JP2013107788A - Method for manufacturing silicon carbide wafer, silicon carbide wafer, silicon carbide semiconductor element, and power converting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a silicon carbide wafer which prevents complication of a manufacture process, does not restrict a silicon carbide substrate, and is capable of more surely converting a basal plane dislocation (BPD) to a threading edge dislocation (TED).SOLUTION: This method includes the first step in which Si ion is injected into one direction of a silicon carbide substrate 1 or the substrate 1 is irradiated with an electron beam, the second step in which the silicon carbide substrate 1 is subjected to annealing, and the third step in which one direction side of the silicon carbide substrate 1 is epitaxially grown to form an epitaxial film 3. The ion to be injected into the silicon carbide substrate is at least one kind selected from a group comprising Si ion, C ion, H ion, He ion, P ion, Al ion B ion and N ion.

Description

  The present invention relates to a method for manufacturing a silicon carbide wafer, a silicon carbide wafer, a silicon carbide semiconductor element, and a power converter.

  Silicon carbide (SiC) is a semiconductor that has excellent physical properties such as a band gap of about 3 times, a saturation drift velocity of about 2 times, and a breakdown electric field strength of about 10 times that of silicon, and a large thermal conductivity. Therefore, it is expected as a material for realizing a next-generation high-voltage / low-loss semiconductor device that greatly surpasses the performance of currently used silicon single crystal semiconductors. As a method for producing a single crystal of silicon carbide, a sublimation method or a CVD method is used.

  Silicon carbide does not have a liquid phase at normal pressure and has a very high sublimation temperature. Therefore, silicon carbide does not contain crystal defects such as dislocations and stacking faults by conventional sublimation methods and CVD methods. It is difficult to perform crystal growth.

Currently available silicon carbide substrates include threading screw dislocations propagating in the c-axis direction of about 10 ² cm ⁻² to 10 ³ cm ⁻² and c-axis direction of about 10 ² cm ⁻² to 10 ⁴ cm ^−2. There exist dislocations (basal plane dislocations) propagating in the direction perpendicular to the c-axis of about 10 ² cm ⁻² to 10 ⁴ cm ⁻² . These dislocation densities vary greatly depending on the quality of the substrate.

  These dislocations inherent in the silicon carbide substrate propagate into the epitaxial film when the epitaxial film is grown on the substrate. At this time, it is known that some dislocations may change the extension direction (propagation direction) when propagating into the epitaxial film (for example, see Non-Patent Document 1).

  For example, one or both ends of basal plane dislocation (hereinafter referred to as BPD) appear on the surface of the substrate. When an epitaxial film is grown on the substrate, most of the BPD in the substrate is converted to threading edge dislocation (hereinafter referred to as TED) in the vicinity of the interface between the substrate and the epitaxial film, and a part of the BPD remains as the BPD. Propagate inside.

  Therefore, in the epitaxial film, TED introduced at the time of epitaxial growth is included in addition to BPD propagated as it is from the substrate. These dislocations lower the withstand voltage and reliability of a semiconductor element formed using the epitaxial film. In particular, the BPD contained in the epitaxial film reduces the reliability and performance of the semiconductor element. On the other hand, TED contained in an epitaxial film is said to have a small adverse effect on the reliability and performance of a semiconductor element (see, for example, Non-Patent Document 2).

  Therefore, a method for converting BPD contained in a silicon carbide substrate into TED and increasing the ratio of TED has been studied.

  (1) The substrate surface is etched using molten KOH. By this etching, the front end portion of the BPD on the substrate surface is selectively deeply etched to generate an etch pit. Thereafter, epitaxial growth is performed on the substrate. The presence of etch pits at the tip of the BPD on the substrate surface increases the rate at which BPD in the substrate is converted to TED (see, for example, Patent Document 1, Non-Patent Document 3, and Non-Patent Document 4).

  (2) Reactive ion etching (RIE) is used to form hexagonal or striped grooves on the substrate surface, and then epitaxial growth is performed on the substrate. Due to the presence of square or stripe-shaped grooves on the substrate surface, the ratio of BPD in the substrate converted to TED increases (see, for example, Patent Document 2, Patent Document 3, and Non-Patent Document 3).

  (3) Chemical mechanical polishing (CMP) and hydrogen etching are performed on the substrate surface. Thereby, the damaged layer on the substrate surface is removed, and the substrate surface is flattened. Thereafter, epitaxial growth is performed on the substrate surface. Thereby, the ratio by which BPD in a board | substrate is converted into TED increases (for example, refer patent document 4 and nonpatent literature 5).

  (4) The main surface of the substrate to be epitaxially grown is a (000-1) C plane. Thereby, the ratio in which BPD in a board | substrate is converted into TED increases (for example, refer patent document 5 and nonpatent literature 5).

  (5) The off angle from the {0001} plane of the substrate to be epitaxially grown is reduced from 8 ° to 4 °. Thereby, the ratio in which BPD in a board | substrate is converted into TED increases (for example, refer nonpatent literature 5 and nonpatent literature 6).

(6) During the epitaxial growth on the substrate surface, the supply of the source gas such as SiH ₄ or C ₃ H ₈ is stopped, and the temperature is maintained in the hydrogen stream to stop the epitaxial growth. After a certain period of time, a second epitaxial growth is performed. At this time, a part of BPD propagated in the epitaxial film during the first epitaxial growth is converted to TED during the second epitaxial growth. An epitaxial film having a low BPD density can be obtained by interrupting and restarting such epitaxial growth in the middle or by repeating the interruption and restart in the middle (for example, see Non-Patent Document 7).

  The methods (1) to (3) described above require etching on the substrate surface before epitaxial growth, and the manufacturing process becomes complicated. Since the method (6) requires steps of interrupting and resuming the epitaxial growth, the manufacturing process is similarly complicated.

  In the method (4), the (0001) Si surface cannot be used. In the method (5), a substrate with an off angle of 8 ° cannot be used, and the epitaxial growth rate is limited.

  As described above, in the conventional technique, the manufacturing process becomes complicated, and it takes time and labor to form a silicon carbide single crystal with reduced BPD. In addition, the substrate surface and the off-angle for epitaxial growth are restricted.

