JP2005140726A - Method for measuring thin film and apparatus for measuring thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for measuring a thin film capable of reducing measurement error due to reflected light from the background of a measurement object and suitable for in-line measurement. <P>SOLUTION: An apparatus for measuring a thin film is calibrated by putting a sample substrate capable of shutting out the influence of background on a stage and measuring a reference light quantity (step S1). Then, the reflectance Rc (λ) of the background is measured by removing the sample substrate from the stage, and measuring the reflected light from the background (step S2). Then, a measured data S (λ) of the reflectance is obtained by putting an actual measurement object on the stage, and acquiring an actual spectrum spectrum data due to the measurement object (step S3). A theoretical formula R(λ) of the reflectance is then produced by using the reflectance Rc (λ) of the background acquired at the step S2 (step S4), and the measured data S (λ) is compared with the theoretical formula R (λ) (step S5). The film thickness of a thin film is calculated by using a curve fitting method (step S6). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thin film measurement method and a thin film measurement apparatus, and for example, irradiates light onto a glass substrate or a transparent resin substrate used in a liquid crystal device (LCD), a plasma display panel (PDP), etc. The present invention relates to a thin film measurement method and a thin film measurement apparatus suitable for in-line measurement for measuring the film thickness and optical constant (refractive index, etc.) of a thin film formed on a substrate.

  There is a film thickness measuring device for measuring the film thickness of a thin film formed on an object to be measured such as an LCD or PDP glass substrate. Such a film thickness measuring device irradiates light toward the thin film. The film thickness of the thin film is measured using interference of light reflected by the front and back surfaces of the thin film.

  In such a film thickness measuring apparatus, when the reflected light from the background behind the object to be measured is taken into the film thickness measuring apparatus, the amount of light measured by the film thickness measuring apparatus increases and the reflectance Since the curve shifts in the increasing direction, a film thickness measurement error occurs. Therefore, it is necessary to block the reflected light from the background as much as possible so as not to be observed by the film thickness measuring device. However, the conventional film thickness measuring device does not consider the reflected light from the background.

  To prevent the reflected light from the background of the measurement object from returning to the film thickness measurement device, (1) ensure a large distance between the measurement object and the background, (2) reflect on the background A method of reflecting the emitted light in a direction different from that of the measurement light, (3) a method of reducing the depth of focus of the optical system, etc. In the method of ensuring a large distance between the substrate and the background, for example, as shown in FIG. 1, the opening 4 is provided in the table 3 on which the measurement object 2 on which the thin film 1 is formed is provided, whereby the light L is emitted. The position of the background to be reflected may be far away from the measurement object. Further, in the method of reflecting the light L reflected in the background in a direction different from that of the measurement light, for example, as shown in FIG. 2, a slope 5 is formed on the table 3 that supports the measurement object 2, and the background (slope 5). It is sufficient that the light L reflected by is reflected in an oblique direction and does not enter the film thickness measuring apparatus. Further, in the method of reducing the focal depth of the optical system as shown in FIG. 3, the light receiving optical system having a shallow focal depth is used to focus on the thin film so that the background is not reflected on the light receiving surface of the film thickness measuring apparatus. That's fine.

  By the way, recently, a film thickness measurement device has been installed in a production line, etc., and the measurement object is not extracted from the production line or the like during the film formation process (in-situ) or immediately after the process. In-line measurement capable of 100% inspection is desired. Since in-line measurement can improve product yield, the need for such a measurement method is increasing. However, any of the background measures such as the above (1) to (3) is limited to a stand-alone film thickness measuring apparatus, and is difficult to apply to in-line measurement.

  In other words, in a film thickness measuring device that can be used for in-line measurement, if the distance from the background is greatly separated or a slope is processed on a member that becomes the background, an existing film thickness measuring device is to be incorporated. It is necessary to remodel the manufacturing line and manufacturing equipment to match the film thickness measuring device, or to replace the manufacturing line and manufacturing device with a new one. It becomes difficult to introduce a film thickness measuring apparatus.

  Also, in the method of greatly separating the distance from the background, the installation location of the film thickness measuring device is restricted, so it interferes with peripheral devices and accessory equipment provided on the production line etc., and the installation location of the film thickness measuring device is Limited.

  Further, in the method of reducing the depth of focus of the optical system of the film thickness measuring apparatus, since focusing must be performed severely on the thin film of the measurement object, it takes time and effort to focus. Also, in the inspection of the measurement object flowing through the production line, the position variation of the measurement object becomes large, and the measurement object tends to be out of the focal position due to vibration during conveyance, so it is difficult to measure the film thickness when the depth of focus is shallow Therefore, film thickness cannot be measured without an autofocus device for automatic focus adjustment.

  The present invention has been made in view of the technical problems as described above. The object of the present invention is to reduce measurement errors caused by reflected light from the background of the measurement object, and to inline measurement. It is another object of the present invention to provide a thin film measuring method and a thin film measuring apparatus which are also suitable.

  The thin film measuring apparatus of the present invention measures a light projecting unit that irradiates light toward a measurement target, an imaging unit that captures light reflected by the measurement target, and a spectral characteristic of the light captured by the imaging unit. A thin film measuring apparatus including a calculation processing unit for obtaining a film thickness or an optical constant of a thin film on the surface of the object, wherein the calculation processing unit irradiates the measurement target having a thin film formed on the surface of the transparent substrate. By comparing the spectral characteristics obtained from the reflected light with the theoretical formula of the spectral characteristics of the reflected light from the measurement object calculated in consideration of the spectral characteristics of the light incident from the background of the measurement object, the thin film The film thickness or optical constant is determined.

  Here, the light incident from the background when acquiring the spectral characteristics of the background may not include disturbance light that directly enters the imaging unit or disturbance light that is reflected by the measurement object and incident on the imaging unit. (The disturbance light is blocked.) Or, if the disturbance light is constant, the disturbance light may be included.

  According to the thin film measuring apparatus of the present invention, when the substrate on which the thin film of the measurement object is formed is a transparent substrate, the spectral characteristics acquired from the reflected light of the light irradiated to the measurement object, and the measurement object Optical constants such as film thickness or refractive index of the thin film can be obtained by comparing with the theoretical formula of the spectral characteristics of the reflected light from the measurement object calculated in consideration of the spectral characteristics of the incident light from the background. Therefore, it is possible to remove or correct the influence of the light reflected on the background of the measurement object and incident on the imaging means, and to measure the film thickness and optical constant of the thin film with high accuracy. In addition, since it is not necessary to reduce the depth of focus of the light receiving optical system, it is also suitable for measuring a measurement object conveyed on the production line, and in-line measurement is possible. Furthermore, there is no need to process the background or increase the distance between the background and the object to be measured, so there is no need to improve the production line or equipment, or to replace with new equipment. In-line measurement of thin film can be made possible by utilizing the retrofit method.

  In one embodiment of the thin film measuring apparatus of the present invention, in consideration of the spectral characteristics of light incident from the background in a state where the measurement object is removed from the measurement object installation position, the light reflected by the measurement object It has a function to calculate the theoretical formula of spectral characteristics. The spectral characteristics of light incident from the background with the measurement object removed may be obtained by measuring the spectral characteristics of the background only with the thin film measuring apparatus without the measurement object, or a configuration that constitutes the background. What was calculated | required by calculation based on the optical constant of a member may be used. In this embodiment, since the theoretical formula of the spectral characteristic of the light reflected from the measurement object is automatically calculated based on the spectral characteristic of the light incident from the background with the measurement object removed, the spectral characteristic There is no need to obtain the theoretical formula of

  In another embodiment of the thin film measuring apparatus of the present invention, a black alumite treatment is applied to the stage on which the measurement object is placed. The black alumite treatment is generally formed on the surface of the stage, but may be formed on the back surface of the stage when the stage is a transparent plate such as a glass plate. According to this embodiment, since the stage is black anodized, the reflected light from the stage as the background is reduced, the S / N ratio during measurement of the thin film is increased, and the measurement accuracy is improved. According to this embodiment, when the stage is a part of the existing equipment, a partial improvement of the existing equipment is required, but a minor improvement is sufficient. In addition, in the case where minor improvements cannot be made, a sheet that has been subjected to black alumite treatment may be bonded to the surface of an existing stage.

