JP2012206874A - Apparatus and method for pulling single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and method for pulling a silicon single crystal, by which the variation in the resistivity distribution along the length direction of the crystal is suppressed.SOLUTION: A control means 8b includes: a crystal diameter calculation means for calculating the average value of the crystal diameters of straight body parts grown in a predetermined measuring period; a pulling rate calculation means for calculating the average value of the pulling rates in a predetermined measuring period; an evaporation rate measuring means for calculating the necessary evaporation rate of a dopant impurity in a silicon melt from the average value of the crystal diameters calculated by the crystal diameter calculation means and the average value of the pulling rates calculated by the pulling rate calculation means; an in-furnace pressure calculation means for calculating necessary pressure in a furnace body from the necessary evaporation rate of the dopant impurity calculated by the evaporation rate calculation means; and an exhaust rate calculation means for calculating the exhaust rate of an inert gas discharged from the furnace body from the necessary pressure in the furnace body calculated by the in-furnace pressure calculation means, and the inert gas is discharged by an exhaust means 21 according to the exhaust rate calculated by the exhaust rate calculation means.

Description

  The present invention relates to a single crystal pulling apparatus and a single crystal pulling method for pulling a single crystal while growing it by the Czochralski method (hereinafter referred to as “CZ method”).

  The CZ method is widely used for the growth of silicon single crystals. In this method, the seed crystal is brought into contact with the surface of the silicon melt contained in the crucible, the crucible is rotated, and the seed crystal is pulled upward while rotating in the opposite direction. In this way, a single crystal is formed.

  In the single crystal growth step by the CZ method, a doping treatment is performed in which a dopant impurity (additive) is added to the silicon melt in the crucible in order to give a predetermined resistivity to the single crystal. Conventionally, this doping process is performed by adding trace elements such as arsenic and antimony as dopant impurities directly to the silicon melt in the quartz glass crucible. Specifically, for example, as shown in Patent Document 1, a particulate trace element for doping is dropped and put into a silicon melt.

By the way, when a highly volatile dopant impurity is used as an additive to the silicon melt, a single crystal is grown at a preset pulling speed, the furnace pressure is changed according to sequential control, and the growth axis in the crystal is increased. Controlling the resistivity distribution in the direction is performed.
Specifically, the furnace pressure is changed to a preset pressure value according to the growth of the single crystal (elapsed pulling time), so that the dopant impurity in the crystal does not become high concentration and the disorder of the crystal is suppressed. This improves the yield of crystals.

JP 2010-64930 A

However, in practice, the growth rate of the crystal varies depending on various conditions (change in the surface temperature of the melt when the seed crystal is brought into contact with the surface of the silicon melt, change in the thickness of the crucible, emissivity of the hot zone, It may vary from operation to operation due to changes in the heater over time.
That is, even if the pulling speed of the crystal is set to the same value, the growing speed may be different.As a result, even if the evaporation amount per unit time changes and the sequential control of the furnace pressure is performed, the crystal length There was a problem that the resistivity distribution in the direction varied greatly.

  The present invention has been made under the circumstances as described above, and adds a dopant impurity to a silicon melt in a crucible and pulls the silicon single crystal from the crucible by the Czochralski method. An object of the present invention is to provide a single crystal pulling apparatus and pulling method capable of suppressing variations in resistivity distribution along the crystal length direction.

  A single crystal pulling apparatus according to the present invention, which has been made to solve the above-mentioned problems, adds a dopant impurity to a silicon melt in a crucible and pulls up the silicon single crystal from the crucible by the Czochralski method. A pulling device, comprising: exhaust means for exhausting the inert gas introduced into the furnace containing the crucible at a predetermined exhaust speed; and control means for controlling the exhaust speed of the exhaust means, the control The means includes a crystal diameter calculating means for calculating a crystal diameter average value of the straight body portion grown in a predetermined measurement period in the step of growing the straight body portion of the single crystal, and a pulling speed average value in the predetermined measurement period. From the pulling speed calculating means for calculating the crystal diameter average value calculated by the crystal diameter calculating means and the pulling speed average value calculated by the pulling speed calculating means, the dopant in the silicon melt An evaporation rate calculating means for calculating a required evaporation rate of a pure product, an in-furnace pressure calculating means for calculating a required pressure in the furnace from a required evaporation rate of the dopant impurity calculated by the evaporation rate calculating means, Exhaust speed calculation means for calculating the exhaust speed of the inert gas exhausted from the furnace body from the necessary pressure in the furnace body calculated by the pressure calculation means, and the exhaust speed calculation means calculated in the exhaust means It is characterized by exhausting according to the exhaust speed.