US Pat. No. 7,279,115 US Pat. No. 7,226,805 US Pat. No. 7,109,521 JP 2005-311348 A Japanese Patent Laying-Open No. 2005-167035

S. Ha, P. Mieszkowski, M. Skowronski, and L. B. Rowland: J. Cryst. Growth 244 (2002) 257. H. Lendenmann, F. Dahlquist, N. Johansson, R. Soderholm, P. A. Nilsson, J. P. Bergman, and P. Skytt: Mater. Sci. Forum 353-356 (2001) 727. JJ Sumakeris, JP Bergman, MK Das, C. Hallin, BA Hull, E. Janzen, H. Lendenmann, MJ O'Loughlin, MJ Paisley, S. Ha, M. Skowronski, JW Palmour, and CH Carter, Jr .: Mater. Sci. Forum 527-529 (2006) 141. Z. Zhang and T.S.Sudarshan: Appl. Phys. Lett. 87 (2005) 151913. H. Tsuchida, T. Miyanagi, I. Kamata, T. Nakamura, K. Izumi, K. Nakayama, R. Ishii, K. Asano, and Y. Sugawara: Mater. Sci. Forum 483-485 (2005) 97. H. Tsuchida, M. Ito, I. Kamata, and M. Nagano: Phys. Status Solidi B 246 (2009) 1553 R. E. Stahlbush, B. L. VanMil, R. L. Myers-Ward, K-K. Lew, D. K. Gaskill, and C. R. Eddy, Jr .: Appl. Phys. Lett. 94 (2009) 041916.

  The present invention has been made in view of the above situation, and provides a method for manufacturing a silicon carbide wafer that prevents the manufacturing process from becoming complicated, that there is no restriction on the silicon carbide substrate, and that BPD can be more reliably converted to TED. With the goal.

  The present invention also provides a silicon carbide single crystal wafer in which the manufacturing process is prevented from being complicated, the silicon carbide substrate is not restricted, and the BPD is converted to TED, and a silicon carbide semiconductor device using the same. Objective.

  Furthermore, an object of the present invention is to provide a power conversion device manufactured from a silicon carbide semiconductor element using a silicon carbide single crystal wafer in which a silicon carbide substrate is not restricted and BPD is converted into TED.

  A first aspect of the present invention that solves the above problems includes a first step of implanting ions or irradiating an electron beam to one surface of a silicon carbide substrate, a second step of annealing the silicon carbide substrate, And a third step of epitaxially growing one surface side of the silicon carbide substrate.

  In the first aspect, a silicon carbide wafer with reduced basal plane dislocations can be obtained.

  According to a second aspect of the present invention, in the method for manufacturing a silicon carbide wafer according to the first aspect, ions implanted into the silicon carbide substrate are Si ions, C ions, H ions, He ions, P ions, The silicon carbide wafer manufacturing method is characterized in that it is at least one selected from the group consisting of Al ions, B ions and N ions.

  In such a second aspect, when these ions are implanted into the silicon carbide substrate, damage is caused near the surface of the substrate, and when the crystal quality is recovered by the subsequent annealing treatment, the basal plane dislocation is formed as a through-blade shape. Converted to dislocation.

According to a third aspect of the present invention, in the method for manufacturing a silicon carbide wafer described in the first or second aspect, the amount of ions implanted into the silicon carbide substrate is 1.0 × 10 ¹⁸ (/ cm ² ) or more and 1.0 × 10 ²¹ (/ cm ² ) or less, the temperature of the heat treatment after ion implantation is 1500 to 2200 ° C., and the heat treatment time is 1 to 120 minutes. It exists in the manufacturing method of a silicon wafer.

  In the third aspect, it is possible to obtain a silicon carbide wafer in which the occurrence of defects in the silicon carbide wafer is suppressed and BPD is converted to TED.

  According to a fourth aspect of the present invention, in the method for manufacturing a silicon carbide wafer according to the first or second aspect, the energy of the electron beam irradiated to the silicon carbide substrate is 100 keV or more, and the heat treatment after the electron beam irradiation. The temperature is 1500 to 2200 ° C., and the time for the heat treatment is 1 to 120 minutes.

  In the fourth aspect, it is possible to obtain a silicon carbide wafer in which the occurrence of defects in the silicon carbide wafer is suppressed and BPD is converted to TED.

  According to a fifth aspect of the present invention, in the method for manufacturing a silicon carbide wafer according to any one of the first to fourth aspects, the first step to the third step are repeated a plurality of times. It exists in the manufacturing method of a silicon carbide wafer.

  In the fifth aspect, a silicon carbide wafer with reduced basal plane dislocations can be obtained more reliably.

  A sixth aspect of the present invention is the method for manufacturing a silicon carbide wafer according to any one of the first to fifth aspects, wherein the third step is repeated a plurality of times. Is in the way.

  In the sixth aspect, a silicon carbide wafer having a desired thickness and lamination can be formed.

  According to a seventh aspect of the present invention, in the method for manufacturing a silicon carbide wafer according to any one of the first to sixth aspects, the epitaxial film is left and the silicon carbide substrate is removed. It exists in the manufacturing method of a silicon carbide wafer.

  In the seventh aspect, since the substrate having a high basal plane dislocation density is removed, it is possible to provide a silicon carbide wafer composed of only crystals with reduced basal plane dislocations.

  According to an eighth aspect of the present invention, in the method for manufacturing a silicon carbide wafer according to the seventh aspect, the epitaxial film that appears when the silicon carbide substrate is removed is further epitaxially grown. It is in the manufacturing method.

  In the eighth aspect, since the epitaxial growth is performed after removing the substrate having a high basal plane dislocation density, a silicon carbide wafer which is composed only of crystals with reduced basal plane dislocations and has a desired thickness and lamination is provided. Can do.

  According to a ninth aspect of the present invention, an ion implanted layer into which ions are implanted or an electron beam irradiated layer irradiated with an electron beam is formed on a bulk silicon carbide substrate, and the ion implanted layer or the electron beam irradiated further. An epitaxial film is formed on the layer, and 20% or more of the basal plane dislocations are converted to threading edge dislocations in a region of 0.1 μm or more and 20 μm or less from the surface of the silicon carbide substrate. In a silicon carbide wafer.

  In the ninth aspect, a silicon carbide wafer is obtained in which basal plane dislocations are intensively converted into threading edge dislocations in the above-described region.

  According to a tenth aspect of the present invention, a plurality of epitaxial films are formed on a bulk silicon carbide substrate, and two adjacent epitaxial films among the plurality of epitaxial films, which are closer to the silicon carbide substrate. A silicon carbide wafer having a first epitaxial film and a second epitaxial film on the far side, wherein the first epitaxial film is irradiated with an ion-implanted layer into which ions are implanted or electron beam irradiation. 20% or more of the basal plane dislocations are converted into threading edge dislocations in the first epitaxial film, and penetrates from the basal plane dislocations in a region within 2 μm in the thickness direction of the first epitaxial film. The silicon carbide wafer is characterized in that 60% or more of the conversion to edge dislocations is performed.

  In the tenth aspect, a silicon carbide wafer is obtained in which basal plane dislocations are intensively converted into threading edge dislocations in the above-described region.

