Silicon single crystal

Abstract

To provide a silicon single crystal having a marking indicating the boundary of each single crystal block in the silicon single crystal grown by intermittently charging a sub-dopant into a melt, forming a plurality of single crystal blocks along the axial direction and controlling the kind and resistivity of each single crystal block when pulling up the silicon single crystal by a Czochralski method.SOLUTION: The single crystal wafer includes a plurality of single crystal blocks 1 having a first resistivity having a variation width within a standard range in a crystal axis direction and continuously formed in the crystal axis direction, and a high resistivity layer 2 having a second resistivity having a peak projecting higher than the standard range at a boundary of the plurality of single crystal blocks.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a silicon single crystal, and more particularly to a silicon single crystal grown by counterdoping, in which a secondary dopant is intermittently introduced into the melt when pulling the silicon single crystal by the Czochralski method to control the resistivity in the axial direction. [Background technology]

[0002] The Czochralski (CZ) method is used to grow silicon single crystals. A quartz crucible is placed inside a chamber and filled with polysilicon. The polysilicon is heated and melted by a heater around the crucible to form a silicon melt. A seed crystal (seed) attached to a seed chuck is then immersed in the silicon melt, and the seed chuck is lifted while the seed chuck and the quartz crucible are rotated in the same direction or in opposite directions.

[0003] Many of the silicon single crystals produced by this CZ method are used as semiconductor materials. The resistivity of the grown silicon single crystal is adjusted by the dopant added to the silicon melt. Dopants are classified as n-type and p-type, and P (phosphorus) is often used as the dopant when growing n-type crystals.

[0004] When dopants are added during the growth of silicon single crystals using the CZ method, a phenomenon is observed in which resistivity changes in the direction of crystal growth. This is due to dopant segregation; as the silicon melt in the crucible decreases during single crystal growth, the dopant concentration in the remaining liquid gradually increases, causing a continuous decrease in the resistivity of the single crystal. The segregation coefficient of P (phosphorus) is 0.35, which is lower than the segregation coefficient of B (boron), which is widely used as a dopant in p-type crystals (0.8). As a result, the drop in resistivity from the top to the bottom is more pronounced compared to p-type crystals. This reduces the portion that can be used as a product, posing a challenge for improving yield.

[0005] To address this issue, for example, Patent Document 1 discloses a method of adding a main dopant and a secondary dopant with a polarity opposite to that of the main dopant and a smaller segregation coefficient (i.e., co-doping) before pulling the crystal. By using this method, the decrease in resistivity caused by the main dopant is offset by the secondary dopant, making it possible to improve the resistivity distribution in the axial direction of the single crystal. However, as mentioned above, the dopant most commonly used in the production of n-type single crystals is P (phosphorus), which has a segregation coefficient of about 0.35. However, B (boron), which is widely used as an element of opposite polarity in the fabrication of devices, has a segregation coefficient of about 0.8, which is larger than that of P (phosphorus), and therefore the above-mentioned technology cannot be used as is.

[0006] To solve this problem, Patent Document 2 discloses a method of continuously adding B (boron) to the main dopant P (phosphorus) during single crystal pulling (i.e., counter-doping). This method makes it possible to produce n-type single crystals with improved axial resistivity distribution by counter-doping with P (phosphorus) as the main dopant and B (boron) as the secondary dopant. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-307305 [Patent Document 2] Japanese Patent Application Publication No. 3-247585 Summary of the Invention [Problem to be solved by the invention]

[0008] Incidentally, there are a wide variety of dopant agents used to control the resistivity of silicon single crystals grown conventionally. Generally, when pulling one or more (multiple) single crystals, the same type of dopant agent is used as the secondary dopant agent to be doped into the main dopant from the start to the completion of pulling. However, in recent years, there has been a strong demand for small-volume, high-mix production, making it necessary to form multiple varieties (varieties with different types of secondary dopants and resistivities) in a single single crystal along the crystal axis. Continuously forming multiple varieties of single crystal blocks along the axis in a single crystal can be achieved by counterdoping, for example, by changing the type and amount of secondary dopant added during single crystal pulling.

