JP2009274920A - Production method of silicon single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method of a silicon single crystal, by which excellent production efficiency is achieved in pulling a silicon single crystal having a large diameter and the crystal quality is made stable. <P>SOLUTION: The production method of a silicon single crystal comprises melting a silicon raw material in a quartz crucible initially charged with the raw material at a charging rate of 40 to 60%, additionally charging the crucible with the silicon raw material to satisfy a target charge amount, and pulling a single crystal from the melt formed in the quartz crucible, wherein preferably, the crucible is additionally charged with the silicon raw material at least twice until satisfying the target charge amount. Thereby, the volume of the quartz crucible used is effectively used, the dissolving time of the silicon raw material supplied in the initial charging is decreased, and a damaged part of the liquid surface is newly formed. This method is optimal upon pulling a silicon single crystal having a diameter of 450 mm by using a quartz crucible in a size of 36 inches (914 mm) to 44 inches (1,118 mm). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a large-diameter silicon single crystal by the Czochralski method (hereinafter referred to as “CZ method”), and more specifically, even when a large-diameter silicon single crystal is pulled up, The present invention relates to a method for producing a silicon single crystal capable of achieving efficiency and stabilization of crystal quality.

  Currently, a silicon single crystal is used as a main substrate material in semiconductor device manufacturing, and the CZ method is widely adopted as this manufacturing method. When a silicon single crystal is grown by the CZ method, a polycrystalline silicon raw material is charged into a melting crucible and melted therein. After the silicon raw material is completely melted, the seed crystal is immersed in a silicon melt using this as a crystal raw material to pull up the silicon single crystal.

  FIG. 1 is a cross-sectional view showing the main configuration of a pulling apparatus applied to the production of a silicon single crystal by the CZ method. As shown in FIG. 1, the pulling apparatus heats a silicon raw material for semiconductor supplied in a crucible 1 and maintains a molten state with a heater 2 and a main chamber 4 in which a heat insulating material 3 is disposed. And a pull chamber 5 for temporarily storing the pulled single crystal, and a top chamber 6 for connecting both the chambers 4 and 5.

  A crucible 1 for melting a crystal raw material is made of a double-layered quartz inner layer holding container (hereinafter referred to as “quartz crucible”) 1a having a bottomed cylindrical shape and a graphite holding the outside of the quartz crucible 1a. The outer layer holding container (hereinafter referred to as “graphite crucible”) 1b is fixed to the upper end portion of the support shaft 7 that can be rotated and moved up and down.

  The heater 2 and the heat insulating material 3 are disposed substantially concentrically outside the crucible 1, and the silicon raw material for semiconductor put into the quartz crucible 1 a, that is, bulk or granular polycrystalline silicon is melted to obtain a crystal raw material. A melt 8 is formed.

  On the central axis of the quartz crucible 1 a filled with the melt 8, a pulling wire 9 that rotates on the same axis as the support shaft 7 in the reverse direction or in the same direction at a predetermined speed is disposed. The winding part 10 is attached above the pull chamber 5. A seed crystal 11 is held at the lower end of the pulling wire 9.

  When pulling up the silicon single crystal using the pulling apparatus configured as described above, a predetermined amount of silicon raw material is put into the quartz crucible 1a and the silicon raw material is put into the crucible in an inert gas atmosphere under reduced pressure. After heating and melting by the heater 2 disposed around 1, the seed crystal 11 held at the lower end of the pulling wire 9 is immersed in the vicinity of the surface of the formed melt 8. Subsequently, while rotating the crucible 1 and the pulling wire 9, the wire 9 is taken up by the reel 10 a and pulled up, and the single crystal 12 is grown on the lower end surface of the seed crystal 11.

  By the way, in response to the recent high integration, low cost, and improved productivity of semiconductor devices, wafers are also required to have a large diameter. To replace the current 300 mm diameter wafer, the diameter of the wafer is 400 mm to 450 mm. There is an urgent need to develop a technology that can handle large-diameter silicon single crystals.

  As technologies necessary for producing a large-diameter silicon single crystal, increasing the capacity of the quartz crucible and increasing the filling amount of the silicon raw material are major issues. Conventionally, although not directly related to the development of a manufacturing technique for a large-diameter silicon single crystal, individual proposals have been made for increasing the capacity of these quartz crucibles and filling amounts of silicon raw materials.

