Cold Crucible

Abstract

The present invention relates to a cold crucible. Cold crucibles are used in the field of producing high temperature single crystal materials. The cold crucible 1' according to the present invention comprises: a cold cage 10 made of a material with good electrical conductivity and equipped with sectors 100 in which the charge is melted; a cooling device 11 containing a heat transfer fluid, which is configured to cool each segment 100 of the cold cage from the inside; Equipped with. At least one sector of the cold crucible is provided with a housing 101, which is removable and which is suitable and intended to accommodate at least one so-called functionalization device 12, 120 of the cold crucible 1'. From this point on, it is possible to functionalize each sector independently from the other sectors, inter alia, by housing therein a functionalization device configured to modify and / or analyze at least one characteristic of the charge in the cold cage, in particular the molten charge.

Description

[Technical field]

[0001] The present invention relates to the field of cold crucibles, which are used with particular advantage in the field of high-temperature material production.

[0002] In a known manner, the cold crucible a so-called cold cage, equipped with sectors made of a good electrical conductor material, generally copper, into which the charge to be melted is intended to be introduced; - a cooling device containing a heat transfer fluid, typically water, a cooling device configured to cool each segment of the cold cage from the inside; Equipped with.

[0003] For operation, each cold crucible uses an external electromagnetic induction coil that surrounds the cold cage and through which an alternating current flows.

[0004] Each cold crucible may further be used in conjunction with a device for continuously supplying the constituent materials of the charge. [Background technology]

[0005] There are several types of cold crucibles, two of which are illustrated in the attached Figures 1 and 2. There are other types of cold crucibles not illustrated herein, including, for example, the so-called double-crucible models. Regardless of the crucible type considered, its operating principle is substantially common to the other types, as will be introduced hereinafter with reference to Figures 1 and 2.

[0006] The cold crucible 1 and the coil 2 are placed in an insulated enclosure 5 at a determined pressure, filled with a monitored atmosphere, preferably oxygen-free, often an inert gas such as argon. Nevertheless, the production of materials in the cold crucible can also be used under oxygen-rich atmospheres.

[0007] When an alternating current is injected into the coil 2 surrounding the cold cage 10, induced currents appear in each of the cooled sectors 100 of the cage, which then give rise to eddy currents across the so-called electromagnetic skin depth of the charge 20 placed in the cage. These eddy currents make it possible to heat the charge 20, if appropriate up to its melting, without the cold crucible 1 being heated.

[0008] Of course, since heating of the charge is achieved by electromagnetic induction, the charge 20 must be electrically conductive. The electromagnetic skin 21 of the charge 20 depends on the resistivity of this charge and on the frequency used for the alternating current injected into the coil 2. It should be noted that this electromagnetic skin 21 is the portion of the charge 20 that is located closest to the cold cage 10.

[0009] The cold crucible 1 can furthermore be used to melt a semiconductor material. For this purpose, the cold crucible 1 is packaged, in a known manner, with a device for preheating the charge 20 to make it conductive. Typically, this preheating device (not shown) comprises a cap made of graphite arranged on the cold crucible 1 and, where appropriate, a gas flow ventilation system arranged to avoid contamination of the charge 20 by the graphite of the cap.

[0010] Known advantages of this technique are in particular the floating of the molten charge 20, which explains the relative oddity of the cold crucible 1, the potential absence of external contamination (in particular by oxygen or graphite) in the material 22 to be produced, as well as the very homogeneous stirring of the material 22 and, above all, of the molten charge 20, which allows the production of alloys.

[0011] Cold crucibles are currently used for the production of metal alloys, for example based on titanium, niobium, etc. In fact, the use of cold crucibles in metallurgy has become a very popular tool in practice due to its stirring qualities, which make it possible to obtain alloys of very homogeneous composition. This homogeneity is ensured by the vigorous stirring due to the presence of very large electromagnetic forces, which can be observed especially throughout the thickness of the electromagnetic skin of the molten charge.

[0012] It is sufficient to interrupt the alternating current through the coil 2 to stop the floating of the molten charge 20, while removing the plug 3 blocking the bottom of the cold crucible 1, as illustrated in FIG. 1, so that the molten charge flows into a mould located below the cold crucible.

[0013] With reference to FIG. 1, the use of a cold crucible 1 to make single crystals, in particular of semiconductor material, is also considered. This technique uses a perfect single crystal seed to start the growth of a single crystal ingot 22. The seed 23 is introduced into a molten charge 20 of the material to be crystallized, then the set constituted by the seed 23 and the single crystal 22 growing on it is displaced upwards (see FIG. 1) or downwards (see FIG. 2, in particular the elements carrying the references 3 (cooled fingers) and 4 (vertical translation tray)), causing the single crystal 22 to grow longitudinally, ideally diametrically.

[0014] A drawback of existing cold crucibles is that they do not allow or do not easily allow for the performance of functions other than those traditionally assigned to them. More specifically, current cold crucibles often have only one function, which is to allow the melting of the charge that they contain. Summary of the Invention [Problem to be solved by the invention]

[0015] The object of the present invention is therefore to provide a cold crucible which makes it possible to overcome all or part of the above-mentioned drawbacks, and more particularly to provide a cold crucible which makes it possible to fulfil functions other than those previously assigned to it, namely, that of enabling the melting of the charge it contains.

