JP6282911B2 - Film thickness measuring apparatus and film thickness measuring method - Google Patents

Description

  Embodiments described herein relate generally to a film thickness measuring apparatus and a film thickness measuring method for measuring a film thickness of a thin film using reflected interference light.

  One method for measuring the thickness of a thin film is reflectance spectroscopy that uses reflected interference light generated by the optical path difference between the front surface reflected light and the back surface reflected light of the thin film. For example, Japanese Unexamined Patent Application Publication No. 2013-79921 (Patent Document 1) discloses a thin film having an unknown refractive index by a method using reflected interference light measured from two directions at different incident angles (hereinafter referred to as two-way reflectance spectroscopy). A technique for measuring the film thickness of the film is disclosed.

  The filling factor (apparent filling factor) of the dielectric thin film varies depending on the manufacturing conditions. On the other hand, the refractive index of the thin film varies depending on the filling rate. For this reason, the refractive index of a thin film changes with manufacturing conditions. The two-way reflectance spectroscopy is convenient because it can measure the thickness of a dielectric thin film whose refractive index is unknown.

JP2013-79921A

  By the way, the user may desire to inspect the moving thin film as it moves. For example, in a production site of a sample on which a thin film to be observed is formed, samples produced one after another may be placed on a belt conveyor and moved to a place away from the sample manufacturing apparatus. In this case, the user may desire to inspect the thin film of the sample being moved on the belt conveyor in consideration of the inspection efficiency.

  However, in the conventional technique of measuring the film thickness of the thin film by two-way reflectance spectroscopy, the observation points on the thin film in both directions are the same, that is, the reflected interference light corresponding to the same film thickness and the same refractive index. Is assumed to be measured. Further, the reflected interference light measurement in each direction is performed with the timing shifted from each other in order to avoid interference of incident light and reflected light from the other direction.

  For this reason, in the conventional technique, when the thin film to be observed continues to move, reflected interference light at different positions in each of the two directions is observed. Therefore, in the conventional technique, an accurate film thickness cannot be obtained when a thin film to be observed is moving.

  The present invention has been made in consideration of the above-described circumstances, and a film thickness measuring apparatus capable of accurately measuring the film thickness of a thin film whose refractive index is unknown even when the thin film is moving, and It aims at providing the film thickness measuring method.

  In order to solve the above-described problem, a film thickness measuring apparatus according to an embodiment of the present invention is based on the wavelength distribution of reflected interference light generated by the optical path difference between the front surface reflected light and the back surface reflected light of the thin film. A film thickness measuring apparatus that measures thickness, and includes an irradiation unit, a light receiving unit, an optical path difference calculation unit, an optical path difference interpolation unit, and a film thickness refractive index calculation unit. The irradiating unit alternately irradiates irradiation light at predetermined time intervals at predetermined incident positions at different incident angles, thereby each of a plurality of measurement positions on the thin film passing through the predetermined irradiation position. Irradiation light is alternately irradiated at different incident angles. The light receiving unit alternately receives the reflected interference light of the irradiation light at each of the plurality of measurement positions at different reflection angles corresponding to different incident angles as each of the plurality of measurement positions passes through the predetermined irradiation position. To do. The optical path difference calculation unit obtains an optical path difference for each of the plurality of measurement positions using the wavelength distribution of the reflected interference light obtained at the incident angle at which the irradiation light is irradiated to each measurement position. The optical path difference interpolation unit estimates the optical path difference when it is assumed that the irradiation light is irradiated at the other incident angle with respect to the measurement position irradiated with the irradiation light at one incident angle for each of the plurality of measurement positions. Is interpolated using the optical path difference obtained by the optical path difference calculation unit at a measurement position within a predetermined distance from the measurement position. The film thickness refractive index calculation unit uses an expression representing the optical path difference as a function of the incident angle, the film thickness, and the refractive index as variables for each of a plurality of measurement positions. The film thickness and refractive index of the thin film at each measurement position are obtained by substituting the obtained optical path difference, and the other incident angle and the optical path difference obtained by the optical path difference interpolation unit into the equation.

1 is a schematic overall configuration diagram showing an example of a film thickness measuring apparatus according to an embodiment of the present invention. (A) is a z direction arrow view which shows an example of a mode that a thin film passes a predetermined irradiation position at constant speed, (b) is a y direction arrow view, (c) is an x direction arrow view. (A) is explanatory drawing which shows an example of the relationship between the size of the irradiation light spot area (predetermined irradiation position) which concerns on this embodiment, and the size of a light reception spot area, (b) is the relationship between a predetermined irradiation position and a measurement position. Explanatory drawing which shows an example. The schematic block diagram which shows the structural example of the function implementation part by CPU of a main control part. Explanatory drawing which shows an example of the wavelength distribution of reflected interference light produced | generated by the wavelength distribution production | generation part. The figure for demonstrating the optical path difference L of the surface reflected light and back surface reflected light of a thin film. (A) is explanatory drawing which shows an example of the relationship between the measurement position and optical path difference in case the film thickness d and refractive index n of a thin film are uniform irrespective of a measurement position, (b) is measurement in the case of nonuniformity Explanatory drawing which shows an example of the relationship between a position and an optical path difference. The figure for demonstrating the simple method of calculating | requiring the film thickness d and refractive index n in each measurement position, without calculating | requiring the interpolation optical path difference L ', when a thin film passes the irradiation position in two-way reflectance spectroscopy. FIG. 9 is an explanatory diagram illustrating an example of an optical path difference measured using irradiation light with an incident angle θA at a measurement position Xn (B) in the example illustrated in FIG. 8. Explanatory drawing which shows an example of a mode that the interpolation optical path difference L 'is calculated | required with the 1st calculation method which concerns on this embodiment. Explanatory drawing which shows an example of a mode that the interpolation optical path difference L 'is calculated | required with the 2nd calculation method which concerns on this embodiment. Explanatory drawing which shows another example of a mode which calculates | requires the interpolation optical path difference L 'with the 2nd calculation method which concerns on this embodiment. The flowchart which shows an example of the procedure at the time of measuring accurately the film thickness d of the thin film whose refractive index n is unknown even if it is a case where the thin film is moving by CPU of the main-control part shown in FIG. (A) is explanatory drawing which shows an example of the relationship between the measurement position which concerns on the comparative example 1, and an optical path difference, (b) is explanatory drawing which shows an example of the relationship between the measured position which concerns on the comparative example 1, and a film thickness. (A) is explanatory drawing which shows an example of the relationship between the measurement position which concerns on the comparative example 2, and an optical path difference, (b) is explanatory drawing which shows an example of the relationship between the measured position which concerns on the comparative example 2, and a film thickness. (A) is explanatory drawing which shows an example of the relationship between the measurement position which concerns on Example 1, and an optical path difference, (b) is explanatory drawing which shows an example of the relationship between the measurement position which concerns on Example 1, and a film thickness. (A) is explanatory drawing which shows an example of the relationship between the measurement position which concerns on Example 2, and an optical path difference, (b) is explanatory drawing which shows an example of the relationship between the measurement position which concerns on Example 2, and a film thickness.

