Method for measuring resistivity of silicon single crystal

Abstract

To provide a method for measuring the resistivity of a silicon single crystal, with which a precise resistivity derived from a dopant can be measured for a silicon single crystal with resistivity of 100 Ω cm or higher, the silicon single crystal being grown with addition of nitrogen by a MCZ method.SOLUTION: There is provided a method for measuring the resistivity of a silicon single crystal with resistivity of 100 Ω cm or higher, the silicon single crystal being grown with addition of nitrogen by an MCZ method. The method includes: performing oxidation heat treatment at a temperature of 1,100 to 1,250°C for 90 to 240 minutes on a substrate sliced from the silicon single crystal to form a thermal oxide film on a surface of the substrate; and measuring the resistivity of the substrate after removing the thermal oxide film from the surface of the substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for measuring the resistivity of a silicon single crystal having a resistivity of 100 Ωcm or more, which is grown by the MCZ method with the addition of nitrogen. [Background technology]

[0002] RF (radio frequency) devices are used for communication purposes in smartphones, etc. Compound semiconductors have been used exclusively for these RF devices, but in recent years, RF devices based on single crystal silicon have come into widespread use due to the advancement of miniaturization in CMOS processes and the need to reduce the cost of device fabrication.

[0003] In RF devices using silicon single crystal wafers, if the resistivity of the substrate is low, that is, if the dopant concentration is high, the conductivity becomes high and loss increases, so there is a demand for a substrate with high resistivity, specifically 100 Ωcm or more. SOI (Silicon On Insulator) wafers, in which a thin oxide film and a thin silicon layer are formed on the surface of a silicon substrate, are sometimes used, and high resistivity is also desired in these cases. There is also a demand for high-resistivity substrates for power devices, as they are used for high-voltage applications.

[0004] In RF (radio frequency) devices and power devices, the presence of oxygen donors in the silicon substrate deteriorates the device's characteristics, so there is a demand for silicon single crystals with a low oxygen concentration to suppress oxygen donors.

[0005] In the CZ method, the silicon raw material melt is contained in a quartz crucible, and oxygen dissolves from the quartz crucible into the raw material melt during crystal pulling, and oxygen is incorporated into the single crystal.

[0006] For example, Patent Document 1 discloses a method for obtaining low-oxygen crystals by specifying the crystal rotation speed and crucible rotation speed under a horizontal magnetic field. Patent Document 2 discloses a method in which the horizontal magnetic field strength is set to 2000 G or more, the quartz crucible rotation speed is set to 0.2 rpm or less, and the crystal rotation speed is set to 5 rpm or less. Patent Document 3 discloses a method for obtaining low-oxygen crystals by specifying the magnetic field strength under a cusp magnetic field at the intersection of the magnetic field minimum plane position, the molten metal surface position, and the midpoint between the upper and lower coils and the inner wall of the quartz crucible.

[0007] Thus, in recent years, the CZ method for producing silicon single crystals has made it possible to stably produce low-oxygen crystals by using magnetic fields such as horizontal and cusp magnetic fields and by appropriately optimizing operational parameters such as the crystal rotation speed, crucible rotation speed, magnetic field strength, and excitation mode.

[0008] However, in low-oxygen silicon single crystals, the dislocation pinning effect of oxygen is weakened, resulting in significant slip generation during long-term high-temperature processes (heat treatments), which poses a problem of reduced yield when manufacturing RF and power devices. One way to improve this slip resistance is to add nitrogen to the silicon single crystal. Because nitrogen in silicon single crystals has a stronger ability to pin dislocations than oxygen, increasing the nitrogen concentration in the silicon single crystal can suppress slip generation during long-term high-temperature device processes.

[0009] However, when nitrogen is added to silicon single crystals, nitrogen donors (NO donors) are formed. These nitrogen donors disappear during high-temperature, long-term processes (heat treatment), so there is no change in resistivity after the process. However, the nitrogen donors remain at the as-grown stage, and in high-resistivity crystals with resistivity of 100 Ωcm or more, the remaining nitrogen donors cause significant changes in resistivity, resulting in a problem of a large deviation from the true resistivity due to the dopant.

