Single crystal pulling equipment

Abstract

To provide a single crystal pulling device that has excellent single crystal cooling performance and allows observation of the liquid surface. [Solution] A single crystal pulling apparatus using the Czochralski method, comprising: a cylindrical first cooling body that surrounds the outer peripheral surface of a single crystal being grown as it is pulled from a melt in a crucible and cools the single crystal; a second cooling body that is an inverted conical cylindrical body that is positioned below the first cooling body and surrounds the outer peripheral surface of the single crystal being grown and cools the single crystal; and an imaging device that observes the liquid surface of the melt, wherein the inner diameter of the upper end of the second cooling body is larger than the outer diameter of the lower end of the first cooling body, and a linear optical path is formed from the liquid surface to the imaging device, through the gap between the lower end of the second cooling body and the outer peripheral surface of the single crystal being grown, and the gap between the upper end of the second cooling body and the lower end of the first cooling body.

Description

[Technical Field]

[0001] The present invention relates to a single crystal pulling apparatus. [Background technology]

[0002] A single crystal pulling apparatus using the Czochralski method is known, which has a cylindrical cooling body that surrounds the outer surface of the single crystal being grown and pulled from the melt in the crucible to cool the single crystal, and an imaging device that observes the liquid surface of the melt in the crucible (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-165790 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, it is claimed that by surrounding the outer peripheral surface of a single crystal being grown with a cooling body to cool the single crystal, the single crystal can be cooled effectively during growth, thereby improving the pulling rate, and that the boundary region between the single crystal and the liquid surface can be observed with an imaging device through a notch provided at the bottom end of the cooling body. However, providing a notch at the bottom end of the cooling body has the problem of deteriorating the uniformity of heat distribution in the circumferential direction at the notch.

[0005] An object of the present invention is to provide a single crystal pulling apparatus which is excellent in single crystal cooling performance and allows observation of the liquid surface. [Means for solving the problem]

[0006] One aspect of the present invention is as follows.

[0007] [1] A single crystal pulling apparatus using the Czochralski method, a cylindrical first cooling body that surrounds the outer peripheral surface of the single crystal being grown and pulled up from the melt in the crucible to cool the single crystal; a second cooling body having an inverted conical cylindrical shape, which is disposed below the first cooling body and surrounds the outer peripheral surface of the single crystal being grown to cool the single crystal; an imaging device for observing the liquid surface of the melt, The inner diameter of the upper end of the second cooling body is larger than the outer diameter of the lower end of the first cooling body, a linear optical path is formed from the liquid surface to the imaging device, through a gap between the lower end of the second cooling body and the outer peripheral surface of the single crystal being grown, and through a gap between the upper end of the second cooling body and the lower end of the first cooling body.

[0008] [2] The single crystal pulling apparatus according to [1], wherein, when the inner diameter of the upper end of the second cooling body is A and the inner diameter of the lower end of the second cooling body is B, 1.1≦A / B≦1.5.

[0009] [3] The single crystal pulling apparatus according to [1] or [2], wherein the distance between the lower end of the second cooling body and the outer circumferential surface of the single crystal being grown is 20 to 70 mm. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a single crystal pulling apparatus that has excellent single crystal cooling performance and allows observation of the liquid surface. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing a single crystal pulling apparatus according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

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

[0013] 1, in one embodiment of the present invention, the single crystal pulling apparatus 1 is a single crystal pulling apparatus 1 using the Czochralski method, and includes a crucible 3 (a double crucible with a quartz crucible inside a graphite crucible) that stores a melt 4 that will be the material for a single crystal 2 such as silicon, a seed pulling device 6 that pulls up a seed 5 that comes into contact with the liquid surface 4a of the melt 4 at the start of growing the single crystal 2 while rotating it about a central axis O, and a control device 7 configured by a computer or the like that controls the rotation speed and pulling speed of the seed 5 by the seed pulling device 6. The seed pulling device 6 includes a seed chuck 6a that holds the seed 5, a wire 6b whose one end is connected to the seed chuck 6a, and a winding device 6c that winds up the wire 6b from the other end. After the lower end of the seed 5 is immersed in the liquid surface 4a, the seed 5 is raised while rotating, thereby forming a neck portion 2a at the lower end of the seed 5, forming a shoulder portion 2b whose diameter gradually increases, and then growing a straight body portion 2c having an approximately cylindrical shape centered on the central axis O.

[0014] In this embodiment, a direction perpendicular to the central axis O is referred to as a radial direction, a direction going around the central axis O is referred to as a circumferential direction, and a cross section perpendicular to the central axis O is referred to as a transverse cross section.

[0015] The single crystal pulling apparatus 1 includes a main chamber 8 having an outer peripheral wall 8a with a circular cross section, a top wall 8b that is annular in top view and connected to the upper end of the outer peripheral wall 8a, and a bottom wall 8c that is connected to the lower end of the outer peripheral wall 8a, and in which a crucible 3 is disposed, and a pull chamber 9 having a peripheral wall 9a that extends upward from the inner peripheral edge of the top wall 8b of the main chamber 8 and a top wall 9b that is connected to the upper end of the peripheral wall 9a, and into which the single crystal 2 being grown is pulled and introduced. Inside the main chamber 8, a heater 10 that surrounds and heats the outer periphery of the crucible 3, and a heat insulating material 11 that surrounds the outer periphery of the crucible 3 and keeps it warm are disposed.

[0016] The single crystal pulling apparatus 1 has a cylindrical first cooling body 12 having a circular cross section centered on a central axis O, which surrounds the outer peripheral surface of the single crystal 2 being grown and pulled up from the liquid surface 4a to cool the single crystal 2. The first cooling body 12 extends downward from the inner peripheral edge of the top wall 8b of the main chamber 8. The first cooling body 12 may be cylindrical, or may be conical or inverted conical. From the viewpoint of improving cooling performance, the first cooling body 12 is preferably configured to have a flow path therein through which a cooling medium circulates that cools the first cooling body 12 by heat exchange.

[0017] The single crystal pulling apparatus 1 has a second cooling body 13 that is disposed below the first cooling body 12 and surrounds the outer peripheral surface of the single crystal 2 being grown to cool the single crystal 2. The second cooling body 13 has an inverted conical cylindrical shape centered on a central axis O. In other words, 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 therein through which a cooling medium that cools the second cooling body 13 by heat exchange flows.

[0018] The single crystal pulling apparatus 1 has an imaging device 14 for observing the liquid surface 4 a. The imaging device 14 is, for example, a camera, a scanner, or an image sensor. As in this embodiment, the imaging device 14 is preferably provided outside a window 15 made of a light-transmitting material provided in the ceiling wall 8 b of the main chamber 8, and the liquid surface 4 a is preferably 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, and a linear optical path L is formed from the liquid surface 4a to the imaging device 14, through a gap G1 between the lower end of the second cooling body 13 and the outer peripheral surface of the single crystal 2 being grown, and a gap G2 between the upper end of the second cooling body 13 and the lower end of the first cooling body 12.

[0020] According to the above configuration, not only is the cooling performance of the cylindrical first cooling body 12 exhibited, but also the cooling performance of the second cooling body 13, whose lower end is brought close to the liquid surface 4a, is exhibited, resulting in an extremely high cooling effect on the single crystal 2 being grown. Furthermore, by forming the second cooling body 13 into an inverted cone shape, the field of view of the imaging device 14 is expanded, and an optical path L passing between the second cooling body 13, the first cooling body 12, and the single crystal 2 being grown can be secured, allowing the liquid surface 4a to be observed by the imaging device 14. In particular, in this embodiment, as shown in FIG. 1 , the optical path L includes the boundary between the single crystal 2 being grown and the melt 4, making it possible to observe this boundary and control the diameter of the single crystal 2 being grown. Furthermore, by observing the liquid surface 4a, it is also possible to control the distance (gap) between the liquid surface 4a and the lower end of the thermal shield 16 (described later) to a predetermined value.

[0021] As described above, when the inner diameter of the upper end of second cooling body 13 is A and the inner diameter of the lower end of second cooling body 13 is B, it is preferable that 1.1≦A / B≦1.5. By making 1.1≦A / B, it is possible to easily ensure the optical path L necessary for observing liquid surface 4a by imaging device 14. By making A / B≦1.5, it is possible to prevent second cooling body 13 from being too far away from single crystal 2 being grown, and the cooling effect of second cooling body 13 from being too reduced.

[0022] The distance D between the lower end of the inner circumferential surface of second cooling body 13 and the outer circumferential surface of 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 preventing contact between second cooling body 13 and single crystal 2 being grown, and by setting the distance D to 70 mm or less, it is possible to prevent the cooling effect of second cooling body 13 from decreasing too much. The length E in the vertical direction from the upper end to the lower end of second cooling body 13 is preferably 100 to 400 mm.

[0023] The lower end of the first cooling body 12 is preferably located lower than the upper end of the second cooling body 13. With this configuration, the cooling effect that decreases as the upper end of the second cooling body 13 widens can be compensated for by the lower end of the first cooling body 12. The lower end of the first cooling body 12 is preferably located at a height that does not block the optical path L that includes the boundary between the single crystal 2 being grown and the melt 4.

[0024] As in this embodiment, the single crystal pulling apparatus 1 preferably includes a thermal shield 16 that divides the interior of the main chamber 8 into a lower space S1 and an upper space S2 and has an opening 16a in the center when viewed from above that connects the lower space S1 and the upper space S2. The single crystal 2 being grown passes through the opening 16a from the liquid surface 4a and is pulled into the pull chamber 9 while being cooled by the second cooling body 13 and the first cooling body 12 in the upper space S2. The inert gas, such as argon, introduced into the pull chamber 9 flows in this order: radially inward of the first cooling body 12, radially inward of the second cooling body 13, the opening 16a of the thermal shield 16, between the liquid surface 4a and the thermal shield 16, and between the outer circumferential surface of the crucible 3 and the thermal insulating material 11, and is then discharged from an outlet (not shown) provided at the bottom of the main chamber 8.

[0025] As in this embodiment, the thermal shield 16 preferably has a bottom wall portion 16b that is annular in top view and has an opening 16a in the center in top view, a cylindrical wall portion 16c that extends upward from the outer periphery of the bottom wall portion 16b, and a flange wall portion 16d that is annular in top view and extends radially outward from the upper end of the cylindrical wall portion 16c and is continuous with the outer periphery wall 8a of the main chamber 8. Note that, although this embodiment shows a form in which the bottom wall portion 16b extends horizontally in the radial direction, the bottom wall portion 16b may be inclined downward from the cylindrical wall portion 16c toward the liquid level 4a.

[0026] From the viewpoint of ensuring the introduction of the inert gas into the thermal shield 16, it is preferable that the lower end of the first cooling body 12 be located below the upper end of the cylindrical wall 16c of the thermal shield 16. It is also desirable that the second cooling body 13 be disposed within the thermal shield 16 so as to cool the single crystal 2 as soon as possible after it has been grown. From this viewpoint, it is preferable that the upper end of the second cooling body 13 be located below the upper end of the cylindrical wall 16c of the thermal shield 16, and that the inner diameter A of the upper end of the second cooling body 13 be smaller than the inner diameter of the upper end of the cylindrical wall 16c of the thermal shield 16. It is preferable that the lower end of the second cooling body 13 be located above the inner peripheral edge of the bottom wall 16b of the thermal shield 16, and that the inner diameter A of the lower end of the second cooling body 13 be equal to or greater than the inner diameter of the inner peripheral edge of the bottom wall 16b of the thermal shield 16. This prevents the evaporant from evaporating from the melt 4 from adhering to the lower end of the second cooling body 13 and solidifying, and also prevents the adhering and solidified adherant matter from falling into the melt 4 and causing dislocations in the single crystal 4 being grown. The inner diameter of the bottom wall portion 16b of the thermal shield 16 is preferably set to a size that does not block the optical path L including the boundary between the single crystal 2 being grown and the melt 4.

[0027] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the above-described embodiments can be modified in various ways without departing from the gist of the present invention. [Explanation of symbols]

[0028] 1. Single crystal pulling device 2. Single crystal 2a Neck 2b Shoulder part 2c Straight body part 3 Crucible 4 Melt 4a Liquid level 5 seed 6 Seed lifting device 6a Seed Chuck 6b wire 6c hoisting device 7 Control Device 8 Main Chamber 8a Outer wall 8b Ceiling wall 8c bottom wall 9 Pull Chamber 9a Peripheral wall 9b Top wall 10 Heater 11. Insulation 12 First cooling body 13 Second cooling body 14 Imaging device 15 Window section 16 Heat shield 16a aperture 16b Bottom wall 16c Cylinder wall 16d Flange wall A Inner diameter B Inner diameter C Outer diameter D distance E Length G1 Gap G2 gap L optical path O center axis S1 lower space S2 upper space

Claims

1. A single crystal pulling apparatus using the Czochralski method, a cylindrical first cooling body that surrounds the outer peripheral surface of the single crystal being grown and pulled up from the melt in the crucible to cool the single crystal; a second cooling body having an inverted conical cylindrical shape, which is disposed below the first cooling body and surrounds the outer peripheral surface of the single crystal being grown to cool the single crystal; an imaging device for observing the liquid surface of the melt, an inner diameter of an upper end of the second cooling body is larger than an outer diameter of a lower end of the first cooling body; a linear optical path is formed from the liquid surface to the imaging device through a gap between the lower end of the second cooling body and the outer peripheral surface of the single crystal being grown, and a gap between the upper end of the second cooling body and the lower end of the first cooling body.

2. 2. The single crystal pulling apparatus according to claim 1, wherein, when the inner diameter of the upper end of the second cooling body is A and the inner diameter of the lower end of the second cooling body is B, 1.1≦A / B≦1.

5.

3. 3. The single crystal pulling apparatus according to claim 1, wherein the distance between the lower end of the second cooling body and the outer peripheral surface of the single crystal being grown is 20 to 70 mm.

Images