  In still another embodiment of the thin film measuring apparatus of the present invention, the object to be measured is a thin film formed on a transparent substrate, and the object to be measured is a thin film formed on an opaque substrate. In the case of a measurement object in which a thin film is formed on a transparent substrate, the spectral characteristics acquired from the reflected light of the light irradiated on the measurement object, and the measurement object The film thickness or optical constant of the thin film is obtained by comparing with the theoretical formula of the spectral characteristic of the reflected light from the measurement object calculated in consideration of the spectral characteristic of the incident light from the background of In the case of a measurement object having a thin film formed thereon, the spectral characteristics obtained from the reflected light of the light irradiated on the measurement object and the reflected light from the measurement object not considering the spectral characteristics of the incident light from the background Compare with theoretical formula of spectral characteristics By, and to obtain the film thickness or optical constants of thin films. According to this embodiment, the thin film can be measured with a single device regardless of whether the object to be measured is a transparent substrate or an opaque substrate. Further, even if the measurement object on the transparent substrate and the measurement object on the opaque substrate can be measured, the operation of the thin film measuring apparatus is not complicated, and the thin film measurement can be easily performed.

  In still another embodiment of the thin film measuring apparatus of the present invention, since the film thickness or optical constant of the thin film is obtained at a plurality of points of the measurement object, the film thickness and optical constant of the thin film are obtained at a plurality of locations. It is possible to know the change in the thickness of the thin film and the gradient characteristic of the optical constant. Note that it is desirable that any point can be selected as the plurality of points.

  In addition, the thin film measuring apparatus of the present invention is particularly suitable for in-line measurement by being incorporated in a production line of an image display device such as a liquid crystal display panel or a plasma display device, and it is necessary to replace or modify existing equipment. Is easy to introduce into these lines.

  The first thin film measurement method of the present invention includes a light projecting unit that irradiates light toward a measurement target, and an imaging unit that captures light reflected by the measurement target, and a spectrum of light captured by the imaging unit. A thin film measurement method for obtaining a film thickness or optical constant of a thin film on the surface of a measurement object based on characteristics, and irradiating light from the light projecting portion to a measurement object installation position where the measurement object is not installed To obtain a spectral characteristic of light incident from the background, and to place a measurement object formed with a thin film on the surface of a transparent substrate at a measurement object installation position, and project the light onto the measurement object. The theory of the spectral characteristics of the reflected light from the measurement object using the step of obtaining the spectral characteristics of the light reflected from the measurement object by irradiating light from the unit and the spectral characteristics of the light incident from the background The process of finding the equation and the measurement object And the spectroscopic characteristics of the light, by comparing the theoretical formula of the spectral characteristics of the light reflected by the measurement object, and a step of obtaining a film thickness or optical constants of thin films.

  According to the first thin film measurement method of the present invention, when the substrate on which the thin film of the measurement object is formed is a transparent substrate, the spectral characteristics acquired from the reflected light of the light irradiated on the measurement object, and the measurement Optical constants such as film thickness or refractive index of the thin film are obtained by comparing with the theoretical formula of the spectral characteristics of the reflected light from the measurement object calculated in consideration of the spectral characteristics of the light incident from the background of the object. Therefore, the influence of the light reflected on the background of the measurement object and incident on the imaging means can be removed or corrected, and the film thickness and optical constant of the thin film can be accurately measured. In addition, since it is not necessary to reduce the depth of focus of the light receiving optical system, it is also suitable for measuring a measurement object conveyed on the production line, and in-line measurement is possible. Furthermore, there is no need to process the background or increase the distance between the background and the object to be measured, so there is no need to improve the production line or equipment, or to replace with new equipment. In-line measurement of thin film can be made possible by utilizing the retrofit method.

  Moreover, according to the first thin film measuring method, the spectral characteristics of light incident from the background can be easily obtained by irradiating the measurement object installation position where the measurement object is not installed. With this thin film measuring apparatus, it is possible to simultaneously measure the spectral characteristics of the background and the film thickness of the thin film.

  The second film thickness measurement method of the present invention includes a light projecting unit that irradiates light toward a measurement target, and an imaging unit that captures the light reflected by the measurement target, and the light captured by the imaging unit. A thin film measuring method for obtaining a film thickness or optical constant of a thin film on the surface of a measurement object based on spectral characteristics, wherein the spectrum of light incident from the background is based on the optical constant of a background member at the measurement object installation position. The measurement object is obtained by installing a measurement object having a thin film formed on the surface of a transparent substrate at a measurement object installation position and irradiating the measurement object with light from the light projecting unit. Obtaining the spectral characteristics of the light reflected from the light, obtaining the theoretical formula of the spectral characteristics of the reflected light from the measurement object using the spectral characteristics of the light incident from the background, and reflecting from the measurement object. The spectral characteristics of measured light and the measurement pair By comparing the theoretical formula of the spectral characteristics of the light reflected by an object, and a step of obtaining a film thickness or optical constants of thin films.

  According to the second thin film measurement method of the present invention, when the substrate on which the thin film of the measurement object is formed is a transparent substrate, the spectral characteristics acquired from the reflected light of the light irradiated on the measurement object, and the measurement Optical constants such as film thickness or refractive index of the thin film are obtained by comparing with the theoretical formula of the spectral characteristics of the reflected light from the measurement object calculated in consideration of the spectral characteristics of the light incident from the background of the object. Therefore, the influence of the light reflected on the background of the measurement object and incident on the imaging means can be removed or corrected, and the film thickness and optical constant of the thin film can be accurately measured. In addition, since it is not necessary to reduce the depth of focus of the light receiving optical system, it is also suitable for measuring a measurement object conveyed on the production line, and in-line measurement is possible. Furthermore, there is no need to process the background or increase the distance between the background and the object to be measured, so there is no need to improve the production line or equipment, or to replace with new equipment. In-line measurement of thin film can be made possible by utilizing the retrofit method.

  In addition, according to the second thin film measuring method, since the spectral characteristics of light incident from the background are obtained based on the optical constants of the background member at the measurement object installation position, it is possible to save the trouble of measuring the spectral characteristics of the background. .

  A third film thickness measurement method of the present invention includes a light projecting unit that irradiates light toward a measurement target, and an imaging unit that captures light reflected by the measurement target, and the light captured by the imaging unit A thin film measurement method for obtaining a film thickness or optical constant of a thin film on the surface of a measurement object on the basis of spectral characteristics, wherein a transparent substrate on which no thin film is formed is installed at the measurement object installation position, and the substrate Irradiating light from the light projecting unit to obtain the spectral characteristics of the light incident from the background, and installing the measurement object having a thin film formed on the surface of the transparent substrate at the measurement object installation position. , By irradiating the measurement object with light from the light projecting unit to obtain spectral characteristics of the light reflected by the measurement object, and using the spectral characteristics of the light incident from the background, the measurement object Finding the theoretical formula for the spectral characteristics of reflected light from objects And comparing the spectral characteristic of the light reflected by the measurement object with the theoretical formula of the spectral characteristic of the reflected light from the measurement object, thereby obtaining a film thickness or an optical constant of the thin film. ing.

  According to the third thin film measuring method of the present invention, when the substrate on which the thin film of the measurement object is formed is a transparent substrate, the spectral characteristics acquired from the reflected light of the light irradiated to the measurement object, and the measurement Optical constants such as film thickness or refractive index of the thin film are obtained by comparing with the theoretical formula of the spectral characteristics of the reflected light from the measurement object calculated in consideration of the spectral characteristics of the light incident from the background of the object. Therefore, the influence of the light reflected on the background of the measurement object and incident on the imaging means can be removed or corrected, and the film thickness and optical constant of the thin film can be accurately measured. In addition, since it is not necessary to reduce the depth of focus of the light receiving optical system, it is also suitable for measuring a measurement object conveyed on the production line, and in-line measurement is possible. Furthermore, there is no need to process the background or increase the distance between the background and the object to be measured, so there is no need to improve the production line or equipment, or to replace with new equipment. In-line measurement of thin film can be made possible by utilizing the retrofit method.

