JPH07330482A - Single crystal growth method and single crystal growth apparatus - Google Patents

Abstract

(57) [Summary] [Structure] In a single crystal growth method of growing a single crystal while pulling it from a melt 33 of a crystal raw material in a crucible 31,
A single crystal growth method in which a single crystal is grown in this step after the crystal 36 'grown initially as a pretreatment step is pulled up and removed once. [Effect] Most of the foreign matter floating near the surface of the melt 33 can be taken into the crystal 36 ′ grown in the pretreatment step, and when pulling up the single crystal in this step, the foreign matter remains in the melt. Is almost nonexistent. Therefore, it becomes possible to grow the single crystal without causing dislocation of the single crystal, and the yield of the single crystal production can be greatly improved.

Description

Detailed Description of the Invention

[0001]

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

[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. 4 is a cross-sectional view schematically showing a single crystal growth apparatus used in the conventional CZ method, and 31 in the figure shows 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.
It is filled with the melt 33 of the crystal raw material melted by. A pulling shaft 34 made of a pulling rod, a wire, or the like is hung on the center axis of the crucible 31. The seed crystal 35 attached to the tip of the pulling shaft 34 via a seed chuck 34a is melted 33 The melt 33 is solidified by growing the single crystal 36 by bringing the melted liquid 33 into contact with the surface and rotating the pull-up shaft 34 in the same axis as the support shaft 38 in the same direction or in the opposite direction at a predetermined speed. .

[0004]

In the above-described single crystal growth method by the CZ method, oxygen mixed in the melt 33 of the raw material crystal (Si) from the quartz inner layer holding container 31a during the single crystal pulling process is Part of it is volatile Si
It becomes O and is deposited on the upper side wall of the crucible 31 and on the inner wall of the pulling chamber 39. However, a part of the deposited SiO may fall into the crucible 31 during pulling and mix into the melt 33. Further, for some reason, foreign matter or the like that was previously present in the pull-up chamber 39 may fall into the crucible 31 and be mixed into the melt 33. Further, the foreign matter adhered to the surface of the lumped Si or the like which is the raw material crystal, or contained therein, or the foreign matter adhered to the quartz inner layer container 31a is melted as the melt 33 is formed by heating. It is taken into the liquid 33.

These foreign matters mainly composed of oxides, quartz, etc. easily float near the surface of the melt 33 during pulling of the single crystal, and when these foreign matters are taken into the growing single crystal 36, they are caused. Then, dislocation occurs.

When dislocations occur during the pulling of the single crystal 36 by the above-mentioned mechanism, not only the single crystal 36 that grows thereafter becomes dislocation-containing, but also a part of the already grown crystal becomes dislocation-forming, The dislocation-free crystal region usable as a product is reduced, and the product yield is reduced.
Therefore, preventing dislocation of the single crystal 36 is one of the most important problems in the single crystal growth method.

On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 64-65086 discloses an apparatus and method for producing a single crystal ingot capable of preventing SiO from falling onto the surface of a molten liquid. Figure 5
FIG. 3 is a cross-sectional view schematically showing a single crystal ingot manufacturing apparatus described in the publication.

This single crystal ingot manufacturing apparatus 41 has almost the same structure as the single crystal growth apparatus shown in FIG. 4, except for a cylinder 43 arranged in the upper center of the pulling chamber 42. Therefore, the cylinder 43 portion will be mainly described here.

In the apparatus 41 for manufacturing a single crystal ingot, one end of the device 41 is airtightly joined to the upper center of the pulling chamber 42 coaxially with the pulling shaft 34, one end of which is airtightly joined to the opening edge of the center of the ceiling of the pulling chamber 42, and the lower end is inside the crucible 31. A cylinder 43 is provided which is located on the surface of the melt 33 and has a collar 43a which is folded back outward from the lower end and expanded.

By arranging such a cylinder 43, the radiant heat received by the single crystal 36 from the melt 33 or the heater 32 made of graphite is effectively blocked, and the heat history during pulling of the single crystal is adjusted and controlled in a wide range. At the same time, by adjusting the gas flow, SiO is prevented from adhering to the upper part of the side wall of the crucible 31 and the upper part of the pulling chamber 42 during the growth of the single crystal 36, and the adhering SiO drops and mixes into the melt 33. It is described that such effects can be prevented.

