SOME PARTICULARITIES OF THE MOLECULAR EXCHANGE IN A HF LOW PRESSURE DISCHARGE

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Submitted on 1 Jan 1979

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SOME PARTICULARITIES OF THE MOLECULAR EXCHANGE IN A HF LOW PRESSURE DISCHARGE

E. Zorina, A. Dobrenin, T. Popova, T. Pavliashvili, O. Tolmatshova, S.

Neustroev, E. Sokolov

To cite this version:

E. Zorina, A. Dobrenin, T. Popova, T. Pavliashvili, O. Tolmatshova, et al.. SOME PARTICULARI- TIES OF THE MOLECULAR EXCHANGE IN A HF LOW PRESSURE DISCHARGE. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-473-C7-474. �10.1051/jphyscol:19797230�. �jpa-00219213�

JOURNAL DE PHYSIQUE CoZZaque C7, suppZ6ment au n07, Tome 40, JuiZZet 1979, page C7- 473

SOME PARTlCULARlWS OT THE MOLECULAR EXCHANGE IN A t-F LOW PRESSURE DISCHARGE

E.N. Zorina, A.V. Dobrenin, T.O. Popova, T.I. Pavliashvili, O.V. Tolmatshova, S.A. Neustroev and E.B. Sokolov.

The particle transport in the interelec- trode space of a HF capacitor discharge is investigated in view of optimieation of thin dielectric film deuposit ion pro- cessus. The concrete process investiga- ted here consists in decomposing organo- -metallic compounds and donor-acceptor complexes in the non-equilibrium plasma of a HF discharge to form a GaN film ona single-cm~%alline surf ace. As basic re-

actants we use organo-metallic compounds and co-ordinate complexes based on them, with low vapor pressure so that the7 can be injested as gases into the plasma re- actor.

In khe discharge column a chemical reac- tion of the next kind is assumed to take place :

R3Ga* NR3 + Nz - ^{4a N}

⁺

^R8(CHj

,CzHj .C3H;,C2Hi) The so-fortaed radicals and hydrocarbons are evacuated as gases, and GaN molecu- les are transported to the single-crys- talline surface and are deposited on it the reaction of GaW formation takes pla- ce either in the HF plasma column, or i8 the electrodes spaces. To avoid nitrogen lattice discontinuities in the deposited film, the reacting mixture partial pres- sure sensibly exceeded the stoichiometric one. The electrical field In the dischar- ge column varied from 80 to 500 v/cm and the plasma parameters were:

10 14 3

4

c

^T=

5 4

ev

; o,lC

T i 5 0,4cvj 10

C

n;< 10Cm

Our ~onclusions on the character of the molecular are based on the analysis of the dependence of the deposition rate on the initial compounds par f ial pressure, the total pressure of the mixture, the processus duration and, mainly, on the

discharge specific power. The obtained linear dependence of the deposition rate on the initial compounds partial pressure and on the total pressure of the gaseous mixture means that the process of GaN film growing is due to gaseous diffusion.

Probably, the GaN formation takes place essentially in the plasma column. On di- electric surfaces (sapphire, Si02). The deposition rate is larger by a factor of

4,5-2 then on conducting ones. This fact

can be explained as the result of an electrical field shielding by the dis- electric surface.

The dependence of the deposition rate on the input power is shown on fig.l and 2.

Probably two compe~ting processes in plas- ma determine the film growing:

1. The GaN formation as a result of the decomposition of the initial compaund.

2. The GaN desorption from the single- -crystalline surf ace.

The first process should be characterized by the curve 2 of fig.1, increasing at low power input and saturated at high po- wer input, when the initial compound en-

tering the plasma reaetor is fully decom- posed within the discharge column. Since the molecule transport to the electrodes is due to diffusion it should depend en- tirely on the molecule concentration va- riation in the plasma column so that the curve 2 of fig.? characterizes also the molecule attachment to the electrodes.

The absorption and desorptlon processus can be characterized by the straight line 3, meaning that the increase of input po- wer causes NGa desorption from the surfa- ce, mainly due to electron and ion bombar- dment. The resulting curve I is a conse-

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797230

quence of t h e s i m u l t a n e o u s occurence o f t h e two p r o c e s s e s .

The e x p e r i m e n t a l d a t a o b t a i n e d i n t h e p r e s e n t paper and shown on f i g . 2 confirm the a - p r i o r i p i c t u r e of f i g . 1 .