Low-resistance P-type silicon carbide crystal, silicon carbide substrate and liquid phase growth method of semiconductor single crystal

Abstract

The invention discloses a low-resistance P-type silicon carbide crystal, a silicon carbide substrate and a liquid phase growth method of a semiconductor single crystal, and belongs to the technical field of semiconductor preparation. The liquid phase growth method for a semiconductor single crystal comprises: a step for forming a protective layer on the surface of a seed crystal; a waiting step of placing the protective layer toward the liquid surface in a state away from the liquid surface of the raw material solution heated to the growth temperature; a step for dissolving the protective layer in the raw material solution by bringing the protective layer into contact with the raw material solution; the protective layer is composed of a material having a melting point higher than the growth temperature and a material soluble in the raw material solution at a temperature lower than the growth temperature. According to the growth method, the seed crystal can be protected from being etched by steam liquid drops in the heating stage, meanwhile, components in a raw material solution cannot be changed, the crystal quality of a semiconductor is improved, and formation of defects in the semiconductor is inhibited.

Description

Technical Field

[0001] The present application relates to a liquid phase growth method of a low-resistance P-type silicon carbide crystal, a silicon carbide substrate and a semiconductor single crystal, and belongs to the technical field of semiconductor preparation. Background Art

[0002] For example, in the prior art such as WO2014192573A1, when a semiconductor single crystal is produced by a liquid phase method, a seed crystal is immersed in a raw material solution, so that the raw material dissolved in the solution around the seed crystal is in a supersaturated state, and crystals are precipitated on the surface of the seed crystal.

[0003] In the waiting state before the start of crystal growth, the surface of the seed crystal is placed relative to the liquid surface in a state away from the liquid surface of the raw material solution heated to the growth temperature. From this waiting state, the seed crystal is lowered to contact the raw material solution, and crystal growth begins. In the waiting state, since the raw material solution is in a high temperature state, the raw material solution evaporates continuously, and the vapor condenses on the surface of the seed crystal. As a result, the surface of the seed crystal may be partially etched by the vapor droplets, forming etch pits, which may cause various defects, voids, inclusions, and other problems in the growing crystal.

[0004] To solve this problem, patent CN116334744A pastes a layer of graphite paper on the surface of the seed crystal to protect the seed crystal from being etched by steam during the heating stage. However, when the graphite paper enters the growth stage and the seed crystal contacts the raw material solution, the graphite paper will dissolve into the solution, causing a sharp increase in carbon concentration, thereby increasing the supersaturation in the solution, affecting the stable growth state of the crystal, and making it difficult to obtain high-quality semiconductor crystals, especially low-resistance silicon carbide crystals. Summary of the invention

[0005] In order to solve the above problems, a liquid phase growth method for low-resistance P-type silicon carbide crystals, silicon carbide substrates and semiconductor single crystals is provided. The growth method can protect the seed crystal from being etched by steam droplets during the heating stage, and at the same time will not cause changes in the composition of the raw material solution, thereby improving the crystallization quality of the semiconductor, reducing the resistance, and inhibiting the formation of defects in the semiconductor.

[0006] According to one aspect of the present application, a low-resistance P-type silicon carbide crystal is provided, wherein the diameter of the silicon carbide crystal is greater than 6 inches, the resistivity of the silicon carbide crystal at any position is <200mΩ·cm, and the resistivity difference in the horizontal plane of the entire silicon carbide crystal is less than 20mΩ·cm, the resistivity difference in the horizontal plane of a 2 / 3 radius area is less than 10mΩ·cm, and the resistivity difference on any axis of the silicon carbide crystal is less than 20mΩ·cm.

[0007] The resistivity difference within the overall horizontal plane of the above-mentioned silicon carbide crystal is below 20mΩ·cm, which means that on any horizontal plane of the silicon carbide crystal, the difference of the maximum resistivity minus the minimum resistivity in the entire area is below 20mΩ·cm; the resistivity difference within the horizontal plane of the 2 / 3 radius area is below 10mΩ·cm, which means that on any horizontal plane of the silicon carbide crystal, only in the 2 / 3 radius area of ​​the silicon carbide crystal, the difference of the maximum resistivity minus the minimum resistivity is below 10mΩ·cm.

