WO1999001886A1

WO1999001886A1 - Plasma reactor with impingement flow for treating surfaces

Info

Publication number: WO1999001886A1
Application number: PCT/DE1998/001780
Authority: WO
Inventors: Bentsian Elkine; Joachim Mayer; Christian Oehr
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 1997-06-30
Filing date: 1998-06-29
Publication date: 1999-01-14
Also published as: DE29800950U1; TW384627B; DE19727857C1

Abstract

The invention relates to a plasma reactor, comprising a reactor gas inlet (7), a gas distribution chamber (17), a plasma treatment chamber (26) said plasma treatment chamber being delimited by a first electrode (13) and a second electrode (4) located opposite said first electrode, a gas extraction chamber (28, 29), and a reactor gas outlet (1). The first electrode (13) separates the gas distribution chamber (17) from the plasma treatment chamber (26), and is provided with gas inlets (18) essentially spread out over its surface, gas being able to pass from the gas distribution chamber (17) into the plasma treatment chamber (26) through said gas inlets (18). The inventive plasma reactor is characterised in that the first electrode also separates the gas extraction chamber (28, 29) from the plasma treatment chamber (26) and is provided with gas outlets (19) essentially spread out over its surface, gas being able to pass out of the plasma treatment chamber (26) and into the gas extraction chamber (28, 29) through said gas outlets (19). The invention also relates to a method for treating substrates with a glow discharge low temperature plasma. According to the inventive method, plasma is excited in a plasma treatment chamber and the excited plasma impinges on the substrate essentially vertically thereto, said substrate being located in the same chamber. The method is characterised in that the gas is extracted in the opposite direction to that in which it impinges on the substrate, also essentially vertically to the substrate.

Description

Impact-flow plasma reactor for surface treatment

The present invention relates to a plasma reactor for treating flat substrates or those with an uneven surface contour, the gas flow is improved, and a method for plasma treatment of such substrates.

Plasmas are partially or fully ionized gases and vapors, the particles of which also contain a large number of excited states. They can be generated and maintained by electromagnetic fields.

The ions, electrons, molecules in electronically excited states present in the plasma and the existing radiation activate and / or etch surfaces or, in the case of many (in particular organic) substances, initiate polymerizations in the gas phase and layer formation on the surface of substrates.

Compounds that are usually not very reactive can also be excited in chemical reactions in plasmas.

The main possibilities of the plasma-substrate interaction are summarized in the following overview:

material

Procedure organic inorganic removal cleaning, etching e.g. Degreasing

Modification activation, e.g. Plasma oxidation e.g. Hydrophilization Structure Plasma Polymerization Plasma CVD

Plasma treatments are carried out under vacuum in special reactors. It is usually important that the substrate is treated evenly.

The most important prerequisite for uniform treatment (especially in the case of layer deposition) is that the performance and material are uniformly uniform for all surfaces to be treated (or coated). This depends on the distribution of the electric fields and gas flows. Almost uniform distribution of electric fields is achieved in the so-called parallel plate reactor [see HV Boenig, Fundamentals of Plasma Chemistry and Plasma Technology, Technomic Publishing AG, Lancaster & Basel, 1988]. The reactors of this type are therefore particularly widespread. However, the reaction gases are led parallel to the substrate and implemented in the chemical reactions. These reactions can lead to both material depletion (eg through depositions) and an increase in the number of moles (eg through fragmentation of starting molecules). Therefore the gas composition at the gas inlet is different than at the gas outlet. This leads to uneven treatment. This phenomenon can be reduced by increasing the gas flow, but at the price of a lower yield and possibly a deterioration in the layer quality.

In addition, problems arise when scaling up the processes in such systems: with larger surfaces to be coated, one is forced to increase the distance between the electrodes and in particular the gas flow disproportionately, in order to be acceptable

To achieve uniformity. However, this changes the relationships between the parameters of the process, and an optimum can often only be found again on the scaled-up system due to a complex series of tests. The results obtained on a smaller laboratory system can only be used to a limited extent.

