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Submitted on 1 Jan 1981
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ARSENIC SULPHIDE AS EVAPORATED DRY PHOTORESIST
A. Buroff
To cite this version:
A. Buroff. ARSENIC SULPHIDE AS EVAPORATED DRY PHOTORESIST. Journal de Physique
Colloques, 1981, 42 (C4), pp.C4-967-C4-969. �10.1051/jphyscol:19814212�. �jpa-00220841�
JOURhTAL D E P H Y S I Q U E
CoZZoque C4, suppZEment au nO1O, P'ome 4 2 , octobre 1981 page C4-967
ARSENIC SULPHIDE AS EVAPORATED DRY PHOTORESIST
A . B u r o f f
CentraZ Laboratory o f Photographic Processes, Bulgarian Academy o f Sciences, 1040 S o f i a , Bulgaria
% b s t r a . c t . - h o s t ar:~orphous s u b s t a n c e s change t h e i r p h y s i c a l and c h e ~ i c a l p r o p e r t i e s o n i l l u m i n a t i o n . The p h o t o s e n s i t i v e s o l u b i l i t y p e r a i t ; t h e u s e o f amorphous a r s e n i c s u l p h i d e a s e v a p o r a t e d p h o t o r e s i s t . An a p p r o p r i a t e s o l v e n t was f'ound kihich f u l l y c i i s s o l v e s t h e exposed a r e d s iv'ithoxt a f f e c t i n g t h e unexposed ones. Thus e x t r e m e l y t h i n l a y e r s o f e v a p o r a t e d
~ r r ~ o r p h o u s a r s e n i c s u l p h i u e c a n be u s e d a s s e n s i t i v e photo- r e s i s t w i t h h i g h r e s o l u t i o n f o r t h e p r o d u c t i o n o f chroaium masks and s e n s i t i z e d o f f s e t p r i n t i n g p l a t e s .
Among t h e numerous c h a l c o g e n i a e g l a s s e s a r s e n i c s u l p h i d e shows o n i l l u m i n a t i o n most s i g n i f i c a n t changes o f i t s physicochemi- c a l p r o p e r t i e s . The p h o t o s e l e c t i v e d i s s o l u t i o n and t h e r e s i s t a n c e t o a c i d s c f t h i s s u b s t a n c e c r e a t e t h e b a s i s l o r i t s a p p l i c a t i o n as i n - o r g a n i c a r y p h o t o r e s i s t . I t i s kriown t h a t a r s e n i c s u l p h i d e c i i s s o l v e s r e a d i l y i n a l k a l i n e s o l u t i o n s ( 1 ) as w e l l as i n some o r g a n i c corn- pounds ( 2 ) . The o p t i m a l r a t i o o f t h e d i s s o l u t i o n r a t e s o f t h e i l l u m i n a t e d and u n i l l u m i n a t e d a r e a s i s u s u a l l y o f t h e o r d e r o f 2:l.
I t i s a l s o known t h a t by u s i n g s u i t a b l e c o n c e n t r a t i o n s a n d s o l v e n t s one c o u l d a c h i e v e a n i n v e r s e r a t i o , i . e . n e g a t i v e u i s s o l u t i o n . I n a l l t h e s e c a s e s r e l a t i v e l y t h i c k a r s e n i c s u l p h i d e l a y e r s s h o u l d be e v a p o r a t e d i n o r d e r t o e n s u r e s u i t a b l e p r o t e c t i o n , s i n c e t h e un- exposed a r e a s d i s s o l v e t o g e t h e r w i t h t h e exposed ones. T h i s l e a d s t o s u b s t a n t i a l l y l o v e r s e n s i t i v i t y which l i m i t s t h e z p p l i c a b i l i t y o f t h i s t y p e r e s i s t f o r p r a c t i c a l p u r p o s e s . O b v i o u s l y t h e a p p l i c a - t i o n o f a s o l v e n t i n which t h e u n i l l u n i n a t e d a r e a s do n o t d i s s o l v e f o r t h e t i m e r e q u i r e d f o r d i s s o l u t i o n o f t h e i l l u n i n a t e d r e g i o n s would l e a d t o a s u b s t a n t i a l improvement i n t h e perforlllance o f t h e e v a p o r a t e d r e s i s t b a s e d on a r s e n i c s u l p h i d e . Such a s o l v e n t w a s found i n o u r L a b o r a t o r y ( 3 ) . T h e t i m e dependence o f t h e d i s s o l u t i o n r a t e i n t h i s s o l v e n t i s p r e s e n t e d i n Fig.1. The same dependence f o r a known s o l v e n t i s g i v e n f o r comparison.
Thus t h i c k n e s s e s o f t h e o r d e r o f 0 , 0 7
-
0 , lpm
p r o v i d e a r e l i a b l e p r o t e c t i o n a g a i n s t t h e a c t i o n o f a c i d s . The s m a l l t h i c k n e s s o f t h e l a y e r s l e a d s $0 a s u b s t a n t i a l i n c r e a s e o f t h e s e n s i t i v i t y-
a b o u t 0 , 4
-
0,6 j/cm.
Another a d v a n t a g e o f t h e s e e x t r e m e l y t h i n l a y e r s i s t h a t t h e y f a c i l i t a t e t h e o p t i c a l p r i n t i n g o f submicron u e t a i l s a s w e l l as t h e r e p r o d u c t i o n o f t h e l a t t e r s by c o n t a c t p r i n t - i n g . T o l e r a n c e s o f 2 10,~ i n t h e exposure and 2 200;; i r , t h e tievelop- ment change t h e l i n e width l e s s t h a n 10%.Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19814212
JOURNAL DE PHYSIQUE
Pix.1 : S o l u b i l i t y o f exposed (1) and unezposed ( 2 ) a r e a s i n a c o n v e n t i o n a l s o l v e n t ( 0 ) a n d i n o u r s o l v e n t
(a
).A t ; r e s e n t t h e z p p l i c a f i o n o f a r s e n i c s u l p h i u e as e v a p o r a t e d p h o t o r e s i s t i s d e v e l o p e d i n o u r L a b o r a t o r y i n two main d i r e c t i o n s : f o r t h e p r o d u c t i o n of' chrol!iiu~l u~ilsks and f o r o f f s e t p r i n t i n g .
n l h e cilromium mask:; r e p r a s e r i t a rc*cd>>:icii s t n c t u r r o f a g l a s s s u b s t r a t e o n t o which C r - and As2S3-layers a r e e v a p o r a t e d . The u s e o f a r s e n i c s u l p h i d e h a s t h e f o l l o w i n g a d v a n t a g e s :
1. iiigiler r e s o l u t i o n i n c o n b i n a t i o n w i t h b e t t e r r e l i a b i l i t y . 2. L o w e r s h e l f - l i f e b o t h b e f o r e and a f t e r exposure.
3. "Pre- and post-baking" i s n o t n e c e s s a r y .
4. The chrorr~iun a n d t h e r e s i s t l a y e r are d e p o s i t e d i n t h e sal::e vacuum c y c l e ; l z y e r s w i t h u n i f o r m t h i c k n e s s a n d ex- c e l l e n t o p t i c a l p r o p e r t i e s o n t o a g r e a t v a r i e t y o f sub- s t r a t e forms and dimensions a r e o b t a i n e d .
5. E e t t e r r e p r o c i u c i b i l i t g .
6 . P o s s i b i l i t y t o copy s t r u c t u r e s v i t h d i f f e r e n t l i n e w i d t h u s i n g one a n d t h e saEe e x p o s u r e and p r o c e s s i n g .
The hydrophoby o f a r s e n i c s u l p h i u e a s w e l l as i t s a b i l i t y t o a c c e p t i n k i s u s e d f o r t h e p r o d u c t i o n o f o f f s e t p r i n t i r g p l a t e s . I n t h i s c a s e a t h i n As2S3 l a y e r i s e v a p o r a t e d o n t o aluminium o f f s e t p l a t e s . A f t e r e x p o s u r e and s e l e c t i v e d i s s o l u t i o n a p o s i t i v e As2S3 image i s o b t a i n e d which i s i n k e d u s i n g t h e c o n v e n t i o n a l t e c h n i q u e . The p r o p e r t i e s o f t h e p l a t e s t h u s s e n s i t i z e d s t r o n g l y depend o n t h e t y p e and s t r u c t u r e o f t h e aluminium s u b s t r a t e . Nore t h a n 50,000 p r i n t s w i t h e x c e p t i o n a l l y h i g h image q u a l i t y c a n be a c h i e v e d u s i n g a n a p p r o r i a t e s u b s t r a t e .
A t p r e s e n t t h e r e i s no s a t i s f a c t o r y e x p l a n a t i o n o f t h e photo- s e l e c t i v e d i s s o l u t i o n o f a r s e n i c sulphide. The following observation..
should b e taken i n t o account f o r t h e e l u c i d a t i o n o f t h i s phenomenon:
1, One and t h e same s o l v e n t can d i s s o l v e n e g a t i v e l y o r posi- t i v e l y depending on i t s concentration.
2. The p o s i t i v e image can be reversed i n t o a negative one by h e a t i n g t h e l a y e r s p r i o r t o o r a f t e r i l l u m i n a t i o n .
The m o s t promising a p p l i c a t i o n o f t h i s evaporated r e s i s t i s expected t o he t h e reproduction o f submicron s t r u c t u r e s , A t p r e s e n t 0,5
pm
d e t a i l s a r e reproduced by o p t i c a l p r i n t i n g a t h = 436 nm.References
1. H B L W R. W., US P a t e n t Nr.376 2325 (1973).
2. KOLOIVIIECS B.T. e t al., Physika i chimia s t e k l a
4
(1978) 351.3. Bulgarian Authorship C e r t i f i c a t e , Appl.Nr.46640/15,02.1980.
4. STOYCHXVA-TOPALOVA R. and BUROFF A., 2nd 1nt.Symp. on Piode1 I n v e s t i g a t i o n s o f t h e Photographic P r o c e s s and New P h o t o r e g i s t e r - i n g Systems, Varna, 1980, P r e p r i n t s F84.