EP2438023A1

EP2438023A1 - Method and facility for depositing layers on a substrate

Info

Publication number: EP2438023A1
Application number: EP10724766A
Authority: EP
Inventors: Eric Tixhon; Gerard Henrion; Thierry Belmonte; Rodrigo Perito CARDOSO
Original assignee: AGC Glass Europe SA
Current assignee: AGC Glass Europe SA
Priority date: 2009-06-05
Filing date: 2010-06-04
Publication date: 2012-04-11
Also published as: EA201190342A1; WO2010139783A1; EP2263983A1

Abstract

The invention relates to a method and facility for depositing various types of high-quality layers on a substrate, combining the use of a gaseous phase containing one or more precursors with the use of the afterglow from microwave plasma in a pressure range close to atmospheric pressure. The substrate is made from inorganic glass or any other material, as long as the coated substrate is used for applications that use an inorganic glass substrate. The invention enables layers to be deposited regardless of the conditions imposed by different manufacturing methods, in particular for substrates with different dimensions, of different types, with different thicknesses and temperatures, for different types of layers, etc. In particular, layers of SiO₂ have been deposited on glass substrates using precursors which would not have been suitable for use by conventional CVD in the considered temperature range.

Description

Method and apparatus for depositing layers on a substrate

FIELD OF THE INVENTION

The invention relates to a method for depositing layers on an inorganic glass substrate in order to modify its properties and to a method for depositing layers on any type of non-glass substrate, provided that said coated substrate is used for applications using inorganic glass substrates, such as display applications and photovoltaic cells.

The invention also relates to an installation for applying the processes in question, in particular continuously.

STATE OF THE ART

Various methods are used to deposit thin film coatings on various substrates. They differ in particular by the way in which the energy is generated for the production and / or the binding to the support of the desired compounds.

Thin film coatings are used in a variety of applications, such as electronics, anti-corrosion and tribological coatings such as refractory layers (nitrides, carbides and titanium or aluminum oxides), coatings with optical properties (antireflective, sunscreens, filters, ..), coatings providing other particular surface properties (antimicrobial, self-cleaning, hydrophilic, hydrophobic, ...), conductive tin oxide layers for various applications (photovoltaic , LED, OLED, organic photovoltaic ...). The substrates concerned can be of various types: glass, steel, ceramic, organic polymers, thermoplastics, etc.

There are four main thin film deposition techniques applicable in particular in the glass field: sol-gel, magnetron, pyrolytic spray, and CVD (Chemical Vapor Deposition).

CVD consists in sending, on a hot substrate, chemical reagents or precursors, previously vaporized and which decompose by pyrolysis in contact with the hot substrate.

This process is commonly applied "on-line" during the production of float glass. In this mode of production, the reaction of the gaseous precursors takes place in the chamber for forming the glass sheet or immediately at the outlet thereof so as to take advantage of the high temperature of the substrate.

Thin layers (of the order of a few tens or hundreds of nm) are thus obtained, in particular of oxides, of great practical interest. The layers obtained are dense, of high purity and generally very chemically stable as well as mechanically.

However, the range of materials that can be deposited is limited because it is difficult to find volatilizable precursors that will pyrolyze in the appropriate temperature range. In particular to deposit in line, by CVD, on a glass ribbon, it is necessary that the precursors pyrolyze in the temperature range of about 500-750 ⁰ C. In addition, for the practice of the CVD technique under satisfactory conditions , the reaction of the precursors with the substrate must be carried out with sufficient kinetics under the conditions that are those used in the production of "float" glass to obtain coatings having a thickness and functional qualities to answer the intended application. The contact time between the substrate and the precursors is indeed limited because of the speed of movement of the glass in the installation. The confined areas in which the operation is conducted, cause the layer to develop in seconds at most. Moreover, the reaction temperature is essentially fixed by the zone of the installation in which the reaction can be carried out. This temperature usually does not exceed 750 ⁰ C. Regardless of the nature of the precursor used and its sensitivity to the reaction temperature, it is also desirable to facilitate the reaction of precursors to improve the utilization efficiency thereof and reduce the amount of effluent to be treated. A possibility to overcome the temperature of the substrate and thus expand the range of precursors usable in CVD and, consequently, the range of depositable materials, is to combine the conventional CVD (possibly at lower temperature) with a device plasma. The literature reports the use of different techniques in which the pyrolysis reactions are accompanied by the use of a plasma.

