CN114196923A

CN114196923A - Boron nitride crucible mold, preparation method and demolding method

Info

Publication number: CN114196923A
Application number: CN202210149841.3A
Authority: CN
Inventors: 何军舫; 王军勇
Original assignee: Boyu Tianjin Semiconductor Material Co ltd; Boyu Zhaoyang Semiconductor Technology Co ltd; Boyu Semiconductor Vessel Craftwork Technology Co ltd
Current assignee: Boyu Tianjin Semiconductor Material Co ltd; Boyu Zhaoyang Semiconductor Technology Co ltd; Boyu Semiconductor Vessel Craftwork Technology Co ltd
Priority date: 2022-02-18
Filing date: 2022-02-18
Publication date: 2022-03-18
Anticipated expiration: 2042-02-18
Also published as: CN114196923B

Abstract

The embodiment of the disclosure discloses a boron nitride crucible mold, a preparation method and a demolding method, wherein the boron nitride crucible mold comprises: the hollow base body comprises a main body, a bottom detachably connected with the main body and a head detachably connected with the main body, the head is provided with a through hole communicated with the inside of the base body, one end of the through hole, far away from the main body, is provided with internal threads, and the head is provided with an exhaust hole communicated with the through hole; and the surface layer is coated on the outer surface of the substrate. The boron nitride crucible mold disclosed by the embodiment of the disclosure can improve the crucible quality.

Description

Boron nitride crucible mold, preparation method and demolding method

Technical Field

The disclosure relates to the technical field of boron nitride crucible preparation, in particular to a boron nitride crucible mold, a preparation method and a demolding method.

Background

The Molecular Beam Epitaxy (MBE) method is mainly used for epitaxial growth of crystals. The MBE crucible is mainly used as a beam source crucible in a Molecular Beam Epitaxy (MBE) method. The pyrolytic boron nitride crucible has the excellent characteristics of high purity, extremely low outgassing rate at high temperature, uniform thickness, good heating consistency, excellent thermal conductivity, thermal shock resistance and the like, so the pyrolytic boron nitride crucible is the most commonly used MBE crucible. To achieve specific evaporation requirements, MBE crucibles are often designed with different opening patterns, and necking crucibles are a common shape.

The inner die of the necking pyrolytic boron nitride crucible is difficult to take out, the manual polishing and oxidation mode is adopted for processing in the current common method, but the difficulty is high on the one hand because the inner die is of a solid structure, and the processing period is too long on the other hand, so that the mass production of the product is seriously limited.

An improved scheme is that a mold is processed to form a hollow structure, so that the mold is conveniently oxidized and removed, but the simple split structure mold has many problems in practice, such as the situation that a seam of a head part is not normal or a gap exists after high-temperature expansion, so that bulges or depressions exist at the seam of a produced crucible, and the quality of the crucible is influenced.

Disclosure of Invention

The embodiment of the disclosure provides a boron nitride crucible mold, a preparation method and a demolding method, which can improve the quality of a boron nitride crucible.

In a first aspect, embodiments of the present disclosure provide a boron nitride crucible mold, including:

the hollow base body comprises a main body, a bottom detachably connected with the main body and a head detachably connected with the main body, the head is provided with a through hole communicated with the inside of the base body, one end of the through hole, far away from the main body, is provided with internal threads, and the head is provided with an exhaust hole communicated with the through hole;

and the surface layer is coated on the outer surface of the substrate.

In an alternative embodiment, the inner surface of the substrate has a relief structure.

In an alternative embodiment, the relief structure is a threaded structure or a honeycomb structure.

In an alternative embodiment, the roughness Ra of the inner surface of the substrate is greater than 3.2 μm.

In an alternative embodiment, the roughness Ra of the outer surface of the substrate is 1.2-3.0 μm.

In an optional embodiment, the surface layer is made of one material selected from pyrolytic boron nitride, pyrolytic graphite, boron carbide, carbon-doped boron nitride, boron-doped pyrolytic graphite and silicon nitride, the thickness of the surface layer is 0.1-0.5mm, and the roughness of the outer surface of the surface layer is less than 0.8 μm.