  According to an eleventh aspect of the present invention, in the silicon carbide wafer described in the tenth aspect, in the first epitaxial film, a region within a range of 0.1 μm or more and 20 μm or less from the interface with the second epitaxial film, 80% or more of conversion from basal plane dislocation to threading edge dislocation is performed in the silicon carbide wafer.

  In the eleventh aspect, a silicon carbide wafer is obtained in which basal plane dislocations are intensively converted into threading edge dislocations in the above-described region.

  According to a twelfth aspect of the present invention, a plurality of epitaxial films are formed on a silicon carbide substrate, two adjacent epitaxial films among the plurality of epitaxial films, wherein the first epitaxial film is closer to the silicon carbide substrate. A silicon carbide wafer having an epitaxial film and a second epitaxial film on the far side, wherein an ion implanted layer into which ions are implanted or an electron beam irradiated layer to which electron beams are irradiated is formed on the first epitaxial film The basal plane dislocations are converted into threading edge dislocations in the first epitaxial film, and the density of the basal plane dislocations included in the second epitaxial film is the density of the basal plane dislocations included in the first epitaxial film. It is in the silicon carbide wafer characterized by being 80% or less.

  In the twelfth aspect, a silicon carbide wafer having a second epitaxial film with a further reduced basal plane dislocation density can be obtained.

  According to a thirteenth aspect of the present invention, there is provided the silicon carbide wafer according to any one of the ninth to twelfth aspects, wherein the silicon carbide substrate is removed.

  In such a thirteenth aspect, a substrate having a high basal plane dislocation density is removed, and a silicon carbide wafer composed only of crystals with reduced basal plane dislocations is obtained.

  According to a fourteenth aspect of the present invention, there is provided the silicon carbide wafer according to the thirteenth aspect, wherein an epitaxial film is formed on the surface on the side where the silicon carbide substrate is removed. .

  In the fourteenth aspect, since the epitaxial growth is performed after removing the substrate having a high basal plane dislocation density, a silicon carbide wafer having only a crystal with reduced basal plane dislocations and having a desired thickness and lamination can be obtained.

  According to a fifteenth aspect of the present invention, there is provided a silicon carbide semiconductor element manufactured using the silicon carbide wafer described in any one of the ninth to fourteenth aspects.

  In the fifteenth aspect, since it is manufactured from a silicon carbide wafer having reduced basal plane dislocations, a reduction in reliability and performance is prevented, and a high-performance semiconductor element utilizing the excellent characteristics of silicon carbide is provided. The

  A sixteenth aspect of the present invention is a power conversion device manufactured using the silicon carbide semiconductor element described in the fifteenth aspect.

  In the sixteenth aspect, the power conversion device can be applied to a high voltage due to the excellent characteristics of silicon carbide, and can perform power conversion with low loss.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the silicon carbide wafer which can prevent complication of a manufacturing process, has no restrictions of a silicon carbide substrate, and can convert BPD to TED more reliably is provided.

  Further, according to the present invention, there is provided a silicon carbide single crystal wafer in which the manufacturing process is prevented from being complicated, the silicon carbide substrate is not restricted, and the BPD is converted to TED, and a silicon carbide semiconductor device using the same. The

  Furthermore, according to the present invention, there is provided a power conversion device manufactured from a silicon carbide semiconductor element using a silicon carbide single crystal wafer in which a silicon carbide substrate is not restricted and BPD is converted to TED.

It is a schematic sectional drawing explaining the silicon carbide wafer which concerns on Embodiment 1. FIG. It is a schematic sectional drawing explaining the manufacturing method of the silicon carbide wafer which concerns on Embodiment 1. FIG. It is a schematic sectional drawing explaining the silicon carbide wafer which concerns on Embodiment 1. FIG. It is a schematic sectional drawing explaining the silicon carbide wafer which concerns on Embodiment 1. FIG. 5 is a schematic cross-sectional view illustrating a silicon carbide wafer according to Embodiment 2. FIG. 10 is a schematic cross-sectional view illustrating a method for manufacturing a silicon carbide wafer according to Embodiment 2. FIG. It is the schematic explaining the silicon carbide wafer which concerns on Embodiment 3, and its manufacturing method. It is a topography image of the silicon carbide wafer which concerns on a comparative example and an Example.

<Embodiment 1>
Hereinafter, a silicon carbide wafer and a manufacturing method thereof according to the present embodiment will be described in detail based on the drawings. FIG. 1 is a schematic cross-sectional view of a silicon carbide wafer, and FIG. 2 is a schematic cross-sectional view illustrating a method for manufacturing a silicon carbide wafer.

  As shown in FIG. 1, in a silicon carbide wafer (hereinafter referred to as a wafer) 10, an ion implantation layer 2 is formed on a silicon carbide substrate (hereinafter referred to as a substrate) 1, and an epitaxial film 3 is formed on the ion implantation layer 2. It is composed of that.

  The silicon carbide substrate described in the claims refers to a substrate obtained by slicing a bulk single crystal made of silicon carbide, or a substrate obtained by epitaxial growth of the substrate.

  In the present embodiment, the substrate 1 (silicon carbide substrate) is obtained by slicing a cylindrical bulk silicon carbide single crystal made of silicon carbide to a thickness of about 300 μm to 400 μm. The bulk silicon carbide single crystal is produced by a sublimation method, an HTCVD method, or the like.

  The substrate 1 has a main surface substantially parallel to the (0001) plane and a crystal polymorph (polytype) of 4H—SiC. However, the present invention is not limited to such a main surface and polytype. For example, a substrate having a plane substantially parallel to the (0001) plane, the (11-20) plane, the (1-100) plane, and the (03-38) plane may be used. Also, any type of polytype of the substrate 1 can be used. From the viewpoint that the polytype is relatively stable and a large-area substrate can be manufactured, it is preferable to use any of 4H—SiC, 6H—SiC, 15R—SiC, and 3C—SiC. The substrate 1 has a crystal growth surface having an inclination angle (off angle) of 0 ° to 10 ° with respect to the basal plane (0001).

  The substrate 1 has a plurality of basal plane dislocations (hereinafter referred to as BPD) 20. In the figure, five BPDs 20 are illustrated. The basal plane dislocation is a dislocation that propagates through a crystal plane (basal plane) perpendicular to the c-axis and has a Burgers vector of a / 3 <11-20>. The substrate 1 also has dislocations that propagate substantially parallel to the c-axis, such as threading edge dislocations and threading screw dislocations, but this is not shown in the figure.

  The ion implantation layer 2 is a layer formed by implanting ions into the substrate 1. Although details will be described later, the ion-implanted layer 2 is formed by implanting ions into the substrate 1 to damage the crystal and further recovering crystallinity by annealing.

  Although ion is not specifically limited, For example, they are Si ion, C ion, H ion, He ion, P ion, Al ion, B ion, and N ion. If the substrate 1 is made of silicon carbide, the ions are preferably Si ions, C ions, H ions, and He ions that are neutral in the silicon carbide. If the substrate 1 is an n-type semiconductor, P ions and N ions that form an n-type semiconductor are used. If the substrate 1 is a p-type semiconductor, Al ions and B ions that form a p-type semiconductor are used. Is preferred. That is, it is preferable to select ions that are neutral in silicon carbide or ions that match the polarity of the substrate 1 into which the ions are implanted.

  Epitaxial film 3 is a thin film made of silicon carbide formed by performing epitaxial growth of silicon carbide on substrate 1 on which ion implantation layer 2 is formed.

  In FIG. 1, five BPDs 20 are present on the substrate 1 as an example. Two of the five BPDs 20 existing on the substrate 1 are directly propagated to the ion implantation layer 2 and the epitaxial film 3, but the remaining three are in the substrate 1 (from the ion implantation layer 2 or the ion implantation layer 2). Is also converted to TED 30 in the lower substrate 1).

  A region R of the substrate 1 that is 0.1 μm or more and within 20 μm from the interface with the epitaxial film 3 is defined as a region R. 20% or more of the BPD 20 included in the substrate 1 is converted into the TED 30 in the region R. In the illustrated example, three of the five BPDs 20 have been converted to TED, and therefore 60% of all BPDs 20 have been converted to TED30.

  As described above, in the wafer 10, the BPD 20 is converted into the TED 30 in the substrate 1 (in the ion implantation layer 2 or in the substrate 1 below the ion implantation layer 2).

  In conventional techniques such as Non-Patent Document 1 and Non-Patent Document 7, the conversion from BPD 20 to TED 30 is performed when an epitaxial film provided on the substrate 1 grows.

  On the other hand, also in the wafer 10 according to the present embodiment, the BPD 20 is converted into the TED 30 when the epitaxial film 3 is grown. In addition, in the region R of the substrate 1, 20% or more of all the BPDs 20 are converted to the TED 30. Therefore, the wafer 10 according to the present embodiment has a further reduced BPD 20.

  Thus, since the BPD 20 is reduced, the wafer 10 according to the present embodiment is suitable as a material for a semiconductor element that requires high voltage resistance and a semiconductor element that requires high reliability. Further, since the conversion from the BPD 20 to the TED 30 is performed inside the substrate 1 (in the ion implantation layer 2 or in the substrate 1 below the ion implantation layer 2) which is an inactive region of the semiconductor element, high reliability is achieved. It is more suitable as a material for obtaining a semiconductor element.

  The wafer 10 is not limited to the off-angle of the substrate 1 or the crystal plane (Si plane, C plane). Therefore, it is possible to provide the wafer 10 having an off angle and a crystal plane suitable for manufacturing a semiconductor element.

  A method for manufacturing the wafer 10 will be described with reference to FIG. First, as shown in FIG. 2A, a substrate 1 is prepared. A plurality of BPDs 20 are present on the substrate 1.

  Next, as shown in FIG. 2B, ions are implanted into the substrate 1 (first step). Although this ion is not specifically limited, For example, Si ion, C ion, H ion, He ion, P ion, Al ion, B ion, and N ion can be used. In this embodiment, Si ions are implanted into the silicon carbide substrate 1.

  As a method for implanting ions into silicon carbide substrate 1, a method using a known ion implantation apparatus may be mentioned. The ion implantation apparatus is an apparatus that ionizes an element to be implanted, draws it out as an ion beam, accelerates it with a high-voltage electric field, and collides the accelerated ions with a sample (silicon carbide substrate 1). With this apparatus, ions are implanted into the silicon carbide substrate 1.

The amount of ions implanted into silicon carbide substrate 1 is preferably 1.0 × 10 ¹⁸ (/ cm ² ) or more and 1.0 × 10 ²¹ (/ cm ² ) or less. With such an implantation amount, as will be described later, BPD 20 of silicon carbide substrate 1 can be converted to TED, and a silicon carbide single crystal with reduced BPD 20 can be manufactured. If a larger amount of ions than the above-described ion implantation amount is implanted, a large amount of defects are generated in silicon carbide substrate 1.

  By implanting Si ions, in the vicinity of the surface of the silicon carbide substrate 1, a damaged layer 2a in which crystal defects are generated by the implanted Si ions is formed. Damage layer 2a is a layer of silicon carbide into which crystal defects are introduced. Thereby, the periphery of the front-end | tip part of BPD20 exists in the damage layer 2a.

  Next, as shown in FIG. 2C, the silicon carbide substrate 1 implanted with ions is annealed (second step). The heating temperature is not particularly limited, but is preferably 1500 to 2200 ° C., more preferably 1600 to 2000 ° C. for about 1 to 120 minutes. The heating is preferably performed in an inert gas atmosphere or in a vacuum. After heating, let it cool at room temperature.

  By this annealing treatment, the crystallinity of the damaged layer 2a is recovered and the ion-implanted layer 2 is obtained. When the ion implantation layer 2 is formed, the BPD 20 is converted into the TED 30. Although the final conversion position depends on the temperature and time of the annealing treatment, it is in the ion implantation layer 2 or in the substrate 1 below the ion implantation layer 2 (region R (see FIG. 1)). Although the theoretical mechanism of this conversion has not yet been clarified, it is presumed that the BPD 20 was converted to TED 30 when the crystallinity of the damaged layer 2a was recovered by the annealing treatment.

  Then, as shown in FIG. 2D, the surface of the ion-implanted layer 2 whose crystallinity has been recovered by annealing is epitaxially grown (third step). Thereby, the epitaxial film 3 is formed. The crystal growth method of the epitaxial film 3 is not particularly limited, but is preferably performed by, for example, a CVD method. Thereafter, the wafer 10 having a predetermined film thickness and lamination can be manufactured.

  During crystal growth of the epitaxial film 3, the TED 30 converted from the BPD 20 propagates as it is from the substrate 1 and the ion implantation layer 2 to the epitaxial film 3. Although not particularly shown, the TED 30 existing in the substrate 1 propagates as it is to the epitaxial film 3 as the TED 30.

  As described above, by implanting ions to form the damaged layer 2a and performing an annealing process, the BPD 20 of the substrate 1 is converted into the TED 30. Therefore, the BPD 20 existing on the substrate 1 does not propagate to the epitaxial film 3 but is converted to the TED 30 and propagates. That is, according to the manufacturing method according to the present invention, the wafer 10 in which the BPD 20 is reduced can be obtained.

