WO2020050146A1 - シリコン試料の炭素濃度評価方法、シリコンウェーハ製造工程の評価方法、シリコンウェーハの製造方法およびシリコン単結晶インゴットの製造方法 - Google Patents

シリコン試料の炭素濃度評価方法、シリコンウェーハ製造工程の評価方法、シリコンウェーハの製造方法およびシリコン単結晶インゴットの製造方法 Download PDF

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WO2020050146A1
WO2020050146A1 PCT/JP2019/034035 JP2019034035W WO2020050146A1 WO 2020050146 A1 WO2020050146 A1 WO 2020050146A1 JP 2019034035 W JP2019034035 W JP 2019034035W WO 2020050146 A1 WO2020050146 A1 WO 2020050146A1
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silicon
evaluation
carbon concentration
sample
evaluated
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English (en)
French (fr)
Japanese (ja)
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貴史 大戸
和隆 江里口
三次　伯知
佐俣　秀一
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株式会社Sumco
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Priority to CN201980057209.2A priority Critical patent/CN112640070B/zh
Priority to DE112019004412.5T priority patent/DE112019004412T5/de
Priority to KR1020217008292A priority patent/KR102513721B1/ko
Publication of WO2020050146A1 publication Critical patent/WO2020050146A1/ja

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
    • 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
    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • C30B15/20—Controlling or regulating
    • 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
    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/26—Testing of individual semiconductor devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere

Definitions

  • the present invention relates to a method for evaluating the carbon concentration of a silicon sample, a method for manufacturing a silicon wafer, a method for manufacturing a silicon wafer, and a method for manufacturing a silicon single crystal ingot.
  • Patent Document 1 In recent years, it has been studied to evaluate the carbon concentration of a silicon sample (for example, see Patent Document 1).
  • a silicon wafer used as a semiconductor substrate reduce impurity contamination that causes deterioration of device characteristics.
  • One object of one embodiment of the present invention is to provide a new method for evaluating the carbon concentration of a silicon sample.
  • One embodiment of the present invention provides Introducing hydrogen atoms into the silicon sample to be evaluated,
  • the evaluation target silicon sample into which the hydrogen atoms have been introduced is subjected to an evaluation by an evaluation method for evaluating a trap level in a silicon band gap, and Ec (conduction band) is included in the evaluation results obtained by the evaluation.
  • Ec conduction band
  • Including Further comprising performing a heat treatment of heating the silicon sample to be evaluated to a heating temperature in the range of 35 ° C. to 80 ° C. using a heating means between the introduction of the hydrogen atoms and the evaluation.
  • Evaluation method hereinafter also referred to as “carbon concentration evaluation method”
  • the temperature of the silicon sample surface may change.
  • the heating temperature relating to the heat treatment of the silicon sample refers to the maximum temperature of the surface of the silicon sample heated by the heat treatment.
  • the evaluation target silicon sample into which the hydrogen atoms have been introduced can be subjected to the evaluation without performing the electron beam irradiation treatment.
  • the carbon concentration of the silicon sample to be evaluated can be evaluated based on the evaluation result regarding the trap level density of Ec-0.15 eV among the evaluation results obtained by the above evaluation.
  • the introduction of the hydrogen atoms can be performed by immersing the silicon sample to be evaluated in a solution.
  • the solution may be a solution containing HF (hydrogen fluoride).
  • the evaluation method may be a DLTS method (Deep-Level ⁇ Transient ⁇ Spectroscopy).
  • a diode before the evaluation by the DLTS method, can be manufactured by forming a semiconductor junction and an ohmic layer on the silicon sample to be evaluated into which the hydrogen atoms have been introduced. It can be evaluated by the law.
  • the heat treatment can be performed before or after the diode is manufactured.
  • the heat treatment can be performed within 18 hours from the introduction of the hydrogen atoms.
  • One embodiment of the present invention provides Evaluating the carbon concentration of the silicon wafer manufactured in the silicon wafer manufacturing process to be evaluated by the above carbon concentration evaluation method, and evaluating the degree of carbon contamination in the silicon wafer manufacturing process to be evaluated based on the result of the above evaluation , (Hereinafter, also referred to as “manufacturing process evaluation method”). About.
  • One embodiment of the present invention provides Evaluating the silicon wafer manufacturing process by the above manufacturing process evaluation method, and, in the silicon wafer manufacturing process where the degree of carbon contamination is determined to be an allowable level as a result of the above evaluation, or as a result of the above evaluation, the degree of carbon contamination After performing a carbon contamination reduction process on a silicon wafer manufacturing process that is determined to exceed the allowable level, in this silicon wafer manufacturing process, manufacturing a silicon wafer, Including, a method of manufacturing a silicon wafer, About.
  • One embodiment of the present invention provides Growing silicon single crystal ingots, The carbon concentration of the silicon sample cut from the silicon single crystal ingot is evaluated by the carbon concentration evaluation method, Based on the results of the above evaluation, determine the production conditions of the silicon single crystal ingot, and, Growing a silicon single crystal ingot under determined manufacturing conditions, Including, a method for producing a silicon single crystal ingot, About.
  • a new method for evaluating the carbon concentration of a silicon sample can be provided.
  • a hydrogen atom is introduced into a silicon sample to be evaluated, and the silicon sample to be evaluated into which the hydrogen atom has been introduced is subjected to evaluation by an evaluation method for evaluating a trap level in a band gap of silicon. And among the evaluation results obtained by the above evaluation, the evaluation results regarding the density of at least one trap level selected from the group consisting of Ec-0.10 eV, Ec-0.13 eV and Ec-0.15 eV Evaluating the carbon concentration of the silicon sample to be evaluated based on the heating temperature of the silicon sample to be evaluated in a range of 35 ° C. to 80 ° C. using a heating means between the introduction of the hydrogen atoms and the evaluation.
  • the present invention relates to a method for evaluating the carbon concentration of a silicon sample, further comprising performing a heat treatment for heating the silicon sample.
  • the trap level of Ec By the introduction of hydrogen atoms performed in the carbon concentration evaluation method, the trap level of Ec can be formed in the band gap of silicon. In this way, it is possible to obtain an evaluation result regarding the density of trap levels of Ec. As an example of such an evaluation result, a peak intensity (DLTS signal intensity) obtained by the evaluation by the DLTS method can be cited. Details of this point will be described later.
  • the trap level of Ec in the band gap of silicon after the introduction of hydrogen atoms is a carbon-related level, and the density of this trap level correlates with the carbon concentration of the silicon sample.
  • the evaluation result regarding the trap level density of Ec obtained by the evaluation performed after the introduction of the hydrogen atom that is, the evaluation result correlated with the trap level density correlates with the carbon concentration of the silicon sample. Furthermore, as a result of intensive studies by the present inventors, subjecting the silicon sample to be evaluated after the introduction of hydrogen atoms to the above heat treatment contributes to increasing the density of trap levels of Ec evaluated by the above evaluation method. It was newly found to do. This is presumed to be due to the fact that the heat treatment promotes the formation of a complex that causes the trap level of Ec. As the density of trap levels increases, for example, in the DLTS method, the value of the measured DLTS signal intensity increases.
  • a value of the trap level density can be obtained as a higher density value for a silicon sample having a certain carbon concentration, even a trace amount of carbon can be detected and evaluated with high sensitivity. That is, it is considered that subjecting the silicon sample to be evaluated after the introduction of the hydrogen atoms to the above-described heat treatment contributes to an improvement in sensitivity of the carbon concentration evaluation.
  • the carbon concentration evaluation method will be described in more detail.
  • the silicon sample to be evaluated by the carbon concentration evaluation method can be, for example, a silicon sample cut out from a silicon single crystal ingot.
  • a sample obtained by further cutting a part of a sample cut into a wafer shape from a silicon single crystal ingot can be subjected to evaluation.
  • the silicon sample to be evaluated can be a silicon sample cut out from various silicon wafers (for example, a polished wafer, an epitaxial wafer, etc.) used as a semiconductor substrate.
  • the silicon wafer may be a silicon wafer that has been subjected to various processings (for example, polishing, etching, cleaning, etc.) that are usually performed on the silicon wafer.
  • the silicon sample may be n-type silicon or p-type silicon.
  • the resistivity of the silicon sample can be, for example, about 1 to 1000 ⁇ cm, but is not particularly limited.
  • the concentration of interstitial oxygen Oi of the silicon sample to be evaluated is not particularly limited.
  • the oxygen concentration of the silicon sample to be evaluated is, for example, 1.0 ⁇ 10 17 atoms / cm 3 or more (eg, 1.0 ⁇ 10 17 to 27.5 ⁇ 10 17 atoms / cm 3 ). it can.
  • the oxygen concentration here is a value measured by the FT-IR method (Fourier Transform Infrared Spectroscopy).
  • FT-IR method Frier Transform Infrared Spectroscopy
  • a silicon sample derived from a silicon single crystal grown by the Czochralski method (CZ method) usually contains oxygen.
  • Patent Document 1 Japanese Patent Application Laid-Open No.
  • the quantified carbon concentration depends on the oxygen concentration.
  • the conventionally proposed luminescence method requires electron beam irradiation. Therefore, in the luminescence method, the accuracy of the carbon concentration evaluation tends to decrease as the silicon sample has a higher oxygen concentration.
  • the carbon-related levels can be formed in an activated state without performing electron beam irradiation. As a result, the carbon concentration can be evaluated without depending on the oxygen concentration.
  • the carbon concentration of a silicon sample having a relatively high oxygen concentration for example, a silicon sample having an oxygen concentration in the above range can be evaluated with high accuracy.
  • do not perform electron beam irradiation treatment means not performing a process of actively irradiating an electron beam to a silicon sample, and is inevitable under sunlight, lighting, or the like. It is assumed that the electron beam irradiation occurring in the above is allowed.
  • An electron beam is a flow of electrons obtained by applying an accelerating voltage to electrons.
  • the electron beam irradiation treatment has problems in that the lead time is long, large-scale equipment is required, the cost is increased, and in addition to the electron beam irradiation step, the production of a protective oxide film and the like are required, and the number of steps is increased.
  • the carbon concentration of the silicon sample can be evaluated without performing the electron beam irradiation treatment.
  • the oxygen concentration of the silicon sample to be evaluated by the above carbon concentration evaluation method is not limited to the range exemplified above.
  • electron beam irradiation can be performed by a known method.
  • Hydrogen atoms are introduced into the silicon sample to be evaluated.
  • a trap level of Ec which is a carbon-related level
  • the introduction of hydrogen atoms may be performed by a dry process (dry process) or a wet process (wet process, that is, use of a solution).
  • introduction of hydrogen atoms by dry treatment can be performed by an ion implantation method, hydrogen plasma, or the like. Note that the introduction of a hydrogen atom in the present invention and the present specification includes an embodiment in which a hydrogen atom is introduced in an ion or plasma state.
  • the solution used here may be an acid solution or a base solution as long as the solution contains a hydrogen atom in any state such as an ionized state (ion) or a salt state.
  • the acid solution include a solution containing HF such as hydrofluoric acid (aqueous hydrofluoric acid), a mixed solution of hydrofluoric acid and nitric acid (hydrofluoric nitric acid), a mixed solution of sulfuric acid and hydrogen peroxide, and a mixed solution of hydrochloric acid and hydrogen peroxide.
  • HF hydrofluoric acid
  • hydrofluoric acid and nitric acid hydrofluoric acid
  • hydrofluoric nitric acid hydrofluoric acid
  • sulfuric acid and hydrogen peroxide a mixed solution of sulfuric acid and hydrogen peroxide
  • hydrochloric acid and hydrogen peroxide hydrochloric acid and hydrogen peroxide
  • the base solution examples include a sodium hydroxide solution, a potassium hydroxide solution, a mixed solution of aqueous ammonia and hydrogen peroxide, and the like.
  • the above-mentioned various solutions are preferably aqueous solutions (solutions containing water), and more preferably aqueous solutions.
  • the acid concentration of the acid solution and the base concentration of the base solution are not particularly limited.
  • the introduction of hydrogen atoms by hydrofluoric acid can be performed by immersing the silicon sample to be measured in 1 to 25% by mass hydrofluoric acid for 1 to 10 minutes.
  • the introduction of hydrogen atoms by hydrofluoric nitric acid involves measuring a silicon sample to be measured using hydrofluoric nitric acid (for example, nitric acid (aqueous nitric acid solution) having an HNO 3 concentration of 69% by mass and hydrofluoric acid (aqueous hydrofluoric acid solution having an HF concentration of 50% by mass). ) For 1 to 10 minutes. After the immersion, the sample to be measured may be subjected to post-treatment such as washing with water and drying as necessary.
  • hydrofluoric nitric acid for example, nitric acid (aqueous nitric acid solution) having an HNO 3 concentration of 69% by mass and hydrofluoric acid (aqueous hydrofluoric acid solution having an HF concentration of 50% by mass).
  • the silicon sample to be evaluated into which hydrogen atoms have been introduced is subjected to a heat treatment, which will be described in detail later, and then subjected to an evaluation by an evaluation method for evaluating a trap level in a band gap of silicon. Details of the heat treatment will be described later.
  • a trap level of Ec-0.10 eV, Ec-0.13 eV, or Ec-0.15 eV is used as the carbon-related level. It is considered that trap levels of Ec-0.10 eV, Ec-0.13 eV and Ec-0.15 eV are formed in an activated state which can be detected by various evaluation methods by introducing hydrogen atoms. It is presumed that the formation is promoted by the heat treatment. Thus, the carbon concentration can be evaluated based on the density of the trap levels (carbon-related levels). The evaluation of the trap level density can be performed by various evaluation methods capable of evaluating the trap level in the band gap of silicon.
  • Examples of such an evaluation method include a DLTS method, a lifetime method, an ICTS method (Isothermal Capacitance Transient Spectroscopy), a low-temperature photoluminescence (PL) method, a cathodoluminescence (CL) method, and the like.
  • ICTS method Isothermal Capacitance Transient Spectroscopy
  • PL low-temperature photoluminescence
  • CL cathodoluminescence
  • carbon concentration evaluation method since the trap level of Ec is formed in an activated state by the introduction of hydrogen atoms, the density of the trap level can be increased without performing the electron beam irradiation treatment. , It is possible to evaluate the carbon concentration.
  • Known techniques can be applied without any limitation to the measurement method using various evaluation methods.
  • the DLTS method is a preferable evaluation method from the viewpoint of enabling more sensitive carbon quantification.
  • Ec-0.10 eV, Ec-0.13 eV, or Ec-0.10 eV is obtained by fitting a DLTS spectrum obtained as the sum of each peak obtained by the DLTS method by a known method.
  • the DLTS spectrum of the trap level of 15 eV can be separated.
  • the trap level density of Ec-0.10 eV is a peak near 76 K
  • the trap level density of Ec-0.13 eV is a peak near 87 K
  • the trap level of Ec-0.15 eV is As for the potential density
  • the carbon concentration can be determined based on the peak intensity (DLTS signal intensity) of the peak near 101K.
  • the peak used to determine the carbon concentration is at least one of the above three peaks, and two or three peaks may be used. Normally, it can be determined that the higher the peak intensity value, the higher the carbon concentration. From the viewpoint of performing a more accurate carbon concentration evaluation, it is preferable to obtain the carbon concentration of the silicon sample to be evaluated based on the evaluation results at Ec-0.13 eV and / or Ec-0.15 eV.
  • the silicon sample to be evaluated is heated to a heating temperature in the range of 35 ° C. to 80 ° C. by using a heating means between the introduction of hydrogen atoms and the above evaluation. Processing is performed. Although the formation process and the annihilation process of the trap level of Ec are competing with each other, the silicon sample to be evaluated after the introduction of the hydrogen atoms is heated to a heating temperature in the above range by using a heating means, whereby the trap of Ec is trapped. It is presumed that the ability to promote the level formation process leads to an increase in the density of trap levels evaluated by the above evaluation method.
  • a heating means for example, a hot plate or the like can be used.
  • a silicon sample to be evaluated after introducing hydrogen atoms can be placed on a hot plate and heated to a heating temperature in the above temperature range.
  • the heating temperature for heating the silicon sample to be evaluated after the introduction of the hydrogen atoms is preferably 40 ° C. or higher from the viewpoint of further increasing the density of the trap level, and is preferably 70 ° C. or lower from the same viewpoint.
  • the atmosphere in which the heat treatment is performed is not particularly limited.
  • the heat treatment can be performed, for example, under an air atmosphere. Further, in the heat treatment, for example, in order to bring the surface temperature of the silicon sample to a desired maximum temperature, for example, the silicon sample to be evaluated after introducing hydrogen atoms is placed on a hot plate set to a predetermined temperature.
  • the silicon sample to be evaluated during the period from the introduction of the hydrogen atoms to the heat treatment and the period from the heat treatment to the evaluation can be placed, for example, in an air atmosphere at room temperature.
  • room temperature can be, for example, a temperature in the range of 15 ° C. to 30 ° C. It is thought that the trap levels of Ec-0.10 eV, Ec-0.13 eV, and Ec-0.15 eV are provided by a complex composed of carbon and hydrogen.
  • the diffusion of the hydrogen atoms follows the complementary error function.
  • the hydrogen atoms are distributed at a high concentration near the silicon sample surface.
  • the supply source of the hydrogen atoms is cut off after the introduction of the hydrogen atoms, it is assumed that the introduced hydrogen atoms diffuse into the silicon sample according to the Gaussian function in the silicon sample to be evaluated.
  • evaluation by various evaluation methods is usually performed on a region (measurement region) having a predetermined depth from the surface of the silicon sample to be evaluated. If the heat treatment is performed while more hydrogen atoms are present in the measurement region, the heat treatment will further promote the formation of the complex (that is, the formation of the trap level of Ec). Conceivable. In consideration of the above points and the diffusion rate of hydrogen atoms in silicon, the above heat treatment is preferably performed within 18 hours (that is, 18 hours or shorter) after the introduction of hydrogen atoms.
  • the evaluation is performed by the DLTS method.
  • a diode semiconductor junction (Schottky junction or pn junction) and an ohmic layer on a measurement sample obtained by cutting out a part of a silicon sample to be evaluated is measured ( DLTS measurement).
  • DLTS measurement a measurement sample obtained by cutting out a part of a silicon sample to be evaluated.
  • the surface of a sample subjected to DLTS measurement has high smoothness. Therefore, the silicon sample to be evaluated before the sample for measurement or the sample for measurement cut out from the silicon sample to be evaluated can be arbitrarily subjected to etching, polishing, or the like for improving the surface smoothness.
  • the etching is preferably mirror etching.
  • the polishing preferably includes a mirror polishing.
  • the silicon sample to be evaluated is a silicon single crystal ingot or a part of an ingot
  • the polishing process a known polishing process applied to a silicon wafer, such as a mirror polishing process, can be performed.
  • a silicon wafer is usually obtained through polishing such as mirror polishing. Therefore, when the silicon sample to be evaluated is a silicon wafer, the surface of the measurement sample cut from the silicon wafer usually has high smoothness without polishing.
  • the heat treatment can be performed before the diode is manufactured in one embodiment, and can be performed after the diode is manufactured in another embodiment. In one embodiment, the heat treatment can be performed before and after the diode is manufactured. As described above, in consideration of the diffusion of hydrogen atoms in silicon, the heat treatment can be performed while more hydrogen atoms are present in the measurement region close to the surface. It is considered that this further promotes the formation of the trap level of Ec. From this point, it is considered that performing the heat treatment before manufacturing the diode is preferable from the viewpoint of further promoting the formation of the trap level of Ec and increasing the trap level density.
  • DLTS measurement is usually performed by the following method.
  • a semiconductor junction Schottky junction or pn junction
  • pn junction Schottky junction or pn junction
  • the transient response of the capacitance (capacitance) of the sample element is measured by periodically applying a voltage while performing a temperature sweep.
  • the application of the voltage is usually performed by alternately and periodically applying a reverse voltage for forming a depletion layer and a pulse voltage for filling a trap level in the depletion layer with carriers.
  • the preferred position and width of the depletion layer formation region depend on the resistivity of the silicon sample.
  • the depletion layer can be formed, for example, with a width of about 1 to 50 ⁇ m, preferably about 1 to 10 ⁇ m, in a region with a depth of about 1 ⁇ m to 60 ⁇ m from the surface of the silicon sample to be evaluated. .
  • the thickness of the silicon sample to be evaluated can be, for example, about 100 to 1000 ⁇ m. However, it is not limited to this range.
  • the position (measurement depth) of the measurement region can be controlled by a reverse voltage applied to form a depletion layer. Further, the width of the formed depletion layer can also be controlled by the reverse voltage.
  • the carbon concentration based on the evaluation result regarding the density of at least one trap level selected from the group consisting of Ec-0.10 eV, Ec-0.13 eV and Ec-0.15 eV can be evaluated using a calibration curve or without a calibration curve.
  • the carbon concentration can be evaluated by a relative criterion for determining that the larger the value obtained as the evaluation result is, the higher the carbon concentration is. For example, it can be determined that the higher the value of the DLTS spectrum peak intensity (DLTS signal intensity), the higher the carbon concentration.
  • the calibration curve may be, for example, a correlation between the density of the trap level obtained from the evaluation result (eg, DLTS signal intensity) obtained for the silicon sample to be evaluated and the known carbon concentration. It is preferable to create a calibration curve as shown.
  • a relational expression for obtaining the density of trap levels from various evaluation results is known.
  • the above-mentioned known carbon concentration can be obtained by measuring by a method other than the evaluation method used for evaluating the silicon sample to be evaluated.
  • the known carbon concentration can be obtained by, for example, the SIMS method or the FT-IR method. Relational expressions for obtaining the carbon concentration from the evaluation results obtained by these methods are also known.
  • the silicon sample to be evaluated by the same evaluation method as the silicon sample to be evaluated to prepare the calibration curve (silicon sample for preparing the calibration curve) and the silicon sample for obtaining the known carbon concentration are the same silicon sample (for example, It is preferable that the sample is a silicon sample cut from the same ingot, the same wafer, or the like) or a silicon sample that has undergone the same manufacturing process. Regarding the preparation of the calibration curve, reference can also be made to paragraphs 0038 to 0040 of Patent Document 1 (JP-A-2017-191800). It is preferable that the silicon sample for preparing the calibration curve is a silicon sample that has been subjected to various processes such as a hydrogen atom introduction process and a heating process in the same manner as the silicon sample to be evaluated.
  • One aspect of the present invention is to evaluate the carbon concentration of a silicon wafer manufactured in a silicon wafer manufacturing process to be evaluated by the carbon concentration evaluation method, and in the silicon wafer manufacturing process to be evaluated based on the result of the evaluation.
  • the present invention relates to a method for evaluating a silicon wafer manufacturing process including evaluating a degree of carbon contamination.
  • one embodiment of the present invention is to evaluate a silicon wafer manufacturing process by the above-described method for evaluating a silicon wafer manufacturing process, and as a result of the evaluation, a silicon wafer manufacturing process in which the degree of carbon contamination is determined to be an allowable level.
  • a silicon wafer manufacturing process in which the degree of carbon contamination is determined to be an allowable level.
  • the silicon wafer manufacturing process to be evaluated in the above-described manufacturing process evaluation method can be a part of or the entire process of manufacturing a product silicon wafer.
  • the production process of a product silicon wafer is generally performed by cutting a wafer from a silicon single crystal ingot (slicing), surface treatment such as polishing and etching, a cleaning process, and a post-process (epitaxial layer) performed as necessary according to the use of the wafer. Formation, etc.). Each of these steps and each process is known.
  • carbon contamination may occur in the silicon wafer due to contact between the silicon wafer and members used in the manufacturing process.
  • degree of carbon contamination By assessing the degree of carbon contamination by evaluating the carbon concentration of the silicon wafers manufactured in the manufacturing process to be evaluated, the tendency of carbon contamination to occur in the product silicon wafer due to the silicon wafer manufacturing process to be evaluated is evaluated. You can figure out. That is, it can be determined that the higher the carbon concentration of the silicon wafer manufactured in the manufacturing process to be evaluated, the more likely it is that carbon contamination occurs in the manufacturing process to be evaluated.
  • the allowable level of the carbon concentration is set in advance, and if the carbon concentration obtained for the silicon wafer manufactured in the silicon wafer manufacturing process of the evaluation target exceeds the allowable level, the manufacturing process of the evaluation target is Therefore, it can be determined that carbon is not likely to be used in the production process of a product silicon wafer because of a high tendency to generate carbon contamination. It is preferable that the silicon wafer manufacturing process to be evaluated, which is determined as described above, be used for manufacturing a product silicon wafer after performing a carbon contamination reduction process. Details of this point will be further described later.
  • the carbon concentration of the silicon wafer manufactured in the silicon wafer manufacturing process to be evaluated is obtained by the above-described carbon concentration evaluation method according to one embodiment of the present invention.
  • the details of the carbon concentration evaluation method are as described in detail above.
  • the silicon wafer to be subjected to the carbon concentration evaluation is at least one silicon wafer manufactured in the silicon wafer manufacturing process to be evaluated, and may be two or more silicon wafers.
  • the carbon concentration of two or more silicon wafers is obtained, for example, the average value, the maximum value, and the like of the obtained carbon concentrations can be used for evaluating the silicon wafer manufacturing process to be evaluated.
  • the silicon wafer may be subjected to carbon concentration evaluation as it is, or a part thereof may be cut out and subjected to carbon concentration evaluation.
  • the average value, maximum value, and the like of the carbon concentrations obtained for the two or more samples are determined as the carbon concentration of the silicon wafer. be able to.
  • the silicon wafer manufacturing process is evaluated by the manufacturing process evaluation method, and as a result of the evaluation, the silicon wafer is manufactured in the silicon wafer manufacturing process in which the degree of carbon contamination is determined to be an allowable level. I do. This makes it possible to ship a high-quality silicon wafer having a low carbon contamination level as a product wafer.
  • a silicon wafer manufacturing process is evaluated by the manufacturing process evaluation method, and as a result of the evaluation, a silicon wafer manufacturing process in which the degree of carbon contamination is determined to exceed an allowable level is determined. After performing the carbon contamination reduction process in the process, a silicon wafer is manufactured in this silicon wafer manufacturing process.
  • the carbon contamination reduction processing includes replacement and cleaning of members included in a silicon wafer manufacturing process.
  • a susceptor made of SiC is used as a susceptor that is a member on which a silicon wafer is placed in a silicon wafer manufacturing process
  • a portion of a contact with the susceptor may be carbon-contaminated due to deterioration of a susceptor used repeatedly. .
  • carbon contamination caused by the susceptor can be reduced.
  • One embodiment of the present invention is to grow a silicon single crystal ingot, to evaluate the carbon concentration of a silicon sample cut out from the silicon single crystal ingot by the carbon concentration evaluation method, based on the result of the evaluation, silicon
  • the present invention relates to a method for manufacturing a silicon single crystal ingot, including determining manufacturing conditions for a single crystal ingot, and growing a silicon single crystal ingot under the determined manufacturing conditions.
  • the silicon single crystal ingot can be grown by a known method such as a CZ method (Czochralski method) and an FZ method (Floating Zone Melting method).
  • carbon may be mixed into a silicon single crystal ingot grown by the CZ method due to carbon mixed in the source polysilicon, CO gas generated during the growth, and the like. It is preferable to evaluate such a mixed carbon concentration and determine the manufacturing conditions based on the evaluation result in order to manufacture a silicon single crystal ingot in which the mixed carbon is suppressed. Therefore, the above-described method for evaluating the concentration of carbon according to one embodiment of the present invention is suitable as a method for evaluating the concentration of mixed carbon.
  • the number of silicon samples subjected to the carbon concentration evaluation is at least one, and may be two or more.
  • the carbon concentrations of two or more silicon samples are obtained, for example, the average value, the maximum value, and the like of the obtained carbon concentrations can be used for determining the manufacturing conditions of the silicon single crystal ingot. For example, if the obtained carbon concentration is at a predetermined allowable level, the silicon single crystal ingot is grown under the manufacturing conditions when the silicon single crystal ingot obtained by cutting out the silicon sample whose carbon concentration has been evaluated is grown.
  • a silicon single crystal ingot with less carbon contamination can be manufactured.
  • the carbon single crystal ingot is grown under the determined production conditions by adopting a means for reducing the carbon concentration, thereby reducing the carbon content. It is possible to manufacture a silicon single crystal ingot with less contamination.
  • means for reducing carbon contamination for example, one or more of the following means (1) to (3) can be adopted for the CZ method. Further, for example, for the FZ method, one or more of the following means (4) to (6) can be adopted. (1) Use a high-grade product with less carbon contamination as the raw material polysilicon.
  • a silicon single crystal ingot and a silicon wafer having a low carbon concentration can be provided.
  • a silicon single crystal pulling apparatus 10 shown in FIG. 1 includes a chamber 11, a support rotation shaft 12 penetrating vertically through a bottom center of the chamber 11, and a graphite susceptor fixed to an upper end of the support rotation shaft 12. 13, a quartz crucible 14 accommodated in the graphite susceptor 13, a heater 15 provided around the graphite susceptor 13, a support shaft drive mechanism 16 for raising and lowering and rotating the support rotation shaft 12, and a seed crystal.
  • a gas inlet 24 for introducing Ar gas into the chamber 11 is provided at an upper portion of the chamber 11. Ar gas is introduced into the chamber 11 from the gas inlet 24 through the gas pipe 25, and the amount of Ar gas is controlled by the conductance valve 26.
  • a gas outlet 27 for exhausting Ar gas in the chamber 11 is provided at the bottom of the chamber 11.
  • Ar gas in the sealed chamber 11 is discharged from the gas discharge port 27 to the outside via the exhaust gas pipe 28.
  • a conductance valve 29 and a vacuum pump 30 are provided in the middle of the exhaust gas pipe 28.
  • the Ar gas in the chamber 11 is sucked by the vacuum pump 30 and the flow rate is controlled by the conductance valve 29 to reduce the pressure in the chamber 11. The state is maintained.
  • a magnetic field supply device 31 for applying a magnetic field to the silicon melt 21 is provided outside the chamber 11.
  • the magnetic field supplied from the magnetic field supply device 31 may be a horizontal magnetic field or a cusp magnetic field.
  • a wafer-shaped sample was cut out from the silicon single crystal ingot grown in the above and processed into a silicon wafer by processing such as mirror polishing.
  • the resistivity was 10-13 ⁇ cm. From this silicon wafer, a silicon sample for SIMS measurement, a silicon sample for oxygen concentration measurement, and a plurality of silicon samples for DLTS measurement were obtained.
  • Carbon concentration measurement by SIMS method and oxygen concentration measurement by FT-IR method The carbon concentration of the above silicon sample for SIMS measurement was evaluated by SIMS method (raster change method). 14 atms / cm 3 .
  • the oxygen concentration of the silicon sample for oxygen concentration measurement determined by the FT-IR method was in the range of 2.0 ⁇ 10 17 to 12.0 ⁇ 10 17 atoms / cm 3 .
  • Example 1 to 3 and Comparative Examples 2 to 4 the produced diodes were placed on a hot plate set at a predetermined temperature for 60 minutes and subjected to the following heat treatment (D).
  • the plurality of silicon samples for DLTS measurement were subjected to heat treatment at different heating temperatures as heat treatment (D) below.
  • the heat treatment of the following (D) was performed within 18 hours after the treatment of the following (A).
  • Comparative Example 1 the following processes (A) to (C) were sequentially performed without performing the following process (D).
  • A immersed in hydrofluoric nitric acid (a mixed solution of nitric acid (aqueous nitric acid solution) having an HNO 3 concentration of 69% by mass and hydrofluoric acid (aqueous hydrofluoric acid solution) having an HF concentration of 50% by mass) for 5 minutes, and then washed with water for 10 minutes
  • B Schottky electrode (Au electrode) formation by vacuum evaporation
  • C Backside ohmic layer formation by gallium rubbing
  • D Arrangement on hot plate (heat treatment)
  • Example 1 to 3 and Comparative Examples 2 to 4 the surface of the silicon sample was applied to the diode Schottky junction after the treatment (D), and in Comparative Example 1, to the diode Schottky junction after the treatment (C). And a reverse voltage for forming a depletion layer having a width of 6 ⁇ m in a region having a depth of 2 ⁇ m and a pulse voltage for capturing carriers in the depletion layer were alternately and periodically applied. The transient response of the capacitance (capacitance) of the diode generated corresponding to the above voltage was measured. The above-described voltage application and capacitance measurement were performed while sweeping the sample temperature within a predetermined temperature range.
  • DLTS signal strength ⁇ C was plotted against temperature to obtain a DLTS spectrum.
  • the measurement frequency was 250 Hz.
  • the obtained DLTS spectrum was subjected to fitting processing (True shape fitting processing) using a program manufactured by SEMILAB, and separated into DLTS spectra having a trap level of Ec-0.15 eV (peak position: temperature 101 K). From the DLTS signal intensity at this peak position, the trap level density was determined by a known relational expression. Table 1 shows the trap level densities obtained for each heat treatment.
  • the trap level densities obtained in Examples 1 to 3 exceeded the value of the trap level density Nt in Comparative Example 1 in which the heat treatment using the heating means was not performed. On the other hand, no peak was detected in Comparative Examples 2 to 4 in which the heating process was performed at a heating temperature exceeding 80 ° C. using the heating means. Can be confirmed to have disappeared. From the above results, it can be confirmed that the heat treatment performed in Examples 1 to 3 can increase the trap state density. If the trap level density can be increased, the carbon concentration can be evaluated with higher sensitivity. An example of the carbon concentration evaluation is as follows.
  • a plurality of silicon single crystal ingots having different carbon concentrations are manufactured by changing at least one manufacturing condition selected from the group consisting of a raw material polysilicon grade, a pulling device, and a growing condition.
  • the silicon samples cut out from each silicon single crystal ingot were subjected to the above-described processes (A) to (D) and DLTS measurement similar to those in the above-described embodiment, and Ec-0.10 eV, Ec-0.13 eV and Ec For one or more trap levels selected from the group consisting of -0.15 eV, the DLTS signal strength at the peak position is determined.
  • the carbon concentration of the silicon sample can be evaluated by a relative criterion for determining that the larger the value of the DLTS signal strength thus obtained is, the higher the carbon concentration is.
  • the processes (A) to (D) and the DLTS measurement similar to those in the above embodiment are performed on a plurality of silicon samples having different carbon concentrations.
  • a calibration curve can be created. The calibration curve thus created can be used to evaluate the carbon concentration of a silicon sample whose carbon concentration is unknown.
  • the present invention is useful in the technical field of silicon single crystal ingots and silicon wafers.

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PCT/JP2019/034035 2018-09-03 2019-08-30 シリコン試料の炭素濃度評価方法、シリコンウェーハ製造工程の評価方法、シリコンウェーハの製造方法およびシリコン単結晶インゴットの製造方法 WO2020050146A1 (ja)

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