  In addition, according to the second thin film measurement method, a transparent substrate on which no thin film is formed is placed at the measurement object placement position, and light is incident on the substrate from the light projecting unit, thereby entering from the background. Since the spectral characteristics of the light are obtained, this process can simultaneously obtain the spectral characteristics of the light reflected on the back side of the substrate as well as the spectral characteristics of the background, thereby simplifying the process of measuring the thickness of the thin film. be able to.

  In the embodiments of the first and third film thickness measuring apparatuses of the present invention, in the step of obtaining the background spectral characteristic, the spectral characteristic of the reflected light from the background in the vicinity of the film thickness measurement position of the measurement object is acquired. I am doing so. In this embodiment, since the spectral characteristic of the reflected light from the background is acquired in the vicinity of the film thickness measurement position of the measurement object, the measurement object installation position is a distance from the thin film measurement device like the conveyor of the production line. Even when the value fluctuates, the film thickness measurement error of the thin film due to the distance fluctuation can be reduced.

  The above-described constituent elements of the present invention can be arbitrarily combined as much as possible.

  According to the thin film measuring method and thin film measuring apparatus of the present invention, the film thickness and optical constant of the thin film can be accurately measured in-line. In addition, it is possible to minimize the improvement without replacing or improving the manufacturing line or manufacturing equipment where the thin film measuring device is installed, or when improvement is required, and for in-line measurement at a low cost. A thin film measuring device can be introduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, the configuration of the thin film measuring apparatus according to the present invention will be described. FIG. 4 is an overall configuration diagram showing a thin film measuring apparatus 11 capable of measuring a two-dimensional film thickness according to Embodiment 1 of the present invention. The thin film measuring apparatus 11 includes a sensor head unit 12, an arithmetic processing unit 13, and an external interface (I / F) unit. In the illustrated example, the external interface unit includes a display device 14 and input / output devices 15 such as a keyboard and a mouse. The sensor head unit 12 and the arithmetic processing unit 13 are connected by a cable 16, the arithmetic processing unit 13 and the display device 14 are connected by a cable 17, and the arithmetic processing unit 13 and the input / output device 15 are connected by a cable 18. .

  FIG. 5 is a block diagram showing an electrical configuration of the thin film measuring apparatus 11. The sensor head unit 12 includes a light projecting unit 19, a light receiving unit 20, a monitor unit 21, and a power supply unit 22. In the sensor head unit 12, the measurement light L emitted from the light projecting unit 19 is projected onto the measurement target 23, and the measurement light L reflected by the measurement target 23 is received and observed by the light receiving unit 20. The monitor unit 21 serves to monitor fluctuations in the light intensity of the measurement light L emitted from the light projecting unit 19 and directly receives a part of the measurement light L emitted from the light projection unit 19. . The power source unit 22 is a power source that supplies power to the light projecting unit 19, the light receiving unit 20, and the monitor unit 21 to drive them. The power supply unit 22 may be provided inside the sensor head unit 12, or may be externally attached to the sensor head unit 12, such as being installed in the arithmetic processing unit 13.

  The arithmetic processing unit 13 includes a light projecting / receiving control unit 24, an A / D conversion unit 25, a nonvolatile memory 26 such as a ROM, an input / output control unit 27, a display control unit 28, and a micro that calculates / controls these. It consists of a main control unit 29 such as a processor (CPU). The light projecting / receiving control unit 24 controls the light projecting unit 19, the light receiving unit 20, the monitor unit 21, and the power supply unit 22. The A / D conversion unit 25 converts analog signals from the light receiving unit 20 and the monitor unit 21 into digital signals. The nonvolatile memory 26 incorporates various programs. The input / output control unit 27 is connected to the input / output device 15 such as a keyboard and a mouse via the cable 18. The display control unit 28 is connected to the display device 14 via the cable 17.

  Accordingly, the light projecting / receiving control unit 24 causes the light projecting unit 19 to emit light at a predetermined timing and irradiates the measurement object 23 with the measurement light L. At the same time, the monitor unit 21 receives a part of the measurement light L emitted from the light projecting unit 19 and outputs a monitor signal corresponding to the received light amount to the A / D conversion unit 25 through the cable 16. The monitor signal (analog signal) is converted into a digital signal by the A / D converter 25 and then sent to the main controller 29. The main control unit 29 calculates the light intensity of the measurement light L emitted from the light projecting unit 19 based on the digitized monitor signal, and when the light intensity is not equal to the predetermined light intensity, the light projecting / receiving is performed. The light projecting unit 19 is controlled through the control unit 24, and feedback control is performed so that the light intensity of the light projecting unit 19 becomes a predetermined light intensity.

  In addition, the image signal of the measurement object 23 imaged by the light receiving unit 20 is output to the A / D conversion unit 25 through the cable 16. The image signal converted into a digital signal by the A / D conversion unit 25 is sent to the main control unit 29, and the film thickness at a predetermined position of the thin film is calculated as described later. The display control unit 28 causes the display device 14 to display the image of the measurement object 23, the calculation result of the film thickness, and the like based on the image signal output from the light receiving unit 20. Further, when data such as a film thickness measurement position and a refractive index are input from the input / output device 15, the input / output control unit 27 transmits the measurement position data and the like to the main control unit 29 and stores them in a hard disk or the like. It memorize | stores in an apparatus (not shown).

  FIG. 6 is a schematic view showing an optical configuration of the sensor head unit 12. The light projecting unit 19 in the sensor head unit 12 includes a light source 30 and a light projecting optical system, and the light projecting optical system includes a light projecting lens 31, a half mirror 32, and an objective lens 33. The light receiving unit 20 includes a light receiving optical system and an imaging unit 36 including a CCD camera and the like. The light receiving optical system includes an objective lens 33, an aperture stop 34, and a multi-spectral filter 35. The monitor unit 21 includes a light receiving element such as a photodiode (PD). The half mirror 32 is arranged at an angle of 45 degrees with respect to the optical axis direction of the measurement light L projected onto the measurement object 23, and the light source 30 and the light projecting lens 31 are incident on one side of the half mirror 32. The monitor unit 21 is disposed at a position facing the light source 30 and the light projecting lens 31 via the half mirror 32. Thus, the measurement light L emitted from the light source 30 passes through the light projection lens 31 and then enters the half mirror 32. Part of the light incident on the half mirror 32 is reflected by the half mirror 32, passes through the objective lens 33 and is projected onto the predetermined two-dimensional area A of the measurement object 23, and the remaining part passes through the half mirror 32. The light is received by the monitor unit 21 as monitoring light. Here, the measurement light L applied to the measurement object 23 is coaxial incident light that is perpendicularly incident on the measurement object 23.

  The half mirror 32 is disposed above the objective lens 33, and an aperture stop 34, a multi-spectral filter 35, and an imaging unit 36 are disposed above the half mirror 32. As shown in FIG. 7, the multi-spectral filter 35 installed between the imaging unit 36 and the measurement object 23 pulses a filter plate 38 having a plurality of spectral filters 37a, 37b,. The angle is changed by being rotated by a rotary actuator 39 such as a step motor. A plurality of apertures are provided concentrically around the rotation axis of the rotary actuator 39 on the outer peripheral portion of the filter plate 38. Transmission spectral filters (bandpasses) each having a different selection wavelength are provided in each of the apertures except for one. Filters 37a, 37b,... Are fitted, and one opening is a through-hole 37 in which a spectral filter is not fitted. As such transmission type spectral filters 37a, 37b,..., A dielectric multilayer film or the like can be used. The filter plate 38 of the multi-spectral filter 35 is disposed close to the aperture stop 34, and the filter plate 38 is rotated by a rotary actuator 39, whereby a through-hole 37 or arbitrary spectral filters 37a, 37b,. Can be moved to a position facing the small hole 34 a of the aperture stop 34. Therefore, when any one of the spectral filters 37a, 37b,... Is located above the small hole 34a, the white light that has passed through the small hole 34a is incident on the spectral filter (for example, 37a) thereabove, Only light in a specific wavelength range determined by the spectral filter enters the imaging unit 36.

  FIG. 8 is a diagram showing the optical system of the thin film measuring apparatus 11 and the behavior of light rays. In the thin film measuring apparatus 11, the measurement light L emitted from the light source 30 is irradiated to the two-dimensional area A of the measurement object 23 through the light projection lens 31, the half mirror 32, and the objective lens 33. The light projecting optical system is of a coaxial incident type, and the light irradiated toward the measurement object 23 is projected almost perpendicularly onto the surface of the measurement object 23.