In an alternative embodiment, the base body has a constricted part, the constricted part forms a groove in the circumferential direction of the base body, and the joint part of the head part and the main body is the minimum outer diameter part of the constricted part.

In a second aspect, an embodiment of the present disclosure provides a method for preparing a boron nitride crucible mold according to any one of the above embodiments, including:

respectively preparing a main body, a bottom and a head;

respectively connecting the bottom and the head with the main body to obtain a matrix;

and forming a surface layer on the outer surface of the substrate.

In an optional embodiment, when the main body, the bottom and the head are prepared, machining allowances of 0.1-0.8mm are reserved respectively, and after the bottom and the head are connected with the main body respectively, the outer surface of the base body is subjected to finish machining.

In a third aspect, embodiments of the present disclosure provide a method for demolding a boron nitride crucible, including:

depositing a boron nitride crucible on the outer surface of the mold in any of the above embodiments;

placing the boron nitride crucible with the mold in a high-temperature furnace, inserting a vent pipe into the mold through the through hole, introducing oxygen to oxidize the mold, wherein a plurality of air distribution holes are formed in the side wall of the vent pipe and are distributed along the axial direction;

removing pyrolytic boron nitride formed by deposition on the surface of the head part;

detaching the head from the body.

In an alternative embodiment, the temperature of the oxidation is from 650 ℃ to 800 ℃.

The embodiment of the disclosure provides a boron nitride crucible mould, including base member and cladding on the top layer of base member surface, the base member adopts the components of a whole that can function independently structure, can obtain the hollow structure's of various appearances mould, hollow structure's mould is easily the later stage oxidation to be got rid of, through the top layer at a base member surface cladding overall structure, avoid the mould can exist when using because of main part and bottom or head seam crossing just or the problem that has the clearance behind the high temperature expansion, lead to the crucible of producing to have the condition of bulging or sunken in seam crossing, can't satisfy the user demand.

Drawings

In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 shows a schematic structural diagram of an embodiment of a boron nitride crucible mold according to an embodiment of the disclosure.

Fig. 2 shows a schematic structural diagram of another embodiment of the boron nitride crucible mold of the embodiment of the disclosure.

Fig. 3 shows a schematic structural diagram of a boron nitride crucible mold according to yet another embodiment of the present disclosure.

Fig. 4 shows a schematic structural view of a vent pipe in an embodiment of the present disclosure.

Fig. 5 shows a schematic view of the structure of the vent pipe extending into the mold in the embodiment of the present disclosure.

The reference numbers illustrate:

1-a substrate; 11-a body; 12-bottom; 13-a head; 14-a through hole; 15-air vent; 2-surface layer; 3-a constriction; 4-a relief structure; 5-hoisting the interface; 6-air distribution holes.

Detailed Description

In order to make the technical solutions of the present disclosure better understood by those skilled in the art, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present disclosure, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.

The terms "first," "second," and the like in the description and claims of the present disclosure and in the above-described drawings are used for distinguishing between different objects and not for describing a particular order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the disclosure. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

Referring to fig. 1 and 2, the disclosed embodiment provides a boron nitride crucible mold, which comprises a hollow base body 1 and a surface layer 2, wherein the base body 1 comprises a main body 11, a bottom part 12 detachably connected with the main body 11 and a head part 13 detachably connected with the main body 11. The surface layer 2 covers the outer surface of the substrate 1.

Referring to fig. 1 to 3, the embodiment of the present disclosure provides a boron nitride crucible mold, including hollow base body 1 and surface layer 2 coated on the outer surface of base body 1, base body 1 adopts a split structure, hollow structure molds of various shapes can be obtained, hollow structure molds are easy to be removed by post oxidation, surface layer 2 coated on the outer surface of base body 1 is an integral structure, thereby avoiding the problem that the mold has a gap at the joint between main body 11 and bottom 12 or head 13 during use or after high temperature expansion, resulting in the situation that the produced crucible has bulge or recess at the joint, and failing to meet the use requirement.

In some embodiments, the base body 1 is a split structure, the base body 1 includes a main body 11, a bottom 12 and a head 13, and two ends of the main body 11 are respectively connected to the bottom 12 and the head 13.

