JP5623071B2 - Method for producing uniformly doped SiC bulk single crystal and uniformly doped SiC substrate - Google Patents

Description

  The present invention relates to a method for the production of a SiC bulk single crystal and a single crystal SiC substrate.

  The semiconductor material silicon carbide (SiC) is also used as a substrate material for high frequency components, among other things, based on excellent physical, chemical and electrical properties. In this case, as little interaction as possible between the original component and the substrate material is important to avoid loss. This is achieved, for example, by having a single crystal SiC substrate as high as possible in addition to high crystal quality. In order to manufacture a SiC bulk single crystal or a SiC substrate having a high resistance characteristic made therefrom, it is necessary to compensate for shallow defects existing in the crystal based on impurities or intrinsic defects. The SiC bulk single crystal thus produced is also called a semi-insulating single crystal.

In order to compensate for so-called shallow defects caused by nitrogen impurities, in particular, so-called shallow defects that are caused by nitrogen impurities, a method for generating additional intrinsic defects during crystal growth is known (see, for example, Patent Documents 1 and 2). ). Thereby, a specific resistance of about 10 ⁵ Ωcm to a maximum of about 10 ¹⁰ Ωcm can be achieved. Because of this very sensitive process control, values of only about 10 ⁶ Ωcm are often obtained. Since the formation of proper intrinsic defects is strongly dependent on the process parameters during crystal growth, slight process variations already lead to non-uniform defect distribution and concomitant non-uniform resistance distribution. Furthermore, intrinsic defects brought about by this kind of aim may disappear again under thermal load, which can lead to a non-uniform resistance distribution or even a complete loss of high resistance properties.

As another method for compensating for a shallow defect, a method is known in which an exogenous deep defect is targeted and injected into a SiC bulk single crystal (see, for example, Patent Document 3). In order to compensate for nitrogen background doping (nitrogen impurities), vanadium is used as a targeted dopant. In this way, a resistivity value of 10 ¹¹ Ωcm is achieved.

  In another known doping method, vanadium is added to a powdered SiC raw material and supplied from the SiC raw material to a growing SiC bulk single crystal (see, for example, Patent Document 4). Thus, a particularly controllable supply that targets vanadium is not possible. Furthermore, since the vanadium component in the SiC raw material becomes poor with time, it is almost impossible to adjust the uniform electrical characteristics in the growing SiC bulk single crystal.

  In another known doping method, a capsule filled with vanadium is placed in a growth crucible, which attempts to avoid dopant deficiency (see, for example, Patent Document 5). However, even with this method, uniform electrical properties cannot be adjusted, particularly in the case of a SiC bulk single crystal having a large diameter of at least 7 inches (7.62 cm).

  With the known co-doping method, a particularly high value can be achieved with respect to the resistivity of the growing SiC bulk single crystal and the SiC substrate made therefrom (see, for example, Patent Document 6). In this co-doping method, nitrogen background doping is compensated by targeted addition of a first dopant having a shallow dopant level. Here, the dopant level is the position of the energy level of the dopant within the band gap of the semiconductor material. The first dopant is in particular aluminum, which acts as an acceptor. The remaining excess in the p-carrier derived from the acceptor dopant is compensated by the simultaneously provided second dopant. The second dopant is vanadium that is deep and has a dopant level that acts as a donor. Due to the addition of the second different dopant, it is particularly difficult for this method to achieve uniform electrical properties and in particular a uniform resistance distribution.

International Patent Application Publication No. 02/097173 International Patent Application Publication No. 2005/012601 International Patent Application Publication No. 98/34281 International Patent Application Publication No. 2006/017074 International Patent Application Publication No. 2006/113657 German Patent Application No. 4325804

  Accordingly, it is an object of the present invention to provide an improved method for the production of SiC bulk single crystals as well as an improved single crystal SiC substrate.

In order to solve the problem, a method according to the features of claim 1 is proposed. The method according to the invention is a method for the production of a SiC bulk single crystal having a resistivity of at least 10 ¹¹ Ωcm and a diameter of at least 7.62 cm, wherein a SiC growth gas phase is generated inside the crystal growth region of the growth crucible SiC bulk single crystal is grown by separation from the SiC growth vapor phase, the SiC growth vapor phase is supplied from the SiC source in the SiC storage region inside the growth crucible, and at least 500 meV spacing from the SiC band edge A growth crucible in which a dopant having a dopant level deep in the region is supplied to the crystal growth region in a gaseous state from a dopant reservoir disposed outside the growth crucible, and the dopant is directed perpendicular to the growth direction. Are introduced into the growth crucible at a number of adjacent locations with respect to the cross section of the growth crucible. It is distributed Te.

