JP2012031023A - Method for producing silicon single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for securely producing a silicon single crystal having only a small variation in specific resistance with no need of complicate control of the atmospheric pressure.SOLUTION: The method for producing a silicon single crystal involves pulling up an n-type silicon single crystal having a specific resistance value of ≥10 Ωcm from a silicon melt containing a volatile dopant added therein by the Chokralski method, wherein the pulling up of the silicon single crystal is started while the atmospheric pressure is being regulated in the pulling up of the silicon single crystal, and after the atmospheric pressure has reached a predetermined pressure, the atmospheric pressure is maintained in the range of the predetermined pressure ±0.5 kPa till the completion of the pulling up.

Description

  The present invention relates to a method for producing a silicon single crystal, and in particular, to produce a silicon single crystal having a specific resistance value of 10 Ω · cm or higher by a Czochralski method from a silicon melt to which a volatile dopant is added. It is about the method.

  In the silicon wafer manufacturing process, in order to change the electrical resistivity of the silicon single crystal, dopant (boron as p-type, phosphorus, arsenic, antimony, etc. as p-type) is added to the silicon melt used to pull up the single crystal. There is a method of adding. In order to lower the electrical resistivity, it is effective to add a dopant such as arsenic, red phosphorus, or antimony.

  However, many dopants added to the silicon melt are generally highly volatile and easily evaporated. When the dopant in the silicon melt evaporates, the silicon melt cannot secure a desired dopant concentration, causing a problem in that the specific resistance value of the product varies.

  For this reason, Patent Document 1 discloses a Ga-doped silicon single crystal manufacturing method in which pulling is performed by the Czochralski method while lowering the atmospheric pressure when pulling up the silicon single crystal. If this method is used, since the evaporation amount of the dopant from the silicon melt can be controlled, the resistivity variation of the silicon single crystal can be suppressed.

  However, in the manufacturing method of Patent Document 1, although the resistivity fluctuation of the silicon single crystal can be suppressed, the control of the pressure atmosphere when pulling up the silicon single crystal is complicated, and the melting is always performed from the start to the end of the pulling. Attention must be paid to the concentration of the solution and the atmospheric pressure. Furthermore, when manufacturing a high-resistance silicon single crystal with a specific resistance value of 10 Ω · cm or more, precise control of the dopant concentration is required. Therefore, further improvement has been desired for use in an actual manufacturing process of a single silicon.

JP 2002-154896 A

  In view of the above problems, the object of the present invention is to reliably produce an n-type silicon single crystal having a specific resistance value of 10 Ω · cm or more and a small variation without requiring complicated control of atmospheric pressure. It is to provide a way that can be done.

  Among the methods for producing a silicon single crystal in which the silicon single crystal is pulled up from a silicon melt added with a volatile dopant by the Czochralski method, the inventors have a specific resistance value of 10 Ω · cm or more. As a result of repeated studies on the silicon single crystal to solve the above problems, the amount of evaporation of the dopant in the liquid is large until the atmospheric pressure when pulling up the silicon single crystal reaches a predetermined pressure. It has been found that after the pressure is gradually reduced to reach a predetermined pressure, variation in the specific resistance value of the silicon single crystal can be suppressed without finely changing the atmospheric pressure. In addition, since the atmospheric pressure is maintained within the predetermined pressure ± 0.5 kPa from the time when the atmospheric pressure reaches the predetermined pressure to the end of the pulling, complicated control is required as compared with the conventional manufacturing method. In other words, it has been found that a silicon single crystal having a small variation in specific resistance can be reliably produced.

In order to achieve the above object, the gist of the present invention is as follows.
(1) A method for producing a silicon single crystal in which an n-type silicon single crystal having a specific resistance value of 10 Ω · cm or more is pulled from a silicon melt to which a volatile dopant is added by a Czochralski method. The pulling of the silicon single crystal is started while adjusting the atmospheric pressure when pulling up the crystal, and after the atmospheric pressure reaches the predetermined pressure, the atmospheric pressure is maintained in the range of the predetermined pressure ± 0.5 kPa until the end of the pulling. A method for producing a silicon single crystal.

(2) The method for producing a silicon single crystal according to (1), wherein the predetermined pressure is 4 kPa.

(3) In the adjustment of the atmospheric pressure, the atmospheric pressure is gradually decreased with a gradient of −0.01 to −0.005 kPa / mm on the basis of the pulling amount of the silicon single crystal. A method for producing a silicon single crystal.

(4) The method for producing a silicon single crystal according to (1), wherein the volatile dopant is arsenic or antimony.

(5) The method for producing a silicon single crystal according to (1), wherein the volatile dopant is charged by a wafer dope method.

(6) A method for producing a silicon single crystal in which an n-type silicon single crystal having a specific resistance value of 10 Ω · cm or more is pulled from a silicon melt to which a volatile dopant has been added by the Czochralski method. The pulling of the silicon single crystal is started while adjusting the atmospheric pressure when pulling up the crystal, and after the atmospheric pressure reaches the first predetermined pressure, the atmospheric pressure is rapidly decreased to the second predetermined pressure, and then A method for producing a silicon single crystal, characterized in that the atmospheric pressure is maintained in a range of the second predetermined pressure ± 0.2 kPa until the end of pulling.

(7) The method for producing a silicon single crystal according to (6), wherein the first predetermined pressure is 4 kPa and the second predetermined pressure is 2 kPa.

(8) The method for producing a silicon single crystal according to (6), wherein a gradient when the atmospheric pressure is rapidly decreased is in a range of −0.08 to −0.02 kPa / mm based on a pulling amount of the silicon single crystal. .

  According to the present invention, it is possible to reliably manufacture an n-type silicon single crystal having a specific resistance value of 10 Ω · cm or more and a small variation without requiring complicated control of atmospheric pressure.

(a) is a graph showing the relationship between the pulling amount (mm) when the silicon single crystal is pulled according to the present invention and the atmospheric pressure (kPa) when pulling, and (b) is obtained. It is the graph which showed the relationship between the length position (mm) toward a tail part from the top part of a silicon single crystal ingot, and the specific resistance value (ohm * cm) of a silicon single crystal. (A) is a graph showing the relationship between the pulling amount (mm) when the silicon single crystal is pulled according to the conventional manufacturing method and the atmospheric pressure (kPa) at the time of pulling, and (b) is obtained. 5 is a graph showing the relationship between the length position (mm) from the top portion to the tail portion of the obtained silicon single crystal ingot and the specific resistance value (Ω · cm) of the silicon single crystal. (a) is a graph showing the relationship between the pulling amount (mm) when pulling up a silicon single crystal according to the present invention and the atmospheric pressure (kPa) during pulling, and (b) was obtained. It is the graph which showed the relationship between the length position (mm) toward a tail part from the top part of a silicon single crystal ingot, and the specific resistance value (ohm * cm) of a silicon single crystal. It is the figure which showed one Embodiment of the pulling apparatus used for the manufacturing method of the silicon single crystal according to this invention.

A method for producing a silicon single crystal according to the present invention will be described with reference to the drawings.
A method for producing a silicon single crystal according to the present invention is a method for producing a silicon single crystal in which a silicon single crystal having a specific resistance value of 10 Ω · cm or more is pulled from a silicon melt to which a volatile dopant is added by a Czochralski method. is there.

  Here, the specific resistance value of the silicon single crystal is limited to 10 Ω · cm or more. This is because the silicon single crystal obtained has a low dopant concentration such that the specific resistance value of the silicon single crystal is 10 Ω · cm or more. It is effective only when pulling up using a melt, and when the specific resistance value is less than 10 Ω · cm (that is, when the dopant concentration contained in the silicon melt is high), This is because the effect (manufacturing a silicon single crystal with small variation in specific resistance without requiring complicated control of atmospheric pressure) cannot be exhibited. When the method according to the present invention is applied to a crystal of less than 10 Ω · cm, evaporation of dopants such as antimony can be easily promoted by reducing the operating pressure in one direction, and a complex atmosphere. This is because variations in specific resistance values can be suppressed without requiring pressure control.

  Then, the present invention starts pulling up the silicon single crystal in a state where the atmospheric pressure when pulling up the silicon single crystal is adjusted, and after the atmospheric pressure reaches a predetermined pressure, the predetermined pressure ± 0.5 until the end of the pulling. The atmospheric pressure is maintained in a range of kPa.

  The atmospheric pressure when pulling up the silicon single crystal is large in the amount of dopant evaporation in the melt until the predetermined pressure is reached, but after reaching the predetermined pressure by gradually decreasing the pressure, the atmospheric pressure is not changed finely. However, since the variation of the specific resistance value of the silicon single crystal is suppressed, maintaining the atmospheric pressure in the range of the predetermined pressure ± 0.5 kPa does not require complicated control as compared with the conventional manufacturing method. Thus, it is possible to reliably manufacture a silicon single crystal with small variations in specific resistance.

  The predetermined pressure is related to the dopant concentration contained in the silicon melt, and the atmosphere in which the variation of the specific resistance value of the silicon single crystal can be suppressed without requiring fine control (increase or decrease in atmospheric pressure). It is a pressure and can take various values depending on the dopant concentration and the specific resistance value of the target silicon single crystal, but in order to obtain a silicon single crystal having a specific resistance value of 10 Ω · cm or more, The predetermined pressure is preferably 4 kPa.

  Here, the predetermined pressure to be maintained is in the range of ± 0.5 kPa, and if it exceeds ± 0.5 kPa, it is too far from the predetermined pressure, and thus the variation in the specific resistance value of the silicon single crystal cannot be sufficiently suppressed. Because.

FIG. 1 is a graph (FIG. 1 (a)) showing a relationship between a pulling amount (mm) when a silicon single crystal is pulled according to the present invention and an atmospheric pressure (kPa) at the time of pulling, and obtained. A graph showing the relationship between the length position (mm) from the top to the tail of a silicon single crystal ingot and the specific resistance (Ω · cm) of the silicon single crystal (Fig. 1 (b)) It is a thing. As for the resistance value with respect to the length position of the silicon single crystal ingot shown in FIG. 1B, several specific resistance values at arbitrary length positions (0 mm, 150 mm, 300 mm, 450 mm, 600 mm) in the ingot were measured. And obtained by averaging.
From Fig. 1, gradually reduce the atmospheric pressure until it reaches 4 kPa (predetermined pressure), and after reaching 4 kPa, make it almost constant (within ± 0.5 kPa) (Fig. 1 (a)). It can be seen that a silicon single crystal having a small thickness can be obtained (FIG. 1B).

On the other hand, FIG. 2 is a graph showing the relationship between the pulling amount (mm) when pulling up the silicon single crystal while gradually reducing the atmospheric pressure according to the conventional manufacturing method, and the atmospheric pressure (kPa) at the time of pulling. (Fig. 2 (a)), and the relationship between the length position (mm) from the top portion to the tail portion of the obtained silicon single crystal ingot and the specific resistance value (Ω · cm) of the silicon single crystal The graph shown (FIG. 2 (b)) is shown. As for the specific resistance value with respect to the length position of the silicon single crystal ingot shown in FIG. 2 (b), several specific resistance values at arbitrary length positions (0mm, 150mm, 300mm, 450mm, 600mm) in the ingot are shown. Obtained by measuring and averaging.
From FIG. 2, since the atmospheric pressure continues to decrease after reaching 4 kPa (predetermined pressure) (FIG. 2 (a)), the resulting silicon single crystal has a specific resistance from where the length exceeds 450mm. It can be seen that the value increases and variation occurs (FIG. 2B).

  In addition, as shown in FIG. 1A, the atmospheric pressure is adjusted by gradually decreasing the atmospheric pressure with a gradient of −0.01 to −0.005 kPa / mm with reference to the pulling amount (mm) of the silicon single crystal. It is preferable to carry out. This is because the evaporation of the dopant in the silicon melt is suppressed by lowering the atmospheric pressure, and variation in the specific resistance value of the silicon single crystal is suppressed. In addition, the gradient is limited because, when the pressure is less than −0.01 kPa / mm, the atmospheric pressure is drastically lowered, and as a result, the dopant concentration in the silicon melt is increased. On the other hand, if it exceeds −0.005 kPa / mm, the reduced pressure is not sufficient and the dopant concentration in the silicon melt is lowered, so that the specific resistance value of the silicon single crystal may be lowered. is there.

  The present invention also starts pulling up the silicon single crystal while adjusting the atmospheric pressure when pulling up the silicon single crystal. After the atmospheric pressure reaches the first predetermined pressure, the atmospheric pressure is increased to the second predetermined pressure. The atmospheric pressure is maintained in the range of the second predetermined pressure ± 0.2 kPa until the end of the pulling. Specifically, in the present invention, as shown in FIG. 3A, after the atmospheric pressure reaches 4 kPa (first predetermined pressure), the atmospheric pressure is increased to 2 kPa (second predetermined pressure). It is also possible to rapidly decrease the pressure and then maintain the pressure range of 2 ± 0.2 kPa until the end of the pulling. If such pressure control is performed, evaporation of the dopant is intentionally promoted by a sudden decrease in the atmospheric pressure, and the dopant concentration in the silicon melt is lowered, so that as shown in FIG. It becomes possible to manufacture a silicon single crystal having a resistance value of (in FIG. 3B, approximately 27 Ω · cm and 50 Ω · cm).

