TWI622673B - Drawing mechanism of ingot growing furnace - Google Patents

Abstract

The invention provides a crystal pulling mechanism of a crystal pulling furnace, comprising: a heat shield reflector, located above the crucible, forming a central opening around the crucible, and passing a crystal ingot grown by the melt in the crucible through the central opening. A seed crystal clip, which is located above the crucible, is provided with a fixed structure to hold the seed crystal; a pulling component, which is connected to the seed crystal clip, and controls the seed crystal to be clamped to pull the crystal ingot from the melt in the crucible Lifting or lowering in the direction; wherein the seed crystal holder has a laterally extending portion perpendicular to the pulling direction, and the projection cover of the seed crystal sandwiching on a plane perpendicular to the pulling direction is covered by a crucible The projection of the ingot grown by the melt on the plane. The crystal pulling mechanism of the invention makes the thermal field at the top of the ingot more stable, significantly improves the uniformity and internal defects of the front end portion of the ingot, and also reduces heat loss, saves energy, and reduces costs.

Description

Crystal pulling mechanism of crystal pulling furnace

The invention relates to the technical field of wafer manufacturing, in particular to a crystal pulling mechanism of a crystal pulling furnace.

In the wafer manufacturing process, a single crystal semiconductor material is usually manufactured by a Czochralski (CZ) method, such as pulling and growing a single crystal silicon ingot. The process of the pulling method is generally: melting a polycrystalline semiconductor raw material such as polycrystalline silicon in a crucible, and then lowering the seed crystal to the molten polycrystalline semiconductor raw material and then slowly raising it to grow a single crystal ingot on the basis of the seed crystal. When growing the ingot, the upper tail cone is formed by reducing the pulling speed and / or the melt temperature, thereby expanding the ingot diameter until the target diameter is reached. After reaching the target diameter, the cylindrical body of the ingot is formed by controlling the pulling speed and the melt temperature. Near the end of the growth process and before the crucible becomes empty, the diameter of the ingot is reduced to form a lower tail cone. The lower tail cone leaves the melt to obtain the final ingot of the semiconductor material.

The crystal pulling furnace usually includes a furnace cavity, a crucible located in the furnace cavity, crucible heating components, a seed crystal holder, and a pulling mechanism. The crucible carries and melts polycrystalline semiconductor raw materials. The crystal clamp is raised and lowered, thereby pulling out a single crystal ingot on the basis of the seed crystal.

The temperature environment around the solidification and cooling of the crystal in the crystal pulling furnace has a great influence on the uniformity of the ingot and internal defects. In order to improve the quality of single crystal semiconductor materials and reduce internal defects, some crystal pulling furnaces are equipped with a thermal mask device, which is positioned on the surface of the melt in the crucible. To save the heat at the interface between the ingot and the melt material and prevent it from being lost from the melt surface. These thermal shields usually include a reflector, which forms a central opening around the crucible above the crucible to allow the ingots grown by the melt to pass through. The patent document published as CN1272146A discloses a thermal shield for a crystal pulling furnace, which surrounds a single crystal blank grown from a crucible filled with semiconductor melt raw materials in the single crystal furnace. The thermal shield includes a reflector having a size and shape that surrounds the central opening of the growing blank to reduce heat transfer from the crucible.

However, even in the existing crystal pulling furnace, even if a thermal masking device is installed, a section of crystal about 500 mm in front of the ingot still has many defects and poor uniformity, which is difficult to meet product quality requirements and is wasted.

In view of the above-mentioned conventional technology, an object of the present invention is to provide an improved crystal pulling mechanism of a crystal pulling furnace, which is used to solve the problem that there are many defects and uniformity when drawing the front end of the crystal ingot from the crystal pulling furnace in the conventional technology. Poor and so on.

In order to achieve the above object and other related objects, the present invention provides a crystal pulling mechanism of a crystal pulling furnace. The crystal pulling furnace includes a furnace cavity and a crucible located in the furnace cavity. The crystal pulling mechanism includes a thermal shield reflector. It is located above the crucible and forms a central opening around the crucible, so that the crystal ingots that are grown by the melt in the crucible pass through the central opening; the seed crystal clamp is located above the crucible and is provided with a fixed The structure holds the seed crystal; a pulling component is connected with the seed crystal clamp, and controls the seed crystal to be lifted or lowered in the pulling direction of the ingot grown by the melt in the crucible; wherein, the The seed crystal holder has a laterally extending portion perpendicular to the pulling direction, and a projection of the seed crystal sandwiching on a plane perpendicular to the pulling direction covers an ingot pulled and grown by the melt in the crucible. A projection on the plane.

As mentioned above, the crystal pulling mechanism of the crystal pulling furnace of the present invention has the following beneficial effects: The crystal pulling mechanism provided by the present invention is configured with a seed crystal holder having a large lateral size, and when the crystal ingot is pulled and grown, the crystal can be made The thermal field for solidification and cooling is more stable, which can improve the uniformity of the ingot and reduce internal defects.

On the one hand, although the existing thermal shield reflector can save the heat at the interface between the ingot and the melt material, since pulling the growing ingot requires space in the pulling direction, it cannot be used to grow the ingot. The front part is insulated, and the lateral large-sized seed crystal clamp proposed by the present invention can play a role of reflecting heat on the top of the ingot, and solves the problem of more heat dissipation in the early stage of ingot growth. The cavity will be evacuated and then filled with high-purity argon to maintain a certain pressure range. When the crystal ingot is drawn, the argon gas flow has a large effect on the thermal field of crystal solidification and cooling. The large horizontal size proposed by the present invention The seed clamp can play a role in shunting the flow of argon gas, which makes the temperature environment above the melt more stable.

The crystal ingot obtained by using the improved crystal pulling mechanism of the present invention has a more stable thermal field at the top of the crystal ingot and a better heat preservation effect. Therefore, the uniformity and internal defects of the front end of the ingot are significantly improved, and the crystal quality of the front end of the ingot is improved. To avoid waste caused by the ingot front end difficult to meet product quality needs, at the same time reduce heat loss, save energy and reduce costs.

1‧‧‧furnace

2‧‧‧ crucible

3‧‧‧ Heat Mask Reflector

4‧‧‧seed clip

5‧‧‧lifting parts

Figures 1a-1c are schematic diagrams showing the initial stage of pulling and growing an ingot using a conventional pulling furnace.

FIG. 2 is a schematic diagram of a crystal pulling mechanism of a crystal pulling furnace according to an embodiment of the present invention.

Figures 3a-3c are schematic diagrams showing the initial stage of pulling and growing an ingot using the crystal pulling mechanism of the present invention.

The following describes specific embodiments of the present invention through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention through the content disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the case of no conflict, the following embodiments and features in the embodiments can be combined with each other.

It should be noted that the illustrations provided in the following embodiments are only a schematic illustration of the basic idea of the present invention, and the drawings only show the components related to the present invention and not the number, shape and For size drawing, the type, quantity, and proportion of each component can be changed at will in actual implementation, and the component layout type may be more complicated.

In the existing crystal pulling furnace, even if a thermal shielding device is installed, a section of crystals about 500 mm in the front end of the ingot still has many defects and poor uniformity, and it is difficult to meet product quality requirements and is wasted. The inventors have studied the reason and found that although the existing thermal shield reflector can save the heat at the interface between the ingot and the melt material, since the growth of the ingot needs to leave space in the pulling direction, it cannot be used for The front part of the ingot grows warm. At the beginning of pulling and growing the ingot, the top of the ingot will dissipate heat quickly, and when the crystal pulling furnace is in operation, the furnace cavity will be evacuated and then filled with high-purity argon to maintain a certain pressure range. The argon gas flow has a large effect on the top of the ingot, which makes the temperature environment for the solidification and cooling of the crystal complicated. Therefore, even with the protection of a thermal mask device, some crystals at the front of the ingot still have internal defects due to the instability of the cooling environment. And poor uniformity.

The initial environment for growing the ingot by using the existing crystal pulling furnace is shown in Figs. 1a-1c, where the dotted arrow indicates the argon gas flow and the solid arrow indicates the heat. On the reflector Under the mask, the heat is only radiated to the surface of the melt; as the seed crystal is pulled upward to form the upper tail cone, the surface of the upper tail cone leaves the melt surface and heat dissipation is intensified, while the surface of the upper tail cone is exposed to downward argon gas. Airflow effect; when the upper tail cone continues to pull upwards and start to form the cylindrical body of the ingot, the downward argon gas flow is shunted on the surface of the upper tail cone to the side wall of the ingot to form a complex temperature environment. Under such a cooling environment, The front section of the cylindrical body of the ingot is difficult to meet the production quality.

In order to solve the above problems, the present invention improves the existing crystal pulling furnace.

Referring to FIG. 2, an embodiment of the present invention provides a crystal pulling mechanism of a crystal pulling furnace. The crystal pulling furnace includes a furnace cavity 1 and a crucible 2 located in the furnace cavity 1. The crystal pulling mechanism includes a thermal shield. The reflector 3 is located above the crucible 2 and forms a central opening around the crucible 2 so that the ingots grown by the melt in the crucible 2 pass through the central opening; the seed crystal clip 4 Is located above the crucible 2 and is provided with a fixed structure to hold the seed crystal; a pulling part 5 is connected to the seed crystal clip 4 and controls the seed crystal clip 4 along the melt in the crucible 2 The pulling direction of the pulling growth ingot is raised or lowered by the pulling member 5; wherein the seed crystal holder 4 has a laterally extending portion perpendicular to the pulling direction, and the seed crystal holder 4 is vertical The projection on the plane in the pulling direction covers the projection on the plane of the ingot grown by the melt pulling in the crucible 2 on the plane.

The heat shield reflector 3 may be single-layered or multi-layered, may be a flat plate type, may have a shape with a certain arc, or other suitable shapes and structures. The heat shield reflector 3 is used for heat insulation and reflection of heat, and a heat insulation material can be used to reduce heat loss.

The central opening formed by the heat shield reflector 3 around the crucible 2 is generally circular, and its diameter is slightly larger than the diameter of the ingot grown by the melt in the crucible 2. For example, its straight The diameter may be about 1.1 times the diameter of the ingot.

As a preferred solution of this embodiment, the projection of the seed crystal clip 4 on a plane perpendicular to the pulling direction covers the central opening formed by the thermal mask reflector 3, so that the seed crystal clip 4 With the cooperation of the heat shield reflector 3, the effect of stabilizing the temperature environment around the crystal is better.

Specifically, the fixing structure holding the seed crystal may be disposed at the center of the seed crystal clip 4. The projection of the seed crystal clip 4 on a plane perpendicular to the pulling direction may be a circle, a square, or other suitable shapes, and the embodiment is preferably a circle. The diameter of the circle is greater than or equal to the diameter of the ingot grown by the melt in the crucible 2. Alternatively, the diameter of the circle is greater than or equal to the diameter of the central opening formed by the heat shield reflector 3.

For example, a circular plate-shaped seed crystal clamp may be used, and the seed crystal is fixed at the center of the seed crystal clamp. The fixed structure of the seed crystal, the thickness of the seed crystal clamp, and other detailed structures may be designed according to actual needs, which is not limited in the present invention.

Specifically, the seed crystal clip 4 may be selected from a material having high temperature resistance and a certain strength. For example, the material of the seed crystal clip 4 may be selected from molybdenum (Mo), nickel (Ni), tungsten (W), and alloys thereof. , Or high melting point, high strength materials such as graphite, or other suitable materials.

Specifically, the furnace cavity 1 is filled with a protective gas. The protective gas may be argon.

Compared with the conventional crystal pulling furnace, in order to stabilize the temperature environment at the beginning of the ingot growth, the present invention uses a seed crystal holder with a large lateral size. The seed clip is used to shield heat dissipation and shunt argon. Under the protection of the large size seed clip, the thermal field of crystal solidification and cooling is more stable, which can improve the uniformity of the ingot and reduce internal defects.

The initial environment for pulling and growing the ingot using the crystal pulling mechanism of this embodiment is shown in Figs. 3a-3b, where the dashed arrow indicates the argon gas flow, and the solid arrow indicates the heat. Under the shield of the reflector, the heat is only radiated to the surface of the melt, and the large-sized seed crystal covers the top surface of the crucible, which can cause the effect of reflecting heat on the top of the ingot. Many problems; as the seed crystal is pulled upward to form the upper tail cone, the surface of the upper tail cone leaves the surface of the melt. Under the large size seed clip cover, the thermal environment around the upper tail cone does not change much, and the heat is dissipated. It is still less. The downward argon gas flow is blocked by the large-sized seed crystal clip. When the upper tail cone continues to pull upwards and starts to form the cylindrical body of the ingot, the downward argon gas flow is blocked by the large-sized seed crystal. The flow is split to the side wall of the ingot, forming a relatively stable thermal field, so that the entire growth process of the cylindrical body of the ingot is in a stable and consistent temperature environment, so the uniformity of the front end portion of the ingot and internal defects are significantly improved.

In summary, the crystal pulling mechanism provided by the present invention is provided with a seed crystal holder having a large lateral size. When the crystal ingot is pulled and grown, the thermal field for crystal solidification and cooling can be more stable, thereby improving the crystal ingot. Uniformity, reducing internal defects. The crystal ingot obtained by using the improved crystal pulling mechanism of the present invention has a more stable thermal field at the top of the crystal ingot and a better heat preservation effect. Therefore, the uniformity and internal defects of the front end of the ingot are significantly improved, and the crystal quality of the front end of the ingot is improved. , To avoid the waste caused by the ingot front end difficult to meet product quality needs, while also reducing heat loss, saving energy and reducing costs.

Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

The above-mentioned embodiments merely illustrate the principle of the present invention and its effects, but are not intended to limit the present invention. Anyone familiar with this technology can work without departing from the spirit and scope of the present invention. Next, the above embodiments are modified or changed. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field to which they belong without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the scope of patent application of the present invention.

Claims (9)

A crystal pulling mechanism of a crystal pulling furnace. The crystal pulling furnace includes a furnace cavity and a crucible located in the furnace cavity. The crystal pulling mechanism includes a thermal shield reflector located above the crucible, and Surround the crucible to form a central opening, so that the ingots that are grown by the melt in the crucible pass through the central opening; a seed crystal clamp is located above the crucible, and the seed crystal is clamped There is a fixed structure to hold the seed crystal; a pulling component connected to the seed crystal clamp, and controlling the seed crystal clamp to be pulled along the pulling direction of the ingot grown by the melt in the crucible The lifting component is raised or lowered; wherein the seed crystal holder has a laterally extending portion perpendicular to the pulling direction, and the projection of the seed crystal holder on a plane perpendicular to the pulling direction covers The projection of the ingot grown by the melt in the crucible on the plane. The crystal pulling mechanism of the crystal pulling furnace according to claim 1, wherein the projection of the seed crystal sandwiched on a plane perpendicular to the pulling direction covers the central opening formed by the thermal mask reflector. The crystal pulling mechanism of the crystal pulling furnace according to claim 1, wherein the fixed structure holding the seed crystal is disposed at a center of the seed crystal holder. The crystal pulling mechanism of the crystal pulling furnace according to claim 3, wherein a projection of the seed crystal on a plane perpendicular to the pulling direction is circular. The crystal pulling mechanism of the crystal pulling furnace according to claim 4, wherein a diameter of the circular shape is greater than or equal to a diameter of a crystal ingot that is grown by being pulled from the melt in the crucible. The crystal pulling mechanism of the crystal pulling furnace according to claim 4, wherein a diameter of the circle is greater than or equal to a diameter of a central opening formed by the heat shield reflector. The crystal pulling mechanism of the crystal pulling furnace according to claim 1, wherein a material of the seed crystal clip is selected from one or more of molybdenum (Mo), nickel (Ni), tungsten (W), and graphite. The crystal pulling mechanism of the crystal pulling furnace according to claim 1, wherein the furnace cavity is filled with a protective gas. The crystal pulling mechanism of the crystal pulling furnace according to claim 8, wherein the protective gas is argon.