JP7420060B2 - Single crystal manufacturing equipment - Google Patents

Description

The present invention relates to a single crystal manufacturing apparatus.

RF (radio frequency) devices are used for communication such as mobile phones.

In RF devices using silicon single crystal wafers, if the substrate resistivity is low, the loss is large due to high conductivity. A low wafer is used.

A wafer called SOI (Silicon on Insulator) in which a thin oxide film and a thin silicon layer are formed on the surface of a silicon substrate is sometimes used, but high resistivity is also desired in this case.

Also, for power devices, relatively high resistivity wafers are desired for high voltage applications, and silicon single crystal wafers with extremely low carbon concentration are required for IGBTs and other devices to obtain good characteristics. It has become to. In other words, in the latest semiconductor devices, it is essential to reduce impurities such as heavy metals and other impurities, as well as dopants and the light element carbon.

There are two types of carbon mixed into silicon single crystals: one is brought in from raw materials, and the other is caused by reactions in the furnace during the crystal manufacturing process. We are trying to reduce the carbon concentration in each of these introduction processes. A new technology has been reported.

Regarding the import from raw materials, there is a problem that some organic matter attached to the surface of raw silicon does not vaporize at high temperatures but carbonizes, and when this is incorporated into the crystal, the carbon concentration in the crystal increases. .

In order to improve this, for example, a method of growing single crystals by the CZ method using a polycrystalline raw material stored in a polyethylene storage bag with little organic contamination including paraffinic hydrocarbons as described in Patent Document 1, Patent Document 1 An example of method 2 is to identify and quantitatively analyze the organic matter on the surface of the polycrystal, select raw materials, and then grow a single crystal using the CZ method.

On the other hand, regarding the contamination of carbon due to the crystal manufacturing process, carbon-containing gas is generated in the furnace due to the reaction between carbon members in the puller furnace and SiO evaporated from the silicon melt during crystal growth, and this carbon-containing gas There is a problem in that carbon concentration increases due to mixing of carbon into the melt.

To solve this problem, for example, there is a method disclosed in Patent Document 3, in which a cylindrical rectifying member is mounted on the graphite crucible to prevent the carbon-containing gas from flowing back toward the melt side. Other examples of growing single crystals by mounting a rectifying member include a method of mounting a quartz rectifying tube and a carbon rectifying tube above a crucible in Patent Document 4, and a method of installing a rectifying tube of quartz and carbon above a crucible in Patent Document 5. There is a method of installing only a quartz rectifier tube.

By growing a single crystal using the above-mentioned rectifying member, it is possible to increase the linear velocity of the inert gas flowing from directly above the silicon raw material melt toward the top of the quartz crucible. It is possible to prevent the carbon-containing gas generated by the reaction of SiO evaporated from the melt from flowing back to the raw material melt side, and as a result, a single crystal with a lower carbon concentration can be grown than in the case without a rectifying member. becomes possible.

However, simply increasing the linear velocity of the inert gas by installing the rectifying member described above cannot suppress the amount of carbon-containing gas produced by the reaction between the carbon member in the puller furnace and SiO evaporated from the silicon melt. Therefore, there is a limit to the carbon reduction effect that can be obtained only by installing the above-mentioned rectifying member. For this reason, the problem has been that products with lower carbon concentrations cannot be manufactured.

Japanese Patent Application Publication No. 2016-113198 Japanese Patent Application Publication No. 2016-210637 JP2012-201564A Japanese Patent Application Publication No. 2010-143776 Japanese Patent Application Publication No. 2010-184839

The present invention has been made to solve the above problems, and an object of the present invention is to provide an apparatus that can produce a single crystal with a lower carbon concentration than the conventional technology.

In order to achieve the above object, the present invention provides a single crystal manufacturing apparatus for growing a single crystal by the Czochralski method, comprising:
a main chamber having a ceiling and housing a crucible containing silicon melt;
a pulling chamber connected upwardly from the ceiling of the main chamber via a gate valve and accommodating a silicon single crystal pulled from the silicon melt;
a heat shielding member disposed to face the silicon melt contained in the crucible;
a rectifier cylinder disposed on the heat shielding member so as to surround the silicon single crystal being pulled;
a cooling cylinder that is arranged to surround the silicon single crystal being pulled, includes a portion extending from the ceiling of the main chamber toward the silicon melt, and is forcibly cooled with a cooling medium;
and a cooling auxiliary cylinder fitted inside the cooling cylinder,
The extended portion of the cooling cylinder has a bottom surface facing the silicon melt,
The single crystal manufacturing apparatus is characterized in that the auxiliary cooling cylinder has at least a first part surrounding the bottom surface of the cooling cylinder and a second part surrounding the upper end of the straightening cylinder. provide.

By using the single crystal manufacturing apparatus of the present invention, it is possible to lower the temperature of the space around the cooling auxiliary cylinder, which is caused by the reaction between the carbon member in the furnace of the single crystal manufacturing apparatus and SiO evaporated from the silicon melt. Generation of carbon-containing gas can be suppressed. In addition, by arranging a straightening tube on top of the heat shielding member and having a structure in which the second part of the cooling auxiliary tube surrounds the upper end of the straightening tube, the carbon-containing gas generated by the above reaction is transferred to the silicon melt. It is also possible to prevent it from spreading to the sides. As a result of the combination of these effects, it becomes possible to efficiently produce a single crystal with a lower carbon concentration than in the prior art.

It is preferable that the rectifier tube is made of synthetic quartz.

By using a rectifying tube made of synthetic quartz, it is possible to produce a single crystal with a lower carbon concentration.

The cooling auxiliary cylinder is made of at least one member selected from the group consisting of a graphite member, a carbon composite member, stainless steel, molybdenum, and tungsten,
The first portion of the auxiliary cooling tube has a structure that covers the bottom surface of the cooling tube, and the gap between the first portion of the auxiliary cooling tube and the bottom surface of the cooling tube is 1.0 mm or less. It is preferable that

By using such a cooling auxiliary tube, a single crystal with a lower carbon concentration can be produced more efficiently.

Preferably, the second portion of the cooling auxiliary tube includes a groove portion that covers an area of 10% or more and 35% or less of the total area of the side surface of the straightening tube.

By using such a structure, it is possible to more reliably obtain the effect that the carbon-containing gas present in the region immediately above the silicon melt is difficult to flow back to the silicon melt side.

In this case, it is more preferable that a gap between both side surfaces of the upper end of the straightening tube and the side surfaces of the groove of the second portion of the cooling auxiliary tube is 5 mm or more and 25 mm or less.

By using such a structure, it is possible to more reliably prevent carbon-containing gas from flowing back to the silicon melt side.

It is preferable that the straightening tube has an opening on a side surface, and that the height of the upper end of the opening of the straightening tube is formed at a height of 35% or less of the total height of the straightening tube.

By using such a straightening cylinder having an opening on the side surface, it is possible to obtain the effect that the carbon-containing gas is less likely to flow back toward the raw material melt side.

As described above, the single crystal production apparatus of the present invention can efficiently produce a single crystal with a lower carbon concentration than the conventional technology.

1 is a schematic cross-sectional view showing an example of a single crystal manufacturing apparatus of the present invention. FIG. 2 is an enlarged schematic cross-sectional view of the surrounding area of the cooling auxiliary cylinder in the example of the single crystal manufacturing apparatus shown in FIG. 1. FIG. FIG. 7 is an enlarged schematic cross-sectional view of the surrounding area of the cooling auxiliary cylinder in another example of the single crystal manufacturing apparatus of the present invention. 2 is a graph showing the solidification rate dependence of carbon concentration in single crystals in Example 1 and Comparative Example 1. 2 is a graph showing the solidification rate dependence of the carbon concentration in a single crystal in Example 2, Comparative Example 1, and Comparative Example 2. 3 is a graph showing the solidification rate dependence of carbon concentration in single crystals in Example 3 and Comparative Example 1. 3 is a graph showing the solidification rate dependence of carbon concentration in single crystals in Example 4 and Comparative Example 1. 1 is a schematic cross-sectional view of a single crystal manufacturing apparatus using a CZ method used in Comparative Example 1. FIG.

The present invention relates to an apparatus for producing a single crystal, such as a silicon single crystal, grown by the Czochralski method (CZ method) or the magnetic field applied CZ method (MCZ method).

As mentioned above, there has been a need to develop an apparatus that can produce single crystals with a lower carbon concentration than conventional techniques.

As a result of intensive studies on the above-mentioned problems, the present inventors arranged a rectifying tube on the heat shielding member so as to surround the silicon single crystal being pulled, and fitted an auxiliary cooling tube inside the cooling tube. The first part of the auxiliary cooling cylinder surrounds the bottom of the cooling cylinder facing the silicon melt, and the second part of the auxiliary cooling cylinder surrounds the upper end of the straightening cylinder. The generation of carbon-containing gas caused by the reaction between the carbon member and SiO evaporated from the silicon melt can be suppressed, and furthermore, the carbon-containing gas generated by the reaction can be suppressed from diffusing toward the silicon melt side. They discovered that it is possible to do this, and completed the present invention.

That is, the present invention is a single crystal manufacturing apparatus for growing a single crystal by the Czochralski method,
a main chamber having a ceiling and housing a crucible containing silicon melt;
a pulling chamber connected upwardly from the ceiling of the main chamber via a gate valve and accommodating a silicon single crystal pulled from the silicon melt;
a heat shielding member disposed to face the silicon melt contained in the crucible;
a rectifier cylinder disposed on the heat shielding member so as to surround the silicon single crystal being pulled;
a cooling cylinder arranged to surround the silicon single crystal being pulled, including a portion extending from the ceiling of the main chamber toward the silicon melt, and forcedly cooled with a cooling medium;
and a cooling auxiliary cylinder fitted inside the cooling cylinder,
The extended portion of the cooling cylinder has a bottom surface facing the silicon melt,
The single crystal manufacturing apparatus is characterized in that the auxiliary cooling cylinder has at least a first part surrounding the bottom surface of the cooling cylinder and a second part surrounding the upper end of the straightening cylinder. be.

Although Patent Documents 1 and 2 mentioned above are related to the present technology in that they focus on the carbon concentration in a single crystal, they are both technologies that focus on carbon contamination brought in from raw silicon. This is a different technology from the present invention, which focuses on carbon pollution caused by the crystal manufacturing process.