  Embodiments of a film thickness measuring apparatus and a film thickness measuring method according to the present invention will be described with reference to the accompanying drawings.

  The film thickness measurement apparatus according to an embodiment of the present invention irradiates irradiation light at two different incident angles θA and θB with respect to the thin film passing through the irradiation region of the irradiation light, and the two types of incident light. The film thickness of the thin film is measured based on the wavelength distribution of the reflected interference light of the thin film corresponding to.

(1. Outline configuration)
FIG. 1 is a schematic overall configuration diagram showing an example of a film thickness measuring apparatus 10 according to an embodiment of the present invention. In the following description, an example in which the normal direction of the thin film is the Z axis, the normal direction of the thin film is perpendicular, and the moving direction of the thin film is the X axis is shown.

  The film thickness measuring device 10 includes an irradiation unit 11, a light receiving unit 12, a spectroscopic unit 13, a conveyor 14, a production device 15, and an information processing device 16. Note that in the film thickness and refractive index calculation processing of the film thickness measuring apparatus 10 according to the present embodiment, the configuration excluding the main control unit of the information processing device 16 is not an essential configuration in the processing and may be omitted as appropriate. For example, when the reflected interference light data of the thin film can be received via the network, the configuration excluding the information processing device 16 is not necessary in the processing.

  The irradiation unit 11 includes a light source 20, a first irradiation unit 21, and a second irradiation unit 22.

  The light source 20 is configured by a halogen lamp, a broadband laser, or the like, emits irradiation light having a predetermined wavelength range, and the illumination light is emitted from the first irradiation unit 21 via a light guide 23 configured by an optical fiber or the like. And to the second irradiation unit 22. Further, shutters 24 and 25 are provided on the optical paths on the light source 20 side of the first irradiation unit 21 and the second irradiation unit 22, respectively.

  The first irradiation unit 21 and the second irradiation unit 22 alternately irradiate the object 26 with irradiation light at predetermined time intervals at different first incident angles θA and second incident angles θB. The object 26 has a substrate 27, and a thin film 28 is formed on the surface of the substrate 27.

  The shutters 24 and 25 are controlled by the information processing device 16 so that irradiation of the irradiation light to the object 26 by the first irradiation unit 21 and irradiation of the irradiation light to the object 26 by the second irradiation unit 22 are performed for a predetermined time. The irradiation light is appropriately shielded so as to be alternately performed at intervals.

  The light receiving unit 12 includes a first light receiving unit 31 and a second light receiving unit 32.

  The first light receiving unit 31 is disposed at a position facing the first irradiation unit 21 through the normal line of the surface of the thin film 28. The first light receiving unit 31 is substantially equal to the first incident angle θA for the first reflected interference light from the thin film 28 of the light irradiated to the thin film 28 by the first irradiation unit 21 at the first incident angle θA. Light is received at the first reflection angle. Further, the second light receiving unit 32 is disposed at a position facing the second irradiation unit 22 through the normal line of the surface of the thin film 28. The second light receiving unit 32 substantially equals the second incident angle θB of the second reflected interference light by the thin film 28 of the light irradiated to the thin film 28 by the second irradiation unit 22 at the second incident angle θB. Light is received at the second reflection angle.

  If one of the incident angles θA and θB is 0 degree, a beam splitter may be used. For example, when the incident angle θA is set to 0 degree, the first light receiving unit 31 is not disposed at a position facing the first irradiation unit 21 through the normal line of the surface of the thin film 28. In this case, for example, the first irradiation unit 21 is arranged parallel to the X axis, and the first light receiving unit 31 is arranged on the normal line of the thin film 28. At this time, the irradiation light emitted from the first irradiation unit 21 in parallel to the X axis is reflected toward the thin film 28 in parallel to the Z axis (parallel to the normal line of the thin film 28) via the beam splitter. Thus, the thin film 28 is irradiated at an incident angle of 0 degree. The first reflected interference light is reflected at a reflection angle of 0 degree (parallel to the Z axis), passes through the beam splitter, and is received by the first light receiving unit 31.

  The spectroscopic unit 13 includes a general spectroscope, and alternately reflects the reflected interference light received by the first light receiving unit 31 and the reflected interference light received by the second light receiving unit 32 via the light guide 33. receive. The spectroscopic unit 13 splits each of the reflected interference light in a predetermined wavelength band, and gives the information processing device 16 information on the intensity of the reflected interference light for each wavelength.

  FIG. 2A is a z-direction arrow view showing an example of how the thin film 28 passes through the predetermined irradiation position 35 at a constant speed, FIG. 2B is a y-direction arrow view, and FIG. FIG. In the following description, an example in which the first incident angle θA is 20 degrees and the second incident angle θB is 30 degrees will be described. 2A, 2B, and 2C, the thin film moves from right to left, from right to left, and from the back of the page to the front, respectively.

  For convenience, the illustration of the shutters 24 and 25 is omitted in FIG. In FIG. 2B, the second irradiation unit 22 and the second light receiving unit 32 are superimposed in the depth direction of the paper surface, respectively, and in FIG. 2C, the first irradiation unit 21 and the first light receiving unit 31 are overlapped. Note that

  As shown in FIG. 2, the object 26 having the thin film 28 is placed on the belt (mounting portion) 36 of the conveyor 14, and the irradiation positions 35 of the first irradiation unit 21 and the second irradiation unit 22 are fixed. Pass at speed.

  The conveyor 14 is composed of a pair of rollers and an endless belt 36 stretched over the roller pairs, and is driven by a drive unit (not shown). The information processing device 16 controls the moving speed of the thin film 28 by controlling the drive unit.

  The production apparatus 15 is an apparatus for producing the object 26 according to predetermined production conditions. The placement unit 36 a of the production line for the object 26 of the production apparatus 15 is connected to the belt 36 of the conveyor 14 and moves the object 26 at the same speed as the belt 36.

  As the thin film 28 of the object 26 according to the present embodiment, for example, a film made of a dielectric such as titanium oxide having a predetermined particle size, an adhesive, or a transparent electrode film such as ITO (Indium Tin Oxide) Etc. can be used. In the case of a dielectric thin film, the film filling rate (apparent filling rate) varies depending on the fabrication conditions. For example, in the case where the object 26 is the dye-sensitized solar cell itself or a sample for inspecting the physical properties of the dye-sensitized solar cell, the manufacturing apparatus 15 forms the thin film 28 on the photoelectrode of the dye-sensitized solar cell. A titanium oxide thin film 28 to be used is formed on the substrate 27.

  The titanium oxide thin film 28 is a porous film obtained, for example, by heating titanium oxide nanoparticles at a predetermined temperature. It is known that the filling rate of the porous film obtained by this kind of baking and sintering varies depending on the production conditions such as heating temperature and heating time. Further, it is known that the refractive index of the porous film varies depending on the filling rate. For this reason, the refractive index of the titanium oxide thin film 28 varies depending on the manufacturing conditions.

