JP2007210865A - Silicon single crystal pulling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon single crystal pulling device of growing a single crystal and keeping good device characteristics and yield in a device process by preventing the variation of an oxygen concentration and a dopant concentration in a narrow range. <P>SOLUTION: A magnetic field impression medium 51 makes the magnetic field intensity (By) of the center (O) the highest with respect to the pulling direction Z. The magnetic field is generated so that the magnetic field intensity (By) may gradually decrease from the center (O) to the upper and lower directions respectively. The device is set so that a molten liquid surface 12a of a silicon molten liquid 12 of a crucible 13 may be located in accordance with the highest center (O) of the magnetic field intensity (By). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a silicon single crystal pulling method for forming a silicon single crystal by the Czochralski method.

  The silicon single crystal is manufactured by heating a polycrystalline silicon raw material housed in a crucible with a heater to form a silicon melt, and pulling up the silicon single crystal from the silicon melt by a CZ (Czochralski) method. A silicon wafer is manufactured by slicing (cutting) a silicon single crystal manufactured by the above method, and a device such as an integrated circuit is formed on the silicon wafer.

These silicon single crystals tend to have a larger diameter in order to form more circuits on a single silicon wafer. On the other hand, problems of the single crystal growth technique accompanying the increase in the diameter of the silicon single crystal include a reduction in oxygen concentration and quality of the single crystal, and an improvement in productivity. In order to deal with such problems, a method of realizing a low oxygen concentration of a single crystal and stabilization of crystal growth by applying a horizontal magnetic field applied CZ (HMCZ) technique in which a horizontal magnetic field is applied to the CZ method is known. Also, by maintaining the solid-liquid interface shape, which is the boundary surface between the silicon single crystal and the silicon melt, in an upward convex shape curved toward the direction of the single crystal, a high G and a surface near the solid-liquid interface can be obtained. A method for obtaining an internal homogenization effect is also known (Patent Document 1).
JP 2001-158690 A

  However, by applying a horizontal magnetic field, the convection state of the silicon melt in the crucible is improved from an unstable state. However, since a large-diameter crucible is used to grow a large-diameter crystal, the amount of the melt increases. However, it was clarified that there was an unstable region because a sufficient effect could not be obtained only by applying a horizontal magnetic field. In particular, when a chamber of a silicon single crystal pulling apparatus is arranged between two magnets arranged parallel to each other using Helmholtz type magnets, a structure with a uniform distribution of horizontal magnetic field strength can be obtained by designing the coil diameter. In order to obtain a magnetic field having the required strength, there has been a problem that the magnet itself becomes enormous and requires a large device space.

  On the other hand, recently, a space-saving horizontal magnetic field magnet has been developed in which a magnet coil is deformed and incorporated in a ring-shaped case surrounding a chamber of a silicon single crystal pulling apparatus. In the case of such a space-saving horizontal magnetic field magnet, a distribution occurs in the magnetic field strength according to the coil design space. As a result of conducting the magnetic field strength distribution and the crystal growth experiment, it became clear that an unstable region occurs in the silicon melt in relation to the magnetic field strength distribution and the magnetic field setting position.

  In such an unstable region of the silicon melt, a non-uniform distribution of impurity concentration (including oxygen concentration) occurs in the silicon single crystal and becomes non-uniform in the growth direction of the silicon single crystal. A large-diameter silicon single crystal has a high productivity because of its productivity, so that the solid-liquid interface shape is an upwardly convex shape so that the crystal growth rate can be increased.

  In this case, in the unstable region of the silicon melt, when viewed in a plane parallel to the wafer surface of the silicon single crystal, a distribution such as non-uniform impurity concentration or a change in value is observed. The impurity concentration is a dopant concentration that determines the oxygen concentration and the carrier concentration of the silicon single crystal, and a distribution is observed concentrically in the plane. When the oxygen concentration and the dopant concentration are in a very small range, the high concentration and the low concentration cause the lack of gettering of heavy metal impurities due to the difference in density of crystal defects in the device process. It can reduce and adversely affect important device characteristics and yields.

