Method for forming thermal oxide film on semiconductor substrate

Abstract

The present invention relates to a method for forming a thermal oxide film on a semiconductor substrate, and the method includes the following steps: a correlation acquisition step, in which a plurality of semiconductor substrates with different compositions of chemical oxide films are prepared in advance, thermal oxide films are formed under the same thermal oxidation treatment conditions, and the correlation between the composition of the chemical oxide film and the thickness of the thermal oxide film is obtained; a substrate cleaning step, in which the semiconductor substrate is cleaned; a thermal oxide film thickness estimation step, in which the composition of the chemical oxide film formed on the semiconductor substrate by the cleaning in the substrate cleaning step is obtained, and based on the correlation, the thickness of the thermal oxide film when the semiconductor substrate is thermally oxidized under the thermal oxidation treatment conditions in the correlation acquisition step is estimated; a thermal oxidation treatment condition determination step, in which, based on the thermal oxidation treatment conditions in the correlation acquisition step, the thermal oxidation treatment conditions are determined such that the thickness of the thermal oxide film is a specified thickness; a thermal oxide film formation step, in which a thermal oxide film is formed on the semiconductor substrate under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination step. Thus, the thermal oxide film can be reproducibly formed to a thin thickness as expected.

Description

Technical Field

[0001] The present invention relates to a method for forming a thermal oxide film on a semiconductor substrate. Background Art

[0002] With the multi-layerization and thinning of semiconductor integrated circuit elements, various films constituting the elements are required to be further thinned. For example, Patent Document 1 describes that in the bonding of silicon wafers, the silicon wafers used need to have OH groups on the surface, and when cleaned with a conventional SC1 cleaning solution, a natural oxide film is formed on the surface. In addition, for example, Patent Document 2 discloses a method for improving the gate characteristics of MOS transistors, which cleans the silicon surface immediately before forming a gate oxide film, and thus forms a gate insulating film on the basis of hydrogen termination (H2-terminate). Therefore, in order to uniformly and reproducibly form an extremely thin silicon oxide film in-plane or between substrates, it is impossible to ignore the influence of the natural oxide film or chemical oxide film (oxide film formed by the cleaning solution used in the cleaning process of the semiconductor substrate) pre-formed on the semiconductor substrate.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Laid-Open No. 09-063910

[0006] Patent Document 2: Japanese Patent Laid-Open No. 2000-216156

[0007] Patent Document 3: Japanese Patent Laid-Open No. 2003-115516

[0008] Patent Document 4: Japanese Patent Laid-Open No. 2002-270596

[0009] Non-Patent Documents

[0010] Non-Patent Document 1: Takagi, Vacuum, 33(11), 854(1990) Summary of the Invention

[0011] Technical Problem to be Solved by the Invention

[0012] In fact, the inventors of the present application have conducted investigations and studies and found that, for example, when the method for cleaning a semiconductor substrate is different, the thickness of the subsequent thermal oxide film will vary. It has also been found that the difference in the thickness of the thermal oxide film does not depend on the thickness of the natural oxide film or chemical oxide film before thermal oxidation. Therefore, before actually performing thermal oxidation on a semiconductor substrate and attempting to evaluate the thickness of the thermal oxide film, it is impossible to know the difference in the thickness of the actually formed thermal oxide film, and thus it is difficult to manage the thermal oxidation process.

[0013] In addition, when evaluating electrical characteristics such as GOI (Gate Oxide Integrity) measurement, if the thickness of the oxide film is uneven, it will affect the measurement results. Therefore, sometimes it is necessary to make the thickness of the oxide film a specified thickness, for example, make it uniformly 5.1 nm. Especially in such a region where the thickness of the oxide film is thin, if the oxide film is thinner than the target thickness, direct tunneling current will be generated, sometimes resulting in the inability to perform GOI measurement. Therefore, it is very important to adjust the thickness of the oxide film.

[0014] Patent Document 3 proposes to use the OH groups contained in the CVD oxide film (evaluating the OH groups in the CVD oxide film by infrared spectroscopy) to be removed in the form of moisture by heating and apply it to the calibration and management of a moisture meter. In the case of Patent Document 3, a heat treatment at a low temperature is performed in advance to the extent that the OH groups contained in the CVD oxide film are formed into moisture and removed, and the relationship with the growth of the thermal oxide film is not discussed. Thus, it is known that OH groups are contained in the oxide film and it is a source of moisture, but the CVD oxide film is thick, and the OH groups contained in an oxide film as thin as the natural oxide film and the subsequent growth of the thermal oxide film are not discussed.

[0015] Patent Document 4 describes that the composition intensities of the low-value oxides of Si 3+ , 1+ , 2+ , Si 2+ , Si 3+ directly above the silicon substrate can be obtained by the Si2p energy spectrum measured by X-ray photoelectron spectroscopy (XPS). However, its purpose is to obtain the surface roughness between silicon and the oxide film, which has no relation to the technology of the present invention for controlling the thickness of the thermal oxide film during thermal oxidation heat treatment.

[0016] The present invention is proposed to solve the above problems, and its purpose is to provide a method for forming a thermal oxide film on a semiconductor substrate, which can reproducibly form the thermal oxide film into a thin thickness as expected.

[0017] Technical means for solving technical problems

[0018] In order to achieve the above object, the present invention provides a method for forming a thermal oxidation film on a semiconductor substrate. The method for forming a thermal oxidation film on a semiconductor substrate includes the following steps: a correlation acquisition step, in which a plurality of semiconductor substrates are prepared in advance. The plurality of semiconductor substrates have chemical oxidation films formed by cleaning, and the compositions of the chemical oxidation films are different. The plurality of semiconductor substrates are thermally oxidized under the same thermal oxidation treatment conditions to form thermal oxidation films, and the correlation between the composition of the chemical oxidation film and the thickness of the thermal oxidation film is obtained; a substrate cleaning step, in which a semiconductor substrate to be formed with a thermal oxidation film is cleaned; a thickness estimation step of the thermal oxidation film, in which the composition of the chemical oxidation film formed on the surface of the semiconductor substrate by the cleaning in the substrate cleaning step is measured, and based on the composition obtained by the measurement and the correlation, the thickness of the thermal oxidation film formed on the surface of the semiconductor substrate to be formed with the thermal oxidation film is estimated when the semiconductor substrate to be formed with the thermal oxidation film is thermally oxidized under the same conditions as the thermal oxidation treatment conditions in the correlation acquisition step; a thermal oxidation treatment condition determination step, in which, based on the thermal oxidation treatment conditions in the correlation acquisition step, the thermal oxidation treatment conditions are determined such that the thickness of the thermal oxidation film formed on the surface of the semiconductor substrate is a specified thickness; and a thermal oxidation film formation step, in which thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination step, thereby forming a thermal oxidation film on the surface of the semiconductor substrate.

[0019] For such a method for forming a thermal oxidation film on a semiconductor substrate, the thermal oxidation film can be formed into a thin thickness as expected with good reproducibility. As a result, the management of the thermal oxidation process becomes simple.

[0020] In addition, the present invention provides a method for forming a thermal oxide film on a semiconductor substrate. The method for forming a thermal oxide film on a semiconductor substrate includes the following steps: a correlation acquisition step, in which a plurality of semiconductor substrates are prepared in advance. The plurality of semiconductor substrates have chemical oxide films formed by cleaning, and the amounts of OH groups contained in the chemical oxide films are different. The plurality of semiconductor substrates are subjected to thermal oxidation treatment under the same thermal oxidation treatment conditions to form thermal oxide films, and the correlation between the amount of OH groups in the chemical oxide films and the thickness of the thermal oxide films is obtained; a substrate cleaning step, in which a semiconductor substrate to be formed with a thermal oxide film is cleaned; a thickness estimation step of the thermal oxide film, in which the amount of OH groups in the chemical oxide film formed on the surface of the semiconductor substrate by the cleaning in the substrate cleaning step is measured, and based on the amount of OH groups obtained by the measurement and the correlation, the thickness of the thermal oxide film formed on the surface of the semiconductor substrate to be formed with the thermal oxide film is estimated assuming that the semiconductor substrate to be formed with the thermal oxide film is subjected to thermal oxidation treatment under the same conditions as the thermal oxidation treatment conditions in the correlation acquisition step; a thermal oxidation treatment condition determination step, in which, based on the thermal oxidation treatment conditions in the correlation acquisition step, the thermal oxidation treatment conditions are determined such that the thickness of the thermal oxide film formed on the surface of the semiconductor substrate is a specified thickness; and a thermal oxide film formation step, in which thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination step to form a thermal oxide film on the surface of the semiconductor substrate.

[0021] For such a method for forming a thermal oxide film on a semiconductor substrate, a thermal oxide film with a certain thickness can be formed with good reproducibility regardless of the chemical oxide film formed by cleaning. As a result, the management of the thermal oxidation process becomes simple.

[0022] At this time, the amount of the OH groups is preferably calculated based on the absorbance of the OH groups near 3300 cm -1 by performing ATR-FT-IR measurement on the chemical oxide film using an ATR measurement prism.

[0023] Compared with conventional transmission FT-IR, ATR-FT-IR has higher sensitivity to OH groups present on the surface, so that a higher-precision evaluation of the amount of OH groups can be performed.

[0024] In addition, the present invention provides a method for forming a thermal oxide film on a semiconductor substrate. The method for forming a thermal oxide film on a semiconductor substrate includes the following steps: a correlation acquisition step, in which a plurality of semiconductor substrates are prepared in advance. The plurality of semiconductor substrates have chemical oxide films formed by cleaning, and the stoichiometric ratios of the constituent elements of the chemical oxide films are different. The plurality of semiconductor substrates are subjected to thermal oxidation treatment under the same thermal oxidation treatment conditions to form thermal oxide films, and the correlation between the stoichiometric ratio of the constituent elements of the chemical oxide film and the thickness of the thermal oxide film is obtained; a substrate cleaning step, in which the semiconductor substrate to be formed with a thermal oxide film is cleaned; a thickness estimation step of the thermal oxide film, in which the stoichiometric ratio of the constituent elements of the chemical oxide film formed on the surface of the semiconductor substrate by the cleaning in the substrate cleaning step is obtained, and based on the obtained stoichiometric ratio of the constituent elements of the chemical oxide film and the correlation, the thickness of the thermal oxide film formed on the surface of the semiconductor substrate to be formed with the thermal oxide film is estimated when the semiconductor substrate to be formed with the thermal oxide film is subjected to thermal oxidation treatment under the same conditions as the thermal oxidation treatment conditions in the correlation acquisition step; a thermal oxidation treatment condition determination step, in which, based on the thermal oxidation treatment conditions in the correlation acquisition step, the thermal oxidation treatment conditions are determined such that the thickness of the thermal oxide film formed on the surface of the semiconductor substrate is a specified thickness; and a thermal oxide film forming step, in which thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination step to form a thermal oxide film on the surface of the semiconductor substrate.

[0025] For such a method for forming a thermal oxide film on a semiconductor substrate, a thermal oxide film can be formed with good reproducibility to a thin thickness as expected.

[0026] At this time, XPS is used to measure respectively the peak intensities of the bond energies of the states in which the substrate atoms of the semiconductor substrate among the constituent elements of the chemical oxide film are not bonded to oxygen atoms, the states in which the substrate atoms are bonded to oxygen atoms to form low-value oxides, and the peak intensities of the bond energies of the states in which the substrate atoms are completely bonded to oxygen atoms. The stoichiometric ratio of the constituent elements of the chemical oxide film is the ratio of the measured peak intensities.

[0027] The XPS method is a method that can simply and highly accurately evaluate the information on the outermost layer of a semiconductor substrate. Thus, a thermal oxide film can be formed with better reproducibility to a thin thickness as expected.

[0028] In addition, the present invention provides a method for forming a thermal oxide film on a semiconductor substrate. The method for forming a thermal oxide film on a semiconductor substrate includes the following steps: a correlation acquisition step, in which a plurality of semiconductor substrates are prepared in advance. The plurality of semiconductor substrates have chemical oxide films formed by cleaning, and the amounts of hydrogen atoms contained in the chemical oxide films are different. The plurality of semiconductor substrates are subjected to thermal oxidation treatment under the same thermal oxidation treatment conditions to form thermal oxide films, and the correlation between the amount of hydrogen atoms in the chemical oxide film and the thickness of the thermal oxide film is obtained; a substrate cleaning step, in which a semiconductor substrate to be formed with a thermal oxide film is cleaned; a thickness estimation step of the thermal oxide film, in which the amount of hydrogen atoms in the chemical oxide film formed on the surface of the semiconductor substrate by the cleaning in the substrate cleaning step is measured, and based on the amount of hydrogen atoms obtained by the measurement and the correlation, the thickness of the thermal oxide film formed on the surface of the semiconductor substrate to be formed with the thermal oxide film is estimated when the semiconductor substrate to be formed with the thermal oxide film is subjected to thermal oxidation treatment under the same conditions as the thermal oxidation treatment conditions in the correlation acquisition step; a thermal oxidation treatment condition determination step, in which, based on the thermal oxidation treatment conditions in the correlation acquisition step, the thermal oxidation treatment conditions are determined such that the thickness of the thermal oxide film formed on the surface of the semiconductor substrate is a specified thickness; and a thermal oxide film formation step, in which thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination step to form a thermal oxide film on the surface of the semiconductor substrate.

[0029] If it is such a method for forming a thermal oxide film on a semiconductor substrate, the thermal oxide film can be formed with a desired thin thickness with good reproducibility. As a result, the management of the thermal oxidation process becomes simple.

[0030] At this time, the semiconductor substrate is a silicon wafer, and the thermal oxide film is a silicon oxide film.

[0031] The method for forming a thermal oxide film on a semiconductor substrate of the present invention is particularly suitable for forming a silicon oxide film on a silicon wafer.

[0032] At this time, the amount of hydrogen atoms can be calculated by performing RBS measurement on the chemical oxide film and based on the ratio of hydrogen atoms in the chemical oxide film obtained.

[0033] If it is such a measurement method, a higher-precision evaluation of the amount of hydrogen atoms can be performed.

[0034] At this time, the amount of hydrogen atoms can be measured by performing ATR-FT-IR measurement on the chemical oxide film using an ATR measurement prism and based on 2130 cm -1It is calculated from the absorbance of the SiH3 groups in the vicinity.

[0035] Compared with conventional transmission FT-IR, ATR-FT-IR is more sensitive to hydrogen atoms present in the chemical oxide film, so that a higher-precision evaluation of the amount of hydrogen atoms can be performed.

[0036] At this time, the specified thickness is 1 to 10 nm.

[0037] If the thickness of the thermally oxidized film formed is within this range, a thin thermally oxidized film with a certain thickness can be formed with better reproducibility.

[0038] At this time, in the thickness estimation step of the thermally oxidized film, when the estimated thickness of the thermally oxidized film is thicker than the specified thickness, in the thermally oxidized treatment condition determination step, the thermally oxidized treatment time can be determined to be shorter than the thermally oxidized treatment time of the thermally oxidized treatment condition in the correlation acquisition step; when the estimated thickness of the thermally oxidized film is thinner than the specified thickness, in the thermally oxidized treatment condition determination step, the thermally oxidized treatment time can be determined to be longer than the thermally oxidized treatment time of the thermally oxidized treatment condition in the correlation acquisition step; when the estimated thickness of the thermally oxidized film is equal to the specified thickness, in the thermally oxidized treatment condition determination step, the thermally oxidized treatment time can be determined to be the same as the thermally oxidized treatment time of the thermally oxidized treatment condition in the correlation acquisition step.

[0039] In addition, in the thickness estimation step of the thermally oxidized film, when the estimated thickness of the thermally oxidized film is thicker than the specified thickness, in the thermally oxidized treatment condition determination step, the thermally oxidized treatment temperature can be determined to be lower than the thermally oxidized treatment temperature of the thermally oxidized treatment condition in the correlation acquisition step; when the estimated thickness of the thermally oxidized film is thinner than the specified thickness, in the thermally oxidized treatment condition determination step, the thermally oxidized treatment temperature can be determined to be higher than the thermally oxidized treatment temperature of the thermally oxidized treatment condition in the correlation acquisition step; when the estimated thickness of the thermally oxidized film is equal to the specified thickness, in the thermally oxidized treatment condition determination step, the thermally oxidized treatment temperature can be determined to be the same as the thermally oxidized treatment temperature of the thermally oxidized treatment condition in the correlation acquisition step.

[0040] Thereby, even if the surface states formed by cleaning are different, a thermally oxidized film with a certain thickness can be formed more simply and stably.

[0041] Advantages of the Invention

[0042] As described above, in the method for forming a thermal oxide film on a semiconductor substrate of the present invention, even for semiconductor substrates having different chemical oxide films, a thermal oxide film can be formed with good reproducibility to a desired thin thickness. As a result, the management of the thermal oxidation process becomes simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a graph showing the relationship between the amount of OH groups (relative absorbance at 3300 cm -1 ) and the thickness of the thermal oxide film.

[0044] Figure 2 It is a graph showing the relationship between the concentration of NH4OH and the amount of OH groups (relative absorbance at 3300 cm -1 ).

[0045] Figure 3 It is a graph showing the relationship between the concentration of O3 and the amount of OH groups (relative absorbance at 3300 cm -1 ).

[0046] Figure 4 It is a graph showing the relationship between the concentration of NH4OH and the surface roughness measured by AFM.

[0047] Figure 5 It is a graph showing the relationship between the concentration of O3 and the surface roughness measured by AFM.

[0048] Figure 6 It is a graph showing the relationship between the concentration of NH4OH and the thickness of the thermal oxide film.

[0049] Figure 7 It is a graph showing the relationship between the concentration of O3 and the thickness of the thermal oxide film.

[0050] Figure 8 It is a graph showing the relationship between the thickness of the chemical oxide film and the thickness of the thermal oxide film.

[0051] Figure 9 It is a graph showing the relationship between the surface roughness measured by AFM and the thickness of the thermal oxide film.

[0052] Figure 10 It is a graph showing the relationship between the ratio of the peak intensity of Si 0～3+ and the thickness of the thermal oxide film.

[0053] Figure 11 It is a graph showing the relationship between the ratio of the peak intensity of Si 4+ and the thickness of the thermal oxide film.

[0054] Figure 12 It is a graph showing an example of X-ray photoelectron spectroscopy (XPS) measurement.

[0055] Figure 13 A diagram showing an example of the XPS energy spectrum of a sample having a silicon oxide film on a silicon substrate.

[0056] Figure 14 A diagram showing the relationship between the concentration of NH4OH and the ratio of the peak intensity of Si 0～3+ .

[0057] Figure 15 A diagram showing the relationship between the concentration of NH4OH and the ratio of the peak intensity of Si 4+ .

[0058] Figure 16 A diagram showing the relationship between the concentration of O3 and the ratio of the peak intensity of Si 0～3+ .

[0059] Figure 17 A diagram showing the relationship between the concentration of O3 and the ratio of the peak intensity of Si 4+ .

[0060] Figure 18 A diagram showing the relationship between the amount of hydrogen atoms (the ratio of hydrogen atoms in the chemical oxide film) determined by RBS measurement and the thickness of the thermal oxide film.

[0061] Figure 19 A diagram showing the relationship between the amount of hydrogen atoms (the absorbance at 2130 cm -1 ) determined by ATR-FT-IR measurement and the thickness of the thermal oxide film.

[0062] Figure 20 A diagram showing the relationship between the concentration of NH4OH and the amount of hydrogen atoms (the ratio of hydrogen atoms in the chemical oxide film: RBS measurement).

[0063] Figure 21 A diagram showing the relationship between the concentration of NH4OH and the amount of hydrogen atoms (the absorbance at 2130 cm -1 : ATR-FT-IR measurement). Detailed Description of the Invention

[0064] The present invention will be described in detail below, but the present invention is not limited thereto.

[0065] As described above, there is a need for a method for forming a thermal oxide film on a semiconductor substrate that can reproducibly form a thermal oxide film with a desired thin thickness even on a semiconductor substrate having a chemical oxide film with a different composition.

[0066] The inventors of the present application have conducted in-depth research on the above technical problems and found that a thermal oxidation film of a semiconductor substrate can be formed with a thickness as thin as expected with good reproducibility by the following method for forming a thermal oxidation film of a semiconductor substrate. As a result, the management of the thermal oxidation process has become simple, and the present invention has been completed. The method for forming a thermal oxidation film of a semiconductor substrate is a method for forming a thermal oxidation film on a semiconductor substrate, and the method has the following steps: a correlation acquisition step, in which a plurality of semiconductor substrates are prepared in advance, the plurality of semiconductor substrates having chemical oxidation films formed by cleaning and the compositions of the chemical oxidation films being different, and the plurality of semiconductor substrates are subjected to thermal oxidation treatment under the same thermal oxidation treatment conditions to form thermal oxidation films, and the correlation between the composition of the chemical oxidation film and the thickness of the thermal oxidation film is obtained; a substrate cleaning step, in which a semiconductor substrate to be formed with a thermal oxidation film is cleaned; a thickness estimation step of the thermal oxidation film, in which the composition of the chemical oxidation film formed on the surface of the semiconductor substrate by the cleaning in the substrate cleaning step is measured, and based on the composition obtained by the measurement and the correlation, the thickness of the thermal oxidation film formed on the surface of the semiconductor substrate to be formed with the thermal oxidation film is estimated assuming that the semiconductor substrate to be formed with the thermal oxidation film is subjected to thermal oxidation treatment under the same conditions as the thermal oxidation treatment conditions in the correlation acquisition step; a thermal oxidation treatment condition determination step, in which, based on the thermal oxidation treatment conditions in the correlation acquisition step, the thermal oxidation treatment conditions are determined such that the thickness of the thermal oxidation film formed on the surface of the semiconductor substrate is a specified thickness; and a thermal oxidation film formation step, in which thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination step to form a thermal oxidation film on the surface of the semiconductor substrate.

[0067] In addition, the inventors of the present application have also found that by the following method for forming a thermal oxide film on a semiconductor substrate, a thermal oxide film with a certain thickness can be formed with good reproducibility regardless of the chemical oxide film formed by cleaning. As a result, the management of the thermal oxidation process becomes simple, and thus the present invention has been completed. The method for forming a thermal oxide film on a semiconductor substrate is a method for forming a thermal oxide film on a semiconductor substrate, and the method has the following steps: a correlation acquisition step, in which a plurality of semiconductor substrates are prepared in advance, the plurality of semiconductor substrates have chemical oxide films formed by cleaning and the amounts of OH groups contained in the chemical oxide films are different, the plurality of semiconductor substrates are subjected to thermal oxidation treatment under the same thermal oxidation treatment conditions to form thermal oxide films, and the correlation between the amount of OH groups in the chemical oxide film and the thickness of the thermal oxide film is obtained; a substrate cleaning step, in which a semiconductor substrate to be formed with a thermal oxide film is cleaned; a thickness estimation step of the thermal oxide film, in which the amount of OH groups in the chemical oxide film formed on the surface of the semiconductor substrate by the cleaning in the substrate cleaning step is measured, and based on the amount of OH groups obtained by the measurement and the correlation, the thickness of the thermal oxide film formed on the surface of the semiconductor substrate to be formed with the thermal oxide film is estimated assuming that the semiconductor substrate to be formed with the thermal oxide film is subjected to thermal oxidation treatment under the same conditions as those in the thermal oxidation treatment in the correlation acquisition step; a thermal oxidation treatment condition determination step, in which, based on the thermal oxidation treatment conditions in the correlation acquisition step, the thermal oxidation treatment conditions are determined such that the thickness of the thermal oxide film formed on the surface of the semiconductor substrate is a specified thickness; and a thermal oxide film formation step, in which thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination step to form a thermal oxide film on the surface of the semiconductor substrate.

[0068] In addition, the inventors of the present application have also found that a thermal oxidation film of a semiconductor substrate can be reproducibly formed to a thin thickness as expected by the following method for forming a thermal oxidation film of a semiconductor substrate. As a result, the management of the thermal oxidation process has become simple, and thus the present invention has been completed. The method for forming a thermal oxidation film of a semiconductor substrate is a method for forming a thermal oxidation film on a semiconductor substrate, and the method includes the following steps: a correlation acquisition step, in which a plurality of semiconductor substrates are prepared in advance, the plurality of semiconductor substrates having a chemical oxidation film formed by cleaning and the stoichiometric ratios of the constituent elements of the chemical oxidation film being different from each other, the plurality of semiconductor substrates are subjected to a thermal oxidation treatment under the same thermal oxidation treatment conditions to form a thermal oxidation film, and the correlation between the stoichiometric ratio of the constituent elements of the chemical oxidation film and the thickness of the thermal oxidation film is obtained; a substrate cleaning step, in which a semiconductor substrate to be formed with a thermal oxidation film is cleaned; a thickness estimation step of the thermal oxidation film, in which the stoichiometric ratio of the constituent elements of the chemical oxidation film formed on the surface of the semiconductor substrate by the cleaning in the substrate cleaning step is obtained, and based on the obtained stoichiometric ratio of the constituent elements of the chemical oxidation film and the correlation, the thickness of the thermal oxidation film formed on the surface of the semiconductor substrate to be formed with the thermal oxidation film is estimated when the semiconductor substrate to be formed with the thermal oxidation film is subjected to a thermal oxidation treatment under the same conditions as the thermal oxidation treatment conditions in the correlation acquisition step; a thermal oxidation treatment condition determination step, in which, based on the thermal oxidation treatment conditions in the correlation acquisition step, the thermal oxidation treatment conditions are determined such that the thickness of the thermal oxidation film formed on the surface of the semiconductor substrate is a specified thickness; and a thermal oxidation film formation step, in which a thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination step to form a thermal oxidation film on the surface of the semiconductor substrate.

