阅读说明：本技术 用于提高外延片波长一致性的石墨基板 (Graphite substrate for improving wavelength uniformity of epitaxial wafer ) 是由 葛永晖 梅劲 陈张笑雄 王慧 于 2021-06-22 设计创作，主要内容包括：本公开提供了一种用于提高外延片波长一致性的石墨基板,属于半导体技术领域。所述石墨基板为多棱柱结构,所述石墨基板的外周壁具有多个棱柱面,且任意相邻的两个所述棱柱面的连接处均具有一个V型槽,所述V型槽沿所述石墨基板的径向向内凹陷,且所述V型槽长度等于所述石墨基板的轴向长度。在本公开提供的石墨基板上生长外延片,可以使得外延片各个区域的发光波长一致,从而可以提高外延片的片内均匀性,保证边缘良率。(The disclosure provides a graphite substrate for improving wavelength consistency of an epitaxial wafer, and belongs to the technical field of semiconductors. The graphite substrate is of a polygonal prism structure, the peripheral wall of the graphite substrate is provided with a plurality of prismatic surfaces, a V-shaped groove is formed in the joint of any two adjacent prismatic surfaces, the V-shaped groove is inwards recessed along the radial direction of the graphite substrate, and the length of the V-shaped groove is equal to the axial length of the graphite substrate. The epitaxial wafer grows on the graphite substrate, so that the light-emitting wavelength of each region of the epitaxial wafer is consistent, the in-wafer uniformity of the epitaxial wafer can be improved, and the edge yield is ensured.)

1. The graphite substrate for improving the wavelength consistency of the epitaxial wafer is characterized in that the graphite substrate is of a polygonal prism structure, the peripheral wall of the graphite substrate is provided with a plurality of prismatic surfaces, a V-shaped groove is formed in the joint of any two adjacent prismatic surfaces, the V-shaped groove is inwards recessed along the radial direction of the graphite substrate, and the length of the V-shaped groove is equal to the axial length of the graphite substrate.

2. The graphite substrate according to claim 1, wherein the upper surface of the graphite substrate has a plurality of circles of grooves for accommodating substrates, the plurality of circles of grooves are annularly arranged on the upper surface of the graphite substrate, one circle of grooves closest to the edge of the graphite substrate among the plurality of circles of grooves is a first circle of grooves, and the first circle of grooves comprises a plurality of first grooves arranged at intervals along the circumferential direction of the graphite substrate;

the plurality of prismatic surfaces correspond to the plurality of first grooves one by one, and each first groove is located between two V-shaped grooves on two sides of the corresponding prismatic surface.

3. The graphite substrate according to claim 2, wherein a minimum distance between each prismatic surface and the corresponding first groove is L1, 10mm L1 mm 50 mm.

4. The graphite substrate according to claim 3, wherein the minimum distance between the side wall of each V-shaped groove and the corresponding first groove is L2, and L2 is L1.

5. The graphite substrate according to claim 2, wherein the first ring of grooves comprises 8-12 first grooves.

6. The graphite substrate according to claim 2, wherein the upper surface of the graphite substrate has n circles of grooves, and n is greater than or equal to 2 and less than or equal to 6.

7. The graphite substrate according to claim 1, wherein each of the prismatic surfaces has a width of 10 to 30 cm.

8. The graphite substrate according to claim 6, wherein the width of the side wall of each V-shaped groove is 2-10 cm.

9. The graphite substrate according to any one of claims 1 to 8, wherein the graphite substrate is a structure having graphite as a base material and a silicon carbide coating layer coated on the surface.

10. The graphite substrate according to claim 9, wherein the graphite substrate has a thickness of 10 to 20 mm.

Technical Field

The disclosure relates to the technical field of semiconductors, and in particular relates to a graphite substrate for improving wavelength consistency of epitaxial wafers.

