JPH0699226B2 - Method and device for manufacturing single crystal ingot - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for growing a single crystal from a melt to efficiently produce a single crystal rod having a uniform longitudinal component.

[Conventional technology]

The Czochralski method is widely adopted when manufacturing a single crystal ingot such as a silicon semiconductor. In this method, the raw material is melted in the crucible, the seed crystal is brought into contact with the melt from above the liquid surface of the raw material melt, and the single crystal grown from the seed crystal is pulled up. At this time, in order to give the single crystal a desired physical property value, the content of impurities is controlled, and a special element called a dopant is added to impart electrical characteristics and the like.

To manufacture a silicon single crystal rod by the Czochralski method, polycrystalline silicon is charged in a quartz bowl-shaped crucible and heated and melted in a furnace maintained in an argon gas atmosphere,
The single crystal is pulled up from the center of the liquid surface. The main manufacturing steps are, as shown in FIG. 3 (a), furnace cleaning, polycrystal loading, melting, soaking, crystal pulling, furnace slow cooling, and crystal unloading, which are repeated in sequence. The impurities in the silicon single crystal include oxygen dissolved from the quartz in the crucible, and the dopant includes phosphorus for adjusting the electric resistance value.

[Problems to be Solved by the Invention]

When a single crystal grows from a melt, solidification proceeds selectively from a pure substance in the melt, so that the impurity concentration in the melt increases as the pulling proceeds. As the impurity concentration of the melt increases, the impurity concentration of the single crystal also increases. Further, when a dopant is added to the melt, for example, when the segregation coefficient of the dopant is less than 1 such as phosphorus with respect to the silicon melt, the dopant concentration of the single crystal increases as the crystal grows. Therefore, the single crystal ingot manufactured by the conventional Czochralski method has the impurity concentration and the dopant concentration changed in the length direction, and the manufacturing yield of the single crystal having the required physical property values is low.

When manufacturing a silicon single crystal, quartz melts into the melt from the contact surface between the melt and the quartz crucible,
As the SiO evaporates, the oxygen concentration in the melt increases.
Therefore, the oxygen concentration of the obtained single crystal rod changes in the lengthwise direction, and the production yield of the single crystal having the required physical property values is low.

The evaporated SiO solidifies and adheres to the inside of the furnace, and if the particles fall, it hinders single crystallization during crystal pulling.
Therefore, it is necessary to carefully clean the furnace, which is a heavy load. Since the steps other than crystal pulling, such as this furnace cleaning step, require time, the efficiency of single crystal production is low.

Further, in the melting step of polycrystalline silicon, when the massive polycrystalline silicon collapses into the melt, argon as an atmospheric gas is entrained, and the bubbles thereof may significantly hinder single crystallization at the time of crystal pulling.

Therefore, the present invention suppresses the fluctuation of the component composition in the melt in the vicinity of the solid-liquid interface during pulling of the single crystal, thereby suppressing the fluctuation of the component in the length direction of the single crystal ingot to obtain the single crystal having a required physical property value. It is an object of the present invention to remarkably improve the production yield of crystals and to significantly increase the ratio of the crystal pulling process to the whole production process to remarkably improve the efficiency of single crystal production.

[Means for Solving the Problems]

The single crystal rod manufacturing method of the present invention, in order to achieve the object, the liquid level of the melt contained in the vertically supported tubular crucible, the magnetic action of the electromagnetic coil wound around the tubular crucible as a center. A single crystal from the melt by swelling in a substantially parabolic shape by bringing the seed crystal into contact with the apex of the parabolic liquid surface and relatively raising the seed crystal from the liquid surface of the melt. It is characterized in that it grows in a non-contact state with the inner wall of the crucible.

Further, the apparatus for producing a single crystal rod of the present invention, a tubular crucible for containing a melt, a crucible lifting mechanism for vertically supporting the tubular crucible and moving it up and down, and a heater provided surrounding the tubular crucible,
An electromagnetic coil provided above the heater to raise the liquid surface of the melt in a substantially parabolic shape by magnetic action, and a single crystal grown from a seed crystal in contact with the apex of the liquid surface of the melt raised And a crystal elevating / lowering mechanism.

