JPH11344314A - Film thickness measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film thickness measuring device capable of measuring the thickness of a thin film on a substrate during the production process of indication element and the like. SOLUTION: A light radiation means 3 radiating light to a thin film 2 on a substrate 1, an observation wavelength forming means 7 forming an observation wavelength from the light having passed the thin film 2, a light intensity detection means 6 detecting the light intensity of a specific wavelength formed by the observation wavelength forming means 7, and a film thickness detection means 9 detecting the film thickness of the thin film based on the light intensity detected by the light intensity detection means 6 are provided. Light is cast on the thin film 2 on the substrate 1 with the light radiation means 3, a specific observation wavelength only is selected from the light having passed the thin film 2 with the observation wavelength forming means 7, the light intensity of the specific wavelength is detected with the light intensity detection means 6 and based on the light intensity, the film thickness of the thin film is detected with the film thickness detection means 9.

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 device for measuring the thickness of a thin film formed on a transparent substrate or a reflective substrate used for a display element or the like, and more particularly to a method for manufacturing a display element or the like. The present invention relates to a film thickness measuring device capable of measuring the thickness of a thin film.

[0002]

2. Description of the Related Art In recent years, flat display devices such as a liquid crystal display device, a plasma display, and electroluminescence have been proposed in place of a deep cathode ray tube because of their advantages such as thinness and light weight, low power consumption, and high visibility. Therefore, it is becoming widely accepted in the market.

[0003] In these flat display elements, a process of forming a thin film having a uniform thickness on a transparent substrate is commonly included. For direct connection, it is important to manage and control the thickness of the thin film.

For example, in a liquid crystal display device, an alignment film for controlling the alignment of liquid crystal molecules is formed on a transparent substrate in accordance with an applied voltage. The degree of the voltage drop generated in the alignment film changes, and an appropriate voltage is not applied to the liquid crystal layer, so that the electro-optical characteristics change. In addition, when the partial thickness unevenness of the alignment film is on the same transparent substrate, the applied voltage to the liquid crystal molecules partially changes, which causes display unevenness.

As described above, the control of the film thickness of the thin film on the substrate has an important meaning. Conventionally, the measurement of the film thickness has been performed by a stylus type film thickness measuring device.

This stylus-type film thickness measuring apparatus moves a stylus along the surface of a thin film and mechanically, electrically or optically reads the vertical movement of the stylus at a portion where the film thickness changes. In this way, the film thickness is measured.

[0007]

However, in the above-mentioned stylus-type film thickness measuring apparatus, it is difficult to measure in the manufacturing process of forming a film on a transparent substrate, and once the transparent substrate is removed from the manufacturing process. Otherwise, the film thickness could not be measured, and in-line automated measurement on the production line was not possible.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a film thickness measuring apparatus capable of measuring the film thickness of a thin film on a substrate during a process of manufacturing a display element or the like, overcoming the above-mentioned problems in the conventional device. And

[0009]

According to a first aspect of the present invention, there is provided a film thickness measuring apparatus for irradiating a thin film on a substrate with light, and a light irradiating means for irradiating the thin film on the substrate. Observation wavelength forming means for forming an observation wavelength from the reflected light;
A point having light intensity detecting means for detecting the light intensity of the specific wavelength formed by the observation wavelength forming means, and film thickness detecting means for detecting the film thickness of the thin film based on the light intensity detected by the light intensity detecting means. is there. By adopting such a configuration, the light irradiation means irradiates the thin film on the substrate with light, and only the specific observation wavelength is selected by the observation wavelength forming means from the light passing through the thin film. Is detected by the light intensity detecting means, and the thickness of the thin film can be detected by the film thickness detecting means based on the light intensity.

A feature of the film thickness measuring apparatus of the present invention according to claims 2 and 3 is that the observation wavelength forming means is constituted by a band-pass filter or a spectroscope. By adopting such a configuration, a band-pass filter or a spectroscope can be used as the observation wavelength forming means as necessary.

According to a fourth aspect of the present invention, there is provided a film thickness measuring apparatus according to the present invention, wherein the substrate is a transparent substrate, and the light irradiated on the thin film from the light irradiating means passes through the transparent substrate and is captured by the observation wavelength forming means. It is in a point. By adopting such a configuration, light having passed through the thin film and having a certain degree of luminous intensity absorbed by the thin film passes through the transparent substrate and is captured by the observation wavelength forming means.

According to a fifth aspect of the present invention, there is provided a film thickness measuring apparatus according to the present invention, wherein the substrate is a reflective substrate, and the light irradiated on the thin film from the light irradiating means is reflected on the surface of the reflective substrate to be transmitted to the observation wavelength forming means. At the point of being captured. By adopting such a configuration, light that has passed through the thin film and has absorbed a certain amount of luminous intensity into the thin film is reflected on the surface of the reflective substrate, passes through the thin film again, and is further absorbed by the luminous intensity. After passing through, it is captured by the observation wavelength forming means.

A feature of the film thickness measuring device according to the present invention according to claims 6 and 7 is that light is visible light or ultraviolet light. By adopting such a configuration, visible light or ultraviolet light can be used as light for measuring the thickness of the thin film, if necessary.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, in a film thickness measuring apparatus of the present invention, a thin film absorbs ultraviolet light or visible light because electrons in the ground state of molecules of the thin film have light energy (E = hν).
It is caused by absorbing and transiting to an excited state. The intensity of the absorption depends on the wavelength, and the absorption spectrum is peculiar to the substance. The strength of the absorption is proportional to the concentration or thickness of the substance, as is known by Lambert-Beer's law. That is, A: absorbance,
When K is the extinction coefficient and d is the thickness, A = K · d.

The film thickness measuring apparatus of the present invention is to project ultraviolet light or visible light onto a thin film formed on a transparent substrate or a reflective substrate and measure the film thickness. The thin film to be measured is mainly formed of an organic compound such as a liquid crystal alignment film, a color filter, a color filter protective film, an insulating film, and has a sufficiently large electron transition intensity in the ultraviolet / visible region, and the substrate has a measurement wavelength. If the light in the region can be transmitted or reflected, the thickness of various thin films can be measured.

Most of the liquid crystal alignment film is formed of a polyimide-based aromatic polymer.
It has relatively strong absorption in the region of ~ 300 nm. When measuring the film thickness of the dry membrane before imidization, the characteristic absorption of the polymer, for example, after confirming the absorption peak possessed by an aromatic ring, etc., using a calibration curve, the film thickness Can be measured.

The thickness of the thin film to be measured may be as thin as possible as long as it has the sensitivity of the measurement, but basically has a property that greatly depends on the absorption intensity of the thin film material.
The lower limit is about nm and the upper limit is about 100 μm, preferably about 10 nm to 10 μm. That is, the film thickness is 5n.
If the thickness is smaller than 100 m, sufficient accuracy cannot be obtained.
Thicker is opaque at the measurement wavelength. However, in the case where the film is thick and opaque, it may be possible to cope with it by changing the measurement wavelength. In this case, a wavelength having a relatively small intensity among the characteristic absorptions may be selected.

The transparent substrate that can be used in the present invention includes:
Soda lime, borosilicate glass, low alkali glass,
Examples include those made of alkali-free glass, quartz, polyethylene phthalate, and polycarbonate, and examples of the reflective substrate include those made of metal such as aluminum.

Next, the thickness of the thin film formed on the transparent substrate or the reflective substrate can be measured at an arbitrary position on the substrate, but it is preferable to keep the measurement position on the substrate constant. The area of the thin film to be measured is usually about 1 to 1000 mm ² , preferably 100 to 1000 mm ^2.
It is about 300 mm ² .

Further, in order to avoid the influence of the absorption of the substrate itself, a region having the same area where no thin film of the same substrate is present is measured as a control, and the film thickness is calculated from the difference in absorbance from the region where the film thickness is measured. Is preferably employed. To calculate the film thickness, another method that can measure the absolute value, for example,
It is necessary to obtain a calibration curve by the stylus method or the like.

The measurement of the in-plane film thickness distribution can also be performed in the same manner as described above in principle, by moving the measurement light.
Alternatively, it becomes possible by moving the substrate on the XY stage.

FIG. 1 shows a first embodiment of a film thickness measuring apparatus of the present invention for measuring the film thickness of a thin film according to the above-described principle.

In FIG. 1, a thin film 2 is formed on a transparent substrate 1, and a deuterium lamp 3 as a light irradiation means for irradiating the transparent substrate 1 with light is arranged near the transparent substrate 1. I have. The wavelength of this deuterium lamp 3 is 190-
The deuterium lamp 3 is covered with a cover (not shown) so that the light from the deuterium lamp 3 is emitted in a direction away from the transparent substrate 1. The deuterium lamp 3 is replaced with 350 to 250
A tungsten lamp having a wavelength of 0 nm may be used.

In the vicinity of the deuterium lamp 3, a pair of reflecting mirrors 4A and 4B for regulating light from the deuterium lamp 3 in a direction perpendicular to the surface of the transparent substrate 1 is provided. . Among these, one reflecting mirror 4A is for forming light transmitted through the transparent substrate 1 in the portion where the thin film 2 is formed, and the other reflecting mirror 4B is for transmitting light in the portion where the thin film 2 is not formed. It forms light that passes through the substrate 1. A plate-shaped chopper 5 for supplying light to the transparent substrate 1 at a predetermined timing is interposed between each of the reflecting mirrors 4A and 4B and the transparent substrate 1.

Further, a luminous intensity detector 6 as luminous intensity detecting means for detecting the luminous intensity of the light passing through the transparent substrate 1 is provided on the opposite side of the deuterium lamp 3 with respect to the transparent substrate 1. In the vicinity of the light intensity detector 6, a band-pass filter 7 as observation wavelength forming means for limiting light incident on the light intensity detector 6 to only a specific wavelength is provided. As the light intensity detector 6, a photomultiplier tube or a photodiode can be used. The pass wavelength width of the band pass filter 7 is 1 nm to 20 nm.
The order of nm is appropriate.

On the other hand, the other ones which reflect the two kinds of light passing through the transparent substrate 1 toward the band-pass filter 7 respectively.
A pair of reflecting mirrors 8A and 8B are disposed at positions facing one of the reflecting mirrors 4A and 4B, respectively.

The light intensity detector 6 is provided with a film thickness detector 9 as a film thickness detecting means for calculating and detecting the film thickness of the thin film 2 from the light intensity of the light detected by the light intensity detector 6. Connected.

The operation of the embodiment having the above-described configuration will be described.

A thin film 2 is partially formed on a transparent substrate 1 in advance.
Is formed, the portion of the transparent substrate 1 where the thin film 2 is formed is located between the two reflecting mirrors 4A and 8A, and the portion of the transparent substrate 1 where the thin film 2 is not formed is the two reflecting mirrors 4B and 4B. 8B.

In such a state, the deuterium lamp 3
Is turned on, and the light from the deuterium lamp 3 is reflected by each of the reflecting mirrors 4A, 4A.
Irradiate the transparent substrate 1 for a certain time via B and the chopper 5. At this time, light reflected by the reflecting mirror 4A passes through the thin film 2 formed on the transparent substrate 1 and then passes through the transparent substrate 1, whereas light reflected by the reflecting mirror 4B passes directly through the transparent substrate 1. I do. Then, the light passing through the thin film 2 and the transparent substrate 1 absorbs more luminous intensity than the light passing only through the transparent substrate 1. After that, each light is reflected by one of the reflecting mirrors 8A and 8B, passes through the band-pass filter 7, and only the wavelength in a specific band is selected and input to the light intensity detector 6.

When two types of light are input to the light intensity detector 6, the light intensity of each light is detected by the light intensity detector 6, and the light intensity of these two lights is input to the film thickness detector 9. By calculating both luminous intensities, the thickness of the thin film 2 is calculated.

According to such a film thickness measuring apparatus of the present embodiment, the light from the deuterium lamp 3 is passed through the transparent substrate 1 on which the thin film 2 is formed, and then the light intensity is passed through the band-pass filter 7. Since the light is input to the detector 6 and the light intensity detector 6 and the film thickness detector 9 measure the film thickness of the thin film 2, for example, in a production line of a liquid crystal display element, the thickness of a thin film such as an alignment film can be easily reduced. Can be measured.

FIG. 2 shows a second embodiment of the film thickness measuring apparatus according to the present invention. In this embodiment, the light transmitted through the thin film 2 on the transparent substrate 1 and the transparent substrate 1 is transmitted to the transparent substrate 1. Two types of light, that is, light that has passed only through the substrate 1, are provided with a time difference and individually input to the luminous intensity detector 6 to detect the thickness of the thin film 2. Only the configuration of the second embodiment that is different from that of the first embodiment will be described.

In the vicinity of the deuterium lamp 1, there is provided a shielding plate 10 having a small hole 11 for passing the light of the deuterium lamp 1 toward the transparent substrate 1. This shielding plate 10
A convex lens 12 is provided between the transparent substrate 1 and the transparent substrate 1 so that light from the small holes 11 is converged in the vicinity of the transparent substrate 1. Further, another convex lens 13 that once converges and converges the expanded light again is provided on the transparent substrate 1.
And a spectroscope 14 as observation wavelength forming means to which the light converged by the convex lens 13 is input. As the spectroscope 14, a diffraction grating, a prism, a monochromator, or the like is used.

According to the film thickness measuring apparatus of the second embodiment having the above-described configuration, the portions of the transparent substrate 1 where the thin film 2 is formed and the portions where the thin film 2 is not formed are sequentially placed on the biconvex lenses 12 and 13. The difference between the absorbance of the thin film 2 and the transparent substrate 1 and the difference of the absorbance of the transparent substrate 1 alone can be detected, and the thickness of the thin film 2 can be detected from the difference in absorbance.

Next, a specific embodiment of the film thickness measuring apparatus of the present invention will be described.

[0037]

EXAMPLE 1 An alignment film liquid SE-2170 (manufactured by Nissan Chemical Industries, Ltd.) was printed on a 0.7 mm thick soda glass transparent substrate in a pattern shown in FIG. The resultant was dried at 100 ° C. for 10 minutes and baked at 2OO ° C. for 30 minutes to form an alignment film 2 as a thin film. In this transparent substrate 1, a control site without the alignment film 2 is indicated by G, and a site where the thickness of the alignment film 2 was measured is indicated by S. Three samples of this transparent substrate 1 (S-1, S
Table 1 shows the absorbance as a result (FIG. 4) obtained by using an ultraviolet-visible-near-infrared spectrophotometer V-550 (manufactured by JASCO) for the absorption spectrum of (−2, S-3).

[0038] As shown in Table 1, the absorbance of each sample was substantially proportional to the absolute value of the film thickness obtained by the stylus method, and it was confirmed that the film thickness could be measured with sufficient accuracy for practical use.

Example 2 On a transparent substrate 1 made of borosilicate glass having a thickness of 0.4 mm, an alignment film liquid A-2504 (manufactured by Chisso Corporation) was applied.
In the same manner as above, printing was performed while changing the solid concentration,
And dried at 270 ° C. for 15 minutes to obtain a thin alignment film 2
Was formed. Three samples of this transparent substrate 1 (A-
The results of measuring the absorption spectra of (1, A-2, A-3) in the same manner as in Example 1 are shown in Table 2.

[0040] As shown in Table 2, the absorbance of each sample was substantially proportional to the absolute value obtained by the stylus method, and it was confirmed that measurement was possible with sufficient accuracy for practical use.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made as needed. For example, the present invention is not limited to the measurement of the thickness of a thin film on a transparent substrate described in the embodiment,
It is of course possible to measure the thickness of the thin film on the reflective substrate.

[0042]

As described above, according to the film thickness measuring apparatus of the present invention, it is possible to measure the film thickness of a thin film on a substrate during a process of manufacturing a display element or the like.

That is, the film thickness measuring apparatus of the present invention according to claim 1 comprises: a light irradiation means for irradiating a thin film on a substrate with light;
Observation wavelength forming means for forming an observation wavelength from the light passing through the thin film, light intensity detection means for detecting the light intensity of a specific wavelength formed by the observation wavelength formation means, and based on the light intensity detected by the light intensity detection means And a film thickness detecting means for detecting the film thickness of the thin film. Only, and the luminous intensity of this specific wavelength is detected by the luminous intensity detecting means,
The thickness of the thin film can be easily detected by the thickness detecting means based on the luminous intensity, and the thickness can be measured during the manufacturing process.

In the film thickness measuring apparatus according to the second and third aspects of the present invention, the observation wavelength forming means is constituted by a band-pass filter or a spectroscope. A pass filter or a spectroscope can be used.

The film thickness measuring apparatus of the present invention according to claim 4 is
The substrate is a transparent substrate, and the light emitted from the light irradiating means to the thin film passes through the transparent substrate and is captured by the observation wavelength forming means. After passing through the substrate, it is captured by the observation wavelength forming means, so that the thickness of the thin film on the transparent substrate can be measured.

According to a fifth aspect of the present invention, there is provided a film thickness measuring apparatus according to the present invention, wherein the substrate is a reflective substrate, and the light applied to the thin film from the light irradiating means is reflected on the surface of the reflective substrate to be transmitted to the observation wavelength forming means. At the point of being captured. By adopting such a configuration, light that has passed through the thin film and has absorbed a certain amount of luminous intensity into the thin film is reflected on the surface of the reflective substrate, passes through the thin film again, and is further absorbed by the luminous intensity. After passing through, it is captured by the observation wavelength forming means, and the thickness of the thin film on the reflective substrate can be measured.

A feature of the film thickness measuring apparatus according to the present invention according to claims 6 and 7 is that light is visible light or ultraviolet light. By adopting such a configuration, visible light or ultraviolet light can be used as light for measuring the thickness of the thin film in accordance with the state of the manufacturing process.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a film thickness measuring apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing a second embodiment of a film thickness measuring apparatus according to the present invention.

FIG. 3 is a plan view showing a transparent substrate in an embodiment of the film thickness measuring apparatus according to the present invention.

4 is a graph showing the absorbance measured in the example of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Thin film 3 Deuterium lamp 4A, 4B, 8A, 8B Reflector 5 Chopper 6 Luminous intensity detector 7 Bandpass filter 9 Film thickness detector 10 Shielding plate 11 Small hole 12, 13 Convex lens 14 Spectroscope

Claims (7)

[Claims] 1. A film thickness measuring apparatus for measuring the thickness of a thin film formed on a substrate, comprising: a light irradiating means for irradiating the thin film on the substrate with light; and forming an observation wavelength from the light passing through the thin film. Observation wavelength forming means; light intensity detecting means for detecting the light intensity of a specific wavelength formed by the observation wavelength forming means; film thickness detection for detecting the thickness of the thin film based on the light intensity detected by the light intensity detecting means Means for measuring film thickness. 2. The film thickness measuring apparatus according to claim 1, wherein said observation wavelength forming means is constituted by a band-pass filter. 3. The film thickness measuring apparatus according to claim 1, wherein said observation wavelength forming means is constituted by a spectroscope. 4. The apparatus according to claim 1, wherein the substrate is a transparent substrate, and the light emitted from the light irradiating means to the thin film passes through the transparent substrate and is captured by the observation wavelength forming means. The film thickness measuring device according to claim 3. 5. The apparatus according to claim 1, wherein the substrate is a reflective substrate, and the light emitted from the light irradiating means to the thin film is reflected by a surface of the reflective substrate and captured by the observation wavelength forming means. The film thickness measuring device according to any one of claims 1 to 3. 6. The film thickness measuring apparatus according to claim 1, wherein the light is visible light. 7. The film thickness measuring apparatus according to claim 1, wherein the light is ultraviolet light.