Cu film: The effect of substrate negative bias voltage

Scripta

METALLURGICA

Vol. 22, Printed

pp. in

757-760, 1988 the U.S.A.

Pergamon Press plc All rights reserved

THE INVESTIGATIONONTHEMICROSTR[L-q~REOFMA6~ETBON SPUTTERING ION PLATED A I / C u FILM: THE EFFECT OF SUBSTRATE NEGATIVE BIAS VOLTAGE

B.O. C h e n , F . J , Wang, Y.K. Wang, J . X . Wang, H.M. I-fan, C.N. Wang, T . Y . N i u a n d H.W. Gao Department of Materials

Engineering,

Dalian

(Received (Revised

Institute

of Technology,Da.lian,

P.R.China

October 26, 1987) March 18, 1988) Introduction

Magnetron Sputtering Ion Plating(MSIP) is an updated technique recently developed by our research group. It is characterized by a p p l y i n g n e g a t i v e b i a s v o l t a g e to the substrate in the glow discharging plasma chamber(Fig. I). This results in the formation of alloy phases in the deposition layer which can firmly join the substrate metal to the film plated(I-4). E v e n i n c a s e o f two i m m i s c i b l e e l e m e n t s , t h e a d h e s i o n i s a l s o s t r o n g e r t h a n t h a t b y t h e u s u a l ion plating techniques because target metal particles c a n be i m p l a n t e d i n t o t h e s u b s t r a t e ( 2 ) . The s u b s t r a t e n e g a t i v e b i a s v o l t a g e ( S N B V ) , a n i m p o r t a n t w o r k i n g p a r a m e t e r f o r t h e MSIP t e c h nique, is the chief factor to enhance the adhesion between film and substrate. The p r e s e n t investigation i s t o v e r i f y t h e e f f e c t o f SNBV on t h e m i c r o s t r u c t u r e of AI/Cu films(Al plated o n t o Cu s u b s t r a t e s ) .

Negative Bias Voltage Substrate Cathod Target (Evaporator)

]

F

Pole-distanceH Cooling-weter !

d__

Magnet

Vacuum Pump ing

.2 Fig.

i D i a g r a m o f CLD-850 MSIP E q u i p m e n t Experimental

Procedure

The p l a t i n g o f A1 o n t o t h e Cu s u b s t r a t e i n t h e CLD-850 MSIP e q u i p m e n t w a s c a r r i e d o u t under the following conditions: p r e s s u r e i n v a c u u m c h a m b e r : 0 . 1 - 0 . 0 1 P a ( f i l e d w i t h Ar)~ power of magnetron evaporator: 9kW; d i s t a n c e from evaporator to substrate: 125mm; p l a t i n g time: 2 0 m i n s . ; SNBV: up t o 2500V. The m i c r o s t r u c t u r e w a s a n a l y s e d u s i n g a n XD-BA x - r a y d t f f r a c t o m e t e r a n d a JEM100CX t r a n s m i s s i o n e l e c t r o n m i c r o s c o p e ( T E M ) . Results and Discussion The s t r u c t u r e s of films plated at different SNBVs w e r e s t u d i e d m a i n l y b y m e a n s o f x ray diffraction. At 750V, t h e f i l m c o n s i s t s o f C u , A1 a n d a l i t t l e A1ZCu; a t 1000V, A1 d e c r e a s e s w h i l e A12Cu i n c r e a s e s w i t h t h e e m e r g e n c e o f A1Cu, A14Cu9 a n d A1Cu3~ a t 1500V, e v e r y phase is approximately a s a b u n d a n t a s a t 1000V e x c e p t t h a t t h e r e i s m o r e A14Cug; a t 1750V, with the disappearance o f A1 a n d d e c r e a s e o f A14Cu9, t h e f i l m c o n s i s t s m a i n l y o f A1Cu, A12Cu,

757 0036-9748/88 $3.00

+ .nn

758

ION

PLATED

AI/Cu

FILM

Vol.

22,

No.

5

AICu3 and Cu; at 2000V, there are only AlCu3 and Cu phases in the film; and at 2500V, AICu3 also disappears and the whole film is composed of an alpha solid solution of Cu and AI. The x-ray diffraction experiment results are listed in TABLE i. TABLE 1 A l l o y and I n t e r m e t a l l i c

750V

lO00V

1500V

1750V

2000V

2500V

a l p h a Cu hkl I / I o 111 100 200 80 220 70 i i i i00 200 80 220 70 i i i 90 200 60 220 100 111 70 200 50 220 30 111 100 200 80 220 70 111 70 200 100 220 40

Compound P h a s e s Formed a t D i f f e r e n t

AICu3 hkl I / I o

AI4Cu9 hkl I / I o

AICu hkl I / I o

CuAI2 hkl I / I o 110 3 112 3

111 2

330 331 421 330 331 633 332 542 402

001 110 203 001 110 201 511

110 211 220 110 310

111 5

111 15 403 25

10 8 8 100 15 8 30 15 15

3 5 3 3 5 2 40

20 10 15 3 2

hkl 111 200 220 200 220

SNBVs

A1 I/Io 30 10 15 10 5

200 10 220 5

112 100

320 60

To stun u p , an a l p h a s o l i d s o l u t i o n o f Cu and A1 e x i s t s a t a l l t h e v o l t a g e s and o n l y p h a s e p r e s e n t a t 2500V; t h e i n t e r m e t a l l i c compounds o f t h e A1-Cu s y s t e m , i . e . , A14Cu9, A1Cu and A12Cu can be f o r m e d i n a c e r t a i n r a n g e o f v o l t a g e s : the higher the t h e r i c h e r t h e Cu c o n t e n t i n t h e p h a s e s f o r m e d . The above r e s u l t s c a n q u a l i t a t i v e l y be a s f o l l o w s . When t h e SNBV i s h i g h , t h e e n e r g y o f A1 i o n s s p u t t e r i n g t h e Cu s u b s t r a t e i s many Cu a t o m s o r i o n s a r e s p u t t e r e d o f f t h e s u b s t r a t e into the film which enhance the o f t h e C u - r i c h p h a s e s . At s u f f i c i e n t l y h i g h v o l t a g e s , t h e amount o f Cu a t o m s o r i o n s i s w h e l m i n g and t h e t e m p e r a t u r e i s s o h i g h t h a t a l l t h e A1 i o n s r e a c h i n g the substrate i n t o t h e a l p h a Cu s o l i d s o l u t i o n .

it

is the A1Cu3, voltage, explained g r e a t and formation so ove rare fused

The s t r u c t u r e o f t h e f i l m p l a t e d a t 1500V i s f u r t h e r s t u d i e d b e c a u s e t h e r e i s a r i c h amount of a l l o y p h a s e s in this condition. Fig. 2 is the x-ray diffraction diagram showing the kinds o f p h a s e s and t h e i r r e l a t i v e a m o u n t s . A1, A12Cu, A1Cu, A14Cug, A1Cu3 and a l p h a Cu a r e i d e n t i f i e d . e x p e r i m e n t s h a v e b e e n done t o s t u d y t h e m i c r o s t r u c t u r e , and t h e o r i e n t a t i o n relationships among t h e s e p h a s e s w e r e o b t a i n e d . F i g . 3 , 4 , 5 , 6 a r e t h e c o m p o s i t e e l e c t r o n d i f f r a c t i o n patterns and t h e t n d e x i n g s o f A12Cu-A1, A14Cu9-A1, A1Cu-A1 and A14Cu9-Cu. T h e s e o r i e n t a t i o n relationships are stmmarized as follows: [101] A12Cu /11013] AI0 (010) A12Cu / / ( 2 0 0 ) A1 [122] A14Cu911[001] A1, ( 0 i l ) A14Cu9//(020) A1 [130] A1Cu / / [ 0 0 1 ] A1, ( 001) A1Cu / / ( 2 Z 0 ) A1 [ 1 7 1 1 ] A 1 4 C u g / / [ 1 1 2 ] Cu, ( 4 i i ) A 1 4 C u 9 1 / ( 1 1 i ) Cu Our s p e c i m e n s f o r TEM w e r e t a k e n p a r a l l e l t o t h e f i l m s u r f a c e so t h a t t h e d e p t h d i s t r i b u t i o n o f p h a s e s i n t h e f i l m c a n n o t be r e v e a l e d by o b s e r v a t i o n s along the direction normal to t h e s u r f a c e a l o n e . For a t h o r o u g h i n v e s t i g a t i o n , cross-section s p e c i m e n s a r e n e c e s s a r y . We h a v e also carried out cross-section o b s e r v a t i o n by T I ~ o f A1/Ni f i l m and r e l e v a n t p a p e r w i l l be p u b lished elsewhere(2). Conclusions 1. SNBV i s an i m p o r t a n t w o r k i n g p a r a m e t e r t o c o n t r o l t h e s t r u c t u r e o f f i l m s made by t h e MSIP t e c h n i q u e , and a v a r i e t y of p h a s e s c a n be r e a l i z e d by p l a t i n g a t d i f f e r e n t SNBVs. 2. The h i g h e r t h e SNBV, t h e r i c h e r t h e C u ( s u b s t r a t e e l e m e n t ) c o n t e n t i n t h e p h a s e s f o r m e d . 3. T h e r e e x i s t s p e c i f i c o r i e n t a t i o n relationships among t h e p h a s e s t h u s o b t a i n e d .

Vol.

22, No.

6

ION P L A T E D

AI/Cu

FILM

759

Reference 1. B.Q. Chen, Y.C. Zhu et al., Heat Treatment Technique, 5, 45 (1984) (Chinese). 2. L.J. Wan, B.Q. Chen and K.U. Kuo, submitted to Thin Solid Film. 3. B.Q. Chen et al., Proc. 8th Int. Symp. Plasma Chem., Tokyo, Japan, Aug.31-Sept.4, 1987. 4. B.~. Chen et al., to be published in Materials Science (1988) (Japan).

ii l!

o

i

a

20

~0

Fig.

50

40

2 X-ray Diffraction

60

qO 2e

8O

70

Diagram of AI/Cu Film Plated

at

1500V.

Ailo~J. cuAi2C~]

"~t,~

. . . . .

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Fig.

3

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Ai(~30l

•

-0-

•

Composite Electron Diffraction Patterns a n d I n d e x i n g s o f CuA12 a n d A1 P h a s e s •

Fig•

4

Composite Electron Diffraction Patterns a n d I n d e x i n g s of. A1Cu a n d A1 P h a s e s .

O ~ o l ~ Oo°

o

rVl'; "o ~'~' "/ "o " I~il--loolJ ~Y:Ci~2]

Fig.

5

Composite Electron

Diffraction

Patterns

and Indexings

o f A14Cu9 a n d A1 P h a s e s .

760

ION PLATED AI/Cu FILM

Vol.

22, No.

O .

•

o. , 4 \ ItF.~',,

I

Q

• 0

.

e0

%

°u

Fig.

6

Composite Electron Diffraction

Patterns

and I n d e x l n g s of A14Cu9 and Cu P h a s e s .

6