GB2185129A - Flow control device for fine particle stream - Google Patents

Abstract

A flow control device for a fine particle stream having a gas exciting means is provided. The device comprises a nozzle which is provided in the flow pathway of the fine particle stream, and a magnetic field forming means for forming a magnetic field is provided in the vicinity of the nozzle. The nozzle may be a convergent-divergent nozzle, and it may be formed of a magnet. The device is used in a thin film forming apparatus to send an excited beam onto a target 6. <IMAGE>

Description

SPECIFICATION Flow control device for fine particle stream Background ofthe invention Fieldoftheinvention This invention relates to a flow control devicefor fine particule stream which is utilized fortransportation or blowing of fine particles, etc., which is expected to be utilized, for example, forfilm forming working, formation of a composite material, doping working with fine particles, or new field forformation offine particles.

In the present specification, the fine particles include atoms, molecules, ultra-fine particles and general fine particles. The ultra-fine particles mean those generally smallerthan 0.5 calm, obtained for example by evaporation in gas, plasma evaporation, chemical vapor reaction, colloidal precipitation in a liquid or pyrolysis of liquid spray. The general fine particles mean fine particles obtained by ordinary methods such as mechanical crushing, crystallization or precipitation sedimentation.

Beam refers to a jet stream flowing in a certain dir ection with directivity with a higher density than the surrounding space, regardless of its cross-sectional shape.

Related background art Generally speaking, fine particles are dispersed or suspended in a carrier gas and transported by the flow ofthe carrier gas. In the prior art, the flow offine particles in transportation of the above fine particles has been controlled merely by confining the whole pathway ofthe fine particles flowing togetherwith the carrier gas through the pressure difference between the upstream side and the downstream side with tubular materials or case members. Accord ingly,theflowofthefine particles will necessarily be spread over the entire space in the tubular materials or the case members confining the flow pathway of the fine particles, although there may be certain dis tribution in strength oftheflow.

Such transportation offine particles is also performed in the field of activated fine particles. For ob taining activated fine particles, there is the method, for example, in which plasma by microwave dis charging is utilized, and this has been practiced in the prior art by a combination of waveguideand of waveguide and quartztube. The waveguide is a tube with are ctangular cross-section and the microwave is trans mitted therethrough to the plasma generating portion. The plasma generating portion is constituted of a quartz tube inserted intothewaveguideatthe greatest electrical field of the microwave.And, activ ation has been effected by permitting a carrier and a source to pass through the quartz tu be. The activated fine particles have been transported togetherwith the carrier gas along the flow pathway through the pressure difference between the upstream side and the downstream side in the flow pathway confined with tubular materials or case members.

Whereas, by confining the whole pathway for the fine particles with tubular materials or case mem bers and transporting the fine particles together with the carrier gas along theflowpathwaythroughthe pressure difference between the upstream side and the downstream side, it is impossible to achieve so high a transportation speed.Also, it is difficultto avoid contact of the wall surface of the tubular material or case member confining the flow pathway of fine particles with fine particles over the entire transportation section. Forthis reason, particularly during transportation of active fine particles to the capturing position thereof, inactivation with lapse of time or inactivation through contact with the wall surface of the tubular material or case member is liable to occu r, whereby there is the problem that the treatment by carrying out the reaction by contact with a reactive gas in the course of transportation, etc., can be done with difficulty.Also, confining the whole pathwayforthe fine particles by tubular materials or case members will lower capturing efficiency ofthe transported fine particles and also will lower utilization efficiency of the carrier gas fortransportation of fine particles due to generation of dead space of flow, etc.

Summary ofthe invention An object of the present invention is to provide a flow control deviceforfine particle stream for trans- porting active fine particles with good efficiencyto the capturing position.

Anotherobjectofthe present invention isto provide a flow control deviceforfine particulestream capable offorming a fine particle stream having strong characteristics of a beam.

Still another object of the present invention isto provide a flow control device for fine particule stream for transporting fine particles through a free space with strong beam characteristic without use of tubular materials, etc.