Background

A semiconductor Light Emitting Diode (LED) is a kind of semiconductor Diode that can convert electrical energy into Light energy. The LED has the advantages of high efficiency, energy conservation and environmental protection, and has wide application in the fields of traffic indication, outdoor full-color display and the like. Particularly, the semiconductor solid-state lighting is realized by utilizing a high-power LED, and the semiconductor solid-state lighting is expected to become a new generation light source to enter thousands of households, thereby causing the revolution of the human lighting history.

The epitaxial wafer is a primary finished product in the LED manufacturing process. When the epitaxial wafer is formed, the substrate is placed on a tray in a reaction chamber of Metal Organic Chemical Vapor Deposition (MOCVD) equipment, heat energy provided by a heating wire in the MOCVD equipment is conducted to the substrate through the tray, raw materials are introduced into the reaction chamber, and semiconductor materials are epitaxially grown on the substrate to form the epitaxial wafer. Most of the current trays use graphite substrates. The graphite substrate is provided with a plurality of grooves, and one substrate can be accommodated in one groove.

In the course of implementing the present disclosure, the inventors found that the prior art has at least the following problems:

the graphite substrate rotates at a high speed in the epitaxial wafer forming process, and gas flows exist on the surface of the graphite substrate at the high rotating speed, so that the gas distribution of a Mo source introduced into a reaction cavity in the epitaxial wafer growth process can be influenced. And the farther from the center of the graphite substrate, the more uneven the distribution of the MO source occurs. Particularly, the edge position of the graphite substrate is subjected to the largest centrifugal force, and the linear velocity is the largest, so that the flow velocity of the MO source airflow is increased, and the phenomenon that the edge wavelength of the graphite substrate is abnormally shorter or longer is caused.

Disclosure of Invention

The embodiment of the disclosure provides a graphite substrate for improving wavelength consistency of epitaxial wafers, which can improve the wavelength consistency of the epitaxial wafers grown in each groove of the graphite substrate. The technical scheme is as follows:

the embodiment of the disclosure provides a graphite substrate for improving wavelength consistency of an epitaxial wafer, the graphite substrate is of a polygonal prism structure, the outer peripheral wall of the graphite substrate is provided with a plurality of prismatic surfaces, any two adjacent prismatic surfaces are provided with a V-shaped groove at the joint, the V-shaped groove is inwards recessed along the radial direction of the graphite substrate, and the length of the V-shaped groove is equal to the axial length of the graphite substrate.

Optionally, the upper surface of the graphite substrate is provided with a plurality of circles of grooves for accommodating substrates, the plurality of circles of grooves are annularly arranged on the upper surface of the graphite substrate, one circle of groove, closest to the edge of the graphite substrate, of the plurality of circles of grooves is a first circle of groove, and the first circle of groove comprises a plurality of first grooves arranged at intervals along the circumferential direction of the graphite substrate;

the plurality of prismatic surfaces correspond to the plurality of first grooves one by one, and each first groove is located between two V-shaped grooves on two sides of the corresponding prismatic surface.

Optionally, the minimum distance between each prismatic surface and the corresponding first groove is L1, and L1 is less than or equal to 10mm and less than or equal to 50 mm.

Optionally, a minimum distance between a side wall of each V-shaped groove and the corresponding first groove is L2, and L2 is L1.

Optionally, the first ring of grooves comprises 8-12 first grooves.

Optionally, n circles of grooves are formed in the upper surface of the graphite substrate, and n is larger than or equal to 2 and smaller than or equal to 6.

Optionally, the width of each prismatic surface is 10-30 cm.

Optionally, the width of the side wall of each V-shaped groove is 2-10 cm.

Optionally, the graphite substrate is a structure which takes graphite as a base material and is plated with a silicon carbide coating on the surface.

Optionally, the graphite substrate has a thickness of 10mm to 20 mm.

