PLANAR PLASMA ETCHING OF
`
`blo AND MoSi, USING NF3
`
`T.P. Chow*tand
`
`A . J . S t e c k l t
`
`*General Electric Corporate Research and Development
`S c h e n e c t a d y . NY 12301
`f R e n s s e l a e r P o l y t e c h n i c I n s t i t u t e
`I n t e g r a t e d C i r c u i t s L a b o r a t o r y
`T r o y , NY
`12181
`
`ABSTRACT
`
`u s i n g
`
`P l a n a r p l a s m a e t c h i n g o f
`hlo and MoSi
`i s r e p o r t e d f o r t h e f i r s % t i m e .
`g a s m i x t u r e s
`NF
`3
`Mo, MoSi , and Si02 were deter-
`R 8 c u r r e n t a n d g a s p r e s -
`The e t c h r a t e s o f
`mined a s a
`f u n c t i o n o f
`sure. The e t c h r a t e s e l e c t i v i t i e s o f
`Mo:Si02 and
`t o b e r e l a t i v e l y c o n s t a n t a t
`BloSi2:Sf02 was found
`r e s p e c t i v e l y 2 - 3 : l a n d 4 - 6 : l o v e r
`a b r o a d r a n g e
`o f p a r a m e t e r s . D i l u t i n g t h e
`t o lO?b i n Argon
`NF3
`l o w e r e d t h e e t c h r a t e b y
`a
`
`f a c t o r of 5-6.
`I m p r o v e d l i n e e d g e p r o f i l e o b t a i n e d w i t h
`e t c h i n g i s shown.
`
`NF3
`
`INTRODUCTION
`
`S I c i r -
`
`
`
`t o a c h i e v e
`
`R e f r a c t o r y m e t a l s a n d t h e i r s i l i c i d e s a r e
`use
`r e c e n t l y b e i n g i n v e s t i g a t e d f o r
`c u i t s d u e t o t h e i r h i g h c o n d u c t i v i t y
`t e r n d e f i n i t i o n o f t h e s e m a t e r i a l u s i n g p l a s m e
`
`
`
`e t c h i n g h a s b e e n i n v e s t i g a t e d
`i
`f i n e l i n e s i n t h e m i c r o n r e g i o n
`p l a s m a e t c h i n g o f r e f r a c t o r y m a t e r i a l s h a s u s e d
`CF / O m i x t u r e s , g e n e r a l l y r e s u l t i n g i n a n i s o -
`4
`2
`
`t r o p i c p r o c e s s w h i c h l i m i t e d t h e d e f i n i t i o n
`NF3 g a s m i x t u r e s h a v e r e c e n t l y b e e n
`t o -1pm.
`r e p o r t e d a s p r o m i s i n g p l a s m a e t c h i n g
`f o r p o l y s i l i c o n a n d s i l i c o n n i t r i d e
`t h i s p a p e r
`we p r e s e n t , f o r t h e f i r s t t i m e , t h e
`r e s u l t s of a s t u d y on t h e e t c h i n g p r o p e r t i e s o f
`NF on Mo and MoSi2 f i l m s ,
`3
`
`down
`
`a
`
`func-
`
`MoSiZ
`110 w h i c h i n
`
`RF
`
`was c h a r a c t e r i z e d a s
`The e t c h r a t e
`t i o n of RF c u r r e n t a n d a m b i e n t p r e s s u r e . I n F i g .
`RF c u r r e n t i s shown f o r 100%
`1 , t h e e t c h r a t e v s .
`and a p r e s s u r e of 100mTorr. E x c e e d i n g l y h i g h
`NF
`3
`e t c h r a t e s O l p m / m i n ) w e r e m e a s u r e d f o r h e a v i l y
`p h o s p h o r u s - d o p e d p o l y - S i o v e r t h e e n t i r e c u r r e n t
`It was g e n e r a l l y f o u n d t h a t t h e
`r a n g e .
`e t c h r a t e
`was h i g h e r t h a n t h a t o f
`t u r n was h i g h e r t h a n t h a t o f S i 0 2 a n d a l l
`The
`c u r r e n t .
