JP4788445B2 - Pulling method of silicon single crystal - Google Patents

Description

  The present invention relates to a method for pulling a silicon single crystal using the Czochralski method. More specifically, the inner wall surface of a quartz crucible is efficiently devitrified (crystallized) during the pulling of the silicon single crystal, and the single crystal over a long time. The present invention relates to a silicon single crystal pulling method capable of preventing dislocation during crystal growth and improving productivity without deteriorating crystal quality even when the crystal is pulled.

  There are various methods for producing a silicon single crystal used for a semiconductor substrate. Among them, the Czochralski method (hereinafter referred to as “CZ method”) is widely adopted as a rotational pulling method.

  FIG. 2 is a diagram schematically showing a main configuration of a pulling apparatus suitable for carrying out a silicon single crystal pulling method by the CZ method. The appearance of the pulling device is composed of a chamber (not shown), and a crucible 1 is disposed at the center thereof. The crucible 1 has a double structure, and has a quartz inner layer holding container (hereinafter simply referred to as a “quartz crucible”) 1a having a bottomed cylindrical shape, and the same holding unit adapted to hold the outside of the quartz crucible 1a. It is composed of a bottom cylindrical graphite outer layer holding container (hereinafter simply referred to as “graphite crucible”) 1b.

  These crucibles 1 are fixed to the upper end of a support shaft 6 that can be rotated and lifted. A resistance heating heater 2 is arranged substantially concentrically outside the crucible 1, and a predetermined weight of the silicon raw material for crystallization charged into the crucible 1 is melted to form a melt 3. .

  On the central axis of the crucible 1 filled with the molten liquid 3, a pulling shaft (or wire, hereinafter referred to as “pulling shaft” rotating on the same axis as the support shaft 6 in the reverse direction or in the same direction at a predetermined speed. 5) is provided, and a seed crystal 7 is held at the lower end of the pulling shaft 5.

  In such a pulling apparatus, the raw material for crystallization is put into the quartz crucible 1a, and the raw material for crystallization is melted in the heater 2 disposed around the crucible 1 in an inert gas atmosphere under reduced pressure. The seed crystal 7 held at the lower end of the pulling shaft 5 is immersed in the surface of the melt 3 formed, and the pulling shaft 5 is pulled upward while rotating the crucible 1 and the pulling shaft 5 to A single crystal 4 is grown on the end face.

  As described above, in the pulling of the silicon single crystal by the CZ method, the molten liquid obtained by melting the silicon raw material for crystallization is held by the quartz crucible among the crucibles having a double structure. When this quartz crucible holds a silicon melt, the surface of the crucible is exposed to a high temperature of 1500 ° C. or higher, and the time varies depending on conditions such as the amount of raw silicon filling, crystal growth rate, etc. It will take ten hours.

  Furthermore, recently, in order to increase the productivity of pulling a single crystal, a recharge pulling method (RCCZ method, for example, written by Fumio Shimura, “Semiconductor Silicon Crystal Engineering” p72-73, Maruzen) has been developed. In such a recharge pulling method, the time during which the quartz crucible is exposed to the silicon melt may exceed 100 hours.

  Usually, the surface of the inner wall of the quartz crucible is gradually grown by generating brown cristobalite called a brownish ring while in contact with the silicon melt in a high temperature state. When this brownish ring peels off during the pulling process of a single crystal, it inhibits crystal growth and causes dislocations in the crystal. In order to prevent such crystallization of the inner surface of the crucible (generation of cristobalite) and dislocation accompanying the separation, various countermeasures have been studied.

  First, in Patent Document 1, in a quartz crucible in which an outer wall portion is made of an opaque glass layer and an inner wall portion is made of a transparent glass layer, the transparent glass layer in the curved portion of the crucible is thickened and the opaque glass layer is made thin, thereby becoming a starting point for crystallization. A crucible in which minute bubbles that can be formed is reduced in the vicinity of the surface is disclosed. However, even with low bubbles, there is a problem that crystallization cannot be completely prevented by long-term use, and further, the quartz crucible itself is deformed and the pulling of the silicon single crystal itself cannot be continued.