The evaporation rate of dopant impurities in the silicon melt is E (cm / sec), the resistivity gradient is m, the effective segregation coefficient is K _eff , the free surface area of the crystal is A (cm ² ), and the crystal unit volume is solidified. When the time to perform is R (sec) and the furnace pressure is PR (Torr), the evaporation rate calculation means calculates the necessary evaporation rate of the dopant impurity by the following equation (1), and calculates the furnace pressure. By means, it is desirable that the necessary pressure in the furnace body is calculated by the following equation (2).

Further, the exhaust means is a vacuum pump for exhausting the atmosphere in the furnace body, and when the frequency of electric power for determining the exhaust speed of the vacuum pump is F (Hz), the exhaust speed calculation means The frequency for determining the exhaust speed is preferably calculated by the following equation (3).

Alternatively, the exhaust means is a throttle valve that is controlled by the opening efficiency of the exhaust port, and when the opening efficiency is X (%), the exhaust speed calculation means causes the inert gas to be exhausted from the furnace body. The opening efficiency that determines the exhaust speed is preferably calculated by the following equation (4).

  Further, the control means sets the measurement period a plurality of times in the step of growing the straight body of the single crystal, and each time the exhaust speed is calculated in each measurement period, according to the exhaust speed, the exhaust means It is desirable to exhaust.

  According to such a configuration, each step of single crystal growth is not simply increased at a preset operating condition (pulling speed), but the exhaust speed (inner pressure) of the furnace atmosphere according to the actual growth speed. Can be fed back to the dopant evaporation rate from the silicon melt. The evaporation rate of the dopant impurity controlled at this time is a value necessary to keep the relationship between the dopant concentration in the crystal and the solidification rate (resistivity gradient) constant, and the dopant concentration in the crystal length direction, that is, The resistivity distribution can be made uniform.

  In addition, the single crystal pulling method according to the present invention, which has been made to solve the above problems, exhausts the inert gas introduced into the furnace body containing the crucible at a predetermined exhaust speed, A single crystal pulling method in which a dopant impurity is added to a silicon melt and a silicon single crystal is pulled up from the crucible by a Czochralski method, and is grown during a predetermined measurement period in a step of growing the straight body of the single crystal. Calculating a crystal diameter average value of the straight body part, calculating a pulling speed average value in the predetermined measurement period, crystal diameter average value calculated by the crystal diameter calculating means, and pulling speed Calculating a necessary evaporation rate of the dopant impurity in the silicon melt from the average pulling rate calculated by the calculating unit; and a dopant concentration calculated by the evaporation rate calculating unit. The step of calculating the required pressure in the furnace from the required evaporation rate of the object, and the exhaust speed of the inert gas exhausted from the furnace from the required pressure in the furnace calculated by the furnace pressure calculation means And a step of exhausting the furnace body in accordance with the calculated exhaust speed.

The evaporation rate of dopant impurities in the silicon melt is E (cm / sec), the resistivity gradient is m, the effective segregation coefficient is K _eff , the free surface area of the crystal is A (cm ² ), and the crystal unit volume is solidified. The required evaporation rate of the dopant impurity is calculated by the following equation (1), where R (sec) is the time to perform and PR (Torr) is the furnace pressure, and the required pressure in the furnace is It is desirable to calculate by 2).

Further, the atmosphere in the furnace body is exhausted by a vacuum pump, and when the frequency of electric power for determining the exhaust speed of the vacuum pump is F (Hz), the frequency for determining the exhaust speed is expressed by the following equation: It is desirable to calculate by (3).

Alternatively, the exhaust speed of the inert gas exhausted from the furnace body is controlled by the opening efficiency of the throttle valve, and when the open efficiency is X (%), the exhaust speed of the inert gas exhausted from the furnace body is The opening efficiency to be determined is preferably calculated by the following formula (4).

  Further, in the step of growing the straight body portion of the single crystal, it is desirable that the measurement period is set a plurality of times, and the exhaust means is evacuated according to the exhaust speed every time the exhaust speed is calculated in each measurement period. .

