JP4084817B2 - Film thickness measuring method and film thickness measuring apparatus - Google Patents

Description

  The present invention relates to a film thickness measuring method and a film thickness measuring apparatus. For example, when a thin film is applied on a flat plate in a manufacturing process such as a liquid crystal display device, the film thickness distribution of the applied thin film of 1000 nm or less is applied. The present invention also relates to a film thickness measuring method and a film thickness measuring apparatus characterized by a configuration for obtaining with high accuracy with a simple apparatus configuration.

  In the manufacturing process of a liquid crystal display device or the like, a number of thin film forming processes such as a photoresist coating process or an antireflection film forming process are required. In such a thin film forming process, a thin film film is required. It is necessary to make the thickness uniform. In particular, as the liquid crystal panel becomes larger, further in-plane uniformity is required to increase the production yield.

  Conventionally, as a method for measuring the film thickness of such a thin film in a non-contact manner, there are known a type using a change in polarization due to interference and a method using a change in spectral reflectance due to interference (for example, see Patent Document 1). It has been.

Among these, the film thickness meter using the spectral reflectance, when white light is reflected by a thin film, provides a spectral reflectance whose reflection intensity varies depending on the wavelength due to interference.
The film thickness and optical constant can be measured by fitting with a waveform obtained by measuring this with a spectroscope or by maximal / minimal analysis.

  However, many of the methods using the wavelength spectral characteristic of interference light and the reflection angle-reflection intensity characteristic are the method of measuring the inside of the substrate for each point, and it is not possible to collectively measure the film thickness uniformity over the entire surface of the substrate in the production line. could not.

  Therefore, one of the present inventors photographed the entire surface of the substrate on the production line with an area sensor, so that the relationship between the maximum value and the minimum value of the intensity of the reflected light and the viewing angle using the optical interference film thickness measurement method. Since a method for measuring the film thickness distribution in the substrate surface by using it has been proposed (see, for example, Patent Document 2), a method based on this proposal will be described with reference to FIGS.

FIG. 12 is a conceptual configuration diagram of a conventional film thickness measuring apparatus, which includes a surface light source 51 and an imaging lens 53 and receives only randomly polarized reflected light having a predetermined wavelength via a filter 54. An area sensor type color CCD camera 52, a measurement panel 55 on which a thin film to be measured is formed, a stage 56 for horizontally mounting and holding the measurement panel 55, and a rail 57 for guiding the stage 56 in a uniaxial direction. .
Note that when a monochromatic light source is used as the surface light source 51, the filter 54 is unnecessary.

FIG. 13 is a graph showing the relationship between the reflection angle and the reflection intensity when the film thickness is 1000 nm, 2000 nm, and 3000 nm. The number and position of peaks and valleys fluctuate with respect to the change in film thickness. Recognize.
In this film thickness measurement method, in order to increase the processing speed, the film thickness is acquired by acquiring the angle of the peak / valley from the acquired data and comparing it with the angle described in the table.
JP 2004-066951 A JP 2004-279296 A

  However, it is necessary to have a film thickness of 1 μm (= 1000 nm) or more so that peaks and valleys begin to appear clearly due to the relationship between reflection angle and reflection intensity. There is a problem that it becomes difficult.

  Therefore, an object of the present invention is to measure the film thickness of a thin film of 1 μm or less with high accuracy and high throughput using the optical interference film thickness measurement method without significantly changing the apparatus configuration.

FIG. 1 is an explanatory diagram of the measurement principle of the present invention. Here, means for solving the problems in the present invention will be described with reference to FIG.
Refer to FIG. 1 (1) In order to achieve the above-mentioned object, the present invention is a film thickness measuring method in which a film 3 having a thickness of 200 nm or less provided with irradiation light from a light source 1 on a substrate 2 as a measurement object. The reflected light caused to interfere with the film 3 is transmitted through the stage moving direction and the optical axis direction by the light receiving means 8 while changing the incident angle of the irradiation light with respect to the main surface of the film 3. the reflection intensity of the transmitted P polarized light deflection filter set axis is measured, and acquires the thickness of the film 3 from the reflection angle taking the minimum value in the intensity variation of the measured reflected light.

As a result of intensive studies by the present inventors, by measuring the angle at which the reflectance of P-polarized light is minimized in the vicinity of the Brewster angle, the basic principle of the conventional optical interference film thickness measurement method can be changed randomly. It has been found that it becomes possible to detect a film thickness of 1 μm or less , particularly 200 nm or less, which was impossible when using polarized light.

That is, the reflection angle takes a minimum value in the intensity variation of the reflected light, since it has a film thickness dependency in 1μm following thickness as shown in FIG. 5, the reflection angle assumes a minimum value - thickness relationship From this, the film thickness can be obtained.
In addition, since the angle with respect to the transmission axis of the polarizing filter 7 changes with reflection positions of reflected light, S-polarized light is inevitably mixed.

  (2) Further, in the above (1), the present invention limits the spectral width of one of the irradiated light or incident light with a wavelength filter, adjusts the relationship between the minimum value and the film thickness in the intensity fluctuation of the reflected light, and measures It is characterized in that the measurement sensitivity at the time of film thickness measurement can be changed by adjusting the resolution.

  In this way, by using the wavelength filter at the time of measurement and limiting the spectrum of the light source 1 on either the light source side or the light receiving side, the relationship between the angle to be detected and the film thickness can be changed. Measurements can be made.

  (3) Further, according to the present invention, in the above (1) or (2), the object to be measured has a reflectance of 4% or less of the transmitted light due to the irradiated light on the back surface side, and the in-plane uniformity of the reflectance is 3 %, The reflection intensity is measured in a state of being placed on the stage 6 via the sample placement member 4 within%.

  In this way, the reflectance of P-polarized light is very low, and most of the light is transmitted when P-polarized light is used. Therefore, the color characteristics of the stage 6 occur on the conventional stage surface, but the back side is affected by the irradiated light. By using the sample mounting member 4 having a reflectance of transmitted light of 4% or less and an in-plane uniformity of reflectance of 3% or less, the back surface reflection is greatly reduced, and the amount of reflected light is minimized. The angle can be easily measured, and the film thickness measurement accuracy can be improved.

(4) Moreover, this invention is a film thickness measuring apparatus. WHEREIN: The light source 1 which irradiates the film 3 with a thickness of 200 nm or less provided on the substrate 2 as the measurement object, and the measurement object are placed and moved. stage 6, the light receiving unit 8 for receiving the reflected light caused interference from coating 3, the transmission axis of P-polarized light in the plane formed direction of the stage movement direction and the optical axis provided on at least one of the light receiving means 8 or the light source 1 setting the polarization filter 7, the film thickness preset the minimum value in fluctuation of the received light intensity of P-polarized light - in that it comprises at least a comparator means for determining the thickness as compared to the reflection angle minimum value characteristic coat 3 Features.

  By providing each of these components, it is possible to measure thin films that were previously difficult to measure without significantly changing the device configuration, thereby reducing the cost and increasing the display quality of large image display devices. The place that contributes to the realization

The polarizing filter 7 for obtaining P-polarized light may be provided on the light receiving means 8 side, may be provided on the light source 1 side, or may be provided on both.
However, from the viewpoint of downsizing or cost reduction of the apparatus configuration, it is desirable to provide the polarizing filter 7 on the light receiving element side.

  In particular, when an area sensor type image sensor such as a CCD camera is used as the light receiving means 8, a large-area image can be acquired at a time, so that measurement can be performed easily and at high speed. Since a special measuring instrument such as a spectroscope is not required, the apparatus configuration can be simplified.

  (5) Further, the present invention includes the wavelength filter for limiting the spectral width of one of the light source 1 or the light receiving means 8 in the above (4), and changing the limited spectral width to change the intensity of reflected light. And an adjustment mechanism for adjusting the measurement resolution by adjusting the relationship between the minimum value and the film thickness.

  As described above, when the spectrum of the light source 1 is limited on either the light source side or the light receiving side using the wavelength filter at the time of measurement, the angle to be detected is provided by the adjustment mechanism that makes the limitation of the spectrum width variable. The film thickness relationship can be changed, and measurement can be performed with an arbitrary relationship.

  (6) Further, in the above (4) or (5), the present invention places the measurement object, the back side has a reflectance of 4% or less with respect to the irradiated light, and the in-plane uniformity of the reflectance. The sample mounting member 4 within 3% is placed on the stage 6.

  In this way, in order to eliminate the back reflection of P-polarized light, the sample mounting provided with the light absorbing member 5 having a reflectance of 4% or less and an in-plane uniformity of the reflectance of 3% or less on the back surface side. By using the mounting member 4, the measurement accuracy can be improved without complicating the apparatus configuration.

  According to the present invention, it is possible to measure a thin film that has been difficult to measure conventionally without changing the basic principle of the conventional optical interference film thickness measuring method and without significantly changing the apparatus configuration. Therefore, it is possible to reduce the cost and improve the display quality of a large-sized image display device or the like.

Here, with reference to FIG. 2 thru | or FIG. 9, the film thickness measuring method of embodiment of this invention is demonstrated.
FIG. 2 is a conceptual configuration diagram of a film thickness measuring apparatus used in the embodiment of the present invention, and shows a sample 11 to be measured and a sample 11 to be measured which are formed of a substrate 12 on which a thin film 13 to be measured is formed. A sample mounting table 14 for horizontally mounting and holding, a stage 17 for mounting and holding the sample mounting table 14 horizontally, a rail 18 for moving the stage 17 in a uniaxial direction, and a surface light source 19 for irradiating the thin film 13 with measurement light. An area sensor type camera 20 provided with an imaging lens 21 and a polarizing filter 22 having a light transmission axis set in a surface direction formed by the stage moving direction and the optical axis.

The sample mounting table 14 is composed of a glass substrate 15 whose back surface is roughened and covered with a black material 16 having a reflectance of 4% or less for measurement light.
It is desirable that the in-plane uniformity of reflectance is within 3%.

  Further, the stage 17 is moved stepwise by a motor (not shown) in accordance with the imaging timing of the camera 20, particularly, at a moving distance corresponding to the expected angle of one pixel of the camera 20.

In addition, the camera 20 is set at a height of H _c from the surface of the sample mounting table 14 at an angle θ _c with respect to the normal line of the sample mounting table 14, and the stage 17 is moved at a predetermined pitch and photographed with the camera each time. To do.

See Figure 3
See FIG. 3. Next, the camera 31 and the distortion caused by projection are removed from the measurement data, and numbers 1, 2,... In vertical pixel rows 32 (1, 2,..., N−1, n rows) corresponding to the moving pitch on 31 stages, the same pixel row 32 has a luminance at the same reflection angle. Therefore, the continuous viewing angle image 33 is created by performing image composition by cutting out each pixel row 32 and arranging only the pixel rows 32 in which the sample 11 to be measured is photographed in the order of photographing.

  Next, angle conversion is performed by arranging the gradation values of the pixels 34 at a specific point from the created continuous viewing angle image 33 to obtain a reflection angle-reflected light intensity characteristic.

See Figure 4
FIG. 4 is an explanatory diagram of the principle of interference, and a wavelength of λ is applied to a sample in which a film 42 having a complex refractive index of N and a thickness of d [nm] is deposited on a substrate 41 having a complex refractive index of N _m . The reflection characteristics when P and S polarized light are incident at an incident angle θ ₀ are described by the Fresnel equation.
Here, in order to simplify the calculation formula, the intensity of incident light is normalized to 1.

Here, assuming that the refraction angle of P and S polarized light entering the coating 42 is θ, the refraction angle of light entering the substrate 41 is θ _m , and the refractive index of air, that is, the incident medium is n ₀ , P, The Fresnel coefficients ρ _0p and ρ _{0s at} the air / film interface of S-polarized light and the Fresnel coefficients ρ _1p and ρ _{1s at the} film interface are
ρ _0p = (n ₀ / cos θ ₀ −N / cos θ) / (n ₀ / cos θ ₀ + N / cos θ) (1)
ρ _1p = (N / cos θ−N _m / cos θ _m ) / (N / cos θ + N _m / cos θ _m )
(2)
ρ _0s = (n ₀ × cos θ ₀ −N × cos θ) / (n ₀ × cos θ ₀ + N × cos θ) (3)
ρ _1s = (N × cos θ−N _m × cos θ _m ) / (N × cos θ + N _m × cos θ _m )
(4)
It is represented by

