JP4785765B2 - Single crystal pulling method - Google Patents

Description

  The present invention relates to a method for pulling a single crystal that is pulled while growing the single crystal by the Czochralski method (hereinafter referred to as “CZ method”).

  The CZ method is widely used for the growth of silicon single crystals. In this method, the seed crystal is brought into contact with the surface of the silicon melt contained in the crucible, the crucible is rotated, and the seed crystal is pulled upward while rotating in the opposite direction. In this way, a single crystal is formed.

  As shown in FIG. 5, in the pulling method using the conventional CZ method, first, raw material polysilicon is loaded into a quartz glass crucible 51 and heated by a heater 52 to obtain a silicon melt M. Thereafter, the silicon single crystal C is pulled by bringing the seed crystal P attached to the pulling wire 50 into contact with the silicon melt M.

In general, prior to the start of pulling, after the temperature of the silicon melt M is stabilized, as shown in FIG. 6, necking is performed in which the seed crystal P is brought into contact with the silicon melt M to dissolve the tip of the seed crystal P. Necking is an indispensable process for removing dislocations generated in a silicon single crystal due to thermal shock generated by contact between the seed crystal P and the silicon melt M. The neck portion P1 is formed by this necking. In order to eliminate the dislocation of the single crystal C formed under the neck portion P1, the neck portion P1 usually has a minimum diameter of 3 to 4 mm and a length of about 15 mm. .
In addition, as a process after the start of pulling, after necking is completed, a crown process for expanding the crystal to the diameter of the straight body part, a straight body process for growing a single crystal as a product, and a single crystal diameter after the straight body process are gradually reduced. The tail process is performed.

  By the way, in recent years, the diameter of single crystals to be grown has been increased, and the production of single crystals having a diameter of 300 mm has become the mainstream. For this reason, the weight of the single crystal to be pulled up is also increasing, and preventing damage to the neck portion P1 at the time of pulling is one of the major issues. In the process of producing a single crystal having a diameter of 300 mm or more, since the strength is insufficient when the minimum diameter of the neck portion P1 is 3 mm or more and less than 4 mm, a single crystal having a neck portion diameter of 4 mm or more and less than 6 mm and having a single crystal weight of 200 kg to 450 kg is used. There is a need for reliable support technology.

  In order to improve the strength of the neck portion, Patent Document 1 discloses that the reduced diameter portion and the enlarged diameter portion are alternately formed on the neck portion, and the minimum diameter of the reduced diameter portion is 5 mm or more. A method is disclosed in which the ratio of the maximum diameter of the portion and the minimum diameter of the reduced diameter portion is made twice or more. According to this method, the strength of the neck portion is improved, and breakage of the neck portion can be greatly reduced as compared with the case where a thin neck portion is simply formed.

However, in the method disclosed in Patent Document 1, with the recent increase in the diameter of the grown single crystal, the diameter of the seed crystal used increases, and the amount of heat shock dislocation generated in the seed crystal correspondingly increases. Therefore, there is a limit to eliminating slip dislocations in a short time.
For this problem, in Patent Document 2, when the reduced diameter portion and the enlarged diameter portion are alternately formed in the neck portion, when the enlarged diameter portion is formed, the enlarged diameter portion is cooled using a rectifying plate, A technique for preventing propagation of heat shock dislocation to a product portion is disclosed.
Japanese Patent Laid-Open No. 11-199384 JP 2006-160552 A

  However, in the method disclosed in Patent Document 2, since it is necessary to arrange a rectifying plate having a movable mechanism in the furnace, the structure in the furnace is complicated, the cost is increased, and control at the time of growing the neck portion is performed. Was not easy. For this reason, the neck portion has a more simplified internal structure, sufficient strength to withstand the pulling of a heavy single crystal, and the propagation of heat shock dislocation from the seed crystal to the straight body portion is prevented. There was a need for a method that could form

  The present invention has been made under the circumstances as described above, and in the single crystal pulling method for pulling a silicon single crystal from a crucible by the Czochralski method, the neck portion breaks when pulling a large-diameter single crystal. It is an object of the present invention to provide a method for pulling a single crystal that can prevent propagation of heat shock dislocation from the seed crystal to the straight body portion without performing the above process.

