JP2019108239A - Method for manufacturing fz silicon raw material rod and method for manufacturing fz silicon single crystal - Google Patents

Abstract

To provide a method for manufacturing an FZ silicon raw material rod, capable of reducing a processing loss due to the mechanical processing of a cone part when preparing an FZ silicon raw material rod using a silicon crystal rod manufactured by the CZ method to improve a yield.SOLUTION: The method for manufacturing an FZ silicon raw material rod when using a CZ silicon crystal rod as a silicon raw material rod in an FZ method comprises: presetting a target shape and allowable range of a cone part of the FZ silicon raw material rod; manufacturing the CZ silicon crystal rod on manufacturing conditions of forming the cone part into the target shape; determining whether or not the shape of the cone part of the CZ silicon crystal rod is in the allowable range; and obtaining the CZ silicon crystal rod as the FZ silicon raw material rod without machining the cone part for the allowable range and obtaining the CZ silicon crystal rod as the FZ silicon raw material rod by machining the cone part so as to be in the allowable range except for the allowable range.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a silicon raw material rod for FZ, which is a silicon raw material rod for FZ method (floating zone method), and more specifically, a silicon crystal rod manufactured by CZ method (Czochralski method) (hereinafter referred to as CZ silicon crystal) The present invention relates to a method of manufacturing a silicon raw material rod for FZ when using as a silicon raw material rod of FZ method).

  Heretofore, silicon wafers manufactured by the FZ method have been used for the manufacture of power devices such as high withstand voltage power devices and thyristors. Further, in recent years, in order to improve the performance of semiconductor devices and to reduce the cost, a large diameter silicon wafer is required, and along with this, the growth of large diameter silicon single crystals is required.

As described above, the FZ method is known as a method for producing a silicon single crystal. A method of producing a silicon single crystal using a general FZ single crystal production apparatus will be described.
First, a silicon crystal rod as a silicon raw material rod is held by the upper holding jig of the upper shaft installed in the chamber. On the other hand, the single-crystal seed (seed crystal) with a small diameter is held by the lower holding jig of the lower shaft located below the silicon crystal rod.

Next, the silicon material rod is melted by the induction heating coil and fused to the seed crystal. After that, a narrowed portion is formed by seed squeezing to eliminate dislocations. Then, a floating zone (also referred to as a melting zone or a melt) is formed between the silicon source rod and the silicon single crystal by lowering the silicon source rod and the silicon single crystal while rotating the upper axis and the lower axis. Is moved to the upper end of the silicon material rod for zoning to grow a silicon single crystal. This growth is performed in an atmosphere in which a slight amount of nitrogen gas is mixed with Ar gas.
As said induction heating coil, the induction heating coil which distribute | circulated the water for cooling of the single roll which consists of copper or silver, or multiple rolls is used.

  Usually, rod-like polycrystalline silicon is used as a raw material of FZ single crystal silicon. However, polycrystalline silicon (polycrystalline silicon rod for FZ) required as a raw material in the FZ method has high purity, is less likely to cause cracks and cracks, and has a uniform grain boundary structure, and is manufactured. It is necessary to have a cylindrical shape with a flat surface, a small number of flats and cranks, and a good surface condition. The production of polycrystalline silicon rods for FZ satisfying such conditions is very low in yield and productivity as compared to the production of polycrystalline silicon having nuggets of acceptable size, which are used in the CZ method. .

  In the production of silicon single crystal by the FZ method, a floating zone exists on the silicon single crystal. That is, since the melting of the raw material and the single crystal growth are simultaneously performed while maintaining the state in which the silicon melt is placed on the silicon single crystal, if the diameter of the silicon raw material rod fluctuates, during the silicon single crystal production The silicon melt overflows, solidification occurs, and the single crystal tends to have dislocations. If such a thing occurs, since the growth of a silicon single crystal can not be performed any more, it will stop operation. And move to the next batch. As a result, the productivity and the yield are greatly reduced. Therefore, for stable operation, a silicon raw material rod with less variation in diameter is suitable, and machining is performed to obtain a desired shape.