  In addition, as the imaging optical system of the light receiving unit 20 in the thin film measuring device 11, a telecentric optical system is employed in order to stabilize the measurement accuracy of the thin film measuring device 11 with respect to the distance variation of the measurement object. In general, there are three types of telecentric optical systems: an image side telecentric optical system, an object side telecentric optical system, and a double side telecentric optical system. Used. In particular, in the thin film measuring apparatus 11 according to the first embodiment, as shown in FIG. 8, an aperture stop 34 is formed on the optical axis of the objective lens 33 near the lower surface of the multi-spectral filter 35 between the objective lens 33 and the imaging unit 36. By arranging the small holes 34a, the imaging optical system is an object side telecentric optical system.

  That is, in this light receiving optical system, the objective lens 33 is constituted by two sets of achromatic lenses, and the small hole 34a of the aperture stop 34 is positioned at the image side focal point of the objective lens 33, and the objective lens 33 and the aperture stop 34 are used. An object side telecentric optical system is configured. The measurement object 23 and the imaging unit 36 are arranged so that the measurement object 23 and the light receiving surface of the imaging unit 36 are in an imaging relationship with respect to the objective lens 33. Therefore, the measurement light L reflected by the predetermined two-dimensional area A enters the multi-spectral filter 35 through the telecentric optical system configured by the objective lens 33 and the aperture stop 34. Therefore, in the thin film measuring apparatus 11, even if the distance between the thin film measuring apparatus 11 and the measurement target 23 changes, an image of the measurement target 23 can be clearly formed on the imaging unit 36. Therefore, it is possible to obtain good characteristics with respect to the distance variation of the measurement object 23.

In this light receiving optical system, the numerical aperture NA on the object side in the light receiving optical system is made small (the aperture aperture has a small hole diameter) in order to reduce the change in reflected light intensity when the distance varies. Here, the numerical aperture NA on the object side in the light receiving optical system is, as shown in FIG. 8, when the spreading angle of the measurement light L that exits the measurement object 23 and passes through the aperture stop 34 is 2w.
Numerical aperture NA = sinw on the object side in the light receiving optical system
It is represented by However, if the numerical aperture NA on the object side in the light receiving optical system is too small, the amount of light passing through the aperture stop 34 is reduced, so that the image becomes dark and the optical image resolution is reduced, resulting in poor measurement position accuracy. Therefore, in the film thickness measuring device 11, the object side in the light receiving optical system is as small as possible so that the change in the reflected light intensity at the time of the distance variation is as small as possible within a range where the optical image resolution of the light receiving optical system does not decrease excessively. The numerical aperture NA = sinw (or the aperture diameter of the aperture stop 34) is determined to be an optimum value.

Further, as shown in FIG. 8, in the thin film measuring apparatus 11 of the present invention, the light projecting optical system is constituted by a coaxial incident optical system, and the numerical aperture NA on the image side (measurement object side) in the light projecting optical system. However, the optical system is configured to be larger than the numerical aperture NA on the object side (measurement object side) in the light receiving optical system determined by the hole diameter of the aperture stop 34. Here, the numerical aperture NA on the image side in the light projecting optical system is the spread angle of the measurement light L irradiated from the light source 30 to the measurement object 23 through the light projecting optical system, as shown in FIG. 9B. When 2u
Image-side numerical aperture NA = sinu in the projection optical system
It is represented by If the surface of the measurement object 23 is a regular reflection surface, the spread of light reflected by the measurement object 23 is determined by the numerical aperture NA on the image side in the light projecting optical system. Further, the numerical aperture NA on the object side in the light receiving optical system is, as described above, when the divergence angle of the measurement light L that exits the measurement object 23 and passes through the aperture stop 34 is 2w.
Numerical aperture NA = sinw on the object side in the light receiving optical system
It is represented by As shown in FIG. 9B, this divergence angle 2w is an angle at which a point on the measurement object 23 is stretched with respect to the small hole 34a ′ of the entrance pupil 34 ′ assumed from the aperture stop 34. You can also.

  Further, a surface of the light source 30 (hereinafter, this surface is referred to as a light source reference surface 30a) and the aperture stop 34 are in an imaging relationship, and as shown in FIG. 9A, the surface of the light source reference surface 30a. The distribution of the amount of emitted light is made uniform in a region of an appropriate size. The uniform distribution of the emitted light amount means that the emitted light amount is uniform and / or the directivity characteristics are the same in the entire light emitting region of the light source reference surface 30a.

  In the configuration of the light source 30, the distribution of the amount of emitted light is uniform in the light emitting region of the light source reference surface 30a (that is, the surface having an imaging relationship with the aperture stop 34). In this way, it can be realized. FIG. 10 shows an example of such a light source 30. The measurement light L emitted from the lamp 42 is transmitted through the condenser lens 43 and the condenser lens 44 and then incident on the diffusion plate 45 having a relatively small diffusion angle. The distribution of the emitted light quantity is made uniform by diffusing the measurement light L with the diffusion plate 45. In such a light source 30, the surface on which the diffusion plate 45 is disposed serves as the light source reference surface 30a.

  Thus, in such an optical system, as shown in FIG. 11A, the light source reference surface 30a and the aperture stop 34 are in an imaging relationship, and from each light spot of the light emitting region 40 of the light source reference surface 30a. The emitted measurement light L is transmitted through the projection lens 31 and the objective lens 33 and is incident on the measurement object 23 coaxially and spreads over the entire two-dimensional area A. Further, the measurement light L is transmitted through the objective lens 33 and the surface of the aperture stop 34. The image is formed inside. Further, as shown in FIG. 11B, the measurement light L reflected at each point of the two-dimensional area A of the measurement object 23 is an image area of the light emitting area 40 in the aperture stop 34 (that is, the aperture stop 34). In the entire illumination area 41). Moreover, since the distribution of the emitted light amount is uniform throughout the light emitting region 40 of the light source reference surface 30a, the light amount distribution is uniform throughout the illumination region 41 of the aperture stop 34. FIGS. 11A and 11B are diagrams conceptually drawn so that light rays travel in one direction.

  Further, the numerical aperture NA on the image side in the light projecting optical system is larger than the numerical aperture NA on the object side in the light receiving optical system. Since the spread of the incident light is equal to the spread of the light reflected by the measurement object 23, the light reflected by the measurement object 23 corresponds to the aperture stop 34 as shown in FIG. 9B. This means that the spot diameter D1 of the light irradiated onto the incident pupil 34 'is larger than the diameter D2 of the small hole 34a' of the entrance pupil 34 '. Therefore, the light reflected by the measurement object 23 irradiates spot light having a larger area than the small hole 34a on the aperture stop 34 (see FIG. 11B). As a result, as shown in FIG. 12A, when the inclination of the measurement object 23 is 0 °, the measurement light L reflected by the two-dimensional area A of the measurement object 23 passes through the small hole 34a and the imaging unit. As shown in FIGS. 12B and 12C, the measurement light L reflected by the two-dimensional region A is small even when the measurement object 23 is inclined, for example, ± 1 °, as shown in FIGS. It passes through the hole 34 a and is imaged by the imaging unit 36, and the measurement target 23 can be observed by the imaging unit 36 even when the tilt of the measurement target 23 varies.

  Furthermore, in this thin film measuring apparatus 11, even if the measurement object 23 is tilted and the light region received by the imaging unit 36 changes, the reflected light intensity observed by the imaging unit 36 does not change, and the measurement object 23 Even when there is a tilt variation, the film thickness can be measured with high accuracy.

  As is apparent from the above description, according to the thin film measuring apparatus 11, the film thickness can be measured even when there are distance fluctuations and inclination fluctuations, and the imaging unit 36 even when there are distance fluctuations and inclination fluctuations. The reflected light intensity observed in Fig. 1 is almost constant, so that the film thickness can be measured with high accuracy, and an optical system suitable for in-line measurement is provided. In addition, regarding the configuration of the telecentric optical system in the thin film measuring apparatus 11, measures for distance variation of the measurement object, measures for tilt variation, and other aspects thereof, Japanese Patent Application No. 2003-321267 filed by the present applicant prior to the present invention. Are disclosed in detail.

  The measurement light L irradiated onto the predetermined two-dimensional area A of the measurement object 23 and reflected by the measurement object 23 passes through the objective lens 33 and then passes through the half mirror 32 and the small hole 34a. The light passes through the spectral filters 37a, 37b,... And enters the imaging unit 36 as a single-wavelength spectral image. The measurement object 23 and the light receiving surface of the imaging unit 36 are in an imaging relationship, and each point in the two-dimensional area A of the measurement object 23 corresponds to each pixel of the imaging unit 36 on a one-to-one basis. Yes. Here, by rotating the multi-spectral filter 35 and sequentially switching the spectral filters 37a, 37b,..., As in the spectral image M of the TFT array substrate shown in FIGS. The spectral images M of various wavelengths f1, f2,... Determined by 37b,... Are observed by the imaging unit 36, and each spectral image M is stored in a storage device such as a hard disk. Next, for example, any one pixel (that is, any arbitrary one in the two-dimensional region A) from among the pixels of the imaging unit 36, such as a point in the pixel opening marked with an X in FIGS. 13 (a) to 13 (f). 1 point), by extracting the spectral reflectance data (reflection spectrum) of the selected pixel from the stored spectral image data of each wavelength, and comparing the spectral reflectance data with the theoretical spectral reflectance, The arithmetic processing unit 13 calculates the film thickness at an arbitrary point selected as described below.

  In the above embodiment, the multi-spectral filter 35 is arranged in the light receiving optical system. However, the multi-spectral filter 35 is arranged in the light projecting optical system so that the monochromatic light of each wavelength is sequentially irradiated onto the measuring object 23. It may be.

ここで、
Ｒa(λ)：波長λの光に対する薄膜反射率
Ｔa(λ)：波長λの光に対する薄膜透過率
Ｒb(λ)：波長λの光に対する基板裏面反射率
Ｔb(λ)：波長λの光に対する基板裏面透過率
Ｒc(λ)：波長λの光に対する背景反射率
ｚ：表面反射受光効率
ｙ：裏面反射受光効率
である。（１）式の各項については、以下に順次説明する。 Next, a method for calculating the thickness of the thin film of the measurement object, particularly a method for calculating the thickness considering the influence of the background will be described. The reflectance R (λ) on the surface of the measurement object 23 is theoretically determined by the refractive indexes n2 and n1 of the substrate 46 and the thin film 47 constituting the measurement object 23, the film thickness d of the thin film 47, the wavelength λ of the irradiation light, and the like. Can be requested. That is, the reflectance R (λ) on the surface of the measurement object 23 is expressed by the following equation (1).

here,
Ra (λ): Thin film reflectance for light of wavelength λ Ta (λ): Thin film transmittance for light of wavelength λ Rb (λ): Substrate back surface reflectance for light of wavelength λ Tb (λ): Light for wavelength λ Substrate back surface transmittance Rc (λ): Background reflectance for light of wavelength λ z: Front surface reflection light reception efficiency y: Back surface reflection light reception efficiency. Each term of the equation (1) will be described in turn below.

As shown in FIG. 14A, the thin film reflectance Ra (λ) is the reflected light Lm (that is, the thin film 47 of the thin film 47) from the surface of the measurement object 23 with respect to the measurement light L 0 incident on the measurement object 23. The light intensity ratio between the light L1 specularly reflected on the surface and the light L2 specularly reflected on the boundary surface between the thin film 47 and the substrate 46). In general, when the thickness of the thin film 47 is d and the refractive index of the thin film 47 is n1, the reflected light obtained by specularly reflecting the measurement light L0 of the wavelength λ incident on the measurement object 23 on the surfaces of the substrate 46 and the thin film 47. The thin film reflectance Ra (λ) of Lm is expressed by the following equation (2). However, A, B, and C are constants determined by the refractive indexes n2 and n1 of the substrate 46 and the thin film 47.

  The above expression (2) is an expression obtained on the assumption that all specularly reflected light theoretically generated when the surface of the measurement object 23 is assumed to be a mirror surface is received. However, in the case of a substrate 46 having irregularities on the surface, such as a plasma display substrate or a resin film substrate, which is the actual measurement object 23, the surface of the thin film 47 as shown in FIG. In addition to the regular reflection lights L1 and L2, diffuse reflection light Ls is also generated on the back surface. Depending on the degree of spread of the diffuse reflected light Ls, the ratio of light actually incident on the imaging unit 36 (light reception ratio) decreases, so the reflected light spectrum represented by the received light data does not match the theoretical reflection spectrum, Measurement accuracy may be reduced.

The surface reflection light receiving efficiency z is the light actually incident on the imaging unit 36 with respect to the theoretical specular reflection light as expressed by the equation (2) (a part of the diffuse reflection light Ls in addition to the regular reflection light L1 and L2). And the reflectance Rz (λ) of the light reflected by the surface of the measurement object 23 and actually received by the imaging unit 36 is the light reception ratio (surface reflection). Using light receiving efficiency z) Rz (λ) = Ra (λ) × z (3)
Can be expressed as This is the first term of the above equation (1).

  When the substrate 46 is transparent, it is necessary to consider reflected light from the back surface of the substrate 46 (hereinafter referred to as “back surface reflected light”). FIG. 15 schematically shows a reflection state when the measurement light is irradiated to the thin film 47 formed on the surface of the transparent substrate 46. In the figure, L0 is the measurement light of wavelength λ, Lm is the reflected light from the substrate surface with respect to the incident measurement light L0, and L3 is the reflected light from the back surface of the substrate 46. Here, when the surface of the substrate 46 is uneven, the reflectance indicated by the reflected light Lm corresponds to Rz (λ) in the equation (3).

As shown in FIG. 15, when the measurement light L <b> 0 reaches the back surface of the substrate 46, the reflected light L <b> 3 reflected by the back surface of the substrate 46 is emitted from the surface of the measurement object 23. The back surface reflected light L3 is incident on the substrate 46 from above, is transmitted through the substrate 46, is reflected at the back surface thereof, is transmitted through the substrate 46 again, and is emitted from the surface of the measurement object 23. When the transmittance at the interface between the substrate 46 and the substrate 46 (including absorption by the thin film 47 and the substrate 46) is Ta (λ) and the reflectance at the back surface of the substrate 46 is Rb (λ), the substantial reflectance is
Ta ² (λ) × Rb (λ) (4)
It becomes.

The back surface reflection light receiving efficiency y is the light reception ratio of the back surface reflected light L3 that actually enters the light receiving unit 20 with respect to the theoretical back surface reflected light reflectance as expressed by equation (4). Is considered in consideration of diffusion on the back surface or the like. The reflectance of the light reflected by the back surface of the substrate 46 and actually received by the imaging unit 36 is Ta ² (λ) × Rb (λ) × y (( ² )) using this light reception ratio (back surface reflection light receiving efficiency y). 5)
Can be expressed as This is the second term of the above equation (1).

When the substrate 46 is transparent, as shown in FIG. 15, the light L4 (hereinafter referred to as “hereinafter referred to as“ L4 ”) is further transmitted through the back surface of the substrate 46, reflected by the background 48, and returned from the surface of the measurement object 23. It is necessary to consider “background reflected light”. The background reflected light L4 is transmitted through the thin film 47 and the substrate 46 and reflected by the background 48, and is transmitted through the substrate 46 and the thin film 47 again and emitted from the surface of the measurement object 23. The transmittance (including absorption by the thin film 47 and the substrate 46) at the interface with Ta (λ), and the transmittance at the back surface of the substrate 46 (including absorption by the medium between the substrate 46 and the background 48) Tb. (λ), where the reflectance of the background 48 is Rc (λ), the theoretical reflectance is
Ta ² (λ) × Tb ² (λ) × Rc (λ) (6)
It becomes. Further, since the background reflected light L4 is also considered to be affected by diffusion by the substrate 46 in the same manner as the back surface reflected light L3, the reflectance of the background reflected light L4 that is reflected by the background 48 and actually received by the imaging unit 36. Using the back surface reflection light receiving efficiency y Ta ² (λ) × Tb ² (λ) × Rc (λ) × y (7)
Can be expressed as This is the third term of the above equation (1).

