JPH0850007A - Method and apparatus for evaluating film thickness - Google Patents

Abstract

PURPOSE:To measure a thickness of an organic film formed on a rough substrate accurately by introducing a monochromic light at right angles to the organic film, and detecting a reflecting light by means of a detector having a photodetecting angle based on an incident point set in a specific range. CONSTITUTION:A light emitted from a light source 11 is turned to a monochromic light of a predetermined wavelength by an interference filter 12 and brought into a sample 5. An optical fiber 21 is set at a fiber-optic head 22. A photodetecting angle PHI of the fiber is set in the range of 35-55 deg. based on a point of incidence (a) as a reference. A distance from a front end of the head 22 to the sample 5 is determined so as to detect a reflecting component which has a solid angle based on the incident point, (a) in the range of 0.01-0.1sr. The reflecting light received by the optical fiber 21 is guided to a photoelectric surface of a photomultiplier tube 3. An output signal from the photomultiplier tube 3 is input to an operating device 4 and processed there to calculate an adsorbance (reflection density) loge (Io/I). Since the adsorbance is proportional to a thickness (d) of a substance, the thickness can hence be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film thickness evaluation method and device, and more specifically, for accurately measuring the film thickness of an organic film formed on a rough substrate and absorbing visible light. The present invention relates to a film thickness evaluation method and apparatus used in.

[0002]

2. Description of the Related Art A technique for highly accurately evaluating and measuring the film thickness of an organic film formed on a rough substrate by coating or the like is
It is desired in many fields of industry. For example, a step of applying a coating material on the surface of a steel plate, a step of applying a photosensitive resin or a photoconductor on the surface of an aluminum plate, a step of applying a photoresist such as a step of applying a photoresist on an IC or the like, and the like. To be

As a method of measuring the film thickness of the organic film as described above, many methods have been proposed in the past. For example,
(1) A method for obtaining a film thickness from infrared absorption, (2) Eddy current type film thickness meter, (3) Radiation (X-ray, β-ray, etc.) film thickness meter, (4) Capacitance film thickness meter, ( 5) Interference fringe type film thickness meter,
(6) Examples include fluorescent X-ray method.

[0004]

However, since all of the above measuring means are intended to measure the organic film on the smooth substrate, when applied to the film thickness measurement of the organic film on the rough substrate. It is difficult to obtain sufficient accuracy. When the fluorescent X-ray method is used, some accuracy can be secured,
It has drawbacks such as a large apparatus configuration and a high price, and maintenance after installation is troublesome.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a film thickness evaluation method and apparatus capable of highly accurately and inexpensively evaluating the film thickness of an organic film formed on a rough substrate. To provide.

[0006]

Means for Solving the Problems As a result of intensive studies made by the present inventors for the above purpose, as a result, an organic film on a substrate having a surface roughness in a specific range is reflected in a specific range. The present invention has been achieved by finding that the influence of scattered light generated by a rough surface can be reduced by measuring the light component.

That is, the first gist of the present invention is a method for evaluating the film thickness of an organic film formed on a rough substrate having Ra of 0.1 to 1 and absorbing visible light. Light-receiving angle (Φ) that is perpendicular to the film and is based on the incident point
In the range of 35 ° to 55 °, the reflected light is received and the absorbance is calculated.

A second aspect of the present invention is a film thickness evaluation apparatus for an organic film formed on a rough substrate having Ra of 0.1 to 1 and absorbing visible light, wherein monochromatic light is used as an organic material. The light irradiator that is vertically incident on the film and the light receiving angle (Φ) with respect to the incident point are arranged in the range of 35 ° to 55 °, and the solid angle with respect to the incident point is 0.01 to 0.1 sr. The film thickness evaluation device is characterized by comprising a detector that receives a reflection component in the range of 1 and a calculation device that calculates the absorbance based on the light reception signal from the detector to evaluate the film thickness.

The present invention will be described in detail below. First, for the understanding of the present invention, the Lambert-Beer law and a film thickness measuring method using the law will be described. In absorption of light, when the incident light intensity of monochromatic light is I ₀ , the transmitted light intensity is I, the absorption coefficient is μ, and the thickness of the substance is d, the transmitted light intensity is I = I ₀ exp (−μd). expressed. This is Lambert-Beer's law.

From the above equation, μd = log _e (I ₀ /
I) and the absorption coefficient for a certain wavelength is considered to be constant, so the absorbance log _e (I ₀ / I) is proportional to the thickness d of the substance. Therefore, the absorbance log _e (I ₀ /
The thickness d of the substance can be measured by measuring I).

In the case of an organic material film on a reflective substrate (rough surface substrate), incident light from the organic material film side is absorbed while passing through the organic material film, reflected by the substrate, and absorbed again, and then the organic material film. Is emitted as reflected light. Also in the case of such a reflection system, the incident light intensity is I ₀ , the reflected light intensity is I, and the absorbance l
By measuring og _e (I ₀ / I), the film thickness of the organic film can be measured. The above-mentioned absorbance log _e (I ₀ / I) in the reflection system is sometimes called reflection density.

In the film thickness measurement using the Lambert-Beer law, it is assumed that the light intensity is attenuated only by absorption. Therefore, when measuring the thickness of the organic film on the rough substrate, light is scattered and the amount of light reaching the detector is attenuated. As a result, it becomes difficult to measure the absorbance accurately. That is, even if the organic film on the substrate has the same thickness, different absorbances may be exhibited when the surface roughness of the substrate is different.

However, the light reflected from the rough substrate shows a very complicated scattering pattern under the influence of the rough surface state, but according to the knowledge of the present inventors, the light has a specific surface roughness. With respect to the organic film on the substrate, the influence of scattered light generated by the rough surface can be reduced by measuring the reflected light component reflected in a specific range.

Next, the film thickness evaluation method according to the present invention will be described. The organic film targeted by the present invention is an organic film formed on a rough substrate having Ra (center line average roughness) of 0.1 to 1. The film thickness of an organic film formed on a rough substrate having an Ra of less than 0.1 can be evaluated with considerable accuracy without the need of the present invention. On the other hand, the organic film formed on the rough substrate having Ra of 1 or more cannot evaluate the film thickness with sufficient accuracy even by the present invention. In the present invention, the preferable organic material film has Ra of 0.4 to 0.7.
Is an organic film formed on the rough substrate of. The present invention can sufficiently demonstrate its true value in the evaluation of the film thickness of such an organic film. In the present invention, Ra is JIS B0 under the conditions of a cutoff value of 0.8 mm and a measurement length of 8 mm.
It is the value measured according to 601.

In principle, the film thickness evaluation method according to the present invention utilizes the above-described absorbance log _e (I ₀ / I) based on the Lambert-Beer law. Therefore, the organic film formed on the substrate needs to be capable of absorbing visible light. In the case of a colorless organic substance, such characteristics can be imparted by blending an appropriate coloring substance with the organic substance before being applied onto the substrate.

In the present invention, monochromatic light is vertically incident on the organic material film, and the light receiving angle (Φ) with reference to the incident point is 35 °.
Reflected light is received by a detector arranged within a range of up to 55 °, and the absorbance (reflection density) log _e (I ₀ / I) is calculated, where the incident light intensity is I ₀ and the reflected light intensity is I. Light receiving angle (Φ)
However, when the reflected light is measured by a detector arranged outside the above range, the surface roughness of the substrate is greatly affected, and the film thickness of the organic film cannot be accurately evaluated.

The reflected light can be measured for the reflection component within an arbitrary range of the solid angle with respect to the incident point, but it is measured for the reflection component within the range of the solid angle of 0.01 to 0.1 sr. preferable. Here, the solid angle means an area cut by a cone having an apex at the incident point from a unit spherical surface having the incident point as the center, and can be determined by the distance between the reflecting surface and the light receiving surface. The wavelength of monochromatic light is usually set to the maximum absorption wavelength of organic substances.

Next, the film thickness evaluation apparatus according to the present invention will be described. The film thickness evaluation apparatus according to the present invention includes a light irradiator for vertically injecting monochromatic light into an organic material film, and a light receiving angle (Φ) with respect to the incident point arranged in a range of 35 ° to 55 ° and the incident point. From a detector that receives a reflection component having a solid angle in the range of 0.01 to 0.1 sr with respect to, and an arithmetic device that evaluates the film thickness by calculating the absorbance based on the received light signal from the detector. Become.

FIG. 1 is an explanatory view of an example of an optical system of a film thickness evaluation apparatus according to the present invention, in which (1) is a light irradiator.
(11) is a light source, (12) is an interference filter, (2) is a detector, (21) is an optical fiber, (22) is an optical fiber head, (3) is a photomultiplier tube, (4) is an arithmetic unit, ( 5) is a sample.

In the optical system shown in FIG. 1, the light source (11)
The light emitted from is converted into monochromatic light having a predetermined wavelength by the interference filter (12) and is incident on the sample (5). The optical fiber (21) is provided in the optical fiber head (22) and has a light receiving angle (Φ) of 3 with respect to the incident point (a).
It is arranged in the range of 5 ° to 55 °. The distance from the tip of the optical fiber head (22) to the sample (5) is set so that the reflected component having a solid angle of 0.01 to 0.1 sr with respect to the incident point (a) can be received. It has been decided.

The reflected light received by the optical fiber (21) is guided to the photocathode of the photomultiplier tube (3), and its output signal is input to the arithmetic unit (4) having an amplifier circuit and a logarithmic conversion circuit. Signal is processed and the absorbance (reflection density)
log _e (I ₀ / I) is calculated. In the optical system shown in FIG. 1, two optical fibers (21) are provided at imaginary circular equidistant positions, that is, at opposite positions (positions different by 180 °), but to further improve measurement accuracy. It may be three or more.

The film thickness evaluation method and apparatus according to the present invention are
It is possible to accurately calculate the absorbance (reflection density) log _e (I ₀ / I) by reducing the influence of scattered light generated by the rough surface. Therefore, the film thickness of the organic film formed on the rough substrate can be accurately controlled by the obtained absorbance (reflection density).

The film thickness evaluation method and apparatus according to the present invention can also be used for measuring the film thickness of an organic film by a calibration curve obtained in advance. In the calibration curve, the film thickness of the organic film compared with the absorbance (reflection density) is
You should use the values determined by the most reliable measurement method possible. In the present invention, the weight of a certain area of the sample coated with the organic substance film is measured, the organic substance film is removed with an organic solvent, and the weight film thickness calculated from the weight difference before and after removal is used. Is recommended.

[0024]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 As the rough substrate, an aluminum substrate was used, which was roughened to various Ras by chemical etching and then anodized. As an organic substance, 630n is obtained by adding a dye.
A light-sensitive organic substance adjusted to have characteristic absorption in m was used. Ra = 0.56, 0.69, 0.76, 0.84 by coating a photosensitive organic material on the rough surface of the aluminum substrate.
Samples were prepared by coating a photosensitive organic compound film having a film thickness of 5 levels on a substrate having 1 level of (μm).

For each sample obtained as described above, 6
A monochromatic light of 30 nm was irradiated as incident light, and the absorbance (reflection density) was calculated from the reflected light. That is, using an apparatus equipped with the optical system shown in FIG. 1, the light receiving angle (Φ) is changed to receive a reflection component having a solid angle of 0.05 sr, the reflection density is calculated, and the reflection density is compared with the weight film thickness. Evaluated. The results are shown in FIGS. 2 shows the case where the light receiving angle is 45 °, FIG. 3 shows the case where the light receiving angle is 30 °, and FIG. 4 shows the case where the light receiving angle is 60 °.
Is the result in the case of.

As is clear from the results shown in the above figures,
It can be seen that when the light receiving angle is 30 ° or 60 °, the distribution of the measured values of the reflection density is wide and the influence of Ra is large. On the other hand, when the light receiving angle is 45 °, the distribution of the measured values of the reflection density is narrow and the influence of Ra is small. By the way, the value of the reflection density decreases as Ra increases. From the above results, it is understood that the film thickness of the photosensitive organic compound film can be accurately measured by measuring the reflection density according to the present invention.

[0028]

According to the present invention described above, it is possible to evaluate the film thickness of an organic film formed on a rough substrate with high accuracy and high speed at low cost under in-line and non-contact conditions. . Therefore, the plant diagnosis of the production line can be performed in real time, and various products in which the organic film is formed on the rough surface substrate can be stably supplied.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an example of an optical system of a film thickness evaluation apparatus according to the present invention.

FIG. 2 shows measurement results when the light receiving angle is 45 °.

FIG. 3 shows measurement results when the light receiving angle is 30 °.

FIG. 4 shows measurement results when the light receiving angle is 60 °.

[Explanation of symbols]

 1: Light irradiator 11: Light source 12: Interference filter 2: Detector 21: Optical fiber 22: Optical fiber head 3: Photomultiplier tube 4: Computing device 5: Sample

Claims (4)

[Claims] 1. A method for evaluating the film thickness of an organic film formed on a roughened substrate having Ra of 0.1 to 1 and absorbing visible light, wherein monochromatic light is vertically incident on the organic film and the incident point. The light receiving angle (Φ) with respect to is used as a reference, the reflected light is received by a detector arranged in the range of 35 ° to 55 °, and the absorbance is calculated, and the film thickness evaluation method. 2. The solid angle based on the incident point is 0.01 to
The film thickness evaluation method according to claim 1, wherein the reflected component in the range of 0.1 sr is received. 3. An apparatus for evaluating the film thickness of an organic film formed on a roughened substrate having Ra of 0.1 to 1 and absorbing visible light, wherein a light irradiator for vertically injecting monochromatic light into the organic film. When,
The light receiving angle (Φ) based on the incident point is arranged in the range of 35 ° to 55 °, and the solid angle based on the incident point is 0.0.
A detector for receiving a reflection component in the range of 1 to 0.1 sr,
A film thickness evaluation device, comprising: a calculation device that evaluates the film thickness by calculating the absorbance based on the received light signal from the detector. 4. The film thickness evaluation apparatus according to claim 3, wherein the detector is a plurality of optical fibers arranged at equal intervals.