JP6981371B2 - Method for manufacturing silicon single crystal - Google Patents

Description

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

Conventionally, when producing a silicon single crystal by the Czochralski method, studies have been made for adjusting the oxygen concentration of the silicon single crystal (see, for example, Patent Document 1).
In the method of Patent Document 1, the wall thickness of the opening, which is the contact portion with the convection of the silicon melt, is made thicker than the wall thickness of the bottom portion of the quartz crucible, and the temperature of the inner wall of the contact portion is set to the temperature of the silicon melt. It is higher than the recrystallization temperature and lower than the temperature other than the contact portion. As a result, the dissolution of oxygen into the silicon melt due to convection from the inner wall of the quartz crucible is suppressed, and the oxygen concentration of the silicon single crystal is lowered.

Japanese Unexamined Patent Publication No. 5-221780

In a single crystal pulling device as in Patent Document 1, when it is desired to aim at the oxygen concentration of the grown silicon single crystal, it is conceivable to make the growing conditions such as the pulling speed or the rotation speed of the silicon single crystal or the quartz crucible the same. Be done.
However, even if the growing conditions are the same, the oxygen concentration of the silicon single crystal may deviate from the target value, and it has been required to suppress the deviation of the oxygen concentration from the target value.

An object of the present invention is to provide a method for producing a silicon single crystal, which can easily suppress the deviation of the oxygen concentration from the target value in the silicon single crystal.

The method for producing a silicon single crystal of the present invention is a method for producing a silicon single crystal by the Czochralski method using a single crystal pulling device, based on a step of measuring the weight of a quartz crucible and the measurement result of the weight. Then, using the step of setting the raising condition so that the oxygen concentration of the silicon single crystal manufactured using the quartz crucible whose weight was measured becomes the target value, and the quartz crucible whose weight was measured, the above It is characterized by having a process of manufacturing a silicon single crystal under set pulling conditions.

According to the present invention, even when the quartz crucible is replaced, the deviation of the oxygen concentration from the target value can be suppressed.

In the step of setting the pulling condition in the method for producing a silicon single crystal of the present invention, the weight of the other quartz crucible and the oxygen concentration of the silicon single crystal produced using the other quartz crucible are reduced to a predetermined oxygen concentration. It is preferable to set the pulling condition based on the relationship between the pulling condition and the measurement result of the weight.

According to the present invention, it is possible to suppress the deviation of the oxygen concentration from the target value by a simple method only referring to the above relationship.

In the step of setting the pulling condition in the method for producing a silicon single crystal of the present invention, the pulling condition is set so that the oxygen concentration becomes a target value at each of a plurality of predetermined positions in the crystal axis direction in the silicon single crystal. It is preferable to set it.

The reason is that when a silicon single crystal is produced under the same pulling conditions in the entire region of the straight body, the oxygen concentration in the melt decreases because the contact area between the inner surface of the quartz crucible and the silicon melt decreases as the solidification rate increases. Therefore, the oxygen concentration on the upper end side in the pulling direction is higher than that on the lower end side.
According to the present invention, it is possible to suppress the deviation of the oxygen concentration from the target value in many regions of the silicon single crystal, and to improve the yield (the ratio of the region of the straight body portion that can be made into a product).

In the method for producing a silicon single crystal of the present invention, the steps for setting the pulling conditions include the pressure inside the chamber of the single crystal pulling device, the flow rate of the inert gas supplied to the chamber, and the rotation speed of the quartz crucible. It is preferable to set at least one of them as the raising condition.

According to the present invention, the target value of oxygen concentration is simply set by setting at least one of the pressure inside the furnace of the chamber, the flow rate of the inert gas supplied to the chamber, and the rotation speed of the quartz crucible. It is possible to suppress the deviation from.

The schematic diagram of the single crystal pulling apparatus which concerns on the related technique of this invention and one Embodiment. Histogram of the weight of a quartz crucible used in the experiments conducted to guide the present invention. A graph showing the relationship between the weight of a quartz crucible and the oxygen concentration of a silicon single crystal, which is the result of an experiment conducted to derive the present invention. The flowchart of the manufacturing method of a silicon single crystal in the said embodiment. The graph which shows the difference (absolute value display) of the oxygen concentration with respect to the target value in each silicon single crystal of Example 1 and Comparative Example 1 which concerns on this invention. The graph which shows the difference (absolute value display) of the oxygen concentration with respect to the target value in each silicon single crystal of Example 2 and Comparative Example 2 which concerns on this invention.

