EFFECTS OF ARGON ON THE PROPERTIES OF RF SPUTTERED AMORPHOUS SILICON

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EFFECTS OF ARGON ON THE PROPERTIES OF RF SPUTTERED AMORPHOUS SILICON

Peng Shao-Qi, Yu Qai, Zhang Xian, Ye Jing

To cite this version:

Peng Shao-Qi, Yu Qai, Zhang Xian, Ye Jing. EFFECTS OF ARGON ON THE PROPERTIES OF RF SPUTTERED AMORPHOUS SILICON. Journal de Physique Colloques, 1981, 42 (C4), pp.C4- 791-C4-794. �10.1051/jphyscol:19814173�. �jpa-00220798�

JOURNAL DE PHYSIQUE

Colloque C4, suppZ6ment au nOIO, Tome 4 2 , octobre 1.981 page C4-791

EFFECTS OF ARGON ON THE P R O P E R T I E S OF RF SPUTTERED AMORPHOUS S I L I C O N

Peng Shao-qi, Y u Bing Qai, Zhang Pei Xian and Ye Xian Jing

Semiconductor Phys. I d . , Department o f Phys., Zhongshan (Sun Yatsenl Ihziversi ty, Cuangzhou, Republic o f China

Abstract.- The E f f e c t s of argon on the properties of rf sputter- ed amorphous s i l i c o n f i l m have been investigated. As the sput- t e r i n g argon pressure i s increased from 2 t o 20 mTorr, t h e content of argon i n t h e amorphous s i l i c o n film increases appa- r e n t l y (Argon/~iliconr from 1 0 ' ~ t o

5

x The o t h e r proper- t i e s measured a8 a function of argon pressure P& show t h a t 818

t h e PA, is increased, the photoconductivity, r e s i s t i v i t y (300K).

conductivity a c t i v a t i o n energy and o p t i c a l gap increase a l s o , while t h e s p i n density deacreaes. It i s apparent t h a t t h e effect8 of argon pressure on t h e properties of rf sputtered amorphous s i l i c o n a r e due t o various factors. The r o l e of argon component i n t h e amorphous s i l i c o n material may be important.

Introduction.

-

The e a r l y works demonstrated t h a t t h e amorphous Siliccn film obtained by rf s p u t t e r i n g was unsuitable f o r e l e c t r o n i c applica- t i o n s beaause of a l a r g e density of defsct-related s t a t e s . The s i t u a - t i o n has been changed recently, t h e s t u d i e s i n past few years showed t h a t t h e q u a l i t y of sputtered amorphous s i l i c o n film can be improved by taking advantage of t h e strong influence of deposition parameters snah as gas pressure, subatrate-target spacing and s u b s t r a t e tempera- t u r e ect., o r by s p u t t e r depositing t h e films i n argon/hydrogen mix- h r e . The i~POrtan<re of argon pressure i n t h e preparation of rf sput- t e r e d amporphotw a i l i r o n has been reported, ( 2 ) (3) but t h e expe- rimental r e s u l t s were not s o agreeable, and t h e i n t e r p r e t a t i o n s of i t s e f f e c t were d i f f e r e n t . The purpose of t h i s paper is t o study systema- t i c a l l y t h e effects O f s p u t t e r i n g argon pressure on t h e properties of amorphous s i l i e o n , and t o f u r t h e r i n v e s t i g a t e t h e r o l e of argon Con-

poaent i n t h e amorphous s i l i a o n material.

Ex~erimental.

-

The amorphous a i l i c o n samples were deposited by r f

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19814173

C4-792 JOURNAL DE PHYSIQUE

sputtering. The substrate-target seperation and t h e rf power during deposition were fixed. The d e t a i l s of t h e s p u t t e r i n g apparatus are given elsewhere.(3) The deposition r a t e was about 300 t o 400 Angstroms per minute, and t h e f i l m thickness was about 2 microns. The pressure of argon gas ( o r hydrogen/argon mixture) during s p u t t e r i n g w a s main- tained a t a value ranging from 2 x

loo3

t o 2 x 10'~ Torr. The substra- t e s of t h e amorphous s i l i c o n samples were g l a s s , aluminum and s i n g l e c r y s t a l s i l i c o n f o r measuring t h e e l e c t r i c a l conductivity, o p t i c a l gap, ESR, AES and i e a r e d absorption, respectively.

The d.c. e l e c t r i c a l conductivity was measured i n a vacuum system An ellipsometric spectrum method was used t o measure the o p t i c a l pro- p e r t i e s of amorphous s i l i c o n material. ( 4 ) ( 5 ) The o p t i c a l gap was de- termined by the l i n e a r portion of p l o t of (&AY)+ a s a function of All.

Results and

-

discussion

- -

I n sunnuarieing t h e e f f e c t s of argon on t h e properties of rf sputtered amorphous s i l i c o n , we found t h a t a s argon pressure P& ( o r Pk+ with a fixed p a r t i a l pressure ratio;&/P*; 0.2 ) was increased from 2 t o 20 mTorr,

1) t h e argon component i n the amorphous s i l i c o n f i l m increased, t h e atomic r a t i o argon/silicon increased from about 1 x 10'~ t o g r 10-2,

2 ) t h e oonductivity a c t i v a t i o n energy, o p t i c a l gap and t h e pho- tooondnctivity increased, while the e l e c t r i c conductivity (300K) and t h e pin dansity decreased (FlG.1 ( a ) , ( b ) , ( c ) , F10.2, FIG 3 , ) ,

3 ) t h e coarse s t r u c t u r e (obourve ^by SML) was unaffected by Ph.

A. a function of s p u t t e r i n g gas pressure, t h e o p t i c a l absorption eodfioian

d

^(PU. decreases monotonously. while the

d

^(PU) has a minimum a t a c e r t a i n Pk (FIG. 1 ( d l ) .

F1G 1 ( a ) and F10 1 ( b ) show t h a t t h e aondttctitity a c t i v a t i o n energy increases more r a p i d l y than t h e o p t i c a l gap. In comparing i t s v a l a w , we can f i n d t h a t t h e r e i s a downward s h i f t of Permi energy EF with t h e s p u t t e r i n g gae pressure.

The experimental r e s u l t s l i s t e d about show t h a t t h e o r i g i n of the e f f e c t s of argon presaur on the properties of rf sputtered amor- phoua s i l i c o n is r a t h e r complicated. Besides t h e reduction i n energe- t i c p a r t i c l e (argon o r s i l i c o n atom) b e t b a r b e n t of the growing f i l m with increased PArr ( l ) ( 2 ) t h e high content of argon i n s p a t t e r e d

amorphous s i l i c o n material and i t s increase with increased PAr a r e

SFTITTERING GAS PRESSURE

ARGON PRESSURE (mTORR ) PIG. 3

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C4-794 JOUENAL DE PHYSIQUE

aonsiderable. To f u r t h e r i n v e s t i g a t e t h e influence of argon component on t h e s t r u c t u r e and e l e c t r o n i c propertiee of amorphoue s i l i c o n mate- rial ^{i 8} i n t e r e s t .

(1) W.T. Parlewicr J. Appl. Phye. 49, (1978). 5595

( 2 ) D.A. Andemon, O. Moddel, ^M. A. Paesler, and W i l l i a m Paul J. Vac. Soi. Tochnol., 16, (1979). 906

(3) Peng Shao-qi, Zhang Poi Xian and Chon Shou Quang, Proc. of t h e National Meeting on Ssnaiconductar Physics

,

^{( H e f} e i China.tQov. ,1979 (4) _No Dary, Cheng Short Ouang, Yu Yh-zheng and Huang Bing Zhong, Acta

% p i c a Sinica, 29, (1980) 673

( 5 Mo W n # e t al. (1981) ( t o be published)