阅读说明：本技术 具有环形形貌的碳化硅晶体及其制备方法和制得的衬底 (Silicon carbide crystal with annular morphology, preparation method thereof and prepared substrate ) 是由 张九阳 李霞 王永方 方帅 张红岩 高超 左康廷 张梦影 苏丽娜 于 2021-08-18 设计创作，主要内容包括：本申请公开了一种具有环形形貌的碳化硅晶体及其制备方法、加工方法和制得的衬底。该碳化硅晶体具有相对的第一主表面和第二主表面,所述碳化硅晶体具有一个靠近所述碳化硅晶体外周侧的环形形貌,所述环形形貌自第一主表面贯穿延伸至第二主表面,所述环形形貌包括刃位错；所述环形形貌内围绕的区域形成目标碳化硅晶体,所述环形形貌外的原子台阶宽度小于所述环形形貌内的原子台阶宽度。本申请发现一种新型环形形貌,并利用该形成的环形形貌的原子台阶宽度的变化规律,准确切割去掉低质量的碳化硅晶体部分,解决了无法准确去边,去边废料率高、资源浪费的问题,并且进一步提高了去边后的碳化硅晶体的质量和直径。(The application discloses a silicon carbide crystal with an annular shape, a preparation method and a processing method thereof, and a prepared substrate. The silicon carbide crystal having opposed first and second major surfaces, the silicon carbide crystal having an annular feature proximate the peripheral side of the silicon carbide crystal, the annular feature extending from the first major surface through to the second major surface, the annular feature including edge dislocations; and forming a target silicon carbide crystal in a region surrounded by the annular shape, wherein the width of atomic steps outside the annular shape is smaller than that of the atomic steps inside the annular shape. The application discovers a novel annular shape, and utilizes the change rule of the width of the atomic step of the formed annular shape to accurately cut and remove the low-quality silicon carbide crystal part, thereby solving the problems of incapability of accurately removing edges, high scrap rate of the removed edges and resource waste, and further improving the quality and the diameter of the silicon carbide crystal after the edges are removed.)

1. A silicon carbide crystal having an annular morphology comprising edge dislocations, wherein the silicon carbide crystal has first and second opposing major surfaces, the silicon carbide crystal having an annular morphology towards an outer peripheral side of the silicon carbide crystal, the annular morphology extending from the first major surface through to the second major surface;

and forming a target silicon carbide crystal in a region surrounded by the annular shape, wherein the width of atomic steps outside the annular shape is smaller than that of the atomic steps inside the annular shape.

2. The silicon carbide crystal with annular morphology according to claim 1 wherein the atomic step width D1 outside the annular morphology, the atomic step width D2 of the annular morphology, and the atomic step width D3 of the silicon carbide crystal inside the annular morphology increase in sequence.

3. The silicon carbide crystal with ring-shaped morphology according to claim 2 wherein the difference between the atomic step width D1 and the atomic step width D3 is not less than 0.05 μ ι η.

4. The silicon carbide crystal with annular morphology according to claim 2, wherein the silicon carbide crystal is a 4H silicon carbide crystal, the atomic step width D1 is 0.16-0.18 μm, the atomic step width D2 is 0.18-0.20 μm, and the atomic step width D3 is greater than 0.2 μm.

5. The silicon carbide crystal with ring morphology as claimed in claim 1 wherein the ring morphology blocks dislocations, including substrate plane dislocations, inward slip of small angle grain boundaries;

the substrate plane dislocation density outside the ring topography is greater than the substrate plane dislocation density inside the ring topography.

6. A method of processing a silicon carbide crystal with annular morphology according to any one of claims 1-5, comprising the steps of:

detecting the position of the annular shape, and cutting along the position of the annular shape to obtain the target silicon carbide crystal;

and testing the atomic step width of the target silicon carbide crystal through an atomic force microscope, testing the position of taking a point from the edge of the target crystal to the center, and cutting the part, which is tested to be larger than 0.05 mu m, of the atomic step width between the two points at the edge along the annular edge where the point close to the outer side is located, so that the high-quality silicon carbide crystal is obtained.

7. The method for processing the silicon carbide crystal with the annular morphology according to claim 6, wherein the points are uniformly taken every 1mm from the edge to the center of the target crystal, and the silicon carbide crystal with high quality is obtained by cutting along the annular edge where the change of the width of the atomic step between two points on the edge is more than 0.05 μm and the point close to the outer side is tested.

8. A high quality silicon carbide crystal produced by the process of any one of claims 6 or 7;

an atomic adjustment width difference between any two points in the high-quality carbonized crystal is not more than 0.05 μm.

9. A method for preparing a silicon carbide crystal with annular morphology according to any one of claims 1 to 5, characterized in that it comprises the following steps:

1) assembling: providing a bearing raw material and a seed crystal arranged at the top in the crucible, placing the crucible in a heat preservation cavity formed by a heat preservation layer, and then moving the crucible into a crystal growth furnace; the heat-insulating layer comprises a heat-insulating ring arranged above the crucible, the heat-insulating ring at least covers the seed crystal and extends inwards from the edge by 0.5mm to 0.5r-0.5mm, and r is the radius of the seed crystal;

2) growing a crystal: and (3) preparing the silicon carbide crystal by crystal growth, wherein the edge of the prepared silicon carbide crystal forms an annular shape approximately corresponding to the covering position of the heat preservation ring.

10. A silicon carbide substrate characterized by being subjected to a step including slicing from the silicon carbide crystal according to any one of claims 1 to 5, the high-quality silicon carbide crystal according to claim 8, or the silicon carbide crystal produced by the production method according to claim 9, to produce a silicon carbide substrate having a ring-shaped morphology.

Technical Field

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

Background

Silicon carbide material has attracted much attention because of its excellent semi-insulating property, and especially for high-power semiconductor devices with special requirements, silicon carbide becomes a potential material of choice for these devices because of its high temperature, high frequency, high power, etc.

