JP7020437B2 - Method for manufacturing silicon single crystal - Google Patents

Description

The present invention relates to a method for producing a silicon single crystal.

There is a CZ (Czochralski) method as a crystal growth method widely used for obtaining a silicon single crystal. In the CZ method, a silicon polycrystalline raw material is melted in a quartz pot to form a silicon melt (raw material melt, also called "melt"), and then the seed crystal is brought into contact with the melt and pulled up to form a single crystal. Is nurturing. Conventionally, silicon single crystals grown by the CZ method have often been used mainly as substrate materials for logic and memory. With respect to these devices, the required impurity concentration is becoming lower due to the progress of miniaturization of the device. Furthermore, in recent years, silicon single crystals grown by the CZ method have come to be used in power device applications and image sensor applications as well, and the types and concentrations of impurities that are problematic in these devices are changing. .. It is becoming more important than ever to control the concentration of impurities in crystals in order to meet the different requirements of each device.

Carbon impurities are one of the problematic impurities in single crystal silicon grown by the CZ method, and various efforts have been made in the long history of the CZ method to reduce the carbon concentration in the crystals. There is.

There are two types of carbon mixed in the silicon single crystal, one is caused by bringing in from the raw material and the other is caused by the reaction in the furnace during the crystal manufacturing process. Has been reported.

Regarding bringing in from raw materials, some organic substances adhering to the surface of raw material silicon are carbonized without being vaporized at high temperatures, and there is a problem that the carbon concentration in the crystals increases when these are incorporated into the crystals. .. In order to improve this, for example, a method of growing a single crystal by the CZ method using a polycrystalline raw material stored in a polyethylene storage bag having less organic contamination such as paraffinic hydrocarbons of Patent Document 1, Patent Document. Examples thereof include a method in which an organic substance on the surface of the polycrystal of No. 2 is identified, quantitatively analyzed, raw materials are selected, and then a single crystal is grown by the CZ method. These technologies focus on carbon contamination brought in from silicon raw materials.

On the other hand, regarding carbon contamination caused by the crystal manufacturing process, carbon-containing gas is generated in the furnace by the reaction between the carbon member in the pulling machine furnace and SiO evaporating from the silicon raw material melt during crystal growth, and this is the raw material melting. There is a problem that the carbon concentration rises when mixed in the liquid. In order to improve this, for example, a method of mounting a cylindrical rectifying member on the graphite crucible of Patent Document 3 to prevent backflow of carbon-containing gas to reduce carbon contamination, or an inert gas of Patent Document 4. There is a method of reducing carbon contamination by specifying conditions such as flow rate, furnace pressure, and heater power. Patent Documents 3 and 4 are all techniques for trying to reduce carbon contamination caused by the crystal manufacturing process by paying attention to the flow direction and the flow velocity of the inert gas during the melting of the raw material and the growth of the crystal.

Normally, the carbon concentration in the crystal is quantified by the FT-IR method, but the lower limit of carbon concentration detection in this method is about 5 × 10 ¹⁴ atoms / cm ³ even if the number of integrations and the reference are improved. be. In order to solve this problem, Patent Document 5 and Non-Patent Document 1 disclose a quantification method using a photoluminescence (PL) method. In particular, Non-Patent Document 2 reports that a carbon concentration of about 3 × 10 ¹³ atoms / cm ³ could be quantified, and the PL method is effective for quantifying a carbon concentration of 5 × 10 ¹⁴ atoms / cm ³ or less. It is a method. However, the PL method is not suitable for in-line measurement because electron beam irradiation is required as a pretreatment for measuring the carbon concentration and the number of steps required for quantifying the carbon concentration increases. Therefore, in the method of quantifying by the PL method every time the crystal growth is completed and controlling the carbon crystal concentration in the crystal based on the quantification result, from the time when the crystal growth is completed until the carbon concentration in the crystal is known. There was a problem that it took a long time and the production efficiency was lowered.

Japanese Unexamined Patent Publication No. 2016-113198 Japanese Unexamined Patent Publication No. 2016-210637 Japanese Unexamined Patent Publication No. 2012-201564 JP-A-2015-017019 Japanese Unexamined Patent Publication No. 04-344443

M. Nakamura et al. , J. Electorochem. Soc. 141 (1993) 3576 Satoko Nakagawa Applied Physics Vol. 84, No. 11 (2015)

The present invention has been made to solve the above problems, and efficiently and easily estimates the carbon concentration in a silicon single crystal produced by the Czochralski method, and the carbon concentration of the silicon single crystal is satisfied. The purpose is to provide a method for determining standards. The present invention also provides a method for efficiently and easily estimating the carbon concentration in a silicon single crystal produced by the Czochralski method and controlling the carbon concentration based on the estimation. Also aims.

In order to achieve the above object, the present invention comprises a raw material melting step of heating a silicon raw material contained in a rutsubo with a heater to melt it into a raw material melt, and heating the raw material melt with the heater. However, in the method for manufacturing a silicon single crystal having a pulling step of pulling the silicon single crystal from the raw material melt, the integrated value ΣPower × Δt calculated from the time difference Δt which is the difference between the heater power power of the heater and the time t. Based on the above, the carbon concentration Cs in the silicon single crystal obtained after the pulling up is estimated, and the standard to be satisfied by the carbon concentration of the silicon single crystal obtained after the pulling up is determined based on the estimated carbon concentration Cs. Provided is a method for producing a silicon single crystal, which is characterized by the above.

In such a method for manufacturing a silicon single crystal, the carbon concentration in the silicon single crystal is estimated from the integrated value ΣPower × Δt (hereinafter, may be simply referred to as “integrated value”) of the heater power and time during operation. Therefore, it is possible to efficiently and easily determine the standard that the carbon concentration of the silicon single crystal obtained after pulling up meets. This eliminates the need to quantify the carbon concentration in the crystal each time the growth of the silicon single crystal is completed, so that the production efficiency can be improved.

At this time, before pulling up the silicon single crystal, the correlation between the carbon concentration Cs and the integrated value ΣPower × Δt was obtained in advance, and after pulling up the silicon single crystal, the silicon single crystal was pulled up. It is preferable to calculate the value of the integrated value ΣPower × Δt and estimate the carbon concentration Cs of the raised silicon single crystal from the calculated value and the correlation.

In this way, by obtaining the correlation between the carbon concentration Cs and the integrated value ΣPower × Δt in advance, it is possible to more accurately estimate the carbon concentration Cs of the raised silicon single crystal.

Further, at this time, it is preferable to obtain the correlation obtained in advance for each pulling machine for pulling the silicon single crystal.

In this way, by obtaining the correlation between the carbon concentration and the integrated value for each raising machine, the correlation can be obtained according to the situation peculiar to the pulling machine, so that the carbon in the silicon single crystal to be pulled up more accurately can be obtained. The concentration can be estimated.

Further, in the method for producing a silicon single crystal of the present invention, after pulling up the silicon single crystal, an integrated value ΣPower × Δt is calculated from the heater power Power and time t at the time of pulling up the silicon single crystal, and the calculated integration is performed. When the value ΣPower × Δt is less than 2861 kW · h, the standard of carbon concentration Cs of Cs <1.0 × 10 ¹⁴ atoms / cm ³ is applied to the silicon single crystal at the solidification rate of 20 to 60% of the raised silicon single crystal. When the product is sorted as a product to be satisfied and the calculated integrated value ΣPower × Δt is 2861 kW · h or more, the silicon single crystal at the solidification rate of 20 to 60% of the raised silicon single crystal has a carbon concentration Cs of Cs ≧ 1.0 ×. It can be sorted as a product that meets the standard of 10 ¹⁴ singles / cm ³ .

Specifically, in this way, products can be sorted according to the carbon concentration standard satisfied by the raised silicon single crystal.

Further, the heater power Power used for calculating the integrated value ΣPower × Δt is the heater power in the raw material melting step, the heater power from the end of the raw material melting step to the start of the pulling step, and once said. It is preferable to use the heater power in the remelting step when the silicon single crystal that has been pulled up halfway is remelted. Further, at this time, it is preferable that the time t used for calculating the integrated value ΣPower × Δt is a time when the temperature of the silicon raw material is 900 ° C. or higher.

