Method for evaluating a silicon substrate and method for managing a manufacturing process of a silicon substrate

Abstract

To provide a method with which, when thermal oxidation is carried out in a device manufacturing process, for example, it is possible to estimate the film thickness of a thermal oxide film more easily with better throughput than a conventional method in which the composition of chemical oxide films is used an indicator.SOLUTION: Provided is a silicon substrate evaluation method comprising: a preparation step for the substrate to be evaluated; a step for completely removing a natural oxide film under an etching-less condition; a step for forming an oxide film for evaluation under an etching-less oxidation condition; a step for measuring the thickness of the oxide film for evaluation; and a step for evaluating the substrate to be evaluated, on the basis of the thickness of the oxide film for evaluation, without applying thermal oxidation to the prepared substrate to be evaluated. The evaluation step includes one or more of (i) a step for evaluating by estimation the thickness of the thermal oxide film of the prepared substrate to be evaluated, and (ii) a step for evaluating by estimation the cleaning history of the prepared substrate to be evaluated.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for evaluating a silicon substrate (silicon wafer) and a method for managing a manufacturing process of a silicon substrate.

Background Art

[0002] In the manufacturing process of a single crystal silicon wafer for semiconductor devices, its main surface is finished in a polishing process. Further, there is a cleaning process to remove abrasive and metal impurities attached to the silicon wafer surface in 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. This SC1 cleaning is a cleaning method using an alkaline cleaning solution obtained by mixing ammonia water and hydrogen peroxide water at an arbitrary ratio. By etching the silicon wafer surface, the attached particles are lifted off, and further, by utilizing the electrostatic repulsion between the silicon wafer and the particles, the particles are removed while suppressing reattachment to the silicon wafer. Also, SC2 cleaning is a cleaning method using a cleaning solution obtained by mixing hydrochloric acid and hydrogen peroxide water at an arbitrary ratio to dissolve and remove metal impurities on the silicon wafer surface. Also, DHF cleaning is a cleaning method for removing the natural oxide film on the silicon wafer surface with dilute hydrofluoric acid. Further, ozone water cleaning having a strong oxidizing power may also be used to remove organic substances attached to the silicon wafer surface and to form a natural oxide film (also called a chemical oxide film) on the silicon wafer surface after DHF cleaning. The surface quality of the silicon wafer after cleaning, such as particles and surface roughness, is important, and these cleanings are combined according to the purpose.

[0003] On the surface of a semiconductor silicon wafer, semiconductor elements such as MOS (Metal Oxide Semiconductor) capacitors and transistors are formed. Insulating films such as gate oxide films formed on these semiconductor elements are used under high electric field strengths, and silicon oxide films, which are easy to form, are often used as these insulating films.

[0004] An ellipsometer can be cited as a method for evaluating the film thickness of an oxide film on a silicon substrate (Patent Document 1). An ellipsometer is a device that measures the phase difference (Δ delta) and the amplitude ratio (Ψ psi) by irradiating a substrate sample with polarized light and measuring the change in the polarization state of the incident light and the reflected light. Taking the silicon oxide film on a silicon substrate as an example, the incident light reflects at the outermost silicon oxide film and the interface between the silicon oxide film and the silicon substrate, thereby changing the polarization state. Note that there are a single-wavelength type that uses a laser as a light source and a spectroscopic type that uses a white light source containing a large number of wavelength components in an ellipsometer. The short-wavelength type is a method of measuring delta and psi for a specific wavelength (for example, 633 nm), and the spectroscopic type can measure delta and psi for each wavelength. It is known that using the spectroscopic type with a large amount of information can evaluate the film thickness more accurately.

[0005] As described above, the information obtained by measuring with an ellipsometer is the phase difference and the amplitude ratio, and the film thickness cannot be directly obtained. To obtain the film thickness, a model corresponding to the substrate sample is created, and a comparison is made between the delta and psi theoretically obtained from this model and the delta and psi obtained by measuring with an ellipsometer. Note that the creation of the model is performed by setting conditions according to the physical properties of the sample. The items of the set conditions include the materials of the substrate and the film, the film thickness of each film layer, the optical constants of the substrate and the film, and the like. In addition, for the setting of each item, a known reference corresponding to the sample, a required dispersion formula showing the wavelength dependence of the dielectric constant and having a plurality of parameters, etc. are usually used.

[0006] Furthermore, a process (also referred to as fitting) is performed to change the distributed parameters and the film thickness of each film layer of the model so that the degree of difference between the two is minimized with respect to the above comparison. The difference between the two is usually obtained by an operation using the least squares method. When it is determined that the result obtained by the least squares method has become small to a certain extent by fitting, the refractive index and extinction coefficient of the film are obtained from the value of the distributed parameter at that time, and the film thickness at that time is specified as the film thickness of the film possessed by the sample, whereby the film thickness can be obtained. Note that model creation, fitting, etc. are generally performed manually or automatically based on a required program using a computer.

[0007] Patent Document 2 describes that the film thickness of the natural oxide film on a silicon wafer obtained by an ellipsometer changes depending on the surface roughness. Specifically, the rougher the surface, the thicker the film thickness value, and a method for quantitatively evaluating the surface roughness from the correlation between the roughness and the film thickness of the natural oxide film is disclosed. In addition, as an index of the surface roughness on a silicon substrate, there is a Haze value obtained by a particle counter. Haze is expressed as so-called cloudiness and is widely used as an index of the roughness of the silicon surface. A high Haze level indicates that the surface of the wafer is rough.

[0008] By the way, a dense silicon oxide film with high insulation is produced by thermally oxidizing a silicon wafer. However, from the viewpoint of particle adhesion, etc., there is a natural oxide film formed by cleaning on the silicon wafer at the time of shipment. Therefore, thermal oxidation is often performed on a silicon wafer on which a natural oxide film is formed. At this time, it is known that the thermal oxide film thickness is affected by the film quality (film thickness and structure) of the natural oxide film before thermal oxidation. In recent years, with the miniaturization and multi-layerization of semiconductor integrated circuits, there has been an increasing 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 ultrathin insulating film, i.e., a silicon oxide film, uniformly and reproducibly in-plane or between substrates. However, as the thickness of the thermal oxide film becomes thinner, the proportion of the natural oxide film thickness before thermal oxidation in the film thickness after thermal oxidation increases, making it more susceptible to the influence of the natural oxide film before the thermal oxidation treatment.

[0009] Patent Document 3 describes the relationship between silicon wafers cleaned under various conditions and the oxide film thickness after thermal oxidation. Specifically, when the NH 4 OH concentration of the SC1 cleaning solution is increased, the amount of OH groups contained in the chemical oxide film increases and the film thickness after thermal oxidation becomes thicker, and a method for controlling the film thickness after thermal oxidation by using the correlation between the composition of the chemical oxide film and the film thickness after thermal oxidation is disclosed.

[0010] Thus, depending on the cleaning conditions of the wafer, the film thickness after thermal oxidation changes. Against this background, in the manufacturing process of silicon wafers, in order to make the thermal oxide films of the manufactured silicon wafers uniform between wafers, it is desirable to clean under the same conditions as much as possible. The cleaning process often consists of a combination of SC1 cleaning, SC2 cleaning, hydrofluoric acid cleaning, and ozone water cleaning. It is desirable not only to make the cleaning flow the same, but also to make the chemical solution concentration, chemical solution temperature, and cleaning time the same. However, in the actual cleaning process, it is difficult to completely avoid a slight change in the chemical solution concentration, for example, at the initial, middle, and end stages of the chemical solution life, or a slight fluctuation in the temperature due to deterioration of the temperature sensor that controls the chemical solution temperature. Even such a slight change in conditions, especially SC1 cleaning, changes the etching behavior, resulting in fluctuations in the film thickness after thermal oxidation. Therefore, in order to confirm whether such film thickness fluctuations have occurred, it is desirable to extract the wafer in the cleaning process, for example, and evaluate the thermal oxide film.

[0011] Generally, in order to evaluate the film thickness after thermal oxidation, it is necessary to actually perform thermal oxidation treatment using an oxidation furnace. However, this not only takes time and effort but also requires significant maintenance and management of the oxidation furnace. Therefore, as disclosed in Patent Document 3, estimating the film thickness after thermal oxidation from the composition of the chemical oxide film after cleaning without performing thermal oxidation treatment is a very effective method. In this case, the higher the throughput and reproducibility, the more suitable it is for manufacturing process management in particular. In addition, if the thermal oxide film can be rapidly evaluated without performing thermal oxidation treatment, the cleaning conditions for controlling the thermal oxide film thickness can be easily determined. Also, for example, in defect analysis, etc., there may be cases where it is necessary to estimate the thermal oxide film thickness of a silicon wafer with an unknown cleaning history. Even in such cases, if the thermal oxide film thickness can be estimated from the information of the native oxide film, it will also be useful analysis information.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0013] As described above, there is a need for a method to estimate the thickness of the thermal oxide film formed on a silicon substrate with good throughput without performing thermal oxidation treatment. As described above, Patent Document 3 discloses a method for estimating the thermal oxide film thickness from the composition of the chemical oxide film before thermal oxidation without performing thermal oxidation treatment. Although this method is excellent in that it does not require actual thermal oxidation treatment, the problem is that it takes time for the analysis and its analysis for evaluating the composition of this chemical oxide film. That is, there has been a need for an index that has a correlation with the thermal oxide film thickness and can be analyzed more simply and with better throughput than the composition of such a chemical oxide film.

[0014] Therefore, the present invention has been made to solve the above problems, and provides a method that can estimate the film thickness of a thermal oxide film more throughput-efficiently and simply than a method using the structure of a conventional chemical oxide film as an index, for example, when performing a thermal oxidation treatment in a device manufacturing process or the like. Further, the present invention provides a method capable of highly accurately controlling a manufacturing process (particularly, a cleaning process) of a silicon substrate that affects the film thickness of the thermal oxide film, and a method for estimating the cleaning history (particularly, the presence or absence of SC1 cleaning) of a silicon substrate with an unknown cleaning history.

Means for Solving the Problems

[0015] In order to achieve the above problems, the present inventors intensively studied an index on a silicon substrate before thermal oxidation that correlates with the thermal oxide film thickness. In particular, since the thermal oxide film thickness depends on the cleaning conditions, attention was paid to whether there is an index that reflects the cleaning history applied to the silicon substrate before thermal oxidation. Furthermore, it was noted that in SC1 cleaning, as the etching action progresses, the structure of the formed chemical oxide film changes (for example, the amount of OH groups increases), and at the same time, the surface roughness of the silicon substrate deteriorates. It was also considered that such changes in the structure of the chemical oxide film and deterioration of the surface roughness can be interpreted as the cleaning history applied to the silicon substrate. Here, it was considered that there is a correlation between the change in the structure of this chemical oxide film and the surface roughness of the silicon substrate. Based on the above considerations, the degree of surface roughness of a silicon substrate formed by SC1 cleaning is also the SC1 cleaning history. If there is an index that reflects such surface roughness, this index is also an index that indirectly reflects the structure of the chemical oxide film. Therefore, it was considered that a correlation relationship with the thermal oxide film thickness could be obtained, and intensive studies were conducted. As a result, for a silicon substrate for which the thermal oxide film thickness is to be estimated, after peeling the native oxide film under conditions without an etching action, it was found that the film thickness of the evaluation oxide film formed under oxidation conditions without an etching action correlates with the thermal oxide film thickness, and by using the film thickness of this evaluation oxide film as an index, the thermal oxide film thickness can be estimated, and the present invention was completed.

[0016] That is, the present invention is a method for evaluating a silicon substrate, comprising: a substrate preparation step of preparing the silicon substrate as a substrate to be evaluated; An oxide film removing step of completely removing the natural oxide film of the substrate to be evaluated under conditions without an etching effect; An evaluation oxide film forming step of forming an evaluation oxide film on the substrate to be evaluated after completely removing the natural oxide film under oxidation conditions without an etching effect; A film thickness measuring step of measuring the film thickness of the evaluation oxide film formed in the evaluation oxide film forming step; An evaluation step of evaluating the substrate to be evaluated based on the film thickness of the evaluation oxide film measured in the film thickness measuring step without performing a thermal oxidation treatment on the prepared substrate to be evaluated, In this evaluation step, (i) A film thickness estimation and evaluation step of estimating and evaluating the film thickness of a thermal oxide film formed when the prepared substrate to be evaluated is subjected to the thermal oxidation treatment; (ii) A cleaning history estimation and evaluation step of estimating and evaluating the cleaning history of the prepared substrate to be evaluated, and providing a method for evaluating a silicon substrate, characterized in that it includes any one or more of the steps.

[0017] With such a method for evaluating a silicon substrate, by using the film thickness of the evaluation oxide film that correlates with the thermal oxide film as an index, the thermal oxide film thickness can be estimated. Also, with such an evaluation method, it is possible to evaluate more simply and with better throughput than analyzing and analyzing the composition of a conventional chemical oxide film. Further, in a normal manufacturing process, the cleaning history of the manufactured silicon substrate is stored as data, but it is assumed that the cleaning history is not stored for some reason, such as when a predetermined period has elapsed. In such a case, by performing the evaluation method of the present invention, it is possible to estimate the cleaning history (especially whether SC1 cleaning has been performed) of a silicon substrate with an unknown cleaning history.

[0018] At this time, in the oxide film removing step, the natural oxide film can be completely removed by hydrofluoric acid cleaning.

[0019] In the present invention, it is important to reflect the cleaning history applied to the silicon substrate for which the thickness of the thermal oxide film or the like is to be estimated in the thickness of the oxide film for evaluation. In the case of hydrofluoric acid cleaning, since there is no etching action on the silicon substrate and the native oxide film can be completely removed, it is suitable.

[0020] Further, in the step of forming the oxide film for evaluation, the oxide film for evaluation can be formed by ozone water or hydrogen peroxide water.

[0021] Similar to the above, by forming the oxide film for evaluation with ozone water or hydrogen peroxide water having no unnecessary etching action, the cleaning history of the silicon substrate, which is the original purpose, can be reflected in the thickness of the oxide film for evaluation, so it is suitable.

[0022] Further, when performing the film thickness estimation evaluation step in the evaluation step, a preliminary - substrate preparation step of preparing in advance a plurality of preliminary substrates that are silicon substrates and are cleaned under the same conditions as a reference; a preliminary - oxide film removal step of completely removing the native oxide film of one of the plurality of prepared preliminary substrates under conditions without an etching action; a preliminary - evaluation - oxide - film formation step of forming an oxide film for evaluation on the preliminary substrate after completely removing the native oxide film under oxidation conditions without an etching action; a preliminary - film - thickness measurement step of measuring the thickness of the oxide film for evaluation formed in the preliminary - evaluation - oxide - film formation step; a preliminary - thermal - oxide - film - thickness measurement step of performing a thermal oxidation treatment on the other of the plurality of prepared preliminary substrates to form a thermal oxide film and measuring the thickness of the thermal oxide film of the preliminary substrate; a correlation - relationship acquisition step of acquiring the correlation between the thickness of the oxide film for evaluation of the preliminary substrate and the thickness of the thermal oxide film of the preliminary substrate, and based on the correlation relationship, the thickness of the thermal oxide film of the substrate to be evaluated can be estimated and evaluated from the thickness of the oxide film for evaluation of the substrate to be evaluated.

[0023] If a correlation relationship is obtained in advance through such preliminary tests, the value of the thermal oxide film thickness of the substrate to be evaluated can be easily estimated.

[0024] Also, based on the film thickness of the thermal oxide film estimated and evaluated in the film thickness estimation and evaluation step of the evaluation process, the cleaning history of the prepared substrate to be evaluated can be estimated and evaluated.

[0025] In this way, the thermal oxide film thickness can be easily evaluated, and based on the estimated and evaluated thermal oxide film thickness as an index, the cleaning history can be easily estimated.

[0026] Also, when estimating and evaluating the cleaning history of the prepared substrate to be evaluated, it is possible to determine and evaluate whether SC1 cleaning has been performed.

[0027] In this way, based on the evaluation oxide film and the estimated and evaluated thermal oxide film thickness as indices, it is possible to easily determine the presence or absence of SC1 cleaning in the cleaning history.

[0028] The present invention is also a method for managing a manufacturing process of a silicon substrate, a substrate preparation step of preparing the silicon substrate as a substrate to be evaluated, an oxide film removal step of completely removing the natural oxide film of the substrate to be evaluated under conditions without an etching effect, an evaluation oxide film formation step of forming an evaluation oxide film on the substrate to be evaluated after completely removing the natural oxide film under oxidation conditions without an etching effect, a film thickness measurement step of measuring the film thickness of the evaluation oxide film formed in the evaluation oxide film formation step, a management step of managing the manufacturing process based on the film thickness of the evaluation oxide film measured in the film thickness measurement step without performing a thermal oxidation treatment on the prepared substrate to be evaluated, In the management step, when the film thickness of the evaluation oxide film deviates from a predetermined film thickness management value set in advance, (i) A film thickness management step of evaluating that the film thickness of the thermal oxide film formed when the above-prepared substrate to be evaluated is subjected to the thermal oxidation treatment fluctuates, (ii) A cleaning management step of investigating the cleaning history of the substrate to be evaluated and modifying the processing conditions of the cleaning treatment in the manufacturing process, characterized by comprising one or more of the above steps, and providing a method for managing a silicon substrate manufacturing process.

[0029] The method using the evaluation oxide film in the evaluation method of the silicon substrate of the present invention described above as an index is more throughput-efficient and simpler than conventional methods, so it can also be used in a method for managing a silicon substrate manufacturing process. With such a management method, fluctuations in the thermal oxide film thickness caused by unintentional and unexpected slight fluctuations in cleaning conditions can be detected quickly. Also, using this result, feedback can be provided to the manufacturing process (cleaning treatment) to correct (improve) the conditions.

[0030] In the method for managing the manufacturing process of the present invention as well, in the oxide film removal step, the natural oxide film can be completely removed by hydrofluoric acid cleaning, and in the evaluation oxide film formation step, the evaluation oxide film can be formed by ozone water or hydrogen peroxide water.

[0031] It is important to reflect the cleaning history of the silicon substrate in the film thickness of the evaluation oxide film. Hydrofluoric acid cleaning is suitable because it has no etching effect on the silicon substrate and can peel off the natural oxide film. Similarly, by forming the evaluation oxide film with ozone water or hydrogen peroxide water that has no unnecessary etching effect, the cleaning history of the silicon substrate, which is the original purpose, can be reflected in the film thickness of the evaluation oxide film, so it is suitable.

[0032] The present invention is also a method for managing a silicon substrate manufacturing process, comprising a management step of managing the manufacturing process based on the film thickness of the thermal oxide film estimated and evaluated in the film thickness estimation and evaluation step of the evaluation step of the above silicon substrate evaluation method, in the management step, When the film thickness of the estimated thermal oxide film deviates from a predetermined film thickness control value set in advance, (i) a film thickness control step of evaluating that the film thickness of the thermal oxide film formed when the prepared substrate to be evaluated is subjected to the thermal oxidation treatment fluctuates; and (ii) a cleaning management step of investigating the cleaning history of the substrate to be evaluated and modifying the processing conditions of the cleaning treatment in the manufacturing process, provided with any one or more of the steps, A method for managing a manufacturing process of a silicon substrate is provided.