Then, the reflectances R _p (λ, θ) and R _s (λ, θ) are Δ = (2π / λ) Nd cos θ ₀ ,
R _p = | ρ _p | ² = | [ρ _0p + ρ _1p exp (−i2Δ)] / [1 + ρ _0p ρ _1p exp (−i2Δ)] | ² (5)
R _s = | ρ _s | ² = | [ρ _0s + ρ _1s exp (−i2Δ)] / [1 + ρ _0s ρ _1s exp (−i2Δ)] | ² (6)
It is represented by

Here, assuming that the spectral characteristic of the light source is I (λ), the total reflectance R _all (θ) including each wavelength component at the reflection angle θ of the incident light from the light source is
R _all (θ) = ∫I (λ) R (λ, θ) dλ (λ: λ _min → λ _max ) (7)
As described above, it is possible to describe by adding together the wavelength intensity and reflection intensity of the light source.

Actually, since a positional change occurs with respect to the polarization axis, S-polarized light is mixed into the light receiving element except for light on the surface where the traveling axis of the stage and the optical axis of the camera intersect. End up.
In this case, the mixing ratio of S-polarized light and P-polarized light is determined from the positional relationship between the measurement point and the optical axis center of the camera.

That is, when the measurement point changes in the Y-axis direction, the angle deviation δ with respect to the polarization axis can be calculated from the positional relationship between the measurement point and the optical axis center of the camera.
The angle-reflection characteristic can be obtained by calculating the angle deviation with respect to the reflectance of the P-polarized light and the S-polarized light calculated by the above formulas (5) and (6).

Specifically, if the angle formed by the incident angle θ and the xy plane at the optical axis center is φ, and the inclination of the optical axis of the camera is γ, the P polarization axis is the transmission axis, so the deviation from the P polarization axis. δ is
δ = cos ⁻¹ (cos γ × cos θ × cos φ + sin γ × sin θ) (8)

Since the P-polarized light and the S-polarized light are mixed at a ratio of R _p / cos δ and R _s / sin δ, respectively, with respect to the deviation δ with respect to the P polarization axis,
R _all (θ) = ∫I (λ) [R _p (λ, θ) / cos δ + R _s (λ, θ) / sin δ] dλ (λ: λ _min → λ _max ) (9)
It becomes.

Further, when the angle characteristic due to various factors such as the tilt of the light source and the peripheral light reduction of the camera is C (θ), the measurement data D (θ) is
D (θ) = C (θ) · R _all (θ) (10)
The characteristics can be described as follows.

In this case, the angle characteristic C (θ) is determined by measuring a substrate whose angle characteristic is known to obtain the angle characteristic, and obtaining a difference between the acquired angle characteristic and the original angle characteristic to determine C (θ).
For example, R _all (θ) is obtained by simulating the angle characteristics at the time of obtaining P-polarized light of a silicon substrate whose angular characteristics are known, and measurement data D (θ) measured on the silicon substrate is divided by R _all (θ). As a result, C (θ) is obtained.

By removing the angle characteristic C (θ) from the image acquired from the sample to be measured using the C (θ) acquired in this way, an accurate minimum angle can be acquired.
Alternatively, the simulation data R _all (θ) multiplied by the characteristic of C (θ) may be directly compared with the actual measurement data D (θ).

Even in the case of a multilayer film, the thickness of the first layer can be measured if the underlying material is uniform.
In this case, a table may be created by measuring an actually measured sample with a constant background, or when the film thickness is determined, the film thickness table is calculated using a simulation using the Fresnel coefficient. You may create it.

See Figure 5
FIG. 5 shows, for example, that the refractive indexes n ₀ , N, and N _m for light having a wavelength of 545 nm are n ₀ = 1, N = 1.7265, and N _m = 1.5414, respectively, and the extinction coefficient is 0, respectively. The relationship between the reflection angle and the reflection intensity with respect to the change in film thickness simulated using P-polarized light is shown as the relationship between the minimum value with respect to the change in film thickness. The angle that becomes the minimum moves.

See FIG.
FIG. 6 is a graph showing the correlation between the change in film thickness and the angle at which the minimum value is obtained, and is a graph showing the relationship between the film thickness and the valley position detected in FIG. The angle taken gradually increases and reaches a local maximum around 90 nm.
By making this correlation into a database, the film thickness can be obtained from the angle at which the measured reflection intensity takes a minimum value.

  When creating a table by simulation, create an accurate table by using the spectral characteristics of the light source and Fresnel coefficients, and correcting the simulation data using the data obtained in advance for the camera and light source angle characteristics. To do.

If the optical constant is unknown and only the film thickness is known, the angle characteristic is actually measured and a database using actual measurement data is created.
An example of the database is shown in FIG.
See FIG.

  However, since most of the light is transmitted due to the use of P-polarized light, the color characteristics of the stage are generated and the polarization state is changed on the conventional stage surface. Since the back surface is removed and the angle at which the amount of reflected light is minimized can be easily measured by placing it on the sample mounting table 14 having a black ground glass so that the back surface is eliminated, this situation will be described with reference to FIG.

FIG. 8 is an explanatory diagram of the reflection / transmittance-reflection angle characteristics. Here, the reflection / transmittance / reflection angle characteristics of the S-polarized light and the P-polarized light having a thickness of 100 nm are shown. ing.
As can be seen from the figure, with S-polarized light, the reflectance always increases and the transmittance decreases as the angle changes.
On the other hand, it can be seen that there is an angle at which the reflectance is close to 0 in the P-polarized light, but conversely, it can be confirmed that light is almost transmitted at that point.

FIG. 9 is an explanatory diagram of the stage surface dependence of the intensity of reflected light of P-polarized light, and since most of the light escapes from the back surface near the angle where the wave of P-polarized light is minimized, it is shown in the figure. In this way, the angle at which the minimum value is taken varies greatly depending on the brightness and color tone of the substrate on which the substrate is installed.

  Therefore, when measuring a thin film on a glass substrate, it is easy to eliminate the back surface reflection and obtain the minimum angle by using a glass substrate made of ground glass with a black back surface on the stage as the sample mounting table 14. I understand that

See FIG. 10. FIG. 10 is an explanatory diagram showing the relationship between the film thickness and the minimum value when light having a spectral band limited by the combination of the fluorescent tube and the RGB filter of the camera is used.
As is apparent from the figure, the relationship between the film thickness and the angle changes in each limited region, and it can be seen that the spectrum of light used for measurement can be changed.

Based on the above, a specific embodiment will be described with reference to FIG.
FIG. 11 is a flowchart of the film thickness measurement process of Example 1 of the present invention.
First, as the first step,
A. Get an image.
In the image acquisition step, the film thickness measuring apparatus shown in FIG. 2 is used, but as the surface light source 19, a fluorescent lamp, for example, a light source color EX-N (three-wavelength emission daylight white fluorescent lamp according to JIS standard) is used. The light acquired by the spectral characteristics of the camera is filtered so that the band of the light source is equal to the state limited to 460 to 610 nm, and the size is set to 800 mm square so that regular reflection can be obtained over the entire measurement area. To do.

Moreover, the glass substrate 15 which comprises this sample mounting base 14 uses the ground glass of the roughness in which the surface of a back surface can fully scatter light.
Moreover, the black material 16 provided on the back surface of the glass substrate 15 is created by spraying and painting black acrylic resin on the back surface.

The camera 20 is installed at a height of H _c = 430 mm from the surface of the sample mounting table 14 at an angle of θ _c = 48 ° with respect to the normal of the sample mounting table 14, and the angle of view of the imaging lens is set to 40. By setting the angle, the data of the reflection angle in the range of 28 ° to 68 ° is acquired.

  Further, if the size of the sample 11 to be measured is 3300 mm × 4400 mm, the stage 17 is set at a measurement limit, that is, a measurement start point, at a position 1064.287 mm (= 430 mm × tan 68 °) from the position directly below the camera 20. For example, a trigger signal is output each time the camera is rotated 1058 at a pitch of 1.31 mm, and the camera takes a picture.

  The acquired image is transferred to the image processing apparatus, and this process is repeated until it passes through the measurement area, that is, until the rear end of the sample 11 to be measured passes through an angle of 28 °, thereby completing the image acquisition process. .

Then
B. Perform image conversion.
In this image conversion step, the distortion of the camera is removed by dividing the measured image D (θ) by the angle characteristic C (θ) described above, and then flat correction is performed to remove the distortion caused by the projection, and then from the corrected image. Only a pixel row corresponding to 1.31 mm on the stage is extracted, rearranged according to the relationship between the angle and the position, and a continuous viewing angle image that can acquire the angle change is synthesized.

Then
C. Perform valley detection.
In this valley detection step, the reflection angle-reflected light intensity characteristic of the image at a specific point, that is, the reflection angle-gradation characteristic, is obtained from the continuous viewing angle image, and this characteristic is differentiated with respect to the angle θ to obtain a step. The extreme value of the tone is obtained, and the reflection angle at which the local minimum value is obtained is taken out.

Finally,
D. Perform film thickness conversion.
In this film thickness conversion step, the film thickness corresponding to the angle at which the angle difference is the smallest is calculated as the film thickness value by comparing the reflection angle, which is the minimum value obtained by valley detection, with a previously created table. This process is completed for all the points in the image, and the film thickness is calculated.

  In the present invention, the transmission axis of the polarizing filter is provided in the direction of the incident surface in the moving direction, and the reflection angle dependence of the reflection intensity of the light that has passed through the transmission axis is used. Can be measured with an accuracy of about ± 3%.

Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations described in the embodiments, and various modifications can be made.
For example, although a 3CCD type color area sensor is used as the light receiving device in the above embodiment, a color area sensor using a single CCD may be used.
Further, the system is not limited to the CCD system, and a CMOS type or MOS type area sensor may be used.

  In addition, the camera tilt angle, the installation height H, and the viewing angle for capturing images set in the above embodiment are merely examples, and can be appropriately changed according to the resolution of the camera used and the numerical aperture of the lens used. Needless to say.

  Further, in the description of the above embodiment, the stage is moved stepwise when acquiring the continuous viewing angle image, but the movement of the stage is not limited to the stepwise movement, and the stage is continuously moved. Each time a distance corresponding to one pixel of the imaging pixel is moved while moving, a trigger signal may be generated to capture an image.

  In the above embodiment, black acrylic resin is used as the black material for coating the back surface of the ground glass having a roughened back surface. However, a Cr film or a Cr oxide film is used, and coating is performed by plating or sputtering. It is good.

In addition, when glass is used as the substrate for the sample mounting table, black coating is possible, and black dye or black pigment may be mixed with the glass itself to form black glass. In short, reflectivity with respect to the wavelength used for measurement. Is 4% or less.
In particular, it is desirable that the in-plane uniformity of the reflectance is within 3%.

  Moreover, the base material of a sample mounting base is not restricted to glass, You may use the plastic plate coated black and the metal plate coated black.

  Furthermore, the black coating may be formed by black Cr plating on the surface of the stage itself by a functional plating method or by black dyeing of black anodized Cu without using a material mounting table.

  In addition, it is possible to obtain not only the film thickness but also optical constants such as refractive index and absorption coefficient by fitting the fluctuation waveform obtained by actual measurement and the theoretically obtained reflection angle-reflection intensity curve, The optimum method should be selected according to the calculation time and measurement purpose.

  In the above-described embodiments, the method for obtaining the film thickness of the transparent electrode in the flat panel display is described. However, the method is not limited to the transparent electrode, and the film thickness of various metal films, organic films, or inorganic films. It is only necessary to be transparent or semi-transparent to the wavelength of the light source. For example, it is provided on the light exit surface of the light guide plate in the sidelight type backlight or the sidelight type frontlight. The present invention is also applied to a process for forming an antireflection film.

  In the above embodiment, the polarizing filter is provided on the light receiving device side. However, if the size of the sample to be measured is relatively small, it may be provided on the sample to be measured side. In order to further reduce noise, it may be provided on both the measured sample side and the light receiving device side.

  As a practical example of the present invention, the film thickness measurement of each coating film in the manufacturing process of a large liquid crystal panel is typical, but it is not limited to a large liquid crystal panel, but various sizes of liquid crystal panels and organic EL It is also applied to a film forming process in an electronic device such as a plasma display panel and a semiconductor device, and further applied to a general process of applying a thin film on a plate-like body. Is applied to all film forming processes for forming a thin film of micron to submicron order on a flat substrate.

It is explanatory drawing of the measurement principle of this invention. It is a notional block diagram of the film thickness measuring apparatus used for embodiment of this invention. It is explanatory drawing of the procedure of image composition and angle conversion. It is explanatory drawing of the principle of interference. It is explanatory drawing of the film thickness dependence of a reflection angle-reflection intensity characteristic. It is explanatory drawing of the correlation of the angle which takes a film thickness change and local minimum. It is an example of a database. It is explanatory drawing of a reflectance and transmittance | permeability-reflection angle characteristic. It is explanatory drawing of the stage surface dependence of the reflected light intensity of P polarized light. It is explanatory drawing of the spectral band dependence of the correlation of the angle which takes a minimum value with a film thickness change. It is a flowchart of the film thickness measurement process of Example 1 of this invention. It is a notional block diagram of the conventional film thickness measuring apparatus. It is a reflection angle-reflection intensity characteristic view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Substrate 3 Coating 4 Sample mounting member 5 Light absorption member 6 Stage 7 Polarizing filter 8 Light receiving means 11 Sample to be measured 12 Substrate 13 Thin film 14 Sample mounting table 15 Glass substrate 16 Black material 17 Stage 18 Rail 19 Surface light source 20 Camera 21 Imaging Lens 22 Polarizing Filter 31 Image 32 Pixel Row 33 Continuous Viewing Angle Image 34 Pixel 41 Substrate 42 Coating 43 Stage 51 Surface Light Source 52 Color CCD Camera 53 Imaging Lens 54 Filter 55 Measurement Panel 56 Stage 57 Rail

Claims (6)

Irradiation light from a light source is incident on a coating having a thickness of 200 nm or less provided on a substrate that is a measurement object, and reflected light that causes interference from the coating is incident on the main surface of the coating. the light receiving means while changing the angle, the reflection intensity of the moving direction of the stage and the P-polarized light which a polarizing filter is transmitted through provided on the plane formed direction of the optical axis the transmission axis of the light is measured, the intensity variation of the reflected light the measurement A film thickness measuring method, comprising: obtaining a film thickness of the film from a reflection angle at which a minimum value is taken. By limiting the spectral width of one of the irradiation light or incident light with a wavelength filter, the relationship between the minimum value and the film thickness in the intensity fluctuation of the reflected light is adjusted, the measurement resolution is adjusted, and the measurement sensitivity during film thickness measurement is increased. The film thickness measuring method according to claim 1, wherein the thickness can be changed. A state where the measurement object is placed on the stage via a sample placement member whose back side has a reflectance of transmitted light by the irradiation light of 4% or less and an in-plane uniformity of the reflectance of 3% or less. The film thickness measuring method according to claim 1, wherein the reflection intensity is measured by the method. A light source for irradiating a film having a thickness of 200 nm or less provided on a substrate as a measurement object, a stage on which the measurement object is placed and moved, and a light receiving means for receiving reflected light causing interference from the film , the light receiving means or polarizing filter having a transmission axis of P-polarized light in the plane formed direction of the stage movement direction and the optical axis provided on at least one of the light source, preset a minimum value of variations in the received light intensity of the P-polarized light A film thickness measuring apparatus comprising at least comparing means for determining the film thickness of the coating film in comparison with the film thickness-reflection angle minimum value characteristic. A wavelength filter for limiting the spectral width of one of the light source or the light receiving means is provided, and the measurement resolution is adjusted by adjusting the relationship between the minimum value and the film thickness in the intensity fluctuation of the reflected light by making the spectral width limit variable. 5. The film thickness measuring apparatus according to claim 4, further comprising an adjusting mechanism for adjusting the thickness. The measurement object is placed, and the sample placement member whose back side has a reflectance of 4% or less with respect to the irradiation light and whose in-plane uniformity of the reflectance is within 3% is placed on the stage. The film thickness measuring apparatus according to claim 4 or 5, characterized by the above.

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