By using the heater power used to calculate the integrated value as these steps, it is possible to use the process in which carbon is significantly mixed in the silicon raw material melt during the silicon single crystal manufacturing process to calculate the integrated value, making it more accurate. Moreover, the carbon concentration in the raised silicon single crystal can be easily estimated. Further, by using the time when the temperature of the silicon raw material is 900 ° C. or higher for the calculation of the integrated value, the carbon concentration in the raised silicon single crystal can be estimated more accurately and easily.

Further, it is preferable that the time difference Δt used for calculating the integrated value ΣPower × Δt is in the range of 10 seconds or more and 10 minutes or less.

By setting the time difference Δt within such a range, the integrated value can be obtained more accurately even when the heater power fluctuates.

Further, it is preferable to calculate the integrated value Power × Δt from the area of the trapezoid formed by the two heater power powers and the time Δt in the interval [t, t + Δt].

Specifically, the calculation of the integrated value can be performed by such a method.

Further, in the method for producing a silicon single crystal of the present invention, it is preferable to use a semiconductor-grade high-purity raw material as the silicon raw material.

By using such a silicon raw material, the carbon concentration in the raised silicon single crystal can be estimated more accurately from the above integrated value.

Further, the present invention comprises a raw material melting step of heating a silicon raw material contained in a rutsubo with a heater to melt the raw material into a raw material melt, and heating the raw material melt with the heater while heating the raw material melt. In the method for manufacturing a silicon single crystal having a pulling step of pulling up the silicon single crystal from the above, before pulling up the silicon single crystal, it is calculated in advance from the heater power Power of the heater and the time difference Δt which is the difference of the time t. The correlation between the integrated value ΣPower × Δt and the carbon concentration Cs in the silicon single crystal obtained after the pulling up is obtained, and the heater power Power of the heater and the time t are adjusted based on the correlation. By doing so, the present invention provides a method for producing a silicon single crystal, which comprises controlling the carbon concentration Cs of the silicon single crystal when the silicon single crystal is pulled up.

In this way, it is also possible to manufacture a silicon single crystal in which the carbon concentration in the raised silicon single crystal is controlled based on the correlation between the integrated value and the carbon concentration.

With the method for producing a silicon single crystal of the present invention, the carbon concentration in the silicon single crystal produced by the Czochralski method is estimated efficiently and easily, and the standard satisfied by the carbon concentration of the silicon single crystal is determined. Can be a method. As a result, it is not necessary to quantify the carbon concentration in the silicon single crystal every time the silicon single crystal growth is completed, so that the time required from the completion of the silicon single crystal growth to the determination of the quantification result can be reduced. This makes it possible to improve production efficiency. Further, the present invention can efficiently and easily estimate the carbon concentration in the silicon single crystal produced by the Czochralski method, and control the carbon concentration in the silicon single crystal based on this.

It is a graph which showed an example of the relationship between the carbon concentration Cs in a silicon single crystal and the integral value ΣPower × Δt. It is a flow chart which concretely showed the outline of the manufacturing method of the silicon single crystal of this invention. In the example, it is a graph which showed the Cs concentration in the straight cylinder of the silicon single crystal at ΣPower × Δt = 2247kW · h. In the comparative example, it is a graph which showed the Cs concentration in the straight cylinder of the silicon single crystal at ΣPower × Δt = 3686kW · h. It is a flow chart which showed the outline of the manufacturing method of the silicon single crystal by a general Czochralski method.

Hereinafter, the present invention will be described in detail with reference to the drawings as an example of embodiments, but the present invention is not limited thereto.

The method for producing a silicon single crystal of the present invention comprises a raw material melting step of heating a silicon raw material contained in a rut with a heater to melt it into a raw material melt, and heating the raw material melt with a heater. It has a pulling process of pulling up a silicon single crystal from the raw material melt, and is obtained after pulling up based on the integrated value ΣPower × Δt calculated from the time difference Δt which is the difference between the heater power power of the heater and the time t. It is characterized in that the carbon concentration Cs in a silicon single crystal is estimated, and the standard to which the carbon concentration of the silicon single crystal obtained after raising is satisfied is determined based on the estimated carbon concentration Cs.