[0008] Optionally, the density of voids with a diameter greater than 50 μm in the silicon carbide crystal is less than 0.2 / cm 2 The density of voids with a diameter less than 50 μm is less than 0.05 / cm 2 .

[0009] Optionally, the BPD density of the silicon carbide crystal is less than 200 / cm 2 ;

[0010] Preferably, the BPD density in the silicon carbide crystal with an angle greater than 30° with the [11-20] direction is less than 50 cm -2 .

[0011] In the P-type silicon carbide crystal obtained by the liquid phase growth method, the BPD along the [11-20] direction is an inherent property brought by the preparation method, and the BPD in other directions will vary with different preparation process parameters. The BPD density in other directions of the silicon carbide crystal of the present application is <50cm -2 , which proves that the BPD density in other directions of the silicon carbide crystal is significantly reduced, and high-quality silicon carbide crystals are obtained.

[0012] Optionally, the stacking fault (SF) density of the silicon carbide crystal is 0 cm -1 .

[0013] The preparation of the low-resistance P-type silicon carbide crystal of the present application depends on the high-quality seed crystal surface when the seed crystal is in contact with the solution and the stable growth state during crystal growth. The following is a liquid phase growth method for achieving high-quality seed crystal surface and stable growth state. However, it is clear to those skilled in the art that with the continuous innovation of scientific research, there will still be new methods in the future that can achieve the adjustment of the stable growth state of the high-quality seed crystal surface. Therefore, the preparation method of the present application is only a method for preparing the low-resistance P-type silicon carbide crystal of the present application, and this method does not constitute a limitation on silicon carbide crystals.

[0014] According to another aspect of the present application, a low-resistance P-type silicon carbide substrate is provided, which is prepared using any of the low-resistance P-type silicon carbide crystals described above.

[0015] According to another aspect of the present application, a liquid phase growth method for a semiconductor single crystal is provided, comprising the following steps:

[0016] A step of forming a protective layer on the surface of the seed crystal;

[0017] A waiting step of placing the protective layer toward a liquid surface of a raw material solution heated to a growth temperature in a state away from the liquid surface of the raw material solution;

[0018] The step of bringing the protective layer into contact with the raw material solution to dissolve the protective layer in the raw material solution;

[0019] The protective layer is composed of a material having a melting point higher than the growth temperature or a material soluble in the raw material solution at a temperature lower than the growth temperature.

[0020] The protective layer can be dissolved in the raw material solution at a temperature lower than the growth temperature. In this way, in order to start crystal growth, as long as the seed crystal is brought into contact with the raw material solution, the protective layer can be dissolved in the raw material solution. Therefore, the protective layer can be easily removed without a special removal process. The protective layer is composed of elements other than the elements that constitute the seed crystal, and even if the protective layer is dissolved in the raw material solution, the concentration of elements that can cause crystal growth in the solution will not change. Therefore, it is possible to suppress changes in the crystal growth rate, etc., so that high-quality crystal growth can be achieved.

[0021] Optionally, the protective layer is composed of an element other than an element constituting the seed crystal.

[0022] Optionally, the protective layer is composed of a metal contained in the raw material solution.

[0023] Optionally, the metal is selected from at least one of Cr, V, and Nb.

[0024] Optionally, the metal is selected from Cr.

[0025] Optionally, the protective layer is made of a material containing silicon dioxide and not containing carbon.

[0026] Optionally, the semiconductor single crystal is a silicon carbide single crystal, and the raw material solution is a silicon-containing solution.

[0027] Optionally, the protective layer has a thickness of 0.1 to 100 μm.

[0028] Optionally, the protective layer is formed by magnetron sputtering, CVD or thermal evaporation.

[0029] The beneficial effects of this application include but are not limited to:

[0030] 1. The low-resistance P-type silicon carbide crystal and silicon carbide substrate of the present application have low resistivity and uniform distribution, and contain voids with lower density and smaller diameter, which can improve the crystal utilization rate and inhibit the formation of microscopic defects, thereby improving the crystal quality, achieving better conduction characteristics in the prepared device and avoiding increased leakage current and reduced breakdown voltage.

[0031] 2. The low-resistance P-type silicon carbide crystal and silicon carbide substrate of the present application have a lower BPD density in the other directions with an angle greater than 30° and less than 150° with the [11-20] direction, and a stacking fault of 0 cm -1 , which can further improve the quality of the silicon carbide crystal and broaden the application prospects of silicon carbide crystals and substrates.