The technical scheme provided by the embodiment of the disclosure has the following beneficial effects:

the graphite substrate is arranged to be of the polygonal prism structure, so that the flow field of high-speed airflow at the edge is adjusted, the influence of the airflow at the edge of the cavity on the growth of the epitaxial wafer is reduced, and the uniformity of the epitaxial wafer is improved. The outer peripheral wall of the graphite substrate is provided with a plurality of prismatic surfaces, a V-shaped groove is formed in the joint of any two adjacent prismatic surfaces, the V-shaped groove is inwards recessed along the radial direction of the graphite substrate, and the length of the V-shaped groove is equal to the axial length of the graphite substrate. Through setting up V type groove, can increase the space that the border air current flows away. The space that the border air current flows away becomes, is favorable to taking away fast of pre-reaction and unnecessary Mo source, and it is good to the uniformity promotion that lies in the epitaxial wafer between the different rings on the graphite substrate. Therefore, by adopting the graphite substrate provided by the present disclosure, the wavelength uniformity of the epitaxial wafer grown in each groove of the graphite substrate can be improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a graphite substrate for improving wavelength uniformity of an epitaxial wafer according to an embodiment of the present disclosure;

fig. 2 is a flow chart of a growth method for growing an epitaxial wafer on a graphite substrate provided by an embodiment of the present disclosure;

FIG. 3 is a schematic illustration of the emission wavelength of an epitaxial wafer grown on a conventional graphite substrate;

fig. 4 is a schematic diagram of the light emission wavelength of an epitaxial wafer grown on a graphite substrate provided by an embodiment of the present disclosure.

Detailed Description

To make the objects, technical solutions and advantages of the present disclosure more apparent, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

Fig. 1 is a schematic structural diagram of a graphite substrate for improving wavelength uniformity of an epitaxial wafer according to an embodiment of the present disclosure, as shown in fig. 1, the graphite substrate 100 has a polygonal prism structure, an outer peripheral wall of the graphite substrate 100 has a plurality of prismatic surfaces 110, and a junction of any two adjacent prismatic surfaces 110 has a V-shaped groove 100a, the V-shaped groove 100a is recessed inward along a radial direction of the graphite substrate 100, and a length of the V-shaped groove 100a is equal to an axial length of the graphite substrate 100.

According to the embodiment of the disclosure, the graphite substrate is arranged to be of the polygonal prism structure, so that the flow field of the edge high-speed airflow is adjusted, the influence of the edge airflow of the cavity on the growth of the epitaxial wafer is reduced, and the uniformity of the epitaxial wafer is improved. The outer peripheral wall of the graphite substrate is provided with a plurality of prismatic surfaces, a V-shaped groove is formed in the joint of any two adjacent prismatic surfaces, the V-shaped groove is inwards recessed along the radial direction of the graphite substrate, and the length of the V-shaped groove is equal to the axial length of the graphite substrate. Through setting up V type groove, can increase the space that the border air current flows away. The space that the border air current flows away becomes, is favorable to taking away fast of pre-reaction and unnecessary Mo source, and it is good to the uniformity promotion that lies in the epitaxial wafer between the different rings on the graphite substrate. Therefore, by adopting the graphite substrate provided by the present disclosure, the wavelength uniformity of the epitaxial wafer grown in each groove of the graphite substrate can be improved.

Alternatively, the upper surface of the graphite base plate 100 has a plurality of turns of grooves 100b for receiving substrates, and the plurality of turns of grooves 100b are annularly arranged on the upper surface of the graphite base plate 100. The one of the plurality of grooves 100b closest to the edge of the graphite substrate 100 is a first groove including a plurality of first grooves 100b-1 arranged at intervals in the circumferential direction of the graphite substrate 100.

The plurality of prismatic surfaces 110 correspond to the plurality of first grooves 100b-1 one by one, and each first groove 100b-1 is located between two V-shaped grooves 100a on both sides of the corresponding prismatic surface 110.

When the epitaxial growth device is used specifically, when a plurality of substrates are placed in the first grooves 100b-1 for epitaxial growth, each substrate can be located between the two V-shaped grooves 100a on the two sides of the corresponding prismatic surface 110, so that the space for flowing away along air flow during the epitaxial growth of each substrate can be increased, pre-reaction and rapid extraction of redundant Mo sources are facilitated, and the wavelength consistency of epitaxial growth epitaxial wafers in the first ring of grooves and other rings of grooves on the edge of the graphite substrate is improved.

