JP3235450B2 - Single crystal pulling silicon seed crystal and single crystal pulling method using the silicon seed crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for pulling a single crystal.
It relates the single crystal pulling method using the silicon seed crystal and the silicon seed crystal, and more particularly is used when growing a silicon single crystal used as a semiconductor material, a single crystal pulling silicon seed crystal and the silicon seed The present invention relates to a method for pulling a single crystal using a crystal.

[0002]

2. Description of the Related Art There are various methods for growing a single crystal. One of them is a pulling method represented by the Czochralski method (hereinafter referred to as CZ method). FIG. 5 shows a conventional C
It is sectional drawing which showed typically the principal part of the single crystal pulling apparatus used for the Z method, and 31 has shown the crucible in the figure.

The crucible 31 comprises a bottomed cylindrical quartz crucible 31a, and a bottomed cylindrical graphite crucible 31b fitted to the outside of the quartz crucible 31a. Reference numeral 31 is supported by a support shaft 39 which rotates at a predetermined speed in the direction of the arrow in the figure. This crucible 3
1, a heater 32 of a resistance heating type and a heater 3
2, a heat retaining cylinder 4 for promoting heat transfer to the crucible 31 is provided.
2 are concentrically arranged, and a crucible 31 is filled with a melt 33 of a single crystal raw material melted by the heater 32.

A lifting shaft 34 made of a lifting rod or a wire is suspended from the center shaft of the crucible 31.
A silicon seed crystal 35 is attached via a.

In order to pull up a single crystal 36 by the above-mentioned single crystal pulling apparatus, first, a silicon seed crystal 35 is immersed in a melt 33 and the silicon seed crystal 35 is melted.
Then, the lifting is started (hereinafter referred to as a seeding step). Thereafter, the silicon seed crystal 35 is squeezed finely at a predetermined pulling speed until the silicon seed crystal 35 has a predetermined diameter.
A neck 36a is formed (hereinafter, referred to as a necking step). Thereafter, the pulling speed is reduced to grow the single crystal 36 to a predetermined diameter to form a shoulder 36b of the single crystal 36 (hereinafter, referred to as a shoulder forming step). Thereafter, a single crystal 36 having a constant diameter and a predetermined length is grown at a constant pulling speed, and the main body (constant diameter portion) 3 of the single crystal 36 is grown.
6c (hereinafter, referred to as a body forming step).

For the purpose of performing the necking step,
This will be described below. In performing the seeding step, the silicon seed crystal bottom 35a is usually preheated to some extent, and then is immersed in the molten liquid 33.
00 ° C. or less) and the melting point of the silicon seed crystal 35 (about 14 ° C.).
10 ° C.). Therefore, at the time of contact with the melt 33, the silicon seed crystal bottom 3
Dislocations due to thermal stress are introduced into 5a. The dislocation is
Since this disturbs later single crystallization, it is necessary to grow the single crystal 36 after eliminating the dislocation. Generally, since the dislocation grows in a direction perpendicular to the growth interface of the single crystal 36, in the necking step, the shape of the growth interface is made convex downward, and the dislocation is eliminated.

Generally, in the necking step,
As the diameter of the neck 36a is reduced, the shape of the growth interface can be made more convex, and the dislocations can be eliminated more efficiently.

[0008]

In the above-mentioned conventional single crystal pulling method, the diameter is about 6 inches and the weight is 80.
12m in diameter to pull up about 36kg of single crystal
In general, a silicon seed crystal 35 of about m was used. At this time, the diameter of the neck 36a is usually about 2 to 3 mm so that the single crystal 36 can be safely pulled up and the dislocation can be efficiently eliminated. However, in response to recent demands for higher integration, lower cost, and higher productivity of semiconductor devices, larger diameter wafers have been required, and recently, for example, a diameter of about 12 inches and a weight of about 300 kg. Single crystal 36
There is a demand for the production of. In this case, the conventional neck 36a
With a diameter (usually about 3 mm), the neck 36a breaks because it cannot withstand the weight of the single crystal 36 to be pulled, and the single crystal 3
6 falls.

