JPH09194290A - Method for pulling up single crystal and apparatus for pulling up single crystal used for this method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for pulling up a single crystal capable of lowering the ratio of a tail part to a main body and shortening the time for molding the tail apart and an apparatus for pulling up the single crystal. SOLUTION: The single crystal 26 is pulled up to a prescribed length in the method for pulling up the single crystal by using a CZ method. The tail apart 26d of the length below the diameter of the single crystal 26 is formed and the tail part 26d is disconnected from a melt 33. This method includes a slow cooling stage for cooling the tail part 26d at a rate of 60 to 250 deg.C/hour from about the m.p. of the single crystal 26 down to about 850 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pulling a single crystal and a single crystal pulling apparatus used in the method, and more specifically to a method for pulling a single crystal for pulling a crystal such as a silicon single crystal used as a semiconductor material. And a single crystal pulling apparatus used in the method.

[0002]

2. Description of the Related Art There are various methods for growing a single crystal, one of which is the Czochralski method (hereinafter referred to as the CZ method). FIG. 5 is a sectional view schematically showing a single crystal pulling apparatus used in the conventional CZ method.
Indicates a crucible.

The crucible 31 comprises a bottomed cylindrical quartz inner layer holding container 31a and a bottomed cylindrical graphite outer layer holding container 31b fitted to the outside of the inner layer holding container 31a. The crucible 31 is supported by a support shaft 38 that rotates at a predetermined speed in the direction of the arrow in the figure. A resistance heating type heater 32 is provided outside the crucible 31.
However, the heat insulating cylinders 37 are arranged concentrically outside the heater 32, and the heater 32 is provided inside the crucible 31.
The molten liquid 33 of the crystallization raw material melted by the above is filled. A pulling shaft 34 made of a pulling rod, a wire, or the like is hung on the central axis of the crucible 31. A seed crystal 35 attached to the tip of the pulling shaft 34 via a seed chuck 34a supports a supporting shaft 3
The single crystal 36 is grown from the surface of the seed crystal 35 by contacting with the surface of the melt 33 while rotating the same in the same axis or in the opposite direction at a predetermined speed as that of 8. This process is called seeding. Next, the seed crystal 35 is gradually pulled up while being continuously rotated, and a single crystal 36 is further grown on the tip of the seed crystal 35.
The diameter of is narrowed to 2-3 mm to form a neck portion 36a having a length of 10 to 20 mm. This process is called necking. Next, the diameter of the single crystal 36 is gradually increased to form the shoulder portion 36b, and then the main body 36c having a predetermined diameter and a predetermined length is formed.

After that, in the final stage of pulling the single crystal, the pulling speed of the single crystal 36 is increased or the temperature of the melt 33 is adjusted so that high-density dislocations are not formed in the main body 36c due to a rapid temperature change. By increasing the height, the diameter of the single crystal 36 is gradually reduced to form the conical tail portion 36d. By gradually reducing the diameter of the single crystal 36, the single crystal 36 near the tail portion 36d is
The temperature is gradually lowered to prevent high density dislocations from occurring in the single crystal 36. When the formation of the tail portion 36d is completed, the single crystal 36 is separated from the melt 33, and the pulling of the single crystal 36 is completed.

[0005]

In recent years, in order to improve the efficiency of LSI manufacturing, the diameter of the single crystal 36 pulled by the above-mentioned CZ method is becoming larger and larger. In the initial stage of pulling the single crystal, it is necessary to form a neck portion 36a having a diameter of 2 to 3 mm.
Since there is a limit to the mechanical strength of
Then, the length of the main body 36c cannot be made too long. On the other hand, if the diameter of the main body 36c becomes large, it is difficult to sharply reduce the diameter. Therefore, it is necessary to increase the length of the tail portion 36d, and the formation time of the tail portion 36d also becomes long.

