JP6954088B2 - Method for manufacturing silicon single crystal - Google Patents

Description

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

In the FZ (Floating Zone) method, a polycrystalline raw material having a high resistivity is melted, _{and a dope gas containing phosphorus (PH 3} ), boron (B ₂ H ₆ ), etc. is blown into the melting zone to control the electrical resistivity. By doing so, a silicon single crystal is grown. In order to control the electrical resistivity of a silicon single crystal, it is necessary to control the growth while considering various conditions of the hot zone.
Therefore, Patent Document 1 states that in the method for producing a silicon single crystal by the FZ method, the electrical resistivity such as neck diameter, melt diameter, zone length, crystal temperature, and upper axial speed is affected during the growth of the silicon single crystal. A technique for growing a silicon single crystal while measuring a plurality of parameters is disclosed.

Japanese Unexamined Patent Publication No. 2015-101521

However, in the technique described in Patent Document 1, various parameters are measured during the growth of the silicon single crystal, the measurement results are analyzed by multivariate analysis, and the dopant supply amount in the next growth is based on the analysis results. Must be adjusted. Therefore, it is necessary to perform complicated processing such as measurement of various parameters and multivariate analysis, which causes a problem that setting of growing conditions in the FZ method becomes complicated.

An object of the present invention is to appropriately obtain the supply amount of a dope gas without performing complicated processing in imparting a desired electrical resistivity to a silicon single crystal in growing a silicon single crystal by the FZ method. It is an object of the present invention to provide a method for producing a single crystal.

The method for producing a silicon single crystal of the present invention is a method for producing a silicon single crystal in which a silicon single crystal is grown by an FZ (Floating Zone) method in which the electrical resistivity is controlled while blowing a dope gas into the melting zone. Based on the first step of acquiring the growth record data of the silicon single crystal by the growing device of the above and the acquired growth record data of the silicon single crystal, the actual value of the electrical resistivity of the silicon single crystal and the silicon Based on the second step of calculating the relationship between the single crystal's dope gas absorption rate and the calculated actual value of the electrical resistivity and the dope gas absorption rate, the silicon single crystal produced using the same growing device. A third step of calculating the dope gas supply amount from the target value of the electric resistivity, and a fourth step of controlling the electric resistivity of the silicon single crystal to be grown while blowing the dope gas according to the calculated dope gas supply amount. It is characterized by carrying out.

According to the present invention, the actual growth data of the silicon single crystal is acquired by the first step, and the relationship between the actual value of the electrical resistivity of the silicon single crystal and the doping gas absorption rate of the silicon single crystal is determined by the second step. I'm calculating. Then, in the third step, the dope gas supply amount according to the target value of the electrical resistivity is calculated, and in the fourth step, the electric resistance of the silicon single crystal to be grown while blowing the dope gas by the calculated dope gas supply amount. The rate can be controlled to grow a silicon single crystal.
Therefore, since the doping gas supply amount is set in consideration of the doping gas absorption rate according to the change in the target resistivity value, the deviation between the target value of the electrical resistivity and the electrical resistivity of the grown silicon single crystal is small. can do.

In the present invention, the relationship between the actual value of the electrical resistivity of the silicon single crystal in the second step and the doping gas absorption rate is preferably a proportional relationship.
For example, if the relationship between the actual value of the electrical resistivity of a silicon single crystal and the dope gas absorption rate is proportional, when the next silicon single crystal is grown, the electricity in the next silicon single crystal growth is according to the proportional relationship. The amount of dope gas supplied can be easily obtained from the target value of resistivity.

In the present invention, in the first step, it is preferable to acquire the previous growing record data of the same growing device.
According to the present invention, since the relationship between the measured value of the electrical resistivity and the dope gas supply amount is obtained using the previous growth record data, the dope gas supply amount can be obtained from the latest growth record data, and electricity can be obtained. It is possible to grow a silicon single crystal having an electrical resistivity that is closer to the target value of the resistivity.