  Based on the arrangement of the dopant reservoir outside the growth crucible according to the invention and also the distribution of the dopant into the growth crucible according to the invention, with respect to the dopant contained therein in the SiC growth gas phase, particularly uniform The ratio can be adjusted. If necessary, the dopant supply during the growth process may be adapted to the changing actual situation. The distribution of the dopant inside the growth crucible is performed in particular by means of a gas distributor. Furthermore, the introduction may be performed at at least two different locations.

Overall, it is achieved that the growing SiC bulk single crystal has largely uniform electrical properties. This is because the corresponding dopant is controlled during the growth process, and is particularly distributed uniformly in the growing SiC bulk single crystal. With the distribution of dopants, SiC bulk single crystals with a very large diameter of 7.62 cm or more with the above-mentioned uniform electrical properties, i.e., almost the same size, especially high resistance, are produced. it can. Thus, unlike the known methods, the method according to the present invention is very large, ie at least 7.62 cm, with a high, ie, at least 10 ¹¹ Ωcm, specific resistance given largely uniformly within the growing bulk single crystal. SiC bulk single crystals having a diameter of

According to a special embodiment, the first and second dopants are supplied to the crystal growth region as follows. That is, the concentration of each dopant inside the cross section of the growth crucible oriented perpendicular to the growth direction is supplied so as to vary by at most 5% around the concentration average value. In this case, the local concentration is determined for each partial surface of any 4 mm ² size of the entire internal cross section of the growth crucible. Thus, the dopant is distributed in a largely uniform manner, especially within this cross section.

  In another special embodiment, the temperature of the dopant reservoir is adjusted independently of the SiC source temperature. Based on this controllability of the dopant reservoir temperature, the dopant addition can be adjusted to be particularly accurate and variable in time. For example, the doping supply can be adapted to the current process conditions and can be varied, especially if necessary. This flexibility in supplying the dopant is not possible in the case of the conventional known methods by adding the dopant directly to the powdered SiC raw material or by arranging the capsule filled with the dopant inside the growth crucible.

  In another particular embodiment, the dopant reservoir is heated separately from the growth crucible heating. As a result, the temperature of the dopant reservoir can be adjusted, in particular varied, with a particularly simple aim.

  In another special embodiment, the dopant reservoir is placed in a cavity provided inside the thermal insulation layer surrounding the growth crucible. As a result, a compact structure of the growth apparatus is obtained.

  In another special embodiment, the position of the dopant reservoir is changed relative to the growth crucible. Thereby, the temperature of the dopant reservoir can be adjusted. In this case, the dopant reservoir is separated or brought closer within the influence range of the heating device for heating the growth crucible.

  According to another particular embodiment, an inert gas is passed through the dopant reservoir. This results in improved transport of gaseous dopant to the growth crucible. Furthermore, the change in inert gas flow provides an additional possibility for adjusting / controlling the amount of dopant produced. Furthermore, the inert gas prevents the supply path to the growth crucible from being blocked by SiC, especially in the case of a long growth time. SiC can reach the cold tube of the feed line from the hot interior space of the growth crucible.

  In other special embodiments, the dopant is introduced into the SiC storage region or directly into the crystal growth region. Upon introduction into the SiC storage region, the dopant reaches the crystal growth region therefrom.

In order to solve the problems related to the SiC substrate, a SiC substrate according to the features of claim 9 is proposed. The single crystal SiC substrate according to the present invention has a substrate main surface, the substrate main surface has a diameter of at least 7.62 cm, is provided with doping with a dopant, and the dopant is spaced at least 500 meV from the SiC band edge. Having a dopant level deep, the local concentration of the dopant required for any partial volume deviates from the overall concentration of the dopant by less than 5%, and the partial volume is any 4 mm ² size on the substrate main surface. It is defined by the partial surface and the substrate thickness perpendicular thereto.

  In this case, the overall concentration is a concentration determined especially as a whole, that is, with respect to the entire SiC substrate. Furthermore, the above-described uniform distribution of dopant applies both in the lateral direction (radial direction) and in the axial direction.

