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CN-121228341-B - Boron nitride composite crucible and application thereof in gallium oxide crystal growth

CN121228341BCN 121228341 BCN121228341 BCN 121228341BCN-121228341-B

Abstract

The invention belongs to the technical field of oxide crystal growth, and particularly relates to a boron nitride composite crucible and application thereof in gallium oxide crystal growth. The preparation method is based on a Chemical Vapor Deposition (CVD) technology, adopts gas gradual change and +temperature accurate control to realize gradient coating preparation, sequentially deposits a boron carbide (B 4 C) coating, a boron carbide-pyrolytic boron nitride (B 4 C-PBN) transitional coating and a Pyrolytic Boron Nitride (PBN) coating on the outer side of a graphite inner core, and the prepared boron nitride composite crucible not only reduces the growth cost of gallium oxide crystals, but also solves the problem of unmatched thermal expansion coefficients by virtue of gradient coating design, improves the sealing performance and service life of the crucible, and realizes the high-quality growth of single crystals or polycrystal by adopting a plurality of gallium oxide crystal growth processes such as a reverse molding method, a VB method and the like without modifying the existing heating system.

Inventors

  • ZHENG WEI
  • LIU SHUYUE
  • HE JUNFANG
  • WANG JUNYONG

Assignees

  • 中山大学
  • 北京博宇半导体工艺器皿技术有限公司

Dates

Publication Date
20260512
Application Date
20251016

Claims (8)

  1. 1. The boron nitride composite crucible is characterized by comprising a graphite inner core and a pyrolytic boron nitride coating from inside to outside, wherein a boron carbide coating is arranged between the graphite inner core and the pyrolytic boron nitride coating, and a boron carbide-pyrolytic boron nitride transition coating is arranged between the boron carbide coating and the pyrolytic boron nitride coating.
  2. 2. A method of preparing a boron nitride composite crucible as set forth in claim 1, wherein said method of preparing comprises the steps of: (1) Processing compact graphite raw materials, preparing a crucible inner core, polishing, cleaning and drying to obtain the graphite inner core; (2) Placing the graphite inner core in a CVD reaction furnace, vacuumizing and heating, continuously introducing carbon-containing gas, gradually introducing boron halide, and carrying out heat preservation deposition to form a boron carbide coating; (3) On the basis of continuously introducing carbon-containing gas and boron halide, gradually introducing a nitrogen source, and carrying out heat preservation deposition to form a boron carbide-pyrolytic boron nitride transition coating; (4) Gradually reducing the flow of the carbon-containing gas, keeping the flow of the boron halide and the nitrogen source unchanged, performing heat preservation and deposition to form a pyrolytic boron nitride coating, and taking out the crucible after the temperature is reduced to the room temperature, thus obtaining the boron nitride composite crucible.
  3. 3. The method for preparing a boron nitride composite crucible according to claim 2, wherein in the step (1), polishing means polishing until the roughness Ra is less than or equal to 0.8 μm, cleaning means ultrasonic cleaning with absolute ethyl alcohol and deionized water, the drying temperature is 120 ℃, and the thickness of the graphite inner core is 1-50mm.
  4. 4. The method according to claim 2, wherein in the step (2), the temperature is 1600-2000 ℃, the flow rate of the carbon-containing gas is 50-200sccm, the initial flow rate of the halide gradually introduced with boron is 5-20sccm, the flow rate is increased to 50-100sccm at a rate of every 5sccm/10min, the deposition time is 1-100 minutes, and the thickness of the boron carbide coating is 5-30 μm.
  5. 5. The method according to claim 2, wherein in the step (3), the temperature of the heat preservation is 1700-2000 ℃, the gradual introduction of the nitrogen source is that the initial flow is 10-30sccm, the initial flow is increased to 100-200sccm at a speed of 10sccm/10min, the deposition time is 2-8 hours, and the thickness of the boron carbide-pyrolytic boron nitride transition coating is 10-50 μm.
  6. 6. The method for producing a boron nitride composite crucible according to claim 2, wherein in the step (4), the deposition time is 5 to 20 hours, the cooling rate is 5 to 20 ℃ per hour, and the thickness of the pyrolytic boron nitride coating is 0.1 to 2mm.
  7. 7. A method for growing gallium oxide crystals using the boron nitride composite crucible of claim 1, comprising the steps of: 1) The preparation of a crucible, namely cleaning the crucible and filling gallium oxide polycrystalline raw materials; 2) Atmosphere control, namely placing the crucible in a growth furnace, vacuumizing and then filling inert gas; 3) Heating and melting, namely completely melting the raw materials by induction heating; 4) Crystallization, namely realizing crystal growth by adopting a reverse mould method or a VB method; 5) And cooling to obtain crystal, namely taking out the crystal after gradient cooling, and carrying out post-treatment.
  8. 8. The method for growing gallium oxide crystals according to claim 7, wherein, The VB method has the technological parameters of heating to 1750-1850 ℃, preserving heat for 2-4 hours, having an axial temperature gradient of 5-15 ℃ per cm and a crucible descending speed of 1-3mm per hour; the technological parameters of the reverse molding method are that the preheating temperature of the mold is 1000 ℃, and the injection rate of the melt is 5-10mL/min.

Description

Boron nitride composite crucible and application thereof in gallium oxide crystal growth Technical Field The invention belongs to the technical field of oxide crystal growth, and particularly relates to a boron nitride composite crucible and application thereof in gallium oxide crystal growth. Background Gallium oxide is used as a third generation wide bandgap semiconductor material, has important application value in the field of high-frequency, high-voltage and high-temperature resistant electronic devices, and the growth quality of crystals (especially single crystals) of the gallium oxide is closely related to the crucible. At present, the crucible technology in the gallium oxide crystal growth field has the following key problems: in the prior art, an iridium crucible (such as Chinese patent CN113774484B and Chinese patent application CN 120575323A) is often adopted, iridium is used as rare noble metal, so that the crystal growth cost is directly high, when the oxygen concentration exceeds 10%, the iridium can undergo oxidation reaction, weight loss is generated during each use, and the production cost is further increased. Resulting in expensive and fragile precious metal crucibles. Some schemes adopt pure ceramic crucible (such as zirconia crucible and boron nitride crucible in Chinese patent application CN 118422314A) to replace iridium crucible, but ceramic material can not induce high-frequency electromagnetic field, heating efficiency is low, preheating device is needed to be additionally arranged, and heating system has complex structure and high energy loss. In order to meet the induction heating requirement, a part of schemes adopt a combined crucible (such as a Chinese patent application CN 120099622A) with a graphite substrate and a ceramic coating, but effective sealing is difficult to form among different materials, oxygen is easy to diffuse to the graphite layer at high temperature to cause oxidation, so that the service life of the crucible is shortened, and meanwhile, the interlayer interface of the traditional combined crucible is obvious, the thermal expansion coefficients are not matched, and the problems of cracking and falling easily occur. Part of the crucible adopts a spraying technology to prepare an inner coating (such as the atmospheric plasma spraying of Chinese patent application CN 118460950A), but the spraying coating has poor compactness, can not effectively isolate a melt from a substrate, needs subsequent annealing and polishing treatment, has complex process and low production efficiency. In summary, the existing crucible technology is difficult to simultaneously meet the growth requirements of gallium oxide crystals with low cost, high heating efficiency, high sealing performance and long service life, and development of a novel crucible and a matched growth method thereof is needed. Disclosure of Invention In order to overcome the defects in the prior art, the invention provides a boron nitride composite crucible and application thereof in gallium oxide crystal growth. According to the invention, the interlayer interface is eliminated through the gradient coating design, the problem of mismatch of thermal expansion coefficients is solved, the tightness and the service life of the crucible are improved, and the boron nitride composite crucible is compatible with a plurality of processes such as a reverse molding method, a VB method and the like, realizes high-quality growth of single crystals or polycrystal, and does not need to modify the existing heating system. And the boron nitride composite crucible is adopted to replace an iridium and other expensive crucible, so that the growth cost of gallium oxide crystals is obviously reduced. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: The first aspect of the present invention provides a boron nitride composite crucible comprising, from the inside to the outside, a graphite inner core and a Pyrolytic Boron Nitride (PBN) coating. Further, a boron carbide (B 4 C) coating is also included between the graphite core and the Pyrolytic Boron Nitride (PBN) coating. Further, a boron carbide-pyrolytic boron nitride (B 4 C-PBN) transitional coating is further arranged between the boron carbide (B 4 C) coating and the Pyrolytic Boron Nitride (PBN) coating, and internal stress caused by difference of thermal expansion coefficients is weakened through the transitional coating. Wherein, the thermal expansion coefficients of the materials of each layer in the boron nitride composite crucible are shown in the following table 1: TABLE 1 MaterialGraphiteBoron carbideBoron carbide/pyrolytic boron nitridePyrolytic boron nitrideCoefficient of thermal expansion (10 -6 mm/°C)43.73.22.6 As an induction heating body, the graphite inner core is made of compact graphite, the thickness of the graphite inner core is 1-50mm, the resistivity of the graphite inner core is matched with that of the exis