Therefore, comparing the volume of the main body 36c constituting the single crystal 36 with the volume of the tail portion 36d, the ratio of the volume of the tail portion 36d to the main body 36c increases as the diameter of the main body 36c increases. growing. Further, the ratio of the formation time of the tail portion 36d to the formation time of the main body 36c also becomes large. Since the tail portion 36d cannot be used for the production of wafers or the like, as the diameter of the single crystal 36 increases, the proportion of the tail portion 36d not used for product production becomes larger than the main body 36c used for product production. In addition, the ratio of the formation time of the tail portion 36d to the formation time of the main body 36c also increases, and as a result, the production efficiency of the main body 36c decreases.

The present invention has been made in view of the above problems, and a single crystal pulling method and a single crystal which can reduce the ratio of the tail portion to the main body and shorten the formation time of the tail portion. An object is to provide a crystal pulling apparatus.

[0008]

Means for Solving the Problems and Effects Thereof In order to achieve the above object, the method for pulling a single crystal according to the present invention comprises:
In a method of pulling a single crystal which is grown while pulling a single crystal from a melt of a crystal raw material in a crucible, a pulling step of pulling the single crystal to a predetermined length, and forming a tail portion having a length equal to or less than a diameter of the single crystal Tail part forming process,
A step of separating the tail portion from the melt, and a step of separating the tail portion from around the melting point of the single crystal at 850 ° C.
It is characterized by including a slow cooling step of cooling up to the vicinity at a rate of 60 to 250 ° C./hour.

According to the above single crystal pulling method, the time for forming the tail portion can be shortened as compared with the conventional method, and the proportion of the tail portion to the main body is small without generating high-density dislocations. A single crystal can be pulled. Therefore, a more inexpensive single crystal can be provided by implementing the above method.

The single crystal pulling apparatus according to the present invention is
In a single crystal pulling apparatus used when pulling a single crystal from a melt of a crystal raw material filled in a crucible, a heating unit for uniformly heating the lower end portion of the pulled single crystal, and the heating unit. It is characterized in that a heating device having a moving mechanism for moving in the vertical direction is additionally provided.

According to the above single crystal pulling apparatus, since the lower end portion of the pulled single crystal can be uniformly heated by the attached heating apparatus, the above-mentioned single crystal pulling apparatus can be used without generating high density dislocations. A tail portion having a length equal to or less than the diameter of the single crystal can be easily formed, and a single crystal having a small proportion of the tail portion with respect to the main body can be pulled up. Therefore, it is possible to provide a single crystal pulling apparatus capable of manufacturing a single crystal at a lower cost than ever before.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION First, an embodiment of a single crystal pulling apparatus used in the method for pulling a single crystal according to the present invention will be described. In the single crystal pulling apparatus according to the embodiment, a normal single crystal pulling apparatus used in the CZ method is
A heating device for uniformly heating the vicinity of the lower end of the single crystal and a heating device having a moving mechanism for vertically moving the heating part are additionally provided.

FIG. 1 is a sectional view schematically showing a single crystal pulling apparatus according to an embodiment.

Since the general structure of the single crystal pulling apparatus used for the CZ method has been described in the section of the prior art, a detailed description of that portion will be omitted here, and a guide with a moving mechanism peculiar to the embodiment will be omitted. The heating device will be described.

The induction heating device refers to a heating system utilizing the resistance loss or the hysteresis loss of the eddy current or the skin current generated in the conductive material by the electromagnetic induction of the alternating electromagnetic field. In this case, a high frequency current is passed through the high frequency coil to generate the current inside the single crystal for heating.

The induction heating apparatus with a moving mechanism 10 according to the embodiment is divided into an induction heating apparatus section 11 and a moving apparatus section 20. The induction heating device section 11 plays a role of connecting the power supply device (not shown), the wiring 14 connected to the power supply device, the wiring 14 and the coil portion 12 in the chamber 39, and the through hole 17 in the upper wall of the chamber 39. The rod-shaped coil extension portion 13 inserted into the coil, the coil portion 12 disposed around the lower end portion of the single crystal 26, and the sliding member 16 supporting the coil extension portion 13 in a vertically movable state. Etc. The coil portion 12 is formed of Mo or W so as to withstand high temperature, and the coil extension portion 13
Has a structure in which an Mo or W wire is used as a central conductor, and an insulating coating made of silicon nitride or the like is applied around the central conductor. Further, in order to maintain the inside of the chamber 39 at a reduced pressure, the insertion portion (through hole 1) of the coil extension 13 is
7) is sealed by an O-ring 15.