The pulling machine that can be used in the method for producing a silicon single crystal of the present invention and the structure of the HZ (hot zone) of the pulling machine are the same as those of a general CZ silicon single crystal pulling machine. The present invention can be widely applied not only to the Czochralski method (CZ method) in which no magnetic field is applied, but also to a method for producing a silicon single crystal grown by the magnetic field applied CZ method (MCZ method).

An outline of a general method for producing a silicon single crystal will be described with reference to FIG. As shown in S1 of FIG. 5, first, as a raw material melting step, the silicon raw material contained in the crucible is heated by a heater to melt it into a raw material melt. Next, the silicon single crystal is pulled up from the raw material melt (S3 in FIG. 5), but usually, the raw material melt has a step of leaving it for a predetermined time for the purpose of degassing the melt. This may be referred to as a power leaving step (S2 in FIG. 5). After the power leaving step (S2), there is a pulling step (S3 in FIG. 5). In the pulling step, a seeding step of attaching the seed crystal to the raw material melt, a shoulder part forming step, a straight body part forming step, and rounding are performed. The part formation stage and the like are included. Further, when a dislocation occurs in the silicon single crystal during the pulling process, a remelting step of remelting the silicon single crystal is included.

After the completion of the pulling step (S3), an afterheat step (AH step, S4 in FIG. 5) for cooling the silicon single crystal or the like is performed. After that, a take-out step (S5 in FIG. 5) of taking out the silicon single crystal from the pulling machine is performed.

In the present invention, the carbon concentration in the raised silicon single crystal is estimated based on the integrated value of the heater power and the time for such a general method for producing a silicon single crystal. At that time, it is preferable to obtain the correlation between the carbon concentration Cs and the integrated value ΣPower × Δt in advance before pulling up the silicon single crystal (before S1 in FIG. 5). Further, after pulling up the silicon single crystal (after S3 in FIG. 5), the integrated value ΣPower × Δt when the silicon single crystal was pulled up was calculated and pulled up from the calculated value and the above correlation. The carbon concentration Cs of a silicon single crystal can be estimated. In other words, the present invention uses the fact that in the pulling machine, the carbon concentration Cs in the pulled silicon single crystal correlates with the integrated value ΣPower × Δt of the heater power during operation and the time, and the integrated value ΣPowerer. This is a method for estimating the carbon concentration from the value of × Δt. Therefore, it is possible to know the carbon concentration at the same time as the growth of the silicon single crystal is completed.

As described above, in the method for producing a silicon single crystal of the present invention, a silicon single crystal can be pulled up by using a general CZ silicon single crystal pulling machine or a hot zone structure thereof. At this time, since the temperature in the furnace, the surface area of the graphite member, and the linear velocity of the inert gas are different for each pulling machine, that is, for each structure of the hot zone, the pulling machine for pulling the silicon single crystal has the above-mentioned correlation obtained in advance. It is preferable to obtain it separately.

The method for producing a silicon single crystal of the present invention efficiently and easily estimates the carbon concentration in a silicon single crystal from the integrated value ΣPower × Δt of the heater power and time during operation, so that the silicon obtained after pulling up can be efficiently and easily obtained. It is possible to determine the standard that the carbon concentration of a single crystal meets. This eliminates the need to measure and quantify the carbon concentration in the crystal by FT-IR or the like each time the growth of the silicon single crystal is completed, so that the production efficiency can be improved.

A more specific embodiment of the method for producing a silicon single crystal of the present invention will be described with reference to FIG.

First, as shown in FIG. 2A, before manufacturing the product, the carbon concentration Cs in the pulled-up silicon single crystal was obtained with respect to the pulling machine to be used for the method for manufacturing the silicon single crystal of the present invention. , The correlation of the integrated value ΣPower × Δt is obtained. This correlation can be obtained experimentally as follows. With respect to the silicon single crystal actually pulled up by the target pulling machine, the carbon concentration in the silicon single crystal is measured by using the photoluminescence method (PL method) or the like. Further, the above integrated value is obtained from the actual heater power and time in each step in the production of the silicon single crystal. This correlation does not necessarily have to be obtained from pulling up the silicon single crystal for the purpose of experiment only, but can also be obtained from the actual data of the silicon single crystal manufactured as an actual product. The carbon concentration and the integrated value have a correlation as shown in FIG. 1 obtained in the examples described later.

At this time, the heater power Power used for calculating the integrated value ΣPower × Δt is the heater power in the raw material melting step (S1 in FIG. 5), from the end of the raw material melting step to the start of the pulling step (power leaving step, It can be the heater power in S2) of FIG. 5 and the heater power in the remelting step when the silicon single crystal once performed halfway in the pulling step is remelted.

After obtaining the above correlation in advance as shown in FIG. 2 (A), then, as shown in FIG. 2 (B), the standard upper limit value of the carbon concentration Cs in the silicon single crystal is set, and the heater is set. From the correlation between the integrated value ΣPower × Δt of power and time, the threshold value of the integrated value ΣPower × Δt is set so that the carbon concentration Cs in the crystal becomes equal to or less than the standard upper limit value.

Next, as shown in FIG. 2 (C), the power leaving step (S2 in FIG. 5) is advanced from the raw material melting step (S1 in FIG. 5).

Next, as shown in FIG. 2D, in the pulling step (S3 in FIG. 5), the straight body portion forming step is advanced from the seeding step.

After that, as shown in FIG. 2 (E), branching occurs depending on whether or not dislocations have occurred. If the remelting step due to dislocation is not performed before the straight body portion forming step, the rounded portion forming step and thereafter (rounded portion forming step, the afterheat (AH) step of S4 in FIG. 5; (S5 crystal extraction step) ((J) in FIG. 2).

If dislocations occur from the seeding step to the straight body formation step, the remelting step is performed, so the integrated value ΣPower × Δt may reach a value higher than the threshold value during the single crystal pulling step. There is. Therefore, when remelting is performed, the integrated value ΣPower × Δt of the heater power and time is calculated after the completion of remelting ((F) in FIG. 2). When the remelting is completed, the integrated value and the threshold value are compared ((G) in FIG. 2), and when the integrated value ΣPower × Δt <threshold value, the silicon single crystal pulling step (S3 in FIG. 5) is performed again. From the seeding stage to the straight body formation stage ((D) in FIG. 2).

On the other hand, if the integrated value ΣPower × Δt ≧ threshold value is reached when the remelting is completed, the product manufacturing is switched to the carbon concentration Cs ≧ standard upper limit value ((H) in FIG. 2). After switching to the production of a product having a carbon concentration Cs ≧ the upper limit of the standard value, the silicon single crystal pulling step (S3 in FIG. 5) and subsequent steps are performed to pull up the silicon single crystal. In this case as well, the remelting step is performed as necessary. In this way, a silicon single crystal is produced as a product having a carbon concentration of Cs ≧ the upper limit of the standard.

As described above, if the integrated value ΣPower × Δt <threshold value after the remelting step, the seeding step to the straight body forming step in the silicon single crystal pulling step (S3 in FIG. 5) are performed again. Proceed ((D) in FIG. 2). In this case, the presence or absence of dislocations is determined again ((E) in FIG. 2), and if dislocations do not occur, the process shifts to the rounded portion forming stage or later ((J) in FIG. 2). When dislocations occur, the remelting step is performed again, the integrated value ΣPower × Δt is calculated, and the integrated value and the threshold value are compared ((F), (G) in FIG. 2).

In the case of shifting to after (J) of FIG. 2, that is, after the rounded portion forming step (rounded portion forming step, the afterheat step of S4 of FIG. 5, the crystal taking-out step of S5 of FIG. 5), after the crystal taking-out step is completed, The integrated value ΣPower × Δt is calculated and compared with the threshold value ((L) in FIG. 2). If the integrated value ΣPower × Δt <threshold value, the product is distributed as a product with carbon concentration Cs <standard upper limit value ((M) in FIG. 2), and if the integrated value ΣPower × Δt ≧ threshold value, the carbon concentration Cs ≧ standard upper limit value. Sort as a product ((I) in FIG. 2).