  In particular, in this embodiment, Si ions as ions, that is, the same elements as those constituting the epitaxial film 3 that is the manufacturing purpose are used. By using this Si ion, the epitaxial film 3 that is not affected by impurities or dopants in the substrate 1 can be manufactured. This effect is the same when using C ions, H ions, or He ions.

  The same effect can be obtained by forming the damaged layer 2a by irradiating an electron beam instead of forming the damaged layer 2a by ion implantation. In this case, in order to form a sufficient defect in the surface layer of the substrate 1, it is necessary to irradiate an electron beam having energy of 100 keV or more. At an energy of 100 keV or less, both Si atoms and C atoms in the SiC single crystal cannot be removed from the interstitial position by an electron beam. However, at an energy of about 100 keV or more, a C atom, and at an energy of about 200 keV or more, an Si atom is removed. It can be removed from the interstitial position with an electron beam, and the damage layer 2a similar to the case of ion implantation can be formed.

  Thereafter, the damage layer 2a is not limited to that by ion implantation, but includes that by electron beam irradiation. In the following description, the ion-implanted layer 2 will be referred to, but the same effect can be obtained even if it is read as an electron beam irradiation layer. An electron beam irradiation layer is obtained by annealing the damage layer 2a formed by irradiating an electron beam.

  Further, in the prior art, in order to convert BPD into TED, an etching process such as molten KOH or RIE is performed on the substrate. In general, when an etching process is performed, a process for polishing and flattening the surface is required when a semiconductor element is manufactured. However, since this manufacturing method does not require such an etching process, the surface of the substrate 1 can be kept flat. Note that ion implantation and electron beam irradiation do not make the surface of the substrate 1 as rough as the etching process, and planarization is not necessary. Thus, the etching process and the flattening process associated therewith are not required, and the manufacturing process can be simplified.

  As shown in FIG. 3, the above-described ion implantation, annealing, and epitaxial growth may be performed any number of times. That is, the wafer 10 may be formed by forming a plurality of pairs of the ion implantation layer 2 and the epitaxial film 3 on the substrate 1. For example, it is assumed that the BPD 20 is not converted to the TED 30 by one ion implantation to annealing treatment. In this case, as shown in the figure, the BPD 20 of the substrate 1 propagates as it is to the first-layer epitaxial film 3 closer to the substrate 1 side. However, by repeating the ion implantation to annealing treatment a plurality of times, the probability that the BPD 20 is converted to the TED 30 increases. For example, by forming the second ion implantation layer 2, the BPD 20 is converted into the TED 30, and the TED 30 propagates to the second epitaxial film 3. Eventually, almost all of the BPD 20 can be converted into the TED 30 in the plurality of wafers 10 as a whole.

  Furthermore, as shown in FIG. 4, the epitaxial film 3 is not limited to one layer, and a plurality of layers may be formed. Thereby, the wafer 10 having a desired thickness and lamination can be formed.

  Further, the thickness of the epitaxial film 3 is not particularly limited. What is necessary is just to set suitably according to the film thickness of the desired epitaxial film 3, and the semiconductor element structure manufactured using this epitaxial film 3. FIG.

  Various silicon carbide semiconductor elements can be manufactured using silicon carbide wafer 10 described above. For example, MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), JFET (Junction Field Effect Transistor), BJT (Bipolar junction transistor), IGBT (Insulated Gate Bipolar Transistor), GTO (Gate Turn-Off thyristor), GCT thyristor ( Gate Commutated Turn-off Thyristor), thyristor, Schottky diode, JBS (Junction Barrier Schottky) diode, MPD (Merged pn diode), pn diode, and the like.

  Since the silicon carbide single crystal obtained by the manufacturing method according to the present invention or a wafer using the same has a reduced BPD 20, a decrease in reliability and performance of a semiconductor element manufactured using the wafer is prevented. A high-performance semiconductor element utilizing the excellent characteristics of silicon carbide can be obtained.

  Moreover, power converters, such as an inverter and a converter, can be manufactured from this silicon carbide semiconductor element. This power conversion device can be applied to a high voltage due to the excellent characteristics of silicon carbide, and can perform power conversion with low loss.

<Embodiment 2>
In the first embodiment, a wafer obtained by slicing a cylindrical bulk single crystal made of silicon carbide is used as the substrate 1, but in the present invention, an epitaxial film is formed on a substrate made of silicon carbide. A thing can also be used as a substrate. In the present embodiment, a wafer 10 manufactured using a substrate 1 on which an epitaxial film is formed and a manufacturing method thereof will be described.

  FIG. 5 is a schematic cross-sectional view of the silicon carbide wafer, and FIG. 6 is a schematic cross-sectional view illustrating a method for manufacturing the silicon carbide wafer. In addition, the same code | symbol is attached | subjected to the same thing as Embodiment 1, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 5A, an epitaxial film 3A formed by epitaxial growth is provided on a substrate 5 obtained by slicing a bulk single crystal made of silicon carbide. The entire substrate 5 on which the epitaxial film 3A is formed is referred to as a substrate 1.

  The wafer 10 according to the present embodiment includes a substrate 1, an ion implantation layer 2 provided on the epitaxial film 3 </ b> A of the substrate 1, and an epitaxial film 3 </ b> B provided on the ion implantation layer 2. Epitaxial films 3A and 3B are all thin films made of silicon carbide produced by a CVD method or the like. The epitaxial film 3A corresponds to the first epitaxial film of claim 10, and the epitaxial film 3B corresponds to the second epitaxial film of claim 10.

  The ion implantation layer 2 is a layer formed by implanting ions into the epitaxial film 3 </ b> A of the substrate 1. Although details will be described later, the ion-implanted layer 2 is formed by implanting ions into the epitaxial film 3A of the substrate 1 to cause damage, and further recovering crystallinity by annealing.

  A plurality of BPDs 20 are present on the substrate 1. In the figure, five BPDs 20 are illustrated. Four BPDs 20 are directly propagated from the substrate 5 to the epitaxial film 3A. One BPD 20 is converted to a TED 30 in the vicinity of the interface between the substrate 1 and the epitaxial film 3A.

  In the epitaxial film 3A (in the ion implantation layer 2 or in the epitaxial film 3A below the ion implantation layer 2), three of the BPDs 20 are converted into TEDs 30. The conversion from the BPD 20 to the TED 30 is performed by implanting ions into the substrate 1 and performing an annealing process, as will be described in detail later.

  Three TEDs 30 converted in the epitaxial film 3A (in the ion implantation layer 2 or in the epitaxial film 3A below the ion implantation layer 2) are propagated as they are to the epitaxial film 3B, and are not converted in the ion implantation layer 2. Two BPDs 20 are propagated as they are.

  The position and ratio of conversion from BPD 20 to TED 30 performed in the epitaxial film 3A are as follows.