Furthermore, in Patent Documents 3 to 5, the linear velocity of the inert gas flowing from directly above the raw material melt toward the upper end of the quartz crucible is increased using a rectifying cylinder or a rectifying member to evaporate from the carbon member and silicon melt in the furnace. Although it is suggested that the carbon-containing gas generated by the reaction of SiO becomes difficult to flow back to the raw material melt side, all of Patent Documents 3 to 5 disclose that the first portion of the single crystal manufacturing apparatus of the present invention is There is no description or suggestion of an auxiliary cooling tube that includes both a second portion and a second portion.

Hereinafter, the present invention will be explained in detail with reference to the drawings, but the present invention is not limited thereto.

By using the single crystal production apparatus of the present invention having the configuration shown above, it is possible to lower the temperature of the space around the cooling auxiliary cylinder, and the carbon member and silicon melt in the furnace of the single crystal production apparatus can be reduced. Generation of carbon-containing gas caused by the reaction of evaporated SiO can be suppressed. In addition, by arranging a straightening tube on top of the heat shielding member and having a structure in which the second part of the cooling auxiliary tube surrounds the upper end of the straightening tube, the carbon-containing gas generated by the above reaction is transferred to the silicon melt. It is also possible to prevent it from spreading to the sides. As a result of the combination of these effects, it becomes possible to efficiently produce a single crystal with a lower carbon concentration than in the prior art.

Hereinafter, each member of the single crystal manufacturing apparatus of the present invention will be explained in more detail.

(1) Main Chamber The main chamber has a ceiling and stores a crucible containing silicon melt.

The crucible may be composed of, for example, a quartz crucible containing a silicon melt and a graphite crucible supporting the quartz crucible.

Including the above, the main chamber can have a structure similar to that of a typical CZ silicon single crystal manufacturing apparatus.

For example, the main chamber may also house a heater. The heater is, for example, disposed so as to surround the crucible, and can melt raw silicon contained in the crucible to form a silicon melt.

If the main chamber includes a heater, the main chamber may contain insulation surrounding the heater.

The crucible may be supported on a crucible support. A crucible shaft may be attached to the crucible support. The crucible shaft can rotate and raise/lower the crucible support and the crucible supported by the crucible support.

(2) Pulling Chamber The pulling chamber is connected upwardly from the ceiling of the main chamber via a gate valve, and accommodates the silicon single crystal pulled from the silicon melt.

Including the above, the pulling chamber can have a structure similar to that of a typical CZ silicon single crystal manufacturing apparatus.

(3) Heat Shielding Member The heat shielding member is arranged to face the silicon melt contained in the crucible. The heat shielding member can cut radiation from the surface of the silicon melt and keep the surface of the silicon melt warm. For example, the heat shielding member may have a shape in which the inner diameter gradually decreases downward and may be disposed so as to face the silicon melt.

The heat shielding member can be housed within the main chamber, for example.

Although the material of the heat shielding member is not particularly limited, the heat shielding member may be made of graphite, for example.

(4) Straightening tube The straightening tube is arranged on the heat shielding member so as to surround the silicon single crystal being pulled. The rectifier tube can surround the silicon single crystal being pulled concentrically with the heat shielding member.

Since the amount of carbon-containing gas generated by the reaction between the carbon member in the furnace and SiO vaporized from the silicon melt increases in proportion to the surface area of the graphite member in the furnace, the rectifier tube should be made of quartz or ceramic. It is preferable that the material is made of synthetic quartz, and it is particularly preferable that the material be made of synthetic quartz.

Further, it is preferable that the rectifier tube used at this time has an opening formed on its side surface.

By using such a straightening tube with an opening on the side surface, the flow velocity of the inert gas flowing from the straightening tube opening toward the outside of the straightening tube, for example, in the direction of the furnace monitoring window in the tube, which will be described later, increases. As a result, it is possible to obtain the effect that the carbon-containing gas is less likely to flow back from the inside of the cylindrical portion or the outside of the cylindrical portion to the raw material melt side.

In addition, the opening of the straightening tube is such that the height of the upper end of the opening is 35% or less of the total height of the straightening tube, and the center of the opening is located at a height of 30 mm from the lower end of the straightening tube. It is preferable to have a structure where the distance is 40 mm or less. Further, it is more preferable that the openings are formed on the side surface of the rectifying cylinder at equal intervals in the circumferential direction, for example, a structure in which openings are provided on three axes at angles of 0°, 120°, and 240°. It can be done. Furthermore, it is preferable that the opening has a length of 50 mm or less from the upper end of the opening to the lower end, and has an open area of 15% or less of the total lateral area of the rectifier tube.

By using such a straightening tube with an opening on the side, the flow velocity of the inert gas flowing from the straightening tube opening toward the outside of the straightening tube, for example, in the direction of the furnace monitoring window in the tube, which will be described later, is further increased. However, as a result, it is possible to obtain the effect that the carbon-containing gas is more difficult to flow backward from the inside of the cylinder part or the outside of the cylinder part to the raw material melt side.

(5) Cooling cylinder The cooling cylinder is arranged to surround the silicon single crystal being pulled, includes a portion extending from the ceiling of the main chamber toward the silicon melt, and is forcibly cooled with a cooling medium. . The portion extending toward the silicon melt has a bottom surface facing the silicon melt.

A cooling cylinder may extend toward the silicon melt and be located in the main chamber at the bottom of the gate valve.

