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WO2022219937A1 - Method for cleaning silicon wafer, and method for producing silicon wafer with native oxide film - Google Patents

Method for cleaning silicon wafer, and method for producing silicon wafer with native oxide film Download PDF

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Publication number
WO2022219937A1
WO2022219937A1 PCT/JP2022/007392 JP2022007392W WO2022219937A1 WO 2022219937 A1 WO2022219937 A1 WO 2022219937A1 JP 2022007392 W JP2022007392 W JP 2022007392W WO 2022219937 A1 WO2022219937 A1 WO 2022219937A1
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Prior art keywords
cleaning
silicon wafer
oxide film
thickness
natural oxide
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PCT/JP2022/007392
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French (fr)
Japanese (ja)
Inventor
康太 藤井
達夫 阿部
健作 五十嵐
剛 大槻
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信越半導体株式会社
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Priority to CN202280026918.6A priority Critical patent/CN117136428A/en
Priority to KR1020237033916A priority patent/KR20230169118A/en
Publication of WO2022219937A1 publication Critical patent/WO2022219937A1/en

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    • 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
    • H01L21/02041—Cleaning
    • H01L21/02043—Cleaning before device manufacture, i.e. Begin-Of-Line process
    • H01L21/02052—Wet cleaning only
    • 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
    • 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
    • C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
    • 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 potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/304—Mechanical treatment, e.g. grinding, polishing, cutting
    • 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
    • H01L21/02104—Forming layers
    • H01L21/02107—Forming insulating materials on a substrate
    • H01L21/02225—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer
    • H01L21/02227—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a process other than a deposition process
    • H01L21/0223—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a process other than a deposition process formation by oxidation, e.g. oxidation of the substrate
    • H01L21/02233—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a process other than a deposition process formation by oxidation, e.g. oxidation of the substrate of the semiconductor substrate or a semiconductor layer
    • H01L21/02236—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a process other than a deposition process formation by oxidation, e.g. oxidation of the substrate of the semiconductor substrate or a semiconductor layer group IV semiconductor
    • H01L21/02238—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a process other than a deposition process formation by oxidation, e.g. oxidation of the substrate of the semiconductor substrate or a semiconductor layer group IV semiconductor silicon in uncombined form, i.e. pure silicon

Definitions

  • the present invention relates to a method for cleaning a silicon wafer and a method for manufacturing a silicon wafer with a natural oxide film.
  • RCA cleaning is a cleaning method in which SC1 (Standard Cleaning 1) cleaning, SC2 (Standard Cleaning 2) cleaning, and DHF (Diluted Hydrofluoric Acid) cleaning are combined according to the purpose.
  • SC1 cleaning mixes ammonia water and hydrogen peroxide water in an arbitrary ratio, lifts off adhering particles by etching the silicon wafer surface with an alkaline cleaning liquid, and further utilizes electrostatic repulsion between the silicon wafer and the particles. This cleaning method removes particles while suppressing redeposition to the silicon wafer.
  • SC2 cleaning is a cleaning method of dissolving and removing metal impurities on the surface of a silicon wafer with a cleaning liquid obtained by mixing hydrochloric acid and hydrogen peroxide water in an arbitrary ratio.
  • DHF cleaning is a cleaning method for removing a native oxide film on the surface of a silicon wafer with dilute hydrofluoric acid.
  • Ozone water cleaning which has a strong oxidizing power, may also be used to remove organic matter adhering to the silicon wafer surface and to form a natural oxide film on the silicon wafer surface after DHF cleaning.
  • the particle quality of silicon wafers after cleaning is important, and these cleanings are combined according to the purpose.
  • Semiconductor elements such as MOS (Metal Oxide Semiconductor) capacitors and transistors are formed on the surface of a semiconductor silicon wafer. Insulating films such as gate oxide films formed in these semiconductor elements are used under high electric field strength, and silicon oxide films are often used as such insulating films because they are easy to form.
  • MOS Metal Oxide Semiconductor
  • Dense silicon oxide films with high insulating properties are produced by thermally oxidizing silicon wafers, but in general, from the viewpoint of particle adhesion, etc., silicon wafers at the time of shipment have a natural oxide film formed during cleaning. . For this reason, thermal oxidation is often applied to silicon wafers on which a natural oxide film is formed. At this time, it is known that the thickness of the thermal oxide film is affected by the film quality (film thickness and structure) of the natural oxide film before thermal oxidation.
  • the thermal oxide film is desired to be thin, the natural oxide film should also be thin, and if the thermal oxide film is to be thick, the natural oxide film should also be thick. Therefore, in recent years, it is especially demanded to control the thickness of the native oxide film within a predetermined range with good reproducibility and high accuracy.
  • Patent Document 1 a silicon wafer that has not been cleaned with hydrofluoric acid (simply referred to as “DHF cleaning” or “HF cleaning”) is SC1 cleaned, and then cleaned with an oxidizing cleaning liquid (ozone water or peroxide A cleaning method is described in which the thickness of the natural oxide film is increased by cleaning with hydrogen water).
  • DHF cleaning is not performed in Patent Document 1
  • particles not removed by SC1 cleaning may remain on the wafer surface, degrading the particle quality.
  • the film thickness of all of the natural oxide films described in the examples is 1.0 nm, and it cannot be said that the film thickness of the natural oxide film can be controlled within a predetermined range.
  • Patent Document 2 after SC1 cleaning, particles not removed by SC1 cleaning are removed by HF cleaning, and then ozone water cleaning is performed to suppress reattachment of particles and reduce surface roughness of the wafer. It describes a cleaning method that However, when the bare surface is cleaned with ozone water, the oxidation progresses rapidly. Therefore, although it is possible to form an oxide film with a uniform thickness with good reproducibility, the rapid oxidation reaction results in the formation of a natural oxide film. It was difficult to change and control the thickness within a predetermined range.
  • An object of the present invention is to provide a method for cleaning a wafer.
  • the present invention has been made to achieve the above objects, and is a method for cleaning a silicon wafer, comprising: a first cleaning step of cleaning the silicon wafer with hydrofluoric acid; a second cleaning step of cleaning the silicon wafer with ozone water; a third cleaning step of cleaning the silicon wafer cleaned with the ozone water with an SC1 cleaning liquid; and cleaning the silicon wafer cleaned with the SC1 cleaning liquid with the ozone water. and a fourth cleaning step.
  • the cleaning method can control the natural oxide film thickness with good reproducibility and high accuracy.
  • the cleaning time of the fourth cleaning step can be adjusted to control the thickness of the natural oxide film formed on the surface of the silicon wafer.
  • a method of cleaning a silicon wafer may be provided in which a relationship is obtained and the cleaning time of the fourth cleaning step is set based on the correlation.
  • the cleaning time can be set more easily.
  • the cleaning time of the fourth cleaning process is set so that the thickness of the natural oxide film formed on the surface of the silicon wafer in the second cleaning process is equal to the thickness of the natural oxide film.
  • a method for cleaning a silicon wafer can be set.
  • the thickness of the native oxide film that has been thinned by the etching of the SC1 cleaning can be made equal to the thickness before the SC1 cleaning.
  • the silicon wafer cleaning method may include an SC2 cleaning step of cleaning the silicon wafer with an SC2 cleaning liquid after the third cleaning step and before the fourth cleaning step.
  • the metal impurities on the surface of the silicon wafer can be dissolved and removed, and the quality of the silicon wafer can be improved.
  • it can be a method for manufacturing a silicon wafer with a natural oxide film, which manufactures a silicon wafer with a natural oxide film by the above-described method for cleaning a silicon wafer.
  • the silicon wafer cleaning method of the present invention particle quality can be improved by performing both HF cleaning and SC1 cleaning. Further, by performing the fourth cleaning step, the cleaning method can control the thickness of the natural oxide film with good reproducibility and high accuracy. As a result, even when a thermal oxide film is formed, it is possible to obtain a silicon wafer in which the film thickness of the thermal oxide film can be easily controlled with high precision.
  • FIG. 1 is a flow chart showing an example of a silicon wafer cleaning method according to the present invention. The difference in the thickness of the native oxide film formed on the silicon wafer surface due to cleaning conditions is shown. The difference in the thickness of the thermal oxide film formed by thermal oxidation depending on the cleaning conditions is shown.
  • the present inventors diligently studied whether it is possible to vary the thickness of the natural oxide film within a predetermined range and control it with high accuracy for silicon wafers that have been subjected to HF cleaning for improving particle quality. did.
  • the present inventors found a method for cleaning a silicon wafer, comprising a first cleaning step of cleaning the silicon wafer with hydrofluoric acid and a second cleaning step of cleaning the silicon wafer cleaned with hydrofluoric acid with ozone water. a cleaning step of cleaning the silicon wafer cleaned with the ozone water with an SC1 cleaning liquid; and a fourth cleaning step of cleaning the silicon wafer cleaned with the SC1 cleaning liquid with the ozone water.
  • FIG. 1 is a flow chart showing an example of a silicon wafer cleaning method according to the present invention.
