Low-dislocation and low-stress P-type silicon carbide crystal and silicon carbide substrate
By setting up an annular droplet removal piece in the silicon carbide liquid phase growth device, the problem of difficulty in removing residual droplets on the surface of silicon carbide single crystal is solved, and the preparation of P-type silicon carbide crystals with low dislocation and low stress is realized, and the quality and production efficiency of the crystal are improved.
Patent Information
- Application Number
- CN202411758469.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-03
- Publication Date
- 2025-03-07
AI Technical Summary
The prior art is difficult to effectively remove residual droplets on the surface of silicon carbide single crystals, resulting in dislocation proliferation and excessive thermal stress during the crystal growth process, and it is impossible to obtain low dislocation and low stress P-type silicon carbide crystals.
By providing an annular droplet removal member in the liquid phase growth device, the residual droplets on the surface of the silicon carbide crystal are removed by using their high wetting properties with the raw material solution, and contacting the crystal by rotating the removal member, efficient removal of the droplets is achieved.
The influence of no residual droplets on the surface of the silicon carbide crystal is achieved, which reduces the dislocation and thermal stress of the crystal, improves the quality consistency and performance stability of the silicon carbide substrate, and reduces production costs.
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Figure CN119571461A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to a low-dislocation, low-stress P-type silicon carbide crystal and a silicon carbide substrate, and belongs to the technical field of silicon carbide material preparation. Background Art
[0002] At present, P-type silicon carbide crystals are grown using a liquid phase growth method, in which the continuous growth of the crystal is achieved through the contact between the seed crystal and the raw material solution and the pulling of the seed crystal. However, due to the wettability of the raw material solution and the SiC single crystal, even if the crystal is separated from the solution after growth, there will still be droplets attached to the crystal surface.
[0003] The droplets on the surface will cause damage to the crystal at three points: 1) Even if the crystal is separated from the solution, the area where the droplet contacts the crystal will still undergo local surface reconstruction at high temperature, resulting in uneven crystal morphology inside and outside the droplet and local dislocation accumulation; 2) During the solidification process when the droplet changes from liquid to solid, the latent heat released locally will cause uneven temperature on the crystal, generating thermal stress and thus causing dislocation proliferation; 3) After the droplet is completely solidified, there is a difference in thermal conductivity between the solid droplet and the crystal, so thermal stress will also be formed during the cooling process. Larger thermal stress will often cause the crystal to crack near the residual droplet.
[0004] In the prior art, the influence of thermal stress is usually reduced by reducing the cooling rate or rotating the crystal after growth to try to remove the droplets. However, these techniques still have limitations, such as:
[0005] 1. Although reducing the cooling rate can reduce the impact of thermal stress to a certain extent, it cannot fundamentally eliminate thermal stress. In addition, excessively reducing the cooling rate will also increase the time cost;
[0006] 2. After the growth is completed, the centrifugal force caused by the rotation of the seed crystal axis can partially remove the droplets on the crystal surface. However, since the surface of the grown crystal is not atomically smooth, there are often large steps of tens of nanometers or even microns. These large steps will hinder the movement of the droplets. Therefore, it is difficult to completely remove the residual solution droplets by rotation.
[0007] In summary, the existing technology cannot effectively remove the residual droplets on the surface of the grown silicon carbide single crystal, and thus cannot obtain a low-dislocation, low-stress P-type silicon carbide crystal. Summary of the invention
[0008] In order to solve the above problems, a low-dislocation, low-stress P-type silicon carbide crystal and a silicon carbide substrate are provided. The overall dislocation of the P-type silicon carbide crystal is lower than that of the current P-type silicon carbide crystal, and the quality of the silicon carbide substrate prepared from the growth surface of the silicon carbide crystal is similar to the quality of the silicon carbide substrate prepared from the rest of the silicon carbide crystal height, which proves that the silicon carbide crystal is not affected by residual droplets and has good overall axial uniformity.