With the intention of achieving more uniform coatings, a so-called "radial flow reactor" [A.R. Reinberg, Ann. Rev. Mater. Sci., V.9, pp.341-372 (1979)]. In this reactor, the process gas is either supplied or extracted through an opening in the middle of an electrode. The gas flow is radially symmetrical.

However, the maximum substrate size for a uniform coating must be much smaller than the reactor dimensions (e.g. 4-inch wafers in a 22-inch reactor). The exact adjustment of the gas flow and the RF power is also necessary for a uniform coating, and the system is not easily scalable.

In yet another modification, which is described in Japanese Patent No. JP 5902375, a "shower electrode" is used, ie the gas inlet is distributed over the surface of the electrode. In such a system, the baffle flow that is favorable for the plasma interaction (eg deposition) is partially realized. In addition, the undesired concentration gradients in the gas phase are reduced somewhat, but not completely eliminated. The object of the invention is to provide a system for the treatment of flat substrates or those with an uneven surface contour in a glow discharge low-temperature plasma and a method for treating flat or three-dimensionally shaped substrates, which ensures increased uniformity of the gas treatment.

This object is achieved by a plasma electrode reactor according to claim 1 and a method according to claim 20. Particularly preferred are reactors according to claim 3, which have a modular structure.

Special configurations of the reactor are shown in FIGS. 1 to 12, in which:

Figure 1 shows an embodiment of the invention with a modular structure in the side

Cut shows

FIG. 2 shows the same configuration, but in the sectional planes A and B of FIG. 1, FIGS. 3a and 3b each show configurations in which the gas can also be conducted with the aid of tubes onto a substrate with an uneven surface contour at a constant distance,

Figure 4 shows a likewise modular design in lateral cross section, in which the upper electrode fastens a frame with parallel to each other

Gas distribution (feed) devices which extend lengthwise over the

Extend electrode,

5 shows the same configuration from above in two different sectional planes E and

F shows, - Figure 6 shows a detail of this embodiment, from which the attachment of the

Can detect gas supply devices in the frame of the electrode

FIG. 7 shows a gas supply device of FIG. 5 in a lateral section,

Figure 8 shows the same device from above in two different cutting heights G, H, - Figure 9 shows the same device in side section I-J

FIG. 10 shows the configuration as in FIG. 4, but with additional waveguides and antennas for the feeding of microwaves into the plasma treatment chamber,

FIG. 11 shows the configuration of FIG. 10 from above in two different sectional planes K, L,

FIG. 12 shows a device with a likewise modular construction in a lateral section, in which the upper electrode comprises, as in FIG. 4, a frame with gas supply devices arranged in parallel, but in this case in FIG Are in the form of elongated tubes with outlet openings directed towards the plasma treatment chamber,

FIG. 13 shows the device of FIG. 12 from above at the cutting height X, Y, and FIG. 14 shows an embodiment similar to that shown in FIG. 12, but in which the outlet openings of the elongated tubes are directed away from the plasma treatment chamber and towards reflectors which do so Distribute gas diffusely in the direction of the substrate.

The plasma electrode reactor according to the invention comprises a reactor gas inlet through which the gas is introduced into the reactor. The gas then enters a gas distribution space without obstructions such as constrictions or the like, so that it is distributed there with a constant pressure. Like the gas extraction space, the gas distribution space is separated from the plasma treatment chamber by a first electrode. In the latter, the gas is excited to a plasma, whereupon it then strikes as a plasma on a substrate and changes it. The substrate is arranged on a counter electrode opposite the first electrode. For example, it can rest (e.g. if, as is often the case, this electrode extends horizontally, especially if it is impermeable and forms the bottom of the plasma electrode reactor). Of course, the substrate can also be attached to or in the vicinity of this second electrode, so that the second electrode does not necessarily have to form the bottom of the system. However, this is preferred.

In order for the gas to strike the substrate essentially perpendicularly, that is to say as a "baffle flow", the first electrode through which the gas passes must have gas inlets distributed essentially over its surface. These can be distributed symmetrically or arranged in rows or the like; the geometry of the arrangement is not important. However, it is necessary that the number of gas inlets is sufficient so that the gas which passes essentially perpendicularly and which is deflected only insignificantly strikes the entire surface of the substrate essentially uniformly and in the same amount. It is particularly advantageous if the inlet cross sections of the individual

Gas inlets are kept as small as possible. Of course, the smaller the inlet cross-sections, the greater the number of gas inlets. The inlet cross sections of the individual gas inlets are preferably not larger than approximately 15.5 mm ^, more preferably not larger than approximately 7 mm 2, and very particularly preferably not larger than approximately 1 mm ^. The geometry of the gas inlets is not essential, for example they can be round or square or they can also be in the form of elongated slots. In the latter case, the inlet cross section is usually somewhat larger than in the first two cases. The characteristic distance between the inlet and outlet openings is preferably less than that Distance between the gas inlets and the substrate to avoid flows parallel to the substrate surface.

After the gas with its constituents that change the substrate has hit it, it should preferably not be drawn off parallel to the substrate, in order to avoid a concentration gradient occurring along the substrate surface. It is therefore provided according to the invention that the gas can also emerge again via gas outlets in the same first electrode, flow through a gas extraction space and then leave the reactor. The gas outlets and the gas extraction space must of course be spatially separated from the gas distribution space and the gas inlets. This principle can be found in a variety of

Embodiments vary, which are specifically explained below with the aid of individual examples. The gas is then extracted from the gas extraction space via a reactor gas outlet, for example with the aid of a vacuum pump.

The principle according to the invention, namely to effect gas inlet and gas outlet through the electrode opposite the substrate to be treated, enables an extremely simple construction of the entire reactor. It is namely not necessary (although of course not excluded) that the components such as electrodes and the like are arranged in an outer reactor chamber which communicates with the surroundings through a gas inlet and outlet. Rather, it is sufficient that the space required for treating the substrate is itself formed by the constituents which are necessarily present anyway. For example, the plasma treatment chamber can be formed by the first electrode (which is equipped with the gas distribution systems described above), the second electrode opposite it which can carry the substrate, and an intermediate frame. If these components are separated from one another and connected to one another by insulating seals, a very simple modular structure is obtained. In a preferred, because very simple, way, it is then possible to form the spaces required for the gas supply or for the removal of the gas by the fact that one of these spaces within the first electrode or in grooves, other recesses or in pipes or others Constructs is arranged within this electrode, while the other of the two spaces is formed on the side of the electrode facing away from the plasma treatment chamber. To separate this last-mentioned space from the outside environment, a cover can be used in a simple manner, which has a recess in its interior, so that when the cover is placed sealingly on the first electrode, such a gas space is formed, which has a reactor gas inlet or outlet can be connected to a vacuum pump or a gas supply device or the like. The other of the two gas spaces can communicate with the environment through a gas inlet or outlet which is guided through the frame of the first electrode. If the four components: (1) second electrode (e.g. in the form of a solid end electrode plate), (2) insulating intermediate frame, (3) first electrode provided with the gas passage openings (also with a fixed outer frame) and (4) cover in the Floor plan have the same external dimensions, for example rectangular or square when viewed from above, they can be used in a simple manner as modular components which are connected to one another by rubber O-rings or the like or other sealing parts. If necessary, individual of these modular parts can be exchanged in a simple manner for other parts, so that a high variability of configurations of the plasma electrode reactor according to the invention with a small number of components is possible.

The intermediate frame lying between the two electrodes can be formed from electrically insulating material. However, a metal component is sometimes recommended because the selection of vacuum and plasma compatible electrically insulating materials is relatively small. Plastics in the plasma treatment chamber should be avoided if possible due to the high outgassing rate and the degradation under the plasma conditions. Glass and ceramics are therefore particularly suitable as insulating materials, but they are often brittle. Your editing options are usually limited and editing is often expensive. Therefore, if metal or another conductive material is used instead, an insulator should be arranged on the side facing the plasma treatment chamber, so that the uniformity of the electric field is not impaired.

The invention will now be explained in more detail with reference to individual exemplary embodiments.

Figures 1 and 2 show a reactor with a lower electrode 4, on which the substrate 5 to be treated is placed or otherwise fastened, the intermediate frame 6 made of an electrically insulating material, e.g. Glass or ceramic, and the upper electrode 13, in which the gas distribution system is installed.

The lid 25 is applied to the upper electrode 13 and has a recess within a frame with approximately the same frame width as that of the intermediate frame 6, so that a cavity 29 is formed between the lid and the electrode. A cover plate 2 rests on the electrode 13. The working gas enters through the reactor gas inlet 7 and is evenly distributed over the gas space 17, which forms grooves in the electrode body 13, which are separated from the suction space 29 by the cover plate 2. Then it will evenly through the outlet passages 18 into the plasma treatment room 26. A uniform distribution is given, for example, if the total cross section of the passages of a groove is significantly smaller than the groove cross section and therefore the pressure drop only takes place in the passages.

The working gas enters the plasma treatment chamber 26 from the openings 18 and strikes the substrate 5 essentially perpendicularly. If the openings 18 are small enough and the working pressure is selected accordingly, the gas dynamic effects ("impingement flow") can lead, for example, to an excellent deposition of plasma polymerization products on the opposite side, i.e. on the substrate. This is a desirable effect. However, the diameter will usually not be able to be reduced arbitrarily for manufacturing reasons. For example, openings less than 0.5 to 1 mm can hardly be drilled mechanically. Laser drilling is possible and can be used here, but relatively expensive. (A baffle flow effect is achieved, for example, if the distance between the gas outlet openings 18 at a distance of approximately 1.5 cm [in the case of an arrangement with an approximately square pattern, see FIG. 2] and the diameter of the openings is approximately 0.8 mm a distance between the electrode 4 and the substrate 5 of approximately 4 cm, the gas pressure during the treatment in the plasma room being 100 Pa and the gas flowing at 0.5 sccm (standard cubic centimeter) per inlet opening).

Passages 19 in the electrode body 13 and openings 20 in the cover plate 2 are provided for evacuating the reactor and suctioning off the reaction products. These passages, like the gas inlet passages 18, are distributed over the electrode surface. Then the gas flow goes through the suction chamber 29 in the cover 25 to the reactor gas outlet 1, which e.g. is connected to a vacuum pump.

The sealing between the reactor components 4, 6, 13 and 25 is carried out by rubber O-rings 3.

Figures 3a and 3b represent two variants of another embodiment of the reactor according to the invention. The structure of the reactor of Figure 3a is similar to that of Figures 1 and 2. The gas port 7 is used as the reactor gas inlet, and the electrode body 13 has a different construction. The working gas is brought from the space 17 through tubes 8 close to the substrate surface. The above applies to the diameter of the tubes: for an even gas distribution in the plasma treatment chamber, the pressure drop should only occur when the gas passes through the tubes. The exhausted gas is extracted through the openings 19 in the cover plate 27 belonging to the electrode 13 (through which the tubes are also carried out concentrically in the illustration of the figure, but this does not necessarily have to be the case with such an arrangement) through the cavity 28 and through the suction connection 1 in the electrode body 13 The advantage of this construction is that the length of the different tubes can be made variable. As a result, the gas supply can be brought to substrates 5 which are not flat but have an uneven surface contour (as shown schematically in the figure). In one embodiment, the tubes are made of an electrically insulating material. In this case, the distribution of the electric fields is not changed significantly compared to a parallel plate reactor. In another embodiment, the tubes are made of a conductive material such as metal. This leads to a substantial enlargement of the electrode surface and additionally also to a hollow cathode effect, whereby the plasma efficiency can be significantly improved.

Figure 3b shows a specific embodiment of the principle shown in Figure 3a, in which the tubes are held reversibly movable along their longitudinal axis. For this purpose, a pressure plate 42 rests on the electrode 13 and can be pressed or released in the direction of the electrode 13 by means of screws 43. O-rings 41 made of a compressible material, for example an elastomer (rubber), are arranged around the tubes. When the screws 43 are loosened, the O-rings 41 lie so loosely around the tubes that they can slide along their longitudinal axis. If the electrode 13 is placed in this state while the - uneven - substrate 5 is already on the lower electrode 4, the tubes automatically slide into a suitable position. The same applies to the insertion of the substrate if it has flowing contours. The pressure plate 42 can then be tightened using the screws. The contact pressure acting on the O-rings 41 changes their shape in such a way that they now fix the tubes in the resulting position. At the same time, the gas seal to the gas space 17 is ensured by the O-rings. With 44 the openings for the tubes in the pressure plate are designated, the other reference numerals correspond to those for Figure 3a. The remaining components of this plasma reactor are omitted in FIG. 3b.

The configuration of FIGS. 4 and 5 differs from the configuration according to FIGS. 1 and 2 in the electrode structure and in the gas flow. A cover 25 is in turn applied to the upper electrode 13 such that a cavity 29 is created. The electrode 13 consists of a frame 16 on which gas distributors 15 are mounted. Such a gas distributor is shown in FIGS. 7 to 9; it consists of a body 10 and a cover plate 11 which are glued together or connected in some other way. Through the deeper groove 30, the working gas is evenly distributed over gas outlet gaps 12, which are between a recess are formed in the body 10 and the cover plate 11. The width of the column 12 can be kept very precise by the webs 31. The webs 31 can be integral components of the body 10 or the plates 11, but they can also be glued on or attached in some other way. The gas is introduced into the gas distributor 15 through a pipe connection 9, which is shown in FIG. 6.

The gas distributors are mounted on the frame 16 and fastened by screws 14. The pipe connection 9 ends in the gas channel 24 (a blind hole) which is connected to the gas inlet 7.

The evacuation (suction) of the gas takes place through the spaces between the gas distributors 15, further through the cavity 29 in the cover 25 and the connection 1.

The gaps between the gas distributors can lead to a hollow cathode effect, which in many cases can increase the plasma efficiency. However, if the associated redistribution of the plasma is undesirable, the effect can possibly be achieved by attaching a flat object, e.g. of a metal sieve 32 are suppressed, which, viewed from the plasma treatment chamber, is arranged in front of the electrode 13 and is electrically connected to it, thus making it a flat electrode. This article can be made of metal or any material provided that it is conductive or coated with a conductive material. Instead of a sieve, a perforated plate or another design with a large number of openings is possible.

The advantage of this system is that the gas exit gaps 12 through which the gas enters the plasma treatment chamber 16 can be made very narrow. The gas dynamic effects mentioned in the first embodiment (FIGS. 1 and 2) can thus be achieved in a particularly effective manner. In addition, this construction is very simple and economical to manufacture, since a large number of gas inlets can be achieved by connecting only two parts, the body 10 and the cover plate 11. It is not necessary to drill a large number of small holes here.

Furthermore, this construction differs from the embodiment of Figures 1 and 2 in that the intermediate frame 6 is made of metal. In order to ensure the electrical insulation between the parts, plastic spacers 33 are therefore used in addition to the O-rings 3. Since the metallic walls of the intermediate frame can play the role of an additional electrode, especially when the system is operated at high frequency, and can thereby impair the uniformity of the distribution of the electric field, disks 23 are made of an insulator, for example Glass provided that shield the metallic walls from the plasma processing chamber.

Figures 10 and 11 represent a modification of the embodiment of Figures 4 and 5. The gas flow is the same. The energy is also fed in here

Microwaves, which are fed in through coaxial (or waveguide) feedthroughs 21, which are introduced in a sealed manner by the cover 25 and further through the spaces between the gas distributors 15 into the plasma treatment space 26. You can e.g. can be radiated into the room 26 by antennas 22. Plasma efficiency is significantly increased by the combined exposure of microwave and radio frequency energy, which is desirable in some cases.

FIGS. 12 and 13 show an embodiment in which the gas routing and distribution are implemented in a manner similar to that in FIGS. 4 and 5. However, tubes 34 with openings 35 are used here as gas distributors. Of course, the same applies to the size of the openings of the tubes as was said previously for the openings of the gas inlets into the plasma treatment chamber. The use of the pipes 34 instead of the gas distributors 15 has the advantage of being particularly simple in construction.

In such a configuration, the plasma treatment room 26 can optionally be dated

Suction chamber 29 in the lid 25 are additionally separated by a metal grid or sieve 39. In this case, the pipes can be made of conductive or non-conductive material.

FIG. 14 shows an embodiment which is very similar to that of FIGS. 12 and 13. Here, however, the tubes are arranged so that their openings do not point to the plasma treatment chamber, but in the opposite direction. The escaping gas strikes reflectors 40 here, which reflect the gas diffusely in the direction of the substrate. Although the gas flow is somewhat more diffuse in this embodiment, there are essentially no gas flows parallel to the substrate.

The small diameter of the gas outlet openings 18, 35 or columns 12 leads, as already explained, to a baffle flow directed towards the substrate, which is advantageous since in most cases it makes better use of the chemicals and a higher treatment rate (for example deposition or etching) ) enables; it also ensures that the pressure drop only takes place in the outlet openings and the gas flows from all these openings are the same. However, such a baffle flow does not have to be optimal for all treatment methods. If necessary, it can lead to a treatment pattern the substrate that corresponds to the distribution of these openings. In order to avoid this, in special cases, as shown in FIG. 14, the gas flow is first directed in the opposite direction and then diffusely reflected by the gas reflectors 40 in the direction of the substrate.

Legend to the figures

1 reactor gas outlet

2 cover plate

3 O-ring

4 counter electrode

5 substrate

6 intermediate frames

7 reactor gas inlet

8 gas inlet tubes

9 pipe connection

10 gas distributor body

11 gap inlet cover plate

12 gas outlet gap

13 gas-permeable first electrode

14 screw

15 gas distributors

16 frame of the first electrode

17 groove (gas channel)

18 gas inlet fine holes

19 suction passages

20 slots

21 MW feed-through (coax or waveguide)

22 MW antenna

23 isolator

24 gas channel (bore)

25 lids

26 plasma room

27 cover plate

28 cavity in the electrode body

29 Cavity in the electrode cover

30 groove

31 spacers (web)

32 metal sieve

33 electrically insulating spacers

34 Pipe gas distributor

35 gas outlet opening

36 gas inlet collector

38 electrode frames

39 metal grille

40 gas reflector

41 O-ring

42 pressure plate

43 screw

44 openings in the pressure plate

Claims

Expectations:

1. plasma reactor comprising a reactor gas inlet (7), a gas distribution space (17), - a plasma treatment chamber (26) which is delimited by a first electrode (13) and an opposite second electrode (4), a gas suction space (28, 29), and a reactor gas outlet (1), the first electrode (13) separating the gas distribution space (17) from the plasma treatment chamber (26) and having gas inlets (18) distributed essentially over their area through which the gas is separated from the gas Distribution space (17) can flow into the plasma treatment chamber (26) is provided, characterized in that the first electrode also separates the gas extraction space (28, 29) from the plasma treatment chamber and with gas outlets (19) distributed essentially over its area, through which the gas from the

Plasma treatment chamber (26) can flow into the gas extraction chamber (29) is provided.

2. Plasma reactor according to claim 1, characterized in that the area of the inlet cross sections of the individual

Gas inlets (18) is not greater than about 16 mm ^, preferably not greater than about 4 mm ^ and most preferably not greater than about 2.5 mm ^.

3. Plasma reactor, in particular according to one of the preceding claims, comprising an end electrode plate (4) made of conductive material, an intermediate frame (6), one with a gas inlet system (7, 17, 18) or gas outlet system (1, 28, 29) and with separate through openings for the gas inlet (8,18) or gas outlet (19) provided electrode (13) made of conductive material and a cover (25) which is provided with a reactor gas inlet (7) or gas outlet (1) The end electrode (4), the intermediate frame (6) and the electrode (13) are sealingly connected to one another to form the plasma treatment chamber (26) and the cover (25) with a recess is attached to a frame (16) of the electrode (13) is placed in such a sealing manner that a gas extraction space (29) or a gas distribution space (17) is formed between the cover (25) and the electrode plate (13).

4. Plasma reactor according to claim 3, characterized in that the cover (25) has a reactor gas outlet (1) and between it and the electrode (13) a gas suction chamber (29) is formed.

5. Plasma reactor according to claim 3 or 4, characterized in that the base plate (4), the intermediate frame (6), the plate (13) and the cover (25) are sealingly connected to one another by O-rings.

6. Plasma reactor according to claim 4 or 5, characterized in that the first electrode (13) to the gas extraction chamber (29) with a passage openings (20) having a cover plate (2) is provided, the grooves (17) in the electrode (13) ) separates from the gas suction chamber (29) and their through openings (20) communicate with the gas outlets (19) of the first electrode (13), such that gas from the plasma treatment chamber (26) passes through the

Gas outlets (19) and the openings (20) flow into the gas suction chamber (29) and can be suctioned off via the reactor gas outlet (1).

7. Plasma reactor according to one of claims 4 to 6, characterized in that the first electrode (13) one by its

Frame (16) laterally extending reactor gas inlet (7), substantially parallel grooves (17) extending across the entire inner surface of the plate connected to the reactor gas inlet (7) and a plurality of arranged within the grooves Has gas passage openings (18) for admitting the gas into the plasma treatment chamber (26), the diameter of the

Gas passage openings (18) is significantly smaller than the cross section of the grooves (17).

8. Plasma reactor according to one of claims 1 to 3, wherein the gas inlets (18) are formed as tubes (8) which through the first electrode (13) into the

Extend the plasma treatment chamber (26) into it.

9. Plasma reactor according to claim 8, characterized in that the tubes (8) protrude to different degrees into the plasma treatment chamber (26), such that the distance between the

Tube ends to the surface of a substrate (5) lying or applied on the second electrode (4) can also be constant if the substrate has an uneven surface contour.

10. Plasma reactor according to claim 8 of 9, characterized in that the tubes (8) are formed from an electrically insulating material or from a conductive material.

11. Plasma reactor according to one of claims 8 to 10, characterized in that between the cover (25) and the first electrode (13) there is a gas distribution space (17) from which gas enters the plasma treatment chamber (26) via the tubes (8) can.

12. Plasma reactor according to claim 11, characterized in that the inlet cross section of the tubes is not greater than about 16 mm ^ preferably not greater than about 4 mm ^ and most preferably not greater than about 2.5 mm ^.

13. A plasma reactor according to one of claims 11 or 12, characterized in that the first electrode (13) to the plasma treatment chamber comprises a cover plate (27) provided with gas outlets (19), such that between the part facing the gas distribution space (17) first electrode (13) and the cover plate (27)

Gas suction chamber (28) is formed, which is connected to a reactor gas outlet (1) arranged laterally in the first electrode (13).

14. Plasma reactor according to one of claims 4 or 5, characterized in that the first electrode (13) one through its

Frame (16) laterally extending reactor gas inlet (7) and on the frame substantially parallel to each other mounted gas distribution devices (15) which communicate with the reactor gas inlet (7).

15. Plasma reactor according to one of the preceding claims, characterized in that coaxial or waveguides are guided through the first electrode (13) into the plasma treatment chamber (26), through which microwave energy can be introduced into the plasma treatment chamber (26).

16. Plasma reactor according to one of the preceding claims, characterized in that between the first electrode (13) and the plasma treatment chamber (26) a flat, with a plurality of openings element (32) made of conductive material is arranged and with the electrode (13) is conductively connected.

17. A method for treating substrates with a glow discharge low-temperature plasma, wherein plasma is excited in a plasma treatment chamber and the excited plasma strikes the substrate in the same chamber substantially perpendicularly, characterized in that the gas suction in the opposite direction to the application of gas to the substrate also takes place essentially perpendicular to the substrate.

18. The method according to claim 17, characterized in that the gas is introduced through openings in the plasma treatment chamber, which are arranged substantially uniformly distributed over the surface of the substrate and each have a cross section of no more than about 16 mm ^, preferably no more have about 4 mm2 and especially not more than 2.5 mm ^.

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