JP2005281018A - Silicon single crystal pulling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon single crystal pulling method for improving the dislocation-free rate in a neck-free method for silicon single crystal purling by Czochralski method and for improving the productivity of a dislocation-free silicon single crystal without complicating the apparatus configuration. <P>SOLUTION: Growth of a single crystal is started by using a single crystal pulling apparatus by Czochralski method which is equipped with a crucible charged with a source silicon melt, a heater to surround and heat the crucible, and a radiation shield to shield the single crystal pulled from radiation heat from the heater, and by bringing a seed crystal into contact with the source silicon melt while controlling the distance between the lower end of the radiation shield and the surface of the source silicon melt surface to ≥80 mm, without carrying out a dash-neck step. Then the single crystal is pulled while controlling the distance between the lower end of the radiation shield and the surface of the source silicon melt to 15 to 50 mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a silicon single crystal pulling method for manufacturing a silicon wafer used as a semiconductor device material, and in particular, a dash neck process in pulling a silicon single crystal by the Czochralski method (CZ method). The present invention relates to a silicon single crystal pulling method for obtaining a dislocation-free crystal without going through.

In the production of a silicon single crystal by the CZ method, a single crystal ingot is grown by bringing a seed crystal made of a silicon single crystal into contact with a raw material silicon melt and then slowly pulling it up while rotating.
In the CZ method, when the seed crystal is brought into contact with the raw material silicon melt, slip dislocation occurs at a high density in the seed crystal due to thermal shock.

  Conventionally, in order to eliminate the dislocation propagating from the slip dislocation to the grown single crystal, after passing through a step of forming a narrowed portion (neck) with a diameter reduced to about 5 mm, a single diameter is obtained until a predetermined diameter is obtained. A method of pulling a dislocation-free silicon single crystal through a shoulder forming step of thickening the crystal has been adopted. Such narrowing from the seed crystal is widely known as the Dash Neck method, and has been a common method in the production of silicon single crystals by the CZ method.

  However, with such a dash-neck method, with the recent increase in the diameter of a silicon single crystal, the strength is insufficient to support a heavy single crystal ingot, and in the pulling process of the single crystal ingot, There is a possibility that a serious accident such as the squeezed portion breaks and the single crystal ingot falls will occur.

Therefore, in recent years, in order to safely grow a high-weight single crystal ingot, after bringing the seed crystal into contact with the raw material silicon melt, the diameter of the single crystal pulled up as it is without passing through the dash neck process has been increased. A no-neck method has been proposed.
In the neckless method, unlike the dash neck method, once the seed crystal is dislocated, the seed crystal must be exchanged. Therefore, it is required to eliminate the dislocation of the seed crystal.

For example, in Patent Document 1, a rectifying jig having an inverted frustoconical side surface surrounding a pulled single crystal is disposed at a predetermined distance from the raw material silicon melt surface, and after preheating the tip of the seed crystal, It describes a method for preventing the introduction of dislocations by making the solution liquid.
FIG. 6 shows an outline of a single crystal pulling apparatus provided with the rectifying jig.
The rectifying jig 12 usually has a lower end for the purpose of oxygen concentration control and growth rate control in order to efficiently discharge evaporated silicon, oxygen and the like from the raw material silicon melt 14 filled in the crucible 14. A distance x (hereinafter also referred to as a gap) between the portion and the raw material silicon melt surface is determined.

According to Patent Document 1, by increasing the gap x, radiant heat from a heater (not shown) around the crucible to the seed crystal 11 is increased, the seed crystal is preheated, and the raw silicon melt 14 and The temperature difference is reduced, the thermal shock during landing is reduced, and the introduction of dislocations is reduced.
Japanese Patent No. 3267225

  However, as described in Patent Document 1, in the state where the gap is increased, the radiant heat from the heater, the crucible, and the raw material silicon melt to the single crystal to be pulled up is not sufficiently shielded, and the single crystal to be lifted up. The cooling efficiency of crystals decreases. For this reason, in order to pull up a dislocation-free single crystal, it is necessary to reduce the pulling speed, resulting in poor single crystal production efficiency.

  Therefore, the present inventors have further studied from the viewpoint of shielding the gap and radiant heat in order to improve the dislocation-free rate in the neckless method, and as a result, the present invention has been completed.

  The present invention has been made to solve the above technical problem, and in the pulling of a silicon single crystal by the CZ method, the dislocation-free rate in the neckless method is improved, without complicating the device configuration. It is an object of the present invention to provide a silicon single crystal pulling method that improves the productivity of dislocation-free silicon single crystals.

