JP2009274916A - Silicon single crystal and production method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon single crystal which can effectively suppress the propagation of slip dislocations when the slip dislocations occur in the last half of a process for forming a straight body part or during a process for forming a tail part of a silicon single crystal; and to provide a production method of the same. <P>SOLUTION: In the last half of a process for forming a straight body part or during a process for forming a tail part of a silicon single crystal 5, boron is added into a silicon melt 3 so that the concentration of boron in the silicon single crystal 5 becomes not lower than 1.0×10<SP>19</SP>atoms/cm<SP>3</SP>. Thereby, the propagation of slip dislocations can be effectively suppressed without substantially causing an adverse effect on the straight body part of the single crystal being a product part. It is preferable that the addition amount of boron into the silicon melt 3 is adjusted within a range of 0.009-0.1 mass% in order to make the concentration of boron the concentration. Further, the boron concentration in the silicon single crystal 5 before addition of boron is set to 5.4×10<SP>18</SP>atoms/cm<SP>3</SP>or lower so as to avoid the effect by lowering of resistivity of the silicon single crystal accompanied by the increase of boron concentration. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a bonded wafer, which is formed by directly bonding an active layer wafer and a support substrate wafer without using an insulating film, and reducing the thickness of the active layer wafer. Is.

  Silicon wafers used for manufacturing semiconductor devices are collected from single crystals grown mainly by the Czochralski method (CZ method). In the CZ method, a seed crystal is immersed in a silicon raw material melt accommodated in a quartz crucible, and the seed crystal is pulled up while rotating the seed crystal and the quartz crucible in opposite directions. This is a method for growing a single crystal.

  In addition, silicon wafers manufactured by the CZ method are becoming larger in diameter due to the expansion of the chip area due to the improvement in the degree of integration of device chips, and currently with crystals of 200 mm (8 inches) to 300 mm (12 inches) in diameter. Device processes are being put into practical use. However, as the diameter of the wafer increases, the device yield increases. On the other hand, in large-diameter crystals and large-capacity crystal growth methods, the seed crystal is in contact with the melt or the cylinder is grown to the desired length. During the tail portion forming process in which the diameter is gradually reduced from the straight body portion of the silicon single crystal having the shape to make the tail portion conical, slip dislocation is likely to occur, which propagates to the straight body portion. Of course, the portion where slip dislocation has occurred cannot be used as a product, and the product yield is lowered. Therefore, various methods for preventing the occurrence of slip dislocation have been studied until now.

  As a method for suppressing the occurrence of slip dislocation, a single crystal growth method using a specially shaped seed crystal is disclosed. For example, as shown in Patent Document 1, the tip of the seed crystal is formed into a conical shape, or as shown in Patent Document 2, a seed crystal having a concavo-convex shape is used, so that the silicon single body is not produced. Since the crystal can be grown, the generation of slip dislocation can be suppressed.

  However, the methods of Patent Document 1 and Patent Document 2 use a specially-shaped seed crystal, and require high-level technology for processing the seed crystal, which increases the cost and occurs during the tail portion forming step. Since slip dislocation is not taken into consideration, slip dislocation occurs in the latter half of the straight body forming process or in the tail forming process, and the seed crystal must be exchanged and the pulling operation must be performed again. The challenges remained.

Furthermore, slip dislocations that are harmful as a product are generally caused by excessive stress when foreign matter or heat shock occurs at the growing interface, and propagate so as to slide on the (111) plane, and the propagation length is Usually, the length is the same as the diameter of the silicon single crystal in the portion where slip dislocation has occurred. Therefore, although the method of the above-mentioned patent document is effective in suppressing the occurrence of slip dislocation, there is no effect of suppressing the propagation of the generated slip dislocation, and therefore means for suppressing the propagation of slip dislocation. There was also a need to develop.
Japanese Patent Laid-Open No. 4-104988 JP-A-2005-28168

  An object of the present invention is to provide silicon that can effectively suppress propagation of slip dislocation when slip dislocation occurs by performing a predetermined treatment in the latter half of the straight body portion forming step of the silicon single crystal or in the tail portion forming step. The object is to provide a single crystal and a method for producing the same.