When the power supply device is turned on, a high-frequency current is passed through the wire 14 and the coil extension 13 to the coil portion 12 in the chamber 39, so that the lower end portion of the single crystal 26 is heated by the above-described action. Has become.

Next, the moving device section 20 will be described.
The moving device section 20 includes a motor 21, a screw rod 22, a support member 23, and a sliding member 24. A screw rod 22 is fixed to a rotary shaft of a motor 21 fixed to the outside of an upper wall of the chamber 39, and a tip end portion of the screw rod 22 is a sliding member 1.
It is rotatably supported by another sliding member 24 connected to the shaft 6. The right side portion of the support member 23 in the figure is fixed to the coil extension portion 13, a screw hole 23 a is formed in the left side portion, and the support member 23 is screwed into the screw rod 22.

Therefore, the motor 21 is operated and the screw rod 2
By rotating 2 clockwise or counterclockwise,
The support member 23 screwed to the screw rod 22 can be moved up and down, and the coil extension 13 and the coil portion 12 fixed to the support member 23 can be moved in the up-down direction according to the up-and-down movement of the support member 23. You can do it.

Although the single crystal pulling apparatus according to the above-mentioned embodiment is provided with the induction heating device 10 with the moving mechanism, the infrared lamp, the carbon heater, the electronic device having the similar moving mechanism instead of the coil portion 12 are provided. A beam, a laser or the like may be attached.

Next, a single crystal pulling method using the single crystal pulling apparatus according to the above embodiment will be described.

First, until the main body 26c of a single crystal is pulled, a method exactly the same as the conventional method of pulling a single crystal by the CZ method is adopted. This method has been described in the section of the prior art. It is omitted, and the process after the main body is pulled up will be described here.

First, the main body 26c having a predetermined length is formed (pulling step). Next, the moving device unit 20 of the induction heating device 10 with the moving mechanism is operated to turn on the coil unit 12.
Is moved downward. That is, until the main body 26c is completely pulled up, the coil portion 12 is positioned near the upper wall of the chamber 39 in order to prevent the temperature from becoming high, and when the main body 26c is completely pulled up, the motor 21 is activated. The screw rod 22 clockwise or counterclockwise to move the coil extension 13 and the coil portion 12 supported by the support member 23 downward,
2 is located near the interface of the melt 33.

Next, a power supply device (not shown) is operated to apply a high frequency current to the coil portion 12 to heat the lower end portion of the single crystal 26. Lower end (area about 3 cm from the liquid surface)
Is uniformly heated to near the temperature of the melt 33, and the single crystal 2
The pulling speed of 6 is 2 to 10 times the normal speed (1.4 to
7.0 mm / min) or by raising the temperature of the melt 33 by about 50 to 100 ° C. to form a tail portion 26 d having a length equal to or less than the diameter of the main body 26 c (tail portion forming step), The portion 26d is separated from the melt 33 (tail portion separating step). The length of the tail portion 26d depends on the pulling speed of the single crystal 26, the melt 33
It can be controlled by the method of raising the temperature.
The diameter can be shortened to about 1/16 of the diameter of 6. Regarding the control of the temperature at the lower end of the single crystal 26,
Using the single crystal 26 in which the thermocouple was embedded beforehand,
The relationship between the temperature at each position of the single crystal 26 under the same conditions and the high-frequency power flowing through the coil portion 12 is obtained in advance, and the data is used to perform this.

