WO2023231259A1

WO2023231259A1 - Thermal field control device for crystal pulling furnace and crystal pulling furnace

Info

Publication number: WO2023231259A1
Application number: PCT/CN2022/122981
Authority: WO
Inventors: 宋振亮; 宋少杰
Original assignee: 西安奕斯伟材料科技有限公司
Priority date: 2022-05-31
Filing date: 2022-09-30
Publication date: 2023-12-07
Also published as: CN114752995A; TWI835330B; TW202302929A

Abstract

A thermal field control device for a crystal pulling furnace and a crystal pulling furnace, the thermal field control device comprising a flow guide cylinder fixedly arranged in the crystal pulling furnace; a heat shielding body consisting of a heat insulating member and the flow guide cylinder and being used for insulating the heat radiated from a silicon melt to a monocrystalline silicon rod, the heat insulating member being arranged between the silicon melt and the monocrystalline silicon rod formed by pulling the silicon melt; and a heat insulating member driver for driving the heat insulating member to move so as to change the distance between the bottom of the heat shielding body and the liquid level of the silicon melt. The heat insulating member is made from a material suitable for mechanical transmission.

Description

A thermal field control device for crystal pulling furnace and crystal pulling furnace

Cross-references to related applications

This application claims priority from Chinese Patent Application No. 202210616029.7 filed in China on May 31, 2022, the entire content of which is incorporated herein by reference.

Technical field

The present application relates to the field of semiconductor silicon wafer production, and in particular to a thermal field control device for a crystal pulling furnace and a crystal pulling furnace.

Background technique

For the production of semiconductor silicon wafers, single crystal silicon rods are usually first produced by direct method, and then slicing, grinding, polishing and possible epitaxial growth can be performed to obtain silicon wafers of the required quality. For direct drawing of single crystal silicon rods, the device used is a crystal pulling furnace. The crucible is placed in the furnace body of the crystal pulling furnace. The high-purity polycrystalline silicon material is contained in the crucible. The silicon melt is obtained by heating, and the seeds are After the crystal is immersed in the silicon melt and undergoes seeding, shoulder setting, equal diameter, finishing, cooling and other processes, a single crystal silicon rod can be finally obtained.

As the semiconductor manufacturing process shortens, the requirements for silicon wafers are getting higher and higher. Generally, silicon wafers without crystal growth defects are required, which requires effective control of crystal growth defects during the process of pulling single crystal silicon rods. According to the V/G theory used to determine crystal growth defects, crystal growth defects in the process of pulling single crystal silicon rods are not only related to the pulling speed V, but also related to the axial temperature gradient G of the single crystal silicon rod, while single crystal silicon The axial temperature gradient G of the rod depends on the thermal field design. Good thermal field design can help single crystal silicon rods to have no growth defects.

The factors that affect the thermal field around the pulled single crystal silicon rod are comprehensive. The heat in the crystal pulling furnace comes from heating the polycrystalline silicon material to melt the solid polycrystalline silicon material into a silicon melt and make the silicon melt. A heater whose body maintains a certain temperature. Therefore, for example, the heat of the heater will be radiated or conducted to the single crystal silicon rod. In addition, since the single crystal silicon rod is drawn from the silicon melt, the silicon melt will also The single crystal silicon rod radiates heat. For another example, the pulled single crystal silicon rod moves through the guide tube in the crystal pulling furnace, so the guide tube will block the heat radiated to the single crystal silicon rod. Therefore, it has become an urgent problem to provide an efficient thermal field control device so that the axial temperature gradient G of the single crystal silicon rod can be accurately controlled, thereby making the single crystal silicon rod free of growth defects.

Contents of the invention

In order to solve the above technical problems, embodiments of the present application are expected to provide a thermal field control device and a crystal pulling furnace for a crystal pulling furnace, which can achieve precise control of the axial temperature gradient of a single crystal silicon rod in a simple and effective manner. , thereby achieving defect-free growth of single crystal silicon.

The technical solution of this application is implemented as follows:

In a first aspect, embodiments of the present application provide a thermal field control device for a crystal pulling furnace. The thermal field control device includes:

The guide tube of the crystal pulling furnace, the guide tube is fixedly arranged in the crystal pulling furnace;

The heat insulating member is disposed between the silicon melt and the single crystal silicon rod drawn from the silicon melt to form a block together with the flow guide tube for blocking the silicon melt from the silicon melt. A heat shield for heat radiated to the single crystal silicon rod, wherein the heat insulator is made of a material suitable for mechanical transmission;

A heat insulating element driver, the heat insulating element driver is used to drive the heat insulating element to move to change the distance between the bottom of the heat shield and the liquid level of the silicon melt and to correspondingly change the distance from the silicon melt. The melt radiates heat to the single crystal silicon rod to obtain the required axial temperature gradient in the single crystal silicon rod.

In a second aspect, embodiments of the present application provide a crystal pulling furnace, which includes the thermal field control device according to the first aspect.

Embodiments of the present application provide a thermal field control device for a crystal pulling furnace and a crystal pulling furnace. The heat shield is disposed between the silicon melt and the single crystal silicon rod. The bottom of the heat shield is in contact with the silicon melt. The distance between the liquid levels is changed, or it is equivalent to changing the heat radiated from the silicon melt to the single crystal silicon rod by moving the heat shield, thereby achieving the control of the single crystal silicon rod in a simple and effective way. The surrounding thermal field is controlled to meet the requirements of the axial temperature gradient of the single crystal silicon rod. Moreover, the guide tube of the crystal pulling furnace is fixedly set, thus avoiding the problem of being made of brittle graphite material. The reason is that it is not suitable for mechanical transmission, otherwise the movement of the guide tube that is prone to breakage is not suitable for achieving the above-mentioned change in spacing.

Description of the drawings

Figure 1 shows a schematic diagram of a thermal field control device according to an embodiment of the present application in a crystal pulling furnace;

Figure 2 is a partial cross-sectional schematic view of a thermal insulation member according to an embodiment of the present application;

Figure 3 is a partial cross-sectional schematic view of a flow guide tube according to an embodiment of the present application;

Figure 4 is a schematic diagram of a crystal pulling furnace according to an embodiment of the present application.

Detailed ways

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application.

Referring to Figure 1, the embodiment of the present application provides a thermal field control device 10 for a crystal pulling furnace 1. For the crystal pulling furnace 1, only its crucible 20 and guide tube 11 are shown in Figure 1. As for other components of the crystal pulling furnace 1, such as the furnace body, heater, etc., those skilled in the art are aware of them and are not shown in Figure 1. The thermal field control device 10 may include:

The flow guide tube 11 of the crystal pulling furnace 1 is fixedly installed in the crystal pulling furnace 1. As known to those skilled in the art, the function of the flow guide tube 11 is to transfer argon gas, for example. A protective gas of the same type is introduced to the liquid level L of the silicon melt SM shown in Figure 1, so as to prevent unnecessary chemical reactions of the silicon melt SM, and during the process of drawing the single crystal silicon rod R , the single crystal silicon rod R will move through the guide tube 11, so the guide tube 11 can shield the heat radiated from the outside to the single crystal silicon rod R. In addition, the guide tube 11 is made of brittle graphite. Made of high-quality materials, it is not suitable for use as a component of mechanical transmission because it is prone to breakage and damage when driven frequently;

Thermal insulation member 12 is disposed between the silicon melt SM and the single crystal silicon rod R drawn from the silicon melt SM to form a barrier together with the flow guide tube 11 The heat shield 10A radiates heat from the silicon melt SM to the single crystal silicon rod R. For example, in FIG. 1 , the heat radiation path schematically shown by the dotted arrow is blocked by the heat shield 10A. Therefore, Heat cannot be radiated to the single crystal silicon rod R, and the heat radiation path schematically shown by the solid arrow below the dotted arrow is not blocked in any way, so the heat from the silicon melt SM will be radiated to the single crystal silicon rod R, Wherein, the material of the heat insulator 12 is different from the material of the guide tube 11, and the heat insulator 12 is made of a material suitable for mechanical transmission;

The heat insulating member driver 13 is used to drive the heat insulating member 12 to move to change the distance D1 between the bottom of the heat shield 10A and the liquid level L of the silicon melt SM. The heat radiated from the silicon melt SM to the single crystal silicon rod R is changed accordingly to obtain the required axial temperature gradient in the single crystal silicon rod R, as can be easily understood with reference to FIG. 1 Yes, when the heat insulator driver 13 drives the heat insulator 12 to move upward, the distance D1 increases, so more heat will be radiated from the silicon melt SM to the single crystal silicon rod R, and when the heat insulator driver 13 drives When the heat insulator 12 moves downward, the distance D1 decreases, so less heat is radiated from the silicon melt SM to the single crystal silicon rod R.

According to the technical solution of the above-mentioned embodiment of the present application, the heat shield 10A is disposed between the silicon melt SM and the single crystal silicon rod R. The distance D1 is changed, or it is equivalent to changing the heat radiated from the silicon melt SM to the single crystal silicon rod R by moving the heat shield 10A, thereby realizing the control of the surroundings of the single crystal silicon rod R in a simple and effective manner. The thermal field is controlled, thereby meeting the requirements of the axial temperature gradient of the single crystal silicon rod R, and the guide tube of the crystal pulling furnace 1 is fixedly set, thus avoiding the passage of the brittle graphite material. Therefore, it is not suitable for mechanical transmission, otherwise the guide tube 11 is prone to breakage to move to achieve the change of the above-mentioned distance D1.

As mentioned above, the heat insulation member 12 is made of a material suitable for mechanical transmission. In an optional embodiment of the present application, the heat insulation member 12 can be made of stainless steel. Steel is a low-cost material. The ductile material is therefore different from graphite, or it will not break even if it is driven frequently and is therefore suitable for mechanical transmission. However, on the other hand, the presence of steel in the crystal pulling furnace 1 may cause metal The introduction of pollution affects the crystal pulling process or may reduce the quality of the pulled single crystal silicon rod R. In this regard, the surface area of the heat insulating member 12 can be smaller than the surface area of the flow guide tube 11. In this way, Compared with using the flow guide tube 11, which is also made of steel, as a moving part to realize the change of the above-mentioned distance D1, the possibility of metal contamination is reduced.

For materials suitable for mechanical transmission, such as the above-mentioned steel, undesirable contamination is often introduced into the crystal pulling furnace 1 due to its presence in the crystal pulling furnace 1. In this regard, in this application In an optional embodiment, referring to FIG. 2 , the heat insulation member 12 may include a body 120 and a coating 121 covering the body 120 . The coating 121 is used to prevent contaminating impurities from the body 120 from escaping. In this way, while ensuring that the heat insulator 12 is suitable for mechanical transmission, the introduction of contamination caused by its material is avoided.

In an optional embodiment of the present application, the heat insulation member 12 can be made of molybdenum. As known to those skilled in the art, metal molybdenum is a conventional material present in the crystal pulling furnace 1, which not only does not introduce pollution but also It has a high thermal radiation reflectivity and can more effectively block the heat from the silicon melt SM.

In an optional embodiment of the present application, referring back to FIG. 1 , the heat insulator 12 can be in the same cylindrical shape as the guide tube 11 , thereby achieving heat isolation for the single crystal silicon rod R more efficiently, and the The inner peripheral wall 12W of the heat insulator 12 extends vertically. As mentioned above, the function of the flow guide tube 11 is to guide the protective gas, such as argon gas, to the liquid level L of the silicon melt SM shown in FIG. 1, so as to prevent unnecessary occurrence of the silicon melt SM. Chemical reaction, therefore, the flow guide tube 11 needs to have a specific shape in order to form a channel that effectively guides the protective gas. Specifically, as shown in FIG. 1, the inner peripheral wall 11W of the flow guide tube 11 has a shape from top to bottom. The tapered portion is therefore easily subject to a large impact force of the protective gas that is guided to flow. When the guide tube 11 is driven to move, it will sway due to the impact force of the air flow. This further causes the connection with the driving device to break due to stress, and even when the shaking amplitude is large, it may collide with the single crystal silicon rod R, causing the single crystal silicon rod R or the guide tube 11 itself to fall. The heat insulator 12 does not need to play the role of guiding air flow, so its inner peripheral wall 12W can extend vertically as mentioned above, thereby avoiding the impact of the flowing protective gas, even if the heat insulator 12 is driven. There will be no shaking when moving. Compared with using the flow guide tube 11 formed with a channel for guiding protective gas as a moving component to achieve the above-mentioned change of the distance D1, component stability is improved and production safety is ensured.

In order to further prevent the heat insulating member 12 from shaking, in an optional embodiment of the present application, still referring to FIG. 1 , the height of the heat insulating member 12 may be smaller than the height of the guide tube 11 . In this way, when the protective gas flows, the "windward surface" of the heat insulating member 12 is further reduced, so the force of the flowing protective gas that the heat insulating member 12 bears is further reduced, thereby further avoiding shaking.

Optionally, when the diameter of the single crystal silicon rod R is 300 mm to 308 mm, see FIG. 1 , the distance between the inner peripheral wall 12W of the heat insulator 12 and the outer peripheral wall of the single crystal silicon rod R is D2 can be between 20mm and 50mm.

Optionally, in the above situation, still referring to FIG. 1 , the distance D3 between the bottom of the flow guide tube 11 and the liquid level of the silicon melt may be between 20 mm and 60 mm. It is easy to understand that, The distance D3 determines the maximum value of the distance D1 between the bottom of the heat shield 10A and the liquid level L of the silicon melt SM, and the minimum value of the distance D1 is determined by the movement of the heat insulator 12, Can be 10mm. When the flow guide tube 11 is fixed, the distance D1 between the bottom of the heat shield 10A and the liquid level L of the silicon melt SM can be changed by changing the distance D3.

In order for the flow guide tube 11 to achieve a thermal insulation effect, in an optional embodiment of the present application, see FIG. 3 , the flow guide tube 11 may include a shell 110 and a thermal insulation material 111 disposed inside the shell. The shell 110 can be made of high-purity graphite, and the outer surface can be covered with a silicon carbide coating. The thermal insulation material 111 can be thermal insulation graphite felt.

Referring to Figure 4, an embodiment of the present application also provides a crystal pulling furnace 1, which may include the thermal field control device 10 described in the previous embodiments of the present application.

As can be easily understood with reference to FIG. 4 , as the single crystal silicon rod R continues to grow, the volume of the silicon melt SM in the crucible 20 gradually decreases. On the one hand, the liquid level L decreases, causing the distance D1 to increase, thereby increasing the distance between the silicon melt and the silicon melt. The heat radiated by SM to the single crystal silicon rod R changes. On the other hand, because there is less silicon melt SM, the heat that the silicon melt SM itself can radiate decreases, which also results in radiation from the silicon melt SM to the single crystal. The heat of the silicon rod R changes, and the combined effect of these two aspects will cause the axial temperature gradient of the single crystal silicon rod R to change, thereby producing crystal growth defects. In the related art, monitoring the distance between the bottom of the flow guide tube and the liquid level of the silicon melt and thereby obtaining the axial temperature gradient required for the single crystal silicon rod is achieved in this way: corresponding monitoring Specifically, a quartz hook is hung at the bottom of the guide tube, a camera is used to capture the reflection of the quartz hook on the liquid surface, and the distance between the quartz hook and the reflection is measured. For control, the crucible is raised and lowered to thereby Ensure that the distance between the bottom of the flow guide tube and the liquid level of the silicon melt meets the requirements for defect-free growth of single crystal silicon rods. However, due to high temperature radiation, liquid level fluctuations, etc., the reflection of the quartz hook on the liquid surface captured by the camera will be very unstable, which will greatly affect the accuracy of monitoring. In this case, the accuracy of the control cannot meet the requirements. , it is difficult to avoid crystal growth defects in single crystal silicon rods. Moreover, since the adjustment of the distance between the bottom of the flow guide tube and the liquid level of the silicon melt must take into account the coordination between the rise of the crucible and the pulling speed of the single crystal silicon rod, otherwise melting back or the single crystal silicon rod will easily occur. This limits the adjustment ability of the above method, especially in the current single crystal silicon rods that are nitrogen-doped to ensure the density of bulk micro defects (BMD). As the nitrogen concentration increases, the single crystal silicon rod ΔG Gradually becomes larger, resulting in a reduction in the defect-free pulling speed area of the single crystal silicon rod. In the actual production process, the adjustment of the distance between the bottom of the guide tube and the liquid level of the silicon melt is not enough to improve the defect distribution in the single crystal silicon rod. , causing crystal growth defects in the silicon rods.

In this regard, referring to Figure 4, in an optional embodiment of the present application, the crystal pulling furnace 1 may also include:

Crucible 20, the crucible is used to accommodate the silicon melt SM;

Crucible driver 30, the crucible driver 30 is used to drive the movement of the crucible 20, as schematically shown by the hollow arrow in Figure 4, to accommodate the crucible in the crucible during drawing of the single crystal silicon rod R. While the amount of silicon melt SM in 20 continues to decrease, the height of the liquid level L of the silicon melt SM is kept constant;

Wherein, the thermal field control device 10 may also include:

Measuring unit 14, the measuring unit 14 is used to measure the moving distance of the heat insulation member 12;

Determining unit 15 , the determining unit 15 is configured to determine the distance D1 between the bottom of the heat shield 10A and the liquid level L of the silicon melt SM based only on the movement distance.

In the above embodiment, the quartz hook and its reflection are no longer used as in the related art, but the distance D1 is accurately obtained simply by measuring the moving distance of the heat insulator 12. When the measurement accuracy can be guaranteed, Accordingly, low control accuracy can be ensured, so the occurrence of crystal growth defects can be avoided. Moreover, by adjusting the movement of the heat insulator 12, a wider adjustment range for the axial temperature gradient of the single crystal silicon rod S can be achieved, and crystal growth defects can be effectively controlled, which is conducive to the growth of the single crystal silicon rod without growth defects. way to grow.

It should be noted that the technical solutions recorded in the embodiments of this application can be combined arbitrarily as long as there is no conflict.

The above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application. should be covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

A thermal field control device for a crystal pulling furnace, the thermal field control device includes:

The guide tube of the crystal pulling furnace, the guide tube is fixedly arranged in the crystal pulling furnace;

The heat insulating member is disposed between the silicon melt and the single crystal silicon rod drawn from the silicon melt to form a block together with the flow guide tube for blocking the silicon melt from the silicon melt. A heat shield for heat radiated to the single crystal silicon rod, wherein the heat insulator is made of a material suitable for mechanical transmission;

A heat insulating element driver, the heat insulating element driver is used to drive the heat insulating element to move to change the distance between the bottom of the heat shield and the liquid level of the silicon melt and to correspondingly change the distance from the silicon melt. The melt radiates heat to the single crystal silicon rod to obtain the required axial temperature gradient in the single crystal silicon rod.
The thermal field control device according to claim 1, wherein the heat insulation member is made of stainless steel, and the surface area of the heat insulation member is smaller than the surface area of the flow guide tube.
The thermal field control device according to claim 1, wherein the thermal insulation member includes a body and a coating covering the body, the coating being used to prevent contaminating impurities from the body from escaping.
The thermal field control device according to any one of claims 1 to 3, wherein the heat insulating member is cylindrical, and the inner peripheral wall of the heat insulating member extends vertically.
The thermal field control device according to claim 4, wherein the height of the heat insulation member is smaller than the height of the flow guide tube.
The thermal field control device according to claim 5, wherein the diameter of the single crystal silicon rod is 300 mm to 308 mm, and the distance between the inner peripheral wall and the outer peripheral wall of the single crystal silicon rod is between 20 mm and 50 mm. between.
The thermal field control device according to claim 6, wherein the distance between the bottom of the flow guide tube and the liquid level of the silicon melt is between 20 mm and 60 mm.
The thermal field control device according to claim 1, wherein the flow guide tube includes a shell and a thermal insulation material disposed inside the shell.
A crystal pulling furnace, which includes the thermal field control device according to any one of claims 1 to 8.