[0009] However, when multiple types of single crystal blocks are continuously formed along the axial direction in a single crystal, there has traditionally been no way to clearly identify the boundaries between adjacent single crystal blocks. As a result, when extracting single crystal blocks that meet a customer's specifications, it is necessary to slice the estimated boundary areas into multiple wafers, evaluate whether these wafers meet the desired specifications, identify the boundaries of the single crystal blocks, and select the single crystal blocks, which requires a lot of time and effort before shipping. Furthermore, if the evaluation results of multiple cut wafers all fail to meet the required standards, it is necessary to cut out different portions into wafers and evaluate them again, which not only requires additional time and effort but also results in the loss of previously evaluated non-conforming portions.

[0010] The present inventors have conducted extensive research on the premise of introducing a secondary dopant during the pulling of a silicon single crystal and performing counter doping to control the resistivity in the axial direction, and have arrived at the present invention. The object of the present invention is to provide a silicon single crystal having markings indicating the boundaries of each single crystal block, which is grown by controlling the type and resistivity of each single crystal block, by intermittently adding a secondary dopant to the melt when pulling the silicon single crystal by the Czochralski method, thereby forming a plurality of single crystal blocks along the axial direction. [Means for solving the problem]

[0011] The silicon single crystal of the present invention, which has been made to solve the above-mentioned problems, is characterized by comprising a plurality of single crystal blocks formed continuously in the crystal axis direction, each having a first resistivity with a fluctuation range within a standard range in the crystal axis direction, and a high resistivity layer having a second resistivity with a peak that protrudes higher than the standard range at the boundary between the plurality of single crystal blocks. Each of the plurality of single crystal blocks preferably contains a p-type dopant and an n-type dopant, and the p-type dopant is preferably at least one of B (boron), Al (aluminum), Ga (gallium), and In (indium), and the n-type dopant is preferably at least one of P (phosphorus), As (arsenic), Sb (antimony), and Bi (bismuth). Furthermore, it is desirable that the maximum value of the first resistivity is 50% or less of the peak value of the second resistivity, or the maximum value of the first resistivity may be 90% or less of the peak value of the second resistivity.

[0012] With a silicon single crystal constructed in this way, the position of the high-resistivity layer can be identified by measuring the resistance value of the crystal side surface and using the second resistivity peak as a marking, making it possible to determine the boundaries between multiple single crystal blocks with high accuracy. Therefore, with the silicon single crystal of the present invention, when the dopant species and resistivity contained in each single crystal block are different from each other, the boundaries between the blocks can be identified and cut with high precision, making it easy to manage products on a block-by-block basis and significantly reducing labor and loss compared to conventional methods. [Effects of the Invention]

[0013] According to the present invention, when pulling a silicon single crystal by the Czochralski method, a secondary dopant is intermittently added to the molten liquid to form a plurality of single crystal blocks along the axial direction, and the type and resistivity of each single crystal block are controlled to grow the silicon single crystal, and a silicon single crystal having markings indicating the boundaries of each single crystal block can be provided. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view schematically showing a silicon single crystal according to the present invention. [Figure 2] FIG. 2 is a schematic graph showing an example of the change in resistivity along the crystal axis direction on the outer peripheral surface of a silicon single crystal of the present invention. [Figure 3] FIG. 3 is a cross-sectional view showing an example of a single crystal pulling apparatus for producing a silicon single crystal. [Figure 4] FIG. 4 is a flow chart showing an example of a method for producing a silicon single crystal according to the present invention. [Figure 5] FIG. 5 is a graph showing the results of the example. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, a silicon single crystal according to the present invention will be described with reference to the drawings. However, this embodiment will be described as an example of the present invention, and the present invention is not limited to this. Fig. 1 is a perspective view showing a silicon single crystal according to the present invention, and Fig. 2 is a schematic graph showing an example of the change in resistivity along the crystal axis direction on the outer peripheral surface of the silicon single crystal according to the present invention. The vertical axis of the graph in Fig. 2 represents the resistivity, and the horizontal axis represents the solidification rate along the crystal axis direction.

[0016] The silicon single crystal C according to the present invention is grown by counterdoping, in which a secondary dopant is intermittently introduced into the melt during pulling by the Czochralski method. As a result, the silicon single crystal C comprises a plurality of single crystal blocks 1a-1e formed continuously in the crystal axis direction and having a first resistivity RA with a fluctuation range (R1-R2) within a standard range in the crystal axis direction, and high-resistivity layers 2a-2d having a second resistivity RB with a peak Rp that protrudes higher than the standard range at the boundaries of the plurality of single crystal blocks 1a-1e.