The cooling medium that forcibly cools the cooling cylinder is not particularly limited.

(6) Cooling auxiliary cylinder The cooling auxiliary cylinder is fitted inside the cooling cylinder. The auxiliary cooling cylinder has at least a first part surrounding the bottom surface of the cooling cylinder and a second part surrounding the upper end of the straightening cylinder.

The cooling auxiliary cylinder is preferably made of at least one member selected from the group consisting of graphite members, carbon composite members, stainless steel, molybdenum, and tungsten. The first part of the auxiliary cooling cylinder has a structure that covers the bottom face of the cooling cylinder facing the silicon melt, and the gap between the first part of the auxiliary cooling cylinder and the bottom face of the cooling cylinder is 1.0 mm or less. Preferably.

By using an auxiliary cooling tube with such a structure, not only does the amount of radiant heat from the high temperature section received by the first part of the auxiliary cooling tube that covers the bottom of the cooling tube increase, but also the first part of the auxiliary cooling tube receives a higher temperature. By doing so, the auxiliary cooling cylinder expands thermally, making it possible to reduce the gap between the cooling cylinder and the bottom surface of the cooling cylinder, making it easier to transfer heat to the cooling cylinder. In addition, the first part of the auxiliary cooling cylinder that covers the bottom of the cooling cylinder becomes high in temperature as it receives radiant heat from the silicon melt and high-temperature parts, and the radiant heat generated by the auxiliary cooling cylinder itself to the bottom of the cooling cylinder increases. Even if there is a gap between the cooling cylinder and the bottom surface, heat can be transferred to the cooling cylinder. This allows the radiant heat from the high temperature areas around the heater and the heat shielding member to be efficiently transferred to the cooling tube, and as a result, the radiant heat from the heat shielding member to the growing crystal is reduced, increasing the crystal growth rate. At the same time, the effect of suppressing the generation of carbon-containing gas caused by the reaction between the carbon member in the furnace and SiO evaporated from the silicon melt can be more reliably obtained.

Preferably, the second portion of the cooling auxiliary tube includes a groove portion that covers an area of 10% or more and 35% or less of the total area of the side surface of the straightening tube.

By using such a structure, it is possible to more reliably obtain the effect that the carbon-containing gas present in the region immediately above the silicon melt is difficult to flow back to the silicon melt side.

In this case, it is more preferable that the gap between both side surfaces of the upper end of the straightening tube and the side surfaces of the groove of the second portion of the cooling auxiliary tube is 5 mm or more and 25 mm or less.

By using such a structure, it is possible to more reliably prevent carbon-containing gas from flowing back to the silicon melt side.

(7) Others The structure of the HZ (hot zone) other than the above can be the same as that of a general CZ silicon single crystal manufacturing apparatus.

For example, a single crystal manufacturing apparatus that performs a magnetic field application CZ method (MCZ method) can further include a magnetic field application device that applies a magnetic field to the silicon melt.

Next, a specific example of the single crystal manufacturing apparatus of the present invention will be described with reference to the drawings. Note that the description of the same components as the conventional device may be omitted as appropriate.

FIG. 1 is a schematic cross-sectional view showing an example of a single crystal manufacturing apparatus of the present invention. FIG. 2 is an enlarged schematic cross-sectional view of the vicinity of the cooling auxiliary tube in the example of the single crystal manufacturing apparatus shown in FIG.

The single crystal manufacturing apparatus 1 shown in FIGS. 1 and 2 includes a ceiling part 21 and a main chamber 2 that stores a quartz crucible 7 that contains a silicon melt 6 and a graphite crucible 8 that supports the crucible 7. A pulling chamber 3 connected to the upper part via a gate valve (not shown), a heat shielding member 12 arranged to face the silicon melt 6, and a rectifying cylinder 14 arranged on the heat shielding member 12. , has a cooling cylinder 13 including a portion 131 extending from the ceiling 21 of the main chamber 2 toward the silicon melt 6, and an auxiliary cooling cylinder 15 fitted inside the cooling cylinder 13.

The main chamber 2 includes a crucible support 16 that supports the graphite crucible 8, a crucible shaft 17 that supports the crucible support 16, a heater 9 that is arranged to surround the graphite crucible 8, and a heater 9 that is arranged to surround the heater 9. A heat insulating material 10 is further stored. The crucible shaft 17 can rotate the silicon melt 6, the quartz crucible 7, the graphite crucible 8, and the crucible support 16 around the rotation shaft 18, and can also raise and lower them.

A cylindrical portion 11 is arranged on a ceiling portion 21 of the main chamber 2 . The cylindrical portion 11 extends from the ceiling portion 21 toward the silicon melt 6, and a heat shielding member 12 is attached to the end portion.

The pulling chamber 3 accommodates the silicon single crystal 5 pulled from the silicon melt 6.

The straightening tube 14 includes an upper end portion 141 on the opposite side from the heat shielding member 12 . The rectifying tube 14 is arranged on the heat shielding member 12 so as to surround the silicon single crystal 5 being pulled. In the example shown in FIGS. 1 and 2, the rectifying cylinder 14 is arranged within the main chamber 2. In the example shown in FIGS.

Cooling tube 13 is arranged so as to surround silicon single crystal 5 that is being pulled. Further, a portion 131 of the cooling cylinder 13 extends from the ceiling portion 21 of the main chamber 2 toward the silicon melt 6. This portion 131 is located within the main chamber 2 and has a bottom surface 132 facing the silicon melt 6. The cooling cylinder 13 further includes a portion 133 that extends upward from the ceiling portion 21 of the main chamber 2 and is fitted inside the upper end portion of the main chamber 2 located directly below a gate valve (not shown). The cooling cylinder 13 is forcibly cooled by a cooling medium supplied by a cooling medium circulation mechanism (not shown).

The auxiliary cooling cylinder 15 has a first portion 151 and a second portion 152. The first portion 151 of the auxiliary cooling cylinder 15 surrounds the bottom surface 132 of the cooling cylinder 13, as shown in FIGS. 1 and 2. More specifically, the first portion 151 of the auxiliary cooling cylinder 15 surrounds a portion 131 of the cooling cylinder 13 including the bottom surface 132 from the top and bottom and from one side. The first portion 151 of the cooling auxiliary cylinder 15 includes a flange portion 153 extending in a direction substantially perpendicular to the pulling direction of the silicon single crystal 5, as shown in FIG.

On the other hand, the second portion 152 of the cooling auxiliary cylinder 15 surrounds the upper end portion 141 of the rectifying cylinder 14 within the main chamber 2, as shown in FIGS. 1 and 2. More specifically, the second portion 152 of the cooling auxiliary cylinder 15 includes the groove portion 154 shown in FIG. 2 . The groove portion 154 accommodates the upper end portion 141 of the flow straightening tube 14 and thereby covers a part of the side surface 142 of the flow straightening tube 14 . Further, the collar 153 of the first portion 151 of the auxiliary cooling tube 15 also surrounds the upper end portion 141 of the rectifying tube 14 as the bottom of the groove portion 154 that is a part of the second portion 152 .

The gap between the first portion 151 (more specifically, the collar portion 153) of the auxiliary cooling cylinder 15 and the bottom surface 132 of the cooling cylinder 13 is represented by "d" shown in FIG. 2. It is preferable that the gap d is 1.0 mm or less. Furthermore, using "a" and "b" shown in FIG. 2, the ratio of the area covered by the groove part 154 of the cooling auxiliary pipe 15 to the total area of the side surface 142 of the straightening pipe 14 can be calculated as "(a/b)". ×100". The ratio a/b is preferably 10% or more and 35% or less. The gap between the auxiliary cooling cylinder 15 and the side surface 142 of the straightening cylinder 14 in the groove 154 of the second portion 152 of the auxiliary cooling cylinder 15 is represented by "c" shown in FIG. The gap c is preferably 5 mm or more and 25 mm or less. Note that a above is an average value in the circumferential direction. On the other hand, it is preferable that the values b to d are approximately constant values over the entire circumferential direction. Therefore, it is preferable that the ratio a/b is an average value in the circumferential direction.

In the above, a case has been described in which there is no opening in the side surface 142 of the rectifying cylinder 14, but as shown in FIG. 3, for example, an opening 143 may be provided in the side surface 142 of the rectifying cylinder 14.

By using the straightening tube 14 having the opening 143 on the side surface 142 as shown in FIG. As a result, the carbon-containing gas from the inside of the cylindrical portion 11 or the outside of the cylindrical portion 11 is less likely to flow back toward the silicon melt 6 side.

The openings 143 shown in FIG. 3 are formed at equal intervals in the circumferential direction of the side surface 142 of the rectifying tube 14.

The openings 143 can be provided, for example, on three axes at angles of 0°, 120°, and 240°. Further, the opening 143 preferably has a structure in which the length from the upper end to the lower end of the opening 143 is 50 mm or less, and an area of 15% or less of the total area of the side surface 142 of the flow straightening tube 14 is opened. The ratio of the open area of the opening 143 to the total area of the side surface 142 of the rectifying tube 14 corresponds to the ratio of the opening area e to the total area f shown in FIG. 3, that is, the ratio e/f.

In addition, the opening 143 of the straightening tube 14 is located at a height of 35% or less of the total height of the straightening tube 14 at the upper end of the opening, and the center of the opening is from the lower end of the straightening tube 14. It is preferable that the structure is provided at a position with a height of 30 mm or more and 40 mm or less.

By using the straightening tube 14 having such an opening 143 on the side surface 142, the flow velocity of the inert gas flowing from the opening 143 of the straightening tube 14 toward the furnace monitoring window in the cylinder part 11 increases, As a result, it is possible to obtain the effect that the carbon-containing gas from the inside of the cylindrical portion 11 or the outside of the cylindrical portion 11 becomes more difficult to flow back toward the silicon melt 6 side.

Next, an example of a single crystal manufacturing method using the single crystal manufacturing apparatus of the present invention will be described with reference to FIGS. 1 and 2. However, the single crystal manufacturing apparatus of the present invention is not limited to the single crystal manufacturing apparatus shown in FIGS. 1 and 2, and the single crystal manufacturing method using the single crystal manufacturing apparatus of the present invention is exemplified below. but not limited to.

First, the seed crystal 4 is immersed in the silicon melt 6, and while rotating the seed crystal 4, the quartz crucible 7, and the graphite crucible 8 about the rotation axis 18, the seed crystal 4 is gently pulled upward to form a rod-shaped silicon monomer. While growing the crystal 5, the quartz crucible 7 and the graphite crucible 8 are raised in accordance with the growth of the crystal so that the height of the melt surface is always kept constant in order to obtain the desired diameter and crystal quality. The crucible shaft 17 can be used to raise the quartz crucible 7 and the graphite crucible 8 and to rotate the quartz crucible 7 and the graphite crucible 8 .

The silicon melt 6 can be obtained by charging raw silicon into a quartz crucible 7 and melting the raw silicon using a heater 9.

The raw material silicon used at this time is preferably a semiconductor grade high purity raw material. The present invention originates from the crystal manufacturing process by adopting a structure in which the first portion 151 of the cooling auxiliary tube 15 surrounds the bottom surface 132 of the cooling tube 13 and the second portion 152 covers the upper end 141 of the rectifying tube 14. This technology reduces carbon pollution, but by using high-purity raw materials, it is possible to reduce the amount of contamination brought in from the raw materials, thereby making it possible to more reliably produce single crystals with low carbon concentrations. . Therefore, it is preferable that the raw material silicon used is a semiconductor grade high purity raw material.

By using the example of the single crystal manufacturing apparatus 1 shown in FIGS. 1 and 2, the radiant heat from the silicon single crystal 5 and the radiant heat from high temperature parts such as the heater 9 can be sufficiently transmitted to the cooling cylinder 13. The generated heat can be removed by forced cooling using a cooling medium. Thereby, silicon single crystals can be manufactured more efficiently.

In the example of the single crystal manufacturing apparatus 1 shown in FIGS. 1 and 2, the space around the auxiliary cooling cylinder 15, for example, around the silicon single crystal 5 directly above the silicon melt, the auxiliary cooling cylinder 15 and the cylindrical part 11, It is possible to lower the temperature of the space surrounded by Thereby, the reaction between the carbon member in the manufacturing apparatus 1 and SiO evaporated from the silicon melt 6 can be suppressed, and the generation of carbon-containing gas can be suppressed. In addition, even if the above reaction occurs and carbon-containing gas is generated, the rectifying tube 14 whose upper end 141 is surrounded by the second portion 152 of the auxiliary cooling tube 15 prevents this carbon-containing gas from flowing back into the silicon melt. can be prevented.

That is, by using an example of the single crystal manufacturing apparatus 1 shown in FIGS. 1 and 2, a single crystal with a low carbon concentration can be efficiently manufactured.

Furthermore, in the example of the single crystal manufacturing apparatus 1 shown in FIGS. 1 and 2, the rectifying tube 14 has an opening 143 on the side surface 142 as shown in FIG. It is possible to further prevent carbon-containing gas from flowing back to the silicon melt 6 side.

Hereinafter, the present invention will be specifically explained using Examples and Comparative Examples, but the present invention is not limited thereto.

In each Example and Comparative Example, a single crystal was manufactured under the following common conditions using the single crystal manufacturing apparatus described below. A crucible with a diameter of 81.28 cm (32 inches) was used. 360 kg of raw silicon was put into this crucible and melted with a heater to obtain a silicon melt. A crystal with a crystal diameter of 300 mm was pulled while applying a horizontal magnetic field to the silicon melt. Samples were cut out from each straight body position of the crystal with a diameter of 300 mm after being pulled, and the carbon concentration was determined using the PL method.

(Example 1)
In Example 1, a single crystal manufacturing apparatus having the same structure as the single crystal manufacturing apparatus 1 described with reference to FIGS. 1 and 2 was used. That is, in Example 1, the rectifying tube 14 is arranged on the heat shielding member 12 so as to concentrically surround the silicon single crystal 5 being pulled, and the second portion 152, which is the lower part of the cooling auxiliary tube 15, straightens the current. A single crystal was manufactured using the cooling auxiliary cylinder 15 having a structure that covered the upper end 141 of the cylinder 14. In this case, the material of the rectifying tube 14 was synthetic quartz, and the material of the auxiliary cooling tube 15 was a graphite material whose thermal conductivity was equal to or higher than that of metal, and whose emissivity was higher than that of metal. The rectifier tube 14 used was a fully closed rectifier tube with no openings on the side surface (ratio e/f=0% in FIG. 3), as shown in FIGS. 1 and 2.

As shown in Figure 2, the ratio of the area of the part covered by the auxiliary cooling tube at the top of the straightening tube to the total area of the side surface of the straightening tube is a/b, and the distance between the side surface of the groove at the bottom of the auxiliary cooling tube and the side surface of the straightening tube. is c, the gap between the cooling auxiliary cylinder and the bottom surface of the cooling cylinder is d, and in Example 1, a/b=35%, c=5 mm, d=0 mm (complete contact), d=1. Single crystals were manufactured using three levels: 0 mm and d=3.0 mm.

(Comparative example 1)
In Comparative Example 1, a single crystal manufacturing apparatus having a structure as shown in FIG. 8 was used. That is, in Comparative Example 1, the straightening tube is not mounted on the heat shielding member 12, and the cooling auxiliary tube 115 is used, which does not have a structure to cover the bottom surface 132 of the cooling tube 13 facing the silicon melt 6. A single crystal was manufactured using a single crystal manufacturing apparatus different from the single crystal manufacturing apparatus of Example 1.

The results of Example 1 and Comparative Example 1 are shown in FIG. In Example 1 using the single crystal manufacturing apparatus according to the present invention, a single crystal with a lower carbon concentration was produced at any solidification rate compared to the case of manufacturing using the manufacturing apparatus of Comparative Example 1 as shown in FIG. It turns out that we were able to obtain crystals. In particular, when the gap d between the cooling auxiliary cylinder and the bottom surface of the cooling cylinder was 0 mm (complete contact) in Example 1, the carbon in the single crystal was The result was that the concentration was reduced by about 89%. Furthermore, as can be seen from FIG. 4, it was confirmed that if the gap d between the auxiliary cooling cylinder and the bottom of the cooling cylinder in Example 1 was 1 mm or less, the carbon concentration in the single crystal could be significantly reduced compared to Comparative Example 1. There is. Therefore, it is preferable that the gap d between the cooling auxiliary cylinder and the bottom surface of the cooling cylinder in the manufacturing apparatus used in the present invention is 1 mm or less. On the other hand, even if the gap d between the cooling auxiliary cylinder and the bottom surface of the cooling cylinder in Example 1 was set to 3 mm, the result was that the carbon concentration in the single crystal was reduced by about 77% compared to Comparative Example 1.

(Example 2)
In Example 2, a single-crystal manufacturing apparatus was prepared that satisfied the two levels of a/b = 10% and a/b = 35% by fixing c = 5 mm and d = 1.0 mm in Fig. 2. A single crystal was produced. In Example 2, as in Example 1, the rectifier tube 14 used had no openings on the sides (ratio e/f=0% in FIG. 3), as shown in FIGS. 1 and 2. It was a rectifier tube with a closed structure.

(Comparative example 2)
Comparative Example 2 was the same as that used in Example 2 except that a/b = 0%, that is, the upper end portion 141 of the straightening tube 14 was not surrounded by the second portion 152 of the auxiliary cooling tube 15. Single crystals were manufactured using a single crystal manufacturing device.

The results of Example 2, Comparative Example 1, and Comparative Example 2 are shown in FIG. In Example 2 using the single crystal manufacturing apparatus according to the present invention, a single crystal with a lower carbon concentration was produced at any solidification rate compared to the case of manufacturing using the manufacturing apparatus of Comparative Example 1 as shown in FIG. It turns out that we were able to obtain crystals. In particular, when the ratio a/b of the area of the portion of the upper end 141 of the straightening tube 14 covered with the cooling auxiliary tube to the total area of the side surface 142 of the straightening tube 141 in Example 2 is 35%, Comparative Example 1 The results showed that the carbon concentration in the single crystal was reduced by about 85% compared to when the single crystal was manufactured using the same manufacturing equipment. Further, as can be seen from FIG. 5, it has been confirmed that when a/b of Example 2 is 10% or more, the carbon concentration in the single crystal is significantly reduced compared to Comparative Examples 1 and 2. Therefore, the lower limit of the ratio of the area of the upper end 141 of the straightening tube 14 covered by the cooling auxiliary tube 15 to the total area of the side surface 142 of the straightening tube 14 in the manufacturing apparatus used in the present invention is set to 10%. It is preferable. On the other hand, in Comparative Example 2 where a/b = 0%, the result was that the carbon concentration in the single crystal was reduced by about 67% compared to Comparative Example 1, but the results of Example 2 It was insufficient compared to

Note that, separately from Example 2, a single crystal was manufactured using a cooling auxiliary cylinder 15 having a structure such that a/b = 40%. In Example 2 where a/b was set to 35% or less, it was easier to secure a field of view for the camera for diameter measurement than when a/b was set to 40%. Considering this point, it is preferable that the upper limit of the ratio of the area of the portion of the upper end 141 of the straightening tube 14 covered by the auxiliary cooling tube 15 to the total area of the side surface 142 of the straightening tube 14 to be 35%. I understand.

(Example 3)
In Example 3, a single crystal was manufactured by fixing a/b = 35% and d = 1.0 mm, and preparing a single crystal manufacturing apparatus that satisfies the two standards of c = 5 mm and c = 25 mm. Ta. In addition, in Example 3, as in Example 1, the rectifying tube 14 used had no openings on the sides (ratio e/f=0% in FIG. 3), as shown in FIGS. 1 and 2. It was a rectifier tube with a closed structure.

The results of Example 3 and Comparative Example 1 are shown in FIG. In Example 3 using the single crystal manufacturing apparatus according to the present invention, a single crystal with a lower carbon concentration was produced at any solidification rate compared to the case of manufacturing using the manufacturing apparatus of Comparative Example 1 as shown in FIG. It turns out that we were able to obtain crystals. In particular, in Example 3, when the distance c between the side surface of the groove 154 of the cooling auxiliary tube 15 and the side surface 142 of the straightening tube 14 was set to 5 mm, the single crystal was manufactured using the single crystal manufacturing apparatus of Comparative Example 1. The result was that the carbon concentration in the single crystal was reduced by about 85% compared to the case where the carbon concentration in the single crystal was reduced by about 85%. Furthermore, as can be seen from FIG. 6, it has been confirmed that when c in Example 3 is 25 mm or less, the carbon concentration in the single crystal is reduced compared to Comparative Example 1.