As a result of repeated studies to solve the above problems, the present inventors have found that the boron concentration in the silicon single crystal, which is usually 5.4 × 10 ¹⁸ atoms / cm ³ or less, is 1.0 × 10 ¹⁹ atoms / cm ^3. By adding boron (B) to the silicon melt so as to become the above, it becomes possible to increase the yield stress of the silicon single crystal and to effectively suppress the propagation of slip dislocations, and to add boron Is performed during the process of forming a tail portion of a single crystal that is not substantially used as a product, and the adverse effect of decreasing the resistivity of the silicon single crystal due to the addition of boron substantially reaches the straight body portion of the single crystal that is the product. Thus, it has been found that a silicon single crystal can be produced with a high product yield.

In order to achieve the above object, the gist of the present invention is as follows.
(1) A step of filling a crucible with a required amount of silicon raw material and heating and melting it to form a silicon melt; after immersing the seed crystal in the melt, the temperature of the melt and the pulling speed of the seed crystal The straight body part forming step of pulling up to a predetermined length in the vertical direction to form a straight body part that becomes a silicon single crystal product having a predetermined diameter while adjusting upward and gradually reducing the diameter of the silicon single crystal And a tail portion forming step of making the tail portion conical, in the method for producing a silicon single crystal by the Czochralski method, in the latter half of the straight body portion forming step or during the tail portion forming step, the silicon single crystal Boron is added to the silicon melt so that the boron concentration in the silicon melt is 1.0 × 10 ¹⁹ atoms / cm ³ or more, and the boron concentration in the silicon single crystal before the boron addition is 5.4 × 10 ¹⁸ atoms / cm ^3. Must be A method for producing a silicon single crystal characterized by the following.

(2) The method for producing a silicon single crystal as described in (1) above, wherein the amount of boron added is 0.009 to 0.1% by mass.

(3) The method for producing a silicon single crystal according to (1) or (2), wherein the diameter of the silicon single crystal in the straight body portion is 200 mm or more.

(4) The length of slip dislocation in the produced silicon single crystal is not more than 91% of the diameter of the silicon single crystal at the propagation start position of slip dislocation, (1), (2) or ( 3) A method for producing a silicon single crystal according to the above.

(5) A silicon single crystal produced by the method for producing a silicon single crystal according to any one of (1) to (4) above.

According to the present invention, the boron concentration in the silicon single crystal is increased during the latter half of the straight body portion forming step or the tail portion forming step during the latter half of the straight body portion forming step or the tail portion forming step. Boron is added to the silicon melt so as to be 1.0 × 10 ¹⁹ atoms / cm ³ or more, and the boron concentration in the silicon single crystal before this boron addition is 5.4 × 10 ¹⁸ atoms / cm ³ or less. Thus, it is possible to effectively suppress the propagation of slip dislocation when slip dislocation occurs while suppressing the occurrence of slip dislocation as in the conventional method.

  A method for producing a silicon wafer according to the invention will be described with reference to the drawings.

  FIG. 1 shows a single crystal pulling apparatus used in the manufacturing method of the present invention, and FIG. 2 shows a silicon single crystal manufactured by the manufacturing method of the present invention. A method for producing a silicon single crystal by the Czochralski method according to the present invention is to fill a crucible 2 composed of a quartz crucible 21 and a graphite crucible 22 using a single crystal pulling apparatus shown in FIG. The process of heating and melting using the heater 10 to form the silicon melt 3 and the seed crystal 4 after immersing the seed crystal 4 in the melt 3, adjusting the liquid temperature and the pulling speed of the melt 3 A straight body portion forming step of pulling up the straight body portion 13 which is a product of the silicon single crystal 5 having a predetermined diameter while being pulled upward, to a predetermined length in the vertical direction, and the diameter of the silicon single crystal 5 is gradually reduced to form a cone. A tail portion forming step for forming a tail portion 14 of a shape.