Although there are the above steps, the heater power Power used when calculating the integrated value ΣPower × Δt is the heater power in the raw material melting step and the power leaving step (pulled up after the completion of the raw material melting step) as described above. It can be the heater power (until before the start of the process). When it is necessary to perform the remelting step, it is preferable that the heater power in the remelting step is also included in the calculation of the integrated value. Further, among these steps, it is preferable that the other steps (for example, S4: afterheat step and S5: take-out step in FIG. 5) are not included in the calculation of the integrated value. This is because the inclusion of carbon in the silicon single crystal during the silicon single crystal manufacturing process is due to the carbon-containing gas generated by the reaction between the carbon member in the puller furnace and the SiO gas evaporating from the silicon melt. Because it is. That is, in the silicon single crystal manufacturing process, the carbon-containing gas generated by the reaction between the carbon member and the SiO gas has a characteristic that the heater power is higher than that of other processes and the evaporation area of SiO is the largest. This is because the power is mainly generated in the three steps of the power leaving step and the remelting step in which the heater power is higher than that of the other steps.

Further, among these three steps, it is considered that the carbon-containing gas generation becomes remarkable when the temperature inside the furnace is high, such as when the temperature of the silicon raw material is high. Therefore, the time t used for calculating the integrated value ΣPower × Δt is set to the time when the temperature of the silicon raw material is 900 ° C. or higher among the three steps of the raw material melting step, the power leaving step, and the remelting step. Is preferable. That is, the heater power when the temperature of the silicon raw material is 900 ° C. or higher and the time difference Δt at the time t are used for calculating the integrated value.

Further, it is preferable that the time difference Δt used for calculating the integrated value ΣPower × Δt is in the range of 10 seconds or more and 10 minutes or less. By setting the time difference Δt within such a range, the integrated value can be obtained more accurately even when the heater power fluctuates during each process. Fluctuations in heater power can occur, for example, due to changes in brightness as the crucible joint passes through the pyrohole. The step size of Δt is more preferably 30 seconds or more and 5 minutes or less, and particularly preferably 1 minute.

The integrated value Power × Δt can be calculated from the area of the trapezoid formed by the two heater power powers and the time Δt in the interval [t, t + Δt]. That is, the above integrated value can be obtained by adding all the areas of the trapezoid formed by the arbitrary interval [t, t + Δt] and the two powers. In particular, it is preferable to obtain it from the total area of the trapezoid in the region where the temperature of the silicon raw material is 900 ° C. or higher among the three steps of the raw material melting step, the power leaving step, and the remelting step.

As the silicon raw material used in the method for producing a silicon single crystal of the present invention, a semiconductor-grade high-purity raw material is preferable. The present invention applies the property that the amount of carbon mixed due to the silicon single crystal manufacturing process is proportional to the integrated value ΣPower × Δt. Therefore, when the amount of carbon mixed in from the silicon raw material is smaller than the amount of carbon mixed in by the silicon single crystal manufacturing process, the variation in carbon concentration between lots of the silicon raw material is smaller, and the raised silicon single crystal is raised. A better correlation is obtained between the carbon concentration in the medium and the integrated value ΣPower × Δt. For this reason, it is preferable that the silicon raw material used in the method for producing a silicon single crystal of the present invention is a semiconductor-grade high-purity raw material. By using such a silicon raw material, the carbon concentration in the raised silicon single crystal can be estimated more accurately from the above integrated value.

Further, as described above, when pulling up a silicon single crystal, there is a correlation between the integrated value calculated from the heater power and time and the carbon concentration. Based on this correlation, it is also possible to produce a silicon single crystal in which the carbon concentration in the raised silicon single crystal is controlled as follows. A raw material melting process in which the silicon raw material contained in such a rutsubo is heated by a heater to melt it into a raw material melt, and a silicon single crystal is pulled up from the raw material melt while heating the raw material melt with a heater. In the method for manufacturing a silicon single crystal having a pulling step, before pulling the silicon single crystal, the integrated value ΣPower × Δt calculated from the time difference Δt, which is the difference between the heater power power of the heater and the time t, is pulled up in advance. When the correlation between the carbon concentration Cs in the silicon single crystal obtained later is obtained, and the silicon single crystal is pulled up by adjusting the heater power Power of the heater and the time t based on the correlation. The carbon concentration Cs of the silicon single crystal can be controlled.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the Examples.

