阅读说明：本技术 图案化的碳化硅籽晶及其加工方法和应用、碳化硅晶体、外延层、半导体器件 (Patterned silicon carbide seed crystal, processing method and application thereof, silicon carbide crystal, epitaxial layer and semiconductor device ) 是由 汪良 张洁 邓树军 于 2019-09-25 设计创作，主要内容包括：本发明涉及碳化硅晶体生长领域,具体而言,提供了一种图案化的碳化硅籽晶及其加工方法和应用、碳化硅晶体、外延层、半导体器件。该图案化的碳化硅籽晶包括籽晶表面,所述籽晶表面包括至少两个凸起,相邻两个凸起之间的凹槽的横截面积由下向上逐渐变大。该碳化硅籽晶的表面呈特定的凹凸结构,因而采用该籽晶进行碳化硅晶体的生长时,碳化硅原子优先生长于相邻两个凸起之间的凹槽,在该凹槽内生长时,缺陷生长方向由纵向逐渐转变为横向,当碳化硅原子填满该凹槽后,碳化硅原子开始纵向生长,因此横向生长的缺陷将消失,从而使碳化硅晶体的缺陷密度得到有效降低。(The invention relates to the field of silicon carbide crystal growth, and particularly provides a patterned silicon carbide seed crystal, a processing method and application thereof, a silicon carbide crystal, an epitaxial layer and a semiconductor device. The patterned silicon carbide seed crystal comprises a seed crystal surface, wherein the seed crystal surface comprises at least two protrusions, and the cross sectional area of a groove between every two adjacent protrusions is gradually increased from bottom to top. The surface of the silicon carbide seed crystal is of a specific concave-convex structure, so when the seed crystal is adopted for growing the silicon carbide crystal, silicon carbide atoms preferentially grow in the groove between the two adjacent bulges, when the silicon carbide crystal grows in the groove, the growth direction of the defects is gradually changed from the longitudinal direction to the transverse direction, and after the groove is filled with the silicon carbide atoms, the silicon carbide atoms start to grow longitudinally, so that the defects growing transversely disappear, and the defect density of the silicon carbide crystal is effectively reduced.)

1. A patterned silicon carbide seed crystal is characterized by comprising a seed crystal surface, wherein the seed crystal surface comprises at least two protrusions, and the cross sectional area of a groove between every two adjacent protrusions is gradually increased from bottom to top.

2. The patterned silicon carbide seed crystal of claim 1 wherein the raised shape comprises at least one of a cone, a truncated cone, a pyramid, or a truncated pyramid;

preferably, the pyramid comprises at least one of a triangular pyramid, a rectangular pyramid, a pentagonal pyramid, or a hexagonal pyramid;

preferably, the polygonal platform comprises at least one of a triangular platform, a square platform, a pentagonal platform or a hexagonal platform;

preferably, the diameter of the bottom surface of the cone or the diameter of the bottom surface of the circular truncated cone are respectively and independently 0.5-5 μm;

preferably, the maximum side length of the base of the pyramid or of the base of the polygon terrace is, independently, 0.5 to 5 μm.

3. The patterned silicon carbide seed crystal of claim 1 or 2, wherein the width of the bottom surface of the groove between two adjacent projections is 0-5 μm;

preferably, the height of at least one of said protrusions is 0.5-10 μm, preferably the height of each protrusion independently is 3-8 μm.

4. A method of processing a patterned silicon carbide seed crystal as claimed in any one of claims 1 to 3, comprising: and photoetching and etching the silicon carbide seed crystal in sequence to obtain the patterned silicon carbide seed crystal.

5. The process of claim 4, wherein the lithography comprises: sequentially arranging a barrier layer and a photoetching plate on the surface of the silicon carbide seed crystal, then irradiating the surface of the silicon carbide seed crystal with light, and finally removing the barrier layer which generates quality change;

preferably, the barrier layer comprises a photoresist or an inorganic non-metallic material;

preferably, the inorganic non-metallic material comprises silicon dioxide, gallium nitride or aluminum oxide;

preferably, the thickness of the barrier layer is 2-10 μm;

preferably, the pattern on the reticle includes at least one of a circle, a triangle, a quadrangle, a pentagon, or a hexagon;

preferably, the diameter of the circle is 0.5-5 μm;

preferably, the largest sides of the triangle, quadrangle, pentagon or hexagon are each independently 0.5-5 μm.