[Related Techniques of the Present Invention]
First, the related technique of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the single crystal pulling device 1 is a device used in the CZ method (Czochralski method), and includes a pulling device main body 2, a memory 3, and a control unit 4.
The pulling device main body 2 includes a chamber 21, a crucible 22 arranged in the chamber 21, a heater 23 for heating the crucible 22, a pulling portion 24, a heat shield 25, a heat insulating material 26, and a crucible drive. It has a crucible 27.
As shown by the alternate long and short dash line, the single crystal pulling device 1 is a device used in the MCZ (Magnetic field applied Czochralski) method, and is a pair of electromagnetic coils arranged across the crucible 22 on the outside of the chamber 21. You may have 28.

A gas introduction port 21A for introducing an inert gas such as Ar gas into the chamber 21 is provided in the upper part of the chamber 21. At the lower part of the chamber 21, a gas exhaust port 21B for discharging the gas in the chamber 21 is provided. A heat insulating material 26 is provided on the inner surface of the chamber 21.

The crucible 22 melts silicon into a silicon melt M. The crucible 22 includes a quartz crucible 221 and a graphite crucible 222 accommodating the quartz crucible 221. The quartz crucible 221 is replaced every time one or more silicon single crystal SMs are grown. On the other hand, the graphite crucible 222 is not replaced every time one silicon single crystal SM is manufactured, and is replaced when it is considered that the quartz crucible 221 cannot be properly supported.

The heater 23 is arranged around the crucible 22 and melts the silicon in the crucible 22. A bottom heater 231 as shown by the alternate long and short dash line may be further provided below the crucible 22.
The pull-up unit 24 includes a cable 241 to which the seed crystal SC is attached to one end, and a pull-up drive unit 242 that raises and lowers and rotates the cable 241.
The heat shield 25 is provided so as to surround the silicon single crystal SM, and blocks radiant heat radiated upward from the heater 23.
The crucible drive unit 27 includes a support shaft 271 that supports the graphite crucible 222 from below, and rotates and raises and lowers the crucible 22 at a predetermined speed.
The hot zone in the single crystal pulling device 1 is a chamber 21, a crucible 22, a heater 23, a cable 241, a heat shield 25, a heat insulating material 26, a support shaft 271, a silicon melt M, a silicon single crystal SM, and the like.

The memory 3 stores various information necessary for manufacturing the silicon single crystal SM, such as the gas flow rate in the chamber 21, the furnace pressure, the power input to the heater 23, and the rotation speed of the crucible 22 and the silicon single crystal SM.
The control unit 4 manufactures the silicon single crystal SM based on various information stored in the memory 3 and the operation of the operator.

[Background to lead to the present invention]
As a result of diligently examining the cause of the deviation of the oxygen concentration from the target value, the present inventor has obtained the finding that the weight of the quartz crucible 221 affects the oxygen concentration. This finding will be described below.

First, after measuring the weight of the quartz crucible 221, the quartz crucible 221 was attached to the single crystal pulling device 1. The pressure inside the chamber 21, which is a factor that affects the oxygen concentration of the silicon single crystal SM, the flow rate of the inert gas supplied to the chamber 21, and the rotation speed of the quartz crucible 221 are set as reference conditions, and one silicon is used. A single crystal SM was produced. The oxygen concentration (ASTM F121-1979) at a predetermined position in the straight body portion of this silicon single crystal SM was measured. FTIR (Fourier Transform Infrared Spectroscopy) was used to measure the oxygen concentration.
Next, one silicon single crystal SM was manufactured under the same pulling conditions as before, except that the used quartz crucible 221 was replaced with a new quartz crucible 221, and the oxygen concentration at the predetermined position was measured.
Then, in the same manner, a plurality of new quartz crucibles 221 were used to produce the same number of silicon single crystal SMs as the quartz crucible 221.
The histogram of the weight of the quartz crucible 221 is shown in FIG. 2, and the relationship between the weight of the quartz crucible 221 and the oxygen concentration is shown in FIG. The horizontal axis of FIGS. 2 and 3 shows the difference from the design value of the weight of the quartz crucible 221. The vertical axis of FIG. 2 shows the frequency. The vertical axis of FIG. 3 shows the difference from the target value of oxygen concentration.

As shown in FIG. 2, the frequency of the weight of the quartz crucible 221 was the largest in the range of the design value + 0.1 kg, and became smaller as the distance from the design value increased. The weight of the quartz crucible 221 varied by about ± 1 kg from the design value even though the quartz crucible 221 was manufactured as designed.
As shown in FIG. 3, there is a negative correlation between the weight of the quartz crucible 221 and the oxygen concentration that the oxygen concentration decreases as the weight of the quartz crucible 221 increases and the oxygen concentration increases as the weight of the quartz crucible 221 decreases. I found out that there is. That is, using one single crystal pulling device 1, a plurality of factors affecting the oxygen concentration, such as the pressure inside the chamber 21, the flow rate of the inert gas supplied to the chamber 21, and the rotation speed of the quartz crucible 221 are made the same. It was found that even in the production of the silicon single crystal SM of the above, the oxygen concentration may deviate significantly from the target value due to the influence of the weight of the quartz crucible 221.

From the above results, based on the measurement result of the weight of the quartz crucible 221, the raising condition is set so that the oxygen concentration of the silicon single crystal SM manufactured by using the quartz crucible 221 in which the weight is measured becomes the target value. By doing so, it is considered that the deviation of the oxygen concentration from the target value can be suppressed.

[Embodiment]
Next, a method for producing a silicon single crystal SM according to an embodiment of the present invention will be described.
In this embodiment, a case where a silicon single crystal SM having a straight body portion having a diameter of 300 mm after cylindrical grinding is manufactured is exemplified, but the diameter after cylindrical grinding may be 200 mm, 450 mm, or another size. good. Further, a dopant for adjusting the resistivity may or may not be added to the silicon melt M.

First, the relationship between the weight of the quartz crucible 221 and the adjustment amount of the oxygen concentration as shown in Table 1 below is stored in the memory 3 of the single crystal pulling device 1. The relationship in Table 1 is the relationship when the diameter of the straight body portion after cylindrical grinding is 300 mm.

In Table 1, "weight of quartz crucible" indicates the weight based on the design value of quartz crucible 221.
The "top part" varies depending on the diameter and resistivity of the silicon single crystal SM, but when the entire straight body part of the silicon single crystal SM is 100%, it is 1% or more and 33% from the upper end of the straight body part in the pulling direction. The following regions are shown, the "bottom portion" indicates a region of 67% or more and 100% or less from the lower end of the straight body portion, and the "middle portion" indicates a region between the top portion and the bottom portion.

The "reference oxygen concentration" uses the quartz crucible 221 whose weight is the design value, and is based on the internal pressure of the chamber 21, the flow rate of the inert gas supplied to the chamber 21, and the rotation speed of the quartz crucible 221 (reference). It is the oxygen concentration of the silicon single crystal SM produced by setting the pulling condition). The reference oxygen concentration is set for each of the top portion, the middle portion and the bottom portion.

The "adjustment amount of oxygen concentration" is an adjustment amount required to set the oxygen concentration of the silicon single crystal as the reference oxygen concentration when producing a silicon single crystal using the quartz crucible 221 whose weight is the value shown in Table 1. Is shown. For example, when a quartz pit 221 whose weight is 1.2 kg lighter than the design value is used, the oxygen concentration in the top portion and the middle portion increases by 2.3% of the reference oxygen concentration with respect to the reference oxygen concentration, and the bottom portion. Oxygen concentration in is increased by 3.1% of the reference oxygen concentration. In order to reduce this increase in oxygen concentration, the raising condition may be set so as to reduce the oxygen concentration.

This adjustment amount may be set as follows, for example.
First, an experiment similar to the experiment for obtaining the relationship shown in FIG. 3 is performed. When a silicon single crystal SM is manufactured using a quartz crucible 221 whose weight is 1.2 kg lighter than the design value under the conditions of raising the standard, the oxygen concentration in the top portion and the middle portion of the silicon single crystal SM is the reference oxygen concentration. It is assumed that the result is obtained that the value is increased by + 2.3% (= reference oxygen concentration + reference oxygen concentration × 2.3%). In this case, the adjustment amount in the top portion and the middle portion is set so as to decrease by 2.3% of the reference oxygen concentration.
That is, the relationship between the oxygen concentration when the silicon single crystal SM is manufactured under the standard pulling condition and the weight of the quartz crucible 221 used for manufacturing the silicon single crystal SM is obtained in advance, and further, the pulling condition is used as the reference. It is necessary to understand in advance how the oxygen concentration changes when the condition is changed from the above-mentioned raising condition.
Then, when the silicon single crystal SM is manufactured using the new quartz crucible 221, the oxygen concentration of the silicon single crystal SM is estimated based on the weight of the new quartz crucible 221 and raised based on this estimated value and the target value. All you have to do is set the conditions.
The relationships in Table 1 may be those created by simulation.

When the silicon single crystal SM is manufactured using a plurality of single crystal pulling devices 1, the relationships in Table 1 are preferably created corresponding to the respective single crystal pulling devices 1.
In the case of the single crystal pulling device 1 of a different model, the heating conditions of the silicon melt M may differ depending on the shape and arrangement of the hot zone, and even if the single crystal pulling device 1 of the same model has the shape of the hot zone. The heating conditions of the silicon melt M may differ depending on the tolerance of the arrangement and the like. This is because if the heating conditions of the silicon melt M are different as described above, the oxygen concentration will be different even if the silicon single crystal SM is produced using the quartz crucible 221 having exactly the same shape under exactly the same pulling conditions.

Next, as shown in FIG. 4, the weight of the quartz crucible 221 used for manufacturing the silicon single crystal SM is measured (step S1), and the quartz crucible 221 is based on the relationship between the measurement result of the weight and Table 1. The conditions for pulling up the silicon single crystal SM to be manufactured using the above are set (step S2).
By the process of this step S2, for example, when the weight of the quartz pit 221 is 0.4 kg heavier than the design value and the target value is the reference oxygen concentration, the raising condition in the top portion and the middle portion is set, and the oxygen concentration is the reference oxygen. The oxygen concentration is set to increase by 0.8% with respect to the concentration, and the pulling condition at the bottom portion is set so that the oxygen concentration increases by 1.5% with respect to the reference oxygen concentration. At this time, the condition to be adjusted with respect to the standard raising condition may be a factor that affects the oxygen concentration. For example, the pressure inside the furnace of the chamber 21, the flow rate of the inert gas supplied to the chamber 21, and the rotation speed of the quartz crucible 221 can be mentioned, and it is preferable to select any one of these factors.
In this case, it is necessary to quantitatively grasp in advance the influence of the pressure inside the furnace of the chamber 21, the flow rate of the inert gas supplied to the chamber 21, or the rotation speed of the quartz crucible 221 on the oxygen concentration of the silicon single crystal. That is, it is necessary to grasp in advance how much the oxygen concentration of the silicon single crystal changes when the pressure inside the chamber 21, the flow rate of the inert gas supplied to the chamber 21 or the rotation speed of the quartz crucible 221 is changed. There is a need.

When the target value is larger or smaller than the reference oxygen concentration, the adjustment amount of the oxygen concentration obtained based on Table 1 may be adjusted in consideration of the increase / decrease amount of the target value with respect to the reference oxygen concentration. For example, when the weight of the quartz pit 221 is 0.4 kg heavier than the design value and the target value is 2% larger than the reference oxygen concentration, the oxygen concentration at the top portion is 0 with respect to the reference oxygen concentration. The raising condition may be set so that the oxygen concentration increases by 8.8% and further increases by 2%, that is, the oxygen concentration increases by 2.8% with respect to the reference oxygen concentration.

After that, the quartz crucible 221 whose weight was measured in step S1 is attached to the single crystal pulling device 1, and a silicon single crystal SM is manufactured under the pulling conditions set in step S2 (step S3). In this step S3, the pulling condition is adjusted for each of the top portion, the middle portion, and the bottom portion based on the adjustment amount obtained based on Table 1.

