Epitaxial wafer manufacturing method

Abstract

To provide a manufacturing method for an epitaxial wafer, capable of stably and easily introducing an oxygen atom layer into an epitaxial layer and manufacturing an epitaxial wafer including an epitaxial layer of high-quality single-crystal silicon.SOLUTION: A manufacturing method for an epitaxial wafer for forming a single-crystal silicon epitaxial layer on a single-crystal silicon wafer includes the steps of removing a natural oxide film from a surface of the single-crystal silicon wafer, after removing the natural oxide film, forming an oxide film by an oxidative solution on the surface of the single-crystal silicon wafer, after forming the oxide film, thinning the oxide film to form an oxygen atom layer, and after forming the oxygen atom layer, performing epitaxial growth of the single-crystal silicon on the surface of the single-crystal silicon wafer including the oxygen atom layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an epitaxial wafer. [Background technology]

[0002] Silicon substrates, which form semiconductor elements such as solid-state imaging devices and other transistors, are required to have the ability to getter away elements that disrupt device characteristics, such as heavy metals. Various gettering methods have been proposed and put into practical use, including providing a polycrystalline silicon (Poly-Si) layer on the backside of the silicon substrate, forming a damaged layer by blasting, using a silicon substrate with a high concentration of boron, and forming precipitates. Gettering by oxygen precipitation involves taking in metals that have a high ionization tendency (low electronegativity) against oxygen, which has a high electronegativity.

[0003] Another method proposed is proximity gettering, which involves forming a gettering layer near the active region of a device. For example, a substrate can be formed by epitaxially growing silicon on a substrate into which carbon has been ion-implanted. Gettering requires elements to diffuse to the gettering site (where the energy of the entire system is reduced by bonding or clustering at the site, rather than by the metal existing as a single element). The diffusion coefficient of metal elements contained in silicon varies depending on the element, and in addition, recent trends toward lower process temperatures have made it difficult for metals to diffuse to the gettering site. Taking this into consideration, the proximity gettering method has been proposed.

[0004] If oxygen can be used for proximity gettering, it is believed that a silicon substrate with a very effective gettering layer will be obtained. In particular, an epitaxial wafer with an oxygen atomic layer in the middle of the epitaxial layer can reliably getter metal impurities even in recent low-temperature processes.

[0005] The above discussion has focused on gettering metal impurities, but it is known that oxygen has the effect of preventing autodoping during epitaxial growth by forming a CVD oxide film on the backside.

[0006] Regarding prior art, Patent Document 1 describes a method of forming a thin layer of oxygen on silicon and then growing silicon on top of it. This method is based on ALD (Atomic Layer Deposition). ALD is a method of adsorbing molecules containing target atoms and then dissociating and desorbing unnecessary atoms (molecules) from the molecules. It utilizes surface bonding, is highly accurate, and has good reaction controllability, making it widely used.

[0007] Patent Document 2 describes a method in which a native oxide film is formed on a clean silicon surface formed by vacuum heating or the like, and then an oxide film or another substance is adsorbed and deposited.

[0008] Patent Documents 3 and 4 show that the introduction of multiple oxygen atomic layers into a silicon substrate makes it possible to improve device characteristics (mobility).

[0009] Patent Document 5 discloses a method for forming an epitaxial layer on an atomic layer having a thickness of 5 nm or less using SiH4 gas, and also discloses a method for forming an oxygen atomic layer using oxygen gas.

[0010] Patent Documents 6 and 7 describe methods for epitaxially growing single-crystal silicon after contacting the surface of a semiconductor substrate with an oxidizing gas or an oxidizing solution to form an oxide film, and Patent Document 6 describes a method in which an oxidizing gas is introduced and then a silicon film-forming gas is introduced.

[0011] Patent Document 8 describes a method in which a native oxide film made of a group IV element on the surface of a wafer is removed, the wafer is oxidized to form an oxygen atomic layer, and then single-crystal silicon is epitaxially grown.

[0012] Patent Document 9 describes a method in which an oxygen-containing precursor is supplied to a CVD epitaxy furnace to form an oxygen-inserted partial monolayer, and then a silicon epitaxial layer is formed.

[0013] Non-Patent Document 1 discloses a method in which a native oxide film is removed by HF, then oxidized in the atmosphere, and then an amorphous silicon film is formed by low-pressure CVD, and then single-crystal silicon is formed by crystallization heat treatment. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-165494 [Patent Document 2] Japanese Patent Application Publication No. 05-243266 [Patent Document 3] U.S. Patent No. 7,153,763 [Patent Document 4] U.S. Patent No. 7,265,002 [Patent Document 5] Japanese Patent Application Publication No. 2019-004050 [Patent Document 6] Japanese Patent Application Laid-Open No. 2008-263025 [Patent Document 7] Japanese Patent Application Laid-Open No. 2009-016637 [Patent Document 8] Patent Publication No. 2021-111696 [Patent Document 9] Japanese Patent Publication No. 2022-22194 [Non-patent literature]

[0015] [Non-Patent Document 1] I. Mizushima et al., Jpn. J. Appl. Phys. 39(2000)2147. Summary of the Invention [Problem to be solved by the invention]

[0016] As mentioned above, the method of gettering metal impurities by forming an oxygen layer within the wafer has been used for some time. However, while this conventional technique can accurately obtain a thin oxygen layer, it has problems such as a complex device configuration and a large number of steps.

[0017] For example, the technology described in Patent Document 1 requires at least two chambers, one for ALD and one for CVD, because ALD cannot epitaxially grow single-crystal silicon, resulting in a problem of complex equipment configuration.

[0018] Furthermore, the techniques described in Patent Documents 5 and 9 have the problem that two chambers with separate exhaust systems must be prepared to prevent an explosion due to a reaction between SiH4 and oxygen.

[0019] Furthermore, the technique described in Patent Document 6 has the problem that a special device that takes safety into consideration is required to prevent an explosion due to a reaction between the oxidizing gas and the silicon film-forming gas.

[0020] Furthermore, the method described in Non-Patent Document 1 requires heat treatment during crystallization, which increases the number of process steps. Furthermore, amorphous silicon generally contains a large amount of hydrogen, which can lead to the formation of hydrogen-induced defects during the crystallization heat treatment.

[0021] Furthermore, the technique described in Patent Document 8 requires a long period of oxidation to form an oxygen atomic layer, and also has the problem that it is difficult to make the oxygen concentration uniform across the wafer surface.

[0022] Furthermore, the prior art has the problem that there is no description of how to stably introduce an oxygen layer or a specific description of how to form a high-quality epitaxial layer of single-crystal silicon.

[0023] For example, Patent Document 2 does not disclose any method for forming an epitaxial layer of single crystal silicon on the surface of a wafer without generating dislocations and stacking faults.

[0024] 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.

[0025] Furthermore, Patent Documents 6 and 7 do not describe a method for removing the native oxide film before contact with an oxidizing gas or an oxidizing solution.

[0026] As described above, while conventional techniques can accurately obtain an oxygen atomic layer, they have problems such as a complex apparatus configuration, instability in introducing the oxygen layer, and inability to obtain a high-quality single-crystal silicon epitaxial layer. Therefore, there is a need for a method for manufacturing an epitaxial wafer that can stably and easily introduce an oxygen atomic layer into an epitaxial layer.

[0027] The present invention has been made in view of the above-mentioned problems of the conventional technology, and an object of the present invention is to provide a method for manufacturing an epitaxial wafer that can stably and easily introduce an oxygen atomic layer into an epitaxial layer and can manufacture an epitaxial wafer having an epitaxial layer of high-quality single crystal silicon. [Means for solving the problem]

[0028] In order to solve the above problems, 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 comprising the steps of: removing a native oxide film from the surface of the single crystal silicon wafer; forming an oxide film on the surface of the single crystal silicon wafer using an oxidizing solution after removing the native oxide film; After forming the oxide film, thinning the oxide film to form an oxygen atomic layer; and 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; The present invention provides a method for producing an epitaxial wafer, comprising:

[0029] By employing such a method for manufacturing an epitaxial wafer, single crystal silicon can be grown without forming dislocations or stacking faults on the surface of the single crystal silicon wafer having the oxygen atomic layer, while leaving the oxygen atomic layer. That is, the method for manufacturing an epitaxial wafer of the present invention makes it possible to stably and easily introduce the oxygen atomic layer into the epitaxial layer, and to manufacture an epitaxial wafer having a high-quality single crystal silicon epitaxial layer.

[0030] Furthermore, for example, the native oxide film can be removed using a solution containing hydrofluoric acid.

[0031] By using a solution containing hydrofluoric acid in this way, the native oxide film can be removed in a short time.

[0032] The oxidizing solution may be an SC1 solution, hydrogen peroxide solution, or ozone water.

[0033] This method allows the oxide film to be formed easily in a short time.

[0034] 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.

[0035] At such a temperature, the single crystal silicon wafer can be easily oxidized without the need for special equipment.

[0036] 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 higher and 30°C or lower.

[0037] At such a temperature, the wafer can be reliably oxidized.

[0038] The oxide film can be thinned by heating the single crystal silicon wafer in a hydrogen atmosphere.

[0039] By carrying out the heat treatment in a hydrogen atmosphere in this way, a part of the oxide film can be stably reduced, thereby making it possible to thin the oxide film.

[0040] 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.

[0041] By setting the temperature within this range, it is possible to reliably reduce a part of the oxide film, thereby making it possible to thin the oxide film.

[0042] Alternatively, the oxide film can be thinned by plasma using a gas containing hydrogen atoms or plasma using an inert gas.

[0043] The plasma method using a gas containing hydrogen atoms can stably reduce a portion of the oxide film at low temperatures, thereby thinning the oxide film.The plasma method using an inert gas can thin the oxide film by sputtering it with high-energy particles generated by the plasma.

[0044] In addition, 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.

[0045] By setting the temperature within this range, epitaxial growth can be achieved without generating defects.

[0046] In addition, 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.

[0047] By setting the pressure within this range, it is possible to epitaxially grow single crystal silicon more stably without generating defects.

[0048] In addition, the planar concentration of oxygen in the oxygen atomic layer is 6×10 14 atoms / cm 2 It can be as follows:

[0049] By setting the oxygen concentration within this range, epitaxial wafers can be stably manufactured without generating defects.

[0050] Furthermore, 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 can be repeated.

[0051] By forming a plurality of oxygen atomic layers in this way, the gettering effect can be enhanced compared to the case of a single layer. [Effects of the Invention]

[0052] As described above, the present invention provides a method for stably and easily introducing an oxygen atomic layer into the epitaxial layer of a silicon epitaxial wafer used in advanced devices, and for producing an epitaxial wafer having a high-quality single-crystal silicon epitaxial layer. It also makes it possible to produce a proximity gettering substrate that exhibits a proximity gettering effect due to the oxygen atomic layer. [Brief explanation of the drawings]

[0053] [Figure 1] 1 is a diagram showing a flow of a method for manufacturing an epitaxial wafer according to the present invention. [Figure 2] 1 is a schematic cross-sectional view of an example of an epitaxial wafer that can be manufactured by the epitaxial wafer manufacturing method of the present invention. [Figure 3] 1 is a schematic cross-sectional view of another example of an epitaxial wafer that can be manufactured by the epitaxial wafer manufacturing method of the present invention. FIG. [Figure 4] 1 is a graph showing the relationship between heating time in a hydrogen atmosphere and oxygen concentration in Example 1 and Comparative Example 1. [Figure 5] 1 is a graph showing the distribution of oxygen concentration in an oxygen atomic layer within a substrate surface in Example 1 and Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0054] As described above, there has been a demand for a method for manufacturing an epitaxial wafer that does not require special equipment or complicated processes, 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.

[0055] As a result of extensive research into the above-mentioned problems, the present inventors have found that 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 comprising the steps of: removing a native oxide film from a surface of the single crystal silicon wafer; after removing the native 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, makes it possible to stably and easily introduce an oxygen atomic layer into the epitaxial layer of single crystal silicon, without forming dislocations and stacking faults in the epitaxial layer, and have completed the present invention.

[0056] That is, 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 comprising the steps of: removing a native oxide film from the surface of the single crystal silicon wafer; forming an oxide film on the surface of the single crystal silicon wafer using an oxidizing solution after removing the native oxide film; After forming the oxide film, thinning the oxide film to form an oxygen atomic layer; and 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; The method for producing an epitaxial wafer is characterized by comprising the steps of:

[0057] The present invention will be described in detail below with reference to the drawings, but the present invention is not limited thereto.

[0058] [Epitaxial wafer] According to the epitaxial wafer manufacturing method of the present invention, it is possible to manufacture, for example, an epitaxial wafer 10A whose cross section is schematically shown in Fig. 2. 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.

[0059] 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 an oxygen atomic layer 2 between the single crystal epitaxial silicon layer 3 and the single crystal silicon wafer 1.

[0060] [Epitaxial wafer manufacturing method]

[0061] FIG. 1 shows a flow of a method for producing an epitaxial wafer according to the present invention.

[0062] The step S11 in FIG. 1 is a step of preparing a single crystal silicon wafer.

[0063] 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) or a substrate manufactured by the floating zone method (hereinafter referred to as the FZ method) may be used. Also, 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.

[0064] S12 in FIG. 1 is a step of removing a native oxide film from the surface of the single crystal silicon wafer prepared in step S11.

[0065] For example, the native oxide film can be removed using a solution containing hydrofluoric acid.

[0066] By using a solution containing hydrofluoric acid in this way, the native oxide film can be removed in a short time.

[0067] In step S12 of removing the native oxide film, for example, hydrofluoric acid or buffered hydrofluoric acid may be used. Buffered hydrofluoric acid is a solution obtained by mixing hydrofluoric acid and ammonium fluoride. The concentration of hydrofluoric acid in the hydrofluoric acid-containing solution 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 hydrofluoric acid-containing solution may be, for example, 10°C or more and 50°C or less. A temperature of 10°C or more can prevent condensation from forming on the wafer after treatment with the hydrofluoric acid-containing solution. Furthermore, a temperature of 50°C or less can reduce the amount of hydrofluoric acid that volatilizes, thereby avoiding safety issues.

[0068] The time for cleaning (removal of native oxide film) with a solution containing hydrofluoric acid can be, for example, until water repellency is confirmed, but can be, for example, 1 second or more and 1 hour or less. If it is 1 second or more, the native oxide film can be removed. Also, if it is 1 hour or less, it can be prevented from taking too long.

[0069] Cleaning with a solution containing hydrofluoric acid (removal of native oxide film) may be performed using a batch-type cleaning device or a single-wafer-type cleaning device.

[0070] In step S12, the native oxide film may be removed using vapor of a solution containing hydrofluoric acid.

[0071] 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 the native oxide film has been removed in step S12.

[0072] Particles are likely to adhere to a hydrophobic surface without an oxide film, but the hydrophilic surface with an oxide film can prevent particle adhesion. For this reason, for example, by immersing a single crystal silicon wafer in an oxidizing solution to form an oxide film on the surface, it is possible to prevent particles from adhering to the single crystal silicon wafer during the transport from the cleaning device to the next process.

[0073] When immersing the single crystal silicon wafer in the oxidizing solution, for example, a batch type apparatus or a single wafer type apparatus may be used.

[0074] As the oxidizing solution, for example, SC1 solution, hydrogen peroxide solution, or ozone water can be used.

[0075] This method allows the oxide film to be formed easily in a short time.

[0076] More specifically, the SC1 solution is a mixture of ammonia, hydrogen peroxide, and water. The hydrogen peroxide oxidizes the surface of a single-crystal silicon wafer, while the ammonia etches the oxide film, thereby lifting off and removing particles adhering to the surface of the single-crystal silicon wafer. 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 a single-crystal silicon wafer. The mixing ratio of the components in the SC1 solution is preferably such that the amount of hydrogen peroxide is greater than the amount of ammonia water. This mixing ratio allows for stable and uniform formation of an oxide film. For example, the mixing ratio of ammonia water (NH3 concentration 28%), hydrogen peroxide water (H2O2 concentration 30%), and water can be 1:1 to 2:5 to 100.

[0077] 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 it is 1 second or more, an oxygen atomic layer can be sufficiently formed. Also, if it is immersed for 1 hour or less, it is possible to prevent the immersion time from taking too long.

[0078] When oxidation is performed using hydrogen peroxide, the concentration of the hydrogen peroxide can be set to, for example, 0.01% or more and 30% or less. A concentration of 0.01% or more ensures the formation of an oxide film. Furthermore, a concentration of 30% or less ensures that the amount of hydrogen peroxide evaporated from the cleaning solution is kept appropriate, preventing an increase in the burden on disposal facilities.

[0079] The time for immersing the single crystal silicon wafer in hydrogen peroxide solution can be, for example, 1 second or more and 1 hour or less. If it is 1 second or more, an oxygen atomic layer can be formed. Also, if it is immersed for 1 hour or less, it is possible to prevent the immersion time from taking too long.

[0080] The temperature of the SC1 solution or 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 formed stably. If the temperature is 80°C or lower, the amount of evaporation of the cleaning solution can be kept constant and an increase in bubbles in the cleaning solution can be prevented, thereby allowing an oxide film to be formed uniformly within the wafer surface. In other words, at such a temperature, single crystal silicon wafers can be easily oxidized without preparing special equipment.

[0081] In the oxide film forming step S13, 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. If the ozone concentration is 1 ppm or more, an oxide film can be stably formed on the surface of the single crystal silicon wafer. Furthermore, by setting the ozone concentration to 500 ppm or less, it is possible to prevent variations in the oxide film thickness caused by fluctuations in ozone concentration due to ozone decomposition or escape into the gas phase.

[0082] 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 condensation from occurring on the wafer after the ozone water treatment. Furthermore, by setting the temperature to 30°C or lower, it is possible to prevent ozone from being decomposed in the ozone water or escaping into the gas phase, thereby ensuring oxidation of the single crystal silicon wafer.

[0083] 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 it is 1 second or more, an oxygen atomic layer can be formed. Also, if it is immersed for 1 hour or less, it is possible to prevent the immersion time from taking too long.

[0084] S14 in FIG. 1 is a step of thinning the oxide film formed in step S13 and forming an oxygen atomic layer.

[0085] The oxide film can be thinned by, for example, heating the single crystal silicon wafer in a hydrogen atmosphere. By performing heat treatment in such a hydrogen atmosphere, the oxide film can be uniformly and stably reduced, thereby thinning the oxide film.

[0086] Heating may be performed under atmospheric pressure or under reduced pressure. A reduced pressure environment refers to, for example, an environment of 100 Pa or more but less than atmospheric pressure. The hydrogen atmosphere may be, for example, a 100% hydrogen atmosphere or a mixture of hydrogen and an inert gas. The inert gas may be any of nitrogen, helium, neon, argon, krypton, and xenon.

[0087] 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 to a thinner film. Furthermore, by setting the temperature to 1250° C. or lower, a general-purpose heating device can be used.

[0088] The heating time can be, for example, 1 second or more and 1 hour or less. If it is 1 second or more, the oxide film can be reduced to a thinner film. Also, if it is 1 hour or less, it can be prevented from taking too long.

[0089] The pressure, heating temperature, and heating time can be changed depending on the thickness of the oxide film. When the oxide film is thick, the pressure, temperature, or heating time can be increased to thin the oxide film and form an oxygen atomic layer. When the oxide film is thin, the pressure, temperature, or heating time can be decreased to prevent the oxide film from being completely removed and the oxygen atomic layer from disappearing.

[0090] The heating of the single crystal silicon wafer in a hydrogen atmosphere may be carried out in a heat treatment furnace or in a single crystal silicon film forming apparatus, which may be of a batch type or a single wafer type.

[0091] Alternatively, the oxide film can be thinned in step S14 by using a plasma containing hydrogen atoms or an inert gas. Examples of the gas include hydrogen molecules, ammonia, nitrogen, argon, helium, neon, krypton, and xenon. These gases may be used in combination.

[0092] In the case of hydrogen molecules and ammonia containing hydrogen atoms, hydrogen radicals generated by plasma can stably reduce the oxide film at low temperatures to make it thinner.

[0093] When nitrogen, argon, helium, neon, krypton, or xenon is used as the inert gas, the oxide film can be thinned by sputtering it with high-energy particles generated by plasma.

[0094] When the oxide film is thinned using the plasma, the thinning may be carried out at room temperature or under heating.

[0095] 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.

[0096] The time of exposure to plasma can be changed depending on the thickness of the oxide film. If the oxide film is thick, the time of exposure to plasma can be extended to thin the oxide film and form an oxygen atomic layer. If the oxide film is thin, the time of exposure to plasma can be shortened to prevent the oxide film from being completely removed and the oxygen atomic layer from disappearing.

[0097] 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.

[0098] For example, monosilane and disilane can be used as gases for epitaxial growth. Nitrogen and hydrogen can also be used as carrier gases. The chamber pressure can be any pressure that does not cause a gas-phase reaction.

[0099] The epitaxial growth apparatus may be of a batch type or a single wafer type.

[0100] 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, the formation of dislocations and stacking faults in the epitaxial layer to be formed can be prevented, resulting in the formation of a more stable, 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 the film at a high temperature. On the other hand, if a thin epitaxial layer is desired, film formation can be performed at a low temperature. In this way, the growth temperature can be changed depending on the desired thickness of the epitaxial layer. Furthermore, within this 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.

[0101] The deposition time can be adjusted to adjust the thickness of the epitaxial layer. When deposition is performed at high temperatures, shortening the deposition time can prevent oxygen from diffusing outward from the single crystal silicon wafer, which can reduce the heat resistance of the oxygen atomic layer.

[0102] Furthermore, the epitaxial growth of single-crystal silicon can be performed, for example, by setting the partial pressure of the silicon source gas to 0.1 Pa or more and 2000 Pa or less. Within this pressure range, single-crystal silicon can be more stably grown without generating dislocations or stacking faults on the oxygen atomic layer.

[0103] In the step S14 of forming an oxygen atomic layer, the plane concentration of oxygen in the oxygen atomic layer is set to 6×10 14 atoms / cm 2By setting the oxygen concentration in the oxygen atomic layer to 6×10 or less, defects are not formed in the epitaxial layer. This is because the crystallinity of the single crystal silicon wafer is maintained when the amount of oxidation (plane concentration of oxygen in the oxygen atomic layer) is small. Therefore, there is no lower limit for the plane concentration of oxygen, as long as it is greater than 0. 14 atoms / cm 2 If the thickness is equal to or less than this, it is possible to prevent defects caused by the oxygen atomic layer from being formed in the epitaxial layer, and also possible to prevent the epitaxial layer from becoming polycrystalline silicon or amorphous silicon.

[0104] Here, the planar oxygen concentration 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 calculated by integrating the product of the volume concentration and depth in a single sputtering operation near the peak.

[0105] By performing the above steps S11 to S15, an epitaxial wafer 10A as shown in FIG. 2 can be obtained, for example.

[0106] According to the investigations of the present inventors, it is possible to form a uniform oxygen atomic layer 2 within the wafer surface by forming an oxide film on the single crystal silicon wafer 1 as described above, thinning the oxide film to form the oxygen atomic layer 2, and then epitaxially growing single crystal silicon. This is thought to be because the oxidation rate of single crystal silicon slows as the oxide film grows, making it easier to control the film thickness of the oxide film than the oxygen atomic layer 2, and also because the thinning of the oxide film progresses more slowly than oxidation, making it easier to control.

[0107] After step S15 of epitaxially growing single crystal silicon, step S13 of forming an oxide film, step S14 of forming an oxygen atomic layer 2, and step S15 of epitaxially growing single crystal silicon are repeatedly performed, thereby forming a plurality of oxygen atomic layers 2, as shown in Fig. 3, for example. That is, according to the method for producing an epitaxial wafer of this embodiment, it is possible to obtain an epitaxial wafer 10B shown in Fig. 3, 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. The uppermost surface of the epitaxial wafer 10B in Fig. 3 is the single crystal epitaxial silicon layer 3.

[0108] By providing a plurality of oxygen atomic layers 2 in this way, the gettering effect can be enhanced compared to when a single oxygen atomic layer 2 is formed.

[0109] The epitaxial wafer manufacturing method of the present invention as described above is a highly versatile method that does not require any special equipment, and is capable of stably and easily forming an oxygen atomic layer for proximity gettering and forming a high-quality epitaxial layer, thereby producing a high-quality epitaxial wafer. [Example]

[0110] EXAMPLES The present invention will be specifically explained below using examples and comparative examples, but the present invention is not limited to these.

[0111] [Example 1 and Comparative Example 1] The conductivity type, diameter, crystal plane orientation and oxygen concentration of the prepared single crystal silicon wafers are as follows: Wafer conductivity type: p-type Diameter: 300mm Crystal plane orientation: (100) Oxygen concentration: 14 ppma (JEITA)

[0112] Next, in order to remove a 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 device, and then rinsed with pure water.

[0113] Then, to form an oxide film, the single crystal silicon wafers were immersed in SC1 solution using a batch-type device. The SC1 solution prepared here was a mixture of ammonia water (NH3 concentration 28%), hydrogen peroxide water (H2O2 concentration 30%), and water in a ratio of 1:1:10, and the solution temperature was 70°C. The immersion time in the SC1 solution was 3 minutes. The single crystal silicon wafers were then rinsed with pure water.

[0114] Next, the single crystal silicon wafer on which the oxide film was formed was transferred into an epitaxial growth apparatus. In Example 1, the oxide film was thinned by heating in a hydrogen atmosphere, and an oxygen atomic layer was formed. The heating temperature was 700°C, and the heating time in Example 1 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 a hydrogen atmosphere in Comparative Example 1 was 0 seconds.

[0115] Then, single crystal silicon was epitaxially grown on the surface of the single crystal silicon wafer on which the oxygen atomic layer had been formed using monosilane. The temperature was 700°C, the monosilane partial pressure was 60 Pa, and the film thickness was 100 nm. Hydrogen was used as the carrier gas. In this manner, epitaxial wafers were produced in each of Example 1 and Comparative Example 1.

[0116] In Example 1, the formation of the oxygen atomic layer and the epitaxial growth of single crystal silicon were carried out in the same chamber.

[0117] 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.

[0118] Thereafter, the planar oxygen concentration in the oxygen atomic layer was measured by SIMS for each of the epitaxial wafers produced in Example 1 and Comparative Example 1. The measurement results are shown in Figure 4. From Figure 4, it can be seen that the oxygen concentration in the oxygen atomic layer can be reduced by heating in a hydrogen atmosphere.

[0119] Furthermore, the results of measuring the oxygen concentration within the substrate surface when the heating time was set to 20 seconds in Example 1 are shown by black circles in Figure 5. It can be seen from Figure 5 that in Example 1, an oxygen atomic layer was formed uniformly within the surface.

[0120] Furthermore, defects of 100 nm or larger were measured for the epitaxial wafers produced in Example 1 and Comparative Example 1 using a SurfScan SP5 manufactured by KLA-Tencor. As a result, in Comparative Example 1, in which the oxide film was not thinned by heating in a hydrogen atmosphere, the number of defects reached the upper limit of measurement (approximately 20,000). However, in the case of Example 1, in which heating was performed in a hydrogen atmosphere, the number of defects was 27 or less in both cases, indicating that a single-crystal silicon epitaxial layer could be formed on the oxygen atomic layer without generating defects.

[0121] 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 a 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 device, then rinsed with pure water, and then heated in a hydrogen atmosphere. The heating temperature was 1150°C and the heating time was 1 minute.

[0122] The wafer was then left in the atmosphere for five hours to form an oxygen atomic layer on the surface of the single crystal silicon wafer.

[0123] Next, single crystal silicon was epitaxially grown on the surface of the single crystal silicon wafer on which the oxygen atomic layer had been formed under the same conditions as in Example 1 and Comparative Example 1. In this manner, an epitaxial wafer was produced in Comparative Example 2.

[0124] The planar oxygen concentration in the oxygen atomic layer was then measured by SIMS at eight points within the wafer surface for the epitaxial wafer produced in Comparative Example 2. The measurement results are shown by triangles in Figure 5. The results in Figure 5 indicate that in Comparative Example 2, in which the oxygen atomic layer was formed by leaving the wafer in air, the oxygen concentration was non-uniform within the wafer surface. This is because the silicon oxidation rate was faster at the periphery of the wafer than at the center. The reason for the change in oxidation rate within the wafer surface is thought to be a change in air flow velocity. A faster air flow velocity provides a greater amount of oxygen, which increases the silicon oxidation rate. From these findings, it is thought that the change in oxygen concentration within the wafer surface was due to a flow velocity distribution in which the air flow velocity increased from the center to the periphery of the wafer.

[0125] Furthermore, when defects of 100 nm or larger were measured for the epitaxial wafer produced in Comparative Example 2 using a SurfScan SP5 manufactured by KLA-Tencor, the number of defects reached the upper limit of measurement (approximately 20,000).

[0126] As described above, in Example 1, which is an example of the present invention, an oxygen atomic layer could be introduced into the epitaxial layer more stably and simply than in Comparative Example 2, in which neither oxide film formation with an oxidizing solution nor thinning of the oxide film was performed, and an epitaxial wafer having a single crystal silicon epitaxial layer of better quality than those in Comparative Example 2 and Comparative Example 1, in which thinning of the oxide layer was not performed, could be manufactured.

[0127] The present 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 method comprising the steps of: removing a native oxide film from a surface of the single crystal silicon wafer; after removing the native 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. [2] The method for producing an epitaxial wafer according to [1], wherein the native oxide film is removed using a solution containing hydrofluoric acid. [3] The method for producing an epitaxial wafer according to [1] or [2], wherein the oxidizing solution is an SC1 solution, hydrogen peroxide solution, or ozone water. [4] A method for producing an epitaxial wafer according to [3], characterized in that 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 set to 20°C or higher and 80°C or lower. [5] The method for producing an epitaxial wafer according to [3], wherein the oxidizing solution is ozone water, and the temperature of the ozone water is set to 10°C or higher and 30°C or lower. [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 method for producing an epitaxial wafer 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. [9] The method for producing an epitaxial wafer according to any one of [1] to [8], wherein in the step of epitaxially growing the single crystal silicon, the single crystal silicon is epitaxially grown at a temperature of 450°C or higher and 800°C or lower.

[10] The method for producing an epitaxial wafer according to any one of [1] to [9], wherein 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] 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 The method for producing an epitaxial wafer according to any one of [1] to

[10] , characterized in that:

[12] The method for producing an epitaxial wafer according to any one of [1] to

[11] , characterized in that 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.

[0128] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0129] 1...single crystal silicon wafer, 2...oxygen atomic layer, 3...single crystal epitaxial silicon layer, 10A and 10B...epitaxial wafer.

Claims

1. A method for manufacturing an epitaxial wafer, which forms a single crystal silicon epitaxial layer on a single crystal silicon wafer, comprising: removing a native oxide film from the surface of the single crystal silicon wafer; forming an oxide film on the surface of the single crystal silicon wafer using an oxidizing solution after removing the native oxide film; After forming the oxide film, thinning the oxide film to form an oxygen atomic layer; and 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; Including, a method for producing an epitaxial wafer, wherein the oxide film is thinned by heating the single crystal silicon wafer in a hydrogen atmosphere, the heating temperature in the hydrogen atmosphere is 600°C or higher and 1250°C or lower, and the heating time is 20 to 600 seconds.

2. 2. The method for producing an epitaxial wafer according to claim 1, wherein the native oxide film is removed using a solution containing hydrofluoric acid.

3. 2. The method for producing an epitaxial wafer according to claim 1, wherein the oxidizing solution is an SC1 solution, a hydrogen peroxide solution, or an ozone solution.

4. 4. The method for producing an epitaxial wafer 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 set to 20°C or higher and 80°C or lower.

5. 4. The method for producing an epitaxial wafer according to claim 3, wherein the oxidizing solution is ozone water, and the temperature of the ozone water is set to 10° C. or higher and 30° C. or lower.

6. 2. The method for producing an epitaxial wafer according to claim 1, wherein the step of epitaxially growing the single crystal silicon comprises epitaxially growing the single crystal silicon at a temperature of 450° C. or higher and 800° C. or lower.

7. 7. The method for producing an epitaxial wafer according to claim 6, wherein the partial pressure of the silicon source gas is set to 0.1 Pa or more and 2000 Pa or less in the step of epitaxially growing the single crystal silicon.

8. In the step of forming the oxygen atomic layer, the plane concentration of oxygen in the oxygen atomic layer is set to 6×10 １４ atoms / cm ２ 2. The method for producing an epitaxial wafer according to claim 1, wherein the following steps are performed:

9. 9. The method for producing an epitaxial wafer according to claim 1, wherein 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.

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