Here, in the Czochralski method, the stress in the crystal 5 is excessive due to the rapid separation of the silicon single crystal 5 from the melt and the growth rate and temperature change of the crystal 5, particularly during the tail portion forming step. And when the foreign matter existing in the silicon melt 3 is disturbed when the foreign matter is taken into the crystal growth interface, slip dislocation occurs in the silicon single crystal 5 and the generated slip dislocation occurs. However, there has been a problem that dislocations propagate upward by the same length as the diameter of the generation position. Therefore, the present inventors have studied to suppress dislocations caused by propagation at the end portion of the straight body portion. By the way, in the literature (T. Fukuda and A. Ohsawa, Proc. Of The 2nd Symp. On Defects in Si, Electrochemical Society, NJ, 1991, vol. 91-9, p. 173) Has been shown to anchor dislocations, resulting in an increase in yield stress. Therefore, the present inventors pay attention to the relationship between the silicon crystal and the boron concentration of the yield stress (FIG. 3), and suppress the occurrence of slip dislocation and also prevent the propagation of slip dislocation. We conducted intensive research on manufacturing methods. As a result, the addition of boron has the adverse effect of reducing the resistivity of the silicon crystal, so the boron concentration in the silicon single crystal is generally 5.4 × 10 ¹⁸ atoms / cm ³ except for some low resistance products. Although it is necessary to make the following, boron is contained in the silicon melt so that it becomes 1.0 × 10 ¹⁹ atoms / cm ³ or more in the end part (defective part) or tail part of the straight body part that is not used as a product. It has been found that the addition of to can effectively suppress the propagation of slip dislocation without substantially adversely affecting the straight body portion of the single crystal as the product portion.

Therefore, the boron concentration in the silicon single crystal 5 before boron addition is set to 5.4 × 10 ¹⁸ atoms / cm ³ or less, and the silicon single crystal is formed in the latter half of the straight body portion forming step or the tail portion forming step. It is necessary to add boron to the silicon melt 3 so that the boron concentration in 5 becomes 1.0 × 10 ¹⁹ atoms / cm ³ or more. Here, the boron concentration in the silicon single crystal 5 before the boron addition is set to 5.4 × 10 ¹⁸ atoms / cm ³ or less is the boron concentration of the silicon single crystal having general physical properties and the silicon crystal. This is to prevent the influence of the decrease in resistivity. The latter half of the straight body portion forming step refers to a portion in a region having a length of 70 to 100% of the entire length L of the straight body portion 13 from the position of the end portion of the straight body portion 13. As shown in FIG. 2, it is preferable in terms of effective use of the silicon single crystal that boron is added particularly when the lower portion of the straight body portion 13 becomes the poor quality portion 15. The defective quality portion 15 is a portion that affects quality and cannot be dispensed as a product. For example, the thermal history and intentionally added impurities are concentrated, and the straight body portion 13 that has exceeded an allowable level is formed. Some of them.

Further, in order to set the boron concentration in the silicon single crystal 5 to 1.0 × 10 ¹⁹ atoms / cm ³ , it is necessary to add boron to the melt 3 and adjust the concentration of the melt 3. Is preferably 0.009 to 0.1% by mass in the silicon melt 3. If it is less than 0.009% by mass, the boron concentration in the silicon single crystal 5 cannot be made 1.0 × 10 ¹⁹ atoms / cm ³ or more. If it exceeds 0.1% by mass, the boron concentration is too high. This is because a compositional supercooling phenomenon due to excessive solute occurs and single crystal growth is inhibited.

