Device for growing shaped single crystals

 

The invention relates to the production of single crystals, to a device for growing single crystals from the melt, and can be used to obtain calibrated profiled bulk single crystals, in particular sapphire. The inventive device for growing shaped single crystal on the seed crystal includes a crucible for the melt, a heater and placed in the crucible former, made in the form of a solid cylinder or prism with continuous horizontal channels at the bottom and with the hearing-impaired Central and inclined channels intersecting horizontal channels, the center channel goes to the seed crystal, and inclined channels open onto the side surface in the upper part of the shaper, the heater is made of separate, identical in length and configuration of the U-shaped curved shape of the crucible slats of the calibrated rods of refractory metals and alloys, gathered in a circle or in the section for forming the shape of the shaper. For growing crystals with cubic and hexagonal lattices total number of lamellae in multiples of 12. The invention eliminates the formation of micropores and Malor class="ptx">

The invention relates to the production of single crystals, namely, devices for growing single crystals from the melt, and can be used to obtain volumetric profilirovannyh single crystals, in particular sapphire.

The technical problem solved by this invention is a growing profiled calibrated bulk single crystals of refractory oxides.

Products in the form of plates or washers quality sapphire single crystals used in optics, optoelectronics and as a substrate in planar epitaxial technology. The product parameters depend on the structural perfection of the original crystals, the presence of these impurities, including low temperature, which is manifested in the form of a gaseous discharge (bubbles).

Important factors determining the purity and structural characteristics of single crystals, are structural features of technological equipment (heater, crucible, shaper, etc.,) that directly affect the state of the melt and the growing crystal.

The known device for growing single crystals of refractory oxide on the seed crystal allow you to get the pipe is a device for growing single crystals, includes a crucible for melting with a lid, placed in the crucible formers attached to the cover and having a capillary system (See. Pat. U.S. No. 3687633, CL 23-273, 1972).

To improve performance in the known device increased the number of formers and the size of the crucible.

The disadvantage of the design is unbalanced thermal field, the increase of the melt and therefore the presence of convective flow in the melt in the melting chamber also increases the likelihood of overheating of the melt and the associated presence of bubbles and, as a consequence, the increase of porosity shaped products.

A device for growing single crystals from melt refractory oxides, including the crucible to melt with a lid, placed in it the formers attached to the cover and having a capillary system. To improve the quality of the crystal formers are installed coaxially, and the height of each subsequent shaper, starting with the Central, lower than the previous one.

The crucible is exposed relative to the heater so that the geometric axis of the crucible coincides with thermal axis. The seed crystal is brought to contact with centrolateral, then include the lifting mechanism pulls the device and start the crystallization. First, the melt crystallizes in the tube of smaller diameter and then in follow-up to the last peripheral tube. Due to the different height of the formers is formed isotherm growth coaxial tubular crystals with the lowest temperature in the center (See.Auth.St. The USSR № 1009117, CL 30 In 15/34, publ. 15.08.90).

The shaper in this device has a concave in the direction of growing crystals (products) isotherm, because the product is grown with a high crystallization rate, and the supercooled melt. This is unacceptable for bulk crystal growth of education in this case on the faces of small angle boundaries (blocks with misorientation 1-2).

This device cannot be used for the growth of bulk single crystals, due to the design of the shaper, not providing the necessary temperature regimes.

A device for growing shaped single crystals, including the growing chamber, structurally, the crucible to melt it set the shaper in the form attached to the base of the nozzle with the protrusions; a nozzle connected with verticalmouse (see RF patent № 1591537, With 30 In 15/34, publ. 15.03.94, bull. No. 5).

The device is intended for the cultivation of products having in cross section a complex geometric shape, and may not be used for growth of large bulk single crystals.

A device for growing shaped crystals from a melt, comprising a crucible with lid, set it the former, having a forming element with a hole in the center for persecution and capillaries to supply the melt during growth. Capillaries made in the form of individual tubes arranged in the beam, and forming element is designed as a detachable cap installed on top of him and having inside a through slot, the shape of which conforms to the shape of the grown crystal (see Ed.St. The USSR № 762256, With 30 In 15/34, publ. 30.07.86, bull. No. 28). The unit is adopted for the prototype.

The disadvantage of this device is the large active surface of capillaries made of refractory metals and alloys capable enough of gases under normal conditions, and when heated to highlight that leads to the formation on the surface of the capillaries of a large number of microscopic bubbles. Subsequent withdrawal of their passing the melt is they lack all of the above devices is that they involve the melt flow in the shaper with superheated bottom of the crucible, the surface of which the bubbles are formed and together with the melt penetrates into the shaper and, as a consequence, the presence of pores in the grown single crystals, which is unacceptable for materials used in optoelectronic industry.

The technical result of the claimed invention is the possibility of growing high-quality large-volume calibrated shaped single crystals due to the exclusion of supercooling of the melt in the growing edges and prevent them polycrystals by creating the respective rising edges of the radial isotherms, as well as eliminate the formation of micro-cavities in single crystals due to the separation of melt and bubbles.

This is achieved by a device for growing shaped single crystal on the seed crystal, comprising a crucible for the melt, a heater and placed in the crucible former, according to the invention, the shaper is made in the form of a solid cylinder or prism with continuous horizontal channels at the bottom and with the hearing-impaired Central and sloping channels, U channels open onto the side surface in the upper part of the shaper, the heater is made of separate, identical in length and configuration of the U-shaped curved shape of the crucible slats of the calibrated rods of refractory metals and alloys, and gathered in a circle or in the section for forming the shape of the shaper. For growing crystals with cubic and hexagonal lattices total number of lamellae in multiples of 12.

The invention consists in that the proposed design of the shaper eliminates the ingress of bubbles at the crystallization front. Two horizontal end-to-end channel, located 2-3 mm above the bottom of the shaper, and serve for the entrance of the melt and to trim large bubbles coming from the bottom of the crucible.

Sloping channels are used for separation of small bubbles trapped in the horizontal channels. As the promotion of small bubbles from the melt horizontal channel vertical channel they are shifted to the top horizontal channel, get in sloping channels and beyond shaper. In the vertical channel rises pure melt feeding the growing crystal.

The total cross-sectional area of horizontal channels determines the flow velocity of the melt and the time nahozdeniya time bubbles are in a horizontal channel, the higher the probability of capture of the bubbles in inclined channels, and accordingly the higher the quality of the grown single crystal. This active surface of the channels is reduced relative to the flowing melt.

The essential difference is the execution of a heater in the form of equal length and configuration of the U-shaped slats of the rods of refractory metals and alloys, curved shape to match the shape of the crucible, gathered in a circle or in the section for forming the shape shaper that provides the creation of appropriate profile of the single crystal radial isotherms.

The creation of a thermal field with the appropriate form shaper and the growing profile of the single crystal radial isotherm can significantly improve the structure of the grown single crystals, eliminating the education on the faces of the grown single crystal neutron polycrystals.

Declared a constructive implementation of the shaper and heater together allow us to create conditions for cultivation of different geometry bulk single crystals. To modify the geometry of the single crystal is enough to change the shape of the shaper and the number of slats connected to the current leads.

Awardnominee enhancing qualitative characteristics, that cannot be achieved by known technical solutions. The absence of pores and small-angle boundaries (IAG) can significantly improve the performance of products and increase the yield of products.

Device for growing single crystals is shown schematically in Fig.1.

The device comprises a crucible 1, a heater 2, made in the form of sections of grooved identical in length and configuration of the U-shaped, bent in the shape of the crucible prothoracic slats 3, the shaper 4, made in the form of a solid cylinder (or rectangular prism) of refractory metals (tungsten, tantalum, molybdenum or their alloys. The shaper 4 is installed on the bottom of the crucible. In the lower part of the shaper 4 is performed through a horizontal intersecting channels 5, the Central channel 6, the lower end connecting with the horizontal channels and the upper opening to the seed crystal, sloping channels 7, one end of which connects with a horizontal channels 5, and the other facing the side surface of the shaper 4.

The device operates as follows.

The crucible 1 with melt and placed in it the shaper 4 is placed in the heater 2, is made of tungsten, Pro heater is assembled in sections.

Section of the heater 2 is collected in accordance with the form shaper 4 in such a way that formed in the heater radial isotherm (see Fig.2 a, b, C) corresponds to the shape of the shaper 4, define the profile of the single crystal. This increases the temperature of the melt on the edges of the shaper 4 and eliminates the occurrence of low-angle boundaries on faces of grown single crystal 8. As the single crystal growth melt from the crucible 1 is fed into the shaper 4 horizontal channels 5. Formed on the bottom surface of the crucible bubbles rise up forming the walls of the shaper 4 and come to the surface of the melt. Small bubbles supercritical sizes can suck together with the melt in a horizontal channels 5. As the melt along the horizontal channels 5 to the Central channel 6 microfuze rise to the upper portions of the horizontal channels 5 and before entry into the vertical channel 6 are captured in a separate sloping channels 7 and facing the side surface of the shaper 4. The melt released from the bubbles in the vertical channel 6 is fed to the crystallization front of the growing crystal.

Thus the proposed invention in the second form in terms excluding the formation of micropores and small-angle structural tumors.

The possibility of growing calibrated bulk single crystals allows to increase the output of products and to reduce waste.

Claims

1. Device for growing shaped single crystal on the seed crystal, comprising a crucible for the melt, a heater and placed in the crucible former, characterized in that the shaper is made in the form of a solid cylinder or prism with continuous horizontal channels at the bottom and with the hearing-impaired Central and inclined channels intersecting horizontal channels, the center channel goes to the seed crystal, and inclined channels open onto the side surface in the upper part of the shaper, the heater is made of separate, identical in length and configuration of the U-shaped curved shape of the crucible slats of the rods of refractory metals and alloys, gathered in a circle or in the section for forming the shape of the shaper.

2. The device under item 1, characterized in that for growing single crystals with cubic and hexagonal lattices total number Lama is

 

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FIELD: crystal growing.

SUBSTANCE: crystal growing apparatus comprises double-section chamber, seed holder fixed on rod, crucible, furnace provided with heater assembled on U-shaped lamellas following the crucible outline, centering ring with closed parts of lamellas attached to it, and water-cooled annular current leads. According to invention, furnace is constructed in the form of two heaters similar in shape, mass, and size, which are mirror reflection of each other; closed parts of U-shaped lamellas are attached to centering ring being moved apart to 90°; rod with seed holder is disposed inside upper heater; free ends of lamellas are connected through conducting adapters to current leads with alternation of current charge signs as follows: "++--"; crucible is supported by insulated supports disposed between heater lamellas; conducting adapters are made from refractory material having resistivity lower than that of lamellas; and ends of adapters connected with lamellas are positioned at the same distance from axis of heater.

EFFECT: enabled growing large-size monocrystals and increased their structural perfection due to lack of supercooling of melt and increased service time of units.

6 cl, 2 dwg

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