The base body 1 is provided with a contraction part 3, the contraction part 3 forms a groove in the circumferential direction of the base body 1, and the joint part of the head part 13 and the main body 11 is the minimum part of the outer diameter of the contraction part 3. The joint between the head 13 and the body 11 is located at the minimum outer diameter of the mold, and the distribution formula is beneficial to the processing of the mold with a split structure.

In the disclosed embodiment, the body 11 and the bottom 12 and the head 13 may be screwed together. The threads between the main body 11 and the bottom 12 and the head 13 are connected by fine threads or T-shaped threads, so that the matching precision can be effectively improved and looseness can be prevented.

In some embodiments, the head 13 has a through hole 14 communicating with the interior of the body 11, and the end of the through hole 14 remote from the body 11 is internally threaded. Internal threads are arranged on the inner wall of the through hole 14 at one end of the raw material main body 11 to form a hoisting interface 5, so that hoisting of a mold can be realized, and after the crucible is formed by deposition, the mold can be removed by directly introducing oxygen for oxidation, so that simplicity and convenience are realized. The inner diameter of the part of the through hole 14 with the internal thread can be larger than the inner diameter of the other parts of the through hole 14, so that the die can be conveniently hung in a deposition furnace. The minimum inner diameter of the through hole 14 enables the insertion of a breather tube during subsequent mold oxidation. The head 13 has a vent hole 15 communicating with the through hole 14. Through set up the exhaust hole 15 that communicates through-hole 14 at head 13, make the interior external pressure balance of base member 1, can guarantee to discharge inside gas smoothly when the mould is in vacuum environment, guarantee the safety in utilization of mould.

Referring to fig. 2 and 3, in some embodiments, at least the inner surface of the body 11 of the matrix 1 has a relief structure 4. The partial inner wall of base member 1 has concave-convex structure 4, can increase mould inner surface area, can effectual promotion oxidation efficiency, reduces the oxidation time, improves production efficiency, improves the productivity. The specific form of the concave-convex structure 4 is not limited, and for example, the concave-convex structure may be a thread structure, a honeycomb structure, or the like, wherein the thread structure may be a T-shaped thread. The concave-convex structure 4 may be provided only on the inner wall of the body 11, the concave-convex structure 4 may be provided on the inner walls of the body 11 and the bottom 12, or the concave-convex structure 4 may be provided on the inner walls of the body 11, the bottom 12, and the head 13.

In some embodiments, the roughness Ra of the inner surface of the substrate 1 is greater than 3.2 μm. The oxidation efficiency can be effectively improved by increasing the surface roughness of the inner wall of the mold. The oxidation efficiency can be further improved by forming the uneven structure 4 on the inner surface of the base 1 and by making the roughness Ra of the inner surface larger than 3.2 μm.

In some embodiments, the roughness Ra of the outer surface of the substrate 1 is 1.2 to 3.0. mu.m. In the embodiment of the disclosure, the outer surface of the substrate 1 is treated to have a roughness Ra of 1.2 to 3.0 μm, so that the bonding strength between the surface layer 2 and the substrate 1 can be improved.

In some embodiments, the material of the surface layer 2 is selected from one of pyrolytic boron nitride, pyrolytic graphite, boron carbide, carbon-doped boron nitride, boron-doped pyrolytic graphite, and silicon nitride. The thickness of the surface layer 2 is 0.1-0.5 mm. The roughness of the outer surface of the skin layer 2 is less than 0.8 μm. The roughness of the outer surface of the skin layer 2 is controlled to be less than 0.8 μm.

The embodiment of the disclosure provides a preparation method of the boron nitride crucible mold of any one of the embodiments, which includes:

preparing a body 11, a bottom 12 and a head 13, respectively;

respectively connecting the bottom 12 and the head 13 with the main body 11 to obtain a matrix 1;

the surface layer 2 is formed on the outer surface of the base 1.

In the preparation method of the boron nitride crucible mold disclosed by the embodiment of the disclosure, the main body 11, the bottom 12 and the head 13 are respectively prepared, then the base body 1 is obtained by assembling, through using a split structure, hollow structure molds with various shapes can be obtained, the preparation difficulty is reduced, the hollow structure molds are easy to remove by later oxidation, the surface layer 2 of the base body 1 is coated with an integral structure, the problem that the gap exists at the joint of the main body 11 and the bottom 12 or the head 13 or after high-temperature expansion when the mold is used is avoided, the condition that the produced crucible bulges or is sunken at the joint is caused, and the use requirement cannot be met.

In some embodiments, the body 11, the bottom 12, and the head 13 are prepared with a machining allowance of 0.1 to 0.8mm, respectively, and the outer surface of the base 1 is finished after the bottom 12 and the head 13 are coupled to the body 11, respectively. Each part of the substrate 1 with the split structure of the embodiment of the disclosure is reserved with a machining allowance of 0.1-0.8mm during machining, and is finish-machined after assembly, so that the smoothness and consistency of the outer side of the substrate 1 can be effectively ensured, the surface roughness Ra of the substrate 1 after finish machining is 1.2-3.0 μm, and the bonding fastness between the substrate 1 and the surface layer 2 can be improved. When the surface of the base body 1 is machined, attention needs to be paid to the fact that the feed direction is opposite to the thread direction, and loosening of threads connected between parts of the base body 1 is avoided.

Preparing the body 11, the bottom 12 and the head 13, respectively, includes: respective green bodies of the body 11, the bottom 12 and the head 13 are prepared, and the concave-convex structure 4 is formed on the inner surfaces of the body 11 and the bottom 12. In some embodiments, the inner surface of the substrate 1 has a relief structure 4. Have concave-convex structure 4 in base member 1 inside, can increase the mould internal surface area, can effectual promotion oxidation efficiency, reduce the oxidation time, improve production efficiency, improve the productivity. The specific form of the concave-convex structure 4 is not limited, and for example, the concave-convex structure may be a thread structure, a honeycomb structure, or the like, wherein the thread structure may be a T-shaped thread. The concavo-convex structure 4 is formed before the body 11, the bottom 12 and the head 13 are connected. The specific manner of forming the concave-convex structure 4 is not limited.

In some embodiments, separately preparing the body 11, the base 12, and the head 13 includes: respective green bodies of the body 11, the bottom 12 and the head 13 are prepared, and the concave-convex structure 4 is formed on the inner surfaces of the body 11 and the bottom 12. The relief structure 4 may be formed by scribing or the like.

In some embodiments, separately preparing the body 11, the base 12, and the head 13 includes: the inner surfaces of the body 11 and the bottom 12 are roughened so that the roughness Ra of the inner surfaces of the body 11 and the bottom 12 is greater than 3.2 μm. The oxidation efficiency can be effectively improved by increasing the surface roughness of the inner wall of the mold. The oxidation efficiency can be further improved by forming the uneven structure 4 on the inner surface of the base 1 and by making the roughness Ra of the inner surface larger than 3.2 μm.

In some embodiments, the material of the surface layer 2 is selected from one of pyrolytic boron nitride, pyrolytic graphite, boron carbide, carbon-doped boron nitride, boron-doped pyrolytic graphite, and silicon nitride. The thickness of the surface layer 2 is 0.1-0.5 mm. The roughness of the outer surface of the skin layer 2 is less than 0.8 μm. The roughness of the outer surface of the surface layer 2 is controlled to be less than 0.8 μm, and the mold is removed at the later stage. The specific process and parameters for forming the surface layer 2 are not particularly limited, and for example, the surface layer 2 may be formed on the surface of the substrate 1 by any known process.

When the mold is prepared, the required mold can be designed and produced according to the shape of the crucible, the mold is split at the position with the minimum caliber of the necking according to the integral necking condition of the necking crucible, and the mold is split into at least two parts. The connection of the minimum caliber adopts fine teeth or T-shaped threaded connection, a proper thread specification is selected according to the size of a reducing part, and the thinnest part of the die design is not less than 0.5 mm. In addition, the thickness difference of each part of the base body 1 (without a hoisting upper opening) needs to be controlled within 10 percent, and the phenomenon that the thermal expansion amount difference at high temperature is caused by an overlarge thickness difference, so that the weak part of the die is broken is avoided.

