Horizontal heat treatment furnace, heat treatment method and silicon wafer manufacturing method

Abstract

The present invention provides a horizontal heat treatment furnace, a heat treatment method, and a method for manufacturing silicon wafers, all of which provide a uniform temperature distribution within the wafer plane. The horizontal heat treatment furnace (1) of the present invention comprises a core tube (11), a heater (15), a door (13), a wafer boat (16, 17), and a fork (18). The core tube (11) has an opening (12) at one end. The heater (15) surrounds the core tube. The door (13) opens and closes the opening of the core tube. The wafer boat (16, 17) is disposed inside the core tube and carries a wafer (W) in an upright state. The fork (18) extends horizontally from the door inside the core tube and supports the wafer boat. The horizontal heat treatment furnace (1) is characterized in that the fork (18) has a frame portion (181) supporting the wafer boat and a space portion (182) surrounded by the frame portion (181).

Description

Technical Field

[0001] This invention relates to a horizontal heat treatment furnace, a heat treatment method, and a method for manufacturing silicon wafers. Background Technology

[0002] A known semiconductor manufacturing apparatus, comprising a reaction tube, a fork, a shielding plate, a rectifier plate, and a heater, includes a cylindrical reaction tube with a gas inlet at one end and a closed cap at the other. Multiple wafers are arranged perpendicularly to the central axis of the reaction tube within the fork. The shielding plate is positioned between the gas inlet and the fork, circumferentially contacting the inner wall of the reaction tube, and has an opening at its bottom. The rectifier plate is positioned between the shielding plate and the fork, circumferentially contacting the inner wall of the reaction tube, and has multiple through holes. The heater is positioned around the reaction tube. This allows for the uniform formation of an oxide film on multiple wafers within the process tube (see Patent Document 1).

[0003] Patent document 1: Japanese Patent Application Publication No. 2016-163025.

[0004] However, in the aforementioned conventional semiconductor manufacturing apparatus, heat treatment is performed with the wafer placed in a fork-like position. Therefore, heat transfer is difficult at the bottom of the wafer due to the fork, resulting in uneven temperature distribution within the wafer surface. Consequently, problems arise such as uneven oxide film thickness and the occurrence of slip dislocations. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a horizontal heat treatment furnace, a heat treatment method and a method for manufacturing silicon wafers that makes the temperature distribution within the wafer surface uniform.

[0006] The present invention solves the above problems by means of a horizontal heat treatment furnace, wherein the horizontal heat treatment furnace includes a core tube, a heater, a door, a wafer boat, and a fork. The core tube has an opening at one end, the heater surrounds the core tube, the door opens and closes the opening of the core tube, the wafer boat is disposed inside the core tube and carries a wafer in an upright state, and the fork extends horizontally from the door inside the core tube and supports the wafer boat. The horizontal heat treatment furnace is characterized in that the fork has a frame portion supporting the wafer boat and a space portion surrounded by the frame portion.

[0007] Furthermore, the present invention solves the above problems by means of a heat treatment method, wherein the wafer is mounted on a wafer boat in an upright state, and the wafer boat is arranged inside the core tube of a horizontal heat treatment furnace while supported by a fork. The fork has a frame portion supporting the wafer boat and a space portion surrounded by the frame portion, and the wafer is heated in this state.

[0008] Furthermore, the present invention solves the above problems by means of a silicon wafer manufacturing method, wherein the silicon wafer is mounted on a wafer boat in an upright state, and the wafer boat is arranged inside the core tube of a horizontal heat treatment furnace while supported by a fork, wherein the fork has a frame portion supporting the wafer boat and a space portion surrounded by the frame portion, and includes a heat treatment method for heating the silicon wafer in this state.

[0009] In the above invention, it is also possible to include a support column and a lifting mechanism. The support column is disposed between the end portion of the fork and the inner surface of the furnace core tube and extends in a vertical direction. The lifting mechanism is disposed at the door to raise and lower the fork. In this case, the support column can be integrally formed with the end portion of the fork or fixed to the furnace core tube.

[0010] In the above invention, it is more preferable that, when the wafer boat is supported by the fork, the area ratio of the space portion to the area of ​​the wafer boat is 60% to 85%. If the area ratio of the space portion to the area of ​​the wafer boat is less than 60%, more heat is blocked by the fork, and the temperature distribution within the wafer surface will not be sufficiently uniform. Conversely, if the area ratio of the space portion to the area of ​​the wafer boat is greater than 85%, the rigidity of the fork decreases, and the wafer boat cannot be firmly supported.

[0011] In the above invention, the fork may also have a bridging portion and multiple spatial portions, wherein the multiple spatial portions are rectangular or square in shape when viewed vertically, and the bridging portion is formed between the multiple spatial portions. In this case, it is preferable that, when the wafer boat is supported by the fork, the spatial portions are located below the wafer mounted on the wafer boat, and the bridging portion is located below the area where the wafer is not present.

[0012] In the above invention, the fork may also be configured such that it has a bridging portion and multiple spatial portions, the multiple spatial portions being triangular in shape when viewed in the vertical direction, and the bridging portion being formed between the multiple spatial portions.

[0013] Invention Effects

[0014] According to the present invention, a horizontal heat treatment furnace, a heat treatment method, and a method for manufacturing silicon wafers are provided, which enable uniform temperature distribution within the wafer surface. Attached Figure Description

[0015] Figure 1 This is a cross-sectional view showing one embodiment of the horizontal heat treatment furnace of the present invention.

[0016] Figure 2 It means Figure 1 A top view of the fork.

[0017] Figure 3A This indicates installation. Figure 1 A cross-sectional view of the wafer, silicon boat, and mother boat in their current state.

[0018] Figure 3B This indicates installation. Figure 1 A cross-sectional view of the wafer, silicon boat, and mother boat in their respective states.

[0019] Figure 4 It is along Figure 1 A cross-sectional view along line IV-IV.

[0020] Figure 5 Other embodiments of the horizontal heat treatment furnace of the present invention are shown in cross-sectional views of the wafer, silicon boat, mother boat, and fork.

[0021] Figure 6 It means Figure 5 A top view of the fork.

[0022] Figure 7 It is along Figure 6 A sectional view along line VII-VII.

[0023] Figure 8 This is a top view illustrating another embodiment of the fork of the present invention.

[0024] Figure 9 This is a top view showing yet another embodiment of the fork of the present invention.

[0025] Figure 10A This is a cross-sectional view (1) showing yet another embodiment of the horizontal heat treatment furnace of the present invention.

[0026] Figure 10B This is a cross-sectional view (2) showing yet another embodiment of the horizontal heat treatment furnace of the present invention.

[0027] Figure 11A This is a cross-sectional view (1) showing yet another embodiment of the horizontal heat treatment furnace of the present invention.

[0028] Figure 11B This is a cross-sectional view (2) showing yet another embodiment of the horizontal heat treatment furnace of the present invention.

[0029] Figure 12 This is a graph showing the heat treatment curves of Embodiment 1 and Comparative Example 1 of the present invention.

[0030] Figure 13 This is a cross-sectional view showing the measurement points of the film thickness in Embodiment 1 and Comparative Example 1 of the present invention.

[0031] Figure 14This is a top view showing the fork used in Comparative Example 1 relative to Embodiment 1 of the present invention.

[0032] Figure 15 These are graphs showing the results of Embodiment 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0033] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a cross-sectional view showing one embodiment of the horizontal heat treatment furnace 1 of the present invention. Figure 2 It means Figure 1 Top view of the fork 18 Figure 3A It means to Figure 1 A cross-sectional view of the wafer W, silicon boat 16, and mother boat 17 before installation. Figure 3B This is a cross-sectional view showing the state after the wafer W, silicon boat 16, and mother boat 17 are assembled in the same way. Figure 4 It is along Figure 1 A cross-sectional view along line IV-IV.

[0034] The horizontal heat treatment furnace 1 of this embodiment includes a furnace core tube 11 that extends horizontally and has a cylindrical cross-section. The furnace core tube 11 is made of quartz. Figure 1 An opening 12 and a door 13 for opening and closing are provided at one end on the right side. Figure 1 The other end on the left side is closed. The door 13, which opens and closes the opening 12, can be moved to the [location not shown in the figure] by means of a conveying mechanism. Figure 1 The gate 13 is in the closed position and the gate 18 is in the open position, which moves to the right from this position. In the open position of the gate 13, the fork 18, described later, also moves to the outside of the furnace core tube 11 to perform the replacement operation of the wafers configured in the silicon boat.

[0035] exist Figure 1 A gas inlet 14 is provided at the closed end of the left side of the furnace core tube 11. Nitrogen, oxygen, argon, or other appropriate gases corresponding to the heat treatment specifications are supplied from the gas inlet 14. A cylindrical heater 15 is provided on the outer periphery of the furnace core tube 11 to heat the wafer W placed inside the furnace core tube 11 to a set temperature.

[0036] The wafer W to be processed in the heat treatment furnace 1 of this embodiment is, for example, a silicon wafer. Multiple wafers W are mounted at intervals in an upright position. Figure 3A The text refers to a silicon boat 16 made of silicon. Figure 3A and Figure 3B The silicon boat 16 is shown in the figure. A wafer W is supported by contact with the silicon boat 16 at three points shown by the cross-sectional lines at the four corners.

[0037] Furthermore, multiple Silicon Boat 16s were mounted on... Figure 1 and Figure 3A The quartz mothership 17 is shown in the image. Figure 3A and Figure 3B The mother boat 17, as shown in the diagram, is supported by a silicon boat 16 that contacts and is positioned at four points indicated by the circular cross-section. Additionally, Figure 1 In the example shown, three silicon boats 16 are carried on a mother boat 17. Figure 5 In the example shown, a silicon boat 16 is mounted on a mother boat 17. Thus, the number of silicon boats 16 mounted on a mother boat 17 can be appropriately varied.

[0038] Silicon Boat 16, equipped with multiple wafer W, Figure 3B As shown, the wafer W, silicon boat 16, and mother boat 17 are mounted on a fork 18 and supported in this state. The silicon boat 16 and mother boat 17 in this embodiment are equivalent to the wafer boat of the present invention, but the wafer boat of the present invention may also be composed of one boat or multiple boats.

[0039] The fork 18 in this embodiment is made of silicon carbide or quartz, and one end is fixed to the door 13. Furthermore, the fork 18 of this embodiment is inserted into the furnace core tube 11 while supporting the wafer W, silicon boat 16, and mother boat 17, and undergoes heat treatment while extending horizontally from the door 13. Specifically, the fork 18 of this embodiment... Figure 2 As shown in the top view, it has a frame portion 181, a space portion 182, and a bridging portion 183. The frame portion 181 supports the mother boat 17, which carries the wafer W and the silicon boat 16, and the space portion 182 is surrounded by the frame portion 181. Figure 1 and Figure 2 In the embodiment shown, three silicon boats 16 are mounted on a mother boat 17, so three space portions 182 are located below each of the three silicon boats 16, and two bridging portions 183 are located below the two parts of the three silicon boats 16 where there is no wafer W. The frame portions 181, space portions 182, and bridging portions 183 are formed such that four frame portions 181 are located below the four parts of the non-wafer W on the end side, base side, and both sides of the whole surrounding the three space portions 182.

[0040] The frame portion 181 and the space portion 182 of the present invention can be changed in various ways as needed. Figures 5-7 This illustrates other embodiments of the horizontal heat treatment furnace 1 of the present invention. Figure 5 This is a cross-sectional view showing the wafer W, silicon boat 16, mother boat 17, and fork 18. Figure 6 It means Figure 5 Top view of the fork 18 Figure 7 It is along Figure 6 A sectional view along line VII-VII. Figures 5-7In the embodiment shown, the mother boat 17 carries a silicon boat 16, so the corresponding fork 18 has a space portion 182 and four frame portions 181 surrounding the space portion 182. Furthermore, the frame portions 181 and the space portion 182 are formed such that the space portion 182 is located below the silicon boat 16, and the four frame portions 181 are located below the four portions of the wafer W that are not present at the end, base, and sides. In this embodiment, there is no bridging portion 183.

[0041] Figure 8 and Figure 9 These are top views illustrating yet another embodiment of the fork 18 of the present invention. In the fork 18 of the two embodiments described above, the space portion 182 is only configured as a rectangular opening, but if the fork 18 is required to have the desired rigidity, a bridging portion 183 as an inclined column may also be provided in the space portion 182. Figure 8 The fork 18 in the implementation method shown in the figure is, in Figure 2 In the embodiment shown in the diagram, each of the three spatial portions 182 is provided with a bridging portion 183 as a diagonal column. Furthermore, Figure 9 The fork 18 in the implementation method shown in the figure is, in Figure 6 The embodiment shown in the figure has a space portion 182 provided with a bridging portion 183 as an oblique column along the diagonal.

[0042] Therefore, the fork 18 in this embodiment has as follows Figure 8 and Figure 9 The diagram shows a plurality of triangular-shaped spatial portions 182 as viewed vertically, with bridging portions 183 formed between these spatial portions 182. By providing bridging portions 183 as inclined columns, the rigidity near the spatial portions 182 can be improved.

[0043] When heat-treating wafer W using the horizontal heat treatment furnace 1 of this embodiment, a silicon boat 16 is placed on a mother boat 17, and multiple wafers W are mounted upright on the silicon boat 16. The mother boat 17, which holds the silicon boat 16 with the wafers W, is mounted on a fork 18. The fork 18 supporting the mother boat 17 is moved together with the door 13, and the fork 18 is inserted through the opening 12 of the furnace core tube 11. The door 13 is then closed, and after a near-sealed seal, predetermined gases such as nitrogen, oxygen, and argon flow out from the gas inlet 14, and the gases are discharged out of the furnace core tube through the gap between the doors 13. This keeps the atmosphere inside the furnace core tube clean, and heat treatments such as dopant diffusion and oxidation of the wafer W are performed. At this time, heat from the heater 15 is transferred to the wafer W from the entire circumference of the furnace core tube 11, but heat transferred from the heater 15 in the lower region of the furnace core tube 11 is also transferred to the wafer W through the space 182 of the fork 18. This allows for a uniform temperature distribution within the wafer surface.

[0044] Thus, the fork 18 of this embodiment can improve heat transfer from the heater 15 by means of the space portion 182, while ensuring the rigidity of supporting the wafer W, silicon boat 16, and mother boat 17 by means of the frame portion 181 and the bridging portion 183. Therefore, the area ratio of the space portion 182 to the overall area of ​​the fork 18 when viewed from above in the vertical direction is a compromise; the larger the area ratio of the space portion 182, the better the heat transfer, but the lower the rigidity. Here, the "area of ​​the fork 18 supporting the mother boat 17" in this embodiment is defined as the projected area when the frame portion 181 extends to the end with a certain width when viewed from the side of the fork 18. The area of ​​the fork 18 supporting the mother boat 17, that is, the area ratio of the space portion 182 to the arrangement area of ​​the wafer boat as referred to in this invention, is the largest. Figure 6 The embodiment shown in the figure is approximately 85%. Furthermore, the area of ​​the fork 18 carrying the mother boat 17, i.e., the space portion 182 referred to in this invention, relative to the area of ​​the wafer boat, is the smallest. Figure 8 The embodiment shown in the figure is approximately 60%. Therefore, considering both heat transfer and rigidity, the area ratio of the area of ​​the fork 18 mounting the mother boat 17, i.e., the space portion 182 referred to in this invention, to the area of ​​the wafer boat is preferably 60% to 85%.

[0045] The fork 18 of the present invention can be modified in various ways as needed. Figure 10A and Figure 10B The right figure is a cross-sectional view showing another embodiment of the heat treatment furnace of the present invention, and the left figure is a cross-sectional view along line XA-XA or XB-XB, omitting illustrations of the gas inlet 14 and the heater 15. Furthermore, Figure 10A This indicates that fork 18 is in the upward position. Figure 10B This indicates that fork 18 is descending to the lower position. Figure 10A and Figure 10B The heat treatment furnace 1 of this embodiment, as shown in the diagram, is relative to... Figure 1 The heat treatment furnace 1 of the embodiment shown in the figure has a different aspect in that it has a lifting mechanism 19 that raises and lowers the fork 18 relative to the door 13 and a support column 20 provided at the end of the fork 18, but the rest of the structure is the same.

[0046] The lifting mechanism 19 is mounted on the inner surface of the door 13, and one end of the fork 18 is fixed. Furthermore, using a drive source (not shown in the figure), the fork 18 is moved... Figure 10A The rising position and Figure 10B The lowering position indicated in the text refers to the vertical movement. Specifically, when the door 13 and fork 18 are inserted into the furnace core tube 11, as shown in the text... Figure 10A The process is performed with the fork 18 raised to the raised position as shown. After the door 13 is closed, as... Figure 10BThe fork 18 is lowered to the lowered position as shown. In this lowered position, the support portion 20 provided at the end of the fork 18 contacts the inner surface of the furnace core tube 11. Thus, during heat treatment, the fork 18 is supported not only by the lifting mechanism 19 at the right end, but also by the support portion 20 at the left end.

[0047] The support portion 20 provided at the end of the fork 18 is as follows: Figure 10A As shown in the left figure, it hangs down from the left and right sides of the end of the fork 18, as... Figure 10B As shown, the support portion 20 is shaped such that when the fork 18 is lowered to the lowered position, the lower end face of the support portion 20 contacts the inner surface of the furnace core tube 11. Therefore, during heat treatment, the support portion 20, located at the end of the fork 18, is supported on the inner surface of the furnace core tube 11 at both the left and right sides, thus preventing deflection and torsion. Furthermore, by providing the support portions 20 at both the left and right ends, obstruction of gas flow by the support portions 20 is prevented, and gas is uniformly supplied directly below the wafer W. Additionally, the shape of the support portion 20 is not limited to... Figure 10A and Figure 10B The shape can also be set as a single point in the center.

[0048] in addition, Figure 10A and Figure 10B The support column 20, as shown in the diagram, is integrally formed with the end portion of the fork 18. However, the support column 20 can also be constructed as a component other than the fork 18 and joined using a coupling mechanism. Furthermore, the support column 20 can be located not only on the side of the fork 18, but also... Figure 11A and Figure 11B It is arranged on the inner surface of the furnace core tube 11 as shown. Figure 11A and Figure 11B The right figure is a cross-sectional view showing another embodiment of the heat treatment furnace of the present invention, and the left figure is a cross-sectional view along line XIA-XIA, omitting illustrations of the gas inlet 14 and the heater 15. Furthermore, Figure 11A This indicates that fork 18 has risen to the rising position. Figure 11B This indicates the state of fork 18 as it descends to the descending position. Figure 11A and Figure 11B The heat treatment furnace 1 of this embodiment, as shown in the diagram, is relative to... Figure 1 The heat treatment furnace 1 of the embodiment shown in the diagram differs in that it has a lifting mechanism 19 for raising and lowering the fork 18 relative to the door 13, and a support column 20 provided at the end of the fork 18, but the rest of the structure is the same. Furthermore, compared to... Figure 10A and Figure 10B The heat treatment furnace 1 of the embodiment shown in the figure has a different fixed position of the support column 20, but the other structures are the same.

[0049] The invention will be described with reference to more detailed embodiments.

[0050] Example 1

[0051] Prepare 150 silicon wafers with a diameter of 200mm, and use... Figure 1 and 2 The heat treatment furnace 1 shown is in accordance with Figure 12 The heat treatment curve shown represents an oxidation heat treatment. That is, as... Figure 12 As shown, a silicon wafer is placed in a furnace core tube 11 at 700°C. After one hour, the temperature is raised to 1150°C, followed by two hours of heat treatment. Then, the temperature is lowered to 700°C for one hour, and the silicon wafer is removed. One wafer is extracted from the silicon wafer after the oxidation heat treatment, and the thickness of the oxide film formed on the surface of the silicon wafer is measured using a film thickness measuring instrument. Figure 13 Measurements were taken at points 1-5 as shown. The results were then... Figure 15 express.

[0052] Comparative Example 1

[0053] In addition to Figure 14 As shown, the fork 18 for the heat treatment furnace 1 is configured without any space 182, and oxidation heat treatment is performed under the same conditions as in Example 1. The thickness of the oxide film formed on the surface of the silicon wafer after the oxidation heat treatment is measured using a film thickness gauge relative to the silicon wafer at the end of the oxidation heat treatment. Figure 13 Measurements were taken at points 1-5 as shown. The results were then... Figure 15 express.

[0054] An Examination of Results

[0055] In Comparative Example 1, the oxide film thickness formed on the silicon wafer was thinner at measurement points 4 and 5 compared to measurement points 1-3, indicating uneven film thickness within the wafer surface. In contrast, it was confirmed that the oxide film thickness of the silicon wafer in Example 1 was approximately equal at all measurement points, showing uniform film thickness within the wafer surface. Therefore, it is inferred that the temperature distribution within the wafer surface became more uniform.

[0056] Explanation of reference numerals in the attached figures

[0057] 1…Heat treatment furnace

[0058] 11…furnace core tube

[0059] 12…Opening

[0060] 13…door

[0061] 14…Gas Inlet Section

[0062] 15… heaters

[0063] 16…Silicon Boat

[0064] 17…mother boat

[0065] 18…fork

[0066] 181…Frame

[0067] 182… Space Department

[0068] 183…Bridging section

[0069] 19… Lifting mechanism

[0070] 20…Pillar Department

[0071] W… wafer.

Claims

1. A horizontal heat treatment furnace, wherein the aforementioned horizontal heat treatment furnace comprises a furnace core tube, a heater, a door, a wafer boat, a fork, a support column, and a lifting mechanism. The aforementioned furnace core tube has an opening at one end. The aforementioned heater surrounds the aforementioned furnace core tube. The aforementioned door opens and closes the opening of the aforementioned furnace core tube. The aforementioned wafer boat is disposed inside the aforementioned furnace core tube, and carries the wafer in an upright position. The aforementioned fork extends horizontally from the aforementioned door inside the aforementioned furnace core tube, supporting the aforementioned wafer boat. The aforementioned support column is disposed between the end portion of the aforementioned fork and the inner surface of the aforementioned furnace core tube, and extends in a vertical direction. The aforementioned lifting mechanism is installed at the aforementioned door to allow the aforementioned forks to rise and fall. The aforementioned horizontal heat treatment furnace is characterized by, The fork has a frame portion that supports the wafer boat and a space portion surrounded by the frame portion.

2. The horizontal heat treatment furnace as described in claim 1, characterized in that, The aforementioned support portion and the end portion of the aforementioned fork are integrally formed.

3. The horizontal heat treatment furnace as described in claim 1 or 2, characterized in that, The aforementioned fork has a bridging section and multiple spatial sections. The aforementioned spatial sections, when viewed vertically, are rectangular or square in shape. The aforementioned bridging portion is formed between the aforementioned multiple spatial portions.

4. The horizontal heat treatment furnace as described in claim 3, characterized in that, When the wafer boat is supported by the fork, the space is located below the wafer mounted on the wafer boat, and the bridging part is located below the area where the wafer does not exist.

5. A horizontal heat treatment furnace, wherein the aforementioned horizontal heat treatment furnace comprises a furnace core tube, a heater, a door, a wafer boat, and forks. The aforementioned furnace core tube has an opening at one end. The aforementioned heater surrounds the aforementioned furnace core tube. The aforementioned door opens and closes the opening of the aforementioned furnace core tube. The aforementioned wafer boat is disposed inside the aforementioned furnace core tube, and carries the wafer in an upright position. The aforementioned fork extends horizontally from the aforementioned door inside the aforementioned furnace core tube, supporting the aforementioned wafer boat. The aforementioned horizontal heat treatment furnace is characterized by, The aforementioned fork has a frame portion, a bridging portion, and multiple spatial portions. The aforementioned frame supports the wafer boat. The shape of the aforementioned multiple spatial sections, when viewed vertically from the perspective of the aforementioned frame, is triangular. The aforementioned bridging portion is formed between the aforementioned multiple spatial portions, and includes at least the inclined column of the aforementioned frame portion.

6. The horizontal heat treatment furnace as described in claim 1 or 5, characterized in that, When the wafer boat is supported by the fork, the area ratio of the space portion to the installation area of ​​the wafer boat is 60% to 85%.

7. A heat treatment method, characterized in that, The wafer is mounted upright on the wafer boat. The aforementioned wafer boat is positioned inside the core tube of a horizontal heat treatment furnace, supported by forks. The forks have a frame portion supporting the wafer boat and a space portion surrounded by the frame portion. Heating the aforementioned wafer in this state, The aforementioned horizontal heat treatment furnace also has a support column and a lifting mechanism. The aforementioned support column is disposed between the end portion of the aforementioned fork and the inner surface of the aforementioned furnace core tube, and extends in a vertical direction. The aforementioned lifting mechanism is located at the door that opens and closes the aforementioned furnace core tube, allowing the aforementioned fork to rise and fall. With the fork raised using the aforementioned lifting mechanism, the fork supporting the aforementioned wafer boat is inserted into the interior of the aforementioned furnace core tube. After the furnace core tube is closed, the fork is lowered by means of the lifting mechanism, and the wafer is heated in a state where the end of the fork, the support column and the furnace core tube are in contact.

8. The heat treatment method according to claim 7, characterized in that, The aforementioned support portion is integrally formed at the end portion of the aforementioned fork. After the furnace core tube is closed, the fork is lowered by means of the lifting mechanism, and the wafer is heated while the end of the fork is in contact with the furnace core tube.

9. The heat treatment method as described in claim 7 or 8, characterized in that, The aforementioned fork has a bridging section and multiple spatial sections. The aforementioned spatial sections, when viewed vertically, are rectangular or square in shape. The aforementioned bridging portion is formed between the aforementioned multiple spatial portions.

10. The heat treatment method as described in claim 9, characterized in that, When the wafer boat is supported by the fork, the space is located below the wafer mounted on the wafer boat, and the bridging part is located below the area where the wafer does not exist.

11. A heat treatment method, characterized in that, The wafer is mounted upright on the wafer boat. The aforementioned wafer boat is positioned inside the core tube of a horizontal heat treatment furnace, supported by forks. The forks have a frame portion supporting the wafer boat and a space portion surrounded by the frame portion. Heating the aforementioned wafer in this state, The heat treatment method is characterized in that... The aforementioned fork has a bridging section and multiple spatial sections. The aforementioned spatial sections, when viewed vertically, form a triangular shape. The aforementioned bridging portion is formed between the aforementioned multiple spatial portions, and includes at least the inclined column of the aforementioned frame portion.

12. The heat treatment method as described in claim 7 or 11, characterized in that, When the wafer boat is supported by the fork, the area ratio of the space portion to the installation area of ​​the wafer boat is 60% to 85%.

13. A method for manufacturing a silicon wafer, characterized in that, The silicon wafer is mounted upright on the wafer boat. The aforementioned wafer boat is positioned inside the core tube of a horizontal heat treatment furnace, supported by forks. The forks have a frame portion supporting the wafer boat and a space portion surrounded by the frame portion. The heat treatment method according to any one of claims 7 or 11, which includes heating the aforementioned silicon wafer in this state.

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