  According to such a method, each step of single crystal growth is not simply raised at a preset operation condition (pulling speed), but the exhaust speed (furnace pressure) of the furnace atmosphere according to the actual growth speed. Can be fed back to the dopant evaporation rate from the silicon melt. The evaporation rate of the dopant impurity controlled at this time is a value necessary to keep the relationship between the dopant concentration in the crystal and the solidification rate (resistivity gradient) constant, and the dopant concentration in the crystal length direction, that is, The resistivity distribution can be made uniform.

  According to the present invention, in a single crystal pulling apparatus that adds a dopant impurity to a silicon melt in a crucible and pulls the silicon single crystal from the crucible by the Czochralski method, the resistivity along the length direction of the crystal. A single crystal pulling apparatus and pulling method that can suppress variation in distribution can be obtained.

FIG. 1 is a block diagram showing the overall configuration of a single crystal pulling apparatus according to the present invention. FIG. 2 is a flow showing the flow of a single crystal pulling process by the single crystal pulling apparatus of FIG. FIG. 3 is a graph showing the experimental results of Example 1 according to the present invention and showing the resistivity distribution in the crystal length direction. FIG. 4 is a graph showing the experimental results of Comparative Example 1 according to the conventional method and showing the resistivity distribution in the crystal length direction. FIG. 5 is a graph showing the experimental results of Example 1 according to the present invention and showing the dislocation-free rate relative to the solidification rate. FIG. 6 is a graph showing the experimental results of Comparative Example 1 according to the conventional method and showing the dislocation-free rate relative to the solidification rate.

Hereinafter, embodiments of a single crystal pulling apparatus and a single crystal pulling method according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of a single crystal pulling apparatus 1 according to the present invention.
This single crystal pulling apparatus 1 includes a furnace body 2 formed by superposing a pull chamber 2b on a cylindrical main chamber 2a, a crucible 3 provided in the furnace body 2, and a semiconductor loaded in the crucible 3. A heater 4 for melting the raw material (raw material polysilicon) M and a pulling mechanism 5 for pulling up the single crystal C to be grown are provided. The crucible 3 has a double structure, and is composed of a quartz glass crucible on the inside and a graphite crucible on the outside.
The pulling mechanism 5 has a winding mechanism 5a driven by a motor and a pulling wire 5b wound up by the winding mechanism 5a, and a seed crystal P is attached to the tip of the wire 5b.

In addition, a gas inlet 18 for introducing a predetermined inert gas (in this embodiment, Ar gas G) into the furnace body 2 is provided at the top of the pull chamber 2b, and at the bottom of the main chamber 2b. A gas discharge port 19 for discharging the gas introduced into the furnace body 2 is provided.
An Ar gas supply source 26 is connected to the gas inlet 18 through a valve 25.
On the other hand, the gas discharge port 19 is connected to a vacuum pump 21 (exhaust means) via a valve 20 for adjusting the gas flow rate. The vacuum pump 21 has an inverter circuit, and the number of rotations of a motor that drives the pump is controlled by an arithmetic control device 8b (control means) of the computer 8.
Accordingly, when the vacuum pump 21 is driven in a state where the valve 20 is opened, the Ar gas G flows from the gas inlet 18 to the gas outlet 19 (that is, a predetermined direction from the upper side to the lower side in the furnace body 2). Gas flow at a flow rate) is formed.

  Further, a radiation shield 6 for rectifying the gas flow in the furnace is provided above and in the vicinity of the crucible 3 in the main chamber 2a. The radiation shield 6 has an upper portion and a lower portion so as to surround the periphery of the single crystal C, and shields extra radiant heat from the heater 4 and the like on the growing single crystal C. The distance dimension (gap) between the lower end of the radiation shield 6 and the melt surface is controlled so as to maintain a predetermined distance according to desired characteristics of the single crystal to be grown.

Further, a pressure sensor 14 for detecting the pressure in the furnace is provided in the furnace body 2, and the detected value is output to the arithmetic control device 8 b of the computer 8.
Further, an imaging device 23 composed of a CCD camera or the like is installed on the outside of the furnace body 2 toward the single crystal C to be grown, and the arithmetic control device 8b is based on the image captured by the imaging device 23. The diameter of C is measured.

As shown in FIG. 1, the single crystal pulling apparatus 1 includes a heater control unit 9 that controls the amount of power supplied to the heater 4 that controls the temperature of the silicon melt M, a motor 10 that rotates the crucible 3, and a motor. And a motor control unit 10a for controlling the number of rotations of ten.
Also, an elevating device 11 that controls the height of the crucible 3, an elevating device control unit 11 a that controls the elevating device 11, and a wire reel rotating device control unit 12 that controls the pulling speed and the number of rotations of the grown crystal. Yes. Each of these control units 9, 10 a, 11 a, 12 is connected to an arithmetic control device 8 b of the computer 8.

The storage device 8a of the computer 8 stores a single crystal growth program P for executing each step of single crystal growth.
This single crystal growth program P does not simply raise each step of single crystal growth under preset operating conditions, but adjusts the exhaust rate (pressure) of the furnace atmosphere in accordance with the actual growth rate to melt silicon. A program configuration for controlling the evaporation rate of the dopant from the liquid M is adopted.

In the storage device 8a, the dopant impurity evaporation rate E (cm / sec), the crystal free surface area A (cm ² ), and the crystal unit volume are solidified as arithmetic expressions used by the single crystal growth program P. Formula (1) which is a correlation formula with time R (sec) is stored. Since the free surface area A of the crystal and the time R during which the crystal unit volume is solidified are determined by the crystal diameter and the pulling speed, the equation (1) is the evaporation rate E of the dopant impurity, the crystal diameter and the pulling speed. It can be said that
Moreover, in Formula (1), m is a resistivity inclination and is a design value preset in the range of _Keff- 1 <m <0. K _eff is an effective segregation coefficient.

この式（１）は、ＢＰＳ（Ｂｕｒｔｏｎ，Ｐｒｉｍ，Ｓｌｉｃｈｔｅｒ）理論（角野浩二、「半導体の結晶欠陥制御の科学と技術」−シリコン編、サイエンスフォーラム、ｐ．１２９）に基づく下記の式（５）から得られた式である。
式（５）は、結晶中のドーパント濃度Ｃ_Ｓ（ａｔｏｍｓ／ｃｍ^３）を求める式であって、Ｃ_Ｌ０（ａｔｏｍｓ／ｃｍ^３）はシリコン溶融液中の初期ドーパント濃度、Ｋ_ｅｆｆは実効偏析係数、Ｅ（ｃｍ／ｓｅｃ）はドーパント不純物の蒸発速度、Ａは自由表面積（ｃｍ^２）、Ｒ（ｓｅｃ）は結晶単位体積が固化する時間、ｇは固化率である。

This equation (1) is expressed by the following equation (5) based on BPS (Burton, Prime, Srichter) theory (Koji Kakuno, “Science and technology of crystal defect control of semiconductors”-Silicon edition, Science Forum, p. 129). Is the formula obtained from
Equation (5) is an equation for determining the dopant concentration C _S (atoms / cm ³ ) in the crystal, where C _L0 (atoms / cm ³ ) is the initial dopant concentration in the silicon melt, and K _eff is the effective segregation coefficient. , E (cm / sec) is the evaporation rate of the dopant impurity, A is the free surface area (cm ² ), R (sec) is the time for the crystal unit volume to solidify, and g is the solidification rate.

この式（５）の両辺の対数をとれば、Ｋ_ｅｆｆ＋Ｅ・Ａ・Ｒ−１が、ドーパント濃度Ｃ_Ｓと固化率ｇの関係の傾きとなる。ここで、Ｋ_ｅｆｆ＋Ｅ・Ａ・Ｒ−１＝ｍとすると、傾きｍが常に設計通りであれば、結晶長さ方向の抵抗率分布（ドーパント不純物の濃度）は常に同じとなる。
即ち、ドーパント不純物の蒸発速度Ｅが、式（１）を満足することにより、抵抗率のばらつきを抑制することができる。

If the logarithm of both sides of the formula (5) is taken, K _eff + E · A · R−1 is the slope of the relationship between the dopant concentration C _S and the solidification rate g. Here, _assuming that K _eff + E · A · R−1 = m, the resistivity distribution (concentration of dopant impurities) in the crystal length direction is always the same if the slope m is always as designed.
That is, when the evaporation rate E of the dopant impurity satisfies the formula (1), variation in resistivity can be suppressed.

In the storage device 8a, the following formula (2), which is a correlation formula between the evaporation rate E of the dopant impurity in the silicon melt and the furnace pressure PR, is used as an arithmetic formula used by the single crystal growth program P. It is remembered.
This formula (2) is obtained from the preliminary pull-up test or measurement data in actual operation.