When the outer part of the matrix 1 is machined, rough machining is firstly carried out, a machining allowance of 0.5-1mm is reserved, a T-shaped groove or a honeycomb hole is machined on the inner wall, the depth of the T-shaped groove is 50-100% of the width of the groove, the depth of the honeycomb hole is 30-70% of the diameter, the surface area of the inner wall can be increased as much as possible under the condition that the use safety of a die is not influenced, and the oxidation rate is increased.

After the T-shaped groove or the honeycomb hole of the inner wall is processed, the inner wall is roughened in a sand blasting mode, so that the roughness of the inner wall of the matrix 1 is larger than 3.2 microns. When sand blasting is carried out, the interface end faces of all parts of the base body 1 need to be protected, so that collision and damage to the edges during sand blasting are prevented, and the flexible protective hoop made of rubber can be used for protecting the end faces.

Accomplish and assemble base member 1 after handling, carry out the finish machining after the fastening, processing is that the screw thread direction of screwing who notices feed direction and each part of base member 1 and be connected is unanimous, it is not hard up to appear in base member 1 after preventing to process, when processing to surplus 0.2mm with ordinary milling cutter, it carries out final finish machining to change ball end mill, ball end mill adds man-hour can effectual protection mould kneck, avoid the kneck to appear collapsing the limit and the mould components of a whole that can function independently that leads to is scrapped, and can effectual control base member 1's roughness is in the within range of demand.

After finishing the finish machining of the matrix 1, cleaning the matrix 1, firstly washing the matrix 1 by using tap water to wash most of graphite powder, then placing the matrix 1 on a cleaning support in an ultrasonic cleaning machine, carrying out ultrasonic cleaning for 15-60min by using pure water for more than 3 times, completely cleaning the graphite powder in the matrix 1 and on the surface of the matrix 1, and then carrying out ultrasonic cleaning again by using acetone and alcohol for not less than 20 min. Then, purging the liquid on the surface of the mold by using nitrogen of 0.1-0.3Mpa, then placing the matrix 1 in an oven, setting the temperature at 105-200 ℃, baking for 30-120min, then cooling and taking out.

The embodiment of the disclosure provides a demolding method of a boron nitride crucible, which comprises the following steps:

placing the boron nitride crucible with the mold in a high-temperature furnace, inserting a vent pipe into the mold through a through hole 14, introducing oxygen to oxidize the mold, wherein a plurality of air distribution holes 6 are formed in the side wall of the vent pipe, and the plurality of air distribution holes 6 are distributed along the axial direction;

removing pyrolytic boron nitride formed by deposition on the surface of the head part 13;

the head 13 is detached from the body 11.

In the demolding method of the boron nitride crucible disclosed by the embodiment of the disclosure, the plurality of air distribution holes 6 are arranged in the oxygen vent pipe, so that the uniform distribution of oxygen in the mold can be ensured, and the oxidation efficiency is improved.

In some embodiments, the temperature of the oxidation is from 650 ℃ to 850 ℃.

And after the production of the crucible is finished, taking the mold with the crucible out of the deposition furnace, and then, treating the PBN at the opening part of the outer edge of the crucible by using abrasive paper to expose the graphite mold inside.

Then horizontally placing the mold with the crucible in an oxidation furnace, extending a vent pipe into the interior of the mold, wherein the distance between the vent pipe and the bottom end is 20-50mm, then heating the oxidation furnace to 750-; the oxidation is continued until the inner mould is completely oxidized and the head 13 of the mould is removed.

Example 1

The body 11, the bottom 12, and the head 13 are prepared separately, and the roughness of the inner surfaces of the body 11, the bottom 12, and the head 13 is about 4 μm. The base 12 and the head 13 are respectively connected with the main body 11 to obtain a matrix 1, the outer surface of the matrix 1 is processed to make the outer surface of the matrix 1 smooth, the roughness of the outer surface of the matrix 1 is 1.84 μm, a surface layer 2 of pyrolytic graphite is formed on the outer surface of the matrix 1, the thickness of the surface layer 2 is 0.3mm, and the roughness of the outer surface of the surface layer 2 is less than 0.8 μm.

Example 2

The body 11, the bottom 12, and the head 13 are prepared separately, and the roughness of the inner surfaces of the body 11, the bottom 12, and the head 13 is about 4 μm. T-shaped threads are scribed on the inner walls of the main body 11 and the bottom 12, the bottom 12 and the head 13 are respectively connected with the main body 11 to obtain a matrix 1, the outer surface of the matrix 1 is processed to make the outer surface of the matrix 1 smooth, the roughness of the outer surface of the matrix 1 is 1.84 mu m, a surface layer 2 of pyrolytic graphite is formed on the outer surface of the matrix 1, the thickness of the surface layer 2 is 0.3mm, and the roughness of the outer surface of the surface layer 2 is less than 0.8 mu m.

Example 3

The body 11, the bottom 12, and the head 13 are prepared separately, and the roughness of the inner surfaces of the body 11, the bottom 12, and the head 13 is about 4 μm. The method comprises the steps of forming a honeycomb structure by scoring on the inner walls of a main body 11 and a bottom 12, respectively connecting the bottom 12 and a head 13 with the main body 11 to obtain a matrix 1, processing the outer surface of the matrix 1 to enable the outer surface of the matrix 1 to be smooth, wherein the roughness of the outer surface of the matrix 1 is 1.84 microns, forming a surface layer 2 of pyrolytic graphite on the outer surface of the matrix 1, the thickness of the surface layer 2 is 0.3mm, and the roughness of the outer surface of the surface layer 2 is less than 0.8 microns.

Next, 1800cc crucibles were prepared using the molds prepared in example 1, example 2, and example 3, respectively, and oxygen was introduced into the molds using a common gas pipe and a vent pipe in the examples of the present disclosure, respectively, to oxidize the crucibles, thereby releasing the molds. The demold time is shown in table 1 below.

TABLE 1

As can be seen from table 1, under the same other conditions, the time for oxidation using the ventilation tube of the embodiment of the present disclosure is shorter than that using a common air tube to introduce oxygen. The mold having the concave-convex structure 4 on the inner surface has a shorter time for oxidative de-molding than the mold having no concave-convex structure 4.

The above are merely exemplary embodiments of the present disclosure, and the scope of the present disclosure should not be limited thereby. That is, all equivalent changes and modifications made in accordance with the teachings of the present disclosure are intended to be included within the scope of the present disclosure. Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. This disclosure is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

Claims

1. A boron nitride crucible mold, comprising:

and the surface layer is coated on the outer surface of the substrate.

2. The boron nitride crucible mold of claim 1, wherein the inner surface of the base body has a relief structure.

3. The boron nitride crucible mold of claim 2, wherein the relief structure is a thread structure or a honeycomb structure.

4. The boron nitride crucible mold of claim 1, wherein the roughness Ra of the inner surface of the base body is greater than 3.2 μ ι η; the roughness Ra of the outer surface of the substrate is 1.2-3.0 μm.

5. The boron nitride crucible mold of claim 1, wherein the surface layer is made of one material selected from pyrolytic boron nitride, pyrolytic graphite, boron carbide, carbon-doped boron nitride, boron-doped pyrolytic graphite and silicon nitride, the thickness of the surface layer is 0.1-0.5mm, and the roughness of the outer surface of the surface layer is less than 0.8 μm.

6. The boron nitride crucible mold of claim 1, wherein the base body has a constricted portion that forms a groove in a circumferential direction of the base body, and an interface of the head portion with the main body is where an outer diameter of the constricted portion is smallest.

7. A method of preparing a boron nitride crucible mold of claim 1, comprising:

respectively preparing a main body, a bottom and a head;

and forming a surface layer on the outer surface of the substrate.

8. The method for producing a boron nitride crucible mold according to claim 7, wherein machining allowances of 0.1 to 0.8mm are reserved in the production of the main body, the bottom, and the head, respectively, and the outer surface of the base body is finish-machined after the bottom and the head are connected to the main body, respectively.

9. A method for demolding a boron nitride crucible, comprising:

depositing a boron nitride crucible on the outer surface of the mold of any one of claims 1-7;

detaching the head from the body.

10. The method for demolding a boron nitride crucible as recited in claim 9, wherein the temperature of the oxidation is 650 ℃ -800 ℃.