s ) b e g i n t o g e l l a f t e r a b o u t 1 month a t room t e m p e r a t u r e . They r e m a i n p h o t o a c t i v e d u r i n g t h e e n t i r e p e r i o d p r i o r t o g e l l formation. I f t h e p o l y m e r s o l u t i o n s a r e k e p t a t 4°C, t h e y a r e s t a b l e up t o a t l e a s t 6 m o n t h s . We h a v e f o u n d t h a t i n h i b i t o r s such as hydroquinone a r e not e f f e c t i v e i n i n c r e a s i n g polymer solution stability. U n l i k e the precursor S i P I polyamic a c i d , the p h o t o s e n s i t i v e a n a l o g u e c a n be p r e c i p i t a t e d i n t o m e t h a n o l t o g i v e a s o l i d w h i c h has shown i n c r e a s e d p h o t o p o l y m e r s h e l f s t a b i l i t y . S e n s i t i z e r s w e r e f o u n d t o be n e c e s s a r y t o e f f e c t a p h o t o c u r e o f t h e P S i P I . S e n s i t i z e r e f f e c t i v e n e s s was m e a s u r e d by c o m p a r i n g f i n a l p o l y m e r f i l m t h i c k n e s s e s a f t e r e x p o s u r e and d e v e l o p m e n t . M i c h l e r ' s k e t o n e was f o u n d t o be most e f f e c t i v e ( T a b l e I I ) . Films prepared u s i n g the M i c h l e r ' s ketone/N-methyldiethanola m i n e s e n s i t i z e r s y s t e m a t 4% l e v e l showed i d e n t i c a l d e v e l o p m e n t b e h a v i o r when e x p o s e d i n e i t h e r a i r o r n i t r o g e n d e m o n s t r a t i n g t h e o x y g e n i n s e n s i t i v i t y o f t h i s s e n s i t i z e r p a c k a g e . Two m i c r o n f i l m s ( a f t e r e q u i v a l e n t e x p o s u r e t i m e s u n d e r RS s u n l a m p s ) m a i n t a i n e d 71% of t h e i r o r i g i n a l t h i c k n e s s a f t e r 6 minutes of d e v e l o p i n g i n 0.5N NaOH. I n s e p a r a t e e x p e r i m e n t s t h e optimum amount o f M i c h l e r ' s k e t o n e f o r a 5 m i n RS sunlamp e x p o s u r e was d e t e r m i n e d t o be a b o u t 4 t o 6% t o p o l y m e r w e i g h t ( T a b l e I I I ) .
21.
Photosensitive Polyimide
DAVIS
Table I I .
Sensitizer None 2,2-Dimethoxy2-phenylacetophenone Benzophenone Michler's Ketone 2-Chlorothioxanthone
Siloxane
265
S e n s i t i z e r E f f e c t i v e n e s s on P S i P I C u r i n g
% Sensitizer in Polymer a
Developer T i m e (min) 0.1 0
d
e
0.5 1.5
32 24
1.5
80
2
60
An e q u a l p e r c e n t a g e o f N - m e t h y l d i e t h a n o l a m i n e each sample b
% Of I n i t i a l Film Thickness After Exposure 0
added t o
0 . 5 N NaOH
"Development t i m e was d e t e r m i n e d by t h e t i m e i t t o o k t o open the pattern. I n i t i a l films dried f i l m (100°C/2 h r ) . Exposed
100°C/1 h r e x c e p t 2 - c h l o r o t h i o x a n t h o n e
5 m i n u t e s 10 i n c h e s u n d e r 4 RS
Table I I I .
sunlamps.
Effect of Sensitizer Concentration on P h o t o c u r e o f P S i P I
% M i c h l e r ' s Ketone 2 4 6 8 10
D e v e l o p e r ^ Time° (min) 2 2 2 3 3
% of I n i t i a l Film Thickness A f t e r Exposure And D e v e l o p m e n t 63 85 91 92 92
Same a s T a b l e I I b
Same a s T a b l e I I
"Same a s T a b l e I I initial
films dried
100°C/lhr
Unlike other photosensitivepolyimides (2), the use of N-phenylmaleimide (10% t o polymer weight) as c r o s s l i n k i n g agent d i d n o t improve t h e p h o t o p o l y m e r i z a t i o n o f P S i P I .
