JP2001021324A - Thickness measuring apparatus of thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the thickness of a thin film stably without being affected by partial inclination and vibration of a substrate. SOLUTION: This thickness measuring apparatus of a thin film includes a light source 1, a branching type optical fiber 2 which introduces a light from the light source 1 to a plurality of portions (two portions in this case) and receives reflected lights from a substrate 3 at the respective portions, a light limiting shutter 4 which cuts off selectively incident lights to be introduced to the plurality of portions of the substrate 3 and a plurality of reflected lights of the substrate 3, a spectroscope 5 which resolves the reflected light introduced by the optical fiber 2 in light intensity of each wavelength, and a computer 6 which analyzes the light intensity of each wavelength and calculates the thickness of a thin film. A halogen lamp having a wavelength region (400-850 nm) near to, e.g. a visible light wavelength region (400-800 nm) is used as the light source 1. Another lamp may be installed in the same light source chamber as the halogen lamp or in another light source chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for measuring the thickness of a thin film. In particular, the present invention relates to a thin film thickness measuring device for measuring the thickness of various thin films formed on a substrate such as a glass substrate or a semiconductor wafer substrate when manufacturing a liquid crystal display device or a semiconductor device.

[0002]

2. Description of the Related Art In recent years, thin film forming techniques such as a plasma process method and a sputtering method have been widely used in the manufacture of electronic components such as semiconductor devices and liquid crystal display devices. By detecting various characteristics of the thin film formed by the thin film forming technique, various parameters for forming the thin film are derived, and various problems at the time of forming the thin film are promptly detected.

In particular, the thickness of a thin film affects not only characteristics such as conductivity or insulating property of the thin film, but also disconnection or short-circuit failure of a wiring film formed on the thin film. And is an important management item in determining reliability.

Conventionally, when measuring the film thickness of a thin film formed by a thin film forming apparatus, a great amount of time is required for measuring the film thickness, and the measuring apparatus becomes large-scale.
Off-line measurement was the main. As a method for measuring the thickness of a thin film, various methods such as a stylus method for directly measuring a step of a thin film and a measurement method using an ellipsometer are used.

FIG. 18 shows a schematic configuration of a film thickness measuring apparatus using an ellipsometer. The thin film measuring device includes a polarizer 101 and an analyzer 102. The light from the light source is
The light is irradiated onto the thin film forming substrate 103 which becomes a work after being polarized by the polarizer 101. The light reflected by the substrate 103 is received by the analyzer 102, and the polarization state of the reflected light is detected by the detector. An optical constant (refractive index, extinction coefficient) of the film thickness is obtained by a detector comparing the polarization state of incident light and the polarization state of reflected light.

However, as shown in FIG.
4 covers the wiring pattern 105 such as metal,
6, the film thickness cannot be measured by the above-described measuring method because there are fine irregularities in that portion.

For this reason, a specific area without the wiring pattern 105 or the like is selected, and a film is formed on that area, or a film is formed on a dummy substrate without a wiring pattern, and the film thickness at an arbitrary point of the thin film is reduced. Measure. Then, the film forming conditions were determined so that the defect of the thin film on the dummy substrate was eliminated, and the film forming conditions were applied to an actual product, and the production was performed on the assumption that the same film was formed. .

[0008] As a measuring method in which the influence of irregularities on the substrate is small, there is a method utilizing light interference. This optical interferometry measures the thickness of a thin film by analyzing the spectrum of light reflected by a substrate or light transmitted through the substrate.

An example of the optical interference method will be described with reference to FIG. Light emitted from the light source is reflected by the substrate 103. The reflected light reflected on the surface side of the substrate 103 is a combination of light reflected on the surface of the thin film 104 and light reflected on the surface of the main body 106 of the substrate 103 excluding the thin film 104.

FIG. 21 shows a graph of FIG. 2 detected by a spectroscope.
6 is a graph showing the relationship between the wavelength of reflected light and the light intensity shown in FIG. In this graph, the horizontal axis represents the wavelength of the reflected light, and the vertical axis represents the light intensity. The light and the light interfere with each other, and the intensity of the light apparently varies with respect to the wavelength of the reflected light. Since this light interference is caused by an optical path difference between light and light, it depends on the film thickness of the thin film 104, the irradiation angle of light, and the like. The wavelength-light intensity curve in the graph also depends on the film thickness of the thin film 104. Change. Therefore, the thickness of the thin film 104 can be obtained by analyzing the wavelength-light intensity curve shape of the graph.

As a method for analyzing a wavelength-light intensity relationship curve as shown in FIG. 21, there is a method called a peak valley method. In this method, a wavelength at which the light intensity has a peak (points a and b in FIG. 21) in a wavelength-light intensity relationship curve is obtained, and the film thickness of the thin film is obtained from the relational expression.

As a film thickness measuring method using a wavelength-light intensity relationship curve, Japanese Patent Application Laid-Open No. Hei 5-10726 discloses an invention of a film thickness measuring method using transmitted light. In this measuring method, a wavelength-light intensity relationship curve of light transmitted through a transparent substrate is obtained using a light source and a sensor. Also,
Rather than simply determining the wavelength at which the light intensity peaks as in the peak-valley method, the film thickness and thickness of the thin film so that the relationship curve is closest to the theoretical relationship curve of wavelength-light intensity determined from the theoretical formula described below. The film thickness is measured by changing the refractive index. Transmittance of the thin film to T, 'the refractive index of the thin film, n' n ₀ the refractive index of air, n _'1 the refractive index of the transparent substrate,
r ₀ is the amplitude reflectance when light enters the thin film from the air, r ₁ is the amplitude reflectance when light enters the transparent substrate from the thin film, and δ is the phase shift when light travels through the thin film , Δ
₀ is the phase shift when light enters the thin film from the air,
When light of [delta] ₁ is a phase shift when entering the transparent substrate from the thin film, the following relation holds.

[0013]

(Equation 3)

The phase shift δ when light passes through the thin film
Depends on the thickness d of the thin film and the wavelength λ of the light, so that the relationship between the wavelength λ and the transmittance T of the thin film can be obtained from equation (1). Therefore, by changing the thickness d of the thin film and the refractive index n ′ of the thin film, the wavelength-light intensity theoretical relation curve obtained from the equation (1) is made closest to the wavelength-light intensity measurement relation curve. The thickness d of the thin film and the refractive index n ′ of the thin film at this time are measured values.

[0015]

In the film thickness measuring apparatus using the ellipsometer shown in FIG. 18, the positional relationship between the substrate 103, the polarizer 101 and the analyzer 102 must be fixed. For this reason, when there is vertical displacement, inclination, vibration, or the like of the substrate 103, it becomes impossible to measure the thickness of the thin film. In particular, in a production line of a liquid crystal display device using a thin glass substrate having a size of several hundred mm square or more and a thin glass substrate of about 0.5 to 1.1 mm, large warpage (partial inclination) and vibration of the substrate occur. . For this reason, in order to use the film thickness measuring apparatus in-line, it is necessary to install a stable large stage so as not to be affected by partial tilt or vibration. Further, the polarizer 101 and the analyzer 10
It is necessary to accurately set the positional relationship between the substrate 2 and the substrate 103 and align the optical axes. Therefore, it is difficult to measure a plurality of locations on the substrate 103 at the same time, or it is not possible to incorporate them in a limited space in-line.

In the above-described method of forming a film on a dummy substrate and measuring the film thickness at an arbitrary point of the thin film, an extra step of forming a film on the dummy substrate is required. Processing is required. For this reason, the number of film thickness measurement locations for one product must be reduced. Therefore, an oversight of the thickness abnormality or a delay in finding the abnormality may cause enormous damage.

Further, in various electronic components, fine patterns such as wiring and other metal films are formed between the substrate and the thin film. As a method of measuring the film thickness while reducing the influence to some extent, the peak valley method, which is the above-described optical interference method, can be mentioned. However, in the peak valley method, it is theoretically impossible to measure the thickness of a thin film unless two or more peaks or valleys of light intensity exist within the measured wavelength range. Even when two or more light intensity peaks or valleys exist, if light absorption by a thin film occurs in a wavelength region near the peak or valley, a phenomenon occurs in which the light intensity peak position shifts. Therefore, the film thickness cannot be measured accurately.

In the film thickness measurement method disclosed in Japanese Patent Application Laid-Open No. Hei 5-10726, since the waveform itself of the wavelength-light intensity curve is analyzed, even if there are no more than two light intensity peaks or valleys. The thickness of a thin film can be measured. However, this measurement does not consider the absorption coefficient of the thin film. Therefore, when there is absorption of the thin film in the measurement wavelength region, it is necessary to shift the measurement wavelength region to a wavelength region where the thin film does not absorb. Therefore, when measuring a plurality of thin films, a large number of light sources having different wavelength ranges are required, and a mechanism for switching the light sources depending on the type of the thin film to be measured is required. Therefore, the thickness of the film thickness measuring device increases, and the cost increases.

Further, since it is necessary to irradiate light in a wide wavelength range and to analyze the light, it takes time to measure the film thickness. Furthermore, since only a transparent substrate is targeted, it is difficult to measure the thickness of a thin film when the substrate is an opaque substrate or when a light-shielding film such as wiring is formed between the thin film and the substrate. Measurement accuracy may decrease.

Further, the positional relationship between the substrate, the light source and the sensor must be fixed. If the substrate has vertical displacement, inclination, vibration, or the like, the optical path may fluctuate. Therefore, it is difficult to accurately measure the film thickness. Particularly, in a production line of a liquid crystal display device using a thin glass substrate having a size of several hundred mm square or more and having a thickness of about 0.5 to 1.1 mm, large warpage (partial inclination) or vibration of the substrate may occur. Occurs. Therefore, in order to measure the film thickness in-line, it is necessary to install a large stage that is stable so as not to be affected by partial tilt or vibration. For this reason, the film thickness measuring device becomes large. In addition, it is necessary to align the optical axis with the positional relationship between the substrate and the sensor accurately. For this reason, it is difficult to simultaneously measure a plurality of locations in the substrate, and it is impossible to incorporate the sensor in a limited space in-line.

Although it is conceivable to measure the film thickness at a plurality of locations while moving the sensor, it is difficult to move the sensor at a high speed while maintaining the optical axis with high precision. Therefore, measurement time is required.

Further, the invention disclosed in Japanese Patent Application Laid-Open No. Hei 5-10726 is a measurement method using transmitted light, so that a light source and a sensor are provided on both sides of a substrate. Therefore, when the distance between the substrate and the light source or the sensor is too short when using in-line, the substrate may come into contact with the light source or the sensor due to the vibration or displacement of the substrate, and the substrate may be broken, It gets hurt.

In addition, since a thin film is measured by using transmitted light, light is difficult to transmit in a portion where a reflective film is formed at a constant area ratio on a substrate, so that measurement is difficult. is there.

Further, when a multilayer thin film is formed on a substrate, each thin film cannot be accurately calculated unless the absorption coefficient of each thin film is taken into consideration. When there is an uneven reflective film patterned at a constant area ratio on the lower glass substrate, and when light is reflected and refracted at each boundary surface of the multilayer film, the reflected light and the refracted light are not reflected. , Complexly distributed. For this reason, there is a problem in that the distribution of transmitted light becomes complicated and it is difficult to measure the thickness of the thin film.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a thin film capable of stably measuring the thickness of a thin film without being affected by partial inclination or vibration of a substrate. To provide a film thickness measuring device.

Another object of the present invention is to provide a thin film thickness measuring apparatus which can be incorporated in a limited space in-line.

Still another object of the present invention is to provide a thin film thickness measuring apparatus capable of measuring a thin film thickness regardless of the type and structure of the thin film.

Still another object of the present invention is to provide a thin film thickness measuring apparatus capable of measuring a film thickness with high accuracy and in a short time.

Still another object of the present invention is to provide a thin film thickness measuring apparatus capable of measuring a thin film thickness with high accuracy even in a portion where a reflective film is formed at a constant area ratio on a substrate. To provide.

Still another object of the present invention is to provide a thin film thickness measuring apparatus capable of measuring the thickness of a thin film of each layer with high accuracy even when a multilayer thin film is formed on a substrate. It is to be.

[0031]

According to a first aspect of the present invention, there is provided an apparatus for measuring the thickness of a thin film, comprising: a light source having a wavelength range of at least about 220 nm to 850 nm; Irradiating means for irradiating the irradiated thin film, light receiving means for receiving light reflected from the thin film or the substrate, spectral means for spectrally dividing the reflected light received by the light receiving means for each wavelength, and spectral light by the spectral means. About 220nm to 8
Calculating means for calculating the thickness of the thin film based on the intensity of the reflected light in the wavelength range of 50 nm.

The thickness of the thin film is measured using the reflected light at the boundary of the thin film. Therefore, the thickness of the thin film can be measured on a transparent substrate such as glass or an opaque substrate such as silicon, and the thickness of the thin film can be measured for a wide range of products. In addition, the film thickness is measured at least for the reflected light intensity in the wavelength range of about 220 nm to 850 nm. For this reason, it is possible to measure the film thickness with up to two lamps (a halogen lamp and a deuterium lamp). In addition, by analyzing the reflected light intensity in at least the wavelength range of about 220 nm to 850 nm, an ITO (indium tin oxide) film generally used for many electronic parts such as a liquid crystal display device, a semiconductor device and an image sensor, It is possible to measure the thickness of most single-layer films such as a silicon film, an amorphous silicon film, and an n ⁺ -type amorphous silicon film, and a multilayer film composed of these films. Therefore, regardless of the type and structure of the thin film, the thickness of the thin film can be measured.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the irradiating means guides the light from the light source and irradiates the thin film formed on the substrate with the optical fiber. And the light receiving means includes an optical fiber that receives the reflected light from the substrate and guides the received reflected light to the spectroscopic means.

The irradiating means and the light receiving means can be constituted only by the optical fiber. For this reason, the thin film thickness measuring device can be downsized, and even if it is an existing or new one, it can be easily incorporated by utilizing an empty space in the line.

According to a third aspect of the present invention, in addition to the configuration of the first or second aspect, the light source includes a plurality of lamps provided in the same housing and having different wavelength ranges.

By arranging a plurality of lamps in the same housing, switching of the light to be applied to the substrate is simplified as compared with the case where the lamps are provided in individual housings, and the structure of the irradiating means for guiding light from the light source is simplified. Can be For this reason,
A thin film thickness measuring device can be miniaturized.

According to a fourth aspect of the present invention, in addition to the configuration of the first or second aspect, the light source includes a plurality of lamps provided in different housings and having different wavelength ranges.

According to a fifth aspect of the present invention, in addition to the constitution of the third or fourth aspect, the plurality of lamps include a deuterium lamp and a halogen lamp.

According to a sixth aspect of the present invention, in addition to the configuration of the third aspect, the plurality of lamps can be turned on independently.

By independently lighting a plurality of lamps, the combination of lighting of the lamps can be changed, and light having various wavelength ranges can be irradiated to the thin film. Therefore, by selecting light in an appropriate wavelength range according to the material of the thin film, it is possible to appropriately measure the thickness of the thin film.

According to a seventh aspect of the present invention, in addition to the configuration of the first or second aspect, the light source is a halogen lamp having a wavelength range of at least about 400 nm to 850 nm, and the calculating means includes a spectrometer. About 40 spectroscopy by means
The thickness of the thin film on the substrate is calculated based on the intensity of the reflected light in the wavelength range from 0 nm to 850 nm.

It is possible to measure the thickness of a thin film using only one halogen lamp. Therefore, it is possible to reduce the size of the thin film thickness measuring device. In addition, from 400 nm to 85
By analyzing the reflected light intensity in the wavelength range of 0 nm, silicon nitride film, amorphous silicon film, n ⁺ type amorphous silicon film, etc., which are generally used for many electronic components such as liquid crystal display devices, semiconductor devices and image sensors Can be measured. In addition, the film thickness can be measured even with a multilayer film of these films. Therefore, regardless of the type and structure of the thin film, the thickness of the thin film can be measured.

According to an eighth aspect of the present invention, in addition to the configuration of any one of the first to seventh aspects, the irradiating means is provided at a position for irradiating the substrate with light substantially perpendicularly. The light receiving means is provided at a position for receiving light reflected substantially perpendicularly to the substrate.

By providing the irradiating means and the light receiving means substantially perpendicularly to the substrate, the irradiating means and the light receiving means can be integrated and incorporated into an empty space of an existing line. Further, since the incident angle of the light is substantially a right angle, the optical path deviation of the reflected light is reduced. Therefore, the thickness of the thin film can be measured without being affected by the vibration and inclination of the substrate, the distance between the substrate and the irradiation means and the light receiving means, and the like.

According to a ninth aspect of the present invention, in addition to the configuration of the eighth aspect of the present invention, the irradiating means guides light from a light source and makes the light substantially perpendicular to the thin film formed on the substrate. And the light receiving means includes a plurality of optical fibers respectively disposed around the optical fibers and receiving the reflected light from the substrate.

Even if the substrate is tilted, the axis is illuminated with light and the reflected light is received by any of the plurality of optical fibers. Therefore, the thickness of the thin film can be measured without being affected by the inclination of the substrate.

According to a tenth aspect of the present invention, in addition to the configuration of the eighth aspect, the light receiving means is provided at a position for receiving the light reflected substantially perpendicular to the substrate. The irradiating means includes an optical fiber, and the irradiating means includes a plurality of optical fibers respectively arranged around the optical fiber, for guiding light from the light source, and irradiating the light substantially perpendicularly to the thin film formed on the substrate.

Even if the substrate is tilted, any one of the lights radiated from the plurality of optical fibers to the axial object is received by one optical fiber located at the center of the plurality of optical fibers. . Therefore, the thickness of the thin film can be measured without being affected by the inclination of the substrate.

According to an eleventh aspect of the present invention, in addition to the configuration of the ninth or tenth aspect, one optical fiber and the plurality of optical fibers are columnar optical fibers having the same diameter. Include six optical fibers.

All the optical fibers have a cylindrical structure. Therefore, the coating of the optical fiber can be easily removed only by applying pressure from the outside. Further, the irradiation means and the light receiving means can be assembled simply by arranging six optical fibers around one optical fiber. Therefore, optimal positioning of the optical fiber can be easily performed.

The twelfth aspect of the present invention relates to the first to first aspects.
In addition to the configuration of the invention according to any one of the first to third aspects, the calculating means may further include: a refractive index of the substrate n ₀ , a refractive index of the thin film n ₁ , a refractive index of air n ₂ , a wavelength of light λ, and a thin film Assuming that the absorption coefficient is k and the reflection intensity of light at the wavelength λ of light is R, the expressions (2) to
The thickness d of the thin film is calculated by the equation (7).

[0052]

(Equation 4)

Equation (2) is an equation taking into account the absorption coefficient k of the thin film. Therefore, the film thickness of a thin film can be measured even in the wavelength range where light is absorbed, and the film thickness can be measured with high accuracy and in a short time without limiting the wavelength range of the light source.
Therefore, the film thickness of the thin film can be measured without reducing the tact of the line, and the in-line use is possible.

The thirteenth aspect of the present invention relates to the first to first aspects.
In addition to the configuration of the invention described in any one of the above, in addition to the configuration of the invention described above, the calculating means sets the refractive index of the substrate to n ₀ , the refractive index of the p-th layer from the substrate to n (p), and the refractive index of air to n (p + 1) ), Where λ is the wavelength of light and k (p) is the absorption coefficient of the thin film of the p-th layer, the expression (8)
The thickness d (p) of the thin film of the p-th layer is calculated by Expression (12).

[0055]

(Equation 5)

Equation (8) gives the absorption coefficient k of the thin film of each layer.
The equation takes into account (p). Therefore, the film thickness can be measured with high accuracy and in a short time without limiting the wavelength range of the light source, such as measuring the thickness of a thin film composed of a multilayer film even in the wavelength range where light is absorbed. For this reason, the film thickness of the thin film can be measured without reducing the tact of the line, and the in-line use is possible.

The invention according to claim 14 is the invention according to claims 1 to 1.
In addition to the configuration of the invention described in any one of 3 above, the thin film includes a transparent conductive film, and the substrate is a substrate coated with a reflective film.

Even if a thin film having an approximate refractive index exists under the thin film whose thickness is to be measured, the influence of the thin film having an approximate refractive index can be obtained by providing a reflective film below the thin film to be measured. The measurement of the thin film can be accurately performed without receiving the influence.

According to a fifteenth aspect of the present invention, in addition to the configuration of the fourteenth aspect, the reflective film has an area of more than 0% and 50% or less of the area of the film thickness measurement region, The calculating means calculates the thickness of the thin film ignoring the reflection on the reflective film.

The inventor of the present invention has assumed that the thickness measurement of a thin film can be performed accurately by assuming that the lower layer of the layer of interest is all a transparent substrate such as a glass substrate. Was confirmed experimentally.

According to a sixteenth aspect of the present invention, in addition to the configuration of the fourteenth aspect, the reflection film has an area of 50 to 100% of the area of the film thickness measurement target area, ,
The thickness of the thin film is measured ignoring the effect of light transmission to the lower thin film.

The inventor of the present invention claimed that the layer of interest was ITO
If the film is a transparent conductive film such as a layer and a reflective film of Ta is formed under the ITO layer, the thickness of the thin film is measured on the assumption that there is a uniform reflective film under the ITO layer. When,
It was experimentally confirmed that the thickness of the thin film could be accurately measured.

According to the seventeenth aspect of the present invention,
In addition to the configuration of the invention according to any one of the sixteenth aspects, the reflection film is a metal film or an alloy film containing tantalum, titanium, aluminum, chromium, or molybdenum as a main component.

These materials are materials generally used for semiconductor devices and liquid crystal display devices. Therefore, by using it as the lower reflective film of the thin film of interest,
Materials and steps for newly forming a reflective film are not required.

[0065]

[First Embodiment] FIG. 1 is a view for explaining a schematic configuration of a thin film thickness measuring apparatus according to a first embodiment of the present invention. This thin film thickness measuring device guides the light source 1 and the light from the light source 1 to a plurality of locations (here, two locations) on the substrate 3 and receives the reflected light from the substrate 3 at each location. The optical fiber 2, a light limiting shutter 4 for selectively blocking incident light guided to a plurality of portions of the substrate 3 and a plurality of reflected lights of the substrate 3, and a reflected light guided by the branched optical fiber 2 for each wavelength. It includes a spectroscope 5 for decomposing into light intensity and a calculator 6 for analyzing the light intensity for each wavelength to calculate the thickness of the thin film.

The light source 1 has, for example, a visible light wavelength range (4
Wavelength range (400 to 850n)
Only halogen lamps with m) are used. However, another lamp may be provided in the same light source room as the halogen lamp or in another light source room, and may be turned on and used at the same time, or may be switched on and used. In addition, for optical components such as the spectroscope 5, components capable of covering the wavelength range are used.

FIG. 2 is a diagram for explaining a schematic configuration of the branch type optical fiber 2. This branch optical fiber 2
An optical fiber 2a for guiding light from the light source 1 onto the substrate 3; and an optical fiber 2b for guiding light from the light source 1 to a measurement point on the substrate 3 and guiding reflected light from the measurement point on the substrate 3 to the spectroscope 5.
And an optical fiber 2c that guides light from the light source 1 to a measurement point on the substrate 3 and guides reflected light from the measurement point on the substrate 3 to the spectroscope 5; An optical fiber 2d for guiding light reflected from a point to the spectroscope 5.

FIG. 3 is a diagram for explaining the branch type optical fiber 2 in more detail. The optical fiber 2a includes two groups of optical fibers 2aa and 2ab. Optical fiber 2a
a guides light from the light source 1 to a measurement point on the substrate 3. The optical fiber 2ab guides light from the light source 1 to a measurement point on the substrate 3.

The optical fiber 2b is composed of two groups of optical fibers 2b.
a and 2bb. The optical fiber 2ba guides light from the light source 1 to a measurement point on the substrate 3. Optical fiber 2bb
Guides the reflected light from the measurement point on the substrate 3 to the spectroscope 5.

The optical fiber 2c is composed of two groups of optical fibers 2c.
a and 2cb. The optical fiber 2ca guides light from the light source 1 to a measurement point on the substrate 3. Optical fiber 2cb
Guides the reflected light from the measurement point on the substrate 3 to the spectroscope 5.

The optical fiber 2d is composed of two groups of optical fibers 2d.
a and 2db. The optical fiber 2 da guides the reflected light from the measurement point on the substrate 3 to the spectroscope 5. The optical fiber 2db transmits the reflected light from the measurement point on the substrate 3 to the spectroscope 5.
Lead to.

FIG. 4 is a diagram for explaining a schematic configuration of the light restricting shutter 4. As shown in FIG. This light restricting shutter 4 is shown in FIG.
Are provided in the middle of each of the optical fibers 2b and 2c. That is, it is provided between the connection point 2x between the optical fibers 2a and 2c (connection point between the optical fibers 2d and 2b) and the measurement point. The light limiting shutter 4b provided in the middle of the optical fiber 2b controls the switching between passing and blocking of incident light to the measuring point on the substrate 3 and reflected light from the measuring point by opening and closing.
Light limiting shutter 4c provided in the middle of optical fiber 2c
Controls switching between passing and blocking of incident light to the measuring point on the substrate 3 and reflected light from the measuring point by opening and closing. Closing one of the light limiting shutters 4b and 4c,
By opening the other, it is possible to select only one of the measurement points on the substrate 3 and the reflected light from the measurement point and guide it to the spectroscope 5. Further, by simultaneously opening the light-limiting shutters 4b and 4c, it is possible to measure the average value of the film thickness at and at the measurement points on the substrate 3.

FIG. 5 is a flowchart for explaining the processing procedure of the film thickness measurement processing executed by the computer 6. First, the light reflected from the substrate 3 is decomposed into light intensity (spectrum) for each wavelength by the spectroscope 5 (S1). Calculator 6
Acquires spectral data for each wavelength from the spectroscope 5 (S2), and calculates the thickness of the thin film using a theoretical formula described later (S3). The computer 6 displays the obtained film thickness on the screen of the computer 6, and stores and stores the data (S4). The computer 6 transfers the stored data to a centralized controller (not shown) (S5).

The centralized controller, which has received the data on the film thickness of the thin film from the computer 6, determines whether the difference in the film thickness between the measurement points in the substrate is exceeded when the film thickness exceeds a predetermined reference value. When it is large, or when the time change of the film thickness at a certain measurement point is large, a process for generating an abnormality such as issuing an alarm is performed.

Here, an example of a method of analyzing the thickness of a thin film will be described. When the refractive index of the substrate is n ₀ , the refractive index of the thin film is n ₁ , the refractive index of air is n ₂ , the absorption coefficient of the thin film is k, the thickness of the thin film is d, and the wavelength of the light source is λ, the reflection from the substrate is given. The light intensity R can be represented by equations (2) to (7).

The optical constants n and k are values that change depending on the wavelength λ of light. By performing a plurality of predetermined representative wavelengths or wavelength samplings (for example,
By performing sampling at intervals of 5 nm from 400 nm to 850 nm), the optical constants n and k are changed, and the upper and lower limits are set for each wavelength λ according to the film thickness assumed from the equations (2) to (7). The thickness d of the thin film is set in advance and is determined within the range of the upper and lower limits. By averaging the thickness d of the thin film at all wavelengths, the thickness of the thin film is obtained.

If the optical constants n and k are not known, the optical constants n and k and the thickness d of the thin film can be obtained as follows. For the thickness d of the thin film, the refractive index n _{1 of} the thin film, and the absorption coefficient k of the thin film for which the values are to be obtained, rough numerical values (for example, the assumed film thickness, the refractive index and the absorption coefficient at a representative wavelength) , Etc.) into equation (2). Next, upper and lower limits of the respective parameters d, n ₁ and k are set. For example, if the film thickness is d,
A value of ± 50% of the film thickness assumed as an initial value is set as an upper limit and a lower limit. The parameters d, n ₁ , and k are changed within the range of the upper limit value and the lower limit value, respectively, and are substituted into the equation (2). The resulting curve is closest to the actually measured wavelength-light intensity curve. Calculate the value of the parameter. More specifically, the difference between the light intensities of both curves is obtained for each wavelength, and each parameter can be obtained by changing the parameter so as to minimize the sum of the square of the difference in the measurement wavelength range. . With this method, the optical constants n and k and the film thickness d of the thin film can be obtained simultaneously.

Further, even when a multilayer thin film is formed on the substrate, the thickness of the thin film of each layer can be calculated in the same manner as described above. Here, the refractive index of the substrate is n
(0), the refractive index of the p-th layer thin film from the substrate is n (p), the refractive index of air is n (p + 1), the absorption coefficient of the p-th layer thin film from the substrate is k (p), and the substrate is the p layer The thickness of the eye thin film is d
(P), assuming that the wavelength of the light source is λ, the relationship shown in equations (8) to (12) is established between the reflected light intensity R (p + 1,0) from the substrate and these parameters.

By sequentially substituting values in the theoretical equation from the substrate to the first thin film, the second thin film, etc., ie, sequentially substituting 1, 2,. Are the optical constants (n (p), k
(P)) and the film thickness d (p). However, when thin films having similar optical constants are stacked adjacent to each other, the analysis is performed using the thin films as the same layer. Since the number of parameters increases as the number of thin films increases, the time required for calculation also increases. Also, as the number of thin films increases, the error from the actual value increases. However, according to the study of the present inventor, it has been confirmed that in a liquid crystal display device, even about three layers can be measured in-line.

The measurement point on the substrate may be one point in order to predict an abnormality of the liquid crystal display device. However, in the case of a substrate for a liquid crystal display device having a size of 1 m square or more, the thickness of the thin film is partially reduced. In many cases, local film thickness abnormalities occur rarely.
Therefore, it is desirable to measure about 3 to 5 points on one substrate.

FIG. 6A is a side view showing an example of the installation of the thin film thickness measuring apparatus according to the present embodiment.
(B) is a plan view thereof. As shown in FIG.
A sensor unit 10 in which a branch type optical fiber 2 shown in FIG. 1 is provided is provided with a support 10 provided in a film forming apparatus.
fixed to a. The branch optical fiber 2 is routed inside the column 10a. The sensor unit 10 has a gate opening (hereinafter, referred to as a “gate valve”) of a film forming apparatus.
The substrate 3 is mounted so as to irradiate light substantially perpendicularly to the substrate 3 located near 13. The distance between the two must be at least 10 mm so that the substrate 3 does not come into contact with the sensor unit 10 during the movement or maintenance of the substrate 3. However, in order to maintain the measurement accuracy, the distance is set to about 100 mm to several tens mm or less. Is preferred.

This film forming apparatus is, for example, a CVD (Chem
ical vapor deposition) apparatus, which forms a film in units of a plurality of substrates, and stores a plurality of formed substrates in trays. These substrates are stored in a load lock 14 provided inside the gate valve 13 in the unload chamber shown in FIG. 6B. Substrate transfer robot 11
Is to take out the substrates one by one from the load lock 14, place them on the robot hand 12, and move them so that the substrate 3 is located directly below the sensor unit 10. When there are a plurality of measurement points in one substrate, the robot 11 sequentially moves the substrate 3 so that the next measurement point is directly below the sensor unit 10 each time measurement of a certain measurement point is completed. Repeat the move. Each time the substrate 3 moves, the sensor unit 10
The film thickness is measured at each measurement point. FIG.
(C) shows the shape of the robot hand 12. Substrate 3
Is often supported in a generally U-shape,
As it moves away from the point at which it is supported, the substrate 3 sags under its own weight. Therefore, the relative position of the substrate 3 is shifted by several mm or slightly inclined. Therefore,
It is necessary for the film thickness measuring device to maintain measurement accuracy with respect to such a deviation or inclination.

Next, the structure of the sensor unit 10 will be described in detail. The optical fiber 2b and the optical fiber 2c described above with reference to FIGS. 2 and 3 are provided at the tip of the sensor unit 10.

The optical fiber 2b includes the optical fibers 2ba and 2bb as described above. As shown in FIG. 7, the optical fiber 2ba is composed of six optical fibers, and is arranged around the optical fiber 2bb. Also, the optical fiber 2bb
And the six optical fibers 2ba have the same diameter. With such a structure, as shown in FIG. 8, six optical fibers 2ba are arranged around optical fiber 2bb, and only by fixing them with a jig, optical fiber 2bb and optical fiber 2ba are connected to each other. Can be parallel. For this reason, the assembly of the optical fiber 2b becomes easy. Further, even if the substrate 3 is tilted at the time of measuring the film thickness, the reflected light of the light emitted from any of the six optical fibers 2ba is received by the optical fiber 2bb. Therefore, the thickness of the thin film can be measured without being affected by the inclination of the substrate 3.

The optical fiber 2c is configured similarly to FIG. FIG. 9 to FIG. 11 are diagrams for explaining the effects of vertical displacement, inclination, and vibration of the substrate on measured values. It is assumed that three layers of a GI layer (silicon nitride), an i layer (amorphous silicon), and an n ⁺ layer (n ⁺ type amorphous silicon) are formed on the substrate.
FIG. 9 is a graph in which the horizontal axis represents the distance between the sensor unit 10 and the substrate 3 and the vertical axis represents the thickness of the thin film measured by the above-described film thickness measuring device. As can be seen from FIG. 9, even in the multilayer structure in which the GI layer, the i layer, and the n ⁺ layer are deposited, each layer is measured with almost no fluctuation due to the movement of the distance. Note that, as described above, the distance between the sensor unit 10 and the substrate 3 is displaced by about several mm due to the warpage of the substrate 3, but the measurement of the thickness of the thin film can be performed without being affected by this. It is possible.

FIG. 10 is a graph in which the horizontal axis represents the inclination angle of the substrate 3 with respect to the sensor unit 10, and the vertical axis represents the film thickness measured by the above-described film thickness measuring device.
When the inclination angle is 3-4 ° or more, the reflected light received is
10% or less as compared with the case where the inclination angle is 0 °, FIG.
As can be seen from the above, even in the multilayer structure in which the GI layer, the i layer, and the n ⁺ layer are stacked, if the inclination of the substrate 3 is 8 ° or less (more preferably, if the inclination of the substrate 3 is 2 ° or less). ), The thickness of the thin film can be measured relatively accurately.

FIG. 11 is a graph showing the influence of the vertical vibration of the substrate 3. The intensity of the reflected light was measured every 10 seconds under the conditions of a vertical amplitude of 4 mm and a frequency of 5 Hz. In the graph of FIG. 11, the measurement time is plotted on the horizontal axis, and the reflection intensity of the reflected light measured by the above-described film thickness measurement device is plotted on the vertical axis. As can be seen from FIG. 11, the reflection intensity is stable even when vibration is applied.

The above-mentioned GI layer, i-layer and n ⁺ are covered so as to cover the reflection film made of tantalum (Ta) as shown in FIG.
The thickness of each layer of the three-layer structure in which the layers were deposited was measured. At this time, the film thickness is measured on the assumption that all layers below the layer of interest are glass substrates. FIG. 13 shows a GI layer, an i-layer, and an n in a portion where a reflective film is not present, inside a display portion of a liquid crystal display device where a reflective film is present at about 10%, and around a display portion of a liquid crystal display device where a reflective film is present at about 50%. ⁺
The thickness of the layer is shown. Variations in the GI layer, the i layer and the n ⁺ layer were ± 2.5%, ± 1.3%, ±
It is about 1.0%, and the measurement result of the film thickness of each layer is stable. This is because by applying substantially perpendicular light to the substrate 3, the influence of light refraction is reduced, and the effect of changing the light reflection direction at the edge of the reflective film is reduced.

In the halogen lamp used as the light source 1 when determining the thickness of the thin film, the light amount and the wavelength distribution change with time. For this reason, when calculating the reflected light intensity R, it is preferable to periodically obtain the spectrum of the irradiation light of the light source 1 using the total reflection substrate and correct various parameters.

Note that, as shown in FIG.
bb may be composed of six optical fibers, and may be arranged around the optical fiber 2ba having the same diameter to constitute the optical fiber 2b. With such a structure, the assembly of the optical fiber 2b is facilitated. Further, even if the substrate 3 is tilted at the time of measuring the film thickness, the reflected light of the light emitted from the optical fiber 2ba is received by any of the six optical fibers 2ba. Therefore, the thickness of the thin film can be measured without being affected by the inclination of the substrate 3. The optical fiber 2c may have the same configuration.

As described above, in the thin film thickness measuring apparatus according to the present embodiment, the structure of the sensor unit 10 is extremely simple. For this reason, miniaturization becomes possible.

Further, when analyzing the measurement of the film thickness, the analysis can be performed only with the wavelength-light intensity curve. Therefore, the thickness of a thin film can be measured in a short time even in a multilayer film or multi-point measurement.

In addition, since the film thickness measuring device is compact,
Easy to incorporate into production line. Furthermore, since the film thickness can be measured in a short time, the film thickness can be measured immediately after the film formation, and the time lag from the occurrence of an abnormality during manufacturing to the discovery can be shortened. Damage can be minimized.

Further, by accumulating and storing the data of the film thickness and analyzing the data, the life of the film forming apparatus or the film forming material, the appropriate maintenance time of the film forming apparatus, the time of changing the film forming conditions, etc. Can be predicted. As a result, unexpected maintenance can be avoided,
The stable operation of the film forming apparatus becomes possible.

[Second Embodiment] A thin film thickness measuring apparatus according to a second embodiment of the present invention is the same as the thin film thickness measuring apparatus according to the first embodiment. Therefore, description will not be repeated. In this embodiment mode, a case where the thickness of an ITO film which is a transparent conductive film having a thickness of 100 nm (= 1000 °) or less is measured. An ITO film generally used for a liquid crystal display device is used as a pixel electrode. FIG.
3 shows a cross-sectional structure of a pixel portion of a transmission type liquid crystal display device. In such a structure, the characteristics of the thin ITO film hardly appear as a distribution of the reflected light intensity. Therefore, it is difficult to measure the thickness of the ITO film by the evaluation method described in the first embodiment.

However, in the case of a liquid crystal display device or the like, for example, an ITO
In many cases, a reflective film such as Ta is formed below the film.
When there is a reflective film such as Ta in the lower layer, the distribution of the reflected light intensity is stabilized, and high-precision measurement can be performed at that portion. The area of the reflective film is 50% or more of the total area.

FIG. 16 shows the results of measuring the thickness of the ITO film using the same light source 1 comprising a halogen lamp (wavelength range of about 400 nm to about 850 nm) as in the first embodiment.
The horizontal axis shows the set film thickness under the production conditions, and the vertical axis shows the measurement result by the film thickness measuring device. When the thickness of the thin film is 60 nm (=
In the case of 600 °), the measured value of the film thickness is stable. I
When the thickness of the TO film is other than 60 nm, there is large variation in measured values. For this reason, it becomes difficult to detect a film thickness abnormality.

For this reason, a halogen lamp and a deuterium lamp are used as the light source 1 and are put in the same light source room and are simultaneously turned on (wavelength range from about 220 nm to about 850 nm).
Then, the thickness of the ITO film was measured. As a result, a graph as shown in FIG. 17 was obtained. As can be seen from this graph, the variation of the measured value is small at any film thickness, and the correlation between the set film thickness and the measured value under the production conditions is high. However, there is a slight difference between the set film thickness and the measured value. This is due to the fact that the absorption coefficient k (p) is kept constant for each wavelength in order to increase the calculation speed (assuming that there is a uniform reflective film under the ITO layer). Therefore, if the relationship between the set film thickness and the measured value is known in advance, accurate measurement of the film thickness becomes possible by correcting the measured value. However, when using a film thickness measurement device in-line to detect a film thickness abnormality,
Only the temporal change of the film thickness at the measurement point need be known. In such a case, it is not necessary to correct the measured value.

As described above, in the film thickness measuring apparatus according to the present embodiment, by using the light source 1 in which the halogen lamp and the deuterium lamp are simultaneously turned on, the wavelength range is from about 220 nm to about 850 nm. A film thickness measurement for light is performed. Generally, to measure a thin film, the film thickness must be measured using light having a short wavelength. Therefore, by simultaneously turning on the deuterium lamp, the thickness of the ITO film can be measured more accurately than when only the halogen lamp is used.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a schematic configuration of a branch type optical fiber 2.

FIG. 3 is a diagram for explaining the branch type optical fiber 2 in more detail;

FIG. 4 is a diagram for explaining a schematic configuration of a light limiting shutter.

FIG. 5 is a flowchart illustrating a processing procedure of the thin film thickness measuring apparatus according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating an example of installation of a thin film thickness measuring device according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating a configuration of an optical fiber 2b.

FIG. 8 is a diagram showing a configuration of an optical fiber 2b.

FIG. 9 is a graph showing the results of measuring the thickness of a thin film when the distance between the sensor unit and the substrate is changed.

FIG. 10 is a graph showing the results of measuring the thickness of a thin film when the inclination angle of the substrate with respect to the sensor unit is changed.

FIG. 11 is a graph showing a temporal change in the intensity of reflected light incident on a sensor unit when a vertical vibration is applied to a substrate.

FIG. 12 shows a GI layer covering a reflective film made of Ta;
FIG. 4 is a diagram showing a three-layer structure in which an i layer and an n ⁺ layer are deposited.

FIG. 13 is a graph showing the results of measuring the thickness of a thin film when the area ratio of the reflective film is changed.

FIG. 14 is a diagram showing a configuration of an optical fiber 2b.

FIG. 15 is a diagram illustrating a cross-sectional structure of a pixel portion of a transmissive liquid crystal display device.

FIG. 16 is a graph showing a measurement result of the thickness of an ITO film when a halogen lamp is used as a light source.

FIG. 17 is a graph showing a measurement result of a film thickness of an ITO film when a halogen lamp and a deuterium lamp are used as light sources.

FIG. 18 is a view for explaining a method of measuring a film thickness using a conventional ellipsometer.

FIG. 19 is a diagram showing an example of a substrate whose film thickness cannot be measured.

FIG. 20 is a diagram illustrating an example of a conventional optical interference method.

FIG. 21 is a diagram illustrating an example of the relationship between the wavelength of reflected light and the light intensity.

[Explanation of symbols]

1 light source, 2 branch type optical fiber, 2a, 2b, 2c,
2d, 2aa, 2ab, 2ba, 2bb, 2ca, 2c
b, 2da, 2db optical fiber, 3,106 substrates,
4, 4b, 4c Light limiting shutter, 5 spectroscope, 6 computer, 10 sensor unit, 10a support, 11 robot, 12 robot hand, 13 gate valve, 1
4 load lock, 101 polarizer, 102 analyzer,
103 thin film forming substrate, 104 thin film layer, 105 wiring pattern.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toru Tanikawa 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 2F065 AA30 CC17 CC25 CC31 DD00 DD02 DD06 DD11 DD14 FF44 GG02 GG23 GG24 HH13 LL02 LL03 LL30 LL33 LL34 LL67

Claims (17)

[Claims] 1. At least about 220 nm to 850 nm
A light source having a wavelength range of: irradiating means for guiding light from the light source to irradiate a thin film formed on a substrate; light receiving means for receiving light reflected from the thin film or the substrate; A spectroscopy unit for separating the reflected light received by the unit for each wavelength, and about 220 nm to 850 nm separated by the spectroscopic unit.
Calculating means for calculating the thickness of the thin film based on the intensity of the reflected light within the wavelength range of. 2. The irradiating unit includes an optical fiber for guiding light from the light source and irradiating the thin film formed on the substrate, and the light receiving unit receives the reflected light from the substrate. And
The thin film thickness measuring device according to claim 1, further comprising an optical fiber for guiding the received reflected light to the spectral unit. 3. The thin film thickness measuring device according to claim 1, wherein the light source includes a plurality of lamps provided in the same housing and having different wavelength ranges. 4. The thin film thickness measuring apparatus according to claim 1, wherein the light source includes a plurality of lamps provided in different housings and having different wavelength ranges. 5. The thin film thickness measuring apparatus according to claim 3, wherein the plurality of lamps include a deuterium lamp and a halogen lamp. 6. The thin film thickness measuring apparatus according to claim 3, wherein each of the plurality of lamps can be turned on independently. 7. The light source is a halogen lamp having a wavelength range of at least about 400 nm to 850 nm;
The thin film thickness measuring device according to claim 1, wherein a thickness of the thin film on the substrate is calculated based on an intensity of the reflected light in a wavelength range from m to 850 nm. 8. The irradiating means is provided at a position for irradiating light substantially perpendicularly to the substrate, and the light receiving means is provided at a position for receiving light reflected substantially perpendicularly to the substrate. The thin film thickness measuring device according to any one of claims 1 to 7, which is provided. 9. The irradiating means includes one optical fiber that guides light from the light source and irradiates light substantially perpendicularly to a thin film formed on the substrate; The thin film thickness measuring device according to claim 8, further comprising a plurality of optical fibers arranged around the fibers and respectively receiving the reflected light from the substrate. 10. The light receiving means includes one optical fiber disposed at a position for receiving light reflected substantially perpendicularly to the substrate, and the irradiating means is disposed around each of the optical fibers. 9. The thin film thickness measuring apparatus according to claim 8, further comprising a plurality of optical fibers for guiding light from the light source and irradiating the light substantially perpendicularly to the thin film formed on the substrate. 11. The optical fiber according to claim 9, wherein the one optical fiber and the plurality of optical fibers are cylindrical optical fibers having the same diameter, and the plurality of optical fibers include six optical fibers. For measuring the thickness of thin films. 12. The calculating means, wherein the refractive index of the substrate is n ₀ , the refractive index of the thin film is n ₁ , the refractive index of air is n ₂ , the wavelength of light is λ, the absorption coefficient of the thin film is k, Further, assuming that the reflection intensity of the light at the wavelength λ of the light is R, the thickness d of the thin film is calculated by the following equation based on the intensity of the reflected light split by the splitting means. A film thickness measuring device for a thin film according to any one of the above. (Equation 1) 13. The calculating means sets a refractive index of the substrate to n ₀ , a refractive index of a p-th thin film from the substrate to n (p),
Assuming that the refractive index of air is n (p + 1), the wavelength of light is λ, and the absorption coefficient of the thin film of the p-th layer is k (p), the following equation is obtained based on the intensity of the reflected light split by the splitting means. The thin film thickness measuring device according to claim 1, wherein a thickness d (p) of the p-th thin film is calculated by an equation. (Equation 2) 14. The thin film includes a transparent conductive film, and the substrate is a substrate coated with a reflective film.
An apparatus for measuring the thickness of a thin film according to claim 1. 15. The reflection film has an area of more than 0% and not more than 50% of the area of the film thickness measurement target area, and the calculating means ignores the reflection at the reflection film and calculates the thickness of the thin film. The apparatus for measuring the thickness of a thin film according to claim 14, wherein the thickness is calculated. 16. The reflection film has an area of 50 to 100% of the area of the film thickness measurement target area, and the calculating means ignores the influence of light transmission to the underlying thin film, and The apparatus for measuring the thickness of a thin film according to claim 14, which measures the thickness. 17. The thin film thickness measuring apparatus according to claim 14, wherein the reflection film is a metal film or an alloy film containing tantalum, titanium, aluminum, chromium, or molybdenum as a main component.