DEVELOPMENT OF BORON AND PHOSPHORUS LIQUID-METAL-ION SOURCES

HAL Id: jpa-00224412

https://hal.archives-ouvertes.fr/jpa-00224412

Submitted on 1 Jan 1984

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

DEVELOPMENT OF BORON AND PHOSPHORUS LIQUID-METAL-ION SOURCES

T. Ishitani, K. Umemura, Y. Kawanami, H. Tamura

To cite this version:

T. Ishitani, K. Umemura, Y. Kawanami, H. Tamura. DEVELOPMENT OF BORON AND PHOS-

PHORUS LIQUID-METAL-ION SOURCES. Journal de Physique Colloques, 1984, 45 (C9), pp.C9-

191-C9-196. �10.1051/jphyscol:1984932�. �jpa-00224412�

DEVELOPMENT OF BORON AND PHOSPHORUS LIQUID-METAL-ION SOURCES T. Ishitani, K. Umemura, Y. Kawanami and H. Tamura

Central Research Laboratory, Hitachi Ltd., Kokubunji, Tokyo 185, Japan-

Résumé - Des sources d'ions à métal liquide (LMIS) de (B) et (P) ont été développées pour l'implantation sans masque dans le sili- cium. La source de (B) qui emploie un émetteur de carbone ou de carbure et un alliage à base de Ni-B a une' durée de vie de plus de 250 heures. La source de (P) utilisant l'alliage Cu-P permet plus de 20 heures de fonctionnement. Les ions issus de ces sour- ces sont analysés en masse et en énergie. Des effets isotopiques ont été observés pour l'émission ionique de B. Des essais prélimi- naires d'implantation de B+ dans Si ont été entrepris en utilisant une colonne ionique avec séparateur de masse.

Abstract - Boron (B) and phosphorus (P) liquid-metal-ion (LMI) sources have been developed for maskless implantation in silicon, The B-LMI source, which employs a carbon or carbide emitter and a Ni-B base alloy as its source material, has a lifetime of more than 250 hours. The P-LMI source utilizing a Cu-P alloy achieves a lifetime of more than 20 hours. The ions emitted from these sources are investigated by mass and energy analyses. Isotope effect has been observed for B ion emission with a B-LMI source.

Focused B implantation in Si was preliminarily carried out using a mass-separated microbeam column.

1. Introduction

LMI sources are now being actively investigated due to" the poten- tially enormorus advantages they offer in focused-ion-beam (FIB) technology, such as maskless implantation, microfabrication, and submicron analysis /1-if/. Considerable interest has also been shown in the diversity of ion species LMI sources provide. For ion implan- tation into Si semiconductors, B, As, and P are the most important dopants. However, it is difficult to construct LMI sources from these materials due to their high melting point (for B ) , high vapour

pressure (for As and P ) , or strong corrosive effect on most metals ( for B). Several LMI sources that use eutectic alloys as the source material have been reported to date /5-7/. For GaAs semiconductors, LMI sources for Be and Si ions have also been developed by employing eutectic alloys /5,8,9/.

Recently, B- and P-LMI sources have been developed by the authors /10,11/. The present paper briefly describes these sources with new additional data on ion emission characteristics. Evidence of isotope

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984932

C9-192 JOURNAL

DE

PHYSIQUE

e f f e c t i n t h e B-LMI s o u r c e i s a l s o p r e s e n t e d . F u r t h e r , p r e l i m i n a r y e x p e r i m e n t s o n

B'-FIB

i m p l a n t a t i o n i n t o S i u s i n g a mass-separated microbeam column /12/ w i t h maximum beam energy of 20 keV a r e d e s c r i b e d . F i n a l l y , t h e h i g h d o s e - r a t e e f f e c t i n

F I B

i m p l a n t a t i o n /13/ i s d i s - cussed.

2.

B- and P-LMI s o u r c e s

The LMI s o u r c e f o r

B

and P i o n s c o n s i s t s o f a n e e d l e e m i t t e r , h e a t e r and e x t r a c t o r . Molten s o u r c e - m a t e r i a l mounted on t h e h e a t e r c o v e r s

t h e e m i t t e r and s t a b l y f l o w s t o t h e e m i t t e r t i p d u r i n g i o n emission.

F o r t h e B-LMI s o u r c e /10/, a combination of c a r b o n o r c a r b i d e n e e d l e s and

Ni-B

base a l l o y s as t h e s o u r c e m a t e r i a l was used. L i t t l e r e a c t i o n i s produced between t h e s e m a t e r i a l s , s o t h e y p r o v i d e a s o u r c e l i f e t i m e of more t h a n 250 hours. F o r t h e P-LMI s o u r c e

/U/, a

combination of m e t a l n e e d l e and Cu-P a l l o y w a s employed.

A

s o u r c e l i f e t i m e of more t h a n 20 hours w a s achieved, which was mainly r e s t r i c t e d by s e l e c t i v e e v a p o r a t i o n o f t h e P element due t o i t s h i g h vapor p r e s s u r e . Thus, t h e r e i s much room f o r improvement of t h e

P

s o u r c e l i f e t i m e .

I o n s e m i t t e d from t h e s o u r c e were i n v e s t i g a t e d by mass and energy a n a l y s e s u s i n g a double-focusing mass s p e c t r o m e t e r w i t h a n e n e r g y r e s o l u t i o n of AE

=

1.1 eV a t E

=

3.2 keV. T h i s r e s o l u t i o n w a s c a l i - b r a t e d u s i n g s u r f a c e - i o n i z e d ~ a + beams.

T y p i c a l mass s p e c t r a f o r i o n s e m i t t e d from t h e l i q u i d

N i

B S i 45 45 1 0 a l l o y a t It = 25 p l and Cu

P

a l l o y a t

It =

80 )1A a r e shown i n Figs.

1

( a ) and ( b ) , r e s p e c t i v e l y . 3 Here, I t i s t o t a l e m i s s i o n c u r r e n t .

O p e r a t i n g t e m p e r a t u r e f o r t h e s e s o u r c e s was 900 - 950 "C f o r t h e B s o u r c e and 750 - ⁸⁰⁰

^"C

f o r t h e P s o u r c e . The B' and

P'

i o n i n t e n - s i t i e s were 25 - ^{35 %} and a b o u t 1 0 % of t o t a l i o n i n t e n s i t y , respec- t i v e l y , depending o n o p e r a t i n g c o n d i t i o n s .

T y p i c a l energy d i s t r i b u t i o n s f o r 'IB',

58~i',

a n d

2 8 ~ i +

i o n s from t h e Ni-B-Si a l l o y a r e shown i n Fig.2 f o r I t

=

40 9 . The o r i g i n of t h e energy axis i s e s t i m a t e d , r a t h e r t h a n c a l i b r a t e d . S i m i l a r e x p e r i - ments f o r t h e Cu-P a l l o y were c a r r i e d o u t . T y p i c a l r e s u l t s of f u l l - width-at-half-maximum (FWHM) v a l u e , AE, f o r v a r i o u s i o n s a r e g i v e n i n T a b l e

1.

I t w a s found t h a t A E v a l u e s f o r doubly-charged i o n s a r e , i n g e n e r a l , have a narrower range t h a n t h o s e f o r s i n g l y - c h a r g e d i o n s , as p o i n t e d o u t i n a p r e v i o u s p a p e r

/l.+/.

The

AE

vs. I t r e s u l t s f o r v a r i o u s i o n s , i.e.

B+

f o r Ni-B-Si a l l o y ,

P+

and

CU+

f o r Cu-P a l l o y , and ~ a ' f o r pure

G a ,

a r e summarized i n Fig.

3 . A s shown, t h e r e i s a s t r o n g mass-dependence, w i t h l i g h t e r i o n s

h a v i n g a narrower AE.

40 20 0 -20 -40 Relative Ion Energy

,

E ( e V )

Fig.2 T y p i c a l energy d i s t r i - b u t i o n s of B,

N i ,

and S i i o n s .

I . I . I , I

0 50 100 150 200

Total Ion Current, IT(

m)

Fig.3

^{A E}

vs. It f o r v a r i o u s

LMI s o u r c e s .

C9-194 JOURNAL DE PHYSIQUE

3. Isocope e f f e c t on B i o n e m i s s i o n

I s o t o p e e f f e c t on

B

i o n s e m i t t e d from t h e B-LMI s o u r c e h a s been observed. The

B++

i o n i n t e n s i t y

i s

a s weak a s 1/30 - 1/50 t h a t f o r

B+

a t It=15 - loo)&, b u t t h e r e i s a c e r t a i n d i f f e r e n c e between P10 and Pll, where Pm i s t h e i n t e n s i t y r a t i o o f m ~ + + t o (*B+

+

m ~ + + ) . F i g u r e 4 shows t h e e x p e r i m e n t a l AP v a l u e s

(=

Pll - PlO) p l o t t e d a s a f u n c t i o n of P

(=

Pll).

A s

shown, t h e Pll v a l u e s a r e l a r g e r by 13 - ^{1 7 % t h a n}

t h e P10 v a l u e s .

The p o s t - i o n i s a t i o n model f o r f i e l d e v a p o r a t i o n proposed by Haydock and Kingham

/l>/

p r e d i c t s s u c h i s o t o p e e f f e c t when a n element w i t h two o r more i s o t o p e s i s f i e l d evaporated. According t o t h a t model, t h e l e s s - m a s s i v e i s o t o p e s t r a v e l f a s t e r and t h u s spend l e s s t i m e i n t h e p o s t - i o n i s a t i o n zone i n which t h e t r a n s i t i o n from t h e s i n g l y - t o doubly-charged i o n s i s e x p e c t e d t o occur.

The s o l i d l i n e i n Fig.4 c o r r e s p o n d s t o t h e t h e o r e t i c a l c u r v e based on t h i s model, e x p r e s s e d as AP = (1/2)

(

AM/Mb)Pb f o r

AM

((Mb and Pb((

1.

Here, AM

= Mb

-

^Ma

^and

^Mm

r e p r e s e n t s t h e mass of i s o t o p e m.

The p o s t - i o n i s a t i o n model e x p l a i n s t h e p r e s e n t i s o t o p e e f f e c t f a i r l y w e l l , a l t h o u g h t h e r e a r e some d i s c r e p a n c i e s between experiment and t h e o r y .

A

similar i s o t o p e e f f e c t h a s been o b s e r v e d f o r f i e l d evapo- r a t i o n o f FeB and

COB

m e t a l l i c g l a s s e s by Menand and ~ i i ~ h a m /16/.

A

more d e t a i l e d d i s c u s s i o n w i l l be p r e s e n t e d elsewhere.

Table

1 AE

v a l u e s f o r v a r i o u s i o n s e m i t t e d from Ni-B-Si and Cu-P LMI-sources a t

I t =

3 0

8' I I I

6

-

4

-

^/' j g / [ L P .

:

2 - ^A-=

_ _ / - - -

--- ^Theory

^CHK)

,/-7 Oo

I I I

1 2 3 4

Fig.4 D i f f e r e n c e i n p o s t - i o n i s a t i o n

p r o b a b i l i t i e s of

''B+

and

llB+ S

*p,

a s a f u n c t i o n o f p o s t - i o n i s a t i o n

p r o b a b i l i t y o f 'IB+,

P. (

Broken

l i n e c o r r e s p o n d s t o t h e t h e o r e t i c a l

P r e l i m i n a r y e x p e r i m e n t s on FIB i m p l a n t a t i o n have been c a r r i n g o u t u s i n g a mass-separated microbeam column, t h e d e t a i l s o f which have been d e s c r i b e d e l s e w h e r e /12/. T h i s column h a s t h e a b i l i t y t o produce sub-pm beams w i t h e n e r g i e s of u p t o 20 keV and h i g h c u r r e n t d e n s i t i e s ,

J,

e.g. s e v e r a l t e n s o f miX/cm2 f o r

B+

beam. These

J

v a l u e s a r e a b o u t t h r e e o r d e r s h i g h e r i n magnitude t h a n t h o s e f o r a c o n v e n t i o n a l implan- t e r u s i n g a n unfocused beam.

F i g u r e 5 shows t h e c a l c u l a t e d maximum t e m p e r a t u r e a t t h e c e n t e r of a s t e a d y - s t a t e unscanned FIB f o r S i and

G a A s

t a r g e t s based on t h e a n a l y t i c a l form of

N i s s i m

e t a1 /17/. I n t h e c a l c u l a t i o n , a t a r g e t back-surface t e m p e r a t u r e of 25

'C

and temperature-dependent t h e r m a l c o n d u c t i v i t y e x p r e s s e d by K(T)

=

A/(T - ^B

⁾

a r e assumed. Here,

A =

299 W/cm and B = -174 "C f o r S i , and

A =

9 1 W/cm and B

=

-182 "C f o r GaAs. I t s h o u l d be noted t h a t even a 1 0 0 keV unscanned beam of

l

p m i n d i a m e t e r w i t h

J =

1 0 A/cm 2 is e x p e c t e d t o i n c r e a s e a S i t a r g e t t e m p e r a t u r e from 25

"C

t o o n l y a b o u t 50

OC*.

No s i g n i f i c a n t FIB-heating h a s a l r e a d y p o i n t e d o u t i n t h e p r e v i o u s

/ 2 / .

R e c e n t l y , a h i g h d o s e - r a t e e f f e c t has been observed f o r

B+

FIB i m p l a n t a t i o n i n t o S i , t h a t i s , h i g h e l e c t r i c a l a c t i v a t i o n i n t h e a n n e a l e d i m p l a n t e d - l a y e r has been r e s u l t e d from enhancement of t h e amorphous zone /13/. T h i s enhancement i s presumably b r o u g h t a b o u t by o v e r l a p p i n g of t h e damage zone s u r r o u n d i n g t h e i o n p a t h w i t h i n some l i f e t i m e of i t s s h r i n k a g e , n o t by FIB h e a t i n g and s e l f - a n n e a l i n g ,

5. Conclusions

B-

and P-LMI s o u r c e s have been developed f o r m a s k l e s s i m p l a n t a t i o n i n t o

S i

semiconductors. The B-LMI s o u r c e , u s i n g a combination of a

c a r b o n o r c a r b i d e e m i t t e r and a

Ni-B

b a s e a l l o y a s i t s s o u r c e m a t e r i a l , h a s a l i f e t i m e of more t h a n 250 h o u r s and p r o v i d e s a

B+

e m i s s i o n c u r r e n t of 25 - 35 % t h e t o t a l e m i s s i o n c u r r e n t .

I s o t o p e v a r i a t i o n s i n

B

i o n e m i s s i o n have been observed. The l 0

+

p r o p o r t i o n of ''B++ t o

(

B

+

''B++) i s 1/30 - 1/50, which i s 13 - ¹⁷

% s m a l l e r t h a n f o r "B++ . T h i s i s o t o p e e f f e c t w a s p r e d i c t e d by t h e p o s t - i o n i s a t i o n model f o r f i e l d e v a p o r a t i o n proposed by Haydock and

~ i n g h a m / l 5 / , a l t h o u g h t h e r e a r e c e r t a i n d i s c r e p a n c i e s between t h e e x p e r i m e n t a l r e s u l t s and theory.

A

P-LMI s o u r c e u t i l i z i n g a Cu-P a l l o y has a l s o been developed.

P+

i o n e m i s s i o n c u r r e n t i s a b o u t 1 0 % o f t o t a l e m i s s i o n c u r r e n t i n t h i s s o u r c e , a n d i t s l i f e t i m e i s more t h a n 20 hours.

Emission c h a r a c t e r i s t i c s f o r t h e

B-

and P-LMI s o u r c e s have been

C9-196 JOURNAL

DE

PHYSIQUE

Fig.5 C a l c u l a t e d maximum temper- a t u r e

a t

t h e c e n t e r of

a

100 keV s t e a d y - s t a t e unscanned beam f o r S i and GaAs t a r g e t s

i n v e s t i g a t e d by

mass

and e n e r g y a n a l y s e s . P r e l i m i n a r y e x p e r i m e n t s

800- on FIB i m p l a n t a t i o n were a l s o

c a r r i e d o u t u s i n g

a

mass-separated

microbeam column. I n t h e s e e x p e r i - 600 ments, h i g h d o s e - r a t e e f f e c t

was

n

observed.

9

-400

R e f e r e n c e s

I I I 1 1 1 1 1 ~ I I I 1-

Si I

--- -

GaAs I

- I I -

-

I

I -

I I

-

1

- I

1 R.L,Kubena, C.L.Anderson, R.L.Seliger, R.A. J u l l e n s , E.H.Stevens, and 1.Lagnado: J. Vac. S c i . Technol. lq(19811916

2 W.L.Brown and A.Wagner: i n Proc. of I n t . I o n E n g i n e e r i n g Congress ISIAT'83 & IPAT'83 (Kyoto, 1983)

3

^M.Komuro: T h i n S o l i d F l l m s =(l9821155

4 Y,Bamba, E-Miyauchi, H.Arimoto, K.Kuramoto A.Takamori, and H,Hashimoto : Japan, J. Appl. Phys. ~ ( 1 9 8 3

j

^L650

5

V.Wang, J.W.Ward, and R.L.Seliger: J. Vac. S c i . Technol. u ( 1 9 8 1 )

1158

l-

6

K.Gamo, T.Ukegawa, Y.Inomoto, K.K.Ka, and S.Namba: Japan. J. Appl.

Phys. 1980 L595

7 K.Gamo, T.Ukegawa, Y.Inomoto, Y.Ochiai, and S.Namba: J. Vac. S c i . Technol. Q ( 1 9 8 1 1 1 1 8 2

8 E.Miyauchi, H,Hashimoto, and T.Utsumi: Japan. J. Appl. Phys.

22

(19831L225

9 K.Gamo, T.Matsui, and S.Namba: Japan. J. Appl. Phys. = ( 1 9 8 3 ) ~ 6 9 2 1 0 T - I s h i t a n i , K.Umemura, S.Hosoki, S.Takayama, and H.Tamura: J. Vac.

S c i . Technol. ( i n p r e s s )

11 T . I s h i t a n i , ~ . ~ m e m ; r a , and H.Tamura: Japan. J. Appl. Phys.

a

(1984)L330

1 2 ~ , ~ s h i t a n i , K.Umemura, and H.Tamura: Nucl. Instrum. Methods

218

(1983 1363

13

M.Tamura, S.Shukuri S.Tachi, T - I s h i t a n i , and H.Tamura: Japan. J.

Appl. Phys. ~ ( 1 9 8 3 3 ~ 6 9 8

1 4 L.W.Swanson: i n Proc. of I n t . I o n E n g i n e e r i n g Congress ISIAT183 &

IPAT'83 (Kyoto, 19831p.325

15

R.Haydock and D.R.Kingham: Phys, Rev. L e t t , -J&(1980)1520

16 A.Menand and D.R.Kingham: J. Phys. D: Appl. Phys. g ( 1 9 8 4 1 2 0 3 1 7 Y . I . N i s s i m , A . L i e t o i l a , R.B.Gold, J.F.Gibbons: J. Appl. Phys.

51

(1980 1274