  The present invention has been made in view of the above circumstances, and the oxygen concentration and the dopant concentration vary within a minute range by suppressing the uneven distribution of the impurity concentration and making the impurity concentration uniform. A silicon single crystal capable of growing a silicon single crystal capable of maintaining good device characteristics and yield in a device process by preventing variation in gettering ability, variation in in-plane distribution of resistance value, etc. An object is to provide a crystal pulling apparatus.

In order to achieve the above object, a silicon single crystal pulling apparatus according to the present invention includes a crucible for storing a silicon melt, a heater for heating the crucible, and a crucible driving means for rotating and / or raising and lowering the crucible. A single crystal pulling apparatus comprising: a chamber that houses the crucible and the heater; and a magnetic field applying means that is provided outside the chamber and applies a magnetic field to the chamber,
The magnetic field applying means is formed along the outer peripheral surface of the chamber, and the above-mentioned problem is solved by being able to form substantially concentric isomagnetic lines from the center of the crucible.
A silicon single crystal pulling apparatus according to the present invention includes a crucible for storing a silicon melt, a heater for heating the crucible, a crucible driving means for rotating and / or raising and lowering the crucible, and a chamber for housing the crucible and the heater. And a single crystal pulling device provided outside the chamber and having a magnetic field applying means for applying a magnetic field to the chamber,
The magnetic field application means is formed along the outer peripheral surface of the chamber, and the magnetic field strength increases unilaterally from the melt surface of the silicon melt stored in the crucible toward the bottom of the crucible, or The above problem has been solved by making it possible to apply a magnetic field so that the magnetic field strength is unilaterally reduced.
According to the present invention, the range of fluctuation of the magnetic field strength when the magnetic field strength unilaterally increases or decreases from the melt surface of the silicon melt stored in the crucible toward the bottom of the crucible is the magnetic field applying means. Is preferably set in the range of 0.6 to 0.9 times the strongest intensity of the magnetic field applied in the chamber.
In the present invention, the magnetic field applying means may be formed in a substantially ring shape so as to surround the chamber.

According to the present invention, a crucible for storing silicon melt, a heater for heating the crucible, a crucible driving means for rotating and / or raising and lowering the crucible, a chamber for housing the crucible and the heater, A single crystal pulling device provided on the outside and having a magnetic field applying means for applying a magnetic field to the chamber, wherein the magnetic field applying means is formed along the outer peripheral surface of the chamber and extends from the center of the crucible. By making it possible to form substantially concentric isomagnetic lines, according to such a silicon single crystal pulling apparatus, the silicon melt of the crucible is concentrically equidistant by the horizontal magnetic field applied by the magnetic field applying means. A line is formed. By forming concentric magnetic field lines concentrically, the convection state of the silicon melt in the crucible can be improved from an unstable state.
Here, as shown in FIG. 3, the range in which the substantially concentric circular isomagnetic lines are formed includes at least the range where the silicon melt in the crucible exists, and the other regions in the chamber are As shown in FIG. 4, the isomagnetic curve may not be concentric, and space saving of the magnetic field applying means may be possible. Moreover, the range in which the isomagnetic field curves are concentric is sufficient if it includes at least the height position where the silicon melt exists.
In addition, as shown in FIG. 3, the direction of the magnetic field is also only required to be substantially straight only in the range where the silicon melt in the crucible exists, and in other portions, it may be slightly deviated from the straight line. Absent.

