JP2018104208A - Evaporation restraining member, single crystal pulling apparatus and method for manufacturing silicon single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a silicon single crystal, capable of manufacturing the silicon single crystal while reducing the evaporation of dopant.SOLUTION: A method for manufacturing a silicon single crystal comprises: arranging an evaporation suppressing member 29 including a ring plate-shaped body part 29A surrounding a silicon single crystal SM below a heat shield body 28 and an extension part 29B extended on the outside obliquely upward from the outer edge of the body part 29A; forming a flow passage R between the upper surface of the body part 29A and the heat shield body 28 during the growth of the silicon single crystal SM; introducing an inert gas G from above into a space between the silicon single crystal SM and the heat shield body 28 while maintaining the state of contacting the lower surface of the body part 29A to a dopant addition melt surface MD; and introducing the inert gas G in a direction separating from the silicon single crystal SM along the flow passage R to send it obliquely upward along the extension part 29B.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an evaporation suppression member, a single crystal pulling apparatus, and a method for manufacturing a silicon single crystal.

Conventionally, the method of Patent Document 1 is known as a method for producing a silicon single crystal using the Czochralski (CZ) method.
In Patent Document 1, in a single crystal pulling apparatus, a quartz ring (evaporation suppression member) that covers a surface of a silicon melt and has standing walls extending in a direction perpendicular to an outer edge and an inner edge is provided under the outer periphery of a heat shield. It is described that it is provided. It is described that by providing this quartz ring, evaporation of oxygen from the silicon melt can be reduced, and a silicon single crystal controlled to a predetermined oxygen concentration can be produced.

JP-A-64-61382

  By the way, when manufacturing a silicon single crystal having a low electrical resistivity, a dopant-added melt obtained by adding a volatile dopant such as arsenic, red phosphorus, and antimony to a silicon melt is used. At this time, when the silicon single crystal is pulled up by the CZ method, an inert gas flows in the chamber, so that the volatile dopant is easily evaporated from the surface of the dopant-added melt on the inert gas. When the volatile dopant evaporates from the surface of the dopant-added melt, the content of the dopant in the silicon single crystal becomes insufficient, and the electrical resistivity of the silicon single crystal increases.

When a silicon single crystal is produced from a dopant-added melt using the single crystal pulling apparatus described in Patent Document 1, the following problems occur.
When the evaporation of the volatile dopant is to be reduced by the single crystal pulling apparatus of Patent Document 1, the bottom surface of the evaporation suppressing member is formed so that the ring width of the evaporation suppressing member is increased and the surface of the silicon melt is covered to the vicinity of the inner wall of the crucible. It is conceivable to increase the area. However, when the area of the bottom surface of the evaporation suppression member is increased in this way, when the growth of the silicon single crystal proceeds and the dopant-added melt decreases, the crucible bottom portion has a reduced diameter shape such as a round bottom. Since the inner wall of the crucible and the outer edge of the evaporation suppression member are in contact with each other, the silicon single crystal may not be pulled any further.

  An object of the present invention is to provide an evaporation suppressing member, a single crystal pulling apparatus, and a method for manufacturing a silicon single crystal, which can manufacture a silicon single crystal while reducing dopant evaporation.

  The evaporation suppression member of the present invention includes a crucible, a crucible driving unit that moves the crucible up and down, a heating unit that heats the crucible and generates a dopant-added melt in which a dopant is added to a silicon melt, and seeds By pulling up the crystal after bringing it into contact with the dopant-added melt, a pulling portion for growing the silicon single crystal, a cylindrical heat shield provided so as to surround the silicon single crystal above the crucible, An evaporation suppression member attached to a single crystal pulling apparatus provided with a chamber containing the crucible, the heating unit, and the heat shield, and an introduction unit provided at an upper portion of the chamber for introducing an inert gas into the chamber. And being formed in an annular plate shape surrounding the silicon single crystal below the heat shield, and forming a flow path between the upper surface and the heat shield. The lower surface is characterized by comprising a main body portion in contact with the dopant-added melt surface and a extended portion extending obliquely upward outwardly from an outer edge of the main body portion.