6. A processing method according to claim 4 or 5, characterized in that the etching comprises dry etching or wet etching, preferably dry etching;

preferably, the dry etching includes: etching the photoetched silicon carbide seed crystal by using etching gas;

preferably, the dry etching satisfies at least one of the following conditions (a) to (d):

(a) the etching gas comprises hydrogen, oxygen or carbon monoxide;

(b) the flow rate of the etching gas is 25-100 mL/min;

(c) the environmental temperature during etching is 80-300 ℃;

(d) the environmental pressure during etching is 100-400 Pa.

7. Use of a patterned silicon carbide seed crystal as claimed in any one of claims 1 to 3 or produced by a process as claimed in any one of claims 4 to 6 in the production of a silicon carbide crystal.

8. A silicon carbide crystal produced using the patterned silicon carbide seed crystal of any one of claims 1 to 3 or produced using the processing method of any one of claims 4 to 6.

9. An epitaxial layer grown on the surface of the silicon carbide crystal of claim 8.

10. A semiconductor device comprising the epitaxial layer of claim 9.

Technical Field

The invention relates to the field of silicon carbide crystal growth, in particular to a patterned silicon carbide seed crystal, a processing method and application thereof, a silicon carbide crystal, an epitaxial layer and a semiconductor device.

Background

SiC is a third generation semiconductor following Si and GaAs as a representative of wide bandgap materials. Compared with Si and GaAs, SiC has more excellent performances such as high breakdown field strength, high thermal conductivity, high bonding energy, high saturated electron drift rate and the like, and has huge application prospects in the aspects of high-frequency, high-power, high-temperature and radiation-resistant devices. In addition, because of the similar lattice constant and thermal expansion coefficient of SiC and GaN, the SiC crystal has a very wide application prospect in the field of photoelectric devices.

The existing method for growing SiC crystals is a physical vapor transport method, and the principle of the method is that a temperature gradient between a bottom raw material and SiC seed crystals is utilized, so that SiC gaseous substances sublimated after high-temperature heating are transported to the upper surface of the low-temperature SiC seed crystals at the top of a crucible, the SiC gaseous substances encounter the low-temperature SiC seed crystals and are slowly crystallized on the surface of the low-temperature SiC seed crystals, and the SiC crystals are grown.

In the above method, during the crystal growth, the SiC gas sublimated onto the seed crystal at the top of the crucible will undergo atomic arrangement growth along the axial direction of the seed crystal (i.e., the silicon carbide single crystal grows longitudinally), but when the original defects of the seed crystal are encountered, the crystal inherits most defects during the growth process. When the obtained SiC crystal is processed into a substrate, defects remain inside the substrate; new defects will be formed after the epitaxial layer grows on the surface of the SiC substrate, and even if the new defects are not formed, the quality of the epitaxial layer growing on the surface of the SiC substrate is adversely affected, so that the yield of devices made of the epitaxial layer is reduced. Therefore, it becomes extremely important how SiC crystals with low defect density are grown.

At present, methods for reducing the defect density of the SiC crystal mostly focus on the aspects of modifying SiC single crystal furnace equipment and optimizing the preparation process of the SiC crystal, however, the methods cannot fundamentally reduce the defect density of the SiC crystal, and the defect density of the SiC crystal cannot be effectively reduced.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

The first purpose of the present invention is to provide a patterned silicon carbide seed crystal, the surface of which has a specific concave-convex structure, so that when the seed crystal is used to grow silicon carbide crystal, silicon carbide atoms preferentially grow in the groove between two adjacent protrusions, when the silicon carbide crystal grows in the groove, the defect growth direction gradually changes from longitudinal to transverse, and when the groove is filled with silicon carbide atoms, the silicon carbide atoms start to grow longitudinally, so that the defects grown transversely disappear, and the defect density of the silicon carbide crystal is effectively reduced.

A second object of the present invention is to provide a method for preparing the above-described patterned silicon carbide seed crystal.

A third object of the invention is to provide a use of the above-described patterned silicon carbide seed crystal in the preparation of a silicon carbide crystal.

It is a fourth object of the present invention to provide a silicon carbide crystal.

A fifth object of the present invention is to provide an epitaxial layer.

A sixth object of the present invention is to provide a semiconductor device.