The modes of development of plasmas and application for the deposition of thin layers are of a great variety. The best studied modes develop in rarefied atmospheres.

Document US 2004/198071, US 6,293,222, US 5,062,508 and FR 2,636,079 are particularly known. These documents all describe processes operating under vacuum or at very low pressure. In US 2004/198071, the layer deposition is carried out in an enclosure whose pressure is reduced to 27 Pa. In US Pat. No. 5,062,508, the gas pressure in the deposition chamber can vary between 1 mbar and 0.1 bar, in particular a pressure of 3mbar is used. US 6,293,222 refers to an earlier document by the same inventor, Fr 2,636,079, where the deposition is at pressures ranging from 0.1 to 20mbar.

These techniques, which can lead to high quality deposits, are difficult to exploit for the production of layers on large substrates.

The implementation of techniques requiring the vacuum of large enclosures on the one hand, and the need to continuously circulate the substrate in these enclosures on the other hand, raise practical difficulties difficult to surmount economically .

To solve these difficulties, the inventors sought to combine the potentialities of conventional CVD treatment processes with the potentialities of an atmospheric pressure plasma (APPECVD) method. Thus, they propose to perform the deposition of layer on substrate of large surfaces, for example glassware type "float", including continuous directly on the production line by a CVD technique favored by the use of the post-discharge a microwave plasma at atmospheric pressure. So it is not a question here of working directly in the plasma as it is the case in a DBD (dielectric barrier discharge) but working in post-discharge plasma, in a place where there is more neither ions nor electrons. We therefore speak here of Remote PECVD and the method used at atmospheric pressure is therefore of the type "APRPECVD" (Atmosperic Pressure Remote Plasma Enhanced CVD).

It is therefore a question of making the highly reactive species created in and coming from the plasma interact with the precursor (s). These species thus contribute to the dissociation of the precursor and therefore to the reactivity of the gaseous mixture. SUMMARY OF THE INVENTION

A first object of the invention is to produce layer deposits of high quality and varied nature on an inorganic glass substrate by combining the use of a gas phase containing one or more precursors with the use of the post-discharge a microwave plasma in a pressure range close to atmospheric pressure. The substrate may also be non-glass as long as the coated substrate is used in applications using inorganic glass substrates.

Another object of the invention is that the production of layer deposits is possible whatever the conditions imposed by different types of manufacture, and in particular for substrates of different dimensions, of different types, thicknesses and temperatures, for natures of different layers, etc.

The object of the invention is a method for depositing a layer on an inorganic glass substrate which comprises the following operations:

- introducing or scrolling a substrate in a reaction chamber maintained at a pressure between 0.5 and 1.1 bar, wherein are injected at least two gas streams, one of the gas stream comprising at least one precursor of the material to be deposited and another of these gas flows being a postdischarge of a microwave plasma obtained by passing a plasmagene gas mixture into one or more resonant cavities fed by at least one microwave generator, the gaseous assembly is directed towards the substrate to be coated, adapting the flows and compositions of the gas flows and / or the power of the at least one microwave generator at the beginning or during the process, so as to obtain optimum reaction characteristics; maintain the substrate in the chamber for a period of time sufficient to obtain a layer of desired thickness. In particular, the pressure of the reaction chamber is between 0.8 and 1 bar.

