JP2011057467A - Single crystal pulling apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To observe a semiconductor crystal or a specified observing position in a crucible from the outside of a chamber without reducing the quality of a semiconductor single crystal by the occurrence of a turbulent flow in a laminar flow tube. <P>SOLUTION: At least one flat plate-shaped observing window 31 is set on the laminar flow tube 15 in a single crystal pulling apparatus 10. The observing window 31 is made of the same quartz glass material as the laminar flow tube 15. The unification of the laminar flow tube 15 and the observing window 31 is performed by welding. The observing window 31 is arranged at a position where an inspection window 18 in the single crystal pulling apparatus 10 and a specified observing position 25 are in series, and the specified observing position 25 is observed from the outside of the chamber 11. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a single crystal pulling apparatus according to the Czochralski method, and more particularly to a single crystal pulling apparatus having a rectifying cylinder for inducing an inert gas in a chamber.

  In a single crystal pulling apparatus for manufacturing a semiconductor single crystal using the Czochralski method, a phenomenon occurs in which SiO evaporated from the surface of the melt condenses and adheres to the surface of the single crystal and parts around the crucible. . For this reason, there is a problem that the fixed SiO is peeled off and mixed into the silicon melt, and the growing silicon single crystal is polycrystallized, resulting in a decrease in the yield of the silicon single crystal.

  In order to cope with this problem, a rectifying cylinder is disposed above the silicon melt contained in the crucible, and the single crystal is pulled up through the rectifying cylinder during single crystal growth, and an inert gas such as Ar is introduced from above. A configuration is known in which it is guided toward the silicon melt and allowed to flow onto the melt surface (see, for example, Patent Documents 1 and 2). According to this configuration, SiO evaporated from the melt surface can be taken into the inert gas and efficiently discharged out of the chamber through the discharge port.

  On the other hand, in the drawing process of pulling a single crystal, it is necessary to secure a diameter of a predetermined thickness so as to withstand the weight of the pulled single crystal while narrowing the diameter to make the seed crystal dislocation-free. It is. Therefore, it is important to accurately measure the aperture diameter of the crystal and control it appropriately. For this reason, in the conventional single crystal pulling apparatus, when there is no rectifying cylinder, a viewing window is provided on the shoulder of the chamber, and a camera such as a CCD camera is arranged outside the viewing window, and the aperture diameter in the chamber is measured. To be done. The chamber is also provided with a viewing window for various purposes such as checking the melting state of silicon when the silicon material in the crucible is heated.

  However, when the rectifying cylinder is provided as described above, there is a problem in that a desired position below the rectifying cylinder cannot be observed from the viewing window if the rectifying cylinder is not a transparent material. Further, even when the rectifying cylinder is formed of a transparent material such as quartz glass, there is a problem that accurate measurement and observation of a desired position becomes difficult due to the curved shape and distortion of the rectifying cylinder.

  For this reason, there is known a single crystal pulling apparatus in which a window portion is provided in a rectifying cylinder made of carbon, and a transparent quartz glass member is fitted into the window section so that the inside of the rectifying cylinder can be observed from the viewing window. (For example, refer to Patent Document 3). However, in the rectifying cylinder disclosed in Patent Document 3, a gap, a step, or the like is generated at a joint portion between the rectifying cylinder and a member fitted into the window portion, and turbulent flow is generated in the rectifying cylinder to reduce SiO removal performance. Has the problem. Further, since the quartz glass is bent with the same diameter as the carbon rectifying cylinder, there is a problem that the quartz glass is distorted and it is difficult to accurately measure and observe a desired position.

JP 2007-112663 A JP 2008-179515 A Japanese Patent Laid-Open No. 10-158091

  Accordingly, the object of the present invention, which has been focused on these points, is to suppress the generation of turbulent flow in the rectifying cylinder, so that the quality of the semiconductor single crystal is not reduced, and the semiconductor crystal or crucible is externally supplied from the outside of the chamber. An object of the present invention is to provide a single crystal pulling apparatus capable of accurately observing a predetermined observation position.

In order to achieve the above object, a single crystal pulling apparatus according to the present invention comprises:
A chamber having a viewing window located obliquely above;
An inert gas introduction part that is provided in an upper portion of the chamber and introduces an inert gas into the chamber;
A crucible disposed in the chamber and capable of storing a melt of a single crystal raw material;
A pulling mechanism capable of moving up and down relatively the single crystal grown from the seed crystal and the melt with respect to the crucible;
A cylinder having an internal space in which a single crystal pulled by the pulling mechanism can be lifted and having a lower end positioned in the vicinity of the surface of the melt and guiding the inert gas introduced from the inert gas introduction portion to the melt surface And a straight rectifying cylinder,
The rectifying tube has a transparent and flat plate-like observation window, and the observation window is made of the same material as the rectifying tube, and is arranged at a position in series with the viewing window and a predetermined observation position. It is characterized by this.

  The rectifying cylinder and the observation window are preferably both made of quartz glass and integrated, and in addition, the rectification cylinder and the observation window are integrated by welding. Is more preferred.

  Furthermore, it is preferable that the observation window has a lateral width in which a central angle of a portion where the observation window is provided on an outer periphery of a cross section of the rectifying cylinder is 45 degrees or less.

  In addition, the joint portion between the inner side surface of the rectifying cylinder and the observation window is subjected to R processing.

  As an embodiment of the present invention, a measurement camera is provided outside the viewing window and in a position in series with the predetermined observation position, the observation window and the viewing window, and the diaphragm in the single crystal diaphragming step It is preferable to measure the diameter or to measure the gap, which is the distance between the lower end of the heat shielding plate of the single crystal pulling apparatus and the melt surface in the crucible.

  Another embodiment of the present invention includes at least two viewing windows and an observation window, and a camera is provided for one of the viewing windows to observe the predetermined observation position. It is preferable that the predetermined position is visible from the viewing window.

  In addition, the chamber has another viewing window, and the flow straightening tube has another transparent and flat observation window, and the other observation window is made of the same material as the flow straightening tube, It can also be arranged at a position in series with the other viewing window and the predetermined observation position.

  In that case, a camera for measurement is provided at a position outside the viewing window and in series with the predetermined observation position, the observation window and the observation window, and the other observation position is observed. It is preferable that the predetermined position can be seen from the viewing window.

  Alternatively, the chamber has another viewing window, the flow straightening tube has another observation plate that is transparent and has a flat plate shape, and the other observation window is made of the same material as the flow straightening tube, It is arranged at a position that is in series with the viewing window and other predetermined observation positions.

  Alternatively, the chamber has another viewing window, and the other viewing window is arranged at a position in series with the observation window and another predetermined observation position.

  Alternatively, the rectifying cylinder has another observation window that is transparent and has a flat plate shape, and the other observation window is made of the same material as the rectification cylinder, and is in series with the observation window and other predetermined observation positions. Place at the position.

  According to the present invention, the rectifying cylinder has a transparent and flat plate-like observation window, and this observation window is made of the same material as the rectifying cylinder and is arranged at a position in series with the observation window and a predetermined observation position. Therefore, it is possible to accurately observe a predetermined observation position in the semiconductor crystal or the crucible from the outside of the chamber while suppressing the generation of turbulent flow in the rectifying cylinder.

It is a mimetic diagram showing a schematic structure of a single crystal pulling device concerning a 1st embodiment of the present invention. FIGS. 2A and 2B illustrate the flow straightening cylinder of FIG. 1, in which FIG. 1A is a perspective view and FIG. It shows the shape of the junction part of the observation window of the rectifying cylinder of FIG. 1, (a) is a cross-sectional view at the position of the observation window, (b) is a circle of a two-dot chain line shown in (a) It is an expanded sectional view of the enclosed part X. It is explanatory drawing which shows the dimension of the rectification | straightening cylinder of FIG. The rectification | straightening cylinder of the single crystal pulling apparatus which concerns on 2nd Embodiment of this invention is shown, Comprising: (a) is a perspective view, (b) is a top view. It is a perspective view which shows the rectification | straightening cylinder of the single crystal pulling apparatus which concerns on 2nd Embodiment of this invention.

(First embodiment)
Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic diagram showing a schematic configuration of a single crystal pulling apparatus according to a first embodiment of the present invention. This single crystal pulling apparatus 10 is mainly composed of a chamber 11, a crucible 12, a heater 13, a heat insulator 14, a rectifying cylinder 15, a heat shielding plate 16, and a pulling mechanism (not shown).

  The chamber 11 is a container sealed from an external atmosphere having a small diameter at the top and a large diameter at the bottom, and a crucible 12, a heater 13, a heat insulator 14 and the like are accommodated in the large diameter bottom. An upper portion of the chamber 11 is provided with an inert gas introduction portion (not shown) for introducing an inert gas into the chamber so that the inert gas flows into the rectifying cylinder 15. Further, an inert gas discharge port 17 is provided at the lower portion of the chamber 11 and is connected to a vacuum pump via an exhaust pipe (not shown). In addition, a viewing window 18 for measuring the diameter of silicon in the drawing process on the single crystal pulling is provided on the shoulder located between the upper portion having a small diameter and the lower portion having a large diameter. Outside, a camera 19 having an imaging element such as a CCD is disposed with the imaging lens facing the viewing window 18.

  The crucible 12 is made of a quartz glass material, is disposed in the chamber 11, has a bottomed substantially cylindrical shape, and stores a silicon melt 20 that is a raw material of a semiconductor single crystal obtained by melting polycrystalline silicon. . The crucible 12 rotates around a central axis at a predetermined speed and is supported by a shaft 21 that can be driven up and down. A heater 13 is disposed around the crucible 12, and a heat insulator 14 is disposed around the heater 13 so as to surround the crucible 12 and the heater.

  The pulling mechanism is configured to include the pulling wire 22, and the pulling wire 22 can be lifted while controlling the speed by a pulling drive unit (not shown) provided on the upper part of the single crystal pulling apparatus 10. When pulling up the single crystal, the seed crystal 23 is attached to the seed holder 24 provided at the lower end of the pull-up wire 22, immersed in the melt in the crucible, and then pulled up while rotating the seed holder 24.

  The rectifying cylinder 15 is a cylindrical member made of, for example, a quartz glass material, and extends from an upper portion having a small diameter of the chamber 11 to the vicinity of the surface of the silicon melt 20. At the time of pulling up the single crystal, the pulled up single crystal is arranged so as to pass through the inside of the rectifying cylinder 15. Further, the inert gas introduced from the above-described inert gas introduction part passes through the inside of the rectifying cylinder 15 and is guided to the surface of the silicon melt 20. Typical dimensions of a flow straightening cylinder used in a single crystal pulling apparatus having a diameter of 200 mm are, for example, a radius of 130 mm, a height of 300 mm, and a thickness of 4 mm.

  The heat shielding plate 16 is provided to suppress the radiant heat that the single crystal receives from the melt in the crucible 12 when the single crystal is pulled, and has a tapered shape whose diameter narrows downward, and its lower end is When the silicon single crystal is pulled, it extends near the surface of the silicon melt and is coupled to the lower end of the rectifying cylinder 15.

  FIG. 2 shows an example of the rectifying cylinder 15 of FIG. 1, in which (a) is a perspective view and (b) is a plan view. The rectifying cylinder 15 includes an observation window 31 at a substantially central portion of the side surface. This observation window 31 is formed by cutting and removing a part of the curved side surface of the rectifying cylinder 15 into a rectangular shape, and is made of the same quartz glass material as that of the rectifying cylinder at that location, transparent, and having a flat plate portion It is a combination. As shown in FIG. 2B, the flat plate portion of the observation window 31 is in contact with the side surface of the rectifying cylinder 15 at the upper and lower center positions, and the outer periphery of the flat plate portion has no gap with the rectifying cylinder 15. Are so coupled.

  Further, the observation window 31 of the rectifying cylinder 15 is arranged at a desired observation position 25 where the single crystal is pulled from the silicon melt 20 and a position in series with the observation window 18. As a result, the observation position 25 can be imaged by the camera 19 through the observation window 18 and the observation window 31.

  FIG. 3 shows the shape of the joint portion of the observation window 31 of the flow straightening cylinder 15 in FIG. 1, wherein (a) is a cross-sectional view at the observation window position, and (b) is shown in (a). It is an expanded sectional view of the part X enclosed with the circle | dot of the dashed-two dotted line. The rectifying cylinder 15 and the observation window 31 are joined together by heating, that is, by heating the welded portion with a quartz welding burner, applying pressure to each other and without any gaps. For this reason, as shown in FIG.3 (b), the rectification | straightening cylinder 15 and the observation window 31 are integrated. Further, at the connecting portion between the rectifying cylinder 15 and the observation window 31, the inner surface is subjected to R processing (radius R = about 3 mm) so that turbulent flow is not generated in the inert gas passing through the rectifying cylinder 15.

  If the observation window 31 having a flat plate portion is enlarged, the rotational symmetry of the rectifying cylinder 15 is lost, so that turbulence occurs and the rectifying effect of the inert gas in the rectifying cylinder 15 is lost. . For this reason, from the viewpoint of the rectifying effect, it is desirable to reduce the lateral width of the observation window 31. Specifically, if the central angle of the portion provided with the observation window on the outer periphery of the cross section of the rectifying cylinder 15 is 45 degrees or less, the rectifying effect of the rectifying cylinder 15 is maintained and the transition of the crystal is caused. It is confirmed that it can be lifted.

  With the configuration as described above, the single crystal pulling apparatus 10 allows the rectifying cylinder 15 to be moved from the inert gas introduction portion when pulling up the single crystal by pulling the seed crystal 23 after contacting the silicon melt 20. The inert gas is introduced, and the inside of the chamber 11 is exhausted by the vacuum pump, so that SiO generated from the surface of the silicon melt 20 is exhausted together with the inert gas from the exhaust port 17. At that time, the observation position 25 can be observed through the observation window 18 and the observation window 31 using the camera 19 in each step. Further, since the observation window 31 is made of flat transparent quartz glass, the camera 19 can obtain an accurate image without being affected by distortion. In particular, in the crystal pulling diaphragm step, the diaphragm diameter is measured based on the camera image, and the pulling drive unit can be controlled by a control device (not shown) according to the measured diaphragm diameter.

  Furthermore, since the observation window 31 and the rectifying cylinder 15 are made of the same quartz glass material and are joined by welding, the observation window 31 or the rectifying cylinder 15 is not deformed or damaged by the stress due to the difference in thermal expansion coefficient. Since there are no gaps or steps between the observation window 31 and the rectifying cylinder 15, it is possible to suppress the occurrence of turbulent flow in the inert gas passing through the rectifying cylinder 15.

  Further, the inner surface of the coupling portion between the rectifying cylinder 15 and the observation window 31 is subjected to R processing, and the central angle of the portion where the observation window is provided on the outer periphery of the cross section of the rectifying cylinder 15 is 45 degrees or less. As a result, the occurrence of turbulent flow in the flow straightening cylinder can be further suppressed.

  Further, when the single crystal is pulled, the shaft 21 is rotated, and the shaft 21 is raised in accordance with the decrease of the silicon melt 20, whereby the measurement position 25 that is the interface between the silicon melt 20 and the single crystal is set. It is possible to observe continuously.

  As described above, according to the present embodiment, the rectifying cylinder is provided with a transparent flat plate-like observation window made of the same quartz glass material as that of the rectifying cylinder, and the semiconductor crystal or the crucible inside the rectifying cylinder through the observation window. Therefore, a predetermined observation position in the semiconductor crystal or the crucible can be set from the outside of the chamber without generating turbulent flow. It becomes possible to observe. This makes it possible to improve the accuracy of control when pulling up the single crystal without reducing the yield of the semiconductor single crystal.

(Second Embodiment)
FIG. 5 shows a rectifying cylinder of a single crystal pulling apparatus according to a second embodiment of the present invention, where (a) is a perspective view and (b) is a plan view. In the present embodiment, another observation window 41 similar to the observation window 31 is provided at a position rotated 90 degrees with respect to the observation window 31 of the rectifying cylinder 15, and the chamber 11 shown in FIG. Another viewing window (not shown) is provided at the corresponding position. Other configurations are the same as those in the first embodiment.

  As a result, it is possible not only to measure the measurement location 25 with the camera 19 but also to visually confirm it through another viewing window and observation window 41. Therefore, the judgment by the person is added to the judgment by the apparatus, and the accuracy of the control for pulling the single crystal can be improved.

(Third embodiment)
FIG. 6 is a perspective view showing a rectifying cylinder of the single crystal pulling apparatus according to the third embodiment of the present invention. As shown in the figure, the rectifying cylinder 15 is further provided with a flat observation window 42 in addition to the configuration of the second embodiment. A corresponding viewing window (not shown) corresponding to the chamber 11 is also provided so that other predetermined positions inside the crucible 12 and the rectifying cylinder 15 can be observed.

  Thus, by providing the flat observation window 42 on the side surface of the rectifying cylinder 15, a desired position different from the measurement position 25 can be accurately observed. Thereby, for example, it is possible to measure a gap which is a distance between the lower end of the heat shielding plate 16 of the single crystal pulling apparatus and the liquid surface of the silicon melt 20.

  In this embodiment, a plurality of observation windows and observation windows are provided to enable observation at different positions. However, the method for observing a plurality of positions is not limited thereto. For example, in the first embodiment, by providing another viewing window in a position that is in series with the observation window 31 and another predetermined observation position, two observation windows and two observation windows can be used for two observation positions. Observation becomes possible. Further, by providing another observation window made of the same material as that of the flat plate-like rectifying cylinder 15 at a position in series with the sighting window 18 of the rectifying cylinder 15 and another predetermined observation position, one observation window is provided. Two observation positions can be observed by the window and the two observation windows.

  In addition, this invention is not limited only to the said embodiment, Many deformation | transformation or a change is possible. For example, although the shape of the observation window is rectangular, the shape is not limited to this, and may be any shape such as a round shape. Further, the quartz glass may be joined to the rectifying cylinder and the observation window by heating with laser light irradiation without using a burner.

  According to the present invention, it is possible to accurately observe a fixed observation position in the single crystal or the crucible from the outside of the chamber while suppressing generation of turbulent flow in the flow straightening cylinder.

DESCRIPTION OF SYMBOLS 10 Single crystal pulling apparatus 11 Chamber 12 Crucible 13 Heater 14 Heat insulator 15 Current-carrying tube 16 Heat shielding board 17 Exhaust port 18 Viewing window 19 Camera 20 Silicon melt 21 Shaft 22 Pulling wire 23 Seed crystal 24 Seed holder 25 Observation position 31 , 41, 42 Observation window

Claims (12)

A chamber having a viewing window located obliquely above;
An inert gas introduction part that is provided in an upper portion of the chamber and introduces an inert gas into the chamber;
A crucible arranged in the chamber and capable of storing a melt of a single crystal raw material;
A pulling mechanism capable of moving up and down relatively the single crystal grown from the seed crystal and the melt with respect to the crucible;
A cylinder having an internal space in which a single crystal pulled by the pulling mechanism can be lifted and having a lower end positioned in the vicinity of the surface of the melt and guiding the inert gas introduced from the inert gas introduction portion to the melt surface A straight rectifier,
The rectifying tube has a transparent and flat plate-like observation window, and the observation window is made of the same material as the rectifying tube, and is arranged at a position in series with the viewing window and a predetermined observation position. A single crystal pulling apparatus.   The single crystal pulling apparatus according to claim 1, wherein the rectifying cylinder and the observation window are both made of quartz glass and integrated.   The single crystal pulling apparatus according to claim 2, wherein the rectifying cylinder and the observation window are integrated by welding.   The said observation window has a horizontal width | variety in which the central angle of the part in which the said observation window is provided in the outer periphery of the cross section of the said rectification | straightening cylinder becomes 45 degrees or less. A single crystal pulling apparatus according to claim 1.   The single crystal pulling apparatus according to any one of claims 1 to 4, wherein a joint portion of the inner surface of the flow straightening tube with the observation window is subjected to R processing.   A measuring camera is provided outside the observation window and in a position in series with the predetermined observation position, the observation window and the observation window, and the diameter of the diaphragm in the single crystal diaphragming step is measured. The single crystal pulling apparatus according to any one of claims 1 to 5.   A camera for measurement is provided outside the viewing window and in a position in series with the predetermined observation position, the observation window and the viewing window, and the lower end of the heat shield plate of the single crystal pulling apparatus and the crucible The single crystal pulling apparatus according to claim 1, wherein a gap that is a distance between the melt surface and the melt surface is measured.   The chamber has another viewing window, and the rectifying cylinder has another observation plate that is transparent and has a flat plate shape. The other observation window is made of the same material as the rectifying cylinder, and the other The single crystal pulling apparatus according to claim 1, wherein the single crystal pulling apparatus is disposed at a position that is in series with the viewing window and the predetermined observation position.   A camera for measurement is provided outside the viewing window and in a position in series with the predetermined observation position, the observation window, and the observation window, to observe the predetermined observation position, and from the other observation window The single crystal pulling apparatus according to claim 8, wherein the predetermined position is visible.   The chamber has another viewing window, the flow straightening tube has another observation plate that is transparent and has a flat plate shape, and the other observation window is made of the same material as the flow straightening tube, and the other viewing window The single crystal pulling apparatus according to any one of claims 1 to 5, wherein the single crystal pulling apparatus is disposed at a position in series with another predetermined observation position.   The said chamber has another observation window, This other observation window is arrange | positioned in the position which is in series with the said observation window and another predetermined observation position, The one of Claims 1-5 characterized by the above-mentioned. The single crystal pulling apparatus according to one item.   The rectifying cylinder is transparent and has a flat plate-like other observation window, and the other observation window is made of the same material as the rectification cylinder, and is positioned in series with the observation window and other predetermined observation positions. The single crystal pulling apparatus according to any one of claims 1 to 5, wherein the single crystal pulling apparatus is arranged.

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