  In the epitaxial film 3A, 20% or more of the BPD propagated from the substrate 1 is converted to TED. In the illustrated example, three BPDs 20 of the four BPDs 20 are converted to TEDs 30 in the ion implantation layer 2, so that 75% of all the BPDs 20 in the ion implantation layer 2 are converted to the TEDs 30.

  Of the epitaxial film 3A (in the ion-implanted layer 2 or in the epitaxial film 3A below the ion-implanted layer 2), a portion having a thickness of 2 μm in the thickness direction is defined as a region R. More than 60% of the conversion from BPD 20 to TED 30 performed in the epitaxial film 3A is performed in the region R. In the illustrated example, three BPDs 20 in the epitaxial film 3 </ b> A are converted into TEDs 30, but two BPDs 20 in the region R are converted into TEDs 30. That is, 67% (2/3 = 0.666...) Of the conversion from BPD 20 to TED 30 performed in the epitaxial film 3A is performed in the region R.

  The reason why the BPD 20 is intensively converted to the TED 30 in the region R having a thickness of 2 μm or less is that the ion implantation layer 2 is formed on the epitaxial film 3A by a series of processes as will be described later, and the annealing process is performed. That is, as described in the first embodiment, by appropriately adjusting the amount (density) of ions implanted into the epitaxial film 3A and the annealing temperature and time, the depth of the position where the BPD 20 is converted to the TED 30 is changed. It is because it can adjust.

  Further, the region R is located at a depth D from the interface between the ion implantation layer 2 and the epitaxial film 3B. The depth D is not particularly limited, but is, for example, 0.1 μm to 20 μm from the interface. This depth D can be controlled by the amount (density) of ions implanted into the epitaxial film 3A and the annealing temperature and time. The depth D tends to increase as the amount of ions to be implanted (the amount of electron beam to be irradiated) increases, as the annealing time increases, and as the annealing temperature increases.

  Here, FIG. 5B illustrates another mode of the wafer 10 in which the ion implantation layer 2 is formed in the epitaxial film 3A.

  As shown in the figure, a substrate 5 provided with an epitaxial film 3 is a substrate 1, an arbitrary number (one layer in the figure) of epitaxial films 3 is formed thereon, and an epitaxial film 3A is formed thereon. The wafer 10 may be formed by forming the ion implantation layer 2 in the epitaxial film 3A and further forming the epitaxial film 3B.

  In this case, the first epitaxial film of claim 10 is the epitaxial film 3A, and the second epitaxial film of claim 10 is the uppermost epitaxial film 3B. That is, another epitaxial film may be interposed between the first epitaxial film 3 </ b> A and the substrate 1.

  Even in such a wafer 10, 20% or more of the BPD propagated to the epitaxial film 3 </ b> A (first epitaxial film) is converted into TED in the ion implantation layer 2, and conversion from BPD to TED is performed in the region R. 60% or more of the Further, the region R is located at a depth D from the interface between the ion implantation layer 2 and the epitaxial film 3B.

  Further, the BPD 20 existing in the epitaxial film 3A and the epitaxial film 3B of the wafer 10 has the following relationship.

  That is, the density of the BPD 20 included in the epitaxial film 3B is 80% or less of the density of the BPD 20 included in the epitaxial film 3A. The density of BPD 20 in epitaxial film 3A is the number per unit area of BPD contained in epitaxial film 3A. The same applies to the density of the BPD 20 of the epitaxial film 3B.

  In the example shown in FIG. 5A, the epitaxial film 3A includes four BPDs 20 (three of which are converted to TEDs 30), and the epitaxial film 3B includes one BPD20. Therefore, the density (1 piece / unit area) of the BPD 20 in the epitaxial film 3A is 80% or less of the density (4 pieces / unit area) of the BPD 20 in the epitaxial film 3B.

  As described above, the wafer 10 has the BPD 20 converted into the TED 30 in the epitaxial film 3A (in the ion implantation layer 2 or in the epitaxial film 3A below the ion implantation layer 2). In the prior art, a very small portion of the BPD 20 is converted to TED 30 in the epitaxial film as it grows. Such conversion from the BPD 20 to the TED 30 occurs at an unspecified place in the depth direction of the epitaxial film.

  On the other hand, in the wafer 10 according to the present embodiment, a part of the BPD 20 is converted into TED by the epitaxial film 3A, as in the conventional technique. In addition to that, in the wafer 10, 20% of the BPD 20 is concentrated in the region R located at the depth D of the epitaxial film 3A (in the ion implantation layer 2 or in the epitaxial film 3A below the ion implantation layer 2). The above has been converted to TED30. Therefore, the wafer 10 according to the present embodiment has a further reduced BPD 20.

  Thus, since the BPD 20 is reduced, the wafer 10 according to the present embodiment is suitable as a material for a semiconductor element that requires high voltage resistance and a semiconductor element that requires high reliability. The wafer 10 is not limited to the off-angle of the substrate 1 or the crystal plane (Si plane, C plane). Therefore, a wafer 10 having an off angle and a crystal plane suitable for manufacturing a semiconductor element is provided.

  A method for manufacturing the wafer 10 will be described with reference to FIG. First, as shown in FIG. 6A, an epitaxial film 3A is formed by epitaxially growing a substrate 5 obtained by slicing a bulk single crystal made of silicon carbide. The entire substrate 5 on which the epitaxial film 3A is formed is referred to as a substrate 1.

  A plurality of BPDs 20 exist on the substrate 5. In the figure, three BPDs 20 are illustrated. When this substrate 5 is epitaxially grown, some BPDs 20 (two BPDs 20 in the figure) are converted to TED 30 at the interface between the substrate 5 and the epitaxial film 3A, and propagate as TED 30 to the epitaxial film 3A. On the other hand, in some cases, the BPD 20 in the substrate 5 propagates as it is to the epitaxial film 3A (in the figure, one BPD 20 propagates as it is).

  Next, as shown in FIG. 6B, ions are implanted into such a substrate 1. In this embodiment, Si ions are implanted into the silicon carbide substrate 1. The ion type, implantation amount, and implantation method are the same as in the first embodiment.

  By implanting Si ions, a damaged layer 2a in which crystal defects are generated by the implanted Si ions is formed in the vicinity of the surface of the epitaxial film 3A (silicon carbide substrate 1). Similar to the first embodiment, the periphery of the tip of the BPD 20 exists in the damage layer 2a.

  Next, as shown in FIG. 6C, the substrate 1 implanted with ions is annealed. By this annealing treatment, the crystallinity of the damaged layer 2a is recovered and becomes the ion implantation layer 2. When the ion implantation layer 2 is formed, the BPD 20 is converted into the TED 30. The heating conditions are the same as in the first embodiment. After heating, let it cool at room temperature.