In growing the above-mentioned heavy single crystal 36, in order to prevent the occurrence of accidents such as dropping of the single crystal 36 and to safely raise the single crystal 36, silicon strength (about 16 kg) is required.
f / mm ² ), it is necessary to increase the diameter of the neck 36a to about 6 mm. However, the neck 36
With the aperture having such a diameter, the dislocation introduced when the silicon seed crystal 35 is immersed in the molten liquid 33 cannot be sufficiently eliminated, and there is a problem that the yield is significantly reduced.

[0010] The present invention has been made in view of the above problems, even when pulling a single crystal having a large weight, shea for pulling a single crystal that can efficiently eliminate the dislocation
The present invention provides a method for pulling a single crystal using the silicon seed crystal, which eliminates the necessity of a necking step and can be safely pulled at a low cost and with a high yield even when a single crystal is heavy. The purpose is.

[0011]

In order to achieve the above object, the silicon seed crystal (1) for pulling a single crystal according to the present invention has an oxygen concentration of 13 to 18 × 10 ¹⁷ / c.
m ³ . The present invention
The oxygen concentration at
It is unified with the value calculated using STM,
Is a value calculated by the following equation. _{[O i] = f c ×} α 03 (× 10 17 atoms / cm 3) where f _c is the conversion factor (4.81), α ₀₃ is 1106cm
^{-1 is} the infrared absorption coefficient due to interstitial oxygen.

According to the single crystal pulling silicon seed crystal (1), the oxygen concentration is 13 to 18 × 10 ¹⁷ / cm.
³ and a general oxygen concentration (11 × 10 ¹⁷ / c
m ³⁾ higher than the dislocation introduced during the deposition solution, shea
The stress level required to propagate in the upward direction of the recon seed crystal can be higher than usual. In other words, the dislocations do not propagate unless a higher than normal stress is applied.If the dislocation-introduced portion is dissolved in the melt at an appropriate speed at the time of the liquid landing, the dislocations can be propagated without propagating the dislocations. The introduced portion can be removed, and a single crystal based on a silicon seed crystal without dislocation can be pulled. Therefore, the dislocation-free ratio of the pulled single crystal can be increased.

Further, the single crystal pulling silicon according to the present invention is provided.
The silicon seed crystal (2) is characterized in that the silicon seed crystal for pulling a single crystal (1) has a silicon seed crystal diameter of 6 mm or more.

According to the single crystal pulling silicon seed crystal (2), the same effect as in the case of pulling a single crystal silicon seed crystal (1) is obtained, the silicon
Since the seed crystal diameter is 6 mm or more, for example, 300 kg
Even in the case of pulling a heavy crystal as described above, the silicon seed crystal has a silicon strength (about 16 kgf / mm).
² ) It has sufficient strength calculated from ² ), and there is no worry about accidents such as dropping of single crystal due to breakage of silicon seed crystal.
The single crystal can be safely pulled.

Further, in the method (1) for pulling a single crystal according to the present invention, the tip portion of the silicon seed crystal is immersed in a molten liquid and melted by using either of the silicon seed crystals (1) or (2). After that, the single crystal is pulled up without forming a neck.

According to the single crystal pulling method (1),
When once melting the tip of the silicon seed crystal having a dislocation introduced during Chakueki, since the propagation of the upward dislocation can stifle by oxygen, no dislocation silico
The single crystal can be pulled up based on the seed crystal. Thereby, since the dislocation hardly propagates in the single crystal to be pulled, a dislocation-free single crystal can be efficiently pulled even if the necking step is omitted. Further, since the necking step can be omitted, there is no need to support the single crystal with a thin neck, and the diameter of the silicon seed crystal becomes the smallest diameter for supporting the single crystal, and the strength of the silicon seed crystal is sufficiently considered. With this arrangement, even a single crystal having a large weight can be safely pulled up without a fear of an accident such as dropping.
Furthermore, since it is not necessary to form the neck, the silicon
The seed crystal can be reduced from about 12 mm in the past to about 6 mm, so that the raw material cost required for the silicon seed crystal can be reduced and the pulling process can be simplified.

Further, the silicon seed crystal (1) or (2) either, i.e. not introduced dislocation Shi
Since a silicon seed crystal is used, dislocations are not easily introduced into a single crystal to be pulled, and the dislocation-free ratio in the single crystal can be improved. Therefore, the yield of the pulled single crystal can be improved.