  For example, in Patent Document 1, as the capacity of a quartz crucible increases, the heater for heating and melting the raw material in the crucible also inevitably increases in size, and the heater itself bends (deforms) due to its own weight and is damaged thereby. In order to solve these problems, there has been proposed a CZ crystal manufacturing apparatus provided with a heater support that supports a heater at another part in addition to a conventional heater support part by an electrode.

  Regarding the increase in the filling amount of the silicon raw material, in Patent Document 2, in the process of manufacturing a silicon single crystal, a step of additionally filling the crucible with the polycrystalline raw material, and a raw material obtained by melting the polycrystalline raw material additionally filled in the crucible There has been proposed a method of increasing the filling amount by repeating the step of forming a melt. However, the proposed method is limited to the multi-pooling method in which a plurality of single crystal rods are manufactured from one crucible by additionally filling a crucible with a polycrystalline raw material after growing a silicon single crystal.

  When manufacturing a large-diameter silicon single crystal, the problems to be solved for increasing the capacity of the quartz crucible are not limited to problems such as bending (deformation) of the heater and damage to the heater resulting therefrom. In addition, in order to solve the problem related to the increase in the filling amount, it is difficult to directly apply the silicon raw material filling technique employed in the multi-pooling method. For this reason, in order to develop a manufacturing technique for a large-diameter silicon single crystal, it is necessary to tackle issues related to increasing the capacity of the quartz crucible and increasing the filling amount of the silicon raw material from a new viewpoint.

Japanese Patent Laid-Open No. 10-167876 Japanese Patent Laid-Open No. 20004315256 Latest silicon device and crystal technology, published by Realize Science and Technology Center, pp. 238-256 “7. Next-generation large-diameter wafer crystal growth, processing, and epitaxial”, December 2005

  In connection with the technology for producing large-diameter silicon single crystals, the production of large-sized crucibles is indispensable due to the increased capacity of quartz crucibles. The ratio of the diameter of the crystal to be grown and the diameter of the quartz crucible is about 1: 3 based on empirical rules. However, in consideration of economy, the single crystal with a diameter of 200 mm is 22 inches (56 cm) and the single crystal with a diameter of 300 mm. On the other hand, a quartz crucible of 32 inches (81 cm) is frequently used. For this reason, Non-Patent Document 1 reports the relationship between the diameter of the single crystal and the quartz crucible as shown in Table 1 regarding the transition so far and the expected size that will be adopted in the future.

  However, when a large-sized quartz crucible is introduced in the production of a large-diameter silicon single crystal, the parts constituting the pulling device are increased in size and the weight is increased. For this reason, it is anticipated that workability and handling will be significantly reduced by increasing the size of the quartz crucible. Therefore, it is necessary to examine an appropriate crucible size from the viewpoint of work efficiency and production efficiency in the operation process of the silicon single crystal without being bound by the crucible size shown in Table 1 above.

  In addition, when the diameter of the silicon single crystal is increased, the quartz crucible becomes larger, and when a large amount of silicon raw material is melted, the melting time becomes longer. When the melting time of the silicon raw material becomes long, the inner surface of the quartz crucible is exposed to a high temperature for a long time by the melt, and in particular, the crucible surface in contact with the melt surface is likely to deteriorate. When the surface of the crucible is deteriorated, impurities contained in the quartz crucible are eluted into the melt, and there is a possibility that the quartz (Si oxide) is peeled off. When these are taken into the crystal from the melt, the grown single crystal is dislocated.

  The present invention has been made in view of a new problem in the development of manufacturing technology for such a large-diameter silicon single crystal, and is excellent in work efficiency and production efficiency in the operation process of the silicon single crystal, and is pulled up. It aims at providing the manufacturing method of the silicon single crystal which can stabilize the quality of a silicon single crystal.

  In order to solve the above-mentioned problems, the present inventors verified the pulling behavior of a large-diameter silicon single crystal using a large quartz crucible by numerical simulation. Conventionally, the ratio of the diameter of the crystal to be grown and the quartz crucible has been determined to be about 1: 3 from an empirical rule. However, as a result of verification, when pulling up a silicon single crystal having a diameter of 450 mm, Table 1 It has been found effective to use a quartz crucible of 36 inches (914 mm) to 44 inches (1118 mm) smaller than the crucible size shown in FIG.

  That is, when a large-sized quartz crucible is used, the convection in the melt becomes more intense, which hinders crystal growth. Further, as described above, when a large amount of silicon raw material is melted using a large-sized quartz crucible, the melting time tends to be long, and deterioration of the crucible surface becomes remarkable.

  2A and 2B are diagrams for explaining the melting state of the silicon raw material in the quartz crucible. FIG. 2A shows the initial charge state, and FIG. 2B shows the middle to late state of melting. Since the silicon raw material 13 filled in the quartz crucible 1a is melted by a heater disposed outside the crucible, the silicon raw material 13 is melted from a location close to the inner surface of the quartz crucible 1a, that is, from the side and below the silicon raw material 13. To go.

When the melting of the silicon raw material 13 progresses and reaches the middle to late stage, the undissolved silicon raw material 13 enters a state of floating in the melt 8 as shown in FIG. At this time, the surface 8a of the melt is in contact with the crucible surface at a certain height position, and the height position is maintained until the undissolved silicon raw material 13 disappears.
In the following description, the phenomenon that the crucible surface is damaged by contact with the melt surface 8a at a certain height is referred to as “liquid level damage”, and the portion of the crucible surface that is in contact with the melt surface 8a is defined as “liquid level damage”. It is called “surface damage part”.

  If the surface of the crucible is in contact with the melt surface 8a and the formation of the liquid surface damage portion is continued for a long time, damage caused by the liquid surface damage on the surface of the crucible in contact with the melt surface 8a becomes significant. Elution and quartz (Si oxide) peeling easily occur. These are incorporated into the crystal during the pulling process, thereby causing dislocation of the single crystal.

  The silicon raw material 13 to be charged into the crucible as the initial charge is made of polycrystalline silicon having various shapes such as rod, lump, or granular, and each is supplied alone or in combination to grow a silicon single crystal. It becomes a raw material of the melt 8. The initial charge shown in FIG. 2 (a) shows a state in which it is supplied in combination.

  Normally, when growing silicon single crystals, the silicon raw material used has a wide variety of shapes, so there is a limit to the amount of solid raw material that can be charged in the crucible, and the target charge amount (final charge amount) is the initial charge. ) Cannot be entered. In the production of large-diameter silicon single crystals, this tendency becomes more prominent.

On the other hand, when the initial charge amount increases, the state where the undissolved silicon raw material floats in the melt as shown in FIG. 2B continues and forms a liquid level damaged portion for a long time.
In order to solve such a problem and replenish the shortage of the melt serving as a crystal raw material to ensure a desired amount of melt, and avoid the formation of a liquid level damaged portion over a long period of time, After the initial charge, an “additional charge” for additionally supplying solid raw materials can be applied.

  3A and 3B are diagrams for explaining the behavior of the melt surface due to the additional charge. FIG. 3A shows the operation of the additional charge, and FIG. 3B shows the behavior of the melt surface due to the additional charge. As shown in FIG. 3 (a), in the additional charge, after the silicon material initially charged in the crucible is melted, the silicon material 13 is further added to the formed melt 8 so that the quartz crucible 1a is filled. The melt amount 8 is increased.

  As shown in FIG. 3B, the additionally charged silicon raw material 13 is in a state of floating in the melt 8 while remaining undissolved, but immediately increases the height position of the surface 8a of the melt, A liquid level damage portion is formed at a position different from the initial charge. The newly formed liquid level damage portion continues until the undissolved silicon raw material 13 is melted.

  That is, by applying the additional charge shown in FIG. 3, the volume of the quartz crucible 1a to be used can be effectively utilized, the melting time of the initially charged silicon raw material 13 can be shortened, and a liquid level damaged portion is newly formed. can do. Thereby, the working efficiency and production efficiency in the production of the silicon single crystal can be improved, and at the same time, the surface deterioration of the quartz crucible 1a depending on the formation time of the liquid level damaged portion can be suppressed.

The present invention has been made on the basis of such findings, and the gist thereof is the following methods (1) to (3) for producing a silicon single crystal.
(1) A method for producing a large-diameter silicon single crystal by the CZ method, in which a silicon raw material initially charged in a quartz crucible at a filling rate of 40 to 60% is melted, and silicon is further filled until a target filling amount is satisfied. After the raw material is additionally charged, the single crystal is pulled up from the melt formed in the quartz crucible. However, the filling rate is represented by (initial charge amount / target filling amount) × 100 (%).

(2) In the method for producing a silicon single crystal according to (1) above, after the silicon material initially charged in the quartz crucible is melted, and further, the silicon material is additionally charged at least twice until the target filling amount is satisfied. It is desirable to pull up the single crystal from the melt formed in the quartz crucible.

(3) Further, in the method for producing a silicon single crystal of (1) and (2) above, when a silicon single crystal having a diameter of 450 mm is pulled using a quartz crucible of 36 inches (914 mm) to 44 inches (1118 mm). It is an optimal manufacturing method.

  According to the method for producing a silicon single crystal of the present invention, it is applied to a technique for producing a large-diameter silicon single crystal having crystal diameters of 400 mm and 450 mm, thereby improving work efficiency and production efficiency in the operation process of the silicon single crystal. Therefore, the melting time of the initially charged silicon raw material is shortened, the deterioration of the crucible surface at the liquid surface damage portion is suppressed, and the dislocation caused by the elution of impurities and the separation of quartz (Si oxide) is prevented. it can.

  Thereby, even when pulling up a large-diameter silicon single crystal, high productivity can be secured and the quality of the obtained silicon single crystal can be stabilized.

  The method for producing a silicon single crystal of the present invention is a method for producing a large-diameter silicon single crystal by a CZ method, wherein a silicon raw material initially charged in a quartz crucible with a filling rate of 40 to 60% is melted, After the silicon raw material is additionally charged until the target filling amount is satisfied, the single crystal is pulled up from the melt formed in the quartz crucible.

  In the manufacturing method of the present invention, a silicon single crystal having a pulling diameter of 450 mm can be targeted. When pulling up a silicon single crystal having a diameter of 450 mm, assuming that the length of the straight body part (body part) is 1800 mm to 2500 mm, the total weight of the pulling is about 800 kg to 1100 kg.

  In order to pull up a silicon single crystal having a diameter of 450 mm, it is effective that the quartz crucible for melting the silicon raw material is 36 inches (914 mm) to 44 inches (1118 mm). It is possible to appropriately control the convection of the melt in the quartz crucible and to efficiently carry in and melt the silicon raw material as will be described later.

  In the manufacturing method of the present invention, an additional charge is applied. Specifically, the initially charged silicon raw material is melted, and the silicon raw material is additionally charged until the target filling amount is satisfied, and then the single crystal is pulled up from the melt formed in the quartz crucible.

  By applying an additional charge, it is possible to limit the initially charged silicon raw material, shorten the melting time, and immediately raise the surface of the melt, thereby forming liquid level damaged portions at different positions on the crucible surface. it can. Thereby, the working efficiency and production efficiency in the production of the silicon single crystal can be improved, and at the same time, the surface deterioration of the quartz crucible can be suppressed.

  In the initial charge to the quartz crucible, the filling rate is set to 40 to 60%. However, the filling rate defined in the present invention is represented by (initial charge amount / target filling amount) × 100 (%).

  Usually, when pulling up a silicon single crystal using a quartz crucible of 30 inches (762 mm) or less, the filling rate is 60 to 70%. However, when this filling rate is applied to a quartz crucible having a large diameter of 36 inches or more, the melting time of the silicon raw material becomes extremely long. For this reason, the upper limit of the filling rate is set to 60%.

  On the other hand, if the filling rate is less than 40%, the initial charge amount becomes too small and the production efficiency may decrease as the number of additional charges increases. Further, since the quartz crucible is exposed to a high temperature in a state where the initial charge amount is excessively small, there is a concern about the bending (deformation) of the quartz crucible. For this reason, the lower limit of the filling rate is set to 40%.

  In the manufacturing method of the present invention, it is desirable that the silicon material initially charged in the quartz crucible is melted and further charged at least twice until the target filling amount is satisfied. By performing the additional charging twice or more, even when a quartz crucible having a large diameter of 36 inches or more is used, the silicon raw material can be charged and melted efficiently in order to achieve the target filling amount. In particular, the melting time of the initially charged silicon raw material can be shortened, the productivity can be ensured, and the surface degradation of the quartz crucible is effective.

  In the manufacturing method of the present invention, the upper limit of the additional charge is not determined, but if the number of additional charges is excessively increased, the production efficiency is lowered. Therefore, the additional charge is set to 5 times or less.

  The contents of the present invention will be described based on the verification results obtained by numerical simulation, assuming the configuration of the pulling apparatus shown in FIG. 1 and assuming the hot zone configuration of 36 inches and 44 inches according to the quartz crucible to be used.

(Example 1: 450 mm diameter x 800 kg weight single crystal pulling)
A silicon single crystal having a diameter of 450 mm, a straight body length of 1800 mm, and a total weight of about 800 kg after pulling was grown. The quartz crucible used was 36 inches (caliber 914 mm, crucible height 600 mm). When a melt is formed to a height of 590 mm in a 36-inch quartz crucible, the weight of the crystal raw material is about 800 kg.