  Then, as shown in FIG. 6D, the surface of the ion-implanted layer 2 whose crystallinity has been recovered by annealing is epitaxially grown. Thereby, the epitaxial film 3B is formed. The crystal growth method of the epitaxial film 3B is not particularly limited, but is preferably performed by, for example, a CVD method.

  During crystal growth of the epitaxial film 3B, the TED 30 converted from the BPD 20 propagates as it is from the ion implantation layer 2 to the epitaxial film 3B.

  As described above, the BPD 20 that has not been converted into the TED 30 when the epitaxial film 3A is formed on the substrate 5 can be converted into the TED 30 by performing ion implantation, annealing, and epitaxial growth. The conversion rate and conversion position from BPD 20 to TED 30 at this time are the same as those shown in FIG. As described above, the manufacturing method according to the present invention can manufacture the wafer 10 in which the BPD 20 is reduced.

  Of course, although not shown in particular, after forming an arbitrary number of epitaxial films 3 on the substrate 1, the ion implantation layer 2 is formed, and further the epitaxial film 3 is formed, as shown in FIG. The wafer 10 can be manufactured. Further, after the epitaxial film 3 is formed, an epitaxial film having an arbitrary film thickness or layer structure may be formed on the epitaxial film 3.

<Embodiment 3>
Although the substrate 10 is included in the wafer 10 described in the first and second embodiments, the substrate 1 may be removed.

  FIG. 7 is a schematic view for explaining the silicon carbide wafer and the manufacturing method thereof according to the present embodiment. In addition, the same code | symbol is attached | subjected to the same thing as Embodiment 1 and Embodiment 2, and the overlapping description is abbreviate | omitted.

  The wafer 10 shown in FIG. 7A is the same as the wafer 10 shown in FIG. As shown in FIG. 7B, the entire substrate 1 of the wafer 10 is removed. The removal method may be performed by an appropriate method such as mechanical polishing, chemical treatment, or ion etching until the ion-implanted layer 2 is eliminated.

  Although the BPD 20 exists in the substrate 1 at a high density, the substrate 1 is removed, so that a wafer 11 having a low BPD density is obtained.

  Further, as shown in FIG. 7C, after obtaining the wafer 11 described above, the epitaxial growth of silicon carbide is further performed once or a plurality of times on the surface on the side where the substrate 1 was present. 3 may be formed. The thickness of the epitaxial film 3 and the number of times of epitaxial growth are not particularly limited. What is necessary is just to set suitably according to the whole film thickness and element structure of a desired wafer. Thereby, a wafer 12 having a low BPD density and having the epitaxial film 3 on the side where the substrate 1 was present can be obtained.

  Although not particularly shown, the ion implantation layer 2 may be left when the substrate 1 is removed. Even in this case, a wafer having a low BPD density can be obtained. Further, with respect to the wafer shown in the second embodiment, the substrate 1 may be removed, or after removing the substrate 1, an epitaxial film may be formed to form a wafer.

Hereinafter, the present invention will be described more specifically with reference to examples.

[Comparative example]
A crystal growth is performed by a CVD method on a 4H—SiC substrate having an off angle of 8 ° in the <11-20> direction to form a first epitaxial film having a thickness of about 20 μm. A board was produced.

[Example]
For the substrate according to the comparative example, after performing the measurement shown in the following test example, ion implantation was performed so that Si ions had an average concentration of 1 × 10 ¹⁹ cm ^{−3 in} the region of a depth of 250 nm from the surface of the epitaxial film. It was. The substrate temperature during ion implantation was 600 ° C. Subsequent to the ion implantation, heat treatment was performed. In this heat treatment, the substrate was placed in a graphite crucible, and the crucible was placed in a graphite cylinder (hot wall) where high frequency induction heating was performed. Argon gas was supplied into the crucible and heated at 1670 ° C. for 3 minutes. The heating rate was 40 ° C./min. After the heat treatment, crystal growth was performed by a CVD method to form a second epitaxial film having a thickness of about 20 μm to obtain a substrate according to the example. Then, the measurement shown in the below-mentioned test example was performed again.

[Test Example 1]
With respect to each of the substrates according to the comparative example and the example, synchrotron radiation reflection topography measurement (SPring-8 synchrotron radiation facility) was performed to obtain a topography image, thereby measuring the distribution of various dislocations in the epitaxial film.

  Specifically, each of the substrates according to the comparative example and the example is irradiated with X-rays (wavelength of 1.54 mm) obtained by monochromatic radiation at an incident angle of about 20 °, and the diffraction vector g = 11−. Reflected light satisfying the condition of 28 was imaged on the nuclear plate to obtain a topography image.

  FIG. 8A is a topographic image of a comparative example, and FIG. 8B is a topographic image of an example obtained after ion implantation, heat treatment, and formation of the second epitaxial film. The linear dark contrast appearing on the substrate according to the comparative example is BPD, the comparatively small fragment (dot) contrast is TED, and the comparatively large circular contrast is TSD (through screw dislocation). . These topographic images show the same region of the substrate, and it was confirmed how dislocations were changed by ion implantation → heating treatment → second epitaxial film formation.

  As indicated by the circles in FIG. 8A, it was confirmed that 18 BPDs propagated from the substrate to the epitaxial film appeared on the substrate according to the comparative example.

  On the other hand, in FIG.8 (b), TED is observed by the substantially same arrangement | positioning (position shown with a white arrow) as the position where BPD was observed in the comparative example. That is, in the comparative example, what appeared on the surface of the epitaxial film as BPD appeared on the epitaxial film as TED after ion implantation → heating treatment → second epitaxial film formation. This is because, in the comparative example, what appeared with a linear contrast changed to a contrast on a small fragment (dot-like) after ion implantation → heating treatment → second epitaxial film formation. To be judged.

  From the observation result of the topography image, a total of 18 BPDs appeared on the surface of the epitaxial film in one region of the substrate shown in the comparative example. Of these, 17 BPDs (in FIG. 8B) , BPD indicated by a white arrow) is converted to TED by ion implantation → heat treatment → second epitaxial film formation, and the remaining one BPD (BPD indicated by a black arrow in FIG. 8B) is converted. It turns out that it remained as BPD.

[Test Example 2]
Regarding the comparative example and the example, the distribution of dislocations was measured in a wider region.

  When the BPD of the comparative example was measured in a wider area, 56 BPDs appeared on the epitaxial film surface. On the other hand, when the BPD of the example was measured for the same region, 51 out of 56 BPDs, corresponding to about 91%, were converted to TED.

[Test Example 3]
Regarding the examples, it was investigated in which depth direction the conversion from BPD to TED caused by ion implantation → heating treatment → second epitaxial film formation was performed from the film surface in the epitaxial film.

  In the synchrotron radiation topography image of the one converted from BPD to TED by ion implantation → heat treatment → second epitaxial film formation by comparing and examining the synchrotron radiation reflection topography acquired in the comparative example and the example, By examining the length of the BPD in the epitaxial film in the direction parallel to the off-tilt of the substrate, the distance from the surface of the epitaxial film where the conversion occurred was obtained. As a result, the frequency with respect to the distance from the surface of the epitaxial film was clarified for the conversion from BPD to TED. As a result, a region of 5.5 μm ± 1 μm from the interface between the first epitaxial film and the second epitaxial film to the first epitaxial film side (5.5 μm corresponds to D in FIG. (2 μm corresponds to R in FIG. 5A), and it was confirmed that 65% or more of the conversion from BPD to TED occurred.

[Test Example 4]
As a result of performing the same experiment and analysis by changing the high-temperature heat treatment temperature after the ion implantation in the range of 1500 to 2200 ° C. and the heat treatment time in the range of 5 to 240 minutes, the conversion from BPD to TED was almost confirmed at 1500 ° C. However, conversion from BPD to TED was confirmed at 1600 ° C. or higher. The probability of conversion from BPD to TED increased as the temperature increased. However, sublimation of the SiC single crystal surface started to accelerate in the temperature range exceeding 2000 ° C., and the heat treatment temperature was inappropriate at 2200 ° C. or higher. . In addition, as the heat treatment time increased, the probability of conversion from BPD to TED increased, but it was almost saturated after 120 minutes. In addition, the position where the conversion from BPD to TED occurs by the heat treatment is from the vicinity of the epitaxial film surface (about 0.1 μm from the surface) to the deep direction (about 20 μm at the maximum from the surface) as the temperature or time of the high temperature heat treatment increases. In all cases, over 60% of the conversion from BPD to TED was performed within a range of ± 1 μm from a certain depth.

  The present invention can be used in an industrial field using a silicon carbide semiconductor element.

DESCRIPTION OF SYMBOLS 1 Silicon carbide substrate 2 Ion implantation layer 2a Damaged layer 3, 3A, 3B Epitaxial film 5 Substrate 20 BPD (basal plane dislocation)
30 TED (penetrating edge dislocation)

Claims (16)

A first step of implanting ions into one surface of the silicon carbide substrate or irradiating with an electron beam;
A second step of annealing the silicon carbide substrate;
And a third step of forming an epitaxial film on one side of the silicon carbide substrate. A method for manufacturing a silicon carbide wafer, comprising: In the manufacturing method of the silicon carbide wafer of Claim 1,
The ions implanted into the silicon carbide substrate are at least one selected from the group consisting of Si ions, C ions, H ions, He ions, P ions, Al ions, B ions, and N ions. A method for manufacturing a silicon carbide wafer. In the manufacturing method of the silicon carbide wafer of Claim 1 or Claim 2,
The amount of ions implanted into the silicon carbide substrate is 1.0 × 10 ¹⁸ (/ cm ² ) or more and 1.0 × 10 ²¹ (/ cm ² ) or less, and the temperature of the heat treatment after ion implantation is 1500. A method for producing a silicon carbide wafer, wherein the temperature is ˜2200 ° C. and the heat treatment time is 1 to 120 minutes. In the manufacturing method of the silicon carbide wafer of Claim 1 or Claim 2,
The energy of the electron beam irradiated to the silicon carbide substrate is 100 keV or more, the temperature of the heat treatment after the electron beam irradiation is 1500 to 2200 ° C., and the heat treatment time is 1 to 120 minutes. A method for producing a silicon wafer. In the manufacturing method of the silicon carbide wafer as described in any one of Claims 1-4,
The method of manufacturing a silicon carbide wafer, wherein the first step to the third step are repeated a plurality of times. In the manufacturing method of the silicon carbide wafer as described in any one of Claims 1-5,
The method of manufacturing a silicon carbide wafer, wherein the third step is repeated a plurality of times. In the manufacturing method of the silicon carbide wafer as described in any one of Claims 1-6,
The method of manufacturing a silicon carbide wafer, wherein the epitaxial film is left and the silicon carbide substrate is removed. In the manufacturing method of the silicon carbide wafer of Claim 7,
A method of manufacturing a silicon carbide wafer, further comprising epitaxially growing an epitaxial film that has appeared by removing the silicon carbide substrate. An ion implanted layer into which ions are implanted or an electron beam irradiated layer irradiated with an electron beam is formed on a bulk silicon carbide substrate, and an epitaxial film is further formed on the ion implanted layer or the electron beam irradiated layer,
A silicon carbide wafer, wherein 20% or more of basal plane dislocations are converted to threading edge dislocations in a region of 0.1 μm or more and 20 μm or less from the surface of the silicon carbide substrate. A plurality of epitaxial films are formed on a bulk silicon carbide substrate,
Two adjacent epitaxial films of the plurality of epitaxial films, a silicon carbide wafer having a first epitaxial film on the side close to the silicon carbide substrate and a second epitaxial film on the far side,
In the first epitaxial film, an ion implanted layer into which ions are implanted or an electron beam irradiated layer irradiated with an electron beam is formed,
In the first epitaxial film, 20% or more of basal plane dislocations are converted into threading edge dislocations,
60% or more of conversion from basal plane dislocations to threading edge dislocations is performed in a region within 2 μm in the thickness direction of the first epitaxial film. In the silicon carbide wafer according to claim 10,
In the first epitaxial film, 80% or more of conversion from basal plane dislocations to threading edge dislocations is performed in a region within 0.1 μm or more and 20 μm or less from the interface with the second epitaxial film. A silicon carbide wafer characterized by the above. A plurality of epitaxial films are formed on the silicon carbide substrate,
Two adjacent epitaxial films of the plurality of epitaxial films, a silicon carbide wafer having a first epitaxial film on the side close to the silicon carbide substrate and a second epitaxial film on the far side,
In the first epitaxial film, an ion implanted layer into which ions are implanted or an electron beam irradiated layer irradiated with an electron beam is formed,
In the first epitaxial film, basal plane dislocations are converted to threading edge dislocations,
A silicon carbide wafer, wherein the density of basal plane dislocations contained in the second epitaxial film is 80% or less of the density of basal plane dislocations contained in the first epitaxial film. In the silicon carbide wafer according to any one of claims 9 to 12,
The silicon carbide wafer, wherein the silicon carbide substrate is removed. The silicon carbide wafer according to claim 13,
An epitaxial film is formed on the surface of the side from which the silicon carbide substrate has been removed.   The silicon carbide semiconductor element produced using the silicon carbide wafer as described in any one of Claims 9-14.   The power converter device produced using the silicon carbide semiconductor element of Claim 15.