[Action]

Hereinafter, with reference to the drawings, the method of the present invention will be specifically described together with its operation.

In FIG. 1, a tubular crucible 1 in which a raw material for a single crystal rod is housed is vertically supported by a crucible lifting mechanism 8. The raw material contained in the tubular crucible 1 is heated and melted by the heater 2 to become a melt 3. An electromagnetic coil 4 is provided above the heater 2. The electromagnetic coil 4 is installed in a tubular crucible 1 up to the position indicated by the alternate long and short dash line.
Is set so that the electromagnetic coil 4 surrounds the tubular crucible 1 when being raised. As a result, the melt 3 is subjected to a magnetic action, and its liquid surface rises in a substantially parabolic shape. In such a state, the seed crystal 5 is lowered from above and brought into contact with the melt 3 at the apex of the formed parabola. Then, the single crystal 6 grows from the seed crystal 5. Then, the single crystal ingot is manufactured by raising the seed crystal 5 and raising the tubular crucible 1. At this time, melt 3
The rise of the seed crystal 5 and the tubular crucible 1 is controlled so that the solid-liquid interface between the single crystal 6 and the single crystal 6 is at a constant position. FIG. 1 shows a state in which the single crystal 6 is grown in this way.

Since the interface between the melt 3 and the single crystal 6 is parabolicly raised by the electromagnetic coil 4, the single crystal 6 is formed in the tubular crucible 1
Can be grown without contact with the inner wall of the. That is, the gap between the inner wall of the tubular crucible 1 and the single crystal 6 is adjusted by adjusting the rising shape of the melt 3 according to the current condition of the electromagnetic coil 4 and adjusting the temperature of the melt 3 near the solid-liquid interface. can do. Therefore, even when a single crystal is manufactured from a raw material that expands during solidification such as silicon, it is possible to reliably pull the crystal in a non-contact state.

According to the method of the present invention, since the flow of the melt 3 is suppressed by the magnetic force of the electromagnetic coil 4 and the amount of the melt 3 in the parabolic raised portion is small, the electromagnetic force is controlled to control the melt 3. By suppressing convection and performing appropriate stirring, mass transfer in the melt 3 during single crystal growth can be suppressed. as a result,
From the initial stage to the final stage of the growth of the single crystal 6, fluctuations in the components of the melt 3 in the vicinity of the solid-liquid interface can be suppressed, and a single crystal ingot having a uniform component in the length direction can be manufactured.

Moreover, since the single crystal 6 grows in a non-contact state with the inner wall of the tubular crucible 1, polycrystallization due to contact stress or the like can be prevented. Further, since the melt 3 is hardly exposed to the atmosphere during the crystal pulling, the evaporation amount of the components in the melt 3 is suppressed, and the contamination in the furnace is significantly suppressed. As a result, it is possible to omit the conventional furnace cleaning process. Further, since the tubular crucible 1 can be made long, the ratio of the crystal pulling step to the entire steps is increased, and the productivity is improved. Moreover, since the single crystal can be forcibly cooled, the crystal pulling time can be shortened and the production efficiency can be remarkably enhanced.

In FIG. 1, the tubular crucible 1 and / or the seed crystal 5
Can be rotated as required. Further, in order to maintain the temperature of the melt 4 in the vicinity of the solid-liquid interface during the growth of the single crystal 6 within an appropriate range and to accelerate the cooling of the single crystal 6, a shield plate 7 is provided above the electromagnetic coil 4. May be.

When the crystal pulling is completed in the example of FIG. 1, the inside of the furnace is gradually cooled, the single crystal rod and the tubular crucible 1 are taken out, a new tubular crucible is charged, raw materials are charged, and the mixture is heated and melted again. Crystal pulling is performed as in. However, a more efficient production can be performed by adopting a cartridge system in which the raw material is melted in another tubular crucible outside the system, soaked, and replaced with the tubular crucible 1 after the crystal pulling is completed. Furthermore, as shown in FIG. 2, the tubular crucible 1 is used as a communication tube, the single crystal 6 is pulled up from one end of the communication tube, and the raw material is charged from the other end, thereby achieving a more efficient continuous production. You can also do it.

Next, the configuration of the device of the present invention will be specifically described with reference to FIG.

The tubular crucible 1 containing the melt 3 as the raw material of the single crystal 6 is
The crucible lifting mechanism 8 vertically moves while being vertically supported. A heater 2 is provided so as to surround the tubular crucible 1, and an electromagnetic coil 4 is arranged above the heater 2. When the tubular crucible 1 is moved up to the position indicated by the alternate long and short dash line so that the liquid surface of the melt 3 is located inside the electromagnetic coil 4, the liquid surface of the melt 3 is almost parabolic due to the magnetic action. It's getting excited. A crystal elevating mechanism 9 is provided above the electromagnetic coil 4 so as to pull up the single crystal 6 grown from the seed crystal 5 brought into contact with the apex of the liquid surface of the melt 3 that has been raised.

In FIG. 1, reference numeral 10 denotes a graphite crucible 10 arranged on the outer side of the tubular crucible 1 in order to protect the tubular crucible 1, and 7 denotes an appropriate temperature range of the melt 3 near the solid-liquid interface during crystal pulling. The shield plate 7 is arranged on the inner peripheral side of the electromagnetic coil 4 in order to maintain the temperature of the single crystal 6 and accelerate the cooling of the single crystal 6.

A case where a single crystal ingot is manufactured using the apparatus shown in FIG. 1 will be described.

First, the tubular crucible 1 is held in the heater 2, that is, at the position indicated by the solid line, and the raw material is charged into the tubular crucible 1. The charged raw material is heated and melted by the heater 2 to become a melt 3, which is soaked.

Then, the crucible raising / lowering mechanism 8 is operated to raise the tubular crucible 1 to the position indicated by the alternate long and short dash line so that the liquid surface of the melt 3 is arranged at a predetermined position in the electromagnetic coil 4. At this liquid surface position, the melt 3 is subjected to the magnetic action of the electromagnetic coil 4, and the liquid surface rises in a substantially parabolic shape. In this state, the crystal lifting mechanism 9
When the seed crystal 5 is lowered from above and brought into contact with the melt 3 at the apex of the parabolic liquid surface, the growth of the single crystal 6 starting from the seed crystal 5 is started.

By operating the crystal elevating mechanism 9 to raise the single crystal 6 and the tubular crucible 1, the single crystal rod can be manufactured. At this time, the operations of the crystal elevating mechanism 9 and the crucible elevating mechanism 8 are controlled so that the solid-liquid interface between the melt 3 and the single crystal 6 is maintained at a constant position. FIG. 1 shows a state in which the single crystal 6 is grown in this way. When the single crystallization of the melt 3 in the tubular crucible 1 is completed, the inside of the furnace is gradually cooled and the single crystal 6 is raised by the crystal elevating mechanism 9 so that the lower end of the single crystal rod comes out of the electromagnetic coil 4. Take it out. Then, a tubular crucible is newly loaded, and the above steps are repeated.

In the apparatus of the present invention shown in FIG. 1, the tubular crucible 1 can be replaced by a cartridge system. For example, a crucible exchange table capable of mounting two tubular crucibles 1 vertically supported and reversing the positional relationship between the two is provided below the heater 2, and the tubular crucible 1 containing the melt 3 is provided. I will put it on. After the crystal pulling is completed and the tubular crucible 1 which has become empty is lowered by the crucible elevating mechanism 8 onto the exchange table to be exchanged, the tubular crucible 1 containing the melt is raised by the crucible elevating mechanism 8. The above steps are repeated.

At this time, the pulled single crystal ingot is taken out of the system, a new seed crystal is attached to the crystal elevating mechanism 9 and lowered, and the next crystal is pulled up. The single crystal rod taken out of the system is slowly cooled in the atmosphere and taken out in the air. Then, the raw material is charged into a new tubular crucible outside the system, heated and melted, and replaced with an empty tubular crucible 1 on the exchange table. In such a cartridge type apparatus, the heater 2 shown in FIG. 1 may be any one that can keep the melt 3 warm. Further, the tubular crucible 1, the graphite crucible 10, the heater 2 and the crucible elevating mechanism 8 shown in FIG.

FIG. 2 shows a case where the tubular crucible 1 formed in a U shape is used.

The tubular crucible 1 constitutes a communication pipe, and is supported by a crucible elevating mechanism 8 so that at least one of the communication pipes is vertical and can move up and down. Then, the single crystal 6 is pulled up from one end of the tubular crucible 1 on the vertically supported side,
Raw materials are charged from the other end by the raw material feeder 11.

The charged raw materials are melted in a state where the tubular crucible 1 is lowered to the position shown by the solid line in FIG. After the melted melt 3 is soaked, the crucible lifting mechanism 8 is operated to raise the tubular crucible 1 to the position shown by the alternate long and short dash line, and the single crystal 6 is grown as in the case of FIG.

While pulling the grown single crystal 6, the raw material is continuously charged from the other end of the tubular crucible 1 by the raw material charging device 11 so that the liquid surface of the melt 3 is maintained at a constant position. After a predetermined amount of single crystal rod is obtained, the lower end of the single crystal rod is placed in the electromagnetic coil 4.
The single crystal 6 is raised by the crystal elevating mechanism 9 so as to go out and taken out of the system. At this time, a large amount of single crystal ingots can be continuously produced by raising the obtained single crystal ingot and cutting the single crystal ingot by an appropriate means to take it out of the system.

With the apparatus described above, as described in connection with the method of the present invention, it is possible to efficiently produce a single crystal ingot having a uniform component in the lengthwise direction, and to obtain a large number of obtained single crystal ingots. Crystallization can be prevented.

〔Example〕

FIG. 3 shows an example of steps for manufacturing a silicon single crystal ingot by the conventional method and the method of the present invention.

FIG. 3 (a) shows a manufacturing process according to the conventional method. That is, in the conventional manufacturing process, SiO attached to the furnace is removed and a bowl-shaped crucible is loaded (furnace cleaning), and a polycrystalline silicon raw material is charged into this bowl-shaped crucible (polycrystalline loading), and raw material is supplied. Heating / melting to form a melt [melting], homogenizing the melt to a predetermined temperature [uniform heating], growing a single crystal from the melt and pulling it [crystal pulling], and pulling the single crystal rod in the furnace A single crystal rod is manufactured through a step of gradually cooling [slow cooling in a furnace] and taking out the single crystal rod from the furnace [crystal extraction]. Then, each of these steps is repeated until the required amount of single crystal ingot is obtained. In the crystal pulling step, a contact for bringing the seed crystal into contact with the liquid surface of the melt, a dash for adjusting the seed crystal, a shoulder for pulling up the seed crystal to thicken the single crystal to a predetermined diameter, and pulling while maintaining a predetermined diameter A straight body and a tail to reduce the diameter are performed in order.

FIG. 3 (b) shows a manufacturing process according to the present invention when the apparatus of FIG. 1 is used.

In this case, the tubular crucible 1 is loaded into a furnace [crucible loading], the polycrystalline silicon raw material is loaded into the tubular crucible 1 [polycrystalline loading], and the raw material is heated and melted to form a melt 3 [melting]. ], The melt 3 is homogenized to a predetermined temperature [uniform heating], the tubular crucible 1 is raised by the crucible lifting mechanism 8 and the liquid surface of the melt 3 is raised by the action of the electromagnetic coil 4 [magnetic levitation],
The single crystal 6 is grown and pulled [crystal pulling], the pulled single crystal rod is gradually cooled in the furnace [slow cooling in the furnace], and the single crystal rod is taken out [crystal take-out] step. Manufactured. And until the required amount of single crystal rod is obtained,
Each of these steps is repeated. The crystal pulling process is the third
This is the same as in the case of FIG. According to this example, the yield of silicon single crystals having a predetermined oxygen concentration is high. Also,
Since the furnace cleaning step is omitted, the manufacturing efficiency is good.

FIG. 3 (c) shows a manufacturing process according to the present invention when the tubular crucible 1 is made replaceable by a cartridge method in the apparatus shown in FIG.

In this case, another tubular crucible 1 is loaded into another furnace during the crystal pulling step [crucible loading], and the polycrystal loading step, the melting step and the soaking step are performed as in FIG. 3 (b). . When the crystal pulling step is completed, the other tubular crucible and the empty tubular crucible 1 are exchanged (crucible exchange), and the magnetic levitation step and the crystal pulling step are performed as in FIG. 3 (b). On the other hand, the pulled single crystal ingot is moved into the furnace outside the system [crystal movement], and the in-furnace slow cooling step and crystal extracting step are performed as in FIG. 3 (b). The crystal pulling process is the same as in the case of FIG. In this example, the process from the crucible loading process to the crucible exchange process and the process from the crucible exchange process to the crystal pulling process are repeated separately, so that the production efficiency is further improved as compared with the production process of FIG. 3B.

FIG. 3 (d) shows a manufacturing process according to the present invention when the apparatus shown in FIG. 2 is used.

In this case, a U-shaped tubular crucible 1 is loaded into the furnace [crucible loading], the tubular crucible 1 is charged with a raw material composed of polycrystalline silicon and a dopant [polycrystalline loading], and the production step (b) Similarly to the above, the melting step, the soaking step, and the magnetic levitation step are performed. In the straight body process during the crystal pulling process, the polycrystalline silicon and the dopant are charged from the raw material charging device 11 while adjusting the concentration so that the liquid surface of the melt 3 is kept constant, and the single crystal rod is cut while being pulled. Then, it is moved into the furnace outside the system [crystal movement], and the slow cooling step in the furnace and the crystal extracting step are performed as in the manufacturing step (b). In this example, since the single crystal ingot is continuously pulled up, the production efficiency is further improved as compared with the production step (c).

〔The invention's effect〕

As described above, according to the present invention, it is possible to manufacture a single crystal in which the fluctuation of the component in the length direction is suppressed, and the manufacturing yield of the single crystal having the required physical property values is significantly improved. During the manufacturing, since the contamination in the furnace is significantly reduced, the furnace cleaning process, which has been a large load in the conventional method, can be significantly shortened, and the manufacturing efficiency is significantly improved. Furthermore, since the raw materials can be dissolved and the components can be adjusted outside the system, the functions can be differentiated and simplified, and the operation can be mechanized and facilitated.

[Brief description of drawings]

1 and 2 are diagrams showing an example of an apparatus for carrying out the method of the present invention and showing an example of the apparatus of the present invention, FIGS.
(D) is a figure which shows the manufacturing process example of the conventional method and this invention method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiji Shinoyama 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa 1st Technical Research Laboratories, Nippon Steel Co., Ltd. (72) Hisao Kuribayashi 3434, Shimada, Hikari City, Yamaguchi Prefecture Inside Nippon Steel Co., Ltd. Hikaru Steel Works (72) Inventor Masahiko Kato 1-1-1 Edamitsu Hachimanto-ku, Kitakyushu, Kitakyushu, Fukuoka Inside Nippon Steel Co., Ltd. Equipment Technology Headquarters (56) Reference JP 63 -270379 (JP, A) JP-A-62-288195 (JP, A)

Claims (2)

[Claims] Claim: What is claimed is: 1. A liquid surface of a melt contained in a vertically supported tubular crucible, which is substantially parabolic in height due to a magnetic action of an electromagnetic coil wound around the tubular crucible as a center. A seed crystal is brought into contact with the apex of the melt, and the seed crystal is relatively elevated from the liquid surface of the melt, thereby growing a single crystal from the melt in a non-contact state with the inner wall of the tubular crucible. And a method for manufacturing a single crystal ingot. 2. A tubular crucible for accommodating a melt, a crucible elevating mechanism for vertically supporting the tubular crucible and elevating the same, a heater surrounding the tubular crucible, and a heater provided above the heater. An electromagnetic coil that raises the liquid surface of the melt in a substantially parabolic shape by magnetic action, and a crystal elevating mechanism that raises a single crystal grown from a seed crystal that is in contact with the apex of the liquid surface of the melt that is raised An apparatus for manufacturing a single crystal ingot.