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Submitted on 1 Jan 1979
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MICROWAVE GENERATION OF A
MAGNETOACTIVE OXYGEN PLASMA FOR OXIDATION
L. Bárdoš, J. Musil
To cite this version:
L. Bárdoš, J. Musil. MICROWAVE GENERATION OF A MAGNETOACTIVE OXYGEN PLASMA FOR OXIDATION. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-449-C7-450.
�10.1051/jphyscol:19797218�. �jpa-00219199�
JOURNAL DE PHYSIQUE ColZoque C7, suppZ6ment au n07, Tome 40, JuiZZet 1979, pageC7- 449
MICROWAVE GENERATION OF A MAGNETOACTIVE OXYGEN PLASMA FOR OXIDATION
L. ~ b r d o s and J. Musil.
Czechoslovak Aaademy o f Sciences, I n s t i t u t e of Plasma Physics, Pod vodGrenskou vezi 4 , 180 69 Prague 8, Czechoslovakia.
1, INTRODUCT ION
In recent years the plasma has growing importance f o r the thin s o l i d surface film creation, Partioularly, the ailicon oxid- a t i o n i n an owgen plasma can be cont- rast t o usual thermal methods favourably carrled out at low temperatures, However, the basic oxidation parameters depend on plaama characteristics and therefore on
the plasma generation system.
In our previous work
111,
the new oxidation method using a microwave magne- toactive oxygen plasma has been described, Detailed experimental study of formation of oxide films on s i l i c o n showed t h a t C21 ( i ) the oxide growth r a t e depena linearlyon the .plasma electron denaity, (iiloxide filma a r e created only i n the
plaama i n which the floating potential (measured with respect t o the ground) is Uf jS
-
10 V.!Chi main aim of the present work is t o describe density and potential r a d i a l profilea f o r two experimental azTange- menta differing i n a way 6md direction of the raicrowave energy introihrction i n t o a d i b e g e tube,
2. EXPERIMENTAL ARFtANGIiXEBT AlOD RESULTS
'Pha oxygen plaama was groduoed i n the quarts tube (i.d. 75 $us) end the direotion
of the s t a t i c mgnetio f i e l d
$
was paral-l e l t o the a d s of the discharge tube, The plarjma was generated e i t h e r i n the circular waveguide (the microwave energy is fed i n t o the discharge tube aiong the direction of the s o ) o r by a helix slow down structure placed coaxially outefde the discharge tube (the energg is fed radially, i.e. perpendicularly t o the
ifo,
o r quasiradially), Plaama could be a l s o produced by the waveguide and the slow down structure operating simultaneously.
Intensity of the s t a t i c magnetic f i e l d was adjustable between an electron cyclotron resonanoe ( s / W = 1 ) and its second harmonic = 2). Rperiments were oarried out i n oxygen a t pressures of the order of 1 0 - ~ ~ o r r and the incident microwave power w a s of the order of 1 kw
(f=2,35 G&), The device operated i n a pulse mode with repetition frequency 50
&.
The average plasma eleotron deaeity was measured by an 8 nrm inerferometer, r a d i a l profiles of the saturated ion our- rent f+, floating plaama potential Uf and axial component Ez of the incident wave e l e c t r i o f i e l d by movable probe. 'Pgpioal r e s u l t s of our meaeurements are given in Hg,l. f o r the waveguide and the .alon down structure.Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797218
3. DISCUSSIOlg
From Fig.1 i t i s clearly seen that:
( i ) Radial profiles N(r) almost constant i n a wide vicinity of the axis can be achieved. N(r) of a plasma produced by waveguide has maxirmun on the axis, by the structure i t has minimum. I n the second case the absolute value of the density is lower. (N(r) produced by waveguide and structttre i s a awn of respeative profiles).
( i i ) While the r a d i a l profile of floating potential of plasma produced by waveguide has smooth minlnnlm on the axis, i t has maximum (close t o aero) on the axis f o r the structure generation. It i e worth- while t o note that absolute values of Uf can be changed by the plasma density and f o r densities greater than 5.10~*cn1-~ Uf in the plasma produced by the waveguide increases t o zero. Idomover, regions of negative potential praatically show the radial distributions of energetic elec- trons. n e s e can be expected around a x i a i n waveguide plasma and on the periphery of the discharge tube in structure pLrr~m~.
( i i i ) Radial profiles of E, fully corres- pond t o the distribution of TEll i n the wavernde and radial feeding fn *he structure experiment.
Electron temperatures mealsured by a hngmir probe on the axis of the dia- oharge tuba were 6 eV, 13 eV and 19 eV f o r atruoture, waveguide and both sources respectively.
Properties of the oxlde films on S i
created i n this experimental arrangement are consietent with radial profiles of
N(r) and Uf(r). It was found that:
(2) Homogeneity of thickness of oxide film is b e t t e r i n the p l + m produced by the waveguide. Homogeneity b e t t e r than 10%
on areas of approximcrtely 12 cm 2 can be achieved.
( i i ) In reglone of strong negative poten- t i a l the growth r a t e of films decreases.
( i i i ) In the plasma generated by the structure with power above 1,5 kPI edges of circular ailiaon s amp lee can be strongly heated by f a s t electrona,
Our experiments demonstrated that the careful d e s i a of the microwave plesma reactor is very important f o r 8uccesFul formetion of the oxide films.
Referencee:
[l] ~.Bbrdog e t al., J. Pbys.
,=,
(1975) ,I1195 121 J.Wsil e t al. ,accepted i n J.Phys.D,(1979).
waveguide h e l i x slow down
s t r u c t u r e
0 1 2 3 0 1 2 3
- r C c m I -r I c m I
-
4oxygen
:p
=5.10 Torr
i W c e / W =1.37
;Fig. 1
