Silicon single crystal growth method

Abstract

Provided is a silicon single crystal growing method in which a silicon single crystal is pulled and made to grow by the Czochralski method from a dopant-added molted liquid in which a dopant has been added to a silicon molten liquid. A critical CV value, which is the product of the dopant concentration C and the pulling velocity V at a time when abnormal growth has occurred in the silicon single crystal, is calculated, and the silicon single crystal is grown with at least one of the dopant concentration C and the pulling velocity V being controlled such that the CV value, which is the product of the dopant concentration C and the pulling velocity V, is less than the critical CV value.

Description

[Technical field]

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

[0002] Conventionally, when growing silicon single crystals using the Czochralski method (hereinafter abbreviated as the "CZ method"), a method is known in which a volatile dopant such as red phosphorus (P), arsenic (As), or antimony (Sb) is added in high concentration to a silicon melt to grow a silicon single crystal with low electrical resistivity (see, for example, Patent Document 1).

[0003] However, when producing silicon single crystals by this method, a large amount of dopant is introduced into the silicon melt, which can cause a large degree of freezing point depression, which is the difference between the freezing point of the silicon melt and the freezing point of a dopant-added melt in which the silicon melt is doped, and can result in constitutional undercooling.

[0004] The condition for constitutional supercooling to occur is formulated as the following equation (1).

[0005]

number

[0006] G: Temperature gradient of the melt at the solid-liquid interface (K / mm) V: Pulling speed (mm / min) m: Freezing point depression (K cm 3 / atoms) C: dopant concentration D: diffusion coefficient (cm 2 / sec) k0: Segregation coefficient

[0007] That is, in formula (1), when the value of the right side is equal to or greater than the value of the left side, constitutional supercooling occurs.

[0008] When constitutional supercooling occurs, the area away from the solid-liquid interface becomes more supercooled than the solid-liquid interface, and the solidification rate is faster in this area. If slight irregularities are created at the solid-liquid interface in such a state, the crystal will grow faster in the convex parts, and the slight irregularities will be amplified, causing abnormal growth such as cell growth. When abnormal growth occurs, the single crystal will have dislocations and it will not be possible to obtain a wafer product.

[0009] Conventionally, in order to suppress the occurrence of cell growth, the critical point for the occurrence of cell growth has been discussed by calculating G / V (the value obtained by dividing the temperature gradient G of the melt at the solid-liquid interface by the pulling speed V), which is the left side of formula (1). In other words, when cell growth occurs, measures are taken to increase G / V. Specifically, in order to suppress the occurrence of abnormal growth, the temperature gradient G of the melt at the solid-liquid interface is calculated, and the pulling conditions are reset to reduce the pulling speed V. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2012-1408 A Summary of the Invention [Problem to be solved by the invention]

[0011] However, calculation of the temperature gradient G of the melt at the solid-liquid interface requires actual measurement data of the solid-liquid interface shape, and it takes time to consider improvement conditions.

[0012] Furthermore, Patent Document 1 discloses a technique for determining a critical pull-up rate so as to slow down the pull-up rate V in order to suppress the generation of dislocations. However, there is a problem in that if the pull-up rate V is reduced too much, the electrical resistivity of the silicon single crystal increases.

[0013] The present invention aims to provide a method for growing silicon single crystals that can set pulling conditions that suppress the occurrence of abnormal growth more quickly and without increasing the electrical resistivity (hereinafter simply referred to as resistivity) of the silicon single crystal. [Means for solving the problem]

[0014] In the present invention, when setting the pulling conditions to suppress the occurrence of abnormal growth, the CV value, which is the product of the dopant concentration C and the pulling rate V, is used as an index for determining the growth conditions. The reason (mechanism) for using the CV value as an index for determining the growth conditions will be explained.

[0015] As described above, the condition for constitutional supercooling to occur is formulated as in Equation (1). Multiplying both sides of Equation (1) by the pulling rate V gives us Equation (2) below.

[0016]

number

[0017] Since all the terms (m, D, k0) on the right side of equation (2) other than the dopant concentration C and the pull rate V are constants, it is possible to consider the occurrence of constitutional supercooling only in terms of the product (CV value) of the pull rate V and the dopant concentration C.

[0018] Conventionally, the critical point for cell growth was investigated by calculating G / V, the left side of equation (1). Calculating G, the temperature gradient of the melt under the solid-liquid interface, required actual measurement data of the solid-liquid interface shape, but by using the CV value as an index, it is possible to more quickly and easily discuss the critical point for cell growth quantitatively.

[0019] The method for growing silicon single crystals of the present invention is a method for growing silicon single crystals by pulling and growing a silicon single crystal from a dopant-added melt in which a dopant is added to a silicon melt by the Czochralski method, in which a critical CV value, which is the product of the dopant concentration C and the pulling rate V at the time when abnormal growth occurs in the silicon single crystal, is calculated, and the silicon single crystal is grown by controlling at least one of the dopant concentration C and the pulling rate V so that the CV value, which is the product of the dopant concentration C and the pulling rate V at the time, falls below the critical CV value.

[0020] The above-mentioned silicon single crystal growth method may include a critical CV value calculation step of calculating the critical CV value, and a pulling condition resetting step of resetting at least one of a pulling rate profile and a resistivity profile in the crystal axis direction so as to fall below the critical CV value calculated in the critical CV value calculation step.

[0021] The above-mentioned silicon single crystal growth method may include, after the critical CV value calculation step and before the pulling condition resetting step, a target CV value profile creation step of creating a target CV value profile using a target CV value calculated in the critical CV value calculation step and which does not exceed the critical CV value at the time point.

[0022] In the silicon single crystal growth method described above, the pulling condition resetting step may create a corrected pulling rate profile that is configured with pulling rates that correspond to the target CV value profile.

[0023] In the silicon single crystal growth method described above, the pulling condition resetting step may create a corrected resistivity profile constituted by resistivities corresponding to the target CV value profile.

[0024] In the above-described method for growing a silicon single crystal, the dopant concentration C is a dopant concentration in the silicon single crystal, and the dopant concentration in the silicon single crystal may be calculated from a resistance value of the silicon single crystal using a relational equation between the dopant concentration in the silicon single crystal and the resistivity of the silicon single crystal. The relational expression may be an Irvine curve.

[0025] According to the present invention, by using the CV value as an index for setting the pulling conditions, the pulling conditions can be set more quickly and without increasing the resistivity of the silicon single crystal. [Brief description of the drawings]

[0026] [Figure 1] 1 is a conceptual diagram showing an example of a configuration of a semiconductor crystal manufacturing apparatus according to an embodiment of the present invention. [Diagram 2] 1 is a flowchart illustrating a method for growing a silicon single crystal according to an embodiment of the present invention. [Diagram 3] 2 is an example of a resistivity profile created when manufacturing a silicon single crystal by a silicon single crystal growth method according to an embodiment of the present invention. [Figure 4] 2 is an example of a pulling rate profile created when producing a silicon single crystal by a silicon single crystal growth method according to an embodiment of the present invention. [Diagram 5] 1 is an example of a graph plotting CV values. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0028] The method for growing a silicon single crystal of the present invention is characterized in that, in order to suppress the occurrence of abnormal growth during pulling of the silicon single crystal, the pulling conditions are reset based on past records when abnormal growth has occurred.

[0029] Specifically, the method focuses on the parameters of the dopant concentration C and the pull-up rate V in the above formula (1), and uses the CV value, which is the product of the dopant concentration C and the pull-up rate V, as an index for setting the pull-up conditions.

[0030] Furthermore, the present invention is suitable for growing silicon single crystals with extremely low resistivity, such as a resistivity of 1.3 mΩ·cm or less when the dopant is red phosphorus, a resistivity of 2.6 mΩ·cm or less when the dopant is arsenic, a resistivity of 20 mΩ·cm or less when the dopant is antimony, and a resistivity of 1.3 mΩ·cm or less when the dopant is boron.

[0031] [Single crystal growth device] 1 is a conceptual diagram showing an example of the configuration of a semiconductor crystal manufacturing apparatus 10 to which a silicon single crystal growth method according to an embodiment of the present invention is applied. The semiconductor crystal manufacturing apparatus 10 manufactures a silicon single crystal 1 using the CZ method.

[0032] The semiconductor crystal manufacturing apparatus 10 includes an apparatus body 11, a memory 12, and a control unit 13. The apparatus body 11 includes a chamber 21, a crucible 22, a heater 23, a pulling unit 24, a heat shield 25, a heat insulator 26, and a crucible drive unit 27. A dopant-added melt MD, which is a silicon melt to which a dopant has been added, is charged into the crucible 22.

[0033] The chamber 21 includes a main chamber 31 and a pull chamber 32 connected to the upper part of the main chamber 31. A gas inlet 33A is provided at the upper part of the pull chamber 32 to introduce an inert gas such as argon (Ar) gas into the chamber 21. A gas exhaust port 33B is provided at the lower part of the main chamber 31 to exhaust gas from the chamber 21 by driving a vacuum pump (not shown).

[0034] The inert gas introduced into chamber 21 from gas inlet 33A flows down between silicon single crystal 1 being grown and thermal shield 25, passes through the gap between the lower end of thermal shield 25 and the liquid surface of dopant-added melt MD, then flows between thermal shield 25 and the inner wall of crucible 22 and toward the outside of crucible 22, then flows down outside crucible 22 and is discharged from gas exhaust outlet 33B.

[0035] The crucible 22 is disposed in the main chamber 31 and stores the dopant-added melt MD. The crucible 22 includes a support crucible 41, a quartz crucible 42 accommodated in the support crucible 41, and a graphite sheet 43 inserted between the support crucible 41 and the quartz crucible 42. Note that the graphite sheet 43 does not necessarily have to be provided.

[0036] The support crucible 41 is made of, for example, graphite or carbon fiber reinforced carbon. The support crucible 41 may be subjected to, for example, a silicon carbide (SiC) surface treatment or a pyrolytic carbon coating treatment. The quartz crucible 42 is mainly composed of silicon dioxide (SiO2). The graphite sheet 43 is made of, for example, expanded graphite.

[0037] The heater 23 is disposed at a predetermined interval outside the crucible 22 and heats the dopant-added melt MD in the crucible 22. The pulling unit 24 includes a cable 51 having the seed crystal 2 attached to one end thereof, and a pulling drive unit 52 that raises, lowers, and rotates the cable 51.

[0038] At least the surface of the thermal shield 25 is made of a carbon material. The thermal shield 25 is provided to surround the silicon single crystal 1 when the silicon single crystal 1 is manufactured. The thermal shield 25 blocks the silicon single crystal 1 being grown from the dopant-added melt MD in the crucible 22, the heater 23, and radiant heat from the sidewall of the crucible 22, and also plays a role in suppressing heat diffusion to the outside in the vicinity of the solid-liquid interface, which is the crystal growth interface, and in controlling the temperature gradient in the center and outer periphery of the silicon single crystal 1 in the pulling axial direction.

[0039] The heat insulating material 26 has a substantially cylindrical shape and is made of a carbon material (e.g., graphite). The heat insulating material 26 is disposed at a predetermined interval outside the heater 23. The crucible driving unit 27 includes a support shaft 53 that supports the crucible 22 from below, and rotates and raises and lowers the crucible 22 at a predetermined speed.

[0040] The memory 12 stores various information necessary for manufacturing the silicon single crystal 1, such as the gas flow rate of Ar gas in the chamber 21, the furnace pressure, the power supplied to the heater 23, the rotation speed of the crucible 22 and the silicon single crystal 1, and the position of the crucible 22. The memory 12 also stores, for example, a resistivity profile and a pulling speed profile.

[0041] The control unit 13 controls each unit based on various information stored in the memory 12 and operations by an operator, to manufacture the silicon single crystal 1.

[0042] [Method for growing silicon single crystals] Next, an example of a method for growing a silicon single crystal according to an embodiment of the present invention will be described with reference to the flowchart shown in Fig. 2. In this embodiment, a case in which a silicon single crystal 1 having a product diameter of 200 mm is produced will be illustrated, but the product diameter is not limited to this. Furthermore, examples of the volatile dopant to be added include, but are not limited to, red phosphorus (P), arsenic (As) and antimony (Sb).

[0043] As shown in the flowchart of Figure 2, the method for growing a silicon single crystal includes a pulling condition setting process S1, a single crystal growing process S2, an abnormal growth determination process S3, a critical CV value calculation process S4, a target CV value profile creation process S5, a pulling condition resetting process S6, and a corrected single crystal growing process S7, and the processes are performed in the above order.

[0044] The pulling condition setting step S1 includes a resistivity profile creation step S1A and a pulling speed profile creation step S1B. The pulling conditions include at least one of a pulling speed profile, which is a planned value of the pulling speed, and a resistivity profile, which is a planned value of the resistivity in the crystal axis direction.

[0045] Furthermore, when the resistivity distribution in the crystal axis direction changes due to a change in the furnace pressure or the flow rate of the inert gas flowing in the furnace, the change in the furnace pressure or the flow rate of the inert gas is included in the change in the resistivity profile.

[0046] The resistivity profile creation step S1A is a step of creating a resistivity profile based on a target resistance value.

[0047] Fig. 3 is an example of a resistivity profile created when manufacturing a silicon single crystal by the silicon single crystal growth method according to the present embodiment. The horizontal axis of Fig. 3 is solidification rate (%), and the vertical axis is resistivity. The solidification rate refers to the ratio of the pulled weight of the silicon single crystal to the amount of silicon raw material put into the crucible.

[0048] The resistivity profile is created based on the target resistance value in the body of the silicon single crystal 1. The target resistivity in the body of the silicon single crystal 1 can be 0.5 mΩ·cm or more and 1.3 mΩ·cm or less when the dopant is red phosphorus. Silicon single crystals with such resistivity are called ultra-low resistivity silicon single crystals.

[0049] The resistivity profile can be calculated prior to pulling the silicon single crystal 1, taking into consideration, for example, the dopant concentration in the dopant-added melt MD at the start of pulling the silicon single crystal 1, the decrease in the dopant concentration in the dopant-added melt MD due to evaporation of the dopant from the dopant-added melt MD, and the increase in the dopant concentration in the dopant-added melt MD due to the segregation phenomenon as the pulling of the silicon single crystal 1 progresses.

[0050] In addition, the resistivity distribution in the longitudinal direction of the pulled silicon single crystal 1 based on the resistivity profile obtained by the above calculation can be measured, and the measurement results can be fed back into the calculation of the resistivity profile, thereby improving the calculation accuracy of the resistivity profile.

[0051] The pull-speed profile creation step S1B is a step of creating a pull-speed profile based on the resistivity profile created in the resistivity profile creation step S1A.

[0052] The pulling rate profile includes information on a target pulling rate to be obtained at the body of the silicon single crystal 1. Fig. 4 shows an example of a pulling rate profile created when manufacturing a silicon single crystal by the silicon single crystal growth method according to this embodiment. The horizontal axis of Fig. 4 is the solidification rate (%), and the vertical axis is the pulling rate.

[0053] The pulling speed profile can be created by setting, for example, eight pulling speeds along the length of the body. In the example shown in Fig. 4, the pulling speed is set relatively fast up to a solidification rate of 40%, and the pulling speed is gradually slowed down as the body length increases (as the solidification rate increases).

[0054] In the pulling condition setting process S1, a resistivity profile and a pulling speed profile are created, and manufacturing conditions for the silicon single crystal 1, such as the oxygen concentration in the silicon single crystal 1, the gas flow rate of Ar gas, the furnace pressure, the rotation speed of the crucible 22 and the silicon single crystal 1, and the position of the crucible 22, are set.

[0055] The control unit 13 stores the set pulling conditions and the like in the memory 12. The control unit 13 reads out the pulling speed profile and the like from the memory 12, and executes each process based on them.

[0056] In the single crystal growth process S2, the control unit 13 first controls a power supply device (not shown) that supplies power to the heater 23, and heats the crucible 22 to melt the silicon raw material and dopant in the crucible 22 and generate a dopant-added melt MD.

[0057] Next, the control unit 13 introduces Ar gas into the chamber 21 from the gas inlet 33A at a predetermined flow rate, and controls a vacuum pump (not shown) to exhaust the gas within the chamber 21 from the gas exhaust port 33B, thereby reducing the pressure within the chamber 21 and maintaining an inert atmosphere under reduced pressure within the chamber 21.

[0058] Next, the control unit 13 controls the pulling-up driving unit 52 to lower the cable 51, thereby causing the seed crystal 2 to be immersed in the dopant-added melt MD.

[0059] Next, the control unit 13 controls the crucible driving unit 27 to rotate the crucible 22 in a predetermined direction, and also controls the pulling driving unit 52 to rotate the cable 51 in a predetermined direction while pulling up the cable 51, thereby growing the silicon single crystal 1. Specifically, the silicon single crystal 1 is grown in the order of the neck portion 3, the shoulder portion, the body portion, and the tail portion.

[0060] Next, the control unit 13 controls the pulling drive unit 52 to separate the tail portion of the silicon single crystal 1 from the dopant-added melt MD. Next, the control unit 13 controls the pulling drive unit 52 to further pull up the cable 51 while cooling the silicon single crystal 1 separated from the dopant-added melt MD.

[0061] Next, after it is confirmed that the cooled silicon single crystal 1 is accommodated in the pull chamber 32 , the silicon single crystal 1 is removed from the pull chamber 32 .

[0062] The abnormal growth determination step S3 is a step for determining whether or not cell growth has occurred in the extracted silicon single crystal 1. At the location where cell growth has occurred, a phenomenon occurs in which the silicon melt locally solidifies into dendrites on the growth surface of the silicon single crystal, i.e., at the solid-liquid interface where the silicon melt in the crucible solidifies and crystallizes, and the silicon single crystal easily becomes polycrystallized. Therefore, whether cell growth has occurred in the silicon single crystal 1 can be determined, for example, by vertically splitting the crystal near where dislocations have occurred, selectively etching the split surface, and then observing the crystal with an optical microscope at a magnification of 50. At the location where cell growth has occurred, linear polycrystalline regions that extend somewhat in the approximate growth direction are observed.

[0063] If cell growth has not occurred (No), the process returns to the pulling condition setting step S1 to continue the production of the silicon single crystal 1. At this time, in the pulling condition setting step S1, the resistivity profile or the like may be created again, or the silicon single crystal 1 may be continuously produced with the same profile. In addition, although it is preferable to replace the crucible 22, the production of the silicon single crystal 1 may be continued without replacing the crucible 22.

[0064] If cell growth has occurred (Yes), a critical CV value calculation step S4, which will be described below, is executed.

[0065] The critical CV value calculation step S4 is a step of calculating the CV value (critical CV value) which is the product of the dopant concentration C and the pulling speed V at the time when cell growth occurs, and creating a critical CV value profile by connecting multiple critical CV values ​​with lines. Note that the "time point" mentioned here literally means "at that time." The "time point" can also be expressed in terms of the solidification rate. For example, if cell growth occurs at a solidification rate of X%, the calculated critical CV value is the critical CV value at the solidification rate of X%. Here, the point in time when cell growth occurs refers to the point in time when the part of the crystal where cell growth occurs was the solid-liquid interface where the melt in the crucible solidified and crystallized during crystal growth, and the critical CV value is the product of the dopant concentration C and the pulling rate V at the point in time when the part of the crystal where cell growth occurs was the solid-liquid interface where the melt in the crucible solidified and crystallized during crystal growth. A plurality of critical CV values ​​are calculated in the length direction of the silicon single crystal 1. The number of calculated critical CV values ​​can be appropriately changed depending on the length of the straight body portion and the position where cell growth has occurred. In addition, in the critical CV value calculation step S4, the positions where cell growth has occurred are also recorded.

[0066] The dopant concentration C is the dopant concentration in the silicon single crystal. The dopant concentration in the silicon single crystal 1 can be calculated from the resistance value of the silicon single crystal using a relational expression between the dopant concentration in the silicon single crystal and the resistivity of the silicon single crystal. As the relational expression, the Irvin curve, ASTM standard F723, or the like can be used.

[0067] The resistivity in the silicon single crystal 1 is measured in the form of an ingot after the outer periphery of the extracted silicon single crystal 1 is ground and before the silicon single crystal 1 is cut into blocks. Alternatively, the resistivity in the silicon single crystal 1 may be measured in the form of a block after the ingot is cut into blocks, or a sample may be cut out and measured. The resistivity may be measured by, for example, a four-probe method. For example, if the dopant is red phosphorus and has a resistivity of 1 mΩ cm, then the dopant concentration C is 7.4 × 10 19 atoms / cm 3 It can be calculated as follows. Specifically, an example of determining the dopant concentration C that constitutes the critical CV value will be described. To determine the dopant concentration C that constitutes the critical CV value, first, a sample is cut out from the crystal, and the resistivity of the area where cell growth has occurred is measured by the four-probe method, and the resistivity is calculated from the measured resistivity using the relational equation between the impurity concentration in the crystal and the resistivity of the crystal.

[0068] The method of acquiring the dopant concentration C in the silicon single crystal is not limited to this, and for example, if it can be measured directly from the silicon single crystal 1, it may be measured directly. Furthermore, the dopant concentration C is not limited to the dopant concentration in the silicon single crystal 1, and may refer to the dopant concentration in the dopant-added melt MD.

[0069] The pulling speed V can be calculated from the pulling speed profile.

[0070] The pulling rate V is not limited to calculation from the pulling rate profile, and may be an actually measured pulling rate. When actually measured, the pulling rate may be an instantaneous rate or an average rate including the time before and after. Therefore, the pulling rate V constituting the critical CV value can be obtained by determining the pulling rate at the time when cell growth occurs from the pulling rate profile or the pulling rate data recorded during crystal growth.

[0071] Figure 5 is an example of a graph plotting CV values, with the solidification rate (%) on the horizontal axis and the CV value on the vertical axis. The critical CV value profile is shown by a solid line. The critical CV value shown by the solid line is the CV value when cell growth occurs. In the example shown in FIG. 5, the critical CV value is 6.5×10 19 It can be seen that it gradually decreases from

[0072] The target CV value profile creation step S5 is a step of creating a target CV value profile using multiple target CV values ​​(target CV values) that do not exceed the multiple critical CV values ​​calculated in the critical CV value calculation step S4. Specifically, a target CV value profile is planned that will result in a smaller CV value than the actual critical CV value at which cell growth occurs. The target CV value profile is shown by a dashed line in Figure 5.

[0073] More specifically, the target CV value profile can be created so that the target CV value is smaller than 90% of the critical CV value at which cell growth occurs, for example.

[0074] If the target CV value is set to 90% or more of the critical CV value, when there is a fluctuation in the dopant concentration near the interface between the crystal and the melt or a fluctuation in the crystal growth rate, the CV value may temporarily reach the critical CV value, causing cell growth in the single crystal and resulting in dislocations. Conversely, when there is no fluctuation in the dopant concentration near the interface between the crystal and the melt and no fluctuation in the crystal growth rate, the target CV value can be set to 90% or more of the critical CV value.

[0075] The target CV value profile is preferably set so that the target CV value constituting the target CV value profile is 50% or more of the critical CV value. If the target CV value falls below 50% of the critical CV value, for example, when the pulling speed V is adjusted, the productivity will be significantly reduced, which is not preferable. It is more preferable that the target CV value profile is set so that the target CV value is 80% or more of the critical CV value.

[0076] For example, the position where cell growth occurred has a solidification rate of 57%, and the CV value at that position is 6×10 19 If so, the CV value at that position is 5.4×10 19 The target CV value profile is considered as follows: In the example shown in Fig. 5, no CV value to refer to is recorded after the solidification rate of 57%, but the operator can set the target CV value based on the trend up to the solidification rate of 57%. The above-mentioned target CV value profile is only an example, and a target CV value profile having a smaller CV value may be used, with emphasis on suppressing the occurrence of cell growth.

[0077] The inventors have investigated a method for predicting the critical point for cell growth in order to suppress the occurrence of cell growth when pulling silicon single crystal 1. As a method for predicting the critical point for cell growth, they have found a method using the critical CV value at the time when cell growth occurs as an index. In other words, they thought that the critical CV value could be an index for setting pulling conditions that suppress the occurrence of cell growth, and they thought that it would be sufficient to reset at least one of the pulling rate profile and the resistivity profile using multiple critical CV values.

[0078] Specifically, it was considered that the occurrence of cell growth could be suppressed by examining a CV value (target CV value) that would not be higher than the critical CV value when cell growth occurs, and setting pulling conditions that would satisfy this target CV value. The reason why the critical CV value was used as an index for determining the pulling conditions in the silicon single crystal growth method of the present invention is as described above.

[0079] In the pulling condition resetting step S6, a modified pulling speed profile is created, which is configured with a pulling speed V corresponding to the target CV value profile created in the target CV value profile creating step S5. Specifically, while the resistivity profile is made similar to the resistivity profile created in the resistivity profile creating step S1A, a modified pulling speed profile is created in which the pulling speed V is reduced to correspond to a target CV value smaller than the critical CV value.

[0080] For example, the target CV value at the position of 20% solidification rate is 5×10 19 and the dopant concentration C based on the resistivity at that position (resistivity obtained by referring to the resistivity profile) is 7.4×10 19 atoms / cm 3 In this case, the pulling speed can be calculated to be 0.68 mm / min. An example of a corrected pulling speed profile corrected based on the target CV value profile is shown by the dashed line in FIG.

[0081] The resistivity profile does not necessarily have to be the same as the resistivity profile created in the resistivity profile creation process S1A, and may be modified based on actual results in order to suppress the occurrence of cell growth. That is, in the pulling condition resetting process S6, a modified resistivity profile composed of resistivities corresponding to the target CV value profile may be created. In other words, in this embodiment, the pulling speed profile is created based on the target CV value profile in the pulling condition resetting step S6, but this is not limited to the above, and the resistivity profile may be corrected based on the target CV value profile in the pulling condition resetting step S6. Since the dopant concentration C and the electrical resistivity have a one-to-one relationship, resistivity By modifying the profile, the dopant concentration C is modified. That is, at least one of the dopant concentration C and the pull rate V may be controlled so that the CV value falls below the critical CV value.

[0082] In the corrected single crystal growing step S7, the silicon single crystal is pulled in the same manner as in the single crystal growing step S2.

[0083] According to the above embodiment, by using the CV value as an indicator for setting the pulling conditions, the pulling conditions can be set more quickly compared to the conventional method that requires reference to the temperature gradient G of the melt below the solid-liquid interface.

[0084] Moreover, by calculating a target CV value and setting pulling conditions that satisfy the target CV value, it is possible to set the pulling conditions without increasing the resistivity of the silicon single crystal 1.

[0085] In addition, since the dopant concentration C constituting the CV value can be calculated from the resistance value of the silicon single crystal 1 and the Irvin curve, etc., it is possible to calculate the pulling speed V more accurately from the CV value, and the pulling speed V is not lowered too much. This makes it possible to suppress an increase in the resistivity of the silicon single crystal caused by an excessive decrease in the pulling speed V.

[0086] In the above embodiment, the resistivity profile and the like are created in accordance with the solidification rate of the silicon single crystal, but the present invention is not limited to this. For example, the resistivity profile and the like may be created in accordance with the position in the longitudinal direction of the silicon single crystal, or the start position of the straight body portion may be made to correspond to 0% and the end position of the straight body portion may be made to correspond to 100%.

[0087] In addition, since there is a one-to-one relationship between the dopant concentration C and the electrical resistivity, the present invention also includes the case where the product of the electrical resistivity and the pull-up rate is used instead of the CV value, which is the product of the dopant concentration C and the pull-up rate V. [Explanation of symbols]

[0088] 1...silicon single crystal, 10...semiconductor crystal manufacturing apparatus, 11...apparatus body, 12...memory, 13...control unit, 21...chamber, 22...crucible, 23...heater, 24...pulling unit, 25...thermal shield, 26...insulating material, 27...crucible drive unit, 33A...gas inlet, 33B...gas exhaust port, C...dopant concentration, V...pulling speed, MD dopant-added melt, S1...pulling condition setting step, S2...single crystal growth step, S3...abnormal growth determination step, S4...critical CV value calculation step, S5...target CV value profile creation step, S6...pulling condition resetting step, S7...corrected single crystal growth step.

Claims

1. A method for growing a silicon single crystal, comprising the steps of: pulling and growing a silicon single crystal from a dopant-added melt obtained by adding a dopant to a silicon melt by a Czochralski method; a critical CV value calculation step of calculating a critical CV value, which is the product of a dopant concentration C and a pulling rate V at a point in time when abnormal growth occurs in the silicon single crystal; a pulling condition resetting step of resetting at least one of a pulling rate profile and a resistivity profile in the crystal axis direction so that a CV value, which is a product of a dopant concentration C and a pulling rate V at the time point, falls below the critical CV value; a corrected single crystal growing step of growing a silicon single crystal by controlling at least one of the dopant concentration C and the pulling speed V based on the profile reset in the pulling condition resetting step.

2. 2. The method for growing a silicon single crystal as described in claim 1, further comprising, after the critical CV value calculation step and before the pulling condition resetting step, a target CV value profile creation step of creating a target CV value profile using a target CV value calculated in the critical CV value calculation step and smaller than the critical CV value at the time point.

3. 3. The silicon single crystal growing method according to claim 2, wherein the resetting of pulling conditions comprises creating a corrected pulling rate profile constituted by a pulling rate corresponding to the target CV value profile.

4. 4. The method for growing a silicon single crystal according to claim 2, wherein in the resetting of pulling conditions, a corrected resistivity profile composed of resistivities corresponding to the target CV value profile is created.

5. 5. The method for growing a silicon single crystal according to claim 1, wherein the dopant concentration C is a dopant concentration in the silicon single crystal, and the dopant concentration in the silicon single crystal is calculated from a resistance value of the silicon single crystal using a relational equation between the dopant concentration in the silicon single crystal and a resistivity of the silicon single crystal.

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