According to the present invention, the dopant-added melt surface can be physically covered with the main-body portion by bringing the main-body portion of the evaporation suppression member into contact with the dopant-added melt surface. Therefore, evaporation of the dopant from the dopant-added melt surface can be reduced.
Further, by providing the main body with an extending portion that extends obliquely upward and outward, the inert gas that has passed through the flow path between the heat shield and the main body is directed obliquely upward, and the dopant-added melt Inert gas flowing on the surface of the dopant-added melt away from the vicinity of the surface can be reduced. As a result, even if the area of the main body part covering the dopant-added melt surface is reduced, the evaporation of the dopant from the dopant-added melt surface outside the main body part can be reduced.
Further, when viewed as the entire evaporation suppression member, the outer side of the evaporation suppression member is bent obliquely upward, so even if the growth of the silicon single crystal progresses and the dopant addition melt decreases, the outer side of the evaporation suppression member decreases. The extension can be continued without contacting the inner wall of the bottom-shaped crucible whose diameter is reduced toward the bottom, such as a round bottom. Therefore, it is possible to provide an evaporation suppressing member capable of manufacturing a silicon single crystal while reducing dopant evaporation.

  In the evaporation suppressing member of the present invention, it is preferable that the main body portion is made of quartz and the extending portion is made of graphite.

  According to this invention, since the main-body part which contacts the dopant addition melt of a main-body part is a product made from quartz, it is hard to react with a dopant addition melt. Therefore, the influence on the quality of the silicon single crystal is reduced. Moreover, since the extension part is made of graphite, the heat shielding property of the extension part can be improved. Therefore, radiant heat from at least one of the dopant-added melt, the crucible and the heating part can be shielded by the extension part, and the temperature gradient in the pulling direction of the growing silicon single crystal can be increased.

  In the evaporation suppressing member of the present invention, it is preferable that a heat insulating material is provided inside the extending portion.

  According to the present invention, since the heat insulating material is provided in the extension part, it is effective that the radiant heat from at least one of the dopant-added melt, the crucible, and the heating part reaches the silicon single crystal. Can be suppressed.

  The single crystal pulling apparatus of the present invention includes a crucible, a crucible driving unit that raises and lowers and rotates the crucible, a heating unit that heats the crucible and generates a dopant-added melt in which a dopant is added to a silicon melt, A pulling part for growing a silicon single crystal by pulling the seed crystal after bringing it into contact with the dopant-added melt, and a cylindrical heat shield provided so as to surround the silicon single crystal above the crucible The crucible, the heating unit and the chamber for housing the thermal shield, the upper part of the chamber, an introduction part for introducing an inert gas into the chamber, and the thermal shield are provided below the thermal shield The above-mentioned evaporation suppression member is provided.

  The method for producing a silicon single crystal of the present invention includes a crucible, a crucible driving unit that moves the crucible up and down, and a heating unit that heats the crucible and generates a dopant-added melt in which a dopant is added to a silicon melt. A pulling part for growing the silicon single crystal by pulling the seed crystal after contacting the dopant-added melt, and a cylindrical heat shield provided so as to surround the silicon single crystal above the crucible A single crystal pulling apparatus including a body, a chamber for housing the crucible, the heating unit, and the heat shield, and an introduction unit provided at an upper portion of the chamber for introducing an inert gas into the chamber. A method for producing a silicon single crystal, comprising: an annular plate-shaped main body surrounding the silicon single crystal below the thermal shield; and an obliquely upward from an outer edge of the main body An evaporation suppressing member having an extending portion extending to the side, and during the growth of the silicon single crystal, a flow path is formed between the upper surface of the main body and the heat shield, While maintaining the state where the lower surface is in contact with the dopant-added melt surface, an inert gas is introduced from above between the silicon single crystal and the heat shield, and the inert gas is introduced along the flow path. Then, it is guided in a direction away from the silicon single crystal, and flows obliquely upward along the extending portion.