The single crystal pulling method (2) according to the present invention is the same as the single crystal pulling method (1),
The length of the silicon seed crystal to be melted is 6 mm or more.

According to the single crystal pulling method (2), since the length of the silicon seed crystal to be melted is 6 mm or more, the dislocation portion into which the dislocation is introduced by the heat shock (the portion where the dislocation exists) is almost dissolved. it can be a divorced seed crystal comprising the rest only a dislocation-free portion. Therefore, the yield of the pulled single crystal can be further improved.

On the other hand, the length of the silicon seed crystal to be dissolved is 6
If the length is shorter than mm, the dislocations may remain, which hinders later single crystallization.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the method for pulling a single crystal using the single crystal pulling silicon seed crystal and the silicon seed crystal according to the present invention will be described with reference to the drawings. Note that components having the same functions as those in the related art are denoted by the same reference numerals.

[0022] <Embodiment> FIG. 1 (a) ~ (d) are according to the embodiment, the single crystal pulling method using the single crystal pulling silicon seed crystal and the silicon seed crystal, shown in the order of steps FIG. 2 is a schematic partial side view, and FIG. 2 is a schematic cross-sectional view showing a state where a single crystal is pulled by a single crystal pulling method according to an embodiment.

[0023] First, having 6mm or more in diameter (l)
The recon seed crystal 15 is lowered to just above the melt 33,
The silicon seed crystal 15 is preheated (FIG. 1A). Siri
The oxygen concentration of the con seed crystal 15 is set to 13 to 18 × 10 ¹⁷ / c
It is set in the range of m ^3. Then, silicon seed crystal 1
5 is applied to the surface of the melt 33 (FIG. 1B). At this time, the tip portion 15a of the silicon seed crystal 15 toward the silicon <br/> seed crystal 15 upwardly, the dislocation (not shown) is introduced by thermal stress acting upon the deposition solution. After this,
The silicon seed crystal 15 is lowered at a predetermined speed, and the tip portion 15a of the silicon seed crystal 15 (a portion where dislocations are introduced).
Is immersed in the molten liquid 33 to be dissolved. The melting length (L) is 6 mm or more (FIG. 1 (c)). Thus, by Komu dissolving tip 15a of the silicon seed crystal 15, the remaining portions of the silicon seed crystal 15 may be only the dislocation-free portion. Thereafter, the conventional necking step is omitted, and the process proceeds to a shoulder forming step, in which the single crystal 16 is grown to a predetermined diameter by pulling at a predetermined pulling speed to form a shoulder 16b (FIG. 1D). ). Thereafter, the process proceeds to a body forming step, in which the main body 16c (FIG. 2) is formed.

[0024] Generally, the stress acting on the silicon seed crystal 15, between the speed of propagation of a silicon seed crystal 15 dislocations said stress introduced into, the established relationship as shown in FIG.

In FIG. 3, the vertical axis indicates the dislocation propagation speed (v), and the horizontal axis indicates the stress (σ) acting on the silicon seed crystal.

When the silicon seed crystal has a general oxygen concentration (11
X10 ¹⁷ / cm ³ ), the graph A indicates that the silicon seed crystal 15 has an oxygen concentration of 13 × 1
0 ¹⁷ / cm ³ , the graph B, the oxygen concentration is 18
When it is × 10 ¹⁷ / cm ³ , graph C is obtained.

That is, when the silicon seed crystal has a general oxygen concentration (graph A), the dislocation propagates when a stress of σ ₁ or more acts (the dislocation propagation speed becomes 0).
On the other hand, in the case of having an oxygen concentration of 13 × 10 ¹⁷ / cm ³ (graph B), the dislocation does not propagate unless a stress of σ ₂ is applied. 10 ¹⁷
In the case where the oxygen concentration is / cm ³ (graph C), the dislocations do not propagate unless a stress of σ ₃ acts. Here, the magnitude of the stress is σ ₁ <σ ₂ <σ
₃ As described above, the higher the oxygen concentration, the more the dislocation propagation can be suppressed.