Further, the storage device 8a stores the following expression (3), which is a correlation expression between the exhaust speed in the furnace and the pressure in the furnace, as an arithmetic expression used by the single crystal growth program P.
Since the exhaust speed in the furnace is controlled by the frequency F (Hz) of power supplied by the inverter circuit of the vacuum pump 21, the expression (3) is a correlation expression between the frequency F and the furnace pressure PR.
This equation (3) is obtained by flowing Ar gas G into the furnace body 2 in advance according to the operating conditions and detecting the pressure in the furnace by the pressure sensor 14.

In the single crystal pulling apparatus 1 configured as described above, the single crystal growth program P is executed, and single crystal growth is performed as follows.
First, the valves 20 and 25 are opened, and the vacuum pump 21 is driven by a command from the arithmetic control device 8b. Thereby, a gas flow of Ar gas G is formed in the furnace body 2 from the gas inlet 18 toward the gas outlet 19 (that is, from the upper side to the lower side), and a predetermined atmosphere is formed ( Step S1) in FIG.

Then, the heater controller 9 is actuated by a command from the arithmetic and control unit 8b, whereby the heater 4 is heated and the raw material polysilicon M is melted in the crucible 3 (step S2 in FIG. 2). Further, a predetermined amount of dopant impurities (for example, any of red phosphorus, arsenic, antimony dope, etc.) is introduced into the silicon melt M in the crucible 3.
Further, the motor control unit 10a and the lifting device control unit 11a are operated by a command from the arithmetic control device 8b, and the crucible 3 is rotated at a predetermined rotational speed at a predetermined height position (step S3 in FIG. 2).

  Next, in accordance with a command from the arithmetic control device 8b, the wire reel rotating device control unit 12 is operated, the winding mechanism 5a is operated, and the wire 5b is lowered. Then, the seed crystal P attached to the wire 5b is brought into contact with the silicon melt M, necking to dissolve the tip of the seed crystal P is performed, and formation of the neck portion is started (step S4 in FIG. 2).

Further, when the neck portion is grown to a predetermined length, the pulling conditions are further adjusted with parameters such as the power supplied to the heater 4 and the pulling speed (usually a speed of several millimeters per minute) by the command of the arithmetic control device 8b. The single crystal C that is the product part is grown.
That is, a crown portion is formed (step S5 in FIG. 2), and then the process proceeds to a straight body portion forming step (step S6 in FIG. 2).

When the process of forming the straight body portion is started and a predetermined measurement period (for example, a time set between 5 and 30 minutes) has elapsed (step S7 in FIG. 2), the arithmetic control device 8b uses the pulling speed calculating means. And the average pull-up speed during the measurement period is calculated (step S8 in FIG. 2).
The arithmetic and control unit 8b functions as a crystal diameter calculating unit, measures the diameter of the single crystal C from the image captured by the imaging device 23, and calculates the average value of the crystal diameter during the measurement time (step in FIG. 2). S9).

The arithmetic and control unit 8b calculates the time R during which the crystal unit volume is solidified and the free surface area A of the crystal from the average value of the crystal diameter and the average pulling speed. Furthermore, the effective segregation coefficient K _eff is calculated from the actual pulling speed average value.
The arithmetic and control unit 8b functions as an evaporation rate calculating unit, and substitutes the calculated time R for the crystal unit volume to solidify, the free surface area A of the crystal, and the effective segregation coefficient K _eff into the equation (1). Thus, the necessary evaporation rate E of the dopant impurity is calculated (step S10 in FIG. 2).

When the required evaporation rate E is obtained in step S10, the arithmetic and control unit 8b functions as a furnace pressure calculation means, substitutes the required evaporation rate E into the equation (2), and is required in the furnace body 2. A pressure value is calculated (step S11 in FIG. 2).
Further, the arithmetic and control unit 8b functions as an exhaust speed calculation means, substitutes the calculated required pressure value into the equation (3), and calculates the required exhaust speed (step S12 in FIG. 2).
When the required exhaust speed is obtained, the arithmetic and control unit 8b controls the vacuum pump 21 to exhaust the interior of the furnace body 2 at the exhaust speed (step S13 in FIG. 2).

And the process of step S7 to step S13 is repeated in multiple times until formation of a straight body part is completed (step S14 of FIG. 2).
When the growth of the straight body portion is completed, the tail process (step S15 in FIG. 2) is performed according to the single crystal growth program P, and the grown single crystal C is finally pulled up to the upper part in the furnace body 2.

As described above, according to the embodiment of the present invention, each step of single crystal growth is not simply raised at a preset operation condition (pulling speed), but the atmosphere in the furnace is changed according to the actual growth speed. The pumping speed (furnace pressure) is adjusted and fed back to the dopant evaporation speed from the silicon melt M.
The evaporation rate of the dopant impurity controlled at this time is a value necessary to keep the relationship between the dopant concentration _CS and the solidification rate g (resistivity gradient) constant, so the dopant concentration in the crystal length direction, That is, the resistivity distribution can be made uniform.

In the above-described embodiment, the vacuum pump 21 has been described as an example of the exhaust means for exhausting the furnace, but is not limited thereto. For example, a throttle valve may be provided as exhaust means, and the effective exhaust speed may be changed by controlling the opening efficiency.
In this case, when the open efficiency is X (%), the open efficiency may be calculated by the following formula (4).

  The single crystal pulling apparatus and single crystal pulling method according to the present invention will be further described based on examples. In this example, a single crystal growth step was performed according to the above embodiment, and the effect of the present invention was verified.

[Example 1]
As Example 1, 140 g of Si raw material was melted in a quartz crucible having a diameter of 22 inches and 700 g of red phosphorus was doped, and according to an embodiment of the present invention, the initial resistivity was 1.2 (mΩcm), and the diameter of the straight barrel portion. A 200 mm single crystal was grown.
More specific experimental conditions include furnace pressure in the range of 300 (Torr) to 500 (Torr), pulling speed in the range of 0.8 (mm / min) to 0.3 (mm / min), inertness The gas flow rate of the gas (Ar) was controlled in the range of 150 (l / min) to 50 (l / min).
And about the single crystal of 3 pulled up, the resistivity distribution of the growth axis direction was measured, 12 single crystals were selected as a sample, and the dislocation-free rate was measured.
The target value of resistivity was 1.2 (mΩcm), and the allowable resistivity range was 1.2 ± 0.1 (mΩcm).
[Comparative Example 1]
As Comparative Example 1, single crystal growth was performed by conventional sequential control. Other conditions were the same as in Example 1.

FIG. 3 shows the resistivity distribution in Example 1, and FIG. 4 shows the resistivity distribution in Comparative Example 1. In the graphs of FIGS. 3 and 4, the horizontal axis represents the solidification rate, and the vertical axis represents the resistivity (mΩcm).
In Example 1, as shown in FIG. 3, the resistivity along the growth axis direction of any single crystal has a small variation from the design value, and the target value is 1.2 ± 0.1 (mΩcm). Within the range.
On the other hand, in Comparative Example 1, as shown in FIG. 4, the resistance value of the two single crystals out of the three greatly varied from the design value.

FIG. 5 shows the dislocation-free rate in Example 1, and FIG. 6 shows the dislocation-free rate in Comparative Example 1. 5 and 6, the horizontal axis represents the solidification rate, and the vertical axis represents the frequency of dislocation. That is, the higher the solidification rate obtained by averaging all samples, the higher the dislocation-free rate.
In Example 1, as shown in FIG. 5, the average solidification rate (non-dislocation rate) was 0.843. On the other hand, in Comparative Example 1, as shown in FIG. 6, the average solidification rate (non-dislocation rate) was 0.7929, and according to Example 1, it was confirmed that the non-dislocation rate was improved.

  From the results of the above examples, it was confirmed that according to the single crystal pulling apparatus and the pulling method according to the present invention, variation in resistivity distribution along the length direction of the crystal was suppressed and productivity was improved. .

1 Single crystal pulling device 2 Furnace 3 Crucible 8b Arithmetic control device (control means)
14 Pressure sensor 21 Vacuum pump (exhaust means)
C Single crystal M Silicon melt

Claims (10)