Sectional drawing of the single crystal pulling apparatus which concerns on one Embodiment of this invention. The expanded sectional view of the evaporation suppression member of the said single crystal pulling apparatus. The expanded sectional view of the evaporation suppression member vicinity in the crucible bottom part at the time of dopant addition melt reduction. The expanded sectional view of the evaporation suppression member of the single crystal pulling device concerning the modification of the present invention. The graph which shows the relationship between the presence or absence of the evaporation suppression member in the Example of this invention, and the dopant evaporation amount of each area.

Hereinafter, as an embodiment of the present invention, a method for producing a silicon single crystal SM by the CZ method will be described with reference to FIGS.
First, the structure of the single crystal pulling apparatus 1 used for the manufacturing method of the silicon single crystal SM will be described.
As shown in FIG. 1, the single crystal pulling apparatus 1 includes a chamber 21, a crucible 22 disposed inside the chamber 21, a crucible driving unit 23, a heating unit 24, a heat insulating cylinder 25, a pulling unit 26, The rectifying cylinder 27, the heat shield 28, and the evaporation suppression member 29 are provided.

In the upper part of the chamber 21, an introduction part 21 </ b> A for introducing an inert gas such as Ar gas into the chamber 21 is provided. An exhaust port 21 </ b> B that exhausts gas inside the chamber 21 by driving a vacuum pump (not shown) is provided at the lower portion of the chamber 21.
An inert gas is introduced into the chamber 21 from the introduction portion 21A in a predetermined gas amount. The introduced inert gas is discharged from the exhaust port 21 </ b> B at the lower part of the chamber 21, so that the inert gas flows downward from the inside of the chamber 21.
The crucible 22 melts polycrystalline silicon, which is a raw material of the silicon single crystal SM, to form a silicon melt M.
The crucible drive unit 23 moves the crucible 22 up and down at a predetermined speed, and rotates the crucible 22 at a predetermined speed around a support shaft 23 </ b> A connected to the lower end of the crucible 22.
The heating unit 24 is disposed outside the crucible 22, and heats the crucible 22 to generate a dopant-added melt MD in which a dopant is added to the silicon melt M.
The heat insulating cylinder 25 is disposed so as to surround the crucible 22 and the heating unit 24.

The pulling unit 26 includes a pulling drive unit 26A and a pulling cable 26B having one end connected to the pulling drive unit 26A. The pulling drive unit 26A moves the pulling cable 26B up and down and rotates at a predetermined speed. At the other end of the pulling cable 26B, a seed holder 26C for holding a seed crystal or a doping device (not shown) is attached. The doping apparatus is for doping the silicon melt M in the crucible 22 with the dopant to generate the dopant-added melt MD.
The rectifying cylinder 27 is provided in a cylindrical shape surrounding the silicon single crystal SM, and guides an inert gas flowing from above to below.
The heat shield 28 is formed in the shape of a truncated cone surrounding the lower part of the rectifying cylinder 27 and the silicon single crystal SM above the crucible 22, and the lower end thereof is connected to the lower end of the rectifying cylinder 27. The heat shield 28 blocks radiant heat radiated upward from the heating unit 24.

The evaporation suppression member 29 includes a quartz main body portion 29A formed in an annular plate shape, and a graphite extension portion 29B extending obliquely upward and outward from the outer edge of the main body portion 29A. The main body 29A includes a protrusion 29C protruding upward from the inner edge. The main body portion 29A and the extending portion 29B are integrated by engaging an engaging portion (not shown) provided on one side with an engaged portion (not shown) provided on the other side. .
The evaporation suppression member 29 is arranged so as to be separated below the thermal shield 28 and surround the silicon single crystal SM via rod-like support members 30 provided at two to four positions at equal intervals in the circumferential direction. Has been. One end of the support member 30 is engaged with the outer peripheral side surface 28B of the heat shield 28, and the other end is engaged with the extending portion 29B.
The evaporation suppression member 29 and the heat shield 28 are arranged so as to coincide with these centers. Further, the upper surface of the main body portion 29A and the upper surface of the extension portion 29B of the evaporation suppression member 29 are arranged so as to be parallel to the bottom surface 28A of the heat shield 28 and the outer peripheral side surface 28B of the heat shield 28, respectively. A flow path R is formed between them. The lower surface of the main body 29A is in contact with the surface of the dopant-added melt MD so that the inert gas G does not flow under the main body 29A. Further, the evaporation suppression member 29 is arranged so that the upper end of the extending portion 29 </ b> B is located above the bottom surface 28 </ b> A of the heat shield 28.