  Thus, the reflectance by the reflected light Lm on the substrate surface represented by the above formula (3), the reflectance by the back surface reflected light L3 represented by the above formula (5), and the above formula (7). It is considered that the reflectance obtained from the reflected light actually measured by the imaging unit 36 is obtained by adding the reflectance of the background reflected light L4 represented. That is, this is the formula of the reflectance R (λ) expressed by the above formula (1) (theoretical calculation formula for calculating the film thickness).

  As can be seen from the equation (1), when there is reflected light L4 from the background 48, the spectral spectrum waveform of the measured waveform becomes higher than the theoretical spectral spectrum waveform as shown in FIG. A film thickness measurement error occurs. Therefore, in order to accurately measure the film thickness of the thin film 47, it is necessary to calculate the film thickness based on the formula (1) in consideration of such influence of the background. A method for measuring the thickness of the thin film based on the equation (1) will be described with reference to the flowchart of FIG. 17 and the process diagram of FIG.

  When the film thickness is measured by the thin film measuring apparatus 11, a reference substrate (sample substrate) 50 is first placed on a background stage 49 as shown in FIG. The light quantity of the light Lt reflected by the sample substrate 50 is measured without being affected by light or disturbance light. Since the sample substrate 50 has optical constants such as reflectance known in advance, the amount of light reflected by the sample substrate 50 is measured, and the output of the light projecting unit 19 of the thin film measuring device 11 is measured based on the amount of light. The sensitivity of the light receiving unit 20 is calibrated to be a predetermined value (step S1).

  In order to measure the reference light amount of the sample substrate 50 without being affected by the background, for example, a substrate having a known optical constant that does not reflect or transmit on the back surface of the substrate may be used. As such a sample substrate 50, for example, a substrate as shown in FIG. 19 may be used. The sample substrate 50 is obtained by performing a fine uneven process on the back surface of the glass plate 51 having a smooth surface, and further performing a black anodize process on the surface subjected to the uneven process to form an uneven anodized layer 52. is there. Note that no thin film is formed on the surface of the glass plate 51. In such a sample substrate 50, the light that has entered the glass plate 51 is absorbed by the anodized layer 52 and is not emitted to the background side, so the amount of light reflected by the sample substrate 50 is the light reflected by the background. Not included.

  As the sample substrate 50 without back surface reflection, a metal substrate such as a Si substrate can also be used. However, since the measurement object 23 for measuring the film thickness is assumed to be a transparent substrate such as a glass substrate in this case, if a metal substrate is used as the sample substrate 50, the reflectance of the sample substrate 50 is assumed. Becomes considerably larger than the reflectance of the substrate 46 of the measurement object 23 (for example, about 40%). Therefore, when the thin film measuring apparatus 11 is calibrated using the sample substrate 50 made of a metal substrate, the S / N ratio is deteriorated and the dynamic range is narrowed when the measurement object 23 is actually measured. On the other hand, since the sample substrate 50 as shown in FIG. 19 has substantially the same reflectivity as a transparent substrate such as a glass substrate used for the measurement object 23, the thin film measuring apparatus 11 is calibrated with this sample substrate 50. By doing this, the S / N ratio and dynamic range when measuring the measurement object 23 can be adjusted to an appropriate range, which is more preferable than using a metal substrate such as a Si substrate.

  Conversely, when the alumite treatment layer 52 is formed on the surface of the glass substrate 51, the reflected light from the sample substrate 50 becomes very small, and the signal level when measuring the measurement object 23 becomes too high. Therefore, it is desirable to use the sample substrate 50 having the alumite treatment layer 52 on the back surface of the glass plate 51.

  Next, as shown in FIG. 18B, the sample substrate 50 is removed from the stage 49, the measurement light L0 is irradiated onto the stage 49, the amount of light Lb reflected by the stage 49 is measured, and the stage 49 (background) ) Is directly measured (step S2). When measuring the reflectance Rc (λ) of the background, the light incident on the imaging unit 36 may include disturbance light, or the disturbance light may be blocked. It is necessary to set the same conditions as when 23 is measured.

  Thereafter, as shown in FIG. 18C, the actual measurement object 32 is placed on the stage 49, the spectral characteristic including the reflected light L4 from the background is acquired, and the reflectance S (λ ) Is calculated (step S3).

  Next, using the background reflectivity Rc (λ) measured in step S2, the theoretical expression of the spectral characteristic considering the reflection from the back surface of the substrate and the reflection from the background (that is, the reflection expressed by the equation (1)). Rate) R (λ) is obtained (step S4). The obtained reflectance R (λ) is a function of the wavelength λ with the film thickness d of the thin film 47 as a parameter. A method of determining the theoretical reflectance R (λ), particularly how to determine the front surface reflection light reception efficiency z and the back surface reflection light reception efficiency y will be described later.

  When the theoretical formula R (λ) of the reflectivity is determined, the waveform of the reflectivity S (λ) actually measured in step S3 is compared with the waveform of the theoretical formula R (λ) (step S5), and the thin film is obtained by the curve fitting method. A film thickness d of 47 is determined (step S6).

  Therefore, according to such a thin film measuring apparatus 11, even when the thin film measuring apparatus 11 is installed later in an existing manufacturing line or manufacturing apparatus, the manufacturing line or manufacturing apparatus or the like is not improved. (Retrofit), the film thickness of the thin film can be accurately measured by removing or correcting the influence of the background. Further, the film thickness of the thin film can be measured at an arbitrary position within the two-dimensional region of the measurement object (see FIG. 13), and the two-dimensional measurement of the film thickness is possible. 100% inspection can be made possible.

  If the thickness of the thin film is known, the optical constant (refractive index, transmittance, etc.) of the thin film can also be measured (step S6).

  A method for obtaining the theoretical formula R (λ) of the reflectance in steps S4 and S5 using the film thickness d as a parameter and determining the film thickness d by the curve fitting method is as follows. The thin film reflectance Ra (λ) in the first term of the equation (1) is a reflectance when the surface of the substrate 46 is assumed to be a mirror surface, and is the refractive index n2 of the substrate 46 and the refractive index of the thin film 47. It can be theoretically obtained by n1, the film thickness d of the thin film 47, the wavelength λ of the irradiation light, and the like. For example, the thin film reflectance Ra (λ) is determined using the equation (2) and is a function of the wavelength λ with the film thickness d of the thin film 47 as a parameter.

  FIG. 18 shows the theoretical reflectance Ra (λ) obtained from the equation (2) for each wavelength λ and the reflectance Rz (λ) = when the surface reflection light receiving efficiency is z = 0.5. It is a wave form diagram which shows the relationship with Ra ((lambda)) xz. The reflectances Ra (λ) and Rz (λ) for each wavelength λ on the substrate 46 change in a sinusoidal shape with a substantially constant amplitude, and the amplitude of the curve of the reflectance Rz (λ) is the reflectance Ra (λ ) Is multiplied by the surface reflection light receiving efficiency z.

  As shown in FIG. 18, the theoretical curve of the reflectance Rz (λ) with the theoretical reflectance Ra (λ) and the surface reflection light receiving efficiency z added thereto changes in a sine wave shape with a predetermined amplitude. The ratio of the amplitude of the curve of Rz (λ) to the amplitude of the curve of Ra (λ) corresponds to the surface reflection light receiving efficiency z. Therefore, after extracting the degree of change in reflectance corresponding to the amplitude from the measured reflectance data S (λ), the ratio of this value to the theoretical reflectance Ra (λ) is calculated. The surface reflection light receiving efficiency z can be determined. In order to obtain the amplitude of the actually measured reflectance data S (λ), the maximum value and the minimum value are extracted from the spectrum and the difference between them is calculated. However, when a spectrum of one period or more is obtained, the difference between the maximum value and the minimum value in any period may be calculated.

  FIG. 19 shows a processing procedure for setting a theoretical curve for measuring the substrate 46 having an uneven surface based on such a principle. First, the maximum value Smax, the minimum value Smin, and the average value Sa are extracted from the actual measurement data S (λ) obtained in step S3 in FIG. 17 (step S11). Then, after assuming that the film thickness d of the thin film 47 of the measurement object 23 is a certain minimum value dx (step S12), the processes of steps S13 to S21 are executed.