A single crystal pulling apparatus for adding a dopant impurity to a silicon melt in a crucible and pulling up a silicon single crystal from the crucible by a Czochralski method,
An exhaust means for exhausting the inert gas introduced into the furnace containing the crucible at a predetermined exhaust speed, and a control means for controlling the exhaust speed of the exhaust means,
The control means includes
In the step of growing the straight body of the single crystal, crystal diameter calculating means for calculating the average crystal diameter of the straight body grown in a predetermined measurement period;
A pulling speed calculating means for calculating a pulling speed average value in the predetermined measurement period;
Evaporation rate calculation means for calculating a necessary evaporation rate of the dopant impurity in the silicon melt from the average crystal diameter value calculated by the crystal diameter calculation unit and the average pulling rate value calculated by the pulling rate calculation unit When,
In-furnace pressure calculation means for calculating a necessary pressure in the furnace body from a necessary evaporation rate of the dopant impurity calculated by the evaporation rate calculation means,
Exhaust speed calculation means for calculating the exhaust speed of the inert gas exhausted from the furnace body from the necessary pressure in the furnace body calculated by the furnace pressure calculation means,
A single crystal pulling apparatus, characterized in that the exhaust means exhausts according to the exhaust speed calculated by the exhaust speed calculation means. Evaporation rate of dopant impurities in the silicon melt is E (cm / sec), resistivity slope is m, effective segregation coefficient is K _eff , crystal free surface area is A (cm ² ), and crystal unit volume is solidified time Is R (sec) and the furnace pressure is PR (Torr),
The evaporation rate calculation means calculates the required evaporation rate of the dopant impurity by the following equation (1), and the furnace pressure calculation means calculates the required pressure in the furnace body by the following equation (2). The single crystal pulling apparatus according to claim 1.

The exhaust means is a vacuum pump for exhausting the atmosphere in the furnace body,
When the frequency of electric power for determining the exhaust speed of the vacuum pump is F (Hz), the frequency for determining the exhaust speed by the exhaust speed calculating means is calculated by the following equation (3). The single crystal pulling apparatus according to claim 2.

The exhaust means is a throttle valve controlled by the opening efficiency of the exhaust port,
When the open efficiency is X (%), the open efficiency for determining the exhaust speed of the inert gas exhausted from the furnace body by the exhaust speed calculating means is calculated by the following equation (4). The single crystal pulling apparatus according to claim 2, wherein the pulling apparatus is a single crystal pulling apparatus.

The control means includes
In the step of growing the straight body of the single crystal, the measurement period is set a plurality of times, and each time the exhaust speed is calculated in each measurement period, the exhaust means is evacuated according to the exhaust speed. The single crystal pulling apparatus according to claim 1 or 2. The inert gas introduced into the furnace containing the crucible is exhausted at a predetermined exhaust speed, and dopant impurities are added to the silicon melt in the crucible, and the silicon single crystal is pulled up from the crucible by the Czochralski method. A single crystal pulling method,
In the step of growing the straight body of the single crystal, calculating a crystal diameter average value of the straight body grown in a predetermined measurement period;
Calculating a pulling speed average value in the predetermined measurement period;
Calculating a required evaporation rate of dopant impurities in the silicon melt from the average crystal diameter calculated by the crystal diameter calculating unit and the average pulling rate calculated by the pulling rate calculating unit;
Calculating a required pressure in the furnace from the required evaporation rate of the dopant impurity calculated by the evaporation rate calculating means;
Calculating the exhaust velocity of the inert gas exhausted from the furnace body from the necessary pressure in the furnace body calculated by the furnace pressure calculation means;
And a step of exhausting the furnace body according to the calculated exhaust speed. Evaporation rate of dopant impurities in the silicon melt is E (cm / sec), resistivity slope is m, effective segregation coefficient is K _eff , crystal free surface area is A (cm ² ), and crystal unit volume is solidified time Is R (sec) and the furnace pressure is PR (Torr),
The required evaporation rate of the dopant impurity is calculated by the following formula (1):
The single crystal pulling method according to claim 6, wherein the necessary pressure in the furnace body is calculated by the following formula (2).

The atmosphere in the furnace body is exhausted by a vacuum pump,
The frequency for determining the exhaust speed is calculated by the following equation (3), where F (Hz) is a frequency of electric power for determining the exhaust speed of the vacuum pump. The single crystal pulling method described in 1.

The exhaust speed of the inert gas exhausted from the furnace body is controlled by the opening efficiency of the throttle valve,
8. The open efficiency that determines the exhaust speed of the inert gas exhausted from the furnace body when the open efficiency is X (%) is calculated by the following equation (4): The single crystal pulling method described.

  In the step of growing the straight body of the single crystal, the measurement period is set a plurality of times, and each time the exhaust speed is calculated in each measurement period, the furnace body is exhausted according to the exhaust speed. The single crystal pulling method according to any one of claims 6 to 9.

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