According to the single crystal pulling silicon seed crystal 15 described above, the oxygen concentration is 13 to 18 × 10 ¹⁷ / cm ^3.
And the general oxygen concentration (11 × 10 ¹⁷ / cm
³ ), the dislocations introduced during the liquid landing are
The stress level required to propagate in the upper direction of the silicon seed crystal 15 can be increased as compared with a normal one. That is, unless a higher level of stress is applied to the silicon seed crystal 15, the dislocations do not propagate. Therefore, the portion where the dislocation was introduced at the time of liquid contact (the tip 1
By dissolving 5a) in the melt at a predetermined speed, the dislocation-introduced portion (tip portion 15a) can be removed without propagating the dislocation, and the silicon seed crystal without dislocation can be removed. Based on the single crystal can be pulled. Therefore, the dislocation-free ratio of the pulled single crystal can be increased.

Also, since the silicon seed crystal diameter (l) is 6 mm or more, a single crystal 1
Even when the silicon seed crystal 15 is pulled, the silicon seed crystal 15 has a sufficient strength calculated from the silicon strength (about 16 kgf / mm ² ). The single crystal 16 can be safely pulled up without worrying about an accident.

Further, according to the single crystal pulling method using the silicon seed crystal 15 described above, the single crystal 16 can be pulled based on the silicon seed crystal 15 having only the dislocation-free portion, and thus the single crystal can be pulled. No dislocation is introduced into the single crystal 16, and the necking step can be omitted. Further, since the necking step is not required, the necessity of supporting the single crystal 16 by the thin neck 36a (FIG. 5) is eliminated, and the diameter of the silicon seed crystal (l), that is, the finest detail in supporting the single crystal 16 Even if the single crystal 16 has a large diameter and a large weight, it can be safely pulled up without a fear of occurrence of an accident such as dropping. Further, since there is no need to form the neck 36a,
The silicon seed crystal 15 can be reduced from about 12 mm in the past to about 6 mm, and the raw material cost required for the silicon seed crystal can be reduced.

Further, by setting the length (L) of the silicon seed crystal 15 to be melted to be at least 6 mm, a portion into which dislocations are introduced can be almost melted, and the rest is a silicon seed crystal comprising only non-dislocation portions. 15 can be set. Silicon seed crystal 15 consisting only of the dislocation-free portion
The single crystal 16 is pulled up using
6 can be improved.

[0032]

EXAMPLES AND COMPARATIVE EXAMPLES Hereinafter, a single crystal was pulled up by a silicon seed crystal for pulling a single crystal and a single crystal pulling method using the silicon seed crystal according to the examples and comparative examples, and the DF (Dislocation Free) ratio was reduced. The result of the examination will be described. In each of the examples and comparative examples, a single crystal having a diameter of about 12 inches, a length of about 1000 mm, and a total weight of about 300 kg was pulled ten times. The DF ratio was represented by the ratio of the number of single crystals in which dislocations did not occur at all among the ten single crystals pulled under the same conditions. The occurrence of the dislocation can be determined by external observation, but in this case, it was determined by observing the sliced single crystal with an X-ray topograph.

FIGS. 4A and 4B are schematic left partial enlarged side views for explaining the single crystal pulling methods according to Examples 1 to 5 and Comparative Examples 1 to 4. Table 1 below shows the growth conditions common to the pulling of each single crystal.

[0034]

[Table 1]

<Example 1> In Example 1, the single crystal 16 was pulled in the following manner by the method shown in FIGS. 1, 2 and 4A and the conditions shown in Table 1. The oxygen concentration of the silicon seed crystal 15 is 13 × 10 ¹⁷ / cm ³ .

First, a silicon seed crystal 1 having a diameter of about 10 mm
5 is lowered to a position immediately above the melt 33 to obtain a silicon seed crystal 1.
5 is preheated, and thereafter, the silicon seed crystal 15 is caused to immerse on the surface of the melt 33 to adapt the silicon seed crystal 15 to the melt 33. Thereafter, lowering the silicon seed 15 at a speed of 0.2 mm / min, the silicon seed crystal 15
Of the silicon seed crystal 15 is melted in a range of about 20 mm from the tip 15 a of the silicon seed crystal 15. Siri at a pulling speed of the rear about 0.3mm / min
The silicon seed crystal 15 is pulled up and the temperature of the heater 32 is adjusted, so that the silicon seed crystal 15 is lowered 100
A shoulder 16b of the single crystal 16 was formed in a range of mm, and was grown until the diameter became 12 inches. Thereafter, the main body 16c having a diameter of 12 inches was grown at a pulling rate of about 0.5 mm / min until the length became about 1000 mm.