However, since the collar 43a of the cylinder 43 does not completely cover the entire upper part of the crucible 31, it is impossible to prevent foreign matter from falling from the periphery of the crucible 31 from entering.
Further, the foreign matter contained in the bulk Si etc. of the raw material is
When suspended inside, it cannot be expected to push the suspended matter toward the side wall of the crucible 31 by the flow of gas, and the foreign substances in the melt 33 are easily taken into the single crystal 36,
There is a problem that the dislocation of the single crystal 36 cannot be completely prevented.

The present invention has been made in view of the above problems, and it is possible to prevent dislocations in a single crystal when the single crystal is pulled and grown, and to greatly improve the yield of the single crystal. An object is to provide a single crystal growth method and a single crystal growth apparatus.

[0013]

In order to achieve the above object, a single crystal growth method according to the present invention is a single crystal growth method in which a single crystal is grown while being pulled from a melt of a crystal raw material in a crucible. The process is characterized in that the initially grown crystal is temporarily pulled up and removed, and then the single crystal is grown in this process.

The single crystal growth apparatus according to the present invention is a single crystal growth apparatus for growing a single crystal while pulling it from a melt of a crystal raw material in a crucible, and pulling it from the upper part of a pulling chamber to the vicinity of the surface of the melt. A tubular body covering the outer periphery of the single crystal to be formed, a plate-like body arranged substantially parallel to the melt surface from the lower end of the tubular body toward the side wall of the crucible, and extending from the plate-like body, A cover body covering the upper side wall of the crucible (hereinafter, referred to as a gas flow rectifying device including the tubular body, the plate body, and the cover body) is provided.

First, the single crystal growth method according to the present invention will be described. In the single crystal growth method, an ordinary single crystal growth apparatus used in the CZ method can be used, but the lower main chamber and the upper pull chamber that form the pulling chamber can be completely isolated. It is necessary to have a partition plate.

With this partition plate, the pull chamber and the main chamber can be completely separated after the crystal grown in the pretreatment step is pulled out of the main chamber. Therefore, the crystal grown in the pretreatment step can be taken out and discarded while the inside of the main chamber is kept in the state of being pulled up, and the single crystal can be pulled up again.

Since the crystal grown in the pretreatment step is discarded, it is not necessary to form a crystal in a good crystal state, and the crystal can be formed in a short time. In order to crystallize most of the melt near the surface and take in foreign substances therein, the diameter of the crystal to be grown is preferably approximately the same as the inner diameter of the crucible. However, convection usually occurs in the molten liquid during pulling, and a flow toward the center occurs near the surface, so if the ratio of the diameter of the single crystal to be pulled to the inner diameter of the crucible is about 0.3 or more, it is sufficient. Foreign substances can be taken in. The length of the single crystal that is initially pulled may be about 5 to 50 mm.

Next, the single crystal growth apparatus according to the present invention will be described. In the single crystal growth apparatus according to the present invention, the above-described gas flow rectifier prevents foreign matter attached to the wall of the pulling chamber or the side wall of the crucible from falling into the crucible and mixing in the melt, and pulling up. The gas introduced from the upper part (pull chamber) of the chamber is circulated in the vicinity of the surface of the melt from the vicinity of the center of the crucible toward the peripheral direction, and a single crystal grows foreign matter floating on the surface of the melt. It works to keep it away from the interface.

For this purpose, it is necessary to keep the plate-like body constituting the gas flow rectifying device at a constant distance from the surface of the molten liquid and to let the flowing gas flow at a specific flow velocity. Since these conditions differ depending on the size of the crucible and the like, it cannot be generally stated that the flow velocity of the gas near the surface of the melt is 1 to 2
It is preferable to set it to be about 0 m / sec. Further, since the liquid level of the melt decreases as the single crystal grows, in order to keep the distance between the melt level and the plate-like body constant, the crucible is moved at a constant speed in accordance with the growth of the single crystal. It is necessary to raise with. This movement is performed by using a support shaft that supports the crucible. Further, it is preferable that the upper part of the cylindrical body is hermetically joined to the ceiling of the pulling chamber so that the gas does not leak from the upper part of the cylindrical body after flowing in from the pull chamber. The material of the gas flow rectifier is preferably non-oxide ceramics such as high-purity carbon or SiC that has heat resistance and does not contaminate the melt or the single crystal.