At present, silicon carbide crystal is produced by adopting a PVT method in industrial production, but because the requirement on the growth condition is higher, the improvement of the performance and the further application and development of the silicon carbide crystal are limited by defects introduced in the growth process. Therefore, improvement of defects is a primary prerequisite for improving the quality of the silicon carbide substrate.

The defects of silicon carbide crystals that we are familiar with at times are mainly: micropipes, triangular defects, voids and cracks, small-angle grain boundaries, traditional dislocations, and other defects (mainly including stacking faults, carrot defects, giant steps, particles, droppings, surface scratches, growth pits, and the like). These defects can have some effect on the quality of the material and further affect the performance of devices made from silicon carbide crystals, which fundamentally limits the development of silicon carbide materials.

The preparation of semi-insulating silicon carbide single crystal which is industrialized at present is based on physical vapor phase method (PVT), which continuously optimizes the process and improves the quality of seed crystal, and further continuously explores for continuously improving the crystal quality to obtain the silicon carbide substrate with low defect density, large size and high quality.

At present, in the growth process of the silicon carbide crystal by the PVT method, edge dislocation can generate slip due to shear stress formed by temperature gradient, so that the slip is carried out from the edge to the center, and the high density of the dislocation at the center of a substrate, the local dislocation accumulation and the like are often caused.

During the crystal growth process, LAGB (small angle grain boundary) is formed at the crystal edge due to the fluctuation of crystal growth parameters, namely (edge dislocation) TED wall is formed. The formation of LAGB generally causes the local stress of a silicon carbide substrate to be poor, the crystallization quality to be poor, the FWHM value measured by corresponding XRD is large, the diffraction peak is widened or an impurity peak appears, and the use of a downstream device is interfered.

The grain boundary type can be divided into a small-angle grain boundary and a large-angle grain boundary, wherein the small-angle grain boundary refers to the grain boundary with the rotation included angle smaller than 10 degrees between two adjacent grains, and the large-angle grain boundary refers to the grain boundary with the rotation angle larger than 10 degrees.

For the seed crystal with local defects on the edge, the defects are transmitted to the grown crystal with high probability in the crystal growing process, so that the crystal always has the defects at the same position, and the high-quality silicon carbide crystal is not obtained.

On the other hand, after the prepared silicon carbide ingot is cut and trimmed due to poor quality of the edge part, the trimming cannot be accurately determined, so that the scrap rate generated by trimming is high, and the quality of the silicon carbide crystal generated after trimming is unstable.

Disclosure of Invention

In order to solve the above problems, the present application provides a silicon carbide crystal having a novel annular morphology. In addition, the change rule of the width of the formed atomic step with the annular shape can be utilized to accurately cut and remove the low-quality silicon carbide crystal part, so that the problems of incapability of accurately removing edges, high edge-removing waste rate and resource waste are solved; and further improves the quality and diameter of the edge-removed silicon carbide crystal.

According to one aspect of the present application, a silicon carbide crystal having an annular morphology, the silicon carbide crystal having opposing first and second major surfaces, the silicon carbide crystal having an annular morphology near an outer peripheral side of the silicon carbide crystal, the annular morphology extending from the first major surface through to the second major surface, the annular morphology comprising edge dislocations;

and forming a target silicon carbide crystal in a region surrounded by the annular shape, wherein the width of atomic steps outside the annular shape is smaller than that of the atomic steps inside the annular shape.

Specifically, one mechanism for forming the change rule of the atomic step width is that the annular shape blocks a large amount of base plane dislocations (hereinafter referred to as BPD) outside, and the base plane dislocations cannot slide inward to be piled up, thereby affecting the difference of the atomic step width caused by the deflection angle. The annular morphology can be directly observed through a laser detector, a microscope, a lattice defect detector or a stress meter and the like, the atomic step width can be detected through an atomic force microscope, and the high-quality and large-size silicon carbide crystal can be obtained by utilizing the annular morphology and the change of the atomic step width.

Optionally, the atomic step width D1 outside the annular morphology, the atomic step width D2 of the annular morphology, and the atomic step width D3 of the silicon carbide crystal inside the annular morphology increase in sequence.

Optionally, the atomic step width D1 differs from the atomic step width D3 by no less than 0.05 μm. Further, the difference between the atomic step width D1 and the atomic step width D3 is not less than 0.15 μm.

Optionally, the silicon carbide crystal is a 4H silicon carbide crystal, the atomic step width D1 is 0.16-0.18 μm, the atomic step width D2 is 0.18-0.20 μm, and the atomic step width D3 is greater than 0.2 μm. The variation in atomic step width D3 is large because: a section of atomic step width sudden-rising section and an atomic step width uniform section extend from the outside to the inside of the annular shape, and the atomic step width change of the sudden-rising section is large.

Further, the silicon carbide crystal is a 4H silicon carbide crystal, the atomic step width D1 is 0.165-0.175 μm, the atomic step width D2 is 0.185-0.199 μm, and the atomic step width D3 is 0.22-0.45 μm.

Optionally, the ring-shaped topography blocks dislocations including substrate plane dislocations, inward slip of small-angle grain boundaries;

the substrate plane dislocation density outside the ring topography is greater than the substrate plane dislocation density inside the ring topography.

The silicon carbide crystal containing the annular morphology is prepared and applied after mastering a related forming mechanism and a testing method thereof, so that waste is changed into valuable materials for optimizing the edge quality of the silicon carbide, the annular morphology, namely the edge dislocation wall, is used for preventing edge dislocation formed in the crystal growth process of the silicon carbide from slipping inwards and preventing edge small-angle crystal boundaries from extending inwards, and a high-quality silicon carbide substrate is obtained by means of special processing equipment and technology.

The silicon carbide crystal having an annular morphology extending throughout from the first major surface to the second major surface, the annular morphology comprising being formed by edge dislocations;

and forming a target silicon carbide crystal in a region surrounded by the annular appearance, wherein the dislocation density outside the annular appearance is greater than the dislocation density inside the annular appearance.

Optionally, the silicon carbide crystal is a 4H polytype silicon carbide crystal having a first major surface and a second major surface opposite the first major surface, the first major surface being a {0001} plane or a plane inclined at an off-angle greater than 0 ° and not greater than 8 ° with respect to the {0001} plane.

Optionally, the stress of the annular feature is greater than the stress outside the annular feature is greater than the stress inside the annular feature.

Optionally, the crystalline quality outside the annular topography is lower than the crystalline quality inside the annular topography.

Optionally, the width of the annular feature is no greater than 5 mm.

Optionally, the silicon carbide crystal size in the annular topography is not less than 150 mm. The silicon carbide crystal size within the annular topography may be 150mm, 200mm, 250mm, 300mm, or 350 mm.

Optionally, the annular feature extends inward at least 3mm as an annular region that is a face that is inclined with respect to a {0004} face by an off angle of less than 0.06 °;

and no small-angle grain boundary exists in the annular region, and the full width at half maximum of the crystallization quality of the annular region is not more than 20 arcsec. Preferably, the annular region and the central region have equal crystalline qualities such as off-angle, low angle grain boundaries, and full width at half maximum.

Optionally, the annular region is a face inclined with respect to an off-angle of {0004} face of no more than 0.05 °; the annular region is free of small-angle grain boundaries, and the full width at half maximum of the crystalline quality of the annular region is not more than 16.6 arcsec.

Optionally, the annular region has a width extending inward from the edge of the substrate of not less than 5 mm. Further, the annular region may have a width value or an upper limit and a lower limit of a width range extending inward from an edge of the substrate of 3mm, 4mm, 5mm, 6mm, 10mm, 15mm, or 20mm, respectively.

Optionally, the dislocation density in the annular region is no higher than 5500/cm²And the dislocation density in the central region is not higher than that in the annular region. Preferably, the upper limit of the dislocation density in the annular region is selected from 4400/cm²、4395/cm²、2600/cm²、2591/cm²。

Optionally, the stress is uniform in the central and annular regions.

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

detecting the position of the annular shape, and cutting along the position of the annular shape to obtain the target silicon carbide crystal;

and testing the atomic step width of the target silicon carbide crystal through an atomic force microscope, testing the position of taking a point from the edge of the target crystal to the center, and cutting the part, which is tested to be larger than 0.05 mu m, of the atomic step width between the two points at the edge along the annular edge where the point close to the outer side is located, so that the high-quality silicon carbide crystal is obtained.

The edge position of the target crystal described in this application is within the area near the edge of the crystal that can be tested, and can be, for example, any area within 1mm or 0.5mm from the edge.

Alternatively, a laser detector, a lattice defect detector, a microscope, a stress gauge, or the like may be used to detect the position of the annular feature.

Specifically, the test point positions are regularly arranged from the edge of the target crystal to the center at intervals so as to obtain the minimum trimming amount and leave the high-quality silicon carbide crystal with the maximum diameter.

Optionally, uniformly taking points every 1mm along the edge of the target crystal to the center, and cutting along the annular edge where the point close to the outer side is located when the change of the width of the atomic step between the two points on the edge is more than 0.05 mu m by testing, so as to obtain the high-quality silicon carbide crystal. Further, the atomic step width variation is greater than 0.06 μm, 0.07 μm, 0.1 μm, or 0.2 μm cut along the annular edge near the outer point.

According to yet another aspect of the present application, there is provided a high quality silicon carbide crystal produced by the processing method of any one of the above;

an atomic adjustment width difference between any two points in the high-quality carbonized crystal is not more than 0.05 μm. Preferably, the difference is not more than 0.04 μm, 0.03 μm, 0.02 μm or 0.01 μm.

According to a further aspect of the present application, there is provided a method of preparing any of the silicon carbide crystals described above, comprising the steps of:

1) assembling: providing a bearing raw material and a seed crystal arranged at the top in the crucible, placing the crucible in a heat preservation cavity formed by a heat preservation layer, and then moving the crucible into a crystal growth furnace; the heat-insulating layer comprises a heat-insulating ring arranged above the crucible, the heat-insulating ring at least covers the seed crystal and extends inwards from the edge by 0.5mm to 0.5r-0.5mm, and r is the radius of the seed crystal;

2) growing a crystal: and (3) preparing the silicon carbide crystal by crystal growth, wherein the edge of the prepared silicon carbide crystal forms an annular shape approximately corresponding to the covering position of the heat preservation ring.

Optionally, the crystal growth stage in step 2) comprises the following steps:

removing impurities: 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 2000-2400K, and controlling the pressure in the crucible to be 0.6 multiplied by 10⁵～3.3×10⁴Pa, introducing inert gas into the crystal growth furnace at a flow rate of 50-500mL/min, moving the crucible upwards at a moving speed of 0.1mm/h and rotating at a speed of 0.5 r/min;

a pressure reduction stage: the pressure is controlled from 0.6X 10⁵～3.3×10⁴Pa, down to 5X 10³Pa-1×10⁴Pa; during the pressure reduction, the crucible moves downwards at the speed of 1mm/h and rotates at the speed of 0.2 r/min; controlling the temperature to be 2400K-2600K;

crystal growth stage: the crystal growth temperature is 2600K-2800K, the crystal growth pressure is 100-; and keeping the reaction time for 80-120 h to obtain the silicon carbide crystal with the annular shape and the controllable diameter.

The invention discloses a ring-shaped appearance based on the growth of silicon carbide crystals by the PVT method, which is applied after mastering relevant forming mechanism and testing method, thereby changing waste into valuable and optimizing the edge quality of silicon carbide, preventing the edge dislocation formed in the silicon carbide crystal growth process from slipping inwards by the aid of the ring-shaped appearance, namely a knife dislocation (TED) wall, and preventing a small-angle edge grain boundary (LAGB) from extending inwards, and obtaining a high-quality silicon carbide substrate by the aid of special processing equipment and special processing technology.

The structure of heat preservation ring that this application provided and the position of setting can construct specific radial temperature gradient distribution in the top of carborundum seed crystal. Specifically, an air layer located above the seed crystal is surrounded on the inner side wall of the heat preservation ring, on one hand, the difference between the heat conductivity of air and the heat conductivity of the heat preservation layer is large, so that the radial temperature gradient of a temperature field generates sudden change at the position of the inner side wall of the heat preservation ring from inside to outside, and then a large temperature difference is formed between the inner side wall and the outer side of the inner side wall of the heat preservation ring, so that a large number of surface or penetrating defects are generated at the position of the inner side wall of the heat preservation ring with the temperature suddenly changed by the crystal in a centralized mode, a large number of defects are gathered to form an annular shape similar to a wall form, the annular shape can simultaneously prevent low-angle crystal boundaries outside the ring from extending inwards and the edge dislocations from sliding inwards, and the problem that the edge defects of the crystal extend or slide towards the middle part is solved; on the other hand, the air layer can also play the effect of homogenizing the temperature field, is favorable to adjusting the radial temperature ladder above the seed crystal, and then reduces or even eliminates the production of crystal middle part defect, promotes the quality of middle part crystal. Under the action of the two aspects, the quality of the middle area of the crystal within the position of the inner side wall of the heat preservation ring is improved, and the dislocation at the edge of the crystal is blocked and cannot slide into the middle area of the crystal at the inner side in the presence of the annular shape, so that the quality of the middle crystal of the silicon carbide crystal is obviously improved, and the silicon carbide crystal, namely the substrate with high quality at the middle part can be obtained after the annular shape and the outer part are removed.

According to still another aspect of the present application, there is provided a silicon carbide substrate obtained by subjecting the silicon carbide crystal according to any one of the above, the high-quality silicon carbide crystal, or the silicon carbide crystal obtained by any one of the above preparation methods to a step including slicing.

Preferably, the silicon carbide crystal further comprises edge deletion: and cutting the silicon carbide substrate along the inner side of the annular shape or close to the inner side of the annular shape to obtain the target silicon carbide substrate. Specifically, the silicon carbide crystal slicing further comprises grinding and polishing steps.

Optionally, the step of edging may be before and/or after slicing. Preferably, the step of edging is after slicing.

The preparation method for preparing the silicon carbide crystal is characterized in that an air layer is arranged between an upper insulating layer and a crucible besides an insulating ring structure. The air layer is arranged to homogenize the temperature field above the seed crystal and further regulate and homogenize the radial temperature gradient above the seed crystal, so that defects generated in the target silicon carbide crystal are inhibited, and edge defects of the target silicon carbide crystal are avoided.

In the present application, the silicon carbide crystal has first and second opposed major surfaces, the annular feature extending across the silicon carbide crystal from the first major surface toward the second major surface in a direction generally perpendicular to the first major surface, the annular feature extending proximate a periphery of the silicon carbide crystal, e.g., a silicon carbide crystal having an annular feature that surrounds a region that includes a central region and an annular region; the ring shape can be observed by using a laser detector, a lattice defect detector, a microscope or a stress meter and the like; the ring-shaped topography includes edge dislocations.

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

1. according to the silicon carbide crystal, the silicon carbide crystal with the novel annular appearance can be accurately cut and removed by utilizing the change rule of the width of the atomic step of the formed annular appearance, and the silicon carbide crystal with high quality and large size can be prepared.

2. According to the silicon carbide crystal of the present application, the crystal quality of the target silicon carbide crystal having the silicon carbide crystal is high, few dislocations are present, small-angle grain boundaries are substantially absent, stress is small, and the surface type quality is high.

3. According to the silicon carbide crystal, the dislocation density of the annular region at the edge of the target silicon carbide crystal is low, and the dislocation density of the central region is low; and the annular area at the edge does not generate small-angle grain boundaries, so that the crystallization quality is high, and the quality of the manufactured downstream device is high.

4. According to the processing method of the silicon carbide crystal, a novel annular shape is found, the change rule of the width of the atomic step of the formed annular shape is utilized, the low-quality silicon carbide crystal part is accurately cut and removed, and the problems that the edge cannot be accurately removed, the edge removal waste rate is high and resources are wasted are solved.

5. According to the silicon carbide crystal preparation method and the substrate, an annular shape is found, and the annular shape is applied after a related forming mechanism and a related testing method are mastered, so that waste is turned into wealth to optimize the edge quality of silicon carbide, the annular shape, namely the edge dislocation wall, is used for preventing edge dislocation formed in the silicon carbide crystal growing process from slipping inwards and preventing edge small-angle crystal boundaries from extending inwards, and the high-quality silicon carbide substrate is obtained by means of special processing equipment and special processing technology.

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 an insulation layer provided in example 1 of the present application;

FIG. 2 is a schematic view of another insulation layer provided in example 1 of the present application;

FIG. 3 is a schematic view of another insulation layer provided in example 1 of the present application;

FIG. 4 is a schematic view of an insulation layer provided in example 3 of the present application;

FIG. 5 is a schematic view of another insulation layer provided in example 3 of the present application;

FIG. 6 is a schematic view of yet another insulation layer provided in example 3 of the present application;

FIG. 7 is a schematic illustration of a primary silicon carbide substrate having an annular topography prepared in accordance with example 8 of the present application;

fig. 8 is a characteristic image of the ring-shaped morphology of the primary silicon carbide substrate a in a laser detector (Candela, equipment model CS920, equipment manufacturer) according to embodiment 8 of the present application;

fig. 9 is a characteristic image of the annular shape of the primary silicon carbide substrate a in a stress detector (instrument manufacturer, suzhou precision optical instrument ltd, equipment model number is qualitative portable polarization stress meter) according to example 8 of the present application;

fig. 10 is a test image of an annular defect lattice distortion detector (instrument manufacturer is soaring crystal semiconductor technologies ltd, equipment model CS10) with an annular shape of a primary silicon carbide substrate a according to embodiment 8 of the present application;

fig. 11 is a polarization observation diagram (a) and a labeled diagram (b) of the ring shape of the primary silicon carbide substrate a in the SiC polished wafer microscope (the instrument manufacturer is olympus, equipment model MX63), and an observation diagram (c) and a labeled diagram (d) under a dark field in example 8 of the present application;

fig. 12 shows Raman mapping (HORIBA, equipment model: HREVOLUTION) of the ring profile of the primary silicon carbide substrate a in example 8 of the present application;

fig. 13 is a graph showing an image ring shape of the primary silicon carbide substrate a in a laser detector (Candela, equipment model CS920, manufactured by the manufacturer of the equipment) and a test result (b) of an atomic force microscope AFM (Park, equipment model NX20, manufactured by the manufacturer of the equipment) of the ring shape of the primary silicon carbide substrate a in example 8 of the present application;

FIG. 14 is a graph showing a test result (a) of ring shape profile of a primary silicon carbide substrate a and a test result (b) of off-angle XRD test (Bruker, equipment model JV-DX, equipment manufacturer) of the ring shape profile of the primary silicon carbide substrate a in a laser detector (Candela, equipment model CS920, equipment manufacturer) according to example 8 of the present application;

FIG. 15 is an image observed by a microscope (the equipment manufacturer is Olympus, equipment model is MX63) after annular stress KOH corrosion of the primary silicon carbide substrate a in example 8 of the present application;

FIG. 16 is a statistical mapping image of dislocations after ring stress KOH etching of a ring shape of a primary silicon carbide substrate a according to example 8 of the present application;

fig. 17 is an observation image of the primary silicon carbide substrate a in the ring shape under polarization by a microscope (the instrument manufacturer is olympus, equipment model MX63) according to example 8 of the present application;

FIG. 18 is an image of a surface profile test (CORNING, FlatMaster200 Semi-Automated Wafer System) of the annular topography of a primary silicon carbide substrate a according to example 8 of the present application, wherein (a) is a wave-Bow surface profile image and (b) is LTV data;

fig. 19 is a graph of a ring shape of a primary silicon carbide substrate a obtained in example 8 of the present application, which is obtained by an atomic force microscope AFM (instrument manufacturer is Park, equipment model is NX20) test result (b) of a ring shape of the primary silicon carbide substrate a and an image test (a) of the ring shape of the primary silicon carbide substrate a in a laser detector (instrument manufacturer is Candela, equipment model is CS 920);

in the figure: 101. an upper heat-insulating layer; 1011. a first external thread; 102. a transition heat-insulating layer; 2. a crucible; 3. silicon carbide seed crystals; 4. silicon carbide powder; 5. a side insulating layer; 501. a second external thread; 6. a temperature measuring hole; 7. an air layer; 701. the inner surface of the upper heat-insulating layer; 702. the inner surface of the transition insulating layer; a heat preservation ring 8; annular topography 91, silicon carbide substrate 92, annular region 93, central region 94.

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.

Example 1

The heat retaining ring structure is not shown in the drawings of this embodiment, and this embodiment mainly explains the structure of the air layer.

The crucible 2 is a graphite crucible, and the size of the silicon carbide seed crystal in the crucible 2 is 100-350 mm.

Referring to fig. 1-3, the insulating layer comprises a lower insulating layer, an upper insulating layer 101, a side insulating layer 5 and a transition insulating layer 102, the lower insulating layer, the upper insulating layer 101, the side insulating layer 5 and the transition insulating layer 102 enclose a heat insulating cavity, and the upper insulating layer 101 is provided with a temperature measuring hole; the transition insulating layer 102 is in threaded connection with at least one of the upper insulating layer 101 and the side insulating layer 5 and is integrally formed with the other, the upper insulating layer 101 is in threaded connection with the side insulating layer 5 through the transition insulating layer 102, and the distance between the crucible 2 arranged in the side insulating layer 5 and the inner surface of the upper insulating layer 101 is adjusted in a rotating manner.

Specifically, lower heat preservation and 5 fixed connection of side heat preservation, like integrated into one piece or screw connection etc. as long as realize that the heat preservation rotates can drive 5 rotations of side heat preservation simultaneously promptly. The crucible is placed on the lower heat-insulating layer, and the movement of the lower heat-insulating layer can drive the crucible to do the same movement. Specifically, the mode of relative rotation between the upper insulating layer 101 and the side insulating layer 5 through the threaded connection of the transition insulating layer 102 may be: the upper insulating layer 101 is fixed on the crystal growth furnace, and the lower insulating layer is installed on the rotary lifting unit. As an implementation mode, the rotary lifting unit comprises a motor, a rotary lifting platform and a supporting rod, the rotary lifting platform is fixed on the top of the supporting rod, the lower heat-insulating layer is fixed on the top of the rotary lifting platform, and the motor drives the supporting rod to drive the rotary lifting platform and the lower heat-insulating layer to rotate and lift. The rotary lifting mechanism can also be other rotary lifting units commonly used in the field as long as the rotary lifting unit can rotate and lift the side heat-insulating layer or the upper heat-insulating layer.

Referring to fig. 1, the inner surface 702 of the transition insulating layer is screw-coupled to the second outer screw 501 outside the side insulating layer 5, the top of the transition insulating layer 102 is integrally formed with the upper insulating layer 101, and the transition insulating layer 102 and the side insulating layer 5 are relatively rotated to adjust the thickness of the air layer 7 between the top of the crucible 2 and the inner surface 701 of the upper insulating layer.

Referring to fig. 2, a first external thread 1011 is provided on the outer side of the upper insulation layer 101 and is in threaded connection with the inner surface 702 of the transition insulation layer, and the inner surface 702 of the transition insulation layer is in threaded connection with a second external thread 501 on the outer side of the side insulation layer 5. The transition insulating layer 102 and the side insulating layer 5 are adjusted to rotate relatively, and/or the transition insulating layer 102 and the upper insulating layer 101 are adjusted to rotate relatively to adjust the thickness of the air layer 7 between the top of the crucible 2 and the inner surface 701 of the upper insulating layer.

Specifically, the shape of the transition insulation layer 102 is not limited as long as the threaded connection portion is cylindrical, such as the circular ring cylindrical structure of fig. 2 or the cylindrical structure with an inwardly extending annular groove of fig. 3. The annular groove of the transition insulation layer 102 of fig. 3 is disposed to protrude from the side insulation layer 5 to form an air layer having a diameter significantly larger than that of the silicon carbide seed crystal 3 above the top opening of the side insulation layer 5 to further avoid edge defects of the growing silicon carbide crystal.

Specifically, the diameter of the air layer 7 is 0.2 to 30cm, preferably 1 to 20cm, more preferably 3 to 15cm larger than the diameter of the silicon carbide seed crystal. The thickness of the air layer is 10-60 mm. Further, the thickness of the air layer 7 in the crystal growth process is 20-50 mm; preferably, the thickness of the air layer 7 during the crystal growth is 30mm to 40 mm. The air layer is arranged in a mode which is beneficial to improving the crystal growth quality and reducing the generation of defects, particularly the defects at the edge of the crystal. Too thick air layer can lead to the reduction of the axis ladder, be unfavorable for guaranteeing the growth rate of crystal, too thin can lead to radial temperature ladder too big, and the shear stress increases, leads to stress concentration in the carborundum crystal.

As a preferred embodiment, it is preferable that the bottom end of the second external thread 501 provided on the outer sidewall of the side insulating layer 5 corresponds to the center position of the crucible 2. The arrangement mode solves the problem of non-visualization in the crucible 2 and the heat preservation layer, is difficult to adjust the central position of the crucible 2 in the thermal field, can obviously reflect the central position of the crucible 2, and can conveniently adjust the central position of the raw material in the crucible 2 in the thermal field in the crystal growth process.

Referring to fig. 1-3, in an assembled state, a crucible 2 is placed in a heat preservation cavity of a heat preservation layer, silicon carbide powder 4 is filled in the crucible 2, a silicon carbide seed crystal 3 is fixed on a crucible cover of the crucible 2, and the heat preservation cavity is of a sealed cavity structure with one position of a temperature measurement hole 6.

Specifically, the crucible 2 is a graphite crucible, and the heat-insulating layer is made of graphite felt.

Example 2

In this embodiment, a schematic view of adding a heat insulating ring structure is described in conjunction with embodiment 1, and in this embodiment, the portion not shown in embodiment 1 is only required to be capable of directly placing a heat insulating ring between the crucible and the upper heat insulating layer.

Referring to fig. 4, the present embodiment is different from embodiment 1 in that the insulating layer includes a lower insulating layer, an upper insulating layer 101, a side insulating layer 5, and an insulating ring 8, the insulating ring 8 is connected between the upper insulating layer 101 and the side insulating layer 5, and the lower insulating layer, the upper insulating layer 101, the side insulating layer 5, and the insulating ring 8 enclose an insulating cavity.

Referring to fig. 5, the embodiment is different from the embodiment of fig. 1 of embodiment 1 in that the insulating layer further includes an insulating ring 8, the top of the insulating ring 8 is connected to the bottom of the upper insulating layer 101, and the bottom of the insulating ring 8 is connected to the top of the transition insulating layer 102. Specifically, the insulating ring 8 may be integrally formed with the upper insulating layer 101 and the transition insulating layer 102, respectively.

Referring to fig. 6, the embodiment is different from the embodiment of fig. 1 of embodiment 1 in that the insulating layer further includes an insulating ring 8, the inner surface of the insulating ring 8 is in threaded connection with the outer surface of the upper insulating layer 101, and the bottom surface of the insulating ring 8 is connected with the top surface of the transition insulating layer 102. Specifically, the bottom surface of the insulating ring 8 and the top surface of the transition insulating layer 102 are integrally formed.

Specifically, in any embodiment, the heat-preserving ring 8 is arranged above the crucible, the heat-preserving ring 8 at least covers 0.5mm to 0.5r-0.5mm of the inward extension of the seed crystal from the edge, and r is the radius of the seed crystal.

Example 3

The method for producing a silicon carbide substrate using the crucible optionally containing the insulating layer and the crucible of example 2 includes the steps of:

1) assembling: providing a bearing raw material and a seed crystal arranged at the top in a crucible, placing the crucible in a heat preservation cavity formed by a heat preservation layer, and then moving the crucible into a crystal growth furnace; wherein, the heat preservation layer comprises a heat preservation ring arranged above the crucible, the heat preservation ring at least covers 0.5mm to 0.5r-0.5mm of the seed crystal extending inwards from the edge, and r is the radius of the seed crystal;

2) growing a crystal: preparing a silicon carbide crystal by crystal growth, wherein the edge of the prepared silicon carbide crystal forms an annular shape approximately corresponding to the covering position of the heat preservation ring;

3) preparing a primary silicon carbide substrate: carrying out steps including slicing on the silicon carbide crystal to obtain a primary silicon carbide substrate with an annular shape;

4) trimming: cutting the initial silicon carbide substrate along the inner side of the annular shape or close to the inner side of the annular shape to obtain a silicon carbide substrate;

wherein the crystal growth stage in step 3) comprises the following steps:

removing impurities: 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 2000-2400K, and controlling the pressure in the crucible to be 0.6 multiplied by 10⁵～3.3×10⁴Pa, introducing inert gas into the crystal growth furnace at a flow rate of 50-500mL/min, moving the crucible upwards at a moving speed of 0.1mm/h and rotating at a speed of 0.5 r/min;

a pressure reduction stage: the pressure is controlled from 0.6X 10⁵～3.3×10⁴Pa, down to 5X 10³Pa-1×10⁴Pa; the crucible is 1mm in the pressure reduction periodMoving downwards at a speed of/h, and rotating at a speed of 0.2 r/min; controlling the temperature to be 2400K-2600K;

crystal growth stage: the crystal growth temperature is 2600K-2800K, the crystal growth pressure is 100-; the holding time is 80-120 h, and the silicon carbide crystal with the ring-shaped appearance and the controllable diameter is prepared.

Example 7

The method for preparing a silicon carbide substrate using the insulating layer and the crucible of fig. 5 in example 3 includes the steps of:

1) assembling: providing a bearing raw material and a seed crystal arranged at the top in a crucible, placing the crucible in a heat preservation cavity formed by a heat preservation layer, and then moving the crucible into a crystal growth furnace; wherein, the heat preservation layer comprises a heat preservation ring arranged above the crucible, the heat preservation ring at least covers the seed crystal, the width D of the seed crystal extending inwards from the edge is 0.5mm to 10mm, and the radius r of the seed crystal can be 24mm-85 mm;

2) growing a crystal: preparing a silicon carbide crystal by crystal growth, wherein the edge of the prepared silicon carbide crystal forms an annular shape approximately corresponding to the covering position of the heat preservation ring;

3) preparing a primary silicon carbide substrate: carrying out steps including slicing on the silicon carbide crystal to obtain a primary silicon carbide substrate with an annular shape;

4) trimming: cutting the initial silicon carbide substrate along the inner side of the annular shape or close to the inner side of the annular shape to obtain a silicon carbide substrate a;

wherein the crystal growth stage in step 3) comprises the following steps:

removing impurities: 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 2000-2400K, and controlling the pressure in the crucible to be 0.6 multiplied by 10⁵～3.3×10⁴Pa, introducing inert gas into the crystal growth furnace at a flow rate of 50-500mL/min, moving the crucible upwards at a moving speed of 0.1mm/h and rotating at a speed of 0.5 r/min;

a pressure reduction stage: the pressure is controlled from 0.6X 10⁵～3.3×10⁴Pa, down to 5X 10³Pa-1×10⁴Pa; reducing blood pressureDuring the process, the crucible moves downwards at the speed of 1mm/h and rotates at the speed of 0.2 r/min; controlling the temperature to be 2400K-2600K;

crystal growth stage: the crystal growth temperature is 2600K-2800K, the crystal growth pressure is 100-; the holding time is 80-120 h, and the silicon carbide crystal with the ring-shaped appearance and the controllable diameter is prepared.

Example 8

This example is different from the production method of example 7 in that the width D of the seed crystal covered with the heat retaining ring extending inward from the edge is different, and silicon carbide substrates b to f are produced, respectively. Comparative example 2 differs from example 8 in that there is no heat retaining ring, and comparative example 2 produces a comparative silicon carbide substrate Da.

TABLE 2

The wider the width of the heat-insulating ring, the larger the radial temperature gradient, when the inner diameter of the heat-insulating ring is smaller than the diameter of the crystal, the abrupt change of the radial gradient can occur at the junction of the heat-insulating ring and the air layer, so that the shearing stress at the junction is large, and the annular appearance is generated; the thickness of the heat preservation ring corresponds to the thickness of an air layer above the crucible, the thickness of the air layer is increased, namely the temperature field is homogenized, and the diameter ladder shaft ladder is reduced, so that the defect degree is reduced; influence trend: the wider the width of the heat-insulating ring is, the smaller the diameter of the ring-shaped appearance is, and the farther away the ring-shaped appearance is from the edge; the narrower the width is, the larger the diameter of the annular shape is, and the closer the annular shape is to the edge; the larger the air layer is, the smaller the diameter ladder is, the lower the annular appearance degree is, and the narrower the width is; the smaller the air layer is, the larger the diameter ladder is, the more the annular appearance degree is intensified, and the wider the width is.

As can be seen from the data in the table, an annular shape is found, edge dislocation walls are used for preventing the inward slip of edge dislocations formed in the crystal growth process of the silicon carbide and the inward extension of edge small-angle grain boundaries, and a high-quality silicon carbide substrate is obtained by means of special processing equipment and processes.

Laser detection, stress detection characterization, lattice distortion detection, microscope polarization and observation under a dark field, Raman mapping test, AFM test and stress deflection angle test are respectively carried out on the initial silicon carbide substrates a-f, especially annular shape areas, of the prepared silicon carbide substrates a-f. The following description will be given taking a primary silicon carbide substrate a as an example.

Referring to fig. 7, a schematic view of a primary silicon carbide substrate a 92 having a ring-shaped profile 91 prepared in example 8 of the present application, which is a ring-shaped wall-like structure penetrating the primary silicon carbide substrate a 92 perpendicular to the {0001} plane. The initial silicon carbide substrate a can observe a circle of regular circular lines at the edge under a transmission light source, the distance between the circular lines and the edge of the substrate is 2-3 mm, and the distance can be adjusted through subsequent regulation and control. And the position and the distance from the ring line to the edge of the ring defect observed by the silicon carbide crystal can completely correspond to each other. After the locating edge cut, the annular feature can be machined away.

Referring to fig. 8, the primary silicon carbide substrate a was tested by laser and the ring-shaped topography was shown as a white ring from the edge of the primary silicon carbide substrate by a laser detector. The circular ring is completely visible, has an equal distance of about 2-3 mm from the edge, and completely corresponds to the position of the annular shape of the detected substrate under the transmission light source in fig. 7.

Referring to fig. 9, the primary silicon carbide substrate a is tested by a stress detector, and the annular shape of the primary silicon carbide substrate a is locally characterized by the stress detector, and the annular shape is represented as a stress ring away from the edge of the silicon carbide substrate by the detection of the stress detector. According to the characterization result, the annular shape is a boundary line between the edge stress concentration region and the central stress good region, that is, the annular shape can be regarded as blocking the edge stress caused by the defect.

Referring to fig. 10, the primary silicon carbide substrate a was tested by a lattice distortion tester, and fig. 10 is an image obtained by testing the ring shape using the lattice distortion tester. Through images, a stress concentration region caused by a large amount of lattice distortion exists on the primary substrate from the edge of the primary substrate to the annular appearance. When the lattice distortion defect extends to the annular shape, the lattice distortion defect is blocked by the annular shape and does not extend further to the inner part of the substrate.

Referring to fig. 11, the ring-shaped topography in the primary silicon carbide substrate a was observed under microscopic polarization and dark field, and fig. 11(a) (b) are ring-shaped topographies observed under microscopic bright field of the wafer after polishing of the primary silicon carbide substrate a. Wherein the normal abrasive sheet is a rough matte surface that is observed under a microscope as a relatively uniform khaki color. Whereas the location with the ring-shaped topography appears as a distinct band with distinct dividing lines. FIG. 11(c) (d) shows that the annular shape has a contrast difference between the light and the shade on the SiC grinding plate and the normal area under the dark field, i.e. the annular shape area is a dark annular band.

Referring to fig. 12, for the ring stress Raman mapping test of the initial silicon carbide substrate a, a near-edge ring shape is selected for the Raman mapping test, and the test region and the result are respectively shown in fig. 12(a) and fig. 12 (b). The comparison of the test result and Raman sub-modes of various crystal forms of SiC shows that the crystal forms are 4H crystal forms in the test range, and multi-type defects of other crystal forms are included.

Referring to fig. 13(a) and (b), for the ring stress AFM test of the initial silicon carbide substrate a, fig. 13(b) 1, 2 and 3 respectively show the outer ring-shaped feature, the inner ring-shaped feature and the inner ring-shaped feature of fig. 13(a), and the atomic step and roughness of the region of the ring-shaped feature are continuously characterized by means of AFM, as shown in fig. 13 (b). The result shows that the atomic steps in the region are normal, and no abnormal broadening, narrowing or sharp change exists, which indicates that the atomic steps in the region are diffused normally; where the atomic step width at position 1 (outside the ring profile) is 0.165 μm, where the atomic step width at position 2 (ring profile) is 0.192 μm, and where the atomic step width at position 3 (inside the ring profile) is 0.22 μm.

Referring to fig. 14(a) and (b), for the ring stress deflection angle test (a) and the result (b) of the primary silicon carbide substrate a, the crystal quality test was performed by XRD on the defect position and both the inner and outer sides, as shown in fig. 14. The XRD diffraction peak at the position 1 in the annular shape has shift and broadening, the cleaning quality gradually becomes better from the inside of the annular shape to the outside of the annular shape, and the FWHM value gradually decreases. The results of XRD measurements of the crystal quality and the off-angle are shown in Table 3, in which the crystal quality gradually improved from the edge inward and the off-angle gradually decreased. The result is mainly due to the fact that the ring morphology blocks the LAGB and part of the dislocation out of the ring, and the LAGB and the dislocation are gathered to cause lattice distortion which is expressed by poor clean quality and increased deflection angle.

TABLE 3

Referring to fig. 15, the ring shape is etched for the initial silicon carbide substrate a using a molten KOH etchant at 500 ℃, and the defect is now a dislocation wall composed of TED, as shown in fig. 15. And various dislocations of TED, TSD and BPD exist outside the dislocation wall and close to one side of the edge, and the dislocation density is obviously higher than that in the TED dislocation wall, namely the TED dislocation wall blocks inward slip of the edge dislocation.

Referring to fig. 16, a dislocation statistics mapping image of a primary silicon carbide substrate with annular stress is obtained by performing KOH etching on a substrate with annular morphology, and mapping is performed to visually display dislocation density distribution. From the results, it was found that dislocation concentrated regions are mainly concentrated on the ring morphology and the outside thereof, and a uniform low density dislocation distribution can be formed inside, and therefore based on the results, edge dislocations can be blocked by the ring morphology, thereby suppressing inward slip of edge dislocations.

Referring to fig. 17, characterization observation of the annular shape 91 of the primary silicon carbide substrate a in the microscopic polarization mode is performed, and as shown in fig. 17, the annular stress is a continuous stress band corresponding to a TED wall after KOH etching. In the annular region 93 outside the annular topography, near the edge of the substrate, the stress performance is poor, corresponding to various dislocation densities outside the TED wall after KOH corrosion. While in the central region 94 within the annular topography, near the center of the substrate, the stress behavior is relatively good, corresponding to a dislocation density inside the etched TED wall that is lower than outside the TED wall.

Referring to fig. 18(a) (b), a face-type characterization was performed for a primary silicon carbide substrate a having a ring-shaped topography, as shown in fig. 18. As can be seen from the test images, the annular shape cannot cause the substrate surface type to be different, which is shown in FIG. 18(a), that is, the warp-bow graph still shows a 'steamed bun' shape with a high center and a low periphery, and there is no difference at a position of a circle near the edge corresponding to the annular shape. The annular shape LTV is further characterized, the edge is not different from the normal shape, and the abnormal LTV rise is avoided, namely, the defect is not caused by the substrate macroscopic surface type factors such as local unevenness.

Example 9

Referring to fig. 19(a) and (b), for AFM testing of another position of the ring-shaped topography of the primary silicon carbide substrate a of example 8, positions 1, 2, 3 and 4 in fig. 19(b) are respectively two position areas outside the ring-shaped topography, the ring-shaped topography and the ring-shaped topography in fig. 19(a), and the atomic step and the roughness of the area where the ring-shaped topography area is located are continuously characterized by means of AFM, as shown in fig. 19 (b).

The atomic step width D1 (position 1) was 0.166. mu.m, the atomic step width D2 (position 1) was 0.189. mu.m, and the atomic step width D3 was 0.363. mu.m and 0.411. mu.m.

A method of processing a silicon carbide crystal, comprising the steps of:

referring to fig. 19(a), the position of the annular feature 2 is detected by a laser detector, and the target silicon carbide crystal is obtained by cutting along the annular feature position 2;

and testing the atomic step width of the target silicon carbide crystal through an atomic force microscope, testing the position of taking points from the edge of the target crystal to the center, uniformly taking points from the edge of the target crystal to the center at intervals of 1mm, and testing that the change of the atomic step width between two adjacent points is not more than 0.05, and 3 points are cut along the annular edge where the point close to the outer side is positioned, so that the high-quality silicon carbide crystal is obtained.

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.