  Therefore, the information processing apparatus 16 according to the present embodiment is configured to be able to accurately measure the film thickness and refractive index of the thin film 28 even while moving the thin film 28 whose refractive index is unknown.

  The information processing apparatus 16 can be constituted by, for example, a desktop type or notebook type personal computer or a workstation. The information processing apparatus 16 includes an input unit 51, a display unit 52, a storage unit 53, and a main control unit 54.

  The input unit 51 is configured by a general input device such as a keyboard, a trackball, a touch panel, and a numeric keypad, and outputs an operation input signal corresponding to a user operation to the main control unit 54. The display unit 52 is configured by a general display output device such as a liquid crystal display or an OLED (Organic Light Emitting Diode) display, and displays various types of information according to the control of the main control unit 54. The storage unit 53 is a storage medium that can be read and written by the CPU. The storage unit 53 stores in advance an expression representing the optical path difference L as a function with the incident angle, the film thickness, and the refractive index as variables.

  The main control unit 54 receives the spectral spectrum of the reflected interference light from the spectral unit 13 and obtains the optical path difference L using this spectral spectrum. In addition, the main control unit 54 obtains the film thickness and the refractive index for each measurement position of the thin film 28 using the formula stored in the storage unit 53. Details of the configuration and operation of the main controller 54 will be described later.

(2. Measurement position of thin film)
FIG. 3A is an explanatory diagram showing an example of the relationship between the size of the irradiation light spot area (predetermined irradiation position 35) and the size of the light receiving spot area 37 according to the present embodiment, and FIG. It is explanatory drawing which shows an example of the relationship between the position 35 and a measurement position.

  In order to efficiently collect the interference signal, it is preferable that the radius r2 of the light receiving spot area 37 is larger than the radius r1 of the irradiation light spot area 35 (see FIG. 3A). The radius r1 of the irradiation light spot area 35 can be controlled by adjusting the numerical aperture of the lenses constituting the irradiation units 21 and 22. The radius r2 of the light receiving spot area 37 can be controlled by adjusting the numerical aperture of the lenses constituting the light receiving units 31 and 32.

  The thin film 28 is placed on the belt 36 and passes through the irradiation position 35. On the other hand, the first irradiation unit 21 and the second irradiation unit 22 alternately irradiate irradiation light at a predetermined time interval with respect to the irradiation position 35 at different first incident angles θA and second incident angles θB. Irradiate. Therefore, the measurement positions X1, X2,..., Xn-1, Xn, Xn + 1,... Xm (where m is a positive integer and n is an even number) on the thin film 28 are adjacent to each other. Irradiation light is irradiated from different incident angles.

  The information processing device 16 can control the measurement position and the interval between the measurement positions by controlling the speed of the belt 36 and the shutters 24 and 25.

  In the following description, the measurement position where the irradiation light is irradiated at the first incident angle θA is expressed as Xn-1 (A), and the measurement position where the irradiation light is irradiated at the second incident angle θB is expressed as Xn (B). It shall be (refer FIG.3 (b)). In addition, the optical path difference obtained by using the wavelength distribution of the reflected interference light obtained by Xn-1 (A) is changed to the wavelength distribution of the reflected interference light obtained by the optical path differences Ln-1 (A) and Xn (B). The optical path difference obtained using is expressed as an optical path difference Ln (B).

  In order to increase the intensity of the reflected interference light, the measurement area size of the thin film 28 may be narrowed instead of or in addition to the method shown in FIG. May be used, or the reflectance of only the substrate 27 may be measured in advance, and a measurement wavelength having a large reflectance may be used based on the result (see, for example, JP-A-2013-79921). ).

(3. Configuration of main control unit)
The main control unit 54 is configured by a storage medium such as a CPU, a RAM, and a ROM, and controls the operation of the film thickness measuring apparatus 10 according to a program stored in the storage medium. The CPU of the main control unit 54 loads a film thickness measurement program stored in a storage medium such as a ROM and data necessary for executing the program into the RAM. In accordance with this program, the CPU executes processing for accurately measuring the film thickness of the thin film 28 whose refractive index is unknown even when the thin film 28 is moving.

  The RAM of the main control unit 54 provides a work area for temporarily storing programs and data executed by the CPU. The storage medium including the ROM of the main control unit 54 stores a startup program for the information processing apparatus 16, a film thickness measurement program, and various data necessary for executing these programs.

  Note that a storage medium such as a ROM has a configuration including a CPU-readable recording medium such as a magnetic or optical recording medium or a semiconductor memory. You may comprise so that a part or all of the program and data in these storage media may be downloaded via an electronic network.

  FIG. 4 is a schematic block diagram illustrating a configuration example of the function realization unit by the CPU of the main control unit 54. In addition, this function realization part may be comprised by hardware logics, such as a circuit, without using CPU.

  As shown in FIG. 4, the CPU of the main control unit 54 performs at least a drive control unit 61, a shutter control unit 62, a wavelength distribution generation unit 63, an optical path difference calculation unit 64, an optical path difference interpolation unit 65, according to a film thickness measurement program. It functions as a film thickness refractive index calculator 66 and a filling factor calculator 67. Each unit 61-67 uses a required work area in the RAM as a temporary storage location for data.

  The drive control unit 61 controls the moving speed of the thin film 28 by controlling the drive unit of the conveyor 14.

  The shutter control unit 62 prevents the first interference unit 21 and the second irradiation unit 35 with respect to the predetermined irradiation position 35 so as to prevent the adverse effect that the reflection interference light with one incident angle is mixed into the reflection interference light with another incident angle. The shutters 24 and 25 are controlled so that irradiation light is alternately irradiated from the irradiation unit 22 at predetermined time intervals.

  FIG. 5 is an explanatory diagram illustrating an example of the wavelength distribution of the reflected interference light generated by the wavelength distribution generation unit 63. FIG. 5 shows an example of the wavelength distribution generated by the wavelength distribution generating unit 63 for the thin film 28 manufactured with the film thickness d = 16 μm and the refractive index n = 1.6. In FIG. 5, the solid line is an example of the wavelength distribution at the measurement position Xn-1 (A) corresponding to the first incident angle θA = 20 degrees, and the broken line is the measurement position Xn corresponding to the second incident angle θB = 30 degrees. An example of the wavelength distribution in (B) is shown respectively.

  Based on the information on the intensity of the reflected interference light at each wavelength generated by the spectroscopic unit 13, the wavelength distribution generating unit 63 is a discrete wavelength distribution composed of data for each predetermined wavelength band for each measurement position Xn. (See FIG. 5).

  The optical path difference calculation unit 64 reflects reflection interference obtained at an incident angle at which irradiation light is irradiated to each measurement position for each of a plurality of measurement positions X1 (A), X2 (B),. An optical path difference L (hereinafter referred to as an actual measured optical path difference L) is obtained using the wavelength distribution of light.

