JP2007008770A - Single crystal pulling apparatus and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single crystal pulling apparatus, with which a high weight dislocation-free single crystal can be grown by a simple technique similar to the conventional technique and the falling of the single crystal into a crucible can be avoided even when breakage of a neck part occurs due to the load of a high weight single crystal, earthquake or the like, and a method for controlling the same. <P>SOLUTION: The single crystal pulling apparatus is equipped with: a pulling means 5 for pulling the single crystal C; a single crystal supporting means 7 in which an adsorption part 7i for adsorbing the upper end C1 of the single crystal C being pulled by the pulling means 5 is provided ascendably/descendably along the pulling path of the single crystal C; a temperature detecting means 22 for detecting the temperature at the upper end part of the single crystal C being pulled by the pulling means 5; and a control means 22b for controlling the operation of the single crystal supporting means 7. The single crystal supporting means 7 has the adsorption part 7i for adsorbing the upper end C1 of the single crystal C, a suction port 7k formed in the adsorption part 7i, a negative pressure generating means 16 for generating a negative pressure for the suction port 7k, and a pad 7j of thermosoftening glass, formed at the periphery of the suction port 7k in the adsorption part 7i. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a single crystal pulling apparatus that pulls a single crystal by the Czochralski method (hereinafter referred to as “CZ method”) and a control method thereof.

  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. 6, in the pulling method using the conventional CZ method, first, raw silicon is loaded into a quartz glass crucible 51 and heated by a heater 52 to obtain a silicon melt M. Thereafter, the seed crystal P attached to the pulling wire 50 is brought into contact with the silicon melt M to pull up the silicon crystal C.

In general, prior to the start of pulling, after the temperature of the silicon melt M is stabilized, as shown in FIG. 7, 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 a thermal shock generated by bringing the seed crystal P into contact with the silicon melt M. The neck portion P1 is formed by this necking. The neck portion P1 is generally required to have a diameter of 3 to 4 mm and a length of 30 to 40 mm or more.
In addition, the processes after the start of pulling are excluding the crown process that expands the crystal to the straight body diameter after necking is completed, the straight body process that grows the single crystal that will be the product, and the single crystal diameter after the straight body process. A tailing process for reducing the size is performed.

By the way, single crystals manufactured by the CZ method have so far been 8 inches in diameter and about 100 kg in weight. Recently, however, a further increase in diameter has been demanded, and with a 12-inch crystal, a single crystal reaching 300 kg has been manufactured.
Here, FIG. 8 is a graph showing the relationship between the time elapsed from the start of necking to the extraction of the crystal and the weight of the crystal to be grown when a single crystal of nearly 300 kg is produced. As shown in this graph, the time from the tail process start to the crystal extraction after the straight body process takes a long time to occupy about half of the total required time.

That is, after starting the tail process, a heavy single crystal must be supported by the neck for a long time. For this reason, when a single crystal having a diameter larger than 12 inches is manufactured in the future, there is a possibility that the single crystal cannot be supported only by the neck portion after the tail process.
Even in the case of a 12-inch crystal, when a large shake such as an earthquake occurs, an external force is applied to the neck portion due to the shake to the weight of the single crystal. There was a risk that the neck would break during the growth of the. As a result, there was a problem that the single crystal fell on the crucible, the crucible and the device were destroyed, and it was very dangerous.

To deal with such a problem, for example, in Patent Document 1 (Japanese Patent Publication No. 7-103000), as shown in FIG. 9, a constricted portion 53 is formed in a part of the single crystal C, and the constricted portion 53 is formed. A pulling device 200 that supports the load of the single crystal C by hooking with a plurality of claws 54 and further fixing the plurality of claws 54 with a ring 55 is disclosed.
Japanese Patent Publication No. 7-103000

  However, in Patent Document 1, the diameter of the constricted portion 53 formed in the single crystal C is formed smaller than the diameter of the grown single crystal. For this reason, the part around the constricted part cannot be used as a product, and there is a problem that the production efficiency is lowered. Moreover, the raw material silicon | silicone for forming the constriction part 53 is needed, and there also existed a subject that cost increased. Furthermore, when the plurality of claws 54 are hooked on the constricted portion 53, the crystal may be shaken in the crucible unless all the claws 54 hold the constricted portion 53 at the same time. In this case, the crystal is dislocated. Thus, there is a problem that a desired dislocation-free crystal cannot be grown.

  The present invention has been made under the circumstances as described above, and it is possible to grow a high-weight dislocation-free single crystal by a simple method similar to the conventional method, which is caused by a load due to the high weight of the single crystal, an earthquake, or the like. An object of the present invention is to provide a single crystal pulling apparatus and a control method therefor that can prevent the single crystal from falling into the crucible even when the neck portion is broken.

  In order to solve the above problems, a single crystal pulling apparatus according to the present invention includes a pulling means for pulling up the single crystal in a single crystal pulling apparatus that pulls a single crystal from a crucible by the Czochralski method. An adsorption part that adsorbs the upper end of the single crystal is provided at the lower end, and the adsorption part is provided so as to be movable up and down along the pulling path of the single crystal, and the upper end temperature of the single crystal is detected. Temperature detecting means for controlling the operation of the single crystal support means, and the single crystal support means includes a suction portion, a suction port formed in the suction portion, and a suction port. A negative pressure generating means for generating pressure, and a heat-softening glass pad formed around the suction port, and the control means detects the temperature detected by the temperature detecting means at a first temperature. Then, formed in the adsorption part The pad is brought into contact with the upper end of the single crystal, and when the temperature detected by the temperature detecting means reaches the second temperature, the negative pressure generating means is driven to suck the upper end of the single crystal through the suction port. Has characteristics.

In order to solve the above-described problems, a method for controlling a single crystal pulling apparatus according to the present invention includes a pulling means for pulling a single crystal from a crucible by the Czochralski method, and an adsorption for adsorbing the upper end of the single crystal. A single crystal support means provided at the lower end, and the adsorption part is provided so as to be movable up and down along the pulling passage of the single crystal; temperature detection means for detecting the upper end temperature of the single crystal; and the single crystal Control means for controlling the operation of the support means, and the single crystal support means includes the suction portion, a suction port formed in the suction portion, and a negative pressure for generating a negative pressure in the suction port. A control method of a single crystal pulling apparatus having a pressure generating means and a thermosoftening glass pad formed around the suction port, wherein the control means has a first temperature detected by the temperature detecting means. When the temperature reaches The step of bringing the formed pad into contact with the upper end of the single crystal, and when the temperature detected by the temperature detecting means reaches a second temperature, the negative pressure generating means is driven and the upper end of the single crystal is moved by the suction port. And a step of sucking.
Preferably, after the step of driving the negative pressure generating means and sucking the upper end portion of the single crystal by the suction port, the step of pulling the single crystal by the single crystal supporting means and the pulling means is executed.

By pulling while supporting the single crystal by the single crystal support means in this way, even if it is a heavy single crystal or even if the neck portion breaks due to shaking such as an earthquake, the single crystal is not dropped. Can be pulled up.
In addition, since the heat softening glass is used as a pad in the adsorption part of the single crystal support means for the single crystal, the adsorption part and the upper end part of the single crystal can be brought into close contact with each other even in a high temperature furnace body. It can be sucked and adsorbed. At that time, the soft state of the thermosoftening glass in the single crystal supporting means is judged by detecting the temperature of the upper end portion of the single crystal in contact therewith, so that the heat softening glass suitable for suction is surely in the soft state. Can be aspirated.

  According to the present invention, a high-weight dislocation-free single crystal can be grown by a simple method similar to the conventional one, and even if the neck portion breaks due to a load or an earthquake due to a high weight of the single crystal, it enters the crucible. It is possible to obtain a single crystal pulling apparatus and its control method capable of avoiding the falling of the single crystal.

Embodiments of a single crystal pulling apparatus and its control method according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram schematically showing the configuration of a single crystal pulling apparatus 1 according to the present invention.
The single crystal pulling apparatus 1 includes a furnace body 2 formed by superposing a pull chamber 2b on a main chamber 2a, a quartz glass crucible 3 provided in the furnace body 2, and the quartz glass crucible 3 loaded. It has a heater 4 for melting the semiconductor raw material (raw silicon) M and a pulling mechanism 5 for pulling up the single crystal C to be grown.
The pulling mechanism 5 includes 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 wire 5b.

  Further, the single crystal pulling apparatus 1 supports the single crystal C by adsorbing the crown portion C1, which is the upper end portion of the single crystal C, in the pulling process after forming the tail portion of the single crystal C. Means 7 are provided. The single crystal support means 7 has a plurality (three in the figure) of cylindrical bodies 7a to 7c having slightly different diameters, and a wire 5b is inserted through the centers of the cylindrical bodies. The cylindrical bodies 7a to 7c are slidably connected to each other, and the entire cylindrical body is configured to be slidable and extendable. Of these, the cylindrical body 7a is fixed to the upper end of the pull chamber 2b without moving up and down. For this reason, the cylindrical bodies 7b and 7c slide up and down with respect to the cylindrical body 7a.

For example, the slide expansion / contraction driving method using the cylindrical bodies 7a to 7c is performed as follows. An annular member 7e for supporting the cylindrical body 7c is provided at the lower peripheral edge of the cylindrical body 7c. One end of a plurality of wires 7f is connected to the annular member 7e at equal intervals, and the other end of the wires 7f is connected to the elevating drive unit 7d. And the raising / lowering drive part 7d drives the winding-up of the wire 7f, and the expansion-contraction operation | movement of the cylindrical bodies 7a-c according to the wire length is performed.
The operation control of the elevating drive unit 7d is performed by the elevating drive control unit 15, and the elevating drive control unit 15 is controlled by the arithmetic control device 8b of the computer 8.

Further, at the lower end of the single crystal support means 7, that is, at the lower end of the cylindrical body 7c, an adsorption portion 7i for adsorbing the crown portion C1, which is the upper end portion of the single crystal C, is formed as shown in FIG. Yes.
A suction port 7k is formed in the suction portion 7i. The suction port 7k is formed in an annular shape as shown in FIG. 3 so that the crown portion C1 can be sucked with a uniform suction force. Moreover, in the adsorption | suction part 7i, the pad 7j formed with the thermosoftening glass is each provided in the circumference | surroundings outside and the circumference | surroundings of the suction port 7k.
The overall shape of the suction portion 7i is formed in an inverted conical shape so as to correspond to the shape of the crown portion C1.

  Further, as shown in FIG. 2, the suction port 7k communicates with a suction passage 7h formed around the passage 7g of the wire 5b, and this suction passage 7h is a vacuum pump 16 (see FIG. 1) which is a negative pressure generating means. )It is connected to the. That is, when the vacuum pump 16 is driven, the suction path 7h is evacuated, and a negative pressure is generated in the suction port 7k to generate an adsorption force. The vacuum pump 16 is controlled by the arithmetic control device 8b of the computer 8.

  In addition, the single crystal pulling apparatus 1 includes a crown portion temperature detector 22 (temperature detection means) in the furnace body 2 that measures the surface temperature of the crown portion C1 of the single crystal C after the tail process. The crown temperature detector 22 is, for example, a reflective thermometer capable of measuring the temperature in a non-contact state with respect to the measurement object, and the detected temperature is notified to the arithmetic control device 8b of the computer 8. It is made like that.

  A single crystal pulling apparatus 1 shown in FIG. 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 quartz glass crucible 3, and a motor. And a motor control unit 10a for controlling the number of rotations of ten. Furthermore, a lifting device 11 for controlling the height of the quartz glass crucible 3, a lifting device control unit 11a for controlling the lifting device 11, a wire reel rotating device control unit 12 for controlling the pulling speed and the number of rotations of the grown crystal, It has. Each of these control units 9, 10 a, 11 a, 12 is connected to an arithmetic control device 8 b of the computer 8.

Next, a single crystal pulling control method in the single crystal pulling apparatus 1 configured as described above will be described based on the flow of FIG. 4 and the process diagram of FIG.
First, raw material silicon M is loaded into the quartz glass crucible 3, and the crystal growth process is started as follows based on the program stored in the storage device 8a of the computer 8 (step S1 in FIG. 4).

First, the heater control unit 9 is operated according to a command from the arithmetic and control unit 8b to heat the heater 4, and the raw material silicon M of the quartz glass crucible 3 is melted.
Further, the motor control unit 10a, the lifting device control unit 11a, and the wire reel rotation device control unit 12 are operated by the command of the arithmetic control device 8b, the quartz glass crucible 3 is rotated, and the winding mechanism 5a is operated to operate the wire. 5b is taken down. Then, the seed crystal P attached to the wire 5b is brought into contact with the silicon melt M, and necking for melting the tip of the seed crystal P is performed to form the neck portion P1.

  Thereafter, the pulling conditions are adjusted by parameters of the power supplied to the heater 4 and the single crystal pulling speed (usually a speed of several millimeters per minute) according to the command of the arithmetic and control unit 8b, and the crystal is expanded to the straight body diameter. From the crown process (forming the crown part C1 which is the upper end part of the single crystal) to the tail process forming the tail part are sequentially performed.

Next, the single crystal C is pulled up by winding the wire 5b. Note that when the single crystal C is completely pulled from the melt, the rotation of the single crystal C is stopped.
When the single crystal C is pulled up to a predetermined position, the temperature of the crown C1 is detected by the crown temperature detector 22 (see FIG. 5A). Here, if the temperature of the crown part C1 is lowered to the first temperature, for example, 700 ° C. (step S2 in FIG. 4), the arithmetic control device 8b causes the lifting and lowering drive part 15 to move the suction part 7i of the single crystal support means 7 to the upper part. Lower (step S3 in FIG. 4).

When the suction portion 7i is lowered by the step S3, the suction portion 7i comes into contact with the crown portion C1 of the single crystal C being pulled up (step S4 in FIG. 4). Here, the lowering operation of the suction portion 7i is stopped, and the suction portion 7i is controlled to rise in synchronization with the pulling operation of the single crystal C.
Further, in the contact between the suction portion 7i and the crown portion C1 in step S4, the pad 7j made of thermosoftening glass and the crown portion C1 come into contact with each other. When the temperature of the crown portion C1 is about 700 ° C., the thermosoftening glass is softened, and the softened pad 7j is in close contact with the crown portion C1. As a result, the atmosphere in the suction path 7h is blocked from the atmosphere in the chamber.

  Further, if the suction path 7h is started to be evacuated while the pad 7j is in a softened state, a vent hole is generated between the pad 7j and the crown portion C1, and there is a possibility that highly accurate evacuation cannot be performed. Therefore, the vacuuming operation is on standby until the pad 7j is solidified, and the single crystal C is continuously pulled up (step S5 in FIG. 4). Usually, the softened thermosoftening glass is solidified when the temperature is lowered to 600 ° C. For this reason, the arithmetic and control unit 8b monitors the temperature change until the temperature detected by the crown temperature detector 22 reaches the second temperature (temperature lower than the first temperature), that is, 600 ° C.

When solidification of the pad 7j is detected by temperature detection (step S6 in FIG. 4), the arithmetic and control unit 8b operates the vacuum pump 16, vacuums the suction path 7h, and sucks the crown portion C1 from the suction port 7k. (Step S7 in FIG. 4). As a result, the single crystal C is completely supported by the single crystal support means 7.
Then, as shown in FIGS. 5B to 5D, the entire length of the cylindrical bodies 7a to 7c is reduced in synchronization with the winding operation of the wire 5b by the pulling mechanism 5, and the single crystal C is taken out. (Step S8 in FIG. 5).

As described above, according to the embodiment of the present invention, by pulling up the single crystal C while supporting the single crystal C by the single crystal support means 7 after the tail step, even if it is a heavy single crystal, an earthquake or the like Even if the neck portion breaks due to shaking, the single crystal C can be pulled up without dropping.
Further, since the heat softening glass is used as the pad 7j in the adsorption portion 7i of the single crystal support means 7 for the single crystal C, the adsorption portion 7i and the tail portion C1 of the single crystal C are used even in the high temperature furnace body 2. Can be brought into close contact with each other and can be reliably sucked and adsorbed.
At that time, since the soft state of the pad 7j (thermosoft glass) is judged by detecting the temperature of the crown portion C1 in contact with the pad 7j (thermosoft glass), the pad 7j is surely sucked when the heat soft glass is suitable for suction. be able to.

  The present invention relates to a single crystal pulling apparatus that pulls 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 schematically showing the configuration of a single crystal pulling apparatus according to the present invention. FIG. 2 is a cross-sectional view schematically showing the structure of the adsorbing portion of the single crystal support means included in the single crystal pulling apparatus of FIG. FIG. 3 is a view of the adsorption portion of the single crystal supporting means included in the single crystal pulling apparatus of FIG. 1 as viewed from below. FIG. 4 is a flowchart for explaining the operation of the single crystal support means in the single crystal pulling apparatus of FIG. FIG. 5 is a process diagram for explaining the operation of the single crystal support means in the single crystal pulling apparatus of FIG. FIG. 6 is a diagram for explaining a pulling method using the conventional CZ method. FIG. 7 is a diagram for explaining formation of a neck portion in a pulling method using a conventional CZ method. FIG. 8 is a graph showing the relationship between the time elapsed from the start of necking to the extraction of the crystal and the weight of the grown crystal in the case of producing a single crystal. FIG. 9 is a view for explaining means for holding a single crystal in a conventional single crystal pulling apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Single crystal pulling apparatus 2 Furnace body 2a Main chamber 2b Pull chamber 3 Quartz glass crucible 4 Heater 5 Pulling mechanism (pulling means)
6 Radiation shield 7 Single crystal support means 7i Suction part 7j Pad 7k Suction port 8 Computer 8a Storage device 8b Arithmetic storage device (control means)
15 Support body 16 Vacuum pump (negative pressure generating means)
21 Rotation drive part 22 Crown part temperature detector (temperature detection means)
C single crystal C1 crown M raw material silicon, silicon melt P seed crystal P1 neck

Claims (3)

In a single crystal pulling apparatus that pulls a single crystal from a crucible by the Czochralski method,
Pulling means for pulling up the single crystal, and a suction unit that sucks the upper end of the single crystal is provided at the lower end, and the suction unit is provided so as to be movable up and down along the pulling path of the single crystal. And temperature detecting means for detecting the upper end temperature of the single crystal, and control means for controlling the operation of the single crystal support means,
The single crystal support means includes the suction portion, a suction port formed in the suction portion, a negative pressure generation means for generating a negative pressure in the suction port, and heat formed around the suction port. And a soft glass pad,
When the temperature detected by the temperature detecting means reaches the first temperature, the control means brings the pad formed on the adsorption portion into contact with the upper end portion of the single crystal, and the temperature detected by the temperature detecting means is the second temperature. When the temperature is reached, the single crystal pulling apparatus is characterized in that the negative pressure generating means is driven and the upper end of the single crystal is sucked by the suction port. Pulling means for pulling up the single crystal from the crucible by the Czochralski method, and a suction portion for sucking the upper end of the single crystal are provided at the lower end, and the suction portion is provided to be movable up and down along the pulling passage of the single crystal. Single crystal support means, temperature detection means for detecting the upper end temperature of the single crystal, and control means for controlling the operation of the single crystal support means, and the single crystal support means includes the adsorption unit A single crystal comprising: a suction port formed in the suction portion; a negative pressure generating means for generating a negative pressure in the suction port; and a thermosoftening glass pad formed around the suction port. A control method for a lifting device,
The control means, when the temperature detected by the temperature detection means reaches a first temperature, the step of contacting the pad formed on the adsorption portion to the upper end portion of the single crystal;
And a step of driving the negative pressure generating means and sucking the upper end portion of the single crystal through the suction port when the temperature detected by the temperature detecting means reaches a second temperature. Control method. The control means drives the negative pressure generating means to suck the upper end of the single crystal through the suction port,
The method for controlling a single crystal pulling apparatus according to claim 2, wherein the step of pulling the single crystal by the single crystal supporting means and the pulling means is executed.

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