CN112501694A

CN112501694A - Silicon carbide wafer, ingot and preparation method thereof

Info

Publication number: CN112501694A
Application number: CN202011349487.6A
Authority: CN
Inventors: 方帅; 高宇晗; 高超; 石志强; 杨世兴; 宗艳民
Original assignee: Shandong Tianyue Advanced Technology Co Ltd
Current assignee: Shandong Tianyue Advanced Technology Co Ltd
Priority date: 2020-11-26
Filing date: 2020-11-26
Publication date: 2021-03-16
Anticipated expiration: 2040-11-26
Also published as: CN112501694B

Abstract

The application relates to a silicon carbide wafer, a crystal ingot and a preparation method thereof, belonging to the field of semiconductor materials. The silicon carbide single crystal wafer contains nitrogen elements, the number of hexagonal color spots is not more than 50, and the sides forming the hexagonal color spots are vertical to the <10-10> direction. The present application finds a novel defect, the hexagonal color spot, present in a nitrogen-containing silicon carbide wafer that is a color different from the color of the silicon carbide bulk region, but not a hexagonal void as opposed to a planar hexagonal void defect, and the hexagonal color spot can cause the silicon carbide wafer to have an uneven resistivity that can seriously affect the electrical performance of the semiconductor devices made from the silicon carbide wafer, such as by making the devices made on the silicon carbide wafer ineffective, thus providing a silicon carbide wafer and silicon carbide ingot that contain a small number of hexagonal color spots.

Description

Silicon carbide wafer, ingot and preparation method thereof

Technical Field

The application relates to a silicon carbide wafer, a crystal ingot and a preparation method thereof, belonging to the field of semiconductor materials.

Background

Silicon carbide single crystal is one of the most important third-generation semiconductor materials, and is widely applied to the fields of power electronics, radio frequency devices, photoelectronic devices and the like because of the excellent properties of large forbidden bandwidth, high saturated electron mobility, strong breakdown field, high thermal conductivity and the like. At present, the main preparation method of the silicon carbide single crystal is a Physical Vapor Transport (PVT) method, and the method is the most successful method for growing the SiC crystal with large diameter so far. The method is mainly used for growing SiC crystals through transporting a gas phase source generated by sublimating a silicon carbide raw material to a seed crystal at high temperature for recrystallization.

The SiC devices that have matured so far include: the silicon carbide Schottky diode mainly adopts a junction type barrier Schottky diode or a mixed p-n Schottky diode structure; the SiC power module is developed rapidly in the fields of photovoltaic power generation, wind power, electric automobiles, locomotive traction, ships and the like; the application of SiC in photoelectric devices mainly comprises green light emitting diodes, blue light emitting diodes and ultraviolet photodiodes.

Some companies have been able to provide Φ 1 inch, 2 inch, 3 inch and 4 inch wafers, although large single wafers are currently available. The existing SiC wafers still have many structural defects, such as micropipes, dislocations, inclusions, and damascene structures, but there is a gap in the mass use of devices, because the performance of the devices depends on the quality of the SiC wafers, and particularly, the defects of the SiC wafers affect the quality of the devices produced. The micropipes, dislocations, inclusions and damascene structures present in silicon carbide single crystal wafers have been known and have been solved in many ways. However, the requirement of the growing quality of the silicon carbide single crystal is high, the influence factors are complex, the knowledge of the defects of the silicon carbide single crystal is not in a complete stage, and the quality of the silicon carbide single crystal is important for the manufactured device, so that the quality of the silicon carbide single crystal wafer needs to be improved continuously to ensure the quality of the manufactured device.

Disclosure of Invention

In order to solve the above problems, the present inventors have found that a novel defect, namely hexagonal color spots, existing in a nitrogen-containing silicon carbide wafer, the color of which is different from that of the main body region of silicon carbide but is not a hexagonal void unlike a planar hexagonal void defect, the hexagonal color spots may make the resistivity of the silicon carbide wafer non-uniform and may seriously affect the electrical properties of a semiconductor device fabricated on the silicon carbide wafer, such as rendering the device fabricated on the silicon carbide wafer useless, and thus have provided a silicon carbide wafer and a silicon carbide ingot containing a small number of hexagonal color spots.

According to an aspect of the present application, there is provided a silicon carbide single crystal wafer containing nitrogen elements, having a number of hexagonal stains of not more than 50, with an edge forming the hexagonal stains being perpendicular to a <10-10> direction.

Optionally, the silicon carbide single crystal wafer has the number of hexagonal color spots not more than 30. Optionally, the silicon carbide single crystal wafer has an upper limit of the number of hexagonal spots selected from 25, 20, 15, 10, 5 and 3 and a lower limit selected from 25, 20, 15, 10, 5, 3 and 0. Preferably, the silicon carbide single crystal wafer has a number of hexagonal spots of not more than 10. More preferably, the silicon carbide single crystal wafer has a number of hexagonal stains of not more than 3. More preferably, the silicon carbide single crystal wafer has a number of hexagonal color spots of 0.

Optionally, the number of hexagonal color spots is less than 0.3 \ square centimeter in density. For example, the number of 4 inch 100mm silicon carbide crystal planes is no greater than 25. Further, the number of hexagonal color spots is less than 0.05 \ square centimeter in density. For example, the number of 4 inch 100mm silicon carbide crystal planes is no greater than 4.

Optionally, the diameter of the silicon carbide single crystal wafer is not less than 75 mm. Preferably, the diameter of the silicon carbide single crystal wafer is not less than 100 mm. More preferably, the diameter of the silicon carbide single crystal wafer is not less than 150 mm.

OptionallyThe content of nitrogen in the silicon carbide single crystal wafer is 5 x 10¹⁷～5×10¹⁹cm^-3. Preferably, the content of nitrogen in the silicon carbide single crystal wafer is 5 x 10¹⁸～1×10¹⁹cm^-3. More preferably, the silicon carbide single crystal wafer is N-type silicon carbide, and the nitrogen content in the silicon carbide single crystal wafer is 6 x 10¹⁸～9×10¹⁸cm^-3。

Optionally, the silicon carbide single crystal wafer is a hexagonal single crystal. Preferably, the crystal form of the silicon carbide single crystal wafer is 4H-SiC or 6H-SiC.

Alternatively, a large amount of hexagonal color spots are generated in the nitrogen-doped N-type silicon carbide single crystal, which has a resistivity of 0.002 Ω · cm to 0.06 Ω · cm when it is an N-type silicon carbide single crystal. Preferably, the resistivity of the silicon carbide single crystal wafer is 0.015-0.028 omega cm. More preferably, the resistivity of the silicon carbide single crystal wafer is 0.018 Ω · cm to 0.022 Ω · cm.

Optionally, the region outside the edge of the hexagonal color spot of the silicon carbide single crystal wafer is a silicon carbide main body region, the edge of the hexagonal color spot is surrounded by a hexagonal region, and the color of the edge of the hexagonal color spot is different from the color of the silicon carbide main body region and the color of the hexagonal region observed by an optical microscope; and/or

The sides of the hexagonal color patches are different from the nitrogen content of the silicon carbide body region and the hexagonal region, respectively. The formation of hexagonal spots may be related to whether the distribution of nitrogen content is uniform, while the color of the edge of the hexagonal spots appears different when observed in different light intensity and aperture modes of an optical microscope, e.g., the color of the edge of the hexagonal spots is whitish when observed in one of the light intensity and aperture modes in a polarization mode, while the main region of silicon carbide is yellow. For example, the color of the edge of the hexagonal color spot is yellowish when viewed with another light intensity and aperture in the polarized mode, while the silicon carbide main region is dark green.

Further, the edge color of the hexagonal color spot includes the condition of uniform and non-uniform color; its boundaries include clear and unclear cases. The shape of a hexagonal stain may appear blurred as a pentagon, quadrangle, trilateral or circle-like shape because one or more sides are short. When the area of the hexagonal color spot is large, the difference between the edge of the hexagonal color spot and the hexagonal area is obvious; however, when the hexagonal mottle region is small, the edges of the hexagonal mottle and the boundaries of the hexagonal region may be blurred and may be merged with each other.

Preferably, the nitrogen content of the hexagonal regions is no less than the nitrogen content of the silicon carbide body regions is greater than the nitrogen content of the sides of the hexagonal color spots. More preferably, the difference between the nitrogen contents of the hexagonal regions and the silicon carbide main body region is a, the difference between the nitrogen contents of the silicon carbide main body region and the silicon carbide main body region is B, and the difference a is not less than B.

Optionally, the difference A is greater than B and the nitrogen content is 4 × 10¹⁸～1×10¹⁹In the N-type silicon carbide of (2), the difference A is in the range of 1.5X 10¹⁸-4.5×10¹⁸cm^-3The difference B is in the range of 0.1X 10¹⁸-2.5×10¹⁸cm^-3。

According to one embodiment, the nitrogen content of the hexagonal regions, the silicon carbide body regions, and the sides of the hexagonal color patches are 4.7 × 10, respectively¹⁸cm^-3、4×10¹⁸cm^-3、7.7×10¹⁸cm^-3。

Optionally, the hexagonal color spots form hexagons on long crystal faces of the silicon carbide single crystal wafer; the edge of the hexagonal color spot extends along the C axis in the silicon carbide single crystal wafer. The crystal form of the silicon carbide single crystal wafer is 4H-SiC or 6H-SiC.

Optionally, the hexagonal color patch is a scalene hexagon. The width of the edge of the hexagonal color spot is not more than 1 mm; and/or the distance between the two sides of the six sides of the hexagonal color spot that are furthest apart is no greater than 5 mm. Preferably, the upper limit of the border width range of the hexagonal color spots is selected from 70 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm or 10 μm. The upper limit of the range of distances between the two most distant sides of the six sides of the hexagonal color spot is selected from 4mm, 3mm, 2mm, 1mm, 800 μm, 500 μm, 400 μm, 300 μm, 200 μm, 100 μm, 50 μm or 10 μm.

Preferably, the ratio of the area of the edges and hexagonal regions of the hexagonal color spots to the area of the silicon carbide single crystal wafer is 0 to 2mm²6 inch.

According to another aspect of the present application, there is provided a method for preparing the silicon carbide single crystal wafer, the method comprising the steps of:

1) preparing a silicon carbide single crystal ingot:

providing a crucible having a nitrogen gas channel disposed within the crucible sidewall and extending around the crucible interior cavity, the nitrogen gas channel having an inner sidewall less dense than an outer sidewall of the nitrogen gas channel;

placing a silicon carbide seed crystal at the inner top of a crucible and a silicon carbide raw material at the inner bottom of the crucible, and placing the crucible in a crystal growth furnace after assembling a heat preservation structure outside the crucible;

growing a silicon carbide single crystal ingot by using a physical vapor transport method, and permeating nitrogen into the inner cavity of the crucible through the nitrogen channel in the growth process of the silicon carbide single crystal to adjust the distribution of nitrogen in the prepared silicon carbide single crystal ingot;

2) and (3) subjecting the prepared silicon carbide single crystal ingot to a step comprising cutting to obtain the silicon carbide single crystal wafer.

Optionally, the nitrogen gas channel is a spiral channel, and the spiral channel spirally extends around the inner cavity of the crucible along the axial direction of the crucible and is wound at least once between the bottom and the top of the crucible.

Preferably, the inner liner and the outer shell are respectively barrel-shaped, the inner liner is sleeved in the outer shell and is tightly detachably connected with the outer shell, a spiral nitrogen channel is formed at the interface of the inner liner and the outer shell, the air inlet and the air outlet of the nitrogen channel are both arranged at the bottom end of the crucible, namely the spiral nitrogen channel is wound twice between the bottom and the top of the crucible, and the principle of introducing nitrogen is similar to that of circulating water.

Optionally, the wall thickness C of the portion of the lining where the nitrogen channel is formed is 3-5mm, the wall thickness C is too small and is easily corroded through, nitrogen directly enters the inner cavity of the crucible to affect crystal growth stability, the wall thickness C is too large and easily hinders diffusion of nitrogen into the crucible, and the arrangement mode increases permeability of nitrogen without affecting heating.

Optionally, the method for growing the silicon carbide single crystal ingot by using the physical vapor transport method comprises the following steps:

controlling the temperature and pressure of the crystal growth furnace and the flow of inert gas introduced into the crystal growth furnace so as to clean and remove impurities in the crystal growth furnace;

a temperature rising stage: adjusting the temperature of the crystal growth furnace to 1800-2400K, and controlling the pressure in the crucible to be 0.6 multiplied by 10⁵～1.2×10⁵Pa, the flow rate of inert gas introduced into the crystal growth furnace is 50-500mL/min, and the flow rate V of nitrogen introduced into the nitrogen channel₁20-200 mL/min;

crystal growth stage: increasing the flow rate V of nitrogen introduced into the nitrogen channel₂50 to 500mL/min, V₂Greater than V₁The crystal growth temperature is 2200K-2800K, the crystal growth pressure is 100-5000Pa, and the holding time is 80-120 h, thus obtaining the silicon carbide single crystal ingot.

Optionally, the crystal growth stage comprises a first crystal growth stage and a second crystal growth stage, the time ratio of the first crystal growth stage to the second crystal growth stage is 1:0.8-1.2, and the nitrogen inlet and the nitrogen outlet of the first crystal growth stage and the second crystal growth stage are exchanged.

Preferably, the flow rate of the inert gas is 300-400 mL/min. More preferably, the inert gas flow rate is 300 mL/min. Preferably, the inert gas is argon and/or helium.

Preferably, the nitrogen flow rate V of the warming stage₁40 to 100 mL/min. More preferably, the nitrogen flow rate V of the warming stage₁The concentration was 60 mL/min. Preferably, the nitrogen flow rate V of the crystal growth stage₂110-400 mL/min. More preferably, the nitrogen flow rate V of the crystal growth stage₂Is 300 mL/min. The number of hexagonal color spots can be reduced by the control mode of nitrogen partial pressure and flow at different stages. Preferably, the nitrogen is high-purity nitrogen with the purity of not less than 99.99 percent.

Optionally, the crucibleCrucible includes inside lining and shell, the inside lining forms the inside wall of nitrogen gas passageway, the shell forms the lateral wall of nitrogen gas passageway, the density of inside lining is less than the density of shell. Preferably, the density of the liner is no greater than 1.75g/cm³. Preferably, the density of the shell is not less than 1.85g/cm³. More preferably, the density of the shell is not less than 1.90g/cm³. Preferably, the crucible is made of graphite. The shell is made of a denser graphite material, so that the loss of the atmosphere at high temperature can be reduced, and particularly, the escape of evaporated silicon atmosphere is prevented, so that the carbon-rich atmosphere which can cause hexagonal color spots is reduced. The nitrogen slowly permeates into the inner liner and diffuses according to concentration gradient, the density of the inner liner and the density of the outer shell are different, the resistance to outward diffusion is larger, so that the nitrogen diffuses more into the inner part, and the nitrogen concentration at the edge of the seed crystal surface is larger than the center of the seed crystal surface in the crucible, so that even if the radial temperature exists in the PVT method, the nonuniformity brought by the PVT method can be balanced by the structure and the ventilation mode, the resistivity is very uniform, and the number of hexagonal color spots is effectively reduced.

Optionally, the silicon carbide raw material is silicon carbide polycrystal or silicon carbide powder. Further, the silicon carbide raw material is silicon carbide powder, the silicon carbide raw material filled in the crucible comprises an upper layer raw material and a lower layer raw material, the upper layer raw material is smaller than the particle size of the lower layer raw material, and the proportion of the upper layer raw material in the silicon carbide raw material is 30-40V%. Preferably, the particle size of the upper layer raw material is 5-10mm, and the particle size of the lower layer raw material is 20-30 mm. The great homogeneity that can increase the interior temperature distribution of bottom raw materials of the thermal radiance of the big granule raw materials between the raw materials of bottom between the gap is great, will make the raw materials evaporation faster under a suitable temperature like this, but the big granule raw materials can cause the unevenness of atmosphere to the transmission of growth intracavity, consequently at the little granule raw materials of raw materials overhead 5-10mm, provide less atmosphere pore, make originally stronger atmosphere flow evenly open through more dense aperture, make the atmosphere more even. After the atmosphere is uniform, the supersaturation degree of the crystal growth surface becomes uniform, so that the crystal growth is more stable, and the number of hexagonal color spots is effectively reduced. On the other hand, the lower layer of raw material is large-particle SIC powder, so that the time for completely carbonizing raw material particles is reduced, and the carbon-rich atmosphere which can cause hexagonal color spots is reduced.

Optionally, the coating is a TaC coating. The arrangement of the coating prevents the back evaporation of the seed crystal in the crystal growth process from causing void defects on hexagonal color spots. Preferably, the coating is formed by a CVD method (chemical vapor deposition), a PVD method (physical vapor deposition) or an MBE method (molecular beam epitaxy).

Optionally, the silicon surface of the silicon carbide seed crystal has a roughness Ra < 0.5. In order to reduce the number of internal dislocations of a silicon carbide single crystal, particularly TSD (threading dislocations). Before crystal growth, the carbon surface of the seed crystal is finely polished to make the surface thereof sufficiently smooth, and the Si surface is also finely polished to make it free from scratches and as smooth as possible.

Optionally, silicon powder is filled in the middle of the silicon carbide raw material. Preferably, the silicon powder is loaded in a loader provided with a through hole, the loader being loaded in the middle of the silicon carbide raw material. Silicon powder is filled in the silicon carbide raw material to compensate silicon in sublimation atmosphere during silicon carbide single crystal growth, and the silicon powder is further placed in the middle because the heating coil in the PVT growth method has the lowest temperature in the heating crucible, so that the silicon powder cannot be volatilized too early in the initial crystal growth stage, and the carbon-rich atmosphere which can cause hexagonal color spots is reduced.

According to another aspect of the present application, there is provided a silicon carbide single crystal ingot which is processed to form a silicon carbide single crystal wafer including a slicing step; the silicon carbide single crystal wafer is selected from any one of the silicon carbide single crystal wafers described above or the silicon carbide single crystal wafer is selected from the silicon carbide single crystal wafer prepared by any one of the methods described above.

Optionally, the silicon carbide single crystal ingot is processed by steps including cutting and polishing to form a silicon carbide single crystal wafer. Further, the silicon carbide single crystal ingot is subjected to end face machining, multi-line cutting, grinding, mechanical polishing, chemical mechanical polishing, cleaning and packaging to form the silicon carbide single crystal wafer which can be used after being opened.

Optionally, the width of the sides of the hexagonal color spot increases, and the distance between two sides of the six sides of the hexagonal color spot that are farthest from each other increases, along the growth direction of the silicon carbide single crystal extending along the C-axis.

Alternatively, hexagonal mottling may occur in a partial region of the silicon carbide single crystal ingot in the growth direction of the silicon carbide single crystal extending along the C-axis, that is, the number of hexagonal mottling differs in silicon carbide wafers produced after the same silicon carbide single crystal ingot is sliced.

Optionally, it includes the method for producing a silicon carbide single crystal ingot of the step 1) in the method for producing a silicon carbide single crystal wafer of any one of the above.

In the application, as a novel defect in a silicon carbide single crystal wafer, each side of the hexagonal color spot is flush with the surface of the silicon carbide main body region, is not a hexagonal pit, but presents a hexagonal or nearly hexagonal shape with a color different from that of the silicon carbide main body region, the area formed by the sides of the hexagonal color spot is defined as the hexagonal color spot, and other properties are referred to in other parts of the application.

Benefits of the present application include, but are not limited to:

1. according to the silicon carbide single crystal wafer, the hexagonal color spots which are novel defects existing in the silicon carbide wafer containing nitrogen are found, the color of the hexagonal color spots is different from that of the silicon carbide main body area, but the hexagonal color spots are not hexagonal holes different from the plane hexagonal void defects, the hexagonal color spots can enable the resistivity of the silicon carbide wafer to be uneven, the electrical performance of a semiconductor device manufactured by the silicon carbide wafer can be seriously affected, for example, the device manufactured on the silicon carbide wafer is made to be invalid, and the silicon carbide wafer contains the hexagonal color spots in a small quantity.

2. According to the silicon carbide single crystal wafer, the defect density of dislocation, carbon inclusion, stacking fault and the like is low, and the resistivity is uniform.

3. According to the preparation method of the silicon carbide single crystal wafer, the prepared silicon carbide wafer has the advantages of less hexagonal color spots, low defect density of dislocation, carbon inclusion, stacking fault and the like and uniform resistivity; the control method is simple and convenient to operate.

4. According to the silicon carbide single crystal ingot, the hexagonal color spots are found to exist in the nitrogen-containing silicon carbide ingot, the color of the hexagonal color spots is different from the color of the silicon carbide main body area, but different from the planar hexagonal void defects, the hexagonal color spots can make the resistivity of the silicon carbide ingot uneven, the silicon carbide single crystal wafer produced by the silicon carbide ingot can be seriously influenced, and further the electrical performance of the produced semiconductor device can be influenced, for example, the device produced on the silicon carbide ingot is made to be invalid, and the silicon carbide ingot contains few hexagonal color spots.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

FIG. 1 is a schematic view of the assembled crucible placed in a crystal growth furnace.

Fig. 2a, 2b and 2c are schematic views showing 3 kinds of hexagonal color spots existing in silicon carbide single crystal wafer 2# at the initial stage of crystal growth in the silicon carbide single crystal ingot according to example 1 of the present application.

Fig. 3a, 3b, and 3c are schematic diagrams of 3 kinds of hexagonal spots present in mid-growth-stage silicon carbide single crystal wafer 8# obtained from the silicon carbide single crystal ingot according to example 1 of the present application, respectively.

Fig. 4a, 4b, and 4C show hexagonal spots at the same C-axis position in 3 consecutive silicon carbide single crystal wafers extending in the growth direction in the silicon carbide single crystal ingot according to example 1 of the present application.

Fig. 5 shows a hexagonal spot of a silicon carbide single crystal wafer 8# according to example 1 of the present application.

Fig. 6 is the hexagonal stain of fig. 5 after etching.

The hexagonal shaped stain associated with nitrogen content in the silicon carbide single crystal wafer of fig. 4c of the silicon carbide single crystal wafer 8# of fig. 7.