[0069] In addition, the inventors of the present application have also found that a thermal oxide film of a semiconductor substrate can be formed with a thickness as thin as expected with good reproducibility by the following method for forming a thermal oxide film of a semiconductor substrate. As a result, the management of the thermal oxidation process has become simple, and thus the present invention has been completed. The method for forming a thermal oxide film of a semiconductor substrate is a method for forming a thermal oxide film on a semiconductor substrate, and the method has the following steps: a correlation acquisition step, in which a plurality of semiconductor substrates are prepared in advance, the plurality of semiconductor substrates having chemical oxide films formed by cleaning and the amounts of hydrogen atoms contained in the chemical oxide films being different from each other, subjecting the plurality of semiconductor substrates to thermal oxidation treatment under the same thermal oxidation treatment conditions to form thermal oxide films, and obtaining the correlation between the amount of hydrogen atoms in the chemical oxide film and the thickness of the thermal oxide film; a substrate cleaning step, in which a semiconductor substrate to be formed with a thermal oxide film is cleaned; a thickness estimation step of the thermal oxide film, in which the amount of hydrogen atoms in the chemical oxide film formed on the surface of the semiconductor substrate by the cleaning in the substrate cleaning step is measured, and based on the amount of hydrogen atoms obtained by the measurement and the correlation, the thickness of the thermal oxide film formed on the surface of the semiconductor substrate to be formed with the thermal oxide film is estimated assuming that the semiconductor substrate to be formed with the thermal oxide film is subjected to thermal oxidation treatment under the same conditions as the thermal oxidation treatment conditions in the correlation acquisition step; a thermal oxidation treatment condition determination step, in which, based on the thermal oxidation treatment conditions in the correlation acquisition step, the thermal oxidation treatment conditions are determined such that the thickness of the thermal oxide film formed on the surface of the semiconductor substrate is a specified thickness; and a thermal oxide film formation step, in which thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination step to form a thermal oxide film on the surface of the semiconductor substrate.

[0070] Hereinafter, description will be made with reference to the drawings.

[0071] The inventors of the present application have conducted in-depth investigations on the fact that if the cleaning method of the semiconductor substrate is different, there will be a difference in the thickness of the formed thermal oxide film, and as a result, it has been found that the composition of the chemical oxide film formed by cleaning the semiconductor substrate has a great influence on the thermal oxidation treatment. And by considering such a phenomenon and adjusting the oxidation conditions, a thermal oxidation method capable of forming a thin thermal oxide film with a specified thickness with good reproducibility has been completed.

[0072] For example, when the semiconductor substrate is a silicon wafer, the chemical oxide film is a silicon oxide film, which can be expressed as SiO x (0 < x ≤ 2). Various analysis results show that the elements related to the composition of the chemical oxide film are silicon, oxygen, and hydrogen. Among them, SiO in the chemical oxide film xThe x is referred to as the oxygen ratio. The oxidation characteristics of the formed thermal oxide film are affected by the oxygen ratio (x) of the chemical oxide film and the silicon interface, and the formation rate of the thermal oxide film changes. The variation of the oxygen ratio means that elements other than oxygen exist in different ratios.

[0073] Hydrogen exists in the form of Si-H or Si-OH. That is, if these H increase, the existing ratio of oxygen is affected and decreases. Compared with other constituent elements such as oxygen or silicon, the ratio of H is small, but it affects the bonding state of silicon by capping silicon in the form of Si-H or existing in the back bond of silicon. In addition, existing in the form of a functional group such as an OH group plays an important role in determining reactivity.

[0074] In addition, silicon and oxygen, which are the main constituent elements, are called low-value oxides because of their different bonding ratios with SiO 2 The low-value oxide has the role of a precursor of the silicon oxide film and is an important constituent for determining the characteristics of the formed thermal oxide film. Thus, by focusing on the oxygen ratio of the chemical oxide film and obtaining the correlation between the composition of the chemical oxide film and the thickness of the thermal oxide film, the thickness of the thermal oxide film can be controlled.

[0075] In the present invention, the semiconductor substrate prepared to obtain the correlation only needs to have a different composition of the chemical oxide film, but this composition includes the amount of OH groups, the stoichiometric ratio of constituent elements, and the amount of hydrogen atoms.

[0076] In addition, in this specification, the oxide film formed by cleaning the semiconductor substrate is defined as the chemical oxide film. Among them, the cleaning method and conditions are not particularly limited. It includes oxide films formed by cleaning with a chemical solution or pure water cleaning, etc.

[0077] The method for forming a thermal oxide film on the semiconductor substrate of the present invention will be described.

[0078] [First Embodiment]

[0079] In the method for forming a thermal oxide film on the semiconductor substrate of the first embodiment of the present invention, before the thermal oxidation treatment of the semiconductor substrate, the composition of the chemical oxide film formed on the surface of the semiconductor substrate after cleaning is measured, and the correlation between the composition of the chemical oxide film and the thickness of the thermal oxide film when the semiconductor substrate is thermally oxidized is obtained in advance, and the thermal oxidation conditions such as the oxidation time are adjusted according to the composition of the chemical oxide film on the surface of the semiconductor substrate to be thermally oxidized after cleaning. Thus, a thin thermal oxide film with a specified thickness can be formed with good reproducibility.

[0080] The method for forming a thermal oxide film on the semiconductor substrate of the first embodiment of the present invention will be described.

[0081] (Relevant relationship acquisition process)

[0082] First, prepare a plurality of semiconductor substrates. As the semiconductor substrate, a silicon wafer is preferably used. At this time, the thermally oxidized film formed is a silicon oxide film. Silicon wafers are widely used as semiconductor substrates. In particular, since a thermally oxidized film is formed in the device manufacturing process, more accurate evaluation can be performed by forming the thermally oxidized film and evaluating the silicon wafer itself.

[0083] First, in order to make the surface of the prepared semiconductor substrate in a state without an oxide film, it is preferable to perform cleaning using HF (hydrofluoric acid). After removing the oxide film by cleaning with HF, further cleaning is performed. The cleaning method performed after HF cleaning is not particularly limited. For example, cleaning using a chemical solution such as SC1 cleaning or O3 cleaning can be performed, or cleaning such as pure water rinsing can also be performed. By the cleaning performed after HF cleaning, a chemical oxide film can be formed on the plurality of prepared semiconductor substrates. At this time, the compositions of the chemical oxide films of the plurality of semiconductor substrates are made different. When performing cleaning by a method using a chemical solution, if cleaning conditions or the like are changed, semiconductor substrates with different chemical oxide film compositions can be made, so it is preferable. It is preferable to perform the cleaning process for obtaining the relevant relationship with as many different cleaning types and / or cleaning conditions as possible.

[0084] Next, measure the composition of the chemical oxide film formed by the cleaning. At this time, there is no particular limitation as long as the difference in the composition of the chemical oxide film can be clearly measured.

[0085] Next, perform a thermal oxidation process on a plurality of semiconductor substrates with different chemical oxide film compositions under the same thermal oxidation treatment conditions to form a thermally oxidized film. The formation conditions of the thermally oxidized film are not particularly limited and can be performed by a usual method. Then, measure the thickness of the formed thermally oxidized film. For example, it can be measured by ellipsometry or the like.

[0086] Find the relevant relationship between the composition of the chemical oxide film thus obtained and the thickness of the formed thermally oxidized film.

[0087] In addition, the measurement of the composition of the chemical oxide film or the measurement of the thickness of the thermally oxidized film can be performed by using a monitor wafer that has undergone the same cleaning process and thermal oxidation process as the semiconductor substrate on which the thermally oxidized film is formed, or by extracting a part of the same processed semiconductor substrate.

[0088] (Substrate cleaning process)

[0089] Next, a semiconductor substrate newly prepared as an object for actually forming a thermal oxide film is cleaned. The cleaning method is not limited, and cleaning according to the purpose such as removing foreign substances, removing metal contaminants, and forming a protective oxide film can be performed.

[0090] (Thermal Oxide Film Thickness Estimation Process)

[0091] First, measure the composition of the chemical oxide film formed on the surface of the semiconductor substrate that is the object of forming the thermal oxide film through the cleaning performed in the substrate cleaning process. Before performing the thermal oxidation treatment, measurements of test pieces, etc. are performed in advance to obtain the composition of the chemical oxide film. Based on the composition of the chemical oxide film and the correlation obtained in the correlation acquisition process, estimate the thickness of the thermal oxide film formed on the surface of the semiconductor substrate that is the object of forming the thermal oxide film when the thermal oxidation treatment is performed on the semiconductor substrate that is the object of forming the thermal oxide film under the same conditions as the thermal oxidation treatment conditions in the correlation acquisition process.

[0092] (Thermal Oxidation Treatment Condition Determination Process)

[0093] Based on the thermal oxidation treatment conditions in the correlation acquisition process, determine the thermal oxidation treatment conditions such that the thickness of the thermal oxide film formed on the surface of the semiconductor substrate is a specified thickness. For example, when it can be estimated that if the treatment is performed under the same conditions as the thermal oxidation treatment conditions in the correlation acquisition process, the film will be formed too thick, determine the actual thermal oxidation treatment conditions by changing the conditions in the direction of thinning the thickness of the formed thermal oxide film from the thermal oxidation treatment conditions in the correlation acquisition process.

[0094] As a method for adjusting the thickness of the thermal oxide film formed on the surface of the semiconductor substrate to a specified thickness, for example, it can be adjusted by the oxidation time. In this case, a calculation formula in which the thickness of the oxide film is proportional to the square root of the oxidation time can be used.

[0095] Specifically, in the thermal oxide film thickness estimation process, when the estimated thickness of the thermal oxide film is thicker than the specified thickness, in the thermal oxidation treatment condition determination process, the thermal oxidation treatment time can be determined to be shorter than the thermal oxidation treatment time of the thermal oxidation treatment conditions in the correlation acquisition process.

[0096] In addition, when the estimated thickness of the thermal oxide film is thinner than the specified thickness, in the thermal oxidation treatment condition determination process, the thermal oxidation treatment time can be determined to be longer than the thermal oxidation treatment time of the thermal oxidation treatment conditions in the correlation acquisition process.

[0097] In addition, when the thickness of the thermally oxidized film estimated is equal to the specified thickness, in the process of determining the thermal oxidation treatment conditions, the thermal oxidation treatment time can be determined to be the same as the thermal oxidation treatment time of the thermal oxidation treatment conditions in the process of obtaining the correlation.

[0098] Alternatively, as a method of adjusting the thickness of the thermally oxidized film formed on the surface of the semiconductor substrate to the specified thickness, for example, it can be adjusted by the oxidation temperature. In this case, the relationship between the oxidation temperature and the thickness of the oxidized film can be obtained in advance and utilized.

[0099] Specifically, in the process of estimating the thickness of the thermally oxidized film, when the thickness of the thermally oxidized film estimated is thicker than the specified thickness, in the process of determining the thermal oxidation treatment conditions, the thermal oxidation treatment temperature can be determined to be lower than the thermal oxidation treatment temperature of the thermal oxidation treatment conditions in the process of obtaining the correlation.

[0100] In addition, when the thickness of the thermally oxidized film estimated is thinner than the specified thickness, in the process of determining the thermal oxidation treatment conditions, the thermal oxidation treatment temperature can be determined to be higher than the thermal oxidation treatment temperature of the thermal oxidation treatment conditions in the process of obtaining the correlation.

[0101] In addition, when the thickness of the thermally oxidized film estimated is equal to the specified thickness, in the process of determining the thermal oxidation treatment conditions, the thermal oxidation treatment temperature can be determined to be the same as the thermal oxidation treatment temperature of the thermal oxidation treatment conditions in the process of obtaining the correlation.

[0102] Alternatively, as a method of adjusting the thickness of the thermally oxidized film formed on the surface of the semiconductor substrate to the specified thickness, the thickness of the thermally oxidized film can be further controlled to the specified thickness by adjusting the components contributing to the oxidation of the semiconductor substrate, such as the oxygen content concentration in the thermal oxidation treatment atmosphere.

[0103] Specifically, in the process of estimating the thickness of the thermally oxidized film, when the thickness of the thermally oxidized film estimated is thicker than the specified thickness, in the process of determining the thermal oxidation treatment conditions, the oxygen content concentration in the thermal oxidation treatment atmosphere can be determined to be lower than the oxygen content concentration in the thermal oxidation treatment atmosphere of the thermal oxidation treatment conditions in the process of obtaining the correlation.

[0104] In addition, when the thickness of the thermally oxidized film estimated is thinner than the specified thickness, in the process of determining the thermal oxidation treatment conditions, the oxygen content concentration in the thermal oxidation treatment atmosphere can be determined to be higher than the oxygen content concentration in the thermal oxidation treatment atmosphere of the thermal oxidation treatment conditions in the process of obtaining the correlation.

[0105] In addition, when the thickness of the thermally oxidized film estimated is equal to the specified thickness, in the process of determining the thermal oxidation treatment conditions, the oxygen concentration in the thermal oxidation treatment atmosphere can be determined to be the same as the oxygen concentration in the thermal oxidation treatment atmosphere of the thermal oxidation treatment conditions in the correlation obtaining process.

[0106] The method for forming the thermally oxidized film is not limited to the above method and can be freely determined, but if it is the above method, it is preferred because it is easy to adjust the thickness of the thermally oxidized film.

[0107] (Thermal Oxide Film Formation Process)

[0108] Perform thermal oxidation treatment under the thermal oxidation treatment conditions determined in the process of determining the thermal oxidation treatment conditions, thereby forming a thermally oxidized film on the surface of the semiconductor substrate.

[0109] [Second Embodiment]

[0110] In the method for forming a thermally oxidized film on a semiconductor substrate according to the second embodiment of the present invention, focusing on the difference in the amount of OH groups contained in the chemical oxide film, before the thermal oxidation treatment of the semiconductor substrate, the correlation between the amount of OH groups in the chemical oxide film formed on the surface of the semiconductor substrate after cleaning and the thickness of the thermally oxidized film when the semiconductor substrate is thermally oxidized is obtained in advance, and the thermal oxidation treatment conditions such as the oxidation time are adjusted according to the amount of OH groups. Thus, an oxide film with a specified thickness can be formed with good reproducibility.

[0111] The inventors of the present application have deeply investigated that if the cleaning method of the semiconductor substrate is different, there will be a difference in the thickness of the formed thermally oxidized film, and as a result, it has been found that the amount of OH groups in the chemical oxide film formed by cleaning the semiconductor substrate has a great influence on the thermal oxidation treatment.

[0112] Figure 1 It is a graph showing the relationship between the amount of OH groups (relative absorbance at 3300 cm -1 ) in the chemical oxide film on the surface of the silicon wafer and the thickness of the silicon thermally oxidized film. It can be seen that as the relative absorbance at 3300 cm -1 becomes larger, the thickness of the thermally oxidized film becomes thicker. This phenomenon is the same as the phenomenon that the oxidation rate of Wet oxidation is greater than that of Dry oxidation when using gas thermal oxidation, and it can be considered that the thickness of the thermally oxidized film after the thermal oxidation treatment is different due to the difference in the amount of OH groups contained in the chemical oxide film formed on the surface of the silicon wafer.

[0113] In addition, the amount of OH groups contained in the chemical oxide film can be obtained by, for example, examining the infrared absorption characteristics of the chemical oxide film. As the measurement of the infrared absorption characteristics, for example, FT-IR measurement can be performed, and the amount of OH groups is calculated from the relative absorbance near 3300 cm -1 . At this time, 3300 cm-1 The relative absorbance value in the vicinity is used as an index indicating the amount of OH groups. In the following description, the "relative absorbance near 3300 cm -1 " may sometimes be expressed as the "amount of OH groups".

[0114] The method for forming a thermal oxide film on a semiconductor substrate according to the second embodiment of the present invention will be described.

[0115] (Correlation acquisition process)

[0116] First, prepare multiple semiconductor substrates in the same manner as in the first embodiment.

[0117] Next, in order to make the state where there is no oxide film on the surface of the prepared semiconductor substrate, it is preferable to perform cleaning using HF (hydrofluoric acid). After removing the oxide film by cleaning with HF, further cleaning is performed. The cleaning method performed after HF cleaning is not particularly limited, but for example, cleaning using a chemical solution such as SC1 cleaning or O3 cleaning can be performed, or cleaning such as pure water rinsing can also be performed. By the cleaning performed after HF cleaning, a chemical oxide film can be formed on the prepared multiple semiconductor substrates. At this time, the amount of OH groups contained in the chemical oxide films of the multiple semiconductor substrates is made different. When performing cleaning by a method using a chemical solution, it is preferable because semiconductor substrates with different amounts of OH groups can be easily made by using chemical solutions with different OH group concentrations. Further, in the case of SC1 cleaning, the higher the NH4OH concentration and the stronger the alkalinity, the greater the absorbance at 3300 cm -1 (that is, a large amount of OH groups is contained), and by changing the concentration of NH4OH, semiconductor substrates with different amounts of OH groups can be made more easily, so it is preferable. It is preferable to perform the cleaning process for obtaining the correlation with as many different cleaning types and / or cleaning conditions as possible.

[0118] Next, measure the amount of OH groups contained in the chemical oxide film formed by cleaning. At this time, it is preferable to perform ATR-FT-IR measurement of the chemical oxide film using an ATR measurement prism. Compared with conventional transmission FT-IR, ATR-FT-IR measurement can evaluate the OH groups present on the surface of the semiconductor substrate with sufficient sensitivity.

[0119] Next, perform a thermal oxidation treatment on multiple semiconductor substrates with different amounts of OH groups contained in the chemical oxide film under the same thermal oxidation treatment conditions to form a thermal oxide film. The formation conditions of the thermal oxide film are not particularly limited, and a usual method can be used. Then, measure the thickness of the formed thermal oxide film. For example, it can be measured by ellipsometry or the like.

[0120] Find the correlation between the amount of OH groups in the chemically oxidized film obtained above and the thickness of the thermally oxidized film formed. It can be found that there is a correlation as shown in -1 near the relative absorbance at around Figure 1 3300 cm

[0121] -1 -1 near the relative absorbance), and it can be found that the greater the amount of OH groups in the chemically oxidized film, the thicker the thermally oxidized film tends to be. Even if the surface states formed by cleaning are different, using this result, it is possible to form a thermally oxidized film with a certain thickness by adjusting the thermal oxidation treatment conditions such as the thermal oxidation time corresponding to the amount of each OH group in the chemically oxidized film formed on the surface of the semiconductor substrate.

[0122] (Substrate cleaning process)

[0123] Next, in the same manner as in the first embodiment, a semiconductor substrate that is actually the object of forming the thermally oxidized film is newly prepared and cleaned. The cleaning method is not limited, and cleaning according to the purpose such as removing foreign substances, removing metal contaminants, and forming a protective oxide film can be performed.

[0124] (Thermally oxidized film thickness estimation process)

[0125] First, measure the amount of OH groups (relative absorbance near 3300 cm -1 -1 -1 -1 -1 -1

[0126] Figure 1 Figure 1 near the relative absorbance) in the chemically oxidized film formed on the surface of the semiconductor substrate that is the object of forming the thermally oxidized film through the cleaning performed in the substrate cleaning process. It can be obtained by the following method: Before performing the thermal oxidation treatment, the relative absorbance near 3300 cm-1 A numerical calculation of the relative absorbance is performed. When the OH concentration in the chemical oxide film after cleaning of the semiconductor substrate, which is the object for actually forming the thermal oxide film, is "0.18", it can be presumed that if the semiconductor substrate is processed under the same conditions as the thermal oxidation treatment conditions in the correlation acquisition process, a thermal oxide film of about 5.15 nm can be formed.

[0127] (Thermal oxidation treatment condition determination process)

[0128] In the same manner as in the first embodiment, based on the thermal oxidation treatment conditions in the correlation acquisition process, the thermal oxidation treatment conditions are determined such that the thickness of the thermal oxide film formed on the surface of the semiconductor substrate is a specified thickness. For example, in the above specific example, when the specified thickness of the thermal oxide film to be formed is 5.1 nm, since it can be presumed that if processed under the same conditions as the thermal oxidation treatment conditions in the correlation acquisition process, the film will be formed too thickly, the actual thermal oxidation treatment conditions are determined by changing the conditions in the direction of decreasing the thickness of the thermal oxide film formed from the thermal oxidation treatment conditions in the correlation acquisition process.

[0129] In addition, the method of adjusting the thickness of the thermal oxide film formed on the surface of the semiconductor substrate to the specified thickness is the same as in the first embodiment.

[0130] (Thermal oxide film formation process)

[0131] Finally, in the same manner as in the first embodiment, thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination process, thereby forming a thermal oxide film on the surface of the semiconductor substrate.

[0132] [Third embodiment]

[0133] Furthermore, in the method for forming a thermal oxide film on a semiconductor substrate according to the third embodiment of the present invention, focusing on the difference in the stoichiometric ratio of the constituent elements of the chemical oxide film, before the thermal oxidation treatment of the semiconductor substrate, the stoichiometric ratio of the constituent elements of the chemical oxide film formed on the surface of the semiconductor substrate after cleaning is obtained, and the correlation between the stoichiometric ratio of the constituent elements of the chemical oxide film and the thickness of the thermal oxide film when the semiconductor substrate is thermally oxidized is obtained in advance. The thermal oxidation conditions, starting with the oxidation time, are adjusted according to the stoichiometric ratio of the constituent elements of the chemical oxide film on the surface of the semiconductor substrate, which is the object for forming the thermal oxide film. Thereby, an oxide film of a specified thickness can be formed with good reproducibility.

[0134] The inventors of the present application have conducted in-depth investigations and found that if the cleaning method of the semiconductor substrate is different, there will be differences in the thickness of the thermally oxidized film formed. As a result, it has been found that the stoichiometric ratio of the constituent elements of the chemical oxide film formed by cleaning the semiconductor substrate has a great influence on the thermal oxidation treatment.

[0135] The method for forming a thermally oxidized film on a semiconductor substrate according to the third embodiment of the present invention will be described.

[0136] (Correlation acquisition process)

[0137] First, prepare multiple semiconductor substrates in the same manner as in the first embodiment.

[0138] Next, in order to make the surface of the prepared semiconductor substrate free of an oxide film, it is preferably cleaned with HF (hydrofluoric acid). After removing the oxide film by cleaning with HF, further cleaning is performed. The cleaning method performed after HF cleaning is not particularly limited. For example, cleaning using a chemical solution such as SC1 cleaning or O3 cleaning can be performed, or pure water rinsing or the like can also be performed. By the cleaning performed after HF cleaning, a chemical oxide film can be formed on the prepared multiple semiconductor substrates. At this time, the stoichiometric ratios of the constituent elements of the chemical oxide films of the multiple semiconductor substrates are made different from each other. When cleaning is performed by a method using a chemical solution, semiconductor substrates having different stoichiometric ratios of the constituent elements of the chemical oxide film can be easily prepared by using various types of chemical solutions having different concentrations, and thus it is preferred. It is preferred to perform the cleaning process for obtaining the correlation with as many different cleaning types and / or cleaning conditions as possible. In addition, the range in which the correlation between the chemical solution concentration and the stoichiometric ratio can be obtained varies depending on the cleaning method. Therefore, in order to obtain the correlation, it is preferred to perform cleaning with as many different cleaning types and / or cleaning conditions as possible and to previously obtain the correlation between multiple cleaning conditions and the stoichiometric ratio.

[0139] Next, the stoichiometric ratio of the constituent elements of the chemical oxide film formed by cleaning is obtained.

[0140] In addition, the method for measuring and evaluating the stoichiometric ratio of the constituent elements of the chemical oxide film is not particularly limited, and any method can be used as long as it can measure the stoichiometric ratio of the constituent elements of the chemical oxide film. For example, the XPS method is a method that can easily and highly accurately evaluate the information on the outermost layer of the semiconductor substrate and can be applied to the evaluation of the stoichiometric ratio of the present invention. The XPS can be used to separately measure the peak intensities of the bond energies of the state in which the substrate atoms of the semiconductor substrate in the constituent elements of the chemical oxide film are not bonded to oxygen atoms, the state in which the substrate atoms are bonded to oxygen atoms to form a low-valence oxide, and the peak intensity of the bond energy of the state in which the substrate atoms are completely bonded to oxygen atoms, and set it as the ratio of the measured peak intensities.

[0141] When the semiconductor substrate is a silicon substrate and the formed oxide film is a silicon oxide film, the constituent elements of the chemical oxide film are Si and O. At this time, the stoichiometric ratio can be set as the ratio of the atomic bonding states of Si atoms and O atoms in the chemical oxide film, that is, the part of the Si-Si bonds in the state not bonded to oxygen atoms, the part of the so-called low-value oxides in the Si-O bonds (silicon oxides) in the state bonded to oxygen atoms, and the ratio of the part of the Si-O bonds completely bonded to oxygen atoms to form SiO2. The existence ratio of each bond can be obtained by measuring the peak intensity of the bond energy using XPS.

[0142] As Figure 12 shown in an example, the XPS method is a method of analyzing the elemental composition or chemical bonding state of the surface of a sample by using a detector 2 to detect the photoelectrons (from the outermost electrons) released from the surface of the sample (the surface of the silicon oxide film 3 formed on silicon 4) by irradiating X-rays from an X-ray source 1 and measuring the kinetic energy. The X-ray source for irradiation at this time is not particularly limited, and any device with an arbitrary energy can be used as long as it can measure the stoichiometric ratio of the constituent elements of the target chemical oxide film. Further, the kinetic energy of the released photoelectrons is affected by the electronic state around the atoms such as the valence electrons (valence number) of the atoms and the distance between atoms. By observing the change in energy (chemical shift), the chemical bonding state can be easily identified. The mean free path of the photoelectrons is 2.1 nm for silicon and 3.3 nm for the silicon oxide film, and it can be considered as one of the methods suitable for evaluating the outermost surface of the silicon substrate.

[0143] Figure 13 An example of the XPS energy spectrum of a sample with a thin silicon oxide film on a silicon substrate is shown. The energy range of the sp3 orbit of the outermost electrons of the silicon present is illustrated. The outermost electrons contribute to the reaction, and the inner electrons that do not contribute to the reaction are omitted. The horizontal axis is the bond energy, and the vertical axis is the count of the photoelectrons. The bond energy varies depending on the bonding state of Si and O, so the bonding state or the bonded atoms can be evaluated. In addition, the vertical axis is the count of the photoelectrons, which varies according to the number of each bonding state.

[0144] When the chemical oxide film is a silicon oxide film, it can be divided into the bonding state (Si 0 ) derived from Si-Si bonds of 99 - 100 eV, and the bonding state (Si 1+～4+ ) corresponding to the bonding state of silicon atoms and oxygen atoms of 101 - 105 eV. Among them, the peak of the Si-Si bond of Si 0 is separated into two because of the spin-orbit interaction. In addition, if one oxygen atom is bonded to one silicon atom, it is Si 1+ , and when four oxygen atoms are bonded to one silicon atom to form SiO2 The state is Si 4+ . Among them, there are four bonding states of silicon atoms and oxygen atoms because the oxide film is thin and a stoichiometric composition may not be formed.

