Thermal insulation system with long service life for silicon carbide crystal growth furnace

Abstract

The invention relates to a thermal insulation system with long service life for a silicon carbide crystal growth furnace. On the basis of composite thermal insulation of soft/hard felts, a C/C composite material is innovatively selected as an innermost layer thermal insulating material, excellent characteristics that the mechanical properties are increased with temperature raised, the linear expansion coefficient is small, the ablative resistance is excellent, the damage tolerance is high, and adhesion does not occur under a high temperatures are utilized, a cylinder with a thickness of 0.5mmis adopted, the upper and lower ends are cut, two fractures exist per round, the fracture width is 1-1.5mm, so that formation of a closed circuit is avoided, because the C/C composite material has anextremely small linear expansion coefficient, the fractures are not closed under a high temperature, and a low obstruction to alternating magnetic field penetration is realized; and damage on thermalinsulation of each layer at an outer side caused by thermal corrosion, thermal shock, chemical corrosion and the like is fully reduced, the overall service life and stability of the thermal insulationsystem are improved, the stability period of a thermal insulation system can be increased from previous 800h to 1500h or more, and people only need to replace an innermost layer thermal insulating soft felt to restore a stable state, and the overall service life is extended by 1 time or more.

Description

technical field [0001] The invention relates to a silicon carbide crystal furnace, in particular to a high-life heat preservation system for a silicon carbide crystal growth furnace. Background technique [0002] The PVT method uses an induction heating single crystal furnace to grow silicon carbide crystals. The crucible (heater) is heated by an induction coil to achieve heat transfer, and the insulation system outside the crucible is used to maintain the temperature of the growth system. Practitioners in this industry know that the morphology, growth rate and quality of silicon carbide crystals are extremely dependent on the thermal field. The thermal insulation performance, stability and life of the insulation system are the decisive factors for the stability of silicon carbide crystal batch growth. [0003] Wrapping C-based insulation materials such as hard insulation felt and soft felt outside the crucible (heater) is a feasible insulation method. First, because the gro...

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Problems solved by technology

[0004] However, C-based thermal insulation hard felt and soft felt may have a shorter lifespan and poor stability

The outer wall of the crucible (outer wall of the heater) is the place with the highest temperature, and the insulation layer at the nearest crucible has been in a high temperature state for a long time, resulting in large thermal shock and large thermal corrosion; when the graphite crucible is at high temperature, the different thermal expansion coefficients between the components cause the internal atmosphere to overflow. The Si component can easily penetrate into the interior of C-based porous insulation (insulation hard felt, insulation soft felt), react with it (Si corrosion), and even crystallize at lower temperature insulation to form silicon carbide, which makes the thermal conductivity of some areas sharply Reinforced, resulting in insulation failure

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