  Thus, the SiC substrate according to the invention is characterized on the one hand by an unusually large diameter and on the other hand by a very uniform incorporation of dopants, resulting in the very uniform electrical properties of the SiC substrate. The specific resistance has little room for fluctuation, if any, over the entire main surface of the substrate. Therefore, the SiC substrate according to the present invention can be used as a high-resistance or semi-insulating substrate for manufacturing high-frequency components with a high yield. Based on the large substrate diameter and the high resistivity that exists very uniformly everywhere on the substrate surface, the production of this type of high-frequency component is efficient and cost-effective. Thus, there has been no advantageous large-area SiC substrate having such a large and uniform dopant distribution. Such a SiC substrate can be produced for the first time by a SiC bulk single crystal grown by the method according to the invention described above.

  According to a special embodiment, the dopant is an acceptor and is at least equal to the impurity acting as a donor.

  According to another particular embodiment, the dopant is vanadium or scandium.

According to another particular embodiment, the dopant is vanadium and has a concentration between 1 · 10 ¹⁶ cm ⁻³ and 5 · 10 ¹⁷ cm ⁻³ .

According to another particular embodiment, the specific resistance determined for any 4 mm ² sized and particularly square partial surface of the main surface of the substrate is at least 10 ¹¹ Ωcm. Therefore, a specific resistance of at least 10 ¹¹ Ωcm can be obtained on the main surface of the substrate, particularly at any location. Therefore, this advantageous SiC substrate has a very high specific resistance. Based on the high resistivity uniformity, this SiC substrate is particularly suitable for the production of high-frequency components.

FIG. 1 is a cross-sectional view showing a first embodiment of a growth apparatus for manufacturing a high-resistance SiC bulk single crystal having one external dopant reservoir. FIG. 2 is a cross-sectional view showing a second embodiment of a growth apparatus for the production of a high resistance SiC bulk single crystal having two external individually heatable dopant reservoirs. FIG. 3 is a cross-sectional view showing a third embodiment of a growth apparatus for the production of a high-resistance SiC bulk single crystal having two external position-changeable dopant reservoirs. FIG. 4 is a cross-sectional view showing a fourth embodiment of a growth apparatus for manufacturing a high-resistance SiC bulk single crystal having two external dopant reservoirs and a dopant supplier to the SiC raw material. FIG. 5 is a cross-sectional view showing a fifth embodiment of a growth apparatus for manufacturing a high-resistance SiC bulk single crystal having two dopant reservoirs passed through an inert gas. FIG. 6 is a cross-sectional view showing a sixth embodiment of a growth apparatus for producing a high-resistance SiC bulk single crystal having two dopant reservoirs through which an inert gas is passed. FIG. 7 is a cross-sectional view showing a seventh embodiment of a growth apparatus for manufacturing a high-resistance SiC bulk single crystal having a dopant introducing portion into a growth crucible by a gas distributor. FIG. 8 is a cross-sectional view showing an eighth embodiment of a growth apparatus for producing a high-resistance SiC bulk single crystal having a dopant introducing portion into a growth crucible by a gas distributor. FIG. 9 is a cross-sectional view showing a ninth embodiment of a growth apparatus for manufacturing a high-resistance SiC bulk single crystal having a dopant reservoir disposed outside the thermal insulation of the growth crucible.

  Other features, advantages and details of the invention will become apparent from the following description of embodiments with reference to the drawings.

  In FIG. 1 to FIG. 9, the same reference numerals are assigned to the portions corresponding to each other.

  FIG. 1 shows a first embodiment of a growth apparatus 1 for producing a high-resistance SiC bulk single crystal 2. The growth apparatus 1 includes a growth crucible 3 made of graphite, and the crucible 3 includes an SiC storage region 4 and a crystal growth region 5. In the SiC storage area 4, for example, there is a powdery SiC raw material 6. The SiC raw material 6 is packed in the SiC storage region 4 of the growth crucible 3 as a pre-made initial material before the growth process.

  A seed crystal (not shown) is attached to the crystal growth region 5 on the inner wall of the growth crucible 3 facing the SiC storage region 4. The SiC bulk single crystal 2 to be grown on the seed crystal is grown by separation from the SiC growth vapor phase 7 formed in the crystal growth region 5.