The silicon single crystal pulling method according to the present invention comprises a crucible filled with a raw material silicon melt, a heater for heating the crucible from the surroundings, and a radiation shield for shielding radiation heat to the single crystal pulled from the heater. In the method of pulling up a silicon single crystal by the Czochralski method provided, the distance between the lower end of the radiation shield and the raw material silicon melt surface is set to 80 mm or more, the seed crystal is deposited on the raw material silicon melt, and a dash neck process is performed. After starting the growth of the single crystal without passing, the distance between the lower end of the radiation shield and the raw material silicon melt surface is set to 15 to 50 mm, and the single crystal is pulled up.
According to the above method, only by moving the radiation shield up and down, without increasing the complexity of the apparatus configuration, it is possible to improve dislocation-free in the no-neck method simply and without incurring a cost burden. .

The radiation shield has a bottom surface parallel to the raw material silicon melt surface and a side surface parallel to the inner peripheral surface of the crucible, and has a cylindrical shape whose diameter is smaller than the inner diameter of the crucible. It is preferable to use what has been used.
As described above, the radiation shield has a bottom surface parallel to the raw material silicon melt surface, and the larger the area, the greater the heat retaining effect, and efficiently using the radiant heat from the crucible and the raw material silicon melt, The seed crystal is preferable because it can be preheated to a high temperature.

As described above, according to the silicon single crystal pulling method according to the present invention, in the pulling of the silicon single crystal by the CZ method, it is possible to suppress the occurrence of slip dislocation when the seed crystal is deposited on the raw material silicon melt. .
Moreover, dislocation-free can be achieved by a neckless method without complicating the apparatus configuration using an existing single crystal pulling apparatus, and the recent 200 mm (8 inches) to 400 mm (16 inches) can be achieved. ) Or larger diameters and weights of silicon single crystal ingots can be sufficiently grown.
Therefore, it is possible to contribute to improvement of productivity, yield, and manufacturing cost of dislocation-free silicon single crystals.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.
1 and 2 schematically show the state in the pulling furnace in the silicon single crystal pulling method according to the present invention.
In the silicon single crystal pulling method according to the present invention, a crucible 3 filled with a raw material silicon melt 4, a heater (not shown) for heating the crucible 3 from the surroundings, and a single crystal 5 pulled from the heater. A single crystal pulling apparatus using the CZ method provided with a radiation shield 2 for shielding radiation heat to the surface is used.

FIG. 1 is a cross-sectional view showing a state in the pulling furnace when the seed crystal 1 is preheated.
At this time, the distance (gap) x between the lower end of the radiation shield 2 and the surface of the raw material silicon melt 4 is 80 mm or more, preferably 100 to 150 mm.
Thus, by taking a large gap x, the radiant heat from the crucible 3 and the raw silicon melt 4 to the seed crystal 1 can be increased, and the radiant heat in the vicinity of the seed crystal 1 is not lost. A heat retention effect can also be obtained.

When the gap x is 80 mm or less, the preheating temperature of the seed crystal 1 is low, and slip dislocation is likely to occur due to thermal shock when the seed crystal 1 is deposited on the raw material silicon melt 4 filled in the crucible 3. Become.
Therefore, by setting the gap x to 80 mm or more, when the seed crystal 1 is deposited, it can be sufficiently preheated using radiant heat as described above, and the occurrence of slip dislocation can be prevented.

  In addition, the shape of the seed crystal 1 is not particularly limited, but from the viewpoint of suppressing thermal shock at the time of landing, it is preferable that the initial landing area is small, and therefore, the tip is tapered with a sharp tip. preferable. In order to appropriately dissolve the seed crystal in the raw material silicon melt without causing dislocation, it is preferable that the diameter of the landing surface is about 6 to 15 mm from the viewpoint of preheating control.

FIG. 2 is a cross-sectional view showing a state in the pulling furnace when pulling up the single crystal 5.
The present invention is a method for pulling a single crystal by a neckless method. In the state shown in FIG. 1, the seed crystal 1 is deposited on the raw material silicon melt 4 without passing through the dash neck process. Then, the crystal diameter is expanded and single crystal growth is started.
In the process of growing the single crystal 5, as shown in FIG. 2, the position of the radiation shield 2 is gradually lowered to approach the surface of the raw material silicon melt 4, and the gap x is 15 to 50 mm as in the conventional case. And
Thus, by reducing the gap x, radiation heat from the crucible 3, the surrounding heater and the raw silicon melt 4 to the single crystal 5 can be shielded, and the cooling efficiency of the single crystal 5 to be pulled up is improved conventionally. Can be held as well.
Therefore, the dislocation-free single crystal can be pulled at the same pulling speed as in the prior art, and the dislocation-free single crystal can be efficiently achieved.

