JP2007248312A - Film thickness measuring method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film thickness measuring method and so forth capable of precisely measuring a thickness of a light transmitting film provided on a support substrate. <P>SOLUTION: In the film thickness measuring method for measuring the film thickness of the film having light transmitting properties provided on the support substrate, light is incident on the film, reflected light obtained by interference between the light reflected by a surface of the film and the light reflected by a surface of the support substrate is dispersed, the amount of light of the separated reflected light is detected, wavelengths where the reflectance is at the minimum or the maximum are acquired by magnifying reflectance at an arbitrary size when calculating the reflectance from the amount of light, and the wavelengths at which the reflectance is at the minimum and the maximum and refractive index of the film are used to measure the thickness of the film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a film thickness measuring method and a film thickness measuring apparatus.

  As a method for measuring the film thickness of the film applied on the support substrate, a contact film thickness measuring method such as a step gauge, a surface roughness meter, an eddy current film thickness meter, a capacitance film thickness meter, a fluorescent X-ray film Examples include a non-contact film thickness measuring method such as a thickness gauge and a light interference film thickness meter, and a photographic method for observing a sample cross section such as an optical microscope and an electron microscope.

  Among these, the contact-type film thickness measurement method has a problem that the measurement object used for measurement cannot be used as a product because it damages the measurement object, and the photographic method also has a cross section of the measurement object. Since it is a destructive inspection to observe, it has the same problem. In addition, when the film thickness is 1 μm or less, both the contact-type film thickness measurement method and the photographic method may cause elastic deformation due to contact at the time of measurement or sample preparation, and there is a possibility that an accurate film thickness cannot be measured. is there.

  Even in the non-contact type film thickness measurement method, the capacitance type film thickness meter has problems in measurement accuracy, resolution, etc., and the fluorescent X-ray film thickness meter has not only limited the material that can be measured, but also the film thickness. When the thickness is around 1 μm, there is a problem of measurement accuracy.

  For this reason, a non-contact, non-destructive measurement technique with high measurement accuracy is desired. As a countermeasure, a film thickness meter using the principle of the optical interference method has been used in many cases.

  Since the optical interference method is an optical measurement, it has an advantage that the film thickness can be measured without physical contact. However, when the surface is rough, scattering increases and the amount of reflected light becomes weak. For this reason, depending on the surface state, the required measurement accuracy may not be obtained, and measurement may not be possible.

  As described above, the optical interference method is based on the precondition that the surface of the object to be measured is a parallel plane. If the surface of the support substrate or the film is rough, a sufficient amount of reflected light is detected by light scattering. Becomes difficult.

  In order to solve this problem, a method is disclosed in which the film thickness is measured using light having a wavelength longer than the ten-point average roughness of the substrate, particularly when the surface of the substrate of the electrophotographic photosensitive member is rough (patent) Reference 1). However, there is a problem that the film thickness cannot be measured when the ten-point average roughness of the substrate is equal to or greater than the wavelength of the measuring light.

  Similarly, there is disclosed a method for measuring the film thickness using light having a wavelength longer than the maximum surface roughness height of the substrate when the surface of the substrate of the electrophotographic photosensitive member is rough. However, there is a problem that the film thickness cannot be measured when the maximum surface roughness height of the substrate is equal to or greater than the wavelength of the measurement light.

In the photoconductive photoconductor, the thickness of the photosensitive layer can be reduced by using interference between reflected light on the surface of the light-transmitting photosensitive layer and reflected light on the surface of the undercoat layer. A measuring method is disclosed (see Patent Document 3). However, this method is suitable for film thickness measurement using the difference in refractive index between the layers of the laminated photoconductive photoconductor, but the film on the support substrate having a rough surface, in particular, the film thickness is 1 μm or less. There is a problem that it is not suitable for film thickness measurement.
JP 2000-356859 A Japanese Patent No. 3534632 JP 2003-287409 A

  The present invention provides a film thickness measuring method and a film thickness measuring apparatus capable of accurately measuring the film thickness of a light-transmitting film provided on a support substrate in view of the problems of the above-described conventional technology. For the purpose.

  A first aspect of the present invention is a film thickness measuring method for measuring a film thickness of a light-transmitting film provided on a support substrate, wherein light is incident on the film and reflected by the surface of the film When the reflected light obtained by interference between the light and the light reflected on the surface of the support substrate is dispersed, the amount of the reflected reflected light is detected, and the reflectance is calculated from the light amount, The wavelength at which the reflectance becomes minimum and maximum is obtained by expanding the reflectance to an arbitrary size, and the film thickness is determined by using the wavelength at which the reflectance is minimum and maximum and the refractive index of the film. It is a film thickness measuring method characterized by measuring.

  According to a second aspect of the present invention, in a film thickness measuring apparatus for measuring a film thickness of a light-transmitting film provided on a support substrate, a light source and light emitted from the light source are transmitted and emitted. And a fiber probe that receives and transmits the reflected light, and a focusing optical system that condenses the light emitted from the fiber probe emitting portion on the film, the light reflected on the surface of the film, and A spectroscopic means for spectroscopically reflecting reflected light obtained by interference with the light reflected by the surface of the support substrate; a light quantity detecting means for detecting the light quantity of the spectroscopically reflected light; and when calculating the reflectance from the light quantity The wavelength at which the reflectance becomes minimum and maximum is obtained by enlarging the reflectance to an arbitrary size, and the film thickness of the film is determined using the wavelength at which the reflectance becomes minimum and maximum and the refractive index of the film. A calculation means for calculating the thickness; Has a film thickness measuring device which is characterized in that is configured to vertically incident on the surface of the film having optical transparency provided the light on a supporting substrate.

  ADVANTAGE OF THE INVENTION According to this invention, the film thickness measuring method and film thickness measuring apparatus which can measure the film thickness of the light-transmitting film | membrane provided on the support substrate accurately can be provided.

  Next, an embodiment of the present invention will be described.

  According to a first embodiment of the present invention, in a film thickness measurement method for measuring a film thickness of a light-transmitting film provided on a support substrate, light is incident on the film and reflected by the surface of the film. When the reflected light obtained by the interference between the reflected light and the light reflected on the surface of the support substrate is dispersed, the amount of the reflected reflected light is detected, and the reflectance is calculated from the amount of light, The wavelength at which the reflectance becomes minimum and maximum is obtained by enlarging the reflectance to an arbitrary size, and the film thickness of the film is determined using the wavelength at which the reflectance becomes minimum and maximum and the refractive index of the film. Is measured.

  According to the first embodiment of the present invention, light is incident on the film, and reflected light obtained by interference between the light reflected on the surface of the film and the light reflected on the surface of the support substrate is reflected. The wavelength at which the reflectivity is minimized and maximized by expanding the reflectivity to an arbitrary size when spectrally detecting and detecting the light amount of the split reflected light and calculating the reflectivity from the light amount And the film thickness of the film is measured using the wavelength at which the reflectance becomes minimum and maximum and the refractive index of the film, so that the film thickness of the film provided on the support substrate can be accurately measured. A measurement method can be provided.

  According to a second embodiment of the present invention, in the film thickness measuring apparatus according to the first embodiment of the present invention, the ten-point average roughness of the support substrate is equal to or greater than the wavelength of the light.

  According to the second embodiment of the present invention, when the ten-point average roughness of the support substrate is equal to or greater than the wavelength of the light, the film thickness measuring method according to the first embodiment of the present invention The film thickness can be accurately measured in the measurement wavelength region shorter than the point average roughness.

  According to a third embodiment of the present invention, in the film thickness measurement method according to the first or second embodiment of the present invention, the ten-point average roughness of the support substrate is 0.7 μm or more and 1.2 μm or less. It is characterized by.

  According to the third embodiment of the present invention, when the ten-point average roughness of the support substrate is 0.7 μm or more and 1.2 μm or less, the film thickness measuring method according to the first embodiment of the present invention. Thus, the film thickness can be accurately measured using light having a wavelength equal to or less than the ten-point average roughness.

  According to a fourth embodiment of the present invention, in the film thickness measurement method according to any one of the first to third embodiments of the present invention, the support substrate has a cylindrical shape.

  According to the fourth embodiment of the present invention, when the support substrate has a cylindrical shape, the film thickness can be accurately measured by the film thickness measuring method according to the first embodiment of the present invention. .

  According to a fifth embodiment of the present invention, in the film thickness measurement method according to any one of the first to fourth embodiments of the present invention, the film thickness is not less than 0.3 μm and not more than 1.5 μm. It is characterized by.

  According to the fifth embodiment of the present invention, when the film thickness is 0.3 μm or more and 1.5 μm or less, the film thickness is measured by the film thickness measuring method according to the first embodiment of the present invention. Can be measured with high accuracy.

  According to a sixth embodiment of the present invention, in the film thickness measurement method according to any one of the first to fifth embodiments of the present invention, the amount of reflected light of a standard sample for calibrating the reflectance of reflected light is reduced. Thus, the reflectance is increased to an arbitrary size.

  According to the sixth embodiment of the present invention, the reflectance is increased to an arbitrary size by reducing the amount of reflected light of the standard sample for calibrating the reflectance of the reflected light. Thickness can be measured accurately.

  According to a seventh embodiment of the present invention, in the film thickness measurement method according to any one of the first to sixth embodiments of the present invention, the diameter of light incident on the film surface is 0.9 mm. As described above, the thickness is 1.5 mm.

  According to the seventh embodiment of the present invention, the diameter of light incident on the surface of the film is 0.9 mm or more and 1.5 mm, so that the support substrate depends on oxidation. Even when there is dirt or the surface roughness of the support substrate is large, the film thickness can be accurately measured.

  In an eighth embodiment of the present invention, in a film thickness measuring apparatus for measuring the film thickness of a light-transmitting film provided on a support substrate, a light source and light emitted from the light source are transmitted and emitted. And a fiber probe for receiving and transmitting the reflected light, and a focusing optical system for condensing the light emitted from the fiber probe emitting portion on the film, and the light reflected by the surface of the film, A spectroscopic means for spectroscopically reflecting reflected light obtained by interference with the light reflected by the surface of the support substrate; a light quantity detecting means for detecting the light quantity of the spectroscopically reflected light; and calculating the reflectance from the light quantity Further, the wavelength at which the reflectance becomes minimum and maximum is obtained by enlarging the reflectance to an arbitrary size, and the wavelength at which the reflectance becomes minimum and maximum and the refractive index of the film are used. Calculation hand to calculate film thickness It has the door, characterized in that is configured to vertically incident on the surface of the film having optical transparency provided the light on a supporting substrate.

  According to an eighth embodiment of the present invention, a light source, a fiber probe that transmits and emits light emitted from the light source and receives and transmits the reflected light, and light emitted from the light source. A focusing optical system for condensing the film; a spectroscopic unit for spectroscopically reflecting reflected light obtained by interference between light reflected from the surface of the film and light reflected from the surface of the support substrate; A light amount detecting means for detecting the amount of reflected light, and calculating the reflectance from the light amount, obtaining a wavelength at which the reflectance is minimized and maximized by expanding the reflectance to an arbitrary size; A light-transmitting film provided on a support substrate, the light source having a calculating means for calculating a film thickness of the film using a wavelength at which the reflectance becomes minimum and maximum and a refractive index of the film Configured to make normal incidence on the surface of Because there can be provided a thickness measuring apparatus capable of measuring the thickness of a film disposed on a supporting substrate accurately.

  According to a ninth embodiment of the present invention, in the film thickness measuring apparatus according to the eighth embodiment of the present invention, the numerical aperture of the focusing optical system is 0.05 or more and 0.3 or less.

  According to the ninth embodiment of the present invention, since the numerical aperture of the focusing optical system is not less than 0.05 and not more than 0.3, good detection light can be obtained. By setting it to 0.3 or less, it is possible to obtain detection light that satisfies the basic principle of “vertical incidence / vertical light reception necessary for interference measurement” at the minimum. It is possible to secure a sufficient amount of light.

  According to a tenth embodiment of the present invention, in the film thickness measuring apparatus according to the eighth or ninth embodiment of the present invention, the focusing optical system is an achromatic lens.

  According to the tenth embodiment of the present invention, since the focusing optical system is an achromatic lens, detection light with good wavelength accuracy can be obtained.

  According to an eleventh embodiment of the present invention, in the film thickness measuring apparatus according to any one of the eighth to tenth embodiments of the present invention, the light source is a halogen-tungsten lamp.

  According to the eleventh embodiment of the present invention, since the light source is a halogen-tungsten lamp, it can emit light in a bright wide wavelength region.

  According to a twelfth embodiment of the present invention, in the film thickness measuring device according to any one of the eighth to eleventh embodiments of the present invention, the spectroscopic means is a diffraction grating, a prism, or a spectroscopic filter. To do.

  According to the twelfth embodiment of the present invention, since the spectroscopic means is a diffraction grating, a prism, or a spectral filter, it is possible to perform spectroscopic analysis with high accuracy.

  According to a thirteenth embodiment of the present invention, in the film thickness measuring apparatus according to any one of the eighth to twelfth embodiments of the present invention, the light amount detecting means is a line sensor or a silicon photodiode array. And

  According to the thirteenth embodiment of the present invention, since the light amount detection means is a line sensor or a silicon photodiode array, the detection light can be detected with high accuracy.

  In a fourteenth embodiment of the present invention, in the film thickness measurement device according to any one of the eighth to thirteenth embodiments of the present invention, the light emitted from the light source is transmitted and emitted, and the reflected light is emitted. It further includes a fiber probe that receives and transmits light, and the end of the fiber probe on the objective lens side is centered on the end of the detection light transmission fiber, which is surrounded by the exit side of the irradiation light guiding fiber. It is comprised as follows.

  According to the fourteenth embodiment of the present invention, the end of the fiber probe on the objective lens side is centered on the end of the detection light transmission fiber, and this is surrounded by the emission side end of the irradiation light guide fiber. Thus, the detection light necessary for interference measurement can be measured with high accuracy.

  According to a fifteenth embodiment of the present invention, in the film thickness measuring device according to any one of the eighth to fourteenth embodiments of the present invention, the refractive index is stored in the computing unit so as to be usable. Features.

  According to the fifteenth embodiment of the present invention, since the refractive index is stored so as to be usable in the calculation means, the film thickness can be calculated with high accuracy.

  According to a sixteenth embodiment of the present invention, in the film thickness measuring device according to any one of the eighth to fifteenth embodiments of the present invention, the spectral light emitted from the light source is provided on the support substrate. It includes a wavelength region that is equal to or greater than the optical absorption edge of the film having s.

  According to the sixteenth embodiment of the present invention, the spectral light emitted from the light source includes a wavelength region that is greater than or equal to the optical absorption edge of the light-transmitting film provided on the support substrate. Necessary detection light can be secured.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  The film thickness measuring method of the present invention measures the film thickness of a light transmissive film (hereinafter referred to as a coat film) provided on a support substrate. Specifically, spectral light is incident on the coating film, and the reflected light obtained by the interference between the light reflected on the surface of the coating film and the light reflected on the surface of the support substrate is dispersed, and the reflected light is dispersed. Detect the amount of light. Furthermore, when calculating the reflectance from the light amount, the wavelength at which the reflectance is minimized and maximized is obtained by expanding the reflectance to an arbitrary size, the wavelength at which the reflectance is minimized and maximized, and the refraction of the coating film The film thickness of the coat film is measured using the rate.

  In the present invention, the coating film is not particularly limited as long as it is optically transparent. That is, the film thickness of the coating film can be measured as long as it is an object to be measured in which a coating film is provided on the support substrate by the method described below. Furthermore, the support substrate may have a ten-point average roughness equal to or greater than the wavelength of the spectrum light used for film thickness measurement.

  The support substrate is not particularly limited as long as it reflects spectrum light used for film thickness measurement. Support substrates having various shapes such as a sheet shape (flat plate shape) and a pipe shape (a cylindrical shape having a curvature) can be used.

  Specific examples of the supporting substrate include a material obtained by molding a metal such as aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum or the like into a sheet or pipe, or a metal oxide such as tin oxide or indium oxide. Examples of the material include a sheet-like or pipe-like plastic, a paper-coated material, a material obtained by further providing a layer in which a metal powder or the like is dispersed in a binder resin.

  A specific example of the object to be measured includes a photoconductive photosensitive member in which an undercoat layer is formed on an aluminum cutting drum.

  In general, the surface of a photoreceptor substrate used in a digital copying machine, a printer, or the like is roughened to scatter laser light or the like. However, in the case of a substrate having a rough surface, it is difficult to measure the film thickness using the conventional optical interference method because interference between the light reflected on the surface of the substrate and the light reflected on the surface of the coating film hardly occurs. It is.

  When an optical scanning device using laser light is used as an exposure means in an image forming apparatus, the light reflected by the surface of the conductive substrate and the surface of the intermediate layer are reflected unless the surface of the substrate is roughened. May interfere with the inside of the photosensitive layer, and an interference pattern may appear on the image. Therefore, in order to suppress interference, the surface of a base body as a support substrate is roughened, or pigment fine particles are dispersed in an intermediate layer and diffusely reflected. As a method for roughening the surface of the substrate, an oxidation treatment such as a mechanical roughening method such as a honing method, an etching method, cutting or grinding, an anodizing method, a boehmite treatment method, a heating oxidation treatment method, or the like is performed. Methods and the like.

  In the present invention, it is important that the support substrate reflects spectrum light used for film thickness measurement. However, since it is affected by surface roughness, the support substrate preferably has a vertical reflectance of about 10%. The ten-point average roughness Rz of the support substrate is preferably 0.7 μm to 1.2 μm.

  The material constituting the coating film is not particularly limited as long as it is a material that transmits spectral light used for film thickness measurement, but is roughly classified into an organic material and an inorganic material.

  Examples of the organic material include resins such as oligomers, thermoplastic resins, and thermosetting resins. Such resins may be added with additives such as pigments, plasticizers, antioxidants, and conductive agents. Such a material needs to be optically transparent, and the additive is preferably dispersed in the resin. Specifically, polyamide resin, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester resin, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, poly Vinyl acetate, polyvinylidene chloride, polyarate, phenoxy resin, polycarbonate resin, cellulose acetate resin, ethyl cellulose, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, polyvinyl alcohol, poly (N-vinylcarbazole), acrylic resin, silicone resin, epoxy resin, A melamine resin, a urethane resin, a phenol resin, an alkyd resin, etc. are mentioned.

  Examples of inorganic materials include metal oxides such as silicon dioxide, glassy networks of metal oxides described in JP-A-3-191361, and materials obtained by thermally cross-linking organometallic compounds.

  The method for forming the coating film is not particularly limited, but is roughly divided into two methods, a wet film forming method and a dry film forming method (vacuum thin film manufacturing method).

  The wet film forming method is formed by forming a coating liquid in which a material for forming a coat film is dissolved or dispersed in a solvent on a substrate, and a drying unit is provided as necessary. Examples of the coating method include blade coating, dip coating, spray coating, beat coating, nozzle coating, and the like. After coating, curing treatment such as drying, heating, and light is performed.

  The dry film formation method is a method of forming a film by depositing molecules or atoms on a substrate under reduced pressure (in a vacuum). Specific examples include vapor deposition, sputtering, and CVD. At this time, polymerization can be performed by heating the substrate during film formation or after film formation.

  FIG. 1 schematically shows an example of a film thickness measuring apparatus according to the present invention. The film thickness measurement apparatus has a light source 11, a fiber probe 12 as a transmission optical system, and an objective lens 13 as a focusing optical system. The light source 11 emits spectrum light. The emitted spectrum light is transmitted to the emission part of the fiber probe 12 by the radiated light transmission fiber 12a, and emitted from the emission part of the fiber probe 12 toward the object to be measured 10. The emitted spectral light is collected by the objective lens 13 onto the coating film of the object to be measured 10 and is incident perpendicularly to the surface of the coating film. The reflected light obtained by the interference between the light reflected on the surface of the coating film and the light reflected on the surface of the support substrate is received by the fiber probe 12 via the objective lens 13 and is reflected by the reflected light transmission fiber 12b. Is transmitted. The transmitted reflected light is split by the spectroscopic means 14, and the light quantity of the reflected reflected light is detected by the light quantity detecting means 15. When calculating the reflectance from the amount of light, the calculation means 16 uses a standard sample for calibrating the reflectance of the reflected light, normalizes the spectral characteristics of the light source and the light receiving element, and sets the reflectance to an arbitrary magnitude. Expand to. As a result, the wavelength at which the reflectance becomes minimum and maximum is obtained. Further, the film thickness of the coat film is calculated using these wavelengths and the refractive index of the coat film.

  The numerical aperture of the objective lens 13 is preferably 0.05 or more and 0.3 or less. By setting the numerical aperture to 0.05 or more, the amount of reflected light necessary for film thickness measurement can be secured. Further, by setting the numerical aperture to 0.3 or less, it is possible to secure spectral light that satisfies the basic principle of “vertical incidence / vertical light reception” necessary for film thickness measurement. Thereby, the film thickness can be accurately measured.

  The diameter of light incident on the film surface on the film surface is preferably 0.9 mm or more and 1.5 mm or less. By setting the diameter of the light incident on the surface of the film to 0.9 mm or more and 1.5 mm or less, it is possible to obtain the reflected light of the irradiated area that is not affected by the oxidation of the support substrate. This can reduce the effect of height.

  If the thickness is 0.9 mm or less, interference light cannot be detected due to the influence of surface properties such as oxidation stains on the support substrate and the pitch of cutting marks. On the contrary, if the thickness is 1.5 mm or more, light is scattered due to the influence of the curvature due to the cylindrical shape.

  The vertical reflectivity of the coat layer interface that contributes to the surface properties of the coat layer is a wavelength of 400 nm to 1000 nm from the viewpoint of ensuring the reflectivity of the support substrate interface with respect to the reflectivity at the coat layer surface (the surface in contact with air). It is preferably 4% or more and less than 90% with respect to the region. When the reflectance at the interface of the coat layer exceeds 90%, the difference between the maximum and minimum of the spectral spectrum intensity to be oscillated becomes small, and the sensitivity of measurement is lowered. On the other hand, if it is 4% or less, the spectral spectrum intensity becomes small, and rapid film thickness measurement becomes difficult.

  Hereinafter, a case where an achromatic lens having a lens diameter of 12.5 mm, a focal length of 15 mm, and a numerical aperture of 0.09 is installed as the objective lens 13 at a distance of 65 mm from the object to be measured will be described. The objective lens 13 is fixed to one end of the lens barrel 17, and the other end of the lens barrel 17 holds an end portion on the emission side of the fiber probe 12. The distance between the objective lens 13 and the surface of the coating film is 65 mm, and the distance between the objective lens 13 and the end on the emission side of the fiber probe 12 is 19.5 mm.

  The light source 11 is preferably a halogen-tungsten lamp, and can emit bright spectrum light in a wide wavelength range from the visible region to the near infrared region.

  As shown in FIG. 2, the end of the fiber probe 12 on the emission side is preferably configured so that the reflected light transmission fiber 12b is surrounded by the radiated light transmission fiber 12a. The light emitted from the fiber probe 12 is collected by the objective lens 13 as a light spot having a diameter of 1.32 mm on the surface of the coating film. That is, the diameter of the end face of the radiated light transmission fiber 12a is 0.2 mm. If the bundle of radiated light transmission fibers 12a shown in FIG. Using (= 65 / 19.5 = 3.3), the diameter of the light spot is 1.32 mm.

  The spectroscopic means 14 is preferably a diffraction grating, and specifically includes a fixed Zernitana diffraction grating having a spectral region of 220 nm to 850 nm and a resolution of 1.23 nm / point. The wavelength resolution of the diffraction grating is preferably 0.7 nm to 1.5 nm / point. Increasing the wavelength resolution of the diffraction grating has the same effect as increasing the sampling frequency when acquiring an electrical signal. As a result, when the film thickness of the coating film is large and when the waveform shape is lost due to scattering, it is possible to perform discrete sampling without missing information, and to accurately measure the film thickness on a support substrate having a rough surface. it can.

  Further, as the spectral means 14 other than the diffraction grating, a prism or a spectral filter can be used. As the spectroscopic means 14 such as a diffraction grating, a rotating type that changes the spectral wavelength region by rotation can be used, but when a fixed spectroscopic means 14 such as a diffraction grating that is spatially fixed is used, Since a space for rotation and a rotation mechanism are not required, the film thickness measuring apparatus can be made compact.

  The light quantity detection means 15 is preferably a line sensor, and specifically, a line sensor having a detection range of 200 nm to 1000 nm and a light receiving element number of 512 is exemplified. As the light quantity detection means 15, a silicon photodiode array can be used in addition to the line sensor. Silicon photodiodes are small, light, and inexpensive, and the circuit configuration is easy even when the film thickness measuring device is downsized and brought into a production line.

  The principle of measuring the thickness of the coat film will be described using the object to be measured shown in FIG. Here, the object to be measured is composed of the support substrate 31 and the coating film 32 having Rz of 0.7 μm to 1.2 μm.

  Consider a case where the film thickness of the coating film 32 is d, the refractive index is n1, and the spectral light is condensed and perpendicularly incident on the surface of the coating film 32 by the objective lens 13.

  A part of the incident spectrum light is reflected perpendicularly to the surface of the coat film 32, and a part of the incident spectrum light is incident on the coat film 32 and reflected perpendicularly to the surface of the support substrate 31. These interfere and become very weak reflected light, but the reflected light is condensed at the end of the reflected light transmission fiber 12 b via the objective lens 13 and transmitted to the spectroscopic means 14. The reflected light is split by the spectroscopic means 14, and the light amount detecting means 15 detects the light amount of the reflected reflected light.

  In FIG. 4, an example of the result measured using the film thickness measuring apparatus of this invention is shown. Here, the reflectance distribution 41 after normalizing the spectral distribution of the light source, the spectral characteristic of the light receiving element, and the reflection characteristic of the standard sample from the reflected light amount detected by the light amount detecting means 15 and the reflected light quantity 41 are calculated by the calculating means 16. A theoretical reflectance curve 42 is shown. The reflectance 42 indicates a theoretical reflectance curve calculated as a continuous reflectance from an optical model by a nonlinear least square method (for example, a curve fitting algorithm such as a simplex method).

  The vibration of the reflectance is a result of the interference of the reflected light, but the amplitude of the vibration of the reflectance appears even in the wavelength region of 400 nm to 600 nm, which is smaller than the ten-point average roughness, and is the lower limit of the ten-point average roughness. It appears even in a certain wavelength region of 700 nm or more. However, when the film thickness is about 0.3 μm to 1.5 μm, the maximum and minimum reflectances necessary for film thickness measurement appear due to the order of interference. In the wavelength region of 0.7 μm to 1.2 μm, which is a region and is equal to or greater than the ten-point average roughness, only a maximum and a minimum of the reflectance may be confirmed.

  When the 10-point average roughness of the support substrate is 0.7 μm to 1.2 μm, most of the light having a wavelength of about 700 nm or less is scattered on the surface of the support substrate, but the weak vertical component in the reflected light If it is possible to detect only the interference waveform, the visibility of the interference waveform capable of measuring the film thickness can be ensured.

  In this case, it is preferable that the spectrum light emitted from the light source includes a wavelength region equal to or greater than the optical absorption edge of the light-transmitting film provided on the support substrate.

  Having light transmittance means that there is no absorption of light, that is, the optical extinction coefficient is zero, but the wavelength has energy equal to or greater than the band gap determined by the film properties even if the extinction coefficient of the film is zero. In the case of the region, light absorption occurs, and interference measurement is not realized.

  In general, when the irregularity of the support substrate has a period and amplitude equal to or larger than the surface roughness of the wavelength of incident light, if the irregularities are periodic, diffraction occurs and strongly reflects at a specific angle. Moreover, if the unevenness is random, it is uniformly scattered in all directions. In addition, when the surface roughness of the support substrate is about the same as the wavelength of the incident light, the scattering is the largest.

  On the other hand, if the wavelength of the incident light is more than an order of magnitude larger than the unevenness of the support substrate, or if the unevenness of the support substrate is a period and amplitude that is an order of magnitude smaller than the wavelength of the incident light, the incident light will follow the Rayleigh scattering mechanism. The light is not scattered by the unevenness of the support substrate, and the reflected light interferes satisfactorily.

  If the wavelength of the spectrum light incident on the coating film is smaller than the unevenness of the support substrate, the reflected light is uniformly scattered in all directions if it is completely random, and if it is periodic, a specific angle (blazed) Reflects strongly at corners. However, even if light is scattered by the support substrate, the vertically reflected light necessary for film thickness measurement is present although it is weak.

  This weak vertical reflected light is not manifested by ordinary light receiving means, so in order to receive the weak vertical reflected light in the scattered light, the state of the light flux is made into a pencil shape (small numerical aperture), Visibility of interference waveforms by increasing the diameter of light incident on the surface of the film, increasing the reflectivity to an arbitrary size, and using vertically incident spectral light with increased coherence Can be improved.

In the case of the present invention, in the wavelength region exceeding 380 nm of the theoretical reflectance curve 42 in FIG. 4, an appropriate maximum and minimum adjacent reflectances are selected, and the wavelengths that give the maximum and minimum are respectively λ _2m and Let λ _{2m + 1} . m is the order of interference and can be determined as appropriate.

Between the thickness d of the coating film, the refractive index n1, and the order of interference m,
2m = 4n ₁ d / λ _2m
2m + 1 = 4n ₁ d / λ _{2m + 1}
Since the relationship is established, if m is deleted,
n ₁ d = λ _2m · λ _{2m +} 1/4 (λ _2m −λ _{2m + 1} )
The relationship is obtained.

Therefore, when λ _2m and λ _{2m + 1} are given, the optical film thickness n ₁ d of the coating film is obtained. Further, given the refractive index n1, the film thickness d of the coat film is
d = λ _2m · λ _{2m + 1} / 4n ₁ (λ _2m −λ _{2m + 1} ) (1)
Can be computed as

The refractive index n ₁ is uniquely determined when the material of the coating film is determined, and the spectral characteristics, that is, the change in refractive index depending on the wavelength (hereinafter referred to as the spectral refractive index) is previously stored in the calculation means 16. Alternatively, it can be stored as a function of wavelength. Thereby, the film thickness d of the coating film can be calculated from λ _2m , λ _{2m + 1} and n ₁ according to the equation (1).

  At this time, as is clear from the equation (1), when calculating the film thickness of the coating film, the absolute value of the reflectance is not required, and if the wavelength that gives the maximum and minimum values can be obtained with high accuracy, The film thickness d of the coating film can be measured using the refractive index. Therefore, in order to increase the accuracy of the wavelength that gives the maximum and minimum reflectance, the reflectance is increased to an arbitrary size.

Generally, the spectrophotometer, spectral reflectance meter, optical interference film thickness meter, etc. directly measure the amount of light reflected from the sample. In order to obtain the reflectance, a standard sample with a known reflectance is used in advance. It is necessary to measure and calibrate. Thus, the reflectance R (λ) of the sample is
R (λ) = (I _s (λ) −I _d (λ)) / (I _r (λ) −I _d (λ)) · r (λ) (2)
Can be calculated as Here, I _s (λ) is the digital data received in the calculation means by receiving the reflected light from the sample, and I _d (λ) is the digital data of the dark current component of the light receiver handled in the calculation means. , I _r (λ) is digital data in which the reflected light from the standard sample is handled in the light receiving calculation means, and r (λ) means the reflectance of the standard sample.

In the present invention, it is preferable to expand R (λ) to an arbitrary size by reducing the amount of reflected light of the standard sample. Specifically, a standard sample having I _r2 (λ) smaller than I _r1 (λ) is prepared for a standard sample having I _r1 (λ) and r ₁ (λ), and I _r2 (λ) and R (λ) is calculated using r ₁ (λ).

That is, when calculating the reflectance from the light amount of the reflected light detected by the light amount detecting means 15, the calculating means 16 enlarges the reflectance to an arbitrary size. Furthermore, after further calculating the theoretical reflectance curve from the optical model for the reflectance that is the measured value, each wavelength that gives the minimum and maximum by differentiating the theoretical reflectance curve, etc. λ _{2m + 1} and λ _2m are obtained, and the film thickness d of the coat film is calculated according to the equation (1) based on the refractive index n ₁ of the coat film.

FIG. 5 shows an example of the reflectance obtained using a normal film thickness measurement method. Here, since the reflectance is not enlarged to an arbitrary size, the maximum and minimum of the reflectance of the reflected light cannot be separated, and it becomes difficult to obtain λ _2m and λ _{2m + 1} , resulting in a decrease in measurement accuracy.

  The computing means 16 preferably stores the spectral refractive index of the coat film so as to be usable. Thereby, the spectral refractive index can be used for the calculation of the film thickness of the coat film. In order to increase the versatility of the film thickness measuring device and to adapt to a plurality of types of objects to be measured, the calculation means 16 preferably stores the spectral refractive index of one or more types of coating films so as to be usable. .

  FIG. 6 shows an example of the spectral refractive index of the coating film used in the present invention.

In the calculation of the film thickness d of the coating film in Expression (1), the spectral refractive index n ₁ is constant in the range of wavelengths λ _{2m to} λ _{2m + 1} . As shown in FIG. 6, since the spectral refractive index generally has a small slope in the wavelength region of 800 nm or more, an error is caused by setting the measurement wavelength region of λ _{2m to} λ _{2m + 1 to} a wavelength region longer than 800 nm. This is because it can be made smaller. However, since the refractive index changes greatly in the wavelength region of 700 nm or less, it is preferable to store the spectral refractive index in the computing unit 16 so that the spectral refractive index can be used from the viewpoint of error reduction.

  In the film thickness measuring apparatus of the present invention, the spectral light emitted from the transmission optical system 12 is condensed on the coating film by the objective lens 13, but as a comparative example, the fiber probe 12 is coated as shown in FIG. When the surface of the film was brought close to a distance of 0.5 mm and the emitted light was directly incident on the surface of the object 10 to be measured, the reflectance was as shown in FIG.

As is apparent from FIG. 8, the reflectance has a very small vibration amplitude, and it is difficult to obtain the wavelengths λ _2m and λ _{2m + 1} and it is difficult to accurately measure the film thickness.

(Examples 1 and 2)
A coating solution comprising 4 parts of alcohol-soluble nylon Amilan CM8000 (manufactured by Toray Industries, Inc.), 70 parts of methanol and 30 parts of n-butanol is dip-coated on an aluminum cylinder having a diameter of 100 mm and a 10-point average roughness of 0.9 μm. It was applied by a construction method, dried by touching and then dried by heating at 130 ° C. for 10 minutes to form a coating film. At this time, the coating liquid is put into a glass cylinder having a diameter of 133 mm and the coating speed is changed to form a coating film having a film thickness of 0.3 μm and 0.7 μm on the aluminum cylinder. Was made.

(Examples 3 and 4)
A coating solution comprising 7 parts of alcohol-soluble nylon Amilan CM8000 (manufactured by Toray Industries, Inc.), 70 parts of methanol and 30 parts of n-butanol on an aluminum cylinder having a diameter of 100 mm and an average 10-point roughness of 0.7 μm. After coating with a finger and drying with a finger, the coating was dried by heating at 130 ° C. for 10 minutes. At this time, the coating liquid is put into a glass cylinder having a diameter of 133 mm and the coating speed is changed to form a coating film having a film thickness of 0.9 μm and 1.2 μm on the aluminum cylinder. Was made.

(Example 5)
A toluene solution of tributoxyzirconium acetylacetonate ZC540 (manufactured by Matsumoto Kosho Co., Ltd.), γ-aminopropyltrimethoxysilane A1110 (manufactured by Nippon Unicar Co., Ltd.) 12 on an aluminum cylinder having a diameter of 100 mm and a ten-point average roughness of 0.7 μm. A coating solution consisting of 150 parts of ethanol, 150 parts of ethanol and 150 parts of n-butanol was applied by a dip coating method, dried by touch and then dried by heating at 130 ° C. for 10 minutes to form a coating film. At this time, the coating solution was put in a glass cylinder having a diameter of 133 mm and coated to form a coating film having a film thickness of 0.3 μm on the aluminum cylinder, and the DUT 5 was prepared.
(Evaluation results)
When the film thicknesses of the coating films of the objects to be measured 1 to 5 were measured using the film thickness measuring apparatus shown in FIG. 1, it was possible to accurately measure with a resolution of 0.01 μm or less.

  The numerical range A to B means A or more and B or less.

  Although the embodiments and examples of the present invention have been specifically described above, the present invention is not limited to these embodiments and examples, and these embodiments and examples of the present invention are not limited thereto. Can be changed or modified without departing from the spirit and scope of the present invention.

  The present invention can be applied to a film thickness measuring method and a film thickness measuring apparatus capable of accurately measuring the film thickness of a light-transmitting coat layer provided on a support substrate.

It is the schematic which shows an example of the film thickness measuring apparatus of this invention. It is sectional drawing which shows an example of the transmission optical system used for the film thickness measuring apparatus of this invention. It is a figure which shows an example of the to-be-measured object used by this invention. It is a figure which shows an example of the result measured using the film thickness measuring apparatus of this invention. It is a figure which shows an example of the reflectance obtained using a normal film thickness measuring method. It is a figure which shows an example of the spectral refractive index of the coat film used by this invention. It is the schematic which shows an example of the film thickness measuring apparatus of a comparative example. It is a figure which shows an example of the reflectance obtained using the film thickness measuring apparatus of a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Measured object 11 Light source 12 Fiber probe 12a Radiation light transmission fiber 12b Reflected light transmission fiber 13 Objective lens 14 Spectroscopic means 15 Light quantity detection means 16 Calculation means 17 Lens barrel 31 Support substrate 32 Coat film 41 Reflected light quantity 42 Reflectance

Claims (16)

In the film thickness measuring method for measuring the film thickness of the light-transmitting film provided on the support substrate,
Light is incident on the film,
The reflected light obtained by interference between the light reflected on the surface of the film and the light reflected on the surface of the support substrate is dispersed to detect the amount of the reflected reflected light,
When calculating the reflectance from the light amount, obtain the wavelength at which the reflectance becomes minimum and maximum by enlarging the reflectance to an arbitrary size,
A film thickness measuring method, comprising: measuring a film thickness of the film by using a wavelength at which the reflectance becomes minimum and maximum and a refractive index of the film.   The film thickness measurement method according to claim 1, wherein the ten-point average roughness of the support substrate is equal to or greater than the wavelength of the light.   The film thickness measuring method according to claim 1 or 2, wherein the ten-point average roughness of the supporting substrate is 0.7 µm or more and 1.2 µm or less.   The film thickness measuring method according to claim 1, wherein the support substrate has a cylindrical shape.   5. The film thickness measuring method according to claim 1, wherein the film has a thickness of not less than 0.3 μm and not more than 1.5 μm.   The film thickness according to any one of claims 1 to 5, wherein the reflectance is increased to an arbitrary size by reducing the amount of reflected light of a standard sample for calibrating the reflectance of the reflected light. Measuring method.   The film thickness measuring method according to any one of claims 1 to 6, wherein a diameter of light incident on the surface of the film is 0.9 mm or more and 1.5 mm or less. In the film thickness measuring device for measuring the film thickness of the light-transmitting film provided on the support substrate,
A light source;
A focusing optical system having a fiber probe that transmits and emits light emitted from the light source and receives and transmits the reflected light, and condenses the light emitted from the fiber probe emitting unit on the film; ,
A spectroscopic means for splitting the reflected light obtained by interference between the light reflected by the surface of the film and the light reflected by the surface of the support substrate;
A light amount detecting means for detecting a light amount of the reflected reflected light;
When calculating the reflectance from the light amount, the wavelength at which the reflectance becomes minimum and maximum is obtained by expanding the reflectance to an arbitrary size, the wavelength at which the reflectance becomes minimum and maximum, and the film And calculating means for calculating the film thickness of the film using the refractive index of
A film thickness measuring apparatus configured to cause the light to vertically enter a surface of a light-transmitting film provided on a support substrate.   The film thickness measuring apparatus according to claim 7, wherein the numerical aperture of the focusing optical system is 0.05 to 0.3.   10. The film thickness measuring device according to claim 8, wherein the focusing optical system is an achromatic lens.   The film thickness measuring device according to any one of claims 8 to 10, wherein the light source is a halogen-tungsten lamp.   The film thickness measuring apparatus according to claim 8, wherein the spectroscopic means is a diffraction grating, a prism, or a spectroscopic filter.   The film thickness measuring device according to any one of claims 8 to 12, wherein the light amount detecting means is a line sensor or a silicon photodiode array.   The objective lens side end of the fiber probe is centered on the end of the detection light transmission fiber, and is configured to surround the emission side end of the irradiation light guiding fiber. Item 14. The film thickness measuring device according to any one of Items 8 to 13.   The film thickness measurement apparatus according to claim 8, wherein the refractive index is stored in the calculation unit so as to be usable.   The spectrum light emitted from the light source includes a wavelength region that is equal to or greater than the optical absorption edge of the light-transmitting film provided on the support substrate. Film thickness measuring device.

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