[0032] 3. In the semiconductor single crystal liquid phase growth method of the present application, the protective layer has a melting point higher than the growth temperature. Therefore, even if the protective layer is heated in the standby state, it will not melt, so the surface of the seed crystal can be protected from being etched by the vapor droplets.

[0033] 4. In the liquid phase growth method of semiconductor single crystals of the present application, the protective layer can be dissolved in the raw material solution at a temperature lower than the growth temperature. Therefore, the protective layer can be dissolved by contacting the seed crystal with the raw material solution during the growth stage. Therefore, the protective layer can be easily removed without a special removal process, thereby improving the convenience of operation.

[0034] 5. In the liquid phase growth method of a semiconductor single crystal of the present application, the protective layer is composed of elements other than the elements constituting the seed crystal. Even if the protective layer is dissolved in the raw material solution, the concentration of elements in the solution that can cause crystal growth will not change. Therefore, the change in the crystal growth rate can be suppressed, thereby achieving high-quality crystal growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0036] Figure 1 is a schematic cross-sectional view of a crystal growth apparatus 1;

[0037] Figure 2 is a flow chart of a method for growing a silicon carbide single crystal;

[0038] Figure 3 is a partial enlarged cross-sectional view of the protective layer 9 and the vicinity of the solution 5;

[0039] Figure 4 is a partial enlarged cross-sectional view of the protective layer 9 and the vicinity of the solution 5;

[0040] Figure 5 is a partial enlarged cross-sectional view of the protective layer 9 and the vicinity of the solution 5;

[0041] Figure 6 It is a partial enlarged cross-sectional view of the protective layer 9 and the vicinity of the solution 5 .

[0042] List of parts and reference numerals:

[0043] 1. Crystal growth equipment; 5. Raw material solution; 5s, liquid surface; 5d, steam droplets; 6. Crucible cover; 6a, opening; 7. Crystal support axis; 8. Seed crystal; 8s, surface; 9, protective layer; 10. Crucible. DETAILED DESCRIPTION

[0044] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0045] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0046] Unless otherwise specified, the methods used in the embodiments of the present application are conventional methods in the prior art.

[0047] Example 1

[0048] <Structures of Crystal Growth Apparatus 1 and Crucible 10>

[0049] Figure 1 A schematic cross-sectional view of a crystal growth apparatus 1 according to the present embodiment is shown. The crystal growth apparatus 1 is an apparatus for growing various semiconductor single crystals using a liquid phase method. In the present embodiment, a case where a single crystal of silicon carbide is grown will be described. The crystal growth apparatus 1 mainly includes a crucible 10, a raw material solution 5, a crystal support shaft 7, and a seed crystal 8.

[0050] The crucible 10 has a central axis CA and has a cylindrical shape. A raw material solution 5 is contained in the crucible 10. The raw material solution 5 is a silicon-based solution. The crucible 10 is self-heated by induction of a high-frequency coil (not shown), providing a heat source for the raw material solution 5 during crystal growth. The crucible 10 is made of a carbon material (graphite). Therefore, carbon atoms can be provided from the crucible 10 to the raw material solution 5.

[0051] The crucible cover 6 is arranged on the upper surface of the crucible 10. The crucible cover 6 has an opening 6a corresponding to the central axis CA. The support shaft 7 is inserted into the opening 6a. The support shaft 7 can rotate around the central axis CA and can move in the up and down direction (z direction). Under the crystal support shaft 7, a seed crystal 8 is installed. The seed crystal 8 is a silicon carbide single crystal. A protective layer 9 is formed on the surface 8s of the seed crystal 8, and the protective layer 9 is a layer for protecting the surface 8s.

[0052] (Characteristics and Specific Examples of Protective Layer 9)

[0053] The material of the protective layer 9 may be a material having the following two characteristics, and various materials may be used: Characteristic 1: a material having a melting point higher than the growth temperature; Characteristic 2: a material that can be dissolved in the raw material solution 5 at a temperature lower than the growth temperature.

[0054] Regarding feature 1, in the waiting state before the start of crystal growth, the surface 8s of the seed crystal 8 is placed opposite to the liquid surface 5s while being away from the liquid surface 5s of the raw material solution 5 heated to the growth temperature. Therefore, in the waiting state, the protective layer 9 is heated to near the growth temperature. However, since the protective layer 9 has the above-mentioned feature 1, the protective layer will not melt, and thus the surface 8s of the seed crystal 8 can be protected from etching by the vapor droplets described later.

[0055] According to feature 2, in order to start crystal growth, protective layer 9 can be dissolved in raw material solution 5 as long as seed crystal 8 is brought into contact with raw material solution 5. Therefore, protective layer 9 can be easily removed without requiring a special removal step, and protective layer 9 does not hinder crystal growth.

[0056] As an embodiment, the material of the protective layer 9 includes feature 3: a material that is difficult to mix into the growing crystal and will not become an impurity even if mixed. In this way, it is possible to grow high-quality crystals. As examples of materials including feature 3, the following materials can be used as co-solvents, for example, any one or a combination of two or more of Cr, Nb, Ti, Sc, Ni, Al, Co, Mn, Mg, Ge, As, Dy, Y, Nd and Fe can be used. The amount of co-solvent added accounts for 30%-70% of the total molar number in the solution. In this embodiment, a co-solvent including Cr is used.

[0057] As an embodiment, the protective layer 9 is a layer composed of elements other than the elements (e.g., Si, C) constituting the seed crystal 8. In addition, in the present embodiment, the protective layer 9 is a layer composed of a metal contained in the raw material solution 5. Specifically, the material constituting the protective layer 9 is at least one of Cr, V, and Nb. More specifically, the protective layer 9 is a film composed of a single metal of Cr.

[0058] The melting point of metal Cr is 1907°C. In addition, according to the Si-Cr phase diagram, the melting point of Si-50% Cr alloy is 1550°C, so the growth temperature can be set within the range of 1550°C to 1907°C. In this embodiment, the growth temperature is set to 1800°C, so the protective layer 9 composed of Cr will not melt due to heating in the waiting state. In addition, by making the protective layer 9 contact the raw material solution 5, the protective layer 9 can be dissolved in the raw material solution 5.

[0059] The required thickness of the protective layer 9 mainly depends on the amount of steam evaporated from the raw material solution 5, that is, the greater the amount of steam, the greater the amount of steam droplets attached to the protective layer 9, and the greater the etching amount, so it is necessary to increase the required thickness of the protective layer 9 so that the etching does not reach the surface 8s of the seed crystal 8. The amount of steam depends on the growth temperature and the composition of the raw material solution 5. Specifically, the lower the growth temperature, the less the amount of steam. Therefore, the lower the growth temperature, the thinner the protective layer 9. The actual thickness of the protective layer 9 can be appropriately determined by experiments, etc. The thickness of the protective layer 9 can be, for example, in the range of 0.1 to 100 μm.

[0060] Various methods can be used to form the protective layer 9. For example, vacuum deposition, CVD, magnetron sputtering, etc. can be used.

[0061] <Crystal Growth Method>

[0062] use Figure 2 Flowchart and Figure 3-Figure 6 A cross-sectional view illustrating a method for liquid phase growth of a silicon carbide single crystal. Figure 3-6 It is a partial enlarged view of the protective layer 9 and the vicinity of the raw material solution 5. In step S10, the protective layer 9 is formed on the surface 8s of the seed crystal 8 (protective layer forming step). In this embodiment, the protective layer 9 of Cr is formed by magnetron sputtering or thermal evaporation.

[0063] In step S20, a preparation process is performed: specifically, polycrystalline silicon and the aforementioned flux are placed in a crucible 10, the upper portion of the crucible 10 is covered with a crucible cover 6, and the crucible 10 is arranged inside the crystal growth device 1. The seed crystal 8 is fixed on the crystal support shaft 7, the seed crystal 8 is placed at a predetermined position inside the crucible 10, and the crystal growth device 1 is sealed.

[0064] In step S25, a heating and temperature raising process is performed: specifically, the internal atmosphere of the crucible 10 is made vacuum and then filled with an inert gas. The temperature in the crucible 10 reaches a predetermined growth temperature by heating by a heating component (not shown). The growth temperature of silicon carbide is generally in the range of 1700 to 2000° C. In this embodiment, the growth temperature is set to 1800° C., which causes polycrystalline silicon and the flux to melt and form a raw material solution 5.

[0065] In step S30, the process waits for a predetermined time in a waiting state (waiting process): In the waiting process, the protective layer 9 is placed opposite to the liquid surface 5s of the raw material solution 5 heated to the growth temperature in a state separated from the liquid surface 5s (refer to Figure 1 ), so the seed crystal 8 can be preheated, the temperature rise amount when the seed crystal 8 contacts the raw material solution 5 can be reduced, and the generation of thermal stress can be suppressed.

[0066] like Figure 3As shown, in the waiting state, due to the high temperature, the raw material solution 5 evaporates continuously (see arrow A1), and the vapor condenses on the surface of the protective layer 9, so that the vapor droplets 5d are attached to the surface of the protective layer 9. Figure 4 As shown, the vapor droplet 5d partially etches the protective layer 9 to form a small etching pit EP. However, the presence of the protective layer 9 prevents the etching pit EP from reaching the surface 8s of the seed crystal 8.

[0067] In step S40, a seed crystal contact process is performed: specifically, after a predetermined time has passed, the position of the seed crystal 8 is lowered. Figure 5 As shown, the protective layer 9 is in contact with the raw material solution 5. Figure 6 As shown, the protective layer 9 is easily dissolved in the raw material solution 5, so that the crystal growth can be started in a clean state without etching pits on the surface 8s of the seed crystal 8. Therefore, the formation of various defects, voids, inclusions, etc. in the growing crystal can be suppressed.

[0068] In step S50, the growth process is performed: during the growth process, the seed crystal 8 is lifted upward at a certain speed according to the crystal growth rate. In step S60, it is determined whether the crystal growth amount reaches the specified amount. If the determination is negative (S60: No), the process returns to step S50 and the crystal growth continues; if the determination result is positive (S60: Yes), the process proceeds to step S70.

[0069] In step S70 , a cooling process is performed: specifically, after the seed crystal 8 is pulled up and separated from the liquid surface, the heating component is turned off.

[0070] In step S80, the furnace opening process is performed: specifically, the furnace is opened and the crystal is taken out.

[0071] <Effect>

[0072] As a comparative example, consider a case where the protective layer of the surface 8s of the seed crystal 8 is composed of a graphite layer, and the graphite layer is removed by dissolving the graphite layer in the raw material solution 5. In this case, in the initial stage of crystal growth, the supersaturation of carbon near the surface 8s will increase sharply, that is, the concentration of elements constituting the growing crystal (silicon carbide) will change. Therefore, adverse effects such as changes in the crystal growth rate may occur, causing the quality of the grown crystal to decrease. In the technology of this specification, in addition to the elements (Si, C) constituting the seed crystal 8, the metal element (Cr) constitutes the protective layer 9. Therefore, even if the protective layer 9 is dissolved in the raw material solution 5, the concentration of the elements constituting the seed crystal 8 will not change sharply. Since changes in the crystal growth rate can be suppressed, high-quality crystal growth can be achieved.

[0073] Example 2

[0074] In Example 2, only the differences from Example 1 are described. The material of the protective layer 9 of this example is different from that of Example 1. In Example 2, the protective layer 9 is made of a material containing silicon dioxide and no carbon. Specifically, the protective layer 9 is a single layer of silicon dioxide.

[0075] Silicon dioxide is a material having the above-mentioned characteristics 1 and 2. Therefore, it has the effect of protecting the seed crystal 8 from the etching of the vapor droplets (S30) and the effect of being able to dissolve the protective layer 9 in the raw material solution 5 and remove it (S40). In addition, since silicon dioxide does not contain carbon, even if the protective layer 9 is dissolved in the raw material solution 5, the supersaturation of carbon element will not change sharply, so that a high-quality silicon carbide single crystal can be grown.

[0076] In the above-mentioned embodiments of the present application, the case of growing silicon carbide crystals is described, but it is not limited to this form. The technology of this specification is applicable to all crystals that can be grown by solution method. For example, the technology of this specification can be applied to single crystal silicon (Si), sapphire (α-Al2O3), tellurium dioxide (TeO2), bismuth germanate (Bi4Ge3O 12 ) and other crystal growth systems.

[0077] The preparation methods of the above-mentioned embodiments 1 and 2 can be used to prepare silicon carbide crystals of 4 inches, 6 inches and 8 inches or larger, wherein the resistivity of the prepared silicon carbide crystals of 6 inches or larger at any position is <200mΩ·cm, and the resistivity difference within the silicon carbide crystal surface is less than 20mΩ·cm, and the resistivity difference on any axis of the silicon carbide crystal is less than 20mΩ·cm; the density of voids with a diameter greater than 50μm in the silicon carbide crystal is <0.05 / cm 2 The density of voids with a diameter less than 50 μm is less than 0.2 / cm 2 ; BPD density of silicon carbide crystal is <200 / cm 2 , and the BPD density in the SiC crystal with an angle greater than 30° with the [11-20] direction is less than 50 cm -2 ; The stacking fault (SF) density of silicon carbide crystal is 0cm -1 .

[0078] The following silicon carbide crystals were prepared according to the preparation methods of the above-mentioned Examples 1 and 2, and the main preparation methods are as follows:

[0079] Silicon carbide crystal 1#

[0080] (1) forming a protective layer of Cr on the surface of the seed crystal by magnetron sputtering;

[0081] (2) placing polycrystalline silicon and a solvent Cr accounting for 50% of the total molar number of the solution into a crucible, fixing a seed crystal with a protective layer on a seed crystal holding shaft, placing the seed crystal at a predetermined position inside the crucible, and sealing the crystal growth device;

[0082] (3) The internal atmosphere of the crucible is vacuumed and then filled with inert gas to make the temperature in the crucible reach 1800° C. The polycrystalline silicon and the auxiliary solvent Cr melt to form a raw material solution;

[0083] (4) lowering the seed crystal position so that the protective layer contacts the raw material solution;

[0084] (5) The seed crystal is lifted upward at a certain speed, and after the crystal growth amount reaches a specified amount, it is cooled and the furnace is opened to obtain silicon carbide crystal 1#.

[0085] Silicon carbide crystal 2#

[0086] (1) forming a protective layer of silicon dioxide on the surface of the seed crystal by magnetron sputtering;

[0087] (2) Same as silicon carbide crystal 1#;

[0088] (3) The inner atmosphere of the crucible is evacuated and then filled with an inert gas to make the temperature in the crucible reach 1700° C. The polycrystalline silicon and the auxiliary solvent Cr accounting for 50% of the total molar number of the solution are melted to form a raw material solution;

[0089] (4) and (5) are the same as those of silicon carbide crystal 1# to obtain silicon carbide crystal 2#.

[0090] Silicon carbide crystal 3#

[0091] (1) forming a Nb protective layer on the surface of the seed crystal by magnetron sputtering;

[0092] (2) Same as silicon carbide crystal 1#;

[0093] (3) The inner atmosphere of the crucible is evacuated and then filled with an inert gas, so that the temperature in the crucible reaches 2000° C., and the polycrystalline silicon and Nb accounting for 50% of the total molar amount of the solvent in the solution are melted to form a raw material solution;

[0094] (4) and (5) are the same as those of silicon carbide crystal 1# to obtain silicon carbide crystal 3#.

[0095] Comparison of silicon carbide crystal D1#

[0096] The difference between the comparative silicon carbide crystal D1# and the silicon carbide crystal 1# is that there is no Cr protective layer in step (1), and the seed crystal is directly in contact with the raw material solution in step (4), and the rest is the same as the silicon carbide crystal 1#, thereby obtaining the comparative silicon carbide crystal D1#.

[0097] The head 1mm position and the tail 1mm position of the silicon carbide crystal prepared above were cut off, and then the crystal was cut, ground and polished into several silicon carbide substrates. Several silicon carbide substrates obtained from each crystal were tested. The specific test results are shown in Table 1.

[0098] The void density, stacking fault, BPD density and resistivity parameters in Table 1 refer to the maximum values ​​obtained from the tests of several silicon carbide substrates obtained from the silicon carbide crystal. Therefore, the parameters of the entire silicon carbide crystal are less than or equal to the values ​​in Table 1. Except for a silicon carbide substrate with the maximum value obtained in a certain test, the parameters of the remaining silicon carbide substrates are less than or equal to the values ​​in Table 1.

[0099] In addition, several substrate sheets are prepared from each silicon carbide crystal rod, and each substrate sheet can calculate the difference between the maximum resistivity and the minimum resistivity in the entire surface (named A1, A2, A3...An, respectively), and can also calculate the difference between the maximum resistivity and the minimum resistivity in a 2 / 3 radius area (named B1, B2, B3...Bn, respectively). Compare several substrate sheets (i.e., compare A1, A2, A3...An with each other), select the largest A value, which is the maximum resistivity difference in the surface of any substrate sheet in Table 1; compare several substrate sheets (i.e., compare B1, B2, B3...Bn with each other), select the largest B value, which is the maximum resistivity difference in the 2 / 3 radius area of ​​any substrate sheet in Table 1. Several substrate sheets prepared from silicon carbide crystal rods were tested at the same axial position, and a difference between the maximum and minimum resistivity values ​​was obtained on each axis (named C1, C2, C3...Cn). C1, C2, C3...Cn were compared, and the largest C value was selected, which is the maximum difference in resistivity on any axis in the crystal in Table 1.

[0100] Table 1

[0101]

[0102]

[0103] The above describes the implementation methods in detail, but these are only examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the above examples. The technical elements described in this article or the drawings exert technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of application. The technology shown here or in the drawings achieves multiple purposes at the same time, and achieving one of the purposes itself has technical applicability. Any modifications, equivalent substitutions, improvements, etc. made within the technical ideas and principles of this application should be included in the scope of protection of this application.

Claims

1. A low-resistance P-type silicon carbide crystal, characterized in that: The diameter of the silicon carbide crystal is more than 6 inches, the resistivity of the silicon carbide crystal at any position is <200mΩ·cm, the resistivity difference in the horizontal plane of the entire silicon carbide crystal is less than 20mΩ·cm, the resistivity difference in the horizontal plane of the 2 / 3 radius area is less than 10mΩ·cm, and the resistivity difference on any axis of the silicon carbide crystal is less than 20mΩ·cm.

2. The low-resistance P-type silicon carbide crystal according to claim 1, characterized in that: The density of voids with a diameter greater than 50 μm in the silicon carbide crystal is less than 0.05 / cm 2 The density of voids with a diameter less than 50 μm is less than 0.2 / cm 2 .

3. The low-resistance P-type silicon carbide crystal according to claim 1, characterized in that: The BPD density of the silicon carbide crystal is less than 200 / cm 2 ; Preferably, the BPD density in the silicon carbide crystal whose angle with the [11-20] direction is greater than 30° and less than 150° is less than 50 cm -2 .

4. The low-resistance P-type silicon carbide crystal according to claim 1, characterized in that: The stacking fault density of the silicon carbide crystal is 0 cm -1 .

5. A low-resistance P-type silicon carbide substrate, characterized in that: It is prepared using the low-resistance P-type silicon carbide crystal described in any one of claims 1 to 4.

6. A method for liquid phase growth of a semiconductor single crystal, characterized in that: The process includes the following steps: A step of forming a protective layer on the surface of the seed crystal; A waiting step of placing the protective layer toward a liquid surface of a raw material solution heated to a growth temperature in a state away from the liquid surface of the raw material solution; The step of bringing the protective layer into contact with the raw material solution to dissolve the protective layer in the raw material solution; The protective layer is composed of a material having a melting point higher than the growth temperature or a material soluble in the raw material solution at a temperature lower than the growth temperature.

7. The method for growing a semiconductor single crystal in liquid phase according to claim 6, characterized in that: The protective layer is composed of an element other than an element constituting the seed crystal; Preferably, the protective layer is composed of the metal contained in the raw material solution; Preferably, the metal is selected from at least one of Cr, V and Nb; More preferably, the metal is selected from Cr.

8. The method for growing a semiconductor single crystal in liquid phase according to claim 6, characterized in that: The protective layer is composed of a material containing silicon dioxide and not containing carbon.

9. The method for growing a semiconductor single crystal in liquid phase according to any one of claims 6 to 8, characterized in that: The semiconductor single crystal is a silicon carbide single crystal, and the raw material solution is a silicon-containing solution; and / or The thickness of the protective layer is 0.1-100 μm.

10. The method for growing a semiconductor single crystal in liquid phase according to any one of claims 6 to 8, characterized in that: The protective layer is formed by magnetron sputtering, CVD or thermal evaporation.

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