The DF ratio of the single crystal 16 produced by the method according to Example 1 was 7/10. That is, generation of dislocations was not confirmed at all in seven of the ten pulled-up layers. The number of drops of the single crystal 16 is 0/1.
0, and the single crystal 16 did not fall.

[0038] <Example 2> In Example 2, the oxygen concentration of 16 × 10 ¹⁷ / cm ³ silica
The other conditions and methods were the same as in Example 1 using the con seed crystal 15.

The DF ratio of the single crystal 16 produced by the method according to Example 2 was 8/10. That is, no occurrence of dislocation was confirmed in eight of the ten pull-ups. The number of drops of the single crystal 16 is 0/1.
0, and the single crystal 16 did not fall.

[0040] In <Embodiment 3> Embodiment 3, the oxygen concentration of 18 × 10 ¹⁷ / cm ³ silica
The other conditions and methods were the same as in Example 1 using the con seed crystal 15.

The DF ratio of the single crystal 16 produced by the method according to Example 3 was 9/10. That is, no occurrence of dislocation was confirmed in 9 of the 10 wires raised. The number of drops of the single crystal 16 is 0/1.
0, and the single crystal 16 did not fall.

<Example 4> In Example 4, a silicon seed crystal 15 having a diameter of about 6 mm was used, and the other conditions and methods were the same as in Example 1. The oxygen concentration of the silicon seed crystal 15 is 13 × 10 ¹⁷ / cm ³ as in the case of the first embodiment.

The DF ratio of the single crystal 16 manufactured by the method according to Example 4 was 7/10. That is, generation of dislocations was not confirmed at all in seven of the ten pulled-up layers. The number of drops of the single crystal 16 is 0/1.
0, and the single crystal 16 did not fall.

<Example 5> In Example 5, a silicon seed crystal 15 having a diameter of about 6 mm was used, and the other conditions and methods were the same as in Example 1. The oxygen concentration of the silicon seed crystal 15 is 16 × 10 ¹⁷ / cm ³ as in the case of the second embodiment.

The DF ratio of the single crystal 16 produced by the method according to Example 5 was 8/10. That is, no occurrence of dislocation was confirmed in eight of the ten pull-ups. The number of drops of the single crystal 16 is 0/1.
0, and the single crystal 16 did not fall.

Comparative Example 1 In Comparative Example 1, the single crystal 26 was pulled up by the method shown in FIGS. 1, 2 and 4A and the conditions shown in Table 1. The method of pulling the single crystal 26 is the same as that of the first embodiment except for the oxygen concentration of the silicon seed crystal 25, and the description is omitted here. Also, Silico
Oxygen concentration in the emissions seed crystal 25 was set to 11 × 10 ¹⁷ / cm ^3.

The DF ratio of the single crystal 26 manufactured by the method of Comparative Example 1 was 6/10. That is, no occurrence of dislocation was confirmed in 6 of the 10 wires raised. The number of drops of the single crystal 26 is 0/1.
0, and the single crystal 26 did not fall.

<Comparative Example 2> In Comparative Example 2, the neck 46a having a diameter of 10 mm was obtained by the method shown in FIGS. 4B and 5 and the conditions shown in Table 1.
Was formed, the single crystal 46 was pulled up. The oxygen concentration of the silicon seed crystal 45 was 16 × as in the case of the second embodiment.
It was set to 10 ¹⁷ / cm ³ . The single crystal 4 to be pulled
The oxygen concentration of No. 6 was 11 × 10 ¹⁷ / cm ³ as before.