[0010] As a solution to this problem, for example, Patent Document 4 discloses a method in which nitrogen-doped silicon single crystals with a resistivity of 1000 Ωcm or more are produced by the FZ method, a sample (silicon single crystal substrate) for resistivity measurement is taken from the crystal, and then heat-treated at a temperature of 900 to 1250°C for 10 to 120 minutes, and then the resistivity is measured. Patent Document 4 also discloses that the sample for resistivity measurement is heat-treated in one of a wet oxygen atmosphere, a dry oxygen atmosphere, and a nitrogen atmosphere, and the resistivity is measured without any treatment after the heat treatment. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-18984 [Patent Document 2] WO2009 / 025340 [Patent Document 3] Patent No. 7124938 [Patent Document 4] WO2005 / 010243 [Patent Document 5] Japanese Patent Application Laid-Open No. 2007-176725 Summary of the Invention [Problem to be solved by the invention]

[0012] However, when heat treatment is performed in an oxygen atmosphere, a thermal oxide film is formed on the sample surface, and if the resistivity is measured while the thermal oxide film remains on the sample surface, accurate resistivity derived from the dopant cannot be obtained. Also, when heat treatment is performed in a nitrogen atmosphere, outward diffusion of nitrogen within the silicon single crystal and inward diffusion from the nitrogen atmosphere occur simultaneously, and nitrogen donors (NO donors) may remain depending on the heat treatment conditions.

[0013] Patent Document 5 discloses a method in which nitrogen-doped silicon single crystals with a resistivity of 1000 Ωcm or more are produced by the FZ method, a sample for resistivity measurement is taken from the crystal, heat treatment and neutron beam irradiation are performed, and then the resistivity is measured. The technique in Patent Document 5 also describes heat treatment of the sample for resistivity measurement in a wet oxygen or dry oxygen atmosphere, followed by neutron beam irradiation, and then measuring the resistivity after neutron beam irradiation, but this also involves measuring the resistivity with the thermal oxide film remaining on the sample surface, which poses a problem in that accurate resistivity derived from the dopant cannot be obtained.

[0014] The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for measuring the resistivity of a silicon single crystal, which can accurately measure the resistivity derived from the dopant for a silicon single crystal having a resistivity of 100 Ωcm or more grown by the MCZ method with the addition of nitrogen. [Means for solving the problem]

[0015] In order to solve the above-mentioned problems, the method for measuring the resistivity of a silicon single crystal of the present invention is a method for measuring the resistivity of a silicon single crystal having a resistivity of 100 Ωcm or more that is grown by the MCZ method with the addition of nitrogen, and comprises the steps of: subjecting a substrate cut out from the silicon single crystal to an oxidation heat treatment at a temperature of 1100 to 1250°C for 90 to 240 minutes to form a thermal oxide film on the surface of the substrate; removing the thermal oxide film from the surface of the substrate; and then measuring the resistivity of the substrate.

[0016] In this method for measuring the resistivity of silicon single crystals, first, nitrogen donors formed in silicon single crystals grown with nitrogen doping are eliminated by performing an oxidation heat treatment at a temperature of 1100 to 1250°C for 90 to 240 minutes, thereby suppressing changes in resistivity due to the remaining nitrogen donors. Next, the thermal oxide film formed on the substrate surface by the oxidation heat treatment is removed, thereby eliminating the influence of the remaining thermal oxide film on the resistivity. As a result, even for nitrogen-doped silicon single crystals with high resistivity of 100 Ωcm or more, accurate resistivity measurements based on the dopant can be made.

[0017] In addition, in the method for measuring the resistivity of a silicon single crystal of the present invention, it is preferable that the thermal oxide film on the substrate surface is removed by etching with hydrofluoric acid (also called hydrofluoric acid), and then the substrate surface is ground.

[0018] Etching with hydrofluoric acid is easy and advantageous in terms of cost, and the thermal oxide film can be reliably removed by subsequently grinding the substrate surface.

[0019] Furthermore, in the method for measuring the resistivity of a silicon single crystal of the present invention, the nitrogen concentration of the silicon single crystal is 3.0×10 14 atoms / cm 3 The oxygen concentration is 8.0 x 10 17 atoms / cm 3 (ASTM'79) or less is preferable.

