DE19807086A1 - Atmospheric pressure plasma deposition for adhesion promoting, corrosion protective, surface energy modification or mechanical, electrical or optical layers - Google Patents

Abstract

An atmospheric pressure plasma deposition process comprises introducing a precursor, aerosol and/or solid powder containing gas phase (2) into a cold plasma jet (30). An atmospheric pressure plasma coating process comprises introducing a gas phase (2), containing one or more precursors, an aerosol and/or a solid powder, into a plasma jet (30) to form particle species which are entrained by the plasma jet for forming a layer (72) on a substrate (70). Independent claims are also included for the following: (i) an apparatus for carrying out the above process, comprising a hollow body (10) for supplying a first gas phase (1), electrodes (40), an electric field generator (50) and a system (20, 21) for supplying a second gas phase (2); (ii) a layer system produced by the above process or the above apparatus and comprising one or more of silicon, carbon, hydrogen, oxygen, nitrogen, phosphorus, boron, selenium, tin, aluminum, titanium and zinc; and (iii) a substrate coated with the above layer system with a layer thickness 0.001-10 mu m.

Description

The invention relates to a method for coating surfaces of a Substrates in a plasma-activated process at atmospheric pressure, a pre direction to carry out the procedure and a procedure according to the special layer system produced in the device as well as a be layered substrate.

Plasma-activated deposition of layers is known. It enables at low temperatures the coating with materials that can be done without Plasma, d. H. purely thermal, only at high temperature, especially in one CVD (Chemical Vapor Deposition) process or not at all let it separate. Silici is an example of a deposition in the CVD process umoxid, an example of a deposition not possible without plasma is a Plasma polymer (R. A. Haefer, surface and thin film technology, Sprin ger publishing house, 1987). Mostly a direct current (DC), high frequency (HF) or a microwave plasma (MW) is used. These plasmas are to be operated as so-called cold plasmas only at low pressures.

Methods are also known in which a so-called thermal plasma is used det and coated under atmospheric pressure. These procedures are called Plasma spraying process called. The gas is discharged in an arc high power to a high temperature to metal or Ke melting ceramic particles that are brought into the discharge and the Melt drops in a hot gas stream at speeds of over 100 m / sec to accelerate. 5 to 100 kW and a high temperature means 4000 to a few 10,000 K. They are called  Melt drops solidify on impact on the surface to be coated and form the desired layer there.

It is also a plasma-activated deposition of layers in the so-called known barrier or corona discharges at atmospheric pressure, DE 195 05 449 C2. It is also known to discharge between two electrodes separated by at least one dielectric barrier when applied an alternating voltage of sufficient amplitude from acetylene or others deposited layers of gas deposited on the electrodes (algae, Proceedings of EMRS 1995, Strasbourg, France). By means of one Processes can also be made of plastics or metals the discharge can be carried out, coated. The ones to be coated Substrates (webs or components) lie during the coating process mostly to ground and are therefore part of the counter electrode. The High-voltage electrode is at a distance of in particular 1 to 2 mm arranged over the substrate to be coated. During the Coating process results in a coating of both Electrode surfaces. The coating of the counter electrode or the to Coating substrate surface is wanted, whereas the coating the high-voltage electrode is disruptive. Due to the parasitic coating the high voltage electrode is the coating process in the shape influences that a coating result that changes with the process time is aimed. In extreme cases, this can clog the discharge gap to lead. In addition, result from the high voltage electrode flaked layer parts also faults on the substrate to be coated.

The invention has for its object a method for coating Surfaces of a substrate in a cold plasma-activated process Temperatures below T = 1000 K and at atmospheric pressure as well as a pre to create direction for performing the method by means of which or a disturbance of the deposition process due to parasitic deposition, So unwanted deposition of material on electrodes or the like avoided becomes. The layer should consist of one or more gaseous precursors  and / or an aerosol and / or a powdery solid on the Substrate are deposited. The substrate is said to be error-free without Fault spots or surfaces are coated.

The object is achieved with a method according to the preamble of claim 1 solved in that a first gas phase by means of an electric field in the plasma state is shifted. The plasma-activated first gas phase forms a plasma jet. A second gas phase is introduced into the plasma jet brings which one or more precursors and / or an aerosol and / or contains a powdery solid. Through physico-chemical reac ions between the plasma-activated first gas phase and the admixed second gas phase are suitable particle species for layer deposition educated. The particle species suitable for layer deposition are included transported and formed by the plasma jet onto the substrate to be coated on this one layer. By means of a device for performing the The method solves the problem in that a hollow body for supply a first gas phase, electrodes, one for generating an electric field suitable generator and one or more means for supplying a second Gas phase are provided. In a layer system, it is solved that the layer system deposited on the substrate silicon and / or Carbon and / or hydrogen and / or oxygen and / or nitrogen and / or phosphorus and / or boron and / or selenium and / the tin and / or Has aluminum and / or titanium and / or zinc. The task is with one Substrate, which is coated with the layer system, solved in that the layer thickness of the deposited layer system at 0.001 to 10 µm lies. Developments of the invention are in the respective dependent An sayings defined.

This provides a method for coating surfaces of a substrate created in a plasma-activated process at atmospheric pressure, which can also operate plasma-activated processes at atmospheric pressure, whereby advantageously investment costs for recipients and pumps and Be drive costs can be saved compared to the prior art, because before one  Batch coating no more pumping period is required. Before the high-voltage electrode becomes partial during the coating process no longer co-coated, which is why even with longer operating times no impairment of the coating process or clogging of the Gap between the electrodes or no flaking of the applied Layer occurs.

Preferably, flow rates in the range of 0.01 up to 10 m / s. Can advantageously by means of the Invention according to the method, significantly thinner layer thicknesses are produced than with the plasma spraying process. There the layer thickness is up to 100 µm a few millimeters, since the powder particles used in the production are a Have size of 5 to 10 microns. Layer thicknesses are according to the invention generated between 1 nm and 10 µm, what with the plasma spray process is not possible due to the system.

According to the invention, it is also advantageous to use gaseous precursors, ie. H. chemical starting compounds, and / or aerosols and / or solid pul deformed particles are coated. This results in larger ones Possibilities of variation for the coating method according to the invention.

A first gas phase is preferred during the flow through the hollow transformed into the plasma state. At the end of the hollow body occurs a plasma jet activates off. The first gas phase is particularly preferred in the hollow body is transformed into the plasma by electrodes provided therein. One of the electrodes can preferably be the electrically conductive wall of the hollow body itself. The generator feeding the electrodes gives preferably an AC voltage with a predetermined one suitable amplitude. But it can also generate DC voltage of a constant field. The course of the AC voltage is preferably sinusoidal or can also be more complicated. At for example, a pulsed DC voltage or a pulsed sine voltage can be provided.  

The formation of an unwanted hot discharge or arc discharge between the electrodes as known in the prior art and for Zer disruption of the electrodes or the substrate to be coated or the abge leads different layer is advantageously avoided in that the gas flow together with the time-variable voltage at the electrodes is provided. One or more dielectrics can also be used be additionally provided between the electrodes and the plasma.

Preferably the speed of the plasma jet after mixing is first and second gas phase greater than a critical speed. Be the velocity of the plasma jet is particularly preferably after the Mi. over about 5 cm / s.

Gases or gas mixtures are preferably supplied as the first gas phase. which has no deposition of layers with a thickness of more than 10 nm possible or those that have no shift deposition on the elec tread or cause the hollow body walls. Therefore are suitable especially noble gases such as argon or oxygen, nitrogen, hydrogen, Nitrous oxide, tetrafluoromethane, carbon dioxide, carbon monoxide, welding rock hexafluoride or suitable mixtures of these gases.

One or more are particularly preferably arranged on the side of the hollow body Nete mixture-promoting means are provided, through which the second gas phase into the plasma of the first gas emerging as a beam at the end of the hollow body phase flows in. The second gas phase preferably contains one or several precursors or precursors suitable for the deposition and / or when using an aerosol, fine droplets of a liquid phase and / or the powder of a solid phase. The second gas phase is made by the entering plasma jet of the first gas phase activated to the desired thereby stimulating chemical substances to deposit a layer. The activation process can transfer energy from the plasma beam, an oxidation or other physico-chemical process.  

This physico-chemical reaction takes place behind that for supplying the first and second gas phase used mixture-promoting agents, in particular in the form of nozzles, in free space. This ensures that suitable for deposition through the physico-chemical reaction Products formed no longer on the electrodes or in the mixture support funds, but as desired on the coating material. To achieve this without problems, the Speed of the plasma jet after the first and selected second gas phase larger than a critical speed, which at Atmospheric pressure and a distance between the mixing point and the end of the mixture-promoting agent with a preferred value of 1 cm is about 5 cm / s. When choosing a different distance between the mixing point and other critical speeds may result at this end.

The deposition process is preferred for the deposition of oxide layers operated in a normal air environment. For depositing non-oxide Layers, for example of plasma polymers, the environment becomes inert held against the layer being formed. Preferably with a Sheath flow made of nitrogen or in a nitrogen purge closed atmosphere, especially in a closed container, worked.

The second gas phase particularly preferably contains hydrocarbon and / or an organosilicon compound and / or organometallic compound and / or organic boron, phosphorus or selenium compounds. Preferably a tin and / or titanium and / or aluminum and / or organic zinc Ver bond provided as an organometallic compound.

A layer system consisting of silicon is preferably provided on the substrate oxide or a hydrocarbon compound or a compound Silicon, carbon and hydrogen or a compound of silicon, Koh lenstoff, oxygen and hydrogen or a compound of silicon, Koh  Oil, nitrogen and hydrogen separated. Alternatively or additionally can be any combination of metals, such as tin, titanium, Aluminum, zinc and / or be deposited from selenium, boron, phosphorus. The The layer thickness is preferably 0.001 to 10 μm. Such a layer is used as an adhesion-promoting layer or as a corrosion protection layer or Modification of the surface energy of the substrate used. The layer can also have a mechanical, electrical or optical function.

In order to explain the invention in more detail, the following are examples games described using the drawings. These show in:

Fig. 1 is a schematic diagram of the inventive device for loading layers with a plasma jet and

Fig. 2 is a schematic diagram of a second embodiment of an inventive device for coating with a plasma jet.

Fig. 1 describes a schematic diagram of a first embodiment of an inventive device for coating a substrate 70th For this purpose, the device has a hollow body 10 . The hollow body can have an arbitrarily shaped cross section. It is preferably round, square or rectangular in cross section.

The wall 11 of the hollow body 10 delimits an interior 12 . Two electrodes 40 are arranged in this interior of the hollow body. An electrode is preferably at ground potential. They are connected to a generator 50 via lines 41 . This feeds the electrodes with an alternating voltage of suitable amplitude. The voltage curve can be sinusoidal or more complicated.

In addition to the hollow body 10 are arranged at an angle to this on two sides mixture-promoting means 20 , 21 are provided. These are preferably cylindrical or tubular. They each have a wall 22 , 23 , which delimits a respective interior 24 , 25 .

The substrate 70 is arranged at a predetermined distance from the hollow body 10 , substantially perpendicular to it. It is preferably moved past it at a constant speed.

For the coating process, a first gas phase 1 is introduced into the interior 12 of the hollow body 10 from its rear end 14 . The first gas phase 1 flows through the hollow body at a predetermined speed. Activation of the first gas phase is brought about by the alternating voltage applied to the electrodes 40 , as a result of which the desired plasma jet 30 is formed. This flows in the direction of the front end 13 of the hollow body 10 . There it emerges from the hollow body 10 . The electrode 40 arranged in the hollow body is surrounded by a dielectric 44 .

A second gas phase 2 is introduced from the rear ends 28 , 29 by the two mixture-promoting means 20 , 21 . The means 20 , 21 are preferably nozzles. The second gas phase 2 flows through the two means 20 , 21 at a predetermined speed and exits at their respective front ends 26 , 27 . The second gas phases 2 hit the plasma jet 30 in the region of a mixing point 60 . A physical-chemical reaction occurs here, which leads to the coating of the surface 71 of the substrate 70 . The desired layer 72 is formed on the surface of the substrate 70 .

In FIG. 2 a second embodiment is a Vorrich tung invention for coating a substrate 70 illustrated by the inventive method. In this case, the coating device is moved past the resting substrate to be coated, in the direction of the arrow. For example, this device according to FIG. 2 serves for the deposition of silicon oxide. Instead of the hollow body 10 with a uniform diameter, as shown in FIG. 1, an essentially cylindrical tube 15 with a tapered front end 16 is provided according to the second embodiment according to FIG. 2. The front end 16 forms a front opening 17 . The cylindrical tube 15 forms the required counter electrode and is at ground potential. It is therefore connected via line 41 to generator 50 generating the electric field.

The high-voltage electrode is formed by a pin-shaped element 42 which is provided substantially centrally in the cylindrical tube 15 and is connected via the line 41 to the high-voltage output of the generator 50 . The high-voltage electrode itself is surrounded by the dielectric 44 , which is thin, in particular 1 to 2 mm thick. The high-voltage electrode and dielectric are surrounded by the plasma formed. The distance between the dielectric of the high-voltage electrode and the inner wall 19 of the cylindrical tube 15 is in the millimeter range.

The two mixture-promoting means 20 , 21 arranged laterally at a distance from the central front opening 17 of the cylindrical tube 15 have a particularly small diameter. It in turn blows the second gas phase into the plasma jet that is formed within the cylindrical tube 15 .

For example, the cylindrical tube 15 can be made of stainless steel and have a diameter of 1.2 cm. The front end tapers, for example, to a diameter of the front opening 17 of 0.8 cm. The electrode 42 can be, for example, a pin with a length of 2 cm and a diameter of 4 mm. The thickness of the dielectric is 1 mm. An ac sine voltage of 12 kV (peak voltage) and a frequency of 20 kHz can be applied to the cylindrical tube 15 to operate the discharge. The first gas phase 1 can be, for example, air with a volume flow of 12 liters per minute. This then flows through the cylindrical tube 15 at a gas velocity of approximately 400 cm / s in the region of the front opening 17 of the tube. The two mixture-promoting means 20 , 21 are arranged, for example, at a distance of 1 cm from the front opening 17 of the cylindrical tube 15 . They have a diameter of 1 mm, for example, and a second gas phase in the form of a nitrogen stream loaded with about 1 volume percent HMDSO (hexamethyldisiloxane) of, for example, 0.8 l / min (total) flows through them. The gas velocity is about 850 cm / s. The substrate 70 is , for example, a distance of 2 cm from the front opening 17 of the cylindrical tube 15 . It is preferably made of metal, in particular aluminum. The area covered by the plasma beam is then about 2 cm ² . A silicon dioxide layer of about 0.4 μm thick can be deposited on an area of this size with alternatively selected stationary operation with a contact time of about 1 s.

Reference list

1

first gas phase

2nd

second gas phase

10th

Hollow body

11

Wall

12th

inner space

13

front end

14

rear end

15

cylindrical tube

16

tapered end

17th

front opening

19th

Inner wall

20th

mixture-promoting agent

21

mixture-promoting agent

22

Wall

23

Wall

24th

inner space

25th

inner space

26

front end

27

front end

28

rear end

29

rear end

30th

Plasma beam

40

Electrodes

41

cables

42

Electrode / pin

44

dielectric

50

generator

60

Mixing point

70

Substrate

71

surface

72

layer

Claims (24)

1. A method for coating surfaces of a substrate in a plasma-activated process at atmospheric pressure, characterized in that
that a first gas phase ( 1 ) is brought into the plasma state by means of an electric field,
that the plasma-activated first gas phase ( 1 ) forms a plasma jet ( 30 ),
that a second gas phase ( 2 ) is introduced into the plasma jet ( 30 ) and contains one or more precursors and / or an aerosol and / or a powdery solid,
that suitable particle species are formed by physico-chemical reactions between the plasma-acti fourth first gas phase ( 1 ) and the admixed second gas phase ( 2 ), and
that the particle species suitable for layer deposition are transported with the plasma jet ( 30 ) onto the substrate ( 70 ) to be coated and form a layer ( 72 ) thereon. 2. The method according to claim 1, characterized in that
that the first gas phase ( 1 ) flows through a hollow body ( 10 , 15 ) which has electrodes ( 40 , 41 , 19 ) for generating the electric field, and
that the plasma jet ( 30 ) is formed when flowing out of the electrode area. 3. The method according to claim 1 or 2, characterized in that an alternating electric field for generating the plasma state is seen before, the alternating field being generated by electrodes charged with alternating voltage ( 40 , 42 , 19 ). 4. The method according to claim 3, characterized, that the alternating electrical field due to sinusoidal voltage curve or pulsed DC voltage curve or pulsed sine voltage ver run is generated. 5. The method according to any one of the preceding claims, characterized in that the plasma is generated by gases or gas mixtures, the no deposition of layers with thicknesses of more than 10 nm or the no layer deposition on the electrodes and / or hollow body walls ( 11 , 19 ) cause. 6. The method according to any one of the preceding claims, characterized, that the plasma from one of the substances noble gas, hydrogen, nitrogen, sow erstoff, nitrous oxide, tetrafluoromethane, carbon dioxide, carbon monoxide, Sulfur hexafluoride alone or a mixture of at least two of the Gases is generated. 7. The method according to claim 6, characterized, that for the deposition of oxide layers the process in normal air is operated. 8. The method according to any one of claims 5 to 7, characterized, that to deposit non-oxide layers the process in opposite the layer being formed is operated in an inert environment, in particular those with a jacket flow of nitrogen or in a ge with nitrogen flushed closed environment.   9. The method according to any one of the preceding claims, characterized, that a flow velocity of 0.01 to 100 for the plasma jet m / s, in particular from 0.2 to 10 m / s, is provided. 10. The method according to any one of the preceding claims, characterized, that the flow rate of the second gas phase is set larger is called the flow rate of the plasma-activated first gas phase. 11. The method according to any one of the preceding claims, characterized, that a second gas phase is supplied, the hydrocarbon and / or an organosilicon compound and / or an organometallic compound dung and / or an organic boron, phosphorus or selenium compound ent holds. 12. The method according to claim 12, characterized, that the second gas phase is a tin and / or titanium and / or aluminum and / or organic zinc compound. 13. Device for performing the method according to one of claims 1 to 12, characterized in that a hollow body ( 10 , 15 ) for supplying a first gas phase ( 1 ), electrodes ( 40 , 42 , 19 ), one for generating an electrical Field suitable generator ( 50 ) and one or more means ( 20 , 21 ) for supplying a two-th gas phase ( 2 ) are provided. 14. The apparatus according to claim 13, characterized in that the one or more electrodes ( 19 , 40 , 42 ) are arranged inside or outside the hollow body ( 10 , 15 ) and / or are part of the hollow body. 15. The apparatus according to claim 14, characterized in that one of the electrodes is an electrically conductive wall ( 19 ) of the hollow body. 16. The device according to one of claims 13 to 15, characterized in that the hollow body ( 15 ) is tubular and is tapered ver at the front end ( 16 ) and has an angular, round, elliptical or unevenly shaped cross section. 17. Device according to one of claims 13 to 16, characterized in that at least one of the electrodes has a dielectric ( 44 ) as insulation ge compared to the plasma. 18. Device according to one of claims 13 to 17, characterized in that one or more mixture-promoting means ( 20 , 21 ) are provided as means for directing the second gas phase, which are arranged in particular laterally of the hollow body ( 10 , 15 ). 19. Device according to one of claims 13 to 18, characterized, that means are provided for arranging one to be coated Substrate at a predetermined distance from the hollow body exit of the Plasma jets, in particular 0.1 to 100 cm.   20. The apparatus according to claim 19, characterized, that the distance is 0.5 to 10 cm. 21. Layer system produced by a method according to one of the first existing claims 1 to 12 and / or by means of a device according to a of claims 13 to 20, characterized, that the layer system deposited on a substrate silicon and / or Carbon and / or hydrogen and / or oxygen and / or nitrogen and / or phosphorus and / or boron and / or selenium and / or tin and / or Has aluminum and / or titanium and / or zinc. 22. Substrate coated with a layer system according to claim 21 and / or by means of a method according to one of claims 1 to 12 and / or in egg ner device according to one of claims 13 to 20, characterized, that the layer thickness of the deposited layer system at 0.001 to Is 10 µm. 23. The substrate according to claim 22, characterized, that the layer system as an adhesion-promoting layer or as a corrosion protective layer or used to modify the surface energy. 24. The substrate according to claim 23, characterized, that the layer system as mechanical or electrical or optical Functional layer is used.