[0016] Other objects, features, and advantages of the present invention will become apparent from a consideration of the following description and the accompanying drawings, and it should be understood that other advantages may be incorporated. [Means for solving the problem]

[0017] To this end, according to one embodiment, the invention provides a cold crucible in which at least one sector of the cold crucible is essentially equipped with a housing, called a (multi)functionalized housing, and is removable, according to the general definition given herein above. The (multi)functionalized housing is suitable (or adapted) and intended to accommodate therein at least one (multi)functionalized device of the sector it comprises, and more generally of the cold crucible itself. The (multi)functionalized device may be comprised by the sector it comprises, and more generally by the cold crucible itself. More specifically, said at least one sector of the cold crucible is removable from at least one of the cooling device and at least one other sector of the cold crucible.

[0018] Where appropriate, the cold crucible further comprises a device for fastening and holding at least one sector, preferably each sector, to at least one of the cooling device and the at least one other sector, the fastening and holding device being configured such that, when fastened and held, said at least one sector forms part of the cold cage.

[0019] It is therefore possible to (multi)functionalize said at least one sector, independent of the other sectors, by accommodating in its housing at least one (multi)functionalization device. A (multi)functionalization device may be defined, without being necessarily limited to this definition, as a device configured to modify and / or analyze at least one characteristic of the charge in the cold cage, in particular the molten charge. A (multi)functionalization device may comprise, and possibly consist of, a device for modifying and / or analyzing at least one characteristic of the charge. Without being limited thereto, a (multi)functionalization device may be: - a device for generating an electromagnetic field, preferably a permanent magnet, - Ferrite, - complementary heating devices (microwave, infrared, ultraviolet...), - an ultrasonic transducer, and - Piezoelectric element It may be one of:

[0020] It is also understood that cold-throughables multi-functionalized in this manner have a great modularity: indeed, many combinations between sectors and (multi-)functionalized devices are conceivable, each potentially allowing one or more specific modifications or analyses of the load.

[0021] The cold crucible according to the invention not only makes it possible to make the sector active in the monitoring or characterization of the charge, in particular the molten charge, but also makes it possible to reduce manufacturing and maintenance costs.

[0022] The cooling device is configured to allow cooling of the cold cage and comprises a channel for the circulation of a heat transfer fluid, which extends partially into at least one sector, preferably into each sector, the (multi)functionalized housing communicating with the part of the circulation channel extending in the sector and possibly forming only one housing. The advantage of this configuration is that the cooling device can then cool not only the sectors, as before, but also the (multi)functionalized device.

[0023] Alternatively, the (multi)functionalized housing may be different from the part of the circulation channel that extends into the sector. This alternative configuration may be preferred when contact between the heat transfer fluid and the (multi)functionalized device is to be avoided. More specifically, such contact may hinder the correct functioning of the (multi)functionalized device or reduce its reliability, accuracy, liveness, etc.

[0024] Preferably, the (multi)functionalized devices are based on a material that is a less good electrical conductor than the base material of the sector, typically copper. In this way, each (multi)functionalized device contained within a sector is not subject to magnetic fields.

[0025] Alternatively or complementary, the (multi)functionalized device may be arranged with a support, more particularly an adapter, based on a material that is a less good electrical conductor than the base material of the sectors, typically copper. For example, the support is configured to electrically insulate the (multi)functionalized device and the sectors that house it from each other. Said support thus enables the sectors to fulfill their electromagnetic shielding role, even when the (multi)functionalized device is based on a material that is as good an electrical conductor as the base material of the sectors, and possibly even better.

[0026] Preferably, the support is configured to accommodate (or adjust) the (multi-)functionalized device to the (multi-)functionalized housing intended to accommodate it. Hereafter, the (multi-)functionalized housing may have a standardized size and shape. Thus, the manufacture of the cold crucible according to the invention is facilitated and its costs are reduced.

[0027] If the (multi-)functionalization device comprises or consists of ferrite, it may be configured to concentrate the electromagnetic field lines located at the periphery of the sector it is housed in. A number of sectors may house such a (multi-)functionalization device, and thus, since each of the sectors is independent, it is possible to concentrate the electromagnetic field lines at several locations of the cold crucible in an independent and modular manner.

[0028] If the (multi)functionalization device comprises or consists of an ultrasonic transducer, it may be configured to characterize the molten charge by measuring the displacement rate of material therein.

[0029] If the (multi)functionalization device comprises or consists of a piezoelectric element, it can be configured to introduce a pressure wave into the charge, in particular the molten charge.

[0030] If the (multi)functionalization device comprises or consists of complementary heating devices (microwave, infrared, ultraviolet) selected depending on the properties of the material to be produced, it can be configured to generate, through the walls of the cold finger, heating parameterized to enhance the thermal properties of the charge.

[0031] If the (multi)functionalization device comprises or consists of a device for generating an electromagnetic field, it can be configured to generate an electromagnetic field, preferably a static (or quasi-static) magnetic field, within the charge, in particular the molten charge, in particular across the electromagnetic skin thickness of the molten charge.

[0032] More specifically, each generating device may be configured to generate an electromagnetic field, and preferably a static magnetic field, of sufficient density to be felt by the molten charge in the cold cage, and more specifically at least across the electromagnetic skin thickness of the molten charge in the cold cage, and preferably only across the electromagnetic skin thickness of the molten charge in the cold cage. Each electromagnetic field may thus act to slow down the electromagnetic stirring of the molten charge.

[0033] Cold crucible according to this last feature therefore makes it possible to continuously produce monocrystalline ingots with a diameter significantly larger than that of the seed that allows its growth to be started. Such monocrystalline ingots can be made of various conducting or semiconducting materials. Wafers cut from monocrystalline ingots of semiconducting material produced in this way can be advantageously used in many fields, in particular in the power electronics field.

[0034] More specifically, each device for generating a magnetic field may be configured to generate an electromagnetic field, and preferably a static magnetic field, having a density substantially higher than 0.02 T, preferably substantially higher than 0.05 T, at a distance substantially greater than 2 mm from one of the inwardly directed edges of the cold cage.

[0035] For example, each device for generating a magnetic field is configured to generate an electromagnetic field, and preferably a static magnetic field, having a density substantially comprised between 0.07 and 0.8 T (more preferably substantially comprised between 0.1 and 0.3 T), at a distance substantially comprised between 0.1 and 12 mm (more preferably substantially comprised between 4 and 10 mm) from one of the inwardly directed edges of the cold cage of the generating device.

[0036] More specifically, each generating device is housed within its sector such that it is positioned by one of the inwardly directed edges of the cold cage at a distance substantially less than 12 mm, preferably substantially less than 9 mm, and even more preferably substantially less than 6 mm, from the molten charge in the cold crucible.

[0037] Each sector is simply made of a resistive material, generally based on copper, and acts as an (electromagnetic) shield to protect the generating device it houses. Indeed, the induced currents in a sector therefore flow naturally across the thickness of the sector's wall, which is for example made from copper.

[0038] Furthermore, each generating device is arranged in the sector that houses it so as to be cooled by a cooling device of the cold crucible. The same cooling device may make it possible to ensure the maintenance of the monitored temperature of the generating device and the sector.

[0039] According to a preferred embodiment of the invention, the at least one generating device comprises at least one permanent magnet. The coupling arrangement of each permanent magnet with the cooling device is then more particularly configured to ensure that the permanent magnet is always maintained at a temperature lower than the Curie temperature at which the magnet loses its magnetization. Preferably, each permanent magnet is more particularly such that it generates a static magnetic field having a density substantially equal to 0.8 T at a distance of 2 mm from its edge. Preferably, each permanent magnet is made of a material having a higher electrical resistivity than the material of construction of the sectors of the cold cage. For example, each permanent magnet is made of a material of the iron and / or neodymium family.

[0040] According to a preferred embodiment of the present invention, at least one device for generating a static magnetic field comprises a plurality of permanent magnets. Preferably, each of the plurality of permanent magnets is arranged relative to one another to generate a stronger static magnetic field, at least in the direction of the inside of the cold cage, in terms of magnetic field value, compared to the static magnetic field generated by each permanent magnet considered separately. For example, each of the plurality of permanent magnets is arranged relative to one another according to the so-called Halbach configuration.

[0041] Optionally, the present invention may further include at least one of the following features. According to one embodiment of the invention, the fastening and holding device comprises a base, typically made of stainless steel, configured to removably fasten each sector of the cold crucible therein, such that the sectors and the base together form a cold cage. Preferably, the fastening of each sector to the base is configured to allow the heat transfer fluid of the cooling device to circulate through the base within the sector. A sealing gasket, for example in the form of a cylinder head gasket or an O-ring gasket, may be arranged, where appropriate, between the base and the sectors, or directly between the sectors and the cooling device, in particular if there is no base. - Preferably, at least one (multi)functionalization device comprises a first part configured to functionalize the cold crucible and a second part, called the support part, configured to support the first part of the (multi)functionalization device and to cooperate closely with the housing of the (multi)functionalization device in the sector. Preferably, the support part of the (multi)functionalization device is configured to support a plurality of permanent magnets, arranged with respect to each other, for example according to the so-called Halbach configuration. Alternatively or complementary, the support is configured to form together with the inner wall of the housing in the sector and, where appropriate, the first part of the (multi)functionalization device which it supports, a circulation path for the heat transfer fluid of the cooling device. According to a particular embodiment, only two sectors opposite each other house (multi-)functionalized devices as introduced herein above. According to another particular embodiment, only three sectors arranged substantially according to a third order rotational symmetry accommodate (multi-)functionalized devices as presented herein above. According to another particular embodiment, only four sectors arranged substantially according to a fourth order rotational symmetry accommodate (multi-)functionalized devices as presented herein above. According to another particular embodiment, one sector out of two adjacent sectors houses a (multi-)functionalized device as introduced herein above. According to another particular embodiment, each sector contains a functionalization device(s) such as those introduced herein above.

[0042] The aims, objectives, as well as features and advantages of the present invention will become apparent from the following detailed description of one embodiment thereof, as illustrated by the accompanying drawings, in which: [Brief description of the drawings]

[0043] [Figure 1] FIG. 1 is a schematic perspective view of a halved prior art cold crucible configured with an electromagnetic induction coil and including a charge from which seeds are gradually removed to grow a single crystal. [Diagram 2] FIG. 2 is a schematic transparent front view of a thermally insulated housing housing a cold crucible according to the prior art other than that illustrated in FIG. 1. [Diagram 3] FIG. 1 shows a perspective view of a preferred embodiment of a cold crucible according to the present invention comprising a cooling device. [Figure 4] FIG. 4 is an exploded perspective view of the cold crucible and cooling device illustrated in FIG. 3, with a static magnetic field generating device as a (multi)functionalization device. [Diagram 5]FIG. 2 is a perspective view of a static magnetic field generating device according to a preferred embodiment of the present invention; [Figure 6] FIG. 2 is a bottom perspective view of a sector according to a preferred embodiment of the present invention; [Figure 7] FIG. 7 is a transparent perspective view of the sector illustrated in FIG. 6. [Figure 8] FIG. 2 is a schematic diagram of a permanent magnet arrangement according to a Halbach configuration and the resulting magnetic contour lines. [Figure 9] 10 shows the results of a multiphysics model simulation illustrating the effectiveness of a cold crucible according to the invention (FIG. 10), at least one sector of which contains a device for generating an electromagnetic field, compared to a cold crucible according to the prior art (FIG. 9). [Figure 10] 10 shows the results of a multiphysics model simulation illustrating the effectiveness of a cold crucible according to the invention (FIG. 10), at least one sector of which contains a device for generating an electromagnetic field, compared to a cold crucible according to the prior art (FIG. 9). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] The drawings are provided as examples and are not intended to limit the present invention. They consist of schematic principle diagrams intended to facilitate understanding of the present invention and are not necessarily drawn to scale for practical use.

[0045] "Lower" and "higher" should be understood as "less than or equal to" and "greater than or equal to", respectively. Equality is excluded in the use of the terms "strictly lower" and "strictly higher". Expressions of the type "equal to, lower, higher" should also be understood as comparisons that may allow for some tolerance, especially depending on the scale of magnitude and measurement uncertainty of the values ​​being compared. Substantially equal, lower, or higher values ​​are within the interpretation of the present invention.

[0046] A parameter "substantially equal to / higher / lower than" a given value should be understood as the parameter being equal to / higher / lower than the given value, within 20%, and sometimes within 10%, of this value. A parameter "substantially including a value between" two given values ​​should be understood as the parameter being a minimum value equal to the smallest given value, within 20%, and sometimes within 10%, of this value, and a maximum value equal to the largest given value, within 20%, and sometimes within 10%, of this value.

[0047] In the context of the present invention, it is specified that the terms "on", "overlying", "covering" or "underlying" or their equivalents do not necessarily mean "in contact".

[0048] "Arranged together" should be understood as two structural elements, one of which is arranged with respect to the other according to a functional relationship between the two structural elements. In particular, one of the elements may be arranged to fulfill a specific function together according to the dimensions and shape of the other element and / or according to a specific arrangement defined with respect to the set-up of the other element. Thus, these terms are intended to cover various relative arrangements of two structural elements, the various forms of which need not be exhaustively detailed.

[0049] An element based on material A should be understood to be an element which comprises this material A and possibly other materials.

[0050] "Electromagnetic field" is a set

[0051]

number

[0052] It should be understood that the boundary is represented by

[0053]

number

[0054] is the electric field,

[0055]

number

[0056] is the magnetic field, the charge q and the velocity vector

[0057]

number

[0058] A particle with

[0059]

number

[0060] The definition of an electromagnetic field here includes the definition of a magnetic field and, more importantly, the definition of a static magnetic field, which represents a particular case of an electromagnetic field.

[0061] A Halbach configuration should be understood as a special arrangement of permanent magnets that enhances the magnetic field on one side of the arrangement and almost cancels the magnetic field on the other side.

[0062] A good conductor of electricity has an electrical resistivity of 6.10 -8 Substantially lower than Ω.m, preferably 2.10 -8 This should be understood as meaning a material with a resistivity substantially below Ω.m.

[0063] As stated at the outset, the object of the present invention is to provide a cold crucible which is capable of performing functions other than those for which it was previously intended, namely, enabling the melting of the charge it contains.

[0064] For this purpose, the present invention more specifically provides, for example as illustrated in FIG. 3, a cold crucible 1' which, in contrast to a conventional cold crucible 1, is essentially such that at least one of its sectors, preferably each of its sectors 100, is provided with a housing, referred to as a (multi-)functionalized housing 101, which is removable.

[0065] The (multi)functionalized housing 101 is suitable (or adapted) and intended to accommodate at least one (multi)functionalized device 12 of the sector 100 it comprises. Said at least one (multi)functionalized device 12 may be included in the cold crucible 1' according to the invention. Alternatively, the (multi)functionalized device 12 may be provided as an attachment to the cold crucible according to the invention. Thus, the invention is highly adaptable to different (multi)functionalized devices 12, some examples of which are presented herein below.

[0066] More specifically, at least one sector 100 of the cold crucible 1′, preferably each sector of the cold crucible, is detachable from at least one of the cooling device 11 and at least one other sector 100 of the cold crucible 1′. Preferably, each sector 100 of the cold crucible is detachable from at least one of the cooling device 11 and each other sector 100 of the cold crucible.

[0067] Where appropriate, the cold crucible 1 further comprises a device 13, 130 for fastening and holding at least one sector 100, preferably each sector, to at least one of the cooling devices 11 and to at least one other sector 100. More specifically, the fastening and holding device 13, 130 may be configured such that, when fastened and held, said at least one sector 100 forms at least a part of the cold cage 10.

[0068] It is therefore possible to (multi)functionalize each sector, independently of the other sectors, by housing in the (multi)functionalization housing 101 it comprises at least one selected (multi)functionalization device 12. The (multi)functionalization device 12 may be defined as a device making it possible to modify or analyze at least one characteristic of the charge in the cold cage, in particular the molten charge, although this definition is not necessarily limiting.

[0069] In a non-limiting manner, the (multi)functionalized device 12 may be a device 120 for generating an electromagnetic field, preferably one of a permanent magnet, a ferrite, an ultrasonic transducer, and a piezoelectric element.

[0070] It is also understood that the cold throughable 1' multi-functionalized in this manner has a great modularity: indeed, many combinations between the sectors 100 and the (multi-)functionalized devices 12 are conceivable, each potentially resulting in one or more specific modifications or analyses of the load 20.

[0071] The cold crucible 1' according to the invention makes it possible to activate sectors in the monitoring or characterization of the charge, in particular the molten charge.

[0072] The cooling device 11 is configured to allow cooling of the cold cage and comprises a channel for the circulation of a heat transfer fluid (typically water) that extends partially into each sector 100, the (multi)functionalized housing 101 communicating with the part of the circulation channel that extends in the sector and possibly forming one integral housing. The advantage of this configuration is that the cooling device 11 can then be used to cool not only the sectors 100, as before, but also the (multi)functionalized device 12. This is particularly advantageous when the (multi)functionalized device 12 includes a permanent magnet, since the latter can be kept at a temperature below its Curie temperature. Since the sectors 100 and the (multi)functionalized devices 12 that they house are thus constantly cooled by water, the temperature of the (multi)functionalized device 12 cannot exceed the operating temperature of the sectors 100, at least to the extent that the (multi)functionalized device 12 itself does not emit heat in a significant manner.

[0073] Alternatively, the (multi)functionalized housing 101 may be distinct from the portion of the circulation channel that extends into the sector 100. This alternative configuration (not shown in the drawings) may be preferred when contact between the heat transfer fluid and the (multi)functionalized device 12 is to be avoided. More specifically, such contact may hinder the normal functioning of the (multi)functionalized device 12 or reduce its reliability, accuracy, liveness, etc.

[0074] Preferably, the (multi)functionalized device 12 is based on a material that is a less good electrical conductor than the material on which the sector 100 is based, typically copper. In this way, it is ensured that the currents (eddy currents) induced by the electromagnetic induction external coil 2 are located at the periphery of the sector 100 of the cold cage 10. In fact, copper is one of the best known electrical conductors and acts as an electromagnetic shield. Thus, each (multi)functionalized device 12 introduced in the sector 100 is not affected by (electro)magnetic fields.

[0075] Alternatively or complementary, the (multi)functionalized device 12 can be arranged with a support 12b, more specifically an adapter, based on a material that is a poorer electrical conductor than the base material of the sectors 100. This poorer electrical conductor material may even consist of an electrical insulator such as a plastic. Said support 12b thus enables the sectors 100 to fulfill their electromagnetic shielding role even when the (multi)functionalized device 12 is based on a material that is as good an electrical conductor as the base material of the sectors 100, and possibly even better.

[0076] The support 12b may further serve as an adapter. As such, it may further enable any type of (multi)functionalized device 12, regardless of its shape and its dimensions, to be adapted to said (multi)functionalized housing 101, which may then have a standardized size and shape. The manufacture of the cold crucible 1' according to the invention is facilitated and its costs are reduced.

[0077] If the (multi-)functionalization device 12 comprises or consists of ferrite, it may be configured to concentrate the electromagnetic field lines located at the periphery of the sector 100 that houses it. A number of sectors 100 may house such a (multi-)functionalization device 12, and thus, since each sector 100 is independent, it is possible to concentrate the electromagnetic field lines at several locations of the cold crucible 1′ in an independent and modular manner.

[0078] If the (multi)functionalization device 12 comprises or consists of an ultrasonic transducer, it may be configured to characterize the molten charge 20 by measuring the displacement velocity of material therein.

[0079] If the (multi)functionalization device 12 comprises or consists of a piezoelectric element, it may be configured to introduce a pressure wave into the charge 20, in particular the molten charge.

[0080] A preferred embodiment of the present invention is described hereinbelow with reference to figures 3 to 7. In this preferred embodiment, the (multi)functionalized device 12 comprises or consists of an (electro)magnetic field generating device. It is to be understood that the characteristics described in detail hereinbelow may be applied mutatis mutandis to the different (multi)functionalized devices 12 described hereinbefore.

[0081] The cold crucible 1' illustrated in Fig. 3 comprises a cold cage 10 having a substantially cylindrical shape defining an internal space intended to receive a charge to be melted. More specifically, the cold cage 10 consists of a number of sectors 100. In a known manner, the sectors 100 are not electrically conducting with one another through at least a portion of their longitudinal edges. In this portion, an air gap may be formed between two adjacent sectors 100. Alternatively, each clearance between two adjacent sectors may be filled with a magnetic insert. More specifically, such an insert may be based on a soft magnetic composite material.

[0082] Each sector 100 of the cold crucible 1' illustrated in Fig. 3 is fastened by a base 130 that serves as a device 13 for fastening and holding the sectors 100. More specifically, the device 13 allows fastening the sectors 100 on the cooling device 11 and holding them in a specific position with respect to each other on the cooling device 11. Fastened and held in this manner, the sectors 100 form an essential part, possibly the whole, of the cold cage 10. Alternatively, the sectors may share the same base 130 to which they are fastened and held, which in turn is fastened to the cooling device 11.

[0083] Thus, the cold crucible 1' illustrated in Fig. 3 comprises a cooling device 11 of the type containing a heat transfer fluid, for example water. Such a cooling device 11 may be as known from the prior art. Thus, the cold crucible 1' according to the invention may not even require the development or adaptation of a known cooling device 11 and may therefore be advantageously used as such.

[0084] As illustrated in Fig. 4, the cooling device 11 may comprise two parts: a first part (bottom of Fig. 4) where the heat transfer fluid is introduced and then extracted from, a second part of the cooling device 11 defining one or more circulation circuits that are partially inside the chilling sector 100.

[0085] A gasket 14, in the form of a cylinder head gasket in the example illustrated in FIG. 4, may be disposed between the second part of the cooling device 11 and each base 130 to ensure a seal between these parts.

[0086] Alternatively, the sectors may extend at their base 130 with inlets and outlets for the heat transfer fluid each protruding from the plane of the base 130 and each intended to be inserted into corresponding holes in the cooling device or in an intermediate part (not shown) between the cooling device and all the sectors 100. The sealing between each sector 100 and the cooling device 11 may then be achieved by one or more O-ring gaskets arranged along the inlet and outlet protrusions for the heat transfer fluid.

[0087] In Fig. 4 a partially exploded view of the cold cage 10 is also represented. The sectors 100 are fastened together by their bases 130. More specifically, one of the sectors 100 is illustrated in an exploded view. Each sector 100 is thus seen to include a housing 101 in which a generating device is accommodated.

[0088] More specifically, the housing 101 is preferably closed by its side opposite the interior space of the cold cage 10, by a plate 102 made of brass or copper, which may be fixed, preferably by welding, in electrical conduction with the other walls defining the housing 101. In fact, a conventional cold crucible, as a cavity, comprises only a part of the heat transfer circulation channel intended to enable its cooling, and therefore it is a priori impossible to accommodate therein any (multi)functionalization device 12, here the generation device 120, without affecting the cooling of the sector. Alternatively, each sector 100 could be designed to present a housing 101 suitable and intended to receive the generation device 120.

[0089] The generating device 120 is as illustrated in FIG. 4 and more specifically as represented in FIG. 5. In particular, this figure illustrates that according to a preferred embodiment of the invention, the generating device 120 essentially comprises two parts 12a and 12b. The first part 12a is configured to generate a static magnetic field. The second part 12b, called the support part, support or adapter, is configured to support the first part 12a of the generating device. More specifically, the support part 12b comprises a substantially longitudinal plate from which two holding elements extend vertically. The first part 12a of the generating device 120 is fastened and held between the two holding elements of the support part 12b. The two holding elements are further configured to provide room for a part of the heat transfer fluid circulation circuit around the first part 12a of the generating device in the sector 100, more specifically in the space of the housing 101 not occupied by the generating device. Thus, the first of the two retaining elements (the element at the bottom in FIG. 5) constitutes a kind of central island on either side where the heat transfer fluid is intended to circulate in opposite directions, and the second of the two retaining elements (the element at the top in FIG. 5) constitutes the interior of the serpentine part of the circulation circuit.

[0090] A bottom perspective view of one of the sectors 100 illustrated in FIG. 3 is illustrated in FIG. 6. It is shown that the housing 101 can be opened by its base 130. A series of through holes and / or material recesses can be provided in the extension of the base 130 for fastening to the base of an adjacent base and / or for fastening to the cooling device 11, in particular through the cylinder head gasket 14. More specifically, the material recesses of two adjacent segments 100 can be intended to cooperate in order to fasten these segments together. It is also shown in FIG. 6 that the generating device is closely accommodated in the housing 101. In particular, the second part 12b comprises a longitudinal plate that is preferably configured to cover the entire inner surface of the housing 101 opposite the internal space of the cold cage 10, the surface of the first part 12a of the generating device resting or at least in contact with the inner surface of the housing 101 that is directed towards the internal space of the cold cage 10. In this way, the support 12b acts as an adapter that makes it possible to avoid any movement of the generating device in the housing 101. The generating device therefore remains fixed in. The set formed by the sector 100 and by the generating device appropriately placed in the sector 100 is therefore also seen to define the aforementioned circulation circuit part in the form of a U-shaped opening at the base 130 of the sector 100. It should be emphasized that in this configuration, the first part 12a of the generating device, which is configured to generate a static magnetic field, is located in the position closest to the internal space of the cold cage 10. More specifically, only the thickness of the longitudinal wall of the sector 100, which is directed towards the internal space of the cold cage 10, separates the first part 12a of the generating device from the latter. For example, the thickness of this wall comprises a thickness between 0.5 and 2 mm, preferably between 0.7 and 1.5 mm. The support 12b therefore acts as an adapter insofar as it allows to achieve or not achieve contact between the (multi)functionalized device and the internal wall of the sector that houses it.

[0091] The generating device is therefore understood to be housed, more particularly within a sector 100 thereof, so as to be positioned with its edge directed towards the inside of the cold cage 10 at a distance substantially less than 12 mm, preferably substantially less than 9 mm, and even more preferably substantially less than 6 mm, from the molten charge 20 in the cold crucible 1'.

[0092] Furthermore, by its mere construction, the generating device appears to be configured to be cooled by the cooling device 11 which is already tasked with cooling the sector 100 in which the generating device is housed.

[0093] A first part 12a of the generating device according to a preferred embodiment of the present invention will be described hereinafter with reference to FIGS.

[0094] As illustrated, the first part 12a of the generating device comprises, in a non-limiting manner, a plurality, i.e. nine, permanent magnets 120. Hereafter, it is understood that the cooling device 11 is preferably configured and / or parameterized to ensure that each permanent magnet is kept at a temperature strictly below the Curie temperature of that magnet, otherwise the magnetization of the permanent magnet would be lost.

[0095] Each permanent magnet may have a substantially cubic geometric shape, the sides of which are, for example, substantially equal to 2 cm. Of course, the geometric shape and dimensions of each permanent magnet should be adapted to the dimensions of the housing 101 and, more generally, of the sectors 100. More specifically, each permanent magnet 120 may be based on a neodymium / iron / boron alloy. Such an alloy has a higher electrical resistivity, and more specifically, at least twice as high, as compared to the copper constituting the sectors 100 of the cold cage 10. The permanent magnets 120 are aligned with each other and remain aligned by and between two holding elements of the support part 12b of the generating device. More specifically, this alignment is such that the permanent magnets 120 are arranged with respect to each other according to the so-called Halbach configuration. Such a configuration is known to make it possible to generate a stronger static magnetic field in one direction perpendicular to the alignment than in another direction perpendicular to the alignment, as illustrated in FIG. 8.

[0096] The arrangement of the alignment on the support part correlates with the intended arrangement of the generating device in the housing 101 of that sector. More specifically, the generating device is arranged in its housing 101 such that the side on which the alignment of the permanent magnets generates a stronger static magnetic field is located directly opposite, and preferably in contact with, the longitudinal wall of the sector 100 that is oriented towards the interior space of the cold cage 10.

[0097] In the permanent magnets as exemplified herein above, the magnetic field generated by Halbach alignment has a maximum density at 2 mm substantially equal to 0.6 T and a maximum density at 12 mm substantially equal to 0.1 T.

[0098] Thus, particularly with this particular arrangement, the generating device is configured to generate a static magnetic field having sufficient density to be felt by the molten charge 20 in the cold cage 10, and more specifically across at least the electromagnetic skin thickness 21 of the molten charge in the cold cage.

[0099] More specifically, the static magnetic field generated by the generating device is such that at a distance substantially greater than 2 mm from the edge of the cold cage 10 directed inward, it has a density substantially greater than 0.02 T, preferably substantially greater than 0.05 T.

[0100] Alternatively or complementary, the static magnetic field generated by the generating device is such that at a distance substantially comprised between 0.1 and 12 mm from one of the edges of the generating device directed towards the inside of the cold cage 10, the static magnetic field has a density substantially comprised between 0.07 and 0.8 T. Preferably, the static magnetic field generated by the generating device is such that at a distance substantially comprised between 4 and 10 mm from one of the edges of the generating device directed towards the inside of the cold cage 10, the static magnetic field has a density substantially comprised between 0.1 and 0.3 T.

[0101] A multiphysics digital model has been developed that makes it possible to show the effectiveness of the cold crucible 1' according to a preferred embodiment of the invention. In Fig. 10 it is shown that the use of permanent magnets 120 in the sector 100 significantly modifies the flow of the molten charge 20 (in the simulation the material is brought to a temperature substantially equal to 1690 ° C) in the cold crucible 1'. This modification leads to a strong deceleration of the stirring vortices in the area of ​​the molten charge 20 closest to the cold crucible 1' and even a reversal of the stirring vortices, which use a rotation direction more favorable for the growth of a single crystal from a seed 23 than in the case of a conventional cold crucible (Fig. 9).

[0102] The cold crucible 1' according to the invention therefore makes it possible, on the one hand, to slow down the stirring that would be observed in a conventional cold crucible and, on the other hand, to reverse the direction of recirculation of the vortex induced in the molten charge 20.

[0103] The use of a "magnetic" cold crucible according to a preferred embodiment of the invention makes it possible to promote the growth of single crystals of larger size compared to conventional cold crucibles, in particular due to the synergistic effect of the two aforementioned technical effects. More specifically, the use of a "magnetic" cold crucible according to a preferred embodiment of the invention makes it possible to promote the growth of single crystals having a diameter larger than that of the seed starting the growth and of a better quality than that obtained by techniques implementing a hot crucible.

[0104] Another advantage associated with the use of a "magnetic" cold crucible according to a preferred embodiment of the present invention is seen when considering a charge consisting of different materials characterized by differences in magnetic susceptibility from one another. For example, such a charge may include ferromagnetic, paramagnetic, or diamagnetic materials. A "magnetic" cold crucible according to a preferred embodiment of the present invention may enable selective sorting of these materials due to the presence of a static magnetic field gradient that extends to the inside of the molten charge 20.

[0105] Other advantages may be achieved through the use of the cold crucible 1' according to a preferred embodiment of the invention, in particular by integrating within the housing 101 sectors not occupied by the generating device and / or making it possible to accommodate at least one of the other (multi)functionalized devices previously described.

[0106] Other advantages may also be achieved through the use of a cold crucible 1' according to a preferred embodiment of the invention, in particular by the arrangement of the sectors 100 housing the generating devices relative to one another. In practice, these sectors 100 may be arranged in one of the following ways: - only two sectors opposite each other house functionalization devices. Only three sectors, which are arranged substantially according to third order rotational symmetry, accommodate functionalization devices. Only four sectors, which are arranged substantially according to a fourth order rotational symmetry, accommodate functionalization devices. one sector of the two adjacent sectors houses a functionalization device; - Each sector houses a generator device.

[0107] Besides the production of oxide single crystals such as sapphire, the cold crucible 1' according to a preferred embodiment of the invention makes it possible to produce large-sized and in particular large-diameter single crystal silicon ingots, in particular for applications in the power electronics sector.

[0108] The present invention is not limited to the embodiments described above, but extends to all embodiments covered by the claims.

[0109] In particular, each generating device is not limited to its embodiment including at least one permanent magnet. Indeed, it is conceivable that the field may be electromagnetic and generated by at least one electromagnet, for example, although this is not preferred, in particular due to the difficulties in electrical connections. It is understood that the electromagnetic field generated by the generating device in the cold crucible 1' according to the preferred embodiment of the invention is not necessarily limited to a static magnetic field, in particular the electromagnetic field generated by the generating device may be a quasi-static magnetic field, by the fact that the supply current of such an electromagnet may vary over time, thereby varying the magnetic field generated by this electromagnet.

[0110] Furthermore, the shape of the sectors is not limited to the substantially parallelepiped shape depicted in Figures 3 to 7, but any shape that allows the sectors 100, when fastened and held together, to form a substantial part, and possibly the entirety, of the cold cage 10. For example, each sector may be substantially shaped like a petal and, together with the other sectors, form the cold cage in a manner similar to the formation of a corolla by the petals of a flower. [Explanation of symbols]

[0111] 1. Cold Crucible 1' Cold Crucible 2 Coil 5. Insulated housing 10. Cold Cage 11 Cooling Device 12 (Multi)functional devices 12a part 12b Supports, parts, supporting parts 13 Fastening retention devices 14 Gasket, cylinder head gasket 20 Charge, molten charge 21 Skin thickness, skin 22 Materials, single crystal ingots, single crystals 23 seeds 100 sectors, segments 101 (Multi)functional Housing 120 Device, Generating Device, Permanent Magnet 130 Device, fastening holding device, base

Claims

1. a so-called cold cage (10), comprising a number of sectors (100) made of a material having good electrical conductivity, typically copper, into which the charge (20) to be melted is intended to be introduced; a cooling device (11) containing a heat transfer fluid, typically water, configured to cool each segment (100) of said cold cage (10) from the inside; In a cold crucible (1') equipped with at least one of the sectors (100) of the cold crucible (1') is provided with a so-called functionalized housing (101) and is removable, said functionalized housing (101) being suitable and intended to accommodate therein at least one functionalized device (12, 120) of the cold crucible, The at least one functionalized device (12, 120) comprises: - a device for generating an electromagnetic field; - Ferrite, - complementary heating devices, - Ultrasonic transducers, and - Piezoelectric element A cold crucible (1') characterized by comprising at least one of the following:

2. The cold crucible (1') according to claim 1, wherein the at least one functionalization device (12, 120) comprises, or may consist of, a device for modifying and / or analyzing at least one characteristic of the charge (20) in the cold cage (10), in particular the molten charge (molten charge).

3. A cold crucible (1') as described in claim 1 or 2, further comprising a device (13, 130) for fastening and holding at least one of the removable sectors (100) to at least one of the cooling device (11) and the at least one other sector (100), the fastening and holding device (13, 130) being configured such that when fastened and held, the at least one removable sector (100) forms part of the cold cage (10).

4. A cold crucible (1') as described in any one of claims 1 to 3, wherein the cooling device (11) is configured to enable cooling of the cold cage and comprises a circulation channel for the heat transfer fluid extending partially within at least one of the sectors, preferably each sector, and the functionalization housing (101) is in communication with the part of the circulation channel extending within the sector, whereby the at least one functionalization device (12, 120) is in turn cooled by the cooling device (11) of the cold crucible (1').

5. A cold crucible (1') according to any one of claims 1 to 4, wherein the functionalization device (12, 120) is based on a material which is a poor electrical conductor compared to the base material of the sectors (100), typically copper.

6. The cold crucible (1') according to any one of claims 1 to 5, wherein the functionalization device (12, 120) may be arranged together with a support (12b) configured to accommodate the at least one functionalization device (12, 120) in the functionalization housing (101).

7. Cold crucible (1') according to claim 6, wherein the support (12b) is based on a material which is a poorer electrical conductor than the base material of the sectors, typically copper.

8. A cold crucible (1') according to claim 6 or 7, wherein the support (12b) electrically insulates the functionalization device (12, 120) from that one of the sectors (100) which houses the functionalization device (12, 120) therebetween.

9. 9. The cold crucible (1') according to any one of claims 1 to 8, wherein the at least one functionalization device (12, 120) comprises an ultrasonic transducer and is configured to characterize the molten charge (20) by measuring the displacement velocity of material therein.

10. 10. The cold crucible (1') according to any one of claims 1 to 9, wherein the at least one functionalization device (12, 120) comprises a piezoelectric element and is configured to introduce a pressure wave into the charge (20), in particular into a molten charge.

11. A cold crucible (1') according to any one of claims 1 to 10, wherein the at least one functionalization device (12, 120) comprises a device (120) for generating an electromagnetic field and is configured to generate an electromagnetic field, preferably a static magnetic field, having a sufficient density to be felt by the molten charge (20) in the cold cage (10) and, more specifically, spanning at least an electromagnetic skin depth (21) of the molten charge in the cold cage.

12. The cold crucible (1') according to claim 11, wherein the generating device (120) comprises at least one permanent magnet.

13. Sector(100) is - only two of said sectors, opposite each other, contain functionalization devices (12, 120); - only three of said sectors, arranged substantially according to third order rotational symmetry, contain functionalization devices (12, 120); - only four of said sectors, arranged substantially according to a fourth order rotational symmetry, contain functionalization devices (12, 120); - one sector of the two adjacent sectors contains a functionalization device (12, 120), and - each sector houses a functionalization device (12, 120); A cold crucible (1') according to any one of claims 1 to 12, configured in one of the following ways:

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