JP6954083B2 - Method for manufacturing silicon raw material rod for FZ and method for manufacturing FZ silicon single crystal - Google Patents

Description

The present invention relates to a method for producing a silicon raw material rod for FZ, which is a silicon raw material rod of the FZ method (floating zone method). The present invention relates to a method for manufacturing a silicon raw material rod for FZ when (also referred to as a rod) is used as a silicon raw material rod for the FZ method.

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

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

Next, the silicon raw material rod is melted by the induction heating coil and fused to the seed crystal. After that, a squeezed portion is formed by a seed squeezing to make it dislocation-free. Then, a floating zone (also referred to as a melt zone or melt) is formed between the silicon raw material rod and the silicon single crystal by lowering the silicon raw material rod and the silicon single crystal while rotating the upper axis and the lower axis, and the floating zone is formed. Is moved to the upper end of the silicon raw material rod and zoned to grow a silicon single crystal. This growth is carried out in an atmosphere in which a trace amount of nitrogen gas is mixed with Ar gas.
As the induction heating coil, an induction heating coil in which single-winding or compound-winding cooling water made of copper or silver is circulated is used.

Usually, rod-shaped polycrystalline silicon is used as a raw material for FZ single crystal silicon. However, the polycrystalline silicon (polycrystalline silicon rod for FZ) required as a raw material in the FZ method has a high purity, is less likely to cause cracks and cracks, has a uniform grain boundary structure, and is a FZ single crystal silicon to be produced. It is required to have a columnar shape with a diameter value suitable for the above, less flatness and crank, and a good surface condition. The production of polycrystalline silicon rods for FZ that satisfy such conditions has a very low yield and productivity as compared with the production of polycrystalline silicon used in the CZ method, which allows a nugget-like size. ..

In the production of a silicon single crystal by the FZ method, a floating band exists on the silicon single crystal. In other words, while the silicon melt remains on the silicon single crystal, the raw material is melted and the single crystal grows at the same time. Therefore, if the diameter of the silicon raw material rod fluctuates, the silicon single crystal is being manufactured. The silicon melt overflows, solidification occurs, and the single crystal tends to undergo dislocation. When such a situation occurs, the silicon single crystal cannot grow any more, and the operation is stopped. Then move to the next batch. As a result, productivity and yield are greatly reduced. Therefore, for stable operation, a silicon raw material rod having a small diameter fluctuation is suitable, and machining is performed so as to obtain a desired shape.

In particular, in the seeding, drawing, and cone manufacturing processes by the FZ method, the amount of intervening silicon melt is smaller than that of forming a straight body portion, and the tip of the silicon raw material rod is, for example, a cone in advance. It is machined into a shape and used.
Machining of silicon raw material rods causes a decrease in yield, but when the end face of a cylindrical silicon raw material rod is a flat surface, seeding, drawing, and manufacturing of the cone part are extremely difficult to create and control recipes. It is difficult to control the desired cone shape by the FZ method.
In the manufacturing process of the cone portion of the FZ silicon single crystal, the diameter of the cone portion is expanded, and at the same time, the diameter of the molten portion is also expanded as the silicon raw material rod is melted, so that the manufacturing recipe and control are difficult. At this time, if the diameter of the silicon raw material rod fluctuates greatly, the control of the production of the cone portion of the FZ silicon single crystal becomes unstable, and the silicon melt overflows, solidifies, or the single crystal undergoes dislocation. It becomes.

Here, the conical shape of the silicon raw material rod machined here is machined with a shape that is unlikely to undergo dislocation in the manufacturing process of the cone portion of the FZ method as a target shape. This shape differs 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. Then, by machining to the target shape, the shapes are aligned, so that the recipe for manufacturing the cone part of the FZ silicon single crystal is suitable, the control is stabilized, and the dislocation rate of the single crystal is reduced. Will be done.
On the contrary, if a silicon raw material rod that deviates from the target shape is used, the recipe for manufacturing the cone part of the FZ silicon single crystal becomes incompatible, the control becomes unstable, the silicon melt overflows or solidifies, or the FZ silicon single crystal is used. It causes the crystal to undergo dislocation.