  For example, the measurement position Xn (B) is a measurement position where irradiation light is irradiated at an incident angle θB. The optical path difference calculation unit 64 obtains the optical path difference Ln (B) at the measurement position Xn (B) using the wavelength distribution of the reflected interference light obtained at the measurement position Xn (B).

  The optical path difference interpolating unit 65 has, for each of the plurality of measurement positions X1 (A), X2 (B),..., Xm, the other incident angle with respect to the measurement position irradiated with the irradiation light at one incident angle. The optical path difference (interpolation optical path difference) L ′, which is an optical path difference estimated when it is assumed that the irradiation light is irradiated, is obtained by the optical path difference calculation unit 64 at a measurement position within a predetermined distance from the measurement position. Obtained using the optical path difference L.

  For example, consider the measurement position Xn (B). The measurement position Xn (B) is a measurement position where the reflected interference light is actually measured with the irradiation light with the incident angle θB. For this reason, the actually measured optical path difference Ln (B) calculated by the optical path difference calculating unit 64 is obtained using the wavelength distribution of the reflected interference light measured with the irradiation light at the incident angle θB. In other words, the measurement position Xn (B) is not irradiated with light from the incident angle θA. The optical path difference interpolating unit 65 calculates the interpolated optical path difference L′ n (A) estimated when the irradiation light is irradiated at the incident angle θA with respect to the measurement position Xn (B) as the measurement position Xn (B). Is obtained using the measured optical path difference L obtained by the optical path difference calculation unit 64 at a measurement position within a predetermined distance.

  The film thickness refractive index calculation unit 66 uses the formula stored in the storage unit 53 for each of the plurality of measurement positions, and the measured incident angle and the measured optical path difference L obtained by the optical path difference calculation unit 64, and the actual measurement. The thickness d and refractive index n of the thin film 28 at each measurement position are obtained by substituting the incident angle and the interpolation optical path difference L ′ obtained by the optical path difference interpolation unit 65 into the equation, and the results are displayed on the display unit. 52.

  The filling rate calculation unit 67 obtains the filling rate of the constituent material of the thin film 28 at each measurement position of the thin film 28 using the refractive index n obtained by the film thickness refractive index calculation unit 66.

(3-1. Calculation Method of Actual Optical Path Difference L)
The optical path difference calculation unit 64 calculates the actually measured optical path difference L using the wavelength distribution of the interference (reflected interference light) of the light reflected at the front and back surfaces of the thin film 28 and each of the interfaces of the thin film 28. Conventionally, various methods are known as a method of calculating the optical path difference L using the wavelength distribution of the reflected interference light, and the optical path difference calculation unit 64 can use any of these methods.

  FIG. 6 is a diagram for explaining the optical path difference L between the front surface reflected light and the back surface reflected light of the thin film 28.

When the irradiated light is incident on the surface 28a of the thin film 28 at an incident angle θ1, if the film thickness is d and the refraction angle is θ2, the reflected light (surface reflected light) on the thin film surface 28a and the reflected light on the thin film back surface 28b ( The process difference ΔS with respect to the back surface reflected light can be written as follows.

Assuming that the refractive index of the thin film 28 is n, the optical path difference L is obtained by multiplying the stroke difference ΔS by the refractive index n.

If the refractive index of the substrate 27 is larger than the refractive index of the thin film 28, the optical path difference L is the peak wavelength lambda _m of the reflected interference light is known to be associated with the following Expression (3).

For this reason, the wavelength distribution of the reflected interference light has a waveform having a plurality of peaks corresponding to each m (see FIG. 5). When the refractive index of the substrate 27 is smaller than the refractive index of the thin film 28, phase inversion occurs at the time of interface reflection. Therefore, L = (m + 1/2) · λ _m may be used instead of the equation (3). .

  Therefore, the optical path difference calculation unit 64 can obtain the measured optical path difference L from the peak wavelength of the wavelength distribution of the reflected interference light (see FIG. 5) for each measurement position using Equation (3). Conventional methods for obtaining the peak position include a method using Fourier transform, a curve fitting method, and a peak valley method, and any of these methods may be used.

  Further, the optical path difference calculation unit 64 may obtain the actually measured optical path difference L by performing discrete Fourier transform on the wavelength distribution of the reflected interference light (see Japanese Patent Application Laid-Open No. 2013-79921), or The actually measured optical path difference L may be obtained by performing a normalized correlation calculation using a predetermined template waveform with respect to the wavelength distribution (see Japanese Patent Laid-Open No. 2013-253803).

(3-2. Method for calculating interpolation optical path difference L ′)
FIG. 7A is an explanatory diagram showing an example of the relationship between the measurement position and the optical path difference when the film thickness d and the refractive index n of the thin film 28 are uniform regardless of the measurement position, and FIG. It is explanatory drawing which shows an example of the relationship between the measurement position and optical path difference in the case.

  As shown in FIG. 7A, when the film thickness d and the refractive index n of the thin film 28 are uniform regardless of the measurement position, reflection is performed at each appropriate measurement position for each of the incident angles θA and θB. What is necessary is just to measure interference light. In this case, the measured optical path difference (for example, Ln + 3 (A) and Ln-2 (B) for each of the measurement positions at appropriate positions (for example, Xn + 3 (A) and Xn-2 (B)) for each of the incident angles θA and θB. ) And the like) can accurately determine the film thickness d and the refractive index n.

  However, the thin film 28 of the object 26 actually produced often has a different film thickness d or refractive index n depending on the measurement position (see FIG. 7B). On the other hand, in the two-way reflectance spectroscopy, the reflected light from each other is scattered. Therefore, the reflected interference light cannot be measured simultaneously from both of the two incident angles θA and θB at the same measurement position. It is necessary to actually measure the reflected interference light alternately at predetermined time intervals from each incident angle. For this reason, when the thin film 28 passes through the irradiation position 35 in the two-way reflectance spectroscopy, the positional relationship between the thin film 28 and the irradiation position 35 changes during the predetermined time interval. The reflected interference light cannot be actually measured from both of the two incident angles θA and θB with respect to the position. Therefore, it is necessary to estimate the film thickness d at each measurement position using the optical path difference L corresponding to the actually measured incident angle.

  FIG. 8 illustrates a simple method for obtaining the film thickness d and the refractive index n at each measurement position without obtaining the interpolation optical path difference L ′ when the thin film 28 passes through the irradiation position 35 in the two-way reflectance spectroscopy. It is a figure for doing. FIG. 9 is an explanatory diagram showing an example of the optical path difference 70 measured using the irradiation light with the incident angle θA at the measurement position Xn (B) in the example shown in FIG.

  As a simple method for estimating the film thickness d and the refractive index n at each measurement position using the optical path difference L corresponding to the actually measured incident angle, a method using the measured optical path difference L between adjacent measurement positions can be considered (FIG. (See broken line 8). In this simple method, the film thickness d and the refractive index n are obtained by substituting the measured optical path difference between adjacent measurement positions and the incident angles θA and θB into the equations stored in the storage unit 53.