Thereafter, the temperature of the tail portion 26d is gradually lowered while controlling the amount of current flowing through the coil portion 12 (gradual cooling step). At this time, the problem is the tail portion 2
The cooling rate is 6d. The cooling rate of the tail portion 26d is preferably 60 to 250 ° C./hour, 150 to 200 ° C.
/ Time is more preferable. When the cooling rate is higher than 275 ° C./hour, the tail portion 26d is rapidly cooled, so that high-density dislocations easily reaching the main body 26c are likely to occur, while the cooling rate is lower than 55 ° C./hour. However, the effect of gradual cooling does not change much, and it takes too much time for cooling, resulting in poor production efficiency.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a single crystal pulling method and a single crystal pulling apparatus used in the method according to the present invention will be described below with reference to the drawings.

[Embodiment 1] Specific conditions of the method for pulling a single crystal according to Embodiment 1 and the apparatus for pulling a single crystal used in the method will be described.

Pressure in chamber 39: 10 Torr Ar gas flow rate: 50 liters / minute Inner diameter of coil part: 330 mm Height of coil part: 25 mm First, 150 kg of silicon raw material is charged into the crucible 31 and melted to have a diameter of 305 mm. The single crystal 26 was pulled until the length of the main body 26c became 60 cm, and then the pulling of the single crystal 26 was once stopped (pulling step).
Next, a high-frequency current is passed through the coil portion 12 moved around the lower end of the single crystal 26 to heat the single crystal 26, and the vicinity of the lower end of the single crystal 26 up to about 3 cm above the melt 33 is semi-melted. The temperature was raised to the state to form the tail portion 26d (tail portion forming step), and the state was maintained for about 10 minutes until the temperature near the lower end portion became stable.

Next, the single crystal 26 and the coil portion 12 are separated by 3 m.
It is raised at a speed of m / min to separate it from the melt 33 (tail part separating step), and the power supplied to the coil part 12 is controlled to cool the tail part 26d to 850 ° C. over 6 hours (slow cooling). Process). FIG. 2 is a graph showing the relationship between the elapsed time after separation from the melt 33 and the temperature of the tail portion 26d. In this way, the tail portion 26 gradually
Since the cooling of d was performed, high-density dislocations did not occur.

FIG. 3 is a front view showing the shape of the pulled single crystal 26, and the neck portion 26a is not shown.
As shown, the shoulder portion 26b has a length of 10 cm,
The length of the main body 26c is 60 cm, the tail portion 26d
Had a length of 2 cm. The time required to form each part of the single crystal 26 is about 1 hour for the neck portion 26a, about 3 hours for the shoulder portion 26b, and about 1 hour for the main body 26c.
2 hours, the tail portion 26d was about 6 hours. In addition, the volume ratio of the main body 26c that can be used as a product to the entire volume of the single crystal 26 was 92%.

[Embodiment 2] As the single crystal pulling apparatus according to Embodiment 2, the same apparatus as in Embodiment 1 was used.

First, the crucible 31 is made of silicon raw material 150
Single crystal 26 with a diameter of 12 inches
Was pulled up until the length of the main body 26c became 60 cm. The diameter of the single crystal 26 was reduced to 250 mm by semi-automatically adjusting the pulling speed while observing the shape of the lower end of the single crystal 26 from the outside of the pulling device to form the tail portion 26d. A high-frequency current is passed through the coil portion 12 moved around the tail portion 26d to heat the single crystal 26, and the temperature is raised until the vicinity of the lower end portion of the single crystal 26 up to about 3 cm above the melt 33 becomes a semi-molten state. The temperature was raised (tail portion forming step), and the state was maintained for about 10 minutes until the temperature near the lower end portion became stable.

Next, the single crystal 26 and the coil portion 12 are separated by 3 m.
It is raised at a speed of m / min to separate it from the melt 33 (tail part separating step), and the power supplied to the coil part 12 is controlled to cool it for 6 hours until the lower end of the main body 26c reaches 850 ° C. (Slow cooling process). In FIG. 2, the elapsed time after separation from the melt 33 and the main body 26
c shows the relationship with the temperature of the lower end. Also in this case, the cooling rate was sufficiently slow, so that high-density dislocations did not occur.