  Patent Documents 2 and 3 disclose a method for preventing deterioration by applying or containing a crystallization accelerator on the inner wall of a quartz crucible and crystallizing the entire inner surface. However, these methods require a step of uniformly applying a crystallization accelerator to the inner wall of the quartz crucible, and there is a problem in that the manufacturing cost increases. Further, even if a crystallization accelerator is applied to the inner wall of the quartz crucible, if the inner wall of the crucible is soiled for some reason, the effect of applying the crystallization accelerator is lost after washing, and the crucible cannot be used. There is a problem that handling is difficult.

  In order to solve the disadvantages of the quartz crucible coated with the crystallization accelerator described above, in Patent Document 4, in a quartz crucible having a two-layer structure composed of a natural quartz glass outer layer and a synthetic quartz glass inner layer, the synthetic quartz glass inner layer has natural quartz. There has been proposed a quartz crucible containing alkali metal ions of Na, K and Li diffused or moved from the outer glass layer. However, the proposed quartz crucible is intended to promote crystallization of the inner surface of the crucible by containing alkali metal ions, but there is a problem that the alkali metal is taken into the crystal and deteriorates the quality. is there.

  Furthermore, Patent Document 5 proposes a method for producing a single crystal that can prevent an inner wall of a quartz crucible from being deteriorated by applying an electric field to the silicon melt and the crucible, and further repair the deteriorated inner wall. Yes. However, this proposed method also has a problem in that the inner wall of the quartz crucible cannot be completely prevented from being pulled for a long time.

Japanese Patent No. 3136533 Japanese Patent Laid-Open No. 08-2932 Japanese Patent No. 3046545 JP 2003-212690 A Special table 2003-505335 gazette

  The present invention has been made in view of the problems of a conventional pulling method using a quartz crucible, and in the process of pulling a silicon single crystal or in the stage before pulling after melting a silicon raw material, the inner wall surface of the quartz crucible By generating a suitable crystallized layer and stabilizing the surface state of the inner wall, dislocations are prevented during single crystal growth, and single crystal yield and productivity can be achieved even during long-term single crystal pulling operations. An object of the present invention is to provide a silicon single crystal pulling method capable of improving the above.

As a result of detailed studies to solve the above-mentioned problems, the present inventors have melted a silicon raw material in a quartz crucible by the CZ method, and when pulling a single crystal from this melt to grow it, By adding an appropriate amount of barium carbonate (BaCO ₃ ) powder to the silicon raw material, dislocations are prevented during single crystal growth, and even during the operation of pulling a single crystal over a long period of time, It has been found that productivity can be improved.

As described above, when the quartz crucible is used for a long time while holding a high-temperature melt of 1500 ° C. or more, cristobalite appears on the inner wall surface of the quartz crucible in contact with the silicon melt. Then, it gradually grows, part of it peels off from the inner wall surface and penetrates into the growth interface of the silicon single crystal to inhibit the growth of the silicon single crystal, but by adding BaCO ₃ powder to the silicon raw material in the crucible, This is considered to be because an appropriate (that is, uniform and difficult to peel off) crystallized layer is efficiently generated on the entire inner wall of the quartz crucible and the surface state of the inner wall can be stabilized.

The ease of crystallization of the inner wall surface of the quartz crucible differs depending on whether the inner wall of the quartz crucible is synthetic quartz or natural quartz. The former is easier to crystallize, and the inner wall of the crucible is a synthetic quartz layer. In this case, it was found that it is effective to add 0.5 to 35 ppm of BaCO ₃ powder in a mass ratio to the silicon raw material in the crucible, and 1 to 70 ppm in the case of the natural quartz layer. The purity of the BaCO ₃ powder to be added is desirably higher.

Furthermore, studies were made on the method of adding BaCO ₃ powder, and an effective method for preventing the incorporation of CO ₂ produced by thermal decomposition of BaCO ₃ into the silicon single crystal as a carbon source was found.