Next, a method for manufacturing the silicon single crystal SM will be described.
In the present embodiment, the case where a silicon single crystal SM having a set diameter of the straight body portion of 200 mm is illustrated, but silicon single crystals SM having other set diameters such as 150 mm, 300 mm, and 450 mm may be manufactured. Good.
The electrical resistivity is preferably 1.2 mΩ · cm to 5.0 mΩ · cm when the dopant is arsenic, and 0.5 mΩ · cm to 2.0 mΩ · cm when red phosphorus is used. In the case of antimony, it is preferably 10 mΩ · cm or more and 30 mΩ · cm or less. Further, as shown in FIG. 2, from the outer peripheral surface of the silicon single crystal SM to the inner edge of the main body portion 29A, the area A, from the inner edge to the outer edge of the main body portion 29A, the area B, and from the outer edge of the main body portion 29A to the inner wall of the crucible 22 Is called area C.

First, in the single crystal pulling apparatus 1, the manufacturing conditions of the silicon single crystal SM, for example, the electrical resistivity, the oxygen concentration, the flow rate of the inert gas, the pressure inside the chamber 21, the rotational speed of the crucible 22 and the silicon single crystal SM, the heating unit 24 heating conditions etc. are set.
Next, the heating unit 24 is controlled based on the set value, and the crucible 22 is heated, so that polycrystalline silicon (silicon raw material) and the dopant in the crucible 22 are melted to generate a dopant-added melt MD. Thereafter, an inert gas is introduced into the chamber 21 from the introducing portion 21A at a predetermined flow rate, and the inside of the chamber 21 is maintained in an inert gas atmosphere under reduced pressure.
Next, the pulling cable 26B is lowered to immerse the seed crystal in the dopant-added melt MD, and the silicon single crystal SM is pulled and grown while rotating the crucible 22 and the pulling cable 26B in a predetermined direction.

During the growth of the silicon single crystal SM, as shown in FIG. 2, the inert gas G flowing downward is guided by the main body 29A in the direction away from the silicon single crystal SM along the flow path R from above the area A. It is burned.
At this time, since the main body portion 29A covers the area B surface of the dopant-added melt MD, evaporation of the dopant from the area B surface can be prevented. And the inert gas G which passed the main-body part 29A is further guide | induced to diagonally upward outer side by the extension part 29B, and becomes difficult to flow to the dopant addition melt MD surface of the area C. For this reason, evaporation of the dopant from the area C can also be reduced. As described above, a silicon single crystal SM having a desired electrical resistivity can be manufactured by suppressing the evaporation of the dopant.

  Further, when viewed as the whole evaporation suppression member 29, the outer side is bent upward, so that as shown in FIG. 3, even if the growth of the silicon single crystal SM proceeds and the dopant-added melt MD decreases, The extending portion 29B outside the evaporation suppression member 29 can continue to be pulled up without contacting the inner surface of the bottom-shaped crucible 22 whose diameter is reduced toward the bottom, such as a round bottom.

  Furthermore, since the upper end of the extension part 29B is located above the bottom face 28A of the heat shield 28, the radiant heat from at least one of the dopant-added melt MD, the crucible 22 and the heating part 24 flows into the flow path. Reaching the silicon single crystal SM via R can be suppressed by the extending portion 29B, and the temperature gradient in the pulling direction of the silicon single crystal SM can be increased. In particular, since the extending portion 29B is made of graphite, the radiant heat can be shielded more effectively, and the temperature gradient in the pulling direction of the silicon single crystal SM can be increased.