[0033] The above-described manufacturing process management method uses the evaluation oxide film as an index, but instead of the evaluation oxide film thickness, the thermal oxide film thickness estimated and evaluated by the above evaluation method can also be used as an index for manufacturing process management. Such a management method can also quickly detect fluctuations in the thermal oxide film thickness, and it is possible to perform feedback and modify the conditions of the cleaning treatment.

Effect of the Invention

[0034] According to the evaluation method of the silicon substrate of the present invention, the thermal oxide film thickness can be evaluated more throughput and simply than in the past. In addition, it is possible to know the cleaning history (particularly whether the silicon substrate has been subjected to SC1 cleaning). Further, according to the manufacturing process management method of the silicon substrate of the present invention, it is possible to quickly detect an unintentional and unexpected slight fluctuation in the thermal oxide film thickness, feedback it to the manufacturing process, and improve the cleaning treatment.

Brief Description of the Drawings

[0035]

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Best Mode for Carrying Out the Invention

[0036] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. <Preliminary Investigation by the Present Inventors> As described above, the present invention is an evaluation method for estimating the thermal oxide film thickness by finding an index correlated with the thermal oxide film thickness. First, generally, for the cleaning of silicon wafers, a combination of SC1, SC2, hydrofluoric acid, and ozone water cleaning is used. Among these cleanings, in particular, SC1 cleaning is a cleaning method involving an etching action, and this etching action progresses more as the ammonia concentration is higher, the chemical solution temperature is higher, and the cleaning time is longer.

[0037] And due to such an etching action, the composition of the chemical oxide film on the silicon substrate changes (for example, the amount of OH groups increases), and the surface roughness also deteriorates. Also, the amount of this change and deterioration becomes more prominent as the etching action is stronger. For example, in SC1 cleaning, when the chemical solution concentration and cleaning time are fixed and the chemical solution temperature is changed between 70°C and 40°C, since the etching action is stronger at 70°C than at 40°C, the composition of the chemical oxide film changes greatly, the surface roughness deteriorates, and the thermal oxide film thickness also increases. Therefore, it can be said that there is a certain correlation between the composition of the chemical oxide film and the wafer surface roughness. And since this wafer surface roughness is caused by the etching action of SC1 cleaning, the rougher the surface roughness, the stronger the etching action. That is, if an index reflecting the wafer surface roughness formed by the etching action of SC1 cleaning applied to the silicon substrate can be found, this index will be an index reflecting the composition of the chemical oxide film, and a correlation with the thermal oxide film thickness will be obtained.

[0038] Subsequently, an index reflecting the wafer surface roughness formed by the etching action of SC1 cleaning will be described. First, the relationship between various wafer surface roughnesses formed in the manufacturing process of silicon wafers and the film thickness of the oxide film will be described. Figure 12 is the investigation flowchart. For the prepared silicon substrate, CMP processing conditions and SC1 cleaning conditions were changed, and a roughening process was performed to form roughness. Next, after the oxide film was completely removed by hydrofluoric acid cleaning in a batch cleaning machine, an oxide film was formed by ozone water cleaning. Since the oxide film of the roughening process was completely removed by hydrofluoric acid cleaning at both levels (CMP level, SC1 level), and the oxide film (reformed native oxide film) formed by ozone water afterwards was formed, it can be interpreted that the oxide film was formed by the same method. After that, Haze measurement was performed using a particle counter, and then the film thickness of the native oxide film was evaluated by spectroscopic ellipsometry.

[0039] Figure 13 shows the results of the native oxide film (the reformed one above) for Haze at each level. At the CMP level (■), the film thickness of the native oxide film was the same even when the Haze value exceeded 10 ppm, but at the SC1 cleaning level (●), it was found that the native oxide film tended to become thicker as the Haze increased. Since the oxide film was formed by the same method, it was estimated that the film thickness would be the same as at the CMP level, but this was not the case for the SC1 cleaning level.

[0040] Furthermore, Figure 14 also shows the results of performing the roughening process in a single-wafer cleaning that combined hydrofluoric acid and ozone water cleaning. The hydrofluoric acid cleaning and ozone water cleaning after the roughening process were also carried out in a single-wafer manner instead of a batch manner. Since the oxide film formation method is different from that of the batch-type ozone water cleaning, it is not possible to compare the film thicknesses at the above-mentioned SC1 level and CMP level with the film thickness at this single-wafer cleaning level, but the influence of Haze within the single-wafer cleaning level can be discussed. As a result, at the single-wafer cleaning level, the native oxide film thickness was the same even when the Haze changed in the same way as at the CMP level. Summarizing the above results, it was newly found that the roughness formed by CMP and single-wafer cleaning combined with hydrofluoric acid and ozone water cleaning does not affect the film thickness of the oxide film, while the roughness formed by SC1 cleaning thickens the film thickness of the oxide film.

[0041] From the above results, it was shown that at the SC1 level, the stronger the SC1 etching action, the worse the surface roughness. As a result, due to the influence of the surface roughness, the film thickness of the oxide film (the above-mentioned re-formed natural oxide film) also increased. In other words, if the film thickness of the oxide film (the above-mentioned re-formed natural oxide film) evaluated by such a method is thick, it can be determined that the silicon substrate has been subjected to SC1 cleaning with a strong etching action.

[0042] <Evaluation Method of Silicon Substrate of the Present Invention> [Evaluation of Thermal Oxide Film Thickness of Silicon Substrate] Based on the results of the above preliminary investigation, the evaluation method of the present invention will be described. FIG. 1 is an example of the evaluation method of the thermal oxide film thickness of the silicon substrate of the present invention. It is a flow for evaluating the substrate to be evaluated which is the actual object of evaluation (the flow of this test). In addition, a preliminary test is performed to obtain a correlation (the relationship between the evaluation oxide film thickness and the thermal oxide film thickness) using a preliminary substrate prepared separately from the substrate to be evaluated in this test, and the correlation can be used for the evaluation of the thermal oxide film thickness of the substrate to be evaluated in this test. The flow of the preliminary test will be described later. Hereinafter, the flow in this test will be described in detail. (S1: Substrate Preparation Step) First, as the S1 step, a silicon substrate for estimating the thermal oxide film thickness is prepared as the substrate to be evaluated. At this time, there are no restrictions on the conductivity type, aperture (diameter), and shape of the silicon substrate. However, it is preferable to prepare the substrate considering the following points regarding the surface roughness. Specifically, it is preferably those with an arithmetic mean height Sa of 0.5 nm or less. The reason for this will be explained using Patent Document 2 and Patent Document 3. Patent Document 3 describes the surface roughness Ra after SC1 cleaning and ozone water cleaning, and the value is about 0.06 to 0.12 nm. Such an Ra value is the roughness value of a silicon wafer used in recent years. Patent Document 2 discloses that the wafer surface roughness affects the natural oxide film thickness measured by an ellipsometer. At this time, the surface roughness value is 0.22 to 2.05 nm in terms of the Ra value of AFM, which is very high compared with the above-mentioned surface roughness value of 0.06 to 0.12 nm.

[0043] Also, although the natural oxide film is generally known to be about 1 nm thick, in Patent Document 2, when the Ra value is 0.22 nm, the natural oxide film thickness is 0.097 nm; when the Ra value is 1.23 nm, the natural oxide film thickness is 1.586 nm; and when the Ra value is 2.05 nm, the natural oxide film thickness is 3.313 nm, all of which are significantly different from about 1 nm. Thus, the surface roughness and natural oxide film thickness in Patent Document 2 are significantly different from those of the silicon wafers used in recent years. The reason for this is presumably that in Patent Document 2, the surface is intentionally roughened using a mixture of hydrofluoric acid and nitric acid, which is not used as a cleaning solution for ordinary silicon wafers. That is, it is difficult to discuss the roughness and natural oxide film thickness in the range where Ra is, for example, 0.06 to 0.12 nm using the correlation disclosed in Patent Document 2, and it is presumably applicable, for example, in the case of extremely rough surfaces where the Ra value exceeds 1 nm.

[0044] From such considerations, for the evaluation of the present invention, it is preferable that Sa is 0.5 nm or less. If the Sa value is 0.5 nm or less, it is possible to prevent the film thickness of the evaluation oxide film described later from deviating significantly from 1 nm due to the influence of roughness. However, generally, the Sa value of the surface of a 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, the cleaning method of the present invention is suitable at least for wafers after DSP processing or CMP processing. In fact, since the wafers subjected to thermal oxidation treatment for device fabrication are silicon wafers that have undergone the DSP process, CMP process, and cleaning process, usually, the surface roughness Sa of the silicon substrate for which the thermal oxide film thickness is to be evaluated is mostly 0.5 nm or less.

[0045] (S2: Oxide film removal step) Subsequently, as the S2 step, the natural oxide film of the substrate to be evaluated is peeled off (completely removed) under conditions without an etching effect. Generally, after the cleaning process, in order to reduce particle adhesion on the silicon wafer, SC1 cleaning or O 3A natural oxide film formed by cleaning is present. However, the film thickness of these natural oxide films varies depending on the cleaning conditions, and as described in Patent Document 3, the thermal oxide film thickness does not depend on the film thickness of this natural oxide film, so it cannot be an indicator of the thermal oxide film. Therefore, it is necessary to completely remove the natural oxide film that has once been formed here and form a new natural oxide film (evaluation oxide film) again in the next S3 step.

[0046] Here, the etching action will be described. The etching action indicates removing silicon, for example, by applying a chemical solution or plasma to silicon. In the cleaning process, SC1 cleaning exhibits this etching action, and hydroxide ions ionized from ammonia cause the etching action. Generally, it is known that when etching progresses, the surface roughness after etching deteriorates. As described above, in the present invention, since the film thickness reflecting the cleaning history applied to the silicon substrate is used as an index, when an unnecessary etching action is applied to the substrate to be evaluated in the S2 step, in addition to the cleaning history that is originally desired to be reflected, the influence caused by the S2 step is also taken into account. Therefore, in the S2 step, it is necessary to remove the oxide film under conditions without an etching action. However, as long as the oxide film is removed with a chemical solution or plasma, when looking at the surface of the silicon substrate from a macro or micro perspective, it is difficult to completely eliminate the etching action and prevent the surface from becoming rough at all. Therefore, in the method for evaluating a silicon substrate of the present invention (also, the method for managing the manufacturing process of the silicon substrate of the present invention described later), "no etching action" is defined as no etching action that creates a surface roughness that affects the evaluation method (management method) of the present invention. In other words, a very slight etching action that can be ignored is allowed.

[0047] An example of that etching action is shown in FIG. 2. FIG. 2 shows the Haze before and after cleaning and the difference before and after cleaning for a silicon substrate that has been subjected to hydrofluoric acid and ozone water cleaning and a silicon substrate that has been subjected to SC1 cleaning. Incidentally, the SC1 cleaning was carried out at 40°C to 70°C for 3 minutes. Looking at the whole, it can be seen that the higher the temperature condition where SC1 cleaning is performed and the stronger the etching effect of SC1, the greater the deterioration of Haze after cleaning. On the other hand, with only hydrofluoric acid and ozone water cleaning, although the Haze value deteriorates slightly, it can be seen that it is very small compared to the SC1 level. Therefore, hydrofluoric acid cleaning and ozone water cleaning make the surface slightly rougher, but the degree is very small, and it can be said that there is no etching effect in the present invention.

[0048] Subsequently, regarding the level of FIG. 2 above, the film thickness of the natural oxide film after further performing additional hydrofluoric acid and ozone water cleaning is shown in FIG. 3. Affected by the wafer surface roughness formed by the etching effect of the above-mentioned SC1 cleaning, the film thickness of the natural oxide film tends to increase as the cleaning temperature increases. Here, compared with the case without SC1 cleaning, the film thickness was the same until the temperature of SC1 cleaning was 40°C, but the film thickness became thicker when the temperature was 45°C or higher. That is, in this case, the etching effect is weak when the chemical solution temperature is up to 40°C, and the wafer surface roughness that affects the film thickness is not created. On the contrary, when the temperature is 45°C or higher, the wafer surface roughness is created, and it is considered that the film thickness of the natural oxide film has fluctuated.

[0049] Therefore, in this case, if the cleaning temperature is at a level of 40°C or lower, although a slight etching effect occurs, it is considered that it does not affect the evaluation method of the present invention, but this is not the case. The reason lies in the etching amount of SC1 cleaning. That is, in the S2 process, as described above, it is necessary to completely peel off the natural oxide film formed on the substrate to be evaluated. And in the S3 process, it is necessary to form an evaluation oxide film. Also, generally, since the film thickness of the natural oxide film is about 1 nm or more, when using SC1 cleaning in the S2 process, the etching amount must be 1 nm or more in order to completely peel off the natural oxide film. Here, Fig. 4 shows the etching amount when etching for 3 minutes under the same cleaning conditions as those in Fig. 3. From this graph, it can be seen that unless the cleaning temperature is at least 70°C or higher, an etching amount exceeding 1 nm cannot be ensured. However, when the cleaning temperature is 70°C, as shown in the graph of Fig. 3, the film thickness becomes significantly thicker, and it is judged that it is affected by the influence caused by the aforementioned S2 process. In addition, although it is easily conceivable to increase the cleaning time at a cleaning temperature of 40°C, since the roughness formed by SC1 cleaning is due to the etching amount, it is difficult to avoid affecting the evaluation method of the present invention even if etching is performed for a long time at a low etching rate.

[0050] Although the method for removing the oxide film in the S2 process is not particularly limited except for the condition of "no etching action", from the above results, it is considered difficult to achieve both the avoidance of creating surface roughness that affects the evaluation method of the present invention and the complete removal of the natural oxide film in SC1 cleaning. Therefore, the inventors also examined other methods. As a result, the most suitable method for peeling the oxide film is hydrofluoric acid cleaning. In addition, if the natural oxide film can be completely peeled off, the conditions for hydrofluoric acid cleaning are not particularly limited. As an example of the conditions, the hydrofluoric acid concentration is 0.3 to 5.0 wt%, the temperature is 10 to 30°C, and the cleaning time is 60 to 360 seconds. As other methods for peeling the oxide film, dry etching methods such as ALE (Atomic Layer Etching) can be mentioned. In this method, conditions can also be applied where only SiO 2 is selectively etched and Si is not etched.

[0051] (S3: Evaluation Oxide Film Formation Step) Next, as the S3 process, an evaluation oxide film is formed on the substrate to be evaluated under oxidation conditions without an etching action. Here too, similar to the S2 process, it is necessary to avoid applying an unnecessary etching effect to the substrate to be evaluated. Here too, "no etching effect" is defined as no etching effect that creates a surface roughness that affects the evaluation method (management method) of the present invention. Both ozone water and hydrogen peroxide water have a very small amount of Haze deterioration before and after cleaning. Therefore, it is preferable to oxidize the wafer surface with ozone water or hydrogen peroxide water that has no etching effect, and ozone water with a stronger oxidizing power is more preferable. An oxide film (reformed natural oxide film) can be easily formed with ozone water or hydrogen peroxide water. For example, the concentration of the ozone water used is in the range of 3 to 25 ppm, the temperature is 10 to 30 °C, and the cleaning time is 60 to 360 seconds. The concentration of the 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. The evaluation oxide film can be formed by such a method. Here, since the film thickness of this evaluation oxide film is used as an index in the S5 process described later, when there are a plurality of substrates to be evaluated, it is particularly preferable that the oxide film formation methods are the same for all of them. For example, comparing the film thicknesses of the evaluation oxide films formed by the same method is more accurate than comparing the film thickness of the evaluation oxide film formed by ozone water with the film thickness of the evaluation oxide film formed by hydrogen peroxide water. Also, even in the case of ozone water cleaning, it is more preferable to have the same conditions rather than having significantly different concentrations and cleaning times, as it enables a higher-precision evaluation. As another oxidation method, an oxide film can also be formed using plasma or the like in a dry method such as ALD (Atomic Layer Deposition). Particularly, the CVD method is effective because it has no etching effect on the silicon substrate.

[0052] (S4: Film Thickness Measurement Process) Next, as the S4 process, the film thickness of the evaluation oxide film is measured. This evaluation oxide film can be measured, for example, with a spectroscopic ellipsometer, and known methods can be used. In this S4 process, the film thickness reflecting the cleaning history of the silicon substrate can be obtained. At this time, it is preferable to make the elapsed time from the S3 process to the S4 process as uniform as possible. This is because the film thickness of the evaluation oxide film formed in the S3 process is oxidized by moisture and oxygen in the air over time, and the oxide film becomes slightly thicker. To suppress this variation, for example, evaluation can be performed with higher accuracy by evaluating after a preset elapsed time such as about 1 hour or 24 hours after the S3 process.

[0053] (S5: Evaluation process [Film thickness estimation evaluation process]) Next, as the S5 process, without performing a thermal oxidation treatment on the prepared substrate to be evaluated, the substrate to be evaluated is evaluated based on the evaluation oxide film thickness obtained in the S4 process. Here, from the evaluation oxide film thickness, the thermal oxide film thickness formed when the prepared substrate to be evaluated is subjected to a thermal oxidation treatment is estimated. Note that the conditions of the above-mentioned thermal oxidation treatment to be assumed are not particularly limited. For example, dry oxidation with oxygen gas or wet oxidation using water vapor can be used. Since the target film thickness to be formed varies depending on the thermal oxidation conditions, etc. in the device manufacturing process, the maximum temperature and time can be adjusted as appropriate. The following will be described more specifically. Here, 3 samples were prepared for each of the 11 levels of samples prepared by changing the cleaning conditions and polishing conditions. Among the 11 levels, 2 levels were cleaned with hydrofluoric acid and ozone water, and the other 9 levels were cleaned with SC1. For one of the 3 samples, Haze was obtained with a particle counter, and then the natural oxide film thickness was evaluated with a spectroscopic ellipsometer. After that, an evaluation oxide film was formed by cleaning with hydrofluoric acid and ozone water, and the film thickness was evaluated with a spectroscopic ellipsometer. Another one was directly subjected to a thermal oxidation treatment, and the thermal oxide film was evaluated with a spectroscopic ellipsometer. The last one imitated Patent Document 3, and the amount of OH groups and the ratio of suboxides were evaluated with ATR-FT-IR and XPS.

[0054] FIG. 5 shows the influence of Haze and the thickness of the native oxide film on the thermal oxide film thickness at each level. In both cases, the correlation coefficient R 2 value is small, indicating that there is no correlation between the Haze of the wafer surface roughness, the thickness of the native oxide film, and the thermal oxide film thickness. This is because other roughness components, such as those in the CMP process, in addition to the SC1 cleaning roughness, are taken into account for Haze. It can also be seen that the thickness of the simple native oxide film cannot be used as an indicator. FIG. 6 shows the case where the composition of the chemical oxide film is indicated by the amount of OH groups and the ratio of the suboxide. R 2 value is higher than that in FIG. 5, indicating a correlation with the thermal oxide film. Therefore, as described in Patent Document 3, it can be seen that the thermal oxide film thickness can be estimated from the composition of the chemical oxide film. FIG. 7 shows the case where the thickness of the evaluation oxide film of the present invention is used as an indicator. R 2 value is very high, above 0.9, indicating a good correlation between the evaluation oxide film thickness and the thermal oxide film thickness. Therefore, it can be estimated that the thicker the evaluation oxide film, the thicker the thermal oxide film thickness. Thus, since the thickness of the evaluation oxide film of the present invention has a very good correlation with the thickness of the thermal oxide film, the thermal oxide film can be estimated with high precision. Note that the two on the left side in the graph (with a thin evaluation oxide film thickness) are those cleaned with hydrofluoric acid and ozone water, and the nine on the right side are those cleaned with SC1. For example, by comparing the thicknesses of the evaluation oxide films of a plurality of substrates to be evaluated, it is possible to perform a comparative evaluation of the magnitudes of the thermal oxide film thicknesses of those substrates to be evaluated.

[0055] Here, the case of conducting a preliminary test will be described. In the evaluation method of the present invention, the thermal oxide film thickness can also be estimated more specifically by obtaining in advance the correlation between the evaluation oxide film thickness and the thermal oxide film thickness as shown in FIG. 7. The flowchart in a typical preliminary test in such a case is shown in FIG. 8. Note that the preliminary test may be conducted before the evaluation process [film thickness estimation evaluation process] of the main test. (S11: Preliminary - Substrate Preparation Step) First, as step S11, prepare a plurality of (here, two) preliminary substrates that serve as a reference and are silicon substrates with the same cleaning conditions. For each set of these two substrates, prepare a plurality of sets with different cleaning conditions for each set. The larger the number of sets, the more preferable it is to obtain a highly accurate correlation relationship, but it can be appropriately determined considering the labor and time. It can be said that the above-mentioned FIG. 7 is 11 sets (11 levels). (S12: Preliminary - Oxide film removal process, Preliminary - Evaluation oxide film formation process, Preliminary - Film thickness measurement process, and Preliminary - Thermal oxide film thickness measurement process) Next, in step S12, perform the same processes as steps S2 - S4 in FIG. 1 on one of the preliminary substrates, and measure the film thickness of the evaluation oxide film on the preliminary substrate. Also, perform thermal oxidation treatment on the other one and evaluate the thermal oxide film thickness. The conditions of this thermal oxidation treatment are preferably the same as those of the thermal oxidation treatment assumed in the above-mentioned present test. (S13: Correlation relationship acquisition process) Next, as step S13, acquire the correlation relationship between the evaluation oxide film thickness (evaluation oxide film thickness of the preliminary substrate) and the thermal oxide film thickness (thermal oxide film thickness of the preliminary substrate). The above is the flow of the preliminary test.

[0056] Perform the above-mentioned preliminary test in advance before the present test, and then the S1 process - S4 process of the present test can be performed. And in step S5, from the evaluation oxide film thickness of the silicon substrate (substrate to be evaluated in the present test) with an unknown thermal oxide film thickness, based on the correlation relationship of S13, the specific value of the thermal oxide film thickness of the substrate to be evaluated can be very easily estimated. Incidentally, as an example of a specific correlation relationship, FIG. 7 can be cited. Here, when the film thickness of the evaluation oxide film of the silicon substrate (substrate to be evaluated in the present test) with an unknown thermal oxide film thickness is 1.265 nm, by substituting it into the correlation formula (correlation relationship) of FIG. 7, the thermal oxide film thickness can be estimated to be 5.147 nm.

[0057] When there are few heat treatment conditions assumed to be applied to the silicon substrate, this method is very useful as it can estimate the actual thermal oxide film thickness. For example, when there are two levels of thermal oxidation conditions, namely one level of dry method and one level of wet method, the thermal oxide film thickness can be easily estimated by obtaining the correlation in advance. When there are a very large number of thermal oxidation treatments applied to the silicon substrate, it is particularly preferable to obtain the correlation for each thermal oxidation condition.

[0058] The evaluation method of the present invention as described above (evaluation of thermal oxide film thickness) is simpler and has better throughput than analyzing and analyzing the composition of the conventional chemical oxide film, and can estimate the thermal oxide film, so it can be said to be a very effective evaluation method.

[0059] [Estimation and evaluation of the cleaning history of the silicon substrate (judgment evaluation of SC1 cleaning)] By the way, in the normal manufacturing process, the cleaning history of the manufactured silicon wafer is stored as data, but it is assumed that the cleaning history is not stored for some reason, such as when a predetermined period has elapsed. In such a case, the cleaning history can be estimated by performing another form of the evaluation method of the present invention using the evaluation oxide film thickness as an index. The content of this cleaning history is not particularly limited, but here, a method for determining whether SC1 cleaning has been performed on the silicon wafer will be described. Fig. 9 shows the flow of the determination evaluation method for this SC1 cleaning. As a procedure, first, the same steps as in steps S1 - S4 of Fig. 1 are performed to measure the evaluation oxide film thickness of the substrate to be evaluated. (S5’: Evaluation step [SC1 determination evaluation step]) After that, as step S5’, without performing a thermal oxidation treatment on the prepared substrate to be evaluated, based on the evaluation oxide film thickness, it is determined and evaluated whether SC1 cleaning has been performed in the cleaning history of the prepared substrate to be evaluated.

[0060] The criteria for determining the presence or absence of SC1 cleaning are not particularly limited. For example, the correlation between the cleaning treatment conditions (conditions with SC1 cleaning and conditions without SC1 cleaning) and the evaluation oxide film thickness (and further, the thermal oxide film thickness if necessary) can be obtained, and the criteria can be determined based on this. For example, taking Figure 7 described above as an example, in the sample of Figure 7, as described above, there are two levels of cleaning with hydrofluoric acid and ozone water, and the film thicknesses of the evaluation oxide films are 1.236 nm and 1.237 nm respectively, which are very thin within this level. The other levels are the levels where SC1 cleaning was performed, and the film thickness of the evaluation oxide film at the level with the least amount of SC1 etching among them is 1.257 nm, which is thicker than the previous 1.236 nm and 1.237 nm. Therefore, if the film thickness of the evaluation oxide film of a silicon wafer (substrate to be evaluated) with an unknown cleaning history is at least 1.257 nm or more, it can be presumed that SC1 cleaning has been performed.

[0061] In addition, the determination and evaluation of the presence or absence of SC1 cleaning in this cleaning history may be performed using the thermally oxidized film thickness estimated from the previously prepared correlation as an index. That is, after performing the film thickness estimation and evaluation process to estimate and evaluate the thermally oxidized film thickness, it is also possible to further determine and evaluate the presence or absence of SC1 cleaning using the thermally oxidized film thickness. For example, in Figure 7, the second sample from the left (cleaning with hydrofluoric acid and ozone water) has a thermally oxidized film thickness of 5.125 nm, and the third sample from the left (SC1 cleaning) has a thermally oxidized film thickness of 5.127 nm. Here, a determination criterion of determining that SC1 cleaning is present when it is 5.127 nm or more can be set. In such an evaluation case as well, as described above, it is preferable to make the elapsed time between the S3 process and the S4 process the same. By the way, when there is no need to estimate and evaluate the thermally oxidized film thickness, the determination and evaluation based on the evaluation oxide film thickness requires fewer process steps and is even more convenient. However, even when using the estimated thermally oxidized film thickness as an index, since it is not necessary to actually form a thermally oxidized film on the substrate to be evaluated, it can be said that it is sufficiently convenient.

[0062] By using the evaluation method of the present invention (SC1 cleaning determination evaluation) as described above, it is possible to determine whether SC1 cleaning has been performed even on a silicon substrate with an unknown cleaning history.

[0063] In the evaluation method of the present invention, in the evaluation step, at least one of the film thickness estimation evaluation step using the above-described evaluation oxide film thickness and the cleaning history estimation evaluation step may be performed. Of course, both may be performed if necessary.

[0064] <Method for managing manufacturing process of silicon substrate of the present invention> The above-described evaluation method of the silicon substrate of the present invention is a method using the evaluation oxide film thickness as an index, and this can also be used for the management of the manufacturing process of the silicon substrate. Fig. 10 shows a typical flowchart thereof. (S21: Substrate preparation step) As the S21 step, for example, a silicon wafer during the manufacturing process (in the manufacturing line) is extracted and prepared as the substrate to be evaluated. Specifically, a silicon wafer that has undergone the same manufacturing process as the silicon wafer actually used in device fabrication is desirable. Generally, a silicon wafer after CMP processing and cleaning can be mentioned. At this time, it cannot be ruled out that there may be unintentional and unexpected slight changes in cleaning conditions (chemical solution concentration change or temperature change) in the cleaning tank. Especially when using SC1 cleaning, due to such changes, the etching action also changes, and as a result, when thermal oxidation treatment is performed, the thermal oxide film thickness fluctuates (the thermal oxide film thickness changes compared to the normal time before the change in cleaning conditions), so special attention is required. Therefore, when using a chemical solution, by extracting at the initial, middle, and end of the chemical solution life, the thermal oxide film thickness can be managed with higher precision.

[0065] (S22: Oxide film removal step ~ Film thickness measurement step) Subsequently, in the S22 step, the same steps as the S2 step - S4 step (and the S11 step - S13 step may also be performed if necessary) in the evaluation method of the silicon substrate of the present invention shown in Fig. 1 are performed to measure the film thickness of the evaluation oxide film.

[0066] (S23 - S27: Management Processes [Film Thickness Management Process][Cleaning Management Process]) In step S23, the film thickness of the oxide film for evaluation is compared with a predetermined film thickness management value (simply referred to as the management value) set in advance. Here, for the calculation of the management value, in advance, for silicon wafers with different manufacturing timings, by performing steps S21 and S22 multiple times, the oxide film thickness for evaluation is obtained, and from these oxide film thicknesses for evaluation, the central value, the upper control limit value, and the lower control limit value can be set by known methods. For example, taking the average value of the film thickness values as the central value, calculating the standard deviation σ of the central value, and setting +3σ as the upper control limit value and -3σ as the lower control limit value with respect to the central value. However, there is no particular limitation on this method for calculating the management value. Considering whether the film thickness of the thermal oxide film formed by thermal oxidation treatment in the device fabrication process downstream, etc., of the silicon wafers manufactured at the same timing as the silicon wafers extracted to obtain the oxide film thickness for evaluation as described above is within the allowable range, the above management value can be determined.

[0067] And when the oxide film thickness for evaluation is within the management value in step S24, it is considered normal, and the silicon wafer is sent to the next step as in step S25. On the other hand, when the management value is exceeded in step S24, as step S26, it is possible to make a judgment during the manufacturing process of the silicon substrate that the thermal oxide film thickness fluctuates in the thermal oxidation treatment in the downstream device process, etc. Also, as step S27, by conducting a cleaning history investigation and feeding back to the cleaning process, the processing conditions of the cleaning process can be corrected and improved. Abnormalities can be detected early, enabling prompt countermeasures.

[0068] For example, in a cleaning line using SC1 cleaning, when the film thickness of the evaluation oxide film exceeds the upper control limit value, since the etching action of SC1 is stronger than normal, it can be easily estimated that the thermal oxide film thickness will increase. In this case, it is effective to investigate the history of chemical solution concentration, chemical solution temperature, and cleaning time. Also, for example, when it often deviates from the control value at the end of the chemical solution life, a slight variation in the chemical solution concentration is suspected. Making the chemical solution into a new solution is also one of the countermeasures. Conversely, when the film thickness of the evaluation oxide film is below the lower control limit value, it is determined that the thermal oxide film is thinner. In this case, it is expected that the etching action of SC1 cleaning is less. Similarly, by investigating the cleaning history and taking countermeasures, the thermal oxide film thickness can be stabilized, and it becomes possible to manufacture good silicon wafers.

[0069] In the management method of the present invention, at least one of the film thickness management step and the cleaning management step using the above-described evaluation oxide film may be performed. FIG. 10 shows an example in which both of them are performed.

[0070] By the way, the above-described management method of the manufacturing process uses the evaluation oxide film thickness as an index. However, in addition, the manufacturing process can also be managed using the thermal oxide film thickness as an index. That is, after performing the film thickness estimation and evaluation step of the silicon substrate evaluation method of the present invention described above to estimate and evaluate the thermal oxide film thickness, further, using the estimated and evaluated thermal oxide film thickness instead of the evaluation oxide film thickness, and based on a separately set predetermined control value (control value of the thermal oxide film thickness), the manufacturing process of the silicon substrate can be managed by performing the same steps as the above-described film thickness management step and cleaning management step. In addition, when there is no need to estimate and evaluate the thermal oxide film thickness, the management method based on the evaluation oxide film thickness requires fewer steps and is even simpler. However, even when using the estimated and evaluated thermal oxide film thickness as an index, since it is not necessary to actually form a thermal oxide film on the substrate to be evaluated, it can be said that it is sufficiently simple.

Example

[0071] Hereinafter, the present invention will be further described based on examples, but these examples are shown illustratively and should not be construed as limiting. First, a method for estimating the thermal oxide film thickness will be described. After preparing a plurality of seven levels (samples A to G) of silicon wafers for which the thermal oxide film is to be estimated, with different CMP processing conditions and cleaning conditions, the following evaluations were carried out. Specifically, the CMP processing conditions and cleaning conditions for each sample were made different as shown in Table 1 below.

[0072] [Table 1]

[0073] (Example 1) For each level of one silicon wafer, hydrofluoric acid cleaning was performed to completely remove the native oxide film, ozone water cleaning was performed, and an evaluation oxide film was formed. The hydrofluoric acid cleaning was at a concentration of 0.5 wt%, a temperature of 25 °C, and a cleaning time of 3 minutes, and the ozone water cleaning was at a concentration of 20 ppm, a temperature of 25 °C, and a cleaning time of 3 min. Next, the film thickness of the evaluation oxide film was evaluated using a spectroscopic ellipsometer M-2000V manufactured by J.A.Woollam. The evaluation oxide film thickness is as shown in Table 2.

[0074] [Table 2]

[0075] As shown in Table 2, a difference in film thickness was observed between levels. The film thickness was in the order of (thick) G > B > E > F > C > A > D (thin). Since the thicker the film thickness of this evaluation oxide film, the thicker the film thickness after thermal oxidation, the film thickness after thermal oxidation was estimated to be (thick) G > B > E > F > C > A > D (thin), and the thermal oxide film thickness could be evaluated. Also, the time required from preparing the samples to estimating the thermal oxide film was about 1 hour.

[0076] Here, verification was conducted on whether the above evaluation was appropriate. Another one for each level was subjected to dry thermal oxidation treatment (maximum temperature reached: 900 °C, time: 60 minutes), and the thickness of the thermal oxide film formed by the thermal oxidation treatment was evaluated using an M-2000V. The thickness of the thermal oxide film among the samples was found to be (thick) G > B > E > F > C > A > D (thin), and it was confirmed that the result was the same as that of the above evaluation method. That is, it was confirmed that the above evaluation method was appropriate.

[0077] (Example 2) Next, when obtaining the correlation between the film thickness of the evaluation oxide film measured in the verification and the like in Example 1 and the thickness of the thermal oxide film, the correlation shown in FIG. 11 was obtained. The correlation coefficient R 2 value was very good, and it was confirmed that there was a good correlation between the evaluation oxide film and the thickness of the thermal oxide film. Regarding this acquisition of the correlation as a preliminary test, next, as the main test, two silicon wafers for which the thickness of the thermal oxide film was to be estimated were prepared, and the thickness of the evaluation oxide film was measured in the same manner as in Example 1. As a result, the thicknesses of the evaluation oxide films were found to be 1.271 nm and 1.314 nm, respectively. Next, by substituting into the correlation (correlation formula) in FIG. 11, when the thickness of the thermal oxide film was obtained, it could be estimated to be 5.153 nm and 5.223 nm. In addition, for silicon wafers similar to each of the two prepared silicon wafers above, thermal oxidation treatment (under the same conditions as in the verification of Example 1) was performed. As a result, the values were almost the same as the estimated thermal oxide film thicknesses above, and it was confirmed that the above evaluation method was appropriate and excellent.

[0078] (Comparative Example) In accordance with the evaluation method of Patent Document 3, ATR-FT-IR measurement was performed on one silicon wafer for each level, and the amount of OH groups was calculated as the composition of the chemical oxide film. The results are as shown in Table 3.

[0079]

Table 3

[0080] As shown in Table 3, there were differences in the amount of OH groups. Here, the amount of OH groups was (large) B > G > E > F > D > A > C (small). The thermally oxidized film thickness estimated from this result was (thick) B > G > E > F > D > A > C (thin). However, it did not completely match the film thickness order after the thermal oxidation treatment verified in Example 1. Therefore, it was shown that the evaluation method of the present invention in Examples 1 and 2, which was consistent with the verification results, had higher estimation accuracy for the thermally oxidized film. Also, the time required from preparing the sample to estimating the order of the thermally oxidized film thickness was about 6 hours. Therefore, it was also shown that Example 1 had better throughput and could more reliably estimate the thermally oxidized film thickness.

[0081] (Example 3) As a method for controlling the manufacturing process of a silicon wafer, the control method of the present invention was implemented. First, in order to determine the range of the control values, two silicon wafers after the cleaning process were taken out, and the film thickness of the evaluation oxide film was measured in the same manner as in Example 1. This measurement was carried out 5 times by changing the manufacturing date (Note that in the silicon wafers manufactured at the same timing as the taken-out silicon wafers, the thermally oxidized film thickness formed when performing the thermal oxidation treatment in the device manufacturing process downstream of the manufacturing line was all within the allowable range.). When the average value of these evaluation oxide film thickness values was calculated, it was found to be 1.241 nm. Next, the standard deviation σ was 0.005 nm. From these results, the central value was set to 1.241 nm, which was the average value. The upper control limit value was set to 1.256 nm at the center line + 3σ, and the lower control limit value was set to 1.226 nm at the center line - 3σ.

[0082] Subsequently, a silicon wafer (substrate to be evaluated) during the manufacturing process was taken out, and the film thickness of the evaluation oxide film was measured in the same manner as in Example 1. As a result, the evaluation oxide film thickness was 1.238 nm, which was a film thickness that satisfied the range of the control values. Therefore, it was determined that there was no abnormality in the manufacturing process, and the manufacturing was continued. In fact, when the silicon wafer at the same manufacturing timing as the taken-out silicon wafer was subjected to thermal oxidation treatment, the thermally oxidized film thickness was within the allowable range.

[0083] Furthermore, when a similar extraction evaluation was performed at a timing different from the above, the film thickness was 1.259 nm, which exceeded the upper control limit value. From this result, it was determined that there was a variation in the thermal oxide film thickness in the process of performing thermal oxidation treatment (thermal oxidation treatment during device fabrication) (the film thickness became larger than the normally formed film thickness value), and a manufacturing history investigation (cleaning history investigation) was carried out. As a result, it was found that there was a defect in the thermocouple that controls the chemical solution temperature in the cleaning process, and the chemical solution temperature was higher than the set temperature. Therefore, it was presumed that the film thickness of the evaluation oxide film also became thicker because the chemical solution temperature became high and the etching proceeded too much. After that, by replacing the thermocouple, after confirming the chemical solution temperature equivalent to the set temperature, the silicon wafer was cleaned, and when the film thickness of the evaluation oxide film was evaluated in the same manner as in Example 1, it was 1.244 nm, and it was confirmed that it was within the range of the control value. After this confirmation, the production of the silicon wafer was restarted. In fact, when the thermal oxide film thickness of the silicon wafer at the same manufacturing timing as the extracted silicon wafer was confirmed, it was out of the allowable range. With the manufacturing process management method of the silicon wafer as described above, it is possible to detect slight variations in the thermal oxide film, provide feedback to the manufacturing process, and quickly improve the conditions in the cleaning process.

[0084] This specification includes the following aspects. [1]: A method for evaluating a silicon substrate, comprising: a substrate preparation step of preparing the silicon substrate as a substrate to be evaluated; an oxide film removal step of completely removing the natural oxide film of the substrate to be evaluated under conditions without an etching effect; an evaluation oxide film formation step of forming an evaluation oxide film on the substrate to be evaluated after completely removing the natural oxide film under oxidation conditions without an etching effect; a film thickness measurement step of measuring the film thickness of the evaluation oxide film formed in the evaluation oxide film formation step; an evaluation step of evaluating the substrate to be evaluated based on the film thickness of the evaluation oxide film measured in the film thickness measurement step without performing a thermal oxidation treatment on the prepared substrate to be evaluated. In the evaluation step, (i) a film thickness estimation and evaluation step of estimating and evaluating the film thickness of a thermal oxide film formed when the prepared substrate to be evaluated is subjected to the thermal oxidation treatment; (ii) a cleaning history estimation and evaluation step of estimating and evaluating the cleaning history of the prepared substrate to be evaluated, and an evaluation method for a silicon substrate including at least one of the above steps. [2]: The evaluation method for a silicon substrate according to [1] above, wherein in the oxide film removal step, the natural oxide film is completely removed by hydrofluoric acid cleaning. [3]: The evaluation method for a silicon substrate according to [1] or [2] above, wherein in the evaluation oxide film formation step, the evaluation oxide film is formed by ozone water or hydrogen peroxide water. [4]: When performing the film thickness estimation and evaluation step in the evaluation step, a preliminary - substrate preparation step of preparing in advance a plurality of preliminary substrates that are silicon substrates and are cleaned under the same conditions as a reference; a preliminary - oxide film removal step of completely removing the natural oxide film of one of the prepared plurality of preliminary substrates under conditions without an etching effect; a preliminary - evaluation oxide film formation step of forming an evaluation oxide film on the preliminary substrate after completely removing the natural oxide film under oxidation conditions without an etching effect; a preliminary - film thickness measurement step of measuring the film thickness of the evaluation oxide film formed in the preliminary - evaluation oxide film formation step; a preliminary - thermal oxide film thickness measurement step of performing a thermal oxidation treatment on another one of the prepared plurality of preliminary substrates to form a thermal oxide film and measuring the film thickness of the thermal oxide film of the preliminary substrate; a correlation relationship acquisition step of acquiring a correlation relationship between the film thickness of the evaluation oxide film of the preliminary substrate and the film thickness of the thermal oxide film of the preliminary substrate, and then Based on the correlation relationship, estimating and evaluating the film thickness of the thermal oxide film of the substrate to be evaluated from the film thickness of the evaluation oxide film of the substrate to be evaluated, and the evaluation method for a silicon substrate according to any one of [1] to [3] above. [5]: Based on the film thickness of the thermal oxide film estimated and evaluated in the film thickness estimation and evaluation step of the evaluation step, The evaluation method of any one of the silicon substrates from [1] to [4] above for presumptively evaluating the cleaning history of the prepared substrate to be evaluated. [6]: The evaluation method of any one of the silicon substrates from [1] to [5] above for determining and evaluating whether SC1 cleaning has been performed when presumptively evaluating the cleaning history of the prepared substrate to be evaluated. [7]: A method for managing a manufacturing process of a silicon substrate, Based on the film thickness of the thermal oxide film presumptively evaluated in the film thickness presumptive evaluation step of the evaluation step of the evaluation method of any one of the silicon substrates from [1] to [6] above, a management step for managing the manufacturing process is provided, In the management step, When the film thickness of the presumptively evaluated thermal oxide film deviates from a preset predetermined film thickness management value, (i) A film thickness management step for evaluating that the film thickness of the thermal oxide film formed when the prepared substrate to be evaluated is subjected to the thermal oxidation treatment fluctuates, and (ii) A method for managing a manufacturing process of a silicon substrate, which includes any one or more of a cleaning history investigation of the substrate to be evaluated and a cleaning management step for correcting the processing conditions of the cleaning treatment in the manufacturing process. [8]: A method for managing a manufacturing process of a silicon substrate, A substrate preparation step of preparing the silicon substrate as a substrate to be evaluated, An oxide film removal step of completely removing the native oxide film of the substrate to be evaluated under conditions without an etching effect, An evaluation oxide film formation step of forming an evaluation oxide film on the substrate to be evaluated after completely removing the native oxide film under oxidation conditions without an etching effect, A film thickness measurement step of measuring the film thickness of the evaluation oxide film formed in the evaluation oxide film formation step, Based on the film thickness of the evaluation oxide film measured in the film thickness measurement step without performing a thermal oxidation treatment on the prepared substrate to be evaluated, a management step for managing the manufacturing process is provided, In the management step, When the film thickness of the evaluation oxide film deviates from a preset predetermined film thickness management value, (i) A film thickness management step of evaluating that the film thickness of the thermal oxide film formed when the prepared substrate to be evaluated is subjected to the thermal oxidation treatment fluctuates; (ii) A method for managing a manufacturing process of a silicon substrate, comprising any one or more of the following steps: a cleaning history investigation of the substrate to be evaluated, and a cleaning management step of modifying the processing conditions of the cleaning treatment in the manufacturing process. [9]: The method for managing a manufacturing process of a silicon substrate according to [8] above, wherein in the oxide film removal step, the natural oxide film is completely removed by hydrofluoric acid cleaning.

[10] : The method for managing a manufacturing process of a silicon substrate according to [8] or [9] above, wherein in the evaluation oxide film formation step, the evaluation oxide film is formed by ozone water or hydrogen peroxide water.

[0085] Note that the present invention is not limited to the above embodiments. The above embodiments are illustrative, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same operational effects is included in the technical scope of the present invention.

Claims

1. A method for evaluating a silicon substrate, comprising: a substrate preparation step of preparing the silicon substrate as a substrate to be evaluated; an oxide film removal step of completely removing the natural oxide film of the substrate to be evaluated under conditions without an etching effect; an evaluation oxide film formation step of forming an evaluation oxide film on the substrate to be evaluated under oxidation conditions without an etching effect after completely removing the natural oxide film; a film thickness measurement step of measuring the film thickness of the evaluation oxide film formed in the evaluation oxide film formation step; an evaluation step of evaluating the substrate to be evaluated based on the film thickness of the evaluation oxide film measured in the film thickness measurement step without performing a thermal oxidation treatment on the prepared substrate to be evaluated, wherein in the evaluation step, (i) a film thickness estimation evaluation step of estimating and evaluating the film thickness of a thermal oxide film formed when the prepared substrate to be evaluated is subjected to the thermal oxidation treatment; (ii) a cleaning history estimation evaluation step of estimating and evaluating the cleaning history of the prepared substrate to be evaluated, and comprising at least one of the above steps. A method for evaluating a silicon substrate.

2. The method for evaluating a silicon substrate according to claim 1, wherein in the oxide film removal step, the natural oxide film is completely removed by hydrofluoric acid cleaning.

3. The method for evaluating a silicon substrate according to claim 1, wherein in the evaluation oxide film formation step, the evaluation oxide film is formed by ozone water or hydrogen peroxide water.

4. The method for evaluating a silicon substrate according to claim 2, wherein in the evaluation oxide film formation step, the evaluation oxide film is formed by ozone water or hydrogen peroxide water.

5. When performing the film thickness estimation evaluation step in the evaluation step, a preliminary - substrate preparation step of preparing in advance a plurality of preliminary substrates that are silicon substrates and are cleaned under the same conditions as a reference; a preliminary - oxide film removal step of completely removing the natural oxide film of one of the prepared plurality of preliminary substrates under conditions without an etching effect; a preliminary - evaluation oxide film formation step of forming an evaluation oxide film on the preliminary substrate after completely removing the natural oxide film under oxidation conditions without an etching effect; a preliminary - film thickness measurement step of measuring the film thickness of the evaluation oxide film formed in the preliminary - evaluation oxide film formation step; a preliminary - thermal oxide film thickness measurement step of performing a thermal oxidation treatment on another one of the prepared plurality of preliminary substrates to form a thermal oxide film and measuring the film thickness of the thermal oxide film of the preliminary substrate, A correlation relationship acquisition step of acquiring a correlation relationship between the film thickness of the evaluation oxide film of the preliminary substrate and the film thickness of the thermal oxide film of the preliminary substrate is performed in advance. The method for evaluating a silicon substrate according to claim 1, wherein based on the correlation relationship, the film thickness of the thermal oxide film of the substrate to be evaluated is estimated and evaluated from the film thickness of the evaluation oxide film of the substrate to be evaluated.

6. When performing the film thickness estimation and evaluation step in the evaluation step, A preliminary substrate preparation step of preparing in advance a plurality of preliminary substrates that serve as a reference, are silicon substrates, and are cleaned under the same conditions. A preliminary oxide film removal step of completely removing the natural oxide film of one of the prepared plurality of preliminary substrates under conditions without an etching effect. A preliminary evaluation oxide film formation step of forming an evaluation oxide film on the preliminary substrate after completely removing the natural oxide film under oxidation conditions without an etching effect. A preliminary film thickness measurement step of measuring the film thickness of the evaluation oxide film formed in the preliminary evaluation oxide film formation step. A preliminary thermal oxide film thickness measurement step of performing a thermal oxidation treatment on the other of the prepared plurality of preliminary substrates to form a thermal oxide film and measuring the film thickness of the thermal oxide film of the preliminary substrate. A correlation relationship acquisition step of acquiring a correlation relationship between the film thickness of the evaluation oxide film of the preliminary substrate and the film thickness of the thermal oxide film of the preliminary substrate is performed in advance. The method for evaluating a silicon substrate according to claim 2, wherein based on the correlation relationship, the film thickness of the thermal oxide film of the substrate to be evaluated is estimated and evaluated from the film thickness of the evaluation oxide film of the substrate to be evaluated.

7. When performing the film thickness estimation and evaluation step in the evaluation step, A preliminary substrate preparation step of preparing in advance a plurality of preliminary substrates that serve as a reference, are silicon substrates, and are cleaned under the same conditions. A preliminary oxide film removal step of completely removing the natural oxide film of one of the prepared plurality of preliminary substrates under conditions without an etching effect. A preliminary evaluation oxide film formation step of forming an evaluation oxide film on the preliminary substrate after completely removing the natural oxide film under oxidation conditions without an etching effect. A preliminary film thickness measurement step of measuring the film thickness of the evaluation oxide film formed in the preliminary evaluation oxide film formation step. A preliminary thermal oxide film thickness measurement step of performing a thermal oxidation treatment on the other of the prepared plurality of preliminary substrates to form a thermal oxide film and measuring the film thickness of the thermal oxide film of the preliminary substrate. A correlation relationship acquisition step of acquiring a correlation relationship between the film thickness of the evaluation oxide film of the preliminary substrate and the film thickness of the thermal oxide film of the preliminary substrate is performed in advance. The method for evaluating a silicon substrate according to claim 3, wherein based on the correlation relationship, the film thickness of the thermal oxide film of the substrate to be evaluated is estimated and evaluated from the film thickness of the evaluation oxide film of the substrate to be evaluated.

8. When performing the film thickness estimation and evaluation step in the evaluation step, A preliminary substrate preparation step of preparing in advance a plurality of preliminary substrates that are reference silicon substrates and are cleaned under the same conditions. A preliminary oxide film removal step of completely removing the native oxide film of one of the prepared plurality of preliminary substrates under conditions without an etching effect. A preliminary evaluation oxide film formation step of forming an evaluation oxide film on the preliminary substrate after completely removing the native oxide film under oxidation conditions without an etching effect. A preliminary film thickness measurement step of measuring the film thickness of the evaluation oxide film formed in the preliminary evaluation oxide film formation step. A preliminary thermal oxide film thickness measurement step of performing a thermal oxidation treatment on the other of the prepared plurality of preliminary substrates to form a thermal oxide film and measuring the film thickness of the thermal oxide film of the preliminary substrate. A correlation relationship acquisition step of acquiring a correlation relationship between the film thickness of the evaluation oxide film of the preliminary substrate and the film thickness of the thermal oxide film of the preliminary substrate is performed in advance. The method for evaluating a silicon substrate according to claim 4, wherein based on the correlation relationship, the film thickness of the thermal oxide film of the substrate to be evaluated is estimated and evaluated from the film thickness of the evaluation oxide film of the substrate to be evaluated.

9. Based on the film thickness of the thermal oxide film estimated and evaluated in the film thickness estimation and evaluation step of the evaluation step, The method for evaluating a silicon substrate according to any one of claims 1 to 8, wherein the cleaning history of the prepared substrate to be evaluated is estimated and evaluated.

10. The method for evaluating a silicon substrate according to any one of claims 1 to 8, wherein when estimating and evaluating the cleaning history of the prepared substrate to be evaluated, it is determined and evaluated whether SC1 cleaning has been performed.

11. The method for evaluating a silicon substrate according to claim 9, wherein when estimating and evaluating the cleaning history of the prepared substrate to be evaluated, it is determined and evaluated whether SC1 cleaning has been performed.

12. A method for managing a manufacturing process of a silicon substrate, Based on the film thickness of the thermal oxide film estimated and evaluated in the film thickness estimation and evaluation step of the evaluation step of the method for evaluating a silicon substrate according to any one of claims 1 to 8, a management step for managing the manufacturing step is provided, In the management step, When the film thickness of the estimated and evaluated thermal oxide film deviates from a predetermined film thickness management value set in advance, (i) a film thickness management step of evaluating that the film thickness of the thermal oxide film formed when the thermal oxidation treatment is performed on the prepared substrate to be evaluated fluctuates; (ii) A method for managing a manufacturing process of a silicon substrate, comprising any one or more of a cleaning history investigation of the substrate to be evaluated and a cleaning management step of correcting processing conditions of a cleaning process in the manufacturing process.

13. A method for managing a manufacturing process of a silicon substrate, Based on the film thickness of the thermal oxide film estimated and evaluated in the film thickness estimation and evaluation step of the evaluation step of the method for evaluating a silicon substrate according to claim 9, a management step for managing the manufacturing step is provided, In the management step, When the film thickness of the estimated and evaluated thermal oxide film deviates from a predetermined film thickness management value set in advance, (i) a film thickness management step of evaluating that the film thickness of the thermal oxide film formed when the thermal oxidation treatment is performed on the prepared substrate to be evaluated fluctuates; (ii) A method for managing a manufacturing process of a silicon substrate, comprising any one or more of a cleaning history investigation of the substrate to be evaluated and a cleaning management step of correcting processing conditions of a cleaning process in the manufacturing process.

14. A method for managing a manufacturing process of a silicon substrate, Based on the film thickness of the thermal oxide film estimated and evaluated in the film thickness estimation and evaluation step of the evaluation step of the method for evaluating a silicon substrate according to claim 10, a management step for managing the manufacturing step is provided, In the management step, When the film thickness of the estimated and evaluated thermal oxide film deviates from a predetermined film thickness management value set in advance, (i) a film thickness management step of evaluating that the film thickness of the thermal oxide film formed when the thermal oxidation treatment is performed on the prepared substrate to be evaluated fluctuates; (ii) A method for managing a manufacturing process of a silicon substrate, comprising any one or more of a cleaning history investigation of the substrate to be evaluated and a cleaning management step of correcting processing conditions of a cleaning process in the manufacturing process.

15. A method for managing a manufacturing process of a silicon substrate, Based on the film thickness of the thermal oxide film estimated and evaluated in the film thickness estimation and evaluation step of the evaluation step of the method for evaluating a silicon substrate according to claim 11, a management step for managing the manufacturing step is provided, In the management step, When the film thickness of the estimated and evaluated thermal oxide film deviates from a preset predetermined film thickness management value, (i) A film thickness management step of evaluating that the film thickness of the thermal oxide film formed when the thermal oxidation treatment is performed on the prepared substrate to be evaluated fluctuates; and (ii) A method for managing a manufacturing process of a silicon substrate, comprising any one or more of a cleaning history investigation of the substrate to be evaluated and a cleaning management step of correcting processing conditions of a cleaning process in the manufacturing process.

16. A method for managing a manufacturing process of a silicon substrate, comprising: A substrate preparation step of preparing the silicon substrate as a substrate to be evaluated; An oxide film removal step of completely removing the natural oxide film of the substrate to be evaluated under conditions without an etching effect; An evaluation oxide film formation step of forming an evaluation oxide film on the substrate to be evaluated after completely removing the natural oxide film under oxidation conditions without an etching effect; A film thickness measurement step of measuring the film thickness of the evaluation oxide film formed in the evaluation oxide film formation step; Based on the film thickness of the evaluation oxide film measured in the film thickness measurement step without performing a thermal oxidation treatment on the prepared substrate to be evaluated, a management step for managing the manufacturing step is provided, In the management step, When the film thickness of the evaluation oxide film deviates from a preset predetermined film thickness management value, (i) A film thickness management step of evaluating that the film thickness of the thermal oxide film formed when the thermal oxidation treatment is performed on the prepared substrate to be evaluated fluctuates; and (ii) A method for managing a manufacturing process of a silicon substrate, comprising any one or more of a cleaning history investigation of the substrate to be evaluated and a cleaning management step of correcting processing conditions of a cleaning process in the manufacturing process.

17. The method for managing a manufacturing process of a silicon substrate according to claim 16, wherein in the oxide film removal step, the natural oxide film is completely removed by hydrofluoric acid cleaning.

18. The method for managing a manufacturing process of a silicon substrate according to claim 16 or claim 17, wherein in the evaluation oxide film formation step, the evaluation oxide film is formed by ozone water or hydrogen peroxide water.

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