[0145] There is also a spin-orbit interaction in the Si-O bond, but it cannot be observed in normal XPS due to energy resolution issues. In addition, Si corresponding to low-value oxides has not been clearly found 1+ to Si 3+ has a low bond energy intensity, but from previous knowledge, it is known that there is energy. The energy spectrum of each peak is separated to obtain the intensity.

[0146] When obtaining the stoichiometric ratio of the constituent elements of the silicon oxide film on the silicon substrate, that is, the ratio of the peak intensities of the bond energies of Si and O, the peak intensity of Si forming the SiO2 composition 4+ is accumulated with the peak intensities of Si that can be oxidized by oxygen 0 to Si 3+ respectively. For Si without a clear peak 1+～3+ , energy spectrum separation is performed. That is, the parts that are likely to be oxidized and are Si components are all added together to set as S i0～3+ , and it is separated from the stoichiometric Si with complete oxidation progress 4+ . The area of the peak intensity obtained as Figure 13 is obtained and set as the ratio of the peak intensities.

[0147] The ratios of the peak intensities of Si 0～3+ obtained as above are all added together, and the ratios (percentages) of Si 4+ to Si 0～3+ and Si 4+ are obtained in the form of the ratio of the peak intensities. The correlation between the ratio of the peak intensities and the thickness of the thermal oxide film is obtained.

[0148] Next, multiple semiconductor substrates with different stoichiometric ratios of the constituent elements of the chemical oxide film are thermally oxidized under the same thermal oxidation treatment conditions to form a thermal oxide film. The formation conditions of the thermal oxide film are not particularly limited and can be carried out by a usual method. Then, the thickness of the formed thermal oxide film is measured. For example, it can be measured by ellipsometry or the like.

[0149] The correlation between the stoichiometric ratio of the constituent elements of the chemical oxide film obtained above and the thickness of the formed thermal oxide film is obtained. Figure 10 is a graph showing the relationship between the ratio of the peak intensity of Si 0～3+ and the thickness of the thermal oxide film, Figure 11 is a graph showing the relationship between the ratio of the peak intensity of Si 4+Graph showing the relationship between the ratio of peak intensities and the thickness of the thermal oxide film. It can be found that there is a correlation as shown in Figure 10 and Figure 11 between the thickness of the thermal oxide film and the stoichiometric ratio of the constituent elements of the chemical oxide film. It can be seen that as the ratio of the peak intensity of Si 0 ～3+ increases, the thickness of the thermal oxide film becomes thicker. In addition, it can be seen that as the ratio of the peak intensity of Si 4+ decreases, the thickness of the thermal oxide film becomes thicker. Even if the surface states formed by cleaning are different, using this result, it is possible to form a thermal oxide film with a certain thickness by adjusting the thermal oxidation treatment conditions such as the thermal oxidation time corresponding to the ratio of the peak intensities of the bonds between Si and O formed on the surface of the semiconductor substrate, that is, the stoichiometric ratio of the constituent elements of the chemical oxide film.

[0150] In addition, the analysis of the stoichiometric ratio of the constituent elements of the chemical oxide film or the measurement of the thickness of the thermal oxide film can be carried out by using control wafers that have undergone the same cleaning treatment and thermal oxidation treatment as the semiconductor substrate on which the thermal oxide film is formed, or by extracting a part of the same processed semiconductor substrate.

[0151] (Substrate cleaning process)

[0152] Next, in the same manner as in the first embodiment, a semiconductor substrate that is actually the object of forming the thermal oxide film is newly prepared and cleaned. The cleaning method is not limited, and cleaning according to the purpose such as removing foreign substances, removing metal contaminants, and forming a protective oxide film can be performed.

[0153] (Thermal oxide film thickness estimation process)

[0154] First, analyze the stoichiometric ratio of the constituent elements of the chemical oxide film formed on the surface of the semiconductor substrate that is the object of forming the thermal oxide film through the cleaning performed in the substrate cleaning process. It can be obtained by the following method: Before performing the thermal oxidation treatment, the bond energies of various bonds between substrate atoms and oxygen atoms of test wafers, etc. are measured in advance in the same manner as in the measurement in the correlation acquisition process, and the stoichiometric ratio of the constituent elements of the chemical oxide film is calculated. Based on the stoichiometric ratio of the constituent elements of the chemical oxide film obtained and the correlation obtained in the correlation acquisition process, the thickness of the thermal oxide film formed on the surface of the semiconductor substrate that is the object of forming the thermal oxide film is estimated assuming that the thermal oxidation treatment is performed on the semiconductor substrate that is the object of forming the thermal oxide film under the same conditions as in the thermal oxidation treatment conditions in the correlation acquisition process.

[0155] Illustrated with a specific example, when obtaining the correlation as shown in Figure 10 the Si after cleaning of the semiconductor substrate that is actually the object of forming the thermal oxide film is obtained0～3+ When the ratio of the peak intensity of bonding, that is, the stoichiometric ratio of the constituent elements of the chemical oxide film, is "81.5%", it can be presumed that if the semiconductor substrate is processed under the same conditions as the thermal oxidation treatment conditions in the correlation acquisition process, a thermal oxide film of about 5.05 nm can be formed.

[0156] (Thermal Oxidation Treatment Condition Determination Process)

[0157] In the same manner as in the first embodiment, based on the thermal oxidation treatment conditions in the correlation acquisition process, the thermal oxidation treatment conditions are determined such that the thickness of the thermal oxide film formed on the surface of the semiconductor substrate is a specified thickness. For example, in the above specific example, when the specified thickness of the thermal oxide film to be formed is 5.10 nm, since it can be presumed that if processed under the same conditions as the thermal oxidation treatment conditions in the correlation acquisition process, it will be formed too thin, the actual thermal oxidation treatment conditions are determined by changing the conditions in the direction of increasing the thickness of the formed thermal oxide film from the thermal oxidation treatment conditions in the correlation acquisition process.

[0158] In addition, the method of adjusting the thickness of the thermal oxide film formed on the surface of the semiconductor substrate to the specified thickness is the same as in the first embodiment.

[0159] (Thermal Oxide Film Formation Process)

[0160] Finally, in the same manner as in the first embodiment, thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination process, thereby forming a thermal oxide film on the surface of the semiconductor substrate.

[0161] [Fourth Embodiment]

[0162] Furthermore, in the method for forming a thermal oxide film on a semiconductor substrate according to the fourth embodiment of the present invention, focusing on the amount of hydrogen atoms contained in the chemical oxide film, before the thermal oxidation treatment of the semiconductor substrate, the amount of hydrogen atoms in the chemical oxide film formed on the surface of the semiconductor substrate after cleaning is measured, and the correlation between the amount of hydrogen atoms and the thickness of the thermal oxide film when the semiconductor substrate is thermally oxidized is obtained in advance. The thermal oxidation conditions such as the oxidation time are adjusted according to the amount of hydrogen atoms in the chemical oxide film on the surface of the semiconductor substrate to be the object of forming the thermal oxide film. Thereby, a thin thermal oxide film with a specified thickness can be formed with good reproducibility.

[0163] The inventors of the present application have deeply investigated that if the cleaning method of the semiconductor substrate is different, there will be a difference in the thickness of the thermally oxidized film formed, and as a result, it has been found that the amount of hydrogen atoms in the chemical oxide film formed by cleaning the semiconductor substrate has a great influence on the thermal oxidation treatment. Further, by considering such a phenomenon and adjusting the oxidation conditions, a thermal oxidation method capable of reproducibly forming a thin thermally oxidized film with a specified thickness has been completed.

[0164] The method for forming a thermally oxidized film on a semiconductor substrate according to the fourth embodiment of the present invention will be described.

[0165] (Correlation acquisition step)

[0166] First, prepare a plurality of semiconductor substrates in the same manner as in the first embodiment.

[0167] Next, in order to make the surface of the prepared semiconductor substrate free of an oxide film, it is preferably cleaned with HF (hydrofluoric acid). After removing the oxide film by cleaning with HF, further cleaning is performed. The cleaning method performed after HF cleaning is not particularly limited, but for example, cleaning using a chemical solution such as SC1 cleaning or O3 cleaning can be performed, or pure water rinsing or the like can also be performed. By the cleaning performed after HF cleaning, a chemical oxide film can be formed on the plurality of prepared semiconductor substrates. At this time, the amount of hydrogen atoms in the chemical oxide films of the plurality of semiconductor substrates is made different. When cleaning is performed by a method using a chemical solution, semiconductor substrates having different amounts of hydrogen atoms in the chemical oxide film can be easily prepared by using various chemical solutions having different concentrations, and thus it is preferred. Further, in the case of SC1 cleaning, the higher the NH4OH concentration and the stronger the alkalinity, the smaller the ratio of hydrogen atoms or the absorbance at 2130 cm -1 becomes (i.e., the amount of hydrogen atoms contained is less), and by changing the NH4OH concentration, semiconductor substrates having different amounts of hydrogen atoms can be more easily prepared, and thus it is preferred. It is preferred to perform the cleaning treatment for obtaining the correlation with as many different cleaning types and / or cleaning conditions as possible. In addition, the range in which the correlation between the chemical solution concentration and the amount of hydrogen atoms can be obtained varies depending on the cleaning method. Therefore, in order to obtain the correlation, it is preferred to perform cleaning with as many different cleaning types and / or cleaning conditions as possible to obtain the correlation between a plurality of cleaning conditions and the amount of hydrogen atoms in advance.

[0168] Next, the amount of hydrogen atoms in the chemical oxide film formed by cleaning is determined.

[0169] In addition, the method for determining the amount of hydrogen atoms in the chemical oxide film and the evaluation method are not particularly limited, and any method can be used as long as it can determine the amount of hydrogen atoms in the chemical oxide film. For example, it can be determined by examining the infrared absorption characteristics of the chemical oxide film. As the measurement of the infrared absorption characteristics, for example, ATR-FT-IR measurement can be performed, and the amount of hydrogen atoms can be calculated based on the absorbance near 2130 cm -1 At this time, the absorbance near 2130 cm -1 is the relative absorbance value corresponding to the stretching vibration of Si-H of SiH3, and it can be used as an index indicating the amount of hydrogen atoms. In addition, as another method for determining the amount of hydrogen atoms, for example, Rutherford backscattering analysis (RBS) can be performed to determine the ratio of hydrogen atoms in the chemical oxide film. At this time, the ratio of hydrogen atoms can be used as an index indicating the amount of hydrogen atoms. Hereinafter, sometimes the "absorbance at 2130 cm -1 " or the "ratio of hydrogen atoms" is referred to as the "amount of hydrogen atoms".

[0170] Next, multiple semiconductor substrates with different amounts of hydrogen atoms in the chemical oxide film are thermally oxidized under the same thermal oxidation treatment conditions to form a thermal oxide film. The formation conditions of the thermal oxide film are not particularly limited, and it can be carried out by a conventional method. Then, the thickness of the formed thermal oxide film is measured. For example, it can be measured by ellipsometry or the like.

[0171] The correlation between the amount of hydrogen atoms in the chemical oxide film obtained above and the thickness of the formed thermal oxide film is obtained. Figure 18 is a graph showing the relationship between the amount of hydrogen atoms (the ratio of hydrogen atoms in the chemical oxide film) obtained by RBS measurement and the thickness of the thermal oxide film, Figure 19 is a graph showing the relationship between the amount of hydrogen atoms (the absorbance at 2130 cm -1 ) obtained by ATR-FT-IR measurement and the thickness of the thermal oxide film. It can be found that there is a correlation as shown in Figure 18 and Figure 19 between the thickness of the thermal oxide film and the amount of hydrogen atoms in the chemical oxide film, and it can be found that the more the amount of hydrogen atoms, the thinner the thickness of the thermal oxide film tends to be. As the main reason for finding such a tendency, it is known that, for example, as shown in Non-Patent Document 1, the silicon surface terminated with hydrogen is stable and loses its activity. Therefore, it is considered that the oxidation rate varies due to the difference in the amount of hydrogen atoms contained in the chemical oxide film formed on the surface by cleaning, and even under the same conditions of thermal oxidation, the film thickness after thermal oxidation will be different. Even if the surface state formed by cleaning is different, using this Figure 18 and Figure 19The result can also form a thin thermal oxide film with a certain thickness by adjusting thermal oxidation treatment conditions such as the thermal oxidation time corresponding to the amount of hydrogen atoms in the chemical oxide film formed on the surface of the semiconductor substrate.

[0172] In addition, the analysis of the amount of hydrogen atoms in the chemical oxide film or the measurement of the thickness of the thermal oxide film can be carried out by using control wafers that have undergone the same cleaning treatment and thermal oxidation treatment as the semiconductor substrate on which the thermal oxide film is formed, or by extracting a part of the same processed semiconductor substrate.

[0173] (Substrate cleaning process)

[0174] Next, in the same manner as in the first embodiment, a semiconductor substrate that is actually the object of forming the thermal oxide film is newly prepared and cleaned. The cleaning method is not limited, and cleaning according to the purpose such as removing foreign substances, removing metal contaminants, and forming a protective oxide film can be performed.

[0175] (Thermal oxide film thickness estimation process)

[0176] First, analyze the amount of hydrogen atoms in the chemical oxide film formed on the surface of the semiconductor substrate that is the object of forming the thermal oxide film through the cleaning performed in the substrate cleaning process. It can be obtained in the following manner: Before performing the thermal oxidation treatment, in the same manner as the measurement in the correlation acquisition process, the absorbance at 2130 cm corresponding to the hydrogen atoms contained in the chemical oxide film of a test piece, etc., or the ratio of hydrogen atoms is measured in advance, and the amount of hydrogen atoms in the chemical oxide film is calculated. Based on the amount of hydrogen atoms in the obtained chemical oxide film and the correlation obtained in the correlation acquisition process, the thickness of the thermal oxide film formed on the surface of the semiconductor substrate that is the object of forming the thermal oxide film is estimated assuming that the thermal oxidation treatment is performed on the semiconductor substrate that is the object of forming the thermal oxide film under the same conditions as those in the correlation acquisition process. -1 Illustrated with a specific example, when obtaining the correlation as shown, when the ratio of hydrogen atoms in the chemical oxide film after cleaning of the semiconductor substrate that is actually the object of forming the thermal oxide film is found to be "10%", it can be estimated that if the semiconductor substrate is processed under the same thermal oxidation treatment conditions as those in the correlation acquisition process, a thermal oxide film of about 5.15 nm can be formed.

[0177] Illustrated with a specific example, when obtaining the correlation as shown Figure 18 When the ratio of hydrogen atoms in the chemical oxide film after cleaning of the semiconductor substrate that is actually the object of forming the thermal oxide film is found to be "10%", it can be estimated that if the semiconductor substrate is processed under the same thermal oxidation treatment conditions as those in the correlation acquisition process, a thermal oxide film of about 5.15 nm can be formed.

[0178] (Thermal oxidation treatment condition determination process)

[0179] In the same manner as in the first embodiment, based on the thermal oxidation treatment conditions in the correlation acquisition process, the thermal oxidation treatment conditions are determined such that the thickness of the thermal oxide film formed on the surface of the semiconductor substrate is a specified thickness. For example, in the above specific example, when the specified thickness of the thermal oxide film to be formed is 5.10 nm, since it can be presumed that if the treatment is performed under the same conditions as the thermal oxidation treatment conditions in the correlation acquisition process, the film will be formed too thick, the actual thermal oxidation treatment conditions are determined by changing the conditions in the direction of thinning the thickness of the formed thermal oxide film from the thermal oxidation treatment conditions in the correlation acquisition process.

[0180] In addition, the method of adjusting the thickness of the thermal oxide film formed on the surface of the semiconductor substrate to the specified thickness is the same as that in the first embodiment.

[0181] (Thermal Oxide Film Formation Process)

[0182] Finally, in the same manner as in the first embodiment, thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination process, thereby forming a thermal oxide film on the surface of the semiconductor substrate.

[0183] By forming a thermal oxide film on the semiconductor substrate through the respective processes of the first to fourth embodiments of the present invention as described above, even for semiconductor substrates having different chemical oxide films, a thin thermal oxide film with a specified thickness can be formed with good reproducibility. In addition, regardless of any type of cleaning, a thin thermal oxide film with a specified thickness can be formed with good reproducibility.

[0184] In addition, in the present invention, when the thickness of the thermal oxide film formed on the surface of the semiconductor substrate is in the range of 1 to 10 nm, more remarkable effects can be obtained, so it is applicable to forming a thermal oxide film in this range.

[0185] Examples

[0186] Hereinafter, the present invention will be specifically described by way of examples, but these examples do not limit the present invention.

[0187] (Experimental Example 1)

[0188] A boron-doped silicon wafer with a diameter of 300 mm and a normal resistivity was prepared, and after initializing the surface of the silicon wafer by cleaning with 0.5% HF, SC1 cleaning was performed at 70 °C. At this time, the NH4OH concentration was changed to 3, 0.3, 0.03, 0.001%. In addition, as another cleaning, O3 cleaning (24 °C) was performed with the O3 concentration oscillated at 3, 20, 40 ppm.

[0189] Then, test pieces were cut out from the silicon wafer in advance for ATR-FT-IR measurement, and the measurement was performed at 3300 cm -1The relative absorbance of NH4OH concentration, O3 concentration and the amount of OH groups in the chemical oxidation film (3300cm -1 The results are shown in Figure 2 、 Figure 3 middle. Figure 2 The concentration of NH4OH and the amount of OH groups (3300 cm -1 The graph shows the relationship between the relative absorbance near the ion source and the ion source. Figure 3 The O3 concentration and the amount of OH groups (3300 cm -1 The relationship between the relative absorbance near Figure 2 As shown in the figure, as the concentration of NH4OH increases, the amount of OH groups (3300cm -1 The relative absorbance near the ) increases, which means that there are a lot of OH groups. On the other hand, Figure 3 As shown, in O 3 In the case of no O 3 Concentration to the amount of OH groups (3300cm -1 The dependence of the relative absorbance near the

[0190] The amount of OH groups (3300cm -1 The reason why the relative absorbance near the cleaning conditions varies depending on the cleaning conditions is that in the case of SC1 cleaning, the higher the NH4OH concentration, the stronger the alkalinity, and the more OH groups are contained, but in the case of O3 cleaning, the chemical solution is almost neutral and the amount of OH groups is small.

[0191] Furthermore, the surface roughness of the cleaned silicon wafer (surface roughness of the chemical oxide film) was measured at 9 points within the surface using AFM (1 μm square). The results showed that there was almost no deviation within the surface and the surface had the same roughness. Figure 4 As shown in the figure, if the NH4OH concentration increases, the surface roughness (Ra) increases, and it can be found that the NH4OH concentration and roughness have a correlation. This is because NH4OH is known to be alkaline, so there is anisotropy in the etching of silicon. By increasing the NH4OH concentration, the etching amount of silicon increases, and the surface orientation dependence is strongly expressed, so the surface roughness increases. On the other hand, Figure 5 As shown, in the case of O3 cleaning, no significant correlation was found as in the case of SC1 cleaning.

[0192] The wafer was thermally oxidized (900°C, 5% oxygen, 60 minutes) so that the thickness of the thermal oxide film was expected to be 5.1 nm, and then the thickness of the thermal oxide film was measured by ellipsometry. Figure 6 、 Figure 7 middle. Figure 6 Graph showing the relationship between the concentration of NH 4 OH and the thickness of the thermal oxide film.Figure 7 It is a graph showing the relationship between the concentration of O3 and the thickness of the thermal oxide film.

[0193] Based on the results of the experiments conducted as described above, the relationship between the characteristic values of the obtained chemical oxide film and the thickness of the thermal oxide film was investigated, and the results are as Figure 8 、 9 shown. No correlation was found between the thickness or surface roughness of the chemical oxide film and the thickness of the thermal oxide film. On the other hand, as Figure 1 shown, a correlation was found between the thickness of the thermal oxide film and the relative absorbance near 3300 cm -1 . Thus, it can be seen that the greater the amount of OH groups, the thicker the thermal oxide film tends to be. It can be known that if the conditions for actually forming the thermal oxide film are determined using the Figure 1 correlation between the thickness of the thermal oxide film and the amount of OH groups (relative absorbance near 3300 cm -1 ), a thermal oxide film with a thickness close to the expected value can be formed.

[0194] (Example 1)

[0195] In this Example 1, on the premise of performing electrical property evaluations such as GOI measurement, the target thickness of the thermal oxide film was set to 5.10 nm, with the goal of making the thicknesses of the thermal oxide films of substrates with different cleaning conditions consistent with this value (5.10 nm). In the above-mentioned electrical property evaluations, it is known that if there is unevenness in the oxide film thickness, it will affect the measurement results. Especially in the range as thin as 1 - 10 nm, if the oxide film is thin, direct tunneling current will be generated, and sometimes GOI measurement cannot be performed. Therefore, adjustment of the film thickness is very important. In addition, in Examples 2 - 8, on the premise of performing electrical property evaluations such as GOI measurement, the goal was also to make the thicknesses of the thermal oxide films of substrates with different cleaning conditions consistent with 5.10 nm.

[0196] In the same manner as in Experimental Example 1 above, the correlation between the amount of OH groups (relative absorbance near 3300 cm -1 ) and the thickness of the thermal oxide film was obtained. First, a plurality of 300 - mm - diameter boron - doped silicon wafers with normal resistivity were prepared. After initializing the surface by cleaning with 0.5% HF, SC1 cleaning (70 °C, NH4OH concentrations: 3, 0.3, 0.03, 0.001%) and O3 cleaning (24 °C, O3 concentrations: 3, 20, 40 ppm) were performed respectively to fabricate wafers with different amounts of OH groups. Then, test pieces were cut from each silicon wafer and ATR - FT - IR measurement was performed. The absorbance at 3300 cm -1The relative absorbance. Then, each wafer under each cleaning condition was subjected to a specified thermal oxidation treatment (900 °C, 5% oxygen, 60 min), the thickness of the thermal oxide film was measured, and the amount of OH groups (relative absorbance around 3300 cm -1 ) and the correlation between the thickness of the thermal oxide film were obtained. At this time, the thickness of the thermal oxide film for obtaining the correlation was about 5.1 nm. Thus, the correlation shown in Figure 1 was obtained.

[0197] Then, two types of wafers (designated as specimens A and B) cleaned under different conditions were prepared. Before the thermal oxidation treatment, ATR-FT-IR measurements were performed in advance using test pieces treated under the same conditions as specimens A and B, and the relative absorbance at 3300 cm -1 was measured. The amounts of OH groups (relative absorbance around 3300 cm -1 ) for specimens A and B were 0.12 and 0.18, respectively. Based on this result and the previously obtained relationship between the amount of OH groups (relative absorbance around 3300 cm -1 ) and the thickness of the oxide film, it was estimated that when the thermal oxidation treatment was performed under the same conditions (900 °C, 5% oxygen, 60 min) as when the correlation was obtained, the thicknesses of the thermal oxide films formed were: 5.05 nm for specimen A and 5.15 nm for specimen B.

[0198] Based on the estimated thicknesses of the thermal oxide films, the oxidation time was adjusted so as to form the target thermal oxide film thickness (5.1 nm). The oxidation time was set to 63 minutes for specimen A and 58 minutes for specimen B, and the actual thermal oxidation treatment was performed. After the thermal oxidation treatment, the thickness of the thermal oxide film was measured by ellipsometry. As a result, the thicknesses of the thermal oxide films of specimens A and B were both 5.1 nm, and the same thickness as the target thickness was achieved.

[0199] (Example 2)

[0200] Using the previously obtained relationship between the thermal oxidation temperature and the thickness of the thermal oxide film, the thermal oxidation temperature was adjusted so as to form the target thermal oxide film thickness (5.1 nm). Except for this, the thermal oxidation treatments of specimens A and B were performed in the same manner as in Example 1 to form a thermal oxide film. Specifically, the thermal oxidation temperature was adjusted to 910 °C for specimen A and 890 °C for specimen B. As a result, both specimens A and B were able to make the thickness of the thermal oxide film 5.1 nm, and the same thickness as the target thickness was achieved.

[0201] As can be seen from Examples 1 and 2, by setting the thermal oxidation conditions according to the amount of OH groups in the chemically oxidized film after cleaning, a thermal oxidized film of the same thickness can be formed regardless of the chemically oxidized film formed on the silicon wafer. This means that even wafers cleaned with different cleaning methods and cleaning conditions can have the thickness of the thermal oxidized film made consistent at the same thickness. As a result, it can be seen that the management of the thermal oxidation process becomes simple.

[0202] (Experimental Example 2)

[0203] A boron-doped silicon substrate with a diameter of 300 mm and a normal resistivity was prepared. After cleaning the surface of the silicon substrate with 0.5% HF to initialize it, SC1 cleaning was performed at 70°C. At this time, the NH4OH concentration was changed to 3, 0.3, 0.03, and 0.01%. In addition, as another cleaning, O3 cleaning (24°C) was performed with the O3 concentration oscillated at 3, 20, and 40 ppm.

[0204] Then, test pieces were cut from the silicon substrate in advance for XPS measurement to measure the peak intensities of Si 0～3+ and Si 4+ , and the ratios of the NH4OH concentration to the peak intensities of Si 0～ 3+ and Si 4+ were compared. The results are shown in Figure 14 , Figure 15 . Figure 14 is a graph showing the relationship between the NH4OH concentration and the ratio of the peak intensity of Si 0～3+ . Figure 15 is a graph showing the relationship between the NH4OH concentration and the ratio of the peak intensity of Si 4+ . In addition, the peak intensities were measured in the same way, and the ratios of the O3 concentration to the peak intensities of Si 0～ 3+ and Si 4+ were compared. The results are shown in Figure 16 , Figure 17 . Figure 16 is a graph showing the relationship between the O3 concentration and the ratio of the peak intensity of Si 0～ 3+. Figure 17 is a graph showing the relationship between the O3 concentration and the ratio of the peak intensity of Si 4+ . As a result, it has the tendency that as the NH4OH concentration increases, the ratio of the peak intensity of Si 0～ 3+ becomes larger, but the ratio of the peak intensity of Si 4+ instead decreases. On the other hand, in the case of O3, no dependence of the O3 concentration on the ratio of the peak intensities of the constituent elements of the chemically oxidized film was found.

[0205] After thermally oxidizing these substrates in such a way that the thickness of the thermal oxide film is expected to be 5.1 nm (900 °C, 5% oxygen, 60 min), the thickness of the thermal oxide film was measured by ellipsometry.

[0206] As a result of the experiments conducted as described above, the correlation shown in Figure 10 , Figure 11 was obtained. As shown in Figure 10 , Figure 11 , it was found that the thickness of the thermal oxide film has a correlation with the ratio of the peak intensities of Si 0～3+ and Si 4+ , and it was known that there is a tendency for the thickness of the thermal oxide film to become thicker as the ratio of the peak intensity of Si 0 ～3+ increases, and there is a tendency for the thickness of the thermal oxide film to become thicker as the ratio of the peak intensity of Si 4+ decreases. In addition, from the correlation between the thickness of the thermal oxide film and the ratio of the peak intensities of the constituent elements of the chemical oxide film shown in Figure 10 , Figure 11 , it was known that, for example, if a detection line as shown by the dashed line in Figure 10 , Figure 11 is drawn, the thickness of the formed thermal oxide film can be estimated from the ratio of the peak intensities of the constituent elements of the chemical oxide film of the silicon substrate as the object, and by determining the conditions for actually forming the thermal oxide film, a thermal oxide film with a thickness close to the expected value can be formed. Although no dependence of the O3 concentration on the stoichiometry was found, a good correlation was found between the stoichiometry and the thickness of the thermal oxide film formed after O3 cleaning.

[0207] (Example 3)

[0208] In the same manner as in Experimental Example 2 above, the correlation between the ratio of the peak intensities of Si 0～3+ and Si 4+ and the thickness of the thermal oxide film was determined. First, a plurality of 300-mm-diameter boron-doped silicon substrates with normal resistivity were prepared. After initializing the surface of the silicon substrates by cleaning with 0.5% HF, SC1 cleaning (70 °C, NH4OH concentration: 3, 0.3, 0.03, 0.01%) and O3 cleaning (24 °C, O3 concentration: 3, 20, 40 ppm) were performed respectively to produce substrates with different ratios of the peak intensities of Si 0～3+ and Si 4+ . Then, test pieces were cut from each silicon substrate for XPS measurement, and the peak intensities of Si 0～3+ and Si 4+ were measured in advance. Then, each substrate under each cleaning condition was subjected to a specified thermal oxidation treatment (900 °C, 5% oxygen, 60 min), the thickness of the thermal oxide film was measured, and the Si 0～3+and Si 4+ The correlation between the ratio of the peak intensities of Figure 10 and Figure 11 and the thickness of the thermal oxide film. At this time, the thickness of the thermal oxide film for obtaining the correlation is about 5.1 nm. Thus, the correlation as shown in Figure 10 and Figure 11 can be obtained. The dashed lines in

[0209] (Oxide film thickness nm) = 0.0342 × (Ratio of peak intensity of Si 0～3+ ) + 2.26

[0210] (Oxide film thickness nm) = -0.0342 × (Ratio of peak intensity of Si 4+ ) + 5.68

[0211] Then, prepare two types of substrates (designated as Specimens A and B) that are cleaned under different conditions. Before the thermal oxidation treatment, XPS measurements are performed in advance using test pieces that have been treated under the same conditions as Specimens A and B to measure the peak intensities of Si 0～3+ and Si 4+ . The results are shown in Table 1. The ratios of the peak intensities of each of Specimens A and B are as follows: The ratio of the peak intensity of Si 0～3+ is 81.5% in Specimen A and 84.5% in Specimen B; the ratio of the peak intensity of Si 4+ is 18.5% in Specimen A and 15.5% in Specimen B.

[0212] [Table 1]

[0213] <![CDATA[Si 0～3+ Ratio of peak intensity of]]> <![CDATA[Si 4+ Ratio of peak intensity]]> Specimen A 81.5％ 18.5％ Specimen B 84.5％ 15.5％

[0214] Based on this result and the previously obtained relationship between the ratio of the peak intensities of Si 0～3+ and Si 4+ and the thickness of the thermal oxide film, it is estimated that when the thermal oxidation treatment is performed under the same conditions (900 °C, 5% oxygen, 60 min) as when obtaining the correlation, the thicknesses of the thermal oxide films formed are as follows: In Specimen A, both Si 0～3+ and Si 4+ are 5.05 nm; in Specimen B, both Si 0～3+ and Si 4+ are 5.15 nm.

[0215] Based on the estimated thickness of the thermal oxide film, adjust the oxidation time to form the target thermal oxide film thickness (5.10 nm). Set the oxidation time to 63 minutes for sample A and 58 minutes for sample B, and perform the actual thermal oxidation treatment. After the thermal oxidation treatment, measure the thickness of the thermal oxide film by ellipsometry. As a result, the thickness of the thermal oxide film is 5.10 nm in both samples A and B, achieving the same thickness as the target thickness.

[0216] (Example 4)

[0217] Utilize the previously obtained relationship between the thermal oxidation temperature and the thickness of the thermal oxide film to adjust the thermal oxidation temperature to form the target thermal oxide film thickness (5.10 nm). Except for this, perform the thermal oxidation treatment of samples A and B in the same manner as in Example 3 to form a thermal oxide film. Specifically, adjust the thermal oxidation temperature to 910 °C for sample A and 890 °C for sample B. As a result, both samples A and B can make the thickness of the thermal oxide film 5.10 nm, achieving the same thickness as the target thickness.

[0218] As shown in Examples 3 and 4, by setting the thermal oxidation conditions according to the stoichiometric ratio of the constituent elements of the chemical oxide film after cleaning, regardless of the chemical oxide film formed on the silicon substrate, a thermal oxide film with a consistent and identical thickness can be formed. This indicates that for substrates cleaned using different cleaning methods and conditions, the thickness of the thermal oxide film can be made consistent at the same thickness. As a result, it can be seen that the management of the thermal oxidation process becomes simple.

[0219] (Experimental Example 3)

[0220] Describe the method of using RBS measurement and adjusting the thermal oxidation treatment conditions to make the thickness of the thermal oxide film the target thickness.

[0221] First, prepare a 300-mm-diameter boron-doped silicon wafer with a normal resistivity. After cleaning the surface of the silicon wafer with 0.5% HF to initialize it, perform SC1 cleaning at 70 °C. At this time, change the NH4OH concentration to 3, 0.3, 0.03, and 0.001%.

[0222] Then, cut test pieces from the silicon wafer in advance for RBS measurement, measure the ratio of hydrogen atoms, and compare the NH4OH concentration with the ratio of hydrogen atoms. The results are shown in Figure 20 in. Figure 20 is a graph showing the relationship between the NH4OH concentration and the ratio of hydrogen atoms in the chemical oxide film obtained by RBS measurement. As a result, as shown in Figure 20As shown, it can be seen that as the concentration of NH4OH increases, the ratio of hydrogen atoms decreases. It can be considered that the ratio of hydrogen atoms varies depending on the cleaning conditions because in the case of SC1 cleaning, the higher the concentration of NH4OH and the stronger the alkalinity, the fewer the hydrogen atoms.

[0223] After all these substrates were thermally oxidized (900 °C, 5% oxygen, 60 minutes) in such a way that the thickness of the thermal oxide film was expected to be 5.10 nm, the thickness of the thermal oxide film was measured by ellipsometry.

[0224] Based on the results of the experiments conducted as described above, the following Figure 18 correlation was obtained. As Figure 18 shown, it was found that the thickness of the thermal oxide film was correlated with the ratio of hydrogen atoms in the chemical oxide film after cleaning, and it was found that the greater the ratio of hydrogen atoms in the chemical oxide film after cleaning, the thinner the film thickness tended to be. Even if the surface states formed by cleaning were different, using this result, by adjusting the thermal oxidation time, etc., it was possible to form a thin thermal oxide film with a specified thickness.

[0225] (Experimental Example 4)

[0226] Furthermore, as another method, a method of measuring by ATR-FT-IR and adjusting the thermal oxidation treatment conditions so that the thickness of the thermal oxide film is the target thickness will be described.

[0227] First, silicon wafers identical to those prepared in Experimental Example 3 were prepared, and then test pieces were cut from the silicon wafers and subjected to ATR-FT-IR measurement to measure the absorbance near 2130 cm -1 and compare the NH4OH concentration with the absorbance near 2130 cm -1 . The results are shown in Figure 21 . Figure 21 is a graph showing the relationship between the NH4OH concentration and the absorbance at 2130 cm -1 obtained by ATR-FT-IR measurement. As a result, it was found that as the NH4OH concentration increased, the absorbance near 2130 cm -1 decreased, and the amount of hydrogen atoms in the chemical oxide film after cleaning decreased.

[0228] After all these wafers were thermally oxidized in the same manner as in Experimental Example 3, the following Figure 19 correlation was obtained. As Figure 19 shown, it was found that the thickness of the thermal oxide film was correlated with the absorbance near 2130 cm -1 in the chemical oxide film after cleaning, and it was found that the absorbance near 2130 cm -1The greater the absorbance in the vicinity, the thinner the film thickness tends to be. Even if the surface states formed by cleaning are different, by utilizing this result and adjusting the thermal oxidation time, etc., a thin thermal oxidation film with a specified thickness can be formed.

[0229] (Example 5)

[0230] In the same manner as in Experimental Example 3 above, the correlation between the ratio of hydrogen atoms obtained by RBS measurement and the thickness of the thermal oxidation film was determined. First, prepare multiple silicon wafers with a diameter of 300 mm, boron-doped with a normal resistivity. After initializing the silicon wafer surface by cleaning with 0.5% HF, perform SC1 cleaning (70 °C, NH4OH concentrations: 3, 0.3, 0.03, 0.001%) respectively to fabricate substrates with different ratios of hydrogen atoms. Then, cut test pieces from each silicon wafer for RBS measurement to pre-determine the ratio of hydrogen atoms. Next, perform a specified thermal oxidation treatment (900 °C, 5% oxygen, 60 minutes) on each substrate under each cleaning condition, measure the thickness of the thermal oxidation film, and determine the correlation between the ratio of hydrogen atoms and the thickness of the thermal oxidation film. At this time, the thickness of the thermal oxidation film for obtaining the correlation was set to about 5.10 nm. Thus, the correlation as shown in Figure 18 is obtained.

[0231] Then, prepare two types of substrates (designated as Specimen A and Specimen B) cleaned under different conditions. Before the thermal oxidation treatment, perform RBS measurement using test pieces treated under the same conditions as Specimen A and Specimen B to measure the ratio of hydrogen atoms. As a result, the ratio of hydrogen atoms in Specimen A and Specimen B respectively is: 10% in Specimen A and 20% in Specimen B.

[0232] Based on this result and the previously determined relationship between the ratio of hydrogen atoms and the thickness of the thermal oxidation film, it is estimated that the thicknesses of the thermal oxidation films formed when performing thermal oxidation treatment under the same conditions (900 °C, 5% oxygen, 60 minutes) as when obtaining the correlation are: 5.15 nm in Specimen A and 5.10 nm in Specimen B respectively.

[0233] Based on the estimated thickness of the thermal oxidation film, adjust the oxidation time in such a way as to form the target thermal oxidation film thickness (5.10 nm) and in such a way that the thickness of the thermal oxidation film is proportional to the square root of the oxidation time. Set the oxidation time to 58 minutes in Specimen A and in Specimen B

[0234] The oxidation time was set to 60 minutes, and the heat treatment temperature and heat treatment atmosphere were set to the same as those in the step of estimating the thickness of the thermal oxide film, i.e., 900 °C and 5% oxygen, and the actual thermal oxidation treatment was carried out. After the thermal oxidation treatment, the thickness of the thermal oxide film was measured by ellipsometry. As a result, the thickness of the thermal oxide film was 5.10 nm in both samples A and B, and the thickness same as the target thickness could be achieved.

[0235] (Example 6)

[0236] Using the relationship between the thermal oxidation temperature and the thickness of the thermal oxide film obtained in advance, the thermal oxidation temperature was adjusted to form a target thickness of the thermal oxide film (5.10 nm). Except for this, the thermal oxidation treatment of samples A and B was carried out in the same manner as in Example 5 to form a thermal oxide film. Specifically, the thermal oxidation temperature was adjusted to 890 °C for sample A and 900 °C for sample B. The heat treatment time and heat treatment atmosphere were set to 60 minutes and 5% oxygen, the same as those in the step of estimating the thickness of the thermal oxide film, and the actual thermal oxidation treatment was carried out. As a result, the thickness of the thermal oxide film could be made 5.10 nm in both samples A and B, and the thickness same as the target thickness could be achieved.

[0237] (Example 7)

[0238] In the same manner as in Experimental Example 4 above, the correlation between the absorbance at around 2130 cm -1 measured by ATR-FT-IR and the thickness of the thermal oxide film was obtained. First, a plurality of boron-doped silicon wafers with a diameter of 300 mm and a normal resistivity were prepared. After the surface of the silicon wafers was initialized by cleaning with 0.5% HF, SC1 cleaning (70 °C, NH4OH concentration: 3, 0.3, 0.03, 0.001%) was carried out respectively to produce substrates with different absorbances at around 2130 cm -1 Then, test pieces were cut from each silicon wafer for ATR-FT-IR measurement, and the absorbance at around 2130 cm -1 was measured in advance. Then, a specified thermal oxidation treatment (900 °C, 5% oxygen, 60 minutes) was carried out on each substrate under each cleaning condition, the thickness of the thermal oxide film was measured, and the correlation between the absorbance at around 2130 cm -1 and the thickness of the thermal oxide film was obtained. At this time, the thickness of the thermal oxide film for obtaining the correlation was set to about 5.10 nm. Thus, the correlation shown in Figure 19 was obtained.

[0239] Then, two types of substrates (designated as samples A and B) cleaned under different conditions were prepared. Before the thermal oxidation treatment, ATR-FT-IR measurement was carried out in advance using test pieces treated under the same conditions as samples A and B, and the absorbance at 2130 cm -1The absorbance in the vicinity. As a result, the ratios of hydrogen atoms in Samples A and B are 0.9 for Sample A and 1.0 for Sample B, respectively.

[0240] Based on this result and the relationship between the absorbance around 2130 cm -1 and the thickness of the thermal oxide film obtained in advance, it is estimated that the thicknesses of the thermal oxide films formed under the same conditions (900 °C, 5% oxygen, 60 minutes) as those for obtaining the correlation are 5.15 nm for Sample A and 5.10 nm for Sample B, respectively.

[0241] Since the thickness of the thermal oxide film is proportional to the square root of the oxidation time, the oxidation time is adjusted based on the estimated thickness of the thermal oxide film so as to form the target thermal oxide film thickness (5.10 nm). The oxidation time is set to 58 minutes for Sample A and 60 minutes for Sample B, and the heat treatment temperature and heat treatment atmosphere are set to 900 °C and 5% oxygen, which are the same as those in the thermal oxide film thickness estimation process, for actual thermal oxidation treatment. After the thermal oxidation treatment, the thickness of the thermal oxide film is measured by ellipsometry. As a result, the thickness of the thermal oxide film is 5.10 nm in both Samples A and B, and the same thickness as the target thickness can be achieved.

[0242] (Example 8)

[0243] The thermal oxidation temperature is adjusted based on the relationship between the thermal oxidation temperature and the thickness of the thermal oxide film obtained in advance so as to form the target thermal oxide film thickness (5.10 nm). Except for this, the thermal oxidation treatment of Samples A and B is performed in the same manner as in Example 7 to form a thermal oxide film. Specifically, the thermal oxidation temperature is adjusted to 890 °C for Sample A and 900 °C for Sample B. The heat treatment time and heat treatment atmosphere are set to 60 minutes and 5% oxygen, which are the same as those in the thermal oxide film thickness estimation process, for actual thermal oxidation treatment. As a result, the thickness of the thermal oxide film can be made 5.10 nm in both Samples A and B, and the same thickness as the target thickness can be achieved.

[0244] As shown in Examples 5 to 8, it can be seen that for any chemical oxide film formed on a silicon wafer, the thermal oxidation conditions can be set according to the amount of hydrogen atoms in the chemical oxide film after cleaning, and a thermal oxide film with a consistent thickness can be formed. This indicates that even for substrates cleaned by different cleaning methods and cleaning conditions, the thickness of the thermal oxide film can be made consistent. As a result, it can be seen that the management of the thermal oxidation process becomes simple.

[0245] In addition, the present invention is not limited to the above embodiments. The above embodiments are illustrative, and any solution that has a substantially identical composition and exhibits the same function and effect as the technical concept described in the claims of the present invention is included within the technical scope of the present invention.

Claims

1. A method for forming a thermal oxide film on a semiconductor substrate, which is a method for forming a thermal oxide film on a semiconductor substrate, characterized in that, This method has the following steps: A correlation obtaining step, in which a plurality of semiconductor substrates are prepared in advance. The plurality of semiconductor substrates have chemical oxide films formed by cleaning and the compositions of the chemical oxide films are different. The plurality of semiconductor substrates are subjected to thermal oxidation treatment under the same thermal oxidation treatment conditions to form thermal oxide films, and the correlation between the composition of the chemical oxide film and the thickness of the thermal oxide film is obtained; A substrate cleaning step, in which a semiconductor substrate to be formed with a thermal oxide film is cleaned; A thickness estimation step of the thermal oxide film, in which the composition of the chemical oxide film formed on the surface of the semiconductor substrate by the cleaning in the substrate cleaning step is measured, and based on the composition obtained by the measurement and the correlation, it is estimated that when the semiconductor substrate to be formed with the thermal oxide film is subjected to thermal oxidation treatment under the same conditions as the thermal oxidation treatment conditions in the correlation obtaining step, the thickness of the thermal oxide film formed on the surface of the semiconductor substrate to be formed with the thermal oxide film; A thermal oxidation treatment condition determination step, in which based on the thermal oxidation treatment conditions in the correlation obtaining step, the thermal oxidation treatment conditions are determined so that the thickness of the thermal oxide film formed on the surface of the semiconductor substrate is a specified thickness; and A thermal oxide film forming step, in which thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination step to form a thermal oxide film on the surface of the semiconductor substrate, The specified thickness is 1 to 10 nm.

2. A method for forming a thermal oxide film on a semiconductor substrate, which is a method for forming a thermal oxide film on a semiconductor substrate, characterized in that, This method has the following steps: A correlation obtaining step, in which a plurality of semiconductor substrates are prepared in advance. The plurality of semiconductor substrates have chemical oxide films formed by cleaning and the amounts of OH groups contained in the chemical oxide films are different. The plurality of semiconductor substrates are subjected to thermal oxidation treatment under the same thermal oxidation treatment conditions to form thermal oxide films, and the correlation between the amount of OH groups in the chemical oxide film and the thickness of the thermal oxide film is obtained; A substrate cleaning step, in which a semiconductor substrate to be formed with a thermal oxide film is cleaned; A thickness estimation step of the thermal oxide film, in which the amount of OH groups in the chemical oxide film formed on the surface of the semiconductor substrate by the cleaning in the substrate cleaning step is measured, and based on the amount of OH groups obtained by the measurement and the correlation, it is estimated that when the semiconductor substrate to be formed with the thermal oxide film is subjected to thermal oxidation treatment under the same conditions as the thermal oxidation treatment conditions in the correlation obtaining step, the thickness of the thermal oxide film formed on the surface of the semiconductor substrate to be formed with the thermal oxide film; a thermal oxidation treatment condition determination step, wherein the thermal oxidation treatment condition is determined based on the thermal oxidation treatment condition in the correlation acquisition step so that the thickness of the thermal oxide film formed on the surface of the semiconductor substrate becomes a predetermined thickness; and a thermal oxidation film forming step, wherein a thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination step, thereby forming a thermal oxidation film on the surface of the semiconductor substrate; The predetermined thickness is 1 to 10 nm.

3. The method for forming a thermal oxide film on a semiconductor substrate according to claim 2, wherein: The amount of the OH group was measured by ATR-FT-IR on the chemical oxidation film using an ATR measurement prism and the amount of the OH group was measured according to 3300 cm -1 It is calculated based on the absorbance of the nearby OH groups.

4. A method for forming a thermal oxide film on a semiconductor substrate, wherein: The method has the following steps: a correlation obtaining step, wherein a plurality of semiconductor substrates are prepared in advance, each of the plurality of semiconductor substrates having a chemical oxide film formed by cleaning, wherein the stoichiometric ratios of constituent elements of the chemical oxide film are different, the plurality of semiconductor substrates are subjected to thermal oxidation treatment under the same thermal oxidation treatment conditions to form thermal oxide films, and a correlation between the stoichiometric ratios of constituent elements of the chemical oxide film and the thickness of the thermal oxide film is obtained; a substrate cleaning step of cleaning the semiconductor substrate on which the thermal oxide film is to be formed; a thermal oxide film thickness estimating step, wherein the stoichiometric ratio of the constituent elements of the chemical oxide film formed on the surface of the semiconductor substrate by the cleaning in the substrate cleaning step is determined, and based on the determined stoichiometric ratio of the constituent elements of the chemical oxide film and the correlation, the thickness of the thermal oxide film formed on the surface of the semiconductor substrate to be formed with the thermal oxide film is estimated when the semiconductor substrate to be formed with the thermal oxide film is subjected to a thermal oxidation treatment under the same conditions as the thermal oxidation treatment conditions in the correlation acquiring step; a thermal oxidation treatment condition determination step, wherein the thermal oxidation treatment condition is determined based on the thermal oxidation treatment condition in the correlation acquisition step so that the thickness of the thermal oxide film formed on the surface of the semiconductor substrate becomes a predetermined thickness; and a thermal oxidation film forming step, wherein a thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination step, thereby forming a thermal oxidation film on the surface of the semiconductor substrate; The predetermined thickness is 1 to 10 nm.

5. The method for forming a thermal oxide film on a semiconductor substrate according to claim 4, wherein: Using XPS, the peak intensities of the bond energy of the constituent elements of the chemical oxidation film in a state where the substrate atoms of the semiconductor substrate are not bonded to oxygen atoms and in a state where the substrate atoms are bonded to oxygen atoms to form a low-value oxide, as well as the peak intensities of the bond energy in a state where the substrate atoms are completely bonded to oxygen atoms are measured respectively. The stoichiometric ratio of the constituent elements of the chemical oxidation film is the ratio of the measured peak intensities.

6. The method for forming a thermal oxide film on a semiconductor substrate according to any one of claims 1 to 5, wherein: The semiconductor substrate is a silicon wafer, and the thermal oxide film is a silicon oxide film.

7. A method for forming a thermal oxide film on a semiconductor substrate, wherein: The method has the following steps: a correlation obtaining step, wherein a plurality of semiconductor substrates are prepared in advance, each of the plurality of semiconductor substrates having a chemical oxide film formed by cleaning, wherein the amount of hydrogen atoms contained in the chemical oxide film varies, the plurality of semiconductor substrates are thermally oxidized under the same thermal oxidation treatment conditions to form thermal oxide films, and a correlation between the amount of hydrogen atoms in the chemical oxide film and the thickness of the thermal oxide film is obtained; a substrate cleaning step of cleaning the semiconductor substrate on which the thermal oxide film is to be formed; a thermal oxide film thickness estimating step, comprising measuring the amount of hydrogen atoms in the chemical oxide film formed on the surface of the semiconductor substrate by the cleaning in the substrate cleaning step, and estimating the thickness of the thermal oxide film formed on the surface of the semiconductor substrate to be formed with the thermal oxide film, assuming that the semiconductor substrate to be formed with the thermal oxide film is subjected to thermal oxidation treatment under the same conditions as the thermal oxidation treatment conditions in the correlation acquiring step, based on the amount of hydrogen atoms obtained by the measurement and the correlation; a thermal oxidation treatment condition determination step, wherein the thermal oxidation treatment condition is determined based on the thermal oxidation treatment condition in the correlation acquisition step so that the thickness of the thermal oxide film formed on the surface of the semiconductor substrate becomes a predetermined thickness; and a thermal oxidation film forming step, wherein a thermal oxidation treatment is performed under the thermal oxidation treatment conditions determined in the thermal oxidation treatment condition determination step, thereby forming a thermal oxidation film on the surface of the semiconductor substrate; The predetermined thickness is 1 to 10 nm.

8. The method for forming a thermal oxide film on a semiconductor substrate according to claim 7, wherein: The semiconductor substrate is a silicon wafer, and the thermal oxide film is a silicon oxide film.

9. The method for forming a thermal oxide film on a semiconductor substrate according to claim 7 or 8, wherein: The amount of hydrogen atoms is calculated from the ratio of hydrogen atoms in the chemical oxide film obtained by performing RBS measurement on the chemical oxide film.

10. The method for forming a thermal oxide film on a semiconductor substrate according to claim 8, wherein: The amount of hydrogen atoms was measured by ATR-FT-IR of the chemical oxidation film using an ATR measurement prism and the results were obtained based on the results at 2130 cm -1 It is calculated based on the absorbance of the nearby SiH3 groups.

11. The method for forming a thermal oxide film on a semiconductor substrate according to any one of claims 1, 2, 4 or 7, wherein: In the thermal oxide film thickness estimation step, When the estimated thickness of the thermal oxidation film is thicker than a predetermined thickness, in the thermal oxidation treatment condition determination step, the thermal oxidation treatment time is determined to be shorter than the thermal oxidation treatment time of the thermal oxidation treatment condition in the correlation acquisition step; When the estimated thickness of the thermal oxidation film is thinner than a predetermined thickness, in the thermal oxidation treatment condition determination step, the thermal oxidation treatment time is determined to be longer than the thermal oxidation treatment time of the thermal oxidation treatment condition in the correlation acquisition step; When the estimated thickness of the thermal oxidation film is equal to the specified thickness, in the thermal oxidation treatment condition determination step, the thermal oxidation treatment time is determined to be the same as the thermal oxidation treatment time of the thermal oxidation treatment condition in the correlation acquisition step.

12. The method for forming a thermal oxide film on a semiconductor substrate according to any one of claims 1, 2, 4 or 7, wherein: In the thermal oxide film thickness estimation step, When the estimated thickness of the thermal oxidation film is thicker than a predetermined thickness, in the thermal oxidation treatment condition determination step, the thermal oxidation treatment temperature is determined to be a temperature lower than the thermal oxidation treatment temperature of the thermal oxidation treatment condition in the correlation acquisition step; When the estimated thickness of the thermal oxidation film is thinner than a predetermined thickness, in the thermal oxidation treatment condition determination step, the thermal oxidation treatment temperature is determined to be a temperature higher than the thermal oxidation treatment temperature of the thermal oxidation treatment condition in the correlation acquisition step; When the estimated thickness of the thermal oxidation film is equal to the specified thickness, in the thermal oxidation treatment condition determination step, the thermal oxidation treatment temperature is determined to be the same temperature as the thermal oxidation treatment temperature of the thermal oxidation treatment condition in the correlation acquisition step.

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