In particular, in the FZ method of seeding, squeezing, and cone manufacturing processes, the amount of silicon melt to be interposed is small compared to forming a straight barrel, and the tip of the silicon material rod is, for example, a cone in advance. It is machined into shape and used.
Machining of silicon raw material rod causes yield reduction, but when the end face of cylindrical silicon raw material rod is flat surface, it is very difficult to create and control the seeding, drawing and cone part production It is difficult to control the desired cone shape by the FZ method.
In the process of manufacturing the cone portion of FZ silicon single crystal, the diameter of the cone portion is expanded and, at the same time, the diameter of the melted portion is also expanded as the silicon material rod is melted, it is difficult to make a recipe or control of manufacture. At this time, if the fluctuation of the diameter of the silicon raw material rod is large, the control of the production of the cone portion of the FZ silicon single crystal becomes unstable, the silicon melt overflows, solidification occurs, and the single crystal has dislocations. It becomes.

The conical shape of the silicon raw material rod machined here is processed in a manufacturing process of a cone portion of the FZ method with a shape which is difficult to be dislocated as a target shape. This shape also varies depending on the FZ single crystal manufacturing apparatus used, the diameter of the silicon raw material rod, and the diameter of the FZ silicon single crystal to be manufactured, so an appropriate shape may be selected. And, by machining to the target shape, the shape is uniform, so the recipe of manufacturing the cone part of FZ silicon single crystal conforms and the control is stabilized, and the dislocation rate of single crystal is reduced. Be done.
Conversely, if the silicon raw material rod deviates from the target shape, the recipe for manufacturing the cone part of FZ silicon single crystal becomes incompatible, control becomes unstable, silicon melt overflows, solidification occurs, or FZ silicon single It causes the crystal to have dislocations.

  In recent years, the demand for polycrystalline silicon (polycrystalline silicon for CZ) used in the CZ method centering on a diameter of 300 mm has significantly increased. From this, as described above, the quality standards such as shape and purity are strict, productivity is low, and the supply of polycrystalline silicon crystal rods for FZ, which is expensive, is under pressure with demand, and the price is also Is also very high. As a result, it becomes difficult to secure a good quality polycrystalline silicon rod for FZ, and it has become difficult to stably manufacture an FZ silicon single crystal.

Therefore, there has been proposed a method of producing a silicon single crystal by the FZ method, in which a silicon crystal rod produced by the CZ method is used as a silicon material rod in the FZ method. (For example, refer to patent documents 1-3).
By using the silicon crystal rod of the CZ method as the silicon raw material rod of the FZ method, it is possible to stably manufacture a uniform silicon raw material rod with high purity, less generation of cracks and cracks, and the like. Furthermore, a silicon raw material rod suitable for the diameter of a silicon single crystal to be manufactured by the FZ method can be manufactured, and a silicon raw material rod with few flats or cranks and a good surface condition can be stably supplied.

JP 2005-306653 A JP, 2013-139388, A JP, 2015-117177, A

  In the CZ method, various methods for improving the manufacturing yield have been advanced in view of the constant cost reduction demand. Among them, for the CZ silicon crystal rod, the role of the cone is an essential part to expand the diameter of the desired crystal, but generally it is not a product other than the straight body. The shape of the cone part is preferred because of its light weight and short production time, and a generally flat shape (low cone height or short cone length) is selected, taking into account the dislocation ratio of crystals. It has

  And, on the other hand, the silicon raw material rod used in the FZ method is, as described above, suitable for seeding, drawing and forming a cone, for example, having a conical shape, and the silicon crystal rod of the CZ method is machined to the target shape, It was inevitable that the yield would decline.

  The present invention has been made in view of the above problems, and when preparing a silicon raw material rod for FZ using a silicon crystal rod manufactured by the CZ method, the processing loss due to machining of the cone portion is reduced and the yield is increased. An object of the present invention is to provide a method of manufacturing a silicon raw material rod for FZ which can be improved.

