JP2001116518A - Method and instrument for measuring film thickness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an instrument for film thickness measurement which can measure the thickness of even a film with distinctive absorption and reflection spectra by using a light interferometer. SOLUTION: This is a method for irradiating a light-transmissive or light- translucent film with light and measuring the thickness by making use of interference caused by an optical path difference correlating to the film thickness. The film to be measured which causes interference when transmitting light is irradiated with the light to find the 1st waveform of the spectrum of the luminous flux interferring after being transmitted and a film as an object of comparison which causes not interference when transmitting the light and is made of the same material with the film to be measured is irradiated with light to find the 2nd waveform of the spectrum of luminous flux having no interference after being transmitted; and the correction spectrum found by operating the 1st waveform and 2nd waveform is used to measure the film thickness and this film thickness measuring instrument uses this film thickness measuring method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film thickness measuring method and a film thickness measuring apparatus utilizing light interference, which can be applied to the measurement of the film thickness of a film having light absorption and scattering.

[0002]

2. Description of the Related Art Conventionally, various methods and apparatuses for measuring a film thickness have been devised. Among them, in the light-transmitting film, non-destructive, non-contact measurement is also possible in the film thickness measurement method and film thickness measurement device using light interference,
Widely used. The method of measuring the film thickness using optical interference is in principle as follows.

When continuous wavelength light is applied to a film, a light beam transmitted through the film, reflected on the bottom surface and returned to the surface, and a light beam reflected on the film surface cause interference. The film thickness is determined by measuring the spectrum of the interference and analyzing the peak position of the interference.

However, the film thickness measuring method and the film thickness measuring apparatus using such light interference are generally applied only to a substantially light-transmitting film.
The present invention can be applied only to a film whose light absorption / reflection spectrum is nearly uniform regardless of the wavelength, or a film whose light absorption / reflectance flat portion covers a considerable wavelength range.

On the other hand, many light-transmitting colored films have a characteristic absorption / reflection spectrum, so that even if the interference of light is measured, the interference wave is reflected in the absorption / reflection spectrum of the light of the film itself. As a result, the peak position of the unevenness of the interference cannot be determined.

Therefore, the above-described conventional method and apparatus for measuring film thickness using optical interference cannot measure the thickness of a translucent film having a characteristic absorption / reflection spectrum.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its object is to
It is an object of the present invention to provide a film thickness measuring method and a film thickness measuring apparatus which enable a film thickness measurement using light interference even for a film having a colored and characteristic absorption / reflection spectrum.

[0008]

The above object is achieved by the present invention described below. That is, the present invention provides a method of <1> irradiating a light-transmitting or light-semi-transmissive film with light and measuring the film thickness using interference generated by an optical path difference correlated with the film thickness. Irradiate light to the film to be measured that causes interference when transmitting light,
A first waveform of a spectral spectrum of a light beam that has caused interference after transmission is obtained. Further, a light is transmitted to a film of the same material as the film to be measured which does not cause interference when light is transmitted. To obtain a second waveform of a spectral spectrum of a light beam that does not include interference after transmission, and the first waveform
A film thickness measuring method characterized in that a film thickness is measured using a corrected spectral spectrum obtained by calculating the second waveform and the second waveform.

<2> The film thickness measuring method according to <1>, wherein the operation is an operation of subtracting the second waveform from the first waveform.

<3> The film thickness measuring method according to <1> or <2>, wherein the film to be compared is formed on the surface of a substrate that scatters light. The surface of the film to be compared may be roughened so as to scatter light, or the light may be scattered on both the substrate surface and the film surface to be compared. May be done.

<4> For a film of the same type as the film to be measured, the relationship between the actual film thickness and a specific peak or a specific valley position of the corrected spectral spectrum is obtained in advance by calculation, and The film thickness measuring method according to any one of <1> to <3>, wherein the actual film thickness is estimated from a first waveform of the spectrum.

<5> A film thickness measuring apparatus using the film thickness measuring method according to any one of <1> to <4>, wherein a light irradiating means for irradiating a film to be measured with light. Detecting means for detecting a light beam that has caused interference after transmission through the film; and obtaining a first waveform of a spectral spectrum of the light beam based on a signal from the detecting means, and calculating a first waveform of the corrected spectral spectrum. And a analyzing unit that performs the measurement.

According to the present invention, the absorption and absorption of the film itself to be measured
By removing as much as possible the spectral spectrum of the luminous flux that does not include interference from the luminous flux spectrum of the interference wave affected by the reflection spectrum, the influence of the absorption / reflection spectrum of the film itself to be measured is reduced. The uneven peak due to interference can be easily observed, and the film thickness can be measured using the peak. Therefore, according to the present invention, it is possible to measure the film thickness using light interference even for a film having a characteristic absorption / reflection spectrum which is colored.

In the present invention, "no interference occurs when light is transmitted" or "luminous flux not containing interference"
In this case, it does not refer to a state in which no light interference is observed, and it is possible to make it easier to observe the uneven peak due to the interference from the first waveform of the spectral spectrum obtained from the film to be measured. As described above, there is no problem as long as the second waveform of the spectral spectrum for comparison and comparison can be obtained, and more specifically, the interference may be smaller than that of the film to be measured.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The present invention is a method of irradiating a light-transmitting or light-semi-transmitting film with light, and measuring the film thickness using interference generated by an optical path difference correlated to the film thickness, wherein the light is transmitted. Irradiate light to the film to be measured, which causes interference at the time,
A first waveform of a spectral spectrum of a light beam that has caused interference after transmission is obtained. Further, a light is transmitted to a film of the same material as the film to be measured which does not cause interference when light is transmitted. To obtain a second waveform of a spectral spectrum of a light beam that does not include interference after transmission, and the first waveform
A film thickness measuring method characterized in that a film thickness is measured using a corrected spectral spectrum obtained by calculating the second waveform, and a film thickness measuring apparatus using the same. First, a method of obtaining the first waveform will be described.

FIG. 1 is a diagram showing a method of measuring a film thickness according to the present invention.
FIG. 3 is a schematic configuration diagram for explaining a method of measuring the first waveform. In the figure, 100 is a film to be measured (a film to be measured), 102 is a base, 104 is a light source (light irradiation means), 1
06 is light emitted from the light source 104, 108 is light 10
6 is reflected by the substrate 102 after passing through the film to be measured 100, and is again transmitted through the film to be measured 100 (hereinafter, referred to as a light flux).
It is referred to as “membrane-permeated specularly reflected light flux”. ), 110 are light 106
Is a light beam reflected on the surface of the film to be measured 100 (hereinafter, referred to as a “film surface regular reflection light beam”), and 112 is a spectrometer (detection unit).

That is, the film to be measured 100 is
Is irradiated with the light 106, the light 106
And the light reflected by the surface of the film 100 to be measured. When the light 106 that has entered the film to be measured 100 reaches the substrate 102, it is specularly reflected here, passes through the film to be measured 100 again, and is detected by the spectrometer 112 as a film-penetrated light beam 108. On the other hand, the light reflected on the surface of the film to be measured 100 is directly detected by the spectrometer 112 as a regular reflection light beam 110 on the film surface.

The film-penetrated specularly reflected light beam 108 and the film surface specularly reflected light beam 110 interfere with each other due to an optical path difference, and the interference is detected by a spectrometer 112 and further analyzed to measure the film thickness. However, the film-penetrated specularly reflected light beam 108 is a light beam that is affected by the absorption / reflection spectrum of light of the film itself inside the film 100 to be measured. On the other hand, the film surface regular reflection light flux 1
Reference numeral 10 denotes a light beam on the surface of the film 100 to be measured, which is affected by the absorption / reflection spectrum of light of the film itself.

The interference between light beams affected by the absorption / reflection spectrum of the light makes it difficult to identify the interference due to the presence of noise due to the influence. That is, when the detection data obtained by the spectrometer 112 is graphed, the unevenness of the peak cannot be clearly discriminated, and it has been difficult to measure the film thickness using the interference. As described above, the first waveform is obtained by irradiating the film to be measured 100 with the light 106 in a normal state and graphing the detection data of the reflected light flux.

Next, a method for obtaining the second waveform will be described. FIG. 2 is a schematic configuration diagram for explaining a method of measuring the second waveform in the film thickness measuring method of the present invention. In the figure, reference numeral 200 denotes a film to be measured (a film to be compared); 202, a substrate having a surface that scatters light;
, A light source (light irradiation means); 206, light emitted from the light source 204; and 212, a spectrometer (detection means). The film to be measured 200 is a film of the same material as the film to be measured 100 in FIG. 1 and its surface is roughened, and it is particularly preferable that the film thickness is the same.

As in the case of measuring the first waveform,
When the light 206 irradiates the film to be measured 200 from the light source 204, the light 206 is split into light that enters the film to be measured 200 and light that reflects on the surface of the film to be measured 200. However, when the light that has entered the film to be measured 200 reaches the base 202,
Here, only a part of the irregularly reflected light flux (hereinafter, referred to as “membrane-penetrated diffusely reflected light flux”) 208 that is diffusely reflected is included in the spectrometer 21.
2 is detected. On the other hand, the light reflected on the surface of the film to be measured 100 is irregularly reflected on the surface of the film to be measured 200, and only a part of the irregularly reflected light beam (hereinafter, referred to as “film surface irregularly reflected light beam”) 210 is detected by the spectrometer 212. You.

Therefore, the diffusely reflected light beam 208 permeating through the membrane is
The film surface irregularly reflected light beam 210 is, in particular, the film penetration diffusely reflected light beam 2
From the intensity of 08, no interference occurs or only slight interference occurs between them, and when the detection data by the spectrometer 212 is graphed, the resulting waveform does not include the interference. It is due to. As described above, by roughening the surface of the base 202, the second waveform, which is the spectrum of the light beam that does not include interference, is obtained.

From the first and second waveforms obtained as described above, a predetermined operation is performed to obtain a spectral spectrum having irregularities, thereby obtaining a film thickness. The predetermined operation is, for example, as follows.

In FIG. 1, light 106 is applied to a film 100 to be measured.
It is assumed that the light is incident and reflected perpendicularly to. Also,
Assuming that the optical thickness of the film to be measured 100 does not depend on the wavelength λ of light, the length is set to d. The speed of light in the air is c, and the time is t. Furthermore, assuming that the spectral intensity of the film surface regular reflection light beam 110 is R (λ) and the film penetration regular reflection light beam 108 is spectral intensity T (λ), the combined light beam at the position of the spectrometer 112 is

[0025]

(Equation 1)

Can be expressed as follows. By transforming this equation, (α
Is a variable that does not include t),

[0027]

(Equation 2)

## EQU1 ## Here, the coefficient term that does not include t is the amplitude of the composite wave,

[0029]

(Equation 3)

Is the spectral intensity measured by the spectrometer 112. Further transforming this,

[0031]

(Equation 4)

If R (λ) and T (λ) can be measured independently,

[0033]

(Equation 5)

Thus, the optical thickness d of the film to be measured 100 can be obtained. In brief, from the first waveform of the spectral spectrum of the luminous flux that has caused the interference, which is affected by the absorption / reflection spectrum of the film to be measured 100 itself, the second waveform of the spectral spectrum of the luminous flux that does not include the interference is I'll subtract. Here, the operation of subtraction means subtracting the intensity at each wavelength of the second waveform graph from the intensity at each wavelength of the first waveform graph.

As described above, from the first waveform and the second waveform, a film of the same type as the film to be measured is determined in advance.
The relationship between the actual film thickness and a specific peak or a specific valley position of the corrected spectral spectrum is obtained in advance by calculation, and the first waveform of the spectral spectrum of the film to be measured later is used to calculate the relationship between the actual film thickness and the film to be measured. The actual film thickness can be estimated.

In the present invention, the light interference device used for obtaining the first waveform and the second waveform includes a light source capable of irradiating light of a continuous wavelength as described above, and a light source of the light from the light source. As long as a spectrometer (detector) capable of detecting the reflected light is provided, various types can be used. The wavelength of the light source is not limited, but is mainly used from ultraviolet light to infrared light.

As the interference form in the first waveform, various forms can be considered as long as the optical path difference is interference between lights related to the film thickness. However, generally, the film to be measured 100 is arranged in contact with the smooth substrate 102 as shown in FIG. 1, and part of the light 106 irradiated from above the film to be measured 100 enters the film, and the film to be measured 100 Specularly reflected light flux 1 that is specularly reflected at the interface between
08, and the interference light of the film surface regular reflection light beam 110 in which a part of the light 106 irradiated from above the measurement target film 100 is specularly reflected on the surface of the measurement target film 100 is observed.

In order to determine the second waveform, the film to be compared which does not cause interference when light is transmitted is not the film itself which causes interference, but the film itself is the object to be measured. It is the same as the membrane. The membrane to be compared is
Specifically, for example, like the film to be measured 200 shown in FIG. 2, the surface is not smooth (roughened), but is arranged on the surface of the substrate 202 that irregularly reflects light, and the light irradiated from above the film to be measured 200. A part of the light 206 enters the film and is diffusely reflected at the interface between the film 200 to be measured and the substrate 202, and as a result, the diffused light flux 208 and the diffused light 210 on the film surface are diffused.
Any film may be used as long as it does not easily cause interference with the film.

The roughened surface capable of irregular reflection as described above specifically has a center line average roughness Ra of:
0.05 μm or more, preferably 0.1 to 10
More preferably, it is in the range of 0 μm. The center line average roughness Ra can be measured according to JIS R1600.

In addition, waveforms for comparison can be obtained by forming a film on a glass plate and collecting its transmission spectrum, or by forming a sufficiently thick film to cut off reflection due to incoming light and collecting only the reflected light spectrum. May be used alone or in combination as the second waveform in the first calculation.

As the film to be measured, any material can be used as long as it can transmit and semi-transmit light in a certain wavelength band. Also, for example, crystals and non-crystals of inorganic materials, such as metals, metal compounds, non-metal elements, non-metal compounds, and oxides thereof, and polymers, oligomers, monomolecular aggregates, carbon aggregates, complex compounds, and pigments Crystals and other substances, such as crystalline and non-crystalline substances of organic materials, alone or compatible, dispersed,
Films composited in various forms, such as lamination, can be applied as the film to be measured.

In particular, the film thickness measuring method and the film thickness measuring apparatus of the present invention can be used to measure light in a certain specific range where it is difficult to measure the film thickness by a general method and a film thickness measuring apparatus using optical interference. It is effective to apply to a material system that absorbs or scatters a wavelength and has a small flat part of the light absorption / reflection spectrum. Many of such substance systems are colored, and there are both single substance systems and composite substance systems. Composite materials include those obtained by adding a small amount of impurities to a metal oxide or glass to form a color, and those obtained by dispersing a dye or pigment in glass or an organic polymer.

The pigments include inorganic pigments and organic pigments. The latter has various colors, has a complicated absorption / reflection spectrum, and has few flat portions. Therefore, it is effective to apply the film thickness measuring method and the film thickness measuring device of the present invention. There are various compounds in organic pigments, but metal or metal-free phthalocyanine pigments; azo pigments such as bisazo pigments and trisazo pigments; squarium compounds; azulenium compounds; perylene pigments; indigo pigments; A cyanine dye; a xanthene dye;

There are various types of films using these organic pigments. Among them, various types of optical filters, charge generation layers of organic electrophotographic photosensitive members, and the like are required to have high film thickness accuracy. It is effective to apply the invention and simply measure the film thickness without contact. In particular, the charge generation layer of the electrophotographic photoreceptor greatly changes the photoreceptor sensitivity depending on its thickness, and therefore, it is important to control and evaluate the thickness.

Organic photoconductors are often used in recent electrophotographic systems, and the same applies to laser beam printers that have become widespread in recent years. Since they use a semiconductor laser as a light source, a photosensitive member having sensitivity to red to infrared light is used. For this purpose, dyes and pigments having the above-mentioned wavelength sensitivity are used in the charge generation layer, and phthalocyanine pigments are one of them.

Next, a method of measuring the film thickness by actually applying the film thickness measuring method of the present invention will be described with reference to specific examples. In this specific example, gallium phthalocyanine chloride was used as the charge generation material of the organic electrophotographic photoreceptor, and after forming charge generation layers having different thicknesses, the correlation between this film thickness and the film thickness measurement according to the present invention was examined. .

Gallium phthalocyanine chloride was used as a charge generation material for an organic electrophotographic photosensitive member. A mixture comprising 15 parts by weight of gallium chloride phthalocyanine, 10 parts by weight of a vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nippon Unicar) and 300 parts by weight of n-butyl alcohol was dispersed in a sand mill for 4 hours. The obtained dispersion was used as a coating liquid for forming a charge generation layer. Apply the coating solution for 30
It was dip-coated on the surface of a mirror-cut aluminum pipe (substrate) having a diameter of 300 mm and a length of 300 mm, and air-dried. The lifting speed of the aluminum pipe during the dip coating was 10
0 mm / min. , 150 mm / min. , 200mm
/ Min. , 250 mm / min. , 300mm / mi
n. , And 350 mm / min. As six types of
Six types of samples having different charge generation layer thicknesses were produced.

The same coating solution as that for forming the charge generation layer was roughened by sandblasting (center line average roughness Ra = 0.2 μm) to a length of 30 mmφ and a length of 30 mm.
On the surface of a 0 mm ED tube aluminum pipe (substrate),
By dip coating under the same conditions as above, six types of comparative samples were prepared.

For each of these samples, a relative reflection spectrum of the formed charge generation layer (film) was collected by using a spectrometry system manufactured by Otsuka Electronics Co., Ltd. using each substrate as a reference. That is, the relative reflection spectrum was obtained by dividing the reflection spectrum of each sample having the charge generation layer formed on the substrate surface by the reflection spectrum of the substrate alone. Light irradiation and spectroscopy were simultaneously performed on the film vertically from above through an optical fiber. The measurement was performed at 12 points for one film, and the average value thereof was defined as a relative reflection spectrum.

The charge generation layer formed on the surface of the mirror-cut aluminum pipe was partially removed with a cotton swab impregnated with n-butyl alcohol, and the step caused by the removal was measured with a stylus thickness gauge. did. This operation was performed five times for one charge generation layer, and the average value was defined as the actual film thickness under each condition (each pulling speed of the aluminum pipe at the time of dip coating).

FIG. 3 is a graph showing a relative reflection spectrum (first waveform) of the charge generation layer formed on the surface of the mirror-polished aluminum pipe (however, for simplification of the graph, there are six types of film thickness). Of these, three types are represented.) Since the unevenness of the spectrum changes depending on the film thickness, it can be seen that interference appears. However, the interference is hidden by a large change in reflectance at 400 to 600 nm due to the absorption characteristics of the pigment included in the charge generation layer. Is not clear.

FIG. 4 is a graph showing the relative reflection spectrum (second waveform) of the charge generation layer formed on the surface of the sample for comparison (however, as in FIG. 3, three types of film thicknesses are represented). Is displayed.) Although the intensity changes depending on the film thickness, the shape does not substantially change, indicating that the spectrum contains almost no interference.

FIG. 5 shows the first waveform shown in FIG.
9 is a graph showing a corrected spectral spectrum after the operation obtained by subtracting the second waveform shown in FIG. That is, from the relative reflection spectrum (first waveform) of the charge generation layer formed on the mirror-polished aluminum pipe surface, the relative reflection spectrum (second waveform) of the charge generation layer formed on the surface of the sample for comparison was obtained. It is subtracted. By observing the corrected spectral spectrum shown in FIG. 5, irregularities due to interference can be clearly confirmed, and when focusing on a specific peak (convex) or a specific valley (concave), the wavelength position shifts with the change in film thickness. You can see that it is doing.

Table 1 shows the relationship between the wavelength position of a specific peak or a specific valley of the corrected spectral spectrum after the calculation in FIG. 5 and the actual film thickness at each coating speed (FIG. 5). Table 1 below also includes the numerical values of the film thickness omitted in (1).)

[0055]

[Table 1]

FIG. 6 is a graph plotting the relationship between the wavelength position of a specific peak (convex) or a specific valley (concave) and the actual film thickness based on Table 1 above. FIG.
In the charge generation layer of the same material whose actual film thickness is unknown, the actual film thickness can be estimated from the uneven position wavelength of the corrected spectral spectrum after calculation by using the graph shown in FIG.

FIG. 7 is a schematic configuration diagram (block diagram) showing an example of the film thickness measuring device 720 of the present invention. The film thickness measuring device 720 includes a light source (light irradiating unit) 704 for irradiating the target film 700 to be measured with light 706 and a sensor for detecting a light flux 714 that causes interference after transmitting through the target film 700. (Detection means) 1 and Sensor (detection means) 1
And the analysis unit 3 that calculates the first waveform of the spectral spectrum of the light flux 714 from the corrected spectral spectrum. The operation of the film thickness measuring device 720 will be described.

When light 706 is emitted from the light source 704,
A part of the light 706 is reflected on the surface of the film 700 to be measured, and a part of the light 706 enters the film 700 to be measured, passes therethrough, and
2, the light is specularly reflected on the surface and emerges again in the air, and
A light beam 714 that interferes with the light reflected on the 00 surface. The light beam 714 is detected by the sensor 1, and the signal is input to the input unit 2.

When the signal is input to the input unit 2, the analysis unit 3 is started by a personal computer or the like. The analysis unit 3 reads a memory such as a calculation formula obtained in advance from a past case from the database 4 and appropriately processes a signal from the input unit 2. Then, the obtained result is output by the output unit 5 such as a monitor or a printing machine, and the measurement of the thickness of the film 700 is completed.

In the database 4, for example, for a film of the same type as the film 700 to be measured, the relationship between the actual film thickness and a specific peak or a specific valley position of the corrected spectral spectrum is obtained in advance by calculation. Enter it. Such a relationship includes, for example, a correlation obtained from FIG. 5 and Table 1. Then, the analysis unit 3 that has read the information on the relationship from the database 4 performs necessary arithmetic processing, and calculates the film thickness in accordance with the correlation.

As described above, according to the film thickness measuring apparatus of the present invention, for a film of the same type as the film to be measured, the actual film thickness and the specific peak or the specific valley position of the corrected spectral spectrum are determined. If the relationship is obtained in advance by calculation, the thickness of the film can be measured simply and easily without contacting another member whose thickness is unknown.

[0062]

As described above, the film thickness measuring method and the film thickness measuring apparatus of the present invention irradiate a light transmitting or semi-transmitting film with light, and generate light caused by an optical path difference correlated to the film thickness. Even though the film thickness is measured using interference, the spectrum of the luminous flux without interference can be calculated from the spectrum of the luminous flux of the interference wave affected by the absorption / reflection spectrum of the film itself to be measured. By removing as much as possible, the influence of the absorption / reflection spectrum of the film itself to be measured is reduced, and it is possible to easily observe uneven peaks due to interference. The film thickness can be measured. Therefore, even for a film having a characteristic absorption / reflection spectrum that is colored, the film thickness can be measured using light interference.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram for explaining a method of measuring a first waveform in a film thickness measuring method of the present invention.

FIG. 2 is a schematic configuration diagram for explaining a method of measuring a second waveform in the film thickness measuring method of the present invention.

FIG. 3 is a relative reflection spectrum (first waveform) of a charge generation layer formed on the surface of a mirror-cut aluminum pipe.

FIG. 4 is a graph showing a relative reflection spectrum (second waveform) of a charge generation layer formed on the surface of a comparative sample.

FIG. 5 is a graph showing the first waveform shown in FIG. 3 and the second waveform shown in FIG. 4;
5 is a graph showing a corrected spectral spectrum after the calculation, in which the waveform of FIG.

6 is a graph in which the relationship between the wavelength position of a specific peak (convex) or a specific valley (concave) and the actual film thickness in the corrected spectral spectrum of the graph of FIG. 5 is plotted.

FIG. 7 is a schematic configuration diagram (block diagram) showing an example of a film thickness measuring device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor 2 Input part 3 Analysis part 4 Database 5 Output part 100, 200, 700 Measurable film 102, 202, 702 Substrate 104, 204, 704 Light source 106, 206, 706 Light 108 Membrane penetration regular reflection light beam 110 Film surface regular reflection Light flux 112, 212 Spectrometer 208 Membrane permeation diffusely reflected light 210 Membrane surface diffusely reflected light 714 Light flux 720 Film thickness measuring device

Claims (5)

[Claims] 1. A method of irradiating a light-transmitting or semi-transmitting film with light and measuring the film thickness using interference caused by an optical path difference correlated with the film thickness. The film to be measured, which causes interference when the light is transmitted, is irradiated with light, and the first waveform of the spectral spectrum of the light beam that has caused the interference after transmission is obtained. Further, no interference occurs when the light is transmitted. Irradiating light to a film to be compared with the same material as the film to be measured to obtain a second waveform of a spectral spectrum of a light beam that does not include interference after transmission, and the first waveform, A film thickness measuring method, wherein the film thickness is measured using a corrected spectral spectrum obtained by calculating the second waveform and the second waveform. 2. The method according to claim 1, wherein the operation is an operation of subtracting the second waveform from the first waveform. 3. The method according to claim 1, wherein the film to be compared is formed on the surface of a substrate that scatters light. 4. A film of the same type as a film to be measured,
The relationship between the actual film thickness and the specific peak or specific valley position of the corrected spectral spectrum is obtained in advance by calculation, and the actual film thickness is estimated from the first waveform of the spectral spectrum of the film to be measured. The method for measuring a film thickness according to claim 1, wherein: 5. A film thickness measuring apparatus using the film thickness measuring method according to claim 1, wherein a light irradiating means for irradiating a film to be measured with light, Detecting means for detecting a light beam that has caused interference after transmission through the film; and an analyzing unit for obtaining a first waveform of the spectral spectrum of the light beam based on a signal from the detecting means and calculating the first waveform from a corrected spectral spectrum which has been obtained in advance. And a film thickness measuring device comprising: