The way to grow crystals and device for its implementation

 

(57) Abstract:

Refers to the growing of crystals in the form of parts of gas turbine engines. The crucible for the work load melt the mixture doped and flux. Download the charge flux crucible for feed material and the hopper for powdered feed material. Camera with crucibles pumped the air, fill their gas compression with a pressure greater than the elasticity of the most volatile component of the mixture. Melt the mixture in the crucible. The level of recharge melt installed, in which the bypass hole of the connecting pipeline is blocked by a float valve. Vacuum chamber with a working liquid. Vise optical system at the level of the working of the melt in the crucible. Lead a seed crystal into contact with the melt and pulling the crystal. The volume of the melt in the crucible is supported automatically. The resulting homogeneous without gas inclusions crystals of semiconductors and oxide ceramics. 2 S. and 3 C. p. F.-ly, 3 ill.

The invention relates to the field of crystal growth, specifically to methods and devices for the extrusion of melt-porous homogeneous crystals, including methods and ostroski).

Known methods of extrusion from the melt of the crystals, which consists in melting the source material, bringing into contact with the molten salt, the temperature control of the melt and the formation of the seed crystal, the pulling of the seed crystal required length and diameter (1).

A device for implementing this method includes a sealed chamber, a heater in the chamber, the stem of the seed holder is introduced into the chamber, a crucible mounted in the cavity of the heater, vacuum system and fill the chamber with gas, the device for pulling the stem of the seed from the camera.

The disadvantage of this method and device for its implementation is the heterogeneity of the composition along the length of the pulling of crystals resulting from the redistribution generated between the solid phase and the melt of the basic components kristallicheskogo substances, as well as alloying and background impurities.

To increase the degree of homogeneity of the crystals using a programmable change in the process of pulling the growth rate or frequency of rotation of the crystal (2).

A device for implementing this method includes a camera with heater, crucible for replica programmers for changes in the crystallization process, given the laws of speed and pulling speed of the seed formed on the crystal.

However, using the above techniques cannot be averaged over the length of the crystals the concentration of all segregating when extruding the melt components. In addition, changes in the basic growth parameters can adversely affect the microstructure of pulling crystals, on the nature of the distribution of point defects and their clusters.

This lack deprived of the means of extrusion with water, for example, in U.S. Pat. USA N4410494. A more immediate solution adopted for the prototype when developing a new method and device, is [3] . According to the prototype method the crystal is grown on a seed crystal from the melt in the crucible is carried out at optical control and automatic maintaining of the level of the working of the melt by feeding it recharge melt under the pressure of the gas, which Supplement the solid feed material.

Device-prototype [3] contains the camera growth crucible for the work of the melt chamber connected with it by means of the pipeline connecting the camera feed from the crucible to the recharge melt, over which is placed a hopper for solid feed material, vacuum system and gas supply in the camera, the optical system control and the machine is fast availability of gas inclusions in the crystal when carrying out processes at a gauge pressure of gas or non stoichiometry and heterogeneity in crystals of substances with high vapor pressure components if they are pulling in a deep vacuum.

The aim of the invention is to obtain uniform without gas inclusions of crystals containing volatile components.

The objective is achieved by the fact that the space of the working vacuum melt, and above recharge melt support excessive pressure during the whole process of pulling in excess of the equilibrium at the melting point of the crystal, the vapor pressure of the melt components; the level of recharge melt during the extrusion constant support in automatic mode synchronously with the maintenance level of the working of the melt in the solid feed material used powdered material.

The pulling device to achieve this goal contains a valve with a by-pass channel on the connecting piping, and control systems and maintain the operating level of the melt contain an additional element, which is connected with the hopper for solid feed material; a valve connecting pipe is made in the form of float and placed in the crucible to recharge melt.

The above new fashion elements and devices make it possible to obtain a homogeneous without gas inclusions crystals of different substances CL is engaged in the process of pulling the vacuum helps to eliminate gas inclusions in the crystal. The working of the melt, and hence the time of his stay in vacuum is minimized, which minimizes and loss of volatile components of the working of the melt. Above the liquid material feed is created and maintained by the excess pressure of the compression gas, the vast evaporation of the volatile components of this material if the gas pressure exceeds the equilibrium at the melting point of the crystal, the vapor pressure of the melt components not less than 30% . This limit is set experimentally and due to the fact that the liquid material feeding have some overheating relative to the melting point. The upper limit is exceeded, the pressure is almost the same as the bottom and not specifically controlled. To increase this limit is impractical because to a significant reduction of evaporation it does not, and useless heat loss by conduction and convection of the gas increase.

Stabilization of the working volume of the melt increases the homogeneity of the crystal and to reduce the probability of capture crystal gas inclusions. In addition, stabilization of the volume allows the exact calculation of baseline data for the preparation of melts with losses on the COI is Holocene crystal.

Its filling while using solid-phase injection leads to almost complete prevention of ash volatile components, homogenization recharge, a significant decrease in energy for the melting of the original charge. The use of a powder mixture as a solid-phase feed simplifies the drawing process and a device for implementing this process.

Applying a liquid sealing work of the melt and the liquid material feeding using boron oxide promotes uniformity of single crystals of group III arsenides.

The use of the connecting pipe with a valve in the form of a float mounted in the cavity of the crucible for liquid material feeding, and with an overflow hole enables you to reliably divide the space from which the gas is evacuated, and the space filled with gas. The float can be easily downloaded the necessary weight that provides the specified differential pressure in these spaces.

The use of contactless control of the melt level and the electric control mechanism powdered makeup allows you to use them for a wide class of substances, including refractory.

In Fig. 1 pre the liquid-phase makeup work melt; in Fig. 3 is a diagram of the position of the valve parts of the site before the beginning of the drawing process.

The method is implemented using a device that consists of a chamber 1 connected to a vacuum system and the gas-filling (not shown). The camera is placed a heater 2, side screen 3, the crucible 4 for the work of the melt 5. The camera entered holder 6 seed, equipped with a mechanism for vertical movement and rotation (not shown). The primary set secondary camera 7 recharge with heater 8 surrounding the crucible 9 for feeding the material 10. A connecting pipe 11 passes through the bottom of the crucible 9, the cover of the chamber 1 and provided with a valve in the form of float 12 and the bypass hole 13, and the throttle bore 14. In the chamber 7 is introduced to the inlet 15 of the hopper 16 with powder feeding mechanism 17 for filing which is enabled by the signal block with the photoresistor 18 produced by using the optical system 19, which monitors the level of the working of the melt in the crucible 4. Also shown is the screen 20 with managerialism 21 and the sealing liquid 22 working melt and feed material, the seed crystal 23.

The process that implements the proposed method, carry out the following image is Asami and flux for the preparation of sealant layer of the liquid working temperature, if you want to get the single crystal compounds decompose at the melting point. Download the charge and flux crucible 9 and the hopper 16, and the composition of the charge differs from the material composition for the preparation of the working of the melt with regard to segregation phenomena and different evaporation rates of the components of the charge - main and impurity additives.

Camera evacuate the air, fill their gas compression, the pressure of which count obviously larger than the elasticity of the most volatile component of the mixture.

Then melt the charge in both crucibles. The level of the melt and flux (22) in the crucible 9 is set so that the bypass hole 13 of the connecting pipe is blocked by a float 12 (Fig. 3). Vacuum chamber 1 with a work melt 5. Vise optical system 19 on the dividing line of the liquid with the wall of the crucible 4. Complete the crucible 9 from the hopper 16 contribution to the establishment in the crucible of the level shown in Fig. 1. In contact with a work melt lead whet your appetite, regulate the temperature of the heater 2 and is pulled with a constant speed crystal of a given diameter. In the process of pulling the volume of the melt in the crucible is supported automatically. When the level in which the material 10 of the liquid feed. The valve (12) POPs up and opens the bypass hole 13 in the connecting pipe 11, through which the melt flows into the working crucible 4 to complement the work of the melt is consumed for the formation of the pulling of the crystal. Throttling hole 14 in the pipe 11 forms droplets and prevents the overgrowth of the walls of the pipeline connecting the recharge material.

P R I m e R 1. In the crucible with a diameter of 120 mm load 1100 g of gallium arsenide and 100 g ligatures gallium arsenide with The additive at a concentration of 1 wt. % (i.e. 1 g Those 100 g ligatures) to provide a concentration of 5 1017at/cm3donors in the crystal pulling from the work of the melt. In the same pot load of 280 g of boron oxide.

In the chamber 7 download the crucible with a diameter of 50 mm 150 g of gallium arsenide doped with tellurium to a concentration of 5 1017at/cm3and 80 g of boron oxide. Crushed gallium arsenide, alloyed with tellurium, loads the hopper 16. The weight of the load in the hopper 5 kg Pressurized chamber with the loaded charge. Evacuated of air. Fill the chamber and the tank with argon to a pressure of 1.2 n/cm2exceeding 30.5% of the vapor pressure of arsenic above the molten gallium arsenide (0,92 n/cm2) is both crucibles. Vacuum chamber with a working liquid. Complement of the hopper crucible to a specified level. Initial optical part of the device to maintain the level of the dividing line of the liquid with the wall of the crucible for the work of the melt.

Produce the persecution and pulling from the work of the melt during its automatic feeding of single crystal with a diameter of 60 mm and a length of 300 mm Over the entire length of the single crystal doped impurity distribution and concentration (50,5) 1017at/cm3. Gas inclusions in the crystal there.

P R I m m e R 2. All conditions of the process of growing GaAs single crystal with a diameter of 60 mm are the same as in example 1, except that the vacuum as a camera with a working temperature, and the camera with the material feed and hopper. Provide a pressure differential of 0.3 n/cm2. Drift, arsenic and loss of stoichiometry only section of the ingot length 800 mm saves single crystal structure, the rest of the polycrystal. The distribution of The length of the ingot due to volatilisation of this mixture is uneven.

P R I m e R 3. The process conditions as in example 1, except that everywhere, including in the camera work melt establish FAV>. Grow a single crystal with a length of 300 mm, 60 mm in diameter with a uniform distribution. When the cutting of single crystal plates found numerous gas pores.

P R I m e R 4. In the crucible with a diameter of 120 mm and a depth of 12 mm load 550 g of bulk material from the fused block of oxides of the following composition; wt. % : Al2O349,0; ZrO246,9; Y2O34,1. This composition is slightly different from the eutectic and calculated distribution ratio of 1.08 Y2O3in ZrO2between liquid and solid phases.

In the chamber 7 download the crucible with a diameter of 50 mm and a depth of 15 mm material composition, wt. % : Al2O349,1; ZrO246,4; Y2O34,5; load powder of the same composition bunker. Composition calculated with respect to the rate of evaporation from the surface of the melt of oxides: 3,1 10-7cm2with Al2O3and 2.4 10-7g/cm2with Y2O3.

Seal chamber with the charge. Evacuated of air. Fill the chamber and the tank with argon to a pressure of 0.5 n/cm2substantially in excess of the pressure of the volatile oxide - Al2O3( 0,05 n/cm2).

Melt the mixture in both crucibles. Again vaccum chamber with rcoi crucible for the work of the melt. Produce the persecution and pulling from the work of melt replenishment cylindrical ingot with a diameter of 60 mm and a length of about 300 mm (weight 4215 g). On cross-sections and top, middle and bottom parts of the ingot detected homogeneous eutectic structure without gas bubbles with an average composition of oxides, wt. % : Al2O349,04 0,2; ZrO246,55 TO 0.17; Y2O34,45 of 0.25.

The strength of all samples cut from these parts of the ingot and tested in bending, not less than 32 kg/mm2.

P R I m e R 5. The process conditions as in example 4, but when pulling vacuumed both cameras working and make-up. On samples cut from the middle and bottom parts of the ingot grown in the process, discovered the heterogeneity of the microstructure is a large Micronesia space, and on the lower edge and dendrites ZrO2. The strength of specimens in the upper part of the ingot 30 kg/mm2in average < 24 kg/mm2at the bottom < 20 kg/mm2.

P R I m e R 6. The condition for carrying out the process as in example 4, but in the process of cultivation is supported by excess argon pressure of 0.5 n/cm2above the melt in both crucibles - working and makeup. In the grown ingot detected gas pores. practical effectiveness of the proposed invention is it allows to obtain a homogeneous without gas inclusions crystals of substances of different classes, such as, for example, semiconductors and oxide ceramics.

(56) 1. K. - T. Wilke. The growth of crystals. Leningrad : Nedra, 1977, S. 335-336.

2. Romanenko Century. N. The management structure of semiconductor crystals. M. : metallurgy, 1976, S. 266-275.

3. U.S. patent N 4036595, class B 01 J 17/18, 1977.

1. The way to grow crystals, including a crystal is grown on a seed crystal from the melt in the crucible at optical control and automatic maintaining of the level of the working of the melt by feeding it recharge melt under the pressure of the gas, which Supplement the solid feed material, characterized in that, in order to obtain a homogeneous crystals without gas inclusions containing volatile components, the space above the working vacuum melt, and above recharge melt support excessive pressure during the whole process of pulling in excess of the vapor pressure of the melt components, the equilibrium at the melting point of the crystal.

2. The method according to p. 1, characterized in that the recharge level of the melt in the process of pulling maintain constant, EA is the fact that as the solid feed material used powdered material.

4. Device for pulling crystals containing chamber growth crucible for the work of the melt chamber connected with it by means of the pipeline connecting the camera feed from the crucible to the recharge melt, over which is placed a hopper for solid feed material, vacuum system and gas supply in the camera, the optical system control and automatically maintain the level of the working of the melt, characterized in that, in order to obtain a homogeneous without gas inclusions of crystals containing volatile components, a connecting pipe provided with a valve and a by-pass channel, and system control and maintain the level of work melt contain an additional element, connected with the hopper for solid feed material.

5. The device according to p. 4, characterized in that the valve connecting pipe is made in the form of float and placed in the crucible to recharge melt.

 

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4 ex

FIELD: metallurgy.

SUBSTANCE: procedure consists in pulling mono-crystal 10 from melt 13 with specified concentration of basic components in crucible-reactor 15, equipped with orifice or orifices 14 and installed inside main crucible 1, in transfer of crucible-reactor 15 relative to main crucible 1, and in control over their speed of transfer and over change of crystal weight by means of computer 3. At pulling crystal 10 composition of basic components of melt in crucible-reactor 15 and main crucible 1 is controlled by means of comparing the composition, corresponding to temperature registered with thermocouple 11 brought to the crystallisation front of growing crystal 10 and transferred together with crystal 10 in crucible-reactor 15, to the composition of melt corresponding to temperature registered with thermocouple 11 at a moment corresponding to a sharp surge in indications on the curve of change in weight of crystal on weight sensor 7 of growing crystal 10 in crucible-reactor 15. Further, the composition of melt in crucible-reactor 15 is compared to a theoretical composition of melt on phase diagram of condition of basic components. In case of agreement between the determined and theoretical compositions, crystal 10 is pulled at rate Vcr, while crucible-reactor 15 is transferred at rate calculated by formula: where is linear rate of crucible-reactor transfer relative to the main crucible; µ is parametre of replenishment; V1 is weight rate of melt coming from the main crucible into the crucible-reactor, Vcr is weight rate of crystal pulling; So is area of cross section of the main crucible; ρ is density of melt. In case of disagreement between the determined and theoretically calculated compositions of melt in basic components in crucible-reactor 15, there is calculated deficit of weight of the main component, which is added to crucible-reactor 15. Further, there is carried out temperature control and the procedure is repeated to complete agreement of the determined and theoretically calculated composition of melt.

EFFECT: production of crystals with specified composition of main components and with intentionally determined concentration profiles by length of mono-crystal of one or several components of additives.

2 cl, 5 ex, 5 dwg

FIELD: metallurgy.

SUBSTANCE: procedure is based on comparison of current parametres of growth of mono crystals at continuous control of weight and constant speed of crystallisation with results of periodic calculations by mathematic formulas describing non linear processes of motion of heat field and front of crystallisation in volume of crucible and at successive change of process parametres of growth. Here is disclosed complex chart of dependencies on time, weight and pulling speed of growing mono crystal at fore part growing. Charge and scull are degassed in vacuum chamber before charge melting.

EFFECT: production of mono crystals of exceptionally big size of cylinder shape due to elimination of radial non-symmetry of temperature field near front of crystallisation; facilitating structural perfection of mono crystal in whole volume owing to constant speed of crystallisation.

6 dwg, 1 ex

FIELD: metallurgy.

SUBSTANCE: into unit of constants of automatic system of control of process there are input process parameters: reference, job definition and practical data of installation and of process of growth facilitating best qualities of mono crystal. There is determined sufficient complex of process parameters staring from degasification of charge and scull and ending with mono crystal cooling ensuring constant rate of crystallisation, turns of growing mono crystal at specified angles with specified pauses, and also calculation of dependencies facilitating fine partial mechanisms of compensation of deviations in weight of growing mono crystal from theoretical one implemented for the first time to ensure qualitative automatic control. Parameters are input into the unit of constants, comparison and calculation of automatic system of control of process. Corresponding automatic systems are connected and their operation is controlled by means of software for visualisation of process.

EFFECT: generation of mono crystal of perfect structure.

1 dwg, 1 ex

FIELD: metallurgy.

SUBSTANCE: according to one of the versions, there described is formation method of monocrystalline sapphire with r-plane, which involves the following stages: stage at which the device with molten metal is inoculated with inoculum having orientation of r-plane, which is almost parallel to longitudinal axis of hole of shaper and parallel to crystal growth direction; stage at which there crystallised is monocrystalline sapphire above shaper; at that, monocrystalline sapphire has orientation of r-axis, which is almost perpendicular to the main surface of sapphire; stage at which monocrystalline sapphire is passed through the first area having the first temperature gradient of less than approximately 26°C/cm; and further stage at which sapphire is passed through the second area having the second temperature gradient of less than approximately 6.4°C/cm; at that, the first area borders with shaper tip and has the length which is less than approximately half an inch, and the other area borders with the first area.

EFFECT: obtaining monocrystalline material showing the absence of small-angle borders.

25 cl, 11 dwg, 1 ex

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