JPH11230860A - Method and device for measuring optical thin film, and device for removing interfering light in optical thin film measurement used for same device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the physical amount of a thin film formed on the surface of a transparent base material, by preventing reflected light from the back surface of the transparent base material from being superimposed on measuring light without any complicated operation. SOLUTION: In an optical thin film measuring method, the surface of a sample 10 in which a thin film 12 is formed on the surface of a transparent substrate 11 is irradiated with a light beam, and reflected light from an irradiation point is detected to measure the physical amount of the thin film 12. A liquid 26 with the approximately same refractive index as that of the substrate 11 is housed in a container to bring the back surface of the substrate 11 into contact with the liquid 26, and light transmitted through the sample 10 and incident into the liquid 26 is absorbed to a light absorbing body 24. In another constitution, a knife edge plate is arranged in the vicinity of the sample without shielding reflected light from the irradiation point so as to shield the light beam reflected at the back surface of the substrate and transmitted through the thin film, and the knife edge of the knife edge plate is located on the side of the reflected light with respect to the irradiation point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a physical quantity such as a thickness, a refractive index or a spectrum of a thin film by detecting a change in a polarization plane, an optical change such as interference or absorption, and an apparatus used in the apparatus. The present invention relates to an optical thin film measurement interference light removing device to be used.

[0002]

2. Description of the Related Art In the manufacture of a liquid crystal display panel, for example, a transparent conductive film or an amorphous silicon film is formed on the surface of a glass substrate, and this is finely processed into a desired shape to form a display element. The thickness and refractive index of this thin film can be measured with an ellipsometer. However, since the reflected light from the back surface of the glass substrate is superimposed on the measurement light which is the interference light of the reflected light on the front surface and the back surface of the thin film, the measurement accuracy deteriorates.

In Japanese Patent Laid-Open Publication No. Hei 3-215957, the back surface of the glass substrate is roughened so that it is irregularly reflected.
The effect has been reduced by an order of magnitude. However, since the reflected light itself from the back surface of the glass substrate cannot be eliminated, it is not suitable when high-precision measurement is required.
In Japanese Patent Application Laid-Open No. 6-34523, the measurement accuracy is improved based on a theoretical formula on the assumption that the measurement light does not interfere with the reflected light from the back surface of the glass substrate. Is unsuitable for measuring

Further, in Japanese Patent Application Laid-Open No. Hei 5-264440, the reflected light from the back surface of the glass substrate is shielded. However, it is necessary to finely adjust the height of the sample mounting stage in order to appropriately shield the light. Is complicated. The above problem also occurs when a physical quantity such as a film thickness, a refractive index or a spectrum of a thin film formed on the surface of the transparent substrate is measured by an optical measurement device other than the ellipsometer.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent the reflected light from the back surface of a transparent substrate from being superimposed on the measuring light without performing a complicated operation in view of such problems. Accordingly, it is an object of the present invention to provide an optical thin film measuring method and apparatus capable of measuring a physical quantity of a thin film formed on a transparent base material surface with high accuracy, and an optical thin film measuring interference light removing apparatus used in the apparatus. .

[0006]

According to the first aspect of the present invention, there is provided an apparatus for removing interference light from measurement of an optical thin film, wherein a sample having a thin film formed on one surface of a transparent substrate is irradiated with a light beam to the one surface. Is used for an optical thin film measuring device that measures the physical quantity of the thin film by detecting reflected light from the irradiation point, and is a liquid or gel-like antireflective substance having a refractive index substantially equal to that of the base material. A container in which the antireflective substance is housed so as to be capable of contacting the surface of the transparent substrate opposite to the one surface; and a container disposed in the container, penetrating the sample and entering the antireflective substance. And a light absorber that absorbs the light.

According to this optical thin film measurement interference light removing device, the refractive index of the transparent substrate and the antireflective substance are substantially equal to each other, so that the intensity of the reflected light on the opposite surface of the transparent substrate can be measured by the optical thin film measurement. The light beam transmitted through the transparent base material becomes negligibly small even when it enters the detection unit of the apparatus, and is reflected by the light absorber because it is absorbed by the light absorber, and enters the detection unit of the optical thin film measurement apparatus. And thus the thickness of the thin film,
There is an effect that a physical quantity such as a refractive index or a spectrum can be measured with high accuracy.

Further, since fine adjustment of the optical thin film measuring device before measurement is not required, there is an effect that the operation is simple. In the optical thin film measurement interference light removing device according to claim 2,
In claim 1, for example, as shown in FIG. 1, a partition member for partitioning between an upper end opening and a bottom surface is disposed in the container, and a chamber is formed between the partition member and the bottom surface, and the antireflection is provided. A hole is formed in the partition member to allow light incident on the substance to pass through the interior of the chamber, and the light absorber is disposed inside the chamber.

According to the optical thin film measurement interference light removing device, there is an effect that the light beam transmitted through the transparent substrate can be surely absorbed by the light absorber. In the optical thin film measurement interference light removing device of claim 3, as shown in FIG. 4, for example, a ring-shaped groove is formed at the upper end of the container, and a ring-shaped seal member is fitted into the groove. A sealing member protrudes from the upper end, and the antireflective substance is placed in the container up to the upper end of the sealing member.

According to the optical thin film measuring and obstructing light removing device, there is an effect that a small container can be used. In the optical thin film measurement interference light removing device of claim 4, as shown in FIG. 2, for example, light incident on the anti-reflective material is provided between the upper end opening and the bottom surface in the container. A movable mask having a movable slit for passing therethrough is arranged, and the light absorber is arranged between the movable mask and the bottom surface.

According to this optical thin film measurement interference light removing device, an arbitrary position on the sample can be measured by moving the optical measurement device following the movement of the slit while the sample is fixed. It has the effect of being able to. In the optical thin-film measurement interference light removing device according to claim 5, as shown in FIG. 5, for example, in the container, the upper end opening of the container is narrower than the cross section of the body portion, and the upper surface of the antireflective substance has the upper end at the upper end. It rises above the opening.

According to the optical thin film measuring and obstructing light removing device, there is an effect that a small container can be used. In the optical thin film measurement interference light removing device according to claim 6, the moving stage for moving the sample in order to change the light irradiation point on the sample according to any one of claims 1 to 3 or claim 5, is provided. Have.

According to the optical thin film measurement interference light removing device, there is an effect that automatic measurement can be performed at an arbitrary light irradiation point on the sample without moving the optical measuring device. In the optical thin film measurement interference light removing device according to claim 7, in any one of claims 1 to 6, the light absorber is formed on an inner wall of the container.

According to an eighth aspect of the present invention, there is provided the optical thin film measuring apparatus according to any one of the first to seventh aspects, wherein the thin film is formed on one surface of the transparent base material. An optical measurement device that irradiates the sample with a light beam to the one surface, detects reflected light from an irradiated point, and measures a physical quantity of the thin film.

In an optical thin film measuring apparatus according to a ninth aspect, for example, as shown in FIG. 6, a sample having a thin film formed on one surface of a transparent base material is irradiated with a light beam on the one surface. An optical measurement device that detects the reflected light from and measures the physical quantity of the thin film, a moving stage that moves the sample to change the irradiation point, and without blocking the reflected light from the irradiation point, In order to block the light beam reflected on the surface opposite to the one surface in the transparent substrate and transmitted through the thin film, a knife edge is positioned on the reflected light side with respect to the irradiation point, and the knife edge is approached to the sample. A knife edge plate disposed.

According to this optical thin-film measuring apparatus, an antireflection substance and a container for accommodating the antireflection substance are not required. According to claim 10, an optical system for irradiating a sample having a thin film formed on one surface of a transparent base material with a light beam, detecting reflected light from an irradiation point, and measuring a physical quantity of the thin film. In a method for measuring a thin film, a liquid or gel-like antireflective substance having a refractive index substantially equal to that of the base material is accommodated in a container, and the surface of the transparent base material facing the one surface is coated with the antireflective material. And the light passing through the sample and entering the antireflective substance is absorbed by the light absorber.

In the eleventh aspect, a sample having a thin film formed on one surface of a transparent substrate is irradiated with a light beam to the one surface, and reflected light from an irradiation point is detected to determine a physical quantity of the thin film. In the optical thin film measuring method for measuring, without blocking light reflected from the irradiation point, a light beam reflected on a surface opposite to the one surface in the transparent base material and transmitted through the thin film is shielded. Next, a knife edge plate is arranged close to the sample, and the knife edge of the knife edge plate is positioned on the reflected light side with respect to the irradiation point.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 shows a schematic configuration of an optical thin film measuring apparatus according to a first embodiment of the present invention. The sample 10 has a thin film 12 formed on a surface 11 a of a transparent substrate 11. For example,
The transparent substrate 11 is a quartz glass substrate, and the thin film 12 is an IT
O film. The sample 10 is placed in an optical thin film measurement and interference light removing device as described below.

The container 20 of this device has a rectangular cross section, and a partition plate 21 is fixed to the inner wall of the container 20 at an intermediate portion between the upper end opening and the bottom surface so as to be parallel to the bottom surface of the container 20. Thereby, a chamber 22 is formed in the lower part of the container 20. An opening 23 is formed at the center of the partition plate 21, and the opening 23 is a hole or a slit whose longitudinal direction is perpendicular to the plane of the paper. A light absorbing surface 24 is attached to the inner wall surface of the chamber 22 to form a black body, and light incident from the opening 23 is absorbed by the black body. The light absorbing surface 24 is, for example, the chamber 2
The inner surface of No. 2 was roughened, and a black paint was applied thereon. On the upper surface of the partition plate 21, support projections 25A and 25B are formed, on which the sample 10 is slidably mounted.

A liquid 26 having a refractive index substantially equal to that of the transparent substrate 11 is stored in the container 20. If the liquid 26 is volatile, a layer of oil 27 is placed on the liquid 26 as a non-volatile liquid having a density less than that of the liquid 26. An ellipsometer including a laser 30 and a polarizer 31 on the incident side, an analyzer 32 and a photodetector 33 on the reflection side is disposed above the optical thin film measurement interference light removing apparatus having such a configuration.

Next, the operation of the first embodiment configured as described above will be described. The light beam emitted from the laser 30 becomes linearly polarized light or circularly polarized light through the polarizer 31 and irradiates the measurement point on the sample 10, while the light reflected on the front and back surfaces of the thin film 12 interferes with each other, The light passes through the analyzer 32 and becomes linearly polarized light, and the intensity is detected by the photodetector 33.
On the other hand, the light beam passes through the thin film 12 and passes through the transparent substrate 11.
Get in. Since the refractive indices of the transparent substrate 11 and the liquid 26 are substantially equal to each other, the intensity of the light reflected on the surface 11b of the transparent substrate 11 becomes negligibly small even when the light enters the analyzer 32. The light beam transmitted through the transparent substrate 11 is transmitted through the aperture 2
3, the light that is absorbed by the light absorbing surface 24 and is weakly diffusely reflected by the light absorbing surface 24 is further absorbed by the light absorbing surface 24 to prevent light from leaking from the opening 23.

The output of the photodetector 33 is read while rotating the polarization plane of the analyzer 32, and the analyzer 3
2 and the angle of the photodetector 33 is changed, and the same is performed.
By analyzing the read data with a signal processing device (not shown), the film thickness and the refractive index of the thin film 12 at the light irradiation point are obtained. By sliding the transparent substrate 11 on the support protrusions 25A and 25B, the film thickness and the refractive index of the thin film 12 at arbitrary points are measured.

According to the first embodiment, since the light reflected on the surface 11b can be ignored, the thickness and the refractive index of the thin film 12 can be measured with high accuracy. Further, since the relationship between the position of the ellipsometer and the position of the opening 23 may be roughly determined, the operation is simple. For example, when the transparent substrate 11 is made of quartz glass, its refractive index is 1.4570 with respect to the wavelength of 632.8 nm of the He—Ne laser beam. When a light beam is incident on the transparent substrate 11 at an incident angle of 60 °, About 81% of it enters the transparent substrate 11. When the liquid 26 does not exist, about 18% of the light that has entered the transparent substrate 11 is reflected by the surface 11b.
5% will be reflected by the surface 11b.

On the other hand, the liquid 26 has, for example, a refractive index
1.4507 cyclohexane (C ₆ H_TenO)
When measured in the state of FIG. 1, the reflectance on the surface 11b is 0.2
%, And the reflected light intensity at the surface 11b becomes
0.17% of the intensity of the incident light on the substrate. Further, the liquid 26
Benzene with a refractive index of 1.5411
By using a mixture of about 7% alcohol
Make the refractive index of the liquid 26 approximately equal to that of quartz glass
And the reflectance at the surface 11b can be reduced to almost zero.
it can.

As the liquid 26, for example, a mixed liquid in which xylene or benzoic acid is mixed in cyclohexane can be used according to the refractive index of the transparent substrate 11. Liquid 26
Instead of this, a gelled substance obtained by absorbing this into a polymer may be used. In this case, the above measurement can be performed with the transparent substrate 11 inclined.

As the light absorbing body, instead of the light absorbing surface 24,
A black dye having strong light absorption may be dissolved in the liquid 26. A light source and a spectroscope are used instead of the laser 30, and an analyzer 32 and a photodetector 33 for the sample 10 are used.
May be changed without changing the angle of the light beam.

Further, the optical measurement device may be configured to measure the spectrum of the thin film 12 by using, for example, a Fourier spectroscope that irradiates the sample 10 with a white light beam instead of the ellipsometer. The above modified example is
The same applies to the following embodiments. [Second Embodiment] FIG. 2A shows a schematic configuration of an optical thin film measuring apparatus according to a second embodiment of the present invention.

In the optical thin film measuring and obstructing light removing device of this device, a partition plate 21A having a relatively large opening formed in the center is used in the container 20A instead of the partition plate 21 of FIG. The movable mask 28 is provided in this opening.
Is arranged. As shown in FIG. 2B, the movable mask 28 has one end and the other end of a curtain 28c wound around rollers 28a and 28b, and a slit 23A is formed on the curtain 28c. By rotating in the same direction, the position of the slit 23A can be adjusted.

In accordance with this adjustment, the ellipsometer above the sample 10 is moved. By this movement and the independent movement of the ellipsometer in the direction perpendicular to the paper surface, measurement can be performed at an arbitrary position on the sample 10 fixed on the partition plate 21A. Other points are the same as those in FIG. Third Embodiment FIG. 3 shows a schematic configuration of an optical thin-film measuring apparatus according to a third embodiment of the present invention.

In the optical thin film measurement interference light removing apparatus of this apparatus, the sample 10 is mounted on the light irradiation point scanning stage 34 in the container 20B, and the sample 10 is movable in a plane perpendicular to the paper. I have. In order to avoid collision with the stage 34, a small partition 21B is arranged in the container 20B, and an opening 23 is formed on the upper surface thereof. According to this optical thin film measuring apparatus, high-precision automatic measurement can be performed at an arbitrary light irradiation point on the sample 10 without moving the ellipsometer.

The other points are the same as those in FIG. [Fourth Embodiment] FIG. 4 shows a schematic configuration of an optical thin film measuring apparatus according to a fourth embodiment of the present invention. In FIG. 3, the liquid 2
6 is at least the surface 11b of the transparent substrate 11 and the partition 2
What is necessary is just to exist between the upper surface of 1B. Therefore, this 4th
In the embodiment, a circular groove is formed in the upper end of the container 20C having substantially the same size as the partition 21B, and the O-ring 29 is fitted into the groove, and the upper surface protrudes from the upper end of the container 20C. Liquid 26 contains O-ring 2 in container 20C.
9, the surface 11b of the transparent substrate 11 is brought into contact with the O-ring 29, so that the liquid 26
Contact.

According to the fourth embodiment, the small container 2
Since 0C is used, the entire device can be downsized. Other points are the same as those in FIG. [Fifth Embodiment] FIG. 5 shows a schematic configuration of an optical thin film measuring apparatus according to a fifth embodiment of the present invention.

In the optical thin film measurement interference light removing apparatus of this apparatus, instead of using the O-ring 29 of FIG.
Utilizing the surface tension of That is, the liquid 26 is put into the bottle-shaped container 20D whose upper end opening is narrower than the body part cross section until it rises higher than the upper end of the container 20D at the center, and the surface 11b of the transparent substrate 11 contacts the upper surface of the liquid 26. I have.

The other points are the same as those in FIG. If the above-mentioned gel-like substance is used instead of the liquid 26, the shape of the protruding upper surface can be stabilized for a long time. Sixth Embodiment FIG. 6 shows a schematic configuration of an optical thin film measuring apparatus according to a sixth embodiment of the present invention.

In this apparatus, the light irradiation point scanning stage 3
The sample 10 is mounted on the sample 4A, and the sample 1 is
0 is free to move. A knife edge plate 20E parallel to the sample 10 is arranged on the reflected light side of the ellipsometer, approaching the upper surface of the sample 10, and the base end thereof is attached to the fixed side. The tip of the knife edge plate 20E
The edge is formed so as not to disturb the reflected light from the light irradiation point, and is located on the side of the reflected light near the light irradiation point. The distance between the tip of the knife edge plate 20E and the light irradiation point is such that the light reflected from the surface 11b is reflected from the surface 11a from the light irradiation point.
Is substantially equal to the distance S to the position at which the position has returned. This distance S is
It is expressed by the following equation.

S = 2d · tan [(sin ⁻¹ {sin (θ / n)}] where θ is the incident angle with respect to the sample 10, d is the thickness of the transparent substrate 11, and n is the transparent substrate 11 Before the measurement, the positional relationship between the ellipsometer and the knife edge plate 20E is adjusted based on the value of S. This adjustment is independent of the position of the stage 34A.

According to the optical thin-film measuring apparatus of the sixth embodiment, the liquid 26 is not required, so that the configuration is simplified.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an optical thin film measurement device according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an optical thin film measuring device according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of an optical thin-film measuring device according to a third embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an optical thin film measurement device according to a fourth embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of an optical thin film measuring device according to a fifth embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of an optical thin film measuring device according to a sixth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 sample 11 transparent substrate 12 thin film 20, 20A to 20D container 20E knife edge plate 21, 21A partition plate 21B partition base 22 chamber 23 opening 23A slit 24 light absorbing surface 25A, 25B support protrusion 26 liquid 27 oil 28 movable mask 29 O-ring 30 Laser 31 polarizer 32 analyzer 33 photodetector

Claims (11)

[Claims] An optical system for irradiating a sample having a thin film formed on one surface of a transparent base material with a light beam, detecting reflected light from an irradiated point, and measuring a physical quantity of the thin film. An anti-reflective substance, which is a liquid or gel-like substance having a refractive index substantially equal to that of the substrate, and the anti-reflection so as to be able to come into contact with the surface of the transparent substrate opposite to the one surface A container for accommodating a substance, and a light absorber disposed in the container and absorbing light transmitted through the sample and incident on the anti-reflection substance, comprising: Removal device. 2. In the container, a partition member for partitioning between an upper end opening and a bottom surface is disposed, a chamber is formed between the partition member and the bottom surface, and light incident on the anti-reflective substance. 2. An optical thin film measuring and obstructing light removing device according to claim 1, wherein a hole is formed in the partition member for allowing the light to pass through the interior of the chamber, and the light absorber is disposed inside the chamber. . 3. An annular groove is formed at an upper end of the container,
The ring-shaped seal member is fitted into the groove, the seal member protrudes from the upper end, and the anti-reflective substance is put in the container up to the upper end of the seal member. Optical thin film measurement interference light removal device. 4. A movable mask having a movable slit formed between the upper end opening and the bottom surface for allowing light incident on the anti-reflective substance to pass therethrough, wherein the light absorber is provided in the container. The optical thin film measurement interference light removing device according to claim 1, wherein is disposed between the movable mask and the bottom surface. 5. The optical device according to claim 1, wherein the upper end opening of the container is narrower than a cross section of the body portion, and the upper surface of the anti-reflection substance is raised above the upper end opening. Thin film measurement interference light removal device. 6. The optical device according to claim 1, further comprising a moving stage for moving the sample to change a light irradiation point on the sample. Thin film measurement interference light removal device. 7. The optical thin film measurement interference light removing apparatus according to claim 1, wherein the light absorber is formed on an inner wall of the container. 8. An optical thin film measuring and obstructing light removing apparatus according to claim 1, further comprising: a sample on which a thin film is formed on one surface of a transparent substrate; An optical measurement device for irradiating a beam, detecting reflected light from an irradiation point, and measuring a physical quantity of the thin film. 9. A light for irradiating a light beam to a sample on which a thin film is formed on one surface of a transparent substrate, and detecting a reflected light from an irradiation point to measure a physical quantity of the thin film. A measuring device, a moving stage for moving the sample to change the irradiation point, and a reflection surface on the surface opposed to the one surface in the transparent substrate without blocking light reflected from the irradiation point. And a knife edge plate having a knife edge positioned on the reflected light side with respect to the irradiation point and arranged in close proximity to the sample in order to block a light beam transmitted through the thin film. Thin film measuring device. 10. An optical system for irradiating a sample having a thin film formed on one surface of a transparent base material with a light beam, detecting reflected light from an irradiated point and measuring a physical quantity of the thin film. In the method for measuring a thin film, an antireflection substance which is a liquid or a gel-like substance having a refractive index substantially equal to that of the base material is contained in a container, and the surface of the transparent base material facing the one surface is formed of the antireflection material. Wherein the light that has passed through the sample and entered the anti-reflective substance is absorbed by a light absorber. 11. An optical system for irradiating a sample having a thin film formed on one surface of a transparent base material with a light beam, detecting reflected light from an irradiation point, and measuring a physical quantity of the thin film. In the method for measuring a target thin film, the light reflected from the irradiation point is not shielded, but the light beam reflected on the surface opposite to the one surface in the transparent base material and transmitted through the thin film is shielded. An optical thin film measurement method, comprising: disposing a knife edge plate close to a sample; and positioning a knife edge of the knife edge plate on a side of reflected light with respect to the irradiation point.