Method for growing silicon wafers and silicon single crystal ingots

Abstract

To provide a silicon wafer that has high-resistance and an extremely low oxygen concentration, and to provide a method for growing an ingot of a silicon single crystal that produces the wafer and has low oxygen and reduced variation in resistivity in a crystal growth direction.SOLUTION: A silicon wafer includes phosphorus and antimony as a dopant element, where oxygen concentration is 5×1017 atoms / cm3 or less and resistivity is 30 Ωcm or more and 1000 Ωcm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for growing silicon wafers and silicon single crystal ingots. [Background technology]

[0002] A method for producing single crystal silicon ingots for use in silicon wafers for insulated gate bipolar transistors (IGBTs) involves growing high-resistivity, low-oxygen single crystal silicon ingots doped with phosphorus as a dopant. However, because phosphorus has a small segregation coefficient, i.e., phosphorus easily segregates, the phosphorus concentration in the silicon melt increases as the ingot is pulled, and the phosphorus concentration incorporated into the crystal also increases, resulting in a low resistivity. This results in a low yield of the ingot portion that meets the desired resistivity range in the resistivity distribution along the crystal length. To address this issue, a technique is known that uses an n-type dopant (antimony or arsenic), which evaporates faster than phosphorus, and controls the amount of dopant evaporated from the silicon melt as the ingot is pulled, thereby improving the yield of the crystal region that meets the desired resistivity (see, for example, Patent Document 1). It is also known to improve yield by counter-doping an n-type impurity, such as phosphorus, with an opposite-polarity p-type impurity, such as aluminum, and to improve resistivity fluctuations caused by aluminum concentrated in the silicon melt in the latter half of crystal pulling by doping with antimony, which has a smaller segregation coefficient than phosphorus (see, for example, Patent Document 2).It is also known to add two n-type dopants together in order to produce semiconductor wafers with low resistivity and fewer dislocations using a smaller amount of dopant than when a single dopant is used (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-31023 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-87008 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-220013 Summary of the Invention [Problem to be solved by the invention]

[0004] For IGBT applications, extremely low oxygen (e.g., 5×10 17 atoms / cm 3 Therefore, in terms of single crystal silicon ingots (hereinafter sometimes referred to as ingots) for producing extremely low oxygen silicon wafers and their manufacturing methods, it is essential to grow as many crystal regions as possible that satisfy the extremely low oxygen concentration in the crystal length direction of the ingot, from the viewpoint of improving product yield.

[0005] In the latter half of ingot growth using the Czochralski method, the silicon melt in the crucible (e.g., a quartz crucible) decreases due to consumption during crystal growth. This requires increased heating of the crucible to maintain the temperature of the silicon melt. This increases the crucible temperature, which tends to cause oxygen to diffuse from the crucible into the silicon melt, increasing the oxygen concentration in the crystal. Therefore, it becomes necessary to promote oxygen evaporation from the silicon melt in order to reduce the oxygen concentration in the silicon melt. Therefore, in the latter half of single crystal growth, the pressure inside the furnace may be reduced or the flow rate of argon gas flowing through the furnace may be increased.

[0006] However, antimony is an element that easily evaporates. Therefore, when growing a single crystal doped with antimony as a dopant, as in conventional techniques (see, for example, Patent Documents 1 to 3), if the pressure inside the furnace is reduced or the flow rate of argon gas flowing through the furnace is increased to promote oxygen evaporation, not only oxygen but also antimony evaporates from the silicon melt. This can result in excessive antimony evaporation in the latter half of the ingot growth. As a result, the dopant concentration in the crystal in the ingot decreases, resulting in a resistivity higher than the desired value, which causes a problem of reduced product yield.

[0007] On the other hand, the ingot growth method described in Patent Document 2, which combines aluminum counterdoping of phosphorus with antimony addition, requires complex concentration management of each dopant, which can ultimately make it difficult to control the resistivity along the crystal growth direction of the ingot. Furthermore, for example, when an extremely low-oxygen atmosphere is desired, it is conceivable that the amount of antimony evaporation increases with oxygen evaporation, resulting in growth conditions in which the antimony concentration gradually decreases along the crystal growth direction of the ingot. However, the growth method described in Patent Document 2 does not anticipate such a case. Furthermore, semiconductor wafers such as those described in Patent Document 3 are limited to those with low resistivity.

