The method of growing refractory single crystals

 

(57) Abstract:

Use: for refractory single crystal type sapphire, ruby, garnet by the Czochralski method. Seed make the appearance of the melt surface of a single crystal. The stretching is carried out at step increase in speed. The melt is cooled at a rate of 0.5 to 2.0oC/h, and the crystal at a rate of 25 - 50oS/h

The invention relates to the cultivation of refractory crystals of sapphire, ruby, garnet, etc. and can be used at the enterprises of optical, chemical and electronic industries.

A method of obtaining single crystals of sapphire seed [1] However, this method does not allow to obtain single crystals of sufficiently large size and high optical quality.

Closest to the invention is a method of growing single crystals of sapphire seed [2] allows to obtain single crystals with a diameter of 150 MM and weighing up to 10 kg, However, the method lacks flexibility and does not allow to obtain crystals of extremely high quality, because the cooling rate of the crystal is too high and not consistent with the speed of its rise is attained by in the method of growing single crystal type sapphire, including the values of the temperature gradients in the range of 0.05 to 1.0aboutC/mm and the vertical temperature gradients to the radial larger units, vacuum melting of the original charge, making priming and pulling the single crystal from the cooling of the melt, the temperature of depositing the seed set for the emergence of a single crystal with a size of 1-3 mm on the surface of the cooled melt. The speed of pulling of the monocrystal change speed of 0.1 mm/h at the beginning of crystallization to 1.0 mm/h in the final stage of the process.

Thanks to this solution it is possible to more precisely and reliably determine the optimum temperature for depositing the seed into the melt regardless of the composition of the initial mixture and of the presence of impurities: no crystal on the surface of the melt indicates exceeding the optimal temperature level. The result is introduced into the melt, the seed crystal can be melted (at the small diameter of the seed) or crack (with a large diameter seed) or be forced to dramatically slow down the rate of the seed. If on the surface of the melt appears a few crystals or floating pieces of ice, this indicates bonigen the promotion and freezing of the melt.

The dierences between the proposed method, which consists in a stepwise increase in the speed of pulling the single crystal from 0.1 mm/h at the beginning of the process to 1.0 mm/h in the final stage, allow you to create optimum conditions for growth of single crystal. The initial stage of the growth process of the crystal, adjustable exhaust velocity of the seed should proceed much slower than subsequent to form a regular crystal lattice, the exception occurrence of dislocations and blocks and formation of bubbles. In later stages of growth the exhaust velocity of the single crystal should be increased in order to avoid biases of the crystal to the walls of the crucible and result in cracking. Usually one third of the process is conducted at a speed of 0.1 mm/h, and the rest at a speed of 1.0 mm/hour, Such is the nature of the seed crystal pulling creates the most favorable conditions to achieve uniformity and frequency of the single crystal with the minimum duration of the process. It also allows you to use the seed minimum thickness required only to withstand the weight of the future of the crystal. When growing sapphire can come from the calculation of the cross-sectional area of the seed in 10 mm21 kg of the single crystal.

aboutWith/including velocity range is determined by the fact that at higher speeds does not have time to form the correct structure of the crystal lattice and is accompanied by the appearance in the crystal puterea same as crystal. The process is completed by cooling the grown crystal with a temperature reduction rate of the 25-50aboutS/H. With a higher cooling rate in the crystals dramatically increases the likelihood of stress, leading to the formation of dislocations and blocks. Slower speeds do not lead to a noticeable improvement in the quality of the crystals, but lengthen the process.

P R I m m e R. Growing produce in electric furnaces / heaters tungsten rods. As charge use fight crystals grown by the Verneuil method or horizontal directional solidification, or pressed tablets. The crucible with the charge placed in the electric furnace, from which it is evacuated to a residual pressure of 10-4-10-6mm RT.article After melting of the charge to visually control the temperature of the melt, observing the condition of its surface. A seed crystal is dipped into a point of the surface of the melt having a temperature of crystallization of what is judged by the presence on the surface of the melt of crystal unit size 1-3 mm After lowering the seed crystal in the melt and the formation of passages include an automatic lifting of the seed. At the initial stage of the process (in this example, over one-third), the rise of the Vedas, the temperature decrease at a rate of 0.5 to 2.0aboutWith the/including the growing Process is finished, when all the melt zakristallizuetsya. The rise of the seed off and set automatic reduction of temperature with a speed of 25-50aboutC. thus the larger the crystal, the slower the decrease of temperature. For example, 30-35aboutS/h is usually used when the mass of the crystal 12-15 kg, 45-50aboutWith a weight of 5 kg.

The proposed method obtained the sapphire crystal diameter up to 160 mm and weight up to 15 kg of Residual stresses in the crystals do not exceed 10-12 kg/cm2the dislocation density 10-102cm-2. Blocks and bubbles are not present in 85-90% of the crystal volume. Ultraviolet border transparency of 0.14 μm.

The METHOD of GROWING REFRACTORY single crystal type sapphire, ruby, YAG garnet, including vacuum melting of the original charge, the introduction of the seed, the pulling of the single crystal and simultaneously cooling the melt and subsequent cooling of the grown single crystal, characterized in that the temperature of the depositing of the seed set to appear on the melt surface of a single crystal of size 1 to 3 mm, the speed of pulling of the single crystal increases stepwise from 0.1 mm/h at the beginning of pulling up to 1.0 mm/h in Konz the 4 - 50oS/h

 

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FIELD: Czochralski method for crystal growth from melt, in particular crystals of heat-resistant multicomponent compounds.

SUBSTANCE: single crystal lithium aluminate LiAlO2 is obtained by using Czochralski method in inductive heating equipment. Crystal growth process includes batch melting containing lithium aluminate in iridium crucible followed by single crystal drawing from melt onto oriented seed crystal in inert gas atmosphere. Beforehand prepared batch-cake obtained by compounding of aluminum oxide and lithium carbonate, wherein lithium carbonate excess is 2-4 % in respect to stoichiometric ratio, is used as raw batch. Mixture is heat treated in two steps: at temperature 700oC in the first step and at 1050oC in the second one with holding for 3 h in each step. To prevent losses of volatile batch components crystallization is carried out under excess (not less than 0.3 atm) pressure of inert gas, and at the beginning of growth process broader surface square is screened, seed crystal is grown up to diameter equal to 0.8 of crucible one, then crystal is drawn up to desired length while finished diameter is decreased up to 0.5-0.6 of crucible one. As a result reusable crystal part has form of truncated cone. Single crystal lithium aluminate produced according to present invention is useful in disc production served as substrate in epitaxial film growth, in particular gallium nitride (GaN) films.

EFFECT: coarse-grained crystals of high quality.

1 ex, 1 tbl, 1 dwg

FIELD: crystal growth.

SUBSTANCE: method comprises crystal growing in two stages: growing alloyed crystals used for making blanks of seeds made of a disk of a given diameter and approximately 5-6-mm thick and subsequent growing of nominally pure crystals.

EFFECT: enhanced quality of crystals.

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FIELD: crystal growth.

SUBSTANCE: method comprises crystal growing in two stages: growing alloyed crystals used for making blanks of seeds made of a disk of a given diameter and approximately 5-6-mm thick and subsequent growing of nominally pure crystals.

EFFECT: enhanced quality of crystals.

3 dwg

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EFFECT: the invention ensures production of chips with high values of LTMC, high homogeneity of ER and high concentration of oxygen, with a low concentration of defects and increased thermostability and radiation resistance.

2 cl, 4 ex, 1 tbl

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EFFECT: enhanced efficiency; possibility of obtaining growth defects-gas bubbles.

3 cl, 2 dwg, 3 ex

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FIELD: devices for continuous grouped growing of the orientated layers of silicon on a carbonic fabric.

SUBSTANCE: the invention is pertaining to the field of growing of polycrystallic layers from a melt of silicon and may be used in production of solar cells (photo-converters) Substance of the invention: the device consist of a crucible for a melt mounted inside a heater, a substrates connected to gears of their relocation and a capillary feeding mechanism. The substrates are made out of a carbonic reticulated fabric, and the capillary feeding mechanism consists of two horizontal sections, located to the left and to the right of the crucible, each of which has a tail swathed by harnesses out of a carbonic thread. The crucible is made with the bottom hollow elongated spout supplied with an independent heater, under the crucible there is a tank for a drain of the crucible residue, the inner surface of which is coated by a layer of a hexagonal boron nitride, and above the crucible a vibrating feeder for feeding the ground silicon is mounted.

EFFECT: the invention ensures growing of polycrystallic layers from a melt of silicon.

1 dwg

FIELD: devices for continuous grouped growing of the orientated layers of silicon on a carbonic fabric.

SUBSTANCE: the invention is pertaining to the field of growing of polycrystallic layers from a melt of silicon and may be used in production of solar cells (photo-converters) Substance of the invention: the device consist of a crucible for a melt mounted inside a heater, a substrates connected to gears of their relocation and a capillary feeding mechanism. The substrates are made out of a carbonic reticulated fabric, and the capillary feeding mechanism consists of two horizontal sections, located to the left and to the right of the crucible, each of which has a tail swathed by harnesses out of a carbonic thread. The crucible is made with the bottom hollow elongated spout supplied with an independent heater, under the crucible there is a tank for a drain of the crucible residue, the inner surface of which is coated by a layer of a hexagonal boron nitride, and above the crucible a vibrating feeder for feeding the ground silicon is mounted.

EFFECT: the invention ensures growing of polycrystallic layers from a melt of silicon.

1 dwg

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