In order to solve the above-described problems, the method for pulling a single crystal according to the present invention is such that the seed crystal is brought into contact with the silicon melt in the crucible, the neck portion is grown , and the weight is 300 mm or more by the Czochralski method. In the single crystal pulling method for pulling up a silicon single crystal of 200 kg to 400 kg , the neck portion includes an enlarged portion for expanding the diameter of the neck portion and a reduced diameter portion for reducing the diameter of the neck portion. When a plurality of the diameter-expanded portions and the diameter-reduced portion are formed alternately in the neck portion, the minimum diameter in each diameter-reduced portion is set within a range of 4.0 mm to 6.0 mm. And forming each reduced diameter portion so that the variation width of the diameter difference from the maximum diameter of each enlarged diameter portion to the minimum diameter of each reduced diameter portion is within a range of 0.5 mm to 2.0 mm, And the length dimension of the said neck part is 200 mm-4 And within 0mm range, and the pulling rate of the neck portion to be grown is, in particular having the features is controlled in the range of 1.5mm / min~5.0mm / min.

According to such a method, even if the single crystal to be pulled has a large diameter and a high weight, it is possible to give the neck portion sufficient strength that does not break during pulling. Propagation of heat shock dislocation to the portion can be prevented.
Further, since it is not necessary to provide a rectifying plate or the like for cooling the neck portion in the furnace body, the cost of the apparatus can be suppressed, and the control in growing the neck portion can be easily performed.

In particular, the pulling speed of the neck portion to be grown is controlled in the range of 1.5 mm / min to 5.0 mm / min. By controlling in this way , it is possible to facilitate the formation of the reduced diameter portion having the desired minimum diameter and the formation of the enlarged diameter portion having the desired maximum diameter.

  According to the present invention, in the pulling method of the single crystal that pulls up the silicon single crystal from the crucible by the Czochralski method, when pulling the large-diameter single crystal, the neck portion does not break and the straight body portion from the seed crystal. It is possible to obtain a single crystal pulling method capable of preventing the propagation of heat shock dislocations.

  Hereinafter, embodiments of a method for pulling a single crystal according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of a single crystal pulling apparatus 1 in which a single crystal pulling method according to the present invention is implemented.

This single crystal pulling apparatus 1 includes a furnace body 2 formed by superposing a pull chamber 2b on a cylindrical main chamber 2a, a crucible 3 provided in the furnace body 2, and a semiconductor loaded in the crucible 3. A heater 4 for melting the raw material (raw material polysilicon) M and a pulling mechanism 5 for pulling up the single crystal C to be grown are provided. The crucible 3 has a double structure, and is composed of a quartz glass crucible on the inside and a graphite crucible on the outside.
The pulling mechanism 5 has a winding mechanism 5a driven by a motor and a pulling wire 5b wound up by the winding mechanism 5a, and a seed crystal P is attached to the tip of the wire 5b.

  Further, a gas introduction port 18 for introducing a predetermined gas (for example, Ar gas) into the furnace body 2 is provided at the upper part of the pull chamber 2b, and the gas chamber is introduced into the furnace body 2 at the bottom of the main chamber 2b. A gas discharge port 19 for discharging gas is provided. For this reason, a gas flow having a predetermined flow rate is formed in the furnace body 2 from above to below.

  Further, in the main chamber 2a, an upper portion and a lower portion are formed so as to surround the periphery of the single crystal C above and in the vicinity of the crucible 3, and extra radiant heat from the heater 4 or the like is applied to the growing single crystal C. A radiation shield 6 is provided for shielding and rectifying the gas flow in the furnace. The distance dimension (gap) between the lower end of the radiation shield 6 and the melt surface is controlled so as to maintain a predetermined distance according to desired characteristics of the single crystal to be grown.

Further, outside the furnace body 2, there is provided a crystal shape detection device 14 that detects the shape and diameter of the neck portion P <b> 1 and the single crystal C grown near the liquid surface M <b> 1 of the silicon melt M.
This crystal shape detection device 14 is provided with a camera port 15 made of translucent heat-resistant glass provided at the upper part of the main chamber 2b, a CCD camera 16 for imaging a predetermined area on the melt surface through the camera port 15, And an image processing device 17 that performs arithmetic processing on an image signal picked up by the CCD camera 16.

The optical axis of the CCD camera 16 is directed to a predetermined spot on the melt surface via the camera port 15, and the CCD camera 16 captures an image of the predetermined spot and sends the captured image to the image processing device 17. It is designed to output.
Further, the image processing device 17 processes the image signal input from the CCD camera 16 to detect the shape and diameter of the crystal pulled from the silicon melt liquid surface, and outputs it to the arithmetic control device 8 b of the computer 8. It is made like that.

  As shown in FIG. 1, the single crystal pulling apparatus 1 includes a heater control unit 9 that controls the amount of power supplied to the heater 4 that controls the temperature of the silicon melt M, a motor 10 that rotates the crucible 3, and a motor. And a motor control unit 10a for controlling the number of rotations of ten. Also, an elevating device 11 that controls the height of the crucible 3, an elevating device control unit 11 a that controls the elevating device 11, and a wire reel rotating device control unit 12 that controls the pulling speed and the number of rotations of the grown crystal. Yes. Each of these control units 9, 10 a, 11 a, 12 is connected to an arithmetic control device 8 b of the computer 8.

  In the single crystal pulling apparatus 1 configured as described above, the raw material polysilicon M is first loaded into the quartz glass crucible 3a, and the flow shown in FIG. 2 is performed based on the program stored in the storage device 8a of the computer 8. The crystal growth process is started.

First, in the furnace body 2, a gas flow of Ar gas is formed from the gas inlet 18 toward the gas outlet 19, that is, from the upper side to the lower side, and a predetermined atmosphere is formed.
And the heater control part 9 is operated by the instruction | command of the calculation control apparatus 8b, the heater 4 is heated, and the raw material polysilicon M is fuse | melted in the crucible 3 (step S1 of FIG. 2).
Further, the motor control unit 10a and the lifting device control unit 11a are operated by a command from the arithmetic control device 8b, and the crucible 3 is rotated at a predetermined rotational speed at a predetermined height position.

  Further, the crystal shape detection device 14 is driven by a command from the arithmetic control device 8b, and the CCD camera 16 starts imaging a predetermined spot on the melt surface, specifically, a crystal pulling spot (step S2 in FIG. 2). The image signal captured by the CCD camera 16 is supplied to the image processing device 17.

  Next, in accordance with a command from the arithmetic control device 8b, the wire reel rotating device control unit 12 is operated, the winding mechanism 5a is operated, and the wire 5b is lowered. Then, the seed crystal P attached to the wire 5b is brought into contact with the silicon melt M, and necking for dissolving the tip portion of the seed crystal P is performed to form the narrowed portion P2 as shown in FIG. Is started (step S3 in FIG. 2).

In forming the neck portion P1, pulling up control is performed based on the shape and diameter of the neck portion P1 detected by the crystal shape detection device 14 (step S4 in FIG. 2).
Specifically, when the growing neck portion P1 is imaged by the CCD camera 16, shape recognition is performed in the image processing unit 17, and the detection result is sent to the arithmetic control device 8b. Then, in the arithmetic control device 8b, as shown in the enlarged view of FIG. 3, the wire reel rotating device control unit 12 is controlled so that a plurality of the enlarged diameter portions 21 and the reduced diameter portions 22 are alternately formed in the neck portion P1.

Here, when the plurality of enlarged diameter portions 21 and the reduced diameter portions 22 are formed in the neck portion P1, the minimum diameter d2 of each reduced diameter portion 22 is a value set within a range of 4.0 mm to 6.0 mm. Pull-up control is performed.
This is because a single crystal having a diameter of 300 mm or more has a weight of 200 kg or more. Further, in order to reliably support a single crystal of up to 400 kg, a diameter of at least 4.0 mm to 6.0 mm is required from the viewpoint of yield and productivity. This is necessary.

Further, the average fluctuation range from the maximum diameter d1 of each enlarged diameter portion 21 to the minimum diameter d2 of each reduced diameter portion 22 is controlled to be a value set within a range of 4.0 mm to 6.0 mm. This is because if the fluctuation width is larger than 2.0 mm, it is difficult to control the formation of the minimum diameter d2 in each reduced diameter portion 22.
Further, the length dimension l of the neck portion P1 is controlled to be in the range of 200 mm to 400 mm. This is because when the length dimension l is shorter than 200 mm, dislocation to the straight body easily occurs, and when it is longer than 400 mm, formation control of the minimum diameter d2 becomes difficult.

Further, during the growth of the neck portion P1, the pulling speed of the wire 5b is controlled in the range of 1.5 mm / min to 5.0 mm / min.
This is because it is difficult to form the minimum diameter d2 of the reduced diameter portion 22 when the pulling speed of the neck portion P1 is higher than 5.0 mm / min, and the diameter value is smaller (thinner) than the target value. This is because it is easy to.
On the other hand, when the pulling speed of the neck portion P1 is lower than 1.5 mm / min, the formation of the minimum diameter d2 is easy, but the growing time of the neck portion P1 becomes long and productivity is lowered.

When the neck portion P1 is grown in this way and the length becomes a value set in the range of 200 mm to 400 mm, the power supplied to the heater 4 and the pulling speed (usually, The pulling conditions are further adjusted using parameters such as a speed of several millimeters per minute), and the single crystal C to be the product portion is grown.
That is, the formation process of the crown portion C1 (step S5 in FIG. 2), the straight body process (step S6 in FIG. 5), and the tail process (step S7 in FIG. 2) are sequentially performed. It is pulled up to the upper part in the furnace body 2.

  As described above, according to the embodiment of the present invention, when forming the neck portion P1, when the plurality of the enlarged diameter portions 21 and the reduced diameter portions 22 are alternately formed, the minimum diameter d2 of each reduced diameter portion 22 is Each reduced diameter portion 22 is formed so as to have a value set within a range of 4.0 mm to 6.0 mm, and the fluctuation range from the maximum diameter d1 of each enlarged diameter portion 21 to the minimum diameter d2 of each reduced diameter portion is variable. It is controlled to be within the range of 0.5 mm to 2.0 mm. Further, the length dimension l of the neck portion P1 is formed within a range of 200 mm to 400 mm, and the pulling speed of the wire 5b is controlled within a range of 1.5 mm / min to 5.0 mm / min.

Thereby, even if the single crystal to be pulled has a large diameter of about 300 mm, for example, and has a high weight of about 250 kg, it is possible to give the neck portion P1 sufficient strength that does not break at the time of pulling, Propagation of dislocations to the product part can be prevented.
Moreover, since it is not necessary to provide a rectifying plate or the like for cooling the neck portion P1 in the furnace body 2, the cost of the apparatus can be suppressed, and control in growing the neck portion can be easily performed.

Then, the manufacturing method of the single crystal which concerns on this invention is further demonstrated based on an Example. In this example, the effect was verified by actually performing an experiment using the single crystal pulling apparatus having the configuration described in the above embodiment.
[Example 1]
In Example 1, a single crystal is pulled a plurality of times based on the method for producing a single crystal according to the present invention, and it is verified whether or not a predetermined neck portion is obtained and whether or not dislocation occurs in the straight body portion of the single crystal. did. Specifically, 250 kg of silicon raw material was charged into a 32-inch quartz glass crucible, and after producing a silicon melt, a single crystal having a diameter of 300 mm was pulled. The minimum diameter of each reduced diameter portion of the neck portion was controlled to be 4.5 mm.

The conditions of the neck part length are 5, 10, 20, 30, 40, 50, and 60 cm, and the condition of the average fluctuation width from the maximum diameter of the expanded part to the minimum diameter of the reduced part is 0.2, 0.00. Experiments were conducted with combinations of 5, 1.0, 2.0, 3.0, 4.0, and 5.0 mm.
In this experiment, the minimum diameter of the neck portion obtained was obtained from the image information captured by the CCD camera and the result of directly measuring the neck portion with a caliper.

The results of this experiment are shown in FIG. In FIG. 4, the vertical axis represents the average fluctuation width (mm) of the neck portion diameter, and the horizontal axis represents the length (cm) of the neck portion.
In FIG. 4, ◯ indicates a case where a desired neck portion is formed and no dislocation having a length of 50 cm or more is obtained in a single crystal straight body portion, and Δ indicates a minimum diameter of the reduced diameter portion is less than 4.5 mm. The case where the part occurred, ▲ is the case where the minimum diameter of the reduced diameter part is less than 4.5 mm, and × is the desired neck part, but there is no dislocation in the straight body part of the single crystal The case of less than 50 cm is shown.

  As a result, the range of the neck part diameter in which the neck part was successfully grown was 4.5 mm to 5.7 mm in diameter. Also, as shown in FIG. 4, the optimum region for the neck length and the neck diameter fluctuation range that can stably obtain a dislocation-free single crystal is that the neck length is 200 mm to 400 mm, and the neck diameter fluctuation The result that the width was in the range of 0.5 mm to 2.0 mm was obtained.

  From the experimental results of the above examples, according to the present invention, it is possible to give the neck portion sufficient strength that does not break during pulling, and it is possible to prevent the propagation of dislocations to the product portion. I confirmed.

  The present invention relates to a method for pulling a single crystal by the Czochralski method and is suitably used in the semiconductor manufacturing industry and the like.

FIG. 1 is a block diagram showing the overall configuration of a single crystal pulling apparatus in which a single crystal pulling method according to the present invention is implemented. FIG. 2 is a flow showing the steps of the single crystal pulling method according to the present invention. FIG. 3 is an enlarged view of a neck portion formed by the pulling method of the present invention. FIG. 4 is a graph showing the results of Example 1. FIG. 5 is a diagram for explaining a pulling method using the conventional CZ method. FIG. 6 is a diagram for explaining formation of a neck portion in a pulling method using a conventional CZ method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Single crystal pulling apparatus 2 Furnace body 2a Main chamber 2b Pull chamber 3 Crucible 4 Heater 5 Pulling mechanism 6 Radiation shield 8 Computer 8a Storage device 8b Arithmetic storage device 14 Crystal shape detection device 15 Camera port 16 CCD camera 17 Image processing device C Single Crystal M Raw material polysilicon, silicon melt P seed crystal P1 neck

Claims (1)

In the method for pulling a single crystal, the seed crystal is brought into contact with the silicon melt in the crucible, the neck portion is grown, and the silicon single crystal having a diameter of 300 mm or more and a weight of 200 kg or more and 400 kg is pulled by the Czochralski method.
In the neck portion, a plurality of enlarged diameter portions that enlarge the diameter of the neck portion and a reduced diameter portion that reduces the diameter of the neck portion are alternately formed,
When forming the plurality of enlarged diameter portions and the reduced diameter portion in the neck portion,
Each reduced diameter part is formed so that the minimum diameter in each reduced diameter part becomes a value set within a range of 4.0 mm to 6.0 mm, and the minimum diameter of each reduced diameter part is determined from the maximum diameter of each enlarged diameter part. Until the fluctuation range of the diameter difference is within the range of 0.5 mm to 2.0 mm,
And the length dimension of the said neck part shall be in the range of 200 mm-400 mm, and the raising speed of the said neck part to be grown is controlled in the range of 1.5 mm / min-5.0 mm / min. A method of pulling a single crystal characterized by

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