First, a silicon seed crystal 45 having a diameter of 12 mm
Of the silicon seed crystal 45
Is preheated, and then the silicon seed crystal 45 is
3 and the silicon seed crystal 45 is melted into the molten liquid 33.
Make it familiar. Thereafter, the heater 3 is moved at a speed of about 4 mm / min.
The silicon seed crystal 45 is pulled up while adjusting the temperature of Step 2, and a neck 46a having a diameter of about 10 mm and a length of about 100 mm is formed.
To form Next, at a lifting speed of 0.3 mm / min
By pulling up the silicon seed crystal 45 and adjusting the temperature of the heater 32, the lower part of the neck
A shoulder 46b of the single crystal 46 was formed in the range of mm, and grown to a diameter of 12 inches. Thereafter, a main body 46c having a diameter of 12 inches was grown at a lifting speed of 0.5 mm / min until the length became 1000 mm.

The DF ratio of the single crystal 46 produced by the method of Comparative Example 2 was 0/10. That is, the occurrence of dislocations was confirmed in all the pulled single crystals 46. On the other hand, the number of drops of the single crystal 46 was 0/10, and no drop of the single crystal 46 occurred.

Comparative Example 3 In Comparative Example 3, after forming a neck 46a having a diameter of 6 mm, the single crystal 46 was pulled up. Other conditions and methods were the same as in Comparative Example 2.

The DF ratio of the single crystal 46 produced by the method of Comparative Example 3 was 1/10. That is, the occurrence of dislocations was confirmed in nine of the ten pull-ups. The number of drops of the single crystal 16 is 0/10,
Single crystal 16 did not fall.

Comparative Example 4 In Comparative Example 4, a single crystal 46 was pulled after forming a neck 46a having a diameter of about 4 mm. Other conditions and methods were the same as in Comparative Example 2.

The DF ratio of the single crystal 46 produced by the method according to Comparative Example 4 was 9/10. That is, no occurrence of dislocation was confirmed in 9 of the 10 wires raised. The falling number of the single crystal 46 is 8/1.
The single crystal 46 fell during the pulling of eight of the ten pulled out.

As is clear from the above results, Example 1
According to the silicon seed crystal 15 according to any one of (1) to (3), the oxygen concentration is 13 × 10 ¹⁷ / cm ³ , 16 × 10 ¹⁷ / cm ³ ,
18 × a 10 ¹⁷ / cm ^3, any of the higher than typical oxygen concentration ^{(11 × 10 17 / cm 3} ) when, thereby, the deposition liquid silicon seed crystal dislocations introduced during 1
The stress level required to propagate in the upper direction of No. 5 could be higher than usual. In other words, the dislocations do not propagate unless a stress higher than usual acts, so that the dislocations are propagated by dissolving the dislocation-introduced portion (tip portion 15a) into the melt at an appropriate speed during the liquid landing. Without dislocations (tip 15a)
Can be removed, and a single crystal based on a silicon seed crystal without dislocations can be pulled. Therefore, the dislocation-free ratio of the pulled single crystal could be increased.

According to the pulling method of the single crystal 16 according to the first to third embodiments, the necessity of the necking step is eliminated, so that it is not necessary to support the single crystal 16 by the thin neck 36a (FIG. 5). The diameter of the silicon seed crystal (10 mm), that is, the smallest diameter for supporting the single crystal 16, and even if the single crystal 16 has a large weight (300 kg), there is no risk of accidents such as dropping and the like. I was able to raise it.

According to the silicon seed crystal 15 according to the fourth and fifth embodiments, the oxygen concentration is 13 × 10 ¹⁷ / cm 3 respectively.
³ , 16 × 10 ¹⁷ / cm ³ , and the silicon seed crystal diameter (l) is 6 mm. Therefore, even when a heavy single crystal 16 of about 300 kg is pulled, the silicon seed crystal 15 has sufficient strength. The single crystal 16 could be safely pulled up with little concern for accidents such as dropping of the single crystal 16 due to breakage of the silicon seed crystal 15. The silicon seed crystal 15 is 6 mm instead of about 12 mm in the past.
Since the thin to the extent of about ¼ by volume, shea
The raw material cost required for the recon seed crystal 15 was able to be reduced.