[Modification]
It should be noted that the present invention is not limited to the above-described embodiment, and various improvements and design changes can be made without departing from the scope of the present invention. The general procedure, structure, and the like may be other structures as long as the object of the present invention can be achieved.
That is, instead of the evaporation suppression member 29 shown in FIGS. 1 to 3, as shown in FIG. 4, an evaporation suppression member 31 having an extending portion 31A provided with a heat insulating material 31B inside may be employed. By providing the heat insulating material 31B inside the extending part 31A, it is possible to suppress the radiant heat from at least one of the dopant-added melt MD, the crucible 22 and the heating part 24 from reaching the silicon single crystal. As a result, the temperature gradient in the pulling direction of the silicon single crystal SM can be increased. For example, a carbon felt material can be used as the heat insulating material 31B. For example, graphite or quartz can be used as the extending portion 31A.
Further, for example, if the evaporation suppression member 29 includes an extending portion 29B that extends obliquely upward and outward without providing the rectifying cylinder 27, the inner surface of the bottom-shaped crucible 22 having a reduced diameter, as in the above embodiment. The silicon single crystal SM can be manufactured by reducing the evaporation of the dopant without contacting the substrate.
Further, the main body portion 29A does not need to react with the dopant-added melt MD and does not affect the quality of the silicon single crystal SM, and may not be made of quartz, and the extending portion 29B may not be made of graphite. The main body portion 29A and the extending portion 29B may be integrally formed of the same material such as quartz.
Further, the extending portion 29B may not be provided so that the main body portion 29A or the extending portion 29B is parallel to the bottom surface 28A of the heat shield 28 and the outer peripheral side surface 28B of the heat shield 28. The upper end of the part 29 </ b> B may be the same height as the lower end of the heat shield 28 or may be lower than the lower end of the heat shield 28.

  Next, although an Example demonstrates further in detail, this invention is not limited at all by these examples.

[Experiment: Investigation of the relationship between the presence or absence of evaporation suppression members and the amount of dopant evaporation in each area]
[Experimental Example 1]
A single crystal pulling apparatus 1 provided with an evaporation suppressing member 29 having an extending portion 29B as shown in FIG. 1 was prepared. The configuration of the single crystal pulling apparatus 1 was set as follows.
<Configuration of single crystal pulling device>
Area A width: 22.5mm
Area B width: 30mm
Area C width: 10 mm to 65 mm Channel R height: 10 mm
Then, a silicon single crystal SM having the following characteristics was manufactured under the following manufacturing conditions with the inside of the chamber 21 being an inert gas atmosphere, and the amount of dopant evaporated in the areas A to C at this time was measured.
In addition, the measurement of the evaporation amount of the dopant was performed as follows. Based on the electrical resistivity of the silicon single crystal SM at this time, the dopant concentration taken into the silicon single crystal SM was calculated, and the amount of evaporation from the dopant-added melt MD was calculated based on the taken-in dopant concentration. The amount of evaporation calculated in this way increases as the electrical resistivity of the silicon single crystal SM increases with respect to a desired value.
<Production conditions>
Flow rate of inert gas: 200L / min
<Characteristics of silicon single crystal>
Dopant: Red phosphorus Electrical resistivity: 0.7 mΩ · cm
Straight body diameter: 205mm
Length of straight body: Over 300mm and 2000mm or less

[Experimental example 2]
A single crystal pulling apparatus different from the single crystal pulling apparatus 1 used in Experimental Example 1 only in that the evaporation suppression member 29 is not provided was prepared. Then, a silicon single crystal SM having the same characteristics as Experimental Example 1 is manufactured under the same manufacturing conditions as in Experimental Example 1 except for the following points, and an area where the distance from the silicon single crystal SM is the same distance as in Experimental Example 1 is obtained. As the area A, the area B, and the area C, the evaporation amount of the dopant at this time was measured.
<Production conditions>
Distance between the lower end of the heat shield 28 and the surface of the dopant-added melt MD (constant during manufacture): 10 mm