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As e x p e c t e d , t h e more i n t e n s e t h e l i g h t s o u r c e , t h e f a s t e r t h e p h o t o c u r e . C u r e s i n a s s h o r t a s 30 s e c o n d s h a v e b e e n o b t a i n e d on a PPG U l t r a v i o l e t P r o c e s s o r . However, w i t h t h i s p o l y m e r s y s t e m , UV r a d i a t i o n a l o n e i s n o t s u f f i c i e n t f o r f a s t c u r e r a t e s . B o t h h e a t and l i g h t a r e r e q u i r e d . T h i s i s demonstrated i n Table IV.
T a b l e I V . E f f e c t o f Heat a n d L i g h t On P h o t o c u r e o f P S i P I
a
P S i P I Sample Exposure 4 RS sunlamps 5 min/80°C 4 RS sunlamps 5 min/10°C Heat lamp 5 min/90°C a
% o f I n i t i a l F i l m Remaining A f t e r Exposure Development 84 36 0 fe
F i l m d r i e d 100°C/1 h r and c o n t a i n 8% M i c h l e r ' s k e t o n e a n d 8% N - m e t h y l d i e t h a n o l a m i n e .
^Film completely l o s t i n spots. F u r t h e r w o r k i s b e i n g done i n t h i s a r e a t o u n d e r s t a n d t h i s phenomenon. Since PSiPI i sa negative acting m a t e r i a l , d i s s o l u t i o n of t h e unexposed a r e a s i s r e q u i r e d f o r p a t t e r n i n g . U n l i k e some p h o t o acting polyimides which r e q u i r e organic solvents t o d i s s o l v e t h e unexposed a r e a ( 2 ) , P S i P I i s d e v e l o p e d i n d i l u t e h y d r o x i d e s o l u t i o n w h i c h makes i t c o m p a t i b l e w i t h p o s i t i v e S h i p l e y d e v e l o p m e n t equipment a n d s h o u l d m i n i m i z e p o l y m e r s w e l l i n g p r o b l e m s a s s o c i a t e d w i t h o r g a n i c d e v e l o p e r s . 0.5N NaOH h a s b e e n f o u n d t o be a c o n v e n i e n t s o l v e n t f o r unexposed P S i P I . Some f i l m t h i c k n e s s l o s s i n exposed a r e a s i s observed d u r i n g development. We h a v e p r e v i o u s l y shown t h a t a 1 h r 100°C d r i e d S i P I f i l m c o n t a i n s a b o u t 22% NMP ( 6 ) . The f i l m t h i c k n e s s l o s s u p o n d e v e l o p m e n t may p a r t i a l l y r e f l e c t t h e l e a c h i n g o f t h e NMP f r o m t h e f i l m . Once t h e P S i P I h a s b e e n p a t t e r n e d , t h e r m a l t e m p e r i n g c o n v e r t s t h e c r o s s l i n k e d m o d i f i e d p o l y a m i c a c i d t o t h e S i P I i m i d e . The c r o s s l i n k s a r e expelled during thermal r i n g closure. The r e s u l t i n g S i P I f i l m h a s b e e n shown t o b e more t h a n a d e q u a t e f o r e l e c t r o n i c a p p l i c a t i o n s and h a s some p r o p e r t i e s , p a r t i c u l a r l y adhesion, which a r e b e t t e r than commercial p o l y i m i d e s ( 6 ) . F i g u r e 1 shows a s e t o f I R s p e c t r a d e m o n s t r a t i n g v a r i o u s s t a g e s o f PSiPI f i l m l i f e . I R spectrum A i s t h e u n c u r e d , untempered f i l m . N o t e t h e m e t h a c r y l a t e d o u b l e bond a t 1640 c m ~ l . I R s p e c t r u m Β shows t h e same f i l m a f t e r UV i r r a d i a t i o n ; t h e a b s e n c e o f t h e c a r b o n c a r b o n d o u b l e bond i s a p p a r e n t . I R s p e c t r u m C shows t h e P S i P I f i l m a f t e r t h e r m a l t e m p e r i n g a t 300°C w h i c h c o n v e r t s i t t o S i P I i m i d e . F o r c o m p a r i s o n , a pure sample o f i m i d i z e d S i P I i s shown i n I R s p e c t r u m D. A l s o , when a s a m p l e o f P S i P I was r i n g c l o s e d a t 300°C, t h e Tg o f t h e r e s u l t a n t p o l y m e r was 190°C w h i c h i s t h e Tg o f u n m o d i f i e d f u l l y i m i d i z e d p o l y i m i d e s i l o x a n e . During t h e f i n a l t h e r m a l tempering o f P S i P I , about 40% weight l o s s o f t h e p o l y m e r i s e x p e c t e d and t h i s i s o b s e r v e d i n a 4 0 % r e d u c t i o n o f t h e ζ ( t h i c k n e s s ) dimension o f t h e polymer. Other
21.
DAVIS
Photosensitive
Polyimide
Ί 1 1 T" T Spectrum B. IEM Modified SiPI After 3 0 sec. UV Exposure.
Spectrum A. IEM Modified SiPI Before UV Exposure.
J 1900
I
267
Siloxane
L
1700
1500
1700 WAVENUMBERS
WAVENUMBERS
"Ί 1 1 1 Spectrum D. Fully Cured Unmodified SiPI Film.
Spectrum C. IEM Modified SiPI After 3 0 0 ° C / 1 hr. Tempering.
Γ
0 80
0 00
J
I
1 900
I 1 700
L
J
F i g u r e 1.
IR Spectra of S i P I
I
1900
1 500
WAVENUMBERS
•
•
1700
1500
WAVENUMBERS
After
Various
Treatments
POLYMERS IN ELECTRONICS
268
p a t t e r n dimensions a r e not e f f e c t e d . Figure 2 demonstrates t h i s phenomenon. A s i m i l a r e f f e c t h a s been p r e v i o u s l y o b s e r v e d ( 7 ) . P S i P I f i l m s a s t h i c k a s 12y h a v e been p a t t e r n e d and r e s o l u t i o n s o f 40y h a v e been a c c o m p l i s h e d . Work i s c o n t i n u i n g t o i m p r o v e t h e r e s o l u t i o n , s e n s i t i v i t y , and speed c a p a b i l i t i e s o f PSiPI.
A - Exposed and developed polymer film before tempering (11.6 ).
Β - Same film after 300 °C/2h bake (8.1 ).
Figure 2. Photographs of PSiPI.
Summary A p h o t o s e n s i t i v e s i l i c o n e p o l y a m i c a c i d has been d e s c r i b e d . This m a t e r i a l i s e a s i l y prepared d i r e c t l y from t h e p r e c u r s o r s i l i c o n e p o l y a m i c a c i d . P r o p e r t i e s and c h a r a c t e r i s t i c s o f t h i s p o l y m e r s y s t e m h a v e b e e n d i s c u s s e d i n c l u d i n g h a n d l i n g , u s e , and p r a c t i c a l photochemistry. Thermal tempering o f t h e p h o t o s e n s i t i v e o r c r o s s l i n k e d polymer g i v e s t h e p o l y i m i d e s i l o x a n e w h i c h has been p r e v i o u s l y shown t o be a n e x c e l l e n t c a n d i d a t e a s a n i n s u l a t i n g p o l y m e r i n electronics. The u s e o f s u c h a d i r e c t l y p a t t e r n a b l e p o l y i m i d e f o r d i e l e c t r i c and p a s s i v a t i o n a p p l i c a t i o n s , p a r t i c u l a r l y i n m i c r o e l e c t r o n i c s , s h o u l d become i n c r e a s i n g l y i m p o r t a n t a s p o l y i m i d e s become more w i d e l y a c c e p t e d i n t h e i n d u s t r y .
21. DAVIS
Photosensitive Polyimide Siloxane
269
Ac kno wl ed gmen t s The author wishes to thank Carol Fasoldt for her excellent technical support and Dr. Stephen Valenty for obtaining FTIR data. Literature Cited 1. 2. 3. 4.
Wilson, Α. Μ., Thin Solid Films, 1981, 83, 145. Rubner, R., Siemens Forsch.-u. Entwickl.-Ber., 1976, 5, 235. Sherter, L.; Wynstra, J., Ind. Eng. Chem., 1956, 48 (1), 86. Ozaki, S.; Hashino, T., Nippon Kagaku Nasshi, 1959, 80, 434; Chem. Abstracts, 1961, 55, 4396i. 5. The author is indebted to the referee for pointing out this possibility. 6. Davis, G. C.; Heath, Β. Α.; Gildenblat, G., Proceedings of the First Technical Conference on Polyimides, in press. 7. Rubner, R.; Ahne, Α.; Kühn, E.; Kololodziej, G., Photogr. Sci. Eng., 1979, 23, 303. RECEIVED September 2,
1983