  When manufacturing a silicon single crystal having two types of resistance values, the change in the atmospheric pressure is reduced in order to minimize the portion where the specific resistance value is not constant and changes (the transition portion of the specific resistance value). Increasing the pressure is effective, and it is preferable that the gradient when rapidly reducing the atmospheric pressure is in a range of −0.08 to −0.02 kPa / mm based on the pulling amount of the silicon single crystal. In the case of −0.08 kPa / mm, as a result of the pressure change becoming too large, evaporation of the dopant in the melt proceeds excessively, and there is a possibility that a desired specific resistance value cannot be obtained for the silicon single crystal, On the other hand, if it exceeds −0.02 kPa / mm, the pressure change becomes too gentle, and the transition portion of the specific resistance value of the silicon single crystal becomes large.

  It is also possible to produce a silicon single crystal having three or more resistance values by further controlling the atmospheric pressure. For example, as described above, after the atmospheric pressure reaches 4 kPa, the atmospheric pressure is rapidly reduced until it reaches 2 kPa, and then maintained in a pressure range of 2 ± 0.2 kPa, and then further reduced to a low pressure atmosphere, Manufacture is possible by performing pressure control that maintains a certain range (for example, ± 0.2 kPa).

  In the present invention, the silicon single crystal is pulled by the Czochralski method. For example, a silicon single crystal pulling apparatus 100 as shown in FIG. 4 can be used as the pulling apparatus. The pulling device 100 includes a crucible 20 filled with the silicon melt 10, and manufactures a silicon single crystal ingot 40 by pulling up the seed crystal 30 while rotating the seed crystal 30 and the crucible 20, respectively. Can do.

  The volatile dopant contained in the silicon melt 10 is preferably an n-type dopant such as arsenic or antimony. When these materials are added to the silicon melt, the volatility is very high and the amount of evaporation is large. Therefore, the evaporation of the dopant is controlled by the present invention to obtain a silicon single crystal with small variation in specific resistance value. This is because the effect of being able to perform is most prominent. In addition, when other dopants, for example, p-type dopants such as boron are added, the evaporation of the dopants is small, so that it is not necessary to optimize the atmospheric pressure at the time of pulling as in the present invention.

  Furthermore, it is preferable that the volatile dopant is introduced into the silicon melt 10 by a wafer dope method. Even when the dopant concentration in the silicon melt 10 is slightly different, the specific resistance value has a large difference. Therefore, it is necessary to add the dopant as little as possible. For this reason, if the wafer dope method is used, it is possible to add a small amount of the dopant by a small amount as compared with the case where the dopant is directly added into the silicon melt 10, and a desired dopant concentration can be surely obtained. Here, the wafer dope method is a method in which a silicon wafer containing a dopant is introduced as a raw material of the silicon melt 10, and since the dopant is contained in the wafer that is the silicon raw material, The dopant can be added simultaneously with the addition.

  The above description is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.

Example 1
As Example 1, a silicon single crystal manufacturing apparatus 100 including a crucible 20 having a silicon melt 10 for pulling up a silicon single crystal as shown in FIG. The silicon single crystal was manufactured by raising 40.
As shown in FIG. 1 (a), the atmospheric pressure when pulling up the silicon single crystal ingot 40 was gradually decreased from 6.7 kPa, and after reaching 4 kPa, maintained at 4.0 kPa until the end of the pulling. .

(Example 2)
As Example 2, using the same silicon single crystal manufacturing apparatus 100 as in Example 1, the silicon single crystal ingot 40 was pulled up by the Czochralski method to manufacture a silicon single crystal.
As shown in FIG. 3 (a), the atmospheric pressure when pulling up the silicon single crystal ingot 40 is gradually decreased from 6.7 kPa, and after reaching 4 kPa, it is rapidly decreased to about 2 kPa, and then lifted. Maintained at 2 ± 0.2 kPa until completion.

(Comparative example)
As a comparative example, using the same silicon single crystal manufacturing apparatus 100 as in Example 1, the silicon single crystal ingot 40 was pulled up by the Czochralski method to manufacture a silicon single crystal.
As for the atmospheric pressure when pulling up the silicon single crystal ingot 40, as shown in FIG. 2 (a), the pulling of the silicon single crystal is started at 6.7 kPa, and the atmospheric pressure is gradually reduced until the pulling is completed. And finally it was 2.7 kPa.

(Evaluation methods)
For the silicon single crystals obtained in Examples 1 and 2 and the comparative example, the specific resistance value (Ω · cm) at each distance (mm) in the tail direction was measured with the top portion of the silicon single crystal ingot being 0 mm. The specific resistance value is measured in the state of a wafer, and the measurement position is a position on the center side of the wafer and 10 mm from the outer peripheral edge of the wafer.
The measurement result of the specific resistance value of Example 1 is shown in Table 1, and a graph showing the relationship between the length position of the silicon single crystal and the average value of the specific resistance value is shown in FIG. The measurement result of the specific resistance value of Example 2 is shown in Table 2, and a graph showing the relationship between the length position of the silicon single crystal and the average value of the specific resistance value is shown in FIG. The measurement result of the specific resistance value of the comparative example is shown in Table 3, and a graph showing the relationship between the length position of the silicon single crystal and the average value of the specific resistance value is shown in FIG.

  From Table 1 and FIG. 1 (b), it was found that the silicon single crystal of Example 1 had a variation in specific resistance value of the silicon single crystal within 3.2 Ω · cm, and the variation was small over the entire length. Also, from Table 2 and FIG. 3 (b), for the silicon single crystal of Example 2, two types of silicon single crystals having different specific resistance values (about 27Ω · cm and about 50Ω · cm) can be manufactured. As for the specific resistance value, the variation in the portion ranging from 0 to 400 mm was within 3.0 Ω · cm, and the variation in the portion ranging from 450 to 800 mm was within 2.0 Ω · cm. On the other hand, from Table 3 and FIG. 2 (b), it was found that the specific resistance value of the silicon single crystal of the comparative example increased from the point where the length exceeded 450 mm and showed a large variation.

  According to the present invention, an n-type silicon single crystal having a specific resistance value of 10 Ω · cm or more and a small variation can be reliably manufactured without requiring complicated control of atmospheric pressure.

100 Silicon single crystal ingot pulling device 10 Silicon melt 20 Crucible 30 Seed crystal 40 Silicon single crystal ingot

Claims (8)

A silicon single crystal manufacturing method for pulling up an n-type silicon single crystal having a specific resistance value of 10 Ω · cm or more from a silicon melt added with a volatile dopant by a Czochralski method,
The pulling up of the silicon single crystal is started while adjusting the atmospheric pressure when pulling up the silicon single crystal, and after the atmospheric pressure reaches a predetermined pressure, the atmospheric pressure is within the predetermined pressure ± 0.5 kPa until the pulling is completed. The manufacturing method of the silicon single crystal characterized by maintaining   The method for producing a silicon single crystal according to claim 1, wherein the predetermined pressure is 4 kPa.   2. The silicon single crystal according to claim 1, wherein in adjusting the atmospheric pressure, the atmospheric pressure is gradually decreased with a gradient of −0.01 to −0.005 kPa / mm on the basis of a pulling amount of the silicon single crystal. Production method.   The method for producing a silicon single crystal according to claim 1, wherein the volatile dopant is arsenic or antimony.   2. The method for producing a silicon single crystal according to claim 1, wherein the introduction of the volatile dopant is performed by a wafer dope method.   A silicon single crystal manufacturing method for pulling up an n-type silicon single crystal having a specific resistance value of 10 Ω · cm or more from a silicon melt added with a volatile dopant by a Czochralski method, the silicon single crystal being pulled up The pulling of the silicon single crystal is started while adjusting the atmospheric pressure at the time, and after the atmospheric pressure reaches the first predetermined pressure, the atmospheric pressure is rapidly decreased to the second predetermined pressure, and then the pulling is completed The method for producing a silicon single crystal, wherein the atmospheric pressure is maintained in a range of the second predetermined pressure ± 0.2 kPa.   The method for producing a silicon single crystal according to claim 6, wherein the first predetermined pressure is 4 kPa and the second predetermined pressure is 2 kPa.   7. The silicon single crystal production according to claim 6, wherein a gradient when the atmospheric pressure is rapidly decreased is in a range of −0.08 to −0.02 kPa / mm based on a pulling amount of the silicon single crystal. Method.

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