In step S13, the reflectance Ra (λ) when the film thickness is dx is calculated using the equation (2). In step S14, the maximum value Ramax and the minimum value Ramin in the curve of the reflectance Ra (λ) are extracted. In the next step S15, the maximum value Ramax and minimum value Ramin of the reflectance Ra (λ) obtained in step S14 and the maximum value Smax and minimum value Smin of the measured data S (λ) obtained in step S11 are obtained. By applying the following equation (8), the surface reflection light receiving efficiency z is calculated.

  Here, (Smax−Smin) and (Ramax−Ramin) are considered to correspond to the amplitudes of the respective spectrums indicated by S (λ) and Ra (λ), respectively. In this case, instead of the maximum value and the maximum value, the maximum value and the minimum value in any one of the cycles may be extracted and applied to the equation (8).

  When the surface reflection / reception efficiency z is calculated in this way, the calculated surface reflection / reception efficiency z and the reflectance Ra (λ) are applied to the equation (3) to calculate model data Rz (λ) (step S16).

Here, the thin film transmittance Ta (λ), the substrate back surface reflectance Rb (λ), and the substrate back surface transmittance Tb (λ) in (1) are obtained by conducting simulations or experiments, or searching from papers or data books. It is inputted and stored in advance in the arithmetic processing unit 13. The average value Rba is obtained from the stored Rb (λ), and the average value Rza is obtained using the model data Rz (λ) obtained in step S16. Using the average values Rba and Rza thus obtained and the average value Sa of S (λ) obtained in step S11, the back surface reflection light receiving efficiency y can be calculated by the following equation (9) (step S17).
y = (Sa−Rza) / Rba (9)

  Therefore, the background reflectance Rc (λ) actually measured in step S2, the Rz (λ) obtained in step S16, the back surface reflection light receiving efficiency y obtained in step S17, and the thin film transmittance Ta ( The theoretical formula R (λ) of the reflectance expressed by the equation (1) is obtained from λ), the substrate back surface reflectance Rb (λ), and the substrate back surface transmittance Tb (λ) (step S18).

  Next, curve fitting is performed by comparing the theoretical formula R (λ) with the actually measured data S (λ). FIG. 20 shows the principle of the curve fitting method. In FIG. 20, S is a reflection spectrum showing actually measured light reception data. RA to RE are theoretical reflection spectra obtained from the theoretical reflectance R (λ) obtained by the equation (1) for each film thickness, and the degree of light interference varies depending on the film thickness. Reflecting this phenomenon, each has a different distribution shape. In the curve fitting method, the least square error with respect to each theoretical curve is obtained in order for the reflection spectrum obtained from the actually measured light reception data S, whereby the theoretical curve having the shape closest to the light reception data S is specified, and the corresponding theoretical curve is obtained. The film thickness d (1000 nm in FIG. 20) is the thickness of the thin film to be measured. In order to execute this method, in step S18, a least square error between the calculated theoretical formula R (λ) and the measured data S (λ) is calculated (step S19). This calculation result is accumulated in the storage device.

  Next, the assumed film thickness d is increased by Δd (step S20), and the processes from steps S13 to S20 are repeated again. The processes in steps S13 to S21 are repeated many times until the assumed film thickness d exceeds the set maximum film thickness dy, and the theoretical formula R (λ) corresponding to each film thickness value for each Δd and the actual measurement data S ( The least square error of λ) is sequentially stored in the storage device.

  When the least square error is obtained for all film thicknesses, the process proceeds to step S22, where the film thickness dz when the least square error is minimized is extracted, and in the final step S23, this film thickness dz is output as a measurement result. The process is terminated.

  In Example 1, the background reflectance Rc (λ) was measured in Step 2 of FIG. 17, but when the substrate of the measurement object is an opaque substrate, it is not affected by the background. Unaffected by Rc (λ). Therefore, in the case of measuring the thickness of a thin film formed on an opaque substrate or the thickness of a thin film formed on a transparent substrate, the type of the substrate can be input from an input / output device such as a keyboard or a changeover switch ( The type of the substrate can be input by operating (not shown), and the measurement processing such as the film thickness can be easily switched according to the input peripheral type of the substrate.

  The measurement process in Example 2 is shown in the flowchart of FIG. After the film thickness measuring device 11 is calibrated (step S1), information on whether it is a transparent substrate or an opaque substrate input from the input / output device 15 is read (step S7). When information indicating that the type of the substrate 46 is a transparent substrate is input, the measurement process is performed by the same processes as steps S2 to S6 of FIG. That is, after measuring the reflectance Rc (λ) of the background (step S2), the reflectance S (λ) is actually measured (step S3 ′), and the theoretical formula R (1) of the reflectance expressed by the equation (1) is used. (λ) is obtained (step S4 ′), and the actual measurement data S (λ) of the reflectance of the measurement object 23 is compared with the theoretical formula R (λ) of the reflectance by the curve fitting method (step S5 ′). The film thickness and the like of the thin film 47 are obtained (step S6). On the other hand, when information indicating that the type of the substrate 46 is an opaque substrate is input, the reflectance S (λ) is calculated without skipping step S2 and actually measuring the reflectance Rc (λ) of the background. An actual measurement (step S3 ′) and a theoretical formula R (λ) = Rz (λ) of the reflectance expressed by the formula (3) not including the background are obtained (step S4 ′), and the reflectance of the measurement object 23 is obtained. Is compared with the theoretical formula R (λ) = Rz (λ) of the reflectance not including the background (step S5 ′), thereby determining the film thickness of the thin film 47 (step S6). . Therefore, according to the second embodiment, in the case of an opaque substrate, the step of measuring the background reflectance Rc (λ) can be skipped, and even when measuring a measurement object on a different type of substrate, thin film measurement is performed. It is possible to avoid the processing in the apparatus 11 from becoming complicated.

  In Example 1, the background reflectance Rc (λ) was actually measured in Step 2 of FIG. 17, but when the background constituent members, optical constants, and optical characteristics are known, the optical properties of the background constituent members are measured. The background reflectance Rc (λ) may be theoretically obtained based on the characteristic value. That is, as shown in the flowchart of FIG. 23, in step S8, the background reflectance Rc (λ) is theoretically obtained based on the value of the optical characteristic of the background constituent member. For example, it is desirable that the reflectance Rc (λ) is automatically calculated by the thin film measuring device 11 when the value of the background optical characteristic is input from the input / output device. According to such a method, the process of actually measuring the reflectance Rc (λ) of the background can be omitted, and in some cases, the process of measuring the film thickness and optical constant of the thin film can be simplified.

  In the fourth embodiment of the present invention, as shown in FIG. 24, the surface of the stage 49 is subjected to black alumite treatment 53. When the stage 49 is a glass plate, the back surface of the stage 49 may be subjected to black alumite treatment. If the stage 49 (background) is subjected to the black alumite treatment 53 in this manner, the reflected light from the background is reduced, so that the background reflectance Rc (λ) can be reduced to reduce the influence of the background. In addition, the accuracy of measuring the film thickness of the thin film 47 can be further increased.

  Further, an antireflection sheet subjected to black alumite treatment may be attached to the surface of the stage 49.

In Example 5 of the present invention, as shown in FIG. 25, when measuring the reflectance of the background in step S2 of FIG. 17, a transparent substrate 46 on which the thin film 47 is not formed is placed on the stage 49. To obtain the reflectance. Since the reflectance obtained in this manner includes the reflectance on the back surface of the substrate 46, this step allows
{Ta ² × Rb + Ta ² × Tb ² × Rc}
Is measured as the background reflectance, the process of obtaining the theoretical formula R (λ) in step 4 of FIG. 17 is simplified.

  The thin film measuring method and the thin film measuring apparatus of the present invention are used for the purpose of measuring in-line the film thickness and optical constant of a thin film formed on the surface of a substrate with the thin film formed on the surface. it can.

It is a schematic sectional drawing explaining the method for reducing the influence of a background in a film thickness measuring apparatus. It is a schematic sectional drawing explaining another method for making the influence of a background small in a film thickness measuring apparatus. It is a schematic sectional drawing explaining another method for making the influence of a background small in a film thickness measuring apparatus. It is a whole block diagram which shows the thin film measuring apparatus by Example 1 of this invention. 1 is a block diagram illustrating an electrical configuration of a thin film measuring apparatus according to Example 1. FIG. FIG. 3 is a schematic diagram illustrating an optical configuration of a sensor head unit used in the film thickness measuring apparatus according to the first embodiment. It is a top view which expands and shows a multispectral filter. It is a figure which shows the behavior of the optical system in the thin film measuring apparatus of Example 1, and its light ray. (A) is a figure explaining the light source reference plane in a light source, (b) is a figure which shows the definition of the numerical aperture seen from the image side, and the numerical aperture of the measurement light reflected by a measurement object. 2 is a schematic side view showing an example of a light source used in the thin film measuring apparatus of Example 1. FIG. In both (a) and (b), the image of the light source is formed on the aperture stop, the image of the measurement object is formed on the imaging unit, and the object-side telecentric optical system is used as the imaging optical system. It is a figure explaining the behavior of the light in 1 thin film measuring apparatus. (A) is a figure which shows the behavior of a light ray when the inclination of a measuring object is 0 degree in the thin film measuring apparatus of Example 1, (b) is the inclination of a measuring object is 1 degree in the thin film measuring apparatus of Example 1. The figure which shows the behavior of the light ray at the time of (a), (c) is a figure which shows the behavior of the light ray when the inclination of a measuring object is -1 degree in the thin film measuring apparatus of Example 1. FIG. (A)-(f) is a figure which shows the image of the TFT array substrate observed through the spectral filter of a different selection wavelength. (A) is a figure explaining thin film reflectance Ra ((lambda)) by the thin film formed on the board | substrate with a mirror surface, (b) is a thin film reflectance by the thin film formed on the board | substrate which has an unevenness | corrugation. It is a figure explaining Rz (λ). It is a figure explaining a mode that the light irradiated to the transparent board | substrate is reflected in the back surface and background of a board | substrate. It is a figure which compares and shows the spectral spectrum waveform when there is reflected light from the background, and the spectral spectrum waveform when there is no reflected light from the background. It is a flowchart explaining the method to measure the film thickness of a thin film based on the theoretical formula of a reflectance. (A)-(c) is a figure explaining the process of measuring the film thickness of a thin film based on the theoretical formula of a reflectance. It is sectional drawing which shows an example of a sample board | substrate. FIG. 18 is a flowchart for explaining steps S4 and S5 in FIG. 17 in detail. It is explanatory drawing which shows the principle of the curve fitting method. It is a flowchart explaining the measurement process process in Example 2 of this invention. It is a flowchart explaining the measurement process process in Example 3 of this invention. It is a figure explaining the measurement state in Example 4 of this invention. It is a figure explaining the measurement state in Example 5 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Thin film measuring device 12 Sensor head part 13 Arithmetic processing part 14 Display apparatus 15 Input / output device 19 Light projection part 20 Light receiving part 23 Measurement object 30 Light source 34 Aperture stop 35 Multi-spectral filter 36 Imaging part 46 Substrate 47 Thin film 48 Background 49 Stage 50 sample substrate

Claims (10)

A light projecting unit that irradiates light toward the measurement target, an imaging unit that captures light reflected by the measurement target, and a film thickness of the thin film on the surface of the measurement target based on the spectral characteristics of the light captured by the imaging unit Or a thin film measuring apparatus comprising an arithmetic processing unit for obtaining an optical constant,
The arithmetic processing unit takes into account the spectral characteristics acquired from the reflected light of the light irradiated on the measurement object having a thin film formed on the surface of the transparent substrate, and the spectral characteristics of the light incident from the background of the measurement object. It is configured to obtain the film thickness or optical constant of the thin film by comparing with the calculated theoretical formula of the spectral characteristic of the reflected light from the measurement object.
A thin film measuring apparatus. The arithmetic processing unit calculates a theoretical formula of spectral characteristics of light reflected from the measurement object in consideration of spectral characteristics of light incident from the background in a state where the measurement object is removed from the measurement object installation position. The thin film measuring apparatus according to claim 1, further comprising: The thin film measuring apparatus according to claim 1, further comprising a stage subjected to black alumite treatment for placing an object to be measured. The measurement method can be switched between when the measurement object is a thin film formed on a transparent substrate and when the measurement object is a thin film formed on an opaque substrate,
In the case of a measurement object with a thin film formed on a transparent substrate, the spectral characteristics obtained from the reflected light of the light irradiated on the measurement object and the spectral characteristics of light incident from the background of the measurement object are considered. The film thickness or optical constant of the thin film is obtained by comparing with the theoretical formula of the spectral characteristic of the reflected light from the measurement object calculated in
In the case of a measurement object in which a thin film is formed on an opaque substrate, it depends on the measurement object that does not take into account the spectral characteristics acquired from the reflected light of the light irradiated to the measurement object and the spectral characteristics of incident light from the background. By comparing the theoretical formula of the spectral characteristics of the reflected light, the film thickness or optical constant of the thin film was obtained.
The thin film measuring apparatus according to claim 1, wherein: The thin film measuring apparatus according to claim 1, wherein the film thickness or optical constant of the thin film is obtained at a plurality of points of the measurement object. The thin film measuring apparatus according to claim 1, which is incorporated in a production line of an image display device such as a liquid crystal display panel or a plasma display device. A light projecting unit that irradiates light toward the measurement object; and an imaging unit that captures the light reflected by the measurement object, and a thin film on the surface of the measurement object based on a spectral characteristic of the light captured by the imaging unit. A thin film measuring method for obtaining a film thickness or an optical constant,
Irradiating light from the light projecting unit to the measurement object installation position where the measurement object is not installed to obtain spectral characteristics of light incident from the background;
A measurement object having a thin film formed on the surface of a transparent substrate is installed at a measurement object installation position, and light is reflected from the measurement object by irradiating the measurement object with light from the light projecting unit. Obtaining spectral characteristics; and
Using the spectral characteristics of the light incident from the background, obtaining a theoretical formula of the spectral characteristics of the reflected light from the measurement object;
A step of obtaining a film thickness or an optical constant of the thin film by comparing the spectral characteristic of the light reflected by the measurement object and the theoretical formula of the spectral characteristic of the reflected light by the measurement object;
A thin film measuring method comprising: A light projecting unit that irradiates light toward the measurement object; and an imaging unit that captures the light reflected by the measurement object, and a thin film on the surface of the measurement object based on a spectral characteristic of the light captured by the imaging unit. A thin film measuring method for obtaining a film thickness or an optical constant,
Obtaining spectral characteristics of light incident from the background based on the optical constant of the background member at the measurement object installation position;
A measurement object having a thin film formed on the surface of a transparent substrate is installed at a measurement object installation position, and light is reflected from the measurement object by irradiating the measurement object with light from the light projecting unit. Obtaining spectral characteristics; and
Using the spectral characteristics of the light incident from the background, obtaining a theoretical formula of the spectral characteristics of the reflected light from the measurement object;
A step of obtaining a film thickness or an optical constant of the thin film by comparing the spectral characteristic of the light reflected by the measurement object and the theoretical formula of the spectral characteristic of the reflected light by the measurement object;
A thin film measuring method comprising: A light projecting unit that irradiates light toward the measurement object; and an imaging unit that captures the light reflected by the measurement object, and a thin film on the surface of the measurement object based on a spectral characteristic of the light captured by the imaging unit. A thin film measuring method for obtaining a film thickness or an optical constant,
A step of obtaining a spectral characteristic of light incident from the background by installing a transparent substrate on which a thin film is not formed at a measurement object installation position and irradiating the substrate with light from the light projecting unit;
A measurement object having a thin film formed on the surface of a transparent substrate is installed at a measurement object installation position, and light is reflected from the measurement object by irradiating the measurement object with light from the light projecting unit. Obtaining spectral characteristics; and
Using the spectral characteristics of the light incident from the background, obtaining a theoretical formula of the spectral characteristics of the reflected light from the measurement object;
A step of obtaining a film thickness or an optical constant of the thin film by comparing the spectral characteristic of the light reflected by the measurement object and the theoretical formula of the spectral characteristic of the reflected light by the measurement object;
A thin film measuring method comprising: The thin film measuring method according to claim 7 or 9, wherein in the step of obtaining the spectral characteristics of the background, spectral characteristics of reflected light from the background in the vicinity of the film thickness measurement position of the measurement object are acquired.

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