[0009] According to one aspect of the present application, a low-dislocation, low-stress P-type silicon carbide crystal is provided, wherein a plurality of silicon carbide substrates are prepared from an area where the P-type silicon carbide crystal is more than 1 mm away from the seed crystal surface, and the BPD density in a square area with a side length of 1 cm within a 2 / 3 radius of any silicon carbide substrate does not exceed 500 / cm 2 , the average BPD density within 2 / 3 radius does not exceed 100 / cm 2 .
[0010] The silicon carbide substrates prepared at any axial position of the silicon carbide crystal have good consistency, and the distribution consistency of BPD in each silicon carbide substrate is good, which proves that the quality of the silicon carbide crystal is high and the available area is significantly increased.
[0011] Optionally, |P1-P2|<100 pieces / cm 2 , P1 represents the average BPD density within 2 / 3 radius of the substrate including the growth surface obtained by the preparation of P-type silicon carbide crystal, and P2 represents the average BPD density within 2 / 3 radius of all silicon carbide substrates obtained by the preparation of P-type silicon carbide crystal.
[0012] The silicon carbide substrate including the growth surface in the present application refers to the first silicon carbide substrate cut from the end position of the growth of the P-type silicon carbide crystal. The silicon carbide substrate is in direct contact with the residual droplets and is most susceptible to the influence of the residual droplets. Due to the influence of the residual droplets on the crystal, the quality difference between the silicon carbide substrate including the growth surface and the silicon carbide substrates obtained at other positions will increase. In the present application, a number of silicon carbide substrates are prepared from silicon carbide crystals, and each silicon carbide substrate is tested to obtain the average value of the BPD density of the silicon carbide substrate. The above-mentioned value of |P1-P2| is used to characterize the difference between the silicon carbide substrate including the growth surface and the overall silicon carbide crystal. The smaller the value, the more uniform the axial quality of the silicon carbide crystal.
[0013] Optionally, |P3-P4|<400 pieces / cm 2 , P3 represents an arbitrary 1 cm area of the silicon carbide substrate including the growth surface 2 The maximum value of the BPD density in the region, P4, represents the average value of the BPD density of the entire silicon carbide substrate including the growth surface.
[0014] P3 represents the quality of a certain microscopic area of the silicon carbide substrate including the growth surface, and P4 represents the quality of the entire silicon carbide substrate including the growth surface. |P3-P4| is used to characterize the microscopic and overall differences of the silicon carbide substrate including the growth surface. The smaller the value, the more uniform the radial quality of the silicon carbide substrate including the growth surface. Since the quality of the silicon carbide substrate including the growth surface in the silicon carbide crystal is the worst, the smaller the value of |P3-P4| in the silicon carbide substrate including the growth surface, it can also indicate that the radial quality of the entire silicon carbide crystal is more uniform.
[0015] Optionally, within a radius of 2 / 3 of any silicon carbide substrate, the BPD density of the direction with an angle greater than 30° and less than 150° with the [11-20] direction in any square area with a side length of 1 cm is ≤ 50 / cm 2 The average BPD density within the 2 / 3 radius with an angle greater than 30° and less than 150° with the [11-20] direction is <20 / cm 2 .
[0016] Optionally, the XRD half-width of any silicon carbide substrate is less than 50 arcsec.
[0017] Optionally, |X1-X2|<5arcsec, X1 represents the average value of the XRD half-width of the substrate including the growth surface prepared from the P-type silicon carbide crystal, and X2 represents the average value of the average value of the XRD half-width of all silicon carbide substrates prepared from the P-type silicon carbide crystal; and / or
[0018] |X3-X1|<10arcsec, X3 represents the XRD half-width at any position of the silicon carbide substrate including the growth surface.
[0019] According to another aspect of the present application, a low dislocation, low stress P-type silicon carbide substrate is provided, wherein the BPD density in a square area with a side length of 1 cm within a 2 / 3 radius of the silicon carbide substrate does not exceed 500 / cm 2 , the average BPD density within 2 / 3 radius does not exceed 100 / cm 2 .
[0020] Optionally, |P3-P4|<400 pieces / cm 2 , P3 represents any 1cm of the silicon carbide 2 The maximum value of the BPD density in the region, P4, represents the average value of the BPD density of the entire silicon carbide substrate.
[0021] Optionally, within the radius of 2 / 3 of the silicon carbide substrate, the BPD density of the direction in any square area with a side length of 1 cm and the [11-20] direction with an angle greater than 30° and less than 150° is ≤50 / cm 2 The average BPD density within the 2 / 3 radius with an angle greater than 30° and less than 150° with the [11-20] direction is <20 / cm 2 .
[0022] Optionally, the XRD half-width of the silicon carbide substrate is below 50 arcsec.
[0023] Optionally, |X5-X4|<10arcsec, X5 represents the XRD half-width at any position of the silicon carbide substrate, and X4 represents the average value of the XRD half-width of the entire silicon carbide substrate.
[0024] The beneficial effects of this application include but are not limited to:
[0025] 1. The low-dislocation, low-stress P-type silicon carbide crystal of the present application has no influence of residual droplets on the crystal surface. Therefore, the quality of the silicon carbide substrate obtained near the crystal surface is consistent with the quality of the silicon carbide substrate at other positions, avoiding the crystal from cracking due to excessive residual stress, increasing the number of silicon carbide substrates that can be prepared from a single crystal, and reducing the production cost of the silicon carbide substrate.
[0026] 2. The low-dislocation, low-stress P-type silicon carbide crystal of the present application not only has a reduced overall dislocation density and thermal stress, but also has a more uniform distribution of BPD density and thermal stress in the axial and radial directions, thereby improving the performance stability and reliability of the silicon carbide substrate.
[0027] 3. The low dislocation, low stress P-type silicon carbide crystal of the present application, the average BPD density of the prepared silicon carbide substrate with an angle between the direction and the [11-20] direction greater than 30° and less than 150° is less than 20 / cm 2 , proving that the silicon carbide crystal can achieve uniform step flow distribution during growth and can avoid BPD proliferation caused by thermal stress. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] 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:
[0029] Figure 1 Schematic diagram of the structure of a conventional liquid phase growth device for silicon carbide crystals.
[0030] Figure 2This is a crystal image grown using a conventional liquid phase growth device for silicon carbide crystals.
[0031] Figure 3 Schematic diagram of the structure of the liquid phase growth device of silicon carbide crystal involved in this embodiment 1.
[0032] Figure 4 Schematic diagram of the structure of the droplet removal component involved in this embodiment 1.
[0033] Figure 5 It is a schematic diagram of the structure of the crucible and the droplet removal member involved in this embodiment 1.
[0034] Figure 6 This is a diagram of the operating steps for removing residual liquid droplets using the liquid phase growth apparatus for silicon carbide crystal involved in Example 1.
[0035] Figure 7 It is a schematic diagram of the structure of the liquid phase growth device of silicon carbide crystal with detection circuit involved in Example 1 before and after the crystal contacts with the droplet removal member.
[0036] List of parts and reference numerals:
[0037] 1. Crucible; 2. Droplet removal member; 21. Contact layer; 22. Support layer; 3. Crystal support shaft; 4. Silicon carbide crystal; 5. Raw material solution; 6. Residual droplets; 7. Support table. DETAILED DESCRIPTION
[0038] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.
[0039] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.
[0040] Unless otherwise specified, the methods used in the embodiments of the present application are conventional methods in the prior art.
[0041] refer to Figure 1 , which is a common liquid phase growth device for silicon carbide crystals. After the growth is completed, there are residual droplets on the surface of the silicon carbide crystal. Taking silicon carbide single crystal as an example, if no droplet removal measures are taken, the crystal will be cooled directly after the growth is completed. Figure 2 , there are traces of residual droplets on the surface of the obtained silicon carbide single crystal. The black area on the left side of the picture is the solidified solution droplet, and a horizontal crack extends from the right side of the droplet to the center of the crystal.
[0042] Example 1
[0043] refer to Figure 3-7The present embodiment relates to a liquid phase growth device for improving the quality of silicon carbide crystal 4, comprising: a crucible 1 capable of accommodating raw material liquid, an annular droplet removal member 2 abutting against the side wall of the crucible 1 is provided on the upper part of the side wall of the crucible 1, the melting point of the droplet removal member 2 is higher than the growth temperature of the semiconductor, and at least the wettability of the surface of the droplet removal member 2 with the raw material solution 5 is greater than the wettability of the silicon carbide crystal 4 with the raw material solution 5; a crystal support shaft 3, the crystal support shaft 3 can drive the silicon carbide crystal 4 to contact with the droplet removal member 2, and drive the silicon carbide crystal 4 to rotate.
[0044] In the liquid phase growth device, an annular droplet removal member 2 is arranged on the upper part of the side wall of the original crucible 1. After the growth of the silicon carbide crystal 4 is completed, the silicon carbide crystal 4 can be driven to contact the droplet removal member 2 through the crystal support shaft 3. Since the wettability of the surface of the droplet removal member 2 with the raw material solution 5 is greater than the wettability of the silicon carbide crystal 4 with the raw material solution 5, the residual droplets 6 on the surface of the silicon carbide crystal 4 can be adsorbed to the surface of the droplet removal member 2, thereby preventing the silicon carbide crystal 4 from increasing dislocations and excessive stress due to the residual droplets 6, thereby obtaining a low-dislocation, low-stress P-type silicon carbide crystal, and the dislocation and stress distribution of the P-type silicon carbide crystal 4 is more uniform. In addition, since the droplet removal member 2 is annular, it can generate uniform heat radiation to the raw material solution 5 in the crucible 1, so that the crystal growth part is heated more evenly, the crystal quality of the silicon carbide crystal 4 is higher, and the dislocation and stress are lower.
[0045] Specifically, at least the surface of the droplet removal member 2 has a higher wettability to the raw material solution 5 than the silicon carbide crystals 4 and the raw material solution 5. The droplet removal member 2 may be entirely made of a material having a higher wettability to the raw material solution 5 than the silicon carbide crystals 4 and the raw material solution 5, or only the surface of the droplet removal member 2 may be made of a material having a higher wettability to the raw material solution 5 than the silicon carbide crystals 4 and the raw material solution 5, and the remaining portion may be made of other materials, and the material of the remaining portion needs to be a material having a melting point above the growth temperature.
[0046] refer to Figure 4 As an embodiment, the droplet removal element 2 includes a contact layer 21 and a support layer 22 from top to bottom, and the wettability of the contact layer 21 to the raw material solution 5 is greater than the wettability of the silicon carbide crystal 4 to the raw material solution 5.
[0047] Taking silicon carbide crystal as an example, the material used for the contact layer 21 needs to meet the following conditions: 1. The melting point is higher than the growth temperature of silicon carbide by liquid phase method; 2. The material has better wettability with the raw material solution 5 (generally Si and other metal co-solvents) than silicon carbide crystal. The material used for the support layer 22 only needs to meet the requirement of having a melting point higher than the growth temperature of silicon carbide by liquid phase method.
[0048] The materials of the contact layer 21 and the support layer 22 can be the same or different. If they are the same, the contact layer 21 and the support layer 22 can be formed as one piece. If they are different, the contact layer 21 and the support layer 22 can be directly abutted and installed in corresponding positions. The contact layer 21 is configured to remove residual droplets 6 on the surface of the silicon carbide crystal 4. The support layer 22 is configured to provide support for the contact layer 21, thereby improving the support of the droplet removal component 2, avoiding the droplet removal component 2 from being offset or falling when the silicon carbide crystal 4 contacts the droplet removal component 2, and improving the removal efficiency of the residual droplets 6.
[0049] As an embodiment, the total thickness of the droplet removal member 2 is 1-10 mm. This thickness can improve the stability of the droplet removal member 2 and reduce the influence of the droplet removal member 2 on the growth of the silicon carbide crystal 4, thereby further improving the quality of the silicon carbide crystal 4.
[0050] Specifically, the thickness of the contact layer 21 and the support layer 22 can be set as required, as long as the above functions can be exerted.
[0051] As a preferred embodiment, the material of the contact layer 21 is selected from at least one of W, Nb, Ta, graphite and carbon-based thermal insulation felt; the material of the support layer 22 is selected from at least one of W, Nb, Ta and graphite.
[0052] The above-mentioned material can not only realize the rapid removal of residual droplets 6 , but also improve the heating uniformity of the raw material solution 5 and the growth surface of the silicon carbide crystal 4 , thereby further improving the growth quality of the silicon carbide crystal 4 .
[0053] refer to Figure 3 As an embodiment, the vertical distance between the droplet removal member 2 and the liquid surface of the initial raw material solution 5 is 5-20 mm. The distance between the droplet removal member 2 and the initial raw material solution 5 can not only prevent the droplet removal member 2 from being wetted by the raw material solution 5, but also ensure uniform heat radiation to the raw material solution 5, improve the crystal growth quality of the silicon carbide crystal 4, and reduce the thermal stress generated during the droplet removal process. If the distance is too close, the droplet removal member 2 is at risk of contacting the raw material solution 5. In addition, it is easy to cause the surface of the droplet removal member to be covered by the solution and fail to remove the residual droplets. The droplet removal member 2 may dissolve in the raw material solution 5, thereby introducing impurities into the raw material solution 5 and reducing the growth quality of the silicon carbide crystal 4. If the distance is too far, the distance required to lift the grown semiconductor crystal 4 upward to the top of the droplet removal member 2 during the droplet removal process is too long. Since it is too far away from the liquid surface of the raw material solution 5, that is, the core high temperature zone, the semiconductor crystal 4 will have a situation where the temperature drops too fast during the lifting process, thereby generating a large stress in the silicon carbide crystal 4.
[0054] Under normal circumstances, when the growth of the silicon carbide crystal 4 is completed, the residual droplets 6 are not spread all over the surface of the silicon carbide crystal 4, but most of them are distributed outside the 1 / 2 radius of the silicon carbide crystal 4. Therefore, the width of the droplet removal member 2 can be set according to the distribution of the residual droplets 6 on the surface of different silicon carbide crystals 4 to ensure that the residual droplets 6 are removed during the entire process of initial contact and rotational contact between the silicon carbide crystal 4 and the droplet removal member 2.
[0055] For silicon carbide crystals, refer to Figure 3 Assuming that the diameter of the silicon carbide crystal 4 is X, the width of the droplet removal member 2 is 0.25-0.5 times the diameter X of the silicon carbide crystal 4. This width can not only ensure the efficient removal of the residual droplets 6, but also reduce the size of the droplet removal member 2 and the crucible 1, saving production costs.
[0056] When the silicon carbide crystal 4 is grown in the liquid phase, the crystal support shaft 3 and the crucible 1 are arranged on the same central axis to ensure that the growth surface of the silicon carbide crystal 4 is heated evenly. Since the droplet removal member 2 is annular, the droplet removal member 2 is also arranged on the same central axis as the crystal support shaft 3 during the growth process. After the growth of the silicon carbide crystal 4 is completed, the crystal support shaft 3 is required to lift the silicon carbide crystal 4 and move the grown silicon carbide crystal 4 to the top of the droplet removal member 2 for removal. Therefore, in order to ensure that the silicon carbide crystal 4 and the droplet removal member 2 do not collide during the lifting process, the droplet removal member 2 needs to maintain a safe distance from the semiconductor, so refer to Figure 3 A safety distance Y is set between the inner diameter of the droplet removal member 2 and the outer diameter of the silicon carbide crystal 4, and the value of Y is 1-10 mm. The difference between the inner diameter of the entire droplet removal member 2 and the diameter of the silicon carbide crystal 4 is 2-20 mm. Under the above setting, the inner diameter of the crucible 1 is equal to the outer diameter of the annular droplet removal member 2, which is 1.5X+2Y to 2X+2Y.
[0057] Specifically, the liquid drop removal member 2 can be arranged on the upper part of the side wall of the crucible 1 in a conventional installation manner, for example, Figure 5 (a), a support platform 7 may be provided at a corresponding position of the side wall of the crucible 1, and the droplet removal member 2 may be placed above the support platform 7 and abut against the side wall of the crucible 1; Figure 5 (b) The upper portion of the crucible 1 is set as an outwardly inclined side surface, and the portion where the droplet removal member 2 contacts the upper portion of the crucible 1 is set as an inwardly inclined side surface, and the two can be abutted and fixed by the inclined side surfaces.
[0058] refer to Figure 6 After the growth of silicon carbide crystal 4 is completed, the first step is to refer to Figure 6 (a), the crystal support shaft 3 drives the silicon carbide crystal 4 to rise; the second step refers to Figure 6(b), the crystal support shaft 3 drives the silicon carbide crystal 4 and approaches the inner wall of the crucible 1, and then drives the silicon carbide crystal 4 to slowly descend, so that the surface of the silicon carbide crystal 4 contacts the droplet removal member 2 but does not collide with it, and then the crystal support shaft 3 rotates to remove the droplets; the third step refers to Figure 6 (c), the crystal support shaft 3 drives the silicon carbide crystal 4 to return to the position coaxial with the crucible 1 to cool down. The distance that the seed crystal support shaft drives the silicon carbide crystal 4 to approach the inner wall of the crucible 1 can be calculated based on the size of the seed crystal, the size of the droplet removal member 2 and the size of the crucible 1, and the setting of the distance can be realized through a preset program; the distance that the seed crystal support shaft drives the silicon carbide crystal 4 to descend, in terms of the original process, the thickness of the silicon carbide crystal 4 grown each time is roughly the same, so the distance can be adjusted based on the previous distance that the silicon carbide crystal 4 is lifted and the estimated thickness of the silicon carbide crystal 4 through a preset program.
[0059] refer to Figure 7 In order to determine whether the residual droplets 6 are in contact with the droplet removal member 2, the liquid phase growth device also needs to have a current detection function. When the silicon carbide crystal 4 grown by the liquid phase method is a conductive silicon carbide crystal 4, a crucible 1 axis is provided under the crucible 1, and a detection circuit is provided between the crucible 1 axis and the seed crystal support axis. When the crystal support axis 3 drives the silicon carbide crystal 4 to contact the droplet removal member 2, the detection circuit is in a conductive state.
[0060] Under this setting, when the growing silicon carbide crystal 4 is separated from the solution and the residual droplets 6 on the surface are not in contact with the droplet removal member 2, Figure 7 (a), the circuit is in the disconnected state, and there is no indication on the ammeter; when the residual droplet 6 contacts the droplet removal member 2, the reference Figure 7 (b), the circuit is in the on state, and the ammeter shows a value. At this time, the downward movement of the crystal support shaft 3 should be stopped immediately to prevent the silicon carbide crystal 4 from colliding with the droplet removal member 2. The above arrangement can achieve accurate control of the descending distance of the silicon carbide crystal 4, improve the safety of the growth device and improve the crystal qualification rate.
[0061] Example 2
[0062] The present embodiment relates to a liquid phase growth method for improving the quality of silicon carbide crystals, which is carried out using the liquid phase growth device in Example 1. In the liquid phase growth method, after the growth of the conductor crystal is completed, the silicon carbide crystal can be driven by the crystal support shaft to contact the droplet removal member, and the silicon carbide crystal is driven to rotate to perform a droplet removal process on the surface of the silicon carbide crystal, and then a cooling process is performed.
[0063] When the liquid phase growth device has the above-mentioned current detection function, in the liquid phase growth method, after the growth of the silicon carbide crystal is completed, the crystal support shaft drives the silicon carbide crystal to contact the droplet removal component, and when the detection circuit is in an on state, the axial downward movement of the crystal support shaft is stopped, and then the crystal support shaft drives the silicon carbide crystal to rotate to perform the droplet removal process on the surface of the silicon carbide crystal.
[0064] The operation of the above-mentioned liquid phase growth method mainly lies in the process of removing liquid droplets after the growth of the silicon carbide crystal. The processes before, during and after the growth of the silicon carbide crystal can all refer to the existing methods in the prior art.
[0065] The following takes silicon carbide crystal as an example to explain the main steps of the liquid phase growth method:
[0066] (1) Preliminary preparation: Install the droplet removal device at the designated position, then fix the crucible on the tray at the lower end of the crystal growth furnace, evenly place the polysilicon material and the flux into the crucible, cover the crucible, keep the sides and top of the crucible warm, fix the seed crystal on the crystal support shaft, close the crystal growth furnace cavity, and place the seed crystal and the crucible at a predetermined height;
[0067] (2) Heating: Evacuate the crucible, then introduce an inert gas protection, the inert gas is argon, helium or neon, the gas pressure is 1E4-1E5Pa, and then heat the crucible to a temperature of 1700-2000°C;
[0068] (3) Seed crystal contact: After reaching the growth temperature, the seed crystal is controlled to lower its position and contact with the raw material solution;
[0069] (4) Growth stage: The seed crystal is pulled up 1-5 mm to form a meniscus with the surface of the raw material solution and start growing;
[0070] (5) Droplet removal stage: reference Figure 4 , pull the crystal to separate it from the liquid surface, and then carry out the aforementioned droplet removal process;
[0071] (6) Cooling and furnace opening stage: Turn off the heating unit, wait for the temperature in the furnace chamber to cool down, open the furnace chamber, and take out the crystal.
[0072] The auxiliary solvent used in the above preparation is selected from at least one of Ti, Cr, Sc, Ni, Al, Co, Mn, Mg, Ge, As, Dy, Y, Nb, Nd or Fe. The amount of the auxiliary solvent added accounts for 30%-70% of the total molar number in the solution.
[0073] The following silicon carbide crystals were prepared by the above preparation method. The specific parameters and the differences in the properties of the prepared silicon carbide crystals are shown in Table 1. Compared with silicon carbide crystal 1#, the comparative silicon carbide crystal D1# in Table 1 does not include step (5). After the crystal growth in step (4) is completed, the cooling and furnace opening stage of step (6) is carried out.
[0074] The tail of each prepared silicon carbide crystal was cut off at a position of 1 mm, and then the crystal was cut, ground, and polished into several silicon carbide substrates. Several silicon carbide substrates obtained from each crystal were tested, and the test results are shown in Table 1.
[0075] Among them, since the silicon carbide substrate containing the growth surface in the crystal is easily affected by residual droplets, the performance of the silicon carbide substrate containing the growth surface is the worst. Some parameters in Table 1 are characterized by the silicon carbide substrate containing the growth surface, representing that the parameters of the overall silicon carbide crystal and other silicon carbide substrates prepared from the silicon carbide crystal are all less than or equal to the values in Table 1.
[0076] Table 1
[0077]
[0078]
[0079] |X3-X1| represents the difference between the XRD half-width at any position of the silicon carbide substrate including the growth surface in the prepared silicon carbide crystal and the average value of the XRD half-width at half-height of the silicon carbide substrate as a whole, and |X5-X4| represents the difference between the XRD half-width at any position of any silicon carbide substrate in the prepared silicon carbide crystal and the average value of the XRD half-width at half-height of the silicon carbide substrate as a whole.
[0080] Due to the surface reconstruction of the crystal in the area covered by the residual droplets in the cooling stage after the end of growth, the crystallinity here is poor. Generally, the silicon carbide substrate including the growth surface can represent the worst crystallinity in the entire crystal. Therefore, for several silicon carbide substrates prepared from the same silicon carbide crystal, when the silicon carbide substrate is a silicon carbide substrate including the growth surface, |X5-X4|=|X3-X1|, and when the silicon carbide substrate is a silicon carbide substrate not including the growth surface, |X5-X4| is less than |X3-X1|.
[0081] According to the data in Table 1 above, the parameters of the comparative silicon carbide crystal D1# are inferior to those of the silicon carbide crystal of the present application, proving that the crystal obtained by removing the residual droplets on the crystal surface by using a droplet removal member and then cooling the crystal is of good quality, with low dislocation and thermal stress, and more uniform distribution of dislocation and thermal stress. In addition, although the various parameters of the comparative silicon carbide crystal D1# in Table 1 were obtained, the crystal is a cracked crystal and cannot be used in practice.
[0082] The above is only the embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.
Claims
1. A low dislocation, low stress P-type silicon carbide crystal, characterized in that: Several silicon carbide substrates are prepared from the region where the P-type silicon carbide crystal is more than 1 mm away from the seed crystal surface, and the BPD density in a square region with any side length of 1 cm within a 2 / 3 radius on any silicon carbide substrate does not exceed 500 / cm 2 , the average BPD density within 2 / 3 radius does not exceed 100 / cm 2 .
2. The low dislocation, low stress P-type silicon carbide crystal according to claim 1, characterized in that: |P1-P2|<100 pieces / cm 2 , P1 represents the average value of BPD density within 2 / 3 radius of the substrate including the growth surface obtained by the preparation of the P-type silicon carbide crystal, and P2 represents the average value of BPD density within 2 / 3 radius of all silicon carbide substrates obtained by the preparation of the P-type silicon carbide crystal; and / or |P3-P4|<400 pieces / cm 2 , P3 represents an arbitrary 1 cm area of the silicon carbide substrate including the growth surface 2 The maximum value of the BPD density in the region, P4, represents the average value of the BPD density of the entire silicon carbide substrate including the growth surface.
3. The low dislocation, low stress P-type silicon carbide crystal according to claim 1, characterized in that: Within the 2 / 3 radius of any silicon carbide substrate, the BPD density of the direction with an angle greater than 30° and less than 150° with the [11-20] direction in any square area with a side length of 1 cm is ≤ 50 / cm 2 The average BPD density within the 2 / 3 radius with an angle greater than 30° and less than 150° with the [11-20] direction is <20 / cm 2 .
4. The low dislocation, low stress P-type silicon carbide crystal according to claim 1, characterized in that: The XRD half-width of any silicon carbide substrate is below 50 arcsec.
5. The low dislocation, low stress P-type silicon carbide crystal according to claim 5, characterized in that: |X1-X2|<5arcsec, X1 represents the average value of the XRD half-width of the substrate including the growth surface prepared from the P-type silicon carbide crystal, and X2 represents the average value of the average value of the XRD half-width of all silicon carbide substrates prepared from the P-type silicon carbide crystal; and / or |X3-X1|<10arcsec, X3 represents the XRD half-width at any position of the silicon carbide substrate including the growth surface.
6. A low dislocation, low stress P-type silicon carbide substrate, characterized in that: The BPD density in a square area with a side length of 1 cm within a 2 / 3 radius of the silicon carbide substrate does not exceed 500 / cm 2 , the average BPD density within 2 / 3 radius does not exceed 100 / cm 2 .
7. The low dislocation, low stress P-type silicon carbide substrate according to claim 6, characterized in that: |P3-P4|<400 pieces / cm 2 , P3 represents any 1cm of the silicon carbide 2 The maximum value of the BPD density in the region, P4, represents the average value of the BPD density of the entire silicon carbide substrate.
8. The low dislocation, low stress P-type silicon carbide substrate according to claim 6, characterized in that: Within the 2 / 3 radius of the silicon carbide substrate, the BPD density of the direction with an angle greater than 30° and less than 150° with the [11-20] direction in any square area with a side length of 1 cm is ≤50 / cm 2 The average BPD density within the 2 / 3 radius with an angle greater than 30° and less than 150° with the [11-20] direction is <20 / cm 2 .
9. The low dislocation, low stress P-type silicon carbide substrate according to claim 1, characterized in that: The XRD half-width of the silicon carbide substrate is less than 50 arcsec.
10. The low dislocation, low stress P-type silicon carbide substrate according to claim 1, characterized in that: |X5-X4|<10arcsec, X5 represents the XRD half-width at any position of the silicon carbide substrate, and X4 represents the average value of the XRD half-width of the entire silicon carbide substrate.