[Evaluation]
FIG. 5 shows the dopant evaporation amount ratio of Experimental Example 1 when the dopant evaporation amount of Experimental Example 2 is set to 100% for the areas A to C, respectively.
The ratio of dopant evaporation in areas A, B, and C in Experimental Example 1 is 68.4%, 0%, and 3.1%. By providing the evaporation suppression member 29, the amount of dopant evaporation can be reduced in all areas. I understood. In particular, in area C, the evaporation amount could be greatly reduced even though the evaporation suppression member 29 did not directly cover the dopant-added melt MD surface.
From the above, it was found that the evaporation of the dopant can be reduced by providing the single crystal pulling apparatus 1 with the evaporation suppressing member 29 including the extending portion 29B.

  DESCRIPTION OF SYMBOLS 1 ... Single crystal pulling apparatus, 21 ... Chamber, 22 ... Crucible, 23 ... Crucible drive part, 24 ... Heating part, 25 ... Heat insulation cylinder, 26 ... Pulling part, 27 ... Rectification cylinder, 28 ... Heat shield, 29, 31 ... Evaporation suppression member, 31A ... extension part, 31B ... insulating material, SM ... silicon single crystal.

Claims (5)

Crucible,
A crucible drive for moving the crucible up and down; and
A heating unit for heating the crucible to generate a dopant-added melt in which a dopant is added to a silicon melt;
A pulling part for growing a silicon single crystal by pulling the seed crystal after contacting the dopant-added melt,
A cylindrical heat shield provided so as to surround the silicon single crystal above the crucible;
A chamber for housing the crucible, the heating unit and the heat shield;
An evaporation suppression member provided in an upper portion of the chamber and attached to a single crystal pulling device including an introduction portion for introducing an inert gas into the chamber;
A main body that is formed in the shape of an annular plate surrounding the silicon single crystal below the thermal shield, and that the upper surface forms a channel between the thermal shield and the lower surface is in contact with the dopant-added melt surface. And
An evaporation suppression member comprising: an extension part extending obliquely upward and outward from an outer edge of the main body part. The evaporation suppression member according to claim 1,
The evaporation suppressing member, wherein the main body is made of quartz, and the extension is made of graphite. The evaporation suppression member according to claim 1 or 2,
An evaporation suppressing member, wherein a heat insulating material is provided inside the extending portion. Crucible,
A crucible drive for moving the crucible up and down; and
A heating unit for heating the crucible to generate a dopant-added melt in which a dopant is added to a silicon melt;
A pulling part for growing a silicon single crystal by pulling the seed crystal after contacting the dopant-added melt,
A cylindrical heat shield provided so as to surround the silicon single crystal above the crucible;
A chamber for housing the crucible, the heating unit and the heat shield;
An introduction part provided at an upper part of the chamber, for introducing an inert gas into the chamber;
A single crystal pulling apparatus comprising: the evaporation suppression member according to claim 1 provided below the thermal shield. Crucible,
A crucible drive for moving the crucible up and down; and
A heating unit for heating the crucible to generate a dopant-added melt in which a dopant is added to a silicon melt;
A pulling part for growing a silicon single crystal by pulling the seed crystal after contacting the dopant-added melt,
A cylindrical heat shield provided so as to surround the silicon single crystal above the crucible;
A chamber for housing the crucible, the heating unit and the heat shield;
A method for producing a silicon single crystal using a single crystal pulling apparatus provided at an upper part of the chamber and having an introduction part for introducing an inert gas into the chamber,
An evaporation suppression member including an annular plate-shaped main body portion surrounding the silicon single crystal below the heat shield, and an extending portion extending obliquely upward and outward from an outer edge of the main body portion, is disposed,
During the growth of the silicon single crystal, a flow path is formed between the upper surface of the main body and the heat shield, while maintaining the state in which the lower surface of the main body is in contact with the dopant-added melt surface, An inert gas is introduced from above between the silicon single crystal and the heat shield, the inert gas is guided in a direction away from the silicon single crystal along the flow path, and obliquely upward along the extending portion. A method for producing a silicon single crystal, characterized by being caused to flow through.

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