阅读说明：本技术 一种InSb晶体生长固液界面控制方法及装置 (InSb crystal growth solid-liquid interface control method and device ) 是由 赵超 董涛 于 2019-09-11 设计创作，主要内容包括：本发明提出了一种InSb晶体生长固液界面控制方法及装置,晶体生长装置包括：炉体、容器、加热组件、提拉组件和冷却组件。容器设于炉体内,加热组件用于加热容器,以熔融容器内的原材料。提拉组件可活动地设于炉体内,提拉组件用于将籽晶与容器内熔融的原材料进行熔接,以进行晶体生长。冷却组件靠近晶体设置,冷却组件用于对晶体进行冷却。根据本发明的晶体生长装置,在晶体生长过程中,可以利用冷却组件对晶体进行冷却降温,以控制晶体生长过成中的温度,从而可以对晶体生长时固液界面的形状进行有效控制,使固液界面有效控制为微凸界面,从而可以降低锑化铟晶体的位错密度,提高锑化铟径向电学参数,进而提高锑化铟晶体材料的质量。(the invention provides a method and a device for controlling a solid-liquid interface for InSb crystal growth, wherein the crystal growth device comprises: furnace body, container, heating element, carry and draw subassembly and cooling module. The container is arranged in the furnace body, and the heating assembly is used for heating the container so as to melt the raw materials in the container. The pulling assembly is movably arranged in the furnace body and is used for fusing the seed crystal and the raw material melted in the container so as to grow the crystal. The cooling assembly is disposed proximate to the crystal and is configured to cool the crystal. According to the crystal growth device, in the crystal growth process, the cooling assembly can be used for cooling the crystal to control the temperature of the crystal during growth, so that the shape of a solid-liquid interface during crystal growth can be effectively controlled, the solid-liquid interface is effectively controlled to be a slightly convex interface, the dislocation density of the indium antimonide crystal can be reduced, the radial electrical parameters of indium antimonide are improved, and the quality of the indium antimonide crystal material is improved.)

1. a crystal growth apparatus, comprising:

A furnace body;

the container is arranged in the furnace body, and raw materials are contained in the container;

a heating assembly for heating the container to melt the raw material within the container;

the pulling assembly is movably arranged in the furnace body and is used for fusing the seed crystals and the raw materials melted in the container so as to grow crystals;

a cooling assembly disposed proximate to the crystal, the cooling assembly for cooling the crystal.

2. The crystal growth apparatus of claim 1, wherein the seed crystal is secured below the pulling assembly, the cooling assembly comprising:

A cooling flow passage located within the pulling assembly; and

And the cooling medium flows in the cooling flow channel to cool the crystal.

3. the crystal growth apparatus of claim 1, further comprising:

The heat preservation cover is covered on the container, an opening is formed in the top of the heat preservation cover, and the lifting assembly movably penetrates through the opening.

4. the crystal growth apparatus of claim 3, wherein a top wall of the heat shield is configured as a taper extending toward the container.

5. the crystal growth apparatus of claim 1, wherein the furnace body is provided with a gas inlet above the crystal and a gas outlet below the crystal.

6. The crystal growth apparatus of claim 1, wherein the crystal includes an equal diameter section having a ratio of a diameter to an inner diameter of the vessel in a range of 1: 1.5-1: 4.

7. A solid-liquid interface control method for InSb crystal growth, characterized by performing crystal growth using the crystal growth apparatus according to any one of claims 1 to 6, the crystal growth comprising: seeding stage, shouldering stage, equal-diameter section growth stage and ending stage.

8. The InSb crystal growth solid-liquid interface control method according to claim 7,

In the stage from the seeding stage to the shouldering stage, the crystal is driven to rotate at a first rotation speed by the pulling assembly;

In the shoulder-laying stage to the equal-diameter section growing stage, the crystal is driven to rotate at a second rotating speed by the pulling assembly;

in the stage from the equal-diameter section growth stage to the ending stage, the crystal is driven to rotate at a third rotating speed by the pulling assembly;

wherein the first rotational speed is greater than the second rotational speed, which is greater than the third rotational speed.

