Method for producing single crystal silicon

Abstract

The present invention is a method for producing a single crystal silicon on the basis of a CZ method using a cusped magnetic field formed by an upper coil and a lower coil provided in a Czochralski furnace, the method being characterized in that, in a straight body step, the rotation speed of the single crystal silicon is 7-12 rpm, the rotation speed of a quartz crucible is 1.0 rpm or less, and the rotation speed of the quartz crucible is 1.0 rpm or less. The silicon single crystal is pulled up by setting the position of a magnetic field minimum surface of the cusped magnetic field within the range of 10 mm downward from the surface of the raw material melt to 5 mm upward from the surface of the raw material melt, and setting the magnetic field strength of the cusped magnetic field at the intersection of the inner wall of the quartz crucible and a surface having the same height as the magnetic field minimum surface to 800-1200 G. As a result, provided is a method for efficiently producing a single crystal silicon having a lower oxygen concentration and a good in-plane distribution of oxygen concentration than in the prior art.

Description

Technical Field

[0001] The present invention relates to a method for producing a single crystal silicon by a CZ method using a cusped magnetic field formed by an upper coil and a lower coil provided in a pulling furnace. Background Art

[0002] In recent years, power devices have attracted attention as devices for achieving power saving. The area where the current flows in power devices may be a thickness range of tens to hundreds of μm from the surface, and depending on the situation, the current may flow through the entire wafer. If there are oxygen precipitates or BMDs (Bulk Micro Defects) in the area where the current flows, poor withstand voltage and leakage may occur.

[0003] In order to avoid the above defects, the single crystal silicon wafer for power devices requires a low oxygen concentration that does not produce oxygen precipitates and a flat in-plane distribution of oxygen concentration. In addition, in RF (high frequency) devices used for communication such as smartphones, if there is an oxygen donor, the high frequency characteristics will deteriorate, so the single crystal silicon wafer for RF devices also requires a low oxygen concentration and a flat in-plane distribution of oxygen concentration.

[0004] As one of the representative methods for manufacturing single crystal silicon for power devices and RF devices, there is the Czochralski (CZ) method. When manufacturing single crystal silicon using the CZ method, the magnetic field application CZ (MCZ) method, which applies a magnetic field to the raw material melt to pull the single crystal, has become the mainstream. As a method for growing low-oxygen crystals for power devices, a method using a horizontal magnetic field and a method using a cusp magnetic field are known.

[0005] As a method of using a horizontal magnetic field, for example, Patent Document 1 discloses a method for obtaining low-oxygen crystals by specifying the crystallization rotation speed and the crucible rotation speed under a horizontal magnetic field, and Patent Document 2 discloses a method for setting the magnetic field strength to greater than 2000 G, the quartz crucible rotation speed to less than 0.2 rpm, and the crystallization rotation speed to less than 5 rpm.

[0006] On the other hand, as a method using a cusp magnetic field, there is a method described in Patent Document 3, for example, which moves the magnetic field center position (=magnetic field minimum plane position) of the cusp magnetic field to a temperature-stable position according to the reduction in silicon melt.

[0007] In addition, Patent Document 4 discloses a method of setting the center position of the magnetic field (= magnetic field minimum surface position) 10 to 100 mm above the liquid surface and setting the crystallization rotation to 15 to 20 rpm, and Patent Document 5 discloses a method of setting the distance from the lower end of the heat shielding material to the melt surface to 50 to 120 mm, setting the center position of the magnetic field between the melt surface and 1 / 2 of the melt depth, and setting the crystallization rotation to more than 13 rpm.

[0008] Patent document 6 discloses a method in which the magnetic field strength of the shear magnetic field is set to 0.05T to 0.12T, the center position of the magnetic field is set to 0mm to -30mm (30mm below) relative to the melt surface, the crystal rotation is set to 8 to 14rpm, and the crucible rotation speed is set to 1.3 to 2.2rpm.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Publication No. 2009-18984

[0012] Patent Document 2: International Publication No. 2009 / 025340

[0013] Patent Document 3: Japanese Patent Application Publication No. 2001-89289

[0014] Patent Document 4: Japanese Patent Application Publication No. 2020-33200

[0015] Patent Document 5: Japanese Patent No. 3783495

[0016] Patent Document 6: Japanese Patent Application Publication No. 2019-31436 Summary of the invention

[0017] 1. Technical issues to be resolved

[0018] In the methods described in Patent Documents 1 and 2, the crystallization rotation speed is set to about 5 rpm (Patent Document 1) or less (Patent Document 2). However, if the crystallization rotation speed is set to a low speed, the following problems arise: the resistivity and the in-plane distribution of oxygen deteriorate, which becomes the main cause of device failure.

[0019] In the method described in Patent Document 3, the position of the magnetic field minimum plane of the tangent magnetic field increases as the solidification rate of the single crystal increases. However, if the position of the magnetic field minimum plane is changed in the product portion, the following problems arise: the change in oxygen concentration in the product portion becomes larger, and the yield is significantly reduced when manufacturing crystals with a narrow standard width of oxygen concentration or low-oxygen crystals.

