Cold crucible cover for top seed crystal temperature gradient method

Abstract

The invention relates to the field of sapphire crystal growth, and particularly relates to a cold crucible cover for a top seed crystal temperature gradient method. The cold crucible cover comprises at least two ring tungsten plates, wherein the ring tungsten plates are same in outer diameter and different in inner diameter, and the ring tungsten plates are sequentially arranged from top to bottom and from small to large based on inner diameters; a gap is reserved between the ring tungsten plates; the temperature gradient of stable crystal growth is acquired when seed crystals inside a crucible are heated by utilizing the top seed crystal temperature gradient method. The cold crucible cover disclosed by the invention has the advantages of good balance, good stability, flexibility in structural design and good consistency.

Description

technical field [0001] The invention relates to the field of sapphire single crystal growth, and more specifically relates to a cold crucible cover for a top seed crystal temperature gradient method. Background technique [0002] At present, the crucible cover of traditional equipment mostly adopts a single-layer insulation structure, which will take away different degrees of heat due to heat radiation, so that the temperature difference between the vertical and horizontal temperature fields when the crystal grows in the crucible is too large, and the temperature gradient cannot be realized. precise control. [0003] Insufficient existing technology: [0004] 1. The structural design is single, and several layers of cover sheets are pasted together without forming a temperature gradient environment that is more suitable for crystal growth; [0005] 2. If the caliber of the cover plate is too large, the sundries or dirt are more likely to fall into the solution and the shou...

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Problems solved by technology

[0004] 1. The structural design is single, and several layers of cover sheets are pasted together without forming a temperature gradient environment that is more suitable for crystal growth;

[0005] 2. If the caliber of the cover plate is too large, the sundries or dirt are more likely to fall into the solution and the shoulder during the narrow neck and shoulder placement process, which will cause defects such as polycrystalline and enveloping of the crystal;

[0006] 3. The cover plate with a single structure is easy to deform after using a certain number of furnaces, which will make the heat preservation effect worse, which will lead to the instability of the temperature field during the crystal growth process and make it difficult to control the crystal diameter, resulting in large-area long angles in the subsequent crystal growth process. Phenomenon, so that the stress is too large in the process of crystal extraction and annealing, resulting in crystal cracking;

[0007] 4. One of the biggest technical difficulties in growing large-sized sapphire crystals is diameter control, and the larger the size of the grown crystal, the more difficult it is to design its excessive temperature field gradient, and the crucible cover plate with a single structure cannot meet the requirements of large-sized sapphire crystals. Crystal diameter temperature gradient requirements

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