[0020] To measure the resistivity of a silicon single crystal, first, the oxygen concentration of the silicon single crystal is set to 8.0 × 10 17 atoms / cm 3By keeping the nitrogen donor concentration at or below (ASTM'79), it is possible to suppress not only the oxygen donor concentration but also the nitrogen donor (NO donor) concentration, enabling more accurate resistivity measurements. However, in low-oxygen silicon single crystals, the dislocation pinning effect of oxygen is weakened, resulting in significant slip generation during high-temperature, long-term processes (heat treatment), which causes a problem of reduced yield during device fabrication. Therefore, the nitrogen concentration of silicon single crystals is set to 3.0 x 10 14 atoms / cm 3 By doing so, it is possible to provide sufficient slip resistance to withstand high-temperature, long-term processes, which in turn makes it possible to prevent a decrease in yield during device fabrication while achieving highly accurate resistivity measurements. [Effects of the Invention]

[0021] The method for measuring the resistivity of silicon single crystals of the present invention can accurately measure the resistivity of silicon single crystals grown by the MCZ method with nitrogen doping and having a resistivity of 100 Ωcm or more. First, nitrogen donors formed in silicon single crystals grown with nitrogen doping are eliminated by performing an oxidation heat treatment at a temperature of 1100 to 1250°C for 90 to 240 minutes, thereby suppressing changes in resistivity due to the remaining nitrogen donors. Next, the thermal oxide film formed on the substrate surface by the oxidation heat treatment is removed, thereby eliminating the influence of the remaining thermal oxide film on the resistivity. As a result, accurate resistivity measurements based on the dopant are possible even for nitrogen-doped silicon single crystals with high resistivities of 100 Ωcm or more. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a flow chart showing an example of a method for measuring the resistivity of a silicon single crystal according to the present invention. [Figure 2] FIG. 1 is a diagram illustrating a pulling apparatus for the MCZ method using a horizontal magnetic field used in the present invention. [Figure 3] FIG. 1 is a diagram illustrating a pulling apparatus for the MCZ method using a cusp magnetic field used in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be described in detail below, but the present invention is not limited thereto.

[0024] As mentioned above, nitrogen donors remain in nitrogen-doped silicon single crystals at the as-grown stage, and particularly in high-resistivity crystals with resistivities of 100 Ωcm or higher, the remaining nitrogen donors significantly change the resistivity, resulting in a problem of a large deviation from the true resistivity due to the dopant. As a solution to this problem, Patent Documents 4 and 5 disclose methods of measuring resistivity after heat treatment in an oxygen atmosphere, or heat treatment in an oxygen atmosphere and neutron irradiation. However, high-temperature heat treatment in an oxygen atmosphere forms a thermal oxide film on the surface of the silicon single crystal substrate, and the presence of this thermal oxide film makes it difficult to obtain accurate resistivity due to the dopant.

[0025] There was a need for a method for measuring the resistivity of silicon single crystals that can accurately measure the resistivity derived from the dopant for silicon single crystals with a resistivity of 100 Ωcm or more grown by the MCZ method with the addition of nitrogen.

[0026] The inventors of the present invention have conducted extensive research into the above-mentioned problems and have found that, for nitrogen donors formed in silicon single crystals grown with nitrogen addition, a thermal oxide film is formed on the substrate surface by performing an oxidation heat treatment at a temperature of 1100 to 1250°C for 90 to 240 minutes, thereby eliminating the nitrogen donors and suppressing changes in resistivity due to the remaining nitrogen donors. Next, they confirmed that removing the thermal oxide film formed on the substrate surface by the oxidation heat treatment can eliminate the effect of the remaining thermal oxide film on resistivity. As a result, they have discovered a method for accurately measuring the resistivity derived from the dopant, even in nitrogen-doped silicon single crystals with high resistivity of 100 Ωcm or more, and have completed the present invention.

[0027] That is, the method for measuring the resistivity of a silicon single crystal of the present invention is a method for measuring the resistivity of a silicon single crystal having a resistivity of 100 Ωcm or more that is grown by the MCZ method with the addition of nitrogen, and is a method in which a substrate cut out from the silicon single crystal is subjected to an oxidation heat treatment at a temperature of 1100 to 1250°C for 90 to 240 minutes to form a thermal oxide film on the substrate surface, and the thermal oxide film is removed from the substrate surface, after which the resistivity of the substrate is measured.

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0029] First, an example of a method for measuring the resistivity of a silicon single crystal according to an embodiment of the present invention will be described with reference to FIGS.

[0030] In the present invention, nitrogen-doped silicon single crystals having a resistivity of 100 Ωcm or more are grown by the magnetic field applied CZ method (MCZ method). The form of the magnetic field used here is not particularly limited, but can be a horizontal magnetic field or a cusp magnetic field.