  In this method, for example, measured optical path differences Ln−1 (A) and Ln (B) of Xn−1 (A) and Xn (B) and incident angles θA and θB are substituted into the formula stored in the storage unit 53. Thus, the film thickness d and the refractive index n are obtained. The obtained film thickness d and refractive index n are handled as calculated values at the measurement position Xn-1 or Xn.

  However, with this simple method, the calculated film thickness d and refractive index n include a large error. For example, consider a case where the film thickness d and the refractive index n calculated using the measured optical path differences Ln-1 (A) and Ln (B) of Xn-1 (A) and Xn (B) are those of Xn. In this case, the measured optical path difference Ln-1 (A) of Xn-1 (A) is nothing more than the value measured from the incident angle θA with Xn.

  However, when the film thickness d and the refractive index n at different measurement positions are different, the measured optical path difference L is naturally different (see Expression (2), FIG. 6, and FIG. 7B). For this reason, for example, the optical path difference 70 actually measured using the irradiation light with the incident angle θA at the measurement position Xn (B) by stopping the belt 36 is the adjacent measurement position Xn−1 (A) or Xn + 1 ( This is different from the actually measured optical path difference Ln-1 (A) or Ln + 1 (A) in A) (see FIG. 9). Therefore, in the simple method shown in FIG. 8, the calculated film thickness d and refractive index n inevitably contain large errors.

  Accordingly, the optical path difference interpolation unit 65 estimates the interpolation optical path when it is assumed that the irradiation light is irradiated at the other incident angle with respect to the measurement position irradiated with the irradiation light at one incident angle for each measurement position. The difference L ′ is obtained.

(3-2-1. First calculation method)
FIG. 10 is an explanatory diagram showing an example of how the interpolation optical path difference L ′ is obtained by the first calculation method according to the present embodiment. Hereinafter, an example in which the interpolation optical path difference L′ n (A) at the measurement position Xn (B) is obtained will be described.

  The calculation method of the first interpolation optical path difference L ′ is as follows. For each measurement position, the interpolation optical path difference L ′ is calculated using the measured optical path differences L at a plurality of other measurement positions of incident angles not actually measured at the measurement position. It is a method to seek. Specifically, the first interpolation optical path difference L ′ is calculated by changing the interpolation optical path difference L′ n (A) at the measurement position Xn (B) to a measurement position within a predetermined distance from the measurement position Xn (B). This is a method of obtaining using corresponding Ln-1 (A), Ln + 1 (A), and the like.

  In this method, when obtaining the interpolated optical path difference L′ n (A) at the measurement position Xn (B), for example, measurement positions at a plurality of positions before and after the measurement position Xn (B) and corresponding to the incident angle θA are measured. The distribution of the measured optical path difference L (A) of the position is used.

  FIG. 10 shows quadratic approximate functions of measured optical path differences Ln−3 (A), Ln−1 (A), Ln + 1 (A), and Ln + 3 (A) at two points before and after the measurement position Xn (B). An example of obtaining it is shown. The optical path difference interpolation unit 65 obtains the value of the quadratic approximate function at the measurement position Xn (B) as the interpolated optical path difference L′ n (A).

  Since the calculation method of the first interpolation optical path difference L ′ uses the distribution of the measured optical path difference L (A) in the vicinity of the measurement position Xn (B), the physical property change of the thin film 28 in the vicinity of the measurement position Xn (B) is determined. The reflected interpolation optical path difference L′ n (A) can be obtained. Therefore, according to the calculation method of the first interpolation optical path difference L ′, the film thickness d and the refractive index n at each measurement position can be obtained more accurately than in the simple method shown in FIG.

(3-2-2. Second calculation method)
FIG. 11 is an explanatory diagram showing an example of how the interpolation optical path difference L ′ is obtained by the second calculation method according to the present embodiment. FIG. 12 is an explanatory diagram showing another example of how the interpolation optical path difference L ′ is obtained by the second calculation method according to the present embodiment.

  The calculation method of the second interpolation optical path difference L ′ is a method for obtaining the interpolation optical path difference L ′ for each measurement position by using the measured optical path differences L at a plurality of other measurement positions at the incident angle actually measured at the measurement position. It is. Specifically, the second interpolation optical path difference L ′ is calculated by calculating the interpolation optical path difference L′ n (A) at the measurement position Xn (B) as a measurement position within a predetermined distance from the measurement position Xn (B) ( This is a method of obtaining using Ln−2 (B), Ln (B) Ln + 2 (B), etc. corresponding to measurement position Xn (B).

  In this method, when the interpolated optical path difference L′ n (A) at the measurement position Xn (B) is obtained, for example, the measurement positions are a plurality of measurement positions before and after the measurement position Xn (B) and correspond to the incident angle θB. The distribution of the measured optical path difference L (B) of the position is used.

  FIG. 11 shows a case where the measured optical path difference change rate between the measurement position Xn (B) and the measurement positions Xn−2 (B) and Xn + 2 (B) before and after the measurement position Xn (B) is obtained. An example is given. In this case, the optical path difference interpolation unit 65 obtains the inclination of the straight line 71 connecting the measured optical path difference Ln−2 (B) and Ln (B) and the inclination of the straight line 72 connecting Ln (B) and Ln + 2 (B). Next, the optical path difference interpolation unit 65 extracts one measurement position Xn−1 (A) and Xn + 1 (A) before and after the measurement position Xn (B) from the measurement positions corresponding to the incident angle θA. Then, the optical path difference interpolation unit 65 passes a value 73 at the measurement position Xn (B) of the straight line having the same inclination as the straight line 71 through the measurement position Xn-1 (A) and a straight line through the measurement position Xn + 1 (A). The average of the values 74 at the measurement position Xn (B) of the straight line having the same inclination as 72 is obtained as the interpolation optical path difference L′ n (A).

  FIG. 12 also shows a quadratic approximation function of the measured optical path differences Ln−2 (B), Ln (B), and Ln + 2 (B) one each before and after the measurement position Xn (B) and the measurement position Xn (B). An example is shown in the case of obtaining. In this case, the optical path difference interpolation unit 65 first obtains a quadratic approximation function of the actually measured optical path differences Ln−2 (B), Ln (B), and Ln + 2 (B) at the measurement position Xn (B). Next, this quadratic approximate function is translated toward the column of the actually measured optical path difference L (A) corresponding to the incident angle θA, and the position where the error is minimized in the least square sense is obtained. Then, the optical path difference interpolation unit 65 sets the value at the measurement position Xn (B) of the quadratic approximate function at the obtained position as the interpolation optical path difference L′ n (A).

  As shown in FIG. 11 and FIG. 12, the calculation method of the second interpolation optical path difference L ′ uses the distribution of the measured optical path difference L (B) in the vicinity of the measurement position Xn (B). ), The interpolated optical path difference L′ n (A) reflecting the physical property change of the thin film 28 can be obtained. For this reason, the film thickness d and the refractive index n at each measurement position can be obtained more accurately than the simple method shown in FIG. 8 by the second interpolation optical path difference L ′ calculation method. Furthermore, the second interpolation optical path difference L ′ can be calculated by using the measured optical path difference Ln (B) at the measurement position for obtaining the interpolation optical path difference L ′, and therefore, compared with the first interpolation optical path difference L ′. The interpolated optical path difference L′ n (A) that more accurately reflects the change in physical properties of the thin film 28 in the vicinity of the measurement position Xn (B) can be obtained.

(3-2-3. Calculation of film thickness and refractive index)
Next, a method for calculating the film thickness d and the refractive index n of the thin film 28 by the film thickness refractive index calculation unit 66 will be described.

If the refractive index of the atmosphere is 1, the expression (3) can be transformed into the following expression (5) using the incident angle θ1 based on the following expression (4) showing the relationship between the incident angle θ1 and the refraction angle θ2. .

  Therefore, it can be seen from equation (5) that if the optical path difference L at two incident angles is obtained, the film thickness d and the refractive index n can be obtained. This equation (5) is stored in the storage unit 53 in advance. Note that Expression (5) may be stored in a storage medium such as the ROM of the main control unit 54.

  The film thickness refractive index calculation unit 66 substitutes the actually measured incident angle and the actually measured optical path difference L and the unmeasured incident angle and the interpolated optical path difference L ′ into the equation (5) for each of the plurality of measurement positions. The film thickness d and the refractive index n of the thin film 28 at each measurement position are obtained. For example, for the measurement position Xn (B), the film thickness refractive index calculation unit 66 includes a set of the incident angle θB and the actually measured optical path difference Ln (B), and a set of the incident angle θA and the interpolated optical path difference L′ n (A). Is substituted into the equation (5), the film thickness d and the refractive index n of the thin film 28 at the measurement position Xn (B) can be obtained.

(3-3. Filling rate)
According to the film thickness refractive index calculation unit 66 according to the present embodiment, the refractive index n of the thin film 28 can be measured. Therefore, by comparing the refractive index n of the thin film 28 with the refractive index of the dielectric crystal constituting the thin film, the filling rate (apparent filling rate) of the dielectric thin film 28 constituting the thin film is obtained. Can be sought.

  For example, when the dielectric is titanium oxide, the content of titanium oxide in the titanium oxide thin film is a (%), and the apparent filling rate of the titanium oxide thin film is b (%) = 100−a (%). . Further, the refractive index of titanium oxide is N1, and the refractive index of another substance (for example, atmospheric gas such as air or resin) filling the space in the thin film is N2.

  Now, it is assumed that the refractive index Na of the titanium oxide thin film is proportional to the content ratio of titanium oxide in the titanium oxide thin film and other substances filling the space in the thin film. This assumption is valid when the titanium oxide is homogeneous. At this time, the refractive index Na of the titanium oxide thin film is given by the following equation (6).

式（６）を変形すると、次の式（７）が得られる。

When Expression (6) is transformed, the following Expression (7) is obtained.

  Therefore, if the refractive indexes N1 and N2 are known, the titanium oxide content a can be obtained by substituting the refractive index obtained by the film thickness refractive index calculating section 66 into the equation (7) as Na. . From this a (%), the apparent filling factor b (%) of the titanium oxide thin film = 100−a (%) can be obtained.

  The filling factor b changes according to the refractive index n. Moreover, it is known that the filling rate b changes according to production conditions. Therefore, the filling rate calculation unit 67 may give information on the filling rate b obtained for each measurement position to the manufacturing apparatus 15. In this case, the production apparatus 15 produces the thin film 28 having the target physical properties as the filling rate b approaches a predetermined value based on the information on the filling rate b of the thin film 28 received from the filling rate calculation unit 67. In addition, the production conditions can be corrected in real time.

(4. Operation)
Next, an example of operation | movement of the film thickness measuring apparatus 10 which concerns on this embodiment is demonstrated.

  FIG. 13 shows a procedure for accurately measuring the film thickness d of the thin film 28 whose refractive index n is unknown even when the thin film 28 is moved by the CPU of the main control unit 54 shown in FIG. It is a flowchart which shows an example. In FIG. 13, a symbol with a number added to S indicates each step of the flowchart.

  This procedure is started when Equation (5) is stored in the storage unit 53 and the object 26 is placed on the belt 36 and moves to the irradiation position 35 while moving at a constant speed.

  First, in step S1, the irradiation unit 11 irradiates the thin film 28 passing through the irradiation position 35 with irradiation light alternately at predetermined time intervals from the incident angles θA and θB. As a result, a series of measurement positions X1 (A), X2 (B),..., Xm on the thin film 28 are irradiated with irradiation light alternately from the incident angles θA and θB. In other words, each time the measurement position passes through the irradiation position 35, the irradiation unit 11 irradiates the irradiation light by alternately changing the incident angle to one of θA and θB. The reflected light of the irradiation light at each measurement position is given to the spectroscopic unit 13 via the light receiving unit 12.

  Next, in step S <b> 2, the spectroscopic unit 13 splits the reflected interference light at each measurement position in a predetermined wavelength band, and gives the wavelength distribution generation unit 63 information on the intensity of the reflected interference light at each wavelength. The wavelength distribution generation unit 63 generates a wavelength distribution for each measurement position Xn based on the intensity information of the reflected interference light at each wavelength generated by the spectroscopic unit 13 (see FIG. 5).

  Next, in step S <b> 3, the optical path difference calculation unit 64 obtains an actually measured optical path difference L based on the actually measured wavelength distribution for each measurement position.

  Next, in step S4, the optical path difference interpolation unit 65 predetermines an interpolated optical path difference L ′ from the measurement position when it is assumed that the irradiation light is irradiated at an incident angle that is not actually measured for each measurement position. Calculation is performed using measured optical path differences L at a plurality of measurement positions within the distance. At this time, the optical path difference interpolation unit 65 may use the calculation method of the first interpolation optical path difference L ′ shown in FIG. 10 or the calculation method of the second interpolation optical path difference L ′ shown in FIG. 11 or FIG. Or an average of values obtained by a plurality of calculation methods may be used as the interpolation optical path difference L ′.

  Next, in step S <b> 5, the film thickness refractive index calculation unit 66 acquires Expression (5) from the storage unit 53.

  Next, in step S6, the film thickness refractive index calculation unit 66 measures the set of the measured incident angle and the measured optical path difference L with respect to the equation (5) acquired from the storage unit 53 for each measurement position. A set of no incident angle and interpolation optical path difference L ′ is substituted.

  Next, in step S7, the film thickness refractive index calculation unit 66 calculates the film thickness d and the refractive index n of the thin film 28 for each measurement position by combining the two formulas obtained in step S6.

  According to the above procedure, even when the thin film 28 is moving, the film thickness d of the thin film 28 whose refractive index n is unknown can be accurately measured.

  The film thickness measuring apparatus 10 according to the present embodiment uses an interpolation optical path corresponding to an incident angle that is not actually measured by a calculation method of the first interpolation optical path difference L ′ or a calculation method of the second interpolation optical path difference L ′. The difference L ′ is calculated using the measured optical path differences L at a plurality of measurement positions within a predetermined distance from the measurement position. For this reason, even if the thin film 28 is moving, two accurate sets of the incident angle and the optical path difference at each measurement position can be obtained. Therefore, according to the film thickness measuring apparatus 10, even when the thin film 28 is moving, the film thickness d and the refractive index n of the thin film 28 whose refractive index n is unknown can be accurately measured.

  In addition, the film thickness measuring apparatus 10 according to the present embodiment can accurately determine the film thickness d and the refractive index n by irradiating light from one incident angle without irradiating light from two incident angles at each measurement position. Can be requested. For example, when the simple method shown in FIG. 8 is employed, the interval between measurement positions must be made as small as possible in order to minimize changes in physical properties at adjacent measurement positions. On the other hand, the film thickness measuring apparatus 10 according to the present embodiment can obtain an accurate interpolated optical path difference L ′ by predicting a physical property change in the vicinity of the measurement position for obtaining the interpolated optical path difference L ′ by the measured optical path difference L. . For this reason, according to the film thickness measuring apparatus 10 according to the present embodiment, the interval of the exposure start timing between the adjacent measurement positions can be widened. For this reason, even if the time required for processing at each measurement position (for example, exposure time, data transfer time, data processing time, etc.) is long and the interval between the exposure start timings is widened, it is easy. Accurate film thickness d and refractive index n can be measured.

  Moreover, according to the film thickness measuring apparatus 10 according to the present embodiment, the film thickness d and the refractive index n can be determined more accurately than the contact method. Since the contact method only measures the position of the surface of the thin film 28, it cannot cope with the deflection of the substrate 27 at all.

  In addition, the film thickness measuring apparatus 10 according to the present embodiment can obtain the filling rate b from the accurately obtained refractive index n. For this reason, the film thickness measuring apparatus 10 can provide the manufacturing apparatus 15 with information on the filling rate b obtained for each measurement position. In this case, the production apparatus 15 produces the thin film 28 having the target physical properties as the filling rate b approaches a predetermined value based on the information on the filling rate b of the thin film 28 received from the filling rate calculation unit 67. In addition, the production conditions can be corrected in real time.

  Therefore, when the manufacturing apparatus 15 is provided, the film thickness measuring apparatus 10 can determine the filling rate b of the thin film 28 from the accurately obtained refractive index n, and uses the information on the filling rate b to manufacture. The filling factor b of the object 26, that is, the refractive index n can be easily optimized. In addition, the film thickness measuring apparatus 10 does not need to include the manufacturing apparatus 15, and in this case, the filling rate calculation unit 67 may not include.

(5. Example)
Comparative Examples 1 and 2 and Examples 1 and 2 relating to the thin film 28 having the film thickness d = 16 μm and the refractive index n = 1.6 whose wavelength distribution is shown in FIG. 5 will be described below.

  Comparative Example 1 is an example in which reflected interference light is measured from two directions at each measurement position by stopping the thin film 28 at each measurement position. On the other hand, in Comparative Example 2 and Examples 1 and 2, the thin film 28 is moved, and the measurement position passing through the irradiation position 35 is alternately irradiated from one direction of the incident angle θA or θB at predetermined time intervals. This is an example in which reflected interference light is measured by irradiating light.

(5-1. Comparative Example 1)
14A is an explanatory diagram illustrating an example of the relationship between the measurement position and the optical path difference according to Comparative Example 1, and FIG. 14B is an explanatory diagram illustrating an example of the relationship between the measurement position and the film thickness according to Comparative Example 1. is there.

  When the thin film 28 is stopped at each measurement position as in the comparative example 1, it takes time for measurement, and it becomes difficult to use the placement unit 36a of the production apparatus 15 and the belt 36 of the conveyor 14 in a coupled manner.

(5-2. Comparative Example 2)
FIG. 15A is an explanatory diagram illustrating an example of the relationship between the measurement position and the optical path difference according to Comparative Example 2, and FIG. 15B is an explanatory diagram illustrating an example of the relationship between the measurement position and the film thickness according to Comparative Example 2. is there.

  Comparative example 2 is an example in which the simple method shown in FIG. 8 is used. That is, in Comparative Example 2, the film thickness d at each measurement position was obtained using the measured optical path difference L between adjacent measurement positions without obtaining the interpolation optical path difference L ′.

  As is apparent from a comparison between FIG. 14B and FIG. 15B, the simple method shown in FIG. 8 has a film thickness d distribution that is completely different from that in the case of stopping. For this reason, the film thickness d obtained by this simple method is considered to have low reliability.

(5-3. Example 1)
FIG. 16A is an explanatory diagram illustrating an example of the relationship between the measurement position and the optical path difference according to the first embodiment, and FIG. 16B is an explanatory diagram illustrating an example of the relationship between the measurement position and the film thickness according to the first embodiment. is there.

  The first embodiment is an example in the case of using the first interpolation optical path difference L ′ calculation method illustrated in FIG. 10. As is apparent from a comparison of FIGS. 14B, 15B, and 16B, the first interpolation optical path difference L ′ shown in FIG. The distribution of the film thickness d is close to that when it is stopped. For this reason, it can be said that the film thickness d obtained by the calculation method of the first interpolation optical path difference L ′ is higher in reliability than the film thickness d obtained by this simple method.

(5-4. Example 2)
FIG. 17A is an explanatory diagram illustrating an example of the relationship between the measurement position and the optical path difference according to the second embodiment, and FIG. 17B is an explanatory diagram illustrating an example of the relationship between the measurement position and the film thickness according to the second embodiment. is there.

  The second embodiment is an example in the case of using the second interpolation optical path difference L ′ calculation method illustrated in FIG. 11. As is apparent from comparison between FIGS. 14B, 15B, and 17B, the calculation method of the second interpolation optical path difference L ′ shown in FIG. The distribution of the film thickness d is close to that in the case of stopping. For this reason, it can be said that the film thickness d obtained by the calculation method of the second interpolation optical path difference L ′ is higher in reliability than the film thickness d obtained by this simple method.

