EP4162090A1

EP4162090A1 - Apparatus for the vapour deposition of a substance on a substrate

Info

Publication number: EP4162090A1
Application number: EP20724072.2A
Authority: EP
Inventors: Frank Mumme
Original assignee: Gemeinnuetzige Kimw Forschungs GmbH
Current assignee: Gemeinnuetzige Kimw Forschungs GmbH
Priority date: 2020-05-05
Filing date: 2020-05-05
Publication date: 2023-04-12
Also published as: WO2021223844A1

Abstract

The invention relates to an apparatus (1) for the vapour deposition of a substance on a substrate, comprising: a reactor (2) with at least one evaporator (15) for the evaporation of pulverulent precursor substance particles, a vacuum pump connection for connecting a vacuum pump, and a substrate carrier (4); a carrier-gas line (14) that is connected to the evaporator (15) and is fed by a carrier-gas supply; and a dosing device (5) for feeding pulverulent precursor substance particles into the carrier-gas line (14), which dosing device (5) comprises a supply container (6) that has an outlet (8) and is intended for supplying the pulverulent precursor substance intended to be fed to the reactor (2), and a screw conveyor (12) that is located below the outlet (8) in a conveying channel (11) and has a conveying direction transverse to the outlet direction of the supply container (6) in order to convey the pulverulent substance from the outlet (8) of the supply container (6) to an opening (20) into the carrier-gas line (14). At least part of the surfaces of the parts (6), (23); (11), (12) that are moved so as to rub against one another in the dosing device (5) in order to convey the pulverulent precursor substance is produced from a material which has a higher sublimation point in relation to the pulverulent precursor substance. A preparation stage (32) for removing at least a proportion of the solid particles contained in the carrier-gas stream carrying the sublimated substance is arranged downstream of the evaporator (15) in the direction of flow of the carrier gas. The invention further relates to a method for providing an evaporated substance as a precursor for a vapour deposition process.

Description

Device for vapor deposition of a substance on a substrate

The invention relates to a device for the vapor deposition of a substance on a substrate

- A reactor with at least one vaporizer for vaporizing powdery precursor particles, from which vaporizing products the layer is deposited on the substrate, with a vacuum pump connection for connecting a vacuum pump for generating the negative pressure required for the deposition in the reactor and with a substrate carrier ,

- A carrier gas line fed by a carrier gas supply and closed to the evaporator

- A metering device for supplying powdery precursor material particles into the carrier gas line, which metering device has a storage container with an outlet for storing the powdered precursor material to be supplied to the reactor and a screw conveyor arranged below the outlet in a conveying channel with a conveying direction transverse to the discharge direction of the storage container for conveying of the powdery substance from the outlet of the supply container to an opening in the carrier gas line, in which the powdered substance is taken up as suspended load by the carrier gas stream flowing therein and fed to the evaporator.

The invention also relates to a method for providing a vaporized substance as a preliminary stage of a vapor deposition process, in which Ver drive a powdery precursor material to provide the substance to be separated in gaseous form by means of a carrier gas flow to an evaporator and is sublimed on this

Devices for vapor deposition of substances are used, for example, to create thin metallic layers. The substance brought into the vapor phase by sublimation from a precursor substance corresponds to the metal to be deposited. So far, the deposition of metallic layers by means of vapor deposition (chemical or physical vapor deposition) a precursor is used in liquid form. This takes place against the background that the metering of the metal into the reactor has to take place in very small amounts and liquid metering of very small or very small amounts is much easier to implement and control than a solid metering. A disadvantage of a system with liquid metering is that about 90% of the liquid introduced into the reactor and evaporated therein is solvent and only 10% represent the actual precursor. With a liquid metering of the precursor used in a metal deposition, the outlay in terms of equipment in or on the reactor is therefore considerable, since an elaborate cooling trap technology must be provided on the outlet side of the reactor in order to recover the solvent. In addition, the reactor tends to become oily when metered in liquid. Nor can it be ruled out that solvent particles are included in the layer applied to the substrate, which impairs the quality of the deposited layer and is therefore undesirable.

Against this background, a solid metering of a precursor for depositing metallic layers on a substrate by vapor deposition would be preferable to a liquid metering. Until recently, however, the dosage of the smallest amounts required was problematic for various reasons. Care must be taken to ensure that the vaporization of the solid particles fed in should take place almost spontaneously and therefore the powdery substance as a precursor may only have a very small grain size. In the case of a powdery substance, the particles of which have a grain size between about 30 and 300 μm, the problem with conveying the solid is that the powdery substance is compacted in the storage container and in the screw conveyor, similar to caking, and the precursor supply from this Basically blocked or at least impaired.