The method for producing a silicon single crystal of the present invention is a method for growing a silicon single crystal using the same growing device by the FZ (Floating Zone) method in which the electric resistance is controlled while blowing a dope gas into the melting zone. It is a manufacturing method, and based on the actual data of growing a silicon single crystal in the previous production of a silicon single crystal and the actual value of the electrical resistance of the silicon single crystal, the doping gas absorption rate of the silicon single crystal in the previous production of the silicon single crystal. If the target value of the electric resistance of the silicon single crystal to be grown this time is larger than the measured value of the electric resistance of the previous silicon single crystal, it is more than the doping gas absorption rate of the previous silicon single crystal. If the electric resistance of the silicon single crystal to be grown this time is smaller than the measured value of the electric resistance of the previous silicon single crystal, the dope gas absorption of the previous silicon single crystal is smaller than the dope gas absorption of the previous silicon single crystal. It is characterized by carrying out a step of controlling the electric resistance of the silicon single crystal to be grown this time by using a large dope gas absorption rate.
According to the present invention as described above, the same actions and effects as described above can be obtained.

In the present invention, it is preferable that the growth record data of the silicon single crystal includes at least the target diameter of the silicon single crystal, the electrical resistivity, the crystal feed rate, the dope gas flow rate, and the dope gas concentration.
Since these data have a great influence on controlling the electrical resistivity of the growing silicon single crystal, the electrical resistivity of the growing silicon single crystal can be controlled with high accuracy.

The schematic diagram which shows the structure of the silicon single crystal growth apparatus which concerns on embodiment of this invention. The flowchart which shows the manufacturing method of the silicon single crystal in the said embodiment. The graph which shows the relationship between the electrical resistivity of a silicon single crystal and the dope gas absorption rate in the said embodiment. The graph which shows the hit rate of the target value of the electrical resistivity of an Example and a comparative example.

[1] Overall Configuration of Silicon Single Crystal Growing Device 1 FIG. 1 shows a schematic view of the silicon single crystal growing device 1 according to the embodiment of the present invention. The silicon single crystal growing apparatus 1 is an apparatus for growing a silicon single crystal 3 from a polycrystalline silicon raw material 2 by an FZ (Floating Zone) method. The silicon single crystal growing device 1 includes a crystal holder 4, a high-frequency induction heating coil 5, a heat insulating cylinder 6, a gas doping device 7, a raw material holder 8, and a product single crystal weight holder 9.

The crystal holder 4 is a member that holds the tip end portion of the silicon single crystal 3, and the seed crystal is fixed on the upper portion, and is pulled downward as the silicon single crystal 3 grows. The product single crystal weight holder 9 comes into contact with the shoulder portion of the silicon single crystal 3 and holds the weight of the silicon single crystal 3.
The raw material holder 8 is composed of a ring-shaped body, and chucks the upper end body of the polycrystalline silicon raw material 2.

The high-frequency induction heating coil 5 is composed of a ring-shaped body and is not shown, but is connected to a high-frequency power source and melts the polycrystalline silicon raw material 2 by high-frequency induction heating to form a silicon melting zone 3A.
The heat insulating cylinder 6 is composed of a ring-shaped body that surrounds the grown silicon single crystal 3. The heat insulating cylinder 6 controls the temperature of the silicon single crystal 3 in the process of solidifying the melting zone 3A.

The gas doping device 7 includes a doping gas nozzle 71, a gas cylinder 72, a flow rate control valve 73, and a controller 74.
The tip of the dope gas nozzle 71 projects in the vicinity of the silicon melting zone 3A, and the dope gas is blown onto the melting zone 3A.
The dope gas is stored in the gas cylinder 72 in a high pressure state. As the dopant of the silicon single crystal 3, for example, phosphorus (PH ₃ ) can be used as the n-type dopant, boron (B ₂ H ₆ ) can be used as the p-type dopant, and the like. Further, as the dope gas, an inert gas such as argon or nitrogen containing these dopants can be used.
The flow rate control valve 73 is a valve that controls the flow rate of the dope gas contained in the gas cylinder 72, and controls the flow rate of the dope gas ejected from the dope gas nozzle 71 based on a control command from the controller 74.

In such a silicon single crystal growing apparatus 1, the upper end of the polycrystalline silicon raw material 2 is held by the raw material holder 8, and the lower end of the polycrystalline silicon raw material 2 is provided by the high frequency induction heating coil 5 fixed in the furnace. Is melted. The seed crystal fixed to the crystal holder 4 is brought into contact with the melting zone 3A of silicon, and the melt is solidified while pulling it downward and increasing the diameter so as to have a desired straight body diameter, and reaches the straight body diameter. After that, the melt is solidified so as to maintain the straight body diameter to produce the silicon single crystal 3. At this time, by moving the polycrystalline silicon raw material 2 downward at the same time, the lower end of the polycrystalline silicon raw material 2 is continuously melted, and an amount of melt required for single crystal formation is supplied.
When the crystals have grown to some extent, they are held by the product single crystal weight holder 9.
In the process of growing the silicon single crystal 3 as described above, the dopant is incorporated into the silicon single crystal 3 by blowing the doping gas onto the formed melting zone 3A via the doping gas nozzle 71.

[2] Method for Producing Silicon Single Crystal Next, a method for producing the silicon single crystal 3 according to the present embodiment will be described with reference to the flowchart shown in FIG.
[2-1] Acquisition of training record data (process S1: first process)
First, the growth record data of the silicon single crystal 3 is acquired. The breeding record data can be adopted as long as it is the past breeding record data in the same breeding device 1, but it is most preferable to adopt the breeding record data at the time of the previous breeding or 2-3 times before. This is because if the actual data is from the previous time or two or three times before, the influence of factors that change with time, such as deterioration of the members in the growing device and the relative positional relationship of the members, is small.
The growing record data to be acquired includes, for example, the material resistivity (Ω · cm) of the polycrystalline silicon raw material 2, the target diameter (mm) of the grown silicon single crystal 3, and the measured electrical resistivity (Ω · cm). Examples include the crystal feed rate (mm / min) of the silicon single crystal 3, the dope gas flow rate (cm ³ / min), and the dope gas concentration (ppm).

[2-2] Calculation of the relationship between electrical resistivity and doped gas absorption rate (step S2: second step)
After acquiring the growth record data of the silicon single crystal 3, the relationship between the electrical resistivity of the silicon single crystal 3 in the same growth device 1 and the doping gas absorption rate of the silicon single crystal 3 is calculated from the growth record data. Here, the doping gas absorption rate is a calculation of how much the dopant gas is absorbed, and when determining the doping amount to be the target value of the electrical resistivity in the next growth of the silicon single crystal 3. This is the index to use.

Specifically, the amount of dope gas f (x) can be obtained as follows using the dope gas absorption rate α.
The impurity concentration Cs of the silicon single crystal 3 calculated based on the target resistance of the silicon single crystal 3 and the difference Cs-Cp (x) of the impurity concentration Cp (x) according to the material length position x were obtained. When the difference Cs-Cp (x) is set to the impurity concentration Cg (x) to be supplied by the gas doping method according to the material length position x, the diameter of the silicon single crystal 3 is Ds (mm) and the crystal feed rate Vc. Assuming that the dope gas concentration is n and the dope gas absorption rate of the silicon single crystal 3 is α, it can be obtained by the following formula (1). Note that A is a constant.

When the relationship between the electrical resistivity of the silicon single crystal 3 and the doping gas absorption rate was investigated for the predetermined growing device 1 based on the acquired growing record data, as shown in FIG. 3, the electrical resistivity and the electrical resistivity were examined. It was confirmed that there is a proportional relationship with the dope gas absorption rate, and that the dope gas absorption rate gradually decreases as the electrical resistivity increases. That is, it was confirmed that the dope gas absorption rate of the silicon single crystal 3 must be calculated according to the electrical resistivity. The measurement results are also shown in Table 1.
The proportional relationship in FIG. 3 is expressed by the following equation (2), where x is the electrical resistivity and y is the doped gas absorption rate.
y = −0.0324x + 72.165 ... (2)
The equation (2) is the result for the predetermined growing apparatus 1, but when the other growing apparatus was also measured, the coefficient values of the equation (2) were different, but all of them had a proportional relationship with a negative gradient. became.

[2-3] Calculation of dope gas supply amount from the target value of electrical resistivity (step S3: third step)
Using the dope gas absorption rate calculated in the second step, the dope gas supply amount in the third step is calculated. The growth of silicon single crystal 3 by the FZ method is premised on small-quantity production of other varieties.
Therefore, the target value of the electrical resistivity of the grown silicon single crystal 3 differs from batch to batch, and the material electrical resistivity of the polycrystalline silicon raw material 2 as a raw material also differs from batch to batch.

Specifically, the required doping amount is calculated by subtracting the material resistivity of the polycrystalline silicon raw material 2 from the target value of the electrical resistivity of the silicon single crystal 3.
After the required doping amount is calculated, the volume of the silicon single crystal produced per unit time is obtained from the crystal feed rate and the target diameter of the silicon single crystal 3, and the required doping amount per unit time is calculated.
Then, using the proportional relationship shown in FIG. 3, the dope gas absorption rate corresponding to the target value of the electrical resistivity is obtained, and the required dope gas flow rate is calculated from the above-mentioned equation (1).

[2-4] Growth of silicon single crystal (step S4: fourth step)
After the indicated value of the dope gas flow rate is calculated, the controller 74 is operated to set the indicated value of the flow rate control valve 73 of the gas doping device 7 to the calculated indicated value.
Next, the high-frequency induction heating coil 5 is switched on, for example, the target diameter is 155 (mm), the crystal feed rate is 2.5 (mm / min), the dope gas concentration is 30 (ppm), and the dope gas flow rate is 13.0 (cm ³ /). It is set to min), and melting of the polycrystalline silicon raw material 2 is started to grow the silicon single crystal 3.

[3] Effects of the Embodiment According to the present embodiment as described above, there are the following effects.
The growth result data of the silicon single crystal 3 is acquired in the first step S1, and the relationship between the actual value of the electrical resistivity of the silicon single crystal 3 and the doping gas absorption rate of the silicon single crystal 3 is calculated in the second step S2. doing. Then, in the third step S3, the dope gas supply amount according to the target value of the electrical resistivity is calculated, and in the fourth step S4, the dope gas is blown by the calculated dope gas supply amount, and the electricity of the silicon single crystal 3 is electric. Silicon single crystal 3 can be grown by controlling the resistivity.
Therefore, since the dope gas supply amount is set in consideration of the dope gas absorption rate according to the change in the target value of the electrical resistivity, the target value of the electrical resistivity and the actual electric resistance of the grown silicon single crystal 3 are set. The deviation from the rate can be reduced.

As shown in FIG. 3, the relationship between the actual value of the electrical resistivity of the silicon single crystal 3 and the doping gas absorption rate is proportional to the negative gradient. Therefore, when the next silicon single crystal 3 is grown, the amount of the dope gas supplied can be easily obtained from the target value of the electrical resistivity in the next growth of the silicon single crystal 3 according to the proportional relationship.

Since the relationship between the measured value of electrical resistivity and the amount of dope gas supplied is obtained using the previous growth record data, the amount of dope gas supply can be obtained from the latest growth record data. Therefore, it is possible to grow a silicon single crystal 3 having an electrical resistivity closer to the target value of the electrical resistivity.
At least the target diameter, electrical resistivity, crystal feed rate, dope gas flow rate, and dope gas concentration of the silicon single crystal 3 are acquired as the growth result data. As a result, it is possible to acquire data that has a great influence on controlling the electrical resistivity of the growing silicon single crystal 3, so that the electrical resistivity of the growing silicon single crystal can be controlled with high accuracy. can.

As described in the above-described embodiment, the relationship between the measured electrical resistivity and the dope gas absorption rate is calculated in the second step from the growing record data in the first step, and is calculated in the third step. From the dope gas absorption rate, the case where the dope gas flow rate in the next growing was set (Example) and the case where the dope gas absorption rate was kept constant without considering the previous dope gas absorption rate were compared (Comparative example). The only difference between the examples and the comparative examples is the flow rate of the dope gas, and the other process conditions are the same.

The specific method of comparison is to determine how much the actual value of the electrical resistivity of the grown silicon single crystal 3 deviates from the target value of the electrical resistivity as the deviation of the hit rate. evaluated. That is, the hit rate is given by the following equation (3).
[Difference in hit rate] = ([Actual value]-[Aim value]) / [Aim value] x 100 (%)
... (3)
The results are shown in FIG. As shown in FIG. 4, it was confirmed that there was little variation in the hit rate in the examples, and there was almost no discrepancy between the target value of the electrical resistivity and the actual value of the grown silicon single crystal 3.

1 ... Growth device, 2 ... Polycrystalline silicon raw material, 3 ... Silicon single crystal, 3A ... Melting zone, 4 ... Crystal holder, 5 ... High frequency induction heating coil, 6 ... Heat insulation cylinder, 7 ... Gas doping device, 8 ... Raw material material Holder, 9 ... Product single crystal weight holder, 30 ... Dope gas concentration, 71 ... Dope gas nozzle, 72 ... Gas cylinder, 73 ... Flow control valve, 74 ... Controller, S1 ... First step, S2 ... Second step, S3 ... 3rd step, S4 ... 4th step.

Claims (4)

A method for producing a silicon single crystal in which a silicon single crystal is grown by the FZ (Floating Zone) method in which the electrical resistivity is controlled while blowing a dope gas onto the melting zone.
The first step of acquiring the growth record data of the silicon single crystal by the predetermined growth device, and
This is the second step of calculating the relationship between the actual value of the electrical resistivity of the silicon single crystal and the doping gas absorption rate of the silicon single crystal based on the acquired data on the actual growth of the silicon single crystal. The relationship between the actual value of the electrical resistivity of the silicon single crystal and the dope gas absorption rate is independent of the amount of the dope gas supplied, and the dope gas absorption rate decreases as the electrical resistivity increases. Process and
The third step of calculating the dope gas supply amount from the target value of the electric resistivity of the silicon single crystal manufactured by using the same growing device based on the relationship between the calculated actual value of the electrical resistivity and the dope gas absorption rate. When,
The fourth step of controlling the electrical resistivity of the silicon single crystal to be grown while blowing the dope gas according to the calculated dope gas supply amount, and
A method for producing a silicon single crystal, which comprises carrying out. In the method for producing a silicon single crystal according to claim 1,
The first step is a method for producing a silicon single crystal, which comprises acquiring data on previous growth results in the same growth apparatus. A method for producing a silicon single crystal in which a silicon single crystal is grown using the same growing device by the FZ (Floating Zone) method in which the electrical resistivity is controlled while blowing a dope gas onto the melting zone.
It is a step of calculating the dope gas absorption rate of the silicon single crystal in the previous silicon single crystal production from the actual result data of growing the silicon single crystal in the previous silicon single crystal production and the actual value of the electrical resistivity of the silicon single crystal. Therefore, the relationship between the actual value of the electrical resistivity of the silicon single crystal and the dope gas absorption rate is independent of the amount of the dope gas supplied, and becomes a proportional relationship in which the dope gas absorption rate decreases as the electrical resistivity increases. Process and
When the target value of the electrical resistivity of the silicon single crystal to be grown this time is larger than the measured value of the electrical resistivity of the previous silicon single crystal, the dope gas absorption rate smaller than the dope gas absorption rate of the previous silicon single crystal is set. If the electrical resistivity of the silicon single crystal to be grown this time is smaller than the measured value of the electrical resistivity of the previous silicon single crystal, use a dope gas absorption rate larger than the dope gas absorption rate of the previous silicon single crystal. The process of controlling the electrical resistivity of the silicon single crystal to be grown this time,
A method for producing a silicon single crystal, which comprises carrying out. In the method for producing a silicon single crystal according to any one of claims 1 to 3.
A method for producing a silicon single crystal, wherein the growth record data of the silicon single crystal includes at least a target diameter of the silicon single crystal, an electrical resistivity, a crystal feed rate, a dope gas flow rate, and a dope gas concentration.

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