[0031] 2, the single crystal manufacturing apparatus with a horizontal magnetic field includes a silicon single crystal pulling apparatus (pulling furnace) 1 having a central axis 10, in which a heat shielding member 12 is arranged so as to face a heater 8 and a raw material melt (silicon melt) 5 contained in a quartz crucible 7, and a horizontal magnetic field generator 20 provided around the pulling furnace 1. By energizing a superconducting coil in the horizontal magnetic field generator 20, a horizontal magnetic field is applied to the silicon melt 5, thereby pulling up a silicon single crystal 4 in the direction of the central axis 10. The silicon single crystal pulling apparatus 1 further includes a seed crystal 2, a seed holder 3, a graphite crucible 6, a heat insulating member 9, and a cylindrical portion 11.

[0032] 3, the single crystal manufacturing apparatus with a cusp magnetic field includes a silicon single crystal pulling apparatus (pulling furnace) 31 having a central axis 40, in which a heat shielding member 43 is arranged so as to face a heater 38 and a raw material melt (silicon melt) 35 contained in a quartz crucible 36, and a cusp magnetic field generator 50 provided around the pulling furnace 31 and having an upper coil (superconducting coil) 50a and a lower coil (superconducting coil) 50b. By passing current through the superconducting coils 50a and 50b, a cusp magnetic field is applied to the silicon melt 35, thereby pulling up a silicon single crystal 34 in the direction of the central axis 40. The silicon single crystal pulling apparatus 31 further includes a seed crystal 32, a seed holder 33, a graphite crucible 37, a heat insulating member 39, and a cylindrical portion 42.

[0033] The cusp magnetic field generator 50 is installed on a vertically movable elevator 50c, and an upper coil 50a and a lower coil 50b are arranged to surround the side of the silicon single crystal pulling apparatus 31. In the cusp magnetic field, repulsive magnetic field lines are generated by passing currents in opposite directions through the two upper and lower coils. By setting the current values of the upper coil 50a and the lower coil 50b to the same value and passing currents in opposite directions through the two upper and lower coils, a magnetic field distribution that is symmetrical both vertically and horizontally is obtained. At this time, the magnetic field strength at the magnetic field minimum point 51, located at the intersection of the central axis 40 and the intermediate plane 41 between the two coils, is 0 G (Gauss). For example, by setting the magnetic field minimum point of the cusp magnetic field 10 mm below the surface of the raw material melt and setting the magnetic field strength at the intersection of the intermediate plane 41 between the upper and lower coils and the crucible wall to 1000 G, an oxygen concentration of 8.0 × 10 17 atoms / cm 3 (ASTM'79) silicon single crystals can be easily produced. The nitrogen concentration of the silicon single crystals is 3.0 x 10 14 atoms / cm 3 It is preferable that the above is set.

[0034] If we consider such a silicon single crystal, first we set the oxygen concentration of the silicon single crystal to 8.0 × 10 17 atoms / cm 3By keeping the nitrogen donor concentration at or below (ASTM'79), it is possible to suppress not only the oxygen donor concentration but also the nitrogen donor (NO donor) concentration, enabling more accurate resistivity measurements. However, in low-oxygen silicon single crystals, the dislocation pinning effect of oxygen is weakened, resulting in significant slip generation during high-temperature, long-term processes (heat treatment), which causes a problem of reduced yield during device fabrication. Therefore, the nitrogen concentration of silicon single crystals is set to 3.0 x 10 14 atoms / cm 3 By doing so, it is possible to provide sufficient slip resistance to withstand high-temperature, long-term processes, which in turn makes it possible to prevent a decrease in yield during device fabrication while achieving highly accurate resistivity measurements.

[0035] As explained above, nitrogen-doped silicon single crystals having a resistivity of 100 Ωcm or more can be grown by the MCZ method using a silicon single crystal pulling apparatus equipped with a horizontal magnetic field or a cusp magnetic field, for example.

[0036] Next, Figure 1 is a flow diagram showing an example of a method for measuring the resistivity of a silicon single crystal. Specific steps are indicated by A to H. After completing the growth of the nitrogen-doped silicon single crystal with a resistivity of 100 Ωcm or more (Step A), the silicon single crystal is subjected to ingot processing (external grinding) (Step B). The silicon single crystal is then sliced using an internal diameter slicer or wire saw (Step C) to obtain silicon single crystal substrates of a predetermined thickness. After completing grinding and acid etching of the substrate surface (Step D), an oxidative heat treatment (Step E) is performed to remove nitrogen donors. The atmosphere during this oxidative heat treatment can be a wet oxygen atmosphere or a dry oxygen atmosphere. The heat treatment is then performed in a dry or wet oxygen atmosphere at a temperature of 1100 to 1250°C for 90 to 240 minutes while maintaining this temperature. By performing this oxidative heat treatment, the nitrogen donors are eliminated, thereby suppressing changes in resistivity due to their remaining.

[0037] If the heat treatment time is less than 90 minutes, the nitrogen donors remain, which is a problem. If the heat treatment time is longer than 240 minutes, for example, 250 minutes or more, the nitrogen donors are completely eliminated, but the longer treatment time causes problems such as a significant reduction in the heater life of the heat treatment furnace and a deterioration in the throughput of resistivity measurement. For these reasons, the heat treatment time is set to 90 to 240 minutes. The heat treatment furnace used for the heat treatment to remove the nitrogen donors may be a horizontal furnace or a vertical furnace.

[0038] After completing the heat treatment (Step E) to remove the nitrogen donors, the thermal oxide film is removed from the substrate surface. By removing the thermal oxide film, the influence of the remaining thermal oxide film on the resistivity can be eliminated. As a result, even for nitrogen-doped silicon single crystals with a high resistivity of 100 Ωcm or more, the resistivity derived from the dopant can be accurately measured.

[0039] At this time, etching can be performed using, for example, hydrofluoric acid (hydrofluoric acid) (Step F). Etching with hydrofluoric acid is easy and cost-effective. If the concentration of hydrofluoric acid is 0.1 wt% or more, it can easily remove the thermal oxide film that has formed due to the heat treatment.

[0040] After the oxide film removal (Step F) is complete, it is preferable to further grind the substrate surface (Step G). Grinding the substrate surface ensures the removal of the thermal oxide film. This grinding is performed using a grinding wheel or grinding pad, and it is preferable to remove at least 5 μm of material. The grit size of the abrasive grains used in this grinding process can be roughly #300 or finely #2000.

[0041] In this way, when etching with hydrofluoric acid and grinding are performed as a method for removing the thermal oxide film, etching with hydrofluoric acid is easy and advantageous in terms of cost, and the thermal oxide film can be reliably removed by subsequently grinding the substrate surface.

[0042] Thereafter, resistivity is measured (Step H), and for the measurement, a four-probe method, a spreading resistance method, a Hall effect method, or the like can be used.

[0043] By using the above conditions, it becomes possible to accurately measure the resistivity of nitrogen-doped silicon single crystals with high resistivity of 100 Ωcm or more grown by the MCZ method. [Example]

[0044] 360 kg of silicon raw material was placed in an 800 mm diameter quartz crucible and melted. A cusp magnetic field was applied, and nitrogen-doped silicon single crystals with a diameter of 300 mm and a target resistivity of 2000 Ωcm (dopant: boron) were pulled using four different pulling devices, one for each device, for a total of four silicon single crystals. The pulled silicon single crystals were then processed into ingots to produce silicon single crystal substrates, which were then heat-treated in an oxygen atmosphere. After the heat treatment, the thermal oxide film on the substrate surface was removed by hydrofluoric acid etching. After the thermal oxide film was removed, the silicon substrates were ground with a #2000 grit grinding wheel, and the resistivity of the silicon substrates was measured using the four-probe method. In this example and the comparative example, the ratio of the measured resistivity to the resistivity estimated from the amount of dopant added (segregation curve) is defined as "(resistivity_measured value) / (resistivity_estimated value)", and when the above ratio is less than 1.05 (less than 5%), it is considered that the resistivity derived from the dopant (boron) is obtained and the resistivity can be measured (evaluated as ○).

[0045] [Example 1] In Example 1, the nitrogen concentration in the silicon single crystal was 3.0 × 10 15 atoms / cm 3 , oxygen concentration is 1.5×10 17 atoms / cm 3Silicon single crystal substrates were prepared from the ASTM '79 section and subjected to heat treatment in a wet oxygen atmosphere. Four combinations of temperature and time were used for the heat treatment: 1100°C for 90 minutes, 1100°C for 240 minutes, 1250°C for 90 minutes, and 1250°C for 240 minutes. After the heat treatment, the thermal oxide film on the substrate surface was removed by hydrofluoric acid etching, followed by grinding with a #2000 grinding wheel. Resistivity measurements were performed using the four-probe method. The results showed that the (measured resistivity) / (calculated resistivity) ratio was 1.00 in all cases, confirming that the elimination of nitrogen donors resulted in highly accurate resistivity derived from the dopant (boron). Table 1 shows the ratio of (measured resistivity) to (calculated resistivity) when resistivity measurements were performed under the conditions of Example 1, as well as whether or not the resistivity measurement was successful.

[0046] [Table 1]

[0047] Separately from Example 1, resistivity measurements were performed under the same conditions as in Example 1, except that the heat treatment for nitrogen donor elimination was performed in a dry oxygen atmosphere. In all cases, the (resistivity_measured value) / (resistivity_calculated value) was 1.00, confirming that the resistivity derived from the dopant (boron) was obtained with high accuracy. Separately from Example 1, resistivity measurements were performed under the same conditions as in Example 1, except that the resistivity in the single crystal was set to 100 Ωcm. In all cases, the resistivity derived from the dopant (boron) was obtained with high accuracy.

[0048] [Example 2] In Example 2, the oxygen concentration in the silicon single crystal was 8.0 × 10 17 atoms / cm 3Resistivity measurements were performed in accordance with ASTM '79, with the other conditions being the same as in Example 1. As a result, in all cases, the (measured resistivity) / (calculated resistivity) ratio was 1.01 or less, confirming that the resistivity derived from the dopant (boron) was accurately obtained by eliminating the nitrogen donor. Table 2 shows the ratio of (measured resistivity) to (calculated resistivity) when resistivity measurements were performed under the conditions of Example 2, and whether or not the resistivity measurement was possible.

[0049] [Table 2]

[0050] Separately from Example 2, resistivity measurements were performed under the same conditions as Example 2, except that the heat treatment for nitrogen donor elimination was performed in a dry oxygen atmosphere, and the other conditions were the same as Example 2. As a result, in all cases, (resistivity_measured value) / (resistivity_calculated value) was 1.01 or less, confirming that the resistivity derived from the dopant (boron) was accurately obtained. Also, separate from Example 2, resistivity measurements were performed under the same conditions as Example 2, except that the resistivity in the single crystal was set to 100 Ωcm, and the other conditions were the same as Example 2, confirming that the resistivity derived from the dopant (boron) was obtained in all cases.

[0051] [Example 3] In Example 3, the nitrogen concentration in the silicon single crystal was 3.0 × 10 14 atoms / cm 3 Resistivity measurements were performed under the same conditions as in Example 1, with the other conditions being the same. As a result, in all cases, (resistivity_measured value) / (resistivity_calculated value) was 1.00, confirming that the resistivity derived from the dopant (boron) was obtained extremely accurately by eliminating the nitrogen donor. Table 3 shows the ratio of (resistivity_measured value) to (resistivity_calculated value) when resistivity measurements were performed under the conditions of Example 3, and whether or not the resistivity measurement was possible.

[0052] [Table 3]

[0053] Separately from Example 3, resistivity measurements were performed under the same conditions as Example 3, except that the heat treatment for nitrogen donor elimination was performed in a dry oxygen atmosphere, and the other conditions were the same as Example 3. As a result, in all cases, (resistivity_measured value) / (resistivity_calculated value) was 1.00, confirming that the resistivity derived from the dopant (boron) was obtained extremely accurately. Also, separate from Example 3, resistivity measurements were performed under the same conditions as Example 3, except that the resistivity in the single crystal was set to 100 Ωcm, and the other conditions were the same as Example 3, confirming that the resistivity derived from the dopant (boron) was obtained in all cases.

[0054] [Example 4] In Example 4, the oxygen concentration in the silicon single crystal was 9.0 × 10 17 atoms / cm 3 Resistivity measurements were carried out in accordance with ASTM '79, with the other conditions being the same as in Example 1. As a result, (resistivity_measured value) / (resistivity_calculated value) was 1.03 to 1.04, and the resistivity derived from the dopant (boron) was obtained. Comparing this result with the results of Examples 1 and 2, It can be seen that Examples 1 and 2 allow for more accurate measurements. Therefore, the oxygen concentration is 8.0 × 10 in Example 2. 17 atoms / cm 3 (ASTM'79) or less is more preferable because it makes it possible to keep the ratio at 1.01 or less. Table 4 shows the ratio of (resistivity_measured value) to (resistivity_calculated value) when the resistivity was measured under the conditions of Example 4, and whether the resistivity measurement was possible or not.

[0055] [Table 4]

[0056] [Comparative Example 1] In Comparative Example 1, resistivity measurements were performed using four combinations of heat treatment temperature and time: 900°C x 90 minutes, 900°C x 240 minutes, 1000°C x 90 minutes, and 1000°C x 240 minutes. Other conditions were the same as in Example 1. The resulting (measured resistivity) / (calculated resistivity) ratio was 1.82 to 3.40, indicating that the residual nitrogen donors after heat treatment altered the resistivity, preventing accurate measurement of the resistivity derived from the dopant (boron). Table 5 shows the ratio of (measured resistivity) to (calculated resistivity) when resistivity measurements were performed under the conditions of Comparative Example 1, as well as whether or not the resistivity could be measured.

[0057] [Table 5]

[0058] In addition, apart from Comparative Example 1, the temperature and time during the heat treatment were changed to 1000°C x 480 minutes, and resistivity measurements were performed under the same conditions as Comparative Example 1 except that the other conditions were the same. As a result, (resistivity_measured value) / (resistivity_calculated value) was 1.50, and the accurate resistivity derived from the dopant (boron) could not be obtained.

[0059] Comparative Example 2 In Comparative Example 2, resistivity measurements were performed using four combinations of heat treatment temperature and time: 1100°C x 30 minutes, 1100°C x 60 minutes, 1250°C x 30 minutes, and 1250°C x 60 minutes. Other conditions were the same as in Example 1. The resulting (measured resistivity) / (calculated resistivity) ratio was 1.05 to 1.45, indicating that the resistivity changed due to the presence of nitrogen donors remaining after heat treatment, preventing accurate resistivity derived from the dopant (boron). Table 6 shows the ratio of (measured resistivity) to (calculated resistivity) when resistivity measurements were performed under the conditions of Comparative Example 2, as well as whether or not resistivity measurements were possible.

[0060] [Table 6]

[0061] As described above, according to the examples of the present invention, by performing an oxidation heat treatment at a temperature of 1100 to 1250°C for 90 to 240 minutes on a silicon single crystal having a resistivity of 100 Ωcm or more and grown by the MCZ method with nitrogen added, it is possible to eliminate nitrogen donors and suppress changes in resistivity due to the remaining nitrogen donors, and by removing the thermal oxide film formed on the substrate surface by the oxidation heat treatment, it is possible to eliminate the influence of the remaining thermal oxide film on the resistivity, and as a result, it is possible to accurately measure the resistivity derived from the dopant even for nitrogen-added silicon single crystal having a high resistivity of 100 Ωcm or more.

[0062] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and that provides similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0063] 1, 31...silicon single crystal pulling apparatus (pulling furnace), 2, 32...seed crystal, 3, 33...Seed holder; 4, 34...Silicon single crystal; 5, 35...raw material melt (silicon melt), 7, 36...quartz crucible, 6, 37...Graphite crucible; 8, 38...Heater; 9, 39...Insulating member; 10, 40... central shaft; 11, 42... cylindrical portion; 12, 43... heat shielding member; 20... horizontal magnetic field generator, 41... intermediate surface, 50... cusp magnetic field generator, 50a...upper coil (superconducting coil), 50b...lower coil (superconducting coil), 50c...lifting device, 51...magnetic field minimum point.

Claims

1. A method for measuring the resistivity of a silicon single crystal grown by an MCZ method with nitrogen added and having a resistivity of 100 Ωcm or more, comprising: a substrate cut from the silicon single crystal is subjected to an oxidation heat treatment at a temperature of 1100 to 1250°C for 90 to 240 minutes to form a thermal oxide film on the surface of the substrate; A method for measuring the resistivity of a silicon single crystal, comprising the steps of removing the thermal oxide film from the surface of the substrate and then measuring the resistivity of the substrate.

2. 2. The method for measuring the resistivity of a silicon single crystal according to claim 1, wherein the thermal oxide film on the surface of the substrate is removed by etching with hydrofluoric acid, and then the surface of the substrate is ground.

3. The nitrogen concentration of the silicon single crystal is 3.0×10 １４ atoms / cm ３ The oxygen concentration is 8.0 x 10 １７ atoms / cm ３ 3. The method for measuring the resistivity of a silicon single crystal according to claim 1, wherein the resistivity is equal to or less than ASTM '79.

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