Crucible for growing crystals

Abstract

The invention relates to a crucible (1) for growing crystals, comprising a crucible lid (2) and a crucible bottom (3), and a crucible wall (4), which extends with respect to a longitudinal central axis (L) of the crucible (1), a growth chamber (5) within the crucible wall (4) being delimited by the crucible lid (2) and the crucible bottom (3). The crucible also comprises a crystal holder (6), which is arranged in an upper region of the crucible (1) and is provided for receiving at least one seed crystal (7). At least one heat-conductive element (13) is arranged between the crystal holder (6) and the crucible lid (2), and at least one cavity (H) is formed between the heat-conductive element (13) and the seed crystal (7) to be received.

Description

[0001] Crucibles for growing crystals

[0002] The invention relates to a crucible for growing crystals, in particular SiC crystals, comprising a crucible lid and a crucible base, as well as a crucible wall extending along a longitudinal central axis of the crucible, and wherein a growth chamber is defined within the crucible wall by means of the crucible lid and the crucible base. Furthermore, the crucible comprises a crystal holder arranged in an upper region of the crucible and designed or provided to receive at least one seed crystal. The crucible is designed to receive starting material intended for deposition on the seed crystal in a growth process.

[0003] JP2007308355 A discloses a device comprising a crucible for growing SiC crystals. A crystal substrate is arranged on the crucible's top surface and a raw material for growing a crystal is accommodated in the bottom region. Furthermore, an upper section of the crucible wall is tapered with respect to its receiving space toward the crucible lid, which is placed on a lower section of the crucible in which the raw material is accommodated. Furthermore, the document discloses controlling the temperature gradient toward the lid, so that it is lower in the region of the crucible lid.

[0004] A disadvantage of such prior art crucibles is that although they have an optimized temperature gradient from the crucible bottom towards the crucible lid, temperature fluctuations and difficult-to-adjust temperature gradients can still occur in the crystal area at the crucible lid, which can lead to stresses in the crystal and a reduction in crystal quality.

[0005] The object of the present invention was to overcome the disadvantages of the prior art and to provide a crucible by means of which a user is able to optimize the heat distribution in the crucible in order to improve the quality of the crystals to be produced.

[0006] This object is achieved by a crucible according to the claims.

[0007] The crucible according to the invention is characterized in that at least one thermally conductive element is arranged between the crystal holder and the crucible lid, wherein at least one cavity is formed between the thermally conductive element and the seed crystal to be accommodated.

[0008] The at least one cavity serves to introduce heat radiation between the thermally conductive element and the seed crystal to be accommodated (in a growth process or operating state of the crucible), thereby enabling improved heat distribution, especially in the area of ​​the crystal to be grown.

[0009] Such a design enables anisotropic thermal conductivity above the crystal to be recorded (during the growth process or operating state). This is primarily influenced by the high thermal conductivity (due to thermal radiation) in the horizontal direction and the low thermal conductivity in the vertical direction.

[0010] Above the seed crystal, a separate (or sealed) area can be formed by the cavity, at least relative to the growth chamber of the crucible. Preferably, the cavity can also be self-contained, and if necessary, this closed cavity can also be gas-tight.

[0011] Geometrically, such a cavity can preferably extend (at least) over the entire crystal, or the receiving area intended for it, in the horizontal (or radial) direction and has a small vertical height.

[0012] The high thermal conductivity in the horizontal direction is achieved by the mentioned thermal radiation in the at least one cavity between the thermally conductive element and the seed crystal (or a holding plate of the crystal), wherein the thermal radiation in the vertical direction (or in the direction of the longitudinal central axis) is hindered by the respective elements, thus realizing the function of a heat spreader.

[0013] Preferably, two cavities can already be formed with a thermally conductive element, namely between the thermally conductive element and the crystal, and between the thermally conductive element and the crucible lid. Thus, the thermally conductive element can be arranged at a distance from both the crucible lid and the seed crystal. By means of such a configuration, the function of the heat spreader can already be provided in multiple ways. Thus, by means of the thermally conductive element (spaced from the crucible lid), two cavities arranged one above the other can be formed, which are separated from each other by the thermally conductive element. The two cavities formed can have the same or different heights.

[0014] The diameter of the cavity can be approximately equal to the diameter of the crystal to be accommodated, but preferably also at least slightly larger, e.g., approximately 101%-105% of the crystal diameter. Furthermore, it is also conceivable to design the cavity with a diameter significantly larger than the crystal diameter.

[0015] In order to generate a significant thermal radiation-driven anisotropy, it may prove advantageous if the at least one cavity has a ratio of a vertical height to a horizontal width of at least 1:10. The vertical height of the cavity may preferably correspond to 1%-10% of its horizontal width (or diameter), in particular 2%-6%.

[0016] The inventive design makes it possible to influence a horizontal temperature gradient on the crystal, or to create a particularly uniform one. This allows, on the one hand, a radial temperature distribution across a cross-section of the crystal in the direction of the longitudinal central axis to be improved, and, on the other hand, the temperature on the rear side of the crystal can be adjusted and maintained more effectively using simple means, thus also making it easier to prevent temperature fluctuations.

[0017] Furthermore, it should be mentioned that the at least one cavity can be limited at its end facing the crucible bottom by the crystal itself to be held (or a holding plate of the crystal), so that this cavity is only created when the crystal is in an inserted state.

[0018] The thermally conductive element can have different geometric shapes which are suitable for forming such a cavity above the crystal; preferably, these can be plate-shaped.

[0019] Furthermore, the crucible wall can be thinner (at least) in the area of ​​the thermally conductive element. For example, when using an inductive heating device, an element forming the cavity can thus be heated more easily.

[0020] Furthermore, the cavity can have a reflective layer that reflects thermal radiation. A reflective layer can be applied to the thermally conductive element; the reflective layer can also have a surface modification that influences the reflective properties of the layer. The reflective layer can be arranged on the radial walls of the cavity.

[0021] According to one possible embodiment, the crystal holder is designed in the form of a hollow cylindrical element with respect to the longitudinal central axis and has a radial shoulder in the direction of the longitudinal central axis for receiving the seed crystal. This embodiment makes it possible to form a likewise cylindrical cavity within the crystal holder, so that such a heat spreader can be implemented particularly easily with regard to the geometric shape of the cavity. Furthermore, the individual elements required for this purpose, as well as the seed crystal, can be easily inserted along the longitudinal central axis in the form of a modular structure, or can be separated from one another again after the process, thus enabling easy replacement of individual components due to wear and tear, as well as reuse of the crucible.For the sake of completeness, it should be mentioned that an inner diameter of the hollow cylindrical element is preferably dimensioned in such a way that it is suitable for the formation of the cavities.

[0022] A preferred embodiment provides for the at least one thermally conductive element to be accommodated in the crystal holder. In this regard, an arrangement for accommodating the element can be provided in the crystal holder (between the crucible lid and the seed crystal to be accommodated). This ensures a particularly reliable and simple implementation of the cavity formation.

[0023] Alternatively, it can also be provided that the at least one thermally conductive element is formed as a separate element between the crucible lid and the crystal or the crystal holder, or is integrated in the crucible lid.

[0024] An advantageous embodiment provides for a plurality of thermally conductive elements to be arranged one above the other, wherein the thermally conductive elements are arranged at a distance from one another so that at least one further cavity is formed between each of the plurality of thermally conductive elements. Attention should be drawn to the aforementioned thermal conductivity in the horizontal direction, or the thermal radiation in the horizontal direction, as well as a blockage in this regard in the vertical direction. This effect is increased by the formation of a plurality of cavities, or an arrangement of a plurality of thermally conductive elements proportionally increases this effect.

[0025] A preferred embodiment is characterized in that the at least one cavity is cylindrical, in particular cylindrical disc-shaped, in order to effect a particularly uniformly distributed heat radiation.

[0026] Furthermore, to promote thermal radiation (particularly infrared radiation), the outer contours of the cavity can be slightly convex. In the case of a cylindrical or disc-shaped cavity, this can, for example, have a convex base, top, and / or lateral surface.

[0027] In a possible further development, it can be provided that the thermally conductive elements are spaced apart by means of spacer elements, wherein the spacer elements are arranged between the elements. The spacer elements can preferably be annular and have a small wall thickness radial to the longitudinal central axis. By means of spacer elements, it is possible, among other things, to construct the cavity(ies) in a variable manner with regard to a modular design, so that different, predefined spacings are possible by means of the spacer elements. Furthermore, the spacer elements themselves can also form part of the thermally conductive element, for example by being shaped as an axial shoulder on the thermally conductive element. The spacer elements preferably form a wall or lateral boundary of the cavity in the radial direction.

[0028] According to one possible embodiment, it can be provided that the at least one thermally conductive element is spaced apart by means of a receiving arrangement, wherein a receiving diameter of the receiving arrangement for receiving the element is designed to decrease radially to the longitudinal center axis, starting from the crucible lid and moving toward the crucible bottom. For example, a funnel-shaped receiving arrangement can be provided, by means of which thermally conductive elements of different sizes can be accommodated, so that the cavities are formed with respect to their geometric relationships with the receiving arrangement. Thus, when multiple thermally conductive elements are used, these elements have different dimensions from one another.

[0029] In a possible refinement, the crystal holder can be provided with a fastening section, wherein the crystal holder is axially accommodated between the crucible wall and the crucible lid by means of the fastening section, in particular mounted on the crucible wall (in a load-transmitting manner). Such a configuration enables particularly simple and stable mounting of the crystal holder in the crucible, as well as any thermally conductive element accommodated therein.

[0030] An advantageous embodiment provides that the at least one thermally conductive element is formed from a material which corresponds to a material of the crucible.

[0031] Furthermore, it can be provided that the at least one thermally conductive element is formed from a material that corresponds to the material of the seed crystal to be accommodated. This can be particularly advantageous, especially for plate-shaped thermally conductive elements or similar geometries, if, for example, scrap material from crystal growth processes, as well as damaged crystal plates or the like, can be used for this purpose, thus enabling a particularly ecological and economical recycling of materials.

[0032] According to one possible embodiment, the at least one thermally conductive element can have an opening in the region of the longitudinal center axis. This can, for example, create a viewing opening for a measuring device or the like, through which opening a rear side of the seed crystal is accessible to the measuring device.

[0033] Preferably, it can be provided that the at least one thermally conductive element has a diameter transverse to the longitudinal central axis which is greater than or equal to a crystal diameter of the seed crystal to be accommodated

[0034] A possible refinement provides that the at least one thermally conductive element has a varying cross-section in the radial direction (above or, if appropriate, below the cavity in the case of multiple elements). Preferably, the thickness of the thermally conductive element decreases in the direction, starting from an outer region, toward the longitudinal central axis or a center of the element. As previously mentioned, a cavity surface can be convex, whereby, for example, the thermally conductive element can have a concave shape.

[0035] In other words, the height of the cavity can be designed to increase in the radial direction, starting from the lateral edge regions of the cavity, toward the longitudinal central axis or cavity center. However, the width of the cavity can also be designed to increase vertically toward the cavity center. Furthermore, the cross-sectional geometry of the cavity can be designed with respect to its delimiting walls such that the walls are concave toward the cavity.

[0036] For a better understanding of the invention, it is explained in more detail using the following figures.

[0037] They show in a highly simplified, schematic representation:

[0038] Fig. 1 A device for producing crystals with a crucible accommodated therein;

[0039] Fig. 2 shows an embodiment of a crucible according to the invention;

[0040] Fig. 3 is a detailed view of the crucible according to Fig. 2;

[0041] Fig. 4 shows a possible arrangement of the thermally conductive elements;

[0042] Fig. 5 shows a possible embodiment of a crystal holder;

[0043] Fig. 6 the crystal holder according to Fig. 5 in plan view;

[0044] Fig. 7 shows another possible design of the crystal holder;

[0045] Fig. 8 a) to c) possible embodiments of a thermally conductive element;

[0046] Fig. 9 shows another possible arrangement of a thermally conductive element;

[0047] Fig. 10 shows another embodiment of a thermally conductive element.

[0048] By way of introduction, it should be noted that in the variously described embodiments, identical parts are provided with identical reference symbols or component designations. The disclosures contained throughout the description can be applied analogously to identical parts with identical reference symbols or component designations. Furthermore, the positional information chosen in the description, such as top, bottom, side, etc., refers to the directly described and illustrated figure, and these positional information must be applied analogously to the new position in the event of a change in position.

[0049] Fig. 1 shows a device for producing single crystals by means of vapor deposition. The device 9 comprises an evacuable chamber 10, with a crucible 1 according to the preamble accommodated therein (whereby a crucible according to the invention can also be accommodated therein in this way). An underside of the crucible lid 2 can form a crystal holder 6 of the crucible 1 and is designed to attach (at least) one seed crystal 7. In a bottom region of the crucible 1, delimited by the crucible wall 4 and the crucible bottom 3, there is a starting material 8, which is intended for crystal growth on the seed crystal 7 and is used up during the growth or breeding process.

[0050] The transition of the starting material into the gas phase is achieved by heating it using at least one heater 11. According to this exemplary embodiment, the heating of the starting material 8 and the crucible 1 by the heater 11 occurs inductively. The crucible 1 arranged in the chamber 10 can also be enclosed by insulation 12 for thermal insulation. The insulation 12 simultaneously prevents heat loss from the crucible 1 and achieves a heat distribution in the interior of the crucible 1 that is favorable for the crystal growth process on the seed crystal 7.

[0051] The material for the chamber 10 is preferably a glass material, in particular quartz glass. The crucible 1 and the insulation 12 surrounding it are preferably made of graphite, with the insulation 12 being formed by a graphite felt or the like.

[0052] When the starting material 8 is heated, its atoms or molecules pass into the gas phase. They can diffuse into the interior of the crucible 1 via the gas phase and deposit on the seed crystal 7, thereby causing crystal growth. The aim is to form a single crystal that is as free of defects as possible. The quality of the crystal forming on the seed crystal 7 depends predominantly on the temperature gradient between the starting material 8 and the seed crystal 7, and also, among other things, on the evaporation rate of the starting material 8. The latter, in turn, depends on the form in which the starting material 8 is made available in the crucible 1. It can prove advantageous if the starting material 8 is formed from a mixture of a powdered raw material and a raw material in the form of lumps.Alternatively, this can also be in the form of particles (especially silicon carbide) with a very limited size distribution.

[0053] Fig. 2 shows a possible embodiment of a crucible 1 according to the invention, which is preferably used for growing SiC crystals.

[0054] This comprises a crucible lid 2, a crucible base 3, and a crucible wall 4, wherein the crucible wall 4 extends with respect to a longitudinal central axis L of the crucible 1 and a growth chamber 5 is delimited within the crucible wall 4 by means of the crucible lid 2 and the crucible base 3. In an upper region of the crucible 1, a crystal holder 6 is arranged, which is intended to hold at least one seed crystal 7. As shown, the crystal holder 6 can also form a separate component of the crucible 1, but can also be a part of the crucible lid 2 or the crucible wall 4. As known from the prior art, the crystal holder 6 can, for example, merely form a holding area for the crystal in the crucible.

[0055] At least one thermally conductive element 13 is provided along the longitudinal central axis between the crystal holder 6 and the crucible lid 2, wherein at least one cavity H is formed between the thermally conductive element 13 and the seed crystal 7 to be accommodated.

[0056] The thermally conductive element 13 can also be arranged at a distance from both the crucible lid 2 and the seed crystal 7 to be accommodated in the crystal holder 6, as shown.

[0057] The at least one thermally conductive element 13 serves to form the cavity H and the associated optimization of the horizontal temperature gradient Th in the region of the crucible lid 2, thus enabling improved temperature distribution in the radial direction and optimally controlling the temperature distribution above the seed crystal 7. The high thermal conductivity is achieved by thermal radiation in these regions; reference is made to the explanations mentioned above in this regard. In the case of inductive heating, the heat input introduced purely by means of the heater would approach zero toward the center of the crucible, so that the thermal radiation to be utilized represents a significant factor in achieving better process conditions and increasing the quality of the crystals to be produced.

[0058] With regard to thermal radiation, reflective layers 30 can preferably be arranged in the (radial) edge regions of the thermally conductive elements 13, e.g., on the inner wall of the crystal holder, as indicated by dashed lines. Depending on its shape, the thermally conductive element can also have such a layer, e.g., if it is cup-shaped or similar and thus has a radial inner wall to form the cavity.

[0059] For example, a reflective layer 30 can be arranged on all components located in the crucible 1, facing the cavity H with respect to the radial extent of the latter, depending on the shape in which the cavity is formed in the crucible.

[0060] Furthermore, insulating layers 31 can also be arranged facing away from the cavity, as is also indicated by dashed lines.

[0061] Furthermore, regardless of the embodiment shown, at least one of the walls defining or forming the cavity H may have a concave curvature or a type of roof shape, so that the heat rays can be better guided or reflected by the respective wall toward the center of the cavity H or toward the longitudinal center axis L. In other words, the cavity may have a slightly convex shape or the like in at least one region. Preferably, the (inner) walls facing the cavity may also be polished or modified to improve their reflective properties.

[0062] As can be seen in Fig. 2, the thermally conductive element 13 can be designed, for example, in the form of a plate and, if necessary, can be disc-shaped.

[0063] As indicated, the crucible lid 2 can have a recess 24 in the region of the longitudinal center axis E, by means of which, for example, an opening for measuring the temperature inside the crucible 1 in the region of the seed crystal 7 is possible.

[0064] The at least one thermally conductive element 13 is preferably arranged parallel to the seed crystal 7 to be accommodated and / or the crucible lid 2 (or preferably perpendicular to the longitudinal central axis L), and extends at least radially over the seed crystal and can thus have a diameter that is equal to or greater than the crystal diameter. Regarding the spacing of the element 13 from the seed crystal 7 (or a holding plate) at a distance 26, different measures can be provided, which will be discussed in more detail later. The distance 26 thus preferably determines the height h of the cavity H.

[0065] As mentioned above, a vertical height h of the cavity H can preferably correspond to 1%-10% of a horizontal width b (or diameter b) of the cavity H, in particular 2%-6%. For example, with crystal diameters of approximately 200 mm, the cavity width b can also be approximately 200 mm, or, as mentioned above, preferably more, wherein a height h can be approximately 2-20 mm, in particular 4-12 mm, depending on the ratio to the specified width.

[0066] The seed crystal 7 can preferably be secured to a holding plate 22 with respect to its receptacle in the crucible 1, which plate corresponds to the properties of the seed crystal 7 in terms of thermal conductivity and thermal expansion coefficient, or has only minor differences compared to the crystal. The holding plate is preferably made of a similar material or a lower-quality material to the seed crystal 7, e.g., SiC, and can be connected to the seed crystal 7 by means of gluing, clamping, bonding, or the like.

[0067] Furthermore, it turns out to be advantageous if the holding plate is equipped with a base with the same diameter as the seed crystal and the seed crystal is thus located lower in the assembly than the rest of the holding arrangement or the crystal holder.

[0068] As shown, the crystal holder 6 can preferably be designed in the form of a hollow cylindrical element with respect to the longitudinal central axis L and, at an end facing away from the crucible lid, can have a radial shoulder 14 in the direction of the longitudinal central axis L for receiving the seed crystal 7. The seed crystal 7 or the holding plate can be mounted in the crystal holder 6 by means of the radial shoulder, which shoulder forms a crystal receiving section 18 of the crystal holder 6. As also shown, the holding plate 22 and the seed crystal 7 are preferably dimensioned such that they have play with respect to their degrees of freedom in the radial direction relative to the crystal holder 6, so that they can expand with respect to their thermal expansion in the direction of the crystal holder 6 and thus also avoid stresses that would be caused by a radial limitation.

[0069] The thermally conductive element 13 itself can be formed from the material of the crucible 1, e.g., graphite, or from the material of the seed crystal 7 to be accommodated. For example, such thermally conductive elements 13 can be manufactured using cuttings or scrap material from the seed crystals from growth or manufacturing processes. The thermally conductive element 13 can also have radial play with respect to its mounting.

[0070] With regard to its arrangement in the crucible 1, the crystal holder 6 can have a fastening section 19, by means of which the crystal holder 6 can be inserted into the crucible 1. As shown in Fig. 2, the crystal holder 6 can be fastened or inserted between the crucible lid 2 and the crucible wall 4 by means of the fastening section 19. The fastening section 19 can be formed in the form of a radial shoulder which extends away from the longitudinal central axis L. Preferably, the fastening section 19 can extend radially up to the outer dimensions of the crucible 1 and thus be flush with the crucible wall 4 and / or the crucible lid 2. Alternatively, the fastening section 19 can also be received within the crucible wall 4 by means of a shoulder or the like, or such a receiving element can also be provided on the crucible lid 2.Preferably, an upper end of the crystal holder can be formed by means of the fastening section.

[0071] Furthermore, the crystal holder 6 can preferably have a spacing section 20, by means of which the crystal receiving section 18 of the crystal holder 6 is arranged at a distance 23 from the crucible lid 2, wherein the at least one thermally conductive element 13 is preferably arranged within this spacing section 20. Alternatively, the crucible lid 2 can also have such a shoulder, so that a corresponding distance for receiving the thermally conductive element(s) 13 is formed between the crucible lid 2 and the crystal receiving section 18 in the axial direction.

[0072] Furthermore, Fig. 2 shows a possible arrangement of the starting material 8 in the crucible 1, which is delimited by a porous or permeable cone towards the longitudinal central axis L, thereby promoting gas circulation towards the centre of the crucible or in this region. Furthermore, a cover element can be arranged above the starting material. As can also be seen from Fig. 2, regardless of the design of the thermally conductive element 13, the wall thickness of the crucible 1 in a region of the crystal holder 6 can be selected to be smaller than a wall thickness in the receiving region for the starting material 8. For example, a first wall thickness, which is arranged closer to the crucible lid 2, can be selected to be smaller than at least a second wall thickness of the crucible wall 4 formed in the direction of the crucible bottom. Preferably, the smaller wall thickness can extend along the longitudinal central axis L from an upper end of the crucible wall 4 (orfrom the crucible lid) at least up to the seed crystal to be accommodated. As can also be seen, a transition region between the wall thicknesses can be conical.

[0073] By designing the wall thicknesses in this way, heating in this area using a heating device can be specifically influenced by the wall thickness. This is particularly useful in combination with a hollow-cylindrical crystal holder, so that, for example, the hollow-cylindrical wall is specifically heated with an inductive heater.

[0074] Preferably, such a wall thickness and a wall thickness of the hollow cylindrical body can be selected such that together they approximately correspond to the lower wall thickness of the crucible or are smaller than this.

[0075] Preferably, it can be provided that a plurality of thermally conductive elements 13 are arranged one above the other with respect to the longitudinal center axis L, wherein the thermally conductive elements 13 are arranged at a distance from one another. In this regard, Fig. 3 shows a detail of the crucible 1 according to Fig. 2, wherein a plurality of thermally conductive elements 13 are arranged between the seed crystal 7 to be accommodated in the crystal holder 6 and the crucible lid 2, each at a distance 27 from one another, wherein such a distance 27 preferably corresponds to a height of the respective cavity H. Thus, cavities H1 and H2 are also formed between the further thermally conductive elements 13.

[0076] To space the respective elements 13 apart, spacer elements 15 can be arranged between the elements 13 in one possible form, said spacer elements 15 preferably being annular. In one possible embodiment, the spacer elements 15 can be inserted in the axial direction, and the thermally conductive elements 13 can be placed on the respective spacer elements 15. Furthermore, the lowermost spacer element 15 can be placed on the back of the seed crystal or the holding plate, so that the latter is additionally fixed in place by the weight of the spacer elements and the element(s). The distances 27 between the elements can vary or can also preferably be uniform. As mentioned at the beginning, it can also be provided that the thermally conductive element 13 encompasses the spacer element 15 by forming the spacer element 15 as a shoulder or the like on the thermally conductive element 13.

[0077] Regardless of the embodiment shown, it can be provided that the spacer elements 15 have a layer 30 that reflects heat radiation facing the cavity H. Furthermore, these can also have a previously mentioned concave curvature with respect to their inner surfaces, so that, for example, the thickness of the spacer elements can vary in a direction parallel to the longitudinal center axis. Furthermore, the spacer elements themselves can be formed from such a material, or from a material corresponding to the thermally conductive elements.

[0078] Furthermore, the thermally conductive elements 13 can each have an opening 21 in the region of the longitudinal central axis L, by means of which openings 21 a continuous opening is formed from the crucible lid 2 to the end face of the seed crystal 7 (or the holding plate 22) facing the crucible lid 2. The openings 21 can preferably be formed concentrically to the longitudinal central axis. As indicated by dashed lines, the holding plate 22 of the seed crystal 7 can also have such an opening. The opening 21 can be made as small as possible so that only one beam path of an optical measurement is possible through it. When forming an opening 21, it can be provided that the cavities H have an opening but are separated from the growth chamber.

[0079] Furthermore, in an embodiment not shown, the holding plate 22 can be pot-shaped, so that a thermally conductive element 13 is distanced from the seed crystal by means of the holding plate and a cavity is formed by means of the pot shape.

[0080] Furthermore, the thermally conductive element 13 can be spaced apart by means of a receiving arrangement 16 to form the cavity H, wherein a receiving diameter 17 of the receiving arrangement 16 is designed to decrease radially to the longitudinal center axis L, starting from the crucible lid 2 in the direction of the crucible bottom 3, as shown in Fig. 4. The respective spacing of the element 13 with respect to the seed crystal 7 and the crucible lid 2 takes place on the one hand by means of the tapering of the receiving diameter 17 and on the other hand by means of the mounting of the element 13 in the receiving arrangement 16 by means of gravity, wherein the element 13 has a predetermined diameter in this regard. When arranging a plurality of elements 13, elements with different diameters can thus be used. Thus, the diameters of the elements and also of the seed crystal (with the holding plate) can preferably become smaller in the axial direction, starting from the crucible lid in the direction of the crucible bottom.

[0081] The receiving arrangement 16 can, as shown in Fig. 4, be designed to taper conically with respect to the reception of the elements, or can be designed to be inclined in the direction of the crucible bottom relative to the longitudinal central axis L. The elements 13 can also have a complementary bevel on their outer surface with respect to this geometric shape. However, the receiving arrangement 16 can also be designed in a stepped manner, as indicated by the dashed lines, so that individual steps are provided for receiving the thermally conductive elements 13.

[0082] With regard to such an embodiment, it should be noted that the lowest cavity H, closest to the crystal, has the aforementioned height and width with respect to its geometric dimensions, and the elements or cavities above it have larger widths with respect to the preferably constant heights, depending on the inclination, and thus become proportionally larger with respect to their horizontal dimensions, but preferably remain constant with respect to their vertical dimensions. Depending on the embodiment of the receiving arrangement, the width of a cavity itself can thus also increase towards the crucible lid.

[0083] The entire receiving arrangement 16 can form part of the crystal holder 6, in particular the spacing section, or can also be formed by means of a separate component of the crucible and arranged between the crystal holder and the crucible lid, or can also be formed or molded into the crucible lid. Furthermore, the receiving arrangement 16 can also have a reflective layer 30 facing the cavity H.

[0084] 5 and 6 show further possible embodiments of the crucible 1 for receiving the elements 13, in which the crystal holder 6 (or a receiving arrangement 16) consists of at least two segments 28 which are joined together in the radial direction. As indicated by dashed lines in Fig. 5, the crucible lid 2 can also be designed in this way and be formed integrally with the segments 28 of the crystal holder 6. As also shown, the spacer elements 15 for spacing the elements 13 can be formed integrally with the crystal holder 6 or with a receiving arrangement. In addition, the spacer elements 15 can be spaced from one another according to a height of the elements, so that the elements are touched on both sides (axially) by the spacer elements.

[0085] With regard to the joining of the segments 28, these may have overlapping or complementary engagement elements or the like, as indicated in Fig. 5 and Fig. 6. With such a design of the crucible lid or the reception of the elements by means of segments, it should be noted for the sake of completeness that the crystal holder may also have other geometric shapes as previously described.

[0086] Furthermore, it can be provided that the spacer elements 15 are omitted and instead of them the thermally conductive elements 13 are formed in one piece with the crystal holder, or the (hollow cylindrical) crystal holder 6 itself can form or encompass the thermally conductive element(s) 13.

[0087] Fig. 7 shows another possible embodiment of the crucible 1, in which the crystal holder 6 is arranged and fastened in the crucible lid 2. In this embodiment, the crucible lid 2 can have an internal thread or a receiving groove in the form of a slotted slot or the like, so that the crystal holder 6 with the seed crystal 7 and thermally conductive element(s) 13 received therein is either screwed in or inserted axially from below and then rotated for fixation. With respect to an internal thread, the crystal holder would have an external thread, and with respect to a receiving groove, a partially arranged annular web or the like, with which the fastening section of the crystal holder would be inserted in the crucible lid.

[0088] Furthermore, in a variant not shown, the crucible lid can also be designed in several parts, so that the crystal holder can be inserted from above into an opening in the crucible lid and the crucible lid is then closed.

[0089] As can be seen from Fig. 8 a) and b), it can be provided that the thermally conductive elements 13 have a varying cross-section in the radial direction (e.g., above the formed cavity). In this regard, a thickness 29 of the element can be designed to decrease, starting from a radially outer region (or a lateral surface) of the element towards a center of the element, wherein the elements are preferably arranged in the crucible such that the thermal radiation within the cavity can be transmitted towards the center of the thermally conductive element by means of the inner surfaces facing the cavity. As can be seen in Fig. 8a, the thermally conductive element 13 can have a concave surface 32 facing the cavity, as indicated by the radius of curvature R, whereby a thickness 29 can be designed to decrease. Furthermore, the opposite surface can also be concave, as indicated by the dashed line, if, for example,by means of which another cavity is defined.

[0090] As can be seen from Fig. 8b, such a surface 32 can also be designed to run obliquely or inclined, so that the cavity becomes uniformly larger towards the center of the element 13.

[0091] Furthermore, with regard to a targeted conduction of the heat radiation, it can also be provided that further surface modifications can be provided with regard to the inner surfaces facing the cavity, e.g. grooves or partially formed inclined surfaces, etc., as well as a polished surface.

[0092] As mentioned at the beginning, the cavity H can thus be convex on at least one of its defining or enveloping surfaces, or, as indicated in Fig. 8c, can be convex on each of these surfaces.

[0093] In this regard, Fig. 8c shows a possible embodiment or arrangement of one or more thermally conductive elements 13 for forming a cavity H, in which all walls delimiting or forming the cavity H, facing the cavity, have concave shapes.

[0094] As mentioned at the beginning, a height h of the cavity H can be formed increasing in the radial direction, starting from the lateral edge regions of the cavity H, in the direction of the longitudinal central axis E.

[0095] As also indicated, a width b of the cavity H can also be increasingly formed along the longitudinal central axis towards the center of the cavity.

[0096] In this case, a single thermally conductive element 13 can be provided, which encloses or forms the at least one cavity H, or several thermally conductive elements can be provided, by means of whose arrangement a cavity H is formed, as indicated by dashed lines. At this point, with regard to the different possible arrangements of thermally conductive elements for forming a cavity, reference should be made to the possible embodiments illustrated in the other figures.

[0097] According to a further possible embodiment, it can be provided that the crucible lid 2 has a receiving arrangement 16 for receiving the thermally conductive elements 13 - as shown in Fig. 9, wherein the receiving arrangement 16 can have an internal thread or the like for receiving the thermally conductive elements 13, so that they can be screwed into the receiving arrangement 16, so that a height h of a respective cavity H can be adjusted by means of a screw-in depth.

[0098] Fig. 10 shows a further possible embodiment of a thermally conductive element 13, in which the thermally conductive element 13 comprises at least one cavity H, or, as shown, can comprise several cavities.

[0099] Furthermore, the thermally conductive element 13 can be designed as a separate component of the crucible that can be inserted between the crucible wall and the crucible lid, as shown, or can also be designed, for example, as a single piece with the crucible lid 2. A further cavity can also be formed between the thermally conductive element 13 and the crucible lid 2, preferably at least radially in a region above the seed crystal 7, as can also be seen in principle in Figures 2 and 3.

[0100] Furthermore, the seed crystal 7 can be attached, e.g., glued, to the underside of another section of the thermally conductive element 13, so that the crystal holder 6 is formed, e.g., by a single surface. It should also be clarified that, in general, a "crystal holder" according to the patent description essentially refers to a predefined receiving area for the seed crystal 7 within the crucible, unless this is more precisely defined geometrically. Furthermore, the thermally conductive element can also replace a previously mentioned holding plate.

[0101] Furthermore, the thermally conductive element 13 can have the aforementioned openings for measuring devices along its longitudinal center axis, as well as any coatings; reference is made to the preceding description in this regard. The exemplary embodiments show possible embodiments. It should be noted at this point that the invention is not limited to the specifically illustrated embodiments; rather, various combinations of the individual embodiments are also possible. This variation possibility, based on the teaching of technical action based on the present invention, lies within the skill of the person skilled in this technical field.

[0102] The scope of protection is determined by the claims. However, the description and drawings must be used to interpret the claims. Individual features or combinations of features from the various embodiments shown and described may represent independent inventive solutions. The problem underlying these independent inventive solutions can be derived from the description.

[0103] All information on value ranges in this description is to be understood as including any and all sub-ranges thereof, e.g. the information 1 to 10 is to be understood as including all sub-ranges starting from the lower limit of 1 and the upper limit of 10, ie all sub-ranges begin with a lower limit of 1 or greater and end with an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

[0104] For the sake of clarity, it should finally be pointed out that, in order to better understand the structure, some elements have been shown out of scale and / or enlarged and / or reduced in size.

[0105] Reference symbol list

[0106] Crucible 31 insulating layer

[0107] Crucible lid 32 Area Crucible bottom Crucible wall L Longitudinal central axis

[0108] Growth chamber Th Temperature gradient horizontal Crystal holder H Cavity Seed crystal h Height

[0109] Starting material b Width of device R Radius of curvature Chamber

[0110] Heating insulation thermally conductive element radial shoulder spacer elements mounting arrangement mounting diameter crystal mounting section fastening section spacing section

[0111] Breakthrough retaining plate distance recess diameter distance distance segments thickness reflective layer

Claims

Patent claims 1. Crucible (1) for growing crystals comprising; - a crucible lid (2) and a crucible bottom (3), and - a crucible wall (4), wherein the crucible wall (4) extends with respect to a longitudinal central axis (L) of the crucible (1) and a growth chamber (5) is delimited within the crucible wall (4) by means of the crucible lid (2) and the crucible bottom (3); - a crystal holder (6), wherein the crystal holder (6) is arranged in an upper region of the crucible (1) and is provided for receiving at least one seed crystal (7); characterized in that at least one thermally conductive element (13) is arranged between the crystal holder (6) and the crucible lid (2), wherein at least one cavity (H) is formed between the thermally conductive element (13) and the seed crystal (7) to be received.

2. Crucible according to (1) claim 1, characterized in that the at least one thermally conductive element (13) is plate-shaped.

3. Crucible (1) according to claim 1 or 2, characterized in that the crystal holder (6) is designed in the form of a hollow cylindrical element with respect to the longitudinal central axis (L) and has a radial shoulder (14) in the direction of the longitudinal central axis (L) for receiving the seed crystal (7).

4. Crucible (1) according to one of claims 1 to 3, characterized in that the at least one thermally conductive element (13) is accommodated in the crystal holder (6).

5. Crucible (1) according to one of claims 1 to 4, characterized in that the cavity (H) is cylindrical, in particular cylindrical disc-shaped.

6. Crucible (1) according to one of claims 1 to 5, characterized in that a plurality of thermally conductive elements (13) are arranged one above the other, wherein the thermally conductive elements (13) are arranged at a distance from one another, so that at least one cavity (H) is formed between the plurality of thermally conductive elements.

7. Crucible (1) according to claim 6, characterized in that the thermally conductive elements (13) are spaced apart by means of (annular) spacer elements (15), wherein the spacer elements (15) are arranged between the thermally conductive elements (13).

8. Crucible (1) according to one of claims 1 to 7, characterized in that the at least one thermally conductive element (13) is spaced apart by means of a receiving arrangement (16) for forming the cavity (H), wherein a receiving diameter (17) of the receiving arrangement (16) for receiving the thermally conductive element (13) is designed to decrease radially to the longitudinal center axis (L), starting from the crucible lid (2) in the direction of the crucible bottom (3).

9. Crucible (1) according to one of claims 1 to 8, characterized in that the crystal holder (6) has a fastening section (19), wherein the crystal holder (6) is received axially between the crucible wall (4) and the crucible lid (2) by means of the fastening section (19).

10. Crucible (1) according to one of claims 1 to 9, characterized in that the at least one thermally conductive element (13) is formed from a material which corresponds to a material of the crucible (1).

11. Crucible (1) according to one of claims 1 to 10, characterized in that the at least one thermally conductive element (13) is formed from a material which corresponds to a material of the seed crystal (7) to be accommodated.

12. Crucible (1) according to one of claims 1 to 11, characterized in that the at least one thermally conductive element (13) has an opening (21) in the region of the longitudinal central axis (L).

13. Crucible (1) according to one of claims 1 to 12, characterized in that the at least one thermally conductive element (13) has a diameter transverse to the longitudinal central axis (L) which is greater than or equal to a crystal diameter of the seed crystal (7) to be accommodated 14. Crucible (1) according to one of claims 1 to 13, characterized in that the at least one thermally conductive element (13) has a decreasing thickness in the radial direction towards the longitudinal central axis (L), so that a height (H) of the cavity increases in the radial direction towards the longitudinal central axis (L).

15. Crucible (1) according to one of claims 1 to 14, characterized in that the at least one cavity (H) extends in a direction transverse to the longitudinal central axis (L) at least over the seed crystal (7) to be accommodated.

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