The plasmagene gas mixture feeding the post-discharge preferably comprises a reactive gas such as oxygen, hydrogen, nitrogen or a mixture thereof and a carrier gas, such as argon, helium or nitrogen or their mixture. In particular, it has been discovered that it is important to optimize the plasma gas mixture so as, on the one hand, to have a homogeneous and non-filamentary plasma and, on the other hand, a maximum quantity of radical species originating from the reactive gas, such as radical oxygen, in the post-discharge. The volume percentage of reactive gas in the plasma gas is thus advantageously between 4-50% by volume, preferably 5-20% by volume and even more preferably between 8-15% by volume.

The plasmagenic gas mixture circulates with a flow rate advantageously between 5 and 100 Nm ³ / h and per meter of treated substrate, preferably between 10 and 50 Nm ³ / h and per meter of treated substrate and, in particular, between 20 and 40 Nm ³ / h and per meter of treated substrate. The precursors of the material to be deposited contained in the gas stream are very advantageously those conventionally used in the technical field of CVD layer deposition, known to those skilled in the art. Typically, an organometallic compound, such as hexamethyldisiloxane (HMDSO) or tetraethylorthosilicate (Teos), is used as the silica layer precursor. The invention makes it possible in particular to use among the precursors those which could not have been by conventional CVD in the temperature range studied. The gas comprising at least one precursor of the material to be deposited also comprises a carrier gas that may be identical to that of the plasma gas mixture. The volume percentage of this precursor gas is chosen in particular as a function of the desired layer thickness, the flow rate of the material to be treated and the yield. Those skilled in the art by routine tests determine these conditions.

This gas is preferably circulated with a flow rate of between 5 and 100 Nm ³ / h and per meter of treated substrate, more preferably between 8 and 50 Nm ³ / h and per meter of treated substrate and, in particular, between 10 and 20 Nm ³ / h and per meter of treated substrate.

The substrate is maintained in the chamber for a period of time advantageously between 0.5 and 10 s, preferably between 1 and 6 s and very preferably between 2 and 4 s.

The process of the invention allows the deposition of layers of different compositions, in particular silica.

Other features of the present invention are described in the subclaims.

The present invention also relates to a process for the deposition of at least one layer on any type of non-glass substrate which comprises the following operations: - introducing or scrolling a substrate in a reaction chamber in which are injected at least two gaseous flow; a gaseous flow comprising at least one precursor of the material to be deposited; another of these gas flows being a post-discharge of a microwave plasma obtained by passing a gas mixture into one or more resonant cavities fed by at least one microwave generator; the two gas flows are directed towards the substrate to be coated; adapting the flow rates and compositions of the gas flows and / or the power of the at least one microwave generator at the beginning or in process course so as to obtain optimal reaction characteristics;

maintain the substrate in the chamber for a period of time sufficient to obtain a layer of desired thickness

said coated non-glass substrate being used for applications using inorganic glass substrates, such as display applications and photovoltaic cells. At the outlet of the gas flow distribution device, the more the (the) gaseous web (s) is (are) homogeneous (s), the more the layer will be of good quality.

It will be noted that the methods of the invention are defined in terms of "operations" rather than "steps", that is to say that the sequence of operations does not necessarily take place in the order in which they are stated. above.

The compositions of the different gaseous mixtures, the time periods for maintaining the substrate in the reaction chamber, the volume percentages and other parameters are similar or identical in the two processes of the invention.

Particularly preferably, a discharge tube, for example quartz, is inserted into the resonant cavity. The discharge tube is supplied with gas via an injection head.

The at least two gas flows are injected into the reaction chamber by an injection system comprising two independent lines, each of the lines per flow considered. An example is shown in FIG. 1.

A first advantage of the methods of the invention is that the number of resonant cavities and the number of generators is not limited. Therefore, it is possible to create a gaseous layer in post-discharge very large dimension which allows the treatment of very large substrate.

A second advantage of the methods of the invention is that it is possible to generate post-discharges in a range of pressures close to atmospheric pressure with powers less than 100 kW per meter of substrate width, preferably less than 50. kW per meter and more preferably less than 20 kW per meter.

Typically, the microwave power absorbed in each discharge tube varies between 500 W and 10 kW, preferably between

600 W and 1200 W.

A third advantage of the processes according to the invention is that the active species generated in post-discharge by virtue of the energy provided by the plasma, by interacting with the precursors, even on a cold substrate, make it possible to deposit layers of high quality and this with high deposit rates.

A fourth advantage of the methods of the invention is that the energy provided by the plasma can be finely modulated, which makes it possible to deposit layers of a wide variety of compositions.

Another advantage of the methods is that they are applicable to both a conductive substrate and an insulating substrate. According to an advantageous embodiment, the methods furthermore comprise the following operation: bringing the atmosphere prevailing in the reaction chamber to a determined pressure.

In a preferred embodiment, the chamber is open and includes an entrance zone and an exit zone for the substrate, which allows the methods of the invention to integrate into a continuous surface treatment operation. Another object of the invention is a depositing facility of a layer on an inorganic glass substrate comprising a chamber, transport means and support means for introducing a substrate into the chamber. At least one microwave generator feeds one or more resonant cavities through which (of) a gas stream flows. This gas stream constituting the postdischarge. One or more other gas streams carrying at least one precursor of the material to be deposited is (are) also injected into the chamber but without passing through the resonant cavities. The gaseous assembly (post-discharge + precursors), in the form of one or more homogeneous sheets (s) is directed to the substrate to be coated. Means for regulating the different gas flows and for controlling the power of the generator are provided, as are means for extracting residual gases.

According to an advantageous embodiment, the chamber is open at both ends, which allows to integrate the deposit facility in a continuous production line. In this context, the chamber can advantageously be integrated into a float glass production line, the support means of the substrate comprising a tin bath.

According to an advantageous embodiment, the installation is integrated into a production line which comprises a annealing gallery, the chamber being placed in this annealing gallery, the support means of the substrate comprising at least one roller.

Another object of the invention is a layer deposition installation on a non-glass substrate provided that said coated non-glass substrate is used for applications using inorganic glass substrates, such as display applications and cells. photovoltaic. BRIEF DESCRIPTION OF THE FIGURES

Other advantages and particularities of the invention will emerge from the following detailed description of particular embodiments of the invention, reference being made to the figures, in which: FIG. 1 is a diagrammatic elevational view of FIG. a layer deposition installation on a glass substrate; FIG. 2 is a schematic sectional view of the portion of the deposition installation in which a glass ribbon circulates. The gas flow supply devices and the ribbon support are also shown schematically.

EXEMPLARY EMBODIMENT

Deposition of layers on soda-lime glass substrate was carried out with the device described in FIGS. 1 and 2. The device illustrated in FIG. 1 comprises a wave generator 1, connected to a distributor 2, itself connected to a plurality of rectangular waveguides 3. Each waveguide 3 comprises a resonant cavity 4 through which a quartz discharge tube 6 is inserted. The tube 6 is supplied with gas via an injection head 5.

The resonant cavities 4 operate at a frequency of 2.45 GHz and at atmospheric pressure. In the example illustrated in FIG. 2, the tube 6 has an inside diameter of 27 mm. Each discharge tube 6 feeds a common nozzle 8 whose end, directed towards the substrate to be coated 13 is open in the form of a slot 9 for the formation of a homogeneous gas layer.

A standing wave is generated by the microwave generator 1 to obtain an electric field of maximum intensity in the discharge tube 6. The microwave power absorbed by resonant cavity varies from 600 to 1000 W according to the incident power supplied and according to the composition of the discharge gases.

A fan (not shown) is used to center the plasma in the discharge tube 6 and to avoid contact with the walls of the tube.