`i n c r e a s e d m o n o t o n i c a l l y w i t h
`was 5 a t 1 A
`e t c h r a t e s e l e c t i v i t y o f M o S i 2 : S i 0 2
`The e t c h
`c u r r e n t .
`RF c u r r e n t a n d
`6 . 2 a t 2A RF
`r e s p e c t i v e l y 3 . 6
`r a t e s e l e c t i v i t y o f
`Mo:Si02 was
`and 2.9 under the
`same c u r r e n t c o n d i t i o n s .
`The
`d i l u t i o n o f NF w i t h A r g o n r e s u l t e d i n
`a s i g n i f i -
`3.
`c a n t d e c r e a s e i n e t c h r a t e . I n F i g . 2 , t h e e t c h
`i n 10% NF3 i s shown a s a f u n c t i o n of
`r a t e o f Mo
`1 A RF c u r r e n t , t h e
`RF c u r r e n t . F o r e x a m p l e , a t
`0
`e t c h r a t e i n
`1Wo NF3 i s 280A/min, while in 100%
`0
`NF3
`t h e e t c h r a t e
`was 2500A/min. This represents
`a change of approximately an order of magnitude.
`
`The p r e s s u r e d e p e n d e n c e o f t h e e t c h r a t e
`i s
`f o r 100% NF3 and a 1 A RF
`i l l u s t r a t e d i n F i g .
`3
`c u r r e n t . The same
`o r d e r i n r e l a t i v e e t c h r a t e
`Mo a n d S i 0 2 i s o b s e r v e d ,
`magnitude between MoSi2,
`The Mo
`e t c h r a t e e x h i b i t s
`a r a t h e r weak p r e s s u r e
`dependence compared to that of Si0 and
`MoSi2
`w h i c h i n c r e a s e s
`a f a c t o r of 2-3 o v e r % h e p r e s s u r e
`up
`t o 1 5 0 mTorr beyond which
`a much more gradual
`i n c r e a s e i s o b s e r v e d .
`
`EXPERIMENTAL PROCEDURE
`
`DISCUSSION AND CONCLUSION
`
`DC Mag-
`
`Mo and MoSi2 f i l m s w e r e d e p o s i t e d b y
`n e t r o n s p u t t e r i n g o n t o o x i d i z e d s i l i c o n s u b -
`s t r a t e s i n a n MRC 6 0 3 s y s t e m . T y p i c a l d e p o s i t i o n
`parameters were
`1-3KW power and
`3-10pm Ar p r e s -
`s u r e . P o s i t i v e p h o t o r e s i s t ( S h i p l e y 1 4 7 0 )
`was
`Mo and MoSi2 f i l m s
`u s e d t o p r o d u c e
`a s t e p i n t h e
`A p a r a l l e l p l a t e
`f o r e t c h r a t e d e t e r m i n a t i o n .
`plasma etcher (ETE)
`was u s e d w i t h v a r i o u s
`NF
`room 3
`m i x t u r e s . T h e e t c h i n g p r o c e s s t o o k p l a c e a t
`t e m p e r a t u r e f o r d u r a t i o n s f r o m
`1 t o 5 m i n u t e s .
`
`EXPERIMENTAL RESULTS
`
`NF3 does not need any oxygen'
`Unlike CF4,
`p r e s e n t i n o d e r t o g e n e r a t e s u f f i c i e n t e t c h i n g
`s p e c i e s .
`The
`r a t e - l i m i t i n g p r o c e s s e s t h a t c a n
`a f f e c t t h e e t c h r a t e a r e d i s s o c i a t i o n o f e t c h i n g
`g a s , f o r m a t i o n o f p r o d u c t m o l e c u l e s a n d t h e i r
`d e s o r p t i o n . The d i s s o c i a t i v e p r o c e s s e s t h a t c a n
`or a t t h e s o l i d
`t a k e p l a c e i n t h e d i s c h a r g e
`f a c e b e i n g e t c h e d i n c l u d e :
`
`NF 3 NF + (3-x)F where
`3
`
`x = 0 , 1 , 2
`
`As
`e x a e c t a l l t h e
`c a s e 1 8 ' , we
`CF4
`i n t h e
`(NF2, NF a n d F ) t o
`f l u o r i n e - b e a r i n g s p e c i e s
`t r i b u t e f l u o r i n e i n t h e e t c h t n g p r o c e s s ,
`6.5
`
`sur-
`
`con-
`
`CH1616-2/80/0000-0149 $00.75 0 1980 IEEE
`
`149
`
`Authorized licensed use limited to: Nicole Hughes. Downloaded on May 18,2020 at 19:53:20 UTC from IEEE Xplore. Restrictions apply.
`
`Micron Ex. 1031, p. 1
`Micron v. Godo Kaisha IP Bridge 1
`IPR2020-01008
`
`

`

`The a u t h o r s a c k n o w l e d g e h e l p f u l d i s c u s s i o n s
`w i t h D.H. Bower, D.M. Brown, B.A. Heath and B.F.
`G r i f f i n g a n d t h a n k
`C . J . Ludwin and
`G . J . Charney
`f o r t e c h n i c a l a s s i s t a n c e .
`
`REFERENCES
`
`Inoue and
`K. S h i b a t a , T.
`T. Mochizuki.
`"A new MOS p r o c e s s u s i n g MoSi
`Ohucki,
`
`17-1, pp. 37-41, Oct. 1977.
`
`g a t e m a t e r i a l " , J a p a n . J . Appl. Phys.. 2 Vol. a s a
`
`K .
`
`K. Kiuchi, T. Hosoya, T.
`
`
`
`F. Yanagawa,
`
`"A 1-pm
`Anlazawa and T. Mano,
`Tsujimani, T.
`hlo-poly 6 4 - k b i t MOSRM~!",
`IEEE T r a n s . E l e c -
`t r o n D e v i c e s , V o l .
`FD-27,
`pp. 1602-107,
`Aug. 1 9 8 0 .
`
`T.P. Chow and A.J. Steckl "Plasma Etching
`C h a r a c t e r i s t i c s o f S p u t t e r e d
`MoSiZ Films",
`Appl. Phys. Lett., Vol. 37, pp. 466-468,
`S e p t . 1 9 8 0 .
`
`T. Blochizuki, T. Tsuj imani,
`and Y . N i s h i , " F i l m P r o p e r t i e s o f
`T h e i r A p p l i c a t i o n t o S e l f - A l i g n e d i o S i 2
`Gate MOSFET",
`IEEE T r a n s . E l e c t r o n D e v i c e s ,
`Vol. ED-77, pp. 1431-1436,
`Aug. 1 9 8 0 .
`
`Kashiwagi
`MoSi
`and
`
`M.
`
`H . G e i p e l , N. H s i e h ,
`I . H .
`Koburger, and E.N. Fuls, "Composite Sili-
`- I n t e r c o n n e c t i o n s f o r
`c i d e G a t e E l e c t r o d e s
`
`VLSI Device Technologies",
`IEEE T r a n s .
`E l e c t r o n D e v i c e s , V o l .
`pp. 1417-
`1 4 2 5 , Aug. 1 9 8 0 .
`
`I s h a q , C.W.
`
`ED-27,
`
`N . J .
`J . R . Verdeyen, "Comparison
`Ianno and
`o f t h e E t c h i n g a n d P l a s m a C h a r a c t e r i s t i c s
`and NF ", i n E x t e n d e d
`o f D i s c h a r g e s i n
`CF
`A b s t r a c t s , E l e c t r o c % e m i c a l 3 S o c i e t y S p r i n g
`MO, May 1 9 8 0 .
`M e e t i n g , S t . L o u i s ,
`
`K.M.
`E i s e l e , " P l a s m a E t c h i n g o f S i l i c o n
`w i t h N i t r o g e n T r i f l u o r i d e " , i n E x t e n d e d
`A b s t r a c t s , E l e c t r o c h e m i c a l S o c i e t y S p r i n g
`la, May 1980.
`M e e t i n g , S t . L o u i s ,
`
`
`
`H . J . W i n t e r s , J.W. Coburn and E. Kay,
`- A
`
`"Plasma Etching
`"Pseudo-Black-Box"
`48, 4973 (1977).
`Approach", J. Appl. Phys.
`
`T h e p o s s i b l e s u r f a c e c h e m i c a l r e a c t i o n s t h a t
`c o u l d o c c u r d u r i n g e t c h i n g i n c l u d e
`MoSi2 + 14F -) MoF6 + 2SiF4
`Mo + 6F + MoF6
`S i 0 +' S i F + O2
`Si 3 4F 3 g i F 4
`The d e s o r p t i o n o f t h e s e p r o d u c t m o l e c u l e s
`f r o m t h e s o l i d s u r f a c e i s t h e t h i r d i m p o r t a n t
`T h e d e s o r p t i o n r a t e d e p e n d s
`s t e p .
`p r e s s u r e o f e a c h r e a c t i o n p r o d u c t a n d g a s f l o w .
`A l s o , i n c o n t r a s t t o
`CF4,
`a l l t h e d i s s o c i a t e d
`NF
`no n o n r e a c t i v e
`c o n s t i t u e n t s o f
`a r e g a s e s ,
`on t h e s u r f a c e . I n a d d i t i o n
`r e s i d u e b e i n g l e f t
`
`
`
`
`
`
`t o t h e s e c h e m i c a l r e a c t i o n s t e p s , p h y s i c a l
`m e c h a n i s m s , s u c h a s s p u t t e r e t c h i n g , c a n a l s o
`p l a y a s i g n i f i c a n t p a r t , p a r t i c u l a r l y i n t h e
`p r e s s u r e r a n g e ( ( 1 5 0 m T o r r ) .
`
`on
`
`t h e v a p o r
`
`low
`
`1, can be due
`a meas-
`
`i n c r e a s e o f v a r i o u s e t c h r a t e s w i t h
`The
`a p p l i e d c u r r e n t , a s
`shown i n F i g ,
`t o a l l of the mechanisms above. However,
`u r e o f t h e
`DC p o t e n t i a l o n t h e R F - c o u p l e d e l e c -
`t r o d e showed a n a p p r o x i m a t e l y c o n s t a n t v o l t a g e o f
`80V w i t h i n t h e c u r r e n t r a n g e . H e n c e , t h e c u r r e n t
`dependence of etch rates are predominantly chemi-
`c a l i n n a t u r e .
`The decrease of
`l o e t c h r a t e
`i s a t t r i b u t e d t o t h e
`NF3 was d i l u t e d ( F i g .
`2 )
`d e c r e a s e i n t h e c o n c e n t r a t i o n o f e t c h i n g s p e c i e s
`b e c a u s e t h e s u r f a c e r e a c t i o n r a t e a n d d e s o r p t i o n
`r a t e of p r o d u c t m o l e c u l e s a r e n o t e x p e c t e d t o
`c h a n g e s i g n i f i c a n t l y .
`
`when
`
`i s p r o b a b l y
`
`However, when t h e p r e s s u r e
`i s v a r i e d b e t w e e n
`80 and 250 m T o r r , a s s h o w n i n F i g . 3 , t h e w e a k
`pressure dependence of
`Mo
`e t c h r a t e
`d u e t o t h e l i m i t i n g e f f e c t o f e i t h e r t h e s u r f a c e
`MoF6 o r b o t h .
`r e a c t i o n r a t e o r d e s o r p t i o n r a t e o f
`I n t h e MoSi2 c a s e , t h e i n i t i a l e t c h r a t e a p p e a r s
`Beyond 150 mTorr.
`t o b e m a s s t r a n s f e r l i m i t e d .
`t h e r e a c t i o n r a t e i s i n c r e a s i n g l y t h e l i m i t i n g
`f a c t o r . M o r e o v e r ,
`when t h e p r e s s u r e i n c r e a s e d t o
`DC p o t e n t i a l on the RF-coupled
`150 mTorr, the
`e l e c t r o d e d r o p p e d t o
`-2OV
`and remained essen-
`t i a l l y c o n s t a n t w i t h f u r t h e r i n c r e a s e i n p r e s -
`sure. Hence,
`no s i g n i f i c a n t p h y s i c a l e t c h i n g
`e x p e c t e d i n t h i s r e g i o n .
`
`i s
`
`.
