TW202338952A - Method for washing silicon wafer, and method for producing silicon wafer with natural oxide film - Google Patents

Abstract

The present invention pertains to a method that is for washing a silicon wafer and that comprises: a test wafer SC1 washing step for producing wafers having different surface roughnesses through washing under different SC1 washing conditions; a step for removing, through washing with hydrofluoric acid, an SC1 oxide film formed as a result of the SC1 washing; a step for forming a natural oxide film through washing with a washing liquid having oxidizing power; a step for obtaining a correlation relationship between the surface roughness obtained as a result of the SC1 washing and the thickness of the natural oxide film; a step for determining a surface roughness from the thickness of a natural oxide film to be formed and the correlation relationship, and determining SC1 washing conditions to obtain said surface roughness, for a wafer to be subjected to natural oxide film formation; a step for performing SC1 washing under the determined SC1 washing conditions; a step for removing an SC1 oxide film formed as a result of the SC1 washing; and a step for washing the wafer from which the SC1 oxide film has been removed, using a washing liquid having oxidizing power, to form the natural oxide film. As a result, provided is a method that is for washing a silicon wafer and that adjusts the surface roughness thereof to control, with good precision and reproducibility, the thickness of the natural oxide film.

Description

Method for cleaning silicon wafer and method for manufacturing silicon wafer with natural oxide film

The invention relates to a method for cleaning silicon wafers and a method for manufacturing silicon wafers with natural oxide films.

In the manufacturing process of a single crystal silicon wafer for semiconductor devices, its main surface is polished in a polishing step. Furthermore, in order to remove the abrasive and metal impurities attached to the surface of the silicon wafer during the polishing step, there is a cleaning step. In this washing step, a washing method called RCA washing is used.

The so-called RCA cleaning is based on the purpose of combining SC1 (Standard Cleaning 1, standard cleaning solution 1) cleaning, SC2 ((Standard Cleaning 2, standard cleaning solution 2) cleaning, DHF (Diluted Hydrofluoric Acid, diluted A method of cleaning by using hydrofluoric acid) cleaning. The so-called SC1 cleaning is a cleaning method that uses an alkaline cleaning solution mixed with ammonia water and hydrogen peroxide water in an arbitrary ratio. The silicon wafer is etched to lift-off the attached particles, and further utilizes the electrostatic repulsion between the silicon wafer and the particles to prevent the particles from reattaching to the silicon wafer and remove the particles. In addition, The so-called SC2 cleaning is a cleaning method that uses a cleaning solution mixed with hydrochloric acid and hydrogen peroxide water in an arbitrary ratio to dissolve and remove metal impurities on the surface of the silicon wafer. In addition, the so-called DHF Cleaning is a cleaning method that uses dilute hydrofluoric acid to remove the chemical oxide film on the surface of the silicon wafer. Furthermore, ozone water cleaning with strong oxidizing power is sometimes used to remove the chemical oxide film that is still attached to the silicon wafer. Organic matter on the surface of the silicon wafer and the natural oxide film are formed on the surface of the silicon wafer cleaned with DHF. Surface quality such as particles and surface roughness of the cleaned silicon wafer are important and will be combined according to the purpose. Such cleaning process.

Semiconductor components such as MOS (Metal Oxide Semiconductor, Metal Oxide Semiconductor) capacitors and transistors can be formed on the surface of the semiconductor silicon wafer. An insulating film such as a gate oxide film formed on these semiconductor elements can be used under high electric field intensity, and a simple silicon oxide film can be used well as the insulating film.

An example of a method for evaluating the film thickness of an oxide film on a silicon wafer is measurement using an ellipsometer. The so-called ellipsometer is an instrument that makes polarized light incident on a substrate sample, and then measures the change in the polarized state of the incident light and reflected light to determine the phase difference (Δ, delta) and amplitude ratio ( Ψ, Psi). Taking the silicon oxide film on a silicon wafer as an example, the incident light will be reflected by the silicon oxide film on the outermost surface and the interface between the silicon oxide film and the silicon wafer, so the polarization state will change. Furthermore, it is known that there are single-wavelength type ellipsometers that use laser as a light source and spectroscopic types that contain multiple wavelength components and use a white light source. The single-wavelength type can measure a specific wavelength (for example, 633 nm). In contrast to the phase difference (Δ) and amplitude ratio (Ψ), the spectroscopic type can measure the phase difference and amplitude ratio for each wavelength, and the film thickness can be evaluated with high accuracy by using the spectroscopic type, which has a large amount of information.

As mentioned above, the information obtained by the ellipsometer measurement is the phase difference and the amplitude ratio, and the film thickness cannot be directly obtained. To obtain the film thickness, a model must be created based on the substrate sample. The phase difference (Δ) and amplitude ratio (Ψ) theoretically calculated based on this model are the same as the phase difference (Δ) and amplitude ratio (Ψ) obtained by measurement using an ellipsometer. Ψ) comparison. Furthermore, the production of the model is carried out by setting conditions according to the physical properties of the sample. The items of the conditions to be set are the materials of the substrate and the film, the film thickness of each film layer, the optical constants of the substrate and the film, etc. In addition, for the setting of each item, a known reference value and a required dispersion relation are generally used based on the sample. This dispersion relation can show the wavelength dependence of the dielectric coefficient and has a plurality of parameters. .

Furthermore, for the above comparison, a process (also called fitting) of changing the parameters of the dispersion relationship equation and the film thickness of each film layer of the model is carried out in such a way that the degree of difference between the two is minimized. . The difference between the two is generally calculated using the least squares method. When the result obtained by fitting and using the least squares method is judged to have become smaller to a certain extent, the wave dispersion relationship equation at that time is The film thickness can be obtained by determining the refractive index and extinction coefficient of the film from the values of the parameters, and specifying the film thickness at this time as the film thickness of the film contained in the sample. Furthermore, model creation and fitting are generally performed manually or automatically using a computer based on a required program.

When there are irregularities (also called roughness or roughness) on the surface of a sample, a consideration method such as effective medium approximation (EMA) may be used (for example, Patent Document 1, etc.). This method is a method that improves the calculation results of the least squares method by defining roughness and voids as a plane layer. In addition, the effective medium approximation is not only applicable when there is roughness on the film surface of the sample, but may also be applied to the interface layer when there is roughness at the interface between the substrate and the film or the interface between film layers. Furthermore, effective medium approximation can sometimes be used as an analytical technique to reduce the value of the refractive index regardless of whether there is roughness. By using the effective medium approximation, the calculation result of the least squares method will of course change, and the value of the resulting film thickness will also change. Therefore, the operator needs to judge whether to use the effective medium approximation based on the calculation results of the least squares method, for example. Medium approximation.

