CN109072477B - Method for producing neutron-irradiated silicon single crystal - Google Patents
Method for producing neutron-irradiated silicon single crystal Download PDFInfo
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- CN109072477B CN109072477B CN201780027040.7A CN201780027040A CN109072477B CN 109072477 B CN109072477 B CN 109072477B CN 201780027040 A CN201780027040 A CN 201780027040A CN 109072477 B CN109072477 B CN 109072477B
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 100
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 100
- 239000010703 silicon Substances 0.000 title claims abstract description 100
- 239000013078 crystal Substances 0.000 title claims abstract description 93
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 28
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 7
- 239000011574 phosphorus Substances 0.000 claims abstract description 7
- 230000001678 irradiating effect Effects 0.000 claims abstract description 6
- 238000011088 calibration curve Methods 0.000 claims description 6
- 239000010453 quartz Substances 0.000 description 23
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 23
- 238000012937 correction Methods 0.000 description 22
- 238000000034 method Methods 0.000 description 20
- 230000007246 mechanism Effects 0.000 description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 10
- 235000012431 wafers Nutrition 0.000 description 10
- 229910002804 graphite Inorganic materials 0.000 description 9
- 239000010439 graphite Substances 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- XLYOFNOQVPJJNP-ZSJDYOACSA-N Heavy water Chemical compound [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 description 8
- 239000007789 gas Substances 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 239000011261 inert gas Substances 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 239000000155 melt Substances 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 238000009826 distribution Methods 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000004992 fission Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000002210 silicon-based material Substances 0.000 description 2
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 229910052770 Uranium Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000005255 beta decay Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000002019 doping agent Substances 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000005468 ion implantation Methods 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 238000009377 nuclear transmutation Methods 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 1
- 239000003870 refractory metal Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 230000002123 temporal effect Effects 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- JFALSRSLKYAFGM-OIOBTWANSA-N uranium-235 Chemical compound [235U] JFALSRSLKYAFGM-OIOBTWANSA-N 0.000 description 1
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/26—Bombardment with radiation
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/06—Silicon
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Abstract
In a method for producing a silicon single crystal of a predetermined resistivity by doping an ingot (I) of a grown silicon single crystal (C) with phosphorus by irradiating the ingot with neutrons under intrinsic conditions, when calculating a target neutron irradiation amount for obtaining the predetermined resistivity, a plurality of neutron irradiation amounts different in neutron irradiation amount are set for each silicon single crystal under the intrinsic conditions and neutrons are irradiated, the resistivity of the doped silicon single crystal obtained for each neutron irradiation amount is measured, a standard curve showing a relationship between the neutron irradiation amount and the resistivity is obtained in advance, and the neutron irradiation amount obtained by using the standard curve so that the resistivity reaches the predetermined resistivity is set as the target neutron irradiation amount.
Description
Technical Field
The present invention relates to a method for producing a neutron irradiated silicon single crystal.
Background
As a method for producing a neutron-irradiated silicon single crystal, there is proposed a method for producing a neutron-irradiated silicon single crystal, the method comprising: a step of growing a silicon single crystal ingot having an average resistivity of 1000 Ω & cm or more while adding nitrogen by the FZ method, a step of subjecting the silicon single crystal ingot to neutron irradiation, and a step of performing heat treatment for recovering damage received by the neutron irradiation, wherein the step of performing the neutron irradiation is performed by performing heat treatment for removing a donor on the silicon single crystal at least before the step of performing the neutron irradiation on the silicon single crystal ingot, and calculating a neutron irradiation amount from the resistivity of the silicon single crystal subjected to the heat treatment for removing the donor, and performing the neutron irradiation step. The neutron irradiation amount N in the neutron irradiation step is calculated based on the raw material resistivity R1 and the target resistivity RT, but the resistivity R2 after the neutron irradiation actually obtained may be greatly deviated from the target resistivity RT due to the addition of nitrogen. Therefore, it is believed that if the heat treatment for eliminating the nitrogen-based donor is performed and then the neutron irradiation amount necessary for obtaining the target resistivity is calculated in advance before the neutron irradiation step using the resistivity evaluation value of the raw silicon single crystal obtained by the evaluation, the influence of the complex donor due to the nitrogen addition is suppressed and a more accurate value can be obtained.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open No. 2007-176725.
Disclosure of Invention
Problems to be solved by the invention
However, even if the neutron irradiation amount N is set to an appropriate value, the resistivity R2 after neutron irradiation actually obtained may be greatly deviated from the target resistivity RT depending on individual differences of apparatuses (nuclear reactors) irradiating neutrons.
The present invention addresses the problem of providing a method for producing a neutron-irradiated silicon single crystal, which can accurately obtain a neutron-irradiated silicon single crystal having a target resistivity.
Means for solving the problems
The present invention solves the above problems by the following means:
in a method for producing a silicon single crystal having a predetermined resistivity by irradiating an ingot of the grown silicon single crystal with neutrons under intrinsic conditions and doping with phosphorus,
when calculating the target neutron irradiation amount for obtaining the predetermined resistivity,
under the intrinsic conditions, a plurality of neutron irradiations with different neutron irradiations are set for each silicon single crystal to irradiate neutrons,
measuring the resistivity of a plurality of the doped silicon single crystals obtained for each neutron irradiation amount,
a calibration curve showing a relationship between the neutron irradiation amount and the resistivity is obtained in advance,
the neutron irradiation amount obtained by the standard curve so that the resistivity becomes the predetermined resistivity is set as the target neutron irradiation amount.
Effects of the invention
According to the present invention, a plurality of neutron irradiations with different neutron irradiations are set for each silicon single crystal under intrinsic conditions including individual differences of neutron irradiators and neutrons are irradiated, the resistivity of a plurality of doped silicon single crystals obtained for each neutron irradiation is measured, and a calibration curve showing a relationship between the neutron irradiations and the resistivity is obtained in advance. When calculating the target neutron irradiation amount for obtaining the predetermined resistivity under the intrinsic conditions, the neutron irradiation amount obtained by using the standard curve so that the resistivity reaches the predetermined resistivity is set as the target neutron irradiation amount, and the neutron irradiation amount in consideration of the variation of the intrinsic conditions is obtained. As a result, a neutron irradiated silicon single crystal having a target resistivity can be accurately obtained.
Drawings
Fig. 1 is a sectional view showing an example of a manufacturing apparatus for manufacturing a silicon single crystal used in the method for manufacturing a neutron irradiated silicon single crystal of the present invention.
Fig. 2 is a schematic view showing an example of a neutron irradiation device used in the method for producing a neutron-irradiated silicon single crystal of the present invention.
Fig. 3 is a graph in which a plurality of doped silicon single crystals obtained for each neutron irradiation amount are processed into a wafer and the resistivity thereof is measured, using a plurality of silicon single crystal ingots, and the wafers are irradiated with neutrons while a plurality of different neutron irradiation amounts are set.
Fig. 4 is a graph showing the measurement of the resistivity in the diameter direction of the sample wafer shown in fig. 3.
Fig. 5 is a graph showing the actual resistivity of each time-series lot of the example (right half) and the comparative example (left half).
Detailed Description
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing an example of an apparatus for manufacturing a silicon single crystal by the Czochralski method (CZ method) used in the method for manufacturing a neutron-irradiated silicon single crystal according to the present invention. The method for producing a neutron irradiated silicon single crystal of the present invention can be applied not only to a silicon single crystal produced by the CZ method but also to a silicon single crystal produced by the float zone method (FZ method). Hereinafter, an example of applying the present invention to a silicon single crystal produced by the CZ method will be described. The apparatus 1 for producing a silicon single crystal according to the present embodiment (hereinafter, also simply referred to as the production apparatus 1) includes a cylindrical 1 st chamber 11 and a cylindrical 2 nd chamber 12, which are connected in an airtight manner.
Inside the 1 st chamber 11, a quartz crucible 21 containing a silicon melt M and a graphite crucible 22 protecting the quartz crucible 21 are supported by a support shaft 23 and can be rotated and lifted by a drive mechanism 24. Further, a ring-shaped heater 25 and a heat insulating cylinder 26 made of a heat insulating material, which is also ring-shaped, are disposed so as to surround the quartz crucible 21 and the graphite crucible 22. The radiant heat from the ring-shaped heater 25 is wound around not only the side portion but also the bottom portion of the graphite crucible 22 to heat the side portion and the bottom portion of the quartz crucible 21. It is considered that when the quartz crucible 21 and the graphite crucible 22 are in the lowered position, the amount of heat from the heater 25 circling around the bottoms of the quartz crucible 21 and the graphite crucible 22 is smaller than when they are in the raised position. A heater may be added below the quartz crucible 21.
A cylindrical heat shield member 27 is provided in the 1 st chamber 11 and above the quartz crucible 21. The heat shielding member 27 is formed of a refractory metal such as molybdenum or tungsten, or a member in which a graphite felt is filled in a case made of carbon or graphite, and rectifies the gas flowing in the 1 st chamber 11 while shielding the radiation from the silicon melt M to the silicon single crystal C. The heat shielding member 27 is fixed to the heat insulating tube 26 by using a bracket 28. A heat shielding portion may be provided at a lower end of the heat shielding member 27 so as to face the entire surface of the silicon melt M, and the surface of the silicon melt M may be kept warm while blocking radiation from the surface of the silicon melt M.
The 2 nd chamber 12 connected to the upper portion of the 1 st chamber 11 contains the grown silicon single crystal C and is a chamber for taking out the same. A pulling mechanism 32 for pulling up the silicon single crystal while rotating the silicon single crystal by a wire 31 is provided in the upper part of the 2 nd chamber 12. The seed crystal S is loaded on a holder at the lower end of the wire 31 suspended by the pulling mechanism 32. Inert gas such as argon is introduced from a gas inlet 13 provided at the upper part of the 1 st chamber 11. The inert gas passes between the silicon single crystal C being pulled and the heat shielding member 27, then passes between the lower end of the heat shielding member 27 and the melt surface of the silicon melt M, further rises to the upper end of the quartz crucible 21, and is discharged from the gas discharge port 14.
A magnetic field generator 41 for applying a magnetic field to the melt M in the crucible 21 made of quartz is disposed outside the 1 st chamber 11 (formed of a non-magnetic shielding material) so as to surround the 1 st chamber 11. The magnetic field generator 41 generates a horizontal magnetic field toward the quartz crucible 21 and is constituted by an electromagnetic coil. The magnetic field generator 41 controls thermal convection generated in the melt M in the quartz crucible 21, thereby making the distribution of impurities in the wafer uniform. In particular, when a silicon single crystal having a large diameter is produced, the effect is large. The magnetic field generator may be a magnetic field generator that generates a longitudinal magnetic field or a cusp magnetic field, if necessary, and the magnetic field generator 41 may be omitted if necessary.
In order to grow a silicon single crystal by the CZ method using the manufacturing apparatus 1 of the present embodiment, first, polycrystalline silicon and, if necessary, a silicon material containing a dopant are filled in the quartz crucible 21, and the heater 25 is energized to melt the silicon material in the quartz crucible 21, thereby producing a silicon melt M. Next, the magnetic field generator 41 is energized to start the application of the horizontal magnetic field to the quartz crucible 21, and the temperature of the silicon melt M is adjusted to the pulling start temperature. After the temperature and magnetic field strength of the silicon melt M are stabilized, inert gas is introduced from the gas inlet 13 and discharged from the gas outlet 14, and the quartz crucible 21 is rotated at a predetermined speed by the drive mechanism 24, so that the seed crystal S mounted on the wire 31 is immersed in the silicon melt M. Then, the wire 31 is slowly pulled while being rotated at a predetermined speed to form a seed crystal extract, and thereafter, the shoulder is extended to a desired diameter to grow a silicon single crystal C having a substantially cylindrical straight portion.
The thermal field is a region which is heated by heat from the heater 25 during the growth of the single crystal, and the material, shape, arrangement, and various thermal characteristics of the 1 st chamber 11, the quartz crucible 21, the graphite crucible 22, the support shaft 23, the heater 25, the heat insulating cylinder 26, the heat shielding member 27, the silicon melt M, the silicon single crystal C, and the like affect the thermal field conditions. In order to suppress the fluctuation of the liquid surface, the height of the melt M in the vertical direction of the liquid surface during the pulling of the silicon single crystal C is controlled to be constant by the drive mechanism 24. The position of the quartz crucible 21 in the vertical direction is moved by the driving mechanism 24 by controlling the driving mechanism 24 based on information such as the position of the quartz crucible 21, the position of the liquid surface of the silicon melt M measured by a CCD camera or the like, the pulling length of the silicon single crystal C, the temperature in the 1 st chamber 11, the surface temperature of the silicon melt M, the inert gas flow rate, and the rotation speed per unit time of the quartz crucible 21.
One of the thermal field conditions is a gap H in the height direction between the lower end of the heat shielding member 27 and the liquid surface of the quartz crucible 21, and the gap H is set to a predetermined value in accordance with the target diameter of the silicon single crystal to be produced, the target oxygen concentration, and other product specifications, and the drive mechanism 24 of the quartz crucible 21, the pulling mechanism 32 of the wire 31, the heating power of the heater 25, and other production conditions are automatically controlled so that the gap H is maintained at the predetermined value during pulling. Further, a target diameter of the silicon single crystal corresponding to the diameter of the silicon wafer is set, and the diameter of the crystal C actually pulled is optically detected and fed back to the pulling rate and other conditions.
The silicon single crystal C after completion of pulling is taken out from the 2 nd chamber 12, and the head and the tail are cut off to prepare only an intermediate portion having a predetermined diameter, and the intermediate portion is conveyed to the neutron irradiation step. Alternatively, instead of the above, the head and tail are not cut off, and the neutron irradiation step is directly carried out.
In the neutron irradiation step, a neutron irradiation device is used to irradiate the silicon single crystal ingot with neutrons. In the case of a neutron irradiation device in which the irradiation direction of the thermal neutron beam is fixed, the irradiation is performed while rotating the silicon single crystal ingot at a constant speed. Fig. 2 is a schematic diagram showing an example of the neutron irradiation device 5, and the neutron irradiation device 5 shown in the figure includes a core 51 for generating and collimating a thermal neutron beam 52, and an ingot container 53 for holding an ingot I to be irradiated with neutrons at a fixed position. The ingot container 53 can rotate at a low speed, and thereby the ingot I also rotates at a constant speed. In the Neutron irradiation step of the present embodiment, phosphorus is added to a silicon single crystal ingot by an NTD (Neutron Transmutation Doping) method, and the method is used to obtain a silicon single crystal ingot for n-type semiconductor.
When a silicon single crystal is irradiated with neutrons, silicon (an isotope of silicon Si, which exists in the silicon) is present28Si(=92.21%)、29Si(=4.70%)、30Si (=3.09%))30Si is irradiated with neutrons, and thereby undergoes an (n, γ) reaction with thermal neutrons having low energy to generate Si31And (3) Si. The31Si undergoes beta decay and converts to stable isotopes over a half-life of 2.6 hours31And P. The neutron irradiation doping method NTD is a method for uniformly doping phosphorus P in silicon by utilizing this reaction. The NTD method has an advantage that the distribution of phosphorus in the silicon single crystal shows uniformity which cannot be obtained by a conventional method (such as ion implantation) of adding an impurity element, and the concentration of phosphorus to be added can be determined with good accuracy by controlling the neutron irradiation time.
Here, the thermal neutron beam from the neutron irradiation device 5 is denoted as φth(n/cm 2Seed sec), when the neutron irradiation time is denoted as t (sec), when an n-type silicon single crystal having a resistivity after neutron irradiation of R2(Ω cm) is produced from a p-type silicon single crystal having a resistivity before neutron irradiation of R1(Ω cm), the following relational expression (1) is established.
[ relational expression 1]
(1.3×1016/R1)+(5×1015/R2)=1.7×10-4×φth×t…(1)。
When an n-type crystal having a resistivity of R2(Ω cm) after neutron irradiation is produced from an n-type silicon single crystal having a resistivity of R1(Ω cm) before neutron irradiation, the following relational expression (2) is satisfied.
[ relational expression 2]
-(5×1016/R1)+(5×1015/R2)=1.7×10-4×φth×t…(2)。
The neutron irradiation device 5 in the neutron irradiation step is inputted with the neutron irradiation amount (phi)th×t)n/cm2The set value of (2).
Nuclear reactors used for neutron irradiation include a light water reactor and a heavy water reactor. In the heavy water reactor, absorption of neutrons is small, and therefore, it is similar to the use of uranium 235 (which is enriched in high-speed neutrons during nuclear fission and releases a large amount of neutrons235Of U) areLight water reactors differ by the small rate of uranium 238 (to release high-speed neutrons during nuclear fission)238U) as a seed source, natural uranium is used as a raw material. The energy of high-speed neutrons is large, and if the number of high-speed neutrons is large, the irradiation damage to the crystal becomes large. Therefore, a heavy water reactor, which has a small amount of high-speed neutrons in the furnace and can reduce damage to the silicon single crystal as compared with a light water reactor, can recover crystal defects and resistivity more easily. Therefore, it is desirable to select a heavy water reactor as a nuclear reactor for irradiating a silicon single crystal ingot with neutrons.
As described above, the neutron irradiation device 5 including a nuclear reactor is not easily purchased or manufactured by the same company as the apparatus 1 for manufacturing a silicon single crystal shown in fig. 1, but belongs to a limited organization or group from the viewpoint of ensuring safety. In addition, it is used not only for irradiating a silicon single crystal with neutrons but also for many purposes. Therefore, the neutron irradiation device 5 has inherent individual differences (variations) in manufacturing. For example, variations in the thermal neutron beam irradiated by the neutron irradiation device 5, the number of ingots I mounted on the neutron irradiation device 5, the mounting method, and state variations inherent to the device exist as individual differences in the manufacturing inherent to the neutron irradiation device 5. Therefore, even if the resistivity R1 before neutron irradiation and the target resistivity R2 after neutron irradiation are substituted into the above relational expression (1) or (2), Φ is obtainedthThe value of x t is input to the neutron irradiation device, and the resistivity varies depending on individual differences in manufacturing inherent to the device.
In the present embodiment, the target neutron irradiation amount Φ for obtaining the predetermined resistivity R2 is calculatedthAt x t, the neutron irradiation amount phi is set for each silicon single crystal under the inherent conditions of a specific neutron irradiation device 5 and the likethIrradiating neutrons with a plurality of neutron irradiations of different x t, measuring resistivity R2 of a plurality of doped silicon single crystals obtained for each neutron irradiation, and obtaining in advance a value indicating the neutron irradiation phithStandard curve of x t versus resistivity R2. When a silicon single crystal ingot to be actually used as a product is irradiated with neutrons, the neutron irradiation amount including a standard curve obtained in advance for each intrinsic condition and having a specific resistivity equal to a predetermined resistivity is set toThe value within the predetermined range is set as a target neutron irradiation amount.
In table 1, a plurality of silicon single crystal ingots I (the number of samples n =386 in the bottom column) having a wafer diameter of 200mm were produced using the silicon single crystal production apparatus 1 using the CZ method shown in fig. 1, and a target resistivity was set to 51 Ω cm using the plurality of silicon single crystal ingots I, and a plurality of different neutron irradiation amounts Φ were setthX t (5 correction coefficients in this example) and neutrons were irradiated, a plurality of doped silicon single crystals obtained for each neutron irradiation amount were processed into wafers, and the resistivity R2 at 5 points in the diameter direction thereof was measured to calculate the average value of the actual resistivities. The Accuracy (Accuracy) is an evaluation value defined by (target resistivity-actual resistivity average)/target resistivity. The closer the absolute value of the value of accuracy is to zero, the closer the actual resistivity is on average to the target resistivity. FIG. 3 is a graph in which the horizontal axis represents a plurality of different neutron irradiation amounts φthThe measured values in table 1 are plotted with the actual resistivity on the ordinate at × t (5 correction coefficients in this example). The straight line shown in fig. 3 is an approximate straight line obtained by the least square method of the actual resistivity for 5 correction coefficients, and it becomes a standard curve of the present embodiment. The correction coefficient is defined as being in the above-mentioned [ relational expression 1]]And [ relation 2]]The factor alpha multiplied by the neutron irradiation amount term is the above-mentioned [ relational expression 1] in consideration of the correction factor alpha]And [ relation 2]]As described below.
[ relational expression 1]
(1.3×1016/R1)+(5×1015/R2)=1.7×10-4×α(φth×t)…(1)。
[ relational expression 2]
-(5×1016/R1)+(5×1015/R2)=1.7×10-4×α(φth×t)…(2)。
When a silicon single crystal ingot I to be actually used as a product is irradiated with neutrons, a value in a predetermined range including a neutron irradiation amount of 50 Ω cm, for example, which is obtained by using a calibration curve obtained in advance for each intrinsic condition (for example, for each neutron irradiation device 5) and which makes the resistivity a predetermined resistivity is set as a target neutron irradiation amount. Here, when the neutron irradiation amount for achieving the target resistivity of 50 Ω cm is obtained from the standard curve shown in fig. 3, the correction coefficient x = 0.9884. Therefore, if the correction coefficient is multiplied by the neutron irradiation amount set at the previous time, the present target neutron irradiation amount is obtained, which is most desirable. However, as shown in table 1 and fig. 3, since there is a certain degree of variation in the actual resistivity, the correction coefficient is not limited to the precise point of x =0.9884, and may be set to a value at least between adjacent correction coefficients 0.9800. If this is generalized, if the neutron irradiation amount is varied by an interval of 0.01 in accordance with the correction coefficient, a value within a range of ± 0.01 can be set in the correction coefficient. In the above example, the correction coefficient x =0.9884 ± 0.01 corresponds to "a value in a predetermined range including the neutron irradiation amount for which the resistivity reaches the predetermined resistivity, which is obtained by using the calibration curve obtained in advance for each intrinsic condition".
[ Table 1]
Fig. 4 is a graph showing the measurement of the resistivity R2 in the diameter direction of the sample wafer shown in table 1 and fig. 3. The horizontal axis represents a position in the diameter direction in which the center of the wafer is expressed as 0mm, and the vertical axis represents the resistivity at each position.
As shown in fig. 4, the resistivity R2 after neutron irradiation shows an in-plane distribution with a low outer periphery and a high central portion due to the self-attenuation of the crystal. Therefore, when the target neutron irradiation amount (or the correction coefficient to the previous set value) is set using only the resistivity of the center portion of the crystal, there is a possibility that the region where the resistivity of the outer peripheral portion of the crystal is low falls below the lower limit of the standard. Therefore, it is desirable to measure 5 or more points on the diameter line in one wafer plane. In the case where the minimum value and the maximum value of the target neutron irradiation amount and the correction coefficient are denoted as Rmin and Rmax, respectively, it is desirable that the target neutron irradiation amount and the correction coefficient are set so as to satisfy a plurality of (Rmax + Rmin, desirably 5 or more)/2 < target resistivity < a plurality of (Rmax, desirably 5 or more). That is, the target resistivity is desirably set between the midpoint of the minimum value Rmin and the maximum value Rmax of the resistivity to the maximum value Rmax.
The right half of fig. 5 is a graph showing the actual resistivity (Rmax, x is Rmin) of the example in which the target neutron irradiation amount (here, the correction coefficient) is set to the optimal value every time based on the standard curve after the standard curve is obtained, the horizontal axis represents the time-series lot, and the vertical axis represents the resistivity and the correction coefficient. On the other hand, the left half of fig. 5 is a diagram showing the actual resistivity (≈ Rmax and × Rmin) of a comparative example in which the correction coefficient of the neutron irradiation amount at the next time is simply set based on the result of the actual resistivity with respect to the previous neutron irradiation amount without obtaining the standard curve. The horizontal axis represents time-series batches, and the vertical axis represents resistivity and a correction coefficient.
In the comparative example on the left half of fig. 5, the correction coefficient α is multiplied by the term of the neutron irradiation amount (Φ th × t) so that the absolute value of the Accuracy of the resistivity (Accuracy) becomes minimum, using the actual resistivity and the target resistivity at the time of irradiation with the previous neutron irradiation amount. However, if such a method is used, the neutron irradiation amount may be influenced by a variation in neutron irradiation amount including a temporal variation in neutron beam. As shown in the comparative example on the left half of fig. 5, in the first time series, although the correction coefficient is frequently changed, the variation in resistivity is not reduced thereafter. In contrast, in the right half example of fig. 5, the correction coefficient is changed based on the standard curve, and therefore the variation in resistivity after the change is small.
Description of the reference numerals
1 … silicon single crystal manufacturing apparatus
11 … Chamber 1
12 … Chamber 2
13 … gas inlet
14 … gas outlet
21 … Quartz crucible
22 … graphite crucible
23 … support shaft
24 … driving mechanism
25 … heater
26 … thermal insulation cylinder
27 … Heat shield Member
28 … bracket
31 … wire
32 … lifting mechanism
41 … magnetic field generating device
M … silicon melt
C … silicon single crystal
S … seed crystal
5 … neutron irradiation device
51 … core
52 … thermal neutron beam
53 … ingot container
I … ingot of a silicon single crystal.
Claims (4)
1. A method for producing a silicon single crystal by doping an ingot of a grown silicon single crystal with phosphorus while irradiating the ingot with neutrons under conditions specific to a specific neutron irradiation apparatus,
when calculating the target neutron irradiation amount for obtaining the predetermined resistivity,
under the intrinsic conditions, a plurality of neutron irradiations with different neutron irradiations are set for each silicon single crystal to irradiate neutrons,
measuring the resistivity of a plurality of the doped silicon single crystals obtained for each neutron irradiation amount,
obtaining in advance a calibration curve showing a relationship between the neutron irradiation amount and the resistivity from the plurality of neutron irradiation amounts and a plurality of resistivities measured for each of the neutron irradiation amounts, the calibration curve taking into consideration a deviation of the resistivity under the intrinsic condition,
and setting a value in a predetermined range including a neutron irradiation amount obtained by using the standard curve so that the resistivity reaches the predetermined resistivity as the target neutron irradiation amount.
2. The method for producing a neutron irradiated silicon single crystal according to claim 1, wherein the resistivity is measured at 5 or more locations on a diameter line measured in one wafer plane.
3. The method for producing a neutron irradiated silicon single crystal according to claim 1, wherein when a minimum value among the measured resistivities is denoted as Rmin and a maximum value is denoted as Rmax,
the target neutron irradiation amount is set so as to satisfy (Rmin + Rmax)/2 or more and the predetermined resistivity or less and Rmax.
4. The method for producing a neutron irradiated silicon single crystal according to claim 2, wherein when a minimum value among the measured resistivities is denoted as Rmin and a maximum value is denoted as Rmax,
the target neutron irradiation amount is set so as to satisfy (Rmin + Rmax)/2 or more and the predetermined resistivity or less and Rmax.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2016136622A JP6565810B2 (en) | 2016-07-11 | 2016-07-11 | Method for producing neutron irradiated silicon single crystal |
| JP2016-136622 | 2016-07-11 | ||
| PCT/JP2017/008459 WO2018012027A1 (en) | 2016-07-11 | 2017-03-03 | Method for producing neutron-irradiated silicon single crystal |
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| Publication Number | Publication Date |
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| CN109072477A CN109072477A (en) | 2018-12-21 |
| CN109072477B true CN109072477B (en) | 2021-12-14 |
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| CN201780027040.7A Active CN109072477B (en) | 2016-07-11 | 2017-03-03 | Method for producing neutron-irradiated silicon single crystal |
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|---|---|
| JP (1) | JP6565810B2 (en) |
| CN (1) | CN109072477B (en) |
| DE (1) | DE112017003487B4 (en) |
| WO (1) | WO2018012027A1 (en) |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2617320A1 (en) | 1976-04-21 | 1977-11-03 | Siemens Ag | Homogeneous phosphorus doping of silicon using thermal neutrons - calculating dosage using reactor-specific constant to increase accuracy |
| CN1010038B (en) * | 1988-03-26 | 1990-10-17 | 河北工学院 | Annealing process of vertically pulled silicon doped by neutron transmutation |
| JP2652110B2 (en) * | 1992-09-18 | 1997-09-10 | 信越半導体株式会社 | Irradiation defect removal method for neutron irradiated FZ silicon single crystal |
| JP2005035816A (en) * | 2003-07-17 | 2005-02-10 | Shin Etsu Handotai Co Ltd | Method for manufacturing silicon single crystal and silicon single crystal |
| JP2007176725A (en) * | 2005-12-27 | 2007-07-12 | Shin Etsu Handotai Co Ltd | Method for manufacturing neutron-irradiated silicon single crystal |
| JP5201077B2 (en) * | 2009-05-15 | 2013-06-05 | 株式会社Ｓｕｍｃｏ | Silicon wafer manufacturing method |
| CN102181926A (en) * | 2011-04-08 | 2011-09-14 | 光为绿色新能源有限公司 | Polycrystalline silicon ingot doping method and ingot casting equipment for implementing method |
| JP6015634B2 (en) * | 2013-11-22 | 2016-10-26 | 信越半導体株式会社 | Method for producing silicon single crystal |
-
2016
- 2016-07-11 JP JP2016136622A patent/JP6565810B2/en active Active
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2017
- 2017-03-03 DE DE112017003487.6T patent/DE112017003487B4/en active Active
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| Publication number | Publication date |
|---|---|
| DE112017003487T5 (en) | 2019-04-25 |
| CN109072477A (en) | 2018-12-21 |
| DE112017003487B4 (en) | 2023-10-26 |
| JP6565810B2 (en) | 2019-08-28 |
| WO2018012027A1 (en) | 2018-01-18 |
| JP2018008830A (en) | 2018-01-18 |
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