JP5404264B2 - Single crystal silicon manufacturing method and single crystal silicon manufacturing apparatus - Google Patents

Description

  The present invention relates to a method for manufacturing single crystal silicon and an apparatus for manufacturing the same, and more particularly, to provide a method capable of effectively avoiding contact between a heat shielding plate and a silicon melt and an apparatus enabling the same. .

  The Czochralski method (CZ method) has been widely adopted as a method for producing single crystal silicon used for silicon wafers of semiconductor materials. The CZ method is a method in which a seed crystal is immersed in a silicon melt in a quartz glass crucible and pulled up while growing single crystal silicon.

  It is generally known that the quality of a single crystal grown by this CZ method depends on the temperature during growth. A factor that greatly affects the temperature of the crystal is the radiant heat received from the melt in the crucible. In order to control this, in a single crystal pulling apparatus by the CZ method, usually around the growing crystal. A heat shielding plate made of graphite or the like is disposed.

  In general, the heat shielding plate has a tapered shape whose diameter narrows downward, and its lower end portion is positioned near the liquid surface of the silicon melt when pulling up the single crystal silicon for the above purpose. It is essential. The control of the distance between the lower end portion of the heat shielding plate and the surface of the silicon melt is very important for controlling the quality of the single crystal silicon that is pulled up.

  However, in the case of the above discrete products, it is necessary to control the interval between the lower end portion of the heat shielding plate and the liquid surface of the silicon melt in a narrow range of several mm to several tens of mm in the latter half of the crystal pulling, Conventionally, it has been difficult to accurately measure the distance between the lower end portion of the heat shield plate and the surface of the silicon melt. Furthermore, if the heat shield plate comes into contact with the silicon melt, the silicon melt may be contaminated and the crystal growth may have to be interrupted. For this reason, various methods for measuring and controlling the distance between the lower end portion of the heat shielding plate and the liquid surface of the silicon melt have been proposed.

  For example, in Patent Document 1, a quartz pin extending to the crucible side is disposed at the lower end portion of the heat shielding plate, and the crucible is raised until the quartz pin comes into contact with the silicon melt in the crucible. Using the distance between the lower end of the shielding plate and the silicon melt as a reference, the distance between the lower end of the heat shielding plate and the surface of the silicon melt is lowered by lowering the crucible until the distance reaches the initial setting value. Is disclosed, and a method that can be used as an initial setting value is disclosed.

  In Patent Document 2, a reference reflector is provided at the lower end of the heat shielding plate, and a mirror image formed by reflecting the reference reflector and the reference reflector on the silicon melt surface is an image of a CCD camera or the like. A method of measuring the distance between the reference reflector and the silicon melt surface by detecting the detection means and calculating the distance between the reference reflector and its mirror image by image processing is disclosed.

  Alternatively, Patent Document 3 constantly detects the length of a growing single crystal straight body portion, and at the growth interface between the single crystal and the silicon melt, for example, using an image detection means such as a CCD camera. A method is also disclosed in which the fusion ring is detected to detect the position of the melt surface during single crystal growth and to measure the distance between the lower end of the heat shielding plate and the liquid surface of the silicon melt.

Japanese Patent Laid-Open No. 62-87481 JP 2007-290906 A JP 2008-189485 A

However, in the method using the quartz pin shown in Patent Document 1, after setting the distance between the heat shielding plate and the silicon melt to the initial setting value, the initial value is affected by fluctuations in pulling conditions due to disturbance, liquid level vibration, and the like. The set value is not maintained, and the distance between the heat shield plate and the silicon melt may become too small, and the heat shield plate and the silicon melt may come into contact with each other.
Further, in the method using the reference reflector and its mirror image described in Patent Document 2, the mirror image is difficult to see due to the influence of liquid surface vibration, and between the lower end portion of the heat shielding plate and the liquid surface of the silicon melt. There is a possibility that the measurement accuracy of the interval is lowered. In addition, since the reference reflector needs to be sufficiently separated from the surface of the silicon melt, it is behind the heat shield plate itself, and effectively between the lower end of the heat shield plate and the surface of the silicon melt. It may be impossible to measure the interval.
Further, in the method of detecting the fusion ring by the image detection means described in Patent Document 3, the size of the fusion ring observed with respect to the change in the distance between the lower end portion of the heat shielding plate and the liquid level of the silicon melt. Since the change in height is not steep, it is difficult to measure the distance between the lower end of the heat shield plate and the liquid level of the silicon melt with high accuracy. As described above, when the measurement accuracy of the distance between the lower end portion of the heat shielding plate and the liquid surface of the silicon melt is lowered, there is a possibility that the heat shielding plate and the silicon melt are brought into contact with each other.

  Therefore, the object of the present invention, which has been made by paying attention to these points, is to make the distance between the surface of the silicon melt and the end of the heat shield plate on the crucible side appropriate before the pulling of the single crystal silicon. A method of manufacturing single crystal silicon that prevents the heat shield plate from coming into contact with the silicon melt during subsequent pulling of the single crystal silicon, and a single crystal silicon manufacturing apparatus that enables the method It is to provide.

The gist configuration of the present invention is as follows.
(1) In manufacturing single crystal silicon by the Czochralski method using a single crystal silicon pulling apparatus in which a heat shielding plate surrounding the single crystal silicon pulling path is installed above the crucible containing the silicon melt. At least two rod-like pins with different lengths extending from the lower end to the crucible side are arranged at the lower end of the heat shielding plate, and the crucible is directed toward the heat shielding plate with the longest rod shape of the rod-like pin. The pin is raised until it comes into contact with the silicon melt in the crucible, and the crucible is lowered until the interval reaches an initial set value based on the interval between the lower end of the heat shield plate and the silicon melt at that time, and then In the process of growing the single crystal by pulling single crystal silicon from the silicon melt, when the shortest pin of the rod pin comes into contact with the silicon melt, at least above the crucible. The stops and the method for producing a single-crystal silicon, characterized in that to avoid contact with the heat shield plate and the silicon melt.

(2) The method for producing single crystal silicon according to (1), wherein the contact of the rod-shaped pin with the silicon melt is electrically detected.

(3) The method for producing single crystal silicon according to (1) or (2), wherein it is visually detected that the rod-shaped pin has contacted the silicon melt.

(4) A crucible for containing a silicon melt, a pulling means for pulling up the single crystal silicon from the silicon melt in the crucible, a heat shielding plate surrounding the pulling path of the single crystal silicon, and a lifting means for the crucible obtaining a single crystal silicon pulling apparatus, attached to a lower end portion of the heat shield plate extends into the crucible side from the lower end, at least two rod-like pins of different lengths, rod-shaped pin the silicon melt Detecting means for detecting contact with the liquid, and raising the crucible toward the heat shield plate until the longest rod-shaped pin of the rod-shaped pin comes into contact with the silicon melt in the crucible, The crucible is lowered until the gap reaches an initial set value based on the gap between the lower end of the heat shield plate and the silicon melt, and then the pulling means is moved from the silicon melt. In the process of growing the single crystal silicon by pulling up the single crystal silicon, when the shortest rod-shaped pin of the rod-shaped pin comes into contact with the silicon melt, at least the rising of the crucible is stopped, and the heat shielding A single crystal silicon pulling apparatus comprising: a control unit that controls driving of the elevating unit based on an output of the detection unit so as to avoid contact between a plate and the silicon melt .

(5) The single crystal silicon pulling apparatus according to (4), wherein the rod-like pin is detachably fitted into a hole provided in a lower end portion of the heat shielding plate. Silicon pulling device.

(6) The single crystal silicon pulling apparatus according to any one of (4) and (5), wherein the diameter of the rod-shaped pin is 2.0 mm or more.

(7) The single crystal silicon pulling apparatus according to any one of (4) to (6), wherein the rod-shaped pin is made of either quartz or silicon crystal.

(8) In the above (4) single-crystal silicon pulling apparatus according to any one of (1) to (7), said detecting means, said rod-shaped pin is a means for electrically detecting that in contact with the silicon melt Single crystal silicon pulling device characterized by

(9) In the above (4) single-crystal silicon pulling apparatus according to any one of the - (8), said detection means, said rod-shaped pin is a means to visually detect that the contact with the silicon melt Single crystal silicon pulling device characterized by

  According to the present invention, by attaching at least two rod-like pins having different lengths to the lower end portion of the above-described heat shield plate, the surface of the silicon melt and the heat shield plate can be High quality to achieve the proper distance from the end on the crucible side, and to pull up the single crystal silicon so that the heat shield plate does not come into contact with the silicon melt during the subsequent pulling of the single crystal silicon Single crystal silicon can be produced.

It is the figure which showed the single crystal silicon pulling apparatus according to this invention. (A)-(e) is the figure which showed the process of pulling up single crystal silicon using the single crystal silicon pulling-up apparatus according to this invention. It is the figure which showed the process of pulling up single crystal silicon using the other single crystal silicon pulling apparatus according to this invention.

Hereinafter, a single crystal silicon pulling apparatus according to the present invention will be described in detail with reference to FIG.
As shown in FIG. 1, a single crystal silicon pulling apparatus 1 according to the present invention includes a cylindrical main chamber 2 and a pulling chamber 3 for sealing the entire apparatus from an external atmosphere, a quartz glass crucible 4 for accommodating polycrystalline silicon, and such quartz. In order to maintain the shape of the glass crucible 4, the graphite crucible 5 that surrounds and accommodates the outer surface of the quartz glass crucible 4, elevating means 6 that moves the quartz glass crucible 4 and the graphite crucible 5 up and down, the quartz glass crucible 4, and the graphite crucible 5. Is heated from the outside, the heater 7 for heating and melting the polycrystalline silicon in the quartz glass crucible 4, the heat insulating material 8 for preventing the heat from the heater 7 from being directly radiated to the main chamber 2, and the inside of the crucible A seed crystal 9 for pulling up single crystal silicon from the silicon melt S, a holder 10 for the seed crystal 9, a pull wire 11 and Pulling means 13 consisting of pulling the driving portion 12, and surrounds the pulling path of the single crystal silicon, comprising a heat shielding plate 14 for shielding the radiant heat for the single crystal silicon during the pulling. Further, two quartz rod-like pins 15A and 15B (15) having different lengths extending to the crucible side are attached to the lower end portion 140 of the heat shielding plate. Here, “the length of the rod-shaped pins 15A and 15B” refers to the distance from the tip of the pin to the heat shielding plate 14. These rod-shaped pins 15A and 15B are detachably fitted in holes (not shown) provided in the lower end portion 140 of the heat shielding plate 14. Since the rod-like pins 15A and 15B are detachable in this way, even if the rod-like pins 15A and 15B are damaged or melted in the silicon melt S, they are replaced with new rod-like pins 15A and 15B. It is preferable from the viewpoint that the apparatus can be used repeatedly. The side wall of the pulling chamber 3 is provided with an inlet (not shown) for supplying an inert gas, and the bottom of the main chamber 2 is used for discharging impurities in the chamber together with the inert gas. A discharge port (not shown) is provided, and the discharge port is connected to a vacuum pump (not shown) via an exhaust pipe (not shown). As a result, when pulling up the single crystal silicon, the main chamber 2 and the pulling chamber 3 can be in a low-pressure inert gas atmosphere. Hereinafter, the step of pulling up the single crystal silicon using the single crystal silicon pulling apparatus 1 will be described in detail with reference to FIG.

  FIGS. 2A to 2E are views showing a process of pulling up single crystal silicon using the single crystal silicon pulling apparatus according to the present invention. First, as shown in FIG. 2A, the quartz glass crucible 4 is determined in advance so that the hot rod pins 15A and 15B do not come into contact with the surface of the silicon melt S in the rotating quartz glass crucible 4. Place in the specified initial position. Next, as shown in FIG. 2 (b), the quartz glass crucible 4 is raised using the elevating means 6 until the longest rod-shaped pin 15 A comes into contact with the silicon melt S. Such contact is visually detected using the CCD camera 17 by checking the fusion ring that emits light when the longest pin 15A contacts the silicon melt S. Note that the length X of the longest pin 15A is, for example, 13 mm. Then, as shown in FIG. 2 (c), as a reference for the interval Y (here, 13 mm) between the lower end portion 140 of the heat shielding plate 14 and the silicon melt S when the longest pin 15A comes into contact with the liquid surface. By lowering the crucible, the interval Y is expanded to an initial setting value (27 mm in this case) appropriate for shielding radiant heat. Here, the initial setting value is set before the seed crystal 9 is brought into contact with the silicon melt S and the lower end 140 of the heat shielding plate 14 and the silicon melt in order to reduce variations in the quality of the produced crystal. This is the distance Y from S. Needless to say, the longest pin 15A is designed such that the pin length X is shorter than the initial set value. Thereafter, as shown in FIG. 2D, the single crystal silicon 17 is pulled up from the silicon melt S to grow the single crystal silicon 17. Specifically, after bringing the seed crystal 9 attached to the seed crystal holder 10 into contact with the silicon melt S, the seed crystal 9 is slowly pulled up by the pulling drive unit 12 through the pulling wire 11. Single crystal silicon 17 having the same crystal arrangement is grown to produce single crystal silicon 17 having a desired diameter. At this time, as shown in FIG. 2 (e), during the growth of the single crystal silicon 17, the interval Y between the lower end portion 140 of the heat shielding plate 14 and the silicon melt S becomes smaller than the initial set value, and the rod shape When the shorter (shortest) rod-like pin 15B than the pin 15A comes into contact with the silicon melt S, the quartz glass crucible 4 stops rising, and the lower end portion 140 of the heat shielding plate 14 and the silicon melt The gap Y with the liquid S is further prevented from being narrowed, and the growth of the single crystal silicon 17 is continued. The length Z of the shorter rod-shaped pin 15B is set to be equal to or greater than the proximity limit interval that can avoid contact between the heat shielding plate 14 and the silicon melt S, and is 6 mm here. Yes. Here, the length Z of the shorter rod-like pin 15B is set to be equal to or greater than the proximity limit interval that can avoid contact between the heat shielding plate 14 and the silicon melt S. Even if a shorter rod-shaped pin is disposed at the lower end portion 140 of the heat shielding plate 13, there is a possibility that the effect of the present invention cannot be effectively obtained by the shorter rod-shaped pin. That is, when a shorter pin-like pin is disposed than the shorter rod-like pin 15B and the shorter pin-shaped pin comes into contact with the silicon melt S, the heat shielding plate 14 and the silicon melt S come into contact with each other. This is because there is a possibility that it will end up.

As described above, by setting the interval Y between the lower end portion 140 of the heat shield plate 14 and the silicon melt S as an initial setting value, the interval Y between the lower end portion 140 of the heat shield plate 14 and the silicon melt S is It becomes an appropriate interval for shielding the radiant heat to the single crystal silicon 17 being pulled up, and it becomes possible to effectively suppress the deterioration of the quality of the single crystal silicon 17 caused by the radiant heat. In addition, as described above, after the pulling of the single crystal silicon 17 is started, the lower end portion 140 of the heat shielding plate 14 and the silicon melt S are affected by fluctuations in pulling conditions due to external factors, liquid level vibration, and the like. When the contact Y between the shorter pin 15B and the silicon melt S is confirmed, at least the ascent of the quartz glass crucible 4 is stopped. In this stopped state, if the pulling of the single crystal silicon 17 is continued, the melt surface turns downward, and the gap Y between the lower end portion 140 of the heat shielding plate 14 and the silicon melt S is further suppressed. Thus, the contact between the heat shielding plate 14 and the silicon melt S can be effectively avoided.
Alternatively, after the steps of FIGS. 2A to 2E, the single crystal silicon 17 is pulled up while keeping the distance Y between the lower end portion 140 of the heat shielding plate 14 and the silicon melt S constant. 3, after the interval Y between the lower end portion 140 of the heat shielding plate 14 and the silicon melt S is widened to a certain extent (to the extent that no liquid is deposited), the single crystal silicon 17 is pulled up. It is also possible to resume.

  In addition, the recording rod pins 15A and 15B shown in FIGS. 1 to 3 are made of quartz, but may be made of silicon crystal or the like as needed. Examples of the material of the rod-like pin 15 that has the least influence on the quality of the single crystal silicon 17 to be manufactured include quartz and silicon crystal.

  In addition, the diameter of the rod-shaped pin 15 is preferably 2.0 mm or more. This is because when the diameter of the rod-shaped pin 15 is less than 2.0 mm, the rod-shaped pin 15 is immediately dissolved when it comes into contact with the silicon melt S, and the same rod-shaped pin 15 is repeatedly brought into contact with the silicon melt S. This is because there is a possibility that it cannot be used.

  In the single crystal silicon 17 pulling apparatus 1 shown in FIGS. 1 to 3, the contact of the rod-shaped pins 15 </ b> A and 15 </ b> B with the silicon melt S is detected by means of visually detecting using the CCD camera 16. However, the means for detecting contact is not limited to this, and it is also possible to detect by means of electrically detecting that the rod-shaped pin 15 has contacted the silicon melt S. Although not shown in the drawings, the means for electrically detecting is, for example, an electric device that is attached to the upper end of the rod-shaped pin 15 and electrically detects that the rod-shaped pin 15 has contacted the silicon melt S and transmits an electric signal. It can be constituted by a sensor and a receiving sensor that receives such an electrical signal.

  The above description shows only a part of the embodiment of the present invention, and these configurations can be combined alternately or various changes can be made without departing from the gist of the present invention. For example, although illustration is omitted, it is also possible to employ a configuration in which three or more rod-like pins 15 are arranged at the lower end portion 140 of the heat shielding plate 14 and the lengths of the rod-like pins 15 are changed stepwise. Is possible.

  As is apparent from the above description, according to the present invention, before pulling up the single crystal silicon, the distance between the liquid surface of the silicon melt and the end portion on the crucible side of the heat shielding plate is set to an appropriate distance, and the subsequent single unit is removed. It is possible to provide a method of manufacturing single crystal silicon in which the heat shielding plate is not brought into contact with the silicon melt when pulling up the crystalline silicon, and a single crystal silicon manufacturing apparatus that enables the method. It was.

DESCRIPTION OF SYMBOLS 1 Single-crystal silicon pulling apparatus 2 Main chamber 3 Pulling chamber 4 Quartz glass crucible 5 Graphite crucible 6 Lifting means 7 Heater 8 Heat insulating material 9 Seed crystal 10 Seed crystal holder 11 Pulling wire 12 Pulling drive part 13 Pulling means 14 Heat shield plate 140 Lower end 15A, 15B Rod-shaped pin 16 CDD camera 17 Single crystal silicon

Claims (9)

In producing single crystal silicon by the Czochralski method using a single crystal silicon pulling apparatus in which a heat shield plate surrounding the pulling path of single crystal silicon is installed above the crucible containing the silicon melt,
At least two rod-like pins with different lengths extending from the lower end to the crucible side are arranged at the lower end of the heat shielding plate,
The crucible is raised toward the heat shield plate until the longest pin-shaped pin of the rod-shaped pin comes into contact with the silicon melt in the crucible, and the distance between the lower end of the heat shield plate and the silicon melt at that time is increased. As a reference, lower the crucible until the interval reaches the default value,
Next, in the process of growing the single crystal silicon by pulling the single crystal silicon from the silicon melt,
When the shortest pin of the rod-shaped pin comes into contact with the silicon melt, at least the rise of the crucible is stopped and the contact between the heat shielding plate and the silicon melt is avoided. Method.   The method for producing single crystal silicon according to claim 1, wherein it is electrically detected that the rod-shaped pin is in contact with the silicon melt.   The method for producing single crystal silicon according to claim 1, wherein it is visually detected that the rod-shaped pin is in contact with the silicon melt. A crucible for containing a silicon melt, a pulling means for pulling up the single crystal silicon from the silicon melt in the crucible, a heat shielding plate surrounding the pulling path of the single crystal silicon, and a single crystal comprising a lifting means for the crucible A silicon pulling device,
Attached to the lower end portion of the heat shield plate extends into the crucible side from the lower end, at least two rod-like pins of different lengths,
Detecting means for detecting that the rod-shaped pin is in contact with the silicon melt;
The crucible is raised toward the heat shielding plate until the longest rod-shaped pin of the rod-shaped pin comes into contact with the silicon melt in the crucible, and the lower end portion of the heat shielding plate and the silicon melt at that time In the process of raising the single crystal silicon by lowering the crucible until the interval reaches an initial set value, and then the pulling means pulls the single crystal silicon from the silicon melt. The detecting means is configured to stop at least the rising of the crucible when the shortest pin-shaped pin of the rod-shaped pin comes into contact with the silicon melt and avoid contact between the heat shielding plate and the silicon melt. Control means for controlling the drive of the lifting means based on the output of
A single crystal silicon pulling apparatus characterized by comprising:   The single crystal silicon pulling device according to claim 4, wherein the rod-like pin is detachably fitted into a hole provided in a lower end portion of the heat shielding plate.   The single crystal silicon pulling apparatus according to claim 4 or 5, wherein the rod-shaped pin has a diameter of 2.0 mm or more.   The single crystal silicon pulling apparatus according to any one of claims 4 to 6, wherein the rod-shaped pin is made of either quartz or silicon crystal. The detection means, the rod-shaped pin is a means for electrically detecting that in contact with the silicon melt, single-crystal silicon pulling apparatus according to any one of claims 4-7. The detection means, the rod-shaped pin is a means to visually detect that the contact with the silicon melt, single-crystal silicon pulling apparatus according to any one of claims 4-8.

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