WO2024009705A1 - Method for manufacturing epitaxial wafer - Google Patents

Method for manufacturing epitaxial wafer Download PDF

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WO2024009705A1
WO2024009705A1 PCT/JP2023/021921 JP2023021921W WO2024009705A1 WO 2024009705 A1 WO2024009705 A1 WO 2024009705A1 JP 2023021921 W JP2023021921 W JP 2023021921W WO 2024009705 A1 WO2024009705 A1 WO 2024009705A1
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crystal silicon
oxide film
single crystal
epitaxial
manufacturing
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PCT/JP2023/021921
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French (fr)
Japanese (ja)
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克佳 鈴木
温 鈴木
剛 大槻
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信越半導体株式会社
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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
    • 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
    • H01L21/02—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 at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/20—Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy
    • 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
    • H01L21/02—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 at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/20—Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy
    • H01L21/2003—Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy characterised by the substrate
    • H01L21/2015—Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy characterised by the substrate the substrate being of crystalline semiconductor material, e.g. lattice adaptation, heteroepitaxy
    • 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
    • H01L21/02—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 at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/322—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to modify their internal properties, e.g. to produce internal imperfections

Definitions

  • the present invention relates to a method for manufacturing an epitaxial wafer.
  • Silicon substrates that form semiconductor devices such as solid-state image sensors and other transistors are required to have the function of gettering heavy metals and other elements that disrupt device characteristics.
  • gettering there are methods such as providing a polycrystalline silicon (Poly-Si) layer on the back surface of the silicon substrate, forming a damaged layer by blasting, using a silicon substrate with a high concentration of boron, and removing precipitates.
  • Various methods have been proposed and put into practical use, such as forming .
  • gettering by oxygen precipitation gettering is performed by incorporating a metal with a high ionization tendency (low electronegativity) against oxygen, which has high electronegativity.
  • proximity gettering in which a gettering layer is formed near the active region of the element, has been proposed.
  • a substrate in which silicon is epitaxially grown on a substrate into which carbon ions are implanted.
  • Gettering requires elements to diffuse to gettering sites (the energy of the entire system is lowered by bonding and clustering at sites rather than by metals existing as a single element).
  • the diffusion coefficient of metal elements contained in silicon differs depending on the element, and in consideration of the fact that metals cannot diffuse to the gettering site due to recent lower process temperatures, a method of proximity gettering has been proposed. .
  • oxygen can be used for proximity gettering, it is thought that the silicon substrate will have a very effective gettering layer.
  • the epitaxial wafer has an oxygen atomic layer in the middle of the epitaxial layer, metal impurities can be reliably gettered even in recent low-temperature processes.
  • Patent Document 1 is a method in which a thin layer of oxygen is formed on silicon and then silicon is further grown.
  • This method is a technology based on ALD ( ⁇ atomic layer deposition'').
  • ALD is a method in which molecules containing target atoms are adsorbed, and then unnecessary atoms (molecules) in the molecules are dissociated and released.It uses surface bonding, has very high precision, and has good reaction controllability. Yes, and widely used.
  • Patent Document 2 describes a method in which a natural oxide film is formed on a silicon clean surface formed by vacuum heating or the like, and then an oxide film or another substance is adsorbed and deposited.
  • Patent Documents 3 and 4 show that by introducing multiple oxygen atomic layers into a silicon substrate, it is possible to improve device characteristics and (mobility).
  • Patent Document 5 shows a method of forming an epitaxial layer using SiH 4 gas on an atomic layer having a thickness of 5 nm or less. Furthermore, a method of forming an oxygen atomic layer using oxygen gas is shown.
  • Patent Documents 6 and 7 describe a method of epitaxially growing single crystal silicon after forming an oxide film by bringing the surface of a semiconductor substrate into contact with an oxidizing gas or an oxidizing solution. Further, Patent Document 6 describes a method in which a silicon film forming gas is flowed after flowing an oxidizing gas.
  • Patent Document 8 describes a method in which a natural oxide film on the surface of a wafer made of group IV elements is removed, the wafer is oxidized to form an oxygen atomic layer, and then single crystal silicon is epitaxially grown.
  • Patent Document 9 describes a method in which a precursor containing oxygen is supplied to a CVD epitaxy furnace to form an oxygen-inserted monolayer, and then a silicon epitaxial layer is formed.
  • Non-Patent Document 1 shows a method of removing a natural oxide film with HF, oxidizing it in the atmosphere, forming an amorphous silicon film by low pressure CVD, and then forming single crystal silicon by crystallization heat treatment.
  • Japanese Patent Application Publication No. 2014-165494 Japanese Patent Application Publication No. 05-243266 US Patent No. 7,153,763 US Patent No. 7,265,002 JP2019-004050A Japanese Patent Application Publication No. 2008-263025 Japanese Patent Application Publication No. 2009-016637 JP 2021-111696 Publication JP2022-22194A
  • Patent Documents 5 and 9 have a problem in that it is necessary to prepare two chambers with separate exhaust systems in order to prevent SiH 4 and oxygen from reacting and exploding.
  • Patent Document 6 has a problem in that a special device with safety in mind is required to prevent the oxidizing gas and the silicon film-forming gas from reacting and exploding.
  • Non-Patent Document 1 requires heat treatment during crystallization, which has the problem of increasing the number of process steps. Furthermore, since amorphous silicon generally contains a large amount of hydrogen, there is a possibility that hydrogen-related defects may be formed during crystallization heat treatment.
  • Patent Document 8 has the problem that, in addition to requiring long-time oxidation to form an oxygen atomic layer, it is difficult to make the oxygen concentration uniform within the wafer surface.
  • the conventional technology has a problem in that there is no description for stably introducing an oxygen layer or specific description for forming an epitaxial layer of high quality single crystal silicon.
  • Patent Document 2 does not describe any method for forming an epitaxial layer of single crystal silicon on a wafer surface without generating dislocations or stacking faults.
  • Patent Documents 3 and 4 do not mention a specific method for growing a silicon wafer into which multiple oxygen atomic layers are introduced.
  • Patent Documents 6 and 7 do not describe a method for removing a natural oxide film before contacting with an oxidizing gas or an oxidizing solution.
  • the present invention has been made in view of the above-mentioned problems of the prior art, and is capable of stably and easily introducing an oxygen atomic layer into an epitaxial layer, as well as an epitaxial layer having a high-quality single-crystal silicon epitaxial layer.
  • An object of the present invention is to provide an epitaxial wafer manufacturing method that can manufacture wafers.
  • the present invention provides an epitaxial wafer manufacturing method for forming a single crystal silicon epitaxial layer on a single crystal silicon wafer, comprising: A process of removing a natural oxide film from the surface of a single crystal silicon wafer, After removing the natural oxide film, forming an oxide film on the surface of the single crystal silicon wafer using an oxidizing solution; After forming the oxide film, thinning the oxide film to form an oxygen atomic layer; and After forming the oxygen atomic layer, forming a single crystal on the surface of the single crystal silicon wafer having the oxygen atomic layer.
  • a method for manufacturing an epitaxial wafer is provided, which includes a step of epitaxially growing silicon.
  • single crystal silicon can be grown without forming dislocations or stacking faults on the surface of a single crystal silicon wafer having an oxygen atomic layer while leaving the oxygen atomic layer. That is, with the epitaxial wafer manufacturing method of the present invention, an oxygen atomic layer can be stably and easily introduced into an epitaxial layer, and an epitaxial wafer having a high-quality single-crystal silicon epitaxial layer can be manufactured.
  • the natural oxide film can be removed using a solution containing hydrofluoric acid.
  • an SC1 solution hydrogen peroxide solution, or ozone water can be used.
  • an oxide film can be easily formed in a short time.
  • the SC1 solution or the hydrogen peroxide solution can be used as the oxidizing solution, and the temperature of the SC1 solution or the hydrogen peroxide solution can be set to 20° C. or higher and 80° C. or lower.
  • single-crystal silicon wafers can be easily oxidized without the need for special equipment.
  • the ozone water can be used as the oxidizing solution, and the temperature of the ozone water can be set to 10°C or more and 30°C or less.
  • the wafer can be reliably oxidized.
  • the oxide film can be thinned by heating the single crystal silicon wafer in a hydrogen atmosphere.
  • the heating temperature in the hydrogen atmosphere can be set to 600° C. or higher and 1250° C. or lower.
  • the oxide film can be thinned by plasma using a gas containing hydrogen atoms or plasma using an inert gas.
  • the oxide film can be thinned by sputtering with high-energy particles generated by the plasma.
  • the single crystal silicon in the step of epitaxially growing the single crystal silicon, can be epitaxially grown at a temperature of 450° C. or higher and 800° C. or lower.
  • the partial pressure of the silicon source gas can be set to 0.1 Pa or more and 2000 Pa or less.
  • single crystal silicon can be epitaxially grown more stably without generating defects.
  • planar concentration of oxygen in the oxygen atomic layer can be 6 ⁇ 10 14 atoms/cm 2 or less.
  • epitaxial wafers can be stably manufactured without generating defects.
  • the steps of forming the oxide film, forming the oxygen atomic layer, and epitaxially growing the single crystal silicon can be repeated.
  • an oxygen atomic layer can be stably and easily introduced into the epitaxial layer, and an epitaxial layer of high-quality single crystal silicon can be introduced into the epitaxial layer. It is possible to provide a method for manufacturing an epitaxial wafer having the following. Furthermore, it becomes possible to manufacture a proximity gettering substrate having a proximity gettering effect due to the oxygen atomic layer.
  • FIG. 2 is a diagram showing a flow of the method for manufacturing an epitaxial wafer of the present invention.
  • 1 is a schematic cross-sectional view of an example of an epitaxial wafer that can be manufactured by the method for manufacturing an epitaxial wafer of the present invention. It is a schematic sectional view of another example of an epitaxial wafer which can be manufactured by the manufacturing method of an epitaxial wafer of the present invention.
  • 2 is a graph showing the relationship between heating time and oxygen concentration in a hydrogen atmosphere in Example 1 and Comparative Example 1.
  • 2 is a graph showing the distribution of oxygen concentration in an oxygen atomic layer within the plane of a substrate in Example 1 and Comparative Example 2.
  • an epitaxial wafer that does not require special equipment or complicated processes, can stably and easily introduce an oxygen atomic layer into an epitaxial layer, and has an epitaxial layer of high-quality single crystal silicon.
  • the present inventor has devised a method for manufacturing an epitaxial wafer in which a single crystal silicon epitaxial layer is formed on a single crystal silicon wafer, in which a natural oxide film is removed from the surface of the single crystal silicon wafer. After removing the natural oxide film, forming an oxide film on the surface of the single crystal silicon wafer using an oxidizing solution; After forming the oxide film, thinning the oxide film to form an oxygen atomic layer. and after forming the oxygen atomic layer, epitaxially growing single crystal silicon on the surface of the single crystal silicon wafer having the oxygen atomic layer.
  • the present invention has been completed by discovering that it is possible to stably and easily introduce an oxygen atomic layer into an epitaxial layer of silicon without forming dislocations or stacking faults on the epitaxial layer.
  • the present invention is an epitaxial wafer manufacturing method for forming a single-crystal silicon epitaxial layer on a single-crystal silicon wafer, comprising: A process of removing a natural oxide film from the surface of a single crystal silicon wafer, After removing the natural oxide film, forming an oxide film on the surface of the single crystal silicon wafer using an oxidizing solution; After forming the oxide film, thinning the oxide film to form an oxygen atomic layer; and After forming the oxygen atomic layer, forming a single crystal on the surface of the single crystal silicon wafer having the oxygen atomic layer.
  • This is a method for manufacturing an epitaxial wafer, characterized by including a step of epitaxially growing silicon.
  • an epitaxial wafer 10A whose cross section is schematically shown in FIG. 2, for example, can be manufactured.
  • the epitaxial wafer that can be manufactured by the epitaxial wafer manufacturing method of the present invention is not limited to that shown in FIG. 2.
  • the epitaxial wafer 10A shown in FIG. 2 has a single crystal epitaxial silicon layer (hereinafter sometimes simply referred to as an epitaxial layer) 3 on a single crystal silicon wafer 1, and has a single crystal epitaxial silicon layer 3 and a single crystal silicon wafer 1. There is an oxygen atomic layer 2 between them.
  • FIG. 1 shows the flow of the method for manufacturing an epitaxial wafer according to the present invention.
  • the step S11 in FIG. 1 is a step of preparing a single crystal silicon wafer.
  • the method for manufacturing the single crystal silicon wafer is not particularly limited.
  • a substrate manufactured by the Czochralski Method (hereinafter referred to as the CZ method) may be used, or a substrate manufactured by the Floating Zone Method (hereinafter referred to as the FZ method) may be used.
  • a substrate in which single crystal silicon is epitaxially grown on a single crystal silicon substrate manufactured by the CZ method or the FZ method may be used.
  • S12 in FIG. 1 is a step of removing a natural oxide film from the surface of the single crystal silicon wafer prepared in step S11.
  • the natural oxide film can be removed using a solution containing hydrofluoric acid.
  • hydrofluoric acid or buffered hydrofluoric acid may be used.
  • Buffered hydrofluoric acid is a solution containing hydrofluoric acid and ammonium fluoride.
  • the concentration of hydrofluoric acid in the solution containing hydrofluoric acid may be any concentration that can remove the native oxide film, and may be, for example, 0.001% or more and 60% or less.
  • the temperature of the solution containing hydrofluoric acid can be, for example, 10°C or higher and 50°C or lower. When the temperature is 10° C. or higher, it is possible to prevent dew condensation from forming on the wafer after processing with a solution containing hydrofluoric acid. Further, by setting the temperature to 50° C. or lower, the amount of hydrofluoric acid that evaporates can be suppressed, and safety problems can be avoided.
  • the time for cleaning with a solution containing hydrofluoric acid can be, for example, until water repellency is confirmed, and can be, for example, 1 second or more and 1 hour or less. If the time is 1 second or more, the natural oxide film can be removed. Further, by setting the time to 1 hour or less, it is possible to prevent it from taking too much time.
  • a batch type cleaning device or a single wafer type cleaning device may be used.
  • the natural oxide film may be removed using vapor of a solution containing hydrofluoric acid.
  • S13 in FIG. 1 is a step of forming an oxide film on the surface of the single crystal silicon wafer using an oxidizing solution after removing the natural oxide film in step S12.
  • a hydrophobic surface without an oxide film tends to attract particles, but a hydrophilic surface with an oxide film can prevent particles from adhering. For this reason, for example, by immersing a single crystal silicon wafer in an oxidizing solution to form an oxide film on the surface, particles can be prevented from adhering to the single crystal silicon wafer before it is transported from the cleaning equipment to the next process. It can be prevented.
  • a batch type device or a single wafer type device may be used, for example.
  • oxidizing solution for example, SC1 solution, hydrogen peroxide solution, or ozone water can be used.
  • an oxide film can be easily formed in a short time.
  • the SC1 solution is a solution that is a mixture of ammonia, hydrogen peroxide, and water, and the hydrogen peroxide solution oxidizes the surface of a single-crystal silicon wafer, while the ammonia etches the oxide film. With this, particles attached to the surface of the single crystal silicon wafer can be lifted off and removed. Therefore, by using the SC1 solution used in the cleaning process of single crystal silicon substrates, an oxide film is formed on the surface of the single crystal silicon wafer.
  • the mixing ratio between each component in the SC1 solution it is preferable that the amount of hydrogen peroxide solution is larger than that of aqueous ammonia. With such a mixing ratio, an oxide film can be formed stably and uniformly.
  • the mixing ratio of aqueous ammonia (NH 3 concentration: 28%), hydrogen peroxide solution (H 2 O 2 concentration: 30%), and water can be 1:1 to 2:5 to 100.
  • the time for immersing the single crystal silicon wafer in the SC1 solution can be, for example, 1 second or more and 1 hour or less. If the heating time is 1 second or more, an oxygen atomic layer can be sufficiently formed. Further, by setting the time to 1 hour or less, it is possible to prevent it from taking too much time.
  • the concentration of the hydrogen peroxide solution can be set to 0.01% or more and 30% or less, for example. If the concentration is 0.01% or more, an oxide film can be reliably formed. Further, if the concentration is 30% or less, the amount of evaporation of hydrogen peroxide from the cleaning liquid can be maintained at an appropriate level, so that an increase in the burden on the disposal equipment can be prevented.
  • the time for immersing the single crystal silicon wafer in the hydrogen peroxide solution can be, for example, 1 second or more and 1 hour or less. If the time is 1 second or more, an oxygen atomic layer can be formed. Further, by setting the time to 1 hour or less, it is possible to prevent it from taking too much time.
  • the temperature of the SC1 solution or the hydrogen peroxide solution as the oxidizing solution can be, for example, 20°C or higher and 80°C or lower. If the temperature is 20° C. or higher, an oxide film can be stably formed. Further, if the temperature is 80° C. or lower, the amount of evaporation of the cleaning liquid can be kept constant and bubbles can be prevented from increasing in the cleaning liquid, so that an oxide film can be formed uniformly within the wafer surface. That is, at such a temperature, a single crystal silicon wafer can be easily oxidized without preparing special equipment.
  • ozone water is used to decompose organic matter and oxidize the surface of the single crystal silicon wafer.
  • the ozone concentration of the ozone water can be, for example, 1 ppm or more and 500 ppm or less.
  • the ozone concentration is 1 ppm or more, an oxide film can be stably formed on the surface of the single crystal silicon wafer.
  • the ozone concentration is 500 ppm or less, it is possible to prevent variations in the oxide film thickness due to fluctuations in the ozone concentration due to ozone decomposition or escape into the gas phase.
  • the temperature of the ozone water can be, for example, 10°C or higher and 30°C or lower.
  • the temperature can be, for example, 10°C or higher and 30°C or lower.
  • 10° C. or higher it is possible to prevent dew condensation from occurring on the wafer after the ozone water treatment.
  • the temperature to 30° C. or lower, it is possible to prevent ozone from decomposing in ozone water or from escaping into the gas phase, thereby making it possible to reliably oxidize the single crystal silicon wafer.
  • the time for immersing the single crystal silicon wafer in ozone water can be, for example, 1 second or more and 1 hour or less. If the time is 1 second or more, an oxygen atomic layer can be formed. Further, by setting the time to 1 hour or less, it is possible to prevent it from taking too much time.
  • S14 in FIG. 1 is a step in which, after forming the oxide film in step S13, the oxide film is thinned to form an oxygen atomic layer.
  • the oxide film can be thinned, for example, by heating a single crystal silicon wafer in a hydrogen atmosphere. By performing heat treatment in a hydrogen atmosphere in this manner, the oxide film can be reduced uniformly and stably, thereby making it possible to reduce the thickness of the oxide film.
  • Heating may be performed in an atmospheric pressure environment or in a reduced pressure environment.
  • the reduced pressure environment refers to, for example, an environment of 100 Pa or more and less than atmospheric pressure.
  • the hydrogen atmosphere for example, an atmosphere containing 100% hydrogen may be used, or an atmosphere containing a mixture of hydrogen and an inert gas may be used.
  • the inert gas any one of nitrogen, helium, neon, argon, krypton, and xenon can be used.
  • the heating temperature can be, for example, 600°C or higher and 1250°C or lower.
  • the oxide film can be reliably reduced and made thinner.
  • a general-purpose heating device can be used.
  • the heating time can be, for example, 1 second or more and 1 hour or less. If the time is 1 second or more, the oxide film can be reduced and made thinner. Further, by setting the time to 1 hour or less, it is possible to prevent it from taking too much time.
  • the above pressure, heating temperature, and heating time can be changed depending on the thickness of the oxide film.
  • the oxide film When the oxide film is thick, the oxide film can be made thinner and an oxygen atomic layer can be formed by increasing the pressure, temperature, or lengthening the heating time.
  • the oxide film When the oxide film is thin, the oxide film can be completely removed and the oxygen atomic layer can be prevented from disappearing by lowering the pressure, lowering the temperature, or shortening the heating time.
  • Heating of the single crystal silicon wafer in a hydrogen atmosphere may be performed in a heat treatment furnace or in a single crystal silicon film forming apparatus.
  • the heating device may be a batch type or a single wafer type.
  • the thinning of the oxide film in step S14 can be performed by plasma using a gas containing hydrogen atoms or plasma using an inert gas.
  • a gas containing hydrogen atoms for example, hydrogen molecules, ammonia, nitrogen, argon, helium, neon, krypton, or xenon can be used. These gases may be used in combination.
  • hydrogen radicals generated by plasma can stably reduce the oxide film at low temperatures and make it thin.
  • the oxide film can be thinned by sputtering with high-energy particles generated by plasma.
  • the oxide film when the oxide film is thinned using the plasma, it may be performed at room temperature or may be performed by heating.
  • the time for exposing the single crystal silicon wafer to plasma depends on the plasma density, ion energy, etc., but by setting it to, for example, 1 second or more and 30 minutes or less, the oxide film can be stably thinned.
  • the time of exposure to plasma can be changed depending on the thickness of the oxide film.
  • the oxide film can be made thinner to form an oxygen atomic layer by increasing the plasma exposure time.
  • the oxide film is thin, by shortening the time of exposure to plasma, it is possible to prevent the oxide film from being completely removed and the oxygen atomic layer disappearing.
  • S15 in FIG. 1 is a step of epitaxially growing single crystal silicon on the surface of the single crystal silicon wafer having the oxygen atomic layer after forming the oxygen atomic layer in step S14.
  • monosilane and disilane can be used as the gas used for epitaxial growth.
  • Nitrogen and hydrogen may also be used as carrier gases.
  • the pressure in the chamber may be any pressure that does not cause a gas phase reaction.
  • a batch type or a single wafer type may be used as the epitaxial growth apparatus.
  • epitaxial growth of single crystal silicon can be performed at a temperature of, for example, 450° C. or higher and 800° C. or lower.
  • a temperature of, for example, 450° C. or higher and 800° C. or lower.
  • the film formation time can be adjusted to adjust the thickness of the epitaxial layer. Furthermore, when forming a film at a high temperature, by shortening the film forming time, it is possible to prevent oxygen from diffusing outward from the single crystal silicon wafer and reducing the heat resistance of the oxygen atomic layer.
  • epitaxial growth of single-crystal silicon can be performed, for example, with the partial pressure of the silicon source gas set to 0.1 Pa or more and 2000 Pa or less. Within this pressure range, single crystal silicon can be more stably formed without generating dislocations or stacking faults on the oxygen atomic layer.
  • step S14 of forming an oxygen atomic layer by setting the plane concentration of oxygen in the oxygen atomic layer to 6 ⁇ 10 14 atoms/cm 2 or less, no defects are formed in the epitaxial layer. This is because the crystallinity of the single crystal silicon wafer is maintained when the amount of oxidation (planar concentration of oxygen in the oxygen atomic layer) is small. Therefore, there is no lower limit to the plane concentration of oxygen, and it is sufficient that it is greater than 0. If the plane concentration of oxygen in the oxygen atomic layer is 6 ⁇ 10 14 atoms/cm 2 or less, defects caused by the oxygen atomic layer can be prevented from being formed in the epitaxial layer, and if the epitaxial layer is polycrystalline. It can prevent it from becoming silicon or amorphous silicon.
  • the planar concentration of oxygen can be measured by SIMS (Secondary Ion Mass Spectrometry).
  • SIMS Secondary Ion Mass Spectrometry
  • a peak is formed at the depth where the oxide layer is formed.
  • the planar concentration can be determined by integrating the product of the volume concentration and depth obtained by one sputtering process near the peak.
  • an epitaxial wafer 10A as shown in FIG. 2, for example, can be obtained.
  • an oxide film is formed on a single crystal silicon wafer 1 as described above, the oxide film is thinned to form an oxygen atomic layer 2, and then single crystal silicon is epitaxially grown. By doing so, a uniform oxygen atomic layer 2 can be formed within the wafer surface. This is because the oxidation rate in single-crystal silicon slows down due to the growth of the oxide film, so the thickness of the oxide film is easier to control than the oxygen atomic layer 2, and the thinning of the oxide film is easier than the oxidation process. This is thought to be because it is easier to control as it progresses slowly.
  • step S15 of epitaxially growing single-crystal silicon repeating step S13 of forming an oxide film, step S14 of forming oxygen atomic layer 2, and step S15 of epitaxially growing single-crystal silicon, for example, as shown in FIG.
  • a plurality of oxygen atomic layers 2 can be formed. That is, according to the method for manufacturing an epitaxial wafer according to this aspect, an epitaxial wafer 10B shown in FIG. 3 is obtained in which oxygen atomic layers 2 and single-crystal epitaxial silicon layers 3 are alternately and repeatedly stacked on a single-crystal silicon wafer 1. be able to.
  • the top surface of the epitaxial wafer 10B in FIG. 3 is a single-crystal epitaxial silicon layer 3.
  • the gettering effect can be enhanced more than when a single oxygen atomic layer 2 is formed.
  • the method for manufacturing an epitaxial wafer of the present invention as described above is a highly versatile method that does not require any special equipment, and also allows stable and simple formation of an oxygen atomic layer for proximity gettering. It is possible to form a high-quality epitaxial layer, and a high-quality epitaxial wafer can be obtained.
  • Example 1 and Comparative Example 1 The conductivity type, diameter, crystal plane orientation, and oxygen concentration of the prepared single crystal silicon wafer are as follows. Wafer conductivity type: p type Diameter: 300mm Crystal plane orientation: (100) Oxygen concentration: 14ppma (JEITA)
  • the single-crystal silicon wafer was subjected to hydrofluoric acid cleaning using a batch-type cleaning apparatus, and then rinsed with pure water.
  • the single crystal silicon wafer was immersed in the SC1 solution using a batch type apparatus.
  • the SC1 solution prepared at this time had a mixing ratio of aqueous ammonia (NH 3 concentration 28%): hydrogen peroxide solution (H 2 O 2 concentration 30%): water of 1:1:10, and the temperature of the solution was 70°C. And so.
  • the immersion time in the SC1 solution was 3 minutes. Thereafter, the single crystal silicon wafer was rinsed with pure water.
  • Example 1 the single crystal silicon wafer with the oxide film formed thereon was transported into an epitaxial growth apparatus.
  • Example 1 the oxide film was thinned by heating in a hydrogen atmosphere to form an oxygen atomic layer.
  • the heating temperature was 700° C.
  • Example 1 the heating time was 20 to 600 seconds.
  • Comparative Example 1 the oxide film was not thinned by heating in a hydrogen atmosphere. That is, the heating time in Comparative Example 1 in a hydrogen atmosphere was 0 seconds.
  • monocrystalline silicon was epitaxially grown using monosilane on the surface of the single-crystal silicon wafer on which the oxygen atomic layer had been formed.
  • the temperature was 700° C.
  • the partial pressure of monosilane was 60 Pa
  • the film thickness was 100 nm.
  • hydrogen was used as the carrier gas. In this way, epitaxial wafers were manufactured in each of Example 1 and Comparative Example 1.
  • Example 1 the formation of the oxygen atomic layer and the epitaxial growth of single crystal silicon were performed in the same chamber.
  • Comparative Example 1 single crystal silicon was epitaxially grown without thinning the oxide film by heating in a hydrogen atmosphere.
  • Example 1 Furthermore, the results of measuring the oxygen concentration within the plane of the substrate when the heating time in Example 1 was 20 seconds are shown by black circles in FIG. From FIG. 5, it can be seen that in Example 1, the oxygen atomic layer could be formed uniformly within the plane.
  • Example 1 As a result of measuring defects with a size of 100 nm or more on the epitaxial wafers manufactured in Example 1 and Comparative Example 1 using SurfScan SP5 manufactured by KLA-Tencor, it was found that the oxide film was thinned by heating in a hydrogen atmosphere. In Comparative Example 1, in which heating was not performed, the number of defects reached the measurement upper limit (approximately 20,000), but in Example 1, in which heating was performed in a hydrogen atmosphere, no defects were present. In the case of , the number was 27 or less, indicating that a single crystal silicon epitaxial layer could be formed on the oxygen atomic layer without generating defects.
  • Comparative Example 2 In Comparative Example 2, first, the same single crystal silicon substrate as in Example 1 and Comparative Example 1 was prepared. Next, in order to remove the natural oxide film from the surface of the prepared single-crystal silicon wafer, the single-crystal silicon wafer was subjected to hydrofluoric acid cleaning using a batch-type cleaning device, followed by deionized water rinsing, and then hydrogen Heated in atmosphere. The heating temperature was 1150° C. and the heating time was 1 minute.
  • Example 2 Under the same conditions as in Example 1 and Comparative Example 1, single crystal silicon was epitaxially grown on the surface of the single crystal silicon wafer on which the oxygen atomic layer was formed. In this manner, an epitaxial wafer was manufactured in Comparative Example 2.
  • Example 1 which is an example of the present invention
  • the oxygen atomic layer is more stable in the epitaxial layer than in Comparative Example 2, in which neither oxide film formation using an oxidizing solution nor thinning of the oxide film was performed.
  • a method for manufacturing an epitaxial wafer in which a single-crystal silicon epitaxial layer is formed on a single-crystal silicon wafer the step of removing a natural oxide film from the surface of the single-crystal silicon wafer; a step of forming an oxide film on the surface of a crystalline silicon wafer using an oxidizing solution; a step of thinning the oxide film to form an oxygen atomic layer after forming the oxide film; and a step of forming an oxygen atomic layer after forming the oxygen atomic layer.
  • a method for manufacturing an epitaxial wafer comprising the step of epitaxially growing single crystal silicon on the surface of the single crystal silicon wafer having the oxygen atomic layer.
  • [5] The method for manufacturing an epitaxial wafer according to [3], characterized in that the ozone water is used as the oxidizing solution, and the temperature of the ozone water is 10°C or more and 30°C or less.
  • [6] The method for producing an epitaxial wafer according to any one of [1] to [5], wherein the oxide film is thinned by heating the single crystal silicon wafer in a hydrogen atmosphere.
  • [7] The method for producing an epitaxial wafer according to [6], wherein the heating temperature in the hydrogen atmosphere is 600°C or higher and 1250°C or lower.

Abstract

The present invention provides a method for manufacturing an epitaxial wafer in which a single crystal silicon epitaxial layer is formed on a single crystal silicon wafer, the method being characterized by comprising: a step for removing a natural oxide film from the surface of the single crystal silicon wafer; a step for forming an oxide film on the surface of the single crystal silicon wafer by using an oxidizing solution after the step for removing the natural oxide film; a step for forming an oxygen atomic layer by thinning the oxide film after forming the oxide film; and a step for epitaxially growing single crystal silicon on the surface of the single crystal silicon wafer having the oxygen atomic layer after forming the oxygen atomic layer. Thereby, it is possible to provide a method for manufacturing an epitaxial wafer that can stably and easily introduce an oxygen atomic layer into an epitaxial layer and that can manufacture an epitaxial wafer having a high-quality single crystal silicon epitaxial layer.

Description

エピタキシャルウェーハの製造方法Epitaxial wafer manufacturing method
　本発明は、エピタキシャルウェーハの製造方法に関する。 The present invention relates to a method for manufacturing an epitaxial wafer.
　固体撮像素子やその他のトランジスタをはじめとした半導体素子を形成するシリコン基板には、重金属をはじめとした素子特性を狂わせる元素をゲッタリングする機能を持つことが求められる。ゲッタリングにはシリコン基板裏面に多結晶シリコン（Ｐｏｌｙ－Ｓｉ）層を持たせたり、ブラスト加工によりダメージを持たせた層を形成する方法や、高濃度ボロンのシリコン基板を利用したり、析出物を形成させたりとさまざまな手法が提案及び実用化されている。酸素析出によるゲッタリングでは、電気陰性度が大きい酸素に対して、イオン化傾向が大きい（電気陰性度が小さい）金属を取り込むことでゲッタリングする。 Silicon substrates that form semiconductor devices such as solid-state image sensors and other transistors are required to have the function of gettering heavy metals and other elements that disrupt device characteristics. For gettering, there are methods such as providing a polycrystalline silicon (Poly-Si) layer on the back surface of the silicon substrate, forming a damaged layer by blasting, using a silicon substrate with a high concentration of boron, and removing precipitates. Various methods have been proposed and put into practical use, such as forming . In gettering by oxygen precipitation, gettering is performed by incorporating a metal with a high ionization tendency (low electronegativity) against oxygen, which has high electronegativity.
　また、素子の活性領域近傍にゲッタリング層を形成する、いわゆる近接ゲッタリングも提案されている。例えば、炭素をイオン注入した基板の上にシリコンをエピタキシャル成長させた基板などがある。ゲッタリングでは、ゲッタリングサイト（金属が単元素で存在するよりもサイトで結合やクラスタリングすることで系全体のエネルギーが低下する）まで元素が拡散する必要がある。シリコン中に含まれる金属元素の拡散係数は元素により異なり、また近年のプロセス低温化によりゲッタリングサイトまで金属が拡散することが出来なくなることを考慮して、近接ゲッタリングの手法が提案されている。 Also, so-called proximity gettering, in which a gettering layer is formed near the active region of the element, has been proposed. For example, there is a substrate in which silicon is epitaxially grown on a substrate into which carbon ions are implanted. Gettering requires elements to diffuse to gettering sites (the energy of the entire system is lowered by bonding and clustering at sites rather than by metals existing as a single element). The diffusion coefficient of metal elements contained in silicon differs depending on the element, and in consideration of the fact that metals cannot diffuse to the gettering site due to recent lower process temperatures, a method of proximity gettering has been proposed. .
　近接ゲッタリングに酸素を用いることが出来れば、非常に有力なゲッタリング層をもったシリコン基板となると考えられる。特に、エピタキシャル層の途中に酸素原子層を有するエピタキシャルウェーハであれば、近年の低温プロセスにおいても確実に金属不純物をゲッタリングすることができる。 If oxygen can be used for proximity gettering, it is thought that the silicon substrate will have a very effective gettering layer. In particular, if the epitaxial wafer has an oxygen atomic layer in the middle of the epitaxial layer, metal impurities can be reliably gettered even in recent low-temperature processes.
　以上、金属不純物をゲッタリングすることを中心に述べてきたが、例えば、酸素の効果としては、ＣＶＤ酸化膜を裏面に形成することでエピタキシャル成長時のオートドープを防ぐ効果が知られている。 The above discussion has focused on gettering metal impurities, but for example, oxygen is known to have the effect of preventing autodoping during epitaxial growth by forming a CVD oxide film on the back surface.
　先行技術について言及する。特許文献１は、構造としてはシリコンの上に酸素の薄い層を形成しさらにシリコンを成長させる方法である。この方法は、ＡＬＤ（「Ａｔｏｍｉｃ　ｌａｙｅｒ　ｄｅｐｏｓｉｔｉｏｎ」、「原子層堆積法」）をベースとした技術である。ＡＬＤは対象原子を含む分子を吸着させ、その後分子中の不要な原子（分子）を解離・脱離させる方法であり、表面結合を利用し、非常に精度よく、また、反応制御性が良好であり、幅広く用いられている。 Refer to prior art. Patent Document 1 is a method in which a thin layer of oxygen is formed on silicon and then silicon is further grown. This method is a technology based on ALD (``atomic layer deposition''). ALD is a method in which molecules containing target atoms are adsorbed, and then unnecessary atoms (molecules) in the molecules are dissociated and released.It uses surface bonding, has very high precision, and has good reaction controllability. Yes, and widely used.
　特許文献２には、真空加熱などにより形成したシリコン清浄表面上に、自然酸化膜を形成してから酸化膜もしくは別の物質を吸着、堆積させる方法が記載されている。 Patent Document 2 describes a method in which a natural oxide film is formed on a silicon clean surface formed by vacuum heating or the like, and then an oxide film or another substance is adsorbed and deposited.
　特許文献３及び４は、シリコン基板に酸素原子層を複数導入することで、デバイス特性の改善、（移動度）向上が可能になることを示している。 Patent Documents 3 and 4 show that by introducing multiple oxygen atomic layers into a silicon substrate, it is possible to improve device characteristics and (mobility).
　特許文献５は、厚さが５ｎｍ以下である原子層の上にＳｉＨ４ガスを用いてエピタキシャル層を形成する方法を示している。また、酸素原子層を酸素ガスにより形成する方法を示している。 Patent Document 5 shows a method of forming an epitaxial layer using SiH 4 gas on an atomic layer having a thickness of 5 nm or less. Furthermore, a method of forming an oxygen atomic layer using oxygen gas is shown.
　特許文献６及び７には、半導体基板の表面を酸化性気体や酸化性溶液に接触させて酸化膜を形成した後に単結晶シリコンをエピタキシャル成長させる方法が記載されている。また、特許文献６には、酸化性ガスを流した後にシリコンの成膜ガスを流す方法が記載されている。 Patent Documents 6 and 7 describe a method of epitaxially growing single crystal silicon after forming an oxide film by bringing the surface of a semiconductor substrate into contact with an oxidizing gas or an oxidizing solution. Further, Patent Document 6 describes a method in which a silicon film forming gas is flowed after flowing an oxidizing gas.
　特許文献８には、ＩＶ族の元素からなるウェーハ表面の自然酸化膜を除去してから、ウェーハを酸化して酸素原子層を形成した後に単結晶シリコンをエピタキシャル成長させる方法が記載されている。 Patent Document 8 describes a method in which a natural oxide film on the surface of a wafer made of group IV elements is removed, the wafer is oxidized to form an oxygen atomic layer, and then single crystal silicon is epitaxially grown.
　特許文献９には、酸素を含む前駆体をＣＶＤエピタキシー炉に供給して酸素挿入部分単層を形成してからシリコンエピタキシャル層を形成する方法が記載されている。 Patent Document 9 describes a method in which a precursor containing oxygen is supplied to a CVD epitaxy furnace to form an oxygen-inserted monolayer, and then a silicon epitaxial layer is formed.
　非特許文献１は、ＨＦによる自然酸化膜除去後に大気中で酸化してから減圧ＣＶＤによりアモルファスシリコンを成膜し、その後結晶化熱処理により単結晶シリコンを形成する方法を示している。 Non-Patent Document 1 shows a method of removing a natural oxide film with HF, oxidizing it in the atmosphere, forming an amorphous silicon film by low pressure CVD, and then forming single crystal silicon by crystallization heat treatment.
特開２０１４－１６５４９４号公報Japanese Patent Application Publication No. 2014-165494 特開平０５－２４３２６６号公報Japanese Patent Application Publication No. 05-243266 米国特許第７，１５３，７６３号明細書US Patent No. 7,153,763 米国特許第７，２６５，００２号明細書US Patent No. 7,265,002 特開２０１９－００４０５０号公報JP2019-004050A 特開２００８－２６３０２５号公報Japanese Patent Application Publication No. 2008-263025 特開２００９－０１６６３７号公報Japanese Patent Application Publication No. 2009-016637 特開２０２１－１１１６９６号公報JP 2021-111696 Publication 特開２０２２－２２１９４号公報JP2022-22194A
　上記のように、ウェーハ内に酸素の層を形成することで金属不純物をゲッタリングする方法は従来から用いられてきた。しかし、従来の技術では、精度よく酸素の薄い層を得られる一方で装置の構成が複雑であったり、工程数が多くなったりという問題があった。 As mentioned above, a method of gettering metal impurities by forming an oxygen layer within a wafer has been used in the past. However, while the conventional techniques can obtain a thin layer of oxygen with high precision, there are problems in that the device configuration is complicated and the number of steps is increased.
　例えば、特許文献１に記載の技術では、ＡＬＤでは単結晶シリコンをエピタキシャル成長させることができないため、ＡＬＤとＣＶＤの少なくとも２つのチャンバーが必要になり、装置の構成が複雑になるという問題があった。 For example, in the technology described in Patent Document 1, single crystal silicon cannot be grown epitaxially by ALD, so at least two chambers for ALD and CVD are required, which makes the configuration of the device complicated.
　また、特許文献５及び９に記載の技術では、ＳｉＨ４と酸素が反応して爆発するのを防ぐため、排気系統を分けた２つのチャンバーを用意する必要があるという問題があった。 Furthermore, the techniques described in Patent Documents 5 and 9 have a problem in that it is necessary to prepare two chambers with separate exhaust systems in order to prevent SiH 4 and oxygen from reacting and exploding.
　また、特許文献６に記載の技術では、酸化性のガスとシリコンの成膜ガスが反応して爆発するのを防ぐため、安全性に配慮した特別な装置が必要であるという問題があった。 Furthermore, the technique described in Patent Document 6 has a problem in that a special device with safety in mind is required to prevent the oxidizing gas and the silicon film-forming gas from reacting and exploding.
　また、非特許文献１に記載の方法では、結晶化する時に熱処理を行う必要があり、プロセスの工程数が多くなるという問題があった。また、アモルファスシリコン中には一般的に多量の水素が含まれるため、結晶化熱処理時に水素起因の欠陥が形成される可能性がある。 Furthermore, the method described in Non-Patent Document 1 requires heat treatment during crystallization, which has the problem of increasing the number of process steps. Furthermore, since amorphous silicon generally contains a large amount of hydrogen, there is a possibility that hydrogen-related defects may be formed during crystallization heat treatment.
　また、特許文献８に記載の技術では、酸素原子層を形成するために長時間の酸化が必要となることに加え、ウェーハ面内で酸素濃度を均一にすることが難しいという問題があった。 Furthermore, the technique described in Patent Document 8 has the problem that, in addition to requiring long-time oxidation to form an oxygen atomic layer, it is difficult to make the oxygen concentration uniform within the wafer surface.
　また、従来の技術では、酸素の層を安定的に導入するための記載や、良質な単結晶シリコンのエピタキシャル層を形成するための具体的な記載がないという問題があった。 Furthermore, the conventional technology has a problem in that there is no description for stably introducing an oxygen layer or specific description for forming an epitaxial layer of high quality single crystal silicon.
　例えば、特許文献２では、転位および積層欠陥を発生させることなくウェーハ表面に単結晶シリコンのエピタキシャル層を形成する方法については何ら記載されていない。 For example, Patent Document 2 does not describe any method for forming an epitaxial layer of single crystal silicon on a wafer surface without generating dislocations or stacking faults.
　また、特許文献３、４では、酸素原子層を複数導入したシリコンウェーハの具体的な成長方法については言及していない。 Furthermore, Patent Documents 3 and 4 do not mention a specific method for growing a silicon wafer into which multiple oxygen atomic layers are introduced.
　また、特許文献６及び７では、酸化性気体や酸化性溶液に接触させる前の自然酸化膜の除去法は記載されていない。 Further, Patent Documents 6 and 7 do not describe a method for removing a natural oxide film before contacting with an oxidizing gas or an oxidizing solution.
　上述のように、従来の技術では、精度よく酸素の原子層を得られる一方で、装置の構成が複雑であったり、酸素の層の導入が安定的ではなかったり、良質な単結晶シリコンのエピタキシャル層を得られなかったりといった問題があった。そのため、酸素原子層をエピタキシャル層に安定的かつ簡便に導入することができるエピタキシャルウェーハの製造方法が必要である。 As mentioned above, although conventional techniques can obtain an atomic layer of oxygen with high precision, the device configuration is complicated, the introduction of the oxygen layer is not stable, and the epitaxial layer of high-quality single crystal silicon is difficult to obtain. There were problems such as not being able to get enough layers. Therefore, there is a need for an epitaxial wafer manufacturing method that can stably and easily introduce an oxygen atomic layer into an epitaxial layer.
　本発明は、上記従来技術の問題点に鑑みてなされたものであって、酸素原子層をエピタキシャル層に安定的かつ簡便に導入することができるとともに、良質な単結晶シリコンのエピタキシャル層を有するエピタキシャルウェーハを製造できるエピタキシャルウェーハの製造方法を提供することを目的とする。 The present invention has been made in view of the above-mentioned problems of the prior art, and is capable of stably and easily introducing an oxygen atomic layer into an epitaxial layer, as well as an epitaxial layer having a high-quality single-crystal silicon epitaxial layer. An object of the present invention is to provide an epitaxial wafer manufacturing method that can manufacture wafers.
　上記課題を解決するために、本発明では、単結晶シリコンウェーハ上に単結晶シリコンエピタキシャル層を形成するエピタキシャルウェーハの製造方法であって、
　単結晶シリコンウェーハの表面から自然酸化膜を除去する工程、
　前記自然酸化膜除去後に、前記単結晶シリコンウェーハの表面に酸化性溶液により酸化膜を形成する工程、
　前記酸化膜を形成した後に、前記酸化膜を薄膜化して、酸素原子層を形成する工程、及び
　前記酸素原子層を形成した後に、前記酸素原子層を有する前記単結晶シリコンウェーハの表面に単結晶シリコンをエピタキシャル成長させる工程
を含むことを特徴とするエピタキシャルウェーハの製造方法を提供する。 In order to solve the above problems, the present invention provides an epitaxial wafer manufacturing method for forming a single crystal silicon epitaxial layer on a single crystal silicon wafer, comprising:
A process of removing a natural oxide film from the surface of a single crystal silicon wafer,
After removing the natural oxide film, forming an oxide film on the surface of the single crystal silicon wafer using an oxidizing solution;
After forming the oxide film, thinning the oxide film to form an oxygen atomic layer; and After forming the oxygen atomic layer, forming a single crystal on the surface of the single crystal silicon wafer having the oxygen atomic layer. A method for manufacturing an epitaxial wafer is provided, which includes a step of epitaxially growing silicon.
　このようなエピタキシャルウェーハの製造方法とすることで、酸素原子層を残した状態で酸素原子層を有する単結晶シリコンウェーハの表面上に転位および積層欠陥を形成することなく単結晶シリコンを成長できる。すなわち、本発明のエピタキシャルウェーハの製造方法であれば、酸素原子層をエピタキシャル層に安定的かつ簡便に導入することができるとともに、良質な単結晶シリコンのエピタキシャル層を有するエピタキシャルウェーハを製造できる。 By using such an epitaxial wafer manufacturing method, single crystal silicon can be grown without forming dislocations or stacking faults on the surface of a single crystal silicon wafer having an oxygen atomic layer while leaving the oxygen atomic layer. That is, with the epitaxial wafer manufacturing method of the present invention, an oxygen atomic layer can be stably and easily introduced into an epitaxial layer, and an epitaxial wafer having a high-quality single-crystal silicon epitaxial layer can be manufactured.
　また、例えば、前記自然酸化膜の除去を、フッ酸を含む溶液により行うことができる。 Furthermore, for example, the natural oxide film can be removed using a solution containing hydrofluoric acid.
　このようにフッ酸を含む溶液を用いることで、短時間で自然酸化膜を除去することができる。 By using a solution containing hydrofluoric acid in this way, the natural oxide film can be removed in a short time.
　また、前記酸化性溶液として、ＳＣ１溶液、過酸化水素水又はオゾン水を用いることができる。 Furthermore, as the oxidizing solution, an SC1 solution, hydrogen peroxide solution, or ozone water can be used.
　このような方法であれば、短時間で簡単に酸化膜を形成することができる。 With such a method, an oxide film can be easily formed in a short time.
　また、前記酸化性溶液として前記ＳＣ１溶液又は前記過酸化水素水を用い、前記ＳＣ１溶液又は前記過酸化水素水の温度を２０℃以上かつ８０℃以下とすることができる。 Furthermore, the SC1 solution or the hydrogen peroxide solution can be used as the oxidizing solution, and the temperature of the SC1 solution or the hydrogen peroxide solution can be set to 20° C. or higher and 80° C. or lower.
　このような温度であれば、特殊な設備を準備することなく簡単に単結晶シリコンウェーハを酸化することができる。 At such temperatures, single-crystal silicon wafers can be easily oxidized without the need for special equipment.
　また、前記酸化性溶液として前記オゾン水を用い、前記オゾン水の温度を１０℃以上かつ３０℃以下とすることができる。 Furthermore, the ozone water can be used as the oxidizing solution, and the temperature of the ozone water can be set to 10°C or more and 30°C or less.
　このような温度であれば、確実にウェーハを酸化することができる。 At such a temperature, the wafer can be reliably oxidized.
　また、前記酸化膜の薄膜化を水素雰囲気中での前記単結晶シリコンウェーハの加熱により行うことができる。 Furthermore, the oxide film can be thinned by heating the single crystal silicon wafer in a hydrogen atmosphere.
　このように水素雰囲気中で熱処理することにより、酸化膜の一部を安定的に還元でき、それにより酸化膜の薄膜化を行うことができる。 By performing heat treatment in a hydrogen atmosphere in this manner, a portion of the oxide film can be stably reduced, thereby making it possible to reduce the thickness of the oxide film.
　この場合、例えば、前記水素雰囲気中での加熱温度を６００℃以上かつ１２５０℃以下とすることができる。 In this case, for example, the heating temperature in the hydrogen atmosphere can be set to 600° C. or higher and 1250° C. or lower.
　このような温度範囲とすることで、確実に酸化膜の一部を還元でき、それにより酸化膜の薄膜化を行うことができる。 With such a temperature range, a part of the oxide film can be reliably reduced, thereby making it possible to reduce the thickness of the oxide film.
　或いは、前記酸化膜の薄膜化を水素原子を含むガスを用いたプラズマ又は不活性ガスを用いたプラズマにより行うことができる。 Alternatively, the oxide film can be thinned by plasma using a gas containing hydrogen atoms or plasma using an inert gas.
　水素原子を含むガスを用いたプラズマによる方法であれば、酸化膜の一部を低温で安定的に還元でき、それにより酸化膜の薄膜化を行うことができる。また、不活性ガスを用いたプラズマによる方法であれば、プラズマにより生成された高エネルギーの粒子により酸化膜をスパッタリングすることで薄膜化することができる。 If a plasma method using a gas containing hydrogen atoms is used, a part of the oxide film can be stably reduced at a low temperature, thereby making it possible to reduce the thickness of the oxide film. Furthermore, in the case of a plasma method using an inert gas, the oxide film can be thinned by sputtering with high-energy particles generated by the plasma.
　また、前記単結晶シリコンのエピタキシャル成長させる工程では、４５０℃以上かつ８００℃以下の温度で前記単結晶シリコンのエピタキシャル成長を行うことができる。 Further, in the step of epitaxially growing the single crystal silicon, the single crystal silicon can be epitaxially grown at a temperature of 450° C. or higher and 800° C. or lower.
　このような温度範囲とすることで、欠陥を発生させることなくエピタキシャル成長できる。 With such a temperature range, epitaxial growth can be performed without generating defects.
　また、前記単結晶シリコンをエピタキシャル成長させる工程で、シリコンの原料ガスの分圧を０．１Ｐａ以上かつ２０００Ｐａ以下とすることができる。 Furthermore, in the step of epitaxially growing single crystal silicon, the partial pressure of the silicon source gas can be set to 0.1 Pa or more and 2000 Pa or less.
　このような圧力範囲とすることで、より安定して欠陥を発生させることなく単結晶シリコンをエピタキシャル成長させることができる。 By using such a pressure range, single crystal silicon can be epitaxially grown more stably without generating defects.
　また、前記酸素原子層の酸素の平面濃度を６×１０１４ａｔｏｍｓ／ｃｍ２以下とすることができる。 Further, the planar concentration of oxygen in the oxygen atomic layer can be 6×10 14 atoms/cm 2 or less.
　このような酸素濃度範囲とすることで、欠陥を発生させることなく安定的にエピタキシャルウェーハを製造することができる。 With such an oxygen concentration range, epitaxial wafers can be stably manufactured without generating defects.
　また、前記単結晶シリコンをエピタキシャル成長させる工程の後に、前記酸化膜を形成する工程と前記酸素原子層を形成する工程と前記単結晶シリコンをエピタキシャル成長させる工程とを繰り返し行うことができる。 Furthermore, after the step of epitaxially growing single crystal silicon, the steps of forming the oxide film, forming the oxygen atomic layer, and epitaxially growing the single crystal silicon can be repeated.
　このように酸素原子層を複数層形成することで、単層の場合よりもゲッタリング効果を高めることができる。 By forming multiple oxygen atomic layers in this way, the gettering effect can be enhanced more than in the case of a single layer.
　以上のように、本発明によれば、先端デバイスで採用されるシリコンエピタキシャルウェーハにおいて、酸素原子層をエピタキシャル層に安定的にかつ簡便に導入することができるとともに、良質な単結晶シリコンのエピタキシャル層を有するエピタキシャルウェーハを製造できる方法を提供することができる。また、酸素原子層による近接ゲッタリング効果を有する近接ゲッタリング基板を製造することが可能となる。 As described above, according to the present invention, in silicon epitaxial wafers used in advanced devices, an oxygen atomic layer can be stably and easily introduced into the epitaxial layer, and an epitaxial layer of high-quality single crystal silicon can be introduced into the epitaxial layer. It is possible to provide a method for manufacturing an epitaxial wafer having the following. Furthermore, it becomes possible to manufacture a proximity gettering substrate having a proximity gettering effect due to the oxygen atomic layer.
本発明のエピタキシャルウェーハの製造方法のフローを示す図である。FIG. 2 is a diagram showing a flow of the method for manufacturing an epitaxial wafer of the present invention. 本発明のエピタキシャルウェーハの製造方法で製造できるエピタキシャルウェーハの一例の概略断面図である。1 is a schematic cross-sectional view of an example of an epitaxial wafer that can be manufactured by the method for manufacturing an epitaxial wafer of the present invention. 本発明のエピタキシャルウェーハの製造方法で製造できるエピタキシャルウェーハの他の一例の概略断面図である。It is a schematic sectional view of another example of an epitaxial wafer which can be manufactured by the manufacturing method of an epitaxial wafer of the present invention. 実施例１及び比較例１における水素雰囲気中での加熱時間と酸素濃度との関係を示すグラフである。2 is a graph showing the relationship between heating time and oxygen concentration in a hydrogen atmosphere in Example 1 and Comparative Example 1. 実施例１と比較例２における基板面内における酸素原子層の酸素濃度の分布を示すグラフである。2 is a graph showing the distribution of oxygen concentration in an oxygen atomic layer within the plane of a substrate in Example 1 and Comparative Example 2.
　上述のように、特殊な装置や、複雑なプロセスが必要なく、また、酸素原子層をエピタキシャル層に安定的かつ簡便に導入することができるとともに、良質な単結晶シリコンのエピタキシャル層を有するエピタキシャルウェーハを製造できるエピタキシャルウェーハの製造方法が求められていた。 As mentioned above, an epitaxial wafer that does not require special equipment or complicated processes, can stably and easily introduce an oxygen atomic layer into an epitaxial layer, and has an epitaxial layer of high-quality single crystal silicon. There has been a need for a method for manufacturing epitaxial wafers that can produce.
　本発明者は、上記課題について鋭意検討を重ねた結果、単結晶シリコンウェーハ上に単結晶シリコンエピタキシャル層を形成するエピタキシャルウェーハの製造方法であって、単結晶シリコンウェーハの表面から自然酸化膜を除去する工程、前記自然酸化膜除去後に、前記単結晶シリコンウェーハの表面に酸化性溶液により酸化膜を形成する工程、前記酸化膜を形成した後に、前記酸化膜を薄膜化して、酸素原子層を形成する工程、及び前記酸素原子層を形成した後に、前記酸素原子層を有する前記単結晶シリコンウェーハの表面に単結晶シリコンをエピタキシャル成長させる工程を含むことを特徴とするエピタキシャルウェーハの製造方法により、単結晶シリコンのエピタキシャル層上に転位および積層欠陥を形成することなく、酸素原子層をエピタキシャル層に安定的かつ簡便に導入することが可能となることを見出し、本発明を完成した。 As a result of intensive studies on the above-mentioned problems, the present inventor has devised a method for manufacturing an epitaxial wafer in which a single crystal silicon epitaxial layer is formed on a single crystal silicon wafer, in which a natural oxide film is removed from the surface of the single crystal silicon wafer. After removing the natural oxide film, forming an oxide film on the surface of the single crystal silicon wafer using an oxidizing solution; After forming the oxide film, thinning the oxide film to form an oxygen atomic layer. and after forming the oxygen atomic layer, epitaxially growing single crystal silicon on the surface of the single crystal silicon wafer having the oxygen atomic layer. The present invention has been completed by discovering that it is possible to stably and easily introduce an oxygen atomic layer into an epitaxial layer of silicon without forming dislocations or stacking faults on the epitaxial layer.
　即ち、本発明は、単結晶シリコンウェーハ上に単結晶シリコンエピタキシャル層を形成するエピタキシャルウェーハの製造方法であって、
　単結晶シリコンウェーハの表面から自然酸化膜を除去する工程、
　前記自然酸化膜除去後に、前記単結晶シリコンウェーハの表面に酸化性溶液により酸化膜を形成する工程、
　前記酸化膜を形成した後に、前記酸化膜を薄膜化して、酸素原子層を形成する工程、及び
　前記酸素原子層を形成した後に、前記酸素原子層を有する前記単結晶シリコンウェーハの表面に単結晶シリコンをエピタキシャル成長させる工程
を含むことを特徴とするエピタキシャルウェーハの製造方法である。 That is, the present invention is an epitaxial wafer manufacturing method for forming a single-crystal silicon epitaxial layer on a single-crystal silicon wafer, comprising:
A process of removing a natural oxide film from the surface of a single crystal silicon wafer,
After removing the natural oxide film, forming an oxide film on the surface of the single crystal silicon wafer using an oxidizing solution;
After forming the oxide film, thinning the oxide film to form an oxygen atomic layer; and After forming the oxygen atomic layer, forming a single crystal on the surface of the single crystal silicon wafer having the oxygen atomic layer. This is a method for manufacturing an epitaxial wafer, characterized by including a step of epitaxially growing silicon.
　以下、本発明について図面を参照しながら詳細に説明するが、本発明はこれらに限定されるものではない。 Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.
　［エピタキシャルウェーハ］
　本発明のエピタキシャルウェーハの製造方法によれば、例えば図２に概略的に断面を示す、エピタキシャルウェーハ１０Ａを製造できる。ただし、本発明のエピタキシャルウェーハの製造方法で製造できるエピタキシャルウェーハは、図２に示すものに限定されない。 [Epitaxial wafer]
According to the epitaxial wafer manufacturing method of the present invention, an epitaxial wafer 10A whose cross section is schematically shown in FIG. 2, for example, can be manufactured. However, the epitaxial wafer that can be manufactured by the epitaxial wafer manufacturing method of the present invention is not limited to that shown in FIG. 2.
　図２に示すエピタキシャルウェーハ１０Ａは、単結晶シリコンウェーハ１上に単結晶エピタキシャルシリコン層（以下、単にエピタキシャル層という場合がある）３を有し、単結晶エピタキシャルシリコン層３と単結晶シリコンウェーハ１との間に酸素原子層２を有している。 The epitaxial wafer 10A shown in FIG. 2 has a single crystal epitaxial silicon layer (hereinafter sometimes simply referred to as an epitaxial layer) 3 on a single crystal silicon wafer 1, and has a single crystal epitaxial silicon layer 3 and a single crystal silicon wafer 1. There is an oxygen atomic layer 2 between them.
　［エピタキシャルウェーハの製造方法］ [Epitaxial wafer manufacturing method]
　図１に、本発明に係るエピタキシャルウェーハの製造方法のフローを示す。 FIG. 1 shows the flow of the method for manufacturing an epitaxial wafer according to the present invention.
　図１のＳ１１の工程は、単結晶シリコンウェーハを準備する工程である。 The step S11 in FIG. 1 is a step of preparing a single crystal silicon wafer.
　ここで、単結晶シリコンウェーハの製造方法は特に限定されない。例えば、チョクラルスキー法（Ｃｚｏｃｈｒａｌｓｋｉ　Ｍｅｔｈｏｄ：以下ＣＺ法という）により製造された基板を用いても良いし、フローティングゾーン法（Ｆｌｏａｔｉｎｇ　Ｚｏｎｅ　Ｍｅｔｈｏｄ：以下ＦＺ法という）により製造された基板を用いても良い。また、ＣＺ法及びＦＺ法により製造された単結晶シリコン基板上に単結晶シリコンをエピタキシャル成長させた基板を用いても良い。 Here, the method for manufacturing the single crystal silicon wafer is not particularly limited. For example, a substrate manufactured by the Czochralski Method (hereinafter referred to as the CZ method) may be used, or a substrate manufactured by the Floating Zone Method (hereinafter referred to as the FZ method) may be used. . Alternatively, a substrate in which single crystal silicon is epitaxially grown on a single crystal silicon substrate manufactured by the CZ method or the FZ method may be used.
　図１のＳ１２は、工程Ｓ１１で準備した単結晶シリコンウェーハの表面から自然酸化膜を除去する工程である。 S12 in FIG. 1 is a step of removing a natural oxide film from the surface of the single crystal silicon wafer prepared in step S11.
　例えば、前記自然酸化膜の除去を、フッ酸を含む溶液により行うことができる。 For example, the natural oxide film can be removed using a solution containing hydrofluoric acid.
　このようにフッ酸を含む溶液を用いることで、短時間で自然酸化膜を除去することができる。 By using a solution containing hydrofluoric acid in this way, the natural oxide film can be removed in a short time.
　自然酸化膜を除去する工程Ｓ１２では、例えば、フッ酸を用いても良いし、バッファードフッ酸を用いてもよい。バッファードフッ酸とは、フッ酸とフッ化アンモニウムとを混合した溶液である。フッ酸を含む溶液におけるフッ酸の濃度は、自然酸化膜を除去できる濃度であればよく、例えば０．００１％以上かつ６０％以下とすることができる。フッ酸を含む溶液の温度は、例えば１０℃以上かつ５０℃以下とすることができる。１０℃以上とすれば、フッ酸を含む溶液で処理した後にウェーハに結露が生じるのを防ぐことができる。また、温度を５０℃以下とすれば、揮発するフッ酸の量を抑えることができ、安全上の問題を回避できる。 In the step S12 of removing the natural oxide film, for example, hydrofluoric acid or buffered hydrofluoric acid may be used. Buffered hydrofluoric acid is a solution containing hydrofluoric acid and ammonium fluoride. The concentration of hydrofluoric acid in the solution containing hydrofluoric acid may be any concentration that can remove the native oxide film, and may be, for example, 0.001% or more and 60% or less. The temperature of the solution containing hydrofluoric acid can be, for example, 10°C or higher and 50°C or lower. When the temperature is 10° C. or higher, it is possible to prevent dew condensation from forming on the wafer after processing with a solution containing hydrofluoric acid. Further, by setting the temperature to 50° C. or lower, the amount of hydrofluoric acid that evaporates can be suppressed, and safety problems can be avoided.
　フッ酸を含む溶液による洗浄（自然酸化膜除去）の時間は、例えば撥水性が確認できるまでとすることができるが、例えば、１秒以上かつ１時間以下とすることができる。１秒以上であれば自然酸化膜を除去することができる。また、１時間以下とすることで時間が掛かりすぎるのを防止することができる。 The time for cleaning with a solution containing hydrofluoric acid (natural oxide film removal) can be, for example, until water repellency is confirmed, and can be, for example, 1 second or more and 1 hour or less. If the time is 1 second or more, the natural oxide film can be removed. Further, by setting the time to 1 hour or less, it is possible to prevent it from taking too much time.
　フッ酸を含む溶液による洗浄（自然酸化膜除去）は、バッチ式の洗浄装置を用いても良いし、枚葉式の洗浄装置を用いても良い。 For cleaning with a solution containing hydrofluoric acid (natural oxide film removal), a batch type cleaning device or a single wafer type cleaning device may be used.
　また、工程Ｓ１２では、フッ酸を含む溶液の蒸気を用いて自然酸化膜を除去してもよい。 Furthermore, in step S12, the natural oxide film may be removed using vapor of a solution containing hydrofluoric acid.
　図１のＳ１３は、工程Ｓ１２での自然酸化膜除去後に、単結晶シリコンウェーハの表面に酸化性溶液により酸化膜を形成する工程である。 S13 in FIG. 1 is a step of forming an oxide film on the surface of the single crystal silicon wafer using an oxidizing solution after removing the natural oxide film in step S12.
　酸化膜のない疎水性の表面はパーティクルが付着しやすいが、酸化膜がある親水性の表面は、パーティクルの付着を防止することができる。このため、例えば、単結晶シリコンウェーハを酸化性溶液に浸漬して表面に酸化膜を形成することで、洗浄装置から次工程に単結晶シリコンウェーハを搬送するまでの間にパーティクルが付着するのを防止することができる。 A hydrophobic surface without an oxide film tends to attract particles, but a hydrophilic surface with an oxide film can prevent particles from adhering. For this reason, for example, by immersing a single crystal silicon wafer in an oxidizing solution to form an oxide film on the surface, particles can be prevented from adhering to the single crystal silicon wafer before it is transported from the cleaning equipment to the next process. It can be prevented.
　酸化性溶液への単結晶シリコンウェーハの浸漬では、例えば、バッチ式の装置を用いても良いし、枚葉式の装置を用いても良い。 For immersing a single crystal silicon wafer in an oxidizing solution, a batch type device or a single wafer type device may be used, for example.
　酸化性溶液として、例えば、ＳＣ１溶液、過酸化水素水又はオゾン水を用いることができる。 As the oxidizing solution, for example, SC1 solution, hydrogen peroxide solution, or ozone water can be used.
　このような方法であれば、短時間で簡単に酸化膜を形成することができる。 With such a method, an oxide film can be easily formed in a short time.
　より具体的には、ＳＣ１溶液とは、アンモニアと過酸化水素水と水とを混合した溶液であり、過酸化水素水により単結晶シリコンウェーハの表面を酸化するとともにアンモニアにより酸化膜をエッチングすることで、単結晶シリコンウェーハ表面に付着したパーティクルをリフトオフして除去することができる。このため、単結晶シリコン基板の洗浄工程で用いられるＳＣ１溶液を用いることで、単結晶シリコンウェーハの表面に酸化膜が形成される。ＳＣ１溶液における各成分間の混合比は、アンモニア水より過酸化水素水の量を多くすることが好ましい。このような混合比とすることで、安定的かつ均一に酸化膜を形成することができる。例えば、アンモニア水（ＮＨ３濃度２８％）、過酸化水素水（Ｈ２Ｏ２濃度３０％）、及び水の混合比を、１：１～２：５～１００とすることができる。 More specifically, the SC1 solution is a solution that is a mixture of ammonia, hydrogen peroxide, and water, and the hydrogen peroxide solution oxidizes the surface of a single-crystal silicon wafer, while the ammonia etches the oxide film. With this, particles attached to the surface of the single crystal silicon wafer can be lifted off and removed. Therefore, by using the SC1 solution used in the cleaning process of single crystal silicon substrates, an oxide film is formed on the surface of the single crystal silicon wafer. As for the mixing ratio between each component in the SC1 solution, it is preferable that the amount of hydrogen peroxide solution is larger than that of aqueous ammonia. With such a mixing ratio, an oxide film can be formed stably and uniformly. For example, the mixing ratio of aqueous ammonia (NH 3 concentration: 28%), hydrogen peroxide solution (H 2 O 2 concentration: 30%), and water can be 1:1 to 2:5 to 100.
　単結晶シリコンウェーハをＳＣ１溶液に浸漬する時間は、例えば１秒以上かつ１時間以下とすることができる。１秒以上であれば酸素原子層を十分に形成することができる。また、１時間以下とすることで時間が掛かりすぎるのを防止することができる。 The time for immersing the single crystal silicon wafer in the SC1 solution can be, for example, 1 second or more and 1 hour or less. If the heating time is 1 second or more, an oxygen atomic layer can be sufficiently formed. Further, by setting the time to 1 hour or less, it is possible to prevent it from taking too much time.
　過酸化水素水を用いて酸化を行う場合には、例えば、過酸化水素水の濃度を０．０１％以上かつ３０％以下とすることができる。濃度が０．０１％以上であれば確実に酸化膜を形成することができる。また、濃度が３０％以下であれば、洗浄液中から過酸化水素水の蒸発量を適正に保つことができるため、廃棄設備への負担が増大することを防ぐことができる。 When performing oxidation using a hydrogen peroxide solution, the concentration of the hydrogen peroxide solution can be set to 0.01% or more and 30% or less, for example. If the concentration is 0.01% or more, an oxide film can be reliably formed. Further, if the concentration is 30% or less, the amount of evaporation of hydrogen peroxide from the cleaning liquid can be maintained at an appropriate level, so that an increase in the burden on the disposal equipment can be prevented.
　単結晶シリコンウェーハを過酸化水素水に浸漬する時間は、例えば１秒以上かつ１時間以下とすることができる。１秒以上であれば酸素原子層を形成することができる。また、１時間以下とすることで時間が掛かりすぎるのを防止することができる。 The time for immersing the single crystal silicon wafer in the hydrogen peroxide solution can be, for example, 1 second or more and 1 hour or less. If the time is 1 second or more, an oxygen atomic layer can be formed. Further, by setting the time to 1 hour or less, it is possible to prevent it from taking too much time.
　酸化性溶液としてのＳＣ１溶液又は過酸化水素水の温度は、例えば２０℃以上かつ８０℃以下とすることができる。２０℃以上であれば、安定的に酸化膜を形成することができる。また、８０℃以下であれば、洗浄液の蒸発量を一定に保ち、洗浄液中に気泡が増加することを防ぐことができるため、ウェーハ面内で均一に酸化膜を形成することができる。すなわち、このような温度であれば、特殊な設備を準備することなく簡単に単結晶シリコンウェーハを酸化することができる。 The temperature of the SC1 solution or the hydrogen peroxide solution as the oxidizing solution can be, for example, 20°C or higher and 80°C or lower. If the temperature is 20° C. or higher, an oxide film can be stably formed. Further, if the temperature is 80° C. or lower, the amount of evaporation of the cleaning liquid can be kept constant and bubbles can be prevented from increasing in the cleaning liquid, so that an oxide film can be formed uniformly within the wafer surface. That is, at such a temperature, a single crystal silicon wafer can be easily oxidized without preparing special equipment.
　酸化膜を形成する工程Ｓ１３において、オゾン水は、有機物の分解及び単結晶シリコンウェーハの表面の酸化のために使われる。オゾン水のオゾン濃度は、例えば、１ｐｐｍ以上かつ５００ｐｐｍ以下とすることができる。オゾン濃度が１ｐｐｍ以上であれば、安定的に単結晶シリコンウェーハの表面に酸化膜を形成することができる。また、オゾン濃度を５００ｐｐｍ以下とすることで、オゾンが分解又は気相中に抜けてオゾン濃度が変動することによる酸化膜厚のばらつきが発生するのを防止することができる。 In step S13 of forming an oxide film, ozone water is used to decompose organic matter and oxidize the surface of the single crystal silicon wafer. The ozone concentration of the ozone water can be, for example, 1 ppm or more and 500 ppm or less. When the ozone concentration is 1 ppm or more, an oxide film can be stably formed on the surface of the single crystal silicon wafer. Further, by setting the ozone concentration to 500 ppm or less, it is possible to prevent variations in the oxide film thickness due to fluctuations in the ozone concentration due to ozone decomposition or escape into the gas phase.
　オゾン水の温度は、例えば１０℃以上かつ３０℃以下とすることができる。１０℃以上とすることで、オゾン水処理後のウェーハで結露が発生するのを防ぐことができる。また、３０℃以下とすることでオゾン水においてオゾンの分解または気相中に抜けることを防止することができ、それにより単結晶シリコンウェーハを確実に酸化することができる。 The temperature of the ozone water can be, for example, 10°C or higher and 30°C or lower. By setting the temperature to 10° C. or higher, it is possible to prevent dew condensation from occurring on the wafer after the ozone water treatment. In addition, by setting the temperature to 30° C. or lower, it is possible to prevent ozone from decomposing in ozone water or from escaping into the gas phase, thereby making it possible to reliably oxidize the single crystal silicon wafer.
　単結晶シリコンウェーハをオゾン水に浸漬する時間は、例えば１秒以上かつ１時間以下とすることができる。１秒以上であれば酸素原子層を形成することができる。また、１時間以下とすることで時間が掛かりすぎるのを防止することができる。 The time for immersing the single crystal silicon wafer in ozone water can be, for example, 1 second or more and 1 hour or less. If the time is 1 second or more, an oxygen atomic layer can be formed. Further, by setting the time to 1 hour or less, it is possible to prevent it from taking too much time.
　図１のＳ１４は、工程Ｓ１３で酸化膜を形成した後に、酸化膜を薄膜化して、酸素原子層を形成する工程である。 S14 in FIG. 1 is a step in which, after forming the oxide film in step S13, the oxide film is thinned to form an oxygen atomic layer.
　酸化膜の薄膜化は、例えば、水素雰囲気中で単結晶シリコンウェーハを加熱することにより行うことができる。このように水素雰囲気中で熱処理することにより、酸化膜を均一かつ安定的に還元でき、それにより酸化膜の薄膜化を行うことができる。 The oxide film can be thinned, for example, by heating a single crystal silicon wafer in a hydrogen atmosphere. By performing heat treatment in a hydrogen atmosphere in this manner, the oxide film can be reduced uniformly and stably, thereby making it possible to reduce the thickness of the oxide film.
　加熱は大気圧環境下で行っても良いし、減圧環境下で行ってもよい。減圧環境とは、例えば、１００Ｐａ以上かつ大気圧未満の環境のことを示す。水素雰囲気として、例えば、水素が１００％の雰囲気を用いても良いし、水素と不活性ガスとを混合した雰囲気を用いても良い。不活性ガスとしては、窒素、ヘリウム、ネオン、アルゴン、クリプトン、及びキセノンのいずれかを用いることができる。 Heating may be performed in an atmospheric pressure environment or in a reduced pressure environment. The reduced pressure environment refers to, for example, an environment of 100 Pa or more and less than atmospheric pressure. As the hydrogen atmosphere, for example, an atmosphere containing 100% hydrogen may be used, or an atmosphere containing a mixture of hydrogen and an inert gas may be used. As the inert gas, any one of nitrogen, helium, neon, argon, krypton, and xenon can be used.
　加熱温度は、例えば、６００℃以上かつ１２５０℃以下とすることができる。６００℃以上とすることで確実に酸化膜を還元して薄膜化することができる。また、１２５０℃以下とすることで汎用的な加熱装置を用いることができる。 The heating temperature can be, for example, 600°C or higher and 1250°C or lower. By setting the temperature to 600° C. or higher, the oxide film can be reliably reduced and made thinner. Further, by setting the temperature to 1250° C. or lower, a general-purpose heating device can be used.
　加熱する時間は、例えば１秒以上かつ１時間以下とすることができる。１秒以上であれば酸化膜を還元して薄膜化できる。また、１時間以下とすることで時間がかかりすぎるのを防止することができる。 The heating time can be, for example, 1 second or more and 1 hour or less. If the time is 1 second or more, the oxide film can be reduced and made thinner. Further, by setting the time to 1 hour or less, it is possible to prevent it from taking too much time.
　また、上記の圧力、加熱温度、加熱時間は、酸化膜の厚さに応じて変えることができる。酸化膜が厚い場合には、圧力を高くする、又は温度を高くする、又は加熱時間を長くすることにより、酸化膜を薄膜化して酸素原子層を形成することができる。酸化膜が薄い場合には、圧力を低くする、又は温度を低くする、又は加熱時間を短くすることにより、酸化膜を全て除去して酸素原子層がなくなってしまうことを防ぐことができる。 Furthermore, the above pressure, heating temperature, and heating time can be changed depending on the thickness of the oxide film. When the oxide film is thick, the oxide film can be made thinner and an oxygen atomic layer can be formed by increasing the pressure, temperature, or lengthening the heating time. When the oxide film is thin, the oxide film can be completely removed and the oxygen atomic layer can be prevented from disappearing by lowering the pressure, lowering the temperature, or shortening the heating time.
　水素雰囲気中での単結晶シリコンウェーハの加熱は熱処理炉で行っても良いし、単結晶シリコンの成膜装置中で行ってもよい。加熱装置には、バッチ式を使用しても良いし、枚葉式を使用しても良い。 Heating of the single crystal silicon wafer in a hydrogen atmosphere may be performed in a heat treatment furnace or in a single crystal silicon film forming apparatus. The heating device may be a batch type or a single wafer type.
　或いは、工程Ｓ１４における酸化膜の薄膜化は、水素原子を含むガスを用いたプラズマ又は不活性ガスを用いたプラズマにより行うことができる。前記ガスとしては、例えば、水素分子、アンモニア、窒素、アルゴン、ヘリウム、ネオン、クリプトン、又はキセノンを用いることができる。これらのガスは混合して用いてもよい。 Alternatively, the thinning of the oxide film in step S14 can be performed by plasma using a gas containing hydrogen atoms or plasma using an inert gas. As the gas, for example, hydrogen molecules, ammonia, nitrogen, argon, helium, neon, krypton, or xenon can be used. These gases may be used in combination.
　水素原子を含む、水素分子およびアンモニアの場合は、プラズマにより生成された水素ラジカルにより、低温で安定して酸化膜を還元して薄膜化することができる。 In the case of hydrogen molecules and ammonia that contain hydrogen atoms, hydrogen radicals generated by plasma can stably reduce the oxide film at low temperatures and make it thin.
　不活性ガスとして、窒素、アルゴン、ヘリウム、ネオン、クリプトン、キセノンを用いる場合は、プラズマにより生成された高エネルギーの粒子により酸化膜をスパッタリングすることで薄膜化することができる。 When nitrogen, argon, helium, neon, krypton, or xenon is used as the inert gas, the oxide film can be thinned by sputtering with high-energy particles generated by plasma.
　なお、前記プラズマを用いて酸化膜を薄膜化する場合には、室温で行っても良いし、加熱し行っても良い。 Note that when the oxide film is thinned using the plasma, it may be performed at room temperature or may be performed by heating.
　前記単結晶シリコンウェーハをプラズマに曝す時間は、プラズマ密度やイオンエネルギーなどに依存するが、例えば１秒以上かつ３０分以下とすることで、安定的に酸化膜を薄膜化することができる。 The time for exposing the single crystal silicon wafer to plasma depends on the plasma density, ion energy, etc., but by setting it to, for example, 1 second or more and 30 minutes or less, the oxide film can be stably thinned.
　また、プラズマに曝す時間は、酸化膜の厚さに応じて変えることができる。酸化膜が厚い場合には、プラズマに曝す時間を長くすることにより、酸化膜を薄膜化して酸素原子層を形成することができる。酸化膜が薄い場合には、プラズマに曝す時間を短くすることにより、酸化膜を全て除去して酸素原子層がなくなってしまうことを防ぐことができる。 Furthermore, the time of exposure to plasma can be changed depending on the thickness of the oxide film. When the oxide film is thick, the oxide film can be made thinner to form an oxygen atomic layer by increasing the plasma exposure time. When the oxide film is thin, by shortening the time of exposure to plasma, it is possible to prevent the oxide film from being completely removed and the oxygen atomic layer disappearing.
　図１のＳ１５は、工程Ｓ１４で酸素原子層を形成した後に、前記酸素原子層を有する前記単結晶シリコンウェーハの表面に単結晶シリコンをエピタキシャル成長させる工程である。 S15 in FIG. 1 is a step of epitaxially growing single crystal silicon on the surface of the single crystal silicon wafer having the oxygen atomic layer after forming the oxygen atomic layer in step S14.
　エピタキシャル成長に使うガスとして、例えば、モノシラン及びジシランを使うことができる。キャリアガスとして窒素及び水素を使用しても良い。また、チャンバーの圧力は気相反応が生じない圧力であればよい。 For example, monosilane and disilane can be used as the gas used for epitaxial growth. Nitrogen and hydrogen may also be used as carrier gases. Further, the pressure in the chamber may be any pressure that does not cause a gas phase reaction.
　エピタキシャル成長装置としてはバッチ式を使用しても良いし、枚葉式を使用しても良い。 As the epitaxial growth apparatus, a batch type or a single wafer type may be used.
　また、単結晶シリコンのエピタキシャル成長を、例えば４５０℃以上かつ８００℃以下の温度で行うことができる。このような温度でエピタキシャル成長を行うことで、形成するエピタキシャル層に転位及び積層欠陥が形成されるのを防止でき、より安定して良質のエピタキシャル層を形成することができる。温度が高いほどエピタキシャル成長レートは高くなるため、高温で成膜することで厚いエピタキシャル層を短時間で形成することができる。一方で、薄いエピタキシャル層を形成したい場合には低温で成膜すればよい。このように、目的とするエピタキシャル層の厚さに応じて成長温度を変えることができる。また、このような温度範囲であれば、酸素原子層から酸素が拡散して酸素原子層が消滅することをより確実に防ぐことができる。 Furthermore, epitaxial growth of single crystal silicon can be performed at a temperature of, for example, 450° C. or higher and 800° C. or lower. By performing epitaxial growth at such a temperature, it is possible to prevent dislocations and stacking faults from being formed in the epitaxial layer to be formed, and it is possible to form a more stable and high-quality epitaxial layer. Since the higher the temperature, the higher the epitaxial growth rate, a thick epitaxial layer can be formed in a short time by forming a film at a high temperature. On the other hand, if a thin epitaxial layer is desired to be formed, the film may be formed at a low temperature. In this way, the growth temperature can be changed depending on the desired thickness of the epitaxial layer. In addition, within such a temperature range, it is possible to more reliably prevent oxygen from diffusing from the oxygen atomic layer and causing the oxygen atomic layer to disappear.
　また、エピタキシャル層の厚さを調整するために成膜時間を調整することができる。また、高温で成膜する場合には、成膜時間を短くすることで、単結晶シリコンウェーハから酸素が外方拡散して、酸素原子層の耐熱性が低下することを防ぐことができる。 Additionally, the film formation time can be adjusted to adjust the thickness of the epitaxial layer. Furthermore, when forming a film at a high temperature, by shortening the film forming time, it is possible to prevent oxygen from diffusing outward from the single crystal silicon wafer and reducing the heat resistance of the oxygen atomic layer.
　また、単結晶シリコンのエピタキシャル成長を、例えば、シリコンの原料ガスの分圧を０．１Ｐａ以上かつ２０００Ｐａ以下として行うことができる。このような圧力範囲であれば、酸素原子層上に転位や積層欠陥を発生させることなく、より安定して単結晶シリコンを成膜することができる。 Furthermore, epitaxial growth of single-crystal silicon can be performed, for example, with the partial pressure of the silicon source gas set to 0.1 Pa or more and 2000 Pa or less. Within this pressure range, single crystal silicon can be more stably formed without generating dislocations or stacking faults on the oxygen atomic layer.
　酸素原子層を形成する工程Ｓ１４において、前記酸素原子層の酸素の平面濃度を６×１０１４ａｔｏｍｓ／ｃｍ２以下とすることで、エピタキシャル層中に欠陥が形成されない。これは、酸化量（酸素原子層の酸素の平面濃度）が少ない場合には単結晶シリコンウェーハの結晶性が保たれるためである。このため、酸素の平面濃度の下限値はなく、０よりも大きければよい。酸素原子層の酸素の平面濃度が６×１０１４ａｔｏｍｓ／ｃｍ２以下であれば、エピタキシャル層に酸素原子層に起因する欠陥が形成されることを防ぐことができ、また、エピタキシャル層が多結晶シリコンまたはアモルファスシリコンになるのを防ぐことができる。 In step S14 of forming an oxygen atomic layer, by setting the plane concentration of oxygen in the oxygen atomic layer to 6×10 14 atoms/cm 2 or less, no defects are formed in the epitaxial layer. This is because the crystallinity of the single crystal silicon wafer is maintained when the amount of oxidation (planar concentration of oxygen in the oxygen atomic layer) is small. Therefore, there is no lower limit to the plane concentration of oxygen, and it is sufficient that it is greater than 0. If the plane concentration of oxygen in the oxygen atomic layer is 6×10 14 atoms/cm 2 or less, defects caused by the oxygen atomic layer can be prevented from being formed in the epitaxial layer, and if the epitaxial layer is polycrystalline. It can prevent it from becoming silicon or amorphous silicon.
　ここで、酸素の平面濃度はＳＩＭＳ（Ｓｅｃｏｎｄａｒｙ　Ｉｏｎ　Ｍａｓｓ　Ｓｐｅｃｔｒｏｍｅｔｒｙ）により測定することができる。酸化層を含むＳｉをＳＩＭＳで測定した場合には、酸化層が形成された深さにピークが形成される。ピーク付近において１回のスパッタリングによる体積濃度と深さの積を積算することで平面濃度を求めることができる。 Here, the planar concentration of oxygen can be measured by SIMS (Secondary Ion Mass Spectrometry). When Si containing an oxide layer is measured by SIMS, a peak is formed at the depth where the oxide layer is formed. The planar concentration can be determined by integrating the product of the volume concentration and depth obtained by one sputtering process near the peak.
　以上のような工程Ｓ１１～Ｓ１５を行うことにより、例えば図２に示すようなエピタキシャルウェーハ１０Ａを得ることができる。 By performing the steps S11 to S15 as described above, an epitaxial wafer 10A as shown in FIG. 2, for example, can be obtained.
　本発明者らの検討によれば、上記のように単結晶シリコンウェーハ１上に酸化膜を形成してから、酸化膜を薄膜化して酸素原子層２を形成し、その後、単結晶シリコンをエピタキシャル成長することにより、ウェーハ面内で均一な酸素原子層２を形成することができる。これは、単結晶シリコンにおける酸化レートは酸化膜の成長により遅くなるため、酸素原子層２よりも酸化膜の方が膜厚の制御が容易であることに加え、酸化膜の薄膜化は酸化よりも緩やかに進行することで制御がしやすいためと考えられる。 According to the studies of the present inventors, an oxide film is formed on a single crystal silicon wafer 1 as described above, the oxide film is thinned to form an oxygen atomic layer 2, and then single crystal silicon is epitaxially grown. By doing so, a uniform oxygen atomic layer 2 can be formed within the wafer surface. This is because the oxidation rate in single-crystal silicon slows down due to the growth of the oxide film, so the thickness of the oxide film is easier to control than the oxygen atomic layer 2, and the thinning of the oxide film is easier than the oxidation process. This is thought to be because it is easier to control as it progresses slowly.
　単結晶シリコンをエピタキシャル成長させる工程Ｓ１５の後に、酸化膜を形成する工程Ｓ１３と酸素原子層２を形成する工程Ｓ１４と単結晶シリコンをエピタキシャル成長させる工程Ｓ１５とを繰り返し行うことで、例えば図３に示すように、酸素原子層２を複数層形成することができる。すなわち、この態様に係るエピタキシャルウェーハの製造方法によれば、図３に示す、単結晶シリコンウェーハ１上に酸素原子層２と単結晶エピタキシャルシリコン層３を交互に繰り返し積層させたエピタキシャルウェーハ１０Ｂを得ることができる。図３のエピタキシャルウェーハ１０Ｂの最上面は、単結晶エピタキシャルシリコン層３である。 After step S15 of epitaxially growing single-crystal silicon, repeating step S13 of forming an oxide film, step S14 of forming oxygen atomic layer 2, and step S15 of epitaxially growing single-crystal silicon, for example, as shown in FIG. In addition, a plurality of oxygen atomic layers 2 can be formed. That is, according to the method for manufacturing an epitaxial wafer according to this aspect, an epitaxial wafer 10B shown in FIG. 3 is obtained in which oxygen atomic layers 2 and single-crystal epitaxial silicon layers 3 are alternately and repeatedly stacked on a single-crystal silicon wafer 1. be able to. The top surface of the epitaxial wafer 10B in FIG. 3 is a single-crystal epitaxial silicon layer 3.
　このように酸素原子層２を複数層設けることで、単層の酸素原子層２を形成する場合よりもゲッタリング効果を高めることができる。 By providing a plurality of oxygen atomic layers 2 in this way, the gettering effect can be enhanced more than when a single oxygen atomic layer 2 is formed.
　以上のような本発明のエピタキシャルウェーハの製造方法であれば、特殊な装置なども不要で汎用性の高い方法であるとともに、近接ゲッタリングのための酸素原子層の安定的かつ簡単な形成や、良質なエピタキシャル層の形成が可能であり、高品質なエピタキシャルウェーハを得ることができる。 The method for manufacturing an epitaxial wafer of the present invention as described above is a highly versatile method that does not require any special equipment, and also allows stable and simple formation of an oxygen atomic layer for proximity gettering. It is possible to form a high-quality epitaxial layer, and a high-quality epitaxial wafer can be obtained.
　以下、実施例及び比較例を用いて本発明を具体的に説明するが、本発明はこれらに限定されるものではない。 Hereinafter, the present invention will be specifically explained using Examples and Comparative Examples, but the present invention is not limited thereto.
　［実施例１及び比較例１］
　準備した単結晶シリコンウェーハの導電型、直径、結晶面方位及び酸素濃度は以下の通りである。
　ウェーハの導電型　　：ｐ型
　直径　　　　　　　　：３００ｍｍ
　結晶面方位　　　　　：（１００）
　酸素濃度　　　　　　：１４ｐｐｍａ　（ＪＥＩＴＡ） [Example 1 and Comparative Example 1]
The conductivity type, diameter, crystal plane orientation, and oxygen concentration of the prepared single crystal silicon wafer are as follows.
Wafer conductivity type: p type Diameter: 300mm
Crystal plane orientation: (100)
Oxygen concentration: 14ppma (JEITA)
　次に、準備した単結晶シリコンウェーハの表面から自然酸化膜を除去するために、バッチ式の洗浄装置で、単結晶シリコンウェーハをフッ酸洗浄に供した後、純水でのリンスに供した。 Next, in order to remove the native oxide film from the surface of the prepared single-crystal silicon wafer, the single-crystal silicon wafer was subjected to hydrofluoric acid cleaning using a batch-type cleaning apparatus, and then rinsed with pure water.
　その後、酸化膜を形成するために、バッチ式の装置で単結晶シリコンウェーハをＳＣ１溶液に浸漬した。このとき用意したＳＣ１溶液は、アンモニア水（ＮＨ３濃度２８％）：過酸化水素水（Ｈ２Ｏ２濃度３０％）：水の混合比を１：１：１０とし、溶液の温度は７０℃とした。ＳＣ１溶液に浸漬した時間は３分である。その後、単結晶シリコンウェーハを純水リンスした。 Thereafter, in order to form an oxide film, the single crystal silicon wafer was immersed in the SC1 solution using a batch type apparatus. The SC1 solution prepared at this time had a mixing ratio of aqueous ammonia (NH 3 concentration 28%): hydrogen peroxide solution (H 2 O 2 concentration 30%): water of 1:1:10, and the temperature of the solution was 70°C. And so. The immersion time in the SC1 solution was 3 minutes. Thereafter, the single crystal silicon wafer was rinsed with pure water.
　次に、酸化膜を形成した単結晶シリコンウェーハをエピタキシャル成長装置内に搬送した。実施例１では、水素雰囲気中で加熱することで酸化膜を薄膜化して、酸素原子層を形成した。加熱温度は７００℃とし、実施例１では加熱時間を２０～６００秒とした。一方、比較例１では、水素雰囲気中で加熱することでの酸化膜の薄膜化は行なわなかった。すなわち、比較例１での水素雰囲気中で加熱時間は０秒である。 Next, the single crystal silicon wafer with the oxide film formed thereon was transported into an epitaxial growth apparatus. In Example 1, the oxide film was thinned by heating in a hydrogen atmosphere to form an oxygen atomic layer. The heating temperature was 700° C., and in Example 1, the heating time was 20 to 600 seconds. On the other hand, in Comparative Example 1, the oxide film was not thinned by heating in a hydrogen atmosphere. That is, the heating time in Comparative Example 1 in a hydrogen atmosphere was 0 seconds.
　その後、酸素原子層を形成した単結晶シリコンウェーハ表面に、モノシランを用いて単結晶シリコンをエピタキシャル成長させた。温度は７００℃とし、モノシランの分圧は６０Ｐａとし、膜厚は１００ｎｍとした。このときキャリアガスには水素を用いた。これにより、実施例１及び比較例１のそれぞれにおいて、エピタキシャルウェーハを製造した。 Thereafter, monocrystalline silicon was epitaxially grown using monosilane on the surface of the single-crystal silicon wafer on which the oxygen atomic layer had been formed. The temperature was 700° C., the partial pressure of monosilane was 60 Pa, and the film thickness was 100 nm. At this time, hydrogen was used as the carrier gas. In this way, epitaxial wafers were manufactured in each of Example 1 and Comparative Example 1.
　なお、実施例１では、酸素原子層の形成と単結晶シリコンのエピタキシャル成長は同一チャンバーで行なった。 In Example 1, the formation of the oxygen atomic layer and the epitaxial growth of single crystal silicon were performed in the same chamber.
　一方、比較例１では、水素雰囲気中で加熱することでの酸化膜の薄膜化を行うことなく、単結晶シリコンをエピタキシャル成長させた。 On the other hand, in Comparative Example 1, single crystal silicon was epitaxially grown without thinning the oxide film by heating in a hydrogen atmosphere.
　その後、実施例１及び比較例１のそれぞれで製造したエピタキシャルウェーハについて、酸素原子層における酸素の平面濃度をＳＩＭＳにより測定した。図４に測定結果を示す。図４から、水素雰囲気で加熱することにより酸素原子層における酸素濃度を低減できることがわかる。 Thereafter, the planar concentration of oxygen in the oxygen atomic layer of each of the epitaxial wafers manufactured in Example 1 and Comparative Example 1 was measured by SIMS. Figure 4 shows the measurement results. It can be seen from FIG. 4 that the oxygen concentration in the oxygen atomic layer can be reduced by heating in a hydrogen atmosphere.
　また、実施例１における加熱時間を２０秒とした場合について基板の面内で酸素濃度測定を行なった結果を図５に黒丸で示す。図５から、実施例１では、酸素原子層を面内均一に形成できていることがわかる。 Furthermore, the results of measuring the oxygen concentration within the plane of the substrate when the heating time in Example 1 was 20 seconds are shown by black circles in FIG. From FIG. 5, it can be seen that in Example 1, the oxygen atomic layer could be formed uniformly within the plane.
　また、実施例１及び比較例１のそれぞれで製造したエピタキシャルウェーハについてＫＬＡ－Ｔｅｎｃｏｒ社製のＳｕｒｆＳｃａｎ　ＳＰ５により１００ｎｍ以上の大きさの欠陥を測定した結果、水素雰囲気中での加熱による酸化膜の薄膜化を行わなかった比較例１では、欠陥数が測定上限（約２００００個）に達したが、水素雰囲気中での加熱を行なった実施例１の水素雰囲気中で加熱した場合には、欠陥はいずれの場合にも２７個以下であり、欠陥を発生させることなく酸素原子層上に単結晶シリコンエピタキシャル層を形成できていることがわかった。 In addition, as a result of measuring defects with a size of 100 nm or more on the epitaxial wafers manufactured in Example 1 and Comparative Example 1 using SurfScan SP5 manufactured by KLA-Tencor, it was found that the oxide film was thinned by heating in a hydrogen atmosphere. In Comparative Example 1, in which heating was not performed, the number of defects reached the measurement upper limit (approximately 20,000), but in Example 1, in which heating was performed in a hydrogen atmosphere, no defects were present. In the case of , the number was 27 or less, indicating that a single crystal silicon epitaxial layer could be formed on the oxygen atomic layer without generating defects.
　［比較例２］
　比較例２では、まず、実施例１及び比較例１と同じ単結晶シリコン基板を準備した。次に、準備した単結晶シリコンウェーハの表面から自然酸化膜を除去するために、バッチ式の洗浄装置で、単結晶シリコンウェーハをフッ酸洗浄に供した後、純水リンスに供してから、水素雰囲気中で加熱した。加熱の温度は１１５０℃とし、時間は１分とした。 [Comparative example 2]
In Comparative Example 2, first, the same single crystal silicon substrate as in Example 1 and Comparative Example 1 was prepared. Next, in order to remove the natural oxide film from the surface of the prepared single-crystal silicon wafer, the single-crystal silicon wafer was subjected to hydrofluoric acid cleaning using a batch-type cleaning device, followed by deionized water rinsing, and then hydrogen Heated in atmosphere. The heating temperature was 1150° C. and the heating time was 1 minute.
　その後、大気中に５時間放置することで単結晶シリコンウェーハの表面に酸素原子層を形成した。 Thereafter, an oxygen atomic layer was formed on the surface of the single crystal silicon wafer by leaving it in the atmosphere for 5 hours.
　次に、実施例１および比較例１と同じ条件で、酸素原子層を形成した単結晶シリコンウェーハ表面に、単結晶シリコンをエピタキシャル成長させた。このようにして、比較例２において、エピタキシャルウェーハを製造した。 Next, under the same conditions as in Example 1 and Comparative Example 1, single crystal silicon was epitaxially grown on the surface of the single crystal silicon wafer on which the oxygen atomic layer was formed. In this manner, an epitaxial wafer was manufactured in Comparative Example 2.
　その後、比較例２で製造したエピタキシャルウェーハについて、面内８点で酸素原子層における酸素の平面濃度をＳＩＭＳにより測定した。図５に測定結果を三角で示す。図５の結果から、大気中放置を行って酸素原子層を形成した比較例２では、酸素濃度がウェーハ面内で不均一になった。これは、ウェーハの中央部よりも外周部の方がシリコンの酸化速度が速かったためである。酸化速度がウェーハ面内で変化する原因としては、空気の流速の変化が考えられる。空気の流速が速い方が酸素の供給量が多いため、シリコンの酸化速度が速くなる。これらのことから、ウェーハ中央部から外周部に向かって空気の流速が速くなる流速分布となっていたことで、ウェーハ面内で酸素濃度が変化したと考えられる。 Thereafter, for the epitaxial wafer manufactured in Comparative Example 2, the plane concentration of oxygen in the oxygen atomic layer was measured at 8 points in the plane by SIMS. Figure 5 shows the measurement results as triangles. From the results shown in FIG. 5, in Comparative Example 2 in which an oxygen atomic layer was formed by leaving the wafer in the atmosphere, the oxygen concentration became non-uniform within the wafer surface. This is because the oxidation rate of silicon was faster at the outer periphery of the wafer than at the center. A possible cause of the change in the oxidation rate within the wafer plane is a change in the air flow rate. The faster the air flow rate, the greater the amount of oxygen supplied, which increases the rate of oxidation of silicon. From these facts, it is considered that the oxygen concentration within the wafer surface changed due to the flow velocity distribution in which the air velocity became faster from the center of the wafer toward the outer periphery.
　また、比較例２で製造したエピタキシャルウェーハについてＫＬＡ－Ｔｅｎｃｏｒ社製のＳｕｒｆＳｃａｎ　ＳＰ５により１００ｎｍ以上の大きさの欠陥を測定した結果、欠陥数は測定上限（約２００００個）に達した。 In addition, as a result of measuring defects with a size of 100 nm or more on the epitaxial wafer manufactured in Comparative Example 2 using SurfScan SP5 manufactured by KLA-Tencor, the number of defects reached the measurement upper limit (approximately 20,000).
　以上に説明したように、本発明の例である実施例１では、酸化性溶液による酸化膜形成及び酸化膜の薄膜化の何れも行わなかった比較例２よりも酸素原子層をエピタキシャル層に安定的にかつ簡便に導入することができたとともに、上記比較例２及び酸化層の薄膜化を行わなかった比較例１よりも良質な単結晶シリコンのエピタキシャル層を有するエピタキシャルウェーハを製造できた。 As explained above, in Example 1, which is an example of the present invention, the oxygen atomic layer is more stable in the epitaxial layer than in Comparative Example 2, in which neither oxide film formation using an oxidizing solution nor thinning of the oxide film was performed. In addition, it was possible to manufacture an epitaxial wafer having a single-crystal silicon epitaxial layer of better quality than Comparative Example 2 and Comparative Example 1 in which the oxide layer was not thinned.
　本明細書は、以下の態様を包含する。
　［１］単結晶シリコンウェーハ上に単結晶シリコンエピタキシャル層を形成するエピタキシャルウェーハの製造方法であって、単結晶シリコンウェーハの表面から自然酸化膜を除去する工程、前記自然酸化膜除去後に、前記単結晶シリコンウェーハの表面に酸化性溶液により酸化膜を形成する工程、前記酸化膜を形成した後に、前記酸化膜を薄膜化して、酸素原子層を形成する工程、及び前記酸素原子層を形成した後に、前記酸素原子層を有する前記単結晶シリコンウェーハの表面に単結晶シリコンをエピタキシャル成長させる工程を含むことを特徴とするエピタキシャルウェーハの製造方法。
　［２］前記自然酸化膜の除去を、フッ酸を含む溶液により行うことを特徴とする［１］に記載のエピタキシャルウェーハの製造方法。
　［３］前記酸化性溶液として、ＳＣ１溶液、過酸化水素水又はオゾン水を用いることを特徴とする［１］又は［２］に記載のエピタキシャルウェーハの製造方法。
　［４］前記酸化性溶液として前記ＳＣ１溶液又は前記過酸化水素水を用い、前記ＳＣ１溶液又は前記過酸化水素水の温度を２０℃以上かつ８０℃以下とすることを特徴とする［３］に記載のエピタキシャルウェーハの製造方法。
　［５］前記酸化性溶液として前記オゾン水を用い、前記オゾン水の温度を１０℃以上かつ３０℃以下とすることを特徴とする［３］に記載のエピタキシャルウェーハの製造方法。
　［６］前記酸化膜の薄膜化を水素雰囲気中での前記単結晶シリコンウェーハの加熱により行うことを特徴とする［１］～［５］のいずれか１つに記載のエピタキシャルウェーハの製造方法。
　［７］前記水素雰囲気中での加熱温度を６００℃以上かつ１２５０℃以下とすることを特徴とする［６］に記載のエピタキシャルウェーハの製造方法。
　［８］前記酸化膜の薄膜化を水素原子を含むガスを用いたプラズマ又は不活性ガスを用いたプラズマにより行うことを特徴とする［１］～［５］のいずれか１つに記載のエピタキシャルウェーハの製造方法。
　［９］前記単結晶シリコンをエピタキシャル成長させる工程では、４５０℃以上かつ８００℃以下の温度で前記単結晶シリコンのエピタキシャル成長を行うことを特徴とする［１］～［８］のいずれか１つに記載のエピタキシャルウェーハの製造方法。
　［１０］前記単結晶シリコンをエピタキシャル成長させる工程で、シリコンの原料ガスの分圧を０．１Ｐａ以上かつ２０００Ｐａ以下とすることを特徴とする［１］～［９］のいずれか１つに記載のエピタキシャルウェーハの製造方法。
　［１１］前記酸素原子層を形成する工程において、前記酸素原子層の酸素の平面濃度を６×１０１４ａｔｏｍｓ／ｃｍ２以下とすることを特徴とする［１］～［１０］のいずれか１つに記載のエピタキシャルウェーハの製造方法。
　［１２］前記単結晶シリコンをエピタキシャル成長させる工程の後に、前記酸化膜を形成する工程と前記酸素原子層を形成する工程と前記単結晶シリコンをエピタキシャル成長させる工程とを繰り返し行うことを特徴とする［１］から［１１］のいずれか一項に記載のエピタキシャルウェーハの製造方法。 The specification includes the following aspects.
[1] A method for manufacturing an epitaxial wafer in which a single-crystal silicon epitaxial layer is formed on a single-crystal silicon wafer, the step of removing a natural oxide film from the surface of the single-crystal silicon wafer; a step of forming an oxide film on the surface of a crystalline silicon wafer using an oxidizing solution; a step of thinning the oxide film to form an oxygen atomic layer after forming the oxide film; and a step of forming an oxygen atomic layer after forming the oxygen atomic layer. . A method for manufacturing an epitaxial wafer, comprising the step of epitaxially growing single crystal silicon on the surface of the single crystal silicon wafer having the oxygen atomic layer.
[2] The method for manufacturing an epitaxial wafer according to [1], wherein the natural oxide film is removed using a solution containing hydrofluoric acid.
[3] The method for producing an epitaxial wafer according to [1] or [2], wherein an SC1 solution, hydrogen peroxide solution, or ozone water is used as the oxidizing solution.
[4] In [3], the SC1 solution or the hydrogen peroxide solution is used as the oxidizing solution, and the temperature of the SC1 solution or the hydrogen peroxide solution is 20°C or higher and 80°C or lower. A method of manufacturing the epitaxial wafer described above.
[5] The method for manufacturing an epitaxial wafer according to [3], characterized in that the ozone water is used as the oxidizing solution, and the temperature of the ozone water is 10°C or more and 30°C or less.
[6] The method for producing an epitaxial wafer according to any one of [1] to [5], wherein the oxide film is thinned by heating the single crystal silicon wafer in a hydrogen atmosphere.
[7] The method for producing an epitaxial wafer according to [6], wherein the heating temperature in the hydrogen atmosphere is 600°C or higher and 1250°C or lower.
[8] The epitaxial method according to any one of [1] to [5], wherein the oxide film is thinned by plasma using a gas containing hydrogen atoms or plasma using an inert gas. Wafer manufacturing method.
[9] According to any one of [1] to [8], in the step of epitaxially growing the single crystal silicon, the epitaxial growth of the single crystal silicon is performed at a temperature of 450° C. or higher and 800° C. or lower. A method for manufacturing an epitaxial wafer.
[10] The method according to any one of [1] to [9], characterized in that in the step of epitaxially growing the single crystal silicon, the partial pressure of the silicon source gas is set to 0.1 Pa or more and 2000 Pa or less. Method for manufacturing epitaxial wafers.
[11] Any one of [1] to [10], wherein in the step of forming the oxygen atomic layer, the planar concentration of oxygen in the oxygen atomic layer is 6×10 14 atoms/cm 2 or less. The method for manufacturing an epitaxial wafer described in .
[12] After the step of epitaxially growing the single crystal silicon, the step of forming the oxide film, the step of forming the oxygen atomic layer, and the step of epitaxially growing the single crystal silicon are repeatedly performed [1 ] to [11]. The method for manufacturing an epitaxial wafer according to any one of [11].
　なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。 Note that the present invention is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any embodiment that has substantially the same configuration as the technical idea stated in the claims of the present invention and has similar effects is the present invention. covered within the technical scope of

Claims (12)

  1. 　単結晶シリコンウェーハ上に単結晶シリコンエピタキシャル層を形成するエピタキシャルウェーハの製造方法であって、
    　単結晶シリコンウェーハの表面から自然酸化膜を除去する工程、
    　前記自然酸化膜除去後に、前記単結晶シリコンウェーハの表面に酸化性溶液により酸化膜を形成する工程、
    　前記酸化膜を形成した後に、前記酸化膜を薄膜化して、酸素原子層を形成する工程、及び
    　前記酸素原子層を形成した後に、前記酸素原子層を有する前記単結晶シリコンウェーハの表面に単結晶シリコンをエピタキシャル成長させる工程
    を含むことを特徴とするエピタキシャルウェーハの製造方法。     A method for manufacturing an epitaxial wafer, comprising forming a single crystal silicon epitaxial layer on a single crystal silicon wafer,
    A process of removing a natural oxide film from the surface of a single crystal silicon wafer,
    After removing the natural oxide film, forming an oxide film on the surface of the single crystal silicon wafer using an oxidizing solution;
    After forming the oxide film, thinning the oxide film to form an oxygen atomic layer; and After forming the oxygen atomic layer, forming a single crystal on the surface of the single crystal silicon wafer having the oxygen atomic layer. A method for manufacturing an epitaxial wafer, comprising a step of epitaxially growing silicon.
  2. 　前記自然酸化膜の除去を、フッ酸を含む溶液により行うことを特徴とする請求項１に記載のエピタキシャルウェーハの製造方法。 The method for manufacturing an epitaxial wafer according to claim 1, wherein the removal of the native oxide film is performed using a solution containing hydrofluoric acid.
  3. 　前記酸化性溶液として、ＳＣ１溶液、過酸化水素水又はオゾン水を用いることを特徴とする請求項１に記載のエピタキシャルウェーハの製造方法。 The method for manufacturing an epitaxial wafer according to claim 1, wherein an SC1 solution, hydrogen peroxide solution, or ozone water is used as the oxidizing solution.
  4. 　前記酸化性溶液として前記ＳＣ１溶液又は前記過酸化水素水を用い、前記ＳＣ１溶液又は前記過酸化水素水の温度を２０℃以上かつ８０℃以下とすることを特徴とする請求項３に記載のエピタキシャルウェーハの製造方法。 The epitaxial method according to claim 3, wherein the SC1 solution or the hydrogen peroxide solution is used as the oxidizing solution, and the temperature of the SC1 solution or the hydrogen peroxide solution is 20° C. or higher and 80° C. or lower. Wafer manufacturing method.
  5. 　前記酸化性溶液として前記オゾン水を用い、前記オゾン水の温度を１０℃以上かつ３０℃以下とすることを特徴とする請求項３に記載のエピタキシャルウェーハの製造方法。 4. The method for manufacturing an epitaxial wafer according to claim 3, wherein the ozone water is used as the oxidizing solution, and the temperature of the ozone water is set to 10° C. or higher and 30° C. or lower.
  6. 　前記酸化膜の薄膜化を水素雰囲気中での前記単結晶シリコンウェーハの加熱により行うことを特徴とする請求項１に記載のエピタキシャルウェーハの製造方法。 The method for manufacturing an epitaxial wafer according to claim 1, wherein the oxide film is thinned by heating the single crystal silicon wafer in a hydrogen atmosphere.
  7. 　前記水素雰囲気中での加熱温度を６００℃以上かつ１２５０℃以下とすることを特徴とする請求項６に記載のエピタキシャルウェーハの製造方法。 7. The method for manufacturing an epitaxial wafer according to claim 6, wherein the heating temperature in the hydrogen atmosphere is 600°C or higher and 1250°C or lower.
  8. 　前記酸化膜の薄膜化を水素原子を含むガスを用いたプラズマ又は不活性ガスを用いたプラズマにより行うことを特徴とする請求項１に記載のエピタキシャルウェーハの製造方法。 The method for manufacturing an epitaxial wafer according to claim 1, wherein the thinning of the oxide film is performed using plasma using a gas containing hydrogen atoms or plasma using an inert gas.
  9. 　前記単結晶シリコンをエピタキシャル成長させる工程では、４５０℃以上かつ８００℃以下の温度で前記単結晶シリコンのエピタキシャル成長を行うことを特徴とする請求項１に記載のエピタキシャルウェーハの製造方法。 The method for manufacturing an epitaxial wafer according to claim 1, wherein in the step of epitaxially growing the single crystal silicon, the epitaxial growth of the single crystal silicon is performed at a temperature of 450° C. or higher and 800° C. or lower.
  10. 　前記単結晶シリコンをエピタキシャル成長させる工程で、シリコンの原料ガスの分圧を０．１Ｐａ以上かつ２０００Ｐａ以下とすることを特徴とする請求項９に記載のエピタキシャルウェーハの製造方法。 The method for manufacturing an epitaxial wafer according to claim 9, characterized in that in the step of epitaxially growing the single crystal silicon, the partial pressure of the silicon source gas is set to 0.1 Pa or more and 2000 Pa or less.
  11. 　前記酸素原子層を形成する工程において、前記酸素原子層の酸素の平面濃度を６×１０１４ａｔｏｍｓ／ｃｍ２以下とすることを特徴とする請求項１に記載のエピタキシャルウェーハの製造方法。 2. The method for manufacturing an epitaxial wafer according to claim 1, wherein in the step of forming the oxygen atomic layer, the planar concentration of oxygen in the oxygen atomic layer is set to 6×10 14 atoms/cm 2 or less.
  12. 　前記単結晶シリコンをエピタキシャル成長させる工程の後に、前記酸化膜を形成する工程と前記酸素原子層を形成する工程と前記単結晶シリコンをエピタキシャル成長させる工程とを繰り返し行うことを特徴とする請求項１から請求項１１のいずれか一項に記載のエピタキシャルウェーハの製造方法。 After the step of epitaxially growing the single-crystal silicon, the step of forming the oxide film, the step of forming the oxygen atomic layer, and the step of epitaxially growing the single-crystal silicon are repeatedly performed. 12. The method for manufacturing an epitaxial wafer according to any one of Item 11.
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JP2009016637A (en) * 2007-07-06 2009-01-22 Shin Etsu Handotai Co Ltd Method of manufacturing semiconductor substrate
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JP2021111696A (en) * 2020-01-10 2021-08-02 信越半導体株式会社 Manufacturing method for epitaxial wafer, and epitaxial wafer
JP2022125625A (en) * 2021-02-17 2022-08-29 信越半導体株式会社 Manufacturing method for epitaxial wafer
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JP2000323689A (en) * 1999-05-14 2000-11-24 Toshiba Corp Semiconductor epitaxial substrate and its manufacture
JP2009016637A (en) * 2007-07-06 2009-01-22 Shin Etsu Handotai Co Ltd Method of manufacturing semiconductor substrate
JP2009289807A (en) * 2008-05-27 2009-12-10 Hitachi Kokusai Electric Inc Method of manufacturing semiconductor device
JP2014165494A (en) * 2013-02-22 2014-09-08 Imec Oxygen monolayer on semiconductor
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JP2021111696A (en) * 2020-01-10 2021-08-02 信越半導体株式会社 Manufacturing method for epitaxial wafer, and epitaxial wafer
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