It should be noted that, in the embodiment of the present disclosure, each prism surface 110 is a plane surface.

Optionally, the minimum distance between each prismatic surface 110 and the corresponding first groove 100b-1 is L1, and L1 is less than or equal to 10mm and less than or equal to 50 mm.

If the distance of L1 is too large, local eddy current is easily formed in the concave of the graphite substrate; if the distance of L1 is too small, the effect of improving the wavelength uniformity of the epitaxial wafer is not obtained.

It should be noted that the minimum distance L1 between each prism surface of the polygonal prism structure and the corresponding first groove 100b-1 may be varied to adapt to different flow field models, so as to improve the uniformity of the wavelength and yield of the epitaxial wafer.

Optionally, a minimum distance between a side wall of each V-shaped groove 100a and the corresponding first groove 100b-1 is L2, and L2 is L1.

By setting the minimum distance between the side wall of each V-groove 100a and the corresponding first groove 100b-1 to be equal to the minimum distance between each prismatic surface 110 and the corresponding first groove 100b-1, the uniformity of Mo source distribution during epitaxial growth can be ensured.

In the disclosed embodiment, each first groove 100b-1 corresponds to two V-grooves 100a on both sides of its corresponding prismatic surface.

Optionally, the first ring of grooves comprises 8-12 first grooves 100 b-1.

The number of the first grooves 100b-1 is not too large, which may affect the uniform distribution of the Mo source during the epitaxial growth process. The number of the first grooves 100b-1 is too small, which reduces the efficiency of epitaxial growth.

Optionally, the upper surface of the graphite substrate 100 has n circles of grooves 100b, where n is greater than or equal to 2 and less than or equal to 6.

If the number of turns of the groove 100b is too large, the uniform distribution of the Mo source in the epitaxial growth process may be affected. If the number of turns of the groove 100b is too small, the efficiency of epitaxial growth is reduced.

Optionally, the width D of each prism surface 110 is 10-30 cm.

If the width D of the prism surface 110 is too wide, a vortex may be generated at a local recessed position of the graphite substrate 100, which may affect the distribution of the flow field; if the width D of the prism surface 110 is too narrow, the difference of the temperature field distribution at the edge of the epitaxial wafer will be obvious, and the uniformity of the epitaxial wafer will be affected.

Optionally, the width d of the side wall of each V-shaped groove 100a is 2-10 cm.

If the width d of the sidewall of each V-groove 100a is too wide, a vortex may be formed at a local position of the graphite substrate 100, which may affect the flow field distribution. If the width d of the sidewall of each V-groove 100a is too narrow, the improvement effect on the uniformity of the epitaxial wafer is not obvious.

Alternatively, the graphite substrate 100 is a structure with graphite as a base material and a silicon carbide coating plated on the surface. Each face of the plurality of grooves 100b on the graphite substrate 100 is also coated with a silicon carbide coating.

Alternatively, the graphite substrate 100 has a thickness of 10mm to 20 mm.

For a better understanding of the present application, the following exemplarily illustrates a specific structure of an epitaxial wafer grown on a graphite substrate and a specific growth process of the epitaxial wafer provided in the embodiments of the present disclosure.

The epitaxial wafer comprises a substrate, and a buffer layer, an undoped gallium nitride layer, an N-type layer, an active layer, a P-type layer and a P-type contact layer which are sequentially stacked on the substrate.

Optionally, the substrate is a sapphire substrate, a Si or SiC substrate.

Optionally, the buffer layer is a GaN layer, and the thickness of the buffer layer is 15-35 nm.

Optionally, the thickness of the undoped GaN layer is 1-5 um.