Patent Document 2 describes that the thickness of a natural oxide film on a silicon wafer obtained using an ellipsometer changes depending on the surface roughness. Specifically, a method is disclosed that quantitatively evaluates surface roughness based on the correlation between surface roughness and the film thickness of a natural oxide film, which increases the film thickness as the surface becomes rougher.

In addition, AFM (Atomic Force Microscopy) is known as a method for evaluating surface roughness on a silicon wafer. As an indicator of surface roughness, the arithmetic mean height of Ra value, Sa value, etc. is often used. Ra is a two-dimensional roughness index based on the arithmetic mean height in the reference length, and Sa is a three-dimensional roughness index that extends Ra to a surface parameter. More specifically, as a method for evaluating roughness, it is also possible to perform transformation into the spatial frequency domain based on spectral analysis. This method can extract components of a specific wavelength from the measured surface profile, which can be represented by parameters related to a specific spatial wavelength and the amplitude intensity at that wavelength, such as PSD (Power Spectrum Density). By performing PSD analysis in this way, the spatial frequency domain of the significantly formed roughness can be specified. In addition, a Haze value obtained by a particle counter using the laser diffraction method can be used as an index. Haze is a value that represents so-called haze and is widely used as an indicator of the roughness of silicon surfaces. The higher the Haze degree, the rougher the surface of the wafer.

Although a highly insulating and dense silicon oxide film can be produced by thermal oxidation of a silicon wafer, from the viewpoint of particle adhesion, etc., there are still natural particles formed during cleaning on the silicon wafer when shipped. Oxide film, so thermal oxidation is mostly performed on silicon wafers with natural oxide films. At this time, it is known that the thickness of the thermal oxidation film is affected by the film quality (film thickness and structure) of the natural oxide film before thermal oxidation.

In recent years, as semiconductor integrated circuits have been miniaturized and multi-layered, various films including insulating films constituting elements have been required to be further thinned. Based on this thinning, it is necessary to form an extremely thin insulating film, that is, a silicon oxide film, uniformly and reproducibly within a plane or between substrates. In order to achieve this, it is necessary to control the film quality and especially the film thickness of the natural oxide film when the silicon wafer is shipped. This film quality will affect the quality of the silicon oxide film. Generally speaking, if the natural oxidation film is thick, the thickness of the thermal oxidation film will also become thicker. When it is desired to make the thermal oxidation film thinner, a thinner natural oxide film is preferable. When it is desired to make the thermal oxidation film thicker, a thicker natural oxide film is also preferable. Therefore, in recent years, it has been particularly desired to control the film thickness of the natural oxide film within a specific range with good reproducibility.

Patent Document 3 describes the relationship between a silicon wafer cleaned under various conditions and the thickness of an oxide film after thermal oxidation. Specifically, it was revealed that if the NH ₄ OH concentration of the SC1 cleaning solution is set to a high concentration, the amount of OH groups contained in the natural oxide film will increase and the film thickness after thermal oxidation will become thicker; by A method of controlling the film thickness after thermal oxidation using the correlation between the composition of the natural oxide film (film quality) and the film thickness after thermal oxidation. [Prior art documents] (Patent documents)

Patent Document 1: Japanese Patent Application Publication No. 2005-283502. Patent Document 2: Japanese Patent Application Laid-Open No. 6-163662. Patent Document 3: Japanese Patent No. 6791453.

[Problem to be solved by the invention] As mentioned above, it is necessary to control the thickness of the natural oxide film and the thermal oxide film on the silicon wafer. Generally speaking, in the manufacturing steps of silicon wafers, the surface roughness of the wafer will be formed during grinding and subsequent cleaning. For cleaning the polished wafer, SC1 cleaning, hydrofluoric acid cleaning and ozone water cleaning are used. However, it is known that in the cleaning step, SC1 cleaning, which is mainly used for etching, will cause the surface to become dirty. Rough.

Patent Document 3 describes the surface roughness Ra after SC1 cleaning and ozone water cleaning, and its value is about 0.06 to 0.12 nm. Such Ra value is the thickness value of silicon wafers used in recent years.

Patent Document 2 discloses that the surface roughness of the wafer affects the thickness of the natural oxide film measured by an ellipsometer, but the surface roughness value at this time is 0.22 to 2.05 nm based on the AFM Ra value. This is very high compared with the above-mentioned surface roughness value of 0.06 to 0.12 nm.

In addition, it is generally known that the thickness of the natural oxide film is about 1 nm. In Patent Document 2, when the Ra value is 0.22 nm, the thickness of the natural oxide film is 0.097 nm. When the Ra value is 1.23 nm, the thickness of the natural oxide film is 0.097 nm. The film thickness of the film is 1.586 nm. When the Ra value is 2.05 nm, the film thickness of the natural oxide film is 3.313 nm. All film thicknesses are very different starting from about 1 nm. In this way, the surface roughness and the thickness of the natural oxide film in Patent Document 2 are very different from the surface roughness and the thickness of the natural oxide film of silicon wafers used in recent years. It is considered that the reason for this is that in the invention described in Patent Document 2, a mixture of hydrofluoric acid and nitric acid, which is not used in general silicon wafer cleaning solutions, is used to intentionally roughen the surface. processing sake. That is, using the correlation disclosed in Patent Document 2, it is difficult to study the roughness and the thickness of the natural oxide film in the range of Ra of 0.06 to 0.12 nm, for example, and it is speculated that Patent Document 2 can only be applied to cases where the Ra value exceeds 1, for example. nm such a very rough situation.

Here, if we focus on the Ra value of AFM and the thickness of the thermal oxide film obtained by spectroscopic ellipsometry when changing the NH ₄ OH concentration in SC1 cleaning described in Patent Document 3, it can be seen that the NH ₄ OH concentration is high. In the case of horizontal AFM, the Ra value is high, and the thickness of the thermal oxidation film also tends to become thicker (Fig. 9 of Patent Document 3). Patent Document 3 discloses the composition (film quality) of the natural oxide film (chemical oxidation film) formed by the cleaning step. For example, the amount of OH groups has a correlation with the thickness of the thermal oxidation film. The amount of the OH groups is It is measured by the ATR (Attenuated Total Reflectance)-FT (Fourier Transform)-IR (Infrared Spectroscopy) method, and it is recorded that when the NH ₄ OH concentration is high, the OH group The amount will increase, so the thermal oxidation film will become thicker.

However, this result can also be explained by the fact that there is a correlation between the Ra value obtained by AFM measurement and the film thickness after thermal oxidation obtained by an ellipsometer as described above. As such, there is no conventional document describing the concept that the surface roughness of the wafer formed by the manufacturing process of silicon wafers used in recent years will have an impact on the natural results obtained by the ellipsometer. The thickness of the oxide film and the thermal oxidation film has an impact. For example, if the wafer surface roughness formed by the manufacturing process of silicon wafers with an Ra value of 0.06 to 0.12 nm is one of the factors that affects the thickness of the oxide film, as long as this is the case, in controlling the natural oxide film and The thickness of the thermal oxide film is considered to be a quality that is equally important as the composition (film quality) of the natural oxide film described above. In addition, this factor is considered useful as long as the thickness of the natural oxide film formed after cleaning can be controlled by appropriately adjusting the surface roughness of the wafer.

Therefore, the present invention is to solve the above problems, and aims to provide a silicon wafer cleaning method that can control the thickness of the natural oxide film with good accuracy and reproducibility by adjusting the surface roughness of the wafer. [Technical means to solve problems]

The present invention is made in order to achieve the above object, and provides a cleaning method of a silicon wafer that can control the natural oxide film of the silicon wafer formed by cleaning by including the following steps. Thick, this step is: SC1 cleaning step of silicon wafers for testing, which involves preparing a plurality of silicon wafers for testing in advance, changing the SC1 cleaning conditions to perform the SC1 cleaning of the silicon wafers for testing, thereby making The aforementioned test silicon wafers with multiple levels of surface roughness; the SC1 oxide film removal step of the aforementioned test silicon wafer, which is carried out by washing with hydrofluoric acid to completely remove the SC1 of the aforementioned test silicon wafer The SC1 oxide film formed in the cleaning step; the natural oxide film formation step of the aforementioned test silicon wafer, which uses a cleaning solution with oxidizing power to clean the aforementioned test silicon wafer from which the aforementioned SC1 oxide film has been removed , to form a natural oxide film; the correlation obtaining step is to obtain the correlation between the surface roughness and the film thickness of the natural oxide film. The surface roughness is formed by the aforementioned test silicon wafer in the aforementioned SC1 cleaning. The natural oxide film is formed on the silicon wafer for the test in the natural oxide film formation step; the SC1 cleaning condition determination step is directed to the silicon wafer for which the natural oxide film is formed, so that by utilizing the aforementioned oxidizing power In such a manner that the thickness of the natural oxide film formed by cleaning with the cleaning solution becomes a specific thickness, the thickness of the silicon wafer to be formed on the target of forming the natural oxide film is determined based on the correlation obtained in the correlation acquisition step. surface roughness, and determine the SC1 cleaning conditions that will result in the previously determined surface roughness; the SC1 cleaning step of the silicon wafer to be formed with the natural oxide film uses the SC1 cleaning condition determination step determined by the aforementioned The aforementioned SC1 cleaning conditions implement SC1 cleaning of the silicon wafer to be formed with the aforementioned natural oxide film; the SC1 oxide film removal step of the silicon wafer to be formed with the aforementioned natural oxide film is to remove the aforementioned natural oxide film after the aforementioned SC1 cleaning step. The silicon wafer to be formed as an oxide film is cleaned with hydrofluoric acid to completely remove the SC1 oxide film formed by the SC1 cleaning; and the oxide film forming step of the silicon wafer to be formed as a natural oxide film is performed using The aforementioned cleaning solution having oxidizing power cleans the silicon wafer to be formed as the natural oxide film from which the SC1 oxide film has been removed, thereby forming a natural oxide film.

With such a silicon wafer cleaning method, by utilizing the correlation between the surface roughness of the wafer and the thickness of the natural oxide film, the thickness of the natural oxide film can be controlled with high accuracy and reproducibility.

At this time, a silicon wafer cleaning method can be provided, in which the SC1 cleaning condition is at least one of the SC1 liquid chemical concentration, cleaning temperature, and cleaning time.

These conditions are easy to change in actual operation, so the cleaning conditions can be easily set.

At this time, the surface roughness can be a roughness component of 60 to 90/μm in the spatial frequency domain.

Such roughness components have a greater impact on the thickness of the oxide film, so more accurate and stable evaluation and control of the film thickness can be achieved.

At this time, the index of the surface roughness can be set as the Haze value of the particle counter.

The Haze value can be easily obtained with a particle counter, so throughput is very high and cleaning conditions can be set quickly and easily.

In this case, the index of the surface roughness can be the average value of the power spectral density of 60 to 90/μm in the spatial frequency domain.

This enables detailed evaluation of roughness, and therefore enables more accurate and stable evaluation and control of film thickness.

At this time, ozone water or hydrogen peroxide water can be used as the cleaning liquid having oxidizing power.

Thereby, ozone water and hydrogen peroxide water have strong oxidizing power, can uniformly oxidize the wafer surface, and can easily and stably form an oxide film.

At this time, a method for manufacturing a silicon wafer with a natural oxide film can be provided, in which a silicon wafer with a natural oxide film is manufactured by the silicon wafer cleaning method of the present invention.

This makes it possible to control the film thickness with high precision and reproducibility, and to manufacture a silicon wafer with a natural oxide film. [Effects of the invention]

As described above, according to the silicon wafer cleaning method of the present invention, by utilizing the correlation between the surface roughness of the wafer and the thickness of the natural oxide film, it becomes possible to control the thickness of the natural oxide film with good accuracy and reproducibility. Film thickness.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

As mentioned above, a silicon wafer cleaning method is sought that can control the thickness of the natural oxide film with good accuracy and reproducibility by adjusting the wafer surface roughness. In order to solve such a problem, the inventors focused on the roughness formed in the silicon wafer manufacturing steps, specifically the roughness formed in the grinding step and the cleaning step, and the natural roughness measured by an ellipsometer. We are committed to studying the relationship between the film thickness of oxide film and thermal oxidation film. As a result, they found that when the average power spectral density (intensity) of a specific frequency band becomes more than a specific value, the thickness of the oxide film becomes thicker, and that by adjusting the specific roughness component, the thickness of the natural oxide film can be controlled. film thickness, and then complete the present invention.