DE 202018 107303 U1 describes a metering device which allows the metering of very small amounts of solids. If high-purity layers are to be produced on a substrate by vapor deposition, it must be ensured that the Substance is not or will not be contaminated by accompanying substances. Even if the metering device described in DE 202018107303 U1 is suitable for metering solids even in the smallest quantities, the risk of possible contamination of the powdery precursor substance introduced into the reactor must be taken into account, as is the case with any metering of solids. The precursor substance can be contaminated when dosing solids, for example, by abrasion of material on the surface on which the powdery precursor substance is transported and / or by abrasion of parts that are used to convey the precursor in the metering device, typically rubbing against each other, such as, for example a helix in a storage container or a screw conveyor in a conveying channel. Both conveying means are typically moved with their outer circumferential surface in a sliding manner with respect to the inner surface of the storage container or of the conveying channel. This contamination problem, which has to be taken into account when dosing solids, does not occur with liquid dosing.

Based on the prior art discussed above, the invention is therefore based on the object of proposing a device for vapor deposition of a substance on a substrate with which not only a substance deposition on the substrate with high purity is possible, but also with the Disadvantages shown above in connection with a liquid dispensing are avoided. At the same time, the invention is based on the object of proposing a corresponding method.

This object is achieved according to the invention by a device of the generic type mentioned at the outset, in which at least some of the upper surfaces of the parts moved against each other by friction in the dosing device for conveying the powdered precursor material are made of a material that is related to the powdered precursor material has a higher sublimation temperature, and that the evaporator in the direction of flow of the carrier gas is followed by a processing stage for removing at least a portion of the solid particles contained in the carrier gas flow entrained with the sublimated substance. This object is also achieved by a method having the features of claim 21.

With this device - the same also applies to the claimed method - the precursor substance is metered in spite of the associated

Contamination problems by means of a solids metering device. The precursor substance is fed to the evaporator in the form of powdery precursor substance particles. The grain size of the substance particles is typically 30 to 300 μm. In this device, at least parts of the abrasion-generating surfaces of the metering device are made of a material that has a higher sublimation temperature than that of the precursor material at the temperature and pressure conditions (negative pressure) given on the evaporator in relation to the pulverulent precursor material to be fed into the reactor. In this respect, the vaporizer is part of a carrier gas purification stage in which entrained solid-state contaminations are removed from the carrier gas stream that carries the sublimed substance with it after the vaporizer. The vaporizer serves as the first stage of the carrier gas purification stage for processing the particles carried in the carrier gas stream - precursor material and contamination - by bringing the precursor material into its gas phase while the contaminants remain as solids in the carrier gas stream. The further processing of the carrier gas flow takes place in a processing stage downstream of the evaporator in the flow direction of the carrier gas flow, in which the contaminations carried along with it are removed as far as possible.

With this device and the claimed method, due to the provision of the carrier gas purification stage with its processing stage downstream of the evaporator, abrasion caused by parts of the metering device moving frictionally against one another can be accepted, contrary to the prevailing teaching. The different sublimation temperature between the precursor material - on the one hand - and the superficial material abrasion of the metering device - on the other hand - is skillfully used in order to be able to separate abrasion-related contamination from the substance to be separated. Even if it is only necessary for the removal of surface abrasion from the metering device from the carrier gas flow that the relevant surfaces of the Metering device have this material, the individual components of the metering device, insofar as they are in contact with the precursor, can be made entirely or the entire metering device from such a material.

The processing stage removes not only abrasion from the metering device as contamination from the carrier gas stream that carries the sublimed precursor substance, but also non-sublimated components of the precursor substance itself. If high-purity layers are to be deposited in the reactor, a high-purity precursor substance is conventionally used . With the described device and the claimed method, there is now the possibility of using less expensive precursor material with solids metering, provided that the impurities contained therein have a higher sublimation temperature under the given pressure conditions on the evaporator.

According to one embodiment, the processing stage has a filter unit through which the carrier gas stream carrying the sublimed substance is passed before the sublimed substance is fed to the substrate on which it is to be deposited. Such a filter unit is typically designed in several stages and has several filter stages connected in series in the flow direction of the carrier gas with descending passage size (porosity). The filter stages of such a filter unit can be provided by beds of spherical material, whereby a spherical material bed with different spherical diameters and thus with different pore volumes is provided through which the carrier gas flow flows. A close-meshed filter, for example a metal filter, can also be part of such a filter unit, sizes of 5 μm and less being meant as close-meshed. According to one exemplary embodiment, it is provided that two or more spherical beds with spheres of different diameters, each forming their own spherical material bed, represent first filter stages, the last filter stage being provided by spherical material with a diameter of approximately 0.5 mm and one or more filters downstream of this, typically metal filters with a decreasing passage size (porosity) up to a metal filter with a porosity of about 1 μm are arranged.

In addition to or as an alternative to such a filter unit, the processing stage can also have a magnetic separator. With this las sen magnetizable substances can be removed from the carrier gas flow in a simple manner. This allows the use of surface material of the metering device which can be magnetized. With such a design of the metering device, the magnetizability of this material is used as a contamination coding in order to recognize abrasion-related contamination by the metering device as such and to remove the gas stream from the carrier. In principle, it is possible to also arrange such a magnetic separator upstream of the evaporator if the precursor particles cannot be magnetized. However, the magnetic separator is preferably located downstream of the evaporator in the direction of flow of the carrier gas stream, since then the separation of the magnetizable solid particles is not impaired by precursor particles or they are entrained. According to one exemplary embodiment, a permanent magnet bed is used as the magnetic separator, provided by a bed of permanent magnets through which the carrier gas flow is passed. The geometry of the Dauermagnetkör is designed so that sufficient porosity remains through which the carrier gas stream can flow.

The parts of the dosing device that are moved relative to one another can, or even the entire dosing device, at least as far as its parts come into contact with the precursor material, can for example be made of a stainless, magnetizable steel. In the device described, this is possible due to the processing stage with a magnetic separator, although Fe contamination must be avoided when vapor deposition of high-purity layers, such as those required for the production of semiconductors, for example. The surface of the parts of the metering device that are moved frictionally against one another or also the entire inner surface of the metering device can be made of a ceramic material exist, either because the relevant parts are made of ceramic or a substrate has such a coating.

A reduction in contamination in the precursor material transported in the carrier gas flow can also be achieved by reducing abrasion in the metering device - above all on the surfaces that are rubbing against one another. This is possible, for example, by coating these surfaces of the metering device with a wear protection layer, a so-called hard layer. Various coatings can be used for this purpose, for example coatings using tungsten, molybdenum, chromium or titanium, each as a carbide coating, nitride coating, oxide coating or in metallic form. If such a coating is used, the metering device can certainly also be made of a material that would otherwise not be used to avoid contamination, such as copper or the like.

When selecting the material for the above-described coating, as well as when selecting the material for the parts of the metering device in question, provision can be made to select a material which contains the substance intended for deposition in the reactor. If, for example, molybdenum is to be deposited on the substrate in the reactor, at least the abrasion-prone surface areas or the entire inner surface of the metering device that comes into contact with the precursor material could be equipped with a molybdenum oxide, molybdenum nitride or molybdenum carbide coating. It is also possible to manufacture at least the parts of the metering device that come into contact with the precursor material from a material which contains the element to be deposited, so that a hard material coating may then not be required. For example, if molybdenum is to be deposited in the reactor, these parts could be made of a nickel-based alloy. The abrasion of such a material is magnetizable and can therefore be removed from the carrier gas flow in the processing stage. Any abrasion slip would then not represent any contamination on the layer to be deposited. Should abrasion from such a surface not completely through the reconditioning stage from the the carrier gas stream carrying the sublimed precursor substance is removed, these particles would in any case not represent any harmful contamination. Such a processing stage downstream of the evaporator must be cleaned from time to time. In order to still allow a continuous separation process, one embodiment of the device according to the invention provides that several evaporators, arranged in parallel in terms of circuitry, as well as a downstream processing stage are assigned to the reactor. In the carrier gas line that feeds the powdery precursor material to the reactor, a multi-way valve is switched on with such a design of the device, through which the carrier gas stream can be fed to one or the other evaporator. This can be a revolver valve, for example. The carrier gas flow is then typically applied to one of the plurality of evaporators, so that the then at least one evaporator and processing stage that is not in use can be cleaned. In an alternative embodiment, the device has a single evaporator, but several processing stages connected in parallel. With such a design of the device, a multi-way valve is connected between the evaporator and the several processing stages, as is described for the embodiment described above.

Particularly advantageous is a design of the metering device such that a ventilation line is connected at its first end to the carrier gas line in the direction of flow of the carrier gas before the entry of the powdery substance particles conveyed through the mouth of the conveying channel passes, and the other end to the inside of the front advice container standing in fluid connection, is connected to this and in which a switching valve is switched on in the section of the carrier gas line between the mouth of the ventilation line and the entrance of the powdery substance particles conveyed through the mouth of the conveying channel.

In a metering device designed in this way, it is provided that the interior of the storage container is also exposed to carrier gas. For this purpose, a ventilation line serves as a branch from the Carrier gas line opens into the interior of the storage container. The ventilation line preferably opens into the interior of the storage container in the area of its end opposite the outlet. A standing body is suitable as a Vorratsbehäl ter. This is typically designed to be cylindrical, has at least one cylindrical inner jacket surface. This metering device has a switching valve which is switched on in the carrier gas line in the direction of flow of the carrier gas upstream of the opening of the powdery substance feed. By means of the switching valve, the carrier gas stream flowing past the mouth of the conveying channel can be passed through or blocked as an inflow into a reactor, typically a CVD reactor. To supply the powdery substance as a precursor of an evaporation device, for example arranged inside a CVD reactor, the switching valve is in its let-through position. This metering device, when used as part of a device, makes use of the fact that the carrier gas line opens into the CVD reactor and that, when the device is in operation, a negative pressure (vacuum), typically between 1 mbar and 50 mbar, prevails in the CVD reactor. With this metering device as part of a device or another system in which the carrier gas flow is connected to a container in which there is negative pressure, the powdery substance in the storage container can be loosened via the ventilation line.

When the powdery substance is fed in, for example as a precursor for feeding it into a CVD reactor, the switching valve is open so that the carrier gas flow passes the mouth of the feed channel and takes the material particles transported out of the mouth by the screw conveyor with it as suspended load. Due to the connection of the carrier gas line to a negative pressure reactor, a corresponding negative pressure is also established in the storage container via the conveyor screw. To loosen the powdery substance in the storage container, the switching valve is closed briefly. If the switching valve is closed, the pressure prevailing in the storage container increases due to the carrier gas supply, which can initially lead to a certain com paction of the powdery substance. If the switching valve is then opened again, the previously im Reservoir prevailing pressure introduced, which leads to a turbulence of the powdery substance located therein. This turbulence caused by the sudden drop in pressure loosens the particle composite of the powdery substance stored in the storage container. The frequency with which such a loosening of the pulverulent substance is brought about will be carried out as a function of the tendency of the pulverulent substance to compaction. This will be done intermittently, about once every minute or once every several minutes. Other frequencies can also be provided for the intermittent pressure increase in the storage container, depending on the substance in the storage container. It is considered sufficient if the switching valve remains closed for only a short time, ie for 0.5 to 3 seconds. In this way, the precursor feed into, for example, a CVD reactor is only interrupted for a short time and is not interrupted, or at least not significantly noticeably, for the deposition process. This concept of uncompacting powdery substance located in the storage container, in particular of small particle size, is particularly effective for the desired loosening of the powdery substance in the storage container. It was surprising to observe that the loosening success described occurs, although the powdery substance contained therein is somewhat compacted as a result of the initially occurring pressure increase in the storage container, thus initially causing exactly the opposite, which is actually to be achieved. The above-described quasi-spontaneous pressure reduction occurs because pressure equalization through the powdery substance stored in the storage container and the conveying channel with the screw conveyor located in it takes place only significantly more slowly for the desired purposes due to the limited gas pathways on this route therefore is negligible. In order to prevent an uncontrolled entry of powdery substance in the storage container into the reactor via the ventilation line when the switching valve is opened, in one embodiment it is provided to separate the supply of powdery substance in the storage container from the ventilation line by means of a filter. This is gas-permeable, but not permeable to the powdery substance. Due to the above-described interrelationship of an initial An increase in pressure in the storage container, followed by a subsequent rapid, quasi-spontaneous decrease in pressure, also ensures that the filter does not clog over time. In order to achieve this, the switching valve that controls this process is opened quickly. For this reason, it is useful to use a magnetic valve as a switching valve. Finally, with each process of increasing the pressure in the storage container, carrier gas first flows into the storage container, thus pushing the substance particles in its pores out of them, so that the quasi-spontaneous pressure reduction required when the switching valve is opened occurs due to the free, clean filter.

Such a dosing device can have at least one cleaning pinion which, in the area of the outlet of the storage container, meshes with the helix of the screw conveyor with its teeth. This pinion is rotatably mounted. The pinion is typically located adjacent to or opposite the outlet. When the screw conveyor rotates, the teeth of the cleaning pinion mesh with the helix of the screw conveyor so that the spaces between the helixes are kept free. Under certain circumstances, compacted powdery material that has collected in the spiral of the screw conveyor, which does not fall out by itself due to its compaction, is brought out by the cleaning pinion. The arrangement of the cleaning pinion in the area of the outlet of the storage container ensures that caking or compaction of the powdery substance does not occur at the beginning of the conveying path within the conveying channel. Preferably, the diameter of the outlet of the storage container or the inlet opening of the conveyor channel for supplying powdery substance to the screw conveyor corresponds to the diameter of the cleaning pinion, but is in any case not significantly larger than the diameter of the cleaning pinion. This ensures that the cleaning pinion cleans the screw conveyor over the entire width of the outlet or the inflow of the powdery substance onto the screw conveyor. The cleaning pinion ensures that at least as far as possible only partially filled spaces between the conveying helix are introduced during a rotational movement of the conveying screw in the area of the outlet of the storage container or the inlet opening of the conveying channel. The outlet of the storage container is typically tapered in the direction of the conveyor screw, typically designed to be conically tapered. To support a loosening of the powdery substance in the storage container, one embodiment of such a metering device provides that one or more mixing tools are arranged within the storage container. In the case of a standing storage container, the axis of rotation of the mixing tool or tools extends in the longitudinal direction of the storage container. Such a mixing tool can, for example, be a mixing helix. Typically this reaches into the outlet. If the outlet is funnel-shaped in the direction of the Förderka channel tapers, the diameter of the conveyor helix is tapered accordingly. The mixing tool (s) are rotationally driven by a drive, typically an electric motor, which is definitely a stepper motor.

The storage container is closed on the top in a sealed manner with a closure body. This closure body can be removed in order to be able to fill the storage container. If one or more mixing tools are provided, when such a closure body is provided, the mixing tool shaft extends through the closure body, for example with a drive section. This passage through the closure body is sealed. The drive for the rotary drive of the mixing tool or tools is located outside the sealing of the closure body.

To support the conveyance of the fine-grained powdery substance by means of the screw conveyor through the conveying channel, a further development provides that the inner wall of the conveying channel has structures and / or is designed accordingly so that powdery substance can adhere to it. This forms a coating that increases wall friction, which promotes the conveying process of the powdery substance through the conveying channel. Thread structures, for example, are suitable as inner wall structures for this purpose. Such a coating that increases wall friction can also be set when the conveying channel opens in the direction of the mouth of the conveying channel has continuously slightly increasing cross-sectional area. This conical enlargement of the conveyor channel with a small angle also causes a layer of material to stick to the inner wall of the conveyor channel.

With a metering device, as described above, delivery rates of 2 g / h and less, even less than 0.1 g / h, can be achieved. It is noteworthy that the metering of the smallest amount is a solid metering.

The invention is described using an exemplary embodiment with reference to the accompanying figures. Show it:

1: A schematic block diagram of a device with a metering device according to the invention,

FIG. 2: an enlarged illustration of a section of the Dosiervor direction of the device of FIG. 1 and FIG. 3: an enlarged illustration of a section of the reactor in the area of its evaporator of the device of FIG. 1.

A device 1 for vapor deposition of a substance on a substrate comprises a reactor 2 which, in the exemplary embodiment shown, is designed as a CVD reactor. Its interior is connected to a vacuum pump. The pressure in the CVD reactor 2 can be reduced sufficiently by means of the vacuum pump in order to be able to carry out a chemical vapor deposition process. The vacuum pump, not shown in the figure, is connected to a pump line 3 opening into the interior of the CVD reactor 2. The CVD reactor 2 can be opened in order to place a substrate to be coated by the CVD process on a carrier 4 and then again to be able to remove. A metering device marked with the reference number 5 is used to supply a precursor for depositing a, for example, metallic layer on a substrate placed on the carrier 4. The metering device 5 ver has a reservoir 6, which is shown in the Embodiment is made cylindrical. The storage container 6 is closed in a sealed manner on the top by a closure body 7. The standing storage container 6 has a conically tapered outlet 8 on the underside. The storage container 6 is mounted on a conveyor block 9, which has a funnel-shaped mouth on its side facing the storage container 6, which continues the tapering of the outlet 8. The configuration of the conveyor block 9 with its individual parts is described in more detail below with reference to the illustration in FIG. The tapered end of the conical outlet-extending taper 10 of the conveyor block 9 opens into a conveyor channel 11 running transversely to the discharge direction from the storage container 6 with a conveyor screw 12 integrated therein. The feed channel 11 opens into a carrier gas line 14. The screw conveyor 12 is used to feed powdery substance stored in the storage container 6 as a precursor for the layer to be deposited into a carrier gas stream flowing through the carrier gas line 14 when the device 1 is operating. The direction of flow of the carrier gas flow is in the direction of the CVD reactor 2. The carrier gas line 14 acts on an evaporator 15. The precursor supplied with the carrier gas flow evaporates at the evaporator 15. The metal released by the evaporation process in a metallic coating then separates the surface of the substrate located on the carrier 4 from. In operation, there is typically a pressure of only 2 to 5 mbar in the CVD reactor 2. The carrier gas line 14 is connected to a carrier gas supply (not shown in the figure) or a carrier gas supply from which the carrier gas flows into the carrier gas line 14 in the direction of the arrow indicated in FIG. A branch 16 of the carrier gas line 14 leads directly into the CVD reactor 2 in a gas shower head 17.

In an alternative embodiment, the carrier gas line 14 and the gas shower head 17 are each connected to their own, independent carrier gas supply. A special feature of the metering device 5 is that the interior of the storage container 6 is also in fluid communication with the carrier gas line 14 stands. For this purpose a ventilation line 18 is provided through which the interior of the storage container 6 is verbun with the carrier gas line 14. In the figure, in a manner not shown in more detail, there is a filter in the region of the mouth 19 of the ventilation line 18, which is permeable to the carrier gas, but not permeable to the powdery substance stored in the Vorratsbe container 6. A switching valve 22 is switched into the carrier gas line 14 between the opening 20 of the conveying channel 11 into the carrier gas line 14 and the opening 21 of the ventilation line 18 into the carrier gas line 14. The switching valve 22 in the illustrated embodiment is a solenoid valve. This is ruled out in a manner not shown to a control unit.