  • the silicon wafer to be cleaned in the present invention is not particularly limited, and examples thereof include polished silicon wafers, epitaxial wafers, SOI wafers, and the like. In particular, it can be suitably applied to cleaning silicon wafers after polishing to which abrasive grains and the like used for polishing have adhered.
  • a silicon wafer is cleaned with hydrofluoric acid (HF cleaning).
  • HF cleaning hydrofluoric acid
  • concentration of HF in the hydrofluoric acid to be used is 0.3 to 3.0% by weight
  • the temperature is 10 to 30° C.
  • the washing time is 60 to 360 seconds.
  • abrasive grains remaining in the polishing process particles strongly associated with the natural oxide film, and metals in the natural oxide film can be removed together with the natural oxide film.
  • the load of SC1 cleaning in the third cleaning step (S3) described later increases, and for example, particles strongly adhered to the native oxide film are difficult to be removed by SC1 cleaning. Particles remain.
  • the "first cleaning step” may be simply referred to as "S1".
  • ozone water used has an ozone concentration of 3 to 25 ppm, a temperature of 10 to 30° C., and a washing time of 60 to 360 seconds.
  • the surface of the silicon wafer becomes a hydrophobic surface, and particles tend to adhere to it. Therefore, reattachment of particles can be suppressed by forming a natural oxide film on the surface of the silicon wafer in a short time by washing with ozone water to make it a hydrophilic surface.
  • the "second cleaning step” may be simply referred to as "S2".
  • the mixing ratio (volume ratio) of the SC1 cleaning solution is, for example, ammonia water (28% by weight):hydrogen peroxide solution (30% by weight):water 1:1:10, temperature is 30 to 80° C., cleaning time is 90 to 360. Seconds are preferred. In addition, it is better to reduce the etching amount of SC1 within a range in which the particle quality can be sufficiently secured.
  • the "third cleaning step” may be simply referred to as "S3".
  • SC2 washing process Further, after SC1 cleaning in S3 and before ozone water cleaning in S4 to be described later, cleaning with SC2 cleaning liquid can be performed. Although metal impurities are removed to some extent by the HF cleaning of S1, SC2 cleaning is effective in further reducing the concentration of metal contaminants, and can be performed as necessary.
  • the silicon wafer that has been cleaned with the SC1 cleaning liquid in S3 and preferably further SC2 cleaned is cleaned with ozone water.
  • This cleaning with ozone water increases the film thickness of the natural oxide film.
  • the "fourth cleaning step” may be simply referred to as "S4".
  • ozone water cleaning of S4 a natural oxide film is already formed on the surface of the silicon wafer. Therefore, compared with the case where the bare surface is oxidized by washing with ozone water, the progress of oxidation is slowed down, and the film thickness of the natural oxide film can be controlled with good reproducibility and high precision.
  • the thickness of the natural oxide film formed on the surface of the silicon wafer is preferable to adjust the thickness of the natural oxide film formed on the surface of the silicon wafer by adjusting the cleaning time. This is because the cleaning time adjustment is the simplest and has the highest controllability and accuracy. At this time, the concentration and temperature can be the same as in S2.
  • Fig. 2 shows the relationship between the cleaning conditions (cleaning process) and the thickness of the native oxide film formed.
  • Silicon wafer after S1, S2 cleaning (S1 ⁇ S2)
  • Silicon wafer after S1, S2, S3 cleaning (S1 ⁇ S2 ⁇ S3)
  • S1, S2, S3, after S4 cleaning (S1 ⁇ S2 ⁇ S3 ⁇ S4)
  • S1 ⁇ S2 ⁇ S3 ⁇ S4 shows the respective natural oxide film thicknesses of silicon wafers that have been subjected to ozone water cleaning for 3 minutes, 12 minutes, and 30 minutes. It can be seen that the thickness of the oxide film formed in S1 ⁇ S2 is reduced by performing SC1 cleaning in S3. This is because the SC1 cleaning (S3) for improving the particle quality etches the natural oxide film. The subsequent S4 cleaning increases the thickness of the natural oxide film.
  • the thickness of the natural oxide film depends on the cleaning time of the ozone water cleaning, and the longer the cleaning time, the thicker the natural oxide film thickness. It is understood that Therefore, by adjusting the cleaning time of S4, it is possible to thicken the natural oxide film thinned by the SC1 cleaning of S3 within a predetermined range.
  • a plurality of silicon wafers on which a natural oxide film is formed such as the silicon wafers after cleaning in S1, S2, and S3, are prepared in advance, and are cleaned by changing the ozone water cleaning time in S4. It is also preferable to investigate and determine the correlation with the increasing natural oxide film thickness, and to set the cleaning time of S4 to achieve the desired thickness based on this correlation. By using such a correlation, the cleaning time can be set more easily.
  • the cleaning time of the fourth cleaning process so that the natural oxide film has the same thickness as the natural oxide film formed in the second cleaning process of S2.
  • the thickness of the natural oxide film thinned by etching in the SC1 cleaning (S3) can be made equal to the thickness before the SC1 cleaning.
  • FIG. 3 shows the oxide film thickness after thermal oxidation with a target thickness of 5.1 nm using a wafer of the same level as the silicon wafer shown in FIG. Comparing the levels, the cleaning levels S1, S2 and S3, which have the thinnest natural oxide film, also have the thinnest thermal oxide film. It can be seen that the thickness of the thermally oxidized film is the thickest at the level of 30 minutes of ozone water cleaning time in S4. Further, from FIG. 3, for example, when the target thickness of the thermal oxide film is 5.09 nm, this can be achieved by setting the ozone cleaning time in S4 to 3 minutes.
  • the cleaning time of S4 is set to 12 minutes in order to improve the electrical characteristics of the oxide film
  • the natural oxide film thickness (FIG. 2) can be obtained equivalent to that of the cleaning levels of S1 and S2.
  • the thickness of the thermal oxide film (FIG. 3) can be the same as that of the cleaning levels S1 and S2.
  • the thickness of the native oxide film can be controlled within a predetermined range with high accuracy.
  • Example 1 A polished silicon wafer was prepared.
  • the prepared silicon wafer was subjected to HF cleaning (S1), then ozone water cleaning (S2), further SC1 cleaning (S3), and finally ozone water cleaning (S4) (Examples 1 and 3). , 5, 7). Further, standards (Examples 2, 4, 6, and 8) were also prepared in which the SC2 cleaning was performed after the SC1 cleaning in S3, and then the ozone water cleaning in S4 was performed.
  • the HF cleaning of S1 had an HF concentration of 0.5% by weight and a cleaning time of 3 minutes.
  • the ozone concentration was 20 ppm and the cleaning time was 3 minutes.
  • the SC1 cleaning of S3 was performed using a mixture of ammonia water (28% by weight):hydrogen peroxide solution (30% by weight):water at a ratio of 1:1:10, a liquid temperature of 70° C., and cleaning time of 3 minutes.
  • SC2 cleaning was performed using a mixture of hydrochloric acid:hydrogen peroxide:water of 1:1:100, and cleaning time was 3 minutes.
  • the ozone concentration was 20 ppm and the cleaning time was 3, 6, 12 and 30 minutes.
  • the quality of particles on the surface of the wafer after cleaning was evaluated with a particle size of 19 nm or more using a particle counter SP5 manufactured by KLA, and the thickness of the natural oxide film was measured according to J. Phys. A. It was evaluated with a spectroscopic ellipsometry M-2000V manufactured by Woollam.
  • Table 1 shows the wafer cleaning conditions, the natural oxide film thickness, and the number of particles in the example.
  • the number of particles detected was 15 to 23 pcs, which was good compared to 72 pcs of the level without HF cleaning (Comparative Example 1), which will be described later. It is considered that the particle quality became good by performing both the HF cleaning of S1 and the SC1 cleaning of S3. The longer the ozone cleaning time in S4 is, the thicker the natural oxide film becomes.
  • Comparative example 1 In Comparative Example 1, the silicon wafer after polishing was prepared in the same manner as in Example, and after SC1 and SC2 cleanings were performed, ozone water cleaning was performed. SC1 and SC2 were performed under the same conditions as in the example, and the cleaning with ozone water was performed at a concentration of 20 ppm for 3 minutes under the same conditions as in S2 of the example. As in the example, the particle quality of the wafer after cleaning was evaluated with a particle counter, and the natural oxide film thickness was evaluated with spectroscopic ellipsometry.
  • Table 2 shows the wafer cleaning conditions, the natural oxide film thickness, and the number of particles in the comparative example.
  • Comparative Example 1 As shown in Table 2, the particle quality in Comparative Example 1 was 72 pcs, which was higher than in Examples 1-8. This is because in Comparative Example 1, only SC1 cleaning was performed without HF cleaning. The thickness of the natural oxide film was the same as in Examples 1 and 2. This is because the ozone water cleaning time is the same as S4 in the first and second embodiments.
  • Comparative Examples 2 and 3 In Comparative Examples 2 and 3, the prepared silicon wafer was subjected to HF cleaning (S1), then ozone water cleaning (S2) for 3 minutes (Comparative Example 2) and 12 minutes (Comparative Example 3), and SC1 cleaning (S3). and SC2 washes. HF cleaning, SC1 cleaning, and SC2 cleaning are the same conditions as in the example. As a result, as shown in Table 2, the particle quality of the resulting natural oxide film was equivalent to that of the example. On the other hand, the thickness of the natural oxide film was 1.022 nm in Comparative Example 2 in which the ozone cleaning time of S2 was 3 minutes, and 1.034 nm in Comparative Example 3 in which the ozone cleaning time was 12 minutes.
  • Comparative Examples 4 and 5 In Comparative Examples 4 and 5, after the silicon wafer was SC1 cleaned, HF cleaning was performed, and ozone water cleaning was performed for 3 minutes (Comparative Example 4) and 12 minutes (Comparative Example 5). SC1 cleaning and HF cleaning are performed under the same conditions as in the example. As shown in Table 2, the particle quality was 25 pcs in Comparative Example 4 and 21 pcs in Comparative Example 5, which were equivalent to those of the example. On the other hand, the natural oxide film thickness was 1.201 nm in Comparative Example 4 in which the ozone cleaning time was 3 minutes, and 1.213 nm in Comparative Example 5 in which the ozone cleaning time was 12 minutes.
  • the natural oxide film thickness can be controlled with high reproducibility and high accuracy while improving the quality of the particles.
  • the present invention is not limited to the above embodiments.
  • the above-described embodiment is an example, and any device having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same effect is the present invention. included in the technical scope of

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Abstract

The present invention is a method for cleaning a silicon wafer, the method comprising: a first cleaning step for cleaning the silicon wafer with hydrofluoric acid; a second cleaning step for cleaning the silicon wafer that has been cleaned with the hydrofluoric acid with ozone water; a third cleaning step for cleaning the silicon wafer that has been cleaned with the ozone water with an SC1 cleaning solution; and a fourth cleaning step for cleaning the silicon wafer that has been cleaned with the SC1 cleaning solution with ozone water. A method for cleaning a silicon wafer is provided, whereby it becomes possible to adjust the thickness of a native oxide film on the silicon wafer to a value falling within a specified range with high reproducibility and with high accuracy while keeping particle quality at a satisfactory level.

Description

シリコンウェーハの洗浄方法及び自然酸化膜付きシリコンウェーハの製造方法Silicon wafer cleaning method and silicon wafer manufacturing method with native oxide film
　本発明は、シリコンウェーハの洗浄方法及び自然酸化膜付きシリコンウェーハの製造方法に関する。 The present invention relates to a method for cleaning a silicon wafer and a method for manufacturing a silicon wafer with a natural oxide film.
　半導体デバイス用の単結晶シリコンウェーハの製造工程において、その主表面は研磨工程において仕上げられる。さらに、シリコンウェーハ表面に研磨工程で付着した研磨剤と金属不純物を除去するために洗浄工程がある。この洗浄工程ではＲＣＡ洗浄と呼ばれる洗浄方法が用いられている。このＲＣＡ洗浄とは、ＳＣ１（Ｓｔａｎｄａｒｄ　Ｃｌｅａｎｉｎｇ　１）洗浄、ＳＣ２（Ｓｔａｎｄａｒｄ　Ｃｌｅａｎｉｎｇ　２）洗浄、ＤＨＦ（Ｄｉｌｕｔｅｄ　Ｈｙｄｒｏｆｌｕｏｒｉｃ　Ａｃｉｄ）洗浄を、目的に応じて組み合わせて行う洗浄方法である。 In the manufacturing process of single crystal silicon wafers for semiconductor devices, the main surface is finished in the polishing process. Furthermore, there is a cleaning process to remove abrasives and metal impurities adhered to the surface of the silicon wafer during the polishing process. In this cleaning process, a cleaning method called RCA cleaning is used. This RCA cleaning is a cleaning method in which SC1 (Standard Cleaning 1) cleaning, SC2 (Standard Cleaning 2) cleaning, and DHF (Diluted Hydrofluoric Acid) cleaning are combined according to the purpose.
　ＳＣ１洗浄は、アンモニア水と過酸化水素水を任意の割合で混合し、アルカリ性の洗浄液によるシリコンウェーハ表面のエッチングによって付着パーティクルをリフトオフさせ、さらにシリコンウェーハとパーティクルの静電気的な反発を利用して、シリコンウェーハへの再付着を抑えながらパーティクルを除去する洗浄方法である。ＳＣ２洗浄は、塩酸と過酸化水素水を任意の割合で混合した洗浄液で、シリコンウェーハ表面の金属不純物を溶解除去する洗浄方法である。また、ＤＨＦ洗浄は、希フッ酸によってシリコンウェーハ表面の自然酸化膜を除去する洗浄方法である。さらに、強い酸化力を有するオゾン水洗浄も使用される場合があり、シリコンウェーハ表面に付着している有機物の除去や、ＤＨＦ洗浄後のシリコンウェーハ表面に自然酸化膜の形成を行っている。洗浄後のシリコンウェーハのパーティクル品質は重要であり、目的に応じてこれらの洗浄を組み合わせて行われている。 SC1 cleaning mixes ammonia water and hydrogen peroxide water in an arbitrary ratio, lifts off adhering particles by etching the silicon wafer surface with an alkaline cleaning liquid, and further utilizes electrostatic repulsion between the silicon wafer and the particles. This cleaning method removes particles while suppressing redeposition to the silicon wafer. SC2 cleaning is a cleaning method of dissolving and removing metal impurities on the surface of a silicon wafer with a cleaning liquid obtained by mixing hydrochloric acid and hydrogen peroxide water in an arbitrary ratio. DHF cleaning is a cleaning method for removing a native oxide film on the surface of a silicon wafer with dilute hydrofluoric acid. Ozone water cleaning, which has a strong oxidizing power, may also be used to remove organic matter adhering to the silicon wafer surface and to form a natural oxide film on the silicon wafer surface after DHF cleaning. The particle quality of silicon wafers after cleaning is important, and these cleanings are combined according to the purpose.
　半導体シリコンウェーハの表面には、ＭＯＳ（Ｍｅｔａｌ　Ｏｘｉｄｅ　Ｓｅｍｉｃｏｎｄｕｃｔｏｒ）キャパシタやトランジスタ等の半導体素子が形成される。これら半導体素子に形成されるゲート酸化膜等の絶縁膜は高い電界強度下で使用され、このような絶縁膜としては形成が簡便なシリコン酸化膜が良く用いられる。 Semiconductor elements such as MOS (Metal Oxide Semiconductor) capacitors and transistors are formed on the surface of a semiconductor silicon wafer. Insulating films such as gate oxide films formed in these semiconductor elements are used under high electric field strength, and silicon oxide films are often used as such insulating films because they are easy to form.
　絶縁性が高い緻密なシリコン酸化膜は、シリコンウェーハを熱酸化することで作製されるが、一般的にパーティクル付着等の観点から出荷時のシリコンウェーハには洗浄で形成した自然酸化膜が存在する。このため、熱酸化は自然酸化膜が形成されたシリコンウェーハに対し処理されることが多い。この際、熱酸化膜の厚さは、熱酸化前の自然酸化膜の膜質（膜厚や構造）に影響されることが知られている。 Dense silicon oxide films with high insulating properties are produced by thermally oxidizing silicon wafers, but in general, from the viewpoint of particle adhesion, etc., silicon wafers at the time of shipment have a natural oxide film formed during cleaning. . For this reason, thermal oxidation is often applied to silicon wafers on which a natural oxide film is formed. At this time, it is known that the thickness of the thermal oxide film is affected by the film quality (film thickness and structure) of the natural oxide film before thermal oxidation.
特開２０１９－２０７９２３号公報JP 2019-207923 A 特開２０１２－１２９４０９号公報JP 2012-129409 A
　近年、半導体集積回路の微細化、多層化に伴って、素子を構成する絶縁膜を含めた各種膜についてより一層の薄膜化が要求されている。この薄膜化により、極薄の絶縁膜即ちシリコン酸化膜を、基板の面内あるいは基板間で均一にかつ再現性良く形成する必要がある。そのためには、シリコン酸化膜の品質に影響を与えるシリコンウェーハ出荷時の自然酸化膜の膜質、特に膜厚を制御することが求められる。一般的には、自然酸化膜が厚いと熱酸化膜の厚さも厚くなる。熱酸化膜を薄くしたい場合は自然酸化膜も薄い方が良く、熱酸化膜を厚くしたい場合は自然酸化膜も厚い方が良い。したがって、所定の範囲内に自然酸化膜の厚さを再現性良くかつ精度高く制御することが、近年特に求められている。 In recent years, with the miniaturization and multi-layering of semiconductor integrated circuits, there is a demand for further thinning of various films, including the insulating films that make up the elements. Due to this thinning, it is necessary to form an ultra-thin insulating film, ie, a silicon oxide film, uniformly within the surface of the substrate or between the substrates with good reproducibility. For this purpose, it is required to control the film quality of the native oxide film at the time of shipment of the silicon wafer, especially the film thickness, which affects the quality of the silicon oxide film. In general, the thicker the natural oxide film, the thicker the thermal oxide film. If the thermal oxide film is desired to be thin, the natural oxide film should also be thin, and if the thermal oxide film is to be thick, the natural oxide film should also be thick. Therefore, in recent years, it is especially demanded to control the thickness of the native oxide film within a predetermined range with good reproducibility and high accuracy.
　特許文献１には、フッ酸による洗浄（単に、「ＤＨＦ洗浄」、「ＨＦ洗浄」とも表記される）をしていないシリコンウェーハをＳＣ１洗浄した後、酸化力を有する洗浄液（オゾン水又は過酸化水素水）で洗浄することで、自然酸化膜厚さを厚くする洗浄方法が記載されている。しかしながら、特許文献１ではＤＨＦ洗浄をしていないため、ＳＣ１洗浄で除去されなかったパーティクルがウェーハ表面に残留し、パーティクル品質が悪化する場合があった。また、実施例に記載の全ての自然酸化膜の膜厚が１．０ｎｍであり、自然酸化膜の膜厚を所定の範囲内に制御できているとは言えない。 In Patent Document 1, a silicon wafer that has not been cleaned with hydrofluoric acid (simply referred to as “DHF cleaning” or “HF cleaning”) is SC1 cleaned, and then cleaned with an oxidizing cleaning liquid (ozone water or peroxide A cleaning method is described in which the thickness of the natural oxide film is increased by cleaning with hydrogen water). However, since DHF cleaning is not performed in Patent Document 1, particles not removed by SC1 cleaning may remain on the wafer surface, degrading the particle quality. In addition, the film thickness of all of the natural oxide films described in the examples is 1.0 nm, and it cannot be said that the film thickness of the natural oxide film can be controlled within a predetermined range.
　特許文献２には、ＳＣ１洗浄した後、ＳＣ１洗浄で除去されなかったパーティクルをＨＦ洗浄で除去し、その後オゾン水洗浄を行うことでパーティクルの再付着を抑制し、かつウェーハの表面粗さを低減させる洗浄方法が記載されている。しかしながら、ベア面に対しオゾン水洗浄を行うことで酸化が急激に進行するため、再現性良く均一な厚さの酸化膜を形成することはできるが、急激な酸化反応であるため自然酸化膜の厚さを所定の範囲内において変化させて制御することは困難であった。 In Patent Document 2, after SC1 cleaning, particles not removed by SC1 cleaning are removed by HF cleaning, and then ozone water cleaning is performed to suppress reattachment of particles and reduce surface roughness of the wafer. It describes a cleaning method that However, when the bare surface is cleaned with ozone water, the oxidation progresses rapidly. Therefore, although it is possible to form an oxide film with a uniform thickness with good reproducibility, the rapid oxidation reaction results in the formation of a natural oxide film. It was difficult to change and control the thickness within a predetermined range.
　本発明は、上記問題を解決するためになされたものであり、パーティクル品質を良好に保ちつつ、シリコンウェーハ上の自然酸化膜の膜厚を所定の範囲内に再現性良くかつ精度高く制御できるシリコンウェーハの洗浄方法を提供することを目的とする。 SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. An object of the present invention is to provide a method for cleaning a wafer.
　本発明は、上記目的を達成するためになされたものであり、シリコンウェーハの洗浄方法であって、シリコンウェーハをフッ酸により洗浄する第１洗浄工程と、前記フッ酸により洗浄された前記シリコンウェーハをオゾン水により洗浄する第２洗浄工程と、前記オゾン水により洗浄された前記シリコンウェーハをＳＣ１洗浄液により洗浄する第３洗浄工程と、前記ＳＣ１洗浄液により洗浄された前記シリコンウェーハをオゾン水により洗浄する第４洗浄工程とを含むシリコンウェーハの洗浄方法を提供する。 The present invention has been made to achieve the above objects, and is a method for cleaning a silicon wafer, comprising: a first cleaning step of cleaning the silicon wafer with hydrofluoric acid; a second cleaning step of cleaning the silicon wafer with ozone water; a third cleaning step of cleaning the silicon wafer cleaned with the ozone water with an SC1 cleaning liquid; and cleaning the silicon wafer cleaned with the SC1 cleaning liquid with the ozone water. and a fourth cleaning step.
　このようなシリコンウェーハの洗浄方法であれば、フッ酸による洗浄（ＨＦ洗浄）とＳＣ１洗浄の両方を行うことで、パーティクル品質を良好にできる。また、第４洗浄工程を行うことで自然酸化膜厚さも再現性良くかつ精度高く制御することができる洗浄方法となる。 With such a silicon wafer cleaning method, particle quality can be improved by performing both cleaning with hydrofluoric acid (HF cleaning) and SC1 cleaning. Further, by performing the fourth cleaning step, the cleaning method can control the natural oxide film thickness with good reproducibility and high accuracy.
　このとき、前記第４洗浄工程の洗浄時間を調整することで前記シリコンウェーハの表面に形成される前記自然酸化膜の厚さを制御するシリコンウェーハの洗浄方法とすることができる。 At this time, the cleaning time of the fourth cleaning step can be adjusted to control the thickness of the natural oxide film formed on the surface of the silicon wafer.
　これにより、簡便に、再現性がより良くかつより精度高くシリコンウェーハの表面に形成される自然酸化膜の厚さを制御することができる。 As a result, it is possible to easily control the thickness of the native oxide film formed on the surface of the silicon wafer with better reproducibility and higher accuracy.
　このとき、予め、自然酸化膜が形成されたシリコンウェーハをオゾン水により洗浄する時間と、前記自然酸化膜が形成されたシリコンウェーハをオゾン水により洗浄することで増加する自然酸化膜厚さとの相関関係を求めておき、該相関関係に基づいて前記第４洗浄工程の洗浄時間を設定するシリコンウェーハの洗浄方法とすることができる。 At this time, the correlation between the time for washing the silicon wafer having the natural oxide film formed thereon with ozone water in advance and the natural oxide film thickness increased by washing the silicon wafer having the natural oxide film formed thereon with the ozone water. A method of cleaning a silicon wafer may be provided in which a relationship is obtained and the cleaning time of the fourth cleaning step is set based on the correlation.
　このような相関関係を用いることで、より簡便に洗浄時間を設定することができる。 By using such a correlation, the cleaning time can be set more easily.
　このとき、前記相関関係に基づいて、前記第２洗浄工程で前記シリコンウェーハの表面に形成された自然酸化膜の厚さと同等の自然酸化膜厚さとなるように前記第４洗浄工程の洗浄時間を設定するシリコンウェーハの洗浄方法とすることができる。 At this time, based on the correlation, the cleaning time of the fourth cleaning process is set so that the thickness of the natural oxide film formed on the surface of the silicon wafer in the second cleaning process is equal to the thickness of the natural oxide film. A method for cleaning a silicon wafer can be set.
　これにより、ＳＣ１洗浄によるエッチングで薄くなった自然酸化膜厚を、ＳＣ１洗浄前と同等の厚さとすることができる。 As a result, the thickness of the native oxide film that has been thinned by the etching of the SC1 cleaning can be made equal to the thickness before the SC1 cleaning.
　このとき、前記第３洗浄工程後かつ前記第４洗浄工程より前にＳＣ２洗浄液により前記シリコンウェーハを洗浄するＳＣ２洗浄工程を含むシリコンウェーハの洗浄方法とすることができる。 At this time, the silicon wafer cleaning method may include an SC2 cleaning step of cleaning the silicon wafer with an SC2 cleaning liquid after the third cleaning step and before the fourth cleaning step.
　これにより、シリコンウェーハ表面の金属不純物を溶解除去して、シリコンウェーハの品質をより良好にすることができる。 As a result, the metal impurities on the surface of the silicon wafer can be dissolved and removed, and the quality of the silicon wafer can be improved.
　このとき、自然酸化膜付きシリコンウェーハの製造方法であって、上記シリコンウェーハの洗浄方法により自然酸化膜付きシリコンウェーハを製造する自然酸化膜付きシリコンウェーハの製造方法とすることができる。 At this time, it can be a method for manufacturing a silicon wafer with a natural oxide film, which manufactures a silicon wafer with a natural oxide film by the above-described method for cleaning a silicon wafer.
　これにより、パーティクル品質が高く、再現性良くかつ精度高く自然酸化膜厚さを制御して、自然酸化膜付きシリコンウェーハを製造することができる。 As a result, it is possible to manufacture silicon wafers with a native oxide film with high particle quality, good reproducibility, and highly accurate control of the native oxide film thickness.
　以上のように、本発明のシリコンウェーハの洗浄方法によれば、ＨＦ洗浄とＳＣ１洗浄の両方を行うことで、パーティクル品質を良好にできる。また、第４洗浄工程を行うことで自然酸化膜厚さを再現性良くかつ精度高く制御することができる洗浄方法となる。その結果、熱酸化膜を形成する場合においても熱酸化膜の膜厚の制御を容易に精度高く行うことが可能なシリコンウェーハを得ることが可能となる。 As described above, according to the silicon wafer cleaning method of the present invention, particle quality can be improved by performing both HF cleaning and SC1 cleaning. Further, by performing the fourth cleaning step, the cleaning method can control the thickness of the natural oxide film with good reproducibility and high accuracy. As a result, even when a thermal oxide film is formed, it is possible to obtain a silicon wafer in which the film thickness of the thermal oxide film can be easily controlled with high precision.
本発明に係るシリコンウェーハの洗浄方法の一例を示すフローチャートである。1 is a flow chart showing an example of a silicon wafer cleaning method according to the present invention. シリコンウェーハ表面に形成された自然酸化膜厚さの洗浄条件による違いを示す。The difference in the thickness of the native oxide film formed on the silicon wafer surface due to cleaning conditions is shown. 熱酸化により形成された熱酸化膜厚さの洗浄条件による違いを示す。The difference in the thickness of the thermal oxide film formed by thermal oxidation depending on the cleaning conditions is shown.
　以下、本発明を詳細に説明するが、本発明はこれらに限定されるものではない。 Although the present invention will be described in detail below, the present invention is not limited to these.
　上述のように、パーティクル品質を良好に保ちつつ、シリコンウェーハ上の自然酸化膜の膜厚を所望の範囲内に再現性良くかつ精度高く制御できるシリコンウェーハの洗浄方法が求められていた。 As described above, there has been a demand for a silicon wafer cleaning method that can control the film thickness of the native oxide film on the silicon wafer within the desired range with good reproducibility and high accuracy while maintaining good particle quality.
　本発明者らは上記課題を解決するために、パーティクル品質向上のためのＨＦ洗浄を行ったシリコンウェーハについて、自然酸化膜の膜厚を所定の範囲内に変動させ精度高く制御できないか、鋭意検討した。 In order to solve the above problems, the present inventors diligently studied whether it is possible to vary the thickness of the natural oxide film within a predetermined range and control it with high accuracy for silicon wafers that have been subjected to HF cleaning for improving particle quality. did.
　その結果、本発明者らは、シリコンウェーハの洗浄方法であって、シリコンウェーハをフッ酸により洗浄する第１洗浄工程と、前記フッ酸により洗浄された前記シリコンウェーハをオゾン水により洗浄する第２洗浄工程と、前記オゾン水により洗浄された前記シリコンウェーハをＳＣ１洗浄液により洗浄する第３洗浄工程と、前記ＳＣ１洗浄液により洗浄された前記シリコンウェーハをオゾン水により洗浄する第４洗浄工程とを含むシリコンウェーハの洗浄方法により、ＨＦ洗浄とＳＣ１洗浄の両方を行うことで、パーティクル品質を良好にでき、また、第４洗浄工程を行うことで自然酸化膜厚さも再現性良くかつ精度高く制御することができる洗浄方法となることを見出し、本発明を完成した。 As a result, the present inventors found a method for cleaning a silicon wafer, comprising a first cleaning step of cleaning the silicon wafer with hydrofluoric acid and a second cleaning step of cleaning the silicon wafer cleaned with hydrofluoric acid with ozone water. a cleaning step of cleaning the silicon wafer cleaned with the ozone water with an SC1 cleaning liquid; and a fourth cleaning step of cleaning the silicon wafer cleaned with the SC1 cleaning liquid with the ozone water. By performing both HF cleaning and SC1 cleaning according to the wafer cleaning method, the particle quality can be improved, and by performing the fourth cleaning process, the native oxide film thickness can be controlled with good reproducibility and high accuracy. The present invention has been completed by finding that the cleaning method can be used.
　以下、図面を参照して説明する。 The following description will be made with reference to the drawings.
　［シリコンウェーハの洗浄方法］
　図１は、本発明に係るシリコンウェーハの洗浄方法の一例を示すフローチャートである。本発明において洗浄するシリコンウェーハとしては特に限定されず、研磨後のシリコンウェーハ、エピタキシャルウェーハ、ＳＯＩウェーハなどが挙げられる。特に、研磨に用いられた砥粒などが付着した研磨後のシリコンウェーハ等の洗浄に好適に適用できる。 [Method for cleaning silicon wafer]
FIG. 1 is a flow chart showing an example of a silicon wafer cleaning method according to the present invention. The silicon wafer to be cleaned in the present invention is not particularly limited, and examples thereof include polished silicon wafers, epitaxial wafers, SOI wafers, and the like. In particular, it can be suitably applied to cleaning silicon wafers after polishing to which abrasive grains and the like used for polishing have adhered.
　（第１洗浄工程）
　まず、図１のＳ１のように、シリコンウェーハをフッ酸により洗浄する（ＨＦ洗浄）。用いるフッ酸のＨＦの濃度は０．３～３．０重量％、温度は１０～３０℃、洗浄時間は６０～３６０秒とすることが好ましい。これにより、例えば研磨工程で残留した砥粒、自然酸化膜と強く結びついたパーティクルや自然酸化膜中の金属を、自然酸化膜と共に除去することができる。この第１洗浄工程（Ｓ１）を実施しないと、後述する第３洗浄工程（Ｓ３）でのＳＣ１洗浄の負荷が大きくなり、例えば自然酸化膜と強く密着したパーティクルのようなＳＣ１洗浄で除去されにくいパーティクルが残留してしまう。以下、「第１洗浄工程」を単に「Ｓ１」ということもある。 (First washing step)
First, as shown in S1 of FIG. 1, a silicon wafer is cleaned with hydrofluoric acid (HF cleaning). It is preferable that the concentration of HF in the hydrofluoric acid to be used is 0.3 to 3.0% by weight, the temperature is 10 to 30° C., and the washing time is 60 to 360 seconds. As a result, for example, abrasive grains remaining in the polishing process, particles strongly associated with the natural oxide film, and metals in the natural oxide film can be removed together with the natural oxide film. If this first cleaning step (S1) is not performed, the load of SC1 cleaning in the third cleaning step (S3) described later increases, and for example, particles strongly adhered to the native oxide film are difficult to be removed by SC1 cleaning. Particles remain. Hereinafter, the "first cleaning step" may be simply referred to as "S1".
　（第２洗浄工程）
　次に、Ｓ２のようにオゾン水により洗浄を行う。用いるオゾン水のオゾンの濃度は３～２５ｐｐｍ、温度は１０～３０℃、洗浄時間は６０～３６０秒とすることが好ましい。Ｓ１のＨＦ洗浄後は、シリコンウェーハ表面が疎水面となりパーティクルが付着しやすい状態となってしまう。そこで、オゾン水洗浄により短時間でシリコンウェーハ表面に自然酸化膜を形成して親水面にすることで、パーティクルの再付着も抑制できる。以下、「第２洗浄工程」を単に「Ｓ２」ということもある。 (Second washing step)
Next, cleaning is performed with ozone water as in S2. It is preferable that the ozone water used has an ozone concentration of 3 to 25 ppm, a temperature of 10 to 30° C., and a washing time of 60 to 360 seconds. After the HF cleaning in S1, the surface of the silicon wafer becomes a hydrophobic surface, and particles tend to adhere to it. Therefore, reattachment of particles can be suppressed by forming a natural oxide film on the surface of the silicon wafer in a short time by washing with ozone water to make it a hydrophilic surface. Hereinafter, the "second cleaning step" may be simply referred to as "S2".
　なお、Ｓ２の工程のオゾン水洗浄の時間を変えることで自然酸化膜厚さを所望の範囲内に変動させることは難しい。表面に酸化膜が存在する場合はシリコンの酸化がシリコンと酸化膜の界面で進行するため、酸化種は酸化膜中を拡散する必要があり、ベア面（むき出しのシリコン面）の酸化の場合よりも酸化の進行が遅れる。これに対してベア面の場合は、酸化膜が存在しないため酸化が急激に進行する。急激な反応を制御することは再現性の観点からも実用性に欠ける。反応性を下げるために、オゾン水濃度を下げることもできるが、その場合酸化反応が面内均一に起こらず、酸化膜の面内ムラが大きくなってしまう。本発明者らが検討した結果、ベア面に対してオゾン水洗浄を行うことで酸化膜厚さを所定の範囲内に変化させるのは困難であった。したがって、後述のようにＳＣ１洗浄（Ｓ３）後に再度オゾン水により洗浄（Ｓ４）することで、自然酸化膜の膜厚を再現性良くかつ精度高く制御できることを見出した。 It should be noted that it is difficult to vary the thickness of the natural oxide film within the desired range by changing the ozone water cleaning time in the step of S2. If there is an oxide film on the surface, the oxidation of silicon proceeds at the interface between the silicon and the oxide film, so the oxidizing species must diffuse in the oxide film. slows down the progress of oxidation. On the other hand, in the case of a bare surface, since no oxide film exists, oxidation proceeds rapidly. Controlling a rapid reaction lacks practicality from the viewpoint of reproducibility. In order to lower the reactivity, the ozone water concentration can be lowered, but in that case, the oxidation reaction does not occur uniformly within the plane, and the oxide film becomes uneven within the plane. As a result of investigation by the present inventors, it was difficult to change the thickness of the oxide film within a predetermined range by cleaning the bare surface with ozone water. Therefore, it was found that the film thickness of the natural oxide film can be controlled with good reproducibility and high accuracy by performing cleaning with ozone water again (S4) after SC1 cleaning (S3), as will be described later.
　（第３洗浄工程）
　次に、Ｓ３のようにＳＣ１洗浄液による洗浄を行う。ＳＣ１洗浄液の混合比（体積比）は例えばアンモニア水（２８重量％）：過酸化水素水（３０重量％）：水を１：１：１０、温度は３０～８０℃、洗浄時間は９０～３６０秒とすることが好ましい。なお、パーティクル品質が十分確保できる範囲内で、ＳＣ１のエッチング量を少なくした方が良い。以下、「第３洗浄工程」を単に「Ｓ３」ということもある。 (Third washing step)
Next, as in S3, cleaning with the SC1 cleaning liquid is performed. The mixing ratio (volume ratio) of the SC1 cleaning solution is, for example, ammonia water (28% by weight):hydrogen peroxide solution (30% by weight):water 1:1:10, temperature is 30 to 80° C., cleaning time is 90 to 360. Seconds are preferred. In addition, it is better to reduce the etching amount of SC1 within a range in which the particle quality can be sufficiently secured. Hereinafter, the "third cleaning step" may be simply referred to as "S3".
　（ＳＣ２洗浄工程）
　また、Ｓ３のＳＣ１洗浄後、かつ、後述のＳ４のオゾン水洗浄の前に、ＳＣ２洗浄液による洗浄を行うこともできる。Ｓ１のＨＦ洗浄で金属不純物はある程度除去されているが、さらに金属汚染濃度を低減させるにはＳＣ２洗浄が有効であり、必要に応じて行うことができる。 (SC2 washing process)
Further, after SC1 cleaning in S3 and before ozone water cleaning in S4 to be described later, cleaning with SC2 cleaning liquid can be performed. Although metal impurities are removed to some extent by the HF cleaning of S1, SC2 cleaning is effective in further reducing the concentration of metal contaminants, and can be performed as necessary.
　（第４洗浄工程）
　次に、Ｓ４のように、Ｓ３でＳＣ１洗浄液により洗浄され、好ましくはさらにＳＣ２洗浄されたシリコンウェーハをオゾン水により洗浄する。このオゾン水洗浄により自然酸化膜の膜厚が増加する。以下、「第４洗浄工程」を単に「Ｓ４」ということもある。Ｓ４のオゾン水洗浄では、シリコンウェーハの表面には既に自然酸化膜が形成されている。そのため、ベアな表面をオゾン水洗浄で酸化する場合に比べて酸化の進行が緩やかになり、自然酸化膜の膜厚を再現性良くかつ高い精度で制御することが可能となる。 (Fourth washing step)
Next, as in S4, the silicon wafer that has been cleaned with the SC1 cleaning liquid in S3 and preferably further SC2 cleaned is cleaned with ozone water. This cleaning with ozone water increases the film thickness of the natural oxide film. Hereinafter, the "fourth cleaning step" may be simply referred to as "S4". In the ozone water cleaning of S4, a natural oxide film is already formed on the surface of the silicon wafer. Therefore, compared with the case where the bare surface is oxidized by washing with ozone water, the progress of oxidation is slowed down, and the film thickness of the natural oxide film can be controlled with good reproducibility and high precision.
　Ｓ４のオゾン水洗浄では、特に洗浄時間を調整することでシリコンウェーハの表面に形成される自然酸化膜厚さを調整することが好ましい。洗浄時間の調整は最も簡便かつ制御性及び精度が高いためである。このとき、濃度と温度はＳ２と同等とすることができる。 In the ozone water cleaning in S4, it is preferable to adjust the thickness of the natural oxide film formed on the surface of the silicon wafer by adjusting the cleaning time. This is because the cleaning time adjustment is the simplest and has the highest controllability and accuracy. At this time, the concentration and temperature can be the same as in S2.
　図２に、洗浄条件（洗浄工程）と形成される自然酸化膜の厚さの関係を示す。Ｓ１，Ｓ２洗浄後（Ｓ１→Ｓ２）のシリコンウェーハ、Ｓ１，Ｓ２，Ｓ３洗浄後（Ｓ１→Ｓ２→Ｓ３）のシリコンウェーハ、Ｓ１，Ｓ２，Ｓ３、Ｓ４洗浄後（Ｓ１→Ｓ２→Ｓ３→Ｓ４）であって、オゾン水洗浄を３分、１２分、３０分実施したシリコンウェーハの、それぞれの自然酸化膜厚さを示している。Ｓ１→Ｓ２で形成された酸化膜は、Ｓ３のＳＣ１洗浄を行うことで膜厚が薄くなることがわかる。これはパーティクル品質を良好にするためのＳＣ１洗浄（Ｓ３）で自然酸化膜がエッチングされるためである。その後Ｓ４洗浄を行うことで自然酸化膜の膜厚が厚くなること、しかも、自然酸化膜の膜厚はオゾン水洗浄の洗浄時間に依存し、洗浄時間が長くなると自然酸化膜厚さが厚くなっていることが分かる。したがって、Ｓ４の洗浄時間を調整することでＳ３のＳＣ１洗浄で薄くなった自然酸化膜を所定の範囲内で厚くすることができることがわかる。 Fig. 2 shows the relationship between the cleaning conditions (cleaning process) and the thickness of the native oxide film formed. Silicon wafer after S1, S2 cleaning (S1→S2) Silicon wafer after S1, S2, S3 cleaning (S1→S2→S3), S1, S2, S3, after S4 cleaning (S1→S2→S3→S4) , and shows the respective natural oxide film thicknesses of silicon wafers that have been subjected to ozone water cleaning for 3 minutes, 12 minutes, and 30 minutes. It can be seen that the thickness of the oxide film formed in S1→S2 is reduced by performing SC1 cleaning in S3. This is because the SC1 cleaning (S3) for improving the particle quality etches the natural oxide film. The subsequent S4 cleaning increases the thickness of the natural oxide film. Moreover, the thickness of the natural oxide film depends on the cleaning time of the ozone water cleaning, and the longer the cleaning time, the thicker the natural oxide film thickness. It is understood that Therefore, by adjusting the cleaning time of S4, it is possible to thicken the natural oxide film thinned by the SC1 cleaning of S3 within a predetermined range.
　予め、Ｓ１，Ｓ２，Ｓ３洗浄後のシリコンウェーハのように自然酸化膜が形成されたシリコンウェーハを複数枚用意し、Ｓ４のオゾン水洗浄する時間を変えて洗浄し、洗浄時間とオゾン水洗浄で増加する自然酸化膜厚さとの相関関係を調査し求めておき、この相関関係に基づいて目的の厚さとなるＳ４の洗浄時間を設定することも好ましい。このような相関関係を用いることで、より簡便に洗浄時間を設定することができる。 A plurality of silicon wafers on which a natural oxide film is formed, such as the silicon wafers after cleaning in S1, S2, and S3, are prepared in advance, and are cleaned by changing the ozone water cleaning time in S4. It is also preferable to investigate and determine the correlation with the increasing natural oxide film thickness, and to set the cleaning time of S4 to achieve the desired thickness based on this correlation. By using such a correlation, the cleaning time can be set more easily.
　さらに、相関関係に基づいて、Ｓ２の第２洗浄工程で形成された自然酸化膜の厚さと同等の自然酸化膜厚さとなるように、第４洗浄工程の洗浄時間を設定することもできる。これにより、ＳＣ１洗浄（Ｓ３）によるエッチングで薄くなった自然酸化膜厚を、ＳＣ１洗浄前と同等の厚さとすることができる。 Further, based on the correlation, it is possible to set the cleaning time of the fourth cleaning process so that the natural oxide film has the same thickness as the natural oxide film formed in the second cleaning process of S2. As a result, the thickness of the natural oxide film thinned by etching in the SC1 cleaning (S3) can be made equal to the thickness before the SC1 cleaning.
　図３は、図２に示したシリコンウェーハと同じ水準のウェーハを用い、狙い厚さ５．１ｎｍで熱酸化した後の酸化膜厚さを示している。各水準間で比較すると、自然酸化膜が最も薄いＳ１，Ｓ２，Ｓ３洗浄水準のものは熱酸化膜の厚さも最も薄く、自然酸化膜が最も厚いＳ１，Ｓ２，Ｓ３，Ｓ４洗浄水準のうちのＳ４におけるオゾン水洗浄時間を３０分とした水準のものでは、熱酸化膜の厚さも最も厚くなることがわかる。また、図３から、例えば狙いの熱酸化膜厚さを５．０９ｎｍとする場合は、Ｓ４のオゾン洗浄時間を３分に設定することで達成することができる。また、例えば酸化膜の電気特性をより良好にするために、Ｓ４の洗浄時間を１２分にすると、Ｓ１，Ｓ２洗浄水準のものと同等の自然酸化膜厚さ（図２）とすることができ、その結果、Ｓ１，Ｓ２洗浄水準のものと同等の熱酸化膜厚さ（図３）とすることもできる。このように、本発明の洗浄方法を用いることで自然酸化膜の厚さを所定の範囲内に精度よく制御することができる。 FIG. 3 shows the oxide film thickness after thermal oxidation with a target thickness of 5.1 nm using a wafer of the same level as the silicon wafer shown in FIG. Comparing the levels, the cleaning levels S1, S2 and S3, which have the thinnest natural oxide film, also have the thinnest thermal oxide film. It can be seen that the thickness of the thermally oxidized film is the thickest at the level of 30 minutes of ozone water cleaning time in S4. Further, from FIG. 3, for example, when the target thickness of the thermal oxide film is 5.09 nm, this can be achieved by setting the ozone cleaning time in S4 to 3 minutes. Further, for example, if the cleaning time of S4 is set to 12 minutes in order to improve the electrical characteristics of the oxide film, the natural oxide film thickness (FIG. 2) can be obtained equivalent to that of the cleaning levels of S1 and S2. As a result, the thickness of the thermal oxide film (FIG. 3) can be the same as that of the cleaning levels S1 and S2. Thus, by using the cleaning method of the present invention, the thickness of the native oxide film can be controlled within a predetermined range with high accuracy.
　［自然酸化膜付きシリコンウェーハの製造方法］
　上記のような本発明に係るシリコンウェーハの洗浄方法により、所望の自然酸化膜厚さを有し、パーティクルレベルが低く良質な自然酸化膜が形成された自然酸化膜付きシリコンウェーハを製造することができる。 [Manufacturing method of silicon wafer with native oxide film]
By the method for cleaning a silicon wafer according to the present invention as described above, it is possible to manufacture a silicon wafer with a natural oxide film having a desired natural oxide film thickness, a low particle level and a good quality natural oxide film formed thereon. can.
　以下、実施例及び比較例を挙げて本発明について具体的に説明するが、これは本発明を限定するものではない。 The present invention will be specifically described below with reference to examples and comparative examples, but these are not intended to limit the present invention.
　（実施例）
　研磨後のシリコンウェーハを用意した。用意したシリコンウェーハをＨＦ洗浄し（Ｓ１）、その後オゾン水洗浄（Ｓ２）を行い、さらにＳＣ１洗浄（Ｓ３）を行った後、最後にオゾン水洗浄（Ｓ４）を行った（実施例１，３，５，７）。また、Ｓ３のＳＣ１洗浄後にＳＣ２洗浄を行った後、Ｓ４のオゾン水洗浄を行う水準（実施例２，４，６，８）も用意した。 (Example)
A polished silicon wafer was prepared. The prepared silicon wafer was subjected to HF cleaning (S1), then ozone water cleaning (S2), further SC1 cleaning (S3), and finally ozone water cleaning (S4) (Examples 1 and 3). , 5, 7). Further, standards (Examples 2, 4, 6, and 8) were also prepared in which the SC2 cleaning was performed after the SC1 cleaning in S3, and then the ozone water cleaning in S4 was performed.
　Ｓ１のＨＦ洗浄は、ＨＦ濃度が０．５重量％で、洗浄時間は３分とした。Ｓ２のオゾン洗浄は、オゾン濃度が２０ｐｐｍで、洗浄時間を３分とした。Ｓ３のＳＣ１洗浄は、アンモニア水（２８重量％）：過酸化水素水（３０重量％）：水を１：１：１０の混合液とし、液温７０℃、洗浄時間を３分とした。ＳＣ２洗浄は、塩酸：過酸化水素：水を１：１：１００の混合液とし、洗浄時間を３分とした。Ｓ４のオゾン洗浄は、オゾン濃度が２０ｐｐｍで、洗浄時間を３、６、１２、３０分とした。洗浄後のウェーハ表面のパーティクル品質をＫＬＡ製パーティクルカウンターＳＰ５の１９ｎｍ以上の粒径で評価し、自然酸化膜厚さをＪ．Ａ．Ｗｏｏｌｌａｍ社製分光エリプソメトリーＭ－２０００Ｖで評価した。 The HF cleaning of S1 had an HF concentration of 0.5% by weight and a cleaning time of 3 minutes. In the ozone cleaning of S2, the ozone concentration was 20 ppm and the cleaning time was 3 minutes. The SC1 cleaning of S3 was performed using a mixture of ammonia water (28% by weight):hydrogen peroxide solution (30% by weight):water at a ratio of 1:1:10, a liquid temperature of 70° C., and cleaning time of 3 minutes. SC2 cleaning was performed using a mixture of hydrochloric acid:hydrogen peroxide:water of 1:1:100, and cleaning time was 3 minutes. In the ozone cleaning of S4, the ozone concentration was 20 ppm and the cleaning time was 3, 6, 12 and 30 minutes. The quality of particles on the surface of the wafer after cleaning was evaluated with a particle size of 19 nm or more using a particle counter SP5 manufactured by KLA, and the thickness of the natural oxide film was measured according to J. Phys. A. It was evaluated with a spectroscopic ellipsometry M-2000V manufactured by Woollam.
　表１に、実施例におけるウェーハの洗浄条件、自然酸化膜厚さ、パーティクル個数を示す。 Table 1 shows the wafer cleaning conditions, the natural oxide film thickness, and the number of particles in the example.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　初めにＳＣ２の有無の影響を比較すると、実施例１と２、実施例３と４、実施例５と６、実施例７と８の対比から明らかなように、パーティクル品質と自然酸化膜の品質（自然酸化膜厚さ）は同等であった。したがって、ＳＣ２洗浄はパーティクル品質、自然酸化膜の品質に影響を与えないことから、シリコンウェーハ表面の金属濃度をより低減したい場合にＳＣ２洗浄を行うことができることがわかる。 First, when comparing the effects of the presence or absence of SC2, as is clear from the comparison of Examples 1 and 2, Examples 3 and 4, Examples 5 and 6, and Examples 7 and 8, the particle quality and the quality of the natural oxide film are compared. (natural oxide film thickness) were the same. Therefore, SC2 cleaning does not affect the quality of particles and the quality of the native oxide film, so it can be seen that SC2 cleaning can be performed when it is desired to further reduce the metal concentration on the surface of the silicon wafer.
　パーティクル品質について、検出されたパーティクル個数は１５～２３ｐｃｓとなり、後述するＨＦ洗浄を行わない水準（比較例１）の７２ｐｃｓと比較すると良好であった。Ｓ１のＨＦ洗浄とＳ３のＳＣ１洗浄の両方を行ったことで、パーティクル品質が良好になったと考えられる。自然酸化膜はＳ４のオゾン洗浄時間が長いほど厚くなり、Ｓ４のオゾン洗浄時間で自然酸化膜厚さを精度高く制御できることがわかる。 Regarding the particle quality, the number of particles detected was 15 to 23 pcs, which was good compared to 72 pcs of the level without HF cleaning (Comparative Example 1), which will be described later. It is considered that the particle quality became good by performing both the HF cleaning of S1 and the SC1 cleaning of S3. The longer the ozone cleaning time in S4 is, the thicker the natural oxide film becomes.
　また、Ｓ４のオゾン水洗浄の時間を、３分（実施例１，２）から１２分（実施例５，６）としたことによる自然酸化膜の厚膜化量は、実施例１，５から１．１９９－１．１２８＝０．０７２ｎｍ、実施例２，６から１．２０３－１．１２９＝０．０７４ｎｍだった。 In addition, the amount of thickening of the natural oxide film by changing the ozone water cleaning time in S4 from 3 minutes (Examples 1 and 2) to 12 minutes (Examples 5 and 6) is 1.199-1.128=0.072 nm, and from Examples 2 and 6, 1.203-1.129=0.074 nm.
　（比較例１）
　比較例１では、実施例と同じ研磨後のシリコンウェーハを用意してＳＣ１とＳＣ２洗浄を行った後、オゾン水洗浄を行った。ＳＣ１、ＳＣ２は実施例と同条件で、オゾン水洗浄は実施例のＳ２と同条件の濃度２０ｐｐｍで３分とした。実施例と同様に、洗浄後のウェーハのパーティクル品質をパーティクルカウンターで評価し、自然酸化膜厚さを分光エリプソメトリーで評価した。 (Comparative example 1)
In Comparative Example 1, the silicon wafer after polishing was prepared in the same manner as in Example, and after SC1 and SC2 cleanings were performed, ozone water cleaning was performed. SC1 and SC2 were performed under the same conditions as in the example, and the cleaning with ozone water was performed at a concentration of 20 ppm for 3 minutes under the same conditions as in S2 of the example. As in the example, the particle quality of the wafer after cleaning was evaluated with a particle counter, and the natural oxide film thickness was evaluated with spectroscopic ellipsometry.
　表２に、比較例におけるウェーハの洗浄条件、自然酸化膜厚さ、パーティクル個数を示す。 Table 2 shows the wafer cleaning conditions, the natural oxide film thickness, and the number of particles in the comparative example.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表２に示すように、比較例１におけるパーティクル品質は７２ｐｃｓと、実施例１～８よりも多かった。比較例１では、ＨＦ洗浄を行わず、ＳＣ１洗浄のみを行ったためである。自然酸化膜厚さは実施例１，２と同等になった。これはオゾン水洗浄時間が実施例１，２のＳ４と同じためである。 As shown in Table 2, the particle quality in Comparative Example 1 was 72 pcs, which was higher than in Examples 1-8. This is because in Comparative Example 1, only SC1 cleaning was performed without HF cleaning. The thickness of the natural oxide film was the same as in Examples 1 and 2. This is because the ozone water cleaning time is the same as S4 in the first and second embodiments.
　（比較例２，３）
　比較例２，３では、用意したシリコンウェーハをＨＦ洗浄（Ｓ１）し、その後オゾン水洗浄（Ｓ２）を３分（比較例２）及び１２分（比較例３）行い、さらにＳＣ１洗浄（Ｓ３）とＳＣ２洗浄を行った。ＨＦ洗浄、ＳＣ１洗浄、ＳＣ２洗浄は実施例と同条件である。この結果、表２に示すように、得られた自然酸化膜のパーティクル品質は実施例と同等であった。一方、自然酸化膜厚さは、Ｓ２のオゾン洗浄時間を３分とした比較例２で１．０２２ｎｍ、１２分とした比較例３で１．０３４ｎｍとなり、厚膜化量（１．０３４－１．０２２＝０．０１２ｎｍ）は、上述の実施例１，５及び実施例２，６で得た厚膜化量（０．０７２ｎｍ，０．０７４ｎｍ）と比較して非常に小さかった。したがって、比較例２，３のような方法では、自然酸化膜厚さを適切に制御することはできない。 (Comparative Examples 2 and 3)
In Comparative Examples 2 and 3, the prepared silicon wafer was subjected to HF cleaning (S1), then ozone water cleaning (S2) for 3 minutes (Comparative Example 2) and 12 minutes (Comparative Example 3), and SC1 cleaning (S3). and SC2 washes. HF cleaning, SC1 cleaning, and SC2 cleaning are the same conditions as in the example. As a result, as shown in Table 2, the particle quality of the resulting natural oxide film was equivalent to that of the example. On the other hand, the thickness of the natural oxide film was 1.022 nm in Comparative Example 2 in which the ozone cleaning time of S2 was 3 minutes, and 1.034 nm in Comparative Example 3 in which the ozone cleaning time was 12 minutes. .022=0.012 nm) was much smaller than the thickening amounts (0.072 nm, 0.074 nm) obtained in Examples 1 and 5 and Examples 2 and 6 described above. Therefore, the methods of Comparative Examples 2 and 3 cannot appropriately control the thickness of the natural oxide film.
　（比較例４，５）
　比較例４，５では、シリコンウェーハをＳＣ１洗浄した後、ＨＦ洗浄を行い、オゾン水洗浄を３分（比較例４）及び１２分（比較例５）行った。ＳＣ１洗浄とＨＦ洗浄は実施例と同条件である。表２に示すように、パーティクル品質は比較例４で２５ｐｃｓ、比較例５で２１ｐｃｓとなり実施例と同等であった。一方、自然酸化膜厚さは、オゾン洗浄時間を３分とした比較例４で１．２０１ｎｍ、１２分とした比較例５で１．２１３ｎｍとなり、厚膜化量（１．２１３－１．２０１＝０．０１２ｎｍ）は、上述の実施例１，５及び実施例２，６で得た厚膜化量（０．０７２ｎｍ，０．０７４ｎｍ）と比較して非常に小さかった。したがって、比較例４，５のような方法では、自然酸化膜厚さを適切に制御することはできない。 (Comparative Examples 4 and 5)
In Comparative Examples 4 and 5, after the silicon wafer was SC1 cleaned, HF cleaning was performed, and ozone water cleaning was performed for 3 minutes (Comparative Example 4) and 12 minutes (Comparative Example 5). SC1 cleaning and HF cleaning are performed under the same conditions as in the example. As shown in Table 2, the particle quality was 25 pcs in Comparative Example 4 and 21 pcs in Comparative Example 5, which were equivalent to those of the example. On the other hand, the natural oxide film thickness was 1.201 nm in Comparative Example 4 in which the ozone cleaning time was 3 minutes, and 1.213 nm in Comparative Example 5 in which the ozone cleaning time was 12 minutes. = 0.012 nm) was much smaller than the thickening amounts (0.072 nm, 0.074 nm) obtained in Examples 1 and 5 and Examples 2 and 6 described above. Therefore, the methods of Comparative Examples 4 and 5 cannot appropriately control the thickness of the natural oxide film.
　以上のとおり、本発明の実施例によれば、パーティクルの品質を向上しつつ、自然酸化膜厚さを高い再現性でかつ精度高く制御することができることがわかった。 As described above, according to the embodiment of the present invention, it was found that the natural oxide film thickness can be controlled with high reproducibility and high accuracy while improving the quality of the particles.
　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。 The present invention is not limited to the above embodiments. The above-described embodiment is an example, and any device having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same effect is the present invention. included in the technical scope of

Claims (6)

  1. 　シリコンウェーハの洗浄方法であって、
    　シリコンウェーハをフッ酸により洗浄する第１洗浄工程と、
    　前記フッ酸により洗浄された前記シリコンウェーハをオゾン水により洗浄する第２洗浄工程と、
    　前記オゾン水により洗浄された前記シリコンウェーハをＳＣ１洗浄液により洗浄する第３洗浄工程と、
    　前記ＳＣ１洗浄液により洗浄された前記シリコンウェーハをオゾン水により洗浄する第４洗浄工程とを含むことを特徴するシリコンウェーハの洗浄方法。     A method for cleaning a silicon wafer,
    a first cleaning step of cleaning the silicon wafer with hydrofluoric acid;
    a second cleaning step of cleaning the silicon wafer cleaned with the hydrofluoric acid with ozone water;
    a third cleaning step of cleaning the silicon wafer cleaned with the ozone water with an SC1 cleaning liquid;
    and a fourth cleaning step of cleaning the silicon wafer, which has been cleaned with the SC1 cleaning liquid, with ozone water.
  2. 　前記第４洗浄工程の洗浄時間を調整することで前記シリコンウェーハの表面に形成される前記自然酸化膜の厚さを制御することを特徴する請求項１に記載のシリコンウェーハの洗浄方法。 3. The method of cleaning a silicon wafer according to claim 1, wherein the thickness of the natural oxide film formed on the surface of the silicon wafer is controlled by adjusting the cleaning time of the fourth cleaning step.
  3. 　予め、自然酸化膜が形成されたシリコンウェーハをオゾン水により洗浄する時間と、前記自然酸化膜が形成されたシリコンウェーハをオゾン水により洗浄することで増加する自然酸化膜厚さとの相関関係を求めておき、該相関関係に基づいて前記第４洗浄工程の洗浄時間を設定することを特徴とする請求項２に記載のシリコンウェーハの洗浄方法。 A correlation between the time for cleaning a silicon wafer having a natural oxide film formed thereon with ozone water and the natural oxide film thickness increased by cleaning the silicon wafer having a natural oxide film formed thereon with ozone water is obtained in advance. 3. The method of cleaning a silicon wafer according to claim 2, wherein the cleaning time of said fourth cleaning step is set based on said correlation.
  4. 　前記相関関係に基づいて、前記第２洗浄工程で前記シリコンウェーハの表面に形成された自然酸化膜の厚さと同等の自然酸化膜厚さとなるように前記第４洗浄工程の洗浄時間を設定することを特徴とする請求項３に記載のシリコンウェーハの洗浄方法。 Based on the correlation, setting the cleaning time of the fourth cleaning step so that the thickness of the natural oxide film formed on the surface of the silicon wafer in the second cleaning step is equal to the thickness of the native oxide film. The method for cleaning a silicon wafer according to claim 3, characterized by:
  5. 　前記第３洗浄工程後かつ前記第４洗浄工程より前にＳＣ２洗浄液により前記シリコンウェーハを洗浄するＳＣ２洗浄工程を含むことを特徴とする請求項１から４のいずれか一項に記載のシリコンウェーハの洗浄方法。 5. The silicon wafer according to any one of claims 1 to 4, further comprising an SC2 cleaning step of cleaning the silicon wafer with an SC2 cleaning solution after the third cleaning step and before the fourth cleaning step. cleaning method.
  6. 　自然酸化膜付きシリコンウェーハの製造方法であって、
    　請求項１から５のいずれか一項に記載のシリコンウェーハの洗浄方法により自然酸化膜付きシリコンウェーハを製造することを特徴する自然酸化膜付きシリコンウェーハの製造方法。     A method for manufacturing a silicon wafer with a native oxide film,
    A method for producing a silicon wafer with a native oxide film, comprising producing a silicon wafer with a native oxide film by the method for cleaning a silicon wafer according to any one of claims 1 to 5.
PCT/JP2022/007392 2021-04-13 2022-02-22 Method for cleaning silicon wafer, and method for producing silicon wafer with native oxide film WO2022219937A1 (en)

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