`
`a
`T y p i c a l SEW m i c r o p h o t o g r a p h s t a k e n f r o m
`0
`a t 100 mTorr
`3000A-thick MoSi2 f i l m e t c h e d i n
`NF
`and 1 A c u r r e n t a r e
`shown
`i n F i g . % ( a ) a n d ( b ) .
`An
`i s obserygf when compared
`improved anisotropy
`CF /O e t c h i n g
`w i t h c o n v e n t i o n a l
`4
`
`2
`I n c o n c l u s i o n , p l a n a r p l a s m a e t c h i n g o f
`i s r e p o r t e d f o r t h e f i r s t
`and MoSiZ w i t h NF3
`time. The
`RF current and pressure dependence of
`e t c h r a t e s
`of Mo, MoSiZ a n d S i 0 h a v e b e e n s t u -
`d i e d . E t c h r a t e s e l e c t l v i t i e s 0 ? 2 - 3 : 1 a n d 4 - 6 : l
`w e r e r e s p e c t i v e l y o b t a i n e d f o r
`Mo over Si02 and
`MoSiz o v e r S i 0 w i t h i n t h e r a n g e o f p a r a m e t e r s
`i n v e s t i g a t e d . % i l u t i n g
`NF
`i n i n e r t g a s e s ( e . g .
`Ar) d e c r e a s e s t h e e t c h r a 2 e s .
`Good a n i s o t r o p i c
`e d g e p r o f i l e h a s b e e n
`shown t o b e o b t a i n a b l e .
`
`Mo
`
`150
`
`6.5
`
`Authorized licensed use limited to: Nicole Hughes. Downloaded on May 18,2020 at 19:53:20 UTC from IEEE Xplore. Restrictions apply.
`
`Micron Ex. 1031, p. 2
`Micron v. Godo Kaisha IP Bridge 1
`IPR2020-01008
`
`

`

`,
`9000 -
`
`10,000
`
`I
`
`I
`
`I
`
`GAS - 100% NF3
`RF CURRENT - IA
`
`I
`-
`
`-
`13,000
`-
`1&000
`
`I
`I
`2 00
`I50
`PRESSURE I mTorr)
`
`2 50
`
`Mo, MoSi2, P o l y S i and S i 0
`F i g . 1 E t c h r a t e s o f
`2
`vs FiF c u r r e n t f o r 100% NF3 a t 100 mTorr
`p r e s s u r e .
`
`Si02
`
`-
`
`1000 -
`--1-1-1=
`018 019 !.IO I.'\
`
`I.;
`
`F i g . 3
`
`1.6
`I.;
`1,'4
`1.;
`( A I
`RF CURRENT
`of Mo, MoSi
`and. S i 0
`E t c h r a t e
`2 vs
`p r e s s u r e f o r 100% NF32at 1 A c u r r e n t .
`
`1.;
`
`1.b
`
`119 2 h
`
`- 400 - I/'
`/2
`
`I
`
`I
`
`/
`
`GAS-IO% N F 3 I S O X A r
`PRESSURE - 200 rnTorr
`
`-
`-
`
`500
`
`.- c
`E
`5
`w 300-
`-
`I- U
`p: 200
`e
`r
`loo-
`
`O O
`
`F i g . 2
`
`E t c h r a t e o f
`NF3 i n A r
`
`I
`I
`1
`2
`RF CURRENT (A)
`
`A 3
`
`Mo v s RF c u r r e n t f o r
`
`10%
`
`F i g . 4 (a) and ( b )
`T y p i c a l SEM microphotographs
`f o r e t c h i n g 3 0 0 0 i MoSi2 over S i 0
`2 '
`
`6.5
`
`151
`
`Authorized licensed use limited to: Nicole Hughes. Downloaded on May 18,2020 at 19:53:20 UTC from IEEE Xplore. Restrictions apply.
`
`Micron Ex. 1031, p. 3
`Micron v. Godo Kaisha IP Bridge 1
`IPR2020-01008
`
`

`

`Authorized licensed use limited to: Nicole Hughes. Downloaded on May 18,2020 at 19:53:20 UTC from IEEE Xplore. Restrictions apply.
`
`Micron Ex. 1031, p. 4
`Micron v. Godo Kaisha IP Bridge 1
`IPR2020-01008
`
`