  The filling rate of the initial charge was varied as 40%, 50%, 60% and 70%. In each prepared quartz crucible, rod-shaped, lump-shaped, or granular polycrystalline silicon was compounded as an initial charge. The silicon raw material filled in the quartz crucible is heated by a heater, melted from the side and bottom of the silicon raw material, and dissolved from the state in which the undissolved silicon raw material floats in the melt until there is no undissolved silicon raw material. did. The dissolution time at this time is shown in Table 2.

  After melting the initial charge silicon raw material, additional charge was performed twice to three times mainly using granular polycrystalline silicon. Table 2 shows the charging status of the additional charge at this time.

  From the results shown in Table 2, when the initial charge filling rate exceeds 60% and reaches 70%, the melting time of the silicon raw material becomes extremely long, and the surface damage of the quartz crucible on the melt surface (liquid surface damage portion) is remarkable. Therefore, it is predicted that dislocations will occur in the pulled single crystal.

(Example 2: 450 mm diameter x 1100 kg weight single crystal pulling)
A silicon single crystal having a diameter of 450 mm, a length of the straight body portion of 2500 mm, and a total weight after pulling of about 1100 kg was grown. The quartz crucible used was 44 inches (diameter 1118 mm, crucible height 625 mm). When a melt is formed to a height of 563 mm in a 44-inch quartz crucible, the weight of the crystal raw material is about 1100 kg.

  As in Example 1, the filling rate of the initial charge was changed to 40%, 50%, 60%, and 70%, and polycrystalline silicon was charged as the initial charge into each prepared quartz crucible. The silicon raw material filled in the quartz crucible is heated by a heater and dissolved until there is no undissolved silicon raw material, and the dissolution time is shown in Table 3.

  After melting the initial charge silicon raw material, additional charge was performed twice to three times mainly using granular polycrystalline silicon. Table 3 shows the state of charging the additional charge at this time.

  From the results shown in Table 3, when the initial charge filling rate exceeds 60% and reaches 70%, the melting time of the silicon raw material becomes extremely long, and the surface damage of the quartz crucible becomes remarkable on the melt surface. It is predicted that dislocations will occur.

  According to the method for producing a silicon single crystal of the present invention, it is applied to a technique for producing a large-diameter silicon single crystal having crystal diameters of 400 mm and 450 mm, thereby improving work efficiency and production efficiency in the operation process of the silicon single crystal. This shortens the dissolution time of the silicon raw material that is initially charged, suppresses deterioration on the surface of the crucible due to the melt surface (liquid surface damage portion), and is effective due to impurity elution and quartz (Si oxide) peeling. Dislocation can be prevented.

  As a result, even when pulling up a large-diameter silicon single crystal, high productivity can be secured and the quality of the obtained silicon single crystal can be stabilized at the same time. It can be suitably used.

It is sectional drawing which shows the principal part structure of the pulling apparatus applied to manufacture of the silicon single crystal by CZ method. It is a figure explaining the fusion | melting state of the silicon raw material in a quartz crucible, (a) shows the state of an initial charge, (b) has shown the state of the intermediate | middle to the latter stage of melting. It is a figure explaining the behavior of the melt surface by additional charge, (a) shows operation of the additional charge, (b) has shown the behavior of the melt surface by the additional charge.

Explanation of symbols

1: quartz crucible, 1a: quartz crucible 1b: graphite crucible, 2: heater 3: heat insulating material, 4: main chamber 5: pull chamber, 6: top chamber 7: support shaft, 8: melt 8a: melt surface, 9: Pull-up wire 10: Winding part 10a: Reel 11: Seed crystal 12: Silicon single crystal 13: Silicon raw material

Claims (3)

A method for producing a large-diameter silicon single crystal by the Czochralski method,
After melting the silicon raw material initially charged in the quartz crucible with a filling rate of 40 to 60% and further charging the silicon raw material until the target filling amount is satisfied, a single crystal is obtained from the melt formed in the quartz crucible. A method for producing a silicon single crystal, characterized by pulling up.
Here, the filling rate is expressed as (initial charge amount / target filling amount) × 100 (%).   The silicon material initially charged in the quartz crucible is melted, and the silicon material is additionally charged at least twice until the target filling amount is satisfied, and then the single crystal is pulled up from the melt formed in the quartz crucible. The method for producing a silicon single crystal according to claim 1.   The method for producing a silicon single crystal according to claim 1 or 2, wherein a quartz crucible of 36 inches (914 mm) to 44 inches (1118 mm) is used when pulling up the silicon single crystal having a diameter of 450 mm.

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