Further, using the single crystal growth apparatus according to the present invention,
When a single crystal is grown by the single crystal growth method according to the present invention, foreign substances are hardly present in the melt because they are incorporated into the crystal grown in the pretreatment step, and moreover, during the pulling of the single crystal. Foreign matter does not fall into the melt and mix. Therefore, the yield of single crystals is further improved.

However, in this case, the diameter of the single crystal formed in the pretreatment step needs to be smaller than the diameter of the cylindrical body, and the distance between the melt and the plate body is smaller than usual. It is necessary to take a large value or reduce the gas flow rate so that the suspended matter gathers in the center of the surface of the melt.

[0022]

According to the method for growing a single crystal having the above-mentioned structure, most of the foreign matters floating near the surface of the melt are taken into the crystal grown in the pretreatment step, and when pulling up the single crystal in this step, There are almost no foreign substances in the melt. Therefore, the single crystal is less likely to have dislocations, and the yield of the single crystal is significantly improved.

According to the single crystal growth apparatus having the above structure,
The gas flow rectifying device prevents foreign matter from falling from the outside of the crucible into the inside of the crucible. Further, the gas flowing into the apparatus from the upper part of the pulling chamber flows from the vicinity of the center of the crucible to the peripheral direction, and the foreign matter floating on the surface of the melt is an interface where a single crystal grows due to the flow of the gas. Can be kept further away. In this way, foreign matter is not mixed into the melt from the outside, and the foreign matter in the melt is kept away from the interface where the single crystal grows. The yield is greatly improved.

[0024]

Embodiments of a single crystal growth method and a single crystal growth apparatus according to the present invention will be described below with reference to the drawings.

[Embodiment 1] FIG. 1 is a sectional view schematically showing a pretreatment step in a single crystal growth method according to an embodiment.

The single crystal growth apparatus shown in FIG. 1 has a pull chamber 39 having a main chamber 39a and a pull chamber 39.
Since the partition plate 11 for isolating the partition b is provided, the partition plate 1 is almost the same as the single crystal growth apparatus (FIG. 4) described in the "Prior Art" section, and therefore the partition plate 1 is used here.
Detailed explanations other than 1 will be omitted.

The partition plate 11 is disposed in the pull chamber 39b, and is normally stored in a storage chamber (not shown). A rail (not shown) is laid in this storage chamber, and the partition plate 11 is arranged so that it can freely slide on the rail. Then, when it becomes necessary to separate the main chamber 39a and the pull chamber 39b from each other, the partition plate 11 is moved to cover the upper portion of the main chamber 39a as shown in FIG. It has become. The O-ring 12 arranged on the partition plate 11 is in close contact with the upper wall of the main chamber 29a to maintain a sealed state. Moreover, since the inside of the main chamber 39a is normally depressurized,
-If the ring 12 is in close contact, there is no problem in the hermeticity, but in order to make the hermetically sealed state more complete, the partition plate 11
The upper surface of the above may be pressed by a spring or the like.

Next, the single crystal growth method according to this embodiment will be described with reference to FIG.

First, in a crucible 31 in which an outer layer container 31b made of graphite and an inner layer container (inner diameter 400 mm) 31a made of quartz are fitted, 65 kg of polycrystal of Si as a raw material for crystal is filled, and further, as an n-type dopant. Add 0.6 g of phosphorus-silicon alloy. Next, the inside of the raising chamber 39 is set to 10T
An argon atmosphere of orr (argon flow rate: 40 liters / minute) is set, the heater 32 is energized, and the heater power is set to 80.
It is set to kw and all the raw material crystals are melted. After all the raw material crystals are melted, the heater power is lowered to 67 kw to stabilize the temperature of the melt 33. Then, as shown in FIG. 1, the lower end of the seed crystal 35 attached to the seed chuck 34a at the tip of the pulling shaft 34 is immersed in the melt 33,
The crucible 31 and the pull-up shaft 34 are rotated in opposite directions, and the rotation speed of the crucible 31 at that time is 1 rpm, the rotation speed of the pull-up shaft 34 is 10 rpm, and the pull-up speed is 0.
Crystal 36 'by setting 3mm / min and pulling
Grow fast. When the diameter of the crystal 36 'reaches 380 mm, the pulling rate is increased to 10 mm / min to separate the crystal 36'. Next, this crystal 36 'is pulled into a pull chamber 39
After being pulled up to the inside of b, the partition plate 11 is moved from the storage chamber to cover the upper part of the main chamber 39a to completely separate the main chamber 39a and the pull chamber 39b. And the crystal 3 from the pull chamber 39b
Promptly remove 6'and discard.

After that, the inside of the pull chamber 39b is made to have the same atmosphere as that of the main chamber 39a, and then the partition plate 1
1 is opened, and the lifting shaft 34 is lowered to the inside of the main chamber 39a. After pulling up the crystal 36 ', the heater power is immediately raised to 70 kw to stabilize the temperature of the melt 33 of the raw material crystal, and pulling up of the single crystal as the main step.

First, the lower end of the seed crystal 35 attached to the seed chuck 34a is dipped in the molten liquid 33 to form a crucible 31.
And the pull-up shaft 34 are rotated in opposite directions, and the rotation speed of the crucible 31 at that time is 1 rpm.
The rotation speed is set to 10 rpm and the pulling speed is set to 1 mm / min to grow a single crystal having a diameter of 6 inches. The length of the body of the single crystal to be grown is 1000 mm,
When the crystal size reaches mm, the crystal diameter is gradually reduced while pulling the crystal, and when the crystal diameter finally becomes 3 mm or less, the crystal is separated from the melt 33 and gradually cooled in the pulling chamber 39 for 1 hour. , The single crystal is taken out of the pulling chamber 39.

FIG. 2 is a graph showing the dislocation-free crystal pulling rates of the single crystals according to this example and the comparative example. here,
The dislocation-free crystal pulling rate indicates the ratio of the dislocation-free crystal number to the total number of crystal pulling. The comparative example shows a dislocation-free crystal pulling rate of a single crystal pulled by the CZ method which is usually performed using the conventional single crystal growing apparatus shown in FIG.

As shown in FIG. 2, according to the single crystal growth method according to Example 1, the dislocation-free crystal pulling rate is significantly improved to 94% as compared with the conventional method of 71%.

Although the method for growing a Si single crystal has been described in the above embodiment, this method can be applied to pulling a single crystal other than Si.

[Embodiment 2] FIG. 3 is a sectional view schematically showing a single crystal growth apparatus according to this embodiment.

The structure is the same as that of the single crystal growth apparatus shown in FIG. 4 except for the gas flow rectifying device 21, so that only the part related to the gas flow rectifying device 21 will be described here.

The gas flow rectifying device 21 includes a pulling shaft 3
4, a cylindrical body 21a having a shape covering the outer peripheral portion of the single crystal 36, and a plate-like body extending from the lower end of the cylindrical body 21a toward the peripheral direction and arranged substantially parallel to the melt surface. It is configured to include a body 21b and a cover body 21c that extends from the peripheral edge of the plate-shaped body 21b and covers the upper side wall of the crucible 31. Further, a collar 2 is provided on the upper end portion of the cylindrical body 21d.
1d is formed, and the collar 21d is formed in the main chamber 39.
It is bolted directly to the ceiling of a. The gas flow rectifying device 21 is a molded body of graphite, and the tubular body 2
The diameter of 1a is 200 mm, and the distance between the side wall of the crucible 31 and the cover body 21c is 20 mm.

Next, a method for pulling a single crystal using the above crystal growth apparatus will be described.

First, a crucible 31 in which a graphite outer layer holding container 31b is fitted with a quartz inner layer container (inner diameter 400 mm) 31a is filled with 65 kg of Si polycrystal as a crystallization raw material, and phosphorus as an n-type dopant. -Add 0.6 g of silicon alloy. Next, the inside of the raising chamber 39 is set to 10T.
An argon atmosphere of orr (argon flow rate: 40 liters / minute) is set, the heater 32 is energized, and the heater power is set to 80.
It is set to kw and all the raw material crystals are melted. After all the raw material crystals are melted, the heater power is reduced to 60 kw to stabilize the temperature of the melt 33. At this time, the distance between the surface of the melt 33 and the plate-like body 21b of the gas flow rectifier 21 is set to 15
mm, and the crucible 31 is raised along with the crystal growth so that this distance is maintained at 15 mm during the crystal growth thereafter.

Next, the lower end of the seed crystal 35 attached to the seed chuck 34a is dipped in the melt 33 to form the crucible 31.
And the pull-up shaft 34 are rotated in opposite directions, and the rotation speed of the crucible 31 at that time is 1 rpm.
The single crystal 3 having a diameter of 6 inches can be obtained by setting the rotation speed of 10 rpm and the pulling speed to 1 mm / min.
Grow 6 The length of the body of the single crystal 36 is 1000 m
m, and when reaching 1000 mm, the crystal diameter is gradually reduced while pulling up the crystal until the crystal diameter is 3 m.
When the temperature becomes m or less, the single crystal 36 is separated from the melt 33, gradually cooled in the pulling chamber 39 for 1 hour, and then the single crystal 36 is taken out of the pulling chamber 39.

FIG. 2 shows a dislocation-free crystal pulling rate of a single crystal manufactured using the single crystal growth apparatus according to the second embodiment, as in the case of the first embodiment. As shown in FIG. 2, the dislocation-free crystal pulling rate of the single crystal produced by using the single crystal growth apparatus according to Example 2 was 96%, which is higher than that obtained by using the conventional apparatus. It can be seen that the dislocation crystal pulling rate is significantly improved.

As described above, in the single crystal growth method and the single crystal growth apparatus according to the above-mentioned embodiment, the probability that the single crystal can be grown without generating dislocations in the single crystal is improved, The crystal yield can be significantly improved.

[0043]

As described above in detail, in the single crystal growth method according to the present invention, foreign matter floating near the surface of the melt can be almost taken into the crystal grown in the pretreatment step. When pulling the single crystal in the process, almost no foreign matter exists in the melt. Therefore, the single crystal can be grown without causing the single crystal to have dislocations, and the yield of the single crystal can be significantly improved.

Further, in the single crystal growth apparatus according to the present invention, by providing the gas flow rectifying device, it is possible to prevent foreign matter existing around the outside of the crucible from falling into the inside of the crucible. Further, by flowing the gas flowing into the gas flow rectifier from the upper part of the pulling chamber toward the peripheral direction from the vicinity of the center of the crucible, the foreign matter floating on the surface of the melt is converted into a single crystal. It can be moved away from the growing interface. Therefore, the single crystal can be grown without causing the single crystal to have dislocations, and the yield of the single crystal production can be significantly improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a pretreatment step in a single crystal growth method according to Example 1 of the present invention.

FIG. 2 is a graph showing dislocation-free crystal pulling rates of single crystals produced in Examples 1 and 2 and Comparative Example.

FIG. 3 is a sectional view schematically showing a single crystal growth apparatus according to a second embodiment.

FIG. 4 is a sectional view schematically showing a single crystal growth apparatus used in a conventional CZ method.

FIG. 5 is a sectional view schematically showing another example of a conventional single crystal manufacturing apparatus.

[Explanation of symbols]

 21a Cylindrical body 21b Plate-like body 21c Cover body 31 Crucible 33 Melt liquid 36 Single crystal 36 'Crystal

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shuichi Inami 4-533 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture Sumitomo Metal Industries, Ltd. (72) Masahiko Okui 4-chome, Kitahama, Chuo-ku, Osaka City, Osaka Prefecture No. 33 Sumitomo Metal Industries, Ltd.

Claims (2)

[Claims] 1. A single crystal growth method for growing a single crystal while pulling it from a melt of a crystal raw material in a crucible, after pulling out and removing the initially grown crystal as a pretreatment step, and then as a single crystal as this step. A method for growing a single crystal, which comprises growing a. 2. A single crystal growth apparatus for growing a single crystal while pulling it from a melt of a crystal raw material in a crucible, in a cylindrical shape covering the outer periphery of the single crystal to be pulled from the upper part of the pulling chamber to the vicinity of the surface of the melt. Body, a plate-like body arranged from the lower end of the cylindrical body to the side wall of the crucible substantially parallel to the melt surface, and a cover body extending from the plate-like body and covering the upper side wall of the crucible An apparatus for growing a single crystal, comprising: