JP4489059B2 - Silicon oxide film evaluation method and semiconductor device manufacturing method - Google Patents

Description

The present invention relates to a silicon oxide film evaluation method for evaluating a silicon oxide film formed on a silicon substrate, and a semiconductor device manufacturing method using the evaluation method.

  In silicon semiconductor elements such as bipolar transistors, MOSFETs, and memory elements, a silicon oxide film formed by thermally oxidizing a silicon substrate is used as the insulating film. Among the silicon oxide films formed by thermal oxidation, the field insulating film for element isolation is thick, but the silicon oxide film used as the dielectric film of the gate insulating film or trench capacitor is very thin. However, further thinning of these thin insulating films is required as the density of semiconductor devices increases.

  In the case of a thin oxide film of about 10 nm or less formed by the thermal oxidation method, this film thickness corresponds to several tens of atomic layers in terms of atomic layers. Therefore, it is desired to evaluate the film quality of the silicon oxide film by physicochemical structural analysis performed at the atomic and molecular level.

  In response to these demands, the same applicant as the present application uses non-destructive, non-contact, and infrared spectroscopic measurements that can be evaluated under atmospheric pressure, and based on the reflectivity of the silicon oxide film, the dielectric of the silicon oxide film An evaluation method for obtaining a function and evaluating the film quality from the dielectric function has been proposed (Japanese Patent Laid-Open No. Hei 6-341952).

In addition, R.A. Brendel et al. Have reported a method for calculating a dielectric function of a silicon oxide film from a Gaussian model (R. Brendelet al., J. Appl. Phys. 71, 1, 1992). The dielectric function of the silicon oxide film in a system in which aluminum is deposited on the silicon oxide film formed on the silicon substrate is calculated.
Japanese Patent Laid-Open No. 6-341952 R. Brendel et al., J. Appl. Phys. 71,1, 1992

  However, in the evaluation method for evaluating the film quality from the dielectric function of the silicon oxide film, the dielectric function of the silicon substrate itself is not particularly taken into consideration. For this reason, for example, in the case of a silicon oxide film formed on a silicon substrate whose electrical resistivity is lowered by the addition of impurities, the change in the dielectric function of the silicon substrate is calculated as the change in the dielectric function of the silicon oxide film. Therefore, accurate film quality evaluation could not be performed.

  In the above evaluation method, the quality of the silicon oxide film formed on the silicon substrate is affected by impurities introduced into the silicon substrate, and the evaluated silicon oxide film is used in an actual semiconductor device. May be different.

  For example, in order to eliminate the influence of reflected light on the back surface of the silicon substrate, when an infrared light absorption region for absorbing infrared light by introducing impurities into the silicon substrate is provided, the impurity concentration of the silicon substrate is actually set. Since the impurity concentration of the silicon substrate used in this semiconductor device is very high, the quality of the silicon oxide film to be evaluated is completely different from that used in an actual semiconductor device.

  In the above evaluation method, in order to derive a complex dielectric constant from the measured reflectance, it is necessary to obtain a solution of simultaneous equations derived from a plurality of measurement conditions. However, this simultaneous equation cannot be solved analytically.

  Therefore, the approximation method is used, but if the rough approximate root value to be determined first is not appropriate, not only the root of the simultaneous equations can be obtained at high speed but also an inappropriate root may be obtained. there were.

  Furthermore, in the above evaluation method, since the noise component included in the measured reflectance is included in the calculated dielectric function, if the dielectric function is further calculated based on the dielectric function, the noise component increases, and the accurate The dielectric function could not be determined.

  A first object of the present invention is to provide a silicon oxide film evaluation method capable of accurately evaluating a silicon oxide film equivalent to that used in an actual semiconductor device.

  A second object of the present invention is to provide a method of manufacturing a semiconductor device that can evaluate a silicon oxide film or the like formed on a silicon substrate in-line.

  The above object is to provide a silicon oxide film evaluation method for evaluating the quality of a silicon oxide film formed on a silicon substrate. The silicon oxide film formed on the silicon substrate is divided into a plurality of times while controlling the film thickness. A plurality of etching steps for etching, a plurality of measuring steps for measuring reflectance or transmittance of the silicon oxide film between the plurality of etching steps, and a plurality of reflectances measured by the plurality of measuring steps Or calculating a plurality of dielectric functions of the silicon oxide film after the plurality of etching processes based on the transmittance, and evaluating the film quality of the silicon oxide film based on the plurality of dielectric functions. This is achieved by a silicon oxide film evaluation method characterized by the following.

  The above object is to provide a silicon oxide film evaluation method for evaluating the film quality of a silicon oxide film formed on a silicon substrate. The silicon oxide film is formed on the silicon substrate in multiple steps while controlling the film thickness. A plurality of forming steps, a plurality of measuring steps for measuring the reflectance or transmittance of the silicon oxide film between the plurality of forming steps, and a plurality of reflectances or transmissions measured by the plurality of measuring steps. And calculating a plurality of dielectric functions of the silicon oxide film after the plurality of forming steps based on a rate, and evaluating the film quality of the silicon oxide film based on the plurality of dielectric functions. This is achieved by the silicon oxide film evaluation method.

  In the above-described silicon oxide film evaluation method, a dielectric function of the silicon substrate is calculated by the above-described silicon substrate evaluation method, and the calculation step includes a plurality of dielectrics for the silicon oxide film using the dielectric function of the silicon substrate. It is desirable to calculate the function.

  In the silicon oxide film evaluation method described above, a silicon substrate model in which the dielectric function of the silicon substrate is determined by a dielectric function theory based on polarization of free electrons is set, and the silicon substrate evaluation method described above is used to reflect the reflectance of the silicon substrate. It is desirable to obtain a dielectric function of the silicon substrate conforming to the silicon substrate model based on the reflectance of the silicon substrate.

  In the above-described silicon oxide film evaluation method, a silicon oxide film model in which a dielectric function of the silicon oxide film is obtained by a dielectric function theory satisfying a Kramers-Kronig relational expression based on polarization of a dipole is set, and the silicon oxide film It is desirable to obtain a plurality of dielectric functions of the silicon oxide film conforming to the silicon oxide film model based on a plurality of reflectances or transmittances of the film.

  The above object is achieved by a method for manufacturing a semiconductor device including a step of evaluating a silicon oxide film using the above-described evaluation method.

  As described above, according to the present invention, in the silicon oxide film evaluation method for evaluating the film quality of the silicon oxide film formed on the silicon substrate, the film thickness of the silicon oxide film formed on the silicon substrate is controlled. While measuring in a plurality of etching steps, a plurality of measuring steps for measuring the reflectance or transmittance of the silicon oxide film between the plurality of etching steps, and the plurality of measuring steps. And a calculation step of calculating a plurality of dielectric functions of the silicon oxide film after the plurality of etching steps based on the plurality of reflectances or transmittances, and based on the plurality of dielectric functions The film quality of the silicon oxide film can be evaluated.

  According to the present invention, in the silicon oxide film evaluation method for evaluating the film quality of the silicon oxide film formed on the silicon substrate, the silicon oxide film is formed on the silicon substrate a plurality of times while controlling the film thickness. A plurality of forming steps formed separately, a plurality of measuring steps for measuring reflectance or transmittance of the silicon oxide film between the plurality of forming steps, and a plurality of measuring steps measured by the plurality of measuring steps And a calculation step of calculating a plurality of dielectric functions of the silicon oxide film after the plurality of forming steps based on reflectance or transmittance. The film quality can be evaluated.

  Further, the dielectric function of the silicon substrate is calculated by the above-described silicon substrate evaluation method, and the calculation step calculates a plurality of dielectric functions for the silicon oxide film using the dielectric function of the silicon substrate. Even when a plurality of dielectric functions are obtained, an accurate dielectric function with few noise components can be obtained, and thereby the film quality can be evaluated.

  In addition, according to the present invention, the method for manufacturing a semiconductor device includes the step of evaluating the silicon oxide film using the evaluation method described above, so that the silicon oxide film or the like formed on the silicon substrate is inlined. Can be evaluated.

[First Reference Example]
A silicon substrate evaluation method and apparatus according to a first reference example of the present invention will be described with reference to FIGS.

Silicon Substrate Evaluation Apparatus FIG. 1 shows a silicon substrate evaluation apparatus according to this reference example.

  The evaluation apparatus shown in FIG. 1 is an external reflection type infrared absorption spectrum measuring apparatus based on Fourier transform infrared spectroscopy (FTIR).

  On the sample moving stage 14, a silicon substrate 18 is placed as a sample to be evaluated, and a gold thin film deposition substrate 19 is placed as a reference substrate to be referred to. Infrared light incident from the illumination system on the right side of the sample moving stage 14 is reflected on the surface of the silicon substrate 18 or the gold thin film deposition substrate 19, and the reflected light is measured and analyzed by the measurement system on the left side.

  At the beginning of measurement, as shown in FIG. 1, the silicon substrate 18 is located at the measurement position. The illumination system on the right side of the sample moving stage 14 is provided with a light source 10 that emits infrared light, and an interferometer 11 and a polarizer 12 are provided on the emission side of the light source 10.

  Infrared light from the light source 10 is emitted as a parallel light beam through the interferometer 11 and the polarizer 12. By providing the polarizer 12, P-wave infrared light having an electric field parallel to the incident surface or S-wave infrared light having an electric field perpendicular to the incident surface is emitted.

The emitted infrared light is reflected and collected by the concave mirror 13 and is incident at an angle inclined from the normal line of the silicon substrate 18. The incident angle can be changed by rotating and moving the concave mirror 13. The reflected light from the silicon substrate 18 is reflected by the concave mirror 15, becomes a parallel light beam, and enters a MCT (Mercury Cadmium Telluride) detector 16. The MCT detector 16 detects reflected light from the silicon substrate 18. A detection signal from the MCT detector 16 is input to the arithmetic unit 17. The computing unit 17 computes the reflectance of the surface of the silicon substrate 18 or the gold thin film deposition substrate 19 to obtain a dielectric function of the silicon substrate as will be described later.

In this reference example, the concave mirrors 14 and 15 are rotated to irradiate a plurality of incident lights incident on the silicon substrate 18 at different angles, and a plurality of incident lights having different incident angles are irradiated from the silicon substrate 18. Each reflected light is measured.

  Further, by rotating the polarizer 12 by 90 °, incident light having an electric field polarized perpendicularly or parallel to the incident surface is irradiated, and a plurality of incident lights having different polarization directions are reflected from the silicon substrate 18. Each light is measured.

  Next, the gold thin film deposition substrate 19 is positioned at the measurement position by moving the sample moving stage 14. Similarly, the reflected light from the silicon substrate 18 with respect to a plurality of incident lights having different incident angles or the reflected light from the silicon substrate 18 with respect to a plurality of incident lights having different polarization directions is measured on the gold thin film deposition substrate 19.

  From the reflected light of the silicon substrate 18 and the gold thin film deposition substrate 19, the reflectance under a plurality of conditions with different incident angles or polarization directions is calculated, and the dielectric function of the silicon substrate is obtained based on the reflectance under the plurality of conditions.

  The silicon substrate is evaluated based on the dielectric function thus obtained.

In addition, in the evaluation method of the silicon substrate of this reference example, with respect to the light reflected on the dielectric surface, the electric field is polarized in the incident plane and the reflection near the Brewster angle, which is the incident angle at which the reflectance becomes zero. Since the rate is not sensitive to the dielectric function of the silicon substrate, the dielectric function of the silicon substrate can be accurately obtained by using the reflectance at an angle other than the vicinity of the Brewster angle in order to obtain it more accurately.

  The Brewster angle of the silicon substrate is close to 75 degrees.

Principle of Silicon Substrate Evaluation Method Next, the principle of the silicon substrate evaluation method of this reference example will be described.

In the silicon substrate evaluation method according to this reference example, the reflectance R from the silicon substrate is expressed by the following equation.

  In the following equation, ε and η are treated as complex numbers.

  From the above equation, it can be seen that the simulation of the actually measured reflectivity R can be performed if the dielectric constant ε is given. Conversely, the dielectric constant ε of the silicon substrate can be obtained from the actually measured reflectance R. When determining the reflectance of a silicon substrate, it is necessary to accurately measure the intensity of incident light as well as the intensity of reflected light. However, even if the light intensity is measured in the irradiation system, the intensity of the incident light on the silicon substrate cannot be accurately known.

Therefore, in this reference example, the intensity of the reflected light from the gold thin film deposition substrate 19 on which a gold thin film having a very high light reflectance is formed is measured, and this is used as the intensity of the incident light.

2. Evaluation Method of Silicon Substrate FIG. 2 shows a procedure of a method for obtaining the dielectric function of the silicon substrate 18 based on the reflectance obtained from the reflected light of the silicon substrate 18 and the gold thin film deposition substrate 19 irradiated with incident light under a plurality of conditions.

  First, a polarization direction, an incident angle θ, and a dielectric constant ε are set as initial values (step S11).

  The incident angle θ and the dielectric constant ε can be known from the measurement conditions.

  Next, the reflectance is calculated from the set dielectric constant ε (step S12).

  Next, the calculated reflectance and the actually measured reflectance are compared (step S13).

  Then, the set value of the dielectric constant ε is changed so that the difference between the calculated value of the reflectance and the actually measured value is minimized, and Steps S11 to S12 are repeated.

  Finally, the dielectric constant ε when the difference between the calculated reflectance value and the actually measured value is minimized is taken as the dielectric constant of the silicon substrate 18.

  By performing such processing over a necessary wave number region, the dielectric function of the silicon substrate 18 can be obtained.

Reference Example 1-1
FIG. 3 shows measured values of reflectivity when irradiated with incident light under a plurality of conditions. The horizontal axis is the angle of incident light with respect to the substrate normal, and the vertical axis is the reflectance.

In the measurement, incident light having a wave number of about 900 to 1400 cm ⁻¹ was used, and measurement was performed using S-polarized light and P-polarized light with respect to incident angles of 45 degrees, 70 degrees, and 80 degrees, respectively.

In FIG. 3, a measurement point A at a wave number of about 1100 cm ⁻¹ is a measured value of reflectance when incident light (P-polarized light) having an electric field polarized in parallel to the incident surface is incident. The measurement point B is a measured value of the reflectance when incident light (S-polarized light) whose electric field is polarized perpendicular to the incident surface is incident.

  Using the measured values of FIG. 3, the dielectric constant of the silicon substrate was determined by the method described above. As a result, it was found that the dielectric constant ε suitable for these measured values was about 14. Conversely, when the dielectric constant ε was set to about 14 and the relationship between the incident angle and the reflectance was calculated, the curves Cs and Cp in FIG. 3 were obtained. Curve Cs is a graph for S-polarized light, and curve Cp is a graph for P-polarized light.

As is apparent from FIG. 3, the measurement points A and B coincide with the curves Cs and Cp, and it can be seen that the obtained dielectric constant is accurate. Although FIG. 3 shows a reference example for a specific wave number, if the same processing is performed for each wave number, the dielectric function of the silicon substrate in a predetermined wave number region can be accurately obtained.

[Second Reference Example]
A silicon oxide film evaluation method and apparatus according to a second reference example of the present invention will be described with reference to FIGS.

Silicon Oxide Film Evaluation Device FIG. 4 shows a silicon oxide film evaluation device according to this reference .

  In the center of the evaluation apparatus shown in FIG. 4, a measurement evaluation apparatus 21 is provided for evaluating the silicon oxide film on the wafer 20. A wafer 20 to be evaluated is placed on a sample stage (not shown) that describes the inside of the measurement evaluation apparatus 21. Infrared light incident from the illumination system on the right side of the moving stage is reflected on the surface of the wafer 20, and the reflected light is measured and analyzed by the measurement system on the left side.

  The illumination system on the right side of the sample stage is provided with a light source 22 that emits infrared light, and an interferometer 23 and a polarizer 24 are provided on the emission side of the light source 22. Infrared light from the light source 22 is emitted as a parallel light beam through an interferometer 23 and a polarizer 24. By providing the polarizer 24, P-wave infrared light having an electric field parallel to the incident surface or S-wave infrared light having an electric field perpendicular to the incident surface is emitted.

  The emitted infrared light is incident on the wafer 20 at an angle inclined from the normal line. The reflected light from the wafer 20 enters an MCT (Mercury Cadmium Telluride) detector 25. The MCT detector 25 detects reflected light from the wafer 20. A detection signal from the MCT detector 25 is input to the calculation unit 26. The calculator 26 calculates the reflectance of the surface of the wafer 20 and obtains a dielectric function of the silicon oxide film as will be described later.

A silicon oxide film forming apparatus 27 is provided on the left side of the measurement evaluation apparatus 21. This silicon oxide film forming apparatus 27 is an apparatus for forming a silicon oxide film by solution processing. The silicon oxide film forming apparatus 27 is provided with a solution tank 28 for an oxidation treatment solution (mixed solution of nitric acid (H ₂ SO ₄ ) and hydrogen peroxide solution (H ₂ O ₂ )).

  The silicon oxide film forming apparatus 27 may be an apparatus that forms a silicon oxide film by chemical vapor deposition or an apparatus that forms a silicon oxide film by thermal oxidation.

A silicon layer forming apparatus 29 is provided on the right side of the measurement evaluation apparatus 21. This silicon layer deposition apparatus 29 is an apparatus for depositing a silicon layer by a chemical vapor deposition method.
The silicon layer deposition apparatus 29 may be an apparatus for depositing a silicon layer by another method. A loading / unloading port 30 for loading / unloading the wafer 20 is provided in front of the silicon layer deposition apparatus 29.

Next, an evaluation method using the silicon oxide film evaluation apparatus according to this reference example will be described. The wafer 20 to be evaluated is provided with an infrared absorption region (not shown) having a high impurity concentration that absorbs infrared light in order to eliminate the influence of reflection from the back surface.

  First, the wafer 20 to be evaluated is carried into the silicon layer deposition apparatus 29 via the carry-in / out entrance 30. In the silicon layer deposition apparatus 29, after cleaning the surface of the wafer 20, a silicon layer having an impurity concentration in an actual semiconductor device is deposited on the wafer 20. At this time, the thickness of the silicon layer needs to be thin enough not to be detected in the measurement by the measurement evaluation apparatus 21, and to be thin enough to block the influence of impurities inside the wafer 20. is there. For example, the thickness of the silicon layer is desirably 1 μm or less.

  Next, the wafer 20 is transferred from the silicon layer deposition apparatus 29 to the silicon oxide film deposition apparatus 27 to form a silicon oxide film on the silicon layer surface. This silicon oxide film is formed on a silicon layer having an impurity concentration in an actual semiconductor device and is not affected by the impurity concentration of the silicon substrate.

  Next, the wafer 20 is transferred from the silicon oxide film forming apparatus 27 to the measurement / evaluation apparatus 21, and the silicon oxide film is measured and evaluated by an infrared external reflection method.

Principle of Silicon Oxide Film Evaluation Method The principle of the silicon oxide film evaluation method according to this reference example will be described with reference to FIG.

  As shown in FIG. 5, by providing an infrared light absorption region 20 a that absorbs infrared light in the silicon substrate 20, it is possible to ignore a reflection component from an interface that is not the measured side of the silicon substrate 20. . High-concentration impurities are added to the infrared light absorption region 20a.

  However, when the silicon oxide film 31 is directly formed on such a silicon substrate 20, high-concentration impurities inside the substrate affect the film quality of the silicon oxide film 31.

In this reference example, in order to remove the influence of such impurities, a silicon layer 32 having an impurity concentration used in an actual semiconductor device is formed on the silicon substrate 20, and a silicon oxide film 31 is formed on the silicon layer 32. To do.

  As a result, the influence of high-concentration impurities inside the substrate can be removed, and the silicon oxide film 31 having the same film quality as the silicon oxide film in the actual semiconductor device can be obtained.

  In addition, if the thickness of the silicon layer 32 is 1 μm or less, the phase of the infrared light does not change significantly due to reflection at the interface of the silicon layer 32, so that the silicon layer 32 does not affect the measurement result. .

  When the thickness of the silicon layer is 1 μm or more, interference fringes are observed, and accurate evaluation of the silicon oxide film becomes impossible. Accordingly, a silicon oxide film equivalent to that used in an actual semiconductor device can be accurately evaluated.

Note that the silicon substrate to which the present reference example is applied is not limited to the one in which an infrared light absorption region is provided. In order to remove the influence of the reflected light from the back surface, it may be applied to a thick silicon substrate, or may be applied to any other silicon substrate. Even in the case of other silicon substrates, an evaluation result useful for an actual semiconductor device can be obtained by providing a silicon layer equivalent to the actual semiconductor device on the silicon substrate.

Reference Example 2-1
FIG. 6 shows an evaluation example of the silicon oxide film. The horizontal axis is the wave number, and the vertical axis is the reflectance.

In this reference example, a silicon layer containing no impurities was formed to a thickness of 0.1 μm on a silicon substrate having an impurity concentration of 10 ¹⁴ atoms / cm ³ . The silicon oxide film is treated with a treatment solution (nitric acid (H ₂
SO ₄ ) and hydrogen peroxide solution (H ₂ O ₂ )) were formed on the silicon layer and measured by the infrared external reflection method.

  In FIG. 5, a characteristic peak of the silicon oxide film is observed, and the influence of impurities from the silicon substrate is eliminated by providing the silicon layer, and interference fringes are generated by the presence of the silicon layer. I understand that there is no.

[Third Reference Example]
A method and apparatus for evaluating the surface chemical bonding state of a silicon substrate according to a third reference example of the present invention will be described with reference to FIGS.

Apparatus for evaluating surface chemical bonding state of silicon substrate FIG. 7 shows an apparatus for evaluating the surface chemical bonding state of a silicon substrate according to this reference example.

  At the center of the evaluation apparatus shown in FIG. 7, a measurement evaluation apparatus 21 is provided for evaluating the silicon oxide film on the wafer 20. A wafer 20 to be evaluated is placed on a sample stage (not shown) that describes the inside of the measurement evaluation apparatus 21. Infrared light incident from the illumination system on the right side of the moving stage is reflected on the surface of the wafer 20, and the reflected light is measured and analyzed by the measurement system on the left side.

  The illumination system on the right side of the sample stage is provided with a light source 22 that emits infrared light, and an interferometer 23 and a polarizer 24 are provided on the emission side of the light source 22. Infrared light from the light source 22 is emitted as a parallel light beam through an interferometer 23 and a polarizer 24. By providing the polarizer 24, P-wave infrared light having an electric field parallel to the incident surface or S-wave infrared light having an electric field perpendicular to the incident surface is emitted.

  The emitted infrared light is incident on the wafer 20 at an angle inclined from the normal line. The reflected light from the wafer 20 enters the MCT detector 25. The MCT detector 25 detects reflected light from the wafer 20. A detection signal from the MCT detector 25 is input to the calculation unit 26. The calculator 26 calculates the reflectance of the surface of the wafer 20 and obtains a dielectric function of the silicon oxide film as will be described later.

A cleaning device 33 is provided on the left side of the measurement evaluation device 21. This cleaning device 33 is a device for cleaning the surface of the silicon substrate by solution processing. The cleaning device 33 is provided with a solution tank 34 for a cleaning solution (ammonium fluoride (NH ⁴ F) solution).

  The cleaning device 33 may be a device that cleans the surface of the silicon substrate by a vapor phase method such as fluorine dry etching, or may be a device that cleans the surface of the silicon substrate by another method.

  A silicon layer forming apparatus 29 is provided on the right side of the measurement evaluation apparatus 21. This silicon layer deposition apparatus 29 is an apparatus for depositing a silicon layer by a chemical vapor deposition method. The silicon layer deposition apparatus 29 may be an apparatus for depositing a silicon layer by another method. A loading / unloading port 30 for loading / unloading the wafer 20 is provided in front of the silicon layer deposition apparatus 29.

Next, an evaluation method using the evaluation apparatus for the surface chemical bonding state of the silicon substrate according to this reference example will be described. The wafer 20 to be evaluated is provided with an infrared absorption region (not shown) having a high impurity concentration that absorbs infrared light in order to eliminate the influence of reflection from the back surface.

  First, the wafer 20 to be evaluated is carried into the silicon layer deposition apparatus 29 via the carry-in / out entrance 30. In the silicon layer deposition apparatus 29, after cleaning the surface of the wafer 20, a silicon layer having an impurity concentration in an actual semiconductor device is deposited on the wafer 20.

  At this time, the thickness of the silicon layer needs to be thin enough not to be detected in the measurement by the measurement evaluation apparatus 21, and to be thin enough to block the influence of impurities inside the wafer 20. is there. For example, the thickness of the silicon layer is desirably 1 μm or less.

Next, the wafer 20 is transferred from the silicon layer forming apparatus 29 to the cleaning apparatus 33 to clean the surface of the silicon substrate. The surface state of the wafer 20 at this time is the surface state of the silicon layer having an impurity concentration in an actual semiconductor device and is not affected by the impurity concentration of the silicon substrate.

  Next, the wafer 20 is moved from the cleaning device 33 to the measurement / evaluation device 21, and the silicon oxide film is measured and evaluated by the infrared external reflection method.

Principle of Evaluation Method of Surface Chemical Bond State of Silicon Substrate The principle of the evaluation method of the surface chemical bond state of the silicon substrate according to this reference example will be described with reference to FIG.

  As shown in FIG. 8, by providing an infrared light absorption region 20 a that absorbs infrared light in the silicon substrate 20, reflection components from the interface other than the measurement target side of the silicon substrate 20 can be ignored. . High-concentration impurities are added to the infrared light absorption region 20a.

  However, when the silicon oxide film 31 is directly formed on such a silicon substrate 20, high-concentration impurities inside the substrate affect the surface chemical bonding state of the silicon substrate 20.

In this reference example, in order to remove the influence of such impurities, a silicon layer 32 having an impurity concentration used in an actual semiconductor device is formed on the silicon substrate 20, and the surface of the silicon layer 32 is cleaned.

  Thereby, it is possible to remove the influence of high concentration impurities inside the substrate and obtain a surface chemical bonding state similar to that of an actual semiconductor device. In addition, if the thickness of the silicon layer 32 is 1 μm or less, the phase of the infrared light does not change significantly due to reflection at the interface of the silicon layer 32, so that the silicon layer 32 does not affect the measurement result. .

  When the thickness of the silicon layer is 1 μm or more, interference fringes are observed, and accurate evaluation of the silicon oxide film becomes impossible. Therefore, it is possible to accurately evaluate the surface chemical bonding state of the silicon substrate equivalent to an actual semiconductor device.

Note that the silicon substrate to which the present reference example is applied is not limited to the one in which an infrared light absorption region is provided. It may be applied to a thick silicon substrate in order to remove the influence of reflected light from the back surface, or may be applied to any other silicon substrate. Even in the case of other silicon substrates, an evaluation result useful for an actual semiconductor device can be obtained by providing a silicon layer equivalent to the actual semiconductor device on the silicon substrate.

Reference Example 3-1
FIG. 9 shows an evaluation example of the silicon oxide film. The horizontal axis is the wave number, and the vertical axis is the reflectance.

In this reference example, a silicon layer containing no impurities was formed to a thickness of 0.1 μm on a silicon substrate having an impurity concentration of 10 ¹⁴ atoms / cm ³ . The silicon oxide film is treated with a treatment solution (nitric acid (H ₂
SO ₄ ) and hydrogen peroxide solution (H ₂ O ₂ )) were formed on the silicon layer and measured by the infrared external reflection method.

  In FIG. 9, a characteristic peak of silicon hydrogen bonding is observed, and the influence of impurities on the silicon substrate is eliminated by providing the silicon layer, and interference fringes are caused by the presence of the silicon layer. I understand that there is no.

If the evaluation can be made according to this reference example, the surface chemical bonding state of the silicon substrate is not limited to silicon hydrogen bonding, but may be other surface chemical bonding states such as silicon fluorine bonding and silicon hydroxyl bonding.

[Fourth Reference Example]
A method and apparatus for manufacturing a semiconductor device according to a fourth reference example of the present invention will be described with reference to FIG.

FIG. 10 shows a semiconductor device manufacturing apparatus according to this reference example.

  In the center of FIG. 10, a measurement evaluation device 21 is provided for evaluating the wafer 20. A wafer 20 to be evaluated is placed on a sample stage (not shown) that describes the inside of the measurement evaluation apparatus 21. Infrared light incident from the illumination system on the right side of the moving stage is reflected on the surface of the wafer 20, and the reflected light is measured and analyzed by the measurement system on the left side.

  The illumination system on the right side of the sample stage is provided with a light source 22 that emits infrared light, and an interferometer 23 and a polarizer 24 are provided on the emission side of the light source 22. Infrared light from the light source 22 is emitted as a parallel light beam through an interferometer 23 and a polarizer 24. By providing the polarizer 24, P-wave infrared light having an electric field parallel to the incident surface or S-wave infrared light having an electric field perpendicular to the incident surface is emitted.

  The emitted infrared light is incident on the wafer 20 at an angle inclined from the normal line. The reflected light from the wafer 20 enters the MCT detector 25. The MCT detector 25 detects reflected light from the wafer 20. A detection signal from the MCT detector 25 is input to the calculation unit 26. The calculator 26 calculates the reflectance of the surface of the wafer 20 and obtains a dielectric function of the silicon oxide film as will be described later.

A cleaning device 35 is provided on the left side of the measurement evaluation device 21. The cleaning device 35 is a device for cleaning the surface of the silicon substrate by solution processing. The cleaning device 35 is provided with a cleaning solution (a solution tank 36 of ammonium fluoride (NH ₄ F)).

  The cleaning device 36 may be a device that cleans the surface of the silicon substrate by a vapor phase method such as fluorine dry etching, or may be a device that cleans the surface of the silicon substrate by another method.

  A silicon oxide film forming device 37 is provided above the cleaning device 35. This silicon oxide film forming apparatus 37 is an apparatus for forming a silicon oxide film by heat treatment. The silicon oxide film forming apparatus 37 is provided with a heater 38.

  The silicon oxide film forming apparatus 27 may be an apparatus for forming a silicon oxide film by a chemical vapor deposition method or an apparatus for forming a silicon oxide film by solution processing.

  A silicon layer forming apparatus 29 is provided on the right side of the measurement evaluation apparatus 21. This silicon layer deposition apparatus 29 is an apparatus for depositing a silicon layer by a chemical vapor deposition method.

  The silicon layer deposition apparatus 29 may be an apparatus for depositing a silicon layer by another method. A loading / unloading port 30 for loading / unloading the wafer 20 is provided in front of the silicon layer deposition apparatus 29.

Next, a manufacturing method using the semiconductor device manufacturing apparatus according to this reference example will be described.

In this reference example, a manufacturing process for forming a silicon oxide film on a silicon substrate is performed. First, the wafer 20 is loaded through the loading / unloading port 30 and the surface of the wafer 20 is cleaned by the cleaning device 35 to remove contaminants and natural oxide films on the surface. Next, it is carried into the silicon layer deposition apparatus 29. In the silicon layer deposition apparatus 29, a silicon layer having an impurity concentration in an actual semiconductor device is deposited on the wafer 20. At this time, the thickness of the silicon layer needs to be thin enough not to be detected in the measurement by the measurement evaluation apparatus 21, and to be thin enough to block the influence of impurities inside the wafer 20. is there. For example, the thickness of the silicon layer is desirably 1 μm or less.

  Next, the wafer 20 is transferred from the silicon layer deposition apparatus 29 to the cleaning apparatus 35 to clean the surface of the wafer 20. Thereafter, the wafer 20 is moved from the cleaning device 35 to the measurement evaluation device 21, and the surface chemical bonding state of the silicon substrate is measured and evaluated by the infrared external reflection method. Next, the wafer 20 is transferred from the measurement evaluation apparatus 21 to the silicon oxide film forming apparatus 37, and a silicon oxide film is formed on the surface of the wafer 20 by thermal oxidation. Thereafter, the wafer 20 is transferred from the silicon oxide film forming apparatus 37 to the measurement / evaluation apparatus 21, and the formed silicon oxide film is measured and evaluated by an infrared external reflection method.

As described above, according to the present reference example, since the quality of the silicon oxide film can be checked in-line immediately after film formation, the production of defective semiconductor devices can be reduced as much as possible, and the manufacturing cost can be reduced. be able to.

  Since the evaluation is performed before and after the silicon oxide film is formed, the manufacturing process can be improved by knowing the relationship between the surface state of the silicon substrate and the film quality of the formed silicon oxide film.

First Embodiment
A silicon oxide film evaluation method and apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

Outline of Evaluation Method for Silicon Oxide Film FIG. 11 shows a procedure of a method for obtaining a dielectric function from reflectances at two or more incident angles.

First, an incident angle θ, a film thickness t, and a refractive index n are set as initial values (step S21). The incident angle θ can be known from the measurement conditions, and the film thickness t is measured by another measurement method. As the refractive index n, a plurality of values within the range of dielectric constant ε (= n ² ) that can be taken as a silicon oxide film are set.

  Next, the reflectance R for each of the set refractive indexes n is obtained from the above-described formula (step S22). Thereby, the graph which shows the relationship between the refractive index n and the calculated value of the reflectance R is obtained.

Next, using the graph showing the relationship between the refractive index n and the calculated value of the reflectance R, the refractive index n of the silicon oxide film is obtained from the measured value of the reflectance R (step S23). From the obtained refractive index n, the dielectric constant ε (= n ² ) can be obtained.

The dielectric function can be obtained by performing the calculation of the dielectric constant ε (= n ² ) in steps S1 to S3 described above over a necessary wave number region.

  By such a method, in order to derive a complex dielectric constant from the measured reflectance, a solution of simultaneous equations derived from a plurality of measurement conditions having different incident angles is obtained.

  However, since these simultaneous equations cannot be solved analytically, an approximate root is obtained using an iterative method.

The principle of the iterative method is described in detail. The iterative method is the following equation f (X) = 0 (1)
This is a technique for obtaining the real root of sequentially in an approximate manner. X represents a plurality of values, for example, coefficients of complex real and imaginary parts.

Formula (1) is converted into the following formula: X = F (X) (2)
Starting from the rough approximate root X ₀ ,
X ₀ = F (X ₀ )
X ₁ = F (X ₁ )
X ₂ = F (X ₂ )
This is a method of finding the roots in successive approximation. In general, iterative formula Xk + 1 = F (Xk) (k = 0, 1, 2,...)
Is repeated to determine a convergence determination condition, for example, the following expression: | Xk + 1−Xk | / | Xk | ≦ δ (δ: convergence determination condition)
Until you are satisfied.

  The type of the iterative method is determined by how F (X) is given. For example, in the Newton-Raphson method, F (X) is determined as follows. Here, in order to simplify the description, the case of one variable will be described as an example.

If the k-th approximate value of the true root α in equation (1) is xk and the error is δk,
α = xk + δk (3)
From the equations (1) and (3), the following equation: f (α) = f (xk + δk) = 0 (4)
Is established.

  When the equation (4) is Taylor-expanded in the vicinity of xk, the following equation is obtained.

f (xk + δk) = f (xk) + δk f '(xk) + δk 2 f "(xk) / 2! +
...
(Xk <ζ <α) (5)
Assuming that δk is sufficiently small, the second and higher terms of δk can be ignored, so the following equation holds.

0 = f (xk + δk) = f (xk) + δk f ′ (xk)
From this, the following equation holds.

δk = −f (xk) / f ′ (xk) (6)
From the equations (3) and (6), the following equation is established.

α = xk + δk = xk−f (xk) / f ′ (xk) (7)
This is used to obtain the next Newton-Raphson iteration.

xk + 1 = xk-f (xk) / f '(xk) (k = 0, 1, 2,...)
The convergence determination condition is an example, and various forms can be used.

  In this iterative method, if an inappropriate value is selected as the rough approximate root xk, convergence may be slow or may not converge. In a worse case, it may converge to a place other than the optimum root.

  FIG. 12A shows an example in which an appropriate value is selected as a rough approximate root and converged.

  FIGS. 12B, 13A, and 13B show examples in which convergence was not successful because an inappropriate value was selected as a rough approximate root. FIG. 12B is an example in which convergence has not occurred because an extremum is included up to the optimum root. FIG. 13A shows an example of circulation without convergence. FIG. 13B shows an example in which the value converges to a value that is not the optimum root that should originally be obtained.

Silicon oxide film evaluation method What is obtained by one iteration is the dielectric constant at a certain wave number. Therefore, by applying the above iterative method for each wave number over a predetermined wave number region, a function of the dielectric constant with respect to the wave number, that is, a dielectric function ε (ω) can be obtained. In order to obtain a dielectric function ε (ω) for each wave number and obtain a continuous dielectric function spectrum, it is necessary to select a rough approximate root εo for each wave number.

  Therefore, this rough approximate root εo is a function εo (ω) of the wave number ω. The evaluation method according to this embodiment appropriately gives the rough approximate root εo (ω).

  A method for obtaining the dielectric function according to this embodiment will be described with reference to the flowcharts of FIGS.

  First, the wave number ωj will be described. The reflectance spectrum for wave numbers that can be measured is the reflectance spectrum for discrete wave numbers. Adjacent wave numbers are close enough to satisfy spectral continuity. The subscript j of the wave number ωj indicates the j + 1-th wave number counted from the first wave number ωo when the dielectric function spectrum is derived. Let ωl be the last wave number when the dielectric function spectrum is derived. εk (ωj) is a dielectric function obtained when the number of iterations of the iterative method applied to obtain the dielectric function with respect to the wave number ωj is k times. In particular, εo (ωj) is a rough approximate root used as an initial value of the iterative method.

  First, a description will be given using the flowchart of FIG.

  First, physical property values, film thickness, refractive index, and wave number table necessary for calculation are set (step S31). Next, it is determined whether or not the wave number ωj is the first wave number ωo for deriving the dielectric function spectrum (step S32). If the wave number ωj is the first wave number ωo, a dielectric function ε (ωo) with respect to the wave number ωo is derived (step S33). Details of step S33 will be described later.

  If the wavenumber ωj is not the first wavenumber ωo, the rough approximate root εo (ωj), which is the initial value of the iterative method, is set to the dielectric function ε (ωj-1) of the previous wavenumber ωj-1 (step S34).

  Since the dielectric function spectrum has continuity, the optimum root can be obtained stably and at high speed by setting the rough approximate root εo (ωj) in this way.

The iterative method is executed using the rough approximate root εo (ωj). The number of iterations k of the iteration method is reset (step S35), and an approximate root εk + 1 (ωj) is obtained from the iteration formula εk + 1 (ωj) = F (εk (ωj)) (step S36).

  Then, it is determined whether or not this approximate root satisfies a predetermined convergence condition (step S37).

  If the convergence condition is not satisfied, the number of iterations is increased by 1 (step S38), the approximate root εk + 1 (ωj) is set as a new rough approximate root εk (ωj) (step S39), and the process returns to step S36. These steps S36 to S39 are repeated until the convergence condition is satisfied.

  If the convergence condition is satisfied, the approximate root εk + 1 (ωj) at that time is set as the dielectric constant ε (ωj) at the wave number ωj (step S40).

  Subsequently, it is determined whether or not the current wave number ωj is the final wave number ωl from which the dielectric function spectrum is derived (step S41).

If it is the final wave number, the calculation of the dielectric function spectrum is completed. If it is not the final wave number, the wave number ωj is set to the next wave number ωj + 1 (step S42), the process returns to step S34, and steps S34 to S42 are repeated until the final wave number ωl is reached.

  Next, the process of deriving the dielectric function ε (ωo) when the wave number ωj is the first wave number ωo (step S33) will be described using the flowchart of FIG. If the rough approximate root at the very first wave number ωo is an inappropriate value, it does not converge properly as described above, so this determination method is very important. In this embodiment, the rough approximate root of the initial wave number ωo can be automatically set to an appropriate value.

  First, an arbitrary value Z within −5−5i ≦ Z ≦ 5 + 5i is selected as the rough approximate root εo (ωo) of the first wave number ωo (step S51). It has been empirically found that selecting a value in this range converges empirically. The iterative method is executed with this value Z as a rough approximate root εo (ωo).

  First, the iteration number k of the iteration method is reset (step S52), and an approximate root εk + 1 (ωo) is obtained from the iterative formula εk + 1 (ωo) = F (εk (ωo)) (step S53).

  Then, it is determined whether or not this approximate root satisfies a predetermined convergence condition (step S54).

  If the convergence condition is satisfied, the approximate root εk + 1 (ωo) at that time is set as the dielectric constant ε (ωo) at the first wave number ωo (step S58), and the process proceeds to step S41 in FIG. If the convergence condition is not satisfied, it is first determined whether or not the number of iterations k exceeds a predetermined maximum value MAX (step S55), and if it exceeds the maximum value, the processing shown in FIGS. 16 and 17 is performed. . If the maximum value is not exceeded, the number of iterations is incremented by 1 (step S56), the approximate root εk + 1 (ωo) is set to a new rough approximate root εk (ωo) (step S57), and the process returns to step S53. These steps S53 to S57 are repeated until the convergence condition is satisfied or the number of iterations k exceeds a predetermined maximum value MAX.

Next, a process in the case where convergence is not successfully performed with an arbitrary value Z initially determined as a rough approximate root εo (ωo) will be described using the flowchart of FIG. As candidate values X and Y of a new rough approximate root εo (ωo), a value obtained by adding or subtracting the value Δ from the first set value Z is selected (step S61). The value Δ is an arbitrary value within the range of 0 ≦ Δ ≦ 5 + 5i. It has been empirically found that selecting a value in this range converges empirically.

  First, the iterative method is executed with the candidate value X as a rough approximate root εo (ωo). The iteration number k of the iteration method is reset (step S62), and an approximate root εk + 1 (ωo) is obtained from the iteration formula εk + 1 (ωo) = F (εk (ωo)) (step S64). Then, the convergence condition value δx by the approximate root is stored (step S65), and it is determined whether or not the value δx satisfies the convergence condition (step S66).

  If the convergence condition is satisfied, the process proceeds to step S58, and the approximate root εk + 1 (ωo) at that time is set as the dielectric constant ε (ωo) at the first wave number ωo, and the process proceeds to step S41 in FIG. .

  If the convergence condition is not satisfied, it is first determined whether or not the number of iterations k exceeds a predetermined maximum value MAX (step S67). If it exceeds the maximum value, a candidate value Y described later is set to a rough approximate root εo. The iterative method is executed as (ωo). If the maximum value is not exceeded, the number of iterations is incremented by 1 (step S68), the approximate root εk + 1 (ωo) is set to a new rough approximate root εk (ωo) (step S69), and the process returns to step S64. These steps S64 to S69 are repeated until the convergence condition is satisfied or the number of iterations k exceeds a predetermined maximum value MAX.

  Next, if the candidate value X does not converge well as the rough approximate root εo (ωo), the iterative method is executed with the candidate value Y as the rough approximate root εo (ωo). The iteration number k of the iteration method is reset (step S71), and an approximate root εk + 1 (ωo) is obtained from the iteration formula εk + 1 (ωo) = F (εk (ωo)) (step S73). Then, the convergence condition value δy by the approximate root is stored (step S74), and it is determined whether or not the value δy satisfies the convergence condition (step S75).

  If the convergence condition is satisfied, the process proceeds to step S58, and the approximate root εk + 1 (ωo) at that time is set as the dielectric constant ε (ωo) at the first wave number ωo, and the process proceeds to step S41 in FIG. . If the convergence condition is not satisfied, it is first determined whether or not the number of iterations k exceeds a predetermined maximum value MAX (step S76), and if it exceeds the maximum value, the candidate values X and Y are also inappropriate. 17 is executed, and the process shown in FIG. If the maximum value is not exceeded, the number of iterations is increased by 1 (step S77), the approximate root εk + 1 (ωo) is set as a new rough approximate root εk (ωo) (step S78), and the process returns to step S73. These steps S73 to S78 are repeated until the convergence condition is satisfied or the number of iterations k exceeds a predetermined maximum value MAX.

  Next, processing when the rough approximate root εo (ωo) does not converge well even if the rough approximate root εo (ωo) is set as the candidate values X and Y will be described using the flowchart of FIG.

  First, the final convergence condition values δx and δy in the case of the candidate values X and Y stored in step S65 and step S74 are compared (step S81). In the processing of FIG. 17, it is determined that the convergence condition is better when the convergence condition values δx and δy are smaller, and a value obtained by adding or subtracting the value Δ to the better candidate value is a new rough approximate root εk (ωo). Set as and run the iterative method.

  If it is determined in step S81 that the convergence condition value δx is smaller than the value δy, a value obtained by adding Δ to the candidate value X is set as a new candidate value X (step S82), and the iterative method is executed.

  The number of iterations k of the iteration method is reset (step S83), and a new candidate value X is set as a rough approximate root εo (ωo) (step S84).

  Subsequently, an approximate root εk + 1 (ωo) is obtained from the iterative expression εk + 1 (ωo) = F (εk (ωo)) (step S85).

  Then, it is determined whether or not the approximate root satisfies a predetermined convergence condition (step S86).

  If the convergence condition is satisfied, the process proceeds to step S58, and the approximate root εk + 1 (ωo) at that time is set as the dielectric constant ε (ωo) at the first wave number ωo, and the process proceeds to step S41 in FIG. .

  If the convergence condition is not satisfied, it is first determined whether or not the number of iterations k exceeds a predetermined maximum value MAX (step S87).

  If the maximum value is not exceeded, the number of iterations is increased by 1 (step S88), and this approximate root εk + 1 (ωo) is set to a new rough approximate root εk (ωo) (step S89), and the process returns to step S85. These steps S85 to S89 are repeated until the convergence condition is satisfied or the number of iterations k exceeds a predetermined maximum value MAX.

  If it is determined in step S87 that the maximum value has been exceeded, the process returns to step S82, and the value Δ is further added to the candidate value X to obtain a new candidate value, and the processes in steps S82 to S89 are performed until the final convergence. repeat.

  If it is determined in step S81 that the convergence condition value δy is smaller than the value δx, a value obtained by subtracting Δ from the candidate value Y is set as a new candidate value Y (step S91), and the iterative method is executed.

  The iteration number k of the iteration method is reset (step S92), and a new candidate value Y is set as a rough approximate root εo (ωo) (step S93).

  Subsequently, an approximate root εk + 1 (ωo) is obtained from the iterative expression εk + 1 (ωo) = F (εk (ωo)) (step S94). Then, it is determined whether or not this approximate root satisfies a predetermined convergence condition (step S95).

  If the convergence condition is satisfied, the process proceeds to step S58, and the approximate root εk + 1 (ωo) at that time is set as the dielectric constant ε (ωo) at the first wave number ωo, and the process proceeds to step S41 in FIG. .

  If the convergence condition is not satisfied, it is first determined whether or not the number of iterations k exceeds a predetermined maximum value MAX (step S96). If the maximum value is not exceeded, the number of iterations is increased by 1 (step S97), and this approximate root εk + 1 (ωo) is set as a new rough approximate root εk (ωo) (step S98), and the process returns to step S94. These steps S94 to S98 are repeated until the convergence condition is satisfied or the number of iterations k exceeds a predetermined maximum value MAX.

  If it is determined in step S95 that the maximum value has been exceeded, the process returns to step S91, and the value Δ is further subtracted from the candidate value Y to obtain a new candidate value. repeat.

Example 1-1
A non-doped (111) silicon substrate having a specific resistance of 100 Ω · cm was used, and a silicon oxide film having a thickness of 10 nm was formed on the silicon substrate by thermal oxidation.

  For this oxide film, the simultaneous equation set using the reflectance measured for infrared light with an incident angle of 70 degrees and 80 degrees by infrared spectroscopy is used. The dielectric function spectrum was obtained. The dielectric function spectrum is shown in FIG.

  The iterative method used to determine the dielectric function spectrum is the Newton-Raphson method. The first wave number when deriving the dielectric function spectrum is 798.395, and the setting process of the rough approximate root of the iterative method for this wave number is as follows. First, an arbitrary value Z = 0.5 + 0.1i within −5−5i ≦ Z ≦ 5 + 5i was selected as a rough approximate root. Since the two variables of the simultaneous equations are the real part and the imaginary part of the dielectric function, Real (Z) = 0.5 is used as the rough approximate root Real (εo (798.395) for the real part of the dielectric function, The iterative method was applied using Imag (Z) = 0.1 as the coarse approximate root Imag (εo (798.395) for the imaginary part.

  The following formula was used as the convergence judgment condition.

δk = | εk + 1 (ω) −εk (ω) | ≦ max (1.0 | εk (ω) |) · EPSR
However, EPSR ~ 2 (u) ^1/2 (u: unit of rounding error)
When this convergence judgment condition is satisfied, the iteration process is terminated.

  In order to determine the appropriateness of the convergence state, the residual R (ω) defined by the following equation was used instead of δx and δy.

R (ω) = Σ (r ^mea (θ, ω) −r ^cal (θ, ω)) / r ^mea (θ, ω)
Where r ^cal (θ, ω) is a reflection coefficient obtained by using the dielectric function ε (ω) calculated from simultaneous equations in the Fresnel equation, and r ^mea (θ, ω) is a reflection coefficient obtained by measurement. It is. The incident angle θ is 70 ° or 80 °.

  In this example, when the iterative method was executed by selecting the value Z = 0.5 + 0.1i as a rough approximate root, the convergence condition was satisfied with 92 iterations. The residual R (798.395) at this time was 6.045E-5.

  Since it has been empirically found that an appropriate dielectric function cannot be obtained unless the residual R (ω) is 1.0E-30 or less, this convergence situation is not appropriate, and probably converges outside the optimum root. It is considered a thing.

  Therefore, Δ = 0.5, and a rough approximate root of the real part of the dielectric function Real (εo (798.395) as Real (X) = Real (Z) as a rough approximate root of the iterative method used at a wave number of 798.395. When + Δ = 1.0 is selected and when Real (Y) = Real (Z) −Δ = 0.0 is selected as a rough approximate root Real (εo (798.395) for the real part of the dielectric function. An iterative method was executed to check the convergence state, and the rough approximate root Imag (εo (798.395) for the imaginary part of the dielectric function was kept at Imag (Z) = 0.1.

  When the candidate value X was used, it converged with 68 iterations, and the residual R (ω) at this time was 6.045E-5. When the candidate value Y was used, it converged with 130 iterations, and the residual R (ω) at this time was 5.655E−32.

  Therefore, the root of the iterative method when the candidate value Y is used is the dielectric function for the initial wave number 798.395 of the dielectric function spectrum. The values at this time are shown below.

ε (798.395) = (− 3.9719, 2.933)
The iterative method was carried out using this value as the rough approximate root of the wave number 802.252 following the wave number of 79.395 at the very first. As a result, the convergence condition was satisfied with 97 iterations. The residual R at this time was 1.672E-32, and it was found that the convergence condition was good.

  The value of the dielectric function at this time is shown below.

ε (802.252) = (− 3.8655, 2.8202)
Similarly, the value of the dielectric function was obtained by executing the iterative method with this value as a rough approximate value of the next wave number 806.109. The above processing was repeated to obtain the dielectric function value for a predetermined wavenumber range.

  The result is the dielectric function spectrum of FIG.

Comparative Example As a comparative example, the value of the dielectric function obtained by selecting the value Z = 0.5 + 0.1i as a rough approximate root ε (798.395) = (1.0158, 0.0016)
Was determined as a rough approximate root for the subsequent wave number. The dielectric function spectrum is shown in FIG.

  As can be seen from FIG. 19, there is a discontinuous portion in the dielectric function spectrum, and it is a strange dielectric function spectrum in which the sign of the imaginary part of the dielectric function spectrum is inverted.

  As described above, when the dielectric constant is obtained, the reflectance and transmittance can be calculated using the Fresnel equation. Therefore, the reflectance was calculated on the contrary using the dielectric functions obtained in the examples and comparative examples. If the calculated dielectric constant is correct, the calculated reflectance should be almost the same as the actually measured value.

FIG. 20 shows the measured reflectance spectrum r ^mea (ω). FIG. 21 shows the reflectance spectrum r ^cal calculated using the dielectric function obtained in this example. It can be seen that the measured values in FIG. 20 agree very well. FIG. 22 is a reflectance spectrum calculated using the dielectric function obtained by the comparative example. It turns out that it is different from the measured value.

[ Second Embodiment]
A silicon oxide film evaluation method and apparatus according to a second embodiment of the present invention will be described with reference to FIGS.

Silicon Oxide Film Evaluation Apparatus FIG. 23 shows a silicon oxide film evaluation apparatus according to this example. In the center of the evaluation apparatus shown in FIG. 23, an infrared spectrometer 41 that measures the reflection spectrum of the wafer 40 is provided. A wafer 40 to be measured is placed on a sample stage (not shown), which describes the inside of the infrared spectrometer 41. Infrared light incident from the illumination system on the right side of the moving stage is reflected by the surface of the wafer 40, and the reflected light is measured and analyzed by the measurement system on the left side.

  The illumination system on the right side of the sample stage is provided with a light source 42 that emits infrared light, and an interferometer 43 and a polarizer 44 are provided on the emission side of the light source 42. Infrared light from the light source 42 is emitted as a parallel light beam through the interferometer 43 and the polarizer 44. By providing the polarizer 44, P-wave infrared light having an electric field parallel to the incident surface or S-wave infrared light having an electric field perpendicular to the incident surface is emitted.

  The emitted infrared light is incident on the wafer 40 at an angle inclined from the normal line. The reflected light from the wafer 40 enters the MCT detector 45. The MCT detector 45 detects reflected light from the wafer 40. A detection signal from the MCT detector 45 is input to the arithmetic unit 46. The arithmetic unit 46 calculates the reflectance of the surface of the wafer 40 and obtains a dielectric function of the silicon substrate and the silicon oxide film as will be described later.

  An etching device 47 is provided on the left side of the infrared spectroscopic device 41. This etching apparatus 47 is an apparatus for etching a silicon oxide film by solution processing. The etching apparatus 47 is provided with a solution tank 48 filled with hydrofluoric acid as an etching solution. The film thickness to be etched is controlled by the concentration of the hydrofluoric acid solution, the etching temperature, and the immersion time in the solution.

  On the right side of the infrared spectroscopic device 41, a carry-in port 49 for carrying the wafer 40 is provided.

Evaluation method of the silicon oxide film Next, the evaluation method will be described using the evaluation apparatus of the silicon oxide film according to the present embodiment.

  First, the wafer 40 to be evaluated is carried into the infrared spectroscopic device 41 through the carry-in / out port 49. In the wafer 40, a silicon oxide film to be evaluated is formed on a silicon substrate. With the infrared spectroscopic device 41, the reflection spectrum of the wafer 40 is measured as it is carried in. The measurement result is stored in the arithmetic unit 46. Next, the wafer 20 is moved from the infrared spectroscopic device 41 to the etching device 47, and the silicon oxide film is etched by a predetermined thickness by the etching device 47. After the etching, the wafer 20 is moved from the etching apparatus 47 to the infrared spectroscopic apparatus 41, and the reflection spectrum of the wafer 40 is measured in a state where the silicon oxide film having a predetermined thickness is etched. The measurement result is stored in the arithmetic unit 46.

  Next, the wafer 20 is transferred again from the infrared spectroscopic device 41 to the etching device 47, and the silicon oxide film is further etched by a predetermined thickness by the etching device 47. After the etching, the wafer 20 is moved from the etching apparatus 47 to the infrared spectroscopic apparatus 41, and the reflection spectrum of the wafer 40 is measured in a state where the silicon oxide film having a predetermined thickness is further etched. The measurement result is stored in the arithmetic unit 46.

  This operation is repeated, and the reflection spectrum is measured every time the silicon oxide film having a predetermined thickness is etched, and is continued until all the silicon oxide films are finally removed. The reflection spectrum of the silicon substrate from which the silicon oxide film has been removed is also measured.

  When the above measurement is completed, a large number of data of the reflection spectra of the silicon substrate and the silicon oxide film having a different film thickness are accumulated in the accumulation arithmetic unit 46.

  Next, the dielectric function of silicon oxide films having different thicknesses is calculated using these measurement data. The calculation procedure will be described with reference to the flowchart of FIG.

  First, the dielectric function of the silicon substrate is calculated (step S101). Since high-concentration impurities were added to the silicon substrate in this example, the dielectric function of the silicon substrate was determined by the dielectric function theory based on the polarization of free electrons (Keihei Kudo, “Basics of Optical Physical Properties”). "Refer 2nd edition, see Ohm.) The induced electric field and dielectric function according to this dielectric function theory are shown below.

  The parameters in the above equation are εo (high frequency dielectric constant), ωp (plasma frequency), and ωτ (damped frequency). When the dielectric function of the silicon substrate is obtained by the above equation, the dielectric function of the silicon oxide film is subsequently calculated (step S102).

  Since the silicon oxide film is a dielectric, the dielectric function of the silicon oxide film was determined by the dielectric function theory that satisfies the Kramers-Kronig relational expression based on the polarization of the dipole. "Refer 2nd edition, see Ohm.)

  The induced electric field and dielectric function according to this dielectric function theory are shown below.

  The parameters in the above equation are εo (high frequency dielectric constant), ωo (resonance frequency), ωp (plasma frequency), ωτ (damping frequency), and σ (Gaussian distribution width). The parameters in the silicon oxide film are determined as follows.

  First, initial values of parameters of the dielectric function model are set (step S103). The initial value at this time is determined empirically, for example.

  Next, the reflectance is calculated by the Fresnel equation (step S104). In this step S104, a dielectric function serving as a base of the silicon oxide film having a thickness to be obtained at present is used.

  In the present embodiment, since the dielectric function serving as the base is obtained as an expression from which the measurement noise is removed, the reflectance calculated here is also obtained by removing the previous measurement noise.

The calculation of the reflectance of the silicon oxide film in step S104 is performed according to the following procedure (refer to Born “Optical Principles 1, 2, and 3”). First, it is assumed that a plurality of layers 102-0, 102-1,..., 102-m are stacked on the silicon substrate 100 as shown in FIG. The reflectance R is obtained from the following equation using the characteristic matrix.

  The unknowns in the above formula are the incident angle θ, the incident light wave number ν, the dielectric functions ε0, ε1,..., Εm in each layer 102-0, 102-1,. , Dm.

  In this embodiment, as the above-described unknown dielectric functions ε0, ε1,..., Εm, values calculated from the formulas of dielectric functions obtained so far are used. This value is a calculated value from the equation of the dielectric function model and does not include measurement noise. Therefore, the reflectance R is an expression that does not include the measurement noise in the background.

  Next, the reflectance calculated by the above equation is compared with the measured reflectance (step S105).

  If the calculated reflectance value does not match the measured value, the parameter value of the dielectric function model is changed (step S107), and the process returns to step S104 again. Various parameters are changed and the processes of steps S104 to S107 are repeated until the calculated reflectance value matches the measured value.

  When the calculated value of the reflectance matches the measured value, the dielectric function is determined by the parameter at that time. This dielectric function is used to calculate the reflectance of the next silicon oxide film.

  Subsequently, the process proceeds to the next etching portion (step S108), and it is determined whether there is data on the reflectance of the next silicon oxide film (step S109). If there is data, the process returns to step S102, and the processes of steps S102 to S109 are repeated.

  Although the reflectance is used in the present embodiment, the same applies even when the transmittance is used.

Example 2-1
In this example, a silicon oxide film having a thickness of 0.2 to 0.5 nm was etched by one etching using a silicon oxide film having an original thickness of 80 nm and previously etched to a thickness of about 9.5 nm. As a result, 14 sets of reflection spectrum data of silicon oxide films having different film thicknesses were obtained.

  FIG. 26 shows the dielectric function of the silicon substrate obtained by the dielectric function theory based on the polarization of free electrons in step S101 of FIG.

  In this embodiment, 14 silicon oxide film dielectric functions were obtained according to the thickness of the silicon oxide film. Of the 14 dielectric functions, the dielectric functions appropriately selected from the thinnest silicon oxide film are shown in FIGS. It can be seen that the dielectric function gradually changes as the silicon oxide film becomes thicker. This indicates that the film quality of the silicon oxide film is not uniform and varies within the film.

  FIGS. 28A to 28D show a comparison between the measured reflectance and the fitted reflectance. The reflectance was recalculated from the obtained dielectric function using the Fresnel equation. The actually measured value is indicated by a dotted line, and the fitted reflectance is indicated by a solid line. FIGS. 28A to 28D correspond to FIGS. 27A to 27D. In either case, it can be seen that the measured value and the calculated value of the reflectance are in good agreement.

  FIG. 29 shows a comparison of reflectance spectra of different portions in the silicon oxide film.

  FIG. 29A shows the reflectance spectrum (dotted line) of the silicon oxide film in the portion closest to the interface with the silicon substrate and the reflectance spectrum (solid line) of the silicon oxide film in the portion 50 nm away from the interface. It can be seen that the film quality is quite different. FIG. 29B shows the reflectance spectrum (dotted line) of the silicon oxide film at a portion 10 nm away from the interface and the reflectance spectrum (solid line) of the silicon oxide film at a portion 50 nm away from the interface. It can be seen that there is almost no change in the film quality.

  FIG. 30 shows an example of a dielectric function obtained by a conventional method. As can be seen from FIG. 29, the noise component in each measurement is superimposed on the dielectric function, and it is understood that an accurate dielectric function is not obtained.

[ Third embodiment]
A silicon oxide film evaluation method and apparatus according to a third embodiment of the present invention will be described with reference to FIG.

A silicon oxide film evaluation apparatus according to this embodiment is shown in FIG. In the center of the evaluation apparatus shown in FIG. 31, an infrared spectroscopic apparatus 41 that measures the reflection spectrum of the wafer 40 is provided. A wafer 40 to be measured is placed on a sample stage (not shown), which describes the inside of the infrared spectrometer 41. Infrared light incident from the illumination system on the right side of the moving stage is reflected by the surface of the wafer 40, and the reflected light is measured and analyzed by the measurement system on the left side.

  The illumination system on the right side of the sample stage is provided with a light source 42 that emits infrared light, and an interferometer 43 and a polarizer 44 are provided on the emission side of the light source 42. Infrared light from the light source 42 is emitted as a parallel light beam through the interferometer 43 and the polarizer 44. By providing the polarizer 44, P-wave infrared light having an electric field parallel to the incident surface or S-wave infrared light having an electric field perpendicular to the incident surface is emitted.

  The emitted infrared light is incident on the wafer 40 at an angle inclined from the normal line. The reflected light from the wafer 40 enters the MCT detector 45. The MCT detector 45 detects reflected light from the wafer 40. A detection signal from the MCT detector 45 is input to the arithmetic unit 46. The arithmetic unit 46 calculates the reflectance of the surface of the wafer 40 and obtains a dielectric function of the silicon substrate and the silicon oxide film as will be described later.

On the left side of the infrared spectroscopic device 41, a heat treatment device 50 and a solution processing device 53 are provided to form a silicon oxide film. The heat treatment apparatus 50 is for forming a silicon oxide film on the wafer 40 by heat treatment. The wafer 40 is heated by the heater 51. The solution processing apparatus 53 is for forming a silicon oxide film on the wafer 40 by solution processing. The wafer 40 is immersed in a solution tank 54 filled with an oxide film forming solution (mixed solution of nitric acid (H ₂ SO ₄ ) and hydrogen peroxide solution (H ₂ O ₂ )).

  On the right side of the infrared spectroscopic device 41, a carry-in port 49 for carrying the wafer 40 is provided. In the sixth embodiment, the reflectance was measured while etching the silicon oxide film formed on the silicon substrate in a plurality of times. However, in this embodiment, the silicon oxide film is divided into the silicon substrate in a plurality of times. The difference is that the reflectance is measured while forming. Other methods for obtaining the dielectric function are the same as those in the sixth embodiment, and thus the description thereof is omitted.

[ Fourth embodiment]
A method and apparatus for manufacturing a semiconductor device according to a fourth embodiment of the present invention will be described with reference to FIG.

  A semiconductor device manufacturing apparatus according to this embodiment is shown in FIG. In the center of the manufacturing apparatus shown in FIG. 32, an infrared spectroscopic device 41 for measuring the reflection spectrum of the wafer 40 is provided. A wafer 40 to be measured is placed on a sample stage (not shown), which describes the inside of the infrared spectrometer 41. Infrared light incident from the illumination system on the right side of the moving stage is reflected by the surface of the wafer 40, and the reflected light is measured and analyzed by the measurement system on the left side.

  The illumination system on the right side of the sample stage is provided with a light source 42 that emits infrared light, and an interferometer 43 and a polarizer 44 are provided on the emission side of the light source 42. Infrared light from the light source 42 is emitted as a parallel light beam through the interferometer 43 and the polarizer 44. By providing the polarizer 44, P-wave infrared light having an electric field parallel to the incident surface or S-wave infrared light having an electric field perpendicular to the incident surface is emitted.

  The emitted infrared light is incident on the wafer 40 at an angle inclined from the normal line. The reflected light from the wafer 40 enters the MCT detector 45. The MCT detector 45 detects reflected light from the wafer 40. A detection signal from the MCT detector 45 is input to the arithmetic unit 46. The arithmetic unit 46 calculates the reflectance of the surface of the wafer 40 and obtains a dielectric function of the silicon substrate and the silicon oxide film as will be described later.

  On the left side of the infrared spectroscopic device 41, a heat treatment device 50 for forming a silicon oxide film and a semiconductor substrate cleaning device 55 for cleaning the wafer are provided. The heat treatment apparatus 50 is for forming a silicon oxide film on the wafer 40 by heat treatment. The wafer 40 is heated by the heater 51. The semiconductor substrate cleaning device 55 is for cleaning the wafer 40 by solution processing. The wafer 40 is immersed in a solution tank 56 filled with a cleaning solution such as a hydrofluoric acid solution.

  On the right side of the infrared spectroscopic device 41, a carry-in port 49 for carrying the wafer 40 is provided. A method for manufacturing a semiconductor device according to this embodiment will be described. First, the wafer 40 is carried into the apparatus from the carry-in port 49. The semiconductor substrate cleaning device 55 removes metal, organic contamination, and natural oxide film on the wafer 40. Thereafter, after the reflection spectrum is measured by the infrared spectroscopic device 41, it is transferred to the heat treatment device 50, and a silicon oxide film is formed.

  When it is desired to evaluate the film quality during the formation of the silicon oxide film, measurement is performed by the infrared spectroscopic device 41, and the silicon oxide film is formed to a predetermined thickness. Those that do not satisfy the standard film quality at this evaluation stage are pulled out at this point and treated so that the subsequent processing steps are not wasted. Further, in a test wafer that performs strict film quality control, it is transferred to the semiconductor substrate cleaning device 55 after the oxide film is formed, the silicon oxide film is etched by a predetermined thickness, and the reflectance measurement and etching by the infrared spectrometer 41 are repeated. Thus, the oxide film structure decomposed in the film thickness direction can be evaluated.

It is a figure which shows the evaluation apparatus of the silicon substrate by the 1st reference example of this invention. It is a flowchart which shows the procedure of the evaluation method of the silicon substrate by the 1st reference example of this invention. It is a graph which shows the measurement result by the evaluation method of the silicon substrate by the 1st reference example of the present invention. It is a figure which shows the evaluation apparatus of the silicon oxide film by the 2nd reference example of this invention. It is explanatory drawing of the evaluation method of the silicon oxide film by the 2nd reference example of this invention. It is a graph which shows the measurement result by the evaluation method of the silicon oxide film by the 2nd reference example of the present invention. It is a figure which shows the evaluation apparatus of the silicon substrate by the 3rd reference example of this invention. It is explanatory drawing of the evaluation method of the silicon substrate by the 3rd reference example of this invention. It is a graph which shows the measurement result by the evaluation method of the silicon substrate by the 3rd reference example of the present invention. It is a figure which shows the manufacturing apparatus of the semiconductor device by the 4th reference example of this invention. It is a flowchart which shows the outline of the evaluation method of the silicon oxide film by the 1st Example of this invention. It is a figure (the 1) which shows the example of convergence by an iterative method. It is a figure (the 2) which shows the example of convergence by an iterative method. It is a flowchart (the 1) which shows the method of calculating | requiring the dielectric function by 1st Example of this invention. It is a flowchart (the 2) which shows the method of calculating | requiring the dielectric function by 1st Example of this invention. It is a flowchart (the 3) which shows the method of calculating | requiring the dielectric function by 1st Example of this invention. It is a flowchart (the 4) which shows the method of calculating | requiring the dielectric function by 1st Example of this invention. It is a graph which shows the dielectric function calculated | required by the 1st Example of this invention. It is a graph which shows the dielectric function calculated | required by the conventional method. It is a graph which shows the measured reflectance spectrum. It is a graph which shows the reflectance spectrum calculated using the dielectric function calculated | required by the 1st Example of this invention. It is a graph which shows the reflectance spectrum calculated using the dielectric function calculated | required by the conventional method. It is a figure which shows the evaluation apparatus of the silicon oxide film by the 2nd Example of this invention. It is a flowchart which shows the method of calculating | requiring the dielectric function by the 2nd Example of this invention. It is a figure for demonstrating the model of a silicon oxide film. It is a graph which shows the dielectric function of the silicon substrate calculated | required by the 2nd Example of this invention. It is a graph which shows the dielectric function of the silicon oxide film calculated | required by the 2nd Example of this invention. It is a graph which shows the reflectance calculated | required by the 2nd Example of this invention. It is a graph which shows the reflectance calculated | required by the 2nd Example of this invention. It is a graph which shows the dielectric function of the silicon oxide film calculated | required by the conventional method. It is a figure which shows the evaluation apparatus of the silicon oxide film by the 3rd Example of this invention. It is a figure which shows the manufacturing apparatus of the semiconductor device by the 4th Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Light source 11 ... Interferometer 12 ... Polarizer 13 ... Concave mirror 14 ... Sample moving stage 15 ... Concave mirror 16 ... MCT detector 17 ... Calculation part 18 ... Silicon substrate 19 ... Gold thin film vapor deposition substrate 20 ... Wafer 21 ... Measurement evaluation apparatus 22 ... light source 23 ... interferometer 24 ... polarizer 25 ... MCT detector 26 ... calculator 27 ... silicon oxide film forming apparatus 28 ... solution tank 29 ... silicon layer film forming apparatus 30 ... loading port 40 ... wafer 41 ... infrared spectroscopy Apparatus 42 ... Light source 43 ... Interferometer 44 ... Polarizer 45 ... MCT detector 46 ... Arithmetic apparatus 47 ... Etching apparatus 48 ... Solution tank 49 ... Loading / unloading port 50 ... Heat treatment apparatus 51 ... Heater 53 ... Solution processing apparatus 54 ... Solution tank 55 ... Semiconductor substrate cleaning device 56 ... Solution tank

Claims (8)

In the silicon oxide film evaluation method for evaluating the film quality of the silicon oxide film formed on the silicon substrate,
A plurality of etching steps for etching the silicon oxide film formed on the silicon substrate in a plurality of times while controlling the film thickness; and
A plurality of measurement steps for measuring the reflectance or transmittance of the silicon oxide film during the plurality of etching steps;
A calculation step of calculating a plurality of dielectric functions of the silicon oxide film after the plurality of etching steps based on the plurality of reflectances or transmittances measured by the plurality of measurement steps;
A method for evaluating a silicon oxide film, wherein the film quality of the silicon oxide film is evaluated based on the plurality of dielectric functions. In the silicon oxide film evaluation method for evaluating the film quality of the silicon oxide film formed on the silicon substrate,
A plurality of forming steps for forming the silicon oxide film in a plurality of times while controlling the film thickness on the silicon substrate,
A plurality of measuring steps for measuring reflectance or transmittance of the silicon oxide film during the plurality of forming steps;
A calculation step of calculating a plurality of dielectric functions of the silicon oxide film after the plurality of formation steps based on the plurality of reflectances or transmittances measured by the plurality of measurement steps;
A method for evaluating a silicon oxide film, wherein the film quality of the silicon oxide film is evaluated based on the plurality of dielectric functions. In the evaluation method of the silicon oxide film according to claim 1 or 2,
A reference substrate having a metal surface is irradiated with a plurality of incident light incident under a plurality of conditions, and reflected light of the reference substrate with respect to the plurality of incident lights is measured, and the plurality of the plurality of incident light is measured with respect to the silicon substrate. Irradiating a plurality of incident light incident under the conditions of the above, measuring the reflected light of the silicon substrate with respect to the plurality of incident light, respectively, based on the reflected light of the reference substrate and the reflected light of the silicon substrate, And calculating a dielectric function of the silicon substrate by calculating a dielectric function of the silicon substrate based on the reflectance under the plurality of conditions. ,
The method for evaluating a silicon oxide film, wherein the calculating step calculates a plurality of dielectric functions for the silicon oxide film using a dielectric function of the silicon substrate. In the evaluation method of the silicon oxide film according to claim 1 or 2,
A silicon substrate model in which the dielectric function of the silicon substrate is determined by a dielectric function theory based on the polarization of free electrons is set up,
A reference substrate having a metal surface is irradiated with a plurality of incident light incident under a plurality of conditions, and reflected light of the reference substrate with respect to the plurality of incident lights is measured, and the plurality of the plurality of incident light is measured with respect to the silicon substrate. Irradiating a plurality of incident light incident under the conditions of the above, measuring the reflected light of the silicon substrate with respect to the plurality of incident light, respectively, based on the reflected light of the reference substrate and the reflected light of the silicon substrate, A step of obtaining the reflectance of the silicon substrate by calculating the reflectance of the silicon substrate under the conditions of
A method for evaluating a silicon oxide film, comprising: obtaining a dielectric function of the silicon substrate conforming to the silicon substrate model based on a reflectance of the silicon substrate. In the evaluation method of the silicon oxide film according to claim 1 or 2,
A silicon oxide film model in which the dielectric function of the silicon oxide film is determined by a dielectric function theory that satisfies the Kramers-Kronig relational expression based on the polarization of the dipole,
A method for evaluating a silicon oxide film, comprising: obtaining a plurality of dielectric functions of the silicon oxide film conforming to the silicon oxide film model based on a plurality of reflectances or transmittances of the silicon oxide film. In the silicon oxide film evaluation method according to claim 5,
The method for evaluating a silicon oxide film, wherein the dielectric function theory is a Gaussian model. In the silicon oxide film evaluation method according to claim 1,
A method for evaluating a silicon oxide film, wherein the thickness of the silicon oxide film etched by each etching step or the thickness of the silicon oxide film formed by each forming step is 50 nm or less.   A method for manufacturing a semiconductor device, comprising a step of evaluating a silicon oxide film using the evaluation method according to claim 1.

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