JP6610816B1 - Silicon single crystal pulling device - Google Patents

Abstract

An oxygen concentration in a silicon single crystal is reduced by improving airtightness of a rectifying cylinder. An outer cylinder arranged on a silicon melt so as to concentrically surround a silicon single crystal to be pulled up and having a window hole, and a window portion arranged inside the outer cylinder and corresponding to the window hole A silicon single crystal pulling device provided with an inner cylinder having an inner cylinder and a window glass attached to the window portion and covering the window hole, attached to an upper end of the inner cylinder, and attached to an upper edge portion of the window glass A cap that contacts the lower edge of the window glass and an edge of the inner cylinder that contacts the window glass, both of which have a tapered shape with the window glass facing outside; Due to its own weight, it is slidable along the contact surface between the lower edge of the window glass and the edge of the inner cylinder that contacts the window glass, and the window glass is attached to the inner surface of the outer cylinder with the cap attached. It is what makes it adhere A silicon single crystal pulling apparatus, wherein the door. [Selection] Figure 1

Description

  The present invention relates to a silicon single crystal pulling apparatus for pulling a silicon single crystal from a silicon melt by a CZ (Czochralski) method.

  Conventionally, silicon single crystals have been manufactured by pulling up by the CZ method. In this method, a polycrystalline silicon raw material is placed in a quartz glass crucible, heated by a graphite heater and melted, a seed crystal attached to the lower end of the upper shaft is immersed in the melt, and the upper shaft is rotated, A silicon single crystal is grown by pulling it up at a low speed. An apparatus for growing a single crystal in this way is a silicon single crystal pulling apparatus.

  Conventionally, oxygen precipitates have been formed in silicon single crystal wafers, and oxygen precipitates have been gettered to contaminate device processes. However, as the cleanliness of device processes has improved in recent years, oxygen precipitates have increased. Rather than improving the gettering ability, it is desired to reduce the number of oxygen precipitates and suppress the generation of crystal defects, and the demand for single crystals with low oxygen concentration is increased in order to reduce oxygen precipitates. I have done it.

A method for producing a single crystal having a low oxygen concentration includes a horizontal magnetic field application CZ method (Horizontal) in which a silicon single crystal pulling apparatus is equipped with a superconducting magnet magnetic field applying device, and the single crystal is pulled up while applying a horizontal magnetic field. A magnetic field applied CZ method (hereinafter, HMCZ method) is generally used (see, for example, Patent Document 1 and Patent Document 2). In this HMCZ method, a single crystal having a low oxygen concentration of, for example, 1 × 10 ¹⁷ atoms / cm ³ (ASTM'79) level can be obtained by rotating the quartz crucible at a low speed (for example, patents). Reference 3).

  However, when the quartz crucible is rotated at a low speed in this way, dislocation of the single crystal often occurs, and when the single crystal becomes dislocation, the pulling is interrupted, the single crystal is melted, and the pulling is performed again. And productivity was getting worse. Therefore, it has been necessary to compensate under conditions other than the magnetic field application so that the crucible rotation can be as high as possible.

  In addition, methods for obtaining low oxygen concentration single crystals other than the MCZ method have been pursued. In a silicon single crystal pulling apparatus provided with a graphite cylinder around a single crystal, it is disclosed that the oxygen concentration of the single crystal can be reduced by using a rectifying cylinder having a quartz plate covering a window hole of the graphite cylinder. (See Patent Document 4). According to this apparatus, the oxygen concentration can be reduced by about 3 ppma (JEITA) than usual.

  Further, Patent Document 5 discloses an apparatus in which a quartz cylinder (quartz cylinder) covering an inner wall of a graphite cylinder is installed as an apparatus for covering the window hole of the graphite cylinder. In this method, in order to prevent iron contamination from the graphite cylinder, a quartz cylinder that covers all of the high-temperature portion of 700 ° C. or more in the graphite cylinder is used, and the inside of the quartz cylinder is rectified with a taper inside. A ring is placed.

  However, in Patent Document 4, a groove is formed in the second cylinder placed inside the graphite cylinder, and a quartz window glass is fitted therein, thereby causing the following problems. First, due to the difference in thermal expansion coefficient between graphite and quartz, even if the structure fits without gaps at room temperature, if graphite expands during pulling, gaps will occur due to the difference in thermal expansion coefficient from quartz. Secondly, when a thin window glass is thermally deformed, it cannot be fitted, so it is necessary to provide a certain degree of tolerance (gap) so that it can be incorporated even with slight thermal deformation. was. Due to the above first and second problems, a gap of about 3% to 10% of the window glass area was formed, and the effect of reducing the oxygen concentration was suppressed.

  In addition, when the quartz cylinder is arranged inside the graphite cylinder as in Patent Document 5, there is no second problem when the window glass is incorporated as described above, but the thermal expansion coefficient of graphite and quartz is The first problem due to the difference occurs. In addition, the quartz cylinder is often used by cutting a commercial product, but the commercial product has a large tolerance, and the gap becomes 2 mm to 3 mm or more on one side. If the outer diameter of the quartz cylinder is turned with high precision so as to eliminate this gap, the processing cost of the quartz cylinder increases, and the surface of the quartz cylinder is contaminated by the machining. It is conceivable to fill the gap with a ring placed on the upper end of the quartz cylinder, but since the quartz cylinder exposed to high temperatures gradually undergoes thermal deformation, a gap is created between the ring and the quartz cylinder, and the gap can be completely blocked. Can not.

  In recent years, an apparatus (for example, see Patent Document 6) in which a cooling effect of a single crystal is enhanced by installing a water-cooled forced cooling cylinder around the single crystal and installing a graphite cylinder below the cylinder. As a result, the high temperature portion of the graphite cylinder was shortened and the growth rate of the single crystal was increased, thereby reducing the influence of iron contamination by the graphite cylinder. For this reason, it is no longer necessary to cover the entire inner surface of the graphite cylinder with a quartz cylinder. Instead, a quartz window glass that can be incorporated into the window portion of the graphite cylinder with high accuracy is used.

JP 11-139899 A JP-A-8-333191 JP 2009-132552 A Japanese Patent Publication No. 6-88864 JP 2007-314375 A Japanese Patent No. 3952356

  Thus, in recent years, in order to cover the window hole of the graphite cylinder, more quartz window glass has been used than the quartz cylinder. The reason for this is that, as described above, the quartz cylinder is a commercial product and has a large tolerance and cannot be incorporated into the graphite cylinder with high accuracy. In addition, if the outer peripheral surface or the inner peripheral surface is turned to improve accuracy, the transparency of the surface is impaired, and fire polishing (flame polishing) is required, which increases the processing cost. Further, since the quartz cylinder is a larger member than the window glass, the amount of deformation due to thermal expansion also increases. Further, the quartz cylinder has distortion, that is, unevenness on the surface, which adversely affects the accuracy of detecting the diameter of the pulled crystal during monitoring in the furnace by a camera. On the other hand, the window glass can be easily polished with high accuracy, can be purchased at a lower cost than the quartz tube, has no distortion, and has a higher accuracy in detecting the diameter of the camera than the quartz tube.

  From the above, as a method for obtaining a single crystal having a low oxygen concentration, there is a merit in using a window glass rather than a quartz cylinder. As described above, a graphite cylinder placed inside a graphite cylinder (hereinafter referred to as an outer cylinder). It is desired to solve the first and second problems in a structure in which a groove is formed in (hereinafter referred to as an inner cylinder) and a quartz window glass is fitted into the groove.

  In a structure in which a groove is formed in a graphite inner cylinder to be placed inside a graphite outer cylinder and a quartz window glass is fitted therein, the first problem is that due to the difference in thermal expansion coefficient between graphite and quartz, room temperature Even if the window glass is inserted without any gap, if the graphite is thermally expanded during pulling, a gap is generated due to the difference in thermal expansion coefficient from quartz. The second problem is that when the thin window glass is thermally deformed, it cannot be fitted into the graphite inner tube, so that a certain degree of tolerance (so that it can be incorporated even if there is slight heat deformation ( It is necessary to provide a gap). For this reason, in this structure, a gap of about 2% to 5% of the area of the window glass is formed, and the effect of reducing the oxygen concentration in the silicon single crystal to be pulled up is suppressed.

  The present invention has been made to solve the above problems, and in a structure in which a window glass is attached to an inner cylinder of a rectifying cylinder installed around a silicon single crystal being pulled, the airtightness of the rectifying cylinder is increased. An object of the present invention is to provide a silicon single crystal pulling apparatus capable of reducing the oxygen concentration in a silicon single crystal to be pulled up.

  In order to achieve the above object, in the present invention, an outer cylinder disposed on the silicon melt so as to concentrically surround the silicon single crystal to be pulled up, and having a window hole, and disposed inside the outer cylinder, A silicon single crystal pulling device comprising an inner cylinder having a window portion corresponding to the window hole, and a window glass attached to the window portion and covering the window hole, and attached to the upper end of the inner cylinder, A cap that contacts the upper edge of the window glass; both the lower edge of the window glass and the edge of the inner cylinder that contacts the window glass have a tapered shape with the window glass facing outside; and The window glass is slidable along a contact surface between a lower edge portion of the window glass and an edge portion of the inner cylinder that contacts the window glass by its own weight, and the window is attached with the cap attached. Glass of the outer cylinder Providing a silicon single crystal pulling apparatus, characterized in that to adhere to the surface.

  According to such a silicon single crystal pulling apparatus, in the structure in which the window glass is attached to the inner cylinder of the rectifying cylinder installed around the silicon single crystal being pulled up, the silicon single crystal that is pulled up by increasing the airtightness of the rectifying cylinder It becomes possible to reduce the oxygen concentration inside.

  That is, both the lower edge of the window glass and the edge of the inner cylinder that contacts the window glass have a tapered shape with the window glass facing outside, and the window glass is separated from the lower edge of the window glass by the weight of the cap. It is slidable along the contact surface with the edge of the inner cylinder that contacts it. Therefore, the gap generated by the difference in thermal expansion coefficient between the inner cylinder and the window glass (the first problem) and the gap considering the thermal deformation of the window glass (the second problem) are caused by attaching the cap. When the window glass slides and the window glass comes into close contact with the inner surface of the outer cylinder, the problem is solved. Thereby, it becomes possible to reduce the oxygen concentration in the silicon single crystal to be raised by increasing the airtightness of the rectifying cylinder.

It is preferable that the upper end side of the inner cylinder is open.
In this case, the attachment of the window glass is facilitated, and when the cap is attached to the upper end of the inner cylinder, the weight of the cap can be effectively transmitted to the window glass via the upper edge of the window glass. It becomes possible.

The cap preferably has a ring shape so as to surround the silicon single crystal to be pulled up concentrically.
In this case, the cap can be put on the entire circumference of the upper end of the inner cylinder, and the position of the cap on the inner cylinder can be stabilized. Moreover, according to such a structure, when several window glass is attached to an inner cylinder, it becomes possible to transmit the self-weight of a cap equally to these several window glass.

Both the upper edge of the window glass and the edge of the cap that contacts the window glass have a tapered shape with the window glass facing outside, and the window glass is placed on the window glass by its own weight. It is preferable that it is slidable along the contact surface of an edge part and the edge part of the said cap which contacts it.
In this case, the window glass can slide along both the contact surface of the inner cylinder and the window glass and the contact surface of the cap and the window glass. Therefore, the sliding of the window glass is performed so that the main surface of the window glass approaches the inner surface of the outer cylinder evenly, that is, the window glass moves in the radial direction perpendicular to the central axis of the inner cylinder or the outer cylinder. Since it can perform, the effect which does not produce a clearance gap between an outer cylinder and a window glass increases more.

The taper angle of the window glass is preferably 30 ° or more and 60 ° or less with respect to the horizontal plane.
In this case, the effect of suppressing the gap between the outer cylinder and the window glass can be improved, the strength of the window glass can be maintained, and the reliability can be improved.

  In other words, by setting the taper angle of the window glass to 30 ° or more with respect to the horizontal plane, the contact area between the window glass and the inner cylinder or cap is increased (the amount of sliding is increased), and a relatively large gap is generated. However, it is possible to compensate for this (fill the gap) by sliding the window glass. Moreover, it becomes easy to slide a window glass by the dead weight of a cap because the taper angle of a window glass shall be 30 degrees or more with respect to a horizontal surface.

  In addition, by setting the taper angle of the window glass to 60 ° or less with respect to the horizontal plane, the strength of the edge of the window glass (the tip of the portion having the tapered shape) can be secured, and the window glass can be made difficult to break. As a result, the reliability of the window glass can be improved.

The outer cylinder and the inner cylinder are made of graphite, and when the window glass is made of quartz, the above-described effect is maximized.
In other words, due to the difference in thermal expansion coefficient between graphite and quartz, even if the structure fits without gaps at room temperature, if graphite expands during pulling, a gap is generated due to the difference in thermal expansion coefficient with quartz. The problem can be solved. In addition, it is possible to solve the problem of tolerance (gap) in consideration of thermal deformation of a thin glass window made of quartz.

  As described above, according to the present invention, in the structure in which the window glass is attached to the inner cylinder of the rectifying cylinder installed around the silicon single crystal being pulled, It is possible to reduce the oxygen concentration.

It is sectional drawing which shows the example of the silicon single crystal pulling apparatus of this invention. It is a perspective view which shows the example of an outer cylinder, an inner cylinder, a window glass, and a cap. It is explanatory drawing which shows the example of an outer cylinder, an inner cylinder, a window glass, and a cap. It is an example of an outer cylinder, an inner cylinder, a window glass, and a cap, and is sectional drawing which shows the flow of the gas in an inner cylinder. It is sectional drawing which shows a mode that a window glass is pressed on the inner surface of an outer cylinder. It is sectional drawing which shows the example of the silicon single crystal pulling apparatus of a conventional structure. It is a perspective view which shows the example of an outer cylinder, an inner cylinder, and a window glass. It is explanatory drawing which shows the example of an outer cylinder, an inner cylinder, and a window glass. It is sectional drawing which shows the flow of the gas in an inner cylinder. It is sectional drawing which shows the relationship between a window glass and the inner surface of an outer cylinder. It is a figure explaining the definition of a taper angle. It is a figure which shows the example of the shape of a window glass.

  As described above, in the manufacture of a silicon single crystal by the CZ method in recent years, an inner cylinder having a window portion inside an outer cylinder arranged on the silicon melt so as to concentrically surround the silicon single crystal to be pulled up. And a structure of a rectifying cylinder that suppresses oxygen mixed in the silicon single crystal during pulling is employed by attaching a window glass to the window portion of the inner cylinder. In the silicon single crystal pulling apparatus having such a structure, the present invention is mainly an invention for further reducing the oxygen concentration in the silicon single crystal to be pulled up by increasing the airtightness of the rectifying cylinder.

  Conventionally, in such a structure, first of all, even if the window glass is fitted without a gap at room temperature due to the difference in thermal expansion coefficient between the inner cylinder and the window glass, the inner cylinder is being pulled during the pulling of the silicon single crystal. When thermal expansion occurs, there is a problem that a gap is generated between the inner cylinder and the window glass due to a difference in thermal expansion coefficient with the window glass (the first problem described above). In addition, if the window glass is thermally deformed before the thin window glass is attached to the inner cylinder, the window glass cannot be fitted into the inner cylinder. There was a problem that a certain degree of tolerance (gap) had to be provided so that the cylinder could be reliably incorporated (second problem described above).

  For this reason, in the structure, a gap of about 2% to 5% of the area of the window glass is generated between the window glass and the inner cylinder during the pulling of the silicon single crystal. For this reason, during the pulling up, an inert gas (for example, Ar gas) flowing from the upper part of the inner cylinder toward the upper surface of the silicon melt disposed at the lower part of the inner cylinder leaks from the gap of the inner cylinder, The amount of the inert gas flowing into the upper surface of the silicon melt is reduced. As a result, there is a problem that the amount of oxygen evaporated from the silicon melt is reduced and the oxygen concentration in the silicon single crystal pulled up from the silicon melt cannot be sufficiently reduced.

  Therefore, in the structure of the rectifying cylinder in which the window glass is attached to the inner cylinder installed around the silicon single crystal being pulled, the gap between the window glass and the inner cylinder is completely eliminated, and the airtightness of the rectifying cylinder is increased. Therefore, the amount of inert gas sprayed on the upper surface of the silicon melt is increased, and as a result, the amount of oxygen evaporated from the silicon melt is increased, and the oxygen evaporated from the silicon melt is discharged, so that the silicon Development of a technique that can further reduce the oxygen concentration in the crystal has been demanded.

  As a result of earnestly studying the above problems, the inventors of the present invention both processed the lower edge of the window glass and the edge of the inner cylinder in contact with the window glass so that the window glass has an outer tapered shape, In addition, by allowing the window glass to slide along the contact surface between the lower edge of the window glass and the edge of the inner cylinder that contacts the window glass by its own weight, there is a gap between the inner cylinder and the window glass. It has been found that even if it occurs, the gap can be closed by sliding the window glass. That is, in a state where a cap that contacts the upper edge of the window glass is attached to the upper end of the inner cylinder, if the window glass slides by its own weight, and is in close contact with the inner surface of the outer cylinder, It has been found that whatever gap is generated, it can be surely closed, and the present invention has been completed.

  That is, the present invention is arranged on the silicon melt so as to concentrically surround the silicon single crystal to be pulled up, and has an outer cylinder having a window hole, arranged inside the outer cylinder, and corresponds to the window hole. A silicon single crystal pulling apparatus comprising an inner cylinder having a window and a window glass attached to the window and covering the window hole, the upper edge of the window glass being attached to an upper end of the inner cylinder A cap that is in contact with a portion, and a lower edge portion of the window glass and an edge portion of the inner cylinder that are in contact with each other have a tapered shape with the window glass being outside, and the window glass is Due to the weight of the cap, it is slidable along the contact surface between the lower edge of the window glass and the edge of the inner cylinder that contacts the window glass, and the window glass is attached to the outer cylinder with the cap attached. Also close to the inner surface A silicon single crystal pulling apparatus, characterized in that it.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings, but the present invention is not limited thereto.

FIG. 1 shows an example of a silicon single crystal pulling apparatus of the present invention.
A quartz crucible 4 held by a graphite crucible 5 is installed in the main chamber 2 of the silicon single crystal pulling apparatus 1, and the graphite crucible 5 rotates around the bottom and is supported by a support shaft 10 that moves up and down. Above the main chamber 2 is provided a pull chamber 21 provided with an opening door for taking out the pulled silicon single crystal 3. The neck portion 23 of the main chamber 2 is provided with a graphite outer cylinder 11 having an upper end airtight and a lower end depending on the silicon melt 18, and a heat insulating ring 12 is attached to the lower end of the graphite outer cylinder 11. ing.

  By attaching the heat insulating ring 12, the silicon single crystal 3 to be pulled up has a sufficient heat shielding effect even when the diameter of the silicon single crystal 3 is increased, and the crystal heat history and the temperature distribution of the crystal are reduced without lowering the pulling speed. Easy to control.

  The graphite outer cylinder 11 and the graphite inner cylinder 13 are made of graphite coated with a SiC film or a pyrolytic carbon film, thereby preventing iron contamination of the single crystal being pulled from the graphite. A transparent plate-like window glass 14 is installed in the graphite inner cylinder 13, and the diameter of the silicon single crystal 3 pulled up by the camera is detected through the window glass 14 to monitor the inside of the furnace. The graphite outer cylinder 11, the graphite inner cylinder 13 and the window glass 14 constitute a so-called rectifying cylinder.

  An atmosphere gas (for example, Ar gas) introduction pipe 22 is provided above the pull chamber 21, and an exhaust gas pipe 24 for exhausting the introduced atmosphere gas is provided at the bottom of the main chamber 2. . Then, after melting the silicon raw material on the outer periphery of the graphite crucible 5, the graphite heater 6 and the heat shield 7 are installed to keep the silicon melt 18 at an appropriate temperature. Further, while introducing the atmospheric gas into the graphite outer cylinder 11 of the silicon single crystal manufacturing apparatus 1 from the introduction tube 22, the seed crystal 17 is immersed in the silicon melt 18 and wound up while rotating the pulling wire 16, so that the silicon single crystal is wound. The crystal 3 is pulled up.

  In such a silicon single crystal pulling apparatus 1, in the present invention, a transparent window glass 14 is installed in the graphite inner cylinder 13 so that the window glass 14 and the graphite inner cylinder 13 are in contact with each other with a taper. The contact surfaces are tapered, and the side surface of the window glass 14 is the inner surface of the graphite outer cylinder 11, that is, a plurality of windows of the graphite outer cylinder 11 due to the weight of the cap 15 installed on the window glass 14. Try to adhere to the pillars between the holes.

  Here, when the contact surfaces of the window glass 14 and the graphite inner cylinder 13 are tapered so that the window glass 14 and the graphite inner cylinder 13 are in contact with each other, the window glass 14 and the graphite inner cylinder 13 are tapered at the contact surfaces of each other. And the window glass 14 is slidable along the contact surface by its own weight.

  Details of the graphite outer cylinder 11, the graphite inner cylinder 13, the window glass 14, and the cap 15 will be described below.

  2, 3, and 4 show a graphite outer cylinder, a graphite inner cylinder, a window glass, and a cap. FIG. 2 is a perspective view of a graphite outer cylinder, a graphite inner cylinder, a window glass, and a cap. FIG. 3 is an explanatory diagram of a graphite inner cylinder, a window glass, and a cap. FIG. 4 shows the relationship between the graphite outer cylinder, the graphite inner cylinder, the window glass, and the cap in a state of being incorporated in the silicon single crystal pulling apparatus. FIG. 4 corresponds to a cross-sectional view taken along the line AA of FIG.

  The graphite outer cylinder 11 and the graphite inner cylinder 13 have a cylindrical shape centering on the central axis (dotted line) AX so as to concentrically surround the silicon single crystal pulled up from the silicon melt. The graphite inner cylinder 13 is disposed inside the graphite outer cylinder 11, and the cap 15 is attached to the upper end of the graphite inner cylinder 13.

  The graphite outer cylinder 11 has a plurality of window holes 11a in the circumferential direction surrounding the central axis AX, that is, in the circumferential direction of a circle centered on the central axis AX. Between the plurality of window holes 11a, pillars 11b of the graphite outer cylinder 11 are formed. Similar to the graphite outer cylinder 11, the graphite inner cylinder 13 has a plurality of window portions 13 a in the circumferential direction surrounding the central axis AX. The plurality of window portions 13a are provided at positions corresponding to the plurality of window holes 11a.

  The plurality of window portions 13a are open at the upper end side of the graphite inner cylinder 13. That is, the plurality of window portions 13 a have a slit shape cut from the upper end side of the graphite inner cylinder 13. This facilitates the attachment of the window glass 14, and when the cap 15 is attached to the upper end of the graphite inner cylinder 13, the weight of the cap 15 is passed through the edge of the window glass 14. Can be effectively communicated to.

  The graphite inner cylinder 13 has a stepped portion for fitting the window glass 14 at the edge portion on the column 13b side among the edge portions exposed to the plurality of window portions 13a. As a result, the window glass 14 can be attached to the window portion 13 a of the graphite inner cylinder 13.

  Moreover, the graphite inner cylinder 13 has a tapered shape 13tp at the edge on the silicon melt side (the lower end side of the graphite inner cylinder 13) among the edge portions exposed to the plurality of window portions 13a. The tapered shape 13tp is paired with the tapered shape 14tp of the lower edge portion of the window glass 14, and constitutes the sliding structure X1 of the window glass 14.

  The slide structure X1 is configured such that the lower edge portion of the window glass 14 and the edge portion of the graphite inner cylinder 13 in contact with the window glass 14 have a tapered shape with the window glass 14 on the outside. Therefore, when a gap is generated between the graphite inner cylinder 13 and the window glass 14, when the cap 15 is attached to the upper end of the graphite inner cylinder 13, the window glass 14 is caused by its own weight. However, it slides along the contact surface between the graphite inner cylinder 13 and the window glass 14, and the gap is closed.

  The cap 15 has a ring shape centering on the central axis AX so as to surround the silicon single crystal to be pulled up concentrically.

  If the cap 15 is ring-shaped, the cap 15 can be put on the entire circumference of the upper end of the graphite inner cylinder 13, and the position of the cap 15 on the graphite inner cylinder 13 can be stabilized. In addition, according to such a structure, when the plurality of window glasses 14 are attached to the graphite inner tube 13, the weight of the cap 15 can be evenly transmitted to the plurality of window glasses 14. However, the cap 15 may be a shape other than the ring shape, for example, a set of a plurality of arc-shaped members corresponding to the one or more window portions 13a.

  The cap 15 has a tapered shape 15tp at an edge portion on the side of the plurality of window portions 13a (upper end side of the graphite inner cylinder 13). The tapered shape 15tp is paired with the tapered shape 14tp of the upper edge portion of the window glass 14, and constitutes the sliding structure X2 of the window glass 14.

  The slide structure X2 is configured such that the upper edge portion of the window glass 14 and the edge portion of the cap 15 in contact with the window glass 14 have a tapered shape with the window glass 14 being the outside. Therefore, when a gap is generated between the graphite inner cylinder 13 and the window glass 14, the window glass 14 slides along the contact surface between the window glass 14 and the cap 15, and the gap is closed. .

  That is, when the cap 15 is attached to the upper end of the graphite inner cylinder 13, for example, as shown in FIG. 5, the window glass 14 has a radial direction perpendicular to the central axis AX by the two slide structures X 1 and X 2. A heading force P is added. Therefore, because of this force P, the window glass 14 moves in the radial direction so that its main surface approaches the inner surface of the graphite outer cylinder 11 evenly, so that the window glass 14 is interposed between the graphite inner cylinder 13 and the window glass 14. The effect of not generating a gap is further increased, and the airtightness of the rectifying cylinder is maintained.

  As described above, the effect of suppressing the gap between the graphite inner cylinder 13 and the window glass 14 is maximized by the two slide structures X1 and X2. However, if at least the slide structure X1 exists, the graphite inner A gap between the tube 13 and the window glass 14 can be suppressed. That is, the slide structure X2 can be omitted.

Here, the taper angle of the window glass 14 is preferably 30 ° or more and 60 ° or less. In this case, as described above, when the graphite inner cylinder 13 and the window glass 14 are in contact with each other with a taper, the graphite inner cylinder 13 is thermally expanded, and the window portion 13a of the graphite inner cylinder 13 is expanded. However, the tapered portions (tapered shapes) 13 _tp , 14 _tp , and 15 _tp come into contact with each other, and the gap between the graphite inner cylinder 13 and the window glass 14 can be reduced.

The taper angle will be described.
The taper angle is defined as the inclination of the tapered surface with respect to the horizontal plane. For example, as shown in FIG. 11, the taper angle θ _ue of the tapered shape formed at the upper edge of the window glass 14 is the inclination of the taper surface S _tp1 with respect to the horizontal plane L _p perpendicular to the main surface S of the window glass 14. It is. Similarly, the taper-shaped taper angle θ _de formed at the lower edge portion of the window glass 14 is the inclination of the taper surface _Stp2 with respect to the horizontal plane L _p perpendicular to the main surface S of the window glass 14.

According to this definition, when the taper angles θ _ue and θ _de of the window glass 14 are 0 °, the normal window in which the upper edge and the lower edge of the window glass 14 are perpendicular to the main surface S of the window glass 14. It turns out that it becomes glass.

Note that the taper angle θ _ue of the upper edge portion of the window glass 14 and the taper angle θ _de of the lower edge portion of the window glass 14 may be the same or different.

  Further, like the window glass 14, the graphite inner cylinder 13 is also tapered. The taper-shaped taper angle of the window portion 13a of the graphite inner cylinder 13 is defined as an angle of the taper surface with respect to a horizontal plane perpendicular to the inner surface or the outer surface of the graphite inner cylinder 13. The taper-shaped taper angle of the graphite inner cylinder 13 is the same as the taper-shaped taper angle of the window glass 14 facing it.

  Thus, by setting the taper angle of the window glass 14 to 30 ° or more, the contact area between the window glass 14 and the graphite inner tube 13 or the cap 15 is increased (the amount of sliding is increased), Even if a large gap is generated, it is possible to compensate (fill the gap) by sliding the window glass 14. Moreover, it becomes easy to slide the window glass 14 by the dead weight of the cap 15 because the taper angle of the window glass 14 is 30 ° or more.

  Moreover, the intensity | strength of the edge part (part which has a taper shape) of the window glass 14 can be ensured by making the taper angle of the window glass 14 60 degrees or less, and the window glass 14 can be made hard to be damaged. The reliability of the window glass 14 can be improved.

  The outer cylinder 11 and the inner cylinder 13 are preferably made of graphite, but may be made of other materials. Similarly, the window glass 14 is preferably made of quartz, but may be made of other materials. That is, if the slide structure X1, X2 has a heat resistance, and the gap formed by considering the difference in thermal expansion coefficient between the inner cylinder 13 and the window glass 14 or the thermal deformation of the window glass 14 can be closed, These materials are not limited.

  As described above, according to the silicon single crystal pulling apparatus as described above, in the structure of the rectifying cylinder in which the window glass 14 is attached to the graphite inner cylinder 13 installed around the silicon single crystal being pulled, the graphite inner cylinder 13 It becomes possible to reduce the oxygen concentration in the silicon single crystal to be pulled up by increasing the hermeticity.

That is, even when the graphite inner cylinder 13 and the window glass 14 are brought into contact with each other with a taper, the graphite inner cylinder 13 is thermally expanded and the window portion 13a of the graphite inner cylinder 13 is expanded. Shape) 13 _tp , 14 _tp , 15 _tp can maintain contact with the window glass 14, and the window glass 14 can be brought into close contact with the graphite outer cylinder 11. Airtightness can be increased by eliminating ventilation from the outside to the outside.

  For example, as shown in FIG. 4, during the pulling of the silicon single crystal, an inert gas (for example, Ar gas) 19 that flows from the upper part of the graphite inner cylinder 13 toward the lower part and blows onto the upper surface of the silicon melt, There is no leakage from the gap between the graphite inner cylinder 13 and the window glass 14. Therefore, the amount of the inert gas 19 sprayed on the upper surface of the silicon melt is increased, and as a result, the oxygen evaporated from the silicon melt is increased and exhausted sufficiently from the lower exhaust gas pipe 24 (see FIG. 1). Can do. As a result, the oxygen concentration in the silicon single crystal to be pulled can be further reduced.

Thus, according to the present invention, the effect of lowering the oxygen concentration in the silicon single crystal to be pulled is higher than that of the conventional structure. Further, the window glass 14 is pressed against the outer graphite-made outer cylinder 11 by the dead weight of the cap 15 installed on the window glass 14, and as shown in FIG. _eg is in close contact with the inner surface of the graphite outer cylinder 11.

  As described above, in the present invention, the ventilation from the inside to the outside of the graphite inner cylinder 13 in the window portion 13a is almost completely blocked, and the amount of gas flowing into the upper surface of the silicon melt is increased compared to the conventional case. The amount of oxygen evaporated from the silicon melt surface around the crystal can be increased. Moreover, the oxygen evaporated from the silicon melt surface is discharged from the exhaust gas pipe 24 at the bottom. Thereby, the oxygen concentration taken into the silicon single crystal from the periphery of the silicon single crystal can be made lower than before.

The effects of the structure of the present invention will be described in comparison with the conventional structure.
6 to 10 show examples of conventional structures. FIG. 6 is an example of a silicon single crystal pulling apparatus, and FIGS. 7 and 8 are examples of an outer cylinder, an inner cylinder, and a window glass. FIG. 9 shows the gas flow in the inner cylinder, and FIG. 10 shows the relationship between the window glass and the inner surface of the outer cylinder.

6 to 10 correspond to FIGS. 1 to 5, respectively.
6 to 10, components corresponding to the components of the apparatus shown in FIGS. 1 to 5 are assigned the same reference numerals as in FIGS. 1 to 5, and detailed descriptions thereof are omitted.

  A major difference between the structure of the present invention and the conventional structure is that the silicon single crystal pulling apparatus 1 ′ having the conventional structure does not have a cap that presses the upper edge of the window glass 14. That is, the upper end side of the window 13a of the graphite inner cylinder 13 is closed and the lower end side is open. Accordingly, the silicon single crystal pulling apparatus 1 ′ having the conventional structure has the graphite inner cylinder 13 and the window glass 14 that do not have a tapered shape at their contact surfaces, and also has a sliding structure of the window glass 14 as in the present invention. I do not have.

  In this case, since the upper edge portion 14ue of the window glass 14 is pressed against the graphite inner cylinder 13 by the weight of the graphite inner cylinder 13, the graphite inner cylinder 13 and the window glass 14 are disposed on the upper end side of the graphite inner cylinder 13. It is difficult for gaps to occur. However, a gap between the graphite inner cylinder 13 and the window glass 14 is likely to occur on the lower end side of the graphite inner cylinder 13. When the gap is generated, the gas leaked from the gap flows out into the main chamber 2 through the window hole 11a of the graphite outer cylinder 11, and as a result, the amount of gas blown onto the upper surface of the silicon melt is reduced. (See FIG. 9).

  A difference in gas flow between the structure of the present invention and the conventional structure depending on the presence or absence of a gap between the graphite inner cylinder 13 and the window glass 14 will be described with reference to FIGS. 4 and 9.

  As apparent from FIG. 4, in the structure of the present invention, the graphite inner cylinder 13 and the window glass 14 are brought into contact with each other with a taper, so that the graphite inner cylinder 13 is thermally expanded, and the window of the graphite inner cylinder 13 is expanded. Even when the portion 13a expands, the tapered portions are always in contact with each other, thereby eliminating air flow from the inside to the outside of the graphite inner tube 13 and improving the airtightness of the graphite inner tube 13. Further, due to the weight of the cap 15 installed on the window glass 14, as shown in FIG. 5, the window glass 14 is pressed against the inner surface of the graphite outer cylinder 11 on the outer side, and the corner 14eg of the window glass 14 is pressed. Adheres closely to the graphite outer cylinder 11.

  Accordingly, the gas 19 flowing into the graphite inner cylinder 13 is sprayed from the lower part of the graphite inner cylinder 13 onto the upper surface of the silicon melt. Thereby, the effect of lowering the oxygen concentration in the silicon single crystal to be pulled up is exhibited to the maximum extent.

  Further, in the structure of the present invention, the gap between the main surface of the window glass 14 and the curved surface of the inner surface of the graphite outer cylinder 11 is substantially reduced by reducing the gap between the cap 15 and the graphite outer cylinder 11 on the outer periphery thereof. Can be closed. That is, the inner side and the outer side of the graphite inner cylinder 13 are completely separated spatially in the radial direction perpendicular to the central axis AX.

  On the other hand, as apparent from FIG. 9, in the conventional structure, when the gas 19 leaks from the gap between the graphite inner cylinder 13 and the window glass 14, the gas 19 passes through the window hole 11 a of the graphite outer cylinder 11. It flows out into the main chamber 2 via. Further, as shown in FIG. 10, when gas flows into the space between the graphite outer cylinder 11 and the graphite inner cylinder 13, that is, between the main surface of the window glass 14 and the graphite outer cylinder 11, The window glass 14 receives a force in a direction away from the graphite outer cylinder 11 due to the pressure of the gas.

  As a result, as shown in FIG. 10, the gap between the graphite outer cylinder 11 and the window glass 14 is widened. This means that the gas 19 leaking from the gap between the graphite inner cylinder 13 and the window glass 14 is more likely to flow into the main chamber 2 via the window hole 11 a of the graphite outer cylinder 11.

By the way, in the conventional structure, in order to reduce the gap between the graphite outer cylinder 11 and the window glass 14 and suppress the flow of the gas 19 as shown in FIGS. 9 and 10, for example, as shown in FIG. contrivance such as the upper edge E _u and lower portions E _d of the window glass 14 in a curved shape is required, processing cost of the window glass 14 is increased. Further, even when the window glass 14 shown in FIG. 12 is used, the gap generated by considering the difference in thermal expansion coefficient between the graphite inner tube 13 and the window glass 14 or the thermal deformation of the window glass 14 Can't be blocked. As a result, in the conventional structure, there is always a problem that the gas flowing in the graphite inner cylinder 13 leaks from the gap and the amount of gas sprayed on the upper surface of the silicon melt is reduced.

In the structure of the present invention, the window glass 14, it is preferable from the viewpoint of suppressing the processing costs is a plate-like, as shown in FIG. 12, the curved shape the upper edge E _u and lower portions E _d It does not matter. The window glass 14 may have an arcuate curved surface whose main surface is along the inner surface of the graphite outer cylinder 11.

As described above, according to the structure of the present invention, the graphite inner cylinder 13 and the window glass 14 are brought into contact with each other with a taper, whereby the graphite inner cylinder 13 is thermally expanded, and the graphite inner cylinder 13 Even when the window portion 13a expands, the tapered portion comes into contact, and ventilation from the inside to the outside of the graphite inner cylinder 13 at the window portion 13a is eliminated, so that airtightness can be enhanced. As a result, the effect of lowering the oxygen concentration in the pulled silicon single crystal is higher than that of the conventional structure. Further, the window glass 14 is pressed against the outer graphite outer cylinder 11 by the weight of the cap 15 installed on the window glass 14, and the vertical corners 14 _{eg of the} window glass 14 are the inner surfaces of the graphite outer cylinder 11. Close contact with.

  As described above, in the structure of the present invention, the ventilation from the inside to the outside of the graphite inner cylinder 13 in the window portion 13a is almost completely blocked, and the amount of gas flowing into the upper surface of the silicon melt can be increased more than before, The amount of oxygen evaporated from the melt surface around the silicon single crystal to be pulled can be increased. Thereby, the concentration of oxygen taken into the silicon single crystal from the periphery of the silicon single crystal can be made lower than before.

  EXAMPLES The present invention will be described in detail below with reference to examples of the present invention, but these do not limit the present invention.

Example 1
In the silicon single crystal pulling apparatus 1 shown in FIGS. 1 to 5, four window portions (cut portions) 13 are provided in a graphite inner tube 13 having a thickness of 10 mm, and there are 10 mm in thickness, 50 mm in width, and vertically long. Four 120 mm window glasses 14 were fitted, and a cap 15 having a height of 20 mm and a taper angle of 45 ° was arranged at the upper end thereof, and incorporated into the silicon single crystal pulling apparatus 1. Here, the window glass 14 and the graphite inner cylinder 13 and the window glass 14 and the cap 15 are in contact at a taper angle of 45 °, and the gap between the window glass 14 and the graphite inner cylinder 13 is determined by the slide structure of the present invention. It was suppressed to about 1% of the window glass area (50 mm × 120 mm).

  In such a silicon single crystal pulling apparatus 1, 100 kg of silicon raw material is charged into a 22-inch (550 mm) quartz crucible, the furnace pressure is 100 mbar, the amount of Ar gas blown to the silicon melt is 100 L / min, and the crucible When a silicon single crystal having a diameter of 205 mm was manufactured at a rotational speed of 8 rpm, the oxygen concentration at a position 100 mm from the seed crystal side became 15.0 ppma (JEITA) in a portion with a pulling diameter of 205 mm or more.

(Example 2)
In the silicon single crystal pulling apparatus 1 shown in FIGS. 1 to 5, four windows (cut portions) 13 are provided in a graphite inner cylinder 13 having a thickness of 10 mm, and the thickness is 10 mm, the width is 50 mm, and the length is long. Four 120 mm window glasses 14 were fitted, and a cap 15 having a height of 20 mm and a taper angle of 45 ° was arranged at the upper end thereof, and incorporated into the silicon single crystal pulling apparatus 1. Here, the window glass 14, the upper edge E _u and lower edge E _d has a curved surface shape, respectively, the taper angle 45 to the window glass 14 and the graphite inner cylinder 13 and the window glass 14 and the cap 15, The gap between the window glass 14 and the graphite inner cylinder 13 is reduced to about 0.2% of the window glass area (50 mm × 120 mm) by the slide structure of the present invention. The adhesion was high.

  In such a silicon single crystal pulling apparatus 1, 100 kg of silicon raw material is charged into a 22-inch (550 mm) quartz crucible, the furnace pressure is 100 mbar, the amount of Ar gas blown to the silicon melt is 100 L / min, and the crucible When a silicon single crystal having a diameter of 205 mm was manufactured at a rotational speed of 8 rpm, the oxygen concentration at a position of 100 mm from the seed crystal side was 14.4 ppma (JEITA) in a portion with a pulling diameter of 205 mm or more.

(Comparative example)
In the silicon single crystal pulling apparatus 1 ′ shown in FIGS. 6 to 10, four counterbore portions having a depth of 5 mm are provided in a graphite inner cylinder 13 having a thickness of 10 mm, and 4 mm in thickness, 50 mm in width, and Four pieces of 120 mm long window glass 14 were fitted and incorporated into the silicon single crystal pulling apparatus 1 ′. Here, the gap between the window glass 14 and the graphite inner cylinder 13 was about 8% of the window glass area (50 mm × 120 mm).

  In such a silicon single crystal pulling apparatus 1 ′, 100 kg of silicon raw material is charged into a 22-inch (550 mm) quartz crucible, the furnace pressure is 100 mbar, and the amount of Ar gas blown to the silicon melt is 100 L / min. When a silicon single crystal having a diameter of 205 mm was manufactured at a crucible rotation speed of 8 rpm, the oxygen concentration at a position 100 mm from the seed crystal side was 16 ppma (JEITA) in a portion with a pulling diameter of 205 mm or more.

  As can be seen from the above results, in Example 1 and Example 2, the oxygen concentration in the silicon single crystal to be pulled up is smaller than that in the comparative example in spite of the same operating conditions. That is, according to the structure of the rectifying cylinder of the present invention, it was proved that the oxygen concentration in the silicon single crystal to be pulled can be lowered as compared with the conventional structure.

  As described above, according to the present invention, in the structure in which the window glass is attached to the inner cylinder of the rectifying cylinder installed around the silicon single crystal being pulled up, the silicon single unit that is pulled up with the airtightness of the rectifying cylinder being increased. It becomes possible to reduce the oxygen concentration in the crystal.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

  DESCRIPTION OF SYMBOLS 1 ... Silicon single crystal pulling apparatus, 2 ... Main chamber, 3 ... Silicon single crystal, 4 ... Quartz crucible, 5 ... Graphite crucible, 6 ... Graphite heater, 7 ... Thermal insulation shield, 10 ... Support shaft, 11 ... Outside graphite Tube: 11a: Window hole, 12: Heat insulation ring, 13: Graphite inner tube, 13a: Window, 13tp: Tapered shape, 14: Window glass, 14tp: Tapered shape, 15 ... Cap, 15tp: Tapered shape, 16 ... Pulling wire, 17 ... seed crystal, 18 ... silicon melt, 21 ... pull chamber, 22 ... gas introduction pipe, 23 ... neck, 24 ... exhaust gas pipe.

Claims (6)

An outer cylinder disposed on the silicon melt so as to concentrically surround the silicon single crystal to be pulled up and having a window hole, and an inner cylinder disposed inside the outer cylinder and having a window corresponding to the window hole And a silicon single crystal pulling device comprising a window glass attached to the window portion and covering the window hole,
A cap attached to the upper end of the inner cylinder, further comprising a cap that contacts the upper edge of the window glass,
Both the lower edge portion of the window glass and the edge portion of the inner cylinder in contact with the window glass have a tapered shape with the window glass being outside, and the window glass is formed by the weight of the cap. It is slidable along the contact surface between the lower edge and the edge of the inner cylinder that contacts the lower edge, and the window glass is brought into close contact with the inner surface of the outer cylinder with the cap attached. A silicon single crystal pulling device.   The silicon single crystal pulling apparatus according to claim 1, wherein the window portion is open at an upper end side of the inner cylinder.   3. The silicon single crystal pulling apparatus according to claim 1, wherein the cap has a ring shape so as to surround the silicon single crystal to be pulled up concentrically.   Both the upper edge of the window glass and the edge of the cap that contacts the window glass have a tapered shape with the window glass facing outside, and the window glass is placed on the window glass by its own weight. The silicon single crystal pulling apparatus according to any one of claims 1 to 3, wherein the silicon single crystal pulling apparatus is slidable along a contact surface between the edge and the edge of the cap that contacts the edge.   5. The silicon single crystal pulling apparatus according to claim 1, wherein a taper angle of the window glass is 30 ° or more and 60 ° or less with respect to a horizontal plane. The silicon single crystal pulling apparatus according to any one of claims 1 to 5, wherein the outer cylinder and the inner cylinder are made of graphite, and the window glass is made of quartz.