  The present invention has been made based on such knowledge, and the gist thereof is the following method for pulling a silicon single crystal.

That is, in the method of melting a silicon raw material for crystallization in a quartz crucible by the CZ method and pulling up a single crystal from the melt, the BaCO ₃ powder is added to the silicon raw material in the quartz crucible in a mass ratio to the silicon raw material. In the method for pulling a silicon single crystal, 0.5 to 35 ppm is added when the inner wall of the quartz crucible is a synthetic quartz layer, and 1 to 70 ppm is added when the inner wall is a natural quartz layer. The addition of BaCO ₃ powder to the silicon raw material in the inside is performed in the circumferential direction of the quartz crucible at the outermost surface of the silicon raw material and in the vicinity of the quartz crucible wall 20 to 100 mm away from the inner wall surface of the quartz crucible in the central axis direction. This is a method for pulling a silicon single crystal that is performed by swaying it .

  The term “synthetic quartz layer” as used herein refers to synthetic quartz formed on the inner wall of a normal quartz crucible (that is, the inner surface side of the crucible side wall and bottom) made of natural quartz (quartz) powder. Layer (usually 5 mm or less in thickness). A quartz crucible provided with such a synthetic quartz layer is referred to as a synthetic quartz crucible. The “natural quartz layer” refers to the inner wall of a normal natural quartz crucible made from the natural quartz powder. Here, it is referred to as a natural quartz layer, corresponding to the synthetic quartz layer.

If the purity of the BaCO ₃ powder is 99% or more, there is no concern about the lifetime reduction of the resulting silicon single crystal, which is desirable.

Further, the addition of BaCO ₃ powder into a silicon material in the quartz crucible, a quartz crucible wall near the outermost surface of the silicon material, Ri by the evenly sprinkle it in the circumferential direction of the quartz crucible, the thermal decomposition of BaCO ₃ in generated, Ru can be effectively evacuate the CO ₂ that could be incorporated into a silicon single crystal as the carbon source.

  According to the pulling method of the silicon single crystal of the present invention, the inner wall surface of the quartz crucible can be devitrified efficiently and substantially uniformly in the pulling process of the silicon single crystal or in the stage before pulling after melting the silicon raw material. The surface state of the inner wall can be stabilized, the crystal pieces can be prevented from peeling from the crucible surface, and the single crystal dislocation can be effectively suppressed. Thereby, the yield and productivity of single crystals can be improved without deteriorating crystal quality.

The silicon single crystal pulling method according to the present invention is based on the CZ method. When a single crystal is pulled from a silicon melt in a quartz crucible and grown, BaCO ₃ powder is synthesized into the silicon raw material in the quartz crucible and the inner wall of the crucible is synthesized. In the case of the quartz layer, 0.5 to 35 ppm is added in a mass ratio with respect to the silicon raw material (hereinafter, the added amount (ppm) of BaCO ₃ powder means the mass ratio with respect to the silicon raw material), and the natural quartz layer. In some cases, 1 to 70 ppm is added.

The reason why the BaCO ₃ powder is added to the silicon raw material in the quartz crucible is to allow barium to exist in the silicon melt and to act as a crystallization nucleus on the inner wall surface of the quartz crucible. As a result, a uniform and difficult-to-peel crystallization layer can be efficiently generated on the entire inner wall of the quartz crucible.

The appropriate range of the BaCO ₃ powder addition amount is when using a synthetic quartz crucible in which a synthetic quartz layer is formed on the inner wall of the crucible and when using a normal quartz crucible (natural quartz crucible) in which the inner wall of the crucible is a natural quartz layer. It is different. Since the former is easier to crystallize, the appropriate range of the BaCO ₃ powder addition amount is lower when the inner wall of the crucible is made of synthetic quartz.

That is, in order to obtain an appropriate (that is, uniform and difficult to peel off) crystallized layer on the inner wall surface of the crucible, when the inner wall of the quartz crucible is a synthetic quartz layer, 0.5 ppm or more of BaCO ₃ powder may be added. In contrast, when the inner wall of the crucible is a natural quartz layer, it is necessary to add at least 1 ppm. In order to sufficiently form the crystallized layer, it is desirable to add 10 ppm or more. Further, in order to avoid the crystallization from proceeding excessively and the crystallization layer from being easily peeled off, when the inner wall of the crucible is a synthetic quartz layer, 35 ppm is the upper limit of the amount of BaCO ₃ powder added, whereas the natural quartz layer In this case, the upper limit is 70 ppm.

The addition of BaCO ₃ powder is performed on the silicon raw material in the quartz crucible. That is, it may be added to the silicon raw material that has been put into the quartz crucible before melting or may be added to the silicon raw material after melting. When adding after melting, it is desirable to add immediately after melting. As a result, a uniform and difficult-to-peel crystallization layer is formed on the inner wall surface of the crucible at an early stage, and the surface of the inner wall of the crucible can be used not only in the silicon single crystal pulling process but also before the silicon raw material is pulled up after melting. The state can be stabilized.

Further, there is no particular limitation as to which part of the silicon raw material in the crucible the BaCO ₃ powder is added. However, when the quality of the single crystal, such as the carbon concentration in the silicon single crystal, is important, as described later, it is dispersed in the circumferential direction of the crucible on the surface of the silicon raw material and in the vicinity of the quartz crucible wall. It is desirable to add.

The reason why BaCO ₃ is added in a powder state is to allow rapid dissolution (thermal decomposition) and dispersion in the silicon melt. The particle size is not particularly limited, but it is desirable to use fine BaCO ₃ as long as it does not interfere with handling.

In the method for pulling a silicon single crystal of the present invention, it is desirable that the purity of the BaCO ₃ powder added to the silicon raw material is 99% or more. This is because the silicon single crystal can be used without fear of a decrease in the lifetime.

Considering the behavior of BaCO ₃ added into the crucible, BaCO ₃ is thermally decomposed into BaO and CO ₂ at 1300 ° C. in a silicon melt, and most of the generated CO ₂ is used as it is in a silicon single crystal as a carbon source. Is taken in. Excessive carbon present in the single crystal may cause oxygen precipitates due to heat treatment in the silicon device manufacturing process, thereby deteriorating the quality of the device. Therefore, depending on the device, the carbon concentration in the silicon single crystal is regulated.

When manufacturing a silicon single crystal for a wafer for such a high quality device, when the BaCO ₃ powder is simply added to the inside of the silicon raw material, as described in Example 1 described later, silicon The carbon concentration of the single crystal increases.

For example, when the upper limit of the carbon concentration of the device is defined as 3 × 10 ¹⁶ atoms / cm ³ , the carbon concentration in the silicon melt is 3 × in order to satisfy this regulation throughout the silicon single crystal to be pulled up. It must be about 10 ¹⁶ atoms / cm ³ or less. If the carbon concentration mixed from the carbon member in the furnace is 1 × 10 ¹⁶ atoms / cm ³ , the remaining 2 × 10 ¹⁶ atoms / cm ³ is the carbon concentration allowed as BaCO ₃ . This is about 2.9 ppm in terms of the amount of BaCO ₃ powder added, and the amount of BaCO ₃ powder added to the crucible is limited to this value or less. Therefore, there is a possibility that a sufficient crystallized layer cannot be obtained particularly when a natural quartz crucible whose inner wall surface is difficult to crystallize compared to a synthetic quartz crucible is used. If the carbon concentration of the device is more stringent, the allowable amount of BaCO ₃ powder added is further limited.

Therefore, even if there is a possibility that BaCO ₃ can be used instead of BaO, it is necessary to examine in detail the conditions for fully exerting the action and effect of the added BaCO ₃ , such as the amount and method of addition. .

In the single crystal pulling method of the present invention, the amount of BaCO ₃ powder added is as described above, and the appropriate range is defined by whether the inner wall of the quartz crucible used is a synthetic quartz layer or a natural quartz layer. The

On the other hand, the method of adding the BaCO ₃ powder, the addition of BaCO ₃ powder into a silicon material in the quartz crucible, a quartz crucible wall near the outermost surface of the silicon raw material, by sprinkle evenly in the circumferential direction of the quartz crucible It is desirable to adopt the embodiment described above.

FIG. 1 is an explanatory view of a method of adding BaCO ₃ powder into a quartz crucible when this embodiment, that is, the method for pulling a silicon single crystal of the present invention is carried out. As shown in the figure, the addition of BaCO ₃ powder is performed evenly in the circumferential direction of the crucible 1a on the outermost surface of the melt 3 held in the quartz crucible 1a and in the vicinity of the wall of the quartz crucible 1a. Do this by shaking. The illustrated example shows a BaCO ₃ powder 8 to which a silicon raw material is melted and a hatched portion in the drawing is added. Even if the silicon raw material is not melted, it may be added uniformly in the same manner as described above.

Here, “spread evenly in the circumferential direction of the crucible” means that the BaCO ₃ powder is dispersed in the circumferential direction of the crucible (that is, over the entire circumference) so that the added amount is seemingly equal. It is not always necessary to disperse them to be strictly equal.

The “near the quartz crucible wall” is a place slightly away from the inner wall surface of the crucible. Although it depends on the size of the crucible, a place that is about 20 to 100 mm away from the inner wall surface of the crucible in the central axis direction is desirable. If BaCO ₃ powder is added so as to be in direct contact with the inner wall of the quartz crucible, only that portion is vigorously devitrified and crystallization progresses excessively. In some cases, it is peeled off from the dough layer of the crucible, which is not desirable.

Thus, by adding BaCO ₃ powder on the top surface of the silicon material, evacuated without fastening the CO ₂ into the melt inside, that CO ₂ can be inhibited from being taken as a carbon source to the silicon single crystal it can. Furthermore, by adding it in the vicinity of the quartz crucible wall, it is possible to promote an appropriate reaction with quartz, and to facilitate the formation of a crystallization layer by acting as a crystallization nucleus on the inner wall surface of the quartz crucible. Become.

That is, by adopting such a method of adding BaCO ₃ powder into the crucible, it is possible to achieve both substantially uniform crystallization (devitrification) on the inner wall surface of the quartz crucible and suppression of an increase in carbon concentration in the silicon single crystal. Can do.

  In order to confirm the effect of the silicon single crystal pulling method of the present invention, the silicon single crystal is pulled under various conditions using the pulling apparatus shown in FIG. 2, and the carbon concentration of the single crystal, the state of the inner wall of the crucible, The crystal yield was investigated.

(Example 1)
A quartz crucible 1a having an inner diameter of 600 mm (using a natural quartz crucible) is filled with 150 kg of silicon raw material, and the addition amount of BaCO ₃ powder (purity: 99.9%) is changed to form a melt 3. The single crystal 4 was pulled up by 1600 mm. At that time, the carbon concentration of the single crystal is compared between the case where the BaCO ₃ powder is simply added to the inside of the raw material in the crucible and the case where it is added using the addition method shown in FIG. did. The addition of BaCO ₃ powder was performed on the silicon raw material after melting. Further, in the addition method shown in FIG. 1, “the vicinity of the quartz crucible wall” was set at a location about 30 mm away from the inner wall surface of the crucible, and BaCO ₃ powder was sprinkled in the circumferential direction of the crucible at that position.

The result is shown in FIG. In the figure, the horizontal axis represents the Ba concentration (atoms / cm ³ ) converted from the added amount of BaCO ₃ powder, which is equal to the added carbon (C) concentration (atoms / cm ³ ). The vertical axis represents the carbon concentration of the pulled single crystal (carbon concentration at the position where the pulling rate is 70%). Also, the ● mark in the figure shows the method of adding BaCO ₃ powder into the silicon raw material in the crucible (hereinafter referred to as “raw material internal addition method”), and the ▲ mark indicates the single crystal pulling method of the present invention. This is a case where the addition method shown in FIG. 1 is used (hereinafter referred to as “the present invention method”).

As shown in FIG. 3, the carbon concentration of the silicon single crystal increases with an increase in the amount of BaCO ₃ powder added in both the raw material internal addition method and the present invention method. Even with the amount of BaCO ₃ powder added, the carbon concentration of the silicon single crystal was lower than in the case of the raw material internal addition method. In the Ba concentration range shown in FIG. 3, Ba was not detected from the pulled silicon crystal, and there was no difference in the lifetime of the single crystal.

4 and 5 are diagrams schematically illustrating the state of the inner wall of the crucible after the single crystal is pulled. 4 shows the state of the inner wall of the crucible when 2.2 g of BaCO ₃ powder is added by the raw material internal addition method, and FIG. 5 shows the state of the inner wall of the crucible when 2.2 g of BaCO ₃ powder is added by the present invention method. Show.

As shown in FIG. 4, when BaCO ₃ powder is added to the inside of the raw material, the devitrification zone 9, the crystallization zone 10 and the brownish ring generation zone 11 are mixed, but when added by the method of the present invention As shown in FIG. 5, the crucible upper part is a devitrification region 9 and the crucible lower part is the entire crystallization region 10, and no brownish ring occurred.

Under the above conditions (that is, the amount of BaCO ₃ powder added is 2.2 g), BaCO ₃ powder is added to the silicon raw material by the raw material internal addition method or the present invention method, and each 10 batches of silicon single crystal is pulled up. It was. As a result, when the raw material internal addition method is used (at this time, the inner wall of the crucible exhibits the state illustrated in FIG. 4), 2 batches out of 10 batches generate dislocations in the crystal during the pulling of the single crystal. It was. However, when the method of the present invention was used (the inner wall of the crucible exhibited the state illustrated in FIG. 5), all 10 batches were dislocation-free throughout the single crystal.

(Example 2)
A quartz crucible 1a having an inner diameter of 600 mm (using a natural quartz crucible) is filled with 150 kg of silicon raw material to obtain a melt 3. Then, 2.2 g of BaCO ₃ powder with a purity of 99.9% (14.7 ppm by mass with respect to the silicon raw material) ) Was added by the method of the present invention, the single crystal 4 having a diameter of 200 mm was pulled up, and the single crystal yield was compared with the case where no BaCO ₃ powder was added.

  In this pulling of the silicon single crystal, first, a 1000 mm single crystal is grown, and after pulling up and taking out this single crystal, a silicon raw material having the same mass is put into the crucible to grow a single crystal of 1000 mm again. It was. Further, after pulling up and taking out this single crystal, a silicon raw material having the same mass as this was charged to pull up a 1600 mm silicon single crystal.

As a result, all three single crystals pulled up were dislocation-free over the entire region, and the crucible was not deformed at all even though the pulling time reached 150 hours. On the other hand, when no BaCO ₃ powder was added, dislocation occurred in the pulled third single crystal, and the straight body of the crucible was slightly deformed.

The three continuous pulling was carried out for each of the five batches when the BaCO ₃ powder was added by the method of the present invention and when the BaCO ₃ powder was not added (comparative example), and the single crystal yields were compared. The single crystal yield was obtained by “(mass of dislocation-free silicon single crystal / mass of silicon raw material used) × 100 (%)”.

The result is shown in FIG. As is clear from this figure, the yield of the single crystal was greatly improved as compared with the comparative example when BaCO ₃ powder was added according to the method of the present invention.

(Example 3)
Example 1 except that a synthetic quartz crucible whose inner wall is a synthetic quartz layer was used, and the amount of BaCO ₃ powder added was 1 g (mass ratio to the silicon raw material was 6.7 ppm, and 2.2 g was added in Example 1). Under the same conditions as above, that is, a crucible with an inner diameter of 600 mm is filled with 150 kg of silicon raw material to form a molten liquid, then BaCO ₃ powder is added by the method of the present invention, and 10 batches of a single crystal having a diameter of 200 mm and 1600 mm are carried out did.

As a result, all single crystals were dislocation-free throughout. When the inner wall of the crucible is a synthetic quartz layer, crystallization is quicker than that of a natural quartz layer. Therefore, even if the addition amount of BaCO ₃ powder is small, the same crystallization effect as in Example 1 can be obtained. It could be confirmed.

Example 4
A quartz crucible with an inner diameter of 800 mm (using a natural quartz crucible) is filled with 300 kg of silicon raw material, and a silicon single crystal with a diameter of 300 mm is melted in the same manner as in Example 1, that is, the silicon raw material in the crucible is melted. After preparing the liquid, BaCO ₃ powder was added to pull up _three single crystals of 1600 mm. In this case, 5 g of BaCO ₃ powder (19 ppm by mass ratio with respect to the silicon raw material) was used, but the crucible was deep, and 3.5 g was added by the method of the present invention, and the remaining 1.5 g was slightly below the silicon raw material. Added to.

  As a result, all single crystals were dislocation-free throughout, and the entire inner wall of the crucible exhibited a uniform devitrification state.

The silicon single crystal pulling method of the present invention is a method of pulling a single crystal from a silicon melt in a quartz crucible and growing it by the CZ method. The silicon raw material in the quartz crucible has a predetermined amount according to the structure of the inner wall of the crucible. By adding BaCO ₃ powder, the inner wall surface of the quartz crucible can be efficiently and substantially devitrified. As a result, the surface state of the inner wall is stabilized, and even during the operation of pulling up a silicon single crystal over a long period of time, it prevents the crystal pieces from peeling from the crucible surface and the deformation of the crucible, and suppresses dislocation of the single crystal. Thus, the single crystal yield and productivity can be improved.

  Therefore, the silicon single crystal pulling method of the present invention can be suitably used for the production of a silicon single crystal.

It is an illustration of a BaCO ₃ powder addition method into the quartz crucible for performing in practicing the pulling method of a silicon single crystal of the present invention. It is a figure which shows typically the structural example of the silicon single crystal pulling-up apparatus suitable for implementation of the manufacturing method of this invention. It is a diagram showing a relationship between carbon concentration of BaCO ₃ powder added amount and the silicon single crystal into the silicon material in the quartz crucible. The state of the crucible inner wall after the single crystal pulling terminated in case of adding BaCO ₃ powder in the silicon raw material is a diagram schematically illustrating. The state of the crucible inner wall after the single crystal pulling terminated in case of adding BaCO ₃ powder as the silicon source in addition method used in pulling method of a silicon single crystal of the present invention is a diagram schematically illustrating. It is a figure which shows the influence which the pulling method of the silicon single crystal of this invention has on a single crystal yield.

Explanation of symbols

1: crucible 1a: quartz crucible 1b: graphite crucible 2: heater 3: molten liquid 4: single crystal 5: pulling shaft 6: support shaft 7: seed crystal 8: BaCO ₃ powder 9: devitrification zone 10: crystallization zone 11 : Brown ring generation area

Claims (2)

In the method of melting a silicon raw material for crystal in a quartz crucible by the Czochralski method and pulling up a single crystal from this melt,
When BaCO ₃ powder is added to the silicon raw material in the quartz crucible in a mass ratio with respect to the silicon raw material and the inner wall of the quartz crucible is a synthetic quartz layer, 0.5 to 35 ppm is added. Is a pulling method of a silicon single crystal to which 1 to 70 ppm is added ,
The addition of BaCO ₃ powder to the silicon raw material in the quartz crucible is carried out on the outermost surface of the silicon raw material and in the vicinity of the quartz crucible wall 20 to 100 mm away from the inner wall surface of the quartz crucible in the central axis direction. A method for pulling a silicon single crystal, wherein the method is performed by swinging evenly in a direction . The method for pulling a silicon single crystal according to claim 1, wherein the purity of the BaCO ₃ powder is 99% or more.

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