Optionally, the N-type layer is a Si-doped GaN layer with a thickness of 1um to 2 um. The doping concentration of Si in the N-type layer may be 10¹⁸cm^-3～10²⁰cm^-3。

Optionally, the active layer comprises n InGaN well layers and n GaN barrier layers which are alternately grown in cycles, and n is larger than or equal to 2 and smaller than or equal to 10. And n is a positive integer. The thickness of each InGaN well layer is 2-3 nm, and the thickness of each GaN barrier layer is 7-10 nm.

Optionally, the P-type layer is a Mg-doped gallium nitride layerThe thickness is 50-100 nm, and the doping concentration of Mg is 10¹⁸cm^-3～10²⁰cm^-3。

Optionally, the P-type contact layer is a Mg-doped gallium nitride layer with a thickness of 10-25 nm and a Mg doping concentration of 5 x 10¹⁹cm^-3～1*10²⁰cm^-3。

It should be noted that the above-mentioned epitaxial wafer is only an exemplary structure, and in the actual epitaxial growth process, other epitaxial structures may also be used, which is not limited in this disclosure.

Fig. 2 is a flowchart of a growth method for growing an epitaxial wafer on a graphite substrate according to an embodiment of the present disclosure, where the growth method includes:

step 201, a substrate is provided.

The substrate can be a sapphire flat sheet substrate.

Further, step 201 may further include:

controlling the temperature to be 1000-1200 ℃, and annealing the substrate for 6-10 minutes in a hydrogen atmosphere;

the substrate is subjected to a nitridation process.

The surface of the substrate is cleaned through the steps, impurities are prevented from being doped into the epitaxial wafer, and the growth quality of the epitaxial wafer is improved.

In this embodiment, a Veeco K465i or C4 or RB MOCVD (Metal Organic Chemical Vapor Deposition) apparatus is used to realize the epitaxial wafer growth method. By using high-purity H₂(Hydrogen) or high purity N₂(Nitrogen) or high purity H₂And high purity N₂The mixed gas of (2) is used as a carrier gas, high-purity NH₃As the nitrogen source, trimethyl gallium (TMGa) and triethyl gallium (TEGa) as gallium sources, trimethyl indium (TMIn) as indium source, silane (SiH4) as N-type dopant, i.e., Si source, trimethyl aluminum (TMAl) as aluminum source, and magnesium diclocide (CP)₂Mg) as a P-type dopant, i.e., a Mg source. The pressure in the reaction chamber is 100-600 torr.

Step 202, a buffer layer is grown on the substrate.

Illustratively, the temperature of the reaction chamber is controlled to be 400-600 ℃, the pressure is controlled to be 200-500 torr, and a buffer layer with the thickness of 15-35 nm is grown.

Step 203, carrying out in-situ annealing treatment on the buffer layer.

Illustratively, the temperature of the reaction chamber is controlled to be 1000-1200 ℃, the pressure is 100-300 mbar, and the nucleation layer is subjected to in-situ annealing treatment for 5-10 minutes.

Step 204, growing an undoped gallium nitride layer on the buffer layer.

Illustratively, the temperature of the reaction chamber is controlled to be 1000-1100 ℃, the pressure is controlled to be 100-500 torr, and an undoped GaN layer with the thickness of 1-5 um is grown.

Step 205, an N-type layer is grown on the undoped gallium nitride layer.

Wherein, the thickness of the N-type layer can be 1-5 um, and the doping concentration of Si in the N-type layer can be 10¹⁸/cm³～10²⁰/cm³。

Illustratively, the temperature in the reaction chamber is controlled to be 1000-1200 ℃, the pressure is controlled to be 100-500 torr, and an N-type layer with the thickness of 1-5 um is grown on the undoped GaN layer.

Step 206, an active layer is grown on the N-type layer.

The active layer comprises n InGaN well layers and n GaN barrier layers which alternately grow in cycles, wherein n is more than or equal to 2 and less than or equal to 10. And n is a positive integer.

Optionally, the thickness of each InGaN well layer is 2-3 nm, and the thickness of each GaN barrier layer is 7-10 nm.

Step 207, a P-type layer is grown on the active layer.

Wherein the P-type layer is a GaN layer doped with Mg, the thickness is 50-100 nm, and the doping concentration of Mg is 10¹⁸cm^-3～10²⁰cm^-3. The growth temperature of the P-type contact layer is 800-1000 ℃, and the growth pressure is 200-500 torr.

Step 208, a P-type contact layer is grown on the P-type layer.

Wherein the P-type contact layer is a Mg-doped gallium nitride layer with the thickness of 10-25 nm and the doping concentration of Mg of 5 x 10¹⁹cm^-3～1*10²⁰cm^-3. The growth temperature of the P-type contact layer is 700-900 ℃, and the growth pressure is 200-400 torr.

One specific implementation of the graphite substrate provided in the embodiments of the present disclosure includes: the graphite substrate 100 has a ten-prism structure, the outer peripheral wall of the graphite substrate 100 has ten prism faces 110, and the joint of any two adjacent prism faces 110 has a V-shaped groove 100a, the V-shaped groove 100a is recessed inwards along the radial direction of the graphite substrate 100, and the length of the V-shaped groove 100a is equal to the axial length of the graphite substrate 100.

The upper surface of the graphite base plate 100 has two circles of grooves 100b for receiving substrates, and the two circles of grooves 100b are annularly arranged on the upper surface of the graphite base plate 100. The two-turn groove 100b includes a first turn of groove near the edge of the graphite substrate 100 and a second turn of groove near the center of the graphite substrate 100. Wherein the first ring of grooves includes ten first grooves 100b-1 arranged at intervals in the circumferential direction of the graphite substrate 100. The second ring of grooves includes four second grooves arranged at intervals in the circumferential direction of the graphite substrate 100.

The ten prism faces 110 correspond to the ten first grooves 100b-1 one by one, and each first groove 100b-1 is located between two V-shaped grooves 100a on both sides of the corresponding prism face 110.

Optionally, a minimum distance between each prismatic surface to the corresponding first groove is L1, and L1 is 30 mm.

Optionally, a minimum distance between a side wall of each V-groove 100a and the corresponding first groove is L2, and L2 is L1.

Optionally, the width D of each prismatic surface 110 is 20 cm.

Optionally, the width d of the sidewall of each V-groove 100a is 6 cm.

Fig. 3 is a schematic view of the emission wavelength of the epitaxial wafer grown on the conventional graphite substrate, and referring to fig. 3, the region of the same epitaxial wafer near the center of the graphite substrate 100 and the region far from the center of the graphite substrate 100 may be different in emission wavelength (i.e., the gray scale difference between the regions near the graphite substrate and far from the graphite substrate in the same epitaxial wafer in fig. 3 is large), and particularly, the difference in emission wavelength between the ten epitaxial wafers far from the center of the graphite substrate 100 is significant (i.e., the gray scale difference between the ten epitaxial wafers located at the outermost circles in fig. 3 is large).

Fig. 4 is a schematic diagram of the emission wavelengths of the epitaxial wafers grown on the graphite substrate according to the embodiment of the present disclosure, and referring to fig. 4, compared to fig. 3, the difference between the emission wavelengths of the region close to the center of the graphite substrate 100 and the region far from the center of the graphite substrate 100 of the same epitaxial wafer is small (i.e., the difference between the gray levels of the region close to the graphite substrate and the region far from the graphite substrate in the same epitaxial wafer in fig. 4 is small), and particularly, the difference between the emission wavelengths of the ten epitaxial wafers far from the center of the graphite substrate 100 is significantly reduced (i.e., the difference between the gray levels of the ten epitaxial wafers located at the outermost circles in fig. 4 is small).