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a silicon wafer having high resistivity and an extremely low oxygen concentration, and to provide a method for growing a silicon single crystal ingot having low oxygen content and little variation in resistivity in the crystal growth direction, for producing the wafer. [Means for solving the problem]

[0009] The inventors have conducted extensive research and have come up with the idea of ​​double doping with phosphorus (P) and antimony (Sb) in order to achieve both control of the change in resistivity of the crystal due to the change in the concentration of the dopant in the melt during the crystal growth process, which is caused by the segregation coefficient and the ease of evaporation, and extremely low oxygen content. The gist of the present invention is as follows:

[0010] (1) Contains phosphorus and antimony as dopant elements; Oxygen concentration is 5×10 17 atoms / cm 3 Below, A silicon wafer with a resistivity of 30 Ωcm or more and 1000 Ωcm or less.

[0011] (2) Phosphorus concentration is 1.0 × 10 12 atoms / cm 3 Over 1.1 x 10 14 atoms / cm 3 below, Antimony concentration is 1.0×10 12 atoms / cm 3 Over 1.1 x 10 14 atoms / cm 3 The silicon wafer according to (1) above, which is:

[0012] (3) The silicon wafer according to (1) or (2) above, wherein the antimony concentration is 50% or more and 200% or less of the phosphorus concentration.

[0013] (4) The phosphorus concentration is lower at the periphery of the wafer than at the center; The silicon wafer according to any one of (1) to (3) above, wherein the antimony concentration is lower in the outer periphery of the wafer than in the center of the wafer.

[0014] (5) The ratio of the phosphorus concentration in the peripheral portion of the wafer to the phosphorus concentration in the center portion of the wafer is 0.93 or more and 1.00 or less, and The silicon wafer according to any one of (1) to (4) above, wherein the ratio of the antimony concentration in the peripheral part of the wafer to the antimony concentration in the center part of the wafer is 0.90 or more and 0.97 or less.

[0015] (6) A method for growing a silicon single crystal ingot, which comprises pulling a silicon single crystal ingot from a silicon melt to which phosphorus and antimony are added, A magnetic field is applied to the silicon melt, and a silicon single crystal ingot growing method, wherein the antimony concentration in the silicon single crystal ingot is decreased as the pulling rate of the silicon single crystal ingot increases.

[0016] (7) passing argon gas through the furnace containing the silicon melt; The pressure inside the furnace is set to 60 Torr or less, The method for growing a silicon single crystal ingot according to (6) above, wherein the flow rate of the argon gas is 100 L / min or more.

[0017] (8) The method for growing a silicon single crystal ingot according to (6) or (7) above, wherein the silicon melt is prepared by adding antimony to a solution in which a polysilicon raw material and phosphorus are dissolved.

[0018] (9) A method for growing a silicon single crystal ingot according to any one of (6) to (8) above, wherein the magnetic field is applied in a cusp magnetic field manner. [Effects of the Invention]

[0019] It is possible to provide a silicon wafer with high resistance and extremely low oxygen concentration, and to provide a method for growing a silicon single crystal ingot for manufacturing the wafer, which has low oxygen content and little variation in resistivity in the crystal growth direction. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is an explanatory diagram illustrating a schematic configuration of a growth apparatus for implementing a method for growing a silicon single crystal ingot according to an embodiment of the present invention. [Figure 2] FIG. 1 is an explanatory diagram of an ingot. [Figure 3] 1 is a graph showing the relationship between solidification rate and resistivity ratio. [Figure 4] 1 is a graph showing the relationship between resistivity specification and yield rate. [Figure 5] 1 is a graph showing the relationship between the solidification rate and the Sb / P concentration ratio. [Figure 6]1 is a graph showing the relationship between the in-plane position of a wafer and the dopant concentration ratio. DETAILED DESCRIPTION OF THE INVENTION

[0021] A method for growing a silicon wafer and a silicon single crystal ingot according to an embodiment of the present invention will be described with reference to the drawings.

[0022] The silicon wafer according to this embodiment contains phosphorus (P) and antimony (Sb) as dopant elements. The oxygen concentration in the silicon wafer is 5×10 17 atoms / cm 3 The resistivity of the silicon wafer is 30 Ωcm or more and 1000 Ωcm or less. The oxygen concentration in the silicon wafer is more preferably 4×10 17 atoms / cm 3 The lower limit of the oxygen concentration in silicon wafers is 1×10 17 atoms / cm 3 It is desirable to have more than this.

[0023] In this embodiment, the resistivity is defined as a value measured by a four-point probe method, and the oxygen concentration of the silicon wafer is defined as a value determined by a measurement method in accordance with ASTM F121-1979.

[0024] The silicon wafer according to this embodiment has a phosphorus concentration of 1.0×10 12 atoms / cm 3 Over 1.1 x 10 14 atoms / cm 3 Below, antimony concentration is 1.0 × 10 12 atoms / cm 3 Over 1.1 x 10 14 atoms / cm 3 By adjusting the phosphorus concentration and antimony concentration within these ranges, the resistivity of the silicon wafer can be adjusted to a predetermined resistivity of 30 Ωcm or more and 1000 Ωcm or less.

[0025] In this embodiment, the phosphorus concentration of a silicon wafer is a value obtained by thinning the silicon wafer by polishing and measuring the phosphorus concentration at the center of the silicon wafer thickness using secondary ion mass spectrometry (SIMS). Accurate measurement of the phosphorus concentration is difficult at the top surface of a silicon wafer due to the large amount of noise present at the top surface. Therefore, accurate measurement of the phosphorus concentration becomes possible by measuring at a depth of 1 μm or more from the wafer surface, excluding the top surface. In this embodiment, to obtain a more accurate value, the value measured at the center in the thickness direction of the silicon wafer is defined as the phosphorus concentration of the silicon wafer.

[0026] In this embodiment, the antimony concentration of a silicon wafer is measured by polishing the silicon wafer to thin it, and then measuring the antimony concentration at the center of the silicon wafer's thickness using secondary ion mass spectrometry (SIMS). Accurate measurement of the antimony concentration is difficult at the top surface of a silicon wafer because of the large amount of noise present at the top surface. Therefore, accurate measurement of the antimony concentration becomes possible if the measurement is performed at a depth of 1 μm or more from the wafer surface, excluding the top surface. In this embodiment, to obtain a more accurate value, the value measured at the center of the silicon wafer's thickness direction is defined as the antimony concentration of the silicon wafer.

[0027] Furthermore, in the silicon wafer according to this embodiment, the antimony concentration is preferably 50% or more and 200% or less of the phosphorus concentration. More preferably, the antimony concentration is 80% or more and 150% or less of the phosphorus concentration. By achieving such a concentration balance between antimony and phosphorus, it is possible to improve the production yield of silicon wafers that satisfy the desired resistivity standard.

[0028] Furthermore, in the silicon wafer according to this embodiment, it is preferable that the phosphorus concentration is lower in the outer periphery of the wafer than in the center, and the antimony concentration is lower in the outer periphery of the wafer than in the center, thereby improving the production yield of silicon wafers that satisfy the desired resistivity standard.

[0029] Furthermore, in the silicon wafer according to this embodiment, the ratio of the phosphorus concentration in the outer periphery of the wafer to the phosphorus concentration in the center of the wafer is preferably 0.93 or more and 1.00 or less. Furthermore, the ratio of the antimony concentration in the outer periphery of the wafer to the antimony concentration in the center of the wafer is preferably 0.90 or more and 0.97 or less. By achieving such a concentration balance between antimony and phosphorus, the in-plane resistivity distribution variation (radial resistivity distribution, RRG: Radial Resistivity Gradient) of the silicon wafer can be reduced to 5% or less.

[0030] Furthermore, in the silicon wafer according to this embodiment, it is preferable that the difference value obtained by subtracting the phosphorus concentration at the peripheral part of the wafer from the phosphorus concentration at the central part of the wafer is smaller than the difference value obtained by subtracting the antimony concentration at the peripheral part of the wafer from the antimony concentration at the central part of the wafer. By doing so, the in-plane resistance distribution variation (RRG) of the silicon wafer can be reduced to 5% or less.

[0031] Furthermore, the silicon wafer according to this embodiment preferably has an in-plane resistance distribution variation (RRG) of 5% or less.

[0032] In addition, the silicon wafer according to this embodiment has a nitrogen concentration of 1×10 13 atoms / cm 3 5x10 or more 15 atoms / cm 3 It is preferable that the nitrogen concentration is less than or equal to 1000 kJ / cm. The addition of nitrogen can widen the pull-speed margin at which defect-free crystals can be grown, thereby increasing the yield of defect-free crystals. If the nitrogen concentration is below the lower limit, it becomes difficult to widen the pull-speed margin at which defect-free crystals can be grown, while if it exceeds the upper limit, the nitrogen in silicon approaches its solubility limit, making it difficult to grow dislocation-free single crystals. The nitrogen concentration in silicon single crystals can be measured by secondary ion mass spectrometry (SIMS).

[0033] Furthermore, the silicon wafer according to this embodiment preferably does not have COPs and does not have dislocation clusters. The absence of COPs means that COPs are not observed, for example, in an infrared tomograph. It also means that dislocation clusters are not observed after secco etching.

[0034] In this embodiment, the nitrogen concentration of a silicon wafer is a value measured by polishing the silicon wafer to thin it, and then measuring the nitrogen concentration at the center of the silicon wafer's thickness using secondary ion mass spectrometry (SIMS). The outermost surface of a silicon wafer contains a lot of noise, making it difficult to measure the nitrogen concentration accurately. Therefore, accurate measurement of the nitrogen concentration is possible if the measurement is performed at a depth of 1 μm or more from the wafer surface, excluding the outermost surface. In this embodiment, to obtain a more accurate value, the value measured at the center of the silicon wafer's thickness direction is defined as the nitrogen concentration of the silicon wafer.

[0035] As an example, the silicon wafer according to this embodiment can be manufactured by cutting out a silicon single crystal ingot grown by a silicon single crystal ingot growing method in which a silicon single crystal ingot is pulled from a silicon melt to which phosphorus and antimony have been added, and a magnetic field is applied to the silicon melt, and the antimony concentration in the silicon single crystal ingot decreases as the amount of the silicon single crystal ingot pulled increases.

[0036] In this embodiment, the silicon single crystal ingot can be grown by the Czochralski (Cz) method, which is a method for growing a silicon single crystal ingot by pulling silicon melted in a crucible upward under a temperature gradient.

[0037] Fig. 1 shows an example of an ingot growth apparatus that realizes the method for growing a silicon single crystal ingot (hereinafter, sometimes simply referred to as an ingot) according to this embodiment. The growth apparatus 100 shown in Fig. 1 can realize the method for growing an ingot according to this embodiment by the Czochralski method.

[0038] The growth apparatus 100 includes a chamber 11 (an example of a furnace), a quartz crucible 12 (hereinafter simply referred to as the crucible 12) that contains the raw material for the ingot 16 (e.g., polysilicon), a heater 14 that heats the raw material in the crucible 12 to form a raw material melt 13 (an example of a silicon melt), a crucible rotation mechanism 15 that rotates the crucible 12 in a circumferential direction, a seed crystal holder 18 that holds a seed crystal 17 for growing the ingot 16, a wire rope 19 to which the seed crystal holder 18 is attached at its tip, a winding mechanism 20 that rotates the wire rope 19 while rotating and pulling up the ingot 16, the seed crystal 17, and the seed crystal holder 18, and a magnet 21 that applies a predetermined magnetic field to the raw material melt 13.

[0039] The crucible 12, heater 14, crucible rotation mechanism 15, wire rope 19, and winding mechanism 20 are housed in a chamber 11. The crucible rotation mechanism 15 is provided below the crucible 12. A magnet 21 is disposed on the outside of the lower part of the chamber 11. The chamber 11 has a supply port 11a through which argon gas is supplied into the chamber 11, and an exhaust port 11b through which the argon gas and vaporized material from the raw material melt 13 are exhausted from the chamber 11.

[0040] In the growth apparatus 100, the ingot 16 is grown as follows. First, predetermined amounts of polysilicon and phosphorus are placed in the crucible 12. Then, while argon gas is flowing through the chamber 11, the crucible 12 is heated by the heater 14 to prepare a solution of polysilicon and phosphorus. Next, while continuing the heating by the heater 14 and the flow of argon gas, antimony is added to the solution to prepare a raw material melt 13, which is a silicon melt to which phosphorus and antimony have been added. A predetermined magnetic field is applied to the solution and the raw material melt 13 by the magnet 21.

[0041] As for phosphorus, dissolving it together with polysilicon as described above can prevent phosphorus from remaining undissolved, thereby making it possible to prepare raw material melt 13 containing a desired concentration of dopant.

[0042] Although antimony has the property of easily evaporating, by preparing a solution of polysilicon and phosphorus as described above and then adding antimony to prepare raw material melt 13, it is possible to avoid a decrease in the antimony concentration due to the evaporation of antimony during raw material melting. This makes it possible to prepare raw material melt 13 containing a desired concentration of dopant. From the viewpoint of further preventing the evaporation of antimony, it is desirable to delay the timing of the addition of antimony, and it is desirable to add antimony to the solution immediately before or immediately after bringing seed crystal 17 into contact with raw material melt 13.

[0043] Furthermore, phosphorus and antimony may be added as solid dopants (granular) made of the respective elements. Since the addition of extremely small amounts of dopant is required to grow a high-resistivity silicon single crystal, the dopant element may be dissolved in silicon, and silicon chunks may be crushed to dilute the dopant concentration, and the dopant may be added in the form of silicon pieces (addition of granular dopant or diluted dopant).

[0044] Next, with a magnetic field applied to the raw material melt 13 and argon gas flowing through the chamber 11, the seed crystal 17 held in the seed crystal holder 18 is brought into contact with the raw material melt 13. Then, the crucible 12 is rotated at a predetermined rotation speed by the crucible rotation mechanism 15, and the seed crystal 17 (i.e., the ingot 16) is wound up by the winding mechanism 20 while being rotated at the predetermined rotation speed, thereby pulling up the seed crystal 17 and the ingot 16 grown below the seed crystal 17. In this manner, an ingot 16 having a predetermined diameter as shown in FIG. 2 can be produced. Note that in FIG. 2, the upper end portion of the ingot 16 is shown as an upper end portion (shoulder portion) 16a, and the lower end portion is shown as a lower end portion (tail portion) 16b.

[0045] During the pulling of the ingot 16, the pressure inside the chamber 11 (inside the furnace) is preferably 60 Torr or less. The pressure inside the chamber 11 is more preferably 20 to 40. The flow rate of the argon gas flowing through the chamber 11 is 100 L / min or more (for example, when the spatial volume inside the chamber 11 is 4 m 3 The flow rate of the argon gas flowing through the chamber 11 is preferably 120 L / min or more and 200 L / min or less. From the raw material melt 13, elemental phosphorus, elemental antimony, phosphorus compounds (such as PxOy), or antimony compounds (such as SbxOy) are vaporized (evaporated) to form gas. The concentration of these gases in the argon gas exhausted from the exhaust port 11b may be measured and the flow rate of the argon gas flowing through the chamber 11 may be changed. The oxygen concentration of a silicon single crystal ingot (ingot 16) that can be grown by the CZ method (growth apparatus 100) is, for example, 1×10 17 atoms / cm 3 can be reduced to a certain extent.

[0046] The magnetic field applied to the raw material melt 13 is preferably a cusp magnetic field. FIG. 1 illustrates an example in which the magnet 21 has a pair of coils 22 that apply a cusp magnetic field. The pair of coils 22 includes a coil 22a that applies a magnetic field to the raw material melt 13 in a direction perpendicular to the silicon melt, and a coil 22b that is positioned below the coil 22a and applies a magnetic field in a vertical direction opposite to that of the coil 22a. By applying a magnetic field to the raw material melt 13, convection of the melt within the raw material melt 13 can be suppressed. [Example]

[0047] An example will be described below.

[0048] Example 1 Using the growth apparatus 100 shown in FIG. 1, a silicon single crystal ingot with a diameter of 200 mm and a length of 1500 mm was grown by the Czochralski method. First, a polysilicon block as a raw material and phosphorus (P) as an n-type dopant were placed in a crucible 12, and the polysilicon and phosphorus were melted in an argon atmosphere. Next, antimony (Sb) as an n-type dopant was added to the molten silicon to produce a raw material melt 13 containing dissolved antimony. Note that in this example, no dopants other than phosphorus (P) and antimony (Sb) were added.

[0049] The amount of dopant added to the silicon melt was adjusted to a dopant amount that was predicted to give a resistivity of 50 Ωcm at the start position of the straight body of the ingot 16. The phosphorus concentration during preparation of the raw material melt 13 was 3.49×10 13 atoms / cm 3 The antimony concentration during preparation of raw material melt 13 was 4.42 × 10 13 atoms / cm 3 The target resistivity of the crystal of the ingot 16 (that is, the target value of the resistivity of the wafer) was set to 60 Ωcm in the crystal growth direction (longitudinal direction) of the ingot 16.

[0050] Furthermore, a seed crystal 17 was brought into contact with the raw material melt 13, and while a cusp magnetic field was applied to the raw material melt 13, the seed crystal 17 and the crucible 12 were rotated while the seed crystal 17 was gradually pulled up, so that a dislocation-free silicon single crystal (i.e., an ingot 16) was grown below the seed crystal 17. At this time, V / G, which is the ratio of V, the growth rate of the silicon single crystal, to G (°C / min), which is the temperature gradient from the melting point at the solid-liquid interface, which is the boundary between the silicon crystal and the raw material melt 13, to 1350°C, was appropriately controlled, and a COP-free and dislocation cluster-free single crystal (ingot 16) was pulled up.

[0051] The flow rate of the argon gas flowing through the chamber 11 was set to 150 L / min, and the internal pressure of the chamber 11 (furnace pressure) was set to 30 Torr.

[0052] (Comparative Example 1) Only antimony was used as the n-type dopant, and the antimony concentration during preparation of raw material melt 13 was 5.41 × 10 13 atoms / cm 3 A silicon single crystal ingot according to Comparative Example 2 was grown in the same manner as in Example 1, except that:

[0053] (Comparative Example 2) Only phosphorus was used as the n-type dopant, and the phosphorus concentration during preparation of raw material melt 13 was 5.34 × 10 13 atoms / cm 3 A silicon single crystal ingot according to Comparative Example 2 was grown in the same manner as in Example 1, except that:

[0054] The silicon single crystal ingots grown in Example 1 and Comparative Examples 1 and 2 were subjected to known processing (cutting, grinding, polishing, etching, cleaning, etc.) to form silicon wafers (hereinafter sometimes simply referred to as wafers). These wafers were then subjected to a heat treatment at 1100°C for 90 minutes to completely eliminate oxygen donors in the wafers.

[0055] <Measurement results of crystal resistivity> For each wafer of Example 1 and Comparative Examples 1 and 2, the resistivity of the center (an example of the central portion) in the radial direction of each wafer was measured by the four-point probe method.

[0056] Figure 3 shows a graph of the resistivity measurement results, organized by the solidification rate (the ratio from the 0 mm position on the straight body (see part A in Figure 2) when the crystal length L is set to 100), which is the length of the straight body of the silicon single crystal ingot (the length of the ingot, see Figure 2).

[0057] 3, the resistivity is shown as a resistivity ratio (a value obtained by dividing the resistivity at each solidification rate by the resistivity at the solidification rate of 10%) normalized by setting the resistivity at a solidification rate of 10% in Example 1 and Comparative Examples 1 and 2 to 1. The resistivities at a solidification rate of 10% in Example 1, Comparative Example 1, and Comparative Example 2 are 62 Ωcm, 79 Ωcm, and 80 Ωcm, respectively.

[0058] The graph shown in Fig. 3 reveals the following: In other words, in the ingot according to Example 1, the amount of change in the resistivity ratio with respect to an increase in the solidification rate (crystal length) is small, and the resistivity ratio fluctuates around 1. In other words, in the ingot according to Example 1, the resistivity along the crystal growth direction (the longitudinal direction of the ingot) is uniform.

[0059] In contrast, in Comparative Example 1, the resistivity ratio generally monotonically decreased with increasing solidification rate (crystal length), and for example, after a solidification rate of 50%, the resistivity ratio significantly deviated to a value smaller than 1. That is, in Comparative Example 1, it is considered that the antimony concentration in the ingot decreased with increasing ingot pulling rate during the ingot growth process.

[0060] Furthermore, in Comparative Example 2, the resistivity ratio generally monotonically increased with increasing solidification rate (crystal length), and for example, at a solidification rate of 40% or more, the resistivity ratio deviated significantly from 1. That is, in Comparative Example 2, contrary to Comparative Example 1, it is considered that the phosphorus concentration in the ingot increased with increasing ingot pulling rate during the ingot growth process.

[0061] In addition, considering the relationship between the solidification rate and the resistivity ratio in Comparative Example 2, it is considered that even in Example 1, the antimony concentration in the ingot decreases as the ingot pulling amount increases during the ingot growth process.

[0062] <Crystal yield> The crystal yield within the specified resistivity standard was determined. The crystal yield was defined as the block length [mm] within the specified resistivity range divided by the total block length (crystal length L, see Figure 2) [mm]. The resistivity standard was determined for each wafer when the measured resistivity was within a range of ±10%, ±8%, or ±5% of the target resistivity value of 50 Ω·cm, which was considered a pass / fail product. The yield of Comparative Example 2, where a resistivity standard within ±10% of 50 Ω·cm was considered a pass / fail product, was set to 1. Figure 4 shows a graph of the normalized yield ratios for the yields of Example 1 and Comparative Examples 1 and 2 for each resistivity standard.

[0063] 4, the ingot according to Example 1 has an extremely favorable yield ratio that is approximately twice as high (i.e., twice the yield) as the ingots according to Comparative Examples 1 and 2. That is, the ingot according to Example 1 has a high yield in terms of resistivity (resistivity yield).

[0064] <Oxygen concentration measurement> The oxygen concentration of each wafer (all sliced ​​wafers) of Example 1 and Comparative Examples 1 and 2 was measured in accordance with ASTM F121-1979. 17 atoms / cm 3 The wafers were extremely low in oxygen.

[0065] The above results demonstrate that the silicon single crystal ingot growth method according to this embodiment can produce extremely low-oxygen silicon wafers. Furthermore, this growth method can produce ingots with uniform resistivity along the crystal growth direction and high resistivity yield.

[0066] Other evaluation results of the ingot and wafer according to Example 1 will be further described below.

[0067] <Antimony / phosphorus concentration ratio> For each wafer in Example 1, the antimony concentration and phosphorus concentration at the center in the radial direction were measured using secondary ion mass spectrometry (SIMS), and the ratio of the antimony concentration to the phosphorus concentration (the value obtained by dividing the antimony concentration by the phosphorus concentration, hereinafter referred to as the Sb / P concentration ratio) was calculated. A graph in which the Sb / P concentration ratio is plotted against the solidification rate is shown in Figure 5. Note that for each wafer in Example 1, the phosphorus concentration was 1.0 x 10 12 atoms / cm 3 Over 1.1 x 10 14 atoms / cm 3 The antimony concentration is 1.0×10 12 atoms / cm 3 Over 1.1 x 10 14 atoms / cm 3 It was as follows.

[0068] 5, it can be seen that the Sb / P concentration ratio tends to decrease as the solidification rate increases for each wafer in Example 1. That is, in Example 1, the antimony concentration in the ingot decreases relative to the phosphorus concentration as the ingot pull rate increases during the ingot growth process. For wafers with a solidification rate in the range of 10% to 70%, the Sb / P concentration ratio is 0.5 to 2, i.e., the antimony concentration is 50% to 200% of the phosphorus concentration.

[0069] <In-plane distribution of antimony and phosphorus concentrations> Furthermore, for each wafer of Example 1 (provided that the wafers had resistivity standards within a range of 10% of a resistivity value of 50 Ω·cm), the antimony concentration and phosphorus concentration were measured at 5 mm intervals along the radial direction from the center of the wafer in an in-plane region excluding a 5 mm area from the wafer periphery. FIG. 6 shows a graph plotting the antimony concentration and phosphorus concentration against the radial distance from the wafer center (in-plane position on the wafer). Note that FIG. 6 shows the dopant concentrations of antimony and phosphorus as a dopant concentration ratio normalized by setting the concentration value of each dopant at the wafer center to 1. FIG. 6 also shows the average value for each wafer of Example 1.

[0070] 6, it can be seen that the average phosphorus concentration of each wafer in Example 1 was lower at the outer periphery (a position 5 mm inward from the outer periphery of the wafer) than at the central portion (center of the wafer). Focusing on the phosphorus concentration at the outer periphery of the wafer and the phosphorus concentration at the center of the wafer, the dopant concentration ratio was 0.93 or more and 1.00 or less for each wafer.

[0071] Furthermore, from the graph shown in FIG. 6, it can be seen that the average value of the antimony concentration for each wafer in Example 1 was lower at the outer periphery of the wafer (a position 5 mm inward from the outer periphery of the wafer) than at the central portion (center of the wafer). When focusing on the antimony concentration at the outer periphery of the wafer and the antimony concentration at the central portion of the wafer, the dopant concentration ratio was 0.90 or more and 0.97 or less for each wafer.

[0072] <Nitrogen concentration> For each wafer in Example 1, the nitrogen concentration at the center of the wafer in the radial direction was further measured by the above-mentioned secondary ion mass spectrometry (SIMS). The nitrogen concentration of each wafer was 1×10 13 atoms / cm 3 More than 1×10 15 atoms / cm 3 It was as follows.

[0073] <Concentration of other unavoidable impurities> When measuring the concentrations of phosphorus, antimony, and nitrogen described above, other unavoidable impurities (e.g., aluminum) are present in an amount of 1 × 10 13 atoms / cm 3 Nothing more was detected.

[0074] <Radial resistivity distribution> Furthermore, for each wafer of Example 1, in the in-plane region excluding 5 mm from the outer periphery of the wafer, the resistivity was measured at a pitch of 2 mm along the radial direction from the center of the wafer. The resistivity was measured by the four-probe method. Then, from the measurement results of the resistivity, the RRG (radial resistivity distribution) indicating the in-plane variation of the resistivity was obtained. When the maximum value of the resistivity was ρMax and the minimum value was ρMin, the RRG was obtained by the following formula (1).

[0075] RRG (%) = {(ρMax - ρMin) / ρMin} × 100 ··· (1)

[0076] For each wafer of Example 1, the RRG was within 4%.

[0077] <COP and dislocation clusters> For each wafer of Example 1, the evaluation of COP and dislocation clusters was performed. For the evaluation of COP, the silicon wafer was subjected to SC-1 cleaning (that is, cleaning with a mixed solution of ammonia water, hydrogen peroxide water, and ultrapure water mixed at 1:1:15), and the surface of the silicon wafer after cleaning was observed and evaluated using a Surfscan SP-1 manufactured by KLA-Tencor as a surface defect inspection device to identify bright point defects (LPD: Light Point Defect) estimated to be surface pits. At that time, the observation mode was the Oblique mode (oblique incidence mode), and the estimation of the surface pits was performed based on the detection size ratio of the Wide / Narrow channels. For the LPD thus identified, it was evaluated whether it was COP using an atomic force microscope (AFM: Atomic Force Microscope). The evaluation of dislocation clusters was confirmed by visual inspection of the surface of the silicon wafer after secco etching. The processing solution for secco etching was HF = 100 cm 3 , K2Cr2O7 = 50 g (0.15 mol / L). As a result, no COP and dislocation clusters were observed on each wafer of Example 1.

[0078] As described above, a method for growing a silicon wafer and an ingot of a single crystal silicon can be provided.

[0079] [Another embodiment] (1) In the above embodiment, the magnetic field applied to the raw material melt 13 is preferably a cusp magnetic field, and Fig. 1 illustrates an example in which the magnet 21 has a pair of coils 22 that apply a cusp magnetic field. However, the magnetic field applied to the raw material melt 13 is not limited to a cusp magnetic field, and may be a transverse magnetic field.

[0080] (2) In the above embodiment, a case where a silicon single crystal ingot having a diameter of 200 mm is grown is described as an example. However, the diameter of the ingot is not limited to 200 mm and may be changed depending on the application, such as to a diameter of 150 mm or 300 mm.

[0081] (3) In the above embodiment, the example was described with the wafer resistivity (target value) being 60 Ωcm. However, this resistivity is not limited to 60 Ωcm. The wafer resistivity is calculated by setting the phosphorus concentration and antimony concentration in the wafer to 1.0×10 12 Over 1.1 x 10 14 atoms / cm 3 or less and 1.0×10 12 Over 1.1 x 10 14 atoms / cm 3 By changing the resistivity within the range below, it is possible to adjust the resistivity to a predetermined value of 30 Ωcm or more and 1000 Ωcm or less.

[0082] The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradiction arises. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0083] The present invention is applicable to methods for growing silicon wafers and silicon single crystal ingots. [Explanation of symbols]

[0084] 100:Growing device 11: Chamber (furnace) 11a: Supply port 11b: Exhaust port 12: Crucible (quartz crucible) 13: Raw material melt (silicon melt) 14: Heater 15: Crucible rotation mechanism 16: Ingot (single crystal silicon ingot) 16a: Upper end 16b: Bottom end 17: Seed crystal 18: Seed crystal holder 19: Wire rope 20: Winding mechanism 21: Magnet 22: Coil L: Crystal length

Claims

1. Contains phosphorus and antimony as dopant elements, リン concentrationが1.0×10 １２ atoms / cm ３ Above 1.1×10 １４ atoms / cm ３ the following, Antimony concentration is 1.0 x 10 １２ atoms / cm ３ 1.1 x 10 １４ atoms / cm ３ The following, and Oxygen concentration is 5 x 10 １７ atoms / cm ３ Below, The concentration of each of the other impurity elements (excluding nitrogen) is less than 1×10 13 atoms / cm 3 , A silicon wafer having a resistivity of 30 Ωcm or more and 1000 Ωcm or less.

2. 2. The silicon wafer according to claim 1, wherein the antimony concentration is 50% or more and 200% or less of the phosphorus concentration.

3. The phosphorus concentration is lower at the periphery of the wafer than at the center, 3. The silicon wafer according to claim 1, wherein the antimony concentration is lower in the outer periphery of the wafer than in the center.

4. The ratio of the phosphorus concentration in the peripheral portion of the wafer to the phosphorus concentration in the center portion of the wafer is 0.93 or more and 1.00 or less, and 3. The silicon wafer according to claim 1, wherein the ratio of the antimony concentration in the outer periphery of the wafer to the antimony concentration in the center of the wafer is 0.90 or more and 0.97 or less.

5. The silicon wafer according to claim 1, wherein the nitrogen concentration is 1×10 13 atoms / cm 3 or more and 1×10 15 atoms / cm 3 or less.

6. A method for growing a silicon single crystal ingot, which comprises pulling a silicon single crystal ingot from a silicon melt containing only phosphorus and antimony, A magnetic field is applied to the silicon melt, and a silicon single crystal ingot growing method, wherein the antimony concentration in the silicon single crystal ingot is decreased as the pulling rate of the silicon single crystal ingot increases.

7. argon gas is passed through a furnace containing the silicon melt; The pressure inside the furnace is set to 60 Torr or less, 7. The method for growing a silicon single crystal ingot according to claim 6, wherein the flow rate of the argon gas is 100 L / min or more.

8. 8. The method for growing a silicon single crystal ingot according to claim 6, wherein the silicon melt is prepared by adding antimony to a solution in which a polysilicon raw material and phosphorus are dissolved.

9. 8. The method for growing a silicon single crystal ingot according to claim 6, wherein the magnetic field is applied in a cusp magnetic field manner.

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