According to an embodiment of the present invention, there is provided a flow control device for a fine particle stream having a gas exciting means, comprising a nozzle provided in the flow pathway ofthe stream and a magneticfieldforming meansforfor ming a magnetic field provided inthevicinityofsaid nozzle.

According to another embodiment of the present invention, there is provided a flow control device for a fine particle stream having a gas exciting means, comprising a convergent-divergent nozzle provided in the flow pathway ofthe stream and a magnetic field forming means forforming a magnetic field provided in the vicinity of said convergent-divergent nozzle.

According to a further embodiment of the present invention, there is provided aflowcontrol device for a fine particle stream having a gas exciting means, comprising a nozzle provided in the flow pathway of the stream, said nozzle being formed of a mag net.

According to a still another embodiment ofthe present invention, there is provided a flow control device for a fine particle stream having a gas exciting means, comprising a convergent-divergent nozzle provided in the flow pathway of the stream, said convergent-divergent nozzle being formed of a magnet.

Briefdescription ofthe drawings Figures lea and 'B illustrate schematicallythe basic principle ofthe present invention; Figures2(a)-(c) each shows an example of the shape of the convergent-divergent nozzle; Figure 3 is a schematic illustration showing one example when the present invention is utilized for thefilm-forming method with ultra-fine particles; Figures 4(a) and (b) are illustrations showing examples of gas phase exciting means; and Figure 5 illustrate schematically a skimmer.

Description ofthe preferred embodiments The present invention is described by referring to Figure 1Awhich illustrates the basic principle ofthe present invention. The non-film-forming gas fed into the upstream chamber3 is subjected to electrical discharge by means of a gas exciting means 9 to form a plasma. The plasma is withdrawn into the nozzle 1 by the pressure difference between the upstream chamber3 and the downstream chamber 4 created bythe vacuum pump 5 and by the magnetic field of the nozzle 1 provided between the both chambers, whereby a jet stream of the active species of the nonfilm-forming gas is formed within the downstream chamber 4. This is blown againstthe film-forming gas, which is in turn blown against the substrate 6.

The nozzle 1 may have any desired shape, but it is more preferably a convergent-divergent nozzle which is gradually narrowed in opening area from the inlet opening latowardthe middle portion until becoming a throat portion 2 and is gradually enlarged in opening area from the throat portion 2toward the outflow opening 1 b, as shown in Figure 2. By use of a convergent-divergent nozzle, the jet stream velocity becomes subsonic or supersonic, whereby the jet stream becomes a beam with a substantially constant cross-sectional area in the flow direction.

The position of the film-forming gas introducing inlet may be either immediately beforethe inlet op- ening 1 a of the nozzle within the upstream chamber 3, within the nozzle 1 or at downstream ofthe outlet opening 1 b within the downstream chamber 4. However, when a convergent-divergent nozzle is used for the nozzle, if the gas introducing opening is provided at the portion on the downstream side (the rightside) ofthe throat portion 2 in the nozzle, it may cause disturbance oftheflow, and therefore location of the gas introducing opening in the nozzle is limited to between the inlet opening 1 a and the throat portion 2. For preventing completely adhesion on the inside of the nozzle, it is more preferably provided at downstream ofthe outlet opening 1 b.

As the gas exciting means 9, by use of microwave, for example, a means for discharging microwave such as a slot antenna or a horn antenna as shown in Figures 4(a) and (b). Otherwise, there is also electrodeless discharging system such as electron cyclotron resonance (ECR), etc., and other discharging systems such as a thermoelectron discharging type, a bipolar discharging type, the magneticfield convergenttype (magnetron discharging type), etc., may be incl u ded.Also, for th e power supply, either direct current or alternating current may be available. Further, itis also possibleto employ a gas phase exciting system by th rowing an electromagnetic wave such as microwave, light, UV-ray, etc., through a quartz glass window, etc.

The magnet constituting the nozzle in the present invention may be any magnet, provided that it can give a magnetic field in the direction from the inlet opening 1 a toward the outlet opening 1 b, and it is not limited to permanent magnets but it may be electromagnets.

When the nozzle as mentioned above is formed of a permanent magnet, its material may be a highly coercive material such as carbon steel, tungsten steel, low chromium steel, high chromium steel, cobalt-chromium steel, KS steel, new KS steel, MT steel, MKsteel, anisotropic MKsteel (Alnico 5), alnico 9, Co-ferrite (OP magnet), Ba-ferrite, MnBi, Pt Fe alloy, Pt-Co alloy, samarium-cobalt alloy, etc.

Also, an electromagnet utilizing the nozzle as the core may be employed, and the material to be used in this case may include high magnetic permeability materials such as pure iron, iron, silicon steel, Bermalloy, Sendust, Deltamax, Sendelta, Bermenorm 5000Z, Bermenzule, Highparco, pressed powder core, soft ferrite, etc.

The size ofthe magneticfield generated by the nozzle 1,when plasma formation is effected by microwave discharging, should preferably be such that resonance conditions of electron cyclotron may be satisfied forfrequency of the microwave.

As another embodiment of the present invention, in place of forming the nozzle itself of a magnet as shown in Figure 1 B, it is also possible to use a constitution in which magnets are arranged around the nozzle in order to form a magnetic field within the nozzle.

In this case, the magnet used is not limited to one cylindrical magnet, but a combination of plural permanent magnets or electromagnets may be employed.

The non-film-forming gas having flowed into the upstream chamber 3 through the non-film-forming gas introducing inlet is subjected to discharge by means of the gas exciting means 9 to become a plasma. The plasma formed flows into the nozzle 1 through the pressure difference between the upstream chamber3 and the downstream chamber 4.

At this time, influenced by the magnetic field in the nozzle 1,the plasma flows into the nozzle 1 efficiently and is withdrawn from the outlet opening 1 b to become a jet stream. By use of a convergent-divergent nozzle, the jet stream becomes a beam and its flow velocity also becomes supersonic. The beam of plasma of the non-film-forming gas jetted into the downstream chamber 4 contacts the film-forming gas flowing in through the film-forming gas introducing inlettodecomposethefilm-forming gas is blown together with the non-firm-forming gas against the substrate 6 to effect film formation, etc.

[Example] Figure 3 is a schematic illustration of an example when the present invention is utilized for film- forming device with ultra-fine particles, wherein 1 is a convergent-divergent nozzle, 3 is an upstream chamber, 4a a first downstream chamber, 4b a second downstream chamber. 9a is a quartzwindow and 9b a waveguide.

The upstream chamber3 and the first downstream chamber 4a are constituted as an integrated unit, and to the first downstream chamber 4a are successively connected so as to be separable from each other through the flanges all with a common diameter (hereinafter called "a common flange") a skimmer7, a gate valve 8 and the second downstream chamber 4b which are respectively formed into units. The upstream chamber 3, the first downstream chamber4a and the second downstream chamber4b are maintained at pressures which are lower stepwise from the upstream chamber3 to the second downstream chamber4b bytheevacuating system as described hereinafter.

The upstream chamber3 is equipped with a gas exciting means9through a common flange. As the gas exciting means 9, there may be employed for example, a horn antenna as shown in Figure 4(a), a slot antenna shown in Figure 4(b) or a various systems as described above. The opening angle ofthe horn antenna is set atthe optimum angle corresponding to its length so that directivity may be the highest. The length of the slot ofthe slot antenna is set at 1/2 ofthe wavelength used, whereby the microwave is sent by way of resonance.

The convergent-divergent nozzle 1 is mounted through a common flange attheside end on the upstream chamber 3 side of the first downstream chamber4a, with the inlet opening 1 a opened to the upstream chamber3 and the outlet opening 1 b opened to the first downstream chamber 4a, under the state protruded into the upstream chamber 3. However, this convergent-divergent nozzle 1 may be also mounted underthe state prptruded into the first downstreamchamber4a.V}/hethertheconvergent- divergent nozzle 1 is protruded to either side may be selected depending on the sizes, amount, properties, etc., of the ultra-fine particles to be transported.

The convergent-divergent nozzle 1 may be one which isgradually narrowed in opening areafrom the inlet opening 1 a to become a throat portion 2, and is again gradually enlarged in opening area to become an outlet opening 1 b, as described above, but is preferablethatthe inside circumferential surface neartheoutletopening lbshould besubstanti- ally parallel to the center axis. This is because the gas flowdirection jetted can be made parallel sofaras possible with ease, since it is influenced to some extent by the direction of the inside circumferential surface nearthe outlet opening 1 b.However, as shown in Figure 2(b) by making the angle a ofthe inside circumferential surface from the throat portion 2 to the outlet opening 1 b with respect to the center axis 7 or less, preferably 5" or less, peel-off phenomenon will not readily occurand theflow ofthe jetted gas is maintained substantially uniformly, and therefore in this case no such parallel portion as mentioned above is not particularly required to be formed. By omitting formation of the parallel portion, fabrication ofthe convergent-divergent nozzle can be done more easily. Also, by making the convergentdivergent nozzle in a rectangular shape as shown in Figure 2(c),the gas can be jetted in shape of slit.The rectangular nozzle is not limited to one shown in Figure 2(c), but a nozzle with an inversed ratio of longitudinal length to lateral length may be also employed.

Here, the above peel-off phenomenon refers to the phenomenon which occurs when there is a protrusion, etc., on the inside surface of the convergentdivergent nozzle 1, that the boundary layer between the inside surface of the convergent-divergent nozzle 1 and the passing fluid becomesthickerto make the flow non-uniform, which tends to occur at a higher velocity of the jet stream. The angle as mentioned above should be preferably made smallerforthe lower inside-surface4inishing precision ofthe convergent-divergent nozzle for prevention of the peeloff phenomenon. The inside surface of the conver gent-divergent nozzle should preferably be finished to 3 or more of inverse triangle marks, optimally four or more, representing surface finishing precision as defined by JIS B 0601.Particularly, the peel-off phen- omenon at the divergent portion of the convergentdivergent nozzle 1 will affect greatly the subsequent flowofthe non-film-forming gas and ultra-fine particles, so that by defining the above finished precision primarily at the divergent portion, the convergentdivergent nozzle can be prepared more easily. Also, for prevention of occurrence of peel-off phenomenon, it is required that the throat portion 2 should be made a smooth curved surface so that the differential coefficient of cross-sectional area change rate may not become infinite.

When the covergent-divergent nozzle 1 is formed of a magnetic material, its material may be a high coercive material as mentioned above. Also, an electromagneticwith the convergent-divergent nozzle 1 being as the core may be also used, and the material used in the case may be a high magnetic permeability material as mentioned above. However, among them, the material having its Curie point higher than the temperature of the beam must be employed.

By use of these materials, a convergent-divergent nozzle having as magnetic field in the direction of from the inlet opening 1 a to the outlet opening within the nozzle is prepared. The size of the magnetic field for plasma formation effected by microwave discharging, should be made such that electron cyclotron resonance conditions may be satisfied for the frequency of microwave.

In another embodiment, when magnets are not the nozzle itself but are provided around the nozzle as shown in Figure 1(b), as the material oftheconvergent-divergent nozzle 1, metals such as iron, stainless steel and others, or otherwise synthetic resins such as acrylic resin, polyvinyl chloride, polyethylene, polystyrene, polypropylene, etc., ceramic materials, quartz, glasses, and other various material can be used. Selection ofthe material may be done in view of inertness to the ultra-fine particles to be formed, workability, gas releasability in the reduced pressure system. Also, the inside surface of the convergent-divergent nozzle 1 may be plated or coated with a material on which adhesion or reaction ofthe ultra-fine particles will hardly occur. Atypical example is a coating of polytetrafluoroetylene, etc.

Themagnet37impartsa magneticfield inthedir- ection offrom the inlet opening 1 a to the outlet opening 1 b to the above convergent-divergent nozzle, and it may be either a permanent magnet or an electromagnet, which is arranged singly or as a combination of plural magnets around the convergentdivergent nozzle 1.

With this arrangement, the plasma within the upstream chamber3 is positivelywithdrawn into the convergent-divergent nozzle 1. Accordingly, it is pos sibleto prevent inactivation of the plasma through contact with the wall surface of the upstream chamber 3.

By controlling adequately the relationship between the pressure ratio P/PO of the pressure Pin the first downstream chamber4a to the pressure P0 in the upstream chamber 3 and the ratio A/A* of the opening area A ofthe outlet opening 1 btothe opening area A* of the throat portion 2, the plasma ofthe non-fiim-forming gas is permitted to pass through the above convergent-divergent nozzle 1 to be formed into a beam, which flows at a supersonic velocity from the first downstream chamber 4a to the second downstream chamber4b.

The skimmer7 is provided for controlling the opening area between the first downstream chamber 4a and the second downstream chamber 4b so that the second downstream chamber 4b can maintain a lower pressure than in thefirstdownstream chamber4a. More specifically, as shown in Figure 5, two sheets of controlling plates 11,1 la each having a V-notch 10, 1 Oa respectively are provided face to face so as to be slidable with each other.The controlling plates 11, 11 a can be slided by external operation, and, depending on the extent two which the both cut portions 10, 1 0a overlap each other, the opening can be controlled to an area which can permit the beam to pass therethrough and can maintain sufficient vacuum degree in the second downstream chamber.

Theshapesofthecutportions 10,l0aandthecon- trolling plates 11,11 a ofthe skimmer7 may be also hemispherical or other shapes other than the shapes shown in the Figure.

The gate valve 8 hasaweir-likevalve 13 which is pulled up or down byturning the handle 12. It is opened during running ofthe beam. By closing ofthe gate valve 8, unit exchange ofthe second downstream chamber4b can be done while maintaining the low pressure within the upstream chamber 3 and the first downstream chamber4a.

In the second downstream chamber4b, a substrate 6 is placed which receives ultra-fine particles transported as the beam to capture them thereon in thefilm state. The substrate 6 is mounted in the second downstream chamber 4b through a common flange, and it is mounted on a substrate holder 16 at the tip end of the slide shaft 15 which is slided by the cylinder 14. In front ofthe substrate 6, shutter 17 is positioned so that the beam can be shielded whenever it is required. Also, the substrate 16 is designed so as to heat or cool the substrate 6 under the optimum temperature condition for collection ofthe ultra-fine particles.

Also, on the tops and bottoms of the upstream chamber3 and the second downstream chamber4b, glass windows 18 are provided respectively th rough common flanges as shown in the Figure so thatthe inside can be observed. Also, although not shown in the Figure, on the front and backsides of the upstream chamber 3, the first downstream chamber4a and the second downstream chamber, there are pro videdsimilarglasswindows(similarto l8inthe Figure) respectivelythrough common flanges. Detaching ofthese glass windows 18, permits various measuring devices, load lock chambers, etc., to be exchanged through common flanges.

The evacuation system in this examples is to be explained below.

The upstream chamber 3 is connected to the main valve 20a through the pressure control valve 19. The first downstream chamber 4a is connected directly to the main valve 20a, and the main valve 20a isconnected to the vacuum pump 5a. The second downstream chamber 4b is connected to the main valve 20b, and further the main valve 20b is connected to the vacuum pump 5b. 21a and 21 bare pressure reducing pumps which are connected through rough evacuating valves 22a and 22b respectively to the main valves 20a, 20b immediately on the upstream side thereof and also connected through the auxiliary valves 23a and 23b through thevacuum pump 5a, and effect rough evacuation within the upstream chamber 3, the first downstream chamber 4a and the second downstream chamber 4b. 24a-24h are valves for ieak and purge ofthe respective chambers 3, 4a, 4b and the pumps Sa, Sb, 21 a and 21 b.

First, by opening the rough evacuating valves 21 a, 21 band the pressure control valve 18, rough evacuation of the upstream chamber 3, the first and the second downstream chambers 4a) 4b is effected by means of pressure reducing pumps 20a and 20b.

Subsequently, the rough evacuating valves 21 a and 21 bare closed and the auxiliaryvaives 23a, 23b and the main valves 20a, 20b are opened, thereby evacuating the upstream chamber 3, the first and a second downstream chambers 4a,4b to sufficient degree ofvacuum by means of the vacuum pumps 5a and 5b.During this operation, by controlling the opening ofthe pressure control valve 19, the vacuum degree in the first downstream chamber 4a is made higherthanthatintheupstreamchamber3,thenthe non-film-forming gas and the film-forming gas are permitted to flow, and further the vacuum degree in the second downstream chamber 4b is controlled by the skimmer 7 to be lower than that in the first downstream chamber 4a. This control can be also effected by controlling the opening ofthe main valve 20b.

And, during formation of ultra-fine particles as well asfilm-forming working by jetting of its beam, the respective chambers 3, 4a, 4b are controiled to be maintained constantly at low pressures. This control may be performed manually, but it may be also be performed by detecting the pressures in the respective chambers 3, 4a, 4b and controlling automatically opening and closing ofthe pressure control valve 19, the main valves 20a, 20b,the skimmer 7, etc., based on the detected pressures.Also, by permitting the non-film-forming gas fed into the upstream chamber 3 to betransporteddirectlythroughtheconvergent- divergent nozzle 1 toward the downstream side, evacuation during transportation can be conducted only on the downstream side, namely in the first and the second downstream chambers 4a, 4b.

Control of the above vacuum degree may be also done by employing the vacuum pump 5a in the up stream chamber3andthefirstdownstream chamber 4a separately for the respective chambers 3 and 4a. However, as shown in this example, by evacuating intheflowdirectionofthebeam byone vacuum pump 5a to thereby control the vacuum degree in the upstream chamber 3 and the first downstream chamber 4a, the pressure differences between both can be maintained constant with ease even when there may be more or less pulses, etc., in the vacuum pump. Accordingly, there is the advantage of maintaining constantlythe flow state which is readily influenced by the fluctuation of the pressure difference.

Aspiration by means of the vacuum pumps 5a, 5b, particularly in the first and the second downstream chamber 4a, 4b, should be preferably done from above the chambers. By performing aspiration from above the chambers, dropping of the beam by gravitational force can be suppressed to some extent.

Having described above about the present Ex ample,thefollowing changes may be possible.

First, the convergent-divergent nozzle 1 can be made movable by slanting upward, downward, rightward and leftward, or scannable at an interval, whereby film formation can be conducted over a wide range. Particularly, such slanting movement or scanning is advantageous when combined with a rectangular nozzle as shown in Figure 2(c).

Also, by providing a plural number of convergentdivergent nozzles 1, a plural number of beams can be generated at once. Particularly, when a plural number of convergent-divergent nozzles 1 are to be provided, by connecting them to the upstream chambers 3 independently of each other, different fine particulate beams can be run at the sametime, whereby it becomes possible to form new fine particles by collision mutually between different fine particles by way of lamination or mixed collection of different fine particles or a crossing mutually between beams.

By holding the substrate 6 movable up and down or left and right or rotatable, it can be made so asto receive the beam over a broad range. Also, by taking up the substrate 6 in a roll and delivering it out suc essivelyfrom the roll to receive the beam, a substrate 6 of long dimension can also be applied with treat mentwith fine particles. Further, treatment with fine particles may be also applied on a drum-shaped substrate 6 under rotation.

In this Example, the device is constituted ofthe generation chamber 3, the first downstream chamber4a and the second downstream chamber 4b, but the second downstream chamber 4b may be omitted, or further downstream chambers ofthe third,thefourth,etc.can be also connected on the downstream side of the second downstream chamber. Further, by applying pressure to the upstream chamber 3, the first downstream chamber 4a can be made an open system, and it is also possible to make the upstream chamber3 an open system by reducing the pressure in the first downstream chamber 4a. Particularly, like an autociave, the upstream chamber3 may be pressurized and the first downstream chamber 4a et seq. can be evacuated.

Also, by arranging plural number of convergent- divergent nozzles 1 in series and controlling the pressure ratio of the respective upstream side and downstream side, the beam speed can be maintained, or formation of dead space can be prevented to the utmost by making the respective chambers spherical.

As described above, according to the present invention, the plasma is brought into the nozzle buy a combination of the pressure difference between the upstream chamber and the downstream chamber 4 and the magnetic field in the nozzle 1, whereby inactivation of the plasma through contact with the wall face in the upstream chamber or with lapse of time can be prevented, and at the same time the plasma can be brought out with good efficiency on the downstream side of the nozzle 1.

Claims (25)

1. Aflow control device for a fine particle stream having a gas exciting means, comprising a nozzle provided in the flow pathway of the stream and a magneticfieldforming meansforforming a magneticfield provided in the vicinity of said nozzle.

2. Aflow control device according to Claim 1, wherein said magneticfield forming means is a magnet.

3. Aflowcontrol device according to Claim 1, wherein said magnetic field forming meanstranspports the plasma exciting means toward a downstream side.

4. Aflow control device according to Claim 2, wherein said magnet is a permanent magnet or an electromagnet.

5. Aflowcontrol device according to Claim 1, wherein said gas exciting means utilizes microwave discharging.

6. Aflow control device according to Claim 4, wherein said permanent magnet comprises a high coercive material.

7. Aflow control device according to Claim 4, wherein said electromagnet comprises a material of high magnetic permeability.

8. Aflow control device for a fine particle stream having a gas exciting means, comprising a convergent-divergent nozzle provided in the flow pathway of the stream and a magnetic field forming means for forming a magnet field provided in the vicinity of said nozzle.

9. A flow control device according to Claim 8, wherein said magnetic field forming means is a magnet.

10. Aflowcontrol device according to Claim 8, wherein said magnetic field forming means transports the plasma formed inan upstream chamber by said gas exciting means through the nozzle toward a downstream side.

11. Aflow control device according to Claim 9, wherein said magnet is a permarientmagnetoran electromagnet.

12. Aflow control device according to Claim 8, wherein said gas phase exciting means utilizes mic rowave discharging.

13. Aflow control device according to Claim 11, wherein said permanent magnet comprises a high coercive material.

14. Aflow control device according to Claim 11, wherein said electromagnet comprises a material of high magnetic permeability.

15. Aflow control device for a fine particle stream having a gas exciting means, comprising a nozzle provided in the flow pathway ofthe stream, said nozzle being formed of a magnet.

16. Aflow control device according to Claim 15, wherein said gas exciting means utilizes microwave discharging.

17. Aflowcontrol device according to Claim 15, wherein said magnet is a permanent magnet or an electromagnet.

18. Aflow control device according to Claim 17, wherein said permanent magnet comprises a high coercive material.

19. Aflow control device according to Claim 17, wherein said electromagnet comprises a material of of high magnetic permeability.

20. Aflow control device for a fine particle stream having a gas exciting means, comprising a convergent-divergent nozzle provided in the flow pathway ofthe stream, said nozzle being formed of a magnet.

21. Aflowcontrol device according to Claim 20, wherein said gas phase exciting means utilizes microwave discharging.

22. Aflow control device according to Claim 20, wherein said magnet is a permanent or an electromagnet.

23. Aflow control device according to Claim 22, wherein said permanent magnet comprises a high coercive material.

24. Aflow control device according to Claim 22, wherein said electromagnet comprises a material of high magnetic permeability.

25. A flow control device substantially as here it before described with reference accompanying drawings.