First, a method for producing a silicon single crystal is performed using a specific silicon pulling machine, and the pulling machine has a solidification rate of 60% in the pulled silicon single crystal as shown in FIG. 2 (A). The correlation between the carbon concentration Cs and the integrated value ΣPower × Δt was obtained. As a result, there was a correlation as shown in FIG. The circles in the graph of FIG. 1 indicate experimental values, and there was a proportional correlation between the carbon concentration Cs and the integrated value.

Next, as shown in FIG. 2 (B), the carbon concentration Cs = 1.0 × 10 ¹⁴ atoms / cm ³ in the silicon single crystal is set as the standard upper limit value of the carbon concentration in the product silicon single crystal. rice field. Further, from the correlation between the carbon concentration Cs in the silicon single crystal and the integrated value ΣPower × Δt (FIG. 1) obtained above, the integrated value ΣPower when Cs = 1.0 × 10 ¹⁴ atoms / cm ³ × Δt = 2861 kW · h was defined as the threshold value of the integrated value during operation.

Next, 410 kg of a polycrystalline raw material (silicon raw material) was melted in a CZ pulling machine, and a crystal having a diameter of 300 mm was pulled up. At that time, dislocations did not occur, and the step of pulling up the silicon single crystal to the step of forming the rounded portion was performed once, and the afterheat step and the crystal extraction step were performed ((C) to (E) in FIGS. 2). ), (J)).

Next, as shown in FIG. 2 (K), the integrated value is calculated after the silicon single crystal extraction is completed, and as shown in FIG. 2 (L), the integrated value ΣPower × Δt <threshold value (= 2861 kW. It was confirmed whether or not h) was satisfied. As a result, the integrated value after the completion of silicon single crystal extraction was ΣPower × Δt = 2266 kW · h, and it was confirmed that ΣPower × Δt <2861 kW · h was satisfied in this operation ((M) in FIG. 2). Finally, for the purpose of confirmation, a sample of a silicon single crystal having a diameter of 300 mm obtained from the above operation was cut out from each straight body position, and the carbon concentration was quantified using the PL method. As a result, as shown in FIG. 3, it was confirmed that Cs <1.0 × 10 ¹⁴ atoms / cm ³ was satisfied over the entire straight body position, and the carbon concentration was controlled by using the integrated value. We were able to produce a silicon single crystal that did not exceed the upper limit of the standard.

From this, in the method for producing a silicon single crystal of the present invention, after pulling up the silicon single crystal, the integrated value ΣPower × Δt was calculated from the heater power Power and time t at the time of pulling up the silicon single crystal, and the calculation was performed. When the integrated value ΣPower × Δt is less than 2861 kW · h, the standard of carbon concentration Cs of Cs <1.0 × 10 ¹⁴ atoms / cm ³ is applied to the silicon single crystal at the solidification rate of 20 to 60% of the raised silicon single crystal. When the product is sorted as a product to satisfy and the calculated integrated value ΣPower × Δt is 2861 kW · h or more, the silicon single crystal at a solidification rate of 20 to 60% of the raised silicon single crystal has a carbon concentration Cs of Cs ≧ 1.0 × 10. It can be sorted as a product that meets the standard of ¹⁴ singles / ^cm3 .

(Comparative example)
Apart from the above examples, the silicon single crystal was produced as follows. First, a raw material melting step and a power leaving step were performed. Since dislocations occurred during the pulling up of the silicon single crystal, a remelting step was performed. After the completion of the remelting step and the completion of the removal of the silicon single crystal, the silicon single crystal having a diameter of 300 mm was pulled up without calculating the integrated value. For the silicon single crystal having a diameter of 300 mm obtained from the above operation, a sample was cut out from each straight body position, and the carbon concentration was quantified using the PL method. As a result, as shown in FIG. 4, it was found that Cs ≧ 1.0 × 10 ¹⁴ atoms / cm ³ in the region after the solidification rate of 20%, which exceeded the standard upper limit value.

Just in case, when the operation data is confirmed after the quantification by the PL method is completed and the integrated value after the completion of the extraction of the silicon single crystal is calculated, it is ΣPower × Δt = 3686kW · h, which is the integrated value. It was found that the threshold value (= 2861 kW · h) was exceeded.