As shown in FIGS. 1 and 2, the radiation shield used in the present invention has a bottom surface parallel to the surface of the raw material silicon melt 4 and a side surface parallel to the inner peripheral surface of the crucible 3, and from the inner diameter of the crucible. Also, it is preferable that the diameter is a cylindrical shape, and the periphery of the bottom is rounded.
When the material and thickness of the radiation shield are the same, the heat insulation effect increases as the area of the bottom surface of the radiation shield parallel to the raw material silicon melt surface increases, and the radiation heat from the crucible and raw material silicon melt is more efficient. The seed crystal can be preheated to a high temperature.

For example, in the state shown in FIG. 3, the inner diameter R of the quartz crucible 3 ′ is 800 mm, the inner diameter r of the radiation shield 2 is 355 mm, the upper end of the quartz crucible 3 ′ and the surface of the raw material silicon melt 4 to the upper end of the quartz crucible 3 ′. The height H is 265 mm, and the seed crystal 1 has a tip angle of 18 °, a landing surface diameter of 8 mm, and a straight body diameter of 12.6 mm. When the seed crystal 1 is preheated for 5 minutes, that is, described later. When the simulation calculation of the tip temperature of the seed crystal was performed under the conditions in the pulling furnace in Example 1, the calculation result as shown in FIG. 4 was obtained.
In the graph shown in FIG. 4, the horizontal axis represents the distance (gap) x between the lower end of the radiation shield 2 and the raw material silicon melt 4 surface, and the vertical axis represents the tip temperature of the seed crystal. Note that the gap x is ∞ when the radiation shield is removed.

From the graph shown in FIG. 4, when the gap x is 80 mm or more, it is recognized that the tip temperature of the seed crystal is 1100 ° C. or more, approaches the temperature of the raw material silicon melt, and becomes higher than when the radiation shield is removed. .
From this, it is also recognized that the radiation shield is disposed at a position where the gap x is 80 mm or more, preferably 100 to 150 mm, so that the radiation heat from the raw material silicon melt and the crucible is not lost.

In addition, as shown in the examples described later, the cylindrical radiation shield whose chamfered bottom is larger in area parallel to the raw material silicon melt, so that radiant heat can be used more efficiently. Although the tip temperature of the seed crystal increases, it is not preferable to use a radiation shield having corners from the viewpoint of mechanical strength and prevention of impurities from being mixed into the raw silicon melt due to defects.
Therefore, in the present invention, it is preferable to use a cylindrical radiation shield having a chamfered bottom.

According to the present invention, in the existing single crystal pulling apparatus using the radiation shield as described above, the radiation shield can be simply and cost-effectively only by moving the radiation shield up and down without complicating the apparatus configuration. In this case, dislocation-free improvement in the neckless method can be achieved.
Furthermore, it can sufficiently cope with the recent growth of silicon single crystal ingots having a large diameter and a high weight of 200 mm (8 inches) to 400 mm (16 inches) or more.

  In addition, the manufacturing method of the silicon seed crystal and the silicon single crystal according to the present invention described above is not limited to the normal Czochralski method, and the MCZ method (Magnetic field CZ) in which a magnetic field is applied when the silicon single crystal is pulled. It is needless to say that the same applies to method), and the term Czochralski method in the present invention includes the MCZ method.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not restrict | limited by the following Example.
[Example 1]
A silicon single crystal was pulled by a single crystal pulling apparatus using a pulling furnace using a pulling furnace provided with a cylindrical radiation shield 2 having a rounded chamfered bottom as shown in FIG.
The inner diameter R of the quartz crucible 3 ′ is 800 mm, the inner diameter r of the radiation shield 2 is 355 mm, the height H from the quartz crucible 3 ′ upper end and the raw material silicon melt 4 surface to the upper end of the quartz crucible 3 ′ is 265 mm, and the lower end of the radiation shield 2 The distance (gap) x from the surface of the raw material silicon melt 4 was 150 mm.
The seed crystal 1 has a tip angle of 18 °, a landing surface diameter of 8 mm, and a straight body diameter of 12.6 mm. After preheating for 5 minutes in the pulling furnace as described above, the seed crystal 1 is melted, The melt was melted until the diameter of the contact surface with the liquid 4 reached 8 mm, and then the radiation shield was gradually lowered to a position where the gap x was 15 to 50 mm, the crystal diameter was expanded, and the pulling of the single crystal was started. .
Table 1 shows the dislocation-free (DF) rate of the seed crystal at this time.
In addition, the tip temperature of the seed crystal by preheating was 1180 degreeC.