A helically designed mixing tool 23 is arranged in the storage container 6. This is constructed in two parts in the illustrated embodiment. A first tool part is located in the cylindrical part of the storage container 6. A second helical section is located in the area of the outlet 8 and extends into the conical taper 10 as part of the outlet of the feed block 9. The drive shaft 24 of the mixing tool 23 extends through the Closure body 7 in a sealed manner and is connected to an electric motor drive 25. The electromotive drive 25, which is also a stepping motor in the illustrated embodiment, is attached to the closure body 7. Since the closure body 7 has to be dismantled from the reservoir 6 to open and refill it and must also be reassembled on it, part of the drive shaft 24 is a coupling piece 26 which is slipped onto the upper section of the drive shaft 24 of the mixing tool 23 in a torque-locking manner. The coupling piece 26 can be withdrawn from the drive shaft together with the closure body 7. The coupling piece 26 extends through the closure body 7 in a sealed manner.

Figure 2 shows the conveyor block 9 in an enlarged and therefore more detailed illustration. In the conveying block 9, a conveying channel pipe 27 is used to form the conveying channel 11. In this is the screw conveyor 12, the outer diameter of the screw conveyor 12 is slightly smaller than the inner diameter of the feed channel pipe 27 and thus of the feed channel 11. On the inner wall of the feed channel pipe 27, thread-like inner wall structures are introduced which serve as a trap for the powdery substance conveyed through the feed channel 11. This serves to form a coating of the powdery substance on the inner wall of the feed channel pipe 27. On its side facing the outlet taper 10 of the feed block 9, the feed channel pipe 27 has an opening 28 through which the powdery substance located in the storage container 6 can pass can penetrate into the conveying channel 12. Opposite this opening 28, a cleaning pinion 29 is rotatably mounted in the conveyor block 9. This meshes with its teeth the conveyor helix of the conveyor screw 12. When the conveyor screw 12 is driven in rotation, the cleaning pinion 29 rotates with it. Because of the teeth of the cleaning pinion 29 engaging in the intervening spaces of the conveyor spiral, compacted powdery substance located therein is removed from them. In a manner not presented, a material trap is connected to the interior space in which the cleaning pinion 29 is arranged, in order to be able to catch the substance pressed out of the interstices of the För spiral. The feed channel pipe 27 is closed by a nozzle 30 at its mouth angeord designated in the carrier gas line 14. The diameter of the nozzle 30 is several times smaller than the diameter of the conveyor channel 11. Flier through this is a certain Venturi effect as a result of the carrier gas stream sweeping past the mouth 20, through which the solid particles conveyed by the screw conveyor 12 are entrained and released as suspended cargo Evaporator 15 are supplied.

When the conveying device 5 is in operation, the mixing tool 23 is driven in rotation by the stepping motor 25 in order to prevent undesired compacting of the material stored therein, which has only a very small grain size and is stored therein. At the same time, the conveying tool 23 serves the purpose of ensuring a replenishment of powdery substance into the outlet 8 and the taper 10 of the conveying block 9. When the device 1 is in operation, the inside of the storage container 6 and the conveying channel 12 owing to the negative pressure in the CVD Reactor 2 also has a negative pressure. This is typically a few mbar higher than the pressure inside the CVD reactor 2.

The powdery substance located in the storage container 6, which has a grain size of 30 to 50 mhp, for example, is loosened once per minute when the device 1 is in operation. For this purpose, the switching valve 22 is closed so that no carrier gas flows past the mouth 20 of the conveyor channel 11. However, the carrier gas supply remains constant. As a result of this, the pressure in the interior of the storage container 6 increases via the ventilation line 18. This initially leads to a certain compaction of the powdery substance stored therein. This pressure increase is used, however, in order to subsequently bring about a pressure decrease that takes place in a short time and thus quasi spontaneously by opening the switching valve 22 again after, for example, 1 to 2 seconds, that is: after a pressure increase has taken place. Due to the then existing direct pathway between the interior of the storage container 6 and the prevailing in the CVD reactor 2 Un, this leads to an effective swirling of the container 6 in the Vorratsbe powdery substance. In this way, a compaction of the solid material supplied as a precursor to the CVD reactor 2 is effectively counteracted and thus a continuous supply of the same with regard to the metering rate is ensured. This measure also loosens up any compaction of powdery substance that may be caused by the mixing tool.

If a powdery substance is mentioned in this context, it goes without saying that this also includes mixtures of substances. In the device 1 shown in the figures, the Ver evaporator 15 is atmospheric in the reactor 2 in an evaporator chamber 31. Downstream of the evaporator 15 in the direction of flow is a processing stage indicated overall by the reference numeral 32. The evaporator 15 and the processing stage 32 together form a carrier gas cleaning stage for separating contaminants carried along in the carrier gas flow. The preparation stage 32 comprises a filter unit 33. The filter unit 33 is composed of several filter stages 34, 34.1, 34.2. In the illustrated embodiment, for example, the filter stage 34 is a bed of spherical material made of spheres with a diameter of approximately 3 mm. The filter stage 34.1 following with decreasing porosity is also a bed of spherical material, formed from spheres with a spherical diameter of approximately 0.5 mm. In the direction of flow of the carrier gas, the filter stages 34, 34.1 are followed by a metal filter, which in turn is composed of several individual filter layers, starting with a passage size of 0.1 mm and ending with a passage size of 1 μm. The processing stage 32 also has a magnetic separator 35, which in the illustrated embodiment is designed as a bed of small permanent magnets. In the illustrated embodiment, these have a diameter of 3 mm and a length of 4 mm. The use of longer permanent magnets is also possible, for example with a length of about 12 mm. The permanent magnets are temperature-stable from 250 ° C to 400 ° C with regard to the temperatures prevailing in this area, depending on the substance to be sublimated.

In the exemplary embodiment shown, the components of the metering device 5 that come into contact with the precursor are made from a stainless, magnetizable steel. Abrasion caused by the parts sliding against each other, namely the mixing tool 23 opposite the inside of the storage container 6 as well as the taper 10 and the screw conveyor 12 opposite the inner wall of the conveyor channel 11 and between the screw conveyor 12 and the cleaning pinion 29, is a contamination of the Precursor substance is not critical, since such abrasion is removed from the carrier gas stream in the carrier gas cleaning stage with the evaporator 15 and the processing stage 32 before the sublimed precursor substance is deposited therefrom on a substrate located on the carrier 4.

On the one hand, the sublimation temperature of such abrasion is above the sublimation temperature of the powdery precursor substance. The abrasion, which is regarded as contamination, does not sublime under the pressure / temperature conditions prevailing at the evaporator 15. This remains in

Form of solid particles in the carrier gas stream. The precursor substance lies however, it is now in its gas phase, which makes it possible to remove the entrained solid particles in the preparation stage 32 without affecting the sublimed substance. In the processing stage 32, the solid debris resulting from the metering device and other solid contaminants that may be carried along are removed by the filter unit 33 and the magnetic separator 35. The carrier gas stream subsequently entering the separation chamber of the reactor 2 - indicated by a block arrow in FIG. 3 - is then to be addressed as free of solids and thus contamination

The invention is described on the basis of exemplary embodiments. Without departing from the scope of the applicable claims, there are also other possibilities for a person skilled in the art to implement the invention without this having to be explained in more detail in the context of these explanations.

List of reference symbols

1 CVD system 35 magnetic separator

2 CVD reactor

3 pump line

4 carriers

5 dosing device

6 storage containers

7 closure body

8 outlet 9 conveyor block

10 rejuvenation

11 conveyor channel

12 screw conveyor

13 stepper motor

14 Carrier gas line

15 evaporator

16 Branch of the carrier gas line

17 gas shower head

18 ventilation duct

19 mouth

20 mouth 21 mouth 22 switching valve

23 Mixing Tool

24 drive shaft

25 Electric motor drive

26 coupling piece

27 Conveyor duct pipe

28 opening

29 cleaning pinion

30 nozzle

31 Verdam horse chamber

32 Preparation level

33 filter unit, 34.1, 34.2 filter stage

Claims

Apparatus for vapor depositing a substance on a substrate comprising

- A reactor (2) with at least one evaporator (15) for the evaporation of powdery precursor particles from which evaporation products from which the layer is deposited on the substrate, with a vacuum pump connection to close a vacuum pump to generate the separation for the deposition in the Reactor (2) required negative pressure and with a substrate carrier (4),

- One fed by a carrier gas supply, to the United steamer (15) connected carrier gas line (14) and

- A metering device (5) for feeding powdery precursor particles into the carrier gas line (14), which dosing device (5) has an outlet (8) having a storage container (6) for storing the powdery precursor material to be fed to the reactor (2) and one below of the outlet (8) in a conveyor channel (11) arranged conveyor screw (12) with a conveying direction transverse to the outlet direction of the storage container (6) for conveying the powdery substance from the outlet (8) of the storage container (6) to an opening (20) ) in the carrier gas line (14), in which the conveyed powdery substance is taken up as suspended load by the carrier gas stream flowing therein and fed to the evaporator (15), characterized in that at least some of the surfaces of the in the metering device (5) parts (6, 23; 11, 12) which are moved against one another by friction for conveying the powdery precursor material are made of a material which, in relation to on the pulverför shaped precursor substance has a higher sublimation temperature, and that the evaporator (15) in the flow direction of the carrier gas is followed by a processing stage (32) for removing at least a portion of the solid particles contained in the carrier gas stream entrained with the sublimed substance. 2. Device according to claim 1, characterized in that the processing stage (32) comprises a filter unit (33) through which the carrier gas stream entrained with the sublimed substance flows.

3. Device according to claim 2, characterized in that the filter unit (33) is designed in several stages and comprises a plurality of filter stages (34, 34.1, 34.2) connected one behind the other in the flow direction of the carrier gas with a passage size decreasing in the flow direction of the carrier gas.

4. Device according to claim 3, characterized in that at least one filter stage is provided by a bed of spherical material. 5. Device according to claim 3 or 4, characterized in that at least one filter stage (34.2) is provided by a close-meshed metal filter.

6. Device according to one of claims 2 to 5, characterized in that the filter stage (34.2) with the smallest passage size of the filter unit (33) has a passage size of about 1 pm.

7. Device according to one of claims 1 to 6, characterized in that the processing stage (32) has a magnetic separator (35).

8. Device according to claim 7, characterized in that the magnetic separator (35) is designed as a magnetic filter from a bed of a large number of permanent magnets, forming a magnetic filter bed.

9. Device according to claim 8, characterized in that the permanent magnets are cuboid bodies. 10. Device according to one of claims 1 to 9, characterized in that at least the mutually moving parts (6, 23; 11, 12) of the metering device (5) are made of a rust-free, magnetizable ferrous metal.

11. Device according to one of claims 1 to 10, characterized in that the material forming the surface of the parts of the metering device that are moved relative to one another is a coating. 12. Device according to claim 11, characterized in that the coating material contains the substance to be deposited in the reactor.

Device according to one of claims 1 to 12, characterized in that the device comprises several evaporators connected to the metering device and a multi-way valve is connected to the carrier gas supply upstream of the evaporators, the carrier gas supply to the inlet and each evaporator unit to one own output of the multi-way valve are connected.

Device according to one of Claims 1 to 13, characterized in that a ventilation line (18) with its first aeration line (18) is attached to the carrier gas line (14) in the direction of flow of the carrier gas before the entry of the powdery substance particles conveyed through the mouth (20) of the conveying channel (11) passes End is connected, the other end, with the interior of the storage container (6) standing in fluid connection, is connected to this and that in the portion of the carrier gas line (14) between the mouth (21) of the ventilation line (18) and the A switching valve (22) is switched on when the powdery substance particles conveyed through the mouth (20) of the conveying channel (11) are reached.

Device according to Claim 14, characterized in that the ventilation line (18) opens into the storage container (6) in the region of the end of the storage container (6) opposite the outlet (8). 16. Device according to claim 14 or 15, characterized in that the storage container (6) is a standing cylindrical container in which the outlet (8) is at the bottom and the upper opening of which is sealed with a closure body (7).

17. Device according to one of claims 14 to 16, characterized in that in the storage container (6) at least one rotationally driven mixing tool (23) is arranged for loosening the pulverulent substance before rateten, the drive shaft (24) of the longitudinal extent of the storage container ( 6) follows and extends through the closure body (7) in a sealed manner with a drive section or a coupling section (26) and is connected to a rotary drive arranged on the outside with respect to the seal.

18. Device according to one of claims 14 to 17, characterized in that in the area of the outlet (8) adjacent to this or opposite at least one rotatably mounted cleaning pinion (29) meshes with the screw conveyor (12).

19. Device according to claim 18, characterized in that the conveying channel (11) has one or more inner wall structures for forming a coating that increases wall friction from the powdery substance.

20. Device according to one of claims 1 to 19, characterized in that the entire inner surface of the metering device is made of a material that is in relation to the powdery

Precursor material has a higher sublimation temperature.

21. A method for providing a vaporized substance as a preliminary stage of a vapor deposition process, in which method a powdery precursor substance for providing the substance to be deposited in gaseous form by means of a carrier gas flow to an evaporator (15) is supplied and sublimed on this, characterized in that after the sublimation of the precursor substance, the carrier gas stream containing the vapor products is cleaned with respect to entrained, non-sublimated solid particles before the substance sublimed from the precursor substance is deposited on a substrate will.

22. The method according to claim 21, characterized in that the carrier gas stream containing the sublimed substance is filtered to remove solid particles entrained therein.

23. The method according to claim 22, characterized in that the carrier gas stream containing the sublimated substance is filtered in a multistage descending manner in the flow direction of the carrier gas stream.

24. The method according to any one of claims 21 to 23, characterized in that the carrier gas stream containing the sublimed substance is passed over a magnetic separator to remove solid particles entrained therein.

25. The method according to claim 24, characterized in that for the magnetic separation of entrained solid particles in the carrier gas stream, a magnetic separator (35) formed from a plurality of permanent magnets is passed through.