According to the embodiment of the disclosure, the graphite substrate is arranged to be of the polygonal prism structure, so that the flow field of the edge high-speed airflow is adjusted, the influence of the edge airflow of the cavity on the growth of the epitaxial wafer is reduced, and the uniformity of the epitaxial wafer is improved. The outer peripheral wall of the graphite substrate is provided with a plurality of prismatic surfaces, a V-shaped groove is formed in the joint of any two adjacent prismatic surfaces, the V-shaped groove is inwards recessed along the radial direction of the graphite substrate, and the length of the V-shaped groove is equal to the axial length of the graphite substrate. Through setting up V type groove, can increase the space that the border air current flows away. The space that the border air current flows away becomes, is favorable to taking away fast of pre-reaction and unnecessary Mo source, and it is good to the uniformity promotion that lies in the epitaxial wafer between the different rings on the graphite substrate. Therefore, by adopting the graphite substrate provided by the present disclosure, the wavelength uniformity of the epitaxial wafer grown in each groove of the graphite substrate can be improved.

Another specific implementation of the graphite substrate provided in the embodiment of the present disclosure includes: the graphite substrate 100 has a ten-prism structure, the outer peripheral wall of the graphite substrate 100 has sixteen prism faces 110, and the joint of any two adjacent prism faces 110 has a V-shaped groove 100a, the V-shaped groove 100a is recessed inwards along the radial direction of the graphite substrate 100, and the length of the V-shaped groove 100a is equal to the axial length of the graphite substrate 100.

The upper surface of the graphite base plate 100 has three rings of grooves 100b for receiving substrates, and the three rings of grooves 100b are annularly arranged on the upper surface of the graphite base plate 100. The three-turn grooves 100b include a first turn groove closest to the edge of the graphite substrate 100, a third turn groove closest to the center of the graphite substrate 100, and a second turn groove between the first turn groove and the third turn groove. Wherein the first ring of grooves comprises sixteen first grooves 100b-1 arranged at intervals along the circumferential direction of the graphite substrate 100. The second ring of grooves includes four second grooves arranged at intervals in the circumferential direction of the graphite substrate 100. The third ring of grooves includes ten third grooves arranged at intervals in the circumferential direction of the graphite substrate 100.

Sixteen prism faces 110 are in one-to-one correspondence with sixteen first grooves 100b-1, and each first groove 100b-1 is located between two V-shaped grooves 100a on both sides of the corresponding prism face 110.

Optionally, a minimum distance between each prismatic surface to the corresponding first groove is L1, and L1 is 20 mm.

Optionally, a minimum distance between a side wall of each V-groove 100a and the corresponding first groove is L2, and L2 is L1.

Optionally, each prismatic surface 110 is 10cm wide.

Optionally, the width of the sidewall of each V-groove 100a is 4 cm.

According to the embodiment of the disclosure, the graphite substrate is arranged to be of the polygonal prism structure, so that the flow field of the edge high-speed airflow is adjusted, the influence of the edge airflow of the cavity on the growth of the epitaxial wafer is reduced, and the uniformity of the epitaxial wafer is improved. The outer peripheral wall of the graphite substrate is provided with a plurality of prismatic surfaces, a V-shaped groove is formed in the joint of any two adjacent prismatic surfaces, the V-shaped groove is inwards recessed along the radial direction of the graphite substrate, and the length of the V-shaped groove is equal to the axial length of the graphite substrate. Through setting up V type groove, can increase the space that the border air current flows away. The space that the border air current flows away becomes, is favorable to taking away fast of pre-reaction and unnecessary Mo source, and it is good to the uniformity promotion that lies in the epitaxial wafer between the different rings on the graphite substrate. Therefore, by adopting the graphite substrate provided by the present disclosure, the wavelength uniformity of the epitaxial wafer grown in each groove of the graphite substrate can be improved.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The use of "first," "second," "third," and similar terms in the description and claims does not indicate any order, quantity, or importance, but rather is used to distinguish one element from another. Also, the use of the terms "a" or "an" and the like do not denote a limitation of quantity, but rather denote the presence of at least one. The word "comprise" or "comprises", and the like, means that the element or item listed before "comprises" or "comprising" covers the element or item listed after "comprising" or "comprises" and its equivalents, and does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", "top", "bottom", and the like are used merely to indicate relative positional relationships, which may also change accordingly when the absolute position of the object being described changes.

Although the present disclosure has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure.