Device for growing single crystals of sapphire

 

The invention relates to the cultivation of molten sapphire crystal by the method of crystallization from the melt. The essence of the invention: a device for growing single crystals of sapphire, containing installed in the vacuum chamber of the crucible with the shaper in the form of a rectangular prism, heater, structurally, reflector, stand under the crucible, heat shields, speed regulation system of lifting the seed crystal and the power of the heater, the shaper is made in the form of sectors formed by a partition in the form of a membrane that is located perpendicular to the faces of the former, or partitions in the form of membranes arranged perpendicular to each other and to the edges of the shaper. The technical result of the device consists in increasing the growth rate and reduce the loss per unit mass of crystals of sapphire, while preserving their quality, and the ability to obtain crystals of a given size. 8 C.p. f-crystals, 3 ill.

The invention relates to a process of growing from a melt of bulk single crystals of sapphire by the method of crystallization from the melt.

A device for the cultivation of monocrystallization with a fixed seed crystal sapphire, the speed regulation system of lifting the seed crystal and the power of the heater.

Structurally with the seed crystal is located on a vertical shaft coaxial with the cylindrical crucible and the shaper (ed.St. NO. 1132606, WITH 30 IN 17/00, 1983).

The disadvantage of this device is the relatively low quality of the crystals due to the presence of inclusions of gas bubbles and blocks for growing single crystal orientation [0001], which are used for cutting plates used in optoelectronics for epitaxy of gallium nitride (GaN) films of ZnO, SiC and other materials.

When cutting a cylindrical single crystal orientation [0001] perpendicular to the axis [1010] of crystals with a diameter of more than 100-150 mm with weight gain crystal output into finished products increases. The performance of the device up to 16 kg fit in a month. The yield does not exceed 50% of the weight of the original download.

A device for growing single crystals of sapphire, which contains installed in a vacuum chamber screens, heater, crucible former, made in the form of coaxially with the seed crystal prism faces which are parallel to crystallographic faces of the latter, shatravka the adjustment of the crystal and the power of the heater. Mainly the seed crystal is made in the form of a rectangular prism, oriented in the direction of [1010], the edges of which coincide with the planes (0001) and (1120), the shaper is made as a rectangular prism, the volume of which is 0,65-0,7 working volume of the crucible, and two side faces shaper parallel to the (0001) plane, and the other two faces shaper parallel to the plane (1120) of the seed crystal, the crucible heater placed inside a cylindrical reflector, the inner diameter of which is of 1.6-1.8, and the height of 0,8-0,9 outer diameter and the height of the crucible, respectively (see EP No. 003419, With 30 In 17/00, 29/00, 09.07.2002, “Method and apparatus for growing single crystals of sapphire by N. Lezcano”). The unit is adopted for the prototype.

This device, convenient operation allows to reduce the inclusion of bubbles in single crystals due to the fact that the crystallographic plane (0001) crystal growth and in contact with the melt does not change its size. This provides the beginnings of layers (levels) of equal size, and, in turn, when these layers are not formed bubbles due to their high coherence.

The possibility of obtaining one C is obtained when the crystal has dimensions, determined by the dimensions of the prismatic shaper (side prism for crystals specified mass must be 300-400 mm), while in industry there is a need in the cylindrical single crystals of various sizes, including a demand for it on a plate obtained by cutting a cylinder of the single crystal with a diameter of about 80 mm

When such required size, you must make cutting rectangular crystal 300300240 mm Additional (deadweight) loss on cutting and polishing is in this case 10% by weight of the crystal.

Another disadvantage is that the growth rate of crystals in the prism, side of which is higher than 100-200 mm, is reduced by 30-40%.

Technical results of the device according to the present invention is to increase the growth rate and reduced losses per unit mass of crystals of sapphire, while preserving their quality, as well as the possibility of obtaining crystals of a given size.

The technical result is achieved in that a device for growing single crystals of sapphire, containing installed in the vacuum chamber of the crucible with the shaper in the form of a rectangular prism, the grow lifting the seed crystal and the power of the heater, according to the invention, the shaper is made in the form of sectors formed by a partition in the form of a membrane that is located perpendicular to the faces of the former, or partitions in the form of membranes arranged perpendicular to each other and faces shaper.

In addition, the side edges of the membranes is rigidly attached to the walls of the shaper; structurally made in the form of a beam or multiple beams, radially arranged and fastened in the center; the seed crystals are attached to the ends of structurally and installed coaxially over the sectors of the shaper; the seed crystal is set coaxially with the shaper; membrane, the shaper and the crucible is made of the same material; the membrane, the shaper and the crucible is made of tungsten, molybdenum or an alloy of tungsten and molybdenum; the membrane is made from a sheet of tungsten with a thickness of 100-300 μm.

The invention consists in the following.

Execution of prismatic formoobrazovateli in the form of secrets leads to membrane walls sectors provide removal of the latent heat of crystallization preventing crystal growth, thereby increasing the rate of growth of Ccih crystals of a given size in one cycle, retaining the benefits of prototype quality crystals, associated with a large mass, but significantly reducing losses on cutting and grinding.

In addition, the execution of the shaper in the form of sectors allows for unloading each sector separately and get more smooth lateral surface, and also, by varying the seed, allows simultaneous growth of crystals of different crystallographic orientation.

Thus, it provides a flexible technology that allows you to expand the range of products and decrease the specific material and energy costs.

To enable the cultivation of a few crystals of different size and orientation is used, depending on the chosen cultivation or structurally located coaxially with the shaper or structurally in the form of a rocker or structurally made in the form of two or more radially arranged and fastened in the center of the rocker.

The use of sheets of molybdenum, tungsten or alloy with the stated thickness for manufacturing shaper and membranes due to structural properties of the material and quality requirements for the orientation when saving requirements for performance, the quality and size of the crystal growth process can be conducted with one seed crystal set in the centre of structurally coaxially with the former, is also divided into sectors.

The device schematically depicted in Fig.1.

Device for growing a single crystal sapphire contains installed in the vacuum chamber 1 by the heater 2, the crucible 3 with the shaper 4, heat-resistant stand 5 under the crucible 3, strukturdaten 6 with the seed crystal, coaxially with the main prism shaper (execution shaper 4 in the form of sectors, as well as the implementation of structurally 6 in the form that allows you to install multiple seed crystals aligned with sectors shaper shown in Fig.2 and 3). The crucible 3 with the shaper 4 and the heater 2 is located inside the cylindrical reflector 7. The camera is placed heat shields 8 and speed regulation system of lifting the seed crystal and the power of the heater (not shown).

In Fig.2 shows the separation shaper one membrane, Fig.3 - separation prism shaper two diaphragms, one of them impaled on another.

The operation of the device is illustrated by the following example.) - Rev. and, separated by a membrane from a tungsten sheets with a thickness of 100 μm to 2 rectangular sector, and the membrane is rigidly attached to the side edges to the walls of the shaper, as shown in Fig.2.

The inner diameter of the crucible is 200 mm, the width of the main faces of the prism shaper respectively 160 and 120 mm

Fill the entire volume of the crucible and sectors shaper original charge, for example, in the form of crushed waste sapphire crystal.

Download the crucible in the chamber 1, placing it on a stand 5 coaxially with the heater 2. Install heat shields 8 and the system power control of the heater and the rate of climb crystals.

Set strukturdaten 6 seed crystals by the number of sectors shaper, as shown in Fig.2 and 3.

The seed crystals are rectangular prisms oriented in the direction of [1010], the edges of which coincide with the planes (0001) and (1120) of each sector shaper.

Since thermal field generated when the device has a strict symmetry relative to the longitudinal axis of the crucible, in which the crystal growth, the process of persecution is the/h

Initial load for growing crystals in 20 kg total yield of the crystal orientation [0001] the most difficult to grow from the point of view of output, amounted to 13.9 kg, i.e. approximately 70%.

When growing, for example, six crystals shaper is divided into rectangular sectors using three membranes and as structurally use three rocker arms arranged radially and stapled in the center.

In this case, the growth rate is 0.2 mm/h and the yield is about 70%.

Thus, the proposed design of the device for growing single crystals compared to the prototype allows to increase the yield of products by approximately 20%, to increase the speed of the growth process, while maintaining the quality of the crystals and the weight of the load.

Claims

1. Device for growing single crystals of sapphire, containing installed in the vacuum chamber of the crucible with the shaper in the form of a rectangular prism, heater, structurally, reflector, stand under the crucible, heat shields, speed regulation system of lifting the seed crystal and the power of the heater, wherein formoobrazovanii shaper, or partitions in the form of membranes arranged perpendicular to each other and to the edges of the shaper.

2. The device under item 1, characterized in that the side edges of the membranes is rigidly attached to the walls of the shaper.

3. Device according to any one of paragraphs.1 and 2, characterized in that at least one of the membranes is performed with at least one vertical recess into which is inserted perpendicular to it located another membrane, the lateral edges of which are attached to the walls of the shaper.

4. Device according to any one of paragraphs.1-3, characterized in that structurally made in the form of a beam or multiple beams, radially arranged and fastened in the center.

5. Device according to any one of paragraphs.1-4, characterized in that the seed crystals are attached to the ends of structurally and installed coaxially over the sectors shaper.

6. Device according to any one of paragraphs.1-3, characterized in that the seed crystal is set coaxially with the shaper.

7. Device according to any one of paragraphs.1-3, characterized in that the membrane, the shaper and the crucible is made of the same material.

8. The device according to p. 7, characterized in that the membrane, the shaper and t is 8, wherein the membrane is made from a sheet of tungsten with a thickness of 100-300 μm.

 

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