  In order to achieve the above object, the present invention is a method for producing a silicon raw material rod for FZ when using a silicon crystal rod produced by the CZ method as a silicon raw material rod for FZ method, A target shape of a cone portion of a rod and an allowable range of the target shape are set, and when the CZ silicon crystal rod is manufactured, the CZ silicon crystal manufactured under the manufacturing conditions in which the cone portion becomes the target shape It is determined whether or not the shape of the cone portion of the rod is within the allowable range, and in the determination, if the shape is within the allowable range, the FZ without machining the cone portion of the CZ silicon crystal rod The silicon raw material rod for the FZ is processed by machining the cone portion of the CZ silicon crystal rod so as to fall within the allowable range if it is not within the allowable range. To provide a method of manufacturing a FZ silicon feed rod, characterized in that the rod.

In this way, first, the cone portion of the CZ silicon crystal rod can be manufactured by the CZ method in a shape very close to the target shape of the cone portion of the silicon material rod for FZ set in advance. And if it is within the set tolerance, it can be used as it is without machining, and it will be machined to be within the tolerance only if it is not within the tolerance, so machining is minimized. Can. Therefore, since the processing loss can be reduced more reliably than in the conventional method in which the cone portion of the CZ silicon crystal rod is manufactured in a substantially flat shape, the yield can be greatly improved.
In addition, the processing loss is more efficient than in the case of merely manufacturing the cone portion of the CZ silicon crystal rod in a slightly conical shape without considering the target shape and the tolerance of the cone portion of the silicon raw material rod for FZ. Can be reduced and the yield can be improved.
In addition, machining can be omitted as described above, and productivity of the FZ silicon material rod can also be improved. In addition, when FZ silicon single crystal is manufactured using the silicon raw material rod for FZ manufactured according to the present invention, it is within the range that conforms to the recipe of manufacturing FZ method manufactured according to the target shape, Can be reduced to the same level as in the past.

  As described above, the CZ method can not be used as a cone portion which is not a product, but can be used as a shape suitable for the FZ method, and the processing loss is reduced. Dramatically improved, productivity improved, and reduced load on the grinding process.

  And when the target shape of the cone part of the silicon raw material rod for FZ is cone-shaped and the target diameter for each position in the height direction of the cone-shaped cone part is D, the target diameter D is taken as the allowable range. The difference between the measured value and the measured value can be within ± 3%.

  In this way, it is possible to ensure that it is within the range that conforms to the recipe of manufacturing of the FZ method manufactured to the target shape. Silicon that has been machined to the target shape like the conventional method in the probability that silicon melt overflows or solidifies or the single crystal has dislocations more surely in the production of the cone part of FZ silicon single crystal When using a raw material rod, it can be suppressed to the same extent.

  Further, the target shape of the cone portion of the FZ silicon raw material rod may be a conical shape having an angle θ at which the tip of the cone portion is selected from the range of 50 ° to 150 °.

  The target shape of the cone part of the raw material rod depends on the FZ single crystal production equipment used, the diameter of the silicon raw material rod, and the diameter of the FZ silicon single crystal to be manufactured, so You can choose the appropriate shape.

  Further, when the shape of the cone portion of the CZ silicon crystal rod is determined, the shape of the cone portion can be calculated and determined from operation data at the time of manufacturing the CZ silicon crystal rod.

  In this way, the shape of the cone portion of the CZ silicon crystal rod can be easily calculated and determined.

  Further, the present invention is a method of heating and melting a silicon raw material rod using an induction heating coil by FZ method to form a floating zone and moving the floating zone to produce an FZ silicon single crystal, The present invention provides a method of producing an FZ silicon single crystal characterized by using, as the silicon material rod, the silicon material rod for FZ manufactured by the method of manufacturing a silicon material rod for FZ of the present invention.

  In this way, despite the fact that FZ silicon single crystal can be manufactured with the same degree of dislocation ratio as the conventional method, it is possible to dramatically improve the overall yield, improve the productivity, and reduce the load on the grinding process. be able to.