The present invention is not limited to the above embodiment. The above embodiment is an example, and any one having substantially the same configuration as the technical idea described in the claims of the present invention and having the same effect and effect is the present invention. It is included in the technical scope of the invention.

Claims (9)

A raw material melting step of melting a silicon raw material contained in a rubbing pot by heating it with a heater to obtain a raw material melt, and pulling a silicon single crystal from the raw material melt while heating the raw material melt with the heater. In a method for producing a silicon single crystal having a pulling process,
Estimating the carbon concentration Cs in the silicon single crystal obtained after the raising is estimated based on the integrated value ΣPower × Δt calculated from the heater power Power of the heater and the time difference Δt which is the difference of the time t .
Before pulling up the silicon single crystal, the correlation between the carbon concentration Cs and the integrated value ΣPower × Δt is obtained in advance.
After pulling up the silicon single crystal, the value of the integrated value ΣPower × Δt when the silicon single crystal is pulled up is calculated, and the carbon concentration Cs of the pulled up silicon single crystal is calculated from the calculated value and the correlation. Do by estimating,
A method for producing a silicon single crystal, which comprises determining a standard to which the carbon concentration of the silicon single crystal obtained after the raising is satisfied, based on the estimated carbon concentration Cs. The method for producing a silicon single crystal according to claim 1 , wherein the correlation obtained in advance is obtained for each pulling machine for pulling the silicon single crystal. After pulling up the silicon single crystal, the integrated value ΣPower × Δt was calculated from the heater power Power and the time t at the time of pulling up the silicon single crystal.
When the calculated integrated value ΣPower × Δt is less than 2861 kW · h, the carbon concentration Cs of the silicon single crystal at the solidification rate of 20 to 60% of the raised silicon single crystal is Cs <1.0 × 10 ¹⁴ atoms / cm. Sorted as products that meet the ³ standards,
When the calculated integrated value ΣPower × Δt is 2861 kW · h or more, the carbon concentration Cs of the silicon single crystal at the solidification rate of 20 to 60% of the raised silicon single crystal is Cs ≧ 1.0 × 10 ¹⁴ atoms / cm. The method for producing a silicon single crystal according to claim 1 or 2 , wherein the product is sorted as a product satisfying the standard of ³ . The heater power Power used for calculating the integrated value ΣPower × Δt is the heater power in the raw material melting step, the heater power from the end of the raw material melting step to the start of the pulling step, and the pulling step once. The method for producing a silicon single crystal according to any one of claims 1 to 3 , wherein the heater power is used in the remelting step in the case of remelting the silicon single crystal that has been carried out halfway. The method for producing a silicon single crystal according to claim 4 , wherein the time t used for calculating the integrated value ΣPower × Δt is set to a time when the temperature of the silicon raw material is 900 ° C. or higher. The silicon single crystal according to any one of claims 1 to 5 , wherein the time difference Δt used for calculating the integrated value ΣPower × Δt is in the range of 10 seconds or more and 10 minutes or less. Production method. Any one of claims 1 to 6 , wherein the integrated value Power × Δt is calculated from the area of a trapezoid formed by the two heater power powers in the interval [t, t + Δt] and the time Δt. The method for producing a silicon single crystal according to the section. The method for producing a silicon single crystal according to any one of claims 1 to 7 , wherein a semiconductor-grade high-purity raw material is used as the silicon raw material. A raw material melting step of melting a silicon raw material contained in a rubbing pot by heating it with a heater to obtain a raw material melt, and pulling a silicon single crystal from the raw material melt while heating the raw material melt with the heater. In a method for producing a silicon single crystal having a pulling process,
Before pulling up the silicon single crystal, the integrated value ΣPower × Δt calculated in advance from the heater power power of the heater and the time difference Δt which is the difference between the time t and the carbon concentration in the silicon single crystal obtained after the pulling up. Find the correlation between Cs
Silicon characterized by controlling the carbon concentration Cs of the silicon single crystal when the silicon single crystal is pulled up by adjusting the heater power power of the heater and the time t based on the correlation. Single crystal manufacturing method.

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