The SiC growth vapor phase 7 is generated by sublimation of the SiC raw material 6 and transport of the sublimated gaseous portion of the SiC raw material in the direction of the growth surface of the SiC bulk single crystal. The SiC growth vapor phase 7 contains at least gas components in the form of Si, Si ₂ C and SiC ₂ . The SiC raw material 6 is transported along the temperature gradient to the growth surface. The temperature in the growth crucible 3 decreases toward the growing SiC bulk single crystal 2. In the embodiment shown in FIG. 1, the SiC bulk single crystal 2 grows in the growth direction 8 from the top to the bottom, and thus in the growth direction 8 from the upper wall of the growth crucible 3 toward the SiC storage region 4.

  Around the growth crucible 3, a heat insulating layer 9 made of, for example, porous graphite is disposed. The thermally insulated growth crucible 3 is disposed in the tubular container 10. The tubular container 10 is a pressure kettle made of a quartz glass tube in this embodiment. A heating coil 11 is disposed around the vessel 10 for heating the growth crucible 3. In particular, the relative position between the heating coil 11 and the growth crucible 3 can be changed in the growth direction 8 in order to adjust the temperature inside the growth crucible 3 or the temperature course and to change it if necessary. The growth crucible 3 is heated to a temperature of 2000 ° C. or higher by the heating coil 11.

  A dopant reservoir 12 is disposed outside the growth crucible 3, that is, below the growth crucible 3, and thus inside the thermal insulating layer 9. In the dopant reservoir 12, for example, a powdery dopant material 13 is present. The dopant reservoir 12 is connected to the inside of the growth crucible 3 by an introduction tube 14. The end of the introduction tube opposite to the dopant storage portion 12 terminates above the SiC storage region 4, that is, inside the crystal growth region 5. But this is not essential. For example, in the case of another embodiment shown in FIGS. 4 to 6, the introduction pipe 14 may be terminated inside the SiC storage region 4. The dopant reservoir 12 is implemented as a separate crucible placed inside a cavity in the thermal insulation layer 9.

The dopant material 13 includes a unique dopant, i.e., vanadium, or a mixed dopant consisting of first and second dopants in the examples. In this case, the first dopant is aluminum and the second dopant is vanadium. These dopants are vaporized or sublimated inside the dopant reservoir 12 and reach the inside of the growth crucible 3 in a gaseous state, so that the dopant is taken into the growing SiC bulk single crystal 2. When vanadium is used as the sole dopant, incorporation of dopant atoms as acceptors having dopant levels at a depth of 700 meV with respect to the SiC band edge is performed. Incorporation of aluminum atoms as shallow acceptors with dopant levels spaced about 250 meV relative to the SiC band edge if co-doping with aluminum and vanadium as the first or second dopant is planned And incorporation of vanadium atoms as deep donors with dopant levels spaced about 1400 meV relative to the SiC band edge.

In both cases, the result is a high-resistance SiC bulk single crystal having a specific resistance of at least 10 ¹¹ Ωcm in the case of single doping, and a high-resistance SiC bulk having a specific resistance of at least 10 ¹² Ωcm in the case of simultaneous doping. A single crystal is formed. Based on the external arrangement of the dopant reservoir 12, it is possible to make adjustments aimed at incorporating dopants, and in particular, it can be variably adjusted, so that the electrical characteristics of a large and uniform high resistance within the growing SiC bulk single crystal 2 can be obtained. can get.

  FIG. 2 shows an alternative embodiment of the growth apparatus 15. The growth apparatus 15 differs from the growth apparatus 1 of FIG. 1 in that it includes two dopant reservoirs 16 and 17 arranged outside the growth crucible, and the dopant reservoir 16 has a first dopant material 18 as a first dopant material 18. Aluminum is accommodated, and vanadium is accommodated as the second dopant material 19 in the dopant reservoir 17. Both dopant stores 16 and 17 are each assigned one dedicated individually controllable heating device 20 or 21. Therefore, the temperature of the dopant storage parts 16 and 17 can be adjusted or controlled individually and independently of the heating of the growth crucible 3 by the heating coil 11. In particular, the heating of the dopant reservoirs 16 and 17 during the course of the growth process can be varied.

  In the case of another embodiment of the growth device 22 shown in FIG. Is achieved by being variable. For this reason, positioning means (not shown) is provided that enables the dopant storage parts 16 and 17 to move in the growth direction 8. Therefore, the cavities 23 and 24 provided for accommodating the dopant reservoirs 16 and 17 inside the thermal insulation layer 9 are larger than the dimensions of the doping reservoirs 16 or 17 in the axial direction, ie in the growth direction 8. .

Based on the variable heating of the dopant reservoirs 16 and 17 and the temperature of the dopant materials 18 and 19 variably adjusted accordingly, the supply of dopants, aluminum and vanadium, can be adjusted and modified very accurately. Can be adapted to different process conditions. In this way, the SiC bulk single crystal 2 to be grown can obtain largely uniform electrical characteristics in the axial direction. Therefore, there is almost the same high specific resistance value at any point in the growth direction 8, and this specific resistance value is at least 10 ¹² Ωcm in the case of simultaneous doping with aluminum and vanadium. All of the single crystal SiC substrates obtained from the SiC bulk single crystal 2 are substantially perpendicular to the growth direction 8 and are cut by a cutter or a saw one after another in the axial direction, so that each has almost the same electrical characteristics.

  In another alternative growth apparatus 25, 26, 27 embodiment according to FIGS. 4-6, each inlet tube 14 for introducing gaseous dopant from the dopant reservoirs 16 and 17 into the inside of the growth crucible 3 comprises a crystal. It has not reached the middle of the growth region 5 and has already terminated in the SiC storage region 4. The resulting flow of gaseous dopant through the SiC raw material 6 is largely uniform in the interior of the internal cross section oriented perpendicular to the growth direction 8 of the growth crucible 3. This produces an advantageous distribution.

Especially in the case of the growth of very large SiC bulk single crystals 2 with a diameter of at least 7.62 cm, the incorporation of the dopant is in the lateral direction (radial direction), ie in any direction perpendicular to the growth direction 8, It is done in a very uniform manner. Therefore, the electrical characteristics of the SiC bulk single crystal 2 hardly change in the lateral direction. In particular, the specific resistance is almost the same high resistance everywhere in the lateral direction, at least 10 ¹² Ωcm for the co-doping method with two dopants, or at least 10 ¹¹ Ωcm for the single doping method with only one dopant. Has a value. In particular, the specific resistance per square partial surface of an arbitrary 4 mm ² size of a disc-shaped SiC substrate made of SiC bulk single crystal 2 is at least 10 ¹² Ωcm or at least 10 depending on the doping method used. ¹¹ Ωcm. The main surface of the SiC substrate is oriented perpendicular to the growth direction 8. In the growth direction 8, this SiC substrate has a substrate thickness of, for example, about 200 μm to 500 μm, in particular 350 μm.

  In the growth apparatuses 26 and 27, an inert gas is additionally passed through the dopant storage parts 16 and 17 which can be further heated by the heating apparatuses 20 and 21. An inert gas is introduced from outside the insulating layer 9 into the dopant reservoirs 16 and 17. From there the inert gas reaches the inside of the growth crucible 3 together with the gaseous dopant, resulting in improved transport of the gaseous dopant to the growth crucible 3 and the additional possibility of adjusting the dopant supply. Furthermore, the inert gas flow largely prevents the inlet tube 14 from being blocked by SiC. In order to supply an inert gas, the dopant reservoirs 16 and 17 are provided with a supply pipe 28 which leads to the outside.

  As shown in FIGS. 2 to 5, the dopant reservoirs 16 and 17 may be arranged independently of each other and particularly juxtaposed. However, according to the growth apparatus 27 shown in FIG. 6, the dopant reservoirs 16 and 17 may be arranged one after the other, that is, in series with each other.

  7 and 8 show other embodiments of different growth devices 29 and 30. FIG. In these figures, the dopant reservoirs 12 or 16 and 17 are not shown together for simplicity. The dopant reservoir is present as in the embodiment according to FIGS. The introduction pipe 14 connected to these dopant reservoirs 12 or 16 and 17 not shown flows into a gas distributor 31 having a number of outlet pipes 32 inside the growth crucible. The outlet tube 32 still terminates inside the SiC storage region 4 (see FIG. 7) or terminates inside the crystal growth region 5 (see FIG. 8). In any case, since the outlet tubes 32 are distributed and arranged within the internal cross section oriented perpendicular to the growth direction 8, the supplied dopant is uniformly distributed within this cross section. To do.

As a result, a particularly uniform distribution of the dopant in the lateral direction occurs both in the SiC growth vapor phase 7 and in the SiC bulk single crystal 2 grown from it. In a SiC substrate consisting of a growing SiC bulk single crystal 2, the local concentration of dopant incorporated for any partial volume that includes the full substrate thickness in the growth direction 8 and is perpendicular to this is 4 mm ² is Only a deviation of 5% or less of the overall concentration of this dopant determined for the entire SiC substrate is shown. Accordingly, in the lateral direction, the dopant concentration varies by at most 5% around the concentration average value, which is the case with a SiC substrate or SiC bulk single crystal 2 diameter of at least 7.62.

  Therefore, based on the above measures, even if the SiC bulk single crystal 2 to be grown has an abnormally large diameter, the SiC bulk single crystal having good uniformity both in the lateral direction and in the axial direction of the dopant incorporated each time. 2 can be manufactured.

  FIG. 9 shows another embodiment of the growth apparatus 33. In this case, the dopant storage part 34 is disposed not only at the outside of the growth crucible 3 but also at the place corresponding to the outside of the attached thermal insulating layer 9. Also in this embodiment, the temperature of the dopant material 13 disposed in the dopant reservoir 34 can be adjusted separately. The supply of gaseous dopant is again effected by the introduction pipe 35 into the growth crucible 3, in the illustrated embodiment directly into the crystal growth region 5.

  The above-described growth apparatus 1, 15, 22, 25-27, 29, 30, 33 and the accompanying growth method for the production of the high-resistance SiC bulk single crystal 2 are the only ones for the simultaneous doping method with at least two dopants. It can also be used for the single doping method with the above dopants. The advantages of a particularly uniform incorporation of the dopant and the resulting particularly uniform high resistance resistivity resulting therefrom are likewise provided in both doping methods.

DESCRIPTION OF SYMBOLS 1 Growth apparatus, 2 SiC bulk single crystal, 3 Growth crucible, 4 SiC storage area, 5 Crystal growth area, 6 SiC raw material, 7 SiC growth gas phase, 9 Thermal insulation layer, 10 Tubular container, 11 Heating coil, 12, 16 , 17 Dopant reservoir, 13, 18, 19 Dopant material, 14 Introductory tube, 15, 22, 25-27, 29, 30, 33 Growth device, 20, 21 Heating device, 23, 24 Cavity, 28 Feed tube, 31 Distributor, 32 outlet tube, 34 dopant reservoir, 35 inlet tube

Claims (7)

A method for the production of a SiC bulk single crystal having a resistivity of at least 10 ¹¹ Ωcm and a diameter of at least 7.62 cm,
a) A SiC growth vapor phase (7) is generated inside the crystal growth region (5) of the growth crucible (3), and a SiC bulk single crystal (2) is grown by separation from the SiC growth vapor phase (7). ,
b) a SiC growth vapor phase (7) is supplied from the SiC source (6) in the SiC storage region (4) inside the growth crucible (3);
c) A dopant (13, 19) having a dopant level at a depth of at least 500 meV with respect to the SiC band edge is extracted from a dopant reservoir (12, 17) disposed outside the growth crucible (3). It is supplied to the crystal growth region (5) in a gaseous state, and the temperature of the dopant reservoir (12, 17) is adjusted without depending on the temperature of the SiC raw material (6), and the dopant reservoir (12 , 17) is supplied from the growth crucible (3, 19) in a number of adjacent locations (32) with respect to the cross-section of the growth crucible (3) oriented perpendicular to the growth direction (8). For the production of SiC bulk single crystals, characterized in that they are distributed inside the growth crucible (3).   The dopant (13, 19) is supplied to the crystal growth region (5) as follows: the dopant inside the cross section of the growth crucible (3) oriented perpendicular to the growth direction (8) 2. The method according to claim 1, wherein the concentration is supplied so as to vary by at most 5% around the concentration average value. The method according to claim 1 or 2, characterized in that the dopant reservoir (17) is heated separately from the heating of the growth crucible (3). 4. The method according to claim 1, wherein the dopant reservoir is arranged in a cavity provided inside the thermal insulation layer surrounding the growth crucible. Method. 5. The method according to claim 1, wherein the position of the dopant reservoir (17) is changed relative to the growth crucible (3). 6. The method according to claim 1, wherein an inert gas is passed through the dopant reservoir. 7. The method according to claim 1, wherein the dopant (13, 19) is introduced into the SiC storage region (4) or directly into the crystal growth region (5).

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