The pulled single crystal 26 is a shoulder
The lengths of the portion 26b and the main body 26c were the same as in the first embodiment, and the length of the tail portion 26d was 6 cm. The time required to form the neck portion 26a, the shoulder portion 26b, and the main body 26c was the same as that in the first embodiment, and it took about 8 hours to form the tail portion 26d. Further, the volume ratio of the main body 26c usable as a product to the volume of the entire single crystal 26 was 88%.

COMPARATIVE EXAMPLE 1 First, the single crystal 36 was pulled under the same conditions as in Example 1 until the single crystal 36 having the main body 36c of 60 cm in length was pulled, and then the single crystal was pulled up. The single crystal 36 was separated from the melt 33 by increasing the speed to 6 times (4.2 mm / min) that when the main body was pulled up. Since the pulling rate of the single crystal was rapidly increased, the tail portion 36d was hardly formed. The time required to form the neck portion 36a, the shoulder portion 36b, and the main body 36c is the same as that of the first embodiment, and the lower end portion of the main body 36c exhibits the cooling rate as shown in FIG. 85 in about 2 hours
Cooled to 0 ° C.

When the pulled single crystal 36 is inspected,
Due to the rapid temperature change after the single crystal 36 was separated from the melt 33, high-density dislocations were generated up to about 31 cm above the separated position. Therefore, the length of the main body that can be used as a product is 60-31 = 29cm
The volume ratio of the main body that can be used as a product to the whole single crystal was as low as 46%.

[Comparative Example 2] A single crystal was pulled by the same method as the conventional method for pulling a single crystal by the CZ method.

First, the length of the main body 36c is about 50.
The single crystal was pulled under exactly the same conditions as in Example 1 until the single crystal 36 having a size of cm was pulled. Then, while observing the shape of the lower end portion of the single crystal 36 from the outside of the single crystal pulling apparatus, the diameter of the single crystal 36 was reduced by semi-automatically adjusting the pulling speed to form the tail portion 36d. At this time, as shown in FIG. 2, the tail portion 36d
The cooling rate was set so that it was cooled from near the melting point of the single crystal to 850 ° C. in 10 hours.

FIG. 4 is a front view showing the shape of the pulled single crystal 36, and the neck portion 36a is not shown.
As shown, the length of the shoulder portion 36b is about 10c.
m, the length of the main body 36c was about 50 cm, and the length of the tail portion 36d was about 35 cm. In addition, single crystal 36
It took about 1 hour for the neck part 36a, about 3 hours for the shoulder part 36b, and the main body 36
c was about 10 hours, and the tail portion 36d was about 10 hours. The volume ratio of the main body 36c usable as a product to the volume of the entire single crystal 36 was 77%.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a single crystal pulling apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the elapsed time after the step of separating the tail portion and the temperature of the lower end of the main body in each example and each comparative example.

FIG. 3 is a front view schematically showing a single crystal according to Example 1.

FIG. 4 is a front view schematically showing a single crystal according to Comparative Example 2.

FIG. 5 is a sectional view schematically showing a single crystal pulling apparatus used in a conventional CZ method.

[Explanation of symbols]

 10 induction heating device with moving mechanism 12 coil part 20 moving device part 26 single crystal 26c main body 26d tail part 31 crucible 33 melt

Claims (2)

[Claims] 1. A method of pulling a single crystal in which a single crystal is grown while being pulled from a melt of a crystal raw material in a crucible, a pulling step of pulling the single crystal to a predetermined length, A step of forming a tail portion, a step of separating the tail portion from the melt, and a step of cooling the tail portion from around the melting point of the single crystal to around 850 ° C. at a rate of 60 to 250 ° C./hour. A method for pulling a single crystal, which comprises a slow cooling step of: 2. A single crystal pulling apparatus used for pulling a single crystal from a melt of a crystal raw material filled in a crucible, a heating unit for uniformly heating the lower end portion of the pulled single crystal, And a heating device having a moving mechanism for moving the heating part in the vertical direction, the single crystal pulling device.