Detailed Description

The present application will be described in detail with reference to examples, but the present application is not limited to these examples.

Unless otherwise specified, the raw materials and catalysts in the examples of the present application were all purchased commercially.

The analysis method in the examples of the present application is as follows:

observing the appearance of the hexagonal color spots by using an Olympus multifunctional optical microscope;

detecting the nitrogen content of the silicon carbide single crystal by using Secondary Ion Mass Spectrometry (SIMS) which is Secondary Ion Mass Spectroscopy;

testing the element composition of the silicon carbide wafer by using a Raman spectrometer;

the half-peak width of the wafer is tested by high-resolution XRD to detect the crystal quality and the crystal structure such as crystal orientation.

Example 1

Referring to fig. 1, the crucible side wall is provided with a nitrogen gas channel 6, the nitrogen gas channel 6 being arranged within the crucible side wall and extending around the crucible inner cavity, the inner side wall of the nitrogen gas channel being less dense than the outer side wall of the nitrogen gas channel.

In one embodiment, the crucible 2 comprises an inner liner 21 and an outer shell 22, the side wall of the crucible forms a nitrogen channel 6, the nitrogen channel 6 is a spiral channel, the spiral channel spirally extends around the inner cavity of the crucible along the axial direction of the crucible, and the nitrogen channel is wound at least once between the bottom and the top of the crucible. For example, the nitrogen gas channel extends from the gas inlet 71 at the bottom of the crucible to the top of the crucible and then extends to the bottom of the crucible to form a gas outlet 72.

Specifically, the liner 21 and the shell 22 are respectively barrel-shaped, the liner 21 is sleeved in the shell 22, the liner 21 and the shell 22 are arranged in a sealing, fitting and splicing manner, a spiral nitrogen channel is formed at the interface of the liner 21 and the shell 22, namely, half of the inner wall of the liner 21 and half of the inner wall of the shell 22 are respectively arranged on the inner wall of the liner 21 and the inner wall of the shell 22, the liner 21 and the shell 22 are spliced to form a spiral channel, the air inlet 71 and the air outlet 72 of the nitrogen channel are both arranged at the bottom end of the crucible, namely.

As an embodiment, the wall thickness C of the part of the inner lining forming the nitrogen channel 6 is 3-5mm, the wall thickness C is too small and is easy to be corroded through, the nitrogen directly flows into the inner cavity of the crucible to influence the crystal growth stability, the wall thickness C is too large and is easy to block the diffusion of the nitrogen to the inner side of the crucible, and the arrangement mode is used for increasing the permeability of the nitrogen under the condition of not influencing the heat generation.

Example 2

Referring to fig. 1, according to an embodiment of the present application, a method of preparing a silicon carbide single crystal ingot using the crucible of example 1 includes the steps of:

1) preparing a silicon carbide single crystal ingot:

providing the crucible of example 1 with a nitrogen channel disposed within the sidewall of the crucible and extending around the crucible interior cavity, the inner sidewall of the nitrogen channel being less dense than the outer sidewall of the nitrogen channel;

placing a silicon carbide seed crystal 1 at the top in a crucible 2 and a silicon carbide raw material 3 at the bottom in the crucible 2, assembling a heat preservation structure 3 outside the crucible 2, placing the crucible in a crystal growth furnace 4, and heating by using an induction coil 5;

the temperature controller 12 controls the temperature of the crystal growth furnace, controls the pressure through the vacuum system 8 and controls the flow of inert gas introduced into the crystal growth furnace 10 through the inert gas system 9 so as to clean and remove impurities in the crystal growth furnace 10;

a temperature rising stage: the temperature of the crystal growth furnace is adjusted to 1800-2400K, and the pressure in the crucible 2 is controlled to be 0.6 multiplied by 10⁵～1.2×10⁵Pa, the flow rate of inert gas introduced into the crystal growth furnace 10 is 50-500mL/min, and the flow rate V of nitrogen introduced into the nitrogen channel₁20-200 mL/min;

crystal growth stage: increasing the flow rate V of nitrogen introduced into the nitrogen channel₂50 to 500mL/min, V₂Greater than V₁The crystal growth temperature is 2200K-2800K, the crystal growth pressure is 100-;

stopping introducing the nitrogen, continuously introducing the inert gas, and keeping the flow of the introduced inert gas unchanged;

and (3) cooling: turning off the intermediate frequency heating power supply, increasing the circulating water flow in the quartz tube of the crystal growth furnace, rapidly cooling the crystal growth furnace chamber for about 10h, and turning off the flow of the protective inert gas after the cooling is finished;

opening the furnace to obtain 4-inch, 6-inch or 8-inch N-type silicon carbide single crystal ingots with uniform resistivity after the temperature reduction is finished;

2) and (3) carrying out the steps including cutting on the prepared silicon carbide single crystal ingot to obtain the silicon carbide single crystal wafer.

The direction of the edge of hexagonal color spots detected by X-ray diffraction was perpendicular to the <10-10> direction.

EXAMPLE 3 preparation of silicon carbide single crystal ingot # 1

The preparation method of the silicon carbide single crystal ingot 1# comprises the following steps:

a crucible of example 1 was provided having a nitrogen gas channel disposed within the sidewall of the crucible and extending around the crucible interior, the nitrogen gas channel having an inner sidewall density of 1.70g/cm³The density of the shell is 1.90g/cm³；

Placing a silicon carbide seed crystal at the inner top of a crucible and a silicon carbide powder at the inner bottom of the crucible, assembling a heat preservation structure outside the crucible and sealing the crucible in a crystal growth furnace;

controlling the temperature and pressure of the crystal growth furnace and the flow of argon introduced into the crystal growth furnace to clean and remove impurities in the crystal growth furnace;

a temperature rising stage: adjusting the temperature of the crystal growth furnace to 2200K, and controlling the pressure in the crucible to be 0.9 multiplied by 10⁵Pa, the flow of argon gas introduced into the crystal growth furnace is 300mL/min, and the flow of nitrogen gas introduced into the nitrogen channel is V₁40 mL/min;

crystal growth stage: increasing the flow rate V of nitrogen introduced into the nitrogen channel₂200mL/min, the crystal growth temperature of 2400K, the crystal growth pressure of 1000Pa and the retention time of 100 h;

stopping introducing the nitrogen, continuously introducing inert gas, and keeping the flow of introduced argon unchanged;

and (3) cooling: turning off the intermediate frequency heating power supply, increasing the circulating water flow in the quartz tube of the crystal growth furnace, rapidly cooling the crystal growth furnace chamber for 10h, and turning off the flow of the protective inert gas after the cooling is finished;

and opening the furnace to obtain the N-type silicon carbide single crystal ingot with uniform resistivity, wherein the N-type silicon carbide single crystal ingot is No. 1 after the temperature reduction is finished.

The silicon carbide single crystal wafer is prepared by subjecting silicon carbide single crystal ingot # 1 to end face machining, multi-wire slicing, grinding, mechanical polishing, chemical mechanical polishing, cleaning and packaging, and forming a 6-inch silicon carbide single crystal wafer ready for use in an open box, and the preparation method is not limited to 6-inch silicon carbide single crystal, and may be 4 inches, 8 inches, 12 inches, and the like. Taking a silicon carbide single crystal wafer with the following dimensions as an example, the silicon carbide single crystal ingot 1# produces a plurality of silicon carbide single crystal wafers with the thickness of 350 ± 25 μm and the dimension of 6 inches, and the silicon carbide single crystal wafer 1#, the silicon carbide single crystal wafer 2#, the silicon carbide single crystal wafer 3#, the silicon carbide single crystal wafer 4# and the like are respectively arranged along the crystal growth direction from the seed crystal, and so on. The silicon carbide single crystal wafer 2# belongs to the initial stage of crystal growth, the silicon carbide single crystal wafer 8# belongs to the middle stage of crystal growth, and the number of hexagonal color spots in the silicon carbide single crystal wafer is the same.

FIGS. 2a, 2b and 2c show 3 different hexagonal spots in a silicon carbide single crystal wafer 1#, respectively. Fig. 3a, 3b, and 3c show 3 different hexagonal color spots present in the silicon carbide single crystal wafer 4#, respectively. Fig. 4a, 4b, and 4c show the extension of the same hexagonal color spot in the silicon carbide single crystal wafers 6#, 7#, and 8#, respectively.

The silicon carbide single crystal wafer has hexagonal color spots of 10 number and nitrogen content of 6-8 × 10¹⁸cm^-3The resistivity was 0.020 to 0.024 Ω · cm, and the total area of the sides and cubic region of the hexagonal mottle was 2 square millimeters.

EXAMPLE 4 preparation of silicon carbide single crystal ingot No. 2

The method for producing the silicon carbide single crystal ingot 2# of the present example is different from the method for producing the silicon carbide single crystal ingot 1# of example 3 in that the crystal growth stage includes a first crystal growth stage and a second crystal growth stage, a time ratio of the first crystal growth stage to the second crystal growth stage is 1:1, a nitrogen gas inlet and a nitrogen gas outlet of the first crystal growth stage and the second crystal growth stage are exchanged, and the specific steps of crystal growth include:

a first crystal growth stage: firstly, increasing the nitrogen flow to 200ml/min, controlling the temperature of an infrared thermometer to 2200K, controlling the absolute pressure in a growth chamber to 1000Pa, and growing for 50 h;

a second crystal growth stage: and exchanging a nitrogen gas inlet and a nitrogen gas outlet, changing the gas inlet in the first stage into the gas outlet, changing the gas outlet into the gas inlet, controlling the temperature of the infrared thermometer to be 2400K, controlling the absolute pressure in the growth chamber to be 1000Pa, and growing for 50 h.

The silicon carbide single crystal wafer has hexagonal spots of 5, and nitrogen content of 8-9 × 10¹⁸cm^-3The resistivity is 0.018-0.021 omega cm, and the total area of the edges and cubic areas of the hexagonal color spots is less than 0.8 square millimeter.

EXAMPLE 5 preparation of silicon carbide single crystal ingot # 3

The silicon carbide single crystal ingot 3# of the present example differs from the method of producing the silicon carbide single crystal ingot 2# of example 4 in that,

a temperature rising stage: adjusting the temperature of the crystal growth furnace to 1800K, and controlling the pressure in the crucible to be 0.6 multiplied by 10⁵Pa, the flow of argon gas introduced into the crystal growth furnace is 50mL/min, and the flow of nitrogen gas introduced into the nitrogen channel is V₁Is 20 mL/min;

the specific steps of crystal growth comprise:

a first crystal growth stage: firstly, increasing the nitrogen flow to 150ml/min, controlling the temperature of an infrared thermometer to 2200K, controlling the absolute pressure in a growth chamber to be 200Pa, and growing for 50 h;

a second crystal growth stage: and exchanging a nitrogen gas inlet and a nitrogen gas outlet, changing the gas inlet in the first stage into the gas outlet, changing the gas outlet into the gas inlet, controlling the temperature of the infrared thermometer to 2200K, controlling the absolute pressure in the growth chamber to be 200Pa, and growing for 50 h.

The silicon carbide single crystal wafer has hexagonal color spots of 8, and nitrogen content of 7-8 × 10¹⁸cm^-3The resistivity was 0.019 to 0.022 Ω · cm, and the total area of the sides and the cubic region of the hexagonal color patch was 1.2 square millimeters.

EXAMPLE 6 preparation of silicon carbide single crystal ingot No. 4

The silicon carbide single crystal ingot 4# of this example is different from the method for producing the silicon carbide single crystal ingot 1# of example 3 in that the silicon carbide raw material charged in the crucible includes an upper layer raw material and a lower layer raw material, the particle size of the upper layer raw material is 8mm, the particle size of the lower layer raw material is 25mm, and the proportion of the upper layer raw material in the silicon carbide raw material is 75V%.

CarbonizingThe number of hexagonal spots in the silicon single crystal wafer is 7, and the nitrogen content is 7-8 × 10¹⁸cm^-3The resistivity was 0.019 to 0.022 Ω · cm, and the total area of the sides and the cubic region of the hexagonal color patch was 1.7 square millimeters.

EXAMPLE 7 preparation of silicon carbide single crystal ingot No. 5

The difference between the method for producing the silicon carbide single crystal ingot 4# of the present example and the method for producing the silicon carbide single crystal ingot 1# of the present example is that the rear surface of the silicon carbide seed crystal is epitaxially coated with TaC, the silicon surface of the silicon carbide seed crystal has a roughness Ra of less than 0.5, and the middle portion of the silicon carbide raw material is filled with silicon powder.

The silicon carbide single crystal wafer has hexagonal spots of 6 number and nitrogen content of 7-8 × 10¹⁸cm^-3The resistivity was 0.019 to 0.022 Ω · cm, and the total area of the sides and the cubic region of the hexagonal color patch was 1.5 square millimeters.

EXAMPLE 8 detection of hexagonal spot defects in silicon carbide single crystal ingot No. 1-5 #

Respectively detecting hexagonal color spots existing in the silicon carbide single crystal ingots 1# -5#, and measuring the sides of the hexagonal color spots to be perpendicular to the X-ray direction finder<10-10>Direction; performing Raman detection to find that the hexagonal color spots are not polytype; the hexagonal color spot corrosivity test shows that the silicon carbide single crystal wafer is not dislocation, particularly not screw dislocation (TSD dislocation for short), the reference picture is a picture of a hexagonal color spot in a silicon carbide single crystal wafer 8# (figure 5) and a picture after etching (figure 6), hexagonal color spots, edge dislocations and screw dislocations are hexagonal etch pits after etching is finished, the figure can show that the etched edge dislocations and screw dislocations are smaller than the etch pits of the hexagonal color spot in general, the screw dislocations are about tens of micrometers higher than the etch pits of the edge dislocations, the etch pits of the edge dislocations are about tens of micrometers to tens of micrometers, the sizes of the etch pits of the edge dislocations are related to the etching process, but the etched edge dislocations and the screw dislocations are smaller than the etch pits of the hexagonal color spot in general, and the distribution of the edge dislocations and the screw dislocations is not obviously related to the hexagonal color spot. The detection structure of nitrogen element shows that the difference of the nitrogen content of the hexagonal area larger than that of the silicon carbide main body area is A, and the silicon carbide main body area is larger than the hexagonal color spotsThe difference of the nitrogen content of the side part is B, and the difference A is larger than the difference B. Referring to FIG. 7, the nitrogen contents of the hexagonal region, the silicon carbide main region and the edge portion of the hexagonal color spot of FIG. 4c in the silicon carbide single crystal wafer 8# were 7.7X 10¹⁸cm^-3、4.7×10¹⁸cm^-3、4×10¹⁸cm^-3。

Comparative example 1 preparation of silicon carbide single crystal ingot D1#

The silicon carbide single crystal ingot D1# of this example was different from the method for producing the silicon carbide single crystal ingot 1# of example 3 in that a nitrogen gas channel was not present in the crucible side wall, and nitrogen gas and argon gas were directly introduced into the growth furnace.

The number of hexagonal color spots in the silicon carbide single crystal wafer was 55, and the nitrogen content was 3X 10¹⁸～5×10¹⁸cm^-3The resistivity was 0.023 to 0.030 Ω · cm, and the total area of the sides and the cubic area of the hexagonal mottles was 3.9 square millimeters.

Comparative example 2 preparation of silicon carbide single crystal ingot D2#

The silicon carbide single crystal ingot D2# of the present example was different from the method for producing silicon carbide single crystal ingot 1# of example 3 in that the nitrogen flow rate in the temperature raising stage was 100mL/min and the nitrogen flow rate in the crystal growth stage was 50 mL/min.

The number of hexagonal color spots in the silicon carbide single crystal wafer was 60, and the nitrogen content was 1X 10¹⁸～2×10¹⁸cm^-3The resistivity was 0.035 to 0.045 Ω · cm, and the total area of the sides and cubic regions of the hexagonal color spot was 4.0 square millimeters.

The above description is only an example of the present application, and the protection scope of the present application is not limited by these specific examples, but is defined by the claims of the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the technical idea and principle of the present application should be included in the protection scope of the present application.

Claims

1. A silicon carbide single crystal wafer comprising nitrogen elements, wherein the silicon carbide single crystal wafer has a number of hexagonal irregularities of not more than 50, and edges forming the hexagonal irregularities are perpendicular to a <10-10> direction.

2. The silicon carbide single crystal wafer according to claim 1, wherein the number of hexagonal spots is not more than 30;

preferably, the silicon carbide single crystal wafer has the number of hexagonal color spots not more than 5;

more preferably, the silicon carbide single crystal wafer has a number of hexagonal stains of not more than 3.

3. The silicon carbide single crystal wafer according to claim 1, wherein the diameter of the silicon carbide single crystal wafer is not less than 75 mm;

preferably, the diameter of the silicon carbide single crystal wafer is not less than 100 mm;

more preferably, the diameter of the silicon carbide single crystal wafer is not less than 150 mm.

4. The silicon carbide single crystal wafer as claimed in claim 1, wherein the nitrogen content in the silicon carbide single crystal wafer is 5 x 10¹⁷～5×10¹⁹cm^-3；

Preferably, the content of nitrogen in the silicon carbide single crystal wafer is 5 x 10¹⁸～1×10¹⁹cm^-3；

More preferably, the silicon carbide single crystal wafer is N-type silicon carbide, and the nitrogen content in the silicon carbide single crystal wafer is 6 x 10¹⁸～9×10¹⁸cm^-3。

5. The silicon carbide single crystal wafer according to claim 1, wherein the silicon carbide single crystal wafer is a hexagonal single crystal; preferably, the crystal form of the silicon carbide single crystal wafer is 4H-SiC or 6H-SiC; and/or

The resistivity of the silicon carbide single crystal wafer is 0.002 omega cm-0.06 omega cm; preferably, the resistivity of the silicon carbide single crystal wafer is 0.015-0.028 omega cm.

6. The silicon carbide single crystal wafer according to any one of claims 1 to 5, wherein the region outside the edge of the hexagonal color spot of the silicon carbide single crystal wafer is a silicon carbide main body region, the edge of the hexagonal color spot is surrounded by a hexagonal region, and the color of the edge of the hexagonal color spot is different from the color of the silicon carbide main body region and the hexagonal region observed by an optical microscope; and/or

The sides of the hexagonal color spots are different from the nitrogen content of the silicon carbide main body region and the hexagonal region respectively;

preferably, the nitrogen content of the hexagonal regions is no less than the nitrogen content of the silicon carbide body regions is greater than the nitrogen content of the sides of the hexagonal color spots;

more preferably, the difference between the nitrogen contents of the hexagonal regions and the silicon carbide main body region is a, the difference between the nitrogen contents of the silicon carbide main body region and the sides of the hexagonal color spots is B, and the difference a is not less than the difference B.

7. The silicon carbide single crystal wafer according to claim 6, wherein the hexagonal color spots form hexagons on a long crystal plane of the silicon carbide single crystal wafer;

the edge of the hexagonal color spot extends along the C axis in the silicon carbide single crystal wafer.

8. The silicon carbide single crystal wafer according to claim 6, wherein the hexagonal color unevenness is a scalene hexagon;

the width of the edge of the hexagonal color spot is not more than 1 mm; and/or

The distance between the two sides farthest away in the six sides of the hexagonal color spot is not more than 5 mm.

9. A method for producing a silicon carbide single crystal wafer as set forth in any one of claims 1 to 8, which comprises the steps of:

1) preparing a silicon carbide single crystal ingot:

10. The method for producing a silicon carbide single crystal wafer according to claim 9, wherein the method for growing a silicon carbide single crystal ingot by physical vapor transport comprises the steps of:

11. The method for preparing a silicon carbide single crystal wafer according to claim 10, wherein the crystal growth stage comprises a first crystal growth stage and a second crystal growth stage, the time ratio of the first crystal growth stage to the second crystal growth stage is 1:0.8-1.2, and the nitrogen gas inlet and the nitrogen gas outlet of the first crystal growth stage are exchanged with those of the second crystal growth stage.

12. The method for producing a silicon carbide single crystal wafer according to any one of claims 9 to 11, wherein the crucible comprises a liner and a shell, the liner forms an inner side wall of the nitrogen gas channel, the shell forms an outer side wall of the nitrogen gas channel, and a density of the liner is lower than a density of the shell;

preferably, the density of the liner is no greater than 1.75g/cm³；

Preferably, the density of the shell is not less than 1.85g/cm³(ii) a More preferably, the density of the crucible is not less than 1.90g/cm³。

13. The method for producing a silicon carbide single crystal wafer according to any one of claims 9 to 11, wherein the silicon carbide raw material charged in the crucible includes an upper layer raw material and a lower layer raw material, the upper layer raw material is smaller than the particle size of the lower layer raw material, and the proportion of the upper layer raw material in the silicon carbide raw material is 30 to 40V%;

preferably, the particle size of the upper layer raw material is 5-10mm, and the particle size of the lower layer raw material is 20-30 mm.

14. The method for producing a silicon carbide single crystal wafer according to any one of claims 9 to 11, wherein the silicon carbide raw material is filled with silicon powder at a middle portion thereof;

preferably, the silicon powder is loaded in a loader provided with a through hole, the loader being loaded in the middle of the silicon carbide raw material.

15. A silicon carbide single crystal ingot, characterized in that the silicon carbide single crystal ingot is processed by a process comprising a slicing step to form a silicon carbide single crystal wafer;

the silicon carbide single crystal wafer is selected from the silicon carbide single crystal wafer according to any one of claims 1 to 8 or the silicon carbide single crystal wafer is selected from the silicon carbide single crystal wafer produced by the method according to any one of claims 9 to 14.

16. The silicon carbide single crystal ingot according to claim 15, wherein the width of the sides of the hexagonal stain increases, and the distance between two sides farthest from among the six sides of the hexagonal stain increases, in the growth direction of the silicon carbide single crystal extending along the C-axis.

17. The method for producing a silicon carbide single crystal ingot according to claim 15 or 16, comprising the method for producing a silicon carbide single crystal ingot according to step 1) in the method for producing a silicon carbide single crystal wafer according to any one of claims 9 to 14.