[0020] When manufacturing a small-diameter single crystal with a diameter of less than 200 mm, there is no problem with the crystal rotation speed described in Patent Documents 4 and 5. However, if the crystal rotation is set to 13 rpm or more when manufacturing a large-diameter single crystal with a diameter of more than 300 mm, the following problem occurs: the diameter variation becomes larger when the single crystal is pulled, and the operation cannot be continued.

[0021] The oxygen concentration described in Patent Document 6 is the result of model prediction based on numerical analysis, and the oxygen concentration is only at one point near the center. In the manufacture of a single crystal with a large diameter of 300 mm or more, if the rotation speed of the quartz crucible is set to a high speed of ≥1.3 rpm as described in Patent Document 6, there are the following problems: the value of the oxygen concentration increases and the in-plane distribution of the oxygen concentration deteriorates.

[0022] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for efficiently producing single crystal silicon having a lower oxygen concentration and a better in-plane distribution of oxygen concentration than in the conventional art.

[0023] (II) Technical solution

[0024] The present invention is completed to achieve the above-mentioned purpose, and provides a method for manufacturing single crystal silicon, which is based on the CZ method using a cusp magnetic field, and the cusp magnetic field is formed by an upper coil and a lower coil of a pulling furnace. The method for manufacturing single crystal silicon is characterized in that, in the straight body process, the rotation speed of the single crystal silicon is set to be greater than 7 rpm and less than 12 rpm, the rotation speed of the quartz crucible is set to be less than 1.0 rpm, the position of the magnetic field minimum surface of the cusp magnetic field is set within the range of 10 mm downward from the surface of the raw material melt to 5 mm upward from the surface of the raw material melt, and the magnetic field strength of the cusp magnetic field at the intersection of the surface at the same height as the magnetic field minimum surface and the inner wall of the quartz crucible is set to 800-1200G, thereby pulling the single crystal silicon.

[0025] According to such a method for manufacturing single crystal silicon, since the problems of increased oxygen concentration and deterioration of in-plane distribution of oxygen concentration when the crucible rotation speed is set to high speed are eliminated, the following single crystals can be efficiently manufactured: low oxygen concentration that meets the quality requirements for power devices and RF devices and good in-plane distribution of oxygen concentration.

[0026] In this case, the following method for producing single crystal silicon can be used. As the single crystal silicon, a single crystal silicon having an oxygen concentration of 2×10 17 atoms / cm 3 Below, and the ROG in the crystal cross section perpendicular to the growth direction of the single crystal silicon is less than 8%.

[0027] The method for producing single crystal silicon of the present invention can stably produce such high-quality single crystal silicon.

[0028] (III) Beneficial effects

[0029] As described above, according to the method for manufacturing single crystal silicon of the present invention, since the problems of increase in oxygen concentration and deterioration in the in-plane distribution of oxygen concentration when the crucible rotation speed is set to high speed are eliminated, the following single crystals can be efficiently manufactured: low oxygen concentration that meets the quality requirements for power devices and RF devices, and good in-plane distribution of oxygen concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a diagram for explaining an example of a single crystal manufacturing apparatus.

[0031] Figure 2 The in-plane distribution of oxygen concentration obtained at a straight length of 100 cm in Examples 1 and 2 is shown.

[0032] Figure 3 This figure shows the dependence of the oxygen concentration in the single crystal on the crucible rotation speed.

[0033] Figure 4 The in-plane distribution of oxygen concentration obtained at a straight length of 100 cm in Comparative Example 2 is shown. DETAILED DESCRIPTION

[0034] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0035] As described above, there is a demand for a method for producing a silicon single crystal that can efficiently produce a single crystal having a lower oxygen concentration than in the related art and a good in-plane distribution of oxygen concentration.

[0036] The present inventors have conducted in-depth research on the above-mentioned technical problems, and as a result, found that, through the following method for manufacturing single crystal silicon, which is based on the use of a cusp magnetic field CZ method, the cusp magnetic field is formed by an upper coil and a lower coil of a pulling furnace, in the straight body process, the rotation speed of the single crystal silicon is set to be greater than 7 rpm and less than 12 rpm, the rotation speed of the quartz crucible is set to be less than 1.0 rpm, the position of the magnetic field minimum surface of the cusp magnetic field is set in the range of 10 mm downward from the surface of the raw material melt to 5 mm upward from the surface of the raw material melt, and the magnetic field strength of the cusp magnetic field at the intersection of the surface at the same height as the magnetic field minimum surface and the inner wall of the quartz crucible is set to 800 to 1200 G, thereby pulling the single crystal silicon, since the problems of increased oxygen concentration and deterioration of the in-plane distribution of oxygen concentration when the crucible rotation speed is set to a high speed are eliminated, the following single crystal can be efficiently manufactured: it is a low oxygen concentration that meets the quality requirements for power devices and RF devices, and the in-plane distribution of oxygen concentration is good, thereby completing the present invention.

[0037] As described above, in recent years, the quality of low-oxygen crystals for power devices and RF devices has been required to be higher than the current level. In particular, the oxygen concentration is preferably 2×10 17 atoms / cm 3 (ASTM'79) or less. In addition, the in-plane distribution of oxygen concentration is preferably uniformized in order to eliminate quality deviations between chips. For example, when the oxygen concentration on the periphery of the wafer is low, slip dislocations may occur on the periphery during heat treatment, which may adversely affect the yield of the device process.