That is to say, the inventor found that the thickness of the natural oxide film can be controlled with good accuracy and reproducibility through a cleaning method of silicon wafer, and then completed the present invention. The cleaning method can control by The thickness of the natural oxide film of the silicon wafer formed by cleaning. This step is: the SC1 cleaning step of the silicon wafer for testing, which is performed by preparing a plurality of silicon wafers for testing in advance and changing the SC1 cleaning conditions. The SC1 cleaning of the aforementioned test silicon wafers is used to produce the aforementioned test silicon wafers with different levels of surface roughness; the SC1 oxide film removal step of the aforementioned test silicon wafers is performed by hydrofluoric acid cleaning Clean, completely remove the SC1 oxide film formed in the SC1 cleaning step of the aforementioned test silicon wafer; the aforementioned natural oxide film formation step of the test silicon wafer uses a cleaning solution with oxidizing power to remove the oxidized film. The silicon wafer used in the aforementioned test to remove the aforementioned SC1 oxide film is washed to form a natural oxide film; the correlation acquisition step obtains the correlation between the surface roughness and the film thickness of the natural oxide film, and the surface roughness is used for the aforementioned test. The natural oxide film is formed on the silicon wafer during the aforementioned SC1 cleaning. The natural oxide film is formed on the aforementioned test silicon wafer during the natural oxide film formation step. The SC1 cleaning condition determination step is based on the natural oxide film formation target. The silicon wafer is determined based on the correlation obtained in the correlation acquisition step so that the thickness of the natural oxide film formed by cleaning with the cleaning solution having oxidizing power becomes a specific thickness. The surface roughness of the silicon wafer to be formed as the natural oxide film is to be formed, and the SC1 cleaning conditions that result in the determined surface roughness are determined; the SC1 cleaning steps of the silicon wafer to be formed as the natural oxide film , which utilizes the SC1 cleaning conditions determined in the SC1 cleaning condition determination step to perform SC1 cleaning of the silicon wafer to be formed as a natural oxide film; and remove the SC1 oxide film from the silicon wafer to be formed as a natural oxide film. Step, which performs hydrofluoric acid cleaning on the silicon wafer to be formed as the natural oxide film after the SC1 cleaning step, and completely removes the SC1 oxide film formed by the SC1 cleaning; and, forming the natural oxide film The step of forming an oxide film on the target silicon wafer uses the aforementioned cleaning solution having oxidizing power to clean the aforementioned natural oxide film forming target silicon wafer from which the aforementioned SC1 oxide film has been removed, thereby forming a natural oxide film.

Hereinafter, description will be made with reference to the drawings.

First, the relationship between various surface roughnesses formed during the manufacturing steps of silicon wafers and the thickness of the oxide film will be described. Figure 2 is its investigation flow chart. For the prepared silicon wafers, CMP processing conditions and SC1 cleaning conditions are changed, and CMP processing or SC1 cleaning, which is a roughening process to form roughness, is performed to prepare silicon wafers of multiple levels. Then, after the oxide film is completely removed by washing with hydrofluoric acid in a batch washing machine, the oxide film is formed by washing with ozone water. At any level, hydrofluoric acid cleaning is used to completely remove the oxide film formed by the SC1 cleaning of the roughening process, and the subsequent ozone water is used to form the oxide film. Therefore, it can be interpreted as silicon crystals at multiple levels. The same method is used to form an oxide film on the circle. After subsequent Haze measurement with a particle counter, some wafers were thermally oxidized with a target film thickness of 5 nm, and a spectroscopic ellipsometer was used to evaluate the properties of the natural oxide film and the oxide film formed with a target film thickness of 5 nm. Film thickness.

Figure 3 is a graph showing the surface roughness (Haze) of the silicon wafer washed with CMP and SC1 and subjected to the roughening treatment in Figure 2 and the thickness of the natural oxide film and the target oxide film of 5 nm. relationship. In the CMP level (■), even if the Haze value exceeds 10 ppm, the film thickness of the natural oxide film and the target oxide film of 5 nm are still the same. However, in the SC1 cleaning level (●), if the Haze value becomes At higher values, both the natural oxide film and the oxide film targeted at 5 nm tend to become thicker. Since the oxide film is formed under the same conditions, it is estimated that the film thickness will be about the same as that of the CMP level. However, this is not the case with the SC1 cleaning level.

Furthermore, Figure 4 shows the surface roughness (Haze) and natural oxide film of the silicon wafer that was subjected to the roughening treatment in Figure 2 using single-wafer cleaning that combined hydrofluoric acid and ozone water cleaning, and the target The thickness of the oxide film is 5 nm. In addition, the hydrofluoric acid cleaning and ozone water cleaning after the roughening treatment are also performed in a single-piece manner rather than in a batch manner. At this time, since the oxide film formation method is different from that of batch-type ozone water, it is not possible to compare the film thickness of the above-mentioned SC1 and CMP levels with the single-wafer cleaning level. However, it is still possible to explore the film thickness within the single-wafer cleaning level. The influence of Haze. As a result, the single-wafer cleaning level was the same as the CMP level. Even if the Haze changed, the film thickness of the natural oxide film and the target 5 nm oxide film remained at the same level. Summarizing the above results, it can be seen that the roughness formed by CMP and single-wafer cleaning will not affect the film thickness of the oxide film, but the surface roughness of the substrate formed by SC1 cleaning will affect the thickness of the oxide film. Thick to thick.

Therefore, it shows the results of additional investigation into the cleaning level of SC1. Figure 5 shows the film thickness and Haze value of the natural oxide film after the following treatment. The treatment is based on the liquid composition NH ₄ OH: H ₂ O ₂ : H ₂ O = 1: 1: 10, washing Batch cleaning was carried out at a cleaning temperature of 80°C and cleaning times of 3, 6, and 12 minutes. SC1 cleaning was performed to roughen the surface, and then hydrofluoric acid cleaning was used to completely remove the oxide film, and ozone water was used. The cleanser. The film thickness of the natural oxide film at the time when no cleaning is performed (set as 0 minutes), which is the reference value, is 1.207 nm. On the other hand, when the cleaning time is 3 minutes, it is 1.258 nm, and when the cleaning time is 6 minutes, it is 1.258 nm. , when the cleaning time is 12 minutes, it is 1.261 nm. From the point that the difference between the average film thickness of 1.259 nm when the cleaning time is 3 minutes, 6 minutes, and 12 minutes and the film thickness of 1.207 nm when no cleaning is performed (washing time of 0 minutes) is 0.052 nm, it can be considered that The roughening treatment results in a thick film of approximately 0.052 nm due to SC1 cleaning. Haze tends to become higher the longer the cleaning time is. On the other hand, if the amount of film thickness is the same when the cleaning time is 3 minutes, 6 minutes, and 12 minutes, it can be considered that all the film is cleaned by SC1. The specific roughness component formed affects the film thickness thickening behavior, and the reason why the film thickness at 3 minutes, 6 minutes, and 12 minutes is the same is because it is related to the film thickness (thickening). The roughness components are of the same degree.

In order to verify this, AFM (atomic force microscopy) was used to evaluate the surface roughness of wafers at typical CMP, SC1 cleaning, and single-wafer cleaning levels. The observation field of view is 1 μm × 1 μm. In addition to the three-dimensional arithmetic mean height Sa, the PSD curve is obtained from the spectral analysis of the surface profile data. Figure 6 shows the AFM measurement results and PSD curves of each sample.

Initially, focus on the CMP level. Regarding the CMP levels, the level with the smallest haze value (CMP-1) and the largest level (CMP-2) are evaluated in Figure 3. In CMP-2, the power spectral density (intensity) in the low-frequency band (1 to 10/μm) is very high, and the roughness is mainly significant on the low-frequency side. AFM images also obtain images with large-scale fluctuations and appear consistent. As mentioned above, the roughness formed by CMP does not affect the thickness of the oxide film, so the components on the low frequency side do not affect the thickness of the oxide film.

Then, focus on the SC1 cleaning level. In the SC1 cleaning level, the evaluation liquid composition is NH ₄ OH: H ₂ O ₂ : H ₂ O = 1: 1: 10, and the cleaning temperature and cleaning time are 60°C/3 minutes, 80°C/3 minutes, and 80°C /12 minutes of three levels. In these cases, if the oxide film is formed by the same method, the film thickness will be thicker with the same thickness. As shown in Figure 6, for all three levels, compared with CMP-2, the roughness in the high-frequency band (10 to 100/μm) is more significant. This is because fine granular roughness can be obtained in AFM images. The situation is consistent. Therefore, the roughness components (spatial frequency domain) formed in CMP and SC1 cleaning are quite different.

Finally, focus on the single-chip cleaning level. Regarding the single-chip cleaning level, the level with the smallest Haze value (single-chip cleaning - 1) and the maximum level (single-chip cleaning - 2) are evaluated in Figure 4. The power spectral density (intensity) of the single chip cleaning level is in the high frequency band (10 ~ 100/μm), which is the middle level of CMP and SC1 cleaning.

The roughness evaluation results and the influence on the film thickness of the oxide film were examined. In particular, the Sa values of both SC1 cleaning -80°C/3 minutes and single-chip cleaning-2 are 0.108 nm. Compared with this, we focus on the change in film thickness of the oxide film in SC1 cleaning -80°C/3 minutes. Thick, the results of single piece washing-2 did not become thicker. If we look at the PSD curves of both, the power spectral density (intensity) in the low frequency band (1 to 10/μm) is about the same. In contrast, the power spectral density (intensity) in the high frequency band (especially above 50/μm) , SC1 cleaning -80℃/3 minutes is greater than single chip cleaning -2. Therefore, although there is not much difference between the two in the AFM image, judging from the PSD curve, the SC1 cleaning -80°C/3 minutes can be said to have the most significant roughness in the higher frequency band. Furthermore, if all the three levels of SC1 cleaning shown in the figure (60°C/3 minutes, 80°C/3 minutes, 80°C/12 minutes) become thicker by the same thickness (about 0.05 nm), It can be seen that the power spectral density (intensity) in the spatial frequency domain range of 60 to 90/μm is the same at all three levels, and is higher than the single chip clean-2. Therefore, it can be seen that the roughness component in the range of 60 to 90/μm is a roughness component that affects the film thickness of the natural oxide film and the target oxide film of 5 nm. By performing such evaluation and control of the surface roughness of the roughness component, the film thickness can be controlled more accurately and stably.

Furthermore, the power spectral density (intensity) of 50/μm or less in the spatial frequency domain has a relationship of 80°C/12 minutes > 80°C/3 minutes > 60°C/3 minutes among the three levels of SC1 cleaning. , and is consistent with the relationship between the Sa value, that is, 80℃/12 minutes > 80℃/3 minutes > 60℃/3 minutes. In the Sa value at this time, the roughness information on the low-frequency side with high intensity is significant. Although the above-mentioned single-wafer cleaning-2 and SC1 cleaning-80°C/3 minutes have the same Sa value of 0.108 nm, it is still considered to be the main reason for the difference in film thickness of the oxide film.

Summarizing the above results, it can be considered that if the roughness component of 60 to 90/μm in the spatial frequency domain, that is, the average power spectral density (intensity) exists above the threshold, the oxide film will become thicker. Here, if the average power spectral density (intensity) of the three levels of SC1 cleaning is calculated in the range of 60 to 90/μm, it is 0.16 nm ³ in SC1 cleaning -60°C/3 minutes. It is 0.18 nm ³ in washing at -80°C/3 minutes, and 0.17 nm ³ in SC1 washing at -80°C/12 minutes. On the other hand, the average value of single-wafer Clean-2 in which the above-mentioned oxide film does not become thick is 0.11 nm ³ . Therefore, the average power spectral density (intensity) of 60 to 90/μm is considered to be 0.15 nm ³ as the threshold value, and it can be determined that there is an average power spectral density (intensity) of 0.15 nm ³ or more on the silicon wafer. The film thickness of the silicon oxide film is affected by the surface roughness of the wafer, and includes the film thickness caused by the surface roughness of the substrate.

Based on the above insights, it can be explained that the surface roughness of a specific wafer is a factor that affects the film thickness of the oxide film (film thickness influencing factor). Here, factors that influence the film thickness of the natural oxide film and the thermal oxide film include, for example, the following two factors: the structure of the natural oxide film (chemical oxide film) described in Patent Document 3 and the structure of the natural oxide film (chemical oxide film) described so far. Surface roughness of silicon wafers.

Here, the surface roughness and the structure of the natural oxide film of the wafer after SC1 cleaning are considered. First of all, the so-called SC1 cleaning always carries out the following reaction. This reaction is the reaction of oxidizing Si by hydrogen peroxide and etching the oxidized SiO _2. For example, it depends on the concentration of the liquid chemical and the cleaning temperature. , cleaning time and other cleaning conditions, and the oxidation and etching behavior changes. Furthermore, under general conditions, the etching reaction of SiO ₂ is rate-determined, so the surface will always be covered by a natural oxide film. The thickness of the natural oxide film after SC1 cleaning will change with the balance of oxidation and etching reactions. Therefore, to control the thickness of the natural oxide film after SC1 cleaning, it is necessary to control the oxidation and etching reactions. This oxidation and etching behavior not only affects the wafer surface roughness, but also affects the structure of the natural oxide film as described in Patent Document 3. That is, to control the natural oxide film after SC1 cleaning and the film thickness after thermal oxidation, it can be said that either of these two factors needs to be controlled. In other words, when the cleaning conditions are inadvertently and slightly changed, the film thickness of the natural oxide film may vary greatly. In particular, the structure of the natural oxide film greatly affects the film thickness after thermal oxidation, and therefore becomes an important quality when controlling the film thickness after thermal oxidation.

Here, in addition to SC1 cleaning, other methods for forming a natural oxide film on the wafer surface include ozone water, hydrogen peroxide water, etc. These only undergo oxidation reactions and do not produce etching reactions. In particular, ozone water has a very strong oxidizing power, so it can form an oxide film in a more controlled manner than SC1 cleaning.

Therefore, the inventor conducted research on whether the film thickness can be controlled by limiting the variation factor of the natural oxide film to the wafer surface roughness. That is, SC1 cleaning is performed on the target wafer where the natural oxide film is to be formed, and a roughness in the range of 60 to 90/μm in the spatial frequency domain is formed. This roughness increases the thickness of the natural oxide film. Thereafter, for example, hydrofluoric acid cleaning is performed to completely peel off the natural oxide film formed in SC1 cleaning, and then a natural oxide film is formed using a cleaning solution with oxidizing power such as ozone water that does not cause etching. . Thereby, it is considered that the film thickness of the natural oxide film can be controlled by limiting the variation factor to the wafer surface roughness.

[How to clean silicon wafers] Based on the above content, the cleaning method of the silicon wafer of the present invention is described in detail below. FIG. 1 is a flow chart showing an example of the silicon wafer cleaning method of the present invention. First, a test silicon wafer was used to obtain the correlation between the surface roughness of the silicon wafer cleaned by SC1 and the thickness of the natural oxide film. This correlation is then used to determine the surface roughness of the silicon wafer to be formed on the natural oxide film formation target, and the silicon wafer is cleaned using SC1 cleaning conditions corresponding to the determined surface roughness of the silicon wafer. The SC1 is washed to form a specific surface roughness, and then after the SC1 oxide film is removed, a natural oxide film is formed. Hereinafter, the silicon wafer cleaning method of the present invention will be described in detail.

(Silicon wafer for testing) First, a plurality of test silicon wafers for obtaining correlation are prepared (S1 in Figure 1). There are no restrictions on the conductivity type and diameter of silicon wafers. Regarding the surface roughness, it is preferable that the surface roughness of the silicon wafer for testing and the silicon wafer to be formed as a natural oxide film described later is 0.5 nm or less in terms of Sa value. The reason is that in such a range, the thickness of the oxide film calculated by a spectroscopic ellipsometer is about 1 nm, which is more suitable for the evaluation of the thickness of the natural oxide film of silicon wafers used in recent years. Furthermore, generally speaking, the Sa value of the surface of the silicon wafer after CMP is 0.1 nm or less, and the Sa value of the back surface (DSP surface) is about 0.2 to 0.4 nm. Therefore, as long as it is at least DSP (double-sided polishing) Wafers that have been subjected to CMP processing after processing can be suitably used in the silicon wafer cleaning method of the present invention.

(SC1 Cleaning Step of Test Silicon Wafers) Next, SC1 cleaning is performed by changing the cleaning conditions for the plurality of prepared test silicon wafers (S2 in Figure 1). As the cleaning conditions, it is desirable to change at least one of the liquid chemical concentration, cleaning temperature, and cleaning time of SC1. The reason is that these conditions are easy to change in actual operation, and the cleaning conditions can be easily set. For example, as long as the liquid chemical concentration is concerned, it can be adjusted in the range of NH ₄ OH: H ₂ O ₂ : H ₂ O = 1:1:5 to 1:1:100. For example, the cleaning temperature can be adjusted within the range of 30 to 90°C. For example, the cleaning time can be adjusted within the range of 0.5 to 10 minutes. One or more of the above conditions can be set, but it is preferable to set more cleaning conditions, and more than three of the above conditions can also be set. By performing SC1 cleaning in this way, roughness can be formed on the surface of the wafer and an oxide film can be formed at the same time.

Furthermore, generally speaking, the oxide films formed during cleaning are sometimes collectively referred to as natural oxide films and chemical oxidation films. However, in this specification, in order to distinguish the types of oxide films, the oxide films formed by SC1 cleaning are It is called "SC1 oxide film", and the oxide film formed by cleaning using a cleaning solution with oxidizing power other than SC1 cleaning is called "natural oxide film".

(SC1 oxide film removal steps for test silicon wafers) Next, the SC1-cleaned silicon wafer for testing is cleaned with hydrofluoric acid to completely remove the SC1 oxide film (S3 in Figure 1). As long as the SC1 oxide film can be completely removed, the hydrofluoric acid cleaning conditions are not limited. For example, an example of the conditions is a hydrofluoric acid concentration of 0.3 to 5.0 wt%, a temperature of 10 to 30°C, and a cleaning time of 60 to 360 seconds. .

(Steps for forming natural oxide film on silicon wafer for testing) Next, a cleaning solution with oxidizing power is used to clean the test silicon wafer from which the SC1 oxide film has been removed, thereby forming a natural oxide film (S4 in Figure 1). As a cleaning liquid having oxidizing power, ozone water or hydrogen peroxide water is preferred, and ozone water with strong oxidizing power is preferred. Ozone water or hydrogen peroxide water has strong oxidizing power, can uniformly oxidize the wafer surface, and can easily and stably form an oxide film. For example, the following conditions can be set: the concentration of ozone water used is in the range of 3 to 25 ppm, the temperature is in the range of 10 to 30°C, and the cleaning time is in the range of 60 to 360 seconds. In addition, for example, the following conditions can be set: the concentration of hydrogen peroxide water used is 0.2 to 5.0 wt%, the temperature is 30 to 90° C., and the cleaning time is 60 to 360 seconds. Furthermore, when a batch washing machine is used, the number of processes can be reduced by performing a series of washings in one batch.

(Steps to obtain relevant relationships) Next, the correlation between the surface roughness of the test silicon wafer on which the oxide film is formed and the film thickness of the natural oxide film is obtained (S5 in Figure 1). The film thickness of the natural oxide film can be measured using a conventional measurement method, for example, using a spectroscopic ellipsometer. For surface roughness indicators, it is easiest to use a particle counter to obtain the Haze value. When using the Haze value, the roughness can be accurately reflected by using the difference (Haze increase, ΔHaze) before and after cleaning. Alternatively, AFM may be used, for example, a roughness index such as Sa may be used, a PSD curve may be obtained from spectral analysis of AFM profile data, and the average value of the power spectral density (intensity) of 60 to 90/μm in the spatial frequency domain may be used. Furthermore, the roughness evaluation only needs to be carried out after SC1 cleaning and before the correlation acquisition step. It can be carried out before hydrofluoric acid cleaning, or it can be carried out after SC1 cleaning, hydrofluoric acid cleaning, or using oxidizing power. The cleaning solution should be used after cleaning. This is because the components of surface roughness that affect the thickness of the oxide film do not substantially change during cleaning with hydrofluoric acid or oxidizing power.

Figure 7 shows the film thickness of the natural oxide film under each cleaning condition. The cleaning conditions are based on the liquid chemical concentration being NH ₄ OH: H ₂ O ₂ : H ₂ O = 1:1:10, and the cleaning temperature. The conditions are set to 40, 50, 55, and 60°C, and the cleaning time is set to 3 and 6 minutes to perform SC1 cleaning, and then perform hydrofluoric acid cleaning and ozone water cleaning. When the cleaning time was 3 or 6 minutes, the film thickness tended to become thicker as the cleaning temperature increased. This is because the higher the cleaning temperature, the more roughness components in the spatial frequency domain of 60 to 90/μm are formed. The Haze value of the particle counter reflects the roughness in the range of 60 to 90/μm, so the Haze value can be set as an index.

Figure 8 shows the relationship between the Haze increase and the film thickness before and after cleaning for a cleaning time of 3 minutes. It can be seen that the Haze increase amount and film thickness also have a good correlation. By operating in this way, the correlation between the surface roughness and the thickness of the natural oxide film can be obtained.

Then, using this correlation, the silicon wafer to be formed as a natural oxide film (S6 in FIG. 1) is cleaned to form a natural oxide film with a target thickness.

(SC1 Cleaning Condition Determination Step) In the SC1 Cleaning Condition Determination Step (S7 in Figure 1), first, the film thickness of the natural oxide film to be formed is initially set. Then, an estimate of the required surface roughness is determined based on the correlation, and SC1 cleaning conditions that become the determined surface roughness are determined. In a specific example, the target film thickness value is set to 1.310 nm. Based on the correlation in Figure 8, the Haze increase corresponding to a film thickness of 1.310 nm is 0.020 ppm. In addition, based on the correlation in Figure 7, it can be seen that in order to achieve the roughness of 0.020 ppm, the following conditions are sufficient: liquid composition NH ₄ OH: H ₂ O ₂ : H ₂ O=1:1:10, The cleaning temperature is 55°C and the cleaning time is 3 minutes. These cleaning conditions were determined as SC1 cleaning conditions.

(SC1 cleaning step for silicon wafers subject to natural oxide film formation) Next, SC1 cleaning is performed using the determined cleaning conditions for the silicon wafer to be formed with a natural oxide film (S8 in Figure 1).

(SC1 oxide film removal step for silicon wafers subject to natural oxide film formation) Next, the silicon wafer to be formed as a natural oxide film is cleaned with hydrofluoric acid to completely remove the SC1 oxide film formed in the SC1 cleaning step (S9 in Figure 1).

(Oxide film formation steps for silicon wafers targeted for natural oxide film formation) Next, when the natural oxide film is formed on the silicon wafer for testing by using the silicon wafer to be formed as a natural oxide film from which the SC1 oxide film has been completely removed (the step of forming the oxide film on the silicon wafer for testing) The same cleaning solution with oxidizing power is used for washing, thereby forming a natural oxide film ((S10 in Figure 1)). In a specific example, ozone water is used for washing to form a natural oxide film. When using a spectroscopic ellipsometer When the natural oxide film of the silicon wafer cleaned with ozone water was evaluated, it was about 1.312 nm, indicating that a natural oxide film can be formed to the same extent as the set value of 1.310 nm.

[Method for manufacturing silicon wafer with natural oxide film] By using the silicon wafer cleaning method of the present invention, it is possible to manufacture a silicon wafer with a natural oxide film while controlling the film thickness with high precision. [Example]

Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these.

(Example) As a test silicon wafer, a plurality of silicon wafers that had been subjected to CMP polishing and single-wafer cleaning were prepared. First, the particle counter SP3 made by KLA was used to obtain the Haze value before SC1 cleaning. Then, in the batch cleaning machine, SC1 cleaning, hydrofluoric acid cleaning, and ozone water cleaning are performed using the cleaning conditions described below. The cleaning conditions of SC1 are set to the liquid composition NH ₄ OH: H ₂ O ₂ : H ₂ O = 1: 1: 10, the cleaning time is 3 minutes, and the cleaning temperature is set to 40, 50, 55, and 60°C. . The hydrofluoric acid cleaning was set to a concentration of 0.5 wt%, a cleaning temperature of 25°C, and a cleaning time of 3 minutes. The ozone water cleaning was set to a concentration of 20 ppm, a cleaning temperature of 25°C, and a cleaning time of 3 minutes. Next, the Haze of the cleaned test silicon wafer was evaluated using SP3. Thereafter, the film thickness of the natural oxide film was evaluated using a spectroscopic ellipsometer M-2000V manufactured by JAWoollam Co., Ltd. The results are shown in Table 1. The higher the cleaning temperature, the greater the increase in Haze and the tendency for the film thickness to become thicker, and a correlation between roughness and film thickness can be obtained.

[Table 1] level SC1 cleaning conditions Haze increase [ppm] Natural oxide film thickness [nm] 1 40℃/3 minutes 0.009 1.281 2 50℃/3 minutes 0.014 1.301 3 55℃/3 minutes 0.020 1.313 4 60℃/3 minutes 0.028 1.330

Then, the target film thickness of the natural oxide film to be formed on the silicon wafer is set to 1.330 nm. Using the obtained correlation, the Haze increase when the target film thickness is set to 1.330 nm is about 0.028 ppm. To achieve this surface roughness, a cleaning temperature of 60°C/a cleaning time of 3 minutes is suitable. Therefore, the SC1 cleaning conditions are determined as follows: liquid composition NH ₄ OH: H ₂ O ₂ : H ₂ O = 1:1:10, cleaning temperature 60°C/washing time 3 minutes.

Next, after SC1 cleaning of the target silicon wafer under the determined cleaning temperature of 60°C/cleaning time of 3 minutes, hydrofluoric acid cleaning and ozone water were performed under the same conditions as when the above correlation was obtained. Wash. Afterwards, when the natural oxide film after cleaning was evaluated using M-2000V, the thickness was found to be 1.332 nm, which was confirmed to be approximately the same as the target setting value of 1.330 nm. In this way, according to embodiments of the present invention, by using the relationship between surface roughness and the thickness of the natural oxide film, the film thickness of the natural oxide film can be controlled.

In addition, the present invention is not limited to the above-mentioned embodiment. The above-mentioned embodiments are only examples, and those which have substantially the same structure as the technical ideas described in the patent application scope of the present invention and can produce the same functions and effects are included in the technical scope of the present invention.

without

FIG. 1 is a flow chart showing an example of the silicon wafer cleaning method of the present invention. Figure 2 shows a flow chart for investigating the relationship between the surface roughness of the silicon wafer and the film thickness of the oxide film. Figure 3 shows a graph showing the relationship between the surface roughness (Haze) and the natural oxide film and the 5 nm oxide film of the silicon wafer cleaned with CMP and SC1 and subjected to the roughening process in Figure 2. Figure 4 shows a graph showing the relationship between the surface roughness (Haze) of a silicon wafer subjected to the roughening process in Figure 2 by single wafer cleaning and the natural oxide film and the 5 nm oxide film. Figure 5 shows that the liquid composition is NH ₄ OH:H ₂ O ₂ :H ₂ O=1:1:10, the cleaning temperature is 80°C, and the cleaning time is 0, 3, 6, and 12 minutes. Figure 2 shows the relationship between the cleaning time and the thickness of Haze and natural oxide film during roughening treatment. Figure 6 shows the AFM measurement results and PSD curves of each sample. Figure 7 is a diagram showing the relationship between SC1 cleaning conditions and the film thickness of the natural oxide film of the sample after hydrofluoric acid cleaning and ozone water cleaning. Figure 8 is a graph showing the relationship between the Haze increase amount and the film thickness of the natural oxide film for each sample.

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Claims (10)

A method for cleaning silicon wafers. The cleaning method is characterized by having the following steps to control the thickness of the natural oxide film of the silicon wafer formed by cleaning. The steps are: The SC1 cleaning step of silicon wafers for testing involves preparing a plurality of silicon wafers for testing in advance, changing the SC1 cleaning conditions to perform the SC1 cleaning of the silicon wafers for testing, thereby producing a plurality of silicon wafers with different surface roughness. A level of silicon wafer used in the aforementioned experiments; The SC1 oxide film removal step of the aforementioned test silicon wafer is performed by cleaning with hydrofluoric acid to completely remove the SC1 oxide film formed in the SC1 cleaning step of the aforementioned test silicon wafer; The step of forming a natural oxide film on the aforementioned test silicon wafer uses a cleaning solution with oxidizing power to clean the aforementioned test silicon wafer from which the aforementioned SC1 oxide film has been removed to form a natural oxide film; Correlation acquisition step, which obtains the correlation between the surface roughness and the film thickness of the natural oxide film. The surface roughness is formed by the aforementioned test silicon wafer in the aforementioned SC1 cleaning. The natural oxide film is the aforementioned test silicon wafer. The silicon wafer is formed during the natural oxide film formation step; The SC1 cleaning condition determination step is such that the thickness of the natural oxide film formed by cleaning with the aforementioned cleaning solution having oxidizing power becomes a specific thickness for the silicon wafer to be formed as a natural oxide film. Based on the correlation obtained in the correlation acquisition step, determine the surface roughness of the silicon wafer to be formed on the natural oxide film formation object, and determine the SC1 cleaning conditions that will result in the determined surface roughness; The SC1 cleaning step of the silicon wafer to be formed with the natural oxide film uses the SC1 cleaning conditions determined by the SC1 cleaning condition determining step to perform SC1 cleaning of the silicon wafer to be formed with the natural oxide film. ; The SC1 oxide film removal step of the silicon wafer to be formed with the natural oxide film is to perform hydrofluoric acid cleaning on the silicon wafer to be formed with the natural oxide film after the SC1 cleaning step to completely remove the silicon wafer formed by the SC1 cleaning step. The SC1 oxide film formed by net; and, The oxide film forming step of the silicon wafer to be formed with the natural oxide film is to use the cleaning solution with oxidizing power to clean the silicon wafer to be formed with the natural oxide film from which the SC1 oxide film has been removed. Natural oxide film. The method for cleaning a silicon wafer according to claim 1, wherein the SC1 cleaning conditions are any one or more of SC1 liquid chemical concentration, cleaning temperature, and cleaning time. The method for cleaning a silicon wafer according to claim 1, wherein the surface roughness is a roughness component of 60 to 90/μm in the spatial frequency domain. The method for cleaning a silicon wafer according to claim 2, wherein the surface roughness is a roughness component of 60 to 90/μm in the spatial frequency domain. The method for cleaning a silicon wafer according to any one of claims 1 to 4, wherein the index of surface roughness is set as the Haze value of a particle counter. The method for cleaning a silicon wafer according to any one of claims 1 to 4, wherein the index of surface roughness is an average value of power spectral density in a spatial frequency domain of 60 to 90/μm. The method for cleaning a silicon wafer according to any one of claims 1 to 4, wherein ozone water or hydrogen peroxide water is used as the aforementioned cleaning liquid with oxidizing power. The method for cleaning a silicon wafer according to claim 5, wherein ozone water or hydrogen peroxide water is used as the aforementioned cleaning liquid with oxidizing power. The method for cleaning a silicon wafer according to claim 6, wherein ozone water or hydrogen peroxide water is used as the cleaning liquid with oxidizing power. A method of manufacturing a silicon wafer with a natural oxide film, characterized in that the silicon wafer with a natural oxide film is produced by the silicon wafer cleaning method described in any one of claims 1 to 9.

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