[0017] In this embodiment, the type and amount of secondary dopant to be added can be changed each time, and the high resistivity layers 2a to 2d are formed at the timing of adding the secondary dopant. Each single crystal block 1 has a first resistivity RA with a fluctuation range (R1-R2) within the standard range as described above, and the maximum value of this first resistivity RA is 50% or less of the peak of the second resistivity RB. The peaks Rp of the second resistivity RB in the high resistivity layers 2a to 2d can be used as markings indicating the boundaries of the plurality of single crystal blocks 1a to 1e in the axial direction of one silicon single crystal C. That is, by measuring the resistivity from the side of the single crystal C using, for example, a four-point probe method, a plurality of peaks Rp can be detected, and their positions can be taken as the boundaries of the plurality of single crystal blocks 1.

[0018] 2 shows a case where the secondary dopant was introduced four times by counter doping (resulting in five single crystal blocks 2 with different properties), but the present invention is not limited to this form, and the number of times the secondary dopant is introduced and the type of dopant used each time are not limited. Each of the plurality of single crystal blocks contains a dopant, and in the case of a p-type dopant, it is desirable that the dopant be at least one of B (boron), Al (aluminum), Ga (gallium), and In (indium), and in the case of an n-type dopant, it is desirable that the dopant be at least one of P (phosphorus), As (arsenic), Sb (antimony), and Bi (bismuth).

[0019] 3 is a cross-sectional view showing an example of a single crystal pulling apparatus for producing silicon single crystal C. This single crystal pulling apparatus 100 includes a furnace body 10 formed by stacking a pull chamber 10b on a cylindrical main chamber 10a, a carbon crucible (or graphite crucible) 20 provided in this furnace body 10 so as to be rotatable about a vertical axis and movable up and down, and a silica glass crucible 3 (hereinafter simply referred to as crucible 3) held by the carbon crucible 20. This crucible 3 is rotatable about a vertical axis together with the rotation of the carbon crucible 20.

[0020] Also, below the carbon crucible 20, there are provided a rotation drive unit 14 such as a rotary motor that rotates the carbon crucible 20 around a vertical axis, and an elevation drive unit 15 that moves the carbon crucible 20 up and down. The rotation drive unit 14 is connected to a rotation drive control unit 14a, and the elevation drive unit 15 is connected to an elevation drive control unit 15a.

[0021] The single crystal pulling apparatus 100 also includes a side heater 4 that uses resistance heating to melt the semiconductor raw material (raw polysilicon) loaded in the crucible 3 to form a silicon melt M (hereinafter also simply referred to as melt M), and a pulling mechanism 9 that winds up a wire 6 and pulls up the grown single crystal C. A seed crystal P is attached to the tip of the wire 6 of the pulling mechanism 9.

[0022] The side heater 4 is connected to a heater control unit 4a that controls the amount of power supplied, and the lifting mechanism 9 is connected to a rotation drive control unit 9a that controls the rotation drive thereof. In this embodiment, the single crystal pulling apparatus 100 has, for example, a magnetic field applying electromagnetic coil 8 installed outside the furnace body 10. When a predetermined current is applied to the magnetic field applying electromagnetic coil 8, a horizontal magnetic field of a predetermined strength (1000 to 4000 Gauss) is applied to the melt M in the crucible 3. The magnetic field applying electromagnetic coil 8 is connected to an electromagnetic coil control unit 8a that controls its operation. That is, in this embodiment, the MCZ method (Magnetic field applied CZ method) is carried out, in which a transverse magnetic field is applied to the molten liquid M to grow a single crystal, thereby controlling the convection of the silicon molten liquid M and stabilizing the single crystallization.

[0023] A radiation shield 7 is disposed above the melt M formed in the crucible 3, surrounding the single crystal C. The radiation shield 7 has openings at the top and bottom, and serves to shield the single crystal C during growth from unnecessary radiant heat from the side heaters 4, the melt M, etc., and also to straighten the gas flow inside the furnace. The gap between the lower end of the radiation shield 7 and the melt surface is controlled to maintain a predetermined constant distance (for example, 50 mm) depending on the desired properties of the single crystal to be grown.

[0024] The single crystal pulling apparatus 100 also includes an optical measurement sensor 16, such as a CCD camera, for measuring the diameter and length (solidification rate) of the silicon single crystal. A small observation window 10a1 is provided on the top surface of the main chamber 10a, and positional changes in the solid-liquid interface can be detected from the outside of this small window 10a1. The solidification rate, expressed as the weight of the single crystal divided by the weight of the initial silicon raw material, can be calculated from the measured single crystal diameter and length.

[0025] Regarding the relationship between dopant concentration and resistivity, a single crystal has a dopant concentration distribution in its length direction (vertical direction during pulling). When the solidification rate of silicon is g, the concentration distribution Cs of the dopant is expressed by the following equation (1). Cs = k × C0 × (1-g) k-1 ···(1) (In equation (1), k is the equilibrium segregation coefficient, and C0 is the initial dopant concentration in the silicon melt. Note that the equilibrium segregation coefficient of boron (B), which is most commonly used as a p-type dopant, is 0.8, and the equilibrium segregation coefficient of phosphorus (P), which is most commonly used as an n-type dopant, is 0.35.)

[0026] To keep the resistivity within the specified range, the relationship between the dopant concentration and the solidification rate during the growth of silicon single crystals is determined in advance, and the dopant concentration is adjusted based on this relationship so that the resistivity of the single crystal falls within the desired range. For example, if P (phosphorus) is used as the dopant and the resistivity of the single crystal head is set in the range of 20 to 100 Ω·cm, 0.1 to 3.5 g of dopant (high concentration (1000 kJ) with a resistivity of 1 to 5 mΩ·cm) is added to a silicon lot of about 150 kg. 19 cm -3 All you have to do is add silicon fragments containing P (phosphorus) to the reactor.

[0027] The single crystal pulling apparatus 100 also includes a dopant supply jig 17 for supplying a dopant (secondary dopant) in, for example, chip form (or powder form, granule form, etc.) to the melt M. The dopant supply jig 17 has a charging container 18 that temporarily stores the dopant to be charged, and a tubular portion (such as a quartz tube) 19 that is connected to the charging container 18 and extends downward. An opening 10a2 is provided in the upper surface of the main chamber 10a, and the tubular portion 19 of the dopant supply jig 17 penetrates this opening 10a2. The tip of this tubular portion 19 is positioned so that the charging of the dopant does not cause vibration of the liquid surface or adhesion of the dopant to the crystal.

[0028] Furthermore, under the condition of applying a horizontal magnetic field of 1000 to 4000 Gauss as in this embodiment, convection in the silicon melt is suppressed. Therefore, when the secondary dopant is added to the silicon melt, the secondary dopant is not immediately stirred, but moves with the convection in a highly concentrated state and reaches the solid-liquid interface between the single crystal and the melt. Thereafter, the secondary dopant is stirred and is uniformly dissolved throughout the melt.

[0029] In this embodiment, the chip-shaped dopant introduced into the melt M is a high-purity (99.9% or higher) dopant, or chips obtained by cleaving silicon wafers with a thickness of 500 μm to 1000 μm sliced ​​from a silicon single crystal containing a secondary dopant or a silicon single crystal containing a primary dopant, and these are used as additives. The resistivity of the silicon single crystal used as the dopant chips is measured and processed to the desired size. The dopant concentration is calculated from the resistivity, and the amount of dopant added can be controlled by the weight of the chips.

[0030] More specifically, the chip-shaped dopant must have a minimum weight so that it is not expelled from the chamber by the inert gas passing directly above the melt surface when it is dropped onto the melt surface. Therefore, the surface area per chip is set to 4 mm 2 However, if the chip size is too large, it takes time to melt and there is an increased risk of it adhering to the single crystal being grown. 2 Similarly, the thickness of the chip is preferably 500 μm or more and 1000 μm or less from the viewpoints of weight and ease of dissolution.

[0031] In addition, this single crystal pulling apparatus 100 is equipped with a computer 11 having a memory device 11a and an arithmetic and control device 11b, and the rotation drive control unit 14a, the elevation drive control unit 15a, the electromagnetic coil control unit 8a, the rotation drive control unit 9a, the measurement sensor 16, the air cylinder drive unit 21a, and the rotation drive control unit 25a are each connected to the arithmetic and control device 11b.

[0032] In the single crystal pulling apparatus 100 configured as above, when growing a single crystal C having a diameter of, for example, 300 mm, pulling is performed as follows. That is, first, raw polysilicon (for example, 470 kg) and silicon chips for doping are loaded into the crucible 3, and the crystal growth process is started based on a program stored in the storage device 11a of the computer 11. When producing an n-type silicon single crystal, for example, silicon chips containing P (phosphorus) are used as the n-type main dopant (other n-type dopants that may be used include As (arsenic), Sb (antimony), and Bi (bismuth)).

[0033] Next, a predetermined atmosphere (mainly an inert gas such as argon gas) is created inside the furnace body 10. For example, a furnace atmosphere with an internal furnace pressure of 60 to 110 torr and an argon gas flow rate of 40 to 110 l / min is created. Then, while the crucible 3 is rotated in a predetermined direction at a predetermined rotation speed (rpm), the raw material polysilicon and the main dopant loaded in the crucible 3 are melted by heating with the side heater 4 to form a molten liquid M (step S1 in FIG. 4). Here, the P (phosphorus) concentration in the molten liquid is, for example, 2.92E14 atoms / cm 3 It is said that. In this step S1, silicon chips for doping may be added into the crucible 3 while the raw polysilicon is being melted.

[0034] Next, a predetermined current is passed through the magnetic field applying electromagnetic coil 8, and a horizontal magnetic field with a magnetic flux density of, for example, 2500 Gauss is applied to the melt M (step S2 in FIG. 4). This magnetic field application suppresses convection in the melt. In addition, the power supplied to the side heater 4, the pulling speed, the strength of the applied magnetic field, etc. are used as parameters to adjust the oxygen concentration of the single crystal to a low oxygen concentration (for example, 0.8E18 atoms / cm) so that the stirring of the melt becomes gentle. 3 The pulling conditions are adjusted to have a diameter of 310 mm and a straight body diameter of 310 mm, and the seed crystal P begins to rotate around its axis at a predetermined rotation speed. The rotation direction is opposite to that of the crucible 3. Then, the wire 6 is lowered, and the seed crystal Sc comes into contact with the molten liquid M. After the tip of the seed crystal Sc is melted, necking occurs, and a neck portion Sc1 is formed.

[0035] Then, the single crystal pulling process is started. That is, the crystal diameter is gradually enlarged to form a shoulder portion C1, and the process proceeds to forming a straight body portion C2 that will become the product portion (step S3 in FIG. 4). When the growth of the single crystal C begins, the computer 11 calculates the solidification rate of the silicon single crystal using the measurement results of the measurement sensor 16 (step S4 in Figure 4), and when a preset solidification rate (e.g., 0.245) is reached (step S5 in Figure 4), 1003 mg of In (indium) with a purity of 99.9% as a secondary dopant having an opposite conductivity type to the primary dopant (the dopant amount is set to achieve the desired resistivity) is added to the melt surface using the dopant supply jig 17 (step S6 in Figure 4).

[0036] Here, because the convection of the melt M is suppressed by the application of a magnetic field, the added secondary dopant is not quickly stirred into the melt M, but instead follows the convection of the melt M and reaches the solid-liquid interface of the single crystal C. At this solid-liquid interface, the secondary dopant (p-type) cancels out the carriers of the main dopant (n-type), forming a high-resistivity layer 2a with a resistivity (second resistivity) having a peak Rp that protrudes higher than the specified range. The resistivity peak Rp of this high-resistivity layer 2a can be used as a marking. Thereafter, as the secondary dopant dissolves throughout the melt M, the resistivity (first resistivity) drops sharply to near the upper limit R2 of the specified range, and then gradually decreases as the pulling process progresses.

[0037] When the solidification rate reaches a value (e.g., 0.398) at which the resistivity falls to near the lower limit (R1) of the standard range (steps S4 and S5 in FIG. 4), 25 mg of Ga (gallium) with a purity of 99.9%, for example, as a secondary dopant having an opposite conductivity type to the primary dopant (the amount of dopant is set so as to obtain the desired resistivity) is introduced onto the melt surface using dopant supply jig 17 (step S6 in FIG. 4).

[0038] The added secondary dopant reaches the solid-liquid interface of the single crystal C along the gentle convection of the melt M, just as it did the previous time the secondary dopant was added. At this solid-liquid interface, the secondary dopant (p-type) cancels out the carriers of the main dopant (n-type), forming a high-resistivity layer 2b with a resistivity (second resistivity) having a peak Rp that protrudes higher than the specified range. After that, as the secondary dopant dissolves throughout the melt M, the resistivity drops sharply to near the upper limit R2 of the desired range, and then gradually decreases as the pulling process progresses.

[0039] The formation of the body portion C2 continues (step S7 in FIG. 4), and when the solidification rate reaches a value (e.g., 0.542) at which the resistivity falls to near the lower limit R1 of the standard range (steps S4 and S5 in FIG. 4), 1.2 mg of, for example, 99.9% pure Al (aluminum) as a secondary dopant having the opposite conductivity type to the primary dopant (the dopant amount is set so as to obtain the desired resistivity) is introduced onto the melt surface using a dopant supply jig 17 (step S6 in FIG. 4).

[0040] The added secondary dopant reaches the solid-liquid interface of the single crystal C along the convection flow of the melt M, just as it did the previous time the secondary dopant was added. At this solid-liquid interface, the secondary dopant (p-type) cancels out the carriers of the main dopant (n-type), forming a high-resistivity layer 2c with a resistivity (second resistivity) having a peak Rp that protrudes higher than the specified range. Thereafter, as the secondary dopant dissolves throughout the melt M, the resistivity drops sharply to near the upper limit R2 of the specified range, and then gradually decreases as pulling proceeds.

[0041] Furthermore, the pulling of the straight body portion C2 continues (step S7 in FIG. 4), and when the solidification rate reaches a value (e.g., 0.654) at which the resistivity falls to near the lower limit R1 of the standard range (steps S4 and S5 in FIG. 4), a secondary dopant having a conductivity type opposite to that of the primary dopant, e.g., 5.303E19 atoms / cm 3 57 mg of silicon chips containing B (boron) (the amount of dopant is set so as to obtain a desired resistivity) are placed on the melt surface using dopant supply jig 17 (step S6 in FIG. 4).

[0042] The added secondary dopant reaches the solid-liquid interface of the single crystal C along the gentle convection of the melt M, just as it did the previous time the secondary dopant was added. At this solid-liquid interface, the secondary dopant (p-type) cancels out the carriers of the main dopant (n-type), forming a high-resistivity layer 2e with a resistivity (second resistivity) having a peak Rp that protrudes higher than the specified range. After that, as the dopant dissolves throughout the melt, the resistivity drops sharply to near the upper limit R2 of the specified range, and then gradually decreases as the pulling process progresses.

[0043] The growth of the single crystal continues, and when the single crystal is pulled up to the desired length without dislocations (step S7 in FIG. 4), the single crystal growth is completed. That is, when the straight body portion C2 is formed to the predetermined length, the process moves to the final tail portion process, in which the contact area between the lower end of the crystal and the melt M is gradually reduced, and the single crystal C and the melt M are separated, thereby producing a silicon single crystal.

[0044] As described above, in the formation of silicon single crystal C, counter-doping is performed multiple times by introducing a secondary dopant having a conductivity type opposite to that of the primary dopant, and the secondary dopant is stirred along with the gentle convection of the molten liquid M. This allows a high concentration of the secondary dopant to reach the solid-liquid interface, forming a high-resistivity layer 2e with a resistivity having a peak Rp that protrudes higher than the standard range. That is, multiple single crystal blocks 1a-1e are formed successively, with the timing of introducing the secondary dopant as the boundary, and high-resistivity layers 2e are formed at the boundaries of these blocks, respectively. The formed silicon single crystal C can be used to identify the position of the high resistance layer 2e by measuring the resistance value of the crystal side surface and using the peak of the second resistivity RB as a marking, so that the boundaries of the multiple single crystal blocks 1a to 1e can be determined with high accuracy. Therefore, according to the silicon single crystal C of the present invention, when the dopant species and resistivity contained in each single crystal block 1a to 1e are different from each other, the boundaries of those blocks can be identified and cut with high precision, making it easy to manage products on a block-by-block basis and significantly reducing labor and loss compared to conventional methods.

[0045] In the above embodiment, the case of producing a silicon single crystal of the present invention has been described by taking as an example a case of producing an n-type silicon single crystal using an n-type dopant as the main dopant, but the present invention is not limited to this, and a p-type silicon single crystal using a p-type dopant as the main dopant may also be used. Furthermore, the maximum value of the first resistivity is not limited to 50% or less of the peak value of the second resistivity, and any value that is 90% or less of the peak value of the second resistivity is fully applicable to the present invention. [Example]

[0046] The silicon single crystal according to the present invention will be further described based on examples. Example 1 In Example 1, 470 kg of silicon raw material was filled into a quartz crucible having a diameter of 32 inches, and P (phosphorus) was added as a main dopant and melted. The P (phosphorus) concentration in the initial molten liquid was 2.92E14 atoms / cm 3 It was decided. The distance between the radiation shield and the melt surface was set to 50 mm, the furnace pressure was set to 65 torr, argon gas was flowed at a flow rate of 90 l / min, and the furnace environment was created with a transverse magnetic field strength of 2500 Gauss. The crucible rotation speed was set to 1 rpm, the crystal rotation speed to 7 rpm (opposite to the crucible rotation direction), and the single crystal was grown at a pulling rate of 1.5 mm / min with a target crystal diameter of 310 mm. The resistivity specification was set to 35 to 45 Ωcm.

[0047] Single crystal pulling was started, and at a solidification rate of 0.245, 1003 mg of In (indium) with a purity of 99.9% was counter-doped as a secondary dopant. Thereafter, at a solidification rate of 0.398, 25 mg of Ga (gallium) with a purity of 99.9% was counter-doped as a secondary dopant. At a solidification rate of 0.532, 1.2 mg of aluminum (Al) with a purity of 99.9% was counter-doped as a secondary dopant. Furthermore, at a solidification rate of 0.654, it is 5.303E19 atoms / cm 3 The silicon boron chips were counter doped with 57 mg of silicon boron chips as a secondary dopant. To add the secondary dopants, a quartz tube was placed in the furnace as shown in FIG. 3, and the respective dopant agents were added to the melt.

[0048] After cooling the pulled single crystal, the resistivity was measured from the side of the crystal using the four-point probe method. Figure 5 shows a graph of the measurement results. The vertical axis of the graph in Figure 5 is resistivity (Ω·cm) and the horizontal axis is solidification rate. Resistivity measurements were taken at 10 mm intervals along the solidification rate (crystal axis). As shown in the graph of Figure 5, a peak of high resistivity was detected near the crystal length position where each secondary dopant agent was added, relative to the base resistivity (resistivity within the specification range). The maximum value of resistivity within the specification range was 50% or less of the high resistivity peak. In this example, the maximum value of resistivity within the specification range was 50% or less of the high resistivity peak, which is desirable for marking, but even if it was 90% or less of the high resistivity peak, it still functioned sufficiently as a marking and the high resistivity peak could be detected. Furthermore, this single crystal was block-cut based on the position of high resistivity, sliced ​​into wafers, and evaluated. It was confirmed that single crystal blocks containing various types of dopants could be obtained with high precision. [Explanation of symbols]

[0049] 1 single crystal block 2 High resistivity layer 3. Quartz glass crucible 4 Side heater 6 wire 7 Radiation Shield C Silicon single crystal M Silicon melt M1 melt surface C Silicon single crystal C2 Straight body part RA First resistivity RB Second resistivity Rp Peak

Claims

1. A silicon single crystal grown by the Czochralski method and containing a p-type dopant and an n-type dopant, a plurality of single crystal blocks formed continuously in the crystal axis direction, the single crystal blocks having a resistivity variation in the crystal axis direction within a resistivity specification range, which is an allowable range of resistivity set before pulling; a boundary portion between the plurality of single crystal blocks, the boundary portion having a resistivity higher than the resistivity standard and a protruding peak, the boundary portion having a resistivity higher than the resistivity standard; A silicon single crystal comprising:

2. each of the plurality of single-crystal blocks includes a p-type dopant and an n-type dopant; In the case of a p-type dopant, at least one of B (boron), Al (aluminum), Ga (gallium), and In (indium) is used.

2. The silicon single crystal according to claim 1, wherein the n-type dopant is at least one of P (phosphorus), As (arsenic), Sb (antimony), and Bi (bismuth).

3. 3. The silicon single crystal according to claim 1, wherein the maximum resistivity of the single crystal block is 50% or less of the peak resistivity.

4. 3. The silicon single crystal according to claim 1, wherein the maximum resistivity of the single crystal block is 90% or less of the peak resistivity.

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