[Action and effect of the embodiment]
According to the above embodiment, based on the relationship between the measurement result of the weight of the quartz crucible 221 and Table 1, the oxygen concentration of the silicon single crystal SM manufactured by using the quartz crucible 221 is raised so as to be the target value. Set the conditions. After that, the silicon single crystal SM is manufactured under the set pulling conditions by using the quartz crucible 221 whose weight has been measured.
Therefore, even when the quartz crucible 221 is replaced, the deviation of the oxygen concentration from the target value can be suppressed.
In Table 1, since the oxygen concentration adjustment amount is set according to the top portion, the middle portion, and the bottom portion, that is, for each of a plurality of predetermined positions in the crystal axis direction in the silicon single crystal SM, the entire area of the straight body portion is set. The deviation of the oxygen concentration from the target value in the above can be suppressed, and the yield can be improved.

[Modification example]
The present invention is not limited to the above embodiment, and various improvements and design changes can be made without departing from the gist of the present invention.

For example, the oxygen concentration adjustment amount in Table 1 may be set to only one for the entire straight body portion, or may be set for each region divided into two or four in the pulling direction. In these cases, it is preferable that the reference oxygen concentration is set for each region in which the adjustment amount is set.
The pulling condition may be set by setting a factor that affects the oxygen concentration. For example, when a silicon single crystal is produced by the MCZ method, the strength of the magnetic field applied to the silicon melt and the position where the magnetic field is applied are set. You may.

The relationship in Table 1 is preferably created corresponding to the diameter of the straight body portion after cylindrical grinding. For example, the relationship of the present embodiment (relationship when the diameter is 300 mm) is a single silicon of 450 mm. It may be used in the case of producing the crystal SM, and in this case, the adjustment amount in the case of 450 mm may be obtained by multiplying the adjustment amount in Table 1 by a coefficient corresponding to the diameter of the straight body portion.
The relationship in Table 1 may be set according to the total usage time of the single crystal pulling device 1. This is because the deterioration of the components of the hot zone affects the oxygen concentration.

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

<Comparative Example 1>
First, a quartz crucible 221 was attached to the single crystal pulling device 1 as shown in FIG. In setting the pulling condition, the oxygen concentration of each of the top part, the middle part and the bottom part becomes the target value based on the oxygen concentration of the silicon single crystal SM previously manufactured without considering the weight of the quartz crucible 221. I went like that. Then, under the set pulling conditions, a silicon single crystal SM having a diameter of 300 mm after cylindrical grinding was manufactured, and the straight body portion was divided into a plurality of blocks. Wafers were acquired from positions corresponding to the top, middle and bottom portions of the block, and the oxygen concentration (ASTM F121-1979) at the center of each wafer was measured by FTIR. After obtaining the absolute value of the difference between the target value corresponding to the acquisition position of each wafer and the measurement result of oxygen concentration (hereinafter referred to as "oxygen concentration difference"), a plurality of wafers acquired from one silicon single crystal SM. The average value of the absolute values of the oxygen concentration differences in the above was calculated.

Replace the quartz crucible 221 and set the raising conditions so that the oxygen concentration of the silicon single crystal SM to be manufactured next becomes the target value based on the oxygen concentration of the silicon single crystal SM manufactured immediately before, and set the silicon single crystal SM. Manufactured. Then, the silicon single crystal SM was subjected to the above-mentioned treatment, and the average value of the absolute values of the oxygen concentration differences was obtained.
In Comparative Example 1, a total of 34 silicon single crystal SMs were produced, and the average value of the absolute values of the oxygen concentration differences was obtained for each silicon single crystal SM. The results are shown in FIG. One data in FIG. 5 and FIG. 6 described later is the value of one silicon single crystal SM.

<Comparative Example 2>
Using a single crystal pulling device 1 different from Comparative Example 1, a silicon single crystal SM having the same size as Comparative Example 1 is subjected to the same processing as in Comparative Example 1 (the pulling conditions are set without considering the weight of the quartz crucible 221). 20 pieces were manufactured, and the average value of the absolute values of the oxygen concentration differences was obtained for each silicon single crystal SM. The results are shown in FIG.

<Example 1>
A quartz crucible 221 was attached to the same single crystal pulling device 1 as in Comparative Example 1. The setting of the pulling condition is based on the relationship between the weight of the quartz crucible 221 and the weight of the quartz crucible 221 and the adjustment amount of the oxygen concentration as shown in Table 1, and the oxygen concentration of each of the top portion, the middle portion and the bottom portion is set. The adjustment amount was obtained so that the target value was obtained, and the adjustment amount was used based on the adjustment amount. Then, under the set pulling conditions, a silicon single crystal SM having the same size as that of Comparative Example 1 was produced, and the average value of the absolute values of the oxygen concentration differences was obtained in the same manner as in Comparative Example 1.
In Example 1, a total of 37 silicon single crystal SMs were produced, and the average value of the absolute values of the oxygen concentration differences was obtained for each silicon single crystal SM. The results are shown in FIG.

<Example 2>
Using the same single crystal pulling device 1 as in Comparative Example 2, the same size silicon single crystal SM as in Example 1 was prepared by the same treatment as in Example 1 (the pulling conditions were set in consideration of the weight of the quartz crucible 221). In this production, the average value of the absolute values of the oxygen concentration differences was obtained for each silicon single crystal SM. The results are shown in FIG.

<Evaluation>
As shown in FIGS. 5 and 6, the average value of the average values of the absolute values of the oxygen concentration differences in each of Example 1 and Comparative Example 1 (hereinafter, simply referred to as “oxygen concentration difference average value”) is connected by a straight line L. , Example 2 and Comparative Example 2 were also connected by a straight line L in the same manner. In each single crystal pulling device 1, the average oxygen concentration difference was smaller in Examples 1 and 2 than in Comparative Examples 1 and 2.
The variation in the average value of the absolute values of the oxygen concentration differences in Examples 1 and 2 was smaller than that in Comparative Examples 1 and 2.
From the above, based on the measurement result of the weight of the quartz crucible 221 and the relationship as shown in Table 1, the oxygen concentration of the silicon single crystal SM manufactured by using the quartz crucible 221 is set as the target value. It was confirmed that the deviation of the oxygen concentration from the target value can be suppressed even when the quartz crucible 221 is replaced by setting the pulling condition.

1 ... Single crystal pulling device, 21 ... Chamber, 221 ... Quartz crucible, SM ... Silicon single crystal.

Claims (4)

It is a method for producing a silicon single crystal by the Czochralski method using a single crystal pulling device.
In order to make the oxygen concentration of the silicon single crystal the reference oxygen concentration when the silicon single crystal is manufactured under the conditions of raising the standard using the weight based on the design value of the quartz crucible and the quartz crucible of the weight. Obtain the relationship with the required adjustment amount of oxygen concentration in advance,
The process of measuring the weight of a quartz crucible,
And the relationship between the adjustment amount of the weight and the oxygen concentration of the quartz crucible, on the basis of the measurement results of the weight, to estimate the oxygen concentration in the silicon single crystal that will be manufactured using a quartz crucible to which the weight has been determined , The process of setting the raising conditions based on the estimated value and the target value,
A method for producing a silicon single crystal, which comprises a step of producing a silicon single crystal under the set pulling conditions using the quartz crucible whose weight has been measured. In the method for producing a silicon single crystal according to claim 1,
The reference oxygen concentration is
The weight is the oxygen concentration of the silicon single crystal manufactured by using the quartz crucible of the design value and under the raising condition of the standard.
A method for producing a silicon single crystal, which is set at each of a plurality of predetermined positions in the crystal axis direction in the silicon single crystal. In the method for producing a silicon single crystal according to claim 1 or 2.
The relationship between the weight of the quartz crucible and the adjustment amount of the oxygen concentration is characterized in that it is produced corresponding to a plurality of the single crystal pulling devices having different heating conditions for the silicon melt. Method. The method for producing a silicon single crystal according to any one of claims 1 to 3.
In the step of setting the pulling condition, at least one of the pressure inside the chamber of the single crystal pulling device, the flow rate of the inert gas supplied to the chamber, and the rotation speed of the quartz crucible is set as the pulling condition. A method for producing a silicon single crystal, which comprises setting as.

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