The flow rates of the gases are controlled by mass flow meters. The gas injection system consists of two independent lines; the first line 10 (illustrated in Fig. 1) is used to bring the plasmagenic mixture into a microwave discharge. In the present embodiment, the plasmagenic mixture is composed of oxygen and argon, oxygen constituting the reactive gas. The purity of the gases used is more than 99.995 vol%.

The total flow rate of the gases injected into each discharge tube is typically regulated between 10 and 100 liter / min. The volume percentage of oxygen in the gaseous mixture is, in the particular example, 10 vol%. Under these conditions, the plasma operates in glow mode.

The nozzle 8 of the tube 6 ends with a rectangular slot 9 of 2 mm high, to create a homogeneous gas sheet comprising the active species that will come into contact with the glass surface at a controlled angle, which can vary from 1 at 90 °.

In practice, and without limitation necessarily related to the example, to obtain a layer over the entire width of a moving substrate, (in particular a float glass ribbon more than 3 meters wide), it is necessary to have a series of injection heads 5 (and therefore resonant cavities 4) next to each other to cover the desired width. In practice, following the parameters described in this example, it is necessary to provide approximately one injection head per 10 cm of substrate to be treated.

The second line is used for the injection of the precursors into the post-discharge plasma. This second line comprises a device 11 for supplying gas illustrated in FIG. 2.

In the ^2nd gas injection line is introduced silica precursor (hexamethyldisiloxane (HMDSO), tetraethylorthosilicate (TEOS), ...). In the case of HMDSO, the purity of the product is about 98%. The amount of vaporized precursors is controlled by a liquid mass flow meter. The precursor is evaporated in argon whose flow rate is fixed as a function of the width of the substrate to be coated and therefore as a function of the number of injection heads 5 (According to the parameters given in this example, the flow of argon will be 20 liters / min multiplied by the number of injection heads 5). In this way, the precursor HMDSO is injected onto the surface of the substrate by the feed device 11.

The Argon / HMDSO mixture is maintained at a temperature of 70 ^° C. until it is injected into the post-discharge leaving the nozzle 8. The mixing between the gas flows (post-discharge + organometallic precursors) is carried out over the substrate 13 in a confined space formed by the substrate 13 and a vault 12 placed a few millimeters from the substrate. This confined space forms a reaction chamber 14. This space can optionally be closed on the sides.

The glass substrate placed in the reaction chamber is heated to a temperature of 400 ^° C. SiO 2 layers having a thickness of between 100 nm and 5 μm have been deposited. These layers are carbon free.

Claims

A method for depositing at least one layer on an inorganic glass substrate (13) which comprises the steps of: introducing or scrolling a substrate (13) into a reaction chamber (14), maintained at a pressure between 0.5 and 1.1 bar, in which at least two gaseous streams are injected, one of the gaseous flows comprising at least one precursor of the material to be deposited and another of these gaseous flows being a post-discharge of a microwave plasma obtained by passage a plasma gas mixture in one or more resonant cavities (4) fed by at least one microwave generator (1); the two gas flows are directed towards the substrate (13) to be coated;

adapting the flow rates and compositions of the gas flows and / or the power of the at least one microwave generator (1) at the beginning or during the process, so as to obtain optimum reaction characteristics;

- Keep the substrate (13) in the chamber (14) for a period of time sufficient to obtain a desired thickness layer.

2. Method according to the preceding claim, characterized in that the resonant cavities (4) operate at a frequency between 400 MHz and 10 GHz, preferably between 2.40 and 2.50 GHz.

3. Process according to any one of the preceding claims, characterized in that the plasmagene gas mixture feeding the post-discharge comprises a reactive gas and a carrier gas, the volume percentage of reactive gas in the plasma gas being between 4-30 % volume, of preferably 5-20% volume and even more preferentially

6-14% volume.

4. Method according to any one of the preceding claims, characterized in that the resonant cavity comprises a discharge tube (6) and the microwave power absorbed in each discharge tube (6) varies between 500 W and 10 kW, preferably between 600 W and 1200 W.

5. Process according to any one of the preceding claims, characterized in that the volume percentage of reactive gas in the plasma gas is between 4-50% volume, preferably 5-20% by volume and even more preferably 8- 15% volume.

6. Process according to any one of the preceding claims, characterized in that the temperature of the substrate in the reaction chamber is between 20 ° and 1000 ^° C., preferably between 100 ° and 750 ^° C., and more preferably between 300 ° and 600 ^° C.

7. Installation for depositing at least one layer on an inorganic glass substrate (13) comprising

at least one reaction chamber (14), transport means and support means (15) for introducing a substrate (13) into the chamber (14);

- At least one microwave generator (1) supplying one or more resonant cavities (4) through which or a gas flow is able to circulate; this gaseous flow constituting the post-discharge; one or more other gas streams carrying at least one precursor of the material to be deposited is (are) also injected into the chamber (14) but without passing through the resonant cavities (4); all the gas flows is directed towards the substrate (13) to be coated.

8. Depositing installation according to the preceding claim, characterized in that each resonant cavity comprises a discharge tube (6).

9. Installation according to the preceding claim, characterized in that all of the discharge tubes (6) feed a device (8) having an outlet slot (9) for obtaining a homogeneous gas layer.

10. Installation according to the preceding claim, characterized in that the slot (9) has a rectangular opening of 1 to 10 mm high, in particular 2 to 6 mm.

11. Installation according to any one of claims 9 and 10, characterized in that the gas layer exiting the device (8) has an inclination angle with respect to the substrate to be coated between 1 ° and 90 °, preferably included between 20 and 80 ° and more preferably between 40 and 70 °.

12. Installation for depositing at least one layer on a non-glass substrate (13) comprising

at least one reaction chamber (14), transport means and support means (15) for introducing a substrate (13) into the chamber (14); - At least one microwave generator (1) supplying one or more resonant cavities (4) through which or a gas flow is able to circulate; this gaseous flow constituting the post-discharge; one or more other gas streams carrying at least one precursor of the material to deposit is (are) also injected into the chamber (14) but without passing through the resonant cavities (4); all the gas flows is directed towards the substrate (13) to be coated; said coated non-glass substrate (13) being used for applications using inorganic glass substrates.

13. Method according to any one of claims 1 to 6, for the deposition of a layer of SiO 2 on a float glass ribbon, characterized in that the flow of precursor gas comprises a compound of organometallic type, in particular chosen from hexamethyldisiloxane (HMDSO), tetraethylorthosilicate (Teos).

14. Process according to the preceding claim, characterized in that the flow of precursor gases comprises an HMDSO / argon mixture which is introduced into the deposition chamber at a temperature of between 30 and 100 ^° C., preferably between 50 and 80 ^° C. .

15. Process according to any one of claims 13 and

14, characterized in that the precursor gas partial pressure in the precursor gas flow is adjusted to obtain SiO 2 deposition rates of between 10 and 2000 nm * m / min. and preferably between 500 and 1000 nm * m / min

16. A method for depositing at least one layer on a non-glass substrate (13) which comprises the following operations: - introducing or scrolling a substrate (13) into a reaction chamber (14) in which at least two gas flows; a gaseous flow comprising at least one precursor of the material to be deposited; another of these gas flows being a post-discharge of a microwave plasma obtained by passing a gas mixture into one or more resonant cavities (4) fed by at least one microwave generator (1); the two gas flows are directed towards the substrate (13) to be coated; adapting the flow rates and compositions of the gas flows and / or the power of the at least one microwave generator (1) at the beginning or during the process, so as to obtain optimum reaction characteristics;

maintaining the substrate in the chamber (14) for a period of time sufficient to obtain a layer of desired thickness; said coated non-glass substrate (13) being used for applications using inorganic glass substrates.