According to the method of pulling single crystal 16 according to Examples 1 to 5, silicon seed crystal 15
Since the length (L) of (15A) is 6 mm or more and 20 mm, most of the dislocation-introduced portion can be melted, and the remainder is a silicon seed crystal 15 (15A) consisting only of a non-dislocation portion. Was completed. Further, the yield of the single crystal 16 (16A) could be improved by pulling up the single crystal 16 (16A) using the silicon seed crystal 15 (15A) composed of only the non-dislocation portion.

On the other hand, the silicon seed crystal 25 according to Comparative Example 1
According to this, the oxygen concentration was about 11 × 10 ¹⁷ / cm ³ , which is about the conventional level, and therefore, the product yield was lower than those of Examples 1 to 3.

According to the method for pulling single crystal 46 according to Comparative Example 2, despite the fact that the oxygen concentration of silicon seed crystal 45 was the same as that of Example 2 (16 × 10 ¹⁷ / cm ³ ). Dislocations occurred in all the pulled single crystals 46. This is considered to be due to the following reasons. First, the silicon seed crystal 45 has a high oxygen concentration (16 ×
10 ¹⁷ / cm ³ ), there is no step of melting the dislocation-introduced tip 15a, and the tip 15a
Since the neck 46a having a normal oxygen concentration (11 × 10 ¹⁷ / cm ³ ) was formed directly from the silicon seed crystal 4
5 can be prevented from propagating, but the neck 46a
The propagation of the dislocations to GaN could not be prevented. Also,
Since the diameter of the neck 46a was as large as 10 mm, the dislocation propagated was not completely removed by such a reduction in the diameter. On the other hand, since the diameter of the neck 46a is as large as 10 mm,
The single crystal 46 did not fall, and safe pulling could be performed.

According to the method for pulling single crystal 46 according to Comparative Example 3, the diameter of neck 46a was reduced to 6 mm, so that the DF ratio was slightly improved as compared with Comparative Example 2. Had a high probability of dislocation, and the product yield was low. This is presumably because even if the diameter of the neck 46a is 6 mm, the propagated dislocations cannot be completely removed with such a degree of reduction. On the other hand,
Since the diameter of the neck 46a is about 6 mm, the single crystal 46
It was possible to safely raise without falling.

Further, according to the method of pulling the single crystal 46 according to Comparative Example 4, since the diameter of the neck 46a is reduced to about 4 mm, the dislocations that have propagated can be removed, and the DF
The rate was greatly improved. However 4m
With a diameter of about m, the strength of the neck 46a was not sufficient, and the single crystal 46 fell with a high probability.

[Brief description of the drawings]

1 (a) to 1 (d) are schematic partial side views showing a single crystal pulling method according to an embodiment of the present invention in the order of steps.

FIG. 2 shows a single crystal pulling method according to the embodiment.
FIG. 4 is a schematic cross-sectional view showing a state where a single crystal is pulled up.

FIG. 3 shows stress acting on a silicon seed crystal and the silicon
4 is a graph showing a relationship between a dislocation existing in a seed crystal and a speed at which dislocations are propagated by stress.

FIGS. 4A and 4B are schematic diagrams illustrating a silicon seed crystal and a method of pulling a single crystal using the silicon seed crystal according to the example, comparative examples 1 and 2, respectively. It is a typical partial enlarged side view.

FIG. 5 is a schematic cross-sectional view showing a main part of a single crystal pulling apparatus used in the CZ method.

[Explanation of symbols]

15, 25, 35, 45 (for pulling single crystal) Silico
Emissions seed crystal 15a, 25a, 35a, 45a (the silicon seed crystal) tip 16, 26, 36 and 46 the single crystal

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C30B 1/00-35/00

Claims (4)

(57) [Claims] 1. An oxygen concentration of 13 to 18 × 10 ¹⁷ / cm ^3.
A single crystal pulling silicon, characterized in that in the range of
Emissions seed crystal. 2. A single crystal pulling silicon <br/> seed crystal according to claim 1, wherein the silicon seed crystal diameter, characterized in that the more than 6 mm. 3. The method according to claim 1 or 2, wherein
A silicon seed crystal, after elaborate dissolved by immersing the tip portion of the silicon seed crystal into the melt, a single crystal pulling method characterized by pulling a single crystal without forming a neck. 4. The length of a silicon seed crystal to be melted is 6 mm.
4. The method for pulling a single crystal according to claim 3, wherein: