Crucible for producing a sic volume mono crystal and a method for growing a sic volume mono crystal

Abstract

The present invention relates to a crucible having a cavity for growing a SiC volume mono crystal by sublimation growth in the growth direction (Y). The crucible comprises an end wall (110) having a seed holder (112) for holding a SiC seed crystal in the cavity, the end wall (110) extending in a direction (r) perpendicular to the growth direction (Y); a side wall (140) extending in the growth direction (Y), the side wall (140) preventing a doping gas from penetrating into the cavity from the outside, the doping gas being for doping the SiC volume mono crystal during sublimation growth; and a diffusion region (114) allowing the doping gas to penetrate into the cavity from the outside, the diffusion region (114) being located between the seed holder (112) and the edge (142) of the side wall (140).

Description

Background Technology

[0001] Silicon carbide (SiC), a semiconductor material, is used for high-frequency components and special light-providing semiconductor components, particularly as a starting material for power electronic semiconductor components, due to its excellent physical, chemical, electrical, and optical properties. For example, as discussed in U.S. Patent US 8,747,982 B2, SiC substrates with large substrate diameters (200 mm or more) and high quality are required for these components. SiC volume monocrystalline with large diameter and high quality is the subject of this description.

[0002] At least these objectives are addressed by independent claims. Advantageous embodiments are addressed by dependent claims.

[0003] More specifically, a mono crystal is a material in which the crystal lattice of the entire sample is continuous and unbroken up to the edges of the sample and has no grain boundaries. The absence of defects associated with grain boundaries can provide mono crystals with properties unique to them, particularly mechanical, optical, and electrical properties. These properties are used industrially, especially in technical applications in optical systems and electronic devices.

[0004] Using a suitable source material, SiC volume monocrystals can be grown, for example, by a physical vapor transport (PVT) process, which describes a vacuum deposition method that can be used to produce monocrystals. PVT is characterized by a process in which a material transitions from a condensed phase to a vapor phase (i.e., sublimation phase) and then again to a thin film condensed phase. The material is transported from the source region to the seed region in the vapor phase. The most common PVT processes are sputtering and evaporation. Other details of the PVT process can be found, for example, in U.S. Patent US 8,747,982 B2.

[0005] Disk-shaped monocrystalline SiC substrates are cut from a SiC volume monocrystalline structure, and subsequently, at least one epitaxial layer, which is also composed of SiC, is provided during the fabrication of the components. In subsequent epitaxial processes, thin single-crystal layers (e.g., SiC, GaN) may first be deposited on the SiC substrates. The quality of this epitaxial layer depends critically on the local orientation of the monocrystalline substrate, that is, on the SiC substrate cut from the SiC volume monocrystalline structure. If local deviations from the optimal orientation occur in the crystal structure of the SiC substrate, this can propagate to the epitaxial layer. The epitaxial layer subsequently also harbors local defects, which can ultimately lead to poor properties of the final products, namely the semiconductor components.

[0006] As illustrated in FIG. 9, PVT crystal growth is performed in a crucible (1100). The crucible is a vessel that can be affected by very high temperatures (2000°C or higher) that allow materials, such as SiC, to sublimate. In particular, the crucible is made of a material capable of withstanding temperatures high enough to melt or sublimate its contents.

[0007] As illustrated in FIG. 10, the crucible (1100) is positioned in a tubular vessel (1200) which can be designed as quartz glass (adapted for induction heating described later) or stainless steel (adapted for resistance heating described later) and forms a reactor which is the core of the plant (2000). For example, the crucible is held by stands (1210) arranged in the tubular vessel (1200). The tubular vessel (1200) is a machine used to perform processes that require elevated temperature and pressure relative to ambient pressure and / or temperature.

[0008] The actual crystal growth takes place in a reactor. The growth structure includes an insulator (1300) arranged around a crucible.

[0009] The walls of the crucible may contain materials such as graphite and carbon. These materials allow the crucible to heat SiC to growth temperatures of 2000°C or higher.

[0010] In particular, to grow a SiC volume mono crystal, a SiC seed crystal (1114) is arranged in a seed holder (1112), which is arranged in the end wall (1110) of the crucible before growth begins. More specifically, the SiC seed crystal (1114) is arranged in the crystal growth area (1124) of the growth crucible (1100), which is preferably completely closed, particularly at least during growth.

[0011] Powdered SiC source material is introduced into the SiC storage area (1120) of the growth crucible. At the start of the growth process, the boundary of the SiC storage area (1120) is indicated by a thick dashed line (1122). The boundary is, for example, a wall made of porous graphite. During growth, the powdered SiC source material is sublimated and the sublimated gaseous components are transported to the crystal growth area (1124), that is, along the Y-axis, so that a SiC growth gas phase is produced there, and a SiC volume mono crystal having a central longitudinal axis along the Y-axis is grown by depositing it from the SiC growth gas phase onto a SiC seed crystal (1114).

[0012] To grow a SiC volume monocrystalline structure, a temperature distribution along the Y-axis is realized in the crucible as shown in FIG. 11. In particular, the dashed line (1130) indicates the highest temperature in FIG. 10 and FIG. 11. In particular, the highest temperature is located at the center of the SiC storage area (1120).

[0013] As illustrated in FIG. 10, heating may also be provided by induction coils (1400) located outside the tubular vessel (1200). In particular, the induction coils (1400) have a radius (R) along the radial axis (R). coilThey are arranged along the circumferential direction in ). Alternatively, according to an unillustrated solution, resistance heaters can be located inside the reactor (1200).

[0014] Induction heating is a process of heating electrically conductive materials by electromagnetic induction through a current passing through an inductor (1400) that generates an electromagnetic field within a coil to indirectly heat the SiC in the storage area, thereby directly raising the temperature of the material in the SiC storage area (1120) and / or raising the temperature of the sidewall (1140) of the crucible. The sidewall (1140) of the crucible has a radius (R) along the direction of growth (Y), i.e., the Y-axis. sidewall It extends along the circumferential direction from the ) The insulator (1300) thermally insulates the crucible and the cavity formed inside the crucible.

[0015] The temperature may be measured by one or more unillustrated pyrometers or one or more thermocouples. In particular, the temperature is measured in the chamber formed by the reactor (1200) but outside the crucible. The vacuum-sealed reactor (1200) may be emptied through the outlet (1500) by one or more unillustrated vacuum pumps. Additionally, the system may be supplied with inert and / or doping gases (e.g., nitrogen) through one or more gas supply lines (1600), and the pressure in the system may be measured and controlled by pressure sensors not illustrated.

[0016] Process parameters such as pressure, temperature, and gas flow can be set, controlled, and stored by computerized system control. The plant control system communicates with all related components (e.g., transducers, pyrometers, vacuum control valves, mass flow controllers (MFCs) for supplying doping gases, and pressure sensors).

[0017] As discussed above, SiC single crystals or substrates produced therefrom must have high quality for subsequent epitaxy processes. For this purpose, it will be ensured that doping gases, such as nitrogen, are present as doping gases in the growth space in a controlled manner throughout the entire growth period and can be incorporated into the crystal lattice of the growing SiC single crystal. Uneven doping gas concentration over the growth period and, consequently, uneven incorporation into the single crystal leads to increased scrap during processing of SiC substrates. More specifically, doping gases, such as nitrogen, affect the brittleness of SiC single crystals. Uneven incorporation of doping gases, particularly nitrogen, into the crystal lattice leads to cracks during crystal processing or to wafer scrap due to excessively high values ​​of bending and warping of SiC substrates. As used herein, bending and warping of semiconductor wafers and substrates measure wafer flatness.

[0018] Doping gas can be introduced into the system by two different methods: the use of gas-permeable culture crucibles or gas-impermeable culture crucibles, and thus gas-permeable crucibles are generally used more frequently.

[0019] When using gas permeable growth configurations, gas supply lines for inert gases and dopant gases controlled by MFCs typically lead to the reactor chamber, and a concentration balance exists between the nitrogen content in the reactor chamber and the nitrogen content inside the growth crucible. The following issues exist in this process: Gas permeability and nitrogen diffusion in the crucible vary with temperature. For example, due to temperature-dependent pore expansion in graphite, the concentration in the crucible varies over the duration of growing SiC volume monocrystallines, as growth is typically performed in temperature ramps to compensate for effects such as powder depletion. Growing SiC volume monocrystallines in temperature ramps also leads to varying nitrogen incorporation into the crystal lattice, as this occurs as a function of temperature.

[0020] This has the effect of nitrogen concentrations changing during the growth period leading to crystal cracks and poor geometric values ​​(bending and / or warping), which are the mentioned development reduction factors.

[0021] Considering the above, the problem lies in the uniform and controlled supply of nitrogen to the crystal growth space of the crucible. Due to the increase in crystal diameter (over 200 mm) and the associated increase in the size of the growth configurations, new solution approaches are required to address these issues. At the same time, the PVT process requires vacuum-tight framework conditions for the process conditions and the materials used.

[0022] Existing solutions propose providing a gas-permeable crucible, for example, a crucible made of graphite. The nitrogen content in the reactor is controlled, for example, by an MFC and selectively introduced into the reactor. In this solution, the growth crucible located in the reactor has a specific permeability, allowing nitrogen to diffuse from the reactor into the growth crucible. However, there is no way to control the nitrogen content in the crucible, which generally follows temperature-dependent diffusion laws. Similarly, the incorporation of nitrogen into the SiC crystal lattice (into the growth space of the crucible) follows temperature-dependent laws, and it is not possible to influence the nitrogen incorporation mechanism in any other way. Due to the permeability of the crucible, gaseous components of the source material (Si and C-containing compounds) can also enter the reactor by diffusion following a radial temperature gradient from the crucible. There, they are deposited on, for example, insulators or reactor walls, on colder zones, causing aging and wear.

[0023] Alternatively, gas impermeable crucibles, such as those made entirely of TaC, may be used. In this design, nitrogen must be supplied directly to the gas impermeable crucible, for example, through a pipe, which leads to significantly increased process effort and significantly higher manufacturing costs. Unless the dopant nitrogen is supplied internally via an additional gas supply, it is not possible to produce N-doped SiC crystals used in power electronic devices. Furthermore, it is disadvantageous that process-related impurities present in the crucible (e.g., water, Na, Ca, etc.), for example, enter the crucible while preparing the crucible with source material and seed before placing the crucible in the reactor, and cannot be removed from the system at the start of the process by a bake-out step under vacuum through diffusion through the crucible walls. However, the advantage of this design is that any gaseous components of the source material enter the reactor by diffusion following a radial temperature gradient from the crucible and cannot cause insulation aging or reactor wear.

[0024] The object of the present invention is, in particular, to provide a solution for a crucible that allows for the provision of a doping gas having a constant concentration. In particular, temperature effects caused by temperature ramps will be prevented. Another object is to minimize process complexity by, for example, providing pipes that directly supply nitrogen to a cavity formed in the crucible. Additionally, effects that interfere with the materials in the crucible will be prevented.

[0025] According to a general example, a specifically arranged diffusion zone that allows doping gas to penetrate into the cavity from the outside solves the problem. More specifically, the diffusion zone according to the general example is located between the edge of the non-permeable seed holder on the end wall and the non-permeable side wall.

[0026] In particular, the diffusion zone defined above is arranged only in the region affected by the smallest temperature gradients during the culture cycle. Given that the temperature of the diffusion zone is nearly constant during the culture cycle, the amount of doping gas in the cavity of the crucible is constant, and thus, control of doping gas incorporation into the crystal lattice is improved.

[0027] The permeability of the culture crucible to doping gas is modified by coating and / or penetration in such a way that the side walls of the culture crucible in the source area and growth space zones, i.e., the radial boundaries, become nearly impermeable to the doping gas. At the same time, seed holders arranged on the end walls of the culture crucible provide a barrier against nitrogen entry across its entire zone.

[0028] This leads to the design of a culture crucible in which the diameter of the crucible is larger than the diameter of the inserted SiC seed and / or a diffusion gap is formed between the edges of the end wall and the side wall. The resulting doping gas ring and / or resulting doping gas diffusion gap between the outer SiC seed diameter and the inner crucible diameter serves as a doping gas diffusion surface and / or doping gas diffusion gap within the culture configuration according to the present invention.

[0029] More specifically, the first embodiment relates to a crucible having a cavity for growing SiC volume monocrystalline by sublimation growth in the direction of growth.

[0030] The above description is referenced in relation to the description of the crucible. In particular, the crucible forms a cavity in which a SiC volume monocrystalline structure grows. The inner surface of the crucible faces the cavity. The outer surface of the crucible faces the reactor described above, that is, is surrounded by a chamber formed by the reactor.

[0031] Advantageously, the crucible has a prismatic shape. The prism is a polyhedron comprising an n-face polygonal base, a second base which is a shifted copy of the first base (shifted rigidly without rotation), and n other faces forming sidewalls that combine the corresponding sides of the two bases. Thus, a closed cavity is realized. This prismatic shape enables the SiC volume monocrystalline material to be easily removed from the cavity, that is, to be placed parallel to the faces forming the sidewalls. Often, the crucible has a cylindrical shape, meaning the bases have circular cross-sections.

[0032] In particular, geometric structures that can be used multiple times are advantageous because the cost of processing / coating the sidewalls, which will be explained later, is high. Therefore, prism geometric structures, especially cylindrical geometric structures, are advantageous because SiC volume monocrystalline structures can be extracted along the growth direction and dead spaces in the cavity can be reduced.

[0033] The above description is referenced in relation to the description of SiC volume monocrystalline. The above description is referenced for the description of sublimation growth. In particular, in the case of a cylinder having a prismatic shape, the growth direction is perpendicular to the extension direction of the base, that is, parallel to the direction of the planes forming the sidewalls.

[0034] According to a first embodiment, the crucible comprises an end wall, e.g., a first base having a prismatic shape. The end wall comprises a seed holder for holding a SiC seed crystal in the cavity. The seed holder and the SiC seed crystal are referred to as a holder-seed unit below. The holder-seed unit reduces the permeability of the end wall to the doping gas. In particular, when considering a growing SiC volume monocrystalline structure, permeability is reduced as the thickness increases. That is, at least a portion or only a part of the end wall is at least impermeable to the doping gas.

[0035] The seed holder can be formed, for example, from polycrystalline SiC. The thermal expansion coefficients of the two components of the holder-seed unit, namely the seed holder and the SiC seed crystal, are subsequently very similar to each other, and therefore the force effects caused on the SiC seed crystal by the temperature of the seed holder are particularly small. However, another holder material, for example, graphite material, is also basically possible.

[0036] The end wall extends perpendicular to the direction of growth. This enables the SiC volume monocrystalline to be easily extracted after growth is complete, that is, the end wall can be moved along the direction of growth together with the holder-seed unit. In particular, in the case of a crucible having a cylindrical shape, the end wall extends radially.

[0037] Furthermore, according to the first embodiment, the crucible includes a side wall extending in the direction of growth. For example, in the case of a crucible having a cylindrical shape, the side wall forms a cylindrical surface extending around the direction of growth and along the circumferential direction in the direction of growth. In this case, the crucible may additionally have a bottom wall opposite to the end wall, and thus, the cavity is closed. However, the bottom wall may have any shape to close the cavity of the crucible.

[0038] Furthermore, the sidewalls are designed to prevent the penetration of doping gases from external sources into the cavity. Penetration (also referred to as imbuing) is the passage of a penetrant (a fluid, such as a doping gas) through parts such as the walls of the crucible or contact areas. This is directly related to the concentration gradient of the penetrant, the intrinsic permeability of the material, and the mass diffusivity of the material. The penetration process involves the diffusion of molecules, referred to as penetrants, through interfaces such as sidewalls. Penetration operates through diffusion; the penetrant will move from a high concentration to a low concentration across the interface. Preventing penetration means that the amount of penetrant passing through this part of the sidewall is negligible (or at least small) compared to another part, namely the diffusion region described later.

[0039] Doping gases enable the doping of materials. Doping is the intentional introduction of impurities into an intrinsic semiconductor, namely a SiC volume monocrystalline material, for the purpose of modulating its electrical, optical, and structural properties. Doped materials are referred to as extrinsic semiconductors.

[0040] According to a first embodiment, a doping gas is used to dope a SiC volume monocrystalline structure during sublimation growth. More specifically, doping materials are provided in the SiC growth gas phase. The doping gases (also referred to as doping materials) are, for example, nitrogen (N), aluminum (Al), vanadium (V), and / or boron (B). The doping materials are supplied in gaseous or solid form. For example, doping metals or metalloids such as Al, V, and B are supplied in solid form, for example, to a crucible containing a source material. Additionally or alternatively, the metals and / or metalloids may be supplied in gaseous form and may enter through diffusion through the crucible. Advantageously, the SiC volume monocrystalline structure is an n-doped SiC crystal containing nitrogen. However, other doping is also fundamentally possible. Advantageously, the polytype of SiC is 4H. 4H is particularly advantageous for use in power electronic devices. However, another SiC polytype is also fundamentally possible.

[0041] According to the first embodiment, to provide a doping gas, a diffusion region is provided that allows the doping gas to penetrate from the outside into the cavity. More specifically, the diffusion region is located between the seed holder and the edge of the sidewall. More specifically, the edge of the sidewall is adjacent to the end wall. Thus, during the growth stage, the diffusion region is positioned to experience smaller temperature changes than the sidewall, for example, near the heated SiC storage region. For other details regarding the temperature distribution, the above description is referenced with reference to FIGS. 10 and FIGS. 11. Examples of realization of the diffusion region are discussed below in other embodiments.

[0042] According to a second embodiment, in addition to the first embodiment, the sidewall comprises or is composed of a material to prevent the penetration of doping gases, and the material comprises at least one of: graphite having a density of 1.8 g / cm³ or more, glass-like carbon, and refractory metal carbide. As used herein, refractory metal carbide can withstand high temperatures during the PCT process. According to an advantageous embodiment, the material comprises graphite having a density of 1.85 g / cm³ or more. Additionally or alternatively, the material comprises graphite having a density of 1.95 g / cm³ or less. The density of the graphite is controlled by using processes such as isostatic pressing. Thus, graphite with a density lower than that of natural graphite can be realized. Advantageously, the sidewall comprises or is composed of a combination of the previously mentioned materials. Thus, the material of the sidewall can prevent the penetration of gases. This avoids the process step of coating the sidewall. Thus, the penetration rate of the crucible can be adjusted by the penetration process.

[0043] As used in this specification, graphite is a crystalline form of the element carbon.

[0044] As used herein, glass-like carbon, often referred to as glassy carbon or glass-like carbon, is a non-graphitizable, or non-graphitizable, carbon that combines glassy and ceramic properties with those of graphite. The most important properties are high temperature resistance, hardness, low density, low electrical resistance, low friction, low thermal resistance, extreme resistance to chemical attack, and impermeability to gases and liquids.

[0045] As used herein, carbide or refractory metal carbide generally describes a compound composed of carbon and a refractory metal.

[0046] According to the third embodiment, in addition to any one of the previous embodiments, the sidewall comprises at least a layer on either an inner surface or an opposite outer surface, the layer is intended to prevent the penetration of doping gas, and the inner surface faces the cavity. Thus, the penetration rate of the crucible can be adjusted by a coating process.

[0047] In particular, as discussed regarding prism geometric structures that can be used several times, it is advantageous to provide layers in the crucible, because the cost of treating / coating the sidewalls is lower than using a crucible made of or containing graphite. Therefore, prism geometric structures combined with layers, especially cylinder geometric structures, are advantageous.

[0048] Advantageously, according to the fourth embodiment in addition to the third embodiment, the layer comprises: at least one of a photoresist, a graphitized sugar layer, TaC, WC, and Ta4HfC5. These materials can be applied as thin films from a solution or from a gaseous phase. These layers are more stable in terms of temperature and chemical properties and are more gas-tight than graphite.

[0049] Advantageously, according to the fifth embodiment in addition to the third or fourth embodiment, the layer has a thickness of 0.5 μm or more, preferably 1 μm or more, and much more preferably 2 μm or more. Optionally, the maximum thickness is 5 μm or less.

[0050] According to the sixth embodiment, in addition to any one of the previous embodiments, the sidewall comprises a layered structure to prevent the penetration of doping gas, and the layered structure comprises alternating first layers and second layers. In the case of a cylindrical shape, each layer forms a cylindrical surface. At least two layers of a first material and two layers of a second material are provided. Advantageously, the first layers comprise graphite and the second layers comprise refractory metal carbide.

[0051] According to the seventh embodiment, in addition to any one of the previous embodiments, the end wall includes a diffusion region. For example, in the case of a circular end wall, the diffusion region forms an annular ring around the seed holder.

[0052] According to this example, the diameter of the crucible is larger than the diameter of the inserted seed holder. According to the first example, the resulting doping gas permeability diameter between the outer seed holder diameter and the inner crucible diameter serves as a doping gas diffusion surface within the culture configuration.

[0053] As the diameter of the seed holder used increases, the size of the diffusion region can also be adjusted by adjusting the growth crucible, thereby making available the amount of doping gas corresponding to the crystal volume and desired doping level.

[0054] According to the eighth embodiment in addition to the seventh embodiment, the diffusion zone on the inner surface of the end wall is greater than 20% and less than 40%, and the inner surface of the end wall faces the cavity. This applies particularly to SiC volume monocrystalline specimens with a diameter greater than 200 mm perpendicular to the direction of growth. The inventors found that these ratios are sufficient to provide the necessary penetration ratios.

[0055] According to the ninth embodiment, in addition to any one of the previous embodiments, the crucible further comprises a sealing element, the sealing element is intended to seal the contact area between the edge of the end wall and the edge of the side wall, thereby controlling and, for example, reducing the penetration of doping gas through the contact area.

[0056] Sealing of the end walls and side walls, and possibly also, if the latter is not designed as a "pot," sealing of the bottom walls and side walls can be optimized by introducing a sealing element containing or composed of graphite, thereby eliminating the effect of doping gas diffusion channels in the contact area. Subsequently, the effect of channels in the end walls and / or the end walls and bottom walls can be ignored, and doping gas diffusion can be considered only through the diffusion area next to the seed holder.

[0057] According to the tenth embodiment, in addition to any one of the previous embodiments, the crucible further comprises a fixing element, the fixing element is intended to fix the end wall to the side wall and thereby adjust the penetration rate of the doping gas through the contact area between the edge of the end wall and the side wall. Accordingly, the thickness of the diffusion gap arranged in the contact area can be determined, for example, by fixing the fixing element, such as a screw, with a specified torque.

[0058] According to the 11th embodiment, in addition to the 10th embodiment, during the growth of a SiC volume monocrystalline, a gap is formed between the edges of the end wall and the side wall, and the gap is intended to move the doping gas. This makes it possible for the seed holder diameter to be equal to the inner diameter of the crucible. A diffusion region is realized by the gap, which forms a doping gas diffusion channel. The channel width can be defined by the gap remaining between the end wall and the side wall while fixing the fixing element, for example, by screwing it with a specified torque, and possibly also by the gap remaining between the base wall and the side wall if the latter is not designed as a "pot".

[0059] Advantageously, the gap is greater than 0.1 mm and less than 0.5 mm. The gap width is measured along the radial and / or longitudinal axis of the crucible. The gap surrounds the crucible in a circumferential direction, thereby forming an annular ring, and the annular ring connects the outer surface of the crucible with the inner surface of the crucible. This applies particularly to SiC volume monocrystals with a diameter greater than 200 mm perpendicular to the direction of growth.

[0060] According to the 12th embodiment, in addition to any one of the previous embodiments, the crucible further comprises a bottom wall, the bottom wall extending perpendicular to the direction of growth so that the bottom wall surrounds the cavity together with the end wall and the side wall. This is one possible solution for closing the cavity.

[0061] In particular, according to the first example of the 12th embodiment, the bottom wall includes a second seed holder for holding a second SiC seed crystal in the cavity, and the crucible includes a second diffusion region that allows the penetration of a doping gas, and the second diffusion region is located between the second seed holder and the second edge of the side wall. In relation to the description of the second seed holder, the second SiC seed crystal, and the second diffusion region, the above description of the second holder, the SiC seed crystal, and the diffusion region is referenced. This solution enables a dual crystal design. For example, if the stand is connected to the bottom wall, a gas-permeable insulating material is introduced between the stand and the growth crucible, so that a second doping diffusion region can also be realized at this location. Alternatively, a perforated or porous stand may be used.

[0062] Alternatively, according to the second example of the 12th embodiment, the bottom wall is not detachably connected to the side wall, thereby forming a pot, and the pot prevents doping gas from penetrating into the cavity from the outside. Optionally, the outer surface of the bottom wall is connected to a stand, the stand is intended to hold the crucible in a growth array, and accordingly, the stand prevents doping gas from penetrating into the cavity from the outside through the bottom wall, and the outer surface faces outward. The non-permeable stand makes it unnecessary to treat the bottom wall to be non-permeable.

[0063] The 13th embodiment relates to a growth arrangement. The growth arrangement comprises a crucible according to any one of the previous embodiments, a reactor forming a chamber, the crucible arranged in the chamber; and a gas inlet for supplying a doping gas to the chamber. For the description of the reactor, the above description is referenced. The gas inlet may be, for example, a valve, a permeable membrane, or something similar.

[0064] Advantageously, the growth array of the 13th embodiment comprises at least one of heating, and the heating surrounds the sidewall to induce heating the sidewall. For the description of induction heating, the above is referenced. Additionally or alternatively, the growth array further comprises a gas outlet for connecting to a vacuum pump to reduce pressure in the chamber. For the description of the gas outlet, the description of the gas inlet is referenced. In particular, the gas outlet can be used to control low pressure, i.e., vacuum, in the reactor chamber. Furthermore, bake-out gases can be extracted through the outlet, thereby reducing fouling of the reactor.

[0065] The 14th aspect relates to a method for growing SiC volume monocrystalline in a cavity by sublimation growth in the direction of growth, and the method is:

[0066] A step of providing at least one SiC seed crystal in a cavity, wherein the SiC seed crystal is arranged on an end wall provided with a seed holder for holding the SiC seed crystal, and the end wall extends perpendicular to the direction of growth;

[0067] A step of closing the cavity with a sidewall extending in the direction of growth, wherein the sidewall prevents doping gas from penetrating into the cavity from the outside, and the doping gas is intended to dope SiC volume monocrystalline during sublimation growth; and

[0068] The method includes the step of doping a SiC volume monocrystalline structure with a doping gas, wherein the doping gas diffuses through a diffusion region that allows the doping gas to penetrate into the cavity from the outside, and the diffusion region is located between the seed holder and the edge of the sidewall.

[0069] For the explanation of the parts mentioned in the 14th embodiment, reference is made to the description of the 1st to 13th embodiments described above. In particular, for example, two SiC seed crystals may be provided jointly. For the explanation of the two SiC seed crystals, the above description is referenced.

[0070] The 15th mode is:

[0071] The step of providing a crucible according to any one of the first to twelfth embodiments or a growth array according to the thirteenth embodiment, and

[0072] The invention relates to a method comprising the step of growing a SiC volume monocrystalline by the method of the 14th embodiment.

[0073] The present invention will now be described in more detail and in an exemplary manner, using advantageous embodiments and with reference to the drawings. The described embodiments, however, are merely possible configurations in which individual features as described above may be provided independently of one another or omitted.

[0074] The attached drawings are incorporated into the specification and form part of the specification to illustrate some embodiments of the present invention. These drawings serve to explain the principles of the present invention together with the description. The drawings are for the sole purpose of illustrating preferred and alternative examples of how the present invention may be made and used, and should not be interpreted as limiting the present invention to only the embodiments illustrated and described. Furthermore, some aspects of the embodiments may form solutions according to the present invention, individually or in different combinations. Accordingly, the embodiments described below may be considered alone or in any combination thereof.

[0075] It should be kept in mind that the described embodiments are merely possible configurations, and individual features as described above may be provided independently of one another or may be completely omitted during the implementation of this invention. As illustrated in the accompanying drawings where similar references refer to similar elements, other features and advantages will become apparent from the following more detailed description of various embodiments of the invention. Brief explanation of the drawing

[0076] In the drawings, FIG. 1 is a drawing illustrating a crucible having an infiltrated sidewall; FIG. 2 is a drawing illustrating a crucible having coated sidewalls; FIG. 3 is a drawing illustrating a crucible having coated and permeated sidewalls; FIG. 4 is a drawing illustrating a crucible for growing more than one SiC single crystal; FIG. 5 is a drawing illustrating a crucible having a fixed element; FIG. 6 is a drawing illustrating details of FIG. 5 having a sealing element; FIG. 7 is a drawing illustrating details of FIG. 5 having a diffusion channel; Fig. 8 is a flowchart for growing SiC volume monocrystalline structures; Fig. 9 is a cross-sectional view of the crucible; FIG. 10 is a cross-sectional view of the crucible of FIG. 9 arranged in a reactor; and Figure 11 is a diagram showing the temperature profile of the reactor of Figure 10. Specific details for implementing the invention

[0077] The present invention is now described with reference to the drawings, first with reference to FIG. 1, which is similar to FIG. 10 described above. More specifically, FIG. 1 illustrates a growth array (10) having a reactor (200) forming a crucible and a chamber, and the crucible is arranged in the chamber.

[0078] The crucible includes a cavity for growing an unillustrated SiC volume monocrystalline crystal by sublimation growth in the growth direction (Y). The crucible includes an end wall (110) having a seed holder (112) for holding an unillustrated SiC seed crystal in the cavity. The end wall (110) extends perpendicular to the growth direction (Y). That is, the end wall (110) extends in the radial direction (R). More specifically, an unillustrated SiC seed crystal is arranged in the crystal growth area (124) of the growth crucible. Furthermore, the crucible includes a side wall (140) and a bottom wall (150) extending in the growth direction (Y). The end wall (110), the side wall (140), and the bottom wall (150) surround the cavity for growing the SiC volume monocrystalline crystal.

[0079] The powdered SiC source material is arranged in the SiC storage area (120) of the crucible. At the start of the growth process, the boundary of the SiC storage area (120) is indicated by a thick dashed line (122). As described above, during growth, the powdered SiC source material is sublimated and the sublimated gaseous components are transported to the crystal growth area (124), i.e., along the Y-axis, so that a SiC growth gas phase is produced there, and a SiC volume mono crystal having a central longitudinal axis along the Y-axis is grown by depositing it from the SiC growth gas phase onto the SiC seed crystal.

[0080] The crucible is held by a stand (210) in the reactor (200). In addition, an insulating part (300) surrounds the crucible. The growth arrangement further includes an induction heating (400), a gas outlet (500), and a gas inlet (600).

[0081] In addition, the end wall (110) includes a diffusion region (114) that allows doping gas to penetrate into the cavity from the outside. The diffusion region (114) is located between the seed holder (112) and the edge (142) of the side wall (140). The edge (142) of the side wall (140) is adjacent to the end wall (110). More specifically, the diffusion region forms an annular ring around the seed holder (112). According to one example, the area of ​​the diffusion region on the inner surface of the end wall (110) is 20% or more and 40% or less, and the inner surface of the end wall (110) faces the cavity. According to another example, the area of ​​the diffusion region on the inner surface of the end wall (110) is 25% or more and 35% or less, and the inner surface of the end wall (110) faces the cavity.

[0082] Accordingly, the arrangement of the diffusion region (114) in the end wall (110) improves the control of the doping amount supplied to the cavity. In particular, the heater (400) heats the SiC storage region (120) in particular, which experiences high temperature changes while the diffusion region (114) experiences small temperature changes during the growth cycle. Thus, the effects caused by the temperature-dependent penetration rates of the end wall (110) can be reduced.

[0083] In addition, the sidewall (140) is designed to prevent doping gas from penetrating into the cavity from the outside, and the doping gas is intended to dope the SiC volume monocrystalline material during sublimation growth. According to the example illustrated in FIG. 1, the sidewall (140) comprises a material to prevent the penetration of doping gas. In particular, the sidewall (140) is infiltrated with a material to prevent the penetration of doping gas. The material comprises, for example: at least one of graphite having a density of 1.8 g / cm³ or more, glass-like carbon, and metal carbide. Advantageously, the material comprises graphite having a density of 1.85 g / cm³ or more. Additionally or alternatively, the material comprises graphite having a density of 1.95 g / cm³ or less. For example, the material comprises graphite having a density of 1.95 g / cm³ or less and 1.8 g / cm³ or more, advantageously 1.85 g / cm³ or more.

[0084] An alternative for a sidewall (140) comprising a material for preventing the penetration of doping gas is illustrated in FIG. 2. FIG. 2 is nearly identical to FIG. 1. FIG. 2 differs from FIG. 1 in terms of the sidewall (140). According to the example illustrated in FIG. 2, the sidewall (140) may comprise an insulating layer (146) on an inner surface and an insulating layer (144) on an opposite outer surface. Each of the layers (144 and 146) prevents the penetration of doping gas. The inner surface faces the cavity. For example, the layer comprises at least one of: a photoresist, a graphitized sugar layer, TaC, WC, and Ta4HfC5 or other refractory metal carbides and / or combinations thereof. According to one example, the layer has a thickness of 0.5 μm or more, preferably 1 μm or more, and even more preferably 2 μm or more. Additionally or alternatively, the maximum thickness is 5 μm or less.

[0085] Another alternative for adjusting the penetration rate of the sidewall (140) of FIG. 1 is illustrated in FIG. 3. According to the example illustrated in FIG. 3, the sidewall (140) containing a non-penetrating material additionally includes insulating layers (144 and 146). For the description of the insulating layers, the description in FIG. 2 is referenced.

[0086] In the examples disclosed with reference to FIGS. 1 to 3, the bottom wall (150) extends in a direction (R) perpendicular to the direction of growth so that the bottom wall (150) surrounds the cavity together with the end wall (110) and the side wall (140).

[0087] According to the examples disclosed with reference to FIGS. 1 to 3, the bottom wall (150) is impermeable to doping gas. For example, the bottom wall (150) comprises a material or layer similar to the side wall (140).

[0088] Additionally or alternatively, the stand (210) is made of a non-permeable material. More specifically, the outer surface of the bottom wall (150) is connected to the stand (210). The stand holds the crucible in the growth array (10). Thus, the stand (210) can prevent doping gas from penetrating into the cavity from the outside through the bottom wall (150).

[0089] Additionally, the bottom wall (150) may not be detachably connected to the side wall (140), thereby forming a pot. The pot prevents doping gas from penetrating into the cavity from the outside. Non-detachability means that the bottom wall (150) and the side wall (140) are designed in such a way that they cannot be removed without causing damage.

[0090] An alternative to the bottom wall (150) of FIGS. 1 to 3 is illustrated in FIG. 4. FIG. 4 is nearly identical to FIG. 3. FIG. 4 differs from FIG. 3 in that the bottom wall (151) and the SiC storage region (121) are taken into account. In particular, in addition to the first crystal growth region (124) of FIGS. 1 to 3, FIG. 4 provides a second crystal growth region (126). The first crystal growth region (124) is arranged at the first end of the crucible along the direction of growth, and the second crystal growth region (126) is arranged at the second opposite end of the crucible in the direction of growth. Thus, two crystals can be grown within one cycle.

[0091] In addition, the bottom wall (151) includes a second seed holder (152) for holding a second, unillustrated SiC seed crystal in the cavity, and the crucible includes a second diffusion region (154) for allowing the penetration of a doping gas, the second diffusion region being located between the second seed holder (152) and the second edge of the side wall (148). That is, as shown in FIG. 4, the bottom wall (151) is similar to the end wall (110) described above in FIG. 1 to 3.

[0092] Another embodiment of the crucible is illustrated in FIG. 5. In particular, FIG. 5 is similar to FIG. 1 through 3 and additionally includes at least one fixing element (170). The fixing elements (170) fix the end wall (110) to the side wall (140). For example, the fixing elements (170) are screws. By adjusting the torque, the penetration rate of the doping gas through the contact area (172) formed between the end wall (110) and the edge (142) of the side wall (142) can be adjusted. The example of FIG. 5 can be adapted to the example illustrated in FIG. 4. In particular, the bottom wall (151) can be fixed to the side wall (140) with a fixing element.

[0093] Details of FIG. 5 are illustrated in FIG. 6 and FIG. 7. In particular, FIG. 6 illustrates the crucible of FIG. 5, and a sealing element (180) is additionally provided. The sealing element seals the contact area (172) between the edge of the end wall (110) and the side wall (140). Thus, the sealing element (180) reduces the penetration of doping gas through the contact area (172). Alternatively, as illustrated in FIG. 7, a gap (190) is formed between the edge of the end wall (110) and the side wall (140). The gap enables the doping gas to move from the outside into the cavity. This may be advantageous if the diameter of the seed holder (113) is as large as (or nearly as large as) the inner diameter of the crucible. For example, the gap is greater than 0.1 mm and less than 0.5 mm.

[0094] Although not illustrated with reference to FIGS. 1 to 6 above, the sidewall may include a layered structure to prevent the penetration of doping gas. The layered structure includes alternating first layers and second layers. For example, the first layers include graphite and the second layers include refractory metal carbides.

[0095] A method for growing such SiC volume monocrystalline crystals by sublimation growth in the direction of growth is described in FIG. 8. According to the method, first, in step (S10), a SiC seed crystal is provided in a cavity. The SiC seed crystal is arranged on an end wall provided with a seed holder for holding the SiC seed crystal. The end wall extends perpendicular to the direction of growth. Additionally, SiC material is provided in a storage region formed in the cavity.

[0096] Next, the method proceeds to close the cavity in step (S12). In particular, a sidewall extending in the direction of growth surrounds the cavity. The sidewall prevents doping gas from penetrating into the cavity from the outside, and the doping gas is intended to dope the SiC volume monocrystalline during sublimation growth.

[0097] Next, the method proceeds to grow a SiC volume monocrystalline crystal in the cavity in step (S14). During growth, a doping gas is provided to dope the SiC volume monocrystalline crystal with the doping gas. The doping gas diffuses through a diffusion region, allowing the doping gas to penetrate into the cavity from the outside, and the diffusion region is located between the seed holder and the edge of the sidewall.

[0098] In particular, a method for growing a SiC volume monocrystalline crystal in a cavity by sublimation growth in the direction of growth uses, for example, any crucible described above in FIGS. 1 to 7. Advantageously, a growth arrangement as described in FIGS. 1 to 7 is used to grow a SiC volume monocrystalline crystal.

Claims

Claim 1 A crucible having a cavity for growing a SiC volume mono crystal by sublimation growth in the direction of growth (Y), the crucible comprising: an end wall (110) having a seed holder (112) for holding a SiC seed crystal in the cavity, the end wall (110) extending in a direction (r) perpendicular to the direction of growth (Y); a side wall (140) extending in the direction of growth (Y), the side wall (140) being infiltrated and / or coated with a material that prevents a doping gas from penetrating into the cavity from the outside, the doping gas being intended to dope the SiC volume mono crystal during sublimation growth; and a diffusion region (114) allowing the doping gas to penetrate into the cavity from the outside, the diffusion region (114) being located between the seed holder (112) and the edge (142) of the side wall (140). Claim 2 A crucible according to claim 1, wherein the side wall (140) comprises a material for preventing the penetration of doping gas, and the material comprises at least one of graphite, glass-like carbon, and refractory metal carbide having a density of 1.8 g / cm³ or more. Claim 3 In claim 1, the sidewall (140) comprises a layer (144, 146) on at least one of an inner surface and an opposite outer surface, said layer is for preventing the penetration of the doping gas, and said inner surface is facing the cavity, crucible. Claim 4 In paragraph 3, the crucible comprises layers (144, 146) including at least one of photoresist, graphitized sugar layer, TaC, WC, and Ta4HfC5. Claim 5 In paragraph 4, the above layers (144, 146) are a crucible having a thickness of 0.5 μm or more. Claim 6 In claim 1, the side wall (140) includes a layered structure to prevent the penetration of doping gas, and the layered structure includes alternating first layers and second layers, a crucible. Claim 7 In claim 1, the end wall (110) comprises the diffusion region (114), forming a crucible. Claim 8 In claim 7, the area of ​​the diffusion region (114) on the inner surface of the end wall (110) is 20% or more and 40% or less, and the inner surface of the end wall (110) faces the cavity, crucible. Claim 9 A crucible according to claim 1, further comprising a sealing element (180), wherein the sealing element (180) seals a contact area (172) between the end wall (110) and the edge (142) of the side wall (140) and thereby reduces the penetration of the doping gas through the contact area (172). Claim 10 A crucible according to claim 1, further comprising a fixing element (170), wherein the fixing element (170) fixes the end wall (110) to the side wall (140) and thereby adjusts the penetration rate of the doping gas through the contact area (172) between the end wall (110) and the edge (142) of the side wall (140). Claim 11 In claim 10, during the growth of the SiC volume monocrystalline, a gap (190) is formed between the end wall (110) and the edge (142) of the side wall (140), and the gap (190) is for moving a doping gas, a crucible. Claim 12 In claim 1, the crucible further comprises a bottom wall (150, 151), said bottom wall (150, 151) extending in a direction (r) perpendicular to the direction of growth (Y) so that the bottom wall surrounds the cavity together with the end wall (110) and the side wall (140); said bottom wall (151) comprises a second seed holder (152) for holding a second SiC seed crystal in the cavity and said crucible comprises a second diffusion region (154) allowing the penetration of the doping gas, said second diffusion region (154) being located between the second seed holder (152) and the second edge (148) of the side wall (140). Claim 13 A growth device (10) comprising: a crucible having a cavity for growing a SiC volume mono crystal by sublimation growth in the growth direction (Y); said crucible comprising: an end wall (110) having a seed holder (112) for holding a SiC seed crystal in said cavity, said end wall (110) extending in a direction (r) perpendicular to said growth direction (Y); a side wall (140) extending in said growth direction (Y), said side wall (140) preventing a doping gas from penetrating into said cavity from the outside, said doping gas being for doping the SiC volume mono crystal during said sublimation growth; A growth apparatus (10), comprising a reactor (200) forming a chamber, wherein the diffusion region (114) allows the doping gas to penetrate into the cavity from the outside, wherein the diffusion region (114) is located between the seed holder (112) and the edge (142) of the side wall (140); the crucible is arranged in the chamber; and a gas inlet (600) for supplying the doping gas to the chamber. Claim 14 A method for growing at least one SiC volume monocrystalline crystal by sublimation growth in a growth direction (Y) in a cavity, the method comprising: providing a SiC seed crystal in the cavity; the SiC seed crystal is arranged in an end wall (110) provided with a seed holder (112) for holding the SiC seed crystal, and the end wall (110) extends in a direction (r) perpendicular to the growth direction (Y); closing the cavity with a side wall (140) extending in the growth direction (Y), wherein the side wall (140) is infiltrated and / or coated with a material that prevents a doping gas from penetrating into the cavity from the outside, and the doping gas is intended to dope the SiC volume monocrystalline crystal during the sublimation growth; A method for growing at least one SiC volume mono crystal, comprising the step of doping the SiC volume mono crystal with the doping gas, wherein the doping gas diffuses through a diffusion region (114) that allows the doping gas to penetrate into the cavity from the outside, and the diffusion region (114) is located between the seed holder (112) and the edge (142) of the sidewall (140). Claim 15 A method for growing at least one SiC volume mono crystal by sublimation growth in the direction of growth in a joint, the method comprising the steps of providing a growth apparatus (10) according to claim 13 and growing the SiC volume mono crystal by the method of claim 14.

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