According to the present invention, the crucible for storing the silicon melt, the heater for heating the crucible, the crucible driving means for rotating and / or raising and lowering the crucible, the chamber for accommodating the crucible and the heater, A single crystal pulling apparatus provided outside the chamber and having a magnetic field applying means for applying a magnetic field to the chamber, wherein the magnetic field applying means is formed along the outer peripheral surface of the chamber, This is because the magnetic field strength can be applied unilaterally from the melt surface of the stored silicon melt toward the bottom of the crucible, or the magnetic field strength can be unilaterally reduced. According to the silicon single crystal pulling apparatus, the oxygen concentration of the pulled silicon single crystal ingot is transferred over the entire length in the growth direction (axial direction) of the silicon single crystal ingot. Decreases at a constant rate of Te, never unstable region is generated.

  The fluctuation range of the magnetic field strength when the magnetic field strength is unidirectionally increased or decreased from the melt surface of the silicon melt stored in the crucible toward the bottom of the crucible is applied to the chamber by the magnetic field applying means. It is only necessary to set the range of 0.6 to 0.9 times the strongest intensity of the magnetic field to be applied, thereby suppressing the uneven distribution of the impurity concentration, and in the range where the oxygen concentration and the dopant concentration are minute. Prevent variation.

  Further, the magnetic field applying means only needs to be formed in a substantially ring shape so as to surround the chamber, and specifically, two or the same height as the axial symmetry is provided on the cylindrical surface concentric with the crucible side wall. The shape is such that three or four ring-shaped magnet coils are attached, in other words, a first cylindrical surface having a vertical axis and a first cylinder having a smaller radius than the first cylinder. A coil shape corresponding to the intersection line with the second cylindrical surface having a horizontal axis line, or a shape in which one of the two axisymmetric coils is plural. Or, these shapes can be changed slightly from the viewpoint of space saving, etc., thereby reducing the size and weight of the silicon single crystal pulling apparatus provided with the horizontal magnetic field applying means. Possible It made.

  According to the silicon single crystal pulling apparatus of the present invention, the oxygen of the pulled silicon single crystal ingot is increased by gradually increasing or decreasing the magnetic field strength monotonously over the entire area from the melt surface of the silicon melt toward the bottom of the crucible. The concentration decreases at a constant rate over the entire length in the growth direction of the silicon single crystal ingot, and an unstable region does not occur. When an unstable portion occurs, the in-plane distribution of oxygen concentration in the silicon single crystal ingot fluctuates greatly in a minute range, which causes insufficient gettering ability of heavy metal impurities due to the difference in density of crystal defects in the device process. Therefore, it is possible to suppress the uneven distribution of the impurity concentration, to prevent the oxygen concentration and the dopant concentration from varying within a minute range, to prevent the variation in resistivity due to the variation in the dopant concentration, and to improve the device characteristics and the convergence in the device process. The rate can be kept good.

  Hereinafter, an embodiment when the single crystal pulling apparatus of the present invention is applied to a silicon single crystal pulling apparatus will be described. FIG. 1 is a side sectional view showing a silicon single crystal pulling apparatus of the present invention, and FIG. 2 is a top sectional view showing the silicon single crystal pulling apparatus when viewed from above. The silicon single crystal pulling apparatus 10 includes a chamber 11, a quartz crucible 13 provided in the chamber 11 for storing a silicon single crystal silicon melt 12, and a side heater for heating the silicon single crystal silicon melt 12. 41, a heat insulating material 19, a crucible driving means 17, and a magnetic field applying means 51 that is provided outside the chamber 11 and applies a horizontal magnetic field to the chamber 11.

  The quartz crucible 13 includes a substantially cylindrical body portion 13a that is open at the top, and a bottom portion 13b that closes the lower portion of the body portion 13a. The outer surface of the quartz crucible 13 is supported by a graphite susceptor (crucible support) 14. The lower surface of the quartz crucible 13 is fixed to the upper end of the support shaft 16 via the graphite susceptor 14, and the lower portion of the support shaft 16 is connected to the crucible driving means 17. A side heater 41 is provided around the outside of the body 13 a of the quartz crucible 13 via a graphite susceptor 14.

  The side heater 41 is formed in a cylindrical shape so as to surround the quartz crucible 13, for example, and heats the quartz crucible 13. A cylindrical heat insulating material 19 surrounding the side heater 41 is provided between the side heater 41 and the chamber 11.

  The magnetic field applying means 51 is a space-saving horizontal magnetic field magnet in which a magnet coil is deformed from a flat shape into a three-dimensional shape and incorporated in a ring-like case so as to surround the chamber 11 of the silicon single crystal pulling apparatus 10. . Such a magnetic field applying means 51 applies a horizontal magnetic field L to the silicon melt 12 stored in the crucible 13 via the side heater 41, the heat insulating material 19, and the chamber 11. Details of such magnetic field application will be described later.

  The crucible driving means 17 has a first rotating motor (not shown) for rotating the crucible 13 and an elevating motor (not shown) for raising and lowering the crucible 13, and the crucible 13 is moved in a predetermined direction by these motors. It is configured to be able to rotate and move up and down. In particular, in the lifting motor, the liquid level 12a of the silicon melt 12 that decreases as the seed crystal 24 is pulled up is maintained at the predetermined position described above. It is configured to raise.

A cylindrical casing 21 having a smaller diameter than the chamber 11 is provided on the upper surface of the chamber 11. A pulling head 22 is provided at the upper end of the casing 21 so as to be turnable in a horizontal state. A wire cable 23 is suspended from the head 22 toward the rotation center of the quartz crucible 13.
Although not shown, the head 22 incorporates a second rotation motor that rotates the head 22 and a pulling motor that winds or feeds the wire cable 23. A seed crystal 24 for pulling up the silicon single crystal ingot 25 by dipping in the silicon melt 12 is attached to the lower end of the wire cable 23 via a holder 23a.

  A gas supply / exhaust means 28 is connected to the chamber 11 for supplying an inert gas such as Ar gas from the upper portion of the chamber 11 and discharging the inert gas from the lower portion of the chamber 11. The gas supply / discharge means 28 has one end connected to the peripheral wall of the casing 21 and the other end connected to a tank of an inert gas (not shown), one end connected to the lower wall of the chamber 11, and the other end vacuumed. And a discharge pipe 30 connected to a pump (not shown). The supply pipe 29 and the discharge pipe 30 are respectively provided with first and second flow rate adjusting valves 31 and 32 for adjusting the flow rate of the inert gas flowing through the pipes 29 and 30.

  Next, a silicon single crystal pulling procedure in the silicon single crystal pulling apparatus 10 having such a configuration and an operation of the present invention will be described. When pulling up a silicon single crystal using the silicon single crystal pulling apparatus 10 of the present embodiment, first, a silicon lump made of polycrystal as a raw material is put in the crucible 13 and melted by the side heater 41 to form silicon. A melt 12 is formed. Then, the seed crystal 24 is suspended from the wire cable 23 via the holder 23a immediately above the melt surface 12a of the silicon melt 12.

  Next, the inert gas is supplied from the supply pipe 29 into the casing 21 by opening the first and second flow rate adjusting valves 31 and 32, and the SiOx gas evaporated from the surface of the silicon melt 12 is converted into the inert gas. At the same time, it is discharged from the discharge pipe 30. In this state, the wire 19 is fed out by a pulling motor (not shown) of the pulling head 22 to lower the seed crystal 24, and the tip of the seed crystal 24 is brought into contact with the melt 12.

  When the tip of the seed crystal 24 is brought into contact with the silicon melt 12, slip dislocation is introduced into the tip due to thermal stress. Thereafter, the seed crystal 24 is gradually pulled up and the seed restricting portion 25 a having a diameter of about 3 mm. Form. The dislocation introduced into the seed crystal 24 disappears by forming the seed restricting portion 25a, and then the dislocation-free silicon single crystal ingot 25 is grown below the seed restricting portion 25a by further pulling up the seed crystal 24. Let

  Thus, when growing the silicon single crystal ingot 25, the silicon melt 12 is heated by the side heater 41 and a magnetic field is applied by the magnetic field applying means 51. At this time, the raising / lowering motor raises the crucible 13 according to the amount of the melt 12 to be reduced, and maintains the surface of the silicon melt 12 that is lowered as the seed crystal 24 is pulled up in a predetermined position.

