Method for Producing Silicon Carbide Substrates

Abstract

A method for producing a silicon carbide substrate (11) includes providing a silicon carbide substrate (11) and irradiating the silicon carbide substrate (11) with particles (14) from the group including electrons, hydrogen atoms, helium atoms, lithium atoms, beryllium atoms, boron atoms, sodium atoms, magnesium atoms, and aluminum atoms. The energy of the particles (14) for irradiation is selected such that the irradiation increases the resistivity (ρ) of at least a portion of the silicon carbide substrate (11) and the silicon carbide substrate (11) is in a semiconducting state after irradiation.

Description

[Technical field]

[0001] The present disclosure relates to methods for producing silicon carbide substrates. [Background technology]

[0002] Power semiconductor devices are often realized as high voltage devices that usually require a thick lightly doped layer. The thick lightly doped layer can be fabricated as a silicon carbide layer, or SiC layer for short. Silicon carbide (abbreviated as SiC) is a wide band gap semiconductor. This layer can be realized as an epitaxial layer, or epilayer for short. For example, a 100 μm thick lightly doped SiC epilayer (approximately 10 14 cm -3 ) are available. Power semiconductor devices blocking voltages above 10 kV require a doping concentration of n ≤ 10 14 cm -3 (10 5 To achieve this, an epilayer with a thickness of over 100 μm (resulting in a resistivity of 100 Ω·cm) is required. However, thick SiC epilayers are expensive.

[0003] Alternatively, the thick lightly doped layer can be realized as a semi-insulating silicon carbide layer or substrate, or SI-SiC layer or substrate for short. However, SI-SiC has a high resistivity (resistivity = 10 9 Bipolar diodes with SI-SiC drift layers exhibited low forward currents in the μA range.

[0004] US Pat. No. 4,201,598 refers to electron irradiation processing of glass passivated semiconductor devices for improved reverse characteristics.

[0005] US Pat. No. 6,974,720 relates to a method of forming a power semiconductor device using a boule-grown silicon carbide drift layer.

[0006] The paper by KANEKO HIROMI et al., APPLIED PHYSICS LETTERS, vol. 98, no. 26, pages 262106; 29 June 2011, concerns the formation of semi-insulating layers in n-type 4H-SiC by electron irradiation.

[0007] The article by NADELLA RK et al., 1998 HIGH-TEMPERATURE ELECTRONIC MATERIALS, DEVICES AND SENSORS CONFERENCE, FEBRUARY 22-27, 1998, BAHIA HOTEL, SAN DIEGO, CALIFORNIA, USA; IEEE SERVICE CENTER; pages 14-17; 22 February 1998, relates to hydrogen and helium implants to obtain high resistivity layers in N-type 4H silicon carbide.

[0008] The article by NADELLA RK et al., APPLIED PHYSICS LETTERS, vol. 70, no. 7, page 886; 17 February 1997, relates to high resistivity layers in n-type 4H silicon carbide by hydrogen ion implantation. Summary of the Invention [Problem to be solved by the invention]

[0009] What is needed is a method for producing silicon carbide substrates with suitable resistivity. [Means for solving the problem]

[0010] According to one embodiment, a method for producing a silicon carbide substrate includes providing a silicon carbide substrate and irradiating the silicon carbide substrate with particles from the group including electrons, hydrogen atoms, helium atoms, lithium atoms, beryllium atoms, boron atoms, sodium atoms, magnesium atoms and aluminum atoms. The energy of the particles for the irradiation is selected such that the irradiation increases the resistivity of at least a portion of the silicon carbide substrate and the silicon carbide substrate is in a semiconducting state after irradiation.

[0011] Here and below, qualitative or quantitative characteristics disclosed regarding resistivity refer specifically to resistivity at room temperature.

[0012] Exemplarily, irradiation with particles induces, for example, an increase in the concentration of silicon vacancies and carbon vacancies in a silicon carbide substrate (SiC substrate for short). These vacancies are point defects. Silicon vacancies can be combined, for example, with n-doping. N-doping is typically due to nitrogen. Nitrogen is present at carbide sites. Carbon vacancies do not bind to nitrogen doping. For these reasons, silicon vacancies cause doping passivation and carbon vacancies cause carrier compensation. Irradiation therefore reduces the concentration of free electrons in the SiC substrate. Irradiation therefore results in passivation of the current dopants and not counterdoping. In this text, the process of irradiating is called irradiation. Irradiation means irradiating a silicon carbide substrate with particles. Irradiation therefore increases the resistivity in at least a portion of the SiC substrate. At least this portion of the SiC substrate is in a semiconducting state after irradiation.

[0013] According to a further embodiment, the resistivity is increased by irradiating the entire SiC substrate, which may also be referred to as an all-SiC substrate or a full SiC substrate.

[0014] According to a further embodiment, the resistivity is increased by irradiation to 10 2 Ω cm~10 5 Ω cm or 10 2 Ω cm~10 4 The resistance increases to the Ω·cm range. 10 2 Ω cm~10 5 Ω cm or 10 2 Ω cm~10 4 A SiC substrate with a resistivity in the range of Ω·cm can be called semiconducting. 14 cm -3 ~10 16 cm -3 may be in the range.

[0015] According to a further embodiment, prior to irradiating the SiC substrate, the SiC substrate is a conductive SiC substrate. Illustratively, the conductive SiC substrate is a 10 -2 The resistivity is less than Ω·cm. The doping concentration of the conductive SiC substrate is 10 18 cm -3 Illustratively, the doping atom is one of nitrogen or a phosphor.

[0016] According to a further embodiment, the entire SiC substrate has n-type conductivity before and after irradiation. According to a further embodiment, the silicon carbide substrate is not attached to a carrier wafer before and during irradiation.

[0017] According to an alternative embodiment, the silicon carbide substrate is attached to a carrier wafer, such as a silicon wafer and / or a glass wafer, prior to and during irradiation.

[0018] According to a further embodiment, the silicon carbide substrate does not include a silicon carbide epitaxial layer.

[0019] According to a further embodiment, the method includes annealing the silicon carbide substrate after irradiation.

[0020] The method for producing a SiC substrate can be used, for example, in the manufacture of a semiconducting SiC substrate. The resistivity of the SiC substrate increases as a result of particle irradiation. The semiconducting SiC substrate is an alternative to both semi-insulating SiC substrates and thick lightly doped semiconducting SiC epilayers.

[0021] According to further embodiments, the SiC substrate can be thick (e.g., 350 μm) and, if necessary, can be mechanically thinned, e.g., to 100 μm. The resistivity of such a SiC substrate can be in the range of 10 to 150 μm, so as to have a medium resistivity SiC for high voltage applications. -2 Ω cm to 10 2 ~10 5It can be increased to the Ω·cm range.

[0022] According to a further embodiment, the energy of the particles for the irradiation is selected such that at least a portion of the particles pass through the SiC substrate, which allows for a high homogeneity of, for example, the net doping concentration, carrier lifetime, resistivity and other parameters of the SiC substrate to be achieved.

[0023] According to a further embodiment, the silicon carbide substrate is homogenous before and after irradiation, meaning, for example, that the net doping concentration is homogenous throughout the volume of the silicon carbide substrate before and after irradiation.

[0024] According to further embodiments, power semiconductor devices can be made from the SiC substrate. The power semiconductor devices can be implemented, for example, as one of thyristors, diodes, gate turn-off thyristors (abbreviated GTO), power metal-insulator-semiconductor field effect transistors (abbreviated power MISFET), power metal-oxide-semiconductor field effect transistors (abbreviated power MOSFET), junction field effect transistors (abbreviated JFET), bipolar junction transistors (abbreviated BJT), insulated gate bipolar transistors (abbreviated IGBT), and integrated gate commutated thyristors (abbreviated IGCT). Thus, the SiC substrate can be used for the production of bipolar and / or MOS chips or devices. Particle irradiation is used to tune the resistivity of the conductive SiC substrate. The conductive SiC substrates can be thick and are inexpensive. They have a thickness of, for example, 350 μm. Thus, the proposed SiC substrate is a cost-effective material for high voltage applications. Irradiation can be done at the boule level, which means that the boule can then be cut on-axis, thus reducing material waste.

[0025] Particle irradiation is used to increase the resistivity of conductive SiC substrates, i.e. to create semiconducting SiC substrates. In this way, irradiation-induced defects (silicon-related) can passivate the nitrogen doping. In fact, irradiation-induced defects (carbon-related) can trap charge carriers. However, at high doping levels, e.g. 10 16 cm -3 At higher levels, the latter effect is not major.

[0026] The present disclosure includes several embodiments of methods for producing SiC substrates. All features described with respect to one of the embodiments are also disclosed herein with respect to the other embodiments, even if the respective feature is not explicitly mentioned in the context of a particular embodiment.

[0027] The accompanying drawings are included to provide a further understanding. In the drawings, elements of the same structure and / or function may be referenced by the same reference numerals. It should be understood that the embodiments shown in the drawings are illustrative representations and are not necessarily drawn to scale. [Brief description of the drawings]

[0028] [Figure 1] 1A-1D are diagrams of silicon carbide substrates and irradiation devices according to different embodiments. [Figure 2A] 1A-1D are diagrams of silicon carbide substrates and irradiation devices according to different embodiments. [Figure 2B] 1A-1D are diagrams of silicon carbide substrates and irradiation devices according to different embodiments. [Figure 3A] 1A-1D are schematic diagrams of methods for producing silicon carbide substrates according to different embodiments. [Figure 3B] 1A-1D are schematic diagrams of methods for producing silicon carbide substrates according to different embodiments. [Figure 4A] 1A-1D are diagrams illustrating the values ​​of methods for producing silicon carbide substrates according to different embodiments. [Figure 4B] 1A-1D are diagrams illustrating the values ​​of methods for producing silicon carbide substrates according to different embodiments. [Diagram 5] FIG. 2 illustrates properties of a silicon carbide substrate according to one embodiment. [Figure 6] FIG. 2 illustrates properties of a silicon carbide substrate according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] FIG. 1 is a diagram of a silicon carbide substrate 11 and an irradiation device 10 according to an embodiment. The silicon carbide substrate 11 is realized as a silicon carbide boule 12, SiC boule for short. After irradiation of the SiC boule 12, the SiC boule 12 is sawn into wafers. The SiC boule 12 typically has a cylindrical shape. The SiC boule 12 is made, for example, using a sublimation recrystallization growth technique, a high-temperature chemical vapor deposition technique (high-temperature CVD technique for short) or another technique. 4H-SiC polytype substrates can be obtained using sublimation recrystallization growth. The irradiation of the silicon carbide boule can be performed from a lateral side, i.e. a side along or parallel to the longitudinal axis or main extension direction of the SiC boule 12, illustratively a side perpendicular to the sawing direction. The boule has an elongated shape. The boule may have the shape of a cylinder and / or a truncated cone. The lateral side may be the outer side of a cylinder or a truncated cone, respectively, extending around the longitudinal axis or main extension axis.

[0030] The irradiation device 10 comprises a SiC substrate 11 and an irradiation source 13. The irradiation source 13 is realized for example as an electron gun and / or an accelerator. Particles 14 with high kinetic energy are applied to the silicon carbide substrate 11 by the irradiation source. In this example, the particles 14 are electrons, denoted as e in FIG. - 3. The energy of the particles 14 for irradiation is high enough that at least some of the particles 14 pass through the SiC substrate 11. The particles 14 for irradiation are electrons. In one example, 50% of the particles 14 pass through the SiC substrate 11. Alternatively, 75% or 90% of the particles 14 pass through the SiC substrate 11. Optionally, a majority of the electrons pass through the SiC substrate 11.

[0031] 2A is a diagram of a SiC substrate 11 and an irradiation device 10 according to a further embodiment, which is a further development of the embodiment shown in FIG. The SiC substrate 11 is realized as a silicon carbide wafer 20 (abbreviated SiC wafer) having a first main side 21 and a second main side 22. During irradiation of the SiC substrate 11, particles 14 penetrate into the first main side 21 of the SiC wafer 20. Optionally, at least a part of the particles 14 leaves the SiC wafer 20 at the second main side 22.

[0032] The particles 14 for irradiation are electrons, e in FIG. - The electrons have energies in the range of, for example, 140 keV to 180 keV. The electron particles 14 for irradiation have energies in the range of, for example, 0.5·10 17 cm -2 ~2·10 19 cm -2 Alternatively, the particles 14 for irradiation, which are electrons, have a dose in the range of, for example, 10 17 cm -2 ~10 19 cm -2 In one example, the SiC substrate 11 is not attached to a carrier wafer, such as a silicon wafer or a glass wafer, before and during irradiation. The SiC substrate 11 does not include a SiC epitaxial layer. The SiC wafer 20 is, for example, a 4H-SiC wafer.

[0033] FIG. 2B is a diagram of a silicon carbide substrate 11 and an irradiation device 10 according to a further embodiment, which is a further development of the embodiment shown in FIG. 1 and FIG. 2A. The particles 14 for irradiation are atoms, which are indicated as A in FIG. 2B. The atoms are ionized. Examples of atoms are hydrogen atoms, helium atoms, lithium atoms, beryllium atoms, boron atoms, sodium atoms, magnesium atoms and aluminum atoms. The doses and energies are described below in the list of FIG. 4A and FIG. 4B. The irradiation source 13 is implemented, for example, as an accelerator. An example of an accelerator is an ion implanter. The implanter is realized, for example, as a high-energy ion implanter. The energy of the particles 14 for irradiation may be high enough that at least a part of the particles 14 passes through the SiC substrate 11. The particles 14 for irradiation are atoms or ions. In one example, 50% of the particles 14 pass through the SiC substrate 11. Alternatively, for example, 75% or 90% of the particles 14 pass through the SiC substrate 11.

[0034] The use of electron and / or ion irradiation has been shown to improve the thermal conductivity of SiC conductive substrates (approximately 10 -2 This is done to increase the resistivity of a silicon wafer (which has a resistivity of ohms-cm).

[0035] Depending on the energy of the particles, e.g. electrons, the resistivity may be increased only in parts of the silicon carbide substrate 11 such that a layer of the silicon carbide substrate 11 becomes semiconducting and another layer of the silicon carbide substrate 11 remains conductive. These layers are arranged perpendicular to the irradiation direction. The type of particles, illustratively heavier particles, may also make the effect of creating a silicon carbide substrate 11 with conductive and semiconducting layers more pronounced.

[0036] FIG. 3A is a schematic diagram of a method for producing a silicon carbide substrate 11 according to an embodiment that is a further development of the embodiment shown in FIG. 1, FIG. 2A and FIG. 2B. The method includes providing a SiC substrate 11 in a providing process 101 and irradiating the SiC substrate 11 with particles 14 from a group including electrons, hydrogen atoms, helium atoms, lithium atoms, beryllium atoms, boron atoms, sodium atoms, magnesium atoms and aluminum atoms in an irradiation process 102. The net doping concentration of electrons in the SiC substrate 11 is homogenous before and after irradiation. The net donor concentration profile is homogenous after irradiation. In one example, the irradiation process 102 does not result in a typical ion implantation profile or only a flat distribution of the net donor concentration.

[0037] Thus, the method includes providing a SiC substrate 11 as a SiC boule 12 and sawing the SiC boule 12 into wafers after irradiating the SiC boule 12. In one example, irradiating the SiC boule 12 is achieved as irradiating the SiC boule 12 from a lateral side of the SiC boule 12.

[0038] 1, in one example, SiC substrate 11 is implemented as a SiC boule 12. Optionally, the method includes annealing SiC substrate 11 after irradiation in an annealing process 103. The method includes sawing SiC boule 12 into wafers in a sawing process 104.

[0039] During the fabrication of a power semiconductor device using the SiC substrate 11, a high temperature process for oxidation or annealing is performed after the ion implantation step. This allows annealing to be performed after the annealing process 103 during the fabrication of the power semiconductor device. The SiC substrate 11 is configured for fabricating a power semiconductor device, for example a high voltage insulated gate bipolar transistor (high voltage IGBT for short). The blocking voltage of the IGBT is, for example, greater than 5 kV, or greater than 10 kV, or greater than 20 kV.

[0040] The chronological order of the annealing process 103 and the sawing process 104 may be reversed.

[0041] In one example, the SiC boule 12 has a diameter in the range of 9 cm to 11 cm. The SiC boule 12 may have a diameter of, for example, 4 inches (approximately 10 cm). For example, the particles 14 for irradiation of the SiC boule 12 are electrons having an energy of 1.5 MeV or more. The particles 14 for irradiation that are electrons may have a diameter of 10 15 cm -2 ~10 19 cm -2 The dose is in the range of

[0042] Figure 3B is a schematic diagram of a method for producing a silicon carbide substrate 11 according to an embodiment that is a further development of the embodiment shown in Figures 1, 2A, 2B and 3A. The method comprises providing a SiC substrate 11 as a SiC wafer 20 in a providing process 101 and irradiating the SiC substrate 11 with particles 14 from the group including electrons, hydrogen atoms, helium atoms, lithium atoms, beryllium atoms, boron atoms, sodium atoms, magnesium atoms and aluminum atoms in an irradiation process 102.

[0043] 2A and 2B, in one example, the SiC substrate 11 is implemented as a SiC wafer 20. Optionally, the method includes annealing the SiC substrate 11 after irradiation in an annealing process not shown, which allows annealing to be performed at a later stage during fabrication of the power semiconductor device.

[0044] Thus, irradiation is performed after sawing the SiC boule into wafers. Optionally, the method includes grinding or backgrinding the SiC wafer 20 before or after irradiation.

[0045] The particles 14 for irradiation are, for example, electrons having an energy in the range of 140 keV to 180 keV. The particles 14 for irradiation are electrons. 17 cm -2 ~2·10 19 cm -2 or 10 17 cm -2 ~10 19 cm -2 This irradiation has a dose in the range of, for example, 10 11 ~10 13 cm -3 In one example, the SiC wafer 20 has a thickness in the range of 80 μm to 120 μm, or 90 μm to 110 μm.

[0046] For stabilization of low thickness SiC wafers, in one example, the SiC wafer 20 is optionally attached to a carrier wafer during irradiation. Alternatively, irradiation is performed using a thick SiC wafer 20 that is subsequently thinned to the desired thickness.

[0047] 4A is a value of a method for producing a SiC substrate 11 according to an embodiment that is a further development of the embodiment shown above. The SiC substrate 11 is a SiC wafer 20. In FIG. 4A, exemplary values ​​for different values ​​of the thickness of the SiC wafer 20 are shown.

[0048] Fig. 4B shows values ​​of a method for producing a SiC substrate 11 according to an embodiment that is a further development of the embodiment shown above. The SiC substrate 11 is a SiC wafer 20. In Fig. 4A a range of values ​​is shown for different values ​​of the thickness of the SiC wafer 20. The values ​​were obtained by Montecarlo simulation.

[0049] In one example, the particles 14 for irradiation are electrons having an energy in the range of 450 keV to 550 keV at a thickness of the SiC wafer 20 in the range of 315 μm to 385 μm. 10 cm -2~2·10 19 cm -2 , or 10 10 cm -2 ~10 19 cm -2 has a dose of

[0050] In a further example, the irradiation particles 14 are hydrogen atoms having an energy in the range of 9 MeV to 11 MeV at a thickness of the SiC wafer 20 in the range of 315 μm to 385 μm. 2 cm -2 ~2·10 10 cm -2 has a dose of

[0051] In one example, the particles 14 for irradiation are helium atoms having an energy in the range of 13.5 MeV to 16.5 MeV at a thickness of the silicon carbide wafer 20 in the range of 45 μm to 55 μm. The particles 14 for irradiation, which are helium atoms, have an energy in the range of 0.5·10 2 cm -2 ~2·10 10 cm -2 has a dose of

[0052] Further values ​​of different atomic energies and doses, as well as thickness values ​​of the SiC wafer 20, are disclosed in Figure 4B. The doses and energies are selected according to the power semiconductor device to be produced using the SiC wafer 20 as a substrate.

[0053] In Fig. 4A and Fig. 4B, a list of particles, energies and dose ranges is disclosed. For each particle, the irradiation energies for SiC substrates 11 with thicknesses of 50 μm, 100 μm and 350 μm are listed. In Fig. 4A and Fig. 4B, the SiC substrate is a SiC wafer 20. The particles 14 are electrons and / or atoms. The atoms are ionized, so the atoms are ions. Thus, it can be said that the particles 14 are electrons and ions. Hydrogen ions can be named protons. Helium ions can be named alpha particles. As shown in the table, particles 14 such as electrons, hydrogen and helium are suitable for SiC wafers 20 with a thickness of 385 μm or less. Irradiation of thicker SiC wafers 20 can also be performed. When the SiC wafer 20 has a thickness in the range of, for example, 5 μm to 10 μm, each of the particles 14 in the group including electrons, hydrogen atoms, helium atoms, lithium atoms, beryllium atoms, boron atoms, sodium atoms, magnesium atoms and aluminum atoms can be used. In one example, the SiC substrate 11 is thinned to about 5 μm to 10 μm.

[0054] Fig. 5 shows the properties of a silicon carbide substrate 11 according to an embodiment that is a further development of the embodiment shown in the figure. In Fig. 5, the resistivity ρ of a low-energy electron irradiated SiC thin film is shown as a function of the dose Do. The circle symbols indicate the values ​​for the semiconducting SiC substrate 11. The resistivity ρ of the conductive SiC substrate 11 is also shown (triangle symbols).

[0055] In the present disclosure, in order to increase the resistivity of the SiC conductive substrate (about 10 -2 ohm cm, electron irradiation / ion implantation is used. The data shown in Figure 5 are for four different doses (10 14 , 10 15 , 10 16 and 10 17 cm -2 ) n-type 4H-SiC epitaxial layer (thickness 100 μm, 3–5·10 μm) irradiated with 160 keV electrons (penetration depth about 120 μm) 14 cm -3This was achieved by performing electrical characterization (IV) of the ZnO thin films. As shown in Figure 5, by increasing the electron dose, the resistivity ρ increases by almost five orders of magnitude. For example, 14 cm -2 The dose is about 10 12 cm -3 This corresponds to an electron concentration of 100 μm. The experiments were carried out on a 100 μm thick semiconductor epilayer grown on a conductive SiC substrate. The top 5 μm of the epilayer was analyzed.

[0056] The 4H-SiC substrate is 10 18 cm -3 (ρ is about 10 -2 According to the results of Figure 5, the doping level is 10 11 ~10 13 cm -3 To achieve an electron concentration of 10 for an energy of 160 keV, 17 ~10 19 cm -2 If higher electron energies (>300 keV) or heavier particles14 (hydrogen, helium) are used, lower doses (<10 14 ~10 16 cm -2 ) can be used.

[0057] The increase in resistivity ρ can be correlated with the reduction of free carriers (compensation) due to the electrical passivation of nitrogen. After irradiation / implantation, the compensation increases with nitrogen doping because radiation-induced point defects can migrate and passivate the nitrogen. The silicon carbide substrate 11 is exemplarily doped with other n-type dopants such as phosphors.

[0058] Figure 6 shows the properties of a silicon carbide substrate 11 according to an embodiment that is a further development of the embodiment shown above. In Figure 6, the net donor concentration NDC as a function of the depth d in the SiC substrate 11 is shown. These values ​​were determined by capacitance-voltage measurements of the irradiated 4H-SiC substrate 11. The irradiation results in a uniform net donor concentration profile in the SiC substrate 11.

[0059] Advantageously, it is more cost-effective to purchase a SiC substrate than to grow a thick epilayer. Semi-insulating SiC substrates (abbreviated as SI-SiC substrates) have too high a resistivity (approximately 10 9 Ω·cm). Advantageously, the SiC semiconductor substrate 11 or wafer 20 can be mechanically thinned (approximately 100 μm).

[0060] The SiC substrate 11 can have the form of a SiC boule 12 or a SiC wafer 20. Whether or not a method for producing the SiC substrate 11 is used can be determined by checking and / or evaluating the SiC substrate 11 after irradiation, checking whether or not a cathode of a power semiconductor device was formed by implantation (if the cathode was formed by implantation, the SiC substrate 11 could have been produced using the described method). The nitrogen content can be checked by secondary ion mass spectrometry (abbreviated SIMS) (if the nitrogen concentration is high and the resistivity is low, the SiC substrate could have been produced using the described method). Carbon vacancies V in the drift layer C Concentration of [V C ] can be measured (carbon vacancies in the drift layer V C If the concentration of is high, the SiC substrate 11 may have been produced by the described method.

[0061] Irradiation creates carbon vacancies Vc that trap carriers, which means that the minority carrier lifetime is shortened. However, 16 cm -3 For doping concentrations above 10 16 cm -3 at least 30% longer than in the case of a doping concentration less than

[0062] The irradiation changes the doping concentration for better blocking capability by increasing resistivity prior to further fabrication processes to fabricate the power semiconductor device. Thus, the irradiation is performed prior to further fabrication processes to fabricate the power semiconductor device, including high temperature operations. These high temperature operations, for example, perform annealing of damage caused by the irradiation.

[0063] While the present disclosure is susceptible to various modifications and alternative forms, details of which have been shown by way of example in the drawings and have been described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the appended claims.

[0064] The embodiments shown in Figures 1-6 above represent exemplary embodiments of the improved method for producing a SiC substrate. Therefore, they do not constitute an exhaustive list of all embodiments of the improved method. The actual method may differ from the illustrated embodiments in terms of, for example, process, dose, energy, arrangement, and device. [Explanation of symbols]

[0065] Reference sign 10 equipment 11 Silicon carbide substrate 12 Silicon carbide boule 13 Irradiation source 14 particles 20 Silicon carbide wafer 21 First main surface 22 Second main surface 101 Delivery Process 102 Irradiation Process 103 Annealing Process 104 Sewing Process d Depth Dosage NDC Net Donor Concentration ρ resistivity

Claims

1. A method for producing a silicon carbide substrate (11), comprising the steps of: Providing the silicon carbide substrate (11); irradiating said silicon carbide substrate (11) with particles (14) from the group consisting of electrons, hydrogen atoms, helium atoms, lithium atoms, beryllium atoms, boron atoms, sodium atoms, magnesium atoms and aluminum atoms; Including, The energy of the particles (14) for irradiation is selected such that the irradiation increases the resistivity (ρ) of at least a portion of the silicon carbide substrate (11) and such that after irradiation the silicon carbide substrate (11) is in a semiconducting state.

2. The method of claim 1 , wherein the resistivity (ρ) is increased by the irradiation throughout the silicon carbide substrate (11).

3. The resistivity (ρ) is increased by 10 ２ Ω cm to 10 ５ 3. The method of claim 1 or 2, wherein the resistivity is increased to the Ω-cm range.

4. Prior to irradiating the silicon carbide substrate (11), the silicon carbide substrate (11) has a resistivity of 10 －２ 3. The method of claim 1 or 2, wherein the substrate is a silicon carbide substrate having a conductivity of Ω-cm or less.

5. 3. The method of claim 1 or 2, wherein the entire silicon carbide substrate (11) has n-type conductivity before and after irradiation.

6. 3. The method of claim 1 or 2, wherein the silicon carbide substrate (11) is provided as a silicon carbide boule (12) and the silicon carbide boule (12) is sawn into wafers after irradiating the silicon carbide boule (12).

7. The method of claim 6, further comprising irradiating the silicon carbide boule (12) from a lateral side of the silicon carbide boule (12).

8. The silicon carbide substrate (11) is provided as a silicon carbide wafer (20) having a first main surface (21) and a second main surface (22); 3. The method of claim 1 or 2, wherein during irradiation of the silicon carbide substrate (11), the particles (14) enter the first main surface (21) of the silicon carbide wafer (20).

9. 0.5・10 １７ cm －２ ~2.10 １９ cm －２ and / or Energy in the range of 140 keV to 180 keV The method according to claim 1 or 2, wherein the particles are electrons having at least one of the following properties:

10. 9. The method of claim 8, wherein the particles (14) for irradiation are electrons having an energy in the range of 450 keV to 550 keV and the thickness of the silicon carbide wafer (20) is in the range of 315 μm to 385 μm.

11. 0.5・10 １０ cm －２ ~2.10 １９ cm －２ The method of claim 8, wherein the particles are electrons having a dose of about 100 nm.

12. 9. The method according to claim 8, wherein the particles are hydrogen atoms having an energy in the range of 9 MeV to 11 MeV, and / or the thickness of the silicon carbide wafer (20) is in the range of 315 μm to 385 μm.

13. 0.5・10 ２ cm －２ ~2.10 １０ cm －２ The method according to claim 8, wherein the particles are hydrogen atoms having a dose of about 100 nm.

14. an energy in the range of 13.5 MeV to 16.5 MeV and a thickness of the silicon carbide wafer (20) in the range of 45 μm to 55 μm; and / or 0.5・10 ２ cm －２ ~2.10 １０ cm －２ Dose of The method of claim 8, wherein the particles are helium atoms having at least one of:

15. 3. The method of claim 1 or 2, wherein the silicon carbide substrate (11) has a homogenous net doping concentration throughout its volume before and after irradiation.

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