[0038] As a countermeasure to this situation, it is important to make the oxygen concentration in the surface uniform. Below, ROG (Radial Oxygen Gradient) is used as an indicator to achieve a good distribution of oxygen concentration in the surface. ROG measures the oxygen concentration at least at the center of the wafer and at a predetermined distance from the periphery of the wafer, and is calculated by the following formula:

[0039] (maximum value - minimum value) × 100 / value obtained by maximum value. In recent years, ROG is also required to be higher than the existing level, and a good distribution satisfying ROG < 8% is required.

[0040] However, in the CZ method, the single crystal is grown while the crystal is rotated during crystallization pulling. In the case of pulling a single crystal with a large diameter of more than 300 mm by the CZ method using a cusp magnetic field, if the crystallization rotation speed is set to an extremely high speed, there is the following problem: the diameter change becomes larger when the single crystal is pulled, and the operation cannot be continued. On the contrary, if the crystallization rotation speed is set to an extremely low speed, there is also the following problem: the in-plane distribution of resistivity and oxygen concentration deteriorates, which becomes the main cause of device failure. In order to avoid these problems, in the CZ method using a cusp magnetic field, it is necessary to avoid conditions where the crystallization rotation speed becomes extremely high or extremely low.

[0041] In addition, in the MCZ method, a silicon melt (hereinafter also referred to as "raw material melt") is contained in a quartz crucible, but during the crystal pulling, oxygen dissolves from the quartz crucible and enters the silicon melt, thereby increasing the oxygen concentration in the single crystal. If the surface (liquid surface) of the silicon melt is overlooked from a vertical direction, in the MCZ method using a horizontal magnetic field, the magnetic field acts in a direction parallel to the magnetic lines of force, thereby suppressing convection, but the magnetic field hardly acts in a direction perpendicular to the magnetic lines of force, so convection becomes active. In this way, since a region with localized active convection is generated, oxygen is easily dissolved from the quartz crucible in a horizontal magnetic field, resulting in a high oxygen concentration in the crystal.

[0042] On the other hand, in the case of a cusp magnetic field, the magnetic field acts on the entire circumference near the inner wall of the quartz crucible (hereinafter, sometimes simply referred to as "crucible wall" or "crucible inner wall"), so the convection near the crucible wall is suppressed throughout the circumference. Therefore, in the cusp magnetic field, if the crucible rotation speed is sufficiently fast and the magnetic field strength is a strong magnetic field, the relative speed between the quartz crucible and the raw material melt becomes high, and the dissolution of oxygen is promoted. On the contrary, if the crucible rotation speed is sufficiently slow and the magnetic field strength is a weak magnetic field, the relative speed between the quartz crucible and the raw material melt becomes low, and the dissolution of oxygen is suppressed.

[0043] In addition to the above, by setting the position of the magnetic field minimum plane in the cusp magnetic field close to or above the solid-liquid interface between the single crystal and the silicon melt, oxygen can easily enter the single crystal side from the layer with low oxygen concentration on the surface of the silicon melt through the natural convection inherent in the cusp magnetic field. Therefore, by using the cusp magnetic field to sufficiently slow down the crucible rotation speed, set the magnetic field strength to a weak magnetic field, and set the position of the magnetic field minimum plane close to or above the solid-liquid interface between the single crystal and the silicon melt, low oxygen concentration in the crystal can be achieved.

[0044] That is, the present invention is characterized in that, in a method for manufacturing single crystal silicon based on the CZ method using a cusp magnetic field, the crystallization rotation speed of the single crystal in the straight body process is set to be greater than 7 rpm and less than 12 rpm, the position of the magnetic field minimum surface of the cusp magnetic field is set within the range of 10 mm downward from the surface of the raw material melt to 5 mm upward from the surface of the raw material melt, the rotation speed of the quartz crucible is set to be less than 1.0 rpm, and the magnetic field strength of the cusp magnetic field at the intersection of the surface at the same height as the magnetic field minimum surface and the inner wall of the quartz crucible (hereinafter sometimes simply expressed as "magnetic field strength") is set to 800 to 1200 G.

[0045] Hereinafter, an example of a single crystal manufacturing apparatus suitable for use in the method for manufacturing single crystal silicon of the present invention will be described with reference to the drawings. In addition, description of the same parts as those of the conventional apparatus may be appropriately omitted.

[0046] Figure 1 An example of a single crystal manufacturing apparatus (single crystal pulling apparatus) is shown. Figure 1The single crystal manufacturing device (single crystal pulling device) 100 includes: a heat insulating material 9; a heater 8 inside the heat insulating material 9; and a heat shielding member 12, which is arranged at the lower end of the cylindrical portion 11 and faces the raw material melt 5 of silicon contained in the quartz crucible 6 arranged in the graphite crucible 7. The single crystal manufacturing device 100 includes: a pulling furnace 1 having a central axis 10; and a magnetic field generating device 30, which is arranged around the pulling furnace 1 and has an upper coil 30a and a lower coil 30b, and by energizing the upper coil 30a and the lower coil 30b, a cusped magnetic field is applied to the silicon melt to pull the single crystal in the central axis direction. In addition, the single crystal 2 held by the seed holder 3 connected to the metal wire is brought into contact with the raw material melt 5 on the central axis 10 of the pulling furnace 1 to perform seeding, expand the diameter of the single crystal silicon, and pull the straight body portion to be the product portion in the pulling direction to produce the single crystal silicon 4.