  In the silicon single crystal pulling apparatus of this embodiment, a horizontal magnetic field is formed in the silicon melt 12 by the magnetic field applying means 51 provided outside the chamber 11. The magnetic field applying means 51 is a horizontal magnetic field magnet in which a magnet coil is deformed in a ring shape so as to surround the chamber 11, and the silicon melt 12 in the crucible 13 is ring-shaped by the magnetic field applying means 51 having such a shape. A magnetic field is applied so that isomagnetic field lines are formed.

  FIG. 3 shows the distribution of the magnetic field formed in the crucible 13 by the magnetic field applying means 51, which is a horizontal magnetic field magnet in which a magnet coil is deformed in a ring shape, by isomagnetic lines. A solid line R indicates a crucible, and a fine arrow indicates a magnetic field line L applied to the crucible. Also, a single crystal ingot S pulled up is shown near the center of the crucible. Then, isomagnetic field lines M are shown so as to surround the crucible. According to FIG. 3, concentric lines are formed concentrically in the crucible by the horizontal magnetic field applied by the magnetic field applying means 51.

  On the other hand, the magnetic field applying means 51 unilaterally increases the magnetic field strength or decreases the magnetic field strength unilaterally from the melt surface of the silicon melt 12 stored in the crucible 13 toward the bottom surface of the crucible. Apply a horizontal magnetic field. FIG. 4 is an explanatory diagram showing the relationship between the magnetic field strength and the silicon melt stored in the crucible. According to FIG. 4, the magnetic field application means 51 generates the magnetic field so that the magnetic field strength By of the center O becomes the highest in the pulling direction Z, and the magnetic field strength By gradually decreases from the center O in the vertical direction. And it sets so that the melt surface 12a of the silicon melt 12 of the crucible 13 may be located according to the center O with the highest magnetic field strength By.

  Thus, by setting the distribution of the magnetic field strength and the position of the melt surface 12 a of the silicon melt 12, the magnetic field strength By of the silicon melt 12 gradually decreases from the melt surface 12 a toward the bottom 13 a of the crucible 13. Thus, the horizontal magnetic field is applied from the magnetic field applying means 51. The gradual decrease rate of the magnetic field strength is such that the magnetic field strength By of the magnetic field applied to the position of the melt surface 12a of the silicon melt 12 is 1, and the position of the bottom 13a of the crucible 13 (from the position of the melt surface 12a in the silicon melt 12 most). The magnetic field strength By applied to the separated lower position may be set to be 0.6 to 0.9 (that is, 0.6 to 0.9 times the strongest magnetic field strength).

  As described above, the magnetic field applying means is a horizontal magnetic field magnet in which the silicon melt 12 is deformed in a ring shape so that the magnetic field strength gradually decreases from the melt surface 12a toward the bottom 13a of the crucible 13. By applying a horizontal magnetic field from 51, as shown in FIG. 3, a ring-shaped isomagnetic field line is formed in the silicon melt 12, and the silicon melt is related to the magnetic field strength distribution and the magnetic field setting position. To prevent unstable areas from occurring. By eliminating the generation of unstable regions of the silicon melt, it is possible to prevent the generation of a non-uniform distribution of impurity concentration in the silicon single crystal and achieve a uniform impurity distribution in the growth direction of the silicon single crystal. It becomes possible.

  Further, by using a horizontal magnetic field magnet in which a magnet coil is deformed in such a ring shape as the magnetic field applying means 51, it is possible to pull up a silicon single crystal having a magnetic field applying means as compared with the case where a conventional Helmholtz type magnet is used. The size of the apparatus can be greatly reduced and reduced in weight.

  The magnetic field applied to the silicon melt 12 of the crucible 13 is not limited to the distribution in which the magnetic field strength decreases unilaterally from the melt surface of the crucible toward the bottom of the crucible as shown in FIG. A horizontal magnetic field may be applied so that the magnetic field strength increases unilaterally from the melt surface of the crucible toward the bottom surface of the crucible. According to FIG. 5, the magnetic field applying means 51 makes the magnetic field strength By of the bottom 13a of the crucible 13 the highest in the pulling direction Z, and the magnetic field strength By gradually decreases from the bottom 13a of the crucible 13 in the vertical direction. Generate a magnetic field.

  Thus, by setting the distribution of the magnetic field strength and the position of the melt surface 12a of the silicon melt 12, the magnetic field strength By gradually decreases from the bottom 13a of the crucible 13 toward the melt surface 12a of the silicon melt 12. Thus, the horizontal magnetic field is applied from the magnetic field applying means 51. The gradual decrease rate of the magnetic field strength is such that when the magnetic field strength of the magnetic field applied to the bottom 13a position of the crucible 13 is 1, the magnetic field strength By applied to the melt surface 12a position of the silicon melt 12 is 0.6 to 0.9. (That is, 0.6 times to 0.9 times the strongest magnetic field strength). By making the distribution of the magnetic field strength with respect to the silicon melt 12 in this way, it is possible to prevent the generation of an unstable region in the silicon melt and to achieve a uniform impurity distribution in the growth direction of the silicon single crystal. It becomes possible.

  The applicant has verified the operation and effect of the present invention. For the verification, a quartz crucible having a diameter of 24 inches was prepared, and 160 kg of polycrystalline silicon as a raw material was charged into the quartz crucible. Then, the quartz crucible was pulled up by a heater, and a silicon single crystal ingot having a diameter of 200 mm was pulled up. A quartz crucible charged with such raw materials was heated to form a silicon melt, and a silicon single crystal ingot having a diameter of 200 mm was pulled up. When pulling up, a space-saving horizontal magnetic field magnet (magnetic field applying means) is incorporated in the silicon melt in the quartz crucible by deforming and incorporating a magnet coil into a ring-shaped case so as to surround the chamber of the silicon single crystal pulling device. A horizontal magnetic field was applied.

  In applying a horizontal magnetic field to the silicon melt, three examples were prepared as examples of the present invention.

  In the first embodiment, as shown in FIG. 6, the magnetic field applying means 51 makes the magnetic field strength By of the center O highest in the pulling direction Z, and the magnetic field strength By gradually decreases from the center O in the vertical direction. A magnetic field was generated to Then, the melt surface 12a of the silicon melt 12 of the crucible 13 is set so as to be aligned with the center O having the highest magnetic field strength By, and the magnetic field strength By is directed from the melt surface 12a toward the bottom 13a of the crucible 13. The silicon single crystal ingot was pulled up by applying a horizontal magnetic field to the silicon melt 12 so as to gradually decrease (Sample 1).

  As a second embodiment of the present invention, as shown in FIG. 7, the magnetic field applying means 51 makes the magnetic field strength By of the center O the highest in the pulling direction Z, and the magnetic field strength in the vertical direction from the center O, respectively. A magnetic field was generated so that By gradually decreased. Then, the melt surface 12a of the silicon melt 12 of the crucible 13 is set to be located below the center O having the highest magnetic field strength By by a distance a, and the melt surface 12a is placed on the bottom 13a of the crucible 13. A silicon single crystal ingot was pulled up by applying a horizontal magnetic field to the silicon melt 12 so that the magnetic field strength By gradually decreased (Sample 2).

  As a third embodiment of the present invention, as shown in FIG. 8, the magnetic field applying means 51 makes the magnetic field strength By of the bottom 13 a of the crucible 13 highest in the pulling direction Z, and from the bottom 13 a of the crucible 13. A magnetic field was generated so that the magnetic field strength By gradually decreased in the vertical direction. Thus, a horizontal magnetic field was applied to the silicon melt 12 so that the magnetic field strength By gradually decreased from the bottom 13a of the crucible 13 toward the melt surface 12a of the silicon melt 12, thereby pulling up the silicon single crystal ingot (sample 3). .

  As a comparative example (conventional example) to be compared with the present invention, as shown in FIG. 9, the magnetic field applying means 61 has the highest magnetic field strength By at the center O with respect to the pulling direction Z, and the vertical direction from the center O. The magnetic field was generated so that the magnetic field strength By gradually decreased. The center O having the highest magnetic field strength By was set to be located in the middle of the silicon melt 12 of the crucible 13. As a result, the magnetic field strength By gradually increases from the melt surface 12a (z = −a position) of the silicon melt 12 toward the bottom 13a of the crucible 13 to the middle of the melt, and then changes after the middle. The silicon single crystal ingot was pulled up by applying a horizontal magnetic field to the silicon melt 12 so that the magnetic field strength By gradually decreased (Sample 4).

  As described above, the length XL in the growth direction and the oxygen concentration Oi of the silicon single crystal ingot pulled up by the embodiments 1 to 3 (samples 1 to 3) of the present invention described above and the comparative example (conventional example: sample 4). The relationship is shown in FIG.

  As shown in FIG. 10 (a), the magnetic field strength By is monotonously increased or decreased gradually over the entire length of the lifting length in the entire region from the melt surface 12a of the silicon melt 12 to the bottom 13a of the crucible 13. In this case, the oxygen concentration Oi of the pulled silicon single crystal ingot decreases at a constant rate over the entire length XL, and no unstable region is observed. On the other hand, the magnetic field strength By gradually increases from the melt surface 12a of the silicon melt 12 toward the bottom 13a of the crucible 13 to the middle of the melt, and after passing the middle, the magnetic field strength By is reversed and gradually decreases. In addition, when a horizontal magnetic field is applied to the silicon melt 12, an unstable portion is generated in the vicinity where the magnetic field strength By gradually changes from gradually increasing.

  Since the silicon melt convection is unstable in such an unstable portion, as shown in FIG. 10B, the in-plane distribution of the oxygen concentration Oi in the silicon single crystal ingot greatly fluctuates within a minute range. If the in-plane distribution of oxygen concentration fluctuates in this way, in the device process, it may cause insufficient gettering of heavy metal impurities due to the difference in density of crystal defects, which may adversely affect device characteristics and yield. . According to the present invention, it is possible to suppress the uneven distribution of the impurity concentration, to prevent the oxygen concentration and the dopant concentration from varying within a minute range, and to maintain good device characteristics and yield in the device process.

  FIG. 11A shows the relationship between the length XL in the growth direction of the silicon single crystal ingot, the magnetic field strength on the surface of the silicon melt, and the magnetic field strength at the bottom of the crucible in the samples 1 and 2 in the above-described embodiment. It is a graph. According to this graph, the magnetic field strength on the surface of the silicon melt is constant over the entire length XL in the growth direction of the silicon single crystal ingot in both samples 1 and 2, and the magnetic field strength at the bottom of the crucible is It gradually increases in a range lower than the magnetic field strength of the liquid surface.

  Due to the distribution of the magnetic field strength, as shown in FIG. 11B, the oxygen concentration Oi of the silicon single crystal ingot in both samples 1 and 2 decreases at a constant rate throughout the entire length XL. As a result, as shown in FIG. 11C, the in-plane distribution of the oxygen concentration Oi in the silicon single crystal ingot is stably distributed without fluctuation.

  FIG. 12A shows the relationship between the length XL in the growth direction of the silicon single crystal ingot, the magnetic field strength on the surface of the silicon melt, and the magnetic field strength at the bottom of the crucible in the sample 4 in the comparative example (conventional example) described above. It is the graph which showed. According to this graph, the magnetic field strength at the surface of the silicon melt is constant over the entire length XL in the growth direction of the silicon single crystal ingot, whereas the magnetic field strength at the bottom of the crucible is equal to that of the silicon single crystal ingot. Near the middle of the length XL in the growth direction, it exceeds the magnetic field strength on the surface of the silicon melt, and then decreases.

  When such a magnetic field strength distribution is obtained, as shown in FIG. 12 (b), fluctuations in the melt convection occur and an unstable portion is formed. As a result, the in-plane distribution of the oxygen concentration greatly fluctuates, This causes insufficient gettering of heavy metal impurities due to the density difference of crystal defects.

  From the above verification results, according to the present invention, a single (monotonic) increase or decrease in the magnetic field strength in the height direction is concentric with the silicon melt in a plane over the entire length of the pulling length. By pulling up the single crystal while maintaining the applied magnetic field, it is possible to suppress the uneven distribution of the impurity concentration and to prevent the oxygen concentration and the dopant concentration from varying within a minute range, In addition, it was confirmed that the device characteristics and yield can be kept good in the device process by reducing the occurrence of in-plane and axial distribution of resistivity.

FIG. 1 is a side sectional view showing an outline of a single crystal pulling apparatus of the present invention. FIG. 2 is a top sectional view of the single crystal pulling method of FIG. FIG. 3 is an explanatory diagram showing magnetic lines of force applied to the silicon melt of the crucible and isomagnetic lines formed thereby. FIG. 4 is an explanatory view showing an embodiment of the present invention. FIG. 5 is an explanatory view showing another embodiment of the present invention. FIG. 6 is an explanatory view showing an embodiment of the present invention. FIG. 7 is an explanatory view showing an embodiment of the present invention. FIG. 8 is an explanatory view showing an embodiment of the present invention. FIG. 9 is an explanatory view showing a conventional comparative example. FIG. 10 is a graph showing verification results of the present invention and the comparative example. FIG. 11 is a graph showing the verification results of the present invention. FIG. 12 is a graph showing a verification result of the comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Silicon single crystal pulling apparatus 12 Silicon melt 12a Melt surface 13 Quartz crucible 19 Side heater 51 Magnetic field application means

Claims (4)

A crucible for storing the silicon melt, a heater for heating the crucible, a crucible driving means for rotating and / or raising and lowering the crucible, a chamber for accommodating the crucible and the heater, and a chamber provided outside the chamber. A single crystal pulling device having magnetic field applying means for applying a magnetic field to the chamber,
The silicon single crystal pulling apparatus, wherein the magnetic field applying means is formed along the outer peripheral surface of the chamber, and is capable of forming substantially concentric isomagnetic lines from the center of the crucible. A crucible for storing the silicon melt, a heater for heating the crucible, a crucible driving means for rotating and / or raising and lowering the crucible, a chamber for accommodating the crucible and the heater, and a chamber provided outside the chamber. A single crystal pulling device having magnetic field applying means for applying a magnetic field to the chamber,
The magnetic field application means is formed along the outer peripheral surface of the chamber, and the magnetic field strength increases unilaterally from the melt surface of the silicon melt stored in the crucible toward the bottom of the crucible, or A silicon single crystal pulling apparatus characterized in that a magnetic field can be applied so that the magnetic field strength is unilaterally reduced.   The fluctuation range of the magnetic field strength when the magnetic field strength is unidirectionally increased or decreased from the melt surface of the silicon melt stored in the crucible toward the bottom of the crucible is applied to the chamber by the magnetic field applying means. 3. The silicon single crystal pulling apparatus according to claim 1, wherein the silicon single crystal pulling apparatus is set in a range of 0.6 to 0.9 times the strongest strength of the magnetic field.   4. The silicon single crystal pulling apparatus according to claim 1, wherein the magnetic field applying means is formed in a substantially ring shape so as to surround the chamber.

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