  Further, the amount of boron calculated to be 0.009 to 0.1% by mass with respect to the melt 3 is crucible using a pipe-shaped dopant supply device 6 that leads from the outside of the furnace to the inside of the furnace as shown in FIG. It is preferable to drop it into the surface of the silicon melt 3 in 2 or into the silicon melt 3 with timing. The dopant supply device 6 includes a dopant holding vessel 7 and a dopant dropping tube 8 outside the furnace, and an isolation valve 9 and a gas purge function (not shown) are provided so that boron can be filled and dropped even during operation. 2), and can be dropped manually or automatically at any drop timing.

  In addition, the diameter of the straight body portion 13 of the silicon single crystal 5 manufactured by the manufacturing method according to the present invention is not particularly limited and varies depending on the product specifications and the like, but the effect of the present invention is more remarkable as large as possible. Therefore, it is preferably 200 mm or more. It is known that the propagation amount of the slip dislocation is usually almost equal to the diameter of the portion where the slip dislocation has occurred, and the propagation length of the slip dislocation that has occurred increases as the diameter of the silicon single crystal increases. This is because the product yield reduction is increased, and the effect of suppressing the propagation of slip dislocations according to the present invention is effectively exhibited.

  Furthermore, due to the effect of inhibiting the propagation of slip dislocations by adding boron, the length of slip dislocations in the produced silicon single crystal can be 91% or less of the diameter of the silicon single crystal at the propagation start position of slip dislocations. Become. In general, the propagation amount of the slip dislocation is equal to the diameter at the slip dislocation propagation start position, but the present invention has an effect of suppressing the propagation of slip dislocation by 9% or more compared to the prior art.

  By the above-described method for producing a silicon single crystal, it is possible to obtain a silicon single crystal in which propagation of slip dislocations, which tends to propagate to the straight body portion of the single crystal, is effectively suppressed.

  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.

(Examples 1-7 and Comparative Examples 1-4)
About the samples 1-11 for evaluation (Examples 1-7 and Comparative Examples 1-4), it produced with the following procedures (1)-(4).
(1) The crucible was filled with a silicon raw material and heated and melted in an atmosphere with a furnace pressure of 4.0 × 10 ³ Pa and an argon gas flow rate of 100 slpm to form a silicon melt of about 1420 ° C. At this time, the boron concentration in the silicon melt was 6.2 × 10 ⁻⁶ mass%.
(2) Thereafter, the seed crystal is immersed in the melt, and the throttle part is formed by pulling up the seed crystal in the same atmosphere at a seed crystal rotation speed of 12 rpm, a crucible rotation speed of 15 rpm, and a pulling speed of 3 to 4 mm / min. After forming the throttle part, the shoulder part was formed by gradually increasing the diameter of the silicon single crystal to 200 mm at a rotational speed of 12 to 15 rpm and a pulling speed of 0.5 to 0.8 mm / min.
(3) After forming the shoulder portion, the seed crystal is subjected to a furnace internal pressure of 4.0 × 10 ^{3 to} 8.0 × 10 ³ Pa, an argon gas flow rate of 50 slpm, a melt temperature of about 1415 ° C., a crystal rotation speed of 15 rpm, and a crucible rotation speed. While adjusting the pulling speed to 6 to 10 rpm and 0.8 to 0.6 mm / min, it was lifted upward to form a straight body portion having a diameter of 200 mm and a length of 1.5 m. The boron concentration in the straight body portion before adding boron to the melt was 9.0 × 10 ¹⁵ atoms / cm ³ .
(4) After forming the straight body portion, boron is added to the melt using a dopant dropping device (sample 1 is not added), and the boron concentration in the silicon single crystal after addition is shown in Table 1. After adjusting for each sample so as to achieve such a value, the diameter of the silicon single crystal was gradually reduced at a rotational speed of 15 rpm and a pulling speed of 0.6 to 1.0 mm / min to form a conical tail portion. Crystal evaluation samples 1 to 11 were produced.

(Evaluation methods)
Measure the boron concentration in the silicon single crystal after boron addition and the slip dislocation propagation rate {(length of slip dislocation / diameter of single crystal at the slip dislocation occurrence location) × 100%} for each sample prepared above. The measurement results are shown in Table 1. Further, the relationship between the boron concentration of each sample and the propagation rate (%) of slip dislocation is plotted, and the result is shown in FIG.

From the results in Table 1, the slip dislocation propagation rate (%) of Examples 1 to 7 (Samples 5 to 11) in which the boron concentration in the silicon single crystal is 1.0 × 10 ¹⁹ (atoms / cm ³ ) or more is the boron concentration. Is smaller than 1.0 × 10 ¹⁹ (atoms / cm ³ ), and the propagation rate is smaller than those of Comparative Examples 1 to 4 (Samples 1 to 4), and the product yield is improved. Moreover, when Examples 1-7 (samples 5-11) are compared, it turns out that the propagation rate of slip dislocation is so small that a boron concentration becomes high.
Further, from the result of FIG. 4, the effect of suppressing the propagation of slip dislocation can be exhibited at the boundary when the boron concentration (atoms / cm ³ ) in the single crystal after addition is 1.0 × 10 ¹⁹ atoms / cm ^3. I understand that.

According to the present invention, the boron concentration in the silicon single crystal is increased during the latter half of the straight body portion forming step or the tail portion forming step during the latter half of the straight body portion forming step or the tail portion forming step. By adding boron to the silicon melt so as to be 1.0 × 10 ¹⁹ atoms / cm ³ or more, the occurrence of slip dislocation is suppressed while the occurrence of slip dislocation is suppressed as in the conventional method. Propagation can be effectively suppressed.

The schematic cross section of a single crystal pulling apparatus and a doppler dropping apparatus used for the manufacturing method of this invention is shown. It is a front view which shows the silicon single crystal manufactured by the manufacturing method of this invention. It is a graph which shows the relationship between the yield stress of a silicon crystal, and a boron concentration. It is the graph which showed the relationship between the boron concentration (atoms / cm < ³ >) in a single crystal, and the propagation rate (%) of a slip dislocation about each sample of an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Single crystal pulling apparatus 2 Crucible 3 Silicon melt 4 Seed crystal 5 Silicon single crystal 6 Dopment drop device 7 Dopment holding container 8 Dopment drop pipe 9 Isolation valve 10 Heater 11 Restriction part 12 Shoulder part 13 Straight body part 14 Tail part 15 Quality defective part 21 Quartz crucible 22 Graphite crucible

Claims (5)

Filling the crucible with the required amount of silicon raw material and heating and melting it to form a silicon melt; after immersing the seed crystal in the melt, the temperature of the melt and the pulling speed are adjusted. To form a straight body part that becomes a silicon single crystal product having a predetermined diameter while being pulled upward, and a straight body part forming step of pulling up to a predetermined length in the vertical direction, and gradually reducing the diameter of the silicon single crystal In the method for producing a silicon single crystal by the Czochralski method, having a tail part forming step for making the part conical,
Boron is added to the silicon melt so that the boron concentration in the silicon single crystal is 1.0 × 10 ¹⁹ atoms / cm ³ or more during the latter half of the straight body portion forming step or the tail portion forming step. A method for producing a silicon single crystal, wherein a boron concentration in the silicon single crystal before addition is 5.4 × 10 ¹⁸ atoms / cm ³ or less.   The method for producing a silicon single crystal according to claim 1, wherein the amount of boron added is 0.009 to 0.1 mass%.   3. The method for producing a silicon single crystal according to claim 1, wherein the diameter of the silicon single crystal in the straight body portion is 200 mm or more.   The length of slip dislocation in the produced silicon single crystal is 91% or less of the silicon single crystal diameter at the propagation start position of slip dislocation. Production method.   A silicon single crystal produced by the method for producing a silicon single crystal according to claim 1.

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