(Example 4)
The ratio of the opening area e of the opening 143 of the side surface 142 of the straightening tube 14 to the total area f of the side surface 142 of the straightening tube 14 is defined as e/f (shown in FIG. 3), and in Example 4, a/b=35. %, d = 1.0 mm, c = 5 mm, and each of the three levels of e/f = 0% (totally closed rectifier tube), e/f = 9%, and e/f = 15%. A single crystal manufacturing apparatus was prepared to meet the requirements, and single crystals were manufactured. Note that the rectifier tube 14 with e/f=9% and e/f=15% has a structure in which openings 143 are provided on three axes at angles of 0°, 120°, and 240°.

In addition to the above conditions, in the straightening tube 14 with e/f = 9%, the height of the upper end of the opening 143 is located at a height of 24% of the total height of the straightening tube 14, and the opening 143 is The structure was such that a region having a length of 30 mm from the upper end to the lower end of the opening 143 was opened.

In addition to the above conditions, in the straightening tube 14 with e/f = 15%, the height of the upper end of the opening 143 is located at a height of 35% of the total height of the straightening tube 14, and the opening 143 is The structure was such that a region having a length of 50 mm from the upper end to the lower end of the opening 143 was opened.

The results of Example 4 and Comparative Example 1 are shown in FIG. In Example 4 using the single crystal manufacturing apparatus according to the present invention, the ratio e/f of the opening area e of the opening 143 of the side surface 142 of the rectifying tube 14 to the total area f of the side surface 142 of the rectifying tube 14 was set to 9. %, the result is that the carbon concentration in the single crystal is reduced by about 93% compared to Comparative Example 1, in which the single crystal was manufactured using a manufacturing apparatus with a conventional structure as shown in FIG. Ta. Furthermore, as can be seen from FIG. 7, it has been confirmed that when the e/f of Example 4 exceeds 0% and is 15% or less, the carbon concentration in the single crystal is significantly reduced compared to Comparative Example 1. .

Also, from Figure 7, when the ratio e/f is set to 9% or 15%, the carbon concentration in the single crystal decreases compared to when e/f is set to 0% (totally closed rectifier structure). It has been confirmed that the effect of opening the side surface 142 of the rectifying tube 14 further reduces the carbon concentration in the single crystal.

Note that the present invention is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any embodiment that has substantially the same configuration as the technical idea stated in the claims of the present invention and has similar effects is the present invention. covered within the technical scope of.

DESCRIPTION OF SYMBOLS 1, 200... Single crystal production apparatus, 2... Main chamber, 21... Ceiling part, 3... Pulling chamber, 4... Seed crystal, 5... Silicon single crystal, 6... Silicon melt, 7... Quartz crucible, 8... Graphite crucible , 9... Heater, 10... Heat insulating material, 11... Cylindrical part, 12... Heat shielding member, 13... Cooling cylinder, 131, 133... Part of cooling cylinder, 132... Bottom surface, 14... Rectifying cylinder, 141... Upper end part, 142... Side surface, 143... Opening, 15, 115... Cooling auxiliary cylinder, 151... First part, 152... Second part, 153... Flange part, 154... Groove part, 16... Crucible support, 17... Crucible shaft, 18... Axis of rotation.

Claims (6)

A single crystal manufacturing device for growing a single crystal by the Czochralski method,
a main chamber having a ceiling and housing a crucible containing silicon melt;
a pulling chamber connected upwardly from the ceiling of the main chamber via a gate valve and accommodating a silicon single crystal pulled from the silicon melt;
a heat shielding member disposed to face the silicon melt contained in the crucible;
a rectifier cylinder disposed on the heat shielding member so as to surround the silicon single crystal being pulled;
a cooling cylinder arranged to surround the silicon single crystal being pulled, including a portion extending from the ceiling of the main chamber toward the silicon melt, and forcedly cooled with a cooling medium;
and a cooling auxiliary cylinder fitted inside the cooling cylinder,
The extended portion of the cooling cylinder has a bottom surface facing the silicon melt,
The auxiliary cooling cylinder is characterized in that it has at least a first part surrounding the bottom surface of the cooling cylinder and a second part surrounding the upper end of the straightening cylinder. 2. The single crystal manufacturing apparatus according to claim 1, wherein the rectifier tube is made of synthetic quartz. The cooling auxiliary cylinder is made of at least one member selected from the group consisting of graphite member, carbon composite member, stainless steel, molybdenum, and tungsten,
The first portion of the auxiliary cooling tube has a structure that covers the bottom surface of the cooling tube, and the gap between the first portion of the auxiliary cooling tube and the bottom surface of the cooling tube is 1.0 mm or less. The single crystal manufacturing apparatus according to claim 1 or 2, characterized in that: Any one of claims 1 to 3, wherein the second portion of the cooling auxiliary tube includes a groove portion that covers an area of 10% to 35% of the total area of the side surface of the straightening tube. 1. The single crystal manufacturing apparatus according to item 1. 5. The single crystal manufacturing apparatus according to claim 4, wherein a gap between both side surfaces of the upper end of the straightening tube and side surfaces of the groove of the second portion of the cooling auxiliary tube is 5 mm or more and 25 mm or less. . The rectifier tube has an opening on a side surface, and the height of the upper end of the opening of the rectifier tube is 35% or less of the total height of the rectifier tube. The single crystal manufacturing apparatus according to any one of claims 1 to 5.

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