N-type silicon carbide single crystal, n-type silicon carbide substrate, and semiconductor device

Abstract

An n-type silicon carbide single crystal, an n-type silicon carbide substrate, and a semiconductor device, belonging to the technical field of semiconductor materials. In a part of the n-type silicon carbide single crystal within ≤10 mm from a seed crystal surface, in a 10 mm annular range at a substrate edge, the threading screw dislocation density is <300 -2, in a central range with a diameter of 130 mm, the threading screw dislocation density is <500 -2, and the number of stripe-like stacking faults is <100; and in a part of the n-type silicon carbide single crystal more than 10 mm from the seed crystal surface, in a 40 mm annular range at the substrate edge, the threading screw dislocation density is <100 -2, in a central range with a diameter of 130 mm, the threading screw dislocation density is <300 -2, and the number of stripe-like stacking faults is <5. The n-type silicon carbide single crystal has low threading screw dislocation density and low stacking fault density, which, compared with other n-type silicon carbide single crystals, significantly improves the resistivity uniformity of wafers prepared from the crystal. The n-type silicon carbide single crystal and the n-type silicon carbide substrate prepared therefrom both have high quality and high uniformity.

Description

An n-type silicon carbide single crystal, an n-type silicon carbide substrate and a semiconductor device

[0001] The present application claims priority to the Chinese Patent Application No. 202410530915.7, filed on April 29, 2024, entitled "An n-type silicon carbide substrate and silicon carbide crystal", and the Chinese Patent Application No. 202411417854.X, filed on October 11, 2024, entitled "An n-type silicon carbide single crystal, an n-type silicon carbide substrate and a semiconductor device", the contents of which are incorporated herein by reference in their entirety. TECHNICAL FIELD

[0002] The present application belongs to the technical field of semiconductor materials, and particularly relates to an n-type silicon carbide single crystal, an n-type silicon carbide substrate and a semiconductor device. BACKGROUND

[0003] In view of the defects in the prior art, the present application aims to provide an n-type silicon carbide single crystal and an n-type silicon carbide substrate. The n-type silicon carbide substrate provided by the present application has a low threading screw dislocation density and a low stacking fault density, and has high quality and high uniformity.

[0004] According to an aspect of the present application, an n-type silicon carbide single crystal is provided, wherein the threading screw dislocation density in a 10mm annular range of a substrate edge of a part of the n-type silicon carbide single crystal with a distance of ≤10mm from a seed surface is <300cm -2 , the threading screw dislocation density in a 130mm diameter range of the center is <500cm -2 , and the number of strip-shaped stacking faults is <100; the threading screw dislocation density in a 40mm annular range of a substrate edge of a part of the n-type silicon carbide single crystal with a distance of >10mm from the seed surface is <100cm -2 , the threading screw dislocation density in a 130mm diameter range of the center is <300cm -2 , and the number of strip-shaped stacking faults is <5.

[0005] Preferably, the threading screw dislocation density in a 10mm annular range of a substrate edge of a part of the n-type silicon carbide single crystal with a distance of ≤10mm from a seed surface is <280cm -2 , the threading screw dislocation density in a 130mm diameter range of the center is <380cm -2 , and the number of strip-shaped stacking faults is <80; the threading screw dislocation density in a 40mm annular range of a substrate edge of a part of the n-type silicon carbide single crystal with a distance of >10mm from the seed surface is <85cm -2 , the threading screw dislocation density in a 130mm diameter range of the center is <265cm -2 , and the number of strip-shaped stacking faults is ≤3.

[0006] Optionally, the n-type silicon carbide single crystal has a through-threading screw dislocation density <50 cm -2 in a 40 mm range of a substrate edge of a portion of the n-type silicon carbide single crystal, which is >20 mm away from a seed surface, and a through-threading screw dislocation density <200 cm -2 in a 130 mm diameter range of a center of the n-type silicon carbide single crystal, and a number of strip-shaped stacking faults ≤3.

[0007] Preferably, the n-type silicon carbide single crystal has a through-threading screw dislocation density <50 cm -2 in a 40 mm range of a substrate edge of a portion of the n-type silicon carbide single crystal, which is >20 mm away from a seed surface, and a through-threading screw dislocation density <155 cm -2 .

[0008] Optionally, the n-type silicon carbide single crystal has a center thickness >10 mm.

[0009] Preferably, the n-type silicon carbide single crystal has a center thickness >30 mm.

[0010] Optionally, the n-type silicon carbide single crystal has a resistivity <25 mΩ·cm, and a difference between a maximum value and a minimum value of the resistivity <2.4 mΩ·cm.

[0011] Preferably, the n-type silicon carbide single crystal has a resistivity of 19-21 mΩ·cm, and a difference between a maximum value and a minimum value of the resistivity in any diameter line segment of 73 points testing of the n-type silicon carbide single crystal <2 mΩ·cm.

[0012] Optionally, the n-type silicon carbide single crystal has a difference between a maximum value and a minimum value of a refractive index under the same wavelength in a range of 250-1800 nm <2%.

[0013] Optionally, the n-type silicon carbide single crystal has a difference between a maximum value and a minimum value of an absorption coefficient under the same wavelength in a range of 250-650 nm <2%.

[0014] According to another aspect of the present application, there is provided an n-type silicon carbide substrate, which is cut, ground and polished from the n-type silicon carbide single crystal according to any one of claims 1-5, and has a through-threading screw dislocation density <100 cm -2 in a 40 mm range of a substrate edge of the n-type silicon carbide substrate, and a through-threading screw dislocation density <300 cm -2 in a 130 mm diameter range of a center of the n-type silicon carbide substrate, and a number of strip-shaped stacking faults <5.

[0015] Preferably, the n-type silicon carbide substrate has a through-threading screw dislocation density <50 cm -2, the density of screw dislocations in the central 130mm diameter range is less than 200cm -2 , the number of ribbon-like dislocations is less than 3.

[0016] Optionally, the resistivity of the n-type silicon carbide substrate is less than 25mΩ·cm, and the difference between the maximum and minimum resistivity is less than 2.4mΩ·cm.

[0017] Preferably, the resistivity of the n-type silicon carbide substrate is 19-21mΩ·cm.

[0018] More preferably, the difference between the maximum and minimum resistivity of the n-type silicon carbide substrate in the 73-point test is less than 2mΩ·cm.

[0019] Optionally, the difference between the maximum and minimum refractive index of the n-type silicon carbide substrate at the same wavelength in the range of 250-1800nm is less than 2%.

[0020] Optionally, the difference between the maximum and minimum absorption coefficient of the n-type silicon carbide substrate at the same wavelength in the range of 250-650nm is less than 2%.

[0021] Optionally, the basal plane dislocation density of the n-type silicon carbide substrate is less than 300cm -2 , and the bending degree is less than 10μm.

[0022] Preferably, the basal plane dislocation density of the n-type silicon carbide substrate is less than 75cm -2 , and the bending degree is less than 8.4μm.

[0023] In another aspect, the application provides a semiconductor device containing the n-type silicon carbide substrate prepared from the n-type silicon carbide single crystal according to any one of the above embodiments or the n-type silicon carbide substrate according to any one of the above embodiments.

[0024] The growth device for growing the n-type silicon carbide single crystal comprises:

[0025] A crucible body, which is hollow inside to form a growth cavity, is divided into an upper crucible and a lower crucible, the wall thickness of the lower crucible is greater than that of the upper crucible, the top of the upper crucible is fixed with a seed crystal, and the top of the upper crucible is further provided with at least two gas passages uniformly distributed along the circumference of the upper crucible, which are arranged between the seed crystal and the inner side wall of the upper crucible.

[0026] A graphite support ring is arranged above the lower crucible and abuts against the inner side wall of the upper crucible, and the wall thickness of the graphite support ring gradually decreases from bottom to top.

[0027] A graphite plate is arranged above the graphite support ring, the graphite plate is a porous structure, and the pore area of the graphite plate gradually decreases from the center to the edge.

[0028] Optionally, the growth device further comprises a heating coil for heating the crucible body and a heat preservation structure arranged outside the crucible body.

[0029] Optionally, the gas passage comprises a gas extraction path and a nitrogen supplement path.

[0030] Optionally, the thickness of the thickest part of the wall of the graphite support ring is 1.5-5 mm, and the thickness of the thinnest part of the wall is 0.2-1 mm.

[0031] The application relates to a growth method for growing an n-type silicon carbide single crystal, which comprises the following steps:

[0032] (1) assembling a growth device;

[0033] (2) impurity removal: controlling the pressure in the growth device to be greater than 500 mbar, and increasing the temperature in the crucible to 2000-2300 DEG C;

[0034] (3) initial crystal growth: reducing the pressure in the growth device to 100-300 mbar at a rate of 100-200 mbar / h, and keeping for 1-10 h;

[0035] (4) stable crystal growth: reducing the pressure in the growth device to 1-20 mbar at a rate of 90-180 mbar / h, opening the device gas extraction path 1# and the device gas extraction path 2#, continuously inputting a doping gas containing nitrogen, the input proportion of normal nitrogen in the doping gas being 10%-50%, and stopping the device gas extraction path 1# and the device gas extraction path 2# after growing for 10-30 h according to different temperature and pressure control;

[0036] (5) hydrogen etching: increasing the pressure to 100-500 mbar at a rate of 100-300 mbar / h, and reducing the temperature to 1000-2000 DEG C, inputting hydrogen, the proportion of hydrogen being 1%-20%, and etching for 3-10 h;

[0037] (6) restarting growth: stopping the input of hydrogen, reducing the pressure in the growth device to 1-20 mbar at a rate of 90-180 mbar / h, opening the nitrogen supplement path 3# and the nitrogen supplement path 4# to supplement nitrogen, the input amount of the supplemented nitrogen being 20%-50% of the input amount of normal nitrogen, and increasing the temperature to 2000-2300 DEG C, wherein the input proportion of normal nitrogen is the same as that in step (4);

[0038] (7) End of growth: after the crystal continues to grow for 50-150 h, the pressure is increased to 700-900 mbar, and slowly decreased to room temperature, the end of crystal growth, and n-type silicon carbide single crystal is obtained.

[0039] Optionally, the cooling rate of step (5) is 1-5°C / min.

[0040] Optionally, the crystal growth thickness of step (4) is 5-10 mm.

[0041] The beneficial effects of the present application include at least one of the following:

[0042] 1. The n-type silicon carbide single crystal provided by the present application has low threading screw dislocation density and low stacking fault density, which improves the resistivity uniformity of the wafer prepared therefrom, and has high quality and high uniformity;

[0043] 2. The n-type silicon carbide single crystal provided by the present application has more large step structures on the crystal surface, which can convert TSD into basal plane defects, and the crystal convexity gradually decreases after restarting growth, and the large steps also gradually decrease;

[0044] 3. The n-type silicon carbide single crystal provided by the present application can obtain a low TSD density in the edge region after the crystal edge reaches a thickness of 10-15 mm, and since the stacking faults in the crystal are mainly deflected by TSD, the edge TSD density of the crystal is low in the later stage, so few stacking faults are also obtained;

[0045] 4. The n-type silicon carbide single crystal provided by the present application increases the nitrogen doping amount in the edge region by an additional nitrogen supplement source, effectively improves the crystal convexity control, atmosphere stability control and doping uniformity during crystal growth;

[0046] 5. The n-type silicon carbide single crystal and the n-type silicon carbide substrate cut therefrom provided by the present application have good yield, performance and reliability at the device end. BRIEF DESCRIPTION OF DRAWINGS

[0047] The drawings described herein are used to provide further understanding of the present application, and form 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:

[0048] FIG. 1 is a schematic diagram of the overall structure of a growth device according to an embodiment of the present application;

[0049] FIG. 2 is a schematic diagram of the structure of a graphite support ring according to an embodiment of the present application;

[0050] FIG. 3 is a schematic diagram of the structure of a graphite plate according to an embodiment of the present application;

[0051] Fig. 4 is a schematic diagram of the TSD and its conversion of the basal plane defects in the growth of the substrate according to the embodiments of the present application;

[0052] Fig. 5 is a schematic diagram of the distribution of dislocations and stacking faults of the pre-substrate according to the embodiments of the present application;

[0053] Fig. 6 is a schematic diagram of the distribution of dislocations and stacking faults of the post-substrate according to the embodiments of the present application;

[0054] Fig. 7 is a 5-point site test diagram according to the embodiments of the present application;

[0055] Fig. 8 is a resistivity 73-point test diagram according to the embodiments of the present application;

[0056] Fig. 9 is a graph of the refractive index at the center of the substrate obtained at a distance of 15 mm from the seed crystal according to the Example 2 of the present application;

[0057] Fig. 10 is a graph of the refractive index at the center of the substrate obtained at a distance of 15 mm from the seed crystal according to the Comparative Example 2 of the present application;

[0058] Fig. 11 is a graph of the absorption coefficient at the center of the substrate obtained at a distance of 15 mm from the seed crystal according to the Example 2 of the present application;

[0059] Fig. 12 is a graph of the absorption coefficient at the center of the substrate obtained at a distance of 15 mm from the seed crystal according to the Comparative Example 2 of the present application.

[0060] List of components and reference numerals:

[0061] 1 - crucible body, 2 - seed crystal, 3 - silicon carbide raw material, 4 - growth chamber; 1# - evacuation path, 2# - evacuation path, 3# - nitrogen make-up path, 4# - nitrogen make-up path, 5 - graphite support ring, 6 - graphite plate. DETAILED DESCRIPTION

[0062] In order to more clearly illustrate the overall concept of the present application, the following will be described in detail in an exemplary manner.

[0063] In the following description, a number of specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that the present application can be practiced without these specific details, other than in the examples, and that the scope of the present application is not limited to the specific embodiments disclosed in the following description.

[0064] In the present application, unless otherwise explicitly specified and limited, a first feature is "on" or "under" a second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. In the description of the present specification, the description referring to the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples.

[0065] Hereinafter, the n-type silicon carbide substrate and the silicon carbide crystal of the present application will be described in detail in connection with exemplary embodiments.

[0066] In one exemplary embodiment of the present application, the present application provides an n-type silicon carbide substrate and an n-type silicon carbide single crystal.

[0067] In one specific embodiment, as shown in FIG. 1, the growth device for growing an n-type silicon carbide single crystal includes a crucible body 1, a graphite support ring 5 and a graphite plate 6. The inside of the crucible body 1 is hollow to form a growth cavity 4. The crucible body is divided into an upper crucible and a lower crucible. The lower crucible is used to hold silicon carbide raw material 3. The wall thickness of the lower crucible is greater than that of the upper crucible. A seed crystal 2 is fixed to the top of the upper crucible. At least two gas passages are uniformly distributed along the circumference of the upper crucible and are arranged between the seed crystal and the inner side wall of the upper crucible. The graphite support ring 5 is arranged above the lower crucible and abuts against the inner side wall of the upper crucible. The wall thickness of the graphite support ring 5 gradually decreases from bottom to top. The graphite plate 6 is arranged above the graphite support ring 5. The graphite plate 6 is of a porous structure and the pore area of the graphite plate 6 gradually decreases from the center to the edge.

[0068] The gas passages are uniformly distributed along the circumference of the upper crucible. In FIG. 1, only two gas passages are shown, which are a first gas passage and a second gas passage. The first gas passage includes a gas extraction path 1# and a nitrogen supplement path 3#. The second gas passage includes a gas extraction path 2# and a nitrogen supplement path 4#. In order to obtain a crystal with a larger convexity at the beginning of growth, the switches of the gas extraction paths 1# and 2# on both sides of the crystal need to be opened during the crystal growth process to reduce the atmosphere on both sides of the crystal and reduce the edge growth rate. Then, a hydrogen etching process is performed. In order to restore the normal morphology of the crystal during the growth of the substrate, the switches of the gas extraction paths 1# and 2# are closed, and the switches of the nitrogen paths 3# and 4# are opened to introduce nitrogen to increase the nitrogen content on the edge of the crystal and improve the uniformity of the substrate resistivity.

[0069] As a preferred embodiment, the gas passages are at least four, each of which comprises a gas extraction passage and a nitrogen supplement passage. The gas extraction passage is opened during step (4) to reduce the edge growth atmosphere, so that the thickness of the crystal center is much greater than the edge thickness (to increase the convexity of the crystal). The nitrogen supplement passage is opened during step (6) to adjust the problem of the nitrogen doping amount of the crystal edge being less than that of the center region caused by the radial temperature gradient, thereby improving the radial uniformity of the nitrogen doping of the crystal.

[0070] Those skilled in the art can understand that the growth device of the present application mainly realizes that the crystal always maintains a slightly convex morphology during the crystal growth process by means of the graphite plate with apertures and the gas passages for extracting or supplementing nitrogen, and realizes the control of the convexity of the crystal, the improvement of the atmosphere stability and the uniformity of the doping by means of the supplement of nitrogen. Other structures of the growth device or the adjustment of the production parameters can also be used to realize the control of the convexity of the crystal, the improvement of the atmosphere stability and the uniformity of the doping, so as to obtain the n-type silicon carbide single crystal of the present application. Therefore, the above-mentioned growth device and the preparation method do not constitute a limitation to the present application.

[0071] As shown in FIG. 2, the wall thickness of the graphite support ring 5 gradually decreases from bottom to top. Among them, the thickness of the thickest part is 1.5-5 mm, and the thickness of the thinnest part is 0.2-1 mm.

[0072] FIG. 3 is a distribution mode of the apertures of the graphite plate 6, and the present application is not limited thereto. The graphite plate 6 can also have various aperture distribution modes. As shown in FIG. 3, the aperture area of the graphite plate 6 gradually decreases from the center to the edge, so that the atmosphere of the crystal center is always greater than that of the edge part of the crystal, so that the crystal can always maintain a slightly convex morphology. The graphite plate 6 is supported by the graphite support ring 5 with uneven wall thickness. During the crystal growth process, the graphite support ring 5 gradually disappears from top to bottom, that is, the height of the graphite support ring 5 continuously decreases, and the graphite plate 6 will gradually move downward with the growth of the crystal, and maintain a relatively stable distance from the surface of the crystal.

[0073] Under the crystal, a graphite support ring with gradually decreasing wall thickness from bottom to top and a graphite plate with apertures are arranged. The aperture area of the graphite plate gradually decreases from the center to the edge. The graphite plate has the effect of preventing the growth process from being affected by the atmosphere turbulence caused by the fluctuation of the growth conditions, increasing the stability of the atmosphere transmission, and also making the atmosphere at the center of the crystal always greater than that at the edge of the crystal, so that the crystal can always maintain a micro-convex morphology. The graphite plate is supported by the graphite support ring with uneven wall thickness. During the crystal growth process, due to the thin overall wall thickness of the graphite support ring and the gradually decreasing wall thickness from bottom to top, the graphite support ring gradually disappears from top to bottom due to the erosion of the silicon-rich atmosphere in the crucible, that is, the height of the graphite support ring continuously decreases, and the graphite plate with apertures will gradually move downward with the growth of the crystal, maintaining a relatively stable distance from the surface of the crystal. If the distance is too far, the effect on the crystal morphology is small; if the distance is too close, the apertures have a greater effect on the local crystal. Therefore, the graphite plate with apertures maintains a similar distance from the surface of the crystal during the crystal growth process, so that the crystal maintains a stable crystal shape during the entire growth process, solving the problem of unstable control of the morphology during the growth process of the crystal with a thickness greater than 30 mm.

[0074] However, in addition to the graphite support ring, other support components can also be used to support the graphite plate and adjust the technology concept of gradually moving the graphite plate downward with the growth of the crystal during the crystal growth process, thereby maintaining a relatively stable distance from the surface of the crystal. For example, a support member with a vertical sliding groove is used to replace the graphite support ring. The support member can include an abutting plate and a support plate. The abutting plate is arranged above the lower crucible and abuts the inner side wall of the upper crucible. A vertical sliding groove is arranged on the abutting plate. The support plate can slide up and down along the vertical sliding groove. The support plate is used to support the graphite plate. As the crystal grows, the support plate slides down along the vertical sliding groove to maintain a relatively stable distance from the surface of the crystal.

[0075] However, Figures 1-3 only show part of the structure of the growth device. The gas passage arranged at the top of the upper crucible is an improvement on the crucible in the prior art. The original gas pipe for maintaining normal n-type silicon carbide single crystal growth operation, which is not shown, is present in the original crucible body, for example. The original gas pipe is used to realize the charging and charging of impurities during the growth process of the crystal, and the doping gas is introduced to realize N-doping during stable crystal growth and restart of the growth.

[0076] In a specific embodiment, the growth method for preparing an n-type silicon carbide substrate using the above-mentioned growth device can be realized by the following steps:

[0077] (1) Assembly of the growth device: assemble the crucible body, the silicon carbide raw material, the graphite support ring, the graphite plate, the seed crystal, the heat preservation structure, and the heating coil.

[0078] (2) Impurity removal: control the pressure in the growth device to be > 500 mbar, and raise the temperature in the crucible to 2000-2300 °C.

[0079] (3) Initial crystal growth: control the pressure in the growth device to be reduced to 100-300 mbar at a rate of 100-200 mbar / h, and maintain for 1-10 h.

[0080] (4) Stable crystal growth: reduce the pressure in the growth device to 1-20 mbar at a rate of 90-180 mbar / h, open the device exhaust port, and continuously introduce a doping gas containing nitrogen, with the proportion of normal nitrogen in the doping gas being 10%-50%. After growing for 10-30 h according to the control temperature and pressure, close the device exhaust port.

[0081] (5) Hydrogen etching: increase the pressure to 100-500 mbar at a rate of 100-300 mbar / h, and decrease the temperature to 1000-2000 °C at a rate of 1-5 °C / min, introduce hydrogen, with the proportion of hydrogen being 1%-20%, and etch for 3-10 h.

[0082] (6) Restarting growth: stop the introduction of hydrogen, reduce the pressure in the growth device to 1-20 mbar at a rate of 90-180 mbar / h, open nitrogen supplement path 3# and nitrogen supplement path 4# to supplement nitrogen, with the amount of the introduced nitrogen being 20%-50% of the amount of the normal nitrogen, and increase the temperature to 2000-2300 °C.

[0083] (7) End of growth: after the crystal continues to grow for 50-150 h, increase the pressure to 700-900 mbar, and slowly decrease to room temperature, and the crystal growth is ended.

[0084] In the processes of stable crystal growth and restarting growth, n-type element doping can be used, which can be nitrogen doping or nitrogen and other element co-doping. The proportion of nitrogen is 10%-50%, and the nitrogen doping concentration is 1 x 10 18 cm -2 to 2 x 10 19 cm -2 .

[0085] When starting the growth, the crystal needs to have a large convexity. When the crystal grows to the center 5-10 mm, increase the pressure and decrease the temperature, then introduce hydrogen, and etch the crystal at 1000-2000 °C to make more steps gather. Then, in the process of restarting the crystal growth, the TSD can be converted into basal plane defects due to the crystal surface having more large steps. At the same time, the convexity of the crystal is gradually reduced after restarting the growth, and the large steps are also gradually reduced.

[0086] Those skilled in the art can understand that, in addition to the etching to generate more steps, other growth parameters can also be used to control the formation of more large-step structures, and then the crystal with more large-step structures on the surface is subjected to re-starting crystal growth to obtain the n-type silicon carbide single crystal of the present application. Therefore, the above preparation method does not constitute a limitation to the present application.

[0087] In one specific embodiment, the n-type silicon carbide single crystal is prepared by using the above growth method or growth device. The stacking faults are tested by the PL method, and the form of the stacking faults in the test is strip-shaped, which is referred to as bar stacking fault (BSF). As shown in FIG. 4, the overall profile schematically shows the final morphology of the grown crystal, the orange part schematically shows the crystal morphology at the first time of stopping the furnace, the vertical line in the figure represents the TSD, the horizontal line intersecting the vertical line represents the basal plane defect converted from the TSD, and the two blue thick horizontal lines respectively mark the positions of the two defect schematic diagrams in FIG. 5 (the lower line) and FIG. 6 (the upper line). A lower TSD density is obtained in the edge region after the crystal edge reaches a thickness of 10-15 mm. At the same time, since the stacking faults in the crystal are mostly deflected from the TSD, the TSD density in the edge region of the crystal in the later stage is low, and therefore, few stacking faults are also obtained. The substrate formed in the early stage of the crystal has more TSD conversion and more stacking faults, and the number of BSF in the substrate formed after the crystal exceeds the thickness of the first grown crystal by 2-5 mm is reduced to 5 or less.

[0088] The TSD low-density region gradually expands from the early stage to the late edge of the crystal, and the overall density gradually decreases. The n-type silicon carbide single crystal can be 4 inches, 6 inches, 8 inches or more than 8 inches. As shown in FIG. 5, the TSD density in the 10 mm annular range of the edge of the n-type silicon carbide substrate obtained within 10 mm from the seed surface of the n-type silicon carbide single crystal is <300 cm -2 , the TSD density in the 130 mm diameter range in the center is <500 cm -2 , and the BSF is <100. As shown in FIG. 6, the TSD density in the 40 mm annular range of the edge of the n-type silicon carbide substrate obtained from the part of the n-type silicon carbide single crystal more than 10 mm from the seed surface is <100 cm -2 , the TSD density in the 130 mm diameter range in the center is <300 cm -2 , and the BSF is <5. Preferably, the TSD density in the 40 mm range of the edge of the obtained n-type silicon carbide substrate more than 20 mm is <50 cm -2 , the TSD density in the 130 mm diameter range in the center is <200 cm -2 , and the BSF is <3.

[0089] In another specific embodiment, the resistivity of the n-type silicon carbide substrate obtained from any location of the n-type silicon carbide single crystal is < 25 mΩ-cm, and the difference between the maximum and minimum resistivity is less than 2.4 mΩ-cm. Further, the resistivity of the n-type silicon carbide substrate obtained from any location of the n-type silicon carbide single crystal is 19-21 mΩ-cm, and the difference between the maximum and minimum resistivity within 73 test points of any diameter line segment is less than 2 mΩ-cm.

[0090] In another specific embodiment, the difference between the maximum and minimum refractive index of the n-type silicon carbide substrate obtained from any location of the n-type silicon carbide single crystal at the same wavelength within the range of 200-1800 nm is < 2%.

[0091] In another specific embodiment, the difference between the maximum and minimum absorption coefficient of the n-type silicon carbide substrate obtained from any location of the n-type silicon carbide single crystal at the same wavelength within the range of 200-700 nm is < 2%.

[0092] Example 1

[0093] This embodiment uses the above-mentioned growth method and growth device to prepare an n-type silicon carbide single crystal, and the specific steps are as follows:

[0094] (1) Assembly of the growth device: assemble the crucible body, the heat preservation structure, and the heating coil.

[0095] (2) Impurity removal: control the pressure in the growth device to be > 500 mbar, and raise the temperature in the crucible to 2200°C.

[0096] (3) Initial crystal growth: control the pressure in the growth device to reduce the pressure to 200 mbar at a rate of 100 mbar / h, and maintain for 5 h.

[0097] (4) Stable crystal growth: reduce the pressure in the growth device to 10 mbar at a rate of 90 mbar / h, open the device exhaust paths 1# and 2#, continuously introduce the doping gas containing nitrogen, and the proportion of the conventional nitrogen in the doping gas is 30%. After 20 h of growth, close the device exhaust paths 1# and 2#.

[0098] (5) Hydrogen etching: increase the pressure to 300 mbar at a rate of 100 mbar / h, and reduce the temperature to 1500°C at a rate of 1-5°C / min, introduce hydrogen, and the proportion of hydrogen is 5%, and etch for 10 h.

[0099] (6) Restarting growth: stop the hydrogen gas input, reduce the pressure in the growth device to 10 mbar at a rate of 90 mbar / h, nitrogen is supplemented by nitrogen supplement path 3# and nitrogen supplement path 4#, the amount of supplemented nitrogen gas input is 30% of the conventional nitrogen gas input, and the temperature is increased to 2200℃, at this time the conventional nitrogen gas input ratio is still 30%.

[0100] (7) End of growth: after the crystal continues to grow for 50h, the pressure is increased to 800mbar, and slowly reduced to room temperature, the crystal growth is ended, and an n-type silicon carbide single crystal is obtained.

[0101] Example 2

[0102] The difference between this embodiment and Example 1 is that in step (4), the input ratio of conventional nitrogen gas is 25%, and the others are the same as Example 1.

[0103] Example 3

[0104] The difference between this embodiment and Example 1 is that in step (4), the input ratio of conventional nitrogen gas is 20%, and the others are the same as Example 1.

[0105] Example 4

[0106] The difference between this embodiment and Example 1 is that in step (6), the amount of supplemented nitrogen gas input is 10% of the conventional nitrogen gas input, and the others are the same as Example 1.

[0107] Example 5

[0108] The difference between this embodiment and Example 1 is that in step (6), the amount of supplemented nitrogen gas input is 65% of the conventional nitrogen gas input, and the others are the same as Example 1.

[0109] Example 6

[0110] This embodiment uses the above-mentioned growth method and growth device to prepare an n-type silicon carbide single crystal, and the specific steps are as follows:

[0111] (1) Assemble the growth device: assemble the crucible body, the heat preservation structure and the heating coil.

[0112] (2) Impurity removal: control the pressure in the growth device to be >500mbar, and increase the temperature in the crucible to 2000℃.

[0113] (3) Initial crystal growth: control the pressure in the growth device to reduce the pressure to 100mbar at a rate of 100mbar / h, and maintain for 1h.

[0114] (4) Stable crystal growth: the pressure in the growth device is reduced to 1 mbar at a rate of 90 mbar / h, the device exhaust path 1# and the device exhaust path 2# are opened, the doping gas containing nitrogen is continuously introduced, the proportion of the conventional nitrogen in the doping gas is 50%, and the growth is performed for 10 h, and then the device exhaust path 1# and the device exhaust path 2# are closed.

[0115] (5) Hydrogen etching: the pressure is increased to 500 mbar at a rate of 300 mbar / h, the temperature is reduced to 1000 ℃ at a rate of 1 ℃ / min, hydrogen is introduced, the proportion of hydrogen is 1%, and etching is performed for 10 h.

[0116] (6) Restart growth: stop introducing hydrogen, reduce the pressure in the growth device to 1 mbar at a rate of 180 mbar / h, open the nitrogen supplement path 3# and the nitrogen supplement path 4# to supplement nitrogen, the amount of the supplemented nitrogen is 20% of the amount of the conventional nitrogen, the temperature is increased to 2200 ℃, and the proportion of the conventional nitrogen is still 50%.

[0117] (7) End of growth: after the crystal continues to grow for 100 h, the pressure is increased to 700 mbar, and then slowly reduced to room temperature, the crystal growth is ended, and an n-type silicon carbide single crystal is obtained.

[0118] Example 7

[0119] In this embodiment, an n-type silicon carbide single crystal is prepared by using the above growth method and growth device, and the specific steps are as follows:

[0120] (1) Assembly of the growth device: assemble the crucible body, the heat preservation structure and the heating coil.

[0121] (2) Impurity removal: control the pressure in the growth device to be greater than 500 mbar, and increase the temperature in the crucible to 2300 ℃.

[0122] (3) Initial crystal growth: control the pressure in the growth device to be reduced to 300 mbar at a rate of 200 mbar / h, and maintain for 10 h.

[0123] (4) Stable crystal growth: reduce the pressure in the growth device to 20 mbar at a rate of 180 mbar / h, open the device exhaust path 1# and the device exhaust path 2#, continuously introduce the doping gas containing nitrogen, the proportion of the conventional nitrogen in the doping gas is 10%, and the growth is performed for 30 h, and then the device exhaust path 1# and the device exhaust path 2# are closed.

[0124] (5) Hydrogen etching: increase the pressure to 100 mbar at a rate of 100 mbar / h, reduce the temperature to 2000 ℃ at a rate of 5 ℃ / min, introduce hydrogen, the proportion of hydrogen is 20%, and etching is performed for 3 h.

[0125] (6) Restarting growth: stop the hydrogen gas input, reduce the pressure in the growth device to 20 mbar at a rate of 90 mbar / h, open nitrogen make-up line 3# and nitrogen make-up line 4# for nitrogen make-up, the input amount of the make-up nitrogen is 50% of the conventional nitrogen input amount, and at the same time, the temperature is increased to 2200℃, at this time, the conventional nitrogen input ratio is still 10%.

[0126] (7) Ending growth: after the crystal continues to grow for 150 h, the pressure is increased to 900 mbar, and slowly reduced to room temperature, and the crystal growth is ended, and an n-type silicon carbide single crystal is obtained.

[0127] Comparative Example 1

[0128] A comparative n-type silicon carbide single crystal is prepared in this comparative example, and the following method is used for preparation:

[0129] (1) Growth device assembly: assemble the crucible body, the heat preservation structure and the heating coil.

[0130] (2) Impurity removal: control the pressure in the growth device to be > 500 mbar, and increase the temperature in the crucible to 2200℃.

[0131] (3) Initial crystal growth: control the pressure in the growth device to reduce the pressure to 200 mbar at a rate of 100 mbar / h, and maintain for 5 h.

[0132] (4) Stable crystal growth: reduce the pressure in the growth device to 10 mbar at a rate of 100 mbar / h, and the doping concentration of nitrogen is 25%.

[0133] (5) Ending growth: after the crystal grows for 120 h, the pressure is increased to 800 mbar, and the temperature is slowly reduced, and a comparative n-type silicon carbide substrate is obtained.

[0134] Comparative Example 2

[0135] Another comparative n-type silicon carbide single crystal is prepared in this comparative example, and the following method is used for preparation by using a growth device on the market instead of the growth device of the present application:

[0136] (1) Growth device assembly: assemble the crucible body, the heat preservation structure and the heating coil.

[0137] (2) Impurity removal: control the pressure in the growth device to be > 500 mbar, and increase the temperature in the crucible to 2200℃.

[0138] (3) Initial crystal growth: control the pressure in the growth device to reduce the pressure to 200 mbar at a rate of 100 mbar / h, and maintain for 5 h.

[0139] (4) Stable growth: the pressure in the growth device was reduced to 10 mbar at a rate of 90 mbar / h, and the growth was performed for 120 h with a nitrogen flow ratio of 25%.

[0140] (5) Hydrogen etching: the pressure was increased to 300 mbar at a rate of 100 mbar / h, and the temperature was decreased to 1500°C at a rate of 1-5°C / min, and hydrogen was introduced with a hydrogen flow ratio of 5%, and etching was performed for 10 h.

[0141] (6) Restart growth: the hydrogen flow was stopped, the pressure in the growth device was reduced to 10 mbar at a rate of 90 mbar / h, and the temperature was increased to 2200°C, and nitrogen was introduced with a nitrogen flow ratio of 25%.

[0142] (7) End growth: after the crystal was continuously grown for 50 h, the pressure was increased to 800 mbar, and the temperature was slowly decreased, to obtain an n-type silicon carbide substrate.

[0143] Test Example

[0144] The n-type silicon carbide single crystal prepared in Examples 1-7 and the comparative n-type silicon carbide single crystal prepared in Comparative Examples 1-2 were cut, ground, and polished to obtain n-type silicon carbide substrates, and the n-type silicon carbide substrates were subjected to performance testing.

[0145] Among them, the resistivity of all n-type silicon carbide substrates of the n-type silicon carbide single crystal was tested, and the in-plane 73-point resistivity of each n-type silicon carbide substrate was tested by a low resistance tester, and the point distribution is shown in FIG. 8. There is a maximum resistivity and a minimum resistivity on any straight line passing through the center in each n-type silicon carbide substrate. The difference between the maximum resistivity and the minimum resistivity on each straight line was calculated, the maximum value of the difference obtained on all straight lines was taken as the maximum difference between the maximum resistivity and the minimum resistivity of the n-type silicon carbide substrate (named as single piece resistivity difference), and the resistivity of the n-type silicon carbide substrate was calculated by averaging the resistivity values obtained at all test points (named as single piece resistivity). All n-type silicon carbide substrates obtained by cutting the n-type silicon carbide single crystal were compared, the maximum value of the maximum difference between the maximum resistivity and the minimum resistivity of the n-type silicon carbide single crystal was taken as the maximum difference between the maximum resistivity and the minimum resistivity of the n-type silicon carbide single crystal, and the resistivity of the n-type silicon carbide single crystal was calculated by averaging the single piece resistivity of all n-type silicon carbide substrates. The test results are shown in Table 1.

[0146] As shown in FIG. 7, the refractive index and absorption coefficient are tested for 5 points uniformly and symmetrically distributed in the silicon carbide substrate. The refractive index of the substrate at 5 points is tested at the same wavelength in the range of 200-1800 nm, and the refractive index values of the substrate at each wavelength are obtained. The difference between the maximum and minimum refractive index at each wavelength is calculated according to the calculation formula: [(maximum refractive index - minimum refractive index) / maximum refractive index] x 100%. The maximum difference between the maximum and minimum refractive index at all wavelengths is taken as the maximum difference between the maximum and minimum refractive index of the silicon carbide substrate (named as single wafer refractive index difference). The maximum value of the maximum and minimum refractive index difference of all n-type silicon carbide substrates is taken as the maximum difference between the maximum and minimum refractive index of the n-type silicon carbide single crystal. The test results are shown in Table 1.

[0147] The absorption coefficient of the substrate at 5 points is tested at the same wavelength in the range of 200-700 nm, and the absorption coefficient values of the substrate at each wavelength are obtained. The difference between the maximum and minimum absorption coefficient at each wavelength is calculated according to the calculation formula: [(maximum absorption coefficient - minimum absorption coefficient) / maximum absorption coefficient] x 100%. The maximum difference between the maximum and minimum absorption coefficient at all wavelengths is taken as the maximum difference between the maximum and minimum absorption coefficient of the silicon carbide substrate (named as single wafer absorption coefficient difference). The maximum value of the maximum and minimum absorption coefficient difference of all n-type silicon carbide substrates is taken as the maximum difference between the maximum and minimum absorption coefficient of the n-type silicon carbide single crystal. The test results are shown in Table 1.

[0148] The bending degree is tested for each n-type silicon carbide substrate, and the maximum value of the bending degree of all n-type silicon carbide substrates is taken as the maximum value of the bending degree of the n-type silicon carbide single crystal.

[0149] The final performance test results are shown in Tables 1-2 and FIGS. 9-14. The TSD density in Table 2 is the threading screw dislocation density, and the BPD density is the basal plane dislocation density.

[0150] Table 1

[0151] Table 2

[0152] As shown in Table 1, the evolution of dislocations and TSDs in the substrate (conversion of TSDs and dislocations, annihilation of TSDs, etc.) is related to the N doping concentration, resulting in changes in TSD density and dislocation number at different resistivities. The substrate resistivity is about 20 mΩcm, which is the best overall.

[0153] The substrate resistivity uniformity is characterized by the maximum value of the difference of 73-point test on any diameter line segment, and the difference of 73-point test on any diameter line segment is less than 2.4 mΩcm. The resistivity uniformity of Example 2 is significantly better than that of Comparative Example 2. It can be seen that the resistivity uniformity of the substrate obtained by the growth method of the present application is significantly improved.

[0154] The present application realizes the uniformity of the refractive index and the absorption coefficient by the resistivity uniformity control and the defect distribution regulation. As shown in FIG. 9 and FIG. 10, the difference between the maximum value and the minimum value of the refractive index uniformity of Example 2 is less than that of Comparative Example 2. As shown in FIG. 11 and FIG. 12, the difference between the maximum value and the minimum value of the absorption coefficient uniformity of Example 2 is less than that of Comparative Example 2.

[0155] The above only describes the embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the scope of claims of the present application.

Claims

1. An n-type silicon carbide single crystal crystal, wherein, The density of penetrating screw dislocations within a 10mm annular region at the edge of the substrate obtained from the portion of the n-type silicon carbide single crystal ≤ 10mm from the seed crystal surface is < 300cm³. -2 The density of through-hole spiral dislocations within a 130mm diameter area at the center is <500cm³. -2 The number of strip-shaped stacking faults is less than 100; The n-type silicon carbide single crystal crystal is obtained from a substrate edge 40 mm annular range of a part of a seed crystal surface with a distance of > 10 mm, and the density of through screw dislocations is < 100 cm -2 The density of through screw dislocations in a central 130 mm diameter range is < 300 cm -2 The number of strip-shaped stacking faults is < 5 strips.

2. The n-type silicon carbide single crystal of claim 1 wherein, The n-type silicon carbide single crystal crystal has a through screw dislocation density of <50 cm-1 in a 40 mm range of a substrate edge from a seed surface of a >20 mm portion -2 , and a through screw dislocation density of <200 cm-1 in a 130 mm diameter range of a center -2 , and a number of strip-shaped stacking faults of ≤3 strips.

3. The n-type silicon carbide single crystal of claim 1 wherein, The n-type silicon carbide single crystal has a central thickness of greater than 10 mm.

4. The n-type silicon carbide single crystal of claim 3 wherein, The n-type silicon carbide single crystal has a central thickness of greater than 30 mm.

5. The n-type silicon carbide single crystal of claim 1 wherein, The n-type silicon carbide single crystal has a resistivity of less than 25 mΩ-cm, and a maximum difference between a maximum and a minimum of the resistivity of less than 2.4 mΩ-cm.

6. The n-type silicon carbide single crystal of claim 5 wherein, The n-type silicon carbide single crystal has a resistivity of 19-21 mΩ-cm, and a maximum difference between a maximum and a minimum of the resistivity in any diameter line segment of a 73-point test of less than 2 mΩ-cm.

7. The n-type silicon carbide single crystal of claim 1 wherein, The n-type silicon carbide single crystal has a maximum difference between a maximum and a minimum of the refractive index at the same wavelength in a range of 250-1800 nm of less than 2%.

8. The n-type silicon carbide single crystal of claim 1 wherein, The n-type silicon carbide single crystal has a maximum difference between a maximum and a minimum of the absorption coefficient at the same wavelength in a range of 250-650 nm of less than 2%.

9. An n-type silicon carbide substrate, wherein, which is produced by cutting, grinding and polishing the n-type silicon carbide single crystal according to any one of claims 1 to 8, the n-type silicon carbide substrate having a through-threading screw dislocation density of <100 cm -2 in a 40 mm annular region around the edge, a through-threading screw dislocation density of <300 cm -2 in a 130 mm diameter central region, and a number of strip-shaped stacking faults of <5 strips.

10. The n-type silicon carbide substrate of Claim 9 wherein, The n-type silicon carbide substrate has a threading screw dislocation density of <50 cm -2 in a 40 mm annular region around the edge, a threading screw dislocation density of <200 cm -2 in a 130 mm diameter region around the center, and a number of threading ribbon dislocations of <3 threads.

11. The n-type silicon carbide substrate of Claim 9 wherein, The n-type silicon carbide substrate has a resistivity of less than 25 mΩ-cm, and a maximum difference between a maximum and a minimum of the resistivity of less than 2.4 mΩ-cm.

12. The n-type silicon carbide substrate of Claim 11 wherein, The n-type silicon carbide substrate has a resistivity of 19-21 mΩ-cm.

13. The n-type silicon carbide substrate of Claim 12 wherein, The n-type silicon carbide substrate has a maximum difference between a maximum and a minimum of the resistivity in any diameter line segment of a 73-point test of less than 2 mΩ-cm.

14. The n-type silicon carbide substrate of Claim 9 wherein, The n-type silicon carbide substrate has a maximum difference between a maximum and a minimum of the refractive index at the same wavelength in a range of 250-1800 nm of less than 2%.

15. The n-type silicon carbide substrate of Claim 9 wherein, The n-type silicon carbide substrate has a maximum difference between a maximum and a minimum of the absorption coefficient at the same wavelength in a range of 250-650 nm of less than 2%.

16. The n-type silicon carbide substrate of Claim 9 wherein, The n-type silicon carbide substrate has a basal plane dislocation density < 300 cm -2 and a bow < 10 μm.

17. A semiconductor device, wherein, The semiconductor device contains an n-type silicon carbide substrate prepared from the n-type silicon carbide single crystal of any one of claims 1-8 or the n-type silicon carbide substrate of any one of claims 9-16.

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