In order to achieve the above purpose of the present invention, the following technical solutions are adopted:

in a first aspect, the invention provides a patterned silicon carbide seed crystal, which comprises a seed crystal surface, wherein the seed crystal surface comprises at least two protrusions, and the cross-sectional area of a groove between every two adjacent protrusions is gradually increased from bottom to top.

As a further preferable technical solution, the shape of the protrusion includes at least one of a cone, a truncated cone, a pyramid, or a multi-truncated pyramid;

preferably, the pyramid comprises at least one of a triangular pyramid, a rectangular pyramid, a pentagonal pyramid, or a hexagonal pyramid;

preferably, the polygonal platform comprises at least one of a triangular platform, a square platform, a pentagonal platform or a hexagonal platform;

preferably, the diameter of the bottom surface of the cone or the diameter of the bottom surface of the circular truncated cone are respectively and independently 0.5-5 μm;

preferably, the maximum side length of the base of the pyramid or of the base of the polygon terrace is, independently, 0.5 to 5 μm.

As a further preferable technical scheme, the width of the bottom surface of the groove between two adjacent bulges is 0-5 μm;

preferably, the height of at least one of said protrusions is 0.5-10 μm, preferably the height of each protrusion independently is 3-8 μm.

In a second aspect, the present invention provides a method for processing the patterned silicon carbide seed crystal, comprising: and photoetching and etching the silicon carbide seed crystal in sequence to obtain the patterned silicon carbide seed crystal.

As a further preferred solution, the lithography comprises: sequentially arranging a barrier layer and a photoetching plate on the surface of the silicon carbide seed crystal, then irradiating the surface of the silicon carbide seed crystal with light, and finally removing the barrier layer which generates quality change;

preferably, the barrier layer comprises a photoresist or an inorganic non-metallic material;

preferably, the inorganic non-metallic material comprises silicon dioxide, gallium nitride or aluminum oxide;

preferably, the thickness of the barrier layer is 2-10 μm;

preferably, the pattern on the reticle includes at least one of a circle, a triangle, a quadrangle, a pentagon, or a hexagon;

preferably, the diameter of the circle is 0.5-5 μm;

preferably, the largest sides of the triangle, quadrangle, pentagon or hexagon are each independently 0.5-5 μm.

As a further preferred technical solution, the etching includes dry etching or wet etching, preferably dry etching;

preferably, etching the silicon carbide seed crystal after photoetching by using etching gas;

preferably, the dry etching satisfies at least one of the following conditions (a) to (d):

(a) the etching gas comprises hydrogen, oxygen or carbon monoxide;

(b) the flow rate of the etching gas is 25-100 mL/min;

(c) the environmental temperature during etching is 80-300 ℃;

(d) the environmental pressure during etching is 100-400 Pa.

In a third aspect, the invention provides a use of the patterned silicon carbide seed crystal or the patterned silicon carbide seed crystal prepared by the processing method in preparing a silicon carbide crystal.

In a fourth aspect, the present invention provides a silicon carbide crystal prepared using the patterned silicon carbide seed crystal described above or a patterned silicon carbide seed crystal prepared using the processing method described above.

In a fifth aspect, the invention provides an epitaxial layer grown on the surface of the silicon carbide crystal.

In a sixth aspect, the present invention provides a semiconductor device comprising the epitaxial layer.

Compared with the prior art, the invention has the beneficial effects that:

the patterned silicon carbide seed crystal provided by the invention is different from the existing silicon carbide seed crystal in structure, the surface of the existing silicon carbide seed crystal is flat, and in the patterned silicon carbide seed crystal, at least two protrusions on the surface of the seed crystal and a groove between two connected protrusions form a specific concave-convex structure, so that the patterned silicon carbide seed crystal with the concave-convex surface is formed.

When the patterned silicon carbide seed crystal is used for growing silicon carbide crystals, silicon carbide atoms preferentially grow in the grooves between the two adjacent bulges, and at the moment, the silicon carbide grows longitudinally. Because the cross-sectional area of the groove is gradually increased from bottom to top, the transverse growth space of silicon carbide atoms is gradually enlarged along with the growth, and the atoms grow in the longitudinal direction and in the transverse direction to fill the enlarged space. The original crystal growth direction is changed due to the bulges in the process of atom arrangement growth, the growth direction of the defects which originally penetrate through the seed crystal is changed, most of the defects are changed into transverse growth due to the transverse arrangement of the atoms, after the grooves are filled with silicon carbide atoms, the originally uneven surface of the seed crystal becomes flat, and the atom arrangement is longitudinally arranged from the position. Because the defects in the silicon carbide atoms are basically changed into transverse growth in the groove between two adjacent bulges, the defects in the transverse growth disappear when the subsequent atoms are longitudinally grown, and the defect density in the silicon carbide crystal is effectively reduced.

Drawings

FIG. 1 is a schematic cross-sectional view of a silicon carbide seed crystal with a surface coated with a photoresist;

FIG. 2 is a schematic illustration of a photolithography process;

FIG. 3 is a schematic cross-sectional structure of a silicon carbide seed crystal after photolithography;

FIG. 4 is a schematic diagram of an etching process;

FIG. 5 is a schematic cross-sectional view of a silicon carbide seed crystal after etching and cleaning;

FIG. 6 is a perspective view of a patterned silicon carbide seed crystal obtained in example 27;

FIG. 7 is a perspective view of a patterned silicon carbide seed crystal obtained in example 28.

Icon: 1-silicon carbide seed crystal; 2-photoresist; 3-photoetching a plate; 4-ultraviolet light; 5-etching gas; 6, etching the area; 7-a patterned silicon carbide seed crystal; 8-bulge; 9-a groove; a-a groove floor; b-a groove top surface; c-the bottom surface of the protrusion; d-the apex of the protrusion.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer.

According to one aspect of the invention, a patterned silicon carbide seed crystal is provided, which comprises a seed crystal surface, wherein the seed crystal surface comprises at least two protrusions, and the cross-sectional area of a groove between two adjacent protrusions is gradually increased from bottom to top.

The patterned silicon carbide seed crystal is different from the existing silicon carbide seed crystal in structure, the surface of the existing silicon carbide seed crystal is flat, and in the patterned silicon carbide seed crystal, at least two protrusions on the surface of the seed crystal and grooves between two adjacent protrusions form a specific concave-convex structure, so that the patterned silicon carbide seed crystal with the concave-convex surface is formed.

When the patterned silicon carbide seed crystal is used for growing silicon carbide crystals, silicon carbide atoms preferentially grow in the grooves between the two adjacent bulges, and at the moment, the silicon carbide grows longitudinally. Because the cross-sectional area of the groove is gradually increased from bottom to top, the transverse growth space of silicon carbide atoms is gradually enlarged along with the growth, and the atoms grow in the longitudinal direction and in the transverse direction to fill the enlarged space. The original crystal growth direction is changed due to the bulges in the process of atom arrangement growth, the growth direction of the defects which originally penetrate through the seed crystal is changed, most of the defects are changed into transverse growth due to the transverse arrangement of the atoms, after the grooves are filled with silicon carbide atoms, the originally uneven surface of the seed crystal becomes flat, and the atom arrangement is longitudinally arranged from the position. Because the defects in the silicon carbide atoms are basically changed into transverse growth in the groove between two adjacent bulges, the defects in the transverse growth disappear when the subsequent atoms are longitudinally grown, and the defect density in the silicon carbide crystal is effectively reduced.

It should be noted that:

for example, as shown in fig. 5, the above-mentioned "cross-sectional area of the groove between two adjacent projections" means a cross-sectional area of the groove 9 in planes parallel to the bottom surface a of the groove. The groove bottom surface a refers to a surface where the groove 9 is connected to the side surface of the protrusion 8.

For example, as shown in fig. 5, the above-mentioned "from bottom to top" means a direction from the bottom surface a of the groove to the top surface b of the groove, that is, a direction in which the groove 9 is opened. The groove top surface b is a plane of the groove 9 away from the groove bottom surface a, and the plane is a virtual plane, and the distance between the plane and the groove bottom surface a is the farthest.

Therefore, the phrase "the cross-sectional area of the groove between two adjacent protrusions gradually increases from bottom to top" means that the cross-sectional area of the groove gradually increases from the bottom of the groove to the opening of the groove.

In a preferred embodiment, the shape of the protrusions comprises at least one of a cone, a truncated cone, a pyramid, or a truncated pyramid. The shapes are regular, silicon carbide atoms can grow uniformly in the grooves between the bulges, the cross sectional areas of the shapes are sequentially increased from top to bottom, and the requirement on the rule of the cross sectional area of the groove between every two adjacent bulges can be met. The shape of the protrusions includes, but is not limited to, a cone, a truncated cone, a pyramid, a truncated pyramid, a combination of a cone and a truncated cone, a combination of a cone and a pyramid, a combination of a pyramid and a truncated pyramid, a combination of a cone, a truncated pyramid and a truncated pyramid, and the like.

The circular truncated cone is a plane parallel to the bottom surface of the circular cone and is cut off by a plane, and the part between the bottom surface and the section is called the circular truncated cone.

"pyramid" means a polyhedron having a polygonal base and triangular sides with a common vertex.

The multi-edge table refers to a table body with polygonal bottom and top surfaces, the number of polygonal sides of the bottom and top surfaces is the same, and the rest surfaces (or called multi-edge table side surfaces) are trapezoidal.

Preferably, the pyramid comprises at least one of a triangular pyramid, a rectangular pyramid, a pentagonal pyramid, or a hexagonal pyramid. The pyramid includes, but is not limited to, a triangular pyramid, a rectangular pyramid, a pentagonal pyramid, a hexagonal pyramid, a combination of a triangular pyramid and a rectangular pyramid, a combination of a pentagonal pyramid and a hexagonal pyramid, a combination of a triangular pyramid, a rectangular pyramid and a pentagonal pyramid, a combination of a rectangular pyramid, a pentagonal pyramid and a hexagonal pyramid, or a combination of a triangular pyramid, a rectangular pyramid, a pentagonal pyramid and a hexagonal pyramid, etc.

Preferably, the polygonal pyramid comprises at least one of a triangular pyramid, a rectangular pyramid, a pentagonal pyramid or a hexagonal pyramid. The multi-edge table includes, but is not limited to, a triangular table, a rectangular table, a pentagonal table, a hexagonal table, a combination of a triangular table and a rectangular table, a combination of a pentagonal table and a hexagonal table, a combination of a triangular table, a rectangular table and a pentagonal table, a combination of a rectangular table, a pentagonal table and a hexagonal table, or a combination of a triangular table, a rectangular table, a pentagonal table and a hexagonal table, etc.

In a preferred embodiment, the diameter of the conical bottom surface or the diameter of the truncated cone bottom surface is each independently 0.5 to 5 μm. The above diameters are typically, but not limited to, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 μm. It should be understood that the "bottom surface of the circular truncated cone" refers to the lower bottom surface of the circular truncated cone, i.e. the bottom surface with a larger area.

Preferably, the maximum side length of the base of the pyramid or of the base of the polygon terrace is, independently, 0.5 to 5 μm. The maximum side length is the length of the longest side length of the pyramid base or the multi-frustum base. The above side length is typically, but not limited to, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 μm. The pyramid bottom surface refers to the surface of the pyramid which is flush with the bottom surface of the groove between two adjacent protrusions. The bottom surface of the polygon table refers to a surface of the polygon table which is flush with the bottom surfaces of the grooves between two adjacent protrusions.

When the diameter of the bottom surface of the cone, the maximum side length of the bottom surface of the pyramid or the maximum side length of the bottom surface of the multi-frustum are respectively and independently in the above range, the size of the sustainable defect related to the growth of the silicon carbide can be completely covered, and the defect can be more favorably transformed and disappeared in the growth process.

In a preferred embodiment, the width of the bottom surface of the groove between two adjacent projections is 0 to 5 μm. An intersection line exists between the side surface of each protrusion and the bottom surface of each groove, and the width of the bottom surface of each groove refers to the shortest distance between two adjacent intersection lines. As shown in FIG. 5, the width of the bottom surface of the groove is the width of the bottom surface a of the groove. The above distance is typically, but not limited to, 0, 0.5. mu.m, 1. mu.m, 1.5. mu.m, 2. mu.m, 2.5. mu.m, 3. mu.m, 3.5. mu.m, 4. mu.m, 4.5. mu.m, or 5. mu.m. The width of the bottom surface of the groove between every two adjacent bulges is not too high, the groove is too large in size due to too high width, when silicon carbide atoms grow in the groove, part of atoms also grow on the bulges, the advantage of preferential growth of the groove cannot be fully embodied, the defect density in the silicon carbide grown on the bulges cannot be reduced, and the reduction degree of the defect density in the silicon carbide crystal is smaller. When the width of the bottom surface of the groove is within the above range, silicon carbide atoms grow substantially entirely in the groove between two adjacent projections, so that the defect density of the silicon carbide crystal is further reduced.

In a preferred embodiment, the height of at least one of the protrusions is 0.5 to 10 μm, preferably the height of each protrusion independently is 3 to 8 μm. The height is typically, but not limited to, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 μm. As shown in fig. 5, the height of the protrusion refers to a vertical distance from a bottom surface c of the protrusion to a top end d (or top surface) of the protrusion. The height corresponds to the depth of the groove. When the height of the projections is within the above range, the grooves between the adjacent two projections can convert longitudinally grown defects in the seed crystal into laterally grown defects as much as possible, thereby further reducing the defect density in the silicon carbide atoms which are subsequently grown longitudinally.

According to another aspect of the present invention, there is provided a method of processing the above-described patterned silicon carbide seed crystal, comprising: and photoetching and etching the silicon carbide seed crystal in sequence to obtain the patterned silicon carbide seed crystal. The processing method has scientific and reasonable process steps, and can obtain the patterned silicon carbide seed crystal with uneven surface and accurate size.

"lithography" refers to a technique of transferring a pattern on a reticle to a substrate by means of a barrier layer under the action of light, and the photolithographic technique has small size limit (up to submicron level) of transferred patterns and high precision. The term "etching" refers to etching a silicon carbide seed crystal with a patterned barrier layer left on the surface after photoetching so as to form a regular concave-convex pattern on the surface of the silicon carbide.

In a preferred embodiment, the lithography comprises: and sequentially arranging a barrier layer and a photoetching plate on the surface of the silicon carbide seed crystal, then irradiating the surface of the silicon carbide seed crystal with light, and finally removing the barrier layer which generates the quality change. When light irradiates the surface of the silicon carbide seed crystal, the light irradiates the exposed blocking layer part to generate qualitative change, and the blocking layer part shielded by the photoetching plate is not irradiated by the light and does not generate qualitative change, so that the pattern on the photoetching plate is copied on the blocking layer, and the blocking layer generating qualitative change is removed finally, and the blocking layer with a specific pattern is left on the surface of the silicon carbide seed crystal.

The process of "removing the barrier layer generating the deterioration" may also be referred to as developing, and the developing solution used for developing is selected from those commonly used in the art, and includes all chemical gases and/or chemical liquids capable of being used for etching and removing the barrier layer generating the deterioration.

Preferably, the barrier layer comprises a photoresist or an inorganic non-metallic material.

Optionally, when the barrier layer is made of photoresist, the barrier layer can be arranged in an optional coating mode (also called gumming), the coating is uniform, the thickness deviation is controlled within 0.5 micrometer, and the photoresist is dried after coating, wherein the drying temperature can be selected from 50-150 ℃. In the removal of the photoresist that has been deteriorated, soaking with a chemical agent (e.g., a developing solution, sulfuric acid or hydrochloric acid) and rinsing with water may be performed in sequence. It should be understood that the soaking time depends on the thickness of the photoresist, and the cleaning time is based on the chemical agent being sufficiently cleaned.

Alternatively, the glue applicator used for gluing includes, but is not limited to, a single-blade glue applicator, a multi-blade glue applicator, a fully automatic glue applicator, a manual glue applicator, or the like.

Preferably, the inorganic non-metallic material comprises silicon dioxide, gallium nitride or aluminum oxide.

Preferably, the thickness of the barrier layer is 2-10 μm. The above thickness is typically, but not limited to, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm. When the thickness of the barrier layer is within the range, photoetching is facilitated, photoetching time and light wavelength are reasonable, protrusions with proper height can be formed in the subsequent etching process, and the depth of the groove between every two adjacent protrusions is reasonable. If the thickness is too small, the illumination time is too short and is not easy to control; if the thickness is too large, a shorter wavelength and a longer time are required to expose it, and the manufacturing cost is too high.

Preferably, the pattern on the reticle includes at least one of a circle, a triangle, a quadrangle, a pentagon, or a hexagon. The figures include circles, triangles, quadrilaterals, pentagons, hexagons, combinations of circles and triangles, combinations of triangles and quadrilaterals, combinations of circles and quadrilaterals, combinations of pentagons and hexagons, or combinations of circles, triangles and quadrilaterals, and the like. The photoetching of the patterns is easy to prepare, the source is rich, the preparation cost of the seed crystal can be reduced, and the patterns are transferred to the barrier layer, so that the projections with regular shapes can be conveniently formed subsequently.

Optionally, the triangle comprises an equilateral triangle.

Optionally, the quadrilateral comprises a rectangle.

Preferably, the diameter of the circle is 0.5-5 μm. The above diameters are typically, but not limited to, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 μm.

Preferably, the largest sides of the triangle, quadrangle, pentagon or hexagon are each independently 0.5-5 μm. The above side length is typically, but not limited to, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 μm. The maximum side length refers to the length of the longest side length in a triangle, a quadrangle, a pentagon or a hexagon.

When the diameter of the circle, the maximum side length of the triangle, the maximum side length of the quadrangle, the maximum side length of the pentagon or the maximum side length of the hexagon is in the above range, the subsequent etching and the longitudinal growth of the silicon carbide crystal are facilitated, the diameter or the length is too small, the transverse size of the bulge after the etching is too small, the subsequent longitudinal growth of the silicon carbide crystal is not facilitated, the diameter or the length is too large, the number of barrier layers to be etched is too large, and the processing cost is high.

Optionally, the light comprises ultraviolet light. Ultraviolet light refers to light having a wavelength of 10 to 400 nm. The ultraviolet light energy is stronger, and photoetching efficiency is higher, and adopts the photoetching equipment of ultraviolet light as the light source more, and the source is extensive, and the alternative is many.

In a preferred embodiment, the etching comprises dry etching or wet etching, preferably dry etching. Dry etching is a technique of performing thin film etching using plasma, and decomposes and ionizes etching gas by gas discharge, and a substrate is etched by generated active groups and ions. Wet etching is a technique of immersing an etching material in an etching solution to perform etching. Compared with wet etching, dry etching can finish the work of transferring and copying the pattern with high quality.

Preferably, the dry etching includes: and etching the photoetched silicon carbide seed crystal by using etching gas.

Preferably, the dry etching satisfies at least one of the following conditions (a) to (d):

(a) the etching gas includes hydrogen, oxygen, or carbon monoxide.

(b) The flow rate of the etching gas is 25-100 mL/min. Typical but non-limiting such flow rates are 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100 mL/min. When the flow of the etching gas is within the range, the etching speed is high, and the etching precision is high. If the flow is too low, the etching speed is too slow; if the flow is too high, the etching precision is lower.

(c) The environment temperature during etching is 80-300 ℃. The above ambient temperature is typically, but not limited to, 80, 90, 100, 120, 160, 180, 200, 220, 260, or 300 ℃. The environmental temperature refers to the temperature in the reaction chamber during etching. When the environmental temperature is in the range, the silicon carbide seed crystal is easy to etch, the etching is difficult due to the excessively low temperature, the etching time is prolonged, and the like, and the etching surface is rough due to vitrification or carbonization of the barrier layer caused by the excessively high temperature, so that the regularity of subsequent crystal growth is reduced.

(d) The environmental pressure during etching is 100-400 Pa. The above ambient pressure is typically, but not limited to, 100, 150, 200, 250, 300, 350 or 400 Pa.

Optionally, a cleaning step is further included after etching, and if the barrier layer cannot be completely removed after etching, the barrier layer needs to be cleaned, so that the barrier layer left on the surface of the seed crystal after etching is removed, and the patterned silicon carbide seed crystal is obtained.

The cleaning process is commonly used in the art, and the invention is not particularly limited thereto, for example: the cleaning agent used for cleaning comprises acid and/or alkali. Cleaning agents include, but are not limited to, acids, bases, or combinations of acids and bases.

Optionally, the acid comprises a mineral acid.

Optionally, the inorganic acid comprises at least one of hydrochloric acid, sulfuric acid, or hydrogen peroxide. Inorganic acids include, but are not limited to, hydrochloric acid, sulfuric acid, hydrogen peroxide, a combination of hydrochloric acid and sulfuric acid, a combination of sulfuric acid and hydrogen peroxide, a combination of hydrochloric acid and hydrogen peroxide, or a combination of hydrochloric acid, sulfuric acid and hydrogen peroxide, and the like.

Optionally, the base comprises an inorganic base.

Alternatively, the inorganic base comprises potassium hydroxide, sodium hydroxide, or aqueous ammonia.

Optionally, the cleaning agent comprises sulfuric acid and hydrogen peroxide.

Optionally, the volume ratio of the 98% sulfuric acid to the 40% hydrogen peroxide is 3:1-5: 1. The above volume ratio is typically, but not limited to, 3:1, 4:1 or 5: 1.

Optionally, the cleaning agent comprises ammonia water and hydrogen peroxide.

Optionally, the volume ratio of the 10% ammonia water to the 40% hydrogen peroxide is 3:1-1: 1. The above volume ratio is typically, but not limited to, 3:1, 2:1 or 1: 1.

The above "concentration" means the mass percentage of the solute in the solution, for example, the sulfuric acid having a concentration of 98% means H in the sulfuric acid solution₂SO₄The mass percentage of the sulfuric acid solution is 98 percent of the total mass of the sulfuric acid solution.

Optionally, before performing photolithography on the silicon carbide seed crystal, the method further comprises a step of cleaning the silicon carbide seed crystal, and a conventional cleaning manner in the field is adopted, so that no particles, organic matters and the like are left on the surface of the seed crystal, the quality of the barrier layer is ensured, and the falling is reduced.

Optionally, the method further comprises a step of drying the silicon carbide seed crystal after cleaning, wherein the drying manner is commonly used in the field, such as spin-drying or drying.

FIGS. 1-6 are schematic diagrams illustrating exemplary processes for preparing a patterned silicon carbide seed crystal using the above-described process, such as FIG. 1 showing a silicon carbide seed crystal 1 having a surface coated with a photoresist 2, with a reticle 3 overlying the silicon carbide seed crystal 1 and the photoresist 2; then, irradiating by using ultraviolet light 4 (as shown in figure 2), and removing the deteriorated photoresist to obtain the silicon carbide seed crystal (as shown in figure 3) after photoetching, wherein the surface of the silicon carbide seed crystal after photoetching is provided with a patterned photoresist; etching the silicon carbide seed crystal after photoetching by using etching gas 5 (the etching process is shown in figure 4), wherein an etching area 6 comprises a part of silicon carbide seed crystal and a part of photoresist (the part above the dotted line in figure 4); and obtaining a patterned silicon carbide seed crystal 7 (as shown in fig. 5) after etching and cleaning, wherein the patterned silicon carbide seed crystal 7 comprises a plurality of protrusions 8 and grooves 9 between two adjacent protrusions 8, and the cross-sectional area of each groove 9 is gradually increased from bottom to top.

According to another aspect of the invention, there is provided the use of a patterned silicon carbide seed crystal as described above in the preparation of a silicon carbide crystal. The patterned silicon carbide seed crystal is applied to the preparation of the silicon carbide crystal, so that the defect density of the silicon carbide crystal can be reduced fundamentally, and the defect density of the silicon carbide crystal is effectively reduced.

It should be noted that the specific growth process of the silicon carbide crystal may be one commonly used in the art, and the present invention is not particularly limited thereto.

According to another aspect of the invention, a silicon carbide crystal is provided, prepared using the patterned silicon carbide seed crystal described above. The silicon carbide crystal is prepared by adopting the patterned silicon carbide seed crystal, so that the silicon carbide crystal has the advantage of low defect density.

According to another aspect of the invention, an epitaxial layer is provided, which is grown on the surface of the silicon carbide crystal. The epitaxial layer grows on the surface of the silicon carbide crystal, so that the defect density on the epitaxial layer is low, and the quality of the epitaxial layer is high.

The "epitaxial layer" refers to that portion of the integrated circuit fabrication process that is grown to be deposited on a wafer substrate made of the silicon carbide crystal described above.

According to another aspect of the present invention, there is provided a semiconductor device including the epitaxial layer. The semiconductor device comprises the epitaxial layer, and the epitaxial layer has the advantages of low defect density and high quality, so that the semiconductor device has the advantage of high cost rate.

The "semiconductor device" refers to an electronic device having conductivity between a good conductor and an insulator and performing a specific function by utilizing the specific electrical characteristics of a semiconductor material, and can be used for generating, controlling, receiving, converting, amplifying a signal, converting energy, or the like.

The present invention will be described in further detail with reference to examples and comparative examples.