Device for growing single crystals of sapphire

 

The invention relates to the cultivation of the melt bulk single crystals of sapphire and are aimed at increasing the service life of structural elements. The essence of the invention: a device for growing single crystals of sapphire, containing installed in a vacuum chamber heater, crucible former, structurally, heat shields, speed regulation system of lifting the seed crystal and the power of the heater, crucible coaxially with him has an insert made of tungsten, which is made in the form of a bowl, the shape of the crucible, or in the form of a set of rings from tungsten rod vertically and horizontally, while the vertical ring mounted coaxially on top of one another, and a horizontal ring mounted concentrically and closely adjacent to each other. In addition, between the liner into a bowl and Cup set basket; the basket is made in the form of 1-3 pairs of curved along the shape of the liner and sealed at the bottom point of tungsten rods, the ends of which protrude above the upper edge of the crucible and curved outwards; the basket is made of tungsten rods with a diameter of 2-3 mm; a liner in the form of a bowl with a wall thickness of 300-500 μm; a crucible made of an alloy of molybdenum and the ox is

The invention relates to the cultivation of the melt bulk single crystals of sapphire using directional solidification and aimed at increasing the service life of structural elements.

A device for growing monocrystalline ribbons sapphire from the melt on a seed crystal. The surface of the main elements of the device - the crucible of molybdenum and tungsten heater - have-resistant coating, and a coating of tungsten deposited on the outer surface of the crucible, and the coating of the molybdenum carbide on the inner surface of the heater.

The device allows to increase the wear resistance of structural elements. However, its disadvantage is a special process operations for coating of tungsten and molybdenum carbide. Since the inner surface of the crucible is not protected, the known device does not provide prevention of contact of the melt with the crucible, and therefore the inside of the crucible is exposed to a corrosive and quickly lose performance (see and.with. NO. 1213781, WITH 30 IN 15/34, 29/20, 1984).

A device for growing bulk single crystals of sapphire, containing installed in a vacuum chamber N. the rise of the seed crystal and the power of the heater (see A. with. THE USSR №1132606, WITH 30 IN 17/00, 11.08.83. Blacken N. And. and others).

This device, decisive same technical problem that the present invention, taken as a prototype.

This device provides a relatively high yield of the product and its quality. A significant component of the cost obtained with the help of this device single crystals are expensive crucible, often to be replaced due to aggressive impact melt with which the inner surface of the crucible is in direct contact. To some extent the problem of increasing the service life of the crucible decides execution of the most refractory and inert among the appropriate structural materials of metal tungsten, which is used in the prototype. Use as a container material tungsten solves the minimization of impurities in the final product. The service life of the crucible can be increased by increasing the thickness of the sheet from which the crucible is made, however, it becomes economically disadvantageous.

Thus, the disadvantage of this device are high costs associated with high cost of container material of tungsten and insufficient service life of the crucible.

Technical is for sapphire crystal growing method of directional crystallization while maintaining yield and quality of the crystals.

The technical result is achieved in that a device for growing single crystals of sapphire, containing installed in a vacuum chamber heater, crucible former, structurally, heat shields, speed regulation system of lifting the seed crystal and the power of the heater according to the invention in the crucible coaxially with him has an insert made of tungsten, which is made in the form of a bowl, the shape of the crucible, or in the form of a set of rings from tungsten rod vertically and horizontally, while the vertical ring mounted coaxially on top of one another, and a horizontal ring mounted concentrically and closely adjacent to each other.

In addition, between the liner into a bowl and Cup set basket; the basket is made in the form of 1-3 pairs of curved along the shape of the liner and sealed at the bottom point of tungsten rods, the ends of which protrude above the upper edge of the crucible and curved outwards; the basket is made of tungsten rods with a diameter of 2-3 mm; a liner in the form of a bowl with a wall thickness of 300-500 μm; a crucible made of an alloy of molybdenum and tungsten; ring liner bonded to each other, and the upper ring is provided with holders.

The invention of the situation>with the wall of the crucible, while retaining the advantages of contact of the melt with tungsten. As a container material for the crucible becomes possible to use an alloy of molybdenum with tungsten, for example commercially available alloy of composition Mo:W=70:30, without compromising the quality of the product. As well as for the manufacture of liners use cheap tungsten rods or thin sheets, in General, achieved a significant reduction of the consumption of scarce tungsten and reduces the cost of construction.

The use of inserts increases the service life of the crucible composed of an alloy of tungsten and molybdenum in two or more times, or when the same resource is significantly to reduce the thickness of the crucible.

Thus, the use of the liner in the Cup, the shape of the crucible, tungsten sheet with a thickness of 300 μm in a crucible with an external diameter of 175 mm allows to reduce the wall thickness of the crucible from 10 to 5 mm and, respectively, the weight of the crucible about 2 times. The cost of the crucible when it is reduced by 40-50%.

An even higher degree of protection of the inner surface of the crucible is achieved by using a basket of tungsten rods installed between the Cup and the crucible, considering that the cost and consumption bars are small. The total thickness of the walls, on Asia the inner surface of the crucible from the melt, however, there are certain difficulties in the manufacture of the Cup.

If the insert is made of tungsten rings, made of rods with a diameter of 2-3 mm, there is a slight chance of contact of the melt of Al2About3with the wall of the crucible, but the service life of the crucible is still significantly higher than in the absence of a liner. The rings of the required diameter of the standard bars is not difficult, the individual rings can be replaced.

Thus, there is a choice of the production version of the liner, each of which leads to the achievement of the technical result.

The device schematically depicted in Fig.1 and consists of a chamber 1, a heater 2, the crucible 3, shaper with liner 4, coasters crucible 5, structurally 6, the reflector 7, heat shields 8, the speed regulation system of lifting the seed crystal and the power of the heater (not labeled).

Below are examples of the operation of the device.

Example 1. In the crucible of an alloy of molybdenum and tungsten set the basket in the form of a pair of curved along the shape of the liner and sealed at the bottom point of tungsten rods, the ends of which for convenience are over ver). Put the shaper of tungsten sheet and loads the raw material in the form of pieces of crystals of Al2About3with the same mass, as in the prototype. Install heat shields and the reflector, insert and center in structurale the seed crystal, is sealed and pumped to the camera, heated crucible, get a melt down on him the seed crystal and hold the growth of single crystal sapphire. Indicators weight and purity of the obtained crystal gas inclusions correspond to those of the prototype. The molybdenum content in the product does not exceed 3 ppm, which is indicative of a very high quality. The number of cycles in one crucible at a thickness of 10 mm compared with the crucible without liner increases in 2 times, and at a thickness of 5 mm corresponds to the prototype.

Example 2. In the crucible of an alloy of molybdenum and tungsten establish a set of rings from tungsten rod with a diameter of 3 mm At the bottom of the crucible rings are installed concentrically one in the other with decreasing diameter so that they tightly to each other. Then get a set of rings with a diameter corresponding to the inner diameter of the crucible, over the entire height of the crucible (Fig.3) what about the example 1. Get the single crystal sapphire, similar in weight and number of gas inclusions crystal of example 1. The molybdenum content in it is 5 ppm. The service life of the crucible with inlay tungsten rings when the thickness of the walls of the crucible 10 mm 1.8 times higher than without the liner, and at a thickness of 5 mm corresponds to the prototype.

Thus, the claimed device through the use of the proposed materials for the manufacture of crucibles and liners, as well as the proposed design implementation liners can improve the service life of the crucible and to reduce the cost of its manufacture while maintaining yield and quality of the crystals.

Claims

1. Device for growing single crystals of sapphire, containing installed in a vacuum chamber heater, crucible former, structurally, heat shields, speed regulation system of lifting the seed crystal and the power of the heater, characterized in that the crucible coaxially with him has an insert made of tungsten, which is made in the form of a bowl, the shape of the crucible, or in the form of a set of rings from tungsten rod vertically and horizontally, while the vertical ring mounted coaxially one to draw on p. 1, characterized in that between the bearing Cup and the crucible set the basket.

3. The device according to p. 2, characterized in that the basket is made in the form of 1-3 pairs of curved along the shape of the liner and sealed at the bottom point of tungsten rods, the ends of which protrude above the upper edge of the crucible and curved outwards.

4. Device according to any one of paragraphs.2 and 3, characterized in that the basket is made of tungsten rods with a diameter of 2-3 mm

5. Device according to any one of paragraphs.1-4, characterized in that the liner is in the form of a bowl with a wall thickness of 300-500 μm.

6. Device according to any one of paragraphs.1-5, characterized in that the crucible is made of an alloy of molybdenum and tungsten.

7. The device under item 1, characterized in that the ring liner bonded to each other, and the upper ring is provided with holders.

 

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