In recent years, the demand for polycrystalline silicon (polycrystalline silicon for CZ) used in the CZ method mainly for diameters of 300 mm has increased significantly. For this reason, as mentioned above, the supply of polycrystalline silicon crystal rods for FZ, which has strict quality standards such as shape and purity, low productivity, and high cost, is tight to meet the demand, and the price is high. Is also very high. As a result, it has become difficult to secure a high-quality polycrystalline silicon rod for FZ, and it has become difficult to stably produce an FZ silicon single crystal.

Therefore, a method for 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 raw material rod by the FZ method, has been proposed. (See, for example, Patent Document 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 produce a uniform silicon raw material rod having high purity and less likely to cause cracks and cracks. Further, it is possible to manufacture a silicon raw material rod suitable for the diameter of the silicon single crystal to be manufactured by the FZ method, and it is possible to stably supply a silicon raw material rod having few flatnesses and cranks and having a good surface condition.

Japanese Unexamined Patent Publication No. 2005-306653 Japanese Unexamined Patent Publication No. 2013-139388 JP 2015-117177

In the CZ method, various methods for improving the manufacturing yield have been promoted due to the continuous demand for cost reduction. Among them, for the silicon crystal rod of the CZ method, the role of the cone part is an indispensable part for expanding the diameter to the desired crystal diameter, but in general, only the straight body part is a product. , The cone part is preferably light in weight and has a short manufacturing time, and a generally flat shape (low cone part height or short cone length) is selected in consideration of the dislocation rate of crystals. I came.

On the other hand, as described above, the silicon raw material rod used in the FZ method has a conical shape suitable for seeding, drawing, and manufacturing a cone portion, and the silicon crystal rod in the CZ method is also machined into a target shape. It was inevitable that the yield would decline.

The present invention has been made in view of the above problems, and when a silicon raw material rod for FZ is prepared 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 reduced. It is an object of the present invention to provide a method for producing 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 a silicon crystal rod produced by the CZ method is used as a silicon raw material rod for the FZ method. When the target shape of the cone portion of the rod and the permissible range of the target shape are set and the CZ silicon crystal rod is manufactured, the cone portion is manufactured under the manufacturing conditions so that the target shape is formed, and the manufactured CZ silicon crystal is manufactured. It is determined whether or not the shape of the cone portion of the rod is within the permissible range, and if it is within the permissible range in the determination, the FZ is performed without machining the cone portion of the CZ silicon crystal rod. The silicon raw material rod for FZ is used, and if it is not within the permissible range, the cone portion of the CZ silicon crystal rod is machined so as to be within the permissible range to obtain the silicon raw material rod for FZ. Provided is a method for manufacturing a silicon raw material rod for FZ.

In this way, first, the cone portion of the CZ silicon crystal rod can be manufactured by the CZ method in a shape extremely close to the target shape of the cone portion of the silicon raw material rod for FZ set in advance. And if it falls within the set predetermined allowable range, it can be used as it is without machining, and only if it does not fall within the allowable range, it is machined so that it falls within the allowable range, so machining can be minimized. Can be done. Therefore, the processing loss can be surely reduced as compared with the conventional method in which the cone portion of the CZ silicon crystal rod is manufactured in a substantially flat shape, and the yield can be greatly improved.
Further, the processing loss is more efficient than the case where the cone portion of the CZ silicon crystal rod is simply manufactured into a slightly conical shape without considering the target shape of the cone portion of the silicon raw material rod for FZ and its allowable range. Can be reduced and the yield can be improved.
Further, as described above, machining can be omitted, and the productivity of the silicon raw material rod for FZ can be improved. Moreover, when an FZ silicon single crystal is produced using the silicon raw material rod for FZ produced in the present invention, the dislocation rate is within a range suitable for the manufacturing recipe of the FZ method produced according to the target shape. Can be suppressed to the same level as before.

As described above, the cone portion, which is not a product in the CZ method, can be used as a shape suitable for the FZ method, and the processing loss is reduced. Dramatic improvement, productivity improvement, and load reduction in the grinding process can be obtained.

Then, when the target shape of the cone portion of the silicon raw material rod for FZ is a conical shape and the target diameter with respect to each position of the conical cone portion in the height direction is D, the target diameter D is set as the permissible range. The difference between the measured value and the measured value can be within ± 3%.

In this way, it is possible to more reliably ensure that the shape is within the range conforming to the recipe for manufacturing the FZ method prepared according to the target shape. In the production of the cone part of the FZ silicon single crystal, the probability that the silicon melt overflows, solidifies, or the single crystal undergoes dislocation is more reliably determined by machining the silicon into a target shape as in the conventional method. It can be suppressed to the same extent as when a raw material rod is used.

Further, the target shape of the cone portion of the silicon raw material rod for FZ can 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 differs 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. You can choose the appropriate shape with.

Further, when determining the shape of the cone portion of the CZ silicon crystal rod, the shape of the cone portion can be calculated and determined from the 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 for producing an FZ silicon single crystal by heating and melting a silicon raw material rod using an induction heating coil by the FZ method to form a floating zone and moving the floating zone. Provided is a method for producing an FZ silicon single crystal, which comprises using the silicon raw material rod for FZ produced by the method for producing a silicon raw material rod for FZ of the present invention as the silicon raw material rod.

In this way, although the FZ silicon single crystal can be produced with a dislocation rate similar to that of the conventional method, the overall yield is dramatically improved, the productivity is improved, and the load on the grinding process is reduced. be able to.

As described above, in the method for producing the silicon raw material rod for FZ and the method for producing the 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 is within the permissible range. Therefore, the processing loss is reduced and the yield is improved. Even if it does not fall within the permissible range, it is extremely close to the target shape, so machining is minimized, machining loss is reduced, and yield reduction can be minimized. If the manufactured silicon raw material rod for FZ is used, the shape of the cone portion is within the permissible range and conforms to the recipe for manufacturing the cone portion of the FZ method. The probability that the liquid will overflow, solidify, or undergo a rearrangement of a single crystal can be suppressed to the same level as when a machined silicon raw material rod by a conventional method is used.

It is a flow chart which shows an example of the manufacturing method of the silicon raw material rod for FZ of this invention, and the manufacturing method of the FZ silicon single crystal. It is the schematic which shows an example of the shape of the silicon crystal rod by the CZ method. It is explanatory drawing which shows the relationship between the target diameter D and the measured value when the angle θ of the cone part of the silicon crystal rod by the CZ method is smaller than a reference. It is explanatory drawing which shows the relationship between the target diameter D and the measured value when the angle θ of the cone part of the silicon crystal rod by the CZ method is larger than a reference. It is explanatory drawing which shows the example of the range of machining when the angle θ of the cone part of the silicon crystal rod by the CZ method is smaller than a reference. It is explanatory drawing which shows the example of the range of machining when the angle θ of the cone part of the silicon crystal rod by the CZ method is larger than a reference. It is a schematic diagram which shows an example of the FZ single crystal manufacturing apparatus which can be used in the manufacturing method of the 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 in the manufacturing method of the silicon raw material 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, a single crystal pulling apparatus by the CZ method that can be used in the method for producing a silicon raw material rod for FZ of the present invention and an FZ single crystal manufacturing apparatus that can be used in the method for producing an FZ silicon single crystal of the present invention will be described. ..
FIG. 8 shows an example of a single crystal pulling device by the CZ method.
As shown in FIG. 8, the single crystal pulling device 41 is arranged around the pulling chamber 42, the crucible 43 (quartz crucible on the inside, and the graphite crucible on the outside) provided in the pulling chamber 42, and the crucible 43 on the outside. A heater 44, a crucible holding shaft 45 for rotating and raising and lowering the crucible 43, a mechanism for rotating and raising and lowering the crucible (not shown), a seed chuck 47 for holding a silicon seed crystal 46, and a wire 48 for pulling up the seed chuck 47. , A winding mechanism (not shown) for rotating or winding the wire 48 is provided. Further, a heat insulating material 49 is arranged 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 a wire 48.

When the CZ silicon crystal rod 50 is grown by using the single crystal pulling device 41 of FIG. 8, the silicon melt 51 in the crucible 43 is held by the seed chuck 47 while rotating the crucible 43. Immerse the seed crystal 46. Then, while rotating and winding the wire 48, the rod-shaped 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 decrease in the liquid level of the melt that crystallizes and decreases during crystal growth. An inert gas is flowed to the side of the crystal in order to rectify the oxidizing vapor generated from the silicon melt 51.

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

Next, FIG. 7 shows an example of the FZ single crystal manufacturing apparatus.
As shown in FIG. 7, the FZ single crystal manufacturing apparatus 30 has a chamber 20, and an upper shaft 3 and a lower shaft 5 that can move up and down and rotate are provided in the chamber 20.
An upper holding jig 4 is attached to the upper shaft 3, and the silicon raw material rod 1 for FZ (manufactured by the method for manufacturing the silicon raw material rod for FZ of the present invention) is held by the upper holding jig 4. There is. A 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 drawing portion 9.

In the chamber 20, an induction heating coil 7b (a single-wound or double-wound cooling water made of copper or silver is circulated) connected to the high-frequency oscillator 7a is arranged. The FZ silicon raw material rod 1 is heated and melted by the induction heating coil 7b to form a 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 in the vertical direction by a moving means, and the upper shaft 3 and the lower shaft 5 are moved to move the floating band 10 to the upper end of the silicon raw material rod 1 for FZ. be able to. If necessary, a gas blowing nozzle 11 for blowing the doping gas into the floating zone 10 can be provided.

Hereinafter, the method for producing the silicon raw material rod for FZ of the present invention will be described by using the above-mentioned CZ single crystal pulling device as an example. FIG. 1 shows an example of a manufacturing flow of a silicon raw material rod for FZ.
First, the target shape of the cone portion of the silicon raw material rod for FZ and its allowable range are set. Here, the target shape is a conical shape in which the angle θ of the tip of the cone portion is a predetermined angle (step 100 in FIG. 1).
The value of the angle θ in this target shape is not particularly limited, and can be appropriately selected from the range of, for example, 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, and the like.

The target shape, that is, a conical shape having a tip having a predetermined angle, can be rephrased as having a target diameter D with respect to each position in the height direction of the cone (or can be said to be the growing direction or the length direction of the cone portion). You can also do it.

In step 101, which will be described later, the CZ silicon crystal rod, which is the base of the silicon raw material rod for FZ, is pulled up with the target shape as the target, but in actual manufacturing, there is a possibility that the target shape is slightly deviated. For example, as shown in FIG. 3, when the cone portion is formed at an angle lower than the target predetermined angle (solid line cone portion in FIG. 3), the measured value D'(for example, the tip) for each position in the height direction. The value of the diameter at the position of the predetermined height H) becomes smaller than the target diameter D, which is the target (the cone portion of the dotted line in FIG. 3).
On the other hand, when the cone portion is formed at an angle exceeding the target predetermined angle, for example, as shown in FIG. 4, the measured value D ″ of the diameter at the position of the predetermined height H from the tip is larger than the target diameter D. Will also grow.

Therefore, the range of allowable deviation from the target shape (allowable range) is also set.
As the allowable range of the target shape, for example, the difference between the target diameter D and the actually measured value with respect to each position in the height direction can be within ± 3%. Such a standard is a range that sufficiently conforms to the recipe for manufacturing the FZ method prepared according to the target shape, and in the manufacturing of the cone portion of the FZ method, the silicon melt overflows and solidification occurs. The probability of single crystal dislocations and the like can be more reliably suppressed to the same extent as in the conventional method.

In addition, instead of expressing the allowable range by using the diameter for each position in the height direction as described above, 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. be. By doing so, the allowable range can be set more easily.

Next, the CZ silicon crystal rod is manufactured by the CZ method under the manufacturing conditions for forming the silicon raw material rod having the target shape set by the cone portion (step 101 in FIG. 1). For example, the single crystal pulling device shown in FIG. 8 can be used to manufacture a CZ silicon crystal rod as described above. At this time, various manufacturing conditions such as the pulling speed of the CZ silicon crystal rod and the heater output 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, the CZ silicon crystal rod 50 including the cone portion, the straight body portion, and the tail portion is obtained.

FIG. 2 shows a manufactured CZ silicon crystal rod 50 obtained by cutting 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 cut tail portion (hereinafter, also simply referred to as a tail portion) 14 manufactured under manufacturing conditions targeting a target shape. The neck portion is removed, and the shape of the cone portion 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 grasped by using an optical method such as a general laser, the position and diameter in the length direction of the cone may be measured with a caliper, or an angle meter may be used for the measurement. Any method can be used as long as the angle θ and the like can be measured or calculated.
Further, the angle θ of the cone portion may be calculated by using the 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 shape can be measured (further, the determination described later) more easily.

Then, it is determined whether or not the shape of the cone portion is within the allowable range set in advance in step 100 (step 103 in FIG. 1). Here, it is determined whether or not 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. In this way, the determination may be made based on the difference between these diameters, or the determination may be made based on the angle range of the tip of the cone portion corresponding to the allowable range at this diameter. The determination in step 103 may be performed based on the permissible range appropriately set in step 100.

In the determination of step 103, when the shape of the cone portion is within the above allowable range, the cone portion is etched, washed, or the like without machining to obtain a silicon raw material rod for FZ (step 104 in FIG. 1).

On the other hand, when the shape of the cone portion is outside the allowable range, the cone portion is machined so as to be within the allowable range (step 105 in FIG. 1). Then, the shape is measured again to determine whether it is within the permissible range. That is, the steps 102 and 103 are performed again.

When the allowable range is set in the angle range of the tip of the cone, the machining method when the angle θ of the tip of the cone is less than the reference (allowable range) in the step 105 is shown in FIG. As described above, the cone portion may be machined so that the angle θ is within the permissible 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 indicate the shape of the cone portion before machining, the shape of the cone portion after machining, and the machining range, respectively.
On the other hand, when the angle θ of the cone portion exceeds the reference (allowable range), the machining method is as shown in FIG. 6 so that the angle θ falls within the allowable range with reference to the tip portion of the cone portion. In addition, the cone portion and the straight body portion may be machined.
Then, when it is determined in the re-judgment that it is within the permissible range, the cone portion is not further machined, and the tail portion 14 is subjected to the necessary machining for attaching to the upper holding jig 4. The surface is etched to remove the processing strain of the silicon crystal rod 1. If it is once determined in step 103 that it is out of the permissible range, the silicon raw material rod for FZ is prepared as described above.

With the manufacturing method as described above, if the shape of the cone portion is within the permissible range, machining can be omitted, so that machining loss is reduced and yield is improved. Further, even if it does not fall within the permissible range, the machining is minimized because it is extremely close to the conical shape of the target shape, the machining loss is reduced as compared with the conventional method, and the decrease in yield 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 CZ silicon crystal rod manufactured as described above is used as a silicon raw material rod for FZ to manufacture an FZ silicon single crystal (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 manufacturing apparatus 30, and as shown in FIG. 2, the upper portion is in a state where the cut tail portion 14 is directed upward and the cone portion 12 is 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 fixing it to the upper holding jig 4 with a screw or the like.

After that, the lower end of the cone portion 12 of the silicon raw material rod 1 for FZ is preheated by a preheater (not shown). 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 silicon raw material rod 1 for FZ is heated and melted by the induction heating coil 7b, it is fused to the seed crystal 8 and the drawn portion 9 is formed by the seed drawing to make it dislocation-free.
Then, while rotating the upper shaft 3 and the lower shaft 5, the FZ silicon single crystal 2 is grown by zoning from the cone portion 12 of the silicon raw material rod 1 for FZ toward the tail portion 14. At this time, by lowering the FZ silicon raw material rod 1 at a predetermined speed, for example, 2.0 to 3.0 mm / min (direction A in FIG. 7), the floating band 10 is reduced to the tail portion 14 of the FZ silicon raw material rod 1. It can be moved to the side for zoning.

At the time of zoning, it is preferable to shift the positions of the rotation axes of the upper shaft 3 and the lower shaft 5 and rotate the FZ silicon raw material rod 1 and the FZ silicon single crystal 2 in an eccentric state. In this way, the melted portion can be agitated at the time of single crystal formation, and the quality of the FZ silicon single crystal 2 to be produced 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 reaches the specified length, it is finished and the disconnection is performed.

With the method for producing an FZ silicon single crystal of the present invention as described above, although the FZ silicon single crystal can be produced with a dislocation rate similar to that of the conventional method, the production process of the raw material rod is also included. It is possible to obtain a dramatic improvement in yield, an improvement in productivity, and a reduction in the load on the grinding process.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited thereto.
(Example)
According to the flow of the present invention shown in FIG. 1, 10 silicon crystal rods for use in the silicon raw material rod of the FZ method were produced by the CZ method using the CZ single crystal pulling device shown in FIG.
A product having a diameter of 150 mm and a length (straight body portion) of 1500 mm was manufactured. The cone portion was manufactured with the conical shape required by the FZ method as the target shape. The target shape is a conical shape having a predetermined height, the angle θ of the tip thereof is 120 °, and the allowable range is that the difference between the target diameter D and the measured value with respect to each position in the height direction of the cone portion is ±. It was set to be within 3%. In other words, this permissible range is 117.1 ° ≤ θ ≤ 123.0 ° in terms of the angle of the tip.

The 10 CZ silicon crystal rods that were pulled up were distributed as shown in Table 1 below when the height of the cone and the diameter of the cone were measured using a caliper and the angle θ at the tip of the cone was calculated. Was. Here, assuming that each has a substantially conical shape, the angle of the tip of the cone portion was simply 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 permissible range, and the remaining four were out of the permissible range. Therefore, the cone portion within the permissible range (117.1 ° ≤ θ ≤ 123.0 ° with respect to the angle θ: 120 °) is not machined, and the cone portion outside the permissible range is within the permissible range. Machining was carried out so as to enter.
Then, after etching each CZ silicon crystal rod, it was used as a silicon raw material rod by the FZ method, and an FZ silicon single crystal was produced using the FZ single crystal production apparatus shown in FIG. 7. Table 2 summarizes the machining-free rate of the cone, the machining loss due to machining, and the dislocation rate by the FZ method.

As shown in Table 2, machining of the cone portion could be omitted for as much as 60% of CZ silicon crystal rods. The processing loss was only 0.2%. In this way, the machining of the cone part was minimal, the recipe was suitable, and the control was stable, so the dislocation rate was the same as that of normal machining, and the yield and productivity were high. Met.

(Comparison example)
By the CZ method, 10 silicon crystal rods for use in the silicon raw material rod of the FZ method were manufactured by using the CZ single crystal pulling device shown in FIG.
A product having a diameter of 150 mm and a length (straight body portion) of 1500 mm was manufactured. The cone portion was manufactured in a relatively flat shape (tip angle θ: 130 ° to 160 °) manufactured by a general CZ method.
The portion was machined until it fell within the same range as the permissible range of the examples (117.1 ° ≤ θ ≤ 123.0 ° with respect to the tip angle θ: 120 °). After etching, it was used as a silicon raw material rod by the FZ method, and an FZ silicon single crystal was produced using the FZ single crystal production apparatus shown in FIG. 7.
Table 3 summarizes the machining unnecessary rate of the cone portion, the machining loss due to machining, and the dislocation formation rate by the FZ method.

As shown in Table 3, since the recipe was suitable and the control was stable, the dislocation rate was the same as that of normal machining, but the yield was due to the machining of the cone part. There was a decline in. The processing loss was 1.2%, which was nearly 6 times that of 0.2% in the examples.

The present invention is not limited to the above embodiment. The above embodiment is an example, and any one having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same effect and effect is the present invention. It is included in the technical scope of the invention.

1 ... Silicon raw material rod for FZ, 2 ... FZ silicon single crystal, 3 ... Upper shaft,
4 ... Upper holding jig, 5 ... Lower shaft, 6 ... Lower holding jig,
7a ... High frequency oscillator, 7b ... Induction heating coil,
8 ... Seed crystal, 9 ... Aperture part, 10 ... Floating zone, 11 ... Gas blowing nozzle,
12 ... Cone part of CZ silicon crystal rod, 13 ... Straight body part of CZ silicon crystal rod,
14 ... CZ silicon crystal rod tail (cut), 20 ... chamber,
30 ... FZ single crystal manufacturing equipment, 31 ... shape of cone before machining,
32 ... Shape of cone after machining, 33 ... Machining range.
41 ... Single crystal pulling device, 42 ... Pulling chamber, 43 ... Crucible, 44 ... Heater,
45 ... Crucible holding shaft, 46 ... Seed crystal, 47 ... Seed chuck,
48 ... wire, 49 ... insulation, 50 ... CZ silicon crystal rod,
51 ... Silicone melt.

Claims (4)

This is a method for manufacturing a silicon raw material rod for FZ when a silicon crystal rod manufactured by the CZ method is used as a silicon raw material rod for the FZ method.
In advance, the target shape of the cone portion of the silicon raw material rod for FZ and the permissible range of the target shape are set.
When manufacturing the CZ silicon crystal rod, the cone portion is manufactured under the manufacturing conditions in which the target shape is obtained.
It is determined whether or not the shape of the cone portion of the manufactured CZ silicon crystal rod is within the permissible range.
In the determination, if it is within the permissible range, the cone portion of the CZ silicon crystal rod is used as the silicon raw material rod for FZ without machining, and if it is not within the permissible range, the permissible range is used. The cone portion of the CZ silicon crystal rod is machined so as to enter the silicon raw material rod for FZ .
When the target shape of the cone portion of the silicon raw material rod for FZ is a conical shape and the target diameter of the conical cone portion with respect to each position in the height direction is D.
A method for producing a silicon raw material rod for FZ , wherein the difference between the target diameter D and the measured value is within ± 3% as the permissible range. The first aspect of claim 1, wherein the target shape of the cone portion of the silicon raw material rod for FZ is a conical shape in which the tip of the cone portion has an angle θ selected from the range of 50 ° to 150 °. A method for manufacturing a silicon raw material rod for FZ. 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 the position and diameter of the cone portion in the height direction at the time of manufacturing the CZ silicon crystal rod. The method for manufacturing a silicon raw material rod for FZ according to claim 1 or 2. A method of producing an FZ silicon single crystal by heating and melting a silicon raw material rod using an induction heating coil by the FZ method to form a floating zone and moving the floating zone.
Production of an FZ silicon single crystal, which comprises using a silicon raw material rod for FZ produced by the method for producing a silicon raw material rod for FZ according to any one of claims 1 to 3 as the silicon raw material rod. Method.

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