  As described above, according to the method of manufacturing a silicon raw material rod for FZ and the method of manufacturing an FZ silicon single crystal of the present invention, machining can be omitted if the shape of the cone portion of the CZ silicon crystal rod falls within the allowable range. Therefore, processing loss is reduced and yield is improved. Even if it does not fall within the allowable range, machining is minimized since it is very close to the target shape, so that processing loss can be reduced and yield loss can be minimized. When the manufactured silicon raw material bar for FZ is used, the shape of the cone part is within the allowable range and conforms to the recipe for manufacturing the cone part of the FZ method. The probability that the liquid overflows, solidifies, or causes dislocation of the single crystal can be suppressed to the same extent as in the case of using the silicon material rod machined by the conventional method.

It is a flowchart which shows an example of the manufacturing method of the silicon | silicone raw material stick | rod for FZ of this invention, and the manufacturing method of FZ silicon single crystal. It is the schematic which shows an example of the shape of the silicon crystal stick by CZ method. It is an explanatory view showing a relation between target diameter D and actual value in case angle (theta) of a cone part of a silicon crystal stick by CZ method is smaller than a standard. It is an explanatory view showing the relation between target diameter D and actual value in case angle (theta) of a cone part of a silicon crystal stick by CZ method is larger than a standard. It is explanatory drawing which shows the example of the range of the machining in case angle (theta) of the cone part of the silicon crystal stick by CZ method is smaller than a reference | standard. It is explanatory drawing which shows the example of the range of the machining in case angle (theta) of the cone part of the silicon crystal stick by CZ method is larger than a reference | standard. It is the schematic which shows an example of the FZ single-crystal manufacturing apparatus which can be used for the manufacturing method of FZ silicon single crystal of this invention. It is the schematic which shows an example of the CZ single crystal pulling apparatus which can be used for the manufacturing method of the silicon | silicone raw material stick | rod for FZ of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.
First, an apparatus for pulling a single crystal by the CZ method which can be used in the method for producing a silicon raw material bar for FZ of the present invention, and an apparatus for producing an FZ single crystal which can be used in the method for producing FZ silicon single crystal of the present invention will be described. .
FIG. 8 shows an example of a single crystal pulling apparatus by the CZ method.
As shown in FIG. 8, the single crystal pulling apparatus 41 is disposed around a pulling chamber 42, a crucible 43 (a quartz crucible inside and a graphite crucible outside) provided in the pulling chamber 42 and the crucible 43. The heater 44, the crucible holding shaft 45 for rotating and elevating the crucible 43 and its rotation and elevating mechanism (not shown), the seed chuck 47 for holding the silicon seed crystal 46, and the wire 48 for pulling up the seed chuck 47 , And a winding mechanism (not shown) for rotating or winding the wire 48. In addition, a heat insulating material 49 is disposed around the outside of the heater 44.
The silicon single crystal (CZ silicon crystal rod 50) is pulled up from the raw material silicon melt 51 by the wire 48.

When growing the CZ silicon crystal rod 50 using the single crystal pulling apparatus 41 of FIG. 8 as described above, the silicon melt 51 in the crucible 43 is held by the seed chuck 47 while rotating the crucible 43. Soak the seed crystal 46 as it is. Then, while rotating and winding the wire 48, the rod-like CZ silicon crystal rod 50 is pulled up from the silicon melt 51.
The crucible 43 can be raised and lowered in the crystal growth axis direction by the crucible holding shaft 45, and raises the crucible 43 so as to compensate for the liquid level descent of the melt which has been crystallized and reduced during crystal growth. An inert gas is flowed to the side of the crystal to rectify the oxidizing vapor emitted from the silicon melt 51.

  In addition, a magnetic field application device can be further provided, and it is also possible to perform a magnetic field application CZ method (MCZ method) for growing the CZ silicon crystal rod 50 while applying a magnetic field.

Next, FIG. 7 shows an example of an FZ single crystal production apparatus.
As shown in FIG. 7, the FZ single crystal manufacturing apparatus 30 has a chamber 20, and in the chamber 20, an upper shaft 3 and a lower shaft 5 which can move up and down and can be rotated are provided.
An upper holding jig 4 is attached to the upper shaft 3, and the upper holding jig 4 holds the silicon raw material bar 1 for FZ (manufactured by the method of manufacturing the silicon raw material bar for FZ of the present invention). There is. The seed crystal 8 is attached to the lower holding jig 6 attached to the lower shaft 5, and the FZ silicon single crystal 2 can be grown above the seed crystal 8 through the narrowed portion 9.

  In the chamber 20, there is disposed an induction heating coil 7b (one which is made of copper or silver and through which cooling water for cooling is wounded) which is connected to the high frequency oscillator 7a. The FZ silicon raw material rod 1 is heated and melted by the induction heating coil 7 b to form the floating zone 10 between the FZ silicon raw material rod 1 and the FZ silicon single crystal 2. The upper shaft 3 and the lower shaft 5 can be moved up and down by the moving means, and the floating zone 10 is moved to the upper end of the FZ silicon raw material rod 1 by moving the upper shaft 3 and the lower shaft 5 be able to. If necessary, a gas spray nozzle 11 may be provided to spray the doping gas into the floating zone 10.

Hereinafter, the method for producing a silicon raw material bar for FZ according to the present invention will be described by taking the case of using the above-mentioned CZ single crystal pulling apparatus as an example. An example of the manufacturing flow of the silicon raw material stick | rod for FZ is shown in FIG.
First, the target shape of the cone portion of the silicon raw material rod for FZ and its allowable range are set. Here, a conical shape in which the angle θ of the tip of the cone portion is a predetermined angle is a target shape (step 100 in FIG. 1).
The value of the angle θ in this target shape is not particularly limited, and can be appropriately selected, for example, from the range of 50 ° to 150 °. It may be set each time according to various conditions, for example, the FZ single crystal manufacturing apparatus to be used, the diameter of the silicon raw material rod, the diameter of the FZ silicon single crystal to be manufactured, etc.

  The above-mentioned target shape, that is, a conical shape having a predetermined angle at the tip, can be reworded as having a target diameter D with respect to each position in the height direction of the cone (or can also be referred to as the growth direction It can also be done.

In step 101 described later, the CZ silicon crystal rod which is the basis of the silicon raw material bar for FZ is pulled up to target the target shape, but there is a possibility that the actual shape may deviate slightly from the target shape. For example, as shown in FIG. 3, when a cone is formed at an angle smaller than the target predetermined angle (a cone of a solid line in FIG. 3), actually measured values D ′ (eg, tip) for each position in the height direction The value of the diameter at the position of the predetermined height H) is smaller than the target diameter D which is the target (the dotted cone portion in FIG. 3).
On the other hand, when the cone portion is formed at an angle exceeding the target predetermined angle, as shown in FIG. 4, for example, the measured value D ′ ′ of the diameter at the predetermined height H from the tip is Will also grow.

Therefore, a range of allowable deviation from the target shape (allowable range) is also set.
As the tolerance of the target shape, for example, the difference between the target diameter D and the actual measurement value can be within ± 3% for each position in the height direction. Such a standard is a range that is sufficiently compatible with the FZ method manufacturing recipe created according to the target shape, and overflows of silicon melt and solidification occur in the FZ method cone part manufacturing. The probability of occurrence of dislocation of a single crystal can be suppressed more reliably to the same extent as in the conventional method.

  In addition, instead of using the diameter for each position in the height direction as described above to represent the allowable range, it is also possible to express and set the allowable range by the angle of the tip of the cone portion corresponding to the allowable range. is there. By doing this, the allowable range can be set more easily.

  Next, a CZ silicon crystal rod is manufactured by the CZ method under manufacturing conditions to be a silicon source rod having a target shape set by the cone part (step 101 in FIG. 1). For example, using the single crystal pulling apparatus shown in FIG. 8, a CZ silicon crystal rod can be manufactured as described above. At this time, various manufacturing conditions such as the pulling speed and the heater output of the CZ silicon crystal rod are controlled so that the cone portion of the CZ silicon crystal rod has a target shape and the straight body portion has a desired diameter. While pulling up. In this way, a CZ silicon crystal rod 50 comprising a cone portion, a straight body portion, and a tail portion is obtained.

FIG. 2 shows the CZ silicon crystal rod 50 manufactured by cutting and processing the tail portion (the upper portion of the CZ silicon crystal rod 50 in FIG. 2). As shown in FIG. 2, it has a cone portion 12, a straight body portion 13 and a tail portion (hereinafter also referred to simply as a tail portion) 14 which has been cut and manufactured under manufacturing conditions aimed at a target shape. The neck is removed and the shape of the cone 12 is measured. Here, the diameter with respect to each position in the height direction as described above, or the angle θ of the tip of the cone portion is measured (step 102 in FIG. 1). The shape may be measured using a general optical method such as a laser, or the position and diameter of the cone in the length direction may be measured with a caliper, or an angle meter may be used. Any method may be used as long as the angle θ or the like can be measured or calculated.
Further, the angle θ or the like of the cone portion may be calculated using operation data when the cone portion is manufactured by the CZ method. If the shape of the cone portion is calculated based on the operation data, the measurement of the shape (and the determination described later) can be performed more easily.

  Then, it is determined whether or not the shape of the cone portion falls within the tolerance set in advance in step 100 (step 103 in FIG. 1). Here, it is determined whether the difference between the target diameter D and the actual value is within ± 3% with respect to each position in the height direction of the cone portion. As described above, the determination may be performed based on the difference between these diameters, or based on the angular range of the tip of the cone portion corresponding to the allowable range of this diameter. The determination in step 103 may be performed based on the tolerance set appropriately in step 100.

  If it is determined in step 103 that the shape of the cone is within the allowable range, etching and cleaning are performed without machining the cone to obtain a silicon raw material bar for FZ (step 104 in FIG. 1).

  On the other hand, if the shape of the cone portion is out of the above-mentioned allowable range, the cone portion is machined so as to be within the above-mentioned allowable range (Step 105 in FIG. 1). Then, the shape is measured again to determine whether it is within the allowable range. That is, step 102 and step 103 are performed again.

In addition, when the tolerance | permissible_range is set by the angle range of a cone part front-end | tip, in said process 105, the method of machining in case angle (theta) of the front-end | tip of a cone part is less than a reference | standard (acceptable range) is shown in FIG. Thus, the cone portion may be machined so that the angle θ falls within the allowable range so as not to change the position of the boundary portion between the cone portion and the straight body portion. Here, reference numerals 31, 32, and 33 respectively indicate the shape of the cone portion before machining, the shape of the cone portion after machining, and the machining range.
On the other hand, when the angle θ of the cone part exceeds the reference (acceptable range), as shown in FIG. 6, the angle θ is within the allowable range with reference to the tip of the cone part. In addition, the cone portion and the straight body portion may be machined.
Then, if it is determined in the re-determination that it is within the allowable range, no further machining of the cone portion is performed, and the necessary processing for attaching the upper holding jig 4 to the tail portion 14 is performed. The surface is etched to remove processing strain of the silicon crystal rod 1. In the step 103, if it is once determined to be out of the allowable range, the silicon raw material bar for FZ is prepared as described above.

  With the manufacturing method as described above, machining can be omitted if the shape of the cone portion falls within the allowable range, so processing loss is reduced and yield is improved. Further, even if it does not fall within the allowable range, machining is minimized since it is very close to the conical shape of the target shape, and processing loss can be reduced compared to the conventional method, and yield loss can be minimized.

Next, the method for producing the FZ silicon single crystal of the present invention will be described by taking the case of using the FZ single crystal production apparatus shown in FIG. 7 as an example. The flow of the manufacturing method is also described in FIG. 1, and the FZ silicon single crystal is manufactured using the CZ silicon crystal rod manufactured as described above as a silicon raw material rod for FZ (step of FIG. 1) 106). More specifically, it is as follows.
The silicon raw material rod 1 for FZ is housed in the chamber 20 of the FZ single crystal production apparatus 30, and as shown in FIG. 2, the upper part with the cut tailed portion 14 upward and the cone 12 directed downward. The tail portion 14 is held by the holding jig 4. Further, the seed crystal 8 is attached to the lower holding jig 6 of the lower shaft 5. At this time, for example, the tail portion 14 may be held by being fixed to the upper holding jig 4 with a screw or the like.

Thereafter, the lower end of the cone portion 12 of the FZ silicon raw material rod 1 is preheated by a preheater (not shown). An Ar gas containing nitrogen gas is supplied from the lower part of the chamber 20 and exhausted from the upper part of the chamber 20. After the lower end of the cone portion 12 of the FZ silicon raw material rod 1 is heated and melted by the induction heating coil 7b, it is fused to the seed crystal 8, and the throttling portion 9 is formed by seed squeezing to make dislocation free.
Then, while rotating the upper shaft 3 and the lower shaft 5, zoning is performed from the cone portion 12 to the tail portion 14 of the FZ silicon material rod 1 to grow the FZ silicon single crystal 2. At this time, the floating zone 10 is set to the tail portion 14 of the silicon material rod 1 for FZ by lowering the silicon material rod 1 for FZ at a predetermined speed, for example, 2.0 to 3.0 mm / min (A direction in FIG. 7). It can be moved to the side and zoned.

At the time of zoning, it is preferable to shift the position of the rotating shaft of the upper shaft 3 and the lower shaft 5 and rotate the silicon raw material rod 1 for FZ and the FZ silicon single crystal 2 in a decentered state. In this way, the molten portion can be stirred during single crystallization, and the quality of the FZ silicon single crystal 2 to be manufactured can be made uniform. The amount of eccentricity at this time may be set according to the diameter of the FZ silicon single crystal 2.
When the zoning has reached a predetermined length, it ends and the separation is performed.

  With such a manufacturing method of FZ silicon single crystal of the present invention, although FZ silicon single crystal can be manufactured with the same degree of dislocation ratio as the conventional method, it is comprehensive including the manufacturing process of its raw material rod Dramatically improve yield, improve productivity, and reduce the load on the grinding process.

Hereinafter, the present invention will be more specifically described with reference to examples of the present invention and comparative examples, but the present invention is not limited to these.
(Example)
According to the flow of the present invention shown in FIG. 1, ten silicon crystal rods for use in the silicon raw material in the FZ method were manufactured by the CZ method using the CZ single crystal pulling apparatus shown in FIG.
In addition, the thing of diameter 150 mm and length (straight body part) 1500 mm was manufactured. The cone part was manufactured with the cone shape required by the FZ method as the target shape. The target shape is a conical shape having a predetermined height, and the angle θ of the tip is 120 °, and as the allowable range, the difference between the target diameter D and the actual value for each position in the height direction of the cone is ± It was 3% or less. In addition, in other words, in the range of the angle of the tip, this allowable range is 117.1 ° ≦ θ ≦ 123.0 °.

  The height of the cone and the diameter of the 10 CZ silicon crystal rods pulled up were measured using a caliper and the angle θ of the tip of the cone was calculated as shown in Table 1 below. Was. Here, assuming that each has a substantially conical shape, the angle of the tip of the cone portion was easily obtained from the diameter of the boundary between the cone portion and the straight body portion and the height of the cone portion.

As shown in Table 1, no. Six of 1-2, 5-7 and 9 were within the tolerance range, and the remaining four were out of tolerance range. Therefore, the cone part within the allowable range (angle θ: 120 °, 117.1 ° ≦ θ ≦ 123.0 °) is not machined for that part, and the cone part outside the allowable range is the allowable range The machine was machined to get into
And after etching each CZ silicon crystal stick, it was used as a silicon raw material stick of FZ method, and FZ silicon single crystal was manufactured using the FZ single crystal manufacturing device shown in FIG. The unnecessary machining ratio of the cone part, the machining loss by machining, and the dislocation ratio in the FZ method are summarized in Table 2.

  As shown in Table 2, machining of the cone part could be omitted for as much as 60% of the CZ silicon crystal rod. The processing loss was also only 0.2%. Thus, the machining of the cone part is minimal, the recipe conforms, and the control is stable, so the dislocation rate is equivalent to that of ordinary machining, and the yield and productivity are high. Met.

(Comparative example)
Ten silicon crystal rods for use in silicon raw material rods of FZ method were manufactured by the CZ method using a CZ single crystal pulling apparatus shown in FIG.
In addition, the thing of diameter 150 mm and length (straight body part) 1500 mm was manufactured. The cone portion was manufactured in a relatively flat shape (tip angle θ: 130 ° to 160 °) manufactured by the general CZ method.
The part was machined until it was in the same range as the tolerance of the example (the tip angle θ: 120 °: 117.1 ° ≦ θ ≦ 123.0 °). After etching, an FZ silicon single crystal was manufactured using the FZ single crystal manufacturing apparatus shown in FIG.
The unnecessary machining ratio of the cone part, the machining loss by machining, and the dislocation ratio in the FZ method are summarized in Table 3.

  As shown in Table 3, since the recipe conformed and the control was stable, the dislocation ratio was equivalent to that of ordinary machining, but the yield due to the machining of the cone part There was a decline in The processing loss was 1.2%, which was nearly six times the 0.2% of the example.

  The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and it has substantially the same configuration as the technical idea described in the claims of the present invention, and any one having the same function and effect can be used. It is included in the technical scope of the invention.

1 ... Silicon material rod for FZ, 2 ... FZ silicon single crystal, 3 ... Upper axis,
4 ... upper holding jig, 5 ... lower shaft, 6 ... lower holding jig,
7a: high frequency oscillator, 7b: induction heating coil,
8: seed crystal, 9: throttle portion, 10: floating zone, 11: nozzle for gas spraying,
12: Cone portion of CZ silicon crystal rod, 13: straight body portion of CZ silicon crystal rod,
14 ... CZ silicon crystal rod tail (cut), 20 ... chamber,
30 ... FZ single crystal manufacturing apparatus, 31 ... shape of cone before machining,
32 ... shape of cone after machining, 33 ... machining range.
41 single crystal pulling apparatus, 42 pulling chamber, 43 crucible, 44 heater,
45 ... crucible holding shaft, 46 ... seed crystal, 47 ... seed chuck,
48 ... wire, 49 ... thermal insulation, 50 ... CZ silicon crystal bar,
51: Silicon melt.

Claims (5)

A method of manufacturing a silicon raw material rod for FZ when using a silicon crystal rod manufactured by the CZ method as a silicon raw material rod for FZ method,
The target shape of the cone portion of the silicon raw material rod for FZ and the allowable range of the target shape are set in advance,
When manufacturing said CZ silicon crystal rod, it manufactures on the manufacturing conditions which a cone part becomes said target shape,
Determining whether the shape of the cone portion of the manufactured CZ silicon crystal rod is within the allowable range;
In this determination, when it is within the allowable range, the cone portion of the CZ silicon crystal rod is not machined and the silicon raw material bar for FZ is used, and when it is not within the allowable range, the allowable range And machining the cone portion of the CZ silicon crystal rod into the silicon raw material rod for FZ to obtain the silicon raw material rod for FZ. Assuming that the target shape of the cone portion of the silicon raw material rod for FZ is a conical shape and the target diameter for each position in the height direction of the conical portion of the conical shape is D,
The method for manufacturing a silicon raw material rod for FZ according to claim 1, wherein a difference between the target diameter D and an actual measurement value is within ± 3% as the allowable range.   The target shape of the cone portion of the FZ silicon raw material rod is a conical shape having an angle θ at which the tip end of the cone portion is selected from the range of 50 ° to 150 °. The manufacturing method of the silicon | silicone raw material stick | rod for FZ as described in 2.   When determining the shape of the cone portion of the CZ silicon crystal rod, the shape of the cone portion is calculated and determined from operation data at the time of manufacturing the CZ silicon crystal rod. The manufacturing method of the silicon | silicone raw material stick | rod for FZ as described in any one of these. According to the FZ method, a silicon raw material rod is heated and melted using an induction heating coil to form a floating zone, and the floating zone is moved to produce an FZ silicon single crystal,
A silicon raw material rod for FZ manufactured by the method for manufacturing a silicon raw material rod for FZ according to any one of claims 1 to 4 is used as the silicon raw material bar, Method.

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