WO2023101160A1

WO2023101160A1 - Method for manufacturing graphite crucible using graphite sheet

Info

Publication number: WO2023101160A1
Application number: PCT/KR2022/013622
Authority: WO
Inventors: 유성운; 이현호; 윤성영; 남신우
Original assignee: 인동첨단소재(주)
Priority date: 2021-12-03
Filing date: 2022-09-13
Publication date: 2023-06-08
Also published as: KR20230083437A

Abstract

The present invention relates to a method for manufacturing a graphite crucible using a graphite sheet, the method being characterized by comprising the steps of: cutting a graphite sheet; applying a foamed adhesive to the surfaces of graphite sheets; laminating and stacking the graphite sheets coated with the foamed adhesive; manufacturing graphite blocks by foaming the stacked graphite sheets under pressurized conditions; and forming a crucible main body by bonding the graphite blocks to each other.

Description

Manufacturing method of graphite crucible using graphite sheet.

The present invention relates to a method for manufacturing a graphite crucible using a graphite sheet, and more particularly, to a method for manufacturing a graphite crucible having excellent heat resistance and durability and applicable to a semiconductor manufacturing process by laminating graphite sheets.

A graphite crucible is used in a process of growing a single crystal, which is a material of a silicon wafer. In general, silicon single crystals are manufactured using a single crystal manufacturing apparatus according to the Czochralski method. For single crystal growth, a crucible placed in a chamber is filled with raw materials for single crystals, and an inert purge gas is introduced into the chamber while the raw materials are introduced into the crucible. A melt is prepared by heating and melting with a heater formed on the outside, and after immersing and adapting the melted seed crystal in the melt, the seed crystal is rotated and raised upward to grow a single crystal at the bottom of the seed crystal. do.

In the process of growing a silicon single crystal, oxygen concentration needs to be controlled. Conventional crucibles are quartz crucibles, and there is a limit to precisely adjusting the oxygen concentration by adjusting the temperature distribution in the crucible.

In order to solve this problem, Korean Patent Registration Publication No. 10-1072664 adjusts temperature distribution by installing a graphite crucible as a heat shield between a quartz crucible and an external heater.

Various technologies for manufacturing such a graphite crucible have been developed. In Korean Patent Registration No. 10-1907818, the characteristics of the graphite crucible base material have a bulk density of 1.65 Mg/m3 or more, a flexural strength of 30 mPa or more, and a shore hardness of 40 or more. A technique that can increase the service life by using the having is known. Such a graphite crucible is characterized by forming a film on the surface of a substrate. In addition, Korean Patent Registration No. 10-0642923 discloses a technique of forming an inner layer of a crucible by laminating high-purity expanded graphite sheets having flexibility.

This prior art is intended to improve the physical properties of the crucible by treating the inner surface of the crucible, and has problems in that cracks or deformation occur because the crucible body is manufactured by general extrusion molding.

The present invention has been made in view of the prior art as described above, and an object of the present invention is to provide a manufacturing method capable of manufacturing a graphite crucible body by laminating a plurality of graphite sheets.

Another object of the present invention is to provide a method capable of manufacturing a high-quality graphite crucible that does not undergo deformation or cracking due to pressure.

The method for manufacturing a graphite crucible of the present invention to solve the above problems includes cutting a graphite sheet, applying a foamed adhesive to the surface of the graphite sheet, and laminating and laminating the graphite sheets coated with the foamed adhesive. It is characterized in that it includes the step of manufacturing a graphite block by foaming the stacked graphite sheets under a pressurized condition, and forming a crucible body by bonding the graphite blocks to each other.

In this case, in the forming of the crucible body, a heat-resistant foaming agent may be applied to each joining portion of the graphite blocks and then pressurized in a joining direction so as to be joined to each other.

In addition, in the forming of the crucible body, the graphite blocks may be bonded to each other using carbon screws after drilling holes in the joint portions.

In the step of laminating and laminating the graphite sheets, a graphite crucible having a desired thickness may be manufactured by laminating and laminating 20 to 50 graphite sheets.

In addition, it is preferable to use the foamed adhesive having a viscosity of less than 10,000cps.

In the method for manufacturing a graphite crucible according to the present invention, a graphite crucible body may be manufactured by stacking a plurality of graphite sheets.

In addition, the manufactured graphite crucible exhibits an effect of not generating deformation or cracking due to pressure.

1 is a conceptual diagram showing a process of manufacturing a crucible by bonding graphite sheets according to the manufacturing method of the present invention.

Hereinafter, the present invention will be described in more detail. Terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventor may appropriately define the concept of terms in order to explain his or her invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

The method for manufacturing a graphite crucible of the present invention includes the steps of cutting a graphite sheet, applying a foamed adhesive to the surface of the graphite sheet, laminating and laminating the graphite sheets coated with the foamed adhesive, and stacking the stacked graphite sheets. It is characterized in that it includes the step of producing a graphite block by foaming under a pressurized condition, and the step of bonding the graphite blocks to each other to form a crucible body.

That is, in the manufacturing method of the graphite crucible of the present invention, a graphite block is manufactured by stacking graphite sheets, and a plurality of graphite blocks are bonded to each other to form a crucible body having a desired shape.

As the graphite sheet, a graphite sheet developed by the applicant may be used, and a graphite sheet having a density of 1.5 g/cm 3 is preferably used. This may be selected in consideration of the degree of foaming when the graphite sheets are stacked and the strength of the crucible. In addition, the graphite sheet is preferably cut to a size of 670 × 930 mm. This is in consideration of the size of the graphite block, and can be cut to an optimal size suitable for assembling a target graphite crucible.

The cut graphite sheet is preferably used after being pretreated by heating at a temperature of 450 to 550°C. Impurities remaining on the surface of the graphite sheet may be removed through the pretreatment, and through this, adhesion of the graphite sheet may be smoothly performed.

The graphite sheets pretreated as described above are laminated and stacked in consideration of the thickness of the crucible body. For example, in case of using a 0.9t graphite sheet, 33 graphite sheets are required to manufacture a 30t thick graphite crucible. However, considering the thickness of a general graphite crucible, a graphite crucible having sufficient durability can be manufactured by laminating 20 to 50 graphite sheets having a thickness of 0.5 to 1.5t.

The graphite sheets are laminated using a foam adhesive. When the foamed adhesive is applied between the graphite sheets, strong adhesion between the graphite sheets is formed by foaming of the foamed adhesive. A commercially available product may be used as the foam adhesive, and a combination of dusty powder and liquid foam is used.

In one embodiment, a foamed adhesive was prepared by mixing liquid foam SMG-200B (Hanmir) and dusty powder SMG-400P (Hanmir) in a weight ratio of 4.5:5.5, and then it was applied to the surface of the graphite sheet. At this time, the foamed adhesive was used after confirming that the viscosity was less than 10,000cps. Since the foam adhesive foams within 30 minutes after application, an appropriate amount should be used. Preferably, it may be applied to a thickness of 0.05 to 0.15t.

The foamed adhesive is applied to both the front and rear surfaces of the graphite sheet, and it is preferable to apply evenly throughout the graphite sheet so that there are no voids. In addition, the foamed adhesive is applied to only one side of the lowermost and uppermost graphite sheets to be laminated. That is, it is preferable to apply the foamed adhesive only to the surface of the graphite sheet to be laminated so as to have a uniform thickness. In addition, since the application of the foamed adhesive must be performed before foaming, it must be completed within 15 to 20 minutes after preparing the foamed adhesive.

The graphite sheets thus laminated are placed on a pressurizing device and pressurized at a pressure of 200 to 300 kgf/m 2 so that foaming occurs in a pressurized state. In this pressurized condition, even if foaming occurs, it is possible to suppress a phenomenon in which the graphite sheets are spread out or the sheets are deformed. In addition, when foaming under pressure, an exothermic reaction occurs due to the reaction of the foamed adhesive. Since the front and rear surfaces of the laminated graphite sheets are fixed by the pressure device, when foaming occurs, the adhesive foamed to the side of the graphite sheet comes out.

It is preferable to maintain the pressurized state for 5 to 10 hours in order to ensure that the foaming occurs sufficiently.

When the foaming process is completed, the completed graphite block is recovered from the pressing device and heated to a temperature of 1,400 to 1,500° C. to remove all impurities and organic substances included in the graphite block. Through this, it is possible to manufacture a graphite block having a low density and high durability.

A desired graphite crucible may be manufactured by manufacturing a plurality of graphite blocks through the above process and bonding the graphite blocks to each other.

Referring to this process through FIG. 1 , a graphite crucible having a hexahedral shape with one surface open may be manufactured by bonding five graphite blocks to each other. In this case, the graphite blocks are formed in a flat shape and are combined, and the graphite blocks may be manufactured into a pot-shaped container by processing a curved surface of the graphite blocks. In addition, a separate graphite block may be manufactured and used as a lid of the graphite crucible.

In order to bond the graphite blocks to each other, each graphite block is drawn and finely processed using a lathe. A heat-resistant foaming agent is applied to a thickness of 0.05 to 0.15 t on the side surface of the graphite block after microprocessing, and then a pressure of 200 to 300 kgf/m 2 is applied along the direction in which the graphite blocks are joined to form a pressurized state. By maintaining this state for 5 to 10 hours, bonding between the graphite blocks is performed.

In addition, bonding strength between the graphite blocks may be increased by drilling a hole in the bonded portion and then coupling a carbon screw to the hole.

The graphite block assembly forms a graphite crucible. The graphite crucible is heated to a temperature of 1,400 to 1,500° C. to remove all impurities and organic substances included in the graphite block, thereby obtaining a graphite crucible.

The graphite crucible manufactured in this way is subjected to a pressure of 100 kgf/m 2 from the top and side for 30 minutes, and checks for deformation or cracks.

Therefore, the graphite crucible manufactured through this manufacturing method has the advantage of being resistant to deformation, cracking, and breakage, and being easy to repair when there is surface damage, compared to conventional graphite pottery.

In one embodiment, four graphite sheets of 650 × 930 mm and a thickness of 10 mm are used as four sides of the crucible, and a graphite sheet of 650 × 650 mm and a thickness of 15 mm is used as a bottom to prepare a hexahedral graphite crucible did

At this time, a foamed adhesive was applied at an average thickness of 0.1 t to the portion where the graphite sheets were joined, and carbon fibers were added to the outer surface of the portion where the graphite sheets were joined, and then the joint was bonded. A graphite crucible was prepared by heat-treating the graphite block assembly formed as described above at 1,400 to 1,500° C. for 2 hours.

In addition, for comparison, a graphite crucible was prepared using a roll-shaped sheet. First, 100 plain weave cotton fabrics (200 × 200 mm) were prepared and liquid polyamic acid was coated on one side of the cotton fabric at 25 ° C through a roll coating process to prepare a sheet. The prepared sheet was cured by hot air for 30 minutes in a heat treatment device having a temperature gradient of 80 to 250 ° C. to prepare a cured sheet, and the prepared cured sheet was wound by winding 10 turns and then repeating 1 turn. The rolled sheet was carbonized at a temperature of 1200° C. for 2 hours and graphitized at a temperature of 2800° C. for 1 hour to prepare a graphite crucible having a thickness of 10 mm.

The thermal diffusivity of the graphite crucibles of Examples and Comparative Examples was measured by a laser flash method (LFA447 from NEIZCH). As a result, the graphite crucible of Example exhibited physical properties equivalent to the thermal diffusivity of 530 mm 2 /s of the graphite crucible of Comparative Example at 525 mm 2 /s. Therefore, it was found that a uniform temperature distribution required as a crucible can be realized.

In addition, after heating the graphite crucibles of Examples and Comparative Examples at 2,000 ° C. for 1 hour in an inert gas atmosphere, the height of the graphite crucible before and after heat treatment, and the change in each dimension for each inner diameter at 100 mm and 150 mm from the top of the crucible As a result of measuring, the graphite crucible of Example showed a dimensional change rate of 0.05% in height, 0.04% in inner diameter at 100 mm, and 0.04% in inner diameter at 150 mm, whereas the graphite crucible of Comparative Example had a dimensional change rate of 0.08% in height and 100 mm in diameter. It was found to be 0.06% of the inner diameter at mm and 0.06% of the inner diameter at 150 mm. These results showed that the graphite crucibles of Examples had excellent durability.

In addition, the Shore hardness of the graphite crucible of Example is 55, whereas the Shore hardness of the graphite crucible of Comparative Example is 42, and there is a difference in hardness, and this result supports the high durability of the graphite crucible of Example.

The rights of the present invention are defined by what is described in the claims, not limited to the embodiments described above, and that those skilled in the art can make various modifications and adaptations within the scope of rights described in the claims. It is self-evident.

Claims

Cutting the graphite sheet;

applying a foamed adhesive to the surface of the graphite sheet;

laminating and laminating graphite sheets coated with the foamed adhesive;

preparing a graphite block by foaming the stacked graphite sheets under a pressurized condition;

bonding the graphite blocks together to form a crucible body;

A method for producing a graphite crucible comprising a.
The method of claim 1,

The method of manufacturing a graphite crucible, characterized in that in the forming of the crucible body, a heat-resistant foaming agent is applied to each joint of the graphite blocks and then pressed in a bonding direction to bond them to each other.
The method of claim 1,

The method of manufacturing a graphite crucible, characterized in that in the forming of the crucible body, the graphite blocks are drilled at joint portions and then bonded to each other using carbon screws.
The method of claim 1,

The method of manufacturing a graphite crucible, characterized in that the step of laminating and stacking the graphite sheets is laminating and stacking 20 to 50 graphite sheets.
The method of claim 1,

The foamed adhesive is a method for producing a graphite crucible, characterized in that the viscosity is less than 10,000cps.