[Example 2]
The silicon single crystal was pulled up in the same manner as in Example 1 except that the gap x when the seed crystal was deposited was 100 mm.
Table 1 shows the DF ratio of the seed crystal.
In addition, the tip temperature of the seed crystal by preheating was 1210 degreeC.

[Example 3]
A silicon single crystal was pulled up by a single crystal pulling apparatus by CZ method using a pulling furnace equipped with a cylindrical radiation shield 2 ′ as shown in FIG.
Other pulling conditions were the same as in Example 1.
Table 1 shows the DF ratio of the seed crystal.

[Comparative Example 1]
The silicon single crystal was pulled up in the same manner as in Example 1 except that the gap x when the seed crystal was deposited was 75 mm.
Table 1 shows the DF ratio of the seed crystal.

[Comparative Example 2]
The silicon single crystal was pulled up in the same manner as in Example 3 except that the gap x when the seed crystal was deposited was 75 mm.
Table 1 shows the DF ratio of the seed crystal.

[Comparative Example 3]
The gap x was fixed to 150 mm by a single crystal pulling apparatus using a pulling furnace equipped with a conventional inverted frustoconical radiation shield 12 as shown in FIG. In the same manner, the silicon single crystal was pulled up.
Table 1 shows the DF ratio of the seed crystal.
In addition, the tip temperature of the seed crystal by preheating was 1100 degreeC.

As shown in Table 1, when the cylindrical radiation shield as shown in FIG. 5 was used (Example 3), it was recognized that the preheating temperature of the seed crystal was the highest and the DF ratio was the highest. .
Further, when a cylindrical radiation shield having a rounded chamfered bottom as shown in FIG. 3 is used (Examples 1 and 2), the gap x is set to 80 mm or more, and the gap x when the single crystal is pulled is 15 to 50 mm. By doing so, the preheating temperature of the seed crystal is higher than that in the case of using a conventional inverted conical radiation shield with a fixed position (Comparative Example 3), and a DF ratio close to that of Example 3 can be obtained. Admitted.

It is the schematic sectional drawing which showed the state in the pulling-up furnace at the time of the preheating of the seed crystal in the silicon single crystal pulling method concerning this invention. It is the schematic sectional drawing which showed the state in the pulling furnace at the time of the single crystal pulling in the silicon single crystal pulling method concerning this invention. 1 is a schematic cross-sectional view showing a state in a pulling furnace of a silicon single crystal pulling apparatus according to Example 1. FIG. It is the graph which showed the relationship between the gap x in the apparatus shown in FIG. 3, and the tip temperature of a seed crystal. It is the schematic sectional drawing which showed the state in the pulling furnace of the silicon single crystal pulling-up apparatus which concerns on Example 3. FIG. It is the schematic sectional drawing which showed the state in the pulling furnace of the conventional silicon single crystal pulling apparatus.

Explanation of symbols

1, 11 Seed crystal 2, 2 ', 12 Radiation shield 3, 13 Crucible 3' Quartz crucible 4, 14 Raw material silicon melt

Claims (2)

Pulling up a silicon single crystal by the Czochralski method, comprising a crucible filled with a raw material silicon melt, a heater for heating the crucible from the surroundings, and a radiation shield for shielding radiation heat to the single crystal pulled from the heater In the method
The distance between the lower end of the radiation shield and the raw material silicon melt surface is set to 80 mm or more, the seed crystal is deposited on the raw material silicon melt, and after starting the growth of the single crystal without going through the dash neck process, the radiation A silicon single crystal pulling method, wherein the distance between the lower end of the shield and the raw material silicon melt surface is 15 to 50 mm, and the single crystal is pulled up.   The radiation shield has a bottom surface parallel to the raw material silicon melt surface and a side surface parallel to the inner peripheral surface of the crucible, and has a cylindrical shape whose diameter is smaller than the inner diameter of the crucible. 2. The method for pulling a silicon single crystal according to claim 1, wherein:

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