9. the InSb crystal growth solid-liquid interface control method according to claim 7,

the container is positioned at a first position in the furnace body from the seeding stage to the shouldering stage;

The container is positioned at a second position in the furnace body from the shouldering stage to the constant-diameter section growing stage;

The container is positioned at a third position in the furnace body from the equal-diameter section growing stage to the ending stage;

Wherein the first position is higher than the second position, which is higher than the third position.

10. The InSb crystal growth solid-liquid interface control method according to claim 7,

in the seeding stage to the shouldering stage, the flow rate of a refrigerant in the cooling assembly is a first flow rate;

In the shoulder-laying stage to the equal-diameter section growing stage, the flow rate of the refrigerant in the cooling assembly is a second flow rate;

In the equal-diameter section growth stage to the ending stage, the flow rate of the refrigerant in the cooling assembly is a third flow rate;

Wherein the first flow rate is less than the second flow rate, which is less than the third flow rate.

Technical Field

the invention relates to the technical field of crystal growth, in particular to a solid-liquid interface control method and a solid-liquid interface control device for InSb crystal growth.

Background

InSb (indium antimonide) is a iii-v group compound semiconductor material, and is used in the fields of thermal imaging, free space communication, optoelectronic integrated circuits, and the like because of its advantages of extremely high electron mobility, very narrow forbidden band width, infrared detection capability, and the like. The material is used for manufacturing a focal plane array detector with a wavelength range of 3-5 mu m on a large scale in the field of infrared detection at present, and the initial unit photosensitive device is developed into a 2048 multiplied by 2048 Focal Plane Array (FPA) at present. Nowadays, as the preparation technology of InSb detectors is matured, the demand for larger-scale and higher-performance detectors is increased, and the larger-size detectors mean that the detectors need to be prepared on larger-size and higher-quality materials, so that the development of larger-size and higher-quality InSb materials is urgent.

Dislocation density and radial electrical parameter uniformity of the InSb crystal are important factors affecting the FPA performance. Where dislocations are discontinuities in the crystal structure, strain fields and/or dangling bond sites may be created, thereby interrupting the transport of charge in the region near the dislocations. This effect can reduce the mobility and minority carrier lifetime at the detector junction, resulting in higher resistance, poor signal-to-noise ratio, and poor uniformity of the detector response in the dislocation regions.

For FPA imaging devices, the performance degradation due to lower wafer quality manifests as dead or dark-spot pixels and pixel clusters, or uneven light response at different parts of the wafer. Non-uniformity of radial electrical parameters can lead to differences in junction depths after PN junction creation, resulting in non-uniform and sometimes unusable properties of the final FPA. Therefore, it is necessary to minimize dislocations in the material and improve radial electrical parameter uniformity.

One of the important causes of dislocation generation is the stress at the growth interface. When the stress is greater than the yield stress, dislocations are generated. The non-uniform distribution of radial electrical parameters in InSb crystals is mainly due to the local "facet" effect, which is particularly severe during InSb crystal growth. The flat solid-liquid interface during crystal growth can minimize growth interface stress and global "facet" effect. However, since a flat solid-liquid interface is extremely unstable during growth and is difficult to maintain all the time, the solid-liquid interface is controlled to have a slightly convex shape, and the solid-liquid interface needs to be carefully controlled during growth to obtain a high-quality InSb material.

the main stream preparation technology of InSb crystal is a Czochralski method. The Czochralski method comprises the steps of filling high-purity raw materials into a hearth, filling hydrogen atmosphere, melting the raw materials filled in a high-purity quartz crucible by using resistance or induction heating, inserting seed crystals into the surface of a melt for welding, slowly lifting the seed crystals upwards, and growing the crystals through the processes of seeding, necking, shoulder rotating, equal-diameter growth, ending and the like. When the InSb crystal grows, no effective solid-liquid interface adjusting method exists due to the special properties of the InSb crystal.

however, the dislocation density and the radial electrical parameter uniformity cannot be effectively reduced in the above method, and the quality of the InSb material is finally affected.

Disclosure of Invention

the invention aims to solve the technical problems of reducing the dislocation density of the indium antimonide crystal, improving the radial electrical parameters of indium antimonide and further improving the quality of the indium antimonide crystal material. The invention provides a method and a device for controlling a solid-liquid interface for InSb crystal growth.

The crystal growth apparatus according to an embodiment of the present invention includes:

A furnace body;

The container is arranged in the furnace body, and raw materials are contained in the container;

A heating assembly for heating the container to melt the raw material within the container;

The pulling assembly is movably arranged in the furnace body and is used for fusing the seed crystals and the raw materials melted in the container so as to grow crystals;

A cooling assembly disposed proximate to the crystal, the cooling assembly for cooling the crystal.

According to the crystal growth device provided by the embodiment of the invention, in the crystal growth process, the crystal can be cooled by the cooling assembly to control the temperature of the crystal during growth, so that the shape of a solid-liquid interface during crystal growth can be effectively controlled, the solid-liquid interface is effectively controlled to be a slightly convex interface, the dislocation density of the indium antimonide crystal can be reduced, the radial electrical parameters of indium antimonide are improved, and the quality of an indium antimonide crystal material is further improved.

according to some embodiments of the invention, the seed crystal is fixed below the pulling assembly, and the cooling assembly comprises:

A cooling flow passage located within the pulling assembly; and

And the cooling medium flows in the cooling flow channel to cool the crystal.

in some embodiments of the invention, the apparatus further comprises:

The heat preservation cover is covered on the container, an opening is formed in the top of the heat preservation cover, and the lifting assembly movably penetrates through the opening.

according to some embodiments of the invention, the top wall of the heat retaining cap is configured as a cone extending towards the container.

according to some embodiments of the invention, the furnace body is provided with a gas inlet and a gas outlet, the gas inlet is located above the crystal, and the gas outlet is located below the crystal.

according to some embodiments of the invention, the crystal comprises an equal diameter section, the ratio of the diameter of the equal diameter section to the inner diameter of the vessel ranging from 1: 1.5-1: 4.

according to the InSb crystal growth solid-liquid interface control method provided by the embodiment of the invention, the crystal growth device is adopted for crystal growth, and the crystal growth comprises the following steps: seeding stage, shouldering stage, equal-diameter section growth stage and ending stage.

According to the InSb crystal growth solid-liquid interface control method provided by the embodiment of the invention, the shape control steps can be designed in a targeted manner according to the solid-liquid interface shape of each stage in the crystal growth process, so that the solid-liquid interface of the whole crystal growth process is stably controlled, and the crystal quality is optimized.

According to some embodiments of the invention, the pulling assembly rotates the crystal at a first rotational speed from the seeding stage to the shouldering stage;

In the shoulder-laying stage to the equal-diameter section growing stage, the crystal is driven to rotate at a second rotating speed by the pulling assembly;

In the stage from the equal-diameter section growth stage to the ending stage, the crystal is driven to rotate at a third rotating speed by the pulling assembly;

Wherein the first rotational speed is greater than the second rotational speed, which is greater than the third rotational speed.

in some embodiments of the invention, the vessel is located at a first position within the furnace body from the seeding stage to the shouldering stage;

The container is positioned at a second position in the furnace body from the shouldering stage to the constant-diameter section growing stage;

The container is positioned at a third position in the furnace body from the equal-diameter section growing stage to the ending stage;

Wherein the first position is higher than the second position, which is higher than the third position.

according to some embodiments of the invention, the flow rate of the refrigerant in the cooling assembly is a first flow rate from the seeding stage to the shouldering stage;

In the shoulder-laying stage to the equal-diameter section growing stage, the flow rate of the refrigerant in the cooling assembly is a second flow rate;

In the equal-diameter section growth stage to the ending stage, the flow rate of the refrigerant in the cooling assembly is a third flow rate;

Wherein the first flow rate is less than the second flow rate, which is less than the third flow rate.

Drawings

FIG. 1 is a schematic view showing the shape of a solid-liquid interface at the time of crystal growth;

FIG. 2 is a schematic structural diagram of a crystal growing apparatus according to an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a crystal growing apparatus according to an embodiment of the present invention;

FIG. 4 is a schematic structural view of a container of a crystal growing apparatus according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a heat-retaining cover of a crystal growing apparatus according to an embodiment of the present invention;

FIG. 6 is a flow chart of a method of growing a crystal according to an embodiment of the present invention.

Detailed Description

To further explain the technical means and effects of the present invention adopted to achieve the intended purpose, the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments.

as shown in FIG. 1, during the growth of the crystal, a solid-liquid interface is formed between the crystal and the melt, and the shape of the solid-liquid interface may be a convex interface, a concave interface, a slightly convex interface, an unstable interface and the like as shown in FIG. 1. In the crystal growth process, such as the growth of InSb (indium antimonide) crystals, a micro-convex solid-liquid interface is maintained, so that the dislocation density can be effectively reduced and the uniformity of radial electrical parameters can be improved, and therefore, in the related technology for improving the quality of InSb materials, no method for effectively controlling the solid-liquid interface of crystal growth is provided.

As shown in fig. 2, a crystal growth apparatus 100 according to an embodiment of the present invention includes: furnace body 10, container 20, heating assembly 30, pulling assembly 40 and cooling assembly 50.

Specifically, the container 20 is provided in the furnace body 10, and the raw material 210 is contained in the container 20. The heating assembly 30 is used to heat the container 20 to melt the raw material 210 within the container 20.

It should be noted that the crystal growth apparatus 100 of the present invention can be used for growth of InSb (indium antimonide) crystals. The container 20 may contain InSb raw material 210, which may be melted to a liquid state within the container 20. It will be appreciated that the invention may also be used for other growths having similar crystals, the InSb crystal growths mentioned above being merely illustrative.

The pulling assembly 40 is movably disposed in the furnace body 10, and the pulling assembly 40 is used for fusing the seed crystal 80 and the raw material 210 melted in the container 20 to grow the crystal 90. The term "movable" as used herein is to be understood as meaning that the pulling assembly 40 can move and rotate within the furnace body 10. For example, when using the apparatus 100 of the present invention to perform InSb crystal growth, the pulling assembly 40 may move the seed crystal 80 to the level of the molten liquid InSb raw material 210 within the vessel 20, fusing the seed crystal 80 to the liquid InSb to perform crystal 90 growth.

A cooling assembly 50 is disposed proximate to the crystal 90, the cooling assembly 50 being configured to cool the crystal 90. It should be noted that the temperature of the crystal 90 can be controlled by cooling the crystal 90 by the cooling assembly 50.

According to the crystal growth device 100 provided by the embodiment of the invention, in the crystal growth process, the cooling component 50 can be used for cooling the crystal to control the temperature during crystal growth, so that the shape of a solid-liquid interface during crystal growth can be effectively controlled, the solid-liquid interface is effectively controlled to be a micro-convex interface, the dislocation density of the indium antimonide crystal can be reduced, the radial electrical parameters of indium antimonide are improved, and the quality of an indium antimonide crystal material is further improved.

according to some embodiments of the present invention, as shown in FIG. 2, a seed crystal 80 may be secured below the pulling assembly 40. Thus, the seed crystal 80 may be moved by the pulling assembly 40 to facilitate growth of the crystal 90. The cooling assembly 50 may include: cooling channel S1 and refrigerant 510.

as shown in FIG. 1, the cooling channel S1 may be located within the pulling assembly 40, and the cooling medium 510 may flow through the cooling channel S1 to cool the crystal 90. For example, the cooling medium 510 may be cooling water or other cooling medium 510 media. The cooling water can circulate in the cooling flow passage S1 in the pulling module 40, and the temperature gradient in the axial direction of the crystal 90 can be controlled by controlling the temperature and flow rate of the cooling water during the growth of the crystal 90, thereby controlling the shape of the solid-liquid interface during the growth of the crystal 90.

in some embodiments of the present invention, as shown in fig. 2 and 5, the apparatus 100 may further comprise: the heat preservation cover 60 is covered on the container 20, the top of the heat preservation cover 60 is provided with an opening 610, and the lifting assembly 40 movably penetrates through the opening 610. As shown in fig. 2, the container 20 may be a crucible, and the heat insulating cover 60 is provided above the crucible. The heat-insulating cover 60 can block the radiation of hot melt from the side wall of the crucible to the crystal 90, improve the axial temperature gradient of the crystal 90, accelerate the conduction of heat in the crystal 90, reduce the radial temperature gradient of the crystal 90, obtain a flat and slightly convex solid-liquid interface and improve the quality of the crystal 90.

according to some embodiments of the present invention, as shown in fig. 5, the top wall of the heat-retaining cover 60 may be configured as a taper extending toward the container 20. Experiments prove that the top wall of the heat-insulating cover 60 is set to be conical extending towards the inside of the container 20, so that the heat-insulating effect of the heat-insulating cover 60 is improved, and the radial temperature gradient of the crystal 90 is reduced, so that the micro-convex solid-liquid interface effect shown in figure 1 is maintained in the growth process of the crystal 90, and the quality of the crystal 90 is improved.

In some embodiments of the present invention, the angle between the top wall of the heat-retaining cover 60 and the side wall of the heat-retaining cover 60 ranges from 0 ° to 60 °. As shown in fig. 5, the angle between the top wall and the side wall of the heat-preserving cover 60 is α, which satisfies the following conditions: alpha is more than or equal to 0 degree and less than or equal to 60 degrees. Through experimental verification, when the following conditions are met: when the alpha is more than or equal to 0 degree and less than or equal to 60 degrees, the processing and the manufacturing of the heat preservation cover 60 are convenient, and the micro-convex solid-liquid interface is favorable for the growth of the crystal 90, thereby improving the quality of the crystal 90.

According to some embodiments of the present invention, as shown in fig. 3, the furnace body 10 may be provided with a gas inlet 110 and a gas outlet 120, the gas inlet 110 being located above the crystal 90, and the gas outlet 120 being located below the crystal 90. For example, when InSb crystal 90 is grown, hydrogen gas may be introduced into furnace body 10 through gas inlet 110, and crystal 90 may be grown in a hydrogen gas atmosphere. Therefore, the crystal 90 can be prevented from being contaminated during growth, and the quality of the crystal 90 is improved.

as shown in fig. 3, the gas inlet 110 may be provided at the top wall of the furnace body 10, and the gas outlet 120 may be provided at the bottom wall of the furnace body 10. It can be understood that the density of hydrogen is relatively low, and the gas inlet 110 is arranged on the top wall of the furnace body 10, and the gas outlet 120 is arranged on the bottom wall of the furnace body 10, so that the furnace body 10 is filled with hydrogen, and the growth quality of the crystal 90 is improved.

in some embodiments of the present invention, during the growth of the crystal 90, gas flows into the furnace body 10 through the gas inlet 110 at a flow rate in the range of 0.02L/min to 10L/min. Experiments prove that when the gas flow rate ranges from 0.02L/min to 10L/min, the corresponding gas atmosphere can be provided for the growth of the crystal 90, and the purging of the crystal 90 and the growth interface caused by gas flow can be weakened, so that the influence of the gas in the furnace body 10 on the solid-liquid interface of the crystal 90 is reduced, and the stability of the solid-liquid interface is improved.

According to some embodiments of the present invention, as shown in FIGS. 2 and 3, crystal 90 may include constant diameter sections having a ratio of diameter to inner diameter of vessel 20, d3/d1, ranging from 1: 1.5-1: 4. it should be noted that the equal diameter section of the crystal 90 can be understood as a cylindrical section of the crystal 90 with equal diameter. The ratio of the constant diameter section of the crystal 90 to the inner diameter of the container 20 is set to be too large, so that the crystal 90 easily touches the container 20 during the growth of the crystal 90, which is not favorable for the growth of the crystal 90. The ratio of the constant diameter section of the crystal 90 to the inner diameter of the container 20 is set to be too small, which is not favorable for controlling the shape of the solid-liquid interface. It was experimentally verified that by setting the range of the ratio of the diameter of the constant-diameter section of crystal 90 to the inner diameter of container 20 to 1: 1.5-1: 4, the growth of the crystal 90 is facilitated, and the shape of the solid-liquid interface during the growth of the crystal 90 is favorably controlled.

According to the InSb crystal growth solid-liquid interface control method provided by the embodiment of the invention, the crystal growth device 100 is adopted for crystal growth, and the crystal growth comprises the following steps: seeding stage, shouldering stage, equal-diameter section growth stage and ending stage.

According to the InSb crystal growth solid-liquid interface control method provided by the embodiment of the invention, the shape control steps can be designed in a targeted manner according to the solid-liquid interface shape of each stage in the crystal growth process, so that the solid-liquid interface of the whole crystal growth process is stably controlled, and the crystal quality is optimized.

according to some embodiments of the present invention, the crystal 90 is rotated by the pulling assembly 40 at a first rotational speed from the seeding stage to the shouldering stage;

in the shoulder-laying stage to the equal-diameter stage, the pulling assembly 40 drives the crystal 90 to rotate at a second rotation speed;

in the stage from the growth stage to the tailing stage of the constant diameter section, the crystal 90 is driven to rotate at a third rotating speed by the pulling assembly 40;

The first rotating speed is greater than the second rotating speed, and the second rotating speed is greater than the third rotating speed.

it should be noted that, as shown in FIG. 2, the pulling assembly 40 may rotate and move the crystal 90 in the up-and-down direction during the growth of the crystal 90. When the rotation speed of the crystal 90 is increased, the solid-liquid interface can be made concave from convex.

during the growth of the crystal 90, the shape of the solid-liquid interface is convex toward the melt at the initial stage of seeding to shouldering, i.e., the convex interface shown in FIG. 1. From the shouldering rear end to the equal-diameter initial stage, the shape of the solid-liquid interface gradually changes from convex to flat, and from the equal-diameter rear stage to the tail stage, the shape of the solid-liquid interface gradually changes from flat to concave, namely the concave interface shown in fig. 2.

in order to keep the solid-liquid interface of the crystal 90 growing in a flat and slightly convex shape during the crystal 90 growing process, i.e. the slightly convex interface shown in fig. 1, the crystal 90 is driven to rotate at a first rotation speed by the pulling assembly 40 from the seeding stage to the shouldering stage; in the shoulder-laying stage to the equal-diameter stage, the pulling assembly 40 drives the crystal 90 to rotate at a second rotation speed lower than the first rotation speed; during the growth phase and the final phase of the constant diameter section, the crystal 90 is pulled by the pulling assembly 40 to rotate at a third rotation speed which is lower than the second rotation speed. Thus, the solid-liquid interface where the crystal 90 grows can be maintained as the slightly convex interface shown in FIG. 1 during the growth of the crystal 90, and the quality of the crystal 90 can be improved.

in some embodiments of the present invention, the container 20 is located at a first position within the furnace body 10 from the seeding stage to the shouldering stage;

In the shoulder-laying stage to the equal-diameter section growing stage, the container 20 is positioned at a second position in the furnace body 10;

From the equal-diameter section growth stage to the ending stage, the container 20 is positioned at a third position in the furnace body 10;

Wherein the first position is higher than the second position, and the second position is higher than the third position.

it should be noted that, as shown in fig. 2, the position of the container 20 can be adjusted by the supporting component 70 during the growth of the crystal 90. When the vessel 20 is positioned higher, a concave solid-liquid interface toward the melt, i.e., the concave interface shown in FIG. 1, is formed due to the greater heat radiation outward from the crystal 90.

during the growth of the crystal 90, the shape of the solid-liquid interface is convex toward the melt at the initial stage of seeding to shouldering, i.e., the convex interface shown in FIG. 1. From the shouldering rear end to the equal-diameter initial stage, the shape of the solid-liquid interface gradually changes from convex to flat, and from the equal-diameter rear stage to the tail stage, the shape of the solid-liquid interface gradually changes from flat to concave, namely the concave interface shown in fig. 2.

In order to maintain the solid-liquid interface of crystal 90 growth in a flat, slightly convex shape during crystal 90 growth, i.e., the slightly convex interface shown in fig. 1, vessel 20 is adjusted to a first, higher position by the support assembly from the seeding stage to the shouldering stage; adjusting the container 20 to a second position of the first position by the support assembly 70 from the shouldering stage to the constant diameter section growing stage; the container 20 is adjusted by the support assembly 70 to a third position lower than the second position from the constant diameter section growing stage to the finishing stage. Thus, the solid-liquid interface where the crystal 90 grows can be maintained as the slightly convex interface shown in FIG. 1 during the growth of the crystal 90, and the quality of the crystal 90 can be improved.

According to some embodiments of the present invention, the flow rate of the cooling medium 510 in the cooling module 50 is a first flow rate from the seeding stage to the shouldering stage;

in the shoulder-laying stage to the equal-diameter section growing stage, the flow rate of the refrigerant 510 in the cooling assembly 50 is a second flow rate;

In the stage from the equal-diameter section growth stage to the tail stage, the flow rate of the refrigerant 510 in the cooling assembly 50 is a third flow rate;

wherein the first flow rate is less than the second flow rate, and the second flow rate is less than the third flow rate.

it should be noted that the axial temperature gradient of the crystal 90 may be adjusted by adjusting the flow rate of the cooling medium 510 in the cooling module 50 during the growth of the crystal 90. As the flow rate of the cooling medium 510 increases, the solid-liquid interface of the crystal 90 during growth transitions from a concave interface to a convex interface.

during the growth of the crystal 90, the shape of the solid-liquid interface is convex toward the melt at the initial stage of seeding to shouldering, i.e., the convex interface shown in FIG. 1. From the shouldering rear end to the equal-diameter initial stage, the shape of the solid-liquid interface gradually changes from convex to flat, and from the equal-diameter rear stage to the tail stage, the shape of the solid-liquid interface gradually changes from flat to concave, namely the concave interface shown in fig. 2.

In order to maintain the solid-liquid interface of the crystal 90 growing in a flat and slightly convex shape during the crystal 90 growing process, i.e. the slightly convex interface shown in fig. 1, the flow rate of the refrigerant 510 in the cooling assembly 50 is a first smaller flow rate from the seeding stage to the shouldering stage; during the shoulder-laying stage to the equal-diameter section growing stage, the flow rate of the refrigerant 510 is increased to a second flow rate larger than the first flow rate; during the equal-diameter stage growth stage to the final stage, the flow rate of the refrigerant 510 is increased to a third flow rate that is greater than the second flow rate. Thus, the solid-liquid interface where the crystal 90 grows can be maintained as the slightly convex interface shown in FIG. 1 during the growth of the crystal 90, and the quality of the crystal 90 can be improved.

the InSb crystal growth method according to an embodiment of the present invention is described in detail below with a specific example:

Firstly, calculating the required raw material 210 amount and crucible size according to the crystal diameter, designing the crucible shape, and keeping the ratio of the diameter of the crystal equal-diameter section to the crucible as 1: 1.5-1: 4.

Then a high-purity isostatic pressing graphite material is selected to manufacture the graphite heat-insulating cover 60, the inner diameter of the heat-insulating cover 60 is equal to that of the graphite crucible, the heat-insulating cover is covered on the graphite crucible, the top of the heat-insulating cover is provided with an opening, the diameter d2 of the opening is 1.5-2 times of the diameter d3 of the isometric section of the crystal 90, the top structure is in an inverted cone shape, the included angle between the top and the side wall of the heat-insulating cover is 0-60 degrees, the heat-insulating cover 60 can block radiation of hot melt from the side wall of the crucible to the crystal 90, the axial temperature gradient of the crystal 90 is improved, the heat in the crystal 90 is. Meanwhile, the heat insulation cover 60 can also reduce the heat radiation of the side surface of the crystal 90 under the heat insulation cover 60, so that the radial shape of a solid-liquid interface is kept.

The top wall of the furnace body 10 is provided with an air inlet 110, and the bottom wall is provided with an air outlet 120. The hydrogen atmosphere is introduced by using the mode of air inlet on the upper surface and air outlet on the lower surface of the furnace body 10, and the gas flow rate is 0.02-10L/min. Because the hydrogen density is low, the method can weaken the purging of the atmosphere flow to the crystal 90 and the growth interface, thereby reducing the influence on the solid-liquid interface of the crystal 90 and improving the stability of the solid-liquid interface. The gas flow rate can prevent the formation of oxidation scum at the solid-liquid interface and can not influence the stability of the solid-liquid interface.

Circulating cooling water is introduced to the seed crystal chuck, and the axial temperature gradient of the crystal 90 can be controlled by controlling the temperature and the flow rate of the circulating cooling water, so that the shape of a solid-liquid interface is controlled. The position of the graphite crucible in the heater is adjusted according to the shape of the solid-liquid interface during the growth of the crystal 90, and generally, when the crucible is at a higher position in the heater, a concave solid-liquid interface toward the melt is formed due to large heat radiation from the crystal 90 to the outside, and conversely, a convex solid-liquid interface toward the melt is obtained. The solid-liquid interface shape can be controlled by controlling the rotation speed of the crystal 90 and the crucible in the growth process, for the growth of the InSb Czochralski method, the rotation speed of the crystal 90 is increased, the solid-liquid interface is changed from convex to concave, the relative rotation speed is reduced, and the liquid level can be flatter. As the crystal transition increases, the interface becomes gradually concave. The effect of increasing the crucible rotation speed is opposite to the effect of increasing the crystal 90 rotation speed.

For example, in the growth process of the InSb crystal 90, the solid-liquid interface has a tendency that the shape of the solid-liquid interface is convex toward the melt in the initial stage from seeding to shouldering, gradually changes from convex to flat in the initial stage from the latter stage of shouldering to the same diameter, and gradually changes from flat to concave in the latter stage to the latter stage.

In order to maintain the flat and slightly convex shape of the solid-liquid interface for crystal 90 growth, the aforementioned process parameters are required to be adjusted according to the shape characteristics of the solid-liquid interface at each stage. The crystal 90 rotation speed is increased in the front section while the graphite crucible is placed in a relatively high position in the heater while the circulating cooling water flow in the seed crystal 80 shaft is reduced to adjust the convex solid-liquid interface to a flat slightly convex solid-liquid interface. The rotation speed of the crystal 90 is gradually reduced in the middle section, while the graphite crucible is gradually lowered, and the flow of the circulating cooling water in the seed crystal 80 rod is gradually increased, thereby maintaining a slightly convex solid-liquid interface. The rotation speed of the crystal 90 is continuously reduced at the rear section, the graphite crucible is continuously and gradually reduced, and the flow rate of the circulating cooling water is continuously and gradually increased, so that the concave solid-liquid interface is adjusted to the flat and slightly convex solid-liquid interface. Finally, the flat and slightly convex solid-liquid interface control in the whole crystal 90 growth process is completed.

in summary, the method for growing a crystal provided by the present invention comprises: seed crystal rotation control, crucible rotation control, heat preservation structure control and the like to form a complete technical scheme. According to the shape of the solid-liquid interface at each stage in the crystal growth process, the shape control step is designed in a targeted manner, the solid-liquid interface in the whole crystal growth process is controlled stably, and the crystal quality is optimized.

While the invention has been described in connection with specific embodiments thereof, it is to be understood that it is intended by the appended drawings and description that the invention may be embodied in other specific forms without departing from the spirit or scope of the invention.