[0047] The magnetic field generating device 30 is disposed on a lifting device 30c that can move up and down in a vertical direction, and an upper coil 30a and a lower coil 30b are arranged in a manner to surround the side of the pulling furnace 1. In the tangential magnetic field, magnetic lines of force that repel each other up and down are generated by passing currents in opposite directions through the upper and lower coils. At this time, due to the effect of the magnetic field distributions formed by the upper coil 30a and the lower coil 30b respectively, an area (magnetic field minimum surface 32) with the minimum magnetic field intensity is formed between the upper coil 30a and the lower coil 30b near the central axis 10. For example, by setting the current values ​​of the upper coil 30a and the lower coil 30b to the same value, and passing currents in opposite directions through the upper and lower coils, a magnetic field distribution that is symmetrical up and down and left and right is formed. At this time, the magnetic field intensity at the intersection of the central axis 10 and the magnetic field minimum surface 32 is the weakest. In addition, Figure 1 3 shows the case where the height position of the magnetic field minimum surface 32 (ie, the height position of the surface 31 at the same height as the magnetic field minimum surface) is the same as the height position of the raw material melt surface 33. Figure 1 The black dotted arrows in the figure represent the actual magnetic field distribution, the white arrow on the central axis represents the dominant component of the magnetic field in the vertical direction, and the white arrow on the midline between the two coils represents the dominant component of the magnetic field in the horizontal direction.

[0048] In addition, by setting the current values ​​of the upper coil 30a and the lower coil 30b to different values ​​and performing unbalanced excitation by passing currents in opposite directions through the upper and lower coils, a vertically asymmetric and left-right symmetric magnetic field distribution (hereinafter referred to as "unbalanced excitation") is obtained. Compared with the case where the current values ​​of the upper and lower coils are set to the same value, the position of the magnetic field minimum surface 32 changes. For example, if it is set as:

[0049] The current value of the upper coil> the current value of the lower coil,

[0050] Compared with the case where the current values ​​of the upper and lower coils are set to the same value, the magnetic field minimum surface 32 is shifted downward.

[0051] If set to:

[0052] The upper coil current value is less than the lower coil current value.

[0053] Then, compared with the case where the current values ​​of the upper and lower coils are set to the same value, the magnetic field minimum surface 32 is shifted upward.

[0054] In the present invention, in the product portion (straight tube process), the position of the magnetic field minimum surface 32 is set within a range of 10 mm downward from the raw material molten surface 33 to 5 mm upward from the raw material molten surface 33, but it is necessary to move the position of the magnetic field minimum surface before pulling the product portion (straight tube process). Regarding the method of moving the magnetic field minimum surface at this time, the position of the magnetic field minimum surface can be moved by moving the magnetic field generating device 30 up and down using the lifting device 30c, or the position of the magnetic field minimum surface can be moved by performing unbalanced excitation with the current values ​​of the upper and lower coils 30a and 30b set to different values.

[0055] Furthermore, as described above, the strength of the convection suppression force near the inner wall of the quartz crucible is determined by the magnetic field strength near the inner wall of the quartz crucible, and therefore the magnetic field strength near the inner wall of the quartz crucible becomes an important factor in determining the oxygen concentration in the MCZ method using a cusp magnetic field. Therefore, the magnetic field strength in the present invention is defined as 800 to 1200 G at the intersection 35 of the surface 31 at the same height as the magnetic field minimum surface and the inner wall of the quartz crucible. In addition, the surface 31 at the same height as the magnetic field minimum surface is a surface including the magnetic field minimum surface 32, and the intersection 35 can also be referred to as a point on the inner wall of the quartz crucible at the same height as the height position of the magnetic field minimum surface 32.

[0056] The structure of the HZ (hot zone) other than the above may be the same as that of a normal CZ silicon single crystal production apparatus, but it is a necessary condition that the rotation speed of the quartz crucible can be set to 1.0 rpm or less.

[0057] In the CZ method, a single crystal is grown while being rotated. However, in order to obtain a single crystal with a low oxygen concentration and a good in-plane distribution of oxygen concentration without impairing operability, in the present invention, the crystallization rotation speed of the single crystal in the straight body process is set to 7 rpm to 12 rpm.

[0058] In the CZ method, a single crystal is grown while the quartz crucible is rotated. However, in the cusp magnetic field, the magnetic field acts on the entire circumference near the crucible wall, so the convection near the crucible wall is suppressed throughout the entire circumference. Therefore, if the rotation speed of the quartz crucible is too high in the cusp magnetic field, the relative speed between the quartz crucible and the raw material melt becomes high, the dissolution of oxygen is promoted, and the increase of the oxygen concentration in the single crystal becomes a problem.

[0059] In addition to the above problems, in particular, in the manufacture of single crystals with a large diameter, such as a diameter of more than 300 mm, if the rotation speed of the quartz crucible is too high, the in-plane distribution of the oxygen concentration deteriorates, which also becomes a problem. In order to solve these problems, in the present invention, the rotation speed of the quartz crucible is set to 1.0 rpm or less. The lower limit of the rotation speed of the quartz crucible is not particularly limited, for example, it can be set to 0.1 rpm or more.

[0060] Thus, by setting the crystallization speed of the single crystal in the straight body process to 7 rpm or more and 12 rpm or less, setting the position of the magnetic field minimum plane of the magnetic field to be within the range of 10 mm downward from the surface of the raw material melt to 5 mm upward from the surface of the raw material melt, setting the rotation speed of the quartz crucible to be less than 1.0 rpm, and setting the magnetic field strength of the shear magnetic field to 800 to 1200 G, it is possible to maintain 2×10 17 atoms / cm 3 A good in-plane distribution of oxygen concentration is obtained at a low oxygen concentration of less than (ASTM'79). In addition, the lower limit of the oxygen concentration is not particularly limited, and is, for example, 5×10 15 atoms / cm 3 (ASTM'79) or more. The lower limit of the in-plane distribution (ROG) of oxygen concentration is also not particularly limited, and is, for example, 0% or more.

[0061] Example

[0062] Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.

[0063] 360 kg of raw materials were melted in a 32-inch (about 800 mm) crucible in a CZ puller, and a cusp magnetic field was applied to pull a single crystal with a diameter of 300 mm. In the present embodiment and the comparative example, symmetrical excitation with the same current value of the upper and lower coils of the cusp magnetic field and unbalanced excitation with different current values ​​between the upper and lower coils were performed. In addition, when unbalanced excitation is performed in the product section, the magnetic field position is set in advance using a lifting device so that the position of the magnetic field minimum surface is 70 mm below the surface of the raw material melt. After that, the unbalance degree is set to a specified value in the non-product section and transferred to the product section.

[0064] At this time, the imbalance between the upper and lower coils is expressed by the following formula:

[0065] Unbalance = lower coil current value / upper coil current value

[0066] The value obtained.

[0067] After the single crystal was pulled, samples were cut from 20 cm, 50 cm, 75 cm, and 100 cm in length, and the in-plane distribution of oxygen concentration was verified using FT-IR. The oxygen concentration values ​​shown below are those at the center of the wafer.

[0068] In addition, ROG measures the oxygen concentration at two locations: the center of the wafer and 2 mm from the periphery of the wafer, and uses the following formula:

[0069] (maximum value - minimum value) × 100 / maximum value. In addition, ROG in the table is the average value between 20 cm and 100 cm in the straight body position.

[0070] (Examples 1 and 2)

[0071] In Examples 1 and 2, single crystal silicon was produced under the following conditions.

[0072] [Straight body process (product department)]

[0073] Position of minimum magnetic field surface: 10mm below the melt surface

[0074] Unbalance between upper and lower coils: 1.00 (upper and lower symmetrical excitation)

[0075] Magnetic field strength at the intersection of the surface at the same height as the magnetic field minimum surface and the inner wall of the crucible: 1000G

[0076] Crucible speed: 0.5 rpm (Example 1), 1.0 rpm (Example 2)

[0077] Single crystal speed: 10rpm

[0078] In Examples 1 and 2, in the straight body process, the magnetic field minimum plane position of the cut magnetic field, the imbalance between the upper and lower coils, the magnetic field strength, and the single crystal rotation speed were fixed, and the crucible rotation speed was set to 0.5 rpm (Example 1) and 1.00 rpm (Example 2), and a total of two single crystals were manufactured. The conditions and results of Examples 1 and 2 are shown in Table 1, and the in-plane distribution of oxygen concentration obtained at 100 cm of the straight body of Examples 1 and 2 is shown in Table 1. Figure 2 .

[0079] [Table 1]

[0080]

[0081] The single crystal silicon manufacturing method of the present invention was successfully pulled up without any dislocation in the straight body process under the conditions of Examples 1 and 2. The crystal quality of the product was also obtained with an oxygen concentration of 2×10 17 atoms / cm 3 (ASTM'79) or less and ROG < 8%. Single crystals with low oxygen concentration and good in-plane distribution of oxygen concentration were successfully pulled without compromising operability.

[0082] (Examples 3 and 4)

[0083] In Examples 3 and 4, single crystal silicon was produced under the following conditions.

[0084] [Straight body process (product department)]

[0085] Position of minimum magnetic field surface: 5mm above the melt surface

[0086] Unbalance: 1.00 (upper and lower symmetrical excitation)

[0087] Magnetic field strength at the intersection of the surface at the same height as the magnetic field minimum surface and the inner wall of the crucible: 800G (Example 3), 1200G (Example 4)

[0088] Crucible speed: 1.00rpm

[0089] Single crystal speed: 10rpm

[0090] In Examples 3 and 4, the magnetic field minimum plane position, unbalance, crucible rotation speed, and single crystal rotation speed of the cusp magnetic field in the straight body process were fixed, and the magnetic field strength was set to 800 G (Example 3) and 1200 G (Example 4), and a total of two single crystals were manufactured. The conditions and results of Examples 3 and 4 are shown in Table 2.

[0091] [Table 2]

[0092]

[0093] The single crystal silicon manufacturing method of the present invention was successfully pulled up without any dislocation in the straight body process when the conditions of Examples 3 and 4 were used. Regarding the crystal quality of the product part, an oxygen concentration of 2×10 17 atoms / cm 3 (ASTM'79) or less and ROG < 8%. Single crystals with low oxygen concentration and good in-plane distribution of oxygen concentration were successfully pulled without compromising operability.

[0094] (Examples 5 and 6)

[0095] In Examples 5 and 6, single crystal silicon was produced under the following conditions.

[0096] [Straight body process (product department)]

[0097] Position of minimum magnetic field surface: 5mm above the melt surface

[0098] Unbalance: 1.00 (upper and lower symmetrical excitation)

[0099] Magnetic field strength at the intersection of the surface at the same height as the magnetic field minimum surface and the inner wall of the crucible: 1000G

[0100] Crucible speed: 1.00rpm

[0101] Single crystal rotation speed: 7rpm (Example 5), 12rpm (Example 6)

[0102] In Examples 5 and 6, the magnetic field minimum plane position, unbalance, magnetic field strength, and crucible rotation speed of the cusp magnetic field in the straight body process were fixed, and the single crystal rotation speed was set to 7 rpm (Example 5) and 12 rpm (Example 6), and a total of two single crystals were manufactured. The conditions and results of Examples 5 and 6 are shown in Table 3.

[0103] [Table 3]

[0104]

[0105] The single crystal silicon manufacturing method of the present invention was successfully pulled up when the conditions of Examples 5 and 6 were used. No dislocation was generated in the straight body process. As for the crystal quality of the product, an oxygen concentration of 2×10 17 atoms / cm 3 (ASTM'79) or less and ROG < 8%. Single crystals with low oxygen concentration and good in-plane distribution of oxygen concentration were successfully pulled without compromising operability.

[0106] (Examples 7 and 8)

[0107] In Examples 7 and 8, single crystal silicon was produced under the following conditions.

[0108] [Straight body process (product department)]

[0109] Position of minimum magnetic field surface: 10mm below the melt surface

[0110] Unbalance: 1.10 (unbalanced excitation)

[0111] Magnetic field strength at the intersection of the surface at the same height as the magnetic field minimum surface and the inner wall of the crucible: 1000G

[0112] Crucible speed: 0.5 rpm (Example 7), 1.0 rpm (Example 8)

[0113] Single crystal speed: 10rpm

[0114] In Examples 7 and 8, the excitation method was changed to unbalanced excitation, the magnetic field minimum surface position, unbalance, magnetic field intensity, and single crystal rotation speed in the straight body process were fixed, and the crucible rotation speed was set to 0.5 rpm (Example 7) and 1.0 rpm (Example 8), and a total of two single crystals were manufactured. The conditions and results of Examples 7 and 8 are shown in Table 4.

[0115] [Table 4]

[0116]

[0117] The single crystal silicon manufacturing method of the present invention was successfully pulled up without any dislocation in the straight body process when the conditions of Examples 7 and 8 were used. Regarding the crystal quality of the product part, an oxygen concentration of 2×10 17 atoms / cm 3 (ASTM'79) or less and ROG < 8%. Single crystals with low oxygen concentration and good in-plane distribution of oxygen concentration were successfully pulled without compromising operability.

[0118] (Examples 9 and 10)

[0119] In Examples 9 and 10, single crystal silicon was produced under the following conditions.

[0120] [Straight body process (product department)]

[0121] Position of minimum magnetic field surface: 10mm below the melt surface

[0122] Unbalance: 1.10 (unbalanced excitation)

[0123] Magnetic field strength at the intersection of the surface at the same height as the magnetic field minimum surface and the inner wall of the crucible: 800G (Example 9), 1200G (Example 10)

[0124] Crucible speed: 1.0rpm

[0125] Single crystal speed: 10rpm

[0126] In Examples 9 and 10, the excitation method was changed to unbalanced excitation, the magnetic field minimum surface position, unbalance, crucible rotation speed, and single crystal rotation speed in the straight body process were fixed, and the magnetic field strength was set to 800G (Example 9) and 1200G (Example 10), and a total of two single crystals were manufactured. The conditions and results of Examples 9 and 10 are shown in Table 5.

[0127] [Table 5]

[0128]

[0129] The single crystal silicon manufacturing method of the present invention was successfully pulled up without any dislocation in the straight body process when the conditions of Examples 9 and 10 were used. Regarding the crystal quality of the product part, an oxygen concentration of 2×10 17 atoms / cm 3 (ASTM'79) or less and ROG < 8%. Single crystals with low oxygen concentration and good in-plane distribution of oxygen concentration were successfully pulled without compromising operability.

[0130] (Examples 11 and 12)

[0131] In Examples 11 and 12, single crystal silicon was produced under the following conditions.

[0132] [Straight body process (product department)]

[0133] Position of minimum magnetic field surface: 10mm below the melt surface

[0134] Unbalance: 1.10 (unbalanced excitation)

[0135] Magnetic field strength at the intersection of the surface at the same height as the magnetic field minimum surface and the inner wall of the crucible: 1000G

[0136] Crucible speed: 1.0rpm

[0137] Single crystal rotation speed: 7rpm (Example 11), 12rpm (Example 12)

[0138] In Examples 11 and 12, the excitation method was changed to unbalanced excitation, the magnetic field minimum surface position, unbalance, magnetic field intensity, and crucible rotation speed in the straight body process were fixed, and the single crystal rotation speed was set to 7 rpm (Example 11) and 12 rpm (Example 12), and a total of two single crystals were manufactured. The conditions and results of Examples 11 and 12 are shown in Table 6.

[0139] [Table 6]

[0140]

[0141] The single crystal silicon manufacturing method of the present invention was successfully pulled up without any dislocation in the straight body process when the conditions of Examples 11 and 12 were used. Regarding the crystal quality of the product part, an oxygen concentration of 2×10 17 atoms / cm 3(ASTM'79) or less and ROG < 8%. Single crystals with low oxygen concentration and good in-plane distribution of oxygen concentration were successfully pulled without compromising operability.

[0142] (Comparative Example 1)

[0143] In Comparative Example 1, a single crystal was produced by setting the crucible rotation speed in the straight body step (product portion) to 1.5 rpm and setting all other conditions to the same conditions as in Example 1. Table 7 shows the conditions and results of Comparative Example 1.

[0144] [Table 7]

[0145]

[0146] Under the conditions of Comparative Example 1, although the single crystal was successfully pulled without any dislocation in the straight body process, the oxygen concentration was higher than 2×10 17 atoms / cm 3 , ROG>8%.

[0147] For the sake of caution, the crucible speed was allocated in the range of 1.0 rpm to 2.2 rpm, and the other conditions were the same as those in Comparative Example 1 to manufacture the single crystal. The results are as follows Figure 3 As shown in FIG. 1 , the oxygen concentration increases monotonically with the increase in the crucible rotation speed. Therefore, it can be seen that in order to obtain a single crystal with a low oxygen concentration and a good in-plane distribution of oxygen concentration that meets the quality requirements for power devices and RF devices, it is necessary to set the crucible rotation speed to less than 1.0 rpm as in the method for manufacturing single crystal silicon of the present invention.

[0148] (Comparative Examples 2 and 3)

[0149] In Comparative Examples 2 and 3, the crystallization rotation speed in the straight body process (product part) was set to 6 rpm (Comparative Example 2) or 13 rpm (Comparative Example 3), and the other conditions were the same as those in Example 1, and the single crystal was pulled. The conditions and results of Comparative Examples 2 and 3 are shown in Table 8, and the in-plane distribution of oxygen concentration obtained at 100 cm of the straight body of Comparative Example 2 is shown in Table 8. Figure 4 .

[0150] [Table 8]

[0151]

[0152] When the crystallization speed of the straight body process (product part) is set to 6rpm, although the single crystal is successfully pulled without generating dislocations once in the straight body process, the in-plane distribution of oxygen deteriorates and ROG ≤ 8% cannot be satisfied. In addition, when the crystallization speed of the straight body process (product part) is set to 13rpm, the crystal deformation is enhanced during pulling and it is difficult to continue the operation. Therefore, it can be seen that in order to obtain a single crystal with a low oxygen concentration and good in-plane distribution of oxygen concentration that meets the quality requirements for power devices and RF devices, it is necessary to set the crystallization speed of the straight body process (product part) to 7rpm or more and 12rpm or less, as in the method for manufacturing single crystal silicon of the present invention.

[0153] (Comparative Examples 4-7)

[0154] In Comparative Examples 4-7, the magnetic field intensity in the straight body process (product part) was set to 700 G (Comparative Example 4) or 1300 G (Comparative Example 5), and the magnetic field minimum plane position in the straight body process was set to 10 mm above the melt surface (Comparative Example 6) or 15 mm below the melt surface (Comparative Example 7) by unbalanced excitation, and the other conditions were the same as those in Example 2, and the single crystal was pulled. The conditions and results of Comparative Examples 4 to 7 are shown in Table 9.

[0155] [Table 9]

[0156]

[0157] When the magnetic field strength in the straight body process (product part) was set to 700G, the crystal deformation was enhanced during the pulling process, making it difficult to continue the operation. On the other hand, when the magnetic field strength in the straight body process (product part) was set to 1300G, the oxygen concentration was higher than 2×10 17 atoms / cm 3 In addition, when the magnetic field minimum surface position of the straight body process (product part) is set 10 mm above the melt surface and 15 mm below the melt surface, the oxygen concentration is also higher than 2×10 17 atoms / cm 3 Therefore, it can be seen that in order to obtain a single crystal with a low oxygen concentration and good in-plane distribution of oxygen concentration that meets the quality requirements for power devices and RF devices, it is necessary to set the absolute value of the magnetic field strength to 800G or more and 1200G or less in the straight body process (product part), and set the position of the magnetic field minimum surface within the range of 10 mm below the surface of the raw material melt to 5 mm above the surface of the raw material melt, as in the method for manufacturing single crystal silicon of the present invention.

[0158] (Comparative Example 8)

[0159] In Comparative Example 8, the crucible rotation speed in the straight body process (product part) was set to 1.5 rpm, and all other conditions were the same as those in Example 7 (unbalanced excitation) to produce a single crystal. The conditions and results of Comparative Example 8 are shown in Table 10.

[0160] [Table 10]

[0161]

[0162] Under the conditions of Comparative Example 8, although the single crystal was successfully pulled without any dislocation in the straight body process, the oxygen concentration was higher than 2×10 17 atoms / cm 3 , ROG>8%. Therefore, it can be seen that even when the excitation method is set to unbalanced excitation, in order to obtain a single crystal with a low oxygen concentration and good in-plane distribution of oxygen concentration that meets the quality requirements for power devices and RF devices, it is necessary to set the crucible rotation speed to 1.0 rpm or less, as in the method for manufacturing single crystal silicon of the present invention.

[0163] (Comparative Examples 9 and 10)

[0164] In Comparative Examples 9 and 10, the crystallization rotation speed in the straight body step (product part) was set to 6 rpm (Comparative Example 9) or 13 rpm (Comparative Example 10), and the other conditions were the same as those in Example 7, and single crystal pulling was performed. The conditions and results of Comparative Examples 9 and 10 are shown in Table 11.

[0165] [Table 11]

[0166]

[0167] When the crystallization speed of the straight body process (product part) is set to 6 rpm, bending (Japanese: kurank) occurs in the straight body process, making it difficult to continue the operation. In addition, when the crystallization speed of the straight body process (product part) is set to 13 rpm, the crystal deformation is enhanced during pulling, making it difficult to continue the operation. Therefore, it can be seen that even when the excitation method is set to unbalanced excitation, in order to obtain a single crystal with a low oxygen concentration and good in-plane distribution of oxygen concentration that meets the quality requirements for power devices and RF devices, it is necessary to set the crystallization speed of the straight body process (product part) to 7 rpm or more and 12 rpm or less, as in the method for manufacturing single crystal silicon of the present invention.

[0168] (Comparative Examples 11-14)

[0169] In Comparative Examples 11 to 14, the magnetic field intensity in the straight body step (product portion) was set to 700 G (Comparative Example 11) or 1300 G (Comparative Example 12), the magnetic field minimum surface position in the straight body step (product portion) was set to 10 mm above the melt surface (Comparative Example 13) or 15 mm below the melt surface (Comparative Example 14), and other conditions were set to the same conditions as in Example 8, and single crystal pulling was carried out. The conditions and results of Comparative Examples 11 to 14 are shown in Table 12.

[0170] [Table 12]

[0171]

[0172] When the magnetic field strength in the straight body process (product part) was set to 700G, the crystal deformation was enhanced during the pulling process, making it difficult to continue the operation. On the other hand, when the magnetic field strength in the straight body process (product part) was set to 1300G, the oxygen concentration was higher than 2×10 17 atoms / cm 3 In addition, when the magnetic field minimum surface position of the straight body process (product part) is set 10 mm above the melt surface and 15 mm below the melt surface, the oxygen concentration is also higher than 2×10 17 atoms / cm 3 Therefore, it can be seen that even when the excitation method is set to unbalanced excitation, in order to obtain a single crystal with a low oxygen concentration and good in-plane distribution of oxygen concentration that meets the quality requirements for power devices and RF devices, it is necessary to set the absolute value of the magnetic field strength to 800G or more and 1200G or less in the straight body process (product part) as in the manufacturing method of the single crystal silicon of the present invention, and set the position of the magnetic field minimum surface to within the range of 10mm downward from the surface of the raw material melt to 5mm upward from the surface of the raw material melt.

[0173] As described above, according to an embodiment of the present invention, the problems of an increase in oxygen concentration and a deterioration in the in-plane distribution of oxygen concentration when the crucible rotation speed is set to a high speed are eliminated, so that the following single crystals can be efficiently manufactured: a low oxygen concentration that meets the quality requirements for power devices and RF devices, and a good in-plane distribution of oxygen concentration.

[0174] The present invention is not limited to the above-described embodiments. The above-described embodiments are illustrative, and any scheme having substantially the same structure and achieving the same function and effect as the technical concept described in the claims of the present invention is included in the technical scope of the present invention.

Claims

1. A method for producing single crystal silicon, which is based on a CZ method using a cusp magnetic field, wherein the cusp magnetic field is formed by an upper coil and a lower coil provided in a pulling furnace, wherein the method for producing single crystal silicon is characterized in that: In the straight body process, the rotation speed of the single crystal silicon is set to be greater than 7 rpm and less than 12 rpm, the rotation speed of the quartz crucible is set to be less than 1.0 rpm, the position of the magnetic field minimum surface of the tangent magnetic field is set within the range of 10 mm downward from the surface of the raw material melt to 5 mm upward from the surface of the raw material melt, and the magnetic field strength of the tangent magnetic field at the intersection of the surface at the same height as the magnetic field minimum surface and the inner wall of the quartz crucible is set to 800 to 1200 G, thereby pulling the single crystal silicon.

2. The method for producing single crystal silicon according to claim 1, characterized in that: As the single crystal silicon, the oxygen concentration is 2×10 17 atoms / cm 3 Below, and the ROG in the crystal cross section perpendicular to the growth direction of the single crystal silicon is less than 8%.

Images