  In addition, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 Film thickness measurement apparatus 11 Irradiation part 12 Light reception part 14 Conveyor 15 Production apparatus 21 1st irradiation unit 22 2nd irradiation unit 24, 25 Shutter 28 Thin film 35 Irradiation position 36 Belt (mounting part)
62 shutter control unit 64 optical path difference calculating unit 65 optical path difference interpolating unit 66 film thickness refractive index calculating unit 67 filling rate calculating unit b filling rate d film thickness n refractive index θA first incident angle θB second incident angle

Claims (11)

A film thickness measuring device that measures the film thickness of the thin film based on the wavelength distribution of the reflected interference light generated by the optical path difference between the front surface reflected light and the back surface reflected light of the thin film,
By irradiating irradiation light alternately at a predetermined time interval with respect to a predetermined irradiation position at different incident angles, it is different from each other for each of a plurality of measurement positions on the thin film passing through the predetermined irradiation position. An irradiating unit that irradiates the irradiation light alternately at an incident angle; and
The reflected interference light of the irradiation light at each of the plurality of measurement positions is alternately changed at different reflection angles corresponding to the different incident angles as each of the plurality of measurement positions passes through the predetermined irradiation position. A light receiving unit for receiving light;
For each of the plurality of measurement positions, an optical path difference calculation unit that obtains an optical path difference using a wavelength distribution of reflected interference light obtained at an incident angle at which the irradiation light is irradiated to each measurement position;
For each of the plurality of measurement positions, an optical path difference estimated when it is assumed that the irradiation light is irradiated at the other incident angle with respect to the measurement position irradiated with the irradiation light at one incident angle, An optical path difference interpolation unit that interpolates using the optical path difference obtained by the optical path difference calculation unit at a measurement position within a predetermined distance from the measurement position;
For each of the plurality of measurement positions, the optical path difference obtained by the one incident angle and the optical path difference calculation unit using an expression representing the optical path difference as a function of the incident angle, the film thickness, and the refractive index as variables. , And the other incident angle and the optical path difference determined by the optical path difference interpolation unit by substituting the optical path difference into the formula, the film thickness refractive index calculation unit for determining the film thickness and refractive index of the thin film at each measurement position;
A film thickness measuring device. The optical path difference interpolation unit
Of the measurement positions within a predetermined distance from the measurement position, according to a plurality of optical path differences obtained by the optical path difference calculation unit at a plurality of measurement positions corresponding to the other incident angle, the measurement position at the measurement position Estimating the optical path difference when the irradiation light is irradiated at the other incident angle,
The film thickness measuring apparatus according to claim 1. The optical path difference interpolation unit
Obtaining a second-order approximation function of the plurality of optical path differences obtained by the optical path difference calculation unit at a plurality of measurement positions corresponding to the other incident angle among the measurement positions within a predetermined distance from the measurement position, The optical path difference at the measurement position of the quadratic approximate function is the optical path difference when the irradiation light is irradiated at the other incident angle at the measurement position.
The film thickness measuring apparatus according to claim 2. The optical path difference interpolation unit
According to the optical path difference obtained by the optical path difference calculation unit at a plurality of measurement positions including the measurement position corresponding to the one incident angle among the measurement positions within a predetermined distance from the measurement position, Estimating the optical path difference when the irradiation light is irradiated at the other incident angle at the measurement position,
The film thickness measuring apparatus according to claim 1. The optical path difference interpolation unit
Obtaining the rate of change between the optical path difference at the measurement position corresponding to the one incident angle and the optical path difference at one measurement position before and after the measurement position among the measurement positions corresponding to the one incident angle, Of the measurement positions corresponding to the other incident angle, the optical path difference of each one measurement position before and after the measurement position and the rate of change obtained from the optical path difference corresponding to the one incident angle, Obtain the optical path difference when the irradiation light is irradiated at the other incident angle at the measurement position,
The film thickness measuring apparatus according to claim 4. The optical path difference interpolation unit
Obtaining a second-order approximation function of the plurality of optical path differences obtained by the optical path difference calculation unit at a plurality of measurement positions corresponding to the one incident angle among the measurement positions within a predetermined distance from the measurement position, Corresponding to the optical path difference obtained by the optical path difference calculating unit at a plurality of measurement positions corresponding to measurement positions within a predetermined distance from the measurement position and the one incident angle among the measurement positions corresponding to the other incident angle Using the quadratic approximation function obtained from the optical path difference to obtain an optical path difference when the irradiation light is irradiated at the other incident angle at the measurement position,
The film thickness measuring apparatus according to claim 4. The irradiation unit is
A first irradiation unit for irradiating the irradiation light at a first incident angle with respect to the predetermined irradiation position, and irradiating the irradiation light at a second incident angle different from the first incident angle. A second irradiation unit, a shutter provided on the optical path of the irradiation light,
Have
A shutter control unit that controls the shutter so that the irradiation light is alternately irradiated from the first irradiation unit and the second irradiation unit to the predetermined irradiation position;
Further equipped with,
The film thickness measuring device according to any one of claims 1 to 6. Using the refractive index obtained by the film thickness refractive index calculation unit, a filling rate calculation unit for obtaining a filling rate of the constituent material of the thin film at each measurement position of the thin film,
The film thickness measuring apparatus according to any one of claims 1 to 7, further comprising: A conveyor having a mounting portion for mounting the thin film, and moving the mounting portion at a constant speed so that the thin film passes through the predetermined irradiation position;
The film thickness measuring apparatus according to any one of claims 1 to 8, further comprising: An apparatus for producing the thin film;
Using the refractive index obtained by the film thickness refractive index calculation unit, a filling rate calculation unit for obtaining the filling rate of the constituent material of the thin film at each measurement position of the thin film;
A conveyor for placing the thin film, and moving the placement part at a constant speed so that the thin film passes through the predetermined irradiation position;
Further comprising
The conveyor is
Carrying the thin film produced by the production apparatus from the production apparatus to the predetermined irradiation position, passing the predetermined irradiation position,
The filling rate calculation unit
Giving the filling rate information to the manufacturing apparatus;
The manufacturing apparatus includes:
Changing the production conditions of the thin film so that the filling rate approaches a predetermined value;
The film thickness measuring device according to any one of claims 1 to 7. A film thickness measuring method for measuring the film thickness of the thin film based on the wavelength distribution of reflected interference light caused by the optical path difference between the front surface reflected light and the back surface reflected light of the thin film,
By irradiating irradiation light alternately at a predetermined time interval with respect to a predetermined irradiation position at different incident angles, it is different from each other for each of a plurality of measurement positions on the thin film passing through the predetermined irradiation position. Irradiating the irradiation light alternately at an incident angle; and
The reflected interference light of the irradiation light at each of the plurality of measurement positions is alternately changed at different reflection angles corresponding to the different incident angles as each of the plurality of measurement positions passes through the predetermined irradiation position. A step of receiving light;
For each of the plurality of measurement positions, obtaining an optical path difference using a wavelength distribution of the reflected interference light obtained at an incident angle at which the irradiation light is irradiated to each measurement position;
For each of the plurality of measurement positions, an optical path difference estimated when it is assumed that the irradiation light is irradiated at the other incident angle with respect to the measurement position irradiated with the irradiation light at one incident angle, Interpolating using the optical path difference obtained in the step of obtaining the optical path difference at a measurement position within a predetermined distance from the measurement position;
For each of the plurality of measurement positions, the optical path difference obtained in the step of obtaining the one incident angle and the optical path difference using an expression representing the optical path difference as a function of the incident angle, the film thickness, and the refractive index as variables. And calculating the film thickness and refractive index of the thin film at each measurement position by substituting the other incident angle and the optical path difference interpolated in the interpolating step into the equation,
A method for measuring a film thickness.

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