JPH04313007A - Film inspecting device - Google Patents

Abstract

PURPOSE:To realize high-accuracy measurement which is not affected by a change in material and disturbance by simultaneously utilizing the light absorbing property of a film in a visible light region and intra-film multi-reflection phenomenon in an infrared region and simultaneously measures the thickness of the film at the same point, and then, adopting the data having high coincidence after comparing the measurements with each other. CONSTITUTION:The component of the light of a light source 1 having a specific wavelength intensity set by a wavelength filter 3 is monitored with a detector 4 after part of the light is branched at a half mirror 2. The light transmitted through the filter 3 is branched at a half mirror 6 after passing through a sample 5 and only the component having the save wavelength as that the filter 3 has enters a photoreceptor element 8 after passing through a wavelength filter 7. The light transmitted through the mirror 6 forms images in the order of wavelength on a line sensor 12 after being scattered by means of a diffraction grating 11. The outputs of the detector 4 and element 8 are fed to a computing element 19 through a divider 15 and the film thickness of the sample 5 is calculated by using the absorption coefficient of the sample 5. The output of the sensor 12 is supplied to a computing element 22 by which the film thickness is identified by comparing the output with inter-peak wavelength-film thickness lookup data. A subtracter finds the difference between both film thicknesses and a discrimination circuit 24 compares the difference with a set reference value. When the difference is smaller than the reference value, the circuit 24 judges that the data are highly reliable and valid.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film detection device that uses light to detect the thickness and material of a film sheet material, coating material, etc. on-line.

0002

[Prior Art] When light is irradiated onto a light-transmitting film such as a film sheet material or coating material, the light is repeatedly reflected on the front and back surfaces of the film, and light with the same wavelength interferes with each other, so the light is not transmitted through the film. The wavelength distribution of light (or reflected light) intensity repeats its strength and weakness regularly with a certain period. This period changes depending on the thickness of the film. Furthermore, a light-transmitting film has light absorption characteristics specific to the material, and the intensity of light transmitted through the sheet material changes depending on the thickness of the film. Conventionally, film thickness has been measured by utilizing such multiple reflection of light within the film or absorption of light by the film.

For example, FIG. 7 is a block diagram of a conventional film thickness measuring device using light absorption, disclosed in Japanese Patent Laid-Open No. 56-44802. In the figure, 55 indicates a film sheet material to be measured. , 56 is a reference light source that generates infrared light;
57 is a detection head, 58 is an amplifier that amplifies the output from the detection head, and 59 is a deviation indicator that indicates the deviation of the amplifier output. The operation is shown below. A reference light source 56 irradiates the film sheet 55 with infrared light matching the absorption wavelength of light possessed by the target film sheet, and the detection head 57 receives the transmitted light. The signal photoelectrically converted by the detection head 57 is amplified by an amplifier 58 and input to a deviation indicator 59. The deviation indicator measures film thickness by detecting changes in signal output corresponding to changes in transmitted light intensity due to film thickness.

FIG. 8 is a block diagram of a conventional film thickness measuring device using optical interference, which is disclosed in Japanese Patent Application Laid-Open No. 115905/1982. In the figure, 60 is a light source, and 61 is a light source 60. Lens system for converting light emitted from into parallel light, 62
is the film surface to be measured, 63 and 64 are lens systems for spreading the beam, 65 is a prism for spectroscopy,
66 is a lens for forming an image, 67 is a light receiving element, 68 is a half mirror, 69 is a prism, 70 is a lens for forming an image, 71 is a light receiving element, 72 is an irradiation part on the sample surface, 73
is a reflective member. The operation will be explained next. The light emitted from the light source 60 is converted into parallel light by the lens system 61, reaches the irradiation section 72, and is reflected by the film 62. The reflected light is turned into parallel light beams by lens systems 63 and 64, then is separated by a prism 65, focused by a lens 66 at different positions depending on the wavelength, and a spectrum is projected onto a light receiving element 67. The spectrum is detected by the output signal from the light receiving element, and the minimum of the obtained spectrum,
Find the wavelength that shows the maximum and calculate the thickness of the film.

FIG. 9 is a block diagram of a conventional film thickness measuring device using light absorption and interference disclosed in Japanese Unexamined Patent Publication No. 56-132507. In the figure, 74 indicates a sample, 75
is a rotating table for rotating the prism 65. Next, the operation will be explained. The light emitted from the light source 60 passes through the lens 61
After the light becomes parallel, the sample 74 is irradiated with it. The irradiated light passes through the sample 74, is widened by the collimating lens systems 63 and 64, and enters the prism 65. Here, the angle of incidence of light on the prism is changed by rotating the rotary table 75 so that the light receiving element 67 can detect spectrum information having a wavelength range corresponding to the material and thickness range of the sample. At this time, the wavelength range of the light incident on the light receiving element 67 is determined depending on whether light absorption or interference is used as the detection principle. The output signal from the light receiving element 67 is obtained by calculating the absorbance of the transmitted light when using light absorption, or by calculating the period from the change in the intensity of the transmitted light with respect to the wavelength when using interference. , find the film thickness.

[0006]

As described above, conventional film thickness measurements have been carried out using either light absorption or light interference. However, in the method using light absorption characteristics, the measurement of film thickness is greatly affected by changes in the absorption coefficient of the material of the film and changes in received light intensity due to ambient light. Furthermore, methods that utilize light interference are greatly affected by changes in the refractive index of the film material. on the other hand,
During the production process of sheet materials, changes in the absorption coefficient may occur due to changes in the mixing ratio of regular materials, changes in the absorption coefficient due to the mixing of different materials or colored substances, or changes in the refractive index due to changes in the composition of the material. In response to such changes in material properties due to unforeseen causes, conventional measurements using only one method cannot detect changes in material properties, resulting in measurement errors, which reduces the reliability of measurement data. There was a point. Furthermore, the material of the membrane flowing in the production process is generally not limited to one type, and may be produced using a mixture of multiple types of materials. Therefore, when applying a measuring device to an actual production line, it is necessary to deal with changes in material quality. In this case, conventionally corrections were made externally on a lot-by-lot basis. In this way, when externally teaching changes in measurement data caused by different materials, it is necessary to input correction data each time a membrane material of a different material flows, which requires complicated work. Since then, automation has become a major problem.

The present invention aims to solve these problems, and even when disturbances occur such as changes in the material of the film or changes in received light intensity due to ambient light, changes in the material can be detected and measurement accuracy can always be maintained. The object of the present invention is to provide a membrane inspection device that can obtain high-quality data.

[0008]

[Means for Solving the Problems] A film inspection device according to the present invention includes a light source having a continuous emission spectrum from the ultraviolet region to the infrared region, and a part of the light emitted from this light source is branched to detect absorption phenomena. a first optical system that monitors the light intensity of a specific wavelength in the first wavelength range that is generated; an irradiation optical system that irradiates the sample with light from the light source; a second optical system that detects light spectrum distribution information; a third optical system that branches part of the transmitted light or reflected light and detects the intensity of light having the same specific wavelength as that of the first optical system; a first calculation means for calculating the thickness of the sample based on the intensity ratio of the light reception intensity of the optical system and the light reception intensity of the third optical system and a predetermined absorption coefficient of the sample; a second calculation means for calculating the thickness of the sample based on the output signal from the optical system; The apparatus is equipped with a determination means for comparing the measured value of the sample thickness and determining the validity of the measured value based on the degree of coincidence between the two measured values.

The second invention also provides a light source having a continuous emission spectrum from the ultraviolet region to the infrared region, and a plurality of light sources that branch part of the light emitted from this light source and monitor the light intensity at a plurality of specific wavelengths. a first optical system comprising a detection unit; an irradiation optical system for irradiating the sample with light from the light source; a second optical system for detecting intensity;
The transmittance expressed by the ratio of the received light intensity at the same wavelength of the first optical system and the second optical system is determined, and from the relative ratio of this transmittance between each wavelength, the distance between each wavelength determined in advance for each material is determined. absorption coefficient identification means for identifying the material of the sample and determining the absorption coefficient at a specific wavelength of the identified sample based on a table storing the transmittance ratio of the sample; The apparatus is equipped with calculation means for calculating the thickness of the sample from the value of the absorption coefficient.

The third invention also provides a light source having a continuous emission spectrum from the ultraviolet region to the infrared region; a first optical system consisting of a detection unit, an irradiation optical system that irradiates the sample with light from the light source, and a second optical system that detects light spectrum distribution information in the infrared region of transmitted light or reflected light from the sample. a third optical system that branches part of the transmitted light or reflected light from the sample and detects the intensity of light having the same plurality of specific wavelengths as the first optical system;
a first calculation means for calculating the thickness of the sample from the light spectral distribution information obtained by the second optical system; A second calculation means for calculating the transmittance of the sample at a certain wavelength, from the film thickness value obtained by the first calculation means and the transmittance at each wavelength calculated by the second calculation means, a plurality of specific wavelengths are calculated. a third calculating means for determining the absorption coefficient in the film; and a film component determining means for comparing the wavelength distribution of the obtained absorption coefficient with the wavelength distribution of the absorption coefficient determined in advance to determine whether the film is a predetermined film component. It is equipped with the following.

Furthermore, a fourth invention provides a light source having a continuous emission spectrum from the ultraviolet region to the infrared region; a first optical system comprising a detection unit; an irradiation optical system that irradiates the sample with light from the light source;
A second optical system that detects optical spectrum distribution information in the infrared region of the transmitted light or reflected light from the sample, which branches part of the transmitted light or reflected light from the sample, and is the same as the first optical system. A third optical system detects the intensity of light at a plurality of specific wavelengths, and the transmittance of the sample at each wavelength is determined from the ratio of the received light intensity at the same wavelength of the first optical system and the third optical system. A material determination means for identifying the material of the sample based on a table storing the transmittance ratio between each wavelength determined in advance for each material from the relative ratio of transmittance between each wavelength; A refractive index identifying means for identifying the refractive index of the sample from the identification results, a transmittance obtained at a specific wavelength of the output signals from the first optical system and the third optical system, and a material determining means identified by the material determining means. A first calculation means for calculating the thickness of the sample based on the absorption coefficient of the sample, and a second calculation means for calculating the thickness of the sample from the output of the refractive index identification means and the output signal from the second optical system. means, and a first calculation means and a second calculation means.
The apparatus is equipped with a determining means for comparing the measured values of the thickness of the sample obtained by the calculating means and determining the validity of the measured value based on the degree of coincidence between the two measured values.

0012

[Operation] Generally, the intensity of light transmitted through a film made of a polymeric material exhibits a wavelength distribution as shown in FIG. That is, in the visible region, the light absorption rate of the film changes greatly depending on the wavelength, and as the wavelength becomes shorter, the absorption rate increases, and light no longer passes near the boundary with the ultraviolet region. In this way, the phenomenon of light absorption by the film appears prominently in the visible region. The intensity of transmitted light at a specific wavelength changes depending on the thickness of the film. On the other hand, in the infrared region, since the transmittance is high and almost constant, multiple reflections occur within the film, and when the repeatedly reflected light passes through the film, it interferes with each wavelength. As a result, the intensity of the transmitted light becomes stronger or weaker depending on the wavelength, and the intensity of the transmitted light periodically repeats its strength and weakness with respect to the wavelength. This period changes depending on the thickness of the film.

The present invention focuses on the fact that such a light absorption phenomenon and an interference phenomenon due to multiple reflection occur simultaneously in the visible region and the infrared region, respectively. That is,
A sample is irradiated with white light having components from the visible region to the infrared region, the transmitted light from the sample is separated into the visible region and the infrared region, and the film is determined based on the detection result of the transmitted light intensity of a specific wavelength in the visible region. In addition to calculating the thickness, the film thickness is also calculated from the detection results of the period of the wavelength distribution of transmitted light intensity in the infrared region, the two obtained film thickness values are compared, and only the data with a high degree of agreement is valid. This increases the reliability of the data. In other words, when a disturbance occurs such as a change in the material of the film or a change in the received light intensity due to disturbance light, the two measured values will not match and will not be selected as data, and the measurement accuracy will always be limited to only the part of the specified material. High data is selected.

Further, the wavelength distribution of the absorption coefficient in the visible region varies depending on the material of the film, as shown in FIG. 4, for example. The second invention focuses on changes in the wavelength distribution of the absorption coefficient depending on the material of the sample, and measures the transmittance at multiple wavelengths in the visible region and calculates the relative transmittance between the obtained wavelengths. Based on the change, the material of the target film is identified from among the multiple films entered in advance, and the absorption coefficient of the film is corrected based on the identification results, thereby correcting the transmitted light intensity obtained in the measurement. It is possible to improve the accuracy of the measurement result of the film thickness calculated from the absorption coefficient obtained.

The third invention simultaneously utilizes the phenomenon that the wavelength distribution of transmittance in the visible region changes depending on the material of the film and the interference phenomenon caused by multiple reflection within the film in the infrared region. In other words, the sample is irradiated with white light, the transmitted light is separated into the visible region and the infrared region, and the results of measuring the transmitted light intensity of multiple wavelengths in the visible region and the wavelength distribution of the transmitted light intensity in the infrared region are obtained. From the film thickness value calculated from the period,
The absorption coefficients at multiple wavelengths are determined, and the material of the target film is identified from the wavelength distribution of the absorption coefficients of the multiple films input in advance based on the measurement results of the absorption coefficients between the respective wavelengths.

The fourth invention also utilizes the light absorption phenomenon in the visible region and the interference phenomenon caused by multiple reflection in the infrared region, and separates the transmitted light into the visible region and the infrared region, and in the visible region, it separates the transmitted light into the visible region and the infrared region. By identifying the material of the film from the measurement results of the transmitted light intensity and correcting the absorption coefficient of the film based on the identification results, we can improve the accuracy of the film measurement values obtained from changes in the transmitted light intensity. The refractive index value of the film is corrected based on the film identification results, and the film thickness is calculated with high accuracy from the wavelength distribution of transmitted light intensity obtained by measurement and the corrected refractive index. The reliability of the data is further increased by comparing the two obtained film thickness values and selecting only the data with a high degree of agreement.

[0017]

[Example] Example 1. Next, one embodiment of the present invention will be described. In FIG. 1, 1 is a continuous wavelength light source having wavelengths from ultraviolet light to infrared light, 2 is a half mirror for branching the light emitted from light source 1, and 3 is a wavelength for selecting a specific wavelength from the light source. A filter, 4 is a detector for monitoring the oscillation intensity from the light source 1, 5 is a sample, 6 is a half mirror for branching the light transmitted through the sample 5, 7 is for selecting a specific wavelength from the transmitted light wavelength filter,
8 is a light receiving element, 9 is a condensing lens for transmitted light, 10 is a slit, 11 is a diffraction grating for wavelength separation, 12 is a line sensor for receiving light, 13 and 14 are amplifiers that amplify the output from the detector, 15 is a divider that takes the ratio between the transmitted light intensity and the monitor intensity, 16 is a log amplifier that takes the logarithm of the output value, 17 is an A/D circuit that converts the output signal from the log amplifier into a digital signal, and 18 is a A preset circuit inputs the previously measured absorption coefficient of the film as a digital signal; 19 is a calculator that calculates a film thickness value based on the output signal from the A/D circuit 17 and a value set by the preset circuit 18; and 20 is a calculation unit from the line sensor 12. 21 is an A/D circuit that converts the output signal of the digital signal into a digital signal; 21 is an arithmetic unit that calculates the peak-to-peak wavelength of the spectrum from the spectral information converted to the digital signal;
2 is an arithmetic unit that calculates the film thickness by comparing the obtained peak-to-peak wavelength with data in a look-up table of peak-to-peak wavelength-film thickness values input in advance; Subtractor for calculating the difference in film thickness values, 2
4 is a data determination circuit that determines the validity of the data based on whether the absolute value of the output from the subtracter 23 is within a set range; 25 is only the film thickness data obtained by measurement that is determined to be valid; This figure shows a data selection circuit that selects .

Next, the operation will be explained. A portion of the light emitted from the light source 1 is split by a half mirror 2, and a wavelength filter 3 monitors only the intensity of a preset specific wavelength using a detector 4. On the other hand, the light that has passed through the half mirror 3 passes through the sample 5 and is split by the half mirror 6. Of the branched lights, only the light having the same wavelength as the wavelength filter 3 is selected by the wavelength filter 7 and is received by the light receiving element 8 . On the other hand, the light transmitted through the half mirror 6 is focused onto a slit 10 by a condenser lens 9, and is incident on a diffraction grating 11. The incident light is dispersed by the diffraction grating, and images are formed on the line sensor 12 installed at the focal plane of the diffraction grating in the order of the wavelength of the light. The output signals from the detector 4 and the light receiving element 8 are amplified by amplifiers 13 and 14, respectively. At this time, the output from the light receiving element 8 is Lambert-
It changes depending on the film thickness according to Beer's law.

[0019]

[Math 1]

The outputs from the amplifiers 13 and 14 are input to a divider 15, where Io/Ii is calculated, and exp
A signal proportional to (-α(λ)d) is output. The log amplifier 16 performs a logarithmic operation on the output from the divider 15, and calculates −α
(λ) Outputs a signal proportional to d. After the output from the log amplifier is converted into a digital signal by the A/D circuit 17, the film thickness d is calculated by the arithmetic unit 19 using the absorption coefficient α inputted in advance. On the other hand, line sensor 1
The output signal from A/D circuit 20 is the spectral information of the transmitted light as a time series signal.
After the signal is converted into a digital signal, it is input to the arithmetic unit 21. The arithmetic unit 21 detects maximum and minimum peak wavelengths of data from changes in the input signal, and calculates the wavelength between each peak. The arithmetic unit 22 compares the obtained peak-to-peak wavelength with data in a look-up table between peak-to-peak wavelength and film thickness determined in advance to identify the film thickness. The film thickness values calculated from the intensity of transmitted light in the visible region and the spectrum in the infrared region are each input to a subtracter 23, and the difference between the two measured values is determined. The difference between the measured values obtained here is input to the judgment circuit 24,
The absolute value of the difference is compared with a preset reference value. In the determination circuit 24, if the difference between the film thickness values obtained by both formulas is larger than the reference value, the obtained data is judged to be unreliable and invalid, and if the difference between the film thickness values is smaller than the reference value, We judge the data to be reliable and valid. The selection circuit 25 outputs only data determined to be valid.

Example 2. Next, the second invention will be explained using figures. In Figure 2, 1 is a light source, 2, 2-1
, 2-2 is a half mirror for splitting light; 3, 3-1, and 3-2 are wavelength filters for selecting specific wavelengths λ0, λ1, and λ2; 4, 4-1, and 4-2 are wavelength filters for selecting specific wavelengths λ0, λ1, and λ2. a detector that receives the light transmitted through the wavelength filter; 5 is a sample; 6;
6-1 and 6-2 are half mirrors for splitting the light transmitted through the sample, and 7, 7-1 and 7-2 are the wavelength λ of the transmitted light.
wavelength filters that select 0, λ1, and λ2, respectively;
8, 8-1, 8-2 are photodetectors, 15, 15-1, 15
-2 is a divider that calculates the ratio of monitor intensity and transmitted light intensity; 1
6, 16-1, 16-2 are log amplifiers that take the logarithm of the output of the divider, 26-1, 26-2 are dividers that take the ratio of the outputs from the log amplifiers, and 27-1, 27-2 are A /D converters, 28-1 and 28-2 are look-up tables that summarize the ratio of film transmittance between two wavelengths as data for each material; 29-1 and 29-2 are subtractors; 30- 1, 30-2 is a determination circuit that determines the magnitude of the operation result of the subtracter; 3
1 is a coincidence judgment circuit that compares the results of both judgment circuits 30-1 and 30-2, 32 is a look-up table that summarizes the transmittance of the film at wavelength λ for each material, 33 is a control circuit, and 34 is a The divider 54 is a latch. Also, Figure 3
indicates the wavelength distribution of transmittance expressed by the ratio of the transmitted light intensity of the film to the monitor intensity, 35 is the distribution curve, A, B,
C indicates the intensity ratio between the transmitted light and the monitor light at the respective wavelengths λ0, λ1, and λ2, that is, the transmittance value. Also,
Figure 4 shows the wavelength distribution of the absorption coefficient α of the film, 36,
37 and 38 are absorption coefficient wavelength distribution curves for film types m1, m2, and m3, respectively, and D, E, and F are wavelengths λ of m1.
0, λ1, λ2, G, H, I are the absorption coefficient values at wavelengths λ0, λ1, λ2 of m2, J
, K, and L indicate the absorption coefficient values of m3 at wavelengths λ0, λ1, and λ2.

Next, the operation will be explained. Light emitted from a light source 1 is split by a half mirror 2. One of the branched lights is split into three by half mirrors 2-1 and 2-2. These three lights are filtered by wavelength selection filters 3, 3-1, and 3-2, λ0, λ1, and
Only light of wavelength λ2 is selected. The intensity of light transmitted through the film attenuates according to the Lambert-Beer law shown in Equation 1 above. At this time, since the absorption coefficient α changes depending on the wavelength, the light transmittance Io/Ii is calculated by curve 3.
It shows the changes shown in 5. Further, the wavelength distribution of the absorption coefficient α differs depending on the material forming the film, and shows changes such as curves 36, 37, and 38 in FIG. 4, for example. The wavelengths selected by the wavelength selection filters 3, 3-1, and 3-2 are wavelengths that exhibit the characteristics of the curve 35, for example, λ.
0, λ1, λ2. wavelength selection filter 3,
The light transmitted through 3-1 and 3-2 is detected by photodetectors 4 and 4, respectively.
-1 and 4-2 are received and detected as monitor intensity. The light transmitted through the half mirror 2 is irradiated onto the sample 5, and the transmitted light is split into three by the half mirrors 6 and 6-1. Similar to the monitor light, the three branched lights are filtered by wavelength selection filters 7, 7-1, and 7-2, respectively.
Only the light of wavelengths 0, λ1, and λ2 is detected by the photodetector 8.
, 8-1 and 8-2, the light is received and converted into an electrical signal. Dividers 15, 15-1, and 15-2 each calculate the ratio between the monitor intensity and the transmitted light intensity, and calculate the ratio of each wavelength λ0, λ1,
Transmittance Io/Ii at λ2 is calculated. The calculated results are input to log amplifiers 16, 16-1, and 16-2, respectively, and a value proportional to -α(λi)·d is output as the calculated result. Among these, the output signals from the log amplifiers 16 and 16-1 are input to the divider 26-1, and α(λ1
)/α(λ0) is output. The output signals from the log amplifiers 16 and 16-2 are input to the other divider, and α(λ2)/α(λ0) is calculated. In addition to this, the output signal from the log amplifier 16 is
The signal is input to the D converter 17 and converted into a digital signal. Further, the results calculated by the dividers 26-1 and 26-2 are input to A/D converters 27-1 and 27-2, respectively, and converted into digital signals. The absorption coefficient α (λi) at each wavelength λ0, λ1, λ2 is determined by measurement for a plurality of film materials assumed in advance, and the ratio of the coefficient values at wavelengths λ0, λ1 is stored in the lookup table of 28-1. α(λ1
)/α(λ0), and the lookup table of 28-2 contains the ratio of coefficient values of wavelengths λ0 and λ2 α(λ2)/α(
λ0) is input in correspondence with the type of membrane material. In the subtracter 29-1, the control circuit 3
In synchronization with the clock signal from 3, the absorption coefficient ratio α(λ1)/α(λ0) at wavelengths λ0 and λ1 is expressed as follows:
The difference between the measured value and the value in the lookup table determined in advance is calculated. Similarly, in the subtracter 29-2, the wavelength λ0,
Regarding the ratio α(λ2)/α(λ0) of the coefficient values of λ2, the difference between the measured value and the value in the lookup table determined in advance is taken. At this time, the lookup table 32
synchronizes with the clock signal of the control circuit 33 and outputs the absorption coefficient α (λ0) of the film at λ0 output from the look-up tables 28-1 and 28-2. On the other hand, the output signals from the subtracters 29-1 and 29-2 are input to judgment circuits 30-1 and 30-2, respectively, and are used to determine whether the absolute value of the subtraction result is larger or smaller than a preset value. Determine the relationship. In the matching degree determination circuit 31,
If the judgment results in both judgment circuits are both small, that is, the ratio of absorption coefficients obtained by measurement α(λ1)/α
(λ0) and α(λ2)/α(λ0) at two wavelengths both agree well with the values in the lookup table, the material of the film to be measured and the value of the film output from the lookup table. It is determined that the material matches. The latch 54 has an absorption coefficient α when the membrane materials match.
(λ0) is output and held. The divider 34 is an A/D
Based on the output signal α(λ0)·d from the converter 17 and the output signal from the latch 54, which is the true absorption coefficient value, division is performed to determine the film thickness d.

Example 3. Next, the third invention will be explained. In Fig. 5, 1 is a light source, 2, 2-1, 2-2 are half mirrors for splitting light, and 3, 3-1, 3-2 are for selecting specific wavelengths λ0, λ1, λ2. wavelength filter; 4, 4-1, and 4-2 are detectors that receive the light that has passed through the wavelength filter; 5 is the sample; and 6, 6-1, and 6-2 are for branching the light that has passed through the sample. -fmirror,
7, 7-1, 7-2 are the wavelengths λ0, λ1, λ of the transmitted light
wavelength filters for selecting 2, 8, 8-1, respectively;
8-2 is a photodetector; 15, 15-1, and 15-2 are dividers that take the ratio of the monitor intensity and the transmitted light intensity; and 16, 16-1, and 16-2 take the logarithm of the output of the divider. log amp,
27-1, 27-2, 27-3 are A/D converters, 28 is a look-up table that summarizes the absorption coefficient of the film at each wavelength as data for each film material, 39-1, 39-2
, 39-3 is a division calculator, 40-1, 40-2, 40-3
41 is a subtracter, 41 is an adder, 42 is a determination circuit that compares the result of addition with a predetermined set value, 43 is a material output circuit that outputs the material of the membrane identified by the result of the determination circuit, 33 is a control circuit, 9 is a lens for condensing transmitted light, 11 is a diffraction grating for wavelength separation, 12 is a line sensor for receiving light,
13 and 14 are amplifiers that amplify the output from the detector; 20
21 is an A/D conversion circuit that converts the output signal from the line sensor 12 into a digital signal, 21 is an arithmetic unit that calculates the peak-to-peak wavelength of the spectrum from the spectrum information converted to the digital signal, and 22 is the calculated peak-to-peak wavelength. This is an arithmetic unit that calculates the film thickness by comparing the wavelength with data in a lookup table of peak-to-peak wavelength-film thickness values input in advance.

Next, the operation will be explained. Light emitted from a light source 1 is split by a half mirror 2. One of the branched lights is split into three by half mirrors 2-1 and 2-2. These three lights are filtered by wavelength selection filters 3, 3-1, and 3-2 to λ0, λ1, and λ, respectively.
Only 2 wavelengths of light are selected. The intensity of light transmitted through the film attenuates according to the Lambert-Beer law shown in Equation 1 above. At this time, since the absorption coefficient α changes depending on the wavelength, the light transmittance Io/Ii shows a change as shown by the curve 35 in FIG. Further, the wavelength distribution of the absorption coefficient α differs depending on the material constituting the film, and shows changes such as curves 36, 37, and 38 in FIG. 4, for example. The wavelengths selected by the wavelength selection filters 3, 3-1, and 3-2 are selected such that the characteristics of the curve 35 appear prominently, for example, λ0, λ1, and λ2. The light transmitted through the wavelength selection filters 3, 3-1, and 3-2 is received by photodetectors 4, 4-1, and 4-2, respectively, and detected as monitor intensity. The light transmitted through half mirror 2 is sample 5.
The transmitted light is split into three by half mirrors 6 and 6-1. Similar to the monitor light, the three branched lights pass through wavelength selection filters 7, 7-1, and 7-1, respectively.
7-2, only the light having wavelengths λ0, λ1, and λ2 is received by photodetectors 8, 8-1, and 8-2, respectively, and converted into electrical signals. Divider 15, 15-1, 15-2
calculates the transmittance Io/Ii at each wavelength λ0, λ1, λ2 by taking the ratio of the monitor intensity and the transmitted light intensity. The calculated results are sent to log amplifiers 16 and 16, respectively.
-1, 16-2 and as the calculation result, -α(λi
)・Outputs a value proportional to d. On the other hand, the light transmitted through the half mirror 6 is incident on the diffraction grating 11 by the condensing lens 9. The incident light is dispersed by the diffraction grating, and images are formed on the line sensor 12 installed at the focal plane of the diffraction grating in the order of the wavelengths of the light. The output signal from the line sensor 12 is the spectral information of the transmitted light as a time series signal, and is sent to the A/D conversion circuit 20.
After the signal is converted into a digital signal, it is input to the arithmetic unit 21. The arithmetic unit 21 detects maximum and minimum peak wavelengths of data from changes in the intensity of the input signal, and calculates the wavelength between each peak. The arithmetic unit 22 compares the obtained peak-to-peak wavelength with data in a look-up table that correlates the peak-to-peak wavelength and film thickness obtained in advance to determine the film thickness. Log amplifier 16, 16-1, 16-2
The output values are input to A/D converters 27-1, 27-2, and 27-3, respectively, and converted into digital signals. Dividers 39-1, 39-2, and 39-3 are A/D converters 2
Division is performed between the output values of 7-1, 27-2, and 27-3 and the film thickness value d, which is the output value of the arithmetic unit 22, and the absorption coefficient α (λi ) is output. The absorption coefficient α (λi) at each wavelength λ0, λ1, λ2 is determined by measurement for a plurality of film materials assumed in advance, and the wavelengths λ0, λ are entered in 28 lookup tables.
The absorption coefficients of 1 and λ2 are input in correspondence with the material of the film. The subtracters 40-1, 40-2, and 40-3 calculate the absorption coefficients at wavelengths λ0, λ1, and λ2.
The difference between the measured value and the value in the lookup table determined in advance is calculated. At this time, data in the lookup table is output in synchronization with the clock from the control circuit 33. The output signals from the subtracters 40-1, 40-2, and 40-3 are input to an adder 41, respectively, and the absolute values of the subtraction results are added. In the determination circuit 42, if the calculation result in the adder is smaller than a preset value, the absorption coefficient α
It is determined that (λo), α(λ1), and α(λ2) closely match the values in the lookup table at the three wavelengths, and a signal is output. In the material output circuit 43,
Based on the output result from the determination circuit 42, the material of the film determined to match is output.

Example 4. Next, the fourth invention will be explained. In FIG. 6, 1 is a light source, 2, 2-1, 2-2 are half mirrors for splitting light, and 3, 3-1, 3-2 are for selecting specific wavelengths λ0, λ1, λ2. wavelength filter; 4, 4-1, and 4-2 are detectors that receive the light that has passed through the wavelength filter; 5 is the sample; and 6, 6-1, and 6-2 are for branching the light that has passed through the sample. -fmirror,
7, 7-1, 7-2 are the wavelengths λ0, λ1, λ of the transmitted light
wavelength filters for selecting 2, 8, 8-1, respectively;
8-2 is a photodetector; 15, 15-1, and 15-2 are dividers that take the ratio of the monitor intensity and the transmitted light intensity; and 16, 16-1, and 16-2 take the logarithm of the output of the divider. log amp,
26-1 and 26-2 are dividers that take the ratio of outputs from log amplifiers, 27-1 and 27-2 are A/D converters, and 28-1
, 28-2 is a look-up table that summarizes the ratio of film transmittance between two wavelengths as data for each film material, 29-1
, 29-2 is a subtracter, 30-1 and 30-2 are determination circuits that determine the magnitude of the operation result of the subtracter, and 31 is 30-1.
, 30-2 is a coincidence determination circuit that compares the results of both determination circuits, 32 is a look-up table that summarizes the absorption coefficient of the film at wavelength λ0 for each material, and 33 is a control circuit. 9 is a condensing lens for transmitted light, 11 is a diffraction grating for wavelength separation, 12 is a line sensor for receiving light, 13 and 14 are amplifiers that amplify the output from the detector, and 20 is an output signal from the line sensor 12. 21 is an arithmetic unit for determining the peak-to-peak wavelength of the spectrum from the spectrum information converted into the digital signal; 22 is the peak-to-peak wavelength inputted in advance from the determined peak-to-peak wavelength; This is an arithmetic unit that calculates the film thickness by comparing it with the data in the wavelength-thickness lookup table. 22-1 is a look-up table into which refractive indexes are collectively input for each film material; 23 is a subtracter that calculates the difference between the two film thickness values obtained by the calculators 19 and 22; and 24 is a subtracter 23. 25 is a data selection circuit that determines the validity of data based on whether the absolute value of the output is within a set range; and 25 is a data selection circuit that selects only those determined to be valid from among the film thickness data obtained by measurement. Shows the circuit.

Next, the operation will be explained. Light emitted from a light source 1 is split by a half mirror 2. One of the branched lights is split into three by half mirrors 2-1 and 2-2. These three lights are filtered by wavelength selection filters 3, 3-1, and 3-2 to λ0, λ1, and λ, respectively.
Only 2 wavelengths of light are selected. The intensity of light transmitted through the film attenuates according to the Lambert-Beer law shown in Equation 1 above. At this time, since the absorption coefficient α changes depending on the wavelength, the light transmittance Io/Ii shows a change as shown by the curve 35 in FIG. Further, the wavelength distribution of the absorption coefficient α differs depending on the material constituting the film, and shows changes such as curves 36, 37, and 38 in FIG. 4, for example. The wavelengths selected by the wavelength selection filters 3, 3-1, and 3-2 are selected such that the characteristics of the curve 35 appear prominently, for example, λ0, λ1, and λ2. The light transmitted through the wavelength selection filters 3, 3-1, and 3-2 is received by photodetectors 4, 4-1, and 4-2, respectively, and detected as monitor intensity. The light transmitted through half mirror 2 is sample 5.
The transmitted light is split into three by half mirrors 6 and 6-1. Similar to the monitor light, the three branched lights pass through wavelength selection filters 7, 7-1, and 7-1, respectively.
7-2, only the light having wavelengths λ0, λ1, and λ2 is received by photodetectors 8, 8-1, and 8-2, respectively, and converted into electrical signals. Divider 15, 15-1, 15-2
calculates the transmittance Io/Ii at each wavelength λ0, λ1, λ2 by taking the ratio of the monitor intensity and the transmitted light intensity. The calculated results are sent to log amplifiers 16 and 16, respectively.
-1, 16-2 and as the calculation result, -α(λi
)・Outputs a value proportional to d. Of these, 16.1
The output signal from the log amplifier 6-1 is input to the divider 26-1, and a value proportional to α(λ1)/α(λ0) is output. The output signal from the 16, 16-2 log amplifier is input to the other divider, and α(λ2)/α
(λ0) is calculated. In addition, the output signal from the log amplifier 16 is input to an A/D converter 17 and converted into a digital signal. Further, the results calculated by the dividers 26-1 and 26-2 are sent to A/D converters 27-1 and 26-2, respectively.
27-2 and is converted into a digital signal. Regarding the materials of multiple films assumed in advance, each wavelength λ0, λ1
, λ2, the absorption coefficient α(λi) is determined by measurement, and 2
The lookup table 8-1 contains the ratio α(λ1)/α(λ0) of the coefficient values of wavelengths λ0 and λ1, and the lookup table 28-2 contains the ratio α(λ2) of the coefficient values of wavelengths λ0 and λ2. )/α(λ0) are input in correspondence with the type of film material. The subtracter 29-1 calculates the difference between the measured value and the value in the lookup table determined in advance with respect to the ratio of absorption coefficients at wavelengths λ0 and λ1. Similarly, the subtracter 29-1 calculates the difference between the measured value and the predetermined value in the look-up table regarding the ratio of absorption coefficients at wavelengths λ0 and λ2. Data in the lookup table is output in synchronization with the clock from the control circuit 33. At this time, the ratio of the two absorption coefficients of the same film material (α(λ1)/α(λ0), α(λ
2)/α(λ0)) is output, and both subtracters 29-1 and 29-2 perform calculations simultaneously. In addition, the look-up table 32 outputs the absorption coefficient α (λ0) at λ0 for the same film material as that output from the look-up tables 28-1 and 28-2 in synchronization with the clock signal of the control circuit 33. do. On the other hand, the output signals from the subtracters 29-1 and 29-2 are input to judgment circuits 30-1 and 30-2, respectively, to determine whether the absolute value of the subtraction result is larger or smaller than a preset value. Determine the size relationship. In the coincidence degree judgment circuit 31, when the judgment results in both judgment circuits are both small, that is, when the ratio of absorption coefficients determined by measurement closely matches the value in the lookup table at both wavelengths, It is determined that the material of the film to be measured matches the material of the film in the lookup table. The look-up table 32 holds the absorption coefficient α (λ0) of the film material determined to be a match, and outputs it to the divider 34. In the divider 34, α(λ0
)・d from the digital signal and the value of α(λ0) which is the output from the lookup table 32.
Calculate. On the other hand, the light transmitted through the half mirror 6 is incident on the diffraction grating 11 by the condenser lens 9. The incident light is dispersed by the diffraction grating, and images are formed on the line sensor 12 installed at the focal plane of the diffraction grating in the order of the wavelengths of the light. The output signal from the line sensor 12 is the spectral information of the transmitted light as a time series signal, which is converted into a digital signal by the A/D conversion circuit 20 and then input to the arithmetic unit 21. Arithmetic unit 2
In step 1, the maximum and minimum peak wavelengths of data are detected from changes in the intensity of the input signal, and the wavelength between each peak is calculated. In addition, refractive indexes corresponding to the materials of a plurality of assumed films are input to the lookup table 22-1.
The refractive index value is output to the calculator 22 in synchronization with a clock signal from the control circuit 33. At this time, the refractive index of the material of the film determined to match the target sample is maintained based on the output signal from the match degree determination circuit 31. The arithmetic unit 22 compares the obtained peak-to-peak wavelength with data in a look-up table between peak-to-peak wavelength and film thickness determined in advance, and also compares the refractive index output from the look-up table 22-1. Using the value, calculate the film thickness. The film thickness value calculated from the intensity and spectrum of transmitted light is
Each is input to the subtracter 23, and the difference between the two measured values is determined. The difference between the measured values obtained here is determined by the judgment circuit 24.
The absolute value of the difference is compared with a preset reference value. In the judgment circuit, if the difference between the film thickness values obtained by both methods is larger than the reference value, the obtained data is judged to be unreliable and invalid, and if the difference in film thickness values is smaller than the reference value, the data is Judged as reliable and valid. The selection circuit 25 selects and outputs only the data determined to be valid by the determination circuit 24.

In the above embodiment, only the film thickness measurement values determined to be valid are output, but it is also possible to output the material of the film determined to be a match by the matching degree judgment circuit 31. good.

[0028]

[Effect of the invention] As described above, in the first invention,
Using the absorption characteristics of the film in the visible region of light and the multiple reflection phenomenon within the film in the infrared region, the film thickness at the same location on the same sample can be measured simultaneously using two methods, and the thickness can be measured by each method. By comparing the obtained measurement results and selecting only data with a high degree of agreement, highly accurate measurement results are obtained without the influence of external disturbances such as changes in film material or changes in received light intensity due to external light. There is an effect that can be obtained.

Further, in the second invention, the material of the film is identified by detecting relative changes in the absorption coefficient at a plurality of wavelengths, and the absorption coefficient of the film is corrected according to the material.
Since the film thickness is calculated from the corrected absorption coefficient and the intensity of transmitted light at a specific wavelength, it is possible to measure the film thickness with high precision, which can also accommodate changes in the material of the film.

In addition, in the third invention, the absorption characteristics of the film in the visible region of light and the multiple reflection phenomenon within the film in the infrared region are simultaneously used, and the transmittance at multiple wavelengths in the visible region is In the outer region, the film thickness value is measured independently at the same location, and the device is configured to determine the material of the film based on the absorption coefficient at multiple wavelengths determined based on both results, so it is possible to determine the film material with high precision. It becomes possible to judge.

Furthermore, in the fourth invention, the optical system is configured to simultaneously detect the absorption characteristics of the film at multiple wavelengths in the visible region and the spectrum information of transmitted light due to multiple reflections within the film in the infrared region. Then, the material of the film is identified from the measurement results of multiple wavelengths in the visible region, and the film thickness value is corrected using the absorption coefficient corresponding to the identified film material. Correct the thickness value using the refractive index corresponding to the identified film material, compare the film thickness measurements in the visible region and the infrared region, and select only the data with a high degree of agreement. By doing so, it becomes possible to measure the film thickness with higher precision and to determine the material of the film at the same time.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a film inspection apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a film inspection apparatus according to a second embodiment of the present invention.

FIG. 3 is a characteristic diagram showing changes in film transmittance with respect to wavelength.

FIG. 4 is a characteristic diagram showing changes in absorption coefficient of a film with respect to wavelength for a plurality of materials.

FIG. 5 is a configuration diagram showing a film inspection apparatus according to Example 3 of the present invention.

FIG. 6 is a configuration diagram showing a film inspection apparatus according to a fourth embodiment of the present invention.

FIG. 7 is a configuration diagram showing a conventional film thickness measuring device that utilizes light absorption.

FIG. 8 is a configuration diagram showing a conventional film thickness measuring device using optical interference.

FIG. 9 is a configuration diagram showing a conventional film thickness measuring device that utilizes light absorption and interference.

[Explanation of symbols]

1. Light source 2 Half mirror 3 Wavelength filter 4 Detector 5 Sample 6 Half mirror 7 Wavelength filter 8 Detector 9. Focusing lens 10 slit 11 Diffraction grating 12 Line sensor 15 Divider 19 Arithmetic unit 21 Arithmetic unit 22 Arithmetic unit 23 Subtractor 24 Data judgment circuit 25 Data selection circuit 26 Divider 28 Lookup table 29 Subtractor 30 Judgment circuit 31 Matching degree judgment circuit 32 Lookup table 33 Control circuit 34 Divider 39 Divider 40 Subtractor 41 Adder 42 Judgment circuit 43 Material output circuit

Claims (4)

[Claims] Claim 1: A light source having a continuous emission spectrum from the ultraviolet region to the infrared region, a part of the light emitted from this light source being branched, and a light intensity of a specific wavelength in a first wavelength region where an absorption phenomenon occurs. an irradiation optical system that irradiates the sample with light from the light source; a second optical system that detects light spectrum distribution information in the infrared region of transmitted light or reflected light from the sample; a third optical system that branches part of the transmitted light or reflected light and detects the intensity of light having the same specific wavelength as that of the first optical system;
A first calculation means calculates the thickness of the sample based on the intensity ratio of the received light intensity of the optical system and the predetermined absorption coefficient of the sample, and the output signal from the second optical system is a second calculation means for calculating the thickness of the sample; and a first calculation means for calculating the thickness of the sample.
The measured value of the sample thickness obtained by the calculating means of
A film inspection device comprising: a determining means for comparing a measured value of the sample thickness obtained by the calculating means, and determining the validity of the measured value from the degree of coincidence between the two measured values. [Claim 2] A light source that has a continuous emission spectrum from the ultraviolet region to the infrared region, and a plurality of detection units that branch part of the light emitted from this light source and monitor the light intensity at a plurality of specific wavelengths. a first optical system, an irradiation optical system that irradiates the sample with light from the light source, and a first optical system that detects the intensity of transmitted light or reflected light from the sample having the same plurality of specific wavelengths as the first optical system; In the second optical system, the transmittance expressed by the ratio of the received light intensity at the same wavelength of the first optical system and the second optical system is determined, and from the relative ratio of this transmittance between each wavelength, it is determined in advance for each material. Absorption coefficient identification means for identifying the material of the sample and determining the absorption coefficient at a specific wavelength of the identified sample based on a table storing the calculated transmittance ratio between each wavelength; and the transmittance at the specific wavelength. and the determined absorption coefficient value. 3. A light source that has a continuous emission spectrum from the ultraviolet region to the infrared region, and a part of the light emitted from this light source is branched to emit light at a plurality of specific wavelengths in a first wavelength region in which an absorption phenomenon occurs. a first optical system consisting of a plurality of detection units that monitors light intensity; an irradiation optical system that irradiates the sample with light from the light source; and an optical spectral distribution information in the infrared region of transmitted light or reflected light from the sample. a second optical system for detection, a third optical system that branches part of the transmitted light or reflected light from the sample and detects the intensity of light of the same plurality of specific wavelengths as the first optical system; A first calculating means calculates the thickness of the sample from the spectral distribution information of light obtained by the optical system; A second calculating means for calculating the transmittance of the sample, from the film thickness value obtained by the first calculating means and the transmittance at each wavelength calculated by the second calculating means, the absorption at a plurality of specific wavelengths is calculated. A third calculating means for calculating a coefficient, and a film component determining means for comparing the wavelength distribution of the obtained absorption coefficient with the wavelength distribution of the absorption coefficient determined in advance and determining whether the film is a predetermined film component. membrane inspection equipment. 4. A light source that has a continuous emission spectrum from the ultraviolet region to the infrared region, and a part of the light emitted from this light source is branched to emit light at a plurality of specific wavelengths in a first wavelength region where an absorption phenomenon occurs. a first optical system consisting of a plurality of detection units that monitors light intensity; an irradiation optical system that irradiates the sample with light from the light source; and an optical spectral distribution information in the infrared region of transmitted light or reflected light from the sample. a second optical system for detection, a third optical system that branches part of the transmitted light or reflected light from the sample and detects the intensity of light of the same plurality of specific wavelengths as the first optical system; The transmittance of the sample at each wavelength is determined from the ratio of the received light intensity at the same wavelength of the optical system and the third optical system, and from the relative ratio of this transmittance between each wavelength, each A material determination means for identifying the material of the sample based on a table storing transmittance ratios between wavelengths; a refractive index identification means for identifying the refractive index of the sample from the material determination result obtained by the material determination means; and a first optical system. and a first calculating means for calculating the thickness of the sample based on the transmittance obtained at a specific wavelength of the output signal from the third optical system and the absorption coefficient of the sample specified by the material determining means. ,
a second calculation means for calculating the thickness of the sample from the output of the refractive index identification means and the output signal from the second optical system, and a thickness of the sample obtained by the first calculation means and the second calculation means; A film inspection device comprising a determining means for comparing measured values of thickness and determining the validity of the measured value based on the degree of coincidence between the two measured values.