Single crystal pulling device

Abstract

Provided is a single crystal pulling device that has excellent single crystal cooling performance and allows observation of the liquid level. A single crystal pulling device according to the Czochralski method is provided with: a cylindrical first cooling body for cooling a growing single crystal by surrounding the outer peripheral surface of the single crystal pulled from a melt in a crucible; a second cooling body, which is disposed below the first cooling body, surrounds the outer peripheral surface of the grown single crystal, and cools the single crystal; and an imaging device for observing the liquid level of the melt, the inner diameter of the upper end of the second cooling body being larger than the outer diameter of the lower end of the first cooling body, and forming a linear optical path. The optical path reaches the imaging device from the liquid surface through a gap between the lower end of the second cooling body and the outer peripheral surface of the growing single crystal and a gap between the upper end of the second cooling body and the lower end of the first cooling body.

Description

Technical Field

[0001] This invention relates to a single crystal pulling device. Background Technology

[0002] A known single crystal pulling device based on the Czeklauski method has a cylindrical cooling body and an imaging device. The cylindrical cooling body cools the single crystal around the outer peripheral surface of the growing single crystal pulled from the melt in the crucible, and the imaging device observes the liquid level of the melt in the crucible (see, for example, Patent Document 1).

[0003] Patent document 1: Japanese Patent Application Publication No. 2003-165790.

[0004] In Patent Document 1, a cooling body is used to cool the single crystal around its outer peripheral surface during cultivation. This effectively cools the single crystal and increases the pulling speed. Furthermore, the boundary region between the single crystal and the liquid surface can be observed using a photographic device through a cut at the lower end of the cooling body. However, if a cut is provided at the lower end of the cooling body, there is a problem of reduced uniformity of heat distribution around the cut. Summary of the Invention

[0005] The purpose of this invention is to provide a single crystal pulling device with excellent cooling performance and the ability to observe the liquid surface.

[0006] One aspect of the present invention is described below. [1] A single-crystal pulling device based on the Czechlausky method. have: A cylindrical first cooling body surrounds the outer peripheral surface of the growing single crystal, which is pulled from the molten liquid in the crucible, and cools the single crystal. A second cooling body in the shape of an inverted cone is disposed below the first cooling body and surrounds the outer peripheral surface of the growing single crystal to cool the single crystal; The imaging device is used to observe the surface of the molten liquid. The inner diameter of the upper end of the second cooling element is larger than the outer diameter of the lower end of the first cooling element. A straight light path is formed, which passes from the liquid surface through the gap between the lower end of the second cooling body and the outer peripheral surface of the growing single crystal, and the gap between the upper end of the second cooling body and the lower end of the first cooling body to the imaging device. [2] As described in [1], the single crystal pulling device, When the inner diameter of the upper end of the second cooling body is set as A and the inner diameter of the lower end of the second cooling body is set as B, 1.1≤A / B≤1.5. [3] As described in [1] or [2], single crystal pulling device, The distance between the lower end of the second cooling body and the outer peripheral surface of the growing single crystal is 20~70mm.

[0010] Invention Effects According to the present invention, a single crystal pulling device with excellent cooling performance and the ability to observe the liquid surface can be provided. Attached Figure Description

[0011] Figure 1 This is a cross-sectional view of a single-crystal pulling apparatus according to one embodiment of the present invention. Detailed Implementation

[0012] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0013] like Figure 1 As shown, in one embodiment of the present invention, the single crystal pulling device 1 is a single crystal pulling device 1 based on the Czeklaussky method, comprising: a crucible 3 (a double-layer crucible in which a quartz crucible is built inside a graphite crucible) storing molten liquid 4 as a material for single crystal 2 such as silicon; a seed crystal pulling device 6, which pulls a seed crystal 5 while rotating it around a central axis O, wherein the seed crystal 5 contacts the liquid surface 4a of the molten liquid 4 at the beginning of the cultivation of the single crystal 2 as the starting point for the cultivation of the single crystal 2; and a control device 7, composed of a computer or the like, controlling the rotation speed and pulling speed of the seed crystal 5 based on the seed crystal pulling device 6. The seed crystal pulling device 6 includes a seed crystal chuck 6a for holding the seed crystal 5, a wire 6b connected to the seed crystal chuck 6a at one end, and a winding device 6c for winding the wire 6b from the other end. After immersing the lower end of the seed crystal 5 in the liquid surface 4a, the seed crystal 5 is rotated and raised, thereby forming a neck 2a at the lower end of the seed crystal 5. After forming a shoulder 2b with a gradually expanding diameter, a roughly cylindrical straight section 2c centered on the central axis O is cultivated.

[0014] In this embodiment, the direction orthogonal to the central axis O is called the radial direction, the direction around the central axis O is called the circumferential direction, and the cross section orthogonal to the central axis O is called the cross section.

[0015] The single crystal pulling apparatus 1 includes: a main cavity 8 having a circular outer peripheral wall 8a, a top wall 8b (viewed as an annular shape) connected to the upper end of the outer peripheral wall 8a, and a bottom wall 8c connected to the lower end of the outer peripheral wall 8a, and a crucible 3 disposed inside; and a pulling cavity 9, into which the growing single crystal 2 is pulled and guided, having a peripheral wall 9a extending upward from the inner peripheral edge of the top wall 8b of the main cavity 8, and a top wall 9b connected to the upper end of the peripheral wall 9a. A heater 10 for heating the outer periphery of the crucible 3 and a heat insulation member 11 for keeping the crucible 3 warm around its outer periphery are disposed within the main cavity 8.

[0016] The single crystal pulling apparatus 1 has a cylindrical first cooling body 12 that cools the single crystal 2 being pulled from the liquid surface 4a. The first cooling body 12 has a circular cross-sectional shape centered on the central axis O. The first cooling body 12 extends downward from the inner periphery of the top wall 8b of the main cavity 8. The first cooling body 12 can be cylindrical, conical, or inverted conical. From the viewpoint of improving cooling performance, the first cooling body 12 is preferably configured to have an internal flow path for the cooling medium that cools the first cooling body 12 by means of heat exchange.

[0017] The single crystal pulling apparatus 1 includes a second cooling body 13, which is disposed below the first cooling body 12 and cools the single crystal 2 around its outer peripheral surface. The second cooling body 13 is in the shape of an inverted cone centered on the central axis O. That is, the inner diameter A of the upper end of the second cooling body 13 is larger than the outer diameter B of the lower end of the second cooling body 13. From the viewpoint of improving cooling performance, the second cooling body 13 is preferably configured to have a flow path inside for the cooling medium that cools the second cooling body 13 by means of heat exchange.

[0018] The single-crystal pulling device 1 includes an imaging device 14 for observing the liquid surface 4a. The imaging device 14 is, for example, a camera, a scanner, or an image sensor. Preferably, as shown in this embodiment, the imaging device 14 is provided outside a window 15 made of a light-transmitting material provided on the top wall 8b of the main cavity 8, and the liquid surface 4a is observed through the window 15.

[0019] In this embodiment, the inner diameter A of the upper end of the second cooling body 13 is larger than the outer diameter C of the lower end of the first cooling body 12, forming a straight light path L. The straight light path L passes from the liquid surface 4a through the gap G1 between the lower end of the second cooling body 13 and the outer peripheral surface of the growing single crystal 2, and the gap G2 between the upper end of the second cooling body 13 and the lower end of the first cooling body 12, and reaches the imaging device 14.

[0020] According to the above scheme, not only the cooling performance of the cylindrical first cooling body 12 is utilized, but also the cooling performance of the second cooling body 13, whose lower end is close to the liquid surface 4a, is utilized, thus achieving a very high cooling effect on the growing single crystal 2. Furthermore, by making the second cooling body 13 into an inverted cone shape, the field of view of the imaging device 14 is expanded, ensuring the light path L passing through the second cooling body 13, the first cooling body 12, and the growing single crystal 2, thus allowing observation of the liquid surface 4a using the imaging device 14. Specifically, in this embodiment, as... Figure 1As shown, the optical path L includes the boundary between the growing single crystal 2 and the molten liquid 4, so the boundary can be observed and the diameter of the growing single crystal 2 can be controlled. Furthermore, by observing the liquid surface 4a, the gap between the liquid surface 4a and the lower end of the heat shield 16 (described later) can be controlled to a predetermined value.

[0021] As described above, when the inner diameter of the upper end of the second cooling body 13 is set to A and the inner diameter of the lower end of the second cooling body 13 is set to B, it is preferable that 1.1 ≤ A / B ≤ 1.5. By setting it to 1.1 ≤ A / B, the optical path L necessary for observation of the liquid surface 4a by the imaging device 14 can be easily ensured. By setting it to A / B ≤ 1.5, it is possible to suppress excessive deviation of the second cooling body 13 from the growing single crystal 2, thus preventing an excessive decrease in the cooling effect based on the second cooling body 13.

[0022] The distance D between the lower end of the inner peripheral surface of the second cooling body 13 and the outer peripheral surface of the single crystal 2 being grown is preferably 20 to 70 mm. By setting the distance D to 20 mm or more, it is possible to easily ensure the optical path L while suppressing contact between the second cooling body 13 and the single crystal 2 being grown. By setting the distance D to 70 mm or less, it is possible to suppress excessive decrease in the cooling effect based on the second cooling body 13. The vertical length E of the second cooling body 13 from the upper end to the lower end is preferably 100 to 400 mm.

[0023] The lower end of the first cooling body 12 is preferably located below the upper end of the second cooling body 13. With this structure, the lower end of the first cooling body 12 can compensate for the reduced cooling effect caused by the increased size of the upper end of the second cooling body 13. Furthermore, the lower end of the first cooling body 12 is preferably located at a height that does not obstruct the optical path L, including the boundary between the growing single crystal 2 and the molten liquid 4.

[0024] Preferably, the single crystal pulling device 1, as shown in this embodiment, has a heat shield 16 that divides the interior of the main cavity 8 into a lower space S1 and an upper space S2, and has an opening 16a at the center in plan view that connects the lower space S1 and the upper space S2. The growing single crystal 2 passes through the opening 16a from the liquid surface 4a and is cooled in the upper space S2 by the second cooler 13 and the first cooler 12, while being pulled into the pulling cavity 9. Inactive gases such as argon introduced into the pulling cavity 9 flow in the following order: radially inside the first cooler 12, radially inside the second cooler 13, through the opening 16a of the heat shield 16, between the liquid surface 4a and the heat shield 16, and between the outer peripheral surface of the crucible 3 and the heat insulation member 11, and are discharged from the outlet (not shown) provided at the bottom of the main cavity 8.

[0025] Preferably, as shown in this embodiment, the heat shield 16 has a top-view annular bottom wall portion 16b with an opening 16a at its central portion, a cylindrical wall portion 16c extending upward from the outer periphery of the bottom wall portion 16b, and a top-view annular flange wall portion 16d extending radially outward from the upper end of the cylindrical wall portion 16c and connected to the outer peripheral wall 8a of the main cavity 8. Furthermore, this embodiment shows the bottom wall portion 16b extending horizontally in the radial direction, but the bottom wall portion 16b may also slope downward from the cylindrical wall portion 16c toward the liquid surface 4a.

[0026] From the viewpoint of reliably introducing inactive gas into the heat shield 16, the lower end of the first cooling body 12 is preferably located below the upper end of the cylindrical wall portion 16c of the heat shield 16. Furthermore, it is desirable to arrange the second cooling body 13 within the heat shield 16 to cool the newly grown single crystal 2 as much as possible. From this viewpoint, the upper end of the second cooling body 13 is preferably located below the upper end of the cylindrical wall portion 16c of the heat shield 16, and the inner diameter A of the upper end of the second cooling body 13 is smaller than the inner diameter of the upper end of the cylindrical wall portion 16c of the heat shield 16. The lower end of the second cooling body 13 is preferably located above the inner periphery of the bottom wall portion 16b of the heat shield 16, and the inner diameter A of the lower end of the second cooling body 13 is greater than or equal to the inner diameter of the inner periphery of the bottom wall portion 16b of the heat shield 16. Therefore, it is possible to prevent the evaporation material from the melt 4 from adhering to and solidifying at the lower end of the second cooling body 13, and to prevent the adhered / solidified material from falling onto the melt 4 and causing dislocations in the growing single crystal 2. In addition, the inner diameter of the bottom wall portion 16b of the heat shield 16 is preferably set to a size that does not obstruct the light path L including the boundary between the growing single crystal 2 and the melt 4.

[0027] The above describes the embodiments of the present invention, but the present invention is not limited to the foregoing embodiments, and various changes can be made to the foregoing embodiments without departing from the spirit of the present invention.

[0028] Explanation of reference numerals in the attached figures 1. Single crystal pulling device 2 Single crystal 2a Neck 2b Shoulder 2c Straight section 3. Crucible 4 Molten liquid 4a Liquid level 5 Seed Crystals 6. Seed crystal pulling device 6a Seed Crystal Chuck 6b wire 6c winding device 7. Control device 8 main cavity 8a Outer peripheral wall 8b Top Wall 8c bottom wall 9. Pulling cavity 9a Zhoubi 9b Top Wall 10 Heaters 11 Thermal insulation components 12 First Cooling Body 13 Second Cooling Body 14 Filming equipment 15. Window section 16. Heat shield 16a Opening 16b Bottom wall section 16c Cylinder wall section 16d Flange wall A inner diameter B Inner Diameter C Outer diameter D Distance E length G1 gap G2 gap L optical path O Central axis S1 Lower Space S2 upper space.

Claims

1. A single-crystal pulling device based on the Czechlausky method, have: A cylindrical first cooling body cools the single crystal around the outer peripheral surface of the single crystal being grown from the molten liquid in the crucible; A second cooling body in the shape of an inverted cone is disposed below the first cooling body and cools the single crystal around the outer peripheral surface of the single crystal being grown; The imaging device was used to observe the surface of the molten liquid. The inner diameter of the upper end of the second cooling element is larger than the outer diameter of the lower end of the first cooling element. A straight light path is formed, which passes from the liquid surface through the gap between the lower end of the second cooling body and the outer peripheral surface of the growing single crystal, and the gap between the upper end of the second cooling body and the lower end of the first cooling body to reach the imaging device.

2. The single-crystal pulling device as described in claim 1, characterized in that, When the inner diameter of the upper end of the second cooling body is set as A and the inner diameter of the lower end of the second cooling body is set as B, 1.1≤A / B≤1.

5.

3. The single-crystal pulling apparatus as described in claim